Simple illustrations of range-dependence and 3-D effects by normal-mode sound propagation modelling
Ivansson, Sven
2016-01-01
As is well known, the sound-speed profile has significant effects on underwater acoustic sound propagation. These effects can be quantified by normal-mode models, for example. The basic case is a laterally homogeneous medium, for which the sound speed and the density depend on depth only and not on horizontal position. Effects of horizontal medium-parameter variation can be quantified by coupled-mode models, with coupling between mode expansions for laterally homogeneous parts of the medium. In the present paper, these effects are illustrated for media with a particularly simple horizontal parameter variation such that mode shapes do not vary with horizontal position. The modal wavenumbers depend on horizontal position, however. At a vertical interface between regions with laterally homogeneous medium parameters, each mode is reflected as well as transmitted. For the media considered, reflection and transmission coefficients can be computed separately for each mode without mode coupling, and this is done recu...
Effective-range dependence of two-dimensional Fermi gases
Schonenberg, L. M.; Verpoort, P. C.; Conduit, G. J.
2017-08-01
The Feshbach resonance provides precise control over the scattering length and effective range of interactions between ultracold atoms. We propose the ultratransferable pseudopotential to model effective interaction ranges -1.5 ≤kF2Reff2≤0 , where Reff is the effective range and kF is the Fermi wave vector, describing narrow to broad Feshbach resonances. We develop a mean-field treatment and exploit the pseudopotential to perform a variational and diffusion Monte Carlo study of the ground state of the two-dimensional Fermi gas, reporting on the ground-state energy, contact, condensate fraction, momentum distribution, and pair-correlation functions as a function of the effective interaction range across the BEC-BCS crossover. The limit kF2Reff2→-∞ is a gas of bosons with zero binding energy, whereas ln(kFa )→-∞ corresponds to noninteracting bosons with infinite binding energy.
Effective-range dependence of resonant Fermi gases
Schonenberg, L. M.; Conduit, G. J.
2017-01-01
A Fermi gas of cold atoms allows precise control over the dimensionless effective range, kFReff , of the Feshbach resonance. Our pseudopotential formalism allows us to create smooth potentials with effective range, -2 ≤kFReff≤2 , which we use for a variational and diffusion Monte Carlo study of the ground state of a unitary Fermi gas. We report values for the universal constants of ξ =0.388 (1 ) and ζ =0.087 (1 ) , and compute the condensate fraction, momentum distribution, and pair correlations functions. Finally, we show that a gas with kFReff≳1.9 is thermodynamically unstable.
Range-Dependent Acoustic Propagation in Shallow Water with Elastic Bottom Effects
2015-09-30
water and sediments at the ocean bottom. The attenuation in near-bottom ocean sediments may be very high. It may be high enough that perturbation...for oceanic T-wave generation," Frank et al., has been published. This article documents the incorporation of seismic -like sources into the PE...contribution to this were supported by this grant. Finally the paper “Traveling wave modal attenuation and interaction with a transversely isotropic
Topographic effects on infrasound propagation.
McKenna, Mihan H; Gibson, Robert G; Walker, Bob E; McKenna, Jason; Winslow, Nathan W; Kofford, Aaron S
2012-01-01
Infrasound data were collected using portable arrays in a region of variable terrain elevation to quantify the effects of topography on observed signal amplitude and waveform features at distances less than 25 km from partially contained explosive sources during the Frozen Rock Experiment (FRE) in 2006. Observed infrasound signals varied in amplitude and waveform complexity, indicating propagation effects that are due in part to repeated local maxima and minima in the topography on the scale of the dominant wavelengths of the observed data. Numerical simulations using an empirically derived pressure source function combining published FRE accelerometer data and historical data from Project ESSEX, a time-domain parabolic equation model that accounted for local terrain elevation through terrain-masking, and local meteorological atmospheric profiles were able to explain some but not all of the observed signal features. Specifically, the simulations matched the timing of the observed infrasound signals but underestimated the waveform amplitude observed behind terrain features, suggesting complex scattering and absorption of energy associated with variable topography influences infrasonic energy more than previously observed. © 2012 Acoustical Society of America.
Stochastic processes and long range dependence
Samorodnitsky, Gennady
2016-01-01
This monograph is a gateway for researchers and graduate students to explore the profound, yet subtle, world of long-range dependence (also known as long memory). The text is organized around the probabilistic properties of stationary processes that are important for determining the presence or absence of long memory. The first few chapters serve as an overview of the general theory of stochastic processes which gives the reader sufficient background, language, and models for the subsequent discussion of long memory. The later chapters devoted to long memory begin with an introduction to the subject along with a brief history of its development, followed by a presentation of what is currently the best known approach, applicable to stationary processes with a finite second moment. The book concludes with a chapter devoted to the author’s own, less standard, point of view of long memory as a phase transition, and even includes some novel results. Most of the material in the book has not previously been publis...
Enhanced effects of subluminal and superluminal propagation
Energy Technology Data Exchange (ETDEWEB)
Xiao Feng; Guo Hong; Li Luming; Liu Cheng; Chen Xuzong
2004-06-21
We have experimentally investigated the enhanced effects of subluminal and superluminal propagation, based on electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA), respectively. By adding only an incoherently pumping laser to each case, the slower subluminal group velocity, and the faster superluminal pulse propagation are, respectively, observed. By only changing the intensity of the incoherent pumping beam, we are able to control, respectively, the subluminal group velocity continuously from v{sub g}=c/20000 to v{sub g}=c/8300, and superluminal group velocity from v{sub g}=-c/1667 to v{sub g}=-c/3030. Qualitative explanations for the two cases are given.
Effective propagation in a perturbed periodic structure
Maurel, Agnès; Pagneux, Vincent
2008-08-01
In a recent paper [D. Torrent, A. Hakansson, F. Cervera, and J. Sánchez-Dehesa, Phys. Rev. Lett. 96, 204302 (2006)] inspected the effective parameters of a cluster containing an ensemble of scatterers with a periodic or a weakly disordered arrangement. A small amount of disorder is shown to have a small influence on the characteristics of the acoustic wave propagation with respect to the periodic case. In this Brief Report, we inspect further the effect of a deviation in the scatterer distribution from the periodic distribution. The quasicrystalline approximation is shown to be an efficient tool to quantify this effect. An analytical formula for the effective wave number is obtained in one-dimensional acoustic medium and is compared with the Berryman result in the low-frequency limit. Direct numerical calculations show a good agreement with the analytical predictions.
System Estimation of Panel Data Models under Long-Range Dependence
DEFF Research Database (Denmark)
Ergemen, Yunus Emre
A general dynamic panel data model is considered that incorporates individual and interactive fixed effects allowing for contemporaneous correlation in model innovations. The model accommodates general stationary or nonstationary long-range dependence through interactive fixed effects and innovat...
Nonlinear effects in infrasound propagation simulations
GAINVILLE, Olaf; Marsden, Olivier
2012-01-01
International audience; In the framework of the Comprehensive Nuclear-Test-Ban Treaty, long range propagation of infrasound through the atmosphere is investigated using numerical models. The study problem is a cylindrical blast in an inhomogeneous atmosphere. Vertical profiles of temperature, wind and density obtained during the Misty Picture High explosive experiment conducted in May 1987 are used. The propagation is modeled using two codes. First, the full 2-D Navier-Stokes equations are so...
Effect of Resolution on Propagating Detonation Wave
Energy Technology Data Exchange (ETDEWEB)
Menikoff, Ralph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2014-07-10
Simulations of the cylinder test are used to illustrate the effect of mesh resolution on a propagating detonation wave. For this study we use the xRage code with the SURF burn model for PBX 9501. The adaptive mesh capability of xRage is used to vary the resolution of the reaction zone. We focus on two key properties: the detonation speed and the cylinder wall velocity. The latter is related to the release isentrope behind the detonation wave. As the reaction zone is refined (2 to 15 cells for cell size of 62 to 8μm), both the detonation speed and final wall velocity change by a small amount; less than 1 per cent. The detonation speed decreases with coarser resolution. Even when the reaction zone is grossly under-resolved (cell size twice the reaction-zone width of the burn model) the wall velocity is within a per cent and the detonation speed is low by only 2 per cent.
Assessment of the hybrid propagation model, Volume 1: Analysis of noise propagation effects
2012-08-31
This is the first of two volumes of a report on the Hybrid Propagation Model (HPM), an advanced prediction model for aviation noise propagation. This volume presents the noise level predictions for eleven different sets of propagation conditions, run...
Design Change Model for Effective Scheduling Change Propagation Paths
Zhang, Hai-Zhu; Ding, Guo-Fu; Li, Rong; Qin, Sheng-Feng; Yan, Kai-Yin
2017-09-01
Changes in requirements may result in the increasing of product development project cost and lead time, therefore, it is important to understand how requirement changes propagate in the design of complex product systems and be able to select best options to guide design. Currently, a most approach for design change is lack of take the multi-disciplinary coupling relationships and the number of parameters into account integrally. A new design change model is presented to systematically analyze and search change propagation paths. Firstly, a PDS-Behavior-Structure-based design change model is established to describe requirement changes causing the design change propagation in behavior and structure domains. Secondly, a multi-disciplinary oriented behavior matrix is utilized to support change propagation analysis of complex product systems, and the interaction relationships of the matrix elements are used to obtain an initial set of change paths. Finally, a rough set-based propagation space reducing tool is developed to assist in narrowing change propagation paths by computing the importance of the design change parameters. The proposed new design change model and its associated tools have been demonstrated by the scheduling change propagation paths of high speed train's bogie to show its feasibility and effectiveness. This model is not only supportive to response quickly to diversified market requirements, but also helpful to satisfy customer requirements and reduce product development lead time. The proposed new design change model can be applied in a wide range of engineering systems design with improved efficiency.
Long-range dependence and sea level forecasting
Ercan, Ali; Abbasov, Rovshan K
2013-01-01
This study shows that the Caspian Sea level time series possess long range dependence even after removing linear trends, based on analyses of the Hurst statistic, the sample autocorrelation functions, and the periodogram of the series. Forecasting performance of ARMA, ARIMA, ARFIMA and Trend Line-ARFIMA (TL-ARFIMA) combination models are investigated. The forecast confidence bands and the forecast updating methodology, provided for ARIMA models in the literature, are modified for the ARFIMA models. Sample autocorrelation functions are utilized to estimate the differencing lengths of the ARFIMA
Disease propagation analysis and mitigation strategies for effective mass dispensing.
Lee, Eva K; Chen, Chien H; Pietz, Ferninand; Benecke, Bernard
2010-11-13
Mass dispensing of medical countermeasures has been proven to be an effective and crucial means to contain the outbreak of highly infectious disease. The large influx of individuals to the point-of dispensing (POD) centers to receive vaccinations or prophylactic treatment, however, raises the potential risk of serious intra-facility cross-infections. To mitigate the effect, a thorough understanding of how disease propagates during the dispensing under different transmission parameters versus POD design and operational factors is necessary. In this study, we employ a large-scale simulation/optimization decision support system, RealOpt, to analyze the propagation of highly infectious disease within dispensing sites. The simulation results are validated and benchmarked by a mathematical model based on ordinary differential equations. Pros and cons of using analytical versus simulation tools are discussed. We further perform sensitivity analysis on the dynamics of intra-POD disease propagation, and explore feasible mitigation strategies for effective mass dispensing.
Establishment of high effective regeneration and propagation ...
African Journals Online (AJOL)
'Indian Magic as the experimental materials and investigated the effects of disinfection and antibrowning agents, culture mediums and hormones proportion on differentiation, multiplication, callus induction and rooting, and also the effects of culture substrates on growth of transplants in greenhouse. The results showed that, ...
Subluminal and superluminal pulse propagation influenced by strong nonlinear effects
Chang, Zengguang; Qi, Yihong; Niu, Yueping; Zhang, Jingtao; Gong, Shangqing
2012-12-01
A scheme is proposed for control of pulse propagation from subluminal to superluminal in a four-level Λ-type atomic system. With the relatively intense probe laser and the appropriate detuning of control field, the medium exhibits much lower absorption in the spectral ranges where the dispersion changes from normal to abnormal in the double electromagnetically induced transparency system than in the single electromagnetically induced transparency system. The transmission intensity can be enhanced by several times for the subluminal pulse propagation and by several orders of magnitude for the superluminal pulse propagation without the large distortion in the former compared with those in the latter. We attribute the dramatic absorption reduction to the enhanced nonlinear effects.
Effective Quark Interactions and QCD-Propagators
Bergerhoff, Bastian; Wetterich, Christof
1997-01-01
We compute the momentum dependence of the effective four quark interaction in QCD after integrating out the gluons. Our method is based on a truncation of exact renormalization group equations which should give reasonable results for momenta above the confinement scale. The difference between the four quark interaction and the heavy quark potential can be minimized for an optimal renormalization scheme in Landau gauge. Within the momentum range relevant for quarkonia our results agree with ph...
Electromagnetic wave propagation in rain and polarization effects
OKAMURA, Sogo; OGUCHI, Tomohiro
2010-01-01
This paper summarizes our study on microwave and millimeter-wave propagation in rain with special emphasis on the effects of polarization. Starting from a recount of our past findings, we will discuss developments with these and how they are connected with subsequent research. PMID:20551593
Effects of heating on impulse propagation in superfused canine myocardium
Simmers, T. A.; de Bakker, J. M.; Wittkampf, F. H.; Hauer, R. N.
1995-01-01
The goal of the study was to quantify the response of myocardial impulse propagation to hyperthermia and identify the temperatures required for transient and permanent block in conduction. Although it is generally accepted that the effects of radiofrequency ablation are thermally mediated, the
Intraband effects on ultrafast pulse propagation in semiconductor ...
Indian Academy of Sciences (India)
2015-11-27
Home; Journals; Pramana – Journal of Physics; Volume 75; Issue 5. Intraband effects on ultrafast pulse propagation in semiconductor optical ... Proceedings of the International Workshop/Conference on Computational Condensed Matter Physics and Materials Science (IWCCMP-2015). Posted on November 27, 2015.
Effects of fear factors in disease propagation
Energy Technology Data Exchange (ETDEWEB)
Wang Yubo; Xiao Gaoxi; Cheng, Tee Hiang [School of Electrical and Electronic Engineering, Nanyang Technology University, Singapore 639798 (Singapore); Wong Limsoon [School of Computing and School of Medicine, National University of Singapore, Singapore 117543 (Singapore); Fu Xiuju [Institute of High Performance Computing, Singapore 138632 (Singapore); Ma, Stefan, E-mail: egxxiao@ntu.edu.sg [Ministry of Health, Singapore 169854 (Singapore)
2011-09-02
Upon an outbreak of a dangerous infectious disease, people generally tend to reduce their contacts with others in fear of getting infected. Such typical actions apparently help slow down the spreading of infection. Thanks to today's broad public media coverage, the fear factor may even contribute to preventing an outbreak from happening. We are motivated to study such effects by adopting a complex network approach. First we evaluate the simple case where connections between individuals are randomly removed due to the fear factor. Then we consider a different case where each individual keeps at least a few connections after contact reduction. Such a case is arguably more realistic since people may choose to keep a few social contacts, e.g., with their family members and closest friends, at any cost. Finally, a study is conducted on the case where connection removals are carried out dynamically while the infection is spreading out. Analytical and simulation results show that the fear factor may not easily prevent an epidemic outbreak from happening in scale-free networks. However, it significantly reduces the fraction of the nodes ever getting infected during the outbreak. (paper)
Effects of fear factors in disease propagation
Wang, Yubo; Wong, Limsoon; Fu, Xiuju; Ma, Stefan; Cheng, Tee Hiang; 10.1088/1751-8113/44/35/355101
2011-01-01
Upon an outbreak of a dangerous infectious disease, people generally tend to reduce their contacts with others in fear of getting infected. Such typical actions apparently help slow down the spreading of infection. Thanks to today's broad public media coverage, the fear factor may even contribute to prevent an outbreak from happening. We are motivated to study such effects by adopting a complex network approach. Firstly we evaluate the simple case where connections between individuals are randomly removed due to fear factor. Then we consider a different case where each individual keeps at least a few connections after contact reduction. Such a case is arguably more realistic since people may choose to keep a few social contacts, e.g., with their family members and closest friends, at any cost. Finally a study is conducted on the case where connection removals are carried out dynamically while the infection is spreading out. Analytical and simulation results show that the fear factor may not easily prevent an ...
Effects of fear factors in disease propagation
Wang, Yubo; Xiao, Gaoxi; Wong, Limsoon; Fu, Xiuju; Ma, Stefan; Hiang Cheng, Tee
2011-09-01
Upon an outbreak of a dangerous infectious disease, people generally tend to reduce their contacts with others in fear of getting infected. Such typical actions apparently help slow down the spreading of infection. Thanks to today's broad public media coverage, the fear factor may even contribute to preventing an outbreak from happening. We are motivated to study such effects by adopting a complex network approach. First we evaluate the simple case where connections between individuals are randomly removed due to the fear factor. Then we consider a different case where each individual keeps at least a few connections after contact reduction. Such a case is arguably more realistic since people may choose to keep a few social contacts, e.g., with their family members and closest friends, at any cost. Finally, a study is conducted on the case where connection removals are carried out dynamically while the infection is spreading out. Analytical and simulation results show that the fear factor may not easily prevent an epidemic outbreak from happening in scale-free networks. However, it significantly reduces the fraction of the nodes ever getting infected during the outbreak.
Record length requirement of long-range dependent teletraffic
Li, Ming
2017-04-01
This article contributes the highlights mainly in two folds. On the one hand, it presents a formula to compute the upper bound of the variance of the correlation periodogram measurement of teletraffic (traffic for short) with long-range dependence (LRD) for a given record length T and a given value of the Hurst parameter H (Theorems 1 and 2). On the other hand, it proposes two formulas for the computation of the variance upper bound of the correlation periodogram measurement of traffic of fractional Gaussian noise (fGn) type and the generalized Cauchy (GC) type, respectively (Corollaries 1 and 2). They may constitute a reference guideline of record length requirement of traffic with LRD. In addition, record length requirement for the correlation periodogram measurement of traffic with either the Schuster type or the Bartlett one is studied and the present results about it show that both types of periodograms may be used for the correlation measurement of traffic with a pre-desired variance bound of correlation estimation. Moreover, real traffic in the Internet Archive by the Special Interest Group on Data Communication under the Association for Computing Machinery of US (ACM SIGCOMM) is analyzed in the case study in this topic.
Zaheer, Muhammad Hamad; Rehan, Muhammad; Mustafa, Ghulam; Ashraf, Muhammad
2014-11-01
This paper proposes a novel state feedback delay-range-dependent control approach for chaos synchronization in coupled nonlinear time-delay systems. The coupling between two systems is esteemed to be nonlinear subject to time-lags. Time-varying nature of both the intrinsic and the coupling delays is incorporated to broad scope of the present study for a better-quality synchronization controller synthesis. Lyapunov-Krasovskii (LK) functional is employed to derive delay-range-dependent conditions that can be solved by means of the conventional linear matrix inequality (LMI)-tools. The resultant control approach for chaos synchronization of the master-slave time-delay systems considers non-zero lower bound of the intrinsic as well as the coupling time-delays. Further, the delay-dependent synchronization condition has been established as a special case of the proposed LK functional treatment. Furthermore, a delay-range-dependent condition, independent of the delay-rate, has been provided to address the situation when upper bound of the delay-derivative is unknown. A robust state feedback control methodology is formulated for synchronization of the time-delay chaotic networks against the L2 norm bounded perturbations by minimizing the L2 gain from the disturbance to the synchronization error. Numerical simulation results are provided for the time-delay chaotic networks to show effectiveness of the proposed delay-range-dependent chaos synchronization methodologies. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.
Wave propagation in metamaterials and effective parameters retrieving
DEFF Research Database (Denmark)
Andryieuski, Andrei; Ha, S.; Sukhorukov, A.
2011-01-01
as handsome for implementation. We set a goal to develop a method which is unambiguous but at the same time simple and straightforward. We assume that this can be done by observing the wave propagation inside a metamaterial slab thick enough to avoid transient effects. First, we formulated a retrieval method...... with a plane wave incident from vacuum. Then we determine the effective refractive index from the propagation constant of the dominating (fundamental) Bloch mode. The Bloch and wave impedances are determined by definition as the proportionality coefficient between the electric and magnetic fields...... complex wave effective parameters. Extending the method further we developed the approach to determine both wave and material effective parameters through the Bloch-mode analysis [3]. The idea is to perform the Bloch mode expansion [4] of the field inside the metamaterial slab when it is illuminated...
Disease Propagation Analysis and Mitigation Strategies for Effective Mass Dispensing*
Lee, Eva K; Chen, Chien H; Pietz, Ferninand; Benecke, Bernard
2010-01-01
Mass dispensing of medical countermeasures has been proven to be an effective and crucial means to contain the outbreak of highly infectious disease. The large influx of individuals to the point-of dispensing (POD) centers to receive vaccinations or prophylactic treatment, however, raises the potential risk of serious intra-facility cross-infections. To mitigate the effect, a thorough understanding of how disease propagates during the dispensing under different transmission parameters versus ...
Effect of fluid salinity on subcritical crack propagation in calcite
Rostom, Fatma; Røyne, Anja; Dysthe, Dag Kristian; Renard, François
2013-01-01
The slow propagation of cracks, also called subcritical crack growth, is a mechanism of fracturing responsible for a ductile deformation of rocks under crustal conditions. In the present study, the double-torsion technique was used to measure the effect of fluid chemistry on the slow propagation of cracks in calcite single crystals at room temperature. Time-lapse images and measurements of force and load-point displacement allowed accurate characterization of crack velocities in a range of 10- 8 to 10- 4 m/s. Velocity curves as a function of energy-release rates were obtained for different fluid compositions, varying NH4Cl and NaCl concentrations. Our results show the presence of a threshold in fluid composition, separating two regimes: weakening conditions where the crack propagation is favored, and strengthening conditions where crack propagation slows down. We suggest that electrostatic surface forces that modify the repulsion forces between the two surfaces of the crack may be responsible for this behavior.
Lipkens, B; Blackstock, D T
1998-09-01
A model experiment was reported to be successful in simulating the propagation of sonic booms through a turbulent atmosphere [B. Lipkens and D. T. Blackstock, J. Acoust. Soc. Am. 103, 148-158 (1998)]. In this study the effect on N wave characteristics of turbulence intensity and propagation distance through turbulence are investigated. The main parameters of interest are the rise time and the peak pressure. The effect of turbulence intensity and propagation distance is to flatten the rise time and peak pressure distributions. Rise time and peak pressure distributions always have positive skewness after propagation through turbulence. Average rise time grows with turbulence intensity and propagation distance. The scattering of rise time data is one-sided, i.e., rise times are almost always increased by turbulence. Average peak pressure decreases slowly with turbulence intensity and propagation distance. For the reported data a threefold increase in average rise time is observed and a maximum decrease of about 20% in average peak pressure. Rise times more than ten times that of the no turbulence value are observed. At most, the maximum peak pressure doubles after propagation through turbulence, and the minimum peak pressure values are about one-half the no-turbulence values. Rounded waveforms are always more common than peaked waveforms.
Effects of moisture on ultrasound propagation in cement mortar
Ju, Taeho; Li, Shuaili; Achenbach, Jan; Qu, Jianmin
2015-03-01
In concrete structures, moisture is often a major cause of chemically related degradations such as alkaline-silica reaction. To develop ultrasonic nondestructive evaluation techniques for monitoring such chemical degradations, it is necessary to understand how moisture affects the propagation of ultrasound in concrete. To this end, the objective of this paper is to experimentally determine the correlation between the moisture content in cement mortar and ultrasonic wave propagation. Specifically, effects of moisture on the ultrasonic phase velocity and attenuation are examined. It is found that, for the cement mortar samples considered in this study, moisture has negligible effect on the ultrasonic phase velocity. However, moisture can significantly increase the attenuation of ultrasound in cement mortar even in the sub-MHz frequency range.
Effect of Electric Field on Outwardly Propagating Spherical Flame
Mannaa, Ossama
2012-06-01
The thesis comprises effects of electric fields on a fundamental study of spherical premixed flame propagation.Outwardly-propagating spherical laminar premixed flames have been investigated in a constant volume combustion vessel by applying au uni-directional electric potential.Direct photography and schlieren techniques have been adopted and captured images were analyzed through image processing. Unstretched laminar burning velocities under the influence of electric fields and their associated Markstein length scales have been determined from outwardly propagating spherical flame at a constant pressure. Methane and propane fuels have been tested to assess the effect of electric fields on the differential diffusion of the two fuels.The effects of varying equivalence ratios and applied voltages have been investigated, while the frequency of AC was fixed at 1 KHz. Directional propagating characteristics were analyzed to identify the electric filed effect. The flame morphology varied appreciably under the influence of electric fields which in turn affected the burning rate of mixtures.The flame front was found to propagate much faster toward to the electrode at which the electric fields were supplied while the flame speeds in the other direction were minimally influenced. When the voltage was above 7 KV the combustion is markedly enhanced in the downward direction since intense turbulence is generated and as a result the mixing process or rather the heat and mass transfer within the flame front will be enhanced.The combustion pressure for the cases with electric fields increased rapidly during the initial stage of combustion and was relatively higher since the flame front was lengthened in the downward direction.
Effect of surface losses on soliton propagation in Josephson junctions
DEFF Research Database (Denmark)
Davidson, A.; Pedersen, Niels Falsig; Pagano, S.
1986-01-01
We have explored numerically the effects on soliton propagation of a third order damping term in the modified sine-Gordon equation. In Josephson tunnel junctions such a term corresponds physically to quasiparticle losses within the metal electrodes of the junction. We find that this loss term plays...... the dominant role in determining the shape and stability of the soliton at high velocity. Applied Physics Letters is copyrighted by The American Institute of Physics....
Rapid assessment of nonlinear optical propagation effects in dielectrics
Hoyo, J. del; de la Cruz, A. Ruiz; Grace, E.; Ferrer, A.; Siegel, J.; Pasquazi, A.; Assanto, G.; Solis, J.
2015-01-01
Ultrafast laser processing applications need fast approaches to assess the nonlinear propagation of the laser beam in order to predict the optimal range of processing parameters in a wide variety of cases. We develop here a method based on the simple monitoring of the nonlinear beam shaping against numerical prediction. The numerical code solves the nonlinear Schrödinger equation with nonlinear absorption under simplified conditions by employing a state-of-the art computationally efficient approach. By comparing with experimental results we can rapidly estimate the nonlinear refractive index and nonlinear absorption coefficients of the material. The validity of this approach has been tested in a variety of experiments where nonlinearities play a key role, like spatial soliton shaping or fs-laser waveguide writing. The approach provides excellent results for propagated power densities for which free carrier generation effects can be neglected. Above such a threshold, the peculiarities of the nonlinear propagation of elliptical beams enable acquiring an instantaneous picture of the deposition of energy inside the material realistic enough to estimate the effective nonlinear refractive index and nonlinear absorption coefficients that can be used for predicting the spatial distribution of energy deposition inside the material and controlling the beam in the writing process. PMID:25564243
Effects of screening on the propagation of graphene surface plasmons
Sasaki, Ken-Ichi; Kumada, Norio
2015-03-01
We investigated surface plasmons in epitaxial graphene, while paying particular attention to the effect of interface states and resistivity on the transport properties. The propagation velocity of the surface plasmons is much slower than the electron Fermi velocity when the screening effect provided by interface states is taken into account. Furthermore, slow-moving surface plasmons undergo a strong diffusion when the Fermi energy is near the Dirac point. This is shown by a numerical simulation of an RLC circuit model and its continuum approximation known as the telegrapher's equation. We could explain recent experimental results for the surface plasmons satisfactorily.
Superluminal propagation of evanescent modes as a quantum effect
Energy Technology Data Exchange (ETDEWEB)
Xion, C.D. [School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu 610054 (China); He, B. [Department of Physics and Astronomy, Hunter College of the City University of New York, 695 Park Avenue, New York, NY 10021 (United States); Wang, Z.Y.
2008-05-15
Contrary to mechanical waves, the two-slit interference experiment of single photons shows that the behavior of classical electromagnetic waves corresponds to the quantum mechanical one of single photons, which is also different from the quantum-field-theory behavior such as the creations and annihilations of photons, the vacuum fluctuations, etc. Owing to a purely quantum effect, quantum tunneling particles including tunneling photons (evanescent modes) can propagate over a spacelike interval. With this picture we conclude that the superluminality of evanescent modes is a quantum mechanical rather than a classical phenomenon. (Abstract Copyright [2008], Wiley Periodicals, Inc.)
Above Bonneville Passage and Propagation Cost Effectiveness Analysis.
Energy Technology Data Exchange (ETDEWEB)
Paulsen, C.M.; Hyman, J.B.; Wernstedt, K.
1993-05-01
We have developed several models to evaluate the cost-effectiveness of alternative strategies to mitigate hydrosystem impacts on salmon and steelhead, and applied these models to areas of the Columbia River Basin. Our latest application evaluates the cost-effectiveness of proposed strategies that target mainstem survival (e.g., predator control, increases in water velocity) and subbasin propagation (e.g., habitat improvements, screening, hatchery production increases) for chinook salmon and steelhead stocks, in the portion of the Columbia Basin bounded by Bonneville, Chief Joseph, Dworshak, and Hells Canyon darns. At its core the analysis primarily considers financial cost and biological effectiveness, but we have included other attributes which may be of concern to the region.
Quantum Gravity Effects in Scalar, Vector and Tensor Field Propagation
Dutta, Anindita
Quantum theory of gravity deals with the physics of the gravitational field at Planck length scale (10-35 m). Even though it is experimentally hard to reach the Planck length scale, on can look for evidence of quantum gravity that is detectable in astrophysics. In this thesis, we try to find effects of loop quantum gravity corrections on observable phenomena. We show that the quantum fluctuation strain for LIGO data would be 10 -125 on the Earth. Th correction is, however, substantial near the black hole horizon. We discuss the effect of this for scalar field propagation followed by vector and tensor fields. For the scalar field, the correction introduces a new asymmetry; for the vector field, we found a new perturbation solution and for the tensor field, we found the corrected Einstein equations which are yet to solve. These will affect phenomena like Hawking radiation, black hole entropy and gravitational waves.
Effects of wind turbine wake on atmospheric sound propagation
DEFF Research Database (Denmark)
Barlas, Emre; Zhu, Wei Jun; Shen, Wen Zhong
2017-01-01
In this paper, we investigate the sound propagation from a wind turbine considering the effects of wake-induced velocity deficit and turbulence. In order to address this issue, an advanced approach was developed in which both scalar and vector parabolic equations in two dimensions are solved. Flow...... source. Unsteady acoustic simulations were carried out with the AL/LES input for three cases with different incoming turbulence intensity, and a moving source approach to mimic the rotating turbine blades. The results show a non-negligible effect of the wake on far-field noise prediction. Particularly...... under stable atmospheric conditions, SPL amplification reaches up to 7.5dB at the wake centre. Furthermore, it was observed that when the turbulence intensity level of the incoming flow is higher, the SPL difference between the moving and the steady source is lower....
Quantum Theory of SASE-FEL with Propagation Effects
Bonifacio, R
2005-01-01
We present a proof of principle of the novel regime of quantum SASE with propagation effects. Using a self-consistent system of Schrodinger-Maxwell equations, we show that the dynamics of the system is determined by a properly defined "quantum FEL-parameter", ρ', which rules the number of photons emitted per electron, as well as the electron recoil in units of ћk. In the limit ρ'>>1 the quantum model reproduces the classical SASE regime with random spiking behavior and broad spectrum. In this limit we show that the equation for the Wigner function reduces to the classical Vlasov equation. In the opposite limit, ρ'<1, we demonstrate "quantum purification" of SASE: the classical spiking behavior disappears and the power spectrum becomes very narrow so that the temporal coherence of the SASE spectrum is dramatically improved. Photon statistics, electron-photon entangled states, minimum uncertainty states and quantum limitations on bunching and energy spre...
Effect of point source and heterogeneity on the propagation of ...
African Journals Online (AJOL)
user
branches, like: Earth Science, Seismology, Geophysics etc. Keeping in the mind the importance of monoclinic medium, many attempt have been made to better understand the propagation pattern of the seismic waves in the medium of monoclinic type. Chattopadhyay and Bandyopadhyay (1986) discussed the propagation ...
Effects of irregularity and anisotropy on the propagation of shear ...
African Journals Online (AJOL)
The propagation of shear waves differs between geo-media due to layer's structure and irregularity present in different layers. This paper studies the propagation of shear waves in a monoclinic layer with irregularity lying between two isotropic semiinfinite elastic medium. The displacement in the monoclinic layer is obtained ...
Surface wave propagation effects on buried segmented pipelines
Directory of Open Access Journals (Sweden)
Peixin Shi
2015-08-01
Full Text Available This paper deals with surface wave propagation (WP effects on buried segmented pipelines. Both simplified analytical model and finite element (FE model are developed for estimating the axial joint pullout movement of jointed concrete cylinder pipelines (JCCPs of which the joints have a brittle tensile failure mode under the surface WP effects. The models account for the effects of peak ground velocity (PGV, WP velocity, predominant period of seismic excitation, shear transfer between soil and pipelines, axial stiffness of pipelines, joint characteristics, and cracking strain of concrete mortar. FE simulation of the JCCP interaction with surface waves recorded during the 1985 Michoacan earthquake results in joint pullout movement, which is consistent with the field observations. The models are expanded to estimate the joint axial pullout movement of cast iron (CI pipelines of which the joints have a ductile tensile failure mode. Simplified analytical equation and FE model are developed for estimating the joint pullout movement of CI pipelines. The joint pullout movement of the CI pipelines is mainly affected by the variability of the joint tensile capacity and accumulates at local weak joints in the pipeline.
Pulsar polarisation below 200 MHz: Average profiles and propagation effects
Noutsos, A.; Sobey, C.; Kondratiev, V. I.; Weltevrede, P.; Verbiest, J. P. W.; Karastergiou, A.; Kramer, M.; Kuniyoshi, M.; Alexov, A.; Breton, R. P.; Bilous, A. V.; Cooper, S.; Falcke, H.; Grießmeier, J.-M.; Hassall, T. E.; Hessels, J. W. T.; Keane, E. F.; Osłowski, S.; Pilia, M.; Serylak, M.; Stappers, B. W.; ter Veen, S.; van Leeuwen, J.; Zagkouris, K.; Anderson, K.; Bähren, L.; Bell, M.; Broderick, J.; Carbone, D.; Cendes, Y.; Coenen, T.; Corbel, S.; Eislöffel, J.; Fender, R.; Garsden, H.; Jonker, P.; Law, C.; Markoff, S.; Masters, J.; Miller-Jones, J.; Molenaar, G.; Osten, R.; Pietka, M.; Rol, E.; Rowlinson, A.; Scheers, B.; Spreeuw, H.; Staley, T.; Stewart, A.; Swinbank, J.; Wijers, R.; Wijnands, R.; Wise, M.; Zarka, P.; van der Horst, A.
2015-04-01
Aims: We present the highest-quality polarisation profiles to date of 16 non-recycled pulsars and four millisecond pulsars, observed below 200 MHz with the LOFAR high-band antennas. Based on the observed profiles, we perform an initial investigation of expected observational effects resulting from the propagation of polarised emission in the pulsar magnetosphere and the interstellar medium. Methods: The polarisation data presented in this paper have been calibrated for the geometric-projection and beam-shape effects that distort the polarised information as detected with the LOFAR antennas. We have used RM Synthesis to determine the amount of Faraday rotation in the data at the time of the observations. The ionospheric contribution to the measured Faraday rotation was estimated using a model of the ionosphere. To study the propagation effects, we have compared our low-frequency polarisation observations with archival data at 240, 400, 600, and 1400 MHz. Results: The predictions of magnetospheric birefringence in pulsars have been tested using spectra of the pulse width and fractional polarisation from multifrequency data. The derived spectra offer only partial support for the expected effects of birefringence on the polarisation properties, with only about half of our sample being consistent with the model's predictions. It is noted that for some pulsars these measurements are contaminated by the effects of interstellar scattering. For a number of pulsars in our sample, we have observed significant variations in the amount of Faraday rotation as a function of pulse phase, which is possibly an artefact of scattering. These variations are typically two orders of magnitude smaller than that observed at 1400 MHz by Noutsos et al. (2009), for a different sample of southern pulsars. In this paper we present a possible explanation for the difference in magnitude of this effect between the two frequencies, based on scattering. Finally, we have estimated the magnetospheric
Effect of point source and heterogeneity on the propagation of ...
African Journals Online (AJOL)
user
1,2,...,6 ij ji. C. C i. = = are the elastic constants. Equations governing the propagation of small elastic disturbances in a perfectly conducting monoclinic medium having electromagnetic force ×. J B. (the Lorentz force, J being the electric current density and B being the magnetic induction vector) as the only body forces are.
Intraband effects on ultrafast pulse propagation in semiconductor ...
Indian Academy of Sciences (India)
propagation of such pulses through a semiconductor optical amplifier (SOA) requires con- sideration of intraband ... sees a fast recovering nonlinear gain which introduces less distortion in the pulse shape and spectrum of the ... modulation technique based on the nonlinearity induced by gain saturation. SOAs work well for ...
Effects of plant growth regulators on in vitro propagation of ...
African Journals Online (AJOL)
Cymbidium faberi Rolfe is one of the oldest cultivated orchids in China, which is often sold as a precious potted specimen because of its beautiful and fragrant flowers in eastern Asia. However, the propagation of C. faberi is greatly restricted by the low seed germination rate due to immature embryo and no endosperm under ...
Effect of point source and heterogeneity on the propagation of ...
African Journals Online (AJOL)
This paper stands to investigate the possibility of propagation of SH waves due to a point source in a magnetoelastic monoclinic layer lying over a heterogeneous monoclinic half-space. The heterogeneity is caused by consideration of quadratic variation in rigidity. The methodology employed combines an efficient ...
Effect of fluid viscosity on wave propagation in a cylindrical bore in ...
Indian Academy of Sciences (India)
Abstract. Wave propagation in a cylindrical bore filled with viscous liquid and situated in a micropolar elastic medium of infinite extent is studied. Frequency equation for surface wave propagation near the surface of the cylindrical bore is obtained and the effect of viscosity and micropolarity on dispersion curves is observed.
Improving Delay-Range-Dependent Stability Condition for Systems with Interval Time-Varying Delay
Directory of Open Access Journals (Sweden)
Wei Qian
2013-01-01
Full Text Available This paper discusses the delay-range-dependent stability for systems with interval time-varying delay. Through defining the new Lyapunov-Krasovskii functional and estimating the derivative of the LKF by introducing new vectors, using free matrices and reciprocally convex approach, the new delay-range-dependent stability conditions are obtained. Two well-known examples are given to illustrate the less conservatism of the proposed theoretical results.
Effect of Acute Cigarette Smoking on Atrial Impulse Propagation
İrfan Barutçu; Murat Yüksel; Mustafa Bulut; Mehmet Vefik Yazıcıoğlu; Göksel Acar; M. Muhsin Türkmen; Ali Metin Esen
2012-01-01
Introduction: Acute cigarette smoking has been associated with sympathetic hyperactivity. We therefore sought to determine whether acute cigarette smoking alters atrial impulse propagation. Materials and Methods: Twenty healthy smokers with a history of active smoking were included to the study. The 12-leads surface ECG recorded at a pepper speed of 50 mm/s was obtained from all participants before and average 15 minutes after smoking one cigarette.Results: The change in maximum and minimum P...
Effects of laser beam propagation and saturation on the spatial shape of sodium laser guide stars
National Research Council Canada - National Science Library
Fabien Marc; Hugues Guillet de Chatellus; Jean-Paul Pique
2009-01-01
... turbulence on the upward propagation of the laser beam. Both shape and intensity of the LGS spot are found to depend strongly on these three effects with important consequences on the precision on the wavefront analysis.
Long-range dependence in returns and volatility of global gold market amid financial crises
Omane-Adjepong, Maurice; Boako, Gideon
2017-04-01
Using sampled historical daily gold market data from 07-03-1985 to 06-01-2015, and building on a related work by Bentes (2016), this paper examines the presence of long-range dependence (LRD) in the world's gold market returns and volatility, accounting for structural breaks. The sampled gold market data was divided into subsamples based on four global crises: the September 1992 collapse of the European Exchange Rate Mechanism (ERM), the Asian financial crisis of mid-1997, the Subprime meltdown of 2007, and the recent European sovereign debt crisis, which hit the world's market with varying effects. LRD test was carried-out on the full-sample and subsample periods using three semiparametric methods-before and after adjusting for structural breaks. The results show insignificant evidence of LRD in gold returns. However, very diminutive evidence is found for periods characterized by financial/economic shocks, with no significant detections for post-shock periods. Collectively, this is indicative that the gold market is less speculative, and hence could be somehow less risky for hedging and portfolio diversification.
Robustness of Estimators of Long-Range Dependence and Self-Similarity under non-Gaussianity
Franzke, Christian L E; Watkins, Nicholas W; Gramacy, Robert B; Hughes, Cecilia
2011-01-01
Long-range dependence and non-Gaussianity are ubiquitous in many natural systems like ecosystems, biological systems and climate. However, it is not always appreciated that both phenomena usually occur together in natural systems and that the superposition of both phenomena constitute the self-similarity of a system. These features, which are common in complex systems, impact the attribution of trends and the occurrence and clustering of extremes. The risk assessment of systems with these properties will lead to different outcomes (e.g. return periods) than the more common assumption of independence of extremes. Two paradigmatic models are discussed which can simultaneously account for long-range dependence and non-Gaussianity: Autoregressive Fractional Integrated Moving Average (ARFIMA) and Linear Fractional Stable Motion (LFSM). Statistical properties of estimators for long-range dependence and self-similarity are critically assessed. It is found that the most popular estimators are not robust. In particula...
Fractality Evidence and Long-Range Dependence on Capital Markets: a Hurst Exponent Evaluation
Oprean, Camelia; Tănăsescu, Cristina
2014-07-01
Since the existence of market memory could implicate the rejection of the efficient market hypothesis, the aim of this paper is to find any evidence that selected emergent capital markets (eight European and BRIC markets, namely Hungary, Romania, Estonia, Czech Republic, Brazil, Russia, India and China) evince long-range dependence or the random walk hypothesis. In this paper, the Hurst exponent as calculated by R/S fractal analysis and Detrended Fluctuation Analysis is our measure of long-range dependence in the series. The results reinforce our previous findings and suggest that if stock returns present long-range dependence, the random walk hypothesis is not valid anymore and neither is the market efficiency hypothesis.
Wave propagation phenomena in metamaterials for retrieving of effective parameters
DEFF Research Database (Denmark)
Andryieuski, Andrei; Malureanu, Radu; Ha, S.
2011-01-01
into account propagation of eigen-waves in multilayered structures (thicknesses 10-100 unit cells). Thus, the question of pa-rameters convergence is naturally resolved in our approach. The method has been tested on complex three-dimensional structures like a split-cube-in-carcass and with circular polarized...... waves on chiral MMs [1, 2]. Elaborating our approach the new method has been established, where the unit-cell volume and face field averaging procedures define wave and input (Bloch) impedances correspond-ingly. The first part of the method involves the extraction of the dominating (fundamental) Bloch...... between constitutive elements, multipoles resonances, multimode or photonic crystal (diffraction type) regimes. There are also technical limitations of the retrieval methods connected with very strong losses, branching ambiguity, convergence to bulk parameters, etc. Moreover, most of the simple methods...
Nguyen-Dinh, Maxime; Gainville, Olaf; Lardjane, Nicolas
2015-10-01
We present new results for the blast wave propagation from strong shock regime to the weak shock limit. For this purpose, we analyse the blast wave propagation using both Direct Numerical Simulation and an acoustic asymptotic model. This approach allows a full numerical study of a realistic pyrotechnic site taking into account for the main physical effects. We also compare simulation results with first measurements. This study is a part of the french ANR-Prolonge project (ANR-12-ASTR-0026).
DEFF Research Database (Denmark)
Hughes, S.; Borri, P.; Knorr, A.
2001-01-01
We present microscopic modeling and experimental measurements of femtosecond-pulse interactions in a semiconductor optical amplifier. Two novel nonlinear propagation effects are demonstrated: pulse breakup in the gain regime and pulse compression in the transparency regime. These propagation...... phenomena highlight the microscopic origin and important role of adiabatic following in semiconductor optical amplifiers. Fundamental light-matter interactions are discussed in detail and possible applications are highlighted....
Directory of Open Access Journals (Sweden)
Abdelhamid Bou-El-Harmel
2017-01-01
Full Text Available In the RFID sensor networks (RSN, the orientations of the antennas used in the network nodes have a significant influence on the propagation characteristics. In this article, we investigated the effects of the two antennas’ orientation of different radiation and polarization on the multipath propagation characteristics. This study is evaluated in a typical indoor environment by computer simulations based on the three-dimensional (3D ray-tracing method. This method is based on geometric optics and uniform diffraction theory and also it offers significant advantages in terms of accurate and comprehensive prediction of propagation characterization. The simulations have been performed at frequency 915 MHz and the propagation characteristics are compared in terms of received power level (Pr and Root-Mean-Square (RMS delay spread for a quasi-isotropic 3D cubic antenna with circular polarization and for an omnidirectional dipole with linear polarization in the LOS, NLOS, and OLOS scenarios.
Directory of Open Access Journals (Sweden)
O. E. Ferencz
2007-06-01
Full Text Available During a routine analysis of whistlers on the wide-band VLF recording of the DEMETER satellite, a specific signal structure of numerous fractional-hop whistlers, termed the "Spiky Whistler" (SpW was identified. These signals appear to be composed of a conventional whistler combined by the compound mode-patterns of guided wave propagation, suggesting a whistler excited by a lightning "tweek" spheric. Rigorous, full-wave modelling of tweeks, formed by the long subionospheric guided spheric propagation and of the impulse propagation across an arbitrarily inhomogeneous ionosphere, gave an accurate description of the SpW signals. The electromagnetic impulses excited by vertical, preferably CG lightning discharge, exhibited the effects of guided behaviour and of the dispersive ionospheric plasma along their paths. This modelling and interpretation provides a consistent way to determine the generation and propagation characteristics of the recorded SpW signals, as well as to describe the traversed medium.
Directory of Open Access Journals (Sweden)
Vojkan M. Radonjić
2011-01-01
Full Text Available Quality transmission of digital signals from a transmitting radio-relay device to a receiving one depends on the impact of environmental effects on the propagation of electromagnetic waves. In this paper some of the most important effects are explained and modeled, especially those characteristic for the frequency range within which the GRC 408E operates. The modeling resulted in the conclusions about the quality of transmission of digital signals in the GRC 408E radio-relay equipment. Propagation of electromagnetic waves A radio-relay link is achieved by direct electromagnetic waves, provided there is a line of sight between the transmitting and receiving antenna of a radio-relay device. Electromagnetic waves on the road are exposed to various environmental influences causing phenomena such as bending, reflection, refraction, absorption and multiple propagation. Due to these environmental effects, the quality of information transmission is not satisfactory and a radio-relay link is not reliable. The approach to the analysis of the quality of links in digital radiorelay devices is different from the one in analog radio-relay devices. Therefore, the quality is seen through errors in the received bit ( BER , the propagation conditions are taken into account, a reservation for the fading is determined by other means, etc.. Phenomena which accompany the propagation of electromagnetic waves in digital radio-relay links The propagation of direct EM waves is followed by the following phenomena: - attenuation due to propagation, - diffraction (changing table, - refraction (refraction, - reflection (refusing, - absorption (absorption and - multiple wave propagation. Each of these has a negative effect on the quality of the received signal at the receiving antenna of the radio-relay device. Attenuation due to propagation of electromagnetic waves The main parameter for evaluating the quality of radio-relay links is the level of the field at the reception
A linearized Eulerian sound propagation model for studies of complex meteorological effects
Blumrich, Reinhard; Heimann, Dietrich
2002-08-01
Outdoor sound propagation is significantly affected by the topography (including ground characteristics) and the state of the atmosphere. The atmosphere on its part is also influenced by the topography. A sound propagation model and a flow model based on a numerical integration of the linearized Euler equations have been developed to take these interactions into account. The output of the flow model enables the calculation of the sound propagation in a three-dimensionally inhomogeneous atmosphere. Rigid, partly reflective, or fully absorptive ground can be considered. The linearized Eulerian (LE) sound propagation model has been validated by means of four different scenarios. Calculations of sound fields above rigid and grass-covered ground including a homogeneous atmosphere deviate from analytic solutions by less-than-or-equal1 dB in most parts of the computed domain. Calculations of sound propagation including wind and temperature gradients above rigid ground agree well with measured scale model data. Calculations of sound propagation over a screen including ground of finite impedance show little deviations to measured scale model data which are probably caused by an insufficient representation of the complex ground impedance. Further calculations included the effect of wind on shading by a screen. The results agree well with the measured scale model data. copyright 2002 Acoustical Society of America.
Autonomic imbalance induced breakdown of long-range dependence in healthy heart rate.
Aoyagi, N; Struzik, Z R; Kiyono, K; Yamamoto, Y
2007-01-01
The investigation of the relation between the long-range correlation property of heart rate and autonomic balance. An investigation of the fractal scaling properties of heart rate variability was carried out by using detrended fluctuation analysis (DFA). Eleven healthy subjects were examined for two consecutive days, which included usual daily activity, strenuous prolonged experimental exercise, and sleep. We also considered two patient groups with autonomic dysfunction characterized by selective sympathetic and parasympathetic dominance. Robust long-range dependence in heart rate is observed only in the state of usual daily activity, characterized by normal heart rate typical of balanced autonomic sympathetic and parasympathetic regulation. This confirms the previously postulated behavioral independence of heart rate regulation, but reveals that the occurrence of 1/f, long-range dependence is restricted to only the state of autonomic balance. Both the sympathetic dominant high heart rate state, realized during strenuous experimental exercise, and the parasympathetic dominant low heart rate state, prevalent in (deep) sleep, are characterized by uncorrelated, near white-noise-like scaling, lacking long-range dependence. Remarkably, the breakdown of the long-range correlations observed in healthy heart rate in the states of sympathetic and parasympathetic dominance is in stark contrast to the increased correlations which have previously been observed in neurogenic parasympathetic and sympathetic dominance in patients suffering from primary autonomic failure and congestive heart failure, respectively. Our findings further reveal the diagnostic capabilities of heart rate dynamics, by differentiating physiological healthy states from pathology.
Zhu, P. Y.; Fung, A. K.
1986-01-01
The effective medium approximation (EMA) formalism developed for scalar wave calculations in solid state physics is generalized to electromagnetic wave scattering in a dense random medium. Results are applied to compute the effective propagation constant in a dense medium involving discrete spherical scatterers. When compared with a common quasicrystalline approximation (QCA), it is found that EMA accounts for backward scattering and the effect of correlation among three scatterers which are not available in QCA. It is also found that there is not much difference in the calculated normalized phase velocity between the use of these two approximations. However, there is a significant difference in the computed effective loss tangent in a nonabsorptive random medium. The computed effective loss tangent using EMA and measurements from a snow medium are compared, showing good agreement.
Lundberg, Wayne Randolph
A semi-empirical nonlinear aeroacoustic propagation theory was developed for the prediction of high-intensity flight/launch noise produced by full-scale aerospace operations. The resulting nonlinear aeroacoustic propagation model was verified by analysis of environmental noise propagation measurements on the Concorde, United States Air Force F-4C and F-16A aircraft and the Peacekeeper rocket. Propagation modeling of both aeroacoustic directivity and nonlinear attenuation effects were separately verified to be accurate. Model parameters were derived to document the extent of each physical acoustic effect. The parameters of nonlinear acoustic propagation were empirically demonstrated to be linearly related through analysis of multiple sources. These results verified the formulation of a Simplified Nonlinear Aeroacoustic Propagation (SNAP) model. Such verification supports the potential for application of SNAP to broadband aeroacoustic noise source propagation calculations.
On modelling of physical effects accompanying the propagation of action potentials in nerve fibres
Engelbrecht, Jüri; Tamm, Kert; Laasmaa, Martin; Vendelin, Marko
2016-01-01
The recent theoretical and experimental studies have revealed many details of signal propagation in nervous systems. In this paper an attempt is made to unify various mathematical models which describe the signal propagation in nerve fibres. The analysis of existing single models permits to select the leading physiological effects. As a result, a more general mathematical model is described based on the coupling of action potentials with mechanical waves in a nerve fibre. The crucial issue is how to model coupling effects which are strongly linked to the ion currents through biomembranes.
Regulatory effects on the population dynamics and wave propagation in a cell lineage model.
Wang, Mao-Xiang; Ma, Yu-Qiang; Lai, Pik-Yin
2016-03-21
We consider the interplay of cell proliferation, cell differentiation (and de-differentiation), cell movement, and the effect of feedback regulations on the population and propagation dynamics of different cell types in a cell lineage model. Cells are assumed to secrete and respond to negative feedback molecules which act as a control on the cell lineage. The cell densities are described by coupled reaction-diffusion partial differential equations, and the propagating wave front solutions in one dimension are investigated analytically and by numerical solutions. In particular, wavefront propagation speeds are obtained analytically and verified by numerical solutions of the equations. The emphasis is on the effects of the feedback regulations on different stages in the cell lineage. It is found that when the progenitor cell is negatively regulated, the populations of the cell lineage are strongly down-regulated with the steady growth rate of the progenitor cell being driven to zero beyond a critical regulatory strength. An analytic expression for the critical regulation strength in terms of the model parameters is derived and verified by numerical solutions. On the other hand, if the inhibition is acting on the differentiated cells, the change in the population dynamics and wave propagation speed is small. In addition, it is found that only the propagating speed of the progenitor cells is affected by the regulation when the diffusion of the differentiated cells is large. In the presence of de-differentiation, the effect on down-regulating the progenitor population is weakened and there is no effect on the propagation speed due to regulation, suggesting that the effect of regulatory control is diminished by de-differentiation pathways. Copyright © 2016 Elsevier Ltd. All rights reserved.
Quantity effect of radial cracks on the cracking propagation behavior and the crack morphology.
Chen, Jingjing; Xu, Jun; Liu, Bohan; Yao, Xuefeng; Li, Yibing
2014-01-01
In this letter, the quantity effect of radial cracks on the cracking propagation behavior as well as the circular crack generation on the impacted glass plate within the sandwiched glass sheets are experimentally investigated via high-speed photography system. Results show that the radial crack velocity on the backing glass layer decreases with the crack number under the same impact conditions during large quantities of repeated experiments. Thus, the "energy conversion factor" is suggested to elucidate the physical relation between the cracking number and the crack propagation speed. Besides, the number of radial crack also takes the determinative effect in the crack morphology of the impacted glass plate. This study may shed lights on understanding the cracking and propagation mechanism in laminated glass structures and provide useful tool to explore the impact information on the cracking debris.
The effect of Kerr nonlinearity and Doppler broadening on slow light propagation
Ali, Hazrat; Ziauddin; Ahmad, Iftikhar
2014-02-01
The influence of Kerr nonlinearity and Doppler broadening on the slow light propagation of a dispersive atomic medium is revisited using a four-level Λ-type (87Rb) atomic system under the condition of electromagnetically induced transparency (EIT). The medium exhibits an EIT process which is accompanied by normal dispersion, i.e., sub-luminal (slow light) pulse propagation. In the presence of Kerr nonlinearity and the Doppler broadening effect the dispersion property of the proposed atomic medium is modified, which leads to enhancement of the positive group index of the medium. The combined effect of Kerr nonlinearity and Doppler broadening on slow light propagation inside the medium is the major motivation for this work.
Mullen, Linda; Alley, Derek; Cochenour, Brandon
2011-04-01
A recent paper described experiments completed to study the effect of scattering on the propagation of modulated light in laboratory tank water [Appl. Opt.48, 2607 (2009)APOPAI0003-693510.1364/AO.48.002607]. Those measurements were limited to a specific scattering agent (Maalox antacid) with a fixed scattering albedo (0.95). The purpose of this paper is to study the effects of different scattering agents and scattering albedos on modulated light propagation in water. The results show that the scattering albedo affects the number of attenuation lengths that the modulated optical signal propagates without distortion, while the type of scattering agent affects the degree to which the modulation is distorted with increasing attenuation length. © 2011 Optical Society of America
A review of ionospheric effects on Earth-space propagation
Klobuchar, J. A.
1984-01-01
A short description is given of each ionospheric total electron content (TEC) effect upon radio waves, along with a representative value of the magnitude of each of these effects under normal ionospheric conditions. A discussion is given of the important characteristics of average ionospheric TEC behavior and the temporal and spatial variability of TEC. Radio waves undergo several effects when they pass through the Earth's ionosphere. One of the most important of these effects is a retardation, or group delay, on the modulation or information carried on the radio wave that is due to its encounter with the free, thermal electrons in the Earth's ionosphere. Other effects the ionosphere has on radio waves include: radio frequency (RF) carrier phase advance; Doppler shift of the RF carrier of the radio wave; Faraday rotation of the plane of polarization of linearly polarized waves; angular refraction or bending of the radio wave path as it travels through the ionosphere; and amplitude and phase scintillations.
Acoustic wave propagation and stochastic effects in metamaterial absorbers
DEFF Research Database (Denmark)
Christensen, Johan; Willatzen, Morten
2014-01-01
We show how stochastic variations of the effective parameters of anisotropic structured metamaterials can lead to increased absorption of sound. For this, we derive an analytical model based on the Bourret approximation and illustrate the immediate connection between material disorder and attenua......We show how stochastic variations of the effective parameters of anisotropic structured metamaterials can lead to increased absorption of sound. For this, we derive an analytical model based on the Bourret approximation and illustrate the immediate connection between material disorder...
Effect of surface deposits on electromagnetic propagation in uniform ducts
Baumeister, Kenneth J.
1991-01-01
A finite-element Galerkin formulation has been used to study the effect of material surface deposits on the reflective characteristics of straight uniform ducts with PEC (perfectly electric conducting) walls. Over a wide frequency range, the effect of both single and multiple dielectric surface deposits on the duct reflection coefficient were examined. The power reflection coefficient was found to be significantly increased by the addition of deposits on the wall.
CSIR Research Space (South Africa)
Mokotedi, O
2011-11-01
Full Text Available - and macro- propagated GN; however, roots of the latter were 32% more efficient in conducting water to the leaves (Table 1). OSCAR MOKOTEDI1,2, PAULA WATT2 , NORMAN PAMMENTER2 Presented at the IURO 2011 Eucalyptus conference in Porto Seguro, Brazil Table...
Wave propagation in magneto-electro-elastic multilayered plates with nonlocal effect
Chen, Jiangyi; Guo, Junhong; Pan, Ernian
2017-07-01
In this paper, analytical solutions for propagation of time-harmonic waves in three-dimensional, transversely isotropic, magnetoelectroelastic and multilayered plates with nonlocal effect are derived. We first convert the time-harmonic wave problem into a linear eigenvalue system, from which we obtain the general solutions of the extended displacements and stresses. The solutions are then employed to derive the propagator matrix which connects the field variables at the upper and lower interfaces of each layer. Making use of the continuity conditions of the physical quantities across the interface, the global propagator relation is assembled by propagating the solutions in each layer from the bottom to the top of the layered plate. From the global propagator matrix, the dispersion equation is obtained by imposing the traction-free boundary conditions on both the top and bottom surfaces of the layered plate. Dispersion curves and mode shapes in layered plates made of piezoelectric BaTiO3 and magnetostrictive CoFe2O4 materials are presented to show the influence of the nonlocal parameter, stacking sequence, as well as the orientation of incident wave on the time-harmonic field response.
