Ultrafast optical excitations in supramolecular metallacycles with charge transfer properties.

PubMed

Flynn, Daniel C; Ramakrishna, Guda; Yang, Hai-Bo; Northrop, Brian H; Stang, Peter J; Goodson, Theodore

2010-02-03

New organometallic materials such as two-dimensional metallacycles and three-dimensional metallacages are important for the development of novel optical, electronic, and energy related applications. In this article, the ultrafast dynamics of two different platinum-containing metallacycles have been investigated by femtosecond fluorescence upconversion and transient absorption. These measurements were carried out in an effort to probe the charge transfer dynamics and the rate of intersystem crossing in metallacycles of different geometries and dimensions. The processes of ultrafast intersystem crossing and charge transfer vary between the two different classes of metallacyclic systems studied. For rectangular anthracene-containing metallacycles, the electronic coupling between adjacent ligands was relatively weak, whereas for the triangular phenanthrene-containing structures, there was a clear interaction between the conjugated ligand and the metal complex center. The transient lifetimes increased with increasing conjugation in that case. The results show that differences in the dimensionality and structure of metallacycles result in different optical properties, which may be utilized in the design of nonlinear optical materials and potential new, longer-lived excited state materials for further electronic applications.

Transient Three-Dimensional Analysis of Side Load in Liquid Rocket Engine Nozzles

NASA Technical Reports Server (NTRS)

Wang, Ten-See

2004-01-01

Three-dimensional numerical investigations on the nozzle start-up side load physics were performed. The objective of this study is to identify the three-dimensional side load physics and to compute the associated aerodynamic side load using an anchored computational methodology. The computational methodology is based on an unstructured-grid, and pressure-based computational fluid dynamics formulation, and a simulated inlet condition based on a system calculation. Finite-rate chemistry was used throughout the study so that combustion effect is always included, and the effect of wall cooling on side load physics is studied. The side load physics captured include the afterburning wave, transition from free- shock to restricted-shock separation, and lip Lambda shock oscillation. With the adiabatic nozzle, free-shock separation reappears after the transition from free-shock separation to restricted-shock separation, and the subsequent flow pattern of the simultaneous free-shock and restricted-shock separations creates a very asymmetric Mach disk flow. With the cooled nozzle, the more symmetric restricted-shock separation persisted throughout the start-up transient after the transition, leading to an overall lower side load than that of the adiabatic nozzle. The tepee structures corresponding to the maximum side load were addressed.

Stress wave calculations in composite plates using the fast Fourier transform.

NASA Technical Reports Server (NTRS)

Moon, F. C.

1973-01-01

The protection of composite turbine fan blades against impact forces has prompted the study of dynamic stresses in composites due to transient loads. The mathematical model treats the laminated plate as an equivalent anisotropic material. The use of Mindlin's approximate theory of crystal plates results in five two-dimensional stress waves. Three of the waves are flexural and two involve in-plane extensional strains. The initial value problem due to a transient distributed transverse force on the plate is solved using Laplace and Fourier transforms. A fast computer program for inverting the two-dimensional Fourier transform is used. Stress contours for various stresses and times after application of load are obtained for a graphite fiber-epoxy matrix composite plate. Results indicate that the points of maximum stress travel along the fiber directions.

Thermoviscoplastic response of thin plates subjected to intense local heating

NASA Technical Reports Server (NTRS)

Byrom, Ted G.; Allen, David H.; Thornton, Earl A.

1992-01-01

A finite element method is employed to investigate the thermoviscoplastic response of a half-cylinder to intense localized transient heating. Thermoviscoplastic material behavior is characterized by the Bodner-Partom constitutive model. Structure geometry is modeled with a three-dimensional assembly of CST-DKT plate elements incorporating the large deflection von Karman assumptions. The paper compares the results of a dynamic analysis with a quasi-static analysis for the half-cylinder structure with a step-function transient temperature loading similar to that which may be encountered with shock wave interference on a hypersonic leading edge.

Metastable dynamical patterns and their stabilization in arrays of bidirectionally coupled sigmoidal neurons

NASA Astrophysics Data System (ADS)

Horikawa, Yo

2013-12-01

Transient patterns in a bistable ring of bidirectionally coupled sigmoidal neurons were studied. When the system had a pair of spatially uniform steady solutions, the instability of unstable spatially nonuniform steady solutions decreased exponentially with the number of neurons because of the symmetry of the system. As a result, transient spatially nonuniform patterns showed dynamical metastability: Their duration increased exponentially with the number of neurons and the duration of randomly generated patterns obeyed a power-law distribution. However, these metastable dynamical patterns were easily stabilized in the presence of small variations in coupling strength. Metastable rotating waves and their pinning in the presence of asymmetry in the direction of coupling and the disappearance of metastable dynamical patterns due to asymmetry in the output function of a neuron were also examined. Further, in a two-dimensional array of neurons with nearest-neighbor coupling, intrinsically one-dimensional patterns were dominant in transients, and self-excitation in these neurons affected the metastable dynamical patterns.

Analytical and computational studies on the vacuum performance of a chevron ejector

NASA Astrophysics Data System (ADS)

Kong, F. S.; Jin, Y. Z.; Kim, H. D.

2016-11-01

The effects of chevrons on the performance of a supersonic vacuum ejector-diffuser system are investigated numerically and evaluated theoretically in this work. A three-dimensional geometrical domain is numerically solved using a fully implicit finite volume scheme based on the unsteady Reynolds stress model. A one-dimensional mathematical model provides a useful tool to reveal the steady flow physics inside the vacuum ejector-diffuser system. The effects of the chevron nozzle on the generation of recirculation regions and Reynolds stress behaviors are studied and compared with those of a conventional convergent nozzle. The present performance parameters obtained from the simulated results and the mathematical results are validated with existing experimental data and show good agreement. Primary results show that the duration of the transient period and the secondary chamber pressure at a dynamic equilibrium state depend strongly on the primary jet conditions, such as inlet pressure and primary nozzle shape. Complicated oscillatory flow, generated by the unsteady movement of recirculation, finally settles into a dynamic equilibrium state. As a vortex generator, the chevron demonstrated its strong entrainment capacity to accelerate the starting transient flows to a certain extent and reduce the dynamic equilibrium pressure of the secondary chamber significantly.

Transient simulation of hydropower station with consideration of three-dimensional unsteady flow in turbine

NASA Astrophysics Data System (ADS)

Huang, W. D.; Fan, H. G.; Chen, N. X.

2012-11-01

To study the interaction between the transient flow in pipe and the unsteady turbulent flow in turbine, a coupled model of the transient flow in the pipe and three-dimensional unsteady flow in the turbine is developed based on the method of characteristics and the fluid governing equation in the accelerated rotational relative coordinate. The load-rejection process under the closing of guide vanes of the hydraulic power plant is simulated by the coupled method, the traditional transient simulation method and traditional three-dimensional unsteady flow calculation method respectively and the results are compared. The pressure, unit flux and rotation speed calculated by three methods show a similar change trend. However, because the elastic water hammer in the pipe and the pressure fluctuation in the turbine have been considered in the coupled method, the increase of pressure at spiral inlet is higher and the pressure fluctuation in turbine is stronger.

Dynamic Simulation of a Wave Rotor Topped Turboshaft Engine

NASA Technical Reports Server (NTRS)

Greendyke, R. B.; Paxson, D. E.; Schobeiri, M. T.

1997-01-01

The dynamic behavior of a wave rotor topped turboshaft engine is examined using a numerical simulation. The simulation utilizes an explicit, one-dimensional, multi-passage, CFD based wave rotor code in combination with an implicit, one-dimensional, component level dynamic engine simulation code. Transient responses to rapid fuel flow rate changes and compressor inlet pressure changes are simulated and compared with those of a similarly sized, untopped, turboshaft engine. Results indicate that the wave rotor topped engine responds in a stable, and rapid manner. Furthermore, during certain transient operations, the wave rotor actually tends to enhance engine stability. In particular, there is no tendency toward surge in the compressor of the wave rotor topped engine during rapid acceleration. In fact, the compressor actually moves slightly away from the surge line during this transient. This behavior is precisely the opposite to that of an untopped engine. The simulation is described. Issues associated with integrating CFD and component level codes are discussed. Results from several transient simulations are presented and discussed.

Single and multiple vortex rings in three-dimensional Bose-Einstein condensates: Existence, stability, and dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Wenlong; Bisset, R. N.; Ticknor, Christopher

In the present work, we explore the existence, stability, and dynamics of single- and multiple-vortex-ring states that can arise in Bose-Einstein condensates. Earlier works have illustrated the bifurcation of such states in the vicinity of the linear limit for isotropic or anisotropic three-dimensional harmonic traps. Here, we extend these states to the regime of large chemical potentials, the so-called Thomas-Fermi limit, and explore their properties such as equilibrium radii and inter-ring distance for multi-ring states, as well as their vibrational spectra and possible instabilities. In this limit, both the existence and stability characteristics can be partially traced to a particlemore » picture that considers the rings as individual particles oscillating within the trap and interacting pairwise with one another. In conclusion, we examine some representative instability scenarios of the multi-ring dynamics, including breakup and reconnections, as well as the transient formation of vortex lines.« less

Single and multiple vortex rings in three-dimensional Bose-Einstein condensates: Existence, stability, and dynamics

DOE PAGES

Wang, Wenlong; Bisset, R. N.; Ticknor, Christopher; ...

2017-04-27

In the present work, we explore the existence, stability, and dynamics of single- and multiple-vortex-ring states that can arise in Bose-Einstein condensates. Earlier works have illustrated the bifurcation of such states in the vicinity of the linear limit for isotropic or anisotropic three-dimensional harmonic traps. Here, we extend these states to the regime of large chemical potentials, the so-called Thomas-Fermi limit, and explore their properties such as equilibrium radii and inter-ring distance for multi-ring states, as well as their vibrational spectra and possible instabilities. In this limit, both the existence and stability characteristics can be partially traced to a particlemore » picture that considers the rings as individual particles oscillating within the trap and interacting pairwise with one another. In conclusion, we examine some representative instability scenarios of the multi-ring dynamics, including breakup and reconnections, as well as the transient formation of vortex lines.« less

The Importance of Detailed Component Simulations in the Feedsystem Development for a Two-Stage-to Orbit Reusable Launch Vehicle

NASA Technical Reports Server (NTRS)

Mazurkivich, Pete; Chandler, Frank; Grayson, Gary

2005-01-01

To meet the requirements for the 2nd Generation Reusable Launch Vehicle (RLV), a unique propulsion feed system concept was identified using crossfeed between the booster and orbiter stages that could reduce the Two-Stage-to-Orbit (TSTO) vehicle weight and development cost by approximately 25%. A Main Propulsion System (MPS) crossfeed water demonstration test program was configured to address all the activities required to reduce the risks for the MPS crossfeed system. A transient, one-dimensional system simulation was developed for the subscale crossfeed water flow tests. To ensure accurate representation of the crossfeed valve's dynamics in the system model, a high-fidelity, three-dimensional, computational fluid-dynamics (CFD) model was employed. The results from the CFD model were used to specify the valve's flow characteristics in the system simulation. This yielded a crossfeed system model that was anchored to the specific valve hardware and achieved good agreement with the measured test data. These results allowed the transient models to be correlated and validated and used for full scale mission predictions. The full scale model simulations indicate crossfeed is ' viable with the system pressure disturbances at the crossfeed transition being less than experienced by the propulsion system during engine start and shutdown transients.

Numerical, analytical, experimental study of fluid dynamic forces in seals

NASA Technical Reports Server (NTRS)

Shapiro, William; Artiles, Antonio; Aggarwal, Bharat; Walowit, Jed; Athavale, Mahesh M.; Preskwas, Andrzej J.

1992-01-01

NASA/Lewis Research Center is sponsoring a program for providing computer codes for analyzing and designing turbomachinery seals for future aerospace and engine systems. The program is made up of three principal components: (1) the development of advanced three dimensional (3-D) computational fluid dynamics codes, (2) the production of simpler two dimensional (2-D) industrial codes, and (3) the development of a knowledge based system (KBS) that contains an expert system to assist in seal selection and design. The first task has been to concentrate on cylindrical geometries with straight, tapered, and stepped bores. Improvements have been made by adoption of a colocated grid formulation, incorporation of higher order, time accurate schemes for transient analysis and high order discretization schemes for spatial derivatives. This report describes the mathematical formulations and presents a variety of 2-D results, including labyrinth and brush seal flows. Extensions of 3-D are presently in progress.

The LATDYN user's manual

NASA Technical Reports Server (NTRS)

Housner, J. M.; Mcgowan, P. E.; Abrahamson, A. L.; Powell, M. G.

1986-01-01

The LATDYN User's Manual presents the capabilities and instructions for the LATDYN (Large Angle Transient DYNamics) computer program. The LATDYN program is a tool for analyzing the controlled or uncontrolled dynamic transient behavior of interconnected deformable multi-body systems which can undergo large angular motions of each body relative other bodies. The program accommodates large structural deformation as well as large rigid body rotations and is applicable, but not limited to, the following areas: (1) development of large flexible space structures; (2) slewing of large space structure components; (3) mechanisms with rigid or elastic components; and (4) robotic manipulations of beam members. Presently the program is limited to two dimensional problems, but in many cases, three dimensional problems can be exactly or approximately reduced to two dimensions. The program uses convected finite elements to affect the large angular motions involved in the analysis. General geometry is permitted. Detailed user input and output specifications are provided and discussed with example runstreams. To date, LATDYN has been configured for CDC/NOS and DEC VAX/VMS machines. All coding is in ANSII-77 FORTRAN. Detailed instructions regarding interfaces with particular computer operating systems and file structures are provided.

Transient Two-Dimensional Analysis of Side Load in Liquid Rocket Engine Nozzles

NASA Technical Reports Server (NTRS)

Wang, Ten-See

2004-01-01

Two-dimensional planar and axisymmetric numerical investigations on the nozzle start-up side load physics were performed. The objective of this study is to develop a computational methodology to identify nozzle side load physics using simplified two-dimensional geometries, in order to come up with a computational strategy to eventually predict the three-dimensional side loads. The computational methodology is based on a multidimensional, finite-volume, viscous, chemically reacting, unstructured-grid, and pressure-based computational fluid dynamics formulation, and a transient inlet condition based on an engine system modeling. The side load physics captured in the low aspect-ratio, two-dimensional planar nozzle include the Coanda effect, afterburning wave, and the associated lip free-shock oscillation. Results of parametric studies indicate that equivalence ratio, combustion and ramp rate affect the side load physics. The side load physics inferred in the high aspect-ratio, axisymmetric nozzle study include the afterburning wave; transition from free-shock to restricted-shock separation, reverting back to free-shock separation, and transforming to restricted-shock separation again; and lip restricted-shock oscillation. The Mach disk loci and wall pressure history studies reconfirm that combustion and the associated thermodynamic properties affect the formation and duration of the asymmetric flow.

Numerical study of vortex rope during load rejection of a prototype pump-turbine

NASA Astrophysics Data System (ADS)

Liu, J. T.; Liu, S. H.; Sun, Y. K.; Wu, Y. L.; Wang, L. Q.

2012-11-01

A transient process of load rejection of a prototype pump-turbine was studied by three dimensional, unsteady simulations, as well as steady calculations.Dynamic mesh (DM) method and remeshing method were used to simulate the rotation of guide vanes and runner. The rotational speed of the runner was predicted by fluid couplingmethod. Both the transient calculation and steady calculation were performed based on turbulence model. Results show that steady calculation results have large error in the prediction of the external characteristics of the transient process. The runaway speed can reach 1.15 times the initial rotational speed during the transient process. The vortex rope occurs before the pump-turbine runs at zero moment point. Vortex rope has the same rotating direction with the runner. The vortex rope is separated into two parts as the flow rate decreases to 0. Pressure level decreases during the whole transient process.The transient simulation result were also compared and verified by experimental results. This computational method could be used in the fault diagnosis of transient operation, as well as the optimization of a transient process.

Three-dimensional time-dependent STAR reactor kinetics analyses coupled with RETRAN and MCPWR system response

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feltus, M.A.

1989-11-01

The operation of a nuclear power plant must be regularly supported by various reactor dynamics and thermal-hydraulic analyses, which may include final safety analysis report (FSAR) design-basis calculations, and conservative and best-estimate analyses. The development and improvement of computer codes and analysis methodologies provide many advantages, including the ability to evaluate the effect of modeling simplifications and assumptions made in previous reactor kinetics and thermal-hydraulic calculations. This paper describes the results of using the RETRAN, MCPWR, and STAR codes in a tandem, predictive-corrective manner for three pressurized water reactor (PWR) transients: (a) loss of feedwater (LOF) anticipated transient without scrammore » (ATWS), (b) station blackout ATWS, and (c) loss of total reactor coolant system (RCS) flow with a scram.« less

SCORE-EVET: a computer code for the multidimensional transient thermal-hydraulic analysis of nuclear fuel rod arrays. [BWR; PWR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benedetti, R. L.; Lords, L. V.; Kiser, D. M.

1978-02-01

The SCORE-EVET code was developed to study multidimensional transient fluid flow in nuclear reactor fuel rod arrays. The conservation equations used were derived by volume averaging the transient compressible three-dimensional local continuum equations in Cartesian coordinates. No assumptions associated with subchannel flow have been incorporated into the derivation of the conservation equations. In addition to the three-dimensional fluid flow equations, the SCORE-EVET code ocntains: (a) a one-dimensional steady state solution scheme to initialize the flow field, (b) steady state and transient fuel rod conduction models, and (c) comprehensive correlation packages to describe fluid-to-fuel rod interfacial energy and momentum exchange. Velocitymore » and pressure boundary conditions can be specified as a function of time and space to model reactor transient conditions such as a hypothesized loss-of-coolant accident (LOCA) or flow blockage.« less

Low-dimensional modelling of a transient cylinder wake using double proper orthogonal decomposition

NASA Astrophysics Data System (ADS)

Siegel, Stefan G.; Seidel, J.?Rgen; Fagley, Casey; Luchtenburg, D. M.; Cohen, Kelly; McLaughlin, Thomas

For the systematic development of feedback flow controllers, a numerical model that captures the dynamic behaviour of the flow field to be controlled is required. This poses a particular challenge for flow fields where the dynamic behaviour is nonlinear, and the governing equations cannot easily be solved in closed form. This has led to many versions of low-dimensional modelling techniques, which we extend in this work to represent better the impact of actuation on the flow. For the benchmark problem of a circular cylinder wake in the laminar regime, we introduce a novel extension to the proper orthogonal decomposition (POD) procedure that facilitates mode construction from transient data sets. We demonstrate the performance of this new decomposition by applying it to a data set from the development of the limit cycle oscillation of a circular cylinder wake simulation as well as an ensemble of transient forced simulation results. The modes obtained from this decomposition, which we refer to as the double POD (DPOD) method, correctly track the changes of the spatial modes both during the evolution of the limit cycle and when forcing is applied by transverse translation of the cylinder. The mode amplitudes, which are obtained by projecting the original data sets onto the truncated DPOD modes, can be used to construct a dynamic mathematical model of the wake that accurately predicts the wake flow dynamics within the lock-in region at low forcing amplitudes. This low-dimensional model, derived using nonlinear artificial neural network based system identification methods, is robust and accurate and can be used to simulate the dynamic behaviour of the wake flow. We demonstrate this ability not just for unforced and open-loop forced data, but also for a feedback-controlled simulation that leads to a 90% reduction in lift fluctuations. This indicates the possibility of constructing accurate dynamic low-dimensional models for feedback control by using unforced and transient forced data only.

Spatiotemporal behavior and nonlinear dynamics in a phase conjugate resonator

NASA Technical Reports Server (NTRS)

Liu, Siuying Raymond

1993-01-01

The work described can be divided into two parts. The first part is an investigation of the transient behavior and stability property of a phase conjugate resonator (PCR) below threshold. The second part is an experimental and theoretical study of the PCR's spatiotemporal dynamics above threshold. The time-dependent coupled wave equations for four-wave mixing (FWM) in a photorefractive crystal, with two distinct interaction regions caused by feedback from an ordinary mirror, was used to model the transient dynamics of a PCR below threshold. The conditions for self-oscillation were determined and the solutions were used to define the PCR's transfer function and analyze its stability. Experimental results for the buildup and decay times confirmed qualitatively the predicted behavior. Experiments were carried out above threshold to study the spatiotemporal dynamics of the PCR as a function of Pragg detuning and the resonator's Fresnel number. The existence of optical vortices in the wavefront were identified by optical interferometry. It was possible to describe the transverse dynamics and the spatiotemporal instabilities by modeling the three-dimensional-coupled wave equations in photorefractive FWM using a truncated modal expansion approach.

Three-dimensional numerical and experimental studies on transient ignition of hybrid rocket motor

NASA Astrophysics Data System (ADS)

Tian, Hui; Yu, Ruipeng; Zhu, Hao; Wu, Junfeng; Cai, Guobiao

2017-11-01

This paper presents transient simulations and experimental studies of the ignition process of the hybrid rocket motors (HRMs) using 90% hydrogen peroxide (HP) as the oxidizer and polymethyl methacrylate (PMMA) and Polyethylene (PE) as fuels. A fluid-solid coupling numerically method is established based on the conserved form of the three-dimensional unsteady Navier-Stokes (N-S) equations, considering gas fluid with chemical reactions and heat transfer between the fluid and solid region. Experiments are subsequently conducted using high-speed camera to record the ignition process. The flame propagation, chamber pressurizing process and average fuel regression rate of the numerical simulation results show good agreement with the experimental ones, which demonstrates the validity of the simulations in this study. The results also indicate that the flame propagation time is mainly affected by fluid dynamics and it increases with an increasing grain port area. The chamber pressurizing process begins when the flame propagation completes in the grain port. Furthermore, the chamber pressurizing time is about 4 times longer than the time of flame propagation.

TEMPEST. Transient 3-D Thermal-Hydraulic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eyler, L.L.

TEMPEST is a transient, three-dimensional, hydrothermal program that is designed to analyze a range of coupled fluid dynamic and heat transfer systems of particular interest to the Fast Breeder Reactor (FBR) thermal-hydraulic design community. The full three-dimensional, time-dependent equations of motion, continuity, and heat transport are solved for either laminar or turbulent fluid flow, including heat diffusion and generation in both solid and liquid materials. The equations governing mass, momentum, and energy conservation for incompressible flows and small density variations (Boussinesq approximation) are solved using finite-difference techniques. Analyses may be conducted in either cylindrical or Cartesian coordinate systems. Turbulence ismore » treated using a two-equation model. Two auxiliary plotting programs, SEQUEL and MANPLOT, for use with TEMPEST output are included. SEQUEL may be operated in batch or interactive mode; it generates data required for vector plots, contour plots of scalar quantities, line plots, grid and boundary plots, and time-history plots. MANPLOT reads the SEQUEL-generated data and creates the hardcopy plots. TEMPEST can be a valuable hydrothermal design analysis tool in areas outside the intended FBR thermal-hydraulic design community.« less

Three-dimensional transient flow of spin-up in a filled cylinder with oblique gravity force

NASA Technical Reports Server (NTRS)

Hung, R. J.; Pan, H. L.

1995-01-01

Three-dimensional transient flow profiles of spin-up in a fully liquid filled cylinder from rest with gravity acceleration at various direction are numerically simulated and studied. Particular interests are concentrated on the development of temporary reverse flow zones and Ekman layer right after the impulsive start of spin-up from rest, and decay before the flow reaching to the solid rotation. Relationship of these flow developments and differences in the Reynolds numbers of the flow and its size selection of grid points concerning the numerical instabilities of flow computations are also discussed. In addition to the gravitational acceleration along the axial direction of the cylindrical container, a series of complicated flow profiles accompanied by three-dimensional transient flows with oblique gravitational acceleration has been studies.

Modeling of bubble dynamics in relation to medical applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amendt, P.A.; London, R.A.; Strauss, M.

1997-03-12

In various pulsed-laser medical applications, strong stress transients can be generated in advance of vapor bubble formation. To better understand the evolution of stress transients and subsequent formation of vapor bubbles, two-dimensional simulations are presented in channel or cylindrical geometry with the LATIS (LAser TISsue) computer code. Differences with one-dimensional modeling are explored, and simulated experimental conditions for vapor bubble generation are presented and compared with data. 22 refs., 8 figs.

BEST3D user's manual: Boundary Element Solution Technology, 3-Dimensional Version 3.0

NASA Technical Reports Server (NTRS)

1991-01-01

The theoretical basis and programming strategy utilized in the construction of the computer program BEST3D (boundary element solution technology - three dimensional) and detailed input instructions are provided for the use of the program. An extensive set of test cases and sample problems is included in the manual and is also available for distribution with the program. The BEST3D program was developed under the 3-D Inelastic Analysis Methods for Hot Section Components contract (NAS3-23697). The overall objective of this program was the development of new computer programs allowing more accurate and efficient three-dimensional thermal and stress analysis of hot section components, i.e., combustor liners, turbine blades, and turbine vanes. The BEST3D program allows both linear and nonlinear analysis of static and quasi-static elastic problems and transient dynamic analysis for elastic problems. Calculation of elastic natural frequencies and mode shapes is also provided.

Collisions between coaxial vortex solitons in the three-dimensional cubic-quintic complex Ginzburg-Landau equation

NASA Astrophysics Data System (ADS)

Mihalache, D.; Mazilu, D.; Lederer, F.; Leblond, H.; Malomed, B. A.

2008-03-01

We present generic outcomes of collisions between stable solitons with intrinsic vorticity S=1 or S=2 in the complex Ginzburg-Landau equation with the cubic-quintic nonlinearity, for the axially symmetric configuration. An essential ingredient of the complex Ginzburg-Landau equation is an effective transverse diffusivity (which is known in models of laser cavities), as vortex solitons cannot be stable without it. For the sake of comparison, results are also included for fundamental three-dimensional solitons, with S=0 . Depending on the collision momentum, χ , three generic outcomes are identified: merger of the solitons into a single one, at small χ ; quasielastic interaction, at large χ ; and creation of an extra soliton, in an intermediate region. In addition to the final outcomes, we also highlight noteworthy features of the transient dynamics.

Transient Three-Dimensional Analysis of Nozzle Side Load in Regeneratively Cooled Engines

NASA Technical Reports Server (NTRS)

Wang, Ten-See

2005-01-01

Three-dimensional numerical investigations on the start-up side load physics for a regeneratively cooled, high-aspect-ratio nozzle were performed. The objectives of this study are to identify the three-dimensional side load physics and to compute the associated aerodynamic side load using an anchored computational methodology. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, and a transient inlet condition based on an engine system simulation. Computations were performed for both the adiabatic and cooled walls in order to understand the effect of boundary conditions. Finite-rate chemistry was used throughout the study so that combustion effect is always included. The results show that three types of shock evolution are responsible for side loads: generation of combustion wave; transitions among free-shock separation, restricted-shock separation, and simultaneous free-shock and restricted shock separations; along with oscillation of shocks across the lip. Wall boundary conditions drastically affect the computed side load physics: the adiabatic nozzle prefers free-shock separation while the cooled nozzle favors restricted-shock separation, resulting in higher peak side load for the cooled nozzle than that of the adiabatic nozzle. By comparing the computed physics with those of test observations, it is concluded that cooled wall is a more realistic boundary condition, and the oscillation of the restricted-shock separation flow pattern across the lip along with its associated tangential shock motion are the dominant side load physics for a regeneratively cooled, high aspect-ratio rocket engine.

Development of a three-dimensional transient code for reactivity-initiated events of BWRs (boiling water reactors) - Models and code verifications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uematsu, Hitoshi; Yamamoto, Toru; Izutsu, Sadayuki

1990-06-01

A reactivity-initiated event is a design-basis accident for the safety analysis of boiling water reactors. It is defined as a rapid transient of reactor power caused by a reactivity insertion of over $1.0 due to a postulated drop or abnormal withdrawal of the control rod from the core. Strong space-dependent feedback effects are associated with the local power increase due to control rod movement. A realistic treatment of the core status in a transient by a code with a detailed core model is recommended in evaluating this event. A three-dimensional transient code, ARIES, has been developed to meet this need.more » The code simulates the event with three-dimensional neutronics, coupled with multichannel thermal hydraulics, based on a nonequilibrium separated flow model. The experimental data obtained in reactivity accident tests performed with the SPERT III-E core are used to verify the entire code, including thermal-hydraulic models.« less

Development of a Three Dimensional Perfectly Matched Layer for Transient Elasto-Dynamic Analyses

DTIC Science & Technology

2006-12-01

MacLean [Ref. 47] intro- duced a small tracked vehicle with dual inertial mass shakers mounted on top as a mobile source. It excited Rayleigh waves, but...routine initializes and set default values for; * the aplication parameters * the material data base parameters * the entries to appear on the...Underground seismic array experiments. National In- stitute of Nuclear Physics, 2005. [47] D. J. MacLean. Mobile source development for seismic-sonar based

Model-free inference of direct network interactions from nonlinear collective dynamics.

PubMed

Casadiego, Jose; Nitzan, Mor; Hallerberg, Sarah; Timme, Marc

2017-12-19

The topology of interactions in network dynamical systems fundamentally underlies their function. Accelerating technological progress creates massively available data about collective nonlinear dynamics in physical, biological, and technological systems. Detecting direct interaction patterns from those dynamics still constitutes a major open problem. In particular, current nonlinear dynamics approaches mostly require to know a priori a model of the (often high dimensional) system dynamics. Here we develop a model-independent framework for inferring direct interactions solely from recording the nonlinear collective dynamics generated. Introducing an explicit dependency matrix in combination with a block-orthogonal regression algorithm, the approach works reliably across many dynamical regimes, including transient dynamics toward steady states, periodic and non-periodic dynamics, and chaos. Together with its capabilities to reveal network (two point) as well as hypernetwork (e.g., three point) interactions, this framework may thus open up nonlinear dynamics options of inferring direct interaction patterns across systems where no model is known.

Numerical Simulation and Analyses of the Loss of Feedwater Transient at the Unit 4 of Kola NPP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stevanovic, Vladimir D.; Stosic, Zoran V.; Kiera, Michael

2002-07-01

A three-dimensional numerical simulation of the loss-of-feed water transient at the horizontal steam generator of the Kola nuclear power plant is performed. Presented numerical results show transient change of integral steam generator parameters, such as steam generation rate, water mass inventory, outlet reactor coolant temperature, as well as detailed distribution of shell side thermal-hydraulic parameters: swell and collapsed levels, void fraction distributions, mass flux vectors, etc. Numerical results are compared with measurements at the Kola NPP. The agreement is satisfactory, while differences are close to or below the measurement uncertainties. Obtained numerical results are the first ones that give completemore » insight into the three-dimensional and transient horizontal steam generator thermal-hydraulics. Also, the presented results serve as benchmark tests for the assessment and further improvement of one-dimensional models of horizontal steam generator built with safety codes. (authors)« less

Towards a Molecular Movie: Real Time Observation of Hydrogen Bond Breaking by Transient 2D-IR Spectroscopy in a Cyclic Peptide

NASA Astrophysics Data System (ADS)

Kolano, Christoph; Helbing, Jan; Sander, Wolfram; Hamm, Peter

Transient two-dimensional infrared spectroscopy (T2D-IR) has been used to observe in real time the non-equilibrium structural dynamics of intramolecular hydrogen bond breaking in a small cyclic disulfide-bridged peptide.

Real-Time Time-Frequency Two-Dimensional Imaging of Ultrafast Transient Signals in Solid-State Organic Materials

PubMed Central

Takeda, Jun; Ishida, Akihiro; Makishima, Yoshinori; Katayama, Ikufumi

2010-01-01

In this review, we demonstrate a real-time time-frequency two-dimensional (2D) pump-probe imaging spectroscopy implemented on a single shot basis applicable to excited-state dynamics in solid-state organic and biological materials. Using this technique, we could successfully map ultrafast time-frequency 2D transient absorption signals of β-carotene in solid films with wide temporal and spectral ranges having very short accumulation time of 20 ms per unit frame. The results obtained indicate the high potential of this technique as a powerful and unique spectroscopic tool to observe ultrafast excited-state dynamics of organic and biological materials in solid-state, which undergo rapid photodegradation. PMID:22399879

STOL aircraft transient ground effects. Part 1: Fundamental analytical study

NASA Technical Reports Server (NTRS)

Goldhammer, M. I.; Crowder, J. P.; Smyth, D. N.

1975-01-01

The first phases of a fundamental analytical study of STOL ground effects were presented. Ground effects were studied in two dimensions to establish the importance of nonlinear effects, to examine transient aspects of ascent and descent near the ground, and to study the modelling of the jet impingement on the ground. Powered lift system effects were treated using the jet-flap analogy. The status of a three-dimensional jet-wing ground effect method was presented. It was shown, for two-dimensional unblown airfoils, that the transient effects are small and are primarily due to airfoil/freestream/ground orientation rather than to unsteady effects. The three-dimensional study showed phenomena similar to the two-dimensional results. For unblown wings, the wing/freestream/ground orientation effects were shown to be of the same order of magnitude as for unblown airfoils. This may be used to study the nonplanar, nonlinear, jet-wing ground effect.

Transient Three-Dimensional Side Load Analysis of Out-of-Round Film Cooled Nozzles

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Lin, Jeff; Ruf, Joe; Guidos, Mike

2010-01-01

The objective of this study is to investigate the effect of nozzle out-of-roundness on the transient startup side loads. The out-of-roundness could be the result of asymmetric loads induced by hardware attached to the nozzle, asymmetric internal stresses induced by previous tests and/or deformation, such as creep, from previous tests. The rocket engine studied encompasses a regeneratively cooled thrust chamber and a film cooled nozzle extension with film coolant distributed from a turbine exhaust manifold. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, and a transient inlet history based on an engine system simulation. Transient startup computations were performed with the out-of-roundness achieved by four degrees of ovalization of the nozzle: one perfectly round, one slightly out-of-round, one more out-of-round, and one significantly out-of-round. The computed side load physics caused by the nozzle out-of-roundness and its effect on nozzle side load are reported and discussed.

Analysis of the three-dimensional structure of a bubble wake using PIV and Galilean decomposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hassan, Y.A.; Schmidl, W.D.; Ortiz-Villafuerte, J.

1999-07-01

Bubbly flow plays a key role in a variety of natural and industrial processes. An accurate and complete description of the phase interactions in two-phase bubbly flow is not available at this time. These phase interactions are, in general, always three-dimensional and unsteady. Therefore, measurement techniques utilized to obtain qualitative and quantitative data from two-phase flow should be able to acquire transient and three-dimensional data, in order to provide information to test theoretical models and numerical simulations. Even for dilute bubble flows, in which bubble interaction is at a minimum, the turbulent motion of the liquid generated by the bubblemore » is yet to be completely understood. For many years, the design of systems with bubbly flows was based primarily on empiricism. Dilute bubbly flows are an extension of single bubble dynamics, and therefore improvements in the description and modeling of single bubble motion, the flow field around the bubble, and the dynamical interactions between the bubble and the flow will consequently improve bubbly flow modeling. The improved understanding of the physical phenomena will have far-reaching benefits in upgrading the operation and efficiency of current processes and in supporting the development of new and innovative approaches. A stereoscopic particle image velocimetry measurement of the flow generated by the passage of a single air-bubble rising in stagnant water, in a circular pipe is presented. Three-dimensional velocity fields within the measurement zone were obtained. Ensemble-averaged instantaneous velocities for a specific bubble path were calculated and interpolated to obtain mean three-dimensional velocity fields. A Galilean velocity decomposition is used to study the vorticity generated in the flow.« less

3-D thermal analysis using finite difference technique with finite element model for improved design of components of rocket engine turbomachines for Space Shuttle Main Engine SSME

NASA Technical Reports Server (NTRS)

Sohn, Kiho D.; Ip, Shek-Se P.

1988-01-01

Three-dimensional finite element models were generated and transferred into three-dimensional finite difference models to perform transient thermal analyses for the SSME high pressure fuel turbopump's first stage nozzles and rotor blades. STANCOOL was chosen to calculate the heat transfer characteristics (HTCs) around the airfoils, and endwall effects were included at the intersections of the airfoils and platforms for the steady-state boundary conditions. Free and forced convection due to rotation effects were also considered in hollow cores. Transient HTCs were calculated by taking ratios of the steady-state values based on the flow rates and fluid properties calculated at each time slice. Results are presented for both transient plots and three-dimensional color contour isotherm plots; they were also converted into universal files to be used for FEM stress analyses.

Ultrafast relaxation dynamics of nitric oxide synthase studied by visible broadband transient absorption spectroscopy

NASA Astrophysics Data System (ADS)

Hung, Chih-Chang; Yabushita, Atsushi; Kobayashi, Takayoshi; Chen, Pei-Feng; Liang, Keng S.

2017-09-01

Ultrafast dynamics of endothelial nitric oxide synthase (eNOS) oxygenase domain was studied by transient absorption spectroscopy pumping at Soret band. The broadband visible probe spectrum has visualized the relaxation dynamics from the Soret band to Q-band and charge transfer (CT) band. Supported by two-dimensional correlation spectroscopy, global fitting analysis has successfully concluded the relaxation dynamics from the Soret band to be (1) electronic transition to Q-band (0.16 ps), (2) ligand dissociation and CT (0.94 ps), (3) relaxation of the CT state (4.0 ps), and (4) ligand rebinding (59 ps).

Mixed quantum-classical electrodynamics: Understanding spontaneous decay and zero-point energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Tao E.; Nitzan, Abraham; Sukharev, Maxim

The dynamics of an electronic two-level system coupled to an electromagnetic field are simulated explicitly for one- and three-dimensional systems through semiclassical propagation of the Maxwell-Liouville equations. Here, we consider three flavors of mixed quantum-classical dynamics: (i) the classical path approximation (CPA), (ii) Ehrenfest dynamics, and (iii) symmetrical quasiclassical (SQC) dynamics. Our findings are as follows: (i) The CPA fails to recover a consistent description of spontaneous emission, (ii) a consistent “spontaneous” emission can be obtained from Ehrenfest dynamics, provided that one starts in an electronic superposition state, and (iii) spontaneous emission is always obtained using SQC dynamics. Using themore » SQC and Ehrenfest frameworks, we further calculate the dynamics following an incoming pulse, but here we find very different responses: SQC and Ehrenfest dynamics deviate sometimes strongly in the calculated rate of decay of the transient excited state. Nevertheless, our work confirms the earlier observations by Miller [J. Chem. Phys. 69, 2188 (1978)] that Ehrenfest dynamics can effectively describe some aspects of spontaneous emission and highlights interesting possibilities for studying light-matter interactions with semiclassical mechanics.« less

Mixed quantum-classical electrodynamics: Understanding spontaneous decay and zero-point energy

NASA Astrophysics Data System (ADS)

Li, Tao E.; Nitzan, Abraham; Sukharev, Maxim; Martinez, Todd; Chen, Hsing-Ta; Subotnik, Joseph E.

2018-03-01

The dynamics of an electronic two-level system coupled to an electromagnetic field are simulated explicitly for one- and three-dimensional systems through semiclassical propagation of the Maxwell-Liouville equations. We consider three flavors of mixed quantum-classical dynamics: (i) the classical path approximation (CPA), (ii) Ehrenfest dynamics, and (iii) symmetrical quasiclassical (SQC) dynamics. Our findings are as follows: (i) The CPA fails to recover a consistent description of spontaneous emission, (ii) a consistent "spontaneous" emission can be obtained from Ehrenfest dynamics, provided that one starts in an electronic superposition state, and (iii) spontaneous emission is always obtained using SQC dynamics. Using the SQC and Ehrenfest frameworks, we further calculate the dynamics following an incoming pulse, but here we find very different responses: SQC and Ehrenfest dynamics deviate sometimes strongly in the calculated rate of decay of the transient excited state. Nevertheless, our work confirms the earlier observations by Miller [J. Chem. Phys. 69, 2188 (1978), 10.1063/1.436793] that Ehrenfest dynamics can effectively describe some aspects of spontaneous emission and highlights interesting possibilities for studying light-matter interactions with semiclassical mechanics.

Mixed quantum-classical electrodynamics: Understanding spontaneous decay and zero-point energy

DOE PAGES

Li, Tao E.; Nitzan, Abraham; Sukharev, Maxim; ...

2018-03-12

The dynamics of an electronic two-level system coupled to an electromagnetic field are simulated explicitly for one- and three-dimensional systems through semiclassical propagation of the Maxwell-Liouville equations. Here, we consider three flavors of mixed quantum-classical dynamics: (i) the classical path approximation (CPA), (ii) Ehrenfest dynamics, and (iii) symmetrical quasiclassical (SQC) dynamics. Our findings are as follows: (i) The CPA fails to recover a consistent description of spontaneous emission, (ii) a consistent “spontaneous” emission can be obtained from Ehrenfest dynamics, provided that one starts in an electronic superposition state, and (iii) spontaneous emission is always obtained using SQC dynamics. Using themore » SQC and Ehrenfest frameworks, we further calculate the dynamics following an incoming pulse, but here we find very different responses: SQC and Ehrenfest dynamics deviate sometimes strongly in the calculated rate of decay of the transient excited state. Nevertheless, our work confirms the earlier observations by Miller [J. Chem. Phys. 69, 2188 (1978)] that Ehrenfest dynamics can effectively describe some aspects of spontaneous emission and highlights interesting possibilities for studying light-matter interactions with semiclassical mechanics.« less

Environmental, Transient, Three-Dimensional, Hydrothermal, Mass Transport Code - FLESCOT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Onishi, Yasuo; Bao, Jie; Glass, Kevin A.

The purpose of the project was to modify and apply the transient, three-dimensional FLESCOT code to be able to effectively simulate cesium behavior in Fukushima lakes/dam reservoirs, river mouths, and coastal areas. The ultimate objective of the FLESCOT simulation is to predict future changes of cesium accumulation in Fukushima area reservoirs and costal water. These evaluation results will assist ongoing and future environmental remediation activities and policies in a systematic and comprehensive manner.

Dynamic characterization of hydrophobic and hydrophilic solutes in oleic-acid enhanced transdermal delivery using two-photon fluorescence microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tseng, Te-Yu; Yang, Chiu-Sheng; Chen, Yang-Fang

In this letter, we propose an efficient methodology of investigating dynamic properties of sulforhodamine B and rhodamine B hexyl ester molecules transporting across ex-vivo human stratum corneum with and without oleic acid enhancement. Three-dimensional, time-lapse fluorescence images of the stratum corneum can be obtained using two-photon fluorescence microscopy. Furthermore, temporal quantifications of transport enhancements in diffusion parameters can be achieved with the use of Fick's second law. Dynamic characterization of solutes transporting across the stratum corneum is an effective method for understanding transient phenomena in transdermal delivery of probe molecules, leading to improved delivery strategies of molecular species for therapeuticmore » purposes.« less

A three-dimensional ParF meshwork assembles through the nucleoid to mediate plasmid segregation

PubMed Central

McLeod, Brett N.; Allison-Gamble, Gina E.; Barge, Madhuri T.; Tonthat, Nam K.; Schumacher, Maria A.; Hayes, Finbarr

2017-01-01

Abstract Genome segregation is a fundamental step in the life cycle of every cell. Most bacteria rely on dedicated DNA partition proteins to actively segregate chromosomes and low copy-number plasmids. Here, by employing super resolution microscopy, we establish that the ParF DNA partition protein of the ParA family assembles into a three-dimensional meshwork that uses the nucleoid as a scaffold and periodically shuttles between its poles. Whereas ParF specifies the territory for plasmid trafficking, the ParG partner protein dictates the tempo of ParF assembly cycles and plasmid segregation events by stimulating ParF adenosine triphosphate hydrolysis. Mutants in which this ParG temporal regulation is ablated show partition deficient phenotypes as a result of either altered ParF structure or dynamics and indicate that ParF nucleoid localization and dynamic relocation, although necessary, are not sufficient per se to ensure plasmid segregation. We propose a Venus flytrap model that merges the concepts of ParA polymerization and gradient formation and speculate that a transient, dynamic network of intersecting polymers that branches into the nucleoid interior is a widespread mechanism to distribute sizeable cargos within prokaryotic cells. PMID:28034957

Time-dependent optical response of three-dimensional Au nanoparticle arrays formed on silica nanowires

NASA Astrophysics Data System (ADS)

Di Mario, Lorenzo; Otomalo, Tadele Orbula; Catone, Daniele; O'Keeffe, Patrick; Tian, Lin; Turchini, Stefano; Palpant, Bruno; Martelli, Faustino

2018-03-01

We present stationary and transient absorption measurements on 3D Au nanoparticle (NP)-decorated Si O2 nanowire arrays. The 3D NP array has been produced by the dewetting of a thin Au film deposited on silica nanowires produced by oxidation of silicon nanowires. The experimental behaviors of the spectral and temporal dynamics observed in the experiment are accurately described by a two-step, three-temperature model. Using an arbitrary set of Au NPs with different aspect ratios, we demonstrate that the width of the experimental spectra, the energy shift of their position with time, and the asymmetry between the two positive wings in the dynamical variation of absorption can all be attributed to the nonuniform shape distribution of the Au NPs in the sample.

Efficient statistically accurate algorithms for the Fokker-Planck equation in large dimensions

NASA Astrophysics Data System (ADS)

Chen, Nan; Majda, Andrew J.

2018-02-01

Solving the Fokker-Planck equation for high-dimensional complex turbulent dynamical systems is an important and practical issue. However, most traditional methods suffer from the curse of dimensionality and have difficulties in capturing the fat tailed highly intermittent probability density functions (PDFs) of complex systems in turbulence, neuroscience and excitable media. In this article, efficient statistically accurate algorithms are developed for solving both the transient and the equilibrium solutions of Fokker-Planck equations associated with high-dimensional nonlinear turbulent dynamical systems with conditional Gaussian structures. The algorithms involve a hybrid strategy that requires only a small number of ensembles. Here, a conditional Gaussian mixture in a high-dimensional subspace via an extremely efficient parametric method is combined with a judicious non-parametric Gaussian kernel density estimation in the remaining low-dimensional subspace. Particularly, the parametric method provides closed analytical formulae for determining the conditional Gaussian distributions in the high-dimensional subspace and is therefore computationally efficient and accurate. The full non-Gaussian PDF of the system is then given by a Gaussian mixture. Different from traditional particle methods, each conditional Gaussian distribution here covers a significant portion of the high-dimensional PDF. Therefore a small number of ensembles is sufficient to recover the full PDF, which overcomes the curse of dimensionality. Notably, the mixture distribution has significant skill in capturing the transient behavior with fat tails of the high-dimensional non-Gaussian PDFs, and this facilitates the algorithms in accurately describing the intermittency and extreme events in complex turbulent systems. It is shown in a stringent set of test problems that the method only requires an order of O (100) ensembles to successfully recover the highly non-Gaussian transient PDFs in up to 6 dimensions with only small errors.

Ultrafast energy- and momentum-resolved dynamics of magnetic correlations in the photo-doped Mott insulator Sr2IrO4.

PubMed

Dean, M P M; Cao, Y; Liu, X; Wall, S; Zhu, D; Mankowsky, R; Thampy, V; Chen, X M; Vale, J G; Casa, D; Kim, Jungho; Said, A H; Juhas, P; Alonso-Mori, R; Glownia, J M; Robert, A; Robinson, J; Sikorski, M; Song, S; Kozina, M; Lemke, H; Patthey, L; Owada, S; Katayama, T; Yabashi, M; Tanaka, Yoshikazu; Togashi, T; Liu, J; Rayan Serrao, C; Kim, B J; Huber, L; Chang, C-L; McMorrow, D F; Först, M; Hill, J P

2016-06-01

Measuring how the magnetic correlations evolve in doped Mott insulators has greatly improved our understanding of the pseudogap, non-Fermi liquids and high-temperature superconductivity. Recently, photo-excitation has been used to induce similarly exotic states transiently. However, the lack of available probes of magnetic correlations in the time domain hinders our understanding of these photo-induced states and how they could be controlled. Here, we implement magnetic resonant inelastic X-ray scattering at a free-electron laser to directly determine the magnetic dynamics after photo-doping the Mott insulator Sr2IrO4. We find that the non-equilibrium state, 2 ps after the excitation, exhibits strongly suppressed long-range magnetic order, but hosts photo-carriers that induce strong, non-thermal magnetic correlations. These two-dimensional (2D) in-plane Néel correlations recover within a few picoseconds, whereas the three-dimensional (3D) long-range magnetic order restores on a fluence-dependent timescale of a few hundred picoseconds. The marked difference in these two timescales implies that the dimensionality of magnetic correlations is vital for our understanding of ultrafast magnetic dynamics.

High Performance Parallel Analysis of Coupled Problems for Aircraft Propulsion

NASA Technical Reports Server (NTRS)

Felippa, C. A.; Farhat, C.; Lanteri, S.; Maman, N.; Piperno, S.; Gumaste, U.

1994-01-01

In order to predict the dynamic response of a flexible structure in a fluid flow, the equations of motion of the structure and the fluid must be solved simultaneously. In this paper, we present several partitioned procedures for time-integrating this focus coupled problem and discuss their merits in terms of accuracy, stability, heterogeneous computing, I/O transfers, subcycling, and parallel processing. All theoretical results are derived for a one-dimensional piston model problem with a compressible flow, because the complete three-dimensional aeroelastic problem is difficult to analyze mathematically. However, the insight gained from the analysis of the coupled piston problem and the conclusions drawn from its numerical investigation are confirmed with the numerical simulation of the two-dimensional transient aeroelastic response of a flexible panel in a transonic nonlinear Euler flow regime.

Freefield vibrations due to dynamic loading on a tunnel embedded in a stratified medium

NASA Astrophysics Data System (ADS)

Clouteau, D.; Arnst, M.; Al-Hussaini, T. M.; Degrande, G.

2005-05-01

An efficient and modular numerical prediction model is developed to predict vibration and re-radiated noise in adjacent buildings from excitation due to metro trains in tunnels for both newly built and existing situations. The three-dimensional dynamic tunnel-soil interaction problem is solved with a subdomain formulation, using a finite element formulation for the tunnel and a boundary element method for the soil. The periodicity of the tunnel and the soil in the longitudinal direction is exploited using the Floquet transform, limiting the discretization effort to a single bounded reference cell. It is demonstrated in the paper how the boundary element method can efficiently be extended to deal with periodic media, reusing the available three-dimensional Green's tensors for layered media. The efficiency of the method is demonstrated with a numerical example, where the case of harmonic and transient point loading on the invert of a shallow cut-and-cover masonry tunnel in Paris is considered. The work described here was carried out under the auspices of the CONVURT project sponsored by the European Community.

Transient carrier dynamics in a Mott insulator with antiferromagnetic order

NASA Astrophysics Data System (ADS)

Iyoda, Eiki; Ishihara, Sumio

2014-03-01

We study transient dynamics of hole carriers injected into a Mott insulator with antiferromagnetic long-range order. This "dynamical hole doping" contrasts with chemical hole doping. The theoretical framework for the transient carrier dynamics is presented based on the two-dimensional t-J model. The time dependencies of the optical conductivity spectra, as well as the one-particle excitation spectra, are calculated based on the Keldysh Green's function formalism at zero temperature combined with the self-consistent Born approximation. In the early stage after dynamical hole doping, the Drude component appears, and then incoherent components originating from hole-magnon scattering start to grow. Fast oscillatory behavior owing to coherent magnon and slow relaxation dynamics are confirmed in the spectra. The time profiles are interpreted as doped bare holes being dressed by magnon clouds and relaxed into spin polaron quasiparticle states. The characteristic relaxation times for Drude and incoherent peaks strongly depend on the momentum of the dynamically doped hole and the exchange constant. Implications for recent pump-probe experiments are discussed.

SIERRA - A 3-D device simulator for reliability modeling

NASA Astrophysics Data System (ADS)

Chern, Jue-Hsien; Arledge, Lawrence A., Jr.; Yang, Ping; Maeda, John T.

1989-05-01

SIERRA is a three-dimensional general-purpose semiconductor-device simulation program which serves as a foundation for investigating integrated-circuit (IC) device and reliability issues. This program solves the Poisson and continuity equations in silicon under dc, transient, and small-signal conditions. Executing on a vector/parallel minisupercomputer, SIERRA utilizes a matrix solver which uses an incomplete LU (ILU) preconditioned conjugate gradient square (CGS, BCG) method. The ILU-CGS method provides a good compromise between memory size and convergence rate. The authors have observed a 5x to 7x speedup over standard direct methods in simulations of transient problems containing highly coupled Poisson and continuity equations such as those found in reliability-oriented simulations. The application of SIERRA to parasitic CMOS latchup and dynamic random-access memory single-event-upset studies is described.

Studying Axon-Astrocyte Functional Interactions by 3D Two-Photon Ca2+ Imaging: A Practical Guide to Experiments and "Big Data" Analysis.

PubMed

Savtchouk, Iaroslav; Carriero, Giovanni; Volterra, Andrea

2018-01-01

Recent advances in fast volumetric imaging have enabled rapid generation of large amounts of multi-dimensional functional data. While many computer frameworks exist for data storage and analysis of the multi-gigabyte Ca 2+ imaging experiments in neurons, they are less useful for analyzing Ca 2+ dynamics in astrocytes, where transients do not follow a predictable spatio-temporal distribution pattern. In this manuscript, we provide a detailed protocol and commentary for recording and analyzing three-dimensional (3D) Ca 2+ transients through time in GCaMP6f-expressing astrocytes of adult brain slices in response to axonal stimulation, using our recently developed tools to perform interactive exploration, filtering, and time-correlation analysis of the transients. In addition to the protocol, we release our in-house software tools and discuss parameters pertinent to conducting axonal stimulation/response experiments across various brain regions and conditions. Our software tools are available from the Volterra Lab webpage at https://wwwfbm.unil.ch/dnf/group/glia-an-active-synaptic-partner/member/volterra-andrea-volterra in the form of software plugins for Image J (NIH)-a de facto standard in scientific image analysis. Three programs are available: MultiROI_TZ_profiler for interactive graphing of several movable ROIs simultaneously, Gaussian_Filter5D for Gaussian filtering in several dimensions, and Correlation_Calculator for computing various cross-correlation parameters on voxel collections through time.

Three-dimensional multi-physics coupled simulation of ignition transient in a dual pulse solid rocket motor

NASA Astrophysics Data System (ADS)

Li, Yingkun; Chen, Xiong; Xu, Jinsheng; Zhou, Changsheng; Musa, Omer

2018-05-01

In this paper, numerical investigation of ignition transient in a dual pulse solid rocket motor has been conducted. An in-house code has been developed in order to solve multi-physics governing equations, including unsteady compressible flow, heat conduction and structural dynamic. The simplified numerical models for solid propellant ignition and combustion have been added. The conventional serial staggered algorithm is adopted to simulate the fluid structure interaction problems in a loosely-coupled manner. The accuracy of the coupling procedure is validated by the behavior of a cantilever panel subjected to a shock wave. Then, the detailed flow field development, flame propagation characteristics, pressure evolution in the combustion chamber, and the structural response of metal diaphragm are analyzed carefully. The burst-time and burst-pressure of the metal diaphragm are also obtained. The individual effects of the igniter's mass flow rate, metal diaphragm thickness and diameter on the ignition transient have been systemically compared. The numerical results show that the evolution of the flow field in the combustion chamber, the temperature distribution on the propellant surface and the pressure loading on the metal diaphragm surface present a strong three-dimensional behavior during the initial ignition stage. The rupture of metal diaphragm is not only related to the magnitude of pressure loading on the diaphragm surface, but also to the history of pressure loading. The metal diaphragm thickness and diameter have a significant effect on the burst-time and burst-pressure of metal diaphragm.

Application of TVD schemes for the Euler equations of gas dynamics. [total variation diminishing for nonlinear hyperbolic systems

NASA Technical Reports Server (NTRS)

Yee, H. C.; Warming, R. F.; Harten, A.

1985-01-01

First-order, second-order, and implicit total variation diminishing (TVD) schemes are reviewed using the modified flux approach. Some transient and steady-state calculations are then carried out to illustrate the applicability of these schemes to the Euler equations. It is shown that the second-order explicit TVD schemes generate good shock resolution for both transient and steady-state one-dimensional and two-dimensional problems. Numerical experiments for a quasi-one-dimensional nozzle problem show that the second-order implicit TVD scheme produces a fairly rapid convergence rate and remains stable even when running with a Courant number of 10 to the 6th.

Geometrically nonlinear analysis of layered composite plates and shells

NASA Technical Reports Server (NTRS)

Chao, W. C.; Reddy, J. N.

1983-01-01

A degenerated three dimensional finite element, based on the incremental total Lagrangian formulation of a three dimensional layered anisotropic medium was developed. Its use in the geometrically nonlinear, static and dynamic, analysis of layered composite plates and shells is demonstrated. A two dimenisonal finite element based on the Sanders shell theory with the von Karman (nonlinear) strains was developed. It is shown that the deflections obtained by the 2D shell element deviate from those obtained by the more accurate 3D element for deep shells. The 3D degenerated element can be used to model general shells that are not necessarily doubly curved. The 3D degenerated element is computationally more demanding than the 2D shell theory element for a given problem. It is found that the 3D element is an efficient element for the analysis of layered composite plates and shells undergoing large displacements and transient motion.

Three-dimensional Dendritic Needle Network model with application to Al-Cu directional solidification experiments

NASA Astrophysics Data System (ADS)

Tourret, D.; Karma, A.; Clarke, A. J.; Gibbs, P. J.; Imhoff, S. D.

2015-06-01

We present a three-dimensional (3D) extension of a previously proposed multi-scale Dendritic Needle Network (DNN) approach for the growth of complex dendritic microstructures. Using a new formulation of the DNN dynamics equations for dendritic paraboloid-branches of a given thickness, one can directly extend the DNN approach to 3D modeling. We validate this new formulation against known scaling laws and analytical solutions that describe the early transient and steady-state growth regimes, respectively. Finally, we compare the predictions of the model to in situ X-ray imaging of Al-Cu alloy solidification experiments. The comparison shows a very good quantitative agreement between 3D simulations and thin sample experiments. It also highlights the importance of full 3D modeling to accurately predict the primary dendrite arm spacing that is significantly over-estimated by 2D simulations.

Three-dimensional Dendritic Needle Network model with application to Al-Cu directional solidification experiments

DOE PAGES

Tourret, D.; Karma, A.; Clarke, A. J.; ...

2015-06-11

We present a three-dimensional (3D) extension of a previously proposed multi-scale Dendritic Needle Network (DNN) approach for the growth of complex dendritic microstructures. Using a new formulation of the DNN dynamics equations for dendritic paraboloid-branches of a given thickness, one can directly extend the DNN approach to 3D modeling. We validate this new formulation against known scaling laws and analytical solutions that describe the early transient and steady-state growth regimes, respectively. Finally, we compare the predictions of the model to in situ X-ray imaging of Al-Cu alloy solidification experiments. The comparison shows a very good quantitative agreement between 3D simulationsmore » and thin sample experiments. It also highlights the importance of full 3D modeling to accurately predict the primary dendrite arm spacing that is significantly over-estimated by 2D simulations.« less

Three-dimensional mapping and regulation of action potential propagation in nanoelectronics-innervated tissues.

PubMed

Dai, Xiaochuan; Zhou, Wei; Gao, Teng; Liu, Jia; Lieber, Charles M

2016-09-01

Real-time mapping and manipulation of electrophysiology in three-dimensional (3D) tissues could have important impacts on fundamental scientific and clinical studies, yet realization is hampered by a lack of effective methods. Here we introduce tissue-scaffold-mimicking 3D nanoelectronic arrays consisting of 64 addressable devices with subcellular dimensions and a submillisecond temporal resolution. Real-time extracellular action potential (AP) recordings reveal quantitative maps of AP propagation in 3D cardiac tissues, enable in situ tracing of the evolving topology of 3D conducting pathways in developing cardiac tissues and probe the dynamics of AP conduction characteristics in a transient arrhythmia disease model and subsequent tissue self-adaptation. We further demonstrate simultaneous multisite stimulation and mapping to actively manipulate the frequency and direction of AP propagation. These results establish new methodologies for 3D spatiotemporal tissue recording and control, and demonstrate the potential to impact regenerative medicine, pharmacology and electronic therapeutics.

Three-dimensional mapping and regulation of action potential propagation in nanoelectronics innervated tissues

PubMed Central

Dai, Xiaochuan; Zhou, Wei; Gao, Teng; Liu, Jia; Lieber, Charles M.

2016-01-01

Real-time mapping and manipulation of electrophysiology in three-dimensional (3D) tissues could impact broadly fundamental scientific and clinical studies, yet realization lacks effective methods. Here we introduce tissue-scaffold-mimicking 3D nanoelectronic arrays consisting of 64 addressable devices with subcellular dimensions and sub-millisecond time-resolution. Real-time extracellular action potential (AP) recordings reveal quantitative maps of AP propagation in 3D cardiac tissues, enable in situ tracing of the evolving topology of 3D conducting pathways in developing cardiac tissues, and probe the dynamics of AP conduction characteristics in a transient arrhythmia disease model and subsequent tissue self-adaptation. We further demonstrate simultaneous multi-site stimulation and mapping to manipulate actively the frequency and direction of AP propagation. These results establish new methodologies for 3D spatiotemporal tissue recording and control, and demonstrate the potential to impact regenerative medicine, pharmacology and electronic therapeutics. PMID:27347837

Visualization of unsteady computational fluid dynamics

NASA Astrophysics Data System (ADS)

Haimes, Robert

1994-11-01

A brief summary of the computer environment used for calculating three dimensional unsteady Computational Fluid Dynamic (CFD) results is presented. This environment requires a super computer as well as massively parallel processors (MPP's) and clusters of workstations acting as a single MPP (by concurrently working on the same task) provide the required computational bandwidth for CFD calculations of transient problems. The cluster of reduced instruction set computers (RISC) is a recent advent based on the low cost and high performance that workstation vendors provide. The cluster, with the proper software can act as a multiple instruction/multiple data (MIMD) machine. A new set of software tools is being designed specifically to address visualizing 3D unsteady CFD results in these environments. Three user's manuals for the parallel version of Visual3, pV3, revision 1.00 make up the bulk of this report.

Visualization of unsteady computational fluid dynamics

NASA Technical Reports Server (NTRS)

Haimes, Robert

1994-01-01

A brief summary of the computer environment used for calculating three dimensional unsteady Computational Fluid Dynamic (CFD) results is presented. This environment requires a super computer as well as massively parallel processors (MPP's) and clusters of workstations acting as a single MPP (by concurrently working on the same task) provide the required computational bandwidth for CFD calculations of transient problems. The cluster of reduced instruction set computers (RISC) is a recent advent based on the low cost and high performance that workstation vendors provide. The cluster, with the proper software can act as a multiple instruction/multiple data (MIMD) machine. A new set of software tools is being designed specifically to address visualizing 3D unsteady CFD results in these environments. Three user's manuals for the parallel version of Visual3, pV3, revision 1.00 make up the bulk of this report.

THREE-DIMENSIONAL NAPL FATE AND TRANSPORT MODEL

EPA Science Inventory

We have added several new and significant capabilities to UTCHEM to make it into a general-purpose NAPL simulator. The simulator is now capable of modeling transient and steady-state three-dimensional flow and mass transport in the groundwater (saturated) and vadose (unsaturated...

Visual scan-path analysis with feature space transient fixation moments

NASA Astrophysics Data System (ADS)

Dempere-Marco, Laura; Hu, Xiao-Peng; Yang, Guang-Zhong

2003-05-01

The study of eye movements provides useful insight into the cognitive processes underlying visual search tasks. The analysis of the dynamics of eye movements has often been approached from a purely spatial perspective. In many cases, however, it may not be possible to define meaningful or consistent dynamics without considering the features underlying the scan paths. In this paper, the definition of the feature space has been attempted through the concept of visual similarity and non-linear low dimensional embedding, which defines a mapping from the image space into a low dimensional feature manifold that preserves the intrinsic similarity of image patterns. This has enabled the definition of perceptually meaningful features without the use of domain specific knowledge. Based on this, this paper introduces a new concept called Feature Space Transient Fixation Moments (TFM). The approach presented tackles the problem of feature space representation of visual search through the use of TFM. We demonstrate the practical values of this concept for characterizing the dynamics of eye movements in goal directed visual search tasks. We also illustrate how this model can be used to elucidate the fundamental steps involved in skilled search tasks through the evolution of transient fixation moments.

Numerical Investigation of Transient Flow in a Prototype Centrifugal Pump during Startup Period

NASA Astrophysics Data System (ADS)

Zhang, Yu-Liang; Zhu, Zu-Chao; Dou, Hua-Shu; Cui, Bao-Ling; Li, Yi; Zhou, Zhao-Zhong

2017-05-01

Transient performance of pumps during transient operating periods, such as startup and stopping, has drawn more and more attentions recently due to the growing engineering needs. During the startup period of a pump, the performance parameters such as the flow rate and head would vary significantly in a broad range. Therefore, it is very difficult to accurately specify the unsteady boundary conditions for a pump alone to solve the transient flow in the absence of experimental results. The closed-loop pipe system including a centrifugal pump is built to accomplish the self-coupling calculation. The three-dimensional unsteady incompressible viscous flow inside the passage of the pump during startup period is numerically simulated using the dynamic mesh method. Simulation results show that there are tiny fluctuations in the flow rate even under stable operating conditions and this can be attributed to influence of the rotor-stator interaction. At the very beginning of the startup, the rising speed of the flow rate is lower than that of the rotational speed. It is also found that it is not suitable to predict the transient performance of pumps using the calculation method of quasi-steady flow, especially at the earlier period of the startup.

