Tilt anisoplanatism in extended turbulence propagation
NASA Astrophysics Data System (ADS)
Magee, Eric P.; Whiteley, Matthew R.; Das, Shashikala T.; Welsh, Byron M.
2003-04-01
The use of high-energy laser (HEL) weapon systems in tactical air-to-ground target engagements offers great promise for revolutionizing the USAF's war-fighting capabilities. Laser directed-energy systems will enable ultra-precision strike with minimal collateral damage and significant stand-off range for the aerial platform. The tactical directed energy application differs in many crucial ways from the conventional approach used in missile defense. Tactical missions occur at much lower altitudes and involve look-down to low-contrast ground targets instead of a high-contrast boosting missile. At these lower altitudes, the strength of atmospheric turbulence is greatly enhanced. Although the target slant ranges are much shorter, tactical missions may still involve moderate values of the Rytov number (0.1-0.5), and small isoplanatic angles compared to the diffraction angle. With increased density of air in the propagation path, and the potential for slow-moving or stationary ground targets, HEL-induced thermal blooming will certainly be a concern. In order to minimize the errors induced by tracking through thermal blooming, offset aimpoint tracking can be used. However, this will result in significant tilt anisoplanatism, thus degrading beam stabilization on target. In this paper we investigate the effects of extended turbulence on tracking (or tilt) anisoplanatism using theory and wave optics simulations. The simulations show good agreement with geometric optics predictions at angles larger than about 5 micro-radians (asymptotic regime) while at smaller angles the agreement is poor. We present a theoretical basis for this observation.
Extended inertial range phenomenology of magnetohydrodynamic turbulence
NASA Technical Reports Server (NTRS)
Matthaeus, William H.; Zhou, YE
1989-01-01
A phenomenological treatment of the inertial range of isotropic statistically steady magnetohydrodynamic turbulence is presented, extending the theory of Kraichnan (1965). The role of Alfven wave propagation is treated on equal footing with nonlinear convection, leading to a simple generalization of the relations between the times characteristic of wave propagation, convection, energy transfer, and decay of triple correlations. The theory leads to a closed-form steady inertial range spectral law that reduces to the Kraichnan and Kolmogorov laws in appropriate limits. The Kraichnan constant is found to be related in a simple way to the Kolmogorov constant; for typical values of the latter constant, the former has values in the range 1.22-1.87. Estimates of the time scale associated with spectral transfer of energy also emerge from the new approach, generalizing previously presented 'golden rules' for relating the spectral transfer time scale to the Alfven and eddy-turnover time scales.
EXTENDED SCALING LAWS IN NUMERICAL SIMULATIONS OF MAGNETOHYDRODYNAMIC TURBULENCE
Mason, Joanne; Cattaneo, Fausto; Perez, Jean Carlos; Boldyrev, Stanislav E-mail: cattaneo@flash.uchicago.edu E-mail: boldyrev@wisc.edu
2011-07-10
Magnetized turbulence is ubiquitous in astrophysical systems, where it notoriously spans a broad range of spatial scales. Phenomenological theories of MHD turbulence describe the self-similar dynamics of turbulent fluctuations in the inertial range of scales. Numerical simulations serve to guide and test these theories. However, the computational power that is currently available restricts the simulations to Reynolds numbers that are significantly smaller than those in astrophysical settings. In order to increase computational efficiency and, therefore, probe a larger range of scales, one often takes into account the fundamental anisotropy of field-guided MHD turbulence, with gradients being much slower in the field-parallel direction. The simulations are then optimized by employing the reduced MHD equations and relaxing the field-parallel numerical resolution. In this work we explore a different possibility. We propose that there exist certain quantities that are remarkably stable with respect to the Reynolds number. As an illustration, we study the alignment angle between the magnetic and velocity fluctuations in MHD turbulence, measured as the ratio of two specially constructed structure functions. We find that the scaling of this ratio can be extended surprisingly well into the regime of relatively low Reynolds number. However, the extended scaling easily becomes spoiled when the dissipation range in the simulations is underresolved. Thus, taking the numerical optimization methods too far can lead to spurious numerical effects and erroneous representation of the physics of MHD turbulence, which in turn can affect our ability to identify correctly the physical mechanisms that are operating in astrophysical systems.
Computation of turbulent flows using an extended k-epsilon turbulence closure model
NASA Technical Reports Server (NTRS)
Chen, Y.-S.; Kim, S.-W.
1987-01-01
An extended kappa-epsilon turbulence model is proposed and tested with successful results. An improved transport equation for the rate of dissipation of the turbulent kinetic energy, epsilon, is proposed. The proposed model gives more effective response to the energy production rate than does the standard kappa-epsilon turbulence model. An extra time scale of the production range is included in the dissipation rate equation. This enables the present model to perform equally well for several turbulent flows with different characteristics, e.g., plane and axisymmetric jets, turbulent boundary layer flow, turbulent flow over a backward-facing step, and a confined turbulent swirling flow. A second-order accurate finite difference boundary layer code and a nearly second-order accurate finite difference elliptic flow solver are used for the present numerical computations.
Extending velocity channel analysis for studying turbulence anisotropies
NASA Astrophysics Data System (ADS)
Kandel, D.; Lazarian, A.; Pogosyan, D.
2016-09-01
We extend the velocity channel analysis (VCA), introduced by Lazarian & Pogosyan, of the intensity fluctuations in the velocity slices of position-position-velocity (PPV) spectroscopic data from Doppler broadened lines to study statistical anisotropy of the underlying velocity and density that arises in a turbulent medium from the presence of magnetic field. In particular, we study analytically how the anisotropy of the intensity correlation in the channel maps changes with the thickness of velocity channels. In agreement with the earlier VCA studies, we find that the anisotropy in the thick channels reflects the anisotropy of the density field, while the relative contribution of density and velocity fluctuations to the thin velocity channels depends on the density spectral slope. We show that the anisotropies arising from Alfvén, slow and fast magnetohydrodynamical modes are different; in particular, the anisotropy in PPV created by fast modes is opposite to that created by Alfvén and slow modes, and this can be used to separate their contributions. We successfully compare our results with the recent numerical study of the PPV anisotropies measured with synthetic observations. We also extend our study to the medium with self-absorption as well as to the case of absorption lines. In addition, we demonstrate how the studies of anisotropy can be performed using interferometers.
NASA Astrophysics Data System (ADS)
Tekriwal, P.
1994-05-01
Standard and extended kappa-epsilon turbulence closure models have been employed for three-dimensional heat transfer calculations for radially outward flow in rectangular and square cooling passages rotating in orthogonal mode. The objective of this modeling effort is to validate the numerical model in an attempt to fill the gap between model predictions and the experimental data for heat transfer in rotating systems. While the trend of heat transfer predictions by the standard kappa-epsilon turbulence model is satisfactory, the differences between the data and the predictions are approximately 30 percent or so in the case of high rotation number flow. The extended kappa-epsilon turbulence model takes an approach where an extra 'source' term based on a second time scale of the turbulent kinetic energy production rate is added to the equation for the dissipation rate of turbulent kinetic energy. This yields a more effective calculation of turbulent kinetic energy as compared to the standard kappa-epsilon turbulence model in the case of high rotation number and high density ratio flow. As a result, comparison with the experimental data available in the literature shows that an improvement of up to a significant 15 percent (with respect to data) in the heat transfer coefficient predictions is achieved over the standard kappa-epsilon model in the case of high rotation number flow. Comparisons between the results of the standard kappa-epsilon model and the extended formulation are made at different rotation numbers, different Reynolds numbers, and varying temperature ratio. The results of the extended kappa-epsilon turbulence model are either as good or better than those of the standard kappa-epsilon model in all these cases of parametric study. Thus, the extended kappa-epsilon turbulence model proves to be more general and reduces the discrepancy between the model predictions and the experimental data for heat transfer in rotating systems.
PREFACE: Complex Dynamics in Spatially Extended Systems
NASA Astrophysics Data System (ADS)
Mosekilde, Erik; Bohr, Tomas; Rasmussen, Jens Juul; Leth Christiansen, Peter
1996-01-01
Self-organization, or the spontaneous emergence of patterns and structures under far-from-equilibrium conditions, turbulence, and related nonlinear dynamic phenomena in spatially extended systems have developed into one of the most exciting topics of modern science. Phenomena of this type arise in a wide variety of different fields, ranging from the development of chemical and biological patterns in reaction-diffusion systems over vortex formation in connection with chemical, optical, hydrodynamic or magnetohydrodynamic turbulence to technical applications in connection with liquid crystal displays or pulse compression in optical communication systems. Lasers often show interesting patterns produced by self-focusing and other nonlinear phenomena, diffusion limited aggregation is known to generate fractal-like structures, and amazing struc- tures also arise in bacterial growth processes or when a droplet of an oil suspension of finely divided magnetic particles is subject to a magnetic field perpendicular to the surface of the cell in which it is contained. In September 1995 the Niels Bohr Institute in Copenhagen was the venue of an International Conference on Complex Dynamics in Spatially Extended Systems. Organizers of the conference were the three Danish centers for nonlinear dynamics: The Center for Chaos and Turbulence Studies (CATS), located at the Niels Bohr Institute; the Center for Modeling, Nonlinear Dynamics and Irreversible Thermodynamics (MIDIT), located at the Technical University of Denmark, and the Center for Nonlinear Dynamics in Continuum Systems, located at the Risø National Laboratories. In the spirit of the successful NATO Advanced Research Workshops on Spatiotemporal Patterns in Nonequilibrium Systems of which the last was held in Santa Fe, New Mexico in 1993, the conference aimed at stimulating new ideas and providing a forum for the exchange of knowledge between leading practitioners of the field. With its 50 invited speakers and more than
Computer correction of turbulent distortions of image of extended objects on near-Earth paths
Averin, A P; Morozov, Yu B; Pryanichkov, V S; Tyapin, V V
2011-05-31
An algorithm of computer-based correction of images of extended objects distorted by turbulent atmosphere is developed. The method of computer correction is used to correct a distorted image of an extended object on a horizontal 2300-m-long observation path. The angular size of the corrected-image region was 15'. (image processing)
Intermittency and extended self-similarity in the solar wind turbulence
NASA Technical Reports Server (NTRS)
Bruno, R.; Carbone, V.
1995-01-01
Using the satellite measurements of the velocity field in the interplanetary plasma. we present some analysis which show the presence of a self-similar intermittent state in the solar wind turbulence. We used the so called Extended Self-Similarity hypothesis, which is well visible in the solar wind turbulence, showing convincing evidences for the presence of universal anomalous scaling laws. Through the Extended Self-Similarity we are able to calculate the scaling exponents of the velocity structure functions with very small uncertainties, and we show that these scaling exponents are in very good agreement with the multifractal models describing intermittency in magnetohydrodynamic flows.
Clear air turbulence - An airborne alert system
NASA Technical Reports Server (NTRS)
Stearns, L. P.; Caracena, F.; Kuhn, P. M.; Kurkowski, R. L.
1981-01-01
An infrared radiometer system has been developed that can alert a pilot of an aircraft 2 to 9 minutes in advance of an encounter with clear air turbulence. The time between the warning and the clear air turbulence event varies with the flight altitude of the aircraft. In turbulence-free areas, the incidence of false alarms is found to be less than one in 3.4 hours of flight time compared to less than one per 10 hours of flight time in areas with turbulence.
Extended mission life support systems
NASA Technical Reports Server (NTRS)
Quattrone, P. D.
1985-01-01
Extended manned space missions which include interplanetary missions require regenerative life support systems. Manned mission life support considerations are placed in perspective and previous manned space life support system technology, activities and accomplishments in current supporting research and technology (SR&T) programs are reviewed. The life support subsystem/system technologies required for an enhanced duration orbiter (EDO) and a space operations center (SOC), regenerative life support functions and technology required for manned interplanetary flight vehicles, and future development requirements are outlined. The Space Shuttle Orbiters (space transportation system) is space cabin atmosphere is maintained at Earth ambient pressure of 14.7 psia (20% O2 and 80% N2). The early Shuttle flights will be seven-day flights, and the life support system flight hardware will still utilize expendables.
Calibration of a universal indicated turbulence system
NASA Technical Reports Server (NTRS)
Chapin, W. G.
1977-01-01
Theoretical and experimental work on a Universal Indicated Turbulence Meter is described. A mathematical transfer function from turbulence input to output indication was developed. A random ergodic process and a Gaussian turbulence distribution were assumed. A calibration technique based on this transfer function was developed. The computer contains a variable gain amplifier to make the system output independent of average velocity. The range over which this independence holds was determined. An optimum dynamic response was obtained for the tubulation between the system pitot tube and pressure transducer by making dynamic response measurements for orifices of various lengths and diameters at the source end.
Extended attention span training system
NASA Technical Reports Server (NTRS)
Pope, Alan T.; Bogart, Edward H.
1991-01-01
Attention Deficit Disorder (ADD) is a behavioral disorder characterized by the inability to sustain attention long enough to perform activities such as schoolwork or organized play. Treatments for this disorder include medication and brainwave biofeedback training. Brainwave biofeedback training systems feed back information to the trainee showing him how well he is producing the brainwave pattern that indicates attention. The Extended Attention Span Training (EAST) system takes the concept a step further by making a video game more difficult as the player's brainwaves indicate that attention is waning. The trainee can succeed at the game only by maintaining an adequate level of attention. The EAST system is a modification of a biocybernetic system that is currently being used to assess the extent to which automated flight management systems maintain pilot engagement. This biocybernetic system is a product of a program aimed at developing methods to evaluate automated flight deck designs for compatibility with human capabilities. The EAST technology can make a contribution in the fields of medical neuropsychology and neurology, where the emphasis is on cautious, conservative treatment of youngsters with attention disorders.
NASA Astrophysics Data System (ADS)
Schlickeiser, R.
2011-05-01
A new transport theory of cosmic rays in magnetized space plasmas with axisymmetric incompressible magnetic turbulence is developed extending the quasilinear approximation to the particle orbit. Arbitrary gyrophase deviations from the unperturbed spiral orbits in the uniform magnetic field are allowed. For quasi-stationary and spatially homogeneous magnetic turbulence, we derive the small Larmor radius approximation gyrophase-averaged cosmic ray Fokker-Planck coefficients. The generalized Fokker-Planck coefficients correctly reduce to their known quasilinear values in the corresponding limit. New forms of the quasilinear Fokker-Planck coefficients in axisymmetric turbulence are derived which no longer involve infinite sums of products of Bessel functions, which facilitate their numerical computation for specified turbulence field correlation tensors. The Fokker-Planck coefficients for arbitrary phase orbits of the cosmic ray particles provide strict upper limits for the perpendicular and pitch-angle Fokker-Planck coefficients, which in turn yield strict upper and lower limits for the perpendicular and parallel spatial diffusion coefficients, respectively, describing the spatial diffusion of the isotropic part of the cosmic ray phase space density. For the associated mean free paths, we find for this general case that the product of the minimum parallel mean free path with the sum of the maximum perpendicular mean free paths equals R 2 L , where RL denotes the cosmic ray gyroradius.
Dynamic Stochastic Superresolution of sparsely observed turbulent systems
Branicki, M.; Majda, A.J.
2013-05-15
Real-time capture of the relevant features of the unresolved turbulent dynamics of complex natural systems from sparse noisy observations and imperfect models is a notoriously difficult problem. The resulting lack of observational resolution and statistical accuracy in estimating the important turbulent processes, which intermittently send significant energy to the large-scale fluctuations, hinders efficient parameterization and real-time prediction using discretized PDE models. This issue is particularly subtle and important when dealing with turbulent geophysical systems with an vast range of interacting spatio-temporal scales and rough energy spectra near the mesh scale of numerical models. Here, we introduce and study a suite of general Dynamic Stochastic Superresolution (DSS) algorithms and show that, by appropriately filtering sparse regular observations with the help of cheap stochastic exactly solvable models, one can derive stochastically ‘superresolved’ velocity fields and gain insight into the important characteristics of the unresolved dynamics, including the detection of the so-called black swans. The DSS algorithms operate in Fourier domain and exploit the fact that the coarse observation network aliases high-wavenumber information into the resolved waveband. It is shown that these cheap algorithms are robust and have significant skill on a test bed of turbulent solutions from realistic nonlinear turbulent spatially extended systems in the presence of a significant model error. In particular, the DSS algorithms are capable of successfully capturing time-localized extreme events in the unresolved modes, and they provide good and robust skill for recovery of the unresolved processes in terms of pattern correlation. Moreover, we show that DSS improves the skill for recovering the primary modes associated with the sparse observation mesh which is equally important in applications. The skill of the various DSS algorithms depends on the energy spectrum
Extended high-angular-frequency analysis of turbulence effects on short-exposure imaging
NASA Astrophysics Data System (ADS)
Tofsted, David H.
2014-04-01
An improved analysis of optical turbulence effects on short-exposure passive (SE) imaging is described, resulting in a new analytic expression for the SE modulation transfer function (MTF). This analysis expands on a 2011 study that examined characteristics of a tilt-phase component discovered in the standard theory of SE turbulence effects characterization. The analysis introduces an improved integration technique and a reformulated phase structure function, facilitating computation of a 38,007 element database of MTF results at low- to high-angular frequencies covering a wide range of diffraction and turbulence conditions. Analysis of this database is described, yielding a new analytic SE MTF, accurate to a root-mean-square error of 0.000218 versus the database. Comparisons show that the new expression is well correlated to an alternative computationally intensive method, and it is a factor 29 to 64 improvement over prior analytic expressions. Limits of applicability of the approach for incoherent imaging are also discussed. The low-computational cost of the new method is suitable for systems performance modeling of turbulence impacts, including path-varying turbulence scenarios.
NASA Astrophysics Data System (ADS)
Frisch, Uriel
1996-01-01
Written five centuries after the first studies of Leonardo da Vinci and half a century after A.N. Kolmogorov's first attempt to predict the properties of flow, this textbook presents a modern account of turbulence, one of the greatest challenges in physics. "Fully developed turbulence" is ubiquitous in both cosmic and natural environments, in engineering applications and in everyday life. Elementary presentations of dynamical systems ideas, probabilistic methods (including the theory of large deviations) and fractal geometry make this a self-contained textbook. This is the first book on turbulence to use modern ideas from chaos and symmetry breaking. The book will appeal to first-year graduate students in mathematics, physics, astrophysics, geosciences and engineering, as well as professional scientists and engineers.
Laser Doppler systems in atmospheric turbulence
NASA Technical Reports Server (NTRS)
Murty, S. S. R.
1976-01-01
The loss of heterodyne signal power for the Marshall Space Flight Center laser Doppler system due to the random changes in the atmospheric index of refraction is investigated. The current status in the physics of low energy laser propagation through turbulent atmosphere is presented. The analysis and approximate evaluation of the loss of the heterodyne signal power due to the atmospheric absorption, scattering, and turbulence are estimated for the conditions of the January 1973 flight tests. Theoretical and experimental signal to noise values are compared. Maximum and minimum values of the atmospheric attenuation over a two way path of 20 km range are calculated as a function of altitude using models of atmosphere, aerosol concentration, and turbulence.
Brenkosh, J.P.
1993-12-23
The X Window System was originally developed in 1984 at Massachusetts Institute of Technology. It provides client-server computing functionality and also facilitates the establishment of a distributed computing environment. Since its inception the X Window System has undergone many enhancements. Despite these enhancements there will always be a functionality desired in the standard released version of X that is not supported or commercially or academically available. The developers of the X Window System have designed it in such a way that it is possible to add functionality that is not included in the standard release. This is called an extension. Extensions are one method used to develop a customized version of the X Window System to support a specialized application. This report presents the mechanics of adding an extension and examines a particular extension that was developed at Sandia National Laboratories to support data compression in X Windows which was one aspect of the Desktop Video and Collaborative Engineering Laboratory Directed Research and Development (LDRD).
Laser system of extended range
NASA Technical Reports Server (NTRS)
Lehr, C. G.
1972-01-01
A pulsed laser system was developed for range measurements from the earth to retroreflecting satellites at distances up to that of the moon. The system has a transportable transmitter unit that can be moved from one location to another. This unit consists of a 0.2 m coude refractor and a high radiance, neodymium-glass, frequency doubled laser that operates in a single transverse mode. It can be used for lunar or distant satellite ranging at any observatory that has a telescope with an aperture diameter of about 1.5 m for the detection of the laser return pulses. This telescope is utilized in the same manner customarily employed for the observation of celestial objects. A special photometric package and the associated electronics are provided for laser ranging.
NASA Technical Reports Server (NTRS)
Cranmer, Steven R.; Wagner, William (Technical Monitor)
2003-01-01
The PI (Cranmer) and Co-I (A. van Ballegooijen) made significant progress toward the goal of building a "unified model" of the dominant physical processes responsible for the acceleration of the solar wind. The approach outlined in the original proposal comprised two complementary pieces: (1) to further investigate individual physical processes under realistic coronal and solar wind conditions, and (2) to extract the dominant physical effects from simulations and apply them to a one-dimensional and time-independent model of plasma heating and acceleration. The accomplishments in the report period are thus divided into these two categories: 1a. Focused Study of Kinetic MHD Turbulence. We have developed a model of magnetohydrodynamic (MHD) turbulence in the extended solar corona that contains the effects of collisionless dissipation and anisotropic particle heating. A turbulent cascade is one possible way of generating small-scale fluctuations (easy to dissipate/heat) from a pre-existing population of low-frequency Alfven waves (difficult to dissipate/heat). We modeled the cascade as a combination of advection and diffusion in wavenumber space. The dominant spectral transfer occurs in the direction perpendicular to the background magnetic field. As expected from earlier models, this leads to a highly anisotropic fluctuation spectrum with a rapidly decaying tail in the parallel wavenumber direction. The wave power that decays to high enough frequencies to become ion cyclotron resonant depends on the relative strengths of advection and diffusion in the cascade. For the most realistic values of these parameters, though, there is insufficient power to heat protons and heavy ions. The dominant oblique waves undergo Landau damping, which implies strong parallel electron heating. We thus investigated the nonlinear evolution of the electron velocity distributions (VDFs) into parallel beams and discrete phase-space holes (similar to those seen in the terrestrial magnetosphere
Direct simulation of turbulent supersonic boundary layers by an extended temporal approach
NASA Astrophysics Data System (ADS)
Maeder, Thierry; Adams, Nikolaus A.; Kleiser, Leonhard
2001-02-01
The present paper addresses the direct numerical simulation of turbulent zero-pressure-gradient boundary layers on a flat plate at Mach numbers 3, 4.5 and 6 with momentum-thickness Reynolds numbers of about 3000. Simulations are performed with an extended temporal direct numerical simulation (ETDNS) method. Assuming that the slow streamwise variation of the mean boundary layer is governed by parabolized Navier Stokes equations, the equations solved locally in time with a temporal DNS are modified by a distributed forcing term so that the parabolized Navier Stokes equations are recovered for the spatial average. The correct mean flow is obtained without a priori knowledge, the streamwise mean-flow evolution being approximated from its upstream history. ETDNS reduces the computational effort by up to two orders of magnitude compared to a fully spatial simulation.
Proton Heating in the Extended Solar Corona Resulting From Kinetic Alfven Turbulence
NASA Astrophysics Data System (ADS)
Cranmer, S. R.; van Ballegooijen, A. A.
2002-12-01
Spectroscopic observations of the solar corona have made it clear that the ``coronal heating problem'' comprises not only the local deposition of heat immediately above the transition region, but also extended heat deposition throughout the (collisionless) acceleration region of the solar wind. The dissipation of magnetohydrodynamic (MHD) waves and/or turbulence has been considered as a likely heating mechanism in the solar wind for several decades. However, it is still not well understood how MHD fluctuations are generated, how they evolve in frequency and wavenumber, or how their damping leads to the observed proton, electron, and ion properties of the fast wind. We present a model of MHD turbulence that specifically addresses the issue of kinetic dissipation and particle heating in the collisionless extended corona. The nonlinear cascade is modeled as a combination of advection and diffusion in wavenumber space, with the dominant cascade occurring in the direction perpendicular to the background magnetic field. This leads to a highly anisotropic fluctuation spectrum (as expected, based on many earlier simulations and scaling models) with a rapidly decreasing power-law tail in the parallel wavenumber direction. In the low-plasma-beta corona, the dominant oblique fluctuations (with dispersion properties of kinetic Alfven waves) are dissipated by electron Landau damping, with only a tiny fraction of the energy going to high-frequency ion cyclotron waves. This implies strong parallel electron heating and weak proton and ion heating, which is not what is observed. We discuss the probable nonlinear evolution of the electron velocity distributions into parallel beams and discrete phase-space holes (similar to those seen in the terrestrial magnetosphere) which can possibly heat protons via stochastic interactions.
CARS system for turbulent flame measurements
NASA Technical Reports Server (NTRS)
Antcliff, R. R.; Jarrett, O., Jr.; Rogers, R. C.
1984-01-01
Simultaneous nitrogen number density and rotational-vibrational temperatures were measured in a turbulent diffusion flame with a Coherent Anti-Stokes Raman Scattering (CARS) instrument. The fuel jet was diluted with nitrogen (20 percent by volume) to allow temperature measurements across the entire jet mixing region. These measurements were compared with fluid dynamics computations. The CARS system incorporated a neodymium YAG laser, an intensified silicon photodiode array detector, and unique dynamic range enhancement methods. Theoretical calculations were based on a parabolic Navier-Stokes computer code. The comparison of these techniques will aid their development in the study of complex flowfields.
NASA Technical Reports Server (NTRS)
Cranmer, Steven R.; Wagner, William (Technical Monitor)
2004-01-01
The PI (Cranmer) and Co-I (A. van Ballegooijen) made substantial progress toward the goal of producing a unified model of the basic physical processes responsible for solar wind acceleration. The approach outlined in the original proposal comprised two complementary pieces: (1) to further investigate individual physical processes under realistic coronal and solar wind conditions, and (2) to extract the dominant physical effects from simulations and apply them to a 1D model of plasma heating and acceleration. The accomplishments in Year 2 are divided into these two categories: 1a. Focused Study of Kinetic Magnetohydrodynamic (MHD) Turbulence. lb. Focused Study of Non - WKB Alfven Wave Rejection. and 2. The Unified Model Code. We have continued the development of the computational model of a time-study open flux tube in the extended corona. The proton-electron Monte Carlo model is being tested, and collisionless wave-particle interactions are being included. In order to better understand how to easily incorporate various kinds of wave-particle processes into the code, the PI performed a detailed study of the so-called "Ito Calculus", i.e., the mathematical theory of how to update the positions of particles in a probabilistic manner when their motions are governed by diffusion in velocity space.
NASA Technical Reports Server (NTRS)
Wagner, William (Technical Monitor); Cranmer, Steven R.
2005-01-01
The paper discusses the following: 1. No-cost Extension. The no-cost extension is required to complete the work on the unified model codes (both hydrodynamic and kinetic Monte Carlo) as described in the initial proposal and previous annual reports. 2. Scientific Accomplishments during the Report Period. We completed a comprehensive model of Alfvtn wave reflection that spans the full distance from the photosphere to the distant heliosphere. 3. Comparison of Accomplishments with Proposed Goals. The proposal contained two specific objectives for Year 3: (1) to complete the unified model code, and (2) to apply it to various kinds of coronal holes (and polar plumes within coronal holes). Although the anticipated route toward these two final goals has changed (see accomplishments 2a and 2b above), they remain the major milestones for the extended period of performance. Accomplishments la and IC were necessary prerequisites for the derivation of "physically relevant transport and mode-coupling terms" for the unified model codes (as stated in the proposal Year 3 goals). We have fulfilled the proposed "core work" to study 4 general types of physical processes; in previous years we studied turbulence, mode coupling (Le., non-WKB reflection), and kinetic wave damping, and accomplishment lb provides the fourth topic: nonlinear steepening.
Extended Huygens-Fresnel principle and optical waves propagation in turbulence: discussion.
Charnotskii, Mikhail
2015-07-01
Extended Huygens-Fresnel principle (EHF) currently is the most common technique used in theoretical studies of the optical propagation in turbulence. A recent review paper [J. Opt. Soc. Am. A31, 2038 (2014)JOAOD60740-323210.1364/JOSAA.31.002038] cites several dozens of papers that are exclusively based on the EHF principle. We revisit the foundations of the EHF, and show that it is burdened by very restrictive assumptions that make it valid only under weak scintillation conditions. We compare the EHF to the less-restrictive Markov approximation and show that both theories deliver identical results for the second moment of the field, rendering the EHF essentially worthless. For the fourth moment of the field, the EHF principle is accurate under weak scintillation conditions, but is known to provide erroneous results for strong scintillation conditions. In addition, since the EHF does not obey the energy conservation principle, its results cannot be accurate for scintillations of partially coherent beam waves. PMID:26367166
In-Service Evaluation of the Turbulence Auto-PIREP System and Enhanced Turbulence Radar Technologies
NASA Technical Reports Server (NTRS)
Prince, Jason B.; Buck, Bill K.; Robinson, Paul A.; Ryan, Tim
2007-01-01
From August 2003 to December 2006, In-Service Evaluations (ISE) of the Turbulence Auto-PIREP System (TAPS) and Enhanced Turbulence (E-Turb) Radar, technologies developed in NASA's Turbulence Prediction and Warning System (TPAWS) element of its Aviation Safety and Security Program (AvSSP), were conducted. NASA and AeroTech Research established an industry team comprising AeroTech, Delta Air Lines, Rockwell Collins, and ARINC to conduct the ISEs. The technologies were installed on Delta aircraft and their effectiveness was evaluated in day-to-day operations. This report documents the establishment and conduct of the ISEs and presents results and feedback from various users.
Market Assessment of Forward-Looking Turbulence Sensing Systems
NASA Technical Reports Server (NTRS)
Kauffmann, Paul
2003-01-01
This viewgraph presentation provides a cost benefit analysis of three next-generation forward-looking turbulence sensing systems: X band turbulence radar system for convective turbulence, LIDAR based turbulence systems to sense clear air turbulence and a combined hybrid system. Parameters for the cost benefit analysis were established using a business model which considered injury rates, cost of injuries, indirect costs, market penetration rate estimates and product success characteristics. Topics covered include: study approach, business case equations, data acquisition, benchmark analysis. Data interpretation from the cost benefit analysis is presented. The researchers conclude that the market potential for these products is based primarily on injury cost reduction and that X band radar systems have the greatest chance for commercial success.
Synchronization in networks of spatially extended systems
Filatova, Anastasiya E.; Hramov, Alexander E.; Koronovskii, Alexey A.; Boccaletti, Stefano
2008-06-15
Synchronization processes in networks of spatially extended dynamical systems are analytically and numerically studied. We focus on the relevant case of networks whose elements (or nodes) are spatially extended dynamical systems, with the nodes being connected with each other by scalar signals. The stability of the synchronous spatio-temporal state for a generic network is analytically assessed by means of an extension of the master stability function approach. We find an excellent agreement between the theoretical predictions and the data obtained by means of numerical calculations. The efficiency and reliability of this method is illustrated numerically with networks of beam-plasma chaotic systems (Pierce diodes). We discuss also how the revealed regularities are expected to take place in other relevant physical and biological circumstances.
