Transient Response Model of Standing Wave Piezoelectric Linear Ultrasonic Motor
Institute of Scientific and Technical Information of China (English)
SHI Yunlai; CHEN Chao; ZHAO Chunsheng
2012-01-01
A transient response model for describing the starting and stopping characteristics of the standing wave piezoelectric linear ultrasonic motor was presented.Based on the contact dynamic model,the kinetic equation of the motor was derived.The starting and stopping characteristics of the standing wave piezoelectric linear ultrasonic motor according to different loads,contact stiffness and inertia mass were described and analyzed,respectively.To validate the transient response model,a standing wave piezoelectric linear ultrasonic motor based on in-plane modes was used to carry out the simulation and experimental study.The corresponding results showed that the simulation of the motor performances based on the proposed model agreed well with the experimental results.This model will helpful to improve the stepping characteristics and the control flexibility of the standing wave piezoelectric linear ultrasonic motor.
Two Mode Resonator and Contact Model for Standing Wave Piezomotor
DEFF Research Database (Denmark)
Andersen, B.; Blanke, Mogens; Helbo, J.
2001-01-01
The paper presents a model for a standing wave piezoelectric motor with a two bending mode resonator. The resonator is modelled using Hamilton's principle and the Rayleigh-Ritz method. The contact is modelled using the Lagrange Multiplier method under the assumption of slip and it is showed how...... to solve the set of differential-algebraic equations. Detailled simulations show resonance frequencies as function of the piezoelement's position, tip trajectories and contact forces. The paper demonstrates that contact stiffness and stick should be included in such model to obtain physically realistic...
Modelling and Experiments of a Standing Wave Piezomotor
DEFF Research Database (Denmark)
Andersen, B.; Helbo, Jan; Blanke, Mogens
The paper presents a new contact model for standing wave piezomotors. The contact model is based on the Hertz theory for normal contact deformations and elastic contact theory for tangential loads. The contact theory is simplified into a model with discrete springs for normal and tangential loads...... which allows the calculation of slip/stick transitions. Simulations show that tip trajectories in general cannot be prescribed. The paper presents the principle of a bending resonator. Experiments indicate that the bending vibrations are too small to generate rotor rotations. However, due to unintended...
Modelling and Experiments of a Standing Wave Piezomotor
DEFF Research Database (Denmark)
Andersen, B.; Helbo, Jan; Blanke, Mogens
2002-01-01
The paper presents a new contact model for standing wave piezomotors. The contact model is based on the Hertz theory for normal contact deformations and elastic contact theory for tangential loads. The contact theory is simplified into a model with discrete springs for normal and tangential loads...... which allows the calculation of slip/stick transitions. Simulations show that tip trajectories in general cannot be prescribed. The paper presents the principle of a bending resonator. Experiments indicate that the bending vibrations are too small to generate rotor rotations. However, due to unintended...
Contact Analysis and Modeling of Standing Wave Linear Ultrasonic Motor
Institute of Scientific and Technical Information of China (English)
SHI Yunlai; ZHAO Chunsheng; ZHANG Jianhui
2011-01-01
A contact model for describing the contact mechanics between the stator and slider of the standing wave linear ultrasonic motor was presented.The proposed model starts from the assumption that the vibration characteristics of the stator is not affected by the contact process.A modified friction models was used to analyze the contact problems.Firstly,the dynamic normal contact force,interface friction force,and steady-state characteristics were analyzed.Secondly,the influences of the contact layer material,the dynamic characteristics of the stator,and the pre-load on motor performance were simulated.Finally,to validate the contact model,a linear ultrasonic motor based on in-plane modes was used as an example.The corresponding results show that a set of simulation of motor performances based on the proposed contact mechanism is in good agreement with experimental results.This model is helpful to understanding the operation principle of the standing wave linear motor and thus contributes to the design of these tvpes of motor.
Unified relativistic physics from a standing wave particle model
Vera, R A
1995-01-01
An extremely simple and unified base for physics comes out by starting all over from a single postulate on the common nature of matter and stationary forms of radiation quanta. Basic relativistic, gravitational (G) and quantum mechanical properties of a standing wave particle model have been derived. This has been done from just dual properties of radiation's and strictly homogeneous relationships for nonlocal cases in G fields. This way reduces the number of independent variables and puts into relief (and avoid) important inhomogeneity errors of some G theories. It unifies and accounts for basic principles and postulates physics. The results for gravity depend on linear radiation properties but not on arbitrary field relations. They agree with the conventional tests. However they have some fundamental differences with current G theories. The particle model, at a difference of the conventional theories, also fixes well-defined cosmological and astrophysical models that are different from the rather convention...
Standing and travelling waves in a spherical brain model: The Nunez model revisited
Visser, S.; Nicks, R.; Faugeras, O.; Coombes, S.
2017-06-01
The Nunez model for the generation of electroencephalogram (EEG) signals is naturally described as a neural field model on a sphere with space-dependent delays. For simplicity, dynamical realisations of this model either as a damped wave equation or an integro-differential equation, have typically been studied in idealised one dimensional or planar settings. Here we revisit the original Nunez model to specifically address the role of spherical topology on spatio-temporal pattern generation. We do this using a mixture of Turing instability analysis, symmetric bifurcation theory, centre manifold reduction and direct simulations with a bespoke numerical scheme. In particular we examine standing and travelling wave solutions using normal form computation of primary and secondary bifurcations from a steady state. Interestingly, we observe spatio-temporal patterns which have counterparts seen in the EEG patterns of both epileptic and schizophrenic brain conditions.
Model independent X-ray standing wave analysis of periodic multilayer structures
Yakunin, S.N.; Makhotkin, I.A.; Chuev, M.A.; Pashaev, E.M.; Zoethout, E.; Louis, E.; Kruijs, van de R.W.E.; Seregin, S.Y.; Subbotin, I.A.; Novikov, D.; Bijkerk, F.; Kovalchuk, M.V.
2014-01-01
We present a model independent approach for the reconstruction of the atomic concentration profile in a nanoscale layered structure, as measured using the X-ray fluorescence yield modulated by an X-ray standing wave (XSW). The approach is based on the direct regularized solution of the system of lin
Model independent X-ray standing wave analysis of periodic multilayer structures
Yakunin, S. N.; Makhotkin, I. A.; van de Kruijs, R. W. E.; Chuev, M. A.; Pashaev, E.M.; Zoethout, E.; E. Louis,; Seregin, Yu; Subbotin, I.A.; Novikov, D. V.; F. Bijkerk,; Kovalchuk, M. V.
2014-01-01
We present a model independent approach for the analysis of X-ray fluorescence yield modulated by an X-ray standing wave (XSW), that allow a fast reconstruction of the atomic distribution function inside a sample without fitting procedure. The approach is based on the direct regularized solution of
Standing Slow-Mode Waves in Hot Coronal Loops: Observations, Modeling, and Coronal Seismology
Wang, Tongjiang
2010-01-01
Strongly damped Doppler shift oscillations are observed frequently associated with flarelike events in hot coronal loops. In this paper, a review of the observed properties and the theoretical modeling is presented. Statistical measurements of physical parameters (period, decay time, and amplitude) have been obtained based on a large number of events observed by SOHO/SUMER and Yohkoh/BCS. Several pieces of evidence are found to support their interpretation in terms of the fundamental standing longitudinal slow mode. The high excitation rate of these oscillations in small- or micro-flares suggest that the slow mode waves are a natural response of the coronal plasma to impulsive heating in closed magnetic structure. The strong damping and the rapid excitation of the observed waves are two major aspects of the waves that are poorly understood, and are the main subject of theoretical modeling. The slow waves are found mainly damped by thermal conduction and viscosity in hot coronal loops. The mode coupling seems ...
Two-Mode Resonator and Contact Model for Standing Wave Piezomotor
DEFF Research Database (Denmark)
Andersen, B.; Blanke, Mogens; Helbo, J.
2001-01-01
The paper presents a model for a standing wave piezoelectric motor with a two bending mode resonator. The resonator is modelled using Hamilton's principle and the Rayleigh-Ritz method. The contact is modelled using the Lagrange Multiplier method under the assumption of slip and it is showed how...... to solve the set of differential-algebraic equations. Detailed simulations show resonance frequencies as function of the piezoelement's position, tip trajectories and contact forces. The paper demonstrates that contact stiffness and stick should be included in such model to obtain physically realistic...
Thick brane isotropization in the 5D anisotropic standing wave braneworld model
Gogberashvili, Merab; Malagon-Morejon, Dagoberto; Mora-Luna, Refugio Rigel; Nucamendi, Ulises
2014-01-01
We study a smooth cosmological solution of the 5D anisotropic standing wave braneworld model generated by gravity coupled to a phantom-like scalar field. In this model the brane emits anisotropic waves into the bulk with different amplitudes along different spatial dimensions. We found a natural mechanism which isotropizes the braneworld, rendering a 3-brane with de Sitter symmetry embedded in a 5D de Sitter space-time for a wide class of initial conditions. The resulting thick geometrical braneworld (a de Sitter 3-brane) possesses a series of remarkable features. By explicitly solving the bulk field equations we are able to give a physical interpretation of the anisotropic dissipation: as the anisotropic energy on the 3-brane rapidly leaks into the bulk, through the nontrivial Weyl tensor components, the bulk becomes less isotropic.
Residual Liquefaction under Standing Waves
DEFF Research Database (Denmark)
Kirca, V.S. Ozgur; Sumer, B. Mutlu; Fredsøe, Jørgen
2012-01-01
This paper summarizes the results of an experimental study which deals with the residual liquefaction of seabed under standing waves. It is shown that the seabed liquefaction under standing waves, although qualitatively similar, exhibits features different from that caused by progressive waves....... The experimental results show that the buildup of pore-water pressure and the resulting liquefaction first starts at the nodal section and spreads towards the antinodal section. The number of waves to cause liquefaction at the nodal section appears to be equal to that experienced in progressive waves for the same...... wave height. Recommendations are made as to how to assess liquefaction potential in standing waves. Copyright © 2012 by the International Society of Offshore and Polar Engineers (ISOPE)....
Model independent X-ray standing wave analysis of periodic multilayer structures
Yakunin, S N; Chuev, M A; Pashaev, E M; Zoethout, E; Louis, E; van de Kruijs, R W E; Seregin, S Yu; Subbotin, I A; Novikov, D V; Bijkerk, F; Kovalchuk, M V
2013-01-01
We present a model independent approach for the reconstruction of the atomic concentration profile in a nanoscale layered structure, as measured using the X-ray fluorescence yield modulated by an X-ray standing wave (XSW). The approach is based on the direct regularized solution of the system of linear equations that characterizes the fluorescence yield. The suggested technique was optimized for, but not limited to, the analysis of periodic layered structures where the XSW is formed under Bragg conditions. The developed approach was applied to the reconstruction of the atomic concentration profiles for LaN/BN multilayers with 50 periods of 35 A thick layers. The object is especially difficult to analyse with traditional methods, as the estimated thickness of the interface region between the constituent materials is comparable to the individual layer thicknesses. However, using the suggested technique it was possible to reconstruct the La atomic profile, showing that the La atoms stay localized within the LaN ...
Students dance longitudinal standing waves
Ruiz, Michael J.
2017-05-01
A demonstration is presented that involves students dancing longitudinal standing waves. The resulting kinaesthetic experience and visualization both contribute towards an understanding of the natural modes of vibrations in open and closed pipes. A video of this fun classroom activity is provided (http://mjtruiz.com/ped/dance/).
Modeling stick-slip-separation dynamics in a bimodal standing wave ultrasonic motor
Li, Xiang; Yao, Zhiyuan; Lv, Qibao; Liu, Zhen
2016-11-01
Ultrasonic motor (USM) is an electromechanical coupling system with ultrasonic vibration, which is driven by the frictional contact force between the stator (vibrating body) and the rotor/slider (driven body). Stick-slip motion can occur at the contact interface when USM is operating, which may affect the performance of the motor. This paper develops a physically-based model to investigate the complex stick-slip-separation dynamics in a bimodal standing wave ultrasonic motor. The model includes both friction nonlinearity and intermittent separation nonlinearity of the system. Utilizing Hamilton's principle and assumed mode method, the dynamic equations of the stator are deduced. Based on the dynamics of the stator and the slider, sticking force during the stick phase is derived, which is used to examine the stick-to-slip transition. Furthermore, the stick-slip-separation kinematics is analyzed by establishing analytical criteria that predict the transition between stick, slip and separation of the interface. Stick-slip-separation motion is observed in the resulting model, and numerical simulations are performed to study the influence of parameters on the range of possible motions. Results show that stick-slip motion can occur with greater preload and smaller voltage amplitude. Furthermore, a dimensionless parameter is proposed to predict the occurrence of stick-slip versus slip-separation motions, and its role in designing ultrasonic motors is discussed. It is shown that slip-separation motion is favorable for the slider velocity.
Gravity Capillary Standing Water Waves
Alazard, Thomas; Baldi, Pietro
2015-09-01
The paper deals with the 2D gravity-capillary water waves equations in their Hamiltonian formulation, addressing the question of the nonlinear interaction of a plane wave with its reflection off a vertical wall. The main result is the construction of small amplitude, standing (namely periodic in time and space, and not travelling) solutions of Sobolev regularity, for almost all values of the surface tension coefficient, and for a large set of time-frequencies. This is an existence result for a quasi-linear, Hamiltonian, reversible system of two autonomous pseudo-PDEs with small divisors. The proof is a combination of different techniques, such as a Nash-Moser scheme, microlocal analysis and bifurcation analysis.
A Mathematical Prediction of Standing Waves
Higgins, Jon
1970-01-01
Presents a problem in standing waves that provides an example of the mathematics used by theoretical physicists to generate predictions of new phenomena from fundamental background knowledge. Mathematical analysis required to solve problem is accomplished by simple graphical processes. (BR)
Stationary solid particle attractors in standing waves
Energy Technology Data Exchange (ETDEWEB)
Lappa, Marcello, E-mail: marlappa@unina.it, E-mail: marcello.lappa@telespazio.com [Telespazio, Via Gianturco 31, Napoli 80046 (Italy)
2014-01-15
The present analysis extends earlier theories on patterns formed by the spontaneous accumulation and ordering of solid particles in certain types of flow by considering the case in which the particle carrier flow has the typical features of a “standing wave.” For the first time an explanation for this phenomenon is elaborated through arguments based on the interplay between vorticity and wave-interference dynamics (following a deductive approach after the so-called phase-locking or “resonance” model originally introduced by Pushkin et al. [Phys. Rev. Lett. 106, 234501 (2011)] and later variants developed by Lappa [Phys. Fluids 25(1), 012101 (2013) and Lappa, Chaos 23(1), 013105 (2013)]). The results of dedicated numerical simulations are used in synergy with available experimental work. An interesting analogy is proposed with the famous Chladni's series of experiments on patterns formed by sand on vibrating plates.
Stationary solid particle attractors in standing waves
Lappa, Marcello
2014-01-01
The present analysis extends earlier theories on patterns formed by the spontaneous accumulation and ordering of solid particles in certain types of flow by considering the case in which the particle carrier flow has the typical features of a "standing wave." For the first time an explanation for this phenomenon is elaborated through arguments based on the interplay between vorticity and wave-interference dynamics (following a deductive approach after the so-called phase-locking or "resonance" model originally introduced by Pushkin et al. [Phys. Rev. Lett. 106, 234501 (2011)] and later variants developed by Lappa [Phys. Fluids 25(1), 012101 (2013) and Lappa, Chaos 23(1), 013105 (2013)]). The results of dedicated numerical simulations are used in synergy with available experimental work. An interesting analogy is proposed with the famous Chladni's series of experiments on patterns formed by sand on vibrating plates.
Residual liquefaction of seabed under standing waves
DEFF Research Database (Denmark)
Kirca, V.S. Ozgur; Sumer, B. Mutlu; Fredsøe, Jørgen
2013-01-01
This paper presents the results of an experimental study of the seabed liquefaction beneath standing waves. Silt (with d50 =0.070mm) was used in the experiments. Two kinds of measurements were carried out: pore water pressure measurements and water surface elevation measurements. These measurements...... were synchronized with video recording of the liquefaction process from the side. The ranges of the various quantities in the experiments were wave height H= 5.9-12.0 cm, wave period T= 1.09s, and water depth h=30 cm. The experiments show that the seabed liquefaction under standing waves, although...... with a diffusion coefficient equal to the coefficient of consolidation. The experiments further show that the number of waves to cause liquefaction at the nodal section appears to be equal to that experienced in progressive waves for the same wave height. © 2013 American Society of Civil Engineers....
Sousa, L J S; Almeida, C A S
2012-01-01
We constructed a six-dimensional version of the standing wave model with an anisotropic 4-brane generated by a phantom-like scalar field. The model represents a braneworld where the compact (on-brane) dimension is assumed to be sufficiently small in order to describe our universe (hybrid compactification). The proposed geometry of the brane and its transverse manifold is non-static, unlike the majority of braneworld models presented in the literature. Furthermore, we have shown that the zero-mode scalar field is localized around the brane. While in the string-like defect the scalar field is localized on a brane with decreasing warp factor, here it was possible to perform the localization with an increasing warp factor.
Standing waves in fiber-optic interferometers.
de Haan, V; Santbergen, R; Tijssen, M; Zeman, M
2011-10-10
A study is presented giving the response of three types of fiber-optic interferometers by which a standing wave through an object is investigated. The three types are a Sagnac, Mach-Zehnder and Michelson-Morley interferometer. The response of the Mach-Zehnder interferometer is similar to the Sagnac interferometer. However, the Sagnac interferometer is much harder to study because of the fact that one input port and output port coincide. Further, the Mach-Zehnder interferometer has the advantage that the output ports are symmetric, reducing the systematic effects. Examples of standing wave light absorption in several simple objects are given. Attention is drawn to the influence of standing waves in fiber-optic interferometers with weak-absorbing layers incorporated. A method is described for how these can be theoretically analyzed and experimentally measured. Further experiments are needed for a thorough comparison between theory and experiment.
Future directions in standing-wave photoemission
Energy Technology Data Exchange (ETDEWEB)
Gray, Alexander X., E-mail: axgray@temple.edu
2014-08-15
Highlights: • Probing magnetic properties at the buried interface with SW-MCD. • Probing electronic structure at the buried interface with resonant SW-XPS and SW-HAXPES. • Probing momentum-resolved electronic structure at a buried interface with SWARPES. • Adding depth resolution to photoemission microscopy with standing-wave excitation. • Standing-wave localization, total reflection and waveguide effects. - Abstract: Over the past decade, standing-wave photoemission (SW-XPS) has evolved into a powerful and versatile non-destructive technique for probing element-specific electronic, magnetic, and structural properties of buried layers and interfaces with sub-nanometer depth resolution. In this article, I will discuss several promising future directions in this emergent field stemming from experimental and theoretical studies wherein SW-XPS is combined with other X-ray techniques, such as magnetic circular dichroism (MCD), hard X-ray photoemission spectroscopy (HAXPES), angle-resolved photoemission (ARPES), and photoemission microscopy (PEEM), adding extra dimensions to the measurement and thus widening the scope of scientific and technological questions accessible via the use of standing waves. I will further discuss examples of recently developed methods for X-ray standing-wave data analysis, which yield layer-resolved matrix-element-weighted densities of states at interfaces as well as Ångstrom-level changes in periodicity of synthetic superlattices. Finally, I will explore the possibility of localizing the standing waves near the surface and within a buried layer by the use of aperiodic superlattices, total reflection, and X-ray waveguide effects.
Standing waves in fiber-optic interferometers
De Haan, V.; Santbergen, R.; Tijssen, M.; Zeman, M.
2011-01-01
A study is presented giving the response of three types of fiber-optic interferometers by which a standing wave through an object is investigated. The three types are a Sagnac, Mach–Zehnder and Michelson–Morley interferometer. The response of the Mach–Zehnder interferometer is similar to the Sagnac
Standing waves for discrete nonlinear Schrodinger equations
Ming Jia
2016-01-01
The discrete nonlinear Schrodinger equation is a nonlinear lattice system that appears in many areas of physics such as nonlinear optics, biomolecular chains and Bose-Einstein condensates. By using critical point theory, we establish some new sufficient conditions on the existence results of standing waves for the discrete nonlinear Schrodinger equations. We give an appropriate example to illustrate the conclusion obtained.
Guitar Strings as Standing Waves: A Demonstration
Davis, Michael
2007-01-01
The study demonstrates the induction of one-dimensional standing waves, called "natural-harmonics" on a guitar to provide a unique tone. The analysis shows that a normally complex vibration is composed of a number of simple and discrete vibrations.
Standing magnetic wave on Ising ferromagnet: Nonequilibrium phase transition
Halder, Ajay; Acharyya, Muktish
2016-12-01
The dynamical response of an Ising ferromagnet to a plane polarised standing magnetic field wave is modelled and studied here by Monte Carlo simulation in two dimensions. The amplitude of standing magnetic wave is modulated along the direction x. We have detected two main dynamical phases namely, pinned and oscillating spin clusters. Depending on the value of field amplitude the system is found to undergo a phase transition from oscillating spin cluster to pinned as the system is cooled down. The time averaged magnetisation over a full cycle of magnetic field oscillations is defined as the dynamic order parameter. The transition is detected by studying the temperature dependences of the variance of the dynamic order parameter, the derivative of the dynamic order parameter and the dynamic specific heat. The dependence of the transition temperature on the magnetic field amplitude and on the wavelength of the magnetic field wave is studied at a single frequency. A comprehensive phase boundary is drawn in the plane described by the temperature and field amplitude for two different wavelengths of the magnetic wave. The variation of instantaneous line magnetisation during a period of magnetic field oscillation for standing wave mode is compared to those for the propagating wave mode. Also the probability that a spin at any site, flips, is calculated. The above mentioned variations and the probability of spin flip clearly distinguish between the dynamical phases formed by propagating magnetic wave and by standing magnetic wave in an Ising ferromagnet.
Saturation process of nonlinear standing waves
Institute of Scientific and Technical Information of China (English)
马大猷; 刘克
1996-01-01
The sound pressure of the nonlinear standing waves is distorted as expected, but also tends to saturate as being found in standing-wave tube experiments with increasing sinusoidal excitation. Saturation conditions were not actually reached, owing to limited excitation power, but the evidence of tendency to saturation is without question. It is the purpose of this investigation to find the law of saturation from the existing experimental data. The results of curve fitting indicate that negative feedback limits the growth of sound pressure with increasing excitation, the growth of the fundamental and the second harmonic by the negative feedback of their sound pressures, and the growth of the third and higher harmonics, however, by their energies (sound pressures squared). The growth functions of all the harmonics are derived, which are confirmed by the experiments. The saturation pressures and their properties are found.
Standing waves for discrete nonlinear Schrodinger equations
Directory of Open Access Journals (Sweden)
Ming Jia
2016-07-01
Full Text Available The discrete nonlinear Schrodinger equation is a nonlinear lattice system that appears in many areas of physics such as nonlinear optics, biomolecular chains and Bose-Einstein condensates. By using critical point theory, we establish some new sufficient conditions on the existence results of standing waves for the discrete nonlinear Schrodinger equations. We give an appropriate example to illustrate the conclusion obtained.
Standing Sound Waves in Air with DataStudio
Kraftmakher, Yaakov
2010-01-01
Two experiments related to standing sound waves in air are adapted for using the ScienceWorkshop data-acquisition system with the DataStudio software from PASCO scientific. First, the standing waves are created by reflection from a plane reflector. The distribution of the sound pressure along the standing wave is measured. Second, the resonance…
A Fresh Look at Longitudinal Standing Waves on a Spring
Rutherford, Casey
2013-01-01
Transverse standing waves produced on a string, as shown in Fig. 1, are a common demonstration of standing wave patterns that have nodes at both ends. Longitudinal standing waves can be produced on a helical spring that is mounted vertically and attached to a speaker, as shown in Fig. 2, and used to produce both node-node (NN) and node-antinode…
Standing Sound Waves in Air with DataStudio
Kraftmakher, Yaakov
2010-01-01
Two experiments related to standing sound waves in air are adapted for using the ScienceWorkshop data-acquisition system with the DataStudio software from PASCO scientific. First, the standing waves are created by reflection from a plane reflector. The distribution of the sound pressure along the standing wave is measured. Second, the resonance…
A Fresh Look at Longitudinal Standing Waves on a Spring
Rutherford, Casey
2013-01-01
Transverse standing waves produced on a string, as shown in Fig. 1, are a common demonstration of standing wave patterns that have nodes at both ends. Longitudinal standing waves can be produced on a helical spring that is mounted vertically and attached to a speaker, as shown in Fig. 2, and used to produce both node-node (NN) and node-antinode…
Theoretical Study on Standing Wave Thermoacoustic Engine
Kalra, S.; Desai, K. P.; Naik, H. B.; Atrey, M. D.
Applications of thermoacoustic engines are not limited to driving pulse tube cryocoolers. The performance of a thermoacoustic engine is governed by various design parameters like type of resonator, stack geometry, frequency, type of working gas etc. and various operating parameters like heat input, charging pressure etc. It is very important to arrive at an optimum configuration of the engine for which a theoretical model is required. In the present work, a theoretical analysis, based on linear acoustic theory of a standing wave type half wavelength thermoacoustic engine is carried out using DeltaEC software. The system dimensions like length of resonator, stack, hot and cold heat exchangers are fixed with a helium-argon mixture as the working gas and a parallel plate type stack. Later on, two plate spacings, corresponding to helium-argon mixture and nitrogen gas, are used for carrying out analysis with helium, argon, nitrogen, carbon dioxide and helium-argon mixture as working gases of the system. The effect of charging pressure on the performance of the system is studied in terms of resonating frequency, onset temperature, pressure amplitude, acoustic power and efficiency. The conclusions derived from the analysis are reported in the paper.
Standing Slow MHD Waves in Radiatively Cooling Coronal Loops
Indian Academy of Sciences (India)
K. S. Al-Ghafri
2015-06-01
The standing slow magneto-acoustic oscillations in cooling coronal loops are investigated. There are two damping mechanisms which are considered to generate the standing acoustic modes in coronal magnetic loops, namely, thermal conduction and radiation. The background temperature is assumed to change temporally due to optically thin radiation. In particular, the background plasma is assumed to be radiatively cooling. The effects of cooling on longitudinal slow MHD modes is analytically evaluated by choosing a simple form of radiative function, that ensures the temperature evolution of the background plasma due to radiation, coincides with the observed cooling profile of coronal loops. The assumption of low-beta plasma leads to neglecting the magnetic field perturbation and, eventually, reduces the MHD equations to a 1D system modelling longitudinal MHD oscillations in a cooling coronal loop. The cooling is assumed to occur on a characteristic time scale, much larger than the oscillation period that subsequently enables using the WKB theory to study the properties of standing wave. The governing equation describing the time-dependent amplitude of waves is obtained and solved analytically. The analytically derived solutions are numerically evaluated to give further insight into the evolution of the standing acoustic waves. We find that the plasma cooling gives rise to a decrease in the amplitude of oscillations. In spite of the reduction in damping rate caused by rising the cooling, the damping scenario of slow standing MHD waves strongly increases in hot coronal loops.
Radiation from cosmic string standing waves
Olum; Blanco-Pillado
2000-05-01
We have simulated large-amplitude standing waves on an Abelian-Higgs cosmic string in classical lattice field theory. The radiation rate falls exponentially with wavelength, as one would expect from the field profile around a gauge string. Our results agree with those of Moore and Shellard, but not with those of Vincent, Antunes, and Hindmarsh. The radiation rate falls too rapidly to sustain a scaling solution via direct radiation of particles from string length. There is thus reason to doubt claims of strong constraints on cosmic string theories from cosmic ray observations.
Onset behavior of standing wave thermoacoustic pressure wave generator
Mehta, Shreya; Desai, Keyur; Naik, Hemant Bhimbhai; Atrey, Milind
2012-06-01
A standing wave type thermoacoustic pressure wave generator for 300 Hz operating frequency is designed and developed for helium as a working fluid. The device is designed as a half wave length resonator. A parallel plate type SS 304 stack is designed and fabricated. An electric heater is used for heat supply to the hot end heat exchanger while a water cooled heat exchanger is used to maintain the other end of the stack near ambient temperature. An acoustic amplifier is used to amplify the pressure ratio generated. Experiments are conducted to study the onset behavior of pressure wave generator in terms of temperature range. Observations are recorded using piezoelectric pressure transducer. The results are obtained with different charging pressure and heat inputs. A pressure ratio of around 1.1 to 1.15 has been obtained using Nitrogen as a working fluid. The onset of thermoacoustic oscillations are studied for different filling pressure and for a range of hot end temperature.
The periodic standing-wave approximation: post-Minkowski computation
Beetle, Christopher; Hernández, Napoleón; Price, Richard H
2007-01-01
The periodic standing wave method studies circular orbits of compact objects coupled to helically symmetric standing wave gravitational fields. From this solution an approximation is extracted for the strong field, slowly inspiralling motion of black holes and binary stars. Previous work on this model has dealt with nonlinear scalar models, and with linearized general relativity. Here we present the results of the method for the post-Minkowski (PM) approximation to general relativity, the first step beyond linearized gravity. We compute the PM approximation in two ways: first, via the standard approach of computing linearized gravitational fields and constructing from them quadratic driving sources for second-order fields, and second, by solving the second-order equations as an ``exact'' nonlinear system. The results of these computations have two distinct applications: (i) The computational infrastructure for the ``exact'' PM solution will be directly applicable to full general relativity. (ii) The results w...
The treatment of radioactive wastewater by ultrasonic standing wave method
Energy Technology Data Exchange (ETDEWEB)
Su-xia, Hou, E-mail: hsxljj@sina.com; Ji-jun, Luo; Bin, He; Ru-song, Li; Tao, Shen
2014-06-01
Highlights: • USWM can be considered as the green cleaning separation techniques. • A physical model of suspended radioactive particle is established. • A computer program is developed to achieve numerical calculation and analysis. • The experimental device for low-level radioactive wastes treatment is designed. • Lots of experimental data are used to analysis the influence of the parameters. - Abstract: The radiation hazards of radionuclide arising from the storage of nuclear weapons cannot be ignored to the operators. Ultrasonic standing wave methods can be considered as the green cleaning separation techniques with high efficiency. The application of ultrasonic standing wave methods for liquid radioactive wastes treatment requires solving many problems connected with the proper selection of the frequency and power of ultrasonic transducers, and the processing time, etc. Based on the model of one single suspended radioactive particle subjected to in the field of ultrasonic standing wave, the principle of the treatment of low-level radioactive wastewater by ultrasound was analyzed. The theoretical and simulation results show that under the action of ultrasonic standing wave, the particle will move toward the wave node plane, and the time of particle reaching the plane become shorter when the radius of particle and the frequency and power of ultrasound was enlarged. The experimental results show that the radioactive concentration of wastewater could be reduced from 400 Bq L{sup −1} to 9.3 Bq L{sup −1} and the decontamination efficiency was 97.68%. The decontamination efficiency could not be obviously improved by further increasing the treating time.
Traveling and Standing Waves in Coupled Pendula and Newton's Cradle
García-Azpeitia, Carlos
2016-12-01
The existence of traveling and standing waves is investigated for chains of coupled pendula with periodic boundary conditions. The results are proven by applying topological methods to subspaces of symmetric solutions. The main advantage of this approach comes from the fact that only properties of the linearized forces are required. This allows to cover a wide range of models such as Newton's cradle, the Fermi-Pasta-Ulam lattice, and the Toda lattice.
On functional equations leading to exact solutions for standing internal waves
Beckebanze, F.; Keady, G.
The Dirichlet problem for the wave equation is a classical example of a problem which is ill-posed. Nevertheless, it has been used to model internal waves oscillating harmonically in time, in various situations, standing internal waves amongst them. We consider internal waves in two-dimensional
Noise-induced standing waves in oscillatory systems with time-delayed feedback
Stich, Michael
2016-01-01
In oscillatory reaction-diffusion systems, time-delay feedback can lead to the instability of uniform oscillations with respect to formation of standing waves. Here, we investigate how the presence of additive, Gaussian white noise can induce the appearance of standing waves. Combining analytical solutions of the model with spatio-temporal simulations, we find that noise can promote standing waves in regimes where the deterministic uniform oscillatory modes are stabilized. As the deterministic phase boundary is approached, the spatio-temporal correlations become stronger, such that even small noise can induce standing waves in this parameter regime. With larger noise strengths, standing waves could be induced at finite distances from the (deterministic) phase boundary. The overall dynamics is defined through the interplay of noisy forcing with the inherent reaction-diffusion dynamics.
Adsorption-Mediated Mass Streaming in a Standing Acoustic Wave
Weltsch, Oren; Offner, Avshalom; Liberzon, Dan; Ramon, Guy Z.
2017-06-01
Oscillating flows can generate nonzero, time-averaged fluxes despite the velocity averaging zero over an oscillation cycle. Here, we report such a flux, a nonlinear resultant of the interaction between oscillating velocity and concentration fields. Specifically, we study a gas mixture sustaining a standing acoustic wave, where an adsorbent coats the solid boundary in contact with the gas mixture. It is found that the sound wave produces a significant, time-averaged preferential flux of a "reactive" component that undergoes a reversible sorption process. This effect is measured experimentally for an air-water vapor mixture. An approximate model is shown to be in good agreement with the experimental observations, and further reveals the interplay between the sound-wave characteristics and the properties of the gas-solid sorbate-sorbent pair. The preferential flux generated by this mechanism may have potential in separation processes.
CFD simulation of a 300 Hz thermoacoustic standing wave engine
Yu, Guoyao; Dai, W.; Luo, Ercang
2010-09-01
High frequency operation of standing wave thermoacoustic heat engines is attractive for space applications due to compact size and high reliability. To expedite practical use, further improvement and optimization should be based on deep understanding and quantitative analysis. This article focuses on using computational fluid dynamics (CFD) to investigate nonlinear phenomena and processes of a 300 Hz standing wave thermoacoustic engine (SWTE). The calculated model was tested in detail, which indicated that the co-axially stacked tube model was suitable for the simulation of SWTEs. Two methods of imposing temperature gradient across the stack were studied, and the processes of mean pressure increasing, pressure wave amplification and saturation were obtained under the thermal boundary condition of applying heating power. The acoustic fields were given, and the flow vortices and their evolution in both ends of the stack and resonator were observed. Moreover, a comparison between the simulation and experiments was made, which demonstrated the validity and power of the CFD simulation for characterizing complicated nonlinear phenomenon involved in the self-excited SWTEs.
Standing Wave Solutions in Nonhomogeneous Delayed Synaptically Coupled Neuronal Networks
Institute of Scientific and Technical Information of China (English)
ZHANG Linghai; STONER Melissa Anne
2012-01-01
The authors establish the existence and stability of standing wave solutions of a nonlinear singularly perturbed system of integral differential equations and a nonlinear scalar integral differential equation.It will be shown that there exist six standing wave solutions ((u(x,t),w(x,t)) =(U(x),W(x)) to the nonlinear singularly perturbed system of integral differential equations.Similarly,there exist six standing wave solutions u(x,t) =U(x) to the nonlinear scalar integral differential equation.The main idea to establish the stability is to construct Evans functions corresponding to several associated eigenvalue problems.
A standing wave braneworld and associated Sturm-Liouville problem
Gogberashvili, Merab; Malagon-Morejon, Dagoberto
2010-01-01
We present a consistent derivation of the recently proposed 5D standing wave braneworld generated by gravity coupled to a phantom-like scalar field by introducing an energy-momentum tensor on the brane with different tensions along different space-time directions and explicitly solve the corresponding junction conditions. We also analyze the Sturm-Liouville problem associated to the correct localization condition of the transverse to the brane metric and scalar fields. It is shown that this condition restricts the physically meaningful space of solutions for the localization of the fluctuations of the model.
Institute of Scientific and Technical Information of China (English)
MIN Qi; YIN Yao; LI Xiaodong; LIU Ke
2011-01-01
A standing-wave tube with tapered section （STTS） was evolved from a standingwave tube with abrupt section （STAS） whose abrupt section was replaced with tapered section. The research was intended to compare the acoustic properties and the extremely nonlinear pure standing waves of STTS with those of STAS. The acoustic properties of the STTS were studied with transfer matrix. It was proved, like the STAS, that the STTS was dissonant standingwave tube. With its dissonant property, the 181 dB extremely nonlinear pure standing wave was obtained in the STTS excited at its first resonance frequency. Then the comparative experimental studies on the saturation properties of the extremely nonlinear standing waves were carried out in the STTS and the STAS with the same length. It was found that the STTS could suppress the harmonics and meanwhile reduce energy loss of the standing wave more effectively. Compared with the STAS, under the same voltage of loudspeaker, the STTS obtained a higher extremely nonlinear pure standing wave. Moreover, it was found for the STTS that the third harmonic of the third resonance frequency was close to the seventh resonance frequency of sound source impedance, to which the valley value of the sound pressure level transfer function corresponded. Because of this, the third harmonic increased rapidly with the increase of fundamental wave and tended to saturate.
Excitation of Standing Waves by an Electric Toothbrush
Cros, Ana; Ferrer-Roca, Chantal
2006-01-01
There are a number of ways of exciting standing waves in ropes and springs using non-commercial vibrators such as loudspeakers, jigsaws, motors, or a simple tuning fork, including the rhythmical shaking of a handheld Slinky. We have come up with a very simple and cheap way of exciting stationary waves in a string, which anyone, particularly…
A standing wave-type noncontact linear ultrasonic motor.
Hu, J; Li, G; Chan, H L; Choy, C L
2001-05-01
In this study, a novel standing wave-type noncontact linear ultrasonic motor is proposed and analyzed. This linear ultrasonic motor uses a properly controlled ultrasonic standing wave to levitate and drive a slider. A prototype of the motor was constructed by using a wedge-shaped aluminum stator, which was placed horizontally and driven by a multilayer PZT vibrator. The levitation and motion of the slider were observed. Assuming that the driving force was generated by the turbulent acoustic streaming in the boundary air layer next to the bottom surface of the slider, a theoretical model was developed. The calculated characteristics of this motor were found to agree quite well with the experimental results. Based on the experimental and theoretical results, guidelines for increasing the displacement and speed of the slider were obtained. It was found that increasing the stator vibration displacement, or decreasing the gradient of the stator vibration velocity and the weight per unit area of the slider, led to an increase of the slider displacement. It was also found that increasing the amplitude and gradient of the stator vibration velocity, or decreasing the weight per unit area of the slider and the driving frequency, gave rise to an increase of the slider speed. There exists an optimum roughness of the bottom surface of the slider at which the slider speed has a maximum.
Standing wave acoustic levitation on an annular plate
Kandemir, Mehmet Hakan; Çalışkan, Mehmet
2016-11-01
In standing wave acoustic levitation technique, a standing wave is formed between a source and a reflector. Particles can be attracted towards pressure nodes in standing waves owing to a spring action through which particles can be suspended in air. This operation can be performed on continuous structures as well as in several numbers of axes. In this study an annular acoustic levitation arrangement is introduced. Design features of the arrangement are discussed in detail. Bending modes of the annular plate, known as the most efficient sound generation mechanism in such structures, are focused on. Several types of bending modes of the plate are simulated and evaluated by computer simulations. Waveguides are designed to amplify waves coming from sources of excitation, that are, transducers. With the right positioning of the reflector plate, standing waves are formed in the space between the annular vibrating plate and the reflector plate. Radiation forces are also predicted. It is demonstrated that small particles can be suspended in air at pressure nodes of the standing wave corresponding to a particular bending mode.
The nonlinear standing wave inside the space of liquid
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Based on the basic equations of hydrodynamics, the nonlinear acoustic wave equation is obtained. By taking into account the boundary condition and properties of nonlinear standing wave, the equation is solved through perturbation method, and the stable expressions of fundamental wave and second harmonic are presented. The sound pressures in an ultrasonic cleaner are measured by hydrophones, and the relationship between the received voltages of hydrophones and the output voltages of the ultrasonic generator is researched. The study shows the existence of the nonlinear effect of liquid and analyzes the frequency spectrum of the received signals by hydrophones, by which the fundamental wave, second and high order harmonics are found coexisting in the bounded space filled with liquids. The theory and experimental results testify the existence of the nonlinear standing wave in liquid. Owing to the restricted applicability of perturbation method, the theoretical results of the fundamental wave and second harmonic are good only for the weak nonlinear phenomenon.
A Standing-Wave Experiment with a Guitar
Inman, Fred W.
2006-10-01
When teaching standing waves, one often uses as examples musical instruments with strings, e.g., pianos, violins, and guitars. In today's popular music culture, young people may be more familiar with guitars than any other string instrument. I was helping my 15-year-old granddaughter make some repairs and adjustments to her electric guitar, and the subject of the spacing between the frets on the fingerboard was raised. I told her that the physics of standing waves and the equal tempered musical scale dictate the location of the frets. The purpose of this paper is to suggest that students might be introduced to the physics of standing waves using a guitar and to the formula for the fret locations. By measuring the positions of the frets, this formula can be tested.
Standing Waves and Inquiry Using Water Droplets
Sinclair, Dina; Vondracek, Mark
2015-01-01
Most high school and introductory college physics classes study simple harmonic motion and various wave phenomena. With the majority of states adopting the Next Generation Science Standards and pushing students to explore the scientific process for themselves, there is a growing demand for hands-on inquiry activities that involve and develop more…
Standing Waves and Inquiry Using Water Droplets
Sinclair, Dina; Vondracek, Mark
2015-01-01
Most high school and introductory college physics classes study simple harmonic motion and various wave phenomena. With the majority of states adopting the Next Generation Science Standards and pushing students to explore the scientific process for themselves, there is a growing demand for hands-on inquiry activities that involve and develop more…
Cooldown Measurements in a Standing Wave Thermoacoustic Refrigerator
Dhuley, R C
2016-01-01
Thermoacoustic Refrigerators (TARs) use acoustic power to generate cold temperatures. Apart from the operating frequency and the mean temperature of the working medium, the charging pressure and the dynamic pressure in the TAR govern its attainable cold temperature. The effect of charging pressure on the dynamic pressure in a loudspeaker driven gas filled standing wave column has been well understood. The present work aims to investigate the effect of charging pressure on the cold end temperature of a standing wave TAR. The cold end temperature lift and the cooldown for several changing pressures are reported. The effect of vacuum around the cold end on the TAR performance is also presented.
Magnetization dynamics and spin pumping induced by standing elastic waves
Azovtsev, A. V.; Pertsev, N. A.
2016-11-01
The magnetization dynamics induced by standing elastic waves excited in a thin ferromagnetic film is described with the aid of micromagnetic simulations taking into account the magnetoelastic coupling between spins and lattice strains. Our calculations are based on the numerical solution of the Landau-Lifshitz-Gilbert equation comprising the damping term and the effective magnetic field with all relevant contributions. The simulations have been performed for 2-nm-thick F e81G a19 film dynamically strained by longitudinal and transverse standing waves with various frequencies, which span a wide range around the resonance frequency νres of coherent magnetization precession in unstrained F e81G a19 film. It is found that standing elastic waves give rise to complex local magnetization dynamics and spatially inhomogeneous dynamic patterns in the form of standing spin waves with the same wavelength. Remarkably, the amplitude of magnetization precession does not go to zero at nodes of these spin waves, which cannot be precisely described by simple analytical formulae. In the steady-state regime, magnetization oscillates with the frequency of the elastic wave, except in the case of longitudinal waves with frequencies well below νres, where the magnetization precesses with variable frequency strongly exceeding the wave frequency. The results obtained for the magnetization dynamics driven by elastic waves are used to calculate the spin current pumped from the dynamically strained ferromagnet into adjacent paramagnetic metal. Numerical calculations demonstrate that the transverse charge current in the paramagnetic layer, which is created by the spin current via inverse spin Hall effect, is high enough to be measured experimentally.
Institute of Scientific and Technical Information of China (English)
Jing-Xin ZHANG; Hua LIU
2009-01-01
This paper extends the conventional concept of radiation stress (Longuet-Higgins and Stewart, 1964)in progressive water waves to standing waves, so that its vertical profile could be defined and calculated in a new technical way. The hydrodynamic numerical model being coupled with the vertically varying radiation stress in standing waves is used to simulate the currents being induced by standing waves in the vertical section. Numerical modeling of suspended sediment transport is then carried out to simulate the evolution of the bed composed of fine sediments by the currents. The scour and deposition patterns simulated are in qualitative agreement with prior laboratory and field observations.
What are the frequencies of standing magnetopause surface waves?
Archer, Martin
2014-01-01
We estimate, for the first time, the distribution of standing magnetopause surface wave (also called Kruskal-Schwartzschild mode) frequencies using realistic models of the magnetosphere and magnetosheath utilising an entire solar cycle's worth of solar wind data. Under non-storm times or northward interplanetary magnetic field (IMF), the most likely fundamental frequency is calculated to be 0.64$\\pm$0.06 mHz, consistent with that previously inferred from observed oscillation periods of the boundary. However, the distributions exhibit significant spread (of order $\\pm$0.3 mHz), much larger than suggested by proponents of discrete, stable "magic" frequencies of magnetospheric oscillation. The frequency is found to be most dependent on the solar wind speed, southward component of the IMF and the Dst index, with the latter two being due to the erosion of the magnetosphere by reconnection and the former an effect of the expression for the surface wave phase speed. Finally, the occurrence of Kruskal-Schwartzschild ...
Quantum Entropic Dynamics of a Trapped Ion in a Standing Wave
Institute of Scientific and Technical Information of China (English)
FANG Mao-Fa; ZHOU Peng; S. Swain
2000-01-01
By performing a unitary transformation, we transform the Hamiltonian of the trapped ion in any position of standing wave to that of the normal Jaynes-Cummings model in ionic bare basis and we obtain a general evolution operator of the trapped ion system. We study the quantum entropic dynamics of the phonons and trapped ion.Our results show that, when the trapped ion is located at the node of standing wave, the quantum entropic dynamics of phonons and trapped ion are the same as the one of the field in the Jaynes-Cummings model.When the trapped ion deviatesfrom the node of standing wave, the entropies of the phonons and ion keep their maximum value except at the initial stage, and the phonons and trapped ion become extremely entangled.
The structure of standing Alfvén waves in a dipole magnetosphere with moving plasma
Directory of Open Access Journals (Sweden)
D. A. Kozlov
2006-03-01
Full Text Available The structure and spectrum of standing Alfvén waves were theoretically investigated in a dipole magnetosphere with moving plasma. Plasma motion was simulated with its azimuthal rotation. The model's scope allowed for describing a transition from the inner plasmasphere at rest to the outer magnetosphere with convecting plasma and, through the magnetopause, to the moving plasma of the solar wind. Solutions were found to equations describing longitudinal and transverse (those formed, respectively, along field lines and across magnetic shells structures of standing Alfvén waves with high azimuthal wave numbers m>>1. Spectra were constructed for a number of first harmonics of poloidal and toroidal standing Alfvén waves inside the magnetosphere. For charged particles with velocities greatly exceeding the velocity of the background plasma, an effective parallel wave component of the electric field appears in the region occupied by such waves. This results in structured high-energy-particle flows and in the appearance of multiband aurorae. The transverse structure of the standing Alfvén waves' basic harmonic was shown to be analogous to the structure of a discrete auroral arc.
Adiabatic asymmetric scattering of atoms in the field of a standing wave
Hakobyan, M V; Ishkhanyan, A M
2015-01-01
A model of the asymmetric coherent scattering process (caused by initial atomic wave-packet splitting in the momentum space) taking place at the large detuning and adiabatic course of interaction for an effective two-state system interacting with a standing wave of laser radiation is discussed. We show that the same form of initial wave-packet splitting may lead to different, in general, diffraction patterns for opposite, adiabatic and resonant, regimes of the standing-wave scattering. We show that the scattering of the Gaussian wave packet in the adiabatic case presents refraction (a limiting form of the asymmetric scattering) in contrast to the bi-refringence (the limiting case of the high-order narrowed scattering) occurring in the resonant scattering.
Precision measurements in ion traps using slowly moving standing waves
Walther, A; Singer, K; Schmidt-Kaler, F
2011-01-01
The present paper describes the experimental implementation of a measuring technique employing a slowly moving, near resonant, optical standing wave in the context of trapped ions. It is used to measure several figures of merit that are important for quantum computation in ion traps and which are otherwise not easily obtainable. Our technique is shown to offer high precision, and also in many cases using a much simpler setup than what is normally used. We demonstrate here measurements of i) the distance between two crystalline ions, ii) the Lamb-Dicke parameter, iii) temperature of the ion crystal, and iv) the interferometric stability of a Raman setup. The exact distance between two ions, in units of standing wave periods, is very important for motional entangling gates, and our method offers a practical way of calibrating this distance in the typical lab situation.
Position-dependent dynamics of a trapped ion in a standing wave laser
Institute of Scientific and Technical Information of China (English)
方卯发
2002-01-01
We have investigated the position-dependent dynamics of a trapped ion in a standing wave laser by transforming it to the Jaynes-Cummings-type system under the Lamb-Dicke limit. A variety of novel phenomena are exhibited,e.g. periodic collapse and revival features and long-time scaled revivals of the ionic inversion, depending on its position in the standing wave. Our result provides a way of producing a system equivalent to the two-photon Jaynes-Cummings model in the trapped ion system, with its exact periodicities.
Attractors and chaos of electron dynamics in electromagnetic standing wave
Esirkepov, Timur Zh; Koga, James K; Kando, Masaki; Kondo, Kiminori; Rosanov, Nikolay N; Korn, Georg; Bulanov, Sergei V
2014-01-01
The radiation reaction radically influences the electron motion in an electromagnetic standing wave formed by two super-intense counter-propagating laser pulses. Depending on the laser intensity and wavelength, either classical or quantum mode of radiation reaction prevail, or both are strong. When radiation reaction dominates, electron motion evolves to limit cycles and strange attractors. This creates a new framework for high energy physics experiments on an interaction of energetic charged particle beams and colliding super-intense laser pulses.
Interaction of aerosol particles with a standing wave optical field
Curry, John J.
2016-09-01
Trajectories of spherical dielectric particles carried across an optical standing wave by a flowing medium are investigated. Trajectories are determined by a three-dimensional Monte Carlo calculation that includes drag forces, Brownian motion, and optical gradient forces. We analyze the case of polystyrene particles with radii of order 100 nm carried across a Gaussian-mode standing wave by slowly flowing air. Particles are injected into the flowing air from a small source area such as the end of a capillary tube. Different sizes are dispersed continuously in space on the opposite side of the standing wave, demonstrating a practical way to sort particles. Certain discrete values of particle size show no interaction with the optical field, independent of intensity. These particles can be sorted with exceptionally high resolution. For example, particles with radii of 275 nm can be sorted with 1 nm resolution. This sorting scheme has the advantages of accommodating a high throughput, producing a continuous stream of continuously dispersed particles, and exhibiting excellent size resolution. The Monte Carlo results are in agreement with those obtained by a much simpler, and faster, fluid calculation based on effective velocities and effective diffusion coefficients, both obtained by averaging trajectories over multiple fringes of the optical field.
Stress wave propagation on standing trees. Part 2, Formation of 3D stress wave contour maps.
Juan Su; Houjiang Zhang; Xiping Wang
2009-01-01
Nondestructive evaluation (NDE) of wood quality in standing trees is an important procedure in the forest operational value chain worldwide. The goal of this paper is to investigate how a stress wave travel in a tree stem as it is introduced into the tree through a mechanical impact. Experimental stress wave data was obtained on freshly cut red pine logs in the...
Feonychev, A. I.
Numerical investigation of thermocapillary flows and crystal growth by the floating zone method had been carried out in the case what free fluid surface oscillates in the form of standing wave by vibration. Two sorts of standing waves were considered. First, it is inertia-capillary standing waves due to vibration motion of fluid column as unit. These waves had been discovered under numerical investigation of problem /1/. Analytical model and the characteristic properties of these waves are described in /2/. Secondly, usual capillary waves generated by vibration of growing crystal were also considered. The effects of these surface waves on fluid flow and heat and mass transfer in process of crystal growth had been investigated over the wide ranges of dimensionless parameters for the Prandtl number is less than 1. The Marangoni number was varied from 140 to 2500, the range of cyclic frequency was between 200 and 76000. Transition from laminar thermocapillary convection to regime of flow with high oscillations (turbulent convection) happens very sharply when dimensionless amplitude (scale for linear dimensions is radius of fluid column) of standing wave reached 0.01112/n, where n is number of standing wave periods are along the length of fluid zone. If configuration of standing wave correlates with thermocapillary flow pattern two specific regimes of flow had been discovered. Flow with small oscillations is located in the range of standing wave amplitude between 0.0028 and 0.00418. In this area, radial macrosegregation of dopant is lowered by the factor of 3-6 depending on the Marangoni number. Next is an area with practically stable flow, in particular is identical to laminar flow without vibration. This area ends very sharply in the boundary of turbulent flow. All the mentioned boundaries are independent of the Marangoni number and frequency of oscillation of standing wave. For oscillatory thermocapillary convection (the Marangoni number is more than 2000
A cylindrical standing wave ultrasonic motor using bending vibration transducer.
Liu, Yingxiang; Chen, Weishan; Liu, Junkao; Shi, Shengjun
2011-07-01
A cylindrical standing wave ultrasonic motor using bending vibration transducer was proposed in this paper. The proposed stator contains a cylinder and a bending vibration transducer. The two combining sites between the cylinder and the transducer locate at the adjacent wave loops of bending vibration of the transducer and have a distance that equal to the half wave length of bending standing wave excited in the cylinder. Thus, the bending mode of the cylinder can be excited by the bending vibration of the transducer. Two circular cone type rotors are pressed in contact to the end rims of the teeth, and the preload between the rotors and stator is accomplished by a spring and nut system. The working principle of the proposed motor was analyzed. The motion trajectories of teeth were deduced. The stator was designed and analyzed with FEM. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 165rpm and maximum torque of 0.45Nm at an exciting voltage of 200V(rms).
Scaling-up ultrasound standing wave enhanced sedimentation filters.
Prest, Jeff E; Treves Brown, Bernard J; Fielden, Peter R; Wilkinson, Stephen J; Hawkes, Jeremy J
2015-02-01
Particle concentration and filtration is a key stage in a wide range of processing industries and also one that can be present challenges for high throughput, continuous operation. Here we demonstrate some features which increase the efficiency of ultrasound enhanced sedimentation and could enable the technology the potential to be scaled up. In this work, 20 mm piezoelectric plates were used to drive 100 mm high chambers formed from single structural elements. The coherent structural resonances were able to drive particles (yeast cells) in the water to nodes throughout the chamber. Ultrasound enhanced sedimentation was used to demonstrate the efficiency of the system (>99% particle clearance). Sub-wavelength pin protrusions were used for the contacts between the resonant chamber and other elements. The pins provided support and transferred power, replacing glue which is inefficient for power transfer. Filtration energies of ∼4 J/ml of suspension were measured. A calculation of thermal convection indicates that the circulation could disrupt cell alignment in ducts >35 mm high when a 1K temperature gradient is present; we predict higher efficiencies when this maximum height is observed. For the acoustic design, although modelling was minimal before construction, the very simple construction allowed us to form 3D models of the nodal patterns in the fluid and the duct structure. The models were compared with visual observations of particle movement, Chladni figures and scanning laser vibrometer mapping. This demonstrates that nodal planes in the fluid can be controlled by the position of clamping points and that the contacts could be positioned to increase the efficiency and reliability of particle manipulations in standing waves.
Attractors and chaos of electron dynamics in electromagnetic standing waves
Energy Technology Data Exchange (ETDEWEB)
Esirkepov, Timur Zh. [QuBS, Japan Atomic Energy Agency, Kizugawa, Kyoto 619-0215 (Japan); Bulanov, Stepan S. [University of California, Berkeley, CA 94720 (United States); Koga, James K.; Kando, Masaki; Kondo, Kiminori [QuBS, Japan Atomic Energy Agency, Kizugawa, Kyoto 619-0215 (Japan); Rosanov, Nikolay N. [Vavilov State Optical Institute, Saint-Petersburg 199034 (Russian Federation); Korn, Georg [ELI Beamline Facility, Institute of Physics, Czech Academy of Sciences, Prague 18221 (Czech Republic); Bulanov, Sergei V., E-mail: bulanov.sergei@jaea.go.jp [QuBS, Japan Atomic Energy Agency, Kizugawa, Kyoto 619-0215 (Japan)
2015-09-25
In an electromagnetic standing wave formed by two super-intense colliding laser pulses, radiation reaction totally modifies the electron motion. The quantum corrections to the electron motion and the radiation reaction force can be independently small or large, depending on the laser intensity and wavelength, thus dividing the parameter space into 4 domains. The electron motion evolves to limit cycles and strange attractors when radiation reaction dominates. This creates a new framework for high energy physics experiments on the interaction of energetic charged particle beams and colliding super-intense laser pulses.
Motion of a charge in a superstrong electromagnetic standing wave
Esirkepov, Timur Z.; Bulanov, Stepan S.; Koga, James K.; Kando, Masaki; Kondo, Kiminori; Rosanov, Nikolay N.; Korn, Georg; Bulanov, Sergei V.