Unsteady thermal blooming of intense laser beams

NASA Astrophysics Data System (ADS)

Ulrich, J. T.; Ulrich, P. B.

1980-01-01

A four dimensional (three space plus time) computer program has been written to compute the nonlinear heating of a gas by an intense laser beam. Unsteady, transient cases are capable of solution and no assumption of a steady state need be made. The transient results are shown to asymptotically approach the steady-state results calculated by the standard three dimensional thermal blooming computer codes. The report discusses the physics of the laser-absorber interaction, the numerical approximation used, and comparisons with experimental data. A flowchart is supplied in the appendix to the report.

CONTAMINANT TRANSPORT RESULTING FROM MULTICOMPONENT NONAQUEOUS PHASE LIQUID POOL DISSOLUTION IN THREE-DIMENSIONAL SUBSURFACE FORMATIONS (R823579)

EPA Science Inventory

A semi-analytical method for simulating transient contaminant transport originating from the dissolution of multicomponent nonaqueous phase liquid (NAPL) pools in three-dimensional, saturated, homogeneous porous media is presented. Each dissolved component may undergo first-order...

Exploring time-resolved photoluminescence for nanowires using a three-dimensional computational transient model.

PubMed

Ren, Dingkun; Scofield, Adam C; Farrell, Alan C; Rong, Zixuan; Haddad, Michael A; Laghumavarapu, Ramesh B; Liang, Baolai; Huffaker, Diana L

2018-04-26

Time-resolved photoluminescence (TRPL) has been implemented experimentally to measure the carrier lifetime of semiconductors for decades. For the characterization of nanowires, the rich information embedded in TRPL curves has not been fully interpreted and meaningfully mapped to the respective material properties. This is because their three-dimensional (3-D) geometries result in more complicated mechanisms of carrier recombination than those in thin films and analytical solutions cannot be found for those nanostructures. In this work, we extend the intrinsic power of TRPL by developing a full 3-D transient model, which accounts for different material properties and drift-diffusion, to simulate TRPL curves for nanowires. To show the capability of the model, we perform TRPL measurements on a set of GaAs nanowire arrays grown on silicon substrates and then fit the measured data by tuning various material properties, including carrier mobility, Shockley-Read-Hall recombination lifetime, and surface recombination velocity at the GaAs-Si heterointerface. From the resultant TRPL simulations, we numerically identify the lifetime characteristics of those material properties. In addition, we computationally map the spatial and temporal electron distributions in nanowire segments and reveal the underlying carrier dynamics. We believe this study provides a theoretical foundation for interpretation of TRPL measurements to unveil the complex carrier recombination mechanisms in 3-D nanostructured materials.

Assessing anthropogenic impacts on limited water resources under semi-arid conditions: three-dimensional transient regional modelling in Jordan

NASA Astrophysics Data System (ADS)

Rödiger, Tino; Magri, Fabien; Geyer, Stefan; Morandage, Shehan Tharaka; Ali Subah, H. E.; Alraggad, Marwan; Siebert, Christian

2017-11-01

Both increasing aridity and population growth strongly stress freshwater resources in semi-arid areas such as Jordan. The country's second largest governorate, Irbid, with over 1 million inhabitants, is already suffering from an annual water deficit of 25 million cubic meters (MCM). The population is expected to double within the next 20 years. Even without the large number of refugees from Syria, the deficit will likely increase to more then 50 MCM per year by 2035 The Governorate's exclusive resource is groundwater, abstracted by the extensive Al Arab and Kufr Asad well fields. This study presents the first three-dimensional transient regional groundwater flow model of the entire Wadi al Arab to answer important questions regarding the dynamic quality and availability of water within the catchment. Emphasis is given to the calculation and validation of the dynamic groundwater recharge, derived from a multi-proxy approach, including (1) a hydrological model covering a 30-years dataset, (2) groundwater level measurements and (3) information about springs. The model enables evaluation of the impact of abstraction on the flow regime and the groundwater budget of the resource. Sensitivity analyses of controlling parameters indicate that intense abstraction in the southern part of the Wadi al Arab system can result in critical water-level drops of 10 m at a distance of 16 km from the production wells. Moreover, modelling results suggest that observed head fluctuations are strongly controlled by anthropogenic abstraction rather than variable recharge rates due to climate changes.

A three-dimensional ParF meshwork assembles through the nucleoid to mediate plasmid segregation.

PubMed

McLeod, Brett N; Allison-Gamble, Gina E; Barge, Madhuri T; Tonthat, Nam K; Schumacher, Maria A; Hayes, Finbarr; Barillà, Daniela

2017-04-07

Genome segregation is a fundamental step in the life cycle of every cell. Most bacteria rely on dedicated DNA partition proteins to actively segregate chromosomes and low copy-number plasmids. Here, by employing super resolution microscopy, we establish that the ParF DNA partition protein of the ParA family assembles into a three-dimensional meshwork that uses the nucleoid as a scaffold and periodically shuttles between its poles. Whereas ParF specifies the territory for plasmid trafficking, the ParG partner protein dictates the tempo of ParF assembly cycles and plasmid segregation events by stimulating ParF adenosine triphosphate hydrolysis. Mutants in which this ParG temporal regulation is ablated show partition deficient phenotypes as a result of either altered ParF structure or dynamics and indicate that ParF nucleoid localization and dynamic relocation, although necessary, are not sufficient per se to ensure plasmid segregation. We propose a Venus flytrap model that merges the concepts of ParA polymerization and gradient formation and speculate that a transient, dynamic network of intersecting polymers that branches into the nucleoid interior is a widespread mechanism to distribute sizeable cargos within prokaryotic cells. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

Efficient Statistically Accurate Algorithms for the Fokker-Planck Equation in Large Dimensions

NASA Astrophysics Data System (ADS)

Chen, N.; Majda, A.

2017-12-01

Solving the Fokker-Planck equation for high-dimensional complex turbulent dynamical systems is an important and practical issue. However, most traditional methods suffer from the curse of dimensionality and have difficulties in capturing the fat tailed highly intermittent probability density functions (PDFs) of complex systems in turbulence, neuroscience and excitable media. In this article, efficient statistically accurate algorithms are developed for solving both the transient and the equilibrium solutions of Fokker-Planck equations associated with high-dimensional nonlinear turbulent dynamical systems with conditional Gaussian structures. The algorithms involve a hybrid strategy that requires only a small number of ensembles. Here, a conditional Gaussian mixture in a high-dimensional subspace via an extremely efficient parametric method is combined with a judicious non-parametric Gaussian kernel density estimation in the remaining low-dimensional subspace. Particularly, the parametric method, which is based on an effective data assimilation framework, provides closed analytical formulae for determining the conditional Gaussian distributions in the high-dimensional subspace. Therefore, it is computationally efficient and accurate. The full non-Gaussian PDF of the system is then given by a Gaussian mixture. Different from the traditional particle methods, each conditional Gaussian distribution here covers a significant portion of the high-dimensional PDF. Therefore a small number of ensembles is sufficient to recover the full PDF, which overcomes the curse of dimensionality. Notably, the mixture distribution has a significant skill in capturing the transient behavior with fat tails of the high-dimensional non-Gaussian PDFs, and this facilitates the algorithms in accurately describing the intermittency and extreme events in complex turbulent systems. It is shown in a stringent set of test problems that the method only requires an order of O(100) ensembles to successfully recover the highly non-Gaussian transient PDFs in up to 6 dimensions with only small errors.

Ultrafast energy- and momentum-resolved dynamics of magnetic correlations in the photo-doped Mott insulator Sr 2IrO 4

DOE PAGES

Dean, M. P. M.; Cao, Y.; Liu, X.; ...

2016-05-09

Measuring how the magnetic correlations evolve in doped Mott insulators has greatly improved our understanding of the pseudogap, non-Fermi liquids and high-temperature superconductivity 1, 2, 3, 4. Recently, photo-excitation has been used to induce similarly exotic states transiently 5, 6, 7. However, the lack of available probes of magnetic correlations in the time domain hinders our understanding of these photo-induced states and how they could be controlled. Here, we implement magnetic resonant inelastic X-ray scattering at a free-electron laser to directly determine the magnetic dynamics after photo-doping the Mott insulator Sr 2IrO 4. We find that the non-equilibrium state, 2more » ps after the excitation, exhibits strongly suppressed long-range magnetic order, but hosts photo-carriers that induce strong, non-thermal magnetic correlations. These two-dimensional (2D) in-plane Néel correlations recover within a few picoseconds, whereas the three-dimensional (3D) long-range magnetic order restores on a fluence-dependent timescale of a few hundred picoseconds. In conclusion, the marked difference in these two timescales implies that the dimensionality of magnetic correlations is vital for our understanding of ultrafast magnetic dynamics.« less

A method for reducing the order of nonlinear dynamic systems

NASA Astrophysics Data System (ADS)

Masri, S. F.; Miller, R. K.; Sassi, H.; Caughey, T. K.

1984-06-01

An approximate method that uses conventional condensation techniques for linear systems together with the nonparametric identification of the reduced-order model generalized nonlinear restoring forces is presented for reducing the order of discrete multidegree-of-freedom dynamic systems that possess arbitrary nonlinear characteristics. The utility of the proposed method is demonstrated by considering a redundant three-dimensional finite-element model half of whose elements incorporate hysteretic properties. A nonlinear reduced-order model, of one-third the order of the original model, is developed on the basis of wideband stationary random excitation and the validity of the reduced-order model is subsequently demonstrated by its ability to predict with adequate accuracy the transient response of the original nonlinear model under a different nonstationary random excitation.

Active region dimensionality and quantum efficiencies of InGaN LEDs from temperature dependent photoluminescence transients

NASA Astrophysics Data System (ADS)

Can, Nuri; Okur, Serdal; Monavarian, Morteza; Zhang, Fan; Avrutin, Vitaliy; Morkoç, Hadis; Teke, Ali; Özgür, Ümit

2015-03-01

Temperature dependent recombination dynamics in c-plane InGaN light emitting diodes (LEDs) with different well thicknesses, 1.5, 2, and 3 nm, were investigated to determine the active region dimensionality and its effect on the internal quantum efficiencies. It was confirmed for all LEDs that the photoluminescence (PL) transients are governed by radiative recombination at low temperatures while nonradiative recombination dominates at room temperature. At photoexcited carrier densities of 3 - 4.5 x 1016 cm-3 , the room-temperature Shockley-Read-Hall (A) and the bimolecular (B) recombination coefficients (A, B) were deduced to be (9.2x107 s-1, 8.8x10-10 cm3s-1), (8.5x107 s-1, 6.6x10-10 cm3s-1), and (6.5x107 s-1, 1.4x10-10 cm3s-1) for the six period 1.5, 2, and 3 nm well-width LEDs, respectively. From the temperature dependence of the radiative lifetimes, τrad α Tn/2, the dimensionality n of the active region was found to decrease consistently with decreasing well width. The 3 nm wide wells exhibited ~T1.5 dependence, suggesting a three-dimensional nature, whereas the 1.5 nm wells were confirmed to be two-dimensional (~T1) and the 2 nm wells close to being two-dimensional. We demonstrate that a combination of temperature dependent PL and time-resolved PL techniques can be used to evaluate the dimensionality as well as the quantum efficiencies of the LED active regions for a better understanding of the relationship between active-region design and the efficiency limiting processes in InGaN LEDs.

Low temperature exciton dynamics and structural changes in perylene bisimide aggregates

NASA Astrophysics Data System (ADS)

Wolter, Steffen; Magnus Westphal, Karl; Hempel, Magdalena; Würthner, Frank; Kühn, Oliver; Lochbrunner, Stefan

2017-09-01

The temperature dependent exciton dynamics of J-aggregates formed by a perylene bisimide dye is investigated down to liquid nitrogen temperature (77 K) by femtosecond pump-probe spectroscopy. The analysis of the transient absorption data using a diffusion model for the excitons does not only reveal an overall decrease of the exciton mobility, but also a change in the dimensionality of the exciton transport at low temperatures. This change in dimensionality is further investigated by kinetic Monte Carlo simulations, identifying weakly interlinked one-dimensional aggregate chains as the most likely structure at low temperatures. This causes the exciton transport to be highly anisotropic.

Simultaneous Detection of Static and Dynamic Signals by a Flexible Sensor Based on 3D Graphene.

PubMed

Xu, Rongqing; Wang, Di; Zhang, Hongchao; Xie, Na; Lu, Shan; Qu, Ke

2017-05-08

A flexible acoustic pressure sensor was developed based on the change in electrical resistance of three-dimensional (3D) graphene change under the acoustic waves action. The sensor was constructed by 3D graphene foam (GF) wrapped in flexible polydimethylsiloxane (PDMS). Tuning forks and human physiological tests indicated that the acoustic pressure sensor can sensitively detect the deformation and the acoustic pressure in real time. The results are of significance to the development of graphene-based applications in the field of health monitoring, in vitro diagnostics, advanced therapies, and transient pressure detection.

Transient analysis using conical shell elements

NASA Technical Reports Server (NTRS)

Yang, J. C. S.; Goeller, J. E.; Messick, W. T.

1973-01-01

The use of the NASTRAN conical shell element in static, eigenvalue, and direct transient analyses is demonstrated. The results of a NASTRAN static solution of an externally pressurized ring-stiffened cylinder agree well with a theoretical discontinuity analysis. Good agreement is also obtained between the NASTRAN direct transient response of a uniform cylinder to a dynamic end load and one-dimensional solutions obtained using a method of characteristics stress wave code and a standing wave solution. Finally, a NASTRAN eigenvalue analysis is performed on a hydroballistic model idealized with conical shell elements.

A minimization principle for the description of modes associated with finite-time instabilities

PubMed Central

Babaee, H.

2016-01-01

We introduce a minimization formulation for the determination of a finite-dimensional, time-dependent, orthonormal basis that captures directions of the phase space associated with transient instabilities. While these instabilities have finite lifetime, they can play a crucial role either by altering the system dynamics through the activation of other instabilities or by creating sudden nonlinear energy transfers that lead to extreme responses. However, their essentially transient character makes their description a particularly challenging task. We develop a minimization framework that focuses on the optimal approximation of the system dynamics in the neighbourhood of the system state. This minimization formulation results in differential equations that evolve a time-dependent basis so that it optimally approximates the most unstable directions. We demonstrate the capability of the method for two families of problems: (i) linear systems, including the advection–diffusion operator in a strongly non-normal regime as well as the Orr–Sommerfeld/Squire operator, and (ii) nonlinear problems, including a low-dimensional system with transient instabilities and the vertical jet in cross-flow. We demonstrate that the time-dependent subspace captures the strongly transient non-normal energy growth (in the short-time regime), while for longer times the modes capture the expected asymptotic behaviour. PMID:27118900

STARS: A general-purpose finite element computer program for analysis of engineering structures

NASA Technical Reports Server (NTRS)

Gupta, K. K.

1984-01-01

STARS (Structural Analysis Routines) is primarily an interactive, graphics-oriented, finite-element computer program for analyzing the static, stability, free vibration, and dynamic responses of damped and undamped structures, including rotating systems. The element library consists of one-dimensional (1-D) line elements, two-dimensional (2-D) triangular and quadrilateral shell elements, and three-dimensional (3-D) tetrahedral and hexahedral solid elements. These elements enable the solution of structural problems that include truss, beam, space frame, plane, plate, shell, and solid structures, or any combination thereof. Zero, finite, and interdependent deflection boundary conditions can be implemented by the program. The associated dynamic response analysis capability provides for initial deformation and velocity inputs, whereas the transient excitation may be either forces or accelerations. An effective in-core or out-of-core solution strategy is automatically employed by the program, depending on the size of the problem. Data input may be at random within a data set, and the program offers certain automatic data-generation features. Input data are formatted as an optimal combination of free and fixed formats. Interactive graphics capabilities enable convenient display of nodal deformations, mode shapes, and element stresses.

Shock Train/Boundary-Layer Interaction in Rectangular Scramjet Isolators

NASA Astrophysics Data System (ADS)

Geerts, Jonathan Simon

Numerous studies of the dual-mode scramjet isolator, a critical component in preventing inlet unstart and/or vehicle loss by containing a collection of flow disturbances called a shock train, have been performed since the dual-mode propulsion cycle was introduced in the 1960s. Low momentum corner flow and other three-dimensional effects inherent to rectangular isolators have, however, been largely ignored in experimental studies of the boundary layer separation driven isolator shock train dynamics. Furthermore, the use of two dimensional diagnostic techniques in past works, be it single-perspective line-of-sight schlieren/shadowgraphy or single axis wall pressure measurements, have been unable to resolve the three-dimensional flow features inside the rectangular isolator. These flow characteristics need to be thoroughly understood if robust dual-mode scramjet designs are to be fielded. The work presented in this thesis is focused on experimentally analyzing shock train/boundary layer interactions from multiple perspectives in aspect ratio 1.0, 3.0, and 6.0 rectangular isolators with inflow Mach numbers ranging from 2.4 to 2.7. Secondary steady-state Computational Fluid Dynamics studies are performed to compare to the experimental results and to provide additional perspectives of the flow field. Specific issues that remain unresolved after decades of isolator shock train studies that are addressed in this work include the three-dimensional formation of the isolator shock train front, the spatial and temporal low momentum corner flow separation scales, the transient behavior of shock train/boundary layer interaction at specific coordinates along the isolator's lateral axis, and effects of the rectangular geometry on semi-empirical relations for shock train length prediction. (Abstract shortened by ProQuest.).

Three-Dimensional Printed Poly(vinyl alcohol) Substrate with Controlled On-Demand Degradation for Transient Electronics.

PubMed

Yoon, Jinsu; Han, Jungmin; Choi, Bongsik; Lee, Yongwoo; Kim, Yeamin; Park, Jinhee; Lim, Meehyun; Kang, Min-Ho; Kim, Dae Hwan; Kim, Dong Myong; Kim, Sungho; Choi, Sung-Jin

2018-05-25

Electronics that degrade after stable operation for a desired operating time, called transient electronics, are of great interest in many fields, including biomedical implants, secure memory devices, and environmental sensors. Thus, the development of transient materials is critical for the advancement of transient electronics and their applications. However, previous reports have mostly relied on achieving transience in aqueous solutions, where the transience time is largely predetermined based on the materials initially selected at the beginning of the fabrication. Therefore, accurate control of the transience time is difficult, thereby limiting their application. In this work, we demonstrate transient electronics based on a water-soluble poly(vinyl alcohol) (PVA) substrate on which carbon nanotube (CNT)-based field-effect transistors were fabricated. We regulated the structural parameters of the PVA substrate using a three-dimensional (3D) printer to accurately control and program the transience time of the PVA substrate in water. The 3D printing technology can produce complex objects directly, thus enabling the efficient fabrication of a transient substrate with a prescribed and controlled transience time. In addition, the 3D printer was used to develop a facile method for the selective and partial destruction of electronics.

Room-temperature ultrafast nonlinear spectroscopy of a single molecule

NASA Astrophysics Data System (ADS)

Liebel, Matz; Toninelli, Costanza; van Hulst, Niek F.

2018-01-01

Single-molecule spectroscopy aims to unveil often hidden but potentially very important contributions of single entities to a system's ensemble response. Albeit contributing tremendously to our ever growing understanding of molecular processes, the fundamental question of temporal evolution, or change, has thus far been inaccessible, thus painting a static picture of a dynamic world. Here, we finally resolve this dilemma by performing ultrafast time-resolved transient spectroscopy on a single molecule. By tracing the femtosecond evolution of excited electronic state spectra of single molecules over hundreds of nanometres of bandwidth at room temperature, we reveal their nonlinear ultrafast response in an effective three-pulse scheme with fluorescence detection. A first excitation pulse is followed by a phase-locked de-excitation pulse pair, providing spectral encoding with 25 fs temporal resolution. This experimental realization of true single-molecule transient spectroscopy demonstrates that two-dimensional electronic spectroscopy of single molecules is experimentally within reach.

On the Locality of Transient Electromagnetic Soundings with a Single-Loop Configuration

NASA Astrophysics Data System (ADS)

Barsukov, P. O.; Fainberg, E. B.

2018-03-01

The possibilities of reconstructing two-dimensional (2D) cross sections based on the data of the profile soundings by the transient electromagnetic method (TEM) with a single ungrounded loop are illustrated on three-dimensional (3D) models. The process of reconstruction includes three main steps: transformation of the responses in the depth dependence of resistivity ρ(h) measured along the profile, with their subsequent stitching into the 2D pseudo section; point-by-point one-dimensional (1D) inversion of the responses with the starting model constructed based on the transformations; and correction of the 2D cross section with the use of 2.5-dimensional (2.5D) block inversion. It is shown that single-loop TEM soundings allow studying the geological media within a local domain the lateral dimensions of which are commensurate with the depth of the investigation. The structure of the medium beyond this domain insignificantly affects the sounding results. This locality enables the TEM to reconstruct the geoelectrical structure of the medium from the 2D cross sections with the minimal distortions caused by the lack of information beyond the profile of the transient response measurements.

Temporal femtosecond pulse shaping dependence of laser-induced periodic surface structures in fused silica

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Xuesong; Jiang, Lan; Li, Xin, E-mail: lixin02@bit.edu.cn

2014-07-21

The dependence of periodic structures and ablated areas on temporal pulse shaping is studied upon irradiation of fused silica by femtosecond laser triple-pulse trains. Three types of periodic structures can be obtained by using pulse trains with designed pulse delays, in which the three-dimensional nanopillar arrays with ∼100–150 nm diameters and ∼200 nm heights are first fabricated in one step. These nanopillars arise from the break of the ridges of ripples in the upper portion, which is caused by the split of orthogonal ripples in the bottom part. The localized transient electron dynamics and corresponding material properties are considered for the morphologicalmore » observations.« less

Probing excitons in transition metal dichalcogenides by Drude-like exciton intraband absorption.

PubMed

Zhao, Siqi; He, Dawei; He, Jiaqi; Zhang, Xinwu; Yi, Lixin; Wang, Yongsheng; Zhao, Hui

2018-05-24

Understanding excitonic dynamics in two-dimensional semiconducting transition metal dichalcogenides is important for developing their optoelectronic applications. Recently, transient absorption techniques based on resonant excitonic absorption have been used to study various aspects of excitonic dynamics in these materials. The transient absorption in such measurements originates from phase-space state filling, bandgap renormalization, or screening effects. Here we report a new method to probe excitonic dynamics based on exciton intraband absorption. In this Drude-like process, probe photons are absorbed by excitons in their intraband excitation to higher energy states, causing a transient absorption signal. Although the magnitude of the transient absorption is lower than that of the resonant techniques, the new method is less restrictive on the selection of probe wavelength, has a larger linear range, and can provide complementary information on photocarrier dynamics. Using the WS2 monolayer and bulk samples as examples, we show that the new method can probe exciton-exciton annihilation at high densities and reveal exciton formation processes. We also found that the exciton intraband absorption cross section of the WS2 monolayer is on the order of 10-18 cm2.

Solar dynamic modules for Space Station Freedom: The relationship between fine-pointing control and thermal loading of the aperture plate

NASA Technical Reports Server (NTRS)

Quinn, Roger D.; Kerslake, Thomas W.

1992-01-01

Dynamic simulations of Space Station Freedom (SSF) configured with solar dynamic (SD) power modules were performed. The structure was subjected to Space Shuttle docking disturbances, while being controlled with a 'natural' vibration and tracking control approach. Three control cases were investigated for the purpose of investigating the relationship between actuator effort, SD pointing, and thermal loading on the receiver aperture plate. Transient, one-dimensional heat transfer analyses were performed to conservatively predict temperatures of the multi-layered receiver aperture plate assembly and thermal stresses in its shield layer. Results indicate that the proposed aperture plate is tolerant of concentrated flux impingement during short-lived structural disturbances. Pointing requirements may be loosened and the requirement control torques lessened from that previously specified. Downsizing and simplifying the joint drive system should result in a considerable savings mass.

RAMONA-4B a computer code with three-dimensional neutron kinetics for BWR and SBWR system transient - user`s manual

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rohatgi, U.S.; Cheng, H.S.; Khan, H.J.

This document is the User`s Manual for the Boiling Water Reactor (BWR), and Simplified Boiling Water Reactor (SBWR) systems transient code RAMONA-4B. The code uses a three-dimensional neutron-kinetics model coupled with a multichannel, nonequilibrium, drift-flux, phase-flow model of the thermal hydraulics of the reactor vessel. The code is designed to analyze a wide spectrum of BWR core and system transients. Chapter 1 gives an overview of the code`s capabilities and limitations; Chapter 2 describes the code`s structure, lists major subroutines, and discusses the computer requirements. Chapter 3 is on code, auxillary codes, and instructions for running RAMONA-4B on Sun SPARCmore » and IBM Workstations. Chapter 4 contains component descriptions and detailed card-by-card input instructions. Chapter 5 provides samples of the tabulated output for the steady-state and transient calculations and discusses the plotting procedures for the steady-state and transient calculations. Three appendices contain important user and programmer information: lists of plot variables (Appendix A) listings of input deck for sample problem (Appendix B), and a description of the plotting program PAD (Appendix C). 24 refs., 18 figs., 11 tabs.« less

Dynamics of internal models in game players

NASA Astrophysics Data System (ADS)

Taiji, Makoto; Ikegami, Takashi

1999-10-01

A new approach for the study of social games and communications is proposed. Games are simulated between cognitive players who build the opponent’s internal model and decide their next strategy from predictions based on the model. In this paper, internal models are constructed by the recurrent neural network (RNN), and the iterated prisoner’s dilemma game is performed. The RNN allows us to express the internal model in a geometrical shape. The complicated transients of actions are observed before the stable mutually defecting equilibrium is reached. During the transients, the model shape also becomes complicated and often experiences chaotic changes. These new chaotic dynamics of internal models reflect the dynamical and high-dimensional rugged landscape of the internal model space.

Si-H bond dynamics in hydrogenated amorphous silicon

NASA Astrophysics Data System (ADS)

Scharff, R. Jason; McGrane, Shawn D.

2007-08-01

The ultrafast structural dynamics of the Si-H bond in the rigid solvent environment of an amorphous silicon thin film is investigated using two-dimensional infrared four-wave mixing techniques. The two-dimensional infrared (2DIR) vibrational correlation spectrum resolves the homogeneous line shapes ( <2.5cm-1 linewidth) of the 0→1 and 1→2 vibrational transitions within the extensively inhomogeneously broadened ( 78cm-1 linewidth) Si-H vibrational band. There is no spectral diffusion evident in correlation spectra obtained at 0.2, 1, and 4ps waiting times. The Si-H stretching mode anharmonic shift is determined to be 84cm-1 and decreases slightly with vibrational frequency. The 1→2 linewidth increases with vibrational frequency. Frequency dependent vibrational population times measured by transient grating spectroscopy are also reported. The narrow homogeneous line shape, large inhomogeneous broadening, and lack of spectral diffusion reported here present the ideal backdrop for using a 2DIR probe following electronic pumping to measure the transient structural dynamics implicated in the Staebler-Wronski degradation [Appl. Phys. Lett. 31, 292 (1977)] in a-Si:H based solar cells.

Modeling of thin-walled structures interacting with acoustic media as constrained two-dimensional continua

NASA Astrophysics Data System (ADS)

Rabinskiy, L. N.; Zhavoronok, S. I.

2018-04-01

The transient interaction of acoustic media and elastic shells is considered on the basis of the transition function approach. The three-dimensional hyperbolic initial boundary-value problem is reduced to a two-dimensional problem of shell theory with integral operators approximating the acoustic medium effect on the shell dynamics. The kernels of these integral operators are determined by the elementary solution of the problem of acoustic waves diffraction at a rigid obstacle with the same boundary shape as the wetted shell surface. The closed-form elementary solution for arbitrary convex obstacles can be obtained at the initial interaction stages on the background of the so-called “thin layer hypothesis”. Thus, the shell–wave interaction model defined by integro-differential dynamic equations with analytically determined kernels of integral operators becomes hence two-dimensional but nonlocal in time. On the other hand, the initial interaction stage results in localized dynamic loadings and consequently in complex strain and stress states that require higher-order shell theories. Here the modified theory of I.N.Vekua–A.A.Amosov-type is formulated in terms of analytical continuum dynamics. The shell model is constructed on a two-dimensional manifold within a set of field variables, Lagrangian density, and constraint equations following from the boundary conditions “shifted” from the shell faces to its base surface. Such an approach allows one to construct consistent low-order shell models within a unified formal hierarchy. The equations of the N th-order shell theory are singularly perturbed and contain second-order partial derivatives with respect to time and surface coordinates whereas the numerical integration of systems of first-order equations is more efficient. Such systems can be obtained as Hamilton–de Donder–Weyl-type equations for the Lagrangian dynamical system. The Hamiltonian formulation of the elementary N th-order shell theory is here briefly described.

Lifetime prediction for the subsurface crack propagation using three-dimensional dynamic FEA model

NASA Astrophysics Data System (ADS)

Yin, Yuan; Chen, Yun-Xia; Liu, Le

2017-03-01

The subsurface crack propagation is one of the major interests for gear system research. The subsurface crack propagation lifetime is the number of cycles remaining for a spall to appear, which can be obtained through either stress intensity factor or accumulated plastic strain analysis. In this paper, the heavy loads are applied to the gear system. When choosing stress intensity factor, the high compressive stress suppresses Mode I stress intensities and severely reduces Mode II stress intensities in the heavily loaded lubricated contacts. Such that, the accumulated plastic strain is selected to calculate the subsurface crack propagation lifetime from the three-dimensional FEA model through ANSYS Workbench transient analysis. The three-dimensional gear FEA dynamic model with the subsurface crack is built through dividing the gears into several small elements. The calculation of the total cycles of the elements is proposed based on the time-varying accumulated plastic strain, which then will be used to calculate the subsurface crack propagation lifetime. During this process, the demonstration from a subsurface crack to a spall can be uncovered. In addition, different sizes of the elements around the subsurface crack are compared in this paper. The influences of the frictional coefficient and external torque on the crack propagation lifetime are also discussed. The results show that the lifetime of crack propagation decreases significantly when the external load T increasing from 100 N m to 150 N m. Given from the distributions of the accumulated plastic strain, the lifetime shares no significant difference when the frictional coefficient f ranging in 0.04-0.06.

Transient Response of a PEM Fuel Cell Representing Variable Load for a Moving Vehicle on Urban Roads

DOT National Transportation Integrated Search

2001-01-01

Three-dimensional numerical simulation of transient response of a Polymer Electrolyte Membrane (PEM) fuel cell subjected to a variable load is developed. The model parameters are typical of experimental cell for a 10-cm2 reactive area with serpentine...

Three-dimensional Finite Element Formulation and Scalable Domain Decomposition for High Fidelity Rotor Dynamic Analysis

NASA Technical Reports Server (NTRS)

Datta, Anubhav; Johnson, Wayne R.

2009-01-01

This paper has two objectives. The first objective is to formulate a 3-dimensional Finite Element Model for the dynamic analysis of helicopter rotor blades. The second objective is to implement and analyze a dual-primal iterative substructuring based Krylov solver, that is parallel and scalable, for the solution of the 3-D FEM analysis. The numerical and parallel scalability of the solver is studied using two prototype problems - one for ideal hover (symmetric) and one for a transient forward flight (non-symmetric) - both carried out on up to 48 processors. In both hover and forward flight conditions, a perfect linear speed-up is observed, for a given problem size, up to the point of substructure optimality. Substructure optimality and the linear parallel speed-up range are both shown to depend on the problem size as well as on the selection of the coarse problem. With a larger problem size, linear speed-up is restored up to the new substructure optimality. The solver also scales with problem size - even though this conclusion is premature given the small prototype grids considered in this study.

Computation of a controlled store separation from a cavity

NASA Technical Reports Server (NTRS)

Atwood, Christopher A.

1993-01-01

Coupling of the Reynolds-averaged Navier-Stokes equations, rigid-body dynamics, and a pitch attitude control law is demonstrated in two- and three-dimensions. The application problem was the separation of a canard-controlled store from an open-flow rectangular cavity bay at a freestream Mach number of 1.2. The transient flowfield was computed using a diagonal scheme in an overset mesh framework, with the resultant aerodynamic loads used as the forcing functions in the nonlinear dynamics equations. The proportional and rate gyro sensitivities were computed a priori using pole placement techniques for the linearized dynamical equations. These fixed gain values were used in the controller for the nonlinear simulation. Reasonable comparison between the full and linearized equations for a perturbed two-dimensional missile was found. Also in two-dimensions, a controlled store was found to possess improved separation characteristics over a canard-fixed store. In three-dimensions, trajectory comparisons with wind-tunnel data for the canard-fixed case will be made. In addition, it will be determined if a canard-controlled store is an effective means of improving cavity store separation characteristics.

Potentials for Spatial Geometry Curriculum Development with Three-Dimensional Dynamic Geometry Software in Lower Secondary Mathematics

ERIC Educational Resources Information Center

Miyazaki, Mikio; Kimiho, Chino; Katoh, Ryuhei; Arai, Hitoshi; Ogihara, Fumihiro; Oguchi, Yuichi; Morozumi, Tatsuo; Kon, Mayuko; Komatsu, Kotaro

2012-01-01

Three-dimensional dynamic geometry software has the power to enhance students' learning of spatial geometry. The purpose of this research is to clarify what potential using three-dimensional dynamic geometry software can offer us in terms of how to develop the spatial geometry curriculum in lower secondary schools. By focusing on the impacts the…

Reponse dynamique des structures sous charges de vent

NASA Astrophysics Data System (ADS)

Gani, Ferawati

The main purpose of this research is to assemble numerical tools that allows realistic dynamic study of structures under wind loading. The availability of such numerical tools is becoming more important for the industry, following previous experiences in structural damages after extreme wind events. The methodology of the present study involves two main steps: (i) preparing the wind loading according to its spatial and temporal correlations by using digitally generated wind or real measured wind; (ii) preparing the numerical model that captures the characteristics of the real structures and respects all the necessary numerical requirements to pursue transient dynamic analyses. The thesis is presented as an ensemble of four articles written for refereed journals and conferences that showcase the contributions of the present study to the advancement of transient dynamic study of structures under wind loading, on the wind model itself (the first article) and on the application of the wind study on complex structures (the next three articles). The articles presented are as follows: (a) the evaluation of three-dimensional correlations of wind, an important issue for more precise prediction of wind loading for flexible and line-like structures, the results presented in this first article helps design engineers to choose a more suitable models to define three-dimensional wind loading; (b) the refinement of design for solar photovoltaic concentrator-tracker structure developed for utility scale, this study addressed concerns related strict operational criteria and fatigue under wind load for a large parabolic truss structure; (c) the study of guyed towers for TLs, the applicability of the static-equivalent method from the current industry documents for the design of this type of flexible TL support was questioned, a simplified method to improve the wind design was proposed; (d) the fundamental issue of nonlinear behaviour under extreme wind loading for single-degree-of-freedom systems is evaluated here, the use of real measured hurricane and winter storm have highlighted the possible interest of taking into account the ductility in the extreme wind loading design. The present research project has shown the versatility of the use of the developed wind study methodology to solve concerns related to different type of complex structures. In addition, this study proposes simplified methods that are useful for practical engineers when there is the need to solve similar problems. Key words: nonlinear, dynamic, wind, guyed tower, parabolic structure, ductility.

Virtual reality in radiology: virtual intervention

NASA Astrophysics Data System (ADS)

Harreld, Michael R.; Valentino, Daniel J.; Duckwiler, Gary R.; Lufkin, Robert B.; Karplus, Walter J.

1995-04-01

Intracranial aneurysms are the primary cause of non-traumatic subarachnoid hemorrhage. Morbidity and mortality remain high even with current endovascular intervention techniques. It is presently impossible to identify which aneurysms will grow and rupture, however hemodynamics are thought to play an important role in aneurysm development. With this in mind, we have simulated blood flow in laboratory animals using three dimensional computational fluid dynamics software. The data output from these simulations is three dimensional, complex and transient. Visualization of 3D flow structures with standard 2D display is cumbersome, and may be better performed using a virtual reality system. We are developing a VR-based system for visualization of the computed blood flow and stress fields. This paper presents the progress to date and future plans for our clinical VR-based intervention simulator. The ultimate goal is to develop a software system that will be able to accurately model an aneurysm detected on clinical angiography, visualize this model in virtual reality, predict its future behavior, and give insight into the type of treatment necessary. An associated database will give historical and outcome information on prior aneurysms (including dynamic, structural, and categorical data) that will be matched to any current case, and assist in treatment planning (e.g., natural history vs. treatment risk, surgical vs. endovascular treatment risks, cure prediction, complication rates).

Transient PVT measurements and model predictions for vessel heat transfer. Part II.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Felver, Todd G.; Paradiso, Nicholas Joseph; Winters, William S., Jr.

2010-07-01

Part I of this report focused on the acquisition and presentation of transient PVT data sets that can be used to validate gas transfer models. Here in Part II we focus primarily on describing models and validating these models using the data sets. Our models are intended to describe the high speed transport of compressible gases in arbitrary arrangements of vessels, tubing, valving and flow branches. Our models fall into three categories: (1) network flow models in which flow paths are modeled as one-dimensional flow and vessels are modeled as single control volumes, (2) CFD (Computational Fluid Dynamics) models inmore » which flow in and between vessels is modeled in three dimensions and (3) coupled network/CFD models in which vessels are modeled using CFD and flows between vessels are modeled using a network flow code. In our work we utilized NETFLOW as our network flow code and FUEGO for our CFD code. Since network flow models lack three-dimensional resolution, correlations for heat transfer and tube frictional pressure drop are required to resolve important physics not being captured by the model. Here we describe how vessel heat transfer correlations were improved using the data and present direct model-data comparisons for all tests documented in Part I. Our results show that our network flow models have been substantially improved. The CFD modeling presented here describes the complex nature of vessel heat transfer and for the first time demonstrates that flow and heat transfer in vessels can be modeled directly without the need for correlations.« less

Numerical analysis of the effect of T-tubule location on calcium transient in ventricular myocytes.

PubMed

George, Uduak Z; Wang, Jun; Yu, Zeyun

2014-01-01

Intracellular calcium (Ca2+) signaling in cardiac myocytes is vital for proper functioning of the heart. Understanding the intracellular Ca2+ dynamics would give an insight into the functions of normal and diseased hearts. In the current study, spatiotemporal Ca2+ dynamics is investigated in ventricular myocytes by considering Ca2+ release and re-uptake via sarcolemma and transverse tubules (T-tubules), Ca2+ diffusion and buffering in the cytosol, and the blockade of Ca2+ activities associated with the sarcoplasmic reticulum. This study is carried out using a three dimensional (3D) geometric model of a branch of T-tubule extracted from the electron microscopy (EM) images of a partial ventricular myocyte. Mathematical modeling is done by using a system of partial differential equations involving Ca2+, buffers, and membrane channels. Numerical simulation results suggest that a lack of T-tubule structure at the vicinity of the cell surface could increase the peak time of Ca2+ concentration in myocytes. The results also show that T-tubules and mobile buffers play an important role in the regulation of Ca2+ transient in ventricular myocytes.

Generation of dark solitons and their instability dynamics in two-dimensional condensates

NASA Astrophysics Data System (ADS)

Verma, Gunjan; Rapol, Umakant D.; Nath, Rejish

2017-04-01

We analyze numerically the formation and the subsequent dynamics of two-dimensional matter wave dark solitons in a Thomas-Fermi rubidium condensate using various techniques. An initially imprinted sharp phase gradient leads to the dynamical formation of a stationary soliton as well as very shallow gray solitons, whereas a smooth gradient only creates gray solitons. The depth and hence, the velocity of the soliton is provided by the spatial width of the phase gradient, and it also strongly influences the snake-instability dynamics of the two-dimensional solitons. The vortex dipoles stemming from the unstable soliton exhibit rich dynamics. Notably, the annihilation of a vortex dipole via a transient dark lump or a vortexonium state, the exchange of vortices between either a pair of vortex dipoles or a vortex dipole and a single vortex, and so on. For sufficiently large width of the initial phase gradient, the solitons may decay directly into vortexoniums instead of vortex pairs, and also the decay rate is augmented. Later, we discuss alternative techniques to generate dark solitons, which involve a Gaussian potential barrier and time-dependent interactions, both linear and periodic. The properties of the solitons can be controlled by tuning the amplitude or the width of the potential barrier. In the linear case, the number of solitons and their depths are determined by the quench time of the interactions. For the periodic modulation, a transient soliton lattice emerges with its periodicity depending on the modulation frequency, through a wave number selection governed by the local Bogoliubov spectrum. Interestingly, for sufficiently low barrier potential, both Faraday pattern and soliton lattice coexist. The snake instability dynamics of the soliton lattice is characteristically modified if the Faraday pattern is present.

Software For Three-Dimensional Stress And Thermal Analyses

NASA Technical Reports Server (NTRS)

Banerjee, P. K.; Wilson, R. B.; Hopkins, D. A.

1994-01-01

BEST3D is advanced engineering software system for three-dimensional thermal and stress analyses, particularly of components of hot sections of gas-turbine engines. Utilizes boundary element method, offering, in many situations, more accuracy, efficiency, and ease of use than finite element method. Performs engineering analyses of following types: elastic, heat transfer, plastic, forced vibration, free vibration, and transient elastodynamic. Written in FORTRAN 77.

Global dynamic modeling of a transmission system

NASA Technical Reports Server (NTRS)

Choy, F. K.; Qian, W.

1993-01-01

The work performed on global dynamic simulation and noise correlation of gear transmission systems at the University of Akron is outlined. The objective is to develop a comprehensive procedure to simulate the dynamics of the gear transmission system coupled with the effects of gear box vibrations. The developed numerical model is benchmarked with results from experimental tests at NASA Lewis Research Center. The modal synthesis approach is used to develop the global transient vibration analysis procedure used in the model. Modal dynamic characteristics of the rotor-gear-bearing system are calculated by the matrix transfer method while those of the gear box are evaluated by the finite element method (NASTRAN). A three-dimensional, axial-lateral coupled bearing model is used to couple the rotor vibrations with the gear box motion. The vibrations between the individual rotor systems are coupled through the nonlinear gear mesh interactions. The global equations of motion are solved in modal coordinates and the transient vibration of the system is evaluated by a variable time-stepping integration scheme. The relationship between housing vibration and resulting noise of the gear transmission system is generated by linear transfer functions using experimental data. A nonlinear relationship of the noise components to the fundamental mesh frequency is developed using the hypercoherence function. The numerically simulated vibrations and predicted noise of the gear transmission system are compared with the experimental results from the gear noise test rig at NASA Lewis Research Center. Results of the comparison indicate that the global dynamic model developed can accurately simulate the dynamics of a gear transmission system.

Sequential picosecond isomerizations in a photochromic ruthenium sulfoxide complex triggered by pump-repump-probe spectroscopy.

PubMed

King, Albert W; Jin, Yuhuan; Engle, James T; Ziegler, Christopher J; Rack, Jeffrey J

2013-02-18

The complex [Ru(bpy)(2)(bpSO)](PF(6))(2), where bpy is 2,2'-bipydine and bpSO is 1,2-bis(phenylsulfinyl)ethane, exhibits three distinct isomers which are accessible upon metal-to-ligand charge-transfer (MLCT) irradiation. This complex and its parent, [Ru(bpy)(2)(bpte)](PF(6))(2), where bpte is 1,2-bis(phenylthio)ethane, have been synthesized and characterized by UV-visible spectroscopy, NMR, X-ray crystallography, and femtosecond transient absorption spectroscopy. A novel method of 2-color Pump-Repump-Probe spectroscopy has been employed to investigate all three isomers of the bis-sulfoxide complex. This method allows for observation of the isomerization dynamics of sequential isomerizations of each sulfoxide from MLCT irradiation of the S,S-bonded complex to ultimately form the O,O-bonded metastable complex. One-dimensional (1-D) and two-dimensional (2-D) (COSY, NOESY, and TOCSY) (1)H NMR data show the thioether and ground state S,S-bonded sulfoxide complexes to be rigorously C(2) symmetric and are consistent with the crystal structures. Transient absorption spectroscopy reveals that the S,S to S,O isomerization occurs with an observed time constant of 56.8 (±7.4) ps. The S,O to O,O isomerization time constant was found to be 59 (±4) ps by pump-repump-probe spectroscopy. The composite S,S- to O,O-isomer quantum yield is 0.42.

Simplification of femtosecond transient absorption microscopy data from CH3NH3PbI3 perovskite thin films into decay associated amplitude maps

NASA Astrophysics Data System (ADS)

Doughty, Benjamin; Simpson, Mary Jane; Yang, Bin; Xiao, Kai; Ma, Ying-Zhong

2016-03-01

This work aims to simplify multi-dimensional femtosecond transient absorption microscopy (TAM) data into decay associated amplitude maps (DAAMs) that describe the spatial distributions of dynamical processes occurring on various characteristic timescales. Application of this method to TAM data obtained from a model methyl-ammonium lead iodide (CH3NH3PbI3) perovskite thin film allows us to simplify the data set comprising 68 time-resolved images into four DAAMs. These maps offer a simple means to visualize the complex electronic excited-state dynamics in this system by separating distinct dynamical processes evolving on characteristic timescales into individual spatial images. This approach provides new insight into subtle aspects of ultrafast relaxation dynamics associated with excitons and charge carriers in the perovskite thin film, which have recently been found to coexist at spatially distinct locations.

Development of a Reduced-Order Three-Dimensional Flow Model for Thermal Mixing and Stratification Simulation during Reactor Transients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Rui

2017-09-03

Mixing, thermal-stratification, and mass transport phenomena in large pools or enclosures play major roles for the safety of reactor systems. Depending on the fidelity requirement and computational resources, various modeling methods, from the 0-D perfect mixing model to 3-D Computational Fluid Dynamics (CFD) models, are available. Each is associated with its own advantages and shortcomings. It is very desirable to develop an advanced and efficient thermal mixing and stratification modeling capability embedded in a modern system analysis code to improve the accuracy of reactor safety analyses and to reduce modeling uncertainties. An advanced system analysis tool, SAM, is being developedmore » at Argonne National Laboratory for advanced non-LWR reactor safety analysis. While SAM is being developed as a system-level modeling and simulation tool, a reduced-order three-dimensional module is under development to model the multi-dimensional flow and thermal mixing and stratification in large enclosures of reactor systems. This paper provides an overview of the three-dimensional finite element flow model in SAM, including the governing equations, stabilization scheme, and solution methods. Additionally, several verification and validation tests are presented, including lid-driven cavity flow, natural convection inside a cavity, laminar flow in a channel of parallel plates. Based on the comparisons with the analytical solutions and experimental results, it is demonstrated that the developed 3-D fluid model can perform very well for a wide range of flow problems.« less

Guide to the Revised Ground-Water Flow and Heat Transport Simulator: HYDROTHERM - Version 3

USGS Publications Warehouse

Kipp, Kenneth L.; Hsieh, Paul A.; Charlton, Scott R.

2008-01-01

The HYDROTHERM computer program simulates multi-phase ground-water flow and associated thermal energy transport in three dimensions. It can handle high fluid pressures, up to 1 ? 109 pascals (104 atmospheres), and high temperatures, up to 1,200 degrees Celsius. This report documents the release of Version 3, which includes various additions, modifications, and corrections that have been made to the original simulator. Primary changes to the simulator include: (1) the ability to simulate unconfined ground-water flow, (2) a precipitation-recharge boundary condition, (3) a seepage-surface boundary condition at the land surface, (4) the removal of the limitation that a specified-pressure boundary also have a specified temperature, (5) a new iterative solver for the linear equations based on a generalized minimum-residual method, (6) the ability to use time- or depth-dependent functions for permeability, (7) the conversion of the program code to Fortran 90 to employ dynamic allocation of arrays, and (8) the incorporation of a graphical user interface (GUI) for input and output. The graphical user interface has been developed for defining a simulation, running the HYDROTHERM simulator interactively, and displaying the results. The combination of the graphical user interface and the HYDROTHERM simulator forms the HYDROTHERM INTERACTIVE (HTI) program. HTI can be used for two-dimensional simulations only. New features in Version 3 of the HYDROTHERM simulator have been verified using four test problems. Three problems come from the published literature and one problem was simulated by another partially saturated flow and thermal transport simulator. The test problems include: transient partially saturated vertical infiltration, transient one-dimensional horizontal infiltration, two-dimensional steady-state drainage with a seepage surface, and two-dimensional drainage with coupled heat transport. An example application to a hypothetical stratovolcano system with unconfined ground-water flow is presented in detail. It illustrates the use of HTI with the combination precipitation-recharge and seepage-surface boundary condition, and functions as a tutorial example problem for the new user.

A numerical and experimental study of three-dimensional liquid sloshing in a rotating spherical container

NASA Technical Reports Server (NTRS)

Chen, Kuo-Huey; Kelecy, Franklyn J.; Pletcher, Richard H.

1992-01-01

A numerical and experimental study of three dimensional liquid sloshing inside a partially-filled spherical container undergoing an orbital rotating motion is described. Solutions of the unsteady, three-dimensional Navier-Stokes equations for the case of a gradual spin-up from rest are compared with experimental data obtained using a rotating test rig fitted with two liquid-filled spherical tanks. Data gathered from several experiments are reduced in terms of a dimensionless free surface height for comparison with transient results from the numerical simulations. The numerical solutions are found to compare favorably with the experimental data.

Deep level study of Mg-doped GaN using deep level transient spectroscopy and minority carrier transient spectroscopy

NASA Astrophysics Data System (ADS)

Duc, Tran Thien; Pozina, Galia; Amano, Hiroshi; Monemar, Bo; Janzén, Erik; Hemmingsson, Carl

2016-07-01

Deep levels in Mg-doped GaN grown by metal organic chemical vapor deposition (MOCVD), undoped GaN grown by MOCVD, and halide vapor phase epitaxy (HVPE)-grown GaN have been studied using deep level transient spectroscopy and minority charge carrier transient spectroscopy on Schottky diodes. One hole trap, labeled HT1, was detected in the Mg-doped sample. It is observed that the hole emission rate of the trap is enhanced by increasing electric field. By fitting four different theoretical models for field-assisted carrier emission processes, the three-dimensional Coulombic Poole-Frenkel (PF) effect, three-dimensional square well PF effect, phonon-assisted tunneling, and one-dimensional Coulombic PF effect including phonon-assisted tunneling, it is found that the one-dimensional Coulombic PF model, including phonon-assisted tunneling, is consistent with the experimental data. Since the trap exhibits the PF effect, we suggest it is acceptorlike. From the theoretical model, the zero field ionization energy of the trap and an estimate of the hole capture cross section have been determined. Depending on whether the charge state is -1 or -2 after hole emission, the zero field activation energy Ei 0 is 0.57 eV or 0.60 eV, respectively, and the hole capture cross section σp is 1.3 ×10-15c m2 or 1.6 ×10-16c m2 , respectively. Since the level was not observed in undoped GaN, it is suggested that the trap is associated with an Mg related defect.

Ultrafast core-loss spectroscopy in four-dimensional electron microscopy

PubMed Central

van der Veen, Renske M.; Penfold, Thomas J.; Zewail, Ahmed H.

2015-01-01

We demonstrate ultrafast core-electron energy-loss spectroscopy in four-dimensional electron microscopy as an element-specific probe of nanoscale dynamics. We apply it to the study of photoexcited graphite with femtosecond and nanosecond resolutions. The transient core-loss spectra, in combination with ab initio molecular dynamics simulations, reveal the elongation of the carbon-carbon bonds, even though the overall behavior is a contraction of the crystal lattice. A prompt energy-gap shrinkage is observed on the picosecond time scale, which is caused by local bond length elongation and the direct renormalization of band energies due to temperature-dependent electron–phonon interactions. PMID:26798793

The investigation of tethered satellite system dynamics

NASA Technical Reports Server (NTRS)

Lorenzini, E.

1985-01-01

A progress report is presented that deals with three major topics related to Tethered Satellite System Dynamics. The SAO rotational dynamics computer code was updated. The program is now suitable to deal with inclined orbits. The output has been also modified in order to show the satellite Euler angles referred to the rotating orbital frame. The three-dimensional high resolution computer program SLACK3 was developed. The code simulates the three-dimensional dynamics of a tether going slack taking into account the effect produced by boom rotations. Preliminary simulations on the three-dimensional dynamics of a recoiling slack tether are shown in this report. A program to evaluate the electric potential around a severed tether is immersed in a plasma. The potential is computed on a three-dimensional grid axially symmetric with respect to the tether longitudinal axis. The electric potential variations due to the plasma are presently under investigation.

Mode-coupling theory for active Brownian particles

NASA Astrophysics Data System (ADS)

Liluashvili, Alexander; Ónody, Jonathan; Voigtmann, Thomas

2017-12-01

We present a mode-coupling theory (MCT) for the slow dynamics of two-dimensional spherical active Brownian particles (ABPs). The ABPs are characterized by a self-propulsion velocity v0 and by their translational and rotational diffusion coefficients Dt and Dr, respectively. Based on the integration-through-transients formalism, the theory requires as input only the equilibrium static structure factors of the passive system (where v0=0 ). It predicts a nontrivial idealized-glass-transition diagram in the three-dimensional parameter space of density, self-propulsion velocity, and rotational diffusivity that arise because at high densities, the persistence length of active swimming ℓp=v0/Dr interferes with the interaction length ℓc set by the caging of particles. While the low-density dynamics of ABPs is characterized by a single Péclet number Pe=v02/DrDt , close to the glass transition the dynamics is found to depend on Pe and ℓp separately. At fixed density, increasing the self-propulsion velocity causes structural relaxation to speed up, while decreasing the persistence length slows down the relaxation. The active-MCT glass is a nonergodic state that is qualitatively different from the passive glass. In it, correlations of initial density fluctuations never fully decay, but also an infinite memory of initial orientational fluctuations is retained in the positions.

A three dimensional immersed smoothed finite element method (3D IS-FEM) for fluid-structure interaction problems

NASA Astrophysics Data System (ADS)

Zhang, Zhi-Qian; Liu, G. R.; Khoo, Boo Cheong

2013-02-01

A three-dimensional immersed smoothed finite element method (3D IS-FEM) using four-node tetrahedral element is proposed to solve 3D fluid-structure interaction (FSI) problems. The 3D IS-FEM is able to determine accurately the physical deformation of the nonlinear solids placed within the incompressible viscous fluid governed by Navier-Stokes equations. The method employs the semi-implicit characteristic-based split scheme to solve the fluid flows and smoothed finite element methods to calculate the transient dynamics responses of the nonlinear solids based on explicit time integration. To impose the FSI conditions, a novel, effective and sufficiently general technique via simple linear interpolation is presented based on Lagrangian fictitious fluid meshes coinciding with the moving and deforming solid meshes. In the comparisons to the referenced works including experiments, it is clear that the proposed 3D IS-FEM ensures stability of the scheme with the second order spatial convergence property; and the IS-FEM is fairly independent of a wide range of mesh size ratio.

Current Technologies Based on the Knowledge of the Stem Cells Microenvironments.

PubMed

Mawad, Damia; Figtree, Gemma; Gentile, Carmine

2017-01-01

The stem cell microenvironment or niche plays a critical role in the regulation of survival, differentiation and behavior of stem cells and their progenies. Recapitulating each aspect of the stem cell niche is therefore essential for their optimal use in in vitro studies and in vivo as future therapeutics in humans. Engineering of optimal conditions for three-dimensional stem cell culture includes multiple transient and dynamic physiological stimuli, such as blood flow and tissue stiffness. Bioprinting and microfluidics technologies, including organs-on-a-chip, are among the most recent approaches utilized to replicate the three-dimensional stem cell niche for human tissue fabrication that allow the integration of multiple levels of tissue complexity, including blood flow. This chapter focuses on the physico-chemical and genetic cues utilized to engineer the stem cell niche and provides an overview on how both bioprinting and microfluidics technologies are improving our knowledge in this field for both disease modeling and tissue regeneration, including drug discovery and toxicity high-throughput assays and stem cell-based therapies in humans.

Direct numerical simulation of stochastically forced laminar plane couette flow: peculiarities of hydrodynamic fluctuations.

PubMed

Khujadze, G; Oberlack, M; Chagelishvili, G

2006-07-21

The background of three-dimensional hydrodynamic (vortical) fluctuations in a stochastically forced, laminar, incompressible, plane Couette flow is simulated numerically. The fluctuating field is anisotropic and has well pronounced peculiarities: (i) the hydrodynamic fluctuations exhibit nonexponential, transient growth; (ii) fluctuations with the streamwise characteristic length scale about 2 times larger than the channel width are predominant in the fluctuating spectrum instead of streamwise constant ones; (iii) nonzero cross correlations of velocity (even streamwise-spanwise) components appear; (iv) stochastic forcing destroys the spanwise reflection symmetry (inherent to the linear and full Navier-Stokes equations in a case of the Couette flow) and causes an asymmetry of the dynamical processes.

Fluid Aspects of Solar Wind Disturbances Driven by Coronal Mass Ejections. Appendix 3

NASA Technical Reports Server (NTRS)

Gosling, J. T.; Riley, Pete

2001-01-01

Transient disturbances in the solar wind initiated by coronal eruptions have been modeled for many years, beginning with the self-similar analytical models of Parker and Simon and Axford. The first numerical computer code (one-dimensional, gas dynamic) to study disturbance propagation in the solar wind was developed in the late 1960s, and a variety of other codes ranging from simple one-dimensional gas dynamic codes through three-dimensional gas dynamic and magnetohydrodynamic codes have been developed in subsequent years. For the most part, these codes have been applied to the problem of disturbances driven by fast CMEs propagating into a structureless solar wind. Pizzo provided an excellent summary of the level of understanding achieved from such simulation studies through about 1984, and other reviews have subsequently become available. More recently, some attention has been focused on disturbances generated by slow CMEs, on disturbances driven by CMEs having high internal pressures, and disturbance propagation effects associated with a structured ambient solar wind. Our purpose here is to provide a brief tutorial on fluid aspects of solar wind disturbances derived from numerical gas dynamic simulations. For the most part we illustrate disturbance evolution by propagating idealized perturbations, mimicking different types of CMEs, into a structureless solar wind using a simple one-dimensional, adiabatic (except at shocks), gas dynamic code. The simulations begin outside the critical point where the solar wind becomes supersonic and thus do not address questions of how the CMEs themselves are initiated. Limited to one dimension (the radial direction), the simulation code predicts too strong an interaction between newly ejected solar material and the ambient wind because it neglects azimuthal and meridional motions of the plasma that help relieve pressure stresses. Moreover, the code ignores magnetic forces and thus also underestimates the speed with which pressure disturbances propagate in the wind.

Application of ESPI techniques for the study of dynamic vibrations

NASA Astrophysics Data System (ADS)

Krupka, Rene

2004-06-01

Full field optical measurement techniques have already entered into various fields of industrial applications covering static as well as dynamic phenomena. The electronic speckle pattern interferometry (ESPI) allows the non contact, sensitive and three dimensional measurement of displacements in the sub micron range of objects with dimensions from mm2 to m2. For dynamic and transient phenomena, the use of pulsed laser have already been reported for various applications and successfully proven for the determination of the structural response of different components. In this paper we would like to present recent developments in the field of pulsed ESPI applications where emphasis is put onto the full field measurement result. The use of a completely computer controlled system allows easy access to mode shape characterization, deformation measurements and the characterization of transient events like shock wave propagation. Recent developments of the 3D-PulseESPI technique led to a very compact and complete system with improved characteristics regarding robustness and operation. The integrated design of the illumination laser and sensors for image acquisition allows easy aiming and adjustments with respect to the object of inspection. The laser is completely computer controlled which is advantageously used in a completely automatic brake squeal inspection system, which captures the squealing signal, automatically fires the laser and provides the complete deformation map of the component under test. Examples of recent applications in the field of dynamic structure response, with an emphasis in the field of automotive applications are given.

NASA-VOF3D: A three-dimensional computer program for incompressible flows with free surfaces

NASA Astrophysics Data System (ADS)

Torrey, M. D.; Mjolsness, R. C.; Stein, L. R.

1987-07-01

Presented is the NASA-VOF3D three-dimensional, transient, free-surface hydrodynamics program. This three-dimensional extension of NASA-VOF2D will, in principle, permit treatment in full three-dimensional generality of the wide variety of applications that could be treated by NASA-VOF2D only within the two-dimensional idealization. In particular, it, like NASA-VOF2D, is specifically designed to calculate confined flows in a low g environment. The code is presently restricted to cylindrical geometry. The code is based on the fractional volume-of-fluid method and allows multiple free surfaces with surface tension and wall adhesion. It also has a partial cell treatment that allows curved boundaries and internal obstacles. This report provides a brief discussion of the numerical method, a code listing, and some sample problems.

Cerebral cortex three-dimensional profiling in human fetuses by magnetic resonance imaging

PubMed Central

Sbarbati, Andrea; Pizzini, Francesca; Fabene, Paolo F; Nicolato, Elena; Marzola, Pasquina; Calderan, Laura; Simonati, Alessandro; Longo, Laura; Osculati, Antonio; Beltramello, Alberto

2004-01-01

Seven human fetuses of crown/rump length corresponding to gestational ages ranging from the 12th to the 16th week were studied using a paradigm based on three-dimensional reconstruction of the brain obtained by magnetic resonance imaging (MRI). The aim of the study was to evaluate brain morphology in situ and to describe developmental dynamics during an important period of fetal morphogenesis. Three-dimensional MRI showed the increasing degree of maturation of the brains; fronto-occipital distance, bitemporal distance and occipital angle were examined in all the fetuses. The data were interpreted by correlation with the internal structure as visualized using high-spatial-resolution MRI, acquired using a 4.7-T field intensity magnet with a gradient power of 20 G cm−1. The spatial resolution was sufficient for a detailed detection of five layers, and the contrast was optimized using sequences with different degrees of T1 and T2 weighting. Using the latter, it was possible to visualize the subplate and marginal zones. The cortical thickness was mapped on to the hemispheric surface, describing the thickness gradient from the insular cortex to the periphery of the hemispheres. The study demonstrates the utility of MRI for studying brain development. The method provides a quantitative profiling of the brain, which allows the calculation of important morphological parameters, and it provides informative regarding transient features of the developing brain. PMID:15198688

Filamentation and light bullet formation dynamics in solid-state dielectric media with weak, moderate and strong anomalous group velocity dispersion

NASA Astrophysics Data System (ADS)

Gražulevičiūtė, I.; Garejev, N.; Majus, D.; Jukna, V.; Tamošauskas, G.; Dubietis, A.

2016-02-01

We present a series of measurements, which characterize filamentation dynamics of intense ultrashort laser pulses in the space-time domain, as captured by means of three-dimensional imaging technique in sapphire and fused silica, in the wavelength range of 1.45-2.25 μm, accessing the regimes of weak, moderate and strong anomalous group velocity dispersion (GVD). In the regime of weak anomalous GVD (at 1.45 μm), pulse splitting into two sub-pulses producing a pair of light bullets with spectrally shifted carrier frequencies in both nonlinear media is observed. In contrast, in the regimes of moderate (at 1.8 μm) and strong (at 2.25 μm) anomalous GVD we observe notably different transient dynamics, which however lead to the formation of a single self-compressed quasistationary light bullet with an universal spatiotemporal shape comprised of an extended ring-shaped periphery and a localized intense core that carries the self-compressed pulse.

Progress Report on SAM Reduced-Order Model Development for Thermal Stratification and Mixing during Reactor Transients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, R.

This report documents the initial progress on the reduced-order flow model developments in SAM for thermal stratification and mixing modeling. Two different modeling approaches are pursued. The first one is based on one-dimensional fluid equations with additional terms accounting for the thermal mixing from both flow circulations and turbulent mixing. The second approach is based on three-dimensional coarse-grid CFD approach, in which the full three-dimensional fluid conservation equations are modeled with closure models to account for the effects of turbulence.

Transient Side Load Analysis of Out-of-Round Film-Cooled Nozzle Extensions

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Lin, Jeff; Ruf, Joe; Guidos, Mike

2012-01-01

There was interest in understanding the impact of out-of-round nozzle extension on the nozzle side load during transient startup operations. The out-of-round nozzle extension could be the result of asymmetric internal stresses, deformation induced by previous tests, and asymmetric loads induced by hardware attached to the nozzle. The objective of this study was therefore to computationally investigate the effect of out-of-round nozzle extension on the nozzle side loads during an engine startup transient. The rocket engine studied encompasses a regeneratively cooled chamber and nozzle, along with a film cooled nozzle extension. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, and transient inlet boundary flow properties derived from an engine system simulation. Six three-dimensional cases were performed with the out-of-roundness achieved by three different degrees of ovalization, elongated on lateral y and z axes: one slightly out-of-round, one more out-of-round, and one significantly out-of-round. The results show that the separation line jump was the primary source of the peak side loads. Comparing to the peak side load of the perfectly round nozzle, the peak side loads increased for the slightly and more ovalized nozzle extensions, and either increased or decreased for the two significantly ovalized nozzle extensions. A theory based on the counteraction of the flow destabilizing effect of an exacerbated asymmetrical flow caused by a lower degree of ovalization, and the flow stabilizing effect of a more symmetrical flow, created also by ovalization, is presented to explain the observations obtained in this effort.

Three-dimensional computational fluid dynamics modelling and experimental validation of the Jülich Mark-F solid oxide fuel cell stack

NASA Astrophysics Data System (ADS)

Nishida, R. T.; Beale, S. B.; Pharoah, J. G.; de Haart, L. G. J.; Blum, L.