Pulsar polarisation below 200 MHz: Average profiles and propagation effects
Noutsos, A.; Sobey, C.; Kondratiev, V.I.; Weltevrede, P.; Verbiest, J.P.W.; Karastergiou, A.; Kramer, M.; Kuniyoshi, M.; Alexov, A.; Breton, R.P.; Bilous, A.V.; Cooper, S.; Falcke, H.; Grießmeier, J.M.; Hassall, T.E.; Hessels, J.W.T.; Keane, E.F.; Osłowski, S.; Pilia, M.; Serylak, M.; Stappers, B.W.; ter Veen, S.; van Leeuwen, J.; Zagkouris, K.; Anderson, K.; Bähren, L.; Bell, M.; Broderick, J.; Carbone, D.; Cendes, Y.; Coenen, T.; Corbel, S.; Eislöffel, J.; Fender, R.; Garsden, H.; Jonker, P.; Law, C.; Markoff, S.; Masters, J.; Miller-Jones, J.; Molenaar, G.; Osten, R.; Pietka, M.; Rol, E.; Rowlinson, A.; Scheers, B.; Spreeuw, H.; Staley, T.; Stewart, A.; Swinbank, J.; Wijers, R.; Wijnands, R.; Wise, M.; Zarka, P.; van der Horst, A.
2015-01-01
Aims. We present the highest-quality polarisation profiles to date of 16 non-recycled pulsars and four millisecond pulsars, observed below 200 MHz with the LOFAR high-band antennas. Based on the observed profiles, we perform an initial investigation of expected observational effects resulting from
Pulsar polarisation below 200 MHz: Average profiles and propagation effects
A. Noutsos; C.A. Sobey; V.I. Kondratiev; P. Weltevrede; J.P.W. Verbiest; A. Karastergiou; M. Kramer; M. Kuniyoshi; A. Alexov; R.P. Breton; A.V. Bilous; S. Cooper; H. Falcke; J.-M. Grießmeier; T.E. Hassall; J.W.T. Hessels; E.F. Keane; S. Oslowski; M. Pilia; M. Serylak; B.W. Stappers; S. ter Veen (Sander); J. van Leeuwen (Joeri); K. Zagkouris; K. Anderson; L. Baehren; M.E. Bell; J.W. Broderick; D. Carbone; Y.N. Cendes; T. Coenen; S. Corbel; J. Eislöffel; R.P. Fender; H. Garsden; P. Jonker; C.J. Law; S. Markoff; J. Masters; J.C.A. Miller-Jones; G.J. Molenaar; R. Osten; M. Pietka; E. Rol; A. Rowlinson; L.H.A. Scheers (Bart); H. Spreeuw; T.D. Staley; A.J. Stewart; J.D. Swinbank; R.A.M.J. Wijers (Ralph); R. Wijnands; M.W. Wise (Michael); P. Zarka; A.J. van der Horst
2015-01-01
htmlabstractAims: We present the highest-quality polarisation profiles to date of 16 non-recycled pulsars and four millisecond pulsars, observed below 200 MHz with the LOFAR high-band antennas. Based on the observed profiles, we perform an initial investigation of expected observational effects
Molecular dynamics simulation of effect of hydrogen atoms on crack propagation behavior of α-Fe
Energy Technology Data Exchange (ETDEWEB)
Song, H.Y., E-mail: gsfshy@sohu.com; Zhang, L.; Xiao, M.X.
2016-12-16
The effect of the hydrogen concentration and hydrogen distribution on the mechanical properties of α-Fe with a pre-existing unilateral crack under tensile loading is investigated by molecular dynamics simulation. The results reveal that the models present good ductility when the front region of crack tip has high local hydrogen concentration. The peak stress of α-Fe decreases with increasing hydrogen concentration. The studies also indicate that for the samples with hydrogen atoms, the crack propagation behavior is independent of the model size and boundaries. In addition, the crack propagation behavior is significantly influenced by the distribution of hydrogen atoms. - Highlights: • The distribution of hydrogen plays a critical role in the crack propagation. • The peak stress decrease with the hydrogen concentration increasing. • The crack deformation behavior is disclosed and analyzed.
[Effects of plant growth regulators on cutting propagation of Rosa laevigata].
Liu, Long-yuan; Zheng, Xuan-xuan; Weng, Huan; Tian, Su-ying
2013-11-01
To explore the optimal plant growth regulator and its suitable concentration for the cutting propagation of Rosa laevigata. The cuttings were dealt with 6 kinds of plant growth regulators (IAA,IBA, NAA, PP333, 2, 4-D and ABT) at different concentrations (100, 200 and 500 mg/L) for 50 seconds. After 30 days growth, by analysis of variance and multiple comparisons,the most suitable cutting propagation method for Rosa laevigata was found. Under the same condition, different concentration of different kinds of plant growth regulators had different effects on cutting propagation of Rosa laevigata. Generally speaking,cuttings soaked with 200 mg/L PP333 for 50 seconds was the best,with the high multiple effectiveness index and average root number (12.42); Cuttings soaked with 200 mg/L IBA for 50 seconds also had significant effects, with the second high multiple effectiveness index and the highest survival rate (96.67%). 200 mg/L PP333 can promote cutting propagation of Rosa laevigata best.
Wave propagation method as an accurate technique for effective refractive index retrieving
DEFF Research Database (Denmark)
Andryieuski, Andrei; Malureanu, Radu; Lavrinenko, Andrei
2009-01-01
An effective parameters retrieval method based on the wave propagation simulation is proposed and compared with the standard S-parameter procedure. The method is free from possible mistakes originated by the multiple branching of solutions in the S-parameter procedure and shows high accuracy. The...
Generalized Efficient Inference on Factor Models with Long-Range Dependence
DEFF Research Database (Denmark)
Ergemen, Yunus Emre
. Short-memory dynamics are allowed in the common factor structure and possibly heteroskedastic error term. In the estimation, a generalized version of the principal components (PC) approach is proposed to achieve efficiency. Asymptotics for efficient common factor and factor loading as well as long......A dynamic factor model is considered that contains stochastic time trends allowing for stationary and nonstationary long-range dependence. The model nests standard I(0) and I(1) behaviour smoothly in common factors and residuals, removing the necessity of a priori unit-root and stationarity testing...
Operational Decision Aids for Exploiting or Mitigating Electromagnetic Propagation Effects
1989-09-01
CORRECTION OF IONOSPHERIC EFFECTS FOR THE PRECISE ORBIT DETERMINATION OF SATELLITES by F.Foucher, R.Fleury and P.Lassudrie-Duchesne 33 THE USE OF...Eventually, three dimensional models will become reality. With TESS(3), we can more fully exploit a wide range of environmental satellites already on orbit ...dane las courbas d’iso-indice caracterise par un effondrement cur use trancha distance se situant entre 50 at 90 km par rapport A l’origina. La but des
Geodetic refraction effects of electromagnetic wave propagation through the atmosphere
1984-01-01
With very few exceptions, geodetic measurements use electro magnetic radiation in order to measure directions, distances, time delays, and Doppler frequency shifts, to name the main ter restrial and space observables. Depending on the wavelength of the radiation and the purpose of the measurements, the follow ing parameters of the electromagnetic wave are measured: ampli tude, phase, angle-of-arrival, polarisation and frequency. Ac curate corrections have to be applied to the measurements in order to take into account the effects of the intervening medium between transmitter and receiver. The known solutions use at mospheric models, special observation programs, remote sensing techniques and instrumental methods. It has been shown that the effects of the earth's atmospheric envelope present a fundamental limitation to the accuracy and precision of geodetic measurements. This applies equally to ter restrial and space applications. Instrumental accuracies are al ready below the atmospherically i...
Nijhof, M.J.J.
2010-01-01
In this work, the accuracy, efficiency and range of applicability of various (approximate) models for viscothermal wave propagation are investigated. Models for viscothermal wave propagation describe thewave behavior of fluids including viscous and thermal effects. Cases where viscothermal effects
Effect of segregations on mechanical properties and crack propagation in spring steel
Directory of Open Access Journals (Sweden)
B. Žužek
2015-10-01
Full Text Available Considerable efforts have been made over the last decades to improve performance of spring steels, which would increase the service time of springs and also allow vehicles weight reduction. There are different possibilities of improving properties of spring steels, from modifying the chemical composition of steels to optimizing the deformation process and changing the heat treatment parameters. Another way of improving steel properties is through refining the microstructure and reducing amount of inclusions. Therefore, the focus of the current investigation was to determine the effect of more uniform and cleaner microstructure obtained through electro-slag remelting (ESR of steel on the mechanical and dynamic properties of spring steel, with special focus on the resistance to fatigue crack propagation. Effect of the microstructure refinement was evaluated in terms of tensile strength, elongation, fracture and impact toughness, and fatigue resistance under bending and tensile loading. After the mechanical tests the fracture surfaces of samples were analyzed using scanning electron microscope (SEM and the influence of microstructure properties on the crack propagation and crack propagation resistance was studied. Investigation was performed on hot rolled, soft annealed and vacuum heat treated 51CrV4 spring steel produced by conventional continuous casting and compared with steel additional refined through ESR. Results shows that elimination of segregations and microstructure refinement using additional ESR process gives some improvement in terms of better repeatability and reduced scattering, but on the other hand it has negative effect on crack propagation resistance and fatigue properties of the spring steel.
Long Range Dependence Prognostics for Bearing Vibration Intensity Chaotic Time Series
Directory of Open Access Journals (Sweden)
Qing Li
2016-01-01
Full Text Available According to the chaotic features and typical fractional order characteristics of the bearing vibration intensity time series, a forecasting approach based on long range dependence (LRD is proposed. In order to reveal the internal chaotic properties, vibration intensity time series are reconstructed based on chaos theory in phase-space, the delay time is computed with C-C method and the optimal embedding dimension and saturated correlation dimension are calculated via the Grassberger–Procaccia (G-P method, respectively, so that the chaotic characteristics of vibration intensity time series can be jointly determined by the largest Lyapunov exponent and phase plane trajectory of vibration intensity time series, meanwhile, the largest Lyapunov exponent is calculated by the Wolf method and phase plane trajectory is illustrated using Duffing-Holmes Oscillator (DHO. The Hurst exponent and long range dependence prediction method are proposed to verify the typical fractional order features and improve the prediction accuracy of bearing vibration intensity time series, respectively. Experience shows that the vibration intensity time series have chaotic properties and the LRD prediction method is better than the other prediction methods (largest Lyapunov, auto regressive moving average (ARMA and BP neural network (BPNN model in prediction accuracy and prediction performance, which provides a new approach for running tendency predictions for rotating machinery and provide some guidance value to the engineering practice.
Radiation Effects and Propagation in Optical Fibers and Components.
Gedam, Subhash Ganpatrao
1987-09-01
The power series expansion method was used to solve the wave equation in step-index optical fiber. The cut off frequencies were calculated using 200 coefficients. The cutoff frequencies of TM modes were found to differ from those of TE modes. This difference, which is the error due to the approximations made, was calculated as a function of the relative refractive index difference (Delta ). The intermodal delay between the TE and TM mode was also calculated. The dispersion curves were plotted for several modes and values of Delta. A polarization control system was designed to be used in a coherent optical communication system, to restore the state of polarization (SOP) of the light output of a singlemode fiber. Rotating quarter wave and half wave plates were used to compensate for the changes in SOP. The sensitivity of the system was greatly improved by utilizing the heterodyne principle. The effects of neutron irradiation were studied on fiber optic materials (glasses), optical fibers, and photodetectors. In case of the heavy metal fluoride glasses, a red shift was found in the UV edge, which increased with neutron fluence. A very small amount of recovery was observed after three weeks. The shift could be due to the occurrence of color centers on irradiation and/or due to the shift in the urbach edge itself. The optical fibers showed an increase in the attenuation in the visible/near IR part of the spectrum. Fibers doped with P in the core showed more induced loss compared to the fibers doped with P in the cladding, and showed little or no recovery after a day. Radiation hardened fibers suffered far less induced loss on irradiation compared to the other fibers and also recovered in attenuation by a factor of 3 to 6 after a day. The responsivity of Si-PIN and Ge-PIN photodiodes degraded after irradiation. The relative responsivity was found to have a spectral dependence in case of Si-photodiode but was found to be independent of wavelength in case of Ge
Energy Technology Data Exchange (ETDEWEB)
Aguirre, R.M.; Paoli, A.L. de [Universidad Nacional de La Plata, and IFLP, Departamento de Fisica, Facultad de Ciencias Exactas, La Plata (Argentina)
2016-11-15
We obtain the covariant propagator at finite temperature for interacting baryons immersed in a strong magnetic field. The effect of the intrinsic magnetic moments on the Green function are fully taken into account. We make an expansion in terms of eigenfunctions of a Dirac field, which leads us to a compact form of its propagator. We present some simple applications of these propagators, where the statistical averages of nuclear currents and energy density are evaluated. (orig.)
Self-focusing effect of annular beams propagating in the atmosphere.
Zhang, Yuqiu; Ji, Xiaoling; Li, Xiaoqing; Li, Qiang; Yu, Hong
2017-09-04
The self-focusing effect of annular beams propagating in the atmosphere to assist delivering powerful laser beams from orbit to the ground is studied in detail. It is found the annular beam is compressed more strongly due to the self-focusing effect as the beam obscure ratio increases. On the other hand, the self-focusing effect between annular, flat-topped and Gaussian beams is compared. It is shown that the self-focusing effect on the annular beam is stronger than that on flat-topped and Gaussian beams. However, the threshold critical power values of annular, flat-topped and Gaussian beams should be in sequence from small to large. Furthermore, the expression of the B integral of annular beams propagating from orbit to the ground in the atmosphere is derived, and the fitting equation related to the B integral of annular beams for maximal compression without filamentation is presented.
Wave propagation retrieval method for metamaterials: Unambiguous restoration of effective parameters
DEFF Research Database (Denmark)
Andryieuski, Andrei; Malureanu, Radu; Lavrinenko, Andrei
2009-01-01
In this brief report we propose a direct method of effective-parameters restoration that is based on the wave propagation phenomenon. It is easy in implementation, has no unambiguity in retrieving effective properties and is applicable to thick metamaterial (MTM) slabs. The method is validated...... on the case studies of fishnet, split cube in carcass, and Jerusalem cross MTMs. The constraints of the method are designated....
Effects of a “day-time” substorm on the ionosphere and radio propagation
Blagoveshchensky, D.; Kalishin, A.; MacDougall, J.
2009-11-01
Propagation mechanisms of lateral (non-great-circle) signals on a high-latitude HF radio path during magnetospheric substorms that occurred in the day-time have been considered. The path is equipped with oblique ionospheric sounding (OIS) from Murmansk to St. Petersburg. The OIS method gives the possibility to determine propagation modes, MOF (maximum observed frequency) values, signal delays, etc. Data of the CUTLASS radar, the IMAGE magnetometer system, the Finnish riometer chain, and the Tromso ionosonde were also used for the analysis. The main results are the following: (1) the lateral signal propagation takes place, as a rule, if the path midpoint is located near the irregularity region that moves sharply from high to low latitudes. The lateral signal propagation appearing during day-time is a new effect. (2) Formation of dense field-aligned irregularities during a substorm leads to decreasing F2MOF values on radio paths. These results can be useful for problems of radiolocation, HF communications and navigation.
Interaction Models for Common Long-Range Dependence in Asset Prices Volatility
Teyssière, G.
We consider a class of microeconomic models with interacting agents which replicate the main properties of asset prices time series: non-linearities in levels and common degree of long-memory in the volatilities and co-volatilities of multivariate time series. For these models, long-range dependence in asset price volatility is the consequence of swings in opinions and herding behavior of market participants, which generate switches in the heteroskedastic structure of asset prices. Thus, the observed long-memory in asset prices volatility might be the outcome of a change-point in the conditional variance process, a conclusion supported by a wavelet anaysis of the volatility series. This explains why volatility processes share only the properties of the second moments of long-memory processes, but not the properties of the first moments.
Common long-range dependence in a panel of hourly Nord Pool electricity prices and loads
DEFF Research Database (Denmark)
Ergemen, Yunus Emre; Haldrup, Niels; Rodríguez-Caballero, Carlos Vladimir
Equilibrium electricity spot prices and loads are often determined simultaneously in a day-ahead auction market for each hour of the subsequent day. Hence daily observations of hourly prices take the form of a periodic panel rather than a time series of hourly observations. We consider novel panel...... data approaches to analyse the time series and the cross-sectional dependence of hourly Nord Pool electricity spot prices and loads for the period 2000-2013. Hourly electricity prices and loads data are characterized by strong serial long-range dependence in the time series dimension in addition...... of the underlying production technology and because the demand is more volatile than the supply, equilibrium prices and loads are argued to identify the periodic power supply curve. The estimated supply elasticities are estimated from fractionally co-integrated relations and range between 0.5 and 1...
Yang, Bing; Liao, Zhen; Qin, Yahang; Wu, Yayun; Liang, Sai; Xiao, Shoune; Yang, Guangwu; Zhu, Tao
2017-05-01
To describe the complicated nonlinear process of the fatigue short crack evolution behavior, especially the change of the crack propagation rate, two different calculation methods are applied. The dominant effective short fatigue crack propagation rates are calculated based on the replica fatigue short crack test with nine smooth funnel-shaped specimens and the observation of the replica films according to the effective short fatigue cracks principle. Due to the fast decay and the nonlinear approximation ability of wavelet analysis, the self-learning ability of neural network, and the macroscopic searching and global optimization of genetic algorithm, the genetic wavelet neural network can reflect the implicit complex nonlinear relationship when considering multi-influencing factors synthetically. The effective short fatigue cracks and the dominant effective short fatigue crack are simulated and compared by the Genetic Wavelet Neural Network. The simulation results show that Genetic Wavelet Neural Network is a rational and available method for studying the evolution behavior of fatigue short crack propagation rate. Meanwhile, a traditional data fitting method for a short crack growth model is also utilized for fitting the test data. It is reasonable and applicable for predicting the growth rate. Finally, the reason for the difference between the prediction effects by these two methods is interpreted.
Effect of micromorphology of cortical bone tissue on crack propagation under dynamic loading
Wang, Mayao; Gao, Xing; Abdel-Wahab, Adel; Li, Simin; Zimmermann, Elizabeth A.; Riedel, Christoph; Busse, Björn; Silberschmidt, Vadim V.
2015-09-01
Structural integrity of bone tissue plays an important role in daily activities of humans. However, traumatic incidents such as sports injuries, collisions and falls can cause bone fracture, servere pain and mobility loss. In addition, ageing and degenerative bone diseases such as osteoporosis can increase the risk of fracture [1]. As a composite-like material, a cortical bone tissue is capable of tolerating moderate fracture/cracks without complete failure. The key to this is its heterogeneously distributed microstructural constituents providing both intrinsic and extrinsic toughening mechanisms. At micro-scale level, cortical bone can be considered as a four-phase composite material consisting of osteons, Haversian canals, cement lines and interstitial matrix. These microstructural constituents can directly affect local distributions of stresses and strains, and, hence, crack initiation and propagation. Therefore, understanding the effect of micromorphology of cortical bone on crack initiation and propagation, especially under dynamic loading regimes is of great importance for fracture risk evaluation. In this study, random microstructures of a cortical bone tissue were modelled with finite elements for four groups: healthy (control), young age, osteoporosis and bisphosphonate-treated, based on osteonal morphometric parameters measured from microscopic images for these groups. The developed models were loaded under the same dynamic loading conditions, representing a direct impact incident, resulting in progressive crack propagation. An extended finite-element method (X-FEM) was implemented to realize solution-dependent crack propagation within the microstructured cortical bone tissues. The obtained simulation results demonstrate significant differences due to micromorphology of cortical bone, in terms of crack propagation characteristics for different groups, with the young group showing highest fracture resistance and the senior group the lowest.
Effect of micromorphology of cortical bone tissue on crack propagation under dynamic loading
Directory of Open Access Journals (Sweden)
Wang Mayao
2015-01-01
Full Text Available Structural integrity of bone tissue plays an important role in daily activities of humans. However, traumatic incidents such as sports injuries, collisions and falls can cause bone fracture, servere pain and mobility loss. In addition, ageing and degenerative bone diseases such as osteoporosis can increase the risk of fracture [1]. As a composite-like material, a cortical bone tissue is capable of tolerating moderate fracture/cracks without complete failure. The key to this is its heterogeneously distributed microstructural constituents providing both intrinsic and extrinsic toughening mechanisms. At micro-scale level, cortical bone can be considered as a four-phase composite material consisting of osteons, Haversian canals, cement lines and interstitial matrix. These microstructural constituents can directly affect local distributions of stresses and strains, and, hence, crack initiation and propagation. Therefore, understanding the effect of micromorphology of cortical bone on crack initiation and propagation, especially under dynamic loading regimes is of great importance for fracture risk evaluation. In this study, random microstructures of a cortical bone tissue were modelled with finite elements for four groups: healthy (control, young age, osteoporosis and bisphosphonate-treated, based on osteonal morphometric parameters measured from microscopic images for these groups. The developed models were loaded under the same dynamic loading conditions, representing a direct impact incident, resulting in progressive crack propagation. An extended finite-element method (X-FEM was implemented to realize solution-dependent crack propagation within the microstructured cortical bone tissues. The obtained simulation results demonstrate significant differences due to micromorphology of cortical bone, in terms of crack propagation characteristics for different groups, with the young group showing highest fracture resistance and the senior group the
Simulation analysis of effects of single fragment size on air-blast wave and fragment propagation
Directory of Open Access Journals (Sweden)
ZHENG Hongwei
2017-12-01
Full Text Available [Objectives] This paper involves the propagation and attenuation of the velocity and energy of air-blast waves and high-velocity fragments while taking their combined effects into account.[Methods] With ANSYS/LS-DYNA software, a simulation model of a columnar TNT air blast is built with prefabricated fragments affixed to its end. When the total quality of fragments is constant, the effects of a single fragment's size on the propagation of the air-blast wave and fragments are studied by changing the size of the single fragment.[Results] The results show that fragments greatly reduce the intensity and velocity of a shockwave, and block the air-blast waves behind them. When the total quality of the fragments remains constant, the effects of single fragment size on blast shockwave propagation characteristics show little difference. The smaller the single fragment, the more kinetic energy the fragments will have and the faster that energy will dissipate.[Conclusions] As a result, more attention should be paid to the combined effects of air-blast waves and high-velocity fragments. Such research can provide reference points for the deeper study of blast loads and their interaction.
The effect of endodontic procedures on apical crack initiation and propagation ex vivo.
Adorno, C G; Yoshioka, T; Jindan, P; Kobayashi, C; Suda, H
2013-08-01
To evaluate the potential effects of endodontic procedures (instrumentation and filling) on crack initiation and propagation in apical dentine. Forty extracted single-rooted premolars with two canals were selected, 1.5 mm of the apex was ground perpendicular to the long axis of the tooth and the surface polished. The specimens were divided into 4 groups. The buccal canals of groups A, B and C were enlarged to size 40 with manual K-files. Group A was filled with gutta-percha using lateral condensation and vertical compaction without sealer. Group B was filled with the same method as group A except only lateral condensation was used. Group C was left unfilled, while group D was left unprepared and unfilled. Images of the resected surface were taken after resection (baseline), after canal preparation, after filling and after 4-week storage. The images were then inspected for cracks originating from the canal. A significant effect of preparation on crack initiation (P 0.05) or 4-week storage on crack initiation (P > 0.05) was found (logistic regression). Fisher's exact test revealed a significant effect of filling on crack propagation (P 0.05). Root canal procedures can potentially initiate and propagate cracks from within the root canal in the apical region. © 2013 International Endodontic Journal. Published by John Wiley & Sons Ltd.
DEFF Research Database (Denmark)
Kifle, Dereje W.; Gimenez, Lucas Chavarria; Wegmann, Bernhard
2014-01-01
, such kind of automated and flexible network operation require a Self Organizing Network algorithm based on network performance parameters being partly derived from the radio measurements. Appropriate radio propagation models are not only needed for network planning tools but also for simulative lab tests...... of the developed Self Organizing Network algorithm controlling the flexible deployment changes enabled by Active Antenna Systems. In this paper, an extension of the existing 3D propagation model is proposed in order to incorporate the the propagation condition variation effects, not considered so far, by changing...... antenna beam orientation like antenna tilting or when users are distributed in the third dimension (height) in multi-floor scenarios. Ray tracing based generated propagation maps that show the realistic propagation effect are used as 3D real world reference for investigation and model approval....
Effects of magnetized plasma on the propagation properties of obliquely incident THz waves
Directory of Open Access Journals (Sweden)
Yunxian Tian
2017-12-01
Full Text Available In this paper, the propagation of obliquely incident terahertz (THz wave in a non-uniform magnetized plasma slab is investigated. The electron density and the collision frequency across the plasma are assumed to have a Gaussian profile. To deal with the non-uniform profile, the plasma slab is divided into a series of subslabs. For more accuracy, twice reflection between the interfaces of each subslab is considered, and the corresponding transmitted and reflected power are derived. Effects of collision frequency, magnetic field amplitude and incident angle on THz wave propagation characteristics are investigated. Specifically, the refraction angles in each subslab are presented. These simulation results are meaningful for the hypersonic flight communication.
Noise propagation effects in power supply distribution systems for high-energy physics experiments
Arteche, F.; Rivetta, C.; Iglesias, M.; Echeverria, I.; Pradas, A.; Arcega, F. J.
2017-12-01
High-energy physics experiments are supplied by thousands of power supply units placed in distant areas from the front-end electronics. The power supply units and the front-end electronics are connected through long power cables that propagate the output noise from the power supplies to the detector. This paper addresses the effect of long cables on the noise propagation and the impact that those cables have on the conducted emission levels required for the power supplies and the selection of EMI filters for the front-end electronic low-voltage input. This analysis is part of the electromagnetic compatibility based design focused on functional safety to define the type of cable, shield connections, EMI filters and power supply specifications required to ensure the successful integration of the detector and, specifically, to achieve the designed performance of the front-end electronics.
Effect of defect length on rolling contact fatigue crack propagation in high strength steel
Directory of Open Access Journals (Sweden)
T. Makino
2015-10-01
Full Text Available The objective of the present paper is to clarify the effect of defect length in depth direction on rolling contact fatigue (RCF crack propagation in high strength steel. RCF test and synchrotron radiation micro computed tomography (SR micro CT imaging were conducted. In the case of the defect with the 15 m diameter, flaking life decreased with increasing defect length. In a comparison of the CT image and the SEM view, the shapes of defects and the locations of the horizontal cracks were almost the same respectively. The mechanism of RCF crack propagation was discussed by finite element (FE analysis. Defects led to higher tensile residual stress than that without defects in the region where the defect exists. The shear stress range at 0.1 mm in depth on the middle line of the defect and the range of mode II stress intensity factor at the bottom of a vertical crack increased with increasing defect length.
Effect of fracture compliance on wave propagation within a fluid-filled fracture.
Nakagawa, Seiji; Korneev, Valeri A
2014-06-01
Open and partially closed fractures can trap seismic waves. Waves propagating primarily within fluid in a fracture are sometimes called Krauklis waves, which are strongly dispersive at low frequencies. The behavior of Krauklis waves has previously been examined for an open, fluid-filled channel (fracture), but the impact of finite fracture compliance resulting from contacting asperities and porous fillings in the fracture (e.g., debris, proppants) has not been fully investigated. In this paper, a dispersion equation is derived for Krauklis wave propagation in a fracture with finite fracture compliance, using a modified linear-slip-interface model (seismic displacement-discontinuity model). The resulting equation is formally identical to the dispersion equation for the symmetric fracture interface wave, another type of guided wave along a fracture. The low-frequency solutions of the newly derived dispersion equations are in good agreement with the exact solutions available for an open fracture. The primary effect of finite fracture compliance on Krauklis wave propagation is to increase wave velocity and attenuation at low frequencies. These effects can be used to monitor changes in the mechanical properties of a fracture.
Modelling and mitigating refractive propagation effects in precision pulsar timing observations
Shannon, R. M.; Cordes, J. M.
2017-01-01
To obtain the most accurate pulse arrival times from radio pulsars, it is necessary to correct or mitigate the effects of the propagation of radio waves through the warm and ionized interstellar medium. We examine both the strength of propagation effects associated with large-scale electron-density variations and the methodology used to estimate infinite frequency arrival times. Using simulations of two-dimensional phase-varying screens, we assess the strength and non-stationarity of timing perturbations associated with large-scale density variations. We identify additional contributions to arrival times that are stochastic in both radio frequency and time and therefore not amenable to correction solely using times of arrival. We attribute this to the frequency dependence of the trajectories of the propagating radio waves. We find that this limits the efficacy of low-frequency (metre-wavelength) observations. Incorporating low-frequency pulsar observations into precision timing campaigns is increasingly problematic for pulsars with larger dispersion measures.
Energy Technology Data Exchange (ETDEWEB)
Francois, Elizabeth Green [Los Alamos National Laboratory; Morris, John S [Los Alamos National Laboratory; Novak, Alan M [Los Alamos National Laboratory; Kennedy, James E [HERE LLC
2010-01-01
Recent dynamic testing of Diaminoazoxyfurazan (DAAF) has focused on understanding the material properties affecting the detonation propagation, spreading, behavior and symmetry. Small scale gap testing and wedge testing focus on the sensitivity to shock with the gap test including the effects of particle size and density. Floret testing investigates the detonation spreading as it is affected by particle size, density, and binder content. The polyrho testing illustrates the effects of density and binder content on the detonation velocity. Finally the detonation spreading effect can be most dramatically seen in the Mushroom and Onionskin tests where the variations due to density gradients, pressing methods and geometry can be seen on the wave breakout behavior.
Li, Zhenglin; Zhang, Renhe; Li, Fenghua
2010-09-01
Ocean reverberation in shallow water is often the predominant background interference in active sonar applications. It is still an open problem in underwater acoustics. In recent years, an oscillation phenomenon of the reverberation intensity, due to the interference of the normal modes, has been observed in many experiments. A coherent reverberation theory has been developed and used to explain this oscillation phenomenon [F. Li et al., Journal of Sound and Vibration, 252(3), 457-468, 2002]. However, the published coherent reverberation theory is for the range independent environment. Following the derivations by F. Li and Ellis [D. D. Ellis, J. Acoust. Soc. Am., 97(5), 2804-2814, 1995], a general reverberation model based on the adiabatic normal mode theory in a range dependent shallow water environment is presented. From this theory the coherent or incoherent reverberation field caused by sediment inhomogeneity and surface roughness can be predicted. Observations of reverberation from the 2001 Asian Sea International Acoustic Experiment (ASIAEX) in the East China Sea are used to test the model. Model/data comparison shows that the coherent reverberation model can predict the experimental oscillation phenomenon of reverberation intensity and the vertical correlation of reverberation very well.
Evidence of Long Range Dependence and Self-similarity in Urban Traffic Systems
Energy Technology Data Exchange (ETDEWEB)
Thakur, Gautam S [ORNL; Helmy, Ahmed [University of Florida, Gainesville; Hui, Pan [Hong Kong University of Science & Technology
2015-01-01
Transportation simulation technologies should accurately model traffic demand, distribution, and assignment parame- ters for urban environment simulation. These three param- eters significantly impact transportation engineering bench- mark process, are also critical in realizing realistic traffic modeling situations. In this paper, we model and charac- terize traffic density distribution of thousands of locations around the world. The traffic densities are generated from millions of images collected over several years and processed using computer vision techniques. The resulting traffic den- sity distribution time series are then analyzed. It is found using the goodness-of-fit test that the traffic density dis- tributions follows heavy-tail models such as Log-gamma, Log-logistic, and Weibull in over 90% of analyzed locations. Moreover, a heavy-tail gives rise to long-range dependence and self-similarity, which we studied by estimating the Hurst exponent (H). Our analysis based on seven different Hurst estimators strongly indicate that the traffic distribution pat- terns are stochastically self-similar (0.5 H 1.0). We believe this is an important finding that will influence the design and development of the next generation traffic simu- lation techniques and also aid in accurately modeling traffic engineering of urban systems. In addition, it shall provide a much needed input for the development of smart cities.
Maupin, Valerie; Näsholm, Sven Peter; Schweitzer, Johannes; Gibbons, Steven J.
2016-04-01
We recently advocated using the reflectivity method, also known as the wavenumber integration method or fast-field program, to model atmospheric infrasound propagation at regional distances. The advantage of the reflectivity method is its ability to model the full wavefield, including diffractive effects with head waves and shadow zone arrivals, in a broad frequency range but still at a relatively low computational cost. Attenuation can easily be included, giving the possibility to analyse relative amplitudes and frequency content of the different arrivals. It has clear advantages compared with ray theory in terms of predicting phases considering the particular frequent occurrence of shadow zone arrivals in infrasound observations. Its main limitation, at least in the traditional form of the method, lies in the fact that it can only handle range-independent models. We presented earlier some reflectivity method simulations of an observed accidental explosion in Norway. Wind intensity and direction are non-negligible parameters for infrasound propagation and these are appropriately taken into account in most infrasound ray-tracing codes. On the other hand, in the previous reflectivity simulations wind was taken into account only through the effective sound speed approximation where the horizontal projection of the wind field is added to the adiabatic sound speed profiles. This approximation is appropriate for dominantly horizontal propagation but can give incorrect arrival times and shadow zone locations for waves which have a significant portion of their propagation path at more vertical incidence, like thermospheric arrivals. We present here how we have modified the original reflectivity algorithm in order to take the wind into account in a more correct fashion, and how this improvement influences the synthetics.
Wave energy converter effects on wave propagation: A sensitivity study in Monterey Bay, CA
Chang, G.; Jones, C. A.; Roberts, J.; Magalen, J.; Ruehl, K.; Chartrand, C.
2014-12-01
The development of renewable offshore energy in the United States is growing rapidly and wave energy is one of the largest resources currently being evaluated. The deployment of wave energy converter (WEC) arrays required to harness this resource could feasibly number in the hundreds of individual devices. The WEC arrays have the potential to alter nearshore wave propagation and circulation patterns and ecosystem processes. As the industry progresses from pilot- to commercial-scale it is important to understand and quantify the effects of WECs on the natural nearshore processes that support a local, healthy ecosystem. To help accelerate the realization of commercial-scale wave power, predictive modeling tools have been developed and utilized to evaluate the likelihood of environmental impact. At present, direct measurements of the effects of different types of WEC arrays on nearshore wave propagation are not available; therefore wave model simulations provide the groundwork for investigations of the sensitivity of model results to prescribed WEC characteristics over a range of anticipated wave conditions. The present study incorporates a modified version of an industry standard wave modeling tool, SWAN (Simulating WAves Nearshore), to simulate wave propagation through a hypothetical WEC array deployment site on the California coast. The modified SWAN, referred to as SNL-SWAN, incorporates device-specific WEC power take-off characteristics to more accurately evaluate a WEC device's effects on wave propagation. The primary objectives were to investigate the effects of a range of WEC devices and device and array characteristics (e.g., device spacing, number of WECs in an array) on nearshore wave propagation using SNL-SWAN model simulations. Results showed that significant wave height was most sensitive to variations in WEC device type and size and the number of WEC devices in an array. Locations in the lee centerline of the arrays in each modeled scenario showed the
Water content and its effect on ultrasound propagation in concrete--the possibility of NDE
Ohdaira; Masuzawa
2000-03-01
It is known that water content or moisture affects the strength of concrete. The purpose of this study is to examine the possibility of the NDE of concrete from a knowledge of the relationship between water content and ultrasonic propagation in concrete. The results of measurements made on the ultrasound velocity and the frequency component on ultrasonic propagation as a function of the water content in concrete are reported. Test pieces of concrete made from common materials were made for the fundamental studies. The test piece dimensions were 10 cm in diameter and 20 cm in length. Test pieces were immersed in water for about 50 days to saturate them. To measure the effect of different water contents, test pieces were put in a drying chamber to change the amount of water between measurements. This procedure was repeated until the concrete was completely dried and the weight no longer changed. Water contents were defined as weight percentage to full dried state. Thus water content could be changed from 8% to 0%. Using the pulse transmission method, ultrasonic propagation in the frequency range 20 to 100 kHz was measured as a function of water content. The sound velocity varied gradually from 3000 m/s to 4500 m/s according to the water content. The frequency of maximum transmission also depended on the water content in this frequency range. It is considered that the ultrasonic NDE of concrete strength is feasible.
McClure, Michelle M; Utter, Fred M; Baldwin, Casey; Carmichael, Richard W; Hassemer, Peter F; Howell, Philip J; Spruell, Paul; Cooney, Thomas D; Schaller, Howard A; Petrosky, Charles E
2008-05-01
Most hatchery programs for anadromous salmonids have been initiated to increase the numbers of fish for harvest, to mitigate for habitat losses, or to increase abundance in populations at low abundance. However, the manner in which these programs are implemented can have significant impacts on the evolutionary trajectory and long-term viability of populations. In this paper, we review the potential benefits and risks of hatchery programs relative to the conservation of species listed under the US Endangered Species Act. To illustrate, we present the range of potential effects within a population as well as among populations of Chinook salmon (Oncorhynchus tshawytscha) where changes to major hatchery programs are being considered. We apply evolutionary considerations emerging from these examples to suggest broader principles for hatchery uses that are consistent with conservation goals. We conclude that because of the evolutionary risks posed by artificial propagation programs, they should not be viewed as a substitute for addressing other limiting factors that prevent achieving viability. At the population level, artificial propagation programs that are implemented as a short-term approach to avoid imminent extinction are more likely to achieve long-term population viability than approaches that rely on long-term supplementation. In addition, artificial propagation programs can have out-of-population impacts that should be considered in conservation planning.
Analysis of the Effect of UTI-UTC to High Precision Orbit Propagation
Directory of Open Access Journals (Sweden)
Dongseok Shin
1999-12-01
Full Text Available As the spatial resolution of remote sensing satellites becomes higher, very accurate determination of the position of a LEO (Low Earth Orbit satellite is demanding more than ever. Non-symmetric Earth gravity is the major perturbation force to LEO satellites. Since the orbit propagation is performed in the celestial frame while Earth gravity is defined in the terrestrial frame, it is required to convert the coordinates of the satellite from one to the other accurately. Unless the coordinate conversion between the two frames is performed accurately the orbit propagation calculates incorrect Earth gravitational force at a specific time instant, and hence, causes errors in orbit prediction. The coordinate conversion between the two frames involves precession, nutation, Earth rotation and polar motion. Among these factors, unpredictability and uncertainty of Earth rotation, called UTI-UTC, is the largest error source. In this paper, the effect of UTI-UTC on the accuracy of the LEO propagation is introduced, tested and analzed. Considering the maximum unpredictability of UTI-UTC, 0.9 seconds, the meaningful order of non-spherical Earth harmonic functions is derived.
Ionospheric effects of X-ray source Scorpius XR-1. [on terrestrial radio propagation
Poppoff, I. G.; Whitten, R. C.; Willoughby, D. S.
1975-01-01
A simple two-ion model was employed to evaluate the ionospheric effects of various nocturnal ionization sources. The model was used to calculate the decay of the electron number density at 90 km with and without illumination by Scorpius XR-1 X rays. Reflection parameters for the determination of the effect of cosmic x-ray sources on radio wave propagation were also obtained. The results obtained in the investigation do not support the proposal made by Anathakrishnan and Ramanathan (1969) that the X-ray source in Scorpius XR-1 affects the nighttime lower ionosphere of the earth.
Quantum effects on propagation of bulk and surface waves in a thin quantum plasma film
Energy Technology Data Exchange (ETDEWEB)
Moradi, Afshin, E-mail: a.moradi@kut.ac.ir [Department of Engineering Physics, Kermanshah University of Technology, Kermanshah (Iran, Islamic Republic of); Department of Nano Sciences, Institute for Studies in Theoretical Physics and Mathematics (IPM), Tehran (Iran, Islamic Republic of)
2015-06-19
The propagation of bulk and surface plasma waves in a thin quantum plasma film is investigated, taking into account the quantum effects. The generalized bulk and surface plasma dispersion relation due to quantum effects is derived, using the quantum hydrodynamic dielectric function and applying appropriate additional boundary conditions. The quantum mechanical and film geometric effects on the bulk and surface modes are discussed. It is found that quantum effects become important for a thin film of small thickness. - Highlights: • New bulk and surface plasma dispersion relations due to quantum effects are derived, in a thin quantum plasma film. • It is found that quantum effects become important for a thin quantum film of small thickness.
2012-12-01
STRUCTURE OF THERMOHALINE STAIRCASES IN THE TROPICAL NORTH ATLANTIC AND THEIR EFFECT ON ACOUSTIC PROPAGATION by Amy C. Bulters December... THERMOHALINE STAIRCASES IN THE TROPICAL NORTH ATLANTIC AND THEIR EFFECT ON ACOUSTIC PROPAGATION 5. FUNDING NUMBERS 6. AUTHOR(S) Amy C. Bulters 7...overlies cold, fresh fluid). The formation of staircases in the thermohaline structure of the ocean has been observed since the late 1960s, with
Trofimov, Vyacheslav A.; Lysak, Tatyana M.
2016-10-01
We investigate the possibility for superluminality effects at the femtosecond pulse propagation in the medium with nanorods, if second harmonic generation (SGH) and two-photon luminescence (TPL) take place. On basis of semiclassical approach, we derive a set of equations, which describe the atomic states and electric fields dynamics. We show the possibility of light acceleration and soliton formation, if nanorod aspect ratio changing occurs due to their reshaping because two photon absorption (TPA) of optical energy, and investigate TPL and SHG in the medium with nanorods under sequential one-photon absorptions.
Diffraction effects in microwave propagation at the origin of superluminal behaviors
Energy Technology Data Exchange (ETDEWEB)
Ranfagni, A. [Istituto di Fisica Applicata ' Nello Carrara' , Consiglio Nazionale delle Ricerche, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze (Italy); Ricci, A.M. [Istituto per le Telecomunicazioni e l' Elettronica della Marina Militare ' Giancarlo Vallauri' (Mariteleradar), Viale Italia 72, 57100 Livorno (Italy); Ruggeri, R. [Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, Sezione di Firenze, Firenze (Italy)], E-mail: rocco.ruggeri@isc.cnr.it; Agresti, A. [Dipartimento di Fisica dell' Universita di Firenze, Firenze (Italy)
2008-10-27
Superluminal behaviors, as evidenced by the presence of forerunners, in advanced position with respect to the main luminal peak, have been revealed in microwave propagation experiments by using a radar technique. The results are interpreted on the basis of (fast) complex waves, usually considered only in the near-field region, but still surviving beyond this limit. Consideration of further diffraction effects, as due to geometrical limitations of the experimental set-up, allows for the obtainment of a plausible description of the results.
Focused sound from three-dimensional sound propagation effects over a submarine canyon.
Chiu, Linus Y S; Lin, Ying-Tsong; Chen, Chi-Fang; Duda, Timothy F; Calder, Brian
2011-06-01
Ship noise data reveal an intensification of the near-surface sound field over a submarine canyon. Numerical modeling of sound propagation is used to study the effect. The noise data were collected during an ocean acoustic and physical oceanography experiment northeast of Taiwan in 2009. In situ measurements of water sound-speed profiles and a database of high-resolution bathymetry are used in the modeling study. The model results suggest that the intensification is caused by three-dimensional sound focusing by the concave canyon seafloor. Uncertainties in the model results from unsampled aspects of the environment are discussed. © 2011 Acoustical Society of America
Long-Term Change of Sound Wave Propagation Attenuation Due to the Effects of Ocean Acidification
Gotoh, S.; Tsuchiya, T.; Hiyoshi, Y.
2014-12-01
In recent years, the concentration of carbon dioxide in the atmosphere is increasing due to global warming. And, the ocean acidification advances because this melts into seawater, pH decrease in seawater are concerned. The sound wave to propagate seawater, pH is known to affect absorption loss (α) by chemical buffer effects of the seawater. However, conventionally, α has not been investigated much in the calculation of pH. Therefore, when calculating the propagation distance in the sonar equation, pH =8~8.1 (Weak alkaline) are used empirically. Therefore we used an actual value of pH of 30 years from 1984 in the sea near the Japan, and investigated change over the years of absorption loss (α) at some frequency. As a result, we found that α value decreases gradually in the past 30 years, as high-latitude decreases. Further, the future, assuming that ocean acidification is more advanced, and to simulate a change of the absorption loss and propagation loss in end of this century using the pH value reported from the "Intergovernmental Panel on Climate Change" (IPCC). As a result, it was just suggested that α decreased more in the end of this century and affected the submarine detection. In addition, in recent years, we examined the effects of noise that offshore wind power construction proceeds in each country emits gives to the underwater sound. As a result, in the end of this century, an underwater noise increases about 17%, and underwater sound environmental degradation of the sea is concerned.
Retardation effects on the dispersion and propagation of plasmons in metallic nanoparticle chains
Downing, Charles A.; Mariani, Eros; Weick, Guillaume
2018-01-01
We consider a chain of regularly-spaced spherical metallic nanoparticles, where each particle supports three degenerate localized surface plasmons. Due to the dipolar interaction between the nanoparticles, the localized plasmons couple to form extended collective modes. Using an open quantum system approach in which the collective plasmons are interacting with vacuum electromagnetic modes and which, importantly, readily incorporates retardation via the light-matter coupling, we analytically evaluate the resulting radiative frequency shifts of the plasmonic bandstructure. For subwavelength-sized nanoparticles, our analytical treatment provides an excellent quantitative agreement with the results stemming from laborious numerical calculations based on fully-retarded solutions to Maxwell’s equations. Indeed, the explicit expressions for the plasmonic spectrum which we provide showcase how including retardation gives rise to a logarithmic singularity in the bandstructure of transverse-polarized plasmons. We further study the impact of retardation effects on the propagation of plasmonic excitations along the chain. While for the longitudinal modes, retardation has a negligible effect, we find that the retarded dipolar interaction can significantly modify the plasmon propagation in the case of transverse-polarized modes. Moreover, our results elucidate the analogy between radiative effects in nanoplasmonic systems and the cooperative Lamb shift in atomic physics.
Low-power 24.1-GHz propagation effects on roadways
Geisheimer, Jonathan L.; Greneker, Eugene F., III; Simas de Oliveria, Marcelo G.
2001-08-01
This paper discusses the experimental design and analysis of low power 24.1 GHz propagation effects on roadways around the Atlanta, Georgia metropolitan area. The transmitter used was a 24.1 GHz Safety Warning System (SWS) transmitter operating in the continuous wave (CW) mode. The Federal Communications Commission (FCC) has licensed the Safety Warning System for Part 90 operation. A Part 90-compliant transmitter was used during the tests. The receiver was a modified Bel 855Sti radar detector that was calibrated in an anechoic chamber. The receiver was placed in a Ford F-150 truck and driven toward the transmitter. Three distinct propagation environments are characterized including a rural road, state route, and interstate highway. Shadowing effects from terrain features such as hills are examined as well as the effects of other vehicles, including large tractor-trailers. Signal strength is analyzed as a function of distance to the transmitter and using probability distribution function (pdf) modeling. It was found that the Weibull distribution provided the best statistical description for both the line of sight and shadowing cases. In many instances, the statistics of the received signal would change rapidly depending on the terrain features and interaction with surrounding traffic. The results provide insight into how the unlicensed 24.1 GHz band in the United States might be used for low power, intelligent transportation system (ITS) applications.
DEFF Research Database (Denmark)
Si, Haiqing; Shen, Wen Zhong; Zhu, Wei Jun
2013-01-01
Acoustic propagation in the presence of a non-uniform mean flow is studied numerically by using two different acoustic propagating models, which solve linearized Euler equations (LEE) and acoustic perturbation equations (APE). As noise induced by turbulent flows often propagates from near field t...
Energy Technology Data Exchange (ETDEWEB)
Lee, Myoung-Jae [Department of Physics, Hanyang University, Seoul 04763 (Korea, Republic of); Research Institute for Natural Sciences, Hanyang University, Seoul 04763 (Korea, Republic of); Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr [Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 15588 (Korea, Republic of); Department of Electrical and Computer Engineering, MC 0407, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0407 (United States)
2017-02-12
High frequency electrostatic wave propagation in a dense and semi-bounded electron quantum plasma is investigated with consideration of the Bohm potential. The dispersion relation for the surface mode of quantum plasma is derived and numerically analyzed. We found that the quantum effect enhances the frequency of the wave especially in the high wave number regime. However, the frequency of surface wave is found to be always lower than that of the bulk wave for the same quantum wave number. The group velocity of the surface wave for various quantum wave number is also obtained. - Highlights: • High frequency electrostatic wave propagation is investigated in a dense semi-bounded quantum plasma. • The dispersion relation for the surface mode of quantum plasma is derived and numerically analyzed. • The quantum effect enhances the frequency of the wave especially in the high wave number regime. • The frequency of surface wave is found to be always lower than that of the bulk wave. • The group velocity of the surface wave for various quantum wave number is also obtained.
Worldline Path-Integral Representations for Standard Model Propagators and Effective Actions
Directory of Open Access Journals (Sweden)
Somdatta Bhattacharya
2017-01-01
Full Text Available We develop the formalism to do worldline calculations relevant for the Standard Model. For that, we first figure out the worldline representations for the free propagators of massless chiral fermions of a single generation and gauge bosons of the Standard Model. Then we extend the formalism to the massive and dressed cases for the fermions and compute the QED vertex. We then go over fermionic one-loop effective actions and anomalies. To our knowledge, in the places where there has been an attempt at deriving the gauge boson propagator, the derivation is somewhat contrived, and we believe our derivation is more straightforward. Moreover, our incorporation of internal degrees of freedom is novel and sports some new features. The derivation of the QED vertex is also new. The treatment of the fermionic one-loop effective actions leads to a particularly economical derivation of chiral anomalies and the gauge anomaly freedom in the Standard Model, improving upon the state of the art in the literature. The appropriate worldline formalism developed thus sets the stage for Standard Model calculations beyond the tree and one-loop cases that incorporate Bern-Kosower type formulae for multiloop amplitudes, relevant for processes at the LHC.
Effect of strong elastic contrasts on the propagation of seismic wave in hard-rock environments
Saleh, R.; Zheng, L.; Liu, Q.; Milkereit, B.
2013-12-01
Understanding the propagation of seismic waves in a presence of strong elastic contrasts, such as topography, tunnels and ore-bodies is still a challenge. Safety in mining is a major concern and seismic monitoring is the main tool here. For engineering purposes, amplitudes (peak particle velocity/acceleration) and travel times of seismic events (mostly blasts or microseismic events) are critical parameters that have to be determined at various locations in a mine. These parameters are useful in preparing risk maps or to better understand the process of spatial and temporal stress distributions in a mine. Simple constant velocity models used for monitoring studies in mining, cannot explain the observed complexities in scattered seismic waves. In hard-rock environments modeling of elastic seismic wavefield require detailed 3D petrophysical, infrastructure and topographical data to simulate the propagation of seismic wave with a frequencies up to few kilohertz. With the development of efficient numerical techniques, and parallel computation facilities, a solution for such a problem is achievable. In this study, the effects of strong elastic contrasts such as ore-bodies, rough topography and tunnels will be illustrated using 3D modeling method. The main tools here are finite difference code (SOFI3D)[1] that has been benchmarked for engineering studies, and spectral element code (SPECFEM) [2], which was, developed for global seismology problems. The modeling results show locally enhanced peak particle velocity due to presence of strong elastic contrast and topography in models. [1] Bohlen, T. Parallel 3-D viscoelastic finite difference seismic modeling. Computers & Geosciences 28 (2002) 887-899 [2] Komatitsch, D., and J. Tromp, Introduction to the spectral-element method for 3-D seismic wave propagation, Geophys. J. Int., 139, 806-822, 1999.
Physics based model of D-region variability related to VLF propagation effects
Chakravarty, S. C.
2012-07-01
D-region (~60-85 km) electron density profiles measured using large number of sounding rocket experiments carried out from two Indian low latitude stations show large variations with solar zenith angle, season and solar activity. Similarly the ground based multi frequency radio wave absorption technique has provided continuous data on the morphology of the hourly electron density variations. However suitable models of the D-region electron density profile variations both during quiet and disturbed solar conditions over the Indian region are lacking. The renewed interest in the study of the VLF/LF propagation anomalies taking place through perturbations in the D-region electron densities due to various geophysical phenomena requires the availability of a baseline D-region model over low latitudes. The purpose of this paper is to critically review the physical processes of D-region production and loss of free electrons, dynamical coupling due to variety of vertically propagating atmospheric waves, sudden changes brought about by the solar energetic events like CMEs and different categories of X-ray flares. Low latitude region is not likely to be affected by the PMSE or PCA type of events but the changes due to lightning induced mesospheric red sprites and LEPs need to be considered. Based on this analysis, a preliminary low latitude D-region electron density profile model development is proposed. Sample results would illustrate key requirements from such a model in terms of its effectiveness to simulate the low latitude observations of VLF/LF amplitude and phase variations using waveguide propagation models like LWPC.
Yudin, M. S.
2017-11-01
In this paper the effects of an inversion layer in a stratified atmosphere on the surface wind speed and pressure are investigated with models based on the compressible Navier-Stokes equations in two dimensions. Artificial compressibility is introduced into the models in order to make the governing equations hyperbolic. For comparison with available simulation data, the physical processes under study are assumed to be adiabatic. Plain orography is considered in surface pressure simulations with a finite-difference version of the model, while surface wind speed effects are estimated in artificial cold front propagation over a hill with a finite-element version of the model. The front surface is described in both models by an equation for advection of a scalar substance, which is solved with a third-order semi-Lagrangian procedure. The results of simulations show various meteorological effects in agreement with observations and in accordance with a theory proposed by Charba [3].
Effects of wind shear and temperature inversion on sound propagation from wind turbines.
Energy Technology Data Exchange (ETDEWEB)
Haan, Henk de [Golder Associates (Canada)], email: Henk_deHaan@golder.com
2011-07-01
Noise impact assessment of wind turbines usually takes into account sound speed and propagation at ground level, and those are influenced by wind shear and atmospheric temperature changes. This paper focuses on a week-long monitoring study and presents the observed and anticipated effects of wind shear and temperature on the level of ground sound emitted from a 65m high wind turbine. Working with anemometers at ground level and turbine height, it is shown that wind shear can influence sound propagation, and that atmospheric stability must be taken into account for accurate wind speed calculations to be made. Temperature must also be addressed and the heating of the earth by solar radiation and the re-radiation of that heat in a day-night cycle, resulting in temperature inversion in the atmosphere, must be taken into account. Observations of temperature changes over a week can then yield sound speed and sound power levels with respect to altitude, and show that sound power levels are higher at ground levels during the night.
A Laboratory Study of the Effects of Interbeds on Hydraulic Fracture Propagation in Shale Formation
Directory of Open Access Journals (Sweden)
Zhiheng Zhao
2016-07-01
Full Text Available To investigate how the characteristics of interbeds affect hydraulic fracture propagation in the continental shale formation, a series of 300 mm × 300 mm × 300 mm concrete blocks with varying interbeds, based on outcrop observation and core measurement of Chang 7-2 shale formation, were prepared to conduct the hydraulic fracturing experiments. The results reveal that the breakdown pressure increases with the rise of thickness and strength of interbeds under the same in-situ field stress and injection rate. In addition, for the model blocks with thick and high strength interbeds, the hydraulic fracture has difficulty crossing the interbeds and is prone to divert along the bedding faces, and the fracturing effectiveness is not good. However, for the model blocks with thin and low strength interbeds, more long branches are generated along the main fracture, which is beneficial to the formation of the fracture network. What is more, combining the macroscopic descriptions with microscopic observations, the blocks with thinner and lower strength interbeds tend to generate more micro-fractures, and the width of the fractures is relatively larger on the main fracture planes. Based on the experiments, it is indicated that the propagation of hydraulic fractures is strongly influenced by the characteristics of interbeds, and the results are instructive to the understanding and evaluation of the fracability in the continental shale formation.
Directory of Open Access Journals (Sweden)
Javier Giovanni Álvarez Herrera
2010-01-01
Full Text Available Rosemary seedlings are obtained by vegetative propagation because the seeds present low viability. Despite being an expanding crop, there is little information on water consumption during the propagation stage. Water levels and irrigation frequencies were therefore applied using a completely randomised design having a 4 x 2 factorial arrangement. The first factor concerned irrigation frequency (4 and 8 days and the second concerned water level (0.6, 0.8, 1.0 and 1.2 evaporation inside the greenhouse. A 1.0 coefficient combined with 4-day irrigation frequency presented the best results regarding height (39.3 cm, fresh weight, dry weight and branch length (146 cm. Water level affected the fresh and dry weight of leaves regardless of frequency. Relative water content in leaves did not present differences due to environmental conditions minimising treatment effect. Rooting percent- tage showed no significant differences regarding irrigation frequency or water level. Irrigation frequency did not affect rosemary growing pattern because sphagnum retains high moisture content. The best branch number (34 was obtained with 1.0 coefficient and 4-day frequency, this being important from the production point of view because this is the material which is sold. Water management changes photoassimilate distribution in rosemary plants.
Effect of diamond nucleation process on propagation losses of AlN/diamond SAW filter.
Elmazria, Omar; El Hakiki, Mohamed; Mortet, Vincent; Assouar, Badreddine M; Nesládek, Milos; Vanecek, Milan; Bergonzo, Philippe; Alnot, Patrick
2004-12-01
In this work, the effect of a diamond nucleation process on freestanding aluminium nitride (AlN)/diamond surface acoustic wave (SAW) device performances was studied. Before diamond deposition, silicon (Si) substrates have been mechanically nucleated, using an ultrasonic vibration table with submicron diamond slurry, and bias-enhanced nucleated (BEN). Freestanding diamond layers obtained on mechanically scratched Si substrates exhibit a surface roughness of R(MS) = 13 nm, whereas very low surface roughness (as low as R(MS) < or = 1 nm) can be achieved on a freestanding BEN diamond layer. Propagation losses have been measured as a function of the operating frequency for the two nucleation techniques. Dispersion curves of phase velocities and electromechanical coupling coefficient (K2) were determined experimentally and by calculation as a function of normalized thickness AlN film (kh(AlN) = 2pi h(AlN)/lambda). Experimental results show that the propagation losses strongly depend on the nucleation technique, and that these losses are weakly increased with frequency when the BEN technique is used.
Directory of Open Access Journals (Sweden)
Javier Giovanni Álvarez Herrera
2010-05-01
Full Text Available Rosemary seedlings are obtained by vegetative propagation because the seeds present low viability. Despite being an expanding crop, there is little information on water consumption during the propagation stage. Water levels and irrigation frequencies were therefore applied using a completely randomised design having a 4 x 2 factorial arrangement. The first factor concerned irrigation frequency (4 and 8 days and the second concerned water level (0.6, 0.8, 1.0 and 1.2 evaporation inside the greenhouse. A 1.0 coefficient combined with 4-day irrigation frequency presented the best results regarding height (39.3 cm, fresh weight, dry weight and branch length (146 cm. Water level affected the fresh and dry weight of leaves regardless of frequency. Relative water content in leaves did not present differences due to environmental conditions minimising treatment effect. Rooting percent- tage showed no significant differences regarding irrigation frequency or water level. Irrigation frequency did not affect rosemary growing pattern because sphagnum retains high moisture content. The best branch number (34 was obtained with 1.0 coefficient and 4-day frequency, this being important from the production point of view because this is the material which is sold. Water management changes photoassimilate distribution in rosemary plants.
Chesnais, Céline; Boutin, Claude; Hans, Stéphane
2012-10-01
This work is devoted to the study of the wave propagation in infinite two-dimensional structures made up of the periodic repetition of frames. Such materials are highly anisotropic and, because of lack of bracing, can present a large contrast between the shear and compression deformabilities. Moreover, when the thickness to length ratio of the frame elements is small, these elements can resonate in bending at low frequencies when compressional waves propagate in the structure. The frame size being small compared to the wavelength of the compressional waves, the homogenization method of periodic discrete media is extended to situations with local resonance, and it is applied to identify the macroscopic behavior at the leading order. In particular, the local resonance in bending leads to an effective mass different from the real mass and to the generalization of the Newtonian mechanics at the macroscopic scale. Consequently, compressional waves become dispersive and frequency bandgaps occur. The physical origin of these phenomena at the microscopic scale is also presented. Finally, a method is proposed for the design of such materials.
Effect of mass transfer on concentration wave propagation during anaerobic digestion of solid waste.
