Breaking a habit: a further role of the phonological loop in action control.

PubMed

Saeki, Erina; Baddeley, Alan D; Hitch, Graham J; Saito, Satoru

2013-10-01

Recent research has suggested that keeping track of a task goal in rapid task switching may depend on the phonological loop component of working memory. In this study, we investigated whether the phonological loop plays a similar role when a single switch extending over several trials is required after many trials on which one has performed a competing task. Participants were shown pairs of digits varying in numerical and physical size, and they were required to decide which digit was numerically or physically larger. An experimental cycle consisted of four blocks of 24 trials. In Experiment 1, participants in the task change groups performed the numerical-size judgment task during the first three blocks, and then changed to the physical-size judgment task in the fourth. Participants in the continuation groups performed only the physical-size judgment task throughout all four blocks. We found negative effects of articulatory suppression on the fourth block, but only in the task change groups. Experiment 2 was a replication, with the modification that both groups received identical instructions and practice. Experiment 3 was a further replication using numerical-size judgment as the target task. The results showed a pattern similar to that from Experiment 1, with negative effects of articulatory suppression found only in the task change group. The congruity of numerical and physical size had a reliable effect on performance in all three experiments, but unlike the task change, it did not reliably interact with articulatory suppression. The results suggest that in addition to its well-established role in rapid task switching, the phonological loop also contributes to active goal maintenance in longer-term action control.

Number versus Extent in Newborns' Spontaneous Preference for Collections of Dots

ERIC Educational Resources Information Center

Turati, Chiara; Gava, Lucia; Valenza, Eloisa; Ghirardi, Valentina

2013-01-01

This study investigated processing of number and extent in newborns. Using visual preference, we showed that newborns discriminated between small sets of dot collections relying solely on implicit numerical information when non-numerical continuous variables were strictly controlled (Experiment 1), and solely on continuous information when…

Mechanical testing of bones: the positive synergy of finite-element models and in vitro experiments.

PubMed

Cristofolini, Luca; Schileo, Enrico; Juszczyk, Mateusz; Taddei, Fulvia; Martelli, Saulo; Viceconti, Marco

2010-06-13

Bone biomechanics have been extensively investigated in the past both with in vitro experiments and numerical models. In most cases either approach is chosen, without exploiting synergies. Both experiments and numerical models suffer from limitations relative to their accuracy and their respective fields of application. In vitro experiments can improve numerical models by: (i) preliminarily identifying the most relevant failure scenarios; (ii) improving the model identification with experimentally measured material properties; (iii) improving the model identification with accurately measured actual boundary conditions; and (iv) providing quantitative validation based on mechanical properties (strain, displacements) directly measured from physical specimens being tested in parallel with the modelling activity. Likewise, numerical models can improve in vitro experiments by: (i) identifying the most relevant loading configurations among a number of motor tasks that cannot be replicated in vitro; (ii) identifying acceptable simplifications for the in vitro simulation; (iii) optimizing the use of transducers to minimize errors and provide measurements at the most relevant locations; and (iv) exploring a variety of different conditions (material properties, interface, etc.) that would require enormous experimental effort. By reporting an example of successful investigation of the femur, we show how a combination of numerical modelling and controlled experiments within the same research team can be designed to create a virtuous circle where models are used to improve experiments, experiments are used to improve models and their combination synergistically provides more detailed and more reliable results than can be achieved with either approach singularly.

Modelling and control issues of dynamically substructured systems: adaptive forward prediction taken as an example

PubMed Central

Tu, Jia-Ying; Hsiao, Wei-De; Chen, Chih-Ying

2014-01-01

Testing techniques of dynamically substructured systems dissects an entire engineering system into parts. Components can be tested via numerical simulation or physical experiments and run synchronously. Additional actuator systems, which interface numerical and physical parts, are required within the physical substructure. A high-quality controller, which is designed to cancel unwanted dynamics introduced by the actuators, is important in order to synchronize the numerical and physical outputs and ensure successful tests. An adaptive forward prediction (AFP) algorithm based on delay compensation concepts has been proposed to deal with substructuring control issues. Although the settling performance and numerical conditions of the AFP controller are improved using new direct-compensation and singular value decomposition methods, the experimental results show that a linear dynamics-based controller still outperforms the AFP controller. Based on experimental observations, the least-squares fitting technique, effectiveness of the AFP compensation and differences between delay and ordinary differential equations are discussed herein, in order to reflect the fundamental issues of actuator modelling in relevant literature and, more specifically, to show that the actuator and numerical substructure are heterogeneous dynamic components and should not be collectively modelled as a homogeneous delay differential equation. PMID:25104902

Real-time feedback control of the plasma density profile on ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Mlynek, A.; Reich, M.; Giannone, L.; Treutterer, W.; Behler, K.; Blank, H.; Buhler, A.; Cole, R.; Eixenberger, H.; Fischer, R.; Lohs, A.; Lüddecke, K.; Merkel, R.; Neu, G.; Ryter, F.; Zasche, D.; ASDEX Upgrade Team

2011-04-01

The spatial distribution of density in a fusion experiment is of significant importance as it enters in numerous analyses and contributes to the fusion performance. The reconstruction of the density profile is therefore commonly done in offline data analysis. In this paper, we present an algorithm which allows for density profile reconstruction from the data of the submillimetre interferometer and the magnetic equilibrium in real-time. We compare the obtained results to the profiles yielded by a numerically more complex offline algorithm. Furthermore, we present recent ASDEX Upgrade experiments in which we used the real-time density profile for active feedback control of the shape of the density profile.

Learning Linear Spatial-Numeric Associations Improves Accuracy of Memory for Numbers

PubMed Central

Thompson, Clarissa A.; Opfer, John E.

2016-01-01

Memory for numbers improves with age and experience. One potential source of improvement is a logarithmic-to-linear shift in children’s representations of magnitude. To test this, Kindergartners and second graders estimated the location of numbers on number lines and recalled numbers presented in vignettes (Study 1). Accuracy at number-line estimation predicted memory accuracy on a numerical recall task after controlling for the effect of age and ability to approximately order magnitudes (mapper status). To test more directly whether linear numeric magnitude representations caused improvements in memory, half of children were given feedback on their number-line estimates (Study 2). As expected, learning linear representations was again linked to memory for numerical information even after controlling for age and mapper status. These results suggest that linear representations of numerical magnitude may be a causal factor in development of numeric recall accuracy. PMID:26834688

Learning Linear Spatial-Numeric Associations Improves Accuracy of Memory for Numbers.

PubMed

Thompson, Clarissa A; Opfer, John E

2016-01-01

Memory for numbers improves with age and experience. One potential source of improvement is a logarithmic-to-linear shift in children's representations of magnitude. To test this, Kindergartners and second graders estimated the location of numbers on number lines and recalled numbers presented in vignettes (Study 1). Accuracy at number-line estimation predicted memory accuracy on a numerical recall task after controlling for the effect of age and ability to approximately order magnitudes (mapper status). To test more directly whether linear numeric magnitude representations caused improvements in memory, half of children were given feedback on their number-line estimates (Study 2). As expected, learning linear representations was again linked to memory for numerical information even after controlling for age and mapper status. These results suggest that linear representations of numerical magnitude may be a causal factor in development of numeric recall accuracy.

Perceived state of self during motion can differentially modulate numerical magnitude allocation.

PubMed

Arshad, Q; Nigmatullina, Y; Roberts, R E; Goga, U; Pikovsky, M; Khan, S; Lobo, R; Flury, A-S; Pettorossi, V E; Cohen-Kadosh, R; Malhotra, P A; Bronstein, A M

2016-09-01

Although a direct relationship between numerical allocation and spatial attention has been proposed, recent research suggests that these processes are not directly coupled. In keeping with this, spatial attention shifts induced either via visual or vestibular motion can modulate numerical allocation in some circumstances but not in others. In addition to shifting spatial attention, visual or vestibular motion paradigms also (i) elicit compensatory eye movements which themselves can influence numerical processing and (ii) alter the perceptual state of 'self', inducing changes in bodily self-consciousness impacting upon cognitive mechanisms. Thus, the precise mechanism by which motion modulates numerical allocation remains unknown. We sought to investigate the influence that different perceptual experiences of motion have upon numerical magnitude allocation while controlling for both eye movements and task-related effects. We first used optokinetic visual motion stimulation (OKS) to elicit the perceptual experience of either 'visual world' or 'self'-motion during which eye movements were identical. In a second experiment, we used a vestibular protocol examining the effects of perceived and subliminal angular rotations in darkness, which also provoked identical eye movements. We observed that during the perceptual experience of 'visual world' motion, rightward OKS-biased judgments towards smaller numbers, whereas leftward OKS-biased judgments towards larger numbers. During the perceptual experience of 'self-motion', judgments were biased towards larger numbers irrespective of the OKS direction. Contrastingly, vestibular motion perception was found not to modulate numerical magnitude allocation, nor was there any differential modulation when comparing 'perceived' vs. 'subliminal' rotations. We provide a novel demonstration that numerical magnitude allocation can be differentially modulated by the perceptual state of self during visual but not vestibular mediated motion. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Active Control of Flow Separation Over an Airfoil

NASA Technical Reports Server (NTRS)

Ravindran, S. S.

1999-01-01

Designing an aircraft without conventional control surfaces is of interest to aerospace community. In this direction, smart actuator devices such as synthetic jets have been proposed to provide aircraft maneuverability instead of control surfaces. In this article, a numerical study is performed to investigate the effects of unsteady suction and blowing on airfoils. The unsteady suction and blowing is introduced at the leading edge of the airfoil in the form of tangential jet. Numerical solutions are obtained using Reynolds-Averaged viscous compressible Navier-Stokes equations. Unsteady suction and blowing is investigated as a means of separation control to obtain lift on airfoils. The effect of blowing coefficients on lift and drag is investigated. The numerical simulations are compared with experiments from the Tel-Aviv University (TAU). These results indicate that unsteady suction and blowing can be used as a means of separation control to generate lift on airfoils.

Experiments study on attitude coupling control method for flexible spacecraft

NASA Astrophysics Data System (ADS)

Wang, Jie; Li, Dongxu

2018-06-01

High pointing accuracy and stabilization are significant for spacecrafts to carry out Earth observing, laser communication and space exploration missions. However, when a spacecraft undergoes large angle maneuver, the excited elastic oscillation of flexible appendages, for instance, solar wing and onboard antenna, would downgrade the performance of the spacecraft platform. This paper proposes a coupling control method, which synthesizes the adaptive sliding mode controller and the positive position feedback (PPF) controller, to control the attitude and suppress the elastic vibration simultaneously. Because of its prominent performance for attitude tracking and stabilization, the proposed method is capable of slewing the flexible spacecraft with a large angle. Also, the method is robust to parametric uncertainties of the spacecraft model. Numerical simulations are carried out with a hub-plate system which undergoes a single-axis attitude maneuver. An attitude control testbed for the flexible spacecraft is established and experiments are conducted to validate the coupling control method. Both numerical and experimental results demonstrate that the method discussed above can effectively decrease the stabilization time and improve the attitude accuracy of the flexible spacecraft.

Linking Physical and Numerical Modelling in Hydrogeology Using Sand Tank Experiments and Comsol Multiphysics

ERIC Educational Resources Information Center

Singha, Kamini; Loheide, Steven P., II

2011-01-01

Visualising subsurface processes in hydrogeology and building intuition for how these processes are controlled by changes in forcing is hard for many undergraduate students. While numerical modelling is one way to help undergraduate students explore outcomes of multiple scenarios, many codes are not user-friendly with respect to defining domains,…

Differences in duration of eye fixation for conditions in a numerical stroop-effect experiment.

PubMed

Crespo, Antonio; Cabestrero, Raúl; Quirós, Pilar

2009-02-01

Durations of eye fixation were recorded for a numerical Stroop effect experiment. Participants (6 men, 19 women; M age=22 yr.) reported the number of characters present in sequences of variable length (2 to 5 characters) while attempting to ignore the identity of the character. Three conditions were included: congruent (the number of characters and the numeral were matched, e.g., responding "two" to 22), incongruent (the number of characters and the numeral were mismatched, e.g., responding "two" to 55), and control (baseline of stimuli made up of "X"s, e.g., responding "two" to XX). Comparisons among the three conditions produced the longest response times and average durations of fixation for the incongruent condition. The shortest response times and average durations of fixation were obtained for the congruent condition.

A numerical cloud model for the support of laboratory experimentation

NASA Technical Reports Server (NTRS)

Hagen, D. E.

1979-01-01

A numerical cloud model is presented which can describe the evolution of a cloud starting from moist aerosol-laden air through the diffusional growth regime. The model is designed for the direct support of cloud chamber laboratory experimentation, i.e., experiment preparation, real-time control and data analysis. In the model the thermodynamics is uncoupled from the droplet growth processes. Analytic solutions for the cloud droplet growth equations are developed which can be applied in most laboratory situations. The model is applied to a variety of representative experiments.

A discontinuous Galerkin method for poroelastic wave propagation: The two-dimensional case

NASA Astrophysics Data System (ADS)

Dudley Ward, N. F.; Lähivaara, T.; Eveson, S.

2017-12-01

In this paper, we consider a high-order discontinuous Galerkin (DG) method for modelling wave propagation in coupled poroelastic-elastic media. The upwind numerical flux is derived as an exact solution for the Riemann problem including the poroelastic-elastic interface. Attenuation mechanisms in both Biot's low- and high-frequency regimes are considered. The current implementation supports non-uniform basis orders which can be used to control the numerical accuracy element by element. In the numerical examples, we study the convergence properties of the proposed DG scheme and provide experiments where the numerical accuracy of the scheme under consideration is compared to analytic and other numerical solutions.

On the granular fingering instability: controlled triggering in laboratory experiments and numerical simulations

NASA Astrophysics Data System (ADS)

Vriend, Nathalie; Tsang, Jonny; Arran, Matthew; Jin, Binbin; Johnsen, Alexander

2017-11-01

When a mixture of small, smooth particles and larger, coarse particles is released on a rough inclined plane, the initial uniform front may break up in distinct fingers which elongate over time. This fingering instability is sensitive to the unique arrangement of individual particles and is driven by granular segregation (Pouliquen et al., 1997). Variability in initial conditions create significant limitations for consistent experimental and numerical validation of newly developed theoretical models (Baker et al., 2016) for finger formation. We present an experimental study using a novel tool that sets the initial fingering width of the instability. By changing this trigger width between experiments, we explore the response of the avalanche breakup to perturbations of different widths. Discrete particle simulations (using MercuryDPM, Thornton et al., 2012) are conducted under a similar setting, reproducing the variable finger width, allowing validation between experiments and numerical simulations. A good agreement between simulations and experiments is obtained, and ongoing theoretical work is briefly introduced. NMV acknowledges the Royal Society Dorothy Hodgkin Research Fellowship.

Optimal Design of Passive Flow Control for a Boundary-Layer-Ingesting Offset Inlet Using Design-of-Experiments

NASA Technical Reports Server (NTRS)

Allan, Brian G.; Owens, Lewis R.; Lin, John C.

2006-01-01

This research will investigate the use of Design-of-Experiments (DOE) in the development of an optimal passive flow control vane design for a boundary-layer-ingesting (BLI) offset inlet in transonic flow. This inlet flow control is designed to minimize the engine fan-face distortion levels and first five Fourier harmonic half amplitudes while maximizing the inlet pressure recovery. Numerical simulations of the BLI inlet are computed using the Reynolds-averaged Navier-Stokes (RANS) flow solver, OVERFLOW, developed at NASA. These simulations are used to generate the numerical experiments for the DOE response surface model. In this investigation, two DOE optimizations were performed using a D-Optimal Response Surface model. The first DOE optimization was performed using four design factors which were vane height and angles-of-attack for two groups of vanes. One group of vanes was placed at the bottom of the inlet and a second group symmetrically on the sides. The DOE design was performed for a BLI inlet with a free-stream Mach number of 0.85 and a Reynolds number of 2 million, based on the length of the fan-face diameter, matching an experimental wind tunnel BLI inlet test. The first DOE optimization required a fifth order model having 173 numerical simulation experiments and was able to reduce the DC60 baseline distortion from 64% down to 4.4%, while holding the pressure recovery constant. A second DOE optimization was performed holding the vanes heights at a constant value from the first DOE optimization with the two vane angles-of-attack as design factors. This DOE only required a second order model fit with 15 numerical simulation experiments and reduced DC60 to 3.5% with small decreases in the fourth and fifth harmonic amplitudes. The second optimal vane design was tested at the NASA Langley 0.3- Meter Transonic Cryogenic Tunnel in a BLI inlet experiment. The experimental results showed a 80% reduction of DPCP(sub avg), the circumferential distortion level at the engine fan-face.

Optimal Design of Passive Flow Control for a Boundary-Layer-Ingesting Offset Inlet Using Design-of-Experiments

NASA Technical Reports Server (NTRS)

Allan, Brian G.; Owens, Lewis R., Jr.; Lin, John C.

2006-01-01

This research will investigate the use of Design-of-Experiments (DOE) in the development of an optimal passive flow control vane design for a boundary-layer-ingesting (BLI) offset inlet in transonic flow. This inlet flow control is designed to minimize the engine fan face distortion levels and first five Fourier harmonic half amplitudes while maximizing the inlet pressure recovery. Numerical simulations of the BLI inlet are computed using the Reynolds-averaged Navier-Stokes (RANS) flow solver, OVERFLOW, developed at NASA. These simulations are used to generate the numerical experiments for the DOE response surface model. In this investigation, two DOE optimizations were performed using a D-Optimal Response Surface model. The first DOE optimization was performed using four design factors which were vane height and angles-of-attack for two groups of vanes. One group of vanes was placed at the bottom of the inlet and a second group symmetrically on the sides. The DOE design was performed for a BLI inlet with a free-stream Mach number of 0.85 and a Reynolds number of 2 million, based on the length of the fan face diameter, matching an experimental wind tunnel BLI inlet test. The first DOE optimization required a fifth order model having 173 numerical simulation experiments and was able to reduce the DC60 baseline distortion from 64% down to 4.4%, while holding the pressure recovery constant. A second DOE optimization was performed holding the vanes heights at a constant value from the first DOE optimization with the two vane angles-of-attack as design factors. This DOE only required a second order model fit with 15 numerical simulation experiments and reduced DC60 to 3.5% with small decreases in the fourth and fifth harmonic amplitudes. The second optimal vane design was tested at the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel in a BLI inlet experiment. The experimental results showed a 80% reduction of DPCPavg, the circumferential distortion level at the engine fan face.

Numerical investigation of two interacting parallel thruster-plumes and comparison to experiment

NASA Astrophysics Data System (ADS)

Grabe, Martin; Holz, André; Ziegenhagen, Stefan; Hannemann, Klaus

2014-12-01

Clusters of orbital thrusters are an attractive option to achieve graduated thrust levels and increased redundancy with available hardware, but the heavily under-expanded plumes of chemical attitude control thrusters placed in close proximity will interact, leading to a local amplification of downstream fluxes and of back-flow onto the spacecraft. The interaction of two similar, parallel, axi-symmetric cold-gas model thrusters has recently been studied in the DLR High-Vacuum Plume Test Facility STG under space-like vacuum conditions, employing a Patterson-type impact pressure probe with slot orifice. We reproduce a selection of these experiments numerically, and emphasise that a comparison of numerical results to the measured data is not straight-forward. The signal of the probe used in the experiments must be interpreted according to the degree of rarefaction and local flow Mach number, and both vary dramatically thoughout the flow-field. We present a procedure to reconstruct the probe signal by post-processing the numerically obtained flow-field data and show that agreement to the experimental results is then improved. Features of the investigated cold-gas thruster plume interaction are discussed on the basis of the numerical results.

Practical Control Algorithms for Nonlinear Dynamical Systems Using Phase-Space Knowledge and Mixed Numeric and Geometric Computation.

DTIC Science & Technology

1997-10-01

Research results include: (1) Developed empirical performance criteria for characterizing stabilities and robustness of the maglev control... Maglev Experience’ at HS󈨥: Fifth International Hybrid Systems Workshop, Notre Dame, IN, Sept. 11-13,1997

S-Duct Engine Inlet Flow Control Using SDBD Plasma Streamwise Vortex Generators

NASA Astrophysics Data System (ADS)

Kelley, Christopher; He, Chuan; Corke, Thomas

2009-11-01

The results of a numerical simulation and experiment characterizing the performance of plasma streamwise vortex generators in controlling separation and secondary flow within a serpentine, diffusing duct are presented. A no flow control case is first run to check agreement of location of separation, development of secondary flow, and total pressure recovery between the experiment and numerical results. Upon validation, passive vane-type vortex generators and plasma streamwise vortex generators are implemented to increase total pressure recovery and reduce flow distortion at the aerodynamic interface plane: the exit of the S-duct. Total pressure recovery is found experimentally with a pitot probe rake assembly at the aerodynamic interface plane. Stagnation pressure distortion descriptors are also presented to show the performance increase with plasma streamwise vortex generators in comparison to the baseline no flow control case. These performance parameters show that streamwise plasma vortex generators are an effective alternative to vane-type vortex generators in total pressure recovery and total pressure distortion reduction in S-duct inlets.

Effects of Non-Symbolic Approximate Number Practice on Symbolic Numerical Abilities in Pakistani Children.

PubMed

Khanum, Saeeda; Hanif, Rubina; Spelke, Elizabeth S; Berteletti, Ilaria; Hyde, Daniel C

2016-01-01

Current theories of numerical cognition posit that uniquely human symbolic number abilities connect to an early developing cognitive system for representing approximate numerical magnitudes, the approximate number system (ANS). In support of this proposal, recent laboratory-based training experiments with U.S. children show enhanced performance on symbolic addition after brief practice comparing or adding arrays of dots without counting: tasks that engage the ANS. Here we explore the nature and generality of this effect through two brief training experiments. In Experiment 1, elementary school children in Pakistan practiced either a non-symbolic numerical addition task or a line-length addition task with no numerical content, and then were tested on symbolic addition. After training, children in the numerical training group completed the symbolic addition test faster than children in the line length training group, suggesting a causal role of brief, non-symbolic numerical training on exact, symbolic addition. These findings replicate and extend the core findings of a recent U.S. laboratory-based study to non-Western children tested in a school setting, attesting to the robustness and generalizability of the observed training effects. Experiment 2 tested whether ANS training would also enhance the consistency of performance on a symbolic number line task. Over several analyses of the data there was some evidence that approximate number training enhanced symbolic number line placements relative to control conditions. Together, the findings suggest that engagement of the ANS through brief training procedures enhances children's immediate attention to number and engagement with symbolic number tasks.

Effects of Non-Symbolic Approximate Number Practice on Symbolic Numerical Abilities in Pakistani Children

PubMed Central

Khanum, Saeeda; Hanif, Rubina; Spelke, Elizabeth S.; Berteletti, Ilaria; Hyde, Daniel C.

2016-01-01

Current theories of numerical cognition posit that uniquely human symbolic number abilities connect to an early developing cognitive system for representing approximate numerical magnitudes, the approximate number system (ANS). In support of this proposal, recent laboratory-based training experiments with U.S. children show enhanced performance on symbolic addition after brief practice comparing or adding arrays of dots without counting: tasks that engage the ANS. Here we explore the nature and generality of this effect through two brief training experiments. In Experiment 1, elementary school children in Pakistan practiced either a non-symbolic numerical addition task or a line-length addition task with no numerical content, and then were tested on symbolic addition. After training, children in the numerical training group completed the symbolic addition test faster than children in the line length training group, suggesting a causal role of brief, non-symbolic numerical training on exact, symbolic addition. These findings replicate and extend the core findings of a recent U.S. laboratory-based study to non-Western children tested in a school setting, attesting to the robustness and generalizability of the observed training effects. Experiment 2 tested whether ANS training would also enhance the consistency of performance on a symbolic number line task. Over several analyses of the data there was some evidence that approximate number training enhanced symbolic number line placements relative to control conditions. Together, the findings suggest that engagement of the ANS through brief training procedures enhances children's immediate attention to number and engagement with symbolic number tasks. PMID:27764117

Tools for controlling protein interactions with light

PubMed Central

Tucker, Chandra L.; Vrana, Justin D.; Kennedy, Matthew J.

2014-01-01

Genetically-encoded actuators that allow control of protein-protein interactions with light, termed ‘optical dimerizers’, are emerging as new tools for experimental biology. In recent years, numerous new and versatile dimerizer systems have been developed. Here we discuss the design of optical dimerizer experiments, including choice of a dimerizer system, photoexcitation sources, and coordinate use of imaging reporters. We provide detailed protocols for experiments using two dimerization systems we previously developed, CRY2/CIB and UVR8/UVR8, for use controlling transcription, protein localization, and protein secretion with light. Additionally, we provide instructions and software for constructing a pulse-controlled LED light device for use in experiments requiring extended light treatments. PMID:25181301

A Numerical Simulation and Statistical Modeling of High Intensity Radiated Fields Experiment Data

NASA Technical Reports Server (NTRS)

Smith, Laura J.

2004-01-01

Tests are conducted on a quad-redundant fault tolerant flight control computer to establish upset characteristics of an avionics system in an electromagnetic field. A numerical simulation and statistical model are described in this work to analyze the open loop experiment data collected in the reverberation chamber at NASA LaRC as a part of an effort to examine the effects of electromagnetic interference on fly-by-wire aircraft control systems. By comparing thousands of simulation and model outputs, the models that best describe the data are first identified and then a systematic statistical analysis is performed on the data. All of these efforts are combined which culminate in an extrapolation of values that are in turn used to support previous efforts used in evaluating the data.

Online machining error estimation method of numerical control gear grinding machine tool based on data analysis of internal sensors

NASA Astrophysics Data System (ADS)

Zhao, Fei; Zhang, Chi; Yang, Guilin; Chen, Chinyin

2016-12-01

This paper presents an online estimation method of cutting error by analyzing of internal sensor readings. The internal sensors of numerical control (NC) machine tool are selected to avoid installation problem. The estimation mathematic model of cutting error was proposed to compute the relative position of cutting point and tool center point (TCP) from internal sensor readings based on cutting theory of gear. In order to verify the effectiveness of the proposed model, it was simulated and experimented in gear generating grinding process. The cutting error of gear was estimated and the factors which induce cutting error were analyzed. The simulation and experiments verify that the proposed approach is an efficient way to estimate the cutting error of work-piece during machining process.

Markov Chains For Testing Redundant Software

NASA Technical Reports Server (NTRS)

White, Allan L.; Sjogren, Jon A.

1990-01-01

Preliminary design developed for validation experiment that addresses problems unique to assuring extremely high quality of multiple-version programs in process-control software. Approach takes into account inertia of controlled system in sense it takes more than one failure of control program to cause controlled system to fail. Verification procedure consists of two steps: experimentation (numerical simulation) and computation, with Markov model for each step.

Numerical modeling of experimental observations on gas formation and multi-phase flow of carbon dioxide in subsurface formations

NASA Astrophysics Data System (ADS)

Pawar, R.; Dash, Z.; Sakaki, T.; Plampin, M. R.; Lassen, R. N.; Illangasekare, T. H.; Zyvoloski, G.

2011-12-01

One of the concerns related to geologic CO2 sequestration is potential leakage of CO2 and its subsequent migration to shallow groundwater resources leading to geochemical impacts. Developing approaches to monitor CO2 migration in shallow aquifer and mitigate leakage impacts will require improving our understanding of gas phase formation and multi-phase flow subsequent to CO2 leakage in shallow aquifers. We are utilizing an integrated approach combining laboratory experiments and numerical simulations to characterize the multi-phase flow of CO2 in shallow aquifers. The laboratory experiments involve a series of highly controlled experiments in which CO2 dissolved water is injected in homogeneous and heterogeneous soil columns and tanks. The experimental results are used to study the effects of soil properties, temperature, pressure gradients and heterogeneities on gas formation and migration. We utilize the Finite Element Heat and Mass (FEHM) simulator (Zyvoloski et al, 2010) to numerically model the experimental results. The numerical models capture the physics of CO2 exsolution, multi-phase fluid flow as well as sand heterogeneity. Experimental observations of pressure, temperature and gas saturations are used to develop and constrain conceptual models for CO2 gas-phase formation and multi-phase CO2 flow in porous media. This talk will provide details of development of conceptual models based on experimental observation, development of numerical models for laboratory experiments and modelling results.

Evaluation of transverse dispersion effects in tank experiments by numerical modeling: parameter estimation, sensitivity analysis and revision of experimental design.

PubMed

Ballarini, E; Bauer, S; Eberhardt, C; Beyer, C

2012-06-01

Transverse dispersion represents an important mixing process for transport of contaminants in groundwater and constitutes an essential prerequisite for geochemical and biodegradation reactions. Within this context, this work describes the detailed numerical simulation of highly controlled laboratory experiments using uranine, bromide and oxygen depleted water as conservative tracers for the quantification of transverse mixing in porous media. Synthetic numerical experiments reproducing an existing laboratory experimental set-up of quasi two-dimensional flow through tank were performed to assess the applicability of an analytical solution of the 2D advection-dispersion equation for the estimation of transverse dispersivity as fitting parameter. The fitted dispersivities were compared to the "true" values introduced in the numerical simulations and the associated error could be precisely estimated. A sensitivity analysis was performed on the experimental set-up in order to evaluate the sensitivities of the measurements taken at the tank experiment on the individual hydraulic and transport parameters. From the results, an improved experimental set-up as well as a numerical evaluation procedure could be developed, which allow for a precise and reliable determination of dispersivities. The improved tank set-up was used for new laboratory experiments, performed at advective velocities of 4.9 m d(-1) and 10.5 m d(-1). Numerical evaluation of these experiments yielded a unique and reliable parameter set, which closely fits the measured tracer concentration data. For the porous medium with a grain size of 0.25-0.30 mm, the fitted longitudinal and transverse dispersivities were 3.49×10(-4) m and 1.48×10(-5) m, respectively. The procedures developed in this paper for the synthetic and rigorous design and evaluation of the experiments can be generalized and transferred to comparable applications. Copyright © 2012 Elsevier B.V. All rights reserved.

Rotordynamic Instability Problems in High-Performance Turbomachinery, 1993

NASA Technical Reports Server (NTRS)

1994-01-01

Numerical, theoretical, and experimental results and control methods for seals, bearings, and dampers with some attention given to variable thermospherical properties and turbulence measurements are reported along with field experiences.

Numerical Modeling of Flow Control in a Boundary-Layer-Ingesting Offset Inlet Diffuser at Transonic Mach Numbers

NASA Technical Reports Server (NTRS)

Allan, Brian G.; Owens, Lewis R.

2006-01-01

This paper will investigate the validation of the NASA developed, Reynolds-averaged Navier-Stokes (RANS) flow solver, OVERFLOW, for a boundary-layer-ingesting (BLI) offset (S-shaped) inlet in transonic flow with passive and active flow control devices as well as a baseline case. Numerical simulations are compared to wind tunnel results of a BLI inlet experiment conducted at the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel. Comparisons of inlet flow distortion, pressure recovery, and inlet wall pressures are performed. The numerical simulations are compared to the BLI inlet data at a free-stream Mach number of 0.85 and a Reynolds number of approximately 2 million based on the fanface diameter. The numerical simulations with and without tunnel walls are performed, quantifying tunnel wall effects on the BLI inlet flow. A comparison is made between the numerical simulations and the BLI inlet experiment for the baseline and VG vane cases at various inlet mass flow rates. A comparison is also made to a BLI inlet jet configuration for varying actuator mass flow rates at a fixed inlet mass flow rate. Overall, the numerical simulations were able to predict the baseline circumferential flow distortion, DPCP avg, very well within the designed operating range of the BLI inlet. A comparison of the average total pressure recovery showed that the simulations were able to predict the trends but had a negative 0.01 offset when compared to the experimental levels. Numerical simulations of the baseline inlet flow also showed good agreement with the experimental inlet centerline surface pressures. The vane case showed that the CFD predicted the correct trends in the circumferential distortion levels for varying inlet mass flow but had a distortion level that was nearly twice as large as the experiment. Comparison to circumferential distortion measurements for a 15 deg clocked 40 probe rake indicated that the circumferential distortion levels are very sensitive to the symmetry of the flow and that a misalignment of the vanes in the experiment could have resulted in this difference. The numerical simulations of the BLI inlet with jets showed good agreement with the circumferential inlet distortion levels for a range of jet actuator mass flow ratios at a fixed inlet mass flow rate. The CFD simulations for the jet case also predicted an average total pressure recovery offset that was 0.01 lower than the experiment as was seen in the baseline. Comparisons of the flow features for the jet cases revealed that the CFD predicted a much larger vortex at the engine fan-face when compare to the experiment.

What Students Learn from Hands-On Activities

ERIC Educational Resources Information Center

Schwichow, Martin; Zimmerman, Corinne; Croker, Steve; Härtig, Hendrik

2016-01-01

The ability to design and interpret controlled experiments is an important scientific process skill and a common objective of science standards. Numerous intervention studies have investigated how the control-of-variables-strategy (CVS) can be introduced to students. However, a meta-analysis of 72 intervention studies found that the opportunity to…

Numerical Modeling of Flow Control in a Boundary-Layer-Ingesting Offset Inlet Diffuser at Transonic Mach Numbers

NASA Technical Reports Server (NTRS)

Allan Brian G.; Owens, Lewis, R.

2006-01-01

This paper will investigate the validation of a NASA developed, Reynolds-averaged Navier-Stokes (RANS) flow solver, OVERFLOW, for a boundary-layer-ingesting (BLI) offset (S-shaped) inlet in transonic flow with passive and active flow control devices as well as the baseline case. Numerical simulations are compared to wind tunnel results of a BLI inlet conducted at the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel. Comparisons of inlet flow distortion, pressure recovery, and inlet wall pressures are performed. The numerical simulations are compared to the BLI inlet data at a freestream Mach number of 0.85 and a Reynolds number of approximately 2 million based on the length of the fan-face diameter. The numerical simulations with and without wind tunnel walls are performed, quantifying effects of the tunnel walls on the BLI inlet flow measurements. The wind tunnel test evaluated several different combinations of jet locations and mass flow rates as well as a vortex generator (VG) vane case. The numerical simulations will be performed on a single jet configuration for varying actuator mass flow rates at a fix inlet mass flow condition. Validation of the numerical simulations for the VG vane case will also be performed for varying inlet mass flow rates. Overall, the numerical simulations were able to predict the baseline circumferential flow distortion, DPCPavg, very well for comparisons made within the designed operating range of the BLI inlet. However the CFD simulations did predict a total pressure recovery that was 0.01 lower than the experiment. Numerical simulations of the baseline inlet flow also showed good agreement with the experimental inlet centerline surface pressures. The vane case showed that the CFD predicted the correct trends in the circumferential distortion for varying inlet mass flow but had a distortion level that was nearly twice as large as the experiment. Comparison to circumferential distortion measurements for a 15 deg clocked 40 probe rake indicated that the circumferential distortion levels are very sensitive to the symmetry of the flow and that a miss alignment of the vanes in the experiment could have resulted in this difference. The numerical simulations of the BLI inlet with jets showed good agreement with the circumferential inlet distortion levels for a range of jet actuator mass flow ratios at a fixed inlet mass flow rate. The CFD simulations for the jet case also predicted an average total pressure recovery that was 0.01 lower than the experiment as was seen in the baseline. Comparison of the flow features the jet case revealed that the CFD predicted a much larger vortex at the engine fan-face when compare to the experiment.

Evaluation of the tripolar electrode stimulation method by numerical analysis and animal experiments for cochlear implants.

PubMed

Miyoshi, S; Sakajiri, M; Ifukube, T; Matsushima, J

1997-01-01

We have proposed the Tripolar Electrode Stimulation Method (TESM) which may enable us to narrow the stimulation region and to move continuously the stimulation site for the cochlear implants. We evaluated whether or not TESM works according to a theory based on numerical analysis using the auditory nerve fiber model. In this simulation, the sum of the excited model fibers were compared with the compound actions potentials obtained from animal experiments. As a result, this experiment showed that TESM could narrow a stimulation region by controlling the sum of the currents emitted from the electrodes on both sides, and continuously move a stimulation site by changing the ratio of the currents emitted from the electrodes on both sides.

Requirements for sustainable schistosomiasis control.

PubMed

Traoré, M

1996-01-01

In Mali the increased transmission of schistosomiasis following the construction of numerous reservoirs and irrigation schemes, together with experience gained in tackling the disease, have led to a major effort to train personnel in control methods, to achieve decentralized delivery and management, and to foster self-reliance in this field. The author outlines the essential components of a sound national control programme requiring long-term commitment.

Modelling of deformation and recrystallisation microstructures in rocks and ice

NASA Astrophysics Data System (ADS)

Bons, Paul D.; Evans, Lynn A.; Gomez-Rivas, Enrique; Griera, Albert; Jessell, Mark W.; Lebensohn, Ricardo; Llorens, Maria-Gema; Peternell, Mark; Piazolo, Sandra; Weikusat, Ilka; Wilson, Chris J. L.

2015-04-01

Microstructures both record the deformation history of a rock and strongly control its mechanical properties. As microstructures in natural rocks only show the final "post-mortem" state, geologists have attempted to simulate the development of microstructures with experiments and later numerical models. Especially in-situ experiments have given enormous insight, as time-lapse movies could reveal the full history of a microstructure. Numerical modelling is an alternative approach to simulate and follow the change in microstructure with time, unconstrained by experimental limitations. Numerical models have been applied to a range of microstructural processes, such as grain growth, dynamic recrystallisation, porphyroblast rotation, vein growth, formation of mylonitic fabrics, etc. The numerical platform "Elle" (www.elle.ws) in particular has brought progress in the simulation of microstructural development as it is specifically designed to include the competition between simultaneously operating processes. Three developments significantly improve our capability to simulate microstructural evolution: (1) model input from the mapping of crystallographic orientation with EBSD or the automatic fabric analyser, (2) measurement of grain size and crystallographic preferred orientation evolution using neutron diffraction experiments and (3) the implementation of the full-field Fast Fourier Transform (FFT) solver for modelling anisotropic crystal-plastic deformation. The latter enables the detailed modelling of stress and strain as a function of local crystallographic orientation, which has a strong effect on strain localisation such as, for example, the formation of shear bands. These models can now be compared with the temporal evolution of crystallographic orientation distributions in in-situ experiments. In the last decade, the possibility to combine experiments with numerical simulations has allowed not only verification and refinement of the numerical simulation technique but also increased significantly the ability to predict and/or interpret natural microstructures. This contribution will present the most recent developments in in-situ and numerical modelling of deformation and recrystallisation microstructures in rocks and in ice.

Active vibration and noise control of vibro-acoustic system by using PID controller

NASA Astrophysics Data System (ADS)

Li, Yunlong; Wang, Xiaojun; Huang, Ren; Qiu, Zhiping

2015-07-01

Active control simulation of the acoustic and vibration response of a vibro-acoustic cavity of an airplane based on a PID controller is presented. A full numerical vibro-acoustic model is developed by using an Eulerian model, which is a coupled model based on the finite element formulation. The reduced order model, which is used to design the closed-loop control system, is obtained by the combination of modal expansion and variable substitution. Some physical experiments are made to validate and update the full-order and the reduced-order numerical models. Optimization of the actuator placement is employed in order to get an effective closed-loop control system. For the controller design, an iterative method is used to determine the optimal parameters of the PID controller. The process is illustrated by the design of an active noise and vibration control system for a cavity structure. The numerical and experimental results show that a PID-based active control system can effectively suppress the noise inside the cavity using a sound pressure signal as the controller input. It is also possible to control the noise by suppressing the vibration of the structure using the structural displacement signal as the controller input. For an airplane cavity structure, considering the issue of space-saving, the latter is more suitable.

Numerical Simulations of Plasma Based Flow Control Applications

NASA Technical Reports Server (NTRS)

Suzen, Y. B.; Huang, P. G.; Jacob, J. D.; Ashpis, D. E.

2005-01-01

A mathematical model was developed to simulate flow control applications using plasma actuators. The effects of the plasma actuators on the external flow are incorporated into Navier Stokes computations as a body force vector. In order to compute this body force vector, the model solves two additional equations: one for the electric field due to the applied AC voltage at the electrodes and the other for the charge density representing the ionized air. The model is calibrated against an experiment having plasma-driven flow in a quiescent environment and is then applied to simulate a low pressure turbine flow with large flow separation. The effects of the plasma actuator on control of flow separation are demonstrated numerically.

Mixing-dependent Reactions in the Hyporheic Zone: Laboratory and Numerical Experiments

NASA Astrophysics Data System (ADS)

Santizo, K. Y.; Eastes, L. A.; Hester, E. T.; Widdowson, M.

2017-12-01

The hyporheic zone is the surface water-groundwater interface surrounding the river's perimeter. Prior research demonstrates the ability of the hyporheic zone to attenuate pollutants when surface water cycles through reactive sediments (non-mixing-dependent reactions). However, the colocation of both surface and ground water within hyporheic sediments also allows mixing-dependent reactions that require mixing of reactants from these two water sources. Recent modeling studies show these mixing zones can be small under steady state homogeneous conditions, but do not validate those results in the laboratory or explore the range of hydrological characteristics that control the extent of mixing. Our objective was to simulate the mixing zone, quantify its thickness, and probe its hydrological controls using a "mix" of laboratory and numerical experiments. For the lab experiments, a hyporheic zone was simulated in a sand mesocosm, and a mixing-dependent abiotic reaction of sodium sulfite and dissolved oxygen was induced. Oxygen concentration response and oxygen consumption were visualized via planar optodes. Sulfate production by the mixing-dependent reaction was measured by fluid samples and a spectrophometer. Key hydrologic controls varied in the mesocosm included head gradient driving hyporheic exchange and hydraulic conductivity/heterogeneity. Results show a clear mixing area, sulfate production, and oxygen gradient. Mixing zone length (hyporheic flow cell size) and thickness both increase with the driving head gradient. For the numerical experiments, transient surface water boundary conditions were implemented together with heterogeneity of hydraulic conductivity. Results indicate that both fluctuating boundary conditions and heterogeneity increase mixing-dependent reaction. The hyporheic zone is deemed an attenuation hotspot by multiple studies, but here we demonstrate its potential for mixing-dependent reactions and the influence of important hydrological parameters.

Sound control by temperature gradients

NASA Astrophysics Data System (ADS)

Sánchez-Dehesa, José; Angelov, Mitko I.; Cervera, Francisco; Cai, Liang-Wu

2009-11-01

This work reports experiments showing that airborne sound propagation can be controlled by temperature gradients. A system of two heated tubes is here used to demonstrate the collimation and focusing of an ultrasonic beam by the refractive index profile created by the temperature gradients existing around the tubes. Numerical simulations supporting the experimental findings are also reported.

When Prior Knowledge Interferes, Inhibitory Control Matters for Learning: The Case of Numerical Magnitude Representations

ERIC Educational Resources Information Center

Laski, Elida V.; Dulaney, Alana

2015-01-01

The present study tested the "interference hypothesis"-that learning and using more advanced representations and strategies requires the inhibition of prior, less advanced ones. Specifically, it examined the relation between inhibitory control and number line estimation performance. Experiment 1 compared the accuracy of adults' (N = 53)…

Re-assessment of feedbacks from biosphere to Indian Monsoon: RegCMv4.4.5.10 simulations

NASA Astrophysics Data System (ADS)

Lodh, A.

2016-12-01

Biosphere feedback plays an important role in the progression of moisture laden Indian summer monsoon winds over the land regions of India, towards the north-western regions of India, during the Indian summer monsoon regime. Hence, for understanding the biosphere-feedback to Indian monsoon numerical experiments for "control" and "design" cases are performed using ICTP RegCMv4.4.5.10 climate model forced with National Center for Atmospheric Research - II reanalysed fields. The RegCMv4.4.5.10 simulations are performed from 00GMT 1st November 1999 to 24 GMT 1st January 2011, with combination of mixed convective parameterization (viz. Emanuel and Grell) schemes over land and ocean, combined with "University of Washington- Planetary boundary layer" (UW-PBL) and Holtslag PBL scheme. Validation studies are then performed for correct representation of Indian summer monsoon features particularly precipitation and soil moisture. Then, four numerical experiments with LULCC change in the climate model are carried out (for the same initial, boundary forcings and time-period as in control experiment) for determining possible influence of vegetation cover (viz. extended desertification, deforestation and increase in afforestation, irrigated land) on Indian monsoon meteorology. Results from the extended desert and deforestation experiment, informs us that the moisture laden easterlies from Bay of Bengal are not able to move towards the land region owing to formation of anomalous anti-cyclone circulations, resulting in decrease in precipitation over India. From irrigation and afforestation experiment, it is found that there is increase in precipitation, precipitable water, recycling ratio, precipitation efficiency and development of anomalous cyclonic circulations over Central and North-west India. More details about the results from the numerical experiments performed will be explained.

Stability of Nonlinear Swarms on Flat and Curved Surfaces

DTIC Science & Technology

numerical experiments have shown that the system either converges to a rotating circular limit cycle with a fixed center of mass, or the agents clump ...Swarming is a near-universal phenomenon in nature. Many mathematical models of swarms exist , both to model natural processes and to control robotic...agents. We study a swarm of agents with spring-like at-traction and nonlinear self-propulsion. Swarms of this type have been studied numerically, but

Numerical Study of Periodic Traveling Wave Solutions for the Predator-Prey Model with Landscape Features

NASA Astrophysics Data System (ADS)

Yun, Ana; Shin, Jaemin; Li, Yibao; Lee, Seunggyu; Kim, Junseok

We numerically investigate periodic traveling wave solutions for a diffusive predator-prey system with landscape features. The landscape features are modeled through the homogeneous Dirichlet boundary condition which is imposed at the edge of the obstacle domain. To effectively treat the Dirichlet boundary condition, we employ a robust and accurate numerical technique by using a boundary control function. We also propose a robust algorithm for calculating the numerical periodicity of the traveling wave solution. In numerical experiments, we show that periodic traveling waves which move out and away from the obstacle are effectively generated. We explain the formation of the traveling waves by comparing the wavelengths. The spatial asynchrony has been shown in quantitative detail for various obstacles. Furthermore, we apply our numerical technique to the complicated real landscape features.

Domain decomposition method for the Baltic Sea based on theory of adjoint equation and inverse problem.

NASA Astrophysics Data System (ADS)

Lezina, Natalya; Agoshkov, Valery

2017-04-01

Domain decomposition method (DDM) allows one to present a domain with complex geometry as a set of essentially simpler subdomains. This method is particularly applied for the hydrodynamics of oceans and seas. In each subdomain the system of thermo-hydrodynamic equations in the Boussinesq and hydrostatic approximations is solved. The problem of obtaining solution in the whole domain is that it is necessary to combine solutions in subdomains. For this purposes iterative algorithm is created and numerical experiments are conducted to investigate an effectiveness of developed algorithm using DDM. For symmetric operators in DDM, Poincare-Steklov's operators [1] are used, but for the problems of the hydrodynamics, it is not suitable. In this case for the problem, adjoint equation method [2] and inverse problem theory are used. In addition, it is possible to create algorithms for the parallel calculations using DDM on multiprocessor computer system. DDM for the model of the Baltic Sea dynamics is numerically studied. The results of numerical experiments using DDM are compared with the solution of the system of hydrodynamic equations in the whole domain. The work was supported by the Russian Science Foundation (project 14-11-00609, the formulation of the iterative process and numerical experiments). [1] V.I. Agoshkov, Domain Decompositions Methods in the Mathematical Physics Problem // Numerical processes and systems, No 8, Moscow, 1991 (in Russian). [2] V.I. Agoshkov, Optimal Control Approaches and Adjoint Equations in the Mathematical Physics Problem, Institute of Numerical Mathematics, RAS, Moscow, 2003 (in Russian).

A compensation controller based on a regional pole-assignment method for AMD control systems with a time-varying delay

NASA Astrophysics Data System (ADS)

Li, Zuohua; Chen, Chaojun; Teng, Jun; Wang, Ying

2018-04-01

Active mass damper/driver (AMD) control system has been proposed as an effective tool for high-rise buildings to resist strong dynamic loads. However, such disadvantage as time-varying delay in AMD control systems impedes their application in practices. Time-varying delay, which has an effect on the performance and stability of single-degree-of-freedom (SDOF) and multi-degree-of-freedom (MDOF) systems, is considered in the paper. In addition, a new time-delay compensation controller based on regional pole-assignment method is presented. To verify its effectiveness, the proposed method is applied to a numerical example of a ten-storey frame and an experiment of a single span four-storey steel frame. Both numerical and experimental results demonstrate that the proposed method can enhance the performances of an AMD control system with time-varying delays.

A reduced energy supply strategy in active vibration control

NASA Astrophysics Data System (ADS)

Ichchou, M. N.; Loukil, T.; Bareille, O.; Chamberland, G.; Qiu, J.

2011-12-01

In this paper, a control strategy is presented and numerically tested. This strategy aims to achieve the potential performance of fully active systems with a reduced energy supply. These energy needs are expected to be comparable to the power demands of semi-active systems, while system performance is intended to be comparable to that of a fully active configuration. The underlying strategy is called 'global semi-active control'. This control approach results from an energy investigation based on management of the optimal control process. Energy management encompasses storage and convenient restitution. The proposed strategy monitors a given active law without any external energy supply by considering purely dissipative and energy-demanding phases. Such a control law is offered here along with an analysis of its properties. A suboptimal form, well adapted for practical implementation steps, is also given. Moreover, a number of numerical experiments are proposed in order to validate test findings.

A time-domain decomposition iterative method for the solution of distributed linear quadratic optimal control problems

NASA Astrophysics Data System (ADS)

Heinkenschloss, Matthias

2005-01-01

We study a class of time-domain decomposition-based methods for the numerical solution of large-scale linear quadratic optimal control problems. Our methods are based on a multiple shooting reformulation of the linear quadratic optimal control problem as a discrete-time optimal control (DTOC) problem. The optimality conditions for this DTOC problem lead to a linear block tridiagonal system. The diagonal blocks are invertible and are related to the original linear quadratic optimal control problem restricted to smaller time-subintervals. This motivates the application of block Gauss-Seidel (GS)-type methods for the solution of the block tridiagonal systems. Numerical experiments show that the spectral radii of the block GS iteration matrices are larger than one for typical applications, but that the eigenvalues of the iteration matrices decay to zero fast. Hence, while the GS method is not expected to convergence for typical applications, it can be effective as a preconditioner for Krylov-subspace methods. This is confirmed by our numerical tests.A byproduct of this research is the insight that certain instantaneous control techniques can be viewed as the application of one step of the forward block GS method applied to the DTOC optimality system.

Managing operational documentation in the ALICE Detector Control System

NASA Astrophysics Data System (ADS)

Lechman, M.; Augustinus, A.; Bond, P.; Chochula, P.; Kurepin, A.; Pinazza, O.; Rosinsky, P.

2012-12-01

ALICE (A Large Ion Collider Experiment) is one of the big LHC (Large Hadron Collider) experiments at CERN in Geneve, Switzerland. The experiment is composed of 18 sub-detectors controlled by an integrated Detector Control System (DCS) that is implemented using the commercial SCADA package PVSSII. The DCS includes over 1200 network devices, over 1,000,000 monitored parameters and numerous custom made software components that are prepared by over 100 developers from all around the world. This complex system is controlled by a single operator via a central user interface. One of his/her main tasks is the recovery of anomalies and errors that may occur during operation. Therefore, clear, complete and easily accessible documentation is essential to guide the shifter through the expert interfaces of different subsystems. This paper describes the idea of the management of the operational documentation in ALICE using a generic repository that is built on a relational database and is integrated with the control system. The experience gained and the conclusions drawn from the project are also presented.

Friction-term response to boundary-condition type in flow models

USGS Publications Warehouse

Schaffranek, R.W.; Lai, C.

1996-01-01

The friction-slope term in the unsteady open-channel flow equations is examined using two numerical models based on different formulations of the governing equations and employing different solution methods. The purposes of the study are to analyze, evaluate, and demonstrate the behavior of the term in a set of controlled numerical experiments using varied types and combinations of boundary conditions. Results of numerical experiments illustrate that a given model can respond inconsistently for the identical resistance-coefficient value under different types and combinations of boundary conditions. Findings also demonstrate that two models employing different dependent variables and solution methods can respond similarly for the identical resistance-coefficient value under similar types and combinations of boundary conditions. Discussion of qualitative considerations and quantitative experimental results provides insight into the proper treatment, evaluation, and significance of the friction-slope term, thereby offering practical guidelines for model implementation and calibration.

Toward a physics-based rate and state friction law for earthquake nucleation processes in fault zones with granular gouge

NASA Astrophysics Data System (ADS)

Ferdowsi, B.; Rubin, A. M.

2017-12-01

Numerical simulations of earthquake nucleation rely on constitutive rate and state evolution laws to model earthquake initiation and propagation processes. The response of different state evolution laws to large velocity increases is an important feature of these constitutive relations that can significantly change the style of earthquake nucleation in numerical models. However, currently there is not a rigorous understanding of the physical origins of the response of bare rock or gouge-filled fault zones to large velocity increases. This in turn hinders our ability to design physics-based friction laws that can appropriately describe those responses. We here argue that most fault zones form a granular gouge after an initial shearing phase and that it is the behavior of the gouge layer that controls the fault friction. We perform numerical experiments of a confined sheared granular gouge under a range of confining stresses and driving velocities relevant to fault zones and apply 1-3 order of magnitude velocity steps to explore dynamical behavior of the system from grain- to macro-scales. We compare our numerical observations with experimental data from biaxial double-direct-shear fault gouge experiments under equivalent loading and driving conditions. Our intention is to first investigate the degree to which these numerical experiments, with Hertzian normal and Coulomb friction laws at the grain-grain contact scale and without any time-dependent plasticity, can reproduce experimental fault gouge behavior. We next compare the behavior observed in numerical experiments with predictions of the Dieterich (Aging) and Ruina (Slip) friction laws. Finally, the numerical observations at the grain and meso-scales will be used for designing a rate and state evolution law that takes into account recent advances in rheology of granular systems, including local and non-local effects, for a wide range of shear rates and slow and fast deformation regimes of the fault gouge.

Reducing Noise in a College Library.

ERIC Educational Resources Information Center

Luyben, Paul D.; And Others

1981-01-01

Discusses an experiment on controlling library noise by rearrangement of furniture groupings and the separation of existing clusters of furniture. While electromechanical tests showed no significant differences, user measures indicated more acceptable noise levels. There are numerous illustrations and 30 references. (RAA)

Optimizing anaerobic soil disinfestation for California strawberries

USDA-ARS?s Scientific Manuscript database

Anaerobic soil disinfestation (ASD), a biological alternative to soil fumigation, can control soilborne pathogens and nematodes in numerous crop production systems. To optimize ASD for California strawberries, a series of field and pot experiments have been conducted since 2003. Overall, ASD treatme...

Constraints on Lithospheric Rheology From Fault Displacement Rate Histories and Numerical Experiments

NASA Astrophysics Data System (ADS)

Lavier, L. L.; Bennett, R. A.; Anderson, M. L.; Matti, J. C.

2005-05-01

Recent displacement rate and geodetic data on the San Andreas, San Jacinto and eastern California shear zone suggest that changes in the geometry and/or the magnitude of the applied forces on the crust (e.g., a general or local change in fault strike relative to plate motion) can generate strain repartitioning within the crust on time scales of millions to thousands of years. The rates over which this repartitioning takes place in response to changing forces are controlled by the rheological evolution of the lithosphere. We investigate the implications of observed fault displacement histories for the rheology of the lithosphere using 2.5 D numerical experiments of deformation in an analogue system. The numerical technique used allows for the spontaneous formation of elastoplastic shear zones and flow in a Maxwell viscoelastic lower crust. The results show that when a strike slip fault is rotated to strike obliquely to the direction of relative plate motion it causes changes in bending and frictional stresses due to the formation of topography. To accommodate these changes, a conjugate system of oblique-striking strike slip faults develops. The total displacement is then slowly distributed over the new fault system on the time scale of mountain building (i.e. million of years). The rate of change is dependent on the strength of the lithosphere as well as the amount of obliquity applied on the initial strike-slip fault. In other numerical experiments we show that in a system of multiple strike-slip fault zones, displacement rate changes can occur over a time scale of about 100 kyr. This time scale corresponds to the Maxwell time at the brittle ductile transition (BDT). In such a system the lithospheric displacement is alternatively distributed (over 100 kyr) in clusters localized in lower crustal channels and over strike-slip fault zones. We show that the clustering time scale is controlled by the ratio of upper to lower crustal strength. This incomplete exercise shows how displacement rates data sets spanning thousands to millions of years can be used to constrain numerical experiments of lithospheric deformation and, in doing so, place new constraints on the rheology of the lithosphere.

The Zombie Instability: Using Numerical Simulation to Design a Laboratory Experiment

NASA Astrophysics Data System (ADS)

Wang, Meng; Pei, Suyang; Jiang, Chung-Hsiang; Hassanzadeh, Pedram; Marcus, Philip

2014-11-01

A new type of finite amplitude-instability has been found in numerical simulations of stratified, rotating, shear flows. The instability occurs via baroclinic critical layers that create linearly unstable vortex layers, which roll-up into vortices. Under the right conditions, those vortices can form a new generation of vortices, resulting in ``vortex self-replication'' that fills the fluid with vortices. Creating this instability in a laboratory would provide further evidence for the existence of the instability, which we first found in numerical simulations of protoplanetary disks. To design a laboratory experiment we need to know how the flow parameters-- shear, rotation and stratification, etc. affect the instability. To build an experiment economically, we also need to know how the finite-amplitude trigger of the instability scales with viscosity and the size of the domain. In this talk, we summarize our findings. We present a map, in terms of the experimentally controllable parameters, that shows where the instability occurs and whether the instability creates a few isolated transient vortices, a few long-lived vortices, or long-lived, self-replicating vortices that fill the entire flow.

Electrostatic and aerodynamic forced vibrations of a thin flexible electrode: Quasi-periodic vs. chaotic oscillations.

PubMed

Madanu, Sushma B; Barbel, Stanley I; Ward, Thomas

2016-06-01

In this paper, transverse vibrations of an electrostatically actuated thin flexible cantilever perturbed by low-speed air flow are studied using both experiments and numerical modeling. In the experiments, the dynamic characteristics of the cantilever are studied by supplying a DC voltage with an AC component for electrostatic forcing and a constant uniform air flow around the cantilever system for aerodynamic forcing. A range of control parameters leading to stable vibrations are established using a dimensionless operating parameter that is the ratio of the induced and the free stream velocities. Numerical results are validated with experimental data. Assuming the amplitude of vibrations are small, then a non-linear dynamic Euler-Bernoulli beam equation with viscous damping and gravitational effects is used to model the equation of motion. Aerodynamic forcing is modelled as a temporally sinusoidal and uniform force acting perpendicular to the beam length. The forcing amplitude is found to be proportional to the square of the air flow velocity. Numerical results strongly agree with the experiments predicting accurate vibration amplitude, displacement frequency, and quasi-periodic displacement of the cantilever tip.

Large number discrimination by mosquitofish.

PubMed

Agrillo, Christian; Piffer, Laura; Bisazza, Angelo

2010-12-22

Recent studies have demonstrated that fish display rudimentary numerical abilities similar to those observed in mammals and birds. The mechanisms underlying the discrimination of small quantities (<4) were recently investigated while, to date, no study has examined the discrimination of large numerosities in fish. Subjects were trained to discriminate between two sets of small geometric figures using social reinforcement. In the first experiment mosquitofish were required to discriminate 4 from 8 objects with or without experimental control of the continuous variables that co-vary with number (area, space, density, total luminance). Results showed that fish can use the sole numerical information to compare quantities but that they preferentially use cumulative surface area as a proxy of the number when this information is available. A second experiment investigated the influence of the total number of elements to discriminate large quantities. Fish proved to be able to discriminate up to 100 vs. 200 objects, without showing any significant decrease in accuracy compared with the 4 vs. 8 discrimination. The third experiment investigated the influence of the ratio between the numerosities. Performance was found to decrease when decreasing the numerical distance. Fish were able to discriminate numbers when ratios were 1:2 or 2:3 but not when the ratio was 3:4. The performance of a sample of undergraduate students, tested non-verbally using the same sets of stimuli, largely overlapped that of fish. Fish are able to use pure numerical information when discriminating between quantities larger than 4 units. As observed in human and non-human primates, the numerical system of fish appears to have virtually no upper limit while the numerical ratio has a clear effect on performance. These similarities further reinforce the view of a common origin of non-verbal numerical systems in all vertebrates.

Rational numbers: componential versus holistic representation of fractions in a magnitude comparison task.

PubMed

Meert, Gaëlle; Grégoire, Jacques; Noël, Marie-Pascale

2009-08-01

This study investigated whether the mental representation of the fraction magnitude was componential and/or holistic in a numerical comparison task performed by adults. In Experiment 1, the comparison of fractions with common numerators (x/a_x/b) and of fractions with common denominators (a/x_b/x) primed the comparison of natural numbers. In Experiment 2, fillers (i.e., fractions without common components) were added to reduce the regularity of the stimuli. In both experiments, distance effects indicated that participants compared the numerators for a/x_b/x fractions, but that the magnitudes of the whole fractions were accessed and compared for x/a_x/b fractions. The priming effect of x/a_x/b fractions on natural numbers suggested that the interference of the denominator magnitude was controlled during the comparison of these fractions. These results suggested a hybrid representation of their magnitude (i.e., componential and holistic). In conclusion, the magnitude of the whole fraction can be accessed, probably by estimating the ratio between the magnitude of the denominator and the magnitude of the numerator. However, adults might prefer to rely on the magnitudes of the components and compare the magnitudes of the whole fractions only when the use of a componential strategy is made difficult.

A numerical investigation of head waves and leaky modes in fluid- filled boreholes.

USGS Publications Warehouse

Paillet, Frederick L.; Cheng, C.H.

1986-01-01

Although synthetic borehole seismograms can be computed for a wide range of borehole conditions, the physical nature of shear and compressional head waves in fluid-filled boreholes is poorly understood. Presents a series of numerical experiments designed to explain the physical mechanisms controlling head-wave propagation in boreholes. These calculations demonstrate the existence of compressional normal modes equivalent to shear normal modes, or pseudo-Rayleigh waves, with sequential cutoff frequencies spaced between the cutoff frequencies for the shear normal modes.-from Authors

Experimental study on line-of-sight (LOS) attitude control using control moment gyros under micro-gravity environment

NASA Astrophysics Data System (ADS)

Kojima, Hirohisa; Hiraiwa, Kana; Yoshimura, Yasuhiro

2018-02-01

This paper presents the results of line-of-sight (LOS) attitude control using control moment gyros under a micro-gravity environment generated by parabolic flight. The W-Z parameters are used to describe the spacecraft attitude. In order to stabilize the current LOS to the target LOS, backstepping-based feedback control is considered using the W-Z parameters. Numerical simulations and experiments under a micro-gravity environment are carried out, and their results are compared in order to validate the proposed control methods.

Discovery of Deep Structure from Unlabeled Data

DTIC Science & Technology

2014-11-01

GPU processors . To evaluate the unsupervised learning component of the algorithms (which has become of less importance in the era of “big data...representations to those in biological visual, auditory, and somatosensory cortex ; and ran numerous control experiments investigating the impact of

FIELD EXPERIENCE IN SAMPLING HAZARDOUS WASTE INCINERATORS

EPA Science Inventory

This paper is for presentation at the 77th annual meeting of the Air Pollution Control Association, June 24-29, 1984. The paper contains much useful, pragmatic information gained through numerous hazardous waste incinerator trial burn-type investigations performed for EPA by the ...

Biodiversity mediates top-down control in eelgrass ecosystems: a global comparative-experimental approach.

PubMed

Duffy, J Emmett; Reynolds, Pamela L; Boström, Christoffer; Coyer, James A; Cusson, Mathieu; Donadi, Serena; Douglass, James G; Eklöf, Johan S; Engelen, Aschwin H; Eriksson, Britas Klemens; Fredriksen, Stein; Gamfeldt, Lars; Gustafsson, Camilla; Hoarau, Galice; Hori, Masakazu; Hovel, Kevin; Iken, Katrin; Lefcheck, Jonathan S; Moksnes, Per-Olav; Nakaoka, Masahiro; O'Connor, Mary I; Olsen, Jeanine L; Richardson, J Paul; Ruesink, Jennifer L; Sotka, Erik E; Thormar, Jonas; Whalen, Matthew A; Stachowicz, John J

2015-07-01

Nutrient pollution and reduced grazing each can stimulate algal blooms as shown by numerous experiments. But because experiments rarely incorporate natural variation in environmental factors and biodiversity, conditions determining the relative strength of bottom-up and top-down forcing remain unresolved. We factorially added nutrients and reduced grazing at 15 sites across the range of the marine foundation species eelgrass (Zostera marina) to quantify how top-down and bottom-up control interact with natural gradients in biodiversity and environmental forcing. Experiments confirmed modest top-down control of algae, whereas fertilisation had no general effect. Unexpectedly, grazer and algal biomass were better predicted by cross-site variation in grazer and eelgrass diversity than by global environmental gradients. Moreover, these large-scale patterns corresponded strikingly with prior small-scale experiments. Our results link global and local evidence that biodiversity and top-down control strongly influence functioning of threatened seagrass ecosystems, and suggest that biodiversity is comparably important to global change stressors. © 2015 John Wiley & Sons Ltd/CNRS.

Error Control with Perfectly Matched Layer or Damping Layer Treatments for Computational Aeroacoustics with Jet Flows

NASA Technical Reports Server (NTRS)

Goodrich, John W.