2015-05-01
Radiation reaction radically influences the electron motion in an electromagnetic standing wave formed by two super-intense colliding laser pulses. Depending on the laser intensity and wavelength, the quantum corrections to the electron motion and the radiation reaction force can be independently small or large, thus dividing the parameter space into 4 regions. When radiation reaction dominates, the electron motion evolves to limit cycles and strange attractors. This creates a new framework for high energy physics experiments on the interaction of energetic charged particle beams and colliding super-intense laser pulses.
Attractors and chaos of electron dynamics in electromagnetic standing waves
Esirkepov, Timur Zh.; Bulanov, Stepan S.; Koga, James K.; Kando, Masaki; Kondo, Kiminori; Rosanov, Nikolay N.; Korn, Georg; Bulanov, Sergei V.
2015-09-01
In an electromagnetic standing wave formed by two super-intense colliding laser pulses, radiation reaction totally modifies the electron motion. The quantum corrections to the electron motion and the radiation reaction force can be independently small or large, depending on the laser intensity and wavelength, thus dividing the parameter space into 4 domains. The electron motion evolves to limit cycles and strange attractors when radiation reaction dominates. This creates a new framework for high energy physics experiments on the interaction of energetic charged particle beams and colliding super-intense laser pulses.
Particle dynamics and pair production in tightly focused standing wave
Jirka, M.; Klimo, O.; Vranić, M.; Weber, S.; Korn, G.
2017-05-01
With the advent of 10 PW laser facilities, new regimes of laser-matter interaction are opening since effects of quantum electrodynamics, such as electron-positron pair production and cascade development, start to be important. The dynamics of light charged particles, such as electrons and positrons, is affected by the radiation reaction force. This effect can strongly influence the interaction of intense laser pulses with matter since it lowers the energy of emitting particles and transforms their energy to the gamma radiation. Consequently, electron-positron pairs can be generated via Breit-Wheeler process. To study this new regime of interaction, numerical simulations are required. With their help it is possible to predict and study quantum effects which may occur in future experiments at modern laser facilities. In this work we present results of electron interaction with an intense standing wave formed by two colliding laser pulses. Due to the necessity to achieve ultra intense laser field, the laser beam has to be focused to a μm-diameter spot. Since the paraxial approximation is not valid for tight focusing, the appropriate model describing the tightly focused laser beam has to be employed. In tightly focused laser beam the longitudinal component of the electromagnetic field becomes significant and together with the ponderomotive force they affect the dynamics of interacting electrons and also newly generated Breit-Wheeler electron-positron pairs. Using the Particle-In-Cell code we study electron dynamics, gamma radiation and pair production in such a configuration for linear polarization and different types of targets.
Exchange anisotropy pinning of a standing spin-wave mode
Magaraggia, R.; Kennewell, K.; Kostylev, M.; Stamps, R. L.; Ali, M.; Greig, D.; Hickey, B. J.; Marrows, C. H.
2011-02-01
Standing spin waves in a thin film are used as sensitive probes of interface pinning induced by an antiferromagnet through exchange anisotropy. Using coplanar waveguide ferromagnetic resonance, pinning of the lowest energy spin-wave thickness mode in Ni80Fe20/Ir25Mn75 exchange-biased bilayers was studied for a range of Ir25Mn75 thicknesses. We show that pinning of the standing mode can be used to amplify, relative to the fundamental resonance, frequency shifts associated with exchange bias. The shifts provide a unique “fingerprint” of the exchange bias and can be interpreted in terms of an effective ferromagnetic film thickness and ferromagnet-antiferromagnet interface anisotropy. Thermal effects are studied for ultrathin antiferromagnetic Ir25Mn75 thicknesses, and the onset of bias is correlated with changes in the pinning fields. The pinning strength magnitude is found to grow with cooling of the sample, while the effective ferromagnetic film thickness simultaneously decreases. These results suggest that exchange bias involves some deformation of magnetic order in the interface region.
Thin film characterization by resonantly excited internal standing waves
Energy Technology Data Exchange (ETDEWEB)
Di Fonzio, S. [SINCROTRONE TRIESTE, Trieste (Italy)
1996-09-01
This contribution describes how a standing wave excited in a thin film can be used for the characterization of the properties of the film. By means of grazing incidence X-ray reflectometry one can deduce the total film thickness. On the other hand in making use of a strong resonance effect in the electric field intensity distribution inside a thin film on a bulk substrate one can learn more about the internal structure of the film. The profile of the internal standing wave is proven by diffraction experiments. The most appropriate non-destructive technique for the subsequent thin film characterization is angularly dependent X-ray fluorescence analysis. The existence of the resonance makes it a powerful tool for the detection of impurities and of ultra-thin maker layers, for which the position can be determined with very high precision (about 1% of the total film thickness). This latter aspect will be discussed here on samples which had a thin Ti marker layer at different positions in a carbon film. Due to the resonance enhancement it was still possible to perform these experiments with a standard laboratory x-ray tube and with standard laboratory tool for marker or impurity detection in thin films.
CSIR Research Space (South Africa)
Shatalov, MY
2011-01-01
Full Text Available Standing waves can exist as stable vibrating patterns in perfect structures such as spherical bodies, and inertial rotation of the body causes precession (Bryan’seffect). However, an imperfection such as light mass anisotropy destroys the standing...
Photo-Ionization of Hydrogen Atom in a Circularly Polarized Standing Electromagnetic Wave
Institute of Scientific and Technical Information of China (English)
LIU Xiang-Tao; ZHANG Qi-Ren; WANG Wan-Zhang
2004-01-01
Applying time-independent non-perturbative formalism to the photo-ionization of hydrogen atom immersed in a strong circularly polarized standing electromagnetic wave, we calculate the shift of energy levels and the distortion of wave functions for the hydrogen atom, the ionization cross section induced by the standing wave, and the angular distribution of photoelectrons and obtain some interesting results.
Herrmann, Michael
2010-01-01
We study heteroclinic standing waves (dark solitons) in discrete nonlinear Schr\\"{o}dinger equations with defocussing nonlinearity. Our main result is a quite elementary existence proof for waves with monotone and odd profile, and relies on minimizing an appropriately defined energy functional. We also study the continuum limit and the numerical approximation of standing waves.
ORBITAL INSTABILITY OF STANDING WAVES FOR THE COUPLED NONLINEAR KLEIN-GORDON EQUATIONS
Institute of Scientific and Technical Information of China (English)
Gan Zaihui; Guo Boling; Zhang Jian
2008-01-01
This paper deals with a type of standing waves for the coupled nonlin-ear Klein-Gordon equations in three space dimensions. First we construct a suitable constrained variational problem and obtain the existence of the standing waves with ground state by using variational argument. Then we prove the orbital instability of the standing waves by defining invariant sets and applying some priori estimates.
Slot-coupled CW standing wave accelerating cavity
Energy Technology Data Exchange (ETDEWEB)
Wang, Shaoheng; Rimmer, Robert; Wang, Haipeng
2017-05-16
A slot-coupled CW standing wave multi-cell accelerating cavity. To achieve high efficiency graded beta acceleration, each cell in the multi-cell cavity may include different cell lengths. Alternatively, to achieve high efficiency with acceleration for particles with beta equal to 1, each cell in the multi-cell cavity may include the same cell design. Coupling between the cells is achieved with a plurality of axially aligned kidney-shaped slots on the wall between cells. The slot-coupling method makes the design very compact. The shape of the cell, including the slots and the cone, are optimized to maximize the power efficiency and minimize the peak power density on the surface. The slots are non-resonant, thereby enabling shorter slots and less power loss.
Design and simulation of a standing wave oscillator based PLL
Institute of Scientific and Technical Information of China (English)
Wei ZHANG; You-de HU; Li-rong ZHENG
2016-01-01
A standing wave oscillator (SWO) is a perfect clock source which can be used to produce a high frequency clock signal with a low skew and high reliability. However, it is difficult to tune the SWO in a wide range of frequencies. We introduce a frequency tunable SWO which uses an inversion mode metal-oxide-semiconductor (IMOS) field-effect transistor as a varactor, and give the simulation results of the frequency tuning range and power dissipation. Based on the frequency tunable SWO, a new phase locked loop (PLL) architecture is presented. This PLL can be used not only as a clock source, but also as a clock distribution network to provide high quality clock signals. The PLL achieves an approximately 50% frequency tuning range when designed in Global Foundry 65 nm 1P9M complementary metal-oxide-semiconductor (CMOS) technology, and can be used directly in a high performance multi-core microprocessor.
Suspension of atoms and gravimetry using a pulsed standing wave
Hughes, K J; Sackett, C A
2009-01-01
Atoms from an otherwise unconfined 87Rb condensate are shown to be suspended against gravity using repeated reflections from a pulsed optical standing wave. Reflection efficiency was optimized using a triple-pulse sequence that, theoretically, provides accuracies better than 99.9%. Experimentally, up to 100 reflections are observed, leading to dynamical suspension for over 100 ms. The velocity sensitivity of the reflections can be used to determine the local gravitational acceleration. Further, a gravitationally sensitive atom interferometer was implemented using the suspended atoms, with packet coherence maintained for a similar time. These techniques could be useful for the precise measurement of gravity when it is impractical to allow atoms to fall freely over a large distance.
Standing Slow MHD Waves in Radiatively Cooling Coronal Loops
Al-Ghafri, Khalil Salim
2015-01-01
The standing slow magneto-acoustic oscillations in cooling coronal loops are investigated. There are two damping mechanisms which are considered to generate the standing acoustic modes in coronal magnetic loops namely thermal conduction and radiation. The background temperature is assumed to change temporally due to optically thin radiation. In particular, the background plasma is assumed to be radiatively cooling. The effects of cooling on longitudinal slow MHD modes is analytically evaluated by choosing a simple form of radiative function that ensures the temperature evolution of the background plasma due to radiation coincides with the observed cooling profile of coronal loops. The assumption of low-beta plasma leads to neglect the magnetic field perturbation and eventually reduces the MHD equations to a 1D system modelling longitudinal MHD oscillations in a cooling coronal loop. The cooling is assumed to occur on a characteristic time scale much larger than the oscillation period that subsequently enables...
RESONANT INTERACTION BETWEEN A PAUL-TRAPPED ION AND A STANDING WAVE LASER
Institute of Scientific and Technical Information of China (English)
FENG MANG; HAI WEN-HUA; ZHU XI-WEN; GAO KE-LIN; SHI LEI
2000-01-01
An ultracold two-level ion experiencing the standing wave of a resonant laser in a Paul trap is investigated in the Lamb-Dicke limit and weak excitation regime, with full consideration of the time-dependence of the trapping potential.The analytical forms of the wave functions of the system can be described with our approach, and the time evolution of the pseudo-energy of the system as well as the squeezing property of the quadrature components is studied in comparison with the treatment of harmonic oscillator model.
Localization of Matter Fields in the 5D Standing Wave Braneworld
Gogberashvili, Merab
2012-01-01
We investigate the localization problem of matter fields within the 5D standing wave braneworld. In this model the brane emits anisotropic waves into the bulk with different amplitudes along different spatial dimensions. We show that in the case of increasing warp factor there exist the pure gravitational localization of all kinds of quantum and classical particles on the brane. For classical particles the anisotropy of the background metric is hidden, brane fields exhibit standard Lorentz symmetry in spite of anisotropic nature of the primordial 5D metric.
Trial Operation of a Stand-alone Wave Power System Successful
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
@@ A group of scientists from the CAS Guangzhou Institute of Energy Conversion succeeded on January 9 in their first sea trial of a stand-alone wave power system, marking significant progress in generating stable electricity with wave energy.
The periodic standing-wave approximation: computations in full general relativity
Hernandez, Napoleon
2008-01-01
The periodic standing wave method studies circular orbits of compact objects coupled to helically symmetric standing wave gravitational fields. From this solution an approximation is extracted for the strong field, slowly inspiralling motion of binary black holes and binary neutron stars. Previous work on this project has developed a method using a few multipoles of specially adapted coordinates well suited both to the radiation and the source regions. This method had previously been applied to linear and nonlinear scalar field models, to linearized gravity, and to a post-Minkowski approximation. Here we present the culmination of this approach: the application of the method in full general relativity. The fundamental equations had previously been developed and the challenge presented by this step is primarily a computational one which was approached with an innovative technique. The numerical results of these computations are compared with the corresponding results from linearized and post-Minkowksi computat...
Luo, Xiaoming; Cao, Juhang; He, Limin; Wang, Hongping; Yan, Haipeng; Qin, Yahua
2017-01-01
The coalescence process of binary droplets in oil under ultrasonic standing waves was investigated with high-speed photography. Three motion models of binary droplets in coalescence process were illustrated: (1) slight translational oscillation; (2) sinusoidal translational oscillation; (3) migration along with acoustic streaming. To reveal the droplets coalescence mechanisms, the influence of main factors (such as acoustic intensity, droplet size, viscosity and interfacial tension, etc) on the motion and coalescence of binary droplets was studied under ultrasonic standing waves. Results indicate that the shortest coalescence time is achieved when binary droplets show sinusoidal translational oscillation. The corresponding acoustic intensity in this case is the optimum acoustic intensity. Under the optimum acoustic intensity, drop size decrease will bring about coalescence time decrease by enhancing the binary droplets oscillation. Moreover, there is an optimum interfacial tension to achieve the shortest coalescence time.
Coherent control of light-matter interactions in polarization standing waves
Fang, Xu; MacDonald, Kevin F.; Plum, Eric; Zheludev, Nikolay I.
2016-08-01
We experimentally demonstrate that standing waves formed by two coherent counter-propagating light waves can take a variety of forms, offering new approaches to the interrogation and control of polarization-sensitive light-matter interactions in ultrathin (subwavelength thickness) media. In contrast to familiar energy standing waves, polarization standing waves have constant electric and magnetic energy densities and a periodically varying polarization state along the wave axis. counterintuitively, anisotropic ultrathin (meta)materials can be made sensitive or insensitive to such polarization variations by adjusting their azimuthal angle.
Standing surface acoustic wave (SSAW)-based microfluidic cytometer.
Chen, Yuchao; Nawaz, Ahmad Ahsan; Zhao, Yanhui; Huang, Po-Hsun; McCoy, J Phillip; Levine, Stewart J; Wang, Lin; Huang, Tony Jun
2014-03-07
The development of microfluidic chip-based cytometers has become an important area due to their advantages of compact size and low cost. Herein, we demonstrate a sheathless microfluidic cytometer which integrates a standing surface acoustic wave (SSAW)-based microdevice capable of 3D particle/cell focusing with a laser-induced fluorescence (LIF) detection system. Using SSAW, our microfluidic cytometer was able to continuously focus microparticles/cells at the pressure node inside a microchannel. Flow cytometry was successfully demonstrated using this system with a coefficient of variation (CV) of less than 10% at a throughput of ~1000 events s(-1) when calibration beads were used. We also demonstrated that fluorescently labeled human promyelocytic leukemia cells (HL-60) could be effectively focused and detected with our SSAW-based system. This SSAW-based microfluidic cytometer did not require any sheath flows or complex structures, and it allowed for simple operation over a wide range of sample flow rates. Moreover, with the gentle, bio-compatible nature of low-power surface acoustic waves, this technique is expected to be able to preserve the integrity of cells and other bioparticles.
Acoustic clouds: standing sound waves around a black hole analogue
Benone, Carolina L; Herdeiro, Carlos; Radu, Eugen
2014-01-01
Under certain conditions sound waves in fluids experience an acoustic horizon with analogue properties to those of a black hole event horizon. In particular, a draining bathtub-like model can give rise to a rotating acoustic horizon and hence a rotating black hole (acoustic) analogue. We show that sound waves, when enclosed in a cylindrical cavity, can form stationary waves around such rotating acoustic black holes. These acoustic perturbations display similar properties to the scalar clouds that have been studied around Kerr and Kerr-Newman black holes; thus they are dubbed acoustic clouds. We make the comparison between scalar clouds around Kerr black holes and acoustic clouds around the draining bathtub explicit by studying also the properties of scalar clouds around Kerr black holes enclosed in a cavity. Acoustic clouds suggest the possibility of testing, experimentally, the existence and properties of black hole clouds, using analog models.
SQUEEZING PROPERTIES OF A TRAPPED ION IN THE STANDING-WAVE LASER
Institute of Scientific and Technical Information of China (English)
FANG MAO-FA; LIU XIANG
2001-01-01
We investigate the squeezing properties of a trapped ion in a standing-wave laser. Our results show that the squeezing of a trapped ion in the standing-wave laser is dependent on its position in the latter, the detuning parameter and the initial average phonon number.
Energy Technology Data Exchange (ETDEWEB)
Lipkens, Bart, E-mail: blipkens@wne.edu [Mechanical Engineering, Western New England University, Springfield, Massachusetts, 01119 (United States); Ilinskii, Yurii A., E-mail: ilinskii@gmail.com; Zabolotskaya, Evgenia A., E-mail: zheniazabolotskaya@gmail.com [Applied Research Laboratories, The University of Texas at Austin, Austin, Texas 78713–8029 (United States)
2015-10-28
Ultrasonic standing waves are widely used for separation applications. In MEMS applications, a half wavelength standing wave field is generated perpendicular to a laminar flow. The acoustic radiation force exerted on the particle drives the particle to the center of the MEMS channel, where concentrated particles are harvested. In macro-scale applications, the ultrasonic standing wave spans multiple wavelengths. Examples of such applications are oil/water emulsion splitting [1], and blood/lipid separation [2]. In macro-scale applications, particles are typically trapped in the standing wave, resulting in clumping or coalescence of particles/droplets. Subsequent gravitational settling results in separation of the secondary phase. An often used expression for the radiation force on a particle is that derived by Gorkov [3]. The assumptions are that the particle size is small relative to the wavelength, and therefore, only monopole and dipole scattering contributions are used to calculate the radiation force. This framework seems satisfactory for MEMS scale applications where each particle is treated separately by the standing wave, and concentrations are typically low. In macro-scale applications, particle concentration is high, and particle clumping or droplet coalescence results in particle sizes not necessarily small relative to the wavelength. Ilinskii et al. developed a framework for calculation of the acoustic radiation force valid for any size particle [4]. However, this model does not take into account particle to particle effects, which can become important as particle concentration increases. It is known that an acoustic radiation force on a particle or a droplet is determined by the local field. An acoustic radiation force expression is developed that includes the effect of particle to particle interaction. The case of two neighboring particles is considered. The approach is based on sound scattering by the particles. The acoustic field at the location of
Standing wave brass-PZT square tubular ultrasonic motor.
Park, Soonho; He, Siyuan
2012-09-01
This paper reports a standing wave brass-PZT tubular ultrasonic motor. The motor is composed of a brass square tube with two teeth on each tube end. Four PZT plates are attached to the outside walls of the brass tube. The motor requires only one driving signal to excite vibration in a single bending mode to generate reciprocating diagonal trajectories of teeth on the brass tube ends, which drive the motor to rotate. Bi-directional rotation is achieved by exciting different pairs of PZT plates to switch the bending vibration direction. Through using the brass-PZT tube structure, the motor can take high magnitude vibration to achieve a high output power in comparison to PZT tube based ultrasonic motors. Prototypes are fabricated and tested. The dimension of the brass-PZT tube is 3.975mm×3.975mm×16mm. Measured performance is a no-load speed of >1000RPM, a stall torque of 370μNm and a maximum output power of 16 mW when a sinusoidal driving voltage of 50V is applied. The working frequencies of the motor are 46,050Hz (clockwise) and 46,200Hz (counter-clockwise).
Institute of Scientific and Technical Information of China (English)
刘正东; 武强; 曾亮; 林宇; 朱诗尧
2001-01-01
The reconstruction of the atom-laser wave function is performed using an interferometric measurement with a standing-wave grating, and the results of this scheme are studied. The relations between the measurement data and the atomic wave function are also presented. This scheme is quite applicable and effectively avoids the initial random phase problem of the method that employs the laser running wave. The information which is encoded in the atom-laser wave is extracted.
Flow under standing waves Part 1. Shear stress distribution, energy flux and steady streaming
DEFF Research Database (Denmark)
Gislason, Kjartan; Fredsøe, Jørgen; Deigaard, Rolf
2009-01-01
The conditions for energy flux, momentum flux and the resulting streaming velocity are analysed for standing waves formed in front of a fully reflecting wall. The exchange of energy between the outer wave motion and the near bed oscillatory boundary layer is considered, determining the horizontal...... energy flux inside and outside the boundary layer. The momentum balance, the mean shear stress and the resulting time averaged streaming velocities are determined. For a laminar bed boundary layer the analysis of the wave drift gives results similar to the original work of Longuet-Higgins from 1953....... The work is extended to turbulent bed boundary layers by application of a numerical model. The similarities and differences between laminar and turbulent flow conditions are discussed, and quantitative results for the magnitude of the mean shear stress and drift velocity are presented. Full two...
Anisotropic Inflation in a 5D Standing Wave Braneworld and Dimensional Reduction
Gogberashvili, Merab; Malagon-Morejon, Dagoberto; Mora-Luna, Refugio Rigel
2012-01-01
We investigate a cosmological solution within the framework of a 5D standing wave braneworld model generated by gravity coupled to a massless scalar phantom-like field. By obtaining a full exact solution of the model we found a novel dynamical mechanism in which the anisotropic nature of the primordial metric gives rise to i) inflation along certain spatial dimensions, and ii) deflation and a shrinking reduction of the number of spatial dimensions along other directions. This dynamical mechanism can be relevant for dimensional reduction in string and other higher dimensional theories in the attempt of getting a 4D isotropic expanding space-time.
Analysis on Non-Resonance Standing Waves and Vibration Tracks of Strings
Fang, Tian-Shen
2007-01-01
This paper presents an experimental technique to observe the vibration tracks of string standing waves. From the vibration tracks, we can analyse the vibration directions of harmonic waves. For the harmonic wave vibrations of strings, when the driving frequency f[subscript s] = Nf[subscript n] (N = 1, 2, 3, 4,...), both resonance and non-resonance…
Standing Waves of the Inhomogeneous Klein-Gordon Equations with Critical Exponent
Institute of Scientific and Technical Information of China (English)
Zai Hui GAN; Jian ZHANG
2006-01-01
This paper is concerned with the standing wave in the inhomogeneous nonlinear Klein-Gordon equations with critical exponent. Firstly, we obtain the existence of standing waves associated with the ground states by using variational calculus as well as a compactness lemma. Next, we establish some sharp conditions for global existence in terms of the characteristics of the ground state. Then,we show that how small the initial data are for the global solutions to exist. Finally, we prove the instability of the standing wave by combining the former results.
The global coherence initiative: creating a coherent planetary standing wave.
McCraty, Rollin; Deyhle, Annette; Childre, Doc
2012-03-01
via biological, electromagnetic, and nonlocal fields, it stands to reason that humans can work together in a co-creative relationship to consciously increase the coherence in the global field environment, which in turn distributes this information to all living systems within the field. GCI was established to help facilitate the shift in global consciousness from instability and discord to balance, cooperation, and enduring peace. A primary goal of GCI is to test the hypothesis that large numbers of people when in a heart-coherent state and holding a shared intention can encode information on the earth's energetic and geomagnetic fields, which act as carrier waves of this physiologically patterned and relevant information. In order to conduct this research, a global network of 12 to 14 ultrasensitive magnetic field detectors specifically designed to measure the earth's magnetic resonances is being installed strategically around the planet. More important is GCI's primary goal to motivate as many people as possible to work together in a more coherent and collaborative manner to increase the collective human consciousness. If we are persuaded that not only external fields of solar and cosmic origins but also human attention and emotion can directly affect the physical world and the mental and emotional states of others (consciousness), it broadens our view of what interconnectedness means and how it can be intentionally utilized to shape the future of the world we live in. It implies that our attitudes, emotions, and intentions matter and that coherent, cooperative intent can have positive effects. GCI hypothesizes that when enough individuals and social groups increase their coherence baseline and utilize that increased coherence to intentionally create a more coherent standing reference wave in the global field, it will help increase global consciousness. This can be achieved when an increasing number of people move towards more balanced and self-regulated emotions
Model for multi-stand management based on structural attributes of individual stands
G.W. Miller; J. Sullivan
1997-01-01
A growing interest in managing forest ecosystems calls for decision models that take into account attribute goals for large forest areas while continuing to recognize the individual stand as a basic unit of forest management. A dynamic, nonlinear forest management model is described that schedules silvicultural treatments for individual stands that are linked by multi-...
Efremov, MA; Petropavlovsky, SV; Fedorov, MV; Schleich, WP; Yakovlev, VP
2005-01-01
The formation of two-dimensional nonspreading atomic wave packets produced in the interaction of a beam of two-level atoms with two standing light waves polarised in the same plane is considered. The mechanism providing a dispersionless particle dynamics is the balance of two processes: a rapid deca
Beswick, Benjamin T.; Hughes, Ifan G.; Gardiner, Simon A.; Astier, Hippolyte P. A. G.; Andersen, Mikkel F.; Daszuta, Boris
2016-12-01
Atom interferometers are a useful tool for precision measurements of fundamental physical phenomena, ranging from the local gravitational-field strength to the atomic fine-structure constant. In such experiments, it is desirable to implement a high-momentum-transfer "beam splitter," which may be achieved by inducing quantum resonance in a finite-temperature laser-driven atomic gas. We use Monte Carlo simulations to investigate these quantum resonances in the regime where the gas receives laser pulses of finite duration and derive an ɛ -classical model for the dynamics of the gas atoms which is capable of reproducing quantum resonant behavior for both zero-temperature and finite-temperature noninteracting gases. We show that this model agrees well with the fully quantum treatment of the system over a time scale set by the choice of experimental parameters. We also show that this model is capable of correctly treating the time-reversal mechanism necessary for implementing an interferometer with this physical configuration and that it explains an unexpected universality in the dynamics.
Nonlinear series resonance and standing waves in dual-frequency capacitive discharges
Wen, De-Qi; Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.; Wang, You-Nian
2017-01-01
It is well-known that the nonlinear series resonance in a high frequency capacitive discharge enhances the electron power deposition and also creates standing waves which produce radially center-high rf voltage profiles. In this work, the dynamics of series resonance and wave effects are examined in a dual-frequency driven discharge, using an asymmetric radial transmission line model incorporating a Child law sheath. We consider a cylindrical argon discharge with a conducting electrode radius of 15 cm, gap length of 3 cm, with a base case having a 60 MHz high frequency voltage of 250 V and a 10 MHz low frequency voltage of 1000 V, with a high frequency phase shift {φ\\text{H}}=π between the two frequencies. For this phase shift there is only one sheath collapse, and the time-averaged spectral peaks of the normalized current density at the center are mainly centered on harmonic numbers 30 and 50 of the low frequency, corresponding to the first standing wave resonance frequency and the series resonance frequency, respectively. The effects of the waves on the series resonance dynamics near the discharge center give rise to significant enhancements in the electron power deposition, compared to that near the discharge edge. Adjusting the phase shift from π to 0, or decreasing the low frequency from 10 to 2 MHz, results in two or more sheath collapses, respectively, making the dynamics more complex. The sudden excitation of the perturbed series resonance current after the sheath collapse results in a current oscillation amplitude that is estimated from analytical and numerical calculations. Self-consistently determining the dc bias and including the conduction current is found to be important. The subsequent slow time variation of the high frequency oscillation is analyzed using an adiabatic theory.
Standing waves in a partitioned tube with passive membrane
Amundsen, David E.; Cox, Edward A.; Mortell, Michael P.
2008-11-01
The propagation of waves within a tube containing disparate gases separated by a passive membrane is modeled and analyzed in the limit of weak dissipation and applied forcing. This provides a simple setting in which to study the nonlinear interactions within and between each gas and provides a paradigm for other similar physical systems such as laminated elastic materials. The associated resonant frequencies are found in terms of a linear functional equation involving a non-trivial combination of the separate natural frequencies. As expected, in the limit that the gases have the same material properties, the modes become commensurate and the model reduces to that of the classical shock tube. However sufficiently away from this limit it is seen that this structure is lost and smooth single mode resonant solutions arise. Using a perturbative approach these solutions are approximated and compared to numerical solutions of the full system. The transition between smooth and discontinuous solutions is also studied both numerically and analytically, based on a dimensionless parameter associated with the relative material difference.
Binder, Philippe; Cunnyngham, Ian
2012-01-01
In a recent note in this journal, Gluck presents a beautiful demonstration of the standing wave generated by a strip of material with linearly varying width (a trapezoid). As expected, the resulting wave envelope (and its shadow) showed a varying wavelength--smaller as the strip width gets larger.
Institute of Scientific and Technical Information of China (English)
LIU Ke; LI Song; GUO Qing; HUANG Dongtao
2005-01-01
A lateral Helmholtz resonator added to a standing wave tube without flow has been validated as a method of noise reduction for combustion noise radiated from combustion channel of rockets or turbines. But in fact there is a flow with low velocity in the combustion channel. Therefore the theoretical analysis carried out is aimed at sound field of standing wave tube with flow and with lateral Helmholtz resonator. Certainly a relevant math-physical model should first be formulated. Here three key problems need to be solved: (1) To formulate the discontinuity condition at the joint between the standing wave tube and Helmholtz resonator in the case of flow. (2) To determine the acoustic impedance of Helnholtz resonator, considering the effects of flow, viscous and multihole. (3) To formulate the reflection condition at the end of the standing wave tube. Some formulas for analysis of the sound field in the tube with flow and with lateral Helmholtz resonator are deduced. These theoretical works have been validated by experiments.
Coronal Seismology of Flare-Excited Standing Slow-Mode Waves Observed by SDO/AIA
Wang, Tongjiang; Ofman, Leon; Davila, Joseph M.
2016-05-01
Flare-excited longitudinal intensity oscillations in hot flaring loops have been recently detected by SDO/AIA in 94 and 131 Å bandpasses. Based on the interpretation in terms of a slow-mode wave, quantitative evidence of thermal conduction suppression in hot (>9 MK) loops has been obtained for the first time from measurements of the polytropic index and phase shift between the temperature and density perturbations (Wang et al. 2015, ApJL, 811, L13). This result has significant implications in two aspects. One is that the thermal conduction suppression suggests the need of greatly enhanced compressive viscosity to interpret the observed strong wave damping. The other is that the conduction suppression provides a reasonable mechanism for explaining the long-duration events where the thermal plasma is sustained well beyond the duration of impulsive hard X-ray bursts in many flares, for a time much longer than expected by the classical Spitzer conductive cooling. In this study, we model the observed standing slow-mode wave in Wang et al. (2015) using a 1D nonlinear MHD code. With the seismology-derived transport coefficients for thermal conduction and compressive viscosity, we successfully simulate the oscillation period and damping time of the observed waves. Based on the parametric study of the effect of thermal conduction suppression and viscosity enhancement on the observables, we discuss the inversion scheme for determining the energy transport coefficients by coronal seismology.
High-fidelity simulation of a standing-wave thermoacoustic-piezoelectric engine
Lin, Jeffrey; Hesselink, Lambertus
2015-01-01
We have carried out wall-resolved fully unstructured Navier--Stokes simulations of a complete standing-wave thermoacoustic piezoelectric (TAP) engine model inspired by the experimental work of Smoker et al. (2012). The computational model is axisymmetric and comprises a 51 cm long cylindrical resonator divided into two sections: one of 19.5 mm in diameter, enclosing a thermoacoustic stack where a linear temperature distribution is imposed via isothermal boundary conditions; the other of 71 mm in diameter, capped by a piezoelectric diaphragm modelled via multi-oscillator broadband time-domain impedance boundary conditions (TDIBCs) matching the measured electromechanical impedance of a PZT-5A diaphragm tuned to the thermoacoustically amplified mode (388 Hz) for maximization of acoustic energy extraction. Simulations were first carried out without energy extraction from quiescent conditions to a limit cycle, for hot-to-cold temperature differences in the range $\\Delta T = 340 - 490\\textrm{ K}$, achieving acousti...
Standing Excitation Waves in the Heart Induced by Strong Alternating Electric Fields
Gray, Richard A.; Mornev, Oleg A.; Jalife, José; Aslanidi, Oleg V.; Pertsov, Arkady M.
2001-10-01
We studied the effect of sinusoidal electric fields on cardiac tissue both experimentally and numerically. We found that periodic forcing at 5-20 Hz using voltage applied in the bathing solution could stop the propagation of excitation waves by producing standing waves of membrane depolarization. These patterns were independent of the driving frequency in contrast to classical standing waves. The stimulus strength required for pattern formation was large compared to the excitation threshold. A novel tridomain representation of cardiac tissue was required to reproduce this behavior numerically.
Overdetermined Shooting Methods for Computing Standing Water Waves with Spectral Accuracy
Wilkening, Jon
2012-01-01
A high-performance shooting algorithm is developed to compute time-periodic solutions of the free-surface Euler equations with spectral accuracy in double and quadruple precision. The method is used to study resonance and its effect on standing water waves. We identify new nucleation mechanisms in which isolated large-amplitude solutions, and closed loops of such solutions, suddenly exist for depths below a critical threshold. We also study degenerate and secondary bifurcations related to Wilton's ripples in the traveling case, and explore the breakdown of self-similarity at the crests of extreme standing waves. In shallow water, we find that standing waves take the form of counter-propagating solitary waves that repeatedly collide quasi-elastically. In deep water with surface tension, we find that standing waves resemble counter-propagating depression waves. We also discuss existence and non-uniqueness of solutions, and smooth versus erratic dependence of Fourier modes on wave amplitude and fluid depth. In t...
DEFF Research Database (Denmark)
Burcharth, H. F.; Larsen, Brian Juul
The investigation concerns the design of a new internal breakwater in the main port of Ibiza. The objective of the model tests was in the first hand to optimize the cross section to make the wave reflection low enough to ensure that unacceptable wave agitation will not occur in the port. Secondly...
A review of stand basal area growth models
Institute of Scientific and Technical Information of China (English)
Sun Hong-gang; Zhang Jian-guo; Duan Ai-guo; He Cai-yun
2007-01-01
Growth and yield modeling has a long history in forestry. The methods of measuring the growth of stand basal area have evolved from those developed in the U.S.A. and Germany during the last century. Stand basal area modeling has progressed rapidly since the first widely used model was published by the U.S. Forest Service. Over the years, a variety of models have been developed for predicting the growth and yield of uneven/even-aged stands using stand-level approaches. The modeling methodology has not only moved from an empirical approach to a more ecological process-based approach but also accommodated a variety of techniques such as: 1) simultaneous equation methods, 2) difference models, 3) artificial neural network techniques, 4) linear/nonlinear regression models, and 5) matrix models. Empirical models using statistical methods were developed to reproduce accurately and precisely field observations. In contrast, process models have a shorter history, developed originally as research and education tools with the aim of increasing the understanding of cause and effect relationships. Empirical and process models can be married into hybrid models in which the shortcomings of both component approaches can, to some extent, be overcome. Algebraic difference forms of stand basal area models which consist of stand age, stand density and site quality can fully describe stand growth dynamics. This paper reviews the current literature regarding stand basal area models, discusses the basic types of models and their merits and outlines recent progress in modeling growth and dynamics of stand basal area. Future trends involving algebraic difference forms, good fitting variables and model types into stand basal area modeling strategies are discussed.
Dynamics models and modeling of tree stand development
Directory of Open Access Journals (Sweden)
M. V. Rogozin
2015-04-01
Full Text Available Brief analysis of scientific works in Russia and in the CIS over the past 100 years. Logical and mathematical models consider the conceptual and show some of the results of their verification. It was found that the models include different laws and the parameters, the sum of which allows you to divide them into four categories: models of static states, development models, models of care for the natural forest and models of cultivation. Each category has fulfilled and fulfills its tasks in economic management. Thus, the model states in statics (table traverse growth played a prominent role in figuring out what may be the most productive (full stands in different regions of the country. However, they do not answer the question of what the initial states lead to the production of complete stands. In a study of the growth of stands used system analysis, and it is observed dominance of works studying static state, snatched from the biological time. Therefore, the real drama of the growth of stands remained almost unexplored. It is no accident there were «chrono-forestry» «plantation forestry» and even «non-traditional forestry», where there is a strong case of a number of new concepts of development stands. That is quite in keeping with Kuhn (Kuhn, 2009 in the forestry crisis began – there were alternative theories and coexist conflicting scientific schools. To develop models of stand development, it is proposed to use a well-known method of repeated observations within 10–20 years, in conjunction with the explanation of the history of the initial density. It mounted on the basis of studying the dynamics of its indicators: the trunk, crown overlap coefficient, the sum of volumes of all crowns and the relative length of the crown. According to these indicators, the researcher selects natural series of development stands with the same initial density. As a theoretical basis for the models it is possible to postulate the general properties of
Damage Detection on Thin-walled Structures Utilizing Laser Scanning and Standing Waves
Energy Technology Data Exchange (ETDEWEB)
Kang, Se Hyeok; Jeon, Jun Young; Kim, Du Hwan; Park, Gyuhae [Chonnam Nat’l Univ., Gwangju (Korea, Republic of); Kang, To; Han, Soon Woo [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2017-05-15
This paper describes wavenumber filtering for damage detection using single-frequency standing wave excitation and laser scanning sensing. An embedded piezoelectric sensor generates ultrasonic standing waves, and the responses are measured using a laser Doppler vibrometer and mirror tilting device. After scanning, newly developed damage detection techniques based on wavenumber filtering are applied to the full standing wave field. To demonstrate the performance of the proposed techniques, several experiments were performed on composite plates with delamination and aluminum plates with corrosion damage. The results demonstrated that the developed techniques could be applied to various structures to localize the damage, with the potential to improve the damage detection capability at a high interrogation speed.
Controlled high-energy ion acceleration with intense chirped standing waves
Mackenroth, Felix; Gonoskov, Arkady; Marklund, Mattias
2016-10-01
We present the latest results of the recently proposed ion acceleration mechanism ``chirped standing wave acceleration''. This mechanism is based on locking the electrons of a thin plasma layer to the moving nodes of a standing wave formed by a chirped laser pulse reflected from a mirror behind the thin layer. The resulting longitudinal charge separation field between the displaced electrons and the residual ions then accelerates the latter. Since the plasma layer is stabilized by the standing wave, the formation of plasma instabilities is suppressed. Furthermore, the experimentally accessible laser chirp provides a versatile tool for manipulating the resulting ion beam in terms of maximum particle energy, particle number and spectral distribution. Through this scheme, proton beams, with energy spectra peaked around 100 MeV, were shown to be feasible for pulse energies at the level of 10 J. Wallenberg Foundation within the Grant ''Plasma based compact ion sources'' (PLIONA).
Sand Bed Morphodynamics under Standing Waves and Vegetated Conditions
Landry, B. J.; Garcia, M. H.
2010-12-01
Littoral processes such as sediment transport, wave attenuation, and boundary layer development are governed by the presence of bathymetric features, which include large-scale sand bars upon which smaller-scale sand ripples are superimposed, as well as the presence of submarine vegetation. Numerous studies on sand ripples and bars have aided to elucidate the dynamics in oscillatory flows; however, the effect of vegetation on the system is less understood. Recent laboratory studies have focused on quantifying wave attenuation by emergent vegetation as a natural method to mitigate storm surges. The emergent vegetation, while promising for coastal protection, alters sediment transport rates directly by the physical presence of the plants near the bed and indirectly from reduction in near-bed shear stresses due to attenuated wave energy. The experimental work herein focuses on the area near the deeply submerged vegetated canopy limit (current work has a ratio of mean still water depth to plant height, H/h, = 7.9) to minimize the effect on the surface waves and discern the direct impact vegetation has on sand bed morphodynamics. Experiments were conducted in the large wave tank (49-m long by 1.83-m wide by 1.22-m deep) in the Ven Te Chow Hydrosystems Laboratory at the University of Illinois in which a high reflection wave forcing was used over a uniform sand bed with a 0.25-mm median sediment diameter in which staggered and uniform arrangements of idealized vegetation (i.e., 6.35-mm diameter rigid wooden cylinders) were positioned along the bed (e.g., at predetermined sand bar troughs and over an entire sand bar). The resulting bathymetric evolution from the vegetated case experiments were compared to the base case of no vegetation using two optical methods: a high-resolution laser displacement sensor for three-dimensional surveys and digitized profiles via high-definition panoramic images of the entire test section. The experimental findings illustrate the profound
Energy Technology Data Exchange (ETDEWEB)
Gray, Alexander; Kronast, Florian; Papp, Christian; Yang, See-Hun; Cramm, Stefan; Krug, Ingo P.; Salmassi, Farhad; Gullikson, Eric M.; Hilken, Dawn L.; Anderson, Erik H.; Fischer, Peter; Durr, Hermann A.; Schneider, Claus M.; Fadley, Charles S.
2010-10-29
We demonstrate the addition of depth resolution to the usual two-dimensional images in photoelectron emission microscopy (PEEM), with application to a square array of circular magnetic Co microdots. The method is based on excitation with soft x-ray standing-waves generated by Bragg reflection from a multilayer mirror substrate. Standing wave is moved vertically through sample simply by varying the photon energy around the Bragg condition. Depth-resolved PEEM images were obtained for all of the observed elements. Photoemission intensities as functions of photon energy were compared to x-ray optical calculations in order to quantitatively derive the depth-resolved film structure of the sample.
Analysis of Nanometer Structure for Chromium Atoms in Gauss Standing Laser Wave
Institute of Scientific and Technical Information of China (English)
ZHANG Wen-Tao; ZHU Bao-Hua; XIONG Xian-Ming
2010-01-01
@@ The equation of motion of two-level chromium atoms in Gauss standing laser wave is discussed and the distribution of chromium atoms is given under different transverse velocity conditions.The results show that the focusing position of atoms will be affected by the transverse velocity of atoms.Based on the four-order Runge-Kutta method,the locus of chromium atoms in Gauss standing laser wave is simulated.The three-dimensional characteristics of nanometer structures are stimulated under perfect and emanative conditions.
Gokirmak, A; Bridgewater, A; Anlage, S M; Gokirmak, Ali; Wu, Dong-Ho; Anlage, Steven M.
1998-01-01
We have developed a method to measure the electric field standing wave distributions in a microwave resonator using a scanned perturbation technique. Fast and reliable solutions to the Helmholtz equation (and to the Schrodinger equation for two dimensional systems) with arbitrarily-shaped boundaries are obtained. We use a pin perturbation to image primarily the microwave electric field amplitude, and we demonstrate the ability to image broken time-reversal symmetry standing wave patterns produced with a magnetized ferrite in the cavity. The whole cavity, including areas very close to the walls, can be imaged using this technique with high spatial resolution over a broad range of frequencies.
Standing torsional waves in a fully saturated, porous, circular cylinder
Solorza, S; 10.1111/j.1365-246X.2004.02198.x
2004-01-01
For dynamic measurement of the elastic moduli of a porous material saturated with viscous fluid using the resonance-bar technique, one also observes attenuation. In this article we have carried out the solution of the boundary-value problem associated with standing torsional oscillations of a finite, poroelastic, circular cylinder cast in the framework of volume-averaged theory of poroelasticity. Analysing this solution by eigenvalue perturbation approach we are able to develop expressions for torsional resonance and temporal attenuation frequencies in which the dependence upon the material properties are transparent. It shows how the attenuation is controlled by the permeability and the fluid properties, and how the resonance frequency drops over its value for the dry solid-frame due to the drag effect of fluid mass. Based upon this work we have a firm basis to determine solid-frame shear modulus, permeability, and tortuosity factor from torsional oscillation experiments.
On standing sausage waves in photospheric magnetic waveguides
Dorotovic, I; Freij, N; Karlovsky, V; Marquez, I
2012-01-01
By focusing on the oscillations of the cross-sectional area and the intensity of magnetic waveguides located in the lower solar atmosphere, we aim to detect and identify magnetohydrodynamic (MHD) sausage waves. Capturing several series of high-resolution images of pores and sunspots and employing wavelet analysis in conjunction with empirical mode decomposition (EMD) makes the MHD wave analysis possible. For this paper, two sunspots and one pore (with a light bridge) were chosen as representative examples of MHD waveguides in the lower solar atmosphere. The sunspots and pore display a range of periods from 4 to 65 minutes. The sunspots support longer periods than the pore - generally enabling a doubling or quadrupling of the maximum pore oscillatory period. All of these structures display area oscillations indicative of MHD sausage modes and in-phase behaviour between the area and intensity, presenting mounting evidence for the presence of the slow sausage mode within these waveguides. The presence of fast an...
Fluorescence x-ray standing wave study on (AlAs)(GaAs) superlattices
Lessmann, A; Munkholm, A; Schuster, M; Riechert, H; Materlik, G
1999-01-01
X-ray standing waves (XSW) were used to investigate the structure of molecular beam epitaxy (MBE) grown (AlAs) sub 3 (GaAs) sub 7 short-period superlattices (SPSL). The modulation of the Al K, As L, and Ga L x-ray fluorescence induced by XSW was measured at the zero-order superlattice (SL) satellite (AlAs)(GaAs)(004,0) and the GaAs(004) substrate Bragg reflection. From the shape of the fluorescence yield modulations and the diffraction pattern, a model of the interfaces is derived by comparing the experimental data with dynamical calculations of the x-ray wave field distribution and reflectivity. A straightforward analysis of the fluorescence measurements at the SL satellite shows that in AlAs layers a high crystalline order is established, whereas in GaAs layers a fraction of the Ga and As atoms is not on ideal lattice sites, but is displaced towards the substrate. The data can be explained by a model in which, at each AlAs/GaAs interface of the GaAs layers, two Ga atom planes are displaced by 0.035 nm and 0...
Fluorescence x-ray standing wave study on (AlAs)(GaAs) superlattices
Energy Technology Data Exchange (ETDEWEB)
Lessmann, A.; Brennan, S.; Munkholm, A. [Stanford Synchrotron Radiation Laboratory SSRL/SLAC, Menlo Park, CA (United States); Schuster, M.; Riechert, H. [Siemens AG, Corporate Technology, Munich (Germany); Materlik, G. [Hamburger Synchrotronstrahlungslabor HASYLAB/DESY, Hamburg (Germany)
1999-05-21
X-ray standing waves (XSW) were used to investigate the structure of molecular beam epitaxy (MBE) grown (AlAs){sub 3}(GaAs){sub 7} short-period superlattices (SPSL). The modulation of the Al K, As L, and Ga L x-ray fluorescence induced by XSW was measured at the zero-order superlattice (SL) satellite (AlAs)(GaAs)(004,0) and the GaAs(004) substrate Bragg reflection. From the shape of the fluorescence yield modulations and the diffraction pattern, a model of the interfaces is derived by comparing the experimental data with dynamical calculations of the x-ray wave field distribution and reflectivity. A straightforward analysis of the fluorescence measurements at the SL satellite shows that in AlAs layers a high crystalline order is established, whereas in GaAs layers a fraction of the Ga and As atoms is not on ideal lattice sites, but is displaced towards the substrate. The data can be explained by a model in which, at each AlAs/GaAs interface of the GaAs layers, two Ga atom planes are displaced by 0.035 nm and 0.008 nm and one As atom plane by 0.023 nm. The displacements within the GaAs layers exhibit a mirror symmetry with respect to the centre of each layer. (author)
Herrmann, Michael
2010-01-01
We study focussing discrete nonlinear Schr\\"{o}dinger equations and present a new variational existence proof for homoclinic standing waves (bright solitons). Our approach relies on the constrained maximization of an energy functional and provides the existence of two one-parameter families of waves with unimodal and even profile function for a wide class of nonlinearities. Finally, we illustrate our results by numerical simulations.
Standing Sound Waves in a tube: Approach analysis \\& sugestions
Vieira, L P; Lara, V O M
2013-01-01
In this paper we attempt to present some questions with respect to the approach used in some brazilian mid-level textbooks on the topic of stationary sound waves in tubes. In addition to ranking the textbooks within a set of criteria, we also present some suggestions for further discussions of this topic. We suggest the use of gifs and animations and the use of two experiments that allow you to view the profiles of variation of pressure and air displacement for the harmonic modes of vibration.
Particle motion of accelerated electrons in standing-wave RF structures
Hammen, A. F. J.; Corstens, J. M.; Botman, J. I. M.; Hagedoorn, H. L.; Theuws, W. H. C.
1999-05-01
A Hamiltonian theory has been formulated, which is used to calculate accelerated particle motion in standing-wave RF structures. In particular, these calculations have been applied to the Eindhoven racetrack microtron accelerating cavity. The calculations are in excellent agreement with simulations performed by particle-tracking codes.
Dynamics of spontaneous radiation of atoms scattered by a resonance standing light wave
Fedorov, MV; Efremov, MA; Yakovlev, VP; Schleich, WP
2003-01-01
The scattering of atoms by a resonance standing light wave is considered under conditions when the lower of two resonance levels is metastable, while the upper level rapidly decays due to mainly spontaneous radiative transitions to the nonresonance levels of an atom. The diffraction scattering regim
Vibration of a single microcapsule with a hard plastic shell in an acoustic standing wave field.
Koyama, Daisuke; Kotera, Hironori; Kitazawa, Natsuko; Yoshida, Kenji; Nakamura, Kentaro; Watanabe, Yoshiaki
2011-04-01
Observation techniques for measuring the small vibration of a single microcapsule of tens of nanometers in an acoustic standing wave field are discussed. First, simultaneous optical observation of a microbubble vibration by two methods is investigated, using a high-speed video camera, which permits two-dimensional observation of the bubble vibration, and a laser Doppler vibrometer (LDV), which can observe small bubble vibration amplitudes at high frequency. Bubbles of tens of micrometers size were trapped at the antinode of an acoustic standing wave generated in an observational cell. Bubble vibration at 27 kHz could be observed and the experimental results for the two methods showed good agreement. The radial vibration of microcapsules with a hard plastic shell was observed using the LDV and the measurement of the capsule vibration with radial oscillation amplitude of tens of nanometers was successful. The acoustic radiation force acting on microcapsules in the acoustic standing wave was measured from the trapped position of the standing wave and the radial oscillation amplitude of the capsules was estimated from the theoretical equation of the acoustic radiation force, giving results in good agreement with the LDV measurements. The radial oscillation amplitude of a capsule was found to be proportional to the amplitude of the driving sound pressure. A larger expansion ratio was observed for capsules closer to the resonance condition under the same driving sound pressure and frequency.
Standing Waves in an Elastic Spring: A Systematic Study by Video Analysis
Ventura, Daniel Rodrigues; de Carvalho, Paulo Simeão; Dias, Marco Adriano
2017-04-01
The word "wave" is part of the daily language of every student. However, the physical understanding of the concept demands a high level of abstract thought. In physics, waves are oscillating variations of a physical quantity that involve the transfer of energy from one point to another, without displacement of matter. A wave can be formed by an elastic deformation, a variation of pressure, changes in the intensity of electric or magnetic fields, a propagation of a temperature variation, or other disturbances. Moreover, a wave can be categorized as pulsed or periodic. Most importantly, conditions can be set such that waves interfere with one another, resulting in standing waves. These have many applications in technology, although they are not always readily identified and/or understood by all students. In this work, we use a simple setup including a low-cost constant spring, such as a Slinky, and the free software Tracker for video analysis. We show they can be very useful for the teaching of mechanical wave propagation and the analysis of harmonics in standing waves.
Acoustic radiation force of high-order Bessel beam standing wave tweezers on a rigid sphere.
Mitri, F G
2009-12-01
Particle manipulation using the acoustic radiation force of Bessel beams is an active field of research. In a previous investigation, [F.G. Mitri, Acoustic radiation force on a sphere in standing and quasi-standing zero-order Bessel beam tweezers, Annals of Physics 323 (2008) 1604-1620] an expression for the radiation force of a zero-order Bessel beam standing wave experienced by a sphere was derived. The present work extends the analysis of the radiation force to the case of a high-order Bessel beam (HOBB) of positive order m having an angular dependence on the phase phi. The derivation for the general expression of the force is based on the formulation for the total acoustic scattering field of a HOBB by a sphere [F.G. Mitri, Acoustic scattering of a high-order Bessel beam by an elastic sphere, Annals of Physics 323 (2008) 2840-2850; F.G. Mitri, Equivalence of expressions for the acoustic scattering of a progressive high order Bessel beam by an elastic sphere, IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 56 (2009) 1100-1103] to derive the general expression for the radiation force function YJm,st(ka,beta,m)Bessel beam standing wave incident upon a rigid sphere immersed in non-viscous water are computed. The rigid sphere calculations for YJm,st(ka,beta,m)Bessel beam standing wave (m=0). The proposed theory is of particular interest essentially due to its inherent value as a canonical problem in particle manipulation using the acoustic radiation force of a HOBB standing wave on a sphere. It may also serve as the benchmark for comparison to other solutions obtained by strictly numerical or asymptotic approaches.
Otosu, Takuhiro; Yamaguchi, Shoichi
2017-07-01
We present standing evanescent-wave fluorescence correlation spectroscopy (SEW-FCS). This technique utilizes the interference of two evanescent waves which generates a standing evanescent-wave. Fringe-pattern illumination created by a standing evanescent-wave enables us to measure the diffusion coefficients of molecules with a super-resolution corresponding to one fringe width. Because the fringe width can be reliably estimated by a simple procedure, utilization of fringes is beneficial to quantitatively analyze the slow diffusion of molecules in a supported lipid bilayer (SLB), a model biomembrane formed on a solid substrate, with the timescale relevant for reliable FCS analysis. Furthermore, comparison of the data between SEW-FCS and conventional total-internal reflection FCS, which can also be performed by the SEW-FCS instrument, effectively eliminates the artifact due to afterpulsing of the photodiode detector. The versatility of SEW-FCS is demonstrated by its application to various SLBs.
Ai, Ye; Sanders, Claire K; Marrone, Babetta L
2013-10-01
A microfluidic device was developed to separate heterogeneous particle or cell mixtures in a continuous flow using acoustophoresis. In this device, two identical surface acoustic waves (SAWs) generated by interdigital transducers (IDTs) propagated toward a microchannel, which accordingly built up a standing surface acoustic wave (SSAW) field across the channel. A numerical model, coupling a piezoelectric effect in the solid substrate and acoustic pressure in the fluid, was developed to provide a better understanding of SSAW-based particle manipulation. It was found that the pressure nodes across the channel were individual planes perpendicular to the solid substrate. In the separation experiments, two side sheath flows hydrodynamically focused the injected particle or cell mixtures into a very narrow stream along the centerline. Particles flowing through the SSAW field experienced an acoustic radiation force that highly depends on the particle properties. As a result, dissimilar particles or cells were laterally attracted toward the pressure nodes at different magnitudes, and were eventually switched to different outlets. Two types of fluorescent microspheres with different sizes were successfully separated using the developed device. In addition, Escherichia coli bacteria premixed in peripheral blood mononuclear cells (PBMCs) were also efficiently isolated using the SSAW-base separation technique. Flow cytometric analysis on the collected samples found that the purity of separated E. coli bacteria was 95.65%.
Shi, Aiwei; Huang, Peixuan; Guo, Shifang; Zhao, Lu; Jia, Yingjie; Zong, Yujin; Wan, Mingxi
2016-07-01
In atherosclerotic inducement in animal models, the conventionally used balloon injury is invasive, produces excessive vessel injuries at unpredictable locations and is inconvenient in arterioles. Fortunately, cavitation erosion, which plays an important role in therapeutic ultrasound in blood vessels, has the potential to induce atherosclerosis noninvasively at predictable sites. In this study, precise spatial control of cavitation erosion for superficial lesions in a vessel phantom was realised by using an ultrasonic standing wave (USW) with the participation of cavitation nuclei and medium-intensity ultrasound pulses. The superficial vessel erosions were restricted between adjacent pressure nodes, which were 0.87 mm apart in the USW field of 1 MHz. The erosion positions could be shifted along the vessel by nodal modulation under a submillimetre-scale accuracy without moving the ultrasound transducers. Moreover, the cavitation erosion of the proximal or distal wall could be determined by the types of cavitation nuclei and their corresponding cavitation pulses, i.e., phase-change microbubbles with cavitation pulses of 5 MHz and SonoVue microbubbles with cavitation pulses of 1 MHz. Effects of acoustic parameters of the cavitation pulses on the cavitation erosions were investigated. The flow conditions in the experiments were considered and discussed. Compared to only using travelling waves, the proposed method in this paper improves the controllability of the cavitation erosion and reduces the erosion depth, providing a more suitable approach for vessel endothelial injury while avoiding haemorrhage.
Zeng, Liang; Smith, Chris; Poelzer, G. Herold; Rodriguez, Jennifer; Corpuz, Edgar; Yanev, George
2014-01-01
In our pilot studies, we found that many introductory physics textbook illustrations with supporting text for sound standing waves of air columns in open-open, open-closed, and closed-closed pipes inhibit student understanding of sound standing wave phenomena due to student misunderstanding of how air molecules move within these pipes. Based on…
Zeng, Liang; Smith, Chris; Poelzer, G. Herold; Rodriguez, Jennifer; Corpuz, Edgar; Yanev, George
2014-01-01
In our pilot studies, we found that many introductory physics textbook illustrations with supporting text for sound standing waves of air columns in open-open, open-closed, and closed-closed pipes inhibit student understanding of sound standing wave phenomena due to student misunderstanding of how air molecules move within these pipes. Based on…
Velocity selective trapping of atoms in a frequency-modulated standing laser wave
Argonov, V Yu
2013-01-01
The wave function of a moderately cold atom in a stationary near-resonant standing light wave delocalizes very fast due to wave packet splitting. However, we show that frequency modulation of the field may suppress packet splitting for some atoms having specific velocities in a narrow range. These atoms remain localized in a small space for a long time. We propose that in a real experiment with cold atomic gas this effect may decrease the velocity distribution of atoms (the field traps the atoms with such specific velocities while all other atoms leave the field)
McLeod, Roger David; McLeod, David Matthew
2009-05-01
Our hydrogen atom interacts with a neutron star. Its stringy TW/SW electron is cut by a neutrino scissor that instantly becomes its end anti-node. The string has one extra neutrino in 100,000. Antimatter remains concealed. Our Dumbo Proton of a TW state is similarly cut. Inside the star, electron string/spring compresses 100,000 and 1836 times more, to proton's linear mass density. Electrostatics encourages that caboose, stringy electron, to couple with a cut proton. Linear charge densities neutralize while composite length contracts 20%. The writhing string evicts an antineutrino at closure on Pauli's authority, becoming Mickey Neutron, with looped quarks. Unstable Mickey Neutron has his ear notch forced into an ear notch of stable Dumbo Proton, achieving immortality in this deuteron marriage. Tritium is in a m'enage a trois. Alpha Nucleus has a # grid. Meta state Ne-20 predicts alpha eviction to O-16. Schr"odinger finally prevails, so string theory and Wave Mechanics can prosper.