Vavilin, Vasily A; Shchelkanov, Micael Yu; Rytov, Sergey V
2002-05-01
A distributed model of anaerobic digestion of solid waste was developed to study effects of mass transfer on the rate of propagation of initiation methanogenic area. The diffusion and advection of volatile fatty acids (VFA) and methanogenic biomass were taken into account in the model of a one-dimensional (ID) reactor. It was considered that VFA inhibits both polymer hydrolysis and acetoclastic methanogenesis. This approach allows to view the bioreactor as an active medium that provokes concentration waves from some area of methanogenic initiation (local VFA depression) to the total reactor volume. The model shows that mass transfer-based acceleration of methane production in the reactor is possible when the intensity of VFA utilization in the methanogenic area is sufficient for a complete digestion of the incoming VFA. Otherwise, initiation methanogenic area will be suppressed by increasing concentration of VFA. The obtained results emphasize the importance of considering spatial heterogeneity of the reaction for the analysis of solid anaerobic digestion in bioreactors and landfills. The digestion of solid waste can be optimized by setting the low rate of mass transfer (mixing or leachate recirculation) during lag-phase of the reaction with subsequent increase in the mass transfer rate in parallel with the propagation of methanogenic population. In this case, the rate of concentration waves substantially increases.
Influence of nanorod absorption spectrum width on superluminality effect for laser pulse propagation
Trofimov, Vyacheslav A.; Lysak, Tatiana M.
2016-03-01
We investigate the influence of the finite absorption spectrum width on the soliton formation and superluminality phenomenon at a femtosecond pulse propagation in a medium with noble nanoparticles. These effects take place if a positive phase-amplitude grating is induced by laser radiation. We take into account the two-photon absorption (TPA) of laser radiation by nanorods, and time-dependent nanorod aspect ratio changing due to their melting or reshaping because of laser energy absorption, and the nanorod absorption spectrum width. On the basis of computer simulation we demonstrate these effects in a medium with positive phase-amplitude grating, induced by laser radiation, if a weak laser energy absorption takes place on the laser pulse dispersion length.
Ma, Q.; Artemyev, A. V.; Mourenas, D.; Li, W.; Thorne, R. M.; Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.; Reeves, G. D.; Spence, H. E.; Wygant, J.
2017-12-01
Satellite observations of a significant population of very oblique chorus waves in the outer radiation belt have fueled considerable interest in the effects of these waves on energetic electron scattering and acceleration. However, corresponding diffusion rates are extremely sensitive to the refractive index N, controlled by hot plasma effects including Landau damping and wave dispersion modifications by suprathermal (15-100 eV) electrons. A combined investigation of wave and electron distribution characteristics obtained from the Van Allen Probes shows that peculiarities of the measured electron distribution significantly reduce Landau damping, allowing wave propagation with high N ˜ 100-200. Further comparing measured refractive indexes with theoretical estimates incorporating hot plasma corrections to the wave dispersion, we provide the first experimental demonstration that suprathermal electrons indeed control the upper limit of the refractive index of highly oblique whistler mode waves. Such results further support the importance of incorporating very oblique waves into radiation belt models.
Moisio, J E; Piili, J; Linna, R P
2016-08-01
We investigate the driven polymer translocation through a nanometer-scale pore in the presence and absence of hydrodynamics both in good and bad solvent. We present our results on tension propagating along the polymer segment on the cis side that is measured for the first time using our method that works also in the presence of hydrodynamics. For simulations we use stochastic rotation dynamics, also called multiparticle collision dynamics. We find that in the good solvent the tension propagates very similarly whether hydrodynamics is included or not. Only the tensed segment is by a constant factor shorter in the presence of hydrodynamics. The shorter tensed segment and the hydrodynamic interactions contribute to a smaller friction for the translocating polymer when hydrodynamics is included, which shows as smaller waiting times and a smaller exponent in the scaling of the translocation time with the polymer length. In the bad solvent hydrodynamics has a minimal effect on polymer translocation, in contrast to the good solvent, where it speeds up translocation. We find that under bad-solvent conditions tension does not spread appreciably along the polymer. Consequently, translocation time does not scale with the polymer length. By measuring the effective friction in a setup where a polymer in free solvent is pulled by a constant force at the end, we find that hydrodynamics does speed up collective polymer motion in the bad solvent even more effectively than in the good solvent. However, hydrodynamics has a negligible effect on the motion of individual monomers within the highly correlated globular conformation on the cis side and hence on the entire driven translocation under bad-solvent conditions.
Self-Assembling Sup-porosity: The Effect On Fluid Flow And Seismic Wave Propagation
Energy Technology Data Exchange (ETDEWEB)
Pyrak-Nolte, Laura J. [Purdue University
2013-04-27
Fractures and joints in the field often contain debris within the void spaces. Debris originates from many different mechanisms: organic and/or inorganic chemical reactions/mineralization, sediment transport, formation of a fracture, mechanical weathering or combinations of these processes. In many cases, the presence of debris forms a sub-porosity within the fracture void space. This sub-porosity often is composed of material that differs from the fracture walls in mineralogy and morphology. The sub-porosity may partially fill voids that are on the order of hundreds of microns and thereby reduce the local porosity to lengths scales on the order of sub-microns to tens of microns. It is quite clear that a sub-porosity affects fracture porosity, permeability and storativity. What is not known is how the existence/formation of a sub-porosity affects seismic wave propagation and consequently our ability to probe changes in the subsurface caused by the formation or alteration of a sub-porosity. If seismic techniques are to be developed to monitor the injection and containment of phases in sequestration reservoirs or the propping of hydraulically induced fracture to enhance oil & gas production, it is important to understand how a sub-porosity within a fracture affects macroscopic seismic and hydraulic measurements. A sub-porosity will directly affect the interrelationship between the seismic and hydraulic properties of a fracture. This reports contains the results of the three main topics of research that were performed (1) to determine the effect of a sub-porosity composed of spherical grains on seismic wave propagation across fractures, (2) to determine the effect of biofilm growth in pores and between grains on seismic wave propagation in sediment, and (3) to determine the effect of the scale of observation (field-of-view) on monitoring alteration the pore space within a fracture caused by reactive flow. A brief summary of the results for each topic is contained in
Directory of Open Access Journals (Sweden)
Soltekin Oguzhan
2017-01-01
Full Text Available Agrobacterium vitis is responsible for the crown gall disease of grapevine which breaks the grapevine trunk vascular system. Nutrient flow is prevented by crown gall and it leads to weak growth and death of the plants. It can be destructive disease often encountered in vineyards and it can be spread in cuttings for propagation. Thermotherapy treatment is an alternative method for eradicating A. vitis from grapevine cuttings but effects of thermotherapy treatments on dormant vine tissue, bud vitality, rooting and shooting of the propagation materials are not yet fully understood. In this research, it is aimed to determine the effects of thermotherapy treatment (Hot water treatment on callus formation (at the basal part and grafting point, grafted vine quality (shoot length, shoot width, root number, shooting and rooting development, fresh and dry weight of shoots and roots and final take in the grafted vine production. Experiment was conducted in the nursery of Manisa Viticultural Research Institute. Rootstocks (Kober 5BB, Couderc 1613 and 41B and scions (Sultan 7 and Manisa sultanı were hot-water treated at 50°C for 30 minutes which is the most common technique against Agrobacterium vitis. After thermotherapy treatment, all rootstocks were grafted with Sultan 7 and Manisa sultanıvarieties. They were kept for 22 days in callusing room for callus development and then they were planted in polyethlyene bags for rooting. At the end of the study, significant treatment x rootstock interaction were observed for the final take of Sultan 7 variety. Thermotherapy treated of 1613C/Sultan 7 combinations had more final take than the control (untreated group. For instance, hot water treated cuttings of 1613C/Sultan 7 combinations had 75% final take while the control group had the 70%. Also there were not observed any adverse effects of HWT on bud and tissue vitality.
Nonlinearity, Breaks, and Long-Range Dependence in Time-Series Models
DEFF Research Database (Denmark)
Hillebrand, Eric Tobias; Medeiros, Marcelo C.
We study the simultaneous occurrence of long memory and nonlinear effects, such as parameter changes and threshold effects, in ARMA time series models and apply our modeling framework to daily realized volatility. Asymptotic theory for parameter estimation is developed and two model building proc...... procedures are proposed. The methodology is applied to stocks of the Dow Jones Industrial Average during the period 2000 to 2009. We find strong evidence of nonlinear effects....
Effect of 3D boundary conditions on rift propagation or failure to break.
Le Pourhiet, Laetitia; Watremez, Louise; Delescluse, Matthias
2017-04-01
Oblique rift segments are generally modelled using two type of set-ups. The first one consist of off-set weak notches which are pulled in a cylindrical manner, the second one consist at pulling obliquely on wide weak zone inside which a system of en-echellon grabben can develop. These two set up produce diverging segments of constant age and younger oblique segments which localise after some delays which depends on the offset of the diverging segments and the rheology of the lithosphere. In this study, we propose a different set-up which consist at seeding only one diverging weak segments and at letting the continental rupture propagate through the model in order to assess 1/ how 3D boundary conditions affect the speed on propagation of the continental break-up and 2/ how the structure that form at the front of the propagating break-up affect the propagation it-self. We find that a cylindrical boundary condition or extension in the direction of propagation favour very rapid continental break-up propagation, narrow rift zones and extremely linear diverging segments. On the contrary, when a slight compression is applied in the direction of rift propagation. The propagation is slow and might even stop completely. This slow down in propagation results in an increase of pre-breakup structuration of the margins and can even cause segmentation of final spreading. The numerical models are finally compared to natural examples from the Atlantic and the South China Sea.
Directory of Open Access Journals (Sweden)
Kumar Rajneesh
2012-01-01
Full Text Available The aim of the present paper is to study the wave propagation in anisotropic viscoelastic medium in the context of the theory threephase- lag model of thermoelasticity. It is found that there exist two quasi-longitudinal waves (qP1, qP2 and two transverse waves (qS1, qS2. The governing equations for homogeneous transversely isotropic thermoviscoelastic are reduced as a special case from the considered model. Different characteristics of waves like phase velocity, attenuation coefficient, specific loss and penetration depth are computed from the obtained results. Viscous effect is shown graphically on different resulting quantities for two-phase-lag model and three-phase-lag model of thermoelasticity. Some particular cases of interest are also deduced from the present investigation.
Effects of laser beam propagation and saturation on the spatial shape of sodium laser guide stars.
Marc, Fabien; Guillet de Chatellus, Hugues; Pique, Jean-Paul
2009-03-30
The possibility to produce diffraction-limited images by large telescopes through Adaptive Optics is closely linked to the precision of measurement of the position of the guide star on the wavefront sensor. In the case of laser guide stars, many parameters can lead to a strong distortion on the shape of the LGS spot. Here we study the influence of both the saturation of the sodium layer excited by different types of lasers, the spatial quality of the laser mode at the ground and the influence of the atmospheric turbulence on the upward propagation of the laser beam. Both shape and intensity of the LGS spot are found to depend strongly on these three effects with important consequences on the precision on the wavefront analysis.
Wave propagation in structured materials as a platform for effective parameters retrieving
DEFF Research Database (Denmark)
Andryieuski, Andrei; Ha, S.; Sukhorukov, A. A.
utilization of the Bloch-mode analysis5. The idea is to perform the Bloch mode expansion6 of the field inside the metamaterial slab when it is illuminated with a plane wave incident from vacuum. Then we determine the effective refractive index from the propagation constant of the dominating (fundamental......) Bloch mode. The Bloch and wave impedances are determined by definition as the proportionality coefficient between electric and magnetic fields of the fundamental Bloch mode volume or surface averaged over the unit cell1. The ratio of the surface averaged fields provides the value of the Bloch impedance...... and, respectively, enables the retrieval of wave EPs. The volume averaging provides the wave impedance, which is needed for the retrieval of the materials parameters. The main advantage of our method is its simple numerical realization. The first part of the method involves the extraction...
An alternative view on the role of the β-effect in the Rossby wave propagation mechanism
Directory of Open Access Journals (Sweden)
Eyal Heifetz
2014-11-01
Full Text Available The role of the β-effect in the Rossby wave propagation mechanism is examined in the linearised shallow water equations directly in momentum–height variables, without recourse to potential vorticity (PV. Rigorous asymptotic expansion of the equations, with respect to the small non-dimensionalised β parameter, reveals in detail how the Coriolis force acting on the small ageostrophic terms translates the geostrophic leading-order solution to propagate westward in concert. This information cannot be obtained directly from the conventional PV perspective on the propagation mechanism. Furthermore, a comparison between the β-effect in planetary Rossby waves and the sloping-bottom effect in promoting topographic Rossby waves shows that the ageostrophic terms play different roles in the two cases. This is despite the fact that from the PV viewpoint whether the advection of mean PV gradient is set up by changes in planetary vorticity or by mean depth is inconsequential.
Control of propagation characteristics of spin wave pulses via elastic and thermal effects
Energy Technology Data Exchange (ETDEWEB)
Gómez-Arista, Ivan [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, CU, 04510 D.F., México (Mexico); Kolokoltsev, O., E-mail: oleg.kolokoltsev@ccadet.unam.mx [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, CU, 04510 D.F., México (Mexico); Acevedo, A.; Qureshi, N. [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, CU, 04510 D.F., México (Mexico); Ordóñez-Romero, César L. [Instituto de Física, Universidad Nacional Autónoma de México, CU, 04510 D.F., México (Mexico)
2017-05-01
A study of the magnetoelastic (ME) and thermal effects governing the phase (φ) and amplitude of magnetostatic surface spin wave (MSSW) pulses propagating in Ga:YIG/GGG and permalloy magnonic waveguides is presented. The ME effects were studied in a flexural configuration, under punctual mechanical force (F). Thermally induced ME and demagnetization phenomena were controlled by optically injected thermal power P{sub th}. It was determined that in an unclamped Ga:YIG waveguide, the force F that induces the phase shift Δφ=π, decreases by a quadratic law in the range from 1 mN to nN, and the P{sub th} at which Δφ=π decreases linearly from mW to μW as the waveguide volume decreases from mm{sup 3} to nm{sup 3}. For nano-volume waveguides the ME control energy (E{sub me}) can be of order of aJ, and the thermal control energy (ΔE{sub th}) can be as small as 50 fJ. The response time of these effects lies in the ns time scale. Both the mechanical and the thermo-magnetic forces provide an effective control of MSSW pulse amplitude, in addition to its phase shift. The thermo-magnetic effect allows one to realize variable delays of a MSSW pulse. - Highlights: • The Magneto-elastic (ME) and optically induced thermal effects governing the phase and amplitude of magnetostatic surface spin wave (MSSW) pulses propagating in Ga:YIG/GGG and permalloy magnonic waveguides are presented. • A mechanical force that causes phase shift Δφ=π for spin waves in the waveguides decreases by a quadratic law in the range from 1 mN to nN, and the optical power that induces the phase shift Δφ=π, decreases linearly from mW to μW as the waveguide volume decreases from mm{sup 3} to nm{sup 3}. • The response time of these effects can lie in the ns time scale.
Light propagation in optical crystal powders: effects of particle size and volume filling factor
Energy Technology Data Exchange (ETDEWEB)
GarcIa-Ramiro, B [Departamento de Fisica Aplicada I, Escuela Tecnica Superior de IngenierIa, Universidad del PaIs Vasco, Alameda Urquijo s/n, 48013 Bilbao (Spain); Illarramendi, M A [Departamento de Fisica Aplicada I, Escuela Tecnica Superior de IngenierIa, Universidad del PaIs Vasco, Alameda Urquijo s/n, 48013 Bilbao (Spain); Aramburu, I [Departamento de Fisica Aplicada I, Escuela Tecnica Superior de IngenierIa, Universidad del PaIs Vasco, Alameda Urquijo s/n, 48013 Bilbao (Spain); Fernandez, J [Departamento de Fisica Aplicada I, Escuela Tecnica Superior de IngenierIa, Universidad del PaIs Vasco, Alameda Urquijo s/n, 48013 Bilbao (Spain); Balda, R [Departamento de Fisica Aplicada I, Escuela Tecnica Superior de IngenierIa, Universidad del PaIs Vasco, Alameda Urquijo s/n, 48013 Bilbao (Spain); Al-Saleh, M [Departamento de Fisica Aplicada I, Escuela Tecnica Superior de IngenierIa, Universidad del PaIs Vasco, Alameda Urquijo s/n, 48013 Bilbao (Spain)
2007-11-14
In this work, we analyse the light propagation in some laser and nonlinear crystal powders. In particular, we study the dependence of the diffusive absorption lengths and the transport lengths on particle size and volume filling factor. The theoretical calculations have been made by assuming a diffusive propagation of light in these materials.
Effect of relative humidity on crack propagation in barrier films for flexible electronics
Vellinga, W. P.; De Hosson, J. Th M.; Bouten, P. C. P.
2012-01-01
A set of propagating cracks in a SiN barrier film on poly ethylene naphthalate (PEN) were subjected to differing levels of relative humidity. It was observed that the propagation speed of the cracks increased for increasing levels of relative humidity. This was shown using two independent,
Early Season Softwood Cuttings Effective for Vegetative Propagation of Juglans cinerea
Paula M. Pijut; Melanie Moore
2002-01-01
Juglans cinerea L. (butternut) is a hardwood species valued for its wood and edible nuts. Information on the vegetative propagation of this species is currently unavailable. Our objective was to determine the conditions necessary for successful stem-cutting propagation of butternut. In 1999 and 2000, 10 trees (each year) were randomly selected from a...
Effect of inter- and intra-annual thermohaline variability on acoustic propagation
Chu, Peter C.; McDonald, Colleen M.; Kucukosmanoglu, Murat; Judono, Albert; Margolina, Tetyana; Fan, Chenwu
2017-05-01
This paper is to answer the question "How can inter- and intra-annual variability in the ocean be leveraged by the submarine Force?" through quantifying inter- and intra-annual variability in (T, S) fields and in turn underwater acoustic characteristics such as transmission loss, signal excess, and range of detection. The Navy's Generalized Digital Environmental Model (GDEM) is the climatological monthly mean data and represents mean annual variability. An optimal spectral decomposition method is used to produce a synoptic monthly gridded (SMG) (T, S) dataset for the world oceans with 1° ×1° horizontal resolution, 28 vertical levels (surface to 3,000 m depth), monthly time increment from January 1945 to December 2014 now available at the NOAA/NCEI website: http://data.nodc.noaa.gov/cgibin/iso?id=gov.noaa.nodc:0140938. The sound velocity decreases from 1945 to 1975 and increases afterwards due to global climate change. Effect of the inter- and intra-annual (T, S) variability on acoustic propagation in the Yellow Sea is investigated using a well-developed acoustic model (Bellhop) in frequencies from 3.5 kHz to 5 kHz with sound velocity profile (SVP) calculated from GDEM and SMG datasets, various bottom types (silty clay, fine sand, gravelly mud, sandy mud, and cobble or gravel) from the NAVOCEANO`s High Frequency Environmental Algorithms (HFEVA), source and receiver depths. Acoustic propagation ranges are extended drastically due to the inter-annual variability in comparison with the climatological SVP (from GDEM). Submarines' vulnerability of detection as its depth varies and avoidance of short acoustic range due to inter-annual variability are also discussed.
The Effect on the Propagation of Blast Pulses of Dry and Dampened Granular Media
Proud, William; Badham, Henry; Chalmers, Max; Nguyen, Thuy-Tien
2015-06-01
The propagation of stress through granular and dampened granular material has been reported in previous papers. With increasing presence of liquid in granular beds the transmission of blast and pressure pulse changes from one of percolation through the bed pores to one of wave transmission through the granules of the bed. It has been shown that limited amounts liquid can retard pressurisation within confined blast-loaded beds by approximately an order of magnitude. This study presents data on percolation through dry and dampened granular beds using a shock tube as the pressure driver. In this scenario the effect of the bed on initial pressure pulse is studied in greater detail. The effect of particle shape and size was investigated using angular grains of quartz sand as well as smooth glass microspheres. The effect of addition of liquids is presented. The pressure range studied is in the range associated with blast injury and with far field effects produced by explosive devices. The Institute of Shock Physics acknowledges the support of AWE, Aldermaston, UK and Imperial College London. The Centre for Blast Injury Studies acknowledges the support of the Royal British Legion and Imperial College London.
The effect of thickness on fatigue crack propagation in 7475-T731 aluminum alloy sheet
Daiuto, R. A.; Hillberry, B. M.
1984-01-01
Tests were conducted on three thicknesses of 7475-T731 aluminum alloy sheet to investigate the effect of thickness on fatigue crack propagation under constant amplitude loading conditions and on retardation following a single peak overload. Constant amplitude loading tests were performed at stress ratios of 0.05 and 0.75 to obtain data for conditions with crack closure and without crack closure, respectively. At both stress ratios a thickness effect was clearly evident, with thicker specimens exhibiting higher growth rates in the transition from plane strain to plane stress region. The effect of thickness for a stress ratio of 0.05 corresponded well with the fracturing mode transitions observed on the specimens. A model based on the strain energy release rate which accounted for the fracture mode transition was found to correlate the thickness effects well. The specimens tested at the stress ratio of 0.75 did not make the transition from tensile mode to shear mode, indicating that another mechanism besides crack closure or fracture mode transition was active.
Fiorino, Steven T.; Bartell, Richard J.; Krizo, Matthew J.; Caylor, Gregory L.; Moore, Kenneth P.; Harris, Thomas R.; Cusumano, Salvatore J.
2008-02-01
The Air Force Institute of Technology Center for Directed Energy (AFIT/CDE) has developed a first principles atmospheric propagation and characterization model called the Laser Environmental Effects Definition and Reference or LEEDR. This package enables the creation of profiles of temperature, pressure, water vapor content, optical turbulence, and atmospheric particulates and hydrometeors as they relate to line-by-line layer extinction coefficient magnitude at wavelengths from the UV to the RF. Worldwide seasonal, diurnal, and geographical variability in these parameters is accessed from probability density function (PDF) databases using a variety of recently available resources to include the Extreme and Percentile Environmental Reference Tables (ExPERT), the Master Database for Optical Turbulence Research in Support of the Airborne Laser, and the Global Aerosol Data Set (GADS). GADS provides aerosol constituent number densities on a 5° x 5° grid worldwide. ExPERT mapping software allows the LEEDR operator to choose from specific site or regional upper air data to characterize correlated molecular absorption, aerosol absorption and scattering by percentile. The integration of the Surface Marine Gridded Climatology database, the Advanced Navy Aerosol Model (ANAM), and the Navy Surface Layer Optical Turbulence (NSLOT) model provides worldwide coverage over all ocean regions on a 1° x 1° grid. Molecular scattering is computed based on Rayleigh theory. Molecular absorption effects are computed for the top 13 absorbing species using line strength information from the HITRAN 2004 database in conjunction with a community standard molecular absorption continuum code. Aerosol scattering and absorption are computed with the Wiscombe Mie model. Each atmospheric particulate/hydrometeor is evaluated based on its wavelength-dependent forward and off-axis scattering characteristics and absorption effects on laser energy delivered at any wavelength from 0.355 μm to 8.6 m
Zhang, Shunzu; Gao, Yuanwen
2017-11-01
A theoretical model is established to study the size-dependent performance of flexural wave propagation in magneto-elastic phononic crystal (PC) nanobeam with surface effect based on Euler-Bernoulli beam theory and Gurtin-Murdoch theory. Considering the magneto-mechanical coupling constitutive relation of magnetostrictive material, the influence of surface effect on band structure is calculated by the plane wave expansion method for PC nanobeam subjected to pre-stress and magnetic field loadings. Through the example of an epoxy/Terfenol-D PC nanobeam, it can be observed that the characteristics of flexural wave band structures are size-dependent, and remarkably affected by surface effect when the dimension of the PC beam reduces to the nanoscale. The edges and width of the band gap with surface effect are higher than those without surface effect, especially for high frequency region. And surface effect gradually reduces with the increasing of bulk layer-to-surface layer thickness ratio until the band gap descends to a constant for the conventional one in the absence of surface effect. The effects of surface elasticity and piezomagneticity on band gap are more prominent than the residual surface stress. In addition, a distinctly nonlinear variation of band gap appears under the combined effects of pre-stress and magnetic field. Moreover, with the varying of filling fraction, multi-peaks of the width of the band gap are obtained and discussed. These results could be helpful for the intelligent regulation of magneto-elastic PC nanobeam and the design of nanobeam-based devices.
Effects of tear size and location on predictions of supraspinatus tear propagation.
Miller, R Matthew; Thunes, James; Musahl, Volker; Maiti, Spandan; Debski, Richard E
2018-02-08
Rotator cuff tears remain a significant clinical problem with a high incidence rate and severe clinical burden. Previous computational models developed to study rotator cuff tears have not modeled tissue damage and tear propagation. The objective of this study was to predict tear propagation for various combinations of tear size and location using an experimentally validated finite element model of supraspinatus tendon. It was hypothesized that larger rotator cuff tears propagate at lower loads than smaller tears, and that posterior tears require higher loads to propagate than anterior tears. Using a previously validated computational model of supraspinatus tendon, tears of size 0.5-1.5 cm were introduced to the tendon geometry in the anterior, middle, and posterior tendon thirds. Cohesive elements were assigned subject-specific failure properties and used to model tissue damage and tear propagation. A displacement of 5 mm was applied to the medial tendon edge to induce tear propagation. Model outputs included critical load required to propagate the tear, and principal stress and maximum principal strain at the anterior and posterior tear tips. For all tear sizes, posterior tears required the highest loads to propagate (247-567 N). Anterior tears generally required the least load to propagate (171-280 N). Stress and strain were larger on the articular side (maximum 33.9% articular strain vs 27.8% bursal strain). Overall, larger tears located in the anterior supraspinatus tendon that interrupt the rotator cable are most at risk for tear propagation, and should be carefully followed by clinicians when considering treatment options. Copyright © 2017 Elsevier Ltd. All rights reserved.
Spread spectrum propagation prediction
Luebbers, Raymond
1989-02-01
In order to efficiently model effects of terrain on wideband radio signals, several basic improvements to the Geometrical Theory of Diffraction (GTD) propagation model were made. As a result of this effort a terrain sensitive propagation model capable of predicting the wideband channel transfer function, including the important channel characterization parameters, has been developed and validated against measurements.
Energy Technology Data Exchange (ETDEWEB)
Okazaki, M.; Hattori, I.; Koizwmi, T.; Shiraiwa, F.
1983-08-01
Effect of strain wave shape on strain-controlled low-cycle fatigue crack propagation of SUS 304 stainless steel was investigated at 600 and 700/sup 0/C. It was found that the rate of crack propagation in a cycle-dependent region was successfully correlated with the range of cyclic J-integral, ..delta..J /SUB f/, regardless of the strain wave shape, frequency, and test temperature. It was also shown that the rate of crack propagation gradually increased from cycle-dependent curve to time-dependent one with decreasing frequency and slow-fast strain wave shape, and that one of the factors governing the rate of crack propagation in such a region was the ratio of the range of creep J-integral to that of total J-integral, ..delta..J /SUB c/ /..delta..J /SUB T/. Based on the results thus obtained, an interaction damage rule proposed semi-empirically was interpreted, with regard to crack propagation. Furthermore, fatigue crack initiation mechanism in slow-fast strain wave shape was studied, and it was shown that grain boundary sliding took an important role in it.
Effect of LOS/NLOS Propagation on 5G Ultra-Dense Networks
DEFF Research Database (Denmark)
Galiotto, Carlo; Pratas, Nuno; Doyle, Linda
2017-01-01
The combined presence of Line-of-Sight (LOS) and Non-Line-of-Sight (NLOS) components in the radio propagation environment can severely degrade the Ultra-Dense Networks (UDNs) performance. Backed by a stochastic geometry model, we show that when the LOS/NLOS propagation components are taken...... with the frequency reuse factor N. Finally, we investigate the energy efficiency of UDNs for which we show that, as a combined result of LOS/NLOS propagation and partial load regime, up to two optimal base station densities exist. As a whole, our work provides novel insights on how to overcome the limitations...
Control of Wave Propagation and Effect of Kerr Nonlinearity on Group Index
Hazrat, Ali; Ziauddin; Iftikhar, Ahmed
2013-07-01
We use four-level atomic system and control the wave propagation via forbidden decay rate. The Raman gain process becomes dominant on electromagnetically induced transparency (EIT) medium by increasing the forbidden decay rate via increasing the number of atoms [G.S. Agarwal and T.N. Dey, Phys. Rev. A 74 (2006) 043805 and K. Harada, T. Kanbashi, and M. Mitsunaga, Phys. Rev. A 73 (2006) 013803]. The behavior of wave propagation is dramatically changed from normal (subluminal) to anomalous (superluminal) dispersion by increasing the forbidden decay rate. The system can also give a control over the group velocity of the light propagating through the medium via Kerr field.
Directory of Open Access Journals (Sweden)
Catherine Ky-Dembele
2011-01-01
Full Text Available Khaya senegalensis is a multipurpose African timber species. The development of clonal propagation could improve plantation establishment, which is currently impeded by mahogany shoot borer. To examine its potential for clonal propagation, the effects of cutting length, leaf area, stockplant maturation, auxin, and smoke solution treatments were investigated. Leafy cuttings rooted well (up to 80% compared to leafless cuttings (0%. Cuttings taken from seedlings rooted well (at least 95%, but cuttings obtained from older trees rooted poorly (5% maximum. The rooting ability of cuttings collected from older trees was improved (16% maximum by pollarding. Auxin application enhanced root length and the number of roots while smoke solution did not improve cuttings' rooting ability. These results indicate that juvenile K. senegalensis is amenable to clonal propagation, but further work is required to improve the rooting of cuttings from mature trees.
On the effect of topography on surface wave propagation in the ambient noise frequency range
Köhler, Andreas; Weidle, Christian; Maupin, Valérie
2012-04-01
Due to the increasing popularity of analyzing empirical Green's functions obtained from ambient seismic noise, more and more regional tomographical studies based on short-period surface waves are published. Results could potentially be biased in mountainous regions where topography is not small compared to the wavelength and penetration depth of the considered waves. We investigate the effect of topography on the propagation of short-period Rayleigh waves empirically by means of synthetic data using a spectral element code and a 3-D model with real topography. We show that topography along a profile through the studied area can result in an underestimation of phase velocities of up to about 0.7% at the shortest investigated period (3 s). Contrary to the expectation that this bias results from the increased surface distance along topography, we find that this error can be estimated by local topographic contrasts in the vicinity of the receiver alone. We discuss and generalize our results by considering topographic profiles through other mountain ranges and find that southern Norway is a good proxy to assess the topography effect. Nevertheless, topographic bias on phase velocity measurements is in general not large enough to significantly affect recovered velocity variations in the ambient noise frequency range.
Ground-Wave Propagation Effects on Transmission Lines through Error Images
Directory of Open Access Journals (Sweden)
Uribe-Campos Felipe Alejandro
2014-07-01
Full Text Available Electromagnetic transient calculation of overhead transmission lines is strongly influenced by the natural resistivity of the ground. This varies from 1-10K (Ω·m depending on several media factors and on the physical composition of the ground. The accuracy on the calculation of a system transient response depends in part in the ground return model, which should consider the line geometry, the electrical resistivity and the frequency dependence of the power source. Up to date, there are only a few reports on the specialized literature about analyzing the effects produced by the presence of an imperfectly conducting ground of transmission lines in a transient state. A broad range analysis of three of the most often used ground-return models for calculating electromagnetic transients of overhead transmission lines is performed in this paper. The behavior of modal propagation in ground is analyzed here into effects of first and second order. Finally, a numerical tool based on relative error images is proposed in this paper as an aid for the analyst engineer to estimate the incurred error by using approximate ground-return models when calculating transients of overhead transmission lines.
DEFF Research Database (Denmark)
Guo, Kai; Friis, Søren Michael Mørk; Christensen, Jesper Bjerge
2017-01-01
We derive from Maxwell's equations full-vectorial nonlinear propagation equations of four-wave mixing valid in straight semiconductor-on-insulator waveguides. Special attention is given to the resulting effective mode area, which takes a convenient form known from studies in photonic crystal fibers...
Effects of internal waves on sound propagation in the shallow waters of the continental shelves
Ong, Ming Yi
2016-01-01
Approved for public release; distribution is unlimited Sound waves propagating through the oceans are refracted by internal waves. In the shallow waters of the continental shelves, an additional downward refraction of sound waves due to internal waves can cause them to interact more often with the seabed, resulting in additional energy from the sound waves being dissipated into the seabed. This study investigates how internal waves affect sound propagation on the continental shelves. It fi...
Ground return effect on wave propagation parameters of overhead power cables
Energy Technology Data Exchange (ETDEWEB)
Malo Machado, V.M.; Brandao Faria, J.A.; Borges da Silva, J.F. (Centro de Electrotecnia da Univ. Tecnia de Lisboa, Inst. Superior Tecnico, Dept. of Electrical Engineering, 1096 Lisboa Codex (PT))
1990-04-01
The propagation properties of overhead three-phase cables are usually analyzed assuming that the pipe conductor establishes a perfect shielding between the inner conductor set and any outer conductor, i.e., the power cable is assumed as an isolated system. The influence of a lossy ground plane in the neighborhood of the cable is examined in this paper. The propagation parameters for both approaches are compared---significative differences being found to exist, in the zero mode, at low working frequencies.
Hinoki, A; Saito, A; Kinoshita, M; Yamamoto, J; Saitoh, D; Takeoka, S
2016-05-01
Ultrathin films (nanosheets) adhere tightly to organ surfaces but prevent adhesion to other organs. The antiadhesive effect of nanosheets and their effect on bacterial propagation were investigated in a murine intestinal adhesion model. Polylactic acid nanosheets (approximately 80 nm thick) were produced. Serosal defects were created by peeling off the intestinal serosa; these were left open or covered with nanosheets or Seprafilm® and the formation of intestinal adhesions was analysed. To examine bacterial propagation, a nanosheet or Seprafilm® was placed on intact murine jejunum followed by Escherichia coli inoculation at the site. Treatment both with nanosheets and with Seprafilm® reduced postoperative intestinal adhesion (mean adhesion score 0·67 for nanosheets, 0·43 for Seprafilm® and 2·87 for no antiadhesive treatment; P propagation in the peritoneal cavity, whereas Seprafilm®-treated mice showed bacterial propagation, leading to increased mortality. Nanosheets may be effective novel antiadhesive agents even in the presence of bacterial contamination. Surgical relevance Intra-abdominal adhesions following surgical contamination can trigger postoperative complications and lead to deterioration in long-term quality of life. However, currently there are no effective antiadhesion materials to prevent the formation of adhesions. Treatment with ultrathin nanosheets effectively reduced postoperative intestinal adhesion in an experimental mouse model, and did not affect bacterial propagation in the peritoneal cavity. These nanosheets are potent novel antiadhesive materials that potentially can be applied even in contaminated conditions. © 2016 BJS Society Ltd Published by John Wiley & Sons Ltd.
Shock wave propagation along constant sloped ocean bottoms.
Maestas, Joseph T; Taylor, Larissa F; Collis, Jon M
2014-12-01
The nonlinear progressive wave equation (NPE) is a time-domain model used to calculate long-range shock propagation using a wave-following computational domain. Current models are capable of treating smoothly spatially varying medium properties, and fluid-fluid interfaces that align horizontally with a computational grid that can be handled by enforcing appropriate interface conditions. However, sloping interfaces that do not align with a horizontal grid present a computational challenge as application of interface conditions to vertical contacts is non-trivial. In this work, range-dependent environments, characterized by sloping bathymetry, are treated using a rotated coordinate system approach where the irregular interface is aligned with the coordinate axes. The coordinate rotation does not change the governing equation due to the narrow-angle assumption adopted in its derivation, but care is taken with applying initial, interface, and boundary conditions. Additionally, sound pressure level influences on nonlinear steepening for range-independent and range-dependent domains are used to quantify the pressures for which linear acoustic models suffice. A study is also performed to investigate the effects of thin sediment layers on the propagation of blast waves generated by explosives buried beneath mud line.
AN EFFECTIVE WAY TO CARRY OUT MASS IN VITRO PROPAGATION OF POTENTILLA ALBA L.
Directory of Open Access Journals (Sweden)
L. I. Tikhomirova
2016-04-01
Full Text Available Despite the plant’s extensive area of distribution, Potentilla alba L. natural resources are scarce and cannot meet the modern needs of the pharmaceutical industry. Because of the mass preparation of medical raw materials by using P. alba, it entered into the list of rare and endangered species plants of the Red Data Book of the Republic of Belarus. This plant is not represented in the wild flora of Western Siberia, but there is a great need for developing a method for the mass propagation of P. alba using in vitro culture in order to obtain a high-quality planting material. At the explant stage, the technique of the P. alba introduction into in vitro culture is developed. This paper reveals the morphogenetic features of the development of P. alba explants of different types and the regenerative capacity of the tissue culture. At the micropropagation stage, the optimum culture media and the growth conditions for the regenerated plants are selected. At the stage of test-tube plants rooting and transferring them into ex vitro conditions, the most effective means of adaptation to non-sterile conditions in hydroponics are proposed.
The effect of magnetic field induced aggregates on ultrasound propagation in aqueous magnetic fluid
Parekh, Kinnari; Upadhyay, R. V.
2017-06-01
Ultrasonic wave propagation in the aqueous magnetic fluid is investigated for different particle concentrations. The sound velocity decreases while acoustic impedance increases with increasing concentrations. The velocity anisotropy is observed upon application of magnetic field. The velocity anisotropy fits with Tarapov's theory suggests the presence of aggregates in the system. We report that these aggregates are thermodynamically unstable and the length of aggregate changes continuously with increasing concentration and, or magnetic field and resulted in a decrease in effective magnetic moment. The Taketomi's theory fits well with the experimental data suggesting that the particle clusters are aligned in the direction of the magnetic field. The radius of cluster found to increase with increasing concentration, and then decreases whereas the elastic force constant increases and then becomes constant. The increase in cluster radius indicates elongation of aggregate length due to tip-to-tip interaction of aggregates whereas for higher concentration, the lateral alignment is more favorable than tip-to-tip alignment of aggregates which reduces the cluster radius making elastic force constant to raise. Optical images show that the chains are fluctuating and confirming the lateral alignment of chains at higher fields.
Diez, A.; Eisen, O.; Hofstede, C.; Lambrecht, A.; Mayer, C.; Miller, H.; Steinhage, D.; Binder, T.; Weikusat, I.
2015-02-01
We investigate the propagation of seismic waves in anisotropic ice. Two effects are important: (i) sudden changes in crystal orientation fabric (COF) lead to englacial reflections; (ii) the anisotropic fabric induces an angle dependency on the seismic velocities and, thus, recorded travel times. Velocities calculated from the polycrystal elasticity tensor derived for the anisotropic fabric from measured COF eigenvalues of the EDML ice core, Antarctica, show good agreement with the velocity trend determined from vertical seismic profiling. The agreement of the absolute velocity values, however, depends on the choice of the monocrystal elasticity tensor used for the calculation of the polycrystal properties. We make use of abrupt changes in COF as a common reflection mechanism for seismic and radar data below the firn-ice transition to determine COF-induced reflections in either data set by joint comparison with ice-core data. Our results highlight the possibility to complement regional radar surveys with local, surface-based seismic experiments to separate isochrones in radar data from other mechanisms. This is important for the reconnaissance of future ice-core drill sites, where accurate isochrone (i.e. non-COF) layer integrity allows for synchronization with other cores, as well as studies of ice dynamics considering non-homogeneous ice viscosity from preferred crystal orientations.
Preliminary study on the effect of stiffness on lamb wave propagation in bovine corneas.
Zhang, Xin-Yu; Yin, Yin; Guo, Yan-Rong; Diao, Xian-Fen; Chen, Xin
2013-01-01
The viscoelastic properties of human cornea could provide valuable information for various clinical applications. Particularly, it will be helpful to achieve a patient-specific biomechanical optimization in LASIK refractive surgery, early detection of corneal ecstatic disease or improved accuracy of intraocular pressure (IOP) measurement. However, there are few techniques that are capable of accurately assessing the corneal elasticity in situ in a nondestructive fashion. In order to develop a quantitative method for assessing both elasticity and viscosity of the cornea, we use ultrasound radiation force to excite Lamb waves in cornea, and a pulse echo transducer to track the tissue vibration. The fresh postmortem bovine eyes were treated via collagen cross-linking to make the cornea stiff. The effect of stiffness was studied by comparing the propagation of Lamb waves in normal and treated corneas. It was found that the waveform of generated Lamb waves changed significantly due to the increase in higher modes in treated corneas. This result indicated that the generated waveform was a complex of multiple harmonics and the varied stiffness will affect the energy distribution over different components. Therefore, it is important for assessing the viscoelastic properties of the cornea to know the components of Lamb wave and calculate the phase velocity appropriately.
Directory of Open Access Journals (Sweden)
Justin Ady
2016-01-01
Full Text Available Tunneling nanotubes (TNTs are ultrafine, filamentous actin-based cytoplasmic extensions which form spontaneously to connect cells at short and long-range distances. We have previously described long-range intercellular communication via TNTs connecting mesothelioma cells in vitro and demonstrated TNTs in intact tumors from patients with mesothelioma. Here, we investigate the ability of TNTs to mediate a viral thymidine kinase based bystander effect after oncolytic viral infection and administration of the nucleoside analog ganciclovir. Using confocal microscopy we assessed the ability of TNTs to propagate enhanced green fluorescent protein (eGFP, which is encoded by the herpes simplex virus NV1066, from infected to uninfected recipient cells. Using time-lapse imaging, we observed eGFP expressed in infected cells being transferred via TNTs to noninfected cells; additionally, increasing fluorescent activity in recipient cells indicated cell-to-cell transmission of the eGFP-expressing NV1066 virus had also occurred. TNTs mediated cell death as a form of direct cell-to-cell transfer following viral thymidine kinase mediated activation of ganciclovir, inducing a unique long-range form of the bystander effect through transmission of activated ganciclovir to nonvirus-infected cells. Thus, we provide proof-of-principle demonstration of a previously unknown and alternative mechanism for inducing apoptosis in noninfected recipient cells. The conceptual advance of this work is that TNTs can be harnessed for delivery of oncolytic viruses and of viral thymidine kinase activated drugs to amplify the bystander effect between cancer cells over long distances in stroma-rich tumor microenvironments.
Effect of near-surface topography on high-frequency Rayleigh-wave propagation
Wang, Limin; Xu, Yixian; Xia, Jianghai; Luo, Yinhe
2015-05-01
Rayleigh waves, which are formed due to interference of P- and Sv-waves near the free surface, propagate along the free surface and vanish exponentially in the vertical direction. Their propagation is strongly influenced by surface topography. Due to the high resolution and precision requirements of near-surface investigations, the high-frequency Rayleigh waves are usually used for near-surface structural detecting. Although there are some numerical studies on high-frequency Rayleigh-wave propagation on topographic free surface, detailed analysis of characters of high-frequency Rayleigh-wave propagation on topographic free surface remains untouched. Hence, research of propagation of Rayleigh waves on complex topographic surface becomes critical for Rayleigh-wave methods in near-surface applications. To study the propagation of high-frequency Rayleigh waves on topographic free surface, two main topographic models are designed in this study. One of the models contains a depressed topographic surface, and another contains an uplifted topographic surface. We numerically simulate the propagation of high-frequency Rayleigh waves on these two topographic surfaces by finite-difference method. Soon afterwards, we analyze the propagation character of high-frequency Rayleigh waves on such topographic models, and compare the variations on its energy and frequency before and after passing the topographic region. At last, we discuss the relationship between the variations and topographical steepness of each model. Our numerical results indicate that influence of depressed topography for high-frequency Rayleigh waves is more distinct than influence of uplifted topography. Rayleigh waves produce new scattering body waves during passing the depressed topography with reduction of amplitude and loss of high-frequency components. Moreover, the steeper the depressed topography is, the more energy of Rayleigh waves is lost. The uplifted topography with gentle slope produces similar
Propagation of ULF waves through the ionosphere: Inductive effect for oblique magnetic fields
Directory of Open Access Journals (Sweden)
M. D. Sciffer
2004-04-01
Full Text Available Solutions for ultra-low frequency (ULF wave fields in the frequency range 1–100mHz that interact with the Earth's ionosphere in the presence of oblique background magnetic fields are described. Analytic expressions for the electric and magnetic wave fields in the magnetosphere, ionosphere and atmosphere are derived within the context of an inductive ionosphere. The inductive shielding effect (ISE arises from the generation of an "inductive" rotational current by the induced part of the divergent electric field in the ionosphere which reduces the wave amplitude detected on the ground. The inductive response of the ionosphere is described by Faraday's law and the ISE depends on the horizontal scale size of the ULF disturbance, its frequency and the ionosphere conductivities. The ISE for ULF waves in a vertical background magnetic field is limited in application to high latitudes. In this paper we examine the ISE within the context of oblique background magnetic fields, extending studies of an inductive ionosphere and the associated shielding of ULF waves to lower latitudes. It is found that the dip angle of the background magnetic field has a significant effect on signals detected at the ground. For incident shear Alfvén mode waves and oblique background magnetic fields, the horizontal component of the field-aligned current contributes to the signal detected at the ground. At low latitudes, the ISE is larger at smaller conductivity values compared with high latitudes.
Key words. Ionosphere (ionosphere-magnetosphere interactions; electric fields and currents; wave propagation
The effect of magnetic field induced aggregates on ultrasound propagation in aqueous magnetic fluid
Energy Technology Data Exchange (ETDEWEB)
Parekh, Kinnari, E-mail: kinnariparekh.rnd@charusat.ac.in [Dr. KC Patel R& D Center, Charotar University of Science & Technology, Changa, 388421 Dist. Anand, Gujarat (India); Upadhyay, R.V. [PD Patel Institute of Applied Sciences, Charotar University of Science & Technology, Changa, 388421 Dist. Anand, Gujarat (India)
2017-06-01
Ultrasonic wave propagation in the aqueous magnetic fluid is investigated for different particle concentrations. The sound velocity decreases while acoustic impedance increases with increasing concentrations. The velocity anisotropy is observed upon application of magnetic field. The velocity anisotropy fits with Tarapov’s theory suggests the presence of aggregates in the system. We report that these aggregates are thermodynamically unstable and the length of aggregate changes continuously with increasing concentration and, or magnetic field and resulted in a decrease in effective magnetic moment. The Taketomi's theory fits well with the experimental data suggesting that the particle clusters are aligned in the direction of the magnetic field. The radius of cluster found to increase with increasing concentration, and then decreases whereas the elastic force constant increases and then becomes constant. The increase in cluster radius indicates elongation of aggregate length due to tip-to-tip interaction of aggregates whereas for higher concentration, the lateral alignment is more favorable than tip-to-tip alignment of aggregates which reduces the cluster radius making elastic force constant to raise. Optical images show that the chains are fluctuating and confirming the lateral alignment of chains at higher fields. - Highlights: • Magnetic field induced aggregates investigated using ultrasonic wave in aqueous magnetic fluid. • Velocity anisotropy induces upon applications of magnetic field. • Tarapov’s theory fit shows reduction in effective magnetic moment as concentration increases. • Taketomi's theory shows alignment of clusters in field direction. • Cluster radius increases and then decreases with increasing volume fractions. • Optical images show that fluctuating chains and lateral alignment of chains at higher fields.
Propagation of ULF waves through the ionosphere: Inductive effect for oblique magnetic fields
Directory of Open Access Journals (Sweden)
M. D. Sciffer
2004-04-01
Full Text Available Solutions for ultra-low frequency (ULF wave fields in the frequency range 1–100mHz that interact with the Earth's ionosphere in the presence of oblique background magnetic fields are described. Analytic expressions for the electric and magnetic wave fields in the magnetosphere, ionosphere and atmosphere are derived within the context of an inductive ionosphere. The inductive shielding effect (ISE arises from the generation of an "inductive" rotational current by the induced part of the divergent electric field in the ionosphere which reduces the wave amplitude detected on the ground. The inductive response of the ionosphere is described by Faraday's law and the ISE depends on the horizontal scale size of the ULF disturbance, its frequency and the ionosphere conductivities. The ISE for ULF waves in a vertical background magnetic field is limited in application to high latitudes. In this paper we examine the ISE within the context of oblique background magnetic fields, extending studies of an inductive ionosphere and the associated shielding of ULF waves to lower latitudes. It is found that the dip angle of the background magnetic field has a significant effect on signals detected at the ground. For incident shear Alfvén mode waves and oblique background magnetic fields, the horizontal component of the field-aligned current contributes to the signal detected at the ground. At low latitudes, the ISE is larger at smaller conductivity values compared with high latitudes. Key words. Ionosphere (ionosphere-magnetosphere interactions; electric fields and currents; wave propagation
Directory of Open Access Journals (Sweden)
R. M. Nagare
2012-02-01
Full Text Available There are not many studies that report water movement in freezing peat. Soil column studies under controlled laboratory settings can help isolate and understand the effects of different factors controlling freezing of the active layer in organic covered permafrost terrain. In this study, four peat Mesocosms were subjected to temperature gradients by bringing the Mesocosm tops in contact with sub-zero air temperature while maintaining a continuously frozen layer at the bottom (proxy permafrost. Soil water movement towards the freezing front (from warmer to colder regions was inferred from soil freezing curves, liquid water content time series and from the total water content of frozen core samples collected at the end of freezing cycle. A substantial amount of water, enough to raise the upper surface of frozen saturated soil within 15 cm of the soil surface at the end of freezing period appeared to have moved upwards during freezing. Diffusion under moisture gradients and effects of temperature on soil matric potential, at least in the initial period, appear to drive such movement as seen from analysis of freezing curves. Freezing front (separation front between soil zones containing and free of ice propagation is controlled by latent heat for a long time during freezing. A simple conceptual model describing freezing of an organic active layer initially resembling a variable moisture landscape is proposed based upon the results of this study. The results of this study will help in understanding, and ultimately forecasting, the hydrologic response of wetland-dominated terrain underlain by discontinuous permafrost.
Energy Technology Data Exchange (ETDEWEB)
Wang, Li; Hong, Xue-Ren, E-mail: hxr_nwnu@163.com; Sun, Jian-An, E-mail: sunja@nwnu.edu.cn; Tang, Rong-An; Yang, Yang; Zhou, Wei-Jun; Tian, Jian-Min; Duan, Wen-Shan
2017-07-12
The propagation of q-Gaussian laser beam in a preformed plasma channel is investigated by means of the variational method. A differential equation for the spot size has been obtained by including the effects of relativistic self-focusing, ponderomotive self-channeling and preformed channel focusing. The propagation behaviors and their corresponding physical conditions are identified. The comparison of the propagation between q-Gaussian and Gaussian laser beams is done by theoretical and numerical analysis. It is shown that, in the same channel, the focusing power of q-Gaussian laser beam is lower than that of Gaussian laser beam, i.e., the q-Gaussian laser beam is easier to focus than Gaussian laser beam. - Highlights: • Some behaviors for Gaussian laser are also found for q-Gaussian one. • The parameter regions corresponding to different laser behaviors are given. • Influence of q on the laser propagation behavior is obvious. • The q-Gaussian laser beam is easier to focus than the Gaussian one.
Energy Technology Data Exchange (ETDEWEB)
Kekesi, R., E-mail: renata.kekesi@csic.es; Meneses-Rodríguez, D.; García-Pérez, F.; González, M. U.; García-Martín, A.; Cebollada, A.; Armelles, G., E-mail: gaspar@imm.cnm.csic.es [IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), Isaac Newton 8, PTM, E-28760 Tres Cantos, Madrid (Spain)
2014-10-07
We have analysed the effect that holes have on the properties of propagative surface plasmon modes in semitransparent nanoperforated Au films. The modes have been excited in Kretschmann configuration. Contrary to continuous films, where only one mode is excited, two modes are observed in Au nanohole array. The origin of this different behavior is discussed using effective optical properties for the nanoperforated films. The presence of the holes affects the effective optical constants of the membranes in two ways: it changes the contribution of the free electrons, and it gives rise to a localized transition due to a hole induced plasmon resonance. This localized transition interacts with the propagative surface plasmon modes, originating the two detected modes.
Skull and cerebrospinal fluid effects on microwave radiation propagation in human brain
Ansari, M. A.; Zarei, M.; Akhlaghipour, N.; Niknam, A. R.
2017-12-01
The determination of microwave absorption distribution in the human brain is necessary for the detection of brain tumors using thermo-acoustic imaging and for removing them using hyperthermia treatment. In contrast to ionizing radiation, hyperthermia treatment can be applied to remove tumors inside the brain without the concern of including secondary malignancies, which typically form from the neuronal cells of the septum pellucidum. The aim of this study is to determine the microwave absorption distribution in an adult human brain and to study the effects of skull and cerebrospinal fluid on the propagation of microwave radiation inside the brain. To this end, we simulate the microwave absorption distribution in a realistic adult brain model (Colin 27) using the mesh-based Monte Carlo (MMC) method. This is because in spite of there being other numerical methods, the MMC does not require a large memory, even for complicated geometries, and its algorithm is simple and easy to implement with low computational cost. The brain model is constructed using high-resolution (1 mm isotropic voxel) and low noise magnetic resonance imaging (MRI) scans and its volume contains 181×217×181 voxels, covering the brain completely. Using the MMC method, the radiative transport equation is solved and the absorbed microwave energy distribution in different brain regions is obtained without any fracture or anomaly. The simulation results show that the skull and cerebrospinal fluid guide the microwave radiation and suppress its penetration through deep brain compartments as a shielding factor. These results reveal that the MMC can be used to predict the amount of required energy to increase the temperature inside the tumour during hyperthermia treatment. Our results also show why a deep tumour inside an adult human brain cannot be efficiently treated using hyperthermia treatment. Finally, the accuracy of the presented numerical method is verified using the signal flow graph technique.
Marginal Ice Zone Oceanographic Variability and Its Effects on Acoustic Propagation
1991-01-01
hybrid acoustic model, incorporates elements of both normal modes and geometric ray acoustics. ASTRAL models propagation at 2000 Hz and assumes...the integral solution to the wave equation via a FF1. Time and transform size restrict the use of the SSPE model at frequencies above 300 Hz. ASTRAL , a
Investigation of wave propagation in double cylindrical rods considering the effect of prestress
Li, Chunlei; Han, Qiang; Liu, Yijie; Liu, Xiucheng; Wu, Bin
2015-09-01
This paper presents the investigation of guided wave propagation in prestressed double-cylinder structure. Based on Hertzian contact theory, the interaction between two rods is treated as a plane strain problem and the stress state in the waveguide under the static load is obtained. The stress state is considered as a prestressed configuration for elastic wave propagation analysis in double cylindrical rods. The elastodynamic equation of the prestressed structure is established with the updated Lagrangian formulation and the wave finite element (WFE) method. Firstly, the equation is verified by the application on an aluminum rod compared with the Euler-Bernoulli beam theory. Then, dispersion curves for single rod and double cylindrical rods without prestress are computed. Besides, at the dimensionless frequency 0.25 the propagating modes in double cylindrical rods are identified with mode shapes and displacement vectors. The guided waves in double rods consist of the modes different from single rod. Particularly, there exist two kinds of torsional-like modes, one of which has a twist center and the other has two. The latter changes obviously with the increase of prestress in the waveguide. At low frequencies, torsional-like modes are very sensitive to the variation of prestress; in addition, the prestress configuration has little influence on propagating modes at mid-frequencies but some at high frequencies.
2008-09-01
showing shot locations (circles) and IMS hydrophone station locations ( triangles ), superimposed on a map of group velocities derived using average fall...E. McDonald (1991). Perth- Bermuda sound propagation (1960): Adiabatic mode interpretation, J. Acoust. Soc. Am. 90: 2586–2594. Jensen, F. B., W. A
Kelvin-Helmholtz billows and their effects on mean state during gravity wave propagation
Directory of Open Access Journals (Sweden)
X. Liu
2009-07-01
Full Text Available The Kelvin-Helmholtz (KH billows which appear in the process of gravity wave (GW propagation are simulated directly by using a compressible nonlinear two-dimensional gravity wave model. The differences between our model and others include: the background field has no special initial configuration and there is no initial triggering mechanism needed in the mesosphere and lower thermosphere (MLT region to excite the KH billows. However, the initial triggering mechanism is performed in the lower atmosphere through GW, which then propagate into the MLT region and form billows. The braid structures and overturning of KH billows, caused by nonlinear interactions between GWs and mean flow, can be resolved precisely by the model. These results support the findings in airglow studies that GWs propagating from below into the MLT region are important sources of KH billows. The onset of small scale waves and the wave energy transfer induce the shallower vertical wave number power spectral densities (PSD. However, most of the slopes are steeper than the expected k_{z}^{−3} power law, which indicates that GWs with 10 km vertical wavelength are still a dominant mode. The results also show that the evolution of mean wind vary substantially between the different processes of GWs propagation. Before the KH billows evolve, the mean wind is accelerated greatly by GWs. By contrast, as the KH billows evolve and mix with mean flow, the mean wind and its peak value decrease.
Hubbard, Marjorie Letitia; Ying, Wenjun; Henriquez, Craig S
2007-11-01
To use microstructural computer models to study how four features of myocardial architecture affect propagation: brick wall tissue structures, jutting at cell ends, gap junction distribution and conductance along cell borders, and increased structural discontinuity. Simulations of longitudinal and transverse plane wave propagation and point propagation were performed in several two-dimensional (2D) microstructural models of adult cardiac tissue. Conduction velocities and maximum upstroke velocities were measured for a range of gap junction conductances and distributions. In tissue models with normal to low connectivity, brick wall architecture and jutting decrease cell-to-cell delay, increase longitudinal conduction velocity, and decrease longitudinal maximum upstroke velocity. Transverse conduction velocity also increases if the overlap or jutting introduces additional lateral (side-to-side) connections between myocytes. Both end-to-end and side-to-side interplicate gap junctions increase longitudinal and transverse conduction velocity; however, side-to-side interplicate gap junctions have the greatest influence on transverse conduction velocity and longitudinal and transverse maximum upstroke velocity. The complex structure of myocardium creates additional pathways of current flow that enhance both longitudinal and transverse propagation. These alternative pathways of current help to maintain conduction as connectivity between cells decreases.
Effect of magnetic field on the propagation of quasi-transverse ...
Indian Academy of Sciences (India)
transverse waves in a nonlinear perfectly conducting nonhomogeneous elastic medium in the presence of a uniform magnetic ﬁeld transverse to the direction of wave propagation. Different types of ﬁgures have been drawn to exhibit the distortion of ...
The Effects of Naturally-Occurring Propagation Disturbances on Discrete Focused Arrays
1983-03-01
scintillation, and the total electron content (TEC), as described in detail in Klobuchar [1981]. The 350-km ionospheric penetration points for the satellites...1757 (1982). Klobuchar , J., "Ionospheric Propagation Considerations for the NAVSTAR- Global Positioning System," Technical Memorandum No. 56, Air Force
Effects of MHD slow shocks propagating along magnetic flux tubes in a dipole magnetic field
Directory of Open Access Journals (Sweden)
N. V. Erkaev
2002-01-01
Full Text Available Variations of the plasma pressure in a magnetic flux tube can produce MHD waves evolving into shocks. In the case of a low plasma beta, plasma pressure pulses in the magnetic flux tube generate MHD slow shocks propagating along the tube. For converging magnetic field lines, such as in a dipole magnetic field, the cross section of the magnetic flux tube decreases enormously with increasing magnetic field strength. In such a case, the propagation of MHD waves along magnetic flux tubes is rather different from that in the case of uniform magnetic fields. In this paper, the propagation of MHD slow shocks is studied numerically using the ideal MHD equations in an approximation suitable for a thin magnetic flux tube with a low plasma beta. The results obtained in the numerical study show that the jumps in the plasma parameters at the MHD slow shock increase greatly while the shock is propagating in the narrowing magnetic flux tube. The results are applied to the case of the interaction between Jupiter and its satellite Io, the latter being considered as a source of plasma pressure pulses.