2009-01-01

In this paper we show by means of numerical experiments that the error introduced in a numerical domain because of a Perfectly Matched Layer or Damping Layer boundary treatment can be controlled. These experimental demonstrations are for acoustic propagation with the Linearized Euler Equations with both uniform and steady jet flows. The propagating signal is driven by a time harmonic pressure source. Combinations of Perfectly Matched and Damping Layers are used with different damping profiles. These layer and profile combinations allow the relative error introduced by a layer to be kept as small as desired, in principle. Tradeoffs between error and cost are explored.

Effects of Pump-turbine S-shaped Characteristics on Transient Behaviours: Model Setup

NASA Astrophysics Data System (ADS)

Zeng, Wei; Yang, Jiandong; Hu, Jinhong

2017-04-01

Pumped storage stations undergo numerous transition processes, which make the pump turbines go through the unstable S-shaped region. The hydraulic transient in S-shaped region has normally been investigated through numerical simulations, while field experiments generally involve high risks and are difficult to perform. In this research, a pumped storage model composed of a piping system, two model units, two electrical control systems, a measurement system and a collection system was set up to study the transition processes. The model platform can be applied to simulate almost any hydraulic transition process that occurs in real power stations, such as load rejection, startup, frequency control and grid connection.

Computer numeric control subaperture aspheric surface polishing-microroughness evaluation

NASA Astrophysics Data System (ADS)

Prochaska, Frantisek; Polak, Jaroslav; Matousek, Ondrej; Tomka, David

2014-09-01

The aim of this work was an investigation of surface microroughness and shape accuracy achieved on an aspheric lens by subaperture computer numeric control (CNC) polishing. Different optical substrates were polished (OHARA S-LAH 58, SF4, ZERODUR) using a POLITEX™ polishing pad, synthetic pitch, and the natural optical pitch. Surface roughness was measured by light interferometer. The best results were achieved on the S-LAH58 glass and the ZERODUR™ using the natural optical pitch. In the case of SF4 glass, the natural optical pitch showed a tendency to scratch the surface. Experiments also indicated a problem in surface form deterioration when using the natural optical pitch, regardless of the type of optical material.

Absence of visual experience modifies the neural basis of numerical thinking.

PubMed

Kanjlia, Shipra; Lane, Connor; Feigenson, Lisa; Bedny, Marina

2016-10-04

In humans, the ability to reason about mathematical quantities depends on a frontoparietal network that includes the intraparietal sulcus (IPS). How do nature and nurture give rise to the neurobiology of numerical cognition? We asked how visual experience shapes the neural basis of numerical thinking by studying numerical cognition in congenitally blind individuals. Blind (n = 17) and blindfolded sighted (n = 19) participants solved math equations that varied in difficulty (e.g., 27 - 12 = x vs. 7 - 2 = x), and performed a control sentence comprehension task while undergoing fMRI. Whole-cortex analyses revealed that in both blind and sighted participants, the IPS and dorsolateral prefrontal cortices were more active during the math task than the language task, and activity in the IPS increased parametrically with equation difficulty. Thus, the classic frontoparietal number network is preserved in the total absence of visual experience. However, surprisingly, blind but not sighted individuals additionally recruited a subset of early visual areas during symbolic math calculation. The functional profile of these "visual" regions was identical to that of the IPS in blind but not sighted individuals. Furthermore, in blindness, number-responsive visual cortices exhibited increased functional connectivity with prefrontal and IPS regions that process numbers. We conclude that the frontoparietal number network develops independently of visual experience. In blindness, this number network colonizes parts of deafferented visual cortex. These results suggest that human cortex is highly functionally flexible early in life, and point to frontoparietal input as a mechanism of cross-modal plasticity in blindness.

Numerical experiments with a wind- and buoyancy-driven two-and-a-half-layer upper ocean model

NASA Astrophysics Data System (ADS)

Cherniawsky, J. Y.; Yuen, C. W.; Lin, C. A.; Mysak, L. A.

1990-09-01

We describe numerical experiments with a limited domain (15°-67°N, 65° west to east) coarse-resolution two-and-a-half-layer upper ocean model. The model consists of two active variable density layers: a Niiler and Kraus (1977) type mixed layer and a pycnocline layer, which overlays a semipassive deep ocean. The mixed layer is forced with a cosine wind stress and Haney type heat and precipitation-evaporation fluxes, which were derived from zonally averaged climatological (Levitus, 1982) surface temperatures and salinities for the North Atlantic. The second layer is forced from below with (1) Newtonian cooling to climatological temperatures and salinities at the lower boundary, (2) convective adjustment, which occurs whenever the density of the second layer is unstable with respect to climatology, and (3) mass entrainment in areas of strong upwelling, when the deep ocean ventilates through the bottom surface. The sensitivity of this model to changes in its internal (mixed layer) and external (e.g., a Newtonian coupling coefficient) parameters is investigated and compared to the results from a control experiment. We find that the model is not overly sensitive to changes in most of the parameters that were tested, albeit these results may depend to some extent on the choice of the control experiment.

Sticking properties of ice grains

NASA Astrophysics Data System (ADS)

Jongmanns, M.; Kumm, M.; Wurm, G.; Wolf, D. E.; Teiser, J.

2017-06-01

We study the size dependence of pull-off forces of water ice in laboratory experiments and numerical simulations. To determine the pull-off force in our laboratory experiments, we use a liquid nitrogen cooled centrifuge. Depending on its rotation frequency, spherical ice grains detach due to the centrifugal force which is related to the adhesive properties. Numerical simulations are conducted by means of molecular dynamics simulations of hexagonal ice using a standard coarse-grained water potential. The pull-off force of a single contact between two spherical ice grains is measured due to strain controlled simulations. Both, the experimental study and the simulations reveal a dependence between the pull-off force and the (reduced) particle radii, which differ significantly from the linear dependence of common contact theories.

Three-dimensional analysis of tokamaks and stellarators

PubMed Central

Garabedian, Paul R.

2008-01-01

The NSTAB equilibrium and stability code and the TRAN Monte Carlo transport code furnish a simple but effective numerical simulation of essential features of present tokamak and stellarator experiments. When the mesh size is comparable to the island width, an accurate radial difference scheme in conservation form captures magnetic islands successfully despite a nested surface hypothesis imposed by the mathematics. Three-dimensional asymmetries in bifurcated numerical solutions of the axially symmetric tokamak problem are relevant to the observation of unstable neoclassical tearing modes and edge localized modes in experiments. Islands in compact stellarators with quasiaxial symmetry are easier to control, so these configurations will become good candidates for magnetic fusion if difficulties with safety and stability are encountered in the International Thermonuclear Experimental Reactor (ITER) project. PMID:18768807

FORCED AIR VENTILATION FOR REMEDIATION OF UNSATURATED SOILS CONTAMINATED BY VOC

EPA Science Inventory

Parameters which were expected to control the removal process of VOCs from contaminated soil during the SVE operation were studied by means of numerical simulations and laboratory experiments in this project. Experimental results of SVE with soil columns in the laboratory indicat...

Computer Series, 83. Bits and Pieces, 34.

ERIC Educational Resources Information Center

Moore, John W., Ed.

1987-01-01

Contains seven articles about computer applications to chemistry instruction. Includes descriptions of a three-dimensional animation of a potential energy surface, numerical solutions of kinetic equations, applications for spectroscopy courses, a computer-controlled experiment on the tin/lead solid/liquid phase diagram, an inexpensive thermistor…

Constrained H1-regularization schemes for diffeomorphic image registration

PubMed Central

Mang, Andreas; Biros, George

2017-01-01

We propose regularization schemes for deformable registration and efficient algorithms for their numerical approximation. We treat image registration as a variational optimal control problem. The deformation map is parametrized by its velocity. Tikhonov regularization ensures well-posedness. Our scheme augments standard smoothness regularization operators based on H1- and H2-seminorms with a constraint on the divergence of the velocity field, which resembles variational formulations for Stokes incompressible flows. In our formulation, we invert for a stationary velocity field and a mass source map. This allows us to explicitly control the compressibility of the deformation map and by that the determinant of the deformation gradient. We also introduce a new regularization scheme that allows us to control shear. We use a globalized, preconditioned, matrix-free, reduced space (Gauss–)Newton–Krylov scheme for numerical optimization. We exploit variable elimination techniques to reduce the number of unknowns of our system; we only iterate on the reduced space of the velocity field. Our current implementation is limited to the two-dimensional case. The numerical experiments demonstrate that we can control the determinant of the deformation gradient without compromising registration quality. This additional control allows us to avoid oversmoothing of the deformation map. We also demonstrate that we can promote or penalize shear whilst controlling the determinant of the deformation gradient. PMID:29075361

Simulation of two-dimensional turbulent flows in a rotating annulus

NASA Astrophysics Data System (ADS)

Storey, Brian D.

2004-05-01

Rotating water tank experiments have been used to study fundamental processes of atmospheric and geophysical turbulence in a controlled laboratory setting. When these tanks are undergoing strong rotation the forced turbulent flow becomes highly two dimensional along the axis of rotation. An efficient numerical method has been developed for simulating the forced quasi-geostrophic equations in an annular geometry to model current laboratory experiments. The algorithm employs a spectral method with Fourier series and Chebyshev polynomials as basis functions. The algorithm has been implemented on a parallel architecture to allow modelling of a wide range of spatial scales over long integration times. This paper describes the derivation of the model equations, numerical method, testing and performance of the algorithm. Results provide reasonable agreement with the experimental data, indicating that such computations can be used as a predictive tool to design future experiments.

Prediction of dynamic and aerodynamic characteristics of the centrifugal fan with forward curved blades

NASA Astrophysics Data System (ADS)

Polanský, Jiří; Kalmár, László; Gášpár, Roman

2013-12-01

The main aim of this paper is determine the centrifugal fan with forward curved blades aerodynamic characteristics based on numerical modeling. Three variants of geometry were investigated. The first, basic "A" variant contains 12 blades. The geometry of second "B" variant contains 12 blades and 12 semi-blades with optimal length [1]. The third, control variant "C" contains 24 blades without semi-blades. Numerical calculations were performed by CFD Ansys. Another aim of this paper is to compare results of the numerical simulation with results of approximate numerical procedure. Applied approximate numerical procedure [2] is designated to determine characteristics of the turbulent flow in the bladed space of a centrifugal-flow fan impeller. This numerical method is an extension of the hydro-dynamical cascade theory for incompressible and inviscid fluid flow. Paper also partially compares results from the numerical simulation and results from the experimental investigation. Acoustic phenomena observed during experiment, during numerical simulation manifested as deterioration of the calculation stability, residuals oscillation and thus also as a flow field oscillation. Pressure pulsations are evaluated by using frequency analysis for each variant and working condition.

Counting on the mental number line to make a move: sensorimotor ('pen') control and numerical processing.

PubMed

Sheridan, Rebecca; van Rooijen, Maaike; Giles, Oscar; Mushtaq, Faisal; Steenbergen, Bert; Mon-Williams, Mark; Waterman, Amanda

2017-10-01

Mathematics is often conducted with a writing implement. But is there a relationship between numerical processing and sensorimotor 'pen' control? We asked participants to move a stylus so it crossed an unmarked line at a location specified by a symbolic number (1-9), where number colour indicated whether the line ran left-right ('normal') or vice versa ('reversed'). The task could be simplified through the use of a 'mental number line' (MNL). Many modern societies use number lines in mathematical education and the brain's representation of number appears to follow a culturally determined spatial organisation (so better task performance is associated with this culturally normal orientation-the MNL effect). Participants (counter-balanced) completed two consistent blocks of trials, 'normal' and 'reversed', followed by a mixed block where line direction varied randomly. Experiment 1 established that the MNL effect was robust, and showed that the cognitive load associated with reversing the MNL not only affected response selection but also the actual movement execution (indexed by duration) within the mixed trials. Experiment 2 showed that an individual's motor abilities predicted performance in the difficult (mixed) condition but not the easier blocks. These results suggest that numerical processing is not isolated from motor capabilities-a finding with applied consequences.

Stratal Control Volumes and Stratal Control Trajectories: A New Method to Constrain, Understand and Reconcile Results from Stratigraphic Outcrop Analysis, Subsurface Analysis and Analogue and Numerical Modelling

NASA Astrophysics Data System (ADS)

Burgess, P. M.; Steel, R. J.

2016-12-01

Decoding a history of Earth's surface dynamics from strata requires robust quantitative understanding of supply and accommodation controls. The concept of stratigraphic solution sets has proven useful in this decoding, but application and development of this approach has so far been surprisingly limited. Stratal control volumes, areas and trajectories are new approaches defined here, building on previous ideas about stratigraphic solution sets, to help analyse and understand the sedimentary record of Earth surface dynamics. They may have particular application reconciling results from outcrop and subsurface analysis with results from analogue and numerical experiments. Stratal control volumes are sets of points in a three-dimensional volume, with axes of subsidence, sediment supply and eustatic rates of change, populated with probabilities derived from analysis of subsidence, supply and eustasy timeseries (Figure 1). These empirical probabilities indicate the likelihood of occurrence of any particular combination of control rates defined by any point in the volume. The stratal control volume can then by analysed to determine which parts of the volume represent relative sea-level fall and rise, where in the volume particular stacking patterns will occur, and how probable those stacking patterns are. For outcrop and subsurface analysis, using a stratal control area with eustasy and subsidence combined on a relative sea-level axis allows similar analysis, and may be preferable. A stratal control trajectory is a history of supply and accommodation creation rates, interpreted from outcrop or subsurface data, or observed in analogue and numerical experiments, and plotted as a series of linked points forming a trajectory through the stratal control volume (Figure 1) or area. Three examples are presented, one from outcrop and two theoretical. Much work remains to be done to build a properly representative database of stratal controls, but careful comparison of stratal control volume and trajectories constructed from outcrop analysis, subsurface analysis and experimental models may help the convergence, reconciliation and future evolution of these different approaches.

Numerical Leak Detection in a Pipeline Network of Complex Structure with Unsteady Flow

NASA Astrophysics Data System (ADS)

Aida-zade, K. R.; Ashrafova, E. R.

2017-12-01

An inverse problem for a pipeline network of complex loopback structure is solved numerically. The problem is to determine the locations and amounts of leaks from unsteady flow characteristics measured at some pipeline points. The features of the problem include impulse functions involved in a system of hyperbolic differential equations, the absence of classical initial conditions, and boundary conditions specified as nonseparated relations between the states at the endpoints of adjacent pipeline segments. The problem is reduced to a parametric optimal control problem without initial conditions, but with nonseparated boundary conditions. The latter problem is solved by applying first-order optimization methods. Results of numerical experiments are presented.

Local Climate Changes Forced by Changes in Land Use and topography in the Aburrá Valley, Colombia.

NASA Astrophysics Data System (ADS)

Zapata Henao, M. Z.; Hoyos Ortiz, C. D.

2017-12-01

One of the challenges in the numerical weather models is the adequate representation of soil-vegetation-atmosphere interaction at different spatial scales, including scenarios with heterogeneous land cover and complex mountainous terrain. The interaction determines the energy, mass and momentum exchange at the surface and could affect different variables including precipitation, temperature and wind. In order to quantify the long-term climate impact of changes in local land use and to assess the role of topography, two numerical experiments were examined. The first experiment allows assessing the continuous growth of urban areas within the Aburrá Valley, a complex terrain region located in Colombian Andes. The Weather Research Forecast model (WRF) is used as the basis of the experiment. The basic setup involves two nested domains, one representing the continental scale (18 km) and the other the regional scale (2 km). The second experiment allows drastic topography modification, including changing the valley configuration to a plateau. The control run for both experiments corresponds to a climatological scenario. In both experiments the boundary conditions correspond to the climatological continental domain output. Surface temperature, surface winds and precipitation are used as the main variables to compare both experiments relative to the control run. The results of the first experiment show a strong relationship between land cover and the variables, specially for surface temperature and wind speed, due to the strong forcing land cover imposes on the albedo, heat capacity and surface roughness, changing temperature and wind speed magnitudes. The second experiment removes the winds spatial variability related with hill slopes, the direction and magnitude are modulated only by the trade winds and roughness of land cover.

Direct numerical simulations of on-demand vortex generators: Mathematical formulation

NASA Technical Reports Server (NTRS)

Koumoutsakos, Petros

1994-01-01

The objective of the present research is the development and application of efficient adaptive numerical algorithms for the study, via direct numerical simulations, of active vortex generators. We are using innovative computational schemes to investigate flows past complex configurations undergoing arbitrary motions. Some of the questions we try to answer are: Can and how may we control the dynamics of the wake? What is the importance of body shape and motion in the active control of the flow? What is the effect of three-dimensionality in laboratory experiments? We are interested not only in coupling our results to ongoing, related experimental work, but furthermore to develop an extensive database relating the above mechanisms to the vortical wake structures with the long-range objective of developing feedback control mechanisms. This technology is very important to aircraft, ship, automotive, and other industries that require predictive capability for fluid mechanical problems. The results would have an impact in high angle of attack aerodynamics and help design ways to improve the efficiency of ships and submarines (maneuverability, vortex induced vibration, and noise).

Direct numerical simulations of on-demand vortex generators: Mathematical formulation

NASA Astrophysics Data System (ADS)

Koumoutsakos, Petros

1994-12-01

The objective of the present research is the development and application of efficient adaptive numerical algorithms for the study, via direct numerical simulations, of active vortex generators. We are using innovative computational schemes to investigate flows past complex configurations undergoing arbitrary motions. Some of the questions we try to answer are: Can and how may we control the dynamics of the wake? What is the importance of body shape and motion in the active control of the flow? What is the effect of three-dimensionality in laboratory experiments? We are interested not only in coupling our results to ongoing, related experimental work, but furthermore to develop an extensive database relating the above mechanisms to the vortical wake structures with the long-range objective of developing feedback control mechanisms. This technology is very important to aircraft, ship, automotive, and other industries that require predictive capability for fluid mechanical problems. The results would have an impact in high angle of attack aerodynamics and help design ways to improve the efficiency of ships and submarines (maneuverability, vortex induced vibration, and noise).

Electrostatic and aerodynamic forced vibrations of a thin flexible electrode: Quasi-periodic vs. chaotic oscillations

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

Madanu, Sushma B.; Barbel, Stanley I.; Ward, Thomas

In this paper, transverse vibrations of an electrostatically actuated thin flexible cantilever perturbed by low-speed air flow are studied using both experiments and numerical modeling. In the experiments, the dynamic characteristics of the cantilever are studied by supplying a DC voltage with an AC component for electrostatic forcing and a constant uniform air flow around the cantilever system for aerodynamic forcing. A range of control parameters leading to stable vibrations are established using a dimensionless operating parameter that is the ratio of the induced and the free stream velocities. Numerical results are validated with experimental data. Assuming the amplitude ofmore » vibrations are small, then a non-linear dynamic Euler-Bernoulli beam equation with viscous damping and gravitational effects is used to model the equation of motion. Aerodynamic forcing is modelled as a temporally sinusoidal and uniform force acting perpendicular to the beam length. The forcing amplitude is found to be proportional to the square of the air flow velocity. Numerical results strongly agree with the experiments predicting accurate vibration amplitude, displacement frequency, and quasi-periodic displacement of the cantilever tip.« less

Synesthesia affects verification of simple arithmetic equations.

PubMed

Ghirardelli, Thomas G; Mills, Carol Bergfeld; Zilioli, Monica K C; Bailey, Leah P; Kretschmar, Paige K

2010-01-01

To investigate the effects of color-digit synesthesia on numerical representation, we presented a synesthete, called SE, in the present study, and controls with mathematical equations for verification. In Experiment 1, SE verified addition equations made up of digits that either matched or mismatched her color-digit photisms or were in black. In Experiment 2A, the addends were presented in the different color conditions and the solution was presented in black, whereas in Experiment 2B the addends were presented in black and the solutions were presented in the different color conditions. In Experiment 3, multiplication and division equations were presented in the same color conditions as in Experiment 1. SE responded significantly faster to equations that matched her photisms than to those that did not; controls did not show this effect. These results suggest that photisms influence the processing of digits in arithmetic verification, replicating and extending previous findings.

The control effect in a detached laminar boundary layer of an array of normal synthetic jets

NASA Astrophysics Data System (ADS)

Valenzuela Calva, Fernando; Avila Rodriguez, Ruben

2016-11-01

In this work, 3D numerical simulations of an array of three normal circular synthetic jets embedded in an attached laminar boundary layer that separates under the influence of an inclined flap are performed for flow separation control. At the beginning of the present study, three cases are used to validate the numerical simulation with data obtained from experiments. The experimental data is chosen based on the cases which presented higher repeatability and reliability. Simulations showed reasonable agreement when compared with experiments. The simulations are undertaken at three synthetic jet operating conditions, i.e. Case A: L = 2, VR = 0.32; Case B: L = 4, VR = 0.64 and Case C: L = 6, VR = 0.96. The vortical structures produced for each synthetic jet operating condition are hairpin vortices for Case A and tilted vortices for Case B and C, respectively. By examining the spatial wall shear stress variations, the effect on the boundary layer prior to separation of the middle synthetic jet is evaluated. For effective flow control, produced at a relatively low the finding from this study suggests that hairpin vortical structures are more desirable structures. Universidad Nacional Autonoma de Mexico.

Modeling the Benchmark Active Control Technology Wind-Tunnel Model for Active Control Design Applications

NASA Technical Reports Server (NTRS)

Waszak, Martin R.

1998-01-01

This report describes the formulation of a model of the dynamic behavior of the Benchmark Active Controls Technology (BACT) wind tunnel model for active control design and analysis applications. The model is formed by combining the equations of motion for the BACT wind tunnel model with actuator models and a model of wind tunnel turbulence. The primary focus of this report is the development of the equations of motion from first principles by using Lagrange's equations and the principle of virtual work. A numerical form of the model is generated by making use of parameters obtained from both experiment and analysis. Comparisons between experimental and analytical data obtained from the numerical model show excellent agreement and suggest that simple coefficient-based aerodynamics are sufficient to accurately characterize the aeroelastic response of the BACT wind tunnel model. The equations of motion developed herein have been used to aid in the design and analysis of a number of flutter suppression controllers that have been successfully implemented.

A Comparison of Three PML Treatments for CAA (and CFD)

NASA Technical Reports Server (NTRS)

Goodrich, John W.

2008-01-01

In this paper we compare three Perfectly Matched Layer (PML) treatments by means of a series of numerical experiments, using common numerical algorithms, computational grids, and code implementations. These comparisons are with the Linearized Euler Equations, for base uniform base flow. We see that there are two very good PML candidates, and that can both control the introduced error. Furthermore, we also show that corners can be handled with essentially no increase in the introduced error, and that with a good PML, the outer boundary is the most significant source of err

Supercomputer analysis of sedimentary basins.

PubMed

Bethke, C M; Altaner, S P; Harrison, W J; Upson, C

1988-01-15

Geological processes of fluid transport and chemical reaction in sedimentary basins have formed many of the earth's energy and mineral resources. These processes can be analyzed on natural time and distance scales with the use of supercomputers. Numerical experiments are presented that give insights to the factors controlling subsurface pressures, temperatures, and reactions; the origin of ores; and the distribution and quality of hydrocarbon reservoirs. The results show that numerical analysis combined with stratigraphic, sea level, and plate tectonic histories provides a powerful tool for studying the evolution of sedimentary basins over geologic time.

Optimal placement of excitations and sensors for verification of large dynamical systems

NASA Technical Reports Server (NTRS)

Salama, M.; Rose, T.; Garba, J.

1987-01-01

The computationally difficult problem of the optimal placement of excitations and sensors to maximize the observed measurements is studied within the framework of combinatorial optimization, and is solved numerically using a variation of the simulated annealing heuristic algorithm. Results of numerical experiments including a square plate and a 960 degrees-of-freedom Control of Flexible Structure (COFS) truss structure, are presented. Though the algorithm produces suboptimal solutions, its generality and simplicity allow the treatment of complex dynamical systems which would otherwise be difficult to handle.

Experimental evaluation of model predictive control and inverse dynamics control for spacecraft proximity and docking maneuvers

NASA Astrophysics Data System (ADS)

Virgili-Llop, Josep; Zagaris, Costantinos; Park, Hyeongjun; Zappulla, Richard; Romano, Marcello

2018-03-01

An experimental campaign has been conducted to evaluate the performance of two different guidance and control algorithms on a multi-constrained docking maneuver. The evaluated algorithms are model predictive control (MPC) and inverse dynamics in the virtual domain (IDVD). A linear-quadratic approach with a quadratic programming solver is used for the MPC approach. A nonconvex optimization problem results from the IDVD approach, and a nonlinear programming solver is used. The docking scenario is constrained by the presence of a keep-out zone, an entry cone, and by the chaser's maximum actuation level. The performance metrics for the experiments and numerical simulations include the required control effort and time to dock. The experiments have been conducted in a ground-based air-bearing test bed, using spacecraft simulators that float over a granite table.

A DIY Ultrasonic Signal Generator for Sound Experiments

ERIC Educational Resources Information Center

Riad, Ihab F.

2018-01-01

Many physics departments around the world have electronic and mechanical workshops attached to them that can help build experimental setups and instruments for research and the training of undergraduate students. The workshops are usually run by experienced technicians and equipped with expensive lathing, computer numerical control (CNC) machines,…

Early stage litter decomposition across biomes

Treesearch

Ika Djukic; Sebastian Kepfer-Rojas; Inger Kappel Schmidt; Klaus Steenberg Larsen; Claus Beier; Björn Berg; Kris Verheyen; Adriano Caliman; Alain Paquette; Alba Gutiérrez-Girón; Alberto Humber; Alejandro Valdecantos; Alessandro Petraglia; Heather Alexander; Algirdas Augustaitis; Amélie Saillard; Ana Carolina Ruiz Fernández; Ana I. Sousa; Ana I. Lillebø; Anderson da Rocha Gripp; André-Jean Francez; Andrea Fischer; Andreas Bohner; Andrey Malyshev; Andrijana Andrić; Andy Smith; Angela Stanisci; Anikó Seres; Anja Schmidt; Anna Avila; Anne Probst; Annie Ouin; Anzar A. Khuroo; Arne Verstraeten; Arely N. Palabral-Aguilera; Artur Stefanski; Aurora Gaxiola; Bart Muys; Bernard Bosman; Bernd Ahrends; Bill Parker; Birgit Sattler; Bo Yang; Bohdan Juráni; Brigitta Erschbamer; Carmen Eugenia Rodriguez Ortiz; Casper T. Christiansen; E. Carol Adair; Céline Meredieu; Cendrine Mony; Charles A. Nock; Chi-Ling Chen; Chiao-Ping Wang; Christel Baum; Christian Rixen; Christine Delire; Christophe Piscart; Christopher Andrews; Corinna Rebmann; Cristina Branquinho; Dana Polyanskaya; David Fuentes Delgado; Dirk Wundram; Diyaa Radeideh; Eduardo Ordóñez-Regil; Edward Crawford; Elena Preda; Elena Tropina; Elli Groner; Eric Lucot; Erzsébet Hornung; Esperança Gacia; Esther Lévesque; Evanilde Benedito; Evgeny A. Davydov; Evy Ampoorter; Fabio Padilha Bolzan; Felipe Varela; Ferdinand Kristöfel; Fernando T. Maestre; Florence Maunoury-Danger; Florian Hofhansl; Florian Kitz; Flurin Sutter; Francisco Cuesta; Francisco de Almeida Lobo; Franco Leandro de Souza; Frank Berninger; Franz Zehetner; Georg Wohlfahrt; George Vourlitis; Geovana Carreño-Rocabado; Gina Arena; Gisele Daiane Pinha; Grizelle González; Guylaine Canut; Hanna Lee; Hans Verbeeck; Harald Auge; Harald Pauli; Hassan Bismarck Nacro; Héctor A. Bahamonde; Heike Feldhaar; Heinke Jäger; Helena C. Serrano; Hélène Verheyden; Helge Bruelheide; Henning Meesenburg; Hermann Jungkunst; Hervé Jactel; Hideaki Shibata; Hiroko Kurokawa; Hugo López Rosas; Hugo L. Rojas Villalobos; Ian Yesilonis; Inara Melece; Inge Van Halder; Inmaculada García Quirós; Isaac Makelele; Issaka Senou; István Fekete; Ivan Mihal; Ivika Ostonen; Jana Borovská; Javier Roales; Jawad Shoqeir; Jean-Christophe Lata; Jean-Paul Theurillat; Jean-Luc Probst; Jess Zimmerman; Jeyanny Vijayanathan; Jianwu Tang; Jill Thompson; Jiří Doležal; Joan-Albert Sanchez-Cabeza; Joël Merlet; Joh Henschel; Johan Neirynck; Johannes Knops; John Loehr; Jonathan von Oppen; Jónína Sigríður Þorláksdóttir; Jörg Löffler; José-Gilberto Cardoso-Mohedano; José-Luis Benito-Alonso; Jose Marcelo Torezan; Joseph C. Morina; Juan J. Jiménez; Juan Dario Quinde; Juha Alatalo; Julia Seeber; Jutta Stadler; Kaie Kriiska; Kalifa Coulibaly; Karibu Fukuzawa; Katalin Szlavecz; Katarína Gerhátová; Kate Lajtha; Kathrin Käppeler; Katie A. Jennings; Katja Tielbörger; Kazuhiko Hoshizaki; Ken Green; Lambiénou Yé; Laryssa Helena Ribeiro Pazianoto; Laura Dienstbach; Laura Williams; Laura Yahdjian; Laurel M. Brigham; Liesbeth van den Brink; Lindsey Rustad; al. et

2018-01-01

Through litter decomposition enormous amounts of carbon is emitted to the atmosphere. Numerous large-scale decomposition experiments have been conducted focusing on this fundamental soil process in order to understand the controls on the terrestrial carbon transfer to the atmosphere. However, previous studies were mostly based on site-specific litter and methodologies...

Toward Active Control of Noise from Hot Supersonic Jets

DTIC Science & Technology

2012-02-15

bears little relevance to practical systems of engineering interest. However, the high Mach number does ensure the formation of strong Mach waves which...waveforms of the experiment and the linear and nonlinear numerical predictions. 5Tam, C. K. W., Viswanathan, K., Ahuja, K. K., and Panda , J., "The

B-52 stability augmentation system reliability

NASA Technical Reports Server (NTRS)

Bowling, T. C.; Key, L. W.

1976-01-01

The B-52 SAS (Stability Augmentation System) was developed and retrofitted to nearly 300 aircraft. It actively controls B-52 structural bending, provides improved yaw and pitch damping through sensors and electronic control channels, and puts complete reliance on hydraulic control power for rudder and elevators. The system has experienced over 300,000 flight hours and has exhibited service reliability comparable to the results of the reliability test program. Development experience points out numerous lessons with potential application in the mechanization and development of advanced technology control systems of high reliability.

A tensor approach to modeling of nonhomogeneous nonlinear systems

NASA Technical Reports Server (NTRS)

Yurkovich, S.; Sain, M.

1980-01-01

Model following control methodology plays a key role in numerous application areas. Cases in point include flight control systems and gas turbine engine control systems. Typical uses of such a design strategy involve the determination of nonlinear models which generate requested control and response trajectories for various commands. Linear multivariable techniques provide trim about these motions; and protection logic is added to secure the hardware from excursions beyond the specification range. This paper reports upon experience in developing a general class of such nonlinear models based upon the idea of the algebraic tensor product.

Absence of visual experience modifies the neural basis of numerical thinking

PubMed Central

Kanjlia, Shipra; Lane, Connor; Feigenson, Lisa; Bedny, Marina

2016-01-01

In humans, the ability to reason about mathematical quantities depends on a frontoparietal network that includes the intraparietal sulcus (IPS). How do nature and nurture give rise to the neurobiology of numerical cognition? We asked how visual experience shapes the neural basis of numerical thinking by studying numerical cognition in congenitally blind individuals. Blind (n = 17) and blindfolded sighted (n = 19) participants solved math equations that varied in difficulty (e.g., 27 − 12 = x vs. 7 − 2 = x), and performed a control sentence comprehension task while undergoing fMRI. Whole-cortex analyses revealed that in both blind and sighted participants, the IPS and dorsolateral prefrontal cortices were more active during the math task than the language task, and activity in the IPS increased parametrically with equation difficulty. Thus, the classic frontoparietal number network is preserved in the total absence of visual experience. However, surprisingly, blind but not sighted individuals additionally recruited a subset of early visual areas during symbolic math calculation. The functional profile of these “visual” regions was identical to that of the IPS in blind but not sighted individuals. Furthermore, in blindness, number-responsive visual cortices exhibited increased functional connectivity with prefrontal and IPS regions that process numbers. We conclude that the frontoparietal number network develops independently of visual experience. In blindness, this number network colonizes parts of deafferented visual cortex. These results suggest that human cortex is highly functionally flexible early in life, and point to frontoparietal input as a mechanism of cross-modal plasticity in blindness. PMID:27638209

An approach of traffic signal control based on NLRSQP algorithm

NASA Astrophysics Data System (ADS)

Zou, Yuan-Yang; Hu, Yu

2017-11-01

This paper presents a linear program model with linear complementarity constraints (LPLCC) to solve traffic signal optimization problem. The objective function of the model is to obtain the minimization of total queue length with weight factors at the end of each cycle. Then, a combination algorithm based on the nonlinear least regression and sequence quadratic program (NLRSQP) is proposed, by which the local optimal solution can be obtained. Furthermore, four numerical experiments are proposed to study how to set the initial solution of the algorithm that can get a better local optimal solution more quickly. In particular, the results of numerical experiments show that: The model is effective for different arrival rates and weight factors; and the lower bound of the initial solution is, the better optimal solution can be obtained.

Manipulator trajectories during orbital servicing mission: numerical simulations and experiments on microgravity simulator

NASA Astrophysics Data System (ADS)

Rybus, T.; Seweryn, K.

2018-06-01

It is considered to use a manipulator-equipped satellite for performing On-Orbit Servicing (OOS) or Active Debris Removal (ADR) missions. In this paper, several possible approaches are reviewed for end-effector (EE) trajectory planning in the Cartesian space, such as application of the Bézier curves for singularity avoidance and method for trajectory optimization. The results of numerical simulations for a satellite equipped with a 7 degree-of-freedom (DoF) manipulator and results of experiments performed on a planar air-bearing microgravity simulator for a simplified two-dimensional (2D) case with a 2-DoF manipulator are presented. Differences between the free-floating case and the case where Attitude and Orbit Control Systems (AOCS) keep constant position and orientation of the satellite are also shown.

Designing a Hybrid Laminar-Flow Control Experiment: The CFD-Experiment Connection

NASA Technical Reports Server (NTRS)

Streett, C. L.

2003-01-01

The NASA/Boeing hybrid laminar flow control (HLFC) experiment, designed during 1993-1994 and conducted in the NASA LaRC 8-foot Transonic Pressure Tunnel in 1995, utilized computational fluid dynamics and numerical simulation of complex fluid mechanics to an unprecedented extent for the design of the test article and measurement equipment. CFD was used in: the design of the test wing, which was carried from definition of desired disturbance growth characteristics, through to the final airfoil shape that would produce those growth characteristics; the design of the suction-surface perforation pattern that produced enhanced crossflow-disturbance growth: and in the design of the hot-wire traverse system that produced minimal influence on measured disturbance growth. These and other aspects of the design of the test are discussed, after the historical and technical context of the experiment is described.

Slew maneuvers of Spacecraft Control Laboratory Experiment (SCOLE)

NASA Technical Reports Server (NTRS)

Kakad, Yogendra P.

1992-01-01

This is the final report on the dynamics and control of slew maneuvers of the Spacecraft Control Laboratory Experiment (SCOLE) test facility. The report documents the basic dynamical equation derivations for an arbitrary large angle slew maneuver as well as the basic decentralized slew maneuver control algorithm. The set of dynamical equations incorporate rigid body slew maneuver and three dimensional vibrations of the complete assembly comprising the rigid shuttle, the flexible beam, and the reflector with an offset mass. The analysis also includes kinematic nonlinearities of the entire assembly during the maneuver and the dynamics of the interactions between the rigid shuttle and the flexible appendage. The equations are simplified and evaluated numerically to include the first ten flexible modes to yield a model for designing control systems to perform slew maneuvers. The control problem incorporates the nonlinear dynamical equations and is expressed in terms of a two point boundary value problem.

Solution of AntiSeepage for Mengxi River Based on Numerical Simulation of Unsaturated Seepage

PubMed Central

Ji, Youjun; Zhang, Linzhi; Yue, Jiannan

2014-01-01

Lessening the leakage of surface water can reduce the waste of water resources and ground water pollution. To solve the problem that Mengxi River could not store water enduringly, geology investigation, theoretical analysis, experiment research, and numerical simulation analysis were carried out. Firstly, the seepage mathematical model was established based on unsaturated seepage theory; secondly, the experimental equipment for testing hydraulic conductivity of unsaturated soil was developed to obtain the curve of two-phase flow. The numerical simulation of leakage in natural conditions proves the previous inference and leakage mechanism of river. At last, the seepage control capacities of different impervious materials were compared by numerical simulations. According to the engineering actuality, the impervious material was selected. The impervious measure in this paper has been proved to be effectible by hydrogeological research today. PMID:24707199

SL3-108-01288

NASA Image and Video Library

1973-07-01

SL3-108-1288 (July-Sept. 1973) --- Astronaut Owen K. Garriott, science pilot of the Skylab 3 mission, is stationed at the Apollo Telescope Mount (ATM) console in the Multiple Docking Adapter (MDA) of the Skylab space station in Earth orbit. This picture was taken with a handheld 35mm Nikon camera. Astronauts Garriott, Alan L. Bean and Jack R. Lousma remained with the Skylab space station cluster in orbit for 59 days conducting numerous medical, scientific and technological experiments. In orbit the MDA functions as a major experiment control center for solar observations. From this console the astronauts actively control the ATM solar physics telescopes. Photo credit: NASA

Physical similarity or numerical representation counts in same-different, numerical comparison, physical comparison, and priming tasks?

PubMed

Zhang, Li; Xin, Ziqiang; Feng, Tingyong; Chen, Yinghe; Szűcs, Denes

2018-03-01

Recent studies have highlighted the fact that some tasks used to study symbolic number representations are confounded by judgments about physical similarity. Here, we investigated whether the contribution of physical similarity and numerical representation differed in the often-used symbolic same-different, numerical comparison, physical comparison, and priming tasks. Experiment 1 showed that subjective physical similarity was the best predictor of participants' performance in the same-different task, regardless of simultaneous or sequential presentation. Furthermore, the contribution of subjective physical similarity was larger in a simultaneous presentation than in a sequential presentation. Experiment 2 showed that only numerical representation was involved in numerical comparison. Experiment 3 showed that both subjective physical similarity and numerical representation contributed to participants' physical comparison performance. Finally, only numerical representation contributed to participants' performance in a priming task as revealed by Experiment 4. Taken together, the contribution of physical similarity and numerical representation depends on task demands. Performance primarily seems to rely on numerical properties in tasks that require explicit quantitative comparison judgments (physical or numerical), while physical stimulus properties exert an effect in the same-different task.

Microfluidic proportional flow controller

PubMed Central

Prentice-Mott, Harrison; Toner, Mehmet; Irimia, Daniel

2011-01-01

Precise flow control in microfluidic chips is important for many biochemical assays and experiments at microscale. While several technologies for controlling fluid flow have been implemented either on- or off-chip, these can provide either high-speed or high-precision control, but seldom could accomplish both at the same time. Here we describe a new on-chip, pneumatically activated flow controller that allows for fast and precise control of the flow rate through a microfluidic channel. Experimental results show that the new proportional flow controllers exhibited a response time of approximately 250 ms, while our numerical simulations suggest that faster actuation down to approximately 50 ms could be achieved with alternative actuation schemes. PMID:21874096

Performance evaluation of Bragg coherent diffraction imaging

NASA Astrophysics Data System (ADS)

Öztürk, H.; Huang, X.; Yan, H.; Robinson, I. K.; Noyan, I. C.; Chu, Y. S.

2017-10-01

In this study, we present a numerical framework for modeling three-dimensional (3D) diffraction data in Bragg coherent diffraction imaging (Bragg CDI) experiments and evaluating the quality of obtained 3D complex-valued real-space images recovered by reconstruction algorithms under controlled conditions. The approach is used to systematically explore the performance and the detection limit of this phase-retrieval-based microscopy tool. The numerical investigation suggests that the superb performance of Bragg CDI is achieved with an oversampling ratio above 30 and a detection dynamic range above 6 orders. The observed performance degradation subject to the data binning processes is also studied. This numerical tool can be used to optimize experimental parameters and has the potential to significantly improve the throughput of Bragg CDI method.

Genetic algorithm based active vibration control for a moving flexible smart beam driven by a pneumatic rod cylinder

NASA Astrophysics Data System (ADS)

Qiu, Zhi-cheng; Shi, Ming-li; Wang, Bin; Xie, Zhuo-wei

2012-05-01

A rod cylinder based pneumatic driving scheme is proposed to suppress the vibration of a flexible smart beam. Pulse code modulation (PCM) method is employed to control the motion of the cylinder's piston rod for simultaneous positioning and vibration suppression. Firstly, the system dynamics model is derived using Hamilton principle. Its standard state-space representation is obtained for characteristic analysis, controller design, and simulation. Secondly, a genetic algorithm (GA) is applied to optimize and tune the control gain parameters adaptively based on the specific performance index. Numerical simulations are performed on the pneumatic driving elastic beam system, using the established model and controller with tuned gains by GA optimization process. Finally, an experimental setup for the flexible beam driven by a pneumatic rod cylinder is constructed. Experiments for suppressing vibrations of the flexible beam are conducted. Theoretical analysis, numerical simulation and experimental results demonstrate that the proposed pneumatic drive scheme and the adopted control algorithms are feasible. The large amplitude vibration of the first bending mode can be suppressed effectively.

Active chatter suppression with displacement-only measurement in turning process

NASA Astrophysics Data System (ADS)

Ma, Haifeng; Wu, Jianhua; Yang, Liuqing; Xiong, Zhenhua

2017-08-01

Regenerative chatter is a major hindrance for achieving high quality and high production rate in machining processes. Various active controllers have been proposed to mitigate chatter. However, most of existing controllers were developed on the basis of multi-states feedback of the system and state observers were usually needed. Moreover, model parameters of the machining process (mass, damping and stiffness) were required in existing active controllers. In this study, an active sliding mode controller, which employs a dynamic output feedback sliding surface for the unmatched condition and an adaptive law for disturbance estimation, is designed, analyzed, and validated for chatter suppression in turning process. Only displacement measurement is required by this approach. Other sensors and state observers are not needed. Moreover, it facilitates a rapid implementation since the designed controller is established without using model parameters of the turning process. Theoretical analysis, numerical simulations and experiments on a computer numerical control (CNC) lathe are presented. It shows that the chatter can be substantially attenuated and the chatter-free region can be significantly expanded with the presented method.

Non-robust numerical simulations of analogue extension experiments

NASA Astrophysics Data System (ADS)

Naliboff, John; Buiter, Susanne

2016-04-01

Numerical and analogue models of lithospheric deformation provide significant insight into the tectonic processes that lead to specific structural and geophysical observations. As these two types of models contain distinct assumptions and tradeoffs, investigations drawing conclusions from both can reveal robust links between first-order processes and observations. Recent studies have focused on detailed comparisons between numerical and analogue experiments in both compressional and extensional tectonics, sometimes involving multiple lithospheric deformation codes and analogue setups. While such comparisons often show good agreement on first-order deformation styles, results frequently diverge on second-order structures, such as shear zone dip angles or spacing, and in certain cases even on first-order structures. Here, we present finite-element experiments that are designed to directly reproduce analogue "sandbox" extension experiments at the cm-scale. We use material properties and boundary conditions that are directly taken from analogue experiments and use a Drucker-Prager failure model to simulate shear zone formation in sand. We find that our numerical experiments are highly sensitive to numerous numerical parameters. For example, changes to the numerical resolution, velocity convergence parameters and elemental viscosity averaging commonly produce significant changes in first- and second-order structures accommodating deformation. The sensitivity of the numerical simulations to small parameter changes likely reflects a number of factors, including, but not limited to, high angles of internal friction assigned to sand, complex, unknown interactions between the brittle sand (used as an upper crust equivalent) and viscous silicone (lower crust), highly non-linear strain weakening processes and poor constraints on the cohesion of sand. Our numerical-analogue comparison is hampered by (a) an incomplete knowledge of the fine details of sand failure and sand properties, and (b) likely limitations to the use of a continuum Drucker-Prager model for representing shear zone formation in sand. In some cases our numerical experiments provide reasonable fits to first-order structures observed in the analogue experiments, but the numerical sensitivity to small parameter variations leads us to conclude that the numerical experiments are not robust.

The emotional valence of a conflict: implications from synesthesia.

PubMed

Perry, Amit; Henik, Avishai

2013-01-01

According to some synesthetes' reports, their experience involves an emotional sensation in which a conflict between the photism and presented color of a stimulus may evoke a feeling of discomfort. In order to investigate the impact of this experience on performance, two experiments were carried out on two synesthetes and their matched control groups. Experiments were tailored for each synesthete according to her unique photism. Participants were presented with stimuli (numerals or words) in colors and were asked to name the color of the stimulus and to ignore its meaning. Incongruent colors were associated with negative or positive emotional words or with non-emotional words. Not surprisingly, an incongruent color (e.g., 5 presented in yellow to a synesthete that sees 5 in red) slowed down color naming. Conflict situations (e.g., a numeral in an incongruent color) created a negative emotional experience. Most importantly, coherence between a conflict or non-conflict emotional experience and the emotion elicited by the color of the stimulus for a given synesthete modulated performance. In particular, synesthetes were faster in coherent than in incoherent situations. This research contributes to the understanding of emotional experience in synesthesia, and also suggests that synesthesia can be used as an instrument to investigate emotional processes in the wider population.

The grain drain. Ozone effects on historical maize and soybean yields

USDA-ARS?s Scientific Manuscript database

Numerous controlled experiments find that elevated ground-level ozone concentrations ([O3]) damage crops and reduce yield. There have been no estimates of the actual field yield losses in the USA from [O3], even though such estimates would be valuable for projections of future food production and fo...

Mechanisms in Psychosocial Interventions for Adults Living with Cancer: Opportunity for Integration of Theory, Research, and Practice

ERIC Educational Resources Information Center

Stanton, Annette L.; Luecken, Linda J.; MacKinnon, David P.; Thompson, Elizabeth H.

2013-01-01

Objective: The diagnosis and treatment of cancer are highly stressful experiences that can profoundly affect emotional and physical well-being. Hundreds of longitudinal investigations that identify risk and protective factors for psychological and physical adjustment in adults living with cancer and numerous randomized controlled psychosocial…

Integrating Pharmacology Topics in High School Biology and Chemistry Classes Improves Performance

ERIC Educational Resources Information Center

Schwartz-Bloom, Rochelle D.; Halpin, Myra J.

2003-01-01

Although numerous programs have been developed for Grade Kindergarten through 12 science education, evaluation has been difficult owing to the inherent problems conducting controlled experiments in the typical classroom. Using a rigorous experimental design, we developed and tested a novel program containing a series of pharmacology modules (e.g.,…

Interaction between numbers and size during visual search.

PubMed

Krause, Florian; Bekkering, Harold; Pratt, Jay; Lindemann, Oliver

2017-05-01

The current study investigates an interaction between numbers and physical size (i.e. size congruity) in visual search. In three experiments, participants had to detect a physically large (or small) target item among physically small (or large) distractors in a search task comprising single-digit numbers. The relative numerical size of the digits was varied, such that the target item was either among the numerically large or small numbers in the search display and the relation between numerical and physical size was either congruent or incongruent. Perceptual differences of the stimuli were controlled by a condition in which participants had to search for a differently coloured target item with the same physical size and by the usage of LCD-style numbers that were matched in visual similarity by shape transformations. The results of all three experiments consistently revealed that detecting a physically large target item is significantly faster when the numerical size of the target item is large as well (congruent), compared to when it is small (incongruent). This novel finding of a size congruity effect in visual search demonstrates an interaction between numerical and physical size in an experimental setting beyond typically used binary comparison tasks, and provides important new evidence for the notion of shared cognitive codes for numbers and sensorimotor magnitudes. Theoretical consequences for recent models on attention, magnitude representation and their interactions are discussed.

Answering the missed call: Initial exploration of cognitive and electrophysiological changes associated with smartphone use and abuse.

PubMed

Hadar, Aviad; Hadas, Itay; Lazarovits, Avi; Alyagon, Uri; Eliraz, Daniel; Zangen, Abraham

2017-01-01

Smartphone usage is now integral to human behavior. Recent studies associate extensive usage with a range of debilitating effects. We sought to determine whether excessive usage is accompanied by measurable neural, cognitive and behavioral changes. Subjects lacking previous experience with smartphones (n = 35) were compared to a matched group of heavy smartphone users (n = 16) on numerous behavioral and electrophysiological measures recorded using electroencephalogram (EEG) combined with transcranial magnetic stimulation (TMS) over the right prefrontal cortex (rPFC). In a second longitudinal intervention, a randomly selected sample of the original non-users received smartphones for 3 months while the others served as controls. All measurements were repeated following this intervention. Heavy users showed increased impulsivity, hyperactivity and negative social concern. We also found reduced early TMS evoked potentials in the rPFC of this group, which correlated with severity of self-reported inattention problems. Heavy users also obtained lower accuracy rates than nonusers in a numerical processing. Critically, the second part of the experiment revealed that both the numerical processing and social cognition domains are causally linked to smartphone usage. Heavy usage was found to be associated with impaired attention, reduced numerical processing capacity, changes in social cognition, and reduced right prefrontal cortex (rPFC) excitability. Memory impairments were not detected. Novel usage over short period induced a significant reduction in numerical processing capacity and changes in social cognition.

Inlet Flow Control and Prediction Technologies for Embedded Propulsion Systems

NASA Technical Reports Server (NTRS)

McMillan, Michelle L.; Gissen, Abe; Vukasinovic, Bojan; Lakebrink, Matthew T.; Glezer, Ari; Mani, Mori; Mace, James

2010-01-01

Fail-safe inlet flow control may enable high-speed cruise efficiency, low noise signature, and reduced fuel-burn goals for hybrid wing-body aircraft. The objectives of this program are to develop flow control and prediction methodologies for boundary-layer ingesting (BLI) inlets used in these aircraft. This report covers the second of a three year program. The approach integrates experiments and numerical simulations. Both passive and active flow-control devices were tested in a small-scale wind tunnel. Hybrid actuation approaches, combining a passive microvane and active synthetic jet, were tested in various geometric arrangements. Detailed flow measurements were taken to provide insight into the flow physics. Results of the numerical simulations were correlated against experimental data. The sensitivity of results to grid resolution and turbulence models was examined. Aerodynamic benefits from microvanes and microramps were assessed when installed in an offset BLI inlet. Benefits were quantified in terms of recovery and distortion changes. Microvanes were more effective than microramps at improving recovery and distortion.

Numerical study of three-dimensional separation and flow control at a wing/body junction

NASA Technical Reports Server (NTRS)

Ash, Robert L.; Lakshmanan, Balakrishnan

1989-01-01

The problem of three-dimensional separation and flow control at a wing/body junction has been investigated numerically using a three-dimensional Navier-Stokes code. The numerical code employs an algebraic grid generation technique for generating the grid for unmodified junction and an elliptic grid generation technique for filleted fin junction. The results for laminar flow past a blunt fin/flat plate junction demonstrate that after grid refinement, the computations agree with experiment and reveal a strong dependency of the number of vortices at the junction on Mach number and Reynolds number. The numerical results for pressure distribution, particle paths and limiting streamlines for turbulent flow past a swept fin show a decrease in the peak pressure and in the extent of the separated flow region compared to the laminar case. The results for a filleted juncture indicate that the streamline patterns lose much of their vortical character with proper filleting. Fillets with a radius of three and one-half times the fin leading edge diameter or two times the incoming boundary layer thickness, significantly weaken the usual necklace interaction vortex for the Mach number and Reynolds number considered in the present study.

Taylor bubbles at high viscosity ratios: experiments and numerical simulations

NASA Astrophysics Data System (ADS)

Hewakandamby, Buddhika; Hasan, Abbas; Azzopardi, Barry; Xie, Zhihua; Pain, Chris; Matar, Omar

2015-11-01

The Taylor bubble is a single long bubble which nearly fills the entire cross section of a liquid-filled circular tube, often occurring in gas-liquid slug flows in many industrial applications, particularly oil and gas production. The objective of this study is to investigate the fluid dynamics of three-dimensional Taylor bubble rising in highly viscous silicone oil in a vertical pipe. An adaptive unstructured mesh modelling framework is adopted here which can modify and adapt anisotropic unstructured meshes to better represent the underlying physics of bubble rising and reduce computational effort without sacrificing accuracy. The numerical framework consists of a mixed control volume and finite element formulation, a `volume of fluid'-type method for the interface-capturing based on a compressive control volume advection method, and a force-balanced algorithm for the surface tension implementation. Experimental results for the Taylor bubble shape and rise velocity are presented, together with numerical results for the dynamics of the bubbles. A comparison of the simulation predictions with experimental data available in the literature is also presented to demonstrate the capabilities of our numerical method. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.

Planar hydrodynamic instability computations and experiments with rugby-shaped hohlraums at the Omega laser

NASA Astrophysics Data System (ADS)

Vandenboomgaerde, M.; Liberatore, S.; Galmiche, D.; Casner, A.; Huser, G.; Jadaud, J. P.; Villette, B.

2008-05-01

Implosion of inertial confinement fusion (ICF) capsule is very sensitive to the growth of sphericity perturbations. The control of the feeding of such perturbations and their transport ('feedthrough') through the ablator is a key point to reach ignition. Since 2002 [1, 2], experiments have been designed and performed on the Omega laser facility in order to study these phenomena in planar geometry. A new 'rugby shaped' hohlraum was used [3, 4]. We present experimental results and comparisons with numerical simulations.

The motion of a cloud of solid spherical particles falling in a cellular flow field at low Stokes number

NASA Astrophysics Data System (ADS)

Marchetti, Benjamin; Bergougnoux, Laurence; Guazzelli, Elisabeth

2017-11-01

We present a jointed experimental and numerical study examining the influence of vortical structures on the settling of a cloud of solid spherical particles under the action of gravity at low Stokes numbers. The two-dimensional model experiment uses electro-convection to generate a two-dimensional array of controlled vortices which mimics a simplified vortical flow. Particle image-velocimetry and tracking are used to examine the motion of the cloud within this vortical flow. The cloud motion is compared to the predictions of a two-way-coupling numerical simulation.

RIM as the data base management system for a material properties data base

NASA Technical Reports Server (NTRS)

Karr, P. H.; Wilson, D. J.

1984-01-01

Relational Information Management (RIM) was selected as the data base management system for a prototype engineering materials data base. The data base provides a central repository for engineering material properties data, which facilitates their control. Numerous RIM capabilities are exploited to satisfy prototype data base requirements. Numerical, text, tabular, and graphical data and references are being stored for five material types. Data retrieval will be accomplished both interactively and through a FORTRAN interface. The experience gained in creating and exercising the prototype will be used in specifying requirements for a production system.

A methodology for designing aircraft to low sonic boom constraints

NASA Technical Reports Server (NTRS)

Mack, Robert J.; Needleman, Kathy E.

1991-01-01

A method for designing conceptual supersonic cruise aircraft to meet low sonic boom requirements is outlined and described. The aircraft design is guided through a systematic evolution from initial three view drawing to a final numerical model description, while the designer using the method controls the integration of low sonic boom, high supersonic aerodynamic efficiency, adequate low speed handling, and reasonable structure and materials technologies. Some experience in preliminary aircraft design and in the use of various analytical and numerical codes is required for integrating the volume and lift requirements throughout the design process.

Analysis of the impact of modification of cold crucible design on the efficiency of the cold crucible induction furnace

NASA Astrophysics Data System (ADS)

Przylucki, R.; Golak, S.; Bulinski, P.; Smolka, J.; Palacz, M.; Siwiec, G.; Lipart, J.; Blacha, L.

2018-05-01

The article includes numerical simulation results for two induction furnace with cold crucible (IFCC). Induction furnaces differ in cold crucible design, while the inductor geometry was preserved for both variants. Numerical simulations were conducted as three dimensional one, with coupled analysis of electromagnetic, thermal and fluid dynamics fields. During the experiment, six calculation variants, differ in amount of molten titanium (three different weights of titanium for each type of cold crucible) were considered. Main parameters controlled during the calculations were: electrical efficiency of the IFCC and the meniscus shape of liquid metal.

Theory and design of variable conductance heat pipes

NASA Technical Reports Server (NTRS)

Marcus, B. D.

1972-01-01

A comprehensive review and analysis of all aspects of heat pipe technology pertinent to the design of self-controlled, variable conductance devices for spacecraft thermal control is presented. Subjects considered include hydrostatics, hydrodynamics, heat transfer into and out of the pipe, fluid selection, materials compatibility and variable conductance control techniques. The report includes a selected bibliography of pertinent literature, analytical formulations of various models and theories describing variable conductance heat pipe behavior, and the results of numerous experiments on the steady state and transient performance of gas controlled variable conductance heat pipes. Also included is a discussion of VCHP design techniques.

Splines and control theory

NASA Technical Reports Server (NTRS)

Zhang, Zhimin; Tomlinson, John; Martin, Clyde

1994-01-01

In this work, the relationship between splines and the control theory has been analyzed. We show that spline functions can be constructed naturally from the control theory. By establishing a framework based on control theory, we provide a simple and systematic way to construct splines. We have constructed the traditional spline functions including the polynomial splines and the classical exponential spline. We have also discovered some new spline functions such as trigonometric splines and the combination of polynomial, exponential and trigonometric splines. The method proposed in this paper is easy to implement. Some numerical experiments are performed to investigate properties of different spline approximations.

Design of BLDCM emulator for transmission control units

NASA Astrophysics Data System (ADS)

Liu, Chang; He, Yongyi; Zhang, Bodong

2018-04-01

According to the testing requirements of the transmission control unit, a brushless DC motor emulating system is designed based on motor simulation and power hardware-in-the-loop. The discrete motor model is established and a real-time numerical method is designed to solve the motor states. The motor emulator directly interacts with power stage of the transmission control unit using a power-efficient circuit topology and is compatible with sensor-less control. Experiments on a laboratory prototype help to verify that the system can emulate the real motor currents and voltages whenever the motor is starting up or suddenly loaded.

Potential Subjective Effectiveness of Active Interior Noise Control in Propeller Airplanes

NASA Technical Reports Server (NTRS)

Powell, Clemans A.; Sullivan, Brenda M.

2000-01-01

Active noise control technology offers the potential for weight-efficient aircraft interior noise reduction, particularly for propeller aircraft. However, there is little information on how passengers respond to this type of interior noise control. This paper presents results of two experiments that use sound quality engineering practices to determine the subjective effectiveness of hypothetical active noise control (ANC) systems in a range of propeller aircraft. The two experiments differed by the type of judgments made by the subjects: pair comparisons based on preference in the first and numerical category scaling of noisiness in the second. Although the results of the two experiments were in general agreement that the hypothetical active control measures improved the interior noise environments, the pair comparison method appears to be more sensitive to subtle changes in the characteristics of the sounds which are related to passenger preference. The reductions in subjective response due to the ANC conditions were predicted with reasonable accuracy by reductions in measured loudness level. Inclusion of corrections for the sound quality characteristics of tonality and fluctuation strength in multiple regression models improved the prediction of the ANC effects.

Taguchi Method Applied in Optimization of Shipley SJR 5740 Positive Resist Deposition

NASA Technical Reports Server (NTRS)

Hui, A.; Blosiu, J. O.; Wiberg, D. V.

1998-01-01

Taguchi Methods of Robust Design presents a way to optimize output process performance through an organized set of experiments by using orthogonal arrays. Analysis of variance and signal-to-noise ratio is used to evaluate the contribution of each of the process controllable parameters in the realization of the process optimization. In the photoresist deposition process, there are numerous controllable parameters that can affect the surface quality and thickness of the final photoresist layer.

Multi-Scale Experiments to Evaluate Mobility Control Methods for Enhancing the Sweep Efficiency of Injected Subsurface Remediation Amendments

DTIC Science & Technology

2010-08-01

petroleum industry. Moreover, heterogeneity control strategies can be applied to improve the efficiency of a variety of in situ remediation technologies...conditions that differ significantly from those found in environmental systems . Therefore many of the design criteria used by the petroleum industry for...were helpful in constructing numerical models in up-scaled systems (2-D tanks). The UTCHEM model was able to successfully simulate 2-D experimental

Laboratory investigations of earthquake dynamics

NASA Astrophysics Data System (ADS)

Xia, Kaiwen

In this thesis this will be attempted through controlled laboratory experiments that are designed to mimic natural earthquake scenarios. The earthquake dynamic rupturing process itself is a complicated phenomenon, involving dynamic friction, wave propagation, and heat production. Because controlled experiments can produce results without assumptions needed in theoretical and numerical analysis, the experimental method is thus advantageous over theoretical and numerical methods. Our laboratory fault is composed of carefully cut photoelastic polymer plates (Homahte-100, Polycarbonate) held together by uniaxial compression. As a unique unit of the experimental design, a controlled exploding wire technique provides the triggering mechanism of laboratory earthquakes. Three important components of real earthquakes (i.e., pre-existing fault, tectonic loading, and triggering mechanism) correspond to and are simulated by frictional contact, uniaxial compression, and the exploding wire technique. Dynamic rupturing processes are visualized using the photoelastic method and are recorded via a high-speed camera. Our experimental methodology, which is full-field, in situ, and non-intrusive, has better control and diagnostic capacity compared to other existing experimental methods. Using this experimental approach, we have investigated several problems: dynamics of earthquake faulting occurring along homogeneous faults separating identical materials, earthquake faulting along inhomogeneous faults separating materials with different wave speeds, and earthquake faulting along faults with a finite low wave speed fault core. We have observed supershear ruptures, subRayleigh to supershear rupture transition, crack-like to pulse-like rupture transition, self-healing (Heaton) pulse, and rupture directionality.

Steering Quantum Dynamics of a Two-Qubit System via Optimal Bang-Bang Control

NASA Astrophysics Data System (ADS)

Hu, Juju; Ke, Qiang; Ji, Yinghua

2018-02-01

The optimization of control time for quantum systems has been an important field of control science attracting decades of focus, which is beneficial for efficiency improvement and decoherence suppression caused by the environment. Based on analyzing the advantages and disadvantages of the existing Lyapunov control, using a bang-bang optimal control technique, we investigate the fast state control in a closed two-qubit quantum system, and give three optimized control field design methods. Numerical simulation experiments indicate the effectiveness of the methods. Compared to the standard Lyapunov control or standard bang-bang control method, the optimized control field design methods effectively shorten the state control time and avoid high-frequency oscillation that occurs in bang-bang control.

Cortical bone drilling: An experimental and numerical study.

PubMed

Alam, Khurshid; Bahadur, Issam M; Ahmed, Naseer

2014-12-16

Bone drilling is a common surgical procedure in orthopedics, dental and neurosurgeries. In conventional bone drilling process, the surgeon exerts a considerable amount of pressure to penetrate the drill into the bone tissue. Controlled penetration of drill in the bone is necessary for safe and efficient drilling. Development of a validated Finite Element (FE) model of cortical bone drilling. Drilling experiments were conducted on bovine cortical bone. The FE model of the bone drilling was based on mechanical properties obtained from literature data and additionally conducted microindentation tests on the cortical bone. The magnitude of stress in bone was found to decrease exponentially away from the lips of the drill in simulations. Feed rate was found to be the main influential factor affecting the force and torque in the numerical simulations and experiments. The drilling thrust force and torque were found to be unaffected by the drilling speed in numerical simulations. Simulated forces and torques were compared with experimental results for similar drilling conditions and were found in good agreement.CONCLUSIONS: FE schemes may be successfully applied to model complex kinematics of bone drilling process.

Numerical and experimental study of the dynamics of a superheated jet

NASA Astrophysics Data System (ADS)

Sinha, Avick; Gopalakrishnan, Shivasubramanian; Balasubramanian, Sridhar

2015-11-01

Flash-boiling is a phenomenon where a liquid experiences low pressures in a system resulting in it getting superheated. The sudden drop in pressures results in accelerated expansion and violent vapour formation. Understanding the physics behind the jet disintegration and flash-boiling phenomenon is still an open problem, with applications in automotive and aerospace combustors. The behaviour of a flash-boiling jet is highly dependent on the input parameters, inlet temperature and pressure. In the present study, the external (outside nozzle) and the internal (inside nozzle) flow characteristics of the two-phase flow has been studied numerically and experimentally. The phase change from liquid to vapour takes place over a finite period of time, modeled sing Homogeneous Relaxation Model (HRM). In order to validate the numerical results, controlled experiments were performed. Optical diagnostic techniques such as Particle Image Velocimetry (PIV) and Shadowgraphy were used to study the flow characteristics. Spray angle, penetration depth, droplet spectra were obtained which provides a better understanding of the break-up mechanism. Linear stability analysis is performed to study the stability characteristics of the jet.