Studies of dissipative standing shock waves around black holes
Das, Santabrata; Mondal, Soumen
2009-01-01
We investigate the dynamical structure of advective accretion flow around stationary as well as rotating black holes. For a suitable choice of input parameters, such as, accretion rate ($\\dot {\\cal M}$) and angular momentum ($\\lambda$), global accretion solution may include a shock wave. The post shock flow is located at few tens of Schwarzchild radius and it is generally very hot and dense. This successfully mimics the so called Compton cloud which is believed to be responsible for emitting hard radiations. Due to the radiative loss, a significant energy from the accreting matter is removed and the shock moves forward towards the black hole in order to maintain the pressure balance across it. We identify the effective area of the parameter space ($\\dot {\\cal M} - \\lambda$) which allows accretion flows to have some energy dissipation at the shock $(\\Delta {\\cal E})$. As the dissipation is increased, the parameter space is reduced and finally disappears when the dissipation is reached its critical value. The d...
A sound nebula: the origin of the Solar System in the field of a standing sound wave
Beck, Svetlana
2016-01-01
According to the planetary origin conceptual model proposed in this paper, the protosun centre of the pre-solar nebula exploded, resulting in a shock wave that passed through it and then returned to the centre, generating a new explosion and shock wave. Recurrent explosions in the nebula resulted in a spherical standing sound wave, whose antinodes concentrated dust into rotating rings that transformed into planets. The extremely small angular momentum of the Sun and the tilt of its equatorial plane were caused by the asymmetry of the first, most powerful explosion. Differences between inner and outer planets are explained by the migration of solid matter, while the Oort cloud is explained by the division of the pre-solar nebula into a spherical internal nebula and an expanding spherical shell of gas. The proposed conceptual model can also explain the origin and evolution of exoplanetary systems and may be of use in searching for new planets.
The operation of stochastic heating mechanisms in an electromagnetic standing wave configuration
Energy Technology Data Exchange (ETDEWEB)
Gell, Y.; Nakach, R.
1991-10-01
The possibility of the operation of stochastic heating mechanisms of charged particles in a configuration consisting of a left-handed circularly polarized standing electromagnetic wave and a uniform magnetic field, has been studied numerically and theoretically. It is found that such a configuration induces stochasticity, the threshold of which is dependent on two independent parameters, determined by the frequency and the amplitude of the wave and the strength of the magnetic field. From the theoretical analysis, it emerges that the origin of onset of large scale stochasticity is the destabilization of fixed points associated with an equation describing the motion of the particles in an electrostatic-type potential having standing wave characteristics. The comparison of the theoretical predictions with the numerical results is found to be quite satisfactory. Possible applications to realistic plasmas have been discussed.
驻波演示实验研究%The Demonstrating Experiment of Standing Waves
Institute of Scientific and Technical Information of China (English)
柳建国; 陈钺
2015-01-01
详析驻波演示实验,分析驻波稳定出现时,因音叉臂的振幅(即入射波源的振幅)恒为A0,故弦线长必为：L=nλ±λ(n=1,2,3,…),以校正一些资料中取L=nλ(n=1,2,3,…)之误.2122%This paper presents a detailed analysis of the standing waves demonstrating experiment. Through investigating that when the standing waves stability appears, the amplitude of the tuning fork arm (i.e., the amplitude of Incident wave source) identically equals toA0, so the length of the string must be L=nλ±λ (n=1, 2, 3,…), this paper corrects the error that some 2 12 documents make taking L=nλ (n=1, 2, 3,…).
Energy Technology Data Exchange (ETDEWEB)
Yamanoi, K.; Yokotani, Y. [Department of Physics, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581 (Japan); Cui, X. [Graduate School of Information Science and Electrical Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395 (Japan); Yakata, S. [Department of Information Electronics, Fukuoka Institute of Technology, 3-30-1 Wajiro-higashi, Higashi-ku, Fukuoka 811-0295 (Japan); Kimura, T., E-mail: t-kimu@phys.kyushu-u.ac.jp [Department of Physics, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581 (Japan); Research Center for Quantum Nano-Spin Sciences, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581 (Japan)
2015-12-21
We have investigated the stability for the resonant spin precession under the strong microwave magnetic field by a specially developed detection method using the anisotropic magnetoresistance effect. The electrically separated excitation and detection circuits enable us to investigate the influence of the heating effect and the nonuniform spin dynamics independently. The large detecting current is found to induce the field shift of the resonant spectra because of the Joule heating. From the microwave power dependence, we found that the linear response regime for the standing spin wave is larger than that for the ferromagnetic resonance. This robust characteristic of the standing spin wave is an important advantage for the high power operation of the spin-wave device.
A study on the Antarctic circumpolar wave mode-A coexistence system of standing and traveling wave
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The Antarctic circumpolar wave (ACW) has become a focus of the air-sea coupled Southern Ocean study since 1996, when it was discovered as an air-sea coupled interannual signal propagating eastward in the region of the Antarctic Circumpolar Current (ACC). In order to analyze the mechanism of discontinuity along the latitudinal propagation, a new idea that ACW is a system with a traveling wave in the Southern Pacific and Atlantic Ocean and with a concurrent standing wave in the southern Indian Ocean is proposed in this paper. Based on the ideal wave principle, the average wave parameters of ACW is achieved using a non-linear approximation method, by which we find that the standing part and the traveling part possess similar radius frequency, proving their belonging to an integral system. We also give the latitudinal distribution of wave speed with which we could tell the reason for steady propagation during the same period. The spatial distribution of the propagation reveals complex process with variant spatial and temporal scales-The ENSO scale oscillation greatly impacts on the traveling process, while the result at the south of Australia indicates little connection between the Indian Ocean and the Pacific, which may be blocked by the vibration at the west of the Pacific. The advective effect of ACC on the propagation process should be examined clearly through dynamical method.
Liu, Yue-Yang; Zhou, Wu-Xing; Chen, Ke-Qiu
2015-12-02
As an important way to control and manage heat transport, thermal rectification has become an elementary issue in the field of phononics and plays a key role in the designing of thermal devices. Here we investigate systematically the standing wave and the accompanying resonance process in asymmetric nanowires to understand the standing wave itself and its great effect on thermal rectification. Results show that the standing wave is sensitive to both the structural and thermal properties of the material, and its great effect on enhancing the thermal rectification is realized not only by the energy-localization nature of the standing wave, but also by the resonance-caused large amplitude and high energy of the standing wave.
Argonov, Victor
2013-01-01
The wave function of a moderately cold atom in a stationary near-resonant standing light wave delocalizes very fast due to wave packet splitting. However, we show that frequency modulation of the field may suppress packet splitting for some atoms having specific velocities in a narrow range. These atoms remain localized in a small space for a long time. We demonstrate and explain this effect numerically and analytically. Also we demonstrate that modulated field can not only trap, but also cool the atoms. We perform a numerical experiment with a large atomic ensebmble having wide initial velocity and energy distribution. During the experiment, most of atoms leave the wave while trapped atoms have narrow energy distribution
Mitri, F G
2017-02-01
The analysis using the partial-wave series expansion (PWSE) method in spherical coordinates is extended to evaluate the acoustic radiation force experienced by rigid oblate and prolate spheroids centered on the axis of wave propagation of high-order Bessel vortex beams composed of progressive, standing and quasi-standing waves, respectively. A coupled system of linear equations is derived after applying the Neumann boundary condition for an immovable surface in a non-viscous fluid, and solved numerically by matrix inversion after performing a single numerical integration procedure. The system of linear equations depends on the partial-wave index n and the order of the Bessel vortex beam m using truncated but converging PWSEs in the least-squares sense. Numerical results for the radiation force function, which is the radiation force per unit energy density and unit cross-sectional surface, are computed with particular emphasis on the amplitude ratio describing the transition from the progressive to the pure standing waves cases, the aspect ratio (i.e., the ratio of the major axis over the minor axis of the spheroid), the half-cone angle and order of the Bessel vortex beam, as well as the dimensionless size parameter. A generalized expression for the radiation force function is derived for cases encompassing the progressive, standing and quasi-standing waves of Bessel vortex beams. This expression can be reduced to other types of beams/waves such as the zeroth-order Bessel non-vortex beam or the infinite plane wave case by appropriate selection of the beam parameters. The results for progressive waves reveal a tractor beam behavior, characterized by the emergence of an attractive pulling force acting in opposite direction of wave propagation. Moreover, the transition to the quasi-standing and pure standing wave cases shows the acoustical tweezers behavior in dual-beam Bessel vortex beams. Applications in acoustic levitation, particle manipulation and acousto
Ingber, Lester; Nunez, Paul L
2011-02-01
The dynamic behavior of scalp potentials (EEG) is apparently due to some combination of global and local processes with important top-down and bottom-up interactions across spatial scales. In treating global mechanisms, we stress the importance of myelinated axon propagation delays and periodic boundary conditions in the cortical-white matter system, which is topologically close to a spherical shell. By contrast, the proposed local mechanisms are multiscale interactions between cortical columns via short-ranged non-myelinated fibers. A mechanical model consisting of a stretched string with attached nonlinear springs demonstrates the general idea. The string produces standing waves analogous to large-scale coherent EEG observed in some brain states. The attached springs are analogous to the smaller (mesoscopic) scale columnar dynamics. Generally, we expect string displacement and EEG at all scales to result from both global and local phenomena. A statistical mechanics of neocortical interactions (SMNI) calculates oscillatory behavior consistent with typical EEG, within columns, between neighboring columns via short-ranged non-myelinated fibers, across cortical regions via myelinated fibers, and also derives a string equation consistent with the global EEG model.
Theoretical comparison of optical traps created by standing wave and single beam
Zemánek, Pavel; Jonáš, Alexandr; Jákl, Petr; Ježek, Jan; Šerý, Mojmír.; Liška, Miroslav
2003-05-01
We used generalised Lorenz-Mie scattering theory (GLMT) to compare submicron-sized particle optical trapping in a single focused beam and a standing wave. We focus especially on the study of maximal axial trapping force, minimal laser power necessary for confinement, axial trap position, and axial trap stiffness in dependency on trapped sphere radius, refractive index, and Gaussian beam waist size. In the single beam trap (SBT), the range of refractive indices which enable stable trapping depends strongly on the beam waist size (it grows with decreasing waist). On the contrary to the SBT, there are certain sphere sizes (non-trapping radii) that disable sphere confinement in standing wave trap (SWT) for arbitrary value of refractive index. For other sphere radii we show that the SWT enables confinement of high refractive index particle in wider laser beams and provides axial trap stiffness and maximal axial trapping force at least by two orders and one order bigger than in SBT, respectively.
Dynamics of Two-Level Trapped Ion in a Standing Wave Laser in Noncommutative Space
Institute of Scientific and Technical Information of China (English)
YANG Xiao-Xue; WU Ying
2007-01-01
We study the dynamics of a two-level trapped ion in a standing wave electromagnetic field in two-dimensional (2D) noncommutative spaces in the Lamb-Dicke regime under the rotating wave approximation. We obtain the explicit analytical expressions for the energy spectra, energy eigenstates, unitary time evolution operator, atomic inversion, and phonon number operators. The Rabi oscillations, the collapse, and revivals in the average atomic inversion and the average phonon number are explicitly shown to contain the information of the parameter of the space noncommutativity,which sheds light on proposing new schemes based on the dynamics of trappedion to test the noncommutativity.
Thin films and buried interfaces characterization with X-ray standing waves
Energy Technology Data Exchange (ETDEWEB)
Lagomarsino, S. [CNR, Rome (Italy). Istituto Elettronica Stato Solido
1996-09-01
The X-ray standing wave techniques is a powerful, non destructive method to study interfaces at the atomic level. Its basic features are described here together with the peculiarities of its applications to epitaxial films and buried interfaces. As examples of applications, experiments carried out on Si/silicide interfaces, on GaAs/InAs/GaAs buried interfaces and on Si/Ge superlattices are shown.
Acoustic radiation force on a rigid elliptical cylinder in plane (quasi)standing waves
Energy Technology Data Exchange (ETDEWEB)
Mitri, F. G., E-mail: F.G.Mitri@ieee.org [Chevron, Area 52 Technology–ETC, Santa Fe, New Mexico 87508 (United States)
2015-12-07
The acoustic radiation force on a 2D elliptical (non-circular) cylinder centered on the axis of wave propagation of plane quasi-standing and standing waves is derived, based on the partial-wave series expansion (PWSE) method in cylindrical coordinates. A non-dimensional acoustic radiation force function, which is the radiation force per unit length, per characteristic energy density and per unit cross-sectional surface of the ellipse, is defined in terms of the scattering coefficients that are determined by applying the Neumann boundary condition for an immovable surface. A system of linear equations involving a single numerical integration procedure is solved by matrix inversion. Numerical simulations showing the transition from the quasi-standing to the (equi-amplitude) standing wave behaviour are performed with particular emphasis on the aspect ratio a/b, where a and b are the ellipse semi-axes, as well as the dimensionless size parameter kb (where k is the wavenumber), without the restriction to a particular range of frequencies. It is found that at high kb values > 1, the radiation force per length with broadside incidence is larger, whereas the opposite situation occurs in the long-wavelength limit (i.e., kb < 1). The results are particularly relevant in acoustic levitation of elliptical cylinders, the acoustic stabilization of liquid columns in a host medium, acousto-fluidics devices, and other particle dynamics applications to name a few. Moreover, the formalism presented here may be effectively applied to compute the acoustic radiation force on other 2D surfaces of arbitrary shape such as super-ellipses, Chebyshev cylindrical particles, or other non-circular geometries.
Variational Approach to the Orbital Stability of Standing Waves of the Gross-Pitaevskii Equation
Hadj Selem, Fouad
2014-08-26
This paper is concerned with the mathematical analysis of a masssubcritical nonlinear Schrödinger equation arising from fiber optic applications. We show the existence and symmetry of minimizers of the associated constrained variational problem. We also prove the orbital stability of such solutions referred to as standing waves and characterize the associated orbit. In the last section, we illustrate our results with few numerical simulations. © 2014 Springer Basel.
Kudo, R.; Usuki, S.; Takahashi, S.; Takamasu, K.
2012-05-01
The miniaturization of microfabricated structures such as patterned semiconductor wafers continues to advance, thereby increasing the demand for a high-speed, nondestructive and high-resolution measurement technique. We propose a novel optical inspecting method for a microfabricated structure using the standing wave illumination (SWI) shift as such a measurement technique. This method is based on a super-resolution algorithm in which the inspection system's resolution exceeds the diffraction limit by shifting the SWI. Resolution beyond the diffraction limit has previously been studied theoretically and realized experimentally. The influence of various experimental error factors needs to be investigated and calibration needs to be performed accordingly when actual applications that utilize the proposed method are constructed. These error factors include errors related to the phase, pitch and shift step size of the standing wave. Identifying the phase accurately is extremely difficult and greatly influences the resolution result. Hence, the SWI phase was focused upon as an experimental error factor. The effect of the phase difference between the actual experimental standing wave and the computationally set standing wave was investigated using a computer simulation. The periodic structure characteristic of a microfabricated structure was analyzed. The following findings were obtained as a result. The influence of an error is divided into three modes depending on the pitch of the periodic structure: (1) if the pitch is comparatively small, the influence of the error is cancelled, allowing the structure of a sample to be resolved correctly; (2) if the pitch of the structure is from 150 to 350 nm, the reconstructed solution shifts in a transverse direction corresponding to a phase gap of SWI; and (3) if it is a comparatively large pitch, then it is difficult to reconstruct the right pitch. Verification was experimentally attempted for mode (2), and the same result as
Pulsed 5 MeV standing wave electron linac for radiation processing
Auditore, L.; Barnà, R. C.; de Pasquale, D.; Italiano, A.; Trifirò, A.; Trimarchi, M.
2004-03-01
Several modern applications of radiation processing require compact and self-contained electron accelerators. To match these requirements, a 5MeV, 1kW electron linac has been developed at the Dipartimento di Fisica (Università di Messina) and will be described in this paper. This standing wave accelerator, driven by a 3GHz, 2.5MW magnetron generator, has an autofocusing structure and will be used to study several applications of radiation processing.
Simplified description of optical forces acting on a nanoparticle in the Gaussian standing wave
Zemánek, Pavel; Jonáš, Alexandr; Liška, Miroslav
2002-05-01
We study the axial force acting on dielectric spherical particles smaller than the trapping wavelength that are placed in the Gaussian standing wave. We derive analytical formulas for immersed particles with relative refractive indices close to unity and compare them with the numerical results obtained by generalized Lorenz-Mie theory (GLMT). We show that the axial optical force depends periodically on the particle size and that the equilibrium position of the particle alternates between the standing-wave antinodes and nodes. For certain particle sizes, gradient forces from the neighboring antinodes cancel each other and disable particle confinement. Using the GLMT we compare maximum axial trapping forces provided by the Gaussian standing-wave trap (SWT) and single-beam trap (SBT) as a function of particle size, refractive index, and beam waist size. We show that the SWT produces axial forces at least ten times stronger and permits particle confinement in a wider range of refractive indices and beam waists compared with those of the SBT.
Standing wave plasmon modes interact in an antenna-coupled nanowire
Day, Jared; Large, Nicolas; Nordlander, Peter; Halas, Naomi
2015-03-01
In a standing wave optical cavity, the coupling of cavity modes, e.g. through a nonlinear medium, results in a rich variety of nonlinear dynamical phenomena, such as frequency pushing and pulling, mode-locking and pulsing, and modal instabilities. Metallic nanowires of finite length support a hierarchy of longitudinal surface plasmon modes with standing wave properties: the plasmonic analog of a Fabry-Pérot cavity. Here we show that positioning the nanowire within the gap of a plasmonic nanoantenna introduces a passive, hybridization-based coupling of the standing-wave nanowire plasmon modes with the antenna structure, mediating an interaction between the nanowire plasmon modes themselves. Frequency pushing and pulling, and the enhancement and suppression of specific plasmon modes, can be controlled and manipulated by nanoantenna position and shape. Dark-field spectroscopy, CL spectroscopy and imaging, and finite-difference time-domain calculations are performed to investigate these surface plasmon ``drift.'' Near-field coupling of nanoantennas to nanowire optical cavities shows that plasmon hybridization is a powerful strategy for controlling the radiative LDOS of nanowires, and could ultimately enable strategies for active control of emission properties in nanowire-based devices. Work funded by the Welch Foundation (C-1220, C-1222), the NSSEFF (N00244-09-1-0067), the ONR (N00014-10-1-0989), and the NSF (ECCS-1040478, CNS-0821727).
Energy Technology Data Exchange (ETDEWEB)
Kronast, F.; Ovsyannikov, R.; Kaiser, A.; Wiemann, C.; Yang, S.-H.; Locatelli, A.; Burgler, D.E.; Schreiber, R.; Salmassi, F.; Fischer, P.; Durr, H.A.; Schneider, C.M.; Eberhardt, W.; Fadley, C.S.
2008-11-24
We present an extension of conventional laterally resolved soft x-ray photoelectron emission microscopy. A depth resolution along the surface normal down to a few {angstrom} can be achieved by setting up standing x-ray wave fields in a multilayer substrate. The sample is an Ag/Co/Au trilayer, whose first layer has a wedge profile, grown on a Si/MoSi2 multilayer mirror. Tuning the incident x-ray to the mirror Bragg angle we set up standing x-ray wave fields. We demonstrate the resulting depth resolution by imaging the standing wave fields as they move through the trilayer wedge structure.
Structural analysis of bismuth nanowire by X-ray standing wave method
Saito, A; Kurata, T; Maruyama, J; Kuwahara, Y; Aono, M; Miki, K
2003-01-01
Bismuth forms perfect wires without any defects on a clean Si(001) surface. Despite the importance of this self-organized nanowire from the viewpoints of both surface science and device application, an analysis of the internal structure of the wire is quite difficult under the condition of a buried interface. In order to clarify the atomic structure of the wire capped by amorphous Si layers, the three-dimensional bismuth atomic site was measured with respect to the substrate Si lattice by the X-ray standing wave method. The results indicate that the absolute height of Bi atoms is 0.26 A upper from the bulklike Si(004) plane of the Si-dimer layer. For the structure inside the (004) plane, Bi atoms are in the range of +-0.5 A in the [110] direction from an intact Si-dimmer position. This result disagrees with recent reports that were derived from other analytical methods used solely for a clean surface. A new model was proposed and it suggests an influence of a burying effect for the wire structure. (author)
A New Gravitational-wave Signature from Standing Accretion Shock Instability in Supernovae
Kuroda, Takami; Kotake, Kei; Takiwaki, Tomoya
2016-09-01
We present results from fully relativistic three-dimensional core-collapse supernova simulations of a non-rotating 15{M}⊙ star using three different nuclear equations of state (EoSs). From our simulations covering up to ˜350 ms after bounce, we show that the development of the standing accretion shock instability (SASI) differs significantly depending on the stiffness of nuclear EoS. Generally, the SASI activity occurs more vigorously in models with softer EoS. By evaluating the gravitational-wave (GW) emission, we find a new GW signature on top of the previously identified one, in which the typical GW frequency increases with time due to an accumulating accretion to the proto-neutron star (PNS). The newly observed quasi-periodic signal appears in the frequency range from ˜100 to 200 Hz and persists for ˜150 ms before neutrino-driven convection dominates over the SASI. By analyzing the cycle frequency of the SASI sloshing and spiral modes as well as the mass accretion rate to the emission region, we show that the SASI frequency is correlated with the GW frequency. This is because the SASI-induced temporary perturbed mass accretion strikes the PNS surface, leading to the quasi-periodic GW emission. Our results show that the GW signal, which could be a smoking-gun signature of the SASI, is within the detection limits of LIGO, advanced Virgo, and KAGRA for Galactic events.
Kashchenko, Serguey
2015-01-01
This monograph examines in detail models of neural systems described by delay-differential equations. Each element of the medium (neuron) is an oscillator that generates, in standalone mode, short impulses also known as spikes. The book discusses models of synaptic interaction between neurons, which lead to complex oscillatory modes in the system. In addition, it presents a solution to the problem of choosing the parameters of interaction in order to obtain attractors with predetermined structure. These attractors are represented as images encoded in the form of autowaves (wave memory). The target audience primarily comprises researchers and experts in the field, but it will also be beneficial for graduate students.
Directory of Open Access Journals (Sweden)
David I Forrester
2014-09-01
Full Text Available Background Forest ecosystem functioning is strongly influenced by the absorption of photosynthetically active radiation (APAR, and therefore, accurate predictions of APAR are critical for many process-based forest growth models. The Lambert-Beer law can be applied to estimate APAR for simple homogeneous canopies composed of one layer, one species, and no canopy gaps. However, the vertical and horizontal structure of forest canopies is rarely homogeneous. Detailed tree-level models can account for this heterogeneity but these often have high input and computational demands and work on finer temporal and spatial resolutions than required by stand-level growth models. The aim of this study was to test a stand-level light absorption model that can estimate APAR by individual species in mixed-species and multi-layered stands with any degree of canopy openness including open-grown trees to closed canopies. Methods The stand-level model was compared with a detailed tree-level model that has already been tested in mixed-species stands using empirical data. Both models were parameterised for five different forests, including a wide range of species compositions, species proportions, stand densities, crown architectures and canopy structures. Results The stand-level model performed well in all stands except in the stand where extinction coefficients were unusually variable and it appears unlikely that APAR could be predicted in such stands using (tree- or stand-level models that do not allow individuals of a given species to have different extinction coefficients, leaf-area density or analogous parameters. Conclusion This model is parameterised with species-specific information about extinction coefficients and mean crown length, diameter, height and leaf area. It could be used to examine light dynamics in complex canopies and in stand-level growth models.
Probing the polarity of ferroelectric thin films with x-ray standing waves
Energy Technology Data Exchange (ETDEWEB)
Bedzyk, M. J. [Department of Materials Science and Engineering and Materials Research Center, Northwestern University, Evanston, Illinois 60208 (United States); Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Kazimirov, A. [Department of Materials Science and Engineering and Materials Research Center, Northwestern University, Evanston, Illinois 60208 (United States); Marasco, D. L. [Department of Materials Science and Engineering and Materials Research Center, Northwestern University, Evanston, Illinois 60208 (United States); Lee, T.-L. [Department of Materials Science and Engineering and Materials Research Center, Northwestern University, Evanston, Illinois 60208 (United States); Foster, C. M. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Advanced Micro Devices, 5204 East Ben White Boulevard, Austin, Texas 78741 (United States); Bai, G.-R. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Lyman, P. F. [Department of Materials Science and Engineering and Materials Research Center, Northwestern University, Evanston, Illinois 60208 (United States); Keane, D. T. [Department of Materials Science and Engineering and Materials Research Center, Northwestern University, Evanston, Illinois 60208 (United States)
2000-03-15
An x-ray-diffraction method that directly senses the phase of the structure factor is demonstrated and used for determining the local polarity of thin ferroelectric films. This method is based on the excitation of an x-ray standing-wave field inside the film as a result of the interference between the strong incident x-ray wave and the weak kinematically Bragg-diffracted x-ray wave from the film. The method is used to sense the displacements of the Pb and Ti sublattices in single-crystal c-domain PbTiO{sub 3} thin films grown by metal-organic chemical-vapor deposition on SrTiO{sub 3}(001) substrates. (c) 2000 The American Physical Society.
Influence of laser power on deposition of the chromium atomic beam in laser standing wave
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
One-dimensional deposition of collimated Cr atomic beam focused by a near-resonant Gaussian standing-laser field with wavelength of 425.55 nm is examined from particle-optics approach by using an adaptive step size,fourth-order Runge-Kutta type algorithm.The influence of laser power on deposition of atoms in laser standing wave is discussed and the simulative result shows that the FWHM of nanometer stripe is 102 nm and contrast is 2:1 with laser power equal to 3 mW,the FWHM is 1.2 nm and contrast is 32:1 with laser power equal to 16 mW,but with laser power increase,equal to 50 mW,the nonmeter structure forms the multi-crests and exacerbates.
Institute of Scientific and Technical Information of China (English)
ZHANG Wen-Tao; ZHU Bao-Hua
2009-01-01
One-dimensional deposition of a neutral chromium atomic beam focused by a near-resonant Gaussian standing-laser field is discussed by using a fourth-order Runge-Kutta type algorithm. The deposition pattern of neutral chromium atoms in a laser standing wave with different laser power is discussed and the simulation result shows that the full width at half maximum (FWHM) of a nanometer stripe is 115nm and the contrast is 2.5:1 with laser power 3.93mW; the FWHM is 0.Snm and the contrast is 27:1 with laser power 16mW, the optimal laser power; but with laser power increasing to 50mW, the nanometer structure forms multi-crests and the quality worsens quickly with increasing laser power.
Influence of laser power on deposition of the chromium atomic beam in laser standing wave
Institute of Scientific and Technical Information of China (English)
ZHANG WenTao; ZHU BaoHua; ZHANG BaoWu; LI TongBao
2009-01-01
One-dimensional deposition of collimated Cr atomic beam focused by a near-resonant Gaussian standing-laser field with wavelength of 425.55 nm is examined from particle-optics approach by using an adaptive step size, fourth-order Runge-Kutta type algorithm. The influence of laser power on depo-sition of atoms in laser standing wave is discussed and the simulative result shows that the FWHM of nanometer stripe is 102 nm and contrast is 2:1 with laser power equal to 3 mW, the FWHM is 1.2 nm and contrast is 32:1 with laser power equal to 16 mW, but with laser power increase, equal to 50 mW, the nonmeter structure forms the multi-crests and exacerbates.
Shields, C. Wyatt; Cruz, Daniela F.; Ohiri, Korine A.; Yellen, Benjamin B.; Lopez, Gabriel P.
2016-01-01
Acoustophoresis refers to the displacement of suspended objects in response to directional forces from sound energy. Given that the suspended objects must be smaller than the incident wavelength of sound and the width of the fluidic channels are typically tens to hundreds of micrometers across, acoustofluidic devices typically use ultrasonic waves generated from a piezoelectric transducer pulsating at high frequencies (in the megahertz range). At characteristic frequencies that depend on the geometry of the device, it is possible to induce the formation of standing waves that can focus particles along desired fluidic streamlines within a bulk flow. Here, we describe a method for the fabrication of acoustophoretic devices from common materials and clean room equipment. We show representative results for the focusing of particles with positive or negative acoustic contrast factors, which move towards the pressure nodes or antinodes of the standing waves, respectively. These devices offer enormous practical utility for precisely positioning large numbers of microscopic entities (e.g., cells) in stationary or flowing fluids for applications ranging from cytometry to assembly. PMID:27022681
Stand diameter distribution modelling and prediction based on Richards function.
Directory of Open Access Journals (Sweden)
Ai-guo Duan
Full Text Available The objective of this study was to introduce application of the Richards equation on modelling and prediction of stand diameter distribution. The long-term repeated measurement data sets, consisted of 309 diameter frequency distributions from Chinese fir (Cunninghamia lanceolata plantations in the southern China, were used. Also, 150 stands were used as fitting data, the other 159 stands were used for testing. Nonlinear regression method (NRM or maximum likelihood estimates method (MLEM were applied to estimate the parameters of models, and the parameter prediction method (PPM and parameter recovery method (PRM were used to predict the diameter distributions of unknown stands. Four main conclusions were obtained: (1 R distribution presented a more accurate simulation than three-parametric Weibull function; (2 the parameters p, q and r of R distribution proved to be its scale, location and shape parameters, and have a deep relationship with stand characteristics, which means the parameters of R distribution have good theoretical interpretation; (3 the ordinate of inflection point of R distribution has significant relativity with its skewness and kurtosis, and the fitted main distribution range for the cumulative diameter distribution of Chinese fir plantations was 0.4∼0.6; (4 the goodness-of-fit test showed diameter distributions of unknown stands can be well estimated by applying R distribution based on PRM or the combination of PPM and PRM under the condition that only quadratic mean DBH or plus stand age are known, and the non-rejection rates were near 80%, which are higher than the 72.33% non-rejection rate of three-parametric Weibull function based on the combination of PPM and PRM.
Stand diameter distribution modelling and prediction based on Richards function.
Duan, Ai-guo; Zhang, Jian-guo; Zhang, Xiong-qing; He, Cai-yun
2013-01-01
The objective of this study was to introduce application of the Richards equation on modelling and prediction of stand diameter distribution. The long-term repeated measurement data sets, consisted of 309 diameter frequency distributions from Chinese fir (Cunninghamia lanceolata) plantations in the southern China, were used. Also, 150 stands were used as fitting data, the other 159 stands were used for testing. Nonlinear regression method (NRM) or maximum likelihood estimates method (MLEM) were applied to estimate the parameters of models, and the parameter prediction method (PPM) and parameter recovery method (PRM) were used to predict the diameter distributions of unknown stands. Four main conclusions were obtained: (1) R distribution presented a more accurate simulation than three-parametric Weibull function; (2) the parameters p, q and r of R distribution proved to be its scale, location and shape parameters, and have a deep relationship with stand characteristics, which means the parameters of R distribution have good theoretical interpretation; (3) the ordinate of inflection point of R distribution has significant relativity with its skewness and kurtosis, and the fitted main distribution range for the cumulative diameter distribution of Chinese fir plantations was 0.4∼0.6; (4) the goodness-of-fit test showed diameter distributions of unknown stands can be well estimated by applying R distribution based on PRM or the combination of PPM and PRM under the condition that only quadratic mean DBH or plus stand age are known, and the non-rejection rates were near 80%, which are higher than the 72.33% non-rejection rate of three-parametric Weibull function based on the combination of PPM and PRM.
Models for a stand-alone PV system
DEFF Research Database (Denmark)
Hansen, A.D.; Sørensen, Poul Ejnar; Hansen, L.H.;
2001-01-01
Energy Centre Denmark. The study is carried out at Risø National Laboratory with the main purpose to establish a library of simple mathematical models for each individual element of a stand-alone PVsystem, namely solar cells, battery, controller, inverter and load. The models for PV module and battery...... that provides a graphical interface for building models as modular block diagrams. Thenon-linear behaviour of the battery, observed in the measurements, is investigated and compared to the KiBaM model's performance. A set of linear Black box models are estimated based on the battery measurements....... The performance of the best linear Blackbox model is compared to the KiBaM model. A validation of each of the implemented mathematical model is performed by an interactive analysis and comparison between simulation results and measurements, acquired from the stand-alone PV system at Risø....
Cooling and trapping of three-level atoms in a bichromatic standing wave
Pu, H.; Cai, T.; Bigelow, N. P.; Grove, T. T.; Gould, P. L.
1995-02-01
We show that a three-level atom in the cascade configuration can be stably trapped and cooled in one dimension by an intense bichromatic standing wave. At the two-photon resonance, rectified dipole forces result in a deep potential well which can be used to localize the atoms in space. In the vicinity of the rectified potential minimum, the spatial dependence of the dressed state energies can lead to a velocity dependence of the force which produces damping of the atomic motion. Consideration of the heating effects of momentum diffusion indicates that cooling and stable trapping at low temperatures is possible in such a bichromatic field.
Normal incidence X-ray standing wave analysis of thin gold films
Satterley, Christopher J.; Lovelock, Kevin R. J.; Thom, Ian; Dhanak, Vinod R.; Buck, Manfred; Jones, Robert G.
2006-11-01
Normal incidence X-ray standing wave (NIXSW) analysis has been successfully performed on epitaxial gold films on mica substrates using reflection from the (1 1 1) planes parallel to the surface. We show that NIXSW can be used to monitor the decrease in order within the gold film caused by annealing, and the position of sulfur within a monolayer of methyl thiolate (CH 3S-) on the surface. The Au-S layer spacing was found to be 2.54 ± 0.05 Å, in close agreement with previous work on a single crystal system.
Beam dynamics studies and parametric characterization of a standing wave electron linac
Dash, R.; Mondal, J.; Sharma, A.; Mittal, K. C.
2013-07-01
This paper presents the results of electron beam tracking simulations for a 30 MeV standing wave electron linac at Electron Beam Centre Kharghar, Navi Mumbai, India. For the pulsed mode operation of the present linac preferential operation parameters have been determined from the results of beam dynamics studies. This electron accelerator is a general purpose facility for generation of Bremsstrahlung X-rays and neutron scattering experiments. This electron accelerator-based experimental neutron facility will be used for measurement of neutron cross-section (n,γ), (n, xn) and (n, f) reactions at different energies for various materials and material irradiation studies.
Influence of Atomic Motion on a Microlaser in an Optical Standing-Wave Cavity
Institute of Scientific and Technical Information of China (English)
张敬涛; 冯勋立; 张文琦; 徐至展
2002-01-01
We study the microlaser in an optical standing-wave cavity injected with two-level atoms. The results have shown the obvious infIuence of atomic centre-of-mass motion on the microlaser, such as the photon distribution, the linewidth and the frequency shift. It was found that when the momentum of atoms is comparable to that of photons, the influence of atomic motion is dominated and the number of photons in the microlaser can be greatly enhanced, owing to part of the atomic kinetic energy being transferred to the resonator. This work provides a comparison of the related studies on the atomic motion under special assumptions.
Institute of Scientific and Technical Information of China (English)
Shunli Chen; Yuan'an Zhao; Hongbo He; Manda Shao
2011-01-01
Single-pulse and multi-pulse damage behaviors of "standard" (with A/4 stack structure) and "modified" (with reduced standing-wave field) HfO2/SiO2 mirror coatings are investigated using a commercial 50-fs, 800-nm Tksapphire laser system. Precise morphologies of damaged sites display strikingly different features when the samples are subjected to various number of incident pulses, which are explained reasonably by the standing-wave field distribution within the coatings. Meanwhile, the single-pulse laser-induced damage threshold of the "standard" mirror is improved by about 14% while suppressing the normalized electric field intensity at the outmost interface of the HfO2 and SiO2 layers by 37%. To discuss the damage mechanism, a theoretical model based on photoionization, avalanche ionization, and decays of electrons is adopted to simulate the evolution curves of the conduction-band electron density during pulse duration.%@@ Single-pulse and multi-pulse damage behaviors of "standard"(with λ/4 stack structure) and "modified"(with reduced standing-wave field) HfO2/SiO2 mirror coatings are investigated using a commercial 50-fs,800-nm Thsapphire laser system.以Precise morphologies of damaged sites display strikingly different features when the samples are subjected to various number of incident pulses, which are explained reasonably by the standing-wave field distribution within the coatings .
Energy Technology Data Exchange (ETDEWEB)
Dubinin, E.M.; Israelevich, P.L.; Nikolaeva, N.S.; Podgornyi, I.M.; Kutiev, I.
1985-06-01
The fine structure and plasma properties of an auroral disturbance observed with the Intercosmos-Bulgaria-1300 satellite are analyzed. The disturbance was detected in the morning sector of the sky at an altitude of about 850 km in December of 1981. Strong jumps (about 80 mV/m) in the electric and magnetic fields and fluctuations of ion density were detected within the disturbance. The electric and magnetic fields were characterized by a distinct spatial-temporal relationship typical for a standing quasi-monochromatic wave with a frequency of 1 Hz. The ratio of the amplitudes of electric and magnetic fluctuations was equal to the velocity of Alfven waves. The strong parallel component of the electric field (about 30 mV/m) and the large ion density of the fluctuations indicate changes in the plasma properties of the disturbance. The possibility of anomalous resistivity effects in the disturbance is also briefly considered. 23 references.
Statistical sampling and modelling for cork oak and eucalyptus stands
Paulo, M.J.
2002-01-01
This thesis focuses on the use of modern statistical methods to solve problems on sampling, optimal cutting time and agricultural modelling in Portuguese cork oak and eucalyptus stands. The results are contained in five chapters that have been submitted for publication as scientific manuscripts.The
Lipkens, B; Costolo, M; Stevens, A; Rietman, Edward
2010-01-01
The separation of micron-sized bacterial spores (Bacillus cereus) from a steady flow of water through the use of ultrasonic standing waves is demonstrated. An ultrasonic resonator with cross-section of 0.0254 m x 0.0254 m has been designed with a flow inlet and outlet for a water stream that ensures laminar flow conditions into and out of the resonator section of the flow tube. A 0.01905-m diameter PZT-4, nominal 2-MHz transducer is used to generate ultrasonic standing waves in the resonator. The acoustic resonator is 0.0356 m from transducer face to the opposite reflector wall with the acoustic field in a direction orthogonal to the water flow direction. At fixed frequency excitation, spores are concentrated at the stable locations of the acoustic radiation force and trapped in the resonator region. The effect of the transducer voltage and frequency on the efficiency of spore capture in the resonator has been investigated. Successful separation of B. cereus spores from water with typical volume flow rates of...
DEFF Research Database (Denmark)
Jensen, Mads Jakob Herring; Bruus, Henrik
2013-01-01
The recent development in the field of microparticle acoutophoresis in microsystems has led to an increased need for more accurate theoretical predections for the acoustic radiation force on a single microparticle in an ultrasonic standing wave. Increasingly detailed analytical solutions of this ......The recent development in the field of microparticle acoutophoresis in microsystems has led to an increased need for more accurate theoretical predections for the acoustic radiation force on a single microparticle in an ultrasonic standing wave. Increasingly detailed analytical solutions...... of this specific problem can be found in the literature [Settnes ans Bruus, Phys. Rev. E 85, 016327 (2012), and references therein], but none have included the complete contribution from thermoviscous effects. Here, we solve this problem numerically by applying a finite-element method to solve directly the mass...... (continuity), momentum (Navier-Stokes), and energy conservation equations using perturbation theory to second order in the imposed time-harmonic ultrasound field. In a two-stage calculation, we first solve the first-order equations resolving the thermoviscous boundary layer surrounding the microparticle...
Wu, Mu-ying; Ling, Dong-xiong; Ling, Lin; Li, William; Li, Yong-qing
2017-01-01
Optical manipulation and label-free characterization of nanoscale structures open up new possibilities for assembly and control of nanodevices and biomolecules. Optical tweezers integrated with Raman spectroscopy allows analyzing a single trapped particle, but is generally less effective for individual nanoparticles. The main challenge is the weak gradient force on nanoparticles that is insufficient to overcome the destabilizing effect of scattering force and Brownian motion. Here, we present standing-wave Raman tweezers for stable trapping and sensitive characterization of single isolated nanostructures with a low laser power by combining a standing-wave optical trap with confocal Raman spectroscopy. This scheme has stronger intensity gradients and balanced scattering forces, and thus can be used to analyze many nanoparticles that cannot be measured with single-beam Raman tweezers, including individual single-walled carbon nanotubes (SWCNT), graphene flakes, biological particles, SERS-active metal nanoparticles, and high-refractive semiconductor nanoparticles. This would enable sorting and characterization of specific SWCNTs and other nanoparticles based on their increased Raman fingerprints. PMID:28211526
Wu, Mu-Ying; Ling, Dong-Xiong; Ling, Lin; Li, William; Li, Yong-Qing
2017-02-01
Optical manipulation and label-free characterization of nanoscale structures open up new possibilities for assembly and control of nanodevices and biomolecules. Optical tweezers integrated with Raman spectroscopy allows analyzing a single trapped particle, but is generally less effective for individual nanoparticles. The main challenge is the weak gradient force on nanoparticles that is insufficient to overcome the destabilizing effect of scattering force and Brownian motion. Here, we present standing-wave Raman tweezers for stable trapping and sensitive characterization of single isolated nanostructures with a low laser power by combining a standing-wave optical trap with confocal Raman spectroscopy. This scheme has stronger intensity gradients and balanced scattering forces, and thus can be used to analyze many nanoparticles that cannot be measured with single-beam Raman tweezers, including individual single-walled carbon nanotubes (SWCNT), graphene flakes, biological particles, SERS-active metal nanoparticles, and high-refractive semiconductor nanoparticles. This would enable sorting and characterization of specific SWCNTs and other nanoparticles based on their increased Raman fingerprints.
Measurements of the force fields within an acoustic standing wave using holographic optical tweezers
Energy Technology Data Exchange (ETDEWEB)
Bassindale, P. G.; Drinkwater, B. W. [Faculty of Engineering, Queens building, University of Bristol, Bristol BS8 1TR (United Kingdom); Phillips, D. B. [Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Barnes, A. C. [Department of Physics, H.H.Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom)
2014-04-21
Direct measurement of the forces experienced by micro-spheres in an acoustic standing wave device have been obtained using calibrated optical traps generated with holographic optical tweezers. A micro-sphere, which is optically trapped in three dimensions, can be moved through the acoustic device to measure forces acting upon it. When the micro-sphere is subjected to acoustic forces, it's equilibrium position is displaced to a position where the acoustic forces and optical forces are balanced. Once the optical trapping stiffness has been calibrated, observation of this displacement enables a direct measurement of the forces acting upon the micro-sphere. The measured forces are separated into a spatially oscillating component, attributed to the acoustic radiation force, and a constant force, attributed to fluid streaming. As the drive conditions of the acoustic device were varied, oscillating forces (>2.5 pN{sub pp}) and streaming forces (<0.2 pN) were measured. A 5 μm silica micro-sphere was used to characterise a 6.8 MHz standing wave, λ = 220 μm, to a spatial resolution limited by the uncertainty in the positioning of the micro-sphere (here to within 2 nm) and with a force resolution on the order of 10 fN. The results have application in the design and testing of acoustic manipulation devices.
Potential health effects of standing waves generated by low frequency noise.
Ziaran, Stanislav
2013-01-01
The main aim is to present the available updated knowledge regarding the potential health effects of standing waves generated by low frequency noise (LFN) from an open window in a moving car where the negative effects of LFN induced by heating components and/or heating, ventilation and air-conditioning are assessed. Furthermore, the assessment of noise in chosen enclosed spaces, such as rooms, offices, and classrooms, or other LFN sources and their effect on the human being were investigated. These types of noise are responsible for disturbance during relaxation, sleep, mental work, education, and concentration, which may reflect negatively on the comfort and health of the population and on the mental state of people such as scientific staff and students. The assessment points out the most exposed areas, and analyzes the conditions of standing wave generation in these rooms caused by outdoor and/or indoor sources. Measurements were made for three different enclosed spaces (office, flat, and passenger car) and sources (traffic specific noise at intersections, noise induced by pipe vibration, and aerodynamic noise) and their operating conditions. For the detection of LFN, the A-weighted sound pressure level and vibration were measured and a fast Fourier transform analysis was used. The LFN sources are specified and the direct effects on the human are reported. Finally, this paper suggests the possibilities for the assessment of LFN and some possible measures that can be taken to prevent or reduce them.
Two-dimensional manipulation of microparticles using phase-controllable ultrasonic standing waves
Courtney, C. R. P.; Ong, C.-K.; Drinkwater, B. W.; Wilcox, P. D.; Grinenko, A.
2012-05-01
The ability to trap, and then manipulate, micro-particles in a fluid, is of interest as a research tool in the biosciences. Applications include tissue engineering, particle sorting and improving alignment with bio-sensors. This paper relates to the use of phase-controllable counter-propagating ultrasonic waves to generate a standing wave with pressure nodes whose positions are determined by the relative phases of the component counter-propagating travelling waves. As dense (relative to the fluid) particles are forced to nodes in the pressure field this allows particles to be trapped at particular points and moved to arbitrary positions. Counter-propagating waves are generated using pairs of opposing transducers, matched and backed to minimise reflection. Using one pair of transducers allows particles to be trapped and manipulated in one dimension. Using two pairs of transducers, positioned orthogonally, and adjusting the relative phases appropriately, allows trapping and manipulation in two dimensions. The device is shown experimentally to be capable of trapping and manipulating 10-micron-diameter polystyrene beads in two dimensions.
An Experimental Study of Nonlinear Standing Waves in Resonators with Numerical Comparison
Finkbeiner, Joshua R.; Raman, Ganesh; Li, Xiaofan; Steinetz, Bruce M.; Daniels, Christopher; Huff, Dennis (Technical Monitor)
2002-01-01
Lawrenson et. al. [Journal of the Acoustic Society of America, Nov. 1998] described the generation of shock-free high-amplitude pressure waves in closed cavities using large equipment and resonators to produce the reported effects. An attempt is made to generate shock-free high-amplitude pressure waves using relatively small resonators. Ambient air is used as the working fluid. A small cylindrical resonator is tested resulting in the lack of a shocked waveform while a larger model of the same shape produces shock waves. A small conical resonator produces shock-free pressure waves at resonance, but the amplitude of these waves is small. A larger cone resonator model produces shock-free pressure waves of higher amplitude. A large horn-cone resonator also produces shock-free high amplitude pressure waves, A numerical model is used to compare the experimental results to theoretical results. The effects of structural resonances on the production of shock-free high-amplitude pressure waves are discussed, especially concerning difficulties encountered when these resonances were in the frequency ranges of interest. Identifying features of a structural resonance are presented.
Energy Technology Data Exchange (ETDEWEB)
Chen, Hsin-Liang, E-mail: hlchen@iner.gov.tw; Tu, Yen-Cheng; Hsieh, Cheng-Chang; Lin, Deng-Lain [Physics Division, Institute of Nuclear Energy Research (INER), Longtan, Taoyuan County 32546, Taiwan (China); Leou, Keh-Chyang [Department of Engineering and System Science, National Tsing Hua University, 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan (China)
2014-09-14
With the characteristics of higher electron density and lower ion bombardment energy, large-area VHF (very high frequency) plasma enhanced chemical vapor deposition has become an essential manufacturing equipment to improve the production throughput and efficiency of thin film silicon solar cell. However, the combination of high frequency and large electrodes leads to the so-called standing wave effect causing a serious problem for the deposition uniformity of silicon thin film. In order to address this issue, a technique based on the idea of simultaneously launching two standing waves that possess similar amplitudes and are out of phase by 90° in time and space is proposed in this study. A linear plasma reactor with discharge length of 54 cm is tested with two different frequencies including 60 and 80 MHz. The experimental results show that the proposed technique could effectively improve the non-uniformity of VHF plasmas from >±60% when only one standing wave is applied to <±10% once two specific standing waves are launched at the same time. Moreover, in terms of the reactor configuration adopted in this study, in which the standing wave effect along the much shorter dimension can be ignored, the proposed technique is applicable to different frequencies without the need to alter the number and arrangement of power feeding points.
Directory of Open Access Journals (Sweden)
Liang Zeng
2014-07-01
Full Text Available In our pilot studies, we found that many introductory physics textbook illustrations with supporting text for sound standing waves of air columns in open-open, open-closed, and closed-closed pipes inhibit student understanding of sound standing wave phenomena due to student misunderstanding of how air molecules move within these pipes. Based on the construct of meaningful learning from cognitive psychology and semiotics, a quasiexperimental study was conducted to investigate the comparative effectiveness of two alternative approaches to student understanding: a traditional textbook illustration approach versus a newly designed air molecule motion illustration approach. Thirty volunteer students from introductory physics classes were randomly assigned to two groups of 15 each. Both groups were administered a presurvey. Then, group A read the air molecule motion illustration handout, and group B read a traditional textbook illustration handout; both groups were administered postsurveys. Subsequently, the procedure was reversed: group B read the air molecule motion illustration handout and group A read the traditional textbook illustration handout. This was followed by a second postsurvey along with an exit research questionnaire. The study found that the majority of students experienced meaningful learning and stated that they understood sound standing wave phenomena significantly better using the air molecule motion illustration approach. This finding provides a method for physics education researchers to design illustrations for abstract sound standing wave concepts, for publishers to improve their illustrations with supporting text, and for instructors to facilitate deeper learning in their students on sound standing waves.
Nemeth, A.A.; Hulscher, S.J.M.H.; Damme, van R.M.J.
2003-01-01
Sand waves form a prominent regular pattern in the offshore seabeds of sandy shallow seas. A two dimensional vertical (2DV) flow and morphological numerical model describing the behaviour of these sand waves has been developed. The model contains the 2DV shallow water equations, with a free water su
Wave groups in uni-directional surface-wave models
Groesen, van E.
1998-01-01
Uni-directional wave models are used to study wave groups that appear in wave tanks of hydrodynamic laboratories; characteristic for waves in such tanks is that the wave length is rather small, comparable to the depth of the layer. In second-order theory, the resulting Nonlinear Schrödinger (NLS) eq
Development of fast two-dimensional standing wave microscopy using acousto-optic deflectors
Gliko, Olga; Reddy, Duemani G.; Brownell, William E.; Saggau, Peter
2008-02-01
A novel scheme for two-dimensional (2D) standing wave fluorescence microscopy (SWFM) using acousto-optic deflectors (AODs) is proposed. Two laser beams were coupled into an inverted microscope and focused at the back focal plane of the objective lens. The position of each of two beams at the back focal plane was controlled by a pair of AODs. This resulted in two collimated beams that interfered in the focal plane, creating a lateral periodic excitation pattern with variable spacing and orientation. The phase of the standing wave pattern was controlled by phase delay between two RF sinusoidal signals driving the AODs. Nine SW patterns of three different orientations about the optical axis and three different phases were generated. The excitation of the specimen using these patterns will result in a SWFM image with enhanced 2D lateral resolution with a nearly isotropic effective point-spread function. Rotation of the SW pattern relative to specimen and varying the SW phase do not involve any mechanical movements and are only limited by the time required for the acoustic wave to fill the aperture of AOD. The resulting total acquisition time can be as short as 100 Âµs and is only further limited by speed and sensitivity of the employed CCD camera. Therefore, this 2D SWFM can provide a real time imaging of subresolution processes such as docking and fusion of synaptic vesicles. In addition, the combination of 2D SWFM with variable angle total internal reflection (TIR) can extend this scheme to fast microscopy with enhanced three-dimensional (3D) resolution.
Energy Technology Data Exchange (ETDEWEB)
NONE
2001-07-01
Previous to this project a scale model 1:50 of the wave energy converter (WEC) Wave Dragon was built by the Danish Maritime Institute and tested in a wave tank at Aalborg University (AAU). The test programs investigated the movements of the floating structure, mooring forces and forces in the reflectors. The first test was followed by test establishing the efficiency in different sea states. The scale model has also been extensively tested in the EU Joule Craft project JOR-CT98-7027 (Low-Pressure Turbine and Control Equipment for Wave Energy Converters /Wave Dragon) at University College Cork, Hydraulics and Maritime Research Centre, Ireland. The results of the previous model tests have formed the basis for a redesign of the WEC. In this project a reconstruction of the scale 1:50 model and sequential tests of changes to the model geometry and mass distribution parameters will be performed. AAU will make the modifications to the model based on the revised Loewenmark design and perform the tests in their wave tank. Grid connection requirements have been established. A hydro turbine with no movable parts besides the rotor has been developed and a scale model 1:3.5 tested, with a high efficiency over the whole head range. The turbine itself has possibilities for being used in river systems with low head and variable flow, an area of interest for many countries around the world. Finally, a regulation strategy for the turbines has been developed, which is essential for the future deployment of Wave Dragon.The video includes the following: 1. Title, 2. Introduction of the Wave Dragon, 3. Model test series H, Hs = 3 m, Rc = 3 m, 4. Model test series H, Hs = 5 m, Rc = 4 m, 5. Model test series I, Hs = 7 m, Rc = 1.25 m, 6. Model test series I, Hs = 7 m, Rc = 4 m, 7. Rolling title. On this VCD additional versions of the video can be found in the directory 'addvideo' for playing the video on PC's. These versions are: Model testing of Wave Dragon, DVD version
Numerical modeling of water waves
Lin, Pengzhi
2008-01-01
Modelling large-scale wave fields and their interaction with coastal and offshore structures has become much more feasible over the last two decades with increases in computer speeds. Wave modelling can be viewed as an extension of wave theory, a mature and widely published field, applied to practical engineering through the use of computer tools. Information about the various wave models which have been developed is often widely scattered in the literature, and consequently this is one of the first books devoted to wave models and their applications. At the core of the book is an introduction to various types of wave models. For each model, the theoretical assumptions, the application range, and the advantages and limitations are elaborated. The combined use of different wave models from large-scale to local-scale is highlighted with a detailed discussion of the application and matching of boundary conditions. At the same time the book provides a grounding in hydrodynamics, wave theory, and numerical methods...
Models for a stand-alone PV system[Photovoltaic
Energy Technology Data Exchange (ETDEWEB)
Hansen, A.D.; Soerensen, P.; Hansen, L.H.; Bindner, H.
2000-12-01
This report presents a number of models for modelling and simulation of a stand-alone photovoltaic (PV) system with a battery bank verified against a system installed at Risoe National Laboratory. The work has been supported by the Danish Ministry of Energy, as a part of the activities in the Solar Energy Centre Denmark. The study is carried out at Risoe National Laboratory with the main purpose to establish a library of simple mathematical models for each individual element of a stand-alone PV system, namely solar cells, battery, controller, inverter and load. The models for PV module and battery are based on the model descriptions found in the literature. The battery model is developed at UMASS and is known as the Kinetic Battery Model (KiBaM). The other component models in the PV system are based on simple electrical knowledge. The implementation is done using Matlab/Simulink, a simulation program that provides a graphical interface for building models as modular block diagrams. The non-linear behaviour of the battery, observed in the measurements, is investigated and compared to the KiBaM model's performance. A set of linear Black box models are estimated based on the battery measurements. The performance of the best linear Black box model is compared to the KiBaM model. A validation of each of the implemented mathematical model is performed by an interactive analysis and comparison between simulation results and measurements, acquired from the stand-alone PV system at Risoe. (au)
Setiawan, Ikhsan; Achmadin, Wahyu N.; Murti, Prastowo; Nohtomi, Makoto
2016-04-01
Thermoacoustic prime mover is an energy conversion device which converts thermal energy into acoustic work (sound wave). The advantages of this machine are that it can work with air as the working gas and does not produce any exhaust gases, so that it is environmentally friendly. This paper describes an experimental study on a standing wave thermoacoustic prime mover with air as the working gas at various pressures from 0.05 MPa to 0.6 MPa. We found that 0.2 MPa is the optimum pressure which gives the lowest onset temperature difference of 355 °C. This pressure value would be more preferable in harnessing low grade heat sources to power the thermoacoustic prime mover. In addition, we find that the lowest onset temperature difference is obtained when rh /δ k ratio is 2.85, where r h is the hydraulic radius of the stack and δ k is the thermal penetration depth of the gas. Moreover, the pressure amplitude of the sound wave is significantly getting larger from 2.0 kPa to 9.0 kPa as the charged pressure increases from 0.05 MPa up to 0.6 MPa.