2018-01-01

This work is among the first where the results of an extensive experimental research programme are compared to performance calculations of a comprehensive computational fluid dynamics model for a solid oxide fuel cell stack. The model, which combines electrochemical reactions with momentum, heat, and mass transport, is used to obtain results for an established industrial-scale fuel cell stack design with complex manifolds. To validate the model, comparisons with experimentally gathered voltage and temperature data are made for the Jülich Mark-F, 18-cell stack operating in a test furnace. Good agreement is obtained between the model and experiment results for cell voltages and temperature distributions, confirming the validity of the computational methodology for stack design. The transient effects during ramp up of current in the experiment may explain a lower average voltage than model predictions for the power curve.

On the origin of reproducible sequential activity in neural circuits

NASA Astrophysics Data System (ADS)

Afraimovich, V. S.; Zhigulin, V. P.; Rabinovich, M. I.

2004-12-01

Robustness and reproducibility of sequential spatio-temporal responses is an essential feature of many neural circuits in sensory and motor systems of animals. The most common mathematical images of dynamical regimes in neural systems are fixed points, limit cycles, chaotic attractors, and continuous attractors (attractive manifolds of neutrally stable fixed points). These are not suitable for the description of reproducible transient sequential neural dynamics. In this paper we present the concept of a stable heteroclinic sequence (SHS), which is not an attractor. SHS opens the way for understanding and modeling of transient sequential activity in neural circuits. We show that this new mathematical object can be used to describe robust and reproducible sequential neural dynamics. Using the framework of a generalized high-dimensional Lotka-Volterra model, that describes the dynamics of firing rates in an inhibitory network, we present analytical results on the existence of the SHS in the phase space of the network. With the help of numerical simulations we confirm its robustness in presence of noise in spite of the transient nature of the corresponding trajectories. Finally, by referring to several recent neurobiological experiments, we discuss possible applications of this new concept to several problems in neuroscience.

On the origin of reproducible sequential activity in neural circuits.

PubMed

Afraimovich, V S; Zhigulin, V P; Rabinovich, M I

2004-12-01

Robustness and reproducibility of sequential spatio-temporal responses is an essential feature of many neural circuits in sensory and motor systems of animals. The most common mathematical images of dynamical regimes in neural systems are fixed points, limit cycles, chaotic attractors, and continuous attractors (attractive manifolds of neutrally stable fixed points). These are not suitable for the description of reproducible transient sequential neural dynamics. In this paper we present the concept of a stable heteroclinic sequence (SHS), which is not an attractor. SHS opens the way for understanding and modeling of transient sequential activity in neural circuits. We show that this new mathematical object can be used to describe robust and reproducible sequential neural dynamics. Using the framework of a generalized high-dimensional Lotka-Volterra model, that describes the dynamics of firing rates in an inhibitory network, we present analytical results on the existence of the SHS in the phase space of the network. With the help of numerical simulations we confirm its robustness in presence of noise in spite of the transient nature of the corresponding trajectories. Finally, by referring to several recent neurobiological experiments, we discuss possible applications of this new concept to several problems in neuroscience.

Three-dimensional analysis of the early development of the dentition

PubMed Central

Peterkova, R; Hovorakova, M; Peterka, M; Lesot, H

2014-01-01

Tooth development has attracted the attention of researchers since the 19th century. It became obvious even then that morphogenesis could not fully be appreciated from two-dimensional histological sections. Therefore, methods of three-dimensional (3D) reconstructions were employed to visualize the surface morphology of developing structures and to help appreciate the complexity of early tooth morphogenesis. The present review surveys the data provided by computer-aided 3D analyses to update classical knowledge of early odontogenesis in the laboratory mouse and in humans. 3D reconstructions have demonstrated that odontogenesis in the early stages is a complex process which also includes the development of rudimentary odontogenic structures with different fates. Their developmental, evolutionary, and pathological aspects are discussed. The combination of in situ hybridization and 3D reconstruction have demonstrated the temporo-spatial dynamics of the signalling centres that reflect transient existence of rudimentary tooth primordia at loci where teeth were present in ancestors. The rudiments can rescue their suppressed development and revitalize, and then their subsequent autonomous development can give rise to oral pathologies. This shows that tooth-forming potential in mammals can be greater than that observed from their functional dentitions. From this perspective, the mouse rudimentary tooth primordia represent a natural model to test possibilities of tooth regeneration. PMID:24495023

Apico-basal forces exerted by apoptotic cells drive epithelium folding.

PubMed

Monier, Bruno; Gettings, Melanie; Gay, Guillaume; Mangeat, Thomas; Schott, Sonia; Guarner, Ana; Suzanne, Magali

2015-02-12

Epithelium folding is a basic morphogenetic event that is essential in transforming simple two-dimensional epithelial sheets into three-dimensional structures in both vertebrates and invertebrates. Folding has been shown to rely on apical constriction. The resulting cell-shape changes depend either on adherens junction basal shift or on a redistribution of myosin II, which could be driven by mechanical signals. Yet the initial cellular mechanisms that trigger and coordinate cell remodelling remain largely unknown. Here we unravel the active role of apoptotic cells in initiating morphogenesis, thus revealing a novel mechanism of epithelium folding. We show that, in a live developing tissue, apoptotic cells exert a transient pulling force upon the apical surface of the epithelium through a highly dynamic apico-basal myosin II cable. The apoptotic cells then induce a non-autonomous increase in tissue tension together with cortical myosin II apical stabilization in the surrounding tissue, eventually resulting in epithelium folding. Together our results, supported by a theoretical biophysical three-dimensional model, identify an apoptotic myosin-II-dependent signal as the initial signal leading to cell reorganization and tissue folding. This work further reveals that, far from being passively eliminated as generally assumed (for example, during digit individualization), apoptotic cells actively influence their surroundings and trigger tissue remodelling through regulation of tissue tension.

Anisotropic Energy Transport Properties of 1,3,5-Triamino-2,4,6-Trinitrobenzene (TATB)

NASA Astrophysics Data System (ADS)

Kroonblawd, Matthew P.

Anisotropic energy transport properties were determined theoretically for crystals of the insensitive explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) using molecular dynamics simulations. Determination of these properties is necessary for the analysis and interpretation of molecular dynamics predictions of transient processes such as shock response and hot spot formation/relaxation and is similarly important for the accurate parameterization of meso- and continuum-scale engineering models aimed at understanding complex processes such as ignition and growth leading to detonation. TATB crystal exhibits a graphitic-like layered packing structure with a two-dimensional hydrogen-bonding network that forms within, but not between, the molecule-thick layers that comprise the crystal. This structure is thought to be the primary factor behind the significant anisotropy in many physical properties of TATB crystals. Anisotropic thermal conductivity coefficients were determined for initially defect-free and defective TATB crystals and isotropic values were determined for the liquid at temperatures and pressures up to (1800 K, 2.0 GPa). The room temperature, atmospheric pressure thermal conductivity for TATB is predicted to be generally greater and more anisotropic than the thermal conductivities of other molecular explosives; conduction within the layers is approximately 70% greater than conduction between the layers. The conductivity is predicted to decrease with temperature approximately as λ ∝ 1/T over the interval 200 K ≤ T ≤ 700 K and to linearly increase with pressure up to 2.5 GPa. Direction-dependent relaxation of idealized one-dimensional hot spots was studied. Results from hot spot relaxation simulations were compared with and fit to solutions for the one-dimensional diffusive heat equation by treating the thermal di.usivity as a parameter to assess the validity of using continuum models to describe heat transport in TATB on length scales below 10 nm. A dissipative particle dynamics (DPD) at constant energy (DPDE) coarsegrained model is developed for TATB and applied to micron-scale shock simulations wherein the predicted shock response is shown to be highly sensitive to a model parameter controlling kinetics of energy transport between inter- and intramolecular degrees of freedom. A generalized crystal-cutting method is developed that enables facile construction of three-dimensionally periodic simulation cells containing arbitrarily oriented single crystals and crystal-crystal interfaces for materials of arbitrary symmetry class. Strategies for non-uniform sampling of molecular dynamics simulations of transient phenomena are proposed that have the potential to drastically reduce data storage costs.

Finite element analysis of steady and transiently moving/rolling nonlinear viscoelastic structure. II - Shell and three-dimensional simulations

NASA Technical Reports Server (NTRS)

Kennedy, Ronald; Padovan, Joe

1987-01-01

In a three-part series of papers, a generalized finite element solution strategy is developed to handle traveling load problems in rolling, moving and rotating structure. The main thrust of this section consists of the development of three-dimensional and shell type moving elements. In conjunction with this work, a compatible three-dimensional contact strategy is also developed. Based on these modeling capabilities, extensive analytical and experimental benchmarking is presented. Such testing includes traveling loads in rotating structure as well as low- and high-speed rolling contact involving standing wave-type response behavior. These point to the excellent modeling capabilities of moving element strategies.

Shock/vortex interaction and vortex-breakdown modes

NASA Technical Reports Server (NTRS)

Kandil, Osama A.; Kandil, H. A.; Liu, C. H.

1992-01-01

Computational simulation and study of shock/vortex interaction and vortex-breakdown modes are considered for bound (internal) and unbound (external) flow domains. The problem is formulated using the unsteady, compressible, full Navier-Stokes (NS) equations which are solved using an implicit, flux-difference splitting, finite-volume scheme. For the bound flow domain, a supersonic swirling flow is considered in a configured circular duct and the problem is solved for quasi-axisymmetric and three-dimensional flows. For the unbound domain, a supersonic swirling flow issued from a nozzle into a uniform supersonic flow of lower Mach number is considered for quasi-axisymmetric and three-dimensional flows. The results show several modes of breakdown; e.g., no-breakdown, transient single-bubble breakdown, transient multi-bubble breakdown, periodic multi-bubble multi-frequency breakdown and helical breakdown.

Three-dimensional transient numerical simulation for intake process in the engine intake port-valve-cylinder system.

PubMed

Luo, Ma-Ji; Chen, Guo-Hua; Ma, Yuan-Hao

2003-01-01

This paper presents a KIVA-3 code based numerical model for three-dimensional transient intake flow in the intake port-valve-cylinder system of internal combustion engine using body-fitted technique, which can be used in numerical study on internal combustion engine with vertical and inclined valves, and has higher calculation precision. A numerical simulation (on the intake process of a two-valve engine with a semi-sphere combustion chamber and a radial intake port) is provided for analysis of the velocity field and pressure field of different plane at different crank angles. The results revealed the formation of the tumble motion, the evolution of flow field parameters and the variation of tumble ratios as important information for the design of engine intake system.

Applying TM-polarization geoelectric exploration for study of low-contrast three-dimensional targets

NASA Astrophysics Data System (ADS)

Zlobinskiy, Arkadiy; Mogilatov, Vladimir; Shishmarev, Roman

2018-03-01

With using new field and theoretical data, it has been shown that applying the electromagnetic field of transverse magnetic (TM) polarization will give new opportunities for electrical prospecting by the method of transient processes. Only applying a pure field of the TM polarization permits poor three-dimensional objects (required metalliferous deposits) to be revealed in a host horizontally-layered medium. This position has good theoretical grounds. There is given the description of the transient electromagnetic method, that uses only the TM polarization field. The pure TM mode is excited by a special source, which is termed as a circular electric dipole (CED). The results of three-dimensional simulation (by the method of finite elements) are discussed for three real geological situations for which applying electromagnetic fields of transverse electric (TE) and transverse magnetic (TM) polarizations are compared. It has been shown that applying the TE mode gives no positive results, while applying the TM polarization field permits the problem to be tackled. Finally, the results of field works are offered, which showed inefficiency of application of the classical TEM method, whereas in contrast, applying the field of TM polarization makes it easy to identify the target.

Dynamic characteristics of hydrocarbon fuel within the channel at supercritical and pyrolysis condition

NASA Astrophysics Data System (ADS)

Yu, Bin; Zhou, Weixing; Qin, Jiang; Bao, Wen

2017-12-01

Regenerative cooling with fuel as the coolant is used in the scramjet engine. In order to grasp the dynamic characteristics of engine fuel supply processes, this article studies the dynamic characteristics of hydrocarbon fuel within the channel. A one-dimensional dynamic model was proved, the thermal energy storage effect, fuel volume effect and chemical dynamic effect have been considered in the model, the ordinary differential equations were solved using a 4th order Runge-Kutta method. The precision of the model was validated by three groups of experimental data. The effects of input signal, working condition, tube size on the dynamic characteristics of pressure, flow rate, temperature have been simulated. It is found that cracking reaction increased the compressibility of the fuel pyrolysis mixture and lead to longer responding time of outlet flow. The responding time of outlet flow can reach 3s when tube is 5m long which will greatly influence the control performance of the engine thrust system. Meanwhile, when the inlet flow rate appears the step change, the inlet pressure leads to overshoot, the overshoot can reach as much as 100%, such highly transient impulse will result in detrimental effect on fuel pump.

Excitonic instability in optically pumped three-dimensional Dirac materials

NASA Astrophysics Data System (ADS)

Pertsova, Anna; Balatsky, Alexander V.

2018-02-01

Recently it was suggested that transient excitonic instability can be realized in optically pumped two-dimensional (2D) Dirac materials (DMs), such as graphene and topological insulator surface states. Here we discuss the possibility of achieving a transient excitonic condensate in optically pumped three-dimensional (3D) DMs, such as Dirac and Weyl semimetals, described by nonequilibrium chemical potentials for photoexcited electrons and holes. Similar to the equilibrium case with long-range interactions, we find that for pumped 3D DMs with screened Coulomb potential two possible excitonic phases exist, an excitonic insulator phase and the charge density wave phase originating from intranodal and internodal interactions, respectively. In the pumped case, the critical coupling for excitonic instability vanishes; therefore the two phases coexist for arbitrarily weak coupling strengths. The excitonic gap in the charge density wave phase is always the largest one. The competition between screening effects and the increase of the density of states with optical pumping results in a rich phase diagram for the transient excitonic condensate. Based on the static theory of screening, we find that under certain conditions the value of the dimensionless coupling constant screening in 3D DMs can be weaker than in 2D DMs. Furthermore, we identify the signatures of the transient excitonic condensate that could be probed by scanning tunneling spectroscopy, photoemission, and optical conductivity measurements. Finally, we provide estimates of critical temperatures and excitonic gaps for existing and hypothetical 3D DMs.

Ultrafast structural molecular dynamics investigated with 2D infrared spectroscopy methods.

PubMed

Kraack, Jan Philip

2017-10-25

Ultrafast, multi-dimensional infrared (IR) spectroscopy has been advanced in recent years to a versatile analytical tool with a broad range of applications to elucidate molecular structure on ultrafast timescales, and it can be used for samples in a many different environments. Following a short and general introduction on the benefits of 2D IR spectroscopy, the first part of this chapter contains a brief discussion on basic descriptions and conceptual considerations of 2D IR spectroscopy. Outstanding classical applications of 2D IR are used afterwards to highlight the strengths and basic applicability of the method. This includes the identification of vibrational coupling in molecules, characterization of spectral diffusion dynamics, chemical exchange of chemical bond formation and breaking, as well as dynamics of intra- and intermolecular energy transfer for molecules in bulk solution and thin films. In the second part, several important, recently developed variants and new applications of 2D IR spectroscopy are introduced. These methods focus on (i) applications to molecules under two- and three-dimensional confinement, (ii) the combination of 2D IR with electrochemistry, (iii) ultrafast 2D IR in conjunction with diffraction-limited microscopy, (iv) several variants of non-equilibrium 2D IR spectroscopy such as transient 2D IR and 3D IR, and (v) extensions of the pump and probe spectral regions for multi-dimensional vibrational spectroscopy towards mixed vibrational-electronic spectroscopies. In light of these examples, the important open scientific and conceptual questions with regard to intra- and intermolecular dynamics are highlighted. Such questions can be tackled with the existing arsenal of experimental variants of 2D IR spectroscopy to promote the understanding of fundamentally new aspects in chemistry, biology and materials science. The final part of the chapter introduces several concepts of currently performed technical developments, which aim at exploiting 2D IR spectroscopy as an analytical tool. Such developments embrace the combination of 2D IR spectroscopy and plasmonic spectroscopy for ultrasensitive analytics, merging 2D IR spectroscopy with ultra-high-resolution microscopy (nanoscopy), future variants of transient 2D IR methods, or 2D IR in conjunction with microfluidics. It is expected that these techniques will allow for groundbreaking research in many new areas of natural sciences.

An adaptive front tracking technique for three-dimensional transient flows

NASA Astrophysics Data System (ADS)

Galaktionov, O. S.; Anderson, P. D.; Peters, G. W. M.; van de Vosse, F. N.

2000-01-01

An adaptive technique, based on both surface stretching and surface curvature analysis for tracking strongly deforming fluid volumes in three-dimensional flows is presented. The efficiency and accuracy of the technique are demonstrated for two- and three-dimensional flow simulations. For the two-dimensional test example, the results are compared with results obtained using a different tracking approach based on the advection of a passive scalar. Although for both techniques roughly the same structures are found, the resolution for the front tracking technique is much higher. In the three-dimensional test example, a spherical blob is tracked in a chaotic mixing flow. For this problem, the accuracy of the adaptive tracking is demonstrated by the volume conservation for the advected blob. Adaptive front tracking is suitable for simulation of the initial stages of fluid mixing, where the interfacial area can grow exponentially with time. The efficiency of the algorithm significantly benefits from parallelization of the code. Copyright

Multidimensional immunolabeling and 4D time-lapse imaging of vital ex vivo lung tissue

PubMed Central

Vierkotten, Sarah; Lindner, Michael; Königshoff, Melanie; Eickelberg, Oliver

2015-01-01

During the last decades, the study of cell behavior was largely accomplished in uncoated or extracellular matrix (ECM)-coated plastic dishes. To date, considerable cell biological efforts have tried to model in vitro the natural microenvironment found in vivo. For the lung, explants cultured ex vivo as lung tissue cultures (LTCs) provide a three-dimensional (3D) tissue model containing all cells in their natural microenvironment. Techniques for assessing the dynamic live interaction between ECM and cellular tissue components, however, are still missing. Here, we describe specific multidimensional immunolabeling of living 3D-LTCs, derived from healthy and fibrotic mouse lungs, as well as patient-derived 3D-LTCs, and concomitant real-time four-dimensional multichannel imaging thereof. This approach allowed the evaluation of dynamic interactions between mesenchymal cells and macrophages with their ECM. Furthermore, fibroblasts transiently expressing focal adhesions markers incorporated into the 3D-LTCs, paving new ways for studying the dynamic interaction between cellular adhesions and their natural-derived ECM. A novel protein transfer technology (FuseIt/Ibidi) shuttled fluorescently labeled α-smooth muscle actin antibodies into the native cells of living 3D-LTCs, enabling live monitoring of α-smooth muscle actin-positive stress fibers in native tissue myofibroblasts residing in fibrotic lesions of 3D-LTCs. Finally, this technique can be applied to healthy and diseased human lung tissue, as well as to adherent cells in conventional two-dimensional cell culture. This novel method will provide valuable new insights into the dynamics of ECM (patho)biology, studying in detail the interaction between ECM and cellular tissue components in their natural microenvironment. PMID:26092995

Programed dynamical ordering in self-organization processes of a nanocube: a molecular dynamics study.

PubMed

Harada, Ryuhei; Mashiko, Takako; Tachikawa, Masanori; Hiraoka, Shuichi; Shigeta, Yasuteru

2018-04-04

Self-organization processes of a gear-shaped amphiphile molecule (1) to form a hexameric structure (nanocube, 16) were inferred from sequential dissociation processes by using molecular dynamics (MD) simulations. Our MD study unveiled that programed dynamic ordering exists in the dissociation processes of 16. According to the dissociation processes, it is proposed that triple π-stacking among three 3-pyridyl groups and other weak molecular interactions such as CH-π and van der Waals interactions, some of which arise from the solvophobic effect, were sequentially formed in stable and transient oligomeric states in the self-organization processes, i.e.12, 13, 14, and 15. By subsequent analyses on structural stabilities, it was found that 13 and 14 are stable intermediate oligomers, whereas 12 and 15 are transient ones. Thus, the formation of 13 from three monomers and of 16 from 14 and two monomers via corresponding transients is time consuming in the self-assembly process.

First-passage dynamics of linear stochastic interface models: weak-noise theory and influence of boundary conditions

NASA Astrophysics Data System (ADS)

Gross, Markus

2018-03-01

We consider a one-dimensional fluctuating interfacial profile governed by the Edwards–Wilkinson or the stochastic Mullins-Herring equation for periodic, standard Dirichlet and Dirichlet no-flux boundary conditions. The minimum action path of an interfacial fluctuation conditioned to reach a given maximum height M at a finite (first-passage) time T is calculated within the weak-noise approximation. Dynamic and static scaling functions for the profile shape are obtained in the transient and the equilibrium regime, i.e. for first-passage times T smaller or larger than the characteristic relaxation time, respectively. In both regimes, the profile approaches the maximum height M with a universal algebraic time dependence characterized solely by the dynamic exponent of the model. It is shown that, in the equilibrium regime, the spatial shape of the profile depends sensitively on boundary conditions and conservation laws, but it is essentially independent of them in the transient regime.

Integrated Aeromechanics with Three-Dimensional Solid-Multibody Structures

NASA Technical Reports Server (NTRS)

Datta, Anubhav; Johnson, Wayne

2014-01-01

A full three-dimensional finite element-multibody structural dynamic solver is coupled to a three-dimensional Reynolds-averaged Navier-Stokes solver for the prediction of integrated aeromechanical stresses and strains on a rotor blade in forward flight. The objective is to lay the foundations of all major pieces of an integrated three-dimensional rotor dynamic analysis - from model construction to aeromechanical solution to stress/strain calculation. The primary focus is on the aeromechanical solution. Two types of three-dimensional CFD/CSD interfaces are constructed for this purpose with an emphasis on resolving errors from geometry mis-match so that initial-stage approximate structural geometries can also be effectively analyzed. A three-dimensional structural model is constructed as an approximation to a UH-60A-like fully articulated rotor. The aerodynamic model is identical to the UH-60A rotor. For preliminary validation measurements from a UH-60A high speed flight is used where CFD coupling is essential to capture the advancing side tip transonic effects. The key conclusion is that an integrated aeromechanical analysis is indeed possible with three-dimensional structural dynamics but requires a careful description of its geometry and discretization of its parts.

A method for analyzing dynamic stall of helicopter rotor blades

NASA Technical Reports Server (NTRS)

Crimi, P.; Reeves, B. L.

1972-01-01

A model for each of the basic flow elements involved in the unsteady stall of a two-dimensional airfoil in incompressible flow is presented. The interaction of these elements is analyzed using a digital computer. Computations of the loading during transient and sinusoidal pitching motions are in good qualitative agreement with measured loads. The method was used to confirm that large torsional response of helicopter blades detected in flight tests can be attributed to dynamic stall.

The dynamic response and shock-recovery of porcine skeletal muscle tissue

NASA Astrophysics Data System (ADS)

Wilgeroth, James Michael; Hazell, Paul; Appleby-Thomas, Gareth James

2012-03-01

A soft-capture system allowing for one-dimensional shock loading and release of soft tissues via the plate-impact technique has been developed. In addition, we present the numerical simulation of a shock-recovery experiment involving porcine skeletal muscle and further investigate the effects of the transient wave on the structure of the tissue via transmission electron microscope (TEM). This paper forms part of an ongoing research programme on the dynamic behaviour of skeletal muscle tissue.

Approximate analysis of thermal convection in a crystal-growth cell for Spacelab 3

NASA Technical Reports Server (NTRS)

Dressler, R. F.

1982-01-01

The transient and steady thermal convection in microgravity is described. The approach is applicable to many three dimensional flows in containers of various shapes with various thermal gradients imposed. The method employs known analytical solutions to two dimensional thermal flows in simpler geometries, and does not require recourse to numerical calculations by computer.

Experimental and CFD-PBM approach coupled with a simplified dynamic analysis of mass transfer in phenol biodegradation in a three phase system of an aerated two-phase partitioning bioreactor for environmental applications

NASA Astrophysics Data System (ADS)

Moradkhani, Hamed; Anarjan Kouchehbagh, Navideh; Izadkhah, Mir-Shahabeddin

2017-03-01

A three-dimensional transient modeling of a two-phase partitioning bioreactor, combining system hydrodynamics, two simultaneous mass transfer and microorganism growth is modeled using computational fluid dynamics code FLUENT 6.2. The simulation is based on standard "k-ɛ" Reynolds-averaged Navier-Stokes model. Population balance model is implemented in order to describe gas bubble coalescence, breakage and species transport in the reaction medium and to predict oxygen volumetric mass transfer coefficient (kLa). Model results are verified against experimental data and show good agreement as 13 classes of bubble size is taking into account. Flow behavior in different operational conditions is studied. Almost at all impeller speeds and aeration intensities there were acceptable distributions of species caused by proper mixing. The magnitude of dissolved oxygen percentage in aqueous phase has a direct correlation with impeller speed and any increasing of the aeration magnitude leads to faster saturation in shorter periods of time.

Application of the Hughes-LIU algorithm to the 2-dimensional heat equation

NASA Technical Reports Server (NTRS)

Malkus, D. S.; Reichmann, P. I.; Haftka, R. T.

1982-01-01

An implicit explicit algorithm for the solution of transient problems in structural dynamics is described. The method involved dividing the finite elements into implicit and explicit groups while automatically satisfying the conditions. This algorithm is applied to the solution of the linear, transient, two dimensional heat equation subject to an initial condition derived from the soluton of a steady state problem over an L-shaped region made up of a good conductor and an insulating material. Using the IIT/PRIME computer with virtual memory, a FORTRAN computer program code was developed to make accuracy, stability, and cost comparisons among the fully explicit Euler, the Hughes-Liu, and the fully implicit Crank-Nicholson algorithms. The Hughes-Liu claim that the explicit group governs the stability of the entire region while maintaining the unconditional stability of the implicit group is illustrated.

Controlling transient chaos in deterministic flows with applications to electrical power systems and ecology

NASA Astrophysics Data System (ADS)

Dhamala, Mukeshwar; Lai, Ying-Cheng

1999-02-01

Transient chaos is a common phenomenon in nonlinear dynamics of many physical, biological, and engineering systems. In applications it is often desirable to maintain sustained chaos even in parameter regimes of transient chaos. We address how to sustain transient chaos in deterministic flows. We utilize a simple and practical method, based on extracting the fundamental dynamics from time series, to maintain chaos. The method can result in control of trajectories from almost all initial conditions in the original basin of the chaotic attractor from which transient chaos is created. We apply our method to three problems: (1) voltage collapse in electrical power systems, (2) species preservation in ecology, and (3) elimination of undesirable bursting behavior in a chemical reaction system.

Simplification of femtosecond transient absorption microscopy data from CH 3NH 3PbI 3 perovskite thin films into decay associated amplitude maps

DOE PAGES

Doughty, Benjamin; Simpson, Mary Jane; Yang, Bin; ...

2016-02-16

Our work aims to simplify multi-dimensional femtosecond transient absorption microscopy (TAM) data into decay associated amplitude maps that describe the spatial distributions of dynamical processes occurring on various characteristic timescales. Application of this method to TAM data obtained from a model methyl-ammonium lead iodide (CH 3NH 3PbI 3) perovskite thin film allows us to simplify the dataset consisting of a 68 time-resolved images into 4 decay associated amplitude maps. Furthermore, these maps provide a simple means to visualize the complex electronic excited-state dynamics in this system by separating distinct dynamical processes evolving on characteristic timescales into individual spatial images. Thismore » approach provides new insight into subtle aspects of ultrafast relaxation dynamics associated with excitons and charge carriers in the perovskite thin film, which have recently been found to coexist at spatially distinct locations.« less

The Southern Ocean's role in ocean circulation and climate transients

NASA Astrophysics Data System (ADS)

Thompson, A. F.; Stewart, A.; Hines, S.; Adkins, J. F.

2017-12-01

The ventilation of deep and intermediate density classes at the surface of the Southern Ocean impacts water mass modification and the air-sea exchange of heat and trace gases, which in turn influences the global overturning circulation and Earth's climate. Zonal variability occurs along the Antarctic Circumpolar Current and the Antarctic margins related to flow-topography interactions, variations in surface boundary conditions, and exchange with northern basins. Information about these zonal variations, and their impact on mass and tracer transport, are suppressed when the overturning is depicted as a two-dimensional (depth-latitude) streamfunction. Here we present an idealized, multi-basin, time-dependent circulation model that applies residual circulation theory in the Southern Ocean and allows for zonal water mass transfer between different ocean basins. This model efficiently determines the temporal evolution of the ocean's stratification, ventilation and overturning strength in response to perturbations in the external forcing. With this model we explore the dynamics that lead to transitions in the circulation structure between multiple, isolated cells and a three-dimensional, "figure-of-eight," circulation in which traditional upper and lower cells are interleaved. The transient model is also used to support a mechanistic explanation of the hemispheric asymmetry and phase lag associated with Dansgaard-Oeschger (DO) events during the last glacial period. In particular, the 200 year lag in southern hemisphere temperatures, following a perturbation in North Atlantic deep water formation, depends critically on the migration of Southern Ocean isopycnal outcropping in response to low-latitude stratification changes. Our results provide a self-consistent dynamical framework to explain various ocean overturning transitions that have occurred over the Earth's last 100,000 years, and motivate an exploration of these mechanisms in more sophisticated climate models.

4D imaging of transient structures and morphologies in ultrafast electron microscopy.

PubMed

Barwick, Brett; Park, Hyun Soon; Kwon, Oh-Hoon; Baskin, J Spencer; Zewail, Ahmed H

2008-11-21

With advances in spatial resolution reaching the atomic scale, two-dimensional (2D) and 3D imaging in electron microscopy has become an essential methodology in various fields of study. Here, we report 4D imaging, with in situ spatiotemporal resolutions, in ultrafast electron microscopy (UEM). The ability to capture selected-area-image dynamics with pixel resolution and to control the time separation between pulses for temporal cooling of the specimen made possible studies of fleeting structures and morphologies. We demonstrate the potential for applications with two examples, gold and graphite. For gold, after thermally induced stress, we determined the atomic structural expansion, the nonthermal lattice temperature, and the ultrafast transients of warping/bulging. In contrast, in graphite, striking coherent transients of the structure were observed in both image and diffraction, directly measuring, on the nanoscale, the longitudinal resonance period governed by Young's elastic modulus. The success of these studies demonstrates the promise of UEM in real-space imaging of dynamics.

Erosion of tungsten armor after multiple intense transient events in ITER

NASA Astrophysics Data System (ADS)

Bazylev, B. N.; Janeschitz, G.; Landman, I. S.; Pestchanyi, S. E.

2005-03-01

Macroscopic erosion by melt motion is the dominating damage mechanism for tungsten armour under high-heat loads with energy deposition W > 1 MJ/m 2 and τ > 0.1 ms. For ITER divertor armour the results of a fluid dynamics simulation of the melt motion erosion after repetitive stochastically varying plasma heat loads of consecutive disruptions interspaced by ELMs are presented. The heat loads for particular single transient events are numerically simulated using the two-dimensional MHD code FOREV-2D. The whole melt motion is calculated by the fluid dynamics code MEMOS-1.5D. In addition for the ITER dome melt motion erosion of tungsten armour caused by the lateral radiation impact from the plasma shield at the disruption and ELM heat loads is estimated.

Transient response of a liquid injector to a steep-fronted transverse pressure wave

NASA Astrophysics Data System (ADS)

Lim, D.; Heister, S.; Stechmann, D.; Kan, B.

2017-12-01

Motivated by the dynamic injection environment posed by unsteady pressure gain combustion processes, an experimental apparatus was developed to visualize the dynamic response of a transparent liquid injector subjected to a single steep-fronted transverse pressure wave. Experiments were conducted at atmospheric pressure with a variety of acrylic injector passage designs using water as the working fluid. High-speed visual observations were made of the injector exit near field, and the extent of backflow and the time to refill the orifice passage were characterized over a range of injection pressures. A companion transient one-dimensional model was developed for interpretation of the results and to elucidate the trends with regard to the strength of the transverse pressure wave. Results from the model were compared with the experimental observations.

Transient response of a liquid injector to a steep-fronted transverse pressure wave

NASA Astrophysics Data System (ADS)

Lim, D.; Heister, S.; Stechmann, D.; Kan, B.

2018-07-01

Motivated by the dynamic injection environment posed by unsteady pressure gain combustion processes, an experimental apparatus was developed to visualize the dynamic response of a transparent liquid injector subjected to a single steep-fronted transverse pressure wave. Experiments were conducted at atmospheric pressure with a variety of acrylic injector passage designs using water as the working fluid. High-speed visual observations were made of the injector exit near field, and the extent of backflow and the time to refill the orifice passage were characterized over a range of injection pressures. A companion transient one-dimensional model was developed for interpretation of the results and to elucidate the trends with regard to the strength of the transverse pressure wave. Results from the model were compared with the experimental observations.

Chaos and crises in a model for cooperative hunting: a symbolic dynamics approach.

PubMed

Duarte, Jorge; Januário, Cristina; Martins, Nuno; Sardanyés, Josep

2009-12-01

In this work we investigate the population dynamics of cooperative hunting extending the McCann and Yodzis model for a three-species food chain system with a predator, a prey, and a resource species. The new model considers that a given fraction sigma of predators cooperates in prey's hunting, while the rest of the population 1-sigma hunts without cooperation. We use the theory of symbolic dynamics to study the topological entropy and the parameter space ordering of the kneading sequences associated with one-dimensional maps that reproduce significant aspects of the dynamics of the species under several degrees of cooperative hunting. Our model also allows us to investigate the so-called deterministic extinction via chaotic crisis and transient chaos in the framework of cooperative hunting. The symbolic sequences allow us to identify a critical boundary in the parameter spaces (K,C(0)) and (K,sigma) which separates two scenarios: (i) all-species coexistence and (ii) predator's extinction via chaotic crisis. We show that the crisis value of the carrying capacity K(c) decreases at increasing sigma, indicating that predator's populations with high degree of cooperative hunting are more sensitive to the chaotic crises. We also show that the control method of Dhamala and Lai [Phys. Rev. E 59, 1646 (1999)] can sustain the chaotic behavior after the crisis for systems with cooperative hunting. We finally analyze and quantify the inner structure of the target regions obtained with this control method for wider parameter values beyond the crisis, showing a power law dependence of the extinction transients on such critical parameters.

Dimensional reduction for a SIR type model

NASA Astrophysics Data System (ADS)

Cahyono, Edi; Soeharyadi, Yudi; Mukhsar

2018-03-01

Epidemic phenomena are often modeled in the form of dynamical systems. Such model has also been used to model spread of rumor, spread of extreme ideology, and dissemination of knowledge. Among the simplest is SIR (susceptible, infected and recovered) model, a model that consists of three compartments, and hence three variables. The variables are functions of time which represent the number of subpopulations, namely suspect, infected and recovery. The sum of the three is assumed to be constant. Hence, the model is actually two dimensional which sits in three-dimensional ambient space. This paper deals with the reduction of a SIR type model into two variables in two-dimensional ambient space to understand the geometry and dynamics better. The dynamics is studied, and the phase portrait is presented. The two dimensional model preserves the equilibrium and the stability. The model has been applied for knowledge dissemination, which has been the interest of knowledge management.

Three-dimensional discrete-time Lotka-Volterra models with an application to industrial clusters

NASA Astrophysics Data System (ADS)

Bischi, G. I.; Tramontana, F.

2010-10-01

We consider a three-dimensional discrete dynamical system that describes an application to economics of a generalization of the Lotka-Volterra prey-predator model. The dynamic model proposed is used to describe the interactions among industrial clusters (or districts), following a suggestion given by [23]. After studying some local and global properties and bifurcations in bidimensional Lotka-Volterra maps, by numerical explorations we show how some of them can be extended to their three-dimensional counterparts, even if their analytic and geometric characterization becomes much more difficult and challenging. We also show a global bifurcation of the three-dimensional system that has no two-dimensional analogue. Besides the particular economic application considered, the study of the discrete version of Lotka-Volterra dynamical systems turns out to be a quite rich and interesting topic by itself, i.e. from a purely mathematical point of view.

[Three-dimensional reconstruction of functional brain images].

PubMed

Inoue, M; Shoji, K; Kojima, H; Hirano, S; Naito, Y; Honjo, I

1999-08-01

We consider PET (positron emission tomography) measurement with SPM (Statistical Parametric Mapping) analysis to be one of the most useful methods to identify activated areas of the brain involved in language processing. SPM is an effective analytical method that detects markedly activated areas over the whole brain. However, with the conventional presentations of these functional brain images, such as horizontal slices, three directional projection, or brain surface coloring, makes understanding and interpreting the positional relationships among various brain areas difficult. Therefore, we developed three-dimensionally reconstructed images from these functional brain images to improve the interpretation. The subjects were 12 normal volunteers. The following three types of images were constructed: 1) routine images by SPM, 2) three-dimensional static images, and 3) three-dimensional dynamic images, after PET images were analyzed by SPM during daily dialog listening. The creation of images of both the three-dimensional static and dynamic types employed the volume rendering method by VTK (The Visualization Toolkit). Since the functional brain images did not include original brain images, we synthesized SPM and MRI brain images by self-made C++ programs. The three-dimensional dynamic images were made by sequencing static images with available software. Images of both the three-dimensional static and dynamic types were processed by a personal computer system. Our newly created images showed clearer positional relationships among activated brain areas compared to the conventional method. To date, functional brain images have been employed in fields such as neurology or neurosurgery, however, these images may be useful even in the field of otorhinolaryngology, to assess hearing and speech. Exact three-dimensional images based on functional brain images are important for exact and intuitive interpretation, and may lead to new developments in brain science. Currently, the surface model is the most common method of three-dimensional display. However, the volume rendering method may be more effective for imaging regions such as the brain.

Electromechanical vortex filaments during cardiac fibrillation

NASA Astrophysics Data System (ADS)

Christoph, J.; Chebbok, M.; Richter, C.; Schröder-Schetelig, J.; Bittihn, P.; Stein, S.; Uzelac, I.; Fenton, F. H.; Hasenfuß, G.; Gilmour, R. F., Jr.; Luther, S.

2018-03-01

The self-organized dynamics of vortex-like rotating waves, which are also known as scroll waves, are the basis of the formation of complex spatiotemporal patterns in many excitable chemical and biological systems. In the heart, filament-like phase singularities that are associated with three-dimensional scroll waves are considered to be the organizing centres of life-threatening cardiac arrhythmias. The mechanisms that underlie the onset, maintenance and control of electromechanical turbulence in the heart are inherently three-dimensional phenomena. However, it has not previously been possible to visualize the three-dimensional spatiotemporal dynamics of scroll waves inside cardiac tissues. Here we show that three-dimensional mechanical scroll waves and filament-like phase singularities can be observed deep inside the contracting heart wall using high-resolution four-dimensional ultrasound-based strain imaging. We found that mechanical phase singularities co-exist with electrical phase singularities during cardiac fibrillation. We investigated the dynamics of electrical and mechanical phase singularities by simultaneously measuring the membrane potential, intracellular calcium concentration and mechanical contractions of the heart. We show that cardiac fibrillation can be characterized using the three-dimensional spatiotemporal dynamics of mechanical phase singularities, which arise inside the fibrillating contracting ventricular wall. We demonstrate that electrical and mechanical phase singularities show complex interactions and we characterize their dynamics in terms of trajectories, topological charge and lifetime. We anticipate that our findings will provide novel perspectives for non-invasive diagnostic imaging and therapeutic applications.

Analysis of high-rise constructions with the using of three-dimensional models of rods in the finite element program PRINS

NASA Astrophysics Data System (ADS)

Agapov, Vladimir

2018-03-01

The necessity of new approaches to the modeling of rods in the analysis of high-rise constructions is justified. The possibility of the application of the three-dimensional superelements of rods with rectangular cross section for the static and dynamic calculation of the bar and combined structures is considered. The results of the eighteen-story spatial frame free vibrations analysis using both one-dimensional and three-dimensional models of rods are presented. A comparative analysis of the obtained results is carried out and the conclusions on the possibility of three-dimensional superelements application in static and dynamic analysis of high-rise constructions are given on its basis.

Growth mechanisms of perturbations in boundary layers over a compliant wall

NASA Astrophysics Data System (ADS)

Malik, M.; Skote, Martin; Bouffanais, Roland

2018-01-01

The temporal modal and nonmodal growth of three-dimensional perturbations in the boundary layer flow over an infinite compliant flat wall is considered. Using a wall-normal velocity and wall-normal vorticity formalism, the dynamic boundary condition at the compliant wall admits a linear dependence on the eigenvalue parameter, as compared to a quadratic one in the canonical formulation of the problem. As a consequence, the continuous spectrum is accurately obtained. This enables us to effectively filter the pseudospectra, which is a prerequisite to the transient growth analysis. An energy-budget analysis for the least-decaying hydroelastic (static divergence, traveling wave flutter, and near-stationary transitional) and Tollmien-Schlichting modes in the parameter space reveals the primary routes of energy flow. Moreover, the maximum transient growth rate increases more slowly with the Reynolds number than for the solid wall case. The slowdown is due to a complex dependence of the wall-boundary condition with the Reynolds number, which translates into a transition of the fluid-solid interaction from a two-way to a one-way coupling. Unlike the solid-wall case, viscosity plays a pivotal role in the transient growth. The initial and optimal perturbations are compared with the boundary layer flow over a solid wall; differences and similarities are discussed.

Triple grouping and period-three oscillations in minority-game dynamics.

PubMed

Dong, Jia-Qi; Huang, Zi-Gang; Huang, Liang; Lai, Ying-Cheng

2014-12-01

Dynamical systems based on the minority game (MG) have been a paradigm for gaining significant insights into a variety of social and biological behaviors. Recently, a grouping phenomenon has been unveiled in MG systems of multiple resources (strategies) in which the strategies spontaneously break into an even number of groups, each exhibiting an identical oscillation pattern in the attendance of game players. Here we report our finding of spontaneous breakup of resources into three groups, each exhibiting period-three oscillations. An analysis is developed to understand the emergence of the striking phenomenon of triple grouping and period-three oscillations. In the presence of random disturbances, the triple-group/period-three state becomes transient, and we obtain explicit formula for the average transient lifetime using two methods of approximation. Our finding indicates that, period-three oscillation, regarded as one of the most fundamental behaviors in smooth nonlinear dynamical systems, can also occur in much more complex, evolutionary-game dynamical systems. Our result also provides a plausible insight for the occurrence of triple grouping observed, for example, in the U.S. housing market.

A theoretical and computational study of lithium-ion battery thermal management for electric vehicles using heat pipes

NASA Astrophysics Data System (ADS)

Greco, Angelo; Cao, Dongpu; Jiang, Xi; Yang, Hong

2014-07-01

A simplified one-dimensional transient computational model of a prismatic lithium-ion battery cell is developed using thermal circuit approach in conjunction with the thermal model of the heat pipe. The proposed model is compared to an analytical solution based on variable separation as well as three-dimensional (3D) computational fluid dynamics (CFD) simulations. The three approaches, i.e. the 1D computational model, analytical solution, and 3D CFD simulations, yielded nearly identical results for the thermal behaviours. Therefore the 1D model is considered to be sufficient to predict the temperature distribution of lithium-ion battery thermal management using heat pipes. Moreover, a maximum temperature of 27.6 °C was predicted for the design of the heat pipe setup in a distributed configuration, while a maximum temperature of 51.5 °C was predicted when forced convection was applied to the same configuration. The higher surface contact of the heat pipes allows a better cooling management compared to forced convection cooling. Accordingly, heat pipes can be used to achieve effective thermal management of a battery pack with confined surface areas.

Simulation of freshwater-saltwater interfaces in the Brooklyn-Queens aquifer system, Long Island, New York

USGS Publications Warehouse

Kontis, Angelo L.

1999-01-01

The seaward limit of the fresh ground-water system underlying Kings and Queens Counties on Long Island, N.Y., is at the freshwater-saltwater transition zone. This zone has been conceptualized in transient-state, three-dimensional models of the aquifer system as a sharp interface between freshwater and saltwater, and represented as a stationary, zero lateral-flow boundary. In this study, a pair of two-dimensional, four-layer ground-water flow models representing a generalized vertical section in Kings County and one in adjacent Queens County were developed to evaluate the validity of the boundary condition used in three-dimensional models of the aquifer system. The two-dimensional simulations used a model code that can simulate the movement of a sharp interface in response to transient stress. Sensitivity of interface movement to four factors was analyzed; these were (1) the method of simulating vertical leakage between freshwater and saltwater; (2) recharge at the normal rate, at 50-percent of the normal rate, and at zero for a prolonged (3-year) period; (3) high, medium, and low pumping rates; and (4) pumping from a hypothetical cluster of wells at two locations. Results indicate that the response of the interfaces to the magnitude and duration of pumping and the location of the hypothetical wells is probably sufficiently slow that the interfaces in three-dimensional models can reasonably be approximated as stationary, zero-lateral- flow boundaries.

Coupling of TRAC-PF1/MOD2, Version 5.4.25, with NESTLE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knepper, P.L.; Hochreiter, L.E.; Ivanov, K.N.

1999-09-01

A three-dimensional (3-D) spatial kinetics capability within a thermal-hydraulics system code provides a more correct description of the core physics during reactor transients that involve significant variations in the neutron flux distribution. Coupled codes provide the ability to forecast safety margins in a best-estimate manner. The behavior of a reactor core and the feedback to the plant dynamics can be accurately simulated. For each time step, coupled codes are capable of resolving system interaction effects on neutronics feedback and are capable of describing local neutronics effects caused by the thermal hydraulics and neutronics coupling. With the improvements in computational technology,more » modeling complex reactor behaviors with coupled thermal hydraulics and spatial kinetics is feasible. Previously, reactor analysis codes were limited to either a detailed thermal-hydraulics model with simplified kinetics or multidimensional neutron kinetics with a simplified thermal-hydraulics model. The authors discuss the coupling of the Transient Reactor Analysis Code (TRAC)-PF1/MOD2, Version 5.4.25, with the NESTLE code.« less

Direct numerical simulation of the laminar-turbulent transition at hypersonic flow speeds on a supercomputer

NASA Astrophysics Data System (ADS)

Egorov, I. V.; Novikov, A. V.; Fedorov, A. V.

2017-08-01

A method for direct numerical simulation of three-dimensional unsteady disturbances leading to a laminar-turbulent transition at hypersonic flow speeds is proposed. The simulation relies on solving the full three-dimensional unsteady Navier-Stokes equations. The computational technique is intended for multiprocessor supercomputers and is based on a fully implicit monotone approximation scheme and the Newton-Raphson method for solving systems of nonlinear difference equations. This approach is used to study the development of three-dimensional unstable disturbances in a flat-plate and compression-corner boundary layers in early laminar-turbulent transition stages at the free-stream Mach number M = 5.37. The three-dimensional disturbance field is visualized in order to reveal and discuss features of the instability development at the linear and nonlinear stages. The distribution of the skin friction coefficient is used to detect laminar and transient flow regimes and determine the onset of the laminar-turbulent transition.

Electron heating and thermal relaxation of gold nanorods revealed by two-dimensional electronic spectroscopy.

PubMed

Lietard, Aude; Hsieh, Cho-Shuen; Rhee, Hanju; Cho, Minhaeng

2018-03-01

To elucidate the complex interplay between the size and shape of gold nanorods and their electronic, photothermal, and optical properties for molecular imaging, photothermal therapy, and optoelectronic devices, it is a prerequisite to characterize ultrafast electron dynamics in gold nanorods. Time-resolved transient absorption (TA) studies of plasmonic electrons in various nanostructures have revealed the time scales for electron heating, lattice vibrational excitation, and phonon relaxation processes in condensed phases. However, because linear spectroscopic and time-resolved TA signals are vulnerable to inhomogeneous line-broadening, pure dephasing and direct electron heating effects are difficult to observe. Here we show that femtosecond two-dimensional electronic spectroscopy, with its unprecedented time resolution and phase sensitivity, can be used to collect direct experimental evidence for ultrafast electron heating, anomalously strong coherent and transient electronic plasmonic responses, and homogenous dephasing processes resulting from electron-vibration couplings even for polydisperse gold nanorods.

Molecular Dynamics Simulation of the Three-Dimensional Ordered State in Laser-Cooled Heavy-Ion Beams

NASA Astrophysics Data System (ADS)

Yuri, Yosuke

A molecular dynamics simulation is performed to study the formation of three-dimensional ordered beams by laser cooling in a cooler storage ring. Ultralow-temperature heavy-ion beams are generated by transverse cooling with displaced Gaussian lasers and resonant coupling. A three-dimensional ordered state of the ion beam is attained at a high line density. The ordered beam exhibits several unique characteristics different from those of an ideal crystalline beam.

Visualization of spatial-temporal data based on 3D virtual scene

NASA Astrophysics Data System (ADS)

Wang, Xianghong; Liu, Jiping; Wang, Yong; Bi, Junfang

2009-10-01

The main purpose of this paper is to realize the expression of the three-dimensional dynamic visualization of spatialtemporal data based on three-dimensional virtual scene, using three-dimensional visualization technology, and combining with GIS so that the people's abilities of cognizing time and space are enhanced and improved by designing dynamic symbol and interactive expression. Using particle systems, three-dimensional simulation, virtual reality and other visual means, we can simulate the situations produced by changing the spatial location and property information of geographical entities over time, then explore and analyze its movement and transformation rules by changing the interactive manner, and also replay history and forecast of future. In this paper, the main research object is the vehicle track and the typhoon path and spatial-temporal data, through three-dimensional dynamic simulation of its track, and realize its timely monitoring its trends and historical track replaying; according to visualization techniques of spatialtemporal data in Three-dimensional virtual scene, providing us with excellent spatial-temporal information cognitive instrument not only can add clarity to show spatial-temporal information of the changes and developments in the situation, but also be used for future development and changes in the prediction and deduction.

Generation of spiral waves pinned to obstacles in a simulated excitable system

NASA Astrophysics Data System (ADS)

Phantu, Metinee; Kumchaiseemak, Nakorn; Porjai, Porramain; Sutthiopad, Malee; Müller, Stefan C.; Luengviriya, Chaiya; Luengviriya, Jiraporn

2017-09-01

Pinning phenomena emerge in many dynamical systems. They are found to stabilize extreme conditions such as superconductivity and super fluidity. The dynamics of pinned spiral waves, whose tips trace the boundary of obstacles, also play an important role in the human health. In heart, such pinned waves cause longer tachycardia. In this article, we present two methods for generating pinned spiral waves in a simulated excitable system. In method A, an obstacle is set in the system prior to an ignition of a spiral wave. This method may be suitable only for the case of large obstacles since it often fails when used for small obstacles. In method B, a spiral wave is generated before an obstacle is placed at the spiral tip. With this method, a pinned spiral wave is always obtained, regardless the obstacle size. We demonstrate that after a transient interval the dynamics of the pinned spiral waves generated by the methods A and B are identical. The initiation of pinned spiral waves in both two- and three-dimensional systems is illustrated.

Ab initio RNA folding by discrete molecular dynamics: From structure prediction to folding mechanisms

PubMed Central

Ding, Feng; Sharma, Shantanu; Chalasani, Poornima; Demidov, Vadim V.; Broude, Natalia E.; Dokholyan, Nikolay V.

2008-01-01

RNA molecules with novel functions have revived interest in the accurate prediction of RNA three-dimensional (3D) structure and folding dynamics. However, existing methods are inefficient in automated 3D structure prediction. Here, we report a robust computational approach for rapid folding of RNA molecules. We develop a simplified RNA model for discrete molecular dynamics (DMD) simulations, incorporating base-pairing and base-stacking interactions. We demonstrate correct folding of 150 structurally diverse RNA sequences. The majority of DMD-predicted 3D structures have <4 Å deviations from experimental structures. The secondary structures corresponding to the predicted 3D structures consist of 94% native base-pair interactions. Folding thermodynamics and kinetics of tRNAPhe, pseudoknots, and mRNA fragments in DMD simulations are in agreement with previous experimental findings. Folding of RNA molecules features transient, non-native conformations, suggesting non-hierarchical RNA folding. Our method allows rapid conformational sampling of RNA folding, with computational time increasing linearly with RNA length. We envision this approach as a promising tool for RNA structural and functional analyses. PMID:18456842

Metamaterials beyond electromagnetism

NASA Astrophysics Data System (ADS)

Kadic, Muamer; Bückmann, Tiemo; Schittny, Robert; Wegener, Martin

2013-12-01

Metamaterials are rationally designed man-made structures composed of functional building blocks that are densely packed into an effective (crystalline) material. While metamaterials are mostly associated with negative refractive indices and invisibility cloaking in electromagnetism or optics, the deceptively simple metamaterial concept also applies to rather different areas such as thermodynamics, classical mechanics (including elastostatics, acoustics, fluid dynamics and elastodynamics), and, in principle, also to quantum mechanics. We review the basic concepts, analogies and differences to electromagnetism, and give an overview on the current state of the art regarding theory and experiment—all from the viewpoint of an experimentalist. This review includes homogeneous metamaterials as well as intentionally inhomogeneous metamaterial architectures designed by coordinate-transformation-based approaches analogous to transformation optics. Examples are laminates, transient thermal cloaks, thermal concentrators and inverters, ‘space-coiling’ metamaterials, anisotropic acoustic metamaterials, acoustic free-space and carpet cloaks, cloaks for gravitational surface waves, auxetic mechanical metamaterials, pentamode metamaterials (‘meta-liquids’), mechanical metamaterials with negative dynamic mass density, negative dynamic bulk modulus, or negative phase velocity, seismic metamaterials, cloaks for flexural waves in thin plates and three-dimensional elastostatic cloaks.

Three-Dimensional Subsurface Flow, Fate and Transport of Microbes and Chemicals (3DFATMIC) Model

EPA Pesticide Factsheets

This model simulates subsurface flow, fate and transport of contaminants that are undergoing chemical or biological transformations. The model is applicable to transient conditions in both saturated and unsaturated zones.

COMMIX-PPC: A three-dimensional transient multicomponent computer program for analyzing performance of power plant condensers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chien, T.H.; Domanus, H.M.; Sha, W.T.

1993-02-01

The COMMIX-PPC computer pregrain is an extended and improved version of earlier COMMIX codes and is specifically designed for evaluating the thermal performance of power plant condensers. The COMMIX codes are general-purpose computer programs for the analysis of fluid flow and heat transfer in complex Industrial systems. In COMMIX-PPC, two major features have been added to previously published COMMIX codes. One feature is the incorporation of one-dimensional equations of conservation of mass, momentum, and energy on the tube stile and the proper accounting for the thermal interaction between shell and tube side through the porous-medium approach. The other added featuremore » is the extension of the three-dimensional conservation equations for shell-side flow to treat the flow of a multicomponent medium. COMMIX-PPC is designed to perform steady-state and transient. Three-dimensional analysis of fluid flow with heat transfer tn a power plant condenser. However, the code is designed in a generalized fashion so that, with some modification, it can be used to analyze processes in any heat exchanger or other single-phase engineering applications. Volume I (Equations and Numerics) of this report describes in detail the basic equations, formulation, solution procedures, and models for a phenomena. Volume II (User's Guide and Manual) contains the input instruction, flow charts, sample problems, and descriptions of available options and boundary conditions.« less

Preliminary Results for the OECD/NEA Time Dependent Benchmark using Rattlesnake, Rattlesnake-IQS and TDKENO

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeHart, Mark D.; Mausolff, Zander; Weems, Zach

2016-08-01

One goal of the MAMMOTH M&S project is to validate the analysis capabilities within MAMMOTH. Historical data has shown limited value for validation of full three-dimensional (3D) multi-physics methods. Initial analysis considered the TREAT startup minimum critical core and one of the startup transient tests. At present, validation is focusing on measurements taken during the M8CAL test calibration series. These exercises will valuable in preliminary assessment of the ability of MAMMOTH to perform coupled multi-physics calculations; calculations performed to date are being used to validate the neutron transport solver Rattlesnake\\cite{Rattlesnake} and the fuels performance code BISON. Other validation projects outsidemore » of TREAT are available for single-physics benchmarking. Because the transient solution capability of Rattlesnake is one of the key attributes that makes it unique for TREAT transient simulations, validation of the transient solution of Rattlesnake using other time dependent kinetics benchmarks has considerable value. The Nuclear Energy Agency (NEA) of the Organization for Economic Cooperation and Development (OECD) has recently developed a computational benchmark for transient simulations. This benchmark considered both two-dimensional (2D) and 3D configurations for a total number of 26 different transients. All are negative reactivity insertions, typically returning to the critical state after some time.« less

Watching hydrogen-bond dynamics in a β-turn by transient two-dimensional infrared spectroscopy

NASA Astrophysics Data System (ADS)

Kolano, Christoph; Helbing, Jan; Kozinski, Mariusz; Sander, Wolfram; Hamm, Peter

2006-11-01

X-ray crystallography and nuclear magnetic resonance measurements provide us with atomically resolved structures of an ever-growing number of biomolecules. These static structural snapshots are important to our understanding of biomolecular function, but real biomolecules are dynamic entities that often exploit conformational changes and transient molecular interactions to perform their tasks. Nuclear magnetic resonance methods can follow such structural changes, but only on millisecond timescales under non-equilibrium conditions. Time-resolved X-ray crystallography has recently been used to monitor the photodissociation of CO from myoglobin on a subnanosecond timescale, yet remains challenging to apply more widely. In contrast, two-dimensional infrared spectroscopy, which maps vibrational coupling between molecular groups and hence their relative positions and orientations, is now routinely used to study equilibrium processes on picosecond timescales. Here we show that the extension of this method into the non-equilibrium regime allows us to observe in real time in a short peptide the weakening of an intramolecular hydrogen bond and concomitant opening of a β-turn. We find that the rate of this process is two orders of magnitude faster than the `folding speed limit' established for contact formation between protein side chains.

Linking a one-dimensional pesticide fate model to a three-dimensional groundwater model to simulate pollution risks of shallow and deep groundwater underlying fractured till.

PubMed

Stenemo, Fredrik; Jørgensen, Peter R; Jarvis, Nicholas

2005-09-01

The one-dimensional pesticide fate model MACRO was loose-linked to the three-dimensional discrete fracture/matrix diffusion model FRAC3DVS to describe transport of the pesticide mecoprop in a fractured moraine till and local sand aquifer (5-5.5 m depth) overlying a regional limestone aquifer (16 m depth) at Havdrup, Denmark. Alternative approaches to describe the upper boundary in the groundwater model were examined. Field-scale simulations were run to compare a uniform upper boundary condition with a spatially variable upper boundary derived from Monte-Carlo simulations with MACRO. Plot-scale simulations were run to investigate the influence of the temporal resolution of the upper boundary conditions for fluxes in the groundwater model and the effects of different assumptions concerning the macropore/fracture connectivity between the two models. The influence of within-field variability of leaching on simulated mecoprop concentrations in the local aquifer was relatively small. A fully transient simulation with FRAC3DVS gave 20 times larger leaching to the regional aquifer compared to the case with steady-state water flow, assuming full connectivity with respect to macropores/fractures across the boundary between the two models. For fully transient simulations 'disconnecting' the macropores/fractures at the interface between the two models reduced leaching by a factor 24. A fully connected, transient simulation with FRAC3DVS, with spatially uniform upper boundary fluxes derived from a MACRO simulation with 'effective' parameters is therefore recommended for assessing leaching risks to the regional aquifer, at this, and similar sites.

One-Dimensional Singlet Exciton Diffusion in Poly(3-hexylthiophene) Crystalline Domains.

PubMed

Tamai, Yasunari; Matsuura, Yuu; Ohkita, Hideo; Benten, Hiroaki; Ito, Shinzaburo

2014-01-16

Singlet exciton dynamics in crystalline domains of regioregular poly(3-hexylthiophene) (P3HT) films was studied by transient absorption spectroscopy. Upon the selective excitation of crystalline P3HT at the absorption edge, no red shift of the singlet exciton band was observed with an elapse of time, suggesting singlet exciton dynamics in relatively homogeneous P3HT crystalline domains without downhill relaxation in the energetic disorder. Even under such selective excitation conditions, the annihilation rate coefficient γ(t) was still dependent on time, γ(t) ∝ t(-1/2), which is attributed to anisotropic exciton diffusion in P3HT crystalline domains. From the annihilation rate coefficient, the singlet exciton diffusion coefficient D and exciton diffusion length LD in the crystalline domains were evaluated to be 7.9 × 10(-3) cm(2) s(-1) and 20 nm, respectively. The origin of the time-dependent exciton dynamics is discussed in terms of dimensionality.

Advanced numerical methods for three dimensional two-phase flow calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toumi, I.; Caruge, D.

1997-07-01

This paper is devoted to new numerical methods developed for both one and three dimensional two-phase flow calculations. These methods are finite volume numerical methods and are based on the use of Approximate Riemann Solvers concepts to define convective fluxes versus mean cell quantities. The first part of the paper presents the numerical method for a one dimensional hyperbolic two-fluid model including differential terms as added mass and interface pressure. This numerical solution scheme makes use of the Riemann problem solution to define backward and forward differencing to approximate spatial derivatives. The construction of this approximate Riemann solver uses anmore » extension of Roe`s method that has been successfully used to solve gas dynamic equations. As far as the two-fluid model is hyperbolic, this numerical method seems very efficient for the numerical solution of two-phase flow problems. The scheme was applied both to shock tube problems and to standard tests for two-fluid computer codes. The second part describes the numerical method in the three dimensional case. The authors discuss also some improvements performed to obtain a fully implicit solution method that provides fast running steady state calculations. Such a scheme is not implemented in a thermal-hydraulic computer code devoted to 3-D steady-state and transient computations. Some results obtained for Pressurised Water Reactors concerning upper plenum calculations and a steady state flow in the core with rod bow effect evaluation are presented. In practice these new numerical methods have proved to be stable on non staggered grids and capable of generating accurate non oscillating solutions for two-phase flow calculations.« less

Three-dimensional modeling of the plasma arc in arc welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, G.; Tsai, H. L.; Hu, J.

2008-11-15

Most previous three-dimensional modeling on gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) focuses on the weld pool dynamics and assumes the two-dimensional axisymmetric Gaussian distributions for plasma arc pressure and heat flux. In this article, a three-dimensional plasma arc model is developed, and the distributions of velocity, pressure, temperature, current density, and magnetic field of the plasma arc are calculated by solving the conservation equations of mass, momentum, and energy, as well as part of the Maxwell's equations. This three-dimensional model can be used to study the nonaxisymmetric plasma arc caused by external perturbations such asmore » an external magnetic field. It also provides more accurate boundary conditions when modeling the weld pool dynamics. The present work lays a foundation for true three-dimensional comprehensive modeling of GTAW and GMAW including the plasma arc, weld pool, and/or electrode.« less

Computational technique and performance of Transient Inundation Model for Rivers--2 Dimensional (TRIM2RD) : a depth-averaged two-dimensional flow model

USGS Publications Warehouse

Fulford, Janice M.

2003-01-01

A numerical computer model, Transient Inundation Model for Rivers -- 2 Dimensional (TrimR2D), that solves the two-dimensional depth-averaged flow equations is documented and discussed. The model uses a semi-implicit, semi-Lagrangian finite-difference method. It is a variant of the Trim model and has been used successfully in estuarine environments such as San Francisco Bay. The abilities of the model are documented for three scenarios: uniform depth flows, laboratory dam-break flows, and large-scale riverine flows. The model can start computations from a ?dry? bed and converge to accurate solutions. Inflows are expressed as source terms, which limits the use of the model to sufficiently long reaches where the flow reaches equilibrium with the channel. The data sets used by the investigation demonstrate that the model accurately propagates flood waves through long river reaches and simulates dam breaks with abrupt water-surface changes.

A smoothed particle hydrodynamics model for droplet and film flow on smooth and rough fracture surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kordilla, Jannes; Tartakovsky, Alexandre M.; Geyer, Tobias

2013-09-01

Flow on fracture surfaces has been identified by many authors as an important flow process in unsaturated fractured rock formations. Given the complexity of flow dynamics on such small scales, robust numerical methods have to be employed in order to capture the highly dynamic interfaces and flow intermittency. In this work we present microscale free-surface flow simulations using a three-dimensional multiphase Smoothed Particle Hydrodynamics (SPH) code. Pairwise solid-fluid and fluid-fluid interaction forces are used to control the wetting behavior and cover a wide range of static and transient contact angles as well as Reynolds numbers encountered in droplet flow onmore » rock surfaces. We validate our model via comparison with existing empirical and semi-analyical solutions for droplet flow. We use the model to investigate the occurence of adsorbed trailing films of droplets under various flow conditions and its importance for the flow dynamics when films and droplets coexist. We show that flow velocities are higher on prewetted surfaces covered by a thin film which is qualitatively attributed to the enhanced dynamic wetting and dewetting at the trailing and advancing contact line.« less

Modeling Primary Breakup: A Three-Dimensional Eulerian Level Set/Vortex Sheet Method for Two-Phase Interface Dynamics

NASA Technical Reports Server (NTRS)

Herrmann, M.

2003-01-01

This paper is divided into four parts. First, the level set/vortex sheet method for three-dimensional two-phase interface dynamics is presented. Second, the LSS model for the primary breakup of turbulent liquid jets and sheets is outlined and all terms requiring subgrid modeling are identified. Then, preliminary three-dimensional results of the level set/vortex sheet method are presented and discussed. Finally, conclusions are drawn and an outlook to future work is given.

Conjugate Compressible Fluid Flow and Heat Transfer in Ducts

NASA Technical Reports Server (NTRS)

Cross, M. F.