Numerical Simulation Applications in the Design of EGS Collab Experiment 1

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

Johnston, Henry; White, Mark D.; Fu, Pengcheng

The United States Department of Energy, Geothermal Technologies Office (GTO) is funding a collaborative investigation of enhanced geothermal systems (EGS) processes at the meso-scale. This study, referred to as the EGS Collab project, is a unique opportunity for scientists and engineers to investigate the creation of fracture networks and circulation of fluids across those networks under in-situ stress conditions. The EGS Collab project is envisioned to comprise three experiments and the site for the first experiment is on the 4850 Level (4,850 feet below ground surface) in phyllite of the Precambrian Poorman formation, at the Sanford Underground Research Facility, locatedmore » at the former Homestake Gold Mine, in Lead, South Dakota. Principal objectives of the project are to develop a number of intermediate-scale field sites and to conduct well-controlled in situ experiments focused on rock fracture behavior and permeability enhancement. Data generated during these experiments will be compared against predictions of a suite of computer codes specifically designed to solve problems involving coupled thermal, hydrological, geomechanical, and geochemical processes. Comparisons between experimental and numerical simulation results will provide code developers with direction for improvements and verification of process models, build confidence in the suite of available numerical tools, and ultimately identify critical future development needs for the geothermal modeling community. Moreover, conducting thorough comparisons of models, modelling approaches, measurement approaches and measured data, via the EGS Collab project, will serve to identify techniques that are most likely to succeed at the Frontier Observatory for Research in Geothermal Energy (FORGE), the GTO's flagship EGS research effort. As noted, outcomes from the EGS Collab project experiments will serve as benchmarks for computer code verification, but numerical simulation additionally plays an essential role in designing these meso-scale experiments. This paper describes specific numerical simulations supporting the design of Experiment 1, a field test involving hydraulic stimulation of two fractures from notched sections of the injection borehole and fluid circulation between sub-horizontal injection and production boreholes in each fracture individually and collectively, including the circulation of chilled water. Whereas the mine drift allows for accurate and close placement of monitoring instrumentation to the developed fractures, active ventilation in the drift cooled the rock mass within the experimental volume. Numerical simulations were executed to predict seismic events and magnitudes during stimulation, initial fracture orientations for smooth horizontal wellbores, pressure requirements for fracture initiation from notched wellbores, fracture propagation during stimulation between the injection and production boreholes, tracer travel times between the injection and production boreholes, produced fluid temperatures with chilled water injections, pressure limits on fluid circulation to avoid fracture growth, temperature environment surrounding the 4850 Level drift, and fracture propagation within a stress field altered by drift excavation, ventilation cooling, and dewatering.« less

An Introduction to Numerical Control. Problems for Numerical Control Part Programming.

ERIC Educational Resources Information Center

Campbell, Clifton P.

This combination text and workbook is intended to introduce industrial arts students to numerical control part programming. Discussed in the first section are the impact of numerical control, training efforts, numerical control in established programs, related information for drafting, and the Cartesian Coordinate System and dimensioning…

Proper Orthogonal Decomposition in Optimal Control of Fluids

NASA Technical Reports Server (NTRS)

Ravindran, S. S.

1999-01-01

In this article, we present a reduced order modeling approach suitable for active control of fluid dynamical systems based on proper orthogonal decomposition (POD). The rationale behind the reduced order modeling is that numerical simulation of Navier-Stokes equations is still too costly for the purpose of optimization and control of unsteady flows. We examine the possibility of obtaining reduced order models that reduce computational complexity associated with the Navier-Stokes equations while capturing the essential dynamics by using the POD. The POD allows extraction of certain optimal set of basis functions, perhaps few, from a computational or experimental data-base through an eigenvalue analysis. The solution is then obtained as a linear combination of these optimal set of basis functions by means of Galerkin projection. This makes it attractive for optimal control and estimation of systems governed by partial differential equations. We here use it in active control of fluid flows governed by the Navier-Stokes equations. We show that the resulting reduced order model can be very efficient for the computations of optimization and control problems in unsteady flows. Finally, implementational issues and numerical experiments are presented for simulations and optimal control of fluid flow through channels.

Impact of the initial specification of moisture and vertical motion on precipitation forecasts with a mesoscale model Implications for a satellite mesoscale data base

NASA Technical Reports Server (NTRS)

Mlynczak, Pamela E.; Houghton, David D.; Diak, George R.

1986-01-01

Using a numerical mesoscale model, four simulations were performed to determine the effects of suppressing the initial mesoscale information in the moisture and wind fields on the precipitation forecasts. The simulations included a control forecast 12-h simulation that began at 1200 GMT March 1982 and three experiment simulations with modifications to the moisture and vertical motion fields incorporated at 1800 GMT. The forecasts from 1800 GMT were compared to the second half of the control forecast. It was found that, compared to the control forecast, suppression of the moisture and/or wind initial field(s) produces a drier forecast. However, the characteristics of the precipitation forecasts of the experiments were not different enough to conclude that either mesoscale moisture or mesoscale vertical velocity at the initial time are more important for producing a forecast closer to that of the control.

Vibration attenuation of the NASA Langley evolutionary structure experiment using H(sub infinity) and structured singular value (micron) robust multivariable control techniques

NASA Technical Reports Server (NTRS)

Balas, Gary J.

1992-01-01

The use is studied of active control to attenuate structural vibrations of the NASA Langley Phase Zero Evolutionary Structure due to external disturbance excitations. H sub infinity and structured singular value (mu) based control techniques are used to analyze and synthesize control laws for the NASA Langley Controls Structures Interaction (CSI) Evolutionary Model (CEM). The CEM structure experiment provides an excellent test bed to address control design issues for large space structures. Specifically, control design for structures with numerous lightly damped, coupled flexible modes, collocated and noncollocated sensors and actuators and stringent performance specifications. The performance objectives are to attenuate the vibration of the structure due to external disturbances, and minimize the actuator control force. The control design problem formulation for the CEM Structure uses a mathematical model developed with finite element techniques. A reduced order state space model for the control design is formulated from the finite element model. It is noted that there are significant variations between the design model and the experimentally derived transfer function data.

Sensitivity study of a dynamic thermodynamic sea ice model

NASA Astrophysics Data System (ADS)

Holland, David M.; Mysak, Lawrence A.; Manak, Davinder K.; Oberhuber, Josef M.

1993-02-01

A numerical simulation of the seasonal sea ice cover in the Arctic Ocean and the Greenland, Iceland, and Norwegian seas is presented. The sea ice model is extracted from Oberhuber's (1990) coupled sea ice-mixed layer-isopycnal general circulation model and is written in spherical coordinates. The advantage of such a model over previous sea ice models is that it can be easily coupled to either global atmospheric or ocean general circulation models written in spherical coordinates. In this model, the thermodynamics are a modification of that of Parkinson and Washington (1979), while the dynamics use the full Hibler (1979) viscous-plastic rheology. Monthly thermodynamic and dynamic forcing fields for the atmosphere and ocean are specified. The simulations of the seasonal cycle of ice thickness, compactness, and velocity, for a control set of parameters, compare favorably with the known seasonal characteristics of these fields. A sensitivity study of the control simulation of the seasonal sea ice cover is presented. The sensitivity runs are carried out under three different themes, namely, numerical conditions, parameter values, and physical processes. This last theme refers to experiments in which physical processes are either newly added or completely removed from the model. Approximately 80 sensitivity runs have been performed in which a change from the control run environment has been implemented. Comparisons have been made between the control run and a particular sensitivity run based on time series of the seasonal cycle of the domain-averaged ice thickness, compactness, areal coverage, and kinetic energy. In addition, spatially varying fields of ice thickness, compactness, velocity, and surface temperature for each season are presented for selected experiments. A brief description and discussion of the more interesting experiments are presented. The simulation of the seasonal cycle of Arctic sea ice cover is shown to be robust.

Detailed Multidimensional Simulations of the Structure and Dynamics of Flames

NASA Technical Reports Server (NTRS)

Patnaik, G.; Kailasanath, K.

1999-01-01

Numerical simulations in which the various physical and chemical processes can be independently controlled can significantly advance our understanding of the structure, stability, dynamics and extinction of flames. Therefore, our approach has been to use detailed time-dependent, multidimensional, multispecies numerical models to perform carefully designed computational experiments of flames on Earth and in microgravity environments. Some of these computational experiments are complementary to physical experiments performed under the Microgravity Program while others provide a fundamental understanding that cannot be obtained from physical experiments alone. In this report, we provide a brief summary of our recent research highlighting the contributions since the previous microgravity combustion workshop. There are a number of mechanisms that can cause flame instabilities and result in the formation of dynamic multidimensional structures. In the past, we have used numerical simulations to show that it is the thermo-diffusive instability rather than an instability due to preferential diffusion that is the dominant mechanism for the formation of cellular flames in lean hydrogen-air mixtures. Other studies have explored the role of gravity on flame dynamics and extinguishment, multi-step kinetics and radiative losses on flame instabilities in rich hydrogen-air flames, and heat losses on burner-stabilized flames in microgravity. The recent emphasis of our work has been on exploring flame-vortex interactions and further investigating the structure and dynamics of lean hydrogen-air flames in microgravity. These topics are briefly discussed after a brief discussion of our computational approach for solving these problems.

Using Nonlinearity and Contact Lines to Control Fluid Flow in Microgravity

NASA Technical Reports Server (NTRS)

Perlin, M.; Schultz, W. W.; Bian, X.; Agarwal, M.

2002-01-01

Slug flows in a tube are affected by surface tension and contact lines, especially under microgravity. Numerical analyses and experiments are conducted of slug flows in small-diameter tubes with horizontal, inclined and vertical orientations. A PID-controlled, meter-long platform capable of following specified motions is used. An improved understanding of the contact line boundary condition for steady and unsteady contact-line motion is expected. Lastly, a direct fluid-handling method using nonlinear oscillatory motion of a tube is presented.

Synchronizing movements with the metronome: nonlinear error correction and unstable periodic orbits.

PubMed

Engbert, Ralf; Krampe, Ralf Th; Kurths, Jürgen; Kliegl, Reinhold

2002-02-01

The control of human hand movements is investigated in a simple synchronization task. We propose and analyze a stochastic model based on nonlinear error correction; a mechanism which implies the existence of unstable periodic orbits. This prediction is tested in an experiment with human subjects. We find that our experimental data are in good agreement with numerical simulations of our theoretical model. These results suggest that feedback control of the human motor systems shows nonlinear behavior. Copyright 2001 Elsevier Science (USA).

High Frequency Excitation for Cavity Flow Control: Combined Experiments and Linear Stability Analysis

DTIC Science & Technology

2009-06-30

Astronautics Journal 18, 1959 (1970). 3 D. Sahoo, A. M. Annaswamy, and F . Alvi, "Active store trajectory control in supersonic cavities using microjets and...and A. F . Ghoneim, "Numerical simulation of the convective instability in a dump combustor", American Institute of Aeronautics and Astronautics Journal...29. 911 (1991). 6 P. C. Kriesels, M. C. A. M. Peters, A. Hirschberg, A. P. J. Wijnands, A. Iafrati, G. Riccardi , R. Piva, and J. C. Bruggeman

Experimental Study of Flexible Plate Vibration Control by Using Two-Loop Sliding Mode Control Strategy

NASA Astrophysics Data System (ADS)

Yang, Jingyu; Lin, Jiahui; Liu, Yuejun; Yang, Kang; Zhou, Lanwei; Chen, Guoping

2017-08-01

It is well known that intelligent control theory has been used in many research fields, novel modeling method (DROMM) is used for flexible rectangular active vibration control, and then the validity of new model is confirmed by comparing finite element model with new model. In this paper, taking advantage of the dynamics of flexible rectangular plate, a two-loop sliding mode (TSM) MIMO approach is introduced for designing multiple-input multiple-output continuous vibration control system, which can overcome uncertainties, disturbances or unstable dynamics. An illustrative example is given in order to show the feasibility of the method. Numerical simulations and experiment confirm the effectiveness of the proposed TSM MIMO controller.

Combined input shaping and feedback control for double-pendulum systems

NASA Astrophysics Data System (ADS)

Mar, Robert; Goyal, Anurag; Nguyen, Vinh; Yang, Tianle; Singhose, William

2017-02-01

A control system combining input shaping and feedback is developed for double-pendulum systems subjected to external disturbances. The proposed control method achieves fast point-to-point response similar to open-loop input-shaping control. It also minimizes transient deflections during the motion of the system, and disturbance-induced residual swing using the feedback control. Effects of parameter variations such as the mass ratio of the double pendulum, the suspension length ratio, and the move distance were studied via numerical simulation. The most important results were also verified with experiments on a small-scale crane. The controller effectively suppresses the disturbances and is robust to modelling uncertainties and task variations.

Effect of Hydrograph Characteristics on Vertical Grain Sorting in Gravel Bed Rivers

NASA Astrophysics Data System (ADS)

Hassan, M. A.; Parker, G.; Egozi, R.

2005-12-01

This study focuses on the formation of armour layers over a range of hydrologic conditions that includes two limiting cases; a relatively flat hydrograph that represents conditions produced by continuous snowmelt and a sharply peaked hydrograph that represents conditions associated with flash floods. To achieve our objective we analyzed field evidence, conducted flume experiments and performed numerical simulations. Sediment supply appears to be a first-order control on bed surface armouring, while the shape of the hydrograph plays a secondary role. All constant hydrograph experiments developed a well-armored structured surface while short asymmetrical hydrographs did not show substantial vertical sorting. All symmetrical hydrographs show some degree of sorting, and the sorting tended to become more pronounced with longer duration. Using the numerical framework of Parker, modified Powell, et al. and Wilcock and Crowe, we were able to achieve similar results.

A Simple Numerical Procedure for the Simulation of "Lifelike" Linear-Sweep Voltammograms

NASA Astrophysics Data System (ADS)

Bozzini, Benedetto P.

2000-01-01

Practical linear-sweep voltammograms seldom resemble the theoretical ones shown in textbooks. This is because several phenomena (activation, mass transport, ohmic resistance) control the kinetics over different potential ranges scanned during the potential sweep. These effects are generally treated separately in the didactic literature, yet they have never been "assembled" in a way that allows the educational use of real experiments. This makes linear-sweep voltammetric experiments almost unusable in the teaching of physical chemistry. A simple approach to the classroom description of "lifelike" experimental results is proposed in this paper. Analytical expressions of linear sweep voltammograms are provided. The actual numerical evaluations can be carried out with a pocket calculator. Two typical examples are executed and comparison with experimental data is described. This approach to teaching electrode kinetics has proved an effective tool to provide students with an insight into the effects of electrochemical parameters and operating conditions.

Answering the missed call: Initial exploration of cognitive and electrophysiological changes associated with smartphone use and abuse

PubMed Central

Hadas, Itay; Lazarovits, Avi; Alyagon, Uri; Eliraz, Daniel; Zangen, Abraham

2017-01-01

Background Smartphone usage is now integral to human behavior. Recent studies associate extensive usage with a range of debilitating effects. We sought to determine whether excessive usage is accompanied by measurable neural, cognitive and behavioral changes. Method Subjects lacking previous experience with smartphones (n = 35) were compared to a matched group of heavy smartphone users (n = 16) on numerous behavioral and electrophysiological measures recorded using electroencephalogram (EEG) combined with transcranial magnetic stimulation (TMS) over the right prefrontal cortex (rPFC). In a second longitudinal intervention, a randomly selected sample of the original non-users received smartphones for 3 months while the others served as controls. All measurements were repeated following this intervention. Results Heavy users showed increased impulsivity, hyperactivity and negative social concern. We also found reduced early TMS evoked potentials in the rPFC of this group, which correlated with severity of self-reported inattention problems. Heavy users also obtained lower accuracy rates than nonusers in a numerical processing. Critically, the second part of the experiment revealed that both the numerical processing and social cognition domains are causally linked to smartphone usage. Conclusion Heavy usage was found to be associated with impaired attention, reduced numerical processing capacity, changes in social cognition, and reduced right prefrontal cortex (rPFC) excitability. Memory impairments were not detected. Novel usage over short period induced a significant reduction in numerical processing capacity and changes in social cognition. PMID:28678870

A ``Cyber Wind Facility'' for HPC Wind Turbine Field Experiments

NASA Astrophysics Data System (ADS)

Brasseur, James; Paterson, Eric; Schmitz, Sven; Campbell, Robert; Vijayakumar, Ganesh; Lavely, Adam; Jayaraman, Balaji; Nandi, Tarak; Jha, Pankaj; Dunbar, Alex; Motta-Mena, Javier; Craven, Brent; Haupt, Sue

2013-03-01

The Penn State ``Cyber Wind Facility'' (CWF) is a high-fidelity multi-scale high performance computing (HPC) environment in which ``cyber field experiments'' are designed and ``cyber data'' collected from wind turbines operating within the atmospheric boundary layer (ABL) environment. Conceptually the ``facility'' is akin to a high-tech wind tunnel with controlled physical environment, but unlike a wind tunnel it replicates commercial-scale wind turbines operating in the field and forced by true atmospheric turbulence with controlled stability state. The CWF is created from state-of-the-art high-accuracy technology geometry and grid design and numerical methods, and with high-resolution simulation strategies that blend unsteady RANS near the surface with high fidelity large-eddy simulation (LES) in separated boundary layer, blade and rotor wake regions, embedded within high-resolution LES of the ABL. CWF experiments complement physical field facility experiments that can capture wider ranges of meteorological events, but with minimal control over the environment and with very small numbers of sensors at low spatial resolution. I shall report on the first CWF experiments aimed at dynamical interactions between ABL turbulence and space-time wind turbine loadings. Supported by DOE and NSF.

Spatial and Temporal Variations in Slip Partitioning During Oblique Convergence Experiments

NASA Astrophysics Data System (ADS)

Beyer, J. L.; Cooke, M. L.; Toeneboehn, K.

2017-12-01

Physical experiments of oblique convergence in wet kaolin demonstrate the development of slip partitioning, where two faults accommodate strain via different slip vectors. In these experiments, the second fault forms after the development of the first fault. As one strain component is relieved by one fault, the local stress field then favors the development of a second fault with different slip sense. A suite of physical experiments reveals three styles of slip partitioning development controlled by the convergence angle and presence of a pre-existing fault. In experiments with low convergence angles, strike-slip faults grow prior to reverse faults (Type 1) regardless of whether the fault is precut or not. In experiments with moderate convergence angles, slip partitioning is dominantly controlled by the presence of a pre-existing fault. In all experiments, the primarily reverse fault forms first. Slip partitioning then develops with the initiation of strike-slip along the precut fault (Type 2) or growth of a secondary reverse fault where the first fault is steepest. Subsequently, the slip on the first fault transitions to primarily strike-slip (Type 3). Slip rates and rakes along the slip partitioned faults for both precut and uncut experiments vary temporally, suggesting that faults in these slip-partitioned systems are constantly adapting to the conditions produced by slip along nearby faults in the system. While physical experiments show the evolution of slip partitioning, numerical simulations of the experiments provide information about both the stress and strain fields, which can be used to compute the full work budget, providing insight into the mechanisms that drive slip partitioning. Preliminary simulations of precut experiments show that strain energy density (internal work) can be used to predict fault growth, highlighting where fault growth can reduce off-fault deformation in the physical experiments. In numerical simulations of uncut experiments with a first non-planar oblique slip fault, strain energy density is greatest where the first fault is steepest, as less convergence is accommodated along this portion of the fault. The addition of a second slip-partitioning fault to the system decreases external work indicating that these faults increase the mechanical efficiency of the system.

Active Noise Control Experiments using Sound Energy Flu

NASA Astrophysics Data System (ADS)

Krause, Uli

2015-03-01

This paper reports on the latest results concerning the active noise control approach using net flow of acoustic energy. The test set-up consists of two loudspeakers simulating the engine noise and two smaller loudspeakers which belong to the active noise system. The system is completed by two acceleration sensors and one microphone per loudspeaker. The microphones are located in the near sound field of the loudspeakers. The control algorithm including the update equation of the feed-forward controller is introduced. Numerical simulations are performed with a comparison to a state of the art method minimising the radiated sound power. The proposed approach is experimentally validated.

Flow pumping system for physiological waveforms.

PubMed

Tsai, William; Savaş, Omer

2010-02-01

A pulsatile flow pumping system is developed to replicate flow waveforms with reasonable accuracy for experiments simulating physiological blood flows at numerous points in the body. The system divides the task of flow waveform generation between two pumps: a gear pump generates the mean component and a piston pump generates the oscillatory component. The system is driven by two programmable servo controllers. The frequency response of the system is used to characterize its operation. The system has been successfully tested in vascular flow experiments where sinusoidal, carotid, and coronary flow waveforms are replicated.

The Numerical Studies Program for the Atmospheric General Circulation Experiment (AGCE) for Spacelab Flights

NASA Technical Reports Server (NTRS)

Fowlis, W. W. (Editor); Davis, M. H. (Editor)

1981-01-01

The atmospheric general circulation experiment (AGCE) numerical design for Spacelab flights was studied. A spherical baroclinic flow experiment which models the large scale circulations of the Earth's atmosphere was proposed. Gravity is simulated by a radial dielectric body force. The major objective of the AGCE is to study nonlinear baroclinic wave flows in spherical geometry. Numerical models must be developed which accurately predict the basic axisymmetric states and the stability of nonlinear baroclinic wave flows. A three dimensional, fully nonlinear, numerical model and the AGCE based on the complete set of equations is required. Progress in the AGCE numerical design studies program is reported.

Investigating Strategies to Increase Persistence and Success Rates among Anatomy & Physiology Students: A Case Study at Austin Community College District

NASA Astrophysics Data System (ADS)

Vedartham, Padmaja B.

Snap-through buckling provides an intricate force-displacement relationship for study. With the possibility for multiple limit points and pitchfork bifurcations and large regions of instability, experimental validation of numerical analysis can become difficult. This requires stabilization of unstable static equilibria, for which limited prior research exists. For all but the simplest cases, more than one actuator is needed, increasing the complexity of the experiment to the point of intractability without a control system. In this thesis, the necessary conditions for stabilization of a buckled beam with pinned boundaries under transverse loading were determined. By combining various nonlinear solution methods, a control system was created that could stabilize any branch of the force-displacement response. Experimental traversal of an unstable branch are presented along with other unstable static equilibrium configurations. The control system had numerical limitations, losing convergence near singular points. The groundwork for experimental stabilization was validated and demonstrated.

Effect of interfacial turbulence and accommodation coefficient on CFD predictions of pressurization and pressure control in cryogenic storage tank

NASA Astrophysics Data System (ADS)

Kassemi, Mohammad; Kartuzova, Olga

2016-03-01

Pressurization and pressure control in cryogenic storage tanks are to a large extent affected by heat and mass transport across the liquid-vapor interface. These mechanisms are, in turn, controlled by the kinetics of the phase change process and the dynamics of the turbulent recirculating flows in the liquid and vapor phases. In this paper, the effects of accommodation coefficient and interfacial turbulence on tank pressurization and pressure control simulations are examined. Comparison between numerical predictions and ground-based measurements in two large liquid hydrogen tank experiments, performed in the K-site facility at NASA Glenn Research Center (GRC) and the Multi-purpose Hydrogen Test Bed (MHTB) facility at NASA Marshall Space Flight Center (MSFC), are used to show the impact of accommodation coefficient and interfacial and vapor phase turbulence on evolution of pressure and temperatures in the cryogenic storage tanks. In particular, the self-pressurization comparisons indicate that: (1) numerical predictions are essentially independent of the magnitude of the accommodation coefficient; and (2) surprisingly, laminar models sometimes provide results that are in better agreement with experimental self-pressurization rates, even in parametric ranges where the bulk flow is deemed fully turbulent. In this light, shortcomings of the present CFD models, especially, numerical treatments of interfacial mass transfer and turbulence, as coupled to the Volume-of-Fluid (VOF) interface capturing scheme, are underscored and discussed.

Active control of sound transmission through a double panel partition

NASA Astrophysics Data System (ADS)

Sas, P.; Bao, C.; Augusztinovicz, F.; Desmet, W.

1995-03-01

The feasibility of improving the insertion loss of lightweight double panel partitions by using small loudspeakers as active noise control sources inside the air gap between both panels of the partition is investigated analytically, numerically and experimentally in this paper. A theoretical analysis of the mechanisms of the fluid-structure interaction of double panel structures is presented in order to gain insight into the physical phenomena underlying the behaviour of a coupled vibro-acoustic system controlled by active methods. The analysis, based on modal coupling theory, enables one to derive some qualitative predictions concerning the potentials and limitations of the proposed approach. The theoretical analysis is valid only for geometrically simple structures. For more complex geometries, numerical simulations are required. Therefore the potential use of active noise control inside double panel structures has been analyzed by using coupled finite element and boundary element methods. To verify the conclusions drawn from the theoretical analysis and the numerical calculation and, above all, to demonstrate the potential of the proposed approach, experiments have been conducted with a laboratory set-up. The performance of the proposed approach was evaluated in terms of relative insertion loss measurements. It is shown that a considerable improvement of the insertion loss has been achieved around the lightly damped resonances of the system for the frequency range investigated (60-220 Hz).

Direct experience while eating: Laboratory outcomes among individuals with eating disorders versus healthy controls.

PubMed

Elices, Matilde; Carmona, Cristina; Narváez, Vanessa; Seto, Victoria; Martin-Blanco, Ana; Pascual, Juan C; Soriano, José; Soler, Joaquim

2017-12-01

To compare individuals with eating disorders (EDs) to healthy controls (HCs) to assess for differences in direct engagement in the eating process. Participants (n=58) were asked to eat an orange slice. To assess the degree of direct engagement with the eating process, participants were asked to write down 10 thoughts about the experience of eating the orange slice. Next, the participants were instructed to classify the main focus of each thought as either experiential ("direct experience") or analytical ("thinking about"). A direct experience index (DEI) was computed by dividing the number of times that participants classified an experience as a "direct experience" (the numerator) by the total number of all observations (i.e., direct experience+thinking about). Participants also completed the Five Facet Mindfulness Questionnaire (FFMQ) and the Experiences Questionnaire (EQ) to assess mindfulness facets and decentering, respectively. Compared to controls, participants in the EDs group presented significantly lower levels of direct experience during the eating task (EDs group: mean=43.54, SD=29.64; HCs group: mean=66.17, SD=22.23, p=0.03). Participants in the EDs group also scored significantly lower on other mindfulness-related variables. These findings suggest that engagement with the direct experience of eating is lower in individuals with EDs. Future research should investigate the role of mindfulness-based interventions to address direct experience while eating in individuals with EDs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Parametric nonfeedback resonance in period doubling systems

NASA Astrophysics Data System (ADS)

Pisarchik, A. N.; Corbalán, R.

1999-02-01

Slow periodic modulation of a control parameter in a period doubling system leads to an interaction between stable and unstable periodic orbits. This causes a resonance in the system response at the modulation frequency. The conditions for this resonance are studied through numerical simulations of quadratic map and laser equations. The results are confirmed by experiments in a CO2 laser with modulated losses.

Small Impacts on Mars: Atmospheric Effects

NASA Technical Reports Server (NTRS)

Greeley, Ronald; Nemtchinov, Ivan V.

2002-01-01

The objectives of this investigation were to study the interaction of the atmosphere with the surface of Mars through the impact of small objects that would generate dust and set the dust into motion in the atmosphere. The approach involved numerical simulations of impacts and experiments under controlled conditions. Attachment: Atmospheric disturbances and radiation impulses caused by large-meteoroid impact in the surface of Mars.

Numerical Simulation and Optimization of Directional Solidification Process of Single Crystal Superalloy Casting

PubMed Central

Zhang, Hang; Xu, Qingyan; Liu, Baicheng

2014-01-01

The rapid development of numerical modeling techniques has led to more accurate results in modeling metal solidification processes. In this study, the cellular automaton-finite difference (CA-FD) method was used to simulate the directional solidification (DS) process of single crystal (SX) superalloy blade samples. Experiments were carried out to validate the simulation results. Meanwhile, an intelligent model based on fuzzy control theory was built to optimize the complicate DS process. Several key parameters, such as mushy zone width and temperature difference at the cast-mold interface, were recognized as the input variables. The input variables were functioned with the multivariable fuzzy rule to get the output adjustment of withdrawal rate (v) (a key technological parameter). The multivariable fuzzy rule was built, based on the structure feature of casting, such as the relationship between section area, and the delay time of the temperature change response by changing v, and the professional experience of the operator as well. Then, the fuzzy controlling model coupled with CA-FD method could be used to optimize v in real-time during the manufacturing process. The optimized process was proven to be more flexible and adaptive for a steady and stray-grain free DS process. PMID:28788535

Self-assembly of silica microparticles in magnetic multiphase flows: Experiment and simulation

NASA Astrophysics Data System (ADS)

Li, Xiang; Niu, Xiao-Dong; Li, You; Chen, Mu-Feng

2018-04-01

Dynamic self-assembly, especially self-assembly under magnetic field, is vital not only for its marvelous phenomenon but also for its mechanisms. Revealing the underlying mechanisms is crucial for a deeper understanding of self-assembly. In this paper, several magnetic induced self-assembly experiments by using the mixed magnetic multiphase fluids comprised of silica microspheres were carried out. The relations of the strength of external magnetic field, the inverse magnetorheological effect, and the structures of self-assembled particles were investigated. In addition, a momentum-exchanged immersed boundary-based lattice Boltzmann method (MEIB-LBM) for modeling multi-physical coupling multiphase flows was employed to numerically study the magnetic induced self-assembly process in detail. The present work showed that the external magnetic field can be used to control the form of self-assembly of nonmagnetic microparticles in a chain-like structure, and the self-assembly process can be classified into four stages with magnetic hysteresis, magnetization of nonmagnetic microparticles, self-assembly in chain-like structures, and the stable chain state. The combination of experimental and numerical results could offer a method to control the self-assembled nonmagnetic microparticles, which can provide the technical and theoretical support for the design and fabrication of micro/nanomaterials.

Design of an ultraprecision computerized numerical control chemical mechanical polishing machine and its implementation

NASA Astrophysics Data System (ADS)

Zhang, Chupeng; Zhao, Huiying; Zhu, Xueliang; Zhao, Shijie; Jiang, Chunye

2018-01-01

The chemical mechanical polishing (CMP) is a key process during the machining route of plane optics. To improve the polishing efficiency and accuracy, a CMP model and machine tool were developed. Based on the Preston equation and the axial run-out error measurement results of the m circles on the tin plate, a CMP model that could simulate the material removal at any point on the workpiece was presented. An analysis of the model indicated that lower axial run-out error led to lower material removal but better polishing efficiency and accuracy. Based on this conclusion, the CMP machine was designed, and the ultraprecision gas hydrostatic guideway and rotary table as well as the Siemens 840Dsl numerical control system were incorporated in the CMP machine. To verify the design principles of machine, a series of detection and machining experiments were conducted. The LK-G5000 laser sensor was employed for detecting the straightness error of the gas hydrostatic guideway and the axial run-out error of the gas hydrostatic rotary table. A 300-mm-diameter optic was chosen for the surface profile machining experiments performed to determine the CMP efficiency and accuracy.

Design and control strategies for CELSS - Integrating mechanistic paradigms and biological complexities

NASA Technical Reports Server (NTRS)

Moore, B., III; Kaufmann, R.; Reinhold, C.

1981-01-01

Systems analysis and control theory consideration are given to simulations of both individual components and total systems, in order to develop a reliable control strategy for a Controlled Ecological Life Support System (CELSS) which includes complex biological components. Because of the numerous nonlinearities and tight coupling within the biological component, classical control theory may be inadequate and the statistical analysis of factorial experiments more useful. The range in control characteristics of particular species may simplify the overall task by providing an appropriate balance of stability and controllability to match species function in the overall design. The ultimate goal of this research is the coordination of biological and mechanical subsystems in order to achieve a self-supporting environment.

Choice of Control Variables in Variational Data Assimilation and Its Analysis and Forecast Impact

NASA Astrophysics Data System (ADS)

Xie, Yuanfu; Sun, Jenny; Fang, Wei-ting

2014-05-01

Choice of control variables directly impacts the analysis qualify of a variational data assimilation and its forecasts. A theory on selecting control variables for wind and moisture field is introduced for 3DVAR or 4DVAR. For a good control variable selection, Parseval's theory is applied to 3-4DVAR and the behavior of different control variables is illustrated in physical and Fourier space in terms of minimization condition, meteorological dynamic scales and practical implementation. The computational and meteorological benefits will be discussed. Numerical experiments have been performed using WRF-DA for wind control variables and CRTM for moisture control variables. It is evident of the WRF forecast improvement and faster convergence of CRTM satellite data assimilation.

Preoperative pain neuroscience education for lumbar radiculopathy: a multicenter randomized controlled trial with 1-year follow-up.

PubMed

Louw, Adriaan; Diener, Ina; Landers, Merrill R; Puentedura, Emilio J

2014-08-15

Multicenter, randomized, controlled trial on preoperative pain neuroscience education (NE) for lumbar radiculopathy. To determine if the addition of NE to usual preoperative education would result in superior outcomes with regard to pain, function, surgical experience, and health care utilization postsurgery. One in 4 patients after lumbar surgery (LS) for radiculopathy experience persistent pain and disability, which is nonresponsive to perioperative treatments. NE focusing on the neurophysiology of pain has been shown to decrease pain and disability in populations with chronic low back pain. Eligible patients scheduled for LS for radiculopathy were randomized to receive either preoperative usual care (UC) or a combination of UC plus 1 session of NE delivered by a physical therapist (verbal one-on-one format) and a NE booklet. Sixty-seven patients completed the following outcomes prior to LS (baseline), and 1, 3, 6, and 12 months after LS: low back pain (numeric rating scale), leg pain (numeric rating scale), function (Oswestry Disability Index), various beliefs and experiences related to LS (10-item survey with Likert scale responses), and postoperative utilization of health care (utilization of health care questionnaire). At 1-year follow-up, there were no statistical differences between the experimental and control groups with regard to primary outcome measure of low back pain (P = 0.183), leg pain (P = 0.075), and function (P = 0.365). In a majority of the categories regarding surgical experience, the NE group scored significantly better: better prepared for LS (P = 0.001); preoperative session preparing them for LS (P < 0.001) and LS meeting their expectations (P = 0.021). Health care utilization post-LS also favored the NE group (P = 0.007) resulting in 45% less health care expenditure compared with the control group in the 1-year follow-up period. NE resulted in significant behavior change. Despite a similar pain and functional trajectory during the 1-year trial, patients with LS who received NE viewed their surgical experience more favorably and used less health care facility in the form of medical tests and treatments. 2.

Field Tested Service Oriented Robotic Architecture: Case Study

NASA Technical Reports Server (NTRS)

Flueckiger, Lorenzo; Utz, Hanz

2012-01-01

This paper presents the lessons learned from six years of experiments with planetary rover prototypes running the Service Oriented Robotic Architecture (SORA) developed by the Intelligent Robotics Group (IRG) at NASA Ames Research Center. SORA relies on proven software methods and technologies applied to the robotic world. Based on a Service Oriented Architecture and robust middleware, SORA extends its reach beyond the on-board robot controller and supports the full suite of software tools used during mission scenarios from ground control to remote robotic sites. SORA has been field tested in numerous scenarios of robotic lunar and planetary exploration. The results of these high fidelity experiments are illustrated through concrete examples that have shown the benefits of using SORA as well as its limitations.

Effect of pulse temporal shape on optical trapping and impulse transfer using ultrashort pulsed lasers.

PubMed

Shane, Janelle C; Mazilu, Michael; Lee, Woei Ming; Dholakia, Kishan

2010-03-29

We investigate the effects of pulse duration on optical trapping with high repetition rate ultrashort pulsed lasers, through Lorentz-Mie theory, numerical simulation, and experiment. Optical trapping experiments use a 12 femtosecond duration infrared pulsed laser, with the trapping microscope's temporal dispersive effects measured and corrected using the Multiphoton Intrapulse Interference Phase Scan method. We apply pulse shaping to reproducibly stretch pulse duration by 1.5 orders of magnitude and find no material-independent effects of pulse temporal profile on optical trapping of 780nm silica particles, in agreement with our theory and simulation. Using pulse shaping, we control two-photon fluorescence in trapped fluorescent particles, opening the door to other coherent control applications with trapped particles.

Mammalian animal models of psychosexual differentiation: when is 'translation' to the human situation possible?

PubMed

Baum, Michael J

2006-11-01

Clinical investigators have been forced primarily to use experiments of nature (e.g., cloacal exstrophy; androgen insensitivity, congenital adrenal hyperplasia) to assess the contribution of fetal sex hormone exposure to the development of male- and female-typical profiles of gender identity and role behavior as well as sexual orientation. In this review, I summarize the results of numerous correlative as well as mechanistic animal experiments that shed significant light on general neuroendocrine mechanisms controlling the differentiation of neural circuits controlling sexual partner preference (sexual orientation) in mammalian species including man. I also argue, however, that results of animal studies can, at best, provide only indirect insights into the neuroendocrine determinants of human gender identity and role behaviors.

Controlling shockwave dynamics using architecture in periodic porous materials

DOE PAGES

Branch, Brittany; Ionita, Axinte; Clements, Bradford E.; ...

2017-04-07

Additive manufacturing (AM) is an attractive approach for the design and fabrication of structures capable of achieving controlled mechanical response of the underlying deformation mechanisms. While there are numerous examples illustrating how the quasi-static mechanical responses of polymer foams have been tailored by additive manufacturing, there is limited understanding of the response of these materials under shockwave compression. Dynamic compression experiments coupled with time-resolved X-ray imaging were performed to obtain insights into the in situ evolution of shockwave coupling to porous, periodic polymer foams. We further demonstrate shock wave modulation or “spatially graded-flow” in shock-driven experiments via the spatial controlmore » of layer symmetries afforded by additive manufacturing techniques at the micron scale.« less

Active control of the spatial MRI phase distribution with optimal control theory

NASA Astrophysics Data System (ADS)

Lefebvre, Pauline M.; Van Reeth, Eric; Ratiney, Hélène; Beuf, Olivier; Brusseau, Elisabeth; Lambert, Simon A.; Glaser, Steffen J.; Sugny, Dominique; Grenier, Denis; Tse Ve Koon, Kevin

2017-08-01

This paper investigates the use of Optimal Control (OC) theory to design Radio-Frequency (RF) pulses that actively control the spatial distribution of the MRI magnetization phase. The RF pulses are generated through the application of the Pontryagin Maximum Principle and optimized so that the resulting transverse magnetization reproduces various non-trivial and spatial phase patterns. Two different phase patterns are defined and the resulting optimal pulses are tested both numerically with the ODIN MRI simulator and experimentally with an agar gel phantom on a 4.7 T small-animal MR scanner. Phase images obtained in simulations and experiments are both consistent with the defined phase patterns. A practical application of phase control with OC-designed pulses is also presented, with the generation of RF pulses adapted for a Magnetic Resonance Elastography experiment. This study demonstrates the possibility to use OC-designed RF pulses to encode information in the magnetization phase and could have applications in MRI sequences using phase images.

Non-linear dynamic characteristics and optimal control of giant magnetostrictive film subjected to in-plane stochastic excitation

NASA Astrophysics Data System (ADS)

Zhu, Z. W.; Zhang, W. D.; Xu, J.

2014-03-01

The non-linear dynamic characteristics and optimal control of a giant magnetostrictive film (GMF) subjected to in-plane stochastic excitation were studied. Non-linear differential items were introduced to interpret the hysteretic phenomena of the GMF, and the non-linear dynamic model of the GMF subjected to in-plane stochastic excitation was developed. The stochastic stability was analysed, and the probability density function was obtained. The condition of stochastic Hopf bifurcation and noise-induced chaotic response were determined, and the fractal boundary of the system's safe basin was provided. The reliability function was solved from the backward Kolmogorov equation, and an optimal control strategy was proposed in the stochastic dynamic programming method. Numerical simulation shows that the system stability varies with the parameters, and stochastic Hopf bifurcation and chaos appear in the process; the area of the safe basin decreases when the noise intensifies, and the boundary of the safe basin becomes fractal; the system reliability improved through stochastic optimal control. Finally, the theoretical and numerical results were proved by experiments. The results are helpful in the engineering applications of GMF.

Maneuver simulations of flexible spacecraft by solving TPBVP

NASA Technical Reports Server (NTRS)

Bainum, Peter M.; Li, Feiyue

1991-01-01

The optimal control of large angle rapid maneuvers and vibrations of a Shuttle mast reflector system is considered. The nonlinear equations of motion are formulated by using Lagrange's formula, with the mast modeled as a continuous beam. The nonlinear terms in the equations come from the coupling between the angular velocities, the modal coordinates, and the modal rates. Pontryagin's Maximum Principle is applied to the slewing problem, to derive the necessary conditions for the optimal controls, which are bounded by given saturation levels. The resulting two point boundary value problem (TPBVP) is then solved by using the quasilinearization algorithm and the method of particular solutions. In the numerical simulations, the structural parameters and the control limits from the Spacecraft Control Lab Experiment (SCOLE) are used. In the 2-D case, only the motion in the plane of an Earth orbit or the single axis slewing motion is discussed. In the 3-D slewing, the mast is modeled as a continuous beam subjected to 3-D deformations. The numerical results for both the linearized system and the nonlinear system are presented to compare the differences in their time response.

Analysis of High Order Difference Methods for Multiscale Complex Compressible Flows

NASA Technical Reports Server (NTRS)

Sjoegreen, Bjoern; Yee, H. C.; Tang, Harry (Technical Monitor)

2002-01-01

Accurate numerical simulations of complex multiscale compressible viscous flows, especially high speed turbulence combustion and acoustics, demand high order schemes with adaptive numerical dissipation controls. Standard high resolution shock-capturing methods are too dissipative to capture the small scales and/or long-time wave propagations without extreme grid refinements and small time steps. An integrated approach for the control of numerical dissipation in high order schemes with incremental studies was initiated. Here we further refine the analysis on, and improve the understanding of the adaptive numerical dissipation control strategy. Basically, the development of these schemes focuses on high order nondissipative schemes and takes advantage of the progress that has been made for the last 30 years in numerical methods for conservation laws, such as techniques for imposing boundary conditions, techniques for stability at shock waves, and techniques for stable and accurate long-time integration. We concentrate on high order centered spatial discretizations and a fourth-order Runge-Kutta temporal discretizations as the base scheme. Near the bound-aries, the base scheme has stable boundary difference operators. To further enhance stability, the split form of the inviscid flux derivatives is frequently used for smooth flow problems. To enhance nonlinear stability, linear high order numerical dissipations are employed away from discontinuities, and nonlinear filters are employed after each time step in order to suppress spurious oscillations near discontinuities to minimize the smearing of turbulent fluctuations. Although these schemes are built from many components, each of which is well-known, it is not entirely obvious how the different components be best connected. For example, the nonlinear filter could instead have been built into the spatial discretization, so that it would have been activated at each stage in the Runge-Kutta time stepping. We could think of a mechanism that activates the split form of the equations only at some parts of the domain. Another issue is how to define good sensors for determining in which parts of the computational domain a certain feature should be filtered by the appropriate numerical dissipation. For the present study we employ a wavelet technique introduced in as sensors. Here, the method is briefly described with selected numerical experiments.

Word problems: a review of linguistic and numerical factors contributing to their difficulty

PubMed Central

Daroczy, Gabriella; Wolska, Magdalena; Meurers, Walt Detmar; Nuerk, Hans-Christoph

2015-01-01

Word problems (WPs) belong to the most difficult and complex problem types that pupils encounter during their elementary-level mathematical development. In the classroom setting, they are often viewed as merely arithmetic tasks; however, recent research shows that a number of linguistic verbal components not directly related to arithmetic contribute greatly to their difficulty. In this review, we will distinguish three components of WP difficulty: (i) the linguistic complexity of the problem text itself, (ii) the numerical complexity of the arithmetic problem, and (iii) the relation between the linguistic and numerical complexity of a problem. We will discuss the impact of each of these factors on WP difficulty and motivate the need for a high degree of control in stimuli design for experiments that manipulate WP difficulty for a given age group. PMID:25883575

Induction of numerical chromosomal aberrations during DNA synthesis using the fungicides nimrod and rubigan-4 in root tips of Vicia faba L.

PubMed

Shahin, S A; el-Amoodi, K H

1991-11-01

The 2 fungicides nimrod and rubigan-4 were tested for genotoxicity using Vicia faba root tips as the biological test system. Treating lateral roots with different concentrations of each fungicide for different periods showed that both fungicides were able to produce numerical but not structural chromosomal aberrations. The percentage of total aberrations in root tips exposed to nimrod reached 54.39% at 250 ppm for 4 h, and 64.69% in root tips exposed to rubigan-4 at 250 ppm for 6 h. The types of numerical chromosomal aberrations produced by both fungicides included: binucleate cells, c-metaphases, sticky chromosomes, polyploid cells, and laggards. Recovery experiments for 24, 48, and 96 h showed no significant differences between the percentage of total aberrations in treated and control groups.

Automated optimal coordination of multiple-DOF neuromuscular actions in feedforward neuroprostheses.

PubMed

Lujan, J Luis; Crago, Patrick E

2009-01-01

This paper describes a new method for designing feedforward controllers for multiple-muscle, multiple-DOF, motor system neural prostheses. The design process is based on experimental measurement of the forward input/output properties of the neuromechanical system and numerical optimization of stimulation patterns to meet muscle coactivation criteria, thus resolving the muscle redundancy (i.e., overcontrol) and the coupled DOF problems inherent in neuromechanical systems. We designed feedforward controllers to control the isometric forces at the tip of the thumb in two directions during stimulation of three thumb muscles as a model system. We tested the method experimentally in ten able-bodied individuals and one patient with spinal cord injury. Good control of isometric force in both DOFs was observed, with rms errors less than 10% of the force range in seven experiments and statistically significant correlations between the actual and target forces in all ten experiments. Systematic bias and slope errors were observed in a few experiments, likely due to the neuromuscular fatigue. Overall, the tests demonstrated the ability of a general design approach to satisfy both control and coactivation criteria in multiple-muscle, multiple-axis neuromechanical systems, which is applicable to a wide range of neuromechanical systems and stimulation electrodes.

Analyses of internal tides generation and propagation over a Gaussian ridge in laboratory and numerical experiments

NASA Astrophysics Data System (ADS)

Dossmann, Yvan; Paci, Alexandre; Auclair, Francis; Floor, Jochem

2010-05-01

Internal tides are suggested to play a major role in the sustaining of the global oceanic circulation [1][5]. Although the exact origin of the energy conversions occurring in stratified fluids is questioned [2], it is clear that the diapycnal energy transfers provided by the energy cascade of internal gravity waves generated at tidal frequencies in regions of steep bathymetry is strongly linked to the general circulation energy balance. Therefore a precise quantification of the energy supply by internal waves is a crucial step in forecasting climate, since it improves our understanding of the underlying physical processes. We focus on an academic case of internal waves generated over an oceanic ridge in a linearly stratified fluid. In order to accurately quantify the diapycnal energy transfers caused by internal waves dynamics, we adopt a complementary approach involving both laboratory and numerical experiments. The laboratory experiments are conducted in a 4m long tank of the CNRM-GAME fluid mechanics laboratory, well known for its large stratified water flume (e.g. Knigge et al [3]). The horizontal oscillation at precisely controlled frequency of a Gaussian ridge immersed in a linearly stratified fluid generates internal gravity waves. The ridge of e-folding width 3.6 cm is 10 cm high and spans 50 cm. We use PIV and Synthetic Schlieren measurement techniques, to retrieve the high resolution velocity and stratification anomaly fields in the 2D vertical plane across the ridge. These experiments allow us to get access to real and exhaustive measurements of a wide range of internal waves regimes by varying the precisely controlled experimental parameters. To complete this work, we carry out some direct numerical simulations with the same parameters (forcing amplitude and frequency, initial stratification, boundary conditions) as the laboratory experiments. The model used is a non-hydrostatic version of the numerical model Symphonie [4]. Our purpose is not only to test the dynamics and energetics of the numerical model, but also to advance the analysis based on combined wavelet and empirical orthogonal function. In particular, we focus on the study of the transient regime of internal wave generation near the ridge. Our analyses of the experimental fields show that, for fixed background stratification and topography, the evolution of the stratification anomaly strongly depends on the forcing frequency. The duration of the transient regime, as well as the amplitude reached in the stationary state vary significantly with the parameter ω/N (where ω is the forcing frequency, and N is the background Brunt-Väisälä frequency). We also observe that, for particular forcing frequencies, for which the ridge slope matches the critical slope of the first harmonic mode, internal waves are excited both at the fundamental and the first harmonic frequency. Associated energy transfers are finally evaluated both experimentally and numerically, enabling us to highlight the similarities and discrepancies between the laboratory experiments and the numerical simulations. References [1] Munk W. and C. Wunsch (1998): Abyssal recipes II: energetics of tidal and wind mixing Deep-Sea Res. 45, 1977-2010 [2] Tailleux R. (2009): On the energetics of stratified turbulent mixing, irreversible thermodynamics, Boussinesq models and the ocean heat engine controversy, J. Fluid Mech. 638, 339-382 [3] Knigge C., D. Etling, A. Paci and O. Eiff (2010): Laboratory experiments on mountain-induced rotors, Quarterly Journal of the Royal Meteorological Society, in press. [4] Auclair F., C. Estournel, J. Floor, C. N'Guyen and P. Marsaleix, (2009): A non-hydrostatic, energy conserving algorithm for regional ocean modelling. Under revision. [5] Wunsch, C. & R. Ferrari (2004): Vertical mixing, energy and the general circulation of the oceans. Annu. Rev. Fluid Mech., 36:281-314.

Numerical Modeling of Arsenic Mobility during Reductive Iron-Mineral Transformations.

PubMed

Rawson, Joey; Prommer, Henning; Siade, Adam; Carr, Jackson; Berg, Michael; Davis, James A; Fendorf, Scott

2016-03-01

Millions of individuals worldwide are chronically exposed to hazardous concentrations of arsenic from contaminated drinking water. Despite massive efforts toward understanding the extent and underlying geochemical processes of the problem, numerical modeling and reliable predictions of future arsenic behavior remain a significant challenge. One of the key knowledge gaps concerns a refined understanding of the mechanisms that underlie arsenic mobilization, particularly under the onset of anaerobic conditions, and the quantification of the factors that affect this process. In this study, we focus on the development and testing of appropriate conceptual and numerical model approaches to represent and quantify the reductive dissolution of iron oxides, the concomitant release of sorbed arsenic, and the role of iron-mineral transformations. The initial model development in this study was guided by data and hypothesized processes from a previously reported,1 well-controlled column experiment in which arsenic desorption from ferrihydrite coated sands by variable loads of organic carbon was investigated. Using the measured data as constraints, we provide a quantitative interpretation of the processes controlling arsenic mobility during the microbial reductive transformation of iron oxides. Our analysis suggests that the observed arsenic behavior is primarily controlled by a combination of reductive dissolution of ferrihydrite, arsenic incorporation into or co-precipitation with freshly transformed iron minerals, and partial arsenic redox transformations.

Feasibility study for a Cryogenic On-Orbit Liquid Depot-Storage, Acquisition and Transfer (COLD-SAT) satellite

NASA Technical Reports Server (NTRS)

Rybak, S. C.; Willen, G. S.; Follett, W. H.; Hanna, G. J.; Cady, E. C.; Distefano, E.; Meserole, J. S.

1990-01-01

This feasibility study presents the conceptual design of a spacecraft for performing a series of cryogenic fluid management flight experiments. This spacecraft, the Cryogenic On-Orbit Liquid Depot-Storage, Acquisition, and Transfer (COLD-SAT) satellite, will use liquid hydrogen as the test fluid, be launched on a Delta expendable launch vehicle, and conduct a series of experiments over a two to three month period. These experiments will investigate the physics of subcritical cryogens in the low gravity space environment to characterize their behavior and to correlate the data with analytical and numerical models of in-space cryogenic fluid management systems. Primary technologies addressed by COLD-SAT are: (1) pressure control; (2) chilldown; (3) no-vent fill; (4) liquid acquisition device fill; (5) pressurization; (6) low-g fill and drain; (7) liquid acquisition device expulsion; (8) line chilldown; (9) thermodynamic state control; and (10) fluid dumping.

Numerical simulation and experimental validation of the dynamics of multiple bubble merger during pool boiling under microgravity conditions.

PubMed

Abarajith, H S; Dhir, V K; Warrier, G; Son, G

2004-11-01

Numerical simulation and experimental validation of the growth and departure of multiple merging bubbles and associated heat transfer on a horizontal heated surface during pool boiling under variable gravity conditions have been performed. A finite difference scheme is used to solve the equations governing mass, momentum, and energy in the vapor liquid phases. The vapor-liquid interface is captured by a level set method that is modified to include the influence of phase change at the liquid-vapor interface. Water is used as test liquid. The effects of reduced gravity condition and orientation of the bubbles on the bubble diameter, interfacial structure, bubble merger time, and departure time, as well as local heat fluxes, are studied. In the experiments, multiple vapor bubbles are produced on artificial cavities in the 2-10 micrometer diameter range, microfabricated on the polished silicon wafer with given spacing. The wafer was heated electrically from the back with miniature strain gage type heating elements in order to control the nucleation superheat. The experiments conducted in normal Earth gravity and in the low gravity environment of KC-135 aircraft are used to validate the numerical simulations.

Numerical analysis and experiment research on fluid orbital performance of vane type propellant management device

NASA Astrophysics Data System (ADS)

Hu, Q.; Li, Y.; Pan, H. L.; Liu, J. T.; Zhuang, B. T.

2015-01-01

Vane type propellant management device (PMD) is one of the key components of the vane-type surface tension tank (STT), and its fluid orbital performance directly determines the STT's success or failure. In present paper, numerical analysis and microgravity experiment study on fluid orbital performance of a vane type PMD were carried out. By using two-phase flow model of volume of fluid (VOF), fluid flow characteristics in the tank with the vane type PMD were numerically calculated, and the rules of fluid transfer and distribution were gotten. A abbreviate model test system of the vane type PMD is established and microgravity drop tower tests were performed, then fluid management and transmission rules of the vane type PMD were obtained under microgravity environment. The analysis and tests results show that the vane type PMD has good and initiative fluid orbital management ability and meets the demands of fluid orbital extrusion in the vane type STT. The results offer valuable guidance for the design and optimization of the new generation of vane type PMD, and also provide a new approach for fluid management and control in space environment.

Coupled numerical modeling of gas hydrates bearing sediments from laboratory to field-scale conditions

NASA Astrophysics Data System (ADS)

Sanchez, M. J.; Santamarina, C.; Gai, X., Sr.; Teymouri, M., Sr.

2017-12-01

Stability and behavior of Hydrate Bearing Sediments (HBS) are characterized by the metastable character of the gas hydrate structure which strongly depends on thermo-hydro-chemo-mechanical (THCM) actions. Hydrate formation, dissociation and methane production from hydrate bearing sediments are coupled THCM processes that involve, amongst other, exothermic formation and endothermic dissociation of hydrate and ice phases, mixed fluid flow and large changes in fluid pressure. The analysis of available data from past field and laboratory experiments, and the optimization of future field production studies require a formal and robust numerical framework able to capture the very complex behavior of this type of soil. A comprehensive fully coupled THCM formulation has been developed and implemented into a finite element code to tackle problems involving gas hydrates sediments. Special attention is paid to the geomechanical behavior of HBS, and particularly to their response upon hydrate dissociation under loading. The numerical framework has been validated against recent experiments conducted under controlled conditions in the laboratory that challenge the proposed approach and highlight the complex interaction among THCM processes in HBS. The performance of the models in these case studies is highly satisfactory. Finally, the numerical code is applied to analyze the behavior of gas hydrate soils under field-scale conditions exploring different features of material behavior under possible reservoir conditions.

Numerical cognition is resilient to dramatic changes in early sensory experience.

PubMed

Kanjlia, Shipra; Feigenson, Lisa; Bedny, Marina

2018-06-20

Humans and non-human animals can approximate large visual quantities without counting. The approximate number representations underlying this ability are noisy, with the amount of noise proportional to the quantity being represented. Numerate humans also have access to a separate system for representing exact quantities using number symbols and words; it is this second, exact system that supports most of formal mathematics. Although numerical approximation abilities and symbolic number abilities are distinct in representational format and in their phylogenetic and ontogenetic histories, they appear to be linked throughout development--individuals who can more precisely discriminate quantities without counting are better at math. The origins of this relationship are debated. On the one hand, symbolic number abilities may be directly linked to, perhaps even rooted in, numerical approximation abilities. On the other hand, the relationship between the two systems may simply reflect their independent relationships with visual abilities. To test this possibility, we asked whether approximate number and symbolic math abilities are linked in congenitally blind individuals who have never experienced visual sets or used visual strategies to learn math. Congenitally blind and blind-folded sighted participants completed an auditory numerical approximation task, as well as a symbolic arithmetic task and non-math control tasks. We found that the precision of approximate number representations was identical across congenitally blind and sighted groups, suggesting that the development of the Approximate Number System (ANS) does not depend on visual experience. Crucially, the relationship between numerical approximation and symbolic math abilities is preserved in congenitally blind individuals. These data support the idea that the Approximate Number System and symbolic number abilities are intrinsically linked, rather than indirectly linked through visual abilities. Copyright © 2018. Published by Elsevier B.V.

Real-time 2D spatially selective MRI experiments: Comparative analysis of optimal control design methods

NASA Astrophysics Data System (ADS)

Maximov, Ivan I.; Vinding, Mads S.; Tse, Desmond H. Y.; Nielsen, Niels Chr.; Shah, N. Jon

2015-05-01

There is an increasing need for development of advanced radio-frequency (RF) pulse techniques in modern magnetic resonance imaging (MRI) systems driven by recent advancements in ultra-high magnetic field systems, new parallel transmit/receive coil designs, and accessible powerful computational facilities. 2D spatially selective RF pulses are an example of advanced pulses that have many applications of clinical relevance, e.g., reduced field of view imaging, and MR spectroscopy. The 2D spatially selective RF pulses are mostly generated and optimised with numerical methods that can handle vast controls and multiple constraints. With this study we aim at demonstrating that numerical, optimal control (OC) algorithms are efficient for the design of 2D spatially selective MRI experiments, when robustness towards e.g. field inhomogeneity is in focus. We have chosen three popular OC algorithms; two which are gradient-based, concurrent methods using first- and second-order derivatives, respectively; and a third that belongs to the sequential, monotonically convergent family. We used two experimental models: a water phantom, and an in vivo human head. Taking into consideration the challenging experimental setup, our analysis suggests the use of the sequential, monotonic approach and the second-order gradient-based approach as computational speed, experimental robustness, and image quality is key. All algorithms used in this work were implemented in the MATLAB environment and are freely available to the MRI community.

Microgravity vibration isolation: Optimal preview and feedback control

NASA Technical Reports Server (NTRS)

Hampton, R. D.; Knospe, C. R.; Grodsinsky, C. M.; Allaire, P. E.; Lewis, D. W.

1992-01-01

In order to achieve adequate low-frequency vibration isolation for certain space experiments an active control is needed, due to inherent passive-isolator limitations. Proposed here are five possible state-space models for a one-dimensional vibration isolation system with a quadratic performance index. The five models are subsets of a general set of nonhomogeneous state space equations which includes disturbance terms. An optimal control is determined, using a differential equations approach, for this class of problems. This control is expressed in terms of constant, Linear Quadratic Regulator (LQR) feedback gains and constant feedforward (preview) gains. The gains can be easily determined numerically. They result in a robust controller and offers substantial improvements over a control that uses standard LQR feedback alone.

Visualization of flow separation and control by vortex generators on an single flap in landing configuration

NASA Astrophysics Data System (ADS)

Součková, Natálie; Kuklová, Jana; Popelka, Lukáš; Matějka, Milan

2012-04-01

This paper focuses on a suppression of the flow separation, which occurs on a deflected flap, by means of vortex generators (VG's). An airfoil NACA 63A421 with a simple flap and vane-type vortex generators were used. The investigation was carried out by using experimental and numerical methods. The data from the numerical simulation of the flapped airfoil without VG's control were used for the vortex generator design. Two sizes, two different shapes and various spacing of the vortex generators were tested. The flow past the airfoil was visualized through three methods, namely tuft filaments technique, oil and thermo camera visualization. The experiments were performed in closed circuit wind tunnels with closed and open test sections. The lift curves for both cases without and with vortex generators were acquired for a lift coefficient improvement determination. The improvement was achieved for several cases by means all of the applied methods.

Optical Sensor/Actuator Locations for Active Structural Acoustic Control

NASA Technical Reports Server (NTRS)

Padula, Sharon L.; Palumbo, Daniel L.; Kincaid, Rex K.

1998-01-01

Researchers at NASA Langley Research Center have extensive experience using active structural acoustic control (ASAC) for aircraft interior noise reduction. One aspect of ASAC involves the selection of optimum locations for microphone sensors and force actuators. This paper explains the importance of sensor/actuator selection, reviews optimization techniques, and summarizes experimental and numerical results. Three combinatorial optimization problems are described. Two involve the determination of the number and position of piezoelectric actuators, and the other involves the determination of the number and location of the sensors. For each case, a solution method is suggested, and typical results are examined. The first case, a simplified problem with simulated data, is used to illustrate the method. The second and third cases are more representative of the potential of the method and use measured data. The three case studies and laboratory test results establish the usefulness of the numerical methods.

Performance Evaluation of UHF RFID Technologies for Real-Time Bus Recognition in the Taipei Bus Station

PubMed Central

Own, Chung-Ming; Lee, Da-Sheng; Wang, Ti-Ho; Wang, De-Jun; Ting, Yu-Lun

2013-01-01

Transport stations such as airports, ports, and railways have adopted blocked-type pathway management to process and control travel systems in a one-directional manner. However, this excludes highway transportation where large buses have great variability and mobility; thus, an instant influx of numerous buses increases risks and complicates station management. Focusing on Taipei Bus Station, this study employed RFID technology to develop a system platform integrated with modern information technology that has numerous characteristics. This modern information technology comprised the following systems: ultra-high frequency (UHF) radio-frequency identification (RFID), ultrasound and license number identification, and backstage graphic controls. In conclusion, the system enabled management, bus companies, and passengers to experience the national bus station's new generation technology, which provides diverse information and synchronization functions. Furthermore, this technology reached a new milestone in the energy-saving and efficiency-increasing performance of Taiwan's buses. PMID:23778192

Music Listening Among Postoperative Patients in the Intensive Care Unit: A Randomized Controlled Trial with Mixed-Methods Analysis

PubMed Central

Ames, Nancy; Shuford, Rebecca; Yang, Li; Moriyama, Brad; Frey, Meredith; Wilson, Florencia; Sundaramurthi, Thiruppavai; Gori, Danelle; Mannes, Andrew; Ranucci, Alexandra; Koziol, Deloris; Wallen, Gwenyth R

2017-01-01

Background: Music listening may reduce the physiological, emotional, and mental effects of distress and anxiety. It is unclear whether music listening may reduce the amount of opioids used for pain management in critical care, postoperative patients or whether music may improve patient experience in the intensive care unit (ICU). Methods: A total of 41 surgical patients were randomized to either music listening or controlled non-music listening groups on ICU admission. Approximately 50-minute music listening interventions were offered 4 times per day (every 4-6 hours) during the 48 hours of patients’ ICU stays. Pain, distress, and anxiety scores were measured immediately before and after music listening or controlled resting periods. Total opioid intake was recorded every 24 hours and during each intervention. Results: There was no significant difference in pain, opioid intake, distress, or anxiety scores between the control and music listening groups during the first 4 time points of the study. However, a mixed modeling analysis examining the pre- and post-intervention scores at the first time point revealed a significant interaction in the Numeric Rating Scale (NRS) for pain between the music and the control groups (P = .037). The Numeric Rating Score decreased in the music group but remained stable in the control group. Following discharge from the ICU, the music group’s interviews were analyzed for themes. Conclusions: Despite the limited sample size, this study identified music listening as an appropriate intervention that improved patients’ post-intervention experience, according to patients’ self-report. Future mixed methods studies are needed to examine both qualitative patient perspectives and methodology to improve music listening in critical care units. PMID:28904523

Testing a model of componential processing of multi-symbol numbers-evidence from measurement units.

PubMed

Huber, Stefan; Bahnmueller, Julia; Klein, Elise; Moeller, Korbinian

2015-10-01

Research on numerical cognition has addressed the processing of nonsymbolic quantities and symbolic digits extensively. However, magnitude processing of measurement units is still a neglected topic in numerical cognition research. Hence, we investigated the processing of measurement units to evaluate whether typical effects of multi-digit number processing such as the compatibility effect, the string length congruity effect, and the distance effect are also present for measurement units. In three experiments, participants had to single out the larger one of two physical quantities (e.g., lengths). In Experiment 1, the compatibility of number and measurement unit (compatible: 3 mm_6 cm with 3 < 6 and mm < cm; incompatible: 3 cm_6 mm with 3 < 6 but cm > mm) as well as string length congruity (congruent: 1 m_2 km with m < km and 2 < 3 characters; incongruent: 2 mm_1 m with mm < m, but 3 > 2 characters) were manipulated. We observed reliable compatibility effects with prolonged reaction times (RT) for incompatible trials. Moreover, a string length congruity effect was present in RT with longer RT for incongruent trials. Experiments 2 and 3 served as control experiments showing that compatibility effects persist when controlling for holistic distance and that a distance effect for measurement units exists. Our findings indicate that numbers and measurement units are processed in a componential manner and thus highlight that processing characteristics of multi-digit numbers generalize to measurement units. Thereby, our data lend further support to the recently proposed generalized model of componential multi-symbol number processing.

Benchmarking computational fluid dynamics models of lava flow simulation for hazard assessment, forecasting, and risk management

USGS Publications Warehouse

Dietterich, Hannah; Lev, Einat; Chen, Jiangzhi; Richardson, Jacob A.; Cashman, Katharine V.

2017-01-01

Numerical simulations of lava flow emplacement are valuable for assessing lava flow hazards, forecasting active flows, designing flow mitigation measures, interpreting past eruptions, and understanding the controls on lava flow behavior. Existing lava flow models vary in simplifying assumptions, physics, dimensionality, and the degree to which they have been validated against analytical solutions, experiments, and natural observations. In order to assess existing models and guide the development of new codes, we conduct a benchmarking study of computational fluid dynamics (CFD) models for lava flow emplacement, including VolcFlow, OpenFOAM, FLOW-3D, COMSOL, and MOLASSES. We model viscous, cooling, and solidifying flows over horizontal planes, sloping surfaces, and into topographic obstacles. We compare model results to physical observations made during well-controlled analogue and molten basalt experiments, and to analytical theory when available. Overall, the models accurately simulate viscous flow with some variability in flow thickness where flows intersect obstacles. OpenFOAM, COMSOL, and FLOW-3D can each reproduce experimental measurements of cooling viscous flows, and OpenFOAM and FLOW-3D simulations with temperature-dependent rheology match results from molten basalt experiments. We assess the goodness-of-fit of the simulation results and the computational cost. Our results guide the selection of numerical simulation codes for different applications, including inferring emplacement conditions of past lava flows, modeling the temporal evolution of ongoing flows during eruption, and probabilistic assessment of lava flow hazard prior to eruption. Finally, we outline potential experiments and desired key observational data from future flows that would extend existing benchmarking data sets.

Wave-filter-based approach for generation of a quiet space in a rectangular cavity

NASA Astrophysics Data System (ADS)

Iwamoto, Hiroyuki; Tanaka, Nobuo; Sanada, Akira

2018-02-01

This paper is concerned with the generation of a quiet space in a rectangular cavity using active wave control methodology. It is the purpose of this paper to present the wave filtering method for a rectangular cavity using multiple microphones and its application to an adaptive feedforward control system. Firstly, the transfer matrix method is introduced for describing the wave dynamics of the sound field, and then feedforward control laws for eliminating transmitted waves is derived. Furthermore, some numerical simulations are conducted that show the best possible result of active wave control. This is followed by the derivation of the wave filtering equations that indicates the structure of the wave filter. It is clarified that the wave filter consists of three portions; modal group filter, rearrangement filter and wave decomposition filter. Next, from a numerical point of view, the accuracy of the wave decomposition filter which is expressed as a function of frequency is investigated using condition numbers. Finally, an experiment on the adaptive feedforward control system using the wave filter is carried out, demonstrating that a quiet space is generated in the target space by the proposed method.

An event-based vibration control for a two-link flexible robotic arm: Numerical and experimental observations

NASA Astrophysics Data System (ADS)

Özer, Abdullah; Eren Semercigil, S.

2008-06-01

Flexible robot manipulators have numerous advantages over their rigid counterparts. They have increased payload-to-weight ratio, they run at higher speeds, use less energy and smaller actuators, and they are safer during interaction with their environments. On the other hand, light design combined with external effects result in components which can oscillate with excessive amplitudes. These oscillations cause deviation from the desired path and long idle periods between tasks in order to perform the intended operation safely and accurately. This paper is on an investigation into the effectiveness of a vibration control technique for a two-link flexible robotic arm. Variable stiffness control (VSC) technique is used to control the excessive oscillations. Owing to its dissipative nature, the technique is stable, it is relatively insensitive to significant parameter changes and suitable to be implemented on existing robots. This research considers that the source of the flexibility is either the joints or the links or both. Simulation results of the response of the arm are presented to show the versatility of the proposed control technique. Experiments are performed on a laboratory prototype and the results are presented to test the validity of simulations.

A study for bank effect on ship traffic in narrow water channels using cellular automata

NASA Astrophysics Data System (ADS)

Sun, Zhuo; Cong, Shuang; Pan, Junnan; Zheng, Jianfeng

2017-12-01

In narrow water channels, bank might affect nearby ships due to hydrodynamic forces (bank effect). To avoid accidents, different sailing rules (i.e., lane-changing, speed control) are required. In this paper, a two-lane cellular automata model is proposed to evaluate such phenomena. Numerical experiments show that ships will form a “slow-moving chunk” in the bank area, which will significantly block the flux. As further study demonstrated to alleviate bank effect, ship speed and bank length should be controlled.

Semi-Numerical Studies of the Three-Meter Spherical Couette Experiment Utilizing Data Assimilation

NASA Astrophysics Data System (ADS)

Burnett, S. C.; Rojas, R.; Perevalov, A.; Lathrop, D. P.

2017-12-01

The model of the Earth's magnetic field has been investigated in recent years through experiments and numerical models. At the University of Maryland, experimental studies are implemented in a three-meter spherical Couette device filled with liquid sodium. The inner and outer spheres of this apparatus mimic the planet's inner core and core-mantle boundary, respectively. These experiments incorporate high velocity flows with Reynolds numbers 108. In spherical Couette geometry, the numerical scheme applied to this work features finite difference methods in the radial direction and pseudospectral spherical harmonic transforms elsewhere [Schaeffer, N. G3 (2013)]. Adding to the numerical model, data assimilation integrates the experimental outer-layer magnetic field measurements. This semi-numerical model can then be compared to the experimental results as well as forecasting magnetic field changes. Data assimilation makes it possible to get estimates of internal motions of the three-meter experiment that would otherwise be intrusive or impossible to obtain in experiments or too computationally expensive with a purely numerical code. If we can provide accurate models of the three-meter device, it is possible to attempt to model the geomagnetic field. We gratefully acknowledge the support of NSF Grant No. EAR1417148 & DGE1322106.

Semi-Numerical Studies of the Three-Meter Spherical Couette Experiment Utilizing Data Assimilation

NASA Astrophysics Data System (ADS)

Burnett, Sarah; Rojas, Ruben; Perevalov, Artur; Lathrop, Daniel; Ide, Kayo; Schaeffer, Nathanael

2017-11-01

The model of the Earth's magnetic field has been investigated in recent years through experiments and numerical models. At the University of Maryland, experimental studies are implemented in a three-meter spherical Couette device filled with liquid sodium. The inner and outer spheres of this apparatus mimic the planet's inner core and core-mantle boundary, respectively. These experiments incorporate high velocity flows with Reynolds numbers 108 . In spherical Couette geometry, the numerical scheme applied to this work features finite difference methods in the radial direction and pseudospectral spherical harmonic transforms elsewhere. Adding to the numerical model, data assimilation integrates the experimental outer-layer magnetic field measurements. This semi-numerical model can then be compared to the experimental results as well as forecasting magnetic field changes. Data assimilation makes it possible to get estimates of internal motions of the three-meter experiment that would otherwise be intrusive or impossible to obtain in experiments or too computationally expensive with a purely numerical code. If we can provide accurate models of the three-meter device, it is possible to attempt to model the geomagnetic field. We gratefully acknowledge the support of NSF Grant No. EAR1417148 & DGE1322106.

Cross-format physical similarity effects and their implications for the numerical cognition architecture

PubMed Central

Cohen, Dale J.; Warren, Erin; Blanc-Goldhammer, Daryn

2013-01-01

The sound |faiv| is visually depicted as a written number word “five” and as an Arabic digit “5.” Here, we present four experiments – two quantity same/different experiments and two magnitude comparison experiments – that assess whether auditory number words (|faiv|), written number words (“five”), and Arabic digits (“5”) directly activate one another and/or their associated quantity. The quantity same/different experiments reveal that the auditory number words, written number words, and Arabic digits directly activate one another without activating their associated quantity. That is, there are cross-format physical similarity effects but no numerical distance effects. The cross-format magnitude comparison experiments reveal significant effects of both physical similarity and numerical distance. We discuss these results in relation to the architecture of numerical cognition. PMID:23624377

Are Arabic and Verbal Numbers Processed in Different Ways?

ERIC Educational Resources Information Center

Kadosh, Roi Cohen; Henik, Avishai; Rubinsten, Orly

2008-01-01

Four experiments were conducted in order to examine effects of notation--Arabic and verbal numbers--on relevant and irrelevant numerical processing. In Experiment 1, notation interacted with the numerical distance effect, and irrelevant physical size affected numerical processing (i.e., size congruity effect) for both notations but to a lesser…

Control of twisted and coiled polymer actuator with anti-windup compensator

NASA Astrophysics Data System (ADS)

Suzuki, Motoya; Kamamichi, Norihiro

2018-07-01

A twisted and coiled polymer actuator (TCPA) is a novel soft actuator. It is fabricated by twisting nylon thread or fishing line. It can be thermally activated and has remarkable properties such as high power/mass ratio and large deformation. By applying conductive nylon fibers to the actuator, it can be electrically driven by Joule heating. However, if a controller of the actuator is designed without considering an input saturation, the control performance may be descended by windup phenomena. In this paper, to solve this problem, a feedback control with an anti-windup compensator is applied. The validity of the applied method is investigated through numerical simulations and experiments.

Feedback control for manipulating magnetization in spin-exchange optical pumping system

NASA Astrophysics Data System (ADS)

Zhang, Ke; Li, Jun; Jiang, Min; Zhao, Nan; Peng, XinHua

2018-08-01

Control of magnetization plays an important role in the scientific and technological field of manipulating spin systems. In this work, we study the problem of manipulating nuclear magnetization in the spin-exchange optical pumping system, including accelerating the recovery of nuclear polarization and fixing it on a specific desired state. A real-time feedback control strategy is exploited here. We have also done some numerical simulations, with the results clearly demonstrating the effectiveness of our method, that the nuclear magnetization is able to be driven towards the equilibrium state at a much faster speed and also can be stabilized to a target state. We expect that our feedback control method can find applications in gyro experiments.

Integrated Controls-Structures Design Methodology for Flexible Spacecraft

NASA Technical Reports Server (NTRS)

Maghami, P. G.; Joshi, S. M.; Price, D. B.

1995-01-01

This paper proposes an approach for the design of flexible spacecraft, wherein the structural design and the control system design are performed simultaneously. The integrated design problem is posed as an optimization problem in which both the structural parameters and the control system parameters constitute the design variables, which are used to optimize a common objective function, thereby resulting in an optimal overall design. The approach is demonstrated by application to the integrated design of a geostationary platform, and to a ground-based flexible structure experiment. The numerical results obtained indicate that the integrated design approach generally yields spacecraft designs that are substantially superior to the conventional approach, wherein the structural design and control design are performed sequentially.

Simulations of Control Schemes for Inductively Coupled Plasma Sources

NASA Astrophysics Data System (ADS)

Ventzek, P. L. G.; Oda, A.; Shon, J. W.; Vitello, P.

1997-10-01

Process control issues are becoming increasingly important in plasma etching. Numerical experiments are an excellent test-bench for evaluating a proposed control system. Models are generally reliable enough to provide information about controller robustness, fitness of diagnostics. We will present results from a two dimensional plasma transport code with a multi-species plasma chemstry obtained from a global model. [1-2] We will show a correlation of external etch parameters (e.g. input power) with internal plasma parameters (e.g. species fluxes) which in turn are correlated with etch results (etch rate, uniformity, and selectivity) either by comparison to experiment or by using a phenomenological etch model. After process characterization, a control scheme can be evaluated since the relationship between the variable to be controlled (e.g. uniformity) is related to the measurable variable (e.g. a density) and external parameter (e.g. coil current). We will present an evaluation using the HBr-Cl2 system as an example. [1] E. Meeks and J. W. Shon, IEEE Trans. on Plasma Sci., 23, 539, 1995. [2] P. Vitello, et al., IEEE Trans. on Plasma Sci., 24, 123, 1996.

Machine Shop. Module 8: CNC (Computerized Numerical Control). Instructor's Guide.

ERIC Educational Resources Information Center

Crosswhite, Dwight

This document consists of materials for a five-unit course on the following topics: (1) safety guidelines; (2) coordinates and dimensions; (3) numerical control math; (4) programming for numerical control machines; and (5) setting and operating the numerical control machine. The instructor's guide begins with a list of competencies covered in the…

Experimental, Numerical, and Analytical Slosh Dynamics of Water and Liquid Nitrogen in a Spherical Tank

NASA Technical Reports Server (NTRS)

Storey, Jedediah Morse

2016-01-01

Understanding, predicting, and controlling fluid slosh dynamics is critical to safety and improving performance of space missions when a significant percentage of the spacecraft's mass is a liquid. Computational fluid dynamics simulations can be used to predict the dynamics of slosh, but these programs require extensive validation. Many experimental and numerical studies of water slosh have been conducted. However, slosh data for cryogenic liquids is lacking. Water and cryogenic liquid nitrogen are used in various ground-based tests with a spherical tank to characterize damping, slosh mode frequencies, and slosh forces. A single ring baffle is installed in the tank for some of the tests. Analytical models for slosh modes, slosh forces, and baffle damping are constructed based on prior work. Select experiments are simulated using a commercial CFD software, and the numerical results are compared to the analytical and experimental results for the purposes of validation and methodology-improvement.

Vortex developments over steady and accelerated airfoils incorporating a trailing edge jet

NASA Technical Reports Server (NTRS)

Finaish, F.; Okong'o, N.; Frigerio, J.

1993-01-01

Computational and experimental studies are conducted to investigate the influence of a trailing edge jet on flow separation and subsequent vortex formation over steady and accelerated airfoils at high angles of attack. A computer code, employing the stream function-vorticity approach, is developed and utilized to conduct numerical experiments on the flow problem. To verify and economize such efforts, an experimental system is developed and incorporated into a subsonic wind tunnel where streamline and vortex flow visualization experiments are conducted. The study demonstrates the role of the trailing edge jet in controlling flow separation and subsequent vortex development for steady and accelerating flow at angles past the static stall angle of attack. The results suggest that the concept of the trailing edge jet may be utilized to control the characteristics of unsteady separated flows over lifting surfaces. This control possibility seems to be quite effective and could have a significant role in controlling unsteady separated flows.

Anticipated Effectiveness of Active Noise Control in Propeller Aircraft Interiors as Determined by Sound Quality Tests

NASA Technical Reports Server (NTRS)

Powell, Clemans A.; Sullivan, Brenda M.

2004-01-01

Two experiments were conducted, using sound quality engineering practices, to determine the subjective effectiveness of hypothetical active noise control systems in a range of propeller aircraft. The two tests differed by the type of judgments made by the subjects: pair comparisons in the first test and numerical category scaling in the second. Although the results of the two tests were in general agreement that the hypothetical active control measures improved the interior noise environments, the pair comparison method appears to be more sensitive to subtle changes in the characteristics of the sounds which are related to passenger preference.

Aerodynamic design of the contoured wind-tunnel liner for the NASA supercritical, laminar-flow-control, swept-wing experiment

NASA Technical Reports Server (NTRS)

Newman, P. A.; Anderson, E. C.; Peterson, J. B., Jr.

1984-01-01

An overview is presented of the entire procedure developed for the aerodynamic design of the contoured wind tunnel liner for the NASA supercritical, laminar flow control (LFC), swept wing experiment. This numerical design procedure is based upon the simple idea of streamlining and incorporates several transonic and boundary layer analysis codes. The liner, presently installed in the Langley 8 Foot Transonic Pressure Tunnel, is about 54 ft long and extends from within the existing contraction cone, through the test section, and into the diffuser. LFC model testing has begun and preliminary results indicate that the liner is performing as intended. The liner design results presented in this paper, however, are examples of the calculated requirements and the hardware implementation of them.

Guidance and Control of a Small Unmanned Aerial Vehicle and Autonomous Flight Experiments

NASA Astrophysics Data System (ADS)

Fujinaga, Jin; Tokutake, Hiroshi; Sunada, Shigeru

This paper describes the development of a fixed-wing small-size UAV and the design of its flight controllers. The developed UAV’s wing span is 0.6m, and gross weight is 0.27kg. In order to ensure robust performances of the longitudinal and lateral-directional motions of the UAV, flight controllers are designed for these motions with μ-synthesis. Numerical simulations show that the designed controllers attain good robust stabilities and performances, and have good tracking performance for command. After an order-reduction and discretization, the designed flight controllers were implemented in the UAV. A flight test was performed, and the ability of the UAV to fly autonomously, passing over waypoints, was demonstrated.

Numerical simulation of temperature and pressure fields in CdTe growth experiment in the Material Science Laboratory (MSL) onboard the International Space Station in relation to dewetting

NASA Astrophysics Data System (ADS)

Sylla, Lamine; Duffar, Thierry

2007-05-01

A global thermal modelling of a cadmium telluride (CdTe) space experiment has been performed to determine the temperature field within the sample cartridge assembly of the Material Science Laboratory-low gradient furnace (MSL-LGF) apparatus. Heat transfer and phase change have been treated with a commercial CFD software based on a control volume technique. This work underlines the difficult compromise between enhancing the crystal quality and the occurrence of the dewetting phenomenon when using a Cd overpressure or inert gas in the ampoule.

Summary of biological spaceflight experiments with cells.

PubMed

Dickson, K J

1991-07-01

Numerous biological experiments with cells have been conducted in space, and the importance of these experiments and this area of study is continually becoming evident. This contribution is a compilation of available information about spaceflight experiments with cells for the purpose of providing a single source of information for those interested in space gravitational cell biology. Experiments focused on a study of the effects of gravity and its absence on cells, cell function, and basic cellular processes have been included. Experiments include those involving viruses, bacteriophage, unicellular organisms, lower fungi, and animal and plant cell and tissue cultures, but exclude experiments with cells that were carried on a flight as part of a whole organism and later removed for study, and experiments with fertilized eggs. In addition, experiments in biotechnology, in which the microgravity environment is employed to study cell purification, cell fusion, protein crystallization, and similar processes, have not been included. Spaceflight experiments conducted by scientists from the U.S., U.S.S.R., and other countries and flown onboard sounding rockets (TEXUS, MAXUS, Consort), biosatellites (Biosatellite II, Cosmos), and various crewed spacecraft including the space shuttle (STS) and Soyuz, and space stations (Salyut, Mir) have been included, as well as high altitude balloon flights. Balloon flights are not spaceflights but can and are used as controls for the effects of space radiation, since organisms carried on balloons may be exposed to some of the same radiation as those taken into space, yet continue to be exposed to Earth's gravitational force. Parabolic flights on aircraft during which periods of microgravity of less than a minute are achieved have arbitrarily been excluded, because even though numerous experiments have been conducted, few results have been published.

Numerical Optimization Using Computer Experiments

NASA Technical Reports Server (NTRS)

Trosset, Michael W.; Torczon, Virginia

1997-01-01

Engineering design optimization often gives rise to problems in which expensive objective functions are minimized by derivative-free methods. We propose a method for solving such problems that synthesizes ideas from the numerical optimization and computer experiment literatures. Our approach relies on kriging known function values to construct a sequence of surrogate models of the objective function that are used to guide a grid search for a minimizer. Results from numerical experiments on a standard test problem are presented.

Measuring strain and rotation fields at the dislocation core in graphene

NASA Astrophysics Data System (ADS)

Bonilla, L. L.; Carpio, A.; Gong, C.; Warner, J. H.

2015-10-01

Strain fields, dislocations, and defects may be used to control electronic properties of graphene. By using advanced imaging techniques with high-resolution transmission electron microscopes, we have measured the strain and rotation fields about dislocations in monolayer graphene with single-atom sensitivity. These fields differ qualitatively from those given by conventional linear elasticity. However, atom positions calculated from two-dimensional (2D) discrete elasticity and three-dimensional discrete periodized Föppl-von Kármán equations (dpFvKEs) yield fields close to experiments when determined by geometric phase analysis. 2D theories produce symmetric fields whereas those from experiments exhibit asymmetries. Numerical solutions of dpFvKEs provide strain and rotation fields of dislocation dipoles and pairs that also exhibit asymmetries and, compared with experiments, may yield information on out-of-plane displacements of atoms. While discrete theories need to be solved numerically, analytical formulas for strains and rotation about dislocations can be obtained from 2D Mindlin's hyperstress theory. These formulas are very useful for fitting experimental data and provide a template to ascertain the importance of nonlinear and nonplanar effects. Measuring the parameters of this theory, we find two characteristic lengths between three and four times the lattice spacings that control dilatation and rotation about a dislocation. At larger distances from the dislocation core, the elastic fields decay to those of conventional elasticity. Our results may be relevant for strain engineering in graphene and other 2D materials of current interest.

Tsunami-induced morphological change of a coastal lake: comparing hydraulic experiment with numerical modeling

NASA Astrophysics Data System (ADS)

Sugawara, D.; Imai, K.; Mitobe, Y.; Takahashi, T.

2016-12-01

Coastal lakes are one of the promising environments to identify deposits of past tsunamis, and such deposits have been an important key to know the recurrence of tsunami events. In contrast to tsunami deposits on the coastal plains, however, relationship between deposit geometry and tsunami hydrodynamic character in the coastal lakes has poorly been understood. Flume experiment and numerical modeling will be important measures to clarify such relationship. In this study, data from a series of flume experiment were compared with simulations by an existing tsunami sediment transport model to examine applicability of the numerical model for tsunami-induced morphological change in a coastal lake. A coastal lake with a non-erodible beach ridge was modeled as the target geomorphology. The ridge separates the lake from the offshore part of the flume, and the lake bottom was filled by sand. Tsunami bore was generated by a dam-break flow, which is capable of generating a maximum near-bed flow speed of 2.5 m/s. Test runs with varying magnitude of the bore demonstrated that the duration of tsunami overflow controls the scouring depth of the lake bottom behind the ridge. The maximum scouring depth reached up to 7 cm, and sand deposition occurred mainly in the seaward-half of the lake. A conventional depth-averaged tsunami hydrodynamic model coupled with the sediment transport model was used to compare the simulation and experimental results. In the Simulation, scouring depth behind the ridge reached up to 6 cm. In addition, the width of the scouring was consistent between the simulation and experiment. However, sand deposition occurred mainly in a zone much far from the ridge, showing a considerable deviation from the experimental results. This may be associated with the lack of model capability to resolve some important physics, such as vortex generation behind the ridge and shoreward migration of hydraulic jump. In this presentation, the results from the flume experiment and the numerical modeling will be compared in detail, including temporal evolution of the morphological change. In addition, model applicability and future improvements will be discussed.

A Monitoring System for the LHCb Data Flow

NASA Astrophysics Data System (ADS)

Barbosa, João; Gaspar, Clara; Jost, Beat; Frank, Markus; Cardoso, Luis G.

2017-06-01

The LHCb experiment uses the LHC accelerator for the collisions that produce the physics data necessary for analysis. The data produced by the detector by measuring the results of the collisions at a rate of 40 MHz are read out by a complex data acquisition (DAQ) system, which is summarily described in this paper. Distributed systems of such dimensions rely on monitoring and control systems that account for the numerous faults that can happen throughout the whole operation. With this in mind, a new system was created to extend the monitoring of the readout system, in this case by providing an overview of what is happening in each stage of the DAQ process, starting in the hardware trigger performed right after the detector measurements and ending in the local storage of the experiment. This system, a complement to the current run control (experimental control system), intends to shorten reaction times when a problem occurs by providing the operators with detailed information of where a certain fault is occurring. The architecture of the tool and its utilization by the experiment operators are described in this paper.

High-order accurate finite-volume formulations for the pressure gradient force in layered ocean models

NASA Astrophysics Data System (ADS)

Engwirda, Darren; Kelley, Maxwell; Marshall, John

2017-08-01

Discretisation of the horizontal pressure gradient force in layered ocean models is a challenging task, with non-trivial interactions between the thermodynamics of the fluid and the geometry of the layers often leading to numerical difficulties. We present two new finite-volume schemes for the pressure gradient operator designed to address these issues. In each case, the horizontal acceleration is computed as an integration of the contact pressure force that acts along the perimeter of an associated momentum control-volume. A pair of new schemes are developed by exploring different control-volume geometries. Non-linearities in the underlying equation-of-state definitions and thermodynamic profiles are treated using a high-order accurate numerical integration framework, designed to preserve hydrostatic balance in a non-linear manner. Numerical experiments show that the new methods achieve high levels of consistency, maintaining hydrostatic and thermobaric equilibrium in the presence of strongly-sloping layer geometries, non-linear equations-of-state and non-uniform vertical stratification profiles. These results suggest that the new pressure gradient formulations may be appropriate for general circulation models that employ hybrid vertical coordinates and/or terrain-following representations.

Numerical optimization of perturbative coils for tokamaks

NASA Astrophysics Data System (ADS)

Lazerson, Samuel; Park, Jong-Kyu; Logan, Nikolas; Boozer, Allen; NSTX-U Research Team

2014-10-01

Numerical optimization of coils which apply three dimensional (3D) perturbative fields to tokamaks is presented. The application of perturbative 3D magnetic fields in tokamaks is now commonplace for control of error fields, resistive wall modes, resonant field drive, and neoclassical toroidal viscosity (NTV) torques. The design of such systems has focused on control of toroidal mode number, with coil shapes based on simple window-pane designs. In this work, a numerical optimization suite based on the STELLOPT 3D equilibrium optimization code is presented. The new code, IPECOPT, replaces the VMEC equilibrium code with the IPEC perturbed equilibrium code, and targets NTV torque by coupling to the PENT code. Fixed boundary optimizations of the 3D fields for the NSTX-U experiment are underway. Initial results suggest NTV torques can be driven by normal field spectrums which are not pitch-resonant with the magnetic field lines. Work has focused on driving core torque with n = 1 and edge torques with n = 3 fields. Optimizations of the coil currents for the planned NSTX-U NCC coils highlight the code's free boundary capability. This manuscript has been authored by Princeton University under Contract Number DE-AC02-09CH11466 with the U.S. Department of Energy.

A numerical study of the effect of geometry variation, turbulence models, and dissipation on the flow past control surfaces

NASA Technical Reports Server (NTRS)

Chaussee, Denny S.

1993-01-01

The steady 3D viscous flow past the ONERA M6 wing and a slender delta wing-body with trailing edge control surfaces has been computed. A cell-centered finite-volume Navier-Stokes patched zonal method has been used for the numerical simulation. Both diagonalized and LUSGS schemes have been implemented. Besides the standard nonplanar zonal interfacing techniques, a new virtual zone capability has been employed. For code validation, the transonic flow past the ONERA M5 wing is calculated for angles-of-attack of 3.06 deg and 5.06 deg and compared with the available experiments. The wing-body computational results are compared with experimental data for both trailing-edge flaps deflected. The experimental flow conditions are M subinfinity = 0.4, a turbulent Reynolds number of 5.41 million based on a mean aerodynamic chord of 25.959 inches, adiabatic wall, and angles-of-attack varying from 0 deg to 23.85 deg. The computational results are presented for the 23.85 deg angle-of-attack case. The effects of the base flow due to a model sting, the varying second and fourth order numerical dissipation, and the turbulence model are all considered.

Simulation of a class of hazardous situations in the ICS «INM RAS - Baltic Sea»

NASA Astrophysics Data System (ADS)

Zakharova, Natalia; Agoshkov, Valery; Aseev, Nikita; Parmuzin, Eugene; Sheloput, Tateana; Shutyaev, Victor

2017-04-01

Development of Informational Computational Systems (ICS) for data assimilation procedures is one of multidisciplinary problems. To study and solve these problems one needs to apply modern results from different disciplines and recent developments in mathematical modeling, theory of adjoint equations and optimal control, inverse problems, numerical methods theory, numerical algebra, scientific computing and processing of satellite data. In this work the results on the ICS development for PC-ICS "INM RAS - Baltic Sea" are presented. We discuss practical problems studied by ICS. The System includes numerical model of the Baltic Sea thermodynamics, the new oil spill model describing the propagation of a slick at the Sea surface (Agoshkov, Aseev et al., 2014) and the optimal ship route calculating block (Agoshkov, Zayachkovsky et al., 2014). The ICS is based on the INMOM numerical model of the Baltic Sea thermodynamics (Zalesny et al., 2013). It is possible to calculate main hydrodynamic parameters (temperature, salinity, velocities, sea level) using user-friendly interface of the ICS. The System includes data assimilation procedures (Agoshkov, 2003, Parmuzin, Agoshkov, 2012) and one can use the block of variational assimilation of the sea surface temperature in order to obtain main hydrodynamic parameters. Main possibilities of the ICS and several numerical experiments are presented in the work. By the problem of risk control is meant a problem of determination of optimal resources quantity which are necessary for decreasing the risk to some acceptable value. Mass of oil slick is chosen as a function of control. For the realization of the random variable the quadratic "functional of cost" is introduced. It comprises cleaning costs and deviation of damage of oil pollution from its acceptable value. The problem of minimization of this functional is solved based on the methods of optimal control and the theory of adjoint equations. The solution of this problem is explicitly found. The study was supported by the Russian Foundation for Basic Research (project 16-31-00510) and by the Russian Science Foundation (project №14-11-00609). V. I. Agoshkov, Methods of Optimal Control and Adjoint Equations in Problems of Mathematical Physics. INM RAS, Moscow, 2003 (in Russian). V. B. Zalesny, A. V. Gusev, V. O. Ivchenko, R. Tamsalu, and R. Aps, Numerical model of the Baltic Sea circulation. Russ. J. Numer. Anal. Math. Modelling 28 (2013), No. 1, 85-100. V.I. Agoshkov, A.O. Zayachkovskiy, R. Aps, P. Kujala, and J. Rytkönen. Risk theory based solution to the problem of optimal vessel route // Russian Journal of Numerical Analysis and Mathematical Modelling. 2014. Volume 29, Issue 2, Pages 69-78. Agoshkov, V., Aseev, N., Aps, R., Kujala, P., Rytkönen, J., Zalesny, V. The problem of control of oil pollution risk in the Baltic Sea // Russian Journal of Numerical Analysis and Mathematical Modelling. 2014. Volume 29, Issue 2, Pages 93-105. E. I. Parmuzin and V. I. Agoshkov, Numerical solution of the variational assimilation problem for sea surface temperature in the model of the Black Sea dynamics. Russ. J. Numer. Anal. Math. Modelling 27 (2012), No. 1, 69-94. Olof Liungman and Johan Mattsson. Scientic Documentation of Seatrack Web; physical processes, algorithms and references, 2011.

Dynamics of Active Separation Control at High Reynolds Numbers

NASA Technical Reports Server (NTRS)

Pack, LaTunia G.; Seifert, Avi

2000-01-01

A series of active flow control experiments were recently conducted at high Reynolds numbers on a generic separated configuration. The model simulates the upper surface of a 20% thick Glauert-Goldschmied type airfoil at zero angle of attack. The flow is fully turbulent since the tunnel sidewall boundary layer flows over the model. The main motivation for the experiments is to generate a comprehensive data base for validation of unsteady numerical simulation as a first step in the development of a CFD design tool, without which it would not be possible to effectively utilize the great potential of unsteady flow control. This paper focuses on the dynamics of several key features of the baseline as well as the controlled flow. It was found that the thickness of the upstream boundary layer has a negligible effect on the flow dynamics. It is speculated that separation is caused mainly by the highly convex surface while viscous effects are less important. The two-dimensional separated flow contains unsteady waves centered on a reduced frequency of 0.9, while in the three dimensional separated flow, frequencies around a reduced frequency of 0.3 and 1 are active. Several scenarios of resonant wave interaction take place at the separated shear-layer and in the pressure recovery region. The unstable reduced frequency bands for periodic excitation are centered on 1.5 and 5, but these reduced frequencies are based on the length of the baseline bubble that shortens due to the excitation. The conventional works well for the coherent wave features. Reproduction of these dynamic effects by a numerical simulation would provide benchmark validation.

Simulating Astrophysical Jets with Inertial Confinement Fusion Machines

NASA Astrophysics Data System (ADS)

Blue, Brent

2005-10-01

Large-scale directional outflows of supersonic plasma, also known as `jets', are ubiquitous phenomena in astrophysics. The traditional approach to understanding such phenomena is through theoretical analysis and numerical simulations. However, theoretical analysis might not capture all the relevant physics and numerical simulations have limited resolution and fail to scale correctly in Reynolds number and perhaps other key dimensionless parameters. Recent advances in high energy density physics using large inertial confinement fusion devices now allow controlled laboratory experiments on macroscopic volumes of plasma of direct relevance to astrophysics. This talk will present an overview of these facilities as well as results from current laboratory astrophysics experiments designed to study hydrodynamic jets and Rayleigh-Taylor mixing. This work is performed under the auspices of the U. S. DOE by Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48, Los Alamos National Laboratory under Contract No. W-7405-ENG-36, and the Laboratory for Laser Energetics under Contract No. DE-FC03-92SF19460.

Modeling Supernova Shocks with Intense Lasers.

NASA Astrophysics Data System (ADS)

Blue, Brent

2006-04-01

Large-scale directional outflows of supersonic plasma are ubiquitous phenomena in astrophysics, with specific application to supernovae. The traditional approach to understanding such phenomena is through theoretical analysis and numerical simulations. However, theoretical analysis might not capture all the relevant physics and numerical simulations have limited resolution and fail to scale correctly in Reynolds number and perhaps other key dimensionless parameters. Recent advances in high energy density physics using large inertial confinement fusion devices now allow controlled laboratory experiments on macroscopic volumes of plasma of direct relevance to astrophysics. This talk will present an overview of these facilities as well as results from current laboratory astrophysics experiments designed to study hydrodynamic jets and Rayleigh-Taylor mixing. This work is performed under the auspices of the U. S. DOE by Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48, Los Alamos National Laboratory under Contract No. W-7405-ENG-36, and the Laboratory for Laser Energetics under Contract No. DE-FC03-92SF19460.

Numerical investigation of design and operation parameters on CHI spheromak performance

NASA Astrophysics Data System (ADS)

O'Bryan, J. B.; Romero-Talamás, C. R.; Woodruff, S.

2017-10-01

Nonlinear, numerical computation with the NIMROD code is used to explore magnetic self-organization in spheromaks formed with coaxial helicity injection, particularly with regard to how externally controllable parameters affect the resulting spheromak performance. The overall goal of our study is to inform the design and operational parameters of a future proof-of-principle spheromak experiment. Our calculations start from vacuum magnetic fields and model multiple distinct phases of evolution. Results indicate that modest changes to the design and operation of past experiments, e.g. SSPX [E.B. Hooper et al. PPCF 2012], could have significantly improved the plasma-current injector coupling efficiency and performance, particularly with respect to peak temperature and lifetime. While we frequently characterize performance relative to SSPX, our conclusions extrapolate to fundamentally different experimental designs. We also explore adiabatic magnetic compression of spheromaks, which may allow for a small-scale, high-performance and high-yield pulsed neutron source. This work is supported by DAPRA under Grant No. N66001-14-1-4044.

Numerical model for the thermal behavior of thermocline storage tanks

NASA Astrophysics Data System (ADS)

Ehtiwesh, Ismael A. S.; Sousa, Antonio C. M.

2018-03-01

Energy storage is a critical factor in the advancement of solar thermal power systems for the sustained delivery of electricity. In addition, the incorporation of thermal energy storage into the operation of concentrated solar power systems (CSPs) offers the potential of delivering electricity without fossil-fuel backup even during peak demand, independent of weather conditions and daylight. Despite this potential, some areas of the design and performance of thermocline systems still require further attention for future incorporation in commercial CSPs, particularly, their operation and control. Therefore, the present study aims to develop a simple but efficient numerical model to allow the comprehensive analysis of thermocline storage systems aiming better understanding of their dynamic temperature response. The validation results, despite the simplifying assumptions of the numerical model, agree well with the experiments for the time evolution of the thermocline region. Three different cases are considered to test the versatility of the numerical model; for the particular type of a storage tank with top round impingement inlet, a simple analytical model was developed to take into consideration the increased turbulence level in the mixing region. The numerical predictions for the three cases are in general good agreement against the experimental results.

Decentralized stabilization of semi-active vibrating structures

NASA Astrophysics Data System (ADS)

Pisarski, Dominik

2018-02-01

A novel method of decentralized structural vibration control is presented. The control is assumed to be realized by a semi-active device. The objective is to stabilize a vibrating system with the optimal rates of decrease of the energy. The controller relies on an easily implemented decentralized switched state-feedback control law. It uses a set of communication channels to exchange the state information between the neighboring subcontrollers. The performance of the designed method is validated by means of numerical experiments performed for a double cantilever system equipped with a set of elastomers with controlled viscoelastic properties. In terms of the assumed objectives, the proposed control strategy significantly outperforms the passive damping cases and is competitive with a standard centralized control. The presented methodology can be applied to a class of bilinear control systems concerned with smart structural elements.

Symbolic Estrangement: Evidence against a Strong Association between Numerical Symbols and the Quantities They Represent

ERIC Educational Resources Information Center

Lyons, Ian M.; Ansari, Daniel; Beilock, Sian L.

2012-01-01

Are numerals estranged from a sense of the actual quantities they represent? We demonstrate that, irrespective of numerical size or distance, direct comparison of the relative quantities represented by symbolic and nonsymbolic formats leads to performance markedly worse than when comparing 2 nonsymbolic quantities (Experiment 1). Experiment 2…

Inlet Flow Control and Prediction Technologies for Embedded Propulsion Systems

NASA Technical Reports Server (NTRS)

McMillan, Michelle L.; Mackie, Scott A.; Gissen, Abe; Vukasinovic, Bojan; Lakebrink, Matthew T.; Glezer, Ari; Mani, Mori; Mace, James L.

2011-01-01

Fail-safe, hybrid, flow control (HFC) is a promising technology for meeting high-speed cruise efficiency, low-noise signature, and reduced fuel-burn goals for future, Hybrid-Wing-Body (HWB) aircraft with embedded engines. This report details the development of HFC technology that enables improved inlet performance in HWB vehicles with highly integrated inlets and embedded engines without adversely affecting vehicle performance. In addition, new test techniques for evaluating Boundary-Layer-Ingesting (BLI)-inlet flow-control technologies developed and demonstrated through this program are documented, including the ability to generate a BLI-like inlet-entrance flow in a direct-connect, wind-tunnel facility, as well as, the use of D-optimal, statistically designed experiments to optimize test efficiency and enable interpretation of results. Validated improvements in numerical analysis tools and methods accomplished through this program are also documented, including Reynolds-Averaged Navier-Stokes CFD simulations of steady-state flow physics for baseline, BLI-inlet diffuser flow, as well as, that created by flow-control devices. Finally, numerical methods were employed in a ground-breaking attempt to directly simulate dynamic distortion. The advances in inlet technologies and prediction tools will help to meet and exceed "N+2" project goals for future HWB aircraft.

Fly-by-feel aeroservoelasticity

NASA Astrophysics Data System (ADS)

Suryakumar, Vishvas Samuel

Recent experiments have suggested a strong correlation between local flow features on the airfoil surface such as the leading edge stagnation point (LESP), transition or the flow separation point with global integrated quantities such as aerodynamic lift. "Fly-By-Feel" refers to a physics-based sensing and control framework where local flow features are tracked in real-time to determine aerodynamic loads. This formulation offers possibilities for the development of robust, low-order flight control architectures. An essential contribution towards this objective is the theoretical development showing the direct relationship of the LESP with circulation for small-amplitude, unsteady, airfoil maneuvers. The theory is validated through numerical simulations and wind tunnel tests. With the availability of an aerodynamic observable, a low-order, energy-based control formulation is derived for aeroelastic stabilization and gust load alleviation. The sensing and control framework is implemented on the Nonlinear Aeroelastic Test Apparatus at Texas A&M University. The LESP is located using hot-film sensors distributed around the wing leading edge. Stabilization of limit cycle oscillations exhibited by a nonlinear wing section is demonstrated in the presence of gusts. Aeroelastic stabilization is also demonstrated on a flying wing configuration exhibiting body freedom flutter through numerical simulations.

Non-linear dynamic characteristics and optimal control of giant magnetostrictive film subjected to in-plane stochastic excitation

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

Zhu, Z. W., E-mail: zhuzhiwen@tju.edu.cn; Tianjin Key Laboratory of Non-linear Dynamics and Chaos Control, 300072, Tianjin; Zhang, W. D., E-mail: zhangwenditju@126.com

2014-03-15

The non-linear dynamic characteristics and optimal control of a giant magnetostrictive film (GMF) subjected to in-plane stochastic excitation were studied. Non-linear differential items were introduced to interpret the hysteretic phenomena of the GMF, and the non-linear dynamic model of the GMF subjected to in-plane stochastic excitation was developed. The stochastic stability was analysed, and the probability density function was obtained. The condition of stochastic Hopf bifurcation and noise-induced chaotic response were determined, and the fractal boundary of the system's safe basin was provided. The reliability function was solved from the backward Kolmogorov equation, and an optimal control strategy was proposedmore » in the stochastic dynamic programming method. Numerical simulation shows that the system stability varies with the parameters, and stochastic Hopf bifurcation and chaos appear in the process; the area of the safe basin decreases when the noise intensifies, and the boundary of the safe basin becomes fractal; the system reliability improved through stochastic optimal control. Finally, the theoretical and numerical results were proved by experiments. The results are helpful in the engineering applications of GMF.« less

The combustion program at CTR

NASA Technical Reports Server (NTRS)

Poinsot, Thierry J.

1993-01-01

Understanding and modeling of turbulent combustion are key problems in the computation of numerous practical systems. Because of the lack of analytical theories in this field and of the difficulty of performing precise experiments, direct numerical simulation (DNS) appears to be one of the most attractive tools to use in addressing this problem. The general objective of DNS of reacting flows is to improve our knowledge of turbulent combustion but also to use this information for turbulent combustion models. For the foreseeable future, numerical simulation of the full three-dimensional governing partial differential equations with variable density and transport properties as well as complex chemistry will remain intractable; thus, various levels of simplification will remain necessary. On one hand, the requirement to simplify is not necessarily a handicap: numerical simulations allow the researcher a degree of control in isolating specific physical phenomena that is inaccessible in experiments. CTR has pursued an intensive research program in the field of DNS for turbulent reacting flows since 1987. DNS of reacting flows is quite different from DNS of non-reacting flows: without reaction, the equations to solve are clearly the five conservation equations of the Navier Stokes system for compressible situations (four for incompressible cases), and the limitation of the approach is the Reynolds number (or in other words the number of points in the computation). For reacting flows, the choice of the equations, the species (each species will require one additional conservation equation), the chemical scheme, and the configuration itself is more complex.

Effects of Formation Heterogeneity in Semi-Confining Shale Layers in Enhancing Mixing and Storage of Dissolved CO2

NASA Astrophysics Data System (ADS)

Illangasekare, T. H.; Agartan Karacaer, E.; Vargas-Johnson, J.; Cihan, A.; Birkholzer, J. T.

2017-12-01

It is expected that heterogeneity of the deep geologic formation to play a key role in both trapping of supercritical CO2 and its mixing in the formation brine. In previously reported research by the authors, a set of laboratory experiments and field-scale simulations were used to show that convective mixing and diffusion controlled trapping are two important mechanisms that contribute to the dissolution trapping in multilayered systems with homogeneous low-permeability zones such as shale. However, these low-permeability layers (e.g. shale) are not always homogeneous due to their composition and texture variations in addition to the presence of faults, fractures and fissures. In this study, we investigated the potential outcomes of heterogeneity present within these semi-confining low-permeability layers in regards to mixing and storage of dissolved CO2. An intermediate-scale laboratory experiment was designed to investigate the contribution of convective mixing, diffusion controlled trapping and back diffusion to long-term storage of dissolved CO2 in multilayered formations with heterogeneous low-permeability layers. The experiment was performed using a surrogate fluid combination to represent dissolved CO2 and brine under ambient pressure and temperature conditions. After verifying the numerical model with the experimental results, different distributions of the same low-permeability materials having similar volume ratios with the experimentally studied scenario were tested numerically. The experiment and modeling results showed that connectivity of higher permeability material within the semi-confining low-permeability layers contributes to mixing through brine leakage between upper and lower aquifers, storage through diffusion, and in the long term, back diffusion of stored mass due to reversed concentration gradient.

Effect of Melt Convection and Solid Transport on Macrosegregation and Grain Structure in Equiaxed Al-Cu Alloys

NASA Technical Reports Server (NTRS)

Rerko, Rodney S.; deGroh, Henry C., III; Beckermann, Christoph; Gray, Hugh R. (Technical Monitor)

2002-01-01

Macrosegregation in metal casting can be caused by thermal and solutal melt convection, and the transport of unattached solid crystals. These free grains can be a result of, for example, nucleation in the bulk liquid or dendrite fragmentation. In an effort to develop a comprehensive numerical model for the casting of alloys, an experimental study has been conducted to generate benchmark data with which such a solidification model could be tested. The specific goal of the experiments was to examine equiaxed solidification in situations where sinking of grains is (and is not) expected. The objectives were: 1) experimentally study the effects of solid transport and thermosolutal convection on macrosegregation and grain size distribution patterns; and 2) provide a complete set of controlled thermal boundary conditions, temperature data, segregation data, and grain size data, to validate numerical codes. The alloys used were Al-1 wt. pct. Cu, and Al-10 wt. pct. Cu with various amounts of the grain refiner TiB2 added. Cylindrical samples were either cooled from the top, or the bottom. Several trends in the data stand out. In attempting to model these experiments, concentrating on experiments that show clear trends or differences is recommended.

Real-time 2D spatially selective MRI experiments: Comparative analysis of optimal control design methods.

PubMed

Maximov, Ivan I; Vinding, Mads S; Tse, Desmond H Y; Nielsen, Niels Chr; Shah, N Jon

2015-05-01

There is an increasing need for development of advanced radio-frequency (RF) pulse techniques in modern magnetic resonance imaging (MRI) systems driven by recent advancements in ultra-high magnetic field systems, new parallel transmit/receive coil designs, and accessible powerful computational facilities. 2D spatially selective RF pulses are an example of advanced pulses that have many applications of clinical relevance, e.g., reduced field of view imaging, and MR spectroscopy. The 2D spatially selective RF pulses are mostly generated and optimised with numerical methods that can handle vast controls and multiple constraints. With this study we aim at demonstrating that numerical, optimal control (OC) algorithms are efficient for the design of 2D spatially selective MRI experiments, when robustness towards e.g. field inhomogeneity is in focus. We have chosen three popular OC algorithms; two which are gradient-based, concurrent methods using first- and second-order derivatives, respectively; and a third that belongs to the sequential, monotonically convergent family. We used two experimental models: a water phantom, and an in vivo human head. Taking into consideration the challenging experimental setup, our analysis suggests the use of the sequential, monotonic approach and the second-order gradient-based approach as computational speed, experimental robustness, and image quality is key. All algorithms used in this work were implemented in the MATLAB environment and are freely available to the MRI community. Copyright © 2015 Elsevier Inc. All rights reserved.

Comparative Laboratory and Numerical Simulations of Shearing Granular Fault Gouge: Micromechanical Processes

NASA Astrophysics Data System (ADS)

Morgan, J. K.; Marone, C. J.; Guo, Y.; Anthony, J. L.; Knuth, M. W.

2004-12-01

Laboratory studies of granular shear zones have provided significant insight into fault zone processes and the mechanics of earthquakes. The micromechanisms of granular deformation are more difficult to ascertain, but have been hypothesized based on known variations in boundary conditions, particle properties and geometries, and mechanical behavior. Numerical simulations using particle dynamics methods (PDM) can offer unique views into deforming granular shear zones, revealing the precise details of granular microstructures, particle interactions, and packings, which can be correlated with macroscopic mechanical behavior. Here, we describe a collaborative program of comparative laboratory and numerical experiments of granular shear using idealized materials, i.e., glass beads, glass rods or pasta, and angular sand. Both sets of experiments are carried out under similar initial and boundary conditions in a non-fracturing stress regime. Phenomenologically, the results of the two sets of experiments are very similar. Peak friction values vary as a function of particle dimensionality (1-D vs. 2-D vs. 3-D), particle angularity, particle size and size distributions, boundary roughness, and shear zone thickness. Fluctuations in shear strength during an experiment, i.e., stick-slip events, can be correlated with distinct changes in the nature, geometries, and durability of grain bridges that support the shear zone walls. Inclined grain bridges are observed to form, and to support increasing loads, during gradual increases in assemblage strength. Collapse of an individual grain bridge leads to distinct localization of strain, generating a rapidly propagating shear surface that cuts across multiple grain bridges, accounting for the sudden drop in strength. The distribution of particle sizes within an assemblage, along with boundary roughness and its periodicity, influence the rate of formation and dissipation of grain bridges, thereby controlling friction variations during shear.

An Experimental Comparison of Two Methods Of Teaching Numerical Control Manual Programming Concepts; Visual Media Versus Hands-On Equipment.

ERIC Educational Resources Information Center

Biekert, Russell

Accompanying the rapid changes in technology has been a greater dependence on automation and numerical control, which has resulted in the need to find ways of preparing programers for industrial machines using numerical control. To compare the hands-on equipment method and a visual media method of teaching numerical control, an experimental and a…

Numerical Investigation of Force-Free Magnetophoresis of Nonspherical Microparticles

NASA Astrophysics Data System (ADS)

Zhang, Jie; Wang, Cheng

2017-11-01

Our group recently demonstrated novel force-free magnetophoresis to separate nonspherical particles by shape. In this approach, a uniform magnetic field is used to generate a magnetic torque, which breaks the rotational symmetry of the particles and leads to shape-dependent lateral migration of the particles. We use direct numerical simulations to gain a better understanding of this magnetophoresis mechanism by focusing on ellipsoidal microparticles - a representative type of nonspherical particles encountered in biomedical engineering. We study key effects that influence the rotational and translational behaviors, including particle-wall separation distance, direction and strength of the magnetic field, particle aspect ratio and size. The numerical results show that the lateral migration is negligible in the absence of the magnetic field. When the magnetic field is applied, the particles migrate laterally. The migration direction depends on the direction of external magnetic fields, which controls the symmetry property of the particle rotation. These findings agree well with experiments. Our numerical simulations yield a comprehensive understanding of particle migration mechanism, and provide useful guidelines on design of separating devices for non-spherical micro-particles.

Iterative LQG Controller Design Through Closed-Loop Identification

NASA Technical Reports Server (NTRS)

Hsiao, Min-Hung; Huang, Jen-Kuang; Cox, David E.

1996-01-01

This paper presents an iterative Linear Quadratic Gaussian (LQG) controller design approach for a linear stochastic system with an uncertain open-loop model and unknown noise statistics. This approach consists of closed-loop identification and controller redesign cycles. In each cycle, the closed-loop identification method is used to identify an open-loop model and a steady-state Kalman filter gain from closed-loop input/output test data obtained by using a feedback LQG controller designed from the previous cycle. Then the identified open-loop model is used to redesign the state feedback. The state feedback and the identified Kalman filter gain are used to form an updated LQC controller for the next cycle. This iterative process continues until the updated controller converges. The proposed controller design is demonstrated by numerical simulations and experiments on a highly unstable large-gap magnetic suspension system.

Deconvolution of acoustic emissions for source localization using time reverse modeling

NASA Astrophysics Data System (ADS)

Kocur, Georg Karl

2017-01-01

Impact experiments on small-scale slabs made of concrete and aluminum were carried out. Wave motion radiated from the epicenter of the impact was recorded as voltage signals by resonant piezoelectric transducers. Numerical simulations of the elastic wave propagation are performed to simulate the physical experiments. The Hertz theory of contact is applied to estimate the force impulse, which is subsequently used for the numerical simulation. Displacements at the transducer positions are calculated numerically. A deconvolution function is obtained by comparing the physical (voltage signal) and the numerical (calculated displacement) experiments. Acoustic emission signals due to pencil-lead breaks are recorded, deconvolved and applied for localization using time reverse modeling.

The dynamics and control of large flexible space structures - 12, supplement 11

NASA Technical Reports Server (NTRS)

Bainum, Peter M.; Reddy, A. S. S. R.; Li, Feiyue; Xu, Jianke

1989-01-01

The rapid 2-D slewing and vibrational control of the unsymmetrical flexible SCOLE (Spacecraft Control Laboratory Experiment) with multi-bounded controls is considered. Pontryagin's Maximum Principle is applied to the nonlinear equations of the system to derive the necessary conditions for the optimal control. The resulting two point boundary value problem is then solved by using the quasilinearization technique, and the near minimum time is obtained by sequentially shortening the slewing time until the controls are near the bang-bang type. The tradeoff between the minimum time and the minimum flexible amplitude requirements is discussed. The numerical results show that the responses of the nonlinear system are significantly different from those of the linearized system for rapid slewing. The SCOLE station-keeping closed loop dynamics are re-examined by employing a slightly different method for developing the equations of motion in which higher order terms in the expressions for the mast modal shape functions are now included. A preliminary study on the effect of actuator mass on the closed loop dynamics of large space systems is conducted. A numerical example based on a coupled two-mass two-spring system illustrates the effect of changes caused in the mass and stiffness matrices on the closed loop system eigenvalues. In certain cases the need for redesigning control laws previously synthesized, but not accounting for actuator masses, is indicated.

Numerical simulations of negatively buoyant jets in an immiscible fluid using the Particle Finite Element Method

NASA Astrophysics Data System (ADS)

Mier-Torrecilla, Monica; Geyer, Adelina; Phillips, Jeremy C.; Idelsohn, Sergio R.; Oñate, Eugenio

2010-05-01

In this work we investigate numerically the injection of a negatively buoyant jet into a homogenous immiscible ambient fluid using the Particle Finite Element Method (PFEM), a newly developed tool that combines the flexibility of particle-based methods with the accuracy of the finite element discretization. In order to test the applicability of PFEM to the study of negatively buoyant jets, we have compared the two-dimensional numerical results with experiments investigating the injection of a jet of dyed water through a nozzle in the base of a cylindrical tank containing rapeseed oil. In both simulations and experiments, the fountain inlet flow velocity and nozzle diameter were varied to cover a wide range of Reynolds Re and Froude numbers Fr, such that 0.1 < Fr < 30, reproducing both weak and strong fountains in a laminar regime (8 < Re < 1350). Numerical results, together with the experimental observations, allow us to describe three different fountain behaviors that have not been previously reported. Based on the Re and Fr values for the numerical and experimental simulations, we have built a regime map to define how these values may control the occurrence of each of the observed flow types. Whereas the Fr number itself provides a prediction of the maximum penetration height of the jet, its combination with the Re number provides a prediction of the flow behavior for a specific nozzle diameter and injection velocity. Conclusive remarks concerning the dynamics of negatively buoyant jets may be applied later on to several geological situations, e.g. the flow structure of a fully submerged subaqueous eruptive vent discharging magma or the replenishment of magma chambers in the Earth's crust.

Model-free learning on robot kinematic chains using a nested multi-agent topology

NASA Astrophysics Data System (ADS)

Karigiannis, John N.; Tzafestas, Costas S.

2016-11-01

This paper proposes a model-free learning scheme for the developmental acquisition of robot kinematic control and dexterous manipulation skills. The approach is based on a nested-hierarchical multi-agent architecture that intuitively encapsulates the topology of robot kinematic chains, where the activity of each independent degree-of-freedom (DOF) is finally mapped onto a distinct agent. Each one of those agents progressively evolves a local kinematic control strategy in a game-theoretic sense, that is, based on a partial (local) view of the whole system topology, which is incrementally updated through a recursive communication process according to the nested-hierarchical topology. Learning is thus approached not through demonstration and training but through an autonomous self-exploration process. A fuzzy reinforcement learning scheme is employed within each agent to enable efficient exploration in a continuous state-action domain. This paper constitutes in fact a proof of concept, demonstrating that global dexterous manipulation skills can indeed evolve through such a distributed iterative learning of local agent sensorimotor mappings. The main motivation behind the development of such an incremental multi-agent topology is to enhance system modularity, to facilitate extensibility to more complex problem domains and to improve robustness with respect to structural variations including unpredictable internal failures. These attributes of the proposed system are assessed in this paper through numerical experiments in different robot manipulation task scenarios, involving both single and multi-robot kinematic chains. The generalisation capacity of the learning scheme is experimentally assessed and robustness properties of the multi-agent system are also evaluated with respect to unpredictable variations in the kinematic topology. Furthermore, these numerical experiments demonstrate the scalability properties of the proposed nested-hierarchical architecture, where new agents can be recursively added in the hierarchy to encapsulate individual active DOFs. The results presented in this paper demonstrate the feasibility of such a distributed multi-agent control framework, showing that the solutions which emerge are plausible and near-optimal. Numerical efficiency and computational cost issues are also discussed.

Exponential lag function projective synchronization of memristor-based multidirectional associative memory neural networks via hybrid control

NASA Astrophysics Data System (ADS)

Yuan, Manman; Wang, Weiping; Luo, Xiong; Li, Lixiang; Kurths, Jürgen; Wang, Xiao

2018-03-01

This paper is concerned with the exponential lag function projective synchronization of memristive multidirectional associative memory neural networks (MMAMNNs). First, we propose a new model of MMAMNNs with mixed time-varying delays. In the proposed approach, the mixed delays include time-varying discrete delays and distributed time delays. Second, we design two kinds of hybrid controllers. Traditional control methods lack the capability of reflecting variable synaptic weights. In this paper, the controllers are carefully designed to confirm the process of different types of synchronization in the MMAMNNs. Third, sufficient criteria guaranteeing the synchronization of system are derived based on the derive-response concept. Finally, the effectiveness of the proposed mechanism is validated with numerical experiments.

Adaptive PID formation control of nonholonomic robots without leader's velocity information.

PubMed

Shen, Dongbin; Sun, Weijie; Sun, Zhendong

2014-03-01

This paper proposes an adaptive proportional integral derivative (PID) algorithm to solve a formation control problem in the leader-follower framework where the leader robot's velocities are unknown for the follower robots. The main idea is first to design some proper ideal control law for the formation system to obtain a required performance, and then to propose the adaptive PID methodology to approach the ideal controller. As a result, the formation is achieved with much more enhanced robust formation performance. The stability of the closed-loop system is theoretically proved by Lyapunov method. Both numerical simulations and physical vehicle experiments are presented to verify the effectiveness of the proposed adaptive PID algorithm. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

A temperature and pressure controlled calibration system for pressure sensors

NASA Technical Reports Server (NTRS)

Chapman, John J.; Kahng, Seun K.

1989-01-01

A data acquisition and experiment control system capable of simulating temperatures from -184 to +220 C and pressures either absolute or differential from 0 to 344.74 kPa is developed to characterize silicon pressure sensor response to temperature and pressure. System software is described that includes sensor data acquisition, algorithms for numerically derived thermal offset and sensitivity correction, and operation of the environmental chamber and pressure standard. This system is shown to be capable of computer interfaced cryogenic testing to within 1 C and 34.47 Pa of single channel or multiplexed arrays of silicon pressure sensors.

Microelectrode for energy and current control of nanotip field electron emitters

NASA Astrophysics Data System (ADS)

Lüneburg, S.; Müller, M.; Paarmann, A.; Ernstorfer, R.

2013-11-01

Emerging experiments and applications in electron microscopy, holography, and diffraction benefit from miniaturized electron guns for compact experimental setups. We present a highly compact microelectrode integrated field emitter that consists of a tungsten nanotip coated with a few micrometers thick polyimide film followed by a several nanometers thick gold film, both positioned behind the exposed emitter apex by approximately 10-30 μm. The control of the electric field strength at the nanometer scale tip apex allows suppression, extraction, and energy tuning of field-emitted electrons. The performance of the microelectrode is demonstrated experimentally and supported by numerical simulations.

Influence of Controlled Viscous Dissipation on Propagation of Strongly Nonlinear Waves in Steel-Based Phononic Crystals

NASA Astrophysics Data System (ADS)

Herbold, Eric

2005-07-01

Strongly nonlinear phononic crystals were assembled from chains of stainless steel spheres with diameter 4.78 mm. Propagation of solitary waves and splitting of initial pulse into train of solitary waves excited by the impact of piston was investigated in different viscous media in experiments and in numerical calculations. Oil of various grades was used to introduce controlled dissipation into the system. Preliminary results indicate that splitting of the initial pulse into the train of solitary waves was dramatically influenced by viscosity. This work was supported by NSF (Grant No. DCMS03013220).

NASA supercritical laminar flow control airfoil experiment

NASA Technical Reports Server (NTRS)

Harvey, W. D.

1982-01-01

The design and goals of experimental investigations of supercritical LFC airfoils conducted in the NASA Langley 8-ft Transonic Pressure Tunnel beginning in March 1982 are reviewed. Topics addressed include laminarization aspects; flow-quality requirements; simulation of flight parameters; the setup of screens, honeycomb, and sonic throat; the design cycle; theoretical pressure distributions and shock-free limits; drag divergence and stability analysis; and the LFC suction system. Consideration is given to the LFC airfoil model, the air-flow control system, airfoil-surface instrumentation, liner design and hardware, and test options. Extensive diagrams, drawings, graphs, photographs, and tables of numerical data are provided.

Film annotation system for a space experiment

NASA Technical Reports Server (NTRS)

Browne, W. R.; Johnson, S. S.

1989-01-01

This microprocessor system was designed to control and annotate a Nikon 35 mm camera for the purpose of obtaining photographs and data at predefined time intervals. The single STD BUSS interface card was designed in such a way as to allow it to be used in either a stand alone application with minimum features or installed in a STD BUSS computer allowing for maximum features. This control system also allows the exposure of twenty eight alpha/numeric characters across the bottom of each photograph. The data contains such information as camera identification, frame count, user defined text, and time to .01 second.

Robust tuning of robot control systems

NASA Technical Reports Server (NTRS)

Minis, I.; Uebel, M.

1992-01-01

The computed torque control problem is examined for a robot arm with flexible, geared, joint drive systems which are typical in many industrial robots. The standard computed torque algorithm is not directly applicable to this class of manipulators because of the dynamics introduced by the joint drive system. The proposed approach to computed torque control combines a computed torque algorithm with torque controller at each joint. Three such control schemes are proposed. The first scheme uses the joint torque control system currently implemented on the robot arm and a novel form of the computed torque algorithm. The other two use the standard computed torque algorithm and a novel model following torque control system based on model following techniques. Standard tasks and performance indices are used to evaluate the performance of the controllers. Both numerical simulations and experiments are used in evaluation. The study shows that all three proposed systems lead to improved tracking performance over a conventional PD controller.

Trait approach motivation moderates the aftereffects of self-control

PubMed Central

Crowell, Adrienne; Kelley, Nicholas J.; Schmeichel, Brandon J.

2014-01-01

Numerous experiments have found that exercising self-control reduces success on subsequent, seemingly unrelated self-control tasks. Such evidence lends support to a strength model that posits a limited and depletable resource underlying all manner of self-control. Recent theory and evidence suggest that exercising self-control may also increase approach-motivated impulse strength. The two studies reported here tested two implications of this increased approach motivation hypothesis. First, aftereffects of self-control should be evident even in responses that require little or no self-control. Second, participants higher in trait approach motivation should be particularly susceptible to such aftereffects. In support, exercising self-control led to increased optimism (Study 1) and broadened attention (Study 2), but only among individuals higher in trait approach motivation. These findings suggest that approach motivation is an important key to understanding the aftereffects of exercising self-control. PMID:25324814

Bimetallic Microswimmers Speed Up in Confining Channels.

PubMed

Liu, Chang; Zhou, Chao; Wang, Wei; Zhang, H P

2016-11-04

Synthetic microswimmers are envisioned to be useful in numerous applications, many of which occur in tightly confined spaces. It is therefore important to understand how confinement influences swimmer dynamics. Here we study the motility of bimetallic microswimmers in linear and curved channels. Our experiments show swimmer velocities increase, up to 5 times, with the degree of confinement, and the relative velocity increase depends weakly on the fuel concentration and ionic strength in solution. Experimental results are reproduced in a numerical model which attributes the swimmer velocity increase to electrostatic and electrohydrodynamic boundary effects. Our work not only helps to elucidate the confinement effect of phoretic swimmers, but also suggests that spatial confinement may be used as an effective control method for them.

Characteristic Analysis and Experiment of a Dynamic Flow Balance Valve

NASA Astrophysics Data System (ADS)

Bin, Li; Song, Guo; Xuyao, Mao; Chao, Wu; Deman, Zhang; Jin, Shang; Yinshui, Liu

2017-12-01

Comprehensive characteristics of a dynamic flow balance valve of water system were analysed. The flow balance valve can change the drag efficient automatically according to the condition of system, and the effective control flowrate is constant in the range of job pressure. The structure of the flow balance valve was introduced, and the theoretical calculation formula for the variable opening of the valve core was derived. A rated pressure of 20kPa to 200kPa and a rated flowrate of 10m3/h were offered in the numerical work. Static and fluent CFX analyses show good behaviours: through the valve core structure optimization and improve design of the compressive spring, the dynamic flow balance valve can stabilize the flowrate of system evidently. And experiments show that the flow control accuracy is within 5%.

Flux control coefficients determined by inhibitor titration: the design and analysis of experiments to minimize errors.

PubMed Central

Small, J R

1993-01-01

This paper is a study into the effects of experimental error on the estimated values of flux control coefficients obtained using specific inhibitors. Two possible techniques for analysing the experimental data are compared: a simple extrapolation method (the so-called graph method) and a non-linear function fitting method. For these techniques, the sources of systematic errors are identified and the effects of systematic and random errors are quantified, using both statistical analysis and numerical computation. It is shown that the graph method is very sensitive to random errors and, under all conditions studied, that the fitting method, even under conditions where the assumptions underlying the fitted function do not hold, outperformed the graph method. Possible ways of designing experiments to minimize the effects of experimental errors are analysed and discussed. PMID:8257434

Review of deployment technology for tethered satellite systems

NASA Astrophysics Data System (ADS)

Yu, B. S.; Wen, H.; Jin, D. P.