Space weather effects on radio propagation: study of the CEDAR, GEM and ISTP storm events
Directory of Open Access Journals (Sweden)
D. V. Blagoveshchensky
2008-06-01
Full Text Available The impact of 14 geomagnetic storms from a list of CEDAR, GEM and ISTP storms, that occurred during 1997–1999, on radio propagation conditions has been investigated. The propagation conditions were estimated through variations of the MOF and LOF (the maximum and lowest operation frequencies on three high-latitude HF radio paths in north-west Russia. Geophysical data of Dst, Bz, AE as well as some riometer data from Sodankyla observatory, Finland, were used for the analysis. It was shown that the storm impact on the ionosphere and radio propagation for each storm has an individual character. Nevertheless, there are common patterns in variation of the propagation parameters for all storms. Thus, the frequency range Δ=MOF−LOF increases several hours before a storm, then it narrows sharply during the storm, and expands again several hours after the end of the storm. This regular behaviour should be useful for the HF radio propagation predictions and frequency management at high latitudes. On the trans-auroral radio path, the time interval when the signal is lost through a storm (tdes depends on the local time. For the day-time storms an average value tdes is 6 h, but for night storms tdes is only 2 h. The ionization increase in the F2 layer before storm onset is 3.5 h during the day-time and 2.4 h at night. Mechanisms to explain the observed variations are discussed including some novel possibilities involving energy input through the cusp.
Space weather effects on radio propagation: study of the CEDAR, GEM and ISTP storm events
Directory of Open Access Journals (Sweden)
D. V. Blagoveshchensky
2008-06-01
Full Text Available The impact of 14 geomagnetic storms from a list of CEDAR, GEM and ISTP storms, that occurred during 1997–1999, on radio propagation conditions has been investigated. The propagation conditions were estimated through variations of the MOF and LOF (the maximum and lowest operation frequencies on three high-latitude HF radio paths in north-west Russia. Geophysical data of D_{st}, B_{z}, AE as well as some riometer data from Sodankyla observatory, Finland, were used for the analysis. It was shown that the storm impact on the ionosphere and radio propagation for each storm has an individual character. Nevertheless, there are common patterns in variation of the propagation parameters for all storms. Thus, the frequency range Δ=MOF−LOF increases several hours before a storm, then it narrows sharply during the storm, and expands again several hours after the end of the storm. This regular behaviour should be useful for the HF radio propagation predictions and frequency management at high latitudes. On the trans-auroral radio path, the time interval when the signal is lost through a storm (t_{des} depends on the local time. For the day-time storms an average value t_{des} is 6 h, but for night storms t_{des} is only 2 h. The ionization increase in the F2 layer before storm onset is 3.5 h during the day-time and 2.4 h at night. Mechanisms to explain the observed variations are discussed including some novel possibilities involving energy input through the cusp.
1985-01-01
this involves a tensor product of l-D splines [De Boor, 1980]. Velocity discontinuities are included by introducing interfaces between layers with...of amplitude ratios of body waves recorded by instruments with widely separated and, often, narrow frequency bands (e.g., Gutenberg , 1958; Solomon...with discontinuities in the earth. We first discuss the attenuation operator which is the domi- nant propagation effect in the coherent portion of
Directory of Open Access Journals (Sweden)
Rajeev Ghatuary
2015-12-01
Full Text Available Rayleigh wave propagation in an isotropic homogeneous initially stressed thermoelastic half-space under the effect of magnetic field has been studied using Green–Lindsay (GL theory of generalized thermoelasticity. The frequency equation has been obtained for Rayleigh waves. The Rayleigh wave velocity is computed numerically for different values of initial stress parameter, magnetic pressure number, thermoelastic coupling parameter, and wave number for aluminium material, and the results obtained are compared graphically.
Effects of pre-cracks on both initiation and propagation of re-bar corrosion in pure carbon dioxide
L’Hostis Valérie; Hiep Dang Vu; François Raoul
2013-01-01
This paper deals with effects of pre-cracks on both initiation and propagation of reinforcement steel corrosion due to carbonation. The ring shaped mortar samples with 8 mm steel bar inside were cracked with different crack widths ranging from 12 micrometers to 600 micrometers and then subjected to carbon dioxide environment for different terms to assess the carbonation profile in cracks and along the interface between steel and concrete, damaged by the internal pressure applied to the ring s...
Suppressive Effects of the Site 1 Protease (S1P) Inhibitor, PF-429242, on Dengue Virus Propagation.
Uchida, Leo; Urata, Shuzo; Ulanday, Gianne Eduard L; Takamatsu, Yuki; Yasuda, Jiro; Morita, Kouichi; Hayasaka, Daisuke
2016-02-10
Dengue virus (DENV) infection causes one of the most widespread mosquito-borne diseases in the world. Despite the great need, effective vaccines and practical antiviral therapies are still under development. Intracellular lipid levels are regulated by sterol regulatory elements-binding proteins (SREBPs), which are activated by serine protease, site 1 protease (S1P). Small compound PF-429242 is known as a S1P inhibitor and the antivirus effects have been reported in some viruses. In this study, we examined the anti-DENV effects of PF-429242 using all four serotypes of DENV by several primate-derived cell lines. Moreover, emergence of drug-resistant DENV mutants was assessed by sequential passages with the drug. DENV dependency on intracellular lipids during their infection was also evaluated by adding extracellular lipids. The addition of PF-429242 showed suppression of viral propagation in all DENV serotypes. We showed that drug-resistant DENV mutants are unlikely to emerge after five times sequential passages through treatment with PF-429242. Although the levels of intracellular cholesterol and lipid droplets were reduced by PF-429242, viral propagations were not recovered by addition of exogenous cholesterol or fatty acids, indicating that the reduction of LD and cholesterol caused by PF-429242 treatment is not related to its mechanism of action against DENV propagation. Our results suggest that PF-429242 is a promising candidate for an anti-DENV agent.
Suppressive Effects of the Site 1 Protease (S1P Inhibitor, PF-429242, on Dengue Virus Propagation
Directory of Open Access Journals (Sweden)
Leo Uchida
2016-02-01
Full Text Available Dengue virus (DENV infection causes one of the most widespread mosquito-borne diseases in the world. Despite the great need, effective vaccines and practical antiviral therapies are still under development. Intracellular lipid levels are regulated by sterol regulatory elements-binding proteins (SREBPs, which are activated by serine protease, site 1 protease (S1P. Small compound PF-429242 is known as a S1P inhibitor and the antivirus effects have been reported in some viruses. In this study, we examined the anti-DENV effects of PF-429242 using all four serotypes of DENV by several primate-derived cell lines. Moreover, emergence of drug-resistant DENV mutants was assessed by sequential passages with the drug. DENV dependency on intracellular lipids during their infection was also evaluated by adding extracellular lipids. The addition of PF-429242 showed suppression of viral propagation in all DENV serotypes. We showed that drug-resistant DENV mutants are unlikely to emerge after five times sequential passages through treatment with PF-429242. Although the levels of intracellular cholesterol and lipid droplets were reduced by PF-429242, viral propagations were not recovered by addition of exogenous cholesterol or fatty acids, indicating that the reduction of LD and cholesterol caused by PF-429242 treatment is not related to its mechanism of action against DENV propagation. Our results suggest that PF-429242 is a promising candidate for an anti-DENV agent.
Shchesnovich, V S
2008-11-15
A light pulse propagating in a suddenly switched-on photonic lattice, when the central frequency lies in the photonic bandgap, is an analog of the Rabi model, where the two-level system is the two resonant (i.e., Bragg-coupled) Fourier modes of the pulse, while the photonic lattice serves as a monochromatic external field. A simple theory of this Rabi oscillations is given and confirmed by the numerical solution of the corresponding Maxwell equations. This is a direct, i.e., temporal analog of the Rabi effect, additionally to the spatial analog in optical beam propagation described previously [Opt. Lett.32, 1920 (2007)]. An additional high-frequency modulation of the Rabi oscillations reflects the lattice-induced energy transfer between the electric and magnetic fields of the pulse.
Effects of pre-cracks on both initiation and propagation of re-bar corrosion in pure carbon dioxide
Hiep Dang, Vu; François, Raoul; L'Hostis, Valérie
2013-07-01
This paper deals with effects of pre-cracks on both initiation and propagation of reinforcement steel corrosion due to carbonation. The ring shaped mortar samples with 8 mm steel bar inside were cracked with different crack widths ranging from 12 micrometers to 600 micrometers and then subjected to carbon dioxide environment for different terms to assess the carbonation profile in cracks and along the interface between steel and concrete, damaged by the internal pressure applied to the ring samples. After carbonation of interface, ring samples were submitted to wetting-drying cycles to study the propagation of corrosion and the effect of corrosion products on healing and then repassivation of steel bar or corrosion cracks development. Results show that irrespective of width of cracks, the carbon dioxide reaches the interface between steel and mortar and propagates along this interface. The samples then subjected to wetting-drying cycles exhibit corrosion development all along the interface,the appearance of oxides does not lead to create corrosion cracks for the duration of the experiments.
Effects of pre-cracks on both initiation and propagation of re-bar corrosion in pure carbon dioxide
Directory of Open Access Journals (Sweden)
L’Hostis Valérie
2013-07-01
Full Text Available This paper deals with effects of pre-cracks on both initiation and propagation of reinforcement steel corrosion due to carbonation. The ring shaped mortar samples with 8 mm steel bar inside were cracked with different crack widths ranging from 12 micrometers to 600 micrometers and then subjected to carbon dioxide environment for different terms to assess the carbonation profile in cracks and along the interface between steel and concrete, damaged by the internal pressure applied to the ring samples. After carbonation of interface, ring samples were submitted to wetting-drying cycles to study the propagation of corrosion and the effect of corrosion products on healing and then repassivation of steel bar or corrosion cracks development. Results show that irrespective of width of cracks, the carbon dioxide reaches the interface between steel and mortar and propagates along this interface. The samples then subjected to wetting-drying cycles exhibit corrosion development all along the interface,the appearance of oxides does not lead to create corrosion cracks for the duration of the experiments.
Study of the solar flares effect on VLF radio signal propagating along NRK-ALG path using LWPC code
Bouderba, Y.; NaitAmor, S.; Tribeche, M.
2016-07-01
The X-ray solar flare emissions penetrate down into the D region of the ionosphere (60-90 km of altitude) and affect the propagating very low frequency (VLF) radio signal. In this paper, we will present the effect of the solar flares on the signal mode composition of the NRK-ALG path during the period from 2007 to 2013. In the Long Wave Propagating Capability (LWPC) code theory, the VLF signal is a sum of discrete modes that propagate to the receiver with different attenuation coefficients. Therefore, an interest is given to the behavior of these coefficients under solar flares. Effectively, from the simulation, we give more explanations about the role of the signal mode composition on the fading displacement since this later is a consequence of the destructive modes interferences. Thus, the sign (positive or negative) of the perturbed signal parameters (amplitude and phase) is found to be depending on the distance between the transmitter and the receiver. Finally, we give the Wait parameters and the electron density variations as a function of solar flares.
The Effects of Internal Tides on Acoustic Propagation in the Philippine Sea
2013-09-01
seismic field in the seabed and sound propagation in the water column (Worcester 2013). This thesis focuses on the data collected during the 2009...midpoint. Equations 2.17 and 2.18 were used to implement the model in Matlab . (2.17) (2.18) Of note, the model is a data driven model that was...experiment in order to conduct a statistical analysis of the eigenrays. The Matlab findpeaks function was used on the SNR data to isolate receptions
Sulistyani Pancaningtyas
2012-01-01
Various efforts have been developed for the optimization of the various stages in vitro micropropagation. The maturation stage and pre-acclimatization plantlets is an important stages that must be considered to produce vigorous plants and ready to be planted in the field. The purpose of this study was to reduced shoot tip necrosis in cocoa planlets to obtaine vigorous planlets from in vitro propagation through the addition of Calcium Chloride (CaCl2). The study used two stages of embryogenic ...
Effects of ion-atom collisions on the propagation and damping of ion-acoustic waves
DEFF Research Database (Denmark)
Andersen, H.K.; D'Angelo, N.; Jensen, Vagn Orla
1968-01-01
Experiments are described on ion-acoustic wave propagation and damping in alkali plasmas of various degrees of ionization. An increase of the ratio Te/Ti from 1 to approximately 3-4, caused by ion-atom collisions, results in a decrease of the (Landau) damping of the waves. At high gas pressure and....../or low wave frequency a "fluid" picture adequately describes the experimental results....
The effects of sound propagation and avoidance behaviour on naval sonar levels received by cetaceans
Wensveen, Paul J.
2012-01-01
The use of active sonar is deemed to be essential for naval operations, but its potential impact on marine life has raised concerns worldwide. In a risk-assessment framework, characterisation of risk of harm is accomplished by combining exposure assessment and dose−response relationships. The overall topic of this thesis is an evaluation of factors that influence exposure assessment, including analysis of how sound levels received by cetaceans are affected by in-situ sound propagation and the...
1993-11-01
paper. The Effects or Man-made Smokes and Battlefield-Induced Smokes on the Propagation of Electromagnetic Radiation Anthony Van de Wal Chief...of Lasers with Selected Data on Optical Technology, Le bilan de liaison a montrd qu’il est possible de ditecter R.J. Pressley Editor, CRC, USA, 1971
Effect of Density and Resistivity Measurement for Foam Flooding Propagation in Static Condition
Irawan, S.; Permatasari, K. A.; Bayuaji, R.
2017-11-01
Foam flooding is one of the method that is currently used to optimize the amount of oil in sub surface. Foam flooding is used to overcome the weakness of water injection, gas injection, and water alternating gas injection. Foam is the mixture of gas, water and surfactant. Foam propagation plays an important part in porous medium, foam propagation is related to intrinsic properties of the fluids such as density and viscosity. Resistivity of the fluids should be taken also because in the end of the experiment, method that is used to track foam propagation in porous medium is resistivity measurement. The objectives of this experiment are to obtain fluid characterization and to understand the phenomena that is possibly occurred during foam injection in porous medium, specifically, to obtain the correlation between density and resistivity measurement. Foam is generated with several concentration of solutions which are various concentration of brine, various concentration of MFOMAX, oil, and distilled water. Several tests should be taken to observe the intrinsic properties of the fluids such as density test, viscosity test, resistivity and conductivity test. Based on the experiment, correlation between density of brine and brine concentration towards resistivity is inversely proportional. Correlation between density of fluid mix with MFOMAX and MFOMAX concentration towards resistivity is proportional.
Lytova, M.; Lorin, E.; Bandrauk, A. D.
2016-07-01
We present a detailed analysis of the propagation dynamics of short and intense circularly polarized pulses in an aligned diatomic gas. Compared to linearly polarized intense pulses, high harmonic generation (HHG) and the coherent generation of attosecond pulses in the intense-circular-polarization case are a new research area. More specifically, we numerically study the propagation of intense and short circularly polarized pulses in the one-electron H2+ molecular gas, using a micro-macro Maxwell-Schrödinger model. In this model, the macroscopic polarization is computed from the solution of a large number of time-dependent Schrödinger equations, the source of dipole moments, and using a trace operator. We focus on the intensity and the phase of harmonics generated in the H2+ gas as a function of the pulse-propagation distance. We show that short coherent circularly polarized pulses of same helicity can be generated in the molecular gas as a result of cooperative phase-matching effects.
Zhao, Ke; Li, Hong-Yu; Liu, Ji-Cai; Wang, Chuan-Kui; Luo, Yi
2005-12-01
The dynamic behaviour of ultrashort (femtosecond) laser pulses in a molecular medium is studied by solving the full Maxwell-Bloch equations beyond the limits of the slowly varying envelope approximation and the rotating-wave approximation under the resonant and the non-resonant conditions. A one-dimensional asymmetric charge-transfer molecule, para-nitroaniline, is used as a model molecule whose electronic properties are calculated with the time-dependent hybrid density functional theory. Under the one-photon resonant condition, 4π pulse is separated into two sub-pulses. The weight of the second-harmonic component mainly contributed by the two-photon excitation becomes stronger with longer propagation time. Under the two-photon resonant condition, the separation of 4π pulse is not induced and many higher-order spectral components beyond the second-harmonic generation occur. Interestingly, when the pulse propagates for long enough, the carrier modification becomes so significant that a continuous spectrum is generated. The Fourier transform of the high-harmonic spectrum demonstrates that an even shorter laser pulse can be produced in both resonant and non-resonant propagations. The effects of permanent dipole moments on the pulse evolution are discussed.
Energy Technology Data Exchange (ETDEWEB)
Zhao Ke [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); Li Hongyu [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); Liu Jicai [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); Wang Chuankui [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); Luo Yi [Theoretical Chemistry, Royal Institute of Technology, AlbaNova, S-10691 Stockholm (Sweden)
2005-12-14
The dynamic behaviour of ultrashort (femtosecond) laser pulses in a molecular medium is studied by solving the full Maxwell-Bloch equations beyond the limits of the slowly varying envelope approximation and the rotating-wave approximation under the resonant and the non-resonant conditions. A one-dimensional asymmetric charge-transfer molecule, para-nitroaniline, is used as a model molecule whose electronic properties are calculated with the time-dependent hybrid density functional theory. Under the one-photon resonant condition, 4{pi} pulse is separated into two sub-pulses. The weight of the second-harmonic component mainly contributed by the two-photon excitation becomes stronger with longer propagation time. Under the two-photon resonant condition, the separation of 4{pi} pulse is not induced and many higher-order spectral components beyond the second-harmonic generation occur. Interestingly, when the pulse propagates for long enough, the carrier modification becomes so significant that a continuous spectrum is generated. The Fourier transform of the high-harmonic spectrum demonstrates that an even shorter laser pulse can be produced in both resonant and non-resonant propagations. The effects of permanent dipole moments on the pulse evolution are discussed.
Zhang, N; Zhang, J W; Yang, Y H; Li, X Y; Lin, J X; Li, Z L; Cheng, L Y; Wang, J F; Mu, C S; Wang, A X
2015-07-01
Clonal propagation is important for the survival and maintenance of the common reed Phragmites australis. Pot culture experiments were conducted to investigate the effects of lead (Pb) concentration (0, 500, 1500, 3000, 4500 mg·kg(-1) ) and water stress on the clonal reproductive ability of this species. The Pb concentration found in plant organs, in decreasing order, was roots >shoots >rhizomes. There was a negative relationship between the growth of clonal propagative modules (excluding axillary shoot buds) and Pb concentrations, which caused a decrease in biomass, rhizome growth and number of axillary and apical rhizome buds. Daughter axillary shoots exhibited a tolerance strategy, with no significant change in their number; the axillary and apical rhizome buds, daughter apical rhizome shoots and rhizomes exhibited compensatory growth during the late stage of Pb (excluding 4500 mg·kg(-1) ) treatment in a wet environment. Pb applications above 500 mg·kg(-1) reduced these parameters significantly in the drought treatment, except for the number of axillary shoot buds, which did not change. Our results indicate that clonal propagative resistance to Pb contamination can occur via tolerance strategies, compensatory growth and a Pb allocation strategy, enabling these reeds to maintain population stability in wet environments. However, clonal modular growth and reproductive ability were inhibited significantly by the interaction between drought and Pb, which would cause a decline in P. australis populations in a dry environment. Lead concentrations of 4500 and 500 mg·kg(-1) in soils might meet or exceed the Pb tolerance threshold of clonally propagated reeds in wet and dry environments, respectively. © 2015 German Botanical Society and The Royal Botanical Society of the Netherlands.
The Effects of Heterogeneities on Seismic Wave Propagation in the Climax Stock
Webb, C. H.; Snelson, C. M.; White, R. L.; Emmitt, R. F.; Barker, D. L.; Abbott, R. E.; Bonal, N. D.
2011-12-01
The Comprehensive Nuclear Test-Ban Treaty requires the ability to detect low-yield (less than 150kton) nuclear events. This kind of monitoring can only be done seismically on a regional scale (within 2000km). At this level, it is difficult to distinguish between low-yield nuclear events and non-nuclear events of similar magnitude. In order to confidently identify a nuclear event, a more detailed understanding of nuclear seismic sources is needed. In particular, it is important to know the effects of local geology on the seismic signal. This study focuses on P-wave velocity in heterogeneous granitoid. The Source Physics Experiment (SPE) is currently performing low-yield tests with chemical explosives at the Nevada National Security Site (NNSS). The exact test site was chosen to be in the Climax Stock, a cretaceous granodiorite and quartz-monzonite pluton located in Area 15 of the NNSS. It has been used in the past for the Hard Hat and Pile Driver nuclear tests, which provided legacy data that can be used to simulate wave propagation. The Climax Stock was originally chosen as the site of the SPE partly because of its assumed homogeneity. It has since been discovered that the area of the stock where the SPE tests are being performed contains a perched water table. In addition, the stock is known to contain an extensive network of faults, joints, and fractures, but the exact effect of these structural features on seismic wave velocity is not fully understood. The SPE tests are designed to seismically capture the explosion phenomena from the near- to the far-field transition of the seismic waveform. In the first SPE experiment, 100kg of chemical explosives were set off at a depth of 55m. The blast was recorded with an array of sensors and diagnostics, including accelerometers, geophones, rotational sensors, short-period and broadband seismic sensors, Continuous Reflectometry for Radius vs. Time Experiment, Time of Arrival, Velocity of Detonation, and infrasound sensors
The Effects of Heterogeneities on Seismic Wave Propagation in the Climax Stock
Energy Technology Data Exchange (ETDEWEB)
Hagan Webb, C., Snelson, C. M., White, R., Emmitt, R., Barker, D., Abbott, R., Bonal, N.
2011-12-01
The Comprehensive Nuclear Test-Ban Treaty requires the ability to detect low-yield (less than 150kton) nuclear events. This kind of monitoring can only be done seismically on a regional scale (within 2000km). At this level, it is difficult to distinguish between low-yield nuclear events and non-nuclear events of similar magnitude. In order to confidently identify a nuclear event, a more detailed understanding of nuclear seismic sources is needed. In particular, it is important to know the effects of local geology on the seismic signal. This study focuses on P-wave velocity in heterogeneous granitoid. The Source Physics Experiment (SPE) is currently performing low-yield tests with chemical explosives at the Nevada National Security Site (NNSS). The exact test site was chosen to be in the Climax Stock, a cretaceous granodiorite and quartz-monzonite pluton located in Area 15 of the NNSS. It has been used in the past for the Hard Hat and Pile Driver nuclear tests, which provided legacy data that can be used to simulate wave propagation. The Climax Stock was originally chosen as the site of the SPE partly because of its assumed homogeneity. It has since been discovered that the area of the stock where the SPE tests are being performed contains a perched water table. In addition, the stock is known to contain an extensive network of faults, joints, and fractures, but the exact effect of these structural features on seismic wave velocity is not fully understood. The SPE tests are designed to seismically capture the explosion phenomena from the near- to the far-field transition of the seismic waveform. In the first SPE experiment, 100kg of chemical explosives were set off at a depth of 55m. The blast was recorded with an array of sensors and diagnostics, including accelerometers, geophones, rotational sensors, short-period and broadband seismic sensors, Continuous Reflectometry for Radius vs. Time Experiment, Time of Arrival, Velocity of Detonation, and infrasound sensors
Robertson, J. S.; Jacobson, M. J.; Siegmann, W. L.; Santandrea, D. P.
1989-01-01
The effects of a ridge on a low-frequency acoustic propagation in quiescent and windy atmospheres are investigated using a parabolic approximation. A logarithmic wind-speed profile, commonly employed to model atmospheric wind currents, is modified and used to model two-dimensional atmospheric flow over a triangularly-shaped hill. The parabolic equation is solved using an implicit finite-difference algorithm. Several examples are examined to determine the combined effects of source-ridge distance, ridge dimensions, wind-speed profile, and CW source frequency on the received acoustic field.
Fort, Joaquim
2011-05-01
It is shown that Lotka-Volterra interaction terms are not appropriate to describe vertical cultural transmission. Appropriate interaction terms are derived and used to compute the effect of vertical cultural transmission on demic front propagation. They are also applied to a specific example, the Neolithic transition in Europe. In this example, it is found that the effect of vertical cultural transmission can be important (about 30%). On the other hand, simple models based on differential equations can lead to large errors (above 50%). Further physical, biophysical, and cross-disciplinary applications are outlined. © 2011 American Physical Society
Ferrarese, Giorgio
2011-01-01
Lectures: A. Jeffrey: Lectures on nonlinear wave propagation.- Y. Choquet-Bruhat: Ondes asymptotiques.- G. Boillat: Urti.- Seminars: D. Graffi: Sulla teoria dell'ottica non-lineare.- G. Grioli: Sulla propagazione del calore nei mezzi continui.- T. Manacorda: Onde nei solidi con vincoli interni.- T. Ruggeri: "Entropy principle" and main field for a non linear covariant system.- B. Straughan: Singular surfaces in dipolar materials and possible consequences for continuum mechanics
Temporal scaling in information propagation.
Huang, Junming; Li, Chao; Wang, Wen-Qiang; Shen, Hua-Wei; Li, Guojie; Cheng, Xue-Qi
2014-06-18
For the study of information propagation, one fundamental problem is uncovering universal laws governing the dynamics of information propagation. This problem, from the microscopic perspective, is formulated as estimating the propagation probability that a piece of information propagates from one individual to another. Such a propagation probability generally depends on two major classes of factors: the intrinsic attractiveness of information and the interactions between individuals. Despite the fact that the temporal effect of attractiveness is widely studied, temporal laws underlying individual interactions remain unclear, causing inaccurate prediction of information propagation on evolving social networks. In this report, we empirically study the dynamics of information propagation, using the dataset from a population-scale social media website. We discover a temporal scaling in information propagation: the probability a message propagates between two individuals decays with the length of time latency since their latest interaction, obeying a power-law rule. Leveraging the scaling law, we further propose a temporal model to estimate future propagation probabilities between individuals, reducing the error rate of information propagation prediction from 6.7% to 2.6% and improving viral marketing with 9.7% incremental customers.
Temporal scaling in information propagation
Huang, Junming; Li, Chao; Wang, Wen-Qiang; Shen, Hua-Wei; Li, Guojie; Cheng, Xue-Qi
2014-06-01
For the study of information propagation, one fundamental problem is uncovering universal laws governing the dynamics of information propagation. This problem, from the microscopic perspective, is formulated as estimating the propagation probability that a piece of information propagates from one individual to another. Such a propagation probability generally depends on two major classes of factors: the intrinsic attractiveness of information and the interactions between individuals. Despite the fact that the temporal effect of attractiveness is widely studied, temporal laws underlying individual interactions remain unclear, causing inaccurate prediction of information propagation on evolving social networks. In this report, we empirically study the dynamics of information propagation, using the dataset from a population-scale social media website. We discover a temporal scaling in information propagation: the probability a message propagates between two individuals decays with the length of time latency since their latest interaction, obeying a power-law rule. Leveraging the scaling law, we further propose a temporal model to estimate future propagation probabilities between individuals, reducing the error rate of information propagation prediction from 6.7% to 2.6% and improving viral marketing with 9.7% incremental customers.
Directory of Open Access Journals (Sweden)
Viviane Maria Gonçalves de Figueiredo
Full Text Available Abstract Objective: This study evaluated the influence of porcelain (VM9, VITA Zahnfabrik, Germany thickness on the flexural strength and crack propagation in bilayered zirconia systems (YZ, VITA Zahnfabrik, Germany. Material and Methods: Thirty zirconia bars (20.0x4.0x1.0 mm and six zirconia blocks (12.0x7.5x1.2 mm were prepared and veneered with porcelain with different thickness: 1 mm, 2 mm, or 3 mm. The bars of each experimental group (n=10 were subjected to four-point flexural strength testing. In each ceramic block, a Vickers indentation was created under a load of 10 kgf for 10 seconds, for the propagation of cracks. Results: The results of flexural strength were evaluated by One-way ANOVA and Tukey's test, with a significance level of 5%. The factor “thickness of the porcelain” was statistically significant (p=0.001 and the l-mm group presented the highest values of flexural strength. The cracks were predominant among the bending specimens with 1 and 2 mm of porcelain, and catastrophic failures were found in 50% of 3-mm-thick porcelain. After the indentation of blocks, the most severe defects were observed in blocks with 3-mm-thick porcelain. Conclusion: The smallest (1 mm thickness of porcelain on the zirconia infrastructure presented higher values of flexural strength. Better resistance to defect propagation was observed near the porcelain/ zirconia interface for all groups. Higher flexural strength was found for a thinner porcelain layer in a bilayered zirconia system. The damage caused by a Vickers indentation near and far the interface with the zirconia shows that the stress profiles are different.
Effects of a "day-time" substorm on the ionosphere and radio propagation
Blagoveshchenskiy, Donat; MacDougall, John, , Dr; Kalishin, Aleksei
Experimental studies were carried out using data from the Tromso ionosonde, the CUTLASS radar, the IMAGE system of magnetometers, the Finnish riometer chain, and oblique ionospheric sounding on a Murmansk - St. Petersburg path. An example of a day-time substorm with amplitude of about 200 nT for October 25, 2003 from 13:00 to 18:00 UT is described. During the substorm there was a southward movement of the region of particle precipitation causing a band of the irregularities to move to latitudes 62 - 64o. The velocity of displacement southward is about 15o per hour. Oblique ionograms on the Murmansk - St. Petersburg radio path showed diffuse traces caused by scatter due to the spread F, or by refraction from ionospheric gradients. Based on this, and a number of other substorm studies, the following conclusions are: 1) During an intensive substorm, precipitation regions with ionospheric irregularities are displaced to 62 - 64o maqgnetc latitude. 2) Increased absorption during the substorm most likely does not affect the amplitude of obliquely propagating signals. Blocking the F2-reflections by intense sporadic Es-layers with high conductivity plays rather a more important part. 3) The usual mechanism of radio propagation along the great circle arc is sometimes changed from reflections via the F2- and E-layers simultaneously to only the reflection via Es-layer. 4) Lateral oblique signal propagation is not observed for every substorm. It is possible if the path midpoint is located near the precipitation region where there are irregularities which are quickly displaced, during the substorm, from high latitudes to lower.
The effect of surface wave propagation on neural responses to vibration in primate glabrous skin.
Directory of Open Access Journals (Sweden)
Louise R Manfredi
Full Text Available Because tactile perception relies on the response of large populations of receptors distributed across the skin, we seek to characterize how a mechanical deformation of the skin at one location affects the skin at another. To this end, we introduce a novel non-contact method to characterize the surface waves produced in the skin under a variety of stimulation conditions. Specifically, we deliver vibrations to the fingertip using a vibratory actuator and measure, using a laser Doppler vibrometer, the surface waves at different distances from the locus of stimulation. First, we show that a vibration applied to the fingertip travels at least the length of the finger and that the rate at which it decays is dependent on stimulus frequency. Furthermore, the resonant frequency of the skin matches the frequency at which a subpopulation of afferents, namely Pacinian afferents, is most sensitive. We show that this skin resonance can lead to a two-fold increase in the strength of the response of a simulated afferent population. Second, the rate at which vibrations propagate across the skin is dependent on the stimulus frequency and plateaus at 7 m/s. The resulting delay in neural activation across locations does not substantially blur the temporal patterning in simulated populations of afferents for frequencies less than 200 Hz, which has important implications about how vibratory frequency is encoded in the responses of somatosensory neurons. Third, we show that, despite the dependence of decay rate and propagation speed on frequency, the waveform of a complex vibration is well preserved as it travels across the skin. Our results suggest, then, that the propagation of surface waves promotes the encoding of spectrally complex vibrations as the entire neural population is exposed to essentially the same stimulus. We also discuss the implications of our results for biomechanical models of the skin.
Figueiredo, Viviane Maria Gonçalves de; Pereira, Sarina Maciel Braga; Bressiani, Eduardo; Valera, Márcia Carneiro; Bottino, Marco Antônio; Zhang, Yu; Melo, Renata Marques de
2017-01-01
This study evaluated the influence of porcelain (VM9, VITA Zahnfabrik, Germany) thickness on the flexural strength and crack propagation in bilayered zirconia systems (YZ, VITA Zahnfabrik, Germany). Thirty zirconia bars (20.0x4.0x1.0 mm) and six zirconia blocks (12.0x7.5x1.2 mm) were prepared and veneered with porcelain with different thickness: 1 mm, 2 mm, or 3 mm. The bars of each experimental group (n=10) were subjected to four-point flexural strength testing. In each ceramic block, a Vickers indentation was created under a load of 10 kgf for 10 seconds, for the propagation of cracks. The results of flexural strength were evaluated by One-way ANOVA and Tukey's test, with a significance level of 5%. The factor "thickness of the porcelain" was statistically significant (p=0.001) and the l-mm group presented the highest values of flexural strength. The cracks were predominant among the bending specimens with 1 and 2 mm of porcelain, and catastrophic failures were found in 50% of 3-mm-thick porcelain. After the indentation of blocks, the most severe defects were observed in blocks with 3-mm-thick porcelain. The smallest (1 mm) thickness of porcelain on the zirconia infrastructure presented higher values of flexural strength. Better resistance to defect propagation was observed near the porcelain/ zirconia interface for all groups. Higher flexural strength was found for a thinner porcelain layer in a bilayered zirconia system. The damage caused by a Vickers indentation near and far the interface with the zirconia shows that the stress profiles are different.
Directory of Open Access Journals (Sweden)
Rasolofosaon P.
2006-11-01
Full Text Available Ce travail constitue le prolongement logique d'un précédent article (O. Coussy, T. Bourbié, 1984 relatif à la propagation, dans le cadre de la théorie de Biot, des ondes acoustiques dans les milieux poreux saturés infinis. Partant des mêmes hypothèses concernant les milieux de propagation, nous étudions l'influence de la présence de discontinuités géométriques planes (milieux semi-infinis libres ou contact entre deux milieux semi-infinis ou à symétrie cylindrique (puits. Après un rappel des lois de comportement hydromécanique du milieu poreux et des équations fondamentales de la poroélasticité dynamique, nous discutons les conditions aux limites à imposer aux interfaces. Nous étudions ensuite les lois générales de la réflexion et de la réfraction en poroélasticité (lois de Snell-Descartes généralisées. L'application de celles-ci à quelques cas particuliers intéressants, met surtout en évidence les phénomènes suivants : -Une onde lente compressive est toujours engendrée à l'interface entre 2 milieux poreux saturés. - Les ondes réfléchies et transmises sont en général inhomogènes. Dans une étape suivante, nous étudions la propagation des ondes acoustiques à la surface libre d'un milieu poreux saturé semi-infini (ondes de Rayleigh et à l'interface plane entre un liquide et un milieu poreux saturé (ondes de Stoneley. Par rapport aux propriétés qu'on leur connaît en élastodynamique classique, en poroélasticité, ces ondes sont légèrement dispersives mais sont notablement atténuées du fait du caractère biphasique du milieu de propagation. Puis enfin nous étudions l'influence d'une source immergée émettant près d'une interface perméable. Nous soulignons le rôle fondamental de la perméabilité et des conditions de flux aux interfaces sur l'atténuation des ondes S et des ondes de surface. Comparativement, l'influence de ces paramètres sur les premières arrivées (ondes P est n
Directory of Open Access Journals (Sweden)
Rasolofosaon P.
2006-11-01
Full Text Available Ce travail constitue le prolongement logique d'un précédent article (O. Coussy, T. Bourbié, 1984 relatif à la propagation, dans le cadre de la théorie de Biot, des ondes acoustiques dans les milieux poreux saturés infinis. Partant des mêmes hypothèses concernant les milieux de propagation, nous étudions l'influence de la présence de discontinuités géométriques planes (milieux semi-infinis libres ou contact entre deux milieux semi-infinis ou à symétrie cylindrique (puits. Après un rappel des lois de comportement hydromécanique du milieu poreux et des équations fondamentales de la poroélasticité dynamique, nous discutons les conditions aux limites à imposer aux interfaces. Nous étudions ensuite les lois générales de la réflexion et de la réfraction en poroélasticité (lois de Snell-Descartes généralisées. L'application de celles-ci à quelques cas particuliers intéressants, met surtout en évidence les phénomènes suivants : -Une onde lente compressive est toujours engendrée à l'interface entre 2 milieux poreux saturés. - Les ondes réfléchies et transmises sont en général inhomogènes. Dans une étape suivante, nous étudions la propagation des ondes acoustiques à la surface libre d'un milieu poreux saturé semi-infini (ondes de Rayleigh et à l'interface plane entre un liquide et un milieu poreux saturé (ondes de Stoneley. Par rapport aux propriétés qu'on leur connaît en élastodynamique classique, en poroélasticité, ces ondes sont légèrement dispersives mais sont notablement atténuées du fait du caractère biphasique du milieu de propagation. Puis enfin nous étudions l'influence d'une source immergée émettant près d'une interface perméable. Nous soulignons le rôle fondamental de la perméabilité et des conditions de flux aux interfaces sur l'atténuation des ondes S et des ondes de surface. Comparativement, l'influence de ces paramètres sur les premières arrivées (ondes P est n
Directory of Open Access Journals (Sweden)
Rasolofosaon P.
2006-11-01
Full Text Available Ce travail constitue le prolongement logique d'un précédent article (O. Coussy, T. Bourbié, 1984 relatif à la propagation, dans le cadre de la théorie de Biot, des ondes acoustiques dans les milieux poreux saturés infinis. Partant des mêmes hypothèses concernant les milieux de propagation, nous étudions l'influence de la présence de discontinuités géométriques planes (milieux semi-infinis libres ou contact entre deux milieux semi-infinis ou à symétrie cylindrique (puits. Après un rappel des lois de comportement hydromécanique du milieu poreux et des équations fondamentales de la poroélasticité dynamique, nous discutons les conditions aux limites à imposer aux interfaces. Nous étudions ensuite les lois générales de la réflexion et de la réfraction en poroélasticité (lois de Snell-Descartes généralisées. L'application de celles-ci à quelques cas particuliers intéressants, met surtout en évidence les phénomènes suivants : -Une onde lente compressive est toujours engendrée à l'interface entre 2 milieux poreux saturés. - Les ondes réfléchies et transmises sont en général inhomogènes. Dans une étape suivante, nous étudions la propagation des ondes acoustiques à la surface libre d'un milieu poreux saturé semi-infini (ondes de Rayleigh et à l'interface plane entre un liquide et un milieu poreux saturé (ondes de Stoneley. Par rapport aux propriétés qu'on leur connaît en élastodynamique classique, en poroélasticité, ces ondes sont légèrement dispersives mais sont notablement atténuées du fait du caractère biphasique du milieu de propagation. Puis enfin nous étudions l'influence d'une source immergée émettant près d'une interface perméable. Nous soulignons le rôle fondamental de la perméabilité et des conditions de flux aux interfaces sur l'atténuation des ondes S et des ondes de surface. Comparativement, l'influence de ces paramètres sur les premières arrivées (ondes P est n
AN EFFECTIVE WAY TO CARRY OUT MASS IN VITRO PROPAGATION OF POTENTILLA ALBA L.
L. I. Tikhomirova; Kechaykin, A. A.; A. I. Shmakov; O. V. Aleksandrova
2016-01-01
Despite the plant’s extensive area of distribution, Potentilla alba L. natural resources are scarce and cannot meet the modern needs of the pharmaceutical industry. Because of the mass preparation of medical raw materials by using P. alba, it entered into the list of rare and endangered species plants of the Red Data Book of the Republic of Belarus. This plant is not represented in the wild flora of Western Siberia, but there is a great need for developing a method for the mass propagation of...
Sonar Performance Estimation Model with Seismo-Acoustic Effects on Underwater Sound Propagation
1989-06-27
a dfluid properties are obtained from Jensen , the properties of clay-silt, sand, 61 and basalt are taken from the paper by Werby and Tango , and the...the power of very loud music may be 30 Watts with a sound pressure of 3 Pascals which corresponds to a sound pressure level near 100dB. The...Underwater Acoustic Propagation, DREA Report 85/105, Sep 1985, Nova Scotia, Canada. 61. Werby, M. F. and Tango , G. J., "Characterization of Average
DEFF Research Database (Denmark)
Henneberg, Kaj-åge; F.A., Roberge
1997-01-01
Computer simulations are used to study passive fiber modulation of propagation in a tightly packed bundle of frog skeletal muscle fibers (uniform fiber radius of 50 mu m). With T = 20 degrees C and a uniform nominal interstitial cleft width (d) over bar = 0.35 mu m, about 92% of the active fiber...... source current (I-ma) enters the passive tissue as a radial load current (I-ep) while the rest flows longitudinally in the cleft between the active and adjacent passive fibers. The conduction velocity of 1.32 m/s was about 30% lower than on an isolated fiber in a Ringer bath, in close agreement...
Pinchuk, Ilya; Lichtenberg, Dov
2017-06-01
LDL peroxidation plays a major role in many physiological and pathophysiological processes. The mechanisms of LDL peroxidation induced by transition metal ions have therefore been studied intensively. It has been proposed that the mechanism involves free radical production that occurs via decomposition of hydroperoxides. This, in turn, requires the cleavage of O-H bonds. Cleavage of O-D bond is slower and comparison of the kinetics in D2O to the kinetics in H2O is therefore a straightforward way to test this aspect of the alleged mechanism. The kinetics of peroxidation exhibit marked deuterium kinetic isotope effects at all the stages of oxidation under all the studied conditions. We found that the rate of propagation of copper-induced peroxidation is a monotonically decreasing function of D2O fraction in D2O/H2O mixtures. The only elementary reaction that involves "exchangeable" hydrogen at this stage is copper-induced decomposition of conjugated hydroperoxides. Therefore, we conclude that the latter step is rate-limiting reaction including cleavage of oxygen-hydrogen bond of hydroperoxide. The lag preceding rapid peroxidation exhibits a biphasic dependence on the fraction of D2O. This may be understood on the basis of the effect of substituting hydrogen atoms by deuterium. Specifically, such substitution is expected to decrease both the rate of initiation of peroxidation and the potency of the antioxidant. We interpret our results in terms of the effects of isotopic substitution on the rates of the reactions that involve the abstraction of "exchangeable" hydrogen atoms of OH groups in tocopherol and hydroperoxides. Copyright © 2017 Elsevier B.V. All rights reserved.
Watkins, Nick; Graves, Timothy; Franzke, Christian; Gramacy, Robert; Tindale, Elizabeth
2017-04-01
Long-Range Dependence (LRD) and heavy-tailed distributions are ubiquitous in natural and socio-economic data. Such data can be self-similar whereby both LRD and heavy-tailed distributions contribute to the self-similarity as measured by the Hurst exponent. Some methods widely used in the physical sciences separately estimate these two parameters, which can lead to estimation bias. Those which do simultaneous estimation are based on frequentist methods such as Whittle's approximate maximum likelihood estimator. Here we present a new and systematic Bayesian framework for the simultaneous inference of the LRD and heavy-tailed distribution parameters of a parametric ARFIMA model with non-Gaussian innovations. As innovations we use the alpha-stable and t-distributions which have power law tails. Our algorithm also provides parameter uncertainty estimates. We test our algorithm using synthetic data, and also data from the Geostationary Operational Environmental Satellite system (GOES) solar X-ray time series. These tests show that our algorithm is able to accurately and robustly estimate the LRD and heavy-tailed distribution parameters. See Physica A: Statistical Mechanics and its Applications, (January 2017), DOI: 10.1016/j.physa.2017.01.028
Graves, Timothy; Franzke, Christian L. E.; Watkins, Nicholas W.; Gramacy, Robert B.; Tindale, Elizabeth
2017-05-01
Long-Range Dependence (LRD) and heavy-tailed distributions are ubiquitous in natural and socio-economic data. Such data can be self-similar whereby both LRD and heavy-tailed distributions contribute to the self-similarity as measured by the Hurst exponent. Some methods widely used in the physical sciences separately estimate these two parameters, which can lead to estimation bias. Those which do simultaneous estimation are based on frequentist methods such as Whittle's approximate maximum likelihood estimator. Here we present a new and systematic Bayesian framework for the simultaneous inference of the LRD and heavy-tailed distribution parameters of a parametric ARFIMA model with non-Gaussian innovations. As innovations we use the α-stable and t-distributions which have power law tails. Our algorithm also provides parameter uncertainty estimates. We test our algorithm using synthetic data, and also data from the Geostationary Operational Environmental Satellite system (GOES) solar X-ray time series. These tests show that our algorithm is able to accurately and robustly estimate the LRD and heavy-tailed distribution parameters.
Chaix, Jean-François; Rossat, Mathieu; Garnier, Vincent; Corneloup, Gilles
2012-06-01
This study compares ultrasonic wave propagation modeling and experimental data in concrete. As a consequence of its composition and manufacturing process, this material has a high elastic scattering (sand and aggregates) and air (microcracks and porosities) content. The behavior of the "Waterman-Truell" and "Generalized Self Consistent Method" dynamic homogenization models are analyzed in the context of an application for strong heterogeneous solid materials, in which the scatterers are of various concentrations and types. The experimental validations of results predicted by the models are carried out by making use of the phase velocity and the attenuation of longitudinal waves, as measured by an immersed transmission setup. The test specimen material has a cement-like matrix containing spherical inclusions of air or glass, with radius close to the ultrasonic wavelength. The models are adapted to the case of materials presenting several types of scattering particle, and allow the propagation of longitudinal waves to be described at the scale of materials such as concrete. The validity limits for frequency and for particle volume ratio can be approached through a comparison with experimental data. The potential of these homogenization models for the prediction of phase velocity and attenuation in strongly heterogeneous solids is demonstrated.
Effects of water saturation on P-wave propagation in fractured coals: An experimental perspective
Liu, Jie; Liu, Dameng; Cai, Yidong; Gan, Quan; Yao, Yanbin
2017-09-01
Internal structure of coalbed methane (CBM) reservoirs can be evaluated through ultrasonic measurements. The compressional wave that propagates in a fractured coal reservoir may indicate the internal coal structure and fluid characteristics. The P-wave propagation was proposed to study the relations between petrophysical parameters (including water saturation, fractures, porosity and permeability) of coals and the P-wave velocity (Vp), using a KON-NM-4A ultrasonic velocity meter. In this study, the relations between Vps and water saturations were established: Type I is mainly controlled by capillary of developed seepage pores. The controlling factors on Type II and Type III are internal homogeneity of pores/fractures and developed micro-fractures, respectively. Micro-fractures density linearly correlates with the Vp due to the fracture volume and dispersion of P-wave; and micro-fractures of types C and D have a priority in Vp. For dry coals, no clear relation exists between porosity, permeability and the Vp. However, as for water-saturated coals, the correlation coefficients of porosity, permeability and Vp are slightly improved. The Vp of saturated coals could be predicted with the equation of Vp-saturated = 1.4952Vp-dry-26.742 m/s. The relation between petrophysical parameters of coals and Vp under various water saturations can be used to evaluate the internal structure in fractured coals. Therefore, these relations have significant implications for coalbed methane (CBM) exploration.
Taghavifar, Hadi; Khalilarya, Shahram; Jafarmadar, Samad; Taghavifar, Hamid
2016-08-01
A multidimensional computational fluid dynamic code was developed and integrated with probability density function combustion model to give the detailed account of multiphase fluid flow. The vapor phase within injector domain is treated with Reynolds-averaged Navier-Stokes technique. A new parameter is proposed which is an index of plane-cut spray propagation and takes into account two parameters of spray penetration length and cone angle at the same time. It was found that spray propagation factor (SPI) tends to increase at lower r/ d ratios, although the spray penetration tends to decrease. The results of SPI obtained by empirical correlation of Hay and Jones were compared with the simulation computation as a function of respective r/ d ratio. Based on the results of this study, the spray distribution on plane area has proportional correlation with heat release amount, NO x emission mass fraction, and soot concentration reduction. Higher cavitation is attributed to the sharp edge of nozzle entrance, yielding better liquid jet disintegration and smaller spray droplet that reduces soot mass fraction of late combustion process. In order to have better insight of cavitation phenomenon, turbulence magnitude in nozzle and combustion chamber was acquired and depicted along with spray velocity.
Directionality and Orientation Effects on the Resistance to Propagating Shear Failure
Leis, B. N.; Barbaro, F. J.; Gray, J. M.
Hydrocarbon pipelines transporting compressible products like methane or high-vapor-pressure (HVP) liquids under supercritical conditions can be susceptible to long-propagating failures. As the unplanned release of such hydrocarbons can lead to significant pollution and/or the horrific potential of explosion and/or a very large fire, design criteria to preclude such failures were essential to environmental and public safety. Thus, technology was developed to establish the minimum arrest requirements to avoid such failures shortly after this design concern was evident. Soon after this technology emerged in the early 1970sit became evident that its predictions were increasinglynon-conservative as the toughness of line-pipe steel increased. A second potentially critical factor for what was a one-dimensional technology was that changes in steel processing led to directional dependence in both the flow and fracture properties. While recognized, this dependence was tacitly ignored in quantifying arrest, as were early observations that indicated propagating shear failure was controlled by plastic collapse rather than by fracture processes.
Front propagation and effect of memory in stochastic desertification models with an absorbing state
Herman, Dor; Shnerb, Nadav M.
2017-08-01
Desertification in dryland ecosystems is considered to be a major environmental threat that may lead to devastating consequences. The concern increases when the system admits two alternative steady states and the transition is abrupt and irreversible (catastrophic shift). However, recent studies show that the inherent stochasticity of the birth-death process, when superimposed on the presence of an absorbing state, may lead to a continuous (second order) transition even if the deterministic dynamics supports a catastrophic transition. Following these works we present here a numerical study of a one-dimensional stochastic desertification model, where the deterministic predictions are confronted with the observed dynamics. Our results suggest that a stochastic spatial system allows for a propagating front only when its active phase invades the inactive (desert) one. In the extinction phase one observes transient front propagation followed by a global collapse. In the presence of a seed bank the vegetation state is shown to be more robust against demographic stochasticity, but the transition in that case still belongs to the directed percolation equivalence class.
Effect of Vertically Propagating Shear Waves on Seismic Behavior of Circular Tunnels
Directory of Open Access Journals (Sweden)
Tohid Akhlaghi
2014-01-01
Full Text Available Seismic design loads for tunnels are characterized in terms of the deformations imposed on the structure by surrounding ground. The free-field ground deformations due to a seismic event are estimated, and the tunnel is designed to accommodate these deformations. Vertically propagating shear waves are the predominant form of earthquake loading that causes the ovaling deformations of circular tunnels to develop, resulting in a distortion of the cross sectional shape of the tunnel lining. In this paper, seismic behavior of circular tunnels has been investigated due to propagation of shear waves in the vertical direction using quasi-static analytical approaches as well as numerical methods. Analytical approaches are based on the closed-form solutions which compute the forces in the lining due to equivalent static ovaling deformations, while the numerical method carries out dynamic, nonlinear soil-structure interaction analysis. Based on comparisons made, the accuracy and reliability of the analytical solutions are evaluated and discussed. The results show that the axial forces determined using the analytical approaches are in acceptable agreement with numerical analysis results, while the computed bending moments are less comparable and show significant discrepancies. The differences between the analytical approaches are also investigated and addressed.
Effect of vertically propagating shear waves on seismic behavior of circular tunnels.
Akhlaghi, Tohid; Nikkar, Ali
2014-01-01
Seismic design loads for tunnels are characterized in terms of the deformations imposed on the structure by surrounding ground. The free-field ground deformations due to a seismic event are estimated, and the tunnel is designed to accommodate these deformations. Vertically propagating shear waves are the predominant form of earthquake loading that causes the ovaling deformations of circular tunnels to develop, resulting in a distortion of the cross sectional shape of the tunnel lining. In this paper, seismic behavior of circular tunnels has been investigated due to propagation of shear waves in the vertical direction using quasi-static analytical approaches as well as numerical methods. Analytical approaches are based on the closed-form solutions which compute the forces in the lining due to equivalent static ovaling deformations, while the numerical method carries out dynamic, nonlinear soil-structure interaction analysis. Based on comparisons made, the accuracy and reliability of the analytical solutions are evaluated and discussed. The results show that the axial forces determined using the analytical approaches are in acceptable agreement with numerical analysis results, while the computed bending moments are less comparable and show significant discrepancies. The differences between the analytical approaches are also investigated and addressed.
Elkamash, I. S.; Kourakis, I.; Haas, F.
2017-10-01
Understanding the transport properties of charged particle beams is important not only from a fundamental point of view but also due to its relevance in a variety of applications. A theoretical model is established in this article, to model the interaction of a tenuous positively charged ion beam with an ultradense quantum electron-ion plasma, by employing a rigorous relativistic quantum-hydrodynamic (fluid plasma) electrostatic model proposed in McKerr et al. [M. McKerr, F. Haas, and I. Kourakis, Phys. Rev. E 90, 033112 (2014), 10.1103/PhysRevE.90.033112]. A nonlinear analysis is carried out to elucidate the propagation characteristics and the existence conditions of large amplitude electrostatic solitary waves propagating in the plasma in the presence of the beam. Anticipating stationary profile excitations, a pseudomechanical energy balance formalism is adopted to reduce the fluid evolution equation to an ordinary differential equation. Exact solutions are thus obtained numerically, predicting localized excitations (pulses) for all of the plasma state variables, in response to an electrostatic potential disturbance. An ambipolar electric field form is also obtained. Thorough analysis of the reality conditions for all variables is undertaken in order to determine the range of allowed values for the solitonic pulse speed and how it varies as a function of the beam characteristics (beam velocity and density).
DEFF Research Database (Denmark)
Stephansen, E.; Mogensen, G.
1979-01-01
of fading,P, the average duration of fades,bar{t}, and the number of fades, N0, is investigated. Results show thatP propto L^{2},bar{t} propto L^{2/3}andN_{0} propto L^{4/3}. This differs from previously published results, where proportionalities of L2,LandL, respectively, have been proposed. Statistical...... results on enhancements above free space level are also presented. The results presented are believed to enable an improved description of the effects of multipath propagation....
Bowen, LI; Zhibin, WANG; Qiuyue, NIE; Xiaogang, WANG; Fanrong, KONG; Zhenyu, WANG
2018-01-01
Intensive collisions between electrons and neutral particles in partially ionized plasmas generated in atmospheric/sub-atmospheric pressure environments can sufficiently affect the propagation characteristics of electromagnetic waves, particularly in the sub-wavelength regime. To investigate the collisional effect in such plasmas, we introduce a simplified plasma slab model with a thickness on the order of the wavelength of the incident electromagnetic wave. The scattering matrix method (SMM) is applied to solve the wave equation in the plasma slab with significant nonuniformity. Results show that the collisions between the electrons and the neutral particles, as well as the incident angle and the plasma thickness, can disturb the transmission and reduce reflection significantly.
Directory of Open Access Journals (Sweden)
Line Hermannsen
Full Text Available Airguns used in seismic surveys are among the most prevalent and powerful anthropogenic noise sources in marine habitats. They are designed to produce most energy below 100 Hz, but the pulses have also been reported to contain medium-to-high frequency components with the potential to affect small marine mammals, which have their best hearing sensitivity at higher frequencies. In shallow water environments, inhabited by many of such species, the impact of airgun noise may be particularly challenging to assess due to complex propagation conditions. To alleviate the current lack of knowledge on the characteristics and propagation of airgun pulses in shallow water with implications for effects on small marine mammals, we recorded pulses from a single airgun with three operating volumes (10 in3, 25 in3 and 40 in3 at six ranges (6, 120, 200, 400, 800 and 1300 m in a uniform shallow water habitat using two calibrated Reson 4014 hydrophones and four DSG-Ocean acoustic data recorders. We show that airgun pulses in this shallow habitat propagated out to 1300 meters in a way that can be approximated by a 18log(r geometric transmission loss model, but with a high pass filter effect from the shallow water depth. Source levels were back-calculated to 192 dB re µPa2s (sound exposure level and 200 dB re 1 µPa dB Leq-fast (rms over 125 ms duration, and the pulses contained substantial energy up to 10 kHz, even at the furthest recording station at 1300 meters. We conclude that the risk of causing hearing damage when using single airguns in shallow waters is small for both pinnipeds and porpoises. However, there is substantial potential for significant behavioral responses out to several km from the airgun, well beyond the commonly used shut-down zone of 500 meters.
Energy Technology Data Exchange (ETDEWEB)
Ghosh, Soumen [Department; Andersen, Amity [Environmental; Gagliardi, Laura [Department; Cramer, Christopher J. [Department; Govind, Niranjan [Environmental
2017-08-16
We present an implementation of a time-dependent semiempirical method (INDO/S) in NWChem using real-time (RT) propagation to address, in principle, the entire spectrum of valence electronic excitations. Adopting this model, we study the UV-visible spectra of medium-sized systems like P3B2, f-coronene, and in addition much larger systems like ubiquitin in the gas phase and the betanin chromophore in the presence of two explicit solvents (water and methanol). RT-INDO/S provides qualitatively and indeed often quantitatively accurate results when compared with RT- TDDFT or experimental spectra. While demonstrated here for INDO/S in particular, our implementation provides a framework for performing electron dynamics in large systems using semiempirical Hartree-Fock (HF) Hamiltonians in general.
Effects of damping on surface-plasmon pulse propagation and refraction
Hohenau, Andreas; Drezet, Aurelien; Weißenbacher, Matthias; Aussenegg, Franz R.; Krenn, Joachim R.
2008-10-01
We discuss the role of damping for surface-plasmon pulse propagation and refraction by analyzing calculated dispersion relations of a metal-dielectric interface. Results for a lossless Drude metal are compared to those for a lossy Drude metal and the application relevant materials gold and silver. We find that the imaginary part of the surface-plasmon wave vector rather than the surface-plasmon group velocity defines if normal or negative refraction takes place at lateral boundaries. As a consequence, the group velocity can be opposite to the energy flow. This is not in contradiction to causality, as due to large damping in regions of negative group velocities surface plasmons on a single interface are overdamped and evanescent in character. In addition, pulse spreading and the implications of the results for multilayer systems are discussed.
The effect of negative feedback on noise propagation in transcriptional gene networks
Hooshangi, Sara; Weiss, Ron
2006-06-01
This paper analyzes how the delay and repression strength of negative feedback in single-gene and multigene transcriptional networks influences intrinsic noise propagation and oscillatory behavior. We simulate a variety of transcriptional networks using a stochastic model and report two main findings. First, intrinsic noise is not attenuated by the addition of negative or positive feedback to transcriptional cascades. Second, for multigene negative feedback networks, synchrony in oscillations among a cell population can be improved by increasing network depth and tightening the regulation at one of the repression stages. Our long term goal is to understand how the noise characteristics of complex networks can be derived from the properties of modules that are used to compose these networks.
Propagation Effect of a Virus Outbreak on a Network with Limited Anti-Virus Ability.
Directory of Open Access Journals (Sweden)
Yonghong Xu
Full Text Available This paper describes a new computer virus spreading model which takes into account the possibility of a virus outbreak on a network with limited anti-virus ability. Then, the model is investigated for the existence of equilibria and their stabilities are proved and illustrated. Moreover, it is found that these two factors are not only relative to the threshold value determining whether the virus becomes extinct or not, but that they are also relative to the virus epidemic levels. Theoretical and experimental results indicate that, in some ways, it would be practically possible to eradicate the virus or suppress its prevalence below a suitable level. Consequently, some suggestions are proposed that may help eradicate or suppress virus propagation over a real computer network.
Determination of the Ionosphere Parameters by Analyzing the Propagation After-Effects
2010-06-27
whereas the long waves are subject to stronger dispersion. Indeed, the phase and group velocity of the propagation are given by: vph = c ( 1 + ω2pe/c...antenna at x is given by equation (A.16) [cf. formula (2.15)]: ϕ(t, z ) = A′(t− |z − x |/vgr(ω0)) 4π|z − x | eiω0(t−|z−x |/ vph (ω0)), where A′(t) = χτ ′(t...carrier oscillation per se, i.e., the wave eiω0t, travels with the corresponding phase velocity vph (ω0) that can also be linearized: vph = vph (ω) ≈ c ( 1
Vila, M M; Ginebra, M P; Gil, F J; Planell, J A
1999-01-01
The aim of this study was to investigate the effect of adding an elastomeric second phase, acrylonitrile-butadiene-styrene, on the fatigue crack propagation behavior of poly(methyl methacrylate) bone cement. Moreover, the influence of porosity and environmental conditions was studied. When comparing the plain cement to the modified cement, a decrease in the crack propagation rate was observed at between 1 and 2 orders of magnitude. The storage in a physiological environment (saline solution at 37 degrees C) also caused a decrease in the crack propagation rate of about 2 orders of magnitude for the plain and modified cement prepared in air or under a vacuum. Porosity did not have any noticeable effect on the fatigue crack propagation behavior of the cement.