2011-01-01

A computational approach to modeling transient, compressible fluid flow with heat transfer in long, narrow ducts is presented. The primary application of the model is for analyzing fluid flow and heat transfer in solid propellant rocket motor nozzle joints during motor start-up, but the approach is relevant to a wide range of analyses involving rapid pressurization and filling of ducts. Fluid flow is modeled through solution of the spatially one-dimensional, transient Euler equations. Source terms are included in the governing equations to account for the effects of wall friction and heat transfer. The equation solver is fully-implicit, thus providing greater flexibility than an explicit solver. This approach allows for resolution of pressure wave effects on the flow as well as for fast calculation of the steady-state solution when a quasi-steady approach is sufficient. Solution of the one-dimensional Euler equations with source terms significantly reduces computational run times compared to general purpose computational fluid dynamics packages solving the Navier-Stokes equations with resolved boundary layers. In addition, conjugate heat transfer is more readily implemented using the approach described in this paper than with most general purpose computational fluid dynamics packages. The compressible flow code has been integrated with a transient heat transfer solver to analyze heat transfer between the fluid and surrounding structure. Conjugate fluid flow and heat transfer solutions are presented. The author is unaware of any previous work available in the open literature which uses the same approach described in this paper.

Application of the finite element groundwater model FEWA to the engineered test facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Craig, P.M.; Davis, E.C.

1985-09-01

A finite element model for water transport through porous media (FEWA) has been applied to the unconfined aquifer at the Oak Ridge National Laboratory Solid Waste Storage Area 6 Engineered Test Facility (ETF). The model was developed in 1983 as part of the Shallow Land Burial Technology - Humid Task (ONL-WL14) and was previously verified using several general hydrologic problems for which an analytic solution exists. Model application and calibration, as described in this report, consisted of modeling the ETF water table for three specialized cases: a one-dimensional steady-state simulation, a one-dimensional transient simulation, and a two-dimensional transient simulation. Inmore » the one-dimensional steady-state simulation, the FEWA output accurately predicted the water table during a long period in which there were no man-induced or natural perturbations to the system. The input parameters of most importance for this case were hydraulic conductivity and aquifer bottom elevation. In the two transient cases, the FEWA output has matched observed water table responses to a single rainfall event occurring in February 1983, yielding a calibrated finite element model that is useful for further study of additional precipitation events as well as contaminant transport at the experimental site.« less

Ultrafast Band Engineering and Transient Spin Currents in Antiferromagnetic Oxides

NASA Astrophysics Data System (ADS)

Gu, Mingqiang; Rondinelli, James M.

2016-04-01

We report a dynamic structure and band engineering strategy with experimental protocols to induce indirect-to-direct band gap transitions and coherently oscillating pure spin-currents in three-dimensional antiferromagnets (AFM) using selective phononic excitations. In the Mott insulator LaTiO3, we show that a photo-induced nonequilibrium phonon mode amplitude destroys the spin and orbitally degenerate ground state, reduces the band gap by 160 meV and renormalizes the carrier masses. The time scale of this process is a few hundreds of femtoseconds. Then in the hole-doped correlated metallic titanate, we show how pure spin-currents can be achieved to yield spin-polarizations exceeding those observed in classic semiconductors. Last, we demonstrate the generality of the approach by applying it to the non-orbitally degenerate AFM CaMnO3. These results advance our understanding of electron-lattice interactions in structures out-of-equilibrium and establish a rational framework for designing dynamic phases that may be exploited in ultrafast optoelectronic and optospintronic devices.

Ultrafast Band Engineering and Transient Spin Currents in Antiferromagnetic Oxides.

PubMed

Gu, Mingqiang; Rondinelli, James M

2016-04-29

We report a dynamic structure and band engineering strategy with experimental protocols to induce indirect-to-direct band gap transitions and coherently oscillating pure spin-currents in three-dimensional antiferromagnets (AFM) using selective phononic excitations. In the Mott insulator LaTiO3, we show that a photo-induced nonequilibrium phonon mode amplitude destroys the spin and orbitally degenerate ground state, reduces the band gap by 160 meV and renormalizes the carrier masses. The time scale of this process is a few hundreds of femtoseconds. Then in the hole-doped correlated metallic titanate, we show how pure spin-currents can be achieved to yield spin-polarizations exceeding those observed in classic semiconductors. Last, we demonstrate the generality of the approach by applying it to the non-orbitally degenerate AFM CaMnO3. These results advance our understanding of electron-lattice interactions in structures out-of-equilibrium and establish a rational framework for designing dynamic phases that may be exploited in ultrafast optoelectronic and optospintronic devices.

Ultrafast band engineering and transient spin currents in antiferromagnetic oxides

DOE PAGES

Gu, Mingqiang; Rondinelli, James M.

2016-04-29

Here, we report a dynamic structure and band engineering strategy with experimental protocols to induce indirect-to-direct band gap transitions and coherently oscillating pure spin-currents in three-dimensional antiferromagnets (AFM) using selective phononic excitations. In the Mott insulator LaTiO 3, we show that a photo-induced nonequilibrium phonon mode amplitude destroys the spin and orbitally degenerate ground state, reduces the band gap by 160 meV and renormalizes the carrier masses. The time scale of this process is a few hundreds of femtoseconds. Then in the hole-doped correlated metallic titanate, we show how pure spin-currents can be achieved to yield spin-polarizations exceeding those observedmore » in classic semiconductors. Last, we demonstrate the generality of the approach by applying it to the non-orbitally degenerate AFM CaMnO 3. These results advance our understanding of electron-lattice interactions in structures out-of-equilibrium and establish a rational framework for designing dynamic phases that may be exploited in ultrafast optoelectronic and optospintronic devices.« less

Investigation of corner shock boundary layer interactions to understand inlet unstart

NASA Astrophysics Data System (ADS)

Funderburk, Morgan

2015-11-01

Inlet unstart is a detrimental phenomenon in dual-mode ramjet/scramjet engines that causes severe loss of thrust, large transient structural load, and potentially a loss of the aircraft. In order to analyze the effects that the corner shock boundary layer interaction (SBLI) has on initiating and perpetuating inlet unstart, a qualitative and quantitative investigation into mean and dynamic features of corner SBLI at various Mach numbers is made. Surface streakline visualization showed that the corner SBLI is highly three-dimensional with a dominant presence of corner separation vortex. Further, the peak r.m.s. pressure was located at the periphery of corner separation vortex, suggesting that the unsteady loading is caused by the corner vortex. Power spectral densities of wall-pressure fluctuations in the peak r.m.s. location were analyzed in order to characterize the dominant frequencies of oscillation of the flow structures and to unravel the dynamic interactions between them in order to expand the operating margin of future hypersonic air breathing vehicles.

Ultrafast Band Engineering and Transient Spin Currents in Antiferromagnetic Oxides

PubMed Central

Gu, Mingqiang; Rondinelli, James M.

2016-01-01

We report a dynamic structure and band engineering strategy with experimental protocols to induce indirect-to-direct band gap transitions and coherently oscillating pure spin-currents in three-dimensional antiferromagnets (AFM) using selective phononic excitations. In the Mott insulator LaTiO3, we show that a photo-induced nonequilibrium phonon mode amplitude destroys the spin and orbitally degenerate ground state, reduces the band gap by 160 meV and renormalizes the carrier masses. The time scale of this process is a few hundreds of femtoseconds. Then in the hole-doped correlated metallic titanate, we show how pure spin-currents can be achieved to yield spin-polarizations exceeding those observed in classic semiconductors. Last, we demonstrate the generality of the approach by applying it to the non-orbitally degenerate AFM CaMnO3. These results advance our understanding of electron-lattice interactions in structures out-of-equilibrium and establish a rational framework for designing dynamic phases that may be exploited in ultrafast optoelectronic and optospintronic devices. PMID:27126354

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aleman, S.E.

This report documents a finite element code designed to model subsurface flow and contaminant transport, named FACT. FACT is a transient three-dimensional, finite element code designed to simulate isothermal groundwater flow, moisture movement, and solute transport in variably saturated and fully saturated subsurface porous media.

The Multi-Dimensional Structure of Radiative Shocks: Suppressed Thermal X-rays and Relativistic Ion Acceleration

NASA Astrophysics Data System (ADS)

Steinberg, Elad; Metzger, Brian D.

2018-06-01

Radiative shocks, behind which gas cools faster than the dynamical time, play a key role in many astrophysical transients, including classical novae and young supernovae interacting with circumstellar material. The dense layer behind high Mach number M ≫ 1 radiative shocks is susceptible to thin-shell instabilities, creating a "corrugated" shock interface. We present two and three-dimensional hydrodynamical simulations of optically-thin radiative shocks to study their thermal radiation and acceleration of non-thermal relativistic ions. We employ a moving-mesh code and a specialized numerical technique to eliminate artificial heat conduction across grid cells. The fraction of the shock's luminosity Ltot radiated at X-ray temperatures kT_sh ≈ (3/16)μ m_p v_sh2 expected from a one-dimensional analysis is suppressed by a factor L(>T_sh/3)/L_tot ≈ 4.5/M^{4/3} for M ≈ 4-36. This suppression results in part from weak shocks driven into under-pressured cold filaments by hot shocked gas, which sap thermal energy from the latter faster than it is radiated. Combining particle-in-cell simulation results for diffusive shock acceleration with the inclination angle distribution across the shock (relative to an upstream magnetic field in the shock plane-the expected geometry for transient outflows), we predict the efficiency and energy spectrum of ion acceleration. Though negligible acceleration is predicted for adiabatic shocks, the corrugated shock front enables local regions to satisfy the quasi-parallel magnetic field geometry required for efficient acceleration, resulting in an average acceleration efficiency of ɛnth ˜ 0.005 - 0.02 for M ≈ 12-36, in agreement with modeling of the gamma-ray nova ASASSN-16ma.

Mapping the dynamics of brain perfusion using functional ultrasound in a rat model of transient middle cerebral artery occlusion

PubMed Central

Brunner, Clément; Isabel, Clothilde; Martin, Abraham; Dussaux, Clara; Savoye, Anne; Emmrich, Julius; Montaldo, Gabriel; Mas, Jean-Louis; Urban, Alan

2015-01-01

Following middle cerebral artery occlusion, tissue outcome ranges from normal to infarcted depending on depth and duration of hypoperfusion as well as occurrence and efficiency of reperfusion. However, the precise time course of these changes in relation to tissue and behavioral outcome remains unsettled. To address these issues, a three-dimensional wide field-of-view and real-time quantitative functional imaging technique able to map perfusion in the rodent brain would be desirable. Here, we applied functional ultrasound imaging, a novel approach to map relative cerebral blood volume without contrast agent, in a rat model of brief proximal transient middle cerebral artery occlusion to assess perfusion in penetrating arterioles and venules acutely and over six days thanks to a thinned-skull preparation. Functional ultrasound imaging efficiently mapped the acute changes in relative cerebral blood volume during occlusion and following reperfusion with high spatial resolution (100 µm), notably documenting marked focal decreases during occlusion, and was able to chart the fine dynamics of tissue reperfusion (rate: one frame/5 s) in the individual rat. No behavioral and only mild post-mortem immunofluorescence changes were observed. Our study suggests functional ultrasound is a particularly well-adapted imaging technique to study cerebral perfusion in acute experimental stroke longitudinally from the hyper-acute up to the chronic stage in the same subject. PMID:26721392

An 8-node tetrahedral finite element suitable for explicit transient dynamic simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Key, S.W.; Heinstein, M.W.; Stone, C.M.

1997-12-31

Considerable effort has been expended in perfecting the algorithmic properties of 8-node hexahedral finite elements. Today the element is well understood and performs exceptionally well when used in modeling three-dimensional explicit transient dynamic events. However, the automatic generation of all-hexahedral meshes remains an elusive achievement. The alternative of automatic generation for all-tetrahedral finite element is a notoriously poor performer, and the 10-node quadratic tetrahedral finite element while a better performer numerically is computationally expensive. To use the all-tetrahedral mesh generation extant today, the authors have explored the creation of a quality 8-node tetrahedral finite element (a four-node tetrahedral finite elementmore » enriched with four midface nodal points). The derivation of the element`s gradient operator, studies in obtaining a suitable mass lumping and the element`s performance in applications are presented. In particular, they examine the 80node tetrahedral finite element`s behavior in longitudinal plane wave propagation, in transverse cylindrical wave propagation, and in simulating Taylor bar impacts. The element only samples constant strain states and, therefore, has 12 hourglass modes. In this regard, it bears similarities to the 8-node, mean-quadrature hexahedral finite element. Given automatic all-tetrahedral meshing, the 8-node, constant-strain tetrahedral finite element is a suitable replacement for the 8-node hexahedral finite element and handbuilt meshes.« less

An investigation of lithium-ion battery thermal management using paraffin/porous-graphite-matrix composite

NASA Astrophysics Data System (ADS)

Greco, Angelo; Jiang, Xi; Cao, Dongpu

2015-03-01

The thermal management of a cylindrical battery cell by a phase change material (PCM)/compressed expanded natural graphite (CENG) is investigated in this study. The transient thermal behaviour of both the battery and the PCM/CENG is described with a simplified one-dimensional model taking into account the physical and phase change properties of the PCM/CENG composite. The 1D analytical/computational model yielded nearly identical results to the three-dimensional simulation results for various cooling strategies. Therefore, the 1D model is sufficient to describe the transient behaviour of the battery cooled by a PCM/CENG composite. Moreover, the maximum temperature reached by the PCM/CENG cooling strategy is much lower than that by the forced convection in the same configuration. In the test case studied, the PCM showed superior transient characteristics to forced convection cooling. The PCM cooling is able to maintain a lower maximum temperature during the melting process and to extend the transient time for temperature rise. Furthermore, the graphite-matrix bulk density is identified as an important parameter for optimising the PCM/CENG cooling strategy.

An Approach for Dynamic Grids

NASA Technical Reports Server (NTRS)

Slater, John W.; Liou, Meng-Sing; Hindman, Richard G.

1994-01-01

An approach is presented for the generation of two-dimensional, structured, dynamic grids. The grid motion may be due to the motion of the boundaries of the computational domain or to the adaptation of the grid to the transient, physical solution. A time-dependent grid is computed through the time integration of the grid speeds which are computed from a system of grid speed equations. The grid speed equations are derived from the time-differentiation of the grid equations so as to ensure that the dynamic grid maintains the desired qualities of the static grid. The grid equations are the Euler-Lagrange equations derived from a variational statement for the grid. The dynamic grid method is demonstrated for a model problem involving boundary motion, an inviscid flow in a converging-diverging nozzle during startup, and a viscous flow over a flat plate with an impinging shock wave. It is shown that the approach is more accurate for transient flows than an approach in which the grid speeds are computed using a finite difference with respect to time of the grid. However, the approach requires significantly more computational effort.

Data center thermal management

DOEpatents

Hamann, Hendrik F.; Li, Hongfei

2016-02-09

Historical high-spatial-resolution temperature data and dynamic temperature sensor measurement data may be used to predict temperature. A first formulation may be derived based on the historical high-spatial-resolution temperature data for determining a temperature at any point in 3-dimensional space. The dynamic temperature sensor measurement data may be calibrated based on the historical high-spatial-resolution temperature data at a corresponding historical time. Sensor temperature data at a plurality of sensor locations may be predicted for a future time based on the calibrated dynamic temperature sensor measurement data. A three-dimensional temperature spatial distribution associated with the future time may be generated based on the forecasted sensor temperature data and the first formulation. The three-dimensional temperature spatial distribution associated with the future time may be projected to a two-dimensional temperature distribution, and temperature in the future time for a selected space location may be forecasted dynamically based on said two-dimensional temperature distribution.

Dynamics of diffusive bubble growth and pressure recovery in a bubbly rhyolitic melt embedded in an elastic solid

USGS Publications Warehouse

Chouet, Bernard A.; Dawson, Phillip B.; Nakano, Masaru

2006-01-01

We present a model of gas exsolution and bubble expansion in a melt supersaturated in response to a sudden pressure drop. In our model, the melt contains a suspension of gas bubbles of identical sizes and is encased in a penny-shaped crack embedded in an elastic solid. The suspension is modeled as a three-dimensional lattice of spherical cells with slight overlap, where each elementary cell consists of a gas bubble surrounded by a shell of volatile-rich melt. The melt is then subjected to a step drop in pressure, which induces gas exsolution and bubble expansion, resulting in the compression of the melt and volumetric expansion of the crack. The dynamics of diffusion-driven bubble growth and volumetric crack expansion span 9 decades in time. The model demonstrates that the speed of the crack response depends strongly on volatile diffusivity in the melt and bubble number density and is markedly sensitive to the ratio of crack thickness to crack radius and initial bubble radius but is relatively insensitive to melt viscosity. The net drop in gas concentration in the melt after pressure recovery represents only a small fraction of the initial concentration prior to the drop, suggesting the melt may undergo numerous pressure transients before becoming significantly depleted of gases. The magnitude of pressure and volume recovery in the crack depends sensitively on the size of the input-pressure transient, becoming relatively larger for smaller-size transients in a melt containing bubbles with initial radii less than 10-5 m. Amplification of the input transient may be large enough to disrupt the crack wall and induce brittle failure in the rock matrix surrounding the crack. Our results provide additional basis for the interpretation of volume changes in the magma conduit under Popocatépetl Volcano during Vulcanian degassing bursts in its eruptive activity in April–May 2000.

Transient Three-Dimensional Startup Side Load Analysis of a Regeneratively Cooled Nozzle

NASA Technical Reports Server (NTRS)

Wang, Ten-See

2008-01-01

The objective of this effort is to develop a computational methodology to capture the startup side load physics and to anchor the computed aerodynamic side loads with the available data from a regeneratively cooled, high-aspect-ratio nozzle, hot-fired at sea level. The computational methodology is based on an unstructured-grid, pressure-based, reacting flow computational fluid dynamics and heat transfer formulation, a transient 5 s inlet history based on an engine system simulation, and a wall temperature distribution to reflect the effect of regenerative cooling. To understand the effect of regenerative wall cooling, two transient computations were performed using the boundary conditions of adiabatic and cooled walls, respectively. The results show that three types of shock evolution are responsible for side loads: generation of combustion wave; transitions among free-shock separation, restricted-shock separation, and simultaneous free-shock and restricted shock separations; along with the pulsation of shocks across the lip, although the combustion wave is commonly eliminated with the sparklers during actual test. The test measured two side load events: a secondary and lower side load, followed by a primary and peak side load. Results from both wall boundary conditions captured the free-shock separation to restricted-shock separation transition with computed side loads matching the measured secondary side load. For the primary side load, the cooled wall transient produced restricted-shock pulsation across the nozzle lip with peak side load matching that of the test, while the adiabatic wall transient captured shock transitions and free-shock pulsation across the lip with computed peak side load 50% lower than that of the measurement. The computed dominant pulsation frequency of the cooled wall nozzle agrees with that of a separate test, while that of the adiabatic wall nozzle is more than 50% lower than that of the measurement. The computed teepee-like formation and the tangential motion of the shocks during lip pulsation also qualitatively agree with those of test observations. Moreover, a third transient computation was performed with a proportionately shortened 1 s sequence, and lower side loads were obtained with the higher ramp rate.

Physical characteristics and dynamics of the coastal Latex09 Eddy derived from in situ data and numerical modeling

NASA Astrophysics Data System (ADS)

Kersalé, M.; Petrenko, A. A.; Doglioli, A. M.; Dekeyser, I.; Nencioli, F.

2013-01-01

investigate the dynamics of a coastal anticyclonic eddy in the western part of the Gulf of Lion (GoL) in the northwestern Mediterranean Sea during the Latex campaign in the summer 2009 (Latex09). The sampling strategy combines sea surface temperature satellite imagery, hull-mounted acoustic Doppler current profiler data, conductivity-temperature-depth casts, and drifter trajectories. Our measurements reveal an anticyclonic eddy (Latex09 eddy) with a diameter of 23 km and maximum depth of 31 m, centered at 3°34'E, 42°33'N. We use a high resolution, three-dimensional, primitive equation numerical model to investigate its generation process and evolution. The model is able to reproduce the observed eddy, in particular its size and position. The model results suggest that the Latex09 eddy is induced by a large anticyclonic circulation in the northwestern part of the GoL, pushed and squeezed toward the coast by a meander of the Northern Current. This represents a new generation mechanism that has not been reported before. The post generation dynamics of the eddy is also captured by the model. The collision of the Latex09 eddy with Cape Creus results in a transient structure, which is depicted by the trajectories of two Lagrangian drifters during Latex09. The transient structure and its advection lead to a transfer of mass and vorticity from the GoL to the Catalan shelf, indicating the importance of mesoscale structures in modulating such exchanges in the region.

Incorporation of Failure Into an Orthotropic Three-Dimensional Model with Tabulated Input Suitable for Use in Composite Impact Problems

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Carney, Kelly S.; Dubois, Paul; Hoffarth, Canio; Khaled, Bilal; Shyamsunder, Loukham; Rajan, Subramaniam; Blankenhorn, Gunther

2017-01-01

The need for accurate material models to simulate the deformation, damage and failure of polymer matrix composites under impact conditions is becoming critical as these materials are gaining increased use in the aerospace and automotive communities. The aerospace community has identified several key capabilities which are currently lacking in the available material models in commercial transient dynamic finite element codes. To attempt to improve the predictive capability of composite impact simulations, a next generation material model is being developed for incorporation within the commercial transient dynamic finite element code LS-DYNA. The material model, which incorporates plasticity, damage and failure, utilizes experimentally based tabulated input to define the evolution of plasticity and damage and the initiation of failure as opposed to specifying discrete input parameters such as modulus and strength. The plasticity portion of the orthotropic, three-dimensional, macroscopic composite constitutive model is based on an extension of the Tsai-Wu composite failure model into a generalized yield function with a non-associative flow rule. For the damage model, a strain equivalent formulation is used to allow for the uncoupling of the deformation and damage analyses. In the damage model, a semi-coupled approach is employed where the overall damage in a particular coordinate direction is assumed to be a multiplicative combination of the damage in that direction resulting from the applied loads in various coordinate directions. For the failure model, a tabulated approach is utilized in which a stress or strain based invariant is defined as a function of the location of the current stress state in stress space to define the initiation of failure. Failure surfaces can be defined with any arbitrary shape, unlike traditional failure models where the mathematical functions used to define the failure surface impose a specific shape on the failure surface. In the current paper, the complete development of the failure model is described and the generation of a tabulated failure surface for a representative composite material is discussed.

Two-and three-dimensional unsteady lift problems in high-speed flight

NASA Technical Reports Server (NTRS)

Lomax, Harvard; Heaslet, Max A; Fuller, Franklyn B; Sluder, Loma

1952-01-01

The problem of transient lift on two- and three-dimensional wings flying at high speeds is discussed as a boundary-value problem for the classical wave equation. Kirchoff's formula is applied so that the analysis is reduced, just as in the steady state, to an investigation of sources and doublets. The applications include the evaluation of indicial lift and pitching-moment curves for two-dimensional sinking and pitching wings flying at Mach numbers equal to 0, 0.8, 1.0, 1.2 and 2.0. Results for the sinking case are also given for a Mach number of 0.5. In addition, the indicial functions for supersonic-edged triangular wings in both forward and reverse flow are presented and compared with the two-dimensional values.

Three-Dimensional Finite Element Ablative Thermal Response and Thermostructural Design of Thermal Protection Systems

NASA Technical Reports Server (NTRS)

Dec, John A.; Braun, Robert D.

2011-01-01

A finite element ablation and thermal response program is presented for simulation of three-dimensional transient thermostructural analysis. The three-dimensional governing differential equations and finite element formulation are summarized. A novel probabilistic design methodology for thermal protection systems is presented. The design methodology is an eight step process beginning with a parameter sensitivity study and is followed by a deterministic analysis whereby an optimum design can determined. The design process concludes with a Monte Carlo simulation where the probabilities of exceeding design specifications are estimated. The design methodology is demonstrated by applying the methodology to the carbon phenolic compression pads of the Crew Exploration Vehicle. The maximum allowed values of bondline temperature and tensile stress are used as the design specifications in this study.

Three-dimensional Bayesian geostatistical aquifer characterization at the Hanford 300 Area using tracer test data

NASA Astrophysics Data System (ADS)

Chen, Xingyuan; Murakami, Haruko; Hahn, Melanie S.; Hammond, Glenn E.; Rockhold, Mark L.; Zachara, John M.; Rubin, Yoram

2012-06-01

Tracer tests performed under natural or forced gradient flow conditions can provide useful information for characterizing subsurface properties, through monitoring, modeling, and interpretation of the tracer plume migration in an aquifer. Nonreactive tracer experiments were conducted at the Hanford 300 Area, along with constant-rate injection tests and electromagnetic borehole flowmeter tests. A Bayesian data assimilation technique, the method of anchored distributions (MAD) (Rubin et al., 2010), was applied to assimilate the experimental tracer test data with the other types of data and to infer the three-dimensional heterogeneous structure of the hydraulic conductivity in the saturated zone of the Hanford formation.In this study, the Bayesian prior information on the underlying random hydraulic conductivity field was obtained from previous field characterization efforts using constant-rate injection and borehole flowmeter test data. The posterior distribution of the conductivity field was obtained by further conditioning the field on the temporal moments of tracer breakthrough curves at various observation wells. MAD was implemented with the massively parallel three-dimensional flow and transport code PFLOTRAN to cope with the highly transient flow boundary conditions at the site and to meet the computational demands of MAD. A synthetic study proved that the proposed method could effectively invert tracer test data to capture the essential spatial heterogeneity of the three-dimensional hydraulic conductivity field. Application of MAD to actual field tracer data at the Hanford 300 Area demonstrates that inverting for spatial heterogeneity of hydraulic conductivity under transient flow conditions is challenging and more work is needed.

Band structure dynamics in indium wires

NASA Astrophysics Data System (ADS)

Chávez-Cervantes, M.; Krause, R.; Aeschlimann, S.; Gierz, I.

2018-05-01

One-dimensional indium wires grown on Si(111) substrates, which are metallic at high temperatures, become insulating below ˜100 K due to the formation of a charge density wave (CDW). The physics of this transition is not conventional and involves a multiband Peierls instability with strong interband coupling. This CDW ground state is readily destroyed with femtosecond laser pulses resulting in a light-induced insulator-to-metal phase transition. The current understanding of this transition remains incomplete, requiring measurements of the transient electronic structure to complement previous investigations of the lattice dynamics. Time- and angle-resolved photoemission spectroscopy with extreme ultraviolet radiation is applied to this end. We find that the transition from the insulating to the metallic band structure occurs within ˜660 fs, which is a fraction of the amplitude mode period. The long lifetime of the transient state (>100 ps) is attributed to trapping in a metastable state in accordance with previous work.

High spatial resolution three-dimensional mapping of vegetation spectral dynamics using computer vision

Treesearch

Jonathan P. Dandois; Erle C. Ellis

2013-01-01

High spatial resolution three-dimensional (3D) measurements of vegetation by remote sensing are advancing ecological research and environmental management. However, substantial economic and logistical costs limit this application, especially for observing phenological dynamics in ecosystem structure and spectral traits. Here we demonstrate a new aerial remote sensing...

Nonlocal continuous models for forced vibration analysis of two- and three-dimensional ensembles of single-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Kiani, Keivan

2014-06-01

Novel nonlocal discrete and continuous models are proposed for dynamic analysis of two- and three-dimensional ensembles of single-walled carbon nanotubes (SWCNTs). The generated extra van der Waals forces between adjacent SWCNTs due to their lateral motions are evaluated via Lennard-Jones potential function. Using a nonlocal Rayleigh beam model, the discrete and continuous models are developed for both two- and three-dimensional ensembles of SWCNTs acted upon by transverse dynamic loads. The capabilities of the proposed continuous models in capturing the vibration behavior of SWCNTs ensembles are then examined through various numerical simulations. A reasonably good agreement between the results of the continuous models and those of the discrete ones is also reported. The effects of the applied load frequency, intertube spaces, and small-scale parameter on the transverse dynamic responses of both two- and three-dimensional ensembles of SWCNTs are explained. The proposed continuous models would be very useful for dynamic analyses of large populated ensembles of SWCNTs whose discrete models suffer from both computational efforts and labor costs.

COMMIX-PPC: A three-dimensional transient multicomponent computer program for analyzing performance of power plant condensers. Volume 1, Equations and numerics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chien, T.H.; Domanus, H.M.; Sha, W.T.

1993-02-01

The COMMIX-PPC computer pregrain is an extended and improved version of earlier COMMIX codes and is specifically designed for evaluating the thermal performance of power plant condensers. The COMMIX codes are general-purpose computer programs for the analysis of fluid flow and heat transfer in complex Industrial systems. In COMMIX-PPC, two major features have been added to previously published COMMIX codes. One feature is the incorporation of one-dimensional equations of conservation of mass, momentum, and energy on the tube stile and the proper accounting for the thermal interaction between shell and tube side through the porous-medium approach. The other added featuremore » is the extension of the three-dimensional conservation equations for shell-side flow to treat the flow of a multicomponent medium. COMMIX-PPC is designed to perform steady-state and transient. Three-dimensional analysis of fluid flow with heat transfer tn a power plant condenser. However, the code is designed in a generalized fashion so that, with some modification, it can be used to analyze processes in any heat exchanger or other single-phase engineering applications. Volume I (Equations and Numerics) of this report describes in detail the basic equations, formulation, solution procedures, and models for a phenomena. Volume II (User`s Guide and Manual) contains the input instruction, flow charts, sample problems, and descriptions of available options and boundary conditions.« less

Mean, covariance, and effective dimension of stochastic distributed delay dynamics

NASA Astrophysics Data System (ADS)

René, Alexandre; Longtin, André

2017-11-01

Dynamical models are often required to incorporate both delays and noise. However, the inherently infinite-dimensional nature of delay equations makes formal solutions to stochastic delay differential equations (SDDEs) challenging. Here, we present an approach, similar in spirit to the analysis of functional differential equations, but based on finite-dimensional matrix operators. This results in a method for obtaining both transient and stationary solutions that is directly amenable to computation, and applicable to first order differential systems with either discrete or distributed delays. With fewer assumptions on the system's parameters than other current solution methods and no need to be near a bifurcation, we decompose the solution to a linear SDDE with arbitrary distributed delays into natural modes, in effect the eigenfunctions of the differential operator, and show that relatively few modes can suffice to approximate the probability density of solutions. Thus, we are led to conclude that noise makes these SDDEs effectively low dimensional, which opens the possibility of practical definitions of probability densities over their solution space.

A note on conservative transport in anisotropic, heterogeneous porous media in the presence of small-amplitude transients

USGS Publications Warehouse

Naff, R.L.

1998-01-01

The late-time macrodispersion coefficients are obtained for the case of flow in the presence of a small-scale deterministic transient in a three-dimensional anisotropic, heterogeneous medium. The transient is assumed to affect only the velocity component transverse to the mean flow direction and to take the form of a periodic function. For the case of a highly stratified medium, these late-time macrodispersion coefficients behave largely as the standard coefficients used in the transport equation. Only in the event that the medium is isotropic is it probable that significant deviations from the standard coefficients would occur.

Computer animation of modal and transient vibrations

NASA Technical Reports Server (NTRS)

Lipman, Robert R.

1987-01-01

An interactive computer graphics processor is described that is capable of generating input to animate modal and transient vibrations of finite element models on an interactive graphics system. The results from NASTRAN can be postprocessed such that a three dimensional wire-frame picture, in perspective, of the finite element mesh is drawn on the graphics display. Modal vibrations of any mode shape or transient motions over any range of steps can be animated. The finite element mesh can be color-coded by any component of displacement. Viewing parameters and the rate of vibration of the finite element model can be interactively updated while the structure is vibrating.

Transient three-dimensional thermal-hydraulic analysis of nuclear reactor fuel rod arrays: general equations and numerical scheme

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wnek, W.J.; Ramshaw, J.D.; Trapp, J.A.

1975-11-01

A mathematical model and a numerical solution scheme for thermal- hydraulic analysis of fuel rod arrays are given. The model alleviates the two major deficiencies associated with existing rod array analysis models, that of a correct transverse momentum equation and the capability of handling reversing and circulatory flows. Possible applications of the model include steady state and transient subchannel calculations as well as analysis of flows in heat exchangers, other engineering equipment, and porous media. (auth)

Development of a new generation solid rocket motor ignition computer code

NASA Technical Reports Server (NTRS)

Foster, Winfred A., Jr.; Jenkins, Rhonald M.; Ciucci, Alessandro; Johnson, Shelby D.

1994-01-01

This report presents the results of experimental and numerical investigations of the flow field in the head-end star grain slots of the Space Shuttle Solid Rocket Motor. This work provided the basis for the development of an improved solid rocket motor ignition transient code which is also described in this report. The correlation between the experimental and numerical results is excellent and provides a firm basis for the development of a fully three-dimensional solid rocket motor ignition transient computer code.

Stability analysis for capillary channel flow: 1d and 3d computations

NASA Astrophysics Data System (ADS)

Grah, Aleksander; Klatte, Jörg; Dreyer, Michael E.

The subject of the presentation are numerical studies on capillary channel flow, based on results of the sounding rocket TEXUS experiments. The flow through a capillary channel is established by a gear pump at the outlet. The channel, consists of two parallel glass plates with a width of 25 mm, a gap of 10 mm and a length of 12 mm. The meniscus of a compensation tube maintains a constant system pressure. Steady and dynamic pressure effects in the system force the surfaces to bend inwards. A maximum flow rate is achieved when the free surface collapses and gas ingestion occurs at the outlet. This critical flow rate depends on the channel geometry, the flow regime and the liquid properties. The aim of the experiments is the determination of the free surface shape and to find the maximum flow rate. In order to study the unsteady liquid loop behavior, a dimensionless one-dimensional model and a corresponding three-dimensional model were developed. The one-dimensional model is based on the unsteady Bernoulli equation, the unsteady continuity equation and geometrical conditions for the surface curvature and the flow cross-section. The experimental and evaluated contour data show good agreement for a sequence of transient flow rate perturbations. In the case of steady flow at maximum flow rate, when the "choking" effect occurs, the surfaces collapse and cause gas ingestion into the channel. This effect is related to the Speed Index. At the critical flow rate the Speed Index reaches the value 1, in analogy to the Mach Number. Unsteady choking does not necessarily cause surface collapse. We show, that temporarily Speed Index values exceeding One may be achieved for a perfectly stable supercritical dynamic flow. As a supercritical criterion for the dynamic free surface stability we define a Dynamic Index considering the local capillary pressure and the convective pressure, which is a function of the local velocity. The Dynamic Index is below One for stable flow while D = 1 indicates surface collapse. This studies lead to a stability diagram, which defines the limits of flow dynamics and the maximum unsteady flow rate.

Burning invariant manifolds for reaction fronts in three-dimensional fluid flows

NASA Astrophysics Data System (ADS)

Mitchell, Kevin; Solomon, Tom

2017-11-01

The geometry of reaction fronts that propagate in fully three-dimensional (3D) fluid flows is studied using the tools of dynamical systems theory. The evolution of an infinitesimal front element is modeled as a six-dimensional ODE-three dimensions for the position of the front element and three for the orientation of its unit normal. This generalizes an earlier approach to understanding front propagation in two-dimensional (2D) fluid flows. As in 2D, the 3D system exhibits prominent burning invariant manifolds (BIMs). In 3D, BIMs are two-dimensional dynamically defined surfaces that form one-way barriers to the propagation of reaction fronts within the fluid. Due to the third dimension, BIMs in 3D exhibit a richer topology than their cousins in 2D. In particular, whereas BIMs in both 2D and 3D can originate from fixed points of the dynamics, BIMs in 3D can also originate from limit cycles. Such BIMs form robust tube-like channels that guide and constrain the evolution of the front within the bulk of the fluid. Supported by NSF Grant CMMI-1201236.

Three-dimensional transient thermoelectric currents in deep penetration laser welding of austenite stainless steel

NASA Astrophysics Data System (ADS)

Chen, Xin; Pang, Shengyong; Shao, Xinyu; Wang, Chunming; Xiao, Jianzhong; Jiang, Ping

2017-04-01

The existence of thermoelectric currents (TECs) in workpieces during the laser welding of metals has been common knowledge for more than 15 years. However, the time-dependent evolutions of TECs in laser welding remain unclear. The present study developed a novel three-dimensional theoretical model of thermoelectric phenomena in the fiber laser welding of austenite stainless steel and used it to observe the time-dependent evolutions of TECs for the first time. Our model includes the complex physical effects of thermal, electromagnetic, fluid and phase transformation dynamics occurring at the millimeter laser ablated zone, which allowed us to simulate the TEC, self-induced magnetic field, Lorentz force, keyhole and weld pool behaviors varying with the welding time for different parameters. We found that TECs are truly three-dimensional, time-dependent, and uneven with a maximum current density of around 107 A/m2 located at the liquid-solid (L/S) interface near the front or bottom part of the keyhole at a laser power of 1.5 kW and a welding speed of 3 m/min. The TEC formed three-dimensional circulations moving from the melting front to solidification front in the solid part of workpiece, after which the contrary direction was followed in the liquid part. High frequency oscillation characteristics (2.2-8.5 kHz) were demonstrated in the TEC, which coincides with that of the keyhole instability (2.0-5.0 kHz). The magnitude of the self-induced magnetic field and Lorentz force can reach 0.1 mT and 1 kN/m3, respectively, which are both consistent with literature data. The predicted results of the weld dimensions by the proposed model agree well with the experimental results. Our findings could enhance the fundamental understanding of thermoelectric phenomena in laser welding.

Dynamics of Solid-Liquid Composite Beams

NASA Astrophysics Data System (ADS)

Matia, Yoav; Gat, Amir

2017-11-01

Solid-liquid composite structures received considerable attention in recent years in various fields such as smart materials, sensors, actuators and soft-robotics. We examine a beam-like appendage embedded with a set of a fluid-filled bladders, interconnected via elastic slender channels; a common arrangement in the abovementioned fields. Viscous flow within such structures is coupled with the elastic deformation of the solid. Beam deformation both creates, and is induced by, a fluidic pressure gradient and viscous flow which deforms the bladders and thus the surrounding solid. Applying concepts from poroelastic analysis, we obtain a set of three interdependent equations relating the fluidic pressure within the channel to the transverse and longitudinal displacements of the beam. Exact and approximate solutions are presented for various configurations. The results are validated and supplemented by a transient three-dimensional numerical study of the fluid-structure-interaction. The two-way coupled fluid-structure-interaction model allows the analysis and design of soft smart-metamaterials with unique mechanical properties, to applications such as touch-sensing surfaces, energy harvesting and protective gear.

Solar maximum mission: Ground support programs at the Harvard Radio Astronomy Station

NASA Technical Reports Server (NTRS)

Maxwell, A.

1983-01-01

Observations of the spectral characteristics of solar radio bursts were made with new dynamic spectrum analyzers of high sensitivity and high reliability, over the frequency range 25-580 MHz. The observations also covered the maximum period of the current solar cycle and the period of international cooperative programs designated as the Solar Maximum Year. Radio data on shock waves generated by solar flares were combined with optical data on coronal transients, taken with equipment on the SMM and other satellites, and then incorporated into computer models for the outward passage of fast-mode MHD shocks through the solar corona. The MHD models are non-linear, time-dependent and for the most recent models, quasi-three-dimensional. They examine the global response of the corona for different types of input pulses (thermal, magnetic, etc.) and for different magnetic topologies (for example, open and closed fields). Data on coronal shocks and high-velocity material ejected from solar flares have been interpreted in terms of a model consisting of three main velocity regimes.

Computer-Assisted Instruction in Engineering Dynamics. CAI-Systems Memo Number 18.

ERIC Educational Resources Information Center

Sheldon, John W.

A 90-minute computer-assisted instruction (CAI) unit course supplemented by a 1-hour lecture on the dynamic nature of three-dimensional rotations and Euler angles was given to 29 undergraduate engineering students. The area of Euler angles was selected because it is essential to problem-working in three-dimensional rotations of a rigid body, yet…

Dynamic 3D echocardiography in virtual reality

PubMed Central

van den Bosch, Annemien E; Koning, Anton HJ; Meijboom, Folkert J; McGhie, Jackie S; Simoons, Maarten L; van der Spek, Peter J; Bogers, Ad JJC

2005-01-01

Background This pilot study was performed to evaluate whether virtual reality is applicable for three-dimensional echocardiography and if three-dimensional echocardiographic 'holograms' have the potential to become a clinically useful tool. Methods Three-dimensional echocardiographic data sets from 2 normal subjects and from 4 patients with a mitral valve pathological condition were included in the study. The three-dimensional data sets were acquired with the Philips Sonos 7500 echo-system and transferred to the BARCO (Barco N.V., Kortrijk, Belgium) I-space. Ten independent observers assessed the 6 three-dimensional data sets with and without mitral valve pathology. After 10 minutes' instruction in the I-Space, all of the observers could use the virtual pointer that is necessary to create cut planes in the hologram. Results The 10 independent observers correctly assessed the normal and pathological mitral valve in the holograms (analysis time approximately 10 minutes). Conclusion this report shows that dynamic holographic imaging of three-dimensional echocardiographic data is feasible. However, the applicability and use-fullness of this technology in clinical practice is still limited. PMID:16375768

Coupling vibration research on Vehicle-bridge system

NASA Astrophysics Data System (ADS)

Zhou, Jiguo; Wang, Guihua

2018-01-01

The vehicle-bridge coupling system forms when vehicle running on a bridge. It will generate a relatively large influence on the driving comfort and driving safe when the vibration of the vehicle is bigger. A three-dimensional vehicle-bridge system with biaxial seven degrees of freedom has been establish in this paper based on finite numerical simulation. Adopting the finite element transient numerical simulation to realize the numerical simulation of vehicle-bridge system coupling vibration. Then, analyze the dynamic response of vehicle and bridge while different numbers of vehicles running on the bridge. Got the variation rule of vertical vibration of car body and bridge, and that of the contact force between the wheel and bridge deck. The research results have a reference value for the analysis about the vehicle running on a large-span cabled bridge.

MODELING MULTICOMPONENT ORGANIC CHEMICAL TRANSPORT IN THREE-FLUID-PHASE POROUS MEDIA

EPA Science Inventory

A two dimensional finite-element model was developed to predict coupled transient flow and multicomponent transport of organic chemicals which can partition between NAPL, water, gas and solid phases in porous media under the assumption of local chemical equilibrium. as-phase pres...

MODELING MULTICOMPONENT ORGANIC CHEMICAL TRANSPORT IN THREE FLUID PHASE POROUS MEDIA

EPA Science Inventory

A two-dimensional finite-element model was developed to predict coupled transient flow and multicomponent transport of organic chemicals which can partition between nonaqueous phase liquid, water, gas and solid phases in porous media under the assumption of local chemical equilib...

Numberical Solution to Transient Heat Flow Problems

ERIC Educational Resources Information Center

Kobiske, Ronald A.; Hock, Jeffrey L.

1973-01-01

Discusses the reduction of the one- and three-dimensional diffusion equation to the difference equation and its stability, convergence, and heat-flow applications under different boundary conditions. Indicates the usefulness of this presentation for beginning students of physics and engineering as well as college teachers. (CC)

Computer program: Jet 3 to calculate the large elastic plastic dynamically induced deformations of free and restrained, partial and/or complete structural rings

NASA Technical Reports Server (NTRS)

Wu, R. W.; Witmer, E. A.

1972-01-01

A user-oriented FORTRAN 4 computer program, called JET 3, is presented. The JET 3 program, which employs the spatial finite-element and timewise finite-difference method, can be used to predict the large two-dimensional elastic-plastic transient Kirchhoff-type deformations of a complete or partial structural ring, with various support conditions and restraints, subjected to a variety of initial velocity distributions and externally-applied transient forcing functions. The geometric shapes of the structural ring can be circular or arbitrarily curved and with variable thickness. Strain-hardening and strain-rate effects of the material are taken into account.

Molecular behavior of zero-dimensional perovskites

PubMed Central

Yin, Jun; Maity, Partha; De Bastiani, Michele; Dursun, Ibrahim; Bakr, Osman M.; Brédas, Jean-Luc; Mohammed, Omar F.

2017-01-01

Low-dimensional perovskites offer a rare opportunity to investigate lattice dynamics and charge carrier behavior in bulk quantum-confined solids, in addition to them being the leading materials in optoelectronic applications. In particular, zero-dimensional (0D) inorganic perovskites of the Cs4PbX6 (X = Cl, Br, or I) kind have crystal structures with isolated lead halide octahedra [PbX6]4− surrounded by Cs+ cations, allowing the 0D crystals to exhibit the intrinsic properties of an individual octahedron. Using both experimental and theoretical approaches, we studied the electronic and optical properties of the prototypical 0D perovskite Cs4PbBr6. Our results underline that this 0D perovskite behaves akin to a molecule, demonstrating low electrical conductivity and mobility as well as large polaron binding energy. Density functional theory calculations and transient absorption measurements of Cs4PbBr6 perovskite films reveal the polaron band absorption and strong polaron localization features of the material. A short polaron lifetime of ~2 ps is observed in femtosecond transient absorption experiments, which can be attributed to the fast lattice relaxation of the octahedra and the weak interactions among them. PMID:29250600

Temperature distributions and thermal stresses in a graded zirconia/metal gas path seal system for aircraft gas turbine engines

NASA Technical Reports Server (NTRS)

Taylor, C. M.; Bill, R. C.

1978-01-01

A ceramic/metallic aircraft gas turbine outer gas path seal designed for improved engine performance was studied. Transient temperature and stress profiles in a test seal geometry were determined by numerical analysis. During a simulated engine deceleration cycle from sea-level takeoff to idle conditions, the maximum seal temperature occurred below the seal surface, therefore the top layer of the seal was probably subjected to tensile stresses exceeding the modulus of rupture. In the stress analysis both two- and three-dimensional finite element computer programs were used. Predicted trends of the simpler and more easily usable two-dimensional element programs were borne out by the three-dimensional finite element program results.

An efficient approach to the analysis of rail surface irregularities accounting for dynamic train-track interaction and inelastic deformations

NASA Astrophysics Data System (ADS)

Andersson, Robin; Torstensson, Peter T.; Kabo, Elena; Larsson, Fredrik

2015-11-01

A two-dimensional computational model for assessment of rolling contact fatigue induced by discrete rail surface irregularities, especially in the context of so-called squats, is presented. Dynamic excitation in a wide frequency range is considered in computationally efficient time-domain simulations of high-frequency dynamic vehicle-track interaction accounting for transient non-Hertzian wheel-rail contact. Results from dynamic simulations are mapped onto a finite element model to resolve the cyclic, elastoplastic stress response in the rail. Ratcheting under multiple wheel passages is quantified. In addition, low cycle fatigue impact is quantified using the Jiang-Sehitoglu fatigue parameter. The functionality of the model is demonstrated by numerical examples.

Dynamic effects of root system architecture improve root water uptake in 1-D process-based soil-root hydrodynamics

NASA Astrophysics Data System (ADS)

Bouda, Martin; Saiers, James E.

2017-12-01

Root system architecture (RSA) can significantly affect plant access to water, total transpiration, as well as its partitioning by soil depth, with implications for surface heat, water, and carbon budgets. Despite recent advances in land surface model (LSM) descriptions of plant hydraulics, descriptions of RSA have not been included because of their three-dimensional complexity, which makes them generally too computationally costly. Here we demonstrate a new, process-based 1D layered model that captures the dynamic shifts in water potential gradients of 3D RSA under different soil moisture conditions: the RSA stencil. Using root systems calibrated to the rooting profiles of four plant functional types (PFT) of the Community Land Model, we show that the RSA stencil predicts plant water potentials within 2% to the outputs of a full 3D model, under the same assumptions on soil moisture heterogeneity, despite its trivial computational cost, resulting in improved predictions of water uptake and soil moisture compared to a model without RSA in a transient simulation. Our results suggest that LSM predictions of soil moisture dynamics and dependent variables can be improved by the implementation of this model, calibrated for individual PFTs using field observations.

The dynamic properties behavior of high strength concrete under different strain rate

NASA Astrophysics Data System (ADS)

Abdullah, Hasballah; Husin, Saiful; Umar, Hamdani; Rizal, Samsul

2005-04-01

This paper present a number experimental data and numerical technique used in the dynamic behavior of high strength concrete. A testing device is presented for the experimental study of dynamic behavior material under high strain rates. The specimen is loaded by means of a high carbon steel Hopkinson pressure bar (40 mm diameter, 3000 mm long input bar and 1500 mm long out put bar) allowing for the testing of specimen diameter is large enough in relation to the size of aggregates. The other method also proposed for measuring tensile strength, the measurement method based on the superposition and concentration of tensile stress wave reflected both from the free-free ends of striking bar and the specimen bar. The compression Hopkinson bar test, the impact tensile test of high strength concrete bars are performed, together with compression static strength test. In addition, the relation between break position under finite element simulation and impact tensile strength are examined. The three-dimensional simulation of the specimen under transient loading are presented and comparisons between the experimental and numerical simulation on strain rate effects of constitutive law use in experimental are study.

Damping of transient energy growth of three-dimensional perturbations in hydromagnetic pipe flow

NASA Astrophysics Data System (ADS)

Åkerstedt, Hans O.

1995-05-01

The stability of infinitesimal three-dimensional perturbations in hydromagnetic pipe flow where the applied magnetic field is in the streamwise direction is considered. The study is limited to the case of small magnetic Reynolds numbers and the main objective of the paper is to study the transient evolution of the kinetic energy. A general effect of the magnetic field is to increase the damping of the eigenvalues of the individual perturbation modes. For the case of infinitely long perturbations, which in the non-magnetic case has been found to have the largest transient growth, the magnetic field perturbations are decoupled from the flow and there is no effect on the stability properties of the flow. For shorter waves, and for moderate values of the interaction parameter ( I = RmA2 ≈ 1-3) the hydromagnetic damping effect on the transient energy growth is, however, substantial, especially for small azimuthal mode numbers n. (Here Rm is the magnetic Reynolds number and A is the Alfvén number.) This parameter range has been found in experiments to give significantly higher transitional Reynolds numbers (Fraim and Heiser, 1968). Since the hydromagnetic damping effect is weak for long waves and large for shorter waves, the implications of the results to ordinary pipe flow is that the energy growth found for short waves may be more crucial as a mechanism for transition than the corresponding growth for longer waves.

[3D visualization and analysis of vocal fold dynamics].

PubMed

Bohr, C; Döllinger, M; Kniesburges, S; Traxdorf, M

2016-04-01

Visual investigation methods of the larynx mainly allow for the two-dimensional presentation of the three-dimensional structures of the vocal fold dynamics. The vertical component of the vocal fold dynamics is often neglected, yielding a loss of information. The latest studies show that the vertical dynamic components are in the range of the medio-lateral dynamics and play a significant role within the phonation process. This work presents a method for future 3D reconstruction and visualization of endoscopically recorded vocal fold dynamics. The setup contains a high-speed camera (HSC) and a laser projection system (LPS). The LPS projects a regular grid on the vocal fold surfaces and in combination with the HSC allows a three-dimensional reconstruction of the vocal fold surface. Hence, quantitative information on displacements and velocities can be provided. The applicability of the method is presented for one ex-vivo human larynx, one ex-vivo porcine larynx and one synthetic silicone larynx. The setup introduced allows the reconstruction of the entire visible vocal fold surfaces for each oscillation status. This enables a detailed analysis of the three dimensional dynamics (i. e. displacements, velocities, accelerations) of the vocal folds. The next goal is the miniaturization of the LPS to allow clinical in-vivo analysis in humans. We anticipate new insight on dependencies between 3D dynamic behavior and the quality of the acoustic outcome for healthy and disordered phonation.

Viability of Cross-Flow Fan with Helical Blades for Vertical Take-off and Landing Aircraft

DTIC Science & Technology

2012-09-01

fluid dynamics (CFD) software, ANSYS - CFX , a three-dimensional (3-D) straight-bladed model was validated against previous study’s experimental results...computational fluid dynamics software (CFD), ANSYS - CFX , a three-dimensional (3-D) straight-bladed model was validated against previous study’s experimental...37 B. SIZING PARAMETERS AND ILLUSTRATION ................................. 37 APPENDIX B. ANSYS CFX PARAMETERS

How well-connected is the surface of the global ocean?

PubMed

Froyland, Gary; Stuart, Robyn M; van Sebille, Erik

2014-09-01

The Ekman dynamics of the ocean surface circulation is known to contain attracting regions such as the great oceanic gyres and the associated garbage patches. Less well-known are the extents of the basins of attractions of these regions and how strongly attracting they are. Understanding the shape and extent of the basins of attraction sheds light on the question of the strength of connectivity of different regions of the ocean, which helps in understanding the flow of buoyant material like plastic litter. Using short flow time trajectory data from a global ocean model, we create a Markov chain model of the surface ocean dynamics. The surface ocean is not a conservative dynamical system as water in the ocean follows three-dimensional pathways, with upwelling and downwelling in certain regions. Using our Markov chain model, we easily compute net surface upwelling and downwelling, and verify that it matches observed patterns of upwelling and downwelling in the real ocean. We analyze the Markov chain to determine multiple attracting regions. Finally, using an eigenvector approach, we (i) identify the five major ocean garbage patches, (ii) partition the ocean into basins of attraction for each of the garbage patches, and (iii) partition the ocean into regions that demonstrate transient dynamics modulo the attracting garbage patches.

Dynamic thermal characteristics of heat pipe via segmented thermal resistance model for electric vehicle battery cooling

NASA Astrophysics Data System (ADS)

Liu, Feifei; Lan, Fengchong; Chen, Jiqing

2016-07-01

Heat pipe cooling for battery thermal management systems (BTMSs) in electric vehicles (EVs) is growing due to its advantages of high cooling efficiency, compact structure and flexible geometry. Considering the transient conduction, phase change and uncertain thermal conditions in a heat pipe, it is challenging to obtain the dynamic thermal characteristics accurately in such complex heat and mass transfer process. In this paper, a ;segmented; thermal resistance model of a heat pipe is proposed based on thermal circuit method. The equivalent conductivities of different segments, viz. the evaporator and condenser of pipe, are used to determine their own thermal parameters and conditions integrated into the thermal model of battery for a complete three-dimensional (3D) computational fluid dynamics (CFD) simulation. The proposed ;segmented; model shows more precise than the ;non-segmented; model by the comparison of simulated and experimental temperature distribution and variation of an ultra-thin micro heat pipe (UMHP) battery pack, and has less calculation error to obtain dynamic thermal behavior for exact thermal design, management and control of heat pipe BTMSs. Using the ;segmented; model, the cooling effect of the UMHP pack with different natural/forced convection and arrangements is predicted, and the results correspond well to the tests.

Runaway transient simulation of a model Kaplan turbine

NASA Astrophysics Data System (ADS)

Liu, S.; Zhou, D.; Liu, D.; Wu, Y.; Nishi, M.

2010-08-01

The runaway transient is a typical transient process of a hydro power unit, where the rotational speed of a turbine runner rapidly increases up to the runaway speed under a working head as the guide vanes cannot be closed due to some reason at the load rejection. In the present paper, the characteristics of the runaway transient of a model Kaplan turbine having ns = 479(m-kW) is simulated by using a time-dependent CFD technique where equation of rotational motion of runner, continuity equation and unsteady RANS equations with RNG k-epsilon turbulence model are solved iteratively. In the calculation, unstructured mesh is used to the whole flow passage, which consists of several sub-domains: entrance, casing, stay vanes + guide vanes, guide section, runner and draft tube. And variable speed sliding mesh technique is used to exchange interface flow information between moving part and stationary part, and three-dimensional unstructured dynamic mesh technique is also adopted to ensure mesh quality. Two cases were treated in the simulation of runaway transient characteristics after load rejection: one is the rated operating condition as the initial condition, and the other is the condition at the maximum head. Regarding the runaway speed, the experimental speed is 1.45 times the initial speed and the calculation is 1.47 times the initial for the former case. In the latter case, the experiment and the calculation are 1.67 times and 1.69 times respectively. From these results, it is recognized that satisfactorily prediction will be possible by using the present numerical method. Further, numerical results show that the swirl in the draft-tube flow becomes stronger in the latter part of the transient process so that a vortex rope will occur in the draft tube and its precession will cause the pressure fluctuations which sometimes affect the stability of hydro power system considerably.

From Two- to Three-Dimensional Structures of a Supertetrahedral Boran Using Density Functional Calculations.

PubMed

Getmanskii, Iliya V; Minyaev, Ruslan M; Steglenko, Dmitrii V; Koval, Vitaliy V; Zaitsev, Stanislav A; Minkin, Vladimir I

2017-08-14

With help of the DFT calculations and imposing of periodic boundary conditions the geometrical and electronic structures were investigated of two- and three-dimensional boron systems designed on the basis of graphane and diamond lattices in which carbons were replaced with boron tetrahedrons. The consequent studies of two- and three-layer systems resulted in the construction of a three-dimensional supertetrahedral borane crystal structure. The two-dimensional supertetrahedral borane structures with less than seven layers are dynamically unstable. At the same time the three-dimensional superborane systems were found to be dynamically stable. Lack of the forbidden electronic zone for the studied boron systems testifies that these structures can behave as good conductors. The low density of the supertetrahedral borane crystal structures (0.9 g cm -3 ) is close to that of water, which offers the perspective for their application as aerospace and cosmic materials. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Modeling and simulation of RF photoinjectors for coherent light sources

NASA Astrophysics Data System (ADS)

Chen, Y.; Krasilnikov, M.; Stephan, F.; Gjonaj, E.; Weiland, T.; Dohlus, M.

2018-05-01

We propose a three-dimensional fully electromagnetic numerical approach for the simulation of RF photoinjectors for coherent light sources. The basic idea consists in incorporating a self-consistent photoemission model within a particle tracking code. The generation of electron beams in the injector is determined by the quantum efficiency (QE) of the cathode, the intensity profile of the driving laser as well as by the accelerating field and magnetic focusing conditions in the gun. The total charge emitted during an emission cycle can be limited by the space charge field at the cathode. Furthermore, the time and space dependent electromagnetic field at the cathode may induce a transient modulation of the QE due to surface barrier reduction of the emitting layer. In our modeling approach, all these effects are taken into account. The beam particles are generated dynamically according to the local QE of the cathode and the time dependent laser intensity profile. For the beam dynamics, a tracking code based on the Lienard-Wiechert retarded field formalism is employed. This code provides the single particle trajectories as well as the transient space charge field distribution at the cathode. As an application, the PITZ injector is considered. Extensive electron bunch emission simulations are carried out for different operation conditions of the injector, in the source limited as well as in the space charge limited emission regime. In both cases, fairly good agreement between measurements and simulations is obtained.

Time-dependent inertia analysis of vehicle mechanisms

NASA Astrophysics Data System (ADS)

Salmon, James Lee

Two methods for performing transient inertia analysis of vehicle hardware systems are developed in this dissertation. The analysis techniques can be used to predict the response of vehicle mechanism systems to the accelerations associated with vehicle impacts. General analytical methods for evaluating translational or rotational system dynamics are generated and evaluated for various system characteristics. The utility of the derived techniques are demonstrated by applying the generalized methods to two vehicle systems. Time dependent acceleration measured during a vehicle to vehicle impact are used as input to perform a dynamic analysis of an automobile liftgate latch and outside door handle. Generalized Lagrange equations for a non-conservative system are used to formulate a second order nonlinear differential equation defining the response of the components to the transient input. The differential equation is solved by employing the fourth order Runge-Kutta method. The events are then analyzed using commercially available two dimensional rigid body dynamic analysis software. The results of the two analytical techniques are compared to experimental data generated by high speed film analysis of tests of the two components performed on a high G acceleration sled at Ford Motor Company.

Dynamic analysis of geometrically non-linear three-dimensional beams under moving mass

NASA Astrophysics Data System (ADS)

Zupan, E.; Zupan, D.

2018-01-01

In this paper, we present a coupled dynamic analysis of a moving particle on a deformable three-dimensional frame. The presented numerical model is capable of considering arbitrary curved and twisted initial geometry of the beam and takes into account geometric non-linearity of the structure. Coupled with dynamic equations of the structure, the equations of moving particle are solved. The moving particle represents the dynamic load and varies the mass distribution of the structure and at the same time its path is adapting due to deformability of the structure. A coupled geometrically non-linear behaviour of beam and particle is studied. The equation of motion of the particle is added to the system of the beam dynamic equations and an additional unknown representing the coordinate of the curvilinear path of the particle is introduced. The specially designed finite-element formulation of the three-dimensional beam based on the weak form of consistency conditions is employed where only the boundary conditions are affected by the contact forces.

Sub-10 fs Time-Resolved Vibronic Optical Microscopy

PubMed Central

2016-01-01

We introduce femtosecond wide-field transient absorption microscopy combining sub-10 fs pump and probe pulses covering the complete visible (500–650 nm) and near-infrared (650–950 nm) spectrum with diffraction-limited optical resolution. We demonstrate the capabilities of our system by reporting the spatially- and spectrally-resolved transient electronic response of MAPbI3–xClx perovskite films and reveal significant quenching of the transient bleach signal at grain boundaries. The unprecedented temporal resolution enables us to directly observe the formation of band-gap renormalization, completed in 25 fs after photoexcitation. In addition, we acquire hyperspectral Raman maps of TIPS pentacene films with sub-400 nm spatial and sub-15 cm–1 spectral resolution covering the 100–2000 cm–1 window. Our approach opens up the possibility of studying ultrafast dynamics on nanometer length and femtosecond time scales in a variety of two-dimensional and nanoscopic systems. PMID:27934055

Transient three-dimensional startup side load analysis of a regeneratively cooled nozzle

NASA Astrophysics Data System (ADS)

Wang, Ten-See

2009-07-01

The objective of this effort is to develop a computational methodology to capture the side load physics and to anchor the computed aerodynamic side loads with the available data by simulating the startup transient of a regeneratively cooled, high-aspect-ratio nozzle, hot-fired at sea level. The computational methodology is based on an unstructured-grid, pressure-based, reacting flow computational fluid dynamics and heat transfer formulation, and a transient inlet history based on an engine system simulation. Emphases were put on the effects of regenerative cooling on shock formation inside the nozzle, and ramp rate on side load reduction. The results show that three types of asymmetric shock physics incur strong side loads: the generation of combustion wave, shock transitions, and shock pulsations across the nozzle lip, albeit the combustion wave can be avoided with sparklers during hot-firing. Results from both regenerative cooled and adiabatic wall boundary conditions capture the early shock transitions with corresponding side loads matching the measured secondary side load. It is theorized that the first transition from free-shock separation to restricted-shock separation is caused by the Coanda effect. After which the regeneratively cooled wall enhances the Coanda effect such that the supersonic jet stays attached, while the hot adiabatic wall fights off the Coanda effect, and the supersonic jet becomes detached most of the time. As a result, the computed peak side load and dominant frequency due to shock pulsation across the nozzle lip associated with the regeneratively cooled wall boundary condition match those of the test, while those associated with the adiabatic wall boundary condition are much too low. Moreover, shorter ramp time results show that higher ramp rate has the potential in reducing the nozzle side loads.

Slow dynamics in translation-invariant quantum lattice models

NASA Astrophysics Data System (ADS)

Michailidis, Alexios A.; Žnidarič, Marko; Medvedyeva, Mariya; Abanin, Dmitry A.; Prosen, Tomaž; Papić, Z.

2018-03-01

Many-body quantum systems typically display fast dynamics and ballistic spreading of information. Here we address the open problem of how slow the dynamics can be after a generic breaking of integrability by local interactions. We develop a method based on degenerate perturbation theory that reveals slow dynamical regimes and delocalization processes in general translation invariant models, along with accurate estimates of their delocalization time scales. Our results shed light on the fundamental questions of the robustness of quantum integrable systems and the possibility of many-body localization without disorder. As an example, we construct a large class of one-dimensional lattice models where, despite the absence of asymptotic localization, the transient dynamics is exceptionally slow, i.e., the dynamics is indistinguishable from that of many-body localized systems for the system sizes and time scales accessible in experiments and numerical simulations.

Tensor of effective susceptibility in random magnetic composites: Application to two-dimensional and three-dimensional cases

NASA Astrophysics Data System (ADS)

Posnansky, Oleg P.

2018-05-01

The measuring of dynamic magnetic susceptibility by nuclear magnetic resonance is used for revealing information about the internal structure of various magnetoactive composites. The response of such material on the applied external static and time-varying magnetic fields encodes intrinsic dynamic correlations and depends on links between macroscopic effective susceptibility and structure on the microscopic scale. In the current work we carried out computational analysis of the frequency dependent dynamic magnetic susceptibility and demonstrated its dependence on the microscopic architectural elements while also considering Euclidean dimensionality. The proposed numerical method is efficient in the simulation of nuclear magnetic resonance experiments in two- and three-dimensional random magnetic media by choosing and modeling the influence of the concentration of components and internal hierarchical characteristics of physical parameters.

Kinetic and dynamic Delaunay tetrahedralizations in three dimensions

NASA Astrophysics Data System (ADS)

Schaller, Gernot; Meyer-Hermann, Michael

2004-09-01

We describe algorithms to implement fully dynamic and kinetic three-dimensional unconstrained Delaunay triangulations, where the time evolution of the triangulation is not only governed by moving vertices but also by a changing number of vertices. We use three-dimensional simplex flip algorithms, a stochastic visibility walk algorithm for point location and in addition, we propose a new simple method of deleting vertices from an existing three-dimensional Delaunay triangulation while maintaining the Delaunay property. As an example, we analyse the performance in various cases of practical relevance. The dual Dirichlet tessellation can be used to solve differential equations on an irregular grid, to define partitions in cell tissue simulations, for collision detection etc.

Recent developments in structural proteomics for protein structure determination.