How turbulence regulates biodiversity in systems with cyclic competition
NASA Astrophysics Data System (ADS)
Grošelj, Daniel; Jenko, Frank; Frey, Erwin
2015-03-01
Cyclic, nonhierarchical interactions among biological species represent a general mechanism by which ecosystems are able to maintain high levels of biodiversity. However, species coexistence is often possible only in spatially extended systems with a limited range of dispersal, whereas in well-mixed environments models for cyclic competition often lead to a loss of biodiversity. Here we consider the dispersal of biological species in a fluid environment, where mixing is achieved by a combination of advection and diffusion. In particular, we perform a detailed numerical analysis of a model composed of turbulent advection, diffusive transport, and cyclic interactions among biological species in two spatial dimensions and discuss the circumstances under which biodiversity is maintained when external environmental conditions, such as resource supply, are uniform in space. Cyclic interactions are represented by a model with three competitors, resembling the children's game of rock-paper-scissors, whereas the flow field is obtained from a direct numerical simulation of two-dimensional turbulence with hyperviscosity. It is shown that the space-averaged dynamics undergoes bifurcations as the relative strengths of advection and diffusion compared to biological interactions are varied.
Turbulent plane Couette flow subject to strong system rotation
NASA Astrophysics Data System (ADS)
Bech, Knut H.; Andersson, Helge I.
1997-09-01
System rotation is known to substantially affect the mean flow pattern as well as the turbulence structure in rotating channel flows. In a numerical study of plane Couette flow rotating slowly about an axis aligned with the mean vorticity, Bech & Andersson (1996a) found that the turbulence level was damped in the presence of anticyclonic system rotation, in spite of the occurrence of longitudinal counter-rotating roll cells. Moreover, the turbulence anisotropy was practically unaffected by the weak rotation, for which the rotation number Ro, defined as the ratio of twice the imposed angular vorticity [Omega] to the shear rate of the corresponding laminar flow, was ±0.01. The aim of the present paper is to explore the effects of stronger anticyclonic system rotation on directly simulated turbulent plane Couette flow. Turbulence statistics like energy, enstrophy and Taylor lengthscales, both componental and directional, were computed from the statistically steady flow fields and supplemented by structural information obtained by conditional sampling.
Flight Tests of the Turbulence Prediction and Warning System (TPAWS)
NASA Technical Reports Server (NTRS)
Hamilton, David W.; Proctor, Fred H.; Ahmad, Nashat N.
2012-01-01
Flight tests of the National Aeronautics and Space Administration's Turbulence Prediction And Warning System (TPAWS) were conducted in the Fall of 2000 and Spring of 2002. TPAWS is a radar-based airborne turbulence detection system. During twelve flights, NASA's B-757 tallied 53 encounters with convectively induced turbulence. Analysis of data collected during 49 encounters in the Spring of 2002 showed that the TPAWS Airborne Turbulence Detection System (ATDS) successfully detected 80% of the events at least 30 seconds prior to the encounter, achieving FAA recommended performance criteria. Details of the flights, the prevailing weather conditions, and each of the turbulence events are presented in this report. Sensor and environmental characterizations are also provided.
Statistical energy conservation principle for inhomogeneous turbulent dynamical systems
Majda, Andrew J.
2015-01-01
Understanding the complexity of anisotropic turbulent processes over a wide range of spatiotemporal scales in engineering shear turbulence as well as climate atmosphere ocean science is a grand challenge of contemporary science with important societal impact. In such inhomogeneous turbulent dynamical systems there is a large dimensional phase space with a large dimension of unstable directions where a large-scale ensemble mean and the turbulent fluctuations exchange energy and strongly influence each other. These complex features strongly impact practical prediction and uncertainty quantification. A systematic energy conservation principle is developed here in a Theorem that precisely accounts for the statistical energy exchange between the mean flow and the related turbulent fluctuations. This statistical energy is a sum of the energy in the mean and the trace of the covariance of the fluctuating turbulence. This result applies to general inhomogeneous turbulent dynamical systems including the above applications. The Theorem involves an assessment of statistical symmetries for the nonlinear interactions and a self-contained treatment is presented below. Corollary 1 and Corollary 2 illustrate the power of the method with general closed differential equalities for the statistical energy in time either exactly or with upper and lower bounds, provided that the negative symmetric dissipation matrix is diagonal in a suitable basis. Implications of the energy principle for low-order closure modeling and automatic estimates for the single point variance are discussed below. PMID:26150510
Statistical energy conservation principle for inhomogeneous turbulent dynamical systems.
Majda, Andrew J
2015-07-21
Understanding the complexity of anisotropic turbulent processes over a wide range of spatiotemporal scales in engineering shear turbulence as well as climate atmosphere ocean science is a grand challenge of contemporary science with important societal impact. In such inhomogeneous turbulent dynamical systems there is a large dimensional phase space with a large dimension of unstable directions where a large-scale ensemble mean and the turbulent fluctuations exchange energy and strongly influence each other. These complex features strongly impact practical prediction and uncertainty quantification. A systematic energy conservation principle is developed here in a Theorem that precisely accounts for the statistical energy exchange between the mean flow and the related turbulent fluctuations. This statistical energy is a sum of the energy in the mean and the trace of the covariance of the fluctuating turbulence. This result applies to general inhomogeneous turbulent dynamical systems including the above applications. The Theorem involves an assessment of statistical symmetries for the nonlinear interactions and a self-contained treatment is presented below. Corollary 1 and Corollary 2 illustrate the power of the method with general closed differential equalities for the statistical energy in time either exactly or with upper and lower bounds, provided that the negative symmetric dissipation matrix is diagonal in a suitable basis. Implications of the energy principle for low-order closure modeling and automatic estimates for the single point variance are discussed below. PMID:26150510
Progress in Development of an Airborne Turbulence Detection System
NASA Technical Reports Server (NTRS)
Hamilton, David W.; Proctor, Fred H.
2006-01-01
Aircraft encounters with turbulence are the leading cause of in-flight injuries (Tyrvanas 2003) and have occasionally resulted in passenger and crew fatalities. Most of these injuries are caused by sudden and unexpected encounters with severe turbulence in and around convective activity (Kaplan et al 2005). To alleviate this problem, the Turbulence Prediction and Warning Systems (TPAWS) element of NASA s Aviation Safety program has investigated technologies to detect and warn of hazardous in-flight turbulence. This effort has required the numerical modeling of atmospheric convection: 1) for characterizing convectively induced turbulence (CIT) environments, 2) for defining turbulence hazard metrics, and 3) as a means of providing realistic three-dimensional data sets that can be used to test and evaluate turbulence detection sensors. The data sets are being made available to industry and the FAA for certification of future airborne turbulence-detection systems (ATDS) with warning capability. Early in the TPAWS project, a radar-based ATDS was installed and flight tested on NASA s research aircraft, a B-757. This ATDS utilized new algorithms and hazard metrics that were developed for use with existing airborne predictive windshear radars, thus avoiding the installation of new hardware. This system was designed to detect and warn of hazardous CIT even in regions with weak radar reflectivity (i.e. 5-15 dBz). Results from an initial flight test of the ATDS were discussed in Hamilton and Proctor (2002a; 2002b). In companion papers (Proctor et al 2002a; 2002b), a numerical simulation of the most significant encounter from that flight test was presented. Since the presentation of these papers a second flight test has been conducted providing additional cases for examination. In this paper, we will present results from NASA s flight test and a numerical model simulation of a turbulence environment encountered on 30 April 2002. Progress leading towards FAA certification of
Extended LES-PaSR model for simulation of turbulent combustion
NASA Astrophysics Data System (ADS)
Sabelnikov, V.; Fureby, C.
2013-03-01
In this work, a novel model for Large Eddy Simulations (LES) of high Reynolds moderate Damköhler number turbulent flames is proposed. The development is motivated by the need for more accurate and versatile LES combustion models for engineering applications such as jet engines. The model is based on the finite rate chemistry approach in which the filtered species equations of a reduced reaction mechanism are solved prior to closure modeling. The modeling of the filtered reaction rate provides the challenge: as most of the chemical activity, and thus also most of the exothermicity occurs on the subgrid scales, this model needs to be based on the properties of fine-scale turbulence and mixing and Arrhenius chemistry. The model developed here makes use of the similarities with the mathematical treatment of multiphase flows together with the knowledge of fine-scale turbulence and chemistry obtained by Direct Numerical Simulation (DNS) and experiments. In the model developed, equations are proposed for the fine-structure composition and volume fraction that are solved together with the LES equations for the resolved scales. If subgrid convection can be neglected, the proposed model simplifies to the Partially Stirred Reactor (PaSR) model. To validate the proposed LES model, comparisons with experimental data and other LES results are made, using other turbulence chemistry interaction models, for a lean premixed bluff-body stabilized flame.
Thermodynamics. II - The extended thermodynamic system
NASA Technical Reports Server (NTRS)
Zeleznik, F. J.
1981-01-01
The algebraic theory of thermodynamics developed in a previous paper is extended to include the algebraic structure that arises from the introduction of a physical body into the theory. The extension is based on very general definitions of both the thermodynamic states of a body and subsystems of that body. The algebraic analysis, which includes bodies in nonuniform states, shows that the set of all thermodynamic states of a body has the same algebraic structure as the set of thermodynamic states and that composite systems are induced by the algebraic structure of thermodynamic states. The analysis also justifies a variational treatment of thermodynamic bodies in uniform as well as nonuniform states. The variational calculation includes all conventional methods of calculation as special cases and helps to illuminate the origin and interpretation of the electrochemical potential.
System and Method for Finite Element Simulation of Helicopter Turbulence
NASA Technical Reports Server (NTRS)
McFarland, R. E. (Inventor); Dulsenberg, Ken (Inventor)
1999-01-01
The present invention provides a turbulence model that has been developed for blade-element helicopter simulation. This model uses an innovative temporal and geometrical distribution algorithm that preserves the statistical characteristics of the turbulence spectra over the rotor disc, while providing velocity components in real time to each of five blade-element stations along each of four blades. for a total of twenty blade-element stations. The simulator system includes a software implementation of flight dynamics that adheres to the guidelines for turbulence set forth in military specifications. One of the features of the present simulator system is that it applies simulated turbulence to the rotor blades of the helicopter, rather than to its center of gravity. The simulator system accurately models the rotor penetration into a gust field. It includes time correlation between the front and rear of the main rotor, as well as between the side forces felt at the center of gravity and at the tail rotor. It also includes features for added realism, such as patchy turbulence and vertical gusts in to which the rotor disc penetrates. These features are realized by a unique real time implementation of the turbulence filters. The new simulator system uses two arrays one on either side of the main rotor to record the turbulence field and to produce time-correlation from the front to the rear of the rotor disc. The use of Gaussian Interpolation between the two arrays maintains the statistical properties of the turbulence across the rotor disc. The present simulator system and method may be used in future and existing real-time helicopter simulations with minimal increase in computational workload.
AMBIPOLAR DIFFUSION HEATING IN TURBULENT SYSTEMS
Li, Pak Shing; Myers, Andrew; McKee, Christopher F. E-mail: atmyers@berkeley.edu
2012-11-20
The temperature of the gas in molecular clouds is a key determinant of the characteristic mass of star formation. Ambipolar diffusion (AD) is considered one of the most important heating mechanisms in weakly ionized molecular clouds. In this work, we study the AD heating rate using two-fluid turbulence simulations and compare it with the overall heating rate due to turbulent dissipation. We find that for observed molecular clouds, which typically have Alfven Mach numbers of {approx}1 and AD Reynolds numbers of {approx}20, about 70% of the total turbulent dissipation is in the form of AD heating. AD has an important effect on the length scale where energy is dissipated: when AD heating is strong, most of the energy in the cascade is removed by ion-neutral drift, with a comparatively small amount of energy making it down to small scales. We derive a relation for the AD heating rate that describes the results of our simulations to within a factor of two. Turbulent dissipation, including AD heating, is generally less important than cosmic-ray heating in molecular clouds, although there is substantial scatter in both.
Atmospheric turbulence and sensor system effects on biometric algorithm performance
NASA Astrophysics Data System (ADS)
Espinola, Richard L.; Leonard, Kevin R.; Byrd, Kenneth A.; Potvin, Guy
2015-05-01
Biometric technologies composed of electro-optical/infrared (EO/IR) sensor systems and advanced matching algorithms are being used in various force protection/security and tactical surveillance applications. To date, most of these sensor systems have been widely used in controlled conditions with varying success (e.g., short range, uniform illumination, cooperative subjects). However the limiting conditions of such systems have yet to be fully studied for long range applications and degraded imaging environments. Biometric technologies used for long range applications will invariably suffer from the effects of atmospheric turbulence degradation. Atmospheric turbulence causes blur, distortion and intensity fluctuations that can severely degrade image quality of electro-optic and thermal imaging systems and, for the case of biometrics technology, translate to poor matching algorithm performance. In this paper, we evaluate the effects of atmospheric turbulence and sensor resolution on biometric matching algorithm performance. We use a subset of the Facial Recognition Technology (FERET) database and a commercial algorithm to analyze facial recognition performance on turbulence degraded facial images. The goal of this work is to understand the feasibility of long-range facial recognition in degraded imaging conditions, and the utility of camera parameter trade studies to enable the design of the next generation biometrics sensor systems.
Extended Solar System Structures Observed by WISE
NASA Astrophysics Data System (ADS)
Sykes, Mark V.; Masci, Frank; Cutri, Roc; Walker, Russell; Mainzer, Amy; Bauer, James; Stevenson, Rachel; Tricarico, Pasquale
2014-11-01
Extended structures associated with recent asteroid collisions and comets were detected by the Infrared Astronomical Satellite, which conducted the first survey of the thermal emission of the sky in 1983. Twenty-seven years later, the Wide-field Infrared Survey Explorer (WISE), conducted a more sensitive survey of the sky at wavelengths spanning the shorter IRAS bandpasses and detected many of these same structures. Initial identifications include asteroid dust bands associated with collisions giving rise to the Karin and Beagle clusters within the Koronis and Themis asteroid families, respectively. An additional pair of bands is associated with the collision giving rise to the Veritas asteroid family. Comet trails associated with short-period comets have also been observed. Type 2 trails, detected by IRAS and possibly associated with asteroid collisions within the past few thousand years, have yet to be identified. Because WISE is significantly more sensitive than IRAS in the mid-infrared, it has detected some trails extending much further over their orbits and will greatly expand the catalog of trails detected in addition to those observed by IRAS and Spitzer (the latter by targeted observations). WISE and the yet more sensitive NEOCAM survey telescope will provide important insights into the recent collisional history of the asteroid belt and the nature and evolution of comets.
NASA Astrophysics Data System (ADS)
Yang, X. I. A.; Meneveau, C.; Marusic, I.; Biferale, L.
2016-08-01
In wall-bounded turbulence, the moment generating functions (MGFs) of the streamwise velocity fluctuations
Response of wind shear warning systems to turbulence with implication of nuisance alerts
NASA Technical Reports Server (NTRS)
Bowles, Roland L.
1988-01-01
The objective was to predict the inherent turbulence response characteristics of candidate wind shear warning system concepts and to assess the potential for nuisance alerts. Information on the detection system and associated signal processing, physical and mathematical models, wind shear factor root mean square turbulence response and the standard deviation of the wind shear factor due to turbulence is given in vugraph form.
Low current extended duration spark ignition system
Waters, Stephen Howard; Chan, Anthony Kok-Fai
2005-08-30
A system for firing a spark plug is disclosed. The system includes a timing controller configured to send a first timing signal and a second timing signal. The system also includes an ignition transformer having a primary winding and a secondary winding and a spark-plug that is operably associated with the secondary winding. A first switching element is disposed between the timing controller and the primary winding of the ignition transformer. The first switching element controls a supply of power to the primary winding based on the first timing signal. Also, a second switching element is disposed between the timing controller and the primary winding of the ignition transformer. The second switching element controls the supply of power to the primary winding based on the second timing signal. A method for firing a spark plug is also disclosed.
Extended length microchannels for high density high throughput electrophoresis systems
Davidson, James C.; Balch, Joseph W.
2000-01-01
High throughput electrophoresis systems which provide extended well-to-read distances on smaller substrates, thus compacting the overall systems. The electrophoresis systems utilize a high density array of microchannels for electrophoresis analysis with extended read lengths. The microchannel geometry can be used individually or in conjunction to increase the effective length of a separation channel while minimally impacting the packing density of channels. One embodiment uses sinusoidal microchannels, while another embodiment uses plural microchannels interconnected by a via. The extended channel systems can be applied to virtually any type of channel confined chromatography.
Modeling mesoscopic phenomena in extended dynamical systems
Bishop, A.; Lomdahl, P.; Jensen, N.G.; Cai, D.S.; Mertenz, F.; Konno, Hidetoshi; Salkola, M.
1997-08-01
This is the final report of a three-year, Laboratory-Directed Research and Development project at the Los Alamos National Laboratory (LANL). We have obtained classes of nonlinear solutions on curved geometries that demonstrate a novel interplay between topology and geometric frustration relevant for nanoscale systems. We have analyzed the nature and stability of localized oscillatory nonlinear excitations (multi-phonon bound states) on discrete nonlinear chains, including demonstrations of successful perturbation theories, existence of quasiperiodic excitations, response to external statistical time-dependent fields and point impurities, robustness in the presence of quantum fluctuations, and effects of boundary conditions. We have demonstrated multi-timescale effects for nonlinear Schroedinger descriptions and shown the success of memory function approaches for going beyond these approximations. In addition we have developed a generalized rate-equation framework that allows analysis of the important creation/annihilation processes in driven nonlinear, nonequilibiium systems.
CEBAF NEW DIGITAL LLRF SYSTEM EXTENDED FUNCTIONALITY
T. Allison; K. Davis; H. Dong; C. Hovater; L. King; J. Musson; T. Plawski
2007-06-18
The new digital LLRF system for the CEBAF 12GeV accelerator will perform a variety of tasks, beyond field control [1]. In this paper we present the superconducting cavity resonance control system designed to minimize RF power during gradient ramp and to minimize RF power during steady state operation. Based on the calculated detuning angle, which represents the difference between reference and cavity resonance frequency, the cavity length will be adjusted with a mechanical tuner. The tuner has two mechanical driving devices, a stepper motor and a piezo-tuner, to yield a combination of coarse and fine control. Although LLRF piezo processing speed can achieve 10 kHz bandwidth, only 10 Hz speed is needed for 12 GeV upgrade. There will be a number of additional functions within the LLRF system; heater controls to maintain cryomodule's heat load balance, ceramic window temperature monitoring, waveguide vacuum interlocks, ARC detector interlock and quench detection. The additional functions will be divided between the digital board, incorporating an Altera FPGA and an embedded EPICS IOC. This paper will also address hardware evolution and test results performed with different SC cavities.
Solar system plasma Turbulence: Observations, inteRmittency and Multifractals
NASA Astrophysics Data System (ADS)
Echim, Marius M.
2016-04-01
The FP7 project STORM is funded by the European Commission to "add value to existing data bases through a more comprehensive interpretation". STORM targets plasma and magnetic field databases collected in the solar wind (Ulysses and also some planetary missions), planetary magnetospheres (Venus Express, Cluster, a few orbits from Cassini), cometary magnetosheaths (e.g. Haley from Giotto observations). The project applies the same package of analysis methods on geomagnetic field observations from ground and on derived indices (e.g. AE, AL, AU, SYM-H). The analysis strategy adopted in STORM is built on the principle of increasing complexity, from lower (like, e.g., the Power Spectral Density - PSD) to higher order analyses (the Probability Distribution Functions - PDFs, Structure Functions - SFs, Fractals and Multifractals - MFs). Therefore STORM targets not only the spectral behavior of turbulent fluctuations but also their topology and scale behavior inferred from advanced mathematical algorithms and geometrical-like analogs. STORM started in January 2013 and ended in December 2015. We will report on a selection of scientific and technical achievements and will highlight: (1) the radial evolution of solar wind turbulence and intermittency based on Ulysses data with some contributions from Venus Express and Cluster; (2) comparative study of fast and slow wind turbulence and intermittency at solar minimum; (3) comparative study of the planetary response (Venus and Earth magnetosheaths) to turbulent solar wind; (4) the critical behavior of geomagnetic fluctuations and indices; (5) an integrated library for non-linear analysis of time series that includes all the approaches adopted in STORM to investigate solar system plasma turbulence. STORM delivers an unprecedented volume of analysed data for turbulence. The project made indeed a systematic survey, orbit by orbit, of data available from ESA repositories and Principal Investigators and provides results ordered as a
Extended professional development for systemic curriculum reform
NASA Astrophysics Data System (ADS)
Kubitskey, Mary Elizabeth
Education standards call for adopting inquiry science instruction. Successful adoption requires professional development (PD) to support teachers, increasing the need for research on PD. This dissertation examines the question: What is the influence of high quality, curriculum aligned, long-term group workshops and related practice on teacher learning? I focus on the following subquestions: (1) What is the influence of high quality, curriculum aligned, long-term, group workshops on teacher knowledge and beliefs? (2) What is the impact of the workshops on teacher practice? (3) What is the influence of practice on student response? (4) What is the impact of practice and student response on teacher knowledge and beliefs? I focus on an instance of PD nested within a long-term systemic change initiative, tracing eleven science teachers' learning from workshops and associated enactments. The data included pre and post-unit interviews (n=22), two post-workshop interviews (n=17), workshop observations (n=2), classroom observations (n=24) and student work (n=351). I used mixed-methods analysis. Quantitative analysis measured teacher learning by comparing pre and post-unit interview ratings. Qualitative components included two case study approaches: logic model technique and cross-case synthesis, examining teacher learning within and across teachers. The findings suggested a teacher-learning model incorporating PD, teacher knowledge, beliefs, practice and student response. PD impacts teachers' knowledge by providing teachers with new knowledge, adapting previous knowledge, or convincing them to value existing knowledge they chose not to use. The workshops can influence beliefs, providing teachers with confidence and motivation to adopt the practice. Beliefs can mediate how knowledge manifested itself in practice that, in turn, impacts students' response. Student response influences the teachers' beliefs, either reinforcing or motivating change. This teacher-learning model
Neuroanatomy of the Extended Circadian Rhythm System
Morin, Lawrence P
2012-01-01
The suprachiasmatic nucleus (SCN), site of the primary clock in the circadian rhythm system, has three major afferent connections. The most important consists of a retinohypothalamic projection through which photic information, received by classical rod/cone photoreceptors and intrinsically photoreceptive retinal ganglion cells, gains access to the clock. This information influences phase and period of circadian rhythms. The two other robust afferent projections are the median raphe serotonergic pathway and the geniculohypothalamic (GHT), NPY-containing pathway from the thalamic intergeniculate leaflet (IGL). Beyond this simple framework, the number of anatomical routes that could theoretically be involved in rhythm regulation is enormous, with the SCN projecting to 15 regions and being directly innervated by about 35. If multisynaptic afferents to the SCN are included, the number expands to approximately brain 85 areas providing input to the SCN. The IGL, a known contributor to circadian rhythm regulation, has a still greater level of complexity. This nucleus connects abundantly throughout the brain (to approximately 100 regions) by pathways that are largely bilateral and reciprocal. Few of these sites have been evaluated for their contributions to circadian rhythm regulation, although most have a theoretical possibility of doing so via the GHT. The anatomy of IGL connections suggests that one of its functions may be regulation of eye movements during sleep. Together, neural circuits of the SCN and IGL are complex and interconnected. As yet, few have been tested with respect to their involvement in rhythm regulation. PMID:22766204
Shock-induced turbulent flow in baffle systems
Kuhl, A.L.; Reichenbach, H.
1993-07-01
Experiments are described on shock propagation through 2-D aligned and staggered baffle systems. Flow visualization was provided by shadow and schlieren photography, recorded by the Cranz-Schardin camera. Also single-frame, infinite-fringe, color interferograms were used. Intuition suggests that this is a rather simple 2-D shock diffraction problem. However, flow visualization reveals that the flow rapidly evolved into a complex 3-D turbulent mixing problem. Mushroom-shaped mixing regions blocked the flow into the next baffle orifice. Thus energy was transferred from the directed kinetic energy (induced by the shock) to rotational energy of turbulent mixing, and then dissipated by molecular effects. These processes dramatically dissipate the strength of the shock wave. The experiments provide an excellent test case that could be used to assess the accuracy of computer code calculations of such problems.
The role of extended conical intersection seams in photochromic systems
NASA Astrophysics Data System (ADS)
Boggio-Pasqua, Martial; Bearpark, Michael J.; Robb, Michael A.
2015-01-01
We describe the role of conical intersections in the mechanism of photochromic molecular systems. In particular, the extended nature of the crossing seam associated with a conical intersection is highlighted and its significance on dihydroazulenes and diarylethenes photochromism is explained.
Mooring system of ocean turbulence observation based on submerged buoy
NASA Astrophysics Data System (ADS)
Song, Da-lei; Sun, Jing-jing; Xue, Bing; Jiang, Qian-li; Wu, Bing-wei
2013-06-01
A comparison experiment has been taken in the Kiaochow Bay between a newly designed mooring turbulence observation instrument (MTOI) and microstructure profiler MSS60 made by Sea & Sun. The whole observing system is based on a submerged buoy, in which the turbulence observation instrument is embedded, with a streamline-shape floating body, which is made of buoyancy material of glass microsphere. For the movement of seawater and the cable shaking strongly anytime influence the behaviors of the floating body, the accelerate sensors are used for the vibration measurement in the instrument together with the shear probe sensor. Both the vibration data and the shear data are acquired by the instrument at the same time. During data processing, the vibration signals can be removed and leave the shear data which we really need. In order to prove the reliability of the new turbulence instrument MTOI, a comparison experiment was designed. The measuring conditions are the same both in time and space. By this way, the two groups of data are comparable. In this paper, the conclusion gives a good similarity of 0.93 for the two groups of shear data in dissipation rate. The processing of the data acquired by MTOI is based on the cross-spectrum analysis, and the dissipation rate of it matches the Nasmyth spectrum well.
Calibration of NASA Turbulent Air Motion Measurement System
NASA Technical Reports Server (NTRS)
Barrick, John D. W.; Ritter, John A.; Watson, Catherine E.; Wynkoop, Mark W.; Quinn, John K.; Norfolk, Daniel R.
1996-01-01
A turbulent air motion measurement system (TAMMS) was integrated onboard the Lockheed 188 Electra airplane (designated NASA 429) based at the Wallops Flight Facility in support of the NASA role in global tropospheric research. The system provides air motion and turbulence measurements from an airborne platform which is capable of sampling tropospheric and planetary boundary-layer conditions. TAMMS consists of a gust probe with free-rotating vanes mounted on a 3.7-m epoxy-graphite composite nose boom, a high-resolution inertial navigation system (INS), and data acquisition system. A variation of the tower flyby method augmented with radar tracking was implemented for the calibration of static pressure position error and air temperature probe. Additional flight calibration maneuvers were performed remote from the tower in homogeneous atmospheric conditions. System hardware and instrumentation are described and the calibration procedures discussed. Calibration and flight results are presented to illustrate the overall ability of the system to determine the three-component ambient wind fields during straight and level flight conditions.
NASA Astrophysics Data System (ADS)
Ouyang, Bing; Hou, Weilin; Gong, Cuiling; Caimi, Frank M.; Dalgleish, Fraser R.; Vuorenkoski, Anni K.
2016-05-01
The Compressive Line Sensing (CLS) active imaging system has been demonstrated to be effective in scattering mediums, such as turbid coastal water through simulations and test tank experiments. Since turbulence is encountered in many atmospheric and underwater surveillance applications, a new CLS imaging prototype was developed to investigate the effectiveness of the CLS concept in a turbulence environment. Compared with earlier optical bench top prototype, the new system is significantly more robust and compact. A series of experiments were conducted at the Naval Research Lab's optical turbulence test facility with the imaging path subjected to various turbulence intensities. In addition to validating the system design, we obtained some unexpected exciting results - in the strong turbulence environment, the time-averaged measurements using the new CLS imaging prototype improved both SNR and resolution of the reconstructed images. We will discuss the implications of the new findings, the challenges of acquiring data through strong turbulence environment, and future enhancements.
Ensemble Kalman filters for dynamical systems with unresolved turbulence
Grooms, Ian; Lee, Yoonsang; Majda, Andrew J.
2014-09-15
Ensemble Kalman filters are developed for turbulent dynamical systems where the forecast model does not resolve all the active scales of motion. Coarse-resolution models are intended to predict the large-scale part of the true dynamics, but observations invariably include contributions from both the resolved large scales and the unresolved small scales. The error due to the contribution of unresolved scales to the observations, called ‘representation’ or ‘representativeness’ error, is often included as part of the observation error, in addition to the raw measurement error, when estimating the large-scale part of the system. It is here shown how stochastic superparameterization (a multiscale method for subgridscale parameterization) can be used to provide estimates of the statistics of the unresolved scales. In addition, a new framework is developed wherein small-scale statistics can be used to estimate both the resolved and unresolved components of the solution. The one-dimensional test problem from dispersive wave turbulence used here is computationally tractable yet is particularly difficult for filtering because of the non-Gaussian extreme event statistics and substantial small scale turbulence: a shallow energy spectrum proportional to k{sup −5/6} (where k is the wavenumber) results in two-thirds of the climatological variance being carried by the unresolved small scales. Because the unresolved scales contain so much energy, filters that ignore the representation error fail utterly to provide meaningful estimates of the system state. Inclusion of a time-independent climatological estimate of the representation error in a standard framework leads to inaccurate estimates of the large-scale part of the signal; accurate estimates of the large scales are only achieved by using stochastic superparameterization to provide evolving, large-scale dependent predictions of the small-scale statistics. Again, because the unresolved scales contain so much energy
Modeling atmospheric turbulence effects on ground-based telescope systems
Flatte, S.M.; Bradford, L.W.; Max, C.E.
1994-12-31
Bester et al. report measurements of atmospheric fluctuations made with the Infrared Spatial Interferometer, which indicated behavior not in accord with the standard Kolmogorov model with only a single constant wind velocity. The numerical simulations use relatively complex models of the atmosphere to investigate both Kolmogorov and non-Kolmogorov models. The authors find that the measurements of Bester et al. for light passing through the upper atmosphere are within the limits of behavior for Kolmogorov models, but often only if the outer scale of turbulent fluctuations is between 15 to 100 meters. The possibility that the measured behavior might be non-Kolmogorov is not excluded. They also examine measurements made along short paths in the surface boundary layer, where some measurements of Bester et al. showed variations in the atmospheric fluctuations with seeing conditions which appeared to be non-Kolmogorov. These variations can perhaps be explained by standard models, but require that seeing improve with increasing wind speed in the surface layer. They discuss some other measurements which lend some support to that idea. However, they cannot exclude non-Kolmogorov behavior. They find that meteorological data is needed concurrent with astronomical observations, to help constrain the models. The size of the outer scale, the wind velocity profile and the turbulence spectrum are important to the ultimate capabilities of interferometers and other systems with adaptive optics.