Bouderba, Yasmina; Nait Amor, Samir; Tribeche, Mouloud
2015-04-01
The VLF radio waves propagating in the Earth-Ionosphere waveguide are sensitive to the ionospheric disturbances due to X rays solar flux. In order to understand the VLF signal response to the solar flares, the LWPC code is used to simulate the signal perturbation parameters (amplitude and phase) at fixed solar zenith angle. In this work, we used the NRK-Algiers signal data and the study was done for different flares classes. The results show that the perturbed parameters increase with the increasing solar flares flux. This increases is due to the growth of the electron density resulting from the changes of the Wait's parameters. However, the behavior of the perturbation parameters as function of distance shows different forms of signal perturbations. It was also observed that the null points move towards the transmitter location when the flare flux increases which is related to the modal composition of the propagating signal. Effectively, for a given mode, the plot of the attenuation coefficient as function of the flare flux shows a decreases when the flux increases which is more significant for high modes. Thus, the solar flares effect is to amplify the VLF signal by reducing the attenuation coefficient.
Turbofan Duct Propagation Model
Lan, Justin H.; Posey, Joe W. (Technical Monitor)
2001-01-01
The CDUCT code utilizes a parabolic approximation to the convected Helmholtz equation in order to efficiently model acoustic propagation in acoustically treated, complex shaped ducts. The parabolic approximation solves one-way wave propagation with a marching method which neglects backwards reflected waves. The derivation of the parabolic approximation is presented. Several code validation cases are given. An acoustic lining design process for an example aft fan duct is discussed. It is noted that the method can efficiently model realistic three-dimension effects, acoustic lining, and flow within the computational capabilities of a typical computer workstation.
Energy Technology Data Exchange (ETDEWEB)
Kochhar, Sunita; Singh, S.P.; Kochhar, V.K. [National Botanical Research Institute, Lucknow 226001 (India)
2008-12-15
Rooting and sprouting behaviour of stem cuttings of biofuel plant Jatropha curcas and their performance under field conditions have been studied in relation to auxin application. Pretreatment with indole-3-butyric acid (IBA) and 1-naphthalene acetic acid (NAA) increased both the rooting and sprouting. Sprouting of buds on the cuttings preceded rooting. The rooting and sprouting in J. curcas was more with IBA than NAA. The endogenous auxin contents were found to increase almost 15 days prior to rooting, indicating that mobilization of auxin rather than the absolute contents of auxin may be involved in root initiation. Indole acetic acid oxidase (IAA-oxidase) seems to be involved for triggering and initiating the roots/root primordia, whereas peroxidase is involved in both root initiation and the elongation processes as supported by the peroxidase and IAA-oxidase isoenzyme analysis in the cuttings. The clonally propagated plants (cutting-raised plants) performed better in the field as compared to those raised from the seeds. The plants produced from auxin-treated cuttings produced fruits and seeds in the same year as compared to the plants raised from seeds or from untreated or control cuttings that did not produce any seeds in 1 year of this study. Jatropha plants in general produce seeds after 2-3 years. (author)
Effect of hydrogen bond anharmonicity on supersonic discrete Davydov soliton propagation.
Cisneros-Ake, Luis A; Minzoni, A A
2012-02-01
We consider the propagation of energy along a protein chain in the Davydov approximation. We study the fully discrete Davydov equations including the anharmonic corrections in the hydrogen bond potential and find approximate variational solutions. We show analytically that for the harmonic interaction of the hydrogen bonds of the Davydov model the waves travel with velocities less than half the sound velocity for the relevant biological parameters. We find, for weak nonlinearity of the hydrogen bonds, two branches of soliton solutions. The first one gives a new type of strongly stable cusped discrete supersonic soliton. The second branch captures the main component of a more complicated breather solution compared to the one studied by Gaididei et al. and reproduces the Davydov soliton of the continuum limit. These results show the possibility of coherent protein chain deformation due to the anharmonicity of the hydrogen bond interactions. These supersonic waves are shown to provide a viable mechanism for energy transport in spite of the temperature influence in the soliton lifetime. © 2012 American Physical Society
Tan, Chee Ghuan; Chia, Wei Ting; Majid, Taksiah A.; Nazri, Fadzli Mohamed; Adiyanto, Mohd Irwan
2017-10-01
On 5th June 2015, a moderate earthquake with Mw 5.9 hit Ranau, resulted in damages of the existing non-seismically designed buildings, such that 61 buildings, including mosques, schools, hospitals and Ranau police headquarters were suffered from different level structural damages. Soft storey irregularity is one of the main reasons of the building damage. This study is to investigate the soft-story effect on the propagation path of plastic hinges RC building under seismic excitation. The plastic hinges formation and seismic performance of five moment resisting RC frames with different infill configurations are studied. The seismic performance of building is evaluated by Incremental Dynamic Analysis (IDA). Open ground soft storey structure shows the lowest seismic resistance, collapses at 0.55g pga. The maximum interstorey drift ratio (IDRmax) in soft storey buildings ranging from 0.53% to 2.96% which are far greater than bare frame ranging from 0.095% to 0.69%. The presence of infill walls creates stiffer upper stories causing moments concentrate at the soft storey, resulting the path of plastic hinge propagation is dominant at the soft storey columns. Hence, the buildings with soft storey are very susceptible under earthquake load.
Tanida, Isei; Shirasago, Yoshitaka; Suzuki, Ryosuke; Abe, Ryo; Wakita, Takaji; Hanada, Kentaro; Fukasawa, Masayoshi
2015-01-01
Multipurpose cohort studies have demonstrated that coffee consumption reduces the risk of hepatocellular carcinoma (HCC). Given that one of the main causes of HCC is hepatitis C virus (HCV) infection, we examined the effect of caffeic acid, a major organic acid derived from coffee, on the propagation of HCV using an in vitro naïve HCV particle-infection and production system within human hepatoma-derived Huh-7.5.1-8 cells. When cells were treated with 1% coffee extract or 0.1% caffeic acid for 1-h post HCV infection, the amount of HCV particles released into the medium at 3 and 4 days post-infection considerably decreased. In addition, HCV-infected cells cultured with 0.001% caffeic acid for 4 days, also released less HCV particles into the medium. Caffeic acid treatment inhibited the initial stage of HCV infection (i.e., between virion entry and the translation of the RNA genome) in both HCV genotypes 1b and 2a. These results suggest that the treatment of cells with caffeic acid may inhibit HCV propagation.
Directory of Open Access Journals (Sweden)
Sulistyani Pancaningtyas
2012-05-01
Full Text Available Various efforts have been developed for the optimization of the various stages in vitro micropropagation. The maturation stage and pre-acclimatization plantlets is an important stages that must be considered to produce vigorous plants and ready to be planted in the field. The purpose of this study was to reduced shoot tip necrosis in cocoa planlets to obtaine vigorous planlets from in vitro propagation through the addition of Calcium Chloride (CaCl2. The study used two stages of embryogenic development. The first was embryo maturation stage and the second was the shoot growth development stage. The study was arranged factorially in experiment design of Completely Randomized Design consisting of two factors i.e. concentration of CaCl2 consisted of 0, 50, 100, 150, and 200 mg/l and clones consisted of Sulawesi 1 and Sca 6. Each experiment was repeated three times, so the number of combination trials were 5x2x3=30 experimental units. The parameters observed included shoot growth percentage and vigorous planlets percentage. The results showed that the addition of CaCl2 at a concentration of 150 mg/l during maturition stage increased the embryos performance and percentage of shoot tip. However, it could not prevent the shoot tip necrosis. Whereas, the addition at a concentration of 50 mg/l during the shoot m growth development stage could reduced necrosis, suggested to increase the quality of in vitro planlets.Key words: Cocoa, necrosis, calcium chloride, somatic embryogenesis, embryos, planlets, in vitro.
Truncation effects in superdiffusive front propagation with Lévy flights.
Del-Castillo-Negrete, D
2009-03-01
A numerical and analytical study of the role of exponentially truncated Lévy flights in the superdiffusive propagation of fronts in reaction-diffusion systems is presented. The study is based on a variation of the Fisher-Kolmogorov equation where the diffusion operator is replaced by a lambda -truncated fractional derivative of order alpha , where 1lambda is the characteristic truncation length scale. For lambda=0 there is no truncation, and fronts exhibit exponential acceleration and algebraically decaying tails. It is shown that for lambda not equal0 this phenomenology prevails in the intermediate asymptotic regime (chit);{1alpha}x1lambda where chi is the diffusion constant. Outside the intermediate asymptotic regime, i.e., for x>1lambda , the tail of the front exhibits the tempered decay varphi approximately e;{-lambdax}x;{(1+alpha)} , the acceleration is transient, and the front velocity v_{L} approaches the terminal speed v_{*}=(gamma-lambda;{alpha}chi)lambda as t-->infinity , where it is assumed that gamma>lambda;{alpha}chi with gamma denoting the growth rate of the reaction kinetics. However, the convergence of this process is algebraic, v_{L} approximately v_{*}-alpha(lambdat) , which is very slow compared to the exponential convergence observed in the diffusive (Gaussian) case. An overtruncated regime in which the characteristic truncation length scale is shorter than the length scale of the decay of the initial condition, 1nu , is also identified. In this extreme regime, fronts exhibit exponential tails, varphi approximately e;{-nux} , and move at the constant velocity v=(gamma-lambda;{alpha}chi)nu .
Knutsson, Magnus; Åbom, Mats
2009-02-01
Charge air coolers (CACs) are used on turbocharged internal combustion engines to enhance the overall gas-exchange performance. The cooling of the charged air results in higher density and thus volumetric efficiency. It is also important for petrol engines that the knock margin increases with reduced charge air temperature. A property that is still not very well investigated is the sound transmission through a CAC. The losses, due to viscous and thermal boundary layers as well as turbulence, in the narrow cooling tubes result in frequency dependent attenuation of the transmitted sound that is significant and dependent on the flow conditions. Normally, the cross-sections of the cooling tubes are neither circular nor rectangular, which is why no analytical solution accounting for a superimposed mean flow exists. The cross-dimensions of the connecting tanks, located on each side of the cooling tubes, are large compared to the diameters of the inlet and outlet ducts. Three-dimensional effects will therefore be important at frequencies significantly lower than the cut-on frequencies of the inlet/outlet ducts. In this study the two-dimensional finite element solution scheme for sound propagation in narrow tubes, including the effect of viscous and thermal boundary layers, originally derived by Astley and Cummings [Wave propagation in catalytic converters: Formulation of the problem and finite element scheme, Journal of Sound and Vibration 188 (5) (1995) 635-657] is used to extract two-ports to represent the cooling tubes. The approximate solutions for sound propagation, accounting for viscothermal and turbulent boundary layers derived by Dokumaci [Sound transmission in narrow pipes with superimposed uniform mean flow and acoustic modelling of automobile catalytic converters, Journal of Sound and Vibration 182 (5) (1995) 799-808] and Howe [The damping of sound by wall turbulent shear layers, Journal of the Acoustical Society of America 98 (3) (1995) 1723-1730], are
Domínguez, Macarena; Muñoz, Víctor; Valdivia, Juan Alejandro
2012-05-01
The propagation of circularly polarized electromagnetic waves along a constant background magnetic field in an electron-positron plasma is calculated by means of both a fluid and a kinetic theory treatment. In the fluid theory, relativistic effects are included in the particle motion, the wave field, and in the thermal motion by means of a function f, which depends only on the plasma temperature. In this work we analyze the consistency of the fluid results with those obtained from a kinetic treatment, based on the relativistic Vlasov equation. The corresponding kinetic dispersion relation is numerically studied for various temperatures, and results are compared with the fluid treatment. Analytic expressions for the Alfvén velocity are obtained for the fluid and kinetic models, and it is shown that, in the kinetic treatment, the Alfvén branch is suppressed for large temperatures.
Energy Technology Data Exchange (ETDEWEB)
Bergeaud, V.; La Hargue, J.P.; Mougery, F. [CS Communication and Systemes, 92 - Clamart (France); Benisti, D.; Comte, M.; Gauthier, P.; Lamare, J. de; Le Fur, J.F.; Petit, A. [CEA Saclay, 91 - Gif sur Yvette (France); Boulet, M.; Scheurer, B. [CEA Bruyeres le Chatel, 91 (France)
2003-07-01
In the frame of the research carried out in the SILVA project, simulation codes have been developed to study the interaction of a laser beam with a vapor containing two species having different atomic structures, one of these species being resonant with the laser frequency. The PRODIGE project consisted in an improvement over the existing codes that were aimed at accelerating the code and reaching the simulation of 3-dimensional effects. The improvements had two aspects: numerical improvement and parallelization. This paper focuses on numerical improvements. These were achieved thanks to an implicit scheme coupling the propagation of the laser and the time evolution of the non-resonant species in the vapor. For similar accuracies, the computation time was decreased by a factor of 40 as compared to predictor corrector integration schemes. (authors)
Size effect in self-propagating exothermic reaction of Al/Ni multilayer block on a Si wafer
Namazu, Takahiro; Ito, Shun; Kanetsuki, Shunsuke; Miyake, Shugo
2017-06-01
In this paper, the threshold size of sputtered Al/Ni multilayer blocks required for inducing a self-propagating exothermic reaction on a Si wafer is described. An Al/Ni multilayer film with a bilayer thickness of 100 nm is deposited on a Si wafer, and then micronsized Al/Ni multilayer blocks from the film are fabricated using a focused ion beam. By inducing small sparks in the vicinity of the blocks, we investigate reactivity. From scanning electron microscopy observations, we confirm that Al/Ni multilayer blocks with high aspect ratios and small widths can react easily. The effect of Al/Ni multilayer block size on reactivity is discussed from the viewpoint of heat conduction from the block to a Si wafer during an exothermic reaction.
The propagation effect of paper version and the iPad version for periodicals
Directory of Open Access Journals (Sweden)
Cong Zhang
2015-04-01
Full Text Available Purpose: Digital journal created a new development pattern. We use journal APP as an example to analyze how to migrate the journal content to Internet and other kind of media. Based on the case study of GQ and other fashion magazines, through text analysis, control experiments, in-depth interviews and other research methods, the authors analyzed the differences and connections between the iPad App and print edition of magazines, discussed the approaches towards operation of new media, offered the tendency of mobile device platform development for China’s periodical publications. Design/methodology/approach: control experiment. Findings: The authors give a stance that the print edition of periodical publication will being alive still, and conclude that journal APP and printed version can be mutually beneficial and achieve a win-win state. And we believe that the journal APP is good at advertising propagation, which will accelerate the development of journal APP in such the information age, and such kind of media can integrate many information with variety of media forms. Research limitations/implications: Because of the limitation of technology, the authors only have the experiment on fashion magazine, which might to some degree simplify the issue under discussion. Practical implications: According to the conclusion of a series of experiments, we can imply the future of the media, and give the suggestion of both paper version and ipad version of the journal. Social implications: Since people can not live without media and media has to develope with the help of public, we have to give the new way of both sunrise media and sunset media. Originality/value: Based on the case study of GQ and other fashion magazines, through text analysis, control experiments, in-depth interviews and other research methods, the authors analyzed the differences and connections between the iPad App and print edition of magazines, discussed the approaches towards
Energy Technology Data Exchange (ETDEWEB)
Damiano, P. A. [Princeton Center for Heliophysics, Princeton Plasma Physics Laboratory, Princeton University, Princeton New Jersey USA; Johnson, J. R. [Princeton Center for Heliophysics, Princeton Plasma Physics Laboratory, Princeton University, Princeton New Jersey USA; Chaston, C. C. [Space Sciences Laboratory, University of California, Berkeley California USA; School of Physics, University of Sydney, Sydney New South Wales Australia
2015-07-01
A new 2-D self-consistent hybrid gyrofluid-kinetic electron model in dipolar coordinates is presented and used to simulate dispersive-scale Alfvén wave pulse propagation from the equator to the ionosphere along an L = 10 magnetic field line. The model is an extension of the hybrid MHD-kinetic electron model that incorporates ion Larmor radius corrections via the kinetic fluid model of Cheng and Johnson (1999). It is found that consideration of a realistic ion to electron temperature ratio decreases the propagation time of the wave from the plasma sheet to the ionosphere by several seconds relative to a ρi=0 case (which also implies shorter timing for a substorm onset signal) and leads to significant dispersion of wave energy perpendicular to the ambient magnetic field. Additionally, ion temperature effects reduce the parallel current and electron energization all along the field line for the same magnitude perpendicular electric field perturbation.
Uncertainty Propagation in OMFIT
Smith, Sterling; Meneghini, Orso; Sung, Choongki
2017-10-01
A rigorous comparison of power balance fluxes and turbulent model fluxes requires the propagation of uncertainties in the kinetic profiles and their derivatives. Making extensive use of the python uncertainties package, the OMFIT framework has been used to propagate covariant uncertainties to provide an uncertainty in the power balance calculation from the ONETWO code, as well as through the turbulent fluxes calculated by the TGLF code. The covariant uncertainties arise from fitting 1D (constant on flux surface) density and temperature profiles and associated random errors with parameterized functions such as a modified tanh. The power balance and model fluxes can then be compared with quantification of the uncertainties. No effort is made at propagating systematic errors. A case study will be shown for the effects of resonant magnetic perturbations on the kinetic profiles and fluxes at the top of the pedestal. A separate attempt at modeling the random errors with Monte Carlo sampling will be compared to the method of propagating the fitting function parameter covariant uncertainties. Work supported by US DOE under DE-FC02-04ER54698, DE-FG2-95ER-54309, DE-SC 0012656.
Kotova, Daria; Klimenko, Maxim; Klimenko, Vladimir; Zakharov, Veniamin
2013-04-01
In this work we have investigated the global ionospheric response to geomagnetic storm on May 2-3, 2010 using GSM TIP (Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere) simulation results. In the GSM TIP storm time model runs, several input parameters such as cross-polar cap potential difference and R2 FAC (Region 2 Field-Aligned Currents) varied as a function of the geomagnetic activity AE-index. Current simulation also uses the empirical model of high-energy particle precipitation by Zhang and Paxton. In this model, the energy and energy flux of precipitating electrons depend on a 3 hour Kp-index. We also have included the 30 min time delay of R2 FAC variations with respect to the variations of cross-polar cap potential difference. In addition, we use the ground-based ionosonde data for comparison our model results with observations. We present an analysis of the physical mechanisms responsible for the ionospheric effects of geomagnetic storms. The obtained simulation results are used by us as a medium for HF radio wave propagation at different latitudes in quiet conditions, and during main and recovery phase of a geomagnetic storm. To solve the problem of the radio wave propagation we used Zakharov's (I. Kant BFU) model based on geometric optics. In this model the solution of the eikonal equation for each of the two normal modes is reduced using the method of characteristics to the integration of the six ray equation system for the coordinates and momentum. All model equations of this system are solved in spherical geomagnetic coordinate system by the Runge-Kutta method. This model was tested for a plane wave in a parabolic layer. In this study, the complex refractive indices of the ordinary and extraordinary waves at ionospheric heights was calculated for the first time using the global first-principal model of the thermosphere-ionosphere system that describes the parameters of an inhomogeneous anisotropic medium during a
Curri, Vittorio; Gaudino, Roberto
2013-01-01
We analyze propagation effects in the coexistence of GPON, XG-PON, RF-Video and TWDM-PON. We show that high power TWDM-PON channels excite Stimulated Raman Scattering inducing extra-loss on GPON due to power depletion. We address the problem through simulations and propose and validate a simple analytical model for the effect
Lysak, T. M.; Trofimov, V. A.
2016-09-01
Based on computer simulation, we demonstrate the possibility of formation of solitons upon propagation of a femtosecond laser pulse in a medium containing gold nanoparticles in the presence of two-photon light absorption. The solitons are formed when the laser pulse induces a positive phase grating. The speed of solitons substantially exceeds the speed of laser radiation propagating in a linear medium.
Greenberg, N. L.; Castro, P. L.; Drinko, J.; Garcia, M. J.; Thomas, J. D.
2000-01-01
Color M-mode echocardiography has recently been utilized to describe diastolic flow propagation velocity (Vp) in the left ventricle. While increasing temporal resolution from 15 to 200 Hz, this M-mode technique requires the user to select a single scanline, potentially limiting quantification of Vp due to the complex three-dimensional inflow pattern. We previously performed computational fluid dynamics simulations to demonstrate the insignificance of the scanline orientation, however geometric complexity was limited. The purpose of this study was to utilize high frame-rate 2D color Doppler images to investigate the importance of scanline selection in patients for the quantification of Vp. 2D color Doppler images were digitally acquired at 50 frames/s in 6 subjects from the apical 4-chamber window (System 5, GE/Vingmed, Milwaukee, WI). Vp was determined for a set of scanlines positioned through 5 locations across the mitral annulus (from the anterior to posterior mitral annulus). An analysis of variance was performed to examine the differences in Vp as a function of scanline position. Vp was not effected by scanline position in sampled locations from the center of the mitral valve towards the posterior annulus. Although not statistically significant, there was a trend to slower propagation velocities on the anterior side of the valve (60.8 +/- 16.7 vs. 54.4 +/- 13.6 cm/s). This study clinically validates our previous numerical experiment showing that Vp is insensitive to small perturbations of the scanline through the mitral valve. However, further investigation is necessary to examine the impact of ventricular geometry in pathologies including dilated cardiomyopathy.
Effect of surface deposits on electromagnetic waves propagating in uniform ducts
Baumeister, Kenneth J.
1990-01-01
A finite-element Galerkin formulation was used to study the effect of material surface deposits on the reflective characteristics of straight uniform ducts with PEC (perfectly electric conducting) walls. Over a wide frequency range, the effect of both single and multiple surface deposits on the duct reflection coefficient were examined. The power reflection coefficient was found to be significantly increased by the addition of deposits on the wall.
49 CFR 195.111 - Fracture propagation.
2010-10-01
... 49 Transportation 3 2010-10-01 2010-10-01 false Fracture propagation. 195.111 Section 195.111... PIPELINE Design Requirements § 195.111 Fracture propagation. A carbon dioxide pipeline system must be designed to mitigate the effects of fracture propagation. [Amdt. 195-45, 56 FR 26926, June 12, 1991] ...
Calculations of precursor propagation in dispersive dielectrics.
Energy Technology Data Exchange (ETDEWEB)
Bacon, Larry Donald
2003-08-01
The present study is a numerical investigation of the propagation of electromagnetic transients in dispersive media. It considers propagation in water using Debye and composite Rocard-Powles-Lorentz models for the complex permittivity. The study addresses this question: For practical transmitted spectra, does precursor propagation provide any features that can be used to advantage over conventional signal propagation in models of dispersive media of interest? A companion experimental study is currently in progress that will attempt to measure the effects studied here.
Shallow water sound propagation with surface waves.
Tindle, Chris T; Deane, Grant B
2005-05-01
The theory of wavefront modeling in underwater acoustics is extended to allow rapid range dependence of the boundaries such as occurs in shallow water with surface waves. The theory allows for multiple reflections at surface and bottom as well as focusing and defocusing due to reflection from surface waves. The phase and amplitude of the field are calculated directly and used to model pulse propagation in the time domain. Pulse waveforms are obtained directly for all wavefront arrivals including both insonified and shadow regions near caustics. Calculated waveforms agree well with a reference solution and data obtained in a near-shore shallow water experiment with surface waves over a sloping bottom.
Mandatori, Antonio; Bertolotti, Mario; Sibilia, Concita; Hoenders, Bert J.; Scalora, Michael
2007-01-01
The effect of the coherence of a beam traveling through a photonic ID structure coupled with a rough glass is studied. The analysis is made for the case of spatial coherence showing the possibility to determine the coherence characteristics of the beam by an examination of the output field. We have
Size effects in quantum well nanostructures on propagation of light pulse
Energy Technology Data Exchange (ETDEWEB)
Golestani, Ali, E-mail: aligolestani.sh@gmail.com [Research Institute for Applied Physics and Astronomy, University of Tabriz, Tabriz (Iran, Islamic Republic of); Hamedi, H.R., E-mail: Hamid.R.Hamedi@gmail.com [Institute of Theoretical Physics and Astronomy, Vilnius University, A. Gostauto 12, LT-01108 Vilnius (Lithuania); Darkhosh, Ahad [Physics Department, Ataturk University, Erzurum (Turkey)
2015-01-01
In this paper, the effect of dimension on dispersion and absorption properties in an AlGaAs/GaAs quantum well (QW) nanostructure is investigated. We use the conduction-band Hamiltonian to calculate the envelope functions and the eigenenergies. The Schrödinger equation is solved numerically using homemade codes. Then we employ the density matrix formalism to evaluate the behavior of optical susceptibly. The impact of the width of the well and the barrier on the linear optical susceptibility behavior is explored. This investigation can be used for the optimal design of quantum well nanostructures to achieve electromagnetically induced transparency, which is much more practical than atomic structures because of their flexible design and the controllable quantum coherence effects.
Directory of Open Access Journals (Sweden)
S. Maekawa
2006-09-01
Full Text Available A superimposed epoch analysis has been undertaken, in order to find the correlation of the ionospheric perturbations with seismic activity. We take the wave path from the Japanese LF transmitter (frequency=40 kHz and an observing station of Kochi (wave path length of 770 km, and a much longer period (of five years than before, is considered. This subionospheric LF propagation can be called "an integrated measurement" in the sense that any earthquakes in the LF sensitive area just around the great-circle path can influence the observed LF signals, so that we define the "effective magnitude" (Meff by integrating the total energy from different earthquakes in the sensitive area on a current day and by converting it back into magnitude. A superimposed epoch analysis for the effective magnitude greater than 6.0 has yielded that the ionosphere is definitely disturbed in terms of both amplitude and dispersion, and that these perturbations tend to take place prior to an earthquake. The statistical z-test has also been performed, which has indicated that the amplitude is definitely depleted 2–6 days before the earthquake day and also that the dispersion is very much enhanced during the same period. This statistical study has given strong support to the existence of seismo-ionospheric perturbations for high seismic activity.
Biofuel effect on flame propagation and soot formation in a DISI engine
Irimescu, A.; Merola, S. S.; Di Iorio, S.; Vaglieco, B. M.
2017-10-01
The use of biofuels, especially in transportation and industrial processes, is seen as one of the most effective solutions to promote the reduction of greenhouse gases and pollutant emissions, as well as to lighten the dependence from petro-fuel producers. Biofuels are defined as a wide range of energy sources derived from biomass. In this category, alcohols produced through fermentation, such as ethanol and butanol, are considered some of the most suitable alternatives for transportation purposes. The benefits of bio-ethanol addition to gasoline have always been recognized for practical reasons. Apart from the variety of sources which it can be produced from, ethanol can raise the octane rating, given its improved anti-knock characteristics, allowing the use of higher compression ratios and higher thermal efficiency. However, ethanol’s high latent heat of vaporization can cause problems during cold-start due to poor evaporation. On the other hand, in hot climates ethanol fuelling can result in adverse effects such as vapour lock. Butanol can be considered as an emergent alternative fuel. Normal butanol has several well-known advantages when compared to ethanol, including increased energy content, greater miscibility with transportation fuels, and lower propensity for water absorption. Despite of these pros, the costs of n-butanol production are higher due to lower yields compared to ethanol. Moreover, vaporization remains a critical aspect of this biofuel. Understanding the effect of biofuels on in-cylinder combustion processes is a key-point for the optimization of fuel flexibility and achieving lower CO2 emissions. To this aim, a combined thermodynamic and optical investigation was performed on a direct injection spark ignition engine fuelled with ethanol, butanol and gasoline. Fuels were compared by fixing the injection and spark ignition strategies. Thermodynamic measurements were coupled with optical investigations based on cycle resolved flame
Particle propagation in cosmological backgrounds
Arteaga, Daniel
2007-01-01
We study the quantum propagation of particles in cosmological backgrounds, by considering a doublet of massive scalar fields propagating in an expanding universe, possibly filled with radiation. We focus on the dissipative effects related to the expansion rate. At first order, we recover the expected result that the decay rate is determined by the local temperature. Beyond linear order, the decay rate has an additional contribution governed by the expansion parameter. This latter contribution is present even for stable particles in the vacuum. Finally, we analyze the long time behaviour of the propagator and briefly discuss applications to the trans-Planckian question.
Energy Technology Data Exchange (ETDEWEB)
Alonzo, F. [Laboratory of Environmental Modelling, DEI/SECRE/LME, Institute of Radioprotection and Nuclear Safety (IRSN), Cadarache, Building 159, BP3, 13115 St-Paul-lez-Durance Cedex (France); Laboratory of Radioecology and Ecotoxicology, DEI/SECRE/LRE, Institute of Radioprotection and Nuclear Safety (IRSN), Cadarache Building 186, BP3, 13115 St-Paul-lez-Durance Cedex (France)], E-mail: frederic.alonzo@irsn.fr; Hertel-Aas, T. [Department of Plant and Environmental Sciences, P.O. Box 5003, Norwegian University of Life Sciences, 1432 Aas (Norway); Gilek, M. [School of Life Sciences, Soedertoern University College, 14189 Huddinge (Sweden); Gilbin, R. [Laboratory of Radioecology and Ecotoxicology, DEI/SECRE/LRE, Institute of Radioprotection and Nuclear Safety (IRSN), Cadarache Building 186, BP3, 13115 St-Paul-lez-Durance Cedex (France); Oughton, D.H. [Department of Plant and Environmental Sciences, P.O. Box 5003, Norwegian University of Life Sciences, 1432 Aas (Norway); Garnier-Laplace, J. [Laboratory of Radioecology and Ecotoxicology, DEI/SECRE/LRE, Institute of Radioprotection and Nuclear Safety (IRSN), Cadarache Building 186, BP3, 13115 St-Paul-lez-Durance Cedex (France)
2008-09-15
This study evaluated the potential effect of ionising radiation on population growth using simple population models and parameter values derived from chronic exposure experiments in two invertebrate species with contrasting life-history strategies. In the earthworm Eisenia fetida, models predicted increasing delay in population growth with increasing gamma dose rate (up to 0.6 generation times at 11 mGy h{sup -1}). Population extinction was predicted at 43 mGy h{sup -1}. In the microcrustacean Daphnia magna, models predicted increasing delay in population growth with increasing alpha dose rate (up to 0.8 generation times at 15.0 mGy h{sup -1}), only after two successive generations were exposed. The study examined population effects of changes in different individual endpoints (including survival, number of offspring produced and time to first reproduction). Models showed that the two species did not respond equally to equivalent levels of change, the fast growing daphnids being more susceptible to reduction in fecundity or delay in reproduction than the slow growing earthworms. This suggested that susceptibility of a population to ionising radiation cannot be considered independent of the species' life history.
Lewis, Matthew; Nelson, Christopher
2012-02-01
Co-propagation of two circularly polarized lasers in an electromagnetically induced transparency four-level W scheme is investigated. Our four level system is produced using the ground state and three Zeeman levels of ultracold magnesium atoms. Parameters are determined such that co-propagation of the two incident optical fields will occur. Group velocities obtained by solving the density matrix master equation for the appropriate coherences are found to be periodic with respect to the phase angle of the Rabi frequency.
1985-11-01
region", Thrane - gives a good revlei ot the salient media effects. Session 11 -Pa er 2.2. Dr. J. A. Klobuchar , et al., "Total electron content and L-band...Ionosphere J. A. Klobuchar , G. J. Bishop, AFGL Hanscom AFB, MA and D. H. Doherty, Emmanuel College, Boston, MA, US 1200 2.3. Variability of...C. Lee, MIT, Cambridge, MA, J. A. Klobuchar and H. C. Carlson, AFGL, Hancom AFB, MA. US 1130 7.7. Direct In-Situ Measurements of Turbulent Zones in
Paolo Delsanto, Pier; Hirsekorn, Sigrun
2004-04-01
Recent experiments on rocks and other materials, such as soil, cement, concrete and damaged elastic materials, have led to the discovery of nonlinear (NL) hysteretic effects in their elastic behaviour. These observations suggest the existence of a NL mesoscopic elasticity universality class, to which all the aforementioned materials belong. The purpose of the present contribution is to search for the basic mathematical roots for nonclassical nonlinearity, in order to explain its universality, classify it and correlate it with the underlying meso- or microscopic interaction mechanisms. In our discussions we explicitly consider two quite different kinds of specimens: a two-bonded-elements structure and a thin multigrained bar. It is remarkable that, although the former includes only one interface and the latter very many interstices, the same "interaction box" formalism can be applied to both. Another important result of the proposed formalism is that the spectral contents of an arbitrary system for any input amplitude may be predicted, under certain assumptions, from the result of a single experiment at a higher amplitude.
Effect of Temperature on Ultrasonic Signal Propagation for Extra Virgin Olive Oil Adulteration
Alias, N. A.; Hamid, S. B. Abdul; Sophian, A.
2017-11-01
Fraud cases involving adulteration of extra virgin olive oil has become significant nowadays due to increasing in cost of supply and highlight given the benefit of extra virgin olive oil for human consumption. This paper presents the effects of temperature variation on spectral formed utilising pulse-echo technique of ultrasound signal. Several methods had been introduced to characterize the adulteration of extra virgin olive oil with other fluid sample such as mass chromatography, standard method by ASTM (density test, distillation test and evaporation test) and mass spectrometer. Pulse-echo method of ultrasound being a non-destructive method to be used to analyse the sound wave signal captured by oscilloscope. In this paper, a non-destructive technique utilizing ultrasound to characterize extra virgin olive oil adulteration level will be presented. It can be observed that frequency spectrum of sample with different ratio and variation temperature shows significant percentages different from 30% up to 70% according to temperature variation thus possible to be used for sample characterization.
Effect of culture medium on propagation and phenotype of corneal stroma-derived stem cells.
Sidney, Laura E; Branch, Matthew J; Dua, Harminder S; Hopkinson, Andrew
2015-12-01
The limbal area of the corneal stroma has been identified as a source of mesenchymal-like stem cells, which have potential for exploitation as a cell therapy. However, the optimal culture conditions are disputed and few direct media comparisons have been performed. In this report, we evaluated several media types to identify the optimal for inducing an in vitro stem cell phenotype. Primary human corneal stroma-derived stem cells (CSSCs) were extracted from corneoscleral rims. Culture in seven different media types was compared: Dulbecco's modified Eagle's medium (DMEM) with 10% fetal bovine serum (FBS); M199 with 20% FBS; DMEM-F12 with 20% serum replacement, basic fibroblast growth factor and leukemia inhibitory factor (SCM); endothelial growth medium (EGM); semi-solid MethoCult; serum-free keratinocyte medium (K-SFM); and StemPro-34. Effects on proliferation, morphology, protein and messenger RNA expression were evaluated. All media supported proliferation of CSSCs with the exception of K-SFM and StemPro-34. Morphology differed between media: DMEM produced large cells, whereas EGM produced very small cells. Culture in M199 produced a typical mesenchymal stromal cell phenotype with high expression of CD105, CD90 and CD73 but not CD34. Culture in SCM produced a phenotype more reminiscent of a progenitor cell type with expression of CD34, ABCG2, SSEA-4 and PAX6. Culture medium can significantly influence CSSC phenotype. SCM produced a cell phenotype closest to that of a pluripotent stem cell, and we consider it to be the most appropriate for development as a clinical-grade medium for the production of CSSC phenotypes suitable for cell therapy. Copyright © 2015 International Society for Cellular Therapy. Published by Elsevier Inc. All rights reserved.
Inhibition Effect of Alpha-Lipoic Acid on the Propagation of Influenza A Virus in MDCK Cells
Directory of Open Access Journals (Sweden)
Si-Wei Bai§, Cui-Ying Chen§, Jun Ji, Qing-Mei Xie*, Yun Ma1, Bao-Li Sun, Chun-Yi Xue1, Yong-Chang Cao1, Jing-Yun Ma and Ying-Zuo Bi
2012-01-01
Full Text Available Influenza A viruses (IAV still pose a threat to animals and humans. Currently, M2 protein ion channel inhibitors and neuraminidase inhibitors are the two main drugs for treating IAV infections by interrupting virus assembly or release respectively, but the emergence of viral resistance was a concern for their long term uses. In this study, the inhibition effect of alpha-lipoic acid (α-LA on IAV propagation has been evaluated in vitro. The results showed that α-LA inhibited IAV replication in MDCK cells at 2mM, and also reduced nucleus translocation of nuclear factor κB (NF-κB p65 at the concentration above 1mM. Additionally, it was found that caspase-3 activity was remarkably inhibited and type I interferons (IFNs were up-regulated following α-LA treatment. This study indicated that α-LA might be a potential anti-influenza virus agent worthy of further investigations.
Transionospheric Propagation Code (TIPC)
Roussel-Dupre, Robert; Kelley, Thomas A.
1990-10-01
The Transionospheric Propagation Code is a computer program developed at Los Alamos National Lab to perform certain tasks related to the detection of VHF signals following propagation through the ionosphere. The code is written in FORTRAN 77, runs interactively and was designed to be as machine independent as possible. A menu format in which the user is prompted to supply appropriate parameters for a given task has been adopted for the input while the output is primarily in the form of graphics. The user has the option of selecting from five basic tasks, namely transionospheric propagation, signal filtering, signal processing, delta times of arrival (DTOA) study, and DTOA uncertainty study. For the first task a specified signal is convolved against the impulse response function of the ionosphere to obtain the transionospheric signal. The user is given a choice of four analytic forms for the input pulse or of supplying a tabular form. The option of adding Gaussian-distributed white noise of spectral noise to the input signal is also provided. The deterministic ionosphere is characterized to first order in terms of a total electron content (TEC) along the propagation path. In addition, a scattering model parameterized in terms of a frequency coherence bandwidth is also available. In the second task, detection is simulated by convolving a given filter response against the transionospheric signal. The user is given a choice of a wideband filter or a narrowband Gaussian filter. It is also possible to input a filter response. The third task provides for quadrature detection, envelope detection, and three different techniques for time-tagging the arrival of the transionospheric signal at specified receivers. The latter algorithms can be used to determine a TEC and thus take out the effects of the ionosphere to first order. Task four allows the user to construct a table of DTOAs vs TECs for a specified pair of receivers.
In clonally propagated crops, non-additive genetic effects can be effectively exploited by the identification of superior genetic individuals as varieties. Cassava (Manihot esculenta Crantz) is a clonally propagated staple food crop that feeds hundreds of millions. We quantified the amount and natur...
1974-09-13
radii of 0.5, I., 3., 5. and 10. Mm. The slope discontinuities appearing on the curves are not real but are a result of the plotting...and G. Hand, "Research on Atmospheric Optical Radiation Fransmi ssion", Johannes Gutenberg University, Mainz Germany, published as AFCRL-72
Zhang, Shifeng; Sheng, James J.
2017-11-01
Low-salinity water imbibition was considered an enhanced recovery method in shale oil/gas reservoirs due to the resulting hydration-induced fractures, as observed at ambient conditions. To study the effect of confining pressure and salinity on hydration-induced fractures, time-elapsed computerized tomography (CT) was used to obtain cross-sectional images of shale cores. Based on the CT data of these cross-sectional images, cut faces parallel to the core axial in the middle of the core and 3D fracture images were also reconstructed. To study the effects of confining pressure and salinity on shale pore fluid flowing, shale permeability was measured with Nitrogen (N2), distilled water, 4% KCl solution, and 8% KCl solution. With confining pressures increased to 2 MPa or more, either in distilled water or in KCl solutions of different salinities, fractures were observed to close instead to propagate at the end of the tests. The intrinsic permeabilities of #1 and #2 Mancos shale cores were 60.0 and 7000 nD, respectively. When tested with distilled water, the permeability of #1 shale sample with 20.0 MPa confining pressure loaded, and #2 shale sample with 2.5 MPa confining pressure loaded, decreased to 0.45 and 15 nD, respectively. Using KCl can partly mitigate shale permeability degradation. Compared to 4% KCl, 8% KCl can decrease more permeability damage. From this point of view, high salinity KCl solution should be required for the water-based fracturing fluid.
Channumsin, Sittiporn; Ceriotti, Matteo; Radice, Gianmarco
2018-02-01
A new type of space debris in near geosynchronous orbit (GEO) was recently discovered and later identified as exhibiting unique characteristics associated with high area-to-mass ratio (HAMR) objects, such as high rotation rates and high reflection properties. Observations have shown that this debris type is very sensitive to environmental disturbances, particularly solar radiation pressure, due to the fact that its motion depends on the actual effective area, orientation of that effective area, reflection properties and the area-to-mass ratio of the object is not stable over time. Previous investigations have modelled this type of debris as rigid bodies (constant area-to-mass ratios) or discrete deformed body; however, these simplifications will lead to inaccurate long term orbital predictions. This paper proposes a simple yet reliable model of a thin, deformable membrane based on multibody dynamics. The membrane is modelled as a series of flat plates, connected through joints, representing the flexibility of the membrane itself. The mass of the membrane, albeit low, is taken into account through lump masses at the joints. The attitude and orbital motion of this flexible membrane model is then propagated near GEO to predict its orbital evolution under the perturbations of solar radiation pressure, Earth's gravity field (J2), third body gravitational fields (the Sun and Moon) and self-shadowing. These results are then compared to those obtained for two rigid body models (cannonball and flat rigid plate). In addition, Monte Carlo simulations of the flexible model by varying initial attitude and deformation angle (different shape) are investigated and compared with the two rigid models (cannonball and flat rigid plate) over a period of 100 days. The numerical results demonstrate that cannonball and rigid flat plate are not appropriate to capture the true dynamical evolution of these objects, at the cost of increased computational time.
Directory of Open Access Journals (Sweden)
Sugiyatno A.
2017-10-01
Full Text Available Japansche citroen (JC rootstock is still the main choice for producing citrus seeds for its high availability and compatibility. Other rootstocks have been used in the production, yet they produce unsatisfying results. Based on the theory, there is an alternative to use rootstock as interstock in order to stimulate the growth of scion. The objective of this reseach is to understand the effect of interstock on the growth of Mandarin cv. Batu 55, Tangerine cv. Pontianak and Lime cv. Nimas. This research was conducted in the screen house of Tlekung Experimental Field of Indonesian Citrus and Subtropical Fruits Research Institute (ICSFRI in Batu-East Java, located on 950 m asl, from January to April 2016. This research was arranged in a CRD design with 4 replications and 24 interstock-scion combination treatments. The interstocks used in this study were Carizzo citrange, Citrumello, Poncirus trifoliata, Volkameriana, Rough lemon, Troyer citrange, Kanci and control (JC combined with 3 scions namely Mandarin cv. Batu 55, Tangerine cv. Pontianak and Lime cv. Nimas propagated by grafting. The result showed the percentage of successful grafting ranged between 37.5% to 100%, while the percentage of the shoot formed on grafted plants was 75%-100%. The use of Poncirus trifoliata as interstock has stimulated fastest bud break on Tangerine cv. Pontianak in just 24.75 days while the Troyer citrange has stimulated better shoot growth in Lime cv. Nimas, resulted to the highest shoot around 52.20 cm which was significantly different from other treatments. Meanwhile, Carizzo citrange has been found to have some influences to the plant diameter and the number of leave of Lime cv. Nimas but showed insignificant effect on the growth of its own diameter. The use of interstock showed that it can be used to promote the growth of scion which usually has slow growth when it is directly grafted on the rootstock.
The NASA radiowave propagation program
Davarian, Faramaz
The objectives of the NASA radiowave Propagation Program are to enable new satellite communication applications and to enhance existing satellite communication networks. These objectives are achieved by supporting radio wave propagation studies and disseminating the study results in a timely fashion. Studies initiated by this program in the 1980s enabled the infant concept of conducting mobile communications via satellite to reach a state of relative maturity in 1990. The program also supported the satellite communications community by publishing and revising two handbooks dealing with radio wave propagation effects for frequencies below and above 10 GHz, respectively. The program has served the international community through its support of the International Telecommunications Union. It supports state of the art work at universities. Currently, the program is focusing on the Advanced Communications Technology Satellite (ACTS) and its propagation needs. An overview of the program's involvement in the ACTS project is given.
Liu, Hao; Kang, Wei; Zhang, Ping; Duan, Huiling; He, X T
2016-01-01
We present a molecular dynamics simulation of shock waves propagating in dense deuterium with the electron force field method [J. T. Su and W. A. Goddard, Phys. Rev. Lett. 99, 185003 (2007)], which explicitly takes the excitation of electrons into consideration. Non-equilibrium features associated with the excitation of electrons are systematically investigated. We show that chemical bonds in D$_2$ molecules lead to a more complicated shock wave structure near the shock front, compared with the results of classical molecular dynamics simulation. Charge separation can bring about accumulation of net charges on the large scale, instead of the formation of a localized dipole layer, which might cause extra energy for the shock wave to propagate. In addition, the simulations also display that molecular dissociation at the shock front is the major factor corresponding to the "bump" structure in the principal Hugoniot. These results could help to build a more realistic picture of shock wave propagation in fuel mater...
Epileptiform discharge propagation
DEFF Research Database (Denmark)
Mălîia, Mihai Dragos; Meritam, Pirgit; Scherg, Michael
2016-01-01
propagation was analyzed using sequential voltage-maps of the averaged spikes, and principal components analysis. When propagation was detected, sources were modeled both at onset and peak. RESULTS: Propagation occurred in half of the patients. The median time of propagation between onset and peak was 17 ms......OBJECTIVE: To investigate how often discharge propagation occurs within the spikes recorded in patients evaluated for epilepsy surgery, and to assess its impact on the accuracy of source imaging. METHODS: Data were analyzed from 50 consecutive patients who had presurgical workup. Discharge....... In 60% of the cases with propagation (15/25 patients) this remained in the same sub-lobar area where onset occurred. The accuracy of source imaging in cases of propagating spikes was 67% when only analyzing onset or peak. This was lower as compared to cases without propagation (79%). Combining source...
Energy Technology Data Exchange (ETDEWEB)
Coddington, P.; Hey, A.; Mandula, J.; Ogilvie, M.
1987-10-22
The fermion propagator in the Landau gauge is calculated for a U(1) lattice gauge theory. In the confined, strong coupling phase, the propagator resembles that of a massive particle. In the weak coupling phase, the propagator is that of a massless particle. An abrupt change occurs at the transition point. The results are compared to simulations of the gluon propagator in SU(3) lattice gauge theory.
Coddington, P.; Hey, A.; Mandula, J.; Ogilvie, M.
1987-10-01
The photon propagator in the Landau gauge is calculated for a U(1) lattice gauge theory. In the confined, strong coupling phase, the propagator resembles that of a massive particle. In the weak coupling phase, the propagator is that of a massless particle. An abrupt change occurs at the transition point. The results are compared to simulations of the gluon propagator in SU(3) lattice gauge theory.
Baker, D A; Bellare, A; Pruitt, L
2003-07-01
Crosslinked ultrahigh molecular weight polyethylene (UHMWPE) has been recently approved by the Food and Drug Administration for use in orthopedic implants. The majority of commercially available UHMWPE orthopedic components are crosslinked using e-beam or gamma radiation. The level of crosslinking is controlled with radiation dose and free radicals are eliminated through heat treatments to prevent long-term degradation associated with chain scission or oxidation mechanisms. Laboratory studies have demonstrated a substantial improvement in the wear resistance of crosslinked UHMWPE. However, a concern about the resistance to fatigue damage remains in the clinical community, especially for tibial components that sustain high cyclic contact stresses. The objective of this study was to investigate both the initiation and propagation aspects of fatigue cracks in radiation crosslinked medical-grade UHMWPE. This work evaluated three levels of radiation, which induced three crosslink densities, on the fatigue crack propagation and total fatigue life behavior. Both as-received UHMWPE, as well as those that underwent an identical thermal history as the crosslinked UHMWPE were used as controls. Fractured crack propagation specimens were examined using scanning electron microscopy to elucidate fatigue fracture mechanisms. The results of this work indicated that a low crosslink density may optimize the fatigue resistance from both a crack initiation and propagation standpoint. Copyright 2003 Wiley Periodicals, Inc.
2015-12-11
Final Report 12/11/2015 DISTRIBUTION A: Distribution approved for public release. AF Office Of Scientific Research (AFOSR)/ RTB1 Arlington, Virginia 22203...propagation in turbulence. 2d ed., SPIE Press, Belling- ham , Washington, USA, 367 pp. Schmidt, J. D., 2010: Numerical simulation of optical wave
DEFF Research Database (Denmark)
Yamamoto, Atsushi; Sakata, T.; Hayashi, T.
2010-01-01
This paper presents a MIMO spatial fading emulator, used to represent a street microcell environment. The fading emulator can reproduce a multipath radio propagation environment with either a uniform or non-uniform angular power spectrum (APS) in the horizontal plane. In this paper, we used...
DEFF Research Database (Denmark)
Kvist, Søren Helstrup; Thaysen, Jesper; Jakobsen, Kaj Bjarne
2010-01-01
The effect of the head size on the ear-to-ear radio-propagation channel as a part of a body-centric wireless network is examined. The channel quality is evaluated at 2.45 GHz in terms of path gain (|S21|) between two monopole antennas that are placed normal to the surface of the head. The investi......The effect of the head size on the ear-to-ear radio-propagation channel as a part of a body-centric wireless network is examined. The channel quality is evaluated at 2.45 GHz in terms of path gain (|S21|) between two monopole antennas that are placed normal to the surface of the head...
Pillco-Tancara Hilda Corina; Quezada-Portugal Jorge Ángel Nicolás
2017-01-01
Strawberry farmers indicate that yields are low compared to other countries. This effect is due to the fact that they plant seedlings that come from stolons since the strawberries are propagated asexual. This con-ventional form of reproduction has disadvantages such as: decreased yield, loss of fruit quality. An alter-native to solve this problem is micropropagation. The present research evaluated the in vitro behavior of two varieties of strawberry (Oso Grande and Sweet Charlie) from leaf...
Liu, Fei; Zhu, Pengfei; Zhang, Lichao; Zhou, Xiujie; Sun, Chongyu; Cheng, Yunhuan
2016-01-01
Domestic sewage sludge and cattle manure are rich in nutrition elements, but without proper disposal, are harmful to the environment. Here with an indoor culture method, we used Eisenia fetida to dispose different ratios of sewage sludge and cattle manure, and thereby investigated the effects and acting rules of these sludge-manure mixtures on the growth and reproduction of E. fetida. We find these mixtures are food sources for E. fetida, and their physiochemical properties are significantly changed after disposal by earthworms. Paired samples t-test shows the average change after different treatments is -20.37% for total organic carbon, 85.71% for total Kjeldahl N, -6.67% for total P, 8.33% for pH, -24.78% for EC (ms·cm-1), and -57.10% for C/N ratio. The average growth rate after treatment CD-70 is 9.20 mg·worm-1·day-1; the average growth rates of E. fetida on day 0–28, day 29–56, and day 57–91 are 9.33, 11.90 and 6.95 mg·worm-1·day-1, respectively, indicating a trend of "rapid—rapidest—slow" growth. Other treatments all show this trend. Though all earthworms developed reproductive rings during the test periods, the appearing time and the cocoon production time both differed among these treatments. The cocoon production amount is maximized to 233 after treatment CD-70. The cocoon production rates are significantly different among these treatments, and the maximum and mean are 0.32 and 0.17–0.32, cocoons·worm-1· day-1, respectively. E. fetida can modestly enrich Cd, but is not very effective over Sb or other heavy metals. E. fetida can remove a part of heavy metals from sewage sludge and cattle manure. Generally, the mixtures of sewage sludge and cattle manure can largely affect the growth and propagation of E. fetida in a ratio-dependent way. PMID:27257977
d'Avila, Maria Paola Santisi
2016-01-01
In this paper, a model of one-directional propagation of three-component seismic waves in a nonlinear multilayered soil profile is coupled with a multi-story multi-span frame model to consider, in a simple way, the soil-structure interaction modelled in a finite element scheme. Modeling the three-component wave propagation enables the effects of a soil multiaxial stress state to be taken into account. These reduce soil strength and increase nonlinear effects, compared with the axial stress state. The simultaneous propagation of three components allows the prediction of the incident direction of seismic loading at the ground surface and the analysis of the behavior of a frame structure shaken by a three-component earthquake. A parametric study is carried out to characterize the changes in the ground motion due to dynamic features of the structure, for different incident wavefield properties and soil nonlinear effects. A seismic response depending on parameters such as the frequency content of soil and structur...
The physical theory and propagation model of THz atmospheric propagation
Wang, R.; Yao, J. Q.; Xu, D. G.; Wang, J. L.; Wang, P.
2011-02-01
Terahertz (THz) radiation is extensively applied in diverse fields, such as space communication, Earth environment observation, atmosphere science, remote sensing and so on. And the research on propagation features of THz wave in the atmosphere becomes more and more important. This paper firstly illuminates the advantages and outlook of THz in space technology. Then it introduces the theoretical framework of THz atmospheric propagation, including some fundamental physical concepts and processes. The attenuation effect (especially the absorption of water vapor), the scattering of aerosol particles and the effect of turbulent flow mainly influence THz atmosphere propagation. Fundamental physical laws are illuminated as well, such as Lamber-beer law, Mie scattering theory and radiative transfer equation. The last part comprises the demonstration and comparison of THz atmosphere propagation models like Moliere(V5), SARTre and AMATERASU. The essential problems are the deep analysis of physical mechanism of this process, the construction of atmospheric propagation model and databases of every kind of material in the atmosphere, and the standardization of measurement procedures.
Directory of Open Access Journals (Sweden)
Guissou, T.
2016-01-01
Full Text Available Description of the subject. Arbuscular mycorrhizal (AM fungi are known to promote plant growth by enhancing mineral uptake in nutrient deficient soils. These beneficial effects on plant growth may vary considerably between cultivars of a given species and between plant species originating from different locations. Objectives. The present experiment evaluated the response of three Sahelian fruit trees: néré (Parkia biglobosa [Jacq.] G.Don, tamarind (Tamarindus indica L., and jujube (Ziziphus mauritiana Lam., originating from five different geographic provenances, to mycorrhizal colonization, evaluate their respective mycorrhizal dependency (MD and analyze their leaf and stem mineral composition. Method. Trees were cultivated in a nursery on pre-sterilized soil substrate low in available P (2.18 μg·g-1 with or without inoculum of Glomus aggregatum (Schenck & Smith emend. Koske. The experiment was arranged in a factorial design for each fruit tree species separately: 5 provenances x 2 AM treatments (inoculated and non-inoculated [control] with 10 replicates per treatment. Plants were harvested six months after inoculation and different parameters were measured. Results. Overall, the results showed significant provenance variations in the plant response to mycorrhizal inoculation. Néré mycorrhizal plants, from two seed sources, tamarind and jujube plants from one seed source had significant higher dry weight and shoot height than those from other provenances. Jujube plants from 3 out of the 5 provenances showed significant higher MD. It then appears that seed provenance happened to be determinant even though AM-root colonization levels (80-90% do not vary much from one provenance to another. In all cases, the fruit trees benefited from AM fungi with increased N, P and K mineral uptake in aerial parts. In particular P uptake was proportional to MD concentration in AM-jujube plants. Conclusions. These results demonstrate the importance of
Energy Technology Data Exchange (ETDEWEB)
Li, Huijuan; Diao, Xiaoxu; Li, Boyuan; Smidts, Carol; Bragg-Sitton, Shannon
2017-03-01
This paper studies the propagation and effects of faults of critical components that pertain to the secondary loop of a nuclear power plant found in Nuclear Hybrid Energy Systems (NHES). This information is used to design an on-line monitoring (OLM) system which is capable of detecting and forecasting faults that are likely to occur during NHES operation. In this research, the causes, features, and effects of possible faults are investigated by simulating the propagation of faults in the secondary loop. The simulation is accomplished by using the Integrated System Failure Analysis (ISFA). ISFA is used for analyzing hardware and software faults during the conceptual design phase. In this paper, the models of system components required by ISFA are initially constructed. Then, the fault propagation analysis is implemented, which is conducted under the bounds set by acceptance criteria derived from the design of an OLM system. The result of the fault simulation is utilized to build a database for fault detection and diagnosis, provide preventive measures, and propose an optimization plan for the OLM system.
Directory of Open Access Journals (Sweden)
B. Vargas-Arista
2013-01-01
Full Text Available The fractography and mechanical behaviour of fatigue crack propagation in the heat-affected zone (HAZ of AISI 4140 steel welded using the shielded metal arc process was analysed. Different austenitic grain size was obtained by normalizing performed at 1200 °C for 5 and 10 hours after welding. Three point bending fatigue tests on pre-cracked specimens along the HAZ revealed that coarse grains promoted an increase in fatigue crack growth rate, hence causing a reduction in both fracture toughness and critical crack length, and a transgranular brittle final fracture with an area fraction of dimple zones connecting cleavage facets. A fractographic analysis proved that as the normalizing time increased the crack length decreased. The increase in the river patterns on the fatigue crack propagation in zone II was also evidenced and final brittle fracture because of transgranular quasicleavage was observed. Larger grains induced a deterioration of the fatigue resistance of the HAZ.
B. Vargas-Arista; J. Teran-Guillen; Solis, J.; García-Cerecero,G.; Martínez-Madrid,M.
2013-01-01
The fractography and mechanical behaviour of fatigue crack propagation in the heat-affected zone (HAZ) of AISI 4140 steel welded using the shielded metal arc process was analysed. Different austenitic grain size was obtained by normalizing performed at 1200 °C for 5 and 10 hours after welding. Three point bending fatigue tests on pre-cracked specimens along the HAZ revealed that coarse grains promoted an increase in fatigue crack growth rate, hence causing a reduction in both fracture toughne...
Surface plasmon propagation near an index step
Berger, C.E.H.; Berger, Charles E.H.; Kooyman, R.P.H.; Greve, Jan
1999-01-01
Propagation effects of surface plasmons on the surface plasmon microscopy (SPM) image of an area around the edge of a cover layer were studied as a function of the wavelength. A phenomenological model that describes these effects of surface plasmon propagation on the observed reflectance is
Directory of Open Access Journals (Sweden)
R. Solis
Full Text Available Abstract The seeds of Plukenetia polyadenia have high levels of unsaturated fatty acids and are used as medicine and food for native people in the Peruvian and Brazilian Amazon. The objective of this study was to develop a method for vegetative propagation of Plukenetia polyadenia by rooting of cuttings. The experiment was laid out in a randomized complete block design with 12 treatments and 3 replications of 8 cuttings, in a 3 × 4 factorial arrangement. The factors were: 3 levels of leaf area (25, 50 and 75% and 3 indole-3-butyric acid - IBA concentrations (9.84, 19.68 and 29.52mM and a control without IBA. Data were submitted to analysis of variance and means were compared by Tukey test at 5% probability. Our results show that the use of cuttings with 50% of leaf area and treatment with 29.52mM of IBA induced high percentages of rooting (93% and the best root formation. Vegetative propagation of Plukenetia polyadenia by cuttings will be used as a tool to conserve and propagate germplasm in breeding programs.
Solis, R; Pezo, M; Diaz, G; Arévalo, L; Cachique, D
2017-01-01
The seeds of Plukenetia polyadenia have high levels of unsaturated fatty acids and are used as medicine and food for native people in the Peruvian and Brazilian Amazon. The objective of this study was to develop a method for vegetative propagation of Plukenetia polyadenia by rooting of cuttings. The experiment was laid out in a randomized complete block design with 12 treatments and 3 replications of 8 cuttings, in a 3 × 4 factorial arrangement. The factors were: 3 levels of leaf area (25, 50 and 75%) and 3 indole-3-butyric acid - IBA concentrations (9.84, 19.68 and 29.52mM) and a control without IBA. Data were submitted to analysis of variance and means were compared by Tukey test at 5% probability. Our results show that the use of cuttings with 50% of leaf area and treatment with 29.52mM of IBA induced high percentages of rooting (93%) and the best root formation. Vegetative propagation of Plukenetia polyadenia by cuttings will be used as a tool to conserve and propagate germplasm in breeding programs.