PubMed

Liu, Hsuan-Liang; Hsu, Jyh-Ping

2005-05-01

The major challenges in structural proteomics include identifying all the proteins on the genome-wide scale, determining their structure-function relationships, and outlining the precise three-dimensional structures of the proteins. Protein structures are typically determined by experimental approaches such as X-ray crystallography or nuclear magnetic resonance (NMR) spectroscopy. However, the knowledge of three-dimensional space by these techniques is still limited. Thus, computational methods such as comparative and de novo approaches and molecular dynamic simulations are intensively used as alternative tools to predict the three-dimensional structures and dynamic behavior of proteins. This review summarizes recent developments in structural proteomics for protein structure determination; including instrumental methods such as X-ray crystallography and NMR spectroscopy, and computational methods such as comparative and de novo structure prediction and molecular dynamics simulations.

Benchmarking the mesoscale variability in global ocean eddy-permitting numerical systems

NASA Astrophysics Data System (ADS)

Cipollone, Andrea; Masina, Simona; Storto, Andrea; Iovino, Doroteaciro

2017-10-01

The role of data assimilation procedures on representing ocean mesoscale variability is assessed by applying eddy statistics to a state-of-the-art global ocean reanalysis (C-GLORS), a free global ocean simulation (performed with the NEMO system) and an observation-based dataset (ARMOR3D) used as an independent benchmark. Numerical results are computed on a 1/4 ∘ horizontal grid (ORCA025) and share the same resolution with ARMOR3D dataset. This "eddy-permitting" resolution is sufficient to allow ocean eddies to form. Further to assessing the eddy statistics from three different datasets, a global three-dimensional eddy detection system is implemented in order to bypass the need of regional-dependent definition of thresholds, typical of commonly adopted eddy detection algorithms. It thus provides full three-dimensional eddy statistics segmenting vertical profiles from local rotational velocities. This criterion is crucial for discerning real eddies from transient surface noise that inevitably affects any two-dimensional algorithm. Data assimilation enhances and corrects mesoscale variability on a wide range of features that cannot be well reproduced otherwise. The free simulation fairly reproduces eddies emerging from western boundary currents and deep baroclinic instabilities, while underestimates shallower vortexes that populate the full basin. The ocean reanalysis recovers most of the missing turbulence, shown by satellite products , that is not generated by the model itself and consistently projects surface variability deep into the water column. The comparison with the statistically reconstructed vertical profiles from ARMOR3D show that ocean data assimilation is able to embed variability into the model dynamics, constraining eddies with in situ and altimetry observation and generating them consistently with local environment.

Dynamic three-dimensional display of common congenital cardiac defects from reconstruction of two-dimensional echocardiographic images.

PubMed

Hsieh, K S; Lin, C C; Liu, W S; Chen, F L

1996-01-01

Two-dimensional echocardiography had long been a standard diagnostic modality for congenital heart disease. Further attempts of three-dimensional reconstruction using two-dimensional echocardiographic images to visualize stereotypic structure of cardiac lesions have been successful only recently. So far only very few studies have been done to display three-dimensional anatomy of the heart through two-dimensional image acquisition because such complex procedures were involved. This study introduced a recently developed image acquisition and processing system for dynamic three-dimensional visualization of various congenital cardiac lesions. From December 1994 to April 1995, 35 cases were selected in the Echo Laboratory here from about 3000 Echo examinations completed. Each image was acquired on-line with specially designed high resolution image grazmber with EKG and respiratory gating technique. Off-line image processing using a window-architectured interactive software package includes construction of 2-D ehcocardiographic pixel to 3-D "voxel" with conversion of orthogonal to rotatory axial system, interpolation, extraction of region of interest, segmentation, shading and, finally, 3D rendering. Three-dimensional anatomy of various congenital cardiac defects was shown, including four cases with ventricular septal defects, two cases with atrial septal defects, and two cases with aortic stenosis. Dynamic reconstruction of a "beating heart" is recorded as vedio tape with video interface. The potential application of 3D display of the reconstruction from 2D echocardiographic images for the diagnosis of various congenital heart defects has been shown. The 3D display was able to improve the diagnostic ability of echocardiography, and clear-cut display of the various congenital cardiac defects and vavular stenosis could be demonstrated. Reinforcement of current techniques will expand future application of 3D display of conventional 2D images.

Operationally Efficient Propulsion System Study (OEPSS) Data Book. Volume 8; Integrated Booster Propulsion Module (BPM) Engine Start Dynamics

NASA Technical Reports Server (NTRS)

Kemp, Victoria R.

1992-01-01

A fluid-dynamic, digital-transient computer model of an integrated, parallel propulsion system was developed for the CDC mainframe and the SUN workstation computers. Since all STME component designs were used for the integrated system, computer subroutines were written characterizing the performance and geometry of all the components used in the system, including the manifolds. Three transient analysis reports were completed. The first report evaluated the feasibility of integrated engine systems in regards to the start and cutoff transient behavior. The second report evaluated turbopump out and combined thrust chamber/turbopump out conditions. The third report presented sensitivity study results in staggered gas generator spin start and in pump performance characteristics.

Non-equlibrium relaxation of vortex lines in disordered type-II superconductors

NASA Astrophysics Data System (ADS)

Dobramysl, Ulrich; Assi, Hiba; Pleimling, Michel; T&äUber, Uwe C.

2013-03-01

Vortex matter in disordered type-II superconductors display a remarkable wealth of behavior, ranging from hexagonally arranged crystals and a vortex liquid to glassy phases. The type and strength of the disorder has a profound influence on the structural properties of the vortex matter: Randomly distributed weak point pinning sites lead to the destruction of long range order and a Bragg glass phase; correlated, columnar disorder can yield a Bose glass phase with infinite tilt modulus. We employ a three-dimensional elastic line model and apply a Langevin molecular dynamics algorithm to simulate the dynamics of vortex lines in a dissipative medium. We investigate the relaxation of a system of lines that were initially prepared in an out-of-equilibrium state and characterize the transient behavior via two-time quantities. We vary the disorder type and strength and compare our results for random and columnar disorder. Research supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-FG02-09ER46613.

Dynamic vibrations in wind energy systems: Application to vertical axis wind turbine

NASA Astrophysics Data System (ADS)

Mabrouk, Imen Bel; El Hami, Abdelkhalak; Walha, Lassâad; Zghal, Bacem; Haddar, Mohamed

2017-02-01

Dynamic analysis of Darrieus turbine bevel spur gear subjected to transient aerodynamic loads is carried out in the present study. The aerodynamic torque is obtained by solving the two dimensional unsteady incompressible Navies Stocks equation with the k-ω shear stress transport turbulence model. The results are presented for several values of tip speed ratio. The two-dimensional Computational Fluid Dynamics model is validated with experimental results. The optimum tip speed ratio is achieved, giving the best overall performance. In this study, we developed a lamped mass dynamic model with 14 degrees of freedom. This model is excited by external and internal issues sources. The main factors of these excitations are the periodic fluctuations of the gear meshes' stiffness and the unsteady aerodynamic torque oscillations. The vibration responses are obtained in time and frequency domains. The originality of our work is the correlation between the complexity of the aerodynamic phenomenon and the non-stationary dynamics vibration of the mechanical gearing system. The effect of the rotational speed on the dynamic behavior of the Darrieus turbine is also discussed. The present study shows that the variation of rotor rotational speed directly affects the torque production. However, there is a small change in the dynamic vibration of the studied gearing system.

Modelling the transient behaviour of pulsed current tungsten-inert-gas weldpools

NASA Astrophysics Data System (ADS)

Wu, C. S.; Zheng, W.; Wu, L.

1999-01-01

A three-dimensional model is established to simulate the pulsed current tungsten-inert-gas (TIG) welding process. The goal is to analyse the cyclic variation of fluid flow and heat transfer in weldpools under periodic arc heat input. To this end, an algorithm, which is capable of handling the transience, nonlinearity, multiphase and strong coupling encountered in this work, is developed. The numerical simulations demonstrate the transient behaviour of weldpools under pulsed current. Experimental data are compared with numerical results to show the effectiveness of the developed model.

New ab initio potential surfaces and three-dimensional quantum dynamics for transition state spectroscopy in ozone photodissociation

NASA Astrophysics Data System (ADS)

Yamashita, Koichi; Morokuma, Keiji; Le Quéré, Frederic; Leforestier, Claude

1992-04-01

New ab initio potential energy surfaces (PESs) of the ground and B ( 1B 2) states of ozone have been calculated with the CASSCF-SECI/DZP method to describe the three-dimensional photodissociation process. The dissociation energy of the ground state and the vertical barrier height of the B PES are obtained to be 0.88 and 1.34 eV, respectively, in better agreement with the experimental values than the previous calculation. The photodissociation autocorrelation function, calculated on the new B PES, based on exact three-dimensional quantum dynamics, reproduces well the main recurrence feature extracted from the experimental spectra.

Two-dimensional airflow modeling underpredicts the wind velocity over dunes

PubMed Central

Michelsen, Britt; Strobl, Severin; Parteli, Eric J. R.; Pöschel, Thorsten

2015-01-01

We investigate the average turbulent wind field over a barchan dune by means of Computational Fluid Dynamics. We find that the fractional speed-up ratio of the wind velocity over the three-dimensional barchan shape differs from the one obtained from two-dimensional calculations of the airflow over the longitudinal cut along the dune’s symmetry axis — that is, over the equivalent transverse dune of same size. This finding suggests that the modeling of the airflow over the central slice of barchan dunes is insufficient for the purpose of the quantitative description of barchan dune dynamics as three-dimensional flow effects cannot be neglected. PMID:26572966

On the analysis of the double Hopf bifurcation in machining processes via centre manifold reduction

NASA Astrophysics Data System (ADS)

Molnar, T. G.; Dombovari, Z.; Insperger, T.; Stepan, G.

2017-11-01

The single-degree-of-freedom model of orthogonal cutting is investigated to study machine tool vibrations in the vicinity of a double Hopf bifurcation point. Centre manifold reduction and normal form calculations are performed to investigate the long-term dynamics of the cutting process. The normal form of the four-dimensional centre subsystem is derived analytically, and the possible topologies in the infinite-dimensional phase space of the system are revealed. It is shown that bistable parameter regions exist where unstable periodic and, in certain cases, unstable quasi-periodic motions coexist with the equilibrium. Taking into account the non-smoothness caused by loss of contact between the tool and the workpiece, the boundary of the bistable region is also derived analytically. The results are verified by numerical continuation. The possibility of (transient) chaotic motions in the global non-smooth dynamics is shown.

Three-dimensional electron diffraction as a complementary technique to powder X-ray diffraction for phase identification and structure solution of powders.

PubMed

Yun, Yifeng; Zou, Xiaodong; Hovmöller, Sven; Wan, Wei

2015-03-01

Phase identification and structure determination are important and widely used techniques in chemistry, physics and materials science. Recently, two methods for automated three-dimensional electron diffraction (ED) data collection, namely automated diffraction tomography (ADT) and rotation electron diffraction (RED), have been developed. Compared with X-ray diffraction (XRD) and two-dimensional zonal ED, three-dimensional ED methods have many advantages in identifying phases and determining unknown structures. Almost complete three-dimensional ED data can be collected using the ADT and RED methods. Since each ED pattern is usually measured off the zone axes by three-dimensional ED methods, dynamic effects are much reduced compared with zonal ED patterns. Data collection is easy and fast, and can start at any arbitrary orientation of the crystal, which facilitates automation. Three-dimensional ED is a powerful technique for structure identification and structure solution from individual nano- or micron-sized particles, while powder X-ray diffraction (PXRD) provides information from all phases present in a sample. ED suffers from dynamic scattering, while PXRD data are kinematic. Three-dimensional ED methods and PXRD are complementary and their combinations are promising for studying multiphase samples and complicated crystal structures. Here, two three-dimensional ED methods, ADT and RED, are described. Examples are given of combinations of three-dimensional ED methods and PXRD for phase identification and structure determination over a large number of different materials, from Ni-Se-O-Cl crystals, zeolites, germanates, metal-organic frameworks and organic compounds to intermetallics with modulated structures. It is shown that three-dimensional ED is now as feasible as X-ray diffraction for phase identification and structure solution, but still needs further development in order to be as accurate as X-ray diffraction. It is expected that three-dimensional ED methods will become crucially important in the near future.

A plasma source driven predator-prey like mechanism as a potential cause of spiraling intermittencies in linear plasma devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reiser, D.; Ohno, N.; Tanaka, H.

2014-03-15

Three-dimensional global drift fluid simulations are carried out to analyze coherent plasma structures appearing in the NAGDIS-II linear device (nagoya divertor plasma Simulator-II). The numerical simulations reproduce several features of the intermittent spiraling structures observed, for instance, statistical properties, rotation frequency, and the frequency of plasma expulsion. The detailed inspection of the three-dimensional plasma dynamics allows to identify the key mechanism behind the formation of these intermittent events. The resistive coupling between electron pressure and parallel electric field in the plasma source region gives rise to a quasilinear predator-prey like dynamics where the axisymmetric mode represents the prey and themore » spiraling structure with low azimuthal mode number represents the predator. This interpretation is confirmed by a reduced one-dimensional quasilinear model derived on the basis of the findings in the full three-dimensional simulations. The dominant dynamics reveals certain similarities to the classical Lotka-Volterra cycle.« less

Three-dimensional kinetic and fluid dynamic modeling and three iterative algorithms for side-pumped alkali vapor lasers

NASA Astrophysics Data System (ADS)

Shen, Binglin; Xu, Xingqi; Xia, Chunsheng; Pan, Bailiang

2017-11-01

Combining the kinetic and fluid dynamic processes in static and flowing-gas diode-pumped alkali vapor lasers, a comprehensive physical model with three cyclically iterative algorithms for simulating the three-dimensional pump and laser intensities as well as temperature distribution in the vapor cell of side-pumped alkali vapor lasers is established. Comparison with measurement of a static side-pumped cesium vapor laser with a diffuse type hollow cylinder cavity, and with classical and modified models is made. Influences of flowed velocity and pump power on laser power are calculated and analyzed. The results have demonstrated that for high-power side-pumped alkali vapor lasers, it is necessary to take into account the three-dimensional distributions of pump energy, laser energy and temperature in the cell to simultaneously obtain the thermal features and output characteristics. Therefore, the model can deepen the understanding of the complete kinetic and fluid dynamic mechanisms of a side-pumped alkali vapor laser, and help with its further experimental design.

Energy transfer mechanisms in layered 2D perovskites.

PubMed

Williams, Olivia F; Guo, Zhenkun; Hu, Jun; Yan, Liang; You, Wei; Moran, Andrew M

2018-04-07

Two-dimensional (2D) perovskite quantum wells are generating broad scientific interest because of their potential for use in optoelectronic devices. Recently, it has been shown that layers of 2D perovskites can be grown in which the average thicknesses of the quantum wells increase from the back to the front of the film. This geometry carries implications for light harvesting applications because the bandgap of a quantum well decreases as its thickness increases. The general structural formula for the 2D perovskite systems under investigation in this work is (PEA) 2 (MA) n-1 [Pb n I 3n+1 ] (PEA = phenethyl ammonium, MA = methyl ammonium). Here, we examine two layered 2D perovskites with different distributions of quantum well thicknesses. Spectroscopic measurements and model calculations suggest that both systems funnel electronic excitations from the back to the front of the film through energy transfer mechanisms on the time scales of 100's of ps (i.e., energy transfer from thinner to thicker quantum wells). In addition, the model calculations demonstrate that the transient absorption spectra are composed of a progression of single exciton and biexciton resonances associated with the individual quantum wells. We find that exciton dissociation and/or charge transport dynamics make only minor contributions to the transient absorption spectra within the first 1 ns after photo-excitation. An analysis of the energy transfer kinetics indicates that the transitions occur primarily between quantum wells with values of n that differ by 1 because of the spectral overlap factor that governs the energy transfer rate. Two-dimensional transient absorption spectra reveal a pattern of resonances consistent with the dominance of sequential energy transfer dynamics.

Energy transfer mechanisms in layered 2D perovskites

NASA Astrophysics Data System (ADS)

Williams, Olivia F.; Guo, Zhenkun; Hu, Jun; Yan, Liang; You, Wei; Moran, Andrew M.

2018-04-01

Two-dimensional (2D) perovskite quantum wells are generating broad scientific interest because of their potential for use in optoelectronic devices. Recently, it has been shown that layers of 2D perovskites can be grown in which the average thicknesses of the quantum wells increase from the back to the front of the film. This geometry carries implications for light harvesting applications because the bandgap of a quantum well decreases as its thickness increases. The general structural formula for the 2D perovskite systems under investigation in this work is (PEA)2(MA)n-1[PbnI3n+1] (PEA = phenethyl ammonium, MA = methyl ammonium). Here, we examine two layered 2D perovskites with different distributions of quantum well thicknesses. Spectroscopic measurements and model calculations suggest that both systems funnel electronic excitations from the back to the front of the film through energy transfer mechanisms on the time scales of 100's of ps (i.e., energy transfer from thinner to thicker quantum wells). In addition, the model calculations demonstrate that the transient absorption spectra are composed of a progression of single exciton and biexciton resonances associated with the individual quantum wells. We find that exciton dissociation and/or charge transport dynamics make only minor contributions to the transient absorption spectra within the first 1 ns after photo-excitation. An analysis of the energy transfer kinetics indicates that the transitions occur primarily between quantum wells with values of n that differ by 1 because of the spectral overlap factor that governs the energy transfer rate. Two-dimensional transient absorption spectra reveal a pattern of resonances consistent with the dominance of sequential energy transfer dynamics.

Monte Carlo Sampling in Fractal Landscapes

NASA Astrophysics Data System (ADS)

Leitão, Jorge C.; Lopes, J. M. Viana Parente; Altmann, Eduardo G.

2013-05-01

We design a random walk to explore fractal landscapes such as those describing chaotic transients in dynamical systems. We show that the random walk moves efficiently only when its step length depends on the height of the landscape via the largest Lyapunov exponent of the chaotic system. We propose a generalization of the Wang-Landau algorithm which constructs not only the density of states (transient time distribution) but also the correct step length. As a result, we obtain a flat-histogram Monte Carlo method which samples fractal landscapes in polynomial time, a dramatic improvement over the exponential scaling of traditional uniform-sampling methods. Our results are not limited by the dimensionality of the landscape and are confirmed numerically in chaotic systems with up to 30 dimensions.

SERS- and Electrochemically Active 3D Plasmonic Liquid Marbles for Molecular-Level Spectroelectrochemical Investigation of Microliter Reactions.

PubMed

Koh, Charlynn Sher Lin; Lee, Hiang Kwee; Phan-Quang, Gia Chuong; Han, Xuemei; Lee, Mian Rong; Yang, Zhe; Ling, Xing Yi

2017-07-17

Liquid marbles are emergent microreactors owing to their isolated environment and the flexibility of materials used. Plasmonic liquid marbles (PLMs) are demonstrated as the smallest spectroelectrochemical microliter-scale reactor for concurrent spectro- and electrochemical analyses. The three-dimensional Ag shell of PLMs are exploited as a bifunctional surface-enhanced Raman scattering (SERS) platform and working electrode for redox process modulation. The combination of SERS and electrochemistry (EC) capabilities enables in situ molecular read-out of transient electrochemical species, and elucidate the potential-dependent and multi-step reaction dynamics. The 3D configuration of our PLM-based EC-SERS system exhibits 2-fold and 10-fold superior electrochemical and SERS performance than conventional 2D platforms. The rich molecular-level electrochemical insights and excellent EC-SERS capabilities offered by our 3D spectroelectrochemical system are pertinent in charge transfer processes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigating anomalous transport of electrolytes in charged porous media

NASA Astrophysics Data System (ADS)

Skjøde Bolet, Asger Johannes; Mathiesen, Joachim

2017-04-01

Surface charge is know to play an important role in microfluidics devices when dealing with electrolytes and their transport properties. Similarly, surface charge could play a role for transport in porous rock with submicron pore sizes. Estimates of the streaming potentials and electro osmotic are mostly considered in simple geometries both using analytic and numerical tools, however it is unclear at present how realistic complex geometries will modify the dynamics. Our work have focused on doing numerical studies of the full three-dimensional Stokes-Poisson-Nernst-Planck problem for electrolyte transport in porous rock. As the numerical implementation, we have used a finite element solver made using the FEniCS project code base, which can both solve for a steady state configuration and the full transient. In the presentation, we will show our results on anomalous transport due to electro kinetic effects such as the streaming potential or the electro osmotic effect.

Computational analysis of the SSME fuel preburner flow

NASA Technical Reports Server (NTRS)

Wang, T. S.; Farmer, R. C.

1986-01-01

A computational fluid dynamics model which simulates the steady state operation of the SSME fuel preburner is developed. Specifically, the model will be used to quantify the flow factors which cause local hot spots in the fuel preburner in order to recommend experiments whereby the control of undesirable flow features can be demonstrated. The results of a two year effort to model the preburner are presented. In this effort, investigating the fuel preburner flowfield, the appropriate transport equations were numerically solved for both an axisymmetric and a three-dimensional configuration. Continuum's VAST (Variational Solution of the Transport equations) code, in conjunction with the CM-1000 Engineering Analysis Workstation and the NASA/Ames CYBER 205, was used to perform the required calculations. It is concluded that the preburner operational anomalies are not due to steady state phenomena and must, therefore, be related to transient operational procedures.

Numerical modeling of cold room's hinged door opening and closing processes

NASA Astrophysics Data System (ADS)

Carneiro, R.; Gaspar, P. D.; Silva, P. D.; Domingues, L. C.

2016-06-01

The need of rationalize energy consumption in agrifood industry has fasten the development of methodologies to improve the thermal and energy performances of cold rooms. This paper presents a three-dimensional (3D) transient Computational Fluid Dynamics (CFD) modelling of a cold room to evaluate the air infiltration rate through hinged doors. A species transport model is used for modelling the tracer gas concentration decay technique. Numerical predictions indicate that air temperature difference between spaces affects the air infiltration. For this case study, the infiltration rate increases 0.016 m3 s-1 per K of air temperature difference. The knowledge about the evolution of air infiltration during door opening/closing times allows to draw some conclusions about its influence on the air conditions inside the cold room, as well as to suggest best practices and simple technical improvements that can minimize air infiltration, and consequently improve thermal performance and energy consumption rationalization.

Flight experiment of thermal energy storage. [for spacecraft power systems

NASA Technical Reports Server (NTRS)

Namkoong, David

1989-01-01

Thermal energy storage (TES) enables a solar dynamic system to deliver constant electric power through periods of sun and shade. Brayton and Stirling power systems under current considerations for missions in the near future require working fluid temperatures in the 1100 to 1300+ K range. TES materials that meet these requirements fall into the fluoride family of salts. Salts shrink as they solidify, a change reaching 30 percent for some salts. Hot spots can develop in the TES container or the container can become distorted if the melting salt cannot expand elsewhere. Analysis of the transient, two-phase phenomenon is being incorporated into a three-dimensional computer code. The objective of the flight program is to verify the predictions of the code, particularly of the void location and its effect on containment temperature. The four experimental packages comprising the program will be the first tests of melting and freezing conducted under microgravity.

Exploring Stability of General Relativistic Accretion Disks

NASA Astrophysics Data System (ADS)

Korobkin, Oleg; Abdikamalov, Ernazar; Schnetter, Erik; Stergioulas, Nikolaos; Zink, Burkhard

2011-04-01

Self-gravitating relativistic disks around black holes can form as transient structures in a number of astrophysical scenarios, involving core collapse of massive stars and mergers of compact ob jects. I will present results on our recent study of the stability of such disks against runaway and non-axisymmetric instabilities, which we explore using three-dimensional hydrodynamics simulations in full general relativity. All of our models develop unstable non-axisymmetric modes on a dynamical timescale. We observe two distinct types of instabilities: the Papaloizou-Pringle and the so-called intermediate type instabilities. The development of the non-axisymmetric mode with azimuthal number m=1 is accompanied by an outspiraling motion of the black hole, which significantly amplifies the growth rate of the m=1 mode in some cases. We will discuss the types, growth rates and pattern speeds of the unstable modes, as well as the detectability of the gravitational waves from such objects.

New core-reflector boundary conditions for transient nodal reactor calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, E.K.; Kim, C.H.; Joo, H.K.

1995-09-01

New core-reflector boundary conditions designed for the exclusion of the reflector region in transient nodal reactor calculations are formulated. Spatially flat frequency approximations for the temporal neutron behavior and two types of transverse leakage approximations in the reflector region are introduced to solve the transverse-integrated time-dependent one-dimensional diffusion equation and then to obtain relationships between net current and flux at the core-reflector interfaces. To examine the effectiveness of new core-reflector boundary conditions in transient nodal reactor computations, nodal expansion method (NEM) computations with and without explicit representation of the reflector are performed for Laboratorium fuer Reaktorregelung und Anlagen (LRA) boilingmore » water reactor (BWR) and Nuclear Energy Agency Committee on Reactor Physics (NEACRP) pressurized water reactor (PWR) rod ejection kinetics benchmark problems. Good agreement between two NEM computations is demonstrated in all the important transient parameters of two benchmark problems. A significant amount of CPU time saving is also demonstrated with the boundary condition model with transverse leakage (BCMTL) approximations in the reflector region. In the three-dimensional LRA BWR, the BCMTL and the explicit reflector model computations differ by {approximately}4% in transient peak power density while the BCMTL results in >40% of CPU time saving by excluding both the axial and the radial reflector regions from explicit computational nodes. In the NEACRP PWR problem, which includes six different transient cases, the largest difference is 24.4% in the transient maximum power in the one-node-per-assembly B1 transient results. This difference in the transient maximum power of the B1 case is shown to reduce to 11.7% in the four-node-per-assembly computations. As for the computing time, BCMTL is shown to reduce the CPU time >20% in all six transient cases of the NEACRP PWR.« less

Defects and spatiotemporal disorder in a pattern of falling liquid columns

NASA Astrophysics Data System (ADS)

Brunet, Philippe; Limat, Laurent

2004-10-01

Disordered regimes of a one-dimensional pattern of liquid columns hanging below an overflowing circular dish are investigated experimentally. The interaction of two basic dynamical modes (oscillations and drift) combined with the occurrence of defects (birth of new columns, disappearances by coalescences of two columns) leads to spatiotemporal chaos. When the flow rate is progressively increased, a continuous transition between transient and permanent chaos is pointed into evidence. We introduce the rate of defects as the sole relevant quantity to quantify this “turbulence” without ambiguity. Statistics on both transient and endlessly chaotic regimes enable to define a critical flow rate around which exponents are extracted. Comparisons are drawn with other interfacial pattern-forming systems, where transition towards chaos follows similar steps. Qualitatively, careful examinations of the global dynamics show that the contamination processes are nonlocal and involve the propagation of blocks of elementary laminar states (such as propagative domains or local oscillations), emitted near the defects, which turn out to be essential ingredients of this self-sustained disorder.

Layer-Dependent Ultrafast Carrier and Coherent Phonon Dynamics in Black Phosphorus.

PubMed

Miao, Xianchong; Zhang, Guowei; Wang, Fanjie; Yan, Hugen; Ji, Minbiao

2018-05-09

Black phosphorus is a layered semiconducting material, demonstrating strong layer-dependent optical and electronic properties. Probing the photophysical properties on ultrafast time scales is of central importance in understanding many-body interactions and nonequilibrium quasiparticle dynamics. Here, we applied temporally, spectrally, and spatially resolved pump-probe microscopy to study the transient optical responses of mechanically exfoliated few-layer black phosphorus, with layer numbers ranging from 2 to 9. We have observed layer-dependent resonant transient absorption spectra with both photobleaching and red-shifted photoinduced absorption features, which could be attributed to band gap renormalization of higher subband transitions. Surprisingly, coherent phonon oscillations with unprecedented intensities were observed when the probe photons were in resonance with the optical transitions, which correspond to the low-frequency layer-breathing mode. Our results reveal strong Coulomb interactions and electron-phonon couplings in photoexcited black phosphorus, providing important insights into the ultrafast optical, nanomechanical, and optoelectronic properties of this novel two-dimensional material.

Minimizing transient influence in WHPA delineation: An optimization approach for optimal pumping rate schemes

NASA Astrophysics Data System (ADS)

Rodriguez-Pretelin, A.; Nowak, W.

2017-12-01

For most groundwater protection management programs, Wellhead Protection Areas (WHPAs) have served as primarily protection measure. In their delineation, the influence of time-varying groundwater flow conditions is often underestimated because steady-state assumptions are commonly made. However, it has been demonstrated that temporary variations lead to significant changes in the required size and shape of WHPAs. Apart from natural transient groundwater drivers (e.g., changes in the regional angle of flow direction and seasonal natural groundwater recharge), anthropogenic causes such as transient pumping rates are of the most influential factors that require larger WHPAs. We hypothesize that WHPA programs that integrate adaptive and optimized pumping-injection management schemes can counter transient effects and thus reduce the additional areal demand in well protection under transient conditions. The main goal of this study is to present a novel management framework that optimizes pumping schemes dynamically, in order to minimize the impact triggered by transient conditions in WHPA delineation. For optimizing pumping schemes, we consider three objectives: 1) to minimize the risk of pumping water from outside a given WHPA, 2) to maximize the groundwater supply and 3) to minimize the involved operating costs. We solve transient groundwater flow through an available transient groundwater and Lagrangian particle tracking model. The optimization problem is formulated as a dynamic programming problem. Two different optimization approaches are explored: I) the first approach aims for single-objective optimization under objective (1) only. The second approach performs multiobjective optimization under all three objectives where compromise pumping rates are selected from the current Pareto front. Finally, we look for WHPA outlines that are as small as possible, yet allow the optimization problem to find the most suitable solutions.

Three-dimensional modeling of flexible pavements : executive summary, August 2001.

DOT National Transportation Integrated Search

2001-08-01

A linear viscoelastic model has been incorporated into a three-dimensional finite element program for analysis of flexible pavements. Linear and quadratic versions of hexahedral elements and quadrilateral axisymmetrix elements are provided. Dynamic p...

Three dimensional modeling of flexible pavements : final report, March 2002.

DOT National Transportation Integrated Search

2001-08-01

A linear viscoelastic model has been incorporated into a three-dimensional finite element program for analysis of flexible pavements. Linear and quadratic versions of hexahedral elements and quadrilateral axisymmetrix elements are provided. Dynamic p...

Three-dimensional imaging of dislocation dynamics during the hydriding phase transformation

NASA Astrophysics Data System (ADS)

Ulvestad, A.; Welland, M. J.; Cha, W.; Liu, Y.; Kim, J. W.; Harder, R.; Maxey, E.; Clark, J. N.; Highland, M. J.; You, H.; Zapol, P.; Hruszkewycz, S. O.; Stephenson, G. B.

2017-05-01

Crystallographic imperfections significantly alter material properties and their response to external stimuli, including solute-induced phase transformations. Despite recent progress in imaging defects using electron and X-ray techniques, in situ three-dimensional imaging of defect dynamics remains challenging. Here, we use Bragg coherent diffractive imaging to image defects during the hydriding phase transformation of palladium nanocrystals. During constant-pressure experiments we observe that the phase transformation begins after dislocation nucleation close to the phase boundary in particles larger than 300 nm. The three-dimensional phase morphology suggests that the hydrogen-rich phase is more similar to a spherical cap on the hydrogen-poor phase than to the core-shell model commonly assumed. We substantiate this using three-dimensional phase field modelling, demonstrating how phase morphology affects the critical size for dislocation nucleation. Our results reveal how particle size and phase morphology affects transformations in the PdH system.

TREDI: A self consistent three-dimensional integration scheme for RF-gun dynamics based on the Lienard-Wiechert potentials formalism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giannessi, Luca; Quattromini, Marcello

1997-06-01

We describe the model for the simulation of charged beam dynamics in radiofrequency injectors used in the three dimensional code TREDI, where the inclusion of space charge fields is obtained by means of the Lienard-Wiechert retarded potentials. The problem of charge screening is analyzed in covariant form and some general recipes for charge assignment and noise reduction are given.

Transient Three-Dimensional Side Load Analysis of Out-of-Round Film Cooled Nozzles

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Lin, Jeff; Ruf, Joe; Guidos, Mike

2010-01-01

The objective of this study is to investigate the effect of nozzle out-of-roundness on the transient startup side loads at a high altitude, with an anchored computational methodology. The out-of-roundness could be the result of asymmetric loads induced by hardware attached to the nozzle, asymmetric internal stresses induced by previous tests, and deformation, such as creep, from previous tests. The rocket engine studied encompasses a regeneratively cooled thrust chamber and a film cooled nozzle extension with film coolant distributed from a turbine exhaust manifold. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, and a transient inlet history based on an engine system simulation. Transient startup computations were performed with the out-of-roundness achieved by four different degrees of ovalization: one perfectly round, one slightly out-of-round, one more out-of-round, and one significantly out-of-round. The results show that the separation-line-jump is the peak side load physics for the round, slightly our-of-round, and more out-of-round cases, and the peak side load increases as the degree of out-of-roundness increases. For the significantly out-of-round nozzle, however, the peak side load reduces to comparable to that of the round nozzle and the separation line jump is not the peak side load physics. The counter-intuitive result of the significantly out-of-round case is found to be related to a side force reduction mechanism that splits the effect of the separation-line-jump into two parts, not only in the circumferential direction and most importantly in time.

Concurrent Computational and Dimensional Analyses of Design of Vehicle Floor-Plates for Landmine-Blast Survivability

DTIC Science & Technology

2014-01-01

soil, etc.) (Ref 6); (b) the kinematic and structural response of the target to blast loading including the role of target design and use of blast...both the role of material behavior under transient-dynamic loading conditions as well as the kinematic and structural responses of the target structure... seats , ammunition storage racks, power-train lines, etc.). Tradition- ally, the floor-rupture problem is solved through the use of thicker floor-plates

Statistical mechanics of neocortical interactions: Stability and duration of the 7±2 rule of short-term-memory capacity

NASA Astrophysics Data System (ADS)

Ingber, Lester

1985-02-01

This paper is an essential addendum to a previous paper [L. Ingber,

Nonmonotonic Classical Magnetoconductivity of a Two-Dimensional Electron Gas in a Disordered Array of Obstacles

NASA Astrophysics Data System (ADS)

Siboni, N. H.; Schluck, J.; Pierz, K.; Schumacher, H. W.; Kazazis, D.; Horbach, J.; Heinzel, T.

2018-02-01

Magnetotransport measurements in combination with molecular dynamics simulations on two-dimensional disordered Lorentz gases in the classical regime are reported. In quantitative agreement between experiment and simulation, the magnetoconductivity displays a pronounced peak as a function of the perpendicular magnetic field B which cannot be explained by existing kinetic theories. This peak is linked to the onset of a directed motion of the electrons along the contour of the disordered obstacle matrix when the cyclotron radius becomes smaller than the size of the obstacles. This directed motion leads to transient superdiffusive motion and strong scaling corrections in the vicinity of the insulator-to-conductor transitions of the Lorentz gas.

Ergodicity breaking and ageing of underdamped Brownian dynamics with quenched disorder

NASA Astrophysics Data System (ADS)

Guo, Wei; Li, Yong; Song, Wen-Hua; Du, Lu-Chun

2018-03-01

The dynamics of an underdamped Brownian particle moving in one-dimensional quenched disorder under the action of an external force is investigated. Within the tailored parameter regime, the transiently anomalous diffusion and ergodicity breaking, spanning several orders of magnitude in time, have been obtained. The ageing nature of the system weakens as the dissipation of the system increases for other given parameters. Its origin is ascribed to the highly local heterogeneity of the disorder. Two kinds of approximations (in the stationary state), respectively, for large bias and large damping are derived. These results may be helpful in further understanding the nontrivial response of nonlinear dynamics, and also have potential applications to experiments and activities of biological processes.

Spontaneous emergence of cataclysmic networks in spatially extended systems

NASA Astrophysics Data System (ADS)

Manrubia, Susanna C.; Poyatos, Juan F.; Pérez-Mercader, Juan

2002-11-01

A system of interacting chemical species able to catalyse each others' production is studied. We consider a two-dimensional surface where single molecules attach, diffuse, catalytically interact, and decay. The population of species molecules and the network of interactions among them are dynamical entities. After a short transient time, robust catalytic cycles emerge and a "stationary" state of high diversity and large population numbers settles down. Population dynamics and physical space select among possible graphs of catalytic interactions. The organization of the system is robust: parasitic invaders are short-lived, their populations are kept at low levels, and are unable to sweep away the emerging catalytic cycles.

Obtaining short-fiber orientation model parameters using non-lubricated squeeze flow

NASA Astrophysics Data System (ADS)

Lambert, Gregory; Wapperom, Peter; Baird, Donald

2017-12-01

Accurate models of fiber orientation dynamics during the processing of polymer-fiber composites are needed for the design work behind important automobile parts. All of the existing models utilize empirical parameters, but a standard method for obtaining them independent of processing does not exist. This study considers non-lubricated squeeze flow through a rectangular channel as a solution. A two-dimensional finite element method simulation of the kinematics and fiber orientation evolution along the centerline of a sample is developed as a first step toward a fully three-dimensional simulation. The model is used to fit to orientation data in a short-fiber-reinforced polymer composite after squeezing. Fiber orientation model parameters obtained in this study do not agree well with those obtained for the same material during startup of simple shear. This is attributed to the vastly different rates at which fibers orient during shearing and extensional flows. A stress model is also used to try to fit to experimental closure force data. Although the model can be tuned to the correct magnitude of the closure force, it does not fully recreate the transient behavior, which is attributed to the lack of any consideration for fiber-fiber interactions.

Determining mode excitations of vacuum electronics devices via three-dimensional simulations using the SOS code

NASA Technical Reports Server (NTRS)

Warren, Gary

1988-01-01

The SOS code is used to compute the resonance modes (frequency-domain information) of sample devices and separately to compute the transient behavior of the same devices. A code, DOT, is created to compute appropriate dot products of the time-domain and frequency-domain results. The transient behavior of individual modes in the device is then plotted. Modes in a coupled-cavity traveling-wave tube (CCTWT) section excited beam in separate simulations are analyzed. Mode energy vs. time and mode phase vs. time are computed and it is determined whether the transient waves are forward or backward waves for each case. Finally, the hot-test mode frequencies of the CCTWT section are computed.

Non-stationary Drainage Flows and Cold Pools in Gentle Terrain

NASA Astrophysics Data System (ADS)

Mahrt, L.

2015-12-01

Previous studies have concentrated on organized topography with well-defined slopes or valleys in an effort to understand the flow dynamics. However, most of the Earth's land surface consists of gentle terrain that is quasi three dimensional. Different scenarios are briefly classified. A network of measurements are analyzed to examine shallow cold pools and drainage flow down the valley which develop for weak ambient wind and relatively clear skies. However, transient modes constantly modulate or intermittently eliminate the cold pool, which makes extraction and analysis of the horizontal structure of the cold pool difficult with traditional analysis methods. Singular value decomposition successfully isolates the effects of large-scale flow from local down-valley cold air drainage within the cold pool in spite of the intermittent nature of this local flow. The traditional concept of a cold pool must be generalized to include cold pool intermittency, complex variation of temperature related to some three-dimensionality and a diffuse cold pool top. Different types of cold pools are classified in terms of the stratification and gradient of potential temperature along the slope. The strength of the cold pool is related to a forcing temperature scale proportional to the net radiative cooling divided by the wind speed above the valley. The scatter is large partly due to nonstationarity of the marginal cold pool in this shallow valley

The short-lived signaling state of the photoactive yellow protein photoreceptor revealed by combined structural probes.

PubMed

Ramachandran, Pradeep L; Lovett, Janet E; Carl, Patrick J; Cammarata, Marco; Lee, Jae Hyuk; Jung, Yang Ouk; Ihee, Hyotcherl; Timmel, Christiane R; van Thor, Jasper J

2011-06-22

The signaling state of the photoactive yellow protein (PYP) photoreceptor is transiently developed via isomerization of its blue-light-absorbing chromophore. The associated structural rearrangements have large amplitude but, due to its transient nature and chemical exchange reactions that complicate NMR detection, its accurate three-dimensional structure in solution has been elusive. Here we report on direct structural observation of the transient signaling state by combining double electron electron resonance spectroscopy (DEER), NMR, and time-resolved pump-probe X-ray solution scattering (TR-SAXS/WAXS). Measurement of distance distributions for doubly spin-labeled photoreceptor constructs using DEER spectroscopy suggests that the signaling state is well ordered and shows that interspin-label distances change reversibly up to 19 Å upon illumination. The SAXS/WAXS difference signal for the signaling state relative to the ground state indicates the transient formation of an ordered and rearranged conformation, which has an increased radius of gyration, an increased maximum dimension, and a reduced excluded volume. Dynamical annealing calculations using the DEER derived long-range distance restraints in combination with short-range distance information from (1)H-(15)N HSQC perturbation spectroscopy give strong indication for a rearrangement that places part of the N-terminal domain in contact with the exposed chromophore binding cleft while the terminal residues extend away from the core. Time-resolved global structural information from pump-probe TR-SAXS/WAXS data supports this conformation and allows subsequent structural refinement that includes the combined energy terms from DEER, NMR, and SAXS/WAXS together. The resulting ensemble simultaneously satisfies all restraints, and the inclusion of TR-SAXS/WAXS effectively reduces the uncertainty arising from the possible spin-label orientations. The observations are essentially compatible with reduced folding of the I(2)' state (also referred to as the 'pB' state) that is widely reported, but indicates it to be relatively ordered and rearranged. Furthermore, there is direct evidence for the repositioning of the N-terminal region in the I(2)' state, which is structurally modeled by dynamical annealing and refinement calculations.

Opinion: Building epithelial architecture: insights from three-dimensional culture models.

PubMed

O'Brien, Lucy Erin; Zegers, Mirjam M P; Mostov, Keith E

2002-07-01

How do individual cells organize into multicellular tissues? Here, we propose that the morphogenetic behaviour of epithelial cells is guided by two distinct elements: an intrinsic differentiation programme that drives formation of a lumen-enclosing monolayer, and a growth factor-induced, transient de-differentiation that allows this monolayer to be remodelled.

For operation of the Computer Software Management and Information Center (COSMIC)

NASA Technical Reports Server (NTRS)

Carmon, J. L.

1983-01-01

Computer programs for large systems of normal equations, an interactive digital signal process, structural analysis of cylindrical thrust chambers, swirling turbulent axisymmetric recirculating flows in practical isothermal combustor geometrics, computation of three dimensional combustor performance, a thermal radiation analysis system, transient response analysis, and a software design analysis are summarized.

Transient dynamics of terrestrial carbon storage: Mathematical foundation and its applications

DOE PAGES

Luo, Yiqi; Shi, Zheng; Lu, Xingjie; ...

2017-01-12

Terrestrial ecosystems have absorbed roughly 30% of anthropogenic CO 2 emissions over the past decades, but it is unclear whether this carbon (C) sink will endure into the future. Despite extensive modeling and experimental and observational studies, what fundamentally determines transient dynamics of terrestrial C storage under global change is still not very clear. Here we develop a new framework for understanding transient dynamics of terrestrial C storage through mathematical analysis and numerical experiments. Our analysis indicates that the ultimate force driving ecosystem C storage change is the C storage capacity, which is jointly determined by ecosystem C input (e.g.,more » net primary production, NPP) and residence time. Since both C input and residence time vary with time, the C storage capacity is time-dependent and acts as a moving attractor that actual C storage chases. The rate of change in C storage is proportional to the C storage potential, which is the difference between the current storage and the storage capacity. The C storage capacity represents instantaneous responses of the land C cycle to external forcing, whereas the C storage potential represents the internal capability of the land C cycle to influence the C change trajectory in the next time step. The influence happens through redistribution of net C pool changes in a network of pools with different residence times. Moreover, this and our other studies have demonstrated that one matrix equation can replicate simulations of most land C cycle models (i.e., physical emulators). As a result, simulation outputs of those models can be placed into a three-dimensional (3-D) parameter space to measure their differences. The latter can be decomposed into traceable components to track the origins of model uncertainty. In addition, the physical emulators make data assimilation computationally feasible so that both C flux- and pool-related datasets can be used to better constrain model predictions of land C sequestration. Altogether, this new mathematical framework offers new approaches to understanding, evaluating, diagnosing, and improving land C cycle models.« less

Transient dynamics of terrestrial carbon storage: Mathematical foundation and its applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Yiqi; Shi, Zheng; Lu, Xingjie

Terrestrial ecosystems have absorbed roughly 30% of anthropogenic CO 2 emissions over the past decades, but it is unclear whether this carbon (C) sink will endure into the future. Despite extensive modeling and experimental and observational studies, what fundamentally determines transient dynamics of terrestrial C storage under global change is still not very clear. Here we develop a new framework for understanding transient dynamics of terrestrial C storage through mathematical analysis and numerical experiments. Our analysis indicates that the ultimate force driving ecosystem C storage change is the C storage capacity, which is jointly determined by ecosystem C input (e.g.,more » net primary production, NPP) and residence time. Since both C input and residence time vary with time, the C storage capacity is time-dependent and acts as a moving attractor that actual C storage chases. The rate of change in C storage is proportional to the C storage potential, which is the difference between the current storage and the storage capacity. The C storage capacity represents instantaneous responses of the land C cycle to external forcing, whereas the C storage potential represents the internal capability of the land C cycle to influence the C change trajectory in the next time step. The influence happens through redistribution of net C pool changes in a network of pools with different residence times. Moreover, this and our other studies have demonstrated that one matrix equation can replicate simulations of most land C cycle models (i.e., physical emulators). As a result, simulation outputs of those models can be placed into a three-dimensional (3-D) parameter space to measure their differences. The latter can be decomposed into traceable components to track the origins of model uncertainty. In addition, the physical emulators make data assimilation computationally feasible so that both C flux- and pool-related datasets can be used to better constrain model predictions of land C sequestration. Altogether, this new mathematical framework offers new approaches to understanding, evaluating, diagnosing, and improving land C cycle models.« less

Transient dynamics of terrestrial carbon storage: Mathematical foundation and numeric examples

DOE PAGES

Luo, Yiqi; Shi, Zheng; Lu, Xingjie; ...

2016-09-16

Terrestrial ecosystems absorb roughly 30% of anthropogenic CO 2 emissions since preindustrial era, but it is unclear whether this carbon (C) sink will endure into the future. Despite extensive modeling, experimental, and observational studies, what fundamentally determines transient dynamics of terrestrial C storage under climate change is still not very clear. Here we develop a new framework for understanding transient dynamics of terrestrial C storage through mathematical analysis and numerical experiments. Our analysis indicates that the ultimate force driving ecosystem C storage change is the C storage capacity, which is jointly determined by ecosystem C input (e.g., net primary production,more » NPP) and residence time. Since both C input and residence time vary with time, the C storage capacity is time-dependent and acts as a moving attractor that actual C storage chases. The rate of change in C storage is proportional to the C storage potential, the difference between the current storage and the storage capacity. The C storage capacity represents instantaneous responses of the land C cycle to external forcing, whereas the C storage potential represents the internal capability of the land C cycle to influence the C change trajectory in the next time step. The influence happens through redistribution of net C pool changes in a network of pools with different residence times. Furthermore, this and our other studies have demonstrated that one matrix equation can exactly replicate simulations of most land C cycle models (i.e., physical emulators). As a result, simulation outputs of those models can be placed into a three-dimensional (3D) parameter space to measure their differences. The latter can be decomposed into traceable components to track the origins of model uncertainty. Moreover, the emulators make data assimilation computationally feasible so that both C flux- and pool-related datasets can be used to better constrain model predictions of land C sequestration. We also propose that the C storage potential be the targeted variable for research, market trading, and government negotiation for C credits.« less

Transient dynamics of terrestrial carbon storage: Mathematical foundation and numeric examples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Yiqi; Shi, Zheng; Lu, Xingjie

Terrestrial ecosystems absorb roughly 30% of anthropogenic CO 2 emissions since preindustrial era, but it is unclear whether this carbon (C) sink will endure into the future. Despite extensive modeling, experimental, and observational studies, what fundamentally determines transient dynamics of terrestrial C storage under climate change is still not very clear. Here we develop a new framework for understanding transient dynamics of terrestrial C storage through mathematical analysis and numerical experiments. Our analysis indicates that the ultimate force driving ecosystem C storage change is the C storage capacity, which is jointly determined by ecosystem C input (e.g., net primary production,more » NPP) and residence time. Since both C input and residence time vary with time, the C storage capacity is time-dependent and acts as a moving attractor that actual C storage chases. The rate of change in C storage is proportional to the C storage potential, the difference between the current storage and the storage capacity. The C storage capacity represents instantaneous responses of the land C cycle to external forcing, whereas the C storage potential represents the internal capability of the land C cycle to influence the C change trajectory in the next time step. The influence happens through redistribution of net C pool changes in a network of pools with different residence times. Furthermore, this and our other studies have demonstrated that one matrix equation can exactly replicate simulations of most land C cycle models (i.e., physical emulators). As a result, simulation outputs of those models can be placed into a three-dimensional (3D) parameter space to measure their differences. The latter can be decomposed into traceable components to track the origins of model uncertainty. Moreover, the emulators make data assimilation computationally feasible so that both C flux- and pool-related datasets can be used to better constrain model predictions of land C sequestration. We also propose that the C storage potential be the targeted variable for research, market trading, and government negotiation for C credits.« less

Computational hemodynamics of an implanted coronary stent based on three-dimensional cine angiography reconstruction.

PubMed

Chen, Mounter C Y; Lu, Po-Chien; Chen, James S Y; Hwang, Ned H C

2005-01-01

Coronary stents are supportive wire meshes that keep narrow coronary arteries patent, reducing the risk of restenosis. Despite the common use of coronary stents, approximately 20-35% of them fail due to restenosis. Flow phenomena adjacent to the stent may contribute to restenosis. Three-dimensional computational fluid dynamics (CFD) and reconstruction based on biplane cine angiography were used to assess coronary geometry and volumetric blood flows. A patient-specific left anterior descending (LAD) artery was reconstructed from single-plane x-ray imaging. With corresponding electrocardiographic signals, images from the same time phase were selected from the angiograms for dynamic three-dimensional reconstruction. The resultant three-dimensional LAD artery at end-diastole was adopted for detailed analysis. Both the geometries and flow fields, based on a computational model from CAE software (ANSYS and CATIA) and full three-dimensional Navier-Stroke equations in the CFD-ACE+ software, respectively, changed dramatically after stent placement. Flow fields showed a complex three-dimensional spiral motion due to arterial tortuosity. The corresponding wall shear stresses, pressure gradient, and flow field all varied significantly after stent placement. Combined angiography and CFD techniques allow more detailed investigation of flow patterns in various segments. The implanted stent(s) may be quantitatively studied from the proposed hemodynamic modeling approach.

Young Infants' Perception of the Trajectories of Two- and Three-Dimensional Objects

ERIC Educational Resources Information Center

Johnson, Scott P.; Bremner, J. Gavin; Slater, Alan M.; Shuwairi, Sarah M.; Mason, Uschi; Spring, Jo; Usherwood, Barrie

2012-01-01

We investigated oculomotor anticipations in 4-month-old infants as they viewed center-occluded object trajectories. In two experiments, we examined performance in two-dimensional (2D) and three-dimensional (3D) dynamic occlusion displays and in an additional 3D condition with a smiley face as the moving target stimulus. Rates of anticipatory eye…

A coupled sharp-interface immersed boundary-finite-element method for flow-structure interaction with application to human phonation.

PubMed

Zheng, X; Xue, Q; Mittal, R; Beilamowicz, S

2010-11-01

A new flow-structure interaction method is presented, which couples a sharp-interface immersed boundary method flow solver with a finite-element method based solid dynamics solver. The coupled method provides robust and high-fidelity solution for complex flow-structure interaction (FSI) problems such as those involving three-dimensional flow and viscoelastic solids. The FSI solver is used to simulate flow-induced vibrations of the vocal folds during phonation. Both two- and three-dimensional models have been examined and qualitative, as well as quantitative comparisons, have been made with established results in order to validate the solver. The solver is used to study the onset of phonation in a two-dimensional laryngeal model and the dynamics of the glottal jet in a three-dimensional model and results from these studies are also presented.

Heat Pipe Vapor Dynamics. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Issacci, Farrokh

1990-01-01

The dynamic behavior of the vapor flow in heat pipes is investigated at startup and during operational transients. The vapor is modeled as two-dimensional, compressible viscous flow in an enclosure with inflow and outflow boundary conditions. For steady-state and operating transients, the SIMPLER method is used. In this method a control volume approach is employed on a staggered grid which makes the scheme very stable. It is shown that for relatively low input heat fluxes the compressibility of the vapor flow is low and the SIMPLER scheme is suitable for the study of transient vapor dynamics. When the input heat flux is high or the process under a startup operation starts at very low pressures and temperatures, the vapor is highly compressible and a shock wave is created in the evaporator. It is shown that for a wide range of input heat fluxes, the standard methods, including the SIMPLER scheme, are not suitable. A nonlinear filtering technique, along with the centered difference scheme, are then used for shock capturing as well as for the solution of the cell Reynolds-number problem. For high heat flux, the startup transient phase involves multiple shock reflections in the evaporator region. Each shock reflection causes a significant increase in the local pressure and a large pressure drop along the heat pipe. Furthermore, shock reflections cause flow reversal in the evaporation region and flow circulations in the adiabatic region. The maximum and maximum-averaged pressure drops in different sections of the heat pipe oscillate periodically with time because of multiple shock reflections. The pressure drop converges to a constant value at steady state. However, it is significantly higher than its steady-state value at the initiation of the startup transient. The time for the vapor core to reach steady-state condition depends on the input heat flux, the heat pipe geometry, the working fluid, and the condenser conditions. However, the vapor transient time, for an Na-filled heat pipe is on the order of seconds. Depending on the time constant for the overall system, the vapor transient time may be very short. Therefore, the vapor core may be assumed to be quasi-steady in the transient analysis of a heat pipe operation.

Evaluation of the parameters affecting bone temperature during drilling using a three-dimensional dynamic elastoplastic finite element model.

PubMed

Chen, Yung-Chuan; Tu, Yuan-Kun; Zhuang, Jun-Yan; Tsai, Yi-Jung; Yen, Cheng-Yo; Hsiao, Chih-Kun

2017-11-01

A three-dimensional dynamic elastoplastic finite element model was constructed and experimentally validated and was used to investigate the parameters which influence bone temperature during drilling, including the drill speed, feeding force, drill bit diameter, and bone density. Results showed the proposed three-dimensional dynamic elastoplastic finite element model can effectively simulate the temperature elevation during bone drilling. The bone temperature rise decreased with an increase in feeding force and drill speed, however, increased with the diameter of drill bit or bone density. The temperature distribution is significantly affected by the drilling duration; a lower drilling speed reduced the exposure duration, decreases the region of the thermally affected zone. The constructed model could be applied for analyzing the influence parameters during bone drilling to reduce the risk of thermal necrosis. It may provide important information for the design of drill bits and surgical drilling powers.

Three-Dimensional Dynamic Deformation Measurements Using Stereoscopic Imaging and Digital Speckle Photography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prentice, H. J.; Proud, W. G.

2006-07-28

A technique has been developed to determine experimentally the three-dimensional displacement field on the rear surface of a dynamically deforming plate. The technique combines speckle analysis with stereoscopy, using a modified angular-lens method: this incorporates split-frame photography and a simple method by which the effective lens separation can be adjusted and calibrated in situ. Whilst several analytical models exist to predict deformation in extended or semi-infinite targets, the non-trivial nature of the wave interactions complicates the generation and development of analytical models for targets of finite depth. By interrogating specimens experimentally to acquire three-dimensional strain data points, both analytical andmore » numerical model predictions can be verified more rigorously. The technique is applied to the quasi-static deformation of a rubber sheet and dynamically to Mild Steel sheets of various thicknesses.« less

Canonical and symplectic analysis for three dimensional gravity without dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Escalante, Alberto, E-mail: aescalan@ifuap.buap.mx; Osmart Ochoa-Gutiérrez, H.

2017-03-15

In this paper a detailed Hamiltonian analysis of three-dimensional gravity without dynamics proposed by V. Hussain is performed. We report the complete structure of the constraints and the Dirac brackets are explicitly computed. In addition, the Faddeev–Jackiw symplectic approach is developed; we report the complete set of Faddeev–Jackiw constraints and the generalized brackets, then we show that the Dirac and the generalized Faddeev–Jackiw brackets coincide to each other. Finally, the similarities and advantages between Faddeev–Jackiw and Dirac’s formalism are briefly discussed. - Highlights: • We report the symplectic analysis for three dimensional gravity without dynamics. • We report the Faddeev–Jackiwmore » constraints. • A pure Dirac’s analysis is performed. • The complete structure of Dirac’s constraints is reported. • We show that symplectic and Dirac’s brackets coincide to each other.« less

Transient behavior of redox flow battery connected to circuit based on global phase structure

NASA Astrophysics Data System (ADS)

Mannari, Toko; Hikihara, Takashi

A Redox Flow Battery (RFB) is one of the promising energy storage systems in power grid. An RFB has many advantages such as a quick response, a large capacity, and a scalability. Due to these advantages, an RFB can operate in mixed time scale. Actually, it has been demonstrated that an RFB can be used for load leveling, compensating sag, and smoothing the output of the renewable sources. An analysis on transient behaviors of an RFB is a key issue for these applications. An RFB is governed by electrical, chemical, and fluid dynamics. The hybrid structure makes the analysis difficult. To analyze transient behaviors of an RFB, the exact model is necessary. In this paper, we focus on a change in a concentration of ions in the electrolyte, and simulate the change with a model which is mainly based on chemical kinetics. The simulation results introduces transient behaviors of an RFB in a response to a load variation. There are found three kinds of typical transient behaviors including oscillations. As results, it is clarified that the complex transient behaviors, due to slow and fast dynamics in the system, arise by the quick response to load.

A three-dimensional autonomous nonlinear dynamical system modelling equatorial ocean flows

NASA Astrophysics Data System (ADS)

Ionescu-Kruse, Delia

2018-04-01

We investigate a nonlinear three-dimensional model for equatorial flows, finding exact solutions that capture the most relevant geophysical features: depth-dependent currents, poleward or equatorial surface drift and a vertical mixture of upward and downward motions.

Transient electro-thermal characterization of Si-Ge heterojunction bipolar transistors

NASA Astrophysics Data System (ADS)

Sahoo, Amit Kumar; Weiß, Mario; Fregonese, Sébastien; Malbert, Nathalie; Zimmer, Thomas

2012-08-01

In this paper, a comprehensive evaluation of the transient self-heating in microwave heterojunction bipolar transistors (HBTs) have been carried out through simulations and measurements. Three dimensional thermal TCAD simulations have been performed to investigate precisely the influence of backend metallization on transient thermal behavior of a submicron SiGe:C BiCMOS technology with fT and fmax of 230 GHz and 290 GHz, respectively. Transient variation of Collector current caused by self-heating is obtained through pulse measurements. For thermal characterization, different electro-thermal networks have been employed at the temperature node of HiCuM compact model. Thermal parameters have been extracted by means of compact model simulation using a scalable transistor library. It has been shown that, the conventional R-C thermal network is not sufficient to accurately model the transient thermal spreading behavior and therefore a recursive network needs to be used. Recursive network is verified with device simulations as well as measurements and found to be in excellent agreement.

A numerical model for dynamic wave rotor analysis

NASA Technical Reports Server (NTRS)

Paxson, D. E.

1995-01-01

A numerical model has been developed which can predict the dynamic (and steady state) performance of a wave rotor, given the geometry and time dependent boundary conditions. The one-dimensional, perfect gas, CFD based code tracks the gasdynamics in each of the wave rotor passages as they rotate past the various ducts. The model can operate both on and off-design, allowing dynamic behavior to be studied throughout the operating range of the wave rotor. The model accounts for several major loss mechanisms including finite passage opening time, fluid friction, heat transfer to and from the passage walls, and leakage to and from the passage ends. In addition, it can calculate the amount of work transferred to and from the fluid when the flow in the ducts is not aligned with the passages such as occurs in off-design operation. Since it is one-dimensional, the model runs reasonably fast on a typical workstation. This paper will describe the model and present the results of some transient calculations for a conceptual four port wave rotor designed as a topping cycle for a small gas turbine engine.

Site-specific vibrational dynamics of the CD3ζ membrane peptide using heterodyned two-dimensional infrared photon echo spectroscopy

NASA Astrophysics Data System (ADS)

Mukherjee, Prabuddha; Krummel, Amber T.; Fulmer, Eric C.; Kass, Itamar; Arkin, Isaiah T.; Zanni, Martin T.

2004-06-01

Heterodyned two-dimensional infrared (2D IR) spectroscopy has been used to study the amide I vibrational dynamics of a 27-residue peptide in lipid vesicles that encompasses the transmembrane domain of the T-cell receptor CD3ζ. Using 1-13C=18O isotope labeling, the amide I mode of the 49-Leucine residue was spectroscopically isolated and the homogeneous and inhomogeneous linewidths of this mode were measured by fitting the 2D IR spectrum collected with a photon echo pulse sequence. The pure dephasing and inhomogeneous linewidths are 2 and 32 cm-1, respectively. The population relaxation time of the amide I band was measured with a transient grating, and it contributes 9 cm-1 to the linewidth. Comparison of the 49-Leucine amide I mode and the amide I band of the entire CD3ζ peptide reveals that the vibrational dynamics are not uniform along the length of the peptide. Possible origins for the large amount of inhomogeneity present at the 49-Leucine site are discussed.

Nonlinear coherent structures in granular crystals

NASA Astrophysics Data System (ADS)

Chong, C.; Porter, Mason A.; Kevrekidis, P. G.; Daraio, C.

2017-10-01

The study of granular crystals, which are nonlinear metamaterials that consist of closely packed arrays of particles that interact elastically, is a vibrant area of research that combines ideas from disciplines such as materials science, nonlinear dynamics, and condensed-matter physics. Granular crystals exploit geometrical nonlinearities in their constitutive microstructure to produce properties (such as tunability and energy localization) that are not conventional to engineering materials and linear devices. In this topical review, we focus on recent experimental, computational, and theoretical results on nonlinear coherent structures in granular crystals. Such structures—which include traveling solitary waves, dispersive shock waves, and discrete breathers—have fascinating dynamics, including a diversity of both transient features and robust, long-lived patterns that emerge from broad classes of initial data. In our review, we primarily discuss phenomena in one-dimensional crystals, as most research to date has focused on such scenarios, but we also present some extensions to two-dimensional settings. Throughout the review, we highlight open problems and discuss a variety of potential engineering applications that arise from the rich dynamic response of granular crystals.

Importance of partitioning membranes of the brain and the influence of the neck in head injury modelling.

PubMed

Kumaresan, S; Radhakrishnan, S

1996-01-01

A head injury model consisting of the skull, the CSF, the brain and its partitioning membranes and the neck region is simulated by considering its near actual geometry. Three-dimensional finite-element analysis is carried out to investigate the influence of the partitioning membranes of the brain and the neck in head injury analysis through free-vibration analysis and transient analysis. In free-vibration analysis, the first five modal frequencies are calculated, and in transient analysis intracranial pressure and maximum shear stress in the brain are determined for a given occipital impact load.

Computational Methods for Structural Mechanics and Dynamics

NASA Technical Reports Server (NTRS)

Stroud, W. Jefferson (Editor); Housner, Jerrold M. (Editor); Tanner, John A. (Editor); Hayduk, Robert J. (Editor)

1989-01-01

Topics addressed include: transient dynamics; transient finite element method; transient analysis in impact and crash dynamic studies; multibody computer codes; dynamic analysis of space structures; multibody mechanics and manipulators; spatial and coplanar linkage systems; flexible body simulation; multibody dynamics; dynamical systems; and nonlinear characteristics of joints.

Three-dimensional flow visualization and vorticity dynamics in revolving wings

NASA Astrophysics Data System (ADS)

Cheng, Bo; Sane, Sanjay P.; Barbera, Giovanni; Troolin, Daniel R.; Strand, Tyson; Deng, Xinyan

2013-01-01

We investigated the three-dimensional vorticity dynamics of the flows generated by revolving wings using a volumetric 3-component velocimetry system. The three-dimensional velocity and vorticity fields were represented with respect to the base axes of rotating Cartesian reference frames, and the second invariant of the velocity gradient was evaluated and used as a criterion to identify two core vortex structures. The first structure was a composite of leading, trailing, and tip-edge vortices attached to the wing edges, whereas the second structure was a strong tip vortex tilted from leading-edge vortices and shed into the wake together with the vorticity generated at the tip edge. Using the fundamental vorticity equation, we evaluated the convection, stretching, and tilting of vorticity in the rotating wing frame to understand the generation and evolution of vorticity. Based on these data, we propose that the vorticity generated at the leading edge is carried away by strong tangential flow into the wake and travels downwards with the induced downwash. The convection by spanwise flow is comparatively negligible. The three-dimensional flow in the wake also exhibits considerable vortex tilting and stretching. Together these data underscore the complex and interconnected vortical structures and dynamics generated by revolving wings.

Overview of aerothermodynamic loads definition study

NASA Technical Reports Server (NTRS)

Gaugler, Raymond E.

1991-01-01

The objective of the Aerothermodynamic Loads Definition Study is to develop methods of accurately predicting the operating environment in advanced Earth-to-Orbit (ETO) propulsion systems, such as the Space Shuttle Main Engine (SSME) powerhead. Development of time averaged and time dependent three dimensional viscous computer codes as well as experimental verification and engine diagnostic testing are considered to be essential in achieving that objective. Time-averaged, nonsteady, and transient operating loads must all be well defined in order to accurately predict powerhead life. Described here is work in unsteady heat flow analysis, improved modeling of preburner flow, turbulence modeling for turbomachinery, computation of three dimensional flow with heat transfer, and unsteady viscous multi-blade row turbine analysis.