Market Assessment of Forward-Looking Turbulence Sensing Systems
NASA Technical Reports Server (NTRS)
Kauffmann, Paul; Sousa-Poza, Andres
2001-01-01
In recognition of the importance of turbulence mitigation as a tool to improve aviation safety, NASA's Aviation Safety Program developed a Turbulence Detection and Mitigation Sub-element. The objective of this effort is to develop highly reliable turbulence detection technologies for commercial transport aircraft to sense dangerous turbulence with sufficient time warning so that defensive measures can be implemented and prevent passenger and crew injuries. Current research involves three forward sensing products to improve the cockpit awareness of possible turbulence hazards. X-band radar enhancements will improve the capabilities of current weather radar to detect turbulence associated with convective activity. LIDAR (Light Detection and Ranging) is a laser-based technology that is capable of detecting turbulence in clear air. Finally, a possible Radar-LIDAR hybrid sensor is envisioned to detect the full range of convective and clear air turbulence. To support decisions relating to the development of these three forward-looking turbulence sensor technologies, the objective of this study was defined as examination of cost and implementation metrics. Tasks performed included the identification of cost factors and certification issues, the development and application of an implementation model, and the development of cost budget/targets for installing the turbulence sensor and associated software devices into the commercial transport fleet.
[Extending the palliative approach across the French health system].
Mino, Jean-Christophe
2015-11-01
The care provision for people at the end of life requires a palliative care approach to be extended across the whole healthcare system. Access to palliative care for everyone requires training for professionals, support for specialised structures and teams as well as clear political will. PMID:26567066
Juarez, Juan C; Brown, David M; Young, David W
2014-05-19
Current Strehl ratio models for actively compensated free-space optical communications terminals do not accurately predict system performance under strong turbulence conditions as they are based on weak turbulence theory. For evaluation of compensated systems, we present an approach for simulating the Strehl ratio with both low-order (tip/tilt) and higher-order (adaptive optics) correction. Our simulation results are then compared to the published models and their range of turbulence validity is assessed. Finally, we propose a new Strehl ratio model and antenna gain equation that are valid for general turbulence conditions independent of the degree of compensation. PMID:24921373
Approaching complexity by stochastic methods: From biological systems to turbulence
NASA Astrophysics Data System (ADS)
Friedrich, Rudolf; Peinke, Joachim; Sahimi, Muhammad; Reza Rahimi Tabar, M.
2011-09-01
This review addresses a central question in the field of complex systems: given a fluctuating (in time or space), sequentially measured set of experimental data, how should one analyze the data, assess their underlying trends, and discover the characteristics of the fluctuations that generate the experimental traces? In recent years, significant progress has been made in addressing this question for a class of stochastic processes that can be modeled by Langevin equations, including additive as well as multiplicative fluctuations or noise. Important results have emerged from the analysis of temporal data for such diverse fields as neuroscience, cardiology, finance, economy, surface science, turbulence, seismic time series and epileptic brain dynamics, to name but a few. Furthermore, it has been recognized that a similar approach can be applied to the data that depend on a length scale, such as velocity increments in fully developed turbulent flow, or height increments that characterize rough surfaces. A basic ingredient of the approach to the analysis of fluctuating data is the presence of a Markovian property, which can be detected in real systems above a certain time or length scale. This scale is referred to as the Markov-Einstein (ME) scale, and has turned out to be a useful characteristic of complex systems. We provide a review of the operational methods that have been developed for analyzing stochastic data in time and scale. We address in detail the following issues: (i) reconstruction of stochastic evolution equations from data in terms of the Langevin equations or the corresponding Fokker-Planck equations and (ii) intermittency, cascades, and multiscale correlation functions.
Extended phase space description of human-controlled systems dynamics
NASA Astrophysics Data System (ADS)
Zgonnikov, Arkady; Lubashevsky, Ihor
2014-03-01
Humans are often incapable of precisely identifying and implementing the desired control strategy in controlling unstable dynamical systems. That is, the operator of a dynamical system treats the current control effort as acceptable even if it deviates slightly from the desired value, and starts correcting the actions only when the deviation has become evident. We argue that the standard Newtonian approach does not allow such behavior to be modeled. Instead, the physical phase space of a controlled system should be extended with an independent phase variable characterizing the motivated actions of the operator. The proposed approach is illustrated via a simple non-Newtonian model capturing the operators' fuzzy perception of their own actions. The properties of the model are investigated analytically and numerically; the results confirm that the extended phase space may aid in capturing the intricate dynamical properties of human-controlled systems.
Extending the infoway benefits evaluation framework for health information systems.
Lau, Francis
2009-01-01
A proposal is made that extends the current Canada Health Infoway Benefits Evaluation (BE) Framework for Health Information Systems (HIS) being deployed in Canada. The current BE framework takes a micro view of HIS quality, use and impact at the local level whereas the extended framework takes into account the broader socio-organizational and contextual aspects known as the meso and macro views of HIS deployment. The meso view addresses the people, organization, network and implementation dimensions. The macro view focuses on the contextual dimensions of technology standard, funding/incentive, legislation/policy and professional practice. Validation of this extended BE framework is being planned through a comparative review of recent HIS evaluation literature, a Delphi-consensus process with HIS experts and users, and multiple validation studies with recent HIS implementation projects in British Columbia. PMID:19380969
Cheng, Mingjian; Zhang, Yixin; Gao, Jie; Wang, Fei; Zhao, Fengsheng
2014-06-20
We model the average channel capacity of optical wireless communication systems for cases of weak to strong turbulence channels, using the exponentiation Weibull distribution model. The joint effects of the beam wander and spread, pointing errors, atmospheric attenuation, and the spectral index of non-Kolmogorov turbulence on system performance are included. Our results show that the average capacity decreases steeply as the propagation length L changes from 0 to 200 m and decreases slowly down or tends to a stable value as the propagation length L is greater than 200 m. In the weak turbulence region, by increasing the detection aperture, we can improve the average channel capacity and the atmospheric visibility as an important issue affecting the average channel capacity. In the strong turbulence region, the increase of the radius of the detection aperture cannot reduce the effects of the atmospheric turbulence on the average channel capacity, and the effect of atmospheric visibility on the channel information capacity can be ignored. The effect of the spectral power exponent on the average channel capacity in the strong turbulence region is higher than weak turbulence region. Irrespective of the details determining the turbulent channel, we can say that pointing errors have a significant effect on the average channel capacity of optical wireless communication systems in turbulence channels. PMID:24979434
Estimating Power System Dynamic States Using Extended Kalman Filter
Huang, Zhenyu; Schneider, Kevin P.; Nieplocha, Jaroslaw; Zhou, Ning
2014-10-31
Abstract—The state estimation tools which are currently deployed in power system control rooms are based on a steady state assumption. As a result, the suite of operational tools that rely on state estimation results as inputs do not have dynamic information available and their accuracy is compromised. This paper investigates the application of Extended Kalman Filtering techniques for estimating dynamic states in the state estimation process. The new formulated “dynamic state estimation” includes true system dynamics reflected in differential equations, not like previously proposed “dynamic state estimation” which only considers the time-variant snapshots based on steady state modeling. This new dynamic state estimation using Extended Kalman Filter has been successfully tested on a multi-machine system. Sensitivity studies with respect to noise levels, sampling rates, model errors, and parameter errors are presented as well to illustrate the robust performance of the developed dynamic state estimation process.
Wind Shear/Turbulence Inputs to Flight Simulation and Systems Certification
NASA Technical Reports Server (NTRS)
Bowles, Roland L. (Editor); Frost, Walter (Editor)
1987-01-01
The purpose of the workshop was to provide a forum for industry, universities, and government to assess current status and likely future requirements for application of flight simulators to aviation safety concerns and system certification issues associated with wind shear and atmospheric turbulence. Research findings presented included characterization of wind shear and turbulence hazards based on modeling efforts and quantitative results obtained from field measurement programs. Future research thrusts needed to maximally exploit flight simulators for aviation safety application involving wind shear and turbulence were identified. The conference contained sessions on: Existing wind shear data and simulator implementation initiatives; Invited papers regarding wind shear and turbulence simulation requirements; and Committee working session reports.
Turbulence Measurements by the DC-8 Meteorological Measurement System
NASA Technical Reports Server (NTRS)
Chan, K. R.; Dean-Day, J.; Bowen, S. W.; Bui, T. P.; Chan, K. Roland (Technical Monitor)
1997-01-01
The instrumentation of a new MMS on the DC-8 aircraft is briefly described. Methods to compute and evaluate the turbulent dissipation rate epsilon, based on theory and MMS data, are discussed. Examples of turbulence measurements during encounters of a wake vortex, wave clouds, persistent contrails, mountain are gravity waves are illustrated.
Extended Duration Orbiter (EDO) Improved Waste Collection System (IWCS)
NASA Technical Reports Server (NTRS)
1992-01-01
This high angle overall view shows the top side components of the Extended Duration Orbiter (EDO) Waste Collection System (WCS) scheduled to fly aboard NASA's Endeavour, Orbiter Vehicle (OV) 105, for the STS-54 mission. Detailed Test Objective 662, Extended duration orbiter WCS evaluation, will verify the design of the new EDO WCS under microgravity conditions for a prolonged period. OV-105 has been modified with additional structures in the waste management compartment (WMC) and additional avionics to support/restrain the EDO WCS. Among the advantages the new IWCS is hoped to have over the currect WCS are greater dependability, better hygiene, virtually unlimited capacity, and more efficient preparation between shuttle missions. Unlike the previous WCS, the improved version will not have to be removed from the spacecraft to be readied for the next flight. The WCS was documented in JSC's Crew Systems Laboratory Bldg 7.
Extended Duration Orbiter (EDO) Improved Waste Collection System (IWCS)
NASA Technical Reports Server (NTRS)
1992-01-01
This overall front view shows the Extended Duration Orbiter (EDO) Waste Collection System (WCS) scheduled to fly aboard NASA's Endeavour, Orbiter Vehicle (OV) 105, for the STS-54 mission. Detailed Test Objective 662, Extended duration orbiter WCS evaluation, will verify the design of the new EDO WCS under microgravity conditions for a prolonged period. OV-105 has been modified with additional structures in the waste management compartment (WMC) and additional avionics to support/restrain the EDO WCS. Among the advantages the new IWCS is hoped to have over the currect WCS are greater dependability, better hygiene, virtually unlimited capacity, and more efficient preparation between shuttle missions. Unlike the previous WCS, the improved version will not have to be removed from the spacecraft to be readied for the next flight. The WCS was documented in JSC's Crew Systems Laboratory Bldg 7.
Extended Darknet: Multi-Dimensional Internet Threat Monitoring System
NASA Astrophysics Data System (ADS)
Shimoda, Akihiro; Mori, Tatsuya; Goto, Shigeki
Internet threats caused by botnets/worms are one of the most important security issues to be addressed. Darknet, also called a dark IP address space, is one of the best solutions for monitoring anomalous packets sent by malicious software. However, since darknet is deployed only on an inactive IP address space, it is an inefficient way for monitoring a working network that has a considerable number of active IP addresses. The present paper addresses this problem. We propose a scalable, light-weight malicious packet monitoring system based on a multi-dimensional IP/port analysis. Our system significantly extends the monitoring scope of darknet. In order to extend the capacity of darknet, our approach leverages the active IP address space without affecting legitimate traffic. Multi-dimensional monitoring enables the monitoring of TCP ports with firewalls enabled on each of the IP addresses. We focus on delays of TCP syn/ack responses in the traffic. We locate syn/ack delayed packets and forward them to sensors or honeypots for further analysis. We also propose a policy-based flow classification and forwarding mechanism and develop a prototype of a monitoring system that implements our proposed architecture. We deploy our system on a campus network and perform several experiments for the evaluation of our system. We verify that our system can cover 89% of the IP addresses while darknet-based monitoring only covers 46%. On our campus network, our system monitors twice as many IP addresses as darknet.
The performance of heterodyne detection system for partially coherent beams in turbulent atmosphere
NASA Astrophysics Data System (ADS)
Chengqiang, Li; Tingfeng, Wang; Heyong, Zhang; Jingjiang, Xie; Lisheng, Liu; Shuai, Zhao; Jin, Guo
2015-12-01
The performance of heterodyne system is discussed for partially coherent beams in turbulent atmosphere by introducing turbulence spectrum of refractive-index fluctuations. Several analytic formulae for the heterodyne detection system using the partially coherent Gaussian Schell-model beam are presented. Based on Tatarskii spectrum model, some numerical results are given for the variation in the heterodyne efficiency with the misalignment angle, detector diameter, turbulence conditions, and parameters of the overlapping beams. According to the numerical results, we find that the turbulent atmosphere degrades the heterodyne efficiency significantly, and the variation in heterodyne efficiency is even slower against the misalignment angle in turbulence. For the deterministic received signal and the detector, the performance of the heterodyne detection can be adjusted by controlling the local oscillator signal parameters.
Extended space expectation values in quantum dynamical system evolutions
Demiralp, Metin
2014-10-06
The time variant power series expansion for the expectation value of a given quantum dynamical operator is well-known and well-investigated issue in quantum dynamics. However, depending on the operator and Hamiltonian singularities this expansion either may not exist or may not converge for all time instances except the beginning of the evolution. This work focuses on this issue and seeks certain cures for the negativities. We work in the extended space obtained by adding all images of the initial wave function under the system Hamiltonian’s positive integer powers. This requires the introduction of certain appropriately defined weight operators. The resulting better convergence in the temporal power series urges us to call the new defined entities “extended space expectation values” even though they are constructed over certain weight operators and are somehow pseudo expectation values.
Gaussianity versus intermittency in solar system plasma turbulence
NASA Astrophysics Data System (ADS)
Echim, M.
2014-12-01
Statistical properties of plasma and magnetic field fluctuations exhibit features linked with the dynamics of the targeted system and sometimes with the physical processes that are at the origin of these fluctuations. Intermittency is sometimes discussed in terms of non-Gaussianity of the Probability Distribution Functions (PDFs) of fluctuations for ranges of spatio/temporal scales. Some examples of self-similarity have been however shown for PDFs whose wings are not Gaussian. In this study we discuss intermittency in terms of non-Gaussianity as well as scale dependence of the higher order moments of PDFs, in particular the flatness. We use magnetic field and plasma data from several space missions, in the solar wind (Ulysses, Cluster, and Venus Express), and in the planetary magnetosheaths (Cluster and Venus Express). We analyze Ulysses data that satisfy a consolidated set of selection criteria able to identify "pure" fast and slow wind. We investigate Venus Express data close to the orbital apogee, in the solar wind, at 0.72 AU, and in the Venus magnetosheath. We study Cluster data in the solar wind (for time intervals not affected by planetary ions effects), and the magnetosheath. We organize our results in three solar wind data bases (one for the solar maximum, 1999-2001, two for the solar minimum, 1997-1998 and respectively, 2007-2008), and two planetary databases (one for the solar maximum, 2000-2001, that includes PDFs obtained in the terrestrial magnetosphere, and one for the solar minimum, 2007-2008, that includes PDFs obtained in the terrestrial and Venus magnetospheres and magnetosheaths). In addition to investigating the statistical properties of fluctuations for the minimum and maximum of the solar cycle we also analyze the similarities and differences between fast and slow wind. We emphasize the importance of our data survey and analysis in the context of understanding the solar wind turbulence and complexity, and the exploitation of data bases and as
Extended Kepler-Coulomb quantum superintegrable systems in three dimensions
NASA Astrophysics Data System (ADS)
Kalnins, E. G.; Kress, J. M.; Miller, W., Jr.
2013-03-01
The quantum Kepler-Coulomb system in three dimensions is well known to be second order superintegrable, with a symmetry algebra that closes polynomially under commutators. This polynomial closure is also typical for second order superintegrable systems in 2D and for second order systems in 3D with nondegenerate (four-parameter) potentials. However, the degenerate three-parameter potential for the 3D Kepler-Coulomb system (also second order superintegrable) is an exception, as its symmetry algebra does not close polynomially. The 3D four-parameter potential for the extended Kepler-Coulomb system is not even second order superintegrable, but Verrier and Evans (2008 J. Math. Phys. 49 022902) showed it was fourth order superintegrable, and Tanoudis and Daskaloyannis (2011 arXiv:11020397v1) showed that, if a second fourth order symmetry is added to the generators, the symmetry algebra closes polynomially. Here, based on the Tremblay, Turbiner and Winternitz construction, we consider an infinite class of quantum extended Kepler-Coulomb three- and four-parameter systems indexed by a pair of rational numbers (k1, k2) and reducing to the usual systems when k1 = k2 = 1. We show these systems to be superintegrable of arbitrarily high order and determine the structure of their symmetry algebras. We demonstrate that the symmetry algebras close algebraically; only for systems admitting extra discrete symmetries is polynomial closure achieved. Underlying the structure theory is the existence of raising and lowering operators, not themselves symmetry operators or even defined independent of basis, that can be employed to construct the symmetry operators and their structure relations.
Flight Tests of the DELICAT Airborne LIDAR System for Remote Clear Air Turbulence Detection
NASA Astrophysics Data System (ADS)
Vrancken, Patrick; Wirth, Martin; Ehret, Gerhard; Witschas, Benjamin; Veerman, Henk; Tump, Robert; Barny, Hervé; Rondeau, Philippe; Dolfi-Bouteyre, Agnès; Lombard, Laurent
2016-06-01
An important aeronautics application of lidar is the airborne remote detection of Clear Air Turbulence which cannot be performed with onboard radar. We report on a DLR-developed lidar system for the remote detection of such turbulent areas in the flight path of an aircraft. The lidar, consisting of a high-power UV laser transmitter and a direct detection system, was installed on a Dutch research aircraft. Flight tests executed in 2013 demonstrated the performance of the lidar system to detect local subtle variations in the molecular backscatter coefficient indicating the turbulence some 10 to 15 km ahead.
Algorithm for Simulating Atmospheric Turbulence and Aeroelastic Effects on Simulator Motion Systems
NASA Technical Reports Server (NTRS)
Ercole, Anthony V.; Cardullo, Frank M.; Kelly, Lon C.; Houck, Jacob A.
2012-01-01
Atmospheric turbulence produces high frequency accelerations in aircraft, typically greater than the response to pilot input. Motion system equipped flight simulators must present cues representative of the aircraft response to turbulence in order to maintain the integrity of the simulation. Currently, turbulence motion cueing produced by flight simulator motion systems has been less than satisfactory because the turbulence profiles have been attenuated by the motion cueing algorithms. This report presents a new turbulence motion cueing algorithm, referred to as the augmented turbulence channel. Like the previous turbulence algorithms, the output of the channel only augments the vertical degree of freedom of motion. This algorithm employs a parallel aircraft model and an optional high bandwidth cueing filter. Simulation of aeroelastic effects is also an area where frequency content must be preserved by the cueing algorithm. The current aeroelastic implementation uses a similar secondary channel that supplements the primary motion cue. Two studies were conducted using the NASA Langley Visual Motion Simulator and Cockpit Motion Facility to evaluate the effect of the turbulence channel and aeroelastic model on pilot control input. Results indicate that the pilot is better correlated with the aircraft response, when the augmented channel is in place.
Extending TOPS: Ontology-driven Anomaly Detection and Analysis System
NASA Astrophysics Data System (ADS)
Votava, P.; Nemani, R. R.; Michaelis, A.
2010-12-01
Terrestrial Observation and Prediction System (TOPS) is a flexible modeling software system that integrates ecosystem models with frequent satellite and surface weather observations to produce ecosystem nowcasts (assessments of current conditions) and forecasts useful in natural resources management, public health and disaster management. We have been extending the Terrestrial Observation and Prediction System (TOPS) to include a capability for automated anomaly detection and analysis of both on-line (streaming) and off-line data. In order to best capture the knowledge about data hierarchies, Earth science models and implied dependencies between anomalies and occurrences of observable events such as urbanization, deforestation, or fires, we have developed an ontology to serve as a knowledge base. We can query the knowledge base and answer questions about dataset compatibilities, similarities and dependencies so that we can, for example, automatically analyze similar datasets in order to verify a given anomaly occurrence in multiple data sources. We are further extending the system to go beyond anomaly detection towards reasoning about possible causes of anomalies that are also encoded in the knowledge base as either learned or implied knowledge. This enables us to scale up the analysis by eliminating a large number of anomalies early on during the processing by either failure to verify them from other sources, or matching them directly with other observable events without having to perform an extensive and time-consuming exploration and analysis. The knowledge is captured using OWL ontology language, where connections are defined in a schema that is later extended by including specific instances of datasets and models. The information is stored using Sesame server and is accessible through both Java API and web services using SeRQL and SPARQL query languages. Inference is provided using OWLIM component integrated with Sesame.
NASA Astrophysics Data System (ADS)
Meneguz, Elena; Turp, Debi; Wells, Helen
2015-04-01
It is well known that encounters with moderate or severe turbulence can lead to passenger injuries and incur high costs for airlines from compensation and litigation. As one of two World Area Forecast Centres (WAFCs), the Met Office has responsibility for forecasting en-route weather hazards worldwide for aviation above a height of 10,000 ft. Observations from commercial aircraft provide a basis for gaining a better understanding of turbulence and for improving turbulence forecasts through verification. However there is currently a lack of information regarding the possible cause of the observed turbulence, or whether the turbulence occurred within cloud. Such information would be invaluable for the development of forecasting techniques for particular types of turbulence and for forecast verification. Of all the possible sources of turbulence, convective activity is believed to be a major cause of turbulence. Its relative importance over the Europe and North Atlantic area has not been yet quantified in a systematic way: in this study, a new approach is developed to automate identification of turbulent encounters in the proximity of convective clouds. Observations of convection are provided from two independent sources: a surface based lightning network and satellite imagery. Lightning observations are taken from the Met Office Arrival Time Detections network (ATDnet). ATDnet has been designed to identify cloud-to-ground flashes over Europe but also detects (a smaller fraction of) strikes over the North Atlantic. Meteosat Second Generation (MSG) satellite products are used to identify convective clouds by applying a brightness temperature filtering technique. The morphological features of cold cloud tops are also investigated. The system is run for all in situ turbulence reports received from airlines for a total of 12 months during summer 2013 and 2014 for the domain of interest. Results of this preliminary short term climatological study show significant intra
NASA Technical Reports Server (NTRS)
Gage, K. S.; Jasperson, W. H.
1977-01-01
An analysis is presented of the tropospheric turbulence data obtained by the Metrac positioning system, a radio location system which employs the Doppler principle to track inexpensive expendable balloon-borne transmitters. A Minneapolis field test of the Metrac system provided one-second samples of transmitter frequency from balloons tracked by four ground stations for more than an hour. The derivation of diffusion coefficients from the turbulence data was conducted by two methods, yielding highly consistent results.
Database of extended radiation maps and its access system
NASA Astrophysics Data System (ADS)
Verkhodanov, O. V.; Naiden, Ya. V.; Chernenkov, V. N.; Verkhodanova, N. V.
2014-01-01
We describe the architecture of the developed computing web server http://cmb.sao.ru allowing to synthesize the maps of extended radiation on the full sphere from the spherical harmonics in the GLESP pixelization grid, smooth them with the power beam pattern with various angular resolutions in the multipole space, and identify regions of the sky with given coordinates. We describe the server access and administration systems as well as the technique constructing the sky region maps, organized in Python in the Django web-application development framework.
Extended performance solar electric propulsion thrust system design
NASA Technical Reports Server (NTRS)
Cake, J. E.; Hawthorne, E. I.; Poeschel, R. L.
1978-01-01
A thrust system design has been established for an extended performance technology, 6.4 kW, 4800 sec specific impulse ion thruster. The configuration is comprised of ten thrusters configured with a power management and control subsystem in a modular thrust system design. The system design approach is an adaptation of that previously established for the baseline technology 2.7 kW, 3000 sec specific impulse ion thruster. The power management and control subsystem design includes a combination of individual electronics for each thruster and a set of electronics with redundancy that are common to all thrusters. The thermal dissipation from all electronics is removed with a common heat pipe/radiator assembly.
Particle deposition due to turbulent diffusion in the upper respiratory system
NASA Technical Reports Server (NTRS)
Hamill, P.
1979-01-01
Aerosol deposition in the upper respiratory system (trachea to segmental bronchi) is considered and the importance of turbulent diffusion as a deposition mechanism is evaluated. It is demonstrated that for large particles (diameter greater than about 5 microns), turbulent diffusion is the dominant deposition mechanism in the trachea. Conditions under which turbulent diffusion may be important in successive generations of the pulmonary system are determined. The probability of particle deposition is compared with probabilities of deposition, as determined by the equations generally used in regional deposition models. The analysis is theoretical; no new experimental data is presented.
Performance characteristics of a scanning laser imaging system through atmospheric turbulence
NASA Astrophysics Data System (ADS)
Nairat, Mazen; Voelz, David
2012-10-01
The transverse angular (spatial) imaging performance of a laser imaging system through atmospheric turbulence is characterized and described in a practical sense. The system is assumed to scan a far-field scene with a collimated Gaussian beam truncated by a circular aperture and a single channel receiver records the returns. The system point spread function is defined as the average beam profile at the scene and the half-angle beam spread is used to characterize the point spread function. A system modulation transfer function is defined that includes the effects of beam diffraction and turbulence. Spatial sampling of the scene is also considered. A normalized resolution metric (Strehl ratio) is applied to investigate the effects of sampling, beam size, turbulence, and beam truncation. The analysis indicates that resolution will be reduced by more than 90% in homogenous turbulence when the beam waist size is on the order of the atmospheric coherence length. Consistency with conventional imaging performance is discussed.
The report gives results of an analysis of flue gas desulfurization by a turbulent contact absorber (TCA) employing lime slurry, including the development of performance equations for the scrubber-hold tank recycle system. Performance characteristics investigated include pressure...
Transient dynamics and nonlinear stability of spatially extended systems.
Handel, Andreas; Grigoriev, Roman O
2006-09-01
As studies of various systems have shown, the sole focus on the eigenvalues in a linear stability analysis can be misleading, especially when the dynamics of disturbances is characterized by strong transient growth. The aim of this paper is to extend the generalized stability analysis, in the context of spatially extended systems, by examining the role of the nonlinear terms in the destabilization process. The critical noise level leading to destabilization is often found to scale as a power of the magnitude of transient amplification. In what follows we show that the power law exponent sensitively depends on the type of nonlinear terms and their potential for generating self-sustaining noise amplification cycles (bootstrapping). We find, however, that the exponents are not universal and also depend on the more subtle details of the transient dynamics. We also show that the basin of attraction of a spatially uniform state is bounded by the stable manifold(s) of nearby saddle(s) which play a major role in the transition. PMID:17025738
Limits of localized control in extended nonlinear systems
NASA Astrophysics Data System (ADS)
Handel, Andreas
We investigate the limits of localized linear control in spatially extended, nonlinear systems. Spatially extended, nonlinear systems can be found in virtually every field of engineering and science. An important category of such systems are fluid flows. Fluid flows play an important role in many commercial applications, for instance in the chemical, pharmaceutical and food-processing industries. Other important fluid flows include air- or water flows around cars, planes or ships. In all these systems, it is highly desirable to control the flow of the respective fluid. For instance control of the air flow around an airplane or car leads to better fuel-economy and reduced noise production. Usually, it is impossible to apply control everywhere. Consider an airplane: It would not be feasibly to cover the whole body of the plane with control units. Instead, one can place the control units at localized regions, such as points along the edge of the wings, spaced as far apart from each other as possible. These considerations lead to an important question: For a given system, what is the minimum number of localized controllers that still ensures successful control? Too few controllers will not achieve control, while using too many leads to unnecessary expenses and wastes resources. To answer this question, we study localized control in a class of model equations. These model equations are good representations of many real fluid flows. Using these equations, we show how one can design localized control that renders the system stable. We study the properties of the control and derive several expressions that allow us to determine the limits of successful control. We show how the number of controllers that are needed for successful control depends on the size and type of the system, as well as the way control is implemented. We find that especially the nonlinearities and the amount of noise present in the system play a crucial role. This analysis allows us to determine under
Modelling atmospheric turbulence effects on ground-based telescope systems
Bradford, L.W.; Flatte, S.M.; Max, C.E.
1993-09-30
Questions still exist concerning the appropriate model for turbulence- induced phase fluctuations seen in ground-based telescopes. Bester et al. used a particular observable (slope of the Allan variance) with an infrared interferometer in an attempt to distinguish models. The authors have calculated that observable for Kolmogorov and {open_quotes}random walk{close_quotes} models with a variety of outer scales and altitude-dependent turbulence and wind velocity. The authors have found that clear distinction between models requires good data on the vertical distribution of wind and turbulence. Furthermore, measurements at time separations of order 60 s are necessary to distinguish the {open_quotes}random walk{close_quotes} model from the Kolmogorov model.
An active control system for the turbulent boundary layer
NASA Astrophysics Data System (ADS)
Lew, James
This thesis presents the development process and the experimental results of a system constructed to apply real-time control to the structures of the turbulent boundary layer region in order to reduce surface shear stress. The system is composed of three main components: an array of MEMS surface shear stress, tauw sensors; a MEMS flap actuator; and a control logic which integrates the hardware components together into a closed system. The objective of this system is to reduce the stress contained in streak-like regions of high tauw. The sensor array, used to image the tauw distribution, is an extension of the thermal based tauw sensor developed by Jiang. Numerous studies have been performed using this device, the results of which have validated its performance. For this study, a new temperature compensation methodology, based on the surface temperature of the sensor chip, was employed in order to account for possible temperature variations at the wall surface. The actuator, a pneumatically driven flap, is developed as part of the present research. The device is, in essence, a 3 mm x 1 mm cantilever beam that sits on top of an inflatable diaphragm and is capable of actuation frequencies of over 200 Hz and amplitudes of over .11 mm. When it is oscillated in the open loop mode, the effect over one cycle of motion is an average reduction by as much as 2.5% in tauw in the region immediately downstream. A neural network is employed to identify the streak-like regions of interest. Results have shown that this network is successful in identifying the streak-like regions of interest. The control logic employs this network in a predictive, feed-forward scheme to determine the appropriate actuator response. Offline studies have shown that under optimal conditions, the signature of the streak-like regions can be eliminated. Online results conform well to the offline predictions. While unable to achieve the optimal conditions, online experiments show that the system is capable
Extending TOPS: Knowledge Management System for Anomaly Detection and Analysis
NASA Astrophysics Data System (ADS)
Votava, P.; Nemani, R. R.; Michaelis, A.