Directory of Open Access Journals (Sweden)
Pillco-Tancara Hilda Corina
2017-08-01
Full Text Available Strawberry farmers indicate that yields are low compared to other countries. This effect is due to the fact that they plant seedlings that come from stolons since the strawberries are propagated asexual. This con-ventional form of reproduction has disadvantages such as: decreased yield, loss of fruit quality. An alter-native to solve this problem is micropropagation. The present research evaluated the in vitro behavior of two varieties of strawberry (Oso Grande and Sweet Charlie from leaf segments with different degrees of maturation (juvenile and adult in two periods of introduction. To induce in vitro propagation, the culture media were supplemented with growth regulators, using two concentrations 4.54 and 9.08 μM of thidiazuron with the combination of three concentrations of 0, 0.98 and 2.5 μM of acid Indolebutyric acid. Explants of leaf segments showing juvenile tissues (May came to form buds. The same did not occur with those that came from adult tissue (June, so it can be noted that those that came from juvenile tissue had a better response in vitro. It was determined that the combination of 9.08 μM thidiazuron and 0.98 μM indolbutyric acid was the most suitable for the in vitro propagation of leaf sections of strawberry leaves in both varieties, since in this medium more formation was obtained Of cell aggregates, for the formation of outbreaks compared to the other treatments.
Liu, Zhong-Bo; Liang, Ying; Jia, Ke-Ning; Fan, Xi-Jun
2012-02-01
In this paper we study influences of Doppler broadening, spontaneously generated coherence, and other system parameters on propagation effect in a quasi lambda-type four-level atomic system. It is shown that when the Doppler broadening is present, generally speaking, the values of gain and intensity of lasing without inversion (i.e. the probe field) in the co-propagating probe and driving fields case are much larger than those in the counter-propagating case; considerably larger gain and intensity of lasing without inversion than those without the Doppler broadening can be obtained by choosing appropriate values of the Doppler broadening width and spontaneously generated coherence strength. The gain and intensity of lasing without inversion increase with the increase of spontaneously generated coherence strength; when spontaneously generated coherence is present, much larger gain and intensity of lasing without inversion than those in the case without spontaneously generated coherence can be obtained. Choosing suitable values of the probe detuning, Rabi frequencies of the driving and pump fields at the entrance of the medium also can remarkably enhance the gain and intensity of lasing without inversion.
Brault, Antoine; Dumas, Laurent; Lucor, Didier
2017-10-01
This work aims at quantifying the effect of inherent uncertainties from cardiac output on the sensitivity of a human compliant arterial network response based on stochastic simulations of a reduced-order pulse wave propagation model. A simple pulsatile output form is used to reproduce the most relevant cardiac features with a minimum number of parameters associated with left ventricle dynamics. Another source of significant uncertainty is the spatial heterogeneity of the aortic compliance, which plays a key role in the propagation and damping of pulse waves generated at each cardiac cycle. A continuous representation of the aortic stiffness in the form of a generic random field of prescribed spatial correlation is then considered. Making use of a stochastic sparse pseudospectral method, we investigate the sensitivity of the pulse pressure and waves reflection magnitude over the arterial tree with respect to the different model uncertainties. Results indicate that uncertainties related to the shape and magnitude of the prescribed inlet flow in the proximal aorta can lead to potent variation of both the mean value and standard deviation of blood flow velocity and pressure dynamics due to the interaction of different wave propagation and reflection features. Lack of accurate knowledge in the stiffness properties of the aorta, resulting in uncertainty in the pulse wave velocity in that region, strongly modifies the statistical response, with a global increase in the variability of the quantities of interest and a spatial redistribution of the regions of higher sensitivity. These results will provide some guidance in clinical data acquisition and future coupling of arterial pulse wave propagation reduced-order model with more complex beating heart models. Copyright © 2016 John Wiley & Sons, Ltd.
Wave propagation in ballistic gelatine.
Naarayan, Srinivasan S; Subhash, Ghatu
2017-04-01
Wave propagation characteristics in long cylindrical specimens of ballistic gelatine have been investigated using a high speed digital camera and hyper elastic constitutive models. The induced transient deformation is modelled with strain rate dependent Mooney-Rivlin parameters which are determined by modelling the stress-strain response of gelatine at a range of strain rates. The varying velocity of wave propagation through the gelatine cylinder is derived as a function of prestress or stretch in the gelatine specimen. A finite element analysis is conducted using the above constitutive model by suitably defining the impulse imparted by the polymer bar into the gelatine specimen. The model results are found to capture the experimentally observed wave propagation characteristics in gelatine effectively. Copyright © 2017 Elsevier Ltd. All rights reserved.
Propagation handbook for wireless communication system design
Crane, Robert K
2003-01-01
PROPAGATION PHENOMENA AFFECTING WIRELESS SYSTEMS Types of SystemsDesign Criteria Antenna Considerations Propagation Effects Propagation Models Model Verification Statistics and RiskList of Symbols ReferencesPROPAGATION FUNDAMENTALSMaxwell's EquationsPlane Waves Spherical Waves Reflection and Refraction Geometrical OpticsRay TracingScalar Diffraction Theory Geometrical Theory of Diffraction List of Symbols ReferencesABSORPTION Molecular Absorption Absorption on a Slant Path ACTS Statistics List of Symbols ReferencesREFRACTION Ray BendingPath Delay ScintillationList of Symbols ReferencesATTENUAT
Okawa, Shinpei; Hirasawa, Takeshi; Kushibiki, Toshihiro; Ishihara, Miya
2017-09-01
Quantitative photoacoustic tomography (QPAT) employing a light propagation model will play an important role in medical diagnoses by quantifying the concentration of hemoglobin or a contrast agent. However, QPAT by the light propagation model with the three-dimensional (3D) radiative transfer equation (RTE) requires a huge computational load in the iterative forward calculations involved in the updating process to reconstruct the absorption coefficient. The approximations of the light propagation improve the efficiency of the image reconstruction for the QPAT. In this study, we compared the 3D/two-dimensional (2D) photon diffusion equation (PDE) approximating 3D RTE with the Monte Carlo simulation based on 3D RTE. Then, the errors in a 2D PDE-based linearized image reconstruction caused by the approximations were quantitatively demonstrated and discussed in the numerical simulations. It was clearly observed that the approximations affected the reconstructed absorption coefficient. The 2D PDE-based linearized algorithm succeeded in the image reconstruction of the region with a large absorption coefficient in the 3D phantom. The value reconstructed in the phantom experiment agreed with that in the numerical simulation, so that it was validated that the numerical simulation of the image reconstruction predicted the relationship between the true absorption coefficient of the target in the 3D medium and the reconstructed value with the 2D PDE-based linearized algorithm. Moreover, the the true absorption coefficient in 3D medium was estimated from the 2D reconstructed image on the basis of the prediction by the numerical simulation. The estimation was successful in the phantom experiment, although some limitations were revealed.
Okawa, Shinpei; Hirasawa, Takeshi; Kushibiki, Toshihiro; Ishihara, Miya
2017-12-01
Quantitative photoacoustic tomography (QPAT) employing a light propagation model will play an important role in medical diagnoses by quantifying the concentration of hemoglobin or a contrast agent. However, QPAT by the light propagation model with the three-dimensional (3D) radiative transfer equation (RTE) requires a huge computational load in the iterative forward calculations involved in the updating process to reconstruct the absorption coefficient. The approximations of the light propagation improve the efficiency of the image reconstruction for the QPAT. In this study, we compared the 3D/two-dimensional (2D) photon diffusion equation (PDE) approximating 3D RTE with the Monte Carlo simulation based on 3D RTE. Then, the errors in a 2D PDE-based linearized image reconstruction caused by the approximations were quantitatively demonstrated and discussed in the numerical simulations. It was clearly observed that the approximations affected the reconstructed absorption coefficient. The 2D PDE-based linearized algorithm succeeded in the image reconstruction of the region with a large absorption coefficient in the 3D phantom. The value reconstructed in the phantom experiment agreed with that in the numerical simulation, so that it was validated that the numerical simulation of the image reconstruction predicted the relationship between the true absorption coefficient of the target in the 3D medium and the reconstructed value with the 2D PDE-based linearized algorithm. Moreover, the the true absorption coefficient in 3D medium was estimated from the 2D reconstructed image on the basis of the prediction by the numerical simulation. The estimation was successful in the phantom experiment, although some limitations were revealed.
Solis, R.; Pezo, M.; Diaz, G.; Arévalo, L.; Cachique, D.
2016-01-01
Abstract The seeds of Plukenetia polyadenia have high levels of unsaturated fatty acids and are used as medicine and food for native people in the Peruvian and Brazilian Amazon. The objective of this study was to develop a method for vegetative propagation of Plukenetia polyadenia by rooting of cuttings. The experiment was laid out in a randomized complete block design with 12 treatments and 3 replications of 8 cuttings, in a 3 × 4 factorial arrangement. The factors were: 3 levels of leaf are...
DEFF Research Database (Denmark)
Sonne, Mads Rostgaard; Carlone, P.; Citarella, R.
2015-01-01
This paper deals with a numerical and experimental investigation on the influence of residual stresses on fatigue crack growth in AA2024-T3 friction stir welded butt joints. An integrated FEM-DBEM procedure for the simulation of crack propagation is proposed and discussed. A numerical FEM model...... of the welding process of precipitation hardenable AA2024-T3 aluminum alloy is employed to infer the process induced residual stress field. The reliability of the FEM simulations with respect to the induced residual stresses is assessed comparing numerical outcomes with experimental data obtained by means...
Shchesnovich, V. S.
2008-01-01
A light pulse propagating in a suddenly switched on photonic lattice, when the central frequency lies in the photonic band gap, is an analog of the Rabi model where the two-level system is the two resonant (i.e. Bragg-coupled) Fourier modes of the pulse, while the photonic lattice serves as a monochromatic external field. A simple theory of these Rabi oscillations is given and confirmed by the numerical solution of the corresponding Maxwell equations. This is a direct, i.e. temporal, analog o...
Neutrino Propagation in Matter
Directory of Open Access Journals (Sweden)
Mattias Blennow
2013-01-01
Full Text Available We describe the effects of neutrino propagation in the matter of the Earth relevant to experiments with atmospheric and accelerator neutrinos and aimed at the determination of the neutrino mass hierarchy and CP violation. These include (i the resonance enhancement of neutrino oscillations in matter with constant or nearly constant density, (ii adiabatic conversion in matter with slowly changing density, (iii parametric enhancement of oscillations in a multilayer medium, and (iv oscillations in thin layers of matter. We present the results of semianalytic descriptions of flavor transitions for the cases of small density perturbations, in the limit of large densities and for small density widths. Neutrino oscillograms of the Earth and their structure after determination of the 1–3 mixing are described. A possibility to identify the neutrino mass hierarchy with the atmospheric neutrinos and multimegaton scale detectors having low energy thresholds is explored. The potential of future accelerator experiments to establish the hierarchy is outlined.
Wave Beam Propagation Through Density Fluctuations
Balakin, A. A.; Bertelli, N.; Westerhof, E.
2011-01-01
Perturbations induced by edge density fluctuations on electron cyclotron wave beams propagating in fusion plasmas are studied by means of a quasi-optical code. The effects of such fluctuations are illustrated here by showing the beam propagation in the case of single harmonic perturbations to the
Energy Technology Data Exchange (ETDEWEB)
Ghorbanpour Arani, A., E-mail: aghorban@kashanu.ac.ir [Faculty of Mechanical Engineering, University of Kashan, Kashan, Islamic Republic of Iran. (Iran, Islamic Republic of); Institute of Nanoscience and Nanotechnology, University of Kashan, Kashan, Islamic Republic of Iran (Iran, Islamic Republic of); Roudbari, M.A. [Faculty of Mechanical Engineering, University of Kashan, Kashan, Islamic Republic of Iran. (Iran, Islamic Republic of)
2014-11-01
This paper investigates the electro-thermal nonlocal wave propagation of fluid-conveying single-walled Boron Nitride nanotubes (SWBNNTs) using nonlocal piezoelasticity with surface stress, initial stress and Knudsen-dependent flow velocity effect. SWBNNT is embedded in a vicsoelastic medium which is simulated as visco-Pasternak foundation. Using Euler–Bernoulli beam (EBB) model, Hamilton's principle and nonlocal piezoelasticity theory, the higher order governing equation is derived. A detailed parametric study is conducted, focusing on the combined effects of the electric parameters, viscoelastic medium, initial stress, surface stress, Knudsen number (Kn) and small scale on the wave propagation behaviour of the fluid-conveying SWBNNT. The results show that for smaller values of wave number the dispersion relation for different fluid viscosities seems to be similar. At the higher values of wave numbers, increase in the wave frequency values is remarkable due to increase in fluid viscosity. The electric field as a smart controller, surface effect, initial stress, temperature change and slip velocity effect have significant role on the wave frequency. The results of this work is hoped to be of use in design and manufacturing of smart MEMS/NEMS in advanced medical applications such as drug delivery systems with great applications in biomechanics.
Directory of Open Access Journals (Sweden)
Jens eStepan
2015-11-01
Full Text Available Antidepressants (ADs are used as first-line treatment for most stress-related psychiatric disorders. The alterations in brain circuit dynamics that can arise from stress exposure and underlie therapeutic actions of ADs remain, however, poorly understood. Here, enabled by a recently developed voltage-sensitive dye imaging assay in mouse brain slices, we examined the impact of chronic stress and concentration-dependent effects of eight clinically used ADs (belonging to different chemical/functional classes on evoked neuronal activity propagations through the hippocampal trisynaptic circuitry (HTC: perforant path - dentate gyrus - area CA3 - area CA1. Exposure of mice to chronic social defeat stress led to markedly weakened activity propagations (HTC-Waves. In contrast, at concentrations in the low micromolar range, all ADs, which were bath applied to slices, caused an amplification of HTC-Waves in CA regions (invariably in area CA1. The fast-acting antidepressant ketamine, the mood stabilizer lithium, and brain-derived neurotrophic factor (BDNF exerted comparable enhancing effects, whereas the antipsychotic haloperidol and the anxiolytic diazepam attenuated HTC-Waves. Collectively, we provide direct experimental evidence that chronic stress can depress neuronal signal flow through the HTC and demonstrate shared opposing effects of ADs. Thus, our study points to a circuit-level mechanism of ADs to counteract stress-induced impairment of hippocampal network function. However, the observed effects of ADs are impossible to depend on enhanced neurogenesis.
Zhen, Yaxin; Zhou, Lin
2017-03-01
Based on nonlocal strain gradient theory, wave propagation in fluid-conveying viscoelastic single-walled carbon nanotubes (SWCNTs) is studied in this paper. With consideration of thermal effect and surface effect, wave equation is derived for fluid-conveying viscoelastic SWCNTs under longitudinal magnetic field utilizing Euler-Bernoulli beam theory. The closed-form expressions are derived for the frequency and phase velocity of the wave motion. The influences of fluid flow velocity, structural damping coefficient, temperature change, magnetic flux and surface effect are discussed in detail. SWCNTs’ viscoelasticity reduces the wave frequency of the system and the influence gets remarkable with the increase of wave number. The fluid in SWCNTs decreases the frequency of wave propagation to a certain extent. The frequency (phase velocity) gets larger due to the existence of surface effect, especially when the diameters of SWCNTs and the wave number decrease. The wave frequency increases with the increase of the longitudinal magnetic field, while decreases with the increase of the temperature change. The results may be helpful for better understanding the potential applications of SWCNTs in nanotechnology.
Diaz, A.; Ramos, J. G.; Friedman, J. S.
2017-09-01
We developed a web-based instructional and research tool that demonstrates the behavior of electromagnetic waves as they propagate through a homogenous medium and through an interface where the second medium can be characterized by an effective complex permittivity and permeability. Either p- or s-polarization wave components can be chosen and the graphical interface includes 2D wave and 3D component representations. The program enables the study of continuity of electromagnetic components, critical angle, Brewster angle, absorption and amplification, behavior of light in sub-unity and negative-index materials, Poynting vector and phase velocity behavior, and positive and negative Goos- Hänchen shifts.
Salomons, E.; Polinder, H.; Lohman, W.; Zhou, H.; Borst, H.
2009-01-01
A new engineering model for sound propagation in cities is presented. The model is based on numerical and experimental studies of sound propagation between street canyons. Multiple reflections in the source canyon and the receiver canyon are taken into account in an efficient way, while weak
Propagation of Significant Figures.
Schwartz, Lowell M.
1985-01-01
Shows that the rules of thumb for propagating significant figures through arithmetic calculations frequently yield misleading results. Also describes two procedures for performing this propagation more reliably than the rules of thumb. However, both require considerably more calculational effort than do the rules. (JN)
Directory of Open Access Journals (Sweden)
azam ranjbar
2017-02-01
Full Text Available Introduction: Miniature rose (Rosa hybrida are well known as one of the world’s most popular ornamental plants cultivated worldwide as potted and/or bed plants. Nowadays, more than 100 million pots of miniature roses are propagated by stem cutting in the commercial greenhouses of European countries such as Denmark and Germany. Some treatments such as application of plant growth regulators and suitable rooting medium could be required for accelerating root formation in rose cuttings. Using plant growth regulators like natural or synthetic auxin is a pre-requirement for the initiation of adventitious root in some stem cuttings and it has been reported that the division of the first initiator cells of root depends on internal or synthetic auxin. Methods of application of these chemicals and suitable concentration could be related to several factors, importantly the plant varieties, type of cuttings and the time of cutting preparation. Various kinds of media such as soil, peat moss, perlite and vermiculite are used as bed substrate according to required ratio. Rooting media must provide appropriate moisture and air ventilation for cuttings establishment, which highly affect the cuttings root formation. Appropriate procedure for using wastes materials as culture bed, especially those materials that produced locally, is main aim of some studies to find an alternative medium in ornamental pot plant production. In this regards, evaluation of agricultural wastes to be used to culture bed and introducing suitable materials could be considered. Accordingly, the objective of the present study was to determine the effects of two types of plant growth regulators and bed combinations on rooting percentage of semi-hardwood cuttings in miniature rose. Materials and Methods: In order to evaluate the effects of different concentrations of indolebutyric acid (IBA and naphtaleneacetic acid (NAA, and two media with different composition on root formation of
Andrew, Ruth E. B.; Gudmundsson, Agust
2008-11-01
Mechanically, many volcanoes may be regarded as elastic inclusions, either softer (with a lower Young's modulus) or stiffer (with a higher Young's modulus) than the host-rock matrix. For example, many central volcanoes (stratovolcanoes, composite volcanoes) are composed of rocks that are softer than the crustal segments that host them. This is particularly clear in Iceland where central volcanoes are mostly made of soft rocks such as rhyolite, pyroclastics, hyaloclastites, and sediments whereas the host rock is primarily stiff basaltic lava flows. Most active central volcanoes also contain fluid magma chambers, and many have collapse calderas. Fluid magma chambers are best modelled as cavities (in three dimensions) or holes (in two dimensions), entire calderas as holes, and the ring faults themselves, which commonly include soft materials such as breccias, as soft inclusions. Many hyaloclastite (basaltic breccias) mountains partly buried in the basaltic lava pile also function as soft inclusions. Modelling volcanoes as soft inclusions or holes, we present three main numerical results. The first, using the hole model, shows the mechanical interaction between all the active central volcanoes in Iceland and, in particular, those forming the two main clusters at the north and south end of the East Volcanic Zone (EVZ). The strong indication of mechanical interaction through shared dykes and faults in the northern cluster of the EVZ is supported by observations. The second model, using a soft inclusion, shows that the Torfajökull central volcano, which contains the largest active caldera in Iceland, suppresses the spreading-generated tensile stress in its surroundings. We propose that this partly explains why the proper rift zone northeast of Torfajökull has not managed to propagate through the volcano. Apparently, Torfajökull tends to slow down the rate of southwest propagation of the rift-zone part of the EVZ. The third model, again using a soft inclusion, indicates
Premixed flame propagation in vertical tubes
Kazakov, Kirill A
2015-01-01
Analytical treatment of premixed flame propagation in vertical tubes with smooth walls is given. Using the on-shell flame description, equations describing quasi-steady flame with a small but finite front thickness are obtained and solved numerically. It is found that near the limits of inflammability, solutions describing upward flame propagation come in pairs having close propagation speeds, and that the effect of gravity is to reverse the burnt gas velocity profile generated by the flame. On the basis of these results, a theory of partial flame propagation driven by the gravitational field is developed. A complete explanation is given of the intricate observed behavior of limit flames, including dependence of the inflammability range on the size of the combustion domain, the large distances of partial flame propagation, and the progression of flame extinction. The role of the finite front-thickness effects is discussed in detail. Also, various mechanisms governing flame acceleration in smooth tubes are ide...
Manga, Etoungh D; Blasco, Hugues; Da-Costa, Philippe; Drobek, Martin; Ayral, André; Le Clezio, Emmanuel; Despaux, Gilles; Coasne, Benoit; Julbe, Anne
2014-09-02
The present study reports on the development of a characterization method of porous membrane materials which consists of considering their acoustic properties upon gas adsorption. Using acoustic microscopy experiments and atomistic molecular simulations for helium adsorbed in a silicalite-1 zeolite membrane layer, we showed that acoustic wave propagation could be used, in principle, for controlling the membranes operando. Molecular simulations, which were found to fit experimental data, showed that the compressional modulus of the composite system consisting of silicalite-1 with adsorbed He increases linearly with the He adsorbed amount while its shear modulus remains constant in a large range of applied pressures. These results suggest that the longitudinal and Rayleigh wave velocities (VL and VR) depend on the He adsorbed amount whereas the transverse wave velocity VT remains constant.
Coherence approach to neutron polarization propagation in instruments
De Haan, V.O.; Van Well, A.A.; Plomp, J.
2008-01-01
The propagation of the mutual coherence function is a well known method to describe the effects of neutron’s propagation through scattering instruments. This method is extended with the description of the coherence matrix to account for neutron polarization effects and its propagation through an
Zandbergen, P A; Hart, T C; Lenzer, K E; Camponovo, M E
2012-04-01
The quality of geocoding has received substantial attention in recent years. A synthesis of published studies shows that the positional errors of street geocoding are somewhat unique relative to those of other types of spatial data: (1) the magnitude of error varies strongly across urban-rural gradients; (2) the direction of error is not uniform, but strongly associated with the properties of local street segments; (3) the distribution of errors does not follow a normal distribution, but is highly skewed and characterized by a substantial number of very large error values; and (4) the magnitude of error is spatially autocorrelated and is related to properties of the reference data. This makes it difficult to employ analytic approaches or Monte Carlo simulations for error propagation modeling because these rely on generalized statistical characteristics. The current paper describes an alternative empirical approach to error propagation modeling for geocoded data and illustrates its implementation using three different case-studies of geocoded individual-level datasets. The first case-study consists of determining the land cover categories associated with geocoded addresses using a point-in-raster overlay. The second case-study consists of a local hotspot characterization using kernel density analysis of geocoded addresses. The third case-study consists of a spatial data aggregation using enumeration areas of varying spatial resolution. For each case-study a high quality reference scenario based on address points forms the basis for the analysis, which is then compared to the result of various street geocoding techniques. Results show that the unique nature of the positional error of street geocoding introduces substantial noise in the result of spatial analysis, including a substantial amount of bias for some analysis scenarios. This confirms findings from earlier studies, but expands these to a wider range of analytical techniques. Copyright © 2012 Elsevier Ltd
Vector wave propagation method.
Fertig, M; Brenner, K-H
2010-04-01
In this paper, we extend the scalar wave propagation method (WPM) to vector fields. The WPM [Appl. Opt.32, 4984 (1993)] was introduced in order to overcome the major limitations of the beam propagation method (BPM). With the WPM, the range of application can be extended from the simulation of waveguides to simulation of other optical elements like lenses, prisms and gratings. In that reference it was demonstrated that the wave propagation scheme provides valid results for propagation angles up to 85 degrees and that it is not limited to small index variations in the axis of propagation. Here, we extend the WPM to three-dimensional vectorial fields (VWPMs) by considering the polarization dependent Fresnel coefficients for transmission in each propagation step. The continuity of the electric field is maintained in all three dimensions by an enhanced propagation vector and the transfer matrix. We verify the validity of the method by transmission through a prism and by comparison with the focal distribution from vectorial Debye theory. Furthermore, a two-dimensional grating is simulated and compared with the results from three-dimensional RCWA. Especially for 3D problems, the runtime of the VWPM exhibits special advantage over the RCWA.
Energy Technology Data Exchange (ETDEWEB)
Yang, Y.F., E-mail: y.yang6@uq.edu.au [University of Queensland, School of Mechanical and Mining Engineering, ARC Centre of Excellence for Design in Light Metals, Brisbane, QLD 4072 (Australia); Wang, H.Y.; Wang, J.G. [Key Laboratory of Automobile Materials of Ministry of Education, Department of Materials Science and Engineering, Jilin University, Nanling Campus, Changchun 130025 (China); Jiang, Q.C., E-mail: jqc@jlu.edu.cn [Key Laboratory of Automobile Materials of Ministry of Education, Department of Materials Science and Engineering, Jilin University, Nanling Campus, Changchun 130025 (China)
2011-06-23
Highlights: > We investigated the effect of C particle size on the self-propagating high temperature reaction mechanism. > Coarse C particle size (>38 {mu}m) resulted in the formation of prior TiC{sub x} layer between Ti and C. > Prior TiC{sub x} layer control the whole reaction of Ni-Ti-C and domain the reaction kinetics. > The selection of C particle size is the most important factor to fabricate TiC/Ni composite using Ti, C and Ni mixtures. - Abstract: Effect of C particle size on the mechanism of self-propagation high-temperature synthesis (SHS) in the Ni-Ti-C system was investigated. Fine C particle resulted in a traditional mechanism of dissolution-precipitation while coarse C particle made the reaction be controlled by a mechanism of the diffusion of C through the TiC{sub x} layer. The whole process can be described: C atoms diffusing through the TiC{sub x} layer dissolved into the Ni-Ti liquid and TiC were formed once the liquid became supersaturated. Simultaneously, the heat generated from the TiC formation made the unstable TiC{sub x} layer break up. However, with the spread of Ti-Ni liquid, a new TiC{sub x} layer was formed again at the interface between spreading liquid and C particle. This process cannot stop until all the C particles are consumed completely.
Wolfe, Marnin D.; Kulakow, Peter; Rabbi, Ismail Y.; Jannink, Jean-Luc
2016-01-01
In clonally propagated crops, nonadditive genetic effects can be effectively exploited by the identification of superior genetic individuals as varieties. Cassava (Manihot esculenta Crantz) is a clonally propagated staple food crop that feeds hundreds of millions. We quantified the amount and nature of nonadditive genetic variation for three key traits in a breeding population of cassava from sub-Saharan Africa using additive and nonadditive genome-wide marker-based relationship matrices. We then assessed the accuracy of genomic prediction for total (additive plus nonadditive) genetic value. We confirmed previous findings based on diallel crosses that nonadditive genetic variation is significant for key cassava traits. Specifically, we found that dominance is particularly important for root yield and epistasis contributes strongly to variation in cassava mosaic disease (CMD) resistance. Further, we showed that total genetic value predicted observed phenotypes more accurately than additive only models for root yield but not for dry matter content, which is mostly additive or for CMD resistance, which has high narrow-sense heritability. We address the implication of these results for cassava breeding and put our work in the context of previous results in cassava, and other plant and animal species. PMID:27587297
Action potential propagation: ion current or intramembrane electric field?
Martí, Albert; Pérez, Juan J; Madrenas, Jordi
2018-01-01
The established action potential propagation mechanisms do not satisfactorily explain propagation on myelinated axons given the current knowledge of biological channels and membranes. The flow across ion channels presents two possible effects: the electric potential variations across the lipid bilayers (action potential) and the propagation of an electric field through the membrane inner part. The proposed mechanism is based on intra-membrane electric field propagation, this propagation can explain the action potential saltatory propagation and its constant delay independent of distance between Ranvier nodes in myelinated axons.
Islam, M J; Reza, A W; Kausar, A S M Z; Ramiah, H
2014-01-01
The advent of technology with the increasing use of wireless network has led to the development of Wireless Body Area Network (WBAN) to continuously monitor the change of physiological data in a cost efficient manner. As numerous researches on wave propagation characterization have been done in intrabody communication, this study has given emphasis on the wave propagation characterization between the control units (CUs) and wireless access point (AP) in a hospital scenario. Ray tracing is a tool to predict the rays to characterize the wave propagation. It takes huge simulation time, especially when multiple transmitters are involved to transmit physiological data in a realistic hospital environment. Therefore, this study has developed an accelerated ray tracing method based on the nearest neighbor cell and prior knowledge of intersection techniques. Beside this, Red-Black tree is used to store and provide a faster retrieval mechanism of objects in the hospital environment. To prove the superiority, detailed complexity analysis and calculations of reflection and transmission coefficients are also presented in this paper. The results show that the proposed method is about 1.51, 2.1, and 2.9 times faster than the Object Distribution Technique (ODT), Space Volumetric Partitioning (SVP), and Angular Z-Buffer (AZB) methods, respectively. To show the various effects on received power in 60 GHz frequency, few comparisons are made and it is found that on average -9.44 dBm, -8.23 dBm, and -9.27 dBm received power attenuations should be considered when human, AP, and CU move in a given hospital scenario.
Mandula, Jeffrey E.
1999-07-01
We discuss the current state of what is known non-perturbatively about the gluon propagator in QCD, with emphasis on the information coming from lattice simulations. We review specification of the lattice Landau gauge and the procedure for calculating the gluon propagator on the lattice. We also discuss some of the difficulties in non-perturbative calculations - especially Gribov copy issues. We trace the evolution of lattice simulations over the past dozen years, emphasizing how the improvement in computations has led not only to more precise determinations of the propagator, but has allowed more detailed information about it to be extracted.
High frequency acoustic propagation under variable sea surfaces
Senne, Joseph
This dissertation examines the effects of rough sea surfaces and sub-surface bubbles on high frequency acoustic transmissions. Owing to the strong attenuation of electromagnetic waves in seawater, acoustic waves are used in the underwater realm much in the same way that electromagnetic waves are used in the atmosphere. The transmission and reception of acoustic waves in the underwater environment is important for a variety of fields including navigation, ocean observation, and real-time communications. Rough sea surfaces and sub-surface bubbles alter the acoustic signals that are received not only in the near-surface water column, but also at depth. This dissertation demonstrates that surface roughness and sub-surface bubbles notably affect acoustic transmissions with frequency ranges typical of underwater communications systems (10-50 kHz). The influence of rough surfaces on acoustic transmissions is determined by modeling forward propagation subject to sea surface dynamics that vary with time scales of less than a second to tens of seconds. A time-evolving rough sea surface model is combined with a rough surface formulation of a parabolic equation model for predicting time-varying acoustic fields. Linear surface waves are generated from surface wave spectra, and evolved in time using a Runge-Kutta integration technique. This evolving, range-dependent surface information is combined with other environmental parameters and fed into the acoustic model, giving an approximation of the time-varying acoustic field. The wide-angle parabolic equation model manages the rough sea surfaces by molding them into the boundary conditions for calculations of the near-surface acoustic field. The influence of sub-surface bubbles on acoustic transmissions is determined by modeling the population of bubbles near the surface and using those populations to approximate the effective changes in sound speed and attenuation. Both range-dependent and range-independent bubble models are
National Research Council Canada - National Science Library
Yudith García- Ramírez; Marisol Freire-Seijo; Ortelio Hurtado
2011-01-01
... the social problems of the countryside in Cuba. Traditional bamboo propagation is affected by long intervals of flowering, the limited stock of plant material, the low percentages of rooting and the limited existence of propagules...
Koksbang, S. M.
2017-03-01
Light propagation in two Swiss-cheese models based on anisotropic Szekeres structures is studied and compared with light propagation in Swiss-cheese models based on the Szekeres models' underlying Lemaitre-Tolman-Bondi models. The study shows that the anisotropy of the Szekeres models has only a small effect on quantities such as redshift-distance relations, projected shear and expansion rate along individual light rays. The average angular diameter distance to the last scattering surface is computed for each model. Contrary to earlier studies, the results obtained here are (mostly) in agreement with perturbative results. In particular, a small negative shift, δ DA≔D/A-DA ,b g DA ,b g , in the angular diameter distance is obtained upon line-of-sight averaging in three of the four models. The results are, however, not statistically significant. In the fourth model, there is a small positive shift which has an especially small statistical significance. The line-of-sight averaged inverse magnification at z =1100 is consistent with 1 to a high level of confidence for all models, indicating that the area of the surface corresponding to z =1100 is close to that of the background.
Cai, J. C.; Mei, D. C.
2009-12-01
The effects of time delay on the decline and propagation processes of population in the Malthus-Verhulst model with cross-correlated noises are investigated separately. Through numerically computing and stochastically simulating, we find that: (i) inclusion of time delay in the decline process, increasing the delay time τ weakens the stability of population with short delay and strengthens it with long delay. The stability of population reduces monotonically as the cross-correlated intensity λ increasing. The population of a species goes to extinction with increasing τ and increasing λ; (ii) inclusion of time delay in the propagation process, the increasing τ strengthens the stability of population and the increasing λ weakens it. The increasing τ slows down the growth process of a species while the increasing λ speeds it up. That is, the increasing delay time does not affect roughly the stability of population with short delay but strengthens it with long delay, and the population of species is restricted in the lower level by the larger delay time. The stability of population is weakened and the replacement of old individuals with young ones is accelerated by the increasing cross-correlation intensity between two noises.
Directory of Open Access Journals (Sweden)
T. R. Robinson
Full Text Available A new theory of the propagation of low power electromagnetic test waves through the upper-hybrid resonance layer in the presence of magnetic field-aligned plasma density striations, which includes the effects of multiple scatter, is presented. The case of sinusoidal striations in a cold magnetoplasma is treated rigorously and then extended, in an approximate manner, to the broad-band striation spectrum and warm plasma cases. In contrast to previous, single scatter theories, it is found that the interaction layer is much broader than the wavelength of the test wave. This is due to the combined electric fields of the scattered waves becoming localised on the contour of a fixed plasma density, which corresponds to a constant value for the local upper-hybrid resonance frequency over the whole interaction region. The results are applied to the calculation of the refractive index of an ordinary mode test wave during modification experiments in the ionospheric F-region. Although strong anomalous absorption arises, no new cutoffs occur at the upper-hybrid resonance, so that in contrast to the predictions of previous single scatter theories, no additional reflections occur there. These results are consistent with observations made during ionospheric modification experiments at Tromsø, Norway.
Key words. Ionosphere (active experiments; ionospheric irregularities Radio science (ionospheric propagation
Directory of Open Access Journals (Sweden)
Gerardo González Oramas
2014-07-01
Full Text Available A study was conducted during 15 months under nursery conditions, with the objective to evaluate the effect of different types of seed (in vitro grown plants (V, bulbils of in vitro plants (BV, rhizomes of in vitro plants (RV, bulblets of field plants (BPC and rhizomes of field plants (RPC in the propagation of the henequen (Agave fourcroydes Lem. over indicators related to the growth in the nursery. The indicators evaluated were: plant height, number of leaves, leaf area, daytime oscillation of the titratable acidity, soluble carbohydrates and reducing sugars content. The results indicate that despite of not showing significant differences in height between BPCs and postures derived from in vitro plants (RV and BV, the latter reached a greater development due to their bigger capacity to accumulate and consume titratable acid and to achieve superior content of reducing sugars and total soluble carbohydrates. It was demostrated that the height is influenced by the type of seed that is used in the henequen propagation of moreover the physiological and biochemical indicators related to the development suggest that postures derived from in vitro plants (RV e BV showed a better response to the biological efficiency. Keywords: henequen, in vitro plant, postures, titrable acid
Propagation of inflationary shocks in Costa Rica
Directory of Open Access Journals (Sweden)
Adolfo Rodríguez Vargas
2013-06-01
Full Text Available Abstract We present an estimation of propagation effects of inflationary shocks to groups and specific products of the CPI using a SVAR framework. We found significant propagation effects for 6 out of the 12 groups of the CPI, which together account for 72% of the basket. These groups include those related to food, home apparel and housekeeping services and transportation. The estimations suggest that shocks to Food and Non-Alcoholic Beverages and to fuels are passed through entirely to the rest of the CPI basket. The majority of the most important propagation effects occur between 6 and 10 months after the shocks. This includes propagation effects stemming from shocks to fuels, products with regulated price, tradables and the IPPI index.
Energy Technology Data Exchange (ETDEWEB)
Shoji, K.; Yoshihara, T. [Central Research Institute of Electric Power Industry, Tokyo (Japan)
1996-12-01
The effect of synthetic plant hormone 4-C1-IAA and TFIBA on root growth in plantlet propagation was clarified by the cuttage and the issue culture of strawberry seedling production. A periwinkle, vine, and azalea are the effect of 4-C1-IAA on root growth, and a promotion effect was recognized for rooting and root elongation. The concentration of 4-C1-IAA in which the growth promotion effect of a root most appears varies depending on the species of a plant. The concentration of a periwinkle was 20 ppm, and that of an azalea was 2000 ppm. The growth promotion effect of a root in 4-C1-IAA and TFIBA was compared with IBA for an azalea. The result showed that 4-C1-IAA is the same in the effect as IBA and that TFIBA is higher than for IBA. The growth of a vine`s terminal bud was promoted by the effect of TFIBA on root growth, and the callus occurring when IBA was treated was not formed. The rooting of a strawberry was promoted by the effect of TFIBA on root growth. The combined use of TFIBA and BA promotes the growth of a side bud and forms a multi-bud plant. However, rooting was inhibited. The callus caused by the effect of BA on root growth could be suppressed through the combined use with TFIBA. 6 refs., 7 figs., 2 tabs.
Vegetative propagation of Chrysophyllum albidum G. Don by leafy ...
African Journals Online (AJOL)
Since the provision of clonally propagated superior genotypes of this species would be beneficial to farmers, investigations were conducted to optimize its vegetative propagation. In the study, the first experiment examining the effect of leaf area on propagation success involved cuttings with leaf areas of 0 (leafless), 20, 40, ...
Mu, C.; Lee, J.; guglielmi, Y.
2013-12-01
A mature bedrock fault zone generally consists of a fault core, a damage zone, and a surrounding host rock with different permeabilities, which mainly depend on the fracture density. However, near the surface, when an active thrust fault propagates from bedrocks into an unconsolidated surface cover, it results in a diffused fault zone, which may influence the hydraulic and mechanical properties around the fault zone. It is thus of great concern to understand to which extent surface soil/gravel hydraulic properties modifications by continuously active faulting can impact geotechnical projects in countries under active tectonic context, such as Taiwan, where active faults often are blinded beneath thick soil/gravel covers. By contrast, it is also interesting to decipher those fault-induced permeability modifications to estimate potential activity precursors to large earthquakes. Here, we combined a variety of measurements and analyses on the Chihshang fault, located at the plate suture between the Philippine Sea and Eurasian plates, which converge at a rapid rate of 8 cm/yr in Taiwan. At the Chinyuan site, the Chihshang fault is propagating from depth to emerge through thick alluvial deposits. We characterized the fault geometry and slip behavior at the shallow level by measuring and analyzing horizontal, vertical displacements, and groundwater table across the surface fault zone. The yielded fault dip of 45o in the shallow alluvium is consistent with the observations from surface ruptures and subsurface core logging. The 7-year-long groundwater table record shows that the piezometric level in the hanging wall is about 8 meter higher than that in the footwall in the summer; and about 10 meter higher in the winter. Repeated slug tests have been monthly conducted since 2007 to provide the average permeability within the fault zone and the presumably low-deformed zone outside of the diffused fault zone. Based on in-situ measurements at four wells across the fault zone
Sound Propagation in the Atmosphere
Attenborough, Keith
Propagation of sound close to the ground outdoors involves geometric spreading, air absorption, interaction with the ground, barriers, vegetation and refraction associated with wind and temperature gradients. After a brief survey of historical aspects of the study of outdoor sound and its applications, this chapter details the physical principles associated with various propagation effects, reviews data that demonstrate them and methods for predicting them. The discussion is concerned primarily with the relatively short ranges and spectra of interest when predicting and assessing community noise rather than the frequencies and long ranges of concern, for example, in infrasonic global monitoring or used for remote sensing of the atmosphere. Specific phenomena that are discussed include spreading losses, atmospheric absorption, diffraction by barriers and buildings, interaction of sound with the ground (ground waves, surface waves, ground impedance associated with porosity and roughness, and elasticity effects), propagation through crops, shrubs and trees, wind and temperature gradient effects, shadow zones and incoherence due to atmospheric turbulence. The chapter concludes by suggesting a few areas that require further research.
David, F; Cadby, J; Bosch, G; Brama, P; van Weeren, R; van Schie, H
2012-09-01
Larger superficial digital flexor tendon (SDFT) injuries have a poorer prognosis than smaller lesions. During the inflammatory phase enlargement of the initial lesion is frequently noted, with biomechanical loading being recently proposed to play an important role. To evaluate the effect of lower limb cast immobilisation on tendon lesion propagation in an equine model of surgically induced SDFT injury. Core lesions were surgically induced in both front SDFTs of 6 young mature horses. At the end of surgery, one leg was randomly placed in a lower limb cast and the other leg (control) was bandaged for 10 days. Computerised ultrasonographic tissue characterisation performed at Days 10, 15, 21, 28, 35 and 42 allowed measurement of lesion length (cm) and width (expressed as a percentage of whole tendon cross-section). On Day 42 horses were subjected to euthanasia and both SDFTs were sectioned every centimetre to assess the lesion length macroscopically. Statistics were performed to compare cast vs. control legs with significance set at Plesion length was 19% shorter (Plesion width 57% smaller (P = 0.0002) in the cast legs (6.13 ± 0.12 cm; 6.90 ± 0.64%) than in the control legs (7.30 ± 0.21 cm; 10.85 ± 1.22%). On Day 42 the lesion length on macroscopic evaluation was 19% shorter (P = 0.04) in the cast (7.00 ± 0.36 cm) than in the control legs (8.33 ± 0.33 cm). Cast immobilisation for 10 days effectively reduced lesion propagation (length and width) compared to bandaging in an in vivo model of artificially-induced tendon lesions. A short period of cast immobilisation during the early phase of tendon healing may be an easy and cost-effective way to reduce the initial enlargement of lesion size and hence to improve prognosis. © 2011 EVJ Ltd.
Zimbelman, Eloise G; Keefe, Robert F
2018-01-01
Real-time positioning on mobile devices using global navigation satellite system (GNSS) technology paired with radio frequency (RF) transmission (GNSS-RF) may help to improve safety on logging operations by increasing situational awareness. However, GNSS positional accuracy for ground workers in motion may be reduced by multipath error, satellite signal obstruction, or other factors. Radio propagation of GNSS locations may also be impacted due to line-of-sight (LOS) obstruction in remote, forested areas. The objective of this study was to characterize the effects of forest stand characteristics, topography, and other LOS obstructions on the GNSS accuracy and radio signal propagation quality of multiple Raveon Atlas PT GNSS-RF transponders functioning as a network in a range of forest conditions. Because most previous research with GNSS in forestry has focused on stationary units, we chose to analyze units in motion by evaluating the time-to-signal accuracy of geofence crossings in 21 randomly-selected stands on the University of Idaho Experimental Forest. Specifically, we studied the effects of forest stand characteristics, topography, and LOS obstructions on (1) the odds of missed GNSS-RF signals, (2) the root mean squared error (RMSE) of Atlas PTs, and (3) the time-to-signal accuracy of safety geofence crossings in forested environments. Mixed-effects models used to analyze the data showed that stand characteristics, topography, and obstructions in the LOS affected the odds of missed radio signals while stand variables alone affected RMSE. Both stand characteristics and topography affected the accuracy of geofence alerts.
Schwadron, Nathan A.; Cooper, John F.; Desai, Mihir; Downs, Cooper; Gorby, Matt; Jordan, Andrew P.; Joyce, Colin J.; Kozarev, Kamen; Linker, Jon A.; Mikíc, Zoran; Riley, Pete; Spence, Harlan E.; Török, Tibor; Townsend, Lawrence W.; Wilson, Jody K.; Zeitlin, Cary
2017-07-01
Particle radiation has significant effects for astronauts, satellites and planetary bodies throughout the Solar System. Acute space radiation hazards pose risks to human and robotic exploration. This radiation also naturally weathers the exposed surface regolith of the Moon, the two moons of Mars, and other airless bodies, and contributes to chemical evolution of planetary atmospheres at Earth, Mars, Venus, Titan, and Pluto. We provide a select review of recent areas of research covering the origin of SEPs from coronal mass ejections low in the corona, propagation of events through the solar system during the anomalously weak solar cycle 24 and important examples of radiation interactions for Earth, other planets and airless bodies such as the Moon.
Directory of Open Access Journals (Sweden)
Rajneesh Kumar
2014-01-01
Full Text Available The present investigation deals with the propagation of waves in fiber-reinforced transversely isotropic thermoelastic solid half space with initial stresses under a layer of inviscid liquid. The secular equation for surface equation in compact form is derived after developing the mathematical model. The phase velocity and attenuation coefficients of plane waves are studied numerically for a particular model. Effects of initial stress and thickness of the layer on the phase velocity, attenuation coefficient, and specific loss of energy are predicted graphically in the certain model. A particular case of Rayleigh wave has been discussed and the dispersion curves of the phase velocity and attenuation coefficients have also been presented graphically. Some other particular cases are also deduced from the present investigation.
Schwadron, Nathan A.; Cooper, John F.; Desai, Mihir; Downs, Cooper; Gorby, Matt; Jordan, Andrew P.; Joyce, Colin J.; Kozarev, Kamen; Linker, Jon A.; Mikíc, Zoran; Riley, Pete; Spence, Harlan E.; Török, Tibor; Townsend, Lawrence W.; Wilson, Jody K.; Zeitlin, Cary
2017-11-01
Particle radiation has significant effects for astronauts, satellites and planetary bodies throughout the Solar System. Acute space radiation hazards pose risks to human and robotic exploration. This radiation also naturally weathers the exposed surface regolith of the Moon, the two moons of Mars, and other airless bodies, and contributes to chemical evolution of planetary atmospheres at Earth, Mars, Venus, Titan, and Pluto. We provide a select review of recent areas of research covering the origin of SEPs from coronal mass ejections low in the corona, propagation of events through the solar system during the anomalously weak solar cycle 24 and important examples of radiation interactions for Earth, other planets and airless bodies such as the Moon.
Quantum noise and superluminal propagation
Energy Technology Data Exchange (ETDEWEB)
Segev, Bilha [Department of Chemistry, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105, (Israel); Milonni, Peter W. [Theoretical Division (T-4), Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Babb, James F. [Institute for Theoretical Atomic and Molecular Physics, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States); Chiao, Raymond Y. [Department of Physics, University of California, Berkeley, Berkeley, California 94720 (United States)
2000-08-01
Causal ''superluminal'' effects have recently been observed and discussed in various contexts. The question arises whether such effects could be observed with extremely weak pulses, and what would prevent the observation of an ''optical tachyon.'' Aharonov, Reznik, and Stern (ARS) [Phys. Rev. Lett. 81, 2190 (1998)] have argued that quantum noise will preclude the observation of a superluminal group velocity when the pulse consists of one or a few photons. In this paper we reconsider this question both in a general framework and in the specific example, suggested by Chiao, Kozhekin, and Kurizki (CKK) [Phys. Rev. 77, 1254 (1996)], of off-resonant, short-pulse propagation in an optical amplifier. We derive in the case of the amplifier a signal-to-noise ratio that is consistent with the general ARS conclusions when we impose their criteria for distinguishing between superluminal propagation and propagation at the speed c. However, results consistent with the semiclassical arguments of CKK are obtained if weaker criteria are imposed, in which case the signal can exceed the noise without being ''exponentially large.'' We show that the quantum fluctuations of the field considered by ARS are closely related to superfluorescence noise. More generally, we consider the implications of unitarity for superluminal propagation and quantum noise and study, in addition to the complete and truncated wave packets considered by ARS, the residual wave packet formed by their difference. This leads to the conclusion that the noise is mostly luminal and delayed with respect to the superluminal signal. In the limit of a very weak incident signal pulse, the superluminal signal will be dominated by the noise part, and the signal-to-noise ratio will therefore be very small. (c) 2000 The American Physical Society.
Directory of Open Access Journals (Sweden)
H. Babaei
2015-12-01
Full Text Available To evaluate the effect of different concentrations of IBA, timing of cuttings and type of plant rootstock in cutting-graft propagation (Omega graft of Ficus benjamin cv. variegate, an experiment was performed as a factorial in a completely randomized design with three replications in Gorgan University of Agricultural Sciences and Natural Resources in 2012. Each replication consisted of ten samples. Treatments were consisted of IBA concentration in four levels, 0 (control, 2000, 4000 and 6000 mg/l, two types of rootstock (Ficus benjamina cv. exotica and Ficus amstel and two timing of cuttings (late June and early September. Percentage of graft success, rooting percentage, average root length, root number, root dry weight and survival percentage were evaluated. The results of this experiment showed that the highest percentage of rooting and number of roots obtained in hormone concentrations of 4000 and 6000 mg/l. The maximum of mean root length and root dry weight were obtained at hormone concentration of 4000 mg/l. The greatest percentages of graft success and survival were obtained in all the treatments that the auxin was applied. Most suitable of rootstock in terms of all traits studied, was Ficus benjamina cv.exotica. Best time of rooting, root characteristics and survival percentage were achieved with the cuttings in September. The highest percentage of graft success was achieved in July. The results indicate the beneficial effects of suitable concentration of auxin, timing of cuttings and type of plant rootstock in propagation of Ficus benjamina cv. variegata by bench grafting.
Energy Technology Data Exchange (ETDEWEB)
Lesur, N
2005-12-15
The behaviour of 2D physically short cracks has been studied for an austenitic stainless steel type A304L. Experimental fatigue tests have shown an increase of the threshold fatigue range when the crack length is increasing from 0.1 to 0.8 mm. This effect is explained in term of crack closure variation. The numerical simulation by mean of finite elements supports such an effect of crack closure when computing is performed in plane stress at R=0.1 and R=0.7. Such behaviour is typical for a material characterized by an isotropic and cinematic constitutive cyclic hardening law. The local plasticity effect is shown to control the crack growth rate and has been related to an effective plastic intensity factor range. (author)
David, P
2013-01-01
Propagation of Waves focuses on the wave propagation around the earth, which is influenced by its curvature, surface irregularities, and by passage through atmospheric layers that may be refracting, absorbing, or ionized. This book begins by outlining the behavior of waves in the various media and at their interfaces, which simplifies the basic phenomena, such as absorption, refraction, reflection, and interference. Applications to the case of the terrestrial sphere are also discussed as a natural generalization. Following the deliberation on the diffraction of the "ground? wave around the ear
Lieske, Mike; Schlurmann, Torsten
2016-04-01
INTRODUCTION & MOTIVATION The design of structures in coastal and offshore areas and their maintenance are key components of coastal protection. Usually, assessments of processes and loads on coastal structures are derived from experiments with flow and wave parameters in separate physical models. However, Peregrin (1976) already points out that processes in natural shallow coastal waters flow and sea state processes do not occur separately, but influence each other nonlinearly. Kemp & Simons (1982) perform 2D laboratory tests and study the interactions between a turbulent flow and following waves. They highlight the significance of wave-induced changes in the current properties, especially in the mean flow profiles, and draw attention to turbulent fluctuations and bottom shear stresses. Kemp & Simons (1983) also study these processes and features with opposing waves. Studies on the wave-current interaction in three-dimensional space for a certain wave height, wave period and water depth were conducted by MacIver et al. (2006). The research focus is set on the investigation of long-crested waves on obliquely opposing and following currents in the new 3D wave-current basin. METHODOLOGY In a first step the flow analysis without waves is carried out and includes measurements of flow profiles in the sweet spot of the basin at predefined measurement positions. Five measuring points in the water column have been delineated in different water depths in order to obtain vertical flow profiles. For the characterization of the undisturbed flow properties in the basin, an uniformly distributed flow was generated in the wave basin. In the second step wave analysis without current, the unidirectional wave propagation and wave height were investigated for long-crested waves in intermediate wave conditions. In the sweet spot of the wave basin waves with three different wave directions, three wave periods and uniform wave steepness were examined. For evaluation, we applied a common
Error Propagation in a System Model
Schloegel, Kirk (Inventor); Bhatt, Devesh (Inventor); Oglesby, David V. (Inventor); Madl, Gabor (Inventor)
2015-01-01
Embodiments of the present subject matter can enable the analysis of signal value errors for system models. In an example, signal value errors can be propagated through the functional blocks of a system model to analyze possible effects as the signal value errors impact incident functional blocks. This propagation of the errors can be applicable to many models of computation including avionics models, synchronous data flow, and Kahn process networks.
Affinity Propagation Clustering Using Path Based Similarity
Yuan Jiang; Yuliang Liao; Guoxian Yu
2016-01-01
Clustering is a fundamental task in data mining. Affinity propagation clustering (APC) is an effective and efficient clustering technique that has been applied in various domains. APC iteratively propagates information between affinity samples, updates the responsibility matrix and availability matrix, and employs these matrices to choose cluster centers (or exemplars) of respective clusters. However, since it mainly uses negative Euclidean distance between exemplars and samples as the simila...
Energy Technology Data Exchange (ETDEWEB)
NA
2002-03-04
The purpose of this Analysis and Model Report (AMR) supporting the Site Recommendation/License Application (SR/LA) for the Yucca Mountain Project is the development of elementary analyses of the interactions of a hypothetical dike with a repository drift (i.e., tunnel) and with the drift contents at the potential Yucca Mountain repository. This effort is intended to support the analysis of disruptive events for Total System Performance Assessment (TSPA). This AMR supports the Process Model Report (PMR) on disruptive events (CRWMS M&O 2000a). This purpose is documented in the development plan (DP) ''Coordinate Modeling of Dike Propagation Near Drifts Consequences for TSPA-SR/LA'' (CRWMS M&O 2000b). Evaluation of that Development Plan and the work to be conducted to prepare Interim Change Notice (ICN) 1 of this report, which now includes the design option of ''Open'' drifts, indicated that no revision to that DP was needed. These analyses are intended to provide reasonable bounds for a number of expected effects: (1) Temperature changes to the waste package from exposure to magma; (2) The gas flow available to degrade waste containers during the intrusion; (3) Movement of the waste package as it is displaced by the gas, pyroclasts and magma from the intruding dike (the number of packages damaged); (4) Movement of the backfill (Backfill is treated here as a design option); (5) The nature of the mechanics of the dike/drift interaction. These analyses serve two objectives: to provide preliminary analyses needed to support evaluation of the consequences of an intrusive event and to provide a basis for addressing some of the concerns of the Nuclear Regulatory Commission (NRC) expressed in the Igneous Activity Issue Resolution Status Report.
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 6; Issue 5. Flood Wave Propagation-The Saint Venant Equations. P P Mujumdar. General Article Volume 6 Issue 5 May 2001 pp 66-73. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/006/05/0066-0073 ...
Entropy Generation Analysis of Wildfire Propagation
Directory of Open Access Journals (Sweden)
Elisa Guelpa
2017-08-01
Full Text Available Entropy generation is commonly applied to describe the evolution of irreversible processes, such as heat transfer and turbulence. These are both dominating phenomena in fire propagation. In this paper, entropy generation analysis is applied to a grassland fire event, with the aim of finding possible links between entropy generation and propagation directions. The ultimate goal of such analysis consists in helping one to overcome possible limitations of the models usually applied to the prediction of wildfire propagation. These models are based on the application of the superimposition of the effects due to wind and slope, which has proven to fail in various cases. The analysis presented here shows that entropy generation allows a detailed analysis of the landscape propagation of a fire and can be thus applied to its quantitative description.
Soluble Aβ aggregates can inhibit prion propagation.
Sarell, Claire J; Quarterman, Emma; Yip, Daniel C-M; Terry, Cassandra; Nicoll, Andrew J; Wadsworth, Jonathan D F; Farrow, Mark A; Walsh, Dominic M; Collinge, John
2017-11-01
Mammalian prions cause lethal neurodegenerative diseases such as Creutzfeldt-Jakob disease (CJD) and consist of multi-chain assemblies of misfolded cellular prion protein (PrPC). Ligands that bind to PrPC can inhibit prion propagation and neurotoxicity. Extensive prior work established that certain soluble assemblies of the Alzheimer's disease (AD)-associated amyloid β-protein (Aβ) can tightly bind to PrPC, and that this interaction may be relevant to their toxicity in AD. Here, we investigated whether such soluble Aβ assemblies might, conversely, have an inhibitory effect on prion propagation. Using cellular models of prion infection and propagation and distinct Aβ preparations, we found that the form of Aβ assemblies which most avidly bound to PrP in vitro also inhibited prion infection and propagation. By contrast, forms of Aβ which exhibit little or no binding to PrP were unable to attenuate prion propagation. These data suggest that soluble aggregates of Aβ can compete with prions for binding to PrPC and emphasize the bidirectional nature of the interplay between Aβ and PrPC in Alzheimer's and prion diseases. Such inhibitory effects of Aβ on prion propagation may contribute to the apparent fall-off in the incidence of sporadic CJD at advanced age where cerebral Aβ deposition is common. © 2017 The Authors.
Finger, R. W.
1974-01-01
The effects of proof overload frequency and magnitude on the cyclic crack growth rates of 304 stainless steel weldments were investigated. The welding procedure employed was typical of those used on over-the-road cryogenic vessels. Tests were conducted at room temperature with an overload ratio of 1.50 to determine the effect of overload frequency. Effect of overload magnitude was determined from tests where a room temperature overload was applied between blocks of 1000 cycles applied at 78 K (-320 F). The cyclic stress level used in all tests was typical of the nominal membrane stress generally encountered in full scale vessels. Test results indicate that judicious selection of proof overload frequency and magnitude can reduce crack growth rates for cyclic stress levels.
A Database for Propagation Models
Kantak, Anil V.; Rucker, James
1997-01-01
The Propagation Models Database is designed to allow the scientists and experimenters in the propagation field to process their data through many known and accepted propagation models. The database is an Excel 5.0 based software that houses user-callable propagation models of propagation phenomena. It does not contain a database of propagation data generated out of the experiments. The database not only provides a powerful software tool to process the data generated by the experiments, but is also a time- and energy-saving tool for plotting results, generating tables and producing impressive and crisp hard copy for presentation and filing.
de Vries, Jeroen; Delalande, M.Y.; Abelmann, Leon; Lodder, J.C.
2011-01-01
It has been suggested that the reversal mechanism in highly exchange coupled systems, like Co/Pt multilayers, takes place by nucleation of a reversed domain, followed by domain wall movement. Based on magnetic force microscopy (MFM) and anomalous Hall effect (AHE) measurements, we show that this
Effect of finite ωτ on cyclotron-wave propagation in metals in the long-wavelength limit
DEFF Research Database (Denmark)
Frandsen, J. B.; Gordon, R A
1976-01-01
Exact calculations of cyclotron-wave dispersion curves have been carried out for a degenerate free-electron metal including finite relaxation time effects. The calculated dispersion curves are shown to differ substantially from the experimental dispersion curves in the long-wavelength limit...
Schouten, R.E.; Zhang, X.; Tijskens, L.M.M.; Kooten, van O.
2008-01-01
Broccoli combines high levels of vitamins, fibres and glucosinolates (GLS) with a low calorie count. GLS are precursors for the characteristic broccoli flavour and have anti-carcinogenic properties. This study describes the effect of controlled atmo¬sphere (CA) and temperature on GLS concentrations
Wave Propagation in Bimodular Geomaterials
Kuznetsova, Maria; Pasternak, Elena; Dyskin, Arcady; Pelinovsky, Efim
2016-04-01
Observations and laboratory experiments show that fragmented or layered geomaterials have the mechanical response dependent on the sign of the load. The most adequate model accounting for this effect is the theory of bimodular (bilinear) elasticity - a hyperelastic model with different elastic moduli for tension and compression. For most of geo- and structural materials (cohesionless soils, rocks, concrete, etc.) the difference between elastic moduli is such that their modulus in compression is considerably higher than that in tension. This feature has a profound effect on oscillations [1]; however, its effect on wave propagation has not been comprehensively investigated. It is believed that incorporation of bilinear elastic constitutive equations within theory of wave dynamics will bring a deeper insight to the study of mechanical behaviour of many geomaterials. The aim of this paper is to construct a mathematical model and develop analytical methods and numerical algorithms for analysing wave propagation in bimodular materials. Geophysical and exploration applications and applications in structural engineering are envisaged. The FEM modelling of wave propagation in a 1D semi-infinite bimodular material has been performed with the use of Marlow potential [2]. In the case of the initial load expressed by a harmonic pulse loading strong dependence on the pulse sign is observed: when tension is applied before compression, the phenomenon of disappearance of negative (compressive) strains takes place. References 1. Dyskin, A., Pasternak, E., & Pelinovsky, E. (2012). Periodic motions and resonances of impact oscillators. Journal of Sound and Vibration, 331(12), 2856-2873. 2. Marlow, R. S. (2008). A Second-Invariant Extension of the Marlow Model: Representing Tension and Compression Data Exactly. In ABAQUS Users' Conference.