Time dependent deformation and stress in the lithosphere. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Yang, M.

1980-01-01

Efficient computer programs incorporating frontal solution and time stepping procedure were developed for the modelling of geodynamic problems. This scheme allows for investigating the quasi static phenomena including the effects of the rheological structure of a tectonically active region. From three dimensional models of strike slip earthquakes, it was found that lateral variation of viscosity affects the characteristics of surface deformations. The vertical deformation is especially informative about the viscosity structure in a strike slip fault zone. A three dimensional viscoelastic model of a thrust earthquake indicated that the transient disturbance on plate velocity due to a great plate boundary earthquake is significant at intermediate distances, but becomes barely measurable 1000 km away from the source.

A critical review on the carrier dynamics in 2D layered materials investigated using THz spectroscopy

NASA Astrophysics Data System (ADS)

Lu, Junpeng; Liu, Hongwei

2018-01-01

Accurately illustrating the photocarrier dynamics and photoelectrical properties of two dimensional (2D) materials is crucial in the development of 2D material-based optoelectronic devices. Considering this requirement, terahertz (THz) spectroscopy has emerged as a befitting characterization tool to provide deep insights into the carrier dynamics and measurements of the electrical/photoelectrical conductivity of 2D materials. THz spectroscopic measurements would provide information of transient behaviors of carriers with high accuracy in a nondestructive and noncontact manner. In this article, we present a comprehensive review on recent research efforts on investigations of 2D materials of graphene and transition metal dichalcogenides (TMDs) using THz spectroscopy. A brief introduction of THz time-domain spectroscopy (THz-TDS) and optical pump-THz probe spectroscopy (OPTP) is provided. The characterization of the electron transport of graphene at equilibrium state and transient behavior at non-equilibrium state is reviewed. We also review the characterizations of TMDs including MoS2 and WSe2. Finally, we conclude the recent reports and give a prospect on how THz characterizations would guide the design and optimization of 2D material-based optoelectronic devices.

Generalized GW+Boltzmann Approach for the Description of Ultrafast Electron Dynamics in Topological Insulators

PubMed Central

Battiato, Marco; Sánchez-Barriga, Jaime

2017-01-01

Quantum-phase transitions between trivial insulators and topological insulators differ from ordinary metal-insulator transitions in that they arise from the inversion of the bulk band structure due to strong spin–orbit coupling. Such topological phase transitions are unique in nature as they lead to the emergence of topological surface states which are characterized by a peculiar spin texture that is believed to play a central role in the generation and manipulation of dissipationless surface spin currents on ultrafast timescales. Here, we provide a generalized GW+Boltzmann approach for the description of ultrafast dynamics in topological insulators driven by electron–electron and electron–phonon scatterings. Taking the prototypical insulator Bi2Te3 as an example, we test the robustness of our approach by comparing the theoretical prediction to results of time- and angle-resolved photoemission experiments. From this comparison, we are able to demonstrate the crucial role of the excited spin texture in the subpicosecond relaxation of transient electrons, as well as to accurately obtain the magnitude and strength of electron–electron and electron–phonon couplings. Our approach could be used as a generalized theory for three-dimensional topological insulators in the bulk-conducting transport regime, paving the way for the realization of a unified theory of ultrafast dynamics in topological materials. PMID:28773171

Generalized GW+Boltzmann Approach for the Description of Ultrafast Electron Dynamics in Topological Insulators.

PubMed

Battiato, Marco; Aguilera, Irene; Sánchez-Barriga, Jaime

2017-07-17

Quantum-phase transitions between trivial insulators and topological insulators differ from ordinary metal-insulator transitions in that they arise from the inversion of the bulk band structure due to strong spin-orbit coupling. Such topological phase transitions are unique in nature as they lead to the emergence of topological surface states which are characterized by a peculiar spin texture that is believed to play a central role in the generation and manipulation of dissipationless surface spin currents on ultrafast timescales. Here, we provide a generalized G W +Boltzmann approach for the description of ultrafast dynamics in topological insulators driven by electron-electron and electron-phonon scatterings. Taking the prototypical insulator Bi 2 Te 3 as an example, we test the robustness of our approach by comparing the theoretical prediction to results of time- and angle-resolved photoemission experiments. From this comparison, we are able to demonstrate the crucial role of the excited spin texture in the subpicosecond relaxation of transient electrons, as well as to accurately obtain the magnitude and strength of electron-electron and electron-phonon couplings. Our approach could be used as a generalized theory for three-dimensional topological insulators in the bulk-conducting transport regime, paving the way for the realization of a unified theory of ultrafast dynamics in topological materials.

Dynamic model of a micro-tubular solid oxide fuel cell stack including an integrated cooling system

NASA Astrophysics Data System (ADS)

Hering, Martin; Brouwer, Jacob; Winkler, Wolfgang

2017-02-01

A novel dynamic micro-tubular solid oxide fuel cell (MT-SOFC) and stack model including an integrated cooling system is developed using a quasi three-dimensional, spatially resolved, transient thermodynamic, physical and electrochemical model that accounts for the complex geometrical relations between the cells and cooling-tubes. The modeling approach includes a simplified tubular geometry and stack design including an integrated cooling structure, detailed pressure drop and gas property calculations, the electrical and physical constraints of the stack design that determine the current, as well as control strategies for the temperature. Moreover, an advanced heat transfer balance with detailed radiative heat transfer between the cells and the integrated cooling-tubes, convective heat transfer between the gas flows and the surrounding structures and conductive heat transfer between the solid structures inside of the stack, is included. The detailed model can be used as a design basis for the novel MT-SOFC stack assembly including an integrated cooling system, as well as for the development of a dynamic system control strategy. The evaluated best-case design achieves very high electrical efficiency between around 75 and 55% in the entire power density range between 50 and 550 mW /cm2 due to the novel stack design comprising an integrated cooling structure.

Characterizing heterogeneous dynamics at hydrated electrode surfaces.

PubMed

Willard, Adam P; Limmer, David T; Madden, Paul A; Chandler, David

2013-05-14

In models of Pt 111 and Pt 100 surfaces in water, motions of molecules in the first hydration layer are spatially and temporally correlated. To interpret these collective motions, we apply quantitative measures of dynamic heterogeneity that are standard tools for considering glassy systems. Specifically, we carry out an analysis in terms of mobility fields and distributions of persistence times and exchange times. In so doing, we show that dynamics in these systems is facilitated by transient disorder in frustrated two-dimensional hydrogen bonding networks. The frustration is the result of unfavorable geometry imposed by strong metal-water bonding. The geometry depends upon the structure of the underlying metal surface. Dynamic heterogeneity of water on the Pt 111 surface is therefore qualitatively different than that for water on the Pt 100 surface. In both cases, statistics of this ad-layer dynamic heterogeneity responds asymmetrically to applied voltage.

Characterizing heterogeneous dynamics at hydrated electrode surfaces

NASA Astrophysics Data System (ADS)

Willard, Adam P.; Limmer, David T.; Madden, Paul A.; Chandler, David

2013-05-01

In models of Pt 111 and Pt 100 surfaces in water, motions of molecules in the first hydration layer are spatially and temporally correlated. To interpret these collective motions, we apply quantitative measures of dynamic heterogeneity that are standard tools for considering glassy systems. Specifically, we carry out an analysis in terms of mobility fields and distributions of persistence times and exchange times. In so doing, we show that dynamics in these systems is facilitated by transient disorder in frustrated two-dimensional hydrogen bonding networks. The frustration is the result of unfavorable geometry imposed by strong metal-water bonding. The geometry depends upon the structure of the underlying metal surface. Dynamic heterogeneity of water on the Pt 111 surface is therefore qualitatively different than that for water on the Pt 100 surface. In both cases, statistics of this ad-layer dynamic heterogeneity responds asymmetrically to applied voltage.

Numerical modelling of Mars supersonic disk-gap-band parachute inflation

NASA Astrophysics Data System (ADS)

Gao, Xinglong; Zhang, Qingbin; Tang, Qiangang

2016-06-01

The transient dynamic behaviour of supersonic disk-gap-band parachutes in a Mars entry environment involving fluid structure interactions is studied. Based on the multi-material Arbitrary Lagrange-Euler method, the coupling dynamic model between a viscous compressible fluid and a flexible large deformation structure of the parachute is solved. The inflation performance of a parachute with a fixed forebody under different flow conditions is analysed. The decelerating parameters of the parachute, including drag area, opening loads, and coefficients, are obtained from the supersonic wind tunnel test data from NASA. Meanwhile, the evolution of the three-dimensional shape of the disk-gap-band parachute during supersonic inflation is presented, and the structural dynamic behaviour of the parachute is predicted. Then, the influence of the presence of the capsule on the flow field of the parachute is investigated, and the wake of unsteady fluid and the distribution of shock wave around the supersonic parachute are presented. Finally, the structural dynamic response of the canopy fabric under high-pressure conditions is comparatively analysed. The results show that the disk-gap-band parachute is well inflated without serious collapse. As the Mach numbers increase from 2.0 to 2.5, the drag coefficients gradually decrease, along with a small decrease in inflation time, which corresponds with test results, and proves the validity of the method proposed in this paper.

Development of an Aeroelastic Modeling Capability for Transient Nozzle Side Load Analysis

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Zhao, Xiang; Zhang, Sijun; Chen, Yen-Sen

2013-01-01

Lateral nozzle forces are known to cause severe structural damage to any new rocket engine in development. Currently there is no fully coupled computational tool to analyze this fluid/structure interaction process. The objective of this study was to develop a fully coupled aeroelastic modeling capability to describe the fluid/structure interaction process during the transient nozzle operations. The aeroelastic model composes of three components: the computational fluid dynamics component based on an unstructured-grid, pressure-based computational fluid dynamics formulation, the computational structural dynamics component developed in the framework of modal analysis, and the fluid-structural interface component. The developed aeroelastic model was applied to the transient nozzle startup process of the Space Shuttle Main Engine at sea level. The computed nozzle side loads and the axial nozzle wall pressure profiles from the aeroelastic nozzle are compared with those of the published rigid nozzle results, and the impact of the fluid/structure interaction on nozzle side loads is interrogated and presented.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doughty, Benjamin; Simpson, Mary Jane; Yang, Bin

Our work aims to simplify multi-dimensional femtosecond transient absorption microscopy (TAM) data into decay associated amplitude maps that describe the spatial distributions of dynamical processes occurring on various characteristic timescales. Application of this method to TAM data obtained from a model methyl-ammonium lead iodide (CH 3NH 3PbI 3) perovskite thin film allows us to simplify the dataset consisting of a 68 time-resolved images into 4 decay associated amplitude maps. Furthermore, these maps provide a simple means to visualize the complex electronic excited-state dynamics in this system by separating distinct dynamical processes evolving on characteristic timescales into individual spatial images. Thismore » approach provides new insight into subtle aspects of ultrafast relaxation dynamics associated with excitons and charge carriers in the perovskite thin film, which have recently been found to coexist at spatially distinct locations.« less

Spontaneous Contractility-Mediated Cortical Flow Generates Cell Migration in Three-Dimensional Environments

PubMed Central

Hawkins, Rhoda J.; Poincloux, Renaud; Bénichou, Olivier; Piel, Matthieu; Chavrier, Philippe; Voituriez, Raphaël

2011-01-01

We present a model of cell motility generated by actomyosin contraction of the cell cortex. We identify, analytically, dynamical instabilities of the cortex and show that they yield steady-state cortical flows, which, in turn, can induce cell migration in three-dimensional environments. This mechanism relies on the regulation of contractility by myosin, whose transport is explicitly taken into account in the model. Theoretical predictions are compared to experimental data of tumor cells migrating in three-dimensional matrigel and suggest that this mechanism could be a general mode of cell migration in three-dimensional environments. PMID:21889440

INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Transient heat conduction in laser diodes

NASA Astrophysics Data System (ADS)

Enders, P.; Galley, J.

1988-11-01

The dynamics of heat transfer in stripe GaAlAs laser diodes is investigated by solving the linear diffusion equation for a quasitwo-dimensional multilayer structure. The calculations are rationalized drastically by the transfer matrix method and also using for the first time the asymptotes of the decay constants. Special attention is given to the convergence of the Fourier series. A comparison with experimental results reveals however that this is essentially the Stefan problem (with moving boundary conditions).

Three-dimensional Modeling of Water Quality and Ecology in Narragansett Bay

EPA Science Inventory

This report presents the methodology to apply, calibrate, and validate the three-dimensional water quality and ecological model provided with the Environmental Fluid Dynamics Code (EFDC). The required advection and dispersion mechanisms are generated simultaneously by the EFDC h...

Dynamical behavior for the three-dimensional generalized Hasegawa-Mima equations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang Ruifeng; Guo Boling; Institute of Applied Physics and Computational Mathematics, P.O. Box 8009, Beijing 100088

2007-01-15

The long time behavior of solution of the three-dimensional generalized Hasegawa-Mima [Phys. Fluids 21, 87 (1978)] equations with dissipation term is considered. The global attractor problem of the three-dimensional generalized Hasegawa-Mima equations with periodic boundary condition was studied. Applying the method of uniform a priori estimates, the existence of global attractor of this problem was proven, and also the dimensions of the global attractor are estimated.

Three-dimensional dynamics of scientific balloon systems in response to sudden gust loadings. [including a computer program user manual

NASA Technical Reports Server (NTRS)

Dorsey, D. R., Jr.

1975-01-01

A mathematical model was developed of the three-dimensional dynamics of a high-altitude scientific research balloon system perturbed from its equilibrium configuration by an arbitrary gust loading. The platform is modelled as a system of four coupled pendula, and the equations of motion were developed in the Lagrangian formalism assuming a small-angle approximation. Three-dimensional pendulation, torsion, and precessional motion due to Coriolis forces are considered. Aerodynamic and viscous damping effects on the pendulatory and torsional motions are included. A general model of the gust field incident upon the balloon system was developed. The digital computer simulation program is described, and a guide to its use is given.

Robustness of a cellular automata model for the HIV infection

NASA Astrophysics Data System (ADS)

Figueirêdo, P. H.; Coutinho, S.; Zorzenon dos Santos, R. M.

2008-11-01

An investigation was conducted to study the robustness of the results obtained from the cellular automata model which describes the spread of the HIV infection within lymphoid tissues [R.M. Zorzenon dos Santos, S. Coutinho, Phys. Rev. Lett. 87 (2001) 168102]. The analysis focused on the dynamic behavior of the model when defined in lattices with different symmetries and dimensionalities. The results illustrated that the three-phase dynamics of the planar models suffered minor changes in relation to lattice symmetry variations and, while differences were observed regarding dimensionality changes, qualitative behavior was preserved. A further investigation was conducted into primary infection and sensitiveness of the latency period to variations of the model’s stochastic parameters over wide ranging values. The variables characterizing primary infection and the latency period exhibited power-law behavior when the stochastic parameters varied over a few orders of magnitude. The power-law exponents were approximately the same when lattice symmetry varied, but there was a significant variation when dimensionality changed from two to three. The dynamics of the three-dimensional model was also shown to be insensitive to variations of the deterministic parameters related to cell resistance to the infection, and the necessary time lag to mount the specific immune response to HIV variants. The robustness of the model demonstrated in this work reinforce that its basic hypothesis are consistent with the three-stage dynamic of the HIV infection observed in patients.

Sub-cycle light transients for attosecond, X-ray, four-dimensional imaging

NASA Astrophysics Data System (ADS)

Fattahi, Hanieh

2016-10-01

This paper reviews the revolutionary development of ultra-short, multi-TW laser pulse generation made possible by current laser technology. The design of the unified laser architecture discussed in this paper, based on the synthesis of ultrabroadband optical parametric chirped-pulse amplifiers, promises to provide powerful light transients with electromagnetic forces engineerable on the electron time scale. By coherent combination of multiple amplifiers operating in different wavelength ranges, pulses with wavelength spectra extending from less than 1 ?m to more than 10 ?m, with sub-cycle duration at unprecedented peak and average power levels can be generated. It is shown theoretically that these light transients enable the efficient generation of attosecond X-ray pulses with photon flux sufficient to image, for the first time, picometre-attosecond trajectories of electrons, by means of X-ray diffraction and record the electron dynamics by attosecond spectroscopy. The proposed system leads to a tool with sub-atomic spatio-temporal resolution for studying different processes deep inside matter.

Three-Dimensional Transient Natural Convection in a Horizontal Cylinder: A Numerical Analysis

DTIC Science & Technology

1980-02-01

A11D 03 _________ 14. MNITORNG AGNCY AME&AORESS(it different from Controlling Office) IS. SECURITY CLASS. (of this report) -~Th /UNCLASSIFIED AISa . OECL...method for the vorticity and - DD IjANඑ 1473 EDITION OF I NOV6 SS OBSOLETE UNCLASSIFIED SECURITY CLASSIFICATION Of THIS PACE,n bt. Nte, -’ ’..r&IeI

Temperature Rise in a Two-Layer Structure Induced by a Rotating or Dithering Laser Beam

DTIC Science & Technology

2012-01-01

References [1] G. Araya and G. Gutierrez, Analytical solution for a transient, three-dimensional temperature dis- tribution due to a moving laser...beam, Int. J. Heat and Mass Transfer 49 ( 2006 ), 4124-4131. [2] R. Bellman, R.E. Marshak, and G.M. Wing, Laplace transform solution of two-medium neutron

Finite element solution of lubrication problems

NASA Technical Reports Server (NTRS)

Reddi, M. M.

1971-01-01

A variational formulation of the transient lubrication problem is presented and the corresponding finite element equations derived for three and six point triangles, and, four and eight point quadrilaterals. Test solutions for a one dimensional slider bearing used in validating the computer program are given. Utility of the method is demonstrated by a solution of the shrouded step bearing.

Inverse energy cascades in three-dimensional turbulence

NASA Technical Reports Server (NTRS)

Hossain, Murshed

1991-01-01

Fully three-dimensional magnetohydrodynamic (MHD) turbulence at large kinetic and low magnetic Reynolds numbers is considered in the presence of a strong uniform magnetic field. It is shown by numerical simulation of a model of MHD that the energy inverse cascades to longer length scales when the interaction parameter is large. While the steady-state dynamics of the driven problem is three-dimensional in character, the behavior has resemblance to two-dimensional hydrodynamics. These results have implications in turbulence theory, MHD power generator, planetary dynamos, and fusion reactor blanket design.

Optimal Control of Induction Machines to Minimize Transient Energy Losses

NASA Astrophysics Data System (ADS)

Plathottam, Siby Jose

Induction machines are electromechanical energy conversion devices comprised of a stator and a rotor. Torque is generated due to the interaction between the rotating magnetic field from the stator, and the current induced in the rotor conductors. Their speed and torque output can be precisely controlled by manipulating the magnitude, frequency, and phase of the three input sinusoidal voltage waveforms. Their ruggedness, low cost, and high efficiency have made them ubiquitous component of nearly every industrial application. Thus, even a small improvement in their energy efficient tend to give a large amount of electrical energy savings over the lifetime of the machine. Hence, increasing energy efficiency (reducing energy losses) in induction machines is a constrained optimization problem that has attracted attention from researchers. The energy conversion efficiency of induction machines depends on both the speed-torque operating point, as well as the input voltage waveform. It also depends on whether the machine is in the transient or steady state. Maximizing energy efficiency during steady state is a Static Optimization problem, that has been extensively studied, with commercial solutions available. On the other hand, improving energy efficiency during transients is a Dynamic Optimization problem that is sparsely studied. This dissertation exclusively focuses on improving energy efficiency during transients. This dissertation treats the transient energy loss minimization problem as an optimal control problem which consists of a dynamic model of the machine, and a cost functional. The rotor field oriented current fed model of the induction machine is selected as the dynamic model. The rotor speed and rotor d-axis flux are the state variables in the dynamic model. The stator currents referred to as d-and q-axis currents are the control inputs. A cost functional is proposed that assigns a cost to both the energy losses in the induction machine, as well as the deviations from desired speed-torque-magnetic flux setpoints. Using Pontryagin's minimum principle, a set of necessary conditions that must be satisfied by the optimal control trajectories are derived. The conditions are in the form a two-point boundary value problem, that can be solved numerically. The conjugate gradient method that was modified using the Hestenes-Stiefel formula was used to obtain the numerical solution of both the control and state trajectories. Using the distinctive shape of the numerical trajectories as inspiration, analytical expressions were derived for the state, and control trajectories. It was shown that the trajectory could be fully described by finding the solution of a one-dimensional optimization problem. The sensitivity of both the optimal trajectory and the optimal energy efficiency to different induction machine parameters were analyzed. A non-iterative solution that can use feedback for generating optimal control trajectories in real time was explored. It was found that an artificial neural network could be trained using the numerical solutions and made to emulate the optimal control trajectories with a high degree of accuracy. Hence a neural network along with a supervisory logic was implemented and used in a real-time simulation to control the Finite Element Method model of the induction machine. The results were compared with three other control regimes and the optimal control system was found to have the highest energy efficiency for the same drive cycle.

Biodynamic profiling of three-dimensional tissue growth techniques

NASA Astrophysics Data System (ADS)

Sun, Hao; Merrill, Dan; Turek, John; Nolte, David

2016-03-01

Three-dimensional tissue culture presents a more biologically relevant environment in which to perform drug development than conventional two-dimensional cell culture. However, obtaining high-content information from inside three dimensional tissue has presented an obstacle to rapid adoption of 3D tissue culture for pharmaceutical applications. Biodynamic imaging is a high-content three-dimensional optical imaging technology based on low-coherence interferometry and digital holography that uses intracellular dynamics as high-content image contrast. In this paper, we use biodynamic imaging to compare pharmaceutical responses to Taxol of three-dimensional multicellular spheroids grown by three different growth techniques: rotating bioreactor, hanging-drop and plate-grown spheroids. The three growth techniques have systematic variations among tissue cohesiveness and intracellular activity and consequently display different pharmacodynamics under identical drug dose conditions. The in vitro tissue cultures are also compared to ex vivo living biopsies. These results demonstrate that three-dimensional tissue cultures are not equivalent, and that drug-response studies must take into account the growth method.

A framework for studying transient dynamics of population projection matrix models.

PubMed

Stott, Iain; Townley, Stuart; Hodgson, David James

2011-09-01

Empirical models are central to effective conservation and population management, and should be predictive of real-world dynamics. Available modelling methods are diverse, but analysis usually focuses on long-term dynamics that are unable to describe the complicated short-term time series that can arise even from simple models following ecological disturbances or perturbations. Recent interest in such transient dynamics has led to diverse methodologies for their quantification in density-independent, time-invariant population projection matrix (PPM) models, but the fragmented nature of this literature has stifled the widespread analysis of transients. We review the literature on transient analyses of linear PPM models and synthesise a coherent framework. We promote the use of standardised indices, and categorise indices according to their focus on either convergence times or transient population density, and on either transient bounds or case-specific transient dynamics. We use a large database of empirical PPM models to explore relationships between indices of transient dynamics. This analysis promotes the use of population inertia as a simple, versatile and informative predictor of transient population density, but criticises the utility of established indices of convergence times. Our findings should guide further development of analyses of transient population dynamics using PPMs or other empirical modelling techniques. © 2011 Blackwell Publishing Ltd/CNRS.

In vitro expansion and differentiation of rat pancreatic duct-derived stem cells into insulin secreting cells using a dynamicthree-dimensional cell culture system.

PubMed

Chen, X C; Liu, H; Li, H; Cheng, Y; Yang, L; Liu, Y F

2016-06-27

In this study, a dynamic three-dimensional cell culture technology was used to expand and differentiate rat pancreatic duct-derived stem cells (PDSCs) into islet-like cell clusters that can secrete insulin. PDSCs were isolated from rat pancreatic tissues by in situ collagenase digestion and density gradient centrifugation. Using a dynamic three-dimensional culture technique, the cells were expanded and differentiated into functional islet-like cell clusters, which were characterized by morphological and phenotype analyses. After maintaining 1 x 108 isolated rat PDSCs in a dynamic three-dimensional cell culture for 7 days, 1.5 x 109 cells could be harvested. Passaged PDSCs expressed markers of pancreatic endocrine progenitors, including CD29 (86.17%), CD73 (90.73%), CD90 (84.13%), CD105 (78.28%), and Pdx-1. Following 14 additional days of culture in serum-free medium with nicotinamide, keratinocyte growth factor (KGF), and b fibroblast growth factor (FGF), the cells were differentiated into islet-like cell clusters (ICCs). The ICC morphology reflected that of fused cell clusters. During the late stage of differentiation, representative clusters were non-adherent and expressed insulin indicated by dithizone (DTZ)-positive staining. Insulin was detected in the extracellular fluid and cytoplasm of ICCs after 14 days of differentiation. Additionally, insulin levels were significantly higher at this time compared with the levels exhibited by PDSCs before differentiation (P < 0.01). By using a dynamic three-dimensional cell culture system, PDSCs can be expanded in vitro and can differentiate into functional islet-like cell clusters.

Assessment of Groundwater Susceptibility to Non-Point Source Contaminants Using Three-Dimensional Transient Indexes.

PubMed

Zhang, Yong; Weissmann, Gary S; Fogg, Graham E; Lu, Bingqing; Sun, HongGuang; Zheng, Chunmiao

2018-06-05

Groundwater susceptibility to non-point source contamination is typically quantified by stable indexes, while groundwater quality evolution (or deterioration globally) can be a long-term process that may last for decades and exhibit strong temporal variations. This study proposes a three-dimensional (3- d ), transient index map built upon physical models to characterize the complete temporal evolution of deep aquifer susceptibility. For illustration purposes, the previous travel time probability density (BTTPD) approach is extended to assess the 3- d deep groundwater susceptibility to non-point source contamination within a sequence stratigraphic framework observed in the Kings River fluvial fan (KRFF) aquifer. The BTTPD, which represents complete age distributions underlying a single groundwater sample in a regional-scale aquifer, is used as a quantitative, transient measure of aquifer susceptibility. The resultant 3- d imaging of susceptibility using the simulated BTTPDs in KRFF reveals the strong influence of regional-scale heterogeneity on susceptibility. The regional-scale incised-valley fill deposits increase the susceptibility of aquifers by enhancing rapid downward solute movement and displaying relatively narrow and young age distributions. In contrast, the regional-scale sequence-boundary paleosols within the open-fan deposits "protect" deep aquifers by slowing downward solute movement and displaying a relatively broad and old age distribution. Further comparison of the simulated susceptibility index maps to known contaminant distributions shows that these maps are generally consistent with the high concentration and quick evolution of 1,2-dibromo-3-chloropropane (DBCP) in groundwater around the incised-valley fill since the 1970s'. This application demonstrates that the BTTPDs can be used as quantitative and transient measures of deep aquifer susceptibility to non-point source contamination.

Dynamic-focusing microscope objective for optical coherence tomography

NASA Astrophysics Data System (ADS)

Murali, Supraja; Rolland, Jannick

2007-01-01

Optical Coherence Tomography (OCT) is a novel optical imaging technique that has assumed significant importance in bio-medical imaging in the last two decades because it is non-invasive and provides accurate, high resolution images of three dimensional cross-sections of body tissue, exceeding the capabilities of the current predominant imaging technique - ultrasound. In this paper, the application of high resolution OCT, known as optical coherence microscopy (OCM) is investigated for in vivo detection of abnormal skin pathology for the early diagnosis of cancer. A main challenge in OCM is maintaining invariant resolution throughout the sample. The technology presented is based on a dynamic focusing microscope imaging probe conceived for skin imaging and the detection of abnormalities in the epithelium. A novel method for dynamic focusing in the biological sample is presented using variable-focus lens technology to obtain three dimensional images with invariant resolution throughout the cross-section and depth of the sample is presented and discussed. A low coherence broadband source centered at near IR wavelengths is used to illuminate the sample. The design, analysis and predicted performance of the dynamic focusing microscope objective designed for dynamic three dimensional imaging at 5μm resolution for the chosen broadband spectrum is presented.

Phase-resolved fluid dynamic forces of a flapping foil energy harvester based on PIV measurements

NASA Astrophysics Data System (ADS)

Liburdy, James

2017-11-01

Two-dimensional particle image velocimetry measurements are performed in a wind tunnel to evaluate the spatial and temporal fluid dynamic forces acting on a flapping foil operating in the energy harvesting regime. Experiments are conducted at reduced frequencies (k = fc/U) of 0.05 - 0.2, pitching angle of, and heaving amplitude of A / c = 0.6. The phase-averaged pressure field is obtained by integrating the pressure Poisson equation. Fluid dynamic forces are then obtained through the integral momentum equation. Results are compared with a simple force model based on the concept of flow impulse. These results help to show the detailed force distributions, their transient nature and aide in understanding the impact of the fluid flow structures that contribute to the power production.

Dynamics of optically levitated microparticles in vacuum placed in 2D and 3D optical potentials possessing orbital angular momentum

NASA Astrophysics Data System (ADS)

Arita, Yoshihiko; Mazilu, Michael; Chen, Mingzhou; Vettenburg, Tom; Auñón, Juan M.; Wright, Ewan M.; Dholakia, Kishan

2017-04-01

We demonstrate the transfer of orbital angular momentum to optically levitated microparticles in vacuum [1]. We prepare two-dimensional and three-dimensional optical potentials. In the former case the microparticle is placed within a Laguerre-Gaussian beam and orbits the annular beam profile with increasing angular velocity as the air drag coefficient is reduced. We explore the particle dynamics as a function of the topological charge of the levitating beam. Our results reveal that there is a fundamental limit to the orbital angular momentum that may be transferred to a trapped particle, dependent upon the beam parameters and inertial forces present. This effect was predicted theoretically [2] and can be understood considering the underlying dynamics arising from the link between the magnitude of the azimuthal index and the beam radius [3]. Whilst a Laguerre-Gaussian beam scales in size with azimuthal index `, recently we have created a "perfect" vortex beam whose radial intensity profile and radius are both independent of topological charge [4, 5]. As the Fourier transform of a perfect vortex yields a Bessel beam. Imaging a perfect vortex, with its subsequent propagation thus realises a complex three dimensional optical field. In this scenario we load individual silica microparticles into this field and observe their trajectories. The optical gradient and scattering forces interplay with the inertial and gravitational forces acting on the trapped particle, including the rotational degrees of freedom. As a result the trapped microparticle exhibits a complex three dimensional motion that includes a periodic orbital motion between the Bessel and the perfect vortex beam. We are able to determine the three dimensional optical potential in situ by tracking the particle. This first demonstration of trapping microparticles within a complex three dimensional optical potential in vacuum opens up new possibilities for fundamental studies of many-body dynamics, mesoscopic entanglement [6, 7], and optical binding [8, 9].

Application of computer generated color graphic techniques to the processing and display of three dimensional fluid dynamic data

NASA Technical Reports Server (NTRS)

Anderson, B. H.; Putt, C. W.; Giamati, C. C.

1981-01-01

Color coding techniques used in the processing of remote sensing imagery were adapted and applied to the fluid dynamics problems associated with turbofan mixer nozzles. The computer generated color graphics were found to be useful in reconstructing the measured flow field from low resolution experimental data to give more physical meaning to this information and in scanning and interpreting the large volume of computer generated data from the three dimensional viscous computer code used in the analysis.

The similarity law for hypersonic flow and requirements for dynamic similarity of related bodies in free flight

NASA Technical Reports Server (NTRS)

Hamaker, Frank M; Neice, Stanford E; Wong, Thomas J

1953-01-01

The similarity law for nonsteady, inviscid, hypersonic flow about slender three-dimensional shapes is derived. Conclusions drawn are shown to be valid for rotational flow. Requirements for dynamic similarity of related shapes in free flight are obtained. The law is examined for steady flow about related three-dimensional shapes. Results of an experimental investigation of the pressures acting on two inclined cones are found to check the law as it applies to bodies of revolution.

Hysteresis, phase transitions, and dangerous transients in electrical power distribution systems

NASA Astrophysics Data System (ADS)

Duclut, Charlie; Backhaus, Scott; Chertkov, Michael

2013-06-01

The majority of dynamical studies in power systems focus on the high-voltage transmission grids where models consider large generators interacting with crude aggregations of individual small loads. However, new phenomena have been observed indicating that the spatial distribution of collective, nonlinear contribution of these small loads in the low-voltage distribution grid is crucial to the outcome of these dynamical transients. To elucidate the phenomenon, we study the dynamics of voltage and power flows in a spatially extended distribution feeder (circuit) connecting many asynchronous induction motors and discover that this relatively simple 1+1 (space+time) dimensional system exhibits a plethora of nontrivial spatiotemporal effects, some of which may be dangerous for power system stability. Long-range motor-motor interactions mediated by circuit voltage and electrical power flows result in coexistence and segregation of spatially extended phases defined by individual motor states, a “normal” state where the motors’ mechanical (rotation) frequency is slightly smaller than the nominal frequency of the basic ac flows and a “stalled” state where the mechanical frequency is small. Transitions between the two states can be initiated by a perturbation of the voltage or base frequency at the head of the distribution feeder. Such behavior is typical of first-order phase transitions in physics, and this 1+1 dimensional model shows many other properties of a first-order phase transition with the spatial distribution of the motors’ mechanical frequency playing the role of the order parameter. In particular, we observe (a) propagation of the phase-transition front with the constant speed (in very long feeders) and (b) hysteresis in transitions between the normal and stalled (or partially stalled) phases.

Hysteresis, phase transitions, and dangerous transients in electrical power distribution systems.

PubMed

Duclut, Charlie; Backhaus, Scott; Chertkov, Michael

2013-06-01

The majority of dynamical studies in power systems focus on the high-voltage transmission grids where models consider large generators interacting with crude aggregations of individual small loads. However, new phenomena have been observed indicating that the spatial distribution of collective, nonlinear contribution of these small loads in the low-voltage distribution grid is crucial to the outcome of these dynamical transients. To elucidate the phenomenon, we study the dynamics of voltage and power flows in a spatially extended distribution feeder (circuit) connecting many asynchronous induction motors and discover that this relatively simple 1+1 (space+time) dimensional system exhibits a plethora of nontrivial spatiotemporal effects, some of which may be dangerous for power system stability. Long-range motor-motor interactions mediated by circuit voltage and electrical power flows result in coexistence and segregation of spatially extended phases defined by individual motor states, a "normal" state where the motors' mechanical (rotation) frequency is slightly smaller than the nominal frequency of the basic ac flows and a "stalled" state where the mechanical frequency is small. Transitions between the two states can be initiated by a perturbation of the voltage or base frequency at the head of the distribution feeder. Such behavior is typical of first-order phase transitions in physics, and this 1+1 dimensional model shows many other properties of a first-order phase transition with the spatial distribution of the motors' mechanical frequency playing the role of the order parameter. In particular, we observe (a) propagation of the phase-transition front with the constant speed (in very long feeders) and (b) hysteresis in transitions between the normal and stalled (or partially stalled) phases.

Travelling-wave solutions of a weakly nonlinear two-dimensional higher-order Kadomtsev-Petviashvili dynamical equation for dispersive shallow-water waves

NASA Astrophysics Data System (ADS)

Seadawy, Aly R.

2017-01-01

The propagation of three-dimensional nonlinear irrotational flow of an inviscid and incompressible fluid of the long waves in dispersive shallow-water approximation is analyzed. The problem formulation of the long waves in dispersive shallow-water approximation lead to fifth-order Kadomtsev-Petviashvili (KP) dynamical equation by applying the reductive perturbation theory. By using an extended auxiliary equation method, the solitary travelling-wave solutions of the two-dimensional nonlinear fifth-order KP dynamical equation are derived. An analytical as well as a numerical solution of the two-dimensional nonlinear KP equation are obtained and analyzed with the effects of external pressure flow.

Energetic ion leakage from foreshock transient cores

NASA Astrophysics Data System (ADS)

Liu, Terry Z.; Angelopoulos, Vassilis; Hietala, Heli

2017-07-01

Earth's foreshock is filled with backstreaming particles that can interact with the ambient solar wind and its discontinuities to form foreshock transients. Many foreshock transients have a core with low dynamic pressure that can significantly perturb the bow shock and the magnetosphere-ionosphere system. Foreshock transients have also been recently recognized as sites of particle acceleration, which may be important for seeding the parent shock with energetic particles. A relevant step of this seeding would be energetic ion leakage into the surrounding foreshock environment. On the other hand, such leakage would also suppress the energetic particle flux contrast across foreshock transients' boundaries masking their perceived contribution to ion energization. To further examine this hypothesis of ion leakage, we report on multipoint case studies of three foreshock transient events selected from a large database. The cases were selected to exemplify, in increasing complexity, the nature and consequences of energetic ion leakage. Ion energy dispersion, observed upstream and/or downstream of the foreshock transients, is explained with a simple, ballistic model of ions leaking from the foreshock transients. Larger energies are required for leaked ions to reach the spacecraft as the distance between the transient and spacecraft increases. Our model, which explains well the observed ion energy dispersion and velocity distributions, can also be used to reveal the shape of the foreshock transients in three dimensions. Our results suggest that ion leakage from foreshock transient cores needs to be accounted for both in statistical studies and in global models of ion acceleration under quasi-parallel foreshock conditions.

Passive mechanism of pitch recoil in flapping insect wings.

PubMed

Ishihara, D; Horie, T

2016-12-20

The high torsional flexibility of insect wings allows for elastic recoil after the rotation of the wing during stroke reversal. However, the underlying mechanism of this recoil remains unclear because of the dynamic process of transitioning from the wing rotation during stroke reversal to the maintenance of a high angle of attack during the middle of each half-stroke, when the inertial, elastic, and aerodynamic effects all have a significant impact. Therefore, the interaction between the flapping wing and the surrounding air was directly simulated by simultaneously solving the incompressible Navier-Stokes equations, the equation of motion for an elastic body, and the fluid-structure interface conditions using the three-dimensional finite element method. This direct numerical simulation controlling the aerodynamic effect revealed that the recoil is the residual of the free pitch vibration induced by the flapping acceleration during stroke reversal in the transient response very close to critical damping due to the dynamic pressure resistance of the surrounding air. This understanding will enable the control of the leading-edge vortex and lift generation, the reduction of the work performed by flapping wings, and the interpretation of the underlying necessity for the kinematic characteristics of the flapping motion.

A recurrence matrix solution for the dynamic response of aircraft in gusts

NASA Technical Reports Server (NTRS)

Houbolt, John C

1951-01-01

A systematic procedure developed for the calculation of the structural response of aircraft flying through a gust by use of difference equations in the solution of dynamic problems is first illustrated by means of a simple-damped-oscillator example. A detailed analysis is then given which leads to a recurrence matrix equation for the determination of the response of an airplane in a gust. The method takes into account wing bending and twisting deformations, fuselage deflection, vertical and pitching motion of the airplane, and some tail forces. The method is based on aerodynamic strip theory, but compressibility and three-dimensional aerodynamic effects can be taken into account approximately by means of over-all corrections. Either a sharp-edge gust or a gust of arbitrary shape in the spanwise or flight directions may be treated. In order to aid in the application of the method to any specific case, a suggested computational procedure is included. The possibilities of applying the method to a variety of transient aircraft problems, such as landing, are brought out. A brief review of matrix algebra, covering the extent to which it is used in the analysis, is also included. (author)

Femtosecond self-reconfiguration of laser-induced plasma patterns in dielectrics

NASA Astrophysics Data System (ADS)

Déziel, Jean-Luc; Dubé, Louis J.; Messaddeq, Sandra H.; Messaddeq, Younès; Varin, Charles

2018-05-01

Laser-induced modification of transparent solids by intense femtosecond laser pulses allows fast integration of nanophotonic and nanofluidic devices with controlled optical properties. Experimental observations suggest that the local and dynamic nature of the interactions between light and the transient plasma plays an important role during fabrication. Current analytical models neglect these aspects and offer limited coverage of nanograting formation on dielectric surfaces. In this paper, we present a self-consistent dynamic treatment of the plasma buildup and its interaction with light within a three-dimensional electromagnetic framework. The main finding of this work is that local light-plasma interactions are responsible for the reorientation of laser-induced periodic plasma patterns with respect to the incident light polarization, when a certain energy density threshold is reached. Plasma reconfiguration occurs within a single laser pulse, on a femtosecond time scale. Moreover, we show that the reconfigured subwavelength plasma structures actually grow into the bulk of the sample, which agrees with the experimental observations of self-organized volume nanogratings. We find that mode coupling of the incident and transversely scattered light with the periodic plasma structures is sufficient to initiate the growth and self-organization of the pattern inside the medium with a characteristic half-wavelength periodicity.

Topological dynamics of vortex-line networks in hexagonal manganites

NASA Astrophysics Data System (ADS)

Xue, Fei; Wang, Nan; Wang, Xueyun; Ji, Yanzhou; Cheong, Sang-Wook; Chen, Long-Qing

2018-01-01

The two-dimensional X Y model is the first well-studied system with topological point defects. On the other hand, although topological line defects are common in three-dimensional systems, the evolution mechanism of line defects is not fully understood. The six domains in hexagonal manganites converge to vortex lines in three dimensions. Using phase-field simulations, we predicted that during the domain coarsening process, the vortex-line network undergoes three types of basic topological changes, i.e., vortex-line loop shrinking, coalescence, and splitting. It is shown that the vortex-antivortex annihilation controls the scaling dynamics.

Deconstructing the “Resting” State: Exploring the Temporal Dynamics of Frontal Alpha Asymmetry as an Endophenotype for Depression

PubMed Central

Allen, John J. B.; Cohen, Michael X

2010-01-01

Asymmetry in frontal electrocortical alpha-band (8–13 Hz) activity recorded during resting situations (i.e., in absence of a specific task) has been investigated in relation to emotion and depression for over 30 years. This asymmetry reflects an aspect of endogenous cortical dynamics that is stable over repeated measurements and that may serve as an endophenotype for mood or other psychiatric disorders. In nearly all of this research, EEG activity is averaged across several minutes, obscuring transient dynamics that unfold on the scale of milliseconds to seconds. Such dynamic states may ultimately have greater value in linking brain activity to surface EEG asymmetry, thus improving its status as an endophenotype for depression. Here we introduce novel metrics for characterizing frontal alpha asymmetry that provide a more in-depth neurodynamical understanding of recurrent endogenous cortical processes during the resting-state. The metrics are based on transient “bursts” of asymmetry that occur frequently during the resting-state. In a sample of 306 young adults, 143 with a lifetime diagnosis of major depressive disorder (62 currently symptomatic), three questions were addressed: (1) How do novel peri-burst metrics of dynamic asymmetry compare to conventional fast-Fourier transform-based metrics? (2) Do peri-burst metrics adequately differentiate depressed from non-depressed participants? and, (3) what EEG dynamics surround the asymmetry bursts? Peri-burst metrics correlated with traditional measures of asymmetry, and were sensitive to both current and past episodes of major depression. Moreover, asymmetry bursts were characterized by a transient lateralized alpha suppression that is highly consistent in phase across bursts, and a concurrent contralateral transient alpha enhancement that is less tightly phase-locked across bursts. This approach opens new possibilities for investigating rapid cortical dynamics during resting-state EEG. PMID:21228910

Lumped-Element Dynamic Electro-Thermal model of a superconducting magnet

NASA Astrophysics Data System (ADS)

Ravaioli, E.; Auchmann, B.; Maciejewski, M.; ten Kate, H. H. J.; Verweij, A. P.

2016-12-01

Modeling accurately electro-thermal transients occurring in a superconducting magnet is challenging. The behavior of the magnet is the result of complex phenomena occurring in distinct physical domains (electrical, magnetic and thermal) at very different spatial and time scales. Combined multi-domain effects significantly affect the dynamic behavior of the system and are to be taken into account in a coherent and consistent model. A new methodology for developing a Lumped-Element Dynamic Electro-Thermal (LEDET) model of a superconducting magnet is presented. This model includes non-linear dynamic effects such as the dependence of the magnet's differential self-inductance on the presence of inter-filament and inter-strand coupling currents in the conductor. These effects are usually not taken into account because superconducting magnets are primarily operated in stationary conditions. However, they often have significant impact on magnet performance, particularly when the magnet is subject to high ramp rates. Following the LEDET method, the complex interdependence between the electro-magnetic and thermal domains can be modeled with three sub-networks of lumped-elements, reproducing the electrical transient in the main magnet circuit, the thermal transient in the coil cross-section, and the electro-magnetic transient of the inter-filament and inter-strand coupling currents in the superconductor. The same simulation environment can simultaneously model macroscopic electrical transients and phenomena at the level of superconducting strands. The model developed is a very useful tool for reproducing and predicting the performance of conventional quench protection systems based on energy extraction and quench heaters, and of the innovative CLIQ protection system as well.

Picosecond view of a martensitic transition and nucleation in the shape memory alloy M n50N i40S n10 by four-dimensional transmission electron microscopy

NASA Astrophysics Data System (ADS)

Zhang, Ming; Cao, Gaolong; Tian, Huanfang; Sun, Shuaishuai; Li, Zhongwen; Li, Xingyuan; Guo, Cong; Li, Zian; Yang, Huaixin; Li, Jianqi

2017-11-01

The photoinduced martensitic (MT) transition and reverse transition in a shape memory alloy M n50N i40S n10 have been examined by using high spatiotemporal resolution four-dimensional transmission electron microscopy (4D-TEM), and the experimental results clearly demonstrate that the MT transition and reverse transition in this Heusler alloy contain a variety of structural dynamic features at picosecond time scales. The 4D-TEM imaging and diffraction observations clearly show that MT transition and MT domain nucleation, which are related to cooperative atomic motions, occur at between 10 and 20 ps, depending on the thickness of the sample. Moreover, a strong coupling between the MT transition and lattice breathing mode is discovered in this system, which can result in a periodic structural oscillation between the MT phase and austenitic (AUS) phase. This allows us to directly observe the MT nucleation and domain wall motions in transient states using high spatiotemporal imaging. A careful analysis of the ultrafast images demonstrates the presence of remarkable transient states, which exhibit the essential features of MT nucleation, lattice symmetry breaking, and a rapid growth of MT plates. These results not only provide insights into the time-resolved structural dynamics and elementary mechanisms that govern the MT transition but also contribute to the development of a novel technique for future 4D-TEM investigations.

Conversion and comparison of the mathematical, three-dimensional, finite-difference, ground-water flow model to the modular, three-dimensional, finite-difference, ground-water flow model for the Tesuque aquifer system in northern New Mexico

USGS Publications Warehouse

Umari, A.M.; Szeliga, T.L.

1989-01-01

The three-dimensional finite-difference groundwater model (using a mathematical groundwater flow code) of the Tesuque aquifer system in northern New Mexico was converted to run using the U.S. Geological Survey 's modular groundwater flow code. Results from the final versions of the predevelopment and 1947 to 2080 transient simulations of the two models are compared. A correlation coefficient of 0.9905 was obtained for the match in block-by-block head-dependent fluxes for predevelopment conditions. There are, however, significant differences in at least two specific cases. In the first case, a difference is associated with the net loss from the Pojoaque River and its tributaries to the aquifer. The net loss by the river is given as 1.134 cu ft/sec using the original groundwater model, which is 38.1% less than the net loss by the river of 1.8319 cu ft/sec computed in this study. In the second case, the large difference is computed for the transient decline in the hydraulic head of a model block near Tesuque Pueblo. The hydraulic-head decline by 2080 is, using the original model, 249 ft, which is 14.7% less than the hydraulic head of 292 ft computed by this study. In general, the differences between the two sets of results are not large enough to lead to different conclusions regarding the behavior of the system at steady state or when pumped. (USGS)

Numerical simulation of the generation, propagation, and diffraction of nonlinear waves in a rectangular basin: A three-dimensional numerical wave tank

NASA Astrophysics Data System (ADS)

Darwiche, Mahmoud Khalil M.

The research presented herein is a contribution to the understanding of the numerical modeling of fully nonlinear, transient water waves. The first part of the work involves the development of a time-domain model for the numerical generation of fully nonlinear, transient waves by a piston type wavemaker in a three-dimensional, finite, rectangular tank. A time-domain boundary-integral model is developed for simulating the evolving fluid field. A robust nonsingular, adaptive integration technique for the assembly of the boundary-integral coefficient matrix is developed and tested. A parametric finite-difference technique for calculating the fluid- particle kinematics is also developed and tested. A novel compatibility and continuity condition is implemented to minimize the effect of the singularities that are inherent at the intersections of the various Dirichlet and/or Neumann subsurfaces. Results are presented which demonstrate the accuracy and convergence of the numerical model. The second portion of the work is a study of the interaction of the numerically-generated, fully nonlinear, transient waves with a bottom-mounted, surface-piercing, vertical, circular cylinder. The numerical model developed in the first part of this dissertation is extended to include the presence of the cylinder at the centerline of the basin. The diffraction of the numerically generated waves by the cylinder is simulated, and the particle kinematics of the diffracted flow field are calculated and reported. Again, numerical results showing the accuracy and convergence of the extended model are presented.

From Glass Formation to Icosahedral Ordering by Curving Three-Dimensional Space.

PubMed

Turci, Francesco; Tarjus, Gilles; Royall, C Patrick

2017-05-26

Geometric frustration describes the inability of a local molecular arrangement, such as icosahedra found in metallic glasses and in model atomic glass formers, to tile space. Local icosahedral order, however, is strongly frustrated in Euclidean space, which obscures any causal relationship with the observed dynamical slowdown. Here we relieve frustration in a model glass-forming liquid by curving three-dimensional space onto the surface of a 4-dimensional hypersphere. For sufficient curvature, frustration vanishes and the liquid "freezes" in a fully icosahedral structure via a sharp "transition." Frustration increases upon reducing the curvature, and the transition to the icosahedral state smoothens while glassy dynamics emerge. Decreasing the curvature leads to decoupling between dynamical and structural length scales and the decrease of kinetic fragility. This sheds light on the observed glass-forming behavior in Euclidean space.

Combustion and Magnetohydrodynamic Processes in Advanced Pulse Detonation Rocket Engines

NASA Astrophysics Data System (ADS)

Cole, Lord Kahil

A number of promising alternative rocket propulsion concepts have been developed over the past two decades that take advantage of unsteady combustion waves in order to produce thrust. These concepts include the Pulse Detonation Rocket Engine (PDRE), in which repetitive ignition, propagation, and reflection of detonations and shocks can create a high pressure chamber from which gases may be exhausted in a controlled manner. The Pulse Detonation Rocket Induced Magnetohydrodynamic Ejector (PDRIME) is a modification of the basic PDRE concept, developed by Cambier (1998), which has the potential for performance improvements based on magnetohydrodynamic (MHD) thrust augmentation. The PDRIME has the advantage of both low combustion chamber seeding pressure, per the PDRE concept, and efficient energy distribution in the system, per the rocket-induced MHD ejector (RIME) concept of Cole, et al. (1995). In the initial part of this thesis, we explore flow and performance characteristics of different configurations of the PDRIME, assuming quasi-one-dimensional transient flow and global representations of the effects of MHD phenomena on the gas dynamics. By utilizing high-order accurate solvers, we thus are able to investigate the fundamental physical processes associated with the PDRIME and PDRE concepts and identify potentially promising operating regimes. In the second part of this investigation, the detailed coupling of detonations and electric and magnetic fields are explored. First, a one-dimensional spark-ignited detonation with complex reaction kinetics is fully evaluated and the mechanisms for the different instabilities are analyzed. It is found that complex kinetics in addition to sufficient spatial resolution are required to be able to quantify high frequency as well as low frequency detonation instability modes. Armed with this quantitative understanding, we then examine the interaction of a propagating detonation and the applied MHD, both in one-dimensional and two-dimensional transient simulations. The dynamics of the detonation are found to be affected by the application of magnetic and electric fields. We find that the regularity of one-dimensional cesium-seeded detonations can be significantly altered by reasonable applied magnetic fields (Bz ≤ 8T), but that it takes a stronger applied field (Bz > 16T) to significantly alter the cellular structure and detonation velocity of a two-dimensional detonation in the time in which these phenomena were observed. This observation is likely attributed to the additional coupling of the two-dimensional detonation with the transverse waves, which are not captured in the one-dimensional simulations. Future studies involving full ionization kinetics including collisional-radiative processes, will be used to examine these processes in further detail.

Flow dynamics and salt transport in a coastal aquifer driven by a stratified saltwater body: Lab experiment and numerical modeling

NASA Astrophysics Data System (ADS)

Oz, Imri; Shalev, Eyal; Yechieli, Yoseph; Gavrieli, Ittai; Gvirtzman, Haim

2014-04-01

This paper examines the transient development and the steady-state configuration of groundwater within a coastal aquifer adjacent to a stratified saltwater body. Such systems consist of three different water types: the regional fresh groundwater, and low and high salinity brines forming the upper and lower water layers of the stratified water body, respectively. The dynamics, location and the geometry of the interfaces and the density-driven circulation flows that develop in the aquifer are examined using laboratory experiments and numerical modeling at the same scale. The results show that the transient intrusion of the different water bodies into the aquifer takes place at different rates, and that the locations of the interfaces between them change with time, before reaching steady-state. Under steady-state conditions both the model and the experiments show the existence of three interfaces between the three water types. The numerical model, which is calibrated against the salinity distribution and groundwater discharge rate in the laboratory experiments, allows the quantification of the flow rates and flow patterns within the aquifer. These flow patterns, which cannot be derived from laboratory experiments, show the transient development of three circulation cells which are confined between the three interfaces. These results confirm the hypothesis that has been previously suggested based solely on a steady-state numerical modeling defined by a conceptual understanding. Parametric analysis shows that the creation of three circulation cells and three interfaces is limited to certain conditions and defines the ranges for the creation of this unique system.

Three-dimensional structural dynamics and fluctuations of DNA-nanogold conjugates by individual-particle electron tomography

NASA Astrophysics Data System (ADS)

Zhang, Lei; Lei, Dongsheng; Smith, Jessica M.; Zhang, Meng; Tong, Huimin; Zhang, Xing; Lu, Zhuoyang; Liu, Jiankang; Alivisatos, A. Paul; Ren, Gang

2016-03-01

DNA base pairing has been used for many years to direct the arrangement of inorganic nanocrystals into small groupings and arrays with tailored optical and electrical properties. The control of DNA-mediated assembly depends crucially on a better understanding of three-dimensional structure of DNA-nanocrystal-hybridized building blocks. Existing techniques do not allow for structural determination of these flexible and heterogeneous samples. Here we report cryo-electron microscopy and negative-staining electron tomography approaches to image, and three-dimensionally reconstruct a single DNA-nanogold conjugate, an 84-bp double-stranded DNA with two 5-nm nanogold particles for potential substrates in plasmon-coupling experiments. By individual-particle electron tomography reconstruction, we obtain 14 density maps at ~2-nm resolution. Using these maps as constraints, we derive 14 conformations of dsDNA by molecular dynamics simulations. The conformational variation is consistent with that from liquid solution, suggesting that individual-particle electron tomography could be an expected approach to study DNA-assembling and flexible protein structure and dynamics.

DynAOI: a tool for matching eye-movement data with dynamic areas of interest in animations and movies.

PubMed

Papenmeier, Frank; Huff, Markus

2010-02-01

Analyzing gaze behavior with dynamic stimulus material is of growing importance in experimental psychology; however, there is still a lack of efficient analysis tools that are able to handle dynamically changing areas of interest. In this article, we present DynAOI, an open-source tool that allows for the definition of dynamic areas of interest. It works automatically with animations that are based on virtual three-dimensional models. When one is working with videos of real-world scenes, a three-dimensional model of the relevant content needs to be created first. The recorded eye-movement data are matched with the static and dynamic objects in the model underlying the video content, thus creating static and dynamic areas of interest. A validation study asking participants to track particular objects demonstrated that DynAOI is an efficient tool for handling dynamic areas of interest.

Real-time application of advanced three-dimensional graphic techniques for research aircraft simulation

NASA Technical Reports Server (NTRS)

Davis, Steven B.

1990-01-01

Visual aids are valuable assets to engineers for design, demonstration, and evaluation. Discussed here are a variety of advanced three-dimensional graphic techniques used to enhance the displays of test aircraft dynamics. The new software's capabilities are examined and possible future uses are considered.

Modeling of combustion processes of stick propellants via combined Eulerian-Lagrangian approach

NASA Technical Reports Server (NTRS)

Kuo, K. K.; Hsieh, K. C.; Athavale, M. M.

1988-01-01

This research is motivated by the improved ballistic performance of large-caliber guns using stick propellant charges. A comprehensive theoretical model for predicting the flame spreading, combustion, and grain deformation phenomena of long, unslotted stick propellants is presented. The formulation is based upon a combined Eulerian-Lagrangian approach to simulate special characteristics of the two phase combustion process in a cartridge loaded with a bundle of sticks. The model considers five separate regions consisting of the internal perforation, the solid phase, the external interstitial gas phase, and two lumped parameter regions at either end of the stick bundle. For the external gas phase region, a set of transient one-dimensional fluid-dynamic equations using the Eulerian approach is obtained; governing equations for the stick propellants are formulated using the Lagrangian approach. The motion of a representative stick is derived by considering the forces acting on the entire propellant stick. The instantaneous temperature and stress fields in the stick propellant are modeled by considering the transient axisymmetric heat conduction equation and dynamic structural analysis.

Interface- and discontinuity-aware numerical schemes for plasma 3-T radiation diffusion in two and three dimensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dai, William W., E-mail: dai@lanl.gov; Scannapieco, Anthony J.

2015-11-01

A set of numerical schemes is developed for two- and three-dimensional time-dependent 3-T radiation diffusion equations in systems involving multi-materials. To resolve sub-cell structure, interface reconstruction is implemented within any cell that has more than one material. Therefore, the system of 3-T radiation diffusion equations is solved on two- and three-dimensional polyhedral meshes. The focus of the development is on the fully coupling between radiation and material, the treatment of nonlinearity in the equations, i.e., in the diffusion terms and source terms, treatment of the discontinuity across cell interfaces in material properties, the formulations for both transient and steady states,more » the property for large time steps, and second order accuracy in both space and time. The discontinuity of material properties between different materials is correctly treated based on the governing physics principle for general polyhedral meshes and full nonlinearity. The treatment is exact for arbitrarily strong discontinuity. The scheme is fully nonlinear for the full nonlinearity in the 3-T diffusion equations. Three temperatures are fully coupled and are updated simultaneously. The scheme is general in two and three dimensions on general polyhedral meshes. The features of the scheme are demonstrated through numerical examples for transient problems and steady states. The effects of some simplifications of numerical schemes are also shown through numerical examples, such as linearization, simple average of diffusion coefficient, and approximate treatment for the coupling between radiation and material.« less

The investigation of tethered satellite system dynamics

NASA Technical Reports Server (NTRS)

Lorenzini, E.

1985-01-01

The tether control law to retrieve the satellite was modified in order to have a smooth retrieval trajectory of the satellite that minimizes the thruster activation. The satellite thrusters were added to the rotational dynamics computer code and a preliminary control logic was implemented to simulate them during the retrieval maneuver. The high resolution computer code for modelling the three dimensional dynamics of untensioned tether, SLACK3, was made fully operative and a set of computer simulations of possible tether breakages was run. The distribution of the electric field around an electrodynamic tether in vacuo severed at some length from the shuttle was computed with a three dimensional electrodynamic computer code.

Multiple-viewing-zone integral imaging using a dynamic barrier array for three-dimensional displays.

PubMed

Choi, Heejin; Min, Sung-Wook; Jung, Sungyong; Park, Jae-Hyeung; Lee, Byoungho

2003-04-21

In spite of many advantages of integral imaging, the viewing zone in which an observer can see three-dimensional images is limited within a narrow range. Here, we propose a novel method to increase the number of viewing zones by using a dynamic barrier array. We prove our idea by fabricating and locating the dynamic barrier array between a lens array and a display panel. By tilting the barrier array, it is possible to distribute images for each viewing zone. Thus, the number of viewing zones can be increased with an increment of the states of the barrier array tilt.

Transient Inverse Calibration of Hanford Site-Wide Groundwater Model to Hanford Operational Impacts - 1943 to 1996

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cole, Charles R.; Bergeron, Marcel P.; Wurstner, Signe K.

2001-05-31

This report describes a new initiative to strengthen the technical defensibility of predictions made with the Hanford site-wide groundwater flow and transport model. The focus is on characterizing major uncertainties in the current model. PNNL will develop and implement a calibration approach and methodology that can be used to evaluate alternative conceptual models of the Hanford aquifer system. The calibration process will involve a three-dimensional transient inverse calibration of each numerical model to historical observations of hydraulic and water quality impacts to the unconfined aquifer system from Hanford operations since the mid-1940s.

Low-dimensional Representation of Error Covariance

NASA Technical Reports Server (NTRS)

Tippett, Michael K.; Cohn, Stephen E.; Todling, Ricardo; Marchesin, Dan

2000-01-01

Ensemble and reduced-rank approaches to prediction and assimilation rely on low-dimensional approximations of the estimation error covariances. Here stability properties of the forecast/analysis cycle for linear, time-independent systems are used to identify factors that cause the steady-state analysis error covariance to admit a low-dimensional representation. A useful measure of forecast/analysis cycle stability is the bound matrix, a function of the dynamics, observation operator and assimilation method. Upper and lower estimates for the steady-state analysis error covariance matrix eigenvalues are derived from the bound matrix. The estimates generalize to time-dependent systems. If much of the steady-state analysis error variance is due to a few dominant modes, the leading eigenvectors of the bound matrix approximate those of the steady-state analysis error covariance matrix. The analytical results are illustrated in two numerical examples where the Kalman filter is carried to steady state. The first example uses the dynamics of a generalized advection equation exhibiting nonmodal transient growth. Failure to observe growing modes leads to increased steady-state analysis error variances. Leading eigenvectors of the steady-state analysis error covariance matrix are well approximated by leading eigenvectors of the bound matrix. The second example uses the dynamics of a damped baroclinic wave model. The leading eigenvectors of a lowest-order approximation of the bound matrix are shown to approximate well the leading eigenvectors of the steady-state analysis error covariance matrix.

A computational procedure for the dynamics of flexible beams within multibody systems. Ph.D. Thesis Final Technical Report

NASA Technical Reports Server (NTRS)

Downer, Janice Diane

1990-01-01

The dynamic analysis of three dimensional elastic beams which experience large rotational and large deformational motions are examined. The beam motion is modeled using an inertial reference for the translational displacements and a body-fixed reference for the rotational quantities. Finite strain rod theories are then defined in conjunction with the beam kinematic description which accounts for the effects of stretching, bending, torsion, and transverse shear deformations. A convected coordinate representation of the Cauchy stress tensor and a conjugate strain definition is introduced to model the beam deformation. To treat the beam dynamics, a two-stage modification of the central difference algorithm is presented to integrate the translational coordinates and the angular velocity vector. The angular orientation is then obtained from the application of an implicit integration algorithm to the Euler parameter/angular velocity kinematical relation. The combined developments of the objective internal force computation with the dynamic solution procedures result in the computational preservation of total energy for undamped systems. The present methodology is also extended to model the dynamics of deployment/retrieval of the flexible members. A moving spatial grid corresponding to the configuration of a deployed rigid beam is employed as a reference for the dynamic variables. A transient integration scheme which accurately accounts for the deforming spatial grid is derived from a space-time finite element discretization of a Hamiltonian variational statement. The computational results of this general deforming finite element beam formulation are compared to reported results for a planar inverse-spaghetti problem.

Dynamics of an HIV-1 infection model with cell mediated immunity

NASA Astrophysics Data System (ADS)

Yu, Pei; Huang, Jianing; Jiang, Jiao

2014-10-01

In this paper, we study the dynamics of an improved mathematical model on HIV-1 virus with cell mediated immunity. This new 5-dimensional model is based on the combination of a basic 3-dimensional HIV-1 model and a 4-dimensional immunity response model, which more realistically describes dynamics between the uninfected cells, infected cells, virus, the CTL response cells and CTL effector cells. Our 5-dimensional model may be reduced to the 4-dimensional model by applying a quasi-steady state assumption on the variable of virus. However, it is shown in this paper that virus is necessary to be involved in the modeling, and that a quasi-steady state assumption should be applied carefully, which may miss some important dynamical behavior of the system. Detailed bifurcation analysis is given to show that the system has three equilibrium solutions, namely the infection-free equilibrium, the infectious equilibrium without CTL, and the infectious equilibrium with CTL, and a series of bifurcations including two transcritical bifurcations and one or two possible Hopf bifurcations occur from these three equilibria as the basic reproduction number is varied. The mathematical methods applied in this paper include characteristic equations, Routh-Hurwitz condition, fluctuation lemma, Lyapunov function and computation of normal forms. Numerical simulation is also presented to demonstrate the applicability of the theoretical predictions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Bing-Bing; Liu, Jian; Wei, Xu

We investigate the transient photoexcited lattice dynamics in a layered perovskite Mott insulator Sr2IrO4 film by femtosecond X-ray diffraction using a laser plasma-based X-ray source. The ultrafast structural dynamics of Sr2IrO4 thin films are determined by observing the shift and broadening of (0012) Bragg diffraction after excitation by 1.5 eV and 3.0 eV pump photons for films with different thicknesses. The observed transient lattice response can be well interpreted as a distinct three-step dynamics due to the propagation of coherent acoustic phonons generated by photoinduced quasiparticles (QPs). Employing a normalized phonon propagation model, we found that the photoinduced angular shiftsmore » of the Bragg peak collapse into a universal curve after introducing normalizedn coordinates to account for different thicknesses and pump photon energies, pinpointing the origin of the lattice distortion and its early evolution. In addition, a transient photocurrent measurement indicates that the photoinduced QPs are charge neutral excitons. Mapping the phonon propagation and correlating its dynamics with the QP by ultrafast X-ray diffraction (UXRD) establish a powerful way to study electron-phonon coupling and uncover the exotic physics in strongly correlated systems under nonequilibrium conditions.« less

Photoinduced coherent acoustic phonon dynamics inside Mott insulator Sr2IrO4 films observed by femtosecond X-ray pulses

NASA Astrophysics Data System (ADS)

Zhang, Bing-Bing; Liu, Jian; Wei, Xu; Sun, Da-Rui; Jia, Quan-Jie; Li, Yuelin; Tao, Ye

2017-04-01

We investigate the transient photoexcited lattice dynamics in a layered perovskite Mott insulator Sr2IrO4 film by femtosecond X-ray diffraction using a laser plasma-based X-ray source. The ultrafast structural dynamics of Sr2IrO4 thin films are determined by observing the shift and broadening of (0012) Bragg diffraction after excitation by 1.5 eV and 3.0 eV pump photons for films with different thicknesses. The observed transient lattice response can be well interpreted as a distinct three-step dynamics due to the propagation of coherent acoustic phonons generated by photoinduced quasiparticles (QPs). Employing a normalized phonon propagation model, we found that the photoinduced angular shifts of the Bragg peak collapse into a universal curve after introducing normalized coordinates to account for different thicknesses and pump photon energies, pinpointing the origin of the lattice distortion and its early evolution. In addition, a transient photocurrent measurement indicates that the photoinduced QPs are charge neutral excitons. Mapping the phonon propagation and correlating its dynamics with the QP by ultrafast X-ray diffraction (UXRD) establish a powerful way to study electron-phonon coupling and uncover the exotic physics in strongly correlated systems under nonequilibrium conditions.