2009-12-01
Terrestrial Observation and Prediction System (TOPS) is a flexible modeling software system that integrates ecosystem models with frequent satellite and surface weather observations to produce ecosystem nowcasts (assessments of current conditions) and forecasts useful in natural resources management, public health and disaster management. We have been extending the Terrestrial Observation and Prediction System (TOPS) to include capability for automated anomaly detection and analysis of both on-line (streaming) and off-line data. While there are large numbers of anomaly detection algorithms for multivariate datasets, we are extending this capability beyond the anomaly detection itself and towards an automated analysis that would discover the possible causes of the anomalies. There are often indirect connections between datasets that manifest themselves during occurrence of external events and rather than searching exhaustively throughout all the datasets, our goal is to capture this knowledge and provide it to the system during automated analysis. This results in more efficient processing. Since we don’t need to process all the datasets using the original anomaly detection algorithms, which is often compute intensive; we achieve data reduction as we don’t need to store all the datasets in order to search for possible connections but we can download selected data on-demand based on our analysis. For example, an anomaly observed in vegetation Net Primary Production (NPP) can relate to an anomaly in vegetation Leaf Area Index (LAI), which is a fairly direct connection, as LAI is one of the inputs for NPP, however the change in LAI could be caused by a fire event, which is not directly connected with NPP. Because we are able to capture this knowledge we can analyze fire datasets and if there is a match with the NPP anomaly, we can infer that a fire is a likely cause. The knowledge is captured using OWL ontology language, where connections are defined in a schema
Linear versus nonlinear response of a forced wave turbulence system.
Cadot, Olivier; Touzé, Cyril; Boudaoud, Arezki
2010-10-01
A vibrating plate is set into a chaotic state of wave turbulence by a forcing having periodic and random components. Both components are weighted in order to explore continuously intermediate forcing from the periodic to the random one, but keeping constant its rms value. The transverse velocity of the plate is measured at the application point of the force. It is found that whatever the detail of the forcing is, the velocity spectra exhibit a universal cascade for frequencies larger than the forcing frequency range. In contrast, the velocity spectra strongly depend on the nature of the forcing within the range of forcing frequencies. The coherence function is used to extract the contribution of the velocity fluctuations that display a linear relationship with the forcing. The nonlinear contribution to the velocity fluctuations is found to be almost constant, about 55% of the total velocity fluctuations whatever the nature of the forcing from random to periodic. On the other hand, the nonlinear contribution to the fluctuations of the injected power depends on the nature of the forcing; it is significantly larger for the periodic forcing (60%) and decreases continuously as the randomness is increased, reaching a value of 40% for the pure random forcing. For all the cases of intermediate forcing from random to periodic, a simple model of the velocity response recovers in a fairly good agreement the probability density function of the injected power. The consequence of the existence of a linear-response component is discussed in the context of the fluctuation-dissipation theorem validation in experiments of out-of-equilibrium systems. PMID:21230369
He, Ping; Basu, Sukanta
2016-05-01
In Wyngaard et al., 1971, a simple model was proposed to estimate Cn2 in the atmospheric surface layer, which only requires routine meteorological information (wind speed and temperature) as input from two heights. This Cn2 model is known to have satisfactory performance in unstable conditions; however, in stable conditions, the model only covers a relatively short range of atmospheric stabilities which significantly limits its applicability during nighttime. To mitigate this limitation, in this study we construct a new Cn2 model utilizing an extensive turbulence dataset generated by a high-fidelity numerical modeling approach (known as direct numerical simulation). The most distinguishing feature of this new Cn2 model is that it covers a wide range of atmospheric stabilities including the strongly stratified (very stable) conditions. To validate this model, approximately four weeks of Cn2 data collected at the Mauna Loa Observatory, Hawaii are used for comparison, and reasonably good agreement is found between the observed and estimated values. PMID:27137570
Stochastic thermodynamics of reactive systems: An extended local equilibrium approach
NASA Astrophysics Data System (ADS)
De Decker, Yannick; Derivaux, Jean-François; Nicolis, Grégoire
2016-04-01
The recently developed extended local equilibrium approach to stochastic thermodynamics is applied to reactive systems. The properties of the fluctuating entropy and entropy production are analyzed for general linear and for prototypical nonlinear kinetic processes. It is shown that nonlinear kinetics typically induces deviations of the mean entropy production from its value in the deterministic (mean-field) limit. The probability distributions around the mean are derived and shown to qualitatively differ in thermodynamic equilibrium, under nonequilibrium conditions and in the vicinity of criticalities associated to the onset of multistability. In each case large deviation-type properties are shown to hold. The results are compared with those of alternative approaches developed in the literature.
Extended depth of field system for long distance iris acquisition
NASA Astrophysics Data System (ADS)
Chen, Yuan-Lin; Hsieh, Sheng-Hsun; Hung, Kuo-En; Yang, Shi-Wen; Li, Yung-Hui; Tien, Chung-Hao
2012-10-01
Using biometric signatures for identity recognition has been practiced for centuries. Recently, iris recognition system attracts much attention due to its high accuracy and high stability. The texture feature of iris provides a signature that is unique for each subject. Currently most commercial iris recognition systems acquire images in less than 50 cm, which is a serious constraint that needs to be broken if we want to use it for airport access or entrance that requires high turn-over rate . In order to capture the iris patterns from a distance, in this study, we developed a telephoto imaging system with image processing techniques. By using the cubic phase mask positioned front of the camera, the point spread function was kept constant over a wide range of defocus. With adequate decoding filter, the blurred image was restored, where the working distance between the subject and the camera can be achieved over 3m associated with 500mm focal length and aperture F/6.3. The simulation and experimental results validated the proposed scheme, where the depth of focus of iris camera was triply extended over the traditional optics, while keeping sufficient recognition accuracy.
Recent insights into instability and transition to turbulence in open-flow systems
NASA Technical Reports Server (NTRS)
Morkovin, Mark V.
1988-01-01
Roads to turbulence in open-flow shear layers are interpreted as sequences of often competing instabilities. These correspond to primary and higher order restructurings of vorticity distributions which culminate in convected spatial disorder (with some spatial coherence on the scale of the shear layer) traditionally called turbulence. Attempts are made to interpret these phenomena in terms of concepts of convective and global instabilities on one hand, and of chaos and strange attractors on the other. The first is fruitful, and together with a review of mechanisms of receptivity provides a unifying approach to understanding and estimating transition to turbulence. In contrast, current evidence indicates that concepts of chaos are unlikely to help in predicting transition in open-flow systems. Furthermore, a distinction should apparently be made between temporal chaos and the convected spatial disorder of turbulence past Reynolds numbers where boundary layers and separated shear layers are formed.
Modeling the pharmacokinetics of extended release pharmaceutical systems
NASA Astrophysics Data System (ADS)
di Muria, Michela; Lamberti, Gaetano; Titomanlio, Giuseppe
2009-03-01
The pharmacokinetic (PK) models predict the hematic concentration of drugs after the administration. In compartment modeling, the body is described by a set of interconnected “vessels” or “compartments”; the modeling consisting of transient mass balances. Usually the orally administered drugs were considered as immediately available: this cannot describe the administration of extended-release systems. In this work we added to the traditional compartment models the ability to account for a delay in administration, relating this delay to in vitro data. Firstly, the method was validated, applying the model to the dosage of nicotine by chewing-gum; the model was tuned by in vitro/in vivo data of drugs (divalproex-sodium and diltiazem) with medium-rate release kinetics, then it was applied in describing in vivo evolutions due to the assumption of fast- and slow-release systems. The model reveals itself predictive, the same of a Level A in vitro/in vivo correlation, but being physically based, it is preferable to a purely statistical method.
Turbulent Motion in Ethyl Acetate-Water System
NASA Astrophysics Data System (ADS)
Ahmad, Jamil
2000-09-01
An overhead projector demonstration is described in which 4 mL of ethyl acetate is added to 10 mL of water contained in a 10-cm diameter Petri dish. Within a minute or so of the addition, image of a turbulent motion appears on the screen, at first at a few centers that eventually organize themselves in a line. The image of the line of turbulence is quite striking and resembles a moving front of dancing flames. The phenomenon arises because as ethyl acetate evaporates from the region where it has spread in the form of a monolayer, fresh material gets transferred to take its place. Because of the viscosity effects, this transfer of the surface film causes movement in the bulk of the material as well, making the process visible.
Sapsis, Themistoklis P; Majda, Andrew J
2013-08-20
A framework for low-order predictive statistical modeling and uncertainty quantification in turbulent dynamical systems is developed here. These reduced-order, modified quasilinear Gaussian (ROMQG) algorithms apply to turbulent dynamical systems in which there is significant linear instability or linear nonnormal dynamics in the unperturbed system and energy-conserving nonlinear interactions that transfer energy from the unstable modes to the stable modes where dissipation occurs, resulting in a statistical steady state; such turbulent dynamical systems are ubiquitous in geophysical and engineering turbulence. The ROMQG method involves constructing a low-order, nonlinear, dynamical system for the mean and covariance statistics in the reduced subspace that has the unperturbed statistics as a stable fixed point and optimally incorporates the indirect effect of non-Gaussian third-order statistics for the unperturbed system in a systematic calibration stage. This calibration procedure is achieved through information involving only the mean and covariance statistics for the unperturbed equilibrium. The performance of the ROMQG algorithm is assessed on two stringent test cases: the 40-mode Lorenz 96 model mimicking midlatitude atmospheric turbulence and two-layer baroclinic models for high-latitude ocean turbulence with over 125,000 degrees of freedom. In the Lorenz 96 model, the ROMQG algorithm with just a single mode captures the transient response to random or deterministic forcing. For the baroclinic ocean turbulence models, the inexpensive ROMQG algorithm with 252 modes, less than 0.2% of the total, captures the nonlinear response of the energy, the heat flux, and even the one-dimensional energy and heat flux spectra. PMID:23918398
Competition between shock and turbulent heating in coronal loop system
NASA Astrophysics Data System (ADS)
Matsumoto, Takuma
2016-08-01
2.5-dimensional magnetohydrodynamic (MHD) simulations are performed with high spatial resolution in order to distinguish between competing models of the coronal heating problem. A single coronal loop powered by Alfvén waves excited in the photosphere is the target of the present study. The coronal structure is reproduced in our simulations as a natural consequence of the transportation and dissipation of Alfvén waves. Further, the coronal structure is maintained as the spatial resolution is changed from 25 to 3 km, although the temperature at the loop top increases with the spatial resolution. The heating mechanisms change gradually across the magnetic canopy at a height of 4 Mm. Below the magnetic canopy, both the shock and the MHD turbulence are dominant heating processes. Above the magnetic canopy, the shock heating rate reduces to less than 10 % of the total heating rate while the MHD turbulence provides significant energy to balance the radiative cooling and thermal conduction loss or gain. The importance of compressibility shown in the present study would significantly impact on the prospects of successful MHD turbulence theory in the solar chromosphere.
DARPA super resolution vision system (SRVS) robust turbulence data collection and analysis
NASA Astrophysics Data System (ADS)
Espinola, Richard L.; Leonard, Kevin R.; Thompson, Roger; Tofsted, David; D'Arcy, Sean
2014-05-01
Atmospheric turbulence degrades the range performance of military imaging systems, specifically those intended for long range, ground-to-ground target identification. The recent Defense Advanced Research Projects Agency (DARPA) Super Resolution Vision System (SRVS) program developed novel post-processing system components to mitigate turbulence effects on visible and infrared sensor systems. As part of the program, the US Army RDECOM CERDEC NVESD and the US Army Research Laboratory Computational & Information Sciences Directorate (CISD) collaborated on a field collection and atmospheric characterization of a two-handed weapon identification dataset through a diurnal cycle for a variety of ranges and sensor systems. The robust dataset is useful in developing new models and simulations of turbulence, as well for providing as a standard baseline for comparison of sensor systems in the presence of turbulence degradation and mitigation. In this paper, we describe the field collection and atmospheric characterization and present the robust dataset to the defense, sensing, and security community. In addition, we present an expanded model validation of turbulence degradation using the field collected video sequences.
The Turbulent Fragmentation Origin of Low-Mass Binary Star Systems
NASA Astrophysics Data System (ADS)
Offner, Stella; Kratter, K. M.; Matzner, C. D.; Krumholz, M. R.; Klein, R. I.
2011-01-01
Using self-gravitating, radiation-hydrodynamic simulations, we compare turbulent fragmentation and disk fragmentation as avenues for forming low-mass binary systems. We employ two dimensionless parameters to characterize the infall rate onto protostellar systems, describe disks' susceptability to fragmentation, and place limits on protostellar system multiplicity. While protostellar disks are predominatly stable in the presence of radiative feedback, purely hydrodynamic systems exhibit fundamentally different parameters and are strongly susceptible to disk fragmentation. Consequently, we find that turbulent fragmentation, occuring on thousand AU scales, is the more common mode of fragmentation and is likely responsible for producing most low-mass binary systems. Although fragmentation in young embedded protostellar disks cannot be directly imaged, turbulent fragmentation on these scales is potentially observable.
Ohira, Yutaka
2013-04-10
We consider particle acceleration by large-scale incompressible turbulence with a length scale larger than the particle mean free path. We derive an ensemble-averaged transport equation of energetic charged particles from an extended transport equation that contains the shear acceleration. The ensemble-averaged transport equation describes particle acceleration by incompressible turbulence (turbulent shear acceleration). We find that for Kolmogorov turbulence, the turbulent shear acceleration becomes important on small scales. Moreover, using Monte Carlo simulations, we confirm that the ensemble-averaged transport equation describes the turbulent shear acceleration.
Spontaneous Charge Carrier Localization in Extended One-Dimensional Systems
NASA Astrophysics Data System (ADS)
Vlček, Vojtěch; Eisenberg, Helen R.; Steinle-Neumann, Gerd; Neuhauser, Daniel; Rabani, Eran; Baer, Roi
2016-05-01
Charge carrier localization in extended atomic systems has been described previously as being driven by disorder, point defects, or distortions of the ionic lattice. Here we show for the first time by means of first-principles computations that charge carriers can spontaneously localize due to a purely electronic effect in otherwise perfectly ordered structures. Optimally tuned range-separated density functional theory and many-body perturbation calculations within the G W approximation reveal that in trans-polyacetylene and polythiophene the hole density localizes on a length scale of several nanometers. This is due to exchange-induced translational symmetry breaking of the charge density. Ionization potentials, optical absorption peaks, excitonic binding energies, and the optimally tuned range parameter itself all become independent of polymer length as it exceeds the critical localization length. Moreover, we find that lattice disorder and the formation of a polaron result from the charge localization in contrast to the traditional view that lattice distortions precede charge localization. Our results can explain experimental findings that polarons in conjugated polymers form instantaneously after exposure to ultrafast light pulses.
Extending human proprioception to cyber-physical systems
NASA Astrophysics Data System (ADS)
Keller, Kevin; Robinson, Ethan; Dickstein, Leah; Hahn, Heidi A.; Cattaneo, Alessandro; Mascareñas, David
2016-04-01
Despite advances in computational cognition, there are many cyber-physical systems where human supervision and control is desirable. One pertinent example is the control of a robot arm, which can be found in both humanoid and commercial ground robots. Current control mechanisms require the user to look at several screens of varying perspective on the robot, then give commands through a joystick-like mechanism. This control paradigm fails to provide the human operator with an intuitive state feedback, resulting in awkward and slow behavior and underutilization of the robot's physical capabilities. To overcome this bottleneck, we introduce a new human-machine interface that extends the operator's proprioception by exploiting sensory substitution. Humans have a proprioceptive sense that provides us information on how our bodies are configured in space without having to directly observe our appendages. We constructed a wearable device with vibrating actuators on the forearm, where frequency of vibration corresponds to the spatial configuration of a robotic arm. The goal of this interface is to provide a means to communicate proprioceptive information to the teleoperator. Ultimately we will measure the change in performance (time taken to complete the task) achieved by the use of this interface.
Imaging through atmospheric turbulence for laser based C-RAM systems: an analytical approach
NASA Astrophysics Data System (ADS)
Buske, Ivo; Riede, Wolfgang; Zoz, Jürgen
2013-10-01
High Energy Laser weapons (HEL) have unique attributes which distinguish them from limitations of kinetic energy weapons. HEL weapons engagement process typical starts with identifying the target and selecting the aim point on the target through a high magnification telescope. One scenario for such a HEL system is the countermeasure against rockets, artillery or mortar (RAM) objects to protect ships, camps or other infrastructure from terrorist attacks. For target identification and especially to resolve the aim point it is significant to ensure high resolution imaging of RAM objects. During the whole ballistic flight phase the knowledge about the expectable imaging quality is important to estimate and evaluate the countermeasure system performance. Hereby image quality is mainly influenced by unavoidable atmospheric turbulence. Analytical calculations have been taken to analyze and evaluate image quality parameters during an approaching RAM object. In general, Kolmogorov turbulence theory was implemented to determine atmospheric coherence length and isoplanatic angle. The image acquisition is distinguishing between long and short exposure times to characterize tip/tilt image shift and the impact of high order turbulence fluctuations. Two different observer positions are considered to show the influence of the selected sensor site. Furthermore two different turbulence strengths are investigated to point out the effect of climate or weather condition. It is well known that atmospheric turbulence degenerates image sharpness and creates blurred images. Investigations are done to estimate the effectiveness of simple tip/tilt systems or low order adaptive optics for laser based C-RAM systems.
Vorontsov, Mikhail; Riker, Jim; Carhart, Gary; Gudimetla, V S Rao; Beresnev, Leonid; Weyrauch, Thomas; Roberts, Lewis C
2009-01-01
Compensation of extended (deep) turbulence effects is one of the most challenging problems in adaptive optics (AO). In the AO approach described, the deep turbulence wave propagation regime was achieved by imaging stars at low elevation angles when image quality improvement with conventional AO was poor. These experiments were conducted at the U.S. Air Force Maui Optical and Supercomputing Site (AMOS) by using the 3.63 m telescope located on Haleakala, Maui. To enhance compensation performance we used a cascaded AO system composed of a conventional AO system based on a Shack-Hartmann wavefront sensor and a deformable mirror with 941 actuators, and an AO system based on stochastic parallel gradient descent optimization with four deformable mirrors (75 control channels). This first-time field demonstration of a cascaded AO system achieved considerably improved performance of wavefront phase aberration compensation. Image quality was improved in a repeatable way in the presence of stressing atmospheric conditions obtained by using stars at elevation angles as low as 15 degrees. PMID:19107154
Transmission analysis of CPolM-based OFDM FSO system in atmospheric turbulence
NASA Astrophysics Data System (ADS)
Su, Yuwei; Bai, Fan; Sato, Takuro
2016-06-01
In this paper, we propose to implement a consecutive polarization modulation (CPolM) scheme to transmit orthogonal frequency division multiplexing (OFDM) signal over the turbulent free-space optical (FSO) links. We analyze the fluctuation of polarization states of an optical wave while propagating through the turbulence channel of which the refractive-index property is described by Kolmogorov spectrum. The transmission performance in terms of signal-to-noise-ratio (SNR), symbol-error-ratio (SER) and outage probability of the proposed system are evaluated. The proposed system provides a more efficient way to compensate scintillation effects in a comparison with the intensity modulation (IM) based OFDM FSO system under a varying degrees of turbulence strength regimes.
A feasibility study for measuring stratospheric turbulence using metrac positioning system
NASA Technical Reports Server (NTRS)
Gage, K. S.; Jasperson, W. H.
1975-01-01
The feasibility of obtaining measurements of Lagrangian turbulence at stratospheric altitudes is demonstrated by using the METRAC System to track constant-level balloons. The basis for current estimates of diffusion coefficients are reviewed and it is pointed out that insufficient data is available upon which to base reliable estimates of vertical diffusion coefficients. It is concluded that diffusion coefficients could be directly obtained from Lagrangian turbulence measurements. The METRAC balloon tracking system is shown to possess the necessary precision in order to resolve the response of constant-level balloons to turbulence at stratospheric altitudes. A small sample of data recorded from a tropospheric tetroon flight tracked by the METRAC System is analyzed to obtain estimates of small-scale three-dimensional diffusion coefficients. It is recommended that this technique be employed to establish a climatology of diffusion coefficients and to ascertain the variation of these coefficients with altitude, season, and latitude.
Kinetic theory and turbulent discontinuities. [shock tube flow
NASA Technical Reports Server (NTRS)
Johnson, J. A., III; I, L.; Li, Y.; Ramaian, R.; Santigo, J. P.
1981-01-01
Shock tube discontinuities were used to test and extend a kinetic theory of turbulence. In shock wave and contact surface fluctuations, coherent phenomena were found which provide new support for the microscopic nonempirical approach to turbulent systems, especially those with boundary layer-like instabilities.
Intermittency of solar system plasma turbulence near Venus and Earth
NASA Astrophysics Data System (ADS)
Teodorescu, Eliza; Echim, Marius; Chang, Tom
2016-04-01
We analyze magnetic field data from Venus Express (VEX) and CLUSTER to investigate the turbulent properties of the solar wind and the Earth's and Venus' magnetosheaths. A systematic study of the PDFs (Probability Distribution Functions) of the measured magnetic fluctuations and their fourth order moments (kurtosis) reveals numerous intermittent time series. The presence of intermittency is marked by non-Gaussian PDFs with heavy wings and a scale dependent kurtosis. Higher order analyses on the scale dependence of several moment orders of the PDFs, the structure functions, along with the scaling of the kurtosis allow for a selection of scales that pertain to different scaling regimes, governed by different physics. On such sub-ranges of scales we investigate the fractal structure of fluctuations through the Rank Ordered Multifractal Analysis - ROMA (Chang and Wu, 2008). ROMA is applied to a selection of intermittent magnetic field time series in the solar wind and planetary magnetosheaths and helps to quantify the turbulence properties through the estimation of a spectrum of local Hurst exponents. Research supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement no 313038/STORM, and a grant of the Romanian Ministry of National Education, CNCS - UEFISCDI, project number PN-II-ID-PCE-2012-4-0418.
Turbine airfoil with an internal cooling system having vortex forming turbulators
Lee, Ching-Pang
2014-12-30
A turbine airfoil usable in a turbine engine and having at least one cooling system is disclosed. At least a portion of the cooling system may include one or more cooling channels having a plurality of turbulators protruding from an inner surface and positioned generally nonorthogonal and nonparallel to a longitudinal axis of the airfoil cooling channel. The configuration of turbulators may create a higher internal convective cooling potential for the blade cooling passage, thereby generating a high rate of internal convective heat transfer and attendant improvement in overall cooling performance. This translates into a reduction in cooling fluid demand and better turbine performance.
Fichtl, G.H.
1983-09-01
When designing a wind energy converison system (WECS), it may be necessary to take into account the distribution of wind across the disc of rotation. The specific engineering applications include structural strength, fatigue, and control. This wind distribution consists of two parts, namely that associated with the mean wind profile and that associated with the turbulence velocity fluctuation field. The work reported herein is aimed at the latter, namely the distribution of turbulence velocity fluctuations across the WECS disk of rotation. A theory is developed for the two-time covariance matrix for turbulence velocity vector components for wind energy conversion system (WECS) design. The theory is developed for homogeneous and iotropic turbulance with the assumption that Taylor's hypothesis is valid. The Eulerian turbulence velocity vector field is expanded about the hub of the WECS. Formulae are developed for the turbulence velocity vector component covariance matrix following the WECS blade elements. It is shown that upon specification of the turbulence energy spectrum function and the WECS rotation rate, the two-point, two-time covariance matrix of the turbulent flow relative to the WECS bladed elements is determined. This covariance matrix is represented as the sum of nonstationary and stationary contributions. Generalized power spectral methods are used to obtain two-point, double frequency power spectral density functions for the turbulent flow following the blade elements. The Dryden turbulence model is used to demonstrate the theory. A discussion of linear system response analysis is provided to show how the double frequency turbulence spectra might be used to calculate response spectra of a WECS to turbulent flow. Finally the spectrum of the component of turbulence normal to the WECS disc of rotation, following the blade elements, is compared with experimental results.
Zhang, Jiankun; Ding, Shengli; Zhai, Huili; Dang, Anhong
2014-12-29
In wireless optical communications (WOC), polarization multiplexing systems and coherent polarization systems have excellent performance and wide applications, while its state of polarization affected by atmospheric turbulence is not clearly understood. This paper focuses on the polarization fluctuations caused by atmospheric turbulence in a WOC link. Firstly, the relationship between the polarization fluctuations and the index of refraction structure parameter is introduced and the distribution of received polarization angle is obtained through theoretical derivations. Then, turbulent conditions are adjusted and measured elaborately in a wide range of scintillation indexes (SI). As a result, the root-mean-square (RMS) variation and probability distribution function (PDF) of polarization angle conforms closely to that of theoretical model. PMID:25607210
Experimental manipulation of wall turbulence: A systems approacha)
NASA Astrophysics Data System (ADS)
McKeon, B. J.; Sharma, A. S.; Jacobi, I.
2013-03-01
We review recent progress, based on the approach introduced by McKeon and Sharma [J. Fluid Mech. 658, 336-382 (2010), 10.1017/S002211201000176X], in understanding and controlling wall turbulence. The origins of this analysis partly lie in nonlinear robust control theory, but a differentiating feature is the connection with, and prediction of, state-of-the-art understanding of velocity statistics and coherent structures observed in real, high Reynolds number flows. A key component of this line of work is an experimental demonstration of the excitation of velocity response modes predicted by the theory using non-ideal, but practical, actuation at the wall. Limitations of the approach and promising directions for future development are outlined.
Laser imaging system for determination of three-dimensional scalar gradients in turbulent flames.
Karpetis, Adonios N; Settersten, Thomas B; Schefer, Robert W; Barlow, Robert S
2004-02-15
An imaging system for the measurement of three-dimensional (3D) scalar gradients in turbulent hydrocarbon flames is described. Combined line imaging of Raman scattering, Rayleigh scattering, and CO laser-induced fluorescence (LIF) allows for simultaneous single-shot line measurements of major species, temperature, mixture fraction, and a one-dimensional surrogate of scalar dissipation rate in hydrocarbon flames, while simultaneous use of two crossed, planar LIF measurements of OH allows for determination of instantaneous flame orientation. In this manner the full 3D scalar dissipation can be estimated in some regions of a turbulent flame on a single-shot basis. PMID:14971751
Solar system plasma turbulence and intermittency at the maximum and minimum of the solar cycle
NASA Astrophysics Data System (ADS)
Echim, Marius M.
2015-04-01
discuss how the exploitation of data bases produced by the FP7 project STORM contribute to developing a (virtual) laboratory for studying solar system plasma turbulence and intermittency. Research supported by the European FP7 Programme (grant agreement 313038/STORM), and a national grant CNCS -UEFISCDI, project number PN-II-ID-PCE-2012-4-0418.
Highly turbulent counterflow flames: A laboratory scale benchmark for practical systems
Coppola, Gianfilippo; Coriton, Bruno; Gomez, Alessandro
2009-09-15
We propose a highly turbulent counterflow flame as a very useful benchmark of complexity intermediate between laminar flames and practical systems. By operating in a turbulent Reynolds number regime of relevance to practical systems such as gas turbines and internal combustion engines, it retains the interaction of turbulence and chemistry of such environments, but offers several advantages including: (a) the achievement of high Reynolds numbers without pilot flames, which is particularly advantageous from a modeling standpoint; (b) control of the transition from stable flames to local extinction/reignition conditions; (c) compactness of the domain by comparison with jet flames, with obvious advantages from both a diagnostic and, especially, a computational viewpoint; and (d) the reduction or, altogether, elimination of soot formation, thanks to the high strain rates and low residence times of such a system, and the establishment of conditions of large stoichiometric mixture fraction, as required for robust flame stabilization. We demonstrate the phenomenology of such highly strained turbulent flames under conditions spanning unpremixed, partially premixed and premixed regimes. The system lends itself to the validation of DNS and other computational models. It is also well-suited for the examination of practical fuel blends - a need that is becoming more and more pressing in view of the anticipated diversification of the future fossil fuel supply. (author)
System for measuring Reynolds in a turbulently flowing fluid. [signal processing
NASA Technical Reports Server (NTRS)
Cheng, D. Y. (Inventor)
1976-01-01
A system for measuring momentum flux in a turbulently flowing fluid includes: a sensing apparatus for dynamically sensing the mainstream and the cross velocity components of the fluid, a transducer operative to provide two electrical output signals representative of the velocity components in the mainstream and in the cross direction, and signal processors to derive the Reynolds stress wave and the Reynolds stress.
On self-organizing during transition from a laminar to a turbulent flow for nonextensive systems
NASA Astrophysics Data System (ADS)
Zaripov, R. G.
2016-06-01
The evolution of parametric q-entropy and q-information divergence to the equilibrium state during spontaneous transitions and transitions from a laminar to a turbulent flow is considered as applied to nonextensive self-organizing systems. The S- and I-theorems on the variations of measures with constant mean energies are proved.
STORM: a new FP7 project devoted to solar system plasma turbulence, intermittency and multifractals
NASA Astrophysics Data System (ADS)
Echim, Marius M.
2013-04-01
In this project we investigate space plasma turbulence from in-situ data gathered over more than 15 years by spacecraft launched by the European Space Agency (ESA). By using large sets of data instead of focusing on particular events, we advance the understanding on the energy transfer, intermittent turbulence and multifractals in space plasmas. Moreover, since the data cover different phases of the solar cycle, we investigate how the features of space plasma turbulence vary with the solar activity and discriminate between effects specific to solar maximum and minimum. We use electromagnetic field and plasma data provided by three core ESA spacecraft: Ulysses, Venus Express and Cluster, as well as other solar system missions (e.g. Giotto, Cassini, Rosetta, Mars Global Surveyor). We also study the fluctuations of ground based geomagnetic time-series as a measure of the global magnetospheric state whose statistical properties may reveal trends linked to the turbulence properties observed in-situ at higher altitudes. A powerful package of nonlinear analysis methods are applied to all data sets: (i) Power Spectral Densities (PSD) and Probability Distribution Functions (PDF), (ii) higher-order methods of analysis for intermittent data, like the partition function multifractal analysis, the Rank Ordered Multifractal analysis; (iii) the wave telescope, (iv) the multi-spacecraft methods adapted to investigate anisotropic turbulence, (v) discriminating statistics for nonlinearity and nonstationarity. The expertise of the Consortium members is complementary and therefore the synergy within them provides a large spectrum of techniques and models, never applied in a coherent approach over the same datasets. STORM is expected to make advancements in understanding and modeling space plasma turbulence in the solar system and to add value to existing data bases collected from decades by space missions of the major national and international space agencies, in particular by the
Extending quantum control of time-independent systems to time-dependent systems
Wang Zhenyu; Liu Renbao
2011-06-15
We establish that if a scheme can control a time-independent system arbitrarily coupled to a generic finite bath over a short period of time T with control precision O(T{sup N+1}), it can also realize the control with the same order of precision on smoothly time-dependent systems. This result extends the validity of various universal dynamical control schemes to arbitrary analytically time-dependent systems.