Propagating Instabilities in Solids
Kyriakides, Stelios
1998-03-01
Instability is one of the factors which limit the extent to which solids can be loaded or deformed and plays a pivotal role in the design of many structures. Such instabilities often result in localized deformation which precipitates catastrophic failure. Some materials have the capacity to recover their stiffness following a certain amount of localized deformation. This local recovery in stiffness arrests further local deformation and spreading of the instability to neighboring material becomes preferred. Under displacement controlled loading the propagation of the transition fronts can be achieved in a steady-state manner at a constant stress level known as the propagation stress. The stresses in the transition fronts joining the highly deformed zone to the intact material overcome the instability nucleation stresses and, as a result, the propagation stress is usually much lower than the stress required to nucleate the instability. The classical example of this class of material instabilities is L/"uders bands which tend to affect mild steels and other metals. Recent work has demonstrated that propagating instabilities occur in several other materials. Experimental and analytical results from four examples will be used to illustrate this point: First the evolution of L=FCders bands in mild steel strips will be revisited. The second example involves the evolution of stress induced phase transformations (austenite to martensite phases and the reverse) in a shape memory alloy under displacement controlled stretching. The third example is the crushing behavior of cellular materials such as honeycombs and foams made from metals and polymers. The fourth example involves the axial broadening/propagation of kink bands in aligned fiber/matrix composites under compression. The microstructure and, as a result, the micromechanisms governing the onset, localization, local arrest and propagation of instabilities in each of the four materials are vastly different. Despite this
Energy Technology Data Exchange (ETDEWEB)
Wei, Hong-Xing [Beijing Advanced Innovation Center for Imaging Technology, Capital Normal University, Beijing 100048 (China); Li, Yong-Dong, E-mail: LYDbeijing@163.com [Beijing Advanced Innovation Center for Imaging Technology, Capital Normal University, Beijing 100048 (China); Department of Mechanical Engineering, Academy of Armored Force Engineering, Beijing 100072 (China); Xiong, Tao [Department of Mechanical Engineering, Academy of Armored Force Engineering, Beijing 100072 (China); Guan, Yong [Beijing Advanced Innovation Center for Imaging Technology, Capital Normal University, Beijing 100048 (China)
2016-09-07
The problem of dispersive SH wave in a piezoelectric/piezomagnetic plate that contains an imperfect interface is considered in the present work. An imperfection coupling model is adopted to describe the magnetic, electric and mechanical imperfections on the interface. A transcendental dispersion equation is derived and numerically solved to get the phase velocity. The validity of the numerical procedure is verified in a degenerated case. The effects of the coupled interfacial imperfections on the dispersion behavior of SH waves are discussed in detail and the related underlying physical mechanisms are explained. - Highlights: • SH-wave is investigated in a multiferroic plate with coupled interfacial imperfections. • SH-wave is affected by both interfacial imperfections and their inter-couplings. • Physical mechanisms of the effects are explained via energy transformations.
Kandula, Max
2012-01-01
The Sound attenuation and dispersion in saturated gas-vapor-droplet mixtures with evaporation has been investigated theoretically. The theory is based on an extension of the work of Davidson (1975) to accommodate the effects of transpiration on the linear particle relaxation processes of mass, momentum and energy transfer. It is shown that the inclusion of transpiration in the presence of mass transfer improves the agreement between the theory and the experimental data of Cole and Dobbins (1971) for sound attenuation in air-water fogs at low droplet mass concentrations. The results suggest that transpiration has an appreciable effect on both sound absorption and dispersion for both low and high droplet mass concentrations.
Javan, N. Sepehri
2017-09-01
The modulation instability of intense circularly polarized laser beam in hot magnetized dusty plasma is studied. A nonlinear equation describing the interaction of laser with dusty plasma in the quasi-neutral approximation is derived. The effect of negative and positive dust grains on the laser modulation growth rate is studied. It is shown that the existence of positive dust grains instead of ions can substantially improve the modulation growth rate.
1984-07-01
Science Division, Library Trans-Australia Airlines, Library Qantas Airways Limited SEC of Vic., Herman Research Laboratory, Library Ansett Airlines of...consideration was given to imposing flight loading limits for particular aircraft to reduce the risk of in-flight structural failure-in effect, to...potential interactions of cracks developing on the other side of the hole, the analysis of crack growth rates was limited to a maximum crack depth of about
Synaptic Contacts Enhance Cell-to-Cell Tau Pathology Propagation
Directory of Open Access Journals (Sweden)
Sara Calafate
2015-05-01
Full Text Available Accumulation of insoluble Tau protein aggregates and stereotypical propagation of Tau pathology through the brain are common hallmarks of tauopathies, including Alzheimer’s disease (AD. Propagation of Tau pathology appears to occur along connected neurons, but whether synaptic contacts between neurons are facilitating propagation has not been demonstrated. Using quantitative in vitro models, we demonstrate that, in parallel to non-synaptic mechanisms, synapses, but not merely the close distance between the cells, enhance the propagation of Tau pathology between acceptor hippocampal neurons and Tau donor cells. Similarly, in an artificial neuronal network using microfluidic devices, synapses and synaptic activity are promoting neuronal Tau pathology propagation in parallel to the non-synaptic mechanisms. Our work indicates that the physical presence of synaptic contacts between neurons facilitate Tau pathology propagation. These findings can have implications for synaptic repair therapies, which may turn out to have adverse effects by promoting propagation of Tau pathology.
Ocegueda, M.; Hernandez, E.; Stepanov, S.; Agruzov, P.; Shamray, A.
2014-06-01
Experimental observations of nonstationary coherent optical phenomena, i.e., optical nutation, free induction, and photon echo, in the acetylene (12C2H2) filled hollow-core photonic-crystal fiber (PCF) are reported. The presented results were obtained for the acetylene vibration-rotational transition P9 at wavelength 1530.37 nm at room temperature under a gas pressure of acetylene molecules' presence inside the effective PCF modal area and by intermolecule collisions. An accelerated attenuation of the optical nutation oscillations is explained by a random orientation of acetylene molecules.
Toth, Laszlo Daniel
2013-05-01
The well-known phenomenon of the formation of a Bose-Einstein condensate (BEC), a striking consequence of the Bose-Einstein statistics, has been traditionally linked to an ensemble of ultra-cold gas molecules. However, classical systems can also exhibit condensation effects; in the field of photonics, for example, signatures of this condensation in the mode dynamics (\\'light condensation\\', LC) have been theoretically investigated and experimentally observed in various types of multimode lasers [1,2 and ref. therein]. © 2013 IEEE.
Preventing Unofficial Information Propagation
Le, Zhengyi; Ouyang, Yi; Xu, Yurong; Ford, James; Makedon, Fillia
Digital copies are susceptible to theft and vulnerable to leakage, copying, or manipulation. When someone (or some group), who has stolen, leaked, copied, or manipulated digital documents propagates the documents over the Internet and/or distributes those through physical distribution channels many challenges arise which document holders must overcome in order to mitigate the impact to their privacy or business. This paper focuses on the propagation problem of digital credentials, which may contain sensitive information about a credential holder. Existing work such as access control policies and the Platform for Privacy Preferences (P3P) assumes that qualified or certified credential viewers are honest and reliable. The proposed approach in this paper uses short-lived credentials based on reverse forward secure signatures to remove this assumption and mitigate the damage caused by a dishonest or honest but compromised viewer.
Directory of Open Access Journals (Sweden)
Jorge Gago
Full Text Available BACKGROUND: Plant acclimation is a highly complex process, which cannot be fully understood by analysis at any one specific level (i.e. subcellular, cellular or whole plant scale. Various soft-computing techniques, such as neural networks or fuzzy logic, were designed to analyze complex multivariate data sets and might be used to model large such multiscale data sets in plant biology. METHODOLOGY AND PRINCIPAL FINDINGS: In this study we assessed the effectiveness of applying neuro-fuzzy logic to modeling the effects of light intensities and sucrose content/concentration in the in vitro culture of kiwifruit on plant acclimation, by modeling multivariate data from 14 parameters at different biological scales of organization. The model provides insights through application of 14 sets of straightforward rules and indicates that plants with lower stomatal aperture areas and higher photoinhibition and photoprotective status score best for acclimation. The model suggests the best condition for obtaining higher quality acclimatized plantlets is the combination of 2.3% sucrose and photonflux of 122-130 µmol m(-2 s(-1. CONCLUSIONS: Our results demonstrate that artificial intelligence models are not only successful in identifying complex non-linear interactions among variables, by integrating large-scale data sets from different levels of biological organization in a holistic plant systems-biology approach, but can also be used successfully for inferring new results without further experimental work.
Gago, Jorge; Martínez-Núñez, Lourdes; Landín, Mariana; Flexas, Jaume; Gallego, Pedro P
2014-01-01
Plant acclimation is a highly complex process, which cannot be fully understood by analysis at any one specific level (i.e. subcellular, cellular or whole plant scale). Various soft-computing techniques, such as neural networks or fuzzy logic, were designed to analyze complex multivariate data sets and might be used to model large such multiscale data sets in plant biology. In this study we assessed the effectiveness of applying neuro-fuzzy logic to modeling the effects of light intensities and sucrose content/concentration in the in vitro culture of kiwifruit on plant acclimation, by modeling multivariate data from 14 parameters at different biological scales of organization. The model provides insights through application of 14 sets of straightforward rules and indicates that plants with lower stomatal aperture areas and higher photoinhibition and photoprotective status score best for acclimation. The model suggests the best condition for obtaining higher quality acclimatized plantlets is the combination of 2.3% sucrose and photonflux of 122-130 µmol m(-2) s(-1). Our results demonstrate that artificial intelligence models are not only successful in identifying complex non-linear interactions among variables, by integrating large-scale data sets from different levels of biological organization in a holistic plant systems-biology approach, but can also be used successfully for inferring new results without further experimental work.
Superluminal graviton propagation
Benakli, Karim; Chapman, Shira; Darmé, Luc; Oz, Yaron
2016-10-01
We use the method of characteristics to study superluminal graviton (which we call the swift graviton) propagation in theories of higher-curvature gravity of the form (Riemann)2 , (Riemann)3 , ∇2(Riemann)2 and (Riemann)4 . We consider a p p -wave background. When probed by gravitons with an appropriate polarization, several of the gravitational theories under consideration exhibit characteristic hypersurfaces outside the flat spacetime light cone.
Beam Propagation Experimental Study.
1983-04-01
Kiuttu C. A. Ekdahl N. F. Roderick F49620-81-C-0016 B. A. Sabol L. A. Wright D. J. Sullivan______________ 3 P;ERFORMING ORGANIZATION NAME AND ADDRESS...pulse * transmission through the atmosphere remain unresolved. The complexity of beam propagation physics and air chemistry makes the prediction of beam...higher front velocities than predicted by Eq. (27). Fessenden et al. 1 6 measured vf - 0.77 v in a detailed series of experiments utilizing the FX-25
Energy Technology Data Exchange (ETDEWEB)
Romero-Garcia, V [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas (Spain); Sanchez-Perez, J V [Centro de Tecnologias Fisicas: Acustica, Materiales y Astrofisica, Universidad Politecnica de Valencia (Spain); Garcia-Raffi, L M, E-mail: virogar1@gmail.com [Instituto Universitario de Matematica Pura y Aplicada, Universidad Politecnica de Valencia (Spain)
2011-07-06
The use of sonic crystals (SCs) as environmental noise barriers has certain advantages from both the acoustical and the constructive points of view with regard to conventional ones. However, the interaction between the SCs and the ground has not been studied yet. In this work we are reporting a semi-analytical model, based on the multiple scattering theory and on the method of images, to study this interaction considering the ground as a finite impedance surface. The results obtained here show that this model could be used to design more effective noise barriers based on SCs because the excess attenuation of the ground could be modelled in order to improve the attenuation properties of the array of scatterers. The results are compared with experimental data and numerical predictions thus finding good agreement between them.
Li, X. D.; Hu, Z. M.; Jiang, Z. L.
2017-09-01
Bio-shock tubes (BSTs) can approximately simulate the typical blast waves produced by nuclear or chemical charge explosions for use in biological damage studies. The profile of an ideal blast wave in air is characterized by the overpressure, the negative pressure, and the positive pressure duration, which are determined by the geometric configurations of BSTs. Numerical experiments are carried out using the Eulerian equations by the dispersion-controlled dissipative scheme to investigate the effect of different structural components on ideal blast waveforms. The results show that cylindrical and conical frustum driver sections with an appropriate length can produce typical blast wave profiles, but a flattened peak pressure may appear when using a tube of a longer length. Neither a double-expansion tube nor a shrinkage tube set in BSTs is practical for the production of an ideal blast waveform. In addition, negative pressure recovery will occur, exceeding the ambient pressure with an increase in pressure in the vacuum section.
Boucaud, Ph.; De Soto, F.; Rodríguez-Quintero, J.; Zafeiropoulos, S.
2017-11-01
The authors of [Phys. Rev. D 94, 014502 (2016)] reported about a careful analysis of the impact of lattice artifacts on the S U (3 ) gauge-field propagators. In particular, they found that the low-momentum behavior of the renormalized propagators depends on the lattice bare coupling and interpreted this as the result of its being affected by discretization artifacts. We discuss here a different interpretation for these results.
Directory of Open Access Journals (Sweden)
I. Dwimahyani
2010-08-01
Full Text Available The study on the effect of gamma irradiation on in-vitro shoot growth of chrysanthemum cv. Yellow Puma has been carried out. The aim of the study was to observe genetic variability of shoot growth caused by gamma irradiation. Shoot explants with four leaves were irradiated by gamma with dose of 10, 15 and 20 Gy with 3 replications at each of dose. The irradiated shoot explants were then transferred into fresh MS solid medium and placed in a growth room. Observation was performed on number of leaves and branches on M1V0 generation, while plantlets height and number of branches were observed a M1V1 generation. Number of survival plantlets and multiplication rate on three subsequent subcultures were observed as well. Results showed that gamma rays with dose of 20 Gy inhibited growth of leaves as much as 50% compared to control (shoots without irradiation, and branches 73.7% in three weeks. Observation on multiplication rate at M1V1 generation showed that gamma irradiation with dose of 10 Gy promoted multiplication rate as much as 10% higher than control. It can be concluded that in vitro mutagenesis using gamma iradiation with dose of 10 to 15 Gy can be used for inducing genetic variability of chrysanthemum cv. Yellow Puma.
Lumsden, N. A.; Lukes, L.; Nelson, J.; Liles, W. C.; Kerby, K. C.; Crowov, F.; Rockway, J.
2015-12-01
The first experiments to study the effects of a solar eclipse on radio wave propagation were done in 1912 utilizing Low Frequency (LF; 30 - 300 kHz) radio waves at a handful of sites across Europe before any theory of the ionosphere had been confirmed and even before the word "ionosphere" existed. In the 1920s, a large cooperative experiment was promoted in the U.S. by Scientific American magazine. They collected over 2000 reports of AM broadcast stations from throughout the U.S. Unfortunately, many of the submissions were unusable because they lacked critical information such as date, time or location. We propose to use the 2017 solar eclipse over the continental U.S. to conduct the first wide-area LF propagation study. To perform this study, we plan to crowdsource the collection of the data by engaging student groups, citizens, and the scientific community. The tools for the different collection stations will consist of a simple homemade antenna, a simple receiver to convert the radio frequency (RF) signals to audio frequencies and a smart phone app. By using the time, date and location features of the smart phone, the problems experienced in the Scientific American experiment will be minimized. By crowdsourcing the observation sites, a number of different short, medium and long-paths studies can be obtained as the total eclipse crosses the continental U.S. The transmitter for this experiment will be WWVB located near Fort Collins, Colorado on 60.000 kHz. This is a U.S. frequency standard that is operated by NIST and transmits time codes. A second frequency, 55.500 kHz transmitted by a LF station in Dixon, CA is also being considered for this experiment. We will present an overall strategy for recruiting participants/crowdsourcing the RF collections during the 2017 total solar eclipse. Preliminary coverage calculations will be presented for WWVB and Dixon, as well as path loss calculations that can be expected during the solar eclipse condition. We will also
Energy Technology Data Exchange (ETDEWEB)
Melchor Garcia, Nicolas Ageo
2005-02-15
This work presents the state of art of the behavior of buried pipelines facing the effect of the propagation of seismic waves. Special attention has been given to the modeling of the soil-piping system. Some analytical models are presented and discussed in great detail. The purpose of this is to contribute, in particular, to the following aspects: First, it attempts to be a reference work for the geotechnical engineers facing problems related to the seismic wave propagation phenomenon in buried structures, since within the consulted literature there are many of the principles presented in here, that are related with the seismic engineering, the reaction module, as well as expressions or investigations performed in piles. Second, a cuasi-static numerical model is presented that analyzes the continuous piping through a stress vector of sinusoidal type. The analysis of the stresses and deformations that the ground transmits to the pipe is made using a ground-to-pipe interaction model. For a low level of deformations an elastic behavior of transference in the interface is considered in the inter-phase ground-piping. In the case of greater deformations it is assumed that sliding is presented because the surrounding ground presents fault by shearing stress in the surrounding ground. The analysis covers solely the case with axial deformations in straight sections. Finally, it intends to give a series of recommendations for future research works on the modeling of buried pipelines. In this work, the influence of several aspects on the response of the pipelines to the propagation of seismic waves is analyzed and discussed; such as the conditions of topography, geology, ground stratigraphy and the rigidity changes in the surrounding ground of the pipe. [Spanish] Este trabajo presenta el estado del arte sobre el comportamiento de tuberias enterradas ante efecto de programacion de ondas sismicas. Una especial atencion ha sido dada a la modelacion del sistema suelo
Directory of Open Access Journals (Sweden)
Kuldeep YADAV
2011-11-01
Full Text Available This study was undertaken with the objective of standardizing the protocol for the micropropagation of Albizia lebbeck (L.. Seeds were collected from three different colored pods (yellow, dark yellow and brownish yellow harvested from field grown Albizia tree from November to January and were surface sterilized using different concentration of mercuric chloride (0.05-0.15% w/v for different exposure durations (2, 5 and 8 min. Seeds collected from dark-yellow colored pod showed the highest germination (83.3 % and short germination time (4.29 days, while those collected from brownish yellow colored pod showedrelatively less germination (53.3% and longer germination time (6.0 days. Success of seed germination increased with maturity upto a certain level after which it declines significantly with increasing harvesting time. A five-minute dip of HgCl2 (0.1% was found to be the optimum duration for giving the maximum (83.3% germinated and healthy seedlings. Increasing time and concentration ofHgCl2 significantly reduced the contamination, but on the other hand it also effected the germination of seeds. Best shoot regeneration response from in vitro nodal segment was obtained on MS medium supplemented with BAP (2.0 mg/l + NAA (0.5 mg/l. The highest percentage of callus induction (85% was also observed in the above same media from in vitro internodal segment. Proliferated micro-shoots showed 60% rooting on half strength medium supplemented with IAA (2.0 mg/l after 4 weeks of culturing. The well rooted micropropagated plantlets were acclimatized and successfully established in pots containing sterilized soil and sand mixture (1:1 with 60% survival rate under field conditions.
Directory of Open Access Journals (Sweden)
Oscar Humberto Alvarado-Sanabria
2014-12-01
Full Text Available The growth and development of cape gooseberry plants obtained from cuttings is affected by microorganisms in the substrate and by the concentration of plant growth regulators applied during planting. Using a factorial design, the effect of four concentrations of indole-3-butyric acid (IBA (0, 800, 1,200, and 1,600 mg L-1 and four suspensions of Trichoderma harzianum (0, 2·10(6, 3·10(6, and 4·10(6 cfu/mL on the growth of cape gooseberry cuttings was evaluated. Apical cuttings were used, 20 cm long, from 20-month-old plants of the Colombian ecotype, which were planted in pots (2 L using peat moss with burned rice husks as the substrate at a 3:1 ratio (v/v. The 800 mg L-1 of IBA application showed the highest accumulation of total dry mass (DM and root DM. Moreover, 800 mg L-1 of IBA resulted in the highest leaf chlorophyll content, showing significant differences from 1,600 mg L-1, which had the lowest value. The 3·10(6 cfu/mL suspension of T. harzianum caused a greater accumulation of root DM and total DM and a higher leaf area in the plants. The most favorable interaction between the factors, which favors the growth of cape gooseberry plants obtained from cuttings, was observed with the application of 800 mg L-1 of IBA and 3·10(6 cfu/mL of T. harzianum.
Mahmoud, Abeer A.
2018-01-01
Some important evolution nonlinear partial differential equations are derived using the reductive perturbation method for unmagnetized collisionless system of five component plasma. This plasma system is a multi-ion contains negatively and positively charged Oxygen ions (heavy ions), positive Hydrogen ions (lighter ions), hot electrons from solar origin and colder electrons from cometary origin. The positive Hydrogen ion and the two types of electrons obey q-non-extensive distributions. The derived equations have three types of ion acoustic waves, which are soliton waves, shock waves and kink waves. The effects of the non-extensive parameters for the hot electrons, the colder electrons and the Hydrogen ions on the propagation of the envelope waves are studied. The compressive and rarefactive shapes of the three envelope waves appear in this system for the first order of the power of the nonlinearity strength with different values of non-extensive parameters. For the second order, the strength of nonlinearity will increase and the compressive type of the envelope wave only appears.
Stojadinović, Bojana; Tenne, Tamar; Zikich, Dragoslav; Rajković, Nemanja; Milošević, Nebojša; Lazović, Biljana; Žikić, Dejan
2015-11-26
The velocity by which the disturbance travels through the medium is the wave velocity. Pulse wave velocity is one of the main parameters in hemodynamics. The study of wave propagation through the fluid-fill elastic tube is of great importance for the proper biophysical understanding of the nature of blood flow through of cardiovascular system. The effect of viscosity on the pulse wave velocity is generally ignored. In this paper we present the results of experimental measurements of pulse wave velocity (PWV) of compression and expansion waves in elastic tube. The solutions with different density and viscosity were used in the experiment. Biophysical model of the circulatory flow is designed to perform measurements. Experimental results show that the PWV of the expansion waves is higher than the compression waves during the same experimental conditions. It was found that the change in viscosity causes a change of PWV for both waves. We found a relationship between PWV, fluid density and viscosity. Copyright © 2015 Elsevier Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
Ricardo Albarracín
2016-01-01
Full Text Available A well-defined condition-monitoring for power transformers is key to implementing a correct condition-based maintenance (CBM. In this regard, partial discharges (PD measurement and its analysis allows to carry out on-line maintenance following the standards IEC-60270 and IEC-60076. However, new PD measurements techniques, such as acoustics or electromagnetic (EM acquisitions using ultra-high-frequency (UHF sensors are being taken into account, IEC-62478. PD measurements with antennas and the effect of their EM propagation in power transformer tanks is an open research topic that is considered in this paper. In this sense, an empty tank model is studied as a rectangular cavity and their resonances are calculated and compared with their measurement with a network analyser. Besides, two low cost improved monopole antennas deployed inside and outside of the tank model capture background noise and PD pulses in three different test objects (Nomex, twisted pair and insulator. The average spectrum of them are compared and can be found that mainly, the antenna frequency response, the frequency content distribution depending on the PD source and the enclosure resonances modes are the main factors to be considered in PD acquisitions with these sensors. Finally, with this set-up, it is possible to measure PD activity inside the tank from outside.
Lederer, Susan M.; Jensen, E. A.; Fane, M.; Smith, D. C.; Holmes, J.; Keller, L. P.; Lindsay, S. S.; Wooden, D. H.; Cintala, M. J.; Zolensky, M. E.
2015-01-01
Comets and asteroids are subjected to extremely cold conditions throughout their lifetimes. During their sojourns in the solar system, they are subjected to collisions at speeds that are easily capable of generating shock waves in their constituent materials. In addition to ices, more common silicate minerals such as olivines and pyroxenes are important components of these objects. The collision-induced shocks could affect the spectral signatures of those mineral components, which could in turn be detected telescopically. We have embarked on a project to determine how impact-generated shock might affect the reflectance spectra and structures of select silicates as both impact speed and target temperature are varied systematically. While the effects of impact speed (in the form of shock stress) on numerous materials have been and continue to be studied, the role of target temperature has received comparatively little attention, presumably because of the operational difficulties it can introduce to experimentation. Our experiments were performed with the vertical gun in the Experimental Impact Laboratory of the Johnson Space Center. A liquid-nitrogen system was plumbed to permit cooling of the target container and its contents under vacuum to temperatures as low as -100 C (173 K). Temperatures were monitored by thermocouples mounted on the outside of the target container. Because those sensors were not in contact with the target material at impact, the measured temperatures are treated as lower limits for the actual values. Peridot (Mg-rich olivine) and enstatite (Mg-rich orthopyroxene) were used as targets, which involved the impact of alumina (Al2O3) spheres at speeds of 2.0 - 2.7 km s(exp -1) and temperatures covering 25 C to -100 C (298 K to 173 K). We have begun collecting and analyzing data in the near to mid-IR with a Fourier-transform infrared spectrometer, and preliminary analyses show that notable differences in absorption-band strength and position occur
Wave propagation in elastic solids
Achenbach, Jan
1984-01-01
The propagation of mechanical disturbances in solids is of interest in many branches of the physical scienses and engineering. This book aims to present an account of the theory of wave propagation in elastic solids. The material is arranged to present an exposition of the basic concepts of mechanical wave propagation within a one-dimensional setting and a discussion of formal aspects of elastodynamic theory in three dimensions, followed by chapters expounding on typical wave propagation phenomena, such as radiation, reflection, refraction, propagation in waveguides, and diffraction. The treat
Stochastic model in microwave propagation
Energy Technology Data Exchange (ETDEWEB)
Ranfagni, A. [“Nello Carrara” Institute of Applied Physics, CNR Florence Research Area, Via Madonna del Piano 10, 50019 Sesto Fiorentino (Italy); Mugnai, D., E-mail: d.mugnai@ifac.cnr.it [“Nello Carrara” Institute of Applied Physics, CNR Florence Research Area, Via Madonna del Piano 10, 50019 Sesto Fiorentino (Italy)
2011-11-28
Further experimental results of delay time in microwave propagation are reported in the presence of a lossy medium (wood). The measurements show that the presence of a lossy medium makes the propagation slightly superluminal. The results are interpreted on the basis of a stochastic (or path integral) model, showing how this model is able to describe each kind of physical system in which multi-path trajectories are present. -- Highlights: ► We present new experimental results on electromagnetic “anomalous” propagation. ► We apply a path integral theoretical model to wave propagation. ► Stochastic processes and multi-path trajectories in propagation are considered.
Wave propagation retrieval method for chiral metamaterials
DEFF Research Database (Denmark)
Andryieuski, Andrei; Malureanu, Radu; Lavrinenko, Andrei
2010-01-01
In this paper we present the wave propagation method for the retrieving of effective properties of media with circularly polarized eigenwaves, in particularly for chiral metamaterials. The method is applied for thick slabs and provides bulk effective parameters. Its strong sides are the absence...
Neutrino propagation in matter with general interactions.
Energy Technology Data Exchange (ETDEWEB)
Grossman, yuval
1999-04-09
We present a general analysis of the effective potential for neutrino propagation in matter, assuming a generic set of Lorentz invariant non-derivative interactions. We find that in addition to the known vector and axial vector terms, in a polarized medium also tensor interactions can play an important role. We compute the effective potential arising from a tensor interaction. We show that the components of the tensor potential transverse to the direction of the neutrino propagation can induce a neutrino spin-flip, similar to the one induced by a transverse magnetic field.
Wave propagation scattering theory
Birman, M Sh
1993-01-01
The papers in this collection were written primarily by members of the St. Petersburg seminar in mathematical physics. The seminar, now run by O. A. Ladyzhenskaya, was initiated in 1947 by V. I. Smirnov, to whose memory this volume is dedicated. The papers in the collection are devoted mainly to wave propagation processes, scattering theory, integrability of nonlinear equations, and related problems of spectral theory of differential and integral operators. The book is of interest to mathematicians working in mathematical physics and differential equations, as well as to physicists studying va
Polarization Shaping for Control of Nonlinear Propagation
Bouchard, Frédéric; Larocque, Hugo; Yao, Alison M.; Travis, Christopher; De Leon, Israel; Rubano, Andrea; Karimi, Ebrahim; Oppo, Gian-Luca; Boyd, Robert W.
2016-12-01
We study the nonlinear optical propagation of two different classes of light beams with space-varying polarization—radially symmetric vector beams and Poincaré beams with lemon and star topologies—in a rubidium vapor cell. Unlike Laguerre-Gauss and other types of beams that quickly experience instabilities, we observe that their propagation is not marked by beam breakup while still exhibiting traits such as nonlinear confinement and self-focusing. Our results suggest that, by tailoring the spatial structure of the polarization, the effects of nonlinear propagation can be effectively controlled. These findings provide a novel approach to transport high-power light beams in nonlinear media with controllable distortions to their spatial structure and polarization properties.
Viscothermal wave propagation including acousto-elastic interaction
Beltman, W.M.
1998-01-01
This research deals with pressure waves in a gas trapped in thin layers or narrow tubes. In these cases viscous and thermal effects can have a significant effect on the propagation of waves. This so-called viscothermal wave propagation is governed by a number of dimensionless parameters. The two
Quantum propagation across cosmological singularities
Gielen, Steffen; Turok, Neil
2017-05-01
The initial singularity is the most troubling feature of the standard cosmology, which quantum effects are hoped to resolve. In this paper, we study quantum cosmology with conformal (Weyl) invariant matter. We show that it is natural to extend the scale factor to negative values, allowing a large, collapsing universe to evolve across a quantum "bounce" into an expanding universe like ours. We compute the Feynman propagator for Friedmann-Robertson-Walker backgrounds exactly, identifying curious pathologies in the case of curved (open or closed) universes. We then include anisotropies, fixing the operator ordering of the quantum Hamiltonian by imposing covariance under field redefinitions and again finding exact solutions. We show how complex classical solutions allow one to circumvent the singularity while maintaining the validity of the semiclassical approximation. The simplest isotropic universes sit on a critical boundary, beyond which there is qualitatively different behavior, with potential for instability. Additional scalars improve the theory's stability. Finally, we study the semiclassical propagation of inhomogeneous perturbations about the flat, isotropic case, at linear and nonlinear order, showing that, at least at this level, there is no particle production across the bounce. These results form the basis for a promising new approach to quantum cosmology and the resolution of the big bang singularity.
Moskalenko, I. V.
2004-01-01
Astrophysics of cosmic rays and gamma rays depends very much on the quality of the data, which become increasingly accurate each year and therefore more constraining. While direct measurements of cosmic rays are possible in only one location on the outskirts of the Milky Way, the Galactic diffuse gamma-ray emission provides insights into the spectra of cosmic rays in distant locations, therefore complementing the local cosmic-ray studies. This connection, however, requires extensive modeling and is yet to be explored in detail. The GUST mission, which is scheduled for launch in 2007 and is capable of measuring gamma-rays in the range 20 MeV - 300 GeV, will change the status quo dramatically. Galactic diffuse gamma-ray emission gathered by GUST will require adequate theoretical models. The efforts will be rewarded by the wealth of information on cosmic ray spectra and fluxes in remote locations. In its turn, a detailed cosmic ray propagation model will provide a reliable basis for other studies such as search for dark matter signals in cosmic rays and diffuse gamma rays, spectrum and origin of the extragalactic gamma-ray emission, theories of nucleosynthesis and evolution of elements etc. In this talk, I will discuss what we can learn studying the cosmic ray propagation and diffuse gamma-ray emission.
2006-09-30
wave equation (PE) [ Hardin and Tappert, 1970], well known as one of the most important wave-theoretic, range-dependent propagation models [ Jensen ...5- REFERENCES F. B. Jensen , W. A. Kuperman, M. B. Porter and H. Schmidt, Computation Ocean Acoustics, Springer, 2000. PUBLICATIONS A. R
Controls on flood and sediment wave propagation
Bakker, Maarten; Lane, Stuart N.; Costa, Anna; Molnar, Peter
2015-04-01
The understanding of flood wave propagation - celerity and transformation - through a fluvial system is of generic importance for flood forecasting/mitigation. In association with flood wave propagation, sediment wave propagation may induce local erosion and sedimentation, which will affect infrastructure and riparian natural habitats. Through analysing flood and sediment wave propagation, we gain insight in temporal changes in transport capacity (the flood wave) and sediment availability and transport (the sediment wave) along the river channel. Heidel (1956) was amongst the first to discuss the progressive lag of sediment concentration behind the corresponding flood wave based on field measurements. Since then this type of hysteresis has been characterized in a number of studies, but these were often based on limited amount of floods and measurement sites, giving insufficient insight into associated forcing mechanisms. Here, as part of a project concerned with the hydrological and geomorphic forcing of sediment transfer processes in alpine environments, we model the downstream propagation of short duration, high frequency releases of water and sediment (purges) from a flow intake in the Borgne d'Arolla River in south-west Switzerland. A total of >50 events were measured at 1 minute time intervals using pressure transducers and turbidity probes at a number of sites along the river. We show that flood and sediment wave propagation can be well represented through simple convection diffusion models. The models are calibrated/validated to describe the set of measured waves and used to explain the observed variation in wave celerity and diffusion. In addition we explore the effects of controlling factors including initial flow depth, flood height, flood duration, bed roughness, bed slope and initial sediment concentration, on the wave propagation processes. We show that the effects of forcing mechanisms on flood and sediment wave propagation will lead to different
Directory of Open Access Journals (Sweden)
Jifei Zhao
2016-06-01
Full Text Available As an important electron source, Micro-Pulse electron Gun (MPG which is qualified for producing high average current, short pulse, low emittance electron bunches steadily holds promise to use as an electron source of Coherent Smith-Purcell Radiation (CSPR, Free Electron Laser (FEL. The stable output of S-band MPG has been achieved in many labs. To establish reliable foundation for the future application of it, the propagation of picosecond electron bunch produced by MPG should be studied in detail. In this article, the MPG which was working on the rising stage of total effective Secondary Electron Yield (SEY curve was introduced. The self-bunching mechanism was discussed in depth both in the multipacting amplifying state and the steady working state. The bunch length broadening induced by the longitudinal space-charge (SC effects was investigated by different theoretical models in different regions. The 2D PIC codes MAGIC and beam dynamic codes TraceWin simulations were also performed in the propagation. The result shows an excellent agreement between the simulation and the theoretical analysis for bunch length evolution.
Research on Trust Propagation Models in Reputation Management Systems
Directory of Open Access Journals (Sweden)
Zhiyuan Su
2014-01-01
Full Text Available Feedback based reputation systems continue to gain popularity in eCommerce and social media systems today and reputation management in large social networks needs to manage cold start and sparseness in terms of feedback. Trust propagation has been widely recognized as an effective mechanism to handle these problems. In this paper we study the characterization of trust propagation models in the context of attack resilience. We characterize trust propagation models along three dimensions: (i uniform propagation and conditional propagation, (ii jump strategies for breaking unwanted cliques, and (iii decay factors for differentiating recent trust history from remote past history. We formally and experimentally show that feedback similarity is a critical measure for countering colluding attacks in reputation systems. Without feedback similarity guided control, trust propagations are vulnerable to different types of colluding attacks.
Surface acoustic wave propagation in graphene film
Energy Technology Data Exchange (ETDEWEB)
Roshchupkin, Dmitry, E-mail: rochtch@iptm.ru; Plotitcyna, Olga; Matveev, Viktor; Kononenko, Oleg; Emelin, Evgenii; Irzhak, Dmitry [Institute of Microelectronics Technology and High-Purity Materials Russian Academy of Sciences, Chernogolovka 142432 (Russian Federation); Ortega, Luc [Laboratoire de Physique des Solides, Univ. Paris-Sud, CNRS, UMR 8502, 91405 Orsay Cedex (France); Zizak, Ivo; Erko, Alexei [Institute for Nanometre Optics and Technology, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein Strasse 15, 12489 Berlin (Germany); Tynyshtykbayev, Kurbangali; Insepov, Zinetula [Nazarbayev University Research and Innovation System, 53 Kabanbay Batyr St., Astana 010000 (Kazakhstan)
2015-09-14
Surface acoustic wave (SAW) propagation in a graphene film on the surface of piezoelectric crystals was studied at the BESSY II synchrotron radiation source. Talbot effect enabled the visualization of the SAW propagation on the crystal surface with the graphene film in a real time mode, and high-resolution x-ray diffraction permitted the determination of the SAW amplitude in the graphene/piezoelectric crystal system. The influence of the SAW on the electrical properties of the graphene film was examined. It was shown that the changing of the SAW amplitude enables controlling the magnitude and direction of current in graphene film on the surface of piezoelectric crystals.
Charland, Jenna; Touboul, Julien; Rey, Vincent
2013-04-01
Wave propagation against current : a study of the effects of vertical shears of the mean current on the geometrical focusing of water waves J. Charland * **, J. Touboul **, V. Rey ** jenna.charland@univ-tln.fr * Direction Générale de l'Armement, CNRS Délégation Normandie ** Université de Toulon, 83957 La Garde, France Mediterranean Institute of Oceanography (MIO) Aix Marseille Université, 13288 Marseille, France CNRS/INSU, IRD, MIO, UM 110 In the nearshore area, both wave propagation and currents are influenced by the bathymetry. For a better understanding of wave - current interactions in the presence of a 3D bathymetry, a large scale experiment was carried out in the Ocean Basin FIRST, Toulon, France. The 3D bathymetry consisted of two symmetric underwater mounds on both sides in the mean wave direction. The water depth at the top the mounds was hm=1,5m, the slopes of the mounds were of about 1:3, the water depth was h=3 m elsewhere. For opposite current conditions (U of order 0.30m/s), a huge focusing of the wave up to twice its incident amplitude was observed in the central part of the basin for T=1.4s. Since deep water conditions are verified, the wave amplification is ascribed to the current field. The mean velocity fields at a water depth hC=0.25m was measured by the use of an electromagnetic current meter. The results have been published in Rey et al [4]. The elliptic form of the "mild slope" equation including a uniform current on the water column (Chen et al [1]) was then used for the calculations. The calculated wave amplification of factor 1.2 is significantly smaller than observed experimentally (factor 2). So, the purpose of this study is to understand the physical processes which explain this gap. As demonstrated by Kharif & Pelinovsky [2], geometrical focusing of waves is able to modify significantly the local wave amplitude. We consider this process here. Since vertical velocity profiles measured at some locations have shown significant
Kim, Youngju; Kwon, Jaeki; Lee, Hyunjung; Jang, Wookil; Choi, Jongkyo; Kim, Sangshik
2011-04-01
In the present study, stress (S) - number of cycles to failure (N) (S-N) fatigue and fatigue crack propagation behaviors of three thermomechanical control process steels with different microstructures but similar yield strengths of approximately 450 MPa were investigated. The P + F steel was predominately pearlite plus ferrite, whereas B1 and B2 steels were both bainitic steels with martensite-austenite and pearlitic islands. Despite the significant difference in microstructural features, the resulting fatigue crack propagation rates and near-threshold Δ K values were comparable with each other. The hard phases, such as pearlite colonies in the P + F specimen, tended to affect fatigue crack propagation behavior in a similar manner, and severe crack branching was observed in intermediate and high Δ K regimes. Despite similar fatigue crack propagation rates and near-threshold Δ K values, the resistance to S-N fatigue was substantially different for each steel specimen. Depending on fatigue crack initiators, such as the ferrite/pearlite phase boundaries for the P + F specimens and the cracked martensite-austenite and/or small pearlitic islands for the bainitic specimens, the cycles for crack initiation varied greatly.
Energy Technology Data Exchange (ETDEWEB)
Wu, Huan Chun; Yang, Bin [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing (China); Chen, Yue Feng; Chen, Xu Dong [Collaborative Innovation Center of Steel Technology, Beijing (China)
2017-06-15
The fatigue crack propagation behaviors of Z3CN20.09M duplex stainless steel (DSS) were investigated by studying oxide films of specimens tested in 290°C water and air. The results indicate that a full oxide film that consisted of oxides and hydroxides was formed in 290°C water. By contrast, only a half-baked oxide film consisting of oxides was formed in 290°C air. Both environments are able to deteriorate the elastic modulus and hardness of the oxide films, especially the 290°C water. The fatigue lives of the specimens tested in 290°C air were about twice of those tested in 290°C water at all strain amplitudes. Moreover, the crack propagation rates of the specimen tested in 290°C water were confirmed to be faster than those tested in 290°C air, which was thought to be due to the deteriorative strength of the oxide films induced by the mutual promotion of oxidation and crack propagation at the crack tip. It is noteworthy that the crack propagation can be postponed by the ferrite phase in the DSS, especially when the specimens were tested in 290°C water.
Broadband unidirectional ultrasound propagation
Energy Technology Data Exchange (ETDEWEB)
Sinha, Dipen N.; Pantea, Cristian
2017-12-12
A passive, linear arrangement of a sonic crystal-based apparatus and method including a 1D sonic crystal, a nonlinear medium, and an acoustic low-pass filter, for permitting unidirectional broadband ultrasound propagation as a collimated beam for underwater, air or other fluid communication, are described. The signal to be transmitted is first used to modulate a high-frequency ultrasonic carrier wave which is directed into the sonic crystal side of the apparatus. The apparatus processes the modulated signal, whereby the original low-frequency signal exits the apparatus as a collimated beam on the side of the apparatus opposite the sonic crystal. The sonic crystal provides a bandpass acoustic filter through which the modulated high-frequency ultrasonic signal passes, and the nonlinear medium demodulates the modulated signal and recovers the low-frequency sound beam. The low-pass filter removes remaining high-frequency components, and contributes to the unidirectional property of the apparatus.
Tunable superluminal propagation on a silicon microchip.
Manipatruni, Sasikanth; Dong, Po; Xu, Qianfan; Lipson, Michal
2008-12-15
We demonstrate tunable superluminal propagation in a silicon microphotonic device in a solid-state room-temperature device of tens of micrometers in dimension allowing easy integration with high-bandwidth room-temperature systems. We achieve tunable negative delays up to 85 ps and effective group indices tunable between -1158 and -312.
Generation and propagation of intense supersonic beams.
Luria, K; Christen, W; Even, U
2011-06-30
Computer simulations and experiments have been performed to quantify the effects of nozzle shape and skimmer placement on high-density supersonic jets. It is shown that the on axis beam intensity achieved is much higher than intensity achieved using standard sonic nozzles. Changes in skimmer design and positioning are required to allow this intense jet to propagate in a typical supersonic beam setup.
Transhorizon Radiowave Propagation due to Evaporation Ducting ...
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 11; Issue 1. Transhorizon Radiowave Propagation due to Evaporation Ducting - The Effect of Tropospheric Weather Conditions on VHF and UHF Radio Paths Over the Sea. Salil David Gunashekar D R Siddle E M Warrington. General Article Volume 11 ...
Vertical laser beam propagation through the troposphere
Minott, P. O.; Bufton, J. L.; Schaefer, W. H.; Grolemund, D. A.
1974-01-01
The characteristics of the earth's atmosphere and its effects upon laser beams was investigated in a series of balloon borne, optical propagation experiments. These experiments were designed to simulate the space to ground laser link. An experiment to determine the amplitude fluctuation, commonly called scintillation, caused by the atmosphere was described.
Wave propagation in axially moving periodic strings
DEFF Research Database (Denmark)
Sorokin, Vladislav S.; Thomsen, Jon Juel
2017-01-01
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 drive...
Optical system defect propagation in ABCD systems
DEFF Research Database (Denmark)
McKinley, W.G.; Yura, H.T.; Hanson, Steen Grüner
1988-01-01
We describe how optical system defects (tilt/jitter, decenter, and despace) propagate through an arbitrary paraxial optical system that can be described by an ABCD ray transfer matrix. A pedagogical example is given that demonstrates the effect of alignment errors on a typical optical system...
MICRO PROPAGATION OF WORMWOOD ( Artemisia annua L ...
African Journals Online (AJOL)
ABSTRACT. A study was carried out to determine the effect of varying concentrations of some plant growth hormones on the in vitro propagation of Artemisia annua from leaf primordial in the Biotechnology. Laboratory of Plant Science Department of Ahmadu. Bello University, Zaria. Leaf primordial from a. Chinyong variety ...
Acoustic energy propagation around railways
Cizkova, Petra
2017-09-01
The article deals with the issues of acoustic energy propagation around railways. The research subject was noise emission spreading into the surroundings during the passage of trains over a directly travelled steel bridge construction. Noise emissions were measured using direct measurements in the field. The measurements were performed in two measurement profiles. The noise exposures A LAE measured near the steel bridge construction were compared against the noise exposures A LAE captured on an open track. From the difference of these data, the noise level of the steel bridge structure was determined. Part of the research was to evaluate the effect of the reconstruction of the railway track superstructure on the acoustic situation in the given section of the railway track. The article describes the methodology of measurements, including the processing and evaluation of measured data. The article points out the noise levels of the steel bridge construction and assesses changes in the acoustic situation after the reconstruction.
Gherm, Vadim E.; Zernov, Nikolay N.
2017-07-01
The detailed effects of the high-frequency radio wave propagation in a stochastic transionospheric propagation channel are discussed. This is a special case of propagation along or almost along the lines of the Earth's magnetic field. In this case, the ionospheric random irregularities of the electron density of the ionosphere may have very high values of the aspect ratio, which stands beyond the range of validity of the traditional analytical approaches utilized to treat the appropriate transionospheric propagation problems. In the consideration presented here, new analytical results are obtained for treating the problem under consideration. Based on the analytical results obtained, the previously developed Hybrid Scintillation Propagation Model is further extended, which also includes the software simulator of the signals propagating on the transionospheric paths with the random electron density irregularities highly elongated in the direction of the Earth's magnetic field.
Blast noise propagation above a snow cover.
Albert, D G; Hole, L R
2001-06-01
A porous medium model of a snow cover, rather than a viscoelastic treatment, has been used to simulate measured, horizontally traveling acoustic waveform propagation above a dry snow cover 11-20 cm thick. The waveforms were produced by explosions of 1-kg charges at propagation distances of 100 to 1400 m. These waveforms, with a peak frequency around 30 Hz, show pulse broadening effects similar to those previously seen for higher-frequency waves over shorter propagation distances. A rigid-ice-frame porous medium ("rigid-porous") impedance model, which includes the effect of the pores within the snow but ignores any induced motion of the ice particles, is shown to produce much better agreement with the measured waveforms compared with a viscoelastic solid treatment of the snow cover. From the acoustic waveform modeling, the predicted average snow cover depth of 18 cm and effective flow resistivities of 16-31 kPa s m(-2) agree with snow pit observations and with previous acoustic measurements over snow. For propagation in the upwind direction, the pulse broadening caused by the snow cover interaction is lessened, but the overall amplitude decay is greater because of refraction of the blast waves.
Enhancing blooming period and propagation coefficient of tulip ...
African Journals Online (AJOL)
Ramash
Means within the columns followed by the same letters are not significantly different at 0.05 level of significance. Figure 2. Effect of GA3, CCC and MH on propagation coefficient of tulip cv. Apeldoorn. control. The propagation coefficient reveals the multiplication rate by overall bulbs and daughter bulbs production by plant.
Propagation predictions and verification for communication and radar
CSIR Research Space (South Africa)
Botha, L
2006-02-01
Full Text Available The study, by CSIR Defence, Peace, Safety and Security is using propagation prediction software to predict the propagation effects of both communication and radar systems. These are the models used in the study: Free Space Model; Rn Model; Ground...
In vitro propagation of the new disease resistant Coffea arabica ...
African Journals Online (AJOL)
Conventional propagation methods do not provide enough planting materials, hence the need to develop alternative methods. The objective of this study was to develop an effective in ... This protocol opens new prospects for massive propagation of Batian in nine months. Keywords: Batian, somatic embryo, Coffea arabica
Characteristic wave diversity in Near Vertical Incidence Skywave propagation
Witvliet, Ben A.; van Maanen, Erik; Petersen, George J.; Westenberg, Albert J.; Bentum, Marinus Jan; Slump, Cornelis H.; Schiphorst, Roelof
2015-01-01
In Near Vertical Incidence Skywave (NVIS) propagation, effective diversity reception can be realized using a dual channel receiver and a dual polarization antenna with polarization matched to the (left hand and right hand) circular polarization of the characteristic waves propagating in the
Micro propagation of wormwood ( Artemisia annua l .) using leaf ...
African Journals Online (AJOL)
Abstract. A study was carried out to determine the effect of varying concentrations of some plant growth hormones on the in vitro propagation of Artemisia annua from leaf ... Therefore, this is a viable approach to the supply of the raw ... Key Words: Artemisia annua, Plant growth hormones, in vitro propagation, leaf primordial ...
Direct FVM Simulation for Sound Propagation in an Ideal Wedge
Directory of Open Access Journals (Sweden)
Hongyu Ji
2016-01-01
Full Text Available The sound propagation in a wedge-shaped waveguide with perfectly reflecting boundaries is one of the few range-dependent problems with an analytical solution. This provides a benchmark for the theoretical and computational studies on the simulation of ocean acoustic applications. We present a direct finite volume method (FVM simulation for the ideal wedge problem, and both time and frequency domain results are analyzed. We also study the broadband problem with large-scale parallel simulations. The results presented in this paper validate the accuracy of the numerical techniques and show that the direct FVM simulation could be applied to large-scale complex acoustic applications with a high performance computing platform.
Aspects of HF radio propagation
Directory of Open Access Journals (Sweden)
Stephane Saillant
2009-06-01
Full Text Available
radio systems. From the point of view Working Group 2 of the COST 296 Action, interest lies with effects associated
with propagation via the ionosphere of signals within the HF band. Several aspects are covered in this paper:
a The directions of arrival and times of flight of signals received over a path oriented along the trough have
been examined and several types of propagation effects identified. Of particular note, combining the HF observations
with satellite measurements has identified the presence of irregularities within the floor of the trough that
result in propagation displaced from the great circle direction. An understanding of the propagation effects that
result in deviations of the signal path from the great circle direction are of particular relevance to the operation
of HF radiolocation systems.
b Inclusion of the results from the above mentioned measurements into a propagation model of the northerly
ionosphere (i.e. those regions of the ionosphere located poleward of, and including, the mid-latitude trough
and the use of this model to predict the coverage expected from transmitters where the signals impinge on the
northerly ionosphere
Propagation of Ion Acoustic Perturbations
DEFF Research Database (Denmark)
Pécseli, Hans
1975-01-01
Equations describing the propagation of ion acoustic perturbations are considered, using the assumption that the electrons are Boltzman distributed and isothermal at all times. Quasi-neutrality is also considered.......Equations describing the propagation of ion acoustic perturbations are considered, using the assumption that the electrons are Boltzman distributed and isothermal at all times. Quasi-neutrality is also considered....
Yang, Mei; Tan, Ling; Xu, Yuanyuan; Zhao, Yihui; Cheng, Fei; Ye, Shaoming; Jiang, Weixin
2015-01-01
Knowing how acid soils and aluminum in soils may limit the growth of Eucalyptus trees in plantations is important because these plantations grow in many tropical and subtropical regions. Seedlings of four vegetatively propagated Eucalyptus clones, E. grandis × E. urophylla ‘GLGU9’(G9), E. grandis × E. urophylla ‘GLGU12’ (G12), E. urophylla × E. camaldulensis ‘GLUC3’ (G3) and E. urophylla ‘GLU4’(G4), were subjected to liquid culture with Hoagland nutrient solution for 40 days, then treated with four different treatments of acid and aluminum for 1 day. The four treatments used either pH 3.0 or 4.0 with or without added aluminum (4.4 mM) in all possible combinations; a control used no added aluminum at pH 4.8. Subsequently, the photosynthetic parameters and morphology of leaves from eucalypt seedlings were determined and observed. The results showed that the tested chlorophyll content, net photosynthetic rate, transpiration rate and water use efficiency were apparently inhibited by aluminum. Under uniform Al concentration (4.4 mM), the Al-induced limitation to photosynthetic parameters increased with pH, indicating acid stimulation to Al toxicity. Among all treatments, the most significant reduction was found in the combination of pH 3.0 and 4.4 mM Al. The photosynthetic and transpiration rates showed similar trends with G9 > G12 > G3 > G4, suggesting that G9 and G12 had higher Al-tolerance than other two clones. Microscopic observation revealed changes in leaf morphology when exposed to Al stress; for example, a reduced thickness of leaf epidermis and palisade tissue, the descendant palisade tissue/spongy tissue ratio and leaf tissue looseness. Overall, the acid and aluminum stress exerted negative effects on the photosynthetic activity of eucalypt seedlings, but the differences in tolerance to Al toxicity between the clones were favorable, offering potential to improve Eucalyptus plantation productivity by selecting Al tolerant clones. PMID
Propagation Engineering in Wireless Communications
Ghasemi, Abdollah; Ghasemi, Farshid
2012-01-01
Wireless communications has seen explosive growth in recent decades, in a realm that is both broad and rapidly expanding to include satellite services, navigational aids, remote sensing, telemetering, audio and video broadcasting, high-speed data communications, mobile radio systems and much more. Propagation Engineering in Wireless Communications deals with the basic principles of radiowaves propagation for frequency bands used in radio-communications, offering descriptions of new achievements and newly developed propagation models. The book bridges the gap between theoretical calculations and approaches, and applied procedures needed for advanced radio links design. The primary objective of this two-volume set is to demonstrate the fundamentals, and to introduce propagation phenomena and mechanisms that engineers are likely to encounter in the design and evaluation of radio links of a given type and operating frequency. Volume one covers basic principles, along with tropospheric and ionospheric propagation,...
Yu, Yi-Cong; Liu, Jing-Feng; Zhuo, Xiao-Lu; Chen, Gengyan; Jin, Chong-Jun; Wang, Xue-Hua
2013-10-07
We investigate the light emission characteristics for single two level quantum dot (QD) in a realistic photonic crystal (PC) L3 cavity based upon the local coupling strength between the QD and cavity together with the Green's function in which the propagation function related to the position of the detector is taken into account. We find for a PC cavity that the line shape of the propagation function in frequency domain is identical to that of the cavity and independent on the detector's position. We confirm that this identity is not influenced by the horizontal decay of the cavity. Furthermore, it is revealed that the vacuum fluorescence spectrum of the coupled system never give the triplet in strong coupling regime. Our work demonstrates that the experimental spectral-triplet in coupled system of single QD and PC cavity cannot be individually understood by vacuum Rabi splitting without including other physics mechanism.
Surface-plasmon-assisted electromagnetic wave propagation.
Yang, Wenbo; Reed, Jennifer M; Wang, Haining; Zou, Shengli
2010-10-21
Using electrodynamics tools, we investigated the effect of surface plasmons on the propagation direction of electromagnetic waves around a spherical silver nanoparticle and nano-structured silver film. The studies showed that the calculated effective index of refraction of a spherical silver nanoparticle from the Kramers-Kronig transformation method may not represent the index of refraction of the system but is consistent with the Poynting vector (the energy flow) direction at the microscopic scale. Using a silver film composed of periodic triangular prisms, we numerically demonstrated that electromagnetic waves may propagate along different directions depending on the incident polarization direction. When the incident polarization is in the plane of incidence and the surface plasmons are excited, the refracted light ray propagates along the same side of the surface normal as the incident wave. When the incident polarization is perpendicular to the plane of incidence, the refracted light ray always propagates on the opposite side of the surface normal. The results show that a silver film composed of periodic nano-sized triangular prisms may be used as a filter to simultaneously generate two polarized light rays of orthogonal polarizations from one light source.
A database for propagation models
Kantak, Anil V.; Suwitra, Krisjani; Le, Choung
1993-01-01
The NASA Propagation Program supports academic research that models various propagation phenomena in the space research frequency bands. NASA supports such research via school and institutions prominent in the field. The products of such efforts are particularly useful for researchers in the field of propagation phenomena and telecommunications systems engineers. The systems engineer usually needs a few propagation parameter values for a system design. Published literature on the subject, such as the Cunsultative Committee for International Radio (CCIR) publications, may help somewhat, but often times, the parameter values given in such publications use a particular set of conditions which may not quite include the requirements of the system design. The systems engineer must resort to programming the propagation phenomena model of interest and to obtain the parameter values to be used in the project. Furthermore, the researcher in the propagation field must then program the propagation models either to substantiate the model or to generate a new model. The researcher or the systems engineer must either be a skillful computer programmer or hire a programmer, which of course increases the cost of the effort. An increase in cost due to the inevitable programming effort may seem particularly inappropriate if the data generated by the experiment is to be used to substantiate the already well-established models, or a slight variation thereof. To help researchers and the systems engineers, it was recommended by the participants of NASA Propagation Experimenters (NAPEX) 15 held in London, Ontario, Canada on 28-29 June 1991, that propagation software should be constructed which will contain models and prediction methods of most propagation phenomenon. Moreover, the software should be flexible enough for the user to make slight changes to the models without expending a substantial effort in programming.
Propagation of ionization waves during ignition of fluorescent lamps
Langer, R.; Garner, R.; Hilscher, A.; Tidecks, R.; Horn, S.
2008-07-01
The propagation of the first ionization wave in a compact fluorescent lamp (T4 tube with standard electrodes) during ignition was investigated for various initial dc-voltages (both polarities measured against ground) and gas compositions (with and without mercury). In addition the effect of the presence of a fluorescent powder coating was studied. The propagation velocity of the initial wave was measured by an assembly of photomultipliers installed along the tube, which detected the light emitted by the wave head. The propagation was found to be faster for positive than for negative polarity. This effect is explained involving processes in the electrode region as well as in the wave head. Waves propagate faster in the presence of a fluorescent powder coating than without it and gases of lighter mass show a faster propagation than gases with higher mass.
Propagation of ionization waves during ignition of fluorescent lamps
Energy Technology Data Exchange (ETDEWEB)
Langer, R; Tidecks, R; Horn, S [Institute of Physics, Chair for Experimental Physics II, University of Augsburg, Universitaetsstrasse 1, D-86159 Augsburg (Germany); Garner, R [Central Research and Services Laboratory, OSRAM SYLVANIA Inc., 71 Cherry Hill Drive, Beverly, MA 01915 (United States); Hilscher, A [OSRAM GmbH, Berliner Allee 65, D-86136 Augsburg (Germany)], E-mail: Reinhard.Langer@physik.uni-augsburg.de
2008-07-21
The propagation of the first ionization wave in a compact fluorescent lamp (T4 tube with standard electrodes) during ignition was investigated for various initial dc-voltages (both polarities measured against ground) and gas compositions (with and without mercury). In addition the effect of the presence of a fluorescent powder coating was studied. The propagation velocity of the initial wave was measured by an assembly of photomultipliers installed along the tube, which detected the light emitted by the wave head. The propagation was found to be faster for positive than for negative polarity. This effect is explained involving processes in the electrode region as well as in the wave head. Waves propagate faster in the presence of a fluorescent powder coating than without it and gases of lighter mass show a faster propagation than gases with higher mass.