VALIDITY OF A TWO-DIMENSIONAL MODEL FOR VARIABLE-DENSITY HYDRODYNAMIC CIRCULATION

EPA Science Inventory

A three-dimensional model of temperatures and currents has been formulated to assist in the analysis and interpretation of the dynamics of stratified lakes. In this model, nonlinear eddy coefficients for viscosity and conductivities are included. A two-dimensional model (one vert...

Role of the noise on the transient dynamics of an ecosystem of interacting species

NASA Astrophysics Data System (ADS)

Spagnolo, B.; La Barbera, A.

2002-11-01

We analyze the transient dynamics of an ecosystem described by generalized Lotka-Volterra equations in the presence of a multiplicative noise and a random interaction parameter between the species. We consider specifically three cases: (i) two competing species, (ii) three interacting species (one predator-two preys), (iii) n-interacting species. The interaction parameter in case (i) is a stochastic process which obeys a stochastic differential equation. We find noise delayed extinction of one of two species, which is akin to the noise-enhanced stability phenomenon. Other two noise-induced effects found are temporal oscillations and spatial patterns of the two competing species. In case (ii) the noise induces correlated spatial patterns of the predator and of the two preys concentrations. Finally, in case (iii) we find the asymptotic behavior of the time average of the ith population when the ecosystem is composed of a great number of interacting species.

Generating one to four-wing hidden attractors in a novel 4D no-equilibrium chaotic system with extreme multistability.

PubMed

Zhang, Sen; Zeng, Yicheng; Li, Zhijun; Wang, Mengjiao; Xiong, Le

2018-01-01

By using a simple state feedback controller in a three-dimensional chaotic system, a novel 4D chaotic system is derived in this paper. The system state equations are composed of nine terms including only one constant term. Depending on the different values of the constant term, this new proposed system has a line of equilibrium points or no equilibrium points. Compared with other similar chaotic systems, the newly presented system owns more abundant and complicated dynamic properties. What interests us is the observation that if the value of the constant term of the system is nonzero, it has no equilibria, and therefore, the Shil'nikov theorem is not suitable to verify the existence of chaos for the lack of heteroclinic or homoclinic trajectory. However, one-wing, two-wing, three-wing, and four-wing hidden attractors can be obtained from this new system. In addition, various coexisting hidden attractors are obtained and the complex transient transition behaviors are also observed. More interestingly, the unusual and striking dynamic behavior of the coexistence of infinitely many hidden attractors is revealed by selecting the different initial values of the system, which means that extreme multistability arises. The rich and complex hidden dynamic characteristics of this system are investigated by phase portraits, bifurcation diagrams, Lyapunov exponents, and so on. Finally, the new system is implemented by an electronic circuit. A very good agreement is observed between the experimental results and the numerical simulations of the same system on the Matlab platform.

Generating one to four-wing hidden attractors in a novel 4D no-equilibrium chaotic system with extreme multistability

NASA Astrophysics Data System (ADS)

Zhang, Sen; Zeng, Yicheng; Li, Zhijun; Wang, Mengjiao; Xiong, Le

2018-01-01

By using a simple state feedback controller in a three-dimensional chaotic system, a novel 4D chaotic system is derived in this paper. The system state equations are composed of nine terms including only one constant term. Depending on the different values of the constant term, this new proposed system has a line of equilibrium points or no equilibrium points. Compared with other similar chaotic systems, the newly presented system owns more abundant and complicated dynamic properties. What interests us is the observation that if the value of the constant term of the system is nonzero, it has no equilibria, and therefore, the Shil'nikov theorem is not suitable to verify the existence of chaos for the lack of heteroclinic or homoclinic trajectory. However, one-wing, two-wing, three-wing, and four-wing hidden attractors can be obtained from this new system. In addition, various coexisting hidden attractors are obtained and the complex transient transition behaviors are also observed. More interestingly, the unusual and striking dynamic behavior of the coexistence of infinitely many hidden attractors is revealed by selecting the different initial values of the system, which means that extreme multistability arises. The rich and complex hidden dynamic characteristics of this system are investigated by phase portraits, bifurcation diagrams, Lyapunov exponents, and so on. Finally, the new system is implemented by an electronic circuit. A very good agreement is observed between the experimental results and the numerical simulations of the same system on the Matlab platform.

Comparison of the Calculations Results of Heat Exchange Between a Single-Family Building and the Ground Obtained with the Quasi-Stationary and 3-D Transient Models. Part 2: Intermittent and Reduced Heating Mode

NASA Astrophysics Data System (ADS)

Staszczuk, Anna

2017-03-01

The paper provides comparative results of calculations of heat exchange between ground and typical residential buildings using simplified (quasi-stationary) and more accurate (transient, three-dimensional) methods. Such characteristics as building's geometry, basement hollow and construction of ground touching assemblies were considered including intermittent and reduced heating mode. The calculations with simplified methods were conducted in accordance with currently valid norm: PN-EN ISO 13370:2008. Thermal performance of buildings. Heat transfer via the ground. Calculation methods. Comparative estimates concerning transient, 3-D, heat flow were performed with computer software WUFI®plus. The differences of heat exchange obtained using more exact and simplified methods have been specified as a result of the analysis.

Transient Performance of a Vertical Axis Wind Turbine

NASA Astrophysics Data System (ADS)

Onol, Aykut; Yesilyurt, Serhat

2016-11-01

A coupled CFD/rotor dynamics modeling approach is presented for the analysis of realistic transient behavior of a height-normalized, three-straight-bladed VAWT subject to inertial effects of the rotor and generator load which is manipulated by a feedback control under standardized wind gusts. The model employs the k- ɛ turbulence model to approximate unsteady Reynolds-averaged Navier-Stokes equations and is validated with data from field measurements. As distinct from related studies, here, the angular velocity is calculated from the rotor's equation of motion; thus, the dynamic response of the rotor is taken into account. Results include the following: First, the rotor's inertia filters large amplitude oscillations in the wind torque owing to the first-order dynamics. Second, the generator and wind torques differ especially during wind transients subject to the conservation of angular momentum of the rotor. Third, oscillations of the power coefficient exceed the Betz limit temporarily due to the energy storage in the rotor, which acts as a temporary buffer that stores the kinetic energy like a flywheel in short durations. Last, average of transient power coefficients peaks at a smaller tip-speed ratio for wind gusts than steady winds. This work was supported by the Sabanci University Internal Research Grant Program (SU-IRG-985).

On the feasibility of a transient dynamic design analysis

NASA Astrophysics Data System (ADS)

Cunniff, Patrick F.; Pohland, Robert D.

1993-05-01

The Dynamic Design Analysis Method has been used for the past 30 years as part of the Navy's efforts to shock-harden heavy shipboard equipment. This method which has been validated several times employs normal mode theory and design shock values. This report examines the degree of success that may be achieved by using simple equipment-vehicle models that produce time history responses which are equivalent to the responses that would be achieved using spectral design values employed by the Dynamic Design Analysis Method. These transient models are constructed by attaching the equipment's modal oscillators to the vehicle which is composed of rigid masses and elastic springs. Two methods have been developed for constructing these transient models. Each method generates the parameters of the vehicles so as to approximate the required damaging effects, such that the transient model is excited by an idealized impulse applied to the vehicle mass to which the equipment modal oscillators are attached. The first method called the Direct Modeling Method, is limited to equipment with at most three-degrees of freedom and the vehicle consists of a single lumped mass and spring. The Optimization Modeling Method, which is based on the simplex method for optimization, has been used successfully with a variety of vehicle models and equipment sizes.

Three-Dimensional, Inelastic Response of Single-Edge Notch Bend Specimens Subjected to Impact Loading

DTIC Science & Technology

1993-08-01

measure the inherent fracture toughness of a material. A thor- ough understanding of the test specimen behavior is a prerequisite to the application of...measured material properties in structural applications . Three- dimensional dynamic analyses are performed for three different specimen configurations...derstanding of the test specimen behavior is a prerequisite to the application of measured ma- terial properties in structural applications . Three

Tachyon condensation due to domain-wall annihilation in Bose-Einstein condensates.

PubMed

Takeuchi, Hiromitsu; Kasamatsu, Kenichi; Tsubota, Makoto; Nitta, Muneto

2012-12-14

We show theoretically that a domain-wall annihilation in two-component Bose-Einstein condensates causes tachyon condensation accompanied by spontaneous symmetry breaking in a two-dimensional subspace. Three-dimensional vortex formation from domain-wall annihilations is considered a kink formation in subspace. Numerical experiments reveal that the subspatial dynamics obey the dynamic scaling law of phase-ordering kinetics. This model is experimentally feasible and provides insights into how the extra dimensions influence subspatial phase transition in higher-dimensional space.

Thermal model development and validation for rapid filling of high pressure hydrogen tanks

DOE PAGES

Johnson, Terry A.; Bozinoski, Radoslav; Ye, Jianjun; ...

2015-06-30

This paper describes the development of thermal models for the filling of high pressure hydrogen tanks with experimental validation. Two models are presented; the first uses a one-dimensional, transient, network flow analysis code developed at Sandia National Labs, and the second uses the commercially available CFD analysis tool Fluent. These models were developed to help assess the safety of Type IV high pressure hydrogen tanks during the filling process. The primary concern for these tanks is due to the increased susceptibility to fatigue failure of the liner caused by the fill process. Thus, a thorough understanding of temperature changes ofmore » the hydrogen gas and the heat transfer to the tank walls is essential. The effects of initial pressure, filling time, and fill procedure were investigated to quantify the temperature change and verify the accuracy of the models. In this paper we show that the predictions of mass averaged gas temperature for the one and three-dimensional models compare well with the experiment and both can be used to make predictions for final mass delivery. Furthermore, due to buoyancy and other three-dimensional effects, however, the maximum wall temperature cannot be predicted using one-dimensional tools alone which means that a three-dimensional analysis is required for a safety assessment of the system.« less

Volumetric MRI of the lungs during forced expiration.

PubMed

Berman, Benjamin P; Pandey, Abhishek; Li, Zhitao; Jeffries, Lindsie; Trouard, Theodore P; Oliva, Isabel; Cortopassi, Felipe; Martin, Diego R; Altbach, Maria I; Bilgin, Ali

2016-06-01

Lung function is typically characterized by spirometer measurements, which do not offer spatially specific information. Imaging during exhalation provides spatial information but is challenging due to large movement over a short time. The purpose of this work is to provide a solution to lung imaging during forced expiration using accelerated magnetic resonance imaging. The method uses radial golden angle stack-of-stars gradient echo acquisition and compressed sensing reconstruction. A technique for dynamic three-dimensional imaging of the lungs from highly undersampled data is developed and tested on six subjects. This method takes advantage of image sparsity, both spatially and temporally, including the use of reference frames called bookends. Sparsity, with respect to total variation, and residual from the bookends, enables reconstruction from an extremely limited amount of data. Dynamic three-dimensional images can be captured at sub-150 ms temporal resolution, using only three (or less) acquired radial lines per slice per timepoint. The images have a spatial resolution of 4.6×4.6×10 mm. Lung volume calculations based on image segmentation are compared to those from simultaneously acquired spirometer measurements. Dynamic lung imaging during forced expiration is made possible by compressed sensing accelerated dynamic three-dimensional radial magnetic resonance imaging. Magn Reson Med 75:2295-2302, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Dynamic Fracture Simulations of Explosively Loaded Cylinders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arthur, Carly W.; Goto, D. M.

2015-11-30

This report documents the modeling results of high explosive experiments investigating dynamic fracture of steel (AerMet® 100 alloy) cylinders. The experiments were conducted at Lawrence Livermore National Laboratory (LLNL) during 2007 to 2008 [10]. A principal objective of this study was to gain an understanding of dynamic material failure through the analysis of hydrodynamic computer code simulations. Two-dimensional and three-dimensional computational cylinder models were analyzed using the ALE3D multi-physics computer code.

Implicitly causality enforced solution of multidimensional transient photon transport equation.

PubMed

Handapangoda, Chintha C; Premaratne, Malin

2009-12-21

A novel method for solving the multidimensional transient photon transport equation for laser pulse propagation in biological tissue is presented. A Laguerre expansion is used to represent the time dependency of the incident short pulse. Owing to the intrinsic causal nature of Laguerre functions, our technique automatically always preserve the causality constrains of the transient signal. This expansion of the radiance using a Laguerre basis transforms the transient photon transport equation to the steady state version. The resulting equations are solved using the discrete ordinates method, using a finite volume approach. Therefore, our method enables one to handle general anisotropic, inhomogeneous media using a single formulation but with an added degree of flexibility owing to the ability to invoke higher-order approximations of discrete ordinate quadrature sets. Therefore, compared with existing strategies, this method offers the advantage of representing the intensity with a high accuracy thus minimizing numerical dispersion and false propagation errors. The application of the method to one, two and three dimensional geometries is provided.

TRANSIENT AMORPHOUS CALCIUM PHOSPHATE IN FORMING ENAMEL

PubMed Central

Beniash, Elia; Metzler, Rebecca A.; Lam, Raymond S.K.; Gilbert, P.U.P.A.

2009-01-01

Enamel, the hardest tissue in the body, begins as a three-dimensional network of nanometer size mineral particles, suspended in a protein gel. This mineral network serves as a template for mature enamel formation. To further understand the mechanisms of enamel formation we characterized the forming enamel mineral at an early secretory stage using x-ray absorption near-edge structure (XANES) spectromicroscopy, transmission electron microscopy (TEM), FTIR microspectroscopy and polarized light microscopy. We show that the newly formed enamel mineral is amorphous calcium phosphate (ACP), which eventually transforms into apatitic crystals. Interestingly, the size, shape and spatial organization of these amorphous mineral particles and older crystals are essentially the same, indicating that the mineral morphology and organization in enamel is determined prior to its crystallization. Mineralization via transient amorphous phases has been previously reported in chiton teeth, mollusk shells, echinoderm spicules and spines, and recent reports strongly suggest the presence transient amorphous mineral in forming vertebrate bones. The present finding of transient ACP in murine tooth enamel suggests that this strategy might be universal. PMID:19217943

Unstructured grid methods for the simulation of 3D transient flows

NASA Technical Reports Server (NTRS)

Morgan, K.; Peraire, J.; Peiro, J.

1994-01-01

A description of the research work undertaken under NASA Research Grant NAGW-2962 has been given. Basic algorithmic development work, undertaken for the simulation of steady three dimensional inviscid flow, has been used as the basis for the construction of a procedure for the simulation of truly transient flows in three dimensions. To produce a viable procedure for implementation on the current generation of computers, moving boundary components are simulated by fixed boundaries plus a suitably modified boundary condition. Computational efficiency is increased by the use of an implicit time stepping scheme in which the equation system is solved by explicit multistage time stepping with multigrid acceleration. The viability of the proposed approach has been demonstrated by considering the application of the procedure to simulation of a transonic flow over an oscillating ONERA M6 wing.

Spatial and Temporal Signatures of Flux Transfer Events in Global Simulations of Magnetopause Dynamics

NASA Technical Reports Server (NTRS)

Kuznetsova, Maria M.; Sibeck, David Gary; Hesse, Michael; Berrios, David; Rastaetter, Lutz; Toth, Gabor; Gombosi, Tamas I.

2011-01-01

Flux transfer events (FTEs) were originally identified by transient bipolar variations of the magnetic field component normal to the nominal magnetopause centered on enhancements in the total magnetic field strength. Recent Cluster and THEMIS multi-point measurements provided a wide range of signatures that are interpreted as evidence for FTE passage (e.g., crater FTE's, traveling magnetic erosion regions). We use the global magnetohydrodynamic (MHD) code BATS-R-US developed at the University of Michigan to model the global three-dimensional structure and temporal evolution of FTEs during multi-spacecraft magnetopause crossing events. Comparison of observed and simulated signatures and sensitivity analysis of the results to the probe location will be presented. We will demonstrate a variety of observable signatures in magnetic field profile that depend on space probe location with respect to the FTE passage. The global structure of FTEs will be illustrated using advanced visualization tools developed at the Community Coordinated Modeling Center

In vivo imaging of cardiac development and function in zebrafish using light sheet microscopy.

PubMed

Weber, Michael; Huisken, Jan

2015-01-01

Detailed studies of heart development and function are crucial for our understanding of cardiac failures and pave the way for better diagnostics and treatment. However, the constant motion and close incorporation into the cardiovascular system prevent in vivo studies of the living, unperturbed heart. The complementary strengths of the zebrafish model and light sheet microscopy provide a useful platform to fill this gap. High-resolution images of the embryonic vertebrate heart are now recorded from within the living animal: deep inside the unperturbed heart we can follow cardiac contractions and measure action potentials and calcium transients. Three-dimensional reconstructions of the entire beating heart with cellular resolution give new insights into its ever-changing morphology and facilitate studies into how individual cells form the complex cardiac network. In addition, cardiac dynamics and robustness are now examined with targeted optical manipulation. Overall, the combination of zebrafish and light sheet microscopy represents a promising addition for cardiac research and opens the door to a better understanding of heart function and development.

A new solution method for wheel/rail rolling contact.

PubMed

Yang, Jian; Song, Hua; Fu, Lihua; Wang, Meng; Li, Wei

2016-01-01

To solve the problem of wheel/rail rolling contact of nonlinear steady-state curving, a three-dimensional transient finite element (FE) model is developed by the explicit software ANSYS/LS-DYNA. To improve the solving speed and efficiency, an explicit-explicit order solution method is put forward based on analysis of the features of implicit and explicit algorithm. The solution method was first applied to calculate the pre-loading of wheel/rail rolling contact with explicit algorithm, and then the results became the initial conditions in solving the dynamic process of wheel/rail rolling contact with explicit algorithm as well. Simultaneously, the common implicit-explicit order solution method is used to solve the FE model. Results show that the explicit-explicit order solution method has faster operation speed and higher efficiency than the implicit-explicit order solution method while the solution accuracy is almost the same. Hence, the explicit-explicit order solution method is more suitable for the wheel/rail rolling contact model with large scale and high nonlinearity.

Study of synthesis techniques for insensitive aircraft control systems

NASA Technical Reports Server (NTRS)

Harvey, C. A.; Pope, R. E.

1977-01-01

Insensitive flight control system design criteria was defined in terms of maximizing performance (handling qualities, RMS gust response, transient response, stability margins) over a defined parameter range. Wing load alleviation for the C-5A was chosen as a design problem. The C-5A model was a 79-state, two-control structure with uncertainties assumed to exist in dynamic pressure, structural damping and frequency, and the stability derivative, M sub w. Five new techniques (mismatch estimation, uncertainty weighting, finite dimensional inverse, maximum difficulty, dual Lyapunov) were developed. Six existing techniques (additive noise, minimax, multiplant, sensitivity vector augmentation, state dependent noise, residualization) and the mismatch estimation and uncertainty weighting techniques were synthesized and evaluated on the design example. Evaluation and comparison of these six techniques indicated that the minimax and the uncertainty weighting techniques were superior to the other six, and of these two, uncertainty weighting has lower computational requirements. Techniques based on the three remaining new concepts appear promising and are recommended for further research.

PUFoam : A novel open-source CFD solver for the simulation of polyurethane foams

NASA Astrophysics Data System (ADS)

Karimi, M.; Droghetti, H.; Marchisio, D. L.

2017-08-01

In this work a transient three-dimensional mathematical model is formulated and validated for the simulation of polyurethane (PU) foams. The model is based on computational fluid dynamics (CFD) and is coupled with a population balance equation (PBE) to describe the evolution of the gas bubbles/cells within the PU foam. The front face of the expanding foam is monitored on the basis of the volume-of-fluid (VOF) method using a compressible solver available in OpenFOAM version 3.0.1. The solver is additionally supplemented to include the PBE, solved with the quadrature method of moments (QMOM), the polymerization kinetics, an adequate rheological model and a simple model for the foam thermal conductivity. The new solver is labelled as PUFoam and is, for the first time in this work, validated for 12 different mixing-cup experiments. Comparison of the time evolution of the predicted and experimentally measured density and temperature of the PU foam shows the potentials and limitations of the approach.

X-ray vision of fuel sprays.

PubMed

Wang, Jin

2005-03-01

With brilliant synchrotron X-ray sources, microsecond time-resolved synchrotron X-ray radiography and tomography have been used to elucidate the detailed three-dimensional structure and dynamics of high-pressure high-speed fuel sprays in the near-nozzle region. The measurement allows quantitative determination of the fuel distribution in the optically impenetrable region owing to the multiple scattering of visible light by small atomized fuel droplets surrounding the jet. X-radiographs of the jet-induced shock waves prove that the fuel jets become supersonic under appropriate injection conditions and that the quantitative analysis of the thermodynamic properties of the shock waves can also be derived from the most direct measurement. In other situations where extremely axial-asymmetric sprays are encountered, mass deconvolution and cross-sectional fuel distribution models can be computed based on the monochromatic and time-resolved X-radiographic images collected from various rotational orientations of the sprays. Such quantitative analysis reveals the never-before-reported characteristics and most detailed near-nozzle mass distribution of highly transient fuel sprays.

The Dependence of Tropical Cyclone Count and Size on Rotation Rate

NASA Astrophysics Data System (ADS)

Chavas, D. R.; Reed, K. A.

2017-12-01

Both theory and idealized equilibrium modeling studies indicate that tropical cyclone size decreases with background rotation rate. In contrast, in real-world observations size tends to increase with latitude. Here we seek to resolve this apparent contradiction via a set of reduced-complexity global aquaplanet simulations with varying planetary rotation rates using the NCAR Community Atmosphere Model 5. The latitudinal distribution of both storm count and size are found to vary markedly with rotation rate, yielding insight into the dynamical constraints on tropical cyclone activity on a rotating planet. Moreover, storm size is found to vary non-monotonically with latitude, indicating that non-equilibrium effects are crucial to the life-cycle evolution of size in nature. Results are then compared to experiments in idealized, time-dependent limited-area modeling simulations using CM1 in axisymmetric and three-dimensional geometry. Taken together, this hierarchy of models is used to quantify the role of equilibrium versus transient controls on storm size and the relevance of each to real storms in nature.

Single-Nanoparticle Photoelectrochemistry at a Nanoparticulate TiO2 -Filmed Ultramicroelectrode.

PubMed

Peng, Yue-Yi; Ma, Hui; Ma, Wei; Long, Yi-Tao; Tian, He

2018-03-26

An ultrasensitive photoelectrochemical method for achieving real-time detection of single nanoparticle collision events is presented. Using a micrometer-thick nanoparticulate TiO 2 -filmed Au ultra-microelectrode (TiO 2 @Au UME), a sub-millisecond photocurrent transient was observed for an individual N719-tagged TiO 2 (N719@TiO 2 ) nanoparticle and is due to the instantaneous collision process. Owing to a trap-limited electron diffusion process as the rate-limiting step, a random three-dimensional diffusion model was developed to simulate electron transport dynamics in TiO 2 film. The combination of theoretical simulation and high-resolution photocurrent measurement allow electron-transfer information of a single N719@TiO 2 nanoparticle to be quantified at single-molecule accuracy and the electron diffusivity and the electron-collection efficiency of TiO 2 @Au UME to be estimated. This method provides a test for studies of photoinduced electron transfer at the single-nanoparticle level. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modeling the heliospheric current sheet: Solar cycle variations

NASA Astrophysics Data System (ADS)

Riley, Pete; Linker, J. A.; Mikić, Z.

2002-07-01

In this report we employ an empirically driven, three-dimensional MHD model to explore the evolution of the heliospheric current sheet (HCS) during the course of the solar cycle. We compare our results with a simpler ``constant-speed'' approach for mapping the HCS outward into the solar wind to demonstrate that dynamic effects can substantially deform the HCS in the inner heliosphere (<~5 AU). We find that these deformations are most pronounced at solar minimum and become less significant at solar maximum, when interaction regions are less effective. Although solar maximum is typically associated with transient, rather than corotating, processes, we show that even under such conditions, the HCS can maintain its structure over the course of several solar rotations. While the HCS may almost always be topologically equivalent to a ``ballerina skirt,'' we discuss an interval approaching the maximum of solar cycle 23 (Carrington rotations 1960 and 1961) when the shape would be better described as ``conch shell''-like. We use Ulysses magnetic field measurements to support the model results.

Unsteady aerodynamic analysis for offshore floating wind turbines under different wind conditions.

PubMed

Xu, B F; Wang, T G; Yuan, Y; Cao, J F

2015-02-28

A free-vortex wake (FVW) model is developed in this paper to analyse the unsteady aerodynamic performance of offshore floating wind turbines. A time-marching algorithm of third-order accuracy is applied in the FVW model. Owing to the complex floating platform motions, the blade inflow conditions and the positions of initial points of vortex filaments, which are different from the fixed wind turbine, are modified in the implemented model. A three-dimensional rotational effect model and a dynamic stall model are coupled into the FVW model to improve the aerodynamic performance prediction in the unsteady conditions. The effects of floating platform motions in the simulation model are validated by comparison between calculation and experiment for a small-scale rigid test wind turbine coupled with a floating tension leg platform (TLP). The dynamic inflow effect carried by the FVW method itself is confirmed and the results agree well with the experimental data of a pitching transient on another test turbine. Also, the flapping moment at the blade root in yaw on the same test turbine is calculated and compares well with the experimental data. Then, the aerodynamic performance is simulated in a yawed condition of steady wind and in an unyawed condition of turbulent wind, respectively, for a large-scale wind turbine coupled with the floating TLP motions, demonstrating obvious differences in rotor performance and blade loading from the fixed wind turbine. The non-dimensional magnitudes of loading changes due to the floating platform motions decrease from the blade root to the blade tip. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Dynamic structure of confined shocks undergoing sudden expansion

NASA Astrophysics Data System (ADS)

Abate, G.; Shyy, W.

2002-01-01

The gas dynamic phenomenon associated with a normal shock wave within a tube undergoing a sudden area expansion consists of highly transient flow and diffraction that give rise to turbulent, compressible, vortical flows. These interactions can occur at time scales typically ranging from micro- to milliseconds. In this article, we review recent experimental and numerical results to highlight the flow phenomena and main physical mechanisms associated with this geometry. The topics addressed include time-accurate shock and vortex locations, flowfield evolution and structure, wall-shock Mach number, two- vs. three-dimensional sudden expansions, and the effect of viscous dissipation on planar shock-front expansions. Between axisymmetric and planar geometries, the flow structure evolves very similarly early on in the sudden expansion process (i.e., within the first two shock tube diameters). Both numerical and experimental studies confirm that the trajectory of the vortex formed at the expansion corner is convected into the flowfield faster in the axisymmetric case than the planar case. The lateral propagation of the vortices correlates very well between axisymmetric and planar geometries. In regard to the rate of dissipation of turbulent kinetic energy (TKE) for a two-dimensional planar shock undergoing a sudden expansion within a confined chamber, calculations show that the solenoidal dissipation is confined to the region of high strain rates arising from the expansion corner. Furthermore, the dilatational dissipation is concentrated mainly at the curvature of the incident, reflected, and barrel shock fronts. The multiple physical mechanisms identified, including shock-strain rate interaction, baroclinic effect, vorticity generation, and different aspects of viscous dissipation, have produced individual and collective flow structures observed experimentally.

Unsteady aerodynamic analysis for offshore floating wind turbines under different wind conditions

PubMed Central

Xu, B. F.; Wang, T. G.; Yuan, Y.; Cao, J. F.

2015-01-01

A free-vortex wake (FVW) model is developed in this paper to analyse the unsteady aerodynamic performance of offshore floating wind turbines. A time-marching algorithm of third-order accuracy is applied in the FVW model. Owing to the complex floating platform motions, the blade inflow conditions and the positions of initial points of vortex filaments, which are different from the fixed wind turbine, are modified in the implemented model. A three-dimensional rotational effect model and a dynamic stall model are coupled into the FVW model to improve the aerodynamic performance prediction in the unsteady conditions. The effects of floating platform motions in the simulation model are validated by comparison between calculation and experiment for a small-scale rigid test wind turbine coupled with a floating tension leg platform (TLP). The dynamic inflow effect carried by the FVW method itself is confirmed and the results agree well with the experimental data of a pitching transient on another test turbine. Also, the flapping moment at the blade root in yaw on the same test turbine is calculated and compares well with the experimental data. Then, the aerodynamic performance is simulated in a yawed condition of steady wind and in an unyawed condition of turbulent wind, respectively, for a large-scale wind turbine coupled with the floating TLP motions, demonstrating obvious differences in rotor performance and blade loading from the fixed wind turbine. The non-dimensional magnitudes of loading changes due to the floating platform motions decrease from the blade root to the blade tip. PMID:25583859

MAGNETAR OUTBURSTS FROM AVALANCHES OF HALL WAVES AND CRUSTAL FAILURES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Xinyu; Levin, Yuri; Beloborodov, Andrei M.

2016-12-20

We explore the interaction between Hall waves and mechanical failures inside a magnetar crust, using detailed one-dimensional models that consider temperature-sensitive plastic flow, heat transport, and cooling by neutrino emission, as well as the coupling of the crustal motion to the magnetosphere. We find that the dynamics is enriched and accelerated by the fast, short-wavelength Hall waves that are emitted by each failure. The waves propagate and cause failures elsewhere, triggering avalanches. We argue that these avalanches are the likely sources of outbursts in transient magnetars.

Analysis of the Pendular and Pitch Motions of a Driven Three-Dimensional Pendulum

ERIC Educational Resources Information Center

Findley, T.; Yoshida, S.; Norwood, D. P.

2007-01-01

A three-dimensional pendulum, modelled after the Laser Interferometer Gravitational-Wave Observatory's suspended optics, was constructed to investigate the pendulum's dynamics due to suspension point motion. In particular, we were interested in studying the pendular-pitch energy coupling. Determination of the pendular's Q value (the quality factor…

Analogy and Dynamic Geometry System Used to Introduce Three-Dimensional Geometry

ERIC Educational Resources Information Center

Mammana, M. F.; Micale, B.; Pennisi, M.

2012-01-01

We present a sequence of classroom activities on Euclidean geometry, both plane and space geometry, used to make three dimensional geometry more catchy and simple. The activity consists of a guided research activity that leads the students to discover unexpected properties of two apparently distant geometrical entities, quadrilaterals and…

Quantum Quench Dynamics

NASA Astrophysics Data System (ADS)

Mitra, Aditi

2018-03-01

Quench dynamics is an active area of study encompassing condensed matter physics and quantum information, with applications to cold-atomic gases and pump-probe spectroscopy of materials. Recent theoretical progress in studying quantum quenches is reviewed. Quenches in interacting one-dimensional systems as well as systems in higher spatial dimensions are covered. The appearance of nontrivial steady states following a quench in exactly solvable models is discussed, and the stability of these states to perturbations is described. Proper conserving approximations needed to capture the onset of thermalization at long times are outlined. The appearance of universal scaling for quenches near critical points and the role of the renormalization group in capturing the transient regime are reviewed. Finally, the effect of quenches near critical points on the dynamics of entanglement entropy and entanglement statistics is discussed. The extraction of critical exponents from the entanglement statistics is outlined.

A Low-Cost PC-Based Image Workstation for Dynamic Interactive Display of Three-Dimensional Anatomy

NASA Astrophysics Data System (ADS)

Barrett, William A.; Raya, Sai P.; Udupa, Jayaram K.

1989-05-01

A system for interactive definition, automated extraction, and dynamic interactive display of three-dimensional anatomy has been developed and implemented on a low-cost PC-based image workstation. An iconic display is used for staging predefined image sequences through specified increments of tilt and rotation over a solid viewing angle. Use of a fast processor facilitates rapid extraction and rendering of the anatomy into predefined image views. These views are formatted into a display matrix in a large image memory for rapid interactive selection and display of arbitrary spatially adjacent images within the viewing angle, thereby providing motion parallax depth cueing for efficient and accurate perception of true three-dimensional shape, size, structure, and spatial interrelationships of the imaged anatomy. The visual effect is that of holding and rotating the anatomy in the hand.

Implementation of a Tabulated Failure Model Into a Generalized Composite Material Model Suitable for Use in Impact Problems

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Carney, Kelly S.; Dubois, Paul; Hoffarth, Canio; Khaled, Bilal; Shyamsunder, Loukham; Rajan, Subramaniam; Blankenhorn, Gunther

2017-01-01

The need for accurate material models to simulate the deformation, damage and failure of polymer matrix composites under impact conditions is becoming critical as these materials are gaining increased use in the aerospace and automotive communities. The aerospace community has identified several key capabilities which are currently lacking in the available material models in commercial transient dynamic finite element codes. To attempt to improve the predictive capability of composite impact simulations, a next generation material model is being developed for incorporation within the commercial transient dynamic finite element code LS-DYNA. The material model, which incorporates plasticity, damage and failure, utilizes experimentally based tabulated input to define the evolution of plasticity and damage and the initiation of failure as opposed to specifying discrete input parameters such as modulus and strength. The plasticity portion of the orthotropic, three-dimensional, macroscopic composite constitutive model is based on an extension of the Tsai-Wu composite failure model into a generalized yield function with a non-associative flow rule. For the damage model, a strain equivalent formulation is used to allow for the uncoupling of the deformation and damage analyses. For the failure model, a tabulated approach is utilized in which a stress or strain based invariant is defined as a function of the location of the current stress state in stress space to define the initiation of failure. Failure surfaces can be defined with any arbitrary shape, unlike traditional failure models where the mathematical functions used to define the failure surface impose a specific shape on the failure surface. In the current paper, the complete development of the failure model is described and the generation of a tabulated failure surface for a representative composite material is discussed.

Novel 16-channel receive coil array for accelerated upper airway MRI at 3 Tesla.

PubMed

Kim, Yoon-Chul; Hayes, Cecil E; Narayanan, Shrikanth S; Nayak, Krishna S

2011-06-01

Upper airway MRI can provide a noninvasive assessment of speech and swallowing disorders and sleep apnea. Recent work has demonstrated the value of high-resolution three-dimensional imaging and dynamic two-dimensional imaging and the importance of further improvements in spatio-temporal resolution. The purpose of the study was to describe a novel 16-channel 3 Tesla receive coil that is highly sensitive to the human upper airway and investigate the performance of accelerated upper airway MRI with the coil. In three-dimensional imaging of the upper airway during static posture, 6-fold acceleration is demonstrated using parallel imaging, potentially leading to capturing a whole three-dimensional vocal tract with 1.25 mm isotropic resolution within 9 sec of sustained sound production. Midsagittal spiral parallel imaging of vocal tract dynamics during natural speech production is demonstrated with 2 × 2 mm(2) in-plane spatial and 84 ms temporal resolution. Copyright © 2010 Wiley-Liss, Inc.

Influence of the medium's dimensionality on defect-mediated turbulence.

PubMed

St-Yves, Ghislain; Davidsen, Jörn

2015-03-01

Spatiotemporal chaos in oscillatory and excitable media is often characterized by the presence of phase singularities called defects. Understanding such defect-mediated turbulence and its dependence on the dimensionality of a given system is an important challenge in nonlinear dynamics. This is especially true in the context of ventricular fibrillation in the heart, where the importance of the thickness of the ventricular wall is contentious. Here, we study defect-mediated turbulence arising in two different regimes in a conceptual model of excitable media and investigate how the statistical character of the turbulence changes if the thickness of the medium is changed from (quasi-) two- dimensional to three dimensional. We find that the thickness of the medium does not have a significant influence in, far from onset, fully developed turbulence while there is a clear transition if the system is close to a spiral instability. We provide clear evidence that the observed transition and change in the mechanism that drives the turbulent behavior is purely a consequence of the dimensionality of the medium. Using filament tracking, we further show that the statistical properties in the three-dimensional medium are different from those in turbulent regimes arising from filament instabilities like the negative line tension instability. Simulations also show that the presence of this unique three-dimensional turbulent dynamics is not model specific.

High-frame-rate full-vocal-tract 3D dynamic speech imaging.

PubMed

Fu, Maojing; Barlaz, Marissa S; Holtrop, Joseph L; Perry, Jamie L; Kuehn, David P; Shosted, Ryan K; Liang, Zhi-Pei; Sutton, Bradley P

2017-04-01

To achieve high temporal frame rate, high spatial resolution and full-vocal-tract coverage for three-dimensional dynamic speech MRI by using low-rank modeling and sparse sampling. Three-dimensional dynamic speech MRI is enabled by integrating a novel data acquisition strategy and an image reconstruction method with the partial separability model: (a) a self-navigated sparse sampling strategy that accelerates data acquisition by collecting high-nominal-frame-rate cone navigator sand imaging data within a single repetition time, and (b) are construction method that recovers high-quality speech dynamics from sparse (k,t)-space data by enforcing joint low-rank and spatiotemporal total variation constraints. The proposed method has been evaluated through in vivo experiments. A nominal temporal frame rate of 166 frames per second (defined based on a repetition time of 5.99 ms) was achieved for an imaging volume covering the entire vocal tract with a spatial resolution of 2.2 × 2.2 × 5.0 mm 3 . Practical utility of the proposed method was demonstrated via both validation experiments and a phonetics investigation. Three-dimensional dynamic speech imaging is possible with full-vocal-tract coverage, high spatial resolution and high nominal frame rate to provide dynamic speech data useful for phonetic studies. Magn Reson Med 77:1619-1629, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

A tool for simulating collision probabilities of animals with marine renewable energy devices.

PubMed

Schmitt, Pál; Culloch, Ross; Lieber, Lilian; Molander, Sverker; Hammar, Linus; Kregting, Louise

2017-01-01

The mathematical problem of establishing a collision probability distribution is often not trivial. The shape and motion of the animal as well as of the the device must be evaluated in a four-dimensional space (3D motion over time). Earlier work on wind and tidal turbines was limited to a simplified two-dimensional representation, which cannot be applied to many new structures. We present a numerical algorithm to obtain such probability distributions using transient, three-dimensional numerical simulations. The method is demonstrated using a sub-surface tidal kite as an example. Necessary pre- and post-processing of the data created by the model is explained, numerical details and potential issues and limitations in the application of resulting probability distributions are highlighted.

Development of a two-dimensional skin friction balance nulling circuit using multivariable control theory

NASA Technical Reports Server (NTRS)

Tripp, John S.; Patek, Stephen D.

1988-01-01

Measurement of planar skin friction forces in aerodynamic testing currently requires installation of two perpendicularly mounted, single-axis balances; consequently, force components must be sensed at two distinct locations. A two-axis instrument developed at the Langley Research Center to overcome this disadvantage allows measurement of a two-dimensional force at one location. This paper describes a feedback-controlled nulling circuit developed for the NASA two-axis balance which, without external compensation, is inherently unstable because of its low friction mechanical design. Linear multivariable control theory is applied to an experimentally validated mathematical model of the balance to synthesize a state-variable feedback control law. Pole placement techniques and computer simulation studies are employed to select eigenvalues which provide ideal transient response with decoupled sensing dynamics.

Data-assisted reduced-order modeling of extreme events in complex dynamical systems

PubMed Central

Koumoutsakos, Petros

2018-01-01

The prediction of extreme events, from avalanches and droughts to tsunamis and epidemics, depends on the formulation and analysis of relevant, complex dynamical systems. Such dynamical systems are characterized by high intrinsic dimensionality with extreme events having the form of rare transitions that are several standard deviations away from the mean. Such systems are not amenable to classical order-reduction methods through projection of the governing equations due to the large intrinsic dimensionality of the underlying attractor as well as the complexity of the transient events. Alternatively, data-driven techniques aim to quantify the dynamics of specific, critical modes by utilizing data-streams and by expanding the dimensionality of the reduced-order model using delayed coordinates. In turn, these methods have major limitations in regions of the phase space with sparse data, which is the case for extreme events. In this work, we develop a novel hybrid framework that complements an imperfect reduced order model, with data-streams that are integrated though a recurrent neural network (RNN) architecture. The reduced order model has the form of projected equations into a low-dimensional subspace that still contains important dynamical information about the system and it is expanded by a long short-term memory (LSTM) regularization. The LSTM-RNN is trained by analyzing the mismatch between the imperfect model and the data-streams, projected to the reduced-order space. The data-driven model assists the imperfect model in regions where data is available, while for locations where data is sparse the imperfect model still provides a baseline for the prediction of the system state. We assess the developed framework on two challenging prototype systems exhibiting extreme events. We show that the blended approach has improved performance compared with methods that use either data streams or the imperfect model alone. Notably the improvement is more significant in regions associated with extreme events, where data is sparse. PMID:29795631

Data-assisted reduced-order modeling of extreme events in complex dynamical systems.

PubMed

Wan, Zhong Yi; Vlachas, Pantelis; Koumoutsakos, Petros; Sapsis, Themistoklis

2018-01-01

The prediction of extreme events, from avalanches and droughts to tsunamis and epidemics, depends on the formulation and analysis of relevant, complex dynamical systems. Such dynamical systems are characterized by high intrinsic dimensionality with extreme events having the form of rare transitions that are several standard deviations away from the mean. Such systems are not amenable to classical order-reduction methods through projection of the governing equations due to the large intrinsic dimensionality of the underlying attractor as well as the complexity of the transient events. Alternatively, data-driven techniques aim to quantify the dynamics of specific, critical modes by utilizing data-streams and by expanding the dimensionality of the reduced-order model using delayed coordinates. In turn, these methods have major limitations in regions of the phase space with sparse data, which is the case for extreme events. In this work, we develop a novel hybrid framework that complements an imperfect reduced order model, with data-streams that are integrated though a recurrent neural network (RNN) architecture. The reduced order model has the form of projected equations into a low-dimensional subspace that still contains important dynamical information about the system and it is expanded by a long short-term memory (LSTM) regularization. The LSTM-RNN is trained by analyzing the mismatch between the imperfect model and the data-streams, projected to the reduced-order space. The data-driven model assists the imperfect model in regions where data is available, while for locations where data is sparse the imperfect model still provides a baseline for the prediction of the system state. We assess the developed framework on two challenging prototype systems exhibiting extreme events. We show that the blended approach has improved performance compared with methods that use either data streams or the imperfect model alone. Notably the improvement is more significant in regions associated with extreme events, where data is sparse.

Dynamic Modeling and Control Studies of a Two-Stage Bubbling Fluidized Bed Adsorber-Reactor for Solid-Sorbent CO{sub 2} Capture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Modekurti, Srinivasarao; Bhattacharyya, Debangsu; Zitney, Stephen E.

2013-07-31

A one-dimensional, non-isothermal, pressure-driven dynamic model has been developed for a two-stage bubbling fluidized bed (BFB) adsorber-reactor for solid-sorbent carbon dioxide (CO{sub 2}) capture using Aspen Custom Modeler® (ACM). The BFB model for the flow of gas through a continuous phase of downward moving solids considers three regions: emulsion, bubble, and cloud-wake. Both the upper and lower reactor stages are of overflow-type configuration, i.e., the solids leave from the top of each stage. In addition, dynamic models have been developed for the downcomer that transfers solids between the stages and the exit hopper that removes solids from the bottom ofmore » the bed. The models of all auxiliary equipment such as valves and gas distributor have been integrated with the main model of the two-stage adsorber reactor. Using the developed dynamic model, the transient responses of various process variables such as CO{sub 2} capture rate and flue gas outlet temperatures have been studied by simulating typical disturbances such as change in the temperature, flowrate, and composition of the incoming flue gas from pulverized coal-fired power plants. In control studies, the performance of a proportional-integral-derivative (PID) controller, feedback-augmented feedforward controller, and linear model predictive controller (LMPC) are evaluated for maintaining the overall CO{sub 2} capture rate at a desired level in the face of typical disturbances.« less

Compartment Venting Analyses of Ares I First Stage Systems Tunnel

NASA Technical Reports Server (NTRS)

Wang, Qunzhen; Arner, Stephen

2009-01-01

Compartment venting analyses have been performed for the Ares I first stage systems tunnel using both the lumped parameter method and the three-dimensional (31)) transient computational fluid dynamics (CFD) approach. The main objective of venting analyses is to predict the magnitudes of differential pressures across the skin so the integrity of solid walls can be evaluated and properly designed. The lumped parameter method assumes the gas pressure and temperature inside the systems tunnel are spatially uniform, which is questionable since the tunnel is about 1,700 in. long and 4 in. wide. Therefore, 31) transient CFD simulations using the commercial CFD code FLUENT are performed in order to examine the gas pressure and temperature variations inside the tunnel. It was found that the uniform pressure and temperature assumptions inside the systems tunnel are valid during ascent. During reentry, the uniform pressure assumption is also reasonable but the uniform temperature assumption is not valid. Predicted pressure and temperature inside the systems tunnel using CFD are also compared with those from the lumped parameter method using the NASA code CHCHVENT. In general, the average pressure and temperature inside the systems tunnel from CFD are between the burst and crush results from CHCHVENT during both ascent and reentry. The skin differential pressure and pressure inside the systems tunnel relative to freestream pressure from CHCHVENT as well as velocity vectors and streamlines are also discussed in detail.

Wave Journal Bearings Under Dynamic Loads

NASA Technical Reports Server (NTRS)

Hendricks, Robert C.; Dimofte, Florin

2002-01-01

The dynamic behavior of the wave journal bearing was determined by running a three-wave bearing with an eccentrically mounted shaft. A transient analysis was developed and used to predict numerical data for the experimental cases. The three-wave journal bearing ran stably under dynamic loads with orbits well inside the bearing clearance. The orbits were almost circular and nearly free of the influence of, but dynamically dependent on, bearing wave shape. Experimental observations for both the absolute bearing-housing-center orbits and the relative bearing-housing-center-to-shaft-center orbits agreed well with the predictions. Moreover, the subsynchronous whirl motion generated by the fluid film was found experimentally and predicted theoretically for certain speeds.

Computation of the three-dimensional medial surface dynamics of the vocal folds.

PubMed

Döllinger, Michael; Berry, David A

2006-01-01

To increase our understanding of pathological and healthy voice production, quantitative measurement of the medial surface dynamics of the vocal folds is significant, albeit rarely performed because of the inaccessibility of the vocal folds. Using an excised hemilarynx methodology, a new calibration technique, herein referred to as the linear approximate (LA) method, was introduced to compute the three-dimensional coordinates of fleshpoints along the entire medial surface of the vocal fold. The results were compared with results from the direct linear transform. An associated error estimation was presented, demonstrating the improved accuracy of the new method. A test on real data was reported including computation of quantitative measurements of vocal fold dynamics.

Application of 3D Laser Scanning Technology in Inspection and Dynamic Reserves Detection of Open-Pit Mine

NASA Astrophysics Data System (ADS)

Hu, Zhumin; Wei, Shiyu; Jiang, Jun

2017-10-01

The traditional open-pit mine mining rights verification and dynamic reserve detection means rely on the total station and RTK to collect the results of the turning point coordinates of mining surface contours. It resulted in obtaining the results of low precision and large error in the means that is limited by the traditional measurement equipment accuracy and measurement methods. The three-dimensional scanning technology can obtain the three-dimensional coordinate data of the surface of the measured object in a large area at high resolution. This paper expounds the commonly used application of 3D scanning technology in the inspection and dynamic reserve detection of open mine mining rights.

Live-cell imaging reveals the dynamics and function of single-telomere TERRA molecules in cancer cells.

PubMed

Avogaro, Laura; Querido, Emmanuelle; Dalachi, Myriam; Jantsch, Michael F; Chartrand, Pascal; Cusanelli, Emilio

2018-04-16

Telomeres cap the ends of eukaryotic chromosomes, protecting them from degradation and erroneous recombination events which may lead to genome instability. Telomeres are transcribed giving rise to telomeric repeat-containing RNAs, called TERRA. The TERRA long noncoding RNAs have been proposed to play important roles in telomere biology, including heterochromatin formation and telomere length homeostasis. While TERRA RNAs are predominantly nuclear and localize at telomeres, little is known about the dynamics and function of TERRA molecules expressed from individual telomeres. Herein, we developed an assay to image endogenous TERRA molecules expressed from a single telomere in living human cancer cells. We show that single-telomere TERRA can be detected as TERRA RNA single particles which freely diffuse within the nucleus. Furthermore, TERRA molecules aggregate forming TERRA clusters. Three-dimensional size distribution and single particle tracking analyses revealed distinct sizes and dynamics for TERRA RNA single particles and clusters. Simultaneous time lapse confocal imaging of TERRA particles and telomeres showed that TERRA clusters transiently co-localize with telomeres. Finally, we used chemically modified antisense oligonucleotides to deplete TERRA molecules expressed from a single telomere. Single-telomere TERRA depletion resulted in increased DNA damage at telomeres and elsewhere in the genome. These results suggest that single-telomere TERRA transcripts participate in the maintenance of genomic integrity in human cancer cells.

Subcycle dynamics of high-order-harmonic generation of He atoms excited by attosecond pulses and driven by near-infrared laser fields: A self-interaction-free time-dependent density-functional-theory approach

NASA Astrophysics Data System (ADS)

Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.

2014-05-01

In the framework of the self-interaction-free time-dependent density-functional theory, we have performed three-dimensional (3D) ab initio calculations of He atoms in near-infrared (NIR) laser fields subject to excitation by a single extreme ultraviolet (XUV) attosecond pulse (SAP). We have explored the dynamical behavior of the subcycle high harmonic generation (HHG) for transitions from the excited states to the ground state and found oscillation structures with respect to the time delay between the SAP and NIR fields. The oscillatory pattern in the photon emission spectra has a period of ˜1.3 fs which is half of the NIR laser optical cycle, similar to that recently measured in the experiments on transient absorption of He [M. Chini et al., Sci. Rep. 3, 1105 (2013), 10.1038/srep01105]. We present the photon emission spectra from 1s2p, 1s3p, 1s4p, 1s5p, and 1s6p excited states as functions of the time delay. We explore the subcycle Stark shift phenomenon in NIR fields and its influence on the photon emission process. Our analysis reveals several interesting features of the subcycle HHG dynamics and we identify the mechanisms responsible for the observed peak splitting in the photon emission spectra.

Upon Generating (2+1)-dimensional Dynamical Systems

NASA Astrophysics Data System (ADS)

Zhang, Yufeng; Bai, Yang; Wu, Lixin

2016-06-01

Under the framework of the Adler-Gel'fand-Dikii(AGD) scheme, we first propose two Hamiltonian operator pairs over a noncommutative ring so that we construct a new dynamical system in 2+1 dimensions, then we get a generalized special Novikov-Veselov (NV) equation via the Manakov triple. Then with the aid of a special symmetric Lie algebra of a reductive homogeneous group G, we adopt the Tu-Andrushkiw-Huang (TAH) scheme to generate a new integrable (2+1)-dimensional dynamical system and its Hamiltonian structure, which can reduce to the well-known (2+1)-dimensional Davey-Stewartson (DS) hierarchy. Finally, we extend the binormial residue representation (briefly BRR) scheme to the super higher dimensional integrable hierarchies with the help of a super subalgebra of the super Lie algebra sl(2/1), which is also a kind of symmetric Lie algebra of the reductive homogeneous group G. As applications, we obtain a super 2+1 dimensional MKdV hierarchy which can be reduced to a super 2+1 dimensional generalized AKNS equation. Finally, we compare the advantages and the shortcomings for the three schemes to generate integrable dynamical systems.

Collisionless Dynamics and the Cosmic Web

NASA Astrophysics Data System (ADS)

Hahn, Oliver

2016-10-01

I review the nature of three-dimensional collapse in the Zeldovich approximation, how it relates to the underlying nature of the three-dimensional Lagrangian manifold and naturally gives rise to a hierarchical structure formation scenario that progresses through collapse from voids to pancakes, filaments and then halos. I then discuss how variations of the Zeldovich approximation (based on the gravitational or the velocity potential) have been used to define classifications of the cosmic large-scale structure into dynamically distinct parts. Finally, I turn to recent efforts to devise new approaches relying on tessellations of the Lagrangian manifold to follow the fine-grained dynamics of the dark matter fluid into the highly non-linear regime and both extract the maximum amount of information from existing simulations as well as devise new simulation techniques for cold collisionless dynamics.

Mitral Annular Dynamics in Mitral Annular Calcification: A Three-Dimensional Imaging Study.

PubMed

Pressman, Gregg S; Movva, Rajesh; Topilsky, Yan; Clavel, Marie-Annick; Saldanha, Jason A; Watanabe, Nozomi; Enriquez-Sarano, Maurice

2015-07-01

The mitral annulus displays complex conformational changes during the cardiac cycle that can now be quantified by three-dimensional echocardiography. Mitral annular calcification (MAC) is increasingly encountered, but its structural and dynamic consequences are largely unexplored. The objective of this study was to describe alterations in mitral annular dimensions and dynamics in patients with MAC. Transthoracic three-dimensional echocardiography was performed in 43 subjects with MAC and 36 age- and sex-matched normal control subjects. Mitral annular dimensions were quantified, using dedicated software, at six time points (three diastolic, three systolic) during the cardiac cycle. In diastole, the calcified annulus was larger and flatter than normal, with increased anteroposterior diameter (29.4 ± 0.6 vs 27.8 ± 0.6 mm, P = .046), reduced height (2.8 ± 0.2 vs 3.6 ± 0.2 mm, P = .006), and decreased saddle shape (8.9 ± 0.6% vs 11.4 ± 0.6%, P = .005). In systole, patients with MAC had greater annular area at all time points (P < .05 for each) compared with control subjects, because of reduced contraction along the anteroposterior diameter (P < .001). Saddle shape increased in early systole (from 10.5% to 13.5%, P = .04) in control subjects but not in those with MAC (P = NS). Valvular alterations were also noted; although mitral valve tent length decreased during systole in both groups, decreases were less in patients with MAC (P < .05 for mid- and late systole). For certain parameters (e.g., annular area), changes were confined largely to those patients with moderate to severe MAC (P = .006 vs control subjects, but nonsignificant for patients with mild MAC). Quantitative three-dimensional echocardiography provides new insights into the dynamic consequences of MAC. This imaging technique demonstrates that the mitral annulus is not made smaller by calcification. However, there is loss of annular contraction, particularly along the anteroposterior diameter, and loss of early systolic folding along the intercommissural diameter. Associated valvular alterations include smaller than usual declines in tenting during systole. These quantitative three-dimensional echocardiographic data provide new insights into the dynamic physiology of the calcified mitral annulus. Copyright © 2015 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.

Evaluation of Start Transient Oscillations with the J-2X Engine Gas Generator Assembly

NASA Technical Reports Server (NTRS)

Hulka, J. R.; Morgan, C. J.; Casiano, M. J.

2015-01-01

During development of the gas generator for the liquid oxygen/liquid hydrogen propellant J-2X rocket engine, distinctive and oftentimes high-amplitude pressure oscillations and hardware vibrations occurred during the start transient of nearly every workhorse gas generator assembly test, as well as during many tests of engine system hardware. These oscillations appeared whether the steady-state conditions exhibited stable behavior or not. They occurred similarly with three different injector types, and with every combustion chamber configuration tested, including chamber lengths ranging over a 5:1 range, several different nozzle types, and with or without a side branch line simulating a turbine spin start gas supply line. Generally, two sets of oscillations occurred, one earlier in the start transient and at higher frequencies, and the other almost immediately following and at lower frequencies. Multiple dynamic pressure measurements in the workhorse combustion chambers indicated that the oscillations were associated with longitudinal acoustic modes of the combustion chambers, with the earlier and higher frequency oscillation usually related to the second longitudinal acoustic mode and the later and lower frequency oscillation usually related to the first longitudinal acoustic mode. Given that several early development gas generator assemblies exhibited unstable behavior at frequencies near the first longitudinal acoustic modes of longer combustion chambers, the start transient oscillations are presumed to provide additional insight into the nature of the combustion instability mechanisms. Aspects of the steadystate oscillations and combustion instabilities from development and engine system test programs have been reported extensively in the three previous JANNAF Liquid Propulsion Subcommittee meetings (see references below). This paper describes the hardware configurations, start transient sequence operations, and transient and dynamic test data during the start transient. The implications of these results on previous analyses and understanding of the combustion instability observed during steady-state conditions, especially the effects of injector influences, is discussed.

iCFD: Interpreted Computational Fluid Dynamics - Degeneration of CFD to one-dimensional advection-dispersion models using statistical experimental design - The secondary clarifier.

PubMed

Guyonvarch, Estelle; Ramin, Elham; Kulahci, Murat; Plósz, Benedek Gy

2015-10-15

The present study aims at using statistically designed computational fluid dynamics (CFD) simulations as numerical experiments for the identification of one-dimensional (1-D) advection-dispersion models - computationally light tools, used e.g., as sub-models in systems analysis. The objective is to develop a new 1-D framework, referred to as interpreted CFD (iCFD) models, in which statistical meta-models are used to calculate the pseudo-dispersion coefficient (D) as a function of design and flow boundary conditions. The method - presented in a straightforward and transparent way - is illustrated using the example of a circular secondary settling tank (SST). First, the significant design and flow factors are screened out by applying the statistical method of two-level fractional factorial design of experiments. Second, based on the number of significant factors identified through the factor screening study and system understanding, 50 different sets of design and flow conditions are selected using Latin Hypercube Sampling (LHS). The boundary condition sets are imposed on a 2-D axi-symmetrical CFD simulation model of the SST. In the framework, to degenerate the 2-D model structure, CFD model outputs are approximated by the 1-D model through the calibration of three different model structures for D. Correlation equations for the D parameter then are identified as a function of the selected design and flow boundary conditions (meta-models), and their accuracy is evaluated against D values estimated in each numerical experiment. The evaluation and validation of the iCFD model structure is carried out using scenario simulation results obtained with parameters sampled from the corners of the LHS experimental region. For the studied SST, additional iCFD model development was carried out in terms of (i) assessing different density current sub-models; (ii) implementation of a combined flocculation, hindered, transient and compression settling velocity function; and (iii) assessment of modelling the onset of transient and compression settling. Furthermore, the optimal level of model discretization both in 2-D and 1-D was undertaken. Results suggest that the iCFD model developed for the SST through the proposed methodology is able to predict solid distribution with high accuracy - taking a reasonable computational effort - when compared to multi-dimensional numerical experiments, under a wide range of flow and design conditions. iCFD tools could play a crucial role in reliably predicting systems' performance under normal and shock events. Copyright © 2015 Elsevier Ltd. All rights reserved.

Linear and Nonlinear Analysis of Magnetic Bearing Bandwidth Due to Eddy Current Limitations

NASA Technical Reports Server (NTRS)

Kenny, Andrew; Palazzolo, Alan

2000-01-01

Finite element analysis was used to study the bandwidth of alloy hyperco50a and silicon iron laminated rotors and stators in magnetic bearings. A three dimensional model was made of a heteropolar bearing in which all the flux circulated in the plane of the rotor and stator laminate. A three dimensional model of a plate similar to the region of a pole near the gap was also studied with a very fine mesh. Nonlinear time transient solutions for the net flux carried by the plate were compared to steady state time harmonic solutions. Both linear and quasi-nonlinear steady state time harmonic solutions were calculated and compared. The finite element solutions for power loss and flux bandwidth were compared to those determined from classical analytical solutions to Maxwell's equations.

Single polymer dynamics under large amplitude oscillatory extension

NASA Astrophysics Data System (ADS)

Zhou, Yuecheng; Schroeder, Charles M.

2016-09-01

Understanding the conformational dynamics of polymers in time-dependent flows is of key importance for controlling materials properties during processing. Despite this importance, however, it has been challenging to study polymer dynamics in controlled time-dependent or oscillatory extensional flows. In this work, we study the dynamics of single polymers in large-amplitude oscillatory extension (LAOE) using a combination of experiments and Brownian dynamics (BD) simulations. Two-dimensional LAOE flow is generated using a feedback-controlled stagnation point device known as the Stokes trap, thereby generating an oscillatory planar extensional flow with alternating principal axes of extension and compression. Our results show that polymers experience periodic cycles of compression, reorientation, and extension in LAOE, and dynamics are generally governed by a dimensionless flow strength (Weissenberg number Wi) and dimensionless frequency (Deborah number De). Single molecule experiments are compared to BD simulations with and without intramolecular hydrodynamic interactions (HI) and excluded volume (EV) interactions, and good agreement is obtained across a range of parameters. Moreover, transient bulk stress in LAOE is determined from simulations using the Kramers relation, which reveals interesting and unique rheological signatures for this time-dependent flow. We further construct a series of single polymer stretch-flow rate curves (defined as single molecule Lissajous curves) as a function of Wi and De, and we observe qualitatively different dynamic signatures (butterfly, bow tie, arch, and line shapes) across the two-dimensional Pipkin space defined by Wi and De. Finally, polymer dynamics spanning from the linear to nonlinear response regimes are interpreted in the context of accumulated fluid strain in LAOE.

Dynamics and Control of Three-Dimensional Perching Maneuver under Dynamic Stall Influence

NASA Astrophysics Data System (ADS)

Feroskhan, Mir Alikhan Bin Mohammad

Perching is a type of aggressive maneuver performed by the class 'Aves' species to attain precision point landing with a generally short landing distance. Perching capability is desirable on unmanned aerial vehicles (UAVs) due to its efficient deceleration process that potentially expands the functionality and flight envelope of the aircraft. This dissertation extends the previous works on perching, which is mostly limited to two-dimensional (2D) cases, to its state-of-the-art threedimensional (3D) variety. This dissertation presents the aerodynamic modeling and optimization framework adopted to generate unprecedented variants of the 3D perching maneuver that include the sideslip perching trajectory, which ameliorates the existing 2D perching concept by eliminating the undesirable undershoot and reliance on gravity. The sideslip perching technique methodically utilizes the lateral and longitudinal drag mechanisms through consecutive phases of yawing and pitching-up motion. Since perching maneuver involves high rates of change in the angles of attack and large turn rates, introduction of three internal variables thus becomes necessary for addressing the influence of dynamic stall delay on the UAV's transient post-stall behavior. These variables are then integrated into a static nonlinear aerodynamic model, developed using empirical and analytical methods, and into an optimization framework that generates a trajectory of sideslip perching maneuver, acquiring over 70% velocity reduction. An impact study of the dynamic stall influence on the optimal perching trajectories suggests that consideration of dynamic stall delay is essential due to the significant discrepancies in the corresponding control inputs required. A comparative study between 2D and 3D perching is also conducted to examine the different drag mechanisms employed by 2D and 3D perching respectively. 3D perching is presented as a more efficient deceleration technique with respect to spatial costs and initial altitude range. Contraction analysis is shown to be a useful technique in identifying the state variables that are required to be tracked for attaining stability of optimal perching trajectories. Based on the selected tracking variables, two sliding control strategies are proposed and comparatively examined to close the control loop and provide the required robustness and convergence to the optimal perching trajectory in the presence of perturbations and dynamic stall model inaccuracies. This dissertation concludes that the sliding controller with the adaptive gain feature is more effective and essential in providing better tracking performance through illustrations of the corresponding convergence area and at higher intensity of perturbations.

The Three-D Flow Structures of Gas and Liquid Generated by a Spreading Flame Over Liquid Fuel

NASA Technical Reports Server (NTRS)

Tashtoush, G.; Ito, A.; Konishi, T.; Narumi, A.; Saito, K.; Cremers, C. J.

1999-01-01

We developed a new experimental technique called: Combined laser sheet particle tracking (LSPT) and laser holographic interferometry (HI), which is capable of measuring the transient behavior of three dimensional structures of temperature and flow both in liquid and gas phases. We applied this technique to a pulsating flame spread over n-butanol. We found a twin vortex flow both on the liquid surface and deep in the liquid a few mm below the surface and a twin vortex flow in the gas phase. The first twin vortex flow at the liquid surface was observed previously by NASA Lewis researchers, while the last two observations are new. These observations revealed that the convective flow structure ahead of the flame leading edge is three dimensional in nature and the pulsating spread is controlled by the convective flow of both liquid and gas.

MODFLOW–LGR—Documentation of ghost node local grid refinement (LGR2) for multiple areas and the boundary flow and head (BFH2) package

USGS Publications Warehouse

Mehl, Steffen W.; Hill, Mary C.