Applicability of Mixing Length Theory to a Turbulent Vortex System
NASA Technical Reports Server (NTRS)
Ragsdale, Robert G.
1961-01-01
The ability of mixing length theory to correlate vortex data is evaluated. Expressions are derived for eddy diffusivity by applying the techniques of von Karman and Prandtl which have been established for pipe flow. Total and static pressures were measured from the outer radius to the exhaust-nozzle radius of a vortex generator for a range of mass flows. These data are combined with Navier-Stokes solutions for this region of a compressible vortex to determine turbulent Reynolds numbers. The Reynolds number is related to Prandtl and Karman functions for various assumed boundary conditions, and the experimental data are used to determine the usefulness of these expressions. The following conclusions were reached: (1) Mixing length functions developed by applying von Karman's similarity hypothesis to vortex motion correlate the data better than do Prandtl functions obtained with the assumption that mixing length is proportional to radius. (2) Some of the expressions developed do not adequately represent the experimental data. (3) The data are correlated with acceptable scatter by evaluating the fluid radial inertia at the outer boundary and the shear stress at the inner boundary. The universal constant K was found to be 0.04 to 0.08, rather than the value of 0.4 which is accepted for rectilinear flow. (4) The data are best correlated by a modified Karman expression which includes an effect of radial inertia, as well as shear stress, on eddy diffusivity.
Modeling Compressed Turbulence
Israel, Daniel M.
2012-07-13
From ICE to ICF, the effect of mean compression or expansion is important for predicting the state of the turbulence. When developing combustion models, we would like to know the mix state of the reacting species. This involves density and concentration fluctuations. To date, research has focused on the effect of compression on the turbulent kinetic energy. The current work provides constraints to help development and calibration for models of species mixing effects in compressed turbulence. The Cambon, et al., re-scaling has been extended to buoyancy driven turbulence, including the fluctuating density, concentration, and temperature equations. The new scalings give us helpful constraints for developing and validating RANS turbulence models.
NASA Astrophysics Data System (ADS)
Bernotas, Marius P.; Nelson, Charles
2016-05-01
The Weibull and Exponentiated Weibull probability density functions have been examined for the free space regime using heuristically derived shape and scale parameters. This paper extends current literature to the underwater channel and explores use of experimentally derived parameters. Data gathered in a short range underwater channel emulator was analyzed using a nonlinear curve fitting methodology to optimize the scale and shape parameters of the PDFs. This method provides insight into the scaled effects of underwater optical turbulence on a long range link, and may yield a general set of equations for determining the PDF for an underwater optical link.
Tensoral: A system for post-processing turbulence simulation data
NASA Technical Reports Server (NTRS)
Dresselhaus, Eliot
1993-01-01
Many computer simulations in engineering and science -- and especially in computational fluid dynamics (CFD) -- produce huge quantities of numerical data. These data are often so large as to make even relatively simple post-processing of this data unwieldy. The data, once computed and quality-assured, is most likely analyzed by only a few people. As a result, much useful numerical data is under-utilized. Since future state-of-the-art simulations will produce even larger datasets, will use more complex flow geometries, and will be performed on more complex supercomputers, data management issues will become increasingly cumbersome. My goal is to provide software which will automate the present and future task of managing and post-processing large turbulence datasets. My research has focused on the development of these software tools -- specifically, through the development of a very high-level language called 'Tensoral'. The ultimate goal of Tensoral is to convert high-level mathematical expressions (tensor algebra, calculus, and statistics) into efficient low-level programs which numerically calculate these expressions given simulation datasets. This approach to the database and post-processing problem has several advantages. Using Tensoral the numerical and data management details of a simulation are shielded from the concerns of the end user. This shielding is carried out without sacrificing post-processor efficiency and robustness. Another advantage of Tensoral is that its very high-level nature lends itself to portability across a wide variety of computing (and supercomputing) platforms. This is especially important considering the rapidity of changes in supercomputing hardware.
Turbulent anomalous transport and anisotropic electron heating in a return current system
Lee, Kuang Wu; Buechner, Joerg
2011-02-15
Anisotropic electron heating due to self-generated electromagnetic turbulences is observed in collisionless return current plasmas. The corresponding energy conversion, electron heating, and associated anomalous momentum transport are investigated by means of a two-dimensional electromagnetic particle-in-cell simulation code. The return current model consists of two counterstreaming electron beams with different temperatures and a stationary ion background. First, a general multifluid dispersion analyzer is presented in a clear matrix form that allows to study electron streaming instabilities. The numerical simulation confirms the predicted electrostatic electron-electron acoustic instability. Generating electromagnetic waves, the system evolves into a nonlinear stage. As a result, the electron drifts are slowed down due to turbulence-induced anomalous momentum exchange. Localized electric and magnetic field fluctuations play major roles in the energy conversion. Perpendicular electron heating follows the growth of magnetic field perturbations and the slowing of the electron drifts. Parallel and perpendicular electron heating occurs at different time scales. It is shown that the longer lasting perpendicular electron heating is caused by preheated parallel electron flows. The deflection of the preheated parallel electron flows in the localized turbulences, which is essentially a two-dimensional effect, leads to perpendicular electron heating even after the saturation of parallel electron heating. We conclude that the self-generated magnetic turbulence dominates the anomalous transport process in the late stage of return current system evolution.
The Formation of Low-mass Binary Star Systems Via Turbulent Fragmentation
NASA Astrophysics Data System (ADS)
Offner, Stella S. R.; Kratter, Kaitlin M.; Matzner, Christopher D.; Krumholz, Mark R.; Klein, Richard I.
2010-12-01
We characterize the infall rate onto protostellar systems forming in self-gravitating radiation-hydrodynamics simulations. Using two dimensionless parameters to determine the disks' susceptibility to gravitational fragmentation, we infer limits on protostellar system multiplicity and the mechanism of binary formation. We show that these parameters give robust predictions even in the case of marginally resolved protostellar disks. We find that protostellar systems with radiation feedback predominately form binaries via turbulent fragmentation, not disk instability, and predict that turbulent fragmentation is the dominant channel for binary formation for low-mass stars. We clearly demonstrate that systems forming in simulations including radiative feedback have fundamentally different parameters than those in purely hydrodynamics simulations.
The Tremblay-Turbiner-Winternitz system as extended Hamiltonian
NASA Astrophysics Data System (ADS)
Chanu, Claudia Maria; Degiovanni, Luca; Rastelli, Giovanni
2014-12-01
We generalize the idea of "extension of Hamiltonian systems"—developed in a series of previous articles—which allows the explicit construction of Hamiltonian systems with additional non-trivial polynomial first integrals of arbitrarily high degree, as well as the determination of new superintegrable systems from old ones. The present generalization, that we call "modified extension of Hamiltonian systems," produces the third independent first integral for the (complete) Tremblay-Turbiner-Winternitz system, as well as for the caged anisotropic oscillator in dimension two.
Wake Turbulence Mitigation for Departures (WTMD) Prototype System - Software Design Document
NASA Technical Reports Server (NTRS)
Sturdy, James L.
2008-01-01
This document describes the software design of a prototype Wake Turbulence Mitigation for Departures (WTMD) system that was evaluated in shadow mode operation at the Saint Louis (KSTL) and Houston (KIAH) airports. This document describes the software that provides the system framework, communications, user displays, and hosts the Wind Forecasting Algorithm (WFA) software developed by the M.I.T. Lincoln Laboratory (MIT-LL). The WFA algorithms and software are described in a separate document produced by MIT-LL.
Renormalized perturbation theory - Vlasov-Poisson system, weak turbulence limit, and gyrokinetics
NASA Astrophysics Data System (ADS)
Zhang, Y. Z.; Mahadjan, S. M.
1988-10-01
The self-consistency of the renormalized perturbation theory of Zhang and Mahajan (1985) is demonstrated by applying it to the Vlasov-Poisson system and showing that the theory has the correct weak turbulence limit. Energy conservation is proved to arbitrary high order for the electrostatic drift waves. The theory is applied to derive renormalized equations for a low-beta gyrokinetic system. Comparison of this theory with other current theories is presented.
Vorontsov, Mikhail; Filimonov, Grigory; Ovchinnikov, Vladimir; Polnau, Ernst; Lachinova, Svetlana; Weyrauch, Thomas; Mangano, Joseph
2016-05-20
The performance of two prominent laser beam projection system types is analyzed through wave-optics numerical simulations for various atmospheric turbulence conditions, propagation distances, and adaptive optics (AO) mitigation techniques. Comparisons are made between different configurations of both a conventional beam director (BD) using a monolithic-optics-based Cassegrain telescope and a fiber-array BD that uses an array of densely packed fiber collimators. The BD systems considered have equal input power and aperture diameters. The projected laser beam power inside the Airy size disk at the target plane is used as the performance metric. For the fiber-array system, both incoherent and coherent beam combining regimes are considered. We also present preliminary results of side-by-side atmospheric beam projection experiments over a 7-km propagation path using both the AO-enhanced beam projection system with a Cassegrain telescope and the coherent fiber-array BD composed of 21 densely packed fiber collimators. Both wave-optics numerical simulation and experimental results demonstrate that, for similar system architectures and turbulence conditions, coherent fiber-array systems are more efficient in mitigation of atmospheric turbulence effects and generation of a hit spot of the smallest possible size on a remotely located target. PMID:27411147
Extending Fuzzy System Concepts for Control of a Vitrification Melter
Whitehouse, J.C.; Sorgel, W.; Garrison, A.; Schalkoff, R.J.
1995-08-16
Fuzzy systems provide a mathematical framework to capture uncertainty. The complete description of real, complex systems or situations often requires far more detail and information than could ever be obtained (or understood). Fuzzy approaches are an alternative technology for both system control and information processing and management. In this paper, we present the design of a fuzzy control system for a melter used in the vitrification of hazardous waste. Design issues, especially those related to melter shutdown and obtaining smooth control surfaces, are addressed. Several extensions to commonly-applied fuzzy techniques, notably adaptive defuzzification and modified rule structures are developed.
Modelling the pressure-strain correlation of turbulence - An invariant dynamical systems approach
NASA Technical Reports Server (NTRS)
Speziale, Charles G.; Sarkar, Sutanu; Gatski, Thomas B.
1991-01-01
The modeling of the pressure-strain correlation of turbulence is examined from a basic theoretical standpoint with a view toward developing improved second-order closure models. Invariance considerations along with elementary dynamical systems theory are used in the analysis of the standard hierarchy of closure models. In these commonly used models, the pressure-strain correlation is assumed to be a linear function of the mean velocity gradients with coefficients that depend algebraically on the anisotropy tensor. It is proven that for plane homogeneous turbulent flows the equilibrium structure of this hierarchy of models is encapsulated by a relatively simple model which is only quadratically nonlinear in the anisotropy tensor. This new quadratic model - the SSG model - is shown to outperform the Launder, Reece, and Rodi model (as well as more recent models that have a considerably more complex nonlinear structure) in a variety of homogeneous turbulent flows. Some deficiencies still remain for the description of rotating turbulent shear flows that are intrinsic to this general hierarchy of models and, hence, cannot be overcome by the mere introduction of more complex nonlinearities. It is thus argued that the recent trend of adding substantially more complex nonlinear terms containing the anisotropy tensor may be of questionable value in the modeling of the pressure-strain correlation. Possible alternative approaches are discussed briefly.
Modeling the pressure-strain correlation of turbulence: An invariant dynamical systems approach
NASA Technical Reports Server (NTRS)
Speziale, Charles G.; Sarkar, Sutanu; Gatski, Thomas B.
1990-01-01
The modeling of the pressure-strain correlation of turbulence is examined from a basic theoretical standpoint with a view toward developing improved second-order closure models. Invariance considerations along with elementary dynamical systems theory are used in the analysis of the standard hierarchy of closure models. In these commonly used models, the pressure-strain correlation is assumed to be a linear function of the mean velocity gradients with coefficients that depend algebraically on the anisotropy tensor. It is proven that for plane homogeneous turbulent flows the equilibrium structure of this hierarchy of models is encapsulated by a relatively simple model which is only quadratically nonlinear in the anisotropy tensor. This new quadratic model - the SSG model - is shown to outperform the Launder, Reece, and Rodi model (as well as more recent models that have a considerably more complex nonlinear structure) in a variety of homogeneous turbulent flows. Some deficiencies still remain for the description of rotating turbulent shear flows that are intrinsic to this general hierarchy of models and, hence, cannot be overcome by the mere introduction of more complex nonlinearities. It is thus argued that the recent trend of adding substantially more complex nonlinear terms containing the anisotropy tensor may be of questionable value in the modeling of the pressure-strain correlation. Possible alternative approaches are discussed briefly.
NASA Astrophysics Data System (ADS)
Rickenstorff, Carolina; Rodrigo, Jóse A.; Alieva, Tatiana
2016-04-01
Different applications such as astronomy, remote optical sensing and free space optical communications, among others, require both numerical and laboratory experimental simulations of beam propagation through turbulent atmosphere prior to an outdoor test. While rotating phase plates or hot chambers can be applied to such studies, they do not allow changing the atmospheric conditions and the propagation distance in situ. In contrast, the spatial light modulators (SLMs) are a flexible alternative for experimental turbulence simulation. In this work we consider an experimental setup comprising two SLMs for studying laser beam propagation in weak atmospheric turbulence. The changes of atmospheric conditions and propagation distances are properly achieved by the adjustment of the phase screens and the focal distances of digital lenses implemented in both SLMs. The proposed system can be completely automatized and all its elements are in fixed positions avoiding mechanical misalignment. Its design, propagation distance and atmospheric condition adjustment are provided. The setup performance is verified by numerical simulation of Gaussian beam propagation in the weak turbulence regime. The obtained parameters: scintillation index, beam wander and spreading are compared to their theoretical counterparts for different propagation distances and atmospheric conditions.
SERT 2 1979 extended flight thruster system performance
NASA Technical Reports Server (NTRS)
Kerslake, W. R.; Ignaczak, L. R.
1979-01-01
Steady state tests of the thruster 2 system on the SERT 2 spacecraft are presented. A direct thrust measurement was obtained for the ion thruster during operations to increase the spacecraft spin rate to maintain spacecraft attitude stability. The continued restart tests of thruster 1 and a report on the general status of all spacecraft systems including the main solar array are presented.
Percolation-based precursors of transitions in extended systems.
Rodríguez-Méndez, Víctor; Eguíluz M, Víctor M; Hernández-García, Emilio; Ramasco, José J
2016-01-01
Abrupt transitions are ubiquitous in the dynamics of complex systems. Finding precursors, i.e. early indicators of their arrival, is fundamental in many areas of science ranging from electrical engineering to climate. However, obtaining warnings of an approaching transition well in advance remains an elusive task. Here we show that a functional network, constructed from spatial correlations of the system's time series, experiences a percolation transition way before the actual system reaches a bifurcation point due to the collective phenomena leading to the global change. Concepts from percolation theory are then used to introduce early warning precursors that anticipate the system's tipping point. We illustrate the generality and versatility of our percolation-based framework with model systems experiencing different types of bifurcations and with Sea Surface Temperature time series associated to El Niño phenomenon. PMID:27412567
Blended particle methods with adaptive subspaces for filtering turbulent dynamical systems
NASA Astrophysics Data System (ADS)
Qi, Di; Majda, Andrew J.
2015-04-01
It is a major challenge throughout science and engineering to improve uncertain model predictions by utilizing noisy data sets from nature. Hybrid methods combining the advantages of traditional particle filters and the Kalman filter offer a promising direction for filtering or data assimilation in high dimensional turbulent dynamical systems. In this paper, blended particle filtering methods that exploit the physical structure of turbulent dynamical systems are developed. Non-Gaussian features of the dynamical system are captured adaptively in an evolving-in-time low dimensional subspace through particle methods, while at the same time statistics in the remaining portion of the phase space are amended by conditional Gaussian mixtures interacting with the particles. The importance of both using the adaptively evolving subspace and introducing conditional Gaussian statistics in the orthogonal part is illustrated here by simple examples. For practical implementation of the algorithms, finding the most probable distributions that characterize the statistics in the phase space as well as effective resampling strategies is discussed to handle realizability and stability issues. To test the performance of the blended algorithms, the forty dimensional Lorenz 96 system is utilized with a five dimensional subspace to run particles. The filters are tested extensively in various turbulent regimes with distinct statistics and with changing observation time frequency and both dense and sparse spatial observations. In real applications perfect dynamical models are always inaccessible considering the complexities in both modeling and computation of high dimensional turbulent system. The effects of model errors from imperfect modeling of the systems are also checked for these methods. The blended methods show uniformly high skill in both capturing non-Gaussian statistics and achieving accurate filtering results in various dynamical regimes with and without model errors.
Infrared Laser System for Extended Area Monitoring of Air Pollution
NASA Technical Reports Server (NTRS)
Snowman, L. R.; Gillmeister, R. J.
1971-01-01
An atmospheric pollution monitoring system using a spectrally scanning laser has been developed by the General Electric Company. This paper will report on an evaluation of a breadboard model, and will discuss applications of the concept to various ambient air monitoring situations. The system is adaptable to other tunable lasers. Operating in the middle infrared region, the system uses retroreflectors to measure average concentrations over long paths at low, safe power levels. The concept shows promise of meeting operational needs in ambient air monitoring and providing new data for atmospheric research.
Extended Evaluations of the Commercial Spectrometer Systems for Safeguards Applications
Duc T. Vo
1999-08-01
Safeguards applications require the best of the spectrometer system with excellent resolution, stability, and throughput. Instruments must perform well in all situations and environments. Data communication to the computer should be convenient, fast, and reliable. The software should have all the necessary tools and be easy to use. Portable systems should be small in size, lightweight, and have a long battery life. Nine commercially available spectrometer systems are tested with five different germanium detectors. Considering the performance of the Digital Signal Processors (DSP), digital-based spectroscope y may become the way of future gamma-ray spectroscopy.
Nonlinear Dynamics of Extended Hydrologic Systems over long time scales
NASA Astrophysics Data System (ADS)
Lall, Upmanu
2014-05-01
We often view our knowledge of hydrology and hence of nature as intransient, at least over the time scales over which we study processes we wish to predict and understand. Over the last few decades, this assumption has come under question, largely because of the vocal expression of a changing climate, but also the recurrent demonstration of significant land use change, both of which significantly affect the boundary conditions for terrestrial hydrology that is our forte. Most recently, the concepts of hydromorphology and social hydrology have entered the discussion, and the notion that climate and hydrology influence human action, which in turn shapes hydrology, is being recognized. Finally, as a field, we seem to be coming to the conclusion that the hydrologic system is an open system, whose boundaries evolve in time, and that the hydrologic system, at many scales, has a profound effect on the systems that drive it -- whether they be the ecological and climatic systems, or the social system. What a mess! Complexity! Unpredictability! At a certain level of abstraction, one can consider the evolution of these coupled systems with nonlinear feedbacks and ask what types of questions are relevant in terms of such a coupled evolution? What are their implications at the planetary scale? What are their implications for a subsistence farmer in an arid landscape who may under external influence achieve a new transient hydro-ecological equilibrium? What are the implications for the economy and power of nations? In this talk, I will try to raise some of these questions and also provide some examples with very simple dynamical systems that suggest ways of thinking about some practical issues of feedback across climate, hydrology and human behavior.
Small-scale universality in fluid turbulence
Schumacher, Jörg; Scheel, Janet D.; Krasnov, Dmitry; Donzis, Diego A.; Yakhot, Victor; Sreenivasan, Katepalli R.
2014-01-01
Turbulent flows in nature and technology possess a range of scales. The largest scales carry the memory of the physical system in which a flow is embedded. One challenge is to unravel the universal statistical properties that all turbulent flows share despite their different large-scale driving mechanisms or their particular flow geometries. In the present work, we study three turbulent flows of systematically increasing complexity. These are homogeneous and isotropic turbulence in a periodic box, turbulent shear flow between two parallel walls, and thermal convection in a closed cylindrical container. They are computed by highly resolved direct numerical simulations of the governing dynamical equations. We use these simulation data to establish two fundamental results: (i) at Reynolds numbers Re ∼ 102 the fluctuations of the velocity derivatives pass through a transition from nearly Gaussian (or slightly sub-Gaussian) to intermittent behavior that is characteristic of fully developed high Reynolds number turbulence, and (ii) beyond the transition point, the statistics of the rate of energy dissipation in all three flows obey the same Reynolds number power laws derived for homogeneous turbulence. These results allow us to claim universality of small scales even at low Reynolds numbers. Our results shed new light on the notion of when the turbulence is fully developed at the small scales without relying on the existence of an extended inertial range. PMID:25024175
NASA Technical Reports Server (NTRS)
1971-01-01
A preliminary plan and procedure are presented for conducting an extended manned test program for a regenerative life support system. Emphasis will be placed on elements associated with long-term system operation and long-term uninterrupted crew confinement.
Extending NASA's SPICE ancillary information system to meet future mission needs
NASA Technical Reports Server (NTRS)
Acton, C.; Bachman, N.; Elson, L.; Semenov, B.; Turner, F.; Wright, E.
2002-01-01
This paper summarizes the architecture, capabilities, characteristics and uses of the current SPICE ancillary information system, and then outlines plans and ideas for how this system can be extended to meet future space mission requirements.
NASA Astrophysics Data System (ADS)
Kiasaleh, Kamran
2002-04-01
The performance of a free-space optical (FSO) communication system is investigated when communication is established via a short-range, turbulent optical channel. The system under investigation utilizes on-off-keying (OOK) modulation combined with direct-detection to establish a duplex communication link. It is further assumed that the optical beam obeys a Gaussian profile. The received signal is detected using a p-i-n diode which is followed by a trans-impedance amplifier (TIA), limiting amplifier, and a clock/data recovery subsystem. Furthermore, it is assumed that optical front-end provides a relatively large aperture so that the impact of turbulence is somewhat mitigated and that the channel/system parameters result in a weak turbulent condition. The performance of the proposed system for a bit error rate of 10-9 in the absence of forward error correction (FEC) is assessed in terms of probability of fade (PF), average number of fades per second (FPS), mean fade duration (MFD), mean-guard-to-mean-burst (MGMB) ratio, and mean time between fades (MTBF).
Percolation-based precursors of transitions in extended systems
Rodríguez-Méndez, Víctor; Eguíluz M, Víctor M.; Hernández-García, Emilio; Ramasco, José J.
2016-01-01
Abrupt transitions are ubiquitous in the dynamics of complex systems. Finding precursors, i.e. early indicators of their arrival, is fundamental in many areas of science ranging from electrical engineering to climate. However, obtaining warnings of an approaching transition well in advance remains an elusive task. Here we show that a functional network, constructed from spatial correlations of the system’s time series, experiences a percolation transition way before the actual system reaches a bifurcation point due to the collective phenomena leading to the global change. Concepts from percolation theory are then used to introduce early warning precursors that anticipate the system’s tipping point. We illustrate the generality and versatility of our percolation-based framework with model systems experiencing different types of bifurcations and with Sea Surface Temperature time series associated to El Niño phenomenon. PMID:27412567
Percolation-based precursors of transitions in extended systems
NASA Astrophysics Data System (ADS)
Rodríguez-Méndez, Víctor; Eguíluz M, Víctor M.; Hernández-García, Emilio; Ramasco, José J.
2016-07-01
Abrupt transitions are ubiquitous in the dynamics of complex systems. Finding precursors, i.e. early indicators of their arrival, is fundamental in many areas of science ranging from electrical engineering to climate. However, obtaining warnings of an approaching transition well in advance remains an elusive task. Here we show that a functional network, constructed from spatial correlations of the system’s time series, experiences a percolation transition way before the actual system reaches a bifurcation point due to the collective phenomena leading to the global change. Concepts from percolation theory are then used to introduce early warning precursors that anticipate the system’s tipping point. We illustrate the generality and versatility of our percolation-based framework with model systems experiencing different types of bifurcations and with Sea Surface Temperature time series associated to El Niño phenomenon.
Multi-level segment analysis: definition and application in turbulent systems
NASA Astrophysics Data System (ADS)
Wang, L. P.; Huang, Y. X.
2015-06-01
For many complex systems the interaction of different scales is among the most interesting and challenging features. It seems not very successful to extract the physical properties in different scale regimes by the existing approaches, such as the structure-function and Fourier spectrum method. Fundamentally, these methods have their respective limitations, for instance scale mixing, i.e. the so-called infrared and ultraviolet effects. To make improvements in this regard, a new method, multi-level segment analysis (MSA) based on the local extrema statistics, has been developed. Benchmark (fractional Brownian motion) verifications and the important case tests (Lagrangian and two-dimensional turbulence) show that MSA can successfully reveal different scaling regimes which have remained quite controversial in turbulence research. In general the MSA method proposed here can be applied to different dynamic systems in which the concepts of multiscale and multifractality are relevant.
Active laser radar systems with stochastic electromagnetic beams in turbulent atmosphere.
Cai, Yangjian; Korotkova, Olga; Eyyuboğlu, Halil T; Baykal, Yahya
2008-09-29
Propagation of stochastic electromagnetic beams through paraxial ABCD optical systems operating through turbulent atmosphere is investigated with the help of the ABCD matrices and the generalized Huygens-Fresnel integral. In particular, the analytic formula is derived for the cross-spectral density matrix of an electromagnetic Gaussian Schell-model (EGSM) beam. We applied our analysis for the ABCD system with a single lens located on the propagation path, representing, in a particular case, the unfolded double-pass propagation scenario of active laser radar. Through a number of numerical examples we investigated the effect of local turbulence strength and lens' parameters on spectral, coherence and polarization properties of the EGSM beam. PMID:18825220
Development and implementation of a robust angle of arrival turbulence measurement system
NASA Astrophysics Data System (ADS)
Manning, Sean; Clare, Bradley A.; Grant, Kenneth J.; Mudge, Kerry A.
2015-11-01
Free space optical communications (FSOC) systems are a promising complement to existing wireless communications technologies. FSOC systems have many significant advantages over traditional radio frequency links, including high bandwidth, no spectrum licensing requirements, low-power consumption, small payloads, low probability of intercept, and greater immunity from interference or jamming. However, atmospheric turbulence (scintillation) imparts significant phase noise onto the laser beam, resulting in intensity fluctuations at the receiver. In order to develop scintillation mitigation strategies, it is necessary to monitor scintillation in parallel to the communications channel. We report on the development and implementation of a robust angle of arrival (AoA) turbulence measurement instrument that is suitable for this task. Several key data acquisition and processing techniques were designed to enhance the reliability and robustness of the scintillation measurement.
NASA Technical Reports Server (NTRS)
Frost, W.; Harper, W. L.
1975-01-01
Flow over surface obstructions can produce significantly large wind shears such that adverse flying conditions can occur for aeronautical systems (helicopters, STOL vehicles, etc.). Atmospheric flow fields resulting from a semi-elliptical surface obstruction in an otherwise horizontally homogeneous statistically stationary flow are modelled with the boundary-layer/Boussinesq-approximation of the governing equation of fluid mechanics. The turbulence kinetic energy equation is used to determine the dissipative effects of turbulent shear on the mean flow. Iso-lines of turbulence kinetic energy and turbulence intensity are plotted in the plane of the flow and highlight regions of high turbulence intensity in the stagnation zone and sharp gradients in intensity along the transition from adverse to favourable pressure gradient. Discussion of the effects of the disturbed wind field in CTOL and STOL aircraft flight path and obstruction clearance standards is given. The results indicate that closer inspection of these presently recommended standards as influenced by wind over irregular terrains is required.
System for measuring three fluctuating velocity components in a turbulently flowing fluid
NASA Technical Reports Server (NTRS)
Cheng, D. Y. (Inventor)
1977-01-01
A system is described for measuring fluid velocity in a turbulently flowing fluid including a sensing apparatus for dynamically sensing the mainstream and two orthogonal cross velocity components of the fluid. A transducer operative is included to provide three electrical output signals representative of the velocity components in the mainstream, and in the cross directions. Signal processors can be utilized to derive the Reynolds stress wave and the Reynolds stress.
Modular open RF architecture: extending VICTORY to RF systems
NASA Astrophysics Data System (ADS)
Melber, Adam; Dirner, Jason; Johnson, Michael
2015-05-01
Radio frequency products spanning multiple functions have become increasingly critical to the warfighter. Military use of the electromagnetic spectrum now includes communications, electronic warfare (EW), intelligence, and mission command systems. Due to the urgent needs of counterinsurgency operations, various quick reaction capabilities (QRCs) have been fielded to enhance warfighter capability. Although these QRCs were highly successfully in their respective missions, they were designed independently resulting in significant challenges when integrated on a common platform. This paper discusses how the Modular Open RF Architecture (MORA) addresses these challenges by defining an open architecture for multifunction missions that decomposes monolithic radio systems into high-level components with welldefined functions and interfaces. The functional decomposition maximizes hardware sharing while minimizing added complexity and cost due to modularization. MORA achieves significant size, weight and power (SWaP) savings by allowing hardware such as power amplifiers and antennas to be shared across systems. By separating signal conditioning from the processing that implements the actual radio application, MORA exposes previously inaccessible architecture points, providing system integrators with the flexibility to insert third-party capabilities to address technical challenges and emerging requirements. MORA leverages the Vehicular Integration for Command, Control, Communication, Computers, Intelligence, Surveillance, and Reconnaissance (C4ISR)/EW Interoperability (VICTORY) framework. This paper concludes by discussing how MORA, VICTORY and other standards such as OpenVPX are being leveraged by the U.S. Army Research, Development, and Engineering Command (RDECOM) Communications Electronics Research, Development, and Engineering Center (CERDEC) to define a converged architecture enabling rapid technology insertion, interoperability and reduced SWaP.
NASA Technical Reports Server (NTRS)
Tchen, C. M.
1986-01-01
Theoretical and numerical works in atmospheric turbulence have used the Navier-Stokes fluid equations exclusively for describing large-scale motions. Controversy over the existence of an average temperature gradient for the very large eddies in the atmosphere suggested that a new theoretical basis for describing large-scale turbulence was necessary. A new soliton formalism as a fluid analogue that generalizes the Schrodinger equation and the Zakharov equations has been developed. This formalism, processing all the nonlinearities including those from modulation provided by the density fluctuations and from convection due to the emission of finite sound waves by velocity fluctuations, treats large-scale turbulence as coalescing and colliding solitons. The new soliton system describes large-scale instabilities more explicitly than the Navier-Stokes system because it has a nonlinearity of the gradient type, while the Navier-Stokes has a nonlinearity of the non-gradient type. The forced Schrodinger equation for strong fluctuations describes the micro-hydrodynamical state of soliton turbulence and is valid for large-scale turbulence in fluids and plasmas where internal waves can interact with velocity fluctuations.