Self-organization of clusters by a standing surface acoustic wave
Taillan, Christophe; Combe, Nicolas; Morillo, Joseph
2017-07-01
The diffusion of clusters on a crystalline substrate submitted to a standing surface acoustic wave (StSAW) is studied using molecular dynamics simulations. The distributions of positions of clusters with two, three, and four atoms are calculated and evidence that the wave encourages the presence of the clusters in the vicinity of the maximum transverse displacement field of the substrate. The physical mechanism leading to this self-organization is expected to be equivalent to the one operating for a single adatom, i.e., the displacement of the clusters induced by the longitudinal displacement field of the wave. The detailed shapes of the distributions of positions of clusters are related to the different clusters' orientation and configurations. Finally, the possibility to use a StSAW to self-organize nanostructures during growth is addressed by simulating a deposition process on the substrate. We evidence that the use of a StSAW allows to especially control the spatial repartition of grown nanostructures.
In vitro ultrasound experiments: Standing wave and multiple reflections influence on the outcome.
Secomski, Wojciech; Bilmin, Krzysztof; Kujawska, Tamara; Nowicki, Andrzej; Grieb, Paweł; Lewin, Peter A
2017-05-01
The purpose of this work was to determine the influence of standing waves and possible multiple reflections under the conditions often encountered in examining the effects of ultrasound exposure on the cell cultures in vitro. More specifically, the goal was to quantitatively ascertain the influence of ultrasound exposure under free field (FF) and standing waves (SW) and multiple reflections (MR) conditions (SWMR) on the biological endpoint (50% cell necrosis). Such information would help in designing the experiments, in which the geometry of the container with biological tissue may prevent FF conditions to be established and in which the ultrasound generated temperature elevation is undesirable. This goal was accomplished by performing systematic, side-by-side experiments in vitro with C6 rat glioma cancer cells using 12 well and 96 well plates. It was determined that to obtain 50% of cell viability using the 12 well plates, the spatial average, temporal average (ISATA) intensities of 0.32W/cm(2) and 5.89W/cm(2) were needed under SWMR and FF conditions, respectively. For 96 well plates the results were 0.80W/cm(2) and 2.86W/cm(2) respectively. The corresponding, hydrophone measured pRMS maximum pressure amplitude values, were 0.71MPa, 0.75MPa, 0.75MPa and 0.73MPa, respectively. These results suggest that pRMS pressure amplitude was independent of the measurement set-up geometry and hence could be used to predict the cells' mortality threshold under any in vitro experimental conditions or even as a starting point for (pre-clinical) in vivo tests. The described procedure of the hydrophone measurements of the pRMS maximum pressure amplitude at the λ/2 distance (here 0.75mm) from the cell's level at the bottom of the dish or plate provides the guideline allowing the difference between the FF and SWMR conditions to be determined in any experimental setup. The outcome of the measurements also indicates that SWMR exposure might be useful at any ultrasound assisted
Amor, Rumelo; Amos, William Bradshaw; McConnell, Gail
2014-01-01
Standing-wave excitation of fluorescence is highly desirable in optical microscopy because it improves the axial resolution. We demonstrate here that multiplanar excitation of fluorescence by a standing wave can be produced in a single-spot laser scanning microscope by placing a plane reflector close to the specimen. We report that the relative intensities in each plane of excitation depend on the Stokes shift of the fluorochrome. We show by the use of dyes specific for the cell membrane how standing-wave excitation can be exploited to generate precise contour maps of the surface membrane of red blood cells, with an axial resolution of ~90 nm. The method, which requires only the addition of a plane mirror to an existing confocal laser scanning microscope, may well prove useful in studying diseases which involve the red cell membrane, such as malaria.
Bashinov, A V; Kim, A V
2016-01-01
We present a comprehensive analysis of longitudinal particle drifting in a standing circularly polarized wave at extreme intensities when quantum radiation reaction (RR) effects should be accounted for. To get an insight into the physics of this phenomenon we made a comparative study considering the RR force in the Landau-Lifshitz or quantum-corrected form, including the case of photon emission stochasticity. It is shown that the cases of circular and linear polarization are qualitatively different. Moreover, specific features of particle dynamics have a strong impact on spatial structures of the electron-positron ($e^-e^+$) density created in vacuum through quantum electrodynamic (QED) cascades in counter-propagating laser pulses. 3D PIC modeling accounting for QED effects confirms realization of different pair plasma structures.
Mitri, F G
2016-01-01
The analysis using the partial-wave series expansion (PWSE) method in spherical coordinates is extended to evaluate the acoustic radiation force experienced by rigid oblate and prolate spheroids centered on the axis of wave propagation of high-order Bessel vortex beams composed of progressive, standing and quasi-standing waves, respectively. A coupled system of linear equations is derived after applying the Neumann boundary condition for an immovable surface in a non-viscous fluid, and solved numerically by matrix inversion after performing a single numerical integration procedure. The system of linear equations depends on the partial-wave index n and the order of the Bessel vortex beam m using truncated but converging PWSEs in the least-squares sense. Numerical results for the radiation force function, which is the radiation force per unit energy density and unit cross-sectional surface, are computed with particular emphasis on the amplitude ratio describing the transition from the progressive to the pure st...
Institute of Scientific and Technical Information of China (English)
杨文星; 陈爱喜
2011-01-01
An alternative scheme is proposed for one-step generation of multiparticle cluster state with trapped ions in thermal motion. In this scheme, the ions are simultaneously illuminated by a standing-wave laser tuned to the carrier. During the operations, the vibrational mode is virtually excited, thus the quantum operations are insensitive to the heating. It is shown that the high fidelity multiparticle entanglement could be generated in just one step even including the small fluctuations of parameters. In addition, the ion does not need to be exactly positioned at the node of the standing wave, which is also important from the viewpoint of experiment.
Matsutani, Akihiro; Takada, Ayako
2016-11-01
We demonstrate a microchannel-free collection method at nodes of liquid standing waves by the vertical vibration of a suspension including yeast cells. The pattern formation of the collection of cells using standing waves in a suspension was investigated by varying the frequency and waveform of vibrations. The single-cell isolation of yeast cells was achieved using a microenclosure array set at the nodes. In addition, we succeeded in the microchannel-free collection of yeast cells in a suspension, where patterns were formed by tapping vibration. The proposed technique is very simple and we believe that it will be useful for single-cell analysis and investigation.
Physical design and cooling test of C-band standing wave accelerating tube
Institute of Scientific and Technical Information of China (English)
Bai Wei; Xu Zhou; Jin Xiao; Li Ming
2006-01-01
The physical design and cooling test of a C-band 2MeV standing wave (SW) accelerating tube are described in this paper. The designed accelerating structure consists of 3-cell buncher and 4-cell accelerating section with a total length of about 163mm , excited with 1MW magnetron. Dynamic simulation presents that about 150mA beam pulse current and 30% capture efficiency can be achieved. By means of nonlinear Gauss fit on electron transverse distribution, the diameter of beam spot FWHM (full width at half maximum of density distribution) is about 0.55mm. Cooling test results of the accelerating tube show that frequencies of cavities are tuned to 5527MHz and the field distribution of bunching section is about 3:9:10.
Energy Technology Data Exchange (ETDEWEB)
Li, Xinbo; Jiang, Hai; Jiao, Xiaoyang; Zhang, Kai; Liu, Guojun; Liu, Jianfang [Jilin University, Changchun (China)
2015-05-15
Based on the lever principle, a novel measurement method for the standing wave levitation force is investigated and the measurement device is developed. The relative levitation force was simulated by MATLAB software, from which the relative levitation force distribution and the curves of relative levitation force in vertical and horizontal directions were obtained. To verify the rationale of the measurement method, a series of experiments were carried out with the designed measurement device system. The levitation force distribution and the curves of levitation force in vertical and horizontal directions were also obtained from the experiment. Comparing the experimental results with the simulation, the levitation force distribution situation from the experimental results and the simulation is identical.
Bazou, Despina; Kearney, Roisin; Mansergh, Fiona; Bourdon, Celine; Farrar, Jane; Wride, Michael
2011-01-01
In the present paper, gene expression analysis of mouse embryonic stem (ES) cells levitated in a novel ultrasound standing wave trap (USWT) (Bazou et al. 2005a) at variable acoustic pressures (0.08–0.85 MPa) and times (5–60 min) was performed. Our results showed that levitation of ES cells at the highest employed acoustic pressure for 60 min does not modify gene expression and cells maintain their pluripotency. Embryoid bodies (EBs) also expressed the early and late neural differentiation markers, which were also unaffected by the acoustic field. Our results suggest that the ultrasound trap microenvironment is minimally invasive as the biologic consequences of ES cell replication and EB differentiation proceed without significantly affecting gene expression. The technique holds great promise in safe cell manipulation techniques for a variety of applications including tissue engineering and regenerative medicine. (E-mail: Bazoud@tcd.ie) PMID:21208732
Temporal coupled mode theory of standing wave resonant cavities for infrared photodetection.
Lesmanne, Emeline; De Lamaestre, Roch Espiau; Fowler, David; Boutami, Salim; Badano, Giacomo
2015-03-23
Standing wave resonating cavities have been proposed in the past to increase the performance of infrared detectors by minimizing the volume of photogeneration, hence the noise, while maintaining the same quantum efficiency. We present an approach based on the temporal coupled mode theory to explain their behavior and limitations. If the ratio of the imaginary part of the absorber's dielectric function to the index of the incident medium ε″(d)/n₀ is larger than 1.4, then the absorption cross section σ(a) can attain its maximum value, which for an isolated cavity is approximately 2λ/π. Besides, for σ(a) to exceed the cavity width, the incident medium refractive index must be close to unity. Metallic loss is negligible in the infrared, making those resonators suitable for integration in infrared photodetectors.
Cavity-enhanced laser cooling of solid-state materials in a standing-wave cavity
Institute of Scientific and Technical Information of China (English)
Youhua Jia; Biao Zhong; Jianping Yin
2008-01-01
We propose a new method to cool the Yba+-doped ZBLANP glass in a standing-wave cavity. There are two advantages of this cavity-enhanced technique: the pumping power is greatly enhanced and the absorption of the cooling material is greatly increased. We introduce the basic principle of the cavity-enhanced laser cooling and discuss the cooling effect of a solid-state material in a cavity. From the theoretical study, it is found that the laser cooling effect is strongly dependent on the reflectivity of the cavity mirrors, the length of the solid material, the surface scattering of the material, and so on. Some optimal parameters for efficient laser cooling are obtained.
Wave Generation in Physical Models
DEFF Research Database (Denmark)
Andersen, Thomas Lykke; Frigaard, Peter
The present book describes the most important aspects of wave generation techniques in physical models. Moreover, the book serves as technical documentation for the wave generation software AwaSys 6, cf. Aalborg University (2012). In addition to the two main authors also Tue Hald and Michael...
Flow under standing waves Part 2. Scour and deposition in front of breakwaters
DEFF Research Database (Denmark)
Gislason, Kjartan; Fredsøe, Jørgen; Sumer, B. Mutlu
2009-01-01
A 3-D general purpose Navier-Stokes solver was used to calculate the 2-D flow in front of the breakwater. The k-omega, SST (shear-stress transport) model was selected as the turbulence model. The morphologic model of the present code couples the flow solution with a sediment transport description...... and routines for, updating the computational mesh based on the mass balance of sediment. Laboratory experiments of scour also were conducted in a wave flume to obtain data for model verification. Both in the numerical simulations and in the laboratory experiment, two kinds of breakwaters were used: A vertical......-wall breakwater; and a sloping-wall breakwater (Slope: 1:1.5). Numerically obtained scour-deposition profiles were compared with the experiments. The numerical results show that the equilibrium scour depth normalized by the wave height decreases with increasing water-depth-to-wave-length ratio. Although...
Institute of Scientific and Technical Information of China (English)
罗志强; 陈志敏
2013-01-01
A three-dimensional (3D) predictor-corrector finite difference method for standing wave is developed. It is applied to solve the 3D nonlinear potential flow equa-tions with a free surface. The 3D irregular tank is mapped onto a fixed cubic tank through the proper coordinate transform schemes. The cubic tank is distributed by the staggered meshgrid, and the staggered meshgrid is used to denote the variables of the flow field. The predictor-corrector finite difference method is given to develop the difference equa-tions of the dynamic boundary equation and kinematic boundary equation. Experimental results show that, using the finite difference method of the predictor-corrector scheme, the numerical solutions agree well with the published results. The wave profiles of the standing wave with different amplitudes and wave lengths are studied. The numerical solutions are also analyzed and presented graphically.
Abnormal Waves Modelled as Second-order Conditional Waves
DEFF Research Database (Denmark)
Jensen, Jørgen Juncher
2005-01-01
The paper presents results for the expected second order short-crested wave conditional of a given wave crest at a specific point in time and space. The analysis is based on the second order Sharma and Dean shallow water wave theory. Numerical results showing the importance of the spectral density......, the water depth and the directional spreading on the conditional mean wave profile are presented. Application of conditional waves to model and explain abnormal waves, e.g. the well-known New Year Wave measured at the Draupner platform January 1st 1995, is discussed. Whereas the wave profile can be modelled...... quite well by the second order conditional wave including directional spreading and finite water depth the probability to encounter such a wave is still, however, extremely rare. The use of the second order conditional wave as initial condition to a fully non-linear three-dimensional analysis...
Near Shore Wave Modeling and applications to wave energy estimation
Zodiatis, G.; Galanis, G.; Hayes, D.; Nikolaidis, A.; Kalogeri, C.; Adam, A.; Kallos, G.; Georgiou, G.
2012-04-01
The estimation of the wave energy potential at the European coastline is receiving increased attention the last years as a result of the adaptation of novel policies in the energy market, the concernsfor global warming and the nuclear energy security problems. Within this framework, numerical wave modeling systems keep a primary role in the accurate description of wave climate and microclimate that is a prerequisite for any wave energy assessment study. In the present work two of the most popular wave models are used for the estimation of the wave parameters at the coastline of Cyprus: The latest parallel version of the wave model WAM (ECMWF version), which employs new parameterization of shallow water effects, and the SWAN model, classically used for near shore wave simulations. The results obtained from the wave models near shores are studied by an energy estimation point of view: The wave parameters that mainly affect the energy temporal and spatial distribution, that is the significant wave height and the mean wave period, are statistically analyzed,focusing onpossible different aspects captured by the two models. Moreover, the wave spectrum distribution prevailing in different areas are discussed contributing, in this way, to the wave energy assessmentin the area. This work is a part of two European projects focusing on the estimation of the wave energy distribution around Europe: The MARINA platform (http://www.marina-platform.info/ index.aspx) and the Ewave (http://www.oceanography.ucy.ac.cy/ewave/) projects.
Evidence of standing waves during a Pi2 pulsation event observed on Cluster
Directory of Open Access Journals (Sweden)
A. B. Collier
2006-10-01
Full Text Available Observations of Pi2 pulsations at middle and low latitudes have been explained in terms of cavity mode resonances, whereas transients associated with field-aligned currents appear to be responsible for the high latitude Pi2 signature.
Data from Cluster are used to study a Pi2 event observed at 18:09 UTC on 21 January 2003, when three of the satellites were within the plasmasphere (L=4.7, 4.5 and 4.6 while the fourth was on the plasmapause or in the plasmatrough (L=6.6. Simultaneous pulsations at ground observatories and the injection of particles at geosynchronous orbit corroborate the occurrence of a substorm.
Evidence of a cavity mode resonance is established by considering the phase relationship between the orthogonal electric and magnetic field components associated with radial and field-aligned standing waves. The relative phase between satellites located on either side of the geomagnetic equator indicates that the field-aligned oscillation is an odd harmonic. Finite azimuthal Poynting flux suggests that the cavity is effectively open ended and the azimuthal wave number is estimated as m~13.5.
Watt-Meyer, O.; Kushner, P. J.
2015-12-01
The winter season over North America during 2013/14 was dominated by a persistent ridge-trough that brought warm and dry conditions to the southwestern U.S., and markedly cold temperatures to central and eastern North America [Wang et al., 2014; Hartmann, 2015]. In addition, several cold air outbreaks occurred during the winter season, the strongest of which was around 7 January 2014 and led to minimum daily temperature records being set at many weather stations including Atlanta, Austin, Chicago and New York [Screen et al., in press]. This study uses a novel decomposition of wave variability into standing and travelling components [Watt-Meyer and Kushner, 2015] to diagnose the anomalous circulation of the 2013/14 winter season. This spectral decomposition is an improvement on previous methods because it explicitly accounts for the covariance between standing and travelling waves, and because the real-space components of the signal can be easily reconstructed. An index representing the ridge-trough dipole is computed using mid-tropospheric heights and shown to be well correlated with surface temperatures over central and eastern North America. The contributions to this dipole index from standing waves, westward travelling waves, and eastward travelling waves are calculated. The analysis demonstrates that the cold air outbreak of 7 January 2014 was driven by a synoptic wave of record breaking amplitude intensifying a persistent background amplification of the typical ridge-trough structure seen during North American winter.
Inverter and Motor Model Adaptation at Stand-Still Using Reference Voltages and Measured Currents
DEFF Research Database (Denmark)
Rasmussen, Henrik; Tønnes, M.; Knudsen, Morten
1995-01-01
A model adaptation method for estimating the electrical parameters of an induction motor at stand-still is described.......A model adaptation method for estimating the electrical parameters of an induction motor at stand-still is described....
A simple model for sizing stand alone photovoltaic systems
Energy Technology Data Exchange (ETDEWEB)
Sidrach-de-Cardona, M. [Departamento Fisica Aplicada II, ETSI Informatica, Universidad de Malaga, 29071 Malaga (Spain); Mora Lopez, Ll. [Departamento Lenguajes y C. Computacion, ETSI Informatica, Universidad de Malaga, 29071 Malaga (Spain)
1998-08-24
We consider a general model for sizing a stand-alone photovoltaic system, using as energy input data the information available in any radiation atlas. The parameters of the model are estimated by multivariate linear regression. The results obtained from a numerical sizing method were used as initial input data to fit the model. The expression proposed allows us to determine the photovoltaic array size, with a coefficient of determination ranging from 0.94 to 0.98. System parameters and mean monthly values for daily global radiation on the solar modules surface are taken as independent variables in the model. It is also shown that the proposed model can be used with the same accuracy for other locations not considered in the estimation of the model
Chen, Hsin-Liang; Tu, Yen-Cheng; Hsieh, Cheng-Chang; Lin, Deng-Lain; Leou, Keh-Chyang
2014-09-01
With the characteristics of higher electron density and lower ion bombardment energy, large-area VHF (very high frequency) plasma enhanced chemical vapor deposition has become an essential manufacturing equipment to improve the production throughput and efficiency of thin film silicon solar cell. However, the combination of high frequency and large electrodes leads to the so-called standing wave effect causing a serious problem for the deposition uniformity of silicon thin film. In order to address this issue, a technique based on the idea of simultaneously launching two standing waves that possess similar amplitudes and are out of phase by 90° in time and space is proposed in this study. A linear plasma reactor with discharge length of 54 cm is tested with two different frequencies including 60 and 80 MHz. The experimental results show that the proposed technique could effectively improve the non-uniformity of VHF plasmas from >±60% when only one standing wave is applied to reactor configuration adopted in this study, in which the standing wave effect along the much shorter dimension can be ignored, the proposed technique is applicable to different frequencies without the need to alter the number and arrangement of power feeding points.
Dynamic Modelling And Simulation Of Sit To Stand On Simmechanics
Directory of Open Access Journals (Sweden)
Kasım Serbest
2012-06-01
Full Text Available In this study, simulation of developed an inverse dynamics model to analysis of sit to stand which is the one of the essential tasks of daily function was carried out. The human body has been composed as a total of 6 rigid- open loop-body model consisted of a foot, a leg, a thigh, a trunk, an arm and a forearm using SimMechanics (2.7.1. Motion of the subject whose anthropometric properties transferred to the SimMechanics model has been viewed with a video camera to drive the joints. The reaction forces when the subject placed on reflective markers performs movements (standing from 20 cm, 40 cm and 50 cm height have been measured by the force plate. It has been benefited by codes created with MATLAB (7.6.0 to digitize monitored the two- dimensional movements. The calculated vertical ground reaction forces, as a result of the simulation of the inverse dynamics model on SimMechanics, have been compared with the measured vertical ground reaction forces and it has been observed the results are close to each other when the subject performs the movements. This study has been shown that SimMechanics was successful to analyse human movements. It is possible to perform different analysis thanks to its flexible structure of the model.
Modeling fluctuations in scattered waves
Jakeman, E
2006-01-01
Fluctuations in scattered waves limit the performance of imaging and remote sensing systems that operate on all wavelengths of the electromagnetic spectrum. To better understand these fluctuations, Modeling Fluctuations in Scattered Waves provides a practical guide to the phenomenology, mathematics, and simulation of non-Gaussian noise models and discusses how they can be used to characterize the statistics of scattered waves.Through their discussion of mathematical models, the authors demonstrate the development of new sensing techniques as well as offer intelligent choices that can be made for system analysis. Using experimental results and numerical simulation, the book illustrates the properties and applications of these models. The first two chapters introduce statistical tools and the properties of Gaussian noise, including results on phase statistics. The following chapters describe Gaussian processes and the random walk model, address multiple scattering effects and propagation through an extended med...
Extraction of olive oil assisted by high-frequency ultrasound standing waves.
Juliano, Pablo; Bainczyk, Fabian; Swiergon, Piotr; Supriyatna, Made Ian Maheswara; Guillaume, Claudia; Ravetti, Leandro; Canamasas, Pablo; Cravotto, Giancarlo; Xu, Xin-Qing
2017-09-01
High-frequency ultrasound standing waves (megasonics) have been demonstrated to enhance oil separation in the palm oil process at an industrial level. This work investigated the application of megasonics in the olive oil process on laboratory and pilot scale levels. Sound pressure level and cavitational yield distribution were characterised with hydrophones and luminol to determine associated physical and sonochemical effects inside the reactor. The effect of water addition (0%, 15%, and 30%), megasonic power levels (0%, 50%, and 100%), and malaxation time (10min, 30min, and 50min) was evaluated using response surface methodology (RSM) in a 700g batch extraction process. The RSM showed that the effect of the megasonic treatment (585kHz) in the presence of a reflector is more prominent at longer malaxation time (50min) and at higher water addition (30%) levels post-malaxation. Longer megasonic treatment of the malaxed paste (up to 15min; 220kJ/kg) increased oil extractability by up to 3.2%. When treating the malaxed paste with the same specific energy, higher oil extractability was obtained with longer treatments and low megasonic power levels in comparison to higher power levels and shorter times. Megasonic treatment of the paste before malaxation (585kHz, 10min, 146kJ/kg) and no water addition provided an increase in oil extractability of up to 3.8% with respect to the non-sonicated control. A double sonication intervention, before and after malaxation, using low (40kHz) and high (585kHz) frequency, respectively, provided up to 2.4% increase in oil extractability. A megasonic intervention post-malaxation (400 and 600kHz, 57-67min, 18-21kJ/kg) on a pilot scale using early-harvest olive fruits resulted in up to 1.7% extra oil extractability. Oil extracted under a high sonication frequency (free radical production regime) did not impact on olive oil quality parameters at reactor characterisation levels. Megasonic standing wave forces can enhance olive oil separation
Numerical Modelling of Wave Run-Up: Regular Waves
DEFF Research Database (Denmark)
Ramirez, Jorge; Frigaard, Peter; Andersen, Thomas Lykke;
2011-01-01
Wave loads are important in problems related to offshore structure, such as wave run-up, slamming. The computation of such wave problems are carried out by CFD models. This paper presents one model, NS3, which solve 3D Navier-Stokes equations and use Volume of Fluid (VOF) method to treat the free...
Numerical Modelling of Wave Run-Up: Regular Waves
DEFF Research Database (Denmark)
Ramirez, Jorge; Frigaard, Peter; Andersen, Thomas Lykke
2011-01-01
Wave loads are important in problems related to offshore structure, such as wave run-up, slamming. The computation of such wave problems are carried out by CFD models. This paper presents one model, NS3, which solve 3D Navier-Stokes equations and use Volume of Fluid (VOF) method to treat the free...
Forest evaporation models: Relationships between stand growth and evaporation
CSIR Research Space (South Africa)
Le Maitre, David C
1997-06-01
Full Text Available The relationships between forest stand structure, growth and evaporation were analysed to determine whether forest evaporation can be estimated from stand growth data. This approach permits rapid assessment of the potential impacts of afforestation...
Sriphutkiat, Yannapol; Zhou, Yufeng
2017-01-07
Accumulation of particles in a high concentration on a microchannel wall is a common phenomenon in a colloidal fluid. Gradual accumulation/deposition of particles can eventually obstruct the fluid flow and lead to clogging, which seriously affects the accuracy and reliability of nozzle-based printing and causes damage to the nozzle. Particle accumulation in a 100 μm microchannel was investigated by light microscopy, and its area growth in an exponential format was used to quantify this phenomenon. The effects of the constriction angle and alginate concentration on particle accumulation were also studied. In order to reduce the clogging problem, an acoustic method was proposed and evaluated here. Numerical simulation was first conducted to predict the acoustic radiation force on the particles in the fluid with different viscosities. Interdigital transducers (IDTs) were fabricated on the LiNbO₃ wafer to produce standing surface acoustic waves (SSAW) in the microchannel. It was found that the actuation of SSAW can reduce the accumulation area in the microchannel by 2 to 3.7-fold. In summary, the particle accumulation becomes significant with the increase of the constriction angle and fluid viscosity. The SSAW can effectively reduce the particle accumulation and postpone clogging.
Commercialization of an S-band standing-wave electron accelerator for industrial applications
Moon, Jin-Hyeok; Kwak, Gyeong-Il; Han, Jae-Ik; Lee, Gyu-Baek; Jeon, Seong-Hwan; Kim, Jae-Young; Hwang, Cheol-Bin; Lee, Gi-Yong; Kim, Young-Man; Park, Sung-Ju
2016-09-01
An electron accelerator system has been developed for use in industrial, as well as possible medical, applications. Based on our experiences achieved during prototype system development and various electron beam acceleration tests, we have built a stable and compact system for sales purposes. We have integrated a self-developed accelerating cavity, an E-gun pulse driver, a radio-frequency (RF) power system, a vacuum system, a cooling system, etc. into a frame with a size of 1800 × 1000 × 1500 mm3. The accelerating structure is a side-coupled standing-wave type operating in the π/2 mode (tuned to~3 GHz). The RF power is provided by using a magnetron driven by a solid-state modulator. The electron gun is a triode type with a dispenser cathode (diameter of 11 mm). The system is capable of delivering a maximum 900-W average electron beam power with tight focusing at the target. Until now, we have performed various electron beam tests and X-ray beam tests after having built the system, have completed the beam assessment for commercializations, and have been preparing full-fledged sales activity. This article reports on our system development processes and on some of our early test results for commercializations.
Forward Modelling of Standing Kink Modes in Coronal Loops II. Applications
Yuan, Ding
2016-01-01
Magnetohydrodynamic waves are believed to play a significant role in coronal heating, and could be used for remote diagnostics of solar plasma. Both the heating and diagnostic applications rely on a correct inversion (or backward modelling) of the observables into the thermal and magnetic structures of the plasma. However, owing to the limited availability of observables, this is an ill-posed issue. Forward Modelling is to establish a plausible mapping of plasma structuring into observables. In this study, we set up forward models of standing kink modes in coronal loops and simulate optically thin emissions in the extreme ultraviolet bandpasses, and then adjust plasma parameters and viewing angles to match three events of transverse loop oscillations observed by the Solar Dynamics Observatory/Atmospheric Imaging Assembly. We demonstrate that forward models could be effectively used to identify the oscillation overtone and polarization, to reproduce the general profile of oscillation amplitude and phase, and t...
Tango waves in a bidomain model of fertilization calcium waves
Li, Yue-Xian
2003-12-01
Fertilization of an egg cell is marked by one or several Ca 2+ waves that travel across the intra-cellular space, called fertilization Ca 2+ waves. Patterns of Ca 2+ waves observed in mature or immature oocytes include traveling fronts and pulses as well as concentric and spiral waves. These patterns have been studied in other excitable media in physical, chemical, and biological systems. Here, we report the discovery of a new wave phenomenon in the numerical study of a bidomain model of fertilization Ca 2+ waves. This wave is a front that propagates in a back-and-forth manner that resembles the movement of tango dancers, thus is called a tango wave. When the medium is excitable, a forward-moving tango wave can generate traveling pulses that propagate down the space without reversal. The study shows that the occurrence of tango waves is related to spatial inhomogeneity in the local dynamics. This is tested and confirmed by simulating similar waves in a medium with stationary spatial inhomogeneity. Similar waves are also obtained in a FitzHugh-Nagumo system with a linear spatial ramp. In both the bidomain model of Ca 2+ waves and the FitzHugh-Nagumo system, the front is stable when the slope of a linear ramp is large. As the slope decreases beyond a critical value, front oscillations occur. The study shows that tango waves facilitate the dispersion of localized Ca 2+. Key features of the bidomain model underlying the occurrence of tango waves are revealed. These features are commonly found in egg cells of a variety of species. Thus, we predict that tango waves can occur in real egg cells provided that a slowly varying inhomogeneity does occur following the sperm entry. The observation of tango wave-like waves in nemertean worm and ascidian eggs seems to support such a prediction.
Large-Scale Forest Modeling: Deducing Stand Density from Inventory Data
Directory of Open Access Journals (Sweden)
Oskar Franklin
2012-01-01
Full Text Available While effects of thinning and natural disturbances on stand density play a central role for forest growth, their representation in large-scale studies is restricted by both model and data availability. Here a forest growth model was combined with a newly developed generic thinning model to estimate stand density and site productivity based on widely available inventory data (tree species, age class, volume, and increment. The combined model successfully coupled biomass, increment, and stand closure (=stand density/self-thinning limited stand density, as indicated by cross-validation against European-wide inventory data. The improvement in model performance attained by including variable stand closure among age cohorts compared to a fixed closure suggests that stand closure is an important parameter for accurate forest growth modeling also at large scales.
Rogue waves in a wave tank: experiments and modeling
Directory of Open Access Journals (Sweden)
A. Lechuga
2013-07-01
Full Text Available In past decades theoretical studies have been carried out with the double aim of improving the knowledge of rogue wave main characteristics and of attempting to predict its sudden appearance. As an effort on this topic we tried the generation of rogue waves in a water wave tank using a symmetric spectrum (Akhmediev et al., 2011a as input on the wave maker. To go on further the next step has been to apply a theoretical model to the envelope of these waves. After some considerations the best model has been an analogue of the Ginzburg–Landau equation.
Linking individual-tree and whole-stand models for forest growth and yield prediction
Directory of Open Access Journals (Sweden)
Quang V Cao
2014-10-01
Full Text Available Background Different types of growth and yield models provide essential information for making informed decisions on how to manage forests. Whole-stand models often provide well-behaved outputs at the stand level, but lack information on stand structures. Detailed information from individual-tree models and size-class models typically suffers from accumulation of errors. The disaggregation method, in assuming that predictions from a whole-stand model are reliable, partitions these outputs to individual trees. On the other hand, the combination method seeks to improve stand-level predictions from both whole-stand and individual-tree models by combining them. Methods Data from 100 plots randomly selected from the Southwide Seed Source Study of loblolly pine (Pinus taeda L. were used to evaluate the unadjusted individual-tree model against the disaggregation and combination methods. Results Compared to the whole-stand model, the combination method did not show improvements in predicting stand attributes in this study. The combination method also did not perform as well as the disaggregation method in tree-level predictions. The disaggregation method provided the best predictions of tree- and stand-level survival and growth. Conclusions The disaggregation approach provides a link between individual-tree models and whole-stand models, and should be considered as a better alternative to the unadjusted tree model.
Wave Numerical Model for Shallow Water
Institute of Scientific and Technical Information of China (English)
徐福敏; 严以新; 张长宽; 宋志尧; 茅丽华
2000-01-01
The history of forecasting wind waves by wave energy conservation equation is briefly described. Several currently used wave numerical models for shallow water based on different wave theories are discussed. Wave energy conservation models for the simulation of shallow water waves are introduced,with emphasis placed on the SWAN model, which takes use of the most advanced wave research achievements and has been applied to several theoretical and field conditions. The characteristics and applicability of the model, the finite difference numerical scheme of the action balance equation and its source terms computing methods are described in detail. The model has been verified with the propagation refraction numerical experiments for waves propagating in following and opposing currents; finally, the model is applied to the Haian Gulf area to simulate the wave height and wave period field there, and the results are compared with observed data.
MICRO-MOTION EFFECT OF A TRAPPED ULTRA-COLD ION IN A STANDING-WAVE LASER
Institute of Scientific and Technical Information of China (English)
JIANG YU-RONG; FENG MANG; GAO KE-LIN; ZHU XI-WEN
2001-01-01
In the absence of the requirements of the Lamb-Dicke limit and rotating wave approximation, we semi-classically investigate the dynamics of a trapped ultra-cold ion in the standing-wave laser, with the consideration of the time- dependent potential and pseudo-potential of the Paul trap. The specific calculations show that the larger the Lamb-Dicke parameter η and the Rabi frequency Ω, the greater the difference between the dynamics in the time-dependent potential and the pseudo-potential.
Cho, Yonggeun
2016-05-04
This paper is devoted to the mathematical analysis of a class of nonlinear fractional Schrödinger equations with a general Hartree-type integrand. We show the well-posedness of the associated Cauchy problem and prove the existence and stability of standing waves under suitable assumptions on the nonlinearity. Our proofs rely on a contraction argument in mixed functional spaces and the concentration-compactness method. © 2015 World Scientific Publishing Company
Nam, Jeonghun; Kim, Jae Young; Lim, Chae Seung
2017-01-01
We present continuous, sheathless microparticle patterning using conductive liquid (CL)-based standing surface acoustic waves (SSAWs). Conventional metal electrodes patterned on a piezoelectric substrate were replaced with electrode channels filled with a CL. The device performance was evaluated with 5-μm fluorescent polystyrene particles at different flow rate and via phase shifting. In addition, our device was further applied to continuous concentration of malaria parasites at the sidewalls of the fluidic channel.
Directory of Open Access Journals (Sweden)
Jeonghun Nam
2017-01-01
Full Text Available We present continuous, sheathless microparticle patterning using conductive liquid (CL-based standing surface acoustic waves (SSAWs. Conventional metal electrodes patterned on a piezoelectric substrate were replaced with electrode channels filled with a CL. The device performance was evaluated with 5-μm fluorescent polystyrene particles at different flow rate and via phase shifting. In addition, our device was further applied to continuous concentration of malaria parasites at the sidewalls of the fluidic channel.
Weeden, George S; Wang, Nien-Hwa Linda
2017-04-14
Simulated Moving Bed (SMB) systems with linear adsorption isotherms have been used for many different separations, including large-scale sugar separations. While SMBs are much more efficient than batch operations, they are not widely used for large-scale production because there are two key barriers. The methods for design, optimization, and scale-up are complex for non-ideal systems. The Speedy Standing Wave Design (SSWD) is developed here to reduce these barriers. The productivity (PR) and the solvent efficiency (F/D) are explicitly related to seven material properties and 13 design parameters. For diffusion-controlled systems, the maximum PR or F/D is controlled by two key dimensionless material properties, the selectivity (α) and the effective diffusivity ratio (η), and two key dimensionless design parameters, the ratios of step time/diffusion time and pressure-limited convection time/diffusion time. The optimum column configuration for maximum PR or F/D is controlled by the weighted diffusivity ratio (η/α(2)). In general, high α and low η/α(2) favor high PR and F/D. The productivity is proportional to the ratio of the feed concentration to the diffusion time. Small particles and high diffusivities favor high productivity, but do not affect solvent efficiency. Simple scaling rules are derived from the two key dimensionless design parameters. The separation of acetic acid from glucose in biomass hydrolysate is used as an example to show how the productivity and the solvent efficiency are affected by the key dimensionless material and design parameters. Ten design parameters are optimized for maximum PR or minimum cost in one minute on a laptop computer. If the material properties are the same for different particle sizes and the dimensionless groups are kept constant, then lab-scale testing consumes less materials and can be done four times faster using particles with half the particle size. Copyright © 2017 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
Giuseppe eMercurio
2014-01-01
Full Text Available We present an analysis method of normal incidence x-ray standing wave (NIXSW data that allows detailed adsorption geometries of complex molecules to be retrieved. This method (Fourier vector analysis is based on the comparison of both the coherence and phase of NIXSW data to NIXSW simulations of different molecular geometries as the relevant internal degrees of freedom are tuned. We introduce this analysis method using the prototypical molecular switch azobenzene (AB adsorbed on the Ag(111 surface as a model system. The application of the Fourier vector analysis to AB/Ag(111 provides, on the one hand, detailed adsorption geometries including dihedral angles, and on the other hand, insights into the dynamics of molecules and their bonding to the metal substrate. This analysis scheme is generally applicable to any adsorbate, it is necessary for molecules with potentially large distortions, and will be particularly valuable for molecules whose distortion on adsorption can be mapped on a limited number of internal degrees of freedom.
Improvements on Mean Free Wave Surface Modeling
Institute of Scientific and Technical Information of China (English)
董国海; 滕斌; 程亮
2002-01-01
Some new results of the modeling of mean free surface of waves or wave set-up are presented. The stream function wave theory is applied to incident short waves. The limiting wave steepness is adopted as the wave breaker index in the calculation of wave breaking dissipation. The model is based on Roelvink (1993), but the numerical techniques used in the solution are based on the Weighted-Average Flux (WAF) method (Watson et al., 1992), with Time-Operator-Splitting (TOS) used for the treatment of the source terms. This method allows a small number of computational points to be used, and is particularly efficient in modeling wave set-up. The short wave (or incident primary wave) energy equation issolved by use of a traditional Lax-Wendroff technique. The present model is found to be satisfactory compared with the measurements conducted by Stive (1983).
A Wave Modulation Model of Ripples over Long Surface Waves
Institute of Scientific and Technical Information of China (English)
CONG Peixiu; ZHENG Guizhen
2011-01-01
A study is presented on the modulation of ripples induced by a long surface wave (LW) and a new theoretical modulation model is proposed. In this model, the wind surface stress modulation is related to the modulation of tipple spectrum. The model results show that in the case of LW propagating in the wind direction with the wave age parameter of LW increasing, the area with enhanced shear stress shifts from the region near the LW crest on the upwind slope to the LW trough. With a smaller wave age parameter of LW, the tipple modulation has the maximum on the upwind slope in the vicinity of LW crest, while with a larger parameter the enhancement of ripple spectrum does not occur in that region. At low winds the amplitude of ripple modulation transfer function (MTF) is larger in the gravity wave range, while at moderate or high winds it changes little in the range from short gravity waves to capillary waves.
Modelling the water balance of an inclined mature beech stand
Janott, Michael; Bittner, Sebastian; Gayler, Sebastian; Priesack, Eckart; Holst, Jutta
2010-05-01
We developed a xylem water transport model for European beech (Fagus sylvatica L.) to scale up organ based processes to the tree level and to quantify their influence on the whole tree transpiration and the water uptake from the soil. To better consider the root-soil interaction a finite element tree crown hydro-dynamics model was extended and further developed based on the 1D porous media equation by including in addition to the explicit 3D architectural representation of the tree crown a corresponding 3D characterisation of the root system. Subsequently this 1D xylem water flow model was coupled to a soil water flow model also derived from the 1D porous media equation. The model was tested using data of a 80 - 90 years old beech stand on a steep NE-slope on Rendzic Leptosol derived from limestone (Weißjura) located close to Tuttlingen, SW-Germany. The above-ground tree architecture of a representative mature beech tree was recorded by a laser scanner and digitized. The root architecture was estimated by applying a virtual root generator since detailed information on root distribution was not available due to the restricted accessibility of roots in soil. Input of measured meteorological and soil data in combination with plant specific parameters from literature enable the appropriate simulation of transpiration and soil water contents. In conclusion, the 1D porous media approach provided a computationally efficient method to simulate water flow in a soil-plant system as represented by mature beech trees. The model is able to reproduce main mechanisms of plant hydro-dynamics including sap flow and root water uptake from soil.
Overview of Wave to Wire Models
DEFF Research Database (Denmark)
Nielsen, Kim; Kramer, Morten Mejlhede; Ferri, Francesco
A “Wave to Wire” (W2W) model is a numerical tool that can calculate the power output from a specified Wave Energy Converter (WEC), under specified ocean wave conditions. The tool can be used to assess and optimize the performance of a Wave Energy Converter (WEC) design and provide knowledge of th...
Kasimov, Aslan R.
2013-03-08
We propose the following model equation, ut+1/2(u2−uus)x=f(x,us) that predicts chaotic shock waves, similar to those in detonations in chemically reacting mixtures. The equation is given on the half line, x<0, and the shock is located at x=0 for any t≥0. Here, us(t) is the shock state and the source term f is taken to mimic the chemical energy release in detonations. This equation retains the essential physics needed to reproduce many properties of detonations in gaseous reactive mixtures: steady traveling wave solutions, instability of such solutions, and the onset of chaos. Our model is the first (to our knowledge) to describe chaos in shock waves by a scalar first-order partial differential equation. The chaos arises in the equation thanks to an interplay between the nonlinearity of the inviscid Burgers equation and a novel forcing term that is nonlocal in nature and has deep physical roots in reactive Euler equations.
Standing Waves in an Elastic Spring: A Systematic Study by Video Analysis
Rodrigues Ventura, Daniel; Simeão de Carvalho, Paulo; Adriano Dias, Marco
2017-01-01
The word "wave" is part of the daily language of every student. However, the physical understanding of the concept demands a high level of abstract thought. In physics, waves are oscillating variations of a physical quantity that involve the transfer of energy from one point to another, without displacement of matter. A wave can be…
Generalized height-diameter models for Populus tremula L. stands
African Journals Online (AJOL)
USER
2010-07-12
Jul 12, 2010 ... variables related to forest growth and yield, succession ... and essential for describing its structure (Dorado et al.,. 2006). ..... an application for major tree species in complex stands of interior ... mixed tropical forests.
Sivakumar, Siddharth S.; Namath, Amalia G.; Galán, Roberto F.
2016-01-01
Previous work from our lab has demonstrated how the connectivity of brain circuits constrains the repertoire of activity patterns that those circuits can display. Specifically, we have shown that the principal components of spontaneous neural activity are uniquely determined by the underlying circuit connections, and that although the principal components do not uniquely resolve the circuit structure, they do reveal important features about it. Expanding upon this framework on a larger scale of neural dynamics, we have analyzed EEG data recorded with the standard 10–20 electrode system from 41 neurologically normal children and adolescents during stage 2, non-REM sleep. We show that the principal components of EEG spindles, or sigma waves (10–16 Hz), reveal non-propagating, standing waves in the form of spherical harmonics. We mathematically demonstrate that standing EEG waves exist when the spatial covariance and the Laplacian operator on the head's surface commute. This in turn implies that the covariance between two EEG channels decreases as the inverse of their relative distance; a relationship that we corroborate with empirical data. Using volume conduction theory, we then demonstrate that superficial current sources are more synchronized at larger distances, and determine the characteristic length of large-scale neural synchronization as 1.31 times the head radius, on average. Moreover, consistent with the hypothesis that EEG spindles are driven by thalamo-cortical rather than cortico-cortical loops, we also show that 8 additional patients with hypoplasia or complete agenesis of the corpus callosum, i.e., with deficient or no connectivity between cortical hemispheres, similarly exhibit standing EEG waves in the form of spherical harmonics. We conclude that spherical harmonics are a hallmark of spontaneous, large-scale synchronization of neural activity in the brain, which are associated with unconscious, light sleep. The analogy with spherical harmonics
Dispersive internal long wave models
Energy Technology Data Exchange (ETDEWEB)
Camassa, R.; Choi, W.; Holm, D.D. [Los Alamos National Lab., NM (United States); Levermore, C.D.; Lvov, Y. [Univ. of Arizona, Tucson, AZ (United States)
1998-11-01
This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). This work is a joint analytical and numerical study of internal dispersive water wave propagation in a stratified two-layer fluid, a problem that has important geophysical fluid dynamics applications. Two-layer models can capture the main density-dependent effects because they can support, unlike homogeneous fluid models, the observed large amplitude internal wave motion at the interface between layers. The authors have derived new model equations using multiscale asymptotics in combination with the method they have developed for vertically averaging velocity and vorticity fields across fluid layers within the original Euler equations. The authors have found new exact conservation laws for layer-mean vorticity that have exact counterparts in the models. With this approach, they have derived a class of equations that retain the full nonlinearity of the original Euler equations while preserving the simplicity of known weakly nonlinear models, thus providing the theoretical foundation for experimental results so far unexplained.
Xie, Kai; Yang, Min; Bai, Bowen; Li, Xiaoping; Zhou, Hui; Guo, Lixin
2016-01-01
Radio blackout during the re-entry has puzzled the aerospace industry for decades and has not yet been completely resolved. To achieve a continuous data link in the spacecraft's re-entry period, a simple and practicable communication method is proposed on the basis that (1) the electromagnetic-wave backscatter of the plasma sheath affects the voltage standing wave ratio (VSWR) of the antenna, and the backscatter is negatively correlated to transmission components, and (2) the transmission attenuation caused by the plasma sheath reduces the channel capacity. We detect the voltage standing wave ratio changes of the antenna and then adjust the information rate to accommodate the varying channel capacity, thus guaranteeing continuous transmission (for fewer critical data). The experiment was carried out in a plasma generator with an 18-cm-thick and 30-cm-diameter hollow propagation path, and the adaptive communication was implemented using spread spectrum frequency, shift key modulation with a variable spreading factor. The experimental results indicate that, when the over-threshold of VSWR was detected, the bit rate reduced to 250 bps from 4 Mbps automatically and the tolerated plasma density increased by an order of magnitude, which validates the proposed scheme. The proposed method has little additional cost, and the adaptive control does not require a feedback channel. The method is therefore applicable to data transmission in a single direction, such as that of a one-way telemetry system.
Johansson; Aubry
2000-05-01
We investigate the long-time evolution of weakly perturbed single-site breathers (localized stationary states) in the discrete nonlinear Schrodinger equation. The perturbations we consider correspond to time-periodic solutions of the linearized equations around the breather, and can be either (i) spatially localized or (ii) spatially extended. For case (i), which corresponds to the excitation of an internal mode of the breather, we find that the nonlinear interaction between the breather and its internal mode always leads to a slow growth of the breather amplitude and frequency. In case (ii), corresponding to interaction between the breather and a standing-wave phonon, the breather will grow provided that the wave vector of the phonon is such that the generation of radiating higher harmonics at the breather is possible. In other cases, breather decay is observed. This condition yields a limit value for the breather frequency above which no further growth is possible. We also discuss another mechanism for breather growth and destruction which becomes important when the amplitude of the perturbation is non-negligible, and which originates from the oscillatory instabilities of the nonlinear standing-wave phonons.
Numerical Modelling of Wave Run-Up
DEFF Research Database (Denmark)
Ramirez, Jorge Robert Rodriguez; Frigaard, Peter; Andersen, Thomas Lykke;
2011-01-01
Wave loads are important in problems related to offshore structure, such as wave run-up, slamming. The computation of such wave problems are carried out by CFD models. This paper presents one model, NS3, which solve 3D Navier-Stokes equations and use Volume of Fluid (VOF) method to treat the free...
Numerical Modelling of Wave Run-Up
DEFF Research Database (Denmark)
Ramirez, Jorge Robert Rodriguez; Frigaard, Peter; Andersen, Thomas Lykke
2011-01-01
Wave loads are important in problems related to offshore structure, such as wave run-up, slamming. The computation of such wave problems are carried out by CFD models. This paper presents one model, NS3, which solve 3D Navier-Stokes equations and use Volume of Fluid (VOF) method to treat the free...
Chemical-reaction model for Mexican wave
Nagatani, Takashi
2003-05-01
We present a chemical-reaction model to describe the Mexican wave ( La Ola) in football stadia. The spectator's action is described in terms of chemical reactions. The model is governed by three reaction rates k 1, k 2, and k3. We study the nonlinear waves on one- and two-dimensional lattices. The Mexican wave is formulated as a clockwise forwardly propagating wave. Waves are growing or disappear, depending on the values of reaction rates. In the specific case of k1= k2= k3=1, the nonlinear-wave equation produces a propagating pulse like soliton.
Wave chaotic experiments and models for complicated wave scattering systems
Yeh, Jen-Hao
Wave scattering in a complicated environment is a common challenge in many engineering fields because the complexity makes exact solutions impractical to find, and the sensitivity to detail in the short-wavelength limit makes a numerical solution relevant only to a specific realization. On the other hand, wave chaos offers a statistical approach to understand the properties of complicated wave systems through the use of random matrix theory (RMT). A bridge between the theory and practical applications is the random coupling model (RCM) which connects the universal features predicted by RMT and the specific details of a real wave scattering system. The RCM gives a complete model for many wave properties and is beneficial for many physical and engineering fields that involve complicated wave scattering systems. One major contribution of this dissertation is that I have utilized three microwave systems to thoroughly test the RCM in complicated wave systems with varied loss, including a cryogenic system with a superconducting microwave cavity for testing the extremely-low-loss case. I have also experimentally tested an extension of the RCM that includes short-orbit corrections. Another novel result is development of a complete model based on the RCM for the fading phenomenon extensively studied in the wireless communication fields. This fading model encompasses the traditional fading models as its high-loss limit case and further predicts the fading statistics in the low-loss limit. This model provides the first physical explanation for the fitting parameters used in fading models. I have also applied the RCM to additional experimental wave properties of a complicated wave system, such as the impedance matrix, the scattering matrix, the variance ratio, and the thermopower. These predictions are significant for nuclear scattering, atomic physics, quantum transport in condensed matter systems, electromagnetics, acoustics, geophysics, etc.
Modeling water waves beyond perturbations
Clamond, Didier
2015-01-01
In this chapter, we illustrate the advantage of variational principles for modeling water waves from an elementary practical viewpoint. The method is based on a `relaxed' variational principle, i.e., on a Lagrangian involving as many variables as possible, and imposing some suitable subordinate constraints. This approach allows the construction of approximations without necessarily relying on a small parameter. This is illustrated via simple examples, namely the Serre equations in shallow water, a generalization of the Klein-Gordon equation in deep water and how to unify these equations in arbitrary depth. The chapter ends with a discussion and caution on how this approach should be used in practice.
Hendaoui, Nordine; Mani, Aladin; Liu, Ning; Tofail, Syed M.; Silien, Christophe; Peremans, André
2017-01-01
A method is proposed to overcome the diffraction limit of spatial resolution in infrared microscopy. To achieve this, standing waves in an attenuated total reflection configuration were generated to spatially modulate the absorbance of adsorbate vibrational transitions. A numerical simulation was undertaken. It showed that chemical imaging with a spatial resolution of approximately 100 nm is achievable in the case of self-assembled patterns (ofoctdecyltrichlorosilane [CH3-(CH2)17-SiCl3]), when probing the methyl modes located near 3.5 micrometres.
McClain, John
This dissertation reports on a novel theoretical and computational framework for calculating low-energy electron reflectivities from crystalline surfaces and its application to two layered systems of two-dimensional materials, graphene and molybdenum disulfide. The framework provides a simple and efficient approach through the matching of a small set of Fourier components of Bloch wave solutions to the Schrodinger Equation in a slab-in-supercell geometry to incoming and outgoing plane waves on both sides of the supercell. The implementation of this method is described in detail for the calculation of reflectivities in the lowest energy range, for which only specular reflection is allowed. This implementation includes the calculation of reflectivities from beams with normal or off-normal incidence. Two different algorithms are described in the case of off-normal incidence which differ in their dependence on the existence of a symmetry with a mirror plane parallel to the crystal surface. Applications to model potentials in one, two, and three dimensions display consistent results when using different supercell sizes and convergent results with the density of Fourier grids. The design of the Bloch wave matching also allows for the accurate modeling of crystalline slabs through the use of realistic potentials determined via density functional theory. The application of the method to low-energy electron scattering from free-standing systems of a few layers of graphene, including the use of these realistic potentials, demonstrates this ability of the method to accurately model real systems. It reproduces the layer-dependent oscillations found in experimental, normal incidence reflectivity curves for a few layers of graphene grown on silicon carbide. The normal incidence reflectivity curves calculated for slabs consisting of few-layer graphene on 10 layers of nickel show some qualitative agreement with experiment. General incidence reflectivity spectra for free-standing
Verification of A Numerical Harbour Wave Model
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
A numerical model for wave propagation in a harbour is verified by use of physical models. The extended time-dependent mild slope equation is employed as the governing equation, and the model is solved by use of ADI method containing the relaxation factor. Firstly, the reflection coefficient of waves in front of rubble-mound breakwaters under oblique incident waves is determined through physical model tests, and it is regarded as the basis for simulating partial reflection boundaries of the numerical model. Then model tests on refraction, diffraction and reflection of waves in a harbour are performed to measure wave height distribution. Comparative results between physical and numerical model tests show that the present numerical model can satisfactorily simulate the propagation of regular and irregular waves in a harbour with complex topography and boundary conditions.
A stand-alone power system to integrate wind, wave and solar energy
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
@@ On 12 October, 2007, an agreement on the construction of a stand-alone renewable energy (RE) system at the Dangan Island was inked between the CAS Guangzhou Institute of Energy Conversion (GIEC) and the Wanshan Exemplary Marine Development Zone in Zhuhai, a coastal city in south China's Guangdong Province.
Directory of Open Access Journals (Sweden)
Shilei Liu
2017-07-01
Full Text Available Acoustic standing waves have been widely used in trapping, patterning, and manipulating particles, whereas one barrier remains: the lack of understanding of force conditions on particles which mainly include acoustic radiation force (ARF and acoustic streaming (AS. In this paper, force conditions on micrometer size polystyrene microspheres in acoustic standing wave fields were investigated. The COMSOL® Mutiphysics particle tracing module was used to numerically simulate force conditions on various particles as a function of time. The velocity of particle movement was experimentally measured using particle imaging velocimetry (PIV. Through experimental and numerical simulation, the functions of ARF and AS in trapping and patterning were analyzed. It is shown that ARF is dominant in trapping and patterning large particles while the impact of AS increases rapidly with decreasing particle size. The combination of using both ARF and AS for medium size particles can obtain different patterns with only using ARF. Findings of the present study will aid the design of acoustic-driven microfluidic devices to increase the diversity of particle patterning.
Chung, Euiheon; Kim, Daekeun; Cui, Yan; Kim, Yang-Hyo; So, Peter T C
2007-09-01
The development of high resolution, high speed imaging techniques allows the study of dynamical processes in biological systems. Lateral resolution improvement of up to a factor of 2 has been achieved using structured illumination. In a total internal reflection fluorescence microscope, an evanescence excitation field is formed as light is total internally reflected at an interface between a high and a low index medium. The excitation region resulting in low background fluorescence. We present even higher resolution wide-field biological imaging by use of standing wave total internal reflection fluorescence (SW-TIRF). Evanescent standing wave (SW) illumination is used to generate a sinusoidal high spatial frequency fringe pattern on specimen for lateral resolution enhancement. To prevent thermal drift of the SW, novel detection and estimation of the SW phase with real-time feedback control is devised for the stabilization and control of the fringe phase. SW-TIRF is a wide-field superresolution technique with resolution better than a fifth of emission wavelength or approximately 100 nm lateral resolution. We demonstrate the performance of the SW-TIRF microscopy using one- and two-directional SW illumination with a biological sample of cellular actin cytoskeleton of mouse fibroblast cells as well as single semiconductor nanocrystal molecules. The results confirm the superior resolution of SW-TIRF in addition to the merit of a high signal/background ratio from TIRF microscopy.
Institute of Scientific and Technical Information of China (English)
伍细如
2015-01-01
proton emits energy wave, electron could sits any position away from nucleus, but be the most stable just when it sits at the trough of energy wave, and this position accords with Bohr radius and Schr?dinger equation.
Energy Technology Data Exchange (ETDEWEB)
Guo, Y.; Hao, Q.; Cheng, X.; Chen, P. F.; Ding, M. D. [School of Astronomy and Space Science and Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education, Nanjing University, Nanjing 210046 (China); Erdélyi, R. [Solar Physics and Space Plasma Research Center (SP2RC), School of Mathematics and Statistics, University of Sheffield, Sheffield S3 7RH (United Kingdom); Srivastava, A. K.; Dwivedi, B. N., E-mail: guoyang@nju.edu.cn [Department of Physics, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)
2015-02-01
We report the observation of the first two harmonics of the horizontally polarized kink waves excited in a coronal loop system lying southeast of AR 11719 on 2013 April 11. The detected periods of the fundamental mode (P {sub 1}), its first overtone (P {sub 2}) in the northern half, and that in the southern one are 530.2 ± 13.3, 300.4 ± 27.7, and 334.7 ± 22.1 s, respectively. The periods of the first overtone in the two halves are the same considering uncertainties in the measurement. We estimate the average electron density, temperature, and length of the loop system as (5.1 ± 0.8) × 10{sup 8} cm{sup –3}, 0.65 ± 0.06 MK, and 203.8 ± 13.8 Mm, respectively. As a zeroth-order estimation, the magnetic field strength, B = 8.2 ± 1.0 G, derived by the coronal seismology using the fundamental kink mode matches with that derived by a potential field model. The extrapolation model also shows the asymmetric and nonuniform distribution of the magnetic field along the coronal loop. Using the amplitude profile distributions of both the fundamental mode and its first overtone, we observe that the antinode positions of both the fundamental mode and its first overtone shift toward the weak field region along the coronal loop. The results indicate that the density stratification and the temperature difference effects are larger than the magnetic field variation effect on the period ratio. On the other hand, the magnetic field variation has a greater effect on the eigenfunction of the first overtone than the density stratification does for this case.