2013-01-01

This report documents the addition of ghost node Local Grid Refinement (LGR2) to MODFLOW-2005, the U.S. Geological Survey modular, transient, three-dimensional, finite-difference groundwater flow model. LGR2 provides the capability to simulate groundwater flow using multiple block-shaped higher-resolution local grids (a child model) within a coarser-grid parent model. LGR2 accomplishes this by iteratively coupling separate MODFLOW-2005 models such that heads and fluxes are balanced across the grid-refinement interface boundary. LGR2 can be used in two-and three-dimensional, steady-state and transient simulations and for simulations of confined and unconfined groundwater systems. Traditional one-way coupled telescopic mesh refinement methods can have large, often undetected, inconsistencies in heads and fluxes across the interface between two model grids. The iteratively coupled ghost-node method of LGR2 provides a more rigorous coupling in which the solution accuracy is controlled by convergence criteria defined by the user. In realistic problems, this can result in substantially more accurate solutions and require an increase in computer processing time. The rigorous coupling enables sensitivity analysis, parameter estimation, and uncertainty analysis that reflects conditions in both model grids. This report describes the method used by LGR2, evaluates accuracy and performance for two-and three-dimensional test cases, provides input instructions, and lists selected input and output files for an example problem. It also presents the Boundary Flow and Head (BFH2) Package, which allows the child and parent models to be simulated independently using the boundary conditions obtained through the iterative process of LGR2.

MODFLOW-2005, the U.S. Geological Survey modular ground-water model - documentation of shared node local grid refinement (LGR) and the boundary flow and head (BFH) package

USGS Publications Warehouse

Mehl, Steffen W.; Hill, Mary C.

2006-01-01

This report documents the addition of shared node Local Grid Refinement (LGR) to MODFLOW-2005, the U.S. Geological Survey modular, transient, three-dimensional, finite-difference ground-water flow model. LGR provides the capability to simulate ground-water flow using one block-shaped higher-resolution local grid (a child model) within a coarser-grid parent model. LGR accomplishes this by iteratively coupling two separate MODFLOW-2005 models such that heads and fluxes are balanced across the shared interfacing boundary. LGR can be used in two-and three-dimensional, steady-state and transient simulations and for simulations of confined and unconfined ground-water systems. Traditional one-way coupled telescopic mesh refinement (TMR) methods can have large, often undetected, inconsistencies in heads and fluxes across the interface between two model grids. The iteratively coupled shared-node method of LGR provides a more rigorous coupling in which the solution accuracy is controlled by convergence criteria defined by the user. In realistic problems, this can result in substantially more accurate solutions and require an increase in computer processing time. The rigorous coupling enables sensitivity analysis, parameter estimation, and uncertainty analysis that reflects conditions in both model grids. This report describes the method used by LGR, evaluates LGR accuracy and performance for two- and three-dimensional test cases, provides input instructions, and lists selected input and output files for an example problem. It also presents the Boundary Flow and Head (BFH) Package, which allows the child and parent models to be simulated independently using the boundary conditions obtained through the iterative process of LGR.

THREE-DIMENSIONAL MODELING OF COHESIVE SEDIMENT TRANSPORT IN A PARTIALLY STRATIFIED MICRO-TIDAL ESTUARY TO ASSESS EFFECTIVENESS OF SEDIMENT TRAPS

EPA Science Inventory

The three-dimensional (3D) finite difference model Environmental Fluid Dynamics Code (EFDC) was used to simulate the hydrodynamics and sediment transport in a partially stratified micro-tidal estuary. The estuary modeled consisted of a 16-km reach of the St. Johns River, Florida,...

Generalized reciprocity theorem for semiconductor devices

NASA Technical Reports Server (NTRS)

Misiakos, K.; Lindholm, F. A.

1985-01-01

A reciprocity theorem is presented that relates the short-circuit current of a device, induced by a carrier generation source, to the minority-carrier Fermi level in the dark. The basic relation is general under low injection. It holds for three-dimensional devices with position dependent parameters (energy gap, electron affinity, mobility, etc.), and for transient or steady-state conditions. This theorem allows calculation of the internal quantum efficiency of a solar cell by using the analysis of the device in the dark. Other applications could involve measurements of various device parameters, interfacial surface recombination velocity at a polcrystalline silicon emitter contact, for rexample, by using steady-state or transient photon or mass-particle radiation.

A theoretical model of speed-dependent steering torque for rolling tyres

NASA Astrophysics Data System (ADS)

Wei, Yintao; Oertel, Christian; Liu, Yahui; Li, Xuebing

2016-04-01

It is well known that the tyre steering torque is highly dependent on the tyre rolling speed. In limited cases, i.e. parking manoeuvre, the steering torque approaches the maximum. With the increasing tyre speed, the steering torque decreased rapidly. Accurate modelling of the speed-dependent behaviour for the tyre steering torque is a key factor to calibrate the electric power steering (EPS) system and tune the handling performance of vehicles. However, no satisfactory theoretical model can be found in the existing literature to explain this phenomenon. This paper proposes a new theoretical framework to model this important tyre behaviour, which includes three key factors: (1) tyre three-dimensional transient rolling kinematics with turn-slip; (2) dynamical force and moment generation; and (3) the mixed Lagrange-Euler method for contact deformation solving. A nonlinear finite-element code has been developed to implement the proposed approach. It can be found that the main mechanism for the speed-dependent steering torque is due to turn-slip-related kinematics. This paper provides a theory to explain the complex mechanism of the tyre steering torque generation, which helps to understand the speed-dependent tyre steering torque, tyre road feeling and EPS calibration.

Numerical simulation of the three-dimensional river antidunes

NASA Astrophysics Data System (ADS)

Iwasaki, T.; Inoue, T.; Onda, S.; Yabe, H.

2017-12-01

This study presents numerical simulations of the formation and development of the three-dimensional river antidunes. We use a Boussinesq type depth-integrated hydrodynamic model to account for the non-hydrostatic pressure effects on the flow field, dissipative feature of the free surface and the bed shear stress distribution. In addition, a non-equilibrium bedload transport model is incorporated into the model to consider the lag effect of the bedload transport on the bedform dynamics. The model is applied to idealized laboratory-scale conditions, i.e., steady water and sediment supplies, uniform sediment and a straight channel with constant slope and channel width, to understand the model performance and applicability. The results show that the model is able to reproduce an upstream-migrating antidunes and associated free surface dynamics. The model also captures the formation of the two dimensional and the three-dimensional antidunes. The antidunes reproduced by the model are somewhat unstable, i.e., the repeated cycle of dissipation and regeneration of antidunes is observed. In addition, as the calculation progresses, the modelled three-dimensional antidunes generally tend to lose their three-dimensionality, i.e., the reduction of the spanwise wavenumber. In the early stage of the calculation, the antidune mode is dominant, whereas, the free bars also develop when the formative condition of bars is satisfied. The numerical results show the coexisting of free bars and antidunes, which are a common evident in flume experiments and field observations.

Accuracy of three-dimensional seismic ground response analysis in time domain using nonlinear numerical simulations

NASA Astrophysics Data System (ADS)

Liang, Fayun; Chen, Haibing; Huang, Maosong

2017-07-01

To provide appropriate uses of nonlinear ground response analysis for engineering practice, a three-dimensional soil column with a distributed mass system and a time domain numerical analysis were implemented on the OpenSees simulation platform. The standard mesh of a three-dimensional soil column was suggested to be satisfied with the specified maximum frequency. The layered soil column was divided into multiple sub-soils with a different viscous damping matrix according to the shear velocities as the soil properties were significantly different. It was necessary to use a combination of other one-dimensional or three-dimensional nonlinear seismic ground analysis programs to confirm the applicability of nonlinear seismic ground motion response analysis procedures in soft soil or for strong earthquakes. The accuracy of the three-dimensional soil column finite element method was verified by dynamic centrifuge model testing under different peak accelerations of the earthquake. As a result, nonlinear seismic ground motion response analysis procedures were improved in this study. The accuracy and efficiency of the three-dimensional seismic ground response analysis can be adapted to the requirements of engineering practice.

Three-dimensional wave evolution on electrified falling films

NASA Astrophysics Data System (ADS)

Tomlin, Ruben; Papageorgiou, Demetrios; Pavliotis, Greg

2016-11-01

We consider the full three-dimensional model for a thin viscous liquid film completely wetting a flat infinite solid substrate at some non-zero angle to the horizontal, with an electric field normal to the substrate far from the flow. Thin film flows have applications in cooling processes. Many studies have shown that the presence of interfacial waves increases heat transfer by orders of magnitude due to film thinning and convection effects. A long-wave asymptotics procedure yields a Kuramoto-Sivashinsky equation with a non-local term to model the weakly nonlinear evolution of the interface dynamics for overlying film arrangements, with a restriction on the electric field strength. The non-local term is always linearly destabilising and produces growth rates proportional to the cube of the magnitude of the wavenumber vector. A sufficiently strong electric field is able promote non-trivial dynamics for subcritical Reynolds number flows where the flat interface is stable in the absence of an electric field. We present numerical simulations where we observe rich dynamical behavior with competing attractors, including "snaking" travelling waves and other fully three-dimensional wave formations. EPSRC studentship (RJT).

Three-dimensional structural dynamics and fluctuations of DNA-nanogold conjugates by individual-particle electron tomography

DOE PAGES

Zhang, Lei; Lei, Dongsheng; Smith, Jessica M.; ...

2016-03-30

DNA base pairing has been used for many years to direct the arrangement of inorganic nanocrystals into small groupings and arrays with tailored optical and electrical properties. The control of DNA-mediated assembly depends crucially on a better understanding of three-dimensional structure of DNA-nanocrystal-hybridized building blocks. Existing techniques do not allow for structural determination of these flexible and heterogeneous samples. Here we report cryo-electron microscopy and negative-staining electron tomography approaches to image, and three-dimensionally reconstruct a single DNA-nanogold conjugate, an 84-bp double-stranded DNA with two 5-nm nanogold particles for potential substrates in plasmon-coupling experiments. By individual-particle electron tomography reconstruction, we obtainmore » 14 density maps at ~ 2-nm resolution . Using these maps as constraints, we derive 14 conformations of dsDNA by molecular dynamics simulations. The conformational variation is consistent with that from liquid solution, suggesting that individual-particle electron tomography could be an expected approach to study DNA-assembling and flexible protein structure and dynamics.« less

Calculation of three-dimensional, inviscid, supersonic, steady flows

NASA Technical Reports Server (NTRS)

Moretti, G.

1981-01-01

A detailed description of a computational program for the evaluation of three dimensional supersonic, inviscid, steady flow past airplanes is presented. Emphasis was put on how a powerful, automatic mapping technique is coupled to the fluid mechanical analysis. Each of the three constituents of the analysis (body geometry, mapping technique, and gas dynamical effects) was carefully coded and described. Results of computations based on sample geometrics and discussions are also presented.

Neurodynamics in the Sensorimotor Loop: Representing Behavior Relevant External Situations

PubMed Central

Pasemann, Frank

2017-01-01

In the context of the dynamical system approach to cognition and supposing that brains or brain-like systems controlling the behavior of autonomous systems are permanently driven by their sensor signals, the paper approaches the question of neurodynamics in the sensorimotor loop in a purely formal way. This is carefully done by addressing the problem in three steps, using the time-discrete dynamics of standard neural networks and a fiber space representation for better clearness. Furthermore, concepts like meta-transients, parametric stability and dynamical forms are introduced, where meta-transients describe the effect of realistic sensor inputs, parametric stability refers to a class of sensor inputs all generating the “same type” of dynamic behavior, and a dynamical form comprises the corresponding class of parametrized dynamical systems. It is argued that dynamical forms are the essential internal representatives of behavior relevant external situations. Consequently, it is suggested that dynamical forms are the basis for a memory of these situations. Finally, based on the observation that not all brain process have a direct effect on the motor activity, a natural splitting of neurodynamics into vertical (internal) and horizontal (effective) parts is introduced. PMID:28217092

Three-Dimensional, Live-Cell Imaging of Chromatin Dynamics in Plant Nuclei Using Chromatin Tagging Systems.

PubMed

Hirakawa, Takeshi; Matsunaga, Sachihiro

2016-01-01

In plants, chromatin dynamics spatiotemporally change in response to various environmental stimuli. However, little is known about chromatin dynamics in the nuclei of plants. Here, we introduce a three-dimensional, live-cell imaging method that can monitor chromatin dynamics in nuclei via a chromatin tagging system that can visualize specific genomic loci in living plant cells. The chromatin tagging system is based on a bacterial operator/repressor system in which the repressor is fused to fluorescent proteins. A recent refinement of promoters for the system solved the problem of gene silencing and abnormal pairing frequencies between operators. Using this system, we can detect the spatiotemporal dynamics of two homologous loci as two fluorescent signals within a nucleus and monitor the distance between homologous loci. These live-cell imaging methods will provide new insights into genome organization, development processes, and subnuclear responses to environmental stimuli in plants.

Three-Dimensional Flow Behavior Inside the Submerged Entry Nozzle

NASA Astrophysics Data System (ADS)

Real-Ramirez, Cesar Augusto; Carvajal-Mariscal, Ignacio; Sanchez-Silva, Florencio; Cervantes-de-la-Torre, Francisco; Diaz-Montes, Jesus; Gonzalez-Trejo, Jesus

2018-05-01

According to various authors, the surface quality of steel depends on the dynamic conditions that occur within the continuous casting mold's upper region. The meniscus, found in that upper region, is where the solidification process begins. The liquid steel is distributed into the mold through a submerged entry nozzle (SEN). In this paper, the dynamic behavior inside the SEN is analyzed by means of physical experiments and numerical simulations. The particle imaging velocimetry technique was used to obtain the vector field in different planes and three-dimensional flow patterns inside the SEN volume. Moreover, large eddy simulation was performed, and the turbulence model results were used to understand the nonlinear flow pattern inside the SEN. Using scaled physical and numerical models, quasi-periodic behavior was observed due to the interaction of two three-dimensional vortices that move inside the SEN lower region located between the exit ports of the nozzle.

A new procedure for dynamic adaption of three-dimensional unstructured grids

NASA Technical Reports Server (NTRS)

Biswas, Rupak; Strawn, Roger

1993-01-01

A new procedure is presented for the simultaneous coarsening and refinement of three-dimensional unstructured tetrahedral meshes. This algorithm allows for localized grid adaption that is used to capture aerodynamic flow features such as vortices and shock waves in helicopter flowfield simulations. The mesh-adaption algorithm is implemented in the C programming language and uses a data structure consisting of a series of dynamically-allocated linked lists. These lists allow the mesh connectivity to be rapidly reconstructed when individual mesh points are added and/or deleted. The algorithm allows the mesh to change in an anisotropic manner in order to efficiently resolve directional flow features. The procedure has been successfully implemented on a single processor of a Cray Y-MP computer. Two sample cases are presented involving three-dimensional transonic flow. Computed results show good agreement with conventional structured-grid solutions for the Euler equations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rowland, Clare E.; Fedin, Igor; Diroll, Benjamin T.

Elevated temperature optoelectronic performance of semiconductor nanomaterials remains an important issue for applications. Here we examine two-dimensional CdSe nanoplatelets (NPs) and CdS/CdSe/CdS shell/core/shell sandwich NPs at temperatures ranging from 300-700 K using static and transient spectroscopies as well as in-situ transmission electron microscopy. NPs exhibit reversible changes in PL intensity, spectral position, and emission linewidth with temperature elevation up to ~500 K, losing a factor of ~8 to 10 in PL intensity at 400 K relative to ambient. Temperature elevation above ~500 K yields thickness dependent, irreversible degradation in optical properties. Electron microscopy relates stability of the NP morphology upmore » to near 600 K followed by sintering and evaporation at still higher temperatures. The mechanism of reversible PL loss, based on differences in decay dynamics between time-resolved photoluminescence and transient absorption, arise primarily from hole trapping in both NPs and sandwich NPs.« less

Effect of load transients on SOFC operation—current reversal on loss of load

NASA Astrophysics Data System (ADS)

Gemmen, Randall S.; Johnson, Christopher D.

The dynamics of solid oxide fuel cell (SOFC) operation have been considered previously, but mainly through the use of one-dimensional codes applied to co-flow fuel cell systems. In this paper several geometries are considered, including cross-flow, co-flow, and counter-flow. The details of the model are provided, and the model is compared with some initial experimental data. For parameters typical of SOFC operation, a variety of transient cases are investigated, including representative load increase and decrease and system shutdown. Of particular note for large load decrease conditions (e.g., shutdown) is the occurrence of reverse current over significant portions of the cell, starting from the moment of load loss up to the point where equilibrated conditions again provide positive current. Consideration is given as to when such reverse current conditions might most significantly impact the reliability of the cell.

Modeling control of eye orientation in three dimensions. I. Role of muscle pulleys in determining saccadic trajectory.

PubMed

Raphan, T

1998-05-01

This study evaluates the effects of muscle axis shifts on the performance of a vector velocity-position integrator in the CNS. Earlier models of the oculomotor plant assumed that the muscle axes remained fixed relative to the head as the eye rotated into secondary and tertiary eye positions. Under this assumption, the vector integrator model generates torsional transients as the eye moves from secondary to tertiary positions of fixation. The torsional transient represents an eye movement response to a spatial mismatch between the torque axes that remain fixed in the head and the displacement plane that changes by half the angle of the change in eye orientation. When muscle axis shifts were incorporated into the model, the torque axes were closer to the displacement plane at each eye orientation throughout the trajectory, and torsional transients were reduced dramatically. Their size and dynamics were close to reported data. It was also shown that when the muscle torque axes were rotated by 50% of the eye rotation, there was no torsional transient and Listing's law was perfectly obeyed. When muscle torque axes rotated >50%, torsional transients reversed direction compared with what occurred for muscle axis shifts of <50%. The model indicates that Listing's law is implemented by the oculomotor plant subject to a two-dimensional command signal that is confined to the pitch-yaw plane, having zero torsion. Saccades that bring the eye to orientations outside Listing's plane could easily be corrected by a roll pulse that resets the roll state of the velocity-position integrator to zero. This would be a simple implementation of the corrective controller suggested by Van Opstal and colleagues. The model further indicates that muscle axis shifts together with the torque orientation relationship for tissue surrounding the eye and Newton's laws of motion form a sufficient plant model to explain saccadic trajectories and periods of fixation when driven by a vector command confined to the pitch-yaw plane. This implies that the velocity-position integrator is probably realized as a subtractive feedback vector integrator and not as a quaternion-based integrator that implements kinematic transformations to orient the eye.

The bomb 14C transient in the Pacific Ocean

NASA Astrophysics Data System (ADS)

Rodgers, Keith B.; Schrag, Daniel P.; Cane, Mark A.; Naik, Naomi H.

2000-04-01

A modeling study of the bomb 14C transient is presented for the Pacific Ocean. A primitive equation ocean circulation model has been configured for a high-resolution domain that accounts for the Indonesian Throughflow (ITF). Four separate runs were performed: (1) seasonal forcing with 20 Sv of ITF transport, (2) seasonal forcing with 10 Sv of ITF transport, (3) seasonal forcing with no ITF transport, and (4) interannual forcing with 15 Sv of ITF transport. This study has two main objectives. First, it is intended to describe the time evolution of the bomb 14C transient. This serves as a tool with which one can identify the physical processes controlling the evolving bomb 14C distribution in the Pacific thermocline and thus provides an interpretive framework for the database of Δ14C measurements in the Pacific. Second, transient tracers are applied to the physical oceanographic problem of intergyre exchange. This is of importance in furthering our understanding of the potential role of the upper Pacific Ocean in climate variability. We use bomb 14C as a dye tracer of intergyre exchange between the subtropical gyres and the equatorial upwelling regions of the equatorial Pacific. Observations show that while the atmospheric Δ14C signal peaked in the early to mid-1960s, the Δ14C levels in the surface water waters of the subtropical gyres peaked near 1970, and the Δ14C of surface waters in the equatorial Pacific continued to rise through the 1980s. It is shown that the model exhibits skill in representing the large-scale observed features observed for the bomb 14C transient in the Pacific Ocean. The model successfully captures the basin-scale inventories of bomb 14C in the tropics as well as in the extratropics of the North Pacific. For the equatorial Pacific this is attributed to the model's high meridional resolution. The discrepancies in the three-dimensional distribution of bomb 14C between the model and data are discussed within the context of the dynamical controls on the Δ14C distribution of bomb 14C in the Pacific.

Studies for the 3-Dimensional Structure, Composition, and Dynamic of Io's Atmosphere

NASA Technical Reports Server (NTRS)

Smyth, William H.

2001-01-01

Research work is discussed for the following: (1) the exploration of new H and Cl chemistry in Io's atmosphere using the already developed two-dimensional multi-species hydrodynamic model of Wong and Smyth; and (2) for the development of a new three-dimensional multi-species hydrodynamic model for Io's atmosphere.

Optimization of coupled multiphysics methodology for safety analysis of pebble bed modular reactor

NASA Astrophysics Data System (ADS)

Mkhabela, Peter Tshepo

The research conducted within the framework of this PhD thesis is devoted to the high-fidelity multi-physics (based on neutronics/thermal-hydraulics coupling) analysis of Pebble Bed Modular Reactor (PBMR), which is a High Temperature Reactor (HTR). The Next Generation Nuclear Plant (NGNP) will be a HTR design. The core design and safety analysis methods are considerably less developed and mature for HTR analysis than those currently used for Light Water Reactors (LWRs). Compared to LWRs, the HTR transient analysis is more demanding since it requires proper treatment of both slower and much longer transients (of time scale in hours and days) and fast and short transients (of time scale in minutes and seconds). There is limited operation and experimental data available for HTRs for validation of coupled multi-physics methodologies. This PhD work developed and verified reliable high fidelity coupled multi-physics models subsequently implemented in robust, efficient, and accurate computational tools to analyse the neutronics and thermal-hydraulic behaviour for design optimization and safety evaluation of PBMR concept The study provided a contribution to a greater accuracy of neutronics calculations by including the feedback from thermal hydraulics driven temperature calculation and various multi-physics effects that can influence it. Consideration of the feedback due to the influence of leakage was taken into account by development and implementation of improved buckling feedback models. Modifications were made in the calculation procedure to ensure that the xenon depletion models were accurate for proper interpolation from cross section tables. To achieve this, the NEM/THERMIX coupled code system was developed to create the system that is efficient and stable over the duration of transient calculations that last over several tens of hours. Another achievement of the PhD thesis was development and demonstration of full-physics, three-dimensional safety analysis methodology for the PBMR to provide reference solutions. Investigation of different aspects of the coupled methodology and development of efficient kinetics treatment for the PBMR were carried out, which accounts for all feedback phenomena in an efficient manner. The OECD/NEA PBMR-400 coupled code benchmark was used as a test matrix for the proposed investigations. The integrated thermal-hydraulics and neutronics (multi-physics) methods were extended to enable modeling of a wider range of transients pertinent to the PBMR. First, the effect of the spatial mapping schemes (spatial coupling) was studied and quantified for different types of transients, which resulted in implementation of improved mapping methodology based on user defined criteria. The second aspect that was studied and optimized is the temporal coupling and meshing schemes between the neutronics and thermal-hydraulics time step selection algorithms. The coupled code convergence was achieved supplemented by application of methods to accelerate it. Finally, the modeling of all feedback phenomena in PBMRs was investigated and a novel treatment of cross-section dependencies was introduced for improving the representation of cross-section variations. The added benefit was that in the process of studying and improving the coupled multi-physics methodology more insight was gained into the physics and dynamics of PBMR, which will help also to optimize the PBMR design and improve its safety. One unique contribution of the PhD research is the investigation of the importance of the correct representation of the three-dimensional (3-D) effects in the PBMR analysis. The performed studies demonstrated that explicit 3-D modeling of control rod movement is superior and removes the errors associated with the grey curtain (2-D homogenized) approximation.

Hydro turbine governor’s power control of hydroelectric unit with sloping ceiling tailrace tunnel

NASA Astrophysics Data System (ADS)

Fu, Liang; Wu, Changli; Tang, Weiping

2018-02-01

The primary frequency regulation and load regulation transient process when the hydro turbine governor is under the power mode of hydropower unit with sloping ceiling tailrace are analysed by field test and numerical simulation in this paper. A simulation method based on “three-zone model” to simulate small fluctuation transient process of the sloping ceiling tailrace is proposed. The simulation model of hydraulic turbine governor power mode is established by governor’s PLC program identification and parameter measurement, and the simulation model is verified by the test. The slow-fast-slow “three-stage regulation” method which can improve the dynamic quality of hydro turbine governor power mode is proposed. The power regulation strategy and parameters are optimized by numerical simulation, the performance of primary frequency regulation and load regulation transient process when the hydro turbine governor is under power mode are improved significantly.

Three-Dimensional Model for Preservation and Restoration of Architectural Heritage

NASA Technical Reports Server (NTRS)

Marchis, Elena

2011-01-01

Thc aim of the research will be to create a model, three-dimensional mathematical. implementation. consultation and assistance to "large" restoration projects that will assist the structural analysis, allowing easier display of dynamic strain. analysis and lighting noise. It could also be a valuable tool for decision support. therefore. may simulate several possible scenarios for intervention, This model appears therefore an excellent support for recovering. ordering and monitoring information about materials and data (stage of restoration. photographs. sampling points. results of diagnostic tests, etc.) collected dynamically during the "life" of the cultural heritage. allowing to document its complete history

Three-dimensional ordering of cold ion beams in a storage ring: A molecular-dynamics simulation study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuri, Yosuke, E-mail: yuri.yosuke@jaea.go.jp

Three-dimensional (3D) ordering of a charged-particle beams circulating in a storage ring is systematically studied with a molecular-dynamics simulation code. An ion beam can exhibit a 3D ordered configuration at ultralow temperature as a result of powerful 3D laser cooling. Various unique characteristics of the ordered beams, different from those of crystalline beams, are revealed in detail, such as the single-particle motion in the transverse and longitudinal directions, and the dependence of the tune depression and the Coulomb coupling constant on the operating points.

Envelope detection using temporal magnetization dynamics of resonantly interacting spin-torque oscillator

NASA Astrophysics Data System (ADS)

Nakamura, Y.; Nishikawa, M.; Osawa, H.; Okamoto, Y.; Kanao, T.; Sato, R.

2018-05-01

In this article, we propose the detection method of the recorded data pattern by the envelope of the temporal magnetization dynamics of resonantly interacting spin-torque oscillator on the microwave assisted magnetic recording for three-dimensional magnetic recording. We simulate the envelope of the waveform from recorded dots with the staggered magnetization configuration, which are calculated by using a micromagnetic simulation. We study the data detection methods for the envelope and propose a soft-output Viterbi algorithm (SOVA) for partial response (PR) system as a signal processing system for three dimensional magnetic recording.

Spatiotemporal dynamics of oscillatory cellular patterns in three-dimensional directional solidification.

PubMed

Bergeon, N; Tourret, D; Chen, L; Debierre, J-M; Guérin, R; Ramirez, A; Billia, B; Karma, A; Trivedi, R

2013-05-31

We report results of directional solidification experiments conducted on board the International Space Station and quantitative phase-field modeling of those experiments. The experiments image for the first time in situ the spatially extended dynamics of three-dimensional cellular array patterns formed under microgravity conditions where fluid flow is suppressed. Experiments and phase-field simulations reveal the existence of oscillatory breathing modes with time periods of several 10's of minutes. Oscillating cells are usually noncoherent due to array disorder, with the exception of small areas where the array structure is regular and stable.

DSMC Studies of the Richtmyer-Meshkov Instability

NASA Astrophysics Data System (ADS)

Gallis, M. A.; Koehler, T. P.; Torczynski, J. R.

2014-11-01

A new exascale-capable Direct Simulation Monte Carlo (DSMC) code, SPARTA, developed to be highly efficient on massively parallel computers, has extended the applicability of DSMC to challenging, transient three-dimensional problems in the continuum regime. Because DSMC inherently accounts for compressibility, viscosity, and diffusivity, it has the potential to improve the understanding of the mechanisms responsible for hydrodynamic instabilities. Here, the Richtmyer-Meshkov instability at the interface between two gases was studied parametrically using SPARTA. Simulations performed on Sequoia, an IBM Blue Gene/Q supercomputer at Lawrence Livermore National Laboratory, are used to investigate various Atwood numbers (0.33-0.94) and Mach numbers (1.2-12.0) for two-dimensional and three-dimensional perturbations. Comparisons with theoretical predictions demonstrate that DSMC accurately predicts the early-time growth of the instability. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Phonon Scattering and Confinement in Crystalline Films

NASA Astrophysics Data System (ADS)

Parrish, Kevin D.

The operating temperature of energy conversion and electronic devices affects their efficiency and efficacy. In many devices, however, the reference values of the thermal properties of the materials used are no longer applicable due to processing techniques performed. This leads to challenges in thermal management and thermal engineering that demand accurate predictive tools and high fidelity measurements. The thermal conductivity of strained, nanostructured, and ultra-thin dielectrics are predicted computationally using solutions to the Boltzmann transport equation. Experimental measurements of thermal diffusivity are performed using transient grating spectroscopy. The thermal conductivities of argon, modeled using the Lennard-Jones potential, and silicon, modeled using density functional theory, are predicted under compressive and tensile strain from lattice dynamics calculations. The thermal conductivity of silicon is found to be invariant with compression, a result that is in disagreement with previous computational efforts. This difference is attributed to the more accurate force constants calculated from density functional theory. The invariance is found to be a result of competing effects of increased phonon group velocities and decreased phonon lifetimes, demonstrating how the anharmonic contribution of the atomic potential can scale differently than the harmonic contribution. Using three Monte Carlo techniques, the phonon-boundary scattering and the subsequent thermal conductivity reduction are predicted for nanoporous silicon thin films. The Monte Carlo techniques used are free path sampling, isotropic ray-tracing, and a new technique, modal ray-tracing. The thermal conductivity predictions from all three techniques are observed to be comparable to previous experimental measurements on nanoporous silicon films. The phonon mean free paths predicted from isotropic ray-tracing, however, are unphysical as compared to those predicted by free path sampling. Removing the isotropic assumption, leading to the formulation of modal ray-tracing, corrects the mean free path distribution. The effect of phonon line-of-sight is investigated in nanoporous silicon films using free path sampling. When the line-of-sight is cut off there is a distinct change in thermal conductivity versus porosity. By analyzing the free paths of an obstructed phonon mode, it is concluded that the trend change is due to a hard upper limit on the free paths that can exist due to the nanopore geometry in the material. The transient grating technique is an optical contact-less laser based experiment for measuring the in-plane thermal diffusivity of thin films and membranes. The theory of operation and physical setup of a transient grating experiment is detailed. The procedure for extracting the thermal diffusivity from the raw experimental signal is improved upon by removing arbitrary user choice in the fitting parameters used and constructing a parameterless error minimizing procedure. The thermal conductivity of ultra-thin argon films modeled with the Lennard-Jones potential is calculated from both the Monte Carlo free path sampling technique and from explicit reduced dimensionality lattice dynamics calculations. In these ultra-thin films, the phonon properties are altered in more than a perturbative manner, referred to as the confinement regime. The free path sampling technique, which is a perturbative method, is compared to a reduced dimensionality lattice dynamics calculation where the entire film thickness is taken as the unit cell. Divergence in thermal conductivity magnitude and trend is found at few unit cell thick argon films. Although the phonon group velocities and lifetimes are affected, it is found that alterations to the phonon density of states are the primary cause of the deviation in thermal conductivity in the confinement regime.

The joy of transient chaos.

PubMed

Tél, Tamás

2015-09-01

We intend to show that transient chaos is a very appealing, but still not widely appreciated, subfield of nonlinear dynamics. Besides flashing its basic properties and giving a brief overview of the many applications, a few recent transient-chaos-related subjects are introduced in some detail. These include the dynamics of decision making, dispersion, and sedimentation of volcanic ash, doubly transient chaos of undriven autonomous mechanical systems, and a dynamical systems approach to energy absorption or explosion.

Mechanism for Broadband White-Light Emission from Two-Dimensional (110) Hybrid Perovskites.

PubMed

Hu, Te; Smith, Matthew D; Dohner, Emma R; Sher, Meng-Ju; Wu, Xiaoxi; Trinh, M Tuan; Fisher, Alan; Corbett, Jeff; Zhu, X-Y; Karunadasa, Hemamala I; Lindenberg, Aaron M

2016-06-16

The recently discovered phenomenon of broadband white-light emission at room temperature in the (110) two-dimensional organic-inorganic perovskite (N-MEDA)[PbBr4] (N-MEDA = N(1)-methylethane-1,2-diammonium) is promising for applications in solid-state lighting. However, the spectral broadening mechanism and, in particular, the processes and dynamics associated with the emissive species are still unclear. Herein, we apply a suite of ultrafast spectroscopic probes to measure the primary events directly following photoexcitation, which allows us to resolve the evolution of light-induced emissive states associated with white-light emission at femtosecond resolution. Terahertz spectra show fast free carrier trapping and transient absorption spectra show the formation of self-trapped excitons on femtosecond time-scales. Emission-wavelength-dependent dynamics of the self-trapped exciton luminescence are observed, indicative of an energy distribution of photogenerated emissive states in the perovskite. Our results are consistent with photogenerated carriers self-trapped in a deformable lattice due to strong electron-phonon coupling, where permanent lattice defects and correlated self-trapped states lend further inhomogeneity to the excited-state potential energy surface.

Processing-Induced Electrically Active Defects in Black Silicon Nanowire Devices.

PubMed

Carapezzi, Stefania; Castaldini, Antonio; Mancarella, Fulvio; Poggi, Antonella; Cavallini, Anna

2016-04-27

Silicon nanowires (Si NWs) are widely investigated nowadays for implementation in advanced energy conversion and storage devices, as well as many other possible applications. Black silicon (BSi)-NWs are dry etched NWs that merge the advantages related to low-dimensionality with the special industrial appeal connected to deep reactive ion etching (RIE). In fact, RIE is a well established technique in microelectronics manufacturing. However, RIE processing could affect the electrical properties of BSi-NWs by introducing deep states into their forbidden gap. This work applies deep level transient spectroscopy (DLTS) to identify electrically active deep levels and the associated defects in dry etched Si NW arrays. Besides, the successful fitting of DLTS spectra of BSi-NWs-based Schottky barrier diodes is an experimental confirmation that the same theoretical framework of dynamic electronic behavior of deep levels applies in bulk as well as in low dimensional structures like NWs, when quantum confinement conditions do not occur. This has been validated for deep levels associated with simple pointlike defects as well as for deep levels associated with defects with richer structures, whose dynamic electronic behavior implies a more complex picture.

Direct observation of ultrafast coherent exciton dynamics in helical π-stacks of self-assembled perylene bisimides

PubMed Central

Sung, Jooyoung; Kim, Pyosang; Fimmel, Benjamin; Würthner, Frank; Kim, Dongho

2015-01-01

Ever since the discovery of dye self-assemblies in nature, there have been tremendous efforts to exploit biomimetic supramolecular assemblies for tailored artificial photon processing materials. This feature necessarily has resulted in an increasing demand for understanding exciton dynamics in the dye self-assemblies. In a sharp contrast with J-type aggregates, however, the detailed observation of exciton dynamics in H-type aggregates has remained challenging. In this study, as we succeed in measuring transient fluorescence from Frenkel state of π-stacked perylene tetracarboxylic acid bisimide dimer and oligomer aggregates, we present an experimental demonstration on Frenkel exciton dynamics of archetypal columnar π–π stacks of dyes. The analysis of the vibronic peak ratio of the transient fluorescence spectra reveals that unlike the simple π-stacked dimer, the photoexcitation energy in the columnar π-stacked oligomer aggregates is initially delocalized over at least three molecular units and moves coherently along the chain in tens of femtoseconds, preceding excimer formation process. PMID:26492820

Laser-Induced Temperature Rise in a Composite Sandwich Structure

DTIC Science & Technology

2013-01-01

Bertolotti and Sibilia, 1981; Burgener and Reedy, 1982; Calder and Sue, 1982; Moody and Hendel, 1982; Sanders, 1984; Araya and Gutierrez, 2006 ...REFERENCES [1] G. Araya , G. and G. Gutierre, Analytical solution for a transient, three-dimensional temperature distribution due to a moving laser...beam, Int. J. Heat and Mass Transfer, 49 ( 2006 ), 4124-4131. [2] N. Asmar, Partial Differential Equations with Fourier Series and Boundary Value

Three Dimensional Transient Analysis of Microstrip Circuits in Multilayered Anisotropic Media

DTIC Science & Technology

1991-11-14

dimensions, resonance is possible within the low gigahertz frequency range. Because the effects of diffraction during proximity-print x-ray lithography ...facilitate lead passage. The simulation results, comparing radi- paksgo and sourcl ation from a gasketed and ungasketed heatsink with an dMD TPI as... lithography are of critical importance, a number of previous researchers have attempted to calculate the diffraction patterns and minimum achievable

Dynamical behavior of the random field on the pulsating and snaking solitons in cubic-quintic complex Ginzburg-Landau equation

NASA Astrophysics Data System (ADS)

Bakhtiar, Nurizatul Syarfinas Ahmad; Abdullah, Farah Aini; Hasan, Yahya Abu

2017-08-01

In this paper, we consider the dynamical behaviour of the random field on the pulsating and snaking solitons in a dissipative systems described by the one-dimensional cubic-quintic complex Ginzburg-Landau equation (cqCGLE). The dynamical behaviour of the random filed was simulated by adding a random field to the initial pulse. Then, we solve it numerically by fixing the initial amplitude profile for the pulsating and snaking solitons without losing any generality. In order to create the random field, we choose 0 ≤ ɛ ≤ 1.0. As a result, multiple soliton trains are formed when the random field is applied to a pulse like initial profile for the parameters of the pulsating and snaking solitons. The results also show the effects of varying the random field of the transient energy peaks in pulsating and snaking solitons.

Computing Finite-Time Lyapunov Exponents with Optimally Time Dependent Reduction

NASA Astrophysics Data System (ADS)

Babaee, Hessam; Farazmand, Mohammad; Sapsis, Themis; Haller, George

2016-11-01

We present a method to compute Finite-Time Lyapunov Exponents (FTLE) of a dynamical system using Optimally Time-Dependent (OTD) reduction recently introduced by H. Babaee and T. P. Sapsis. The OTD modes are a set of finite-dimensional, time-dependent, orthonormal basis {ui (x , t) } |i=1N that capture the directions associated with transient instabilities. The evolution equation of the OTD modes is derived from a minimization principle that optimally approximates the most unstable directions over finite times. To compute the FTLE, we evolve a single OTD mode along with the nonlinear dynamics. We approximate the FTLE from the reduced system obtained from projecting the instantaneous linearized dynamics onto the OTD mode. This results in a significant reduction in the computational cost compared to conventional methods for computing FTLE. We demonstrate the efficiency of our method for double Gyre and ABC flows. ARO project 66710-EG-YIP.

Three dimensional cross-correlation dynamic light scattering by non-ergodic turbid media.

PubMed

Haro-Pérez, C; Ojeda-Mendoza, G J; Rojas-Ochoa, L F

2011-06-28

We investigate dynamic light scattering by non-ergodic turbid media with an adapted version of the method proposed by Pusey and van Megen [Physica A 157, 705 (1989)]. Our formulation follows the derivation of the original method by extending it to the three dimensional cross-correlation scheme (3DDLS). The main finding is an expression to obtain the dynamic structure factor from light scattering that takes into account the system turbidity and the peculiarities of the 3D geometry. From 3DDLS measurements in well-controlled solid-like systems of different turbidity, we confirm that our results can be interpreted reasonably well by the theoretical approach described here. Good agreement is found with earlier reported results on similar systems.

Three-Dimensional Multiscale Modeling of Dendritic Spacing Selection During Al-Si Directional Solidification

NASA Astrophysics Data System (ADS)

Tourret, Damien; Clarke, Amy J.; Imhoff, Seth D.; Gibbs, Paul J.; Gibbs, John W.; Karma, Alain

2015-08-01

We present a three-dimensional extension of the multiscale dendritic needle network (DNN) model. This approach enables quantitative simulations of the unsteady dynamics of complex hierarchical networks in spatially extended dendritic arrays. We apply the model to directional solidification of Al-9.8 wt.%Si alloy and directly compare the model predictions with measurements from experiments with in situ x-ray imaging. We focus on the dynamical selection of primary spacings over a range of growth velocities, and the influence of sample geometry on the selection of spacings. Simulation results show good agreement with experiments. The computationally efficient DNN model opens new avenues for investigating the dynamics of large dendritic arrays at scales relevant to solidification experiments and processes.

Linking brain, mind and behavior.

PubMed

Makeig, Scott; Gramann, Klaus; Jung, Tzyy-Ping; Sejnowski, Terrence J; Poizner, Howard

2009-08-01

Cortical brain areas and dynamics evolved to organize motor behavior in our three-dimensional environment also support more general human cognitive processes. Yet traditional brain imaging paradigms typically allow and record only minimal participant behavior, then reduce the recorded data to single map features of averaged responses. To more fully investigate the complex links between distributed brain dynamics and motivated natural behavior, we propose the development of wearable mobile brain/body imaging (MoBI) systems that continuously capture the wearer's high-density electrical brain and muscle signals, three-dimensional body movements, audiovisual scene and point of regard, plus new data-driven analysis methods to model their interrelationships. The new imaging modality should allow new insights into how spatially distributed brain dynamics support natural human cognition and agency.

Lorentz quantum mechanics

NASA Astrophysics Data System (ADS)

Zhang, Qi; Wu, Biao

2018-01-01

We present a theoretical framework for the dynamics of bosonic Bogoliubov quasiparticles. We call it Lorentz quantum mechanics because the dynamics is a continuous complex Lorentz transformation in complex Minkowski space. In contrast, in usual quantum mechanics, the dynamics is the unitary transformation in Hilbert space. In our Lorentz quantum mechanics, three types of state exist: space-like, light-like and time-like. Fundamental aspects are explored in parallel to the usual quantum mechanics, such as a matrix form of a Lorentz transformation, and the construction of Pauli-like matrices for spinors. We also investigate the adiabatic evolution in these mechanics, as well as the associated Berry curvature and Chern number. Three typical physical systems, where bosonic Bogoliubov quasi-particles and their Lorentz quantum dynamics can arise, are presented. They are a one-dimensional fermion gas, Bose-Einstein condensate (or superfluid), and one-dimensional antiferromagnet.

Modeling the defrost process in complex geometries - Part 1: Development of a one-dimensional defrost model

NASA Astrophysics Data System (ADS)

van Buren, Simon; Hertle, Ellen; Figueiredo, Patric; Kneer, Reinhold; Rohlfs, Wilko

2017-11-01

Frost formation is a common, often undesired phenomenon in heat exchanges such as air coolers. Thus, air coolers have to be defrosted periodically, causing significant energy consumption. For the design and optimization, prediction of defrosting by a CFD tool is desired. This paper presents a one-dimensional transient model approach suitable to be used as a zero-dimensional wall-function in CFD for modeling the defrost process at the fin and tube interfaces. In accordance to previous work a multi stage defrost model is introduced (e.g. [1, 2]). In the first instance the multi stage model is implemented and validated using MATLAB. The defrost process of a one-dimensional frost segment is investigated. Fixed boundary conditions are provided at the frost interfaces. The simulation results verify the plausibility of the designed model. The evaluation of the simulated defrost process shows the expected convergent behavior of the three-stage sequence.

Optical properties and electronic energy relaxation of metallic Au144(SR)60 nanoclusters.

PubMed

Yi, Chongyue; Tofanelli, Marcus A; Ackerson, Christopher J; Knappenberger, Kenneth L

2013-12-04

Electronic energy relaxation of Au144(SR)60(q) ligand-protected nanoclusters, where SR = SC6H13 and q = -1, 0, +1, and +2, was examined using femtosecond time-resolved transient absorption spectroscopy. The observed differential transient spectra contained three distinct components: (1) transient bleaches at 525 and 600 nm, (2) broad visible excited-state absorption (ESA), and (3) stimulated emission (SE) at 670 nm. The bleach recovery kinetics depended upon the excitation pulse energy and were thus attributed to electron-phonon coupling typical of metallic nanostructures. The prominent bleach at 525 nm was assigned to a core-localized plasmon resonance (CLPR). ESA decay kinetics were oxidation-state dependent and could be described using a metal-sphere charging model. The dynamics, emission energy, and intensity of the SE peak exhibited dielectric-dependent responses indicative of Superatom charge transfer states. On the basis of these data, the Au144(SR)60 system is the smallest-known nanocluster to exhibit quantifiable electron dynamics and optical properties characteristic of metals.

Transient Characterization of Type B Particles in a Transport Riser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shadle, L.J.; Monazam, E.R.; Mei, J.S.

2007-01-01

Simple and rapid dynamic tests were used to evaluate fluid dynamic behavior of granular materials in the transport regime. Particles with densities ranging from 189 to 2,500 kg/m3 and Sauter mean size from 61 to 812 μm were tested in a 0.305 m diameter, 15.5 m height circulating fluidized bed (CFB) riser. The transient tests involved the abrupt stoppage of solids flow for each granular material over a wide range gas flow rates. The riser emptying time was linearly related to the Froude number in each of three different operating regimes. The flow structure along the height of the risermore » followed a distinct pattern as tracked through incremental pressures. These results are discussed to better understand the transformations that take place when operating over various regimes. During the transients the particle size distribution was measured. The effects of pressure, particle size, and density on test performance are also presented.« less

The Impact of Three-Dimensional Computational Modeling on Student Understanding of Astronomy Concepts: A Qualitative Analysis. Research Report

ERIC Educational Resources Information Center

Hansen, John; Barnett, Michael; MaKinster, James; Keating, Thomas

2004-01-01

In this study, we explore an alternate mode for teaching and learning the dynamic, three-dimensional (3D) relationships that are central to understanding astronomical concepts. To this end, we implemented an innovative undergraduate course in which we used inexpensive computer modeling tools. As the second of a two-paper series, this report…

Comparing the Impact of Dynamic and Static Media on Students' Learning of One-Dimensional Kinematics

ERIC Educational Resources Information Center

Mešic, Vanes; Dervic, Dževdeta; Gazibegovic-Busuladžic, Azra; Salibašic, Džana; Erceg, Nataša

2015-01-01

In our study, we aimed to compare the impact of simulations, sequences of printed simulation frames and conventional static diagrams on the understanding of students with regard to the one-dimensional kinematics. Our student sample consisted of three classes of middle years students (N = 63; mostly 15 year-olds). These three classes served as…

Computer program determines vibration in three-dimensional space of hydraulic lines excited by forced displacements

NASA Technical Reports Server (NTRS)

Dodge, W. G.

1968-01-01

Computer program determines the forced vibration in three dimensional space of a multiple degree of freedom beam type structural system. Provision is made for the longitudinal axis of the analytical model to change orientation at any point along its length. This program is used by industries in which structural design dynamic analyses are performed.

Interpretation of energy deposition data from historical operation of the transient test facility (TREAT)

DOE PAGES

DeHart, Mark D.; Baker, Benjamin A.; Ortensi, Javier

2017-07-27

The Transient Test Reactor (TREAT) at Idaho National Laboratory will resume operations in late 2017 after a 23 year hiatus while maintained in a cold standby state. Over that time period, computational power and simulation capabilities have increased substantially and now allow for new multiphysics modeling possibilities that were not practical or feasible for most of TREAT's operational history. Hence the return of TREAT to operational service provides a unique opportunity to apply state-of-the-art software and associated methods in the modeling and simulation of general three-dimensional steady state and kinetic behavior for reactor operation, and for coupling of the coremore » power transient model to experiment simulations. However, measurements taken in previous operations were intended to predict power deposition in experimental samples, with little consideration of three-dimensional core power distributions. Hence, interpretation of data for the purpose of validation of modern methods can be challenging. For the research discussed herein, efforts are described for the process of proper interpretation of data from the most recent calibration experiments performed in the core, the M8 calibration series (M8-CAL). These measurements were taken between 1990 and 1993 using a set of fission wires and test fuel pins to estimate the power deposition that would be produced in fast reactor test fuel pins during the M8 experiment series. Because of the decision to place TREAT into a standby state in 1994, the M8 series of transients were never performed. However, potentially valuable information relevant for validation is available in the M8-CAL measurement data, if properly interpreted. This article describes the current state of the process of recovery of useful data from M8-CAL measurements and quantification of biases and uncertainties to potentially apply to the validation of multiphysics methods.« less

Interpretation of energy deposition data from historical operation of the transient test facility (TREAT)

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeHart, Mark D.; Baker, Benjamin A.; Ortensi, Javier

The Transient Test Reactor (TREAT) at Idaho National Laboratory will resume operations in late 2017 after a 23 year hiatus while maintained in a cold standby state. Over that time period, computational power and simulation capabilities have increased substantially and now allow for new multiphysics modeling possibilities that were not practical or feasible for most of TREAT's operational history. Hence the return of TREAT to operational service provides a unique opportunity to apply state-of-the-art software and associated methods in the modeling and simulation of general three-dimensional steady state and kinetic behavior for reactor operation, and for coupling of the coremore » power transient model to experiment simulations. However, measurements taken in previous operations were intended to predict power deposition in experimental samples, with little consideration of three-dimensional core power distributions. Hence, interpretation of data for the purpose of validation of modern methods can be challenging. For the research discussed herein, efforts are described for the process of proper interpretation of data from the most recent calibration experiments performed in the core, the M8 calibration series (M8-CAL). These measurements were taken between 1990 and 1993 using a set of fission wires and test fuel pins to estimate the power deposition that would be produced in fast reactor test fuel pins during the M8 experiment series. Because of the decision to place TREAT into a standby state in 1994, the M8 series of transients were never performed. However, potentially valuable information relevant for validation is available in the M8-CAL measurement data, if properly interpreted. This article describes the current state of the process of recovery of useful data from M8-CAL measurements and quantification of biases and uncertainties to potentially apply to the validation of multiphysics methods.« less

Structure and Dynamics of the Solar Corona

NASA Technical Reports Server (NTRS)

Schnack, D. D.

1994-01-01

Advanced computational techniques were used to study solar coronal heating and coronal mass ejections. A three dimensional, time dependent resistive magnetohydrodynamic code was used to study the dynamic response of a model corona to continuous, slow, random magnetic footpoint displacements in the photosphere. Three dimensional numerical simulations of the response of the corona to simple smooth braiding flows in the photosphere were calculated to illustrate and understand the spontaneous formation of current filaments. Two dimensional steady state helmet streamer configurations were obtained by determining the time asymptotic state of the interaction of an initially one dimensinal transponic solar wind with a spherical potential dipole field. The disruption of the steady state helmet streamer configuration was studied as a response to shearing of the magnetic footpoints of the closed field lines under the helmet.

Transient synchrony among populations of five foliage-feeding Lepidoptera

Treesearch

Maartje J. Klapwijk; Jonathan A. Walter; Anikó Hirka; György Csóka; Christer Björkman; Andrew M. Liebhold

2018-01-01

Studies of transient population dynamics have largely focused on temporal changes in dynamical behaviour, such as the transition between periods of stability and instability. This study explores a related dynamic pattern, namely transient synchrony during a 49-year period among populations of five sympatric species of forest insects that share host tree resources. The...

Influence of Different Three-Dimensional Open Porous Titanium Scaffold Designs on Human Osteoblasts Behavior in Static and Dynamic Cell Investigations

PubMed Central

Markhoff, Jana; Wieding, Jan; Weissmann, Volker; Pasold, Juliane; Jonitz-Heincke, Anika; Bader, Rainer

2015-01-01

In the treatment of osseous defects micro-structured three-dimensional materials for bone replacement serve as leading structure for cell migration, proliferation and bone formation. The scaffold design and culture conditions are crucial for the limited diffusion distance of nutrients and oxygen. In static culture, decreased cell activity and irregular distribution occur within the scaffold. Dynamic conditions entail physical stimulation and constant medium perfusion imitating physiological nutrient supply and metabolite disposal. Therefore, we investigated the influence of different scaffold configurations and cultivation methods on human osteoblasts. Cells were seeded on three-dimensional porous Ti-6Al-4V scaffolds manufactured with selective laser melting (SLM) or electron beam melting (EBM) varying in porosity, pore size and basic structure (cubic, diagonal, pyramidal) and cultured under static and dynamic conditions. Cell viability, migration and matrix production were examined via mitochondrial activity assay, fluorescence staining and ELISA. All scaffolds showed an increasing cell activity and matrix production under static conditions over time. Expectations about the dynamic culture were only partially fulfilled, since it enabled proliferation alike the static one and enhanced cell migration. Overall, the SLM manufactured scaffold with the highest porosity, small pore size and pyramidal basic structure proved to be the most suitable structure for cell proliferation and migration. PMID:28793519

Influence of Different Three-Dimensional Open Porous Titanium Scaffold Designs on Human Osteoblasts Behavior in Static and Dynamic Cell Investigations.

PubMed

Markhoff, Jana; Wieding, Jan; Weissmann, Volker; Pasold, Juliane; Jonitz-Heincke, Anika; Bader, Rainer

2015-08-24

In the treatment of osseous defects micro-structured three-dimensional materials for bone replacement serve as leading structure for cell migration, proliferation and bone formation. The scaffold design and culture conditions are crucial for the limited diffusion distance of nutrients and oxygen. In static culture, decreased cell activity and irregular distribution occur within the scaffold. Dynamic conditions entail physical stimulation and constant medium perfusion imitating physiological nutrient supply and metabolite disposal. Therefore, we investigated the influence of different scaffold configurations and cultivation methods on human osteoblasts. Cells were seeded on three-dimensional porous Ti-6Al-4V scaffolds manufactured with selective laser melting (SLM) or electron beam melting (EBM) varying in porosity, pore size and basic structure (cubic, diagonal, pyramidal) and cultured under static and dynamic conditions. Cell viability, migration and matrix production were examined via mitochondrial activity assay, fluorescence staining and ELISA. All scaffolds showed an increasing cell activity and matrix production under static conditions over time. Expectations about the dynamic culture were only partially fulfilled, since it enabled proliferation alike the static one and enhanced cell migration. Overall, the SLM manufactured scaffold with the highest porosity, small pore size and pyramidal basic structure proved to be the most suitable structure for cell proliferation and migration.

Beating the curse of dimension with accurate statistics for the Fokker-Planck equation in complex turbulent systems.

PubMed

Chen, Nan; Majda, Andrew J

2017-12-05

Solving the Fokker-Planck equation for high-dimensional complex dynamical systems is an important issue. Recently, the authors developed efficient statistically accurate algorithms for solving the Fokker-Planck equations associated with high-dimensional nonlinear turbulent dynamical systems with conditional Gaussian structures, which contain many strong non-Gaussian features such as intermittency and fat-tailed probability density functions (PDFs). The algorithms involve a hybrid strategy with a small number of samples [Formula: see text], where a conditional Gaussian mixture in a high-dimensional subspace via an extremely efficient parametric method is combined with a judicious Gaussian kernel density estimation in the remaining low-dimensional subspace. In this article, two effective strategies are developed and incorporated into these algorithms. The first strategy involves a judicious block decomposition of the conditional covariance matrix such that the evolutions of different blocks have no interactions, which allows an extremely efficient parallel computation due to the small size of each individual block. The second strategy exploits statistical symmetry for a further reduction of [Formula: see text] The resulting algorithms can efficiently solve the Fokker-Planck equation with strongly non-Gaussian PDFs in much higher dimensions even with orders in the millions and thus beat the curse of dimension. The algorithms are applied to a [Formula: see text]-dimensional stochastic coupled FitzHugh-Nagumo model for excitable media. An accurate recovery of both the transient and equilibrium non-Gaussian PDFs requires only [Formula: see text] samples! In addition, the block decomposition facilitates the algorithms to efficiently capture the distinct non-Gaussian features at different locations in a [Formula: see text]-dimensional two-layer inhomogeneous Lorenz 96 model, using only [Formula: see text] samples. Copyright © 2017 the Author(s). Published by PNAS.

Optimal energy growth in a stably stratified shear flow

NASA Astrophysics Data System (ADS)

Jose, Sharath; Roy, Anubhab; Bale, Rahul; Iyer, Krithika; Govindarajan, Rama

2018-02-01

Transient growth of perturbations by a linear non-modal evolution is studied here in a stably stratified bounded Couette flow. The density stratification is linear. Classical inviscid stability theory states that a parallel shear flow is stable to exponentially growing disturbances if the Richardson number (Ri) is greater than 1/4 everywhere in the flow. Experiments and numerical simulations at higher Ri show however that algebraically growing disturbances can lead to transient amplification. The complexity of a stably stratified shear flow stems from its ability to combine this transient amplification with propagating internal gravity waves (IGWs). The optimal perturbations associated with maximum energy amplification are numerically obtained at intermediate Reynolds numbers. It is shown that in this wall-bounded flow, the three-dimensional optimal perturbations are oblique, unlike in unstratified flow. A partitioning of energy into kinetic and potential helps in understanding the exchange of energies and how it modifies the transient growth. We show that the apportionment between potential and kinetic energy depends, in an interesting manner, on the Richardson number, and on time, as the transient growth proceeds from an optimal perturbation. The oft-quoted stabilizing role of stratification is also probed in the non-diffusive limit in the context of disturbance energy amplification.

Excitonic gap formation in pumped Dirac materials

NASA Astrophysics Data System (ADS)

Triola, Christopher; Pertsova, Anna; Markiewicz, Robert S.; Balatsky, Alexander V.

2017-05-01

Recent pump-probe experiments demonstrate the possibility that Dirac materials may be driven into transient excited states describable by two chemical potentials, one for the electrons and one for the holes. Given the Dirac nature of the spectrum, such an inverted population allows the optical tunability of the density of states of the electrons and holes, effectively offering control of the strength of the Coulomb interaction. Here we discuss the feasibility of realizing transient excitonic instabilities in optically pumped Dirac materials. We demonstrate, theoretically, the reduction of the critical coupling leading to the formation of a transient condensate of electron-hole pairs and identify signatures of this state. Furthermore, we provide guidelines for experiments by both identifying the regimes in which such exotic many-body states are more likely to be observed and estimating the magnitude of the excitonic gap for a few important examples of existing Dirac materials. We find a set of material parameters for which our theory predicts large gaps and high critical temperatures and which could be realized in future Dirac materials. We also comment on transient excitonic instabilities in three-dimensional Dirac and Weyl semimetals. This study provides an example of a transient collective instability in driven Dirac materials.

Gravitational instantons, self-duality, and geometric flows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bourliot, F.; Estes, J.; Petropoulos, P. M.

2010-05-15

We discuss four-dimensional 'spatially homogeneous' gravitational instantons. These are self-dual solutions of Euclidean vacuum Einstein equations. They are endowed with a product structure RxM{sub 3} leading to a foliation into three-dimensional subspaces evolving in Euclidean time. For a large class of homogeneous subspaces, the dynamics coincides with a geometric flow on the three-dimensional slice, driven by the Ricci tensor plus an so(3) gauge connection. The flowing metric is related to the vielbein of the subspace, while the gauge field is inherited from the anti-self-dual component of the four-dimensional Levi-Civita connection.

Fully Three-Dimensional Virtual-Reality System

NASA Technical Reports Server (NTRS)

Beckman, Brian C.

1994-01-01

Proposed virtual-reality system presents visual displays to simulate free flight in three-dimensional space. System, virtual space pod, is testbed for control and navigation schemes. Unlike most virtual-reality systems, virtual space pod would not depend for orientation on ground plane, which hinders free flight in three dimensions. Space pod provides comfortable seating, convenient controls, and dynamic virtual-space images for virtual traveler. Controls include buttons plus joysticks with six degrees of freedom.

Dynamics of Multistage Gear Transmission with Effects of Gearbox Vibrations

NASA Technical Reports Server (NTRS)

Choy, F. K.; Tu, Y. K.; Zakrajsek, J. J.; Townsend, Dennis P.

1990-01-01

A comprehensive approach is presented in analyzing the dynamic behavior of multistage gear transmission systems with the effects of gearbox induced vibrations and mass imbalances of the rotor. The modal method, with undamped frequencies and planar mode shapes, is used to reduce the degrees of freedom of the gear system for time-transient dynamic analysis. Both the lateral and torsional vibration modes of each rotor-bearing-gear stage as well as the interstage vibrational characteristics are coupled together through localized gear mesh tooth interactions. In addition, gearbox vibrations are also coupled to the rotor-bearing-gear system dynamics through bearing support forces between the rotor and the gearbox. Transient and steady state dynamics of lateral and torsional vibrations of the geared system are examined in both time and frequency domains to develop interpretations of the overall modal dynamic characteristics under various operating conditions. A typical three-stage geared system is used as an example. Effects of mass imbalance and gearbox vibrations on the system dynamic behavior are presented in terms of modal excitation functions for both lateral and torsional vibrations. Operational characteristics and conclusions are drawn from the results presented.

Dynamic X-ray diffraction imaging of the ferroelectric response in bismuth ferrite

DOE PAGES

Laanait, Nouamane; Saenrang, Wittawat; Zhou, Hua; ...

2017-03-21

In this study, X-ray diffraction imaging is rapidly emerging as a powerful technique by which one can capture the local structure of crystalline materials at the nano- and meso-scale. Here, we present investigations of the dynamic structure of epitaxial monodomain BiFeO 3 thin-films using a novel full-field Bragg diffraction imaging modality. By taking advantage of the depth penetration of hard X-rays and their exquisite sensitivity to the atomic structure, we imaged in situ and in operando, the electric field-driven structural responses of buried BiFeO 3 epitaxial thin-films in micro-capacitor devices, with sub-100 nm lateral resolution. These imaging investigations were carriedmore » out at acquisition frame rates that reached up to 20 Hz and data transfer rates of 40 MB/s, while accessing diffraction contrast that is sensitive to the entire three-dimensional unit cell configuration. We mined these large datasets for material responses by employing matrix decomposition techniques, such as independent component analysis. We found that this statistical approach allows the extraction of the salient physical properties of the ferroelectric response of the material, such as coercive fields and transient spatiotemporal modulations in their piezoelectric response, and also facilitates their decoupling from extrinsic sources that are instrument specific.« less

Computational Fluid Dynamics Modeling of Bacillus anthracis ...

EPA Pesticide Factsheets

Journal Article Three-dimensional computational fluid dynamics and Lagrangian particle deposition models were developed to compare the deposition of aerosolized Bacillus anthracis spores in the respiratory airways of a human with that of the rabbit, a species commonly used in the study of anthrax disease. The respiratory airway geometries for each species were derived from computed tomography (CT) or µCT images. Both models encompassed airways that extended from the external nose to the lung with a total of 272 outlets in the human model and 2878 outlets in the rabbit model. All simulations of spore deposition were conducted under transient, inhalation-exhalation breathing conditions using average species-specific minute volumes. Four different exposure scenarios were modeled in the rabbit based upon experimental inhalation studies. For comparison, human simulations were conducted at the highest exposure concentration used during the rabbit experimental exposures. Results demonstrated that regional spore deposition patterns were sensitive to airway geometry and ventilation profiles. Despite the complex airway geometries in the rabbit nose, higher spore deposition efficiency was predicted in the upper conducting airways of the human at the same air concentration of anthrax spores. This greater deposition of spores in the upper airways in the human resulted in lower penetration and deposition in the tracheobronchial airways and the deep lung than that predict

Simulation of Combustion Systems with Realistic g-jitter

NASA Technical Reports Server (NTRS)

Mell, William E.; McGrattan, Kevin B.; Baum, Howard R.

2003-01-01

In this project a transient, fully three-dimensional computer simulation code was developed to simulate the effects of realistic g-jitter on a number of combustion systems. The simulation code is capable of simulating flame spread on a solid and nonpremixed or premixed gaseous combustion in nonturbulent flow with simple combustion models. Simple combustion models were used to preserve computational efficiency since this is meant to be an engineering code. Also, the use of sophisticated turbulence models was not pursued (a simple Smagorinsky type model can be implemented if deemed appropriate) because if flow velocities are large enough for turbulence to develop in a reduced gravity combustion scenario it is unlikely that g-jitter disturbances (in NASA's reduced gravity facilities) will play an important role in the flame dynamics. Acceleration disturbances of realistic orientation, magnitude, and time dependence can be easily included in the simulation. The simulation algorithm was based on techniques used in an existing large eddy simulation code which has successfully simulated fire dynamics in complex domains. A series of simulations with measured and predicted acceleration disturbances on the International Space Station (ISS) are presented. The results of this series of simulations suggested a passive isolation system and appropriate scheduling of crew activity would provide a sufficiently "quiet" acceleration environment for spherical diffusion flames.

Dynamic Reconstruction Algorithm of Three-Dimensional Temperature Field Measurement by Acoustic Tomography

PubMed Central

Li, Yanqiu; Liu, Shi; Inaki, Schlaberg H.

2017-01-01

Accuracy and speed of algorithms play an important role in the reconstruction of temperature field measurements by acoustic tomography. Existing algorithms are based on static models which only consider the measurement information. A dynamic model of three-dimensional temperature reconstruction by acoustic tomography is established in this paper. A dynamic algorithm is proposed considering both acoustic measurement information and the dynamic evolution information of the temperature field. An objective function is built which fuses measurement information and the space constraint of the temperature field with its dynamic evolution information. Robust estimation is used to extend the objective function. The method combines a tunneling algorithm and a local minimization technique to solve the objective function. Numerical simulations show that the image quality and noise immunity of the dynamic reconstruction algorithm are better when compared with static algorithms such as least square method, algebraic reconstruction technique and standard Tikhonov regularization algorithms. An effective method is provided for temperature field reconstruction by acoustic tomography. PMID:28895930