Linear optical coherence tomography system with extended measurement range.
Koch, Peter; Hellemanns, Volker; Hüttmann, Gereon
2006-10-01
Optical coherence tomography (OCT) sensors traditionally use scanning optical delay lines with moving parts and a single detector. OCT systems with a linear detector array (linear OCT or L-OCT) are simple and robust, but a detector with approximately 10,000 pixels is needed for an imaging depth of 2mm, which is necessary for most biomedical applications. We present a new optical setup for L-OCT with an increased measurement range. An additional grating performs a reduction of the spatial frequencies of the fringe pattern on the detector without loss in the signal-to-noise ratio, so the signal can be sampled with a minimal number of pixels. The theory for this approach is addressed and the first measurements are presented. PMID:16969410
Extended atmospheres of comets and outer planet-satellite systems
NASA Technical Reports Server (NTRS)
Smyth, William H.; Marconi, Max L.
1992-01-01
For the hydrogen coma of comet P/Halley, both a Lyman-alpha image and extensive Lyman-alpha scan data obtained by the Pioneer Venus Orbiter Ultraviolet spectrometer as well as H-alpha ground-based spectral observations obtained by the University of Wisconsin Space Physics Group were successfully interpreted and analyzed with our Monte Carlo particle trajectory model. The excellent fit of the model and the Halley data and the water production rate determined near perihelion (9 Feb. 1986) from 13 Dec. 1985 to 13 Jan. 1986 and from 1 Feb. to 7 Mar. 1986 are discussed. Studies for the circumplanetary distribution of atomic hydrogen in the Saturn and Neptune systems were undertaken for escape of H atoms from Titan and Triton, respectively. The discovery of a new mechanism which can dramatically change the normal cylindrically symmetric distribution of hydrogen about the planet is discussed. The implications for the Titan-Saturn and Triton-Neptune are summarized.
Effects of turbulence on the geodynamic laser ranging system
NASA Technical Reports Server (NTRS)
Churnside, James H.
1993-01-01
The Geodynamic Laser Ranging System (GLRS) is one of several instruments being developed by the National Aeronautics and Space Administration (NASA) for implementation as part of the Earth Observing System in the mid-1990s (Cohen et al., 1987; Bruno et al., 1988). It consists of a laser transmitter and receiver in space and an array of retroreflectors on the ground. The transmitter produces short (100 ps) pulses of light at two harmonics (0.532 and 0.355 microns) of the Nd:YAG laser. These propagate to a retroreflector on the ground and return. The receiver collects the reflected light and measures the round-trip transit time. Ranging from several angles accurately determines the position of the retroreflector, and changes in position caused by geophysical processes can be monitored.
Nonimaging active system determination of target shape through turbulent medium
NASA Astrophysics Data System (ADS)
Chandler, Susan M.; Lukesh, Gordon W.
2001-01-01
Image reconstruction techniques for atmospheric applications often work best with an initial estimate of the object support. This paper examines the ability of a non-imaging laser pointing system to obtain an estimate of target size and shape based on the statistics of the return signal. Fundamental limits on system pointing, such as the tracking errors, corrupt a simple raster scan that would provide gross object shape form the convolution of the far-field pattern with the target. Using techniques developed previously for the estimation of pointing performance, it is possible to distinguish between simple shapes such as bars, circles and T's based on the statistics of the received time signal. Simulated space objects, such as those illuminated during field experiments, may also be distinguished.
Turbulent traveling-wave convection in a two-layer system
NASA Astrophysics Data System (ADS)
Stamp, Andrew P.; Griffiths, Ross W.
1997-04-01
When layers of salt and sugar solution are separated by a "diffusive" interface, interfacial waves are spontaneously generated by the turbulent convection once the system evolves to a critical value of the density-anomaly ratio Rρ≡βΔS/αΔT (Stamp et al., to appear in J. Fluid Mech). The waves modulate the interfacial fluxes by modifying the interface thickness and thereby organize the otherwise random convective motions into coherent large-scale circulations. In narrow rectangular channels a wide range of conditions give rise to a single wave which propagates back-and-forth, resulting in quasi-periodic reversals of tank-scale circulations. Here it is shown that in annular and equant rectangular cavities this same coupling phenomenon produces turbulent convection cells of a traveling-wave nature, coupled to large-amplitude solitary waves on the interface.
The Turbulent Origin of Outflow and Spin Misalignment in Multiple Star Systems
NASA Astrophysics Data System (ADS)
Offner, Stella S. R.; Dunham, Michael M.; Lee, Katherine I.; Arce, Héctor G.; Fielding, Drummond B.
2016-08-01
The protostellar outflows of wide-separation forming binaries frequently appear misaligned. We use magneto-hydrodynamic simulations to investigate the alignment of protostellar spin and molecular outflows for forming binary pairs. We show that the protostellar pairs, which form from turbulent fragmentation within a single parent core, have randomly oriented angular momentum. Although the pairs migrate to closer separations, their spins remain partially misaligned. We produce 12CO(2-1) synthetic observations of the simulations and characterize the outflow orientation in the emission maps. The CO-identified outflows exhibit a similar random distribution and are also statistically consistent with the observed distribution of molecular outflows. We conclude that the observed misalignment provides a clear signature of binary formation via turbulent fragmentation. The persistence of misaligned outflows and stellar spins following dynamical evolution may provide a signature of binary origins for more evolved multiple star systems.
NASA Astrophysics Data System (ADS)
Giannuzzi, M.
2014-07-01
In electronic systems the presence of bluff bodies, sharp corners and bends are the cause of flow separation and large recirculation bubbles. Since the recirculation vortices develop they encapsulate the heat from an electronic component becoming one of the major contributors of malfunction. Going in depth in this, some numerical simulations of conjugate heat transfer for a heat wall-mounted cube have been performed using the commercial CFD code scSTREAM V11 by Software Cradle Co, Ltd. It is well known that the reliability of CFD analysis depends heavily on the turbulent model employed together with the wall functions implemented. The three low- Reynolds k - epsilon turbulent models developed by Abe-Nagano-Kondoh have been validated against experimental data consisting mainly of velocity profiles and surface temperature distributions provided in literature. The performed validation shows a satisfactory agreement between the measured and simulated data. The turbulent model chosen is then used for the CFD simulation of a complex electronic system.
Extending Hydrologic Information Systems to accommodate Arctic marine observations data
NASA Astrophysics Data System (ADS)
Hersh, Eric S.; Maidment, David R.
2014-04-01
The Chukchi Sea Offshore Monitoring in Drilling Area - Chemical and Benthos (COMIDA CAB) project characterizes the biota and chemistry of the continental shelf ecosystem of a region of the Chukchi Sea to form a baseline survey of environmental conditions before drilling for oil commences. This paper describes the COMIDA CAB project data and processing methods, which provide a novel approach to data tracking and archiving from marine sampling cruises. This approach features an adaptation of the Consortium of Universities for the Advancement of Hydrologic Science. Observations Data Model for application with physical, chemical, and biological oceanographic data - a new extension of the CUAHSI Hydrologic Information System - thus bringing hydroinformatics into the oceanographic realm. Environmental sampling has been carried out by five separate scientific teams who characterize particular classes of physical, chemical and biological variables, and who each have their own methods of processing samples in their laboratories following the two sampling cruises made to the Chukchi Sea in the summers of 2009 and 2010. The results of their observations and analyses are stored in data files, mostly in Excel format, whose structure is defined differently by each scientific team. In all, the 2009 and 2010 COMIDA CAB field efforts yielded a database of 510,405 data values. Of these, 474,129 were derived from continuous in-situ data sonde profiles and 36,276 were derived from non-sonde extracted samples of the sediment, epibenthos, and water column. These data values represent 301 variables measured at 65 sites and originated from 26 different source files. The biological observations represented 519 distinct taxa. The data from these files are transformed and synthesized into a comprehensive project database in which a set of standardized descriptors of each observed data value are specified and each data value is linked to the data file from which it was created to establish a
NASA Technical Reports Server (NTRS)
Perras, G. H.; Dasey, T. J.
2000-01-01
Potential adaptive wake vortex spacing systems may need to rely on wake vortex decay rather than wake vortex transport in reducing wake separations. A wake vortex takeoff-spacing system in particular will need to rely on wake decay. Ambient turbulence is the primary influence on wake decay away from the ground. This study evaluated 18 months of ambient turbulence measurements at Dallas/Ft. Worth (DFW) Airport. The measurements show minor variation in the turbulence levels at various times of the year or times of the day for time periods when a departure system could be used. Arrival system operation was also examined, and a slightly lower overall turbulence level was found as compared to departure system benefit periods. The Sarpkaya model, a validated model of wake vortex behavior, was applied to various turbulence levels and compared to the DFW turbulence statistics. The results show that wake vortices from heavy aircraft on takeoff should dissipate within one minute for the majority of the time and will rarely last two minutes. These results will need to be verified by wake vortex measurements on departure.
The Turbulent Life of Phytoplankton
NASA Technical Reports Server (NTRS)
Ghosal, S.; Rogers, M.; Wray, A.
2000-01-01
Phytoplankton is a generic name for photosynthesizing microscopic organisms that inhabit the upper sunlit layer (euphotic zone) of almost all oceans and bodies of freshwater. They are agents for "primary production," the incorporation of carbon from the environment into living organisms, a process that, sustains the aquatic food web. It is estimated that phytoplankton contribute about half of the global primary production, the other half being due to terrestrial plants. By sustaining the aquatic food web and controlling the biogeochemical cycles through primary production, phytoplankton exert a dominant influence on life on earth. Turbulence influences this process in three very important ways. First, essential mineral nutrients are transported from the deeper layers to the euphotic zone through turbulence. Second, turbulence helps to suspend phytoplankton in the euphotic zone since in still water, the phytoplankton, especially the larger species, tend to settle out of the sunlit layers. Third, turbulence transports phytoplankton from the surface to the dark sterile waters, and this is an important mechanism of loss. Thus, stable phytoplankton populations are maintained through a delicate dynamic balance between the processes of turbulence, reproduction, and sinking. The first quantitative model for this was introduced by Riley, Stommel and Bumpus in 1949. This is an attempt to extend their efforts through a combination of analysis and computer simulation in order to better understand the principal qualitative aspects of the physical/biological coupling of this natural system.
Forecasting of Optical Turbulence in Support of Realtime Optical Imaging and Communication Systems
NASA Astrophysics Data System (ADS)
Alliss, R.; Felton, B.
2012-09-01
Optical turbulence (OT) acts to distort light in the atmosphere, degrading imagery from large astronomical and imaging telescopes and possibly reducing data quality of free space optical communication (FSOC) links. Some of the degradation due to optical turbulence can be corrected by adaptive optics. However, the severity of optical turbulence, and thus the amount of correction required, is largely dependent upon the turbulence at the location of interest. In addition, clouds, precipitation, and inhomogeneities in atmospheric temperature and moisture all have the potential to disrupt imaging and communications through the atmosphere. However, there are strategies that can be employed to mitigate the atmospheric impacts. These strategies require an accurate characterization of the atmosphere through which the communications links travel. To date these strategies have been to climatological characterize OT and its properties. Recently efforts have been developed to employ a realtime forecasting system which provides planners useful information for maintaining links and link budgets. The strength of OT is characterized by the refractive index structure function Cn2, which in turn is used to calculate atmospheric seeing parameters. Atmospheric measurements provided by local instrumentation are valuable for link characterization, but provide an incomplete picture of the atmosphere. While attempts have been made to characterize Cn2 using empirical models, Cn2 can be calculated more directly from Numerical Weather Prediction (NWP) simulations using pressure, temperature, thermal stability, vertical wind shear, turbulent Prandtl number, and turbulence kinetic energy (TKE). During realtime FSOC demonstrations, in situ measurements are supplemented with NWP simulations, which provide near realtime characterizations and forecasts of the Cn2, the Fried Coherence Length (ro), and time-varying, three-dimensional characterizations of the atmosphere. The three dimensional Weather
NASA Astrophysics Data System (ADS)
Kawaguchi, Y.; Li, F. C.; Yu, B.; Wei, J. J.
It is well known that a small amount of chemicals such as water-soluble polymers or surfactants dramatically suppresses turbulence when they are added to liquid flow at large Reynolds number. In the last two decades, the application of surfactants to heat transportation systems such as district heating and cooling systems has attracted much interest among researchers. It has been revealed that 70% of the pumping power used to drive hot water in primary pipelines or district heating systems was saved by adding only a few hundred ppm of surfactant into the circulating water. The technological achievement requires a new design strategy for pipeline networks and heat exchangers to handle the drag reducing liquid flow. In the case of a Newtonian fluid such as water or air, the knowledge for designing fluid systems has been accumulated and the accuracy of numerical prediction is sufficient. On the other hand, the design system for surfactant solutions is not mature because drag-reducing flow phenomena are much more complicated than for Newtonian flow, for example, the friction factor for a surfactant solution depends not only on Reynolds number but also pipe diameter. In order to provide a design strategy for heat transportation systems using surfactant additives, we are now carrying out both experimental and numerical studies for surfactant solutions. In this lecture, experimental and numerical studies on the turbulence structure in drag reducing flow will be introduced. The result of an application study relating to the air conditioning system will be also shown.
Extended performance solar electric propulsion thrust system study. Volume 2: Baseline thrust system
NASA Technical Reports Server (NTRS)
Poeschel, R. L.; Hawthorne, E. I.
1977-01-01
Several thrust system design concepts were evaluated and compared using the specifications of the most advanced 30- cm engineering model thruster as the technology base. Emphasis was placed on relatively high-power missions (60 to 100 kW) such as a Halley's comet rendezvous. The extensions in thruster performance required for the Halley's comet mission were defined and alternative thrust system concepts were designed in sufficient detail for comparing mass, efficiency, reliability, structure, and thermal characteristics. Confirmation testing and analysis of thruster and power-processing components were performed, and the feasibility of satisfying extended performance requirements was verified. A baseline design was selected from the alternatives considered, and the design analysis and documentation were refined. The baseline thrust system design features modular construction, conventional power processing, and a concentractor solar array concept and is designed to interface with the space shuttle.
Chaotic transport in Hamiltonian systems perturbed by a weak turbulent wave field
Abdullaev, S. S.
2011-08-15
Chaotic transport in a Hamiltonian system perturbed by a weak turbulent wave field is studied. It is assumed that a turbulent wave field has a wide spectrum containing up to thousands of modes whose phases are fluctuating in time with a finite correlation time. To integrate the Hamiltonian equations a fast symplectic mapping is derived. It has a large time-step equal to one full turn in angle variable. It is found that the chaotic transport across tori caused by the interactions of small-scale resonances have a fractal-like structure with the reduced or zero values of diffusion coefficients near low-order rational tori thereby forming transport barriers there. The density of rational tori is numerically calculated and its properties are investigated. It is shown that the transport barriers are formed in the gaps of the density of rational tori near the low-order rational tori. The dependencies of the depth and width of transport barriers on the wave field spectrum and the correlation time of fluctuating turbulent field (or the Kubo number) are studied. These numerical findings may have importance in understanding the mechanisms of transport barrier formation in fusion plasmas.
Multiple Current Sheet Systems in the Outer Heliosphere: Energy Release and Turbulence
NASA Astrophysics Data System (ADS)
Burgess, D.; Gingell, P. W.; Matteini, L.
2016-05-01
In the outer heliosphere, beyond the solar wind termination shock, it is expected that the warped heliospheric current sheet forms a region of closely packed, multiple, thin current sheets. Such a system may be subject to the ion-kinetic tearing instability, and hence may generate magnetic islands and hot populations of ions associated with magnetic reconnection. Reconnection processes in this environment have important implications for local particle transport, and for particle acceleration at reconnection sites and in turbulence. We study this complex environment by means of three-dimensional hybrid simulations over long timescales, in order to capture the evolution from linear growth of the tearing instability to a fully developed turbulent state at late times. The final state develops from the highly ordered initial state via both forward and inverse cascades. Component and spectral anisotropy in the magnetic fluctuations is present when a guide field is included. The inclusion of a population of newborn interstellar pickup protons does not strongly affect these results. Finally, we conclude that reconnection between multiple current sheets can act as an important source of turbulence in the outer heliosphere, with implications for energetic particle acceleration and propagation.
Manned orbital systems concepts study. Book 2: Requirements for extended-duration missions
NASA Technical Reports Server (NTRS)
1975-01-01
In order to provide essential data needed in long-range program planning, the Manned Orbital Systems Concepts (MOSC) study attempted to define, evaluate, and compare concepts for manned orbital systems that provide extended experiment mission capabilities in space, flexibility of operation, and growth potential. Specific areas discussed include roles and requirements for man in future space missions, requirements for extended capability, mission/payload concepts, and preliminary design and operational requirements.
Analysis on Chopper's output mode of the extended blackbody radiation calibration system
NASA Astrophysics Data System (ADS)
Yu, Xun; Wei, Yu-han; Hu, Tie-li; Shang, Xiao-yan; Wu, Ji-an
2009-05-01
In the extended blackbody radiant system, Chopper plays a very important role.Herein the chopper's working principle is analyzed in the system of black body radical calibration, and the chopper's closed-loop control motor is simulated. With SimPowerSystems toolbox of MATLAB, the model of DC motor driving systems is built and its startup, steady state and speed regulation performance are simulated. Experiment result shows that the output is steady, accurate, reliable and could drive the chopper evenly which can satisfy technological requirement of the extended black body radiation calibration system.
Distinguishing ichthyogenic turbulence from geophysical turbulence
NASA Astrophysics Data System (ADS)
Pujiana, Kandaga; Moum, James N.; Smyth, William D.; Warner, Sally J.
2015-05-01
Measurements of currents and turbulence beneath a geostationary ship in the equatorial Indian Ocean during a period of weak surface forcing revealed unexpectedly strong turbulence beneath the surface mixed layer. Coincident with the turbulence was a marked reduction of the current speeds registered by shipboard Doppler current profilers, and an increase in their variability. At a mooring 1 km away, measurements of turbulence and currents showed no such anomalies. Correlation with the shipboard echo sounder measurements indicate that these nighttime anomalies were associated with fish aggregations beneath the ship. The fish created turbulence by swimming against the strong zonal current in order to remain beneath the ship, and their presence affected the Doppler speed measurements. The principal characteristics of the resultant ichthyogenic turbulence are (i) low wave number roll-off of shear spectra in the inertial subrange relative to geophysical turbulence, (ii) Thorpe overturning scales that are small compared with the Ozmidov scale, and (iii) low mixing efficiency. These factors extend previous findings by Gregg and Horne (2009) to a very different biophysical regime and support the general conclusion that the biological contribution to mixing the ocean via turbulence is negligible.
A simplified free-space adaptive optics system against atmospheric turbulence
NASA Astrophysics Data System (ADS)
Sharma, Sanjay
2012-03-01
Optical free-space communications have the distinct advantages over conventional radio frequency and microwave systems in terms of information capacity and increased security. However, optical carrier frequencies drastically suffer due to atmospheric turbulence. This effect is a random process and time-varying process; therefore, it is very difficult to overcome the effect. Adaptive optics is the technology used to mitigate chaotic optical wave-front distortions in real time by measuring the wave-front distortion with the help of a sensor and then adapting the wave-front corrector to lessen the phase distortions and ultimately to recover a closely approximated signal to its original counterpart. But these systems are too expensive and large. This study employs the various aspects of Adaptive Optics system, such as wave-front corrector, wave-front sensors and analytical analysis of open and closed-loop systems using loop equations, in order to make free-space optics communication links more vulnerable against atmospheric turbulence and wave-front phase distributions. The purpose of this study is to investigate a wave-front sensorless adaptive optics system, which would provide reduced complexity, size and cost.
A discrete analog of the extended Bass algorithm for stabilizing constant linear systems
NASA Technical Reports Server (NTRS)
Armstrong, E. S.; Rublein, G. T.
1976-01-01
Two methods for stabilizing constant linear systems, namely, the extended Bass algorithm for continuous systems and a discrete system analog, are discussed. For the continuous algorithm, a new result on the degree of stability of the closed-loop eigenvalues is presented, and for both methods, typical results and asymptotic trends in the data are illustrated through an example computation.
Talbot, L.; Cheng, R.K.
1993-12-01
Turbulent combustion is the dominant process in heat and power generating systems. Its most significant aspect is to enhance the burning rate and volumetric power density. Turbulent mixing, however, also influences the chemical rates and has a direct effect on the formation of pollutants, flame ignition and extinction. Therefore, research and development of modern combustion systems for power generation, waste incineration and material synthesis must rely on a fundamental understanding of the physical effect of turbulence on combustion to develop theoretical models that can be used as design tools. The overall objective of this program is to investigate, primarily experimentally, the interaction and coupling between turbulence and combustion. These processes are complex and are characterized by scalar and velocity fluctuations with time and length scales spanning several orders of magnitude. They are also influenced by the so-called {open_quotes}field{close_quotes} effects associated with the characteristics of the flow and burner geometries. The authors` approach is to gain a fundamental understanding by investigating idealized laboratory flames. Laboratory flames are amenable to detailed interrogation by laser diagnostics and their flow geometries are chosen to simplify numerical modeling and simulations and to facilitate comparison between experiments and theory.
The extended depth of field microscope imaging system with the phase pupil mask
NASA Astrophysics Data System (ADS)
Lyu, Qinghua; Zhai, Zhongsheng; Sharp, Martin; French, Paul
2015-11-01
A `0/π' phase pupil mask was developed to extend the depth of field of a circularly symmetric optical microscope imaging system. The modulation transfer function curves, the normalized point spread function figures and the spot diagrams of the imaging system with the optimal mask were analyzed and simulated. The results show that the large depth of field imaging system with the `0/π' phase pupil mask has a high resolution in a long frequency band and can obtain clear images without any post-processing. The experimental results also demonstrate that the depth of field of the imaging system is extended successfully.
An atmospheric turbulence generator for dynamic tests with LINC-NIRVANA's adaptive optics system
NASA Astrophysics Data System (ADS)
Meschke, D.; Bizenberger, P.; Gaessler, W.; Zhang, X.; Mohr, L.; Baumeister, H.; Diolaiti, E.
2010-07-01
LINC-NIRVANA[1] (LN) is an instrument for the Large Binocular Telescope[2] (LBT). Its purpose is to combine the light coming from the two primary mirrors in a Fizeau-type interferometer. In order to compensate turbulence-induced dynamic aberrations, the layer oriented adaptive optics system of LN[3] consists of two major subsystems for each side: the Ground-Layer-Wavefront sensor (GLWS) and the Mid- and High-Layer Wavefront sensor (MHLWS). The MHLWS is currently set up in a laboratory at the Max-Planck-Institute for Astronomy in Heidelberg. To test the multi-conjugate AO with multiple simulated stars in the laboratory and to develop the necessary control software, a dedicated light source is needed. For this reason, we designed an optical system, operating in visible as well as in infrared light, which imitates the telescope's optical train (f-ratio, pupil position and size, field curvature). By inserting rotating surface etched glass phase screens, artificial aberrations corresponding to the atmospheric turbulence are introduced. In addition, different turbulence altitudes can be simulated depending on the position of these screens along the optical axis. In this way, it is possible to comprehensively test the complete system, including electronics and software, in the laboratory before integration into the final LINC-NIRVANA setup. Combined with an atmospheric piston simulator, also this effect can be taken into account. Since we are building two identical sets, it is possible to feed the complete instrument with light for the interferometric combination during the assembly phase in the integration laboratory.
Introduction to quantum turbulence
Barenghi, Carlo F.; Skrbek, Ladislav; Sreenivasan, Katepalli R.
2014-01-01
The term quantum turbulence denotes the turbulent motion of quantum fluids, systems such as superfluid helium and atomic Bose–Einstein condensates, which are characterized by quantized vorticity, superfluidity, and, at finite temperatures, two-fluid behavior. This article introduces their basic properties, describes types and regimes of turbulence that have been observed, and highlights similarities and differences between quantum turbulence and classical turbulence in ordinary fluids. Our aim is also to link together the articles of this special issue and to provide a perspective of the future development of a subject that contains aspects of fluid mechanics, atomic physics, condensed matter, and low-temperature physics. PMID:24704870
Introduction to quantum turbulence.
Barenghi, Carlo F; Skrbek, Ladislav; Sreenivasan, Katepalli R
2014-03-25
The term quantum turbulence denotes the turbulent motion of quantum fluids, systems such as superfluid helium and atomic Bose-Einstein condensates, which are characterized by quantized vorticity, superfluidity, and, at finite temperatures, two-fluid behavior. This article introduces their basic properties, describes types and regimes of turbulence that have been observed, and highlights similarities and differences between quantum turbulence and classical turbulence in ordinary fluids. Our aim is also to link together the articles of this special issue and to provide a perspective of the future development of a subject that contains aspects of fluid mechanics, atomic physics, condensed matter, and low-temperature physics. PMID:24704870
Eighmy, T. Taylor; Bishop, P. L.
1985-01-01
This research documents an effect of reactor turbulence on the ability of gram-negative wastewater biofilm bacteria to actively transport l-aspartate via a binding-protein-mediated transport system. Biofilms which were not preadapted to turbulence and which possessed two separate and distinct aspartate transport systems (systems 1 and 2) were subjected to a turbulent flow condition in a hydrodynamically defined closed-loop reactor system. A shear stress treatment of 3.1 N · m−2 for 10 min at a turbulent Reynolds number (Re = 11,297) inactivated the low-affinity, high-capacity binding-protein-mediated transport system (system 2) and resolved the high-affinity, low-capacity membrane-bound proton symport system (system 1). The Kt and Vmax values for the resolved system were statistically similar to Kt and Vmax values for system 1 when system 2 was inactivated either by osmotic shock or arsenate, two treatments which are known to inactivate binding-protein-mediated transport systems. We hypothesize that shear stress disrupts system 2 by deforming the outer membranes of the firmly adhered gram-negative bacteria. PMID:16346830
Robust extended dissipative control for sampled-data Markov jump systems
NASA Astrophysics Data System (ADS)
Shen, Hao; Park, Ju H.; Zhang, Lixian; Wu, Zheng-Guang
2014-08-01
This paper investigates the problem of the sampled-data extended dissipative control for uncertain Markov jump systems. The systems considered are transformed into Markov jump systems with polytopic uncertainties and sawtooth delays by using an input delay approach. The focus is on the design of a mode-independent sampled-data controller such that the resulting closed-loop system is mean-square exponentially stable with a given decay rate and extended dissipative. A novel exponential stability criterion and an extended dissipativty condition are established by proposing a new integral inequality. The reduced conservatism of the criteria is demonstrated by two numerical examples. Furthermore, a sufficient condition for the existence of a desired mode-independent sampled-data controller is obtained by solving a convex optimisation problem. Finally, a resistance, inductance and capacitance (RLC) series circuit is employed to illustrate the effectiveness of the proposed approach.
ERIC Educational Resources Information Center
Ferran, C.; Bosch, S.; Carnicer, A.
2012-01-01
A practical activity designed to introduce wavefront coding techniques as a method to extend the depth of field in optical systems is presented. The activity is suitable for advanced undergraduate students since it combines different topics in optical engineering such as optical system design, aberration theory, Fourier optics, and digital image…
Stirring turbulence with turbulence
NASA Astrophysics Data System (ADS)
Cekli, Hakki Ergun; Joosten, René; van de Water, Willem
2015-12-01
We stir wind-tunnel turbulence with an active grid that consists of rods with attached vanes. The time-varying angle of these rods is controlled by random numbers. We study the response of turbulence on the statistical properties of these random numbers. The random numbers are generated by the Gledzer-Ohkitani-Yamada shell model, which is a simple dynamical model of turbulence that produces a velocity field displaying inertial-range scaling behavior. The range of scales can be adjusted by selection of shells. We find that the largest energy input and the smallest anisotropy are reached when the time scale of the random numbers matches that of the largest eddies of the wind-tunnel turbulence. A large mismatch of these times creates a highly intermittent random flow with interesting but quite anomalous statistics.
Design of a collective scattering system for electron gyroscale turbulence study in KSTAR
NASA Astrophysics Data System (ADS)
Lee, Woochang; Park, Hyeon; Lee, Dongjae; Leem, Juneeok; Nam, Yongun
2015-11-01
The design characteristics of a multi-channel collective (or coherent) scattering system for electron scale turbulence study in KSTAR, which is planned to be installed in 2016, are investigated. A few critical issues are discussed in depth such as effect of the Faraday rotation of the electric field polarization of probing and scattered, the probing wave frequency which is related to the optics for measurement of electron gyro scale turbulence, the wave polarization to minimize absorption of the probing power by electron cyclotron resonant layers, and the probing power. A proper and feasible optics with 300 GHz probing wave, which is based on these issues, provides a simultaneous measurement of electron density fluctuations at four discrete poloidal wave numbers up to 21 cm-1. The upper limit corresponds to the normalized wave number k⊥ρe of 0.2 in KSTAR plasmas. To detect scattered wave power and extract phase information, a quadrature detection system consisting of four-channel antenna/detector array and electronics will be employed. Work supported by NRF Korea under grant numbers NRF-2015M1A7A1A02002627 and NRF-2014M1A7A1A03029865.
Robust energy transfer mechanism via precession resonance in nonlinear turbulent wave systems
NASA Astrophysics Data System (ADS)
Lucas, Dan; Bustamante, Miguel; Quinn, Brenda
2014-11-01
The precise mechanisms by which energy is most efficiently transferred in a turbulent system remain an important open question for the fluid mechanics community. In this talk we present a newly discovered resonance which is found to drive transfers across the spectrum of Fourier modes in a nonlinear wave system. Quadratic nonlinearity results in modes interacting in triads and, by considering the ``truly dynamical degrees of freedom'' (amplitudes and triad phases) and the precessional frequencies of the triads, we show transfers are maximal when the precession resonates with the nonlinear temporal frequencies. This can lead to a collective state of synchronised triads with intense cascades at intermediate nonlinearity; we find greatest transfer between the traditional weak and strong turbulence regimes and discover that this new mechanism is dominant here. We present the effect in a hierarchy of models including a full DNS of the Charney-Hasegawa-Mima equation and confirm analytical predictions. Supported by Science Foundation Ireland (SFI) under Grant Number 12/IP/1491.