Modeling Water Waves with Smoothed Particle Hydrodynamics
2013-09-30
flows, such as undertow, longshore currents, and rip currents. APPROACH The approach is based on improving various aspects of the SPH code ...Smoothed Particle Hydrodynamics ( SPH ) is a meshless numerical method that is being developed for the study of nearshore waves and other Navy needs. The...Lagrangian nature of SPH allows the modeling of wave breaking, surf zones, ship waves, and wave-structure interaction, where the free surface becomes
Modelling and Simulation of Wave Loads
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Thoft-Christensen, Palle
A simple model of the wave load on slender members of offshore structures is described. The wave elevation of the sea state is modelled by a stationary Gaussian process. A new procedure to simulate realizations of the wave loads is developed. The simulation method assumes that the wave particle...... velocity can be approximated by a Gaussian Markov process. Known approximate results for the first-passage density or equivalently, the distribution of the extremes of wave loads are presented and compared with rather precise simulation results. It is demonstrated that the approximate results...
Modelling and Simulation of Wave Loads
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Thoft-Christensen, Palle
1985-01-01
A simple model of the wave load on stender members of offshore structures is described . The wave elevation of the sea stateis modelled by a stationary Gaussian process. A new procedure to simulate realizations of the wave loads is developed. The simulation method assumes that the wave particle...... velocity can be approximated by a Gaussian Markov process. Known approximate results for the first passage density or equivalently, the distribution of the extremes of wave loads are presented and compared with rather precise simulation results. It is demonstrated that the approximate results...
Analytical Formulation of Equatorial Standing Wave Phenomena: Application to QBO and ENSO
Pukite, P. R.
2016-12-01
inversion of the biennial mode lasting from 1980 to 1996. The parsimony of these analytical models arises from applying only known cyclic forcing terms to fundamental wave equation formulations. This raises the possibility that both QBO and ENSO can be predicted years in advance, apart from a metastable biennial phase inversion in ENSO.
FORWARD MODELING OF STANDING KINK MODES IN CORONAL LOOPS. II. APPLICATIONS
Energy Technology Data Exchange (ETDEWEB)
Yuan, Ding; Doorsselaere, Tom Van, E-mail: DYuan2@uclan.ac.uk [Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B bus 2400, B-3001 Leuven (Belgium)
2016-04-15
Magnetohydrodynamic waves are believed to play a significant role in coronal heating, and could be used for remote diagnostics of solar plasma. Both the heating and diagnostic applications rely on a correct inversion (or backward modeling) of the observables into the thermal and magnetic structures of the plasma. However, due to the limited availability of observables, this is an ill-posed issue. Forward modeling is designed to establish a plausible mapping of plasma structuring into observables. In this study, we set up forward models of standing kink modes in coronal loops and simulate optically thin emissions in the extreme ultraviolet bandpasses, and then adjust plasma parameters and viewing angles to match three events of transverse loop oscillations observed by the Solar Dynamics Observatory/Atmospheric Imaging Assembly. We demonstrate that forward models could be effectively used to identify the oscillation overtone and polarization, to reproduce the general profile of oscillation amplitude and phase, and to predict multiple harmonic periodicities in the associated emission intensity and loop width variation.
方形薄板二维驻波的研究%Research of 2-dimensional standing waves in square plate
Institute of Scientific and Technical Information of China (English)
方奕忠; 王钢; 沈韩; 崔新图; 廖德驹; 冯饶慧
2014-01-01
通过对多种振源情形下的方形薄板二维驻波图形（克拉尼图形）的观测与研究，得到不同频率下驻波图形的波节数 n＋1，m＋1及波矢 k ，从而导出波速（相速）u 。实验结果与理论解析解（严格解）相比较符合得很好。%2-dimensional standing waves in square plates (Chladni figures) in several cases was studied both experimentally and theoretically .Wave nodes and wave vector of the standing wave fig-ures were gotten at different frequency ,and the wave velocity was deduced .The results of the experi-ment agreed well to the analytic solutions of theory .
Iwakami, Wakana; Yamada, Shoichi
2013-01-01
The systematic research of flow patterns behind the accretion shock wave is conducted using three-dimensional hydrodynamics simulations for core-collapse supernovae in this study. Changing the accretion rate and neutrino luminosity, the steady solutions of the one-dimensional irrotational accretion flow passing through the spherical shock wave are evolved by imposing a random perturbation with 1% amplitude at the onset of the simulations. Depending on the accretion rate and neutrino luminosity, various flow patterns appear behind the shock wave. We classified them into the three fundamental flow patterns: (1) sloshing motion, (2) spiral motion, (3) multiple high-entropy bubbles, and the two anomalous flow patterns: (4) spiral motion with buoyant bubbles, and (5) spiral motion with pulsating rotational velocity. The sloshing and spiral motions tend to be dominant in the higher accretion rate and lower neutrino luminosity, and the generations of multiple buoyant bubbles tend to prevail in the lower accretion ra...
Travelling waves in hybrid chemotaxis models
Franz, Benjamin; Painter, Kevin J; Erban, Radek
2013-01-01
Hybrid models of chemotaxis combine agent-based models of cells with partial differential equation models of extracellular chemical signals. In this paper, travelling wave properties of hybrid models of bacterial chemotaxis are investigated. Bacteria are modelled using an agent-based (individual-based) approach with internal dynamics describing signal transduction. In addition to the chemotactic behaviour of the bacteria, the individual-based model also includes cell proliferation and death. Cells consume the extracellular nutrient field (chemoattractant) which is modelled using a partial differential equation. Mesoscopic and macroscopic equations representing the behaviour of the hybrid model are derived and the existence of travelling wave solutions for these models is established. It is shown that cell proliferation is necessary for the existence of non-transient (stationary) travelling waves in hybrid models. Additionally, a numerical comparison between the wave speeds of the continuum models and the hybr...
Model-based internal wave processing
Energy Technology Data Exchange (ETDEWEB)
Candy, J.V.; Chambers, D.H.
1995-06-09
A model-based approach is proposed to solve the oceanic internal wave signal processing problem that is based on state-space representations of the normal-mode vertical velocity and plane wave horizontal velocity propagation models. It is shown that these representations can be utilized to spatially propagate the modal (dept) vertical velocity functions given the basic parameters (wave numbers, Brunt-Vaisala frequency profile etc.) developed from the solution of the associated boundary value problem as well as the horizontal velocity components. Based on this framework, investigations are made of model-based solutions to the signal enhancement problem for internal waves.
Zhang, Xiaoqing; Feng, Heying; Qu, Chengwu
2016-10-01
Nonlinear standing waves and acoustic streaming in an axial-symmetrical resonator with exponentially varying cross-sectional area were studied. A two-dimensional gas-kinetic Bhatnagar-Gross-Krook scheme based on the non-structure triangular grid was established to simulate nonlinear acoustic oscillations in the resonator. Details of the transient and steady flow fields and streaming were developed. The effects of winding index of the exponential-shape resonator, the displacement amplitude of the acoustic piston on the streaming, and the vortex pattern were analyzed. The results demonstrate that the acoustic streaming pattern in such resonators is different from the typical Rayleigh flow in a constant cross-sectional area resonator. No obvious shock wave appeared inside the exponential-shape resonator. The comparison reveals that with increasing the displacement amplitude of the acoustic piston energy dissipation is accompanied by vortex break-up from a first-level to a second-level transition, and even into turbulent flow. This research demonstrates that the exponential-shape resonator, especially that with a winding index of 2.2 exhibits better acoustic features and suppression effects on shock-wave, acoustic streaming, and the vortex.
Mud-Wave Interaction: A Viscoelastic Model
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
This study is devoted to the interaction between water surface waves and a thin layer of viscoelastic mud on the bottom. On the assumption that the mud layer is comparable in thickness with the wave boundary layer and is much smaller than the wavelength, a two-layer Stokes boundary layer model is adopted to determine the mud motions under the waves. Analytical expressions are derived for the near-bottom water and mud velocity fields, surface wave-damping rate, and interface wave amplitude and phase lag. Examined in particular is how these kinematic quantities may depend on the viscous and elastic properties of the mud.
Protopapa, M L; De Tomasi, F; Di Giulio, M; Perrone, M R; Scaglione, S
2002-01-01
The standing-wave electric field pattern that forms inside an optical coating as a consequence of laser irradiation is one of the factors influencing the coating laser-induced damage threshold. The influence of the standing-wave electric field profile on the damage resistance to ultraviolet radiation of hafnium dioxide (HfO sub 2) thin films was investigated in this work. To this end, HfO sub 2 thin films of different thicknesses deposited by the electron beam evaporation technique at the same deposition conditions were analyzed. Laser damage thresholds of the samples were measured at 308 nm (XeCl laser) by the photoacoustic beam deflection technique and microscopic inspections. The dependence of the laser damage threshold on the standing-wave electric field pattern was analyzed.
Institute of Scientific and Technical Information of China (English)
方天申
2015-01-01
讨论纵向驱动弦时的次频驻波振动现象，与弦运动轨迹的观察方法。根据弦运动轨迹，用仿真分析谐波振动可获得弦振动的有关物理信息。实验观察到，可出现非共振驻波（次频振动）振幅可比共振驻波振幅大的多现象。%It presents an experimental technique to observe the vibration tracks of string standing waves,and a subharmonic vibration of strings. The amplitude of a non-resonance subharmonic standing wave may be greater than that of a resonance standing wave in a longitudinally driven string.
Institute of Scientific and Technical Information of China (English)
LI Song; LIU Ke; GUO Qing; HUANG Dongtao
2005-01-01
Based on the theoretical analysis of a standing wave tube with flow and lateral Helmholtz resonator, a relevant experimental apparatus were set up, and were successfully used to validate the the analysis above. Meanwhile an end correction and an equivalent radius coefficient covered in the theoretical analysis were also determined by experiments. Furthermore several results obtained from the theoretical analysis and experiments were used to discuss the effects of flow on the performance of Helmholtz resonator and the sound field in the standing wave tube. It is shown that using Helmholtz resonator for the standing wave tube with flow is still a good measure for noise reduction, even though the effect of noise reduction could be reduced because of flow.
Opdriftsbaserede modeller for Wave Star
DEFF Research Database (Denmark)
Kramer, Morten
Formålet med dette skrift er at få en forhåndsvurdering af mulige effektforøgelser for Wave Star ved anvendelse af aktiv akkumulatordrift. Disse vurderinger baseres på simuleringsmodeller for driften af Wave Star i uregelmæssige bølger. Modellen er udarbejdet i programmeringssproget Delphi og er en...
Modeling, Design and Simulation of Stand-Alone Photovoltaic Power Systems with Battery Storage
Abd Essalam BADOUD; Mabrouk KHEMLICHE
2013-01-01
Stand alone renewable energy based on photovoltaic systems accompanied with battery storage system are beginning to play an important role over the world to supply power to remote areas. The objective of the study reported in this paper is to elaborate and design a bond graphs model for sizing stand-alone domestic solar photovoltaic electricity systems and simulating the performance of the systems in a tropical climate. The systems modelled consist of an array of PV modules, a lead-acid batte...
Takahashi, K.; Waters, C. L.; Kletzing, C.; Kurth, W. S.; Smith, C. W.; Glassmeier, K. H.
2015-12-01
The power spectrum of the compressional component of magnetic field observed by the Van Allen Probes spacecraft near the magnetospheric equator in the dayside plasmasphere sometimes exhibits regularly spaced multiple peaks at frequencies below 50 mHz. We show by detailed analysis of events observed on two separate days in early 2014 that the frequencies change smoothly with the radial distance of the spacecraft and appear at or very near the frequencies of the odd harmonics of mutiharmonic toroidal standing Alfvén waves seen in the azimuthal component of the magnetic field. Even though the compressional component had low amplitude on one of the selected days, its spectral properties are highlighted by computing the ratio of the spectral powers of time series data obtained from spatially separated two Van Allen Probes spacecraft. The spectral similarity of the compressional and azimuthal components suggests that the compressional component contain field line resonance characteristics.
Takahashi, Kazue; Waters, Colin; Glassmeier, Karl-Heinz; Kletzing, Craig A.; Kurth, William S.; Smith, Charles W.
2015-12-01
The power spectrum of the compressional component of magnetic fields observed by the Van Allen Probes spacecraft near the magnetospheric equator in the dayside plasmasphere sometimes exhibits regularly spaced multiple peaks at frequencies below 50 mHz. We show by detailed analysis of events observed on two separate days in early 2014 that the frequencies change smoothly with the radial distance of the spacecraft and appear at or very near the frequencies of the odd harmonics of mutiharmonic toroidal mode standing Alfvén waves seen in the azimuthal component of the magnetic field. Even though the compressional component had a low amplitude on one of the selected days, its spectral properties are highlighted by computing the ratio of the spectral powers of time series data obtained from two spatially separated Van Allen Probes spacecraft. The spectral similarity of the compressional and azimuthal components suggests that the compressional component contains field line resonance characteristics.
Design of cavities of a standing wave accelerating tube for a 6 MeV electron linear accelerator
Directory of Open Access Journals (Sweden)
S Zarei
2017-08-01
Full Text Available Side-coupled standing wave tubes in mode are widely used in the low-energy electron linear accelerator, due to high accelerating gradient and low sensitivity to construction tolerances. The use of various simulation software for designing these kinds of tubes is very common nowadays. In this paper, SUPERFISH code and COMSOL are used for designing the accelerating and coupling cavities for a 6 MeV electron linear accelerator. Finite difference method in SUPERFISH code and Finite element method in COMSOL are used to solve the equations. Besides, dimension of accelerating and coupling cavities and also coupling iris dimension are optimized to achieve resonance frequency of 2.9985 MHz and coupling constant of 0.0112. Considering the results of this study and designing of the RF energy injection port subsequently, the construction of 6 MeV electron tube will be provided
Experimental Evaluation of Balance Prediction Models for Sit-to-Stand Movement in the Sagittal Plane
Directory of Open Access Journals (Sweden)
Oscar David Pena Cabra
2013-01-01
Full Text Available Evaluation of balance control ability would become important in the rehabilitation training. In this paper, in order to make clear usefulness and limitation of a traditional simple inverted pendulum model in balance prediction in sit-to-stand movements, the traditional simple model was compared to an inertia (rotational radius variable inverted pendulum model including multiple-joint influence in the balance predictions. The predictions were tested upon experimentation with six healthy subjects. The evaluation showed that the multiple-joint influence model is more accurate in predicting balance under demanding sit-to-stand conditions. On the other hand, the evaluation also showed that the traditionally used simple inverted pendulum model is still reliable in predicting balance during sit-to-stand movement under non-demanding (normal condition. Especially, the simple model was shown to be effective for sit-to-stand movements with low center of mass velocity at the seat-off. Moreover, almost all trajectories under the normal condition seemed to follow the same control strategy, in which the subjects used extra energy than the minimum one necessary for standing up. This suggests that the safety considerations come first than the energy efficiency considerations during a sit to stand, since the most energy efficient trajectory is close to the backward fall boundary.
Bazou, Despina; Kuznetsova, Larisa A; Coakley, W Terence
2005-03-01
2-D mammalian cell aggregates can be formed and levitated in a 1.5 MHz single half wavelength ultrasound standing wave trap. The physical environment of cells in such a trap has been examined. Attention was paid to parameters such as temperature, acoustic streaming, cavitation and intercellular forces. The extent to which these factors might be intrusive to a neural cell aggregate levitated in the trap was evaluated. Neural cells were exposed to ultrasound at a pressure amplitude of 0.54 MPa for 30 s; a small aggregate had been formed at the center of the trap. The pressure amplitude was then decreased to 0.27 MPa for 2 min, at which level the aggregation process continued at a slower rate. The pressure amplitude was then decreased to 0.06 MPa for 1 h. Temperature measurements that were conducted in situ with a 200 microm thermocouple over a 30 min period showed that the maximum temperature rise was less than 0.5 K. Acoustic streaming was measured by the particle image velocimetry method (PIV). It was shown that the hydrodynamic stress imposed on cells by acoustic streaming is less than that imposed by gentle preparative centrifugation procedures. Acoustic spectrum analysis showed that cavitation activity does not occur in the cell suspensions sonicated at the above pressures. White noise was detected only at a pressure amplitude of 1.96 MPa. Finally, it was shown that the attractive acoustic force between ultrasonically agglomerated cells is small compared with the normal attractive van der Waals force that operates at close cell surface separations. It is concluded that the standing wave trap operates only to concentrate cells locally, as in tissue, and does not modify the in vitro expression of surface receptor interactions.
Mapping a plasmonic hologram with photosensitive polymer films: standing versus propagating waves.
Papke, Thomas; Yadavalli, Nataraja Sekhar; Henkel, Carsten; Santer, Svetlana
2014-08-27
We use a photosensitive layer containing azobenzene moieties to map near-field intensity patterns in the vicinity of nanogrids fabricated within a thin silver layer. It is known that azobenzene containing films deform permanently during irradiation, following the pattern of the field intensity. The photosensitive material reacts only to stationary waves whose intensity patterns do not change in time. In this study, we have found a periodic deformation above the silver film outside the nanostructure, even if the latter consists of just one groove. This is in contradiction to the widely accepted viewpoint that propagating surface plasmon modes dominate outside nanogrids. We explain our observation based on an electromagnetic hologram formed by the constructive interference between a propagating surface plasmon wave and the incident light. This hologram contains a stationary intensity and polarization grating that even appears in the absence of the polymer layer.
Shields, C. Wyatt; Cruz, Daniela F.; Ohiri, Korine A.; Yellen, Benjamin B.; Lopez, Gabriel P.
2016-01-01
Acoustophoresis refers to the displacement of suspended objects in response to directional forces from sound energy. Given that the suspended objects must be smaller than the incident wavelength of sound and the width of the fluidic channels are typically tens to hundreds of micrometers across, acoustofluidic devices typically use ultrasonic waves generated from a piezoelectric transducer pulsating at high frequencies (in the megahertz range). At characteristic frequencies that depend on the ...
Instability analysis of resonant standing waves in a parametrically excited boxed basin
Energy Technology Data Exchange (ETDEWEB)
Sirwah, Magdy A [Department of Mathematics, Faculty of Science, Tanta University, Tanta (Egypt)], E-mail: magdysirwah@yahoo.com
2009-06-15
Two-mode parametric excited interfacial waves of incompressible immiscible liquids in an infinite boxed basin subjected to a vertical excitation are studied. The method of multiple time scales is used to obtain uniform solutions of the second-order system as well as the third-order one, which in turn leads to the solvability conditions of the two orders including the cubic interaction terms. The different cases of resonance that arise among the natural frequencies together with the frequency of the vertical vibration of the box are demonstrated theoretically and numerical computations of one of these cases (the two-to-one internal resonance and the principal parametric resonance) have been performed in detail in order to investigate the behavior of the resonant waves, especially the qualitative one. The autonomous system of four first-order differential equations for the modulation of the amplitudes and phases of the resonant waves is derived. Some numerical applications are achieved to show the stability criteria of the excited liquids inside the considered basin.
Modeling higher education attractiveness to stand global environment
Directory of Open Access Journals (Sweden)
Leonel Cezar Rodrigues
2016-01-01
Full Text Available Inabilities to deal with the changing environment may lead Higher Education Institutions (HEI to loose institutional attractiveness. Digital transformation requires global insertion as essential feature to institutional attractiveness. Processes for international education seem to lack the links between real environmental trends and the internal capabilities to global education. HEI managers may approach endeavors to internationalize education combining ambidextrous strategy supported by consolidated resilience capabilities. The latest ones refer to building internal value attributes to increase institutional attractiveness assuring solid standing in the global environment. In this article, a theoretical essay, we approach the problem of creating resilience as a way of backing up ambidexterity to generate institutional attractiveness. The set of value attributes, on the other hand, may originate strategic routes to strengthen internal competences and to make the institution more attractive, as a dynamic capability.
Directional wave measurements and modelling
Digital Repository Service at National Institute of Oceanography (India)
Anand, N.M.; Nayak, B.U.; Bhat, S.S.; SanilKumar, V.
Some of the results obtained from analysis of the monsoon directional wave data measured over 4 years in shallow waters off the west coast of India are presented. The directional spectrum computed from the time series data seems to indicate...
Baroclinic stationary waves in aquaplanet models
Lucarini, V.; Zappa, G.
2012-04-01
An aquaplanet model is used to study the nature of the highly persistent low frequency waves that have been observed in models forced by zonally symmetric boundary conditions. Using the Hayashi spectral analysis of the extratropical waves, we find that a quasi-stationary (QS) wave five belongs to a wave packet obeying a well defined dispersion relation with eastward group velocity. The components of the dispersion relation with k>5 baroclinically convert eddy available potential energy into eddy kinetic energy, while those with kinverse energy cascade, which had been previously proposed as a main forcing for this type of waves, only acts as a positive feedback on its predominantly baroclinic energetics. The QS wave is reinforced by a phase lock to an analogous pattern in the tropical convection, which provides further amplification to the wave. We also find that the Pedlosky bounds on the phase speed of unstable waves provide guidance in explaining the latitudinal structure of the energy conversion, which is shown to be more enhanced where the zonal westerly surface wind is weaker. The wave energy is then trapped in the wave guide created by the upper tropospheric jet stream. In agreement with Green's theory, as the equator to pole SST difference is reduced the stationary marginally stable component shifts toward higher wavenumbers, while the wave five becomes neutral and westward propagating. Some properties of the aquaplanet QS waves are found in interesting agreement with a low frequency wave observed by Salby (1982) in the southern hemisphere DJF, so that this perspective on low frequency variability might be, apart from its value in terms of basic geophysical fluid dynamics, of specific interest for studying the Earth's atmosphere.
Efficient Focusing Models for Generation of Freak Waves
Institute of Scientific and Technical Information of China (English)
ZHAO Xi-zeng; SUN Zhao-chen; LIANG Shu-xiu
2009-01-01
Four focusing models for generation of freak waves are presented. An extreme wave focusing model is presented on the basis of the enhanced High-Order Spectral (HOS) method and the importance of the nonlinear wave-wave interaction is evaluated by comparison of the calculated results with experimental and theoretical data. Based on the modification of the Longuet-Higgins model, four wave models for generation of freak waves (a. Extreme wave model + random wave model; b. Extreme wave model + regular wave model; c. Phase interval modulation wave focusing model; d. Number modulation wave focusing model with the same phase) are proposed. By use of different energy distribution techniques in the four models, freak wave events are obtained with different H_(max)/H_s in finite space and time.
X-ray standing wave studies of strained InxGa1-xAs/InP short-period superlattices
Aruta, Carmela; Lamberti, Carlo; Gastaldi, Luigi; Boscherini, Federico
2003-05-01
We report an x-ray standing wave (XSW) study on a set of structurally well-characterized InxGa1-xAs/InP short-period superlattices grown by metal-organic chemical vapor deposition and chemical-beam epitaxy techniques. It was possible to model the x-ray standing wave profiles only once the superlattice period has been assumed to be constituted by four layers of well-defined chemical composition [barrier (InP), first interface (InAs0.7P0.3), well (In0.53Ga0.47As), and second interface (In0.53Ga0.47As0.7P0.3)], and of variable thickness. The thickness of the four layers have been obtained by fitting the high resolution x-ray diffraction profiles of the heterostructures. The presence of partially disordered interface layers, as evidenced by a transmission electron microscopy study, causes a significant reduction of the coherent fraction, F, of both Ga and As atoms. The difference in F values among measured samples illustrates how the XSW can provide important information on the quality of semiconductor superlattices. Comparison with a "long period (160 Å)" In0.53Ga0.47As/InP superlattice, where the role played by InAs0.7P0.3 and In0.53Ga0.47As0.7P0.3 interface layers is negligible, confirms this picture. The coherent fraction of both As and Ga correlates well with the average perpendicular lattice misfit determined by x-ray diffraction.
Fast acoustic streaming in standing waves: generation of an additional outer streaming cell.
Reyt, Ida; Daru, Virginie; Bailliet, Hélène; Moreau, Solène; Valière, Jean-Christophe; Baltean-Carlès, Diana; Weisman, Catherine
2013-09-01
Rayleigh streaming in a cylindrical acoustic standing waveguide is studied both experimentally and numerically for nonlinear Reynolds numbers from 1 to 30 [Re(NL)=(U0/c0)(2)(R/δν)(2), with U0 the acoustic velocity amplitude at the velocity antinode, c0 the speed of sound, R the tube radius, and δν the acoustic boundary layer thickness]. Streaming velocity is measured by means of laser Doppler velocimetry in a cylindrical resonator filled with air at atmospheric pressure at high intensity sound levels. The compressible Navier-Stokes equations are solved numerically with high resolution finite difference schemes. The resonator is excited by shaking it along the axis at imposed frequency. Results of measurements and of numerical calculation are compared with results given in the literature and with each other. As expected, the axial streaming velocity measured and calculated agrees reasonably well with the slow streaming theory for small ReNL but deviates significantly from such predictions for fast streaming (ReNL>1). Both experimental and numerical results show that when ReNL is increased, the center of the outer streaming cells are pushed toward the acoustic velocity nodes until counter-rotating additional vortices are generated near the acoustic velocity antinodes.
Probing inflation models with gravitational waves
Domcke, Valerie
2016-01-01
A direct detection of primordial gravitational waves is the ultimate probe for any inflation model. While current CMB bounds predict the generic scale-invariant gravitational wave spectrum from slow-roll inflation to be below the reach of upcoming gravitational wave interferometers, this prospect may dramatically change if the inflaton is a pseudoscalar. In this case, a coupling to any abelian gauge field leads to a tachyonic instability for the latter and hence to a new source of gravitational waves, directly related to the dynamics of inflation. In this contribution we discuss how this setup enables the upcoming gravitational wave interferometers advanced LIGO/VIRGO and eLISA to probe the microphysics of inflation, distinguishing between different universality classes of single-field slow-roll inflation models. We find that the prime candidate for an early detection is a Starobinsky-like model.
THE DIABATIC WAVES IN BAROTROPIC MODEL
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The equations of barotropic model are used to discuss the effects of diabatic factors such as heating of convective condensation, evaporation-wind feedback and CISK on the Rossby wave and the Kelvin wave. In low latitudes we have obtained the angular frequency and analyzed the period and stability of waves. The result shows the existence of the diabatic factors not only enlarges the period of adiabatic waves but also changes the stability of waves. Thus we think that the so-called intraseasonal oscillation and some other low-frequency oscillations are a kind of diabatic waves which are important factors producing the long-term weather changes and short-term climatic evolution.
Neural network modelling of rainfall interception in four different forest stands
Directory of Open Access Journals (Sweden)
Ibrahim Yurtseven
2013-12-01
Full Text Available The objective of this study is to reveal whether it is possible to predict rainfall, throughfall and stemflow in forest ecosystems with less effort, using several measurements of rainfall interception (hereafter interception and an artificial neural network based linear regression model (ANN model. To this end, the Kerpe Research Forest in the province of Kocaeli, which houses stands of mixed deciduous-broadleaf forest (Castanea sativa Mill., Fagus orientalis Lipsky, Quercus spp., black pine (Pinus nigra Arnold, maritime pine (Pinus pinaster Aiton and Monterey pine (Pinus radiata D. Don, was selected study site. Four different forest stands were observed for a period of two years, during which rainfall, throughfall and stemflow measurements were conducted. These measurements were separately calculated for each individual stand, based on interception values and the use of stemflow data in strict accordance with the rainfall data, and the measured throughfall interception values were compared with values estimated by the ANN model. In this comparison, 70% of the total data was used for testing, and 30% was used for estimation and performance evaluation. No significant differences were found between values predicted with the help of the model and the measured values. In other words, interception values predicted by the ANN models were parallel with the measured values. In this study, the most success was achieved with the models of the Monterey pine stand (r2 = 0.9968; Mean Squared Error MSE = 0.16 and the mixed deciduous forest stand (r2 = 0.9964; MSE = 0.08, followed by models of the maritime pine stand (r2 = 0.9405; MSE = 1.27 and the black pine stand (r2 = 0.843, MSE = 17.36.
Neural network modelling of rainfall interception in four different forest stands
Directory of Open Access Journals (Sweden)
İbrahim Yurtseven
2013-11-01
Full Text Available The objective of this study is to reveal whether it is possible to predict rainfall, through fall and stem flow in forest ecosystems with less effort, using several measurements of rainfall interception (hereafter ‘interception’ and an artificial neural network based linear regression model (ANN model. To this end, the Kerpe Research Forest in the province of Kocaeli, which houses stands of mixed deciduous-broadleaf forest (Castanea sativa Mill., Fagusorientalis Lipsky, Quercus spp., black pine (Pinus nigra Arnold, maritime pine (Pinus pinaster Aiton and Monterey pine (Pinus radiata D. Don, was selected study site. Four different forest stands were observed for a period of two years, during which rainfall, throughfall and stemflow measurements were conducted. These measurements were separately calculated for each individual stand, based on interception values and the use of stemflow data in strict accordance with the rainfall data, and the measured throughfall interceptionvalues were compared with values estimated by the ANN model.In this comparison, 70% of the total data was used for testing, and 30% was used for estimation and performance evaluation. No significant differences were found between values predicted with the help of the model and the measured values. In other words, interception values predicted by the ANN models were parallel with the measured values. In this study, the most success was achieved with the models of the Monterey pine stand (r2 = 0.9968; Mean Squared Error MSE = 0.16 and the mixed deciduous forest stand (r2 = 0.9964; MSE = 0.08, followed by models of the maritime pine stand (r2 = 0.9405; MSE = 1.27 and the black pine stand (r2 = 0.843, MSE = 17.36.
DEFF Research Database (Denmark)
Ambühl, Simon; Kofoed, Jens Peter; Sørensen, John Dalsgaard
2015-01-01
Wave models used for site assessments are subjected to model uncertainties, which need to be quantified when using wave model results for probabilistic reliability assessments. This paper focuses on determination of wave model uncertainties. Four different wave models are considered, and validation...... uncertainties can be implemented in probabilistic reliability assessments....
Goos-Hänchen shift in a standing-wave-coupled electromagnetically-induced-transparency medium
Zhang, Xiao-Jun; Wang, Hai-Hua; Liang, Zhi-Peng; Xu, Yan; Fan, Cun-Bo; Liu, Cheng-Zhi; Gao, Jin-Yue
2015-03-01
The Goos-Hänchen shift of the system composed by two cavity walls and an intracavity atomic sample is presented. The atomic sample is treated as a four-level double-Λ system, driven by the two counterpropagating coupling fields. The probe field experiences the discontinuous refractive index variation and is reflected. Moreover, under the phase-matching condition, the four-wave mixing effect based on electromagnetically induced transparency can cause effective reflection. The Goos-Hänchen shifts appear in both situations and are carefully investigated in this article. We refer to the first one with the incident and reflected light having identical wavelength as the linear Goos-Hänchen shift, and the second one with the reflection wavelength determined by the phase-matching condition as the nonlinear Goos-Hänchen shift. The differences between the two kinds of shifts, such as the incident angle range, conditions for the shift peaks, and controllability, are discussed.
Directory of Open Access Journals (Sweden)
Paulo JA
2016-06-01
Full Text Available A generalized non-linear tree crown diameter model was developed with the aim of allowing the computation of tree crown diameter over a large range of tree dimensions, and allowing its inclusion in forest growth and yield models. The model was formulated to provide biological meaning to the predicted values. Due to the nested structure of the data analyzed (trees within stands, both mixed- and fixed-effect models were developed. Since tree crown diameter is not frequently measured in forest inventories, the validation of the mixed model was carried out by considering the population specific response. The results demonstrate that when the measurements required for the mixed model calibration are not available, the use of the fixed effect model results in less biased and more accurate estimates. The fixed model was applied to the data from the two last Portuguese National Forest Inventories (NFI to analyze the change in stand crown cover and assess the stocking evolution of cork oak stands in Portugal between 1996 and 2006. Results showed an increase in the frequency of stands with crown cover lower than 20%, as well as a decrease in the frequency of stands with crown cover between 20 and 40%. Average crown cover values were significantly different in the two NFI, with a decrease from 28.0 to 26.5% over the considered period.
Baroclinic stationary waves in aquaplanet models
Zappa, Giuseppe; Navarra, Antonio; 10.1175/2011JAS3573.1
2011-01-01
An aquaplanet model is used to study the nature of the highly persistent low frequency waves that have been observed in models forced by zonally symmetric boundary conditions. Using the Hayashi spectral analysis of the extratropical waves, we find that a quasi-stationary (QS) wave five belongs to a wave packet obeying a well defined dispersion relation with eastward group velocity. The components of the dispersion relation with k>5 baroclinically convert eddy available potential energy into eddy kinetic energy, while those with k<5 are baroclinically neutral. In agreement with the Green's model of baroclinic instability, the wave five is weakly unstable, and the inverse energy cascade, which had been previously proposed as a main forcing for this type of waves, only acts as a positive feedback on its predominantly baroclinic energetics. The QS wave is reinforced by a phase lock to an analogous pattern in the tropical convection, which provides further amplification to the wave. We also find that the Pedlos...
Travelling Waves in Hybrid Chemotaxis Models
Franz, Benjamin
2013-12-18
Hybrid models of chemotaxis combine agent-based models of cells with partial differential equation models of extracellular chemical signals. In this paper, travelling wave properties of hybrid models of bacterial chemotaxis are investigated. Bacteria are modelled using an agent-based (individual-based) approach with internal dynamics describing signal transduction. In addition to the chemotactic behaviour of the bacteria, the individual-based model also includes cell proliferation and death. Cells consume the extracellular nutrient field (chemoattractant), which is modelled using a partial differential equation. Mesoscopic and macroscopic equations representing the behaviour of the hybrid model are derived and the existence of travelling wave solutions for these models is established. It is shown that cell proliferation is necessary for the existence of non-transient (stationary) travelling waves in hybrid models. Additionally, a numerical comparison between the wave speeds of the continuum models and the hybrid models shows good agreement in the case of weak chemotaxis and qualitative agreement for the strong chemotaxis case. In the case of slow cell adaptation, we detect oscillating behaviour of the wave, which cannot be explained by mean-field approximations. © 2013 Society for Mathematical Biology.
Variational modelling of nonlinear water waves
Kalogirou, Anna; Bokhove, Onno
2015-11-01
Mathematical modelling of water waves is demonstrated by investigating variational methods. A potential flow water wave model is derived using variational techniques and extented to include explicit time-dependence, leading to non-autonomous dynamics. As a first example, we consider the problem of a soliton splash in a long wave channel with a contraction at its end, resulting after a sluice gate is removed at a finite time. The removal of the sluice gate is included in the variational principle through a time-dependent gravitational potential. A second example involving non-autonomous dynamics concerns the motion of a free surface in a vertical Hele-Shaw cell. Explicit time-dependence now enters the model through a linear damping term due to the effect of wall friction and a term representing the motion of an artificially driven wave pump. In both cases, the model is solved numerically using a Galerkin FEM and the numerical results are compared to wave structures observed in experiments. The water wave model is also adapted to accommodate nonlinear ship dynamics. The novelty is this case is the coupling between the water wave dynamics, the ship dynamics and water line dynamics on the ship. For simplicity, we consider a simple ship structure consisting of V-shaped cross-sections.
Institute of Scientific and Technical Information of China (English)
朱卫卫; 张秋菊; 张延惠; 焦扬
2015-01-01
The motions of charged particles in electromagnetic fields composed of two or more laser beams show a variety of forms due to the adjustable properties of electromagnetic fields. In this paper, we consider the periodic laser standing wave field composed of two laser beams with opposite propagating directions. The movement of electrons in the standing wave field shows a periodic behavior, accompanied with the obvious radiation, especially when electrons are captured by the laser standing wave field. This phenomenon has aroused much interest of us. Under the existing experimental conditions, the free electron beam with low energy from an electron gun or the relativistic electron beam generated from laser acceleration can be easily obtained and injected into the periodic standing wave field. In this paper, using the single-electron model and the classical radiation theory of charged particles, we study the motion and radiation processes of low and high energy electrons in the polarized laser standing wave field. The results show that when the direction of incident electrons with low-speed is perpendicular to the direction of the laser standing wave electric field, the one-dimensional nearly periodic motion of electrons evolves into a two-dimensional folded movement by gradually increasing the light intensity of the laser standing wave field, and the strong terahertz radiation at micrometer wavelength is produced. High energy electrons generate the high-frequency radiation with the wavelength at several nanometers when the incident direction of high energy electrons is perpendicular or parallel to the direction of the laser standing wave electric field. In the case of low-energy electron, the motion of electron, frequency and intensity of radiation are affected by the laser intensity. In the case of incident high-energy electrons, the laser intensity affects the intensity of electronic radiation, and the initial electron energy influences radiation frequency. The
Hydraulic Model Tests on Modified Wave Dragon
DEFF Research Database (Denmark)
Hald, Tue; Lynggaard, Jakob
A floating model of the Wave Dragon (WD) was built in autumn 1998 by the Danish Maritime Institute in scale 1:50, see Sørensen and Friis-Madsen (1999) for reference. This model was subjected to a series of model tests and subsequent modifications at Aalborg University and in the following...... are found in Hald and Lynggaard (2001). Model tests and reconstruction are carried out during the phase 3 project: ”Wave Dragon. Reconstruction of an existing model in scale 1:50 and sequentiel tests of changes to the model geometry and mass distribution parameters” sponsored by the Danish Energy Agency...
Energy Technology Data Exchange (ETDEWEB)
Vesa, Lauri [ForestCalc Consulting Oy Ltd., 80230 Joensuu (Finland); Palander, Teijo [School of Forest Sciences, University of Eastern Finland, 80100 Joensuu (Finland)
2010-09-15
The value and volumes of industrial stump fuel supply are increasing for energy production. Accurate estimates of aboveground and belowground biomass of trees are important when estimating the potential of stumps as a bioenergy source. In this study two stump biomass equations were adapted and tested using them as calibrated stump biomass models computed as the cumulative sum by a local stand. In addition, variables derived from stem measurements of the forest harvester data were examined to predict stump biomass of a stand by applying regression analysis. The true stump yield (dry weight) was used as the reference data in the study. Both biomass models performed well (adjusted R{sup 2} {proportional_to} 0.84) and no advance was found in using other stem dimensions as independent variables in the model. The stand-level model can be used in innovative stump biomass prediction tools for increasing efficiency of energy wood procurement planning to stands within a certain area. In practice, wood procurement managers would need to adapt developed system and decide whether the degree of accuracy/precision provided by the models is acceptable in their local stand harvesting conditions. (author)
Models for Predicting the Biomass of Cunninghamialanceolata Trees and Stands in Southeastern China.
Guangyi, Mei; Yujun, Sun; Saeed, Sajjad
2017-01-01
Using existing equations to estimate the biomass of a single tree or a forest stand still involves large uncertainties. In this study, we developed individual-tree biomass models for Chinese Fir (Cunninghamia lanceolata.) stands in Fujian Province, southeast China, by using 74 previously established models that have been most commonly used to estimate tree biomass. We selected the best fit models and modified them. The results showed that the published model ln(B(Biomass)) = a + b * ln(D) + c * (ln(H))2 + d * (ln(H))3 + e * ln(WD) had the best fit for estimating the tree biomass of Chinese Fir stands. Furthermore, we observed that variables D(diameter at breast height), H (height), and WD(wood density)were significantly correlated with the total tree biomass estimation model. As a result, a natural logarithm structure gave the best estimates for the tree biomass structure. Finally, when a multi-step improvement on tree biomass model was performed, the tree biomass model with Tree volume(TV), WD and biomass wood density conversion factor (BECF),achieved the highest simulation accuracy, expressed as ln(TB) = -0.0703 + 0.9780 * ln(TV) + 0.0213 * ln(WD) + 1.0166 * ln(BECF). Therefore, when TV, WD and BECF were combined with tree biomass volume coefficient bi for Chinese Fir, the stand biomass (SB)model included both volume(SV) and coefficient bi variables of the stand as follows: bi = Exp(-0.0703+0.9780*ln(TV)+0.0213 * ln(WD)+1.0166*ln(BECF)). The stand biomass model is SB = SV/TV * bi.
On the modelling of equatorial waves
Constantin, A.
2012-03-01
The present theory of geophysical waves that either raise or lower the equatorial thermocline, based on the reduced-gravity shallow-water equations on the β-plane, ignores vertical variations of the flow. In particular, the vertical structure of the Equatorial Undercurrent is absent. As a remedy we propose a simple approach by modeling this geophysical process as a wave-current interaction in the f-plane approximation, the underlying current being of positive constant vorticity. The explicit dispersion relation allows us to conclude that, despite its simplicity, the proposed model captures to a reasonable extent essential features of equatorial waves.
Photovoltaic Module Simulink Model for a Stand-alone PV System
Qi, Chen; Ming, Zhu
Photovoltaic(PV) Module is indispensable of a stand-alone PV system. In this paper, a one-diode equivalent circuit-based versatile simulation model in the form of masked block PV module is proposed. By the model, it is allowed to estimate behavior of PV module with respect changes on irradiance intensity, ambient temperature and parameters of the PV module. In addition, the model is capable of function of Maximum Power Point Tracking (MPPT) which can be used in the dynamic simulation of stand-alone PV systems.
Energy Technology Data Exchange (ETDEWEB)
Ross, N., E-mail: rossn2282@gmail.com; Kostylev, M., E-mail: mikhail.kostylev@uwa.edu.au [School of Physics, University of Western Australia, Crawley, WA (Australia); Stamps, R. L. [School of Physics, University of Western Australia, Crawley, WA (Australia); SUPA School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)
2014-09-21
Standing spin wave mode frequencies and linewidths in partially disordered perpendicular magnetized arrays of sub-micron Permalloy discs are measured using broadband ferromagnetic resonance and compared to analytical results from a single, isolated disc. The measured mode structure qualitatively reproduces the structure expected from the theory. Fitted demagnetizing parameters decrease with increasing array disorder. The frequency difference between the first and second radial modes is found to be higher in the measured array systems than predicted by theory for an isolated disc. The relative frequencies between successive spin wave modes are unaffected by reduction of the long-range ordering of discs in the array. An increase in standing spin wave resonance linewidth at low applied magnetic fields is observed and grows more severe with increased array disorder.
Study on Solitary Waves of a General Boussinesq Model
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
In this paper, we employ the bifurcation method of dynamical systems to study the solitary waves and periodic waves of a generalized Boussinesq equations. All possible phase portraits in the parameter plane for the travelling wave systems are obtained. The possible solitary wave solutions, periodic wave solutions and cusp waves for the general Boussinesq type fluid model are also investigated.
-Advanced Models for Tsunami and Rogue Waves
Directory of Open Access Journals (Sweden)
D. W. Pravica
2012-01-01
Full Text Available A wavelet , that satisfies the q-advanced differential equation for , is used to model N-wave oscillations observed in tsunamis. Although q-advanced ODEs may seem nonphysical, we present an application that model tsunamis, in particular the Japanese tsunami of March 11, 2011, by utilizing a one-dimensional wave equation that is forced by . The profile is similar to tsunami models in present use. The function is a wavelet that satisfies a q-advanced harmonic oscillator equation. It is also shown that another wavelet, , matches a rogue-wave profile. This is explained in terms of a resonance wherein two small amplitude forcing waves eventually lead to a large amplitude rogue. Since wavelets are used in the detection of tsunamis and rogues, the signal-analysis performance of and is examined on actual data.
Modelling Variable Fire Severity in Boreal Forests: Effects of Fire Intensity and Stand Structure.
Miquelajauregui, Yosune; Cumming, Steven G; Gauthier, Sylvie
2016-01-01
It is becoming clear that fires in boreal forests are not uniformly stand-replacing. On the contrary, marked variation in fire severity, measured as tree mortality, has been found both within and among individual fires. It is important to understand the conditions under which this variation can arise. We integrated forest sample plot data, tree allometries and historical forest fire records within a diameter class-structured model of 1.0 ha patches of mono-specific black spruce and jack pine stands in northern Québec, Canada. The model accounts for crown fire initiation and vertical spread into the canopy. It uses empirical relations between fire intensity, scorch height, the percent of crown scorched and tree mortality to simulate fire severity, specifically the percent reduction in patch basal area due to fire-caused mortality. A random forest and a regression tree analysis of a large random sample of simulated fires were used to test for an effect of fireline intensity, stand structure, species composition and pyrogeographic regions on resultant severity. Severity increased with intensity and was lower for jack pine stands. The proportion of simulated fires that burned at high severity (e.g. >75% reduction in patch basal area) was 0.80 for black spruce and 0.11 for jack pine. We identified thresholds in intensity below which there was a marked sensitivity of simulated fire severity to stand structure, and to interactions between intensity and structure. We found no evidence for a residual effect of pyrogeographic region on simulated severity, after the effects of stand structure and species composition were accounted for. The model presented here was able to produce variation in fire severity under a range of fire intensity conditions. This suggests that variation in stand structure is one of the factors causing the observed variation in boreal fire severity.
Studies on stand dynamic growth model for larch in Jilin in China
Institute of Scientific and Technical Information of China (English)
WENGGuo-qing; CHENXue-feng
2004-01-01
The stand growth and yield dynamic models for Larch in Jilin Province were developed based on the forest growth theories with the forest continuous inventory data. The results indicated that the developed models had high precision, and they could be used for the updating data of inventory of planning and designing and optimal decision of forest management.
Standing-wave excited hard x-ray phototemission studies on a Au-sandwiched Fe/MgO interface
Energy Technology Data Exchange (ETDEWEB)
Doering, Sven; Keutner, Christoph; Schoenbohm, Frank; Berges, Ulf; Westphal, Carsten [DELTA/Experimentelle Physik I, TU Dortmund, Otto-Hahn-Str. 4, 44221 Dortmund (Germany); Buergler, Daniel E.; Schneider, Claus M. [IFF-9, Forschungszentrum Juelich, 52425 Juelich (Germany); Gorgoi, Mihaela; Schaefers, Franz [Helmholtzzentrum Berlin fuer Materialien und Energie, Albert Einstein Str. 15, 12489 Berlin (Germany)
2011-07-01
Magnetic tunnel junctions (MTJs) consisting of a thin layer-stack of Fe/MgO/Fe show a high tunnel-magneto resistance (TMR) ratio at room temperature. The strength of this effect is mainly driven by the interface and thus the Fe/MgO interface has been subject of many studies during the last years. Quite recently, calculations predicted an even higher TMR ratio for modified interfaces. In that work it was proposed that a monolayer of Au at the interface prevents the oxidation of the Fe-layer, and thus an increase of the TMR effect is expected. Up to now there is no experimental evidence that a well-defined Au monolayer can be prepared with the objective of preventing the Fe oxidation at the interface. In this work we studied a Au-modified interface with standing-wave excited hard X-ray photoemission. The goal of this study was the determination of the effective roughness of the Au layer. Our data-analysis shows that Au does not grow as a protective monolayer nor any hint of FeO formation was found.
Kolaini, Ali R.; Doty, Benjamin; Chang, Zensheu
2012-01-01
Loudspeakers have been used for acoustic qualification of spacecraft, reflectors, solar panels, and other acoustically responsive structures for more than a decade. Limited measurements from some of the recent speaker tests used to qualify flight hardware have indicated significant spatial variation of the acoustic field within the test volume. Also structural responses have been reported to differ when similar tests were performed using reverberant chambers. To address the impact of non-uniform acoustic field on structural responses, a series of acoustic tests were performed using a flat panel and a 3-ft cylinder exposed to the field controlled by speakers and repeated in a reverberant chamber. The speaker testing was performed using multi-input-single-output (MISO) and multi-input-multi-output (MIMO) control schemes with and without the test articles. In this paper the spatial variation of the acoustic field due to acoustic standing waves and their impacts on the structural responses in RAT and DFAT (both using MISO and MIMO controls for DFAT) are discussed in some detail.
Sakata, O.; Hashizume, H.
1995-02-01
An ultrahigh vacuum (UHV) diffractometer has been designed for studies of surface structures using the grazing-angle x-ray standing-wave method. The design is featured by a horizontal plane of diffraction for use at a vertical-wiggler source of synchrotron radiation. A sample is horizontally mounted in an UHV chamber (4×10-7 Pa) placed on crossed swivels, which control the glancing-incidence angle of x rays on the sample surface with a 50-μrad accuracy. The chamber accepts a sample from a transportation vessel under high vacuum. A beryllium window allows x-ray fluorescence to reach a semiconductor detector at short access. The whole assembly sits on a high-precision rotary table, regulating the sample Δθ angle with a reproducibility of better than 0.5 μrad required for control of the x-ray field profile. The system has been successfully applied to an accurate determination of the in-plane ordering of As atoms on a Si(111) surface with a 1×1 structure.
Turbulent Spot Pressure Fluctuation Wave Packet Model
Energy Technology Data Exchange (ETDEWEB)
Dechant, Lawrence J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2017-05-01
Wave packet analysis provides a connection between linear small disturbance theory and subsequent nonlinear turbulent spot flow behavior. The traditional association between linear stability analysis and nonlinear wave form is developed via the method of stationary phase whereby asymptotic (simplified) mean flow solutions are used to estimate dispersion behavior and stationary phase approximation are used to invert the associated Fourier transform. The resulting process typically requires nonlinear algebraic equations inversions that can be best performed numerically, which partially mitigates the value of the approximation as compared to a more complete, e.g. DNS or linear/nonlinear adjoint methods. To obtain a simpler, closed-form analytical result, the complete packet solution is modeled via approximate amplitude (linear convected kinematic wave initial value problem) and local sinusoidal (wave equation) expressions. Significantly, the initial value for the kinematic wave transport expression follows from a separable variable coefficient approximation to the linearized pressure fluctuation Poisson expression. The resulting amplitude solution, while approximate in nature, nonetheless, appears to mimic many of the global features, e.g. transitional flow intermittency and pressure fluctuation magnitude behavior. A low wave number wave packet models also recover meaningful auto-correlation and low frequency spectral behaviors.
Mesoscale Wind Predictions for Wave Model Evaluation
2016-06-07
N0001400WX20041(B) http://www.nrlmry.navy.mil LONG TERM GOALS The long-term goal is to demonstrate the significance and importance of high...ocean waves by an appropriate wave model. OBJECTIVES The main objectives of this project are to: 1. Build the infrastructure to generate the...temperature for all COAMPS grids at the resolution of each of these grids. These analyses are important for the proper 2 specification of the lower
The Standing Wave Phenomenon in Radio Telescopes; Frequency Modulation of the WSRT Primary Beam
Popping, Attila
2007-01-01
Inadequacies in the knowledge of the primary beam response of current interferometric arrays often form a limitation to the image fidelity. We hope to overcome these limitations by constructing a frequency-resolved, full-polarization empirical model for the primary beam of the Westerbork Synthesis Radio Telescope (WSRT). Holographic observations, sampling angular scales between about 5 arcmin and 11 degrees, were obtained of a bright compact source (3C147). These permitted measurement of voltage response patterns for seven of the fourteen telescopes in the array and allowed calculation of the mean cross-correlated power beam. Good sampling of the main-lobe, near-in, and far-side-lobes out to a radius of more than 5 degrees was obtained. A robust empirical beam model was detemined in all polarization products and at frequencies between 1322 and 1457 MHz with 1 MHz resolution. Substantial departures from axi-symmetry are apparent in the main-lobe as well as systematic differences between the polarization proper...
Directory of Open Access Journals (Sweden)
Yun-Li Chen
2007-01-01
Full Text Available Utilizing Ground Penetrating Radar (GPR, emitted electromagnetic (EM standing waves can be generated in underground voids. This phenomenon can be employed for the detection of subterranean voids and fractures when one has a proper understanding of relation between the widest inner length in an underground vacant space and half an EM wavelength. In this study, indoor and outdoor small-scale experiments verified the generation of EM standing waves. These responses were then applied in an arched-top cave covered by a single layer of backfill at Gongzihliao, Taiwan. Further studies were carried out at two other sites, including a fracture located in a granite mountain without regolith on the surface at Kinmen, and a deteriorating fishing port in Nanfangao, northeast Taiwan. Applying a band-pass filter with bandwidth narrower than a typical two-octave bandwidth produced the required standing waves with recognizable positions of minimum amplitude. A hyperbolic travel-time (HTT curve revealing the minimum amplitude, known as standing-wave nodes, indicates the presence of an underground hollow diffractor with the widest inner length in the vacant space being larger than half an EM wavelength. However, a HTT curve without nodal points signifies a hollow object with the widest inner length smaller than half an EM wavelength or an underground solid diffractor. An underground arched-top cave was detected by nodal points in the arc-like curves. When emitting the radar waves toward a wall, the interval of the nodes was used for estimating the wavelength of receiving GPR signals. Identifying the occurrence of nodal points in HTT or HTTlike curves in radargrams may assist the GPR interpreting work for underground tunnels, drainages, cavities, fractures, or solid objects.
Comparison of N and C dynamics in two Norway spruce stands using a process oriented simulation model
DEFF Research Database (Denmark)
Eckersten, H.; Beier, C.
1998-01-01
) was located in south-west Sweden (Skogaby) growing on a loamy sand soil. The old stand (70 years old) was growing on a sandy soil in western Denmark (Klosterhede). Differences in specific rates of processes between the two sites were estimated in terms of parameter values derived by calibration of the model......Nitrogen and carbon dynamics of two Norway spruce stands were compared using a dynamic soil-plant simulation model (SOILN). The objectives were to evaluate differences in properties between the two stands and to explore the consequences on C and N dynamics. The young stand (25 years old...... whereas growth was more similar. The soil carbon balance was positive and soil CIN ratio increased for the young stand. For the old stand the soil carbon balance was negative and the C/N ratio decreased. The soil mineral N levels were much lower in the younger stand which was explained by a higher plant...
Traveling waves for models of phase transitions of solids driven by configurational forces
Kawashima, Shuichi
2009-01-01
This article is concerned with the existence of traveling wave solutions, including standing waves, to some models based on configurational forces, describing respectively the diffusionless phase transformations of solid materials, e.g., Steel, and phase transitions due to interface motion by interface diffusion, e.g., Sintering. These models are recently proposed by Alber and Zhu. We consider both the order-parameter-conserved case and the non-conserved one, under suitable assumptions. Also we compare our results with the corresponding ones for the Allen-Cahn and the Cahn-Hilliard equations coupled with linear elasticity, which are models for diffusion-dominated phase transformations in elastic solids.
Wave Modeling of the Solar Wind.
Ofman, Leon
The acceleration and heating of the solar wind have been studied for decades using satellite observations and models. However, the exact mechanism that leads to solar wind heating and acceleration is poorly understood. In order to improve the understanding of the physical mechanisms that are involved in these processes a combination of modeling and observational analysis is required. Recent models constrained by satellite observations show that wave heating in the low-frequency (MHD), and high-frequency (ion-cyclotron) range may provide the necessary momentum and heat input to coronal plasma and produce the solar wind. This review is focused on the results of several recent solar modeling studies that include waves explicitly in the MHD and the kinetic regime. The current status of the understanding of the solar wind acceleration and heating by waves is reviewed.
Photoemission-monitored x-ray standing wave studies of molecular adsorbate surface structure
Lee, J J
2002-01-01
The influence of non-dipole photoemission terms on the accuracy of photoemission-monitored NIXSW structure determinations has been studied. An experimental survey has been made of values of the incoherent dipole-quadrupole parameter as a function of energy and atomic number for the Is states of elements between carbon and chlorine inclusive. These values are compared with recent theoretical calculations. The contribution of the coherent dipole-quadrupole interference terms, whose form has been theoretically derived recently, has been experimentally measured for Is photoemission from clean Al(111). The coherent dipole-quadrupole effect is found to be small and easily corrected for, while the previously-known incoherent effect is shown to result in tolerable errors in most cases. Adsorption of methyl thiol (CH sub 3 SH) on Pt(111), followed by annealing to approx 220 K is believed to result in the formation of methyl thiolate (-SCH sub 3). Two structural models are consistent with NIXSW data presented here: co-...
Simulation modeling of wheeled vehicle dynamics on the stand "Roller"
Directory of Open Access Journals (Sweden)
G. O. Kotiev
2014-01-01
Full Text Available The tests are an integral part of the wheeled vehicle design, manufacturing, and operation. The need for their conducting arises from the research and experimental activities to assess the qualitative and quantitative characteristics of the vehicles in general, as well as the individual components and assemblies. It is obvious that a variety of design features of wheeled vehicles request a development of methods both for experimental studies and for creating the original bench equipment for these purposes.The main positive feature of bench tests of automotive engineering is a broad capability to control the combinations of traction loads, speed rates, and external input conditions. Here, the steady state conditions can be used for a long time, allowing all the necessary measurements to be made, including those with video and photo recording experiment.It is known that the benefits of test "M" type (using a roller dynamometer include a wide range of test modes, which do not depend on the climatic conditions, as well as a capability to use a computer-aided testing programs. At the same time, it is known that the main drawback of bench tests of full-size vehicle is that the tire rolling conditions on the drum mismatch to the real road pavements, which are difficult to simulate on the drum surface. This problem can be solved owing to wheeled vehicle tests at the benches "Roller" to be, in efficiency, the most preferable research method. The article gives a detailed presentation of developed at BMSTU approach to its solving.Problem of simulation mathematical modeling has been solved for the vehicle with the wheel formula 8 × 8, and individual wheel-drive.The simulation results have led to the conclusion that the proposed principle to simulate a vehicle rolling on a smooth non-deformable support base using a bench " Roller " by simulation modeling is efficient.