2018-03-01

Tethered satellite systems (TSSs) have attracted significant attention due to their potential and valuable applications for scientific research. With the development of various launched on-orbit missions, the deployment of tethers is considered a crucial technology for operation of a TSS. Both past orbiting experiments and numerical results have shown that oscillations of the deployed tether due to the Coriolis force and environmental perturbations are inevitable and that the impact between the space tether and end-body at the end of the deployment process leads to complicated nonlinear phenomena. Hence, a set of suitable control methods plays a fundamental role in tether deployment. This review article summarizes previous work on aspects of the dynamics, control, and ground-based experiments of tether deployment. The relevant basic principles, analytical expressions, simulation cases, and experimental results are presented as well.

Numerical experiments of volcanic dominated rifts and passive margins

NASA Astrophysics Data System (ADS)

Korchinski, Megan; Teyssier, Christian; Rey, Patrice; Whitney, Donna; Mondy, Luke

2017-04-01

Continental rifting is driven by plate tectonic forces (passive rifting), thermal thinning of the lithosphere over a hotspot (active rifting), or a combination of the two. Successful rifts develop into passive margins where pre-drift stretching is accompanied by normal faulting, clastic sedimentation, and various degrees of magmatism. The structure of volcanic passive margins (VPM) differs substantially from margins that are dominated by sedimentation. VPMs are typically narrow, with a lower continental crust that is intruded by magma and can flow as a low-viscosity layer. To investigate the role of the deep crust in the early development of VPMs, we have developed a suite of 2D thermomechanical numerical experiments (Underworld code) in which the density and viscosity of the deep crust and the density of the rift basin fill are systematically varied. Our experiments show that, for a given rifting velocity, the viscosity of the deep crust and the density of the rift basin fill exert primary controls on early VPM development. The viscosity of the deep crust controls the degree to which the shallow crust undergoes localised faulting or distributed thinning. A weak deep crust localises rifting and is efficiently exhumed to the near-surface, whereas a strong deep crust distributes shallow crust extension and remains buried. A high density rift basin fill results in gravitational loading and increased subsidence rate in cases in which the viscosity of the deep crust is sufficiently low to allow that layer to be displaced by the sinking basin fill. At the limit, a low viscosity deep crust overlain by a thick basalt-dominated fill generates a gravitational instability, with a drip of cool basalt that sinks and ponds at the Moho. Experiment results indicate that the deep crust plays a critical role in the dynamic development of volcanic dominated rifts and passive margins. During rifting, the deep continental crust is heated and readily responds to solicitations of the shallow crust (rooting of normal faults, exhumation of the deep crust in normal fault footwalls). Gravitational instabilities caused by high density rift infill similar to those observed in our numerical experiments may be present in the Mesoproterozoic ( 1100 Ma) North American Midcontinent Rift System (MRS). The MRS is a failed rift that is filled with >20 km of dominantly basaltic volcanic deposits, and therefore represents an end member VPM (high density basin fill) where the initial structure of a pre-drift VPM is preserved. Magmatism occurred in two pulses over <15 Ma involving deep mantle melting first (>150 km), then shallow melting (40-70 km). Post-rift subsidence accumulated up to 10 km of clastic sediments in the center of the basin. Evidence of cool, dense rocks sinking into a low-viscosity deep crust as predicted in our numerical experiments may be present in the western arm of the MRS, where crustal density analyses suggest the presence of dense bodies (eclogite) at the base of the crust.

Numerical simulations of SHPB experiments for the dynamic compressive strength and failure of ceramics

NASA Astrophysics Data System (ADS)

Anderson, Charles E., Jr.; O'Donoghue, Padraic E.; Lankford, James; Walker, James D.

1992-06-01

Complementary to a study of the compressive strength of ceramic as a function of strain rate and confinement, numerical simulations of the split-Hopkinson pressure bar (SHPB) experiments have been performed using the two-dimensional wave propagation computer program HEMP. The numerical effort had two main thrusts. Firstly, the interpretation of the experimental data relies on several assumptions. The numerical simulations were used to investigate the validity of these assumptions. The second part of the effort focused on computing the idealized constitutive response of a ceramic within the SHPB experiment. These numerical results were then compared against experimental data. Idealized models examined included a perfectly elastic material, an elastic-perfectly plastic material, and an elastic material with failure. Post-failure material was modeled as having either no strength, or a strength proportional to the mean stress. The effects of confinement were also studied. Conclusions concerning the dynamic behavior of a ceramic up to and after failure are drawn from the numerical study.

Healthcare Seeking Intention if Diagnosed with HIV Among Young MSM in Taiwan: A Theory-Based Comparison by Voluntary Counseling and Testing Experience.

PubMed

Li, Min-Jung; Huang, Jiun-Hau

2018-05-28

The number of HIV cases in Taiwan exceeded 30,000 in 2016. Per the UNAIDS 90-90-90 target, 81% of people living with HIV should receive medication. However, numerous previous studies focused on adherence rather than the initial healthcare seeking intention if diagnosed with HIV (HIV HSI). Based on the Theory of Planned Behavior (TPB), anonymous online survey data were collected from December 2016 through February 2017 from 2709 young MSM (YMSM) ages 15-39. Multivariate logistic regression found the significant factors and strengths of associations with HIV HSI varied by their HIV voluntary counseling and testing (VCT) experience. YMSM without VCT experience perceiving high support from salient others (AOR = 1.28) and high control under facilitating conditions (AOR = 2.73) had higher HIV HSI. YMSM with VCT experience perceiving high control under facilitating (AOR = 1.79) and constraining (AOR = 1.54) conditions had higher HIV HSI. Regardless of VCT experience, YMSM with positive attitudes toward positive healthcare seeking outcomes (AOR = 3.72-3.95) had highest HIV HSI, highlighting the importance of increasing positive outcome expectations in YMSM.

Controlling three-dimensional vortices using multiple and moving external fields

NASA Astrophysics Data System (ADS)

Das, Nirmali Prabha; Dutta, Sumana

2017-08-01

Spirals or scroll wave activities in cardiac tissues are the cause of lethal arrhythmias. The external control of these waves is thus of prime interest to scientists and physicians. In this article, we demonstrate the spatial control of scroll waves by using external electric fields and thermal gradients in experiments with the Belousov-Zhabotinsky reaction. We show that a scroll ring can be made to trace cyclic trajectories under a rotating electric field. Application of a thermal gradient in addition to the electric field deflects the motion and changes the nature of the trajectory. Our experimental results are analyzed and corroborated by numerical simulations based on an excitable reaction diffusion model.

Numerical modeling of aquifer thermal energy storage

NASA Astrophysics Data System (ADS)

Tsang, C. F.; Doughty, C.; Kincaid, C. T.

1982-12-01

During 1981 and 1982, Auburn University has been performing a three cycle ATES field experiment in Mobile County, Alabama. Details of the experiment are described elsewhere in this volume. Concurrent with the first two cycles (59 C and 82 C), Lawrence Berkeley Laboratory (LBL) did numerical simulations based on field operating conditions to predict the outcome of each cycle before its conclusion. Prior to the third cycle, a series of numerical simulations were made to aid in the design of an experiment that would yield the highest recovery factor possible.

Experimental Demonstration of a Quantum Router

DTIC Science & Technology

2015-07-22

shown in Fig. 2a can generate polarization entangled photon pairs if the pump beam is set at H V+ polarization. For our experiment, however, we set the... entanglement fidelity) through exact numerical simulation . The PBS2 and PBS3 in Fig. 2c make another Mach-Zehnder interferometer, which requires similar phase...showing entanglement generated between the initially unentangled control and signal photons, and confirm that the qubit state of the signal photon is

Magnetic Field Applications in Semiconductor Crystal Growth and Metallurgy

NASA Technical Reports Server (NTRS)

Mazuruk, Konstantin; Ramachandran, Narayanan; Grugel, Richard; Curreri, Peter A. (Technical Monitor)

2002-01-01

The Traveling Magnetic Field (TMF) technique, recently proposed to control meridional flow in electrically conducting melts, is reviewed. In particular, the natural convection damping capability of this technique has been numerically demonstrated with the implication of significantly improving crystal quality. Advantages of the traveling magnetic field, in comparison to the more mature rotating magnetic field method, are discussed. Finally, results of experiments with mixing metallic alloys in long ampoules using TMF is presented

AI in manufacturing

NASA Astrophysics Data System (ADS)

Gross, John E.; Minato, Rick; Smith, David M.; Loftin, R. B.; Savely, Robert T.

1991-10-01

AI techniques are shown to have been useful in such aerospace industry tasks as vehicle configuration layouts, process planning, tool design, numerically-controlled programming of tools, production scheduling, and equipment testing and diagnosis. Accounts are given of illustrative experiences at the production facilities of three major aerospace defense contractors. Also discussed is NASA's autonomous Intelligent Computer-Aided Training System, for such ambitious manned programs as Space Station Freedom, which employs five different modules to constitute its job-independent training architecture.

Thermal analysis of the vortex tube based thermocycler for fast DNA amplification: Experimental and two-dimensional numerical results

NASA Astrophysics Data System (ADS)

Raghavan, V.; Whitney, Scott E.; Ebmeier, Ryan J.; Padhye, Nisha V.; Nelson, Michael; Viljoen, Hendrik J.; Gogos, George

2006-09-01

In this article, experimental and numerical analyses to investigate the thermal control of an innovative vortex tube based polymerase chain reaction (VT-PCR) thermocycler are described. VT-PCR is capable of rapid DNA amplification and real-time optical detection. The device rapidly cycles six 20μl 96bp λ-DNA samples between the PCR stages (denaturation, annealing, and elongation) for 30cycles in approximately 6min. Two-dimensional numerical simulations have been carried out using computational fluid dynamics (CFD) software FLUENT v.6.2.16. Experiments and CFD simulations have been carried out to measure/predict the temperature variation between the samples and within each sample. Heat transfer rate (primarily dictated by the temperature differences between the samples and the external air heating or cooling them) governs the temperature distribution between and within the samples. Temperature variation between and within the samples during the denaturation stage has been quite uniform (maximum variation around ±0.5 and 1.6°C, respectively). During cooling, by adjusting the cold release valves in the VT-PCR during some stage of cooling, the heat transfer rate has been controlled. Improved thermal control, which increases the efficiency of the PCR process, has been obtained both experimentally and numerically by slightly decreasing the rate of cooling. Thus, almost uniform temperature distribution between and within the samples (within 1°C) has been attained for the annealing stage as well. It is shown that the VT-PCR is a fully functional PCR machine capable of amplifying specific DNA target sequences in less time than conventional PCR devices.

Antenna Technology Shuttle Experiment (ATSE)

NASA Technical Reports Server (NTRS)

Freeland, R. E.; Mettler, E.; Miller, L. J.; Rahmet-Samii, Y.; Weber, W. J., III

1987-01-01

Numerous space applications of the future will require mesh deployable antennas of 15 m in diameter or greater for frequencies up to 20 GHz. These applications include mobile communications satellites, orbiting very long baseline interferometry (VLBI) astrophysics missions, and Earth remote sensing missions. A Lockheed wrap rip antennas was used as the test article. The experiments covered a broad range of structural, control, and RF discipline objectives, which is fulfilled in total, would greatly reduce the risk of employing these antenna systems in future space applications. It was concluded that a flight experiment of a relatively large mesh deployable reflector is achievable with no major technological or cost drivers. The test articles and the instrumentation are all within the state of the art and in most cases rely on proven flight hardware. Every effort was made to design the experiments for low cost.

Optimal control of a coupled partial and ordinary differential equations system for the assimilation of polarimetry Stokes vector measurements in tokamak free-boundary equilibrium reconstruction with application to ITER

NASA Astrophysics Data System (ADS)

Faugeras, Blaise; Blum, Jacques; Heumann, Holger; Boulbe, Cédric

2017-08-01

The modelization of polarimetry Faraday rotation measurements commonly used in tokamak plasma equilibrium reconstruction codes is an approximation to the Stokes model. This approximation is not valid for the foreseen ITER scenarios where high current and electron density plasma regimes are expected. In this work a method enabling the consistent resolution of the inverse equilibrium reconstruction problem in the framework of non-linear free-boundary equilibrium coupled to the Stokes model equation for polarimetry is provided. Using optimal control theory we derive the optimality system for this inverse problem. A sequential quadratic programming (SQP) method is proposed for its numerical resolution. Numerical experiments with noisy synthetic measurements in the ITER tokamak configuration for two test cases, the second of which is an H-mode plasma, show that the method is efficient and that the accuracy of the identification of the unknown profile functions is improved compared to the use of classical Faraday measurements.

Geometric controls of the flexural gravity waves on the Ross Ice Shelf

NASA Astrophysics Data System (ADS)

Sergienko, O. V.

2017-12-01

Long-period ocean waves, formed locally or at distant sources, can reach sub-ice-shelf cavities and excite coupled motion in the cavity and the ice shelf - flexural gravity waves. Three-dimensional numerical simulations of the flexural gravity waves on the Ross Ice Shelf show that propagation of these waves is strongly controlled by the geometry of the system - the cavity shape, its water-column thickness and the ice-shelf thickness. The results of numerical simulations demonstrate that propagation of the waves is spatially organized in beams, whose orientation is determined by the direction of the of the open ocean waves incident on the ice-shelf front. As a result, depending on the beams orientation, parts of the Ross Ice Shelf experience significantly larger flexural stresses compared to other parts where the flexural gravity beams do not propagate. Very long-period waves can propagate farther away from the ice-shelf front exciting flexural stresses in the vicinity of the grounding line.

LLL 8080 BASIC-II interpreter user's manual

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

McGoldrick, P.R.; Dickinson, J.; Allison, T.G.

1978-04-03

Scientists are finding increased applications for microprocessors as process controllers in their experiments. However, while microprocessors are small and inexpensive, they are difficult to program in machine or assembly language. A high-level language is needed to enable scientists to develop their own microcomputer programs for their experiments on location. Recognizing this need, LLL contracted to have such a language developed. This report describes the resulting LLL BASIC interpreter, which opeates with LLL's 8080-based MCS-8 microcomputer system. All numerical operations are done using Advanced Micro Device's Am9511 arithmetic processor chip or optionally by using a software simulation of that chip. 1more » figure.« less

Spectral Analysis of Forecast Error Investigated with an Observing System Simulation Experiment

NASA Technical Reports Server (NTRS)

Prive, N. C.; Errico, Ronald M.

2015-01-01

The spectra of analysis and forecast error are examined using the observing system simulation experiment (OSSE) framework developed at the National Aeronautics and Space Administration Global Modeling and Assimilation Office (NASAGMAO). A global numerical weather prediction model, the Global Earth Observing System version 5 (GEOS-5) with Gridpoint Statistical Interpolation (GSI) data assimilation, is cycled for two months with once-daily forecasts to 336 hours to generate a control case. Verification of forecast errors using the Nature Run as truth is compared with verification of forecast errors using self-analysis; significant underestimation of forecast errors is seen using self-analysis verification for up to 48 hours. Likewise, self analysis verification significantly overestimates the error growth rates of the early forecast, as well as mischaracterizing the spatial scales at which the strongest growth occurs. The Nature Run-verified error variances exhibit a complicated progression of growth, particularly for low wave number errors. In a second experiment, cycling of the model and data assimilation over the same period is repeated, but using synthetic observations with different explicitly added observation errors having the same error variances as the control experiment, thus creating a different realization of the control. The forecast errors of the two experiments become more correlated during the early forecast period, with correlations increasing for up to 72 hours before beginning to decrease.

Coherent control schemes for the photoionization of neon and helium in the Extreme Ultraviolet spectral region.

PubMed

Giannessi, Luca; Allaria, Enrico; Prince, Kevin C; Callegari, Carlo; Sansone, Giuseppe; Ueda, Kiyoshi; Morishita, Toru; Liu, Chien Nan; Grum-Grzhimailo, Alexei N; Gryzlova, Elena V; Douguet, Nicolas; Bartschat, Klaus

2018-05-17

The seeded Free-Electron Laser (FEL) FERMI is the first source of short-wavelength light possessing the full coherence of optical lasers, together with the extreme power available from FELs. FERMI provides longitudinally coherent radiation in the Extreme Ultraviolet and soft x-ray spectral regions, and therefore opens up wide new fields of investigation in physics. We first propose experiments exploiting this property to provide coherent control of the photoionization of neon and helium, carry out numerical calculations to find optimum experimental parameters, and then describe how these experiments may be realized. The approach uses bichromatic illumination of a target and measurement of the products of the interaction, analogous to previous Brumer-Shapiro-type experiments in the optical spectral range. We describe operational schemes for the FERMI FEL, and simulate the conditions necessary to produce light at the fundamental and second or third harmonic frequencies, and to control the phase with respect to the fundamental. We conclude that a quantitative description of the phenomena is extremely challenging for present state-of-the-art theoretical and computational methods, and further development is necessary. Furthermore, the intensity available may already be excessive for the experiments proposed on helium. Perspectives for further development are discussed.

A global strategy based on experiments and simulations for squeal prediction on industrial railway brakes

NASA Astrophysics Data System (ADS)

Sinou, J.-J.; Loyer, A.; Chiello, O.; Mogenier, G.; Lorang, X.; Cocheteux, F.; Bellaj, S.

2013-09-01

This paper presents an overview of recent experimental and numerical investigations on industrial railway brakes. The goal of the present study is to discuss the relevance of the mechanical modeling strategy for squeal prediction. Specific experimental set-ups based on transient and controlled braking tests are designed for this purpose. Measurements are performed on it to investigate the dynamic behavior of TGV squeal noise and its squeal characterization through experiments. It will be demonstrated that it is possible to build consistent and efficient finite element models to simulate squeal events in TGV brake systems. The numerical strategy will be presented, including not only the modeling of the TGV brake system and the stability analysis, but also the transient nonlinear dynamic and computational process based on efficient reduced basis. This complete numerical strategy allows us to perform relevance squeal prediction on industrial railway brakes. This study comes within the scope of a research program AcouFren that is supported by ADEME (Agence De l'Environnement et de la Maîtrise de l'Energie) concerning the reduction of the squeal noise generated by high power railway disc brakes. experiments with an evolution of the rotational speed of the disc: these tests are called "transient braking tests" and correspond to real braking tests, experiments with a controlled steady rotational speed (i.e. dynamic fluctuations in rotational speed are not significant): these tests are called "controlled braking tests". In the present study, the Continuous Wavelet Transform (CWT) [20] is used to study the time-history responses of the TGV brake system. So, a brief basic theory of the wavelet analysis that transforms a signal into wavelets that are well localized both in frequency and time is presented in this part of the paper. Considering a function f(t), the associated Continuous Wavelet Transform (CWT) corresponds to a wavelet transform given by W(a,b)=∫-∞+∞f(t)ψa,b*(t) dt where ψ(t)={1}/{√{a}}ψ({t-b}/{a}) where a and b define the scale parameter and the time translation factor, respectively. The asterisk ψa,b* indicates the complex conjugate of ψ that are the daughter wavelets (i.e. the dilated and shifted versions of the "'mother"' wavelet ψ that is continuous in both time and frequency). The mother wavelet must satisfy an admissibility criterion in order to get a stably invertible transform.

Female control of paternity in the sexually cannibalistic spider Argiope keyserlingi.

PubMed Central

Elgar, M A; Schneider, J M; Herberstein, M E

2000-01-01

Sexual conflict theory predicts an antagonistic coevolution, with each sex evolving adaptations and counter-adaptations to overcome a temporary dominance of the other sex over the control of paternity. Polyandry allows sexual selection to operate after mating has commenced, with male and female interests competing for control of fertilization. There are numerous examples of male control of paternity, but few studies have unambiguously revealed female control. Attributing variance in paternity to females is often difficult since male and female influences cannot be separated unambiguously. However, we show that polyandrous female orb-web spiders Argiope keserlingi (Arancidae) control the paternity of their offspring by adjusting the timing of sexual cannibalism. Our experiments reveal that females copulating with relatively smaller males delay sexual cannibalism, thereby prolonging the duration of copulation, and that these males consequently fertilize relatively more eggs. PMID:11133035

Zero Power Non-Contact Suspension System with Permanent Magnet Motion Feedback

NASA Astrophysics Data System (ADS)

Sun, Feng; Oka, Koichi

This paper proposes a zero power control method for a permanent magnetic suspension system consisting mainly of a permanent magnet, an actuator, sensors, a suspended iron ball and a spring. A system using this zero power control method will consume quasi-zero power when the levitated object is suspended in an equilibrium state. To realize zero power control, a spring is installed in the magnetic suspension device to counterbalance the gravitational force on the actuator in the equilibrium position. In addition, an integral feedback loop in the controller affords zero actuator current when the device is in a balanced state. In this study, a model was set up for feasibility analysis, a prototype was manufactured for experimental confirmation, numerical simulations of zero power control with nonlinear attractive force were carried out based on the model, and experiments were completed to confirm the practicality of the prototype. The simulations and experiments were performed under varied conditions, such as without springs and without zero power control, with springs and without zero power control, with springs and with zero power control, using different springs and integral feedback gains. Some results are shown and analyzed in this paper. All results indicate that this zero power control method is feasible and effective for use in this suspension system with a permanent magnet motion feedback loop.

The distance effect in numerical memory-updating tasks.

PubMed

Lendínez, Cristina; Pelegrina, Santiago; Lechuga, Teresa

2011-05-01

Two experiments examined the role of numerical distance in updating numerical information in working memory. In the first experiment, participants had to memorize a new number only when it was smaller than a previously memorized number. In the second experiment, updating was based on an external signal, which removed the need to perform any numerical comparison. In both experiments, distance between the memorized number and the new one was manipulated. The results showed that smaller distances between the new and the old information led to shorter updating times. This graded facilitation suggests that the process by which information is substituted in the focus of attention involves maintaining the shared features between the new and the old number activated and selecting other new features to be activated. Thus, the updating cost may be related to amount of new features to be activated in the focus of attention.

The contributions of numerical acuity and non-numerical stimulus features to the development of the number sense and symbolic math achievement.

PubMed

Starr, Ariel; DeWind, Nicholas K; Brannon, Elizabeth M

2017-11-01

Numerical acuity, frequently measured by a Weber fraction derived from nonsymbolic numerical comparison judgments, has been shown to be predictive of mathematical ability. However, recent findings suggest that stimulus controls in these tasks are often insufficiently implemented, and the proposal has been made that alternative visual features or inhibitory control capacities may actually explain this relation. Here, we use a novel mathematical algorithm to parse the relative influence of numerosity from other visual features in nonsymbolic numerical discrimination and to examine the strength of the relations between each of these variables, including inhibitory control, and mathematical ability. We examined these questions developmentally by testing 4-year-old children, 6-year-old children, and adults with a nonsymbolic numerical comparison task, a symbolic math assessment, and a test of inhibitory control. We found that the influence of non-numerical features decreased significantly over development but that numerosity was a primary determinate of decision making at all ages. In addition, numerical acuity was a stronger predictor of math achievement than either non-numerical bias or inhibitory control in children. These results suggest that the ability to selectively attend to number contributes to the maturation of the number sense and that numerical acuity, independent of inhibitory control, contributes to math achievement in early childhood. Copyright © 2017 Elsevier B.V. All rights reserved.

Analysis of Residual Acceleration Effects on Transport and Segregation During Directional Solidification of Tin-Bismuth in the MEPHISTO Furnace Facility

NASA Technical Reports Server (NTRS)

Alexander J. Iwan D. (Principal Investigator)

1996-01-01

The objective of this work is to approach the problem of determining the transport conditions (and effects of residual acceleration) during the plane-front directional solidification of a tin-bismuth alloy under low gravity conditions. The work involves using a combination of 2- and 3-D numerical models, scaling analyses, ID models and the results of ground-based and low-gravity experiments. The latter are to be conducted during the MEPHISTO experiment scheduled for USMP-3 in early 1996. The models will be used to predict the response of the transport conditions and consequent solute segregation in directionally solidifying tin-bismuth melt. Real-time Seebeck voltage variations across a Sn-Bi melt during directional solidification in MEPHISTO on USMP-1 show a distinct variation which can be correlated with thruster firings. The Seebeck voltage measurement is related to the response of the instantaneous average melt composition at the melt-solid interface. This allows a direct comparison of numerical simulations with the Seebeck signals obtained on USMP-1. The effects of such accelerations on composition for a directionally solidifying Sn-Bi alloy have been simulated numerically. USMP-1 acceleration data was used to assist in our choice of acceleration magnitude and orientation. The results show good agreement with experimental observations. The USMP-3 experiments took place earlier this year (February 22 through March 6). There were several differences between the USMP-3 experiments as compared to USMP-1. Firstly a more concentrated alloy was solidified and, secondly, Primary Reaction Control System thruster burns were requested at particular times during four separate growth runs. This allowed us to monitor the response Seebeck response under well-characterized growth conditions. In addition, we carried out simulations during the experiment in order to interpret the Seebeck signal. Preliminary results are described here.

Anchoring effects in the judgment of confidence: semantic or numeric priming?

PubMed

Carroll, Steven R; Petrusic, William M; Leth-Steensen, Craig

2009-02-01

Over the last decade, researchers have debated whether anchoring effects are the result of semantic or numeric priming. The present study tested both hypotheses. In four experiments involving a sensory detection task, participants first made a relative confidence judgment by deciding whether they were more or less confident than an anchor value in the correctness of their decision. Subsequently, they expressed an absolute level of confidence. In two of these experiments, the relative confidence anchor values represented the midpoints between the absolute confidence scale values, which were either explicitly numeric or semantic, nonnumeric representations of magnitude. In two other experiments, the anchor values were drawn from a scale modally different from that used to express the absolute confidence (i.e., nonnumeric and numeric, respectively, or vice versa). Regardless of the nature of the anchors, the mean confidence ratings revealed anchoring effects only when the relative and absolute confidence values were drawn from identical scales. Together, the results of these four experiments limit the conditions under which both numeric and semantic priming would be expected to lead to anchoring effects.

Numerical simulations of the flow with the prescribed displacement of the airfoil and comparison with experiment

NASA Astrophysics Data System (ADS)

Řidký, V.; Šidlof, P.; Vlček, V.

2013-04-01

The work is devoted to comparing measured data with the results of numerical simulations. As mathematical model was used mathematical model whitout turbulence for incompressible flow In the experiment was observed the behavior of designed NACA0015 airfoil in airflow. For the numerical solution was used OpenFOAM computational package, this is open-source software based on finite volume method. In the numerical solution is prescribed displacement of the airfoil, which corresponds to the experiment. The velocity at a point close to the airfoil surface is compared with the experimental data obtained from interferographic measurements of the velocity field. Numerical solution is computed on a 3D mesh composed of about 1 million ortogonal hexahedron elements. The time step is limited by the Courant number. Parallel computations are run on supercomputers of the CIV at Technical University in Prague (HAL and FOX) and on a computer cluster of the Faculty of Mechatronics of Liberec (HYDRA). Run time is fixed at five periods, the results from the fifth periods and average value for all periods are then be compared with experiment.

Virtual experiments: a new approach for improving process conceptualization in hillslope hydrology

NASA Astrophysics Data System (ADS)

Weiler, Markus; McDonnell, Jeff

2004-01-01

We present an approach for process conceptualization in hillslope hydrology. We develop and implement a series of virtual experiments, whereby the interaction between water flow pathways, source and mixing at the hillslope scale is examined within a virtual experiment framework. We define these virtual experiments as 'numerical experiments with a model driven by collective field intelligence'. The virtual experiments explore the first-order controls in hillslope hydrology, where the experimentalist and modeler work together to cooperatively develop and analyze the results. Our hillslope model for the virtual experiments (HillVi) in this paper is based on conceptualizing the water balance within the saturated and unsaturated zone in relation to soil physical properties in a spatially explicit manner at the hillslope scale. We argue that a virtual experiment model needs to be able to capture all major controls on subsurface flow processes that the experimentalist might deem important, while at the same time being simple with few 'tunable parameters'. This combination makes the approach, and the dialog between experimentalist and modeler, a useful hypothesis testing tool. HillVi simulates mass flux for different initial conditions under the same flow conditions. We analyze our results in terms of an artificial line source and isotopic hydrograph separation of water and subsurface flow. Our results for this first set of virtual experiments showed how drainable porosity and soil depth variability exert a first order control on flow and transport at the hillslope scale. We found that high drainable porosity soils resulted in a restricted water table rise, resulting in more pronounced channeling of lateral subsurface flow along the soil-bedrock interface. This in turn resulted in a more anastomosing network of tracer movement across the slope. The virtual isotope hydrograph separation showed higher proportions of event water with increasing drainable porosity. When combined with previous experimental findings and conceptualizations, virtual experiments can be an effective way to isolate certain controls and examine their influence over a range of rainfall and antecedent wetness conditions.

Dynamics of Active Separation Control at High Reynolds Numbers

NASA Technical Reports Server (NTRS)

Pack, LaTunia G.; Seifert, Avi

2000-01-01

A series of active flow control experiments were recently conducted at high Reynolds numbers on a generic separated configuration. The model simulates the upper surface of a 20% thick Glauert-Goldschmied type airfoil at zero angle of attack. The flow is fully turbulent since the tunnel sidewall boundary layer flows over the model. The main motivation for the experiments is to generate a comprehensive data base for validation of unsteady numerical simulation as a first step in the development of a CFD design tool, without which it would not be possible to effectively utilize the great potential of unsteady flow control. This paper focuses on the dynamics of several key features of the baseline as well as the controlled flow. It was found that the thickness of the upstream boundary layer has a negligible effect on the flow dynamics. It is speculated that separation is caused mainly by the highly convex surface while viscous effects are less important. The two-dimensional separated flow contains unsteady waves centered on a reduced frequency of 0.8, while in the three dimensional separated flow, frequencies around a reduced frequency of 0.3 and 1 are active. Several scenarios of resonant wave interaction take place at the separated shear-layer and in the pressure recovery region. The unstable reduced frequency bands for periodic excitation are centered on 1.5 and 5, but these reduced frequencies are based on the length of the baseline bubble that shortens due to the excitation. The conventional swept wing-scaling works well for the coherent wave features. Reproduction of these dynamic effects by a numerical simulation would provide benchmark validation.

Effect of Residual Noncondensables on Pressurization and Pressure Control of a Zero-Boil-Off Tank in Microgravity

NASA Technical Reports Server (NTRS)

Kassemi, Mohammad; Hylton, Sonya; Kartizova, Olga

2013-01-01

The Zero-Boil-Off Tank (ZBOT) Experiment is a small-scale experiment that uses a transparent ventless Dewar and a transparent simulant phase-change fluid to study sealed tank pressurization and pressure control with applications to on-surface and in-orbit storage of propellant cryogens. The experiment will be carried out under microgravity conditions aboard the International Space Station in the 2014 timeframe. This paper presents preliminary results from ZBOT's ground-based research that focuses on the effects of residual noncondensable gases in the ullage on both pressurization and pressure reduction trends in the sealed Dewar. Tank pressurization is accomplished through heating of the test cell wall in the wetted and un-wetted regions simultaneously or separately. Pressure control is established through mixing and destratification of the bulk liquid using a temperature controlled forced jet flow with different degrees of liquid jet subcooling. A Two-Dimensional axisymmetric two-phase CFD model for tank pressurization and pressure control is also presented. Numerical prediction of the model are compared to experimental 1g results to both validate the model and also indicate the effect of the noncondensable gas on evolution of pressure and temperature distributions in the ullage during pressurization and pressure control. Microgravity simulations case studies are also performed using the validated model to underscore and delineate the profound effect of the noncondensables on condensation rates and interfacial temperature distributions with serious implications for tank pressure control in reduced gravity.

Flowering in space

NASA Astrophysics Data System (ADS)

Zheng, Hui Qiong

2018-05-01

The reproductive success of plants is often dependent on their flowering time being adapted to the terrestrial environment, in which gravity remain constant. Whether plants can follow the same rule to determine their flowering time under microgravity in space is unknown. Although numerous attempts have been made to grow a plant through a complete life cycle in space, apparently no published information exists concerning the flowering control of plants under microgravity in space. Here, we focused on two aspects. Firstly the environmental and intrinsic factors under microgravity related to flowering control. Secondly, the plant-derived regulators are involved in flowering control under microgravity condition. The potential environmental and intrinsic factors affect plant flowering under microgravity may include light, biological circadian clock as well as long-distance signaling, while the plant-derived flowering regulators in response to microgravity could include gibberellic acid, ethylene, microRNA and sugar. The results we have obtained from the space experiments on board the Chinese recoverable satellites (the SJ-8 and the SJ-10) and the experiment on the Chinese space lab TG-2 are also introduced. We conclude by suggesting that long-term space experiments from successive generations and a systematic analysis of regulatory networks at the molecular level is needed to understand the mechanism of plant flowering control under microgravity conditions in space.

On the ability of plant life-history strategies to shape bio-geomorphologic interactions

NASA Astrophysics Data System (ADS)

Schwarz, Christian; van Belzen, Jim; Zhu, ZhenChang; Bouma, Tjeerd; van de Koppel, Johan; Gourgue, Olivier; Temmerman, Stijn

2017-04-01

Previous work studying bio-geomorphologic interactions in intertidal habitats underlined the importance of wetland vegetation shaping their environment (e.g. tidal channel networks). Up to this point the potential of wetland vegetation to shape their environment was linked to their physical plant properties, such as stiffness, stem diameter or stem density. However the effect of life-history strategies, i.e. the mode of plant proliferation such as sexual reproduction from seeds, non-sexual lateral expansion or a combination of the former two was hitherto ignored. We present numerical experiments based on a wetland ecosystem present in the Western Scheldt Estuary (SW, the Netherlands) showing the importance of life-history strategies shaping bio-geomorphologic interactions. We specifically compare two extremes in life-history strategies, (1) one species solely establishing from seeds and relying on their mass recruitment (Salicornia europea); And a second species (Spartina anglica) which relies on a mixed establishment strategy consisting of seed dispersal and asexual lateral expansion through tillering, with a very low seed recruitment success per year. Based on conducted numerical experiments using TELEMAC2D we show that the Spartina-case facilitates relative low channel densities with pronounced channel networks, whereas the Salicornia-case favors high channel densities with less pronounced intertidal channels. The conducted numerical experiments are the first indication showing that plant proliferation strategies exert a major control on emerging patterns in bio-geomorphologic systems. This provides a deeper understanding in the constraining factors and dynamics shaping the emergence and resilience of bio-geomorphologic systems.

Numerical Study of the Influences of a Monsoon Gyre on Intensity Changes of Typhoon Chan-Hom (2015)

NASA Astrophysics Data System (ADS)

Liang, Jia; Wu, Liguang; Gu, Guojun

2018-05-01

Typhoon Chan-Hom (2015) underwent a weakening in the tropical western North Pacific (WNP) when it interacted with a monsoon gyre, but all operational forecasts failed to predict this intensity change. A recent observational study indicated that it resulted from its interaction with a monsoon gyre on the 15-30-day timescale. In this study, the results of two numerical experiments are presented to investigate the influence of the monsoon gyre on the intensity changes of Typhoon Chan-Hom (2015). The control experiment captures the main observed features of the weakening process of Chan-Hom (2015) during a sharp northward turn in the Philippine Sea, including the enlargement of the eye size, the development of strong convection on the eastern side of the monsoon gyre, and the corresponding strong outer inflow. The sensitivity experiment suggests that intensity changes of Chan-Hom (2015) were mainly associated with its interaction with the monsoon gyre. When Chan-Hom (2015) initially moved westward in the eastern part of the monsoon gyre, the monsoon gyre enhanced the inertial stability for the intensification of the typhoon. With its coalescence with the monsoon gyre, the development of the strong convection on the eastern side of the monsoon gyre prevented moisture and mass entering the inner core of Chan-Hom (2015), resulting in the collapse of the eyewall. Thus, the weakening happened in the deep tropical WNP region. The numerical simulations confirm the important effects of the interaction between tropical cyclones and monsoon gyres on tropical cyclone intensity.

Electrohydrodynamic coalescence of droplets using an embedded potential flow model

NASA Astrophysics Data System (ADS)

Garzon, M.; Gray, L. J.; Sethian, J. A.

2018-03-01

The coalescence, and subsequent satellite formation, of two inviscid droplets is studied numerically. The initial drops are taken to be of equal and different sizes, and simulations have been carried out with and without the presence of an electrical field. The main computational challenge is the tracking of a free surface that changes topology. Coupling level set and boundary integral methods with an embedded potential flow model, we seamlessly compute through these singular events. As a consequence, the various coalescence modes that appear depending upon the relative ratio of the parent droplets can be studied. Computations of first stage pinch-off, second stage pinch-off, and complete engulfment are analyzed and compared to recent numerical studies and laboratory experiments. Specifically, we study the evolution of bridge radii and the related scaling laws, the minimum drop radii evolution from coalescence to satellite pinch-off, satellite sizes, and the upward stretching of the near cylindrical protrusion at the droplet top. Clear evidence of partial coalescence self-similarity is presented for parent droplet ratios between 1.66 and 4. This has been possible due to the fact that computational initial conditions only depend upon the mother droplet size, in contrast with laboratory experiments where the difficulty in establishing the same initial physical configuration is well known. The presence of electric forces changes the coalescence patterns, and it is possible to control the satellite droplet size by tuning the electrical field intensity. All of the numerical results are in very good agreement with recent laboratory experiments for water droplet coalescence.

A Coupled Thermal–Hydrological–Mechanical Damage Model and Its Numerical Simulations of Damage Evolution in APSE

PubMed Central

Wei, Chenhui; Zhu, Wancheng; Chen, Shikuo; Ranjith, Pathegama Gamage

2016-01-01

This paper proposes a coupled thermal–hydrological–mechanical damage (THMD) model for the failure process of rock, in which coupling effects such as thermally induced rock deformation, water flow-induced thermal convection, and rock deformation-induced water flow are considered. The damage is considered to be the key factor that controls the THM coupling process and the heterogeneity of rock is characterized by the Weibull distribution. Next, numerical simulations on excavation-induced damage zones in Äspö pillar stability experiments (APSE) are carried out and the impact of in situ stress conditions on damage zone distribution is analysed. Then, further numerical simulations of damage evolution at the heating stage in APSE are carried out. The impacts of in situ stress state, swelling pressure and water pressure on damage evolution at the heating stage are simulated and analysed, respectively. The simulation results indicate that (1) the v-shaped notch at the sidewall of the pillar is predominantly controlled by the in situ stress trends and magnitude; (2) at the heating stage, the existence of confining pressure can suppress the occurrence of damage, including shear damage and tensile damage; and (3) the presence of water flow and water pressure can promote the occurrence of damage, especially shear damage. PMID:28774001

On Electromagnetic Modulation of Flow Instabilities, Mixing and Heat Transfer in Conducting and Magnetized Fluids

NASA Astrophysics Data System (ADS)

Kenjeres, S.

2016-09-01

In the present paper we give a concise review of some recent highlights of our research dealing with electromagnetic control of flow, mixing and heat transfer of electrically conductive or magnetized fluids. We apply a combination of state-of-art numerical (DNS and LES) and experimental (PIV and LIF) techniques to provide fundamental insights into the complex phenomena of interactions between imposed (or induced) electromagnetic fields and underlying fluid flow. Our analysis covers an extensive range of working fluids, i.e. weakly- and highly-electrically-conductive, as well as magnetized fluids. These interactions are defined through the presence of different types of body forces acting per volume of fluid. A fully closed system of governing equations containing an extended set of the Navier-Stokes and a simplified set of the Maxwell equations is presented. The four characteristic examples are selected: the electromagnetic control of self-sustained jet oscillations, the electromagnetic enhancement of heat transfer in thermal convection, the wake interactions behind magnetic obstacles and finally, the thermo-magnetic convection in differentially heated cubical enclosure. The comparative assessment between experimental and numerical results is presented. It is concluded that generally good agreement between simulations and experiments is obtained for all cases considered, proving the concept of electromagnetic modulation, which can be used in numerous technological applications.

Characterization and modeling of turbidity density plume induced into stratified reservoir by flood runoffs.

PubMed

Chung, S W; Lee, H S

2009-01-01

In monsoon climate area, turbidity flows typically induced by flood runoffs cause numerous environmental impacts such as impairment of fish habitat and river attraction, and degradation of water supply efficiency. This study was aimed to characterize the physical dynamics of turbidity plume induced into a stratified reservoir using field monitoring and numerical simulations, and to assess the effect of different withdrawal scenarios on the control of downstream water quality. Three different turbidity models (RUN1, RUN2, RUN3) were developed based on a two-dimensional laterally averaged hydrodynamic and transport model, and validated against field data. RUN1 assumed constant settling velocity of suspended sediment, while RUN2 estimated the settling velocity as a function of particle size, density, and water temperature to consider vertical stratification. RUN3 included a lumped first-order turbidity attenuation rate taking into account the effects of particles aggregation and degradable organic particles. RUN3 showed best performance in replicating the observed variations of in-reservoir and release turbidity. Numerical experiments implemented to assess the effectiveness of different withdrawal depths showed that the alterations of withdrawal depth can modify the pathway and flow regimes of the turbidity plume, but its effect on the control of release water quality could be trivial.

Experiments in cooperative-arm object manipulation with a two-armed free-flying robot. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Koningstein, Ross

1990-01-01

Developing computed-torque controllers for complex manipulator systems using current techniques and tools is difficult because they address the issues pertinent to simulation, as opposed to control. A new formulation of computed-torque (CT) control that leads to an automated computer-torque robot controller program is presented. This automated tool is used for simulations and experimental demonstrations of endpoint and object control from a free-flying robot. A new computed-torque formulation states the multibody control problem in an elegant, homogeneous, and practical form. A recursive dynamics algorithm is presented that numerically evaluates kinematics and dynamics terms for multibody systems given a topological description. Manipulators may be free-flying, and may have closed-chain constraints. With the exception of object squeeze-force control, the algorithm does not deal with actuator redundancy. The algorithm is used to implement an automated 2D computed-torque dynamics and control package that allows joint, endpoint, orientation, momentum, and object squeeze-force control. This package obviates the need for hand-derivation of kinematics and dynamics, and is used for both simulation and experimental control. Endpoint control experiments are performed on a laboratory robot that has two arms to manipulate payloads, and uses an air bearing to achieve very-low drag characteristics. Simulations and experimental data for endpoint and object controllers are presented for the experimental robot - a complex dynamic system. There is a certain rather wide set of conditions under which CT endpoint controllers can neglect robot base accelerations (but not motions) and achieve comparable performance including base accelerations in the model. The regime over which this simplification holds is explored by simulation and experiment.

Quantifying a threat: Evidence of a numeric processing bias.

PubMed

Hamamouche, Karina A; Niemi, Laura; Cordes, Sara

2017-06-01

Humans prioritize the processing of threats over neutral stimuli; thus, not surprisingly, the presence of threats has been shown to alter performance on both perceptual and cognitive tasks. Yet whether the quantification process is disrupted in the presence of threat is unknown. In three experiments, we examined numerical estimation and discrimination abilities in adults in the context of threatening (spiders) and non-threatening (e.g., flowers) stimuli. Results of the numerical estimation task (Experiment 1) showed that participants underestimated the number of threatening relative to neutral stimuli. Additionally, numerical discrimination data reveal that participants' abilities to discriminate between the number of entities in two arrays were worsened when the arrays consisted of threatening entities versus neutral entities (Experiment 2). However, discrimination abilities were enhanced when threatening content was presented immediately before neutral dot arrays (Experiment 3). Together, these studies suggest that threats impact our processing of visual numerosity via changes in attention to numerical stimuli, and that the nature of the threat (intrinsic or extrinsic to the stimulus) is vital in determining the direction of this impact. Intrinsic threat content in stimuli impedes its own quantification; yet threat that is extrinsic to the sets to be enumerated enhances numerical processing for subsequently presented neutral stimuli. Copyright © 2017 Elsevier B.V. All rights reserved.

Synchronization of natural convection in thermostatically-controlled adjacent cavities

NASA Astrophysics Data System (ADS)

Chavez-Martinez, Rafael; Sanchez-Lopez, Mario; Solorio-Ordaz, Francisco Javier; Sen, Mihir

2017-11-01

Synchronization is a phenomenon observed in complex dynamical systems. It was first noticed by Huygens in the 17th century, and since then has been observed in systems of different types such as mechanical, biological and social. In thermal systems, numerical and analytical studies have found that two or more similar heat sources, with independent thermostatic temperature control and communicating with each other through a common interface, can have temperature oscillations. In the present study, laboratory experiments were carried out to study the thermal synchronization in two cuboid rooms separated by a common wall. Computer-based thermostats independently control the temperature of each cavity. The experiments show the effect of the ambient temperature and the initial condition in the cavities on the phase difference Δϕ . The results demonstrate in-phase and out-of-phase synchronization. An increase of the temperature difference between the cavity and the ambient, ΔT , increases Δϕ . When ΔT <2° C, Δϕ oscillates around zero. Δϕ is negative independently of the initial condition. The results of these experiments will be useful in the desing of heating in full-scale buildings. This work is supported by DGAPA-UNAM Grant PAPIIT-IN114216.

The dilemma of controlling cultural eutrophication of lakes

PubMed Central

Schindler, David W.

2012-01-01

The management of eutrophication has been impeded by reliance on short-term experimental additions of nutrients to bottles and mesocosms. These measures of proximate nutrient limitation fail to account for the gradual changes in biogeochemical nutrient cycles and nutrient fluxes from sediments, and succession of communities that are important components of whole-ecosystem responses. Erroneous assumptions about ecosystem processes and lack of accounting for hysteresis during lake recovery have further confused management of eutrophication. I conclude that long-term, whole-ecosystem experiments and case histories of lake recovery provide the only reliable evidence for policies to reduce eutrophication. The only method that has had proven success in reducing the eutrophication of lakes is reducing input of phosphorus. There are no case histories or long-term ecosystem-scale experiments to support recent claims that to reduce eutrophication of lakes, nitrogen must be controlled instead of or in addition to phosphorus. Before expensive policies to reduce nitrogen input are implemented, they require ecosystem-scale verification. The recent claim that the ‘phosphorus paradigm’ for recovering lakes from eutrophication has been ‘eroded’ has no basis. Instead, the case for phosphorus control has been strengthened by numerous case histories and large-scale experiments spanning several decades. PMID:22915669

Bubble-facilitated VOC transport: Laboratory experiments and numerical modelling

NASA Astrophysics Data System (ADS)

Mumford, K. G.; Soucy, N. C.

2017-12-01

Most conceptual and numerical models of vapor intrusion assume that the transport of volatile organic compounds (VOCs) from the source to near the building foundation is a diffusion-limited processes. However, the transport of VOCs by mobilized gas bubbles through the saturated zone could lead to increased rates of transport and advection through the unsaturated zone, thereby increasing mass flux and risks associated with vapor intrusion. This mobilized gas could be biogenic (methanogenic) but could also result from the partitioning of VOC to trapped atmospheric gases in light non-aqueous phase liquid (LNAPL) smear zones. The potential for bubble-facilitated VOC transport to increase mass flux was investigated in a series of 1D and 2D laboratory experiments. Pentane source zones were emplaced in sand using sequential drainage and imbibition steps to mimic a water table fluctuation and trap air alongside LNAPL residual. This source was placed below an uncontaminated, water saturated sand (occlusion zone) and a gravel-sized (glass beads) unsaturated zone. Water was pumped laterally through the source zone and occlusion zone to deliver the dissolved gases (air) that are required for the expansion of trapped gas bubbles. Images from 2D flow cell experiments were used to demonstrate fluid rearrangement in the source zone and gas expansion to the occlusion zone, and 1D column experiments were used to measure gas-phase pentane mass flux. This flux was found to be 1-2 orders of magnitude greater than that measured in diffusion-dominated control columns, and showed intermittent behavior consistent with bubble transport by repeated expansion, mobilization, coalescence and trapping. Numerical simulation results under a variety of conditions using an approach that couples macroscopic invasion percolation with mass transfer (MIP-MT) between the aqueous and gas phases will also be presented. The results of this study demonstrate the potential for bubble-facilitated transport to increase transport rates linked to vapor intrusion, and will serve as a basis for further development of conceptual and numerical models to investigate the conditions under which this mechanism may play an important role.

Computation of aerodynamic interference effects on oscillating airfoils with controls in ventilated subsonic wind tunnels

NASA Technical Reports Server (NTRS)

Fromme, J. A.; Golberg, M. A.

1979-01-01

Lift interference effects are discussed based on Bland's (1968) integral equation. A mathematical existence theory is utilized for which convergence of the numerical method has been proved for general (square-integrable) downwashes. Airloads are computed using orthogonal airfoil polynomial pairs in conjunction with a collocation method which is numerically equivalent to Galerkin's method and complex least squares. Convergence exhibits exponentially decreasing error with the number n of collocation points for smooth downwashes, whereas errors are proportional to 1/n for discontinuous downwashes. The latter can be reduced to 1/n to the m+1 power with mth-order Richardson extrapolation (by using m = 2, hundredfold error reductions were obtained with only a 13% increase of computer time). Numerical results are presented showing acoustic resonance, as well as the effect of Mach number, ventilation, height-to-chord ratio, and mode shape on wind-tunnel interference. Excellent agreement with experiment is obtained in steady flow, and good agreement is obtained for unsteady flow.

Development of high velocity gas gun with a new trigger system-numerical analysis

NASA Astrophysics Data System (ADS)

Husin, Z.; Homma, H.

2018-02-01

In development of high performance armor vests, we need to carry out well controlled experiments using bullet speed of more than 900 m/sec. After reviewing trigger systems used for high velocity gas guns, this research intends to develop a new trigger system, which can realize precise and reproducible impact tests at impact velocity of more than 900 m/sec. A new trigger system developed here is called a projectile trap. A projectile trap is placed between a reservoir and a barrel. A projectile trap has two functions of a sealing disk and triggering. Polyamidimide is selected for the trap material and dimensions of the projectile trap are determined by numerical analysis for several levels of launching pressure to change the projectile velocity. Numerical analysis results show that projectile trap designed here can operate reasonably and stresses caused during launching operation are less than material strength. It means a projectile trap can be reused for the next shooting.

Numerical Investigation of Flow in a Centrifugal Compressor

NASA Astrophysics Data System (ADS)

Grishin, Yu. A.; Bakulin, V. N.

2015-09-01

With the use of the domestic software suite of computational hydrodynamics Flow Vision based on application of the method of control volumes, numerical simulation of air composition and delivery by a centrifugal compressor employed for supercharging a piston engine has been carried out. The head-flow characteristics of the compressor, as well as the 3D fields of flow velocity and pressure distributions in the elements of the compressor flow passage, including the interblade channels of the impeller, have been obtained for various regimes. In the regimes of diminished air flow rate, surging phenomena are identified, characterized by a return flow. The application of the technique of numerical experiment will make it possible from here on to carry out design optimization of the compressor flow passage profile and thus to improve its basic characteristics — the degree of pressure increase, compressed air flow rate, and the efficiency — as well as to reduce the costs of the development and production of compressors.

Analysis of wind-blown sand movement over transverse dunes.

PubMed

Jiang, Hong; Huang, Ning; Zhu, Yuanjian

2014-12-01

Wind-blown sand movement often occurs in a very complicated desert environment where sand dunes and ripples are the basic forms. However, most current studies on the theoretic and numerical models of wind-blown sand movement only consider ideal conditions such as steady wind velocity, flat sand surface, etc. In fact, the windward slope gradient plays a great role in the lift-off and sand particle saltation. In this paper, we propose a numerical model for the coupling effect between wind flow and saltating sand particles to simulate wind-blown sand movement over the slope surface and use the SIMPLE algorithm to calculate wind flow and simulate sands transport by tracking sand particle trajectories. We furthermore compare the result of numerical simulation with wind tunnel experiments. These results prove that sand particles have obvious effect on wind flow, especially that over the leeward slope. This study is a preliminary study on windblown sand movement in a complex terrain, and is of significance in the control of dust storms and land desertification.

Analysis of Wind-blown Sand Movement over Transverse Dunes

PubMed Central

Jiang, Hong; Huang, Ning; Zhu, Yuanjian

2014-01-01

Wind-blown sand movement often occurs in a very complicated desert environment where sand dunes and ripples are the basic forms. However, most current studies on the theoretic and numerical models of wind-blown sand movement only consider ideal conditions such as steady wind velocity, flat sand surface, etc. In fact, the windward slope gradient plays a great role in the lift-off and sand particle saltation. In this paper, we propose a numerical model for the coupling effect between wind flow and saltating sand particles to simulate wind-blown sand movement over the slope surface and use the SIMPLE algorithm to calculate wind flow and simulate sands transport by tracking sand particle trajectories. We furthermore compare the result of numerical simulation with wind tunnel experiments. These results prove that sand particles have obvious effect on wind flow, especially that over the leeward slope. This study is a preliminary study on windblown sand movement in a complex terrain, and is of significance in the control of dust storms and land desertification. PMID:25434372

Fluidic Vectoring of a Planar Incompressible Jet Flow

NASA Astrophysics Data System (ADS)

Mendez, Miguel Alfonso; Scelzo, Maria Teresa; Enache, Adriana; Buchlin, Jean-Marie

2018-06-01

This paper presents an experimental, a numerical and a theoretical analysis of the performances of a fluidic vectoring device for controlling the direction of a turbulent, bi-dimensional and low Mach number (incompressible) jet flow. The investigated design is the co-flow secondary injection with Coanda surface, which allows for vectoring angles up to 25° with no need of moving mechanical parts. A simple empirical model of the vectoring process is presented and validated via experimental and numerical data. The experiments consist of flow visualization and image processing for the automatic detection of the jet centerline; the numerical simulations are carried out solving the Unsteady Reynolds Average Navier- Stokes (URANS) closed with the k - ω SST turbulence model, using the PisoFoam solver from OpenFOAM. The experimental validation on three different geometrical configurations has shown that the model is capable of providing a fast and reliable evaluation of the device performance as a function of the operating conditions.

Macroscopic analysis of gas-jet wiping: Numerical simulation and experimental approach

NASA Astrophysics Data System (ADS)

Lacanette, Delphine; Gosset, Anne; Vincent, Stéphane; Buchlin, Jean-Marie; Arquis, Éric

2006-04-01

Coating techniques are frequently used in industrial processes such as paper manufacturing, wire sleeving, and in the iron and steel industry. Depending on the application considered, the thickness of the resulting substrate is controlled by mechanical (scraper), electromagnetic (if the entrained fluid is appropriated), or hydrodynamic (gas-jet wiping) operations. This paper deals with the latter process, referred to as gas-jet wiping, in which a turbulent slot jet is used to wipe the coating film dragged by a moving substrate. This mechanism relies on the gas-jet-liquid film interaction taking place on the moving surface. The aim of this study is to compare the results obtained by a lubrication one-dimensional model, numerical volume of fluid-large eddy simulation (VOF-LES) modeling and an experimental approach. The investigation emphasizes the effect of the controlling wiping parameters, i.e., the pressure gradient and shear stress distributions induced by the jet, on the shape of the liquid film. Those profiles obtained experimentally and numerically for a jet impinging on a dry fixed surface are compared. The effect of the substrate motion and the presence of the dragged liquid film on these actuators are analyzed through numerical simulations. Good agreement is found between the film thickness profile in the wiping zone obtained from the VOF-LES simulations and with the analytical model, provided that a good model for the wiping actuators is used. The effect of the gas-jet nozzle to substrate standoff distance on the final coating thickness is analyzed; the experimental and predicted values are compared for a wide set of conditions. Finally, the occurrence of the splashing phenomenon, which is characterized by the ejection of droplets from the runback film flow at jet impingement, thus limiting the wiping process, is investigated through experiments and numerical simulations.

Numerical modeling of zero-offset laboratory data in a strong topographic environment: results for a spectral-element method and a discretized Kirchhoff integral method

NASA Astrophysics Data System (ADS)

Favretto-Cristini, Nathalie; Tantsereva, Anastasiya; Cristini, Paul; Ursin, Bjørn; Komatitsch, Dimitri; Aizenberg, Arkady M.

2014-08-01

Accurate simulation of seismic wave propagation in complex geological structures is of particular interest nowadays. However conventional methods may fail to simulate realistic wavefields in environments with great and rapid structural changes, due for instance to the presence of shadow zones, diffractions and/or edge effects. Different methods, developed to improve seismic modeling, are typically tested on synthetic configurations against analytical solutions for simple canonical problems or reference methods, or via direct comparison with real data acquired in situ. Such approaches have limitations, especially if the propagation occurs in a complex environment with strong-contrast reflectors and surface irregularities, as it can be difficult to determine the method which gives the best approximation of the "real" solution, or to interpret the results obtained without an a priori knowledge of the geologic environment. An alternative approach for seismics consists in comparing the synthetic data with high-quality data collected in laboratory experiments under controlled conditions for a known configuration. In contrast with numerical experiments, laboratory data possess many of the characteristics of field data, as real waves propagate through models with no numerical approximations. We thus present a comparison of laboratory-scaled measurements of 3D zero-offset wave reflection of broadband pulses from a strong topographic environment immersed in a water tank with numerical data simulated by means of a spectral-element method and a discretized Kirchhoff integral method. The results indicate a good quantitative fit in terms of time arrivals and acceptable fit in amplitudes for all datasets.

Constraints on the rheology of the partially molten mantle from numerical models of laboratory experiments

NASA Astrophysics Data System (ADS)

Rudge, J. F.; Alisic Jewell, L.; Rhebergen, S.; Katz, R. F.; Wells, G. N.

2015-12-01

One of the fundamental components in any dynamical model of melt transport is the rheology of partially molten rock. This rheology is poorly understood, and one way in which a better understanding can be obtained is by comparing the results of laboratory deformation experiments to numerical models. Here we present a comparison between numerical models and the laboratory setup of Qi et al. 2013 (EPSL), where a cylinder of partially molten rock containing rigid spherical inclusions was placed under torsion. We have replicated this setup in a finite element model which solves the partial differential equations describing the mechanical process of compaction. These computationally-demanding 3D simulations are only possible due to the recent development of a new preconditioning method for the equations of magma dynamics. The experiments show a distinct pattern of melt-rich and melt-depleted regions around the inclusions. In our numerical models, the pattern of melt varies with key rheological parameters, such as the ratio of bulk to shear viscosity, and the porosity- and strain-rate-dependence of the shear viscosity. These observed melt patterns therefore have the potential to constrain rheological properties. While there are many similarities between the experiments and the numerical models, there are also important differences, which highlight the need for better models of the physics of two-phase mantle/magma dynamics. In particular, the laboratory experiments display more pervasive melt-rich bands than is seen in our numerics.

Electro-Optic Quantum Memory for Light Using Two-Level Atoms

NASA Astrophysics Data System (ADS)

Hétet, G.; Longdell, J. J.; Alexander, A. L.; Lam, P. K.; Sellars, M. J.

2008-01-01

We present a simple quantum memory scheme that allows for the storage of a light field in an ensemble of two-level atoms. The technique is analogous to the NMR gradient echo for which the imprinting and recalling of the input field are performed by controlling a linearly varying broadening. Our protocol is perfectly efficient in the limit of high optical depths and the output pulse is emitted in the forward direction. We provide a numerical analysis of the protocol together with an experiment performed in a solid state system. In close agreement with our model, the experiment shows a total efficiency of up to 15%, and a recall efficiency of 26%. We suggest simple realizable improvements for the experiment to surpass the no-cloning limit.

Electro-optic quantum memory for light using two-level atoms.

PubMed

Hétet, G; Longdell, J J; Alexander, A L; Lam, P K; Sellars, M J

2008-01-18

We present a simple quantum memory scheme that allows for the storage of a light field in an ensemble of two-level atoms. The technique is analogous to the NMR gradient echo for which the imprinting and recalling of the input field are performed by controlling a linearly varying broadening. Our protocol is perfectly efficient in the limit of high optical depths and the output pulse is emitted in the forward direction. We provide a numerical analysis of the protocol together with an experiment performed in a solid state system. In close agreement with our model, the experiment shows a total efficiency of up to 15%, and a recall efficiency of 26%. We suggest simple realizable improvements for the experiment to surpass the no-cloning limit.

Seismic wave propagation in granular media

NASA Astrophysics Data System (ADS)

Tancredi, Gonzalo; López, Francisco; Gallot, Thomas; Ginares, Alejandro; Ortega, Henry; Sanchís, Johnny; Agriela, Adrián; Weatherley, Dion

2016-10-01

Asteroids and small bodies of the Solar System are thought to be agglomerates of irregular boulders, therefore cataloged as granular media. It is a consensus that many asteroids might be considered as rubble or gravel piles.Impacts on their surface could produce seismic waves which propagate in the interior of these bodies, thus causing modifications in the internal distribution of rocks and ejections of particles and dust, resulting in a cometary-type comma.We present experimental and numerical results on the study of propagation of impact-induced seismic waves in granular media, with special focus on behavior changes by increasing compression.For the experiment, we use an acrylic box filled with granular materials such as sand, gravel and glass spheres. Pressure inside the box is controlled by a movable side wall and measured with sensors. Impacts are created on the upper face of the box through a hole, ranging from free-falling spheres to gunshots. We put high-speed cameras outside the box to record the impact as well as piezoelectic sensors and accelerometers placed at several depths in the granular material to detect the seismic wave.Numerical simulations are performed with ESyS-Particle, a software that implements the Discrete Element Method. The experimental setting is reproduced in the numerical simulations using both individual spherical particles and agglomerates of spherical particles shaped as irregular boulders, according to rock models obtained with a 3D scanner. The numerical experiments also reproduces the force loading on one of the wall to vary the pressure inside the box.We are interested in the velocity, attenuation and energy transmission of the waves. These quantities are measured in the experiments and in the simulations. We study the dependance of these three parameters with characteristics like: impact speed, properties of the target material and the pressure in the media.These results are relevant to understand the outcomes of impacts in rubble/gravel pile asteroids.

Nonlinear Geometric Effects in Mechanical Bistable Morphing Structures

NASA Astrophysics Data System (ADS)

Chen, Zi; Guo, Qiaohang; Majidi, Carmel; Chen, Wenzhe; Srolovitz, David J.; Haataja, Mikko P.

2012-09-01

Bistable structures associated with nonlinear deformation behavior, exemplified by the Venus flytrap and slap bracelet, can switch between different functional shapes upon actuation. Despite numerous efforts in modeling such large deformation behavior of shells, the roles of mechanical and nonlinear geometric effects on bistability remain elusive. We demonstrate, through both theoretical analysis and tabletop experiments, that two dimensionless parameters control bistability. Our work classifies the conditions for bistability, and extends the large deformation theory of plates and shells.

Evaluation of liquid aerosol transport through porous media

NASA Astrophysics Data System (ADS)

Hall, R.; Murdoch, L.; Falta, R.; Looney, B.; Riha, B.

2016-07-01

Application of remediation methods in contaminated vadose zones has been hindered by an inability to effectively distribute liquid- or solid-phase amendments. Injection as aerosols in a carrier gas could be a viable method for achieving useful distributions of amendments in unsaturated materials. The objectives of this work were to characterize radial transport of aerosols in unsaturated porous media, and to develop capabilities for predicting results of aerosol injection scenarios at the field-scale. Transport processes were investigated by conducting lab-scale injection experiments with radial flow geometry, and predictive capabilities were obtained by developing and validating a numerical model for simulating coupled aerosol transport, deposition, and multi-phase flow in porous media. Soybean oil was transported more than 2 m through sand by injecting it as micron-scale aerosol droplets. Oil saturation in the sand increased with time to a maximum of 0.25, and decreased with radial distance in the experiments. The numerical analysis predicted the distribution of oil saturation with only minor calibration. The results indicated that evolution of oil saturation was controlled by aerosol deposition and subsequent flow of the liquid oil, and simulation requires including these two coupled processes. The calibrated model was used to evaluate field applications. The results suggest that amendments can be delivered to the vadose zone as aerosols, and that gas injection rate and aerosol particle size will be important controls on the process.

Comparing the Degree of Land-Atmosphere Interaction in Four Atmospheric General Circulation Models

NASA Technical Reports Server (NTRS)

Koster, Randal D.; Dirmeyer, Paul A.; Hahmann, Andrea N.; Ijpelaar, Ruben; Tyahla, Lori; Cox, Peter; Suarez, Max J.; Houser, Paul R. (Technical Monitor)

2001-01-01

Land-atmosphere feedback, by which (for example) precipitation-induced moisture anomalies at the land surface affect the overlying atmosphere and thereby the subsequent generation of precipitation, has been examined and quantified with many atmospheric general circulation models (AGCMs). Generally missing from such studies, however, is an indication of the extent to which the simulated feedback strength is model dependent. Four modeling groups have recently performed a highly controlled numerical experiment that allows an objective inter-model comparison of land-atmosphere feedback strength. The experiment essentially consists of an ensemble of simulations in which each member simulation artificially maintains the same time series of surface prognostic variables. Differences in atmospheric behavior between the ensemble members then indicates the degree to which the state of the land surface controls atmospheric processes in that model. A comparison of the four sets of experimental results shows that feedback strength does indeed vary significantly between the AGCMs.

Near Field Observations of Seismicity in Volcanic Environments: A Read-Made Field Laboratory

NASA Astrophysics Data System (ADS)

Bean, C. J.; Thun, J.; Eibl, E. P. S.; Benson, P. M.; Rowley, P.; Lokmer, I.; Cauchie, L.

2017-12-01

Volcanic environments experience periods of rapid stress fluctuations and consequent seismicity. This volcano seismicity is diverse in character, spanning the range from discrete high frequency events through low-frequency earthquakes and tremor. The inter-relationships between these events appear to be controlled by edifice rheology, stress state and the presence of fluids (which help modulate the stress field). In general volcanoes are accessible to instrumentation, allowing near-field access to the seismicity at play. Here we present results from a range of field, numerical and laboratory experiments that demonstrate the controls that rheology and strain rate play on seismicity type. In particular we demonstrate the role played by internal friction angles on the initiation and evolution of seismicity, in dry weak-compliant volcanic materials. Furthermore we show the importance of near field observation in constraining details of the seismic source, in a meso-scale field setting.

Numerical Modeling of Active Flow Control in a Boundary Layer Ingesting Offset Inlet

NASA Technical Reports Server (NTRS)

Allan, Brian G.; Owens, Lewis R.; Berrier, Bobby L.

2004-01-01

This investigation evaluates the numerical prediction of flow distortion and pressure recovery for a boundary layer ingesting offset inlet with active flow control devices. The numerical simulations are computed using a Reynolds averaged Navier-Stokes code developed at NASA. The numerical results are validated by comparison to experimental wind tunnel tests conducted at NASA Langley Research Center at both low and high Mach numbers. Baseline comparisons showed good agreement between numerical and experimental results. Numerical simulations for the inlet with passive and active flow control also showed good agreement at low Mach numbers where experimental data has already been acquired. Numerical simulations of the inlet at high Mach numbers with flow control jets showed an improvement of the flow distortion. Studies on the location of the jet actuators, for the high Mach number case, were conducted to provide guidance for the design of a future experimental wind tunnel test.

Flow-induced phase separation of active particles is controlled by boundary conditions.

PubMed

Thutupalli, Shashi; Geyer, Delphine; Singh, Rajesh; Adhikari, Ronojoy; Stone, Howard A

2018-05-22

Active particles, including swimming microorganisms, autophoretic colloids, and droplets, are known to self-organize into ordered structures at fluid-solid boundaries. The entrainment of particles in the attractive parts of their spontaneous flows has been postulated as a possible mechanism underlying this phenomenon. Here, combining experiments, theory, and numerical simulations, we demonstrate the validity of this flow-induced ordering mechanism in a suspension of active emulsion droplets. We show that the mechanism can be controlled, with a variety of resultant ordered structures, by simply altering hydrodynamic boundary conditions. Thus, for flow in Hele-Shaw cells, metastable lines or stable traveling bands can be obtained by varying the cell height. Similarly, for flow bounded by a plane, dynamic crystallites are formed. At a no-slip wall, the crystallites are characterized by a continuous out-of-plane flux of particles that circulate and re-enter at the crystallite edges, thereby stabilizing them. At an interface where the tangential stress vanishes, the crystallites are strictly 2D, with no out-of-plane flux. We rationalize these experimental results by calculating, in each case, the slow viscous flow produced by the droplets and the long-ranged, many-body active forces and torques between them. The results of numerical simulations of motion under the action of the active forces and torques are in excellent agreement with experiments. Our work elucidates the mechanism of flow-induced phase separation in active fluids, particularly active colloidal suspensions, and demonstrates its control by boundaries, suggesting routes to geometric and topological phenomena in an active matter.

Rapid convergence of optimal control in NMR using numerically-constructed toggling frames

NASA Astrophysics Data System (ADS)

Coote, Paul; Anklin, Clemens; Massefski, Walter; Wagner, Gerhard; Arthanari, Haribabu

2017-08-01

We present a numerical method for rapidly solving the Bloch equation for an arbitrary time-varying spin-1/2 Hamiltonian. The method relies on fast, vectorized computations such as summation and quaternion multiplication, rather than slow computations such as matrix exponentiation. A toggling frame is constructed in which the Hamiltonian is time-invariant, and therefore has a simple analytical solution. The key insight is that constructing this frame is faster than solving the system dynamics in the original frame. Rapidly solving the Bloch equations for an arbitrary Hamiltonian is particularly useful in the context of NMR optimal control. Optimal control theory can be used to design pulse shapes for a range of tasks in NMR spectroscopy. However, it requires multiple simulations of the Bloch equations at each stage of the algorithm, and for each relevant set of parameters (e.g. chemical shift frequencies). This is typically time consuming. We demonstrate that by working in an appropriate toggling frame, optimal control pulses can be generated much faster. We present a new alternative to the well-known GRAPE algorithm to continuously update the toggling-frame as the optimal pulse is generated, and demonstrate that this approach is extremely fast. The use and benefit of rapid optimal pulse generation is demonstrated for 19F fragment screening experiments.

Virtual Planning, Control, and Machining for a Modular-Based Automated Factory Operation in an Augmented Reality Environment

PubMed Central

Pai, Yun Suen; Yap, Hwa Jen; Md Dawal, Siti Zawiah; Ramesh, S.; Phoon, Sin Ye

2016-01-01

This study presents a modular-based implementation of augmented reality to provide an immersive experience in learning or teaching the planning phase, control system, and machining parameters of a fully automated work cell. The architecture of the system consists of three code modules that can operate independently or combined to create a complete system that is able to guide engineers from the layout planning phase to the prototyping of the final product. The layout planning module determines the best possible arrangement in a layout for the placement of various machines, in this case a conveyor belt for transportation, a robot arm for pick-and-place operations, and a computer numerical control milling machine to generate the final prototype. The robotic arm module simulates the pick-and-place operation offline from the conveyor belt to a computer numerical control (CNC) machine utilising collision detection and inverse kinematics. Finally, the CNC module performs virtual machining based on the Uniform Space Decomposition method and axis aligned bounding box collision detection. The conducted case study revealed that given the situation, a semi-circle shaped arrangement is desirable, whereas the pick-and-place system and the final generated G-code produced the highest deviation of 3.83 mm and 5.8 mm respectively. PMID:27271840

Virtual Planning, Control, and Machining for a Modular-Based Automated Factory Operation in an Augmented Reality Environment.

PubMed

Pai, Yun Suen; Yap, Hwa Jen; Md Dawal, Siti Zawiah; Ramesh, S; Phoon, Sin Ye

2016-06-07

This study presents a modular-based implementation of augmented reality to provide an immersive experience in learning or teaching the planning phase, control system, and machining parameters of a fully automated work cell. The architecture of the system consists of three code modules that can operate independently or combined to create a complete system that is able to guide engineers from the layout planning phase to the prototyping of the final product. The layout planning module determines the best possible arrangement in a layout for the placement of various machines, in this case a conveyor belt for transportation, a robot arm for pick-and-place operations, and a computer numerical control milling machine to generate the final prototype. The robotic arm module simulates the pick-and-place operation offline from the conveyor belt to a computer numerical control (CNC) machine utilising collision detection and inverse kinematics. Finally, the CNC module performs virtual machining based on the Uniform Space Decomposition method and axis aligned bounding box collision detection. The conducted case study revealed that given the situation, a semi-circle shaped arrangement is desirable, whereas the pick-and-place system and the final generated G-code produced the highest deviation of 3.83 mm and 5.8 mm respectively.

Virtual Planning, Control, and Machining for a Modular-Based Automated Factory Operation in an Augmented Reality Environment

NASA Astrophysics Data System (ADS)

Pai, Yun Suen; Yap, Hwa Jen; Md Dawal, Siti Zawiah; Ramesh, S.; Phoon, Sin Ye

2016-06-01

This study presents a modular-based implementation of augmented reality to provide an immersive experience in learning or teaching the planning phase, control system, and machining parameters of a fully automated work cell. The architecture of the system consists of three code modules that can operate independently or combined to create a complete system that is able to guide engineers from the layout planning phase to the prototyping of the final product. The layout planning module determines the best possible arrangement in a layout for the placement of various machines, in this case a conveyor belt for transportation, a robot arm for pick-and-place operations, and a computer numerical control milling machine to generate the final prototype. The robotic arm module simulates the pick-and-place operation offline from the conveyor belt to a computer numerical control (CNC) machine utilising collision detection and inverse kinematics. Finally, the CNC module performs virtual machining based on the Uniform Space Decomposition method and axis aligned bounding box collision detection. The conducted case study revealed that given the situation, a semi-circle shaped arrangement is desirable, whereas the pick-and-place system and the final generated G-code produced the highest deviation of 3.83 mm and 5.8 mm respectively.

Three-dimensional Diffusive Strip Method

NASA Astrophysics Data System (ADS)

Martinez-Ruiz, Daniel; Meunier, Patrice; Duchemin, Laurent; Villermaux, Emmanuel

2016-11-01

The Diffusive Strip Method (DSM) is a near-exact numerical method developed for mixing computations at large Péclet number in two-dimensions. The method consists in following stretched material lines to compute a-posteriori the resulting scalar field is extended here to three-dimensional flows, following surfaces. We describe its 3D peculiarities, and show how it applies to a simple Taylor-Couette configuration with non-rotating boundary conditions at the top end, bottom and outer cylinder. This flow produces an elaborate, although controlled, steady 3D flow which relies on the Ekman pumping arising from the rotation of the inner cylinder is both studied experimentally, and numerically modeled. A recurrent two-cells structure appears formed by stream tubes shaped as nested tori. A scalar blob in the flow experiences a Lagrangian oscillating dynamics with stretchings and compressions, driving the mixing process, and yielding both rapidly-mixed and nearly pure-diffusive regions. A triangulated-surface method is developed to calculate the blob elongation and scalar concentration PDFs through a single variable computation along the advected blob surface, capturing the rich evolution observed in the experiments.

pypet: A Python Toolkit for Data Management of Parameter Explorations

PubMed Central

Meyer, Robert; Obermayer, Klaus

2016-01-01

pypet (Python parameter exploration toolkit) is a new multi-platform Python toolkit for managing numerical simulations. Sampling the space of model parameters is a key aspect of simulations and numerical experiments. pypet is designed to allow easy and arbitrary sampling of trajectories through a parameter space beyond simple grid searches. pypet collects and stores both simulation parameters and results in a single HDF5 file. This collective storage allows fast and convenient loading of data for further analyses. pypet provides various additional features such as multiprocessing and parallelization of simulations, dynamic loading of data, integration of git version control, and supervision of experiments via the electronic lab notebook Sumatra. pypet supports a rich set of data formats, including native Python types, Numpy and Scipy data, Pandas DataFrames, and BRIAN(2) quantities. Besides these formats, users can easily extend the toolkit to allow customized data types. pypet is a flexible tool suited for both short Python scripts and large scale projects. pypet's various features, especially the tight link between parameters and results, promote reproducible research in computational neuroscience and simulation-based disciplines. PMID:27610080

Displaying uncertainty: investigating the effects of display format and specificity.

PubMed

Bisantz, Ann M; Marsiglio, Stephanie Schinzing; Munch, Jessica

2005-01-01

We conducted four studies regarding the representation of probabilistic information. Experiments 1 through 3 compared performance on a simulated stock purchase task, in which information regarding stock profitability was probabilistic. Two variables were manipulated: display format for probabilistic information (blurred and colored icons, linguistic phrases, numeric expressions, and combinations) and specificity level (in which the number and size of discrete steps into which the probabilistic information was mapped differed). Results indicated few performance differences attributable to display format; however, performance did improve with greater specificity. Experiment 4, in which participants generated membership functions corresponding to three display formats, found a high degree of similarity in functions across formats and participants and a strong relationship between the shape of the membership function and the intended meaning of the representation. These results indicate that participants can successfully interpret nonnumeric representations of uncertainty and can use such representations in a manner similar to the way numeric expressions are used in a decision-making task. Actual or potential applications of this research include the use of graphical representations of uncertainty in systems such as command and control and situation displays.

pypet: A Python Toolkit for Data Management of Parameter Explorations.

PubMed

Meyer, Robert; Obermayer, Klaus

2016-01-01

pypet (Python parameter exploration toolkit) is a new multi-platform Python toolkit for managing numerical simulations. Sampling the space of model parameters is a key aspect of simulations and numerical experiments. pypet is designed to allow easy and arbitrary sampling of trajectories through a parameter space beyond simple grid searches. pypet collects and stores both simulation parameters and results in a single HDF5 file. This collective storage allows fast and convenient loading of data for further analyses. pypet provides various additional features such as multiprocessing and parallelization of simulations, dynamic loading of data, integration of git version control, and supervision of experiments via the electronic lab notebook Sumatra. pypet supports a rich set of data formats, including native Python types, Numpy and Scipy data, Pandas DataFrames, and BRIAN(2) quantities. Besides these formats, users can easily extend the toolkit to allow customized data types. pypet is a flexible tool suited for both short Python scripts and large scale projects. pypet's various features, especially the tight link between parameters and results, promote reproducible research in computational neuroscience and simulation-based disciplines.

Enabling the detection of UV signal in multimodal nonlinear microscopy with catalogue lens components.

PubMed

Vogel, Martin; Wingert, Axel; Fink, Rainer H A; Hagl, Christian; Ganikhanov, Feruz; Pfeffer, Christian P

2015-10-01

Using an optical system made from fused silica catalogue optical components, third-order nonlinear microscopy has been enabled on conventional Ti:sapphire laser-based multiphoton microscopy setups. The optical system is designed using two lens groups with straightforward adaptation to other microscope stands when one of the lens groups is exchanged. Within the theoretical design, the optical system collects and transmits light with wavelengths between the near ultraviolet and the near infrared from an object field of at least 1 mm in diameter within a resulting numerical aperture of up to 0.56. The numerical aperture can be controlled with a variable aperture stop between the two lens groups of the condenser. We demonstrate this new detection capability in third harmonic generation imaging experiments at the harmonic wavelength of ∼300 nm and in multimodal nonlinear optical imaging experiments using third-order sum frequency generation and coherent anti-Stokes Raman scattering microscopy so that the wavelengths of the detected signals range from ∼300 nm to ∼660 nm. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Performance evaluation of Bragg coherent diffraction imaging

DOE PAGES

Ozturk, Hande; Huang, X.; Yan, H.; ...

2017-10-03

In this study, we present a numerical framework for modeling three-dimensional (3D) diffraction data in Bragg coherent diffraction imaging (Bragg CDI) experiments and evaluating the quality of obtained 3D complex-valued real-space images recovered by reconstruction algorithms under controlled conditions. The approach is used to systematically explore the performance and the detection limit of this phase-retrieval-based microscopy tool. The numerical investigation suggests that the superb performance of Bragg CDI is achieved with an oversampling ratio above 30 and a detection dynamic range above 6 orders. The observed performance degradation subject to the data binning processes is also studied. Furthermore, this numericalmore » tool can be used to optimize experimental parameters and has the potential to significantly improve the throughput of Bragg CDI method.« less

Unsteady heat transfer performance of heat pipe with axially swallow-tailed microgrooves

NASA Astrophysics Data System (ADS)

Zhang, R. P.

2017-04-01

A mathematical model is developed for predicting the transient heat transfer and fluid flow of heat pipe with axially swallow-tailed microgrooves. The effects of liquid convective heat transfer in the microgrooves, liquid-vapor interfacial phase-change heat transfer and liquid-vapor interfacial shear stress are accounted for in the present model. The coupled non-linear control equations are solved numerically. Mass flow rate at the interface is obtained from the application of kinetic theory. Time variation of wall temperature is studied from the initial startup to steady state. The numerical results are verified by experiments. Time constants for startup and shutdown operation are defined to determine how fast a heat pipe responds to an applied input heat flux, which slightly decreases with increasing heat load.

A method for development of efficient 3D models for neutronic calculations of ASTRA critical facility using experimental information

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

Balanin, A. L.; Boyarinov, V. F.; Glushkov, E. S.

The application of experimental information on measured axial distributions of fission reaction rates for development of 3D numerical models of the ASTRA critical facility taking into account azimuthal asymmetry of the assembly simulating a HTGR with annular core is substantiated. Owing to the presence of the bottom reflector and the absence of the top reflector, the application of 2D models based on experimentally determined buckling is impossible for calculation of critical assemblies of the ASTRA facility; therefore, an alternative approach based on the application of the extrapolated assembly height is proposed. This approach is exemplified by the numerical analysis ofmore » experiments on measurement of efficiency of control rods mockups and protection system (CPS).« less

Controlling Air Traffic (Simulated) in the Presence of Automation (CATS PAu) 1995: A Study of Measurement Techniques for Situation Awareness in Air Traffic Control

NASA Technical Reports Server (NTRS)

French, Jennifer R.

1995-01-01

As automated systems proliferate in aviation systems, human operators are taking on less and less of an active role in the jobs they once performed, often reducing what should be important jobs to tasks barely more complex than monitoring machines. When operators are forced into these roles, they risk slipping into hazardous states of awareness, which can lead to reduced skills, lack of vigilance, and the inability to react quickly and competently when there is a machine failure. Using Air Traffic Control (ATC) as a model, the present study developed tools for conducting tests focusing on levels of automation as they relate to situation awareness. Subjects participated in a two-and-a-half hour experiment that consisted of a training period followed by a simulation of air traffic control similar to the system presently used by the FAA, then an additional simulation employing automated assistance. Through an iterative design process utilizing numerous revisions and three experimental sessions, several measures for situational awareness in a simulated Air Traffic Control System were developed and are prepared for use in future experiments.

Effects of stochastic noise on dynamical decoupling procedures

NASA Astrophysics Data System (ADS)

Bernád, J. Z.; Frydrych, H.

2014-06-01

Dynamical decoupling is an important tool to counter decoherence and dissipation effects in quantum systems originating from environmental interactions. It has been used successfully in many experiments; however, there is still a gap between fidelity improvements achieved in practice compared to theoretical predictions. We propose a model for imperfect dynamical decoupling based on a stochastic Ito differential equation which could explain the observed gap. We discuss the impact of our model on the time evolution of various quantum systems in finite- and infinite-dimensional Hilbert spaces. Analytical results are given for the limit of continuous control, whereas we present numerical simulations and upper bounds for the case of finite control.

Microelectrode for energy and current control of nanotip field electron emitters

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

Lüneburg, S.; Müller, M., E-mail: m.mueller@fhi-berlin.mpg.de; Paarmann, A., E-mail: alexander.paarmann@fhi-berlin.mpg.de

2013-11-18

Emerging experiments and applications in electron microscopy, holography, and diffraction benefit from miniaturized electron guns for compact experimental setups. We present a highly compact microelectrode integrated field emitter that consists of a tungsten nanotip coated with a few micrometers thick polyimide film followed by a several nanometers thick gold film, both positioned behind the exposed emitter apex by approximately 10–30 μm. The control of the electric field strength at the nanometer scale tip apex allows suppression, extraction, and energy tuning of field-emitted electrons. The performance of the microelectrode is demonstrated experimentally and supported by numerical simulations.

Focusing light through random scattering media by four-element division algorithm

NASA Astrophysics Data System (ADS)

Fang, Longjie; Zhang, Xicheng; Zuo, Haoyi; Pang, Lin

2018-01-01

The focusing of light through random scattering materials using wavefront shaping is studied in detail. We propose a newfangled approach namely four-element division algorithm to improve the average convergence rate and signal-to-noise ratio of focusing. Using 4096 independently controlled segments of light, the intensity at the target is 72 times enhanced over the original intensity at the same position. The four-element division algorithm and existing phase control algorithms of focusing through scattering media are compared by both of the numerical simulation and the experiment. It is found that four-element division algorithm is particularly advantageous to improve the average convergence rate of focusing.

Computerized Numerical Control Curriculum Guide.

ERIC Educational Resources Information Center

Reneau, Fred; And Others

This guide is intended for use in a course in programming and operating a computerized numerical control system. Addressed in the course are various aspects of programming and planning, setting up, and operating machines with computerized numerical control, including selecting manual or computer-assigned programs and matching them with…

Bubble Dynamics on a Heated Surface

NASA Technical Reports Server (NTRS)

Kassemi, M.; Rashidnia, N.

1999-01-01

In this work, we study steady and oscillatory thermocapillary and natural convective flows generated by a bubble on a heated solid surface. The interaction between gas and vapor bubbles with the surrounding fluid is of interest for both space and ground-based processing. A combined numerical-experimental approach is adopted here. The temperature field is visualized using Mach-Zehnder and/or Wollaston Prism Interferometry and the flow field is observed by a laser sheet flow visualization technique. A finite element numerical model is developed which solves the transient two-dimensional continuity, momentum, and energy equations and includes the effects of temperature-dependent surface tension and bubble surface deformation. Below the critical Marangoni number, the steady state low-g and 1-g temperature and velocity fields predicted by the finite element model are in excellent agreement with both the visualization experiments in our laboratory and recently published experimental results in the literature. Above the critical Marangoni number, the model predicts an oscillatory flow which is also closely confirmed by experiments. It is shown that the dynamics of the oscillatory flow are directly controlled by the thermal and hydrodynamic interactions brought about by combined natural and thermocapillary convection. Therefore, as numerical simulations show, there are considerable differences between the 1-g and low-g temperature and flow fields at both low and high Marangoni numbers. This has serious implications for both materials processing and fluid management in space.

Thermal Hydraulic Computational Fluid Dynamics Simulations and Experimental Investigation of Deformed Fuel Assemblies

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

Mays, Brian; Jackson, R. Brian

2017-03-08

The project, Toward a Longer Life Core: Thermal Hydraulic CFD Simulations and Experimental Investigation of Deformed Fuel Assemblies, DOE Project code DE-NE0008321, was a verification and validation project for flow and heat transfer through wire wrapped simulated liquid metal fuel assemblies that included both experiments and computational fluid dynamics simulations of those experiments. This project was a two year collaboration between AREVA, TerraPower, Argonne National Laboratory and Texas A&M University. Experiments were performed by AREVA and Texas A&M University. Numerical simulations of these experiments were performed by TerraPower and Argonne National Lab. Project management was performed by AREVA Federal Services.more » The first of a kind project resulted in the production of both local point temperature measurements and local flow mixing experiment data paired with numerical simulation benchmarking of the experiments. The project experiments included the largest wire-wrapped pin assembly Mass Index of Refraction (MIR) experiment in the world, the first known wire-wrapped assembly experiment with deformed duct geometries and the largest numerical simulations ever produced for wire-wrapped bundles.« less

Prediction of tropical cyclone over North Indian Ocean using WRF model: sensitivity to scatterometer winds, ATOVS and ATMS radiances

NASA Astrophysics Data System (ADS)

Dodla, Venkata B.; Srinivas, Desamsetti; Dasari, Hari Prasad; Gubbala, Chinna Satyanarayana

2016-05-01

Tropical cyclone prediction, in terms of intensification and movement, is important for disaster management and mitigation. Hitherto, research studies were focused on this issue that lead to improvement in numerical models, initial data with data assimilation, physical parameterizations and application of ensemble prediction. Weather Research and Forecasting (WRF) model is the state-of-art model for cyclone prediction. In the present study, prediction of tropical cyclone (Phailin, 2013) that formed in the North Indian Ocean (NIO) with and without data assimilation using WRF model has been made to assess impacts of data assimilation. WRF model was designed to have nested two domains of 15 and 5 km resolutions. In the present study, numerical experiments are made without and with the assimilation of scatterometer winds, and radiances from ATOVS and ATMS. The model performance was assessed in respect to the movement and intensification of cyclone. ATOVS data assimilation experiment had produced the best prediction with least errors less than 100 km up to 60 hours and producing pre-deepening and deepening periods accurately. The Control and SCAT wind assimilation experiments have shown good track but the errors were 150-200 km and gradual deepening from the beginning itself instead of sudden deepening.

Automated monitor and control for deep space network subsystems

NASA Technical Reports Server (NTRS)

Smyth, P.

1989-01-01

The problem of automating monitor and control loops for Deep Space Network (DSN) subsystems is considered and an overview of currently available automation techniques is given. The use of standard numerical models, knowledge-based systems, and neural networks is considered. It is argued that none of these techniques alone possess sufficient generality to deal with the demands imposed by the DSN environment. However, it is shown that schemes that integrate the better aspects of each approach and are referenced to a formal system model show considerable promise, although such an integrated technology is not yet available for implementation. Frequent reference is made to the receiver subsystem since this work was largely motivated by experience in developing an automated monitor and control loop for the advanced receiver.

Application of geometric approximation to the CPMG experiment: Two- and three-site exchange.

PubMed

Chao, Fa-An; Byrd, R Andrew

2017-04-01

The Carr-Purcell-Meiboom-Gill (CPMG) experiment is one of the most classical and well-known relaxation dispersion experiments in NMR spectroscopy, and it has been successfully applied to characterize biologically relevant conformational dynamics in many cases. Although the data analysis of the CPMG experiment for the 2-site exchange model can be facilitated by analytical solutions, the data analysis in a more complex exchange model generally requires computationally-intensive numerical analysis. Recently, a powerful computational strategy, geometric approximation, has been proposed to provide approximate numerical solutions for the adiabatic relaxation dispersion experiments where analytical solutions are neither available nor feasible. Here, we demonstrate the general potential of geometric approximation by providing a data analysis solution of the CPMG experiment for both the traditional 2-site model and a linear 3-site exchange model. The approximate numerical solution deviates less than 0.5% from the numerical solution on average, and the new approach is computationally 60,000-fold more efficient than the numerical approach. Moreover, we find that accurate dynamic parameters can be determined in most cases, and, for a range of experimental conditions, the relaxation can be assumed to follow mono-exponential decay. The method is general and applicable to any CPMG RD experiment (e.g. N, C', C α , H α , etc.) The approach forms a foundation of building solution surfaces to analyze the CPMG experiment for different models of 3-site exchange. Thus, the geometric approximation is a general strategy to analyze relaxation dispersion data in any system (biological or chemical) if the appropriate library can be built in a physically meaningful domain. Published by Elsevier Inc.

Temporal and spatial temperature measurement in insulator-based dielectrophoretic devices.

PubMed

Nakano, Asuka; Luo, Jinghui; Ros, Alexandra

2014-07-01

Insulator-based dielectrophoresis is a relatively new analytical technique with a large potential for a number of applications, such as sorting, separation, purification, fractionation, and preconcentration. The application of insulator-based dielectrophoresis (iDEP) for biological samples, however, requires the precise control of the microenvironment with temporal and spatial resolution. Temperature variations during an iDEP experiment are a critical aspect in iDEP since Joule heating could lead to various detrimental effects hampering reproducibility. Additionally, Joule heating can potentially induce thermal flow and more importantly can degrade biomolecules and other biological species. Here, we investigate temperature variations in iDEP devices experimentally employing the thermosensitive dye Rhodamin B (RhB) and compare the measured results with numerical simulations. We performed the temperature measurement experiments at a relevant buffer conductivity range commonly used for iDEP applications under applied electric potentials. To this aim, we employed an in-channel measurement method and an alternative method employing a thin film located slightly below the iDEP channel. We found that the temperature does not deviate significantly from room temperature at 100 μS/cm up to 3000 V applied such as in protein iDEP experiments. At a conductivity of 300 μS/cm, such as previously used for mitochondria iDEP experiments at 3000 V, the temperature never exceeds 34 °C. This observation suggests that temperature effects for iDEP of proteins and mitochondria under these conditions are marginal. However, at larger conductivities (1 mS/cm) and only at 3000 V applied, temperature increases were significant, reaching a regime in which degradation is likely to occur. Moreover, the thin layer method resulted in lower temperature enhancement which was also confirmed with numerical simulations. We thus conclude that the thin film method is preferable providing closer agreement with numerical simulations and further since it does not depend on the iDEP channel material. Overall, our study provides a thorough comparison of two experimental techniques for direct temperature measurement, which can be adapted to a variety of iDEP applications in the future. The good agreement between simulation and experiment will also allow one to assess temperature variations for iDEP devices prior to experiments.

Hydrodynamics and PIV study in the impingement zone formed by a droplet train

NASA Astrophysics Data System (ADS)

Kanjirakat, Anoop; Sadr, Reza; Zhang, Taolue; Muthusamy, Jayaveera; Alvarado, Jorge; Texas A; M University at Qatar Collaboration; Texas A; M University College Station Collaboration

2016-11-01

Droplet impingement is encountered in numerous technical applications, such as ink jet printing, spray cooling, and fuel injection in internal combustion engines. Even though many studies in droplet impingement were conducted in past, not many have measured the near-wall velocities in the droplet impingement zone. With the goal of gaining a better understanding of the hydrodynamics in the impingement zone, well-controlled experiments are performed in combination with micro-PIV measurements and numerical simulations. Hydrodynamics of HFE-7100 droplets generated using a piezoelectric droplet generator, impinging on a pre-wetted surface is investigated. Micro-PIV studies in the high-velocity impingement zone are performed using one-micron meter fluorescent particles dispersed in HFE-7100 along with the double exposed images. Three-dimensional and 2D-axisymmetric numerical modeling for a transient droplet crown development is performed. The interface between the gas and the liquid is modeled using a Volume of Fluid (VOF) method. Numerical simulation results obtained are observed to be in good agreement with that of the experimental observations. Supported by National Priority Research Program (NPRP) of Qatar National Research Fund (QNRF), Grant No.: NPRP 6-1304-2-525.

Melt Stabilization of PbSnTe in a Magnetic Field

NASA Technical Reports Server (NTRS)

Fripp, Archibald L.; Debnam, William J.; Rosch, William; Chait, Arnon; Yao, Minwu; Szofran, Frank R.

1999-01-01

Both the experimental observation and numerical simulation indicate that the Bridgman growth of PbSnTe under the microgravity environment in space is still greatly influenced by buoyancy-induced convection. The application of a magnetic field during the semiconductor growth can dampen the convective flow in the metal-like melt. However, for Bridgman growth of PbSnTe on earth (with either vertical or horizontal configuration), both experimental observation and numerical modeling suggest that even with a strong magnetic furnace (5-Tesla constant axial magnetic field), the convective flow in the melt still cannot be sufficiently suppressed to reach the diffusion-controlled level. In order to completely dampen the buoyancy-induced convection on earth, estimates based on scaling analysis indicate that for common experimental conditions, an extremely high magnetic field is required, far beyond the capacity of the experimental apparatus currently available. Therefore, it is proposed that only the combination of microgravity environment and magnetic damping will produce the desired diffusion-controlled growth state for this particular material. The primary objectives of this study are to provide a quantitative understanding of the complex transport phenomena during solidification of non-dilute binarys, to furnish a numerical tool for furnace design and growth condition optimization, to provide estimates of the required magnetic field strength for low gravity growth, and to assess the role of magnetic damping for space and earth control of the double-diffusive convection. As an integral part of a NASA research program, our numerical simulation supports both the flight and ground-based experiments in an effort to bring together a complete picture of the complex physical phenomena involved in the crystal growth process. For Bridgman growth of PbSnTe under microgravity (with both vertical and horizontal configurations), the simulations suggest that a moderate axial magnetic field of only a few kilo-Gauss in strength could effectively eliminate buoyancy-induced convection in the melt and control solute segregation. Therefore, this work confirms the idea that the combination of microgravity environment and the magnetic damping will indeed be sufficient to produce the desired diffusion-controlled growth state for PbSnTe.

Numerical modeling of dune progression in a high amplitude meandering channel

USDA-ARS?s Scientific Manuscript database

Laboratory experiments carried out by Abad and Garcia (2009) in a high-amplitude Kinoshita meandering channel show bed morphodynamics to comprise steady (local scour and deposition) and unsteady (migrating bedforms) components. The experiments are replicated with a numerical model. The sediment tran...

Discomfort analysis in computerized numeric control machine operations.

PubMed

Muthukumar, Krishnamoorthy; Sankaranarayanasamy, Krishnasamy; Ganguli, Anindya Kumar

2012-06-01

The introduction of computerized numeric control (CNC) technology in manufacturing industries has revolutionized the production process, but there are some health and safety problems associated with these machines. The present study aimed to investigate the extent of postural discomfort in CNC machine operators, and the relationship of this discomfort to the display and control panel height, with a view to validate the anthropometric recommendation for the location of the display and control panel in CNC machines. The postural discomforts associated with CNC machines were studied in 122 male operators using Corlett and Bishop's body part discomfort mapping, subject information, and discomfort level at various time intervals from starting to end of a shift. This information was collected using a questionnaire. Statistical analysis was carried out using ANOVA. Neck discomfort due to the positioning of the machine displays, and shoulder and arm discomfort due to the positioning of controls were identified as common health issues in the operators of these machines. The study revealed that 45.9% of machine operators reported discomfort in the lower back, 41.8% in the neck, 22.1% in the upper-back, 53.3% in the shoulder and arm, and 21.3% of the operators reported discomfort in the leg. Discomfort increased with the progress of the day and was highest at the end of a shift; subject age had no effect on patient tendency to experience discomfort levels.

Discomfort Analysis in Computerized Numeric Control Machine Operations

PubMed Central

Sankaranarayanasamy, Krishnasamy; Ganguli, Anindya Kumar

2012-01-01

Objectives The introduction of computerized numeric control (CNC) technology in manufacturing industries has revolutionized the production process, but there are some health and safety problems associated with these machines. The present study aimed to investigate the extent of postural discomfort in CNC machine operators, and the relationship of this discomfort to the display and control panel height, with a view to validate the anthropometric recommendation for the location of the display and control panel in CNC machines. Methods The postural discomforts associated with CNC machines were studied in 122 male operators using Corlett and Bishop's body part discomfort mapping, subject information, and discomfort level at various time intervals from starting to end of a shift. This information was collected using a questionnaire. Statistical analysis was carried out using ANOVA. Results Neck discomfort due to the positioning of the machine displays, and shoulder and arm discomfort due to the positioning of controls were identified as common health issues in the operators of these machines. The study revealed that 45.9% of machine operators reported discomfort in the lower back, 41.8% in the neck, 22.1% in the upper-back, 53.3% in the shoulder and arm, and 21.3% of the operators reported discomfort in the leg. Conclusion Discomfort increased with the progress of the day and was highest at the end of a shift; subject age had no effect on patient tendency to experience discomfort levels. PMID:22993720

Computer Numerical Control: Instructional Manual. The North Dakota High Technology Mobile Laboratory Project.

ERIC Educational Resources Information Center

Sinn, John W.

This instructional manual contains five learning activity packets for use in a workshop on computer numerical control for computer-aided manufacturing. The lessons cover the following topics: introduction to computer-aided manufacturing, understanding the lathe, using the computer, computer numerically controlled part programming, and executing a…

IMP: Using microsat technology to support engineering research inside of the International Space Station

NASA Astrophysics Data System (ADS)

Carroll, Kieran A.

2000-01-01

This paper describes an International Space Station (ISS) experiment-support facility being developed by Dynacon for the Canadian Space Agency (CSA), based on microsatellite technology. The facility is called the ``Intravehicular Maneuverable Platform,'' or IMP. The core of IMP is a small, free-floating platform (or ``bus'') deployed inside one of the pressurized crew modules of ISS. Exchangeable experimental payloads can then be mounted to the IMP bus, in order to carry out engineering development or demonstration tests, or microgravity science experiments: the bus provides these payloads with services typical of a standard satellite bus (power, attitude control, etc.). The IMP facility takes advantage of unique features of the ISS, such as the Shuttle-based logistics system and the continuous availability of crew members, to greatly reduce the expense of carrying out space engineering experiments. Further cost reduction has been made possible by incorporating technology that Dynacon has developed for use in a current microsatellite mission. Numerous potential payloads for IMP have been identified, and the first of these (a flexible satellite control experiment) is under development by Dynacon and the University of Toronto's Institute for Aerospace Studies, for the CSA. .

Transport properties of strongly correlated electrons in quantum dots studied with a simple circuit model.

PubMed

Martins, G B; Büsser, C A; Al-Hassanieh, K A; Anda, E V; Moreo, A; Dagotto, E

2006-02-17

Numerical calculations are shown to reproduce the main results of recent experiments involving nonlocal spin control in quantum dots [Craig, Science 304, 565 (2004).]. In particular, the experimentally reported zero-bias-peak splitting is clearly observed in our studies. To understand these results, a simple "circuit model" is introduced and shown to qualitatively describe the experiments. The main idea is that the splitting originates in a Fano antiresonance, which is caused by having one quantum dot side connected in relation to the current's path. This scenario provides an explanation of the results of Craig et al. that is an alternative to the RKKY proposal, also addressed here.

"It's overwhelming... everything seems to be too much:" A theory of crisis for individuals with severe persistent mental illness.

PubMed

Ball, Jeffrey S; Links, Paul S; Strike, Carol; Boydell, Katherine M

2005-01-01

Crisis in individuals with severe persistent mental illness (SPMI) is a poorly understood phenomenon for which traditional crisis models do not apply. In this study we explored the crisis experience using in-depth interviews conducted with individuals with severe persistent mental illness from two community support programs. A grounded theory of the crisis experience was developed and the results illustrate that underlying vulnerability sets the stage for crisis occurrence which involves feeling overwhelmed and lacking control and manifests as agitation/anger/aggression, being low, feeling anxious, or euphoria. Immediate responses to crises involve getting help or managing alone and numerous factors contribute to crisis resolution and prevention.

Beam Shaping for CARS Measurements in Turbulent Environments

NASA Technical Reports Server (NTRS)

Magnotti, Gaetano; Cutler, Andrew D.; Danehy, Paul M.

2010-01-01

This paper describes a new technique to mitigate the effect of beam steering on CARS measurements in turbulent, variable density environments. The new approach combines Planar BOXCARS phase-matching with elliptical shaping of one of the beams to generate a signal insensitive to beam steering, while keeping the same spatial resolution. Numerical and experimental results are provided to demonstrate the effectiveness of this approach. One set of experiments investigated the effect of beam shaping in the presence of a controlled and well quantified displacement of the beams at the focal plane. Another set of experiments, more qualitative, proved the effectiveness of the technique in the presence of severe beam steering due to turbulence.

Reliable numerical computation in an optimal output-feedback design

NASA Technical Reports Server (NTRS)

Vansteenwyk, Brett; Ly, Uy-Loi

1991-01-01

A reliable algorithm is presented for the evaluation of a quadratic performance index and its gradients with respect to the controller design parameters. The algorithm is a part of a design algorithm for optimal linear dynamic output-feedback controller that minimizes a finite-time quadratic performance index. The numerical scheme is particularly robust when it is applied to the control-law synthesis for systems with densely packed modes and where there is a high likelihood of encountering degeneracies in the closed-loop eigensystem. This approach through the use of an accurate Pade series approximation does not require the closed-loop system matrix to be diagonalizable. The algorithm was included in a control design package for optimal robust low-order controllers. Usefulness of the proposed numerical algorithm was demonstrated using numerous practical design cases where degeneracies occur frequently in the closed-loop system under an arbitrary controller design initialization and during the numerical search.

Using a hybrid model to predict solute transfer from initially saturated soil into surface runoff with controlled drainage water.

PubMed

Tong, Juxiu; Hu, Bill X; Yang, Jinzhong; Zhu, Yan

2016-06-01

The mixing layer theory is not suitable for predicting solute transfer from initially saturated soil to surface runoff water under controlled drainage conditions. By coupling the mixing layer theory model with the numerical model Hydrus-1D, a hybrid solute transfer model has been proposed to predict soil solute transfer from an initially saturated soil into surface water, under controlled drainage water conditions. The model can also consider the increasing ponding water conditions on soil surface before surface runoff. The data of solute concentration in surface runoff and drainage water from a sand experiment is used as the reference experiment. The parameters for the water flow and solute transfer model and mixing layer depth under controlled drainage water condition are identified. Based on these identified parameters, the model is applied to another initially saturated sand experiment with constant and time-increasing mixing layer depth after surface runoff, under the controlled drainage water condition with lower drainage height at the bottom. The simulation results agree well with the observed data. Study results suggest that the hybrid model can accurately simulate the solute transfer from initially saturated soil into surface runoff under controlled drainage water condition. And it has been found that the prediction with increasing mixing layer depth is better than that with the constant one in the experiment with lower drainage condition. Since lower drainage condition and deeper ponded water depth result in later runoff start time, more solute sources in the mixing layer are needed for the surface water, and larger change rate results in the increasing mixing layer depth.

Porous media deformation due to fluid flow: From hydrofracture formation to seismic liquefaction, a numerical and experimental study

NASA Astrophysics Data System (ADS)

Toussaint, R.; Turkaya, S.; Eriksen, F.; Clément, C.; Sanchez-Colina, G.; Maloy, K. J.; Flekkoy, E.; Aharonov, E.; Lengliné, O.; Daniel, G.; Altshuler, E.; Batista-Leyva, A.; Niebling, M.

2016-12-01

We present here the deformation of porous media in two different situations: 1. The formation of channels and fracture during pressurization of pore fluids, as happens during eruptions or injection of fluids and gas into soils and rocks. 2. The liquefaction of soils at different degrees of saturations during Earthquakes. The formation of channels during hydrofracture and pneumatic fractures is studied in laboratory experiments and in numerical models. The experiments are done on different types of porous media in Hele-Shaw cells, where fluid is injected at controlled overpressures, and various boundary conditions are used. Using fast cameras, we determine the strain and velocity fields from the images. We also record the characteristics of micro-seismic emissions during the process, and link this seismic record features and the direct image of the displacement responsible for the seismic sources in the medium. We also carry out numerical simulations, using coupled fluid/solid hydrid models that capture solid stress, pore pressure, solid and fluid elasticity - a full poro-elasto-plastic model using granular representation of the solid and a continuous one for the fluid.Next, Soil liquefaction is a significant natural hazard associated with earthquakes. Some of its devastating effects include tilting and sinking of buildings and bridges, and destruction of pipelines. Conventional geotechnical engineering assumes liquefaction occurs via elevated pore pressure. This assumption guides construction for seismically hazardous locations, yet evidence suggests that liquefaction strikes also under currently unpredicted conditions. We show, using theory, simulations and experiments, another mechanism for liquefaction in saturated soils, without high pore fluid pressure and without special soils, whereby liquefaction is controlled by buoyancy forces. This new mechanism enlarges the window of conditions under which liquefaction is predicted to occur, and may explain previously not understood cases such as liquefaction in well-compacted soils, under drained conditions, repeated liquefaction cases, far-field liquefaction and the basics of sinking in quicksand. These results may greatly impact hazard assessment and mitigation in seismically active areas.

On the role of entailment patterns and scalar implicatures in the processing of numerals

PubMed Central

Panizza, Daniele; Chierchia, Gennaro; Clifton, Charles

2009-01-01

There has been much debate, in both the linguistics and the psycholinguistics literature, concerning numbers and the interpretation of number denoting determiners ('numerals'). Such debate concerns, in particular, the nature and distribution of upper-bounded ('at-least') interpretations vs. lower-bounded ('exact') construals. In the present paper we show that the interpretation and processing of numerals are affected by the entailment properties of the context in which they occur. Experiment 1 established off-line preferences using a questionnaire. Experiment 2 investigated the processing issue through an eye tracking experiment using a silent reading task. Our results show that the upper-bounded interpretation of numerals occurs more often in an upward entailing context than in a downward entailing context. Reading times of the numeral itself were longer when it was embedded in an upward entailing context than when it was not, indicating that processing resources were required when the context triggered an upper-bounded interpretation. However, reading of a following context that required an upper-bounded interpretation triggered more regressions towards the numeral when it had occurred in a downward entailing context than in an upward entailing one. Such findings show that speakers' interpretation and processing of numerals is systematically affected by the polarity of the sentence in which they occur, and support the hypothesis that the upper-bounded interpretation of numerals is due to a scalar implicature. PMID:20161494

Collapse of a Liquid Column: Numerical Simulation and Experimental Validation

NASA Astrophysics Data System (ADS)

Cruchaga, Marcela A.; Celentano, Diego J.; Tezduyar, Tayfun E.

2007-03-01

This paper is focused on the numerical and experimental analyses of the collapse of a liquid column. The measurements of the interface position in a set of experiments carried out with shampoo and water for two different initial column aspect ratios are presented together with the corresponding numerical predictions. The experimental procedure was found to provide acceptable recurrence in the observation of the interface evolution. Basic models describing some of the relevant physical aspects, e.g. wall friction and turbulence, are included in the simulations. Numerical experiments are conducted to evaluate the influence of the parameters involved in the modeling by comparing the results with the data from the measurements. The numerical predictions reasonably describe the physical trends.

Progress Towards Fuselage Drag Reduction via Active Flow Control: A Combined CFD and Experimental Effort

NASA Technical Reports Server (NTRS)

Schaeffler, Norman W.; Allan, Brian G.; Lienard, Caroline; LePape, Arnaud

2010-01-01

A combined computational and experimental effort has been undertaken to study fuselage drag reduction on a generic, non-proprietary rotorcraft fuselage by the application of active ow control. Fuselage drag reduction is an area of research interest to both the United States and France and this area is being worked collaboratively as a task under the United States/France Memorandum of Agreement on Helicopter Aeromechanics. In the first half of this task, emphasis is placed on the US generic fuselage, the ROBIN-mod7, with the experimental work being conducted on the US side and complementary US and French CFD analysis of the baseline and controlled cases. Fuselage simulations were made using Reynolds-averaged Navier-Stokes ow solvers and with multiple turbulence models. Comparisons were made to experimental data for numerical simulations of the isolated fuselage and for the fuselage as installed in the tunnel, which includes modeling of the tunnel contraction, walls, and support fairing. The numerical simulations show that comparisons to the experimental data are in good agreement when the tunnel and model support are included. The isolated fuselage simulations compare well to each other, however, there is a positive shift in the centerline pressure when compared to the experiment. The computed flow separation locations on the rear ramp region had only slight differences with and without the tunnel walls and model support. For the simulations, the flow control slots were placed at several locations around the flow separation lines as a series of eight slots that formed a nearly continuous U-shape. Results from the numerical simulations resulted in an estimated 35% fuselage drag reduction from a steady blowing flow control configuration and a 26% drag reduction for unsteady zero-net-mass flow control configuration. Simulations with steady blowing show a delayed flow separation at the rear ramp of the fuselage that increases the surface pressure acting on the ramp, thus decreasing the overall fuselage pressure drag.

Long-Term Bioeffects of 435-MHz Radiofrequency Radiation on Selected Blood-Borne Endpoints in Cannulated Rats. Volume 4. Plasma Catecholamines.

DTIC Science & Technology

1987-08-01

out. To use each animal as its own control , arterial blood was sampled by means of chronically implanted aortic cannulas 112,13,14]. This simple...APPENDIX B STATISTICAL METHODOLOGY 37 APPENDIX B STATISTICAL METHODOLOGY The balanced design of this experiment (requiring that 25 animals from each...protoccl in that, in numerous cases, samples were collected at odd intervals (invalidating the orthogonality of the design ) and the number of samples’taken

System Identification of a Vortex Lattice Aerodynamic Model

NASA Technical Reports Server (NTRS)

Juang, Jer-Nan; Kholodar, Denis; Dowell, Earl H.

2001-01-01

The state-space presentation of an aerodynamic vortex model is considered from a classical and system identification perspective. Using an aerodynamic vortex model as a numerical simulator of a wing tunnel experiment, both full state and limited state data or measurements are considered. Two possible approaches for system identification are presented and modal controllability and observability are also considered. The theory then is applied to the system identification of a flow over an aerodynamic delta wing and typical results are presented.

Intermittency of intermittencies

NASA Astrophysics Data System (ADS)

Hramov, Alexander E.; Koronovskii, Alexey A.; Moskalenko, Olga I.; Zhuravlev, Maxim O.; Ponomarenko, Vladimir I.; Prokhorov, Mikhail D.

2013-09-01

A phenomenon of intermittency of intermittencies is discovered in the temporal behavior of two coupled complex systems. We observe for the first time the coexistence of two types of intermittent behavior taking place simultaneously near the boundary of the synchronization regime of coupled chaotic oscillators. This phenomenon is found both in the numerical and physiological experiments. The laws for both the distribution and mean length of laminar phases versus the control parameter values are analytically deduced. A very good agreement between the theoretical results and simulation is shown.

On The Behavior of Subgradient Projections Methods for Convex Feasibility Problems in Euclidean Spaces

PubMed Central

Butnariu, Dan; Censor, Yair; Gurfil, Pini; Hadar, Ethan

2010-01-01

We study some methods of subgradient projections for solving a convex feasibility problem with general (not necessarily hyperplanes or half-spaces) convex sets in the inconsistent case and propose a strategy that controls the relaxation parameters in a specific self-adapting manner. This strategy leaves enough user-flexibility but gives a mathematical guarantee for the algorithm’s behavior in the inconsistent case. We present numerical results of computational experiments that illustrate the computational advantage of the new method. PMID:20182556

On The Behavior of Subgradient Projections Methods for Convex Feasibility Problems in Euclidean Spaces.

PubMed

Butnariu, Dan; Censor, Yair; Gurfil, Pini; Hadar, Ethan

2008-07-03

We study some methods of subgradient projections for solving a convex feasibility problem with general (not necessarily hyperplanes or half-spaces) convex sets in the inconsistent case and propose a strategy that controls the relaxation parameters in a specific self-adapting manner. This strategy leaves enough user-flexibility but gives a mathematical guarantee for the algorithm's behavior in the inconsistent case. We present numerical results of computational experiments that illustrate the computational advantage of the new method.

Solvent viscosity and friction in protein folding dynamics.

PubMed

Hagen, Stephen J

2010-08-01

The famous Kramers rate theory for diffusion-controlled reactions has been extended in numerous ways and successfully applied to many types of reactions. Its application to protein folding reactions has been of particular interest in recent years, as many researchers have performed experiments and simulations to test whether folding reactions are diffusion-controlled, whether the solvent is the source of the reaction friction, and whether the friction-dependence of folding rates generally can provide insight into folding dynamics. These experiments involve many practical difficulties, however. They have also produced some unexpected results. Here we briefly review the Kramers theory for reactions in the presence of strong friction and summarize some of the subtle problems that arise in the application of the theory to protein folding. We discuss how the results of these experiments ultimately point to a significant role for internal friction in protein folding dynamics. Studies of friction in protein folding, far from revealing any weakness in Kramers theory, may actually lead to new approaches for probing diffusional dynamics and energy landscapes in protein folding.

A new smooth robust control design for uncertain nonlinear systems with non-vanishing disturbances

NASA Astrophysics Data System (ADS)

Xian, Bin; Zhang, Yao

2016-06-01

In this paper, we consider the control problem for a general class of nonlinear system subjected to uncertain dynamics and non-varnishing disturbances. A smooth nonlinear control algorithm is presented to tackle these uncertainties and disturbances. The proposed control design employs the integral of a nonlinear sigmoid function to compensate the uncertain dynamics, and achieve a uniformly semi-global practical asymptotic stable tracking control of the system outputs. A novel Lyapunov-based stability analysis is employed to prove the convergence of the tracking errors and the stability of the closed-loop system. Numerical simulation results on a two-link robot manipulator are presented to illustrate the performance of the proposed control algorithm comparing with the layer-boundary sliding mode controller and the robust of integration of sign of error control design. Furthermore, real-time experiment results for the attitude control of a quadrotor helicopter are also included to confirm the effectiveness of the proposed algorithm.

Spatial correlations and probability density function of the phase difference in a developed speckle-field: numerical and natural experiments

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

Mysina, N Yu; Maksimova, L A; Ryabukho, V P

Investigated are statistical properties of the phase difference of oscillations in speckle-fields at two points in the far-field diffraction region, with different shapes of the scatterer aperture. Statistical and spatial nonuniformity of the probability density function of the field phase difference is established. Numerical experiments show that, for the speckle-fields with an oscillating alternating-sign transverse correlation function, a significant nonuniformity of the probability density function of the phase difference in the correlation region of the field complex amplitude, with the most probable values 0 and p, is observed. A natural statistical interference experiment using Young diagrams has confirmed the resultsmore » of numerical experiments. (laser applications and other topics in quantum electronics)« less

Flowfield visualization for SSME hot gas manifold

NASA Technical Reports Server (NTRS)

Roger, Robert P.

1988-01-01

The objective of this research, as defined by NASA-Marshall Space Flight Center, was two-fold: (1) to numerically simulate viscous subsonic flow in a proposed elliptical two-duct version of the fuel side Hot Gas Manifold (HGM) for the Space Shuttle Main Engine (SSME), and (2) to provide analytical support for SSME related numerical computational experiments, being performed by the Computational Fluid Dynamics staff in the Aerophysics Division of the Structures and Dynamics Laboratory at NASA-MSFC. Numerical results of HGM were calculations to complement both water flow visualization experiments and air flow visualization experiments and air experiments in two-duct geometries performed at NASA-MSFC and Rocketdyne. In addition, code modification and improvement efforts were to strengthen the CFD capabilities of NASA-MSFC for producing reliable predictions of flow environments within the SSME.

A Comparison of Metamodeling Techniques via Numerical Experiments

NASA Technical Reports Server (NTRS)

Crespo, Luis G.; Kenny, Sean P.; Giesy, Daniel P.

2016-01-01

This paper presents a comparative analysis of a few metamodeling techniques using numerical experiments for the single input-single output case. These experiments enable comparing the models' predictions with the phenomenon they are aiming to describe as more data is made available. These techniques include (i) prediction intervals associated with a least squares parameter estimate, (ii) Bayesian credible intervals, (iii) Gaussian process models, and (iv) interval predictor models. Aspects being compared are computational complexity, accuracy (i.e., the degree to which the resulting prediction conforms to the actual Data Generating Mechanism), reliability (i.e., the probability that new observations will fall inside the predicted interval), sensitivity to outliers, extrapolation properties, ease of use, and asymptotic behavior. The numerical experiments describe typical application scenarios that challenge the underlying assumptions supporting most metamodeling techniques.

Proposal and verification numerical simulation for a microwave forward scattering technique at upper hybrid resonance for the measurement of electron gyroscale density fluctuations in the electron cyclotron frequency range in magnetized plasmas

NASA Astrophysics Data System (ADS)

Kawamori, E.; Igami, H.

2017-11-01

A diagnostic technique for detecting the wave numbers of electron density fluctuations at electron gyro-scales in an electron cyclotron frequency range is proposed, and the validity of the idea is checked by means of a particle-in-cell (PIC) numerical simulation. The technique is a modified version of the scattering technique invented by Novik et al. [Plasma Phys. Controlled Fusion 36, 357-381 (1994)] and Gusakov et al., [Plasma Phys. Controlled Fusion 41, 899-912 (1999)]. The novel method adopts forward scattering of injected extraordinary probe waves at the upper hybrid resonance layer instead of the backward-scattering adopted by the original method, enabling the measurement of the wave-numbers of the fine scale density fluctuations in the electron-cyclotron frequency band by means of phase measurement of the scattered waves. The verification numerical simulation with the PIC method shows that the technique has a potential to be applicable to the detection of electron gyro-scale fluctuations in laboratory plasmas if the upper-hybrid resonance layer is accessible to the probe wave. The technique is a suitable means to detect electron Bernstein waves excited via linear mode conversion from electromagnetic waves in torus plasma experiments. Through the numerical simulations, some problems that remain to be resolved are revealed, which include the influence of nonlinear processes such as the parametric decay instability of the probe wave in the scattering process, and so on.

On the assimilation of satellite derived soil moisture in numerical weather prediction models

NASA Astrophysics Data System (ADS)

Drusch, M.

2006-12-01

Satellite derived surface soil moisture data sets are readily available and have been used successfully in hydrological applications. In many operational numerical weather prediction systems the initial soil moisture conditions are analysed from the modelled background and 2 m temperature and relative humidity. This approach has proven its efficiency to improve surface latent and sensible heat fluxes and consequently the forecast on large geographical domains. However, since soil moisture is not always related to screen level variables, model errors and uncertainties in the forcing data can accumulate in root zone soil moisture. Remotely sensed surface soil moisture is directly linked to the model's uppermost soil layer and therefore is a stronger constraint for the soil moisture analysis. Three data assimilation experiments with the Integrated Forecast System (IFS) of the European Centre for Medium-range Weather Forecasts (ECMWF) have been performed for the two months period of June and July 2002: A control run based on the operational soil moisture analysis, an open loop run with freely evolving soil moisture, and an experimental run incorporating bias corrected TMI (TRMM Microwave Imager) derived soil moisture over the southern United States through a nudging scheme using 6-hourly departures. Apart from the soil moisture analysis, the system setup reflects the operational forecast configuration including the atmospheric 4D-Var analysis. Soil moisture analysed in the nudging experiment is the most accurate estimate when compared against in-situ observations from the Oklahoma Mesonet. The corresponding forecast for 2 m temperature and relative humidity is almost as accurate as in the control experiment. Furthermore, it is shown that the soil moisture analysis influences local weather parameters including the planetary boundary layer height and cloud coverage. The transferability of the results to other satellite derived soil moisture data sets will be discussed.

Numerical experiments on the accuracy of ENO and modified ENO schemes

NASA Technical Reports Server (NTRS)

Shu, Chi-Wang

1990-01-01

Further numerical experiments are made assessing an accuracy degeneracy phenomena. A modified essentially non-oscillatory (ENO) scheme is proposed, which recovers the correct order of accuracy for all the test problems with smooth initial conditions and gives comparable results with the original ENO schemes for discontinuous problems.

Phonological experience modulates voice discrimination: Evidence from functional brain networks analysis.

PubMed

Hu, Xueping; Wang, Xiangpeng; Gu, Yan; Luo, Pei; Yin, Shouhang; Wang, Lijun; Fu, Chao; Qiao, Lei; Du, Yi; Chen, Antao

2017-10-01

Numerous behavioral studies have found a modulation effect of phonological experience on voice discrimination. However, the neural substrates underpinning this phenomenon are poorly understood. Here we manipulated language familiarity to test the hypothesis that phonological experience affects voice discrimination via mediating the engagement of multiple perceptual and cognitive resources. The results showed that during voice discrimination, the activation of several prefrontal regions was modulated by language familiarity. More importantly, the same effect was observed concerning the functional connectivity from the fronto-parietal network to the voice-identity network (VIN), and from the default mode network to the VIN. Our findings indicate that phonological experience could bias the recruitment of cognitive control and information retrieval/comparison processes during voice discrimination. Therefore, the study unravels the neural substrates subserving the modulation effect of phonological experience on voice discrimination, and provides new insights into studying voice discrimination from the perspective of network interactions. Copyright © 2017. Published by Elsevier Inc.

Neural computing for numeric-to-symbolic conversion in control systems

NASA Technical Reports Server (NTRS)

Passino, Kevin M.; Sartori, Michael A.; Antsaklis, Panos J.

1989-01-01

A type of neural network, the multilayer perceptron, is used to classify numeric data and assign appropriate symbols to various classes. This numeric-to-symbolic conversion results in a type of information extraction, which is similar to what is called data reduction in pattern recognition. The use of the neural network as a numeric-to-symbolic converter is introduced, its application in autonomous control is discussed, and several applications are studied. The perceptron is used as a numeric-to-symbolic converter for a discrete-event system controller supervising a continuous variable dynamic system. It is also shown how the perceptron can implement fault trees, which provide useful information (alarms) in a biological system and information for failure diagnosis and control purposes in an aircraft example.

Active flow control of subsonic flow in an adverse pressure gradient using synthetic jets and passive micro flow control devices

NASA Astrophysics Data System (ADS)

Denn, Michael E.

Several recent studies have shown the advantages of active and/or passive flow control devices for boundary layer flow modification. Many current and future proposed air vehicles have very short or offset diffusers in order to save vehicle weight and create more optimal vehicle/engine integration. Such short coupled diffusers generally result in boundary layer separation and loss of pressure recovery which reduces engine performance and in some cases may cause engine stall. Deployment of flow control devices can alleviate this problem to a large extent; however, almost all active flow control devices have some energy penalty associated with their inclusion. One potential low penalty approach for enhancing the diffuser performance is to combine the passive flow control elements such as micro-ramps with active flow control devices such as synthetic jets to achieve higher control authority. The goal of this dissertation is twofold. The first objective is to assess the ability of CFD with URANS turbulence models to accurately capture the effects of the synthetic jets and micro-ramps on boundary layer flow. This is accomplished by performing numerical simulations replicating several experimental test cases conducted at Georgia Institute of Technology under the NASA funded Inlet Flow Control and Prediction Technologies Program, and comparing the simulation results with experimental data. The second objective is to run an expanded CFD matrix of numerical simulations by varying various geometric and other flow control parameters of micro-ramps and synthetic jets to determine how passive and active control devices interact with each other in increasing and/or decreasing the control authority and determine their influence on modification of boundary layer flow. The boundary layer shape factor is used as a figure of merit for determining the boundary layer flow quality/modification and its tendency towards separation. It is found by a large number of numerical experiments and the analysis of simulation data that a flow control device's influence on boundary layer quality is a function of three factors: (1) the strength of the longitudinal vortex emanating from the flow control device or devices, (2) the height of the vortex core above the surface and, when a synthetic jet is present, (3) the momentum added to the boundary layer flow.

Numerical sensitivity analysis of a variational data assimilation procedure for cardiac conductivities

NASA Astrophysics Data System (ADS)

Barone, Alessandro; Fenton, Flavio; Veneziani, Alessandro

2017-09-01

An accurate estimation of cardiac conductivities is critical in computational electro-cardiology, yet experimental results in the literature significantly disagree on the values and ratios between longitudinal and tangential coefficients. These are known to have a strong impact on the propagation of potential particularly during defibrillation shocks. Data assimilation is a procedure for merging experimental data and numerical simulations in a rigorous way. In particular, variational data assimilation relies on the least-square minimization of the misfit between simulations and experiments, constrained by the underlying mathematical model, which in this study is represented by the classical Bidomain system, or its common simplification given by the Monodomain problem. Operating on the conductivity tensors as control variables of the minimization, we obtain a parameter estimation procedure. As the theory of this approach currently provides only an existence proof and it is not informative for practical experiments, we present here an extensive numerical simulation campaign to assess practical critical issues such as the size and the location of the measurement sites needed for in silico test cases of potential experimental and realistic settings. This will be finalized with a real validation of the variational data assimilation procedure. Results indicate the presence of lower and upper bounds for the number of sites which guarantee an accurate and minimally redundant parameter estimation, the location of sites being generally non critical for properly designed experiments. An effective combination of parameter estimation based on the Monodomain and Bidomain models is tested for the sake of computational efficiency. Parameter estimation based on the Monodomain equation potentially leads to the accurate computation of the transmembrane potential in real settings.

Does plasticity in plant physiological traits explain the rapid increase in water use efficiency? An ecohydrological modeling approach

NASA Astrophysics Data System (ADS)

Mastrotheodoros, Theodoros; Fatichi, Simone; Pappas, Christoforos; Molnar, Peter; Burlando, Paolo

2016-04-01

The rise of atmospheric CO2 concentration is expected to stimulate plant productivity by enhancing photosynthesis and reducing stomatal conductance and thus increasing plant water use efficiency (WUE) worldwide. An analysis of eddy covariance flux tower data from 21 forested ecosystems across the north hemisphere detected an unexpectedly large increase in WUE (Keenan et al, 2013), which was six times larger than the increase found by most previous studies based on controlled experiments (e.g., FACE), leaf-scale analyses, and numerical modelling. This increase could be solely attributed to the increase in atmospheric CO2 since other confounding factors were ruled out. Here, we investigate the potential contribution of plant plasticity, reflected in the temporal adjustment of major plant physiological traits, on changes in WUE using the ecohydrological model Tethys and Chloris (T&C). We hypothesize that the increase in WUE can be attributed to small variations in plant physiological traits, undetectable through observations, eventually triggered by the atmospheric CO2 increase. Data from the 21 sites in the above mentioned study are used to force the model. Simulation results with and without plasticity in the physiological traits (i.e., model parameters in our numerical experiments) are compared with the observed trends in WUE. We test several plant adaptation strategies in being effective in explaining the observed increase in WUE using a multifactorial numerical experiment in which we perturb in a systematic way selected plant parameters. Keenan, T. F., Hollinger, D. Y., Bohrer, G., Dragoni, D., Munger, J. W., Schmid, H. P., and Richardson, A. D. (2013). Increase in forest water-use efficiency as atmospheric carbon dioxide concentrations rise. Nature, 499(7458), 324-7.

Experiments Using a Ground-Based Electrostatic Levitator and Numerical Modeling of Melt Convection for the Iron-Cobalt System in Support of Space Experiments

NASA Astrophysics Data System (ADS)

Lee, Jonghyun; SanSoucie, Michael P.

2017-08-01

Materials research is being conducted using an electromagnetic levitator installed in the International Space Station. Various metallic alloys were tested to elucidate unknown links among the structures, processes, and properties. To accomplish the mission of these space experiments, several ground-based activities have been carried out. This article presents some of our ground-based supporting experiments and numerical modeling efforts. Mass evaporation of Fe50Co50, one of flight compositions, was predicted numerically and validated by the tests using an electrostatic levitator (ESL). The density of various compositions within the Fe-Co system was measured with ESL. These results are being served as reference data for the space experiments. The convection inside a electromagnetically-levitated droplet was also modeled to predict the flow status, shear rate, and convection velocity under various process parameters, which is essential information for designing and analyzing the space experiments of some flight compositions influenced by convection.

Displacement control of an antagonistic-type twisted and coiled polymer actuator

NASA Astrophysics Data System (ADS)

Suzuki, Motoya; Kamamichi, Norihiro

2018-03-01

A novel artificial muscle actuator referred to as a twisted and coiled polymer actuator can be easily fabricated by commercially available nylon fibers. It can be thermally activated and has remarkable properties such as large deformation and flexibility. The actuator uses conductive nylon fibers and can be activated by Joule heating and is easily controlled electrically. However, asymmetric response characteristics due to a speed difference in heating-cooling are a problem. In the case of actuation in air, the cooling speed depends on the external temperature, and is slower than the heating speed. To solve these problems, we apply an antagonistic structure. The validity of the applied method is investigated through numerical simulations and experiments. The response characteristics of the PID feedback control and the 2-DOF control of the displacement are investigated.

A New Unified Analysis of Estimate Errors by Model-Matching Phase-Estimation Methods for Sensorless Drive of Permanent-Magnet Synchronous Motors and New Trajectory-Oriented Vector Control, Part II

NASA Astrophysics Data System (ADS)

Shinnaka, Shinji

This paper presents a new unified analysis of estimate errors by model-matching extended-back-EMF estimation methods for sensorless drive of permanent-magnet synchronous motors. Analytical solutions about estimate errors, whose validity is confirmed by numerical experiments, are rich in universality and applicability. As an example of universality and applicability, a new trajectory-oriented vector control method is proposed, which can realize directly quasi-optimal strategy minimizing total losses with no additional computational loads by simply orienting one of vector-control coordinates to the associated quasi-optimal trajectory. The coordinate orientation rule, which is analytically derived, is surprisingly simple. Consequently the trajectory-oriented vector control method can be applied to a number of conventional vector control systems using model-matching extended-back-EMF estimation methods.

Optimality of affine control system of several species in competition on a sequential batch reactor

NASA Astrophysics Data System (ADS)

Rodríguez, J. C.; Ramírez, H.; Gajardo, P.; Rapaport, A.

2014-09-01

In this paper, we analyse the optimality of affine control system of several species in competition for a single substrate on a sequential batch reactor, with the objective being to reach a given (low) level of the substrate. We allow controls to be bounded measurable functions of time plus possible impulses. A suitable modification of the dynamics leads to a slightly different optimal control problem, without impulsive controls, for which we apply different optimality conditions derived from Pontryagin principle and the Hamilton-Jacobi-Bellman equation. We thus characterise the singular trajectories of our problem as the extremal trajectories keeping the substrate at a constant level. We also establish conditions for which an immediate one impulse (IOI) strategy is optimal. Some numerical experiences are then included in order to illustrate our study and show that those conditions are also necessary to ensure the optimality of the IOI strategy.

Active control of convection

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

Bau, H.H.

Using stability theory, numerical simulations, and in some instances experiments, it is demonstrated that the critical Rayleigh number for the bifurcation (1) from the no-motion (conduction) state to the motion state and (2) from time-independent convection to time-dependent, oscillatory convection in the thermal convection loop and Rayleigh-Benard problems can be significantly increased or decreased. This is accomplished through the use of a feedback controller effectuating small perturbations in the boundary data. The controller consists of sensors which detect deviations in the fluid`s temperature from the motionless, conductive values and then direct actuators to respond to these deviations in such amore » way as to suppress the naturally occurring flow instabilities. Actuators which modify the boundary`s temperature/heat flux are considered. The feedback controller can also be used to control flow patterns and generate complex dynamic behavior at relatively low Rayleigh numbers.« less

Scaled laboratory experiments explain the kink behaviour of the Crab Nebula jet.

PubMed

Li, C K; Tzeferacos, P; Lamb, D; Gregori, G; Norreys, P A; Rosenberg, M J; Follett, R K; Froula, D H; Koenig, M; Seguin, F H; Frenje, J A; Rinderknecht, H G; Sio, H; Zylstra, A B; Petrasso, R D; Amendt, P A; Park, H S; Remington, B A; Ryutov, D D; Wilks, S C; Betti, R; Frank, A; Hu, S X; Sangster, T C; Hartigan, P; Drake, R P; Kuranz, C C; Lebedev, S V; Woolsey, N C

2016-10-07

The remarkable discovery by the Chandra X-ray observatory that the Crab nebula's jet periodically changes direction provides a challenge to our understanding of astrophysical jet dynamics. It has been suggested that this phenomenon may be the consequence of magnetic fields and magnetohydrodynamic instabilities, but experimental demonstration in a controlled laboratory environment has remained elusive. Here we report experiments that use high-power lasers to create a plasma jet that can be directly compared with the Crab jet through well-defined physical scaling laws. The jet generates its own embedded toroidal magnetic fields; as it moves, plasma instabilities result in multiple deflections of the propagation direction, mimicking the kink behaviour of the Crab jet. The experiment is modelled with three-dimensional numerical simulations that show exactly how the instability develops and results in changes of direction of the jet.

Visualizing the BEC-BCS crossover in a two-dimensional Fermi gas: Pairing gaps and dynamical response functions from ab initio computations

NASA Astrophysics Data System (ADS)

Vitali, Ettore; Shi, Hao; Qin, Mingpu; Zhang, Shiwei

2017-12-01

Experiments with ultracold atoms provide a highly controllable laboratory setting with many unique opportunities for precision exploration of quantum many-body phenomena. The nature of such systems, with strong interaction and quantum entanglement, makes reliable theoretical calculations challenging. Especially difficult are excitation and dynamical properties, which are often the most directly relevant to experiment. We carry out exact numerical calculations, by Monte Carlo sampling of imaginary-time propagation of Slater determinants, to compute the pairing gap in the two-dimensional Fermi gas from first principles. Applying state-of-the-art analytic continuation techniques, we obtain the spectral function and the density and spin structure factors providing unique tools to visualize the BEC-BCS crossover. These quantities will allow for a direct comparison with experiments.

Demonstration of a tool for automatic learning and re-use of knowledge in the activated sludge process.

PubMed

Comas, J; Rodríguez-Roda, I; Poch, M; Gernaey, K V; Rosen, C; Jeppsson, U

2006-01-01

Wastewater treatment plant operators encounter complex operational problems related to the activated sludge process and usually respond to these by applying their own intuition and by taking advantage of what they have learnt from past experiences of similar problems. However, previous process experiences are not easy to integrate in numerical control, and new tools must be developed to enable re-use of plant operating experience. The aim of this paper is to investigate the usefulness of a case-based reasoning (CBR) approach to apply learning and re-use of knowledge gained during past incidents to confront actual complex problems through the IWA/COST Benchmark protocol. A case study shows that the proposed CBR system achieves a significant improvement of the benchmark plant performance when facing a high-flow event disturbance.

The precipitation forecast sensitivity to data assimilation on a very high resolution domain

NASA Astrophysics Data System (ADS)

Palamarchuk, Iuliia; Ivanov, Sergiy; Ruban, Igor

2016-04-01

Last developments in computing technologies allow the implementation of a very high resolution in numerical weather prediction models. Due to that fact, simulation and quantitative analysis of mesoscale processes with a horizontal scale of few kilometers become available. This is crucially important in studies of precipitation including their life-cycle. However, new opportunities generate prerequisites to revising existing knowledge, both in meteorology and numerics. The latter associates, in particular, with formulation of the initial conditions involving the data assimilation. Depending on applied techniques, observational data types and spatial resolution the precipitation prediction appears quite sensitive. The impact of the data assimilation on resulting fields is presented using the Harmonie-38h1.2 model with the AROME physical package. The numerical experiments were performed for the Finland domain with the horizontal grid of 2.5 km and 65 vertical levels for the August 2010 period covering the BaltRad experiment. The initial conditions formulation included downscaling from the MARS archive and involving observations through 3DVAR data assimilation. The treatment of both conventional and radar observations in numerical experiments was used. The earlier included the SYNOP, SHIP, PILOT, TEMP, AIREP and DRIBU types. The background error covariances required for the variational assimilation have already been computed from the ensemble perturbed analysis with the purely statistical balance by the HIRLAM community. Deviations among the model runs started from the MARS, conventional and radar data assimilation were complex. In the focus therefore is to know how the model system reacts on involvement of observations. The contribution from observed variables included in the control vector, such as humidity and temperature, was expected to be largest. Nevertheless, revealing of such impact is not so straightforward task. Major changes occur within the lower 3-km layer of the atmosphere for all predicted variables. However, those changes were not directly associated with observation locations, as it often shows single observation experiments. Moreover, the model response to observations with lead time produces weak mesoscale spots of opposite signs. Special attention is paid to precipitation, cloud and rain water, vertical velocity fields. A complex chain of interactions among radiation, temperature, humidity, stratification and other atmospheric characteristics results in changes of local updraft and downdraft flows and following cloud formation processes and precipitation release. One can assume that those features would arise due to both, atmospheric physics and numeric effects. The latter becomes more evident in simulations on very high resolution domains.

Laboratory Scale Experiments and Numerical Modeling of Cosolvent flushing of NAPL Mixtures in Saturated Porous Media

NASA Astrophysics Data System (ADS)

Agaoglu, B.; Scheytt, T. J.; Copty, N. K.

2011-12-01

This study examines the mechanistic processes governing multiphase flow of a water-cosolvent-NAPL system in saturated porous media. Laboratory batch and column flushing experiments were conducted to determine the equilibrium properties of pure NAPL and synthetically prepared NAPL mixtures as well as NAPL recovery mechanisms for different water-ethanol contents. The effect of contact time was investigated by considering different steady and intermittent flow velocities. A modified version of multiphase flow simulator (UTCHEM) was used to compare the multiphase model simulations with the column experiment results. The effect of employing different grid geometries (1D, 2D, 3D), heterogeneity and different initial NAPL saturation configurations were also examined in the model. It is shown that the change in velocity affects the mass transfer rate between phases as well as the ultimate NAPL recovery percentage. The experiments with slow flow rate flushing of pure NAPL and the 3D UTCHEM simulations gave similar effluent concentrations and NAPL cumulative recoveries. The results were less consistent for fast non-equilibrium flow conditions. The dissolution process from the NAPL mixture into the water-ethanol flushing solutions was found to be more complex than dissolution expressions incorporated in the numerical model. The dissolution rate of individual organic compounds (namely Toluene and Benzene) from a mixture NAPL into the ethanol-water flushing solution is found not to correlate with their equilibrium solubility values.The implications of this controlled experimental and modeling study on field cosolvent remediation applications are discussed.

Thrust shock vector control of an axisymmetric conical supersonic nozzle via secondary transverse gas injection

NASA Astrophysics Data System (ADS)

Zmijanovic, V.; Lago, V.; Sellam, M.; Chpoun, A.

2014-01-01

Transverse secondary gas injection into the supersonic flow of an axisymmetric convergent-divergent nozzle is investigated to describe the effects of the fluidic thrust vectoring within the framework of a small satellite launcher. Cold-flow dry-air experiments are performed in a supersonic wind tunnel using two identical supersonic conical nozzles with the different transverse injection port positions. The complex three-dimensional flow field generated by the supersonic cross-flows in these test nozzles was examined. Valuable experimental data were confronted and compared with the results obtained from the numerical simulations. Different nozzle models are numerically simulated under experimental conditions and then further investigated to determine which parameters significantly affect thrust vectoring. Effects which characterize the nozzle and thrust vectoring performances are established. The results indicate that with moderate secondary to primary mass flow rate ratios, ranging around 5 %, it is possible to achieve pertinent vector side forces. It is also revealed that injector positioning and geometry have a strong effect on the shock vector control system and nozzle performances.

NIMROD: A computational laboratory for studying nonlinear fusion magnetohydrodynamics

NASA Astrophysics Data System (ADS)

Sovinec, C. R.; Gianakon, T. A.; Held, E. D.; Kruger, S. E.; Schnack, D. D.

2003-05-01

Nonlinear numerical studies of macroscopic modes in a variety of magnetic fusion experiments are made possible by the flexible high-order accurate spatial representation and semi-implicit time advance in the NIMROD simulation code [A. H. Glasser et al., Plasma Phys. Controlled Fusion 41, A747 (1999)]. Simulation of a resistive magnetohydrodynamics mode in a shaped toroidal tokamak equilibrium demonstrates computation with disparate time scales, simulations of discharge 87009 in the DIII-D tokamak [J. L. Luxon et al., Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] confirm an analytic scaling for the temporal evolution of an ideal mode subject to plasma-β increasing beyond marginality, and a spherical torus simulation demonstrates nonlinear free-boundary capabilities. A comparison of numerical results on magnetic relaxation finds the n=1 mode and flux amplification in spheromaks to be very closely related to the m=1 dynamo modes and magnetic reversal in reversed-field pinch configurations. Advances in local and nonlocal closure relations developed for modeling kinetic effects in fluid simulation are also described.

Laboratory and numerical investigations of kinetic interface sensitive tracers transport for immiscible two-phase flow porous media systems

NASA Astrophysics Data System (ADS)

Tatomir, Alexandru Bogdan A. C.; Sauter, Martin

2017-04-01

A number of theoretical approaches estimating the interfacial area between two fluid phases are available (Schaffer et al.,2013). Kinetic interface sensitive (KIS) tracers are used to describe the evolution of fluid-fluid interfaces advancing in two phase porous media systems (Tatomir et al., 2015). Initially developed to offer answers about the supercritical (sc)CO2 plume movement and the efficiency of trapping in geological carbon storage reservoirs, KIS tracers are tested in dynamic controlled laboratory conditions. N-octane and water, analogue to a scCO2 - brine system, are used. The KIS tracer is dissolved in n-octane, which is injected as the non-wetting phase in a fully water saturated porous media column. The porous system is made up of spherical glass beads with sizes of 100-250 μm. Subsequently, the KIS tracer follows a hydrolysis reaction over the n-octane - water interface resulting in an acid and phenol which are both water soluble. The fluid-fluid interfacial area is described numerically with the help of constitutive-relationships derived from the Brooks-Corey model. The specific interfacial area is determined numerically from pore scale calculations, or from different literature sources making use of pore network model calculations (Joekar-Niasar et al., 2008). This research describes the design of the laboratory setup and compares the break-through curves obtained with the forward model and in the laboratory experiment. Furthermore, first results are shown in the attempt to validate the immiscible two phase flow reactive transport numerical model with dynamic laboratory column experiments. Keywords: Fluid-fluid interfacial area, KIS tracers, model validation, CCS, geological storage of CO2

Mountain bicycle frame testing as an example of practical implementation of hybrid simulation using RTFEM

NASA Astrophysics Data System (ADS)

Mucha, Waldemar; Kuś, Wacław

2018-01-01

The paper presents a practical implementation of hybrid simulation using Real Time Finite Element Method (RTFEM). Hybrid simulation is a technique for investigating dynamic material and structural properties of mechanical systems by performing numerical analysis and experiment at the same time. It applies to mechanical systems with elements too difficult or impossible to model numerically. These elements are tested experimentally, while the rest of the system is simulated numerically. Data between the experiment and numerical simulation are exchanged in real time. Authors use Finite Element Method to perform the numerical simulation. The following paper presents the general algorithm for hybrid simulation using RTFEM and possible improvements of the algorithm for computation time reduction developed by the authors. The paper focuses on practical implementation of presented methods, which involves testing of a mountain bicycle frame, where the shock absorber is tested experimentally while the rest of the frame is simulated numerically.

Initializing numerical weather prediction models with satellite-derived surface soil moisture: Data assimilation experiments with ECMWF's Integrated Forecast System and the TMI soil moisture data set

NASA Astrophysics Data System (ADS)

Drusch, M.

2007-02-01

Satellite-derived surface soil moisture data sets are readily available and have been used successfully in hydrological applications. In many operational numerical weather prediction systems the initial soil moisture conditions are analyzed from the modeled background and 2 m temperature and relative humidity. This approach has proven its efficiency to improve surface latent and sensible heat fluxes and consequently the forecast on large geographical domains. However, since soil moisture is not always related to screen level variables, model errors and uncertainties in the forcing data can accumulate in root zone soil moisture. Remotely sensed surface soil moisture is directly linked to the model's uppermost soil layer and therefore is a stronger constraint for the soil moisture analysis. For this study, three data assimilation experiments with the Integrated Forecast System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF) have been performed for the 2-month period of June and July 2002: a control run based on the operational soil moisture analysis, an open loop run with freely evolving soil moisture, and an experimental run incorporating TMI (TRMM Microwave Imager) derived soil moisture over the southern United States. In this experimental run the satellite-derived soil moisture product is introduced through a nudging scheme using 6-hourly increments. Apart from the soil moisture analysis, the system setup reflects the operational forecast configuration including the atmospheric 4D-Var analysis. Soil moisture analyzed in the nudging experiment is the most accurate estimate when compared against in situ observations from the Oklahoma Mesonet. The corresponding forecast for 2 m temperature and relative humidity is almost as accurate as in the control experiment. Furthermore, it is shown that the soil moisture analysis influences local weather parameters including the planetary boundary layer height and cloud coverage.

Technical Report on Occupations in Numerically Controlled Metal-Cutting Machining.

ERIC Educational Resources Information Center

Manpower Administration (DOL), Washington, DC. U.S. Employment Service.

At the present time, only 5 percent of the short-run metal-cutting machining in the United States is done by numerically controlled machined tools, but within the next decade it is expected to increase by 50 percent. Numerically controlled machines use taped data which is changed into instructions and directs the machine to do certain steps…

Multi-Objective Control Optimization for Greenhouse Environment Using Evolutionary Algorithms

PubMed Central

Hu, Haigen; Xu, Lihong; Wei, Ruihua; Zhu, Bingkun

2011-01-01

This paper investigates the issue of tuning the Proportional Integral and Derivative (PID) controller parameters for a greenhouse climate control system using an Evolutionary Algorithm (EA) based on multiple performance measures such as good static-dynamic performance specifications and the smooth process of control. A model of nonlinear thermodynamic laws between numerous system variables affecting the greenhouse climate is formulated. The proposed tuning scheme is tested for greenhouse climate control by minimizing the integrated time square error (ITSE) and the control increment or rate in a simulation experiment. The results show that by tuning the gain parameters the controllers can achieve good control performance through step responses such as small overshoot, fast settling time, and less rise time and steady state error. Besides, it can be applied to tuning the system with different properties, such as strong interactions among variables, nonlinearities and conflicting performance criteria. The results implicate that it is a quite effective and promising tuning method using multi-objective optimization algorithms in the complex greenhouse production. PMID:22163927

Coordinate Systems, Numerical Objects and Algorithmic Operations of Computational Experiment in Fluid Mechanics

NASA Astrophysics Data System (ADS)

Degtyarev, Alexander; Khramushin, Vasily

2016-02-01

The paper deals with the computer implementation of direct computational experiments in fluid mechanics, constructed on the basis of the approach developed by the authors. The proposed approach allows the use of explicit numerical scheme, which is an important condition for increasing the effciency of the algorithms developed by numerical procedures with natural parallelism. The paper examines the main objects and operations that let you manage computational experiments and monitor the status of the computation process. Special attention is given to a) realization of tensor representations of numerical schemes for direct simulation; b) realization of representation of large particles of a continuous medium motion in two coordinate systems (global and mobile); c) computing operations in the projections of coordinate systems, direct and inverse transformation in these systems. Particular attention is paid to the use of hardware and software of modern computer systems.

Numerical investigation of flow on NACA4412 aerofoil with different aspect ratios

NASA Astrophysics Data System (ADS)

Demir, Hacımurat; Özden, Mustafa; Genç, Mustafa Serdar; Çağdaş, Mücahit

2016-03-01

In this study, the flow over NACA4412 was investigated both numerically and experimentally at a different Reynolds numbers. The experiments were carried out in a low speed wind tunnel with various angles of attack and different Reynolds numbers (25000 and 50000). Airfoil was manufactured using 3D printer with a various aspect ratios (AR = 1 and AR = 3). Smoke-wire and oil flow visualization methods were used to visualize the surface flow patterns. NACA4412 aerofoil was designed by using SOLIDWORKS. The structural grid of numerical model was constructed by ANSYS ICEM CFD meshing software. Furthermore, ANSYS FLUENT™ software was used to perform numerical calculations. The numerical results were compared with experimental results. Bubble formation was shown in CFD streamlines and smoke-wire experiments at z / c = 0.4. Furthermore, bubble shrunk at z / c = 0.2 by reason of the effects of tip vortices in both numerical and experimental studies. Consequently, it was seen that there was a good agreement between numerical and experimental results.

Isotope effects on desorption kinetics of hydrogen isotopes implanted into stainless steel by glow discharge

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

Matsuyama, M.; Kondo, M.; Noda, N.

2015-03-15

In a fusion device the control of fuel particles implies to know the desorption rate of hydrogen isotopes by the plasma-facing materials. In this paper desorption kinetics of hydrogen isotopes implanted into type 316L stainless steel by glow discharge have been studied by experiment and numerical calculation. The temperature of a maximum desorption rate depends on glow discharge time and heating rate. Desorption spectra observed under various experimental conditions have been successfully reproduced by numerical simulations that are based on a diffusion-limited process. It is suggested, therefore, that desorption rate of a hydrogen isotope implanted into the stainless steel ismore » limited by a diffusion process of hydrogen isotope atoms in bulk. Furthermore, small isotope effects were observed for the diffusion process of hydrogen isotope atoms. (authors)« less

Boundary-fitted coordinate systems for numerical solution of partial differential equations - A review

NASA Technical Reports Server (NTRS)

Thompson, J. F.; Warsi, Z. U. A.; Mastin, C. W.

1982-01-01

A comprehensive review of methods of numerically generating curvilinear coordinate systems with coordinate lines coincident with all boundary segments is given. Some general mathematical framework and error analysis common to such coordinate systems is also included. The general categories of generating systems are those based on conformal mapping, orthogonal systems, nearly orthogonal systems, systems produced as the solution of elliptic and hyperbolic partial differential equations, and systems generated algebraically by interpolation among the boundaries. Also covered are the control of coordinate line spacing by functions embedded in the partial differential operators of the generating system and by subsequent stretching transformation. Dynamically adaptive coordinate systems, coupled with the physical solution, and time-dependent systems that follow moving boundaries are treated. References reporting experience using such coordinate systems are reviewed as well as those covering the system development.

Two-dimensional numerical simulation of flow around three-stranded rope

NASA Astrophysics Data System (ADS)

Wang, Xinxin; Wan, Rong; Huang, Liuyi; Zhao, Fenfang; Sun, Peng

2016-08-01

Three-stranded rope is widely used in fishing gear and mooring system. Results of numerical simulation are presented for flow around a three-stranded rope in uniform flow. The simulation was carried out to study the hydrodynamic characteristics of pressure and velocity fields of steady incompressible laminar and turbulent wakes behind a three-stranded rope. A three-cylinder configuration and single circular cylinder configuration are used to model the three-stranded rope in the two-dimensional simulation. The governing equations, Navier-Stokes equations, are solved by using two-dimensional finite volume method. The turbulence flow is simulated using Standard κ-ɛ model and Shear-Stress Transport κ-ω (SST) model. The drag of the three-cylinder model and single cylinder model is calculated for different Reynolds numbers by using control volume analysis method. The pressure coefficient is also calculated for the turbulent model and laminar model based on the control surface method. From the comparison of the drag coefficient and the pressure of the single cylinder and three-cylinder models, it is found that the drag coefficients of the three-cylinder model are generally 1.3-1.5 times those of the single circular cylinder for different Reynolds numbers. Comparing the numerical results with water tank test data, the results of the three-cylinder model are closer to the experiment results than the single cylinder model results.

Self-Reported Presence and Experience of Pain in Adults with Down Syndrome.

PubMed

de Knegt, Nanda C; Lobbezoo, Frank; Schuengel, Carlo; Evenhuis, Heleen M; Scherder, Erik J A

2017-07-01

The aim was to examine whether the presence of pain (based on physical conditions and participants' report) and self-reported pain experience in adults with Down syndrome (DS) differ from general population controls. Cross-sectional study of 224 adults with DS (mean age = 38.1 years, mild-severe intellectual disabilities) and 142 age-matched controls (median age = 40.5 years, mean estimated IQ = 105.7) in the Netherlands. File-based medical information was evaluated. Self-reported presence and experience of pain were assessed in rest and after movement during a test session (affect with facial affective scale (FAS: 0.04-0.97), intensity assessed with numeric rating scale (NRS: 0-10). Compared with controls, more DS participants had physical conditions that may cause pain and/or discomfort ( p  = .004, 50% vs 35%), but fewer DS participants reported pain during the test session ( p  = .003, 58% vs 73%). Of the participants who indicated pain and comprehended self-reporting scales ( n  = 198 FAS, n  = 161 NRS), the DS group reported a higher pain affect and intensity than the controls ( p  < .001, FAS: 0.75-0.85 vs 0.50-0.59, NRS: 6.00-7.94 vs 2.00-3.73). Not all adults with DS and painful/discomforting physical conditions reported pain. Those who did indicated a higher pain experience than adults from the general population. Research into spontaneous self-report of pain, repeated pain assessment, and acute pain is needed in people with DS for more insight into pain experience and mismatches between self-report and medical information. © 2016 American Academy of Pain Medicine. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com

Spray combustion experiments and numerical predictions

NASA Technical Reports Server (NTRS)

Mularz, Edward J.; Bulzan, Daniel L.; Chen, Kuo-Huey

1993-01-01

The next generation of commercial aircraft will include turbofan engines with performance significantly better than those in the current fleet. Control of particulate and gaseous emissions will also be an integral part of the engine design criteria. These performance and emission requirements present a technical challenge for the combustor: control of the fuel and air mixing and control of the local stoichiometry will have to be maintained much more rigorously than with combustors in current production. A better understanding of the flow physics of liquid fuel spray combustion is necessary. This paper describes recent experiments on spray combustion where detailed measurements of the spray characteristics were made, including local drop-size distributions and velocities. Also, an advanced combustor CFD code has been under development and predictions from this code are compared with experimental results. Studies such as these will provide information to the advanced combustor designer on fuel spray quality and mixing effectiveness. Validation of new fast, robust, and efficient CFD codes will also enable the combustor designer to use them as additional design tools for optimization of combustor concepts for the next generation of aircraft engines.

Of Huge Mice and Tiny Elephants: Exploring the Relationship Between Inhibitory Processes and Preschool Math Skills

PubMed Central

Merkley, Rebecca; Thompson, Jodie; Scerif, Gaia

2016-01-01

The cognitive mechanisms underpinning the well-established relationship between inhibitory control and early maths skills remain unclear. We hypothesized that a specific aspect of inhibitory control drives its association with distinct math skills in very young children: the ability to ignore stimulus dimensions that are in conflict with task-relevant representations. We used an Animal Size Stroop task in which 3- to 6-year-olds were required to ignore the physical size of animal pictures to compare their real-life dimensions. In Experiment 1 (N = 58), performance on this task correlated with standardized early mathematics achievement. In Experiment 2 (N = 48), performance on the Animal Size Stroop task related to the accuracy of magnitude comparison, specifically for trials on which the physical size of dot arrays was incongruent with their numerosity. This highlights a process-oriented relationship between interference control and resolving conflict between discrete and continuous quantity, and in turn calls for further detailed empirical investigations of whether, how and why inhibitory processes matter to emerging numerical cognition. PMID:26779057

Of Huge Mice and Tiny Elephants: Exploring the Relationship Between Inhibitory Processes and Preschool Math Skills.

PubMed

Merkley, Rebecca; Thompson, Jodie; Scerif, Gaia

2015-01-01

The cognitive mechanisms underpinning the well-established relationship between inhibitory control and early maths skills remain unclear. We hypothesized that a specific aspect of inhibitory control drives its association with distinct math skills in very young children: the ability to ignore stimulus dimensions that are in conflict with task-relevant representations. We used an Animal Size Stroop task in which 3- to 6-year-olds were required to ignore the physical size of animal pictures to compare their real-life dimensions. In Experiment 1 (N = 58), performance on this task correlated with standardized early mathematics achievement. In Experiment 2 (N = 48), performance on the Animal Size Stroop task related to the accuracy of magnitude comparison, specifically for trials on which the physical size of dot arrays was incongruent with their numerosity. This highlights a process-oriented relationship between interference control and resolving conflict between discrete and continuous quantity, and in turn calls for further detailed empirical investigations of whether, how and why inhibitory processes matter to emerging numerical cognition.

Decentralized control scheme for myriapod robot inspired by adaptive and resilient centipede locomotion.

PubMed

Yasui, Kotaro; Sakai, Kazuhiko; Kano, Takeshi; Owaki, Dai; Ishiguro, Akio

2017-01-01

Recently, myriapods have attracted the attention of engineers because mobile robots that mimic them potentially have the capability of producing highly stable, adaptive, and resilient behaviors. The major challenge here is to develop a control scheme that can coordinate their numerous legs in real time, and an autonomous decentralized control could be the key to solve this problem. Therefore, we focus on real centipedes and aim to design a decentralized control scheme for myriapod robots by drawing inspiration from behavioral experiments on centipede locomotion under unusual conditions. In the behavioral experiments, we observed the response to the removal of a part of the terrain and to amputation of several legs. Further, we determined that the ground reaction force is significant for generating rhythmic leg movements; the motion of each leg is likely affected by a sensory input from its neighboring legs. Thus, we constructed a two-dimensional model wherein a simple local reflexive mechanism was implemented in each leg. We performed simulations by using this model and demonstrated that the myriapod robot could move adaptively to changes in the environment and body properties. Our findings will shed new light on designing adaptive and resilient myriapod robots that can function under various circumstances.

Numerical verification of three point bending experiment of magnetorheological elastomer (MRE) in magnetic field

NASA Astrophysics Data System (ADS)

Miedzinska, Danuta; Boczkowska, Anna; Zubko, Konrad

2010-07-01

In the article a method of numerical verification of experimental results for magnetorheological elastomer samples (MRE) is presented. The samples were shaped into cylinders with diameter of 8 mm and height of 20 mm with various carbonyl iron volume shares (1,5%, 11,5% and 33%). The diameter of soft ferromagnetic substance particles ranged from 6 to 9 μm. During the experiment, initially bended samples were exposed to the magnetic field with intensity levels at 0,1T, 0,3T, 0,5T, 0,7 and 1T. The reaction of the sample to the field action was measured as a displacement of a specimen. Numerical calculation was carried out with the MSC Patran/Marc computer code. For the purpose of numerical analysis the orthotropic material model with the material properties of magnetorheological elastomer along the iron chains, and of the pure elastomer along other directions, was applied. The material properties were obtained from the experimental tests. During the numerical analysis, the initial mechanical load resulting from cylinder deflection was set. Then, the equivalent external force, that was set on the basis of analytical calculations of intermolecular reaction within iron chains in the specific magnetic field, was put on the bended sample. Correspondence of such numerical model with results of the experiment was verified. Similar results of the experiments and both theoretical and FEM analysis indicates that macroscopic modeling of magnetorheological elastomer mechanical properties as orthotropic material delivers accurate enough description of the material's behavior.

Mobile robot trajectory tracking using noisy RSS measurements: an RFID approach.

PubMed

Miah, M Suruz; Gueaieb, Wail

2014-03-01

Most RF beacons-based mobile robot navigation techniques rely on approximating line-of-sight (LOS) distances between the beacons and the robot. This is mostly performed using the robot's received signal strength (RSS) measurements from the beacons. However, accurate mapping between the RSS measurements and the LOS distance is almost impossible to achieve in reverberant environments. This paper presents a partially-observed feedback controller for a wheeled mobile robot where the feedback signal is in the form of noisy RSS measurements emitted from radio frequency identification (RFID) tags. The proposed controller requires neither an accurate mapping between the LOS distance and the RSS measurements, nor the linearization of the robot model. The controller performance is demonstrated through numerical simulations and real-time experiments. ©2013 Published by ISA. All rights reserved.

Application-oriented integrated control center (AICC) for heterogeneous optical networks

NASA Astrophysics Data System (ADS)

Zhao, Yongli; Zhang, Jie; Cao, Xuping; Wang, Dajiang; Wu, Koubo; Cai, Yinxiang; Gu, Wanyi

2011-12-01

Various broad bandwidth services have being swallowing the bandwidth resource of optical networks, such as the data center application and cloud computation. There are still some challenges for future optical networks although the available bandwidth is increasing with the development of transmission technologies. The relationship between upper application layer and lower network resource layer is necessary to be researched further. In order to improve the efficiency of network resources and capability of service provisioning, heterogeneous optical networks resource can be abstracted as unified Application Programming Interfaces (APIs) which can be open to various upper applications through Application-oriented Integrated Control Center (AICC) proposed in the paper. A novel Openflow-based unified control architecture is proposed for the optimization of cross layer resources. Numeric results show good performance of AICC through simulation experiments.

A Study on the Propulsive Mechanism of a Double Jointed Fish Robot Utilizing Self-Excitation Control

NASA Astrophysics Data System (ADS)

Nakashima, Motomu; Ohgishi, Norifumi; Ono, Kyosuke

This paper describes a numerical and experimental study of a double jointed fish robot utilizing self-excitation control. The fish robot is composed of a streamlined body and a rectangular caudal fin. The body length is 280mm and it has a DC motor to actuate its first joint and a potentiometer to detect the angle of its second joint. The signal from the potentiometer is fed back into the DC motor, so that the system can be self-excited. In order to obtain a stable oscillation and a resultant stable propulsion, a torque limiter circuit is employed. From the experiment, it has been found that the robot can stably propel using this control and the maximum propulsive speed is 0.42m/s.

On the kinematic criterion for the inception of breaking in surface gravity waves: Fully nonlinear numerical simulations and experimental verification

NASA Astrophysics Data System (ADS)

Khait, A.; Shemer, L.

2018-05-01

The evolution of unidirectional wave trains containing a wave that gradually becomes steep is evaluated experimentally and numerically using the Boundary Element Method (BEM). The boundary conditions for the nonlinear numerical simulations corresponded to the actual movements of the wavemaker paddle as recorded in the physical experiments, allowing direct comparison between the measured in experiments' characteristics of the wave train and the numerical predictions. The high level of qualitative and quantitative agreement between the measurements and simulations validated the kinematic criterion for the inception of breaking and the location of the spilling breaker, on the basis of the BEM computations and associated experiments. The breaking inception is associated with the fluid particle at the crest of the steep wave that has been accelerated to match and surpass the crest velocity. The previously observed significant slow-down of the crest while approaching breaking is verified numerically; both narrow-/broad-banded wave trains are considered. Finally, the relative importance of linear and nonlinear contributions is analyzed.

Microbiological and Hydrogeochemical Controls on Anaerobic Biodegradation of Petroleum Hydrocarbons: Case Study from Fort McCoy, WI

NASA Astrophysics Data System (ADS)

Schreiber, M. E.; Zwolinski, M. D.; Taglia, P. J.; Bahr, J. M.; Hickey, W. J.

2001-05-01

We are investigating the role of anaerobic processes that control field-scale BTEX loss using a variety of experimental and numerical techniques. Tracer tests, laboratory microcosms, and in situ microcosms (ISMs) were designed to examine BTEX biodegradation under intrinsic and enhanced anaerobic conditions in a BTEX plume at Fort McCoy, WI. In the tracer tests, addition of nitrate resulted in loss of toluene, ethylbenzene, and m, p-xylenes but not benzene. Laboratory microcosm and ISM experiments confirmed that nitrate addition is not likely to enhance benzene biodegradation at the site. Excess nitrate losses were observed in both field and laboratory experiments, indicating that reliance on theoretical stoichiometric equations to estimate contaminant mass losses should be re-evaluated. To examine changes in microbial community during biodegradation of BTEX under enhanced nitrate-reducing conditions, DNA was extracted from laboratory microcosm sediment, the 16S-rRNA gene was amplified using eubacterial primers, and products were separated by denaturing gradient gel electrophoresis. Banding patterns suggest that nitrate caused more of a community change than BTEX. These data suggest that nitrate plays an important role in microbial population selection. Numerical simulations were conducted to simulate the evolution of the BTEX plume and to quantify BTEX losses due to intrinsic and nitrate-enhanced biodegradation. Results suggest that the majority of intrinsic BTEX mass loss has occurred under aerobic and iron-reducing conditions. Due to depletion of solid-phase Fe(III) over time, however, future BTEX losses under iron-reducing conditions will decrease, and methanogenesis will play an increasingly important role in controlling biodegradation. The simulations also suggest that although nitrate addition will decrease TEX concentrations, source removal with intrinsic biodegradation is likely the most effective treatment method for the site.

Quiet Short-Haul Research Aircraft - A summary of flight research since 1981

NASA Technical Reports Server (NTRS)

Riddle, Dennis W.; Stevens, Victor C.; Eppel, Joseph C.

1988-01-01

The Quiet Short-Haul Research Aircraft (QSRA), designed for flight investigation into powered-lift terminal area operations, first flew in 1978 and has flown 600 hours since. This report summarizes QSRA research since 1981. Numerous aerodynamic flight experiments have been conducted including research with an advanced concept stability and control augmentation and pilot display system for category III instrument landings. An electromechanical actuator system was flown to assess performance and reliability. A second ground-based test was conducted to further evaluate circulation-control-wing/upper-surface-blowing performance. QSRA technology has been transferred through reports, guest pilot evaluations and airshow participation. QSRA future research thoughts and an extensive report bibliography are also presented.

Controlling directed transport of matter-wave solitons using the ratchet effect

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

Rietmann, M.; Carretero-Gonzalez, R.; Chacon, R.

2011-05-15

We demonstrate that directed transport of bright solitons formed in a quasi-one-dimensional Bose-Einstein condensate can be reliably controlled by tailoring a weak optical lattice potential, biharmonic in both space and time, in accordance with the degree of symmetry breaking mechanism. By considering the regime where matter-wave solitons are narrow compared to the lattice period, (i) we propose an analytical estimate for the dependence of the directed soliton current on the biharmonic potential parameters that is in good agreement with numerical experiments, and (ii) we show that the dependence of the directed soliton current on the number of atoms is amore » consequence of the ratchet universality.« less

Applications

NASA Astrophysics Data System (ADS)

Stern, Arthur M.

1986-07-01

Economic incentives have spurred numerous applications of genetically engineered organisms in manufacture of pharmaceuticals and industrial chemicals. These successes, involving a variety of methods of genetic manipulation, have dispelled early fears that genetic engineering could not be handled safely, even in the laboratory. Consequently, the potential for applications in the wider environment without physical containment is being considered for agriculture, mining, pollution control, and pest control. These proposed applications range from modest extensions of current plant breeding techniques for new disease-resistant species to radical combinations of organisms (for example, nitrogen-fixing corn plants). These applications raise concerns about potential ecological impacts (see chapter 5), largely because of adverse experiences with both deliberate and inadvertent introductions of nonindigenous species.

Coherent population trapping with a controlled dissipation: applications in optical metrology

NASA Astrophysics Data System (ADS)

Nicolas, L.; Delord, T.; Jamonneau, P.; Coto, R.; Maze, J.; Jacques, V.; Hétet, G.

2018-03-01

We analyze the properties of a pulsed coherent population trapping protocol that uses a controlled decay from the excited state in a Λ-level scheme. We study this problem analytically and numerically and find regimes where narrow transmission, absorption, or fluorescence spectral lines occur. We then look for optimal frequency measurements using these spectral features by computing the Allan deviation in the presence of ground state decoherence and show that the protocol is on a par with Ramsey-CPT. We discuss possible implementations with ensembles of alkali atoms and single ions and demonstrate that typical pulsed-CPT experiments that are realized on femto-second timescales can be implemented on micro-seconds timescales using this scheme.

Professional mathematicians differ from controls in their spatial-numerical associations.

PubMed

Cipora, Krzysztof; Hohol, Mateusz; Nuerk, Hans-Christoph; Willmes, Klaus; Brożek, Bartosz; Kucharzyk, Bartłomiej; Nęcka, Edward

2016-07-01

While mathematically impaired individuals have been shown to have deficits in all kinds of basic numerical representations, among them spatial-numerical associations, little is known about individuals with exceptionally high math expertise. They might have a more abstract magnitude representation or more flexible spatial associations, so that no automatic left/small and right/large spatial-numerical association is elicited. To pursue this question, we examined the Spatial Numerical Association of Response Codes (SNARC) effect in professional mathematicians which was compared to two control groups: Professionals who use advanced math in their work but are not mathematicians (mostly engineers), and matched controls. Contrarily to both control groups, Mathematicians did not reveal a SNARC effect. The group differences could not be accounted for by differences in mean response speed, response variance or intelligence or a general tendency not to show spatial-numerical associations. We propose that professional mathematicians possess more abstract and/or spatially very flexible numerical representations and therefore do not exhibit or do have a largely reduced default left-to-right spatial-numerical orientation as indexed by the SNARC effect, but we also discuss other possible accounts. We argue that this comparison with professional mathematicians also tells us about the nature of spatial-numerical associations in persons with much less mathematical expertise or knowledge.

A control method for bilateral teleoperating systems

NASA Astrophysics Data System (ADS)

Strassberg, Yesayahu

1992-01-01

The thesis focuses on control of bilateral master-slave teleoperators. The bilateral control issue of teleoperators is studied and a new scheme that overcomes basic unsolved problems is proposed. A performance measure, based on the multiport modeling method, is introduced in order to evaluate and understand the limitations of earlier published bilateral control laws. Based on the study evaluating the different methods, the objective of the thesis is stated. The proposed control law is then introduced, its ideal performance is demonstrated, and conditions for stability and robustness are derived. It is shown that stability, desired performance, and robustness can be obtained under the assumption that the deviation of the model from the actual system satisfies certain norm inequalities and the measurement uncertainties are bounded. The proposed scheme is validated by numerical simulation. The simulated system is based on the configuration of the RAL (Robotics and Automation Laboratory) telerobot. From the simulation results it is shown that good tracking performance can be obtained. In order to verify the performance of the proposed scheme when applied to a real hardware system, an experimental setup of a three degree of freedom master-slave teleoperator (i.e. three degree of freedom master and three degree of freedom slave robot) was built. Three basic experiments were conducted to verify the performance of the proposed control scheme. The first experiment verified the master control law and its contribution to the robustness and performance of the entire system. The second experiment demonstrated the actual performance of the system while performing a free motion teleoperating task. From the experimental results, it is shown that the control law has good performance and is robust to uncertainties in the models of the master and slave.

Learning Model and Form of Assesment toward the Inferensial Statistical Achievement by Controlling Numeric Thinking Skills

ERIC Educational Resources Information Center

Widiana, I. Wayan; Jampel, I. Nyoman

2016-01-01

This study aimed to find out the effect of learning model and form of assessment toward inferential statistical achievement after controlling numeric thinking skills. This study was quasi experimental study with 130 students as the sample. The data analysis used ANCOVA. After controlling numeric thinking skills, the result of this study show that:…

Fluid flow analysis and vertical gradient freeze crystal growth in a travelling magnetic field

NASA Astrophysics Data System (ADS)

Lantzsch, R.; Grants, I.; Galindo, V.; Patzold, O.; Gerbeth, G.; Stelter, M.; Croll, A.

2006-12-01

In bulk crystal growth of semiconductors the concept of remote flow control by means of alternating magnetic fields has attracted considerable interest (see, e.g., te{1,2,3,4,5,6}). In this way the melt flow can be tailored for growth under optimised conditions to improve the crystal properties and/or the growth yield. A promising option is to apply an axially travelling magnetic wave to the melt (Travelling Magnetic Field - TMF). It introduces a mainly axial Lorentz force, which leads to meridional flow patterns. In recent numerical studies te{3}, te{6} the TMF has been recognised to be a versatile and efficient tool to control the heat and mass transport in the melt. For the Vertical Bridgman/Vertical Gradient Freeze (VB/VGF) growth, the beneficial effect of an adequately adjusted TMF-induced flow was clearly demonstrated in te{6} in terms of the reduction of thermal shear stress at the solid-liquid interface. In this paper, we present experimental and numerical results on the TMF driven convection in an isothermal model fluid as well as first VGF-TMF crystal growth experiments. The model investigations are focused on the transition from laminar to instationary flow conditions that should be avoided in crystal growth applications. The VGF experiments were aimed at growing Ga doped germanium single crystals under the influence of the travelling field in a newly developed VGF-TMF equipment. Figs 4, Refs 10.

A Novel Method Of Gradient Forming and Fluid Manipulation in Reduced Gravity Environments

NASA Technical Reports Server (NTRS)

Ramachandran N.; Leslie, F.

1999-01-01

The use of magnetic fields to control the motion and position of non-conducting liquids has received growing interest in recent times. The possibility of using the forces exerted by a nonuniform magnetic field on a ferrofluid to not only achieve fluid manipulation but also to actively control fluid motion makes it an attractive candidate for applications such as heat transfer in space systems. Terrestrial heat transfer equipment often relies on the normal gravitational force to hold liquid in a desired position or to provide a buoyant force to enhance the heat transfer rate. The residual gravitational force present in a space environment may no longer serve these useful functions and other forces, such as surface tension, can play a significant role in determining heat transfer rates. Although typically overwhelmed by gravitational forces in terrestrial applications, the body force induced in a ferrofluid by a nonuniform magnetic field can help to achieve these objectives in a microgravity environment. This paper will address the fluid manipulation aspect and will comprise of results from model fluid experiments and numerical modeling of the problem. Results from a novel method of forming concentration gradients that are applicable to low gravity applications will be presented. The ground based experiments are specifically tailored to demonstrate the magnetic manipulation capability of a ferrofluid and show that gravitational effects can be countered in carefully designed systems. The development of governing equations for the system will be presented along with a sampling of numerical results.

The challenges of numerically simulating analogue brittle thrust wedges

NASA Astrophysics Data System (ADS)

Buiter, Susanne; Ellis, Susan

2017-04-01

Fold-and-thrust belts and accretionary wedges form when sedimentary and crustal rocks are compressed into thrusts and folds in the foreland of an orogen or at a subduction trench. For over a century, analogue models have been used to investigate the deformation characteristics of such brittle wedges. These models predict wedge shapes that agree with analytical critical taper theory and internal deformation structures that well resemble natural observations. In a series of comparison experiments for thrust wedges, called the GeoMod2004 (1,2) and GeoMod2008 (3,4) experiments, it was shown that different numerical solution methods successfully reproduce sandbox thrust wedges. However, the GeoMod2008 benchmark also pointed to the difficulties of representing frictional boundary conditions and sharp velocity discontinuities with continuum numerical methods, in addition to the well-known challenges of numerical plasticity. Here we show how details in the numerical implementation of boundary conditions can substantially impact numerical wedge deformation. We consider experiment 1 of the GeoMod2008 brittle thrust wedge benchmarks. This experiment examines a triangular thrust wedge in the stable field of critical taper theory that should remain stable, that is, without internal deformation, when sliding over a basal frictional surface. The thrust wedge is translated by lateral displacement of a rigid mobile wall. The corner between the mobile wall and the subsurface is a velocity discontinuity. Using our finite-element code SULEC, we show how different approaches to implementing boundary friction (boundary layer or contact elements) and the velocity discontinuity (various smoothing schemes) can cause the wedge to indeed translate in a stable manner or to undergo internal deformation (which is a fail). We recommend that numerical studies of sandbox setups not only report the details of their implementation of boundary conditions, but also document the modelling attempts that failed. References 1. Buiter and the GeoMod2004 Team, 2006. The numerical sandbox: comparison of model results for a shortening and an extension experiment. Geol. Soc. Lond. Spec. Publ. 253, 29-64 2. Schreurs and the GeoMod2004 Team, 2006. Analogue benchmarks of shortening and extension experiments. Geol. Soc. Lond. Spec. Publ. 253, 1-27 3. Buiter, Schreurs and the GeoMod2008 Team, 2016. Benchmarking numerical models of brittle thrust wedges, J. Struct. Geol. 92, 140-177 4. Schreurs, Buiter and the GeoMod2008 Team, 2016. Benchmarking analogue models of brittle thrust wedges, J. Struct. Geol. 92, 116-13

Decoupling control of steering and driving system for in-wheel-motor-drive electric vehicle

NASA Astrophysics Data System (ADS)

Zhang, Han; Zhao, Wanzhong

2018-02-01

To improve the maneuverability and stability of in-wheel-motor-drive electric vehicle, a control strategy based on nonlinear decoupling control method is proposed in this paper, realizing the coordinated control of the steering and driving system. At first, the nonlinear models of the in-wheel-motor-drive electric vehicle and its sub-system are constructed. Then the inverse system decoupling theory is applied to decompose the nonlinear system into several independent subsystems, which makes it possible to realize the coordinated control of each subsystem. Next, the μ-Synthesis theory is applied to eliminate the influence of model uncertainty, improving the stability, robustness and tracking performance of in-wheel-motor-drive electric vehicle. Simulation and experiment results and numerical analyses, based on the electric vehicle actuated by in-wheel-motors, prove that the proposed control method is effective to accomplish the decoupling control of the steering and driving system in both simulation and real practice.

An Entropy-Based Approach to Nonlinear Stability

NASA Technical Reports Server (NTRS)

Merriam, Marshal L.

1989-01-01

Many numerical methods used in computational fluid dynamics (CFD) incorporate an artificial dissipation term to suppress spurious oscillations and control nonlinear instabilities. The same effect can be accomplished by using upwind techniques, sometimes augmented with limiters to form Total Variation Diminishing (TVD) schemes. An analysis based on numerical satisfaction of the second law of thermodynamics allows many such methods to be compared and improved upon. A nonlinear stability proof is given for discrete scalar equations arising from a conservation law. Solutions to such equations are bounded in the L sub 2 norm if the second law of thermodynamics is satisfied in a global sense over a periodic domain. It is conjectured that an analogous statement is true for discrete equations arising from systems of conservation laws. Analysis and numerical experiments suggest that a more restrictive condition, a positive entropy production rate in each cell, is sufficient to exclude unphysical phenomena such as oscillations and expansion shocks. Construction of schemes which satisfy this condition is demonstrated for linear and nonlinear wave equations and for the one-dimensional Euler equations.

Analytical guidance law development for aerocapture at Mars

NASA Technical Reports Server (NTRS)

Calise, A. J.

1992-01-01

During the first part of this reporting period research has concentrated on performing a detailed evaluation, to zero order, of the guidance algorithm developed in the first period taking the numerical approach developed in the third period. A zero order matched asymptotic expansion (MAE) solution that closely satisfies a set of 6 implicit equations in 6 unknowns to an accuracy of 10(exp -10), was evaluated. Guidance law implementation entails treating the current state as a new initial state and repetitively solving the MAE problem to obtain the feedback controls. A zero order guided solution was evaluated and compared with optimal solution that was obtained by numerical methods. Numerical experience shows that the zero order guided solution is close to optimal solution, and that the zero order MAE outer solution plays a critical role in accounting for the variations in Loh's term near the exit phase of the maneuver. However, the deficiency that remains in several of the critical variables indicates the need for a first order correction. During the second part of this period, methods for computing a first order correction were explored.

Microfluidic based high throughput synthesis of lipid-polymer hybrid nanoparticles with tunable diameters

PubMed Central

Feng, Qiang; Zhang, Lu; Liu, Chao; Li, Xuanyu; Hu, Guoqing; Sun, Jiashu; Jiang, Xingyu

2015-01-01

Core-shell hybrid nanoparticles (NPs) for drug delivery have attracted numerous attentions due to their enhanced therapeutic efficacy and good biocompatibility. In this work, we fabricate a two-stage microfluidic chip to implement a high-throughput, one-step, and size-tunable synthesis of mono-disperse lipid-poly (lactic-co-glycolic acid) NPs. The size of hybrid NPs is tunable by varying the flow rates inside the two-stage microfluidic chip. To elucidate the mechanism of size-controllable generation of hybrid NPs, we observe the flow field in the microchannel with confocal microscope and perform the simulation by a numerical model. Both the experimental and numerical results indicate an enhanced mixing effect at high flow rate, thus resulting in the assembly of small and mono-disperse hybrid NPs. In vitro experiments show that the large hybrid NPs are more likely to be aggregated in serum and exhibit a lower cellular uptake efficacy than the small ones. This microfluidic chip shows great promise as a robust platform for optimization of nano drug delivery system. PMID:26180574

[Dermatomycoses and medically important fungi that are necessary subjects of study for dermatology specialists -a personal experience].

PubMed

Nishikawa, Takeji

2015-01-01

Among the numerous skin diseases, dermatomycosis is the one caused by fungus (parasite) infecting the skin (host) . Once diagnosis is made, dermatomycosis can be cured with the use of appropriate anti-fungal drugs. Therefore, it is a much more easily treatable disease compareds with intractable skin diseases. From his own experience, the author shows that dermatomycoses are good subspecialties to deal with because many of them are controllable. At the same time, the author points out that basic research on medically important fungi needs to be done as collaborative studies with basic scientists and dermatology specialists. This brief review covers several topics including diagnostics of medical mycoses, imported medical mycoses, tinea, and cutaneous deep mycoses.

Damping Mechanisms for Microgravity Vibration Isolation (MSFC Center Director's Discretionary Fund Final Report, Project No. 94-07)

NASA Technical Reports Server (NTRS)

Whorton, M. S.; Eldridge, J. T.; Ferebee, R. C.; Lassiter, J. O.; Redmon, J. W., Jr.

1998-01-01

As a research facility for microgravity science, the International Space Station (ISS) will be used for numerous investigations such as protein crystal growth, combustion, and fluid mechanics experiments which require a quiescent acceleration environment across a broad spectrum of frequencies. These experiments are most sensitive to low-frequency accelerations and can tolerate much higher accelerations at higher frequency. However, the anticipated acceleration environment on ISS significantly exceeds the required acceleration level. The ubiquity and difficulty in characterization of the disturbance sources precludes source isolation, requiring vibration isolation to attenuate the anticipated disturbances to an acceptable level. This memorandum reports the results of research in active control methods for microgravity vibration isolation.

Towards monitoring real-time cellular response using an integrated microfluidics-MALDI/nESI-ion mobility-mass spectrometry platform

PubMed Central

Enders, Jeffrey R.; Marasco, Christina C.; Kole, Ayeeshik; Nguyen, Bao; Sundarapandian, Sevugarajan; Seale, Kevin T.; Wikswo, John P.; McLean, John A.

2014-01-01

The combination of microfluidic cell trapping devices with ion mobility-mass spectrometry offers the potential for elucidating in real time the dynamic responses of small populations of cells to paracrine signals, changes in metabolite levels, and delivery of drugs and toxins. Preliminary experiments examining peptides in methanol and recording the interactions of yeast and Jurkat cells with their superfusate have identified instrumental setup and control parameters and on-line desalting procedures. Numerous initial experiments demonstrate and validate this new instrumental platform. Future outlooks and potential applications are addressed, specifically how this instrumentation may be used for fully automated systems biology studies of the significantly interdependent, dynamic internal workings of cellular metabolic and signaling pathways. PMID:21073240

Preliminary analysis of pilot ratings of 'part line' information importance

NASA Technical Reports Server (NTRS)

Pritchett, Amy; Hansman, R. John

1993-01-01

With the introduction of digital datalink communications into the Air Traffic Control (ATC) system, there is concern over the potential loss of situational awareness by flight crews due to the reduction in the 'Party Line Information' (PLI). This information is available to the pilot by overhearing communications between ATC and other aircraft. A survey was distributed to determine current PLI use by several pilot operational groups, experience levels and geographic regions. The survey identified numerous important elements. PLI was rated the highest for operations near or on approach to the airport. Several significant variations were found between pilots from different operational groups and experience levels. Traffic and weather information were the most frequently cited as information required to obtain global situation awareness.

Force-controlled absorption in a fully-nonlinear numerical wave tank

NASA Astrophysics Data System (ADS)

Spinneken, Johannes; Christou, Marios; Swan, Chris

2014-09-01

An active control methodology for the absorption of water waves in a numerical wave tank is introduced. This methodology is based upon a force-feedback technique which has previously been shown to be very effective in physical wave tanks. Unlike other methods, an a-priori knowledge of the wave conditions in the tank is not required; the absorption controller being designed to automatically respond to a wide range of wave conditions. In comparison to numerical sponge layers, effective wave absorption is achieved on the boundary, thereby minimising the spatial extent of the numerical wave tank. In contrast to the imposition of radiation conditions, the scheme is inherently capable of absorbing irregular waves. Most importantly, simultaneous generation and absorption can be achieved. This is an important advance when considering inclusion of reflective bodies within the numerical wave tank. In designing the absorption controller, an infinite impulse response filter is adopted, thereby eliminating the problem of non-causality in the controller optimisation. Two alternative controllers are considered, both implemented in a fully-nonlinear wave tank based on a multiple-flux boundary element scheme. To simplify the problem under consideration, the present analysis is limited to water waves propagating in a two-dimensional domain. The paper presents an extensive numerical validation which demonstrates the success of the method for a wide range of wave conditions including regular, focused and random waves. The numerical investigation also highlights some of the limitations of the method, particularly in simultaneously generating and absorbing large amplitude or highly-nonlinear waves. The findings of the present numerical study are directly applicable to related fields where optimum absorption is sought; these include physical wavemaking, wave power absorption and a wide range of numerical wave tank schemes.

A regulator for pressure-controlled total-liquid ventilation.

PubMed

Robert, Raymond; Micheau, Philippe; Avoine, Olivier; Beaudry, Benoit; Beaulieu, Alexandre; Walti, Hervé

2010-09-01

Total-liquid ventilation (TLV) is an innovative experimental method of mechanical-assisted ventilation in which lungs are totally filled and then ventilated with a tidal volume of perfluorochemical liquid by using a dedicated liquid ventilator. Such a novel medical device must resemble other conventional ventilators: it must be able to conduct controlled-pressure ventilation. The objective was to design a robust controller to perform pressure-regulated expiratory flow and to implement it on our latest liquid-ventilator prototype (Inolivent-4). Numerical simulations, in vitro experiments, and in vivo experiments in five healthy term newborn lambs have demonstrated that it was efficient to generate expiratory flows while avoiding collapses. Moreover, the in vivo results have demonstrated that our liquid ventilator can maintain adequate gas exchange, normal acid-base equilibrium, and achieve greater minute ventilation, better oxygenation and CO2 extraction, while nearing flow limits. Hence, it is our suggestion to perform pressure-controlled ventilation during expiration with minute ventilation equal or superior to 140 mL x min(-1) x kg(-1) in order to ensure PaCO2 below 55 mmHg. From a clinician's point of view, pressure-controlled ventilation greatly simplifies the use of the liquid ventilator, which will certainly facilitate its introduction in intensive care units for clinical applications.

Modeling of turbulent separated flows for aerodynamic applications

NASA Technical Reports Server (NTRS)

Marvin, J. G.

1983-01-01

Steady, high speed, compressible separated flows modeled through numerical simulations resulting from solutions of the mass-averaged Navier-Stokes equations are reviewed. Emphasis is placed on benchmark flows that represent simplified (but realistic) aerodynamic phenomena. These include impinging shock waves, compression corners, glancing shock waves, trailing edge regions, and supersonic high angle of attack flows. A critical assessment of modeling capabilities is provided by comparing the numerical simulations with experiment. The importance of combining experiment, numerical algorithm, grid, and turbulence model to effectively develop this potentially powerful simulation technique is stressed.

Comparative study of the influence of natural convection on directional solidification of Al 3.5 wt% Ni and Al 7 wt% Si alloys

NASA Astrophysics Data System (ADS)

Zhou, B. H.; Jung, H.; Mangelinck-Noël, N.; Nguyen-Thi, H.; Billia, B.; Liu, Q. S.; Lan, C. W.

We present numerical simulations of thermosolutal convection for directional solidification of Al 3.5 wt% Ni and Al 7 wt% Si. Numerical results predict that fragmentation of dendrite arms resulting from dissolution could be favored in Al 7 wt% Si, but not in Al 3.5 wt% Ni. Corresponding experiments are in qualitative agreement with the numerical predictions. Distinguishing the two fragmentation mechanisms, namely dissolution and remelting, is critical during experiments on earth, when fluid flow is dominant.

Plasma Jet Simulations Using a Generalized Ohm's Law

NASA Technical Reports Server (NTRS)

Ebersohn, Frans; Shebalin, John V.; Girimaji, Sharath S.

2012-01-01

Plasma jets are important physical phenomena in astrophysics and plasma propulsion devices. A currently proposed dual jet plasma propulsion device to be used for ISS experiments strongly resembles a coronal loop and further draws a parallel between these physical systems [1]. To study plasma jets we use numerical methods that solve the compressible MHD equations using the generalized Ohm s law [2]. Here, we will discuss the crucial underlying physics of these systems along with the numerical procedures we utilize to study them. Recent results from our numerical experiments will be presented and discussed.

Advanced rotorcraft control using parameter optimization

NASA Technical Reports Server (NTRS)

Vansteenwyk, Brett; Ly, Uy-Loi

1991-01-01

A reliable algorithm for the evaluation of a quadratic performance index and its gradients with respect to the controller design parameters is presented. The algorithm is part of a design algorithm for an optimal linear dynamic output feedback controller that minimizes a finite time quadratic performance index. The numerical scheme is particularly robust when it is applied to the control law synthesis for systems with densely packed modes and where there is a high likelihood of encountering degeneracies in the closed loop eigensystem. This approach through the use of a accurate Pade series approximation does not require the closed loop system matrix to be diagonalizable. The algorithm has been included in a control design package for optimal robust low order controllers. Usefulness of the proposed numerical algorithm has been demonstrated using numerous practical design cases where degeneracies occur frequently in the closed loop system under an arbitrary controller design initialization and during the numerical search.

Habitat management of organic vineyard in Northern Italy: the role of cover plants management on arthropod functional biodiversity.

PubMed

Burgio, G; Marchesini, E; Reggiani, N; Montepaone, G; Schiatti, P; Sommaggio, D

2016-12-01

The effect of cover plants on arthropod functional biodiversity was investigated in a vineyard in Northern Italy, through a 3-year field experiment. The following six ground cover plants were tested: Sweet Alyssum; Phacelia; Buckwheat; Faba Bean; Vetch and Oat; control. Arthropods were sampled using different techniques, including collection of leaves, vacuum sampling and sweeping net. Ground cover plant management significantly affected arthropod fauna, including beneficial groups providing ecosystem services like biological control against pests. Many beneficial groups were attracted by ground cover treatments in comparison with control, showing an aggregative numerical response in the plots managed with some of the selected plant species. Alyssum, Buckwheat and 'Vetch and Oat' mixture showed attractiveness on some Hymenoptera parasitoid families, which represented 72.3% of the insects collected by sweeping net and 45.7 by vacuum sampling. Phytoseiidae mites showed a significant increase on leaves of the vineyard plots managed with ground covers, in comparison with control, although they did not show any difference among the treatments. In general, the tested ground cover treatments did not increase dangerous Homoptera populations in comparison with control, with the exception of Alyssum. The potential of ground cover plant management in Italian vineyards is discussed: the overall lack of potential negative effects of the plants tested, combined with an aggregative numerical response for many beneficials, seems to show a potential for their use in Northern Italy vineyards.

Flow dynamics in hyper-saline aquifers: hydro-geophysical monitoring and modeling

NASA Astrophysics Data System (ADS)

Haaken, Klaus; Piero Deidda, Gian; Cassiani, Giorgio; Deiana, Rita; Putti, Mario; Paniconi, Claudio; Scudeler, Carlotta; Kemna, Andreas

2017-03-01

Saline-freshwater interaction in porous media is a phenomenon of practical interest particularly for the management of water resources in arid and semi-arid environments, where precious freshwater resources are threatened by seawater intrusion and where storage of freshwater in saline aquifers can be a viable option. Saline-freshwater interactions are controlled by physico-chemical processes that need to be accurately modeled. This in turn requires monitoring of these systems, a non-trivial task for which spatially extensive, high-resolution non-invasive techniques can provide key information. In this paper we present the field monitoring and numerical modeling components of an approach aimed at understanding complex saline-freshwater systems. The approach is applied to a freshwater injection experiment carried out in a hyper-saline aquifer near Cagliari (Sardinia, Italy). The experiment was monitored using time-lapse cross-hole electrical resistivity tomography (ERT). To investigate the flow dynamics, coupled numerical flow and transport modeling of the experiment was carried out using an advanced three-dimensional (3-D) density-driven flow-transport simulator. The simulation results were used to produce synthetic ERT inversion results to be compared against real field ERT results. This exercise demonstrates that the evolution of the freshwater bulb is strongly influenced by the system's (even mild) hydraulic heterogeneities. The example also highlights how the joint use of ERT imaging and gravity-dependent flow and transport modeling give fundamental information for this type of study.

SHEFEX II Flight Instrumentation And Preparation Of Post Flight Analysis

NASA Astrophysics Data System (ADS)

Thiele, Thomas; Siebe, Frank; Gulhan, Ali

2011-05-01

A main disadvantage of modern TPS systems for re- entry vehicles is the expensive manufacturing and maintenance process due to the complex geometry of these blunt nose configurations. To reduce the costs and to improve the aerodynamic performance the German Aerospace Center (DLR) is following a different approach using TPS structures consisting of flat ceramic tiles. To test these new sharp edged TPS structures the SHEFEX I flight experiment was designed and successfully performed by DLR in 2005. To further improve the reliability of the sharp edged TPS design at even higher Mach numbers, a second flight experiment SHEFEX II will be performed in September 2011. In comparison to SHEFEX I the second flight experiment has a fully symmetrical shape and will reach a maximum Mach number of about 11. Furthermore the vehicle has an active steering system using four canards to control the flight attitude during re-entry, e.g. roll angle, angle of attack and sideslip. After a successful flight the evaluation of the flight data will be performed using a combination of numerical and experimental tools. The data will be used for the improvement of the present numerical analysis tools and to get a better understanding of the aerothermal behaviour of sharp TPS structures. This paper presents the flight instrumentation of the SHEFEX II TPS. In addition the concept of the post flight analysis is presented.

Human Infants' Preference for Left-to-Right Oriented Increasing Numerical Sequences

PubMed Central

de Hevia, Maria Dolores; Girelli, Luisa; Addabbo, Margaret; Macchi Cassia, Viola

2014-01-01

While associations between number and space, in the form of a spatially oriented numerical representation, have been extensively reported in human adults, the origins of this phenomenon are still poorly understood. The commonly accepted view is that this number-space association is a product of human invention, with accounts proposing that culture, symbolic knowledge, and mathematics education are at the roots of this phenomenon. Here we show that preverbal infants aged 7 months, who lack symbolic knowledge and mathematics education, show a preference for increasing magnitude displayed in a left-to-right spatial orientation. Infants habituated to left-to-right oriented increasing or decreasing numerical sequences showed an overall higher looking time to new left-to-right oriented increasing numerical sequences at test (Experiment 1). This pattern did not hold when infants were presented with the same ordinal numerical information displayed from right to left (Experiment 2). The different pattern of results was congruent with the presence of a malleable, context-dependent baseline preference for increasing, left-to-right oriented, numerosities (Experiment 3). These findings are suggestive of an early predisposition in humans to link numerical order with a left-to-right spatial orientation, which precedes the acquisition of symbolic abilities, mathematics education, and the acquisition of reading and writing skills. PMID:24802083

Abstract numerical discrimination learning in rats.

PubMed

Taniuchi, Tohru; Sugihara, Junko; Wakashima, Mariko; Kamijo, Makiko

2016-06-01

In this study, we examined rats' discrimination learning of the numerical ordering positions of objects. In Experiments 1 and 2, five out of seven rats successfully learned to respond to the third of six identical objects in a row and showed reliable transfer of this discrimination to novel stimuli after being trained with three different training stimuli. In Experiment 3, the three rats from Experiment 2 continued to be trained to respond to the third object in an object array, which included an odd object that needed to be excluded when identifying the target third object. All three rats acquired this selective-counting task of specific stimuli, and two rats showed reliable transfer of this selective-counting performance to test sets of novel stimuli. In Experiment 4, the three rats from Experiment 3 quickly learned to respond to the third stimulus in object rows consisting of either six identical or six different objects. These results offer strong evidence for abstract numerical discrimination learning in rats.

Numerical calculation of protein-ligand binding rates through solution of the Smoluchowski equation using smoothed particle hydrodynamics

DOE PAGES

Pan, Wenxiao; Daily, Michael; Baker, Nathan A.

2015-05-07

Background: The calculation of diffusion-controlled ligand binding rates is important for understanding enzyme mechanisms as well as designing enzyme inhibitors. Methods: We demonstrate the accuracy and effectiveness of a Lagrangian particle-based method, smoothed particle hydrodynamics (SPH), to study diffusion in biomolecular systems by numerically solving the time-dependent Smoluchowski equation for continuum diffusion. Unlike previous studies, a reactive Robin boundary condition (BC), rather than the absolute absorbing (Dirichlet) BC, is considered on the reactive boundaries. This new BC treatment allows for the analysis of enzymes with “imperfect” reaction rates. Results: The numerical method is first verified in simple systems and thenmore » applied to the calculation of ligand binding to a mouse acetylcholinesterase (mAChE) monomer. Rates for inhibitor binding to mAChE are calculated at various ionic strengths and compared with experiment and other numerical methods. We find that imposition of the Robin BC improves agreement between calculated and experimental reaction rates. Conclusions: Although this initial application focuses on a single monomer system, our new method provides a framework to explore broader applications of SPH in larger-scale biomolecular complexes by taking advantage of its Lagrangian particle-based nature.« less

Numerical simulation of the heat transfer at cooling a high-temperature metal cylinder by a flow of a gas-liquid medium

NASA Astrophysics Data System (ADS)

Makarov, S. S.; Lipanov, A. M.; Karpov, A. I.

2017-10-01

The numerical modeling results for the heat transfer during cooling a metal cylinder by a gas-liquid medium flow in an annular channel are presented. The results are obtained on the basis of the mathematical model of the conjugate heat transfer of the gas-liquid flow and the metal cylinder in a two-dimensional nonstationary formulation accounting for the axisymmetry of the cooling medium flow relative to the cylinder longitudinal axis. To solve the system of differential equations the control volume approach is used. The flow field parameters are calculated by the SIMPLE algorithm. To solve iteratively the systems of linear algebraic equations the Gauss-Seidel method with under-relaxation is used. The results of the numerical simulation are verified by comparing the results of the numerical simulation with the results of the field experiment. The calculation results for the heat transfer parameters at cooling the high-temperature metal cylinder by the gas-liquid flow are obtained with accounting for evaporation. The values of the rate of cooling the cylinder by the laminar flow of the cooling medium are determined. The temperature change intensity for the metal cylinder is analyzed depending on the initial velocity of the liquid flow and the time of the cooling process.

Possible effects of two-phase flow pattern on the mechanical behavior of mudstones

NASA Astrophysics Data System (ADS)

Goto, H.; Tokunaga, T.; Aichi, M.

2016-12-01

To investigate the influence of two-phase flow pattern on the mechanical behavior of mudstones, laboratory experiments were conducted. In the experiment, air was injected from the bottom of the water-saturated Quaternary Umegase mudstone sample under hydrostatic external stress condition. Both axial and circumferential strains at half the height of the sample and volumetric discharge of water at the outlet were monitored during the experiment. Numerical simulation of the experiment was tried by using a simulator which can solve coupled two-phase flow and poroelastic deformation assuming the extended-Darcian flow with relative permeability and capillary pressure as functions of the wetting-phase fluid saturation. In the numerical simulation, the volumetric discharge of water was reproduced well while both strains were not. Three dimensionless numbers, i.e., the viscosity ratio, the Capillary number, and the Bond number, which characterize the two-phase flow pattern (Lenormand et al., 1988; Ewing and Berkowitz, 1998) were calculated to be 2×10-2, 2×10-11, and 7×10-11, respectively, in the experiment. Because the Bond number was quite small, it was possible to apply Lenormand et al. (1988)'s diagram to evaluate the flow regime, and the flow regime was considered to be capillary fingering. While, in the numerical simulation, air moved uniformly upward with quite low non-wetting phase saturation conditions because the fluid flow obeyed the two-phase Darcy's law. These different displacement patterns developed in the experiment and assumed in the numerical simulation were considered to be the reason why the deformation behavior observed in the experiment could not be reproduced by numerical simulation, suggesting that the two-phase flow pattern could affect the changes of internal fluid pressure patterns during displacement processes. For further studies, quantitative analysis of the experimental results by using a numerical simulator which can solve the coupled processes of two-phase flow through preferential flow paths and deformation of porous media is needed. References: Ewing R. P., and B. Berkowitz (1998), Water Resour. Res., 34, 611-622. Lenormand, R., E. Touboul, and C. Zarcone (1988), J. Fluid Mech., 189, 165-187.

Numerical Investigation of the Performance of a Supersonic Combustion Chamber and Comparison with Experiments

NASA Astrophysics Data System (ADS)

Banica, M. C.; Chun, J.; Scheuermann, T.; Weigand, B.; Wolfersdorf, J. v.

2009-01-01

Scramjet powered vehicles can decrease costs for access to space but substantial obstacles still exist in their realization. For example, experiments in the relevant Mach number regime are difficult to perform and flight testing is expensive. Therefore, numerical methods are often employed for system layout but they require validation against experimental data. Here, we validate the commercial code CFD++ against experimental results for hydrogen combustion in the supersonic combustion facility of the Institute of Aerospace Thermodynamics (ITLR) at the Universität Stuttgart. Fuel is injected through a lobed a strut injector, which provides rapid mixing. Our numerical data shows reasonable agreement with experiments. We further investigate effects of varying equivalence ratios on several important performance parameters.

The Madden-Julian Oscillation and its Impact on Northern Hemisphere Weather Predictability during Wintertime

NASA Technical Reports Server (NTRS)

Jones, Charles; Waliser, Duane E.; Lau, K. M.; Stern, W.

2003-01-01

The Madden-Julian Oscillation (MJO) is known as the dominant mode of tropical intraseasonal variability and has an important role in the coupled-atmosphere system. This study used twin numerical model experiments to investigate the influence of the MJO activity on weather predictability in the midlatitudes of the Northern Hemisphere during boreal winter. The National Aeronautics and Space Administration (NASA) Goddard laboratory for the Atmospheres (GLA) general circulation model was first used in a 10-yr simulation with fixed climatological SSTs to generate a validation data set as well as to select initial conditions for active MJO periods and Null cases. Two perturbation numerical experiments were performed for the 75 cases selected [(4 MJO phases + Null phase) _ 15 initial conditions in each]. For each alternative initial condition, the model was integrated for 90 days. Mean anomaly correlations in the midlatitudes of the Northern Hemisphere (2O deg N_60 deg.N) and standardized root-mean-square errors were computed to validate forecasts and control run. The analyses of 500-hPa geopotential height, 200-hPa Streamfunction and 850-hPa zonal wind component systematically show larger predictability during periods of active MJO as opposed to quiescent episodes of the oscillation.

Systematic optimization of human pluripotent stem cells media using Design of Experiments

NASA Astrophysics Data System (ADS)

Marinho, Paulo A.; Chailangkarn, Thanathom; Muotri, Alysson R.

2015-05-01

Human pluripotent stem cells (hPSC) are used to study the early stages of human development in vitro and, increasingly due to somatic cell reprogramming, cellular and molecular mechanisms of disease. Cell culture medium is a critical factor for hPSC to maintain pluripotency and self-renewal. Numerous defined culture media have been empirically developed but never systematically optimized for culturing hPSC. We applied design of experiments (DOE), a powerful statistical tool, to improve the medium formulation for hPSC. Using pluripotency and cell growth as read-outs, we determined the optimal concentration of both basic fibroblast growth factor (bFGF) and neuregulin-1 beta 1 (NRG1β1). The resulting formulation, named iDEAL, improved the maintenance and passage of hPSC in both normal and stressful conditions, and affected trimethylated histone 3 lysine 27 (H3K27me3) epigenetic status after genetic reprogramming. It also enhances efficient hPSC plating as single cells. Altogether, iDEAL potentially allows scalable and controllable hPSC culture routine in translational research. Our DOE strategy could also be applied to hPSC differentiation protocols, which often require numerous and complex cell culture media.

A Framework for Debugging Geoscience Projects in a High Performance Computing Environment

NASA Astrophysics Data System (ADS)

Baxter, C.; Matott, L.

2012-12-01

High performance computing (HPC) infrastructure has become ubiquitous in today's world with the emergence of commercial cloud computing and academic supercomputing centers. Teams of geoscientists, hydrologists and engineers can take advantage of this infrastructure to undertake large research projects - for example, linking one or more site-specific environmental models with soft computing algorithms, such as heuristic global search procedures, to perform parameter estimation and predictive uncertainty analysis, and/or design least-cost remediation systems. However, the size, complexity and distributed nature of these projects can make identifying failures in the associated numerical experiments using conventional ad-hoc approaches both time- consuming and ineffective. To address these problems a multi-tiered debugging framework has been developed. The framework allows for quickly isolating and remedying a number of potential experimental failures, including: failures in the HPC scheduler; bugs in the soft computing code; bugs in the modeling code; and permissions and access control errors. The utility of the framework is demonstrated via application to a series of over 200,000 numerical experiments involving a suite of 5 heuristic global search algorithms and 15 mathematical test functions serving as cheap analogues for the simulation-based optimization of pump-and-treat subsurface remediation systems.

Pseudogap and Fermi-Surface Topology in the Two-Dimensional Hubbard Model

NASA Astrophysics Data System (ADS)

Wu, Wei; Scheurer, Mathias S.; Chatterjee, Shubhayu; Sachdev, Subir; Georges, Antoine; Ferrero, Michel

2018-04-01

One of the distinctive features of hole-doped cuprate superconductors is the onset of a "pseudogap" below a temperature T* . Recent experiments suggest that there may be a connection between the existence of the pseudogap and the topology of the Fermi surface. Here, we address this issue by studying the two-dimensional Hubbard model with two distinct numerical methods. We find that the pseudogap only exists when the Fermi surface is holelike and that, for a broad range of parameters, its opening is concomitant with a Fermi-surface topology change from electronlike to holelike. We identify a common link between these observations: The polelike feature of the electronic self-energy associated with the formation of the pseudogap is found to also control the degree of particle-hole asymmetry, and hence the Fermi-surface topology transition. We interpret our results in the framework of an SU(2) gauge theory of fluctuating antiferromagnetism. We show that a mean-field treatment of this theory in a metallic state with U(1) topological order provides an explanation of this polelike feature and a good description of our numerical results. We discuss the relevance of our results to experiments on cuprates.

Properties of atomic pairs produced in the collision of Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Ziń, Paweł; Wasak, Tomasz

2018-04-01

During a collision of Bose-Einstein condensates correlated pairs of atoms are emitted. The scattered massive particles, in analogy to photon pairs in quantum optics, might be used in the violation of Bell's inequalities, demonstration of Einstein-Podolsky-Rosen correlations, or sub-shot-noise atomic interferometry. Usually, a theoretical description of the collision relies either on stochastic numerical methods or on analytical treatments involving various approximations. Here, we investigate elastic scattering of atoms from colliding elongated Bose-Einstein condensates within the Bogoliubov method, carefully controlling performed approximations at every stage of the analysis. We derive expressions for the one- and two-particle correlation functions. The obtained formulas, which relate the correlation functions to the condensate wave function, are convenient for numerical calculations. We employ the variational approach for condensate wave functions to obtain analytical expressions for the correlation functions, whose properties we analyze in detail. We also present a useful semiclassical model of the process and compare its results with the quantum one. The results are relevant for recent experiments with excited helium atoms, as well as for planned experiments aimed at investigating the nonclassicality of the system.

Numerical Model of Flame Spread Over Solids in Microgravity: A Supplementary Tool for Designing a Space Experiment

NASA Technical Reports Server (NTRS)

Shih, Hsin-Yi; Tien, James S.; Ferkul, Paul (Technical Monitor)

2001-01-01

The recently developed numerical model of concurrent-flow flame spread over thin solids has been used as a simulation tool to help the designs of a space experiment. The two-dimensional and three-dimensional, steady form of the compressible Navier-Stokes equations with chemical reactions are solved. With the coupled multi-dimensional solver of the radiative heat transfer, the model is capable of answering a number of questions regarding the experiment concept and the hardware designs. In this paper, the capabilities of the numerical model are demonstrated by providing the guidance for several experimental designing issues. The test matrix and operating conditions of the experiment are estimated through the modeling results. The three-dimensional calculations are made to simulate the flame-spreading experiment with realistic hardware configuration. The computed detailed flame structures provide the insight to the data collection. In addition, the heating load and the requirements of the product exhaust cleanup for the flow tunnel are estimated with the model. We anticipate that using this simulation tool will enable a more efficient and successful space experiment to be conducted.

Importance of inlet boundary conditions for numerical simulation of combustor flows

NASA Technical Reports Server (NTRS)

Sturgess, G. J.; Syed, S. A.; Mcmanus, K. R.

1983-01-01

Fluid dynamic computer codes for the mathematical simulation of problems in gas turbine engine combustion systems are required as design and diagnostic tools. To eventually achieve a performance standard with these codes of more than qualitative accuracy it is desirable to use benchmark experiments for validation studies. Typical of the fluid dynamic computer codes being developed for combustor simulations is the TEACH (Teaching Elliptic Axisymmetric Characteristics Heuristically) solution procedure. It is difficult to find suitable experiments which satisfy the present definition of benchmark quality. For the majority of the available experiments there is a lack of information concerning the boundary conditions. A standard TEACH-type numerical technique is applied to a number of test-case experiments. It is found that numerical simulations of gas turbine combustor-relevant flows can be sensitive to the plane at which the calculations start and the spatial distributions of inlet quantities for swirling flows.

Contribution to study of interfaces instabilities in plane, cylindrical and spherical geometry

NASA Astrophysics Data System (ADS)

Toque, Nathalie

1996-12-01

This thesis proposes several experiments of hydrodynamical instabilities which are studied, numerically and theoretically. The experiments are in plane and cylindrical geometry. Their X-ray radiographies show the evolution of an interface between two solid media crossed by a detonation wave. These materials are initially solid. They become liquide under shock wave or stay between two phases, solid and liquid. The numerical study aims at simulating with the codes EAD and Ouranos, the interfaces instabilities which appear in the experiments. The experimental radiographies and the numerical pictures are in quite good agreement. The theoretical study suggests to modelise a spatio-temporal part of the experiments to obtain the quantitative development of perturbations at the interfaces and in the flows. The models are linear and in plane, cylindrical and spherical geometry. They preceed the inoming study of transition between linear and non linear development of instabilities in multifluids flows crossed by shock waves.

Composite body movements modulate numerical cognition: evidence from the motion-numerical compatibility effect

PubMed Central

Cheng, Xiaorong; Ge, Hui; Andoni, Deljfina; Ding, Xianfeng; Fan, Zhao

2015-01-01

A recent hierarchical model of numerical processing, initiated by Fischer and Brugger (2011) and Fischer (2012), suggested that situated factors, such as different body postures and body movements, can influence the magnitude representation and bias numerical processing. Indeed, Loetscher et al. (2008) found that participants’ behavior in a random number generation task was biased by head rotations. More small numbers were reported after leftward than rightward head turns, i.e., a motion-numerical compatibility effect. Here, by carrying out two experiments, we explored whether similar motion-numerical compatibility effects exist for movements of other important body components, e.g., arms, and for composite body movements as well, which are basis for complex human activities in many ecologically meaningful situations. In Experiment 1, a motion-numerical compatibility effect was observed for lateral rotations of two body components, i.e., the head and arms. Relatively large numbers were reported after making rightward compared to leftward movements for both lateral head and arm turns. The motion-numerical compatibility effect was observed again in Experiment 2 when participants were asked to perform composite body movements of congruent movement directions, e.g., simultaneous head left turns and arm left turns. However, it disappeared when the movement directions were incongruent, e.g., simultaneous head left turns and arm right turns. Taken together, our results extended Loetscher et al.’s (2008) finding by demonstrating that their effect is effector-general and exists for arm movements. Moreover, our study reveals for the first time that the impact of spatial information on numerical processing induced by each of the two sensorimotor-based situated factors, e.g., a lateral head turn and a lateral arm turn, can cancel each other out. PMID:26594188

A comparison of solute-transport solution techniques based on inverse modelling results

USGS Publications Warehouse

Mehl, S.; Hill, M.C.

2000-01-01

Five common numerical techniques (finite difference, predictor-corrector, total-variation-diminishing, method-of-characteristics, and modified-method-of-characteristics) were tested using simulations of a controlled conservative tracer-test experiment through a heterogeneous, two-dimensional sand tank. The experimental facility was constructed using randomly distributed homogeneous blocks of five sand types. This experimental model provides an outstanding opportunity to compare the solution techniques because of the heterogeneous hydraulic conductivity distribution of known structure, and the availability of detailed measurements with which to compare simulated concentrations. The present work uses this opportunity to investigate how three common types of results-simulated breakthrough curves, sensitivity analysis, and calibrated parameter values-change in this heterogeneous situation, given the different methods of simulating solute transport. The results show that simulated peak concentrations, even at very fine grid spacings, varied because of different amounts of numerical dispersion. Sensitivity analysis results were robust in that they were independent of the solution technique. They revealed extreme correlation between hydraulic conductivity and porosity, and that the breakthrough curve data did not provide enough information about the dispersivities to estimate individual values for the five sands. However, estimated hydraulic conductivity values are significantly influenced by both the large possible variations in model dispersion and the amount of numerical dispersion present in the solution technique.Five common numerical techniques (finite difference, predictor-corrector, total-variation-diminishing, method-of-characteristics, and modified-method-of-characteristics) were tested using simulations of a controlled conservative tracer-test experiment through a heterogeneous, two-dimensional sand tank. The experimental facility was constructed using randomly distributed homogeneous blocks of five sand types. This experimental model provides an outstanding opportunity to compare the solution techniques because of the heterogeneous hydraulic conductivity distribution of known structure, and the availability of detailed measurements with which to compare simulated concentrations. The present work uses this opportunity to investigate how three common types of results - simulated breakthrough curves, sensitivity analysis, and calibrated parameter values - change in this heterogeneous situation, given the different methods of simulating solute transport. The results show that simulated peak concentrations, even at very fine grid spacings, varied because of different amounts of numerical dispersion. Sensitivity analysis results were robust in that they were independent of the solution technique. They revealed extreme correlation between hydraulic conductivity and porosity, and that the breakthrough curve data did not provide enough information about the dispersivities to estimate individual values for the five sands. However, estimated hydraulic conductivity values are significantly influenced by both the large possible variations in model dispersion and the amount of numerical dispersion present in the solution technique.

Dynamic acousto-optic control of a strongly coupled photonic molecule

PubMed Central

Kapfinger, Stephan; Reichert, Thorsten; Lichtmannecker, Stefan; Müller, Kai; Finley, Jonathan J.; Wixforth, Achim; Kaniber, Michael; Krenner, Hubert J.

2015-01-01

Strongly confined photonic modes can couple to quantum emitters and mechanical excitations. To harness the full potential in quantum photonic circuits, interactions between different constituents have to be precisely and dynamically controlled. Here, a prototypical coupled element, a photonic molecule defined in a photonic crystal membrane, is controlled by a radio frequency surface acoustic wave. The sound wave is tailored to deliberately switch on and off the bond of the photonic molecule on sub-nanosecond timescales. In time-resolved experiments, the acousto-optically controllable coupling is directly observed as clear anticrossings between the two nanophotonic modes. The coupling strength is determined directly from the experimental data. Both the time dependence of the tuning and the inter-cavity coupling strength are found to be in excellent agreement with numerical calculations. The demonstrated mechanical technique can be directly applied for dynamic quantum gate operations in state-of-the-art-coupled nanophotonic, quantum cavity electrodynamic and optomechanical systems. PMID:26436203

FVMS: A novel SiL approach on the evaluation of controllers for autonomous MAV

NASA Astrophysics Data System (ADS)

Sampaio, Rafael C. B.; Becker, Marcelo; Siqueira, Adriano A. G.; Freschi, Leonardo W.; Montanher, Marcelo P.

The originality of this work is to propose a novel SiL (Software-in-the-Loop) platform using Microsoft Flight Simulator (MSFS) to assist control design regarding the stabilization problem found in © AscTec Pelican platform. Aerial Robots Team (USP/EESC/LabRoM/ART) has developed a custom C++/C# software named FVMS (Flight Variables Management System) that interfaces the communication between the virtual Pelican and the control algorithms allowing the control designer to perform fast full closed loop real time algorithms. Emulation of embedded sensors as well as the possibility to integrate OpenCV Optical Flow algorithms to a virtual downward camera makes the SiL even more reliable. More than a strictly numeric analysis, the proposed SiL platform offers an unique experience, simultaneously offering both dynamic and graphical responses. Performance of SiL algorithms is presented and discussed.

Tobacco Control in Oman: It’s Time to Get Serious!

PubMed Central

Al-Lawati, Jawad; Mabry, Ruth M.; Al-Busaidi, Zakiya Q

2017-01-01

Tobacco use is the world’s leading cause of preventable morbidity and mortality. Although Oman remains a country with the lowest tobacco use in the Arab Gulf States, the prevalence of tobacco use is projected to increase to 33.3% by 2025. In 2005, Oman acceded to the World Health Organization’s Framework Convention on Tobacco Control, an international treaty with numerous obligations aiming to reduce the global burden of tobacco use. This paper documents, for the first time, Oman’s experience in tobacco control by providing a descriptive analysis of the evolution of tobacco control policies in relation to the country’s international obligations. In order to curb tobacco use and maintain current low prevalence levels, the paper concludes that Oman needs to accelerate action in adopting the highest attainable policies recommended by the World Health Organization’s MPOWER package. PMID:28042396

Payload specialist station study: Volume 2, part 3: Program analysis and planning for phase C/D

NASA Technical Reports Server (NTRS)

1976-01-01

The controls and displays (C&D) required at the Orbiter aft-flight deck (AFD) and the core C&D required at the Payload Specialist Station (PSS) are identified in this document. The AFD C&D Concept consists of a multifunction display system (MFDS) and elements of multiuse mission support equipment (MMSE). The MFDS consists of two CRTs, a display electronics unit (DEU), and a keyboard. The MMSE consists of a manual pointing controller (MPC), five digit numeric displays, 10 character alphanumeric legends, event timers, analog meters, rotary and toggle switches. The MMSE may be hardwired to the experiment, or interface with a data bus at the PSS for signal processing. The MFDS has video capability, with alphanumeric and graphic overlay features, on one CRT and alphanumeric and graphic (tricolor) capability on a second CRT. The DEU will have the capability to communicate, via redundant data buses, with both the spacelab experiment and subsystem computers.

The effects of a housing mobility experiment on participants' residential environments

PubMed Central

Nguyen, Quynh C.; Acevedo-Garcia, Dolores; Schmidt, Nicole M.; Osypuk, Theresa L.

2017-01-01

We used the Moving to Opportunity (MTO) housing experiment to inform how housing choice vouchers and housing mobility policies can assist families living in high-poverty areas to make opportunity moves to higher quality neighborhoods, across a wide range of neighborhood attributes. We compared the neighborhood attainment of the three randomly-assigned MTO treatment groups (Low Poverty voucher, Section 8 voucher, Control group) at 1997 and 2002 locations (4-7 years after baseline), by using survey reports, and by linking residential histories to numerous different administrative and population-based datasets. Compared to controls, families in Low-Poverty and Section 8 groups experienced substantial improvements in neighborhood conditions across diverse measures, including economic conditions, social systems (e.g., collective efficacy), physical features of the environment (e.g., tree cover) and health outcomes. The Low-poverty voucher group moreover achieved better neighborhood attainment compared to Section 8. Treatment effects were largest for New York and Los Angeles. We discuss the implications of our findings for expanding affordable housing policy. PMID:28966541

Flow Navigation by Smart Microswimmers via Reinforcement Learning

NASA Astrophysics Data System (ADS)

Colabrese, Simona; Gustavsson, Kristian; Celani, Antonio; Biferale, Luca

2017-04-01

Smart active particles can acquire some limited knowledge of the fluid environment from simple mechanical cues and exert a control on their preferred steering direction. Their goal is to learn the best way to navigate by exploiting the underlying flow whenever possible. As an example, we focus our attention on smart gravitactic swimmers. These are active particles whose task is to reach the highest altitude within some time horizon, given the constraints enforced by fluid mechanics. By means of numerical experiments, we show that swimmers indeed learn nearly optimal strategies just by experience. A reinforcement learning algorithm allows particles to learn effective strategies even in difficult situations when, in the absence of control, they would end up being trapped by flow structures. These strategies are highly nontrivial and cannot be easily guessed in advance. This Letter illustrates the potential of reinforcement learning algorithms to model adaptive behavior in complex flows and paves the way towards the engineering of smart microswimmers that solve difficult navigation problems.

Scaled laboratory experiments explain the kink behaviour of the Crab Nebula jet

PubMed Central

Li, C. K.; Tzeferacos, P.; Lamb, D.; Gregori, G.; Norreys, P. A.; Rosenberg, M. J.; Follett, R. K.; Froula, D. H.; Koenig, M.; Seguin, F. H.; Frenje, J. A.; Rinderknecht, H. G.; Sio, H.; Zylstra, A. B.; Petrasso, R. D.; Amendt, P. A.; Park, H. S.; Remington, B. A.; Ryutov, D. D.; Wilks, S. C.; Betti, R.; Frank, A.; Hu, S. X.; Sangster, T. C.; Hartigan, P.; Drake, R. P.; Kuranz, C. C.; Lebedev, S. V.; Woolsey, N. C.

2016-01-01

The remarkable discovery by the Chandra X-ray observatory that the Crab nebula's jet periodically changes direction provides a challenge to our understanding of astrophysical jet dynamics. It has been suggested that this phenomenon may be the consequence of magnetic fields and magnetohydrodynamic instabilities, but experimental demonstration in a controlled laboratory environment has remained elusive. Here we report experiments that use high-power lasers to create a plasma jet that can be directly compared with the Crab jet through well-defined physical scaling laws. The jet generates its own embedded toroidal magnetic fields; as it moves, plasma instabilities result in multiple deflections of the propagation direction, mimicking the kink behaviour of the Crab jet. The experiment is modelled with three-dimensional numerical simulations that show exactly how the instability develops and results in changes of direction of the jet. PMID:27713403

Periodically modulated dark states

NASA Astrophysics Data System (ADS)

Han, Yingying; Zhang, Jun; Zhang, Wenxian

2018-04-01

Phenomena of electromagnetically induced transparency (PEIT) may be interpreted by the Autler-Townes Splitting (ATS), where the coupled states are split by the coupling laser field, or by the quantum destructive interference (QDI), where the atomic phases caused by the coupling laser and the probe laser field cancel. We propose modulated experiments to explore the PEIT in an alternative way by periodically modulating the coupling and the probe fields in a Λ-type three-level system initially in a dark state. Our analytical and numerical results rule out the ATS interpretation and show that the QDI interpretation is more appropriate for the modulated experiments. Interestingly, dark state persists in the double-modulation situation where control and probe fields never occur simultaneously, which is significant difference from the traditional dark state condition. The proposed experiments are readily implemented in atomic gases, artificial atoms in superconducting quantum devices, or three-level meta-atoms in meta-materials.

Ecohydrological Interfaces as Dynamic Hotspots of Biogeochemical Cycling

NASA Astrophysics Data System (ADS)

Krause, Stefan; Lewandowski, Joerg; Hannah, David; McDonald, Karlie; Folegot, Silvia; Baranov, Victor

2016-04-01

Ecohydrological interfaces, represent the boundaries between water-dependent ecosystems that can alter substantially the fluxes of energy and matter. There is still a critical gap of understanding the organisational principles of the drivers and controls of spatially and temporally variable ecohydrological interface functions. This knowledge gap limits our capacity to efficiently quantify, predict and manage the services provided by complex ecosystems. Many ecohydrological interfaces are characterized by step changes in microbial metabolic activity, steep redox gradients and often even thermodynamic phase shifts, for instance at the interfaces between atmosphere and water or soil matrix and macro-pores interfaces. This paper integrates investigations from point scale laboratory microcosm experiments with reach and subcatchment scale tracer experiments and numerical modeling studies to elaborate similarities in the drivers and controls that constitute the enhanced biogeochemical activity of different types of ecohydrologica interfaces across a range of spatial and temporal scales. We therefore combine smart metabolic activity tracers to quantify the impact of bioturbating benthic fauna onto ecosystem respiration and oxygen consumption and investigate at larger scale, how microbial metabolic activity and carbon turnover at the water-sediment interface are controlled by sediment physical and chemical properties as well as water temperatures. Numerical modeling confirmed that experimentally identified hotspots of streambed biogeochemical cycling were controlled by patterns of physical properties such as hydraulic conductivities or bioavailability of organic matter, impacting on residence time distributions and hence reaction times. In contrast to previous research, our investigations thus confirmed that small-scale variability of physical and chemical interface properties had a major impact on biogeochemical processing at the investigated ecohydrological interfaces. Our results furthermore indicate that to fully understand spatial patterns and temporal dynamics of ecohydrological interface functioning, including hotspots and hot moments, detailed knowledge of the impacts of biological behavior on the physic-chemical ecosystem conditions, and vice-versa, is required.

Ecohydrological Interfaces as Dynamic Hotspots of Biogeochemical Cycling

NASA Astrophysics Data System (ADS)

Krause, S.

2015-12-01

Ecohydrological interfaces, represent the boundaries between water-dependent ecosystems that can alter substantially the fluxes of energy and matter. There is still a critical gap of understanding the organisational principles of the drivers and controls of spatially and temporally variable ecohydrological interface functions. This knowledge gap limits our capacity to efficiently quantify, predict and manage the services provided by complex ecosystems. Many ecohydrological interfaces are characterized by step changes in microbial metabolic activity, steep redox gradients and often even thermodynamic phase shifts, for instance at the interfaces between atmosphere and water or soil matrix and macro-pores interfaces. This paper integrates investigations from point scale microcosm experiments with reach and subcatchment scale tracer experiments and numerical modeling studies to elaborate similarities in the drivers and controls that constitute the enhanced biogeochemical activity of different types of ecohydrologica interfaces across a range of spatial and temporal scales. We therefore combine smart metabolic activity tracers to quantify the impact of bioturbating benthic fauna onto ecosystem respiration and oxygen consumption and investigate at larger scale, how microbial metabolic activity and carbon turnover at the water-sediment interface are controlled by sediment physical and chemical properties as well as water temperatures. Numerical modeling confirmed that experimentally identified hotspots of streambed biogeochemical cycling were controlled by patterns of physical properties such as hydraulic conductivities or bioavailability of organic matter, impacting on residence time distributions and hence reaction times. In contrast to previous research, our investigations thus confirmed that small-scale variability of physical and chemical interface properties had a major impact on biogeochemical processing at the investigated ecohydrological interfaces. Our results furthermore indicate that to fully understand spatial patterns and temporal dynamics of ecohydrological interface functioning, including hotspots and hot moments, detailed knowledge of the impacts of biological behavior on the physic-chemical ecosystem conditions, and vice-versa, is required.

Uniform magnetic fields and double-wrapped coil systems: improved techniques for the design of bioelectromagnetic experiments.

PubMed

Kirschvink, J L

1992-01-01

A common mistake in biomagnetic experimentation is the assumption that Helmholtz coils provide uniform magnetic fields; this is true only for a limited volume at their center. Substantial improvements on this design have been made during the past 140 years with systems of three, four, and five coils. Numerical comparisons of the field uniformity generated by these designs are made here, along with a table of construction details and recommendations for their use in experiments in which large volumes of uniform intensity magnetic exposures are needed. Double-wrapping, or systems of bifilar windings, can also help control for the non-magnetic effects of the electric coils used in many experiments. In this design, each coil is wrapped in parallel with two separate, adjacent strands of copper wire, rather than the single strand used normally. If currents are flowing in antiparallel directions, the magnetic fields generated by each strand will cancel and yield virtually no external magnetic field, whereas parallel currents will yield an external field. Both cases will produce similar non-magnetic effects of ohmic heating, and simple measures can reduce the small vibration and electric field differences. Control experiments can then be designed such that the only major difference between treated and untreated groups is the presence or absence of the magnetic field. Double-wrapped coils also facilitate the use of truly double-blind protocol, as the same apparatus can be used either for experimental or control groups.

The quest for stall-free dynamic lift

NASA Technical Reports Server (NTRS)

Tung, C.; Mcalister, K. W.; Carr, Lawrence W.; Duque, E.; Zinner, R.

1992-01-01

During the past decade, numerous major effects have addressed the question of how to control or alleviate dynamic stall effects on helicopter rotors, but little concrete evidence of any significant reduction of the adverse characteristics of the dynamic stall phenomenon has been demonstrated. Nevertheless, it is important to remember that the control of dynamic stall is an achievable goal. Experiments performed at the US Army Aeroflight-dynamics Directorate more than a decade ago demonstrated that dynamic stall is not an unavoidable penalty of high amplitude motion, and that airfoils can indeed operate dynamically at angles far above the static-stall angle without necessarily forming a stall vortex. These experiments, one of them featuring a slat that was designed from static airfoil considerations, showed that unsteadiness can be a very beneficial factor in the development of high-lift devices for helicopter rotors. The experience drawn from these early experiments is now being focused on a program for the alleviation of dynamic-stall effects on helicopter rotors. The purpose of this effort is to demonstrate that rotor stall can be controlled through an improved understanding of the unsteady effects on airfoil stall and to document the role of specific means that lead to stall alleviation in the three dimensional unsteady environment of helicopter rotors in forward flight. The first concept to be addressed in this program will be a slatted airfoil. A two dimensional unsteady Navier-Stokes code has been modified to compute the flow around a two-element airfoil.

Hyperthermia in bone generated with MR imaging-controlled focused ultrasound: control strategies and drug delivery.

PubMed

Staruch, Robert; Chopra, Rajiv; Hynynen, Kullervo

2012-04-01

To evaluate the feasibility of achieving image-guided drug delivery in bone by using magnetic resonance (MR) imaging-controlled focused ultrasound hyperthermia and temperature-sensitive liposomes. Experiments were approved by the institutional animal care committee. Hyperthermia (43°C, 20 minutes) was generated in 10-mm-diameter regions at a muscle-bone interface in nine rabbit thighs by using focused ultrasound under closed-loop temperature control with MR thermometry. Thermosensitive liposomal doxorubicin was administered systemically during heating. Heating uniformity and drug delivery were evaluated for control strategies with the temperature control image centered 10 mm (four rabbits) or 0 mm (five rabbits) from the bone. Simulations estimated temperature elevations in bone. Drug delivery was quantified by using the fluorescence of doxorubicin extracted from bone marrow and muscle and was compared between treated and untreated thighs by using the one-sided Wilcoxon signed rank test. With ultrasound focus and MR temperature control plane 0 mm and 10 mm from the bone interface, average target region temperatures were 43.1°C and 43.3°C, respectively; numerically estimated bone temperatures were 46.8°C and 78.1°C. The 10-mm offset resulted in thermal ablation; numerically estimated muscle temperature was 66.1°C at the bone interface. Significant increases in doxorubicin concentration occurred in heated versus unheated marrow (8.2-fold, P = .002) and muscle (16.8-fold, P = .002). Enhancement occurred for 0- and 10-mm offsets, which suggests localized drug delivery in bone is possible with both hyperthermia and thermal ablation. MR imaging-controlled focused ultrasound can achieve localized hyperthermia in bone for image-guided drug delivery in bone with temperature-sensitive drug carriers. © RSNA, 2012.

Efficient vitrification of mouse embryos using the Kitasato Vitrification System as a novel vitrification device.

PubMed

Momozawa, Kenji; Matsuzawa, Atsushi; Tokunaga, Yukio; Abe, Shiori; Koyanagi, Yumi; Kurita, Miho; Nakano, Marina; Miyake, Takao

2017-04-24

Currently, the cryopreservation of embryos and oocytes is essential for assisted reproductive technology (ART) laboratories worldwide. This study aimed to evaluate the efficacy of the Kitasato Vitrification System (KVS) as a vitrification device for the cryopreservation of mouse embryos to determine whether this novel device can be adapted to the field of ART. In Experiment 1, blastocysts were vitrified using the KVS. Vitrified blastocysts were warmed and subsequently cultured for 72 h. In Experiment 2, 2-cell-stage embryos were vitrified using the KVS, and vitrified embryos were warmed and subsequently cultured for 96 h. In Experiment 3, we evaluated the in vivo developmental potential of vitrified 2-cell-stage embryos using the KVS, and in Experiment 4, we evaluated the cooling and warming rates for these devices using a numerical simulation. In Experiment 1, there were no significant differences between the survival rates of the KVS and a control device. However, re-expanded (100%) and hatching (91.8%) rates were significantly higher for blastocysts vitrified using the KVS. In Experiment 2, there were no significant differences between the survival rates, or rates of development to the blastocyst stage, of vitrified and fresh embryos. In Experiment 3, after embryo transfer, 41% of the embryos developed into live offspring. In Experiment 4, the cooling and warming rates of the KVS were 683,000 and 612,000 °C/min, respectively, exceeding those of the control device. Our study clearly demonstrates that the KVS is a novel vitrification device for the cryopreservation of mouse embryos at the blastocyst and 2-cell stage.

2D transient granular flows over obstacles: experimental and numerical work

NASA Astrophysics Data System (ADS)

Juez, Carmelo; Caviedes-Voullième, Daniel; Murillo, Javier; García-Navarro, Pilar

2016-04-01

Landslides are an ubiquitous natural hazard, and therefore human infrastructure and settlements are often at risk in mountainous regions. In order to better understand and predict landslides, systematic studies of the phenomena need to be undertaken. In particular, computational tools which allow for analysis of field problems require to be thoroughly tested, calibrated and validated under controlled conditions. And to do so, it is necessary for such controlled experiments to be fully characterized in the same terms as the numerical model requires. This work presents an experimental study of dry granular flow over a rough bed with topography which resembles a mountain valley. It has an upper region with a very high slope. The geometry of the bed describes a fourth order polynomial curve, with a low point with zero slope, and afterwards a short region with adverse slope. Obstacles are present in the lower regions which are used as model geometries of human structures. The experiments consisted of a sudden release a mass of sand on the upper region, and allowing it to flow downslope. Furthermore, it has been frequent in previous studies to measure final states of the granular mass at rest, but seldom has transient data being provided, and never for the entire field. In this work we present transient measurements of the moving granular surfaces, obtained with a consumer-grade RGB-D sensor. The sensor, developed for the videogame industry, allows to measure the moving surface of the sand, thus obtaining elevation fields. The experimental results are very consistent and repeatable. The measured surfaces clearly show the distinctive features of the granular flow around the obstacles and allow to qualitatively describe the different flow patterns. More importantly, the quantitative description of the granular surface allows for benchmarking and calibration of predictive numerical models, key in scaling the small-scale experimental knowledge into the field. In addition, as the material is traditionally oriented in a predominant longitudinal direction and the layer of the mass is thin in comparison to the scale of interest, the depth-averaged procedure can be performed in the mass and momentum equations. Regarding the friction theory embedded in the landslide motion, a Coulomb-like basal friction law can be assumed as a first attempt of reproducing the phenomena. On the other hand, the presence of obstacles, involves the study of the development of schock waves imposing the simulation of the granular behavior by means of a schock-tracking numerical scheme. The numerical scheme employed, is based on an approximate solvers based on Roe approaches, devoting especial attention to the frictional source terms. This work was partially funded by the ITN-Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7-PEOPLE-2013-ITN under REA grant agreement n_607394-SEDITRANS. The granular experiments were funded by DGA, Diputación General de Aragón, España.

Active elimination of radio frequency interference for improved signal-to-noise ratio for in-situ NMR experiments in strong magnetic field gradients

NASA Astrophysics Data System (ADS)

Ibrahim, M.; Pardi, C. I.; Brown, T. W. C.; McDonald, P. J.

2018-02-01

Improvement in the signal-to-noise ratio of Nuclear Magnetic Resonance (NMR) systems may be achieved either by increasing the signal amplitude or by decreasing the noise. The noise has multiple origins - not all of which are strictly "noise": incoherent thermal noise originating in the probe and pre-amplifiers, probe ring down or acoustic noise and coherent externally broadcast radio frequency transmissions. The last cannot always be shielded in open access experiments. In this paper, we show that pulsed, low radio-frequency data communications are a significant source of broadcast interference. We explore two signal processing methods of de-noising short T2∗ NMR experiments corrupted by these communications: Linear Predictive Coding (LPC) and the Discrete Wavelet Transform (DWT). Results are shown for numerical simulations and experiments conducted under controlled conditions with pseudo radio frequency interference. We show that both the LPC and DWT methods have merit.

The place-value of a digit in multi-digit numbers is processed automatically.

PubMed

Kallai, Arava Y; Tzelgov, Joseph

2012-09-01

The automatic processing of the place-value of digits in a multi-digit number was investigated in 4 experiments. Experiment 1 and two control experiments employed a numerical comparison task in which the place-value of a non-zero digit was varied in a string composed of zeros. Experiment 2 employed a physical comparison task in which strings of digits varied in their physical sizes. In both types of tasks, the place-value of the non-zero digit in the string was irrelevant to the task performed. Interference of the place-value information was found in both tasks. When the non-zero digit occupied a lower place-value, it was recognized slower as a larger digit or as written in a larger font size. We concluded that place-value in a multi-digit number is processed automatically. These results support the notion of a decomposed representation of multi-digit numbers in memory. PsycINFO Database Record (c) 2012 APA, all rights reserved.

ODIN-object-oriented development interface for NMR.

PubMed

Jochimsen, Thies H; von Mengershausen, Michael

2004-09-01

A cross-platform development environment for nuclear magnetic resonance (NMR) experiments is presented. It allows rapid prototyping of new pulse sequences and provides a common programming interface for different system types. With this object-oriented interface implemented in C++, the programmer is capable of writing applications to control an experiment that can be executed on different measurement devices, even from different manufacturers, without the need to modify the source code. Due to the clear design of the software, new pulse sequences can be created, tested, and executed within a short time. To post-process the acquired data, an interface to well-known numerical libraries is part of the framework. This allows a transparent integration of the data processing instructions into the measurement module. The software focuses mainly on NMR imaging, but can also be used with limitations for spectroscopic experiments. To demonstrate the capabilities of the framework, results of the same experiment, carried out on two NMR imaging systems from different manufacturers are shown and compared with the results of a simulation.

Astrophysical particle acceleration mechanisms in colliding magnetized laser-produced plasmas

DOE PAGES

Fox, W.; Park, J.; Deng, W.; ...

2017-08-11

Significant particle energization is observed to occur in numerous astrophysical environments, and in the standard models, this acceleration occurs alongside energy conversion processes including collisionless shocks or magnetic reconnection. Recent platforms for laboratory experiments using magnetized laser-produced plasmas have opened opportunities to study these particle acceleration processes in the laboratory. Through fully kinetic particle-in-cell simulations, we investigate acceleration mechanisms in experiments with colliding magnetized laser-produced plasmas, with geometry and parameters matched to recent high-Mach number reconnection experiments with externally controlled magnetic fields. 2-D simulations demonstrate significant particle acceleration with three phases of energization: first, a “direct” Fermi acceleration driven bymore » approaching magnetized plumes; second, x-line acceleration during magnetic reconnection of anti-parallel fields; and finally, an additional Fermi energization of particles trapped in contracting and relaxing magnetic islands produced by reconnection. Furthermore, the relative effectiveness of these mechanisms depends on plasma and magnetic field parameters of the experiments.« less

Effect of relative volume on radio transmitter expulsion in subadult common carp

USGS Publications Warehouse

Penne, C.R.; Ahrens, N.L.; Summerfelt, R.C.; Pierce, C.L.

2007-01-01

Expulsion of surgically implanted radio transmitters is a problem in some fish telemetry studies. We conducted a 109-d experiment to test the hypothesis that variation in relative volume of transmitters surgically implanted in subadult common carp Cyprinus carpio would affect transmitter expulsion. We also necropsied fish at the end of the experiment to evaluate histological evidence for the mechanism of expulsion. Survival rate was high during our experiment; all control fish and 88% of the fish subjected to the implantation surgery survived. Expulsion rate was low; of the 23 fish that received transmitters and survived the experiment, only two (9%) expelled the transmitters. One of these expulsions occurred through a rupture of the incision and the other occurred via the intestine. Retained transmitters were all encapsulated by tissue, and most exhibited multiple adhesions to the intestine, gonads, and body wall. Adhesions were more numerous in fish that received larger transmitters. ?? Copyright by the American Fisheries Society 2007.

[Effects of finitude salience and social value intention on emotional responses of "kandoh" (the state of being emotionally moved) associated with sadness].

PubMed

Kato, Juri; Murata, Koji

2013-06-01

Two experiments investigated whether emotional responses of "kandoh" (the state of being emotionally moved) associated with sadness were facilitated by the factors of "finitude salience" and "social value intention". We predicted that participants who strongly intended social value would be more strongly moved by movies that portrayed social values than participants who weakly intended social value. Furthermore we predicted that this difference would increase in the finitude salience condition. In both experiments, participants assigned to the finitude salience condition subtracted the years of the person's birth from death. In the control condition, participants performed the same task in the form of simple numerical calculations. Then all participants watched a movie that portrayed family love and death in Experiment 1 (N = 88). We used another movie that described friendship and separation in Experiment 2 (N = 82). The results supported the two hypotheses that social value intention facilitated emotional responses of "kandoh" and this effect increased under finitude salience.

Mathematical modeling for control zika transmission

NASA Astrophysics Data System (ADS)

Nugraha, Edwin Setiawan; Naiborhu, Janson; Nuraini, Nuning; Ahmadin

2017-11-01

After 70 years since the zika was identified in Uganda, zika is now documented in 62 countries. In general, people infected with this disease do not experience severe conditions, but for pregnant women can cause serious problems because the zika can spread to the fetus. One result, zika can cause abnormalities in the fetal brain called microcephaly. Control and prevention are very important to reduce the spread of this disease. Here, we discussed the problem of optimal control in the model of zika transmission associated with the use of insecticide-treated nets (ITN) and indoor residual spraying (IRS). Using the approach of optimal control theory, we completed the objective function so that the infected population and its control cost are minimum. Numerically using the Forward-Backward Sweep Method, we obtained the control design of ITN and IRS as a function of time. The results show that the use of both simultaneously is more effective in reducing the population of infection than the use of ITN alone or the IRS alone.

SEMTAP (Serpentine End Match TApe program): The Easy Way to Program Your Numerically Controlled Router for the Production of SEM Joints

Treesearch

Ronald E. Coleman

1977-01-01

SEMTAP (Serpentine End Match TApe Program) is an easy and inexpensive method of programing a numerically controlled router for the manufacture of SEM (Serpentine End Matching) joints. The SEMTAP computer program allows the user to issue commands that will accurately direct a numerically controlled router along any SEM path. The user need not be a computer programer to...

Thematic analysis of blog narratives written by people with Alzheimer's disease and other dementias and care partners.

PubMed

Kannaley, Kristie; Mehta, Shreya; Yelton, Brooks; Friedman, Daniela B

2018-01-01

Limited research takes a socio-biographical approach to study the experiences and perspectives of individuals affected by Alzheimer's disease and related dementias. The purpose of this study was to thematically analyze blog narratives written by people with Alzheimer's disease and related dementia and care partners in order to increase understanding of their experiences. Nineteen blogs written by people with Alzheimer's disease and related dementia and 44 blogs written by care partners were analyzed. The first two authors utilized line-by-line open coding to analyze five posts from each group for the development of a codebook. Using NVivo software, the first author proceeded to code the remaining blogs for emergent themes and subcategories. Emergent themes included (1) effects of Alzheimer's disease and related dementia on the person with Alzheimer's disease and related dementia and/or the care partner; (2) seeing the positives; (3) feeling out of control; (4) advocacy and empowerment; (5) coping mechanisms and compensatory strategies; and (6) candid descriptions of experiences with Alzheimer's disease and related dementia. These themes also encompassed numerous subcategories that are discussed in this paper. Results from this study provide insights into the experiences of individuals affected by Alzheimer's disease and related dementia. Writers discussed several topics that are consistent with research on illness narratives of individuals with chronic diseases, including loss of identity, strategies for coping, and poignant descriptions of life with the disease. This study provides information in the form of overlapping themes from first-person perspectives of numerous individuals affected by Alzheimer's disease and related dementia. This type of data is crucial to understand the experiences of people who live with ADRD.

Ultrafast Optical Modulation of Second- and Third-Harmonic Generation from Cut-Disk-Based Metasurfaces

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

Sartorello, Giovanni; Olivier, Nicolas; Zhang, Jingjing

2016-08-17

We design and fabricate a metasurface composed of gold cut-disk resonators that exhibits a strong coherent nonlinear response. We experimentally demonstrate all-optical modulation of both second- and third-harmonic signals on a subpicosecond time scale. Pump probe experiments and numerical models show that the observed effects are due to the ultrafast response of the electronic excitations in the metal under external illumination. These effects pave the way for the development of novel active nonlinear metasurfaces with controllable and switchable coherent nonlinear response.

A New Finite-Time Observer for Nonlinear Systems: Applications to Synchronization of Lorenz-Like Systems.

PubMed

Aguilar-López, Ricardo; Mata-Machuca, Juan L

2016-01-01

This paper proposes a synchronization methodology of two chaotic oscillators under the framework of identical synchronization and master-slave configuration. The proposed methodology is based on state observer design under the frame of control theory; the observer structure provides finite-time synchronization convergence by cancelling the upper bounds of the main nonlinearities of the chaotic oscillator. The above is showed via an analysis of the dynamic of the so called synchronization error. Numerical experiments corroborate the satisfactory results of the proposed scheme.

A New Finite-Time Observer for Nonlinear Systems: Applications to Synchronization of Lorenz-Like Systems

PubMed Central

Aguilar-López, Ricardo

2016-01-01

This paper proposes a synchronization methodology of two chaotic oscillators under the framework of identical synchronization and master-slave configuration. The proposed methodology is based on state observer design under the frame of control theory; the observer structure provides finite-time synchronization convergence by cancelling the upper bounds of the main nonlinearities of the chaotic oscillator. The above is showed via an analysis of the dynamic of the so called synchronization error. Numerical experiments corroborate the satisfactory results of the proposed scheme. PMID:27738651

Bioconvection in spatially extended domains

NASA Astrophysics Data System (ADS)

Karimi, A.; Paul, M. R.

2013-05-01

We numerically explore gyrotactic bioconvection in large spatially extended domains of finite depth using parameter values from available experiments with the unicellular alga Chlamydomonas nivalis. We numerically integrate the three-dimensional, time-dependent continuum model of Pedley [J. Fluid Mech.10.1017/S0022112088002393 195, 223 (1988)] using a high-order, parallel, spectral-element approach. We explore the long-time nonlinear patterns and dynamics found for layers with an aspect ratio of 10 over a range of Rayleigh numbers. Our results yield the pattern wavelength and pattern dynamics which we compare with available theory and experimental measurement. There is good agreement for the pattern wavelength at short times between numerics, experiment, and a linear stability analysis. At long times we find that the general sequence of patterns given by the nonlinear evolution of the governing equations correspond qualitatively to what has been described experimentally. However, at long times the patterns in numerics grow to larger wavelengths, in contrast to what is observed in experiment where the wavelength is found to decrease with time.

A Validation Approach for Quasistatic Numerical/Experimental Indentation Analysis in Soft Materials Using 3D Digital Image Correlation.

PubMed

Felipe-Sesé, Luis; López-Alba, Elías; Hannemann, Benedikt; Schmeer, Sebastian; Diaz, Francisco A

2017-06-28

A quasistatic indentation numerical analysis in a round section specimen made of soft material has been performed and validated with a full field experimental technique, i.e., Digital Image Correlation 3D. The contact experiment specifically consisted of loading a 25 mm diameter rubber cylinder of up to a 5 mm indentation and then unloading. Experimental strains fields measured at the surface of the specimen during the experiment were compared with those obtained by performing two numerical analyses employing two different hyperplastic material models. The comparison was performed using an Image Decomposition new methodology that makes a direct comparison of full-field data independently of their scale or orientation possible. Numerical results show a good level of agreement with those measured during the experiments. However, since image decomposition allows for the differences to be quantified, it was observed that one of the adopted material models reproduces lower differences compared to experimental results.

A Validation Approach for Quasistatic Numerical/Experimental Indentation Analysis in Soft Materials Using 3D Digital Image Correlation

PubMed Central

Felipe-Sesé, Luis; López-Alba, Elías; Hannemann, Benedikt; Schmeer, Sebastian; Diaz, Francisco A.

2017-01-01

A quasistatic indentation numerical analysis in a round section specimen made of soft material has been performed and validated with a full field experimental technique, i.e., Digital Image Correlation 3D. The contact experiment specifically consisted of loading a 25 mm diameter rubber cylinder of up to a 5 mm indentation and then unloading. Experimental strains fields measured at the surface of the specimen during the experiment were compared with those obtained by performing two numerical analyses employing two different hyperplastic material models. The comparison was performed using an Image Decomposition new methodology that makes a direct comparison of full-field data independently of their scale or orientation possible. Numerical results show a good level of agreement with those measured during the experiments. However, since image decomposition allows for the differences to be quantified, it was observed that one of the adopted material models reproduces lower differences compared to experimental results. PMID:28773081

The numerical simulation of heat transfer during a hybrid laser-MIG welding using equivalent heat source approach

NASA Astrophysics Data System (ADS)

Bendaoud, Issam; Matteï, Simone; Cicala, Eugen; Tomashchuk, Iryna; Andrzejewski, Henri; Sallamand, Pierre; Mathieu, Alexandre; Bouchaud, Fréderic

2014-03-01

The present study is dedicated to the numerical simulation of an industrial case of hybrid laser-MIG welding of high thickness duplex steel UR2507Cu with Y-shaped chamfer geometry. It consists in simulation of heat transfer phenomena using heat equivalent source approach and implementing in finite element software COMSOL Multiphysics. A numerical exploratory designs method is used to identify the heat sources parameters in order to obtain a minimal required difference between the numerical results and the experiment which are the shape of the welded zone and the temperature evolution in different locations. The obtained results were found in good correspondence with experiment, both for melted zone shape and thermal history.

LACIS-T - A moist air wind tunnel for investigating the interactions between cloud microphysics and turbulence

NASA Astrophysics Data System (ADS)

Niedermeier, Dennis; Voigtländer, Jens; Siebert, Holger; Desai, Neel; Shaw, Raymond; Chang, Kelken; Krueger, Steven; Schumacher, Jörg; Stratmann, Frank

2017-11-01

Turbulence - cloud droplet interaction processes have been investigated primarily through numerical simulation and field measurements over the last ten years. However, only in the laboratory we can be confident in our knowledge of initial and boundary conditions, and are able to measure for extended times under statistically stationary and repeatable conditions. Therefore, the newly built turbulent wind tunnel LACIS-T (Turbulent Leipzig Aerosol Cloud Interaction Simulator) is an ideal facility for pursuing mechanistic understanding of these processes. Within the tunnel we are able to adjust precisely controlled turbulent temperature and humidity fields so as to achieve supersaturation levels allowing for detailed investigations of the interactions between cloud microphysical processes (e.g., cloud droplet activation) and the turbulent flow, under well-defined and reproducible laboratory conditions. We will present the fundamental operating principle, first results from ongoing characterization efforts, numerical simulations as well as first droplet activation experiments.

Sampling-free Bayesian inversion with adaptive hierarchical tensor representations

NASA Astrophysics Data System (ADS)

Eigel, Martin; Marschall, Manuel; Schneider, Reinhold

2018-03-01

A sampling-free approach to Bayesian inversion with an explicit polynomial representation of the parameter densities is developed, based on an affine-parametric representation of a linear forward model. This becomes feasible due to the complete treatment in function spaces, which requires an efficient model reduction technique for numerical computations. The advocated perspective yields the crucial benefit that error bounds can be derived for all occuring approximations, leading to provable convergence subject to the discretization parameters. Moreover, it enables a fully adaptive a posteriori control with automatic problem-dependent adjustments of the employed discretizations. The method is discussed in the context of modern hierarchical tensor representations, which are used for the evaluation of a random PDE (the forward model) and the subsequent high-dimensional quadrature of the log-likelihood, alleviating the ‘curse of dimensionality’. Numerical experiments demonstrate the performance and confirm the theoretical results.

On the buckling of elastic rings by external confinement.

PubMed

Hazel, Andrew L; Mullin, Tom

2017-05-13

We report the results of an experimental and numerical investigation into the buckling of thin elastic rings confined within containers of circular or regular polygonal cross section. The rings float on the surface of water held in the container and controlled removal of the fluid increases the confinement of the ring. The increased compressive forces can cause the ring to buckle into a variety of shapes. For the circular container, finite perturbations are required to induce buckling, whereas in polygonal containers the buckling occurs through a linear instability that is closely related to the canonical Euler column buckling. A model based on Kirchhoff-Love beam theory is developed and solved numerically, showing good agreement with the experiments and revealing that in polygons increasing the number of sides means that buckling occurs at reduced levels of confinement.This article is part of the themed issue 'Patterning through instabilities in complex media: theory and applications.' © 2017 The Author(s).

On the prediction of spray angle of liquid-liquid pintle injectors

NASA Astrophysics Data System (ADS)

Cheng, Peng; Li, Qinglian; Xu, Shun; Kang, Zhongtao

2017-09-01

The pintle injector is famous for its capability of deep throttling and low cost. However, the pintle injector has been seldom investigated. To get a good prediction of the spray angle of liquid-liquid pintle injectors, theoretical analysis, numerical simulations and experiments were conducted. Under the hypothesis of incompressible and inviscid flow, a spray angle formula was deduced from the continuity and momentum equations based on a control volume analysis. The formula was then validated by numerical and experimental data. The results indicates that both geometric and injection parameters affect the total momentum ratio (TMR) and then influence the spray angle formed by liquid-liquid pintle injectors. TMR is the pivotal non-dimensional number that dominates the spray angle. Compared with gas-gas pintle injectors, spray angle formed by liquid-liquid injectors is larger, which benefits from the local high pressure zone near the pintle wall caused by the impingement of radial and axial sheets.

Models of volcanic eruption hazards

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

Wohletz, K.H.

1992-01-01

Volcanic eruptions pose an ever present but poorly constrained hazard to life and property for geothermal installations in volcanic areas. Because eruptions occur sporadically and may limit field access, quantitative and systematic field studies of eruptions are difficult to complete. Circumventing this difficulty, laboratory models and numerical simulations are pivotal in building our understanding of eruptions. For example, the results of fuel-coolant interaction experiments show that magma-water interaction controls many eruption styles. Applying these results, increasing numbers of field studies now document and interpret the role of external water eruptions. Similarly, numerical simulations solve the fundamental physics of high-speed fluidmore » flow and give quantitative predictions that elucidate the complexities of pyroclastic flows and surges. A primary goal of these models is to guide geologists in searching for critical field relationships and making their interpretations. Coupled with field work, modeling is beginning to allow more quantitative and predictive volcanic hazard assessments.« less

Temporal and Spatio-Temporal Dynamic Instabilities: Novel Computational and Experimental approaches

NASA Astrophysics Data System (ADS)

Doedel, Eusebius J.; Panayotaros, Panayotis; Lambruschini, Carlos L. Pando

2016-11-01

This special issue contains a concise account of significant research results presented at the international workshop on Advanced Computational and Experimental Techniques in Nonlinear Dynamics, which was held in Cusco, Peru in August 2015. The meeting gathered leading experts, as well as new researchers, who have contributed to different aspects of Nonlinear Dynamics. Particularly significant was the presence of many active scientists from Latin America. The topics covered in this special issue range from advanced numerical techniques to novel physical experiments, and reflect the present state of the art in several areas of Nonlinear Dynamics. It contains seven review articles, followed by twenty-one regular papers that are organized in five categories, namely (1) Nonlinear Evolution Equations and Applications, (2) Numerical Continuation in Self-sustained Oscillators, (3) Synchronization, Control and Data Analysis, (4) Hamiltonian Systems, and (5) Scaling Properties in Maps.

On the buckling of elastic rings by external confinement

PubMed Central

Hazel, Andrew L.

2017-01-01

We report the results of an experimental and numerical investigation into the buckling of thin elastic rings confined within containers of circular or regular polygonal cross section. The rings float on the surface of water held in the container and controlled removal of the fluid increases the confinement of the ring. The increased compressive forces can cause the ring to buckle into a variety of shapes. For the circular container, finite perturbations are required to induce buckling, whereas in polygonal containers the buckling occurs through a linear instability that is closely related to the canonical Euler column buckling. A model based on Kirchhoff–Love beam theory is developed and solved numerically, showing good agreement with the experiments and revealing that in polygons increasing the number of sides means that buckling occurs at reduced levels of confinement. This article is part of the themed issue ‘Patterning through instabilities in complex media: theory and applications.’ PMID:28373386

Models of volcanic eruption hazards

NASA Astrophysics Data System (ADS)

Wohletz, K. H.

Volcanic eruptions pose an ever present but poorly constrained hazard to life and property for geothermal installations in volcanic areas. Because eruptions occur sporadically and may limit field access, quantitative and systematic field studies of eruptions are difficult to complete. Circumventing this difficulty, laboratory models and numerical simulations are pivotal in building our understanding of eruptions. For example, the results of fuel-coolant interaction experiments show that magma-water interaction controls many eruption styles. Applying these results, increasing numbers of field studies now document and interpret the role of external water eruptions. Similarly, numerical simulations solve the fundamental physics of high-speed fluid flow and give quantitative predictions that elucidate the complexities of pyroclastic flows and surges. A primary goal of these models is to guide geologists in searching for critical field relationships and making their interpretations. Coupled with field work, modeling is beginning to allow more quantitative and predictive volcanic hazard assessments.

Finger-Based Numerical Skills Link Fine Motor Skills to Numerical Development in Preschoolers.

PubMed

Suggate, Sebastian; Stoeger, Heidrun; Fischer, Ursula

2017-12-01

Previous studies investigating the association between fine-motor skills (FMS) and mathematical skills have lacked specificity. In this study, we test whether an FMS link to numerical skills is due to the involvement of finger representations in early mathematics. We gave 81 pre-schoolers (mean age of 4 years, 9 months) a set of FMS measures and numerical tasks with and without a specific finger focus. Additionally, we used receptive vocabulary and chronological age as control measures. FMS linked more closely to finger-based than to nonfinger-based numerical skills even after accounting for the control variables. Moreover, the relationship between FMS and numerical skill was entirely mediated by finger-based numerical skills. We concluded that FMS are closely related to early numerical skill development through finger-based numerical counting that aids the acquisition of mathematical mental representations.

Language and number: a bilingual training study.

PubMed

Spelke, E S; Tsivkin, S

2001-01-01

Three experiments investigated the role of a specific language in human representations of number. Russian-English bilingual college students were taught new numerical operations (Experiment 1), new arithmetic equations (Experiments 1 and 2), or new geographical or historical facts involving numerical or non-numerical information (Experiment 3). After learning a set of items in each of their two languages, subjects were tested for knowledge of those items, and new items, in both languages. In all the studies, subjects retrieved information about exact numbers more effectively in the language of training, and they solved trained problems more effectively than untrained problems. In contrast, subjects retrieved information about approximate numbers and non-numerical facts with equal efficiency in their two languages, and their training on approximate number facts generalized to new facts of the same type. These findings suggest that a specific, natural language contributes to the representation of large, exact numbers but not to the approximate number representations that humans share with other mammals. Language appears to play a role in learning about exact numbers in a variety of contexts, a finding with implications for practice in bilingual education. The findings prompt more general speculations about the role of language in the development of specifically human cognitive abilities.