NASA Astrophysics Data System (ADS)
Zhu, Lin; Luo, Xudong; Ma, Hongru
2016-03-01
We analytically extend the scope of transformation optics (TO) to metamaterial-modified wireless power transfer (WPT) systems and demonstrate that the extended TO can help design the highly efficient WPT. The methodology is based on rigorous scattering theory, enabling an equivalent model under certain circumstances to be established, that can significantly simplify investigating metamaterial-enhanced WPT. More important, from the analytical study on the equivalent model, we prove that TO is still applicable, even when the conditions of complementary media are not satisfied. Our findings are verified numerically using our methodology as well as COMSOL simulations. Moreover, a further study also indicates the extended TO explanation as well as the analysis of the equivalent model could help improve the transfer efficiency of WPT significantly. The demonstrations are not restricted to any specific frequency, and the conclusions could be extended to a broad range of wavelengths, including applications to active cloaks and other related devices.
The onset of vortex turbulence
Huber, G. . Center for Polymer Studies Lawrence Berkeley Lab., CA )
1992-12-01
It is the goal of this thesis to investigate some of the unusual and spectacular properties near the transition to turbulence in a two-dimensional field of limit-cycle oscillators. Of particular interest are the dynamics of topological defects (vortices) associated with the onset of turbulence. The complex Ginzburg-Landau equation describes an extended reaction-diffusion system close to the bifurcation of a steady state into a stable, periodic orbit. In the jargon of nonlinear dynamics, it is the amplitude equation corresponding to a Hopf bifurcation. Because of the generality of the assumptions under which it is derived, the complex Ginzburg-Landau equation describes systems in contexts other than chemical reactions with diffusion. Examples include Rayleigh-Benard convection and the phase fields of multimode lasers. The reaction-diffusion model is however, a sufficiently general model to frame our discussion.
Influence of atmospheric turbulence on OAM-based FSO system with use of realistic link model
NASA Astrophysics Data System (ADS)
Li, Ming; Yu, Zhongyuan; Cvijetic, Milorad
2016-04-01
We study the influence of atmospheric turbulence on OAM-based free-space optical (FSO) communication by using the Pump turbulence spectrum model which accurately characterizes the realistic FSO link. A comprehensive comparison is made between the Pump and Kolmogorov spectrum models with respect to the turbulence impact. The calculated results show that obtained turbulence-induced crosstalk is lower, which means that a higher channel capacity is projected when the realistic Pump spectrum is used instead of the Kolmogorov spectrum. We believe that our results prove that performance of practical OAM-based FSO is better than one predicted by using the original Kolmogorov turbulence model.
NASA Astrophysics Data System (ADS)
Hasan, Omar M.; Taha, Mohamed; Abu Sharkh, Osama
2016-06-01
In this paper, we investigate outage capacity, outage probability, and outage rate performance of multiple-input multiple-output (MIMO) free-space optical system operating over strong turbulence channels. The MIMO optical system employs intensity modulation direct detection with on-off signaling, and equal gain combining technique at the receiver. We derived novel closed-form expressions for three system metrics, namely, outage capacity, outage probability, and outage rate. Expressions derived here are based on the generalized Gamma-Gamma channel model, which is based on scintillation theory that assumes that the irradiance of the received optical wave is modeled as the product of small-scale and large-scale turbulence eddies. The results are evaluated for different values of received signal-to-noise ratios, strong turbulence conditions, and several values of transmit/receive diversity.
Edge of chaos and genesis of turbulence.
Chian, Abraham C-L; Muñoz, Pablo R; Rempel, Erico L
2013-11-01
The edge of chaos is analyzed in a spatially extended system, modeled by the regularized long-wave equation, prior to the transition to permanent spatiotemporal chaos. In the presence of coexisting attractors, a chaotic saddle is born at the basin boundary due to a smooth-fractal metamorphosis. As a control parameter is varied, the chaotic transient evolves to well-developed transient turbulence via a cascade of fractal-fractal metamorphoses. The edge state responsible for the edge of chaos and the genesis of turbulence is an unstable traveling wave in the laboratory frame, corresponding to a saddle point lying at the basin boundary in the Fourier space. PMID:24329334
NASA Astrophysics Data System (ADS)
Wang, Xudong; Syrmos, Vassilis L.
2004-07-01
In this paper, an adaptive reconfigurable control system based on extended Kalman filter approach and eigenstructure assignments is proposed. System identification is carried out using an extended Kalman filter (EKF) approach. An eigenstructure assignment (EA) technique is applied for reconfigurable feedback control law design to recover the system dynamic performance. The reconfigurable feedforward controllers are designed to achieve the steady-state tracking using input weighting approach. The proposed scheme can identify not only actuator and sensor variations, but also changes in the system structures using the extended Kalman filtering method. The overall design is robust with respect to uncertainties in the state-space matrices of the reconfigured system. To illustrate the effectiveness of the proposed reconfigurable control system design technique, an aircraft longitudinal vertical takeoff and landing (VTOL) control system is used to demonstrate the reconfiguration procedure.
Siemieniuch, C E; Sinclair, M A
2014-01-01
Socio-technical issues for Systems of Systems (SoS) differ in several ways from those for systems, mainly because the individual systems that are components of the SoS are usually owned by different organisations, each responsible for the optimisation and operation of its own system. Consequently, management of the SoS is about negotiation and management of the interfaces. Because of issues of Intellectual Property Rights (IPRs), commercial confidence, and the like, there is seldom sufficient, timely information in circulation about the SoS. Surprises are endemic to SoS, and resilience is a fundamental requirement. This paper outlines the different characteristics of SoS compared to ordinary systems, discusses many of the socio-technical issues involved, and then outlines a generic approach to these issues, treating the SoS as a 'wicked problem'. Endemic to this is the need for governance, which is discussed briefly. This is followed by a description of the evident gaps in knowledge about the functioning of SoS, and a listing of tool classes, the development of which would enable progress to be made more effectively. Finally, the paper discusses how the SoS approach might be the best way to entrain ICT to address global drivers, thus pointing to the importance of the SoS approach. PMID:24011651
Local heterogeneities in cardiac systems suppress turbulence by generating multi-armed rotors
NASA Astrophysics Data System (ADS)
Zhang, Zhihui; Steinbock, Oliver
2016-05-01
Ventricular fibrillation is an extremely dangerous cardiac arrhythmia that is linked to rotating waves of electric activity and chaotically moving vortex lines. These filaments can pin to insulating, cylindrical heterogeneities which swiftly become the new rotation backbone of the local wave field. For thin cylinders, the stabilized rotation is sufficiently fast to repel the free segments of the turbulent filament tangle and annihilate them at the system boundaries. The resulting global wave pattern is periodic and highly ordered. Our cardiac simulations show that also thicker cylinders can establish analogous forms of tachycardia. This process occurs through the spontaneous formation of pinned multi-armed vortices. The observed number of wave arms N depends on the cylinder radius and is associated to stability windows that for N = 2, 3 partially overlap. For N = 1, 2, we find a small gap in which the turbulence is removed but the pinned rotor shows complex temporal dynamics. The relevance of our findings to human cardiology are discussed in the context of vortex pinning to more complex-shaped anatomical features and remodeled myocardium.
NASA Astrophysics Data System (ADS)
Bian, Shiyao; Ceccio, Steven L.; Driscoll, James F.
2004-11-01
Simultaneous measurements of velocity and concentration fields are of great importance to understand the mechanism of turbulent mixing. We are developing a combined cinematographic particle image velocimetry (CPIV) and cinematographic planar laser-induced fluorescence (CPLIF) system that is capable of recording velocity fields and concentration profiles at 2 kHz with a spatial resolution of 0.5 mm. Two registered cameras will be used to the CPIV and a third for the CPLIF. We are validating the system through the examination of a well-characterized flow: the round turbulent jet. A series of measurements are performed in the self-similar far field of an axisymmetric turbulent water jet. Mean and fluctuating velocity and concentration quantities are obtained by simultaneous CPLIF and CPIV measurements. The precision of single and duel camera CPIV is investigated. [Sponsored by National Science Foundation Grant: CTM 0203140
Angle extended linear MEMS scanning system for 3D laser vision sensor
NASA Astrophysics Data System (ADS)
Pang, Yajun; Zhang, Yinxin; Yang, Huaidong; Zhu, Pan; Gai, Ye; Zhao, Jian; Huang, Zhanhua
2016-09-01
Scanning system is often considered as the most important part for 3D laser vision sensor. In this paper, we propose a method for the optical system design of angle extended linear MEMS scanning system, which has features of huge scanning degree, small beam divergence angle and small spot size for 3D laser vision sensor. The principle of design and theoretical formulas are derived strictly. With the help of software ZEMAX, a linear scanning optical system based on MEMS has been designed. Results show that the designed system can extend scanning angle from ±8° to ±26.5° with a divergence angle small than 3.5 mr, and the spot size is reduced for 4.545 times.
Tactical missile turbulence problems
NASA Technical Reports Server (NTRS)
Dickson, Richard E.
1987-01-01
Of particular interest is atmospheric turbulence in the atmospheric boundary layer, since this affects both the launch and terminal phase of flight, and the total flight for direct fire systems. Brief discussions are presented on rocket artillery boost wind problems, mean wind correction, turbulent boost wind correction, the Dynamically Aimed Free Flight Rocket (DAFFR) wind filter, the DAFFR test, and rocket wake turbulence problems. It is concluded that many of the turbulence problems of rockets and missiles are common to those of aircraft, such as structural loading and control system design. However, these problems have not been solved at this time.
Extended Attention Span Training System: Video Game Neurotherapy for Attention Deficit Disorder.
ERIC Educational Resources Information Center
Pope, Alan T.; Bogart, Edward H.
1996-01-01
Describes the Extended Attention Span Training (EAST) system for modifying attention deficits, which takes the concept of biofeedback one step further by making a video game more difficult as the player's brain waves indicate that attention is waning. Notes contributions of this technology to neuropsychology and neurology, where the emphasis is on…
Federal Register 2010, 2011, 2012, 2013, 2014
2010-08-16
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Kang, Yu; Zhai, Di-Hua; Liu, Guo-Ping; Zhao, Yun-Bo
2016-05-01
An extended asynchronous switching model is investigated for a class of switched stochastic nonlinear retarded systems in the presence of both detection delay and false alarm, where the extended asynchronous switching is described by two independent and exponentially distributed stochastic processes, and further simplified as Markovian. Based on the Razumikhin-type theorem incorporated with average dwell-time approach, the sufficient criteria for global asymptotic stability in probability and stochastic input-to-state stability are given, whose importance and effectiveness are finally verified by numerical examples. PMID:26068932
Definition study for an extended manned test of a regenerative life support system
NASA Technical Reports Server (NTRS)
1971-01-01
A program was defined which consists of extended ground-based manned tests of regenerative life support systems. The tests are to evaluate prototypes of advanced life support systems under operational, integrated conditions, thus providing data for the design of efficient environmental control and life support systems for use in long-duration space missions. The requirements are defined for test operations to provide a simulation of an orbiting space laboratory. The features of Phase A and B programs are described. These tests use proven backup equipment to ensure successful evaluation of the advanced subsystems. A pre-tests all-systems checkout period is provided to minimize equipment problems during extended testing and to familiarize all crew and operating staff members with test equipment and procedures.
Data-driven prediction and prevention of extreme events in a spatially extended excitable system
NASA Astrophysics Data System (ADS)
Bialonski, Stephan; Ansmann, Gerrit; Kantz, Holger
2015-10-01
Extreme events occur in many spatially extended dynamical systems, often devastatingly affecting human life, which makes their reliable prediction and efficient prevention highly desirable. We study the prediction and prevention of extreme events in a spatially extended system, a system of coupled FitzHugh-Nagumo units, in which extreme events occur in a spatially and temporally irregular way. Mimicking typical constraints faced in field studies, we assume not to know the governing equations of motion and to be able to observe only a subset of all phase-space variables for a limited period of time. Based on reconstructing the local dynamics from data and despite being challenged by the rareness of events, we are able to predict extreme events remarkably well. With small, rare, and spatiotemporally localized perturbations which are guided by our predictions, we are able to completely suppress extreme events in this system.
NASA Astrophysics Data System (ADS)
Papp, John Laszlo
2000-10-01
The successful application of CFD and turbulence modeling methods to an aerospike nozzle system first involves the successful simulation of its key flow components. This report addresses the task using the Chien low-Re k-epsilon and the Yakhot et al. high-Re RNG k-epsilon turbulence models. An improved implicit axis of symmetry boundary condition is also developed to increase stability and lower artificial dissipation. Grid adaptation through the SAGE post-processing package is used throughout the study. The RNG model, after low-Re modifications, and the Chien low-Re k-epsilon model are applied to the supersonic axisymmetric base flow problem. Both models predict a peak recirculation velocity almost twice as large as experiment. The RNG model predicts a flatter base pressure and lower recirculation velocity more consistent with experimental data using less grid points than a comparable Chien model solution. The turbulent quantities predicted by both models are typical of other numerical results and generally under predict peak values obtained in experiment suggesting that too little turbulent eddy viscosity is produced. After several test cases, the full 3-D aerospike nozzle is simulated using both the Chien and modified RNG low-Re models. The Chien model outperforms the RNG model in all circumstances. The surface pressure predicted by the Chien model along the nozzle center-plane is very near experiment while mid-plane results are not as close but useful for design purposes. The lack of a thick boundary layer along the nozzle surface in RNG simulations is the cause of poor surface pressure comparisons. Although initial base flow comparisons between the model predictions and experiment are poor, the profiles are relatively flat. To accelerate the progress to a steady-state solution, a process involving the artificial lowering of the base pressure and subsequent iteration to a new steady state is undertaken. After several of these steps, the resulting steady
Open-loop correction of horizontal turbulence: system design and result.
Mu, Quanquan; Cao, Zhaoliang; Li, Dayu; Hu, Lifa; Xuan, Li
2008-08-10
Adaptive optics systems often work in a closed-loop configuration due to the hysteretic and nonlinearity properties of conventional deformable mirrors. Because of the high-precision wavefront generation and nonhysteretic properties of liquid-crystal devices, the open-loop control becomes possible. Open-loop control is a requirement for advanced adaptive optics concepts. We designed an open-loop adaptive optics system with a liquid-crystal-on-silicon wavefront corrector. This system is simple, fast, and can save much more light compared to conventional liquid-crystal-based closed-loop systems. The detailed principle, construction, and operation are discussed. The 500 m horizontal turbulence correction experiment was done using a 250 mm telescope in the laboratory. The whole system can reach a 60 Hz correction frequency. Evaluation of the correction precision was done at closed-loop configuration, which is 0.2 lambda (lambda=0.633 microm) in peak to valley. The dynamic image under open-loop correction got the same resolution compared to closed-loop correction. The whole system reached 0.68 arc sec resolution capability at open-loop correction, which is slightly larger than the system's diffraction-limited resolution of 0.65 arc sec. PMID:18690274
A POD-based analysis of turbulence in the reduced nonlinear dynamics system
NASA Astrophysics Data System (ADS)
Nikolaidis, M.-A.; Farrell, B. F.; Ioannou, P. J.; Gayme, D. F.; Lozano-Durán, A.; Jiménez, J.
2016-04-01
The structure of turbulence in a reduced model of turbulence (RNL) is analyzed by means of a Proper Orthogonal Decomposition (POD modes). POD analysis was carried out on two different components of the flow, the roll/streak and the perturbation structure. The POD structure in both RNL and direct numerical simulations (DNS) is similar and this correspondence suggests that the dynamics retained in RNL are the essential dynamical ingredients underlying the self-sustaining mechanism of the turbulent state.
NASA Technical Reports Server (NTRS)
Katzberg, S. J.
1972-01-01
A primary limitation of many solid-state photodetectors used in electro-optical systems such as the facsimile camera is their slow response in converting light intensities into electrical signals. An optical feedback technique is presented which can extend the frequency response of systems that use these detectors by orders of magnitude without significantly degrading their signal-to-noise performance. This technique is analyzed to predict improvement, implemented, and evaluated to verify analytical results.
NASA Astrophysics Data System (ADS)
Lynch, Gillian C.; Pettitt, B. Montgomery
1997-11-01
The extended system Hamiltonian for carrying out grand canonical ensemble molecular dynamics simulations is reformulated. This new Hamiltonian includes a generalized treatment of the reference state partition function of the total chemical potential that reproduces the ideal gas behavior and various previous partitionings of ideal and excess terms. Initial calculations are performed on a system of Lennard-Jones particles near the triple point and on liquid water at room temperature.
Controlling chaos in spatially extended beam-plasma system by the continuous delayed feedback
Hramov, Alexander E.; Koronovskii, Alexey A.; Rempen, Irene S.
2006-03-15
In this paper we discuss the control of complex spatio-temporal dynamics in a spatially extended nonlinear system (fluid model of Pierce diode) based on the concepts of controlling chaos in the systems with few degrees of freedom. A presented method is connected with stabilization of unstable homogeneous equilibrium state and the unstable spatio-temporal periodical states analogous to unstable periodic orbits of chaotic dynamics of the systems with few degrees of freedom. We show that this method is effective and allows to achieve desired regular dynamics chosen from a number of possible in the considered system.
A Huygens principle for diffusion and anomalous diffusion in spatially extended systems
Gottwald, Georg A.; Melbourne, Ian
2013-01-01
We present a universal view on diffusive behavior in chaotic spatially extended systems for anisotropic and isotropic media. For anisotropic systems, strong chaos leads to diffusive behavior (Brownian motion with drift) and weak chaos leads to superdiffusive behavior (Lévy processes with drift). For isotropic systems, the drift term vanishes and strong chaos again leads to Brownian motion. We establish the existence of a nonlinear Huygens principle for weakly chaotic systems in isotropic media whereby the dynamics behaves diffusively in even space dimension and exhibits superdiffusive behavior in odd space dimensions. PMID:23653481
NASA Technical Reports Server (NTRS)
Devasirvatham, D. M. J.; Hodge, D. B.
1981-01-01
A model of the microwave and millimeter wave link in the presence of atmospheric turbulence is presented with emphasis on satellite communications systems. The analysis is based on standard methods of statistical theory. The results are directly usable by the design engineer.
Spatial and spectral evolution of turbulence
Guercan, O. D.; Diamond, P. H.; Hahm, T. S.
2007-05-15
Spreading of turbulence as a result of nonlinear mode couplings and the associated spectral energy transfer is studied. A derivation of a simple two-field model is presented using the weak turbulence limit of the two-scale direct interaction approximation. This approach enables the approximate overall effect of nonlinear interactions to be written in the form of Fick's law and leads to a coupled reaction-diffusion system for turbulence intensity. For this purpose, various classes of triad interactions are examined, and the effects that do not lead to spreading are neglected. It is seen that, within this framework, large scale, radially extended eddies are the most effective structures in promoting spreading of turbulence. Thus, spectral evolution that tends toward such eddies facilitates spatial spreading. Self-consistent evolution of the background profile is also considered, and it is concluded that the profile is essentially slaved to the turbulence in this phase of rapid evolution, as opposed to the case of avalanches, where it is the turbulence intensity that would be slaved to the evolving profile. The characteristic quantity describing the evolving background profile is found to be the mean ''potential vorticity'' (PV). It is shown that the two-field model with self-consistent mean PV evolution can be reduced to a single Fisher-like turbulence intensity transport equation. In addition to the usual nonlinear diffusion term, this equation also contains a 'pinch' of turbulence intensity. It is also noted that internal energy spreads faster than kinetic energy because of the respective spectral tendencies of these two quantities.
NASA Technical Reports Server (NTRS)
Manning, Robert M.
2005-01-01
Solutions are derived for the generalized mutual coherence function (MCF), i.e., the second order moment, of a random wave field propagating through a random medium within the context of the extended parabolic equation. Here, "generalized" connotes the consideration of both the transverse as well as the longitudinal second order moments (with respect to the direction of propagation). Such solutions will afford a comparison between the results of the parabolic equation within the pararaxial approximation and those of the wide-angle extended theory. To this end, a statistical operator method is developed which gives a general equation for an arbitrary spatial statistical moment of the wave field. The generality of the operator method allows one to obtain an expression for the second order field moment in the direction longitudinal to the direction of propagation. Analytical solutions to these equations are derived for the Kolmogorov and Tatarskii spectra of atmospheric permittivity fluctuations within the Markov approximation.
A knowledge based application of the extended aircraft interrogation and display system
NASA Technical Reports Server (NTRS)
Glover, Richard D.; Larson, Richard R.
1991-01-01
A family of multiple-processor ground support test equipment was used to test digital flight-control systems on high-performance research aircraft. A unit recently built for the F-18 high alpha research vehicle project is the latest model in a series called the extended aircraft interrogation and display system. The primary feature emphasized monitors the aircraft MIL-STD-1553B data buses and provides real-time engineering units displays of flight-control parameters. A customized software package was developed to provide real-time data interpretation based on rules embodied in a highly structured knowledge database. The configuration of this extended aircraft interrogation and display system is briefly described, and the evolution of the rule based package and its application to failure modes and effects testing on the F-18 high alpha research vehicle is discussed.
ERIC Educational Resources Information Center
Starratt, Robert J.
2004-01-01
In this article, the author discusses how superintendents function in an environment of nearly continuous turbulence challenged by concerns and pressures that compete for their attention and resolution. The turbulence is inescapable. Today it constitutes the natural--but not the exceptional--environment of school board politics, local…
Structure Theory for Extended Kepler-Coulomb 3D Classical Superintegrable Systems
NASA Astrophysics Data System (ADS)
Kalnins, Ernie G.; Miller, Willard, Jr.
2012-06-01
The classical Kepler-Coulomb system in 3 dimensions is well known to be 2nd order superintegrable, with a symmetry algebra that closes polynomially under Poisson brackets. This polynomial closure is typical for 2nd order superintegrable systems in 2D and for 2nd order systems in 3D with nondegenerate (4-parameter) potentials. However the degenerate 3-parameter potential for the 3D extended Kepler-Coulomb system (also 2nd order superintegrable) is an exception, as its quadratic symmetry algebra doesn't close polynomially. The 3D 4-parameter potential for the extended Kepler-Coulomb system is not even 2nd order superintegrable. However, Verrier and Evans (2008) showed it was 4th order superintegrable, and Tanoudis and Daskaloyannis (2011) showed that in the quantum case, if a second 4th order symmetry is added to the generators, the double commutators in the symmetry algebra close polynomially. Here, based on the Tremblay, Turbiner and Winternitz construction, we consider a! n infinite class of classical extended Kepler-Coulomb 3- and 4-parameter systems indexed by a pair of rational numbers (k1,k2) and reducing to the usual systems when k1=k2=1. We show these systems to be superintegrable of arbitrarily high order and work out explicitly the structure of the symmetry algebras determined by the 5 basis generators we have constructed. We demonstrate that the symmetry algebras close rationally; only for systems admitting extra discrete symmetries is polynomial closure achieved. Underlying the structure theory is the existence of raising and lowering constants of the motion, not themselves polynomials in the momenta, that can be employed to construct the polynomial symmetries and their structure relations.
A nonequilibrium statistical field theory of swarms and other spatially extended complex systems
Millonas, M.M. Santa Fe Inst., NM )
1993-01-01
A class of models with applications to swarm behavior as well as many other types of spatially extended complex biological and physical systems is studied. Internal fluctuations can play an active role in the organization of the phase structure of such systems. Consequently, it is not possible to fully understand the behavior of these systems without explicitly incorporating the fluctuations. In particular, for the class of models studied here the effect of internal fluctuations due to finite size is a renormalized decrease in the temperature near the point of spontaneous symmetry breaking. We briefly outline how these models can be applied to the behavior of an ant swarm.
A nonequilibrium statistical field theory of swarms and other spatially extended complex systems
Millonas, M.M. |
1993-07-01
A class of models with applications to swarm behavior as well as many other types of spatially extended complex biological and physical systems is studied. Internal fluctuations can play an active role in the organization of the phase structure of such systems. Consequently, it is not possible to fully understand the behavior of these systems without explicitly incorporating the fluctuations. In particular, for the class of models studied here the effect of internal fluctuations due to finite size is a renormalized decrease in the temperature near the point of spontaneous symmetry breaking. We briefly outline how these models can be applied to the behavior of an ant swarm.
Spreading and wandering of Gaussian–Schell model laser beams in an anisotropic turbulent ocean
NASA Astrophysics Data System (ADS)
Wu, Yuqian; Zhang, Yixin; Zhu, Yun; Hu, Zhengda
2016-09-01
The effect of anisotropic turbulence on the spreading and wandering of Gaussian–Schell model (GSM) laser beams propagating in an ocean is studied. The long-term spreading of a GSM beam propagating through the paraxial channel of a turbulent ocean is also developed. Expressions of random wander for such laser beams are derived in an anisotropic turbulent ocean based on the extended Huygens–Fresnel principle. We investigate the influence of parameters in a turbulent ocean on the beam wander and spreading. Our results indicate that beam spreading and random beam wandering are smaller without considering the anisotropy of turbulence in the oceanic channel. Salinity fluctuation has a greater contribution to both the beam spreading and beam wander than that of temperature fluctuations in a turbulent ocean. Our results could be helpful for designing a free-space optical wireless communication system in an oceanic environment.
Interacting Thin Film Systems Probed by Electron Induced Extended Fine Structure
NASA Astrophysics Data System (ADS)
Idzerda, Yves Ulrich
In order to obtain information on the structure and dynamics of various systems including interacting thin films, it is necessary to be able to measure local structure information with surface sensitivity. Three techniques of Electron Induced Extended Fine Structure (EIEFS), the electron analog of Extended X-ray Absorption Fine Structure (EXAFS), are described, compared, and applied to thin film systems. Surface Extended Electron Loss Fine Structure (SEELFS), Extended Appearence Potential Fine Structure (EAPFS) and Auger-Monitored Extended Fine Structure (AMEFS), are all local structure probes with varying degrees of surface sensitivity, and all yield similar information. Our results show that each technique can be measured by commercially available electron optics, SEELFS and AMEFS by either a cylindrical mirror analyzer (CMA) or by low energy electron diffraction (LEED) optics and EAPFS by the LEED optics. We have addressed questions concerning proper phase shifts for the analysis, short data ranges, required use of undifferentiated data, and experimental difficulties. Investigations of carbon, oxygen, sodium, potassium, cesium, and sulfur on Cu(111) and titanium on silicon demonstrate that SEELFS is applicable to single monolayer coverages of very low Z adsorbates and thin films. Many of the theoretical difficulties surrounding the analysis of SEELFS can be circumvented by the use of standards and the ratio technique analysis developed for EXAFS. We also find in our studies of silicon, titanium, and aluminum oxide that systems with plasmon losses in the region of interest cannot be analyzed, but systems with other characteristic losses which are very sharp or very broad can be. Examination of EAPFS shows that it is more surface sensitive and is applicable to single monolayer coverages (of a broader range of elements than SEELFS) and thin films. Unfortunately, EAPFS is not applicable to single crystal systems with low electron binding energies where diffraction
NASA Astrophysics Data System (ADS)
Vanag, Vladimir K.
1999-05-01
Spatially extended dynamical systems are ubiquitous and include such things as insect and animal populations; complex chemical, technological, and geochemical processes; humanity itself, and much more. It is clearly desirable to have a certain universal tool with which the highly complex behaviour of nonlinear dynamical systems can be analyzed and modelled. For this purpose, cellular automata seem to be good candidates. In the present review, emphasis is placed on the possibilities that various types of probabilistic cellular automata (PCA), such as DSMC (direct simulation Monte Carlo) and LGCA (lattice-gas cellular automata), offer. The methods are primarily designed for modelling spatially extended dynamical systems with inner fluctuations accounted for. For the Willamowskii-Roessler and Oregonator models, PCA applications to the following problems are illustrated: the effect of fluctuations on the dynamics of nonlinear systems; Turing structure formation; the effect of hydrodynamic modes on the behaviour of nonlinear chemical systems (stirring effects); bifurcation changes in the dynamical regimes of complex systems with restricted geometry or low spatial dimension; and the description of chemical systems in microemulsions.
NASA Astrophysics Data System (ADS)
Aggarwal, Priyanka; Syed, Zainab; El-Sheimy, Naser
2009-05-01
Navigation includes the integration of methodologies and systems for estimating time-varying position, velocity and attitude of moving objects. Navigation incorporating the integrated inertial navigation system (INS) and global positioning system (GPS) generally requires extensive evaluations of nonlinear equations involving double integration. Currently, integrated navigation systems are commonly implemented using the extended Kalman filter (EKF). The EKF assumes a linearized process, measurement models and Gaussian noise distributions. These assumptions are unrealistic for highly nonlinear systems like land vehicle navigation and may cause filter divergence. A particle filter (PF) is developed to enhance integrated INS/GPS system performance as it can easily deal with nonlinearity and non-Gaussian noises. In this paper, a hybrid extended particle filter (HEPF) is developed as an alternative to the well-known EKF to achieve better navigation data accuracy for low-cost microelectromechanical system sensors. The results show that the HEPF performs better than the EKF during GPS outages, especially when simulated outages are located in periods with high vehicle dynamics.
An Extended Membrane System with Active Membranes to Solve Automatic Fuzzy Clustering Problems.
Peng, Hong; Wang, Jun; Shi, Peng; Pérez-Jiménez, Mario J; Riscos-Núñez, Agustín
2016-05-01
This paper focuses on automatic fuzzy clustering problem and proposes a novel automatic fuzzy clustering method that employs an extended membrane system with active membranes that has been designed as its computing framework. The extended membrane system has a dynamic membrane structure; since membranes can evolve, it is particularly suitable for processing the automatic fuzzy clustering problem. A modification of a differential evolution (DE) mechanism was developed as evolution rules for objects according to membrane structure and object communication mechanisms. Under the control of both the object's evolution-communication mechanism and the membrane evolution mechanism, the extended membrane system can effectively determine the most appropriate number of clusters as well as the corresponding optimal cluster centers. The proposed method was evaluated over 13 benchmark problems and was compared with four state-of-the-art automatic clustering methods, two recently developed clustering methods and six classification techniques. The comparison results demonstrate the superiority of the proposed method in terms of effectiveness and robustness. PMID:26790484
Contributions to the simulation of turbulence
NASA Technical Reports Server (NTRS)
Dutton, J. A.; Kerman, B. R.; Petersen, E. L.
1976-01-01
The simulation modeling of turbulence in the boundary layer in consolidated in terms of boundary layer similarity principles and empirical results. The modeling is extended for some aspects of the nonlinear and non-Gaussian structure of the turbulence. Properties of the discrete gust form structure of the modeled turbulence are identified.
Workshop on Computational Turbulence Modeling
NASA Technical Reports Server (NTRS)
1993-01-01
This document contains presentations given at Workshop on Computational Turbulence Modeling held 15-16 Sep. 1993. The purpose of the meeting was to discuss the current status and future development of turbulence modeling in computational fluid dynamics for aerospace propulsion systems. Papers cover the following topics: turbulence modeling activities at the Center for Modeling of Turbulence and Transition (CMOTT); heat transfer and turbomachinery flow physics; aerothermochemistry and computational methods for space systems; computational fluid dynamics and the k-epsilon turbulence model; propulsion systems; and inlet, duct, and nozzle flow.