Modeling the effect of wave-vegetation interaction on wave setup
van Rooijen, A. A.; McCall, R. T.; van Thiel de Vries, J. S. M.; van Dongeren, A. R.; Reniers, A. J. H. M.; Roelvink, J. A.
2016-06-01
Aquatic vegetation in the coastal zone attenuates wave energy and reduces the risk of coastal hazards, e.g., flooding. Besides the attenuation of sea-swell waves, vegetation may also affect infragravity-band (IG) waves and wave setup. To date, knowledge on the effect of vegetation on IG waves and wave setup is lacking, while they are potentially important parameters for coastal risk assessment. In this study, the storm impact model XBeach is extended with formulations for attenuation of sea-swell and IG waves, and wave setup effects in two modes: the sea-swell wave phase-resolving (nonhydrostatic) and the phase-averaged (surfbeat) mode. In surfbeat mode, a wave shape model is implemented to capture the effect of nonlinear wave-vegetation interaction processes on wave setup. Both modeling modes are verified using data from two flume experiments with mimic vegetation and show good skill in computing the sea-swell and IG wave transformation, and wave setup. In surfbeat mode, the wave setup prediction greatly improves when using the wave shape model, while in nonhydrostatic mode (nonlinear) intrawave effects are directly accounted for. Subsequently, the model is used for a range of coastal geomorphological configurations by varying bed slope and vegetation extent. The results indicate that the effect of wave-vegetation interaction on wave setup may be relevant for a range of typical coastal geomorphological configurations (e.g., relatively steep to gentle slope coasts fronted by vegetation).
Simple opdriftsbaserede modeller for Wave Star
DEFF Research Database (Denmark)
Kramer, Morten
Wave Star modellen er udarbejdet i programmeringssproget Delphi. Modellerne er en videre udarbejdelse af tidligere anvendte Excel-modeller. I forhold til Excelmodellerne udmærker de nye Dephi-modeller sig ved at beregningerne udføres mange gange hurtigere og modellerne kan håndtere lange tidsserier...
Mitri, F G
2016-01-01
Analytical expressions for the axial and transverse acoustic radiation forces as well as the radiation torque per length are derived for a rigid elliptical cylinder placed arbitrarily in the field of in plane progressive, quasi-standing or standing waves. The rigid elliptical cylinder case is important to be considered as a first-order approximation of the behavior of a fluid particle suspended in air, because of the significant acoustic impedance mismatch at the particle's boundary. Based on the partial-wave series expansion method in cylindrical coordinates, non-dimensional acoustic radiation force and torque functions are derived and defined in terms of the scattering coefficients of the elliptic cylinder. A coupled system of linear equations is obtained after applying the Neumann boundary condition for an immovable surface in a non-viscous fluid, and solved numerically by matrix inversion after performing a single numerical integration procedure. Computational results for the non-dimensional force compone...
Effect of different tree mortality patterns on stand development in the forest model SIBYLA
Directory of Open Access Journals (Sweden)
Trombik Jiří
2016-09-01
Full Text Available Forest mortality critically affects stand structure and the quality of ecosystem services provided by forests. Spruce bark beetle (Ips typographus generates rather complex infestation and mortality patterns, and implementation of such patterns in forest models is challenging. We present here the procedure, which allows to simulate the bark beetle-related tree mortality in the forest dynamics model Sibyla. We explored how sensitive various production and stand structure indicators are to tree mortality patterns, which can be generated by bark beetles. We compared the simulation outputs for three unmanaged forest stands with 40, 70 and 100% proportion of spruce as affected by the disturbance-related mortality that occurred in a random pattern and in a patchy pattern. The used tree species and age class-specific mortality rates were derived from the disturbance-related mortality records from Slovakia. The proposed algorithm was developed in the SQLite using the Python language, and the algorithm allowed us to define the degree of spatial clustering of dead trees ranging from a random distribution to a completely clustered distribution; a number of trees that died in either mode is set to remain equal. We found significant differences between the long-term developments of the three investigated forest stands, but we found very little effect of the tested mortality modes on stand increment, tree species composition and diversity, and tree size diversity. Hence, our hypothesis that the different pattern of dead trees emergence should affect the competitive interactions between trees and regeneration, and thus affect selected productivity and stand structure indicators was not confirmed.
Frontal Plane Modelling of Human Dynamics during Standing in Narrow-Stance
Sonobe, M.; Yamaguchi, H.; Hino, J.
2016-09-01
Standing ride type vehicles like electric skateboards have been developed in recent years. Although these vehicles have advantages as being compact and low cost due to their simple structure, it is necessary to improve the riding quality. Therefore, the system aiding riders to keep their balance on a skateboard by feedback control or feedforward control has been required. To achieve it, a human balance model should be built as simple as possible. In this study, we focus on the human balance modelling during standing when the support surface moves largely. We restricted the model on frontal plane and narrow stance because the restrictions allow us to assume single-degree-of-freedom model. The balance control system is generally assumed as a delayed feedback control system. The model was identified through impulse response test and frequency response test. As a result, we found the phase between acceleration of the skateboard and posture angle become opposite phase in low frequency range.
Energy Technology Data Exchange (ETDEWEB)
Zargham, Ardalan, E-mail: zargham@ifp.uni-bremen.d [Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen (Germany); Schmidt, Thomas; Flege, Jan Ingo; Sauerbrey, Marc; Hildebrand, Radowan [Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen (Germany); Roehe, Sarah; Baeumer, Marcus [Applied and Physical Chemistry, University of Bremen, Leobener Str. 2, 28359, Bremen (Germany); Falta, Jens [Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen (Germany)
2010-02-15
We present a promising combination of methods to precisely determine the morphology of nanostructures, drawing on the example of monodisperse CoPt{sub 3} nanoparticle films deposited by spin coating and dip coating techniques on functionalized Au substrates. Ex-situ X-ray standing waves in total external reflection combined with X-ray reflectivity measurements were employed to determine element-specific atomic-density distributions in vertical direction.
Modeling of random wave transformation with strong wave-induced coastal currents
Institute of Scientific and Technical Information of China (English)
Zheng Jinhai; H. Mase; Li Tongfei
2008-01-01
The propagation and transformation of multi-directional and uni-directional random waves over a coast with complicated bathymetric and geometric features are studied experimentally and numerically. Laboratory investigation indicates that wave energy convergence and divergence cause strong coastal currents to develop and inversely modify the wave fields. A coastal spectral wave model, based on the wave action balance equation with diffraction effect (WABED), is used to simulate the transformation of random waves over the complicated bathymetry. The diffraction effect in the wave model is derived from a parabolic approximation of wave theory, and the mean energy dissipation rate per unit horizontal area due to wave breaking is parameterized by the bore-based formulation with a breaker index of 0.73. The numerically simulated wave field without considering coastal currents is different from that of experiments, whereas model results considering currents clearly reproduce the intensification of wave height in front of concave shorelines.
-Advanced Models for Tsunami and Rogue Waves
Pravica, D. W.; Randriampiry, N.; Spurr, M. J.
2012-01-01
A wavelet ${K}_{q}(t)$ , that satisfies the q-advanced differential equation ${K}_{q}^{\\prime }(t)={K}_{q}(qt)$ for $q>1$ , is used to model N-wave oscillations observed in tsunamis. Although q-advanced ODEs may seem nonphysical, we present an application that model tsunamis, in particular the Japanese tsunami of March 11, 2011, by utilizing a one-dimensional wave equation that is forced by ${F}_{q}(t,x)={K}_{q}{(t)}_{q}\\text{S}\\text{i}\\text{n}(x)$ . The profile ${F}_{q}$ is similar to tsunam...
Energy Technology Data Exchange (ETDEWEB)
Siebert, M.
2006-10-30
In this thesis, the incorporation of Mg and Si in GaN-films grown on (0001)-sapphire substrates is investigated in detail by applying several synchrotron radiation techniques. The segregational behavior of Si and Mg is investigated by X-ray-photoelectron-spectroscopy (XPS) and XPS-microscopy. For the first time, it is revealed that also Si segregates to the surface and stabilizes surface facets along high-symmetry directions. Additionally, it is found that Mg also segregates to the crystal surface at concentrations far below the threshold condition for the formation of pyramidal defects. For the first time, the technique of X-ray standing waves (XSW), which allows to directly conclude on the crystal and defect structure on the atomic scale, is successfully applied to thick crystals with high defect density. In order to compensate for the high crystal mosaicity of GaN, which significantly reduces the accuracy of the XSW-measurements, the experiments were performed in near-backscattering geometry, as in this setup the intrinsic reflection width becomes large as compared to the tilt mosaicity. Influences of doped crystal material are suppressed by using a thick undoped high quality GaN-film for the formation of a standing wave field, which is used for the investigation of a thin doped film deposited on top. By performing the XSW measurements with probe signals of different surface sensitivity (fluorescence and photoelectrons) the incorporation behavior within the bulk crystal is compared to regions close to the surface. Within this thesis a technique is suggested that allows to determine the non-dipole contributions to the yield by comparing Auger electron and photoelectron secondary signals. The XSW-measurements on Si-doped samples reveal that Si is solely incorporated on substitutional Ga-sites both within the bulk crystal and close to the surface. In the bulk, Si is homogeneously distributed, distorting the crystal lattice in their vicinity. At the surface Si is
Kuznetsova, Larisa A; Martin, Stacey P; Coakley, W Terence
2005-12-15
The capture of 200 nm biotinylated latex beads from suspensions of concentration 10(7) to 2.5 x 10(8) particle/ml on an immuno-coated surface of the acoustic reflector in an ultrasound standing wave (USW) resonator has been studied while the acoustic pathlength was less than one half wavelength (lambda/2). The particles were delivered to the reflector's surface by acoustically induced flow. The capture dependencies on suspension concentration, duration of experiments and acoustic pressure have been established at 1.09, 1.46 and 1.75 MHz. Five-fold capture increase has been obtained at 1.75 MHz in comparison to the control (no ultrasound) situation. The contrasting behaviours of 1, 0.5 and 0.2 mum fluorescent latex beads in a lambda/4 USW resonator at 1.46 MHz have been characterized. The particle movements were observed with an epi-fluorescent microscope and the velocities of the particles were measured by particle image velocimetry (PIV). The experiments showed that whereas the trajectories of 1 mum particles were mainly affected by the direct radiation force, 0.5 mum particles were influenced both by the radiation force and acoustic streaming. The 0.2 mum latex beads followed acoustic streaming in the chamber and were not detectably affected by the radiation force. The streaming-associated behaviour of the 200 nm particles has implications for enhanced immunocapture of viruses and macromolecules (both of which are also too small to experience significant acoustic radiation force).
A Comparison of Nature Waves and Model Waves with Special Reference to Wave Grouping
DEFF Research Database (Denmark)
Burcharth, Hans F.
This paper represents a comparative analyses of the occurrence of wave grouping in field storm waves and laboratory waves with similar power spectra and wave height distribution.......This paper represents a comparative analyses of the occurrence of wave grouping in field storm waves and laboratory waves with similar power spectra and wave height distribution....
Model for predicting mountain wave field uncertainties
Damiens, Florentin; Lott, François; Millet, Christophe; Plougonven, Riwal
2017-04-01
Studying the propagation of acoustic waves throughout troposphere requires knowledge of wind speed and temperature gradients from the ground up to about 10-20 km. Typical planetary boundary layers flows are known to present vertical low level shears that can interact with mountain waves, thereby triggering small-scale disturbances. Resolving these fluctuations for long-range propagation problems is, however, not feasible because of computer memory/time restrictions and thus, they need to be parameterized. When the disturbances are small enough, these fluctuations can be described by linear equations. Previous works by co-authors have shown that the critical layer dynamics that occur near the ground produces large horizontal flows and buoyancy disturbances that result in intense downslope winds and gravity wave breaking. While these phenomena manifest almost systematically for high Richardson numbers and when the boundary layer depth is relatively small compare to the mountain height, the process by which static stability affects downslope winds remains unclear. In the present work, new linear mountain gravity wave solutions are tested against numerical predictions obtained with the Weather Research and Forecasting (WRF) model. For Richardson numbers typically larger than unity, the mesoscale model is used to quantify the effect of neglected nonlinear terms on downslope winds and mountain wave patterns. At these regimes, the large downslope winds transport warm air, a so called "Foehn" effect than can impact sound propagation properties. The sensitivity of small-scale disturbances to Richardson number is quantified using two-dimensional spectral analysis. It is shown through a pilot study of subgrid scale fluctuations of boundary layer flows over realistic mountains that the cross-spectrum of mountain wave field is made up of the same components found in WRF simulations. The impact of each individual component on acoustic wave propagation is discussed in terms of
Standing detonation wave engine
Kasimov, Aslan
2015-10-08
A detonation engine can detonate a mixture of fuel and oxidizer within a cylindrical detonation region to produce work. The detonation engine can have a first and a second inlet having ends fluidly connected from tanks to the detonation engine. The first and second inlets can be aligned along a common axis. The inlets can be connected to nozzles and a separator can be positioned between the nozzles and along the common axis.
de Campos Valadares, Eduardo; Alves, Esdras Garcia
2005-05-01
Local "reversal of gravity" can be simulated with an inverted pendulum whose pivot is made to oscillate vertically. A beautiful demonstration of this surprising effect can be found in Ref. 1. In this case, the pendulum is a piece of plastic straw and its pivot pin is fixed at the end of a plastic ruler that is made to oscillate vertically by a small eccentric motor. A theoretical treatment of this inverted pendulum may be found in Ref. 2.
DEFF Research Database (Denmark)
Ambühl, Simon; Kofoed, Jens Peter; Sørensen, John Dalsgaard
2014-01-01
Wave models used for site assessments are subject to model uncertainties, which need to be quantified when using wave model results for probabilistic reliability assessments. This paper focuses on determination of wave model uncertainties. Considered are four different wave models and validation...... data is collected from published scientific research. The bias, the root-mean-square error as well as the scatter index are considered for the significant wave height as well as the mean zero-crossing wave period. Based on an illustrative generic example it is shown how the estimated uncertainties can...
Modeling of Rayleigh wave dispersion in Iberia
Directory of Open Access Journals (Sweden)
José Badal
2011-01-01
Full Text Available Phase and group velocities of 15–70 s Rayleigh waves propagating across the Iberian Peninsula have been transformed into local dispersion curves by linear inversion of travel times. The procedure permits that the waveform dispersion to be obtained as a continuous period-dependent velocity function at grid points belonging to the area probed by the waves, thus providing phase- and group-velocity contour maps for several periods within the interval of interest. The regionalization process rests on a homogeneous initial data set in which the number of observations remains almost constant for all periods of reference. Damped least-squares inversion of the local dispersion curves for shear-wave velocity structure is performed to obtain depth-dependent S-wave velocity profiles at the grid points covering the model region. The reliability of the results should improve significantly owing to the use of phase and group velocities simultaneously. On this basis, we have built horizontal depth sections that give an updated view of the seismic velocity structure of the peninsula at lithospheric and upper mantle depths (20–200 km. After averaging all the pure-path S-wave velocities previously determined at each grid point, the velocity-depth models so obtained for major tectonic units allow the comparison between the Hercynian basement and other areas of Mesozoic folding and Tertiary basins.
Wave climatology of the Indian Ocean derived from altimetry and wave model
Digital Repository Service at National Institute of Oceanography (India)
Vethamony, P.; Rao, L.V.G.; Kumar, R.; Sarkar, A.; Mohan, M.; Sudheesh, K.; Karthikeyan, S.B.
month. Similar procedure is followed for Geosat data for comparison purpose. The wave model, WAVEIN has been run using ECMWF winds to hindcast waves over the Indian Ocean and to compare with Geosat wave parameters. As altimeter does not provide wave...
A Boussinesq Equation-Based Model for Nearshore Wave Breaking
Institute of Scientific and Technical Information of China (English)
余建星; 张伟; 王广东; 杨树清
2004-01-01
Based on the wave breaking model by Li and Wang (1999), this work is to apply Dally' s analytical solution to the wave-height decay irstead of the empirical and semi-empirical hypotheses of wave-height distribution within the wave breaking zone. This enhances the applicability of the model. Computational results of shoaling, location of wave breaking, wave-height decay after wave breaking, set-down and set-up for incident regular waves are shown to have good agreement with experimental and field data.
Discrete particle modelling of granular roll waves
Tsang, Jonathan; Dalziel, Stuart; Vriend, Nathalie
2016-11-01
A granular current flowing down an inclined chute or plane can undergo an instability that leads to the formation of surface waves, known as roll waves. Examples of roll waves are found in avalanches and debris flows in landslides, and in many industrial processes. Although related to the Kapitza instability of viscous fluid films, granular roll waves are not yet as well understood. Laboratory experiments typically measure the surface height and velocity of a current as functions of position and time, but they do not give insight into the processes below the surface: in particular, the possible formation of a boundary layer at the free surface as well as the base. To overcome this, we are running discrete particle model (DPM) simulations. Simulations are validated against our laboratory experiments, but they also allow us to examine a much larger range of parameters, such as material properties, chute geometry and particle size dispersity, than that which is possible in the lab. We shall present results from simulations in which we vary particle size and dispersity, and examine the implications on roll wave formation and propagation. Future work will include simulations in which the shape of the chute is varied, both cross-sectionally and in the downstream direction. EPSRC studentship (Tsang) and Royal Society Research Fellowship (Vriend).
Gusev, Vitalyi E; Lomonosov, Alexey M; Ni, Chenyin; Shen, Zhonghua
2017-09-01
An analytical theory accounting for the influence of hysteretic nonlinearity of micro-inhomogeneous plate material on the Lamb waves near the S1 zero group velocity point is developed. The theory predicts that the main effect of the hysteretic quadratic nonlinearity consists in the modification of the frequency and the induced absorption of the Lamb modes. The effects of the nonlinear self-action in the propagating and standing Lamb waves are expected to be, respectively, nearly twice and three times stronger than those in the plane propagating acoustic waves. The theory is restricted to the simplest hysteretic nonlinearity, which is influencing only one of the Lamé moduli of the materials. However, possible extensions of the theory to the cases of more general hysteretic nonlinearities are discussed as well as the perspectives of its experimental testing. Applications include nondestructive evaluation of micro-inhomogeneous and cracked plates. Copyright © 2017 Elsevier B.V. All rights reserved.
Modeling, Design and Simulation of Stand-Alone Photovoltaic Power Systems with Battery Storage
Directory of Open Access Journals (Sweden)
Abd Essalam BADOUD
2013-06-01
Full Text Available Stand alone renewable energy based on photovoltaic systems accompanied with battery storage system are beginning to play an important role over the world to supply power to remote areas. The objective of the study reported in this paper is to elaborate and design a bond graphs model for sizing stand-alone domestic solar photovoltaic electricity systems and simulating the performance of the systems in a tropical climate. The systems modelled consist of an array of PV modules, a lead-acid battery, and a number of direct current appliances. This paper proposes the combination of lead acid battery system with a typical stand alone photovoltaic energy system under variable loads. The main activities of this work purpose to establish library graphical models for each individual component of standalone photovoltaic system. Control strategy has been considered to achieve permanent power supply to the load via photovoltaic/battery based on the power available from the sun. The complete model was simulated under two testing including sunny and cloudy conditions. Simulation of the system using Symbols software was performed and the results of simulation show the superior stable control system and high efficiency. These results have been contrasted with real measured data from a measurement campaign plant carried on electrical engineering laboratory of Grenoble using various interconnection schemes are presented.
Phase Diagram of a Holographic Superconductor Model with s-wave and d-wave
Nishida, Mitsuhiro
2014-01-01
We consider a holographic model with a scalar field, a tensor field and a direct coupling between them as a superconductor with an s-wave and a d-wave. We find a rich phase structure in our model. Depending on the direct coupling, the model exhibits coexistence of the s-wave and the d-wave, and/or order competition, and has a triple point.
CMS-Wave Model: Part 5. Full-plane Wave Transformation and Grid Nesting
2012-04-01
are available in previous reports and CHETNs (Lin et al. 2006; Demirbilek et al. 2007). CMS -Wave is part of the Coastal Modeling System ( CMS ...the U.S. Army Corps of Engineers’ (USACE) Surface-water Modeling System (SMS). The CMS -Wave FP option is available in SMS Version 11.1 and higher...ERDC/CHL CHETN-IV-81 April 2012 Approved for public release; distribution is unlimited. CMS -Wave Model: Part 5. Full-plane Wave Transformation
Liang, Fuyou; Oshima, Marie; Huang, Huaxiong; Liu, Hao; Takagi, Shu
2015-10-01
Free outflow boundary conditions have been widely adopted in hemodynamic model studies, they, however, intrinsically lack the ability to account for the regulatory mechanisms of systemic hemodynamics and hence carry a risk of producing incorrect results when applied to vascular segments with multiple outlets. In the present study, we developed a multiscale model capable of incorporating global cardiovascular properties into the simulation of blood flows in local vascular segments. The multiscale model was constructed by coupling a three-dimensional (3D) model of local arterial segments with a zero-one-dimensional (0-1-D) model of the cardiovascular system. Numerical validation based on an idealized model demonstrated the ability of the multiscale model to preserve reasonable pressure/flow wave transmission among different models. The multiscale model was further calibrated with clinical data to simulate cerebroarterial hemodynamics in a patient undergoing carotid artery operation. The results showed pronounced hemodynamic changes in the cerebral circulation following the operation. Additional numerical experiments revealed that a stand-alone 3D model with free outflow conditions failed to reproduce the results obtained by the multiscale model. These results demonstrated the potential advantage of multiscale modeling over single-scale modeling in patient-specific hemodynamic studies. Due to the fact that the present study was limited to a single patient, studies on more patients would be required to further confirm the findings.
X-ray standing-wave study of (AlAs){sub m}(GaAs){sub n} short-period superlattices
Energy Technology Data Exchange (ETDEWEB)
Lessmann, A.; Brennan, S.; Munkholm, A. [Stanford Synchrotron Radiation Laboratory SSRL/SLAC, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Schuster, M.; Riechert, H. [Siemens AG, Corporate Technology, Otto-Hahn-Ring 6, D-81739 Munich (Germany); Materlik, G. [Hamburger Synchrotronstrahlungslabor HASYLAB am Deutschen Elektronen-Synchrotron DESY, Notkestrasse 85, D-22603 Hamburg (Germany)
1999-04-01
X-ray standing-waves (XSW) are used for an investigation of the structure of (AlAs){sub m}(GaAs){sub n} short-period superlattices (SL{close_quote}s). The XSW induced modulation of x-ray fluorescence from the Al, As, and Ga atoms and the total photoelectron yield are monitored around the 0th order SL satellite (AlAs)(GaAs)(004,0) and the GaAs(004) substrate Bragg reflection. From the specific shape of these modulations and the sample reflectivity, an atomic model about the interfaces is derived. This is accomplished by comparing the experimental data with dynamical calculations of x-ray wavefield distribution and reflectivity, which are based on the Takagi-Taupin equation. The fluorescence measurements at the 0th order SL satellite reveal a high crystalline order in the AlAs layers of the short-period SL, whereas in the GaAs layers, a fraction of the Ga and As atoms is not on the ideal lattice positions. From the analysis, a model of the atomic distribution along the [001] direction can be determined. This reveals that at each internal interface in the GaAs layers, two Ga atom planes are shifted by up to 0.035 nm and one As atom plane by 0.023 nm. At each interface, the shifts are directed towards the substrate. In addition, the XSW field at the GaAs(004) substrate reflection results in a moir{acute e} or beating effect in the SL structure, which can be used to determine the information depth {Lambda}{sub e} of total electron-yield measurements in a more detailed approach. {copyright} {ital 1999} {ital The American Physical Society}
System design optimization for stand-alone photovoltaic systems sizing by using superstructure model
Azau, M. A. M.; Jaafar, S.; Samsudin, K.
2013-06-01
Although the photovoltaic (PV) systems have been increasingly installed as an alternative and renewable green power generation, the initial set up cost, maintenance cost and equipment mismatch are some of the key issues that slows down the installation in small household. This paper presents the design optimization of stand-alone photovoltaic systems using superstructure model where all possible types of technology of the equipment are captured and life cycle cost analysis is formulated as a mixed integer programming (MIP). A model for investment planning of power generation and long-term decision model are developed in order to help the system engineer to build a cost effective system.
Stand dynamics and tree coexistence in an analytical structured model: the role of recruitment.
Angulo, Óscar; Bravo de la Parra, Rafael; López-Marcos, Juan C; Zavala, Miguel A
2013-09-21
Understanding the mechanisms of coexistence and niche partitioning in plant communities is a central question in ecology. Current theories of forest dynamics range between the so-called neutral theories which assume functional equivalence among coexisting species to forest simulators that explain species assemblages as the result of tradeoffs in species individual strategies at several ontogenetic stages. Progress in these questions has been hindered by the inherent difficulties of developing analytical size-structured models of stand dynamics. This precludes examination of the relative importance of each mechanism on tree coexistence. In previous simulation and analytical studies emphasis has been given to interspecific differences at the sapling stage, and less so to interspecific variation in seedling recruitment. In this study we develop a partial differential equation model of stand dynamics in which competition takes place at the recruitment stage. Species differ in their size-dependent growth rates and constant mortality rates. Recruitment is described as proportional to the basal area of conspecifics, to account for fecundity and seed supply per unit of basal area, and is corrected with a decreasing function of species specific basal area to account for competition. We first analyze conditions for population persistence in monospecific stands and second we investigate conditions of coexistence for two species. In the monospecific case we found a stationary stand structure based on an inequality between mortality rate and seed supply. In turn, intra-specific competition does not play any role on the asymptotic extinction or population persistence. In the two-species case we found that coexistence can be attained when the reciprocal negative effect on recruitment follows a given relation with respect to intraspecific competition. Specifically a tradeoff between recruitment potential (i.e. shade tolerance or predation avoidance) and fecundity or growth rate
Effects of wave-induced forcing on a circulation model of the North Sea
Staneva, Joanna; Alari, Victor; Breivik, Øyvind; Bidlot, Jean-Raymond; Mogensen, Kristian
2017-01-01
The effect of wind waves on water level and currents during two storms in the North Sea is investigated using a high-resolution Nucleus for European Modelling of the Ocean (NEMO) model forced with fluxes and fields from a high-resolution wave model. The additional terms accounting for wave-current interaction that are considered in this study are the Stokes-Coriolis force, the sea-state-dependent energy and momentum fluxes. The individual and collective role of these processes is quantified and the results are compared with a control run without wave effects as well as against current and water-level measurements from coastal stations. We find a better agreement with observations when the circulation model is forced by sea-state-dependent fluxes, especially in extreme events. The two extreme events, the storm Christian (25-27 October 2013), and about a month later, the storm Xaver (5-7 December 2013), induce different wave and surge conditions over the North Sea. Including the wave effects in the circulation model for the storm Xaver raises the modelled surge by more than 40 cm compared with the control run in the German Bight area. For the storm Christian, a difference of 20-30 cm in the surge level between the wave-forced and the stand-alone ocean model is found over the whole southern part of the North Sea. Moreover, the modelled vertical velocity profile fits the observations very well when the wave forcing is accounted for. The contribution of wave-induced forcing has been quantified indicating that this represents an important mechanism for improving water-level and current predictions.
Wave-to-wire Modelling of Wave Energy Converters
DEFF Research Database (Denmark)
Ferri, Francesco
, but talking about renewable energy partially ravels the problem out. Wave energy is a large, mostly untapped, renewable energy resource. It has the potential to contribute significantly to the future energy mix, but the sector has not yet rolled off into the market in consequence of a number of technical...... and non-technical issues. These can be efficiently summarised in the cost of the energy produced by the various wave energy converters: If compared with other renewable energy technologies the cost of energy from the ocean waves is still significantly higher. Holding the comparison it also important...... to noticed that there is not a clear front runner in the wave energy sector, which fades effort and funding over a too broad frame. In order to assist efficient development and analysis of wave energy converters and therefore to accelerate the sector progression towards commercialisation, a generally...
Analysis of Vibrating String Standing Wave Formed by Origin%利用Origin分析弦振动形成驻波的规律
Institute of Scientific and Technical Information of China (English)
李生仁; 白琼燕; 杨军; 李春望
2014-01-01
In this paper, analyzing the movement of the tiny sport on string section through wave equation in theory, deriving the relationship among the wavelength, the string tension, frequency and the density of strings when standing wave forms. Meanwhile, with evenly string vibration tester XZDY-type B, obtaining a lot of experimental data. And processing the data under the environment of Origin fitting processing system, making the data relationship chart to enable experimental data vis-ualization and informationization, the law that formed standing wave audio-visual and easier to understand.%本文通过波动方程和对弦上某一微小段的运动理论分析，推导出弦振动形成驻波时波长、弦中张力、频率和弦线密度之间的关系。同时借助XZDY-B型均匀弦振动仪，获得大量的实验数据，并在Origin环境下对数据进行系统的拟合处理，做出了数据间的关系图，使实验数据可视化和信息化，使弦振动形成驻波的规律更为直观，更容易理解。
Global MHD modeling of resonant ULF waves: Simulations with and without a plasmasphere
Claudepierre, S. G.; Toffoletto, F. R.; Wiltberger, M.
2016-01-01
We investigate the plasmaspheric influence on the resonant mode coupling of magnetospheric ultralow frequency (ULF) waves using the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic (MHD) model. We present results from two different versions of the model, both driven by the same solar wind conditions: one version that contains a plasmasphere (the LFM coupled to the Rice Convection Model, where the Gallagher plasmasphere model is also included) and another that does not (the stand-alone LFM). We find that the inclusion of a cold, dense plasmasphere has a significant impact on the nature of the simulated ULF waves. For example, the inclusion of a plasmasphere leads to a deeper (more earthward) penetration of the compressional (azimuthal) electric field fluctuations, due to a shift in the location of the wave turning points. Consequently, the locations where the compressional electric field oscillations resonantly couple their energy into local toroidal mode field line resonances also shift earthward. We also find, in both simulations, that higher-frequency compressional (azimuthal) electric field oscillations penetrate deeper than lower frequency oscillations. In addition, the compressional wave mode structure in the simulations is consistent with a radial standing wave oscillation pattern, characteristic of a resonant waveguide. The incorporation of a plasmasphere into the LFM global MHD model represents an advance in the state of the art in regard to ULF wave modeling with such simulations. We offer a brief discussion of the implications for radiation belt modeling techniques that use the electric and magnetic field outputs from global MHD simulations to drive particle dynamics.
Global MHD modeling of resonant ULF waves: Simulations with and without a plasmasphere.
Claudepierre, S G; Toffoletto, F R; Wiltberger, M
2016-01-01
We investigate the plasmaspheric influence on the resonant mode coupling of magnetospheric ultralow frequency (ULF) waves using the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic (MHD) model. We present results from two different versions of the model, both driven by the same solar wind conditions: one version that contains a plasmasphere (the LFM coupled to the Rice Convection Model, where the Gallagher plasmasphere model is also included) and another that does not (the stand-alone LFM). We find that the inclusion of a cold, dense plasmasphere has a significant impact on the nature of the simulated ULF waves. For example, the inclusion of a plasmasphere leads to a deeper (more earthward) penetration of the compressional (azimuthal) electric field fluctuations, due to a shift in the location of the wave turning points. Consequently, the locations where the compressional electric field oscillations resonantly couple their energy into local toroidal mode field line resonances also shift earthward. We also find, in both simulations, that higher-frequency compressional (azimuthal) electric field oscillations penetrate deeper than lower frequency oscillations. In addition, the compressional wave mode structure in the simulations is consistent with a radial standing wave oscillation pattern, characteristic of a resonant waveguide. The incorporation of a plasmasphere into the LFM global MHD model represents an advance in the state of the art in regard to ULF wave modeling with such simulations. We offer a brief discussion of the implications for radiation belt modeling techniques that use the electric and magnetic field outputs from global MHD simulations to drive particle dynamics.
Generative Modeling for Machine Learning on the D-Wave
Energy Technology Data Exchange (ETDEWEB)
Thulasidasan, Sunil [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Information Sciences Group
2016-11-15
These are slides on Generative Modeling for Machine Learning on the D-Wave. The following topics are detailed: generative models; Boltzmann machines: a generative model; restricted Boltzmann machines; learning parameters: RBM training; practical ways to train RBM; D-Wave as a Boltzmann sampler; mapping RBM onto the D-Wave; Chimera restricted RBM; mapping binary RBM to Ising model; experiments; data; D-Wave effective temperature, parameters noise, etc.; experiments: contrastive divergence (CD) 1 step; after 50 steps of CD; after 100 steps of CD; D-Wave (experiments 1, 2, 3); D-Wave observations.
Bartelink, H.H.
2000-01-01
Models estimating growth and yield of forest stands provide important tools for forest management. Pure stands have been modeled extensively and successfully for decades; however, relatively few models for mixed-species stands have been developed. A spatially explicit, mechanistic model (COMMIX) is
Astrophysical Model Selection in Gravitational Wave Astronomy
Adams, Matthew R.; Cornish, Neil J.; Littenberg, Tyson B.
2012-01-01
Theoretical studies in gravitational wave astronomy have mostly focused on the information that can be extracted from individual detections, such as the mass of a binary system and its location in space. Here we consider how the information from multiple detections can be used to constrain astrophysical population models. This seemingly simple problem is made challenging by the high dimensionality and high degree of correlation in the parameter spaces that describe the signals, and by the complexity of the astrophysical models, which can also depend on a large number of parameters, some of which might not be directly constrained by the observations. We present a method for constraining population models using a hierarchical Bayesian modeling approach which simultaneously infers the source parameters and population model and provides the joint probability distributions for both. We illustrate this approach by considering the constraints that can be placed on population models for galactic white dwarf binaries using a future space-based gravitational wave detector. We find that a mission that is able to resolve approximately 5000 of the shortest period binaries will be able to constrain the population model parameters, including the chirp mass distribution and a characteristic galaxy disk radius to within a few percent. This compares favorably to existing bounds, where electromagnetic observations of stars in the galaxy constrain disk radii to within 20%.
Subject-specific musculoskeletal model of the lower limb in a lying and standing position.
Hausselle, J; Assi, A; El Helou, A; Jolivet, E; Pillet, H; Dion, E; Bonneau, D; Skalli, W
2014-04-01
Accurate estimation of joint loads implies using subject-specific musculoskeletal models. Moreover, as the lines of action of the muscles are dictated by the soft tissues, which are in turn influenced by gravitational forces, we developed a method to build subject-specific models of the lower limb in a functional standing position. Bones and skin envelope were obtained in a standing position, whereas muscles and a set of bony landmarks were obtained from conventional magnetic resonance images in a lying position. These muscles were merged with the subject-specific skeletal model using a nonlinear transformation, taking into account soft tissue movements and gravitational effects. Seven asymptomatic lower limbs were modelled using this method, and results showed realistic deformations. Comparing the subject-specific skeletal model to a scaled reference model rendered differences in terms of muscle length up to 4% and in terms of moment arm for adductor muscles up to 30%. These preliminary findings enlightened the importance of subject-specific modelling in a functional position.
A WEAKLY NONLINEAR WATER WAVE MODEL TAKING INTO ACCOUNT DISPERSION OF WAVE PHASE VELOCITY
Institute of Scientific and Technical Information of China (English)
李瑞杰; 李东永
2002-01-01
This paper presents a weakly nonlinear water wave model using a mild slope equation and a new explicit formulation which takes into account dispersion of wave phase velocity, approximates Hedges' (1987) nonlinear dispersion relationship, and accords well with the original empirical formula. Comparison of the calculating results with those obtained from the experimental data and those obtained from linear wave theory showed that the present water wave model considering the dispersion of phase velocity is rational and in good agreement with experiment data.
Detailed modeling of mountain wave PSCs
Directory of Open Access Journals (Sweden)
S. Fueglistaler
2003-01-01
Full Text Available Polar stratospheric clouds (PSCs play a key role in polar ozone depletion. In the Arctic, PSCs can occur on the mesoscale due to orographically induced gravity waves. Here we present a detailed study of a mountain wave PSC event on 25-27 January 2000 over Scandinavia. The mountain wave PSCs were intensively observed by in-situ and remote-sensing techniques during the second phase of the SOLVE/THESEO-2000 Arctic campaign. We use these excellent data of PSC observations on 3 successive days to analyze the PSCs and to perform a detailed comparison with modeled clouds. We simulated the 3-dimensional PSC structure on all 3 days with a mesoscale numerical weather prediction (NWP model and a microphysical box model (using best available nucleation rates for ice and nitric acid trihydrate particles. We show that the combined mesoscale/microphysical model is capable of reproducing the PSC measurements within the uncertainty of data interpretation with respect to spatial dimensions, temporal development and microphysical properties, without manipulating temperatures or using other tuning parameters. In contrast, microphysical modeling based upon coarser scale global NWP data, e.g. current ECMWF analysis data, cannot reproduce observations, in particular the occurrence of ice and nitric acid trihydrate clouds. Combined mesoscale/microphysical modeling may be used for detailed a posteriori PSC analysis and for future Arctic campaign flight and mission planning. The fact that remote sensing alone cannot further constrain model results due to uncertainities in the interpretation of measurements, underlines the need for synchronous in-situ PSC observations in campaigns.
Effects of wave-induced forcing on a circulation model of the North Sea
Staneva, Joanna; Alari, Victor; Breivik, Øyvind; Bidlot, Jean-Raymond; Mogensen, Kristian
2017-04-01
The effect of wind waves on water level and currents during two storms in the North Sea is investigated using a high-resolution NEMO model forced with fluxes and fields from a high-resolution wave model. The additional terms accounting for wave-current interaction that are considered in this study are the Stokes-Coriolis force and the sea-state dependent energy and momentum fluxes. The individual and collective role of these processes is quantified and the results are compared with a control run without wave effects as well as against current and water level measurements from coastal stations. We find a better agreement with observations when the circulation model is forced by sea-state dependent fluxes, especially in extreme events. The two extreme events, the storm Christian (25-27 October 2013), and about a month later, the storm Xaver (5-7 December 2013), induce different wave and surge conditions over the North Sea. Including the wave effects in the circulation model for the storm Xaver raises the modelled surge by more than 40 cm compared with the control run in the German Bight area. For the storm Christian, a difference of 20-30 cm in the surge level between the wave-forced and the stand-alone ocean model is found over the whole southern part of the North Sea. Moreover, the modelled vertical velocity profile fits the observations very well when the wave forcing is accounted for. The contribution of wave-induced forcing has been quantified indicating that this represents an important mechanism for improving water level and current predictions.
Applicability of WaveWatch-III wave model to fatigue assessment of offshore floating structures
Zou, Tao; Kaminski, Miroslaw Lech
2016-09-01
In design and operation of floating offshore structures, one has to avoid fatigue failures caused by action of ocean waves. The aim of this paper is to investigate the applicability of WaveWatch-III wave model to fatigue assessment of offshore floating structures. The applicability was investigated for Bluewaters' FPSO (Floating Production, Storage and Offloading) which had been turret moored at Sable field for half a decade. The waves were predicted as sea-state time series consisting of one wind sea and one swell. The predicted waves were compared with wave data obtained from ERA-interim and buoy measurements. Furthermore, the fatigue calculations were also carried out for main deck and side shell locations. It has been concluded that predicted fatigue damages of main deck using WaveWatch-III are in a very good agreement regardless of differences in predicted wind waves and swells caused by differences in wave system partitioning. When compared to buoy measurements, the model underestimates fatigue damages of side shell by approximately 30 %. The reason for that has been found in wider directional spreading of actual waves. The WaveWatch-III wave model has been found suitable for the fatigue assessment. However, more attention should be paid on relative wave directionality, wave system partitioning and uncertainty analysis in further development.
Deterministic combination of numerical and physical coastal wave models
DEFF Research Database (Denmark)
Zhang, H.W.; Schäffer, Hemming Andreas; Jakobsen, K.P.
2007-01-01
A deterministic combination of numerical and physical models for coastal waves is developed. In the combined model, a Boussinesq model MIKE 21 BW is applied for the numerical wave computations. A piston-type 2D or 3D wavemaker and the associated control system with active wave absorption provides...
Coupled wave-atmosphere-ocean modeling under RCP8.5 emissions during the 21st century
de Vries, Hylke; Semedo, Alvaro; Sterl, Andreas
2016-04-01
Most climate models have no explicit treatment of surface ocean waves. As a result, wave climatologies are usually obtained off-line, using atmospheric forcing as input. In recent years attempts have been made to incorporate surface ocean wave models into GCMs, giving the possibility of interactions between components. In the presence of waves the atmospheric winds are modified due to different drag-coefficient and breaking waves will have also influence vertical ocean mixing. As such the waves may play a role in solving long-standing ocean and atmospheric biases. Recently we have coupled the global wave model WAM into EC-Earth GCM (v3.0.1). EC-Earth is based on the IFS atmospheric model and the NEMO/LIM ocean/sea ice model. First results are presented from a 140-year (1961-2100) continuous transient, coupled simulation under RCP8.5 emission scenario. As the modelled climate warms during the transient period, (arctic) sea-ice gradually diminishes, allowing surface waves to penetrate to higher and higher latitudes. Eventually Arctic sea-ice completely disappears in the simulation in late summer. We will discuss swell and wind-wave climatologies, Stokes drift patterns as well as other relevant wave parameters.
Energy Technology Data Exchange (ETDEWEB)
Mellit, A. [University Center of Medea, Institute of Engineering Sciences, Ain Dahab (Algeria); Benghanem, M. [University of Sciences Technology Houari Boumediene (USTHB), Faculty of ElectricalEngineering, El-Alia, Algiers (Algeria); Hadj Arab, A. [Development Center of Renewable Energy (CDER), Bouzareah, Algiers (Algeria); Guessoum, A. [Ministry for the Higher Education and Scientific Research, Algiers (Algeria)
2004-07-01
The main of this work is to train the RBF-IIR model to learn the prediction and modeling of the signals from stand-alone PV system. Once trained, the RBF-IIR estimates these signals faster. The validation of the model was performed with unknown signals data, which the network has not seen before. The ability of the network to make acceptable predictions even in an unusual day is an advantage of the present method. The estimation with correlation coefficient varied between 82 to 99 % was obtained. This accuracy is well within the acceptable level used by design engineers. The advantage of this model is to predict of different signal coming from the stand-alone prediction signals allow to analyzing and studying the performance of the PV systems and the sizing of PV system. Also this model have been compared between different neural networks structures, and given good results. (orig.)
Impact of surface waves in a Regional Climate Model
DEFF Research Database (Denmark)
Rutgersson, Anna; Sætra, Oyvind; Semedo, Alvaro
2010-01-01
A coupled regional atmosphere-wave model system is developed with the purpose of investigating the impact of climate changes on the wave field, as well as feed-back effects of the wave field on the atmospheric parameters. This study focuses on the effects of introducing a two-way atmosphere-wave...... coupling on the atmosphere as well as on wave parameters. The model components are the regional climate model RCA, and the third generation wave model WAM. Two different methods are used for the coupling, using the roughness length and only including the effect of growing sea, and using the wave age...... and introducing the reduction of roughness due to decaying sea (swell). Introducing a two-way coupling results in an altered frequency distribution of wind speed and wave heights. When only including growing sea the impact of waves on the long term mean atmospheric parameters is limited, inducing a reduction...
Directory of Open Access Journals (Sweden)
W. W. Verstraeten
2005-01-01
Full Text Available This paper focuses on the quantification of the green – vegetation related – water flux of forest stands in the temperate lowland of Flanders. The underlying reason of the research was to develop a methodology for assessing the impact of forests on the hydrologic cycle in comparison to agriculture. The tested approach for calculating the water use by forests was based on the application of the soil water balance model WAVE. The study involved the collection of data from 14 forest stands, the calibration and validation of the WAVE model, and the comparison of the water use (WU components – transpiration, soil and interception evaporation – between forest and cropland. For model calibration purposes simulated and measured time series of soil water content at different soil depths, period March 2000–August 2001, were compared. A multiple-site validation was conducted as well. Actual tree transpiration calculated with sap flow measurements in three forest stands gave similar results for two of the three stands of pine (Pinus sylvestris L., but WAVE overestimated the actual measured transpiration for a stand of poplar (Populus sp.. A useful approach to compare the WU components of forest versus cropland is scenario analysis based on the validated WAVE model. The statistical Profile Analysis method was implemented to explore and analyse the simulated WU time series. With an average annual rainfall of 819 mm, the results reveal that forests in Flanders consume more water than agricultural crops. A 30 years average of 491 mm for 10 forests stands versus 398 mm for 10 cropped agricultural fields was derived. The WU components, on yearly basis, also differ between the two land use types (transpiration: 315 mm for forest and 261 mm for agricultural land use; soil evaporation: 47 mm and 131 mm, for forest and cropland, respectively. Forest canopy interception evaporation was estimated at 126 mm, while it was negligible for cropland.
Forward Modelling of Standing Kink Modes in Coronal Loops I. Synthetic Views
Yuan, Ding
2016-01-01
Kink magnetohydrodynamic (MHD) waves are frequently observed in various magnetic structures of the solar atmosphere. They may contribute significantly to coronal heating and could be used as a tool to diagnose the solar plasma. In this study, we synthesise the \\ion{Fe}{9} $\\lambda171.073$ emission of a coronal loop supporting a standing kink MHD mode. The kink MHD wave solution of a plasma cylinder is mapped into a semi-torus structure to simulate a curved coronal loop. We decompose the solution into a quasi-rigid kink motion and a quadrupole term, which dominate the plasma inside and outside the flux tube, respectively. At the loop edges, the line-of-sight integrates relatively more ambient plasma, and the background emission becomes significant. The plasma motion associated with the quadrupole term causes spectral line broadening and emission suppression. The periodic intensity suppression will modulate the integrated intensity and the effective loop width, which both exhibit oscillatory variations at half ...
FORWARD MODELING OF STANDING KINK MODES IN CORONAL LOOPS. I. SYNTHETIC VIEWS
Energy Technology Data Exchange (ETDEWEB)
Yuan, Ding; Doorsselaere, Tom Van, E-mail: DYuan2@uclan.ac.uk [Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B bus 2400, B-3001 Leuven (Belgium)
2016-04-15
Kink magnetohydrodynamic (MHD) waves are frequently observed in various magnetic structures of the solar atmosphere. They may contribute significantly to coronal heating and could be used as a tool to diagnose the solar plasma. In this study, we synthesize the Fe ix λ171.073 Å emission of a coronal loop supporting a standing kink MHD mode. The kink MHD wave solution of a plasma cylinder is mapped into a semi-torus structure to simulate a curved coronal loop. We decompose the solution into a quasi-rigid kink motion and a quadrupole term, which dominate the plasma inside and outside of the flux tube, respectively. At the loop edges, the line of sight integrates relatively more ambient plasma, and the background emission becomes significant. The plasma motion associated with the quadrupole term causes spectral line broadening and emission suppression. The periodic intensity suppression will modulate the integrated intensity and the effective loop width, which both exhibit oscillatory variations at half of the kink period. The quadrupole term can be directly observed as a pendular motion at the front view.
Modeling Pancake Formation with a Coupled Wave-Ice Model
Veeramony, J.; Orzech, M.; Shi, F.; Bateman, S. P.; Calantoni, J.
2016-12-01
Recent results from the ONR-sponsored Arctic Sea State DRI cruise (Thomson et al., 2016, EOS, in press) suggest that small-scale pancake ice formation is an important process in the initial recovery and refreezing of the Arctic pack ice each autumn. Ocean surface waves and ambient temperature play significant roles in shaping and/or limiting the pancake growth patterns, which may either facilitate or delay the recovery of the ice pack. Here we apply a phase-resolving, coupled wave-ice system, consisting of a CFD wave model (NHWAVE) and a discrete-element ice model (LIGGGHTS), to investigate the formation processes of pancake ice under different conditions. A series of simulations is run, each beginning with a layer of disconnected ice particles floating on the ocean surface. Wave conditions and ice bonding properties are varied to examine the effects of mild versus stormy conditions, wind waves versus swell, and warmer versus colder temperatures. Model runs are limited to domains of O(1 sq km). Initial tests have shown some success in replicating qualitative results from the Sea State cruise, including the formation of irregularly shaped pancakes from the "frazil" ice layer, changes in formation processes caused by varying ambient temperature (represented through variations in ice bonding strength), occasional rafting of one pancake on top of another, and increased wave attenuation as pancakes grow larger.
Study of molecule-metal interfaces by means of the normal incidence X-ray standing wave technique
Energy Technology Data Exchange (ETDEWEB)
Mercurio, Giuseppe
2012-07-01
Functional surfaces based on monolayers of organic molecules are currently subject of an intense research effort due to their applications in molecular electronics, sensing and catalysis. Because of the strong dependence of organic based devices on the local properties of the molecule-metal interface, a direct investigation of the interface chemistry is of paramount importance. In this context, the bonding distance, measured by means of the normal incidence X-ray standing wave technique (NIXSW), provides a direct access to the molecule-metal interactions. At the same time, NIXSW adsorption heights are used to benchmark different density functional theory (DFT) schemes and determine the ones with predictive power for similar systems. This work investigates the geometric and chemical properties of different molecule/metal interfaces, relevant to molecular electronics and functional surfaces applications, primarily by means of the NIXSW technique. All NIXSW data are analyzed with the newly developed open source program Torricelli, which is thoroughly documented in the thesis. In order to elucidate the role played by the substrate within molecule/metal interfaces, the prototype organic molecule 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) is explored on the Ag(110) surface. The molecule results more distorted and at smaller bonding distances on the more reactive Ag(110) surface, in comparison with the Ag(100), the Ag(111) and Au(111) substrates. This conclusion follows from the detailed molecular adsorption geometry obtained from the differential analysis of nonequivalent carbon and oxygen species (including a careful error analysis). Subsequently, the chemisorptive PTCDA/Ag(110) interaction is tuned by the co-deposition of an external alkali metal, namely K. As a consequence, the functional groups of PTCDA unbind from the surface, which, in turn, undergoes major reconstruction. In fact, the resulting nanopatterned surface consists of alternated up and down
Underwater Noise Modelling of Wave Energy Devices
Energy Technology Data Exchange (ETDEWEB)
NONE
2009-07-01
Future large-scale implementation of wave energy converts (WECs) will introduce an anthropogenic activity in the ocean which may contribute to underwater noise. The Ocean houses several marine species with acoustic sensibility; consequently the potential impact of the underwater noise needs to be addressed. At present, there are no acoustic impact studies based on acquired data. The WEAM project (Wave Energy Acoustic Monitoring) aims at developing an underwater noise monitoring plan for WECs. The development of an acoustic monitoring plan must consider the sound propagation in the ocean, identify noise sources, understand the operational characteristics and select adequate instrumentation. Any monitoring strategy must involve in-situ measurements. However, the vast distances which sound travels within the ocean, can make in-situ measurements covering the entire area of interest, impracticable. This difficulty can be partially overcome through acoustic numerical modelling. This paper presents a synthetic study, on the application of acoustic forward modelling and the evaluation of the impact of noise produced by wave energy devices on marine mammals using criteria based on audiograms of dolphins, or other species. The idea is to illustrate the application of that methodology, and to show to what extent it allows for estimating distances of impacts due to acoustic noise.
Trailed vorticity modeling for aeroelastic wind turbine simulations in stand still
Pirrung, Georg; Madsen, Helge; Schreck, Scott
2016-09-01
Current fast aeroelastic wind turbine codes suitable for certification lack an induction model for standstill conditions. A trailed vorticity model previously used as addition to a blade element momentum theory based aerodynamic model in normal operation has been extended to allow computing the induced velocities in standstill. The model is validated against analytical results for an elliptical wing in constant inflow and against stand still measurements from the NREL/NASA Phase VI unsteady experiment. The extended model obtains good results in case of the elliptical wing, but underpredicts the steady loading for the Phase VI blade in attached flow. The prediction of the dynamic force coefficient loops from the Phase VI experiment is improved by the trailed vorticity modeling in both attached flow and stall in most cases. The exception is the tangential force coefficient in stall, where the codes and measurements deviate and no clear improvement is visible.
Inflationary gravitational waves in collapse scheme models
Energy Technology Data Exchange (ETDEWEB)
Mariani, Mauro, E-mail: mariani@carina.fcaglp.unlp.edu.ar [Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque S/N, 1900 La Plata (Argentina); Bengochea, Gabriel R., E-mail: gabriel@iafe.uba.ar [Instituto de Astronomía y Física del Espacio (IAFE), UBA-CONICET, CC 67, Suc. 28, 1428 Buenos Aires (Argentina); León, Gabriel, E-mail: gleon@df.uba.ar [Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria – Pab. I, 1428 Buenos Aires (Argentina)
2016-01-10
The inflationary paradigm is an important cornerstone of the concordance cosmological model. However, standard inflation cannot fully address the transition from an early homogeneous and isotropic stage, to another one lacking such symmetries corresponding to our present universe. In previous works, a self-induced collapse of the wave function has been suggested as the missing ingredient of inflation. Most of the analysis regarding the collapse hypothesis has been solely focused on the characteristics of the spectrum associated to scalar perturbations, and within a semiclassical gravity framework. In this Letter, working in terms of a joint metric-matter quantization for inflation, we calculate, for the first time, the tensor power spectrum and the tensor-to-scalar ratio corresponding to the amplitude of primordial gravitational waves resulting from considering a generic self-induced collapse.
Inflationary gravitational waves in collapse scheme models
Directory of Open Access Journals (Sweden)
Mauro Mariani
2016-01-01
Full Text Available The inflationary paradigm is an important cornerstone of the concordance cosmological model. However, standard inflation cannot fully address the transition from an early homogeneous and isotropic stage, to another one lacking such symmetries corresponding to our present universe. In previous works, a self-induced collapse of the wave function has been suggested as the missing ingredient of inflation. Most of the analysis regarding the collapse hypothesis has been solely focused on the characteristics of the spectrum associated to scalar perturbations, and within a semiclassical gravity framework. In this Letter, working in terms of a joint metric-matter quantization for inflation, we calculate, for the first time, the tensor power spectrum and the tensor-to-scalar ratio corresponding to the amplitude of primordial gravitational waves resulting from considering a generic self-induced collapse.
WEMo (Wave Exposure Model): Formulation, Procedures and Validation
Malhotra, Amit; Mark S. Fonseca
2007-01-01
This report describes the working of National Centers for Coastal Ocean Service (NCCOS) Wave Exposure Model (WEMo) capable of predicting the exposure of a site in estuarine and closed water to local wind generated waves. WEMo works in two different modes: the Representative Wave Energy (RWE) mode calculates the exposure using physical parameters like wave energy and wave height, while the Relative Exposure Index (REI) empirically calculates exposure as a unitless index. Detailed working of th...
Yakunin, S.N.; Makhotkin, I.; Chuyev, M.A.; Seregin, A.Y.; Pashayev, E.M.; Louis, E.; Kruijs, van de R.W.E.; Bijkerk, F.; Kovalchuk, M.V.
2012-01-01
Structural analysis of periodic multilayers with small period thickness (~4 nm) is a challenging task, especially when thicknesses of intermixed interfaces become comparable to individual layer thicknesses. In general, angular dependent X-ray fluorescence measurements, excited by the X-ray standing
Surface-wave mode coupling : modelling and inverting waveforms including body-wave phases
Marquering, H.A.
1996-01-01
This thesis is concerned with a similar problem as addressed by Li & Tanimoto (1993) in the surfacewave mode approach. In this thesis it is shown that surface-wave mode coupling is required when body-wave phases in laterally heterogeneous media are modelled by surface-wave mode summation. An efficie
Wave equation modelling using Julia programming language
Kim, Ahreum; Ryu, Donghyun; Ha, Wansoo
2016-04-01
Julia is a young high-performance dynamic programming language for scientific computations. It provides an extensive mathematical function library, a clean syntax and its own parallel execution model. We developed 2d wave equation modeling programs using Julia and C programming languages and compared their performance. We used the same modeling algorithm for the two modeling programs. We used Julia version 0.3.9 in this comparison. We declared data type of function arguments and used inbounds macro in the Julia program. Numerical results showed that the C programs compiled with Intel and GNU compilers were faster than Julia program, about 18% and 7%, respectively. Taking the simplicity of dynamic programming language into consideration, Julia can be a novel alternative of existing statically typed programming languages.