Laser beam propagation generation and propagation of customized light
Forbes, Andrew
2014-01-01
""The text is easy to read and is accompanied by beautiful illustrations. It is an excellent book for anyone working in laser beam propagation and an asset for any library.""-Optics & Photonics News, July 2014
An Immunization Strategy Based on Propagation Mechanism
Directory of Open Access Journals (Sweden)
Yixin Zhu
2014-01-01
Full Text Available With the ubiquity of smart phones, wearable equipment, and wireless sensors, the topologies of networks composed by them change along with time. The immunization strategies in which network immune nodes are chosen by analyzing the static aggregation network topologies have been challenged. The studies about interaction propagations between two pathogens show that the interaction can change propagation threshold and the final epidemic size of each other, which provides a new thinking of immunization method. The eradication or inhibition of the virus can be achieved through the spread of its opposite party. Here, we put forward an immunization strategy whose implementation does not depend on the analysis of network topology. The immunization agents are randomly placed on a few of individuals of network and spread out from these individuals on network in a propagation method. The immunization agents prevent virus infecting their habitat nodes with certain immune success rate. The analysis and simulation of evolution equation of the model show that immune propagation has a significant impact on the spread threshold and steady-state density of virus on a finite size of BA networks. Simulations on some real-world networks also suggest that the immunization strategy is feasible and effective.
Generation and propagation of optical vortices
Rozas, David
Optical vortices are singularities in phase fronts of laser beams. They are characterized by a dark core whose size (relative to the size of the background beam) may dramatically affect their behavior upon propagation. Previously, only large-core vortices have been extensively studied. The object of the research presented in this dissertation was to explore ways of generating small-core optical vortices (also called optical vortex filaments ), and to examine their propagation using analytical, numerical and experimental methods. Computer-generated holography enabled us to create arbitrary distributions of optical vortex filaments for experimental exploration. Hydrodynamic analogies were used to develop an heuristic model which described the dependence of vortex motion on other vortices and the background beam, both qualitatively and quantitatively. We predicted that pair of optical vortex filaments will rotate with angular rates inversely proportional to their separation distance (just like vortices in a fluid). We also reported the first experimental observation of this novel fluid-like effect. It was found, however, that upon propagation in linear media, the fluid-like rotation was not sustained owing to the overlap of diffracting vortex cores. Further numerical studies and experiments showed that rotation angle may be enhanced in nonlinear self-defocusing media. The results presented in this thesis offer us a better understanding of dynamics of propagating vortices which may result in applications in optical switching, optical data storage, manipulation of micro-particles and optical limiting for eye protection.
Detonation propagation in a high loss configuration
Energy Technology Data Exchange (ETDEWEB)
Jackson, Scott I [Los Alamos National Laboratory; Shepherd, Joseph E [CALTECH
2009-01-01
This work presents an experimental study of detonation wave propagation in tubes with inner diameters (ID) comparable to the mixture cell size. Propane-oxygen mixtures were used in two test section tubes with inner diameters of 1.27 mm and 6.35 mm. For both test sections, the initial pressure of stoichiometric mixtures was varied to determine the effect on detonation propagation. For the 6.35 mm tube, the equivalence ratio {phi} (where the mixture was {phi} C{sub 3}H{sub 8} + 50{sub 2}) was also varied. Detonations were found to propagate in mixtures with cell sizes as large as five times the diameter of the tube. However, under these conditions, significant losses were observed, resulting in wave propagation velocities as slow as 40% of the CJ velocity U{sub CJ}. A review of relevant literature is presented, followed by experimental details and data. Observed velocity deficits are predicted using models that account for boundary layer growth inside detonation waves.
Investigation into stress wave propagation in metal foams
Directory of Open Access Journals (Sweden)
Li Lang
2015-01-01
Full Text Available The aim of this study is to investigate stress wave propagation in metal foams under high-speed impact loading. Three-dimensional Voronoi model is established to represent real closed-cell foam. Based on the one-dimensional stress wave theory and Voronoi model, a numerical model is developed to calculate the velocity of elastic wave and shock wave in metal foam. The effects of impact velocity and relative density of metal foam on the stress wave propagation in metal foams are explored respectively. The results show that both elastic wave and shock wave propagate faster in metal foams with larger relative density; with increasing the impact velocity, the shock wave propagation velocity increase, but the elastic wave propagation is not sensitive to the impact velocity.
Anderson, T. S.; Miller, R.; Greenfield, R.; Fisk, D.
2002-12-01
The propagation of seismic waves through regions of complex topography is not thoroughly understood. Surface waves, are of particular interest, as they are large in amplitude and can characterize the source depth, magnitude, and frequency content. The amplitude and frequency content of seismic waves that propagate in regions with large topographical variations are affected by both the scattering and blockage of the wave energy. The ability to predict the 3-d scattering due to topography will improve the understanding of both regional scale surface wave magnitudes, and refine surface wave discriminants as well as at the local scale (Smart Weapons Test Range, Yuma Proving Ground, Arizona. The result of the KGS characterization study is a high-resolution 3-d model that is used in our seismic simulations. The velocities Vs, Vp are calculated by tomography and refraction, attenuation coefficients estimated from the surface wave and from p-waves and are provided in a model with attributes resolved in 3-d to 0.5 meters. In the present work, we present comparisons of synthetic data with seismic data collected at the Smart Weapons Test Range to benchmark the accuracy achieved in simulating 3-d wave propagation in the vicinity of a topographical anomaly (trench). Synthetic seismograms are generated using a 3-d 8th order staggered grid visco-elastic finite difference code that accounts for topography. The geologic model is based on the Yuma site characterization. The size of these calculations required use of the DoD High Performance Computers and parallelized code. Results are compared with field data. Preliminary results show an excellent match with field data using the 3-d fdtd technique.
Radio Wave Propagation in Tunnels
National Research Council Canada - National Science Library
Lee, Jeho
2000-01-01
This report examines the radio propagation model for narrow and long tunnels. Modal analysis is used to model the path gain in 2-D and 3-D rectangular tunnels and the coupling loss of L, T and cross tunnels...
Propagation engineering in wireless communications
Ghasemi, Abdollah; Ghasemi, Farshid
2016-01-01
This book covers the basic principles for understanding radio wave propagation for common frequency bands used in radio-communications. This includes achievements and developments in propagation models for wireless communication. This book is intended to bridge the gap between the theoretical calculations and approaches to the applied procedures needed for radio links design in a proper manner. The authors emphasize propagation engineering by giving fundamental information and explain the use of basic principles together with technical achievements. This new edition includes additional information on radio wave propagation in guided media and technical issues for fiber optics cable networks with several examples and problems. This book also includes a solution manual - with 90 solved examples distributed throughout the chapters - and 158 problems including practical values and assumptions.
Wave propagation in electromagnetic media
Davis, Julian L
1990-01-01
This is the second work of a set of two volumes on the phenomena of wave propagation in nonreacting and reacting media. The first, entitled Wave Propagation in Solids and Fluids (published by Springer-Verlag in 1988), deals with wave phenomena in nonreacting media (solids and fluids). This book is concerned with wave propagation in reacting media-specifically, in electro magnetic materials. Since these volumes were designed to be relatively self contained, we have taken the liberty of adapting some of the pertinent material, especially in the theory of hyperbolic partial differential equations (concerned with electromagnetic wave propagation), variational methods, and Hamilton-Jacobi theory, to the phenomena of electromagnetic waves. The purpose of this volume is similar to that of the first, except that here we are dealing with electromagnetic waves. We attempt to present a clear and systematic account of the mathematical methods of wave phenomena in electromagnetic materials that will be readily accessi...
Propagation in Diagonal Anisotropic Chirowaveguides
Directory of Open Access Journals (Sweden)
S. Aib
2017-01-01
Full Text Available A theoretical study of electromagnetic wave propagation in parallel plate chirowaveguide is presented. The waveguide is filled with a chiral material having diagonal anisotropic constitutive parameters. The propagation characterization in this medium is based on algebraic formulation of Maxwell’s equations combined with the constitutive relations. Three propagation regions are identified: the fast-fast-wave region, the fast-slow-wave region, and the slow-slow-wave region. This paper focuses completely on the propagation in the first region, where the dispersion modal equations are obtained and solved. The cut-off frequencies calculation leads to three cases of the plane wave propagation in anisotropic chiral medium. The particularity of these results is the possibility of controlling the appropriate cut-off frequencies by choosing the adequate physical parameters values. The specificity of this study lies in the bifurcation modes confirmation and the possible contribution to the design of optical devices such as high-pass filters, as well as positive and negative propagation constants. This negative constant is an important feature of metamaterials which shows the phenomena of backward waves. Original results of the biaxial anisotropic chiral metamaterial are obtained and discussed.
Simulation of Radiowave Propagation in a Dense Urban Environment
National Research Council Canada - National Science Library
Chung, Chris V
2007-01-01
One objective of this thesis was to investigate the effect of details, such as the windows of high-rise buildings, on the radio wave propagation in the dense urban environment through modeling and simulations...
Takemura, Shunsuke; Kobayashi, Manabu; Yoshimoto, Kazuo
2017-09-01
For practical modelling of high-frequency (>1 Hz) seismic wave propagation, we analysed the apparent radiation patterns and attenuations of P and S waves using observed Hi-net velocity seismograms for small-to-moderate crustal earthquakes in the Chugoku region, southwestern Japan. By comparing observed and simulated seismograms, we estimated practical parameter sets of crustal small-scale velocity heterogeneity and intrinsic attenuations of P and S waves (QP.int-1 and QS.int-1). Numerical simulations of seismic wave propagation were conducted via the finite-difference method using a 1-D crustal velocity structure model with additional 3-D small-scale velocity heterogeneity and intrinsic attenuation. The estimated crustal small-scale velocity heterogeneity is stochastically characterized by an exponential-type power spectral density function with correlation length of 1 km and root-mean-square value of 0.03. Estimated QP.int-1 and QS.int-1 values range from 10-2.6 to 10-2.0 and 10-2.8 to 10-2.4, respectively, indicating QP.int-1 > QS.int-1 for high frequencies (>1 Hz). Intrinsic attenuation dominates over scattering attenuation, which is caused by small-scale velocity heterogeneity. The crustal parameters obtained in this study are useful for evaluating peak ground velocities and coda envelopes for moderate crustal earthquakes via physical-based simulations using a 3-D heterogeneous structure model.
DEFF Research Database (Denmark)
Andersen, Rikke K; Zimmer, Jens; Wahlberg, Lars U
2008-01-01
propagated and maintained for more than 6 months with a cell population doubling time of 21.5 days. The replacement of EGF by leukemia inhibitory factor (LIF) resulted in a cell population doubling time of 19.8 days, corresponding to a 10-fold increase in estimated cell numbers over a period of 70 days......Tissue blocks containing neural precursor cells were isolated from the rat forebrain subventricular zone (SVZ) and ventral mesencephalon (VM) and propagated as neural tissue-spheres (NTS). In the presence of fibroblast growth factor-2 (FGF2) and epidermal growth factor (EGF), SVZ-derived NTS were......, at which point these NTS ceased to grow. In the presence of FGF2 and LIF, VM-derived NTS displayed a cell population doubling time of 24.6 days, which was maintained over a period of more than 200 days. However, when LIF was replaced by EGF, the cell numbers only increased 1.2 fold over 50 days. Using...
Sonic boom propagation through atmospheric turbulence
Yamashita, Hiroshi; Obayashi, Shigeru; 山下, 博; 大林, 茂
2009-01-01
The effect of the homogeneous atmospheric turbulence on the sonic boom propagation has been investigated. The turbulence field is represented by a finite sum of discrete Fourier modes based on the von Karman and Pao energy spectrum. The sonic boom signature is calculated by the modified Waveform Parameter Method, considering the turbulent velocities. The results show that in 59 % of the cases, the intensity of the sonic boom had decreased, and in other 41 % of the cases had increased the soni...
Propagation and Purification of Baculovirus oryctes Huger
Directory of Open Access Journals (Sweden)
Susamto Somowiyarjo
1995-12-01
Full Text Available An isolate of Baculovirus oryctes, a possible biological control agent for coconut beetle (Oryctes rhinoceros Huger from East Java was propagated and purified. The virus could be transmitted by feeding the imago with 10% sucrose containing virus from homogenate of infected beetles. Effectivity of virus to 9 healthy females by sexual copulation. Virus be succesfully purified by a method of Payne. Key words: Baculovirus oryctes, transmission, purification
Directory of Open Access Journals (Sweden)
Othman Al-Khudairi
2017-10-01
Full Text Available In this paper, the sensitivity of the structural integrity of wind turbine blades to debonding of the shear web from the spar cap was investigated. In this regard, modal analysis, static and fatigue testing were performed on a 45.7 m blade for three states of the blade: (i as received blade (ii when a crack of 200 mm was introduced between the web and the spar cap and (iii when the crack was extended to 1000 mm. Calibration pull-tests for all three states of the blade were performed to obtain the strain-bending moment relationship of the blade according to the estimated target bending moment (BM which the blade is expected to experience in its service life. The resultant data was used to apply appropriate load in the fatigue tests. The blade natural frequencies in flapwise and edgewise directions over a range of frequency domain were found by modal testing for all three states of the blade. The blade first natural frequency for each state was used for the flapwise fatigue tests. These were performed in accordance with technical specification IEC TS 61400-23. The fatigue results showed that, for a 200 mm crack between the web and spar cap at 9 m from the blade root, the crack did not propagate at 50% of the target BM up to 62,110 cycles. However, when the load was increased to 70% of target BM, some damages were detected on the pressure side of the blade. When the 200 mm crack was extended to 1000 mm, the crack began to propagate when the applied load exceeded 100% of target BM and the blade experienced delaminations, adhesive joint failure, compression failure and sandwich core failure.
Al-Khudairi, Othman; Hadavinia, Homayoun; Little, Christian; Gillmore, Gavin; Greaves, Peter; Dyer, Kirsten
2017-10-03
In this paper, the sensitivity of the structural integrity of wind turbine blades to debonding of the shear web from the spar cap was investigated. In this regard, modal analysis, static and fatigue testing were performed on a 45.7 m blade for three states of the blade: (i) as received blade (ii) when a crack of 200 mm was introduced between the web and the spar cap and (iii) when the crack was extended to 1000 mm. Calibration pull-tests for all three states of the blade were performed to obtain the strain-bending moment relationship of the blade according to the estimated target bending moment (BM) which the blade is expected to experience in its service life. The resultant data was used to apply appropriate load in the fatigue tests. The blade natural frequencies in flapwise and edgewise directions over a range of frequency domain were found by modal testing for all three states of the blade. The blade first natural frequency for each state was used for the flapwise fatigue tests. These were performed in accordance with technical specification IEC TS 61400-23. The fatigue results showed that, for a 200 mm crack between the web and spar cap at 9 m from the blade root, the crack did not propagate at 50% of the target BM up to 62,110 cycles. However, when the load was increased to 70% of target BM, some damages were detected on the pressure side of the blade. When the 200 mm crack was extended to 1000 mm, the crack began to propagate when the applied load exceeded 100% of target BM and the blade experienced delaminations, adhesive joint failure, compression failure and sandwich core failure.
Microscopic Mechanisms for Propagating Deformation Fronts
Franklin, Scott
2001-03-01
Alloys often deform through the propagation of slowly moving ( cm/s) fronts separating strained and unstrained regions. Theories for these Portevin-Le Chatelier (PLC) fronts are mostly on the macroscopic level, dealing with strains instead of dislocation populations. In these models diffusion, a possible mechanism for propagation, fails to produce front behavior consistent with experiments. Previous work* used a nonlocal strain-rate to successfully reproduce many different aspects of experimentally observed fronts. Ananthakrishna has proposed a set of equations that describe the evolution of different dislocation populations. These equations reproduce the temporal behavior of the PLC effect, serrated stress-strain curves accompanying smooth loading. It is natural to ask whether diffusive or other spatial coupling terms added to this model result in fronts. I will discuss simulations of these equations with added spatial terms and attempt to compare the results with experiments. *S. Franklin, F. Mertens, and M. Marder, Phys. Rev. E V. 62 (2000)
Method and apparatus for charged particle propagation
Hershcovitch, A.
1996-11-26
A method and apparatus are provided for propagating charged particles from a vacuum to a higher pressure region. A generator includes an evacuated chamber having a gun for discharging a beam of charged particles such as an electron beam or ion beam. The beam is discharged through a beam exit in the chamber into a higher pressure region. A plasma interface is disposed at the beam exit and includes a plasma channel for bounding a plasma maintainable between a cathode and an anode disposed at opposite ends thereof. The plasma channel is coaxially aligned with the beam exit for propagating the beam from the chamber, through the plasma, and into the higher pressure region. The plasma is effective for pumping down the beam exit for preventing pressure increase in the chamber and provides magnetic focusing of the beam discharged into the higher pressure region 24. 7 figs.
QUENCH FRONT PROPAGATION IN THE ANNULAR CHANNEL
Directory of Open Access Journals (Sweden)
Jan Stepanek
2016-12-01
Full Text Available Understanding the quench front propagation during bottom core reflooding is crucial for the effective cooling during the LOCA accident. The results presented in this paper were obtained on an experimental loop with an annular test section. The test section consists of a vertical electrically heated stainless steel tube with outer diameter 9 mm and length of 1.7 m. The heated tube is placed inside a glass tube with the inner diameter 14.5 mm. Water mass flux during the reflooding is in the range from 100 kg.m−2.s−1 up to 140 kg.m−2.s−1 and the initial wall temperature of the stainless steel tube is in the range from 250 °C up to 800 °C. The presented results show the influence of the initial conditions on the quench front propagation and the complexity of the phenomenon.
Propagation of Gaussian Beams through Active GRIN Materials
Energy Technology Data Exchange (ETDEWEB)
Gomez-Varela, A I; Flores-Arias, M T; Bao-Varela, C; Gomez-Reino, C [Grupo de ' Microoptica y Optica GRIN' , Unidad asociada al Instituto de Ciencias de Materiales de Aragon, ICMA/CSIC, Zaragoza, Espana y Escuela de Optica y OptometrIa, Campus Sur s/n, Universidade de Santiago, E15782 Santiago de Compostela (Spain); De la Fuente, X, E-mail: maite.flores@usc.es [Instituto de Ciencia de Materiales de Aragon (Universidad de Zaragoza-CSIC), Maria de Luna 3, E50018 Zaragoza (Spain)
2011-01-01
We discussed light propagation through an active GRIN material that exhibits loss or gain. Effects of gain or loss in GRIN materials can be phenomenologically taken into account by using a complex refractive index in the wave equation. This work examines the implication of using a complex refractive index on light propagation in an active GRIN material illuminated by a non-uniform monochromatic wave described by a Gaussian beam. We analyze how a Gaussian beam is propagated through the active material in order to characterize it by the beam parameters and the transverse irradiance distribution.
Surface plasmon polariton propagation in organic nanofiber based plasmonic waveguides
DEFF Research Database (Denmark)
Leißner, Till; Lemke, Christoph; Jauernik, Stephan
2013-01-01
Plasmonic wave packet propagation is monitored in dielectric-loaded surface plasmon polariton waveguides realized from para-hexaphenylene nanofibers deposited onto a 60 nm thick gold film. Using interferometric time resolved two-photon photoemission electron microscopy we are able to determine...... phase and group velocity of the surface plasmon polariton (SPP) waveguiding mode (0.967c and 0.85c at λLaser = 812nm) as well as the effective propagation length (39 μm) along the fiber-gold interface. We furthermore observe that the propagation properties of the SPP waveguiding mode are governed...
Semisupervised kernel matrix learning by kernel propagation.
Hu, Enliang; Chen, Songcan; Zhang, Daoqiang; Yin, Xuesong
2010-11-01
The goal of semisupervised kernel matrix learning (SS-KML) is to learn a kernel matrix on all the given samples on which just a little supervised information, such as class label or pairwise constraint, is provided. Despite extensive research, the performance of SS-KML still leaves some space for improvement in terms of effectiveness and efficiency. For example, a recent pairwise constraints propagation (PCP) algorithm has formulated SS-KML into a semidefinite programming (SDP) problem, but its computation is very expensive, which undoubtedly restricts PCPs scalability in practice. In this paper, a novel algorithm, called kernel propagation (KP), is proposed to improve the comprehensive performance in SS-KML. The main idea of KP is first to learn a small-sized sub-kernel matrix (named seed-kernel matrix) and then propagate it into a larger-sized full-kernel matrix. Specifically, the implementation of KP consists of three stages: 1) separate the supervised sample (sub)set X(l) from the full sample set X; 2) learn a seed-kernel matrix on X(l) through solving a small-scale SDP problem; and 3) propagate the learnt seed-kernel matrix into a full-kernel matrix on X . Furthermore, following the idea in KP, we naturally develop two conveniently realizable out-of-sample extensions for KML: one is batch-style extension, and the other is online-style extension. The experiments demonstrate that KP is encouraging in both effectiveness and efficiency compared with three state-of-the-art algorithms and its related out-of-sample extensions are promising too.
Liu, Huilong; Lü, Yanfei; Zhang, Jing; Xia, Jing; Pu, Xiaoyun; Dong, Yuan; Li, Shutao; Fu, Xihong; Zhang, Angfeng; Wang, Changjia; Tan, Yong; Zhang, Xihe
2015-01-01
This paper studies the propagation properties of controllable hollow flat-topped beams (CHFBs) in turbulent atmosphere based on ABCD matrix, sets up a propagation model and obtains an analytical expression for the propagation. With the help of numerical simulation, the propagation properties of CHFBs in different parameters are studied. Results indicate that in turbulent atmosphere, with the increase of propagation distance, the darkness of CHFBs gradually annihilate, and eventually evolve into Gaussian beams. Compared with the propagation properties in free space, the turbulent atmosphere enhances the diffraction effect of CHFBs and reduces the propagation distance for CHFBs to evolve into Gaussian beams. In strong turbulence atmospheric propagation, Airy disk phenomenon will disappear. The study on the propagation properties of CHFBs in turbulence atmosphere by using ABCD matrix is simple and convenient. This method can also be applied to study the propagation properties of other hollow laser beams in turbulent atmosphere.
DEFF Research Database (Denmark)
Wahlberg, Magnus; Larsen, Ole Næsbye
2017-01-01
As an acoustic signal travels from the source to a receiver, it is affected by a variety of physical processes, all dictated by properties of the signal and the environment. The signal energy is weakened by geometric attenuation as well as absorption by the medium. The temporal and spectral prope...... communication sounds for airborne acoustics and bottom and surface effects for underwater sounds. Refraction becomes very important close to shadow zones. For echolocation signals, geometric attenuation and sound absorption have the largest effects on the signals....
Can Neural Activity Propagate by Endogenous Electrical Field?
Qiu, Chen; Shivacharan, Rajat S.; Zhang, Mingming
2015-01-01
It is widely accepted that synaptic transmissions and gap junctions are the major governing mechanisms for signal traveling in the neural system. Yet, a group of neural waves, either physiological or pathological, share the same speed of ∼0.1 m/s without synaptic transmission or gap junctions, and this speed is not consistent with axonal conduction or ionic diffusion. The only explanation left is an electrical field effect. We tested the hypothesis that endogenous electric fields are sufficient to explain the propagation with in silico and in vitro experiments. Simulation results show that field effects alone can indeed mediate propagation across layers of neurons with speeds of 0.12 ± 0.09 m/s with pathological kinetics, and 0.11 ± 0.03 m/s with physiologic kinetics, both generating weak field amplitudes of ∼2–6 mV/mm. Further, the model predicted that propagation speed values are inversely proportional to the cell-to-cell distances, but do not significantly change with extracellular resistivity, membrane capacitance, or membrane resistance. In vitro recordings in mice hippocampi produced similar speeds (0.10 ± 0.03 m/s) and field amplitudes (2.5–5 mV/mm), and by applying a blocking field, the propagation speed was greatly reduced. Finally, osmolarity experiments confirmed the model's prediction that cell-to-cell distance inversely affects propagation speed. Together, these results show that despite their weak amplitude, electric fields can be solely responsible for spike propagation at ∼0.1 m/s. This phenomenon could be important to explain the slow propagation of epileptic activity and other normal propagations at similar speeds. SIGNIFICANCE STATEMENT Neural activity (waves or spikes) can propagate using well documented mechanisms such as synaptic transmission, gap junctions, or diffusion. However, the purpose of this paper is to provide an explanation for experimental data showing that neural signals can propagate by means other than synaptic
Propagating Class and Method Combination
DEFF Research Database (Denmark)
Ernst, Erik
1999-01-01
This paper presents a mixin based class and method combination mechanism with block structure propagation. Traditionally, mixins can be composed to form new classes, possibly merging the implementations of methods (as in CLOS). In our approach, a class or method combination operation may cause any...... number of implicit combinations. For example, it is possible to specify separate aspects of a family of classes, and then combine several aspects into a full-fledged class family. The combination expressions would explicitly combine whole-family aspects, and by propagation implicitly combine the aspects...... for each member of the class family, and again by propagation implicitly compose each method from its aspects. As opposed to CLOS, this is type-checked statically; and as opposed to other systems for advanced class combination/ merging/weaving, it is integrated directly in the language, ensuring a clear...
Signal propagation in nerve fiber
Zayko, Yuriy N.
2007-05-01
In this paper the problem of signal propagation in nerve fiber is considered. Ohm losses and heat processes were taken into account. These permit to combine the two stages (metabolic and non-metabolic) of propagation and Na + and K + ions transmission through cell membrane due propagation. Electrodynamics of nerve fiber with losses is described by telegraph equations. Heat processes in fiber are described by an equation of entropy transfer. Ion motion at metabolic stage against the electro-chemical potential is described by negative conductance, responsible for the escape flow. The running- wave-type solutions of these equations are studied. An integral and an explicit solution of the given system are obtained. The solution represented by a series of quasi-harmonic pulses is investigated numerically. This proves the applicability of telegraph equation to the problem considered. Different types of solitary waves corresponding to various types of conductivity are also investigated.
Propagation of Cigarette Static Burn
Directory of Open Access Journals (Sweden)
Miura K
2014-12-01
Full Text Available A propagation model of cigarette static burn at the cigarette periphery is proposed. Propagation of cigarette static burn is characterized by intermittent burn of the cigarette paper. The burning rate depends on the period of flash burn of the paper and is independent of the burning width. By measuring the local temperature near the front line of the burning propagation, the rate-determining step was identified as the time required to ignite the paper. A mathematical analysis was performed by calculating the heat transfer at the periphery during the paper heating period, and it was revealed that the thermal properties of the cigarette are the dominant factors of cigarette static burn. Modeling results showed good agreement with measured data.
Wave propagation in nanostructures nonlocal continuum mechanics formulations
Gopalakrishnan, Srinivasan
2013-01-01
Wave Propagation in Nanostructures describes the fundamental and advanced concepts of waves propagating in structures that have dimensions of the order of nanometers. The book is fundamentally based on non-local elasticity theory, which includes scale effects in the continuum model. The book predominantly addresses wave behavior in carbon nanotubes and graphene structures, although the methods of analysis provided in this text are equally applicable to other nanostructures. The book takes the reader from the fundamentals of wave propagation in nanotubes to more advanced topics such as rotating nanotubes, coupled nanotubes, and nanotubes with magnetic field and surface effects. The first few chapters cover the basics of wave propagation, different modeling schemes for nanostructures and introduce non-local elasticity theories, which form the building blocks for understanding the material provided in later chapters. A number of interesting examples are provided to illustrate the important features of wave behav...
Modeling the Propagation of Mobile Phone Virus under Complex Network
Yang, Wei; Wei, Xi-liang; Guo, Hao; An, Gang; Guo, Lei
2014-01-01
Mobile phone virus is a rogue program written to propagate from one phone to another, which can take control of a mobile device by exploiting its vulnerabilities. In this paper the propagation model of mobile phone virus is tackled to understand how particular factors can affect its propagation and design effective containment strategies to suppress mobile phone virus. Two different propagation models of mobile phone viruses under the complex network are proposed in this paper. One is intended to describe the propagation of user-tricking virus, and the other is to describe the propagation of the vulnerability-exploiting virus. Based on the traditional epidemic models, the characteristics of mobile phone viruses and the network topology structure are incorporated into our models. A detailed analysis is conducted to analyze the propagation models. Through analysis, the stable infection-free equilibrium point and the stability condition are derived. Finally, considering the network topology, the numerical and simulation experiments are carried out. Results indicate that both models are correct and suitable for describing the spread of two different mobile phone viruses, respectively. PMID:25133209
Modeling the propagation of mobile phone virus under complex network.
Yang, Wei; Wei, Xi-liang; Guo, Hao; An, Gang; Guo, Lei; Yao, Yu
2014-01-01
Mobile phone virus is a rogue program written to propagate from one phone to another, which can take control of a mobile device by exploiting its vulnerabilities. In this paper the propagation model of mobile phone virus is tackled to understand how particular factors can affect its propagation and design effective containment strategies to suppress mobile phone virus. Two different propagation models of mobile phone viruses under the complex network are proposed in this paper. One is intended to describe the propagation of user-tricking virus, and the other is to describe the propagation of the vulnerability-exploiting virus. Based on the traditional epidemic models, the characteristics of mobile phone viruses and the network topology structure are incorporated into our models. A detailed analysis is conducted to analyze the propagation models. Through analysis, the stable infection-free equilibrium point and the stability condition are derived. Finally, considering the network topology, the numerical and simulation experiments are carried out. Results indicate that both models are correct and suitable for describing the spread of two different mobile phone viruses, respectively.
Velocity and directionality of the electrohysterographic signal propagation.
Directory of Open Access Journals (Sweden)
Lasse Lange
Full Text Available OBJECTIVE: The initiation of treatment for women with threatening preterm labor requires effective distinction between true and false labor. The electrohysterogram (EHG has shown great promise in estimating and classifying uterine activity. However, key issues remain unresolved and no clinically usable method has yet been presented using EHG. Recent studies have focused on the propagation velocity of the EHG signals as a potential discriminator between true and false labor. These studies have estimated the propagation velocity of individual spikes of the EHG signals. We therefore focus on estimating the propagation velocity of the entire EHG burst recorded during a contraction in two dimensions. STUDY DESIGN: EHG measurements were performed on six women in active labor at term, and a total of 35 contractions were used for the estimation of propagation velocity. The measurements were performed using a 16-channel two-dimensional electrode grid. The estimates were calculated with a maximum-likelihood approach. RESULTS: The estimated average propagation velocity was 2.18 (±0.68 cm/s. No single preferred direction of propagation was found. CONCLUSION: The propagation velocities estimated in this study are similar to those reported in other studies but with a smaller intra- and inter-patient variation. Thus a potential tool has been established for further studies on true and false labor contractions.
Wave equations for pulse propagation
Energy Technology Data Exchange (ETDEWEB)
Shore, B.W.
1987-06-24
Theoretical discussions of the propagation of pulses of laser radiation through atomic or molecular vapor rely on a number of traditional approximations for idealizing the radiation and the molecules, and for quantifying their mutual interaction by various equations of propagation (for the radiation) and excitation (for the molecules). In treating short-pulse phenomena it is essential to consider coherent excitation phenomena of the sort that is manifest in Rabi oscillations of atomic or molecular populations. Such processes are not adequately treated by rate equations for excitation nor by rate equations for radiation. As part of a more comprehensive treatment of the coupled equations that describe propagation of short pulses, this memo presents background discussion of the equations that describe the field. This memo discusses the origin, in Maxwell's equations, of the wave equation used in the description of pulse propagation. It notes the separation into lamellar and solenoidal (or longitudinal and transverse) and positive and negative frequency parts. It mentions the possibility of separating the polarization field into linear and nonlinear parts, in order to define a susceptibility or index of refraction and, from these, a phase and group velocity. The memo discusses various ways of characterizing the polarization characteristics of plane waves, that is, of parameterizing a transverse unit vector, such as the Jones vector, the Stokes vector, and the Poincare sphere. It discusses the connection between macroscopically defined quantities, such as the intensity or, more generally, the Stokes parameters, and microscopic field amplitudes. The material presented here is a portion of a more extensive treatment of propagation to be presented separately. The equations presented here have been described in various books and articles. They are collected here as a summary and review of theory needed when treating pulse propagation.
Trust Propagation in Small Worlds
DEFF Research Database (Denmark)
Gray, Elizabeth; Seigneur, Jean-Marc; Chen, Yong
2003-01-01
do not scale well. We aim to develop trust-based security mechanisms using small world concepts to optimise formation and propagation of trust amongst entities in these vast networks. In this regard, we surmise that in a very large mobile ad hoc network, trust, risk, and recommendations can...... be propagated through relatively short paths connecting entities. Our work describes the design of trust-formation and risk-assessment systems, as well as that of an entity recognition scheme, within the context of the small world network topology....
Vegetative propagation of Bambusa vulgaris
Directory of Open Access Journals (Sweden)
Rafael Malfitano Braga
2017-06-01
Full Text Available Bamboo is an important source of raw material of multiple uses. The development of simple techniques for its propagation is a practical way to enable its implementation in ownership of low technology. The present work had the objective of evaluating artisanal propagation methods for Bambusa vulgaris. Two types of propagules were tested, with buds budded or not, and three relative positions to the removal of vegetative material on the culm. The best propagule was with only one node, extracted from the lower thirds of the stem, presenting 72% of rooting. This result demonstrates its potential for seedling production of this species under low tech.
DEFF Research Database (Denmark)
Sørensen, Paul Haase; Taylor, John C.
1984-01-01
Processes with coloured particles in the initial state are generally infrared divergent. We investigate the effect of this on processes with colourless particles in the initial state, when the amplitude is near an intermediate quark pole. The result is a characteristic logarithmic depedence...... on the 'binding energy'(even though spectator interactions are taken into account), and the result is gauge-invariant. Summed to all orders the logarithms could perhaps suppress the quark pole....
Directory of Open Access Journals (Sweden)
Stephen R. Scherrer
2018-01-01
Full Text Available Background Passive acoustic telemetry using coded transmitter tags and stationary receivers is a popular method for tracking movements of aquatic animals. Understanding the performance of these systems is important in array design and in analysis. Close proximity detection interference (CPDI is a condition where receivers fail to reliably detect tag transmissions. CPDI generally occurs when the tag and receiver are near one another in acoustically reverberant settings. Here we confirm transmission multipaths reflected off the environment arriving at a receiver with sufficient delay relative to the direct signal cause CPDI. We propose a ray-propagation based model to estimate the arrival of energy via multipaths to predict CPDI occurrence, and we show how deeper deployments are particularly susceptible. Methods A series of experiments were designed to develop and validate our model. Deep (300 m and shallow (25 m ranging experiments were conducted using Vemco V13 acoustic tags and VR2-W receivers. Probabilistic modeling of hourly detections was used to estimate the average distance a tag could be detected. A mechanistic model for predicting the arrival time of multipaths was developed using parameters from these experiments to calculate the direct and multipath path lengths. This model was retroactively applied to the previous ranging experiments to validate CPDI observations. Two additional experiments were designed to validate predictions of CPDI with respect to combinations of deployment depth and distance. Playback of recorded tags in a tank environment was used to confirm multipaths arriving after the receiver’s blanking interval cause CPDI effects. Results Analysis of empirical data estimated the average maximum detection radius (AMDR, the farthest distance at which 95% of tag transmissions went undetected by receivers, was between 840 and 846 m for the deep ranging experiment across all factor permutations. From these results, CPDI was
Propagation with Chipping Technique in Leucojum aestivum L.
Directory of Open Access Journals (Sweden)
Nilüfer SEYİDOĞLU
2009-01-01
Full Text Available Chipping technique is a method for use to propagate bulb at high amounts. This method is used to propagate geophyte species that compose well basal plate such as Leucojum, Galanthus, Fritillaria, Narcissus,Chionodoxa, Nerine, Scilla, Sternbergia. This study aimed to obtain bulbil from Leucojum aestivum by chipping technique with application of different size divided bulbs and bulb sizes. As a result, application of dividing into four pieces of large bulbs (11/12 cm were found to be effective.
Propagating synchrony in feed-forward networks.
Jahnke, Sven; Memmesheimer, Raoul-Martin; Timme, Marc
2013-01-01
Coordinated patterns of precisely timed action potentials (spikes) emerge in a variety of neural circuits but their dynamical origin is still not well understood. One hypothesis states that synchronous activity propagating through feed-forward chains of groups of neurons (synfire chains) may dynamically generate such spike patterns. Additionally, synfire chains offer the possibility to enable reliable signal transmission. So far, mostly densely connected chains, often with all-to-all connectivity between groups, have been theoretically and computationally studied. Yet, such prominent feed-forward structures have not been observed experimentally. Here we analytically and numerically investigate under which conditions diluted feed-forward chains may exhibit synchrony propagation. In addition to conventional linear input summation, we study the impact of non-linear, non-additive summation accounting for the effect of fast dendritic spikes. The non-linearities promote synchronous inputs to generate precisely timed spikes. We identify how non-additive coupling relaxes the conditions on connectivity such that it enables synchrony propagation at connectivities substantially lower than required for linearly coupled chains. Although the analytical treatment is based on a simple leaky integrate-and-fire neuron model, we show how to generalize our methods to biologically more detailed neuron models and verify our results by numerical simulations with, e.g., Hodgkin Huxley type neurons.
Ultrashort Pulse Propagation in Nonlinear Dispersive Fibers
Agrawal, Govind P.
Ultrashort optical pulses are often propagated through optical waveguides for a variety of applications including telecommunications and supercontinuum generation [1]. Typically the waveguide is in the form of an optical fiber but it can also be a planar waveguide. The material used to make the waveguide is often silica glass, but other materials such as silicon or chalcogenides have also been used in recent years. What is common to all such materials is they exhibit chromatic dispersion as well as the Kerr nonlinearity. The former makes the refractive index frequency dependent, whereas the latter makes it to depend on the intensity of light propagating through the medium [2]. Both of these effects become more important as optical pulses become shorter and more intense. For pulses not too short (pulse widths > 1 ns) and not too intense (peak powers < 10 mW), the waveguide plays a passive role (except for small optical losses) and acts as a transporter of optical pulses from one place to another, without significantly affecting their shape or spectrum. However, as pulses become shorter and more intense, both the dispersion and the Kerr nonlinearity start to affect the shape and spectrum of an optical pulse during its propagation inside the waveguide. This chapter focuses on silica fibers but similar results are expected for other waveguides made of different materials
Reece-Hoyes, John S; Walhout, Albertha J M
2018-01-02
Generating stocks of Entry and Destination vectors for use in the Gateway recombinatorial cloning system requires transforming them into Escherichia coli strain DB3.1, where they can replicate because this strain is immune to the effects of the ccdB gene carried in the Gateway cassette. However, mutations in the ccdB gene can arise at low frequency, and these mutant plasmids will consequently allow growth of standard cloning strains of E. coli (e.g., DH5α). Therefore, after making new stocks of Gateway plasmids, their ability to grow in cloning strains of E. coli must be tested. This involves obtaining multiple stocks of vector, each arising from a single plasmid grown in a single DB3.1 bacterial colony, and transforming each stock into both DB3.1 and the preferred cloning strain of E. coli in a controlled fashion. Only vector stocks that effectively kill the standard cloning strain (i.e., no or few colonies are obtained after transformation) should be used in Gateway cloning reactions. The sequence can be performed in 3 d. © 2018 Cold Spring Harbor Laboratory Press.
Oestmann, Jan; Tiemeyer, Bärbel
2017-04-01
Drainage of peatlands for agriculture, forestry and peat extraction turned these landscapes into hotspots of greenhouse gas emissions. Climate protection now fosters rewetting projects to restore the natural peatland function as a sink of atmospheric carbon. One possible way to combine ecological and economical goals is Sphagnum farming, i.e. the cultivation of Sphagnum mosses as high-quality substrates for horticulture. This project scientifically evaluates the attempt of commercial Sphagnum farming on former peat extraction sites in north-western Germany. The exchange of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) of the whole peatland-based production chain comprising a donor mire, a propagation area, an irrigation polder and a cultivation site will be determined in a high temporal resolution for two years using manual chambers. This will allow evaluating the greenhouse gas balance of Sphagnum farming sites in comparison to near-natural sites and the potential of Sphagnum farming for restoring drained peatlands to sinks of atmospheric carbon. The influence of different irrigation techniques will also be tested. Additionally, selected plots will be equipped with open top chambers in order to examine the greenhouse gas exchange under potential future climate change conditions. Finally, a 13C pulse labeling experiment will make it possible to trace the newly sequestered CO2 in biomass, soil, respiration and dissolved organic carbon.
Bocchialini, K.; Grison, B.; Menvielle, M.; Chambodut, A.; Cornilleau-Wehrlin, N.; Fontaine, D.; Marchaudon, A.; Pick, M.; Pitout, F.; Schmieder, B.; Régnier, S.; Zouganelis, I.
2017-12-01
From the list of 32 SSCs over the year 2002, we performed a multi-criteria analysis based on propagation time, velocity comparison, sense of the magnetic field rotation, radio waves to associate them with solar sources, identify their causes in the interplanetary medium and then look at the response of the terrestrial ionized and neutral environment to them. The complex interactions between two (or more) CMEs and the modification in their trajectory have been examined using joint white light and multiple-wavelength radio observations. The structures at L_1 after the 32 SSCs are regarded as Magnetic Clouds (MCs), ICMEs without a MC structure, Miscellaneous structures, CIRs/SIRs, and shock-only events. In terms of geoeffectivity, generally CMEs with velocities at the Sun larger than 1000 km.s-1 have larger probabilities to trigger moderate or intense storms. The most geoeffective events are MCs, since 92% of them trigger moderate or intense storms. The geoeffective events trigger an increased and combined AKR and NTC wave activity in the magnetosphere, an enhanced convection in the ionosphere and a stronger response in the thermosphere.
Pathogen Propagation Model with Superinfection in Vegetatively Propagated Plants on Lattice Space.
Directory of Open Access Journals (Sweden)
Yuma Sakai
Full Text Available Many clonal plants have two reproductive patterns, seed propagation and vegetative propagation. By vegetative propagation, plants reproduce the genetically identical offspring with a low mortality, because resources are supplied from the other individuals through interconnected ramets at vegetative-propagated offspring. However, the ramets transport not only resources but also systemic pathogen. Pathogens evolve to establish and spread widely within the plant population. The superinfection, which is defined as the ability that an established pathogen spreads widely by infecting to already-infected individuals with other strains of a pathogen, is important to the evolution of pathogens. We examine the dynamics of plant reproduction and pathogen propagation considering spatial structure and the effect of superinfection on genetic diversity of pathogen by analysis of several models, 1-strain and multiple-strain models, on two-dimensional square lattice. In the analysis of 1-strain model, we derive equilibrium value by mean-field approximation and pair approximation, and its local stability by Routh-Hurwitz stability criterion. In the multiple-strain models, we analyze the dynamics by numerical simulation of mean-field approximation, pair approximation and Monte Carlo simulation. Through the analyses, we show the effect of parameter values to dynamics of models, such as transition of dominant strain of pathogen, competition between plants and pathogens and density of individuals. As a result, (i The strain with intermediate cost becomes dominant when both superinfection rate and growth rate are low. (ii The competition between plants and pathogens occurs in the phase of coexistence of various strains by pair approximation and Monte Carlo simulation. (iii Too high growth rate leads to the decrease of plant population in all models. (iv Pathogens are easy to maintain their genetic diversity with low superinfection rate. However, if they do not
Pathogen Propagation Model with Superinfection in Vegetatively Propagated Plants on Lattice Space.
Sakai, Yuma; Takada, Takenori
2016-01-01
Many clonal plants have two reproductive patterns, seed propagation and vegetative propagation. By vegetative propagation, plants reproduce the genetically identical offspring with a low mortality, because resources are supplied from the other individuals through interconnected ramets at vegetative-propagated offspring. However, the ramets transport not only resources but also systemic pathogen. Pathogens evolve to establish and spread widely within the plant population. The superinfection, which is defined as the ability that an established pathogen spreads widely by infecting to already-infected individuals with other strains of a pathogen, is important to the evolution of pathogens. We examine the dynamics of plant reproduction and pathogen propagation considering spatial structure and the effect of superinfection on genetic diversity of pathogen by analysis of several models, 1-strain and multiple-strain models, on two-dimensional square lattice. In the analysis of 1-strain model, we derive equilibrium value by mean-field approximation and pair approximation, and its local stability by Routh-Hurwitz stability criterion. In the multiple-strain models, we analyze the dynamics by numerical simulation of mean-field approximation, pair approximation and Monte Carlo simulation. Through the analyses, we show the effect of parameter values to dynamics of models, such as transition of dominant strain of pathogen, competition between plants and pathogens and density of individuals. As a result, (i) The strain with intermediate cost becomes dominant when both superinfection rate and growth rate are low. (ii) The competition between plants and pathogens occurs in the phase of coexistence of various strains by pair approximation and Monte Carlo simulation. (iii) Too high growth rate leads to the decrease of plant population in all models. (iv) Pathogens are easy to maintain their genetic diversity with low superinfection rate. However, if they do not superinfect, the
Gluon propagator at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Mandula, J.E.; Ogilvie, M.
1988-01-28
The Landau gauge gluon propagator at finite temperature above and below the deconfinement transition is measured using lattice Monte Carlo simulation. The color electric and magnetic masses are determined. The most striking result of the calculation is that the time component of the gluon field appears to acquire a vacuum expected value in the deconfined region.
Near earth propagation: physics revealed
Wert, R.; Goroch, A.; Worthington, E.; Wong, V.
2007-04-01
Both the military and consumer sectors are pursuing distributed networked systems and sensors. A major stumbling block to deployment of these sensors will be the radio frequency (RF) propagation environment within a few wavelengths of the earth. Increasing transmit power (battery consumption) is not a practical solution to the problem. This paper will discuss some of the physical phenomena related to the near earth propagation (NEP) problem. When radiating near the earth the communications link is subjected to a list of physical impairments. On the list are the expected Fresnel region encroachment and multipath reflections. Additionally, radiation pattern changes and near earth boundary layer perturbations exist. A significant amount of data has been collected on NEP. Disturbances in the NEP atmosphere can have a time varying attenuation related to the time of day and these discoveries will be discussed. Solutions, or workarounds, to the near earth propagation problem hinge on dynamic adaptive RF elements. Adaptive RF elements will allow the distributed sensor to direct energy, beam form, impedance correct, increase communication efficiency, and decrease battery consumption. Small electrically controllable elements are under development to enable antenna impedance matching in a dynamic environment. Additionally, small dynamic beam forming arrays are under development to focus RF energy in the direction of need. With an increased understanding of the near earth propagation problem, distributed autonomous networked sensors can become a reality within a few centimeters of the earth.
Invisibility cloaking without superluminal propagation
Energy Technology Data Exchange (ETDEWEB)
Perczel, Janos; Leonhardt, Ulf [School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS (United Kingdom); Tyc, Tomas, E-mail: jp394@st-andrews.ac.uk, E-mail: tomtyc@physics.muni.cz, E-mail: ulf@st-andrews.ac.uk [Faculty of Science, Kotlarska 2 and Faculty of Informatics, Botanicka 68a, Masaryk University, 61137 Brno (Czech Republic)
2011-08-15
Conventional cloaking based on Euclidean transformation optics requires that the speed of light should tend to infinity on the inner surface of the cloak. Non-Euclidean cloaking still needs media with superluminal propagation. Here we show by giving an example that this is no longer necessary.
Wave equations for pulse propagation
Shore, B. W.
1987-06-01
Theoretical discussions of the propagation of pulses of laser radiation through atomic or molecular vapor rely on a number of traditional approximations for idealizing the radiation and the molecules, and for quantifying their mutual interaction by various equations of propagation (for the radiation) and excitation (for the molecules). In treating short-pulse phenomena it is essential to consider coherent excitation phenomena of the sort that is manifest in Rabi oscillations of atomic or molecular populations. Such processes are not adequately treated by rate equations for excitation nor by rate equations for radiation. As part of a more comprehensive treatment of the coupled equations that describe propagation of short pulses, this memo presents background discussion of the equations that describe the field. This memo discusses the origin, in Maxwell's equations, of the wave equation used in the description of pulse propagation. It notes the separation into lamellar and solenoidal (or longitudinal and transverse) and positive and negative frequency parts. It mentions the possibility of separating the polarization field into linear and nonlinear parts, in order to define a susceptibility or index of refraction and, from these, a phase and group velocity.
Ultraviolet asymptotics of glueball propagators
Bochicchio, Marco; Muscinelli, Samuele P.
2013-08-01
We point out that perturbation theory in conjunction with the renormalization group ( RG) puts a severe constraint on the structure of the large- N non-perturbative glueball propagators in SU( N) pure Y M, in QCD and in = 1 SU SY QCD with massless quarks, or in any confining asymptotically-free gauge theory massless in perturbation theory. For the scalar and pseudoscalar glueball propagators in pure Y M and QCD with massless quarks we check in detail the RG-improved estimate to the order of the leading and next-to-leading logarithms by means of a remarkable three-loop computation by Chetyrkin et al. We investigate as to whether the aforementioned constraint is satisfied by any of the scalar or pseudoscalar glueball propagators computed in the framework of the AdS String/ large- N Gauge Theory correspondence and of a recent proposal based on a Topological Field Theory underlying the large- N limit of Y M . We find that none of the proposals for the scalar or the pseudoscalar glueball propagators based on the AdS String/large- N Gauge Theory correspondence satisfies the constraint, actually as expected, since the gravity side of the correspondence is in fact strongly coupled in the ultraviolet. On the contrary, the Topological Field Theory satisfies the constraint that follows by the asymptotic freedom.
Radio frequency propagation made easy
Faruque, Saleh
2015-01-01
This book introduces Radio Frequency Propagation to a broad audience. The author blends theory and practice to bring readers up-to-date in key concepts, underlying principles and practical applications of wireless communications. The presentation is designed to be easily accessible, minimizing mathematics and maximizing visuals.
Global Bifurcation of a Novel Computer Virus Propagation Model
Directory of Open Access Journals (Sweden)
Jianguo Ren
2014-01-01
Full Text Available In a recent paper by J. Ren et al. (2012, a novel computer virus propagation model under the effect of the antivirus ability in a real network is established. The analysis there only partially uncovers the dynamics behaviors of virus spread over the network in the case where around bifurcation is local. In the present paper, by mathematical analysis, it is further shown that, under appropriate parameter values, the model may undergo a global B-T bifurcation, and the curves of saddle-node bifurcation, Hopf bifurcation, and homoclinic bifurcation are obtained to illustrate the qualitative behaviors of virus propagation. On this basis, a collection of policies is recommended to prohibit the virus prevalence. To our knowledge, this is the first time the global bifurcation has been explored for the computer virus propagation. Theoretical results and corresponding suggestions may help us suppress or eliminate virus propagation in the network.
Sound wave propagation in weakly polydisperse granular materials.
Mouraille, O; Luding, S
2008-11-01
Dynamic simulations of wave propagation are performed in dense granular media with a narrow polydisperse size-distribution and a linear contact-force law. A small perturbation is created on one side of a static packing and its propagation, for both P- and S-waves, is examined. A size variation comparable to the typical contact deformation already changes sound propagation considerably. The transmission spectrum becomes discontinuous, i.e., a lower frequency band is transmitted well, while higher frequencies are not, possibly due to attenuation and scattering. This behaviour is qualitatively reproduced for (i) Hertz non-linear contacts, for (ii) frictional contacts, (iii) for a range of smaller amplitudes, or (iv) for larger systems. This proves that the observed wave propagation and dispersion behaviour is intrinsic and not just an artifact of (i) a linear model, (ii) a frictionless packing, (iii) a large amplitude non-linear wave, or (iv) a finite size effect.
Dispersion Management of Propagating Waveguide Modes on the Water Surface.
Fu, Shenhe; Zhou, Jianying; Li, Yongyao; Shemer, Lev; Arie, Ady
2017-04-07
We report on the theoretical and experimental study of the generation of propagating waveguide modes on the water surface. These propagating modes are modulated in the transverse direction in a manner that satisfies boundary conditions on the walls of the water tank. It is shown that the propagating modes possess both anomalous and normal dispersion regimes, in contrast to the extensively studied zero mode that, in the case of deep water, only has normal dispersion with a fixed frequency independent dispersion coefficient. Importantly, by using a carrier frequency at which the group velocity dispersion crosses zero, a linear nonspreading and shape-preserving wave packet is observed. By increasing the wave steepness, nonlinear effects become pronounced, thereby enabling the first observation of linearly chirped parabolic water wave pulses in the anomalous dispersion regime. This parabolic wave maintains its linear frequency chirp and does not experience wave breaking during propagation.
Cornilleau-Wehrlin, Nicole; Bocchialini, Karine; Menvielle, Michel; Chambodut, Aude; Fontaine, Dominique; Grison, Benjamin; Marchaudon, Aurélie; Pick, Monique; Pitout, Frédéric; Schmieder, Brigitte; Régnier, Stéphane; Zouganelis, Yannis
2017-04-01
Taking the 32 sudden storm commencements (SSC) listed by the observatory de l'Ebre / ISGI over the year 2002 (maximal solar activity) as a starting point, we performed a statistical analysis of the related solar sources, solar wind signatures, and terrestrial responses. For each event, we characterized and identified, as far as possible, (i) the sources on the Sun (Coronal Mass Ejections -CME-), with the help of a series of criteria (velocities, drag coefficient, radio waves, helicity), as well as (ii) the structure and properties in the interplanetary medium, at L1, of the event associated to the SSC: magnetic clouds -MC-, non-MC interplanetary coronal mass ejections -ICME-, co-rotating/stream interaction regions -SIR/CIR-, shocks only and unclear events that we call "miscellaneous" events. The observed Sun-to-Earth travel times are compared to those estimated using existing simple models of propagation in the interplanetary medium. This comparison is used to statistically assess performances of various models. The geoeffectiveness of the events, classified by category at L1, is analysed by their signatures in the Earth ionized (magnetosphere and ionosphere) and neutral (thermosphere) environments, using a broad set of in situ, remote and ground based instrumentation. The role of the presence of a unique or of a multiple source at the Sun, of its nature, halo or non halo CME, is also discussed. The set of observations is statistically analyzed so as to evaluate and compare the geoeffectiveness of the events. The results obtained for this set of geomagnetic storms started by SSCs is compared to the overall statistics of year 2002, relying on already published catalogues of events, allowing assessing the relevance of our approach (for instance the all 12 well identified Magnetic Clouds of 2002 give rise to SSCs).
A local-ether model of propagation of electromagnetic wave
Energy Technology Data Exchange (ETDEWEB)
Su, C.C. [Dept. of Electrical Engineering, National Tsinghua University, Hsinchu (Taiwan)
2001-07-01
It is pointed out that the classical propagation model can be in accord with the Sagnac effect due to earth's rotational and orbital motions in the high-precision GPS (global positioning system) and interplanetary radar, if the reference frame of the classical propagation medium is endowed with a switchability according to the location of the wave. Accordingly, it is postulated that, as in the obsolete theory, electromagnetic waves propagate via a medium like the ether. However, the ether is not universal. It is proposed that in the region under sufficient influence of the gravity due to the earth, the sun, or another celestial body, there forms a local ether, which in turn is stationary with respect to the gravitational potential of the respective body. For earthbound and interplanetary propagation, the medium is stationary in a geocentric and a heliocentric inertial frame, respectively. An electromagnetic wave propagates at a constant speed with respect to the associated local ether, independent of the motions of source and receiver. Based on this local-ether model of wave propagation, a wide variety of earthbound, interplanetary, and interstellar propagation phenomena are accounted for. Strong evidence of this new classical model is its consistent account of the Sagnac effect due to earth's motions among GPS, the intercontinental microwave link, and the interplanetary radar. Moreover, as examined within the present precision, this model is still in accord with the Michelson-Morley experiment. To test the local-ether propagation model, a one-way-link rotor experiment is proposed. (orig.)
Interactive Sound Propagation using Precomputation and Statistical Approximations
Antani, Lakulish
Acoustic phenomena such as early reflections, diffraction, and reverberation have been shown to improve the user experience in interactive virtual environments and video games. These effects arise due to repeated interactions between sound waves and objects in the environment. In interactive applications, these effects must be simulated within a prescribed time budget. We present two complementary approaches for computing such acoustic effects in real time, with plausible variation in the sound field throughout the scene. The first approach, Precomputed Acoustic Radiance Transfer, precomputes a matrix that accounts for multiple acoustic interactions between all scene objects. The matrix is used at run time to provide sound propagation effects that vary smoothly as sources and listeners move. The second approach couples two techniques---Ambient Reverberance, and Aural Proxies---to provide approximate sound propagation effects in real time, based on only the portion of the environment immediately visible to the listener. These approaches lie at different ends of a space of interactive sound propagation techniques for modeling sound propagation effects in interactive applications. The first approach emphasizes accuracy by modeling acoustic interactions between all parts of the scene; the second approach emphasizes efficiency by only taking the local environment of the listener into account. These methods have been used to efficiently generate acoustic walkthroughs of architectural models. They have also been integrated into a modern game engine, and can enable realistic, interactive sound propagation on commodity desktop PCs.
Simulations of Seismic Wave Propagation on Mars
Bozdağ, Ebru; Ruan, Youyi; Metthez, Nathan; Khan, Amir; Leng, Kuangdai; van Driel, Martin; Wieczorek, Mark; Rivoldini, Attilio; Larmat, Carène S.; Giardini, Domenico; Tromp, Jeroen; Lognonné, Philippe; Banerdt, Bruce W.
2017-10-01
We present global and regional synthetic seismograms computed for 1D and 3D Mars models based on the spectral-element method. For global simulations, we implemented a radially-symmetric Mars model with a 110 km thick crust (Sohl and Spohn in J. Geophys. Res., Planets 102(E1):1613-1635, 1997). For this 1D model, we successfully benchmarked the 3D seismic wave propagation solver SPECFEM3D_GLOBE (Komatitsch and Tromp in Geophys. J. Int. 149(2):390-412, 2002a; 150(1):303-318, 2002b) against the 2D axisymmetric wave propagation solver AxiSEM (Nissen-Meyer et al. in Solid Earth 5(1):425-445, 2014) at periods down to 10 s. We also present higher-resolution body-wave simulations with AxiSEM down to 1 s in a model with a more complex 1D crust, revealing wave propagation effects that would have been difficult to interpret based on ray theory. For 3D global simulations based on SPECFEM3D_GLOBE, we superimposed 3D crustal thickness variations capturing the distinct crustal dichotomy between Mars' northern and southern hemispheres, as well as topography, ellipticity, gravity, and rotation. The global simulations clearly indicate that the 3D crust speeds up body waves compared to the reference 1D model, whereas it significantly changes surface waveforms and their dispersive character depending on its thickness. We also perform regional simulations with the solver SES3D (Fichtner et al. Geophys. J. Int. 179:1703-1725, 2009) based on 3D crustal models derived from surface composition, thereby addressing the effects of various distinct crustal features down to 2 s. The regional simulations confirm the strong effects of crustal variations on waveforms. We conclude that the numerical tools are ready for examining more scenarios, including various other seismic models and sources.
Laser beam propagation through random media
Andrews, Larry C
2005-01-01
Since publication of the first edition of this text in 1998, there have been several new, important developments in the theory of beam wave propagation through a random medium, which have been incorporated into this second edition. Also new to this edition are models for the scintillation index under moderate-to-strong irradiance fluctuations; models for aperture averaging based on ABCD ray matrices; beam wander and its effects on scintillation; theory of partial coherence of the source; models of rough targets for ladar applications; phase fluctuations; analysis of other beam shapes; plus exp
Fractional Dynamics of Computer Virus Propagation
Directory of Open Access Journals (Sweden)
Carla M. A. Pinto
2014-01-01
Full Text Available We propose a fractional model for computer virus propagation. The model includes the interaction between computers and removable devices. We simulate numerically the model for distinct values of the order of the fractional derivative and for two sets of initial conditions adopted in the literature. We conclude that fractional order systems reveal richer dynamics than the classical integer order counterpart. Therefore, fractional dynamics leads to time responses with super-fast transients and super-slow evolutions towards the steady-state, effects not easily captured by the integer order models.
Oxyhydrogen ignition and flame propagation under cryogenic temperatures
Energy Technology Data Exchange (ETDEWEB)
Hayashi, A.K.; Fujiwara, T.
1983-03-01
One dimensional numerical calculations were performed for ignition and flame propagation of oxyhydrogen mixtures under cryogenic conditions. Three aspects on ignition problems were studied an effect of ambient temperature on the minimum ignition energy, an effect of initial pressure on the minimum ignition energy per mass, and an effect of energy deposit rate on the minimum ignition energy.