Workshop on Computational Turbulence Modeling
Not Available
1993-01-01
This document contains presentations given at Workshop on Computational Turbulence Modeling held 15-16 Sep. 1993. The purpose of the meeting was to discuss the current status and future development of turbulence modeling in computational fluid dynamics for aerospace propulsion systems. Papers cover the following topics: turbulence modeling activities at the Center for Modeling of Turbulence and Transition (CMOTT); heat transfer and turbomachinery flow physics; aerothermochemistry and computational methods for space systems; computational fluid dynamics and the k-epsilon turbulence model; propulsion systems; and inlet, duct, and nozzle flow. Separate abstracts have been prepared for articles from this report.
Extended Logic Intelligent Processing System for a Sensor Fusion Processor Hardware
NASA Technical Reports Server (NTRS)
Stoica, Adrian; Thomas, Tyson; Li, Wei-Te; Daud, Taher; Fabunmi, James
2000-01-01
The paper presents the hardware implementation and initial tests from a low-power, highspeed reconfigurable sensor fusion processor. The Extended Logic Intelligent Processing System (ELIPS) is described, which combines rule-based systems, fuzzy logic, and neural networks to achieve parallel fusion of sensor signals in compact low power VLSI. The development of the ELIPS concept is being done to demonstrate the interceptor functionality which particularly underlines the high speed and low power requirements. The hardware programmability allows the processor to reconfigure into different machines, taking the most efficient hardware implementation during each phase of information processing. Processing speeds of microseconds have been demonstrated using our test hardware.
Advanced Extended Plate and Beam Wall System in a Cold-Climate House
Mallay, Dave; Wiehagen, Joseph; Kochkin, Vladimir
2016-01-01
This report presents the design and evaluation of an innovative wall system. This highly insulated (high-R) light-frame wall system for use above grade in residential buildings is referred to as Extended Plate & Beam (EP&B). The EP&B design is the first of its kind to be featured in a new construction test house (NCTH) for the DOE Building America program. The EP&B wall design integrates standard building methods and common building products to construct a high-R wall that minimizes transition risks and costs to builders.
NASA Astrophysics Data System (ADS)
Lee, Joon Sang
The compressible filtered Navier-Stokes equations were solved using a second order accurate finite volume method with low Mach number preconditioning. A dynamic subgrid-scale stress model accounted for the subgrid-scale turbulence. The study focused on the effects of buoyancy and rotation on the structure of turbulence and transport processes including heat transfer. Several different physical arrangements were studied as outlined below. The effects of buoyancy were first studied in a vertical channel using large eddy simulation (LES). The walls were maintained at constant temperatures, one heated and the other cooled. Results showed that aiding and opposing buoyancy forces emerge near the heated and cooled walls, respectively. In the aiding flow, the turbulent intensities and heat transfer were suppressed at large values of Grashof number. In the opposing flow, however, turbulence was enhanced with increased velocity fluctuations. Another buoyancy study considered turbulent flow in a vertically oriented annulus. Isoflux wall boundary conditions with low and high heating were imposed on the inner wall while the outer wall was adiabatic. The results showed that the strong heating and buoyancy force caused distortions of the flow structure resulting in reduction of turbulent intensities, shear stress, and turbulent heat flux, particularly near the heated wall. Flow in an annular pipe with and without an outer wall rotation about its axis was first investigated at moderate Reynolds numbers. When the outer pipe wall was rotated, a significant reduction of turbulent kinetic energy was realized near the rotating wall. Secondly, a large eddy simulation has been performed to investigate the effect of swirl on the heat and momentum transfer in an annular pipe flow with a rotating inner wall. The simulations indicated that the Nusselt number and the wall friction coefficient increased with increasing rotation speed of the wall. It was also observed that the axial velocity
The Turbulent Origin of Spin-Orbit Misalignment in Planetary Systems
Fielding, Drummond B.; McKee, Christopher F.; Socrates, Aristostle; Cunningham, Andrew J.; Klein, Richard I.
2015-05-13
The turbulent environment from which stars form may lead to misalignment between the stellar spin and the remnant protoplanetary disk. By using hydrodynamic and magnetohydrodynamic simulations, we demonstrate that a wide range of stellar obliquities may be produced as a by-product of forming a star within a turbulent environment. We present a simple semi-analytic model that reveals this connection between the turbulent motions and the orientation of a star and its disk. Our results are consistent with the observed obliquity distribution of hot Jupiters. Migration of misaligned hot Jupiters may, therefore, be due to tidal dissipation in the disk, rather than tidal dissipation of the star-planet interaction.
Calibrating Multi-machine Power System Parameters with the Extended Kalman Filter
Kalsi, Karanjit; Sun, Yannan; Huang, Zhenyu; Du, Pengwei; Diao, Ruisheng; Anderson, Kevin K.; Li, Yulan; Lee, Barry
2012-07-24
Large-scale renewable resources and novel smart-grid technologies continue to increase the complexity of power systems. As power systems continue to become more complex, accurate modeling for planning and operation becomes a necessity. Inaccurate system models would result in an unreliable assessment of system security conditions and could cause large-scale blackouts. This motivates the need for model parameter calibration, since some or all of the model parameters could be unknown or inaccurate. In this paper, the extended Kalman filter is used to calibrate the parameters of a multi-machine power system. The calibration performance is tested under varying fault locations, parameter errors and measurement noise giving an insight into how many generators and which generators could be difficult to calibrate.
The variational two-electron reduced-density-matrix method for extended systems
NASA Astrophysics Data System (ADS)
Rubin, Nicholas C.
In this thesis we develop the variational two-electron reduced-density-matrix method for extended systems. Extended systems are represented in two ways: i) lattice models describing the dominant valence electronic structure with periodic boundaries to account for their extended nature and ii) a crystalline-orbital basis built from atomic orbitals using the generalization of molecular orbital theory to polymers. The first part of this thesis (Ch. 3--4) examines the performance of the variational 2-RDM method on lattice systems with tunable electron correlation. The first of these systems is the classic Hubbard model with linear and ladder lattice topologies. Because electron correlation functions, such as charge- and spin-ordering, are linear functions of the 2-RDM, the difference in electronic structure between one- and quasi-one-dimensional systems is accurately characterized. The second model contains only two-body interactions and is unique among typical spin models in that it does not have a mean-field reference wave function. The ground state wave functions from all Hamiltonians in the model have the same 1-electron reduced density matrix; consequently, one-electron theories are largely inapplicable. The superconducting eta-pairing ground states make the model a unique tool for demonstrating the necessary N-representability in highly correlated environments. The second part of this thesis (Ch. 5--6) develops a formalism for modeling materials by solving the full Schrodinger equation. Crystalline-orbital Hartree-Fock provides a set of orbitals and integral tensors for the variational 2-RDM method. We demonstrate that time-reversal symmetry, which is implicitly included in position space electronic structure calculations, must be explicitly included as an N-representability constraint on the 2-RDM when using a momentum space basis. The necessity of these equality constraints is demonstrated by the accurate recovery of the binding energy of two polymers and the
Optimization of wavefront-coded infinity-corrected microscope systems with extended depth of field
Zhao, Tingyu; Mauger, Thomas; Li, Guoqiang
2013-01-01
The depth of field of an infinity-corrected microscope system is greatly extended by simply applying a specially designed phase mask between the objective and the tube lens. In comparison with the method of modifying the structure of objective, it is more cost effective and provides improved flexibility for assembling the system. Instead of using an ideal optical system for simulation which was the focus of the previous research, a practical wavefront-coded infinity-corrected microscope system is designed in this paper by considering the various aberrations. Two new optimization methods, based on the commercial optical design software, are proposed to design a wavefront-coded microscope using a non-symmetric phase mask and a symmetric phase mask, respectively. We use polynomial phase mask and rational phase mask as examples of the non-symmetric and symmetric phase masks respectively. Simulation results show that both optimization methods work well for a 32 × infinity-corrected microscope system with 0.6 numerical aperture. The depth of field is extended to about 13 times of the traditional one. PMID:24010008
NASA Astrophysics Data System (ADS)
Strelnikov, B.; Lubken, F.-J.; Rapp, M.; Krein, G.; Henkel, H.; Heckl, H.-J.
2015-09-01
Leibniz Institute of Atmospheric Physics (TAP) at the Rostock University in Kuhlungsborn, Germany together with the company von Hoerner and Sulger GmbH (vH&S) in Schwetzingen, Germany develop a new instrumental setup for 3-dimensional in-situ turbulence and temperature measurements in the mesosphere and lower thermosphere (MLT) region. The setup consists of a mother payload carrying a new generation CONE instrument and three identical daughter payloads that will be ejected from the main payload at a predefined altitude. When ejected, all the payloads measure densities of neutral air and one of the plasma species, either electrons or ions. Each payload has its own telemetry and positioning system and sends all the data directly down to the ground. The new measurements will thereby yield four simultaneously measured profiles of neutral and plasma densities, neutral air temperature, and turbulence energy dissipation rate, separated by up to some hundreds of meters. Important for turbulence studies, these measurements will infer spectra information that cover a wide range of spatial scale characteristics for MLT turbulence in both horizontal and vertical directions.
Extended quantification of the generalized recurrence plot
NASA Astrophysics Data System (ADS)
Riedl, Maik; Marwan, Norbert; Kurths, Jürgen
2016-04-01
The generalized recurrence plot is a modern tool for quantification of complex spatial patterns. Its application spans the analysis of trabecular bone structures, Turing structures, turbulent spatial plankton patterns, and fractals. But, it is also successfully applied to the description of spatio-temporal dynamics and the detection of regime shifts, such as in the complex Ginzburg-Landau- equation. The recurrence plot based determinism is a central measure in this framework quantifying the level of regularities in temporal and spatial structures. We extend this measure for the generalized recurrence plot considering additional operations of symmetry than the simple translation. It is tested not only on two-dimensional regular patterns and noise but also on complex spatial patterns reconstructing the parameter space of the complex Ginzburg-Landau-equation. The extended version of the determinism resulted in values which are consistent to the original recurrence plot approach. Furthermore, the proposed method allows a split of the determinism into parts which based on laminar and non-laminar regions of the two-dimensional pattern of the complex Ginzburg-Landau-equation. A comparison of these parts with a standard method of image classification, the co-occurrence matrix approach, shows differences especially in the description of patterns associated with turbulence. In that case, it seems that the extended version of the determinism allows a distinction of phase turbulence and defect turbulence by means of their spatial patterns. This ability of the proposed method promise new insights in other systems with turbulent dynamics coming from climatology, biology, ecology, and social sciences, for example.
NASA Astrophysics Data System (ADS)
Amato, Alberto; Fortini, Stefania; Watteaux, Romain; Diano, Marcello; Espa, Stefania; Esposito, Serena; Ferrante, Maria I.; Peters, Francesc; Iudicone, Daniele; Ribera d'Alcalà, Maurizio
2016-03-01
In recent years, there has been a renewed interest in the impact of turbulence on aquatic organisms. In response to this interest, a novel instrument has been constructed, TURBOGEN, that generates turbulence in water volumes up to 13 l. TURBOGEN is fully computer controlled, thus, allowing for a high level of reproducibility and for variations of the intensity and characteristics of turbulence during the experiment. The calibration tests, carried out by particle image velocimetry, showed TURBOGEN to be successful in generating isotropic turbulence at the typical relatively low levels of the marine environment. TURBOGEN and its sizing have been devised with the long-term scope of analyzing in detail the molecular responses of plankton to different mixing regimes, which is of great importance in both environmental and biotechnological processes.
Amato, Alberto; Fortini, Stefania; Watteaux, Romain; Diano, Marcello; Espa, Stefania; Esposito, Serena; Ferrante, Maria I; Peters, Francesc; Iudicone, Daniele; Ribera d'Alcalà, Maurizio
2016-03-01
In recent years, there has been a renewed interest in the impact of turbulence on aquatic organisms. In response to this interest, a novel instrument has been constructed, TURBOGEN, that generates turbulence in water volumes up to 13 l. TURBOGEN is fully computer controlled, thus, allowing for a high level of reproducibility and for variations of the intensity and characteristics of turbulence during the experiment. The calibration tests, carried out by particle image velocimetry, showed TURBOGEN to be successful in generating isotropic turbulence at the typical relatively low levels of the marine environment. TURBOGEN and its sizing have been devised with the long-term scope of analyzing in detail the molecular responses of plankton to different mixing regimes, which is of great importance in both environmental and biotechnological processes. PMID:27036831
MHD Turbulence and Magnetic Dynamos
NASA Technical Reports Server (NTRS)
Shebalin, John V
2014-01-01
Incompressible magnetohydrodynamic (MHD) turbulence and magnetic dynamos, which occur in magnetofluids with large fluid and magnetic Reynolds numbers, will be discussed. When Reynolds numbers are large and energy decays slowly, the distribution of energy with respect to length scale becomes quasi-stationary and MHD turbulence can be described statistically. In the limit of infinite Reynolds numbers, viscosity and resistivity become zero and if these values are used in the MHD equations ab initio, a model system called ideal MHD turbulence results. This model system is typically confined in simple geometries with some form of homogeneous boundary conditions, allowing for velocity and magnetic field to be represented by orthogonal function expansions. One advantage to this is that the coefficients of the expansions form a set of nonlinearly interacting variables whose behavior can be described by equilibrium statistical mechanics, i.e., by a canonical ensemble theory based on the global invariants (energy, cross helicity and magnetic helicity) of ideal MHD turbulence. Another advantage is that truncated expansions provide a finite dynamical system whose time evolution can be numerically simulated to test the predictions of the associated statistical mechanics. If ensemble predictions are the same as time averages, then the system is said to be ergodic; if not, the system is nonergodic. Although it had been implicitly assumed in the early days of ideal MHD statistical theory development that these finite dynamical systems were ergodic, numerical simulations provided sufficient evidence that they were, in fact, nonergodic. Specifically, while canonical ensemble theory predicted that expansion coefficients would be (i) zero-mean random variables with (ii) energy that decreased with length scale, it was found that although (ii) was correct, (i) was not and the expected ergodicity was broken. The exact cause of this broken ergodicity was explained, after much
Statistical Mechanics of Turbulent Dynamos
NASA Technical Reports Server (NTRS)
Shebalin, John V.
2014-01-01
Incompressible magnetohydrodynamic (MHD) turbulence and magnetic dynamos, which occur in magnetofluids with large fluid and magnetic Reynolds numbers, will be discussed. When Reynolds numbers are large and energy decays slowly, the distribution of energy with respect to length scale becomes quasi-stationary and MHD turbulence can be described statistically. In the limit of infinite Reynolds numbers, viscosity and resistivity become zero and if these values are used in the MHD equations ab initio, a model system called ideal MHD turbulence results. This model system is typically confined in simple geometries with some form of homogeneous boundary conditions, allowing for velocity and magnetic field to be represented by orthogonal function expansions. One advantage to this is that the coefficients of the expansions form a set of nonlinearly interacting variables whose behavior can be described by equilibrium statistical mechanics, i.e., by a canonical ensemble theory based on the global invariants (energy, cross helicity and magnetic helicity) of ideal MHD turbulence. Another advantage is that truncated expansions provide a finite dynamical system whose time evolution can be numerically simulated to test the predictions of the associated statistical mechanics. If ensemble predictions are the same as time averages, then the system is said to be ergodic; if not, the system is nonergodic. Although it had been implicitly assumed in the early days of ideal MHD statistical theory development that these finite dynamical systems were ergodic, numerical simulations provided sufficient evidence that they were, in fact, nonergodic. Specifically, while canonical ensemble theory predicted that expansion coefficients would be (i) zero-mean random variables with (ii) energy that decreased with length scale, it was found that although (ii) was correct, (i) was not and the expected ergodicity was broken. The exact cause of this broken ergodicity was explained, after much
Probe systems for measuring static pressure and turbulence intensity in fluid streams
NASA Technical Reports Server (NTRS)
Rossow, Vernon J. (Inventor)
1993-01-01
A method and an apparatus for measuring time-averaged static or ambient pressure and turbulence intensity in a turbulent stream are discussed. The procedure involves placing a plurality of probes in the stream. Each probe responds in a different manner to characteristics of the fluid stream, preferably as a result of having varying cross sections. The responses from the probes are used to eliminate unwanted components in the measured quantities for accurate determination of selected characteristics.
Extended performance solar electric propulsion thrust system study. Volume 1: Executive summary
NASA Technical Reports Server (NTRS)
Poeschel, R. L.; Hawthorne, E. I.
1977-01-01
Several thrust system design concepts were evaluated and compared using the specifications of the most advanced 30 cm engineering model thruster as the technology base. The extensions in thruster performance required for the Halley's comet mission were defined and alternative thrust system concepts were designed. Confirmation testing and analysis of thruster and power-processing components were performed, and the feasibility of satisfying extended performance requirements was verified. A baseline design was selected from the alternatives considered, and the design analysis and documentation were refined. A program development plan was formulated that outlines the work structure considered necessary for developing, qualifying, and fabricating the flight hardware for the baseline thrust system within the time frame of a project to rendezvous with Halley's comet. An assessment was made of the costs and risks associated with a baseline thrust system as provided to the mission project under this plan. Critical procurements and interfaces were identified and defined. Results are presented.
Numerical simulation of turbulence in the presence of shear
NASA Technical Reports Server (NTRS)
Shaanan, S.; Ferziger, J. H.; Reynolds, W. C.
1975-01-01
The numerical calculations are presented of the large eddy structure of turbulent flows, by use of the averaged Navier-Stokes equations, where averages are taken over spatial regions small compared to the size of the computational grid. The subgrid components of motion are modeled by a local eddy-viscosity model. A new finite-difference scheme is proposed to represent the nonlinear average advective term which has fourth-order accuracy. This scheme exhibits several advantages over existing schemes with regard to the following: (1) the scheme is compact as it extends only one point away in each direction from the point to which it is applied; (2) it gives better resolution for high wave-number waves in the solution of Poisson equation, and (3) it reduces programming complexity and computation time. Examples worked out in detail are the decay of isotropic turbulence, homogeneous turbulent shear flow, and homogeneous turbulent shear flow with system rotation.
Magnetohydrodynamic Turbulence
NASA Astrophysics Data System (ADS)
Montgomery, David C.
2004-01-01
Magnetohydrodynamic (MHD) turbulence theory is modeled on neutral fluid (Navier-Stokes) turbulence theory, but with some important differences. There have been essentially no repeatable laboratory MHD experiments wherein the boundary conditions could be controlled or varied and a full set of diagnostics implemented. The equations of MHD are convincingly derivable only in the limit of small ratio of collision mean-free-paths to macroscopic length scales, an inequality that often goes the other way for magnetofluids of interest. Finally, accurate information on the MHD transport coefficients-and thus, the Reynolds-like numbers that order magnetofluid behavior-is largely lacking; indeed, the algebraic expressions used for such ingredients as the viscous stress tensor are often little more than wishful borrowing from fluid mechanics. The one accurate thing that has been done extensively and well is to solve the (strongly nonlinear) MHD equations numerically, usually in the presence of rectangular periodic boundary conditions, and then hope for the best when drawing inferences from the computations for those astrophysical and geophysical MHD systems for which some indisputably turbulent detailed data are available, such as the solar wind or solar prominences. This has led to what is perhaps the first field of physics for which computer simulations are regarded as more central to validating conclusions than is any kind of measurement. Things have evolved in this way due to a mixture of the inevitable and the bureaucratic, but that is the way it is, and those of us who want to work on the subject have to live with it. It is the only game in town, and theories that have promised more-often on the basis of some alleged ``instability''-have turned out to be illusory.
Fuel cell powered small unmanned aerial systems (UASs) for extended endurance flights
NASA Astrophysics Data System (ADS)
Chu, Deryn; Jiang, R.; Dunbar, Z.; Grew, Kyle; McClure, J.
2015-05-01
Small unmanned aerial systems (UASs) have been used for military applications and have additional potential for commercial applications [1-4]. For the military, these systems provide valuable intelligence, surveillance, reconnaissance and target acquisition (ISRTA) capabilities for units at the infantry, battalion, and company levels. The small UASs are light-weight, manportable, can be hand-launched, and are capable of carrying payloads. Currently, most small UASs are powered by lithium-ion or lithium polymer batteries; however, the flight endurance is usually limited less than two hours and requires frequent battery replacement. Long endurance small UAS flights have been demonstrated through the implementation of a fuel cell system. For instance, a propane fueled solid oxide fuel cell (SOFC) stack has been used to power a small UAS and shown to extend mission flight time. The research and development efforts presented here not only apply to small UASs, but also provide merit to the viability of extending mission operations for other unmanned systems applications.
Kalay, Berfin; Demiralp, Metin
2014-10-06
The expectation value definitions over an extended space from the considered Hilbert space of the system under consideration is given in another paper of the second author in this symposium. There, in that paper, the conceptuality rather than specification is emphasized on. This work uses that conceptuality to investigate the time evolutions of the position related operators' expectation values not in its standard meaning but rather in a new version of the definition over not the original Hilbert space but in the space obtained by extensions via introducing the images of the given initial wave packet under the positive integer powers of the system Hamiltonian. These images may not be residing in the same space of the initial wave packet when certain singularities appear in the structure of the system Hamiltonian. This may break down the existence of the integrals in the definitions of the expectation values. The cure is the use of basis functions in the abovementioned extended space and the sandwiching of the target operator whose expectation value is under questioning by an appropriately chosen operator guaranteeing the existence of the relevant integrals. Work specifically focuses on the hydrogen-like quantum systems whose Hamiltonians contain a polar singularity at the origin.
Extended Lyα emission around quasars with eclipsing damped Lyα systems
NASA Astrophysics Data System (ADS)
Fathivavsari, H.; Petitjean, P.; Noterdaeme, P.; Pâris, I.; Finley, H.; López, S.; Srianand, R.
2016-09-01
We present spectroscopic observations of six high redshift (zem > 2) quasars, which have been selected for their Lyman α (Lyα) emission region being only partially covered by a strong proximate (zabs ˜ zem) coronagraphic damped Lyα system (DLA). We detected spatially extended Lyα emission envelopes surrounding these six quasars, with projected spatial extent in the range 26 ≤ dLyα ≤ 51 kpc. No correlation is found between the quasar ionizing luminosity and the Lyα luminosity of their extended envelopes. This could be related to the limited covering factor of the extended gas and/or due to the AGN being obscured in other directions than towards the observer. Indeed, we find a strong correlation between the luminosity of the envelope and its spatial extent, which suggests that the envelopes are probably ionized by the AGN. The metallicity of the coronagraphic DLAs is low and varies in the range -1.75 < [Si/H] < -0.63. Highly ionized gas is observed to be associated with most of these DLAs, probably indicating ionization by the central AGN. One of these DLAs has the highest Al III/Si II ratio ever reported for any intervening and/or proximate DLA. Most of these DLAs are redshifted with respect to the quasar, implying that they might represent infalling gas probably accreted on to the quasar host galaxies through filaments.
Kwon, Gayeung; Lee, Jiyun; Lim, Young-Hee
2016-01-01
Dairy Propionibacterium freudenreichii is a candidate non-lactic acid probiotic. However, little information is available on the effect of P. freudenreichii on lifespan extension in humans. The aim of this study was to evaluate the effects of P. freudenreichii on lifespan extension and to elucidate the mechanism of P. freudenreichii-dependent lifespan extension in Caenorhabditis elegans. The results showed that P. freudenreichii significantly (p < 0.05) extended the lifespan of C. elegans compared with Escherichia coli OP50, a standard food for the worm. Analysis of age-related biomarkers showed that P. freudenreichii retards ageing. Moreover, P. freudenreichii increased resistance against a human pathogen, Salmonella typhimurium, through the activation of skn-1, which is involved in pathogen resistance in C. elegans. Furthermore, P. freudenreichii-fed daf-16, jnk-1, skn-1 or daf-7 loss-of-function mutants showed an extended mean lifespan compared with E. coli OP50-fed worms. However, the increase in lifespan was not observed in pmk-1, sek-1, mek-1, dbl-1, daf-12 or daf-2 mutants, which suggests potential roles for these genes in P. freudenreichii-induced longevity in C. elegans. In conclusion, P. freudenreichii extends the lifespan of C. elegans via the p38 MAPK pathway involved in stress response and the TGF-β pathways associated with anti-inflammation processes in the immune system. PMID:27531646
Kwon, Gayeung; Lee, Jiyun; Lim, Young-Hee
2016-01-01
Dairy Propionibacterium freudenreichii is a candidate non-lactic acid probiotic. However, little information is available on the effect of P. freudenreichii on lifespan extension in humans. The aim of this study was to evaluate the effects of P. freudenreichii on lifespan extension and to elucidate the mechanism of P. freudenreichii-dependent lifespan extension in Caenorhabditis elegans. The results showed that P. freudenreichii significantly (p < 0.05) extended the lifespan of C. elegans compared with Escherichia coli OP50, a standard food for the worm. Analysis of age-related biomarkers showed that P. freudenreichii retards ageing. Moreover, P. freudenreichii increased resistance against a human pathogen, Salmonella typhimurium, through the activation of skn-1, which is involved in pathogen resistance in C. elegans. Furthermore, P. freudenreichii-fed daf-16, jnk-1, skn-1 or daf-7 loss-of-function mutants showed an extended mean lifespan compared with E. coli OP50-fed worms. However, the increase in lifespan was not observed in pmk-1, sek-1, mek-1, dbl-1, daf-12 or daf-2 mutants, which suggests potential roles for these genes in P. freudenreichii-induced longevity in C. elegans. In conclusion, P. freudenreichii extends the lifespan of C. elegans via the p38 MAPK pathway involved in stress response and the TGF-β pathways associated with anti-inflammation processes in the immune system. PMID:27531646
An Integrated Nonlinear Analysis library - (INA) for solar system plasma turbulence
NASA Astrophysics Data System (ADS)
Munteanu, Costel; Kovacs, Peter; Echim, Marius; Koppan, Andras
2014-05-01
We present an integrated software library dedicated to the analysis of time series recorded in space and adapted to investigate turbulence, intermittency and multifractals. The library is written in MATLAB and provides a graphical user interface (GUI) customized for the analysis of space physics data available online like: Coordinated Data Analysis Web (CDAWeb), Automated Multi Dataset Analysis system (AMDA), Planetary Science Archive (PSA), World Data Center Kyoto (WDC), Ulysses Final Archive (UFA) and Cluster Active Archive (CAA). Three main modules are already implemented in INA : the Power Spectral Density (PSD) Analysis, the Wavelet and Intemittency Analysis and the Probability Density Functions (PDF) analysis.The layered structure of the software allows the user to easily switch between different modules/methods while retaining the same time interval for the analysis. The wavelet analysis module includes algorithms to compute and analyse the PSD, the Scalogram, the Local Intermittency Measure (LIM) or the Flatness parameter. The PDF analysis module includes algorithms for computing the PDFs for a range of scales and parameters fully customizable by the user; it also computes the Flatness parameter and enables fast comparison with standard PDF profiles like, for instance, the Gaussian PDF. The library has been already tested on Cluster and Venus Express data and we will show relevant examples. Research supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement no 313038/STORM, and a grant of the Romanian Ministry of National Education, CNCS UEFISCDI, project number PN-II-ID PCE-2012-4-0418.
Samanta, Devranjan; Dubief, Yves; Holzner, Markus; Schäfer, Christof; Morozov, Alexander N; Wagner, Christian; Hof, Björn
2013-06-25
Turbulence is ubiquitous in nature, yet even for the case of ordinary Newtonian fluids like water, our understanding of this phenomenon is limited. Many liquids of practical importance are more complicated (e.g., blood, polymer melts, paints), however; they exhibit elastic as well as viscous characteristics, and the relation between stress and strain is nonlinear. We demonstrate here for a model system of such complex fluids that at high shear rates, turbulence is not simply modified as previously believed but is suppressed and replaced by a different type of disordered motion, elasto-inertial turbulence. Elasto-inertial turbulence is found to occur at much lower Reynolds numbers than Newtonian turbulence, and the dynamical properties differ significantly. The friction scaling observed coincides with the so-called "maximum drag reduction" asymptote, which is exhibited by a wide range of viscoelastic fluids. PMID:23757498
Verification of Gamma Knife extend system based fractionated treatment planning using EBT2 film
Natanasabapathi, Gopishankar; Bisht, Raj Kishor
2013-12-15
Purpose: This paper presents EBT2 film verification of fractionated treatment planning with the Gamma Knife (GK) extend system, a relocatable frame system for multiple-fraction or serial multiple-session radiosurgery.Methods: A human head shaped phantom simulated the verification process for fractionated Gamma Knife treatment. Phantom preparation for Extend Frame based treatment planning involved creating a dental impression, fitting the phantom to the frame system, and acquiring a stereotactic computed tomography (CT) scan. A CT scan (Siemens, Emotion 6) of the phantom was obtained with following parameters: Tube voltage—110 kV, tube current—280 mA, pixel size—0.5 × 0.5 and 1 mm slice thickness. A treatment plan with two 8 mm collimator shots and three sectors blocking in each shot was made. Dose prescription of 4 Gy at 100% was delivered for the first fraction out of the two fractions planned. Gafchromic EBT2 film (ISP Wayne, NJ) was used as 2D verification dosimeter in this process. Films were cut and placed inside the film insert of the phantom for treatment dose delivery. Meanwhile a set of films from the same batch were exposed from 0 to 12 Gy doses for calibration purposes. An EPSON (Expression 10000 XL) scanner was used for scanning the exposed films in transparency mode. Scanned films were analyzed with inhouse written MATLAB codes.Results: Gamma index analysis of film measurement in comparison with TPS calculated dose resulted in high pass rates >90% for tolerance criteria of 1%/1 mm. The isodose overlay and linear dose profiles of film measured and computed dose distribution on sagittal and coronal plane were in close agreement.Conclusions: Through this study, the authors propose treatment verification QA method for Extend frame based fractionated Gamma Knife radiosurgery using EBT2 film.
NASA Astrophysics Data System (ADS)
Khallaf, Haitham S.; Garrido-Balsells, José M.; Shalaby, Hossam M. H.; Sampei, Seiichi
2015-12-01
The performance of multiple-input multiple-output free space optical (MIMO-FSO) communication systems, that adopt multipulse pulse position modulation (MPPM) techniques, is analyzed. Both exact and approximate symbol-error rates (SERs) are derived for both cases of uncorrelated and correlated channels. The effects of background noise, receiver shot-noise, and atmospheric turbulence are taken into consideration in our analysis. The random fluctuations of the received optical irradiance, produced by the atmospheric turbulence, is modeled by the widely used gamma-gamma statistical distribution. Uncorrelated MIMO channels are modeled by the α-μ distribution. A closed-form expression for the probability density function of the optical received irradiance is derived for the case of correlated MIMO channels. Using our analytical expressions, the degradation of the system performance with the increment of the correlation coefficients between MIMO channels is corroborated.