Optimization of multi-model ensemble forecasting of typhoon waves
Directory of Open Access Journals (Sweden)
Shun-qi Pan
2016-01-01
Full Text Available Accurately forecasting ocean waves during typhoon events is extremely important in aiding the mitigation and minimization of their potential damage to the coastal infrastructure, and the protection of coastal communities. However, due to the complex hydrological and meteorological interaction and uncertainties arising from different modeling systems, quantifying the uncertainties and improving the forecasting accuracy of modeled typhoon-induced waves remain challenging. This paper presents a practical approach to optimizing model-ensemble wave heights in an attempt to improve the accuracy of real-time typhoon wave forecasting. A locally weighted learning algorithm is used to obtain the weights for the wave heights computed by the WAVEWATCH III wave model driven by winds from four different weather models (model-ensembles. The optimized weights are subsequently used to calculate the resulting wave heights from the model-ensembles. The results show that the Optimization is capable of capturing the different behavioral effects of the different weather models on wave generation. Comparison with the measurements at the selected wave buoy locations shows that the optimized weights, obtained through a training process, can significantly improve the accuracy of the forecasted wave heights over the standard mean values, particularly for typhoon-induced peak waves. The results also indicate that the algorithm is easy to implement and practical for real-time wave forecasting.
Horizontal circulation and jumps in Hamiltonian wave models
Gagarina, E.; Vegt, van der J.; Bokhove, O.
2013-01-01
We are interested in the numerical modeling of wave-current interactions around surf zones at beaches. Any model that aims to predict the onset of wave breaking at the breaker line needs to capture both the nonlinearity of the wave and its dispersion. We have therefore formulated the Hamiltonian dyn
Standing surface acoustic waves in LiNbO3 studied by time resolved X-ray diffraction at Petra III
Directory of Open Access Journals (Sweden)
T. Reusch
2013-07-01
Full Text Available We have carried out time resolved stroboscopic diffraction experiments on standing surface acoustic waves (SAWs of Rayleigh type on a LiNbO3 substrate. A novel timing system has been developed and commissioned at the storage ring Petra III of Desy, allowing for phase locked stroboscopic diffraction experiments applicable to a broad range of timescales and experimental conditions. The combination of atomic structural resolution with temporal resolution on the picosecond time scale allows for the observation of the atomistic displacements for each time (or phase point within the SAW period. A seamless transition between dynamical and kinematic scattering regimes as a function of the instantaneous surface amplitude induced by the standing SAW is observed. The interpretation and control of the experiment, in particular disentangling the diffraction effects (kinematic to dynamical diffraction regime from possible non-linear surface effects is unambiguously enabled by the precise control of phase between the standing SAW and the synchrotron bunches. The example illustrates the great flexibility and universality of the presented timing system, opening up new opportunities for a broad range of time resolved experiments.
Directory of Open Access Journals (Sweden)
2009-03-01
Full Text Available The main purpose of this research was to analyse the effects of stand structure on biomass allocation and on the accurancy of estimation models for volume and aboveground biomass of Italian stone pine (Pinus pinea L.. Although the species is widely distributed on Mediterranean coasts, few studies on forest biomass estimation have focused on pinewoods. The research was carried out in the Castelfusano’s pinewood (Rome and concerned the two most common structural types: (a 50 years-old pinewood originated by broadcast seeding; and (b 62 years-old pinewood originated by partial seeding alternating worked strips to firm strips. Some 83 sample trees were selected for stem volume estimation and a subset of 32 trees used to quantify the total epigeous biomass, the wooden biomass compartment, including stem and big branches (diameter > 3 cm and the photosynthetic biomass, including thin branches (diameter < 3 cm and needles. Collected data were used to elaborate allometric relations for stem volume, total biomass and specific relations for both compartments, based on one (d2 or two (d2h indipendent variables, for both structural types. Furthermore, pinewood specific biomass expansion factors (BEF - indexes used to estimate carbon stocks starting from stem biomass data - were obtained. The achieved estimation models were subjected to both parallelism and coincidence tests, showing significant effects of stand structure on the accurancy of the allometric relations. The effects of stand structure and reliability of tree height curves on the accurancy of estimation models for volume and aboveground biomass and on biomass allocation in different compartments are analysed and discussed.
Control of spiral waves and turbulent states in a cardiac model by travelling-wave perturbations
Institute of Scientific and Technical Information of China (English)
王鹏业; 谢平; 尹华伟
2003-01-01
We propose a travelling-wave perturbation method to control the spatiotemporal dynamics in a cardiac model.It is numerically demonstrated that the method can successfully suppress the wave instability(alternans in action potential duration) in the one-dimensional case and convert spiral waves and turbulent states to the normal travelling wave states in the two-dimensional case.An experimental scheme is suggested which may provide a new design for a cardiac defibrillator.
Simulation and modeling for the stand-off radiation detection system (SORDS) using GEANT4
Energy Technology Data Exchange (ETDEWEB)
Hoover, Andrew S [Los Alamos National Laboratory; Wallace, Mark [Los Alamos National Laboratory; Galassi, Mark [Los Alamos National Laboratory; Mocko, Michal [Los Alamos National Laboratory; Palmer, David [Los Alamos National Laboratory; Schultz, Larry [Los Alamos National Laboratory; Tornga, Shawn [Los Alamos National Laboratory
2009-01-01
A Stand-Off Radiation Detection System (SORDS) is being developed through a joint effort by Raytheon, Los Alamos National Laboratory, Bubble Technology Industries, Radiation Monitoring Devices, and the Massachusetts Institute of Technology, for the Domestic Nuclear Detection Office (DNDO). The system is a mobile truck-based platform performing detection, imaging, and spectroscopic identification of gamma-ray sources. A Tri-Modal Imaging (TMI) approach combines active-mask coded aperture imaging, Compton imaging, and shadow imaging techniques. Monte Carlo simulation and modeling using the GEANT4 toolkit was used to generate realistic data for the development of imaging algorithms and associated software code.
Measurement and modeling of bed shear stress under solitary waves
Digital Repository Service at National Institute of Oceanography (India)
Jayakumar, S.; Guard, P.A.; Baldock, T.E.
convolution integration methods forced with the free stream velocity and incorporating a range of eddy viscosity models. Wave friction factors were estimated from skin shear stress at different instances over the wave (viz., time of maximum positive total...
Wave-like free-standing NiCo2O4 cathode for lithium-oxygen battery with high discharge capacity
Shen, Chen; Wen, Zhaoyin; Wang, Fan; Rui, Kun; Lu, Yan; Wu, Xiangwei
2015-10-01
A novel free-standing air electrode for Li-O2 battery with a wave-like microstructure is designed and synthesized through a facile electrochemical deposition process. Interconnected NiCo2O4 nanosheets with planes grown almost parallel to the surface of Ni foam build up continues porous catalytic surface with open space for the growth of Li2O2 discharge product. Li-O2 battery with the synthesized cathode delivers a high discharge capacity of 7004 mAh g-1 at 40 mA g-1 with a charge potential lower than 3.6 V (vs. Li/Li+), and significantly lower impedance compared to conventional electrode. Flower-like Li2O2 particles with a large size are observed as discharge products, consisting with the high discharge capacity. The unique wave-like microstructure and DMSO-based electrolyte with a high-doner-number are proposed to be responsible for the high discharge capacity, and the formation of large size Li2O2 discharge products. In addition, the electrode also exhibits stable cycle performance up to 100 cycles at the current density of 100 mA g-1 due to the robust composition and microstructure of the free-standing design.
Electronic standing waves on the surface of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}
Energy Technology Data Exchange (ETDEWEB)
Vershinin, M.; Misra, S.; Abe, Y.; Ono, S.; Ando, Y.; Yazdani, A
2004-08-01
Scanning tunneling microscopy (STM) measurements have shown that electronic states at the surface of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} single crystals form standing wave patterns at temperatures far below the superconducting transition. It has been shown that these patterns are consistent with those expected from the interference of well-defined quasi-particles around the Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} Fermi surface. We have extended STM measurements of these standing wave patterns to higher temperatures and have found that four unit-cell periodicity patterns observed in the superconducting state persist well above T{sub C}, in the pseudogap state. In this regime, many different experimental studies of the cuprates have long claimed the absence of well-defined quasi-particles. If the pseudogap regime is indeed devoid of any coherent quasi-particles then our results suggest that other phenomena, such as stripe formation, must play a role in formation of these patterns.
Lee, Junseok
2016-01-01
This paper presents W-waveform Standing Surface Acoustic Waves (W-SSAW), and as its application, patterning of two groups of microparticles with different sizes alternately without fixing firstly patterned particles. W-SSAW is constructed by two standing surface acoustic waves of frequencies $f$ and $2f$. Combined with linear phase modulation to translate Gor'kov potential at a constant speed, W-SSAW can selectively trap particles. The trapped particles follow the moving Gor'kov potential maintaining force equilibrium between Stokes' drag and the radiation force by W-SSAW. There exist two asymmetric equilibrium positions every period, and by the asymmetry, each group of particles is trapped at different equilibrium positions to form an alternate pattern. This technique is extended to two-dimensional alternate patterning by maintaining phase difference $90^\\circ$ between X- and Y-directional W-SSAWs. The patterning method utilizing W-SSAW is advantageous over SSAW-based patterning in that it does not require t...
3D mmWave Channel Model Proposal
DEFF Research Database (Denmark)
Thomas, Timothy; Nguyen, Huan Cong; R. MacCartney Jr., George
2014-01-01
There is growing interest in using millimeter wave (mmWave) frequencies for future access communications based on the enormous amount of available spectrum. To characterize the mmWave channel in urban areas, wideband propagation measurements at 73 GHz have recently been made in New York City. Using...... mmWave channel model is developed with special emphasis on using the ray tracer to determine elevation model parameters. The channel model includes distance-dependent elevation modeling which is critical for the expected 2D arrays which will be employed at mmWave....
A new statistical model of wave heights based on the concept of wave breaking critical zone
Institute of Scientific and Technical Information of China (English)
YANG Jiaxuan; LI Xunqiang; ZHU Shouxian; ZHANG Wenjing; WANG Lei
2015-01-01
When waves propagate from deep water to shallow water, wave heights and steepness increase and then waves roll back and break. This phenomenon is called surf. Currently, the present statistical calculation model of surf was derived mainly from the wave energy conservation equation and the linear wave dispersion relation, but it cannot reflect accurately the process which is a rapid increasing in wave height near the broken point. So, the concept of a surf breaking critical zone is presented. And the nearshore is divided as deep water zone, shallow water zone, surf breaking critical zone and after breaking zone. Besides, the calculation formula for the height of the surf breaking critical zone has founded based on flume experiments, thereby a new statistical calculation model on the surf has been established. Using the new model, the calculation error of wave height maximum is reduced from 17.62% to 6.43%.
Lamb wave propagation modeling for structure health monitoring
Institute of Scientific and Technical Information of China (English)
Xiaoyue ZHANG; Shenfang YUAN; Tong HAO
2009-01-01
This study aims to model the propagation of Lamb waves used in structure health monitoring. A number of different numerical computational techniques have been developed for wave propagation studies. The local interaction simulation approach, used for modeling sharp interfaces and discontinuities in complex media (LISA/SIM theory), has been effectively applied to numerical simulations of elastic wave interaction. This modeling is based on the local interaction simulation approach theory and is finally accomplished through the finite elements software Ansys11. In this paper, the Lamb waves propagating characteristics and the LISA/SIM theory are introduced. The finite difference equations describing wave propagation used in the LISA/SIM theory are obtained. Then, an anisotropic metallic plate model is modeled and a simulating Lamb waves signal is loaded on. Finally, the Lamb waves propagation modeling is implemented.
WAVE ATTENUATION OVER MUD BED: A PSEUDO-PLASTIC MODEL
Institute of Scientific and Technical Information of China (English)
Zhang Qing-he; Onyx W.H. Wai; Joseph H. W. Lee
2003-01-01
A two-layer model, with the upper layer being the perfect fluid and the lower layer being the pseudo-plastic fluid describing water wave attenuation over mud bed, was established. A simplified method based on the principle of equivalent work was applied to solve the boundary value problems. The computational results of the model show that the two-layer perfect fluid model and the perfect-viscous fluid model are all special cases of the present model. The complex nonlinear properties of wave attenuation over mud bed, can be explained by the present model, e.g., the wave dissipation rate decreases with the wave height in certain cases, while the small wave propagates over mud bed with less energy dissipation and large wave attenuates rapidly in other cases. Other factors influencing the wave attenuation were also discussed.
MODELING ON THE CYCLIC OPERATION OF STANDING COLUMN WELLS UNDER REGIONAL GROUNDWATER FLOW*
Institute of Scientific and Technical Information of China (English)
LEE Kun Sang
2011-01-01
Coupled hydrogeological-thermal simulation of the Standing Column Well (SCW) system is essential to provide an optimized configuration and operation schedule for boreholes on the site.This paper presents numerical investigations and thermo-hydraulic evaluation of standing column well system operating under cyclic flow regime.A three-dimensional numerical model for groundwater flow and heat transport is used to analyze the heat exchange in the ground.The model includes the effects of convective and conductive heat transfer, heat loss to the adjacent confining strata, and hydraulic anisotropy.The operation scenario consists of cyclic injection and recovery and four periods per year to simulate the seasonal temperature conditions.For different parameters of the system, performances have been evaluated in terms of variations in recovery temperature.The calculated temperatures at the producing pipe are relatively constant within a certain range through the year and fluctuating quarterly a year.Pipe-to-pipe distance, injection/production rate, ground thickness, and permeability considered in the model are shown to impact the predicted temperature profiles at each stage and the recovery water temperature.The influence of pressure gradient, which determines the velocity of regional groundwater flow, is most substantial.
Directory of Open Access Journals (Sweden)
Fei Wang
2017-07-01
Full Text Available The optimized dispatch of different distributed generations (DGs in stand-alone microgrid (MG is of great significance to the operation’s reliability and economy, especially for energy crisis and environmental pollution. Based on controllable load (CL and combined cooling-heating-power (CCHP model of micro-gas turbine (MT, a multi-objective optimization model with relevant constraints to optimize the generation cost, load cut compensation and environmental benefit is proposed in this paper. The MG studied in this paper consists of photovoltaic (PV, wind turbine (WT, fuel cell (FC, diesel engine (DE, MT and energy storage (ES. Four typical scenarios were designed according to different day types (work day or weekend and weather conditions (sunny or rainy in view of the uncertainty of renewable energy in variable situations and load fluctuation. A modified dispatch strategy for CCHP is presented to further improve the operation economy without reducing the consumers’ comfort feeling. Chaotic optimization and elite retention strategy are introduced into basic particle swarm optimization (PSO to propose modified chaos particle swarm optimization (MCPSO whose search capability and convergence speed are improved greatly. Simulation results validate the correctness of the proposed model and the effectiveness of MCPSO algorithm in the optimized operation application of stand-alone MG.
FEM modelling of shoes insoles components for standing and walking simulation
Directory of Open Access Journals (Sweden)
Braun Barbu
2017-01-01
Full Text Available The paper presents a research stage in which a new method applied for foot insoles components rapid prototyping was successfully tested in case of two young persons with small orthopaedic diseases. The research in this stage is focused on the FEA model analysis before and after prototyping, the model consisting in two sets of specific items to be inserted into the plantar supporters, with orthopaedic correction role. The simulation and testing was performed in condition of wearing shoes containing such of plantar supporters, when standing and walking, these situations being the most common. The main studied problem was to verify if the CAD modelled orthotic items to be prototyped should resist in case of static and dynamic loads, similar to those found in case of standing and walking. It was demonstrated a good correlation in terms of testing results before and after items prototyping, especially for the second person. Besides, it was demonstrated that the FEA analysis applied method could be successfully used to verify the prototyped orthotic items endurance and resistance.
Rogue waves in a water tank: Experiments and modeling
Lechuga, Antonio
2013-04-01
Recently many rogue waves have been reported as the main cause of ship incidents on the sea. One of the main characteristics of rogue waves is its elusiveness: they present unexpectedly and disappear in the same wave. Some authors (Zakharov and al.2010) are attempting to find the probability of their appearances apart from studyingthe mechanism of the formation. As an effort on this topic we tried the generation of rogue waves in a water wave tank using a symmetric spectrum(Akhmediev et al. 2011) as input on the wave maker. The produced waves were clearly rogue waves with a rate (maximum wave height/ Significant wave height) of 2.33 and a kurtosis of 4.77 (Janssen 2003, Onorato 2006). These results were already presented (Lechuga 2012). Similar waves (in pattern aspect, but without being extreme waves) were described as crossing waves in a water tank(Shemer and Lichter1988). To go on further the next step has been to apply a theoretical model to the envelope of these waves. After some considerations the best model has been an analogue of the Ginzburg-Landau equation. This apparently amazing result is easily explained: We know that the Ginzburg-Landau model is related to some regular structures on the surface of a liquid and also in plasmas, electric and magnetic fields and other media. Another important characteristic of the model is that their solutions are invariants with respectto the translation group. The main aim of this presentation is to extract conclusions of the model and the comparison with the measured waves in the water tank.The nonlinear structure of waves and their regularity make suitable the use of the Ginzburg-Landau model to the envelope of generated waves in the tank,so giving us a powerful tool to cope with the results of our experiment.
Experimental Modeling of the Overtopping Flow on the Wave Dragon Wave Energy Converter
DEFF Research Database (Denmark)
Parmeggiani, Stefano; Kofoed, Jens Peter; Friis-Madsen, Erik
2011-01-01
The Wave Dragon Wave Energy Converter is currently facing a precommercial phase. At this stage of development a reliable overtopping model is highly required, in order to predict the performance of the device at possible deployment locations. A model formulation derived for an overtopping device...... with general geometry has been used so far. The paper presents an updated formulation drawn through the tank testing of a scaled model the Wave Dragon. The sensitivity analysis of the main features influencing the overtopping flow led to an updated model formulation which can be specifically suited...... for the Wave Dragon....
Experimental Modeling of the Overtopping Flow on the Wave Dragon Wave Energy Converter
DEFF Research Database (Denmark)
Parmeggiani, Stefano; Kofoed, Jens Peter; Friis-Madsen, Erik
2011-01-01
The Wave Dragon Wave Energy Converter is currently facing a precommercial phase. At this stage of development a reliable overtopping model is highly required, in order to predict the performance of the device at possible deployment locations. A model formulation derived for an overtopping device...... with general geometry has been used so far. The paper presents an updated formulation drawn through the tank testing of a scaled model the Wave Dragon. The sensitivity analysis of the main features influencing the overtopping flow led to an updated model formulation which can be specifically suited...... for the Wave Dragon....
Directory of Open Access Journals (Sweden)
Melewanto Patabang
2014-04-01
Full Text Available Growth modeling and yield simulation of forest is a very important aspect in forest management including community forests. Stand growth model is an abstraction of the dynamic nature of a forest stand, including growth, ingrowths, mortality, and other changes in the structure and composition of the stand. In forest management, growth estimation plays an important role in supporting the sustainability of the benefits value of the community forests. The objectives of the research were to find out the stand growth model and the potential of community's pine forest. The study was conducted at the location of the community pine forests in District Mengkendek Tana Toraja Regency. Sample location, as representative of stand age classes that distribute on some villages in Mengkendek District, were selected by purposive sampling.The study results indicate that the most suitable model for upper trees mean height (H is Weibull Model, for growth diameter and growth volume is Logistic Model . The stand mean height (h can be presented as a function of H and Relative Spacing Ratio (Sr on the basis of function log Sr = 0,197 – 0,653 log H, then the tree volume, can be estimated on the basis of function log V = -1,70 + 0,94logD + 1,50logh, and then the growth function of volume on the basis of function V = 1.008 / 1 + 251.322 exp(-0.373t. Further, the maximum value of stand Annual Increment was 18 m3ha-1year-1, attained at the age of 20 years.Keywords: community's pine forest, stand growth, tree volume, annual increment
A stand-alone demography and landscape structure module for Earth system models
Nieradzik, L. P.; Haverd, V.; Smith, B.; Cook, G. D.; Briggs, P.; Roxburgh, S.; Liedloff, A.; Meyer, C.; Canadell, J.
2013-12-01
We propose and demonstrate a new approach for the simulation of woody ecosystem stand dynamics, demography and disturbance-mediated heterogeneity suitable for continental to global applications and designed for coupling to the terrestrial ecosystem component of any earth system model (Haverd et al., 2013). The approach is encoded in a model called Populations-Order-Physiology (POP). We demonstrate the behaviour and performance of POP coupled to the Community Atmosphere Biosphere Land Exchange model (CABLE) for two contrasting applications: (i) to the Northern Australian Tropical Transect, featuring gradients in savanna vegetation cover, rainfall and fire disturbance and (ii) to a set of globally distributed forest locations coinciding with observations of forest biomass allometry. Along the Northern Australian Tropical Transect, CABLE-POP is able to simultaneously reproduce observation-based estimates of key functional and structural variables, namely gross primary production, tree foliage projective cover, basal area and maximum tree height. This application particularly demonstrates the ability of POP to quantify the contributions of drought and fire to tree mortality. Drought is manifested as an increase in mortality due to a decline in growth efficiency, while fires are treated as partial disturbance events, with tree mortality depending on tree size and fire intensity. In the application to global forests, POP is integrated with global forest data by calibrating it against paired observations of stem biomass and number density. The calibrated POP model is then coupled with CABLE and the coupled model is evaluated against leaf-stem allometry observations from forest stands ranging in age from 20 to 400 years. Results indicate that, in contrast to simulations from many global land surface models (Wolf et al., 2011), simulated biomass pools conform well with observed allometry. We conclude that POP, which can readily be coupled to the terrestrial carbon cycle
A Reaction-Diffusion Model of Cholinergic Retinal Waves
Lansdell, Benjamin; Ford, Kevin; Kutz, J. Nathan
2014-01-01
Prior to receiving visual stimuli, spontaneous, correlated activity in the retina, called retinal waves, drives activity-dependent developmental programs. Early-stage waves mediated by acetylcholine (ACh) manifest as slow, spreading bursts of action potentials. They are believed to be initiated by the spontaneous firing of Starburst Amacrine Cells (SACs), whose dense, recurrent connectivity then propagates this activity laterally. Their inter-wave interval and shifting wave boundaries are the result of the slow after-hyperpolarization of the SACs creating an evolving mosaic of recruitable and refractory cells, which can and cannot participate in waves, respectively. Recent evidence suggests that cholinergic waves may be modulated by the extracellular concentration of ACh. Here, we construct a simplified, biophysically consistent, reaction-diffusion model of cholinergic retinal waves capable of recapitulating wave dynamics observed in mice retina recordings. The dense, recurrent connectivity of SACs is modeled through local, excitatory coupling occurring via the volume release and diffusion of ACh. In addition to simulation, we are thus able to use non-linear wave theory to connect wave features to underlying physiological parameters, making the model useful in determining appropriate pharmacological manipulations to experimentally produce waves of a prescribed spatiotemporal character. The model is used to determine how ACh mediated connectivity may modulate wave activity, and how parameters such as the spontaneous activation rate and sAHP refractory period contribute to critical wave size variability. PMID:25474327
Coupling atmospheric and ocean wave models for storm simulation
DEFF Research Database (Denmark)
Du, Jianting
This thesis studies the wind-wave interactions through the coupling between the atmospheric model and ocean surface wave models. Special attention is put on storm simulations in the North Sea for wind energy applications in the coastal zones. The two aspects, namely storm conditions and coastal...... areas, are challenging for the wind-wave coupling system because: in storm cases, the wave field is constantly modified by the fast varying wind field; in coastal zones, the wave field is strongly influenced by the bathymetry and currents. Both conditions have complex, unsteady sea state varying...... with time and space that challenge the current coupled modeling system. The conventional approach of estimating the momentum exchange is through parameterizing the aerodynamic roughness length (z0) with wave parameters such as wave age, steepness, significant wave height, etc. However, it is found in storm...
Song, Junho; Pulkkinen, Aki; Huang, Yuexi; Hynynen, Kullervo
2012-02-01
Standing-wave formation in an ex vivo human skull was investigated using a clinical prototype of a 30-cm diameter with 15-cm radius of curvature, low-frequency (230 kHz), hemispherical transcranial magnetic resonance-guided focused ultrasound phased array. Experimental and simulation studies were conducted with changing aperture size and f -number configurations of the phased array and qualitatively and quantitatively examined the acoustic pressure variation at the focus due to standing waves. The results demonstrated that the nodes and antinodes of standing wave produced by the small-aperture array were clearly seen at approximately every 3 mm. The effect of the standing wave became more pronounced as the focus was moved closer to skull base. However, a sharp focus was seen for the full array, and there was no such standing-wave pattern in the acoustic plane or near the skull base. This study showed that the fluctuation pressure amplitude would be greatly reduced by using a large-scale, hemispherical phased array with a low f-number.
Faraday pilot-wave dynamics: modelling and computation
Milewski, Paul A.; Galeano-Rios, Carlos A.; Nachbin, André; Bush, John W. M.
2015-01-01
A millimetric droplet bouncing on the surface of a vibrating fluid bath can self-propel by virtue of a resonant interaction with its own wave field. This system represents the first known example of a pilot-wave system of the form envisaged by Louis de Broglie in his double-solution pilot-wave theory. We here develop a fluid model of pilot-wave hydrodynamics by coupling recent models of the droplet’s bouncing dynamics with a more realistic model of weakly viscous quasi-potential wave generati...
Competition between the s-wave and p-wave superconductivity phases in a holographic model
Nie, Zhang-Yu; Gao, Xin; Zeng, Hui
2013-01-01
We build a holographic superconductor model with a scalar triplet charged under an SU(2) gauge field in the bulk. In this model, the s-wave and p-wave condensates can be consistently realized. We find that there are totally four phases in this model, namely, the normal phase without any condensate, s-wave phase, p-wave phase and the s+p coexisting phase. By calculating Gibbs free energy, the s+p coexisting phase turns out to be thermodynamically favored once it can appear. The phase diagram with the dimension of the scalar operator and temperature is drawn. The temperature range for the s+p coexisting phase is very narrow, which shows the competition between the s-wave and p-wave orders in the superconductor model.
Wind waves in tropical cyclones: satellite altimeter observations and modeling
Golubkin, Pavel; Kudryavtsev, Vladimir; Chapron, Bertrand
2016-04-01
Results of investigation of wind-wave generation by tropical cyclones using satellite altimeter data are presented. Tropical cyclones are generally relatively small rapidly moving low pressure systems that are capable of generating severe wave conditions. Translation of a tropical cyclone leads to a prolonged period of time surface waves in the right sector remain under high wind forcing conditions. This effect has been termed extended fetch, trapped fetch or group velocity quasi-resonance. A tropical cyclone wave field is thus likely more asymmetrical than the corresponding wind field: wind waves in the tropical cyclone right sector are more developed with larger heights than waves in the left one. A dataset of satellite altimeter intersections of the Western Pacific tropical cyclones was created for 2010-2013. Data from four missions were considered, i.e., Jason-1, Jason-2, CryoSat-2, SARAL/AltiKa. Measurements in the rear-left and front-right sectors of tropical cyclones were examined for the presence of significant wave asymmetry. An analytical model is then derived to efficiently describe the wave energy distribution in a moving tropical cyclone. The model essentially builds on a generalization of the self-similar wave growth model and the assumption of a strongly dominant single spectral mode in a given quadrant of the storm. The model provides a criterion to anticipate wave enhancement with the generation of trapped abnormal waves. If forced during a sufficient timescale interval, also defined from this generalized self-similar wave growth model, waves can be trapped and large amplification of the wave energy will occur in the front-right storm quadrant. Remarkably, the group velocity and corresponding wavelength of outrunning wave systems will become wind speed independent and solely relate to the translating velocity. The resulting significant wave height also only weakly depends on wind speed, and more strongly on the translation velocity. Satellite
Modeling Technology in Traveling-Wave Fault Location
Directory of Open Access Journals (Sweden)
Tang Jinrui
2013-06-01
Full Text Available Theoretical research and equipment development of traveling-wave fault location seriously depend on digital simulation. Meanwhile, the fault-generated transient traveling wave must be transferred through transmission line, mutual inductor and secondary circuit before it is used. So this paper would maily analyze and summarize the modeling technology of transmission line and mutual inductor on the basis of the research achievement. Firstly several models of transmission line (multiple Π or T line model, Bergeron line model and frequency-dependent line model are compared in this paper with analysis of wave-front characteristics and characteristic frequency of traveling wave. Then modeling methods of current transformer, potential transformer, capacitive voltage transformer, special traveling-wave sensor and secondary cable are given. Finally, based on the difficult and latest research achievements, the future trend of modeling technology in traveling-wave fault location is prospected.
Directory of Open Access Journals (Sweden)
Xiaolu Tang
Full Text Available Chinese fir (Cunninghamia lanceolata [Lamb.] Hook is one of the most important plantation tree species in China with good timber quality and fast growth. It covers an area of 8.54 million hectare, which corresponds to 21% of the total plantation area and 32% of total plantation volume in China. With the increasing market demand, an accurate estimation and prediction of merchantable volume at tree- and stand-level is becoming important for plantation owners. Although there are many studies on the total tree volume estimation from allometric models, these allometric models cannot predict tree- and stand-level merchantable volume at any merchantable height, and the stand-level merchantable volume model was not seen yet in Chinese fir plantations. This study aimed to develop (1 a compatible taper function for tree-level merchantable volume estimation, and (2 a stand-level merchantable volume model for Chinese fir plantations. This "taper function system" consisted in a taper function, a merchantable volume equation and a total tree volume equation. 46 Chinese fir trees were felled to develop the taper function in Shitai County, Anhui province, China. A second-order continuous autoregressive error structure corrected the inherent serial autocorrelation of different observations in one tree. The taper function and volume equations were fitted simultaneously after autocorrelation correction. The compatible taper function fitted well to our data and had very good performances in diameter and total tree volume prediction. The stand-level merchantable volume equation based on the ratio approach was developed using basal area, dominant height, quadratic mean diameter and top diameter (ranging from 0 to 30 cm as independent variables. At last, a total stand-level volume table using stand basal area and dominant height as variables was proposed for local forest managers to simplify the stand volume estimation.
Numerical modelling in wave energy conversion systems
Energy Technology Data Exchange (ETDEWEB)
El Marjani, A. [Labo. de Turbomachines, Ecole Mohammadia d' Ingenieurs (EMI), Universite Mohammed V Agdal, Av Ibn Sina, B.P. 765 Agdal, Rabat (Morocco); Castro Ruiz, F.; Rodriguez, M.A.; Parra Santos, M.T. [Depto. de Ingenieria Energetica y Fluidomecanica, Escuela Tecnica Superior de Ingenieros Industriales, Universidad de Valladolid, Paseo del Cauce s/n, E-47011 Valladolid (Spain)
2008-08-15
This paper deals with a numerical modelling devoted to predict the flow characteristics in the components of an oscillating water column (OWC) system used for the wave energy capture. In the present paper, the flow behaviour is modelled by using the FLUENT code. Two numerical flow models have been elaborated and tested independently in the geometries of an air chamber and a turbine, which is chosen of a radial impulse type. The flow is assumed to be three-dimensional (3D), viscous, turbulent and unsteady. The FLUENT code is used with a solver of the coupled conservation equations of mass, momentum and energy, with an implicit time scheme and with the adoption of the dynamic mesh and the sliding mesh techniques in areas of moving surfaces. Turbulence is modelled with the k-{epsilon} model. The obtained results indicate that the developed models are well suitable to analyse the air flows both in the air chamber and in the turbine. The performances associated with the energy transfer processes have been well predicted. For the turbine, the numerical results of pressure and torque were compared to the experimental ones. Good agreements between these results have been observed. (author)
Model fitting of kink waves in the solar atmosphere: Gaussian damping and time-dependence
Morton, R. J.; Mooroogen, K.
2016-09-01
Aims: Observations of the solar atmosphere have shown that magnetohydrodynamic waves are ubiquitous throughout. Improvements in instrumentation and the techniques used for measurement of the waves now enables subtleties of competing theoretical models to be compared with the observed waves behaviour. Some studies have already begun to undertake this process. However, the techniques employed for model comparison have generally been unsuitable and can lead to erroneous conclusions about the best model. The aim here is to introduce some robust statistical techniques for model comparison to the solar waves community, drawing on the experiences from other areas of astrophysics. In the process, we also aim to investigate the physics of coronal loop oscillations. Methods: The methodology exploits least-squares fitting to compare models to observational data. We demonstrate that the residuals between the model and observations contain significant information about the ability for the model to describe the observations, and show how they can be assessed using various statistical tests. In particular we discuss the Kolmogorov-Smirnoff one and two sample tests, as well as the runs test. We also highlight the importance of including any observational trend line in the model-fitting process. Results: To demonstrate the methodology, an observation of an oscillating coronal loop undergoing standing kink motion is used. The model comparison techniques provide evidence that a Gaussian damping profile provides a better description of the observed wave attenuation than the often used exponential profile. This supports previous analysis from Pascoe et al. (2016, A&A, 585, L6). Further, we use the model comparison to provide evidence of time-dependent wave properties of a kink oscillation, attributing the behaviour to the thermodynamic evolution of the local plasma.
Modeling the Buoyancy System of a Wave Energy Power Plant
DEFF Research Database (Denmark)
Pedersen, Tom S.; Nielsen, Kirsten M.
2009-01-01
A nonlinear dynamic model of the buoyancy system in a wave energy power plant is presented. The plant ("Wave Dragon") is a floating device using the potential energy in overtopping waves to produce power. A water reservoir is placed on top of the WD, and hydro turbines lead the water to the sea...
Modelling wave transformation across a fringing reef using swash
Zijlema, M.
2012-01-01
This paper presents the application of the open source non-hydrostatic wave-flow model SWASH to wave propagation over a fringing reef, and the results are discussed and compared with observations obtained from a laboratory experiment subjected to various incident wave conditions. This study focus no
Modelling wave transformation across a fringing reef using SWASH
Zijlema, M.
2012-01-01
This paper presents the application of the open source non-hydrostatic wave-flow model SWASH to wave propagation over a fringing reef, and the results are discussed and compared with observations obtained from a laboratory experiment subjected to various incident wave conditions. This study focus no
Modeling the Buoyancy System of a Wave Energy Power Plant
DEFF Research Database (Denmark)
Pedersen, Tom S.; Nielsen, Kirsten M.
2009-01-01
A nonlinear dynamic model of the buoyancy system in a wave energy power plant is presented. The plant ("Wave Dragon") is a floating device using the potential energy in overtopping waves to produce power. A water reservoir is placed on top of the WD, and hydro turbines lead the water to the sea...
Primordial gravitational waves from the space-condensate inflation model
Koh, Seoktae; Tumurtushaa, Gansukh
2015-01-01
We consider the space-condensate inflation model to study the primordial gravitational waves generated in the early Universe. We calculate the energy spectrum of gravitational waves induced by the space-condensate inflation model for full frequency range with assumption that the phase transition between two consecutive regimes to be abrupt during evolution of the Universe. The suppression of energy spectrum is found in our model for the decreasing frequency of gravitational waves depending on the model parameter. To realize the suppression of energy spectrum of the primordial gravitational waves, we study an existence of the early phase transition during inflation for the space-condensate inflation model.
Reißenweber, Marina; Krempel, Sandro; Lindner, Gerhard
2013-12-01
With an acoustic levitator small particles can be aggregated near the nodes of a standing pressure field. Furthermore it is possible to atomize liquids on a vibrating surface. We used a combination of both mechanisms and atomized several liquids simultaneously, consecutively and emulsified in the ultrasonic field. Using a high-speed camera we observed the coagulation of the spray droplets into single large levitated droplets resolved in space and time. In case of subsequent atomization of two components the spray droplets of the second component were deposited on the surface of the previously coagulated droplet of the first component without mixing.
Optimal parametric modelling of measured short waves
Digital Repository Service at National Institute of Oceanography (India)
Mandal, S.
The spectral analysis of measured short waves can efficiently be carried out by the fast Fourier transform technique. Even though many present techniques can be used for the simulation of time series waves, these may not provide accurate...
Numerical modelling of nearshore wave transformation
Digital Repository Service at National Institute of Oceanography (India)
Chandramohan, P.; Nayak, B.U.; SanilKumar, V.
A software has been developed for numerical refraction study based on finite amplitude wave theories. Wave attenuation due to shoaling, bottom friction, bottom percolation and viscous dissipation has also been incorporated. The software...
Modelling and Simulation of Three Level Inverters for Main Drive of the Plate Mill Rolling Stand
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Gasiyarov Vadim R.
2016-01-01
Full Text Available This paper addresses a modelling and a simulation of three level inverters for main drive of the plate mill rolling stand. The main purpose of the article is to develop of a mathematical description of the three level voltage source inverter based on a space vector pulse width modulation and to simulate a consumption current by the main electric drive based on 18-pulse rectification circuit. A twelve-megawatt synchronous motor as a load has been used. The modelling results were simulated at the Matlab/Simulink program. It can allow us to estimate an electromagnetic compatibility of the main electric drive based on transients of the consumption current. The research results can be used to assess the electromagnetic compatibility of powerful three level natural point clamped converters with different types of the space vector pulse width modulation on a load or a grid.
Song, Junho; Pulkkinen, Aki; Huang, Yuexi; Hynynen, Kullervo
2011-01-01
Standing wave formation in an ex vivo human skull was investigated using a clinical prototype of a 30 cm diameter with 15 cm radius of curvature, low frequency (230 kHz), hemispherical transcranial Magnetic Resonance guided Focused Ultrasound (MRgFUS) phased-array. Experimental and simulation studies were conducted with changing aperture size and f-number configurations of the phased array, and qualitatively and quantitatively examined the acoustic pressure variation at the focus due to stand...
Weakly nonlinear models for internal waves: inverse scattering transform and solitary wave contents
Chen, Shengqian
2016-01-01
The time evolution emanating from ``internal dam-break'' initial conditions is studied for a class of models of stratified Euler fluids in configurations close to two-homogeneous layers separated by a thin diffused interface. Direct numerical simulations and experiments in wave tanks show that such initial conditions eventually give rise to coherent structures that are close to solitary-wave solutions moving ahead of a region of dispersive wave motion and turbulent mixing close to the location of the initial dam step. A priori theoretical predictions of the main features of these solitary waves, such as their amplitudes and speeds, appear to be unavailable, even for simplified models of wave evolution in stratified fluids. With the aim of providing estimates of the existence, amplitude and speed of such solitary waves, an approach based on Inverse Scattering Transform (IST) for completely integrable models is developed here and tested against direct numerical simulations of Euler fluids and some of their mode...
Modeling of aqueous foam blast wave attenuation
Directory of Open Access Journals (Sweden)
Domergue L.
2011-01-01
Full Text Available The use of aqueous foams enables the mitigation of blast waves induced by the explosion of energetic materials. The two-phase confinement gives rise to interphase interactions between the gaseous and liquid phases, which role have been emphasized in shock-tube studies with solid foams [1, 2]. Multifluid formalism enables the thermo-mechanical disequilibria between phases to be taken into account. The flow model ensures the correct estimation of the acoustic impedance of the two-phase media. As for the numerical scheme, Riemann solvers are used to describe the microscopic fluid interactions, the summation of which provides the multiphase flux. The role of the different transfer mechanisms is evaluated in the case where the liquid ligaments of the foam matrix have been shattered into droplets by the shock impingement. Characteristics of blast waves in heterogeneous media leads to a decrease of overpressure. The numerical results have been compared favorably to experimental data [3, 4].
Accurate finite element modeling of acoustic waves
Idesman, A.; Pham, D.
2014-07-01
In the paper we suggest an accurate finite element approach for the modeling of acoustic waves under a suddenly applied load. We consider the standard linear elements and the linear elements with reduced dispersion for the space discretization as well as the explicit central-difference method for time integration. The analytical study of the numerical dispersion shows that the most accurate results can be obtained with the time increments close to the stability limit. However, even in this case and the use of the linear elements with reduced dispersion, mesh refinement leads to divergent numerical results for acoustic waves under a suddenly applied load. This is explained by large spurious high-frequency oscillations. For the quantification and the suppression of spurious oscillations, we have modified and applied a two-stage time-integration technique that includes the stage of basic computations and the filtering stage. This technique allows accurate convergent results at mesh refinement as well as significantly reduces the numerical anisotropy of solutions. We should mention that the approach suggested is very general and can be equally applied to any loading as well as for any space-discretization technique and any explicit or implicit time-integration method.
Mitri, F. G.
2016-07-01
This paper presents two key contributions; the first concerns the development of analytical expressions for the axial and transverse acoustic radiation forces exerted on a 2D rigid elliptical cylinder placed in the field of plane progressive, quasi-standing, or standing waves with arbitrary incidence. The second emphasis is on the acoustic radiation torque per length. The rigid elliptical cylinder case is important to be considered as a first-order approximation of the behavior of a cylindrical fluid column trapped in air because of the significant acoustic impedance mismatch at the particle boundary. Based on the rigorous partial-wave series expansion method in cylindrical coordinates, non-dimensional acoustic radiation force and torque functions are derived and defined in terms of the scattering coefficients of the elliptic cylinder. A coupled system of linear equations is obtained after applying the Neumann boundary condition for an immovable surface in a non-viscous fluid and solved numerically by matrix inversion after performing a single numerical integration procedure. Computational results for the non-dimensional force components and torque, showing the transition from the progressive to the (equi-amplitude) standing wave behavior, are performed with particular emphasis on the aspect ratio a/b, where a and b are the semi-axes of the ellipse, the dimensionless size parameter, as well as the angle of incidence ranging from end-on to broadside incidence. The results show that the elliptical geometry has a direct influence on the radiation force and torque, so that the standard theory for circular cylinders (at normal incidence) leads to significant miscalculations when the cylinder cross section becomes non-circular. Moreover, the elliptical cylinder experiences, in addition to the acoustic radiation force, a radiation torque that vanishes for the circular cylinder case. The application of the formalism presented here may be extended to other 2D surfaces of
Design of a Stand-Alone Photovoltaic (PV Models for Home Lightings and Clean Environment
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Vincent Anayochukwu Ani
2016-01-01
Full Text Available This paper gives a well-documented health risks of fuel-based lighting (kerosene lamps and fuel-powered generators and proposed a design of a stand-alone solar PV system for sustainable home lightings in rural Nigerian area. The design was done in three different patterns of electricity consumptions with energy efficient lightings (EELs using two different battery types (Rolls Surrette 6CS25PS and hoppecke 10 OpzS 1000 on; i judicious power consumption, ii normal power consumption, iii excess power consumption; and compared them with the incandescent light bulb consumption. The stand-alone photovoltaic energy systems were designed to match the rural Nigerian sunlight and weather conditions to meet the required lightings of the household. The objective function and constraints for the design models were formulated and optimization procedure were used to demonstrate the best solution (reliability at the lowest lifecycle cost. Initial capital costs as well as annualized costs over 5, 10, 15, 20, and 25 years were quantified and documented. The design identified the most cost-effective and reliable solar and battery array among the patterns of electricity consumption with energy efficient lighting options (judicious power consumption, normal power consumption, and excess power consumption.
A full-wave Helmholtz model for continuous-wave ultrasound transmission.
Huttunen, Tomi; Malinen, Matti; Kaipio, Jari P; White, Phillip Jason; Hynynen, Kullervo
2005-03-01
A full-wave Helmholtz model of continuous-wave (CW) ultrasound fields may offer several attractive features over widely used partial-wave approximations. For example, many full-wave techniques can be easily adjusted for complex geometries, and multiple reflections of sound are automatically taken into account in the model. To date, however, the full-wave modeling of CW fields in general 3D geometries has been avoided due to the large computational cost associated with the numerical approximation of the Helmholtz equation. Recent developments in computing capacity together with improvements in finite element type modeling techniques are making possible wave simulations in 3D geometries which reach over tens of wavelengths. The aim of this study is to investigate the feasibility of a full-wave solution of the 3D Helmholtz equation for modeling of continuous-wave ultrasound fields in an inhomogeneous medium. The numerical approximation of the Helmholtz equation is computed using the ultraweak variational formulation (UWVF) method. In addition, an inverse problem technique is utilized to reconstruct the velocity distribution on the transducer which is used to model the sound source in the UWVF scheme. The modeling method is verified by comparing simulated and measured fields in the case of transmission of 531 kHz CW fields through layered plastic plates. The comparison shows a reasonable agreement between simulations and measurements at low angles of incidence but, due to mode conversion, the Helmholtz model becomes insufficient for simulating ultrasound fields in plates at large angles of incidence.
Directory of Open Access Journals (Sweden)
Melewanto Patabang
2014-04-01
Full Text Available Growth modeling and yield simulation of forest is a very important aspect in forest management including community forests. Stand growth model is an abstraction of the dynamic nature of a forest stand, including growth, ingrowths, mortality, and other changes in the structure and composition of the stand. In forest management, growth estimation plays an important role in supporting the sustainability of the benefits value of the community forests. The objectives of the research were to find out the stand growth model and the potential of community's pine forest. The study was conducted at the location of the community pine forests in District Mengkendek Tana Toraja Regency. Sample location, as representative of stand age classes that distribute on some villages in Mengkendek District, were selected by purposive sampling.The study results indicate that the most suitable model for upper trees mean height (H is Weibull Model, for growth diameter and growth volume is Logistic Model . The stand mean height (h can be presented as a function of H and Relative Spacing Ratio (Sr on the basis of function log Sr = 0,197 – 0,653 log H, then the tree volume, can be estimated on the basis of function log V = -1,70 + 0,94logD + 1,50logh, and then the growth function of volume on the basis of function V = 1.008 / 1 + 251.322 exp(-0.373t. Further, the maximum value of stand Annual Increment was 18 m3ha-1year-1, attained at the age of 20 years.
A Continuum Model of Actin Waves in Dictyostelium discoideum
Khamviwath, Varunyu; Hu, Jifeng; Othmer, Hans G.
2013-01-01
Actin waves are complex dynamical patterns of the dendritic network of filamentous actin in eukaryotes. We developed a model of actin waves in PTEN-deficient Dictyostelium discoideum by deriving an approximation of the dynamics of discrete actin filaments and combining it with a signaling pathway that controls filament branching. This signaling pathway, together with the actin network, contains a positive feedback loop that drives the actin waves. Our model predicts the structure, composition, and dynamics of waves that are consistent with existing experimental evidence, as well as the biochemical dependence on various protein partners. Simulation suggests that actin waves are initiated when local actin network activity, caused by an independent process, exceeds a certain threshold. Moreover, diffusion of proteins that form a positive feedback loop with the actin network alone is sufficient for propagation of actin waves at the observed speed of . Decay of the wave back can be caused by scarcity of network components, and the shape of actin waves is highly dependent on the filament disassembly rate. The model allows retraction of actin waves and captures formation of new wave fronts in broken waves. Our results demonstrate that a delicate balance between a positive feedback, filament disassembly, and local availability of network components is essential for the complex dynamics of actin waves. PMID:23741312
Modelling of the Overtopping Flow on the Wave Dragon Wave Energy Converter
DEFF Research Database (Denmark)
Parmeggiani, Stefano; Pecher, Arthur; Kofoed, Jens Peter
2010-01-01
The Wave Dragon is a floating slack-moored Wave Energy Converter of the overtopping type, which is facing now the last phase of development before the commercial exploitation: the deployment of a full-scale demonstrator. In this phase a modelling tool allowing for accurate predictions of the perf......The Wave Dragon is a floating slack-moored Wave Energy Converter of the overtopping type, which is facing now the last phase of development before the commercial exploitation: the deployment of a full-scale demonstrator. In this phase a modelling tool allowing for accurate predictions...
Model Predictive Control of a Wave Energy Converter
DEFF Research Database (Denmark)
Andersen, Palle; Pedersen, Tom Søndergård; Nielsen, Kirsten Mølgaard;
2015-01-01
In this paper reactive control and Model Predictive Control (MPC) for a Wave Energy Converter (WEC) are compared. The analysis is based on a WEC from Wave Star A/S designed as a point absorber. The model predictive controller uses wave models based on the dominating sea states combined with a model...... connecting undisturbed wave sequences to sequences of torque. Losses in the conversion from mechanical to electrical power are taken into account in two ways. Conventional reactive controllers are tuned for each sea state with the assumption that the converter has the same efficiency back and forth. MPC...
A general multivariate qualitative model for sizing stand-alone photovoltaic systems
Energy Technology Data Exchange (ETDEWEB)
Sidrach-de-Cardona, M. [Dpto. Fisica Aplicada II, E.T.S.I. Informatica, Universidad de Malaga, 29071 Malaga (Spain); Mora Lopez, L. [Dpto. Lenguajes y C. Computacion, E.T.S.I. Informatica, Universidad de Malaga, 29071 Malaga (Spain)
1999-10-01
We considered a general model for sizing a stand-alone photovoltaic system, using as energy input data the information available in any irradiation atlas. The parameters of the model are estimated by multivariate linear regression. The results obtained from the numerical loss of load probability size method (LOLP) were used as initial input data to fit the mode. For this fit we have used daily global irradiation data taken from 222 US meteorological stations for the period 1961-1990. The expression proposed allows us to determine the photovoltaic array size, with a coefficient of determination to 0.96. This coefficient is independent of the used LOLP value. System parameters and mean monthly values for daily global irradiation on the modules surface are taken as independent variables in the model. It also shows that the proposed model can be used with the same accuracy for other locations not considered in the estimation of the model. We also propose a model which would allow us to calculate optimum tilts for the array surface taking the latitude into account as well as the variability of the incident irradiation.
Modeling the Cerebellar Microcircuit: New Strategies for a Long-Standing Issue
D’Angelo, Egidio; Antonietti, Alberto; Casali, Stefano; Casellato, Claudia; Garrido, Jesus A.; Luque, Niceto Rafael; Mapelli, Lisa; Masoli, Stefano; Pedrocchi, Alessandra; Prestori, Francesca; Rizza, Martina Francesca; Ros, Eduardo
2016-01-01
The cerebellar microcircuit has been the work bench for theoretical and computational modeling since the beginning of neuroscientific research. The regular neural architecture of the cerebellum inspired different solutions to the long-standing issue of how its circuitry could control motor learning and coordination. Originally, the cerebellar network was modeled using a statistical-topological approach that was later extended by considering the geometrical organization of local microcircuits. However, with the advancement in anatomical and physiological investigations, new discoveries have revealed an unexpected richness of connections, neuronal dynamics and plasticity, calling for a change in modeling strategies, so as to include the multitude of elementary aspects of the network into an integrated and easily updatable computational framework. Recently, biophysically accurate “realistic” models using a bottom-up strategy accounted for both detailed connectivity and neuronal non-linear membrane dynamics. In this perspective review, we will consider the state of the art and discuss how these initial efforts could be further improved. Moreover, we will consider how embodied neurorobotic models including spiking cerebellar networks could help explaining the role and interplay of distributed forms of plasticity. We envisage that realistic modeling, combined with closed-loop simulations, will help to capture the essence of cerebellar computations and could eventually be applied to neurological diseases and neurorobotic control systems. PMID:27458345
Wave Prediction Model To Study On The Wave Height Variation In Terengganu Coast Of Malaysia
Directory of Open Access Journals (Sweden)
Nur Amalina Abdul Latif
2015-08-01
Full Text Available Abstract In this study the significant wave height at the Terengganu and the change of wave height at Kuala Terengganu to Merang shoreline were simulated by using the 2D Near-Shore Wave 2D NSW model. The significant wave height by the 2D NSW model at Kuala Terengganu to Merang shoreline from 2008-2012 were simulated. The model was forced by ECMWF European Centre for Medium Range Weather Forecast data. The simulated significant wave height by the 2D NSW model at Airport Kuala Terengganu AWAC station was compared with the observed significant wave height. The mean annual significant wave height indicate the higher wave height with average mean value in a range of 1.08-1.10 m in Kuala Terengganu to Batu Rakit area and lower in Merang area with average mean value in a range of 0.74 m. The detailed 5 years simulation period demonstrates that the strong variability of wave height exists during North-East monsoon. The findings of this study could be useful for the erosive calculation shoreline protection and coastal zone management activities.
Simulation of Typhoon-Driven Waves in the Yangtze Estuary with Multiple-Nested Wave Models
Institute of Scientific and Technical Information of China (English)
XU Fu-min; Will Perrie; ZHANG Jun-lun; SONG Zhi-yao; Bechara Toulany
2005-01-01
Typhoon-generated waves are simulated with two numerical wave models, the SWAN model for the coastal and Yangtze Estuary domain, nested within the WAVEWATCHIII (WW3) for the basin-scale East China Sea domain. Typhoon No. 8114 is chosen because it was very strong, and generated high waves in the Estuary. WW3 was implemented for the East China Sea coarse-resolution computational domain, to simulate the waves over a large spatial scale and provide boundary conditions for SWAN model simulations, implemented on a fine-resolution nested domain for the Yangtze Estuary area. The Takahashi wind model is applied to the simulation of the East China Sea scale (3-hourly) and Yangtze Estuary scale (1-hourly) winds. Simulations of significant wave heights in the East China Sea show that the highest waves are on the right side of the storm track, and maxima tend to occur at the eastern deep-water open boundary of the Yangtze Estuary. In the Yangtze Estuary, incoming swell is dominant over locally generated waves before the typhoon approaches the Estuary. As the typhoon approaches the Estuary, wind waves and swell coexist, and the wave direction is mainly influenced by the swell direction and the complex topography.
A wave guide model of lightning currents and their electromagnetic field
Volland, H.
1980-01-01
Lightning channels are considered as resonant wave guides in which only standing resonant wave modes can be excited. Two types of discharging currents develop. Type 1 is an aperiodic wave; type 2 is a damped oscillation. The electromagnetic radiation field of both types of currents is calculated and compared with the observation.
Lee, Junseok; Kang, Byungjun; Lee, Hyungsuk
2016-01-01
This paper describes continuously phase-modulated standing surface acoustic waves (CPM-SSAW) and its application for particle separation in multiple pressure nodes. A linear change of phase in CPM-SSAW applies a force to particles whose magnitude depends on their size and contrast factors. During continuous phase modulation, we demonstrate that particles with the target dimension are translated in the direction of moving pressure nodes, whereas smaller particles show oscillatory movements. The rate of phase modulation is optimized for separation of target particles from the relationship between mean particle velocity and period of oscillation. The developed technique is applied to separate particles of the target dimension from the particle mixture. Furthermore, we also demonstrate human keratinocyte cells can be separated in the cell and bead mixture. The separation technique is incorporated with a microfluidic channel spanning multiple pressure nodes, which is advantageous over separation in a single pressu...
Directory of Open Access Journals (Sweden)
Banani Basu
2010-05-01
Full Text Available In this paper, we propose a technique based on two evolutionary algorithms simulated annealing and particle swarm optimization to design a linear array of half wavelength long parallel dipole antennas that will generate a pencil beam in the horizontal plane with minimum standing wave ratio (SWR and fixed side lobe level (SLL. Dynamic range ratio of current amplitude distribution is kept at a fixed value. Two different methods have been proposed withdifferent inter-element spacing but with same current amplitude distribution. First one uses a fixed geometry and optimizes the excitation distribution on it. In the second case further reduction of SWR is done via optimization of interelement spacing while keeping the amplitude distribution same as before. Coupling effect between the elements is analyzed using induced EMF method and minimized interms of SWR. Numerical results obtained from SA are validated by comparing with results obtained using PSO.
Development of A New Waveguide Arc /Standing-wave Protecting Device%新型波导电弧/驻波保护装置的研制
Institute of Scientific and Technical Information of China (English)
钱锰
2001-01-01
The waveguide arc is one of the important reasons of damaging klystron. The practical block diagram , improvement circuit and relevant data of arc/standing-wave are given in this paper. The selection of the key device is analyzed. Finally, the experimental results and characteristic curve are also given.%波导电弧（俗称打火）/驻波过大是损坏速调管的重要原因之一。本文给出了电弧/驻波保护装置的实用框图、改进电路及有关数据，并对关键器件的选择进行了详细分析，最后给出了实验结果及特性曲线。
Lee, Junseok; Rhyou, Chanryeol; Kang, Byungjun; Lee, Hyungsuk
2017-04-01
This paper describes continuously phase-modulated standing surface acoustic waves (CPM-SSAW) and its application for particle separation in multiple pressure nodes. A linear change of phase in CPM-SSAW applies a force to particles whose magnitude depends on their size and contrast factors. During continuous phase modulation, we demonstrate that particles with a target dimension are translated in the direction of moving pressure nodes, whereas smaller particles show oscillatory movements. The rate of phase modulation is optimized for separation of target particles from the relationship between mean particle velocity and period of oscillation. The developed technique is applied to separate particles of a target dimension from the particle mixture. Furthermore, we also demonstrate human keratinocyte cells can be separated in the cell and bead mixture. The separation technique is incorporated with a microfluidic channel spanning multiple pressure nodes, which is advantageous over separation in a single pressure node in terms of throughput.
Yong, Peng; Huang, Jianping; Li, Zhenchun; Liao, Wenyuan; Qu, Luping; Li, Qingyang; Liu, Peijun
2017-02-01
In finite-difference (FD) method, numerical dispersion is the dominant factor influencing the accuracy of seismic modelling. Various optimized FD schemes for scalar wave modelling have been proposed to reduce grid dispersion, while the optimized time-space domain FD schemes for elastic wave modelling have not been fully investigated yet. In this paper, an optimized FD scheme with Equivalent Staggered Grid (ESG) for elastic modelling has been developed. We start from the constant P- and S-wave speed elastic wave equations and then deduce analytical plane wave solutions in the wavenumber domain with eigenvalue decomposition method. Based on the elastic plane wave solutions, three new time-space domain dispersion relations of ESG elastic modelling are obtained, which are represented by three equations corresponding to P-, S- and converted-wave terms in the elastic equations, respectively. By using these new relations, we can study the dispersion errors of different spatial FD terms independently. The dispersion analysis showed that different spatial FD terms have different errors. It is therefore suggested that different FD coefficients to be used to approximate the three spatial derivative terms. In addition, the relative dispersion error in L2-norm is minimized through optimizing FD coefficients using Newton's method. Synthetic examples have demonstrated that this new optimal FD schemes have superior accuracy for elastic wave modelling compared to Taylor-series expansion and optimized space domain FD schemes.
Ollett, E.; Clark, A.
2017-05-01
The Home Office Centre for Applied Science and Technology (CAST) has a longstanding history in the evaluation of passive and active millimetre wave (mmW) systems for stand-off detection. The requirements for stand-off detection have evolved greatly over the last decade due to changes in threat, as has the capability of technologies. CAST has worked with these changes to evaluate systems alongside other government departments, developing expertise in the standard of technology from low to high technology readiness level (TRL) as well as understanding the limitations in detection. In this paper I discuss the work that has been undertaken by CAST since 2007, exploring the developments in methodology that have become necessary for trials to capture the requirements successfully. This involves utilising aspects of test protocols to ensure consistency across testing between CAST and other organisations, allowing for a fair comparison of data. The trials undertaken vary from evaluating the system capability in a static setting to the capability in a crowded environment such as a shopping centre. Understanding the performance capability of passive and active (mmW) systems in crowded places is particularly important given the current threat status of the UK.
Wave climatology of Lake Erie based on an unstructured-grid wave model
Niu, Qianru; Xia, Meng
2016-10-01
Hindcast of wave dynamics in Lake Erie during 2002 to 2012 was conducted using a state-of-art finite-volume coastal ocean surface wave model (FVCOM-SWAVE). After model calibration, the surface gravity wave dynamics were examined from the aspects of wave climate and seasonality, inter-basin wave interactions, as well as its potential susceptibility to regional climate change. Compared to the Central and Eastern Basins, the Western Basin has relatively gentle wave climate. The Western Basin and the nearshore areas are most susceptible to the wave-induced bottom orbital oscillations on the seasonal mean scale, and the offshore Central Basin is sensitive to them as well during episodic events. Profound seasonality was found in both mean and extreme wave dynamics during ice-free cycles. Mean significant wave height (SWH) is highest during fall with more occurrences of extreme events (SWH > 3.1 m) and is lowest during summer, which is controlled by wind speed and direction collectively. Besides, swells generated in the Central and Eastern Basins could interact with each other under various wind directions, whereas wave generated in the Central Basin could hardly propagate into the Western Basin. In addition, the regression analysis of surrounding meteorological stations indicates increasing SWH in the Western Basin and decreasing SWH in the Eastern Basin.
Wave Climate and Wave Mixing in the Marginal Ice Zones of Arctic Seas, Observations and Modelling
2015-09-30
PROJECTS Section). With the group of Rogers, observation/modeling study of an energetic wave event in the Arctic marginal zone was conducted ...floe. (right) Surface elevation in the lee of a 5 mm thick polypropylene floe (thick black curves) and incident wave (grey), normalised with respect...Toffoli, A., Marusic, I., Klewicki, J., Hutchins, N., Suslov, S., Walker, D., Chung, D., “A Thermally Stratified Sea-Ice-Wave Interaction Facility”, ARC
An Efficient Hydrodynamic Model for Surface Waves
Institute of Scientific and Technical Information of China (English)
WANG Kun; JIN Sheng; LU Gang
2009-01-01
In the present study,a semi-implicit finite difference model for non-bydrostatic,free-surface flows is analyzed and discussed.The governing equations are the three-dimensional free-surface Reynolds-averaged Navier-Stokes equations defined on a general,irregular domain of arbitrary scale.At outflow,a combination of a sponge layer technique and a radiation boundary condition is applied to minimize wave reflection.The equations are solved with the fractional step method where the hydrostatic pressure component is determined first,while the non-hydrostatic component of the pressure is computed from the pressure Poisson equation in which the coefficient matrix is positive definite and symmetric.The advectiou and horizontal viscosity terms are discretized by use of a semi-Lagrangian approach.The resulting model is computationally efficient and unrestricted to the CFL condition.The developed model is verified against analytical solutions and experimental data,with excellent agreement.
KINEMATIC WAVE PROPERTIES OF ANISOTROPIC DYNAMICS MODEL FOR TRAFFIC FLOW
Institute of Scientific and Technical Information of China (English)
姜锐; 吴清松; 朱祚金
2002-01-01
The analyses of kinematic wave properties of a new dynamics model for traffic flow are carried out. The model does not exhibit the problem that one characteristic speed is always greater than macroscopic traffic speed, and therefore satisfies the requirement that traffic flow is anisotropic. Linear stability analysis shows that the model is stable under certain condition and the condition is obtained. The analyses also indicate that the model has a hierarchy of first-and second-order waves, and allows the existence of both smooth traveling wave and shock wave. However, the model has a distinctive criterion of shock wave compared with other dynamics models, and the distinction makes the model more realistic in dealing with some traffic problems such as wrong-way travel analysis.
A hydrodynamic model of nearshore waves and wave-induced currents
Directory of Open Access Journals (Sweden)
Ahmed Khaled Seif
2011-09-01
Full Text Available In This study develops a quasi-three dimensional numerical model of wave driven coastal currents with accounting the effects of the wave-current interaction and the surface rollers. In the wave model, the current effects on wave breaking and energy dissipation are taken into account as well as the wave diffraction effect. The surface roller associated with wave breaking was modeled based on a modification of the equations by Dally and Brown (1995 and Larson and Kraus (2002. Furthermore, the quasi-three dimensional model, which based on Navier-Stokes equations, was modified in association with the surface roller effect, and solved using frictional step method. The model was validated by data sets obtained during experiments on the Large Scale Sediment Transport Facility (LSTF basin and the Hazaki Oceanographical Research Station (HORS. Then, a model test against detached breakwater was carried out to investigate the performance of the model around coastal structures. Finally, the model was applied to Akasaki port to verify the hydrodynamics around coastal structures. Good agreements between computations and measurements were obtained with regard to the cross-shore variation in waves and currents in nearshore and surf zone.
Federal Laboratory Consortium — The Electrical Systems Laboratory (ESL)houses numerous electrically driven drive stands. A drive stand consists of an electric motor driving a gearbox and a mounting...
Pulsar average wave forms and hollow-cone beam models
Backer, D. C.
1976-01-01
Pulsar wave forms have been analyzed from observations conducted over a wide radio-frequency range to assess the wave-form morphologies and to measure wave-form widths. The results of the analysis compare favorably with the predictions of a model with a hollow-cone beam of fixed dimensions and with random orientation of both the observer and the cone axis with respect to the pulsar spin axis. A class of three-component wave forms is included in the model by adding a central pencil beam to the hollow-cone hypothesis. The consequences of a number of discrepancies between observations and quantitative predictions of the model are discussed.
Modeling deflagration waves out of hot spots
Partom, Yehuda
2017-01-01
It is widely accepted that shock initiation and detonation of heterogeneous explosives comes about by a two-step process known as ignition and growth. In the first step a shock sweeping through an explosive cell (control volume) creates hot spots that become ignition sites. In the second step, deflagration waves (or burn waves) propagate out of those hot spots and transform the reactant in the cell into reaction products. The macroscopic (or average) reaction rate of the reactant in the cell depends on the speed of those deflagration waves and on the average distance between neighboring hot spots. Here we simulate the propagation of deflagration waves out of hot spots on the mesoscale in axial symmetry using a 2D hydrocode, to which we add heat conduction and bulk reaction. The propagation speed of the deflagration waves may depend on both pressure and temperature. It depends on pressure for quasistatic loading near ambient temperature, and on temperature at high temperatures resulting from shock loading. From the simulation we obtain deflagration fronts emanating out of the hot spots. For 8 to 13 GPa shocks, the emanating fronts propagate as deflagration waves to consume the explosive between hot spots. For higher shock levels deflagration waves may interact with the sweeping shock to become detonation waves on the mesoscale. From the simulation results we extract average deflagration wave speeds.
Fraser, R.; Coulaud, M.; Aeschlimann, V.; Lemay, J.; Deschenes, C.
2016-11-01
With the growing proportion of inconstant energy source as wind and solar, hydroelectricity becomes a first class source of peak energy in order to regularize the grid. The important increase of start - stop cycles may then cause a premature ageing of runners by both a higher number of cycles in stress fluctuations and by reaching a higher stress level in absolute. Aiming to sustain good quality development on fully homologous scale model turbines, the Hydraulic Machines Laboratory (LAMH) of Laval University has developed a methodology to operate model size turbines on transient regimes such as start-up, stop or load rejection on its test stand. This methodology allows maintaining a constant head while the wicket gates are opening or closing in a representative speed on the model scale of what is made on the prototype. This paper first presents the opening speed on model based on dimensionless numbers, the methodology itself and its application. Then both its limitation and the first results using a bulb turbine are detailed.
Experimental Update of the Overtopping Model Used for the Wave Dragon Wave Energy Converter
DEFF Research Database (Denmark)
Parmeggiani, Stefano; Kofoed, Jens Peter; Friis-Madsen, Erik
2013-01-01
An overtopping model specifically suited for Wave Dragon is needed in order to improve the reliability of its performance estimates. The model shall be comprehensive of all relevant physical processes that affect overtopping and flexible to adapt to any local conditions and device configuration....... An experimental investigation is carried out to update an existing formulation suited for 2D draft-limited, low-crested structures, in order to include the effects on the overtopping flow of the wave steepness, the 3D geometry of Wave Dragon, the wing reflectors, the device motions and the non-rigid connection...... of which can be measured in real-time. Instead of using new fitting coefficients, this approach allows a broader applicability of the model beyond the Wave Dragon case, to any overtopping WEC or structure within the range of tested conditions. Predictions reliability of overtopping over Wave Dragon...
Directory of Open Access Journals (Sweden)
Cristina Alegria
2011-11-01
Full Text Available Uneven aged maritime pine stands established by natural regeneration have a great expression in Portugal. These stands being overstocked, as opposed to those established from plantations, provide straight and cylindrical tree boles and logs with less knots that makes them very suitable for certain industrial purposes. Therefore, the aim of this study was to fit a set of equations to predict total volume and merchantable volumes to any merchantable limit for uneven aged maritime pine stands established by natural regeneration in the central inland region of Portugal. Data were collected in 30 circular sampling plots of 500 m2 of area, on 1426 trees and 314 sample trees for volume assessment, corresponding to 2353 diameter/height mea-surements. A total height equation, a total volume equation, a volume ratio equation to any top height limit and a taper equation, over bark, were fitted. To select among the best models, several statistics were computed during model fitting and the independent validation procedure to evaluate model fitting, collinearity and prediction performances. A ranking index was used to support the final decision. The models selected were then fitted again using robust regression and weighted regression techniques, because studentized residuals distribution normality and homogeneity assumptions were not observed. This research showed that the models selected for these stands were not the same as those selected in previous studies for the species in this region, suggesting that these results may be due to the influence of stand density conditions on diameter and total height growth, and consequently, on stem form and volume. This set of equations will also be included as components in a single tree growth and yield model developed for these stands.
A Holographic P-wave Superconductor Model
Cai, Rong-Gen; Li, Li-Fang
2014-01-01
We study a holographic p-wave superconductor model in a four dimensional Einstein-Maxwell-complex vector field theory with a negative cosmological constant. The complex vector field is charged under the Maxwell field. We solve the full coupled equations of motion of the system and find black hole solutions with the vector hair. The vector hairy black hole solutions are dual to a thermal state with the U(1) symmetry as well as the spatial rotational symmetry breaking spontaneously. Depending on two parameters, the mass and charge of the vector field, we find a rich phase structure: zeroth order, first order and second order phase transitions can happen in this model. We also find "retrograde condensation" in which the hairy black hole solution exists only for the temperatures above a critical value with the free energy much larger than the black hole without hair. We construct the phase diagram for this system in terms of the temperature and charge of the vector field.
High order Hamiltonian water wave models with wave-breaking mechanism
Kurnia, R.; Groesen, van E.
2014-01-01
Based on the Hamiltonian formulation of water waves, using Hamiltonian consistent modelling methods, we derive higher order Hamiltonian equations by Taylor expansions of the potential and the vertical velocity around the still water level. The polynomial expansion in wave height is mixed with pseudo
Experimental Modelling of the Overtopping Flow on the Wave Dragon Wave Energy Converter
DEFF Research Database (Denmark)
Parmeggiani, Stefano; Kofoed, Jens Peter
The Wave Dragon is a floating slack-moored Wave Energy Converter (WEC) of the overtopping type. Oncoming waves are focused by two wing reflectors towards the ramp of the device, surge-up and overtop into a reservoir placed at a higher level than the surface of the sea. The energy production takes...... place as the water is led back to the sea through a set of low-head hydro-turbines. After many years of development, Wave Dragon (WD) is now facing the phase of pre-commercial demonstration. In this phase it is very important to be able to use the available data to predict the performances of the device...... at different scales and locations. A flexible and comprehensive modelling tool is therefore highly required. Wave Dragon produces power through different steps of energy conversion: 1. Primary energy conversion: overtopping – The energy content of the wave (partly in the kinetic and partly in the potential...
The use of a wave boundary layer model in SWAN
DEFF Research Database (Denmark)
Du, Jianting; Bolaños, Rodolfo; Larsén, Xiaoli Guo
2017-01-01
A Wave Boundary Layer Model (WBLM) is implemented in the third-generation ocean wave model SWAN to improve the wind-input source function under idealized, fetch-limited condition. Accordingly, the white capping dissipation parameters are re-calibrated to fit the new wind-input source function...
Development of a coupled wave-flow-vegetation interaction model
Beudin, Alexis; Kalra, Tarandeep; Ganju, Neil Kamal; Warner, John C.
2017-01-01
Emergent and submerged vegetation can significantly affect coastal hydrodynamics. However, most deterministic numerical models do not take into account their influence on currents, waves, and turbulence. In this paper, we describe the implementation of a wave-flow-vegetation module into a Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system that includes a flow model (ROMS) and a wave model (SWAN), and illustrate various interacting processes using an idealized shallow basin application. The flow model has been modified to include plant posture-dependent three-dimensional drag, in-canopy wave-induced streaming, and production of turbulent kinetic energy and enstrophy to parameterize vertical mixing. The coupling framework has been updated to exchange vegetation-related variables between the flow model and the wave model to account for wave energy dissipation due to vegetation. This study i) demonstrates the validity of the plant posture-dependent drag parameterization against field measurements, ii) shows that the model is capable of reproducing the mean and turbulent flow field in the presence of vegetation as compared to various laboratory experiments, iii) provides insight into the flow-vegetation interaction through an analysis of the terms in the momentum balance, iv) describes the influence of a submerged vegetation patch on tidal currents and waves separately and combined, and v) proposes future directions for research and development.
Development of a coupled wave-flow-vegetation interaction model
Beudin, Alexis; Kalra, Tarandeep S.; Ganju, Neil K.; Warner, John C.
2017-03-01
Emergent and submerged vegetation can significantly affect coastal hydrodynamics. However, most deterministic numerical models do not take into account their influence on currents, waves, and turbulence. In this paper, we describe the implementation of a wave-flow-vegetation module into a Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system that includes a flow model (ROMS) and a wave model (SWAN), and illustrate various interacting processes using an idealized shallow basin application. The flow model has been modified to include plant posture-dependent three-dimensional drag, in-canopy wave-induced streaming, and production of turbulent kinetic energy and enstrophy to parameterize vertical mixing. The coupling framework has been updated to exchange vegetation-related variables between the flow model and the wave model to account for wave energy dissipation due to vegetation. This study i) demonstrates the validity of the plant posture-dependent drag parameterization against field measurements, ii) shows that the model is capable of reproducing the mean and turbulent flow field in the presence of vegetation as compared to various laboratory experiments, iii) provides insight into the flow-vegetation interaction through an analysis of the terms in the momentum balance, iv) describes the influence of a submerged vegetation patch on tidal currents and waves separately and combined, and v) proposes future directions for research and development.
Modeling and Control Of Surface Acoustic Wave Motors
Feenstra, P.J.
2005-01-01
This thesis introduces Rayleigh waves and describes the generation of Rayleigh waves. Furthermore, the principle of operation of a SAW motor is analyzed. The analysis is based on a contact model, which describes the behavior between slider and stator. Due to the contact model, the microscopic and
A consistent collinear triad approximation for operational wave models
Salmon, J. E.; Smit, P. B.; Janssen, T. T.; Holthuijsen, L. H.
2016-08-01
In shallow water, the spectral evolution associated with energy transfers due to three-wave (or triad) interactions is important for the prediction of nearshore wave propagation and wave-driven dynamics. The numerical evaluation of these nonlinear interactions involves the evaluation of a weighted convolution integral in both frequency and directional space for each frequency-direction component in the wave field. For reasons of efficiency, operational wave models often rely on a so-called collinear approximation that assumes that energy is only exchanged between wave components travelling in the same direction (collinear propagation) to eliminate the directional convolution. In this work, we show that the collinear approximation as presently implemented in operational models is inconsistent. This causes energy transfers to become unbounded in the limit of unidirectional waves (narrow aperture), and results in the underestimation of energy transfers in short-crested wave conditions. We propose a modification to the collinear approximation to remove this inconsistency and to make it physically more realistic. Through comparison with laboratory observations and results from Monte Carlo simulations, we demonstrate that the proposed modified collinear model is consistent, remains bounded, smoothly converges to the unidirectional limit, and is numerically more robust. Our results show that the modifications proposed here result in a consistent collinear approximation, which remains bounded and can provide an efficient approximation to model nonlinear triad effects in operational wave models.
Modelling of Performance of Caisson Type Breakwaters under Extreme Waves
Güney Doǧan, Gözde; Özyurt Tarakcıoǧlu, Gülizar; Baykal, Cüneyt
2016-04-01
Many coastal structures are designed without considering loads of tsunami-like waves or long waves although they are constructed in areas prone to encounter these waves. Performance of caisson type breakwaters under extreme swells is tested in Middle East Technical University (METU) Coastal and Ocean Engineering Laboratory. This paper presents the comparison of pressure measurements taken along the surface of caisson type breakwaters and obtained from numerical modelling of them using IH2VOF as well as damage behavior of the breakwater under the same extreme swells tested in a wave flume at METU. Experiments are conducted in the 1.5 m wide wave flume, which is divided into two parallel sections (0.74 m wide each). A piston type of wave maker is used to generate the long wave conditions located at one end of the wave basin. Water depth is determined as 0.4m and kept constant during the experiments. A caisson type breakwater is constructed to one side of the divided flume. The model scale, based on the Froude similitude law, is chosen as 1:50. 7 different wave conditions are applied in the tests as the wave period ranging from 14.6 s to 34.7 s, wave heights from 3.5 m to 7.5 m and steepness from 0.002 to 0.015 in prototype scale. The design wave parameters for the breakwater were 5m wave height and 9.5s wave period in prototype. To determine the damage of the breakwater which were designed according to this wave but tested under swell waves, video and photo analysis as well as breakwater profile measurements before and after each test are performed. Further investigations are carried out about the acting wave forces on the concrete blocks of the caisson structures via pressure measurements on the surfaces of these structures where the structures are fixed to the channel bottom minimizing. Finally, these pressure measurements will be compared with the results obtained from the numerical study using IH2VOF which is one of the RANS models that can be applied to simulate
Modeling of Two Different Water Uptake Approaches for Mono- and Mixed-Species Forest Stands
Directory of Open Access Journals (Sweden)
Martin Gutsch
2015-06-01
Full Text Available To assess how the effects of drought could be better captured in process-based models, this study simulated and contrasted two water uptake approaches in Scots pine and Scots pine-Sessile oak stands. The first approach consisted of an empirical function for root water uptake (WU1. The second approach was based on differences of soil water potential along a soil-plant-atmosphere continuum (WU2 with total root resistance varying at low, medium and high total root resistance levels. Three data sets on different time scales relevant for tree growth were used for model evaluation: Two short-term datasets on daily transpiration and soil water content as well as a long-term dataset on annual tree ring increments. Except WU2 with high total root resistance, all transpiration outputs exceeded observed values. The strongest correlation between simulated and observed annual tree ring width occurred with WU2 and high total root resistance. The findings highlighted the importance of severe drought as a main reason for small diameter increment. However, if all three data sets were taken into account, no approach was superior to the other. We conclude that accurate projections of future forest productivity depend largely on the realistic representation of root water uptake in forest model simulations.
Species composition and model of the riparian stand structure in the Nature Reserve “Krajkowo”
Directory of Open Access Journals (Sweden)
Marek Szczerba
2013-09-01
Full Text Available The aim of this study is to describe the riparian stand composition and to compare its diameter at breast height (d.b.h. structure with the theoretical d.b.h. structure of selection stand. The riparian stand of the Nature Reserve “Krajkowo” has the traits of an uneven-aged, multi-layer, mixed forest with many dead or dying old trees. There were 14 tree species in the experimental plots. Quercus robur and Ulmus laevis dominated in the stands. The trees’ distribution in d.b.h. classes was similar to the theoretical d.b.h. structure of selection stand. The differences between the actual and theoretical number of trees in d.b.h. classes were caused by natural effects of site and biotic factors on the composition and structure of the riparian forest.
Improving Short Wave Breaking Behavior In Surfbeat Models
Roelvink, J.; Daly, C.; Vandongeren, A. R.; van Thiel de Vries, J.; McCall, R.
2009-12-01
In present surfzone modeling three approaches are widely applied: short-wave resolving models, ‘surfbeat’ models, which resolve wave energy modulations on the time-scale of wave groups and their associated infragravity waves, and wave averaged models. In all three approaches, wave breaking is a process that is highly schematized and governed by several empirical coefficients. In this presentation we will focus on the breaking process in ‘surfbeat’ models, such as XBeach (Roelvink et al, 2009). These models need to describe the short wave dissipation by breaking as a function of the slowly-varying short wave energy or wave height. The model usually applied is that by Roelvink (1993), which combines a probability that waves are breaking as function of wave heigth over water depth ratio H/h with a bore-type dissipation formulation similar to that by Battjes and Janssen (1978). A drawback of such a formulation is that there is no ‘memory’ in the breaking process, and the amount of breaking instantly varies with the water depth (though the wave height itself does have a memory). For cases with bichromatic waves, or for long-period swell, this does not reflect reality enough: waves that start breaking do not instantly stop breaking once the water depth increases, but continue until some lower threshold is reached. This concept was captured in Dally’s (1992) wave-by-wave approach, where individual waves are tracked in a probabilistic setting. We have now implemented a similar formulation in XBeach, where the property that waves are breaking is tracked; it is switched on when H/h exceeds a first criterion; this property is propagated using an advection equation and when H/h gets below a second criterion breaking is switched off. This formulation can do two things the previous one can’t: maintain groupiness inside the surf zone and have a maximum of wave breaking in the trough after a steep bar, as was observed for instance in Arcilla et al’s (1994) test 1
Rogue wave variational modelling through the interaction of two solitary waves
Gidel, Floriane; Bokhove, Onno
2016-04-01
The extreme and unexpected characteristics of Rogue waves have made them legendary for centuries. It is only on the 1st of January 1995 that these mariners' tales started to raise scientist's curiosity, when such a wave was recorded in the North Sea; a sudden wall of water hit the Draupner offshore platform, more than twice higher than the other waves, providing evidence of the existence of rogue or freak waves. Since then, studies have shown that these surface gravity waves of high amplitude (at least twice the height of the other sea waves [Dyste et al., 2008]) appear in non-linear dispersive water motion [Drazin and Johnson, 1989], at any depth, and have caused a lot of damage in recent years [Nikolkina and Didenkulova, 2011 ]. So far, most of the studies have tried to determine their probability of occurrence, but no conclusion has been achieved yet, which means that we are currently unenable to predict or avoid these monster waves. An accurate mathematical and numerical water-wave model would enable simulation and observation of this external forcing on boats and offshore structures and hence reduce their threat. In this work, we aim to model rogue waves through a soliton splash generated by the interaction of two solitons coming from different channels at a specific angle. Kodama indeed showed that one way to produce extreme waves is through the intersection of two solitary waves, or one solitary wave and its oblique reflection on a vertical wall [Yeh, Li and Kodama, 2010 ]. While he modelled Mach reflection from Kadomtsev-Petviashvili (KP) theory, we aim to model rogue waves from the three-dimensional potential flow equations and/or their asymptotic equivalent described by Benney and Luke [Benney and Luke, 1964]. These theories have the advantage to allow wave propagation in several directions, which is not the case with KP equations. The initial solitary waves are generated by removing a sluice gate in each channel. The equations are derived through a
Modelling leaf, plant and stand flammability for ecological and operational decision making
Zylstra, Philip
2014-05-01
Numerous factors have been found to affect the flammability of individual leaves and plant parts; however the way in which these factors relate to whole plant flammability, fire behaviour and the overall risk imposed by fire is not straightforward. Similarly, although the structure of plant communities is known to affect the flammability of the stand, a quantified, broadly applicable link has proven difficult to establish and validate. These knowledge gaps have presented major obstacles to the integration into fire behaviour science of research into factors affecting plant flammability, physiology, species succession and structural change, so that the management of ecosystems for fire risk is largely uninformed by these fields. The Forest Flammability Model (Zylstra, 2011) is a process-driven, complex systems model developed specifically to address this disconnect. Flame dimensions and position are calculated as properties emerging from the capacity for convective heat to propagate flame between horizontally and vertically separated leaves, branches, plants and plant strata, and this capacity is determined dynamically from the ignitability, combustibility and sustainability of those objects, their spatial arrangement and a vector-based model of the plume temperature from each burning fuel. All flammability properties as well as the physics of flame dimensions, angle and temperature distributions and the vertical structure of wind within the plant array use published sub-models which can be replaced as further work is developed. This modular structure provides a platform for the immediate application of new work on any aspect of leaf flammability or fire physics. Initial validation of the model examined its qualitative predictions for trends in forest flammability as a function of time since fire. The positive feedback predicted for the subalpine forest examined constituted a 'risky prediction' by running counter to the expectations of the existing approach, however
Travelling wave analysis of a mathematical model of glioblastoma growth.
Gerlee, Philip; Nelander, Sven
2016-06-01
In this paper we analyse a previously proposed cell-based model of glioblastoma (brain tumour) growth, which is based on the assumption that the cancer cells switch phenotypes between a proliferative and motile state (Gerlee and Nelander, 2012). The dynamics of this model can be described by a system of partial differential equations, which exhibits travelling wave solutions whose wave speed depends crucially on the rates of phenotypic switching. We show that under certain conditions on the model parameters, a closed form expression of the wave speed can be obtained, and using singular perturbation methods we also derive an approximate expression of the wave front shape. These new analytical results agree with simulations of the cell-based model, and importantly show that the inverse relationship between wave front steepness and speed observed for the Fisher equation no longer holds when phenotypic switching is considered.
Latitudinal effect on the growth dynamics of harvested stands of Typha: A modeling approach
Hai, Dinh Ngoc; Asaeda, Takashi; Manatunge, Jagath
2006-12-01
A model was developed for Typha, to examine the effects of latitudinal changes in temperature and radiation on the partitioning of total biomass during the growing season into rhizomes, roots, flowering and vegetative shoots, and inflorescences. Regardless of initial rhizome biomass, both above and belowground biomasses converge on a equilibrium value, with the balance between total production and metabolic loss being latitude-specific. If aboveground biomass is harvested just once, then both above and belowground biomasses return to equilibrium values after several years. If the aboveground biomass is harvested annually, then both above and belowground biomasses converge on smaller equilibrium values, which are determined by the balance between the sum of production prior to harvesting and after harvesting, and the sum of annual metabolic losses and a loss due to harvesting. The model could be used in wetland management activities to predict the potential growth of Typha in given conditions as well as the responses of Typha stands to harvesting over a wide range of latitudes for times ranging from a season to several years.
Ground Signatures of EMIC Waves obtained From a 3D Global Wave Model
Rankin, R.; Sydorenko, D.; Zong, Q.; Zhang, L.
2016-12-01
EMIC waves generated in the inner magnetosphere are important drivers of radiation belt particle loss. Van Allen Probes and ground observations of EMIC waves suggest that localized magnetospheric sources inject waves that are guided along geomagnetic field lines and then reflected and refracted in the low altitude magnetosphere [Kim, E.-H., and J. R. Johnson (2016), Geophys. Res. Lett., 43, 13-21, doi:10.1002/2015GL066978] before entering the ionosphere. The waves then spread horizontally within the F-region waveguide and propagate to the ground. To understand the observed properties of EMIC waves, a global 3D model of ULF waves in Earth's magnetosphere, ionosphere, and neutral atmosphere has been developed. The simulation domain extends from Earth's surface to a spherical boundary a few tens of thousands of km in radius. The model uses spherical coordinates and incorporates an overset Yin-Yang grid that eliminates the singularity at the polar axis and improves uniformity of the grid in the polar areas [Kageyama, A., and T. Sato (2004), Geochem. Geophys. Geosyst., 5, Q09005, doi:10.1029/2004GC000734]. The geomagnetic field in the model is general, but is dipole in this study. The plasma is described as a set of electron and multiple species ion conducting fluids. Realistic 3D density profiles of various ion species as well as thermospheric parameters are provided by the Canadian Ionosphere Atmosphere Model (C-IAM) [Martynenko O.V. et al. (2014), J. Atmos. Solar-Terr. Phys., 120, 51-61, doi:10.1016/j.jastp.2014.08.014]. The global ULF wave model is applied to study propagation of EMIC waves excited in the equatorial plane near L=7. Wave propagation along field lines, reflection and refraction in the zone of critical frequencies, and further propagation through the ionosphere to the ground are discussed.
Institute of Scientific and Technical Information of China (English)
王倩楠; 晁栋梁; 周万海; 陈云贵; 吴朝玲
2013-01-01
Considerable irreversible capacity loss was observed after the electrode standing at small state-of-charge (SOC) for only a short term. Influence of SOC, standing time and the replacement elements of LaNi5-type hydrogen storage alloys to standing was discussed. Charge-transfer resistance, exchange current density (I0), and hydrogen diffusion coefficient were determined based on the study of electrochemical impedance spectrum (EIS), linear polarization (LP) and constant potential step (CPS), respectively. The oxi-dation of metal Ni on the alloy surface after standing was responsible for the rapid deterioration of capacity, charge-transfer resistance and I0. Galvanostatic, LP, EIS and CPS measurements suggested the presence of an oxide and/or corrosion layer on the alloy surface of raw material and electrode after standing at 0%SOC for 2 d. It was proved that the first small semicircle in high-frequency region of EIS was related to this layer. Novel EIS model in metal hydride electrode was proposed accordingly.
Breidenbach, Johannes; McRoberts, Ronald E; Astrup, Rasmus
2016-02-01
Due to the availability of good and reasonably priced auxiliary data, the use of model-based regression-synthetic estimators for small area estimation is popular in operational settings. Examples are forest management inventories, where a linking model is used in combination with airborne laser scanning data to estimate stand-level forest parameters where no or too few observations are collected within the stand. This paper focuses on different approaches to estimating the variances of those estimates. We compared a variance estimator which is based on the estimation of superpopulation parameters with variance estimators which are based on predictions of finite population values. One of the latter variance estimators considered the spatial autocorrelation of the residuals whereas the other one did not. The estimators were applied using timber volume on stand level as the variable of interest and photogrammetric image matching data as auxiliary information. Norwegian National Forest Inventory (NFI) data were used for model calibration and independent data clustered within stands were used for validation. The empirical coverage proportion (ECP) of confidence intervals (CIs) of the variance estimators which are based on predictions of finite population values was considerably higher than the ECP of the CI of the variance estimator which is based on the estimation of superpopulation parameters. The ECP further increased when considering the spatial autocorrelation of the residuals. The study also explores the link between confidence intervals that are based on variance estimates as well as the well-known confidence and prediction intervals of regression models.
Directory of Open Access Journals (Sweden)
Sghaier T
2016-02-01
Full Text Available Thuya (Tetraclinis articulata (Vahl Mast is a Mediterranean forest species mainly occupying semiarid environments in North African countries, where it provides important ecological and economical services, such as biodiversity conservation, soil protection against erosion, fuelwood, timber for fencing, construction and handicraft, resins, etc. Despite the importance of the species, there is a severe lack of scientific knowledge as regards the management of these forests or modeling tools to support multifunctional forest management decision making. In the present work, we developed a stand-level integrated model for the management of Thuya forests in Tunisia. The model comprises a family of site index curves, built using the Generalized Algebraic Difference Approach (GADA method, which provides predictions for stand growth, aboveground biomass, total and merchantable volumes, along with a non-linear system of stand level equations presented as stand density management diagrams (SDMD. The developed model has been used to define, characterize and compare four different management specific schedules for different site qualities and multifunctional objectives.
Sediment mathematical model for sand ridges and sand waves
Institute of Scientific and Technical Information of China (English)
LI Daming; WANG Xiao; WANG Xin; LI Yangyang
2016-01-01
A new theoretical model is formulated to describe internal movement mechanisms of the sand ridges and sand waves based on the momentum equation of a solid-liquid two-phase flow under a shear flow. Coupling this equation with two-dimensional shallow water equations and wave reflection-diffraction equation of mild slope, a two-dimensional coupling model is established and a validation is carried out by observed hydrogeology, tides, waves and sediment. The numerical results are compared with available observations. Satisfactory agreements are achieved. This coupling model is then applied to the Dongfang 1-1 Gas Field area to quantitatively predict the movement and evolution of submarine sand ridges and sand waves. As a result, it is found that the sand ridges and sand waves movement distance increases year by year, but the development trend is stable.
Directory of Open Access Journals (Sweden)
Gao Hongtao
2015-09-01
Full Text Available Floating-type wave energy converter has the advantages of high wave energy conversion efficiency, strong shock resistance ability in rough sea and stable output power. So it is regarded as a promising energy utilization facility. The research on hydrodynamic performance of wave capture buoys is the precondition and key to the wave energy device design and optimization. A simplified motion model of the buoys in the waves is established. Based on linear wave theory, the equations of motion of buoys are derived according to Newton’s second law. The factors of wave and buoys structural parameters on wave energy absorption efficiency are discussed in the China’s Bohai Sea with short wave period and small wave height. The results show that the main factor which affects the dynamic responses of wave capture buoys is the proximity of the natural frequency of buoys to the wave period. And the incoming wave power takes a backseat role to it at constant wave height. The buoys structural parameters such as length, radius and immersed depth, influence the wave energy absorption efficiency, which play significant factors in device design. The effectiveness of this model is validated by the sea tests with small-sized wave energy devices. The establishment methods of motion model and analysis results are expected to be helpful for designing and manufacturing of floating-type wave energy converter.
Experimental Update of the Overtopping Model Used for the Wave Dragon Wave Energy Converter
Energy Technology Data Exchange (ETDEWEB)
Parmeggiani, Stefano [Wave Dragon Ltd., London (United Kingdom); Kofoed, Jens Peter [Aalborg Univ. (Denmark). Department of Civil Engineering; Friis-Madsen, Erik [Wave Dragon Ltd., London (United Kingdom)
2013-04-15
An overtopping model specifically suited for Wave Dragon is needed in order to improve the reliability of its performance estimates. The model shall be comprehensive of all relevant physical processes that affect overtopping and flexible to adapt to any local conditions and device configuration. An experimental investigation is carried out to update an existing formulation suited for 2D draft-limited, low-crested structures, in order to include the effects on the overtopping flow of the wave steepness, the 3D geometry of Wave Dragon, the wing reflectors, the device motions and the non-rigid connection between platform and reflectors. The study is carried out in four phases, each of them specifically targeted at quantifying one of these effects through a sensitivity analysis and at modeling it through custom-made parameters. These are depending on features of the wave or the device configuration, all of which can be measured in real-time. Instead of using new fitting coefficients, this approach allows a broader applicability of the model beyond the Wave Dragon case, to any overtopping WEC or structure within the range of tested conditions. Predictions reliability of overtopping over Wave Dragon increased, as the updated model allows improved accuracy and precision respect to the former version.
Experimental Update of the Overtopping Model Used for the Wave Dragon Wave Energy Converter
Directory of Open Access Journals (Sweden)
Erik Friis-Madsen
2013-04-01
Full Text Available An overtopping model specifically suited for Wave Dragon is needed in order to improve the reliability of its performance estimates. The model shall be comprehensive of all relevant physical processes that affect overtopping and flexible to adapt to any local conditions and device configuration. An experimental investigation is carried out to update an existing formulation suited for 2D draft-limited, low-crested structures, in order to include the effects on the overtopping flow of the wave steepness, the 3D geometry of Wave Dragon, the wing reflectors, the device motions and the non-rigid connection between platform and reflectors. The study is carried out in four phases, each of them specifically targeted at quantifying one of these effects through a sensitivity analysis and at modeling it through custom-made parameters. These are depending on features of the wave or the device configuration, all of which can be measured in real-time. Instead of using new fitting coefficients, this approach allows a broader applicability of the model beyond the Wave Dragon case, to any overtopping WEC or structure within the range of tested conditions. Predictions reliability of overtopping over Wave Dragon increased, as the updated model allows improved accuracy and precision respect to the former version.
Modeling sheet-flow sand transport under progressive surface waves
Kranenburg, W.M.
2013-01-01
In the near-shore zone, energetic sea waves generate sheet-flow sand transport. In present day coastal models, wave-induced sheet-flow sand transport rates are usually predicted with semi-empirical transport formulas, based on extensive research on this phenomenon in oscillatory flow tunnels. Howeve
Modeling radar backscatter from breaking waves on the surface
Melief, H.W.; Greidanus, H.S.F.; Hoogeboom, P.; Genderen, P. van
2003-01-01
A model for describing radar sea clutter is proposed. It consists of two parts, an oceanographic and an electromagnetic one. The former contains swell, small capillary and gravity waves as well as breaking wave events. The latter combines ray tracing, Bragg scattering and the Method of Moments. It i
Numerical Modelling of Wind Waves. Problems, Solutions, Verifications, and Applications
Polnikov, Vladislav
2011-01-01
The time-space evolution of the field is described by the transport equation for the 2-dimensional wave energy spectrum density, S(x,t), spread in the space, x, and time, t. This equation has the forcing named the source function, F, depending on both the wave spectrum, S, and the external wave-making factors: local wind, W(x, t), and local current, U(x, t). The source function contains certain physical mechanisms responsible for a wave spectrum evolution. It is used to distinguish three terms in function F: the wind-wave energy exchange mechanism, In; the energy conservative mechanism of nonlinear wave-wave interactions, Nl; and the wave energy loss mechanism, Dis. Differences in mathematical representation of the source function terms determine general differences between wave models. The problem is to derive analytical representations for the source function terms said above from the fundamental wave equations. Basing on publications of numerous authors and on the last two decades studies of the author, th...
Attenuation of surface waves due to monsoon rains: A model study for the north Indian Ocean
Digital Repository Service at National Institute of Oceanography (India)
Vethamony, P.; Kumar, B.P.; Sarma, Y.V.B.
The dynamic interaction of intense rain with waves based on momentum exchange is applied to a second generation wave model to predict wave attenuation during monsoon. The scheme takes into account the characteristics of rain and wave parameters...
Scroll wave dynamics in a model of the heterogeneous heart
Konovalov, P. V.; Pravdin, S. F.; Solovyova, O. E.; Panfilov, A. V.
2016-07-01
Scroll waves are found in physical, chemical and biological systems and underlie many significant processes including life-threatening cardiac arrhythmias. The theory of scroll waves predicts scroll wave dynamics should be substantially affected by heterogeneity of cardiac tissue together with other factors including shape and anisotropy. In this study, we used our recently developed analytical model of the human ventricle to identify effects of shape, anisotropy, and regional heterogeneity of myocardium on scroll wave dynamics. We found that the main effects of apical-base heterogeneity were an increased scroll wave drift velocity and a shift towards the region of maximum action potential duration. We also found that transmural heterogeneity does not substantially affect scroll wave dynamics and only in extreme cases changes the attractor position.
Statistical model on the surface elevation of waves with breaking
Institute of Scientific and Technical Information of China (English)
2008-01-01
In the surface wind drift layer with constant momentum flux, two sets of the consistent surface eleva- tion expressions with breaking and occurrence conditions for breaking are deduced from the first in- tegrals of the energy and vortex variations and the kinetic and mathematic breaking criterions, then the expression of the surface elevation with wave breaking is established by using the Heaviside function. On the basis of the form of the sea surface elevation with wave breaking and the understanding of small slope sea waves, a triple composite function of real sea waves is presented including the func- tions for the breaking, weak-nonlinear and basic waves. The expression of the triple composite func- tion and the normal distribution of basic waves are the expected theoretical model for surface elevation statistics.
Digital Repository Service at National Institute of Oceanography (India)
Samiksha, S.V.; Polnikov, V.G.; Vethamony, P.; Rashmi, R.; Pogarskii, F.; Sudheesh, K.
for the model comparison. Based on the error estimates of significant wave heights and spectral wave energy, improvement achieved in wave prediction using ModWAM is demonstrated. We find that the ModWAM improved the accuracy of significant wave height prediction...
Stochastic waves in a Brusselator model with nonlocal interaction.
Biancalani, Tommaso; Galla, Tobias; McKane, Alan J
2011-08-01
We show that intrinsic noise can induce spatiotemporal phenomena such as Turing patterns and traveling waves in a Brusselator model with nonlocal interaction terms. In order to predict and to characterize these stochastic waves we analyze the nonlocal model using a system-size expansion. The resulting theory is used to calculate the power spectra of the stochastic waves analytically and the outcome is tested successfully against simulations. We discuss the possibility that nonlocal models in other areas, such as epidemic spread or social dynamics, may contain similar stochastically induced patterns.
Coupling model for waves propagating over a porous seabed
Directory of Open Access Journals (Sweden)
C.C. Liao
2015-03-01
Full Text Available The wave–seabed interaction issue is of great importance for the design of foundation around marine infrastructures. Most previous investigations for such a problem have been limited to uncoupled or one-way coupled methods connecting two separated wave and seabed sub models with the continuity of pressures at the seabed surface. In this study, a strongly coupled model was proposed to realize both wave and seabed processes in a same program and to calculate the wave fields and seabed response simultaneously. The information between wave fields and seabed fields were strongly shared and thus results in a more profound investigation of the mechanism of the wave–seabed interaction. In this letter, the wave and seabed models were validated with previous experimental tests. Then, a set of application of present model were discussed in prediction of the wave-induced seabed response. Numerical results show the wave-induced liquefaction area of coupled model is smaller than that of uncoupled model.
Modelling wave-boundary layer interaction for wind power applications
Jenkins, A. D.; Barstad, I.; Gupta, A.; Adakudlu, M.
2012-04-01
Marine wind power production facilities are subjected to direct and indirect effects of ocean waves. Direct effects include forces due to wave orbital motions and slamming of the water surface under breaking wave conditions, corrosion and icing due to sea spray, and the effects of wave-generated air bubbles. Indirect effects include include the influence of waves on the aerodynamic sea-surface roughness, air turbulence, the wind velocity profile, and air velocity oscillations, wave-induced currents and sediment transport. Field observations within the boundary layers from floating measurement may have to be corrected to account for biases induced as a result of wave-induced platform motions. To estimate the effect of waves on the atmospheric boundary layer we employ the WRF non-hydrostatic mesoscale atmosphere model, using the default YSU planetary boundary layer (PBL) scheme and the WAM spectral wave model, running simultaneously and coupled using the open-source coupler MCEL which can interpolate between different model grids and timesteps. The model is driven by the WRF wind velocity at 10 m above the surface. The WRF model receives from WAM updated air-sea stress fields computed from the wind input source term, and computes new fields for the Charnock parameter and marine surface aerodynamic roughness. Results from a North Atlantic and Nordic Seas simulation indicate that the two-way coupling scheme alters the 10 metre wind predicted by WRF by up to 10 per cent in comparison with a simulation using a constant Charnock parameter. The changes are greatest in developing situations with passages of fronts, moving depressions and squalls. This may be directly due to roughness length changes, or may be due to changes in the timing of front/depression/squall passages. Ongoing work includes investigating the effect of grid refinement/nesting, employing different PBL schemes, and allowing the wave field to change the direction of the total air-sea stress.
Traveling waves in an optimal velocity model of freeway traffic
Berg, Peter; Woods, Andrew
2001-03-01
Car-following models provide both a tool to describe traffic flow and algorithms for autonomous cruise control systems. Recently developed optimal velocity models contain a relaxation term that assigns a desirable speed to each headway and a response time over which drivers adjust to optimal velocity conditions. These models predict traffic breakdown phenomena analogous to real traffic instabilities. In order to deepen our understanding of these models, in this paper, we examine the transition from a linear stable stream of cars of one headway into a linear stable stream of a second headway. Numerical results of the governing equations identify a range of transition phenomena, including monotonic and oscillating travelling waves and a time- dependent dispersive adjustment wave. However, for certain conditions, we find that the adjustment takes the form of a nonlinear traveling wave from the upstream headway to a third, intermediate headway, followed by either another traveling wave or a dispersive wave further downstream matching the downstream headway. This intermediate value of the headway is selected such that the nonlinear traveling wave is the fastest stable traveling wave which is observed to develop in the numerical calculations. The development of these nonlinear waves, connecting linear stable flows of two different headways, is somewhat reminiscent of stop-start waves in congested flow on freeways. The different types of adjustments are classified in a phase diagram depending on the upstream and downstream headway and the response time of the model. The results have profound consequences for autonomous cruise control systems. For an autocade of both identical and different vehicles, the control system itself may trigger formations of nonlinear, steep wave transitions. Further information is available [Y. Sugiyama, Traffic and Granular Flow (World Scientific, Singapore, 1995), p. 137].
On the modeling of wave-enhanced turbulence nearshore
Moghimi, Saeed; Thomson, Jim; Özkan-Haller, Tuba; Umlauf, Lars; Zippel, Seth
2016-07-01
A high resolution k-ω two-equation turbulence closure model, including surface wave forcing was employed to fully resolve turbulence dissipation rate profiles close to the ocean surface. Model results were compared with observations from Surface Wave Instrument Floats with Tracking (SWIFTs) in the nearshore region at New River Inlet, North Carolina USA, in June 2012. A sensitivity analysis for different physical parameters and wave and turbulence formulations was performed. The flux of turbulent kinetic energy (TKE) prescribed by wave dissipation from a numerical wave model was compared with the conventional prescription using the wind friction velocity. A surface roughness length of 0.6 times the significant wave height was proposed, and the flux of TKE was applied at a distance below the mean sea surface that is half of this roughness length. The wave enhanced layer had a total depth that is almost three times the significant wave height. In this layer the non-dimensionalized Terray scaling with power of - 1.8 (instead of - 2) was applicable.
Yuan, Kai; Knoop, Victor L.; Hoogendoorn, Serge P.
2017-01-01
On freeways, congestion always leads to capacity drop. This means the queue discharge rate is lower than the pre-queue capacity. Our recent research findings indicate that the queue discharge rate increases with the speed in congestion, that is the capacity drop is strongly correlated with the congestion state. Incorporating this varying capacity drop into a kinematic wave model is essential for assessing consequences of control strategies. However, to the best of authors' knowledge, no such a model exists. This paper fills the research gap by presenting a Lagrangian kinematic wave model. "Lagrangian" denotes that the new model is solved in Lagrangian coordinates. The new model can give capacity drops accompanying both of stop-and-go waves (on homogeneous freeway section) and standing queues (at nodes) in a network. The new model can be applied in a network operation. In this Lagrangian kinematic wave model, the queue discharge rate (or the capacity drop) is a function of vehicular speed in traffic jams. Four case studies on links as well as at lane-drop and on-ramp nodes show that the Lagrangian kinematic wave model can give capacity drops well, consistent with empirical observations.
Solvable Model of Spiral Wave Chimeras
DEFF Research Database (Denmark)
Martens, Erik Andreas; Laing, Carlo R.; Strogatz, Steven H.
2010-01-01
Spiral waves are ubiquitous in two-dimensional systems of chemical or biological oscillators coupled locally by diffusion. At the center of such spirals is a phase singularity, a topological defect where the oscillator amplitude drops to zero. But if the coupling is nonlocal, a new kind of spiral...... can occur, with a circular core consisting of desynchronized oscillators running at full amplitude. Here, we provide the first analytical description of such a spiral wave chimera and use perturbation theory to calculate its rotation speed and the size of its incoherent core....
Matda, Y.; Crawford, F. W.
1974-01-01
An economical low noise plasma simulation model is applied to a series of problems associated with electrostatic wave propagation in a one-dimensional, collisionless, Maxwellian plasma, in the absence of magnetic field. The model is described and tested, first in the absence of an applied signal, and then with a small amplitude perturbation, to establish the low noise features and to verify the theoretical linear dispersion relation at wave energy levels as low as 0.000,001 of the plasma thermal energy. The method is then used to study propagation of an essentially monochromatic plane wave. Results on amplitude oscillation and nonlinear frequency shift are compared with available theories. The additional phenomena of sideband instability and satellite growth, stimulated by large amplitude wave propagation and the resulting particle trapping, are described.
Modeling of Mud-Wave Interaction: Mud-Induced Wave Transport & Wave-Induced Mud Transport
2007-11-01
seabed. This can be a fairly rapid process (i.e. of the order of tens of seconds, up to a few minutes at most, e.g. Foda and Zhang (1994); Lindenberg...response of cohesive sediments to water waves, PhD-dissertation, University of California, Berkeley, USA. Chou, H.-T., M.A. Foda and J.R. Hunt, 1993...Dingemans, M.W., 1997, Water wave propagation over uneven bottoms; Part I & II, World Scientific, Singapore. Foda , M.A. and S.-Y. Tzang, 1994
Stochastic analysis and modeling of abnormally large waves
Kuznetsov, Konstantin; Shamin, Roman; Yudin, Aleksandr
2016-04-01
In this work stochastics of amplitude characteristics of waves during the freak waves formation was estimated. Also amplitude characteristics of freak wave was modeling with the help of the developed Markov model on the basis of in-situ and numerical experiments. Simulation using the Markov model showed a great similarity of results of in-situ wave measurements[1], results of directly calculating the Euler equations[2] and stochastic modeling data. This work is supported by grant of Russian Foundation for Basic Research (RFBR) n°16-35-00526. 1. K. I. Kuznetsov, A. A. Kurkin, E. N. Pelinovsky and P. D. Kovalev Features of Wind Waves at the Southeastern Coast of Sakhalin according to Bottom Pressure Measurements //Izvestiya, Atmospheric and Oceanic Physics, 2014, Vol. 50, No. 2, pp. 213-220. DOI: 10.1134/S0001433814020066. 2. R.V. Shamin, V.E. Zakharov, A.I. Dyachenko. How probability for freak wave formation can be found // THE EUROPEAN PHYSICAL JOURNAL - SPECIAL TOPICS Volume 185, Number 1, 113-124, DOI: 10.1140/epjst/e2010-01242-y 3.E. N. Pelinovsky, K. I. Kuznetsov, J. Touboul, A. A. Kurkin Bottom pressure caused by passage of a solitary wave within the strongly nonlinear Green-Naghdi model //Doklady Physics, April 2015, Volume 60, Issue 4, pp 171-174. DOI: 10.1134/S1028335815040035
Nonlinear Pressure Wave Analysis by Concentrated Mass Model
Ishikawa, Satoshi; Kondou, Takahiro; Matsuzaki, Kenichiro
A pressure wave propagating in a tube often changes to a shock wave because of the nonlinear effect of fluid. Analyzing this phenomenon by the finite difference method requires high computational cost. To lessen the computational cost, a concentrated mass model is proposed. This model consists of masses, connecting nonlinear springs, connecting dampers, and base support dampers. The characteristic of a connecting nonlinear spring is derived from the adiabatic change of fluid, and the equivalent mass and equivalent damping coefficient of the base support damper are derived from the equation of motion of fluid in a cylindrical tube. Pressure waves generated in a hydraulic oil tube, a sound tube and a plane-wave tube are analyzed numerically by the proposed model to confirm the validity of the model. All numerical computational results agree very well with the experimental results carried out by Okamura, Saenger and Kamakura. Especially, the numerical analysis reproduces the phenomena that a pressure wave with large amplitude propagating in a sound tube or in a plane tube changes to a shock wave. Therefore, it is concluded that the proposed model is valid for the numerical analysis of nonlinear pressure wave problem.
Haverd, V.; Smith, B.; Nieradzik, L. P.; Briggs, P. R.
2014-02-01
Poorly constrained rates of biomass turnover are a key limitation of Earth system models (ESM). In light of this, we recently proposed a new approach encoded in a model called Populations-Order-Physiology (POP), for the simulation of woody ecosystem stand dynamics, demography and disturbance-mediated heterogeneity. POP is suitable for continental to global applications and designed for coupling to the terrestrial ecosystem component of any ESM. POP bridges the gap between first generation Dynamic Vegetation Models (DVMs) with simple large-area parameterisations of woody biomass (typically used in current ESMs) and complex second generation DVMs, that explicitly simulate demographic processes and landscape heterogeneity of forests. The key simplification in the POP approach, compared with second-generation DVMs, is to compute physiological processes such as assimilation at grid-scale (with CABLE or a similar land surface model), but to partition the grid-scale biomass increment among age classes defined at sub grid-scale, each subject to its own dynamics. POP was successfully demonstrated along a savanna transect in northern Australia, replicating the effects of strong rainfall and fire disturbance gradients on observed stand productivity and structure. Here, we extend the application of POP to a range of forest types around the globe, employing paired observations of stem biomass and density from forest inventory data to calibrate model parameters governing stand demography and biomass evolution. The calibrated POP model is then coupled to the CABLE land surface model and the combined model (CABLE-POP) is evaluated against leaf-stem allometry observations from forest stands ranging in age from 3 to 200 yr. Results indicate that simulated biomass pools conform well with observed allometry. We conclude that POP represents a preferable alternative to large-area parameterisations of woody biomass turnover, typically used in current ESMs.
Directory of Open Access Journals (Sweden)
V. Haverd
2014-02-01
Full Text Available Poorly constrained rates of biomass turnover are a key limitation of Earth system models (ESM. In light of this, we recently proposed a new approach encoded in a model called Populations-Order-Physiology (POP, for the simulation of woody ecosystem stand dynamics, demography and disturbance-mediated heterogeneity. POP is suitable for continental to global applications and designed for coupling to the terrestrial ecosystem component of any ESM. POP bridges the gap between first generation Dynamic Vegetation Models (DVMs with simple large-area parameterisations of woody biomass (typically used in current ESMs and complex second generation DVMs, that explicitly simulate demographic processes and landscape heterogeneity of forests. The key simplification in the POP approach, compared with second-generation DVMs, is to compute physiological processes such as assimilation at grid-scale (with CABLE or a similar land surface model, but to partition the grid-scale biomass increment among age classes defined at sub grid-scale, each subject to its own dynamics. POP was successfully demonstrated along a savanna transect in northern Australia, replicating the effects of strong rainfall and fire disturbance gradients on observed stand productivity and structure. Here, we extend the application of POP to a range of forest types around the globe, employing paired observations of stem biomass and density from forest inventory data to calibrate model parameters governing stand demography and biomass evolution. The calibrated POP model is then coupled to the CABLE land surface model and the combined model (CABLE-POP is evaluated against leaf-stem allometry observations from forest stands ranging in age from 3 to 200 yr. Results indicate that simulated biomass pools conform well with observed allometry. We conclude that POP represents a preferable alternative to large-area parameterisations of woody biomass turnover, typically used in current ESMs.
Numerical Modelling of Solitary Wave Experiments on Rubble Mound Breakwaters
Guler, H. G.; Arikawa, T.; Baykal, C.; Yalciner, A. C.
2016-12-01
Performance of a rubble mound breakwater protecting Haydarpasa Port, Turkey, has been tested under tsunami attack by physical model tests conducted at Port and Airport Research Institute (Guler et al, 2015). It is aimed to understand dynamic force of the tsunami by conducting solitary wave tests (Arikawa, 2015). In this study, the main objective is to perform numerical modelling of solitary wave tests in order to verify accuracy of the CFD model IHFOAM, developed in OpenFOAM environment (Higuera et al, 2013), by comparing results of the numerical computations with the experimental results. IHFOAM is the numerical modelling tool which is based on VARANS equations with a k-ω SST turbulence model including realistic wave generation, and active wave absorption. Experiments are performed using a Froude scale of 1/30, measuring surface elevation and flow velocity at several locations in the wave channel, and wave pressure around the crown wall of the breakwater. Solitary wave tests with wave heights of H=7.5 cm and H=10 cm are selected which represent the results of the experiments. The first test (H=7.5 cm) is the case that resulted in no damage whereas the second case (H=10 cm) resulted in total damage due to the sliding of the crown wall. After comparison of the preliminary results of numerical simulations with experimental data for both cases, it is observed that solitary wave experiments could be accurately modeled using IHFOAM focusing water surface elevations, flow velocities, and wave pressures on the crown wall of the breakwater (Figure, result of sim. at t=29.6 sec). ACKNOWLEDGEMENTSThe authors acknowledge developers of IHFOAM, further extend their acknowledgements for the partial supports from the research projects MarDiM, ASTARTE, RAPSODI, and TUBITAK 213M534. REFERENCESArikawa (2015) "Consideration of Characteristics of Pressure on Seawall by Solitary Waves Based on Hydraulic Experiments", Jour. of Japan. Soc. of Civ. Eng. Ser. B2 (Coast. Eng.), Vol 71, p I