Science.gov

Sample records for controlled spatial separation

  1. Controlled spatial separation of spins and coherent dynamics in spin-orbit-coupled nanostructures

    NASA Astrophysics Data System (ADS)

    Lo, Shun-Tsung; Chen, Chin-Hung; Fan, Ju-Chun; Smith, L. W.; Creeth, G. L.; Chang, Che-Wei; Pepper, M.; Griffiths, J. P.; Farrer, I.; Beere, H. E.; Jones, G. A. C.; Ritchie, D. A.; Chen, Tse-Ming

    2017-07-01

    The spatial separation of electron spins followed by the control of their individual spin dynamics has recently emerged as an essential ingredient in many proposals for spin-based technologies because it would enable both of the two spin species to be simultaneously utilized, distinct from most of the current spintronic studies and technologies wherein only one spin species could be handled at a time. Here we demonstrate that the spatial spin splitting of a coherent beam of electrons can be achieved and controlled using the interplay between an external magnetic field and Rashba spin-orbit interaction in semiconductor nanostructures. The technique of transverse magnetic focusing is used to detect this spin separation. More notably, our ability to engineer the spin-orbit interactions enables us to simultaneously manipulate and probe the coherent spin dynamics of both spin species and hence their correlation, which could open a route towards spintronics and spin-based quantum information processing.

  2. Controlled spatial separation of spins and coherent dynamics in spin-orbit-coupled nanostructures

    PubMed Central

    Lo, Shun-Tsung; Chen, Chin-Hung; Fan, Ju-Chun; Smith, L. W.; Creeth, G. L.; Chang, Che-Wei; Pepper, M.; Griffiths, J. P.; Farrer, I.; Beere, H. E.; Jones, G. A. C.; Ritchie, D. A.; Chen, Tse-Ming

    2017-01-01

    The spatial separation of electron spins followed by the control of their individual spin dynamics has recently emerged as an essential ingredient in many proposals for spin-based technologies because it would enable both of the two spin species to be simultaneously utilized, distinct from most of the current spintronic studies and technologies wherein only one spin species could be handled at a time. Here we demonstrate that the spatial spin splitting of a coherent beam of electrons can be achieved and controlled using the interplay between an external magnetic field and Rashba spin–orbit interaction in semiconductor nanostructures. The technique of transverse magnetic focusing is used to detect this spin separation. More notably, our ability to engineer the spin–orbit interactions enables us to simultaneously manipulate and probe the coherent spin dynamics of both spin species and hence their correlation, which could open a route towards spintronics and spin-based quantum information processing. PMID:28691707

  3. Controlled spatial separation of spins and coherent dynamics in spin-orbit-coupled nanostructures.

    PubMed

    Lo, Shun-Tsung; Chen, Chin-Hung; Fan, Ju-Chun; Smith, L W; Creeth, G L; Chang, Che-Wei; Pepper, M; Griffiths, J P; Farrer, I; Beere, H E; Jones, G A C; Ritchie, D A; Chen, Tse-Ming

    2017-07-10

    The spatial separation of electron spins followed by the control of their individual spin dynamics has recently emerged as an essential ingredient in many proposals for spin-based technologies because it would enable both of the two spin species to be simultaneously utilized, distinct from most of the current spintronic studies and technologies wherein only one spin species could be handled at a time. Here we demonstrate that the spatial spin splitting of a coherent beam of electrons can be achieved and controlled using the interplay between an external magnetic field and Rashba spin-orbit interaction in semiconductor nanostructures. The technique of transverse magnetic focusing is used to detect this spin separation. More notably, our ability to engineer the spin-orbit interactions enables us to simultaneously manipulate and probe the coherent spin dynamics of both spin species and hence their correlation, which could open a route towards spintronics and spin-based quantum information processing.

  4. Spatially Distributed Forcing for Boundary Layer Separation Control on a Wall Mounted Hump

    NASA Astrophysics Data System (ADS)

    Borgmann, David; Little, Jesse; Woszidlo, Rene

    2016-11-01

    Numerous successful efforts on controlling flow separation have been demonstrated using spatially distributed actuators. These include both steady and unsteady forcing from discrete locations in the vicinity of separation. Despite this, there are many open questions on the actual flow control mechanism. A canonical hump model is used to investigate these physics in a subsonic wind tunnel. Reynolds number independence is achieved above 0.72 ×106 and testing is performed up to 2.2 ×106. The efficacy of discrete steady jets is studied as a function of spacing, momentum coefficient, velocity ratio and mass flux. Highly-resolved surface pressure data for the controlled flow are compared to an inviscid solution establishing a figure of merit. Results indicate the inviscid limit is reached for a momentum coefficient of 1% with actuator spacing of 0.5% span. A comparison of steady discrete jets with sweeping jets actuators of equivalent cross-sectional area is undertaken. Surface flow visualization and PIV are employed to extract detailed information on the baseline and controlled flow field. This importance of establishing critical baseline features is also discussed with respect to establishing proper boundary conditions for accompanying numerical simulations. Supported by The Boeing Company.

  5. Controlling Separation in Turbomachines

    NASA Technical Reports Server (NTRS)

    Evans, Simon; Himmel, Christoph; Power, Bronwyn; Wakelam, Christian; Xu, Liping; Hynes, Tom; Hodson, Howard

    2010-01-01

    Four examples of flow control: 1) Passive control of LP turbine blades (Laminar separation control). 2) Aspiration of a conventional axial compressor blade (Turbulent separation control). 3) Compressor blade designed for aspiration (Turbulent separation control). 4.Control of intakes in crosswinds (Turbulent separation control).

  6. Controllably releasing long-lived quantum memory for photonic polarization qubit into multiple spatially-separate photonic channels

    NASA Astrophysics Data System (ADS)

    Chen, Lirong; Xu, Zhongxiao; Zeng, Weiqing; Wen, Yafei; Li, Shujing; Wang, Hai

    2016-09-01

    We report an experiment in which long-lived quantum memories for photonic polarization qubits (PPQs) are controllably released into any one of multiple spatially-separate channels. The PPQs are implemented with an arbitrarily-polarized coherent signal light pulses at the single-photon level and are stored in cold atoms by means of electromagnetic-induced-transparency scheme. Reading laser pulses propagating along the direction at a small angle relative to quantum axis are applied to release the stored PPQs into an output channel. By changing the propagating directions of the read laser beam, we controllably release the retrieved PPQs into 7 different photonic output channels, respectively. At a storage time of δt = 5 μs, the least quantum-process fidelity in 7 different output channels is ~89%. At one of the output channels, the measured maximum quantum-process fidelity for the PPQs is 94.2% at storage time of δt = 0.85 ms. At storage time of 6 ms, the quantum-process fidelity is still beyond the bound of 78% to violate the Bell’s inequality. The demonstrated controllable release of the stored PPQs may extend the capabilities of the quantum information storage technique.

  7. Controllably releasing long-lived quantum memory for photonic polarization qubit into multiple spatially-separate photonic channels

    PubMed Central

    Chen, Lirong; Xu, Zhongxiao; Zeng, Weiqing; Wen, Yafei; Li, Shujing; Wang, Hai

    2016-01-01

    We report an experiment in which long-lived quantum memories for photonic polarization qubits (PPQs) are controllably released into any one of multiple spatially-separate channels. The PPQs are implemented with an arbitrarily-polarized coherent signal light pulses at the single-photon level and are stored in cold atoms by means of electromagnetic-induced-transparency scheme. Reading laser pulses propagating along the direction at a small angle relative to quantum axis are applied to release the stored PPQs into an output channel. By changing the propagating directions of the read laser beam, we controllably release the retrieved PPQs into 7 different photonic output channels, respectively. At a storage time of δt = 5 μs, the least quantum-process fidelity in 7 different output channels is ~89%. At one of the output channels, the measured maximum quantum-process fidelity for the PPQs is 94.2% at storage time of δt = 0.85 ms. At storage time of 6 ms, the quantum-process fidelity is still beyond the bound of 78% to violate the Bell’s inequality. The demonstrated controllable release of the stored PPQs may extend the capabilities of the quantum information storage technique. PMID:27667262

  8. On-line feedback control of human visually guided slow ramp tracking: effects of spatial separation of visual cues.

    PubMed

    Reed, Daniel W; Liu, Xuguang; Miall, R Christopher

    2003-03-06

    Visual feedback control of tracking movements is dependent upon a visual comparison of the guiding target and moving limb positions but the human fovea greatly restricts the area of high acuity vision. The effect of vertically separating the target and movement cues in a slow movement task is investigated. Subjects track a slow constant velocity target in the horizontal plane with wrist flexion controlled cursor movements. The effects of changes in the vertical distance between the two cues upon tracking performance were observed. When both cursors were at the same level, tracking was most accurate but showed significant intermittency around 2 Hz in frequency. Increased separation of cues reduced significantly both accuracy and intermittency; tracking was smoother but less accurate. Thus, feedback control is dependent upon the efficiency of positional comparison and hence becomes less effective as the cue separation increases. These results also support previous studies suggesting each cue makes an equal contribution to visuomotor feedback control, each acting as a reference to the other.

  9. Fusion of spatially separated vowel formant cues.

    PubMed

    Takanen, Marko; Raitio, Tuomo; Santala, Olli; Alku, Paavo; Pulkki, Ville

    2013-12-01

    Previous studies on fusion in speech perception have demonstrated the ability of the human auditory system to group separate components of speech-like sounds together and consequently to enable the identification of speech despite the spatial separation between the components. Typically, the spatial separation has been implemented using headphone reproduction where the different components evoke auditory images at different lateral positions. In the present study, a multichannel loudspeaker system was used to investigate whether the correct vowel is identified and whether two auditory events are perceived when a noise-excited vowel is divided into two components that are spatially separated. The two components consisted of the even and odd formants. Both the amount of spatial separation between the components and the directions of the components were varied. Neither the spatial separation nor the directions of the components affected the vowel identification. Interestingly, an additional auditory event not associated with any vowel was perceived at the same time when the components were presented symmetrically in front of the listener. In such scenarios, the vowel was perceived from the direction of the odd formant components.

  10. Differential effects of osmotic and SSR149415 challenges in maternally separated and control rats: the role of vasopressin on spatial learning.

    PubMed

    Hernandez, Vito S; Ruíz-Velazco, Silvia; Zhang, Limei

    2012-10-24

    Maternal separation (MS) has been demonstrated to up-regulate the hypothalamic vasopressin (VP) system. Intracerebrally released VP has been demonstrated to affect several types of animal behaviour, such as active/passive avoidance, social recognition, and learning and memory. However, the role of VP in spatial learning remains unclear. In the present study, we investigated the effects of an osmotic challenge and a V1b receptor-specific (V1bR) antagonist, SSR149415, on spatial learning of maternally separated and animal facility reared (AFR) adult male Wistar rats. The osmotic challenge was applied by injecting a hypertonic saline solution, 1h before the Morris water maze test (MWM). V1bR antagonist SSR149415 (5mg/kg) was injected i.p. twice (1h and 30 min) previous to the MWM. A combined treatment with both osmotic challenge and the SSR149415 was applied to the third group whereas rats for basal condition were injected with isotonic saline. Under basal condition no differences between AFR and MS groups were observed. MS rats showed severe impairment during the MWM after the osmotic challenge, but not after the administration of SSR149415. For AFR rats, the opposite phenomenon was observed. The joint application of SSR149415 and osmotic challenge restored the spatial learning ability for both groups. The differential impairment produced by osmotic stress-induced up-regulation and SSR149415 induced V1bR blockage in MS and control rats suggested that VP involvement in spatial learning depends on the individual intrinsic ligand-receptor functional state.

  11. Improved spatial separation of neutral molecules

    NASA Astrophysics Data System (ADS)

    Kienitz, Jens S.; Długołecki, Karol; Trippel, Sebastian; Küpper, Jochen

    2017-07-01

    We have developed and experimentally demonstrated an improved electrostatic deflector for the spatial separation of molecules according to their dipole-moment-to-mass ratio. The device features a very open structure that allows for significantly stronger electric fields as well as for stronger deflection without molecules crashing into the device itself. We have demonstrated its performance using the prototypical carbonyl sulfide molecule and we discuss opportunities regarding improved quantum-state-selectivity for complex molecules and the deflection of unpolar molecules.

  12. Running enhances spatial pattern separation in mice

    PubMed Central

    Creer, David J.; Romberg, Carola; Saksida, Lisa M.; van Praag, Henriette; Bussey, Timothy J.

    2010-01-01

    Increasing evidence suggests that regular exercise improves brain health and promotes synaptic plasticity and hippocampal neurogenesis. Exercise improves learning, but specific mechanisms of information processing influenced by physical activity are unknown. Here, we report that voluntary running enhanced the ability of adult (3 months old) male C57BL/6 mice to discriminate between the locations of two adjacent identical stimuli. Improved spatial pattern separation in adult runners was tightly correlated with increased neurogenesis. In contrast, very aged (22 months old) mice had impaired spatial discrimination and low basal cell genesis that was refractory to running. These findings suggest that the addition of newly born neurons may bolster dentate gyrus-mediated encoding of fine spatial distinctions. PMID:20133882

  13. Aging affects spatial reconstruction more than spatial pattern separation performance even after extended practice.

    PubMed

    Clark, Rachel; Tahan, Asli C; Watson, Patrick D; Severson, Joan; Cohen, Neal J; Voss, Michelle

    2017-03-21

    Although the hippocampus experiences age-related anatomical and functional deterioration, the effects of aging vary across hippocampal-dependent cognitive processes. In particular, whether or not the hippocampus is known to be required for a spatial memory process is not an accurate predictor on its own of whether aging will affect performance. Therefore, the primary objective of this study was to compare the effects of healthy aging on a test of spatial pattern separation and a test of spatial relational processing, which are two aspects of spatial memory that uniquely emphasize the use of multiple hippocampal-dependent processes. Spatial pattern separation supports spatial memory by preserving unique representations for distinct locations. Spatial relational processing forms relational representations of objects to locations or between objects and other objects in space. To test our primary objective, 30 young (18-30 years; 21F) and 30 older participants (60-80 years; 21F) all completed a spatial pattern separation task and a task designed to require spatial relational processing through spatial reconstruction. To ensure aging effects were not due to inadequate time to develop optimal strategies or become comfortable with the testing devices, a subset of participants had extended practice across three sessions on each task. Results showed that older adults performed more poorly than young on the spatial reconstruction task that emphasized the use of spatial relational processing, and that age effects persisted even after controlling for pattern separation performance. Further, older adults performed more poorly on spatial reconstruction than young adults even after three testing sessions each separated by 7-10 days, suggesting effects of aging are resistant to extended practice and likely reflect genuine decline in hippocampal memory abilities.

  14. ISOTOPE SEPARATING APPARATUS CONTROL

    DOEpatents

    Barnes, S.W.

    1959-08-25

    An improved isotope separating apparatus of the electromagnetic type, commonly referred to as a calutron, is described. Improvements in detecting and maintaining optimum position and focus of the ion beam are given. The calutron collector is provided with an additional electrode insulated from and positioned between the collecting pockets. The ion beams are properly positioned and focused until the deionizing current which flows from ground to this additional electrode ts a minimum.

  15. Alleviation of parasitic reactions for III-nitride epitaxy in MOCVD with a spatial separated source delivery method by controlling the main reaction type

    NASA Astrophysics Data System (ADS)

    Yang, Haojun; Wu, Haiyan; Hu, Wei; Ma, Ziguang; Jiang, Yang; Wang, Wenxin; Jia, Haiqiang; Zhou, Junming; Chen, Hong

    2017-05-01

    A spatial separated source delivery (SSSD) method has been proposed to alleviate parasitic reactions between group III precursors and ammonia (NH3) in gas phase using the MOCVD. AlGaN alloys and GaN films grown on sapphire has been prepared with this method. The influence of parasitic reactions on the qualities and properties of AlGaN and GaN films is investigated in detail. High-resolution X-ray diffraction (HRXRD) measurements show that the aluminum composition in materials rises up close to the ratio of trimethylaluminum (TMAl) supply when the supply ratio of TMAl is 0.2, 0.3 and 0.4 respectively, which demonstrates that the parasitic reactions are suppressed mostly. In-situ monitor reflectometer spectra for GaN show that the growth rate gets a 20% increase in comparison with materials grown without the SSSD method. Subsequently, the relationship between parasitic reactions and other reaction types are elucidated. The effect of the SSSD method on parasitic reactions is also systematically studied. Reactions are controlled to change from combination reactions to pyrolysis reactions and surface reactions with the SSSD method. A 2-inch GaN/AlGaN heterostructure is also prepared to evaluate the uniform electrical properties grown with this method. The result indicates that the SSSD method provides a better way to prepare high-quality III-nitride materials, especially for AlN and related alloys.

  16. Electron beam control for barely separated beams

    DOEpatents

    Douglas, David R.; Ament, Lucas J. P.

    2017-04-18

    A method for achieving independent control of multiple beams in close proximity to one another, such as in a multi-pass accelerator where coaxial beams are at different energies, but moving on a common axis, and need to be split into spatially separated beams for efficient recirculation transport. The method for independent control includes placing a magnet arrangement in the path of the barely separated beams with the magnet arrangement including at least two multipole magnets spaced closely together and having a multipole distribution including at least one odd multipole and one even multipole. The magnetic fields are then tuned to cancel out for a first of the barely separated beams to allow independent control of the second beam with common magnets. The magnetic fields may be tuned to cancel out either the dipole component or tuned to cancel out the quadrupole component in order to independently control the separate beams.

  17. Spatial valley separation in strained graphene pn junction

    NASA Astrophysics Data System (ADS)

    Tian, HongYu; Wang, Jun

    2017-09-01

    Valleytronics in analogy to spintronics aims to use the electron valley degree of freedom to carry and manipulate information, and one of urgent tasks in this field is to generate valley-polarized electrons. In this work, we propose using the electron focusing effect in a strained graphene pn junction to separate valleys spatially through a beam of valley-unpolarized electrons, since the strain-induced pseudo-gauge potentials are opposite for K and K^\\prime valleys and severely affect the trajectories of K and K^\\prime electron propagation. We numerically simulate this valley-separated Veselago lens effect in a lattice model and demonstrate that pseudo-gauge potentials can efficiently control valley separation patterns.

  18. Work control in separations facilities

    SciTech Connect

    Olson, L.D.

    1990-01-01

    The topic addressed in this technical review is the development and implementation of a work control program in one of the chemical separations facilities at the Savannah River Site (SRS) in Aiken, SC. This program will be used as a pilot for the Nuclear Materials Processing Division at the site. The SRS Work Control Pilot program is based on the Institute of Nuclear Power Operations (INPO) good practices and guidelines for the conduct of maintenance and complies with SRS quality assurance and DOE orders on maintenance management. The program follows a ten-step process for control of maintenance and maintenance-related activities in a chemical separations facility. The program took the existing maintenance planning and scheduling system and upgraded it to comply with all INPO work control and related guidelines for histories, post-maintenance testing and scheduling. The development process of adapting a nuclear-related- based plan to a batch/continuous chemical separations plant was a challenge. There were many opportunities to develop improvements in performance while being creative and realistic in applying reactor maintenance technology to chemical plant maintenance. This pilot program for work control in a nonreactor nuclear facility will provide valuable information for applying a controlled maintenance process to a multiphase chemical operating plant environment.

  19. Work control in separations facilities

    SciTech Connect

    Olson, L.D.

    1990-12-31

    The topic addressed in this technical review is the development and implementation of a work control program in one of the chemical separations facilities at the Savannah River Site (SRS) in Aiken, SC. This program will be used as a pilot for the Nuclear Materials Processing Division at the site. The SRS Work Control Pilot program is based on the Institute of Nuclear Power Operations (INPO) good practices and guidelines for the conduct of maintenance and complies with SRS quality assurance and DOE orders on maintenance management. The program follows a ten-step process for control of maintenance and maintenance-related activities in a chemical separations facility. The program took the existing maintenance planning and scheduling system and upgraded it to comply with all INPO work control and related guidelines for histories, post-maintenance testing and scheduling. The development process of adapting a nuclear-related- based plan to a batch/continuous chemical separations plant was a challenge. There were many opportunities to develop improvements in performance while being creative and realistic in applying reactor maintenance technology to chemical plant maintenance. This pilot program for work control in a nonreactor nuclear facility will provide valuable information for applying a controlled maintenance process to a multiphase chemical operating plant environment.

  20. Spatial interference from well-separated split condensates

    SciTech Connect

    Zawadzki, M. E.; Griffin, P. F.; Riis, E.; Arnold, A. S.

    2010-04-15

    We use magnetic levitation and a variable-separation dual optical plug to obtain clear spatial interference between two condensates axially separated by up to 0.25 mm - the largest separation observed with this kind of interferometer. Clear planar fringes are observed using standard (i.e., nontomographic) resonant absorption imaging. The effect of a weak inverted parabola potential on fringe separation is observed and agrees well with theory.

  1. Interaction dynamics of spatially separated cavitation bubbles in water.

    PubMed

    Tinne, Nadine; Schumacher, Silvia; Nuzzo, Valeria; Arnold, Cord L; Lubatschowski, Holger; Ripken, Tammo

    2010-01-01

    We present a high-speed photographic analysis of the interaction of cavitation bubbles generated in two spatially separated regions by femtosecond laser-induced optical breakdown in water. Depending on the relative energies of the femtosecond laser pulses and their spatial separation, different kinds of interactions, such as a flattening and deformation of the bubbles, asymmetric water flows, and jet formation were observed. The results presented have a strong impact on understanding and optimizing the cutting effect of modern femtosecond lasers with high repetition rates (>1 MHz).

  2. Interaction dynamics of spatially separated cavitation bubbles in water

    NASA Astrophysics Data System (ADS)

    Tinne, Nadine; Schumacher, Silvia; Nuzzo, Valeria; Arnold, Cord L.; Lubatschowski, Holger; Ripken, Tammo

    2010-11-01

    We present a high-speed photographic analysis of the interaction of cavitation bubbles generated in two spatially separated regions by femtosecond laser-induced optical breakdown in water. Depending on the relative energies of the femtosecond laser pulses and their spatial separation, different kinds of interactions, such as a flattening and deformation of the bubbles, asymmetric water flows, and jet formation were observed. The results presented have a strong impact on understanding and optimizing the cutting effect of modern femtosecond lasers with high repetition rates (>1 MHz).

  3. Perceiving the coherent movements of spatially-separated features

    NASA Technical Reports Server (NTRS)

    Mowafy, Lyn; Lappin, Joseph S.

    1991-01-01

    When a partially-occluded object is represented in an image, it is defined by a set of spatially-separated features that may be registered at different spatial scales. To understand the image, human vision must organize these fragmented optical features into common and distinct object surfaces. Although the common fate of moving features often is considered a primary source of reliable information for image segmentation, little is known of the visual system's capacity to discriminate the coherent relative movements of spatially-separated features. In a series of experiments, observers viewed elements whose movements were correlated (direction and magnitude) or were uncorrelated. Our results indicate that observers can discriminate the two types of movement about as well as they can detect any movement at all. Moreover, the ability to perceive coherent movements is maintained under a variety of conditions including differences in the elements' spatial frequency content, spatial position and contrast, and temporal phase shifts between the spatially-correlated displacements. These results suggest that coherent relative motion may be a fundamental source of information exploited by vision, despite considerable variability in the spatial and temporal characteristics of the individual features.

  4. Porous polymers by controlling phase separation during vapor deposition polymerization.

    PubMed

    Tao, Ran; Anthamatten, Mitchell

    2013-11-01

    A template-free method is described to fabricate continuous-phase, porous polymer films by simultaneous phase separation during vapor deposition polymerization. The technique involves concurrent polymerization, crosslinking, and phase separation of condensed species and reaction products. Deposited films form open-cell, macroporous structures consisting of crosslinked and glassy poly(glycidyl methacrylate). By limiting phase separation during vapor phase deposition, spatially dependent morphologies, such as layered morphologies, can be grown. Results show that combining vapor deposition polymerization with phase separation establishes morphological control, which may be applied to applications including cellular scaffolds, thin cushions and vibration dampers, and membranes for separations.

  5. Blind separation of incoherent and spatially disjoint sound sources

    NASA Astrophysics Data System (ADS)

    Dong, Bin; Antoni, Jérôme; Pereira, Antonio; Kellermann, Walter

    2016-11-01

    Blind separation of sound sources aims at reconstructing the individual sources which contribute to the overall radiation of an acoustical field. The challenge is to reach this goal using distant measurements when all sources are operating concurrently. The working assumption is usually that the sources of interest are incoherent - i.e. statistically orthogonal - so that their separation can be approached by decorrelating a set of simultaneous measurements, which amounts to diagonalizing the cross-spectral matrix. Principal Component Analysis (PCA) is traditionally used to this end. This paper reports two new findings in this context. First, a sufficient condition is established under which "virtual" sources returned by PCA coincide with true sources; it stipulates that the sources of interest should be not only incoherent but also spatially orthogonal. A particular case of this instance is met by spatially disjoint sources - i.e. with non-overlapping support sets. Second, based on this finding, a criterion that enforces both statistical and spatial orthogonality is proposed to blindly separate incoherent sound sources which radiate from disjoint domains. This criterion can be easily incorporated into acoustic imaging algorithms such as beamforming or acoustical holography to identify sound sources of different origins. The proposed methodology is validated on laboratory experiments. In particular, the separation of aeroacoustic sources is demonstrated in a wind tunnel.

  6. Three dimensional spatial separation of cells in response to microtopography.

    PubMed

    Leclerc, Alexandre; Tremblay, Dominique; Hadjiantoniou, Sebastian; Bukoreshtliev, Nickolay V; Rogowski, Jacob L; Godin, Michel; Pelling, Andrew E

    2013-11-01

    Cellular organization, migration and proliferation in three-dimensions play a critical role in numerous physiological and pathological processes. Nano- and micro-fabrication approaches have demonstrated that nano- and micro-scale topographies of the cellular microenvironment directly impact organization, migration and proliferation. In this study, we investigated these dynamics of two cell types (NIH3T3 fibroblast and MDCK epithelial cells) in response to microscale grooves whose dimensions exceed typical cell sizes. Our results demonstrate that fibroblasts display a clear preference for proliferating along groove ridges whereas epithelial cells preferentially proliferate in the grooves. Importantly, these cell-type dependent behaviours were also maintained when in co-culture. We show that it is possible to spatially separate a mixed suspension of two cell types by allowing them to migrate and proliferate on a substrate with engineered microtopographies. This ability may have important implications for investigating the mechanisms that facilitate cellular topographic sensing. Moreover, our results may provide insights towards the controlled development of complex three-dimensional multi-cellular constructs.

  7. Robust creation of entanglement between ions in spatially separate cavities.

    PubMed

    Browne, Daniel E; Plenio, Martin B; Huelga, Susana F

    2003-08-08

    We present a protocol that allows the generation of a maximally entangled state between individual atoms held in spatially separate cavities. Assuming perfect detectors and neglecting spontaneous emission from the atoms, the resulting idealized scheme is deterministic. Under more realistic conditions, when the atom-cavity interaction departs from the strong coupling regime, and considering imperfect detectors, we show that the scheme is robust against experimental inefficiencies and yields probabilistic entanglement of very high fidelity.

  8. Cyclone separator having boundary layer turbulence control

    DOEpatents

    Krishna, Coimbatore R.; Milau, Julius S.

    1985-01-01

    A cyclone separator including boundary layer turbulence control that is operable to prevent undue build-up of particulate material at selected critical areas on the separator walls, by selectively varying the fluid pressure at those areas to maintain the momentum of the vortex, thereby preventing particulate material from inducing turbulence in the boundary layer of the vortical fluid flow through the separator.

  9. Neuropsychological evidence for separating components of visuo-spatial working memory.

    PubMed

    Darling, S; Della Sala, S; Logie, R H; Cantagallo, A

    2006-02-01

    There is increasing evidence to support the idea that visuo-spatial working memory can be segregated into separate cognitive subsystems. However, the nature of these systems remains unclear. In this paper we report data from two brain injured patients suggesting that information about visual appearance is retained in a different subsystem from information about spatial location, and that this differential processing can be observed when the style of presentation (sequential or simultaneous) is controlled.

  10. Response of axisymmetric separated flow to its spatially localized perturbation

    NASA Astrophysics Data System (ADS)

    Dovgal, A. V.; Zanin, B. Yu.; Sorokin, A. M.

    2016-11-01

    The flow past an axisymmetric body with laminar boundary-layer separation in a low-velocity air stream has been studied. The hot-wire technique was employed to identify the variation of velocity field induced by a local stationary perturbation of separation region at the stern of the experimental model. A large-scale influence upon the near-wall flow due to a cylinder roughness element provided on the model surface was observed. The obtained data substantiate the possibility of controlling the laminar boundary-layer separation on an axisymmetric body using a local external forcing.

  11. Simultaneous Multiple-Location Separation Control

    NASA Technical Reports Server (NTRS)

    Greenblatt, David (Inventor)

    2009-01-01

    A method of controlling a shear layer for a fluid dynamic body introduces first periodic disturbances into the fluid medium at a first flow separation location. Simultaneously, second periodic disturbances are introduced into the fluid medium at a second flow separation location. A phase difference between the first and second periodic disturbances is adjusted to control flow separation of the shear layer as the fluid medium moves over the fluid dynamic body.

  12. Resonant indirect exchange via spatially separated two-dimensional channel

    SciTech Connect

    Rozhansky, I. V.; Krainov, I. V.; Averkiev, N. S.; Aronzon, B. A.; Davydov, A. B.; Kugel, K. I.; Tripathi, V.; Lähderanta, E.

    2015-06-22

    We apply the resonant indirect exchange interaction theory to explain the ferromagnetic properties of the hybrid heterostructure consisting of a InGaAs-based quantum well (QW) sandwiched between GaAs barriers with spatially separated Mn δ-layer. The experimentally obtained dependence of the Curie temperature on the QW depth exhibits a peak related to the region of resonant indirect exchange. We suggest the theoretical explanation and a fit to this dependence as a result of the two contributions to ferromagnetism—the intralayer contribution and the resonant exchange contribution provided by the QW.

  13. Implementing of Quantum Cloning with Spatially Separated Quantum Dot Spins

    NASA Astrophysics Data System (ADS)

    Wen, Jing-Ji; Yeon, Kyu-Hwang; Du, Xin; Lv, Jia; Wang, Ming; Wang, Hong-Fu; Zhang, Shou

    2016-07-01

    We propose some schemes for implementing optimal symmetric (asymmetric) 1 → 2 universal quantum cloning, optimal symmetric (asymmetric) 1 → 2 phase-covariant cloning, optimal symmetric 1 → 3 economical phase-covariant cloning and optimal symmetric 1 → 3 economical real state cloning with spatially separated quantum dot spins by choosing the single-qubit rotation angles appropriately. The decoherences of the spontaneous emission of QDs, cavity decay and fiber loss are suppressed since the effective long-distance off-resonant interaction between two distant QDs is mediated by the vacuum fields of the fiber and cavity, and during the whole process no system is excited.

  14. Plasmons in spatially separated double-layer graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Bagheri, Mehran; Bahrami, Mousa

    2014-05-01

    Motivated by innovative progresses in designing multi-layer graphene nanostructured materials in the laboratory, we theoretically investigate the Dirac plasmon modes of a spatially separated double-layer graphene nanoribbon system, made up of a vertically offset armchair and metallic graphene nanoribbon pair. We find striking features of the collective excitations in this novel Coulomb correlated system, where both nanoribbons are supposed to be either intrinsic (undoped/ungated) or extrinsic (doped/gated). In the former, it is shown the low-energy acoustical and the high-energy optical plasmon modes are tunable only by the inter-ribbon charge separation. In the later, the aforementioned plasmon branches are modified by the added doping factor. As a result, our model could be useful to examine the existence of a linear Landau-undamped low-energy acoustical plasmon mode tuned via the inter-ribbon charge separation as well as doping. This study might also be utilized for devising novel quantum optical waveguides based on the Coulomb coupled graphene nanoribbons.

  15. Plasmons in spatially separated double-layer graphene nanoribbons

    SciTech Connect

    Bagheri, Mehran; Bahrami, Mousa

    2014-05-07

    Motivated by innovative progresses in designing multi-layer graphene nanostructured materials in the laboratory, we theoretically investigate the Dirac plasmon modes of a spatially separated double-layer graphene nanoribbon system, made up of a vertically offset armchair and metallic graphene nanoribbon pair. We find striking features of the collective excitations in this novel Coulomb correlated system, where both nanoribbons are supposed to be either intrinsic (undoped/ungated) or extrinsic (doped/gated). In the former, it is shown the low-energy acoustical and the high-energy optical plasmon modes are tunable only by the inter-ribbon charge separation. In the later, the aforementioned plasmon branches are modified by the added doping factor. As a result, our model could be useful to examine the existence of a linear Landau-undamped low-energy acoustical plasmon mode tuned via the inter-ribbon charge separation as well as doping. This study might also be utilized for devising novel quantum optical waveguides based on the Coulomb coupled graphene nanoribbons.

  16. Spatially Separated Spin Carriers in Spin-Semiconducting Graphene Nanoribbons

    NASA Astrophysics Data System (ADS)

    Wang, Z. F.; Jin, Shuo; Liu, Feng

    2013-08-01

    A graphene nanoribbon with sawtooth edges has a ferromagnetic ground state. Using first-principles and tight-binding model calculations, we show that, under a transverse electrical field, the sawtooth graphene nanoribbons become a spin semiconductor whose charge carriers are not only spin polarized in energy space but also spatially separated at different edges. Low-energy excitation produces spin-up electrons localized at one edge and spin-down holes at the opposite edge, and the excitation energy of spin carries can be tuned by the electric field to reach a new state of spin gapless semiconductor. Also, the spin semiconducting states are shown to be robust against at least 10% edge disorder. These features demonstrate a good tunability of spin carriers for spintronics applications.

  17. Spatially Separated Spin Carriers in Spin-Semiconducting Graphene Nanoribbons

    NASA Astrophysics Data System (ADS)

    Wang, Zhengfei; Jin, Shuo; Liu, Feng

    2014-03-01

    A graphene nanoribbon with sawtooth edges has a ferromagnetic ground state. Using first-principles and tight-binding model calculations, we show that, under a transverse electrical field, the sawtooth graphene nanoribbons become a spin semiconductor whose charge carriers are not only spin polarized in energy space but also spatially separated at different edges. Low-energy excitation produces spin-up electrons localized at one edge and spin-down holes at the opposite edge, and the excitation energy of spin carries can be tuned by the electric field to reach a new state of spin gapless semiconductor. Also, the spin semiconducting states are shown to be robust against at least 10% edge disorder. These features demonstrate a good tunability of spin carriers for spintronics applications. This work was supported by DOE-BES (No. DE-FG02-04ER46148) and NSF-MRSEC (No. DMR-1121252).

  18. Managing Flap Vortices via Separation Control

    NASA Technical Reports Server (NTRS)

    Greenblatt, David

    2006-01-01

    A pilot study was conducted on a flapped semi-span model to investigate the concept and viability of near-wake vortex management by means of boundary layer separation control. Passive control was achieved using a simple fairing and active control was achieved via zero mass-flux blowing slots. Vortex sheet strength, estimated by integrating surface pressures, was used to predict vortex characteristics based on inviscid rollup relations and vortices trailing the flaps were mapped using a seven-hole probe. Separation control was found to have a marked effect on vortex location, strength, tangential velocity, axial velocity and size over a wide range of angles of attack and control conditions. In general, the vortex trends were well predicted by the inviscid rollup relations. Manipulation of the separated flow near the flap edges exerted significant control over either outboard or inboard edge vortices while producing small lift and moment excursions. Unsteady surface pressures indicated that dynamic separation and attachment control can be exploited to perturb vortices at wavelengths shorter than a typical wingspan. In summary, separation control has the potential for application to time-independent or time-dependent wake alleviation schemes, where the latter can be deployed to minimize adverse effects on ride-quality and dynamic structural loading.

  19. Separate mechanisms recruited by exogenous and endogenous spatial cues: evidence from a spatial Stroop paradigm.

    PubMed

    Funes, María Jesús; Lupiáñez, Juan; Milliken, Bruce

    2007-04-01

    The present experiments tested whether endogenous and exogenous cues produce separate effects on target processing. In Experiment 1, participants discriminated whether an arrow presented left or right of fixation pointed to the left or right. For 1 group, the arrow was preceded by a peripheral noninformative cue. For the other group, the arrow was preceded by a central, symbolic, informative cue. The 2 types of cues modulated the spatial Stroop effect in opposite ways, with endogenous cues producing larger spatial Stroop effects for valid trials and exogenous cues producing smaller spatial Stroop effects for valid trials. In Experiments 2A and 2B, the influence of peripheral noninformative and peripheral informative cues on the spatial Stroop effect was directly compared. The spatial Stroop effect was smaller for valid than for invalid trials for both types of cues. These results point to a distinction between the influence of central and peripheral attentional cues on performance and are not consistent with a unitary view of endogenous and exogenous attention.

  20. Status and outlook of flow separation control

    NASA Technical Reports Server (NTRS)

    Gad-El-hak, Mohamed; Bushnell, Dennis M.

    1991-01-01

    Under certain conditions, wall-bounded flows separate. To improve the performance of natural or man-made flow systems, it may be beneficial to delay or advance this detachment process. The present article reviews the status and outlook of separation control for both steady and unsteady flows. Both passive and active techniques to prevent or to provoke flow detachment are considered and suggestions are made for further research.

  1. Control of vortical separation on conical bodies

    NASA Technical Reports Server (NTRS)

    Mourtos, Nikos J.; Roberts, Leonard

    1987-01-01

    In a variety of aeronautical applications, the flow around conical bodies at incidence is of interest. Such applications include, but are not limited to, highly maneuverable aircraft with delta wings, the aerospace plane and nose portions of spike inlets. The theoretical model used has three parts. First, the single line vortex model is used within the framework of slender body theory, to compute the outer inviscid field for specified separation lines. Next, the three dimensional boundary layer is represented by a momentum equation for the cross flow, analogous to that for a plane boundary layer; a von Karman Pohlhausen approximation is applied to solve this equation. The cross flow separation for both laminar and turbulent layers is determined by matching the pressure at the upper and lower separation points. This iterative procedure yields a unique solution for the separation lines and consequently for the position of the vortices and the vortex lift on the body. Lastly, control of separation is achieved by blowing tangentially from a slot located along a cone generator. It is found that for very small blowing coefficients, the separation can be postponed or suppressedy completely.

  2. Separation control with fluidic oscillators in water

    NASA Astrophysics Data System (ADS)

    Schmidt, H.-J.; Woszidlo, R.; Nayeri, C. N.; Paschereit, C. O.

    2017-08-01

    The present study assesses the applicability of fluidic oscillators for separation control in water. The first part of this work evaluates the properties of the fluidic oscillators including frequency, cavitation effects, and exerted thrust. Derived from the governing internal dynamics, the oscillation frequency is found to scale directly with the jet's exit velocity and the size of the fluidic oscillator independent of the working fluid. Frequency data from various experiments collapse onto a single curve. The occurrence of cavitation is examined by visual inspection and hydrophone measurements. The oscillation frequency is not affected by cavitation because it does not occur inside the oscillators. The spectral information obtained with the hydrophone provide a reliable indicator for the onset of cavitation at the exit. The performance of the fluidic oscillators for separation control on a bluff body does not seem to be affected by the presence of cavitation. The thrust exerted by an array of fluidic oscillators with water as the working fluid is measured to be even larger than theoretically estimated values. The second part of the presented work compares the performance of fluidic oscillators for separation control in water with previous results in air. The array of fluidic oscillators is installed into the rear end of a bluff body model. The drag improvements based on force balance measurements agree well with previous wind tunnel experiments on the same model. The flow field is examined by pressure measurements and with particle image velocimetry. Similar performance and flow field characteristics are observed in both water and air.

  3. Passive separation control by acoustic resonance

    NASA Astrophysics Data System (ADS)

    Yang, S. L.; Spedding, G. R.

    2013-10-01

    At transitional Reynolds numbers, the laminar boundary layer separation and possible reattachment on a smooth airfoil, or wing section, are notoriously sensitive to small variations in geometry or in the fluid environment. We report here on the results of a pilot study that adds to this list of sensitivities. The presence of small holes in the suction surface of an Eppler 387 wing has a transformative effect upon the aerodynamics, by changing the mean chordwise separation line location. These changes are not simply a consequence of the presence of the small cavities, which by themselves have no effect. Acoustic resonance in the backing cavities generates tones that interact with intrinsic flow instabilities. Possible consequences for passive flow control strategies are discussed together with potential problems in measurements through pressure taps in such flow regimes.

  4. CONTROL SYSTEM FOR ISOTOPE SEPARATING APPARATUS

    DOEpatents

    Barnes, S.W.

    1960-01-26

    A method is described for controlling the position of the ion beams in a calutron used for isotope separation. The U/sup 238/ beams is centered over the U/sup 235/ receiving pocket, the operator monitoring the beam until a maximum reading is achieved on the meter connected to that pocket. Then both beams are simultaneously shifted by a preselected amount to move the U/sup 235/ beam over the U/sup 235/ pocket. A slotted door is placed over the entrance to that pocket during the U/sup 238/ beam centering to reduce the contamination to the pocket, while allowing enough beam to pass for monitoring purposes.

  5. Virtual Human Analogs to Rodent Spatial Pattern Separation and Completion Memory Tasks

    ERIC Educational Resources Information Center

    Paleja, Meera; Girard, Todd A.; Christensen, Bruce K.

    2011-01-01

    Spatial pattern separation (SPS) and spatial pattern completion (SPC) have played an increasingly important role in computational and rodent literatures as processes underlying associative memory. SPS and SPC are complementary processes, allowing the formation of unique representations and the reconstruction of complete spatial environments based…

  6. Virtual Human Analogs to Rodent Spatial Pattern Separation and Completion Memory Tasks

    ERIC Educational Resources Information Center

    Paleja, Meera; Girard, Todd A.; Christensen, Bruce K.

    2011-01-01

    Spatial pattern separation (SPS) and spatial pattern completion (SPC) have played an increasingly important role in computational and rodent literatures as processes underlying associative memory. SPS and SPC are complementary processes, allowing the formation of unique representations and the reconstruction of complete spatial environments based…

  7. Control of Flow Separation Using Adaptive Airfoils

    NASA Technical Reports Server (NTRS)

    Chandrasekhara, M. S.; Wilder, M. C.; Carr, L. W.; Davis, Sanford S. (Technical Monitor)

    1996-01-01

    A novel way of controlling flow separation is reported. The approach involves using an adaptive airfoil geometry that changes its leading edge shape to adjust to the instantaneous flow at high angles of attack such that the flow over it remains attached. In particular, a baseline NACA 0012 airfoil, whose leading edge curvature could be changed dynamically by 400% was tested under quasi-steady compressible flow conditions. A mechanical drive system was used to produce a rounded leading edge to reduce the strong local flow acceleration around its nose and thus reduce the strong adverse pressure gradient that follows such a rapid acceleration. Tests in steady flow showed that at M = 0.3, the flow separated at about 14 deg. angle of attack for the NACA 0012 profile but could be kept attached up to an angle of about 18 deg by changing the nose curvature. No significant hysteresis effects were observed; the flow could be made to reattach from its separated state at high angles by changing the leading edge curvature.

  8. Influences of modulation and spatial separation on detection of a masked broadband target1

    PubMed Central

    Kopčo, Norbert; Shinn-Cunningham, Barbara G.

    2008-01-01

    Experiments explored the influence of amplitude modulation and spatial separation on detectability of a broadband noise target masked by an independent broadband noise. Thresholds were measured for all combinations of six spatial configurations of target and masker and five modulation conditions. Masker level was either fixed (Experiment 1) or roved between intervals within a trial to reduce the utility of overall intensity as a cue (Experiment 2). After accounting for acoustic changes, thresholds depended on whether a target and a masker were colocated or spatially separated, but not on the exact spatial configuration. Moreover, spatial unmasking exceeded that predicted by better-ear acoustics only when modulation cues for detection were weak. Roving increased the colocated but not the spatially separated thresholds, resulting in an increase in spatial release from masking. Differences in both how performance changed over time and the influence of spatial separation support the idea that the cues underlying performance depend on the modulation characteristics of the target and masker. Analysis suggests that detection is based on overall intensity when target and masker modulation and spatial cues are the same, on spatial attributes when sources are separated and modulation provides no target glimpses, and on modulation discrimination in the remaining conditions. PMID:19062862

  9. Simultaneous and spatially separated detection of multiple orbital angular momentum states

    NASA Astrophysics Data System (ADS)

    Tudor, R.; Mihailescu, M.; Kusko, C.; Paun, I. A.; Nan, A. E.; Kusko, M.

    2016-06-01

    We present a method for spatially separated detection of multiple orbital angular momentum (OAM) states, simultaneous. The starting point is the generation of axially superposed Laguerre-Gauss beams, carrying multiple OAM states using a single computer generated hologram. The information contained in the OAM superposition is transferred to the first diffraction order and is detected at the receiver with a reading mask, which contains two perpendicular superposed fork-like holograms, ensuring the spatial separation of the OAM states. The dynamic of the process is studied in terms of the number of generated OAM states and the constructive parameters values. The experimental investigations use an optical arrangement based on a spatial light modulator in the transmitter unit and an amplitude mask in the receiver unit. This proof of concept experiment demonstrates the possibility of simultaneously detection of multiple OAM states in points located at different coordinates, controlled through the design of the holograms and shows the capability of our proposed method to increase the capacity of free-space optical communication channels.

  10. Tangential synthetic jets for separation control

    NASA Astrophysics Data System (ADS)

    Esmaeili Monir, H.; Tadjfar, M.; Bakhtian, A.

    2014-02-01

    A numerical study of separation control has been made to investigate aerodynamic characteristics of a NACA23012 airfoil with a tangential synthetic jet. Simulations are carried out at the chord Reynolds number of Re=2.19×106. The present approach relies on solving the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations. The turbulence model used in the present computation is the Spalart-Allmaras one-equation model. All computations are performed with a finite volume based code. Stall characteristics are significantly improved by controlling the formation of separation vortices in the flow. We placed the synthetic jet at the 12% chord, xj=0.12c, where we expected the separation to occur. Two distinct jet oscillating frequencies: Fj+=0.159 and Fj+=1 were considered. We studied the effect of blowing ratio, Vj/U∞, where it was varied from 0 to 5. The inclined angle of the synthetic jet was varied from αj=0° up to αj=83°. For the non-zero inclined angles, the local maximum in the aerodynamic performance, Cl/Cd, of 6.89 was found for the inclined angle of about 43°. In the present method, by means of creating a dent on the airfoil, linear momentum is transferred to the flow system in tangential direction to the airfoil surface. Thus the absolute maximum of 11.19 was found for the tangential synthetic jet at the inclined angle of the jet of 0°. The mechanisms involved for a tangential jet appear to behave linearly, as by multiplying the activation frequency of the jet by a factor produces the same multiplication factor in the resulting frequency in the flow. However, the mechanisms involved in the non-zero inclined angle cases behave nonlinearly when the activation frequency is multiplied.

  11. Single-step spatial rotation error separation technique for the ultraprecision measurement of surface profiles.

    PubMed

    Hou, Maosheng; Qiu, Lirong; Zhao, Weiqian; Wang, Fan; Liu, Entao; Ji, Lin

    2014-01-20

    To improve the measurement accuracy of the profilometer for large optical surfaces, a new single-step spatial rotation error separation technique (SSEST) is proposed to separate the surface profile error and spindle spatial rotation error, and a novel SSEST-based system for surface profile measurement is developed. In the process of separation, two sets of measured results at the ith measurement circle are obtained before and after the rotation of error separation table, the surface profile error and spatial rotation error of spindle can be determined using discrete Fourier-transform and harmonic analysis. Theoretical analyses and experimental results indicate that SSEST can accurately separate spatial rotation error of spindle from the measured surface profile results within the range of 1-100 upr and improve the accuracy of surface profile measurements.

  12. Impulsive Injection for Compressor Stator Separation Control

    NASA Technical Reports Server (NTRS)

    Culley, Dennis E.; Braunscheidel, Edward P.; Bright, Michelle M.

    2005-01-01

    Flow control using impulsive injection from the suction surface of a stator vane has been applied in a low speed axial compressor. Impulsive injection is shown to significantly reduce separation relative to steady injection for vanes that were induced to separate by an increase in vane stagger angle of 4 degrees. Injected flow was applied to the airfoil suction surface using spanwise slots pitched in the streamwise direction. Injection was limited to the near-hub region, from 10 to 36 percent of span, to affect the dominant loss due to hub leakage flow. Actuation was provided externally using high-speed solenoid valves closely coupled to the vane tip. Variations in injected mass, frequency, and duty cycle are explored. The local corrected total pressure loss across the vane at the lower span region was reduced by over 20 percent. Additionally, low momentum fluid migrating from the hub region toward the tip was effectively suppressed resulting in an overall benefit which reduced corrected area averaged loss through the passage by 4 percent. The injection mass fraction used for impulsive actuation was typically less than 0.1 percent of the compressor through flow.

  13. Amplitude Scaling of Active Separation Control

    NASA Technical Reports Server (NTRS)

    Stalnov, Oksana; Seifert, Avraham

    2010-01-01

    Three existing and two new excitation magnitude scaling options for active separation control at Reynolds numbers below one Million. The physical background for the scaling options was discussed and their relevance was evaluated using two different sets of experimental data. For F+ approx. 1, 2D excitation: a) The traditional VR and C(mu) - do not scale the data. b) Only the Re*C(mu) is valid. This conclusion is also limited for positive lift increment.. For F+ > 10, 3D excitation, the Re corrected C(mu), the St corrected velocity ratio and the vorticity flux coefficient, all scale the amplitudes equally well. Therefore, the Reynolds weighted C(mu) is the preferred choice, relevant to both excitation modes. Incidence also considered, using Ue from local Cp.

  14. Electric currents couple spatially separated biogeochemical processes in marine sediment.

    PubMed

    Nielsen, Lars Peter; Risgaard-Petersen, Nils; Fossing, Henrik; Christensen, Peter Bondo; Sayama, Mikio

    2010-02-25

    Some bacteria are capable of extracellular electron transfer, thereby enabling them to use electron acceptors and donors without direct cell contact. Beyond the micrometre scale, however, no firm evidence has previously existed that spatially segregated biogeochemical processes can be coupled by electric currents in nature. Here we provide evidence that electric currents running through defaunated sediment couple oxygen consumption at the sediment surface to oxidation of hydrogen sulphide and organic carbon deep within the sediment. Altering the oxygen concentration in the sea water overlying the sediment resulted in a rapid (<1-h) change in the hydrogen sulphide concentration within the sediment more than 12 mm below the oxic zone, a change explicable by transmission of electrons but not by diffusion of molecules. Mass balances indicated that more than 40% of total oxygen consumption in the sediment was driven by electrons conducted from the anoxic zone. A distinct pH peak in the oxic zone could be explained by electrochemical oxygen reduction, but not by any conventional sets of aerobic sediment processes. We suggest that the electric current was conducted by bacterial nanowires combined with pyrite, soluble electron shuttles and outer-membrane cytochromes. Electrical communication between distant chemical and biological processes in nature adds a new dimension to our understanding of biogeochemistry and microbial ecology.

  15. Phase separation in fluids exposed to spatially periodic external fields.

    PubMed

    Vink, R L C; Archer, A J

    2012-03-01

    When a fluid is confined within a spatially periodic external field, the liquid-vapor transition is replaced by a different transition called laser-induced condensation (LIC) [Götze et al., Mol. Phys. 101, 1651 (2003)]. In d=3 dimensions, the periodic field induces an additional phase, characterized by large density modulations along the field direction. At the triple point, all three phases (modulated, vapor, and liquid) coexist. At temperatures slightly above the triple point and for low (high) values of the chemical potential, two-phase coexistence between the modulated phase and the vapor (liquid) is observed; by increasing the temperature further, both coexistence regions terminate in critical points. In this paper, we reconsider LIC using the Ising model to resolve a number of open issues. To be specific, we (1) determine the universality class of the LIC critical points and elucidate the nature of the correlations along the field direction, (2) present a mean-field analysis to show how the LIC phase diagram changes as a function of the field wavelength and amplitude, (3) develop a simulation method by which the extremely low tension of the interface between modulated and vapor or liquid phase can be measured, (4) present a finite-size scaling analysis to accurately extract the LIC triple point from finite-size simulation data, and (5) consider the fate of LIC in d=2 dimensions.

  16. Individual Differences in Spatial Pattern Separation Performance Associated with Healthy Aging in Humans

    ERIC Educational Resources Information Center

    Stark, Shauna M.; Yassa, Michael A.; Stark, Craig E. L.

    2010-01-01

    Rodent studies have suggested that "pattern separation," the ability to distinguish among similar experiences, is diminished in a subset of aged rats. We extended these findings to the human using a task designed to assess spatial pattern separation behavior (determining at time of test whether pairs of pictures shown during the study were in the…

  17. Individual Differences in Spatial Pattern Separation Performance Associated with Healthy Aging in Humans

    ERIC Educational Resources Information Center

    Stark, Shauna M.; Yassa, Michael A.; Stark, Craig E. L.

    2010-01-01

    Rodent studies have suggested that "pattern separation," the ability to distinguish among similar experiences, is diminished in a subset of aged rats. We extended these findings to the human using a task designed to assess spatial pattern separation behavior (determining at time of test whether pairs of pictures shown during the study were in the…

  18. Interference of two pulse-like spatial beams with arbitrary transverse separation

    NASA Astrophysics Data System (ADS)

    Flórez, Jefferson; Álvarez, Juan-Rafael; Calderón-Losada, Omar; José Salazar-Serrano, Luis; Valencia, Alejandra

    2016-12-01

    We report the observation of interference in position and transverse momentum variables between two parallel-propagating Gaussian beams separated by an arbitrary distance. This resembles the Alford and Gold effect that has been reported for the time-frequency degree of freedom, and constitutes a method for spatial intensity shaping of light beams. We observe this interference by using a tunable beam displacer, which plays the role of a Michelson interferometer for the transverse spatial variables. Additionally, we employ the interference pattern as a function of the separation between the beams to determine the spatial coherence length of the original beam.

  19. Numerical modeling of active separation control by synthetic jets

    NASA Astrophysics Data System (ADS)

    Aram, Shawn

    Zero-Net Mass-Flux (ZNMF) actuators or synthetic jet actuators are versatile micro scale devices with numerous applications in the field of fluid mechanics. The primary focus of the current work is to use time-accurate simulations to study the interaction of these jets with cross flows and to optimize their performance for the control of boundary layer separation. This study consists of four parts. In the first part, a class of phenomenology-based models is proposed to reproduce the flow associated with synthetic jets in grazing flows and simplify the task of ZNMF-based flow control simulations. The proposed models have a non-uniform jet velocity profile with only two spatial degrees of freedom and a uniform slip velocity on the slot-flow boundary. A comparison of key integral quantities associated with the momentum, energy and vorticity fluxes shows that the models with a non-uniform jet velocity during the expulsion phase and uniform jet velocity during the ingestion phase can predict these quantities with good accuracy, whereas a simple plug flow model with a zero slip and uniform jet velocity under-predicts these three quantities during the expulsion phase. Based on our initial analysis, three of the simplest models are selected for further study, including an assessment of their performance for a canonical separated flow at different forcing frequencies. A key finding is that a simple plug-flow type model can predict incorrect trends for separation reduction with the jet frequency. A preliminary attempt is also made to provide empirical closure to these models. The effect of synthetic jets orientation on its interaction with a zero pressure gradient laminar boundary layer is explored in the second part. A rectangular slot is chosen in this study and streamwise and spanwise orientations of this slot are examined. The orientation of the slot is found to have a significant impact on its interaction with the boundary layer. The dominant feature in the streamwise

  20. Feeling better: Separate pathways for targeted enhancement of spatial and temporal touch

    PubMed Central

    Yau, Jeffrey M.; Celnik, Pablo; Hsiao, Steven S.; Desmond, John E.

    2013-01-01

    We perceive spatial form and temporal frequency by touch. Although distinct somatosensory neurons represent spatial and temporal information, these neural populations are intermixed throughout the somatosensory system. Here, we show that spatial and temporal touch can be dissociated and separately enhanced via cortical pathways that are normally associated with vision and audition. In Experiments 1 and 2, we found that anodal transcranial direct current stimulation (tDCS) applied over visual cortex, but not auditory cortex, enhances tactile perception of spatial orientation. In Experiments 3 and 4, we found that anodal tDCS over auditory cortex, but not visual cortex, enhances tactile perception of temporal frequency. This double-dissociation reveals separate cortical pathways that selectively support spatial and temporal channels. These results bolster the emerging view that sensory areas process multiple modalities and suggest that supramodal domains may be more fundamental to cortical organizational. PMID:24390826

  1. Spatial constancy mechanisms in motor control

    PubMed Central

    Medendorp, W. Pieter

    2011-01-01

    The success of the human species in interacting with the environment depends on the ability to maintain spatial stability despite the continuous changes in sensory and motor inputs owing to movements of eyes, head and body. In this paper, I will review recent advances in the understanding of how the brain deals with the dynamic flow of sensory and motor information in order to maintain spatial constancy of movement goals. The first part summarizes studies in the saccadic system, showing that spatial constancy is governed by a dynamic feed-forward process, by gaze-centred remapping of target representations in anticipation of and across eye movements. The subsequent sections relate to other oculomotor behaviour, such as eye–head gaze shifts, smooth pursuit and vergence eye movements, and their implications for feed-forward mechanisms for spatial constancy. Work that studied the geometric complexities in spatial constancy and saccadic guidance across head and body movements, distinguishing between self-generated and passively induced motion, indicates that both feed-forward and sensory feedback processing play a role in spatial updating of movement goals. The paper ends with a discussion of the behavioural mechanisms of spatial constancy for arm motor control and their physiological implications for the brain. Taken together, the emerging picture is that the brain computes an evolving representation of three-dimensional action space, whose internal metric is updated in a nonlinear way, by optimally integrating noisy and ambiguous afferent and efferent signals. PMID:21242137

  2. Blind separation of sound sources from the principle of least spatial entropy

    NASA Astrophysics Data System (ADS)

    Dong, Bin; Antoni, Jérôme; Zhang, Erliang

    2014-04-01

    The aim of the paper is to offer a method for separating incoherent and compact sound sources which may overlap in both the space and frequency domains. This is found of interest in acoustical applications involving the identification and ranking of sound sources stemming from different physical origins. The principle proceeds in two steps, the first one being reminiscent to source reconstruction (e.g. as in near-field acoustical holography) and the second one to blind source separation. Specifically, the source mixture is first expanded into a linear combination of spatial basis functions whose coefficients are set by backpropagating the pressures measured by an array of microphones to the source domain. This leads to a formulation similar, but no identical, to blind source separation. In the second step, these coefficients are blindly separated into uncorrelated latent variables, assigned to incoherent "virtual sources". These are shown to be defined up to an arbitrary rotation. A unique set of sound sources is finally recovered by searching for that rotation (by conjugate gradient descent in the Stiefel manifold of unitary matrices) which maximizes their spatial compactness, as measured either by their spatial variance or their spatial entropy. This results in the proposal of two separation criteria coined "least spatial variance" and "least spatial entropy", respectively. The same concept of spatial entropy, which is central to the paper, is also exploited in defining a new criterion, the entropic L-curve, dedicated to determining the number of active sound sources. The idea consists in considering the number of sources that achieves the best compromise between a low spatial entropy (as expected from compact sources) and a low statistical entropy (as expected from a low residual error). The proposed methodology is validated on both laboratory experiments and numerical data, and illustrated on an industrial example concerned with the ranking of sound sources on

  3. Seafloor observations indicate spatial separation of coseismic and postseismic slips in the 2011 Tohoku earthquake

    PubMed Central

    Iinuma, Takeshi; Hino, Ryota; Uchida, Naoki; Nakamura, Wataru; Kido, Motoyuki; Osada, Yukihito; Miura, Satoshi

    2016-01-01

    Large interplate earthquakes are often followed by postseismic slip that is considered to occur in areas surrounding the coseismic ruptures. Such spatial separation is expected from the difference in frictional and material properties in and around the faults. However, even though the 2011 Tohoku Earthquake ruptured a vast area on the plate interface, the estimation of high-resolution slip is usually difficult because of the lack of seafloor geodetic data. Here using the seafloor and terrestrial geodetic data, we investigated the postseismic slip to examine whether it was spatially separated with the coseismic slip by applying a comprehensive finite-element method model to subtract the viscoelastic components from the observed postseismic displacements. The high-resolution co- and postseismic slip distributions clarified the spatial separation, which also agreed with the activities of interplate and repeating earthquakes. These findings suggest that the conventional frictional property model is valid for the source region of gigantic earthquakes. PMID:27853138

  4. Seafloor observations indicate spatial separation of coseismic and postseismic slips in the 2011 Tohoku earthquake.

    PubMed

    Iinuma, Takeshi; Hino, Ryota; Uchida, Naoki; Nakamura, Wataru; Kido, Motoyuki; Osada, Yukihito; Miura, Satoshi

    2016-11-17

    Large interplate earthquakes are often followed by postseismic slip that is considered to occur in areas surrounding the coseismic ruptures. Such spatial separation is expected from the difference in frictional and material properties in and around the faults. However, even though the 2011 Tohoku Earthquake ruptured a vast area on the plate interface, the estimation of high-resolution slip is usually difficult because of the lack of seafloor geodetic data. Here using the seafloor and terrestrial geodetic data, we investigated the postseismic slip to examine whether it was spatially separated with the coseismic slip by applying a comprehensive finite-element method model to subtract the viscoelastic components from the observed postseismic displacements. The high-resolution co- and postseismic slip distributions clarified the spatial separation, which also agreed with the activities of interplate and repeating earthquakes. These findings suggest that the conventional frictional property model is valid for the source region of gigantic earthquakes.

  5. Seafloor observations indicate spatial separation of coseismic and postseismic slips in the 2011 Tohoku earthquake

    NASA Astrophysics Data System (ADS)

    Iinuma, Takeshi; Hino, Ryota; Uchida, Naoki; Nakamura, Wataru; Kido, Motoyuki; Osada, Yukihito; Miura, Satoshi

    2016-11-01

    Large interplate earthquakes are often followed by postseismic slip that is considered to occur in areas surrounding the coseismic ruptures. Such spatial separation is expected from the difference in frictional and material properties in and around the faults. However, even though the 2011 Tohoku Earthquake ruptured a vast area on the plate interface, the estimation of high-resolution slip is usually difficult because of the lack of seafloor geodetic data. Here using the seafloor and terrestrial geodetic data, we investigated the postseismic slip to examine whether it was spatially separated with the coseismic slip by applying a comprehensive finite-element method model to subtract the viscoelastic components from the observed postseismic displacements. The high-resolution co- and postseismic slip distributions clarified the spatial separation, which also agreed with the activities of interplate and repeating earthquakes. These findings suggest that the conventional frictional property model is valid for the source region of gigantic earthquakes.

  6. Separate Mechanisms Recruited by Exogenous and Endogenous Spatial Cues: Evidence from a Spatial Stroop Paradigm

    ERIC Educational Resources Information Center

    Funes, Maria Jesus; Lupianez, Juan; Milliken, Bruce

    2007-01-01

    The present experiments tested whether endogenous and exogenous cues produce separate effects on target processing. In Experiment 1, participants discriminated whether an arrow presented left or right of fixation pointed to the left or right. For 1 group, the arrow was preceded by a peripheral noninformative cue. For the other group, the arrow was…

  7. Interaction mechanisms of cavitation bubbles induced by spatially and temporally separated fs-laser pulses.

    PubMed

    Tinne, Nadine; Kaune, Brigitte; Krüger, Alexander; Ripken, Tammo

    2014-01-01

    The emerging use of femtosecond lasers with high repetition rates in the MHz regime together with limited scan speed implies possible mutual optical and dynamical interaction effects of the individual cutting spots. In order to get more insight into the dynamics a time-resolved photographic analysis of the interaction of cavitation bubbles is presented. Particularly, we investigated the influence of fs-laser pulses and their resulting bubble dynamics with various spatial as well as temporal separations. Different time courses of characteristic interaction effects between the cavitation bubbles were observed depending on pulse energy and spatio-temporal pulse separation. These ranged from merely no interaction to the phenomena of strong water jet formation. Afterwards, the mechanisms are discussed regarding their impact on the medical application of effective tissue cutting lateral to the laser beam direction with best possible axial precision: the mechanical forces of photodisruption as well as the occurring water jet should have low axial extend and a preferably lateral priority. Furthermore, the overall efficiency of energy conversion into controlled mechanical impact should be maximized compared to the transmitted pulse energy and unwanted long range mechanical side effects, e.g. shock waves, axial jet components. In conclusion, these experimental results are of great importance for the prospective optimization of the ophthalmic surgical process with high-repetition rate fs-lasers.

  8. Interaction Mechanisms of Cavitation Bubbles Induced by Spatially and Temporally Separated fs-Laser Pulses

    PubMed Central

    Tinne, Nadine; Kaune, Brigitte; Krüger, Alexander; Ripken, Tammo

    2014-01-01

    The emerging use of femtosecond lasers with high repetition rates in the MHz regime together with limited scan speed implies possible mutual optical and dynamical interaction effects of the individual cutting spots. In order to get more insight into the dynamics a time-resolved photographic analysis of the interaction of cavitation bubbles is presented. Particularly, we investigated the influence of fs-laser pulses and their resulting bubble dynamics with various spatial as well as temporal separations. Different time courses of characteristic interaction effects between the cavitation bubbles were observed depending on pulse energy and spatio-temporal pulse separation. These ranged from merely no interaction to the phenomena of strong water jet formation. Afterwards, the mechanisms are discussed regarding their impact on the medical application of effective tissue cutting lateral to the laser beam direction with best possible axial precision: the mechanical forces of photodisruption as well as the occurring water jet should have low axial extend and a preferably lateral priority. Furthermore, the overall efficiency of energy conversion into controlled mechanical impact should be maximized compared to the transmitted pulse energy and unwanted long range mechanical side effects, e.g. shock waves, axial jet components. In conclusion, these experimental results are of great importance for the prospective optimization of the ophthalmic surgical process with high-repetition rate fs-lasers. PMID:25502697

  9. Does common spatial origin promote the auditory grouping of temporally separated signal elements in grey treefrogs?

    PubMed

    Bee, Mark A; Riemersma, Kasen K

    2008-09-01

    'Sequential integration' represents a form of auditory grouping in which temporally separated sounds produced by the same source are perceptually bound together over time into a coherent 'auditory stream'. In humans, sequential integration plays important roles in music and speech perception. In this study of the grey treefrog (Hyla chrysoscelis), we took advantage of female selectivity for advertisement calls with conspecific pulse rates to investigate common spatial location as a cue for sequential integration. We presented females with two temporally interleaved pulse sequences with pulse rates of 25 pulses/s, which is half the conspecific pulse rate and more similar to that of H. versicolor, a syntopically breeding heterospecific. We tested the hypothesis that common spatial origin between the two pulse sequences would promote their integration into a coherent auditory stream with an attractive conspecific pulse rate. As the spatial separation between the speakers broadcasting the interleaved pulse sequences decreased from 180° to 0°, more females responded and females exhibited shorter response latencies and travelled shorter distances en route to a speaker. However, even in the 180° condition, most females (74%) still responded. Detailed video analyses revealed no evidence to suggest that patterns of female phonotaxis resulted from impaired abilities to localize sound sources in the spatially separated conditions. Together, our results suggest that females were fairly permissive of spatial incoherence between the interleaved pulses sequences and that common spatial origin may be only a relatively weak cue for sequential integration in grey treefrogs.

  10. Does common spatial origin promote the auditory grouping of temporally separated signal elements in grey treefrogs?

    PubMed Central

    Bee, Mark A.; Riemersma, Kasen K.

    2008-01-01

    ‘Sequential integration’ represents a form of auditory grouping in which temporally separated sounds produced by the same source are perceptually bound together over time into a coherent ‘auditory stream’. In humans, sequential integration plays important roles in music and speech perception. In this study of the grey treefrog (Hyla chrysoscelis), we took advantage of female selectivity for advertisement calls with conspecific pulse rates to investigate common spatial location as a cue for sequential integration. We presented females with two temporally interleaved pulse sequences with pulse rates of 25 pulses/s, which is half the conspecific pulse rate and more similar to that of H. versicolor, a syntopically breeding heterospecific. We tested the hypothesis that common spatial origin between the two pulse sequences would promote their integration into a coherent auditory stream with an attractive conspecific pulse rate. As the spatial separation between the speakers broadcasting the interleaved pulse sequences decreased from 180° to 0°, more females responded and females exhibited shorter response latencies and travelled shorter distances en route to a speaker. However, even in the 180° condition, most females (74%) still responded. Detailed video analyses revealed no evidence to suggest that patterns of female phonotaxis resulted from impaired abilities to localize sound sources in the spatially separated conditions. Together, our results suggest that females were fairly permissive of spatial incoherence between the interleaved pulses sequences and that common spatial origin may be only a relatively weak cue for sequential integration in grey treefrogs. PMID:19727419

  11. Experimental realization of spatially separated entanglement with continuous variables using laser pulse trains

    PubMed Central

    Zhang, Yun; Okubo, Ryuhi; Hirano, Mayumi; Eto, Yujiro; Hirano, Takuya

    2015-01-01

    Spatially separated entanglement is demonstrated by interfering two high-repetition squeezed pulse trains. The entanglement correlation of the quadrature amplitudes between individual pulses is interrogated. It is characterized in terms of the sufficient inseparability criterion with an optimum result of in the frequency domain and in the time domain. The quantum correlation is also observed when the two measurement stations are separated by a physical distance of 4.5 m, which is sufficiently large to demonstrate the space-like separation, after accounting for the measurement time. PMID:26278478

  12. Spatially controlled amyloid reactions using organic electronics.

    PubMed

    Gabrielsson, Erik O; Tybrandt, Klas; Hammarström, Per; Berggren, Magnus; Nilsson, K Peter R

    2010-10-04

    Abnormal protein aggregates, so called amyloid fibrils, are mainly known as pathological hallmarks of a wide range of diseases, but in addition these robust well-ordered self-assembled natural nanostructures can also be utilized for creating distinct nanomaterials for bioelectronic devices. However, current methods for producing amyloid fibrils in vitro offer no spatial control. Herein, we demonstrate a new way to produce and spatially control the assembly of amyloid-like structures using an organic electronic ion pump (OEIP) to pump distinct cations to a reservoir containing a negatively charged polypeptide. The morphology and kinetics of the created proteinaceous nanomaterials depends on the ion and current used, which we leveraged to create layers incorporating different conjugated thiophene derivatives, one fluorescent (p-FTAA) and one conducting (PEDOT-S). We anticipate that this new application for the OEIP will be useful for both biological studies of amyloid assembly and fibrillogenesis as well as for creating new bioelectronic nanomaterials and devices.

  13. Unit Performance, Situational Factors, and Employee Attitudes in Spatially Separated Work Units.

    ERIC Educational Resources Information Center

    Porter, Lyman W.; And Others

    This study investigated relationships between work unit performance, employee attitudes, and situational characteristics among 411 female clerical workers in 37 branch banks. The work units were characterized by spatial separation and performance of similar functions. Two independent dimensions of performance were empirically identified and their…

  14. The spatial isomorphism problem for close separable nuclear C*-algebras.

    PubMed

    Christensen, Erik; Sinclair, Allan M; Smith, Roger R; White, Stuart A; Winter, Wilhelm

    2010-01-12

    The Kadison-Kastler problem asks whether close C*-algebras on a Hilbert space must be spatially isomorphic. We establish this when one of the algebras is separable and nuclear. We also apply our methods to the study of near inclusions of C*-algebras.

  15. Operating parameter optimization of single color and four-color spatially separated QWIP focal plane array

    NASA Technical Reports Server (NTRS)

    Rafol, S. B.; Gunapala, S. D.; Bandara, S.; Liu, J. K.; Mumolo, J.; Trinh, J.; Jhabvala, M.

    2003-01-01

    This paper will report on the characterization of spatially separated four-color QWIP FPA and LWIR QWIP camera. Optimization of operating parameters for each color and the best optimized operating parameters for all four-color operating simultaneously will be discussed.

  16. On the control of a canonical separated flow

    NASA Astrophysics Data System (ADS)

    Griffin, John C.

    Flow separation is generally an undesirable phenomenon that produces adverse effects to ideal aerodynamic performance. Control of ow separation is a complex problem and thus a popular area of research. A common obstacle is the lack of understanding of the complex fluid mechanics in cases of ow separation, evident by the substantial amount of ow control achieved through trial-and-error methods. The purpose of this work is to better understand the nature of separation for improved active control methods, which includes closed-loop control via reduced order methods. Control of a canonical separation problem, with the key features of separated flow, is achieved at a chord Reynolds number of 105. Separation is created on a at plate model, void of curvature that would otherwise include effects particular to the type of aerodynamic body. The characteristics of the imposed separation are evaluated with the intent of having a nominally two-dimensional separation, with the same essential flow characteristics of a more traditionally stalled airfoil. Results provide a reduced-order estimation technique that is used to identify global, dynamic modes through experimental measurements. Reattachment of the baseline separation is first achieved in open-loop control via ZNMF actuation. Efficient reattachment is reached by targeting the identified characteristic flow frequencies, which is able to reattach the separated flow with less than a quarter of the control effort as a comparison case with high-frequency forcing. The baseline and control results are used to identify a reduced-order model suitable for closed-loop control, with benefits of set-point tracking and full boundary layer attachment with minimum control effort.

  17. Multi-Antenna Data Collector for Smart Metering Networks with Integrated Source Separation by Spatial Filtering

    NASA Astrophysics Data System (ADS)

    Quednau, Philipp; Trommer, Ralph; Schmidt, Lorenz-Peter

    2016-03-01

    Wireless transmission systems in smart metering networks share the advantage of lower installation costs due to the expandability of separate infrastructure but suffer from transmission problems. In this paper the issue of interference of wireless transmitted smart meter data with third party systems and data from other meters is investigated and an approach for solving the problem is presented. A multi-channel wireless m-bus receiver was developed to separate the desired data from unwanted interferers by spatial filtering. The according algorithms are presented and the influence of different antenna types on the spatial filtering is investigated. The performance of the spatial filtering is evaluated by extensive measurements in a realistic surrounding with several hundreds of active wireless m-bus transponders. These measurements correspond to the future environment for data-collectors as they took place in rural and urban areas with smart gas meters equipped with wireless m-bus transponders installed in almost all surrounding buildings.

  18. Spatial memory-related brain activity in normally reared and different maternal separation models in rats.

    PubMed

    Banqueri, María; Méndez, Marta; Arias, Jorge L

    2017-09-08

    Early life stress comprises a wide range of adverse events that can occur in the subject's early developmental stages: from child abuse to rodent repeated maternal separation models. This study used young adult male Wistar rats that were maternally raised (AFR), maternally separated from post-natal day (PND) 1 to PND10 (MS10), or maternally separated from PND1 to PND21 (MS21), to assess the effects of maternal separation on spatial learning and memory using the Morris Water Maze (MWM). We also performed quantitative cytochrome oxidase (COx) histochemistry on some selected brain areas in order to find out whether maternal separation affects brain energy metabolism. We obtained a similar spatial learning pattern in maternally raised and maternally separated subjects, with MS10 showing faster acquisition; however, different brain networks with different energy consumptions were used by each group. MS10 spent more energy to get the same behavioral outputs, whereas MS21 resembled AFR more in term of energy demands. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. The effect of spatial separation on informational masking of speech in normal-hearing and hearing-impaired listeners

    NASA Astrophysics Data System (ADS)

    Arbogast, Tanya L.; Mason, Christine R.; Kidd, Gerald

    2005-04-01

    The ability to understand speech in a multi-source environment containing informational masking may depend on the perceptual arrangement of signal and masker objects in space. In normal-hearing listeners, Arbogast et al. [J. Acoust. Soc. Am. 112, 2086-2098 (2002)] found an 18-dB spatial release from a primarily informational masker, compared to 7 dB for a primarily energetic masker. This article extends the earlier work to include the study of listeners with sensorineural hearing loss. Listeners performed closed-set speech recognition in two spatial conditions: 0° and 90° separation between signal and masker. Three maskers were tested: (1) the different-band sentence masker was designed to be primarily informational; (2) the different-band noise masker was a control for the different-band sentence; and (3) the same-band noise masker was designed to be primarily energetic. The spatial release from the different-band sentence was larger than for the other maskers, but was smaller (10 dB) for the hearing-impaired group than for the normal-hearing group (15 dB). The smaller benefit for the hearing-impaired listeners can be partially explained by masker sensation level. However, the results suggest that hearing-impaired listeners can use the perceptual effect of spatial separation to improve speech recognition in the presence of a primarily informational masker. .

  20. Separation control in a conical diffuser with an annular inlet

    NASA Astrophysics Data System (ADS)

    Pong Lo, Kin; Elkins, Christopher; Eaton, John

    2010-11-01

    Conical diffusers are commonly used in turbomachines to slow down the flow and recover pressure. In typical applications such as the diffuser behind a power turbine, the inlet to the diffuser is an annulus. A large central separation bubble forms if the central hub ends abruptly. A long streamlined tail cone can eliminate the separation, but it is often unfeasible for structural reasons. Experiments were performed to investigate various means to manage both the central separation bubble and any separation on the outer diffuser walls. The Reynolds number is 66000 based on the annulus bulk velocity and hydraulic diameter. Full-field, three-component velocity data were measured using magnetic resonance velocimetry. The central separation bubble behind the hub extends the full length of the diffuser in the absence of any control. A Coanda jet at the end of the hub can strongly reduce or completely eliminate the central separation bubble. However this can cause separation from the conical diffuser walls in some cases. A step in the outer diffuser wall acts to fix the location of separation making it more amenable to control. Several control mechanisms for this outer separation bubble are under investigation.

  1. Active-Adaptive Control of Inlet Separation Using Supersonic Microjets

    NASA Technical Reports Server (NTRS)

    Alvi, Farrukh S.

    2007-01-01

    Flow separation in internal and external flows generally results in a significant degradation in aircraft performance. For internal flows, such as inlets and transmission ducts in aircraft propulsion systems, separation is undesirable as it reduces the overall system performance. The aim of this research has been to understand the nature of separation and more importantly, to explore techniques to actively control it. In this research, we extended our investigation of active separation control (under a previous NASA grant) where we explored the use of microjets for the control of boundary layer separation. The geometry used for the initial study was a simple diverging Stratford ramp, equipped with arrays of microjets. These early results clearly show that the activation of microjets eliminated flow separation. Furthermore, the velocity-field measurements, using PIV, also demonstrate that the gain in momentum due to the elimination of separation is at least an order of magnitude larger (two orders of magnitude larger in most cases) than the momentum injected by the microjets and is accomplished with very little mass flow through the microjets. Based on our initial promising results this research was continued under the present grant, using a more flexible model. This model allows for the magnitude and extent of separation as well as the microjet parameters to be independently varied. The results, using this model were even more encouraging and demonstrated that microjet control completely eliminated significant regions of flow separation over a wide range of conditions with almost negligible mass flow. Detailed studies of the flowfield and its response to microjets were further examined using 3-component PIV and unsteady pressure measurements, among others. As the results presented this report will show, microjets were successfully used to control the separation of a much larger extent and magnitude than demonstrated in our earlier experiments. In fact, using the

  2. Spatial and temporal control of surfactant systems.

    PubMed

    Liu, Xiaoyang; Abbott, Nicholas L

    2009-11-01

    This paper reviews some recent progress on approaches leading to spatial and temporal control of surfactant systems. The approaches revolve around the use of redox-active and light-sensitive surfactants. Perspectives are presented on experiments that have realized approaches for active control of interfacial properties of aqueous surfactant systems, reversible control of microstructures and nanostructures formed within bulk solutions, and in situ manipulation of the interactions of surfactants with polymers, DNA and proteins. A particular focus of this review is devoted to studies of amphiphiles that contain the redox-active group ferrocene - reversible control of the oxidation state of ferrocene leads to changes in the charge/hydrophobicity of these amphiphiles, resulting in substantial changes in their self-assembly. Light-sensitive surfactants containing azobenzene, which undergo changes in shape/polarity upon illumination with light, are a second focus of this review. Examples of both redox-active and light-sensitive surfactants that lead to large (>20mN/m) and spatially localized ( approximately mm) changes in surface tensions on a time scale of seconds are presented. Systems that permit reversible transformations of bulk solution nanostructures - such as micelle-to-vesicle transitions or monomer-to-micelle transitions - are also described. The broad potential utility of these emerging classes of amphiphiles are illustrated by the ability to drive changes in functional properties of surfactant systems, such as rheological properties and reversible solubilization of oils, as well as the ability to control interactions of surfactants with biomolecules to modulate their transport into cells.

  3. Imaging single photons in non-separable states of polarization and spatial-mode

    NASA Astrophysics Data System (ADS)

    Cheng, Xinru; Galvez, Enrique J.

    2014-10-01

    Non-separable superpositions of polarization and spatial mode of a single photon produce a state that has a polarization that depends on the transverse position, and contains all states of polarization represented on the Poincaré sphere. We have done measurements of the space-dependent state of polarization of single photons prepared in distinct 2×2 (qubit-qubit) and 2×3 (qubit-qutrit) non-separable superpositions of Laguerre-Gauss spatial and polarization states. Detection was done by polarimetry of the light projected at distinct locations in the transverse plane. The polarization patterns had a C-point polarization singularity (lemon, star or monstar) at the center of the transverse wavefunction.

  4. Pattern analysis based models of masking by spatially separated sound sources

    NASA Astrophysics Data System (ADS)

    Gilkey, Robert H.

    1992-06-01

    One goal of this program is to examine masking among spatially separated sound sources. The results indicate that masking release on the order of 8-20 dB can be observed in free-field masking situations when the signal and the masker are spatially separated by 90 degrees. This magnitude of masking release is comparable to that observed in traditional binaural masking level difference experiments, where the stimuli are presented through headphones. However, while masking release observed in headphone studies is typically assumed to be based on interaural differences in phase or on interaural differences in intensity, we observed substantial masking release in the median plane where interaural differences are minimal. Our own headphone masking research is also questioning traditional models of binaural masking. Work is underway to develop a neural network based model of sound localization. The results of these studies will have implications for the development of virtual environments and auditory displays.

  5. Control of volume resistivity in inorganic organic separators

    NASA Technical Reports Server (NTRS)

    Sheibley, D. W.; Manzo, M. A.

    1979-01-01

    Control of resistivity in NASA inorganic-organic separators is achieved by incorporating small percentages of high surface area, fine particle silica with other ingredients in the separator coating. The volume resistivity is predictable from the surface area of filler particles in the coating. The approach is applied to two polymer- plasticizer -filler coating systems, where the filler content of each is below the generally acknowledged critical pigment volume concentration of the coating. Application of these coating systems to 0.0254 cm thick (10-mil) fuel cell grade asbestos sheet produces inexpensive, flexible, microporous separators that perform as well as the original inorganic-organic concept, the Astropower separator.

  6. Phase Separation of Dirac Electrons in Topological Insulators at the Spatial Limit.

    PubMed

    Parra, Carolina; Rodrigues da Cunha, Thiago Henrique; Contryman, Alex W; Kong, Desheng; Montero-Silva, Francisco; Rezende Gonçalves, Pedro Henrique; Dos Reis, Diogo Duarte; Giraldo-Gallo, Paula; Segura, Rodrigo; Olivares, Fernanda; Niestemski, Francis; Cui, Yi; Magalhaes-Paniago, Rogerio; Manoharan, Hari C

    2017-01-11

    In this work we present unique signatures manifested by the local electronic properties of the topological surface state in Bi2Te3 nanostructures as the spatial limit is approached. We concentrate on the pure nanoscale limit (nanoplatelets) with spatial electronic resolution down to 1 nm. The highlights include strong dependencies on nanoplatelet size: (1) observation of a phase separation of Dirac electrons whose length scale decreases as the spatial limit is approached, and (2) the evolution from heavily n-type to lightly n-type surface doping as nanoplatelet thickness increases. Our results show a new approach to tune the Dirac point together with reduction of electronic disorder in topological insulator (TI) nanostructured systems. We expect our work will provide a new route for application of these nanostructured Dirac systems in electronic devices.

  7. Management of Vortices Trailing Flapped Wings via Separation Control

    NASA Technical Reports Server (NTRS)

    Greenblatt, David

    2005-01-01

    A pilot study was conducted on a flapped semi-span model to investigate the concept and viability of near-wake vortex management via separation control. Passive control was achieved by means of a simple fairing and active control was achieved via zero mass-flux blowing slots. Vortex sheet strength, estimated by integrating surface pressure ports, was used to predict vortex characteristics by means of inviscid rollup relations. Furthermore, vortices trailing the flaps were mapped using a seven-hole probe. Separation control was found to have a marked effect on vortex location, strength, tangential velocity, axial velocity and size over a wide range of angles of attack and control conditions. In general, the vortex trends were well predicted by the inviscid rollup relations. Manipulation of the separated flow near the flap edges exerted significant control over both outboard and inboard edge vortices while producing negligible lift excursions. Dynamic separation and attachment control was found to be an effective means for dynamically perturbing the vortex from arbitrarily long wavelengths down to wavelengths less than a typical wingspan. In summary, separation control has the potential for application to time-independent or time-dependent wake alleviation schemes, where the latter can be deployed to minimize adverse effects on ride-quality and dynamic structural loading.

  8. Jet vortex generators for turbulent flow separation control

    NASA Technical Reports Server (NTRS)

    Selby, G.; Lin, J.; Howard, F.

    1990-01-01

    A parametric study was performed with jet vortex generators to determine their effectiveness in controlling flow separation associated with low-speed turbulent flow over a two-dimensional rearward-facing ramp. Results indicate that flow separation control can be accomplished with the level of control achieved being a function of jet speed, jet orientation (with respect to the free-stream direction), and orifice pattern (double row of jets vs. single row). Compared to slot blowing, jet vortex generators can provide an equivalent level of flow control over a larger spanwise region (for constant jet flow area and speed).

  9. Jet vortex generators for turbulent flow separation control

    NASA Technical Reports Server (NTRS)

    Selby, Gregory; Lin, J.; Howard, F.

    1990-01-01

    A parametric study was performed with jet vortex generators to determine their effectiveness in controlling flow separation associated with low speed turbulent flow over a two dimensional rearward-facing ramp. Results indicate that flow separation control can be accomplished with the level of control achieved being a function of jet speed, jet orientation (with respect to the free stream direction), and orifice pattern (double row of jets vs. single row). Compared to slot blowing, jet vortex generators can provide an equivalent level of flow control over a larger spanwise region (for constant jet flow area and speed).

  10. Spatial patterning of P granules by RNA-induced phase separation of the intrinsically-disordered protein MEG-3.

    PubMed

    Smith, Jarrett; Calidas, Deepika; Schmidt, Helen; Lu, Tu; Rasoloson, Dominique; Seydoux, Geraldine

    2016-12-03

    RNA granules are non-membrane bound cellular compartments that contain RNA and RNA binding proteins. The molecular mechanisms that regulate the spatial distribution of RNA granules in cells are poorly understood. During polarization of the C. elegans zygote, germline RNA granules, called P granules, assemble preferentially in the posterior cytoplasm. We present evidence that P granule asymmetry depends on RNA-induced phase separation of the granule scaffold MEG-3. MEG-3 is an intrinsically disordered protein that binds and phase separates with RNA in vitro. In vivo, MEG-3 forms a posterior-rich concentration gradient that is anti-correlated with a gradient in the RNA-binding protein MEX-5. MEX-5 is necessary and sufficient to suppress MEG-3 granule formation in vivo, and suppresses RNA-induced MEG-3 phase separation in vitro. Our findings suggest that MEX-5 interferes with MEG-3's access to RNA, thus locally suppressing MEG-3 phase separation to drive P granule asymmetry. Regulated access to RNA, combined with RNA-induced phase separation of key scaffolding proteins, may be a general mechanism for controlling the formation of RNA granules in space and time.

  11. Spatial patterning of P granules by RNA-induced phase separation of the intrinsically-disordered protein MEG-3

    PubMed Central

    Smith, Jarrett; Calidas, Deepika; Schmidt, Helen; Lu, Tu; Rasoloson, Dominique; Seydoux, Geraldine

    2016-01-01

    RNA granules are non-membrane bound cellular compartments that contain RNA and RNA binding proteins. The molecular mechanisms that regulate the spatial distribution of RNA granules in cells are poorly understood. During polarization of the C. elegans zygote, germline RNA granules, called P granules, assemble preferentially in the posterior cytoplasm. We present evidence that P granule asymmetry depends on RNA-induced phase separation of the granule scaffold MEG-3. MEG-3 is an intrinsically disordered protein that binds and phase separates with RNA in vitro. In vivo, MEG-3 forms a posterior-rich concentration gradient that is anti-correlated with a gradient in the RNA-binding protein MEX-5. MEX-5 is necessary and sufficient to suppress MEG-3 granule formation in vivo, and suppresses RNA-induced MEG-3 phase separation in vitro. Our findings suggest that MEX-5 interferes with MEG-3’s access to RNA, thus locally suppressing MEG-3 phase separation to drive P granule asymmetry. Regulated access to RNA, combined with RNA-induced phase separation of key scaffolding proteins, may be a general mechanism for controlling the formation of RNA granules in space and time. DOI: http://dx.doi.org/10.7554/eLife.21337.001 PMID:27914198

  12. Who plans for health improvement? SEA, HIA and the separation of spatial planning and health planning

    SciTech Connect

    Bond, Alan; Cave, Ben; Ballantyne, Rob

    2013-09-15

    This study examines whether there is active planning for health improvement in the English spatial planning system and how this varies across two regions using a combination of telephone surveys and focus group interviews in 2005 and 2010. The spatial planning profession was found to be ill-equipped to consider the health and well-being implications of its actions, whilst health professionals are rarely engaged and have limited understanding and aspirations when it comes to influencing spatial planning. Strategic Environmental Assessment was not considered to be successful in integrating health into spatial plans, given it was the responsibility of planners lacking the capacity to do so. For their part, health professionals have insufficient knowledge and understanding of planning and how to engage with it to be able to plan for health gains rather than simply respond to health impacts. HIA practice is patchy and generally undertaken by health professionals outside the statutory planning framework. Thus, whilst appropriate assessment tools exist, they currently lack a coherent context within which they can function effectively and the implementation of the Kiev protocol requiring the engagement of health professionals in SEA is not to likely improve the consideration of health in planning while there continues to be separation of functions between professions and lack of understanding of the other profession. -- Highlights: ► Health professionals have limited aspirations for health improvement through the planning system. ► Spatial planners are ill-equipped to understand the health and well-being implications of their activities. ► SEA and HIA currently do not embed health consideration in planning decisions. ► The separation of health and planning functions is problematic for the effective conduct of SEA and/or HIA.

  13. Level measurement and control strategies for subsea separators

    NASA Astrophysics Data System (ADS)

    Hjertaker, Bjorn T.; Johansen, Geir A.; Jackson, Peter

    2001-07-01

    Level monitoring instrumentation is an essential part of hydrocarbon processing facilities, and has, together with separator technology, been widely addressed over the last decade. Key issues are production capacity, product enhancement, and well-flow control. The reliability and accuracy of the level instrumentation, and its ability to monitor all the interface layers of the separator, including the thickness of the foam and the oil-water emulsion, are particularly important when considering the level instrumentation as the main sensing element in the automatic control of the separator vessel. Lately, industry focus has been placed on optimal automatic control to improve the quality of the production output, and to minimize the use of expensive and environmentally undesirable separation enhancing chemicals. Recent developments in hydrocarbon production include subsea separation stations, where the constraints placed on the reliability and accuracy of the level instrumentation are especially demanding. This paper presents level interface monitoring developments based on electrical, ultrasonic, thermal, and nucleonic physical principles for three-phase hydrocarbon separators, and introduces the notion of tomometry, meaning multi-point cross-sectional metering aiming to acquire information on the cross-sectional flow-component distribution in the process vessel intended for control purposes.

  14. Initial Development of a Spatially Separated Speech-in-Noise and Localization Training Program

    PubMed Central

    Tyler, Richard S.; Witt, Shelley A.; Dunn, Camille C.; Wang, Wenjun

    2010-01-01

    Objective This article describes the initial development of a novel approach for training hearing-impaired listeners to improve their ability to understand speech in the presence of background noise and to also improve their ability to localize sounds. Design Most people with hearing loss, even those well fit with hearing devices, still experience significant problems understanding speech in noise. Prior research suggests that at least some subjects can experience improved speech understanding with training. However, all training systems that we are aware of have one basic, critical limitation. They do not provide spatial separation of the speech and noise, therefore ignoring the potential benefits of training binaural hearing. In this paper we describe our initial experience with a home-based training system that includes spatially separated speech-in-noise and localization training. Results Throughout the development of this system patient input, training and preliminary pilot data from individuals with bilateral cochlear implants were utilized. Positive feedback from subjective reports indicated that some individuals were engaged in the treatment, and formal testing showed benefit. Feedback and practical issues resulted from the reduction of an eight-loudspeaker to a two-loudspeaker system. Conclusions These preliminary findings suggest we have successfully developed a viable spatial hearing training system that can improve binaural hearing in noise and localization. Applications include, but are not limited to, hearing with hearing aids and cochlear implants. PMID:20701836

  15. Separation of spatial and temporal structure of auroral particle precipitation (Invited)

    NASA Astrophysics Data System (ADS)

    Boudouridis, A.; Spence, H.

    2013-12-01

    Knowledge of the dominant temporal and spatial scales of auroral features is instrumental in understanding the various mechanisms responsible for auroral particle precipitation. Single spacecraft data suffer from temporal/spatial ambiguity. In an effort to separate the temporal and spatial variations of the aurora, we use electron and ion precipitation data from two co-orbiting satellites, F6 and F8 of the Defense Meteorological Satellite Program (DMSP). The two spacecraft have almost identical polar orbits with a small difference in period. As a result the time difference between the two measurements varies with time. We use two statistical tools in order to determine the most probable lifetimes and spatial dimensions of the prevalent auroral features, Cross Correlation Analysis (CCA) and Cross Spectral Analysis (CSA). The CCA is applied to the magnetic latitude series of electron and ion, integral number and energy fluxes measured by the two DMSP spacecraft. As one spacecraft overtakes the other, the variable time lag between the two measurements results in different cross correlation of the two series. We explore the dependence of this variation on the time lag between the satellites. We find that the electron precipitation exhibits a decreasing correlation between the two spacecraft with increasing time lag, whereas there is only a small similar effect for the ion precipitation data. For the CSA we compute the so-called coherence function as a function of frequency (or inverse wavelength), and hence size of the auroral features. The coherence function is a measure of the stability of auroral features of different sizes. We investigate its variation as a function of the time separation between the two DMSP spacecraft measurements. We show that the coherence function of both electrons and ions remains high for up to 1.5 min spacecraft separations for all features larger than about 100 km in width. For smaller features the coherence is lower even for time lags of

  16. Debris control design achievements of the booster separation motors

    NASA Technical Reports Server (NTRS)

    Smith, G. W.; Chase, C. A.

    1985-01-01

    The stringent debris control requirements imposed on the design of the Space Shuttle booster separation motor are described along with the verification program implemented to ensure compliance with debris control objectives. The principal areas emphasized in the design and development of the Booster Separation Motor (BSM) relative to debris control were the propellant formulation and nozzle closures which protect the motors from aerodynamic heating and moisture. A description of the motor design requirements, the propellant formulation and verification program, and the nozzle closures design and verification are presented.

  17. Phase separation explains a new class of self-organized spatial patterns in ecological systems.

    PubMed

    Liu, Quan-Xing; Doelman, Arjen; Rottschäfer, Vivi; de Jager, Monique; Herman, Peter M J; Rietkerk, Max; van de Koppel, Johan

    2013-07-16

    The origin of regular spatial patterns in ecological systems has long fascinated researchers. Turing's activator-inhibitor principle is considered the central paradigm to explain such patterns. According to this principle, local activation combined with long-range inhibition of growth and survival is an essential prerequisite for pattern formation. Here, we show that the physical principle of phase separation, solely based on density-dependent movement by organisms, represents an alternative class of self-organized pattern formation in ecology. Using experiments with self-organizing mussel beds, we derive an empirical relation between the speed of animal movement and local animal density. By incorporating this relation in a partial differential equation, we demonstrate that this model corresponds mathematically to the well-known Cahn-Hilliard equation for phase separation in physics. Finally, we show that the predicted patterns match those found both in field observations and in our experiments. Our results reveal a principle for ecological self-organization, where phase separation rather than activation and inhibition processes drives spatial pattern formation.

  18. Successful retrieval of competing spatial environments in humans involves hippocampal pattern separation mechanisms

    PubMed Central

    Kyle, Colin T; Stokes, Jared D; Lieberman, Jennifer S; Hassan, Abdul S; Ekstrom, Arne D

    2015-01-01

    The rodent hippocampus represents different spatial environments distinctly via changes in the pattern of “place cell” firing. It remains unclear, though, how spatial remapping in rodents relates more generally to human memory. Here participants retrieved four virtual reality environments with repeating or novel landmarks and configurations during high-resolution functional magnetic resonance imaging (fMRI). Both neural decoding performance and neural pattern similarity measures revealed environment-specific hippocampal neural codes. Conversely, an interfering spatial environment did not elicit neural codes specific to that environment, with neural activity patterns instead resembling those of competing environments, an effect linked to lower retrieval performance. We find that orthogonalized neural patterns accompany successful disambiguation of spatial environments while erroneous reinstatement of competing patterns characterized interference errors. These results provide the first evidence for environment-specific neural codes in the human hippocampus, suggesting that pattern separation/completion mechanisms play an important role in how we successfully retrieve memories. DOI: http://dx.doi.org/10.7554/eLife.10499.001 PMID:26613414

  19. Application of THz probe radiation in low-coherent tomographs based on spatially separated counterpropagating beams

    SciTech Connect

    Kuritsyn, I I; Shkurinov, A P; Nazarov, M M; Mandrosov, V I; Cherkasova, O P

    2013-10-31

    A principle of designing a high-resolution low-coherent THz tomograph, which makes it possible to investigate media with a high spatial resolution (in the range λ{sub 0} – 2λ{sub 0}, where λ{sub 0} is the average probe wavelength) is considered. The operation principle of this tomograph implies probing a medium by radiation with a coherence length of 8λ{sub 0} and recording a hologram of a focused image of a fixed layer of this medium using spatially separated counterpropagating object and reference beams. Tomograms of the medium studied are calculated using a temporal approach based on application of the time correlation function of probe radiation. (terahertz radiation)

  20. Analysis of stratocumulus cloud fields using LANDSAT imagery: Size distributions and spatial separations

    NASA Technical Reports Server (NTRS)

    Welch, R. M.; Sengupta, S. K.; Chen, D. W.

    1990-01-01

    Stratocumulus cloud fields in the FIRE IFO region are analyzed using LANDSAT Thematic Mapper imagery. Structural properties such as cloud cell size distribution, cell horizontal aspect ratio, fractional coverage and fractal dimension are determined. It is found that stratocumulus cloud number densities are represented by a power law. Cell horizontal aspect ratio has a tendency to increase at large cell sizes, and cells are bi-fractal in nature. Using LANDSAT Multispectral Scanner imagery for twelve selected stratocumulus scenes acquired during previous years, similar structural characteristics are obtained. Cloud field spatial organization also is analyzed. Nearest-neighbor spacings are fit with a number of functions, with Weibull and Gamma distributions providing the best fits. Poisson tests show that the spatial separations are not random. Second order statistics are used to examine clustering.

  1. The effect of spatial separation on informational and energetic masking of speech.

    PubMed

    Arbogast, Tanya L; Mason, Christine R; Kidd, Gerald

    2002-11-01

    The effect of spatial separation of sources on the masking of a speech signal was investigated for three types of maskers, ranging from energetic to informational. Normal-hearing listeners performed a closed-set speech identification task in the presence of a masker at various signal-to-noise ratios. Stimuli were presented in a quiet sound field. The signal was played from 0 degrees azimuth and a masker was played either from the same location or from 90 degrees to the right. Signals and maskers were derived from sentences that were preprocessed by a modified cochlear-implant simulation program that filtered each sentence into 15 frequency bands, extracted the envelopes from each band, and used these envelopes to modulate pure tones at the center frequencies of the bands. In each trial, the signal was generated by summing together eight randomly selected frequency bands from the preprocessed signal sentence. Three maskers were derived from the preprocessed masker sentences: (1) different-band sentence, which was generated by summing together six randomly selected frequency bands out of the seven bands not present in the signal (resulting in primarily informational masking); (2) different-band noise, which was generated by convolving the different-band sentence with Gaussian noise; and (3) same-band noise, which was generated by summing the same eight bands from the preprocessed masker sentence that were used in the signal sentence and convolving the result with Gaussian noise (resulting in primarily energetic masking). Results revealed that in the different-band sentence masker, the effect of spatial separation averaged 18 dB (at 51% correct), while in the different-band and same-band noise maskers the effect was less than 10 dB. These results suggest that, in these conditions, the advantage due to spatial separation of sources is greater for informational masking than for energetic masking.

  2. Biexcitons formed from spatially separated electrons and holes in quasi-zero-dimensional semiconductor nanosystems

    SciTech Connect

    Pokutnyi, S. I.

    2013-12-15

    A theory of biexcitons (formed from spatially separated electron and holes) in nanosystems that consist of zinc-selenide quantum dots synthesized in borosilicate glassy matrices is developed. The dependences of the total energy and the binding energy of the singlet ground biexciton state in such a system on the spacing between the quantum-dot surfaces and the quantum-dot radius are derived by the variational method. It is shown that biexciton formation is of the threshold character and possible in nanosystems, in which the spacing between the quantum-dot surfaces is larger than a certain critical spacing.

  3. Spatial Electron-hole Separation in a One Dimensional Hybrid Organic–Inorganic Lead Iodide

    PubMed Central

    Savory, Christopher N.; Palgrave, Robert G.; Bronstein, Hugo; Scanlon, David O.

    2016-01-01

    The increasing efficiency of the inorganic-organic hybrid halides has revolutionised photovoltaic research. Despite this rapid progress, the significant issues of poor stability and toxicity have yet to be suitably overcome. In this article, we use Density Functional Theory to examine (Pb2I6) · (H2DPNDI) · (H2O) · (NMP), an alternative lead-based hybrid inorganic-organic solar absorber based on a photoactive organic cation. Our results demonstrate that optical properties suitable for photovoltaic applications, in addition to spatial electron-hole separation, are possible but efficient charge transport may be a limiting factor. PMID:26858147

  4. Spatial Electron-hole Separation in a One Dimensional Hybrid Organic-Inorganic Lead Iodide.

    PubMed

    Savory, Christopher N; Palgrave, Robert G; Bronstein, Hugo; Scanlon, David O

    2016-02-09

    The increasing efficiency of the inorganic-organic hybrid halides has revolutionised photovoltaic research. Despite this rapid progress, the significant issues of poor stability and toxicity have yet to be suitably overcome. In this article, we use Density Functional Theory to examine (Pb2I6) · (H2DPNDI) · (H2O) · (NMP), an alternative lead-based hybrid inorganic-organic solar absorber based on a photoactive organic cation. Our results demonstrate that optical properties suitable for photovoltaic applications, in addition to spatial electron-hole separation, are possible but efficient charge transport may be a limiting factor.

  5. Analysis of Rawinsonde Spatial Separation for Space Launch Vehicle Applications at the Eastern Range

    NASA Technical Reports Server (NTRS)

    Decker, Ryan K.

    2017-01-01

    Spatial separation of HR rawinsonde data is directly correlated with climatological tropospheric wind environment over ER. Stronger winds in the winter result in further downrange drift. Lighter winds in the summer result in the less horizontal drift during ascent. Maximum downrange distance can exceed 200 km during winter months. Data could misrepresent the environment the vehicle will experience during ascent. PRESTO uses all available data sources to produce the best representative, vertically complete atmosphere for launch vehicle DOL operations. Capability planned for use by NASA Space Launch System vehicle's first flight scheduled for Fall 2018.

  6. Spatial pattern separation of chemicals and frequency-independent components by terahertz spectroscopic imaging

    NASA Astrophysics Data System (ADS)

    Watanabe, Yuuki; Kawase, Kodo; Ikari, Tomofumi; Ito, Hiromasa; Ishikawa, Youichi; Minamide, Hiroaki

    2003-10-01

    We separated the component spatial patterns of frequency-dependent absorption in chemicals and frequency-independent components such as plastic, paper, and measurement noise in terahertz (THz) spectroscopic images, using known spectral curves. Our measurement system, which uses a widely tunable coherent THz-wave parametric oscillator source, can image at a specific frequency in the range 1-2 THz. The component patterns of chemicals can easily be extracted by use of the frequency-independent components. This method could be successfully used for nondestructive inspection for the detection of illegal drugs and devices of bioterrorism concealed, e.g., inside mail and packages.

  7. Continuous measurement of two spatially separated superconducting qubits: Quantum trajectories and feedback

    NASA Astrophysics Data System (ADS)

    Schwartz, M. E.; Roch, N.; Motzoi, F.; Whaley, B.; Korotkov, A. N.; Sarovar, M.; Siddiqi, I.

    2014-03-01

    Measurement can be harnessed to probabilistically generate entanglement in the absence of local interactions, for example between spatially separated quantum objects. Continuous weak measurement allows us to observe the dynamics associated with this process. In particular, we perform joint dispersive readout of two superconducting transmon qubits separated by one meter of coaxial cable. We track the evolution of a joint quantum state under the influence of measurement, both as an ensemble and as a set of individual quantum trajectories. We analyze the statistics of such quantum trajectories and find good agreement with a Bayesian formalism for a two-body quantum system. Such tracking opens the door to continuous feedback-stabilized remote entanglement. This work was supported by the Army Research Office and by the Fannie and John Hertz Foundation.

  8. Control of flow separation in airfoil/wing design applications

    NASA Technical Reports Server (NTRS)

    Gally, Thomas A.

    1994-01-01

    Existing aerodynamic design methods have generally concentrated on the optimization of airfoil or wing shapes to produce a minimum drag while satisfying some basic constraints such as lift, pitching moment, or thickness. Since the minimization of drag almost always precludes the existence of separated flow, the evaluation and validation of these design methods for their robustness and accuracy when separated flow is present has not been aggressively pursued. However, two new applications for these design tools may be expected to include separated flow and the issues of aerodynamic design with this feature must be addressed. The first application of the aerodynamic design tools is the design of airfoils or wings to provide an optimal performance over a wide range of flight conditions (multipoint design). While the definition of 'optimal performance' in the multipoint setting is currently being hashed out, it is recognized that given a wide enough range of flight conditions, it will not be possible to ensure a minimum drag constraint at all conditions, and in fact some amount of separated flow (presumably small) may have to be allowed at the more demanding flight conditions. Thus a multipoint design method must be tolerant of the existence of separated flow and may include some controls upon its extent. The second application is in the design of wings with extended high speed buffet boundaries of their flight envelopes. Buffet occurs on a wing when regions of flow separation have grown to the extent that their time varying pressures induce possible destructive effects upon the wing structure or adversely effect either the aircraft controllability or the passenger comfort. A conservative approach to the expansion of the buffet flight boundary is to simply expand the flight envelope of nonseparated flow under the assumption that buffet will also thus be alleviated. However, having the ability to design a wing with separated flow and thus to control the location, extent

  9. Spatial Heterogeneity in Cancer Control Planning and Cancer Screening Behavior.

    PubMed

    Mobley, Lee R; Kuo, Tzy-Mey; Urato, Matthew; Subramanian, Sujha; Watson, Lisa; Anselin, Luc

    2012-01-01

    Each state is autonomous in its comprehensive cancer control (CCC) program, and considerable heterogeneity exists in the program plans. However, researchers often focus on the concept of nationally representative data and pool observations across states using regression analysis to come up with average effects when interpreting results. Due to considerable state autonomy and heterogeneity in various dimensions-including culture, politics, historical precedent, regulatory environment, and CCC efforts-it is important to examine states separately and to use geographic analysis to translate findings in place and time. We used 100 percent population data for Medicare-insured persons aged 65 or older and examined predictors of breast cancer (BC) and colorectal cancer (CRC) screening from 2001-2005. Examining BC and CRC screening behavior separately in each state, we performed 100 multilevel regressions. We summarize the state-specific findings of racial disparities in screening for either cancer in a single bivariate map of the 50 states, producing a separate map for African American and for Hispanic disparities in each state relative to whites. The maps serve to spatially translate the voluminous regression findings regarding statistically significant disparities between whites and minorities in cancer screening within states. Qualitative comparisons can be made of the states' disparity environments or for a state against a national benchmark using the bivariate maps. We find that African Americans in Michigan and Hispanics in New Jersey are significantly more likely than whites to utilize CRC screening and that Hispanics in 6 states are significantly and persistently more likely to utilize mammography than whites. We stress the importance of spatial translation research for informing and evaluating CCC activities within states and over time.

  10. Optimal control of an asymptotic model of flow separation

    NASA Astrophysics Data System (ADS)

    Qadri, Ubaid; Schmid, Peter; LFC-UK Team

    2015-11-01

    In the presence of surface imperfections, the boundary layer developing over an aircraft wing can separate and reattach, leading to a small separation bubble. We are interested in developing a low-order model that can be used to control the onset of separation at high Reynolds numbers typical of aircraft flight. In contrast to previous studies, we use a high Reynolds number asymptotic description of the Navier-Stokes equations to describe the motion of motion of the fluid. We obtain a steady solution to the nonlinear triple-deck equations for the separated flow over a small bump at high Reynolds numbers. We derive for the first time the adjoint of the nonlinear triple-deck equations and use it to study optimal control of the separated flow. We calculate the sensitivity of the properties of the separation bubble to local base flow modifications and steady forcing. We assess the validity of using this simplified asymptotic model by comparing our results with those obtained using the full Navier-Stokes equations.

  11. Reticulated Nanoporous Polymers by Controlled Polymerization-Induced Microphase Separation

    SciTech Connect

    Seo, Myungeun; Hillmyer, Marc A.

    2013-04-08

    Materials with percolating mesopores are attractive for applications such as catalysis, nanotemplating, and separations. Polymeric frameworks are particularly appealing because the chemical composition and the surface chemistry are readily tunable. We report on the preparation of robust nanoporous polymers with percolating pores in the 4- to 8-nanometer range from a microphase-separated bicontinuous precursor. We combined polymerization-induced phase separation with in situ block polymer formation from a mixture of multifunctional monomers and a chemically etchable polymer containing a terminal chain transfer agent. This marriage results in microphase separation of the mixture into continuous domains of the etchable polymer and the emergent cross-linked polymer. Precise control over pore size distribution and mechanical integrity renders these materials particularly suited for various advanced applications.

  12. Low-Pressure Turbine Separation Control: Comparison With Experimental Data

    NASA Technical Reports Server (NTRS)

    Garg, Vijay K.

    2002-01-01

    The present work details a computational study, using the Glenn HT code, that analyzes the use of vortex generator jets (VGJs) to control separation on a low-pressure turbine (LPT) blade at low Reynolds numbers. The computational results are also compared with the experimental data for steady VGJs. It is found that the code determines the proper location of the separation point on the suction surface of the baseline blade (without any VGJ) for Reynolds numbers of 50,000 or less. Also, the code finds that the separated region on the suction surface of the blade vanishes with the use of VGJs. However, the separated region and the wake characteristics are not well predicted. The wake width is generally over-predicted while the wake depth is under-predicted.

  13. Closed-loop Separation Control Using Oscillatory Flow Excitation

    NASA Technical Reports Server (NTRS)

    Allan, Brian G.; Juang, Jer-Nan; Raney, David L.; Seifert, Avi; Pack, latunia G.; Brown, Donald E.

    2000-01-01

    Design and implementation of a digital feedback controller for a flow control experiment was performed. The experiment was conducted in a cryogenic pressurized wind tunnel on a generic separated configuration at a chord Reynolds number of 16 million and a Mach number of 0.25. The model simulates the upper surface of a 20% thick airfoil at zero angle-of-attack. A moderate favorable pressure gradient, up to 55% of the chord, is followed by a severe adverse pressure gradient which is relaxed towards the trailing edge. The turbulent separation bubble, behind the adverse pressure gradient, is then reduced by introducing oscillatory flow excitation just upstream of the point of flow separation. The degree of reduction in the separation region can be controlled by the amplitude of the oscillatory excitation. A feedback controller was designed to track a given trajectory for the desired degree of flow reattachment and to improve the transient behavior of the flow system. Closed-loop experiments demonstrated that the feedback controller was able to track step input commands and improve the transient behavior of the open-loop response.

  14. The Role of Vorticity Injection in Separation Control

    NASA Astrophysics Data System (ADS)

    Taira, Kunihiko; Munday, Phillip

    2013-11-01

    Large eddy simulation is performed to examine the role of vorticity injection in separation control of spanwise periodic flow over a NACA0012 airfoil. The computations are conducted with a high-fidelity LES solver CharLES with sufficient grid resolution to resolve the near-wall turbulence at a moderate Reynolds number of Re = 23 , 000 . The actuator input is introduced to the flow field through the velocity boundary condition to specify the desired vorticity flux input. The aim of this investigation is to analyze the influence of the injected vorticity magnitude and direction on the separation physics over the airfoil such that the separation is delayed. The vortical perturbation is added to break apart the large spanwise vortices responsible for causing separation and hence delay stall. The range of the vorticity injected is chosen to match those from commonly used flow control devices for separation control. In this study, particular focus is placed on examining the interaction between the actuator input and the inherent Kelvin-Helmholtz and spanwise instabilities. Work supported by AFOSR (Award No. FA9550-13-1-0183).

  15. Spatial separation and bidirectional trafficking of proteins using a multi-functional reporter

    PubMed Central

    Svendsen, Soshana; Zimprich, Chad; McDougall, Mark G; Klaubert, Dieter H; Los, Georgyi V

    2008-01-01

    Background The ability to specifically label proteins within living cells can provide information about their dynamics and function. To study a membrane protein, we fused a multi-functional reporter protein, HaloTag®, to the extracellular domain of a truncated integrin. Results Using the HaloTag technology, we could study the localization, trafficking and processing of an integrin-HaloTag fusion, which we showed had cellular dynamics consistent with native integrins. By labeling live cells with different fluorescent impermeable and permeable ligands, we showed spatial separation of plasma membrane and internal pools of the integrin-HaloTag fusion, and followed these protein pools over time to study bi-directional trafficking. In addition to combining the HaloTag reporter protein with different fluorophores, we also employed an affinity tag to achieve cell capture. Conclusion The HaloTag technology was used successfully to study expression, trafficking, spatial separation and real-time translocation of an integrin-HaloTag fusion, thereby demonstrating that this technology can be a powerful tool to investigate membrane protein biology in live cells. PMID:18384686

  16. Binding energy of excitons formed from spatially separated electrons and holes in insulating quantum dots

    SciTech Connect

    Pokutnyi, S. I.; Kulchin, Yu. N.; Dzyuba, V. P.

    2015-10-15

    It is found that the binding energy of the ground state of an exciton formed from an electron and a hole spatially separated from each other (the hole is moving within a quantum dot, and the electron is localized above the spherical (quantum dot)–(insulating matrix) interface) in a nanosystem containing insulating Al{sub 2}O{sub 3} quantum dots is substantially increased (by nearly two orders of magnitude) compared to the exciton binding energy in an Al{sub 2}O{sub 3} single crystal. It is established that, in the band gap of an Al{sub 2}O{sub 3} nanoparticle, a band of exciton states (formed from spatially separated electrons and holes) appears. It is shown that there exists the possibility of experimentally detecting the ground and excited exciton states in the band gap of Al{sub 2}O{sub 3} nanoparticles at room temperature from the absorption spectrum of the nanosystem.

  17. Part Ia: Spatial separation on McGurk effect applying three-dimensional sounds

    NASA Astrophysics Data System (ADS)

    Riederer, Klaus A. J.

    2003-10-01

    The dependence of sound direction on the McGurk effect [McGurk and McDonald, Nature (London) 264, 746-748 (1976)] is less known. Jones and Munhall [Canadian Acoust. 25, 13-19 (1997)] concluded with no spatial separation dependence, applying 30° horizontally spaced loudspeakers. Current dual study investigated the full 360° horizontal space applying head-related transfer functions (HRTFs) from a Cortex dummy head [Riederer, J. Audio Eng. Soc. (Abstracts) 46, 1036 (1998), preprint 4846]. Dry acoustic /ipi/ and /iti/ recorded from a professional speaker were convolved with HRTFs, measured at azimuths 0°, +/-40°, +/-90°, +/-130°, and 180°, headphones (Sennheiser HD580) equalized. DVcam-recorded visual /ipi/, /iti/ (and black screen) were randomly presented synchronously with the 3-D sounds using Presentation 0.20 [http://nbs.neuro-bs.com]. Totally 1024 incongruent audiovisual stimuli were perceived by eight 20-30-year-old normal hearing (<=20 dBHL) native subjects (2 female) as follows. Visual /ipi/ + auditory /iti/: /ipi/ 59.96%, /iti/ 15.63%, and /ipti/ 24.02% visual /iti/ + auditory /ipi/: 66.02%, 22.07%, and 11.52%, respectfully. No significant dependence of spatial separation was found for the McGurk effect, except for reaction times. The obtained fusions were atypically weak, probably because visual /iti/ was less pronounced than visual /ipi/. [Work supported by Graduate School of Electronics, Telecommunication and Automation.

  18. Spatial separation of Golgi and ER during mitosis protects SREBP from unregulated activation

    PubMed Central

    Bartz, René; Sun, Li-Ping; Bisel, Blaine; Wei, Jen-Hsuan; Seemann, Joachim

    2008-01-01

    Sterol regulatory element-binding proteins (SREBPs) are membrane-bound transcription factors that reside as inactive precursors in the endoplasmic reticulum (ER) membrane. After sterol depletion, the proteins are transported to the Golgi apparatus, where they are cleaved by site-1 protease (S1P). Cleavage releases the active transcription factors, which then enter the nucleus to induce genes that regulate cellular levels of cholesterol and phospholipids. This regulation depends on the spatial separation of the Golgi and the ER, as mixing of the compartments induces unregulated activation of SREBPs. Here, we show that S1P is localized to the Golgi, but cycles continuously through the ER and becomes trapped when ER exit is inhibited. During mitosis, S1P is associated with mitotic Golgi clusters, which remain distinct from the ER. In mitotic cells, S1P is active, but SREBP is not cleaved as S1P and SREBP reside in different compartments. Together, these results indicate that the spatial separation of the Golgi and the ER is maintained during mitosis, which is essential to protect the S1P substrate SREBP from unregulated activation during mitosis. PMID:18323777

  19. Spatial separation of Golgi and ER during mitosis protects SREBP from unregulated activation.

    PubMed

    Bartz, René; Sun, Li-Ping; Bisel, Blaine; Wei, Jen-Hsuan; Seemann, Joachim

    2008-04-09

    Sterol regulatory element-binding proteins (SREBPs) are membrane-bound transcription factors that reside as inactive precursors in the endoplasmic reticulum (ER) membrane. After sterol depletion, the proteins are transported to the Golgi apparatus, where they are cleaved by site-1 protease (S1P). Cleavage releases the active transcription factors, which then enter the nucleus to induce genes that regulate cellular levels of cholesterol and phospholipids. This regulation depends on the spatial separation of the Golgi and the ER, as mixing of the compartments induces unregulated activation of SREBPs. Here, we show that S1P is localized to the Golgi, but cycles continuously through the ER and becomes trapped when ER exit is inhibited. During mitosis, S1P is associated with mitotic Golgi clusters, which remain distinct from the ER. In mitotic cells, S1P is active, but SREBP is not cleaved as S1P and SREBP reside in different compartments. Together, these results indicate that the spatial separation of the Golgi and the ER is maintained during mitosis, which is essential to protect the S1P substrate SREBP from unregulated activation during mitosis.

  20. Spatial separation of individual substances in effloresced crystals of ternary ammonium sulphate/dicarboxylic acid/water aerosols.

    PubMed

    Treuel, Lennart; Sandmann, Alice; Zellner, Reinhard

    2011-04-18

    This work examines the crystals resulting from the efflorescence of internally mixed aqueous aerosols comprising ammonium sulphate and different dicarboxylic acids. Most studies on the deliquescence of aerosols use previously effloresced aerosols in their experiments. However, during efflorescence a highly supersaturated solution crystallises in a kinetically controlled way unlike the case of thermodynamically controlled crystallisation. Herein the distribution of individual substances within the effloresced crystals is investigated using Raman scanning experiments. The data presented show an intriguingly complex behaviour of these ternary and quarternary aerosols. A spatial separation of substances in the crystals resulting from the efflorescence of previously internally mixed ternary salt/dicarboxylic acid/water aerosol droplets is demonstrated and mechanistic aspects are discussed.

  1. Concurrent emotional pictures modulate temporal order judgments of spatially separated audio-tactile stimuli.

    PubMed

    Jia, Lina; Shi, Zhuanghua; Zang, Xuelian; Müller, Hermann J

    2013-11-06

    Although attention can be captured toward high-arousal stimuli, little is known about how perceiving emotion in one modality influences the temporal processing of non-emotional stimuli in other modalities. We addressed this issue by presenting observers spatially uninformative emotional pictures while they performed an audio-tactile temporal-order judgment (TOJ) task. In Experiment 1, audio-tactile stimuli were presented at the same location straight ahead of the participants, who had to judge "which modality came first?". In Experiments 2 and 3, the audio-tactile stimuli were delivered one to the left and the other to the right side, and participants had to judge "which side came first?". We found both negative and positive high-arousal pictures to significantly bias TOJs towards the tactile and away from the auditory event when the audio-tactile stimuli were spatially separated; by contrast, there was no such bias when the audio-tactile stimuli originated from the same location. To further examine whether this bias is attributable to the emotional meanings conveyed by the pictures or to their high arousal effect, we compared and contrasted the influences of near-body threat vs. remote threat (emotional) pictures on audio-tactile TOJs in Experiment 3. The bias manifested only in the near-body threat condition. Taken together, the findings indicate that visual stimuli conveying meanings of near-body interaction activate a sensorimotor functional link prioritizing the processing of tactile over auditory signals when these signals are spatially separated. In contrast, audio-tactile signals from the same location engender strong crossmodal integration, thus counteracting modality-based attentional shifts induced by the emotional pictures. © 2013 Published by Elsevier B.V.

  2. Separation Control in a Multistage Compressor Using Impulsive Surface Injection

    NASA Technical Reports Server (NTRS)

    Wundrow, David W.; Braunscheidel, Edward P.; Culley, Dennis E.; Bright, Michelle M.

    2006-01-01

    Control of flow separation using impulsive surface injection is investigated within the multistage environment of a low speed axial-flow compressor. Measured wake profiles behind a set of embedded stator vanes treated with suction-surface injection indicate significant reduction in flow separation at a variety of injection-pulse repetition rates and durations. The corresponding total pressure losses across the vanes reveal a bank of repetition rates at each pulse duration where the separation control remains nearly complete. This persistence allows for demands on the injected-mass delivery system to be economized while still achieving effective flow control. The response of the stator-vane boundary layers to infrequently applied short injection pulses is described in terms of the periodic excitation of turbulent strips whose growth and propagation characteristics dictate the lower bound on the band of optimal pulse repetition rates. The eventual falloff in separation control at higher repetition rates is linked to a competition between the benefits of pulse-induced mixing and the aggravation caused by the periodic introduction of low-momentum fluid. Use of these observations for impulsive actuator design is discussed and their impact on modeling the time-average effect of impulsive surface injection for multistage steady-flow simulation is considered.

  3. Fluid Mechanics of Wing Adaptation for Separation Control

    NASA Technical Reports Server (NTRS)

    Chandrasekhara, M. S.; Wilder, M. C.; Carr, L. W.; Davis, Sanford S. (Technical Monitor)

    1997-01-01

    The unsteady fluid mechanics associated with use of a dynamically deforming leading edge airfoil for achieving compressible flow separation control has been experimentally studied. Changing the leading edge curvature at rapid rates dramatically alters the flow vorticity dynamics which is responsible for the many effects observed in the flow.

  4. Interaction dynamics of temporal and spatial separated cavitation bubbles in water

    NASA Astrophysics Data System (ADS)

    Tinne, N.; Ripken, T.; Lubatschowski, H.

    2010-02-01

    The LASIK procedure is a well established laser based treatment in ophthalmology. Nowadays it includes a cutting of the corneal tissue bases on ultra short pulses which are focused below the tissue surface to create an optical breakdown and hence a dissection of the tissue. The energy of the laser pulse is absorbed by non-linear processes that result in an expansion of a cavitation bubble and rupturing of the tissue. Due to a reduction of the duration of treatment the current development of ultra short laser systems points to higher repetition rates. This in turn results in a probable interaction between different cavitation bubbles of adjacent optical breakdowns. While the interaction of one single laser pulse with biological tissue is analyzed reasonably well experimentally and theoretically, the interaction of several spatial and temporal following pulses is scarcely determined yet. We present a high-speed photography analysis of cavitation bubble interaction for two spatial separated laser-induced optical breakdowns varying the laser pulse energy as well as the spatial distance. Depending on a change of these parameters different kinds of interactions such as a flattening and deformation of bubble shape, asymmetric water streams and jet formation were observed. The results of this research can be used to comprehend and optimize the cutting effect of ultra short pulse laser systems with high repetition rates (> 1 MHz).

  5. Toward the optimization of control of unsteady separation

    NASA Technical Reports Server (NTRS)

    Shen, S. F.; Xiao, Zheng-Hua

    1992-01-01

    Regardless of our understanding of the complicated physical process, means can always be found to alter the occurrence and development of unsteady separation. To be able to optimize the control of separation, however, requires the identification of the critical aspects to which the intervention may be focused and achieve the desired result with minimum waste of effort. The Lagrangian analysis of unsteady boundary-layer traces the trajectories of individual fluid particles and reveals the 'bad seeds' that, through extreme deformation in the direction normal to the wall, eventually develop into a virtual barrier and cause the ejection of boundary-layer material into the main stream. It follows logically that separation can be triggered or delayed most effectively by targeting these 'bad seeds.' Since they are normally interior points of the boundary layer, attempts to influence them through the boundary conditions are necessarily indirect. Furthermore, as the strategy has to be the modification of the growing process of the 'bad seeds,' whatever may be the intervention scheme, it needs to be strong enough and early enough. In Shen and Wu, examples of how acceleration/deceleration of the two dimensional body, as well as the moving wall of a rotating cylinder, may affect the development of the bad seed toward separation are shown. In fact it was mentioned therein that the results might be the first step for a feasibility study of the control of unsteady separation. Presented are additional results of applying suction to an impulsively started circular cylinder.

  6. Flow Separation Control Over a Ramp Using Sweeping Jet Actuators

    NASA Technical Reports Server (NTRS)

    Koklu, Mehti; Owens, Lewis R.

    2014-01-01

    Flow separation control on an adverse-pressure-gradient ramp model was investigated using various flow-control methods in the NASA Langley 15-Inch Wind Tunnel. The primary flow-control method studied used a sweeping jet actuator system to compare with more classic flow-control techniques such as micro-vortex generators, steady blowing, and steady- and unsteady-vortex generating jets. Surface pressure measurements and a new oilflow visualization technique were used to characterize the effects of these flow-control actuators. The sweeping jet actuators were run in three different modes to produce steady-straight, steady-angled, and unsteady-oscillating jets. It was observed that all of these flow-control methods are effective in controlling the separated flows on the ramp model. The steady-straight jet energizes the boundary layer by momentum addition and was found to be the least effective method for a fixed momentum coefficient. The steady-angled jets achieved better performance than the steady-straight jets because they generate streamwise vortices that energize the boundary layer by mixing high-momentum fluid with near wall low-momentum fluid. The unsteady-oscillating jets achieved the best performance by increasing the pressure recovery and reducing the downstream flow separation. Surface flow visualizations indicated that two out-of-phase counter-rotating vortices are generated per sweeping jet actuator, while one vortex is generated per vortex-generating jets. The extra vortex resulted in increased coverage, more pressure recovery, and reduced flow separation.

  7. Demonstration of Separation Control Using Glow-Discharge Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.; Ashpis, David E.

    2003-01-01

    Active flow control of boundary-layer separation using glow-discharge plasma actuators is studied experimentally. Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modem low-pressure-turbine airfoil. The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2%) and high (2.5%) free-stream turbulence intensities are set using passive grids. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface-flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the base and controlled flows are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control.

  8. Computation of a controlled store separation from a cavity

    NASA Technical Reports Server (NTRS)

    Atwood, Christopher A.

    1993-01-01

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

  9. Design and Synthesis of TiO2 Hollow Spheres with Spatially Separated Dual Cocatalysts for Efficient Photocatalytic Hydrogen Production

    PubMed Central

    Jiang, Qianqian; Li, Li; Bi, Jinhong; Liang, Shijing; Liu, Minghua

    2017-01-01

    TiO2 hollow spheres modified with spatially separated Ag species and RuO2 cocatalysts have been prepared via an alkoxide hydrolysis–precipitation method and a facile impregnation method. High-resolution transmission electron microscopy studies indicate that Ag species and RuO2 co-located on the inner and outer surface of TiO2 hollow spheres, respectively. The resultant catalysts show significantly enhanced activity in photocatalytic hydrogen production under simulated sunlight attributed to spatially separated Ag species and RuO2 cocatalysts on TiO2 hollow spheres, which results in the efficient separation and transportation of photogenerated charge carriers. PMID:28336859

  10. Experimental models of small closed systems with spatially separated unicellular organism-based components.

    PubMed

    Pis'man, T I; Pechurkin, N S; Sarangova, A B; Somova, L A

    1999-01-01

    Experimental models of small biotic cycles of different degree of closure and complexity with spatially separated components based on unicellular organisms have been studied. Gas closure of components looped into "autotroph-heterotroph" (chlorella-yeast) system doubled the lifetime of the system (as opposed to individually cultivated components). Higher complexity of the heterotroph component consisting of two yeast species also increased the lifetime of the system through more complete utilization of the substrate by competing yeast species. The lifetime of gas and substrate closed "producer-consumer" trophic chain (chlorella-paramecia) increased to 7 months. In 60 days the components' numbers reached their steady state followed by more than 40 cycles of the medium. The role of a predator organism (protozoan) in nitrogen cycling was demonstrated; reproduction of protozoa correlated directly with their emission of nitrogen in the ammonia form that is most optimum for growth of chlorella.

  11. Physical optimization of quantum error correction circuits with spatially separated quantum dot spins.

    PubMed

    Wang, Hong-Fu; Zhu, Ai-Dong; Zhang, Shou

    2013-05-20

    We propose an efficient protocol for optimizing the physical implementation of three-qubit quantum error correction with spatially separated quantum dot spins via virtual-photon-induced process. In the protocol, each quantum dot is trapped in an individual cavity and each two cavities are connected by an optical fiber. We propose the optimal quantum circuits and describe the physical implementation for correcting both the bit flip and phase flip errors by applying a series of one-bit unitary rotation gates and two-bit quantum iSWAP gates that are produced by the long-range interaction between two distributed quantum dot spins mediated by the vacuum fields of the fiber and cavity. The protocol opens promising perspectives for long distance quantum communication and distributed quantum computation networks.

  12. The temporal and spatial separation of specific syntheses in the process of chondrogenesis (electron microscopic investigation).

    PubMed

    Kerkis, A Y; Kristolyubova, N B

    1975-05-01

    The ultrastructural of the chondroblasts was investigated in vitro by the methods of light and electron microscopy, determining the degree of differentiation of the individual cells. It was found that in the process of differentiation, the surface area of the membranes of the rough endoplasmic reticulum undergoes a five-fold increase, while the concentration of free ribosomes in the cytoplasm decreases. The total concentration of free ribosomes and those attached to the membranes per unit volume is unchanged and is approximately 5500 ribosomes per mu3. The use of H3-proline showed that collagen is synthesized on free polyribosomes in the cytoplasm, and not on the rough endoplasmic reticulum. A hypothesis was advanced on the temporal and spatial separation of specific syntheses in the cartilage, playing an important role in the differentiation of the chondroblasts.

  13. Controller Design Based on Nonlinear Separation Control Method for OTEC Pilot Plant

    NASA Astrophysics Data System (ADS)

    Nakamura, Masatoshi; Sugi, Takenao; Ikegami, Yasuyuki; Uehara, Haruo

    An OTEC (Ocean Thermal Energy Conversion) pilot plant consists of two parts; an OTEC system of main part and a heat reservoir system of sub part. The nonlinear separation control method was applied to the controller design for the OTEC pilot plant. The nonlinear separation models were constructed for the OTEC system and the heat reservoir system. The controller for the OTEC system and the heat reservoir system was designed by using the both nonlinear separation models. A detail simulation study showed that the multi-layer controller for the OTEC pilot plant brought a satisfactory control performance by comparing a conventional PI control.

  14. 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.

  15. Spatial Pattern Separation Differences in Older Adult Carriers and Non-Carriers for the Apolipoprotein E Epsilon 4 Allele

    PubMed Central

    Sheppard, David P.; Graves, Lisa V.; Holden, Heather M.; Delano-Wood, Lisa; Bondi, Mark W.; Gilbert, Paul E.

    2015-01-01

    We examined the performance of healthy young (n=57) and older adults (n=43) genotyped as apolipoprotein E-ε4 (APOE-ε4) carriers or APOE-ε4 non-carriers on a delayed match-to-sample task involving varying degrees of spatial interference hypothesized to assess spatial pattern separation. Older adult ε4 carriers were further divided into “impaired” and “unimpaired” groups based on their performance on a standardized test of verbal memory. We found that performance on the spatial pattern separation test increased as a function of decreased spatial interference across all groups. The older ε4 carriers in the impaired group performed significantly worse (p < .05) than unimpaired ε4 carriers, ε4 non-carriers, and young adults. The data suggest that spatial pattern separation may be less efficient in a subset of healthy older adults with subtle memory decline who are carriers of the ε4 allele. However, pattern separation performance may be comparable to that of young adults in a subset of older adult ε4 carriers and more broadly among non-carriers. Our findings offer additional evidence that pattern separation may vary in older adults, and they provide novel insight into pattern separation efficiency in ε4-positive older adults. PMID:25957133

  16. Spatial separation of two different pathways accounting for the generation of calcium signals in astrocytes

    PubMed Central

    Oschmann, Franziska; Mergenthaler, Konstantin; Obermayer, Klaus

    2017-01-01

    Astrocytes integrate and process synaptic information and exhibit calcium (Ca2+) signals in response to incoming information from neighboring synapses. The generation of Ca2+ signals is mostly attributed to Ca2+ release from internal Ca2+ stores evoked by an elevated metabotropic glutamate receptor (mGluR) activity. Different experimental results associated the generation of Ca2+ signals to the activity of the glutamate transporter (GluT). The GluT itself does not influence the intracellular Ca2+ concentration, but it indirectly activates Ca2+ entry over the membrane. A closer look into Ca2+ signaling in different astrocytic compartments revealed a spatial separation of those two pathways. Ca2+ signals in the soma are mainly generated by Ca2+ release from internal Ca2+ stores (mGluR-dependent pathway). In astrocytic compartments close to the synapse most Ca2+ signals are evoked by Ca2+ entry over the plasma membrane (GluT-dependent pathway). This assumption is supported by the finding, that the volume ratio between the internal Ca2+ store and the intracellular space decreases from the soma towards the synapse. We extended a model for mGluR-dependent Ca2+ signals in astrocytes with the GluT-dependent pathway. Additionally, we included the volume ratio between the internal Ca2+ store and the intracellular compartment into the model in order to analyze Ca2+ signals either in the soma or close to the synapse. Our model results confirm the spatial separation of the mGluR- and GluT-dependent pathways along the astrocytic process. The model allows to study the binary Ca2+ response during a block of either of both pathways. Moreover, the model contributes to a better understanding of the impact of channel densities on the interaction of both pathways and on the Ca2+ signal. PMID:28192424

  17. Spatial separation of two different pathways accounting for the generation of calcium signals in astrocytes.

    PubMed

    Oschmann, Franziska; Mergenthaler, Konstantin; Jungnickel, Evelyn; Obermayer, Klaus

    2017-02-01

    Astrocytes integrate and process synaptic information and exhibit calcium (Ca2+) signals in response to incoming information from neighboring synapses. The generation of Ca2+ signals is mostly attributed to Ca2+ release from internal Ca2+ stores evoked by an elevated metabotropic glutamate receptor (mGluR) activity. Different experimental results associated the generation of Ca2+ signals to the activity of the glutamate transporter (GluT). The GluT itself does not influence the intracellular Ca2+ concentration, but it indirectly activates Ca2+ entry over the membrane. A closer look into Ca2+ signaling in different astrocytic compartments revealed a spatial separation of those two pathways. Ca2+ signals in the soma are mainly generated by Ca2+ release from internal Ca2+ stores (mGluR-dependent pathway). In astrocytic compartments close to the synapse most Ca2+ signals are evoked by Ca2+ entry over the plasma membrane (GluT-dependent pathway). This assumption is supported by the finding, that the volume ratio between the internal Ca2+ store and the intracellular space decreases from the soma towards the synapse. We extended a model for mGluR-dependent Ca2+ signals in astrocytes with the GluT-dependent pathway. Additionally, we included the volume ratio between the internal Ca2+ store and the intracellular compartment into the model in order to analyze Ca2+ signals either in the soma or close to the synapse. Our model results confirm the spatial separation of the mGluR- and GluT-dependent pathways along the astrocytic process. The model allows to study the binary Ca2+ response during a block of either of both pathways. Moreover, the model contributes to a better understanding of the impact of channel densities on the interaction of both pathways and on the Ca2+ signal.

  18. Dissecting galaxies: spatial and spectral separation of emission excited by star formation and AGN activity

    NASA Astrophysics Data System (ADS)

    Davies, Rebecca L.; Groves, Brent; Kewley, Lisa J.; Dopita, Michael A.; Hampton, Elise J.; Shastri, Prajval; Scharwächter, Julia; Sutherland, Ralph; Kharb, Preeti; Bhatt, Harish; Jin, Chichuan; Banfield, Julie; Zaw, Ingyin; James, Bethan; Juneau, Stéphanie; Srivastava, Shweta

    2016-10-01

    The optical spectra of Seyfert galaxies are often dominated by emission lines excited by both star formation and active galactic nucleus (AGN) activity. Standard calibrations (such as for the star formation rate) are not applicable to such composite (mixed) spectra. In this paper, we describe how integral field data can be used to spectrally and spatially separate emission associated with star formation from emission associated with accretion on to an AGN. We demonstrate our method using integral field data for two AGN host galaxies (NGC 5728 and NGC 7679) from the Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7). The spectra of NGC 5728 and NGC 7679 form clear sequences of AGN fraction on standard emission line ratio diagnostic diagrams. We show that the emission line luminosities of the majority (>85 per cent) of spectra along each AGN fraction sequence can be reproduced by linear superpositions of the emission line luminosities of one AGN dominated spectrum and one star formation dominated spectrum. We separate the Hα, Hβ, [N II]λ6583, [S II]λλ6716, 6731, [O III]λ5007 and [O II]λλ3726, 3729 luminosities of every spaxel into contributions from star formation and AGN activity. The decomposed emission line images are used to derive the star formation rates and AGN bolometric luminosities for NGC 5728 and NGC 7679. Our calculated values are mostly consistent with independent estimates from data at other wavelengths. The recovered star-forming and AGN components also have distinct spatial distributions which trace structures seen in high-resolution imaging of the galaxies, providing independent confirmation that our decomposition has been successful.

  19. Active Flow Effectors for Noise and Separation Control

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.

    2011-01-01

    New flow effector technology for separation control and enhanced mixing is based upon shape memory alloy hybrid composite (SMAHC) technology. The technology allows for variable shape control of aircraft structures through actively deformable surfaces. The flow effectors are made by embedding shape memory alloy actuator material in a composite structure. When thermally actuated, the flow effector def1ects into or out of the flow in a prescribed manner to enhance mixing or induce separation for a variety of applications, including aeroacoustic noise reduction, drag reduction, and f1ight control. The active flow effectors were developed for noise reduction as an alternative to fixed-configuration effectors, such as static chevrons, that cannot be optimized for airframe installation effects or variable operating conditions and cannot be retracted for off-design or fail-safe conditions. Benefits include: Increased vehicle control, overall efficiency, and reduced noise throughout all f1ight regimes, Reduced flow noise, Reduced drag, Simplicity of design and fabrication, Simplicity of control through direct current stimulation, autonomous re sponse to environmental heating, fast re sponse, and a high degree of geometric stability. The concept involves embedding prestrained SMA actuators on one side of the chevron neutral axis in order to generate a thermal moment and def1ect the structure out of plane when heated. The force developed in the host structure during def1ection and the aerodynamic load is used for returning the structure to the retracted position. The chevron design is highly scalable and versatile, and easily affords active and/or autonomous (environmental) control. The technology offers wide-ranging market applications, including aerospace, automotive, and any application that requires flow separation or noise control.

  20. Extended high-frequency bandwidth improves reception of speech in spatially separated masking speech

    PubMed Central

    Levy, Suzanne Carr; Freed, Daniel J.; Nilsson, Michael; Moore, Brian C.J.; Puria, Sunil

    2015-01-01

    Objectives The hypothesis that extending the audible frequency bandwidth beyond the range currently implemented in most hearing aids can improve speech understanding was tested for normal-hearing and hearing-impaired participants using target sentences and spatially separated masking speech. Design The Hearing in Noise Test (HINT) speech corpus was re-recorded and four masking talkers were recorded at a sample rate of 44.1 kHz. All talkers were male native speakers of American English. Reception threshold for Sentences (RTS) were measured in two spatial configurations. In the asymmetric configuration, the target was presented from −45° azimuth and two colocated masking talkers were presented from +45° azimuth. In the diffuse configuration, the target was presented from 0° azimuth and four masking talkers were each presented from a different azimuth: +45°, +135°, −135°, and −45°. The new speech sentences, masking materials and configurations, collectively termed the ‘Hearing in Speech Test (HIST)’, were presented using lowpass filter cutoff frequencies of 4, 6, 8, and 10 kHz. For the normal-hearing participants, stimuli were presented in the sound field using loudspeakers. For the hearing-impaired participants, the spatial configurations were simulated using earphones, and a multi-band wide dynamic range compressor with a modified CAM2 fitting algorithm was used to compensate for each participant’s hearing loss. Results For the normal-hearing participants (N=24, mean age 40 years), the RTS improved significantly by 3.0 dB when the bandwidth was increased from 4 to 10 kHz, and a significant improvement of 1.3 dB was obtained from extending the bandwidth from 6 to 10 kHz, in both spatial configurations. Hearing-impaired participants (N=25, mean age 71 years) also showed a significant improvement in RTS with extended bandwidth, but the effect was smaller than for the normal-hearing participants. The mean decrease in RTS when the bandwidth was

  1. Distinct, but not completely separate spatial transport routes in the nuclear pore complex

    PubMed Central

    2013-01-01

    The nuclear pore complex (NPC), which provides the permeable and selective transport path between the nucleus and cytoplasm of eukaryotic cells, allows both the passive diffusion of small molecules in a signal-independent manner and the transport receptor-facilitated translocation of cargo molecules in a signal-dependent manner. However, the spatial and functional relationships between these two transport pathways, which represent critical information for unraveling the fundamental nucleocytoplasmic transport mechanism, remain in dispute. The direct experimental examination of passive and facilitated transport with a high spatiotemporal resolution under real-time trafficking conditions in native NPCs is still difficult. To address this issue and further define these transport mechanisms, we recently developed single-point edge-excitation sub-diffraction (SPEED) microscopy and a deconvolution algorithm to directly map both passive and facilitated transport routes in three dimensions (3D) in native NPCs. Our findings revealed that passive and facilitated transport occur through spatially distinct transport routes. Signal-independent small molecules exhibit a high probability of passively diffusing through an axial central viscous channel, while transport receptors and their cargo complexes preferentially travel through the periphery, around this central channel, after interacting with phenylalanine-glycine (FG) filaments. Strikingly, these two distinct transport zones are not completely separate either spatially or functionally. Instead, their conformations are closely correlated and simultaneously regulated. In this review, we will specifically highlight a detailed procedure for 3D mapping of passive and facilitated transport routes, demonstrate the correlation between these two distinct pathways, and finally, speculate regarding the regulation of the transport pathways driven by the conformational changes of FG filaments in NPCs. PMID:23669120

  2. Optimal Control Modification for Time-Scale Separated Systems

    NASA Technical Reports Server (NTRS)

    Nguyen, Nhan T.

    2012-01-01

    Recently a new optimal control modification has been introduced that can achieve robust adaptation with a large adaptive gain without incurring high-frequency oscillations as with the standard model-reference adaptive control. This modification is based on an optimal control formulation to minimize the L2 norm of the tracking error. The optimal control modification adaptive law results in a stable adaptation in the presence of a large adaptive gain. This study examines the optimal control modification adaptive law in the context of a system with a time scale separation resulting from a fast plant with a slow actuator. A singular perturbation analysis is performed to derive a modification to the adaptive law by transforming the original system into a reduced-order system in slow time. A model matching conditions in the transformed time coordinate results in an increase in the actuator command that effectively compensate for the slow actuator dynamics. Simulations demonstrate effectiveness of the method.

  3. Experimental Test of Compatibility-Loophole-Free Contextuality with Spatially Separated Entangled Qutrits

    NASA Astrophysics Data System (ADS)

    Hu, Xiao-Min; Chen, Jiang-Shan; Liu, Bi-Heng; Guo, Yu; Huang, Yun-Feng; Zhou, Zong-Quan; Han, Yong-Jian; Li, Chuan-Feng; Guo, Guang-Can

    2016-10-01

    The physical impact and the testability of the Kochen-Specker (KS) theorem is debated because of the fact that perfect compatibility in a single quantum system cannot be achieved in practical experiments with finite precision. Here, we follow the proposal of A. Cabello and M. T. Cunha [Phys. Rev. Lett. 106, 190401 (2011)], and present a compatibility-loophole-free experimental violation of an inequality of noncontextual theories by two spatially separated entangled qutrits. A maximally entangled qutrit-qutrit state with a fidelity as high as 0.975 ±0.001 is prepared and distributed to separated spaces, and these two photons are then measured locally, providing the compatibility requirement. The results show that the inequality for noncontextual theory is violated by 31 standard deviations. Our experiments pave the way to close the debate about the testability of the KS theorem. In addition, the method to generate high-fidelity and high-dimension entangled states will provide significant advantages in high-dimension quantum encoding and quantum communication.

  4. An adaptable computer control system for the Daresbury Recoil Separator

    NASA Astrophysics Data System (ADS)

    Morrison, T. P.

    1986-10-01

    This paper describes a computer system for the setting and control of all the magnets and high voltage supplies of a many element spectrometer using an LSI11/23 running RT11 with CAMAC input/output. Magnetic field strengths are measured by an inexpensive and easily constructed system of Hall probes and temperature transducers. The software calculates the field strength in each magnet by applying a temperature correction and a quadratic calibration to the measured Hall voltage. Keyboard commands to the system provide many facilities for setting up and control of the separator. Communication with a remote processor via an X25 link is also described.

  5. Chemistry with spatial control using particles and streams†

    PubMed Central

    Kalinin, Yevgeniy V.; Murali, Adithya

    2012-01-01

    Spatial control of chemical reactions, with micro- and nanometer scale resolution, has important consequences for one pot synthesis, engineering complex reactions, developmental biology, cellular biochemistry and emergent behavior. We review synthetic methods to engineer this spatial control using chemical diffusion from spherical particles, shells and polyhedra. We discuss systems that enable both isotropic and anisotropic chemical release from isolated and arrayed particles to create inhomogeneous and spatially patterned chemical fields. In addition to such finite chemical sources, we also discuss spatial control enabled with laminar flow in 2D and 3D microfluidic networks. Throughout the paper, we highlight applications of spatially controlled chemistry in chemical kinetics, reaction-diffusion systems, chemotaxis and morphogenesis. PMID:23145348

  6. Control of Systems With Slow Actuators Using Time Scale Separation

    NASA Technical Reports Server (NTRS)

    Stepanyan, Vehram; Nguyen, Nhan

    2009-01-01

    This paper addresses the problem of controlling a nonlinear plant with a slow actuator using singular perturbation method. For the known plant-actuator cascaded system the proposed scheme achieves tracking of a given reference model with considerably less control demand than would otherwise result when using conventional design techniques. This is the consequence of excluding the small parameter from the actuator dynamics via time scale separation. The resulting tracking error is within the order of this small parameter. For the unknown system the adaptive counterpart is developed based on the prediction model, which is driven towards the reference model by the control design. It is proven that the prediction model tracks the reference model with an error proportional to the small parameter, while the prediction error converges to zero. The resulting closed-loop system with all prediction models and adaptive laws remains stable. The benefits of the approach are demonstrated in simulation studies and compared to conventional control approaches.

  7. Optimal Control of Airfoil Flow Separation using Fluidic Excitation

    NASA Astrophysics Data System (ADS)

    Shahrabi, Arireza F.

    This thesis deals with the control of flow separation around a symmetric airfoils with the aid of multiple synthetic jet actuators (SJAs). CFD simulation methods have been implemented to uncover the flow separation regimes and associated properties such as frequencies and momentum ratio. In the first part of the study, the SJA was studied thoroughly. Large Eddy Simulations (LES) were performed for one individual cavity; the time history of SJA of the outlet velocity profile and the net momentum imparted to the flow were analyzed. The studied SJA is asymmetrical and operates with the aid of a piezoelectric (PZT) ceramic circular plate actuator. A three-dimensional mesh for the computational domain of the SJA and the surrounding volume was developed and was used to evaluate the details of the airflow conditions inside the SJA as well as at the outlet. The vibration of the PZT ceramic actuator was used as a boundary condition in the computational model to drive the SJA. Particular attention was given to developing a predictive model of the SJA outlet velocity. Results showed that the SJA velocity output is correlated to the PZT ceramic plate vibration, especially for the first frequency mode. SJAs are a particular class of zero net mass flux (ZNMF) fluidic devices with net imparted momentum to the flow. The net momentum imparted to the flow in the separated region is such that positive enhancement during AFC operations is achieved. Flows around the NACA 0015 airfoil were simulated for a range of operating conditions. Attention was given to the active open and closed loop control solutions for an airfoil with SJA at different angles of attack and flap angles. A large number of simulations using RANS & LES models were performed to study the effects of the momentum ratio (Cμ) in the range of 0 to 11% and of the non-dimensional frequency, F+, in the range of 0 to 2 for the control of flow separation at a practical angle of attack and flap angle. The optimum value of C

  8. Separation control over a grooved surface inspired by dolphin skin.

    PubMed

    Lang, Amy W; Jones, Emily M; Afroz, Farhana

    2017-02-10

    Over many decades the biological surfaces of aquatic swimmers have been studied for their potential as drag reducing surfaces. The hydrodynamic benefit of riblets, or grooves embedded parallel to the flow which appear on surfaces such as shark skin, have been well documented. However the skin of dolphins is embedded with sinusoidal grooves that run perpendicular or transverse to the flow over their bodies. It is theorized that the transverse grooves present on dolphin skin trap vortices between them, creating a partial slip condition over the surface and inducing turbulence augmentation in the boundary layer, thus acting as a potential mechanism to reduce flow separation and thus pressure drag. In an attempt to test this hypothesis and study these effects, an adverse pressure gradient was induced above a flat plate resulting in a controlled region of flow separation occurring within a tripped, turbulent boundary layer. Small transverse grooves of both rectangular and sinusoidal shape were 3D printed and mounted to the plate to measure their effect on the boundary layer flow. The results were compared to a flat plate without grooves using digital particle image velocimetry (DPIV). The strength of the adverse pressure gradient was varied, and the observed control in flow separation and other effects upon the boundary layer are discussed.

  9. Control of flow separation and mixing by aerodynamic excitation

    NASA Technical Reports Server (NTRS)

    Rice, Edward J.; Abbott, John M.

    1990-01-01

    The recent research progress in the control of shear flows using unsteady aerodynamic excitation conducted at the NASA Lewis Research Center is reviewed. The program is of fundamental nature concentrating on the physics of the unsteady aerodynamic processes. This field of research is a fairly new development with great promise in the areas of enhanced mixing and flow separation control. Enhanced mixing research reported in this paper include influence of core turbulence, forced pairing of coherent structures, and saturation of mixing enhancement. Separation flow control studies included are for a two-dimensional diffuser, conical diffusers, and single airfoils. Ultimate applications of this research include aircraft engine inlet flow control at high angle of attack, wide angle diffusers, highly loaded airfoils as in turbomachinery, and ejector/suppressor nozzles for the supersonic transport. An argument involving the Coanda Effect is made here that all of the above mentioned application areas really only involve forms of shear layer mixing enhancement. The program also includes the development of practical excitation devices which might be used in aircraft applications.

  10. Control of flow separation and mixing by aerodynamic excitation

    NASA Technical Reports Server (NTRS)

    Rice, Edward J.; Abbott, John M.

    1990-01-01

    The recent research progress in the control of shear flows using unsteady aerodynamic excitation conducted at the NASA Lewis Research Center is reviewed. The program is of fundamental nature concentrating on the physics of the unsteady aerodynamic processes. This field of research is a fairly new development with great promise in the areas of enhanced mixing and flow separation control. Enhanced mixing research reported in this paper include influence of core turbulence, forced pairing of coherent structures, and saturation of mixing enhancement. Separation flow control studies included are for a two-dimensional diffuser, conical diffusers, and single airfoils. Ultimate applications of this research include aircraft engine inlet flow control at high angle of attack, wide angle diffusers, highly loaded airfoils as in turbomachinery, and ejector/suppressor nozzles for the supersonic transport. An argument involving the Coanda Effect is made here that all of the above mentioned application areas really only involve forms of shear layer mixing enhancement. The program also includes the development of practical excitation devices which might be used in aircraft applications.

  11. Control of flow separation and mixing by aerodynamic excitation

    NASA Technical Reports Server (NTRS)

    Rice, Edward J.; Abbott, John M.

    1990-01-01

    The recent research in the control of shear flows using unsteady aerodynamic excitation conducted at the NASA Lewis Research Center is reviewed. The program is of a fundamental nature, concentrating on the physics of the unsteady aerodynamic processes. This field of research is a fairly new development with great promise in the areas of enhanced mixing and flow separation control. Enhanced mixing research includes influence of core turbulence, forced pairing of coherent structures, and saturation of mixing enhancement. Separation flow control studies included are for a two-dimensional diffuser, conical diffusers, and single airfoils. Ultimate applications include aircraft engine inlet flow control at high angle of attack, wide angle diffusers, highly loaded airfoils as in turbomachinery, and ejector/suppressor nozzles for the supersonic transport. An argument involving the Coanda Effect is made that all of the above mentioned application areas really only involve forms of shear layer mixing enhancement. The program also includes the development of practical excitation devices which might be used in aircraft applications.

  12. Controlled propulsion and separation of helical particles at the nanoscale.

    PubMed

    Alcanzare, Maria Michiko T; Thakore, Vaibhav; Ollila, Santtu T T; Karttunen, Mikko; Ala-Nissila, Tapio

    2017-02-22

    Controlling the motion of nano and microscale objects in a fluid environment is a key factor in designing optimized tiny machines that perform mechanical tasks such as transport of drugs or genetic material in cells, fluid mixing to accelerate chemical reactions, and cargo transport in microfluidic chips. Directed motion is made possible by the coupled translational and rotational motion of asymmetric particles. A current challenge in achieving directed and controlled motion at the nanoscale lies in overcoming random Brownian motion due to thermal fluctuations in the fluid. We use a hybrid lattice-Boltzmann molecular dynamics method with full hydrodynamic interactions and thermal fluctuations to demonstrate that controlled propulsion of individual nanohelices in an aqueous environment is possible. We optimize the propulsion velocity and the efficiency of externally driven nanohelices. We quantify the importance of the thermal effects on the directed motion by calculating the Péclet number for various shapes, number of turns and pitch lengths of the helices. Consistent with the experimental microscale separation of chiral objects, our results indicate that in the presence of thermal fluctuations at Péclet numbers >10, chiral particles follow the direction of propagation according to its handedness and the direction of the applied torque making separation of chiral particles possible at the nanoscale. Our results provide criteria for the design and control of helical machines at the nanoscale.

  13. Unconscious inhibition separates two forms of cognitive control

    PubMed Central

    Boy, Frederic; Husain, Masud; Sumner, Petroc

    2010-01-01

    In the human brain, cognitive-control processes are generally considered distinct from the unconscious mechanisms elicited by subliminal priming. Here, we show that cognitive control engaged in situations of response conflict interacts with the negative (inhibitory) phase of subliminal priming. Thus, cognitive control may surprisingly share common processes with nonconscious brain mechanisms. In contrast, our findings reveal that subliminal inhibition does not, however, interact with control adaptation—the supposed modulation of current control settings by previous experience of conflict. Therefore, although influential models have grouped immediate cognitive control and control adaptation together as products of the same conflict detection and control network, their relationship to subliminal inhibition separates them. Overall, these results suggest that the important distinction lies not between cognitive or top-down processes on the one hand and nonconscious priming mechanisms on the other hand but between responsive (poststimulus) mechanisms that deal with sensorimotor activation after it has occurred and preparatory (prestimulus) mechanisms that are modulated before stimulus arrival. PMID:20534462

  14. The Investigation of Blowing Parameter Similarity for Controlling Flow Separation over Control Surface

    NASA Astrophysics Data System (ADS)

    Wang, Y. K.; Wu, P.; Deng, X. Y.; Zheng, W. L.; Zhang, Y. H.

    2011-09-01

    Because the flight performance of aircraft is so dependent on aerodynamic efficiency of elevator, it is very important to improve the flow separation over the control surfaces at high deflection angle in order to keep the aircraft having good flight capability, especially for the modern aircraft with tailless aerodynamic configuration. A new flow control technique to improve the flow separation over the control surface by microblowing at the flow separated position is discussed in this paper. Furthermore, the effect of the various blowing parameters are also investigated in detail, and based on these studies, the parameter similarity about this flow control technique is discussed.

  15. Robot Control Based On Spatial-Operator Algebra

    NASA Technical Reports Server (NTRS)

    Rodriguez, Guillermo; Kreutz, Kenneth K.; Jain, Abhinandan

    1992-01-01

    Method for mathematical modeling and control of robotic manipulators based on spatial-operator algebra providing concise representation and simple, high-level theoretical frame-work for solution of kinematical and dynamical problems involving complicated temporal and spatial relationships. Recursive algorithms derived immediately from abstract spatial-operator expressions by inspection. Transition from abstract formulation through abstract solution to detailed implementation of specific algorithms to compute solution greatly simplified. Complicated dynamical problems like two cooperating robot arms solved more easily.

  16. Control of spatial orienting: context-specific proportion cued effects in an exogenous spatial cueing task.

    PubMed

    Gough, Alex; Garcia, Jesse; Torres-Quesada, Maryem; Milliken, Bruce

    2014-11-01

    Cognitive control refers to the ability to adjust strategy use based on the demands of a current context or task. Recent research using attentional filtering tasks has shown that cognitive control can adapt rapidly and automatically in accord with learning that is specific to particular tasks, items, and contexts (Crump, Gong, & Milliken, 2006; Fernandez-Duque & Knight, 2008; Jacoby, Lindsay, & Hessels, 2003). However, the role of context-specific control has not been investigated in detail in spatial orienting tasks. In a series of three experiments, the proportion of validly cued trials in an exogenous spatial cueing task was manipulated for one context but not for another context, with the two contexts intermixed randomly across trials. The results revealed that spatial/temporal contextual cues in conjunction, but not individually, produced context-specific control over spatial orienting. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. Passive Separation Control on a Body at Transonic Speed

    NASA Astrophysics Data System (ADS)

    Layukallo, Thombi; Hayashi, Daisuke; Nakamura, Yoshiaki

    The present paper proposes a new approach to control flow separation around a body. Flow separation is controlled by inserting simple tabs inside the separated region to suppress the reverse flow action. This is expected to increase the pressure in the base region of the body, thus reducing drag. Moreover, flow instability is also expected to decrease because of change in the wake profile. The cases considered in the present investigation are flows around a circular cylinder at M=0.6 and 0.73. Tabs having lengths of 10% and 20% of the cylinder diameter were used. The results show that the base pressure of the cylinder can be increased when these tabs are inserted inside the separated region. The smallest drag on the cylinder/tab body was achieved when the two pairs of tabs were installed on both sides of the cylinder at angles of ±120° and ±140°, measured from the front stagnation point of the cylinder. Compared to the plain cylinder, drag was reduced by 32% at M=0.6 and by 18% at M=0.73. Schlieren photography reveals that the vortex formation length is increased when the tabs are installed. Moreover, the tabs greatly suppress the level of pressure fluctuations on the cylinder surface. This can be attributed to change in the wake profile that is associated with drag reduction. Furthermore, the frequency of the Karman vortex street is also increased. The analysis of the results was assisted by numerical calculations based on Large Eddy Simulation (LES). From these results, five significant effects of the tabs were identified: restriction of the reverse flow action, trapping of vorticity in the region upstream of the tabs, suppression of the shear layers’ movement, more rapid vortex roll-up downstream of the body, and reduced strength of the downstream vortices.

  18. Spectrometer Baseline Control Via Spatial Filtering

    NASA Technical Reports Server (NTRS)

    Burleigh, M. R.; Richey, C. R.; Rinehart, S. A.; Quijada, M. A.; Wollack, E. J.

    2016-01-01

    An absorptive half-moon aperture mask is experimentally explored as a broad-bandwidth means of eliminating spurious spectral features arising from reprocessed radiation in an infrared Fourier transform spectrometer. In the presence of the spatial filter, an order of magnitude improvement in the fidelity of the spectrometer baseline is observed. The method is readily accommodated within the context of commonly employed instrument configurations and leads to a factor of two reduction in optical throughput. A detailed discussion of the underlying mechanism and limitations of the method are provided.

  19. Spectrometer Baseline Control Via Spatial Filtering

    NASA Technical Reports Server (NTRS)

    Burleigh, M. R.; Richey, C. R.; Rinehart, S. A.; Quijada, M. A.; Wollack, E. J.

    2016-01-01

    An absorptive half-moon aperture mask is experimentally explored as a broad-bandwidth means of eliminating spurious spectral features arising from reprocessed radiation in an infrared Fourier transform spectrometer. In the presence of the spatial filter, an order of magnitude improvement in the fidelity of the spectrometer baseline is observed. The method is readily accommodated within the context of commonly employed instrument configurations and leads to a factor of two reduction in optical throughput. A detailed discussion of the underlying mechanism and limitations of the method are provided.

  20. On spatial spillover in feedforward and feedback noise control

    NASA Astrophysics Data System (ADS)

    Xie, Antai; Bernstein, Dennis

    2017-03-01

    Active feedback noise control for rejecting broadband disturbances must contend with the Bode integral constraint, which implies that suppression over some frequency range gives rise to amplification over another range at the performance microphone. This is called spectral spillover. The present paper deals with spatial spillover, which refers to the amplification of noise at locations where no microphone is located. A spatial spillover function is defined, which is valid for both feedforward and feedback control with scalar and vector control inputs. This function is numerically analyzed and measured experimentally. Obstructions are introduced in the acoustic space to investigate their effect on spatial spillover.

  1. SNARC Struggles: Instant Control over Spatial-Numerical Associations

    ERIC Educational Resources Information Center

    Pfister, Roland; Schroeder, Philipp A.; Kunde, Wilfried

    2013-01-01

    Numbers and space are tightly linked--a phenomenon that is referred to as the spatial-numerical association of response codes (SNARC) effect (Dehaene, Bossini, & Giraux, 1993). The present study investigates how quickly and flexibly the behavioral impact of such spatial-numerical associations can be controlled. Participants performed a parity…

  2. Mechanisms of spatial attention control in frontal and parietal cortex

    PubMed Central

    Szczepanski, Sara M.; Konen, Christina S.; Kastner, Sabine

    2010-01-01

    Theories of spatial attentional control have been largely based upon studies of patients suffering from visuo-spatial neglect, resulting from circumscribed lesions of frontal and posterior parietal cortex. In the intact brain, the control of spatial attention has been related to a distributed fronto-parietal attention network. Little is known about the nature of the control mechanisms exerted by this network. Here, we used a novel region-of-interest approach to relate activations of the attention network to recently described topographic areas in frontal (FEF, PreCC/IFS) and parietal cortex (IPS1-IPS5, SPL1) and to examine their spatial attention signals. We found that attention signals in most topographic areas were spatially-specific, with stronger responses when attention was directed to the contralateral than to the ipsilateral visual field. Importantly, two hemispheric asymmetries were found. First, a region in only right, but not left superior parietal lobule (SPL1) carried spatial attention signals. Second, left FEF and left posterior parietal cortex (IPS1/2) generated stronger contralateral biasing signals than their counterparts in the right hemisphere. These findings are the first to characterize spatial attention signals in topographic frontal and parietal cortex and provide a neural basis in support of an interhemispheric competition account of spatial attentional control. PMID:20053897

  3. SNARC Struggles: Instant Control over Spatial-Numerical Associations

    ERIC Educational Resources Information Center

    Pfister, Roland; Schroeder, Philipp A.; Kunde, Wilfried

    2013-01-01

    Numbers and space are tightly linked--a phenomenon that is referred to as the spatial-numerical association of response codes (SNARC) effect (Dehaene, Bossini, & Giraux, 1993). The present study investigates how quickly and flexibly the behavioral impact of such spatial-numerical associations can be controlled. Participants performed a parity…

  4. Spatially controlled, in situ synthesis of polymers

    DOEpatents

    Caneba, Gerard T.; Tirumala, Vijaya Raghavan; Mancini, Derrick C.; Wang, Hsien-Hau

    2005-03-22

    An in situ polymer microstructure formation method. The monomer mixture is polymerized in a solvent/precipitant through exposure to ionizing radiation in the absence any chemical mediators. If an exposure mask is employed to block out certain regions of the radiation cross section, then a patterned microstructure is formed. The polymerization mechanism is based on the so-called free-radical retrograde-precipitation polymerization process, in which polymerization occurs while the system is phase separating above the lower critical solution temperature. This method was extended to produce a crosslinked line grid-pattern of poly (N-isopropylacrylamide), which has been known to have thermoreversible properties.

  5. Separation Control Over A Wall-Mounted Hump

    NASA Technical Reports Server (NTRS)

    Greenblatt, D.; Paschal, K. B.; Schaeffler, N. W.; Washburn, A. E.; Harris, J.; Yao, C. S.

    2007-01-01

    Separation control by means of steady suction or zero efflux oscillatory jets is known to be effective in a wide variety of flows under different flow conditions. Control is effective when applied in a nominally two-dimensional manner, for example, at the leading-edge of a wing or at the shoulder of a deflected flap. Despite intuitive understanding of the flow, at present there is no accepted theoretical model that can adequately explain or describe the observed effects of the leading parameters such as reduced suction-rate, or frequency and momentum input. This difficulty stems partly from the turbulent nature of the flows combined with superimposed coherent structures, which are usually driven by at least one instability mechanism. The ever increasing technological importance of these flows has spurned an urgent need to develop turbulence models with a predictive capability. Present attempts to develop such models are hampered in one way or another by incomplete data sets, uncertain or undocumented inflow and boundary conditions, or inadequate flow-field measurements. This paper attempts to address these issues by conducting an experimental investigation of a lowspeed separated flow over a wall-mounted hump model. The model geometry was designed by Seifert & Pack, who measured static and dynamic pressures on the model for a wide range of Reynolds and Mach numbers and control conditions. This paper describes the present experimental setup, as well as the types and range of data acquired. Sample data is presented and future work is discussed.

  6. Spatially Resolved Photoemission Spectroscopy to Probe Electronic Phase Separation in Manganites and Related Compounds

    NASA Astrophysics Data System (ADS)

    Das Sarma, Dipankar

    2005-03-01

    Manganese oxides that exhibit colossal magnetoresistance (CMR) are often characterised by a competition of different electronic phases that critically influence their properties and leads to the coexistence of spatially separated competing phases. Despite extensive experimentation, characteristic length-scales associated with phase coexistence remains an important open question. While theoretical work has pointed to a nanometric length-scale, experiments have uncovered multiple length-scales ranging from the atomic to the sub-micron, covering many orders of magnitude. The role of chemical inhomogeneity in driving this phenomenon is not well understood. Moreover, these early experiments were carried out on polycrystalline and thin film specimens. Here we use a spatially resolved, direct spectroscopic probe for electronic structure with an additional unique sensitivity to chemical compositions to investigate high quality single crystal sample of La1/4Pr3/8Ca3/8MnO3. The formation of distinct electronic domains is observed in absence of any perceptible chemical inhomogeneity, where the relevant length-scale is at least an order of magnitude larger than all previous estimates. The present results, exhibiting memory effects in the domain morphology, suggest that electronic domain formation is intimately connected with long-range strains, often thought to be an important ingredient in the physics of this effect. Additionally, we have also applied this technique to a variety of related materials, such as (LuMnO3)0.79(La5/8Sr3/8MnO3)0.21, and Sr2FexMo1-xO6. Our preliminary results in all these cases suggest that the existence of spatially inhomogeneous electronic phases plays important roles in determining many of the interesting properties of such systems. This work is carried out in collaboration with M. Bertolo, G. Cautero, S-W. Cheong, A. Fujimori, T. Y. Koo, S.R. Krishnakumar, U. Manju, S. Ray, S. La Rosa P. A. Sharma and D. Topwal.

  7. Control of separation and quantitative analysis by GC-FTIR

    NASA Astrophysics Data System (ADS)

    Semmoud, A.; Huvenne, Jean P.; Legrand, P.

    1992-03-01

    Software for 3-D representations of the 'Absorbance-Wavenumber-Retention time' is used to control the quality of the GC separation. Spectral information given by the FTIR detection allows the user to be sure that a chromatographic peak is 'pure.' The analysis of peppermint essential oil is presented as an example. This assurance is absolutely required for quantitative applications. In these conditions, we have worked out a quantitative analysis of caffeine. Correlation coefficients between integrated absorbance measurements and concentration of caffeine are discussed at two steps of the data treatment.

  8. Passive Flow Separation Control Mechanism Inspired by Shark Skin

    NASA Astrophysics Data System (ADS)

    Oakley, India; Lang, Amy

    2015-11-01

    The following experimental work seeks to examine shark scales as passive flow-actuated separation control mechanisms. It is hypothesized that the actuation of these scales can in fact reduce pressure drag by inhibiting flow reversal and thereby prevent flow separation. In order to examine this mechanism at a fundamental level, three-dimensional sharkskin scales were simplified and modeled as two-dimensional flaps. To further simplify the experiment, the flaps were observed within a laminar boundary layer. The laminar boundary layer was grown over a long flat plate that was placed inside a water tunnel. A rotating cylinder was also used to induce an unsteady, increasing adverse pressure gradient, which generated a reversing flow. In order to visualize the potential actuation of the two-dimensional flaps DPIV (digital particle image velocimetry) was utilized. Three main objectives for this work included, the actuation of the two-dimensional flaps, the resistance to a reversed flow as a result of flap actuation and the prevention of flow separation. However once the experiment was conducted the flaps did not perform as previously hypothesized. The adverse pressure gradient induced by the rotating cylinder did not produce a reversing flow powerful enough to actuate the flaps. NSF REU Site Award 1358991.

  9. Blood plasma separation in microfluidic channels using flow rate control.

    PubMed

    Yang, Sung; Undar, Akif; Zahn, Jeffrey D

    2005-01-01

    Several studies have clearly shown that cardiac surgery induces systemic inflammatory responses, particularly when cardiopulmonary bypass (CPB) is used. CPB induces complex inflammatory responses. Considerable evidence suggests that systemic inflammation causes many postoperative complications. Currently, there is no effective method to prevent this systemic inflammatory response syndrome in patients undergoing CPB. The ability to clinically intervene in inflammation, or even study the inflammatory response to CPB, is limited by the lack of timely measurements of inflammatory responses. In this study, a microfluidic device for continuous, real-time blood plasma separation, which may be integrated with downstream plasma analysis device, is introduced. This device is designed to have a whole blood inlet, a purified plasma outlet, and a concentrated blood cell outlet. The device is designed to separate plasma with up to 45% hematocrit of the inlet blood and is analyzed using computational fluid dynamics simulation. The simulation results show that 27% and 25% of plasma can be collected from the total inlet blood volume for 45% and 39% hematocrit, respectively. The device's functionality was demonstrated using defibrinated sheep blood (hematocrit=39%). During the experiment, all the blood cells traveled through the device toward the concentrated blood outlet while only the plasma flowed towards the plasma outlet without any clogging or lysis of cells. Because of its simple structure and control mechanism, this microdevice is expected to be used for highly efficient, realtime, continuous cell-free plasma separation.

  10. Spatially separated charge densities of electrons and holes in organic-inorganic halide perovskites

    SciTech Connect

    Li, Dan; Liang, Chunjun E-mail: zhqhe@bjtu.edu.cn; Zhang, Huimin; You, Fangtian; He, Zhiqun E-mail: zhqhe@bjtu.edu.cn; Zhang, Chunxiu

    2015-02-21

    Solution-processable methylammonium lead trihalide perovskites exhibit remarkable high-absorption and low-loss properties for solar energy conversion. Calculation from density functional theory indicates the presence of non-equivalent halogen atoms in the unit cell because of the specific orientation of the organic cation. Considering the 〈100〉 orientation as an example, I{sub 1}, one of the halogen atoms, differs from the other iodine atoms (I{sub 2} and I{sub 3}) in terms of its interaction with the organic cation. The valance-band-maximum (VBM) and conduction-band-minimum (CBM) states are derived mainly from 5p orbital of I{sub 1} atom and 6p orbital of Pb atom, respectively. The spatially separated charge densities of the electrons and holes justify the low recombination rate of the pure iodide perovskite. Chlorine substitution further strengthens the unique position of the I{sub 1} atom, leading to more localized charge density around the I{sub 1} atom and less charge density around the other atoms at the VBM state. The less overlap of charge densities between the VBM and CBM states explains the relatively lower carrier recombination rate of the iodine-chlorine mixed perovskite. Chlorine substitution significantly reduces the effective mass at a direction perpendicular to the Pb-Cl bond and organic axis, enhancing the carrier transport property of the mixed perovskite in this direction.

  11. Construction of Light-Harvesting Polymeric Vesicles in Aqueous Solution with Spatially Separated Donors and Acceptors.

    PubMed

    Li, Huimei; Liu, Yannan; Huang, Tong; Qi, Meiwei; Ni, Yunzhou; Wang, Jie; Zheng, Yongli; Zhou, Yongfeng; Yan, Deyue

    2017-07-01

    This communication describes polymer vesicles self-assembled from hyperbranched polymers (branched polymersomes (BPs)) as scaffolds, conceptually mimicking the natural light-harvesting system in aqueous solution. The system is constructed with hydrophobic 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) as donors encapsulated in the hydrophobic hyperbranched cores of the vesicles and the hydrophilic Rhodamine B (RB) as acceptors incorporated on the surface of the vesicles through the cyclodextrin (CD)/RB host-guest interactions, through which the donors and acceptors are spatially separated to effectively avoid the self-quenching between donors. This vesicular light harvesting system has presented good energy transfer efficiency of about 80% in water, and can be used as the ink to write multiclolor letters. In addition, due to the giant dimension of BPs, the real-time fluorescent images of the vesicles under an optical microscope can be observed to prove the light-harvesting process. It is supposed that such a vesicular light-harvesting antenna can be used to construct artificial photosynthesis systems in the future. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Adenovirus replication and transcription sites are spatially separated in the nucleus of infected cells.

    PubMed Central

    Pombo, A; Ferreira, J; Bridge, E; Carmo-Fonseca, M

    1994-01-01

    We have visualized the intranuclear topography of adenovirus replication and transcription in infected HeLa cells. The results show that viral DNA replication occurs in multiple foci that are highly organized in the nucleoplasm. Pulse-chase experiments indicate that newly synthesized viral double-stranded DNA molecules are displaced from the replication foci and spread throughout the nucleoplasm, while the single-stranded DNA replication intermediates accumulate in adjacent sites. Double-labelling experiments and confocal microscopy show that replication occurs in foci localized at the periphery of the sites where single-stranded DNA accumulates. The simultaneous visualization of viral replication and transcription reveals that the sites of transcription are predominantly separated from the sites of replication. Transcription is detected adjacent to the replication foci and extends around the sites of single-stranded DNA accumulation. These data indicate that newly synthesized double-stranded DNA molecules are displaced from the replication foci and spread in the surrounding nucleoplasm, where they are used as templates for transcription. Splicing snRNPs are shown to co-localize with the sites of transcription and to be excluded from the sites of replication. This provides evidence that splicing of viral RNAs occurs co-transcriptionally and that the sites of viral DNA replication are spatially distinct from the sites of RNA transcription and processing. Images PMID:7957073

  13. Adenovirus replication and transcription sites are spatially separated in the nucleus of infected cells.

    PubMed

    Pombo, A; Ferreira, J; Bridge, E; Carmo-Fonseca, M

    1994-11-01

    We have visualized the intranuclear topography of adenovirus replication and transcription in infected HeLa cells. The results show that viral DNA replication occurs in multiple foci that are highly organized in the nucleoplasm. Pulse-chase experiments indicate that newly synthesized viral double-stranded DNA molecules are displaced from the replication foci and spread throughout the nucleoplasm, while the single-stranded DNA replication intermediates accumulate in adjacent sites. Double-labelling experiments and confocal microscopy show that replication occurs in foci localized at the periphery of the sites where single-stranded DNA accumulates. The simultaneous visualization of viral replication and transcription reveals that the sites of transcription are predominantly separated from the sites of replication. Transcription is detected adjacent to the replication foci and extends around the sites of single-stranded DNA accumulation. These data indicate that newly synthesized double-stranded DNA molecules are displaced from the replication foci and spread in the surrounding nucleoplasm, where they are used as templates for transcription. Splicing snRNPs are shown to co-localize with the sites of transcription and to be excluded from the sites of replication. This provides evidence that splicing of viral RNAs occurs co-transcriptionally and that the sites of viral DNA replication are spatially distinct from the sites of RNA transcription and processing.

  14. Separating anisotropic material effects in the control signals of inverter-fed AC machines

    NASA Astrophysics Data System (ADS)

    Wolbank, Thomas M.; Machl, Juergen L.; Hauser, Hans

    2004-05-01

    In the non-model-based mechanical sensorless control of AC machines the flux/rotor position can be estimated by evaluating the current response to voltage pulses. This current slope is modulated by all spatial saliencies in the machine. Sources of these saliencies can be various, for instance the saturation of the machine by the main flux, the slotting, lamination material anisotropy as well as eccentricity. Measurements are performed on specially designed machines enabling the separation of the effects of material anisotropy as well as eccentricity in the current slopes.

  15. Laminar separation control effects of shortfin mako shark skin

    NASA Astrophysics Data System (ADS)

    Bradshaw, Michael Thomas

    Shark skin is investigated as a means of laminar flow separation control due to its preferential flow direction as well as the potential for scales to erect and obstruct low-momentum backflow resulting from an adverse pressure gradient acting on the boundary layer. In this study, the effect of the scales on flow reversal is observed in laminar flow conditions. This is achieved by comparing the flow over a pectoral fin from a shortfin mako shark to that over the same fin that is painted to neutralize the effect of the scales on the flow. The effect of the scales on flow reversal is also observed by comparing the flow over a smooth PVC cylinder to that over the same cylinder with samples of mako shark skin affixed to the entire circumference of the cylinder. These samples were taken from the flank region of the shark because the scales at this location have been shown to have the greatest angle of erection compared to the scales on the rest of the shark's body. Scales at this location have an average crown length of 220 microm with a maximum bristling angle of proximately 50 degrees. Because these scales have the highest bristling angle, they have the best potential for separation control. All data was taken using time-resolved Digital Particle Image Velocimetry. The flow over the pectoral fin was analyzed at multiple angles of attack. It was found that the shark skin had the effect of decreasing the size of the separated region over both the pectoral fin and the cylinder as well as decreasing the magnitudes of the reversing flow found in these regions. For all Reynolds numbers tested, drag reduction over 28% was found when applying the sharkskin to the cylinder.

  16. Numerical simulation of flow separation control by oscillatory fluid injection

    NASA Astrophysics Data System (ADS)

    Resendiz Rosas, Celerino

    2005-07-01

    In this work, numerical simulations of flow separation control are performed. The separation control technique studied is called "synthetic jet actuation". The developed code employs a cell centered finite volume scheme which handles viscous, steady and unsteady compressible turbulent flows. The pulsating zero mass jet flow is simulated by imposing a harmonically varying transpiration boundary condition on the airfoil's surface. Turbulence is modeled with the algebraic model of Baldwin and Lomax. The application of synthetic jet actuators is based in their ability to energize the boundary layer, thereby providing significant increase in the lift coefficient. This has been corroborated experimentally and it is corroborated numerically in this research. The performed numerical simulation investigates the flow over a NACA0015 airfoil. For this flow Re = 9 x 105 and the reduced frequency and momentum coefficient are F + = 1.1 and Cmu = 0.04 respectively. The oscillatory injection takes place at 12.27% chord from the leading edge. A maximum increase in the mean lift coefficient of 93% is predicted by the code. A discrepancy of approximately 10% is observed with corresponding experimental data from the literature. The general trend is, however, well captured. The discrepancy is attributed to the modeling of the injection boundary condition and to the turbulence model. A sensitivity analysis of the lift coefficient to different values of the oscillation parameters is performed. It is concluded that tangential injection, F+ ≈ O(1) and the utilized grid resolution around the site of injection are optimal. Streamline fields obtained for different angles of injection are analyzed. Flow separation and attachment as functions of the injection angle and of the velocity of injection can be observed. It is finally concluded that a reliable numerical tool has been developed which can be utilized as a support tool in the optimization of the synthetic jet operation and in the

  17. Control of Spatially Inhomogeneous Shear Flows

    DTIC Science & Technology

    2011-10-01

    input B2 consists of an array of localized actuators described by an analytical Gaussian function . The temporal forcing of the system is provided by the...easily access the tools of linear control theory . For our application, a basis of approximate balanced modes (Rowley 2005) is computed using a snapshot...the red line depicts the evolution of the energy- density of a TS wavepacket , whereas the black line shows the same quantity when feedback control (case

  18. False Discovery Control in Large-Scale Spatial Multiple Testing

    PubMed Central

    Sun, Wenguang; Reich, Brian J.; Cai, T. Tony; Guindani, Michele; Schwartzman, Armin

    2014-01-01

    Summary This article develops a unified theoretical and computational framework for false discovery control in multiple testing of spatial signals. We consider both point-wise and cluster-wise spatial analyses, and derive oracle procedures which optimally control the false discovery rate, false discovery exceedance and false cluster rate, respectively. A data-driven finite approximation strategy is developed to mimic the oracle procedures on a continuous spatial domain. Our multiple testing procedures are asymptotically valid and can be effectively implemented using Bayesian computational algorithms for analysis of large spatial data sets. Numerical results show that the proposed procedures lead to more accurate error control and better power performance than conventional methods. We demonstrate our methods for analyzing the time trends in tropospheric ozone in eastern US. PMID:25642138

  19. Daily Access to Sucrose Impairs Aspects of Spatial Memory Tasks Reliant on Pattern Separation and Neural Proliferation in Rats

    ERIC Educational Resources Information Center

    Reichelt, Amy C.; Morris, Margaret J.; Westbrook, Reginald Frederick

    2016-01-01

    High sugar diets reduce hippocampal neurogenesis, which is required for minimizing interference between memories, a process that involves "pattern separation." We provided rats with 2 h daily access to a sucrose solution for 28 d and assessed their performance on a spatial memory task. Sucrose consuming rats discriminated between objects…

  20. Separation of spatial-temporal patterns ('climatic modes') by combined analysis of really measured and generated numerically vector time series

    NASA Astrophysics Data System (ADS)

    Feigin, A. M.; Mukhin, D.; Volodin, E. M.; Gavrilov, A.; Loskutov, E. M.

    2013-12-01

    The new method of decomposition of the Earth's climate system into well separated spatial-temporal patterns ('climatic modes') is discussed. The method is based on: (i) generalization of the MSSA (Multichannel Singular Spectral Analysis) [1] for expanding vector (space-distributed) time series in basis of spatial-temporal empirical orthogonal functions (STEOF), which makes allowance delayed correlations of the processes recorded in spatially separated points; (ii) expanding both real SST data, and longer by several times SST data generated numerically, in STEOF basis; (iii) use of the numerically produced STEOF basis for exclusion of 'too slow' (and thus not represented correctly) processes from real data. The application of the method allows by means of vector time series generated numerically by the INM RAS Coupled Climate Model [2] to separate from real SST anomalies data [3] two climatic modes possessing by noticeably different time scales: 3-5 and 9-11 years. Relations of separated modes to ENSO and PDO are investigated. Possible applications of spatial-temporal climatic patterns concept to prognosis of climate system evolution is discussed. 1. Ghil, M., R. M. Allen, M. D. Dettinger, K. Ide, D. Kondrashov, et al. (2002) "Advanced spectral methods for climatic time series", Rev. Geophys. 40(1), 3.1-3.41. 2. http://83.149.207.89/GCM_DATA_PLOTTING/GCM_INM_DATA_XY_en.htm 3. http://iridl.ldeo.columbia.edu/SOURCES/.KAPLAN/.EXTENDED/.v2/.ssta/

  1. Daily Access to Sucrose Impairs Aspects of Spatial Memory Tasks Reliant on Pattern Separation and Neural Proliferation in Rats

    ERIC Educational Resources Information Center

    Reichelt, Amy C.; Morris, Margaret J.; Westbrook, Reginald Frederick

    2016-01-01

    High sugar diets reduce hippocampal neurogenesis, which is required for minimizing interference between memories, a process that involves "pattern separation." We provided rats with 2 h daily access to a sucrose solution for 28 d and assessed their performance on a spatial memory task. Sucrose consuming rats discriminated between objects…

  2. Spatial control of chirality in supramolecular aggregates.

    PubMed

    Castriciano, Maria A; Gentili, Denis; Romeo, Andrea; Cavallini, Massimiliano; Scolaro, Luigi Monsù

    2017-03-09

    Chirality is one of the most intriguing properties of matter related to a molecule's lack of mirror symmetry. The transmission of chirality from the molecular level up to the macroscopic scale has major implications in life sciences but it is also relevant for many chemical applications ranging from catalysis to spintronic. These technological applications require an accurate control of morphology, homogeneity and chiral handedness of thin films and nanostructures. We demonstrate a simple approach to specifically transfer chirality to the model supramolecular system of J aggregates of the protonated form of tetrakis(4-sulfonatophenyl)-porphyrin by utilizing a soft lithography technique. This approach successfully allows the fabrication of an ordered distribution of sub-micrometric structures in precise and controllable positions with programmed chirality, providing a fundamental breakthrough toward the exploitation of chiral supramolecular aggregates in technological applications, such as sensors, non-linear optics and spintronic.

  3. Spatial control of chirality in supramolecular aggregates

    PubMed Central

    Castriciano, Maria A.; Gentili, Denis; Romeo, Andrea; Cavallini, Massimiliano; Scolaro, Luigi Monsù

    2017-01-01

    Chirality is one of the most intriguing properties of matter related to a molecule’s lack of mirror symmetry. The transmission of chirality from the molecular level up to the macroscopic scale has major implications in life sciences but it is also relevant for many chemical applications ranging from catalysis to spintronic. These technological applications require an accurate control of morphology, homogeneity and chiral handedness of thin films and nanostructures. We demonstrate a simple approach to specifically transfer chirality to the model supramolecular system of J aggregates of the protonated form of tetrakis(4-sulfonatophenyl)-porphyrin by utilizing a soft lithography technique. This approach successfully allows the fabrication of an ordered distribution of sub-micrometric structures in precise and controllable positions with programmed chirality, providing a fundamental breakthrough toward the exploitation of chiral supramolecular aggregates in technological applications, such as sensors, non-linear optics and spintronic. PMID:28275239

  4. Spatial control of chirality in supramolecular aggregates

    NASA Astrophysics Data System (ADS)

    Castriciano, Maria A.; Gentili, Denis; Romeo, Andrea; Cavallini, Massimiliano; Scolaro, Luigi Monsù

    2017-03-01

    Chirality is one of the most intriguing properties of matter related to a molecule’s lack of mirror symmetry. The transmission of chirality from the molecular level up to the macroscopic scale has major implications in life sciences but it is also relevant for many chemical applications ranging from catalysis to spintronic. These technological applications require an accurate control of morphology, homogeneity and chiral handedness of thin films and nanostructures. We demonstrate a simple approach to specifically transfer chirality to the model supramolecular system of J aggregates of the protonated form of tetrakis(4-sulfonatophenyl)-porphyrin by utilizing a soft lithography technique. This approach successfully allows the fabrication of an ordered distribution of sub-micrometric structures in precise and controllable positions with programmed chirality, providing a fundamental breakthrough toward the exploitation of chiral supramolecular aggregates in technological applications, such as sensors, non-linear optics and spintronic.

  5. Control of Spatially Inhomogeneous Shear Flows

    DTIC Science & Technology

    2009-11-27

    control approach, that minimises an objective function which measures the perturbation energy , was formulated where the Orr- Sommerfeld and Squire...hydrodynamic stability analysis by considering a finite-time horizon over which energy amplification, driven by a specific input (disturbances/actuator) and...layers subject to free-stream turbulence. Int. J. Heat Fluid Flow, 29(3):841–855, 2008. [14] B. Moore. Principal component analysis in linear systems

  6. Plasmid Transfer between Spatially Separated Donor and Recipient Bacteria in Earthworm-Containing Soil Microcosms

    PubMed Central

    Daane, L. L.; Molina, J.; Sadowsky, M. J.

    1997-01-01

    Most gene transfer studies have been performed with relatively homogeneous soil systems in the absence of soil macrobiota, including invertebrates. In this study we examined the influence of earthworm activity (burrowing, casting, and feeding) on transfer of plasmid pJP4 between spatially separated donor (Alcaligenes eutrophus) and recipient (Pseudomonas fluorescens) bacteria in nonsterile soil columns. A model system was designed such that the activity of earthworms would act to mediate cell contact and gene transfer. Three different earthworm species (Aporrectodea trapezoides, Lumbricus rubellus, and Lumbricus terrestris), representing each of the major ecological categories (endogeic, epigeic, and anecic), were evaluated. Inoculated soil microcosms, with and without added earthworms, were analyzed for donor, recipient, and transconjugant bacteria at 5-cm-depth intervals by using selective plating techniques. Transconjugants were confirmed by colony hybridization with a mer gene probe. The presence of earthworms significantly increased dispersal of the donor and recipient strains. In situ gene transfer of plasmid pJP4 from A. eutrophus to P. fluorescens was detected only in earthworm-containing microcosms, at a frequency of (symbl)10(sup2) transconjugants per g of soil. The depth of recovery was dependent on the burrowing behavior of each earthworm species; however, there was no significant difference in the total number of transconjugants among the earthworm species. Donor and recipient bacteria were recovered from earthworm feces (casts) of all three earthworm species, with numbers up to 10(sup6) and 10(sup4) bacteria per g of cast, respectively. A. trapezoides egg capsules (cocoons) formed in the inoculated soil microcosms contained up to 10(sup7) donor and 10(sup6) recipient bacteria per g of cocoon. No transconjugant bacteria, however, were recovered from these microhabitats. To our knowledge, this is the first report of gene transfer between physically

  7. Placement and characterization of pairs of luminescent molecules in spatially separated regions of nanostructured thin films.

    PubMed

    Minoofar, Payam N; Hernandez, Raquel; Chia, Shinye; Dunn, Bruce; Zink, Jeffrey I; Franville, Anne-Christine

    2002-12-04

    Methods of making mesostructured sol-gel silicate thin films containing two different molecules deliberately placed in two different spatially separated regions in a one-step, one-pot preparation are developed and demonstrated. When the structure-directing agent is the surfactant cetyltrimethylammonium bromide, the structure is 2-D hexagonal with lattice spacings between 31.6 and 42.1 angstroms depending on the dopant molecules and their concentrations. The three general strategies that are used to place the molecules are philicity (like dissolves like), bonding, and bifunctionality. These strategies take advantage of the different chemical and physical properties of the regions of the films. These regions are the inorganic silicate framework, the hydrophobic organic interior of the micelles, and the ionic interface between them. Luminescent molecules that possess the physical and chemical properties appropriate for the desired strategies are chosen. Lanthanide and ruthenium complexes with condensable trialkoxysilane groups are incorporated into the silicate framework. 1,4-Naphthoquinone, pyrene, rhodamine 6G and coumarin 540A, and lanthanides with no condensable trialkoxysilanes occupy the hydrophobic core of micelles by virtue of their hydrophobicity. The locations of the molecules are determined by luminescence spectroscopy and by luminescence lifetime measurements. In all cases, the long-range order templated into the thin film is verified by X-ray diffraction. The simultaneous placement of two molecules in the structured film and the maintenance of long-range order require a delicate balance among film preparation methodology, design of the molecules to be incorporated in specific regions, and concentrations of all of the species.

  8. On the use of a spatial cue as prior information for stereo sound source separation based on spatially weighted non-negative tensor factorization

    NASA Astrophysics Data System (ADS)

    Mitsufuji, Yuki; Roebel, Axel

    2014-12-01

    This paper proposes a new method to enhance the performance of non-negative tensor factorization (NTF), one of the most prevalent source separation techniques nowadays. The enhancement is mainly achieved by introducing weights on bin-wise NTF cost functions, which differentiates NTF target components from other components so that the target should be approximated more precisely than others. Assuming sources are distributed sparsely in a 2-D sound field, the target components approximating a target source are exclusively selected by a user, or from accompanying images by means of providing a spatial cue to an NTF framework. The spatial cue is given in a similar format to the well-known binaural feature, inter-channel level difference (IID). This helps incorporate the spatial cue into the system, since the similar features of this format can be easily calculated from every spectrogram bin. The weighting functions are designed taking into account the distance between the spatial cue and the calculated features. Namely, the largest values are assigned to the spectrogram bins where the features present the highest similarity to the spatial cue, and the value decreases in proportion to the distance between them. The method is evaluated in terms of separation quality, comparing the proposed algorithm to the conventional NTF technique, PARAFAC-NTF, as well as other source separation techniques. The evaluation results measured by the metric signal-to-distortion ratio (SDR), signal-to-interference ratio (SIR), and signal-to-artifact ratio (SAR) demonstrate the effectiveness of the new method, improved primarily by the weighting function and the initialization based on IID, while demonstrating a decrease in computational costs, a significant problem with NTF.

  9. Separation control in a conical diffuser with an annular inlet: center body wake separation

    NASA Astrophysics Data System (ADS)

    Lo, Kin Pong; Elkins, Christopher J.; Eaton, John K.

    2012-11-01

    In many practical applications of conical diffusers, the flow is fed by an annular flow passage formed by a center body. Flow separation, which occurs if the center body ends abruptly, is undesirable because it degrades the diffuser performance. The present experiment utilizes magnetic resonance velocimetry to acquire three-component mean velocity measurements for a set of conical diffusers with an annular inlet. The results show strong coupling between the diffuser wall boundary layer development and the wake of the center body. Coanda blowing is used to mitigate the center body wake separation. The diffuser wall boundary layer is thick in the absence of the central separation bubble and separates when Coanda blowing is too strong.

  10. Computational analysis of stall and separation control in centrifugal compressors

    NASA Astrophysics Data System (ADS)

    Stein, Alexander

    2000-10-01

    A numerical technique for simulating unsteady viscous fluid flow in turbomachinery components has been developed. In this technique, the three-dimensional form of the Reynolds averaged Navier-Stokes equations is solved in a time-accurate manner. The flow solver is used to study fluid dynamic phenomena that lead to instabilities in centrifugal compressors. The results indicate that large flow incidence angles, at reduced flow rates, can cause boundary layer separation near the blade leading edge. This mechanism is identified as the primary factor in the stall inception process. High-pressure jets upstream of the compressor face are studied as a means of controlling compressor instabilities. Steady jets are found to alter the leading edge flow pattern and effectively suppress compressor instabilities. Yawed jets are more effective than parallel jets and an optimum yaw angle exists for each compression system. Numerical simulations utilizing pulsed jets have also been done. Pulsed jets are found to yield additional performance enhancements and lead to a reduction in external air requirements for operating the jets. Jets pulsed at higher frequencies perform better than low-frequency jets. These findings suggest that air injection is a viable means of alleviating compressor instabilities and could impact gas turbine technology. Results concerning the optimization of practical air injection systems and implications for future research are discussed. The flow solver developed in this work, along with the postprocessing tools developed to interpret the results, provide a rational framework for analyzing and controlling current and next generation compression systems.

  11. Controlled shear filtration: A novel technique for animal cell separation.

    PubMed

    Vogel, J H; Kroner, K H

    1999-06-20

    A novel rotary microfiltration technique specifically suited for the separation of animal cells has been developed. The concept allows the independent adjustment of wall shear stress, transmembrane pressure, and residence time, allowing straightforward optimization of the microfiltration process. By using a smooth, conically shaped rotor, it is possible to establish a controlled shear field in which animal cells experience a significant hydrodynamic lift away from the membrane surface. It is shown in preliminary experiments that shear-induced cell-rupture speeds up membrane clogging and that cell debris poses the most significant problem in harvesting of BHK cell cultures by dynamic microfiltration. However, a threshold value of shear stability exists which depends on the frequency of passing the shear field, the residence time in the shear field, as well as on cell status. By operating close to this threshold value, cell viability can be maintained while concentration polarization is efficiently minimized. By applying this concept, it is possible to attain flux rates several times higher compared to conventional crossflow filtration. Controlled shear filtration (CSF) can be used for batch harvesting as well as for cell retention in high cell density systems. In batch harvesting of hIL-2 from rBHK cell culture, a constant flux rate of 290 L h-1 m-2 has been adjusted without indication of membrane clogging or fouling.

  12. Exploring active flow control for efficient control of separation on an Ahmed model

    NASA Astrophysics Data System (ADS)

    McNally, Jonathan; Alvi, Farrukh

    2016-11-01

    Active flow control is applied to an Ahmed model with a rear slant angle of 25°, where a typical flow field consists of a three-dimensional separation region on the rear slant of the bluff body. Linear arrays of discrete microjets, previously proven to effectively control this separation, are investigated further. A principal aim of this experimental study is to examine the sensitivity of control as the actuator location is shifted with respect to the separation location. Aerodynamic force and surface pressure measurements, combined with the velocity field obtained using particle image velocimetry, provide a measure of control efficacy and insight into the interaction of jet arrays with the local flow field, including the separating shear layer. An energy balance is conducted to characterize control efficiency for multiple positions over a range of microjet array blowing conditions. Results show that moving the actuator array further into the separation region requires higher microjet momentum to obtain a desired aerodynamic benefit. An empirical relationship is also developed for determining the required jet velocity as a function of position by relating the jet penetration distance to local flow features and length scales. Partial support by FCAAP and NSF.

  13. Feedback control of optical beam spatial profiles using thermal lensing.

    PubMed

    Liu, Zhanwei; Fulda, Paul; Arain, Muzammil A; Williams, Luke; Mueller, Guido; Tanner, D B; Reitze, D H

    2013-09-10

    A method for active control of the spatial profile of a laser beam using adaptive thermal lensing is described. A segmented electrical heater was used to generate thermal gradients across a transmissive optical element, resulting in a controllable thermal lens. The segmented heater also allows the generation of cylindrical lenses, and provides the capability to steer the beam in both horizontal and vertical planes. Using this device as an actuator, a feedback control loop was developed to stabilize the beam size and position.

  14. Visual Spatial Attention Training Improve Spatial Attention and Motor Control for Unilateral Neglect Patients.

    PubMed

    Wang, Wei; Ji, Xiangtong; Ni, Jun; Ye, Qian; Zhang, Sicong; Chen, Wenli; Bian, Rong; Yu, Cui; Zhang, Wenting; Shen, Guangyu; Machado, Sergio; Yuan, Tifei; Shan, Chunlei

    2015-01-01

    To compare the effect of visual spatial training on the spatial attention to that on motor control and to correlate the improvement of spatial attention to motor control progress after visual spatial training in subjects with unilateral spatial neglect (USN). 9 cases with USN after right cerebral stroke were randomly divided into Conventional treatment group + visual spatial attention and Conventional treatment group. The Conventional treatment group + visual spatial attention received conventional rehabilitation therapy (physical and occupational therapy) and visual spatial attention training (optokinetic stimulation and right half-field eye patching). The Conventional treatment group was only treated with conventional rehabilitation training (physical and occupational therapy). All patients were assessed by behavioral inattention test (BIT), Fugl-Meyer Assessment of motor function (FMA), equilibrium coordination test (ECT) and non-equilibrium coordination test (NCT) before and after 4 weeks treatment. Total scores in both groups (without visual spatial attention/with visual spatial attention) improved significantly (BIT: P=0.021/P=0.000, d=1.667/d=2.116, power=0.69/power=0.98, 95%CI[-0.8839,45.88]/95%CI=[16.96,92.64]; FMA: P=0.002/P=0.000, d=2.521/d=2.700, power=0.93/power=0.98, 95%CI[5.707,30.79]/95%CI=[16.06,53.94]; ECT: P=0.002/ P=0.000, d=2.031/d=1.354, power=0.90/power=0.17, 95%CI[3.380,42.61]/95%CI=[-1.478,39.08]; NCT: P=0.013/P=0.000, d=1.124/d=1.822, power=0.41/power=0.56, 95%CI[-7.980,37.48]/95%CI=[4.798,43.60],) after treatment. Among the 2 groups, the group with visual spatial attention significantly improved in BIT (P=0.003, d=3.103, power=1, 95%CI[15.68,48.92]), FMA of upper extremity (P=0.006, d=2.771, power=1, 95%CI[5.061,20.14]) and NCT (P=0.010, d=2.214, power=0.81-0.90, 95%CI[3.018,15.88]). Correlative analysis shows that the change of BIT scores is positively correlated to the change of FMA total score (r=0.77, P<;0.01), FMA of upper extremity

  15. Freezing-induced phase separation and spatial microheterogeneity in protein solutions.

    PubMed

    Dong, Jinping; Hubel, Allison; Bischof, John C; Aksan, Alptekin

    2009-07-30

    Amid decades of research, the basic mechanisms of lyo-/cryostabilization of proteins and more complex organisms have not yet been fully established. One major bottleneck is the inability to probe into and control the molecular level interactions. The molecular interactions are responsible for the significant differences in the outcome of the preservation processes. (1) In this communication, we have utilized confocal Raman microspectroscopy to quantify the freezing-induced microheterogeneity and phase separation (solid and liquid) in a frozen solution composed of a model protein (lysozyme) and a lyo-/cryoprotectant (trehalose), which experienced different degrees of supercooling. Detailed quantitative spectral analysis was performed across the ice, the freeze-concentrated liquid (FCL) phases, and the interface region between them. It was established that the characteristics of the microstructures observed after freezing depended not only on the concentration of trehalose in the solution but also on the degree of supercooling. It was shown that, when samples were frozen after high supercooling, small amounts of lysozyme and trehalose were occluded in the ice phase. Lysozyme preserved its native-like secondary structure in the FCL region but was denatured in the ice phase. Also, it was observed that induction of freezing after a high degree of supercooling of high trehalose concentrations resulted in aggregation of the sugar and the protein.

  16. A spatial operator algebra for manipulator modeling and control

    NASA Technical Reports Server (NTRS)

    Rodriguez, G.; Jain, A.; Kreutz-Delgado, K.

    1991-01-01

    A recently developed spatial operator algebra for manipulator modeling, control, and trajectory design is discussed. The elements of this algebra are linear operators whose domain and range spaces consist of forces, moments, velocities, and accelerations. The effect of these operators is equivalent to a spatial recursion along the span of a manipulator. Inversion of operators can be efficiently obtained via techniques of recursive filtering and smoothing. The operator algebra provides a high-level framework for describing the dynamic and kinematic behavior of a manipulator and for control and trajectory design algorithms. The interpretation of expressions within the algebraic framework leads to enhanced conceptual and physical understanding of manipulator dynamics and kinematics.

  17. Spatial Mode Control of High-Order Harmonics

    SciTech Connect

    Mercer, I.; Mevel, E.; Zerne, R.; LHuillier, A.; Antoine, P.; Wahlstroem, C. |

    1996-08-01

    We demonstrate that the spatial mode of high-order harmonics can be continuously controlled. The control is achieved by spatially modulating the degree of elliptical polarization of the fundamental field using birefringent optics. A highly sensitive relationship between the efficiency of harmonic generation and the degree of laser elliptical polarization leads to atoms emitting harmonics only in regions of linear polarization. The harmonics are emitted as annular beams whose angles of divergence can be continuously varied. {copyright} {ital 1996 The American Physical Society.}

  18. Effects of temporal and spatial cueing on anticipatory postural control in a rapid interceptive task.

    PubMed

    Huntley, Andrew H; Zettel, John L

    2015-04-10

    Balance disruptions induced by voluntary focal arm actions are accommodated via anticipatory postural adjustments, but how this coordinated control is organized by the central nervous system remains unclear: either as combined or separate streams of postural-focal motor commands. For example, a focal arm task that dictates extremely tight temporal constraints may induce a focal response in absence of an anticipatory postural adjustment, providing evidence for separate focal-postural control streams. This study sought to probe the organization of focal-postural control via an interceptive task with very little available response time, and to determine whether focal-postural coordination depends on temporal and/or spatial foreknowledge of the task. Ten healthy young adults (5 males and 5 females; 20-29 years) reacted to catch a ball when standing under four conditions of temporal and spatial foreknowledge. Response onset was characterized by muscle activity from both postural and focal arm muscles. The catching task resulted in rapid muscle responses, but there was no difference between the fastest focal and postural muscle onsets. As expected, temporal cuing resulted in faster focal and postural onsets compared to spatial and control cuing trials. The accompaniment and time-locking of focal and postural muscle onsets, suggests that postural-focal coupling remains intact even under external time constraints and provides evidence for a single combined command stream of postural and focal control under such circumstances.

  19. On spatial scaling & environmental controls of soil organic carbon stocks

    NASA Astrophysics Data System (ADS)

    Mishra, U.; Riley, W. J.; Koven, C. D.

    2014-12-01

    Spatial heterogeneity of terrestrial land surface modulates the fluxes of energy, moisture, and greenhouse gases. However, representing the terrestrial heterogeneity of biogeochemistry in earth system models (ESMs) remains a critical scientific challenge. We investigated the impact of spatial scaling on environmental controls and predicted soil organic carbon (SOC) stocks across the state of Alaska, USA. We used over 500 soil profile observations and environmental factors such as topography, climate, land cover types, and surficial geology to predict the SOC stocks at 50 m spatial resolution. We upscaled both the predicted SOC stocks and environmental variables from finer to coarser spatial scales (100 m, 200 m, 500 m, 1 km, 2 km, 5 km, and 10 km) and generated SOC stock estimates for each scale till the predicted variance of SOC stocks became constant. We found different environmental factors as statistically significant predictors at different spatial scales. Topographic attributes were important predictors at finer scales whereas surficial geology types became significant predictors at larger spatial scales. Only elevation, temperature, potential evapotranspiration, and barren land cover types were significant predictors at all scales. The controls (predictive power) of these environmental variables on SOC stocks decreased with upscaling. Highest and lowest decrease in predictive power was observed for potential evapotranspiration (55%) and elevation (25%). Similarly, intermediate decrease was observed for temperature (45%), and barren land cover types (45%). The predicted variance of SOC stocks decreased by 45% as the spatial scaling was increased from 50 m to 10km. We believe the statistical structure of the scaling behavior of SOC stocks can inform ESMs in appropriately representing the spatial heterogeneity of SOC stocks.

  20. High resolution Hall measurements across the VO2 metal-insulator transition reveal impact of spatial phase separation

    PubMed Central

    Yamin, Tony; Strelniker, Yakov M.; Sharoni, Amos

    2016-01-01

    Many strongly correlated transition metal oxides exhibit a metal-insulator transition (MIT), the manipulation of which is essential for their application as active device elements. However, such manipulation is hindered by lack of microscopic understanding of mechanisms involved in these transitions. A prototypical example is VO2, where previous studies indicated that the MIT resistance change correlate with changes in carrier density and mobility. We studied the MIT using Hall measurements with unprecedented resolution and accuracy, simultaneously with resistance measurements. Contrast to prior reports, we find that the MIT is not correlated with a change in mobility, but rather, is a macroscopic manifestation of the spatial phase separation which accompanies the MIT. Our results demonstrate that, surprisingly, properties of the nano-scale spatially-separated metallic and semiconducting domains actually retain their bulk properties. This study highlights the importance of taking into account local fluctuations and correlations when interpreting transport measurements in highly correlated systems. PMID:26783076

  1. Separation of the global and local components in functional near-infrared spectroscopy signals using principal component spatial filtering.

    PubMed

    Zhang, Xian; Noah, Jack Adam; Hirsch, Joy

    2016-01-01

    Global systemic effects not specific to a task can be prominent in functional near-infrared spectroscopy (fNIRS) signals and the separation of task-specific fNIRS signals and global nonspecific effects is challenging due to waveform correlations. We describe a principal component spatial filter algorithm for separation of the global and local effects. The effectiveness of the approach is demonstrated using fNIRS signals acquired during a right finger-thumb tapping task where the response patterns are well established. Both the temporal waveforms and the spatial pattern consistencies between oxyhemoglobin and deoxyhemoglobin signals are significantly improved, consistent with the basic physiological basis of fNIRS signals and the expected pattern of activity associated with the task.

  2. Shifting Attentional Priorities: Control of Spatial Attention through Hemispheric Competition

    PubMed Central

    Szczepanski, Sara M.; Kastner, Sabine

    2013-01-01

    Regions of frontal and posterior parietal cortex are known to control the allocation of spatial attention across the visual field. However, the neural mechanisms underlying attentional control in the intact human brain remain unclear, with some studies supporting a hemispatial theory emphasizing a dominant function of the right hemisphere and others supporting an interhemispheric competition theory. We previously found neural evidence to support the latter account, in which topographically organized frontoparietal areas each generate a spatial bias, or “attentional weight,” toward the contralateral hemifield, with the sum of the weights constituting the overall bias that can be exerted across visual space. Here, we used a multimodal approach consisting of functional magnetic resonance imaging (fMRI) of spatial attention signals, behavioral measures of spatial bias, and fMRI-guided single-pulse transcranial magnetic stimulation (TMS) to causally test this interhemispheric competition account. Across the group of fMRI subjects, we found substantial individual differences in the strengths of the frontoparietal attentional weights in each hemisphere, which predicted subjects’ respective behavioral preferences when allocating spatial attention, as measured by a landmark task. Using TMS to interfere with attentional processing within specific topographic frontoparietal areas, we then demonstrated that the attentional weights of individual subjects, and thus their spatial attention behavior, could be predictably shifted toward one visual field or the other, depending on the site of interference. The results of our multimodal approach, combined with an emphasis on neural and behavioral individual differences, provide compelling evidence that spatial attention is controlled through competitive interactions between hemispheres rather than a dominant right hemisphere in the intact human brain. PMID:23516306

  3. Spatial Analysis of Childhood Cancer: A Case/Control Study

    PubMed Central

    Ramis, Rebeca; Gómez-Barroso, Diana; Tamayo, Ibon; García-Pérez, Javier; Morales, Antonio; Pardo Romaguera, Elena; López-Abente, Gonzalo

    2015-01-01

    Background Childhood cancer was the leading cause of death among children aged 1-14 years for 2012 in Spain. Leukemia has the highest incidence, followed by tumors of the central nervous system (CNS) and lymphomas (Hodgkin lymphoma, HL, and Non-Hodgkin’s lymphoma, NHL). Spatial distribution of childhood cancer cases has been under concern with the aim of identifying potential risk factors. Objective The two objectives are to study overall spatial clustering and cluster detection of cases of the three main childhood cancer causes, looking to increase etiological knowledge. Methods We ran a case-control study. The cases were children aged 0 to 14 diagnosed with leukemia, lymphomas (HL and NHL) or CNS neoplasm in five Spanish regions for the period 1996-2011. As a control group, we used a sample from the Birth Registry matching every case by year of birth, autonomous region of residence and sex with six controls. We geocoded and validated the address of the cases and controls. For our two objectives we used two different methodologies. For the first, for overall spatial clustering detection, we used the differences of K functions from the spatial point patterns perspective proposed by Diggle and Chetwynd and the second, for cluster detection, we used the spatial scan statistic proposed by Kulldorff with a level for statistical significance of 0.05. Results We had 1062 cases of leukemia, 714 cases of CNS, 92 of HL and 246 of NHL. Accordingly we had 6 times the number of controls, 6372 controls for leukemia, 4284 controls for CNS, 552 controls for HL and 1476 controls for NHL. We found variations in the estimated empirical D(s) for the different regions and cancers, including some overall spatial clustering for specific regions and distances. We did not find statistically significant clusters. Conclusions The variations in the estimated empirical D(s) for the different regions and cancers could be partially explained by the differences in the spatial distribution of

  4. Spatial analysis of childhood cancer: a case/control study.

    PubMed

    Ramis, Rebeca; Gómez-Barroso, Diana; Tamayo, Ibon; García-Pérez, Javier; Morales, Antonio; Pardo Romaguera, Elena; López-Abente, Gonzalo

    2015-01-01

    Childhood cancer was the leading cause of death among children aged 1-14 years for 2012 in Spain. Leukemia has the highest incidence, followed by tumors of the central nervous system (CNS) and lymphomas (Hodgkin lymphoma, HL, and Non-Hodgkin's lymphoma, NHL). Spatial distribution of childhood cancer cases has been under concern with the aim of identifying potential risk factors. The two objectives are to study overall spatial clustering and cluster detection of cases of the three main childhood cancer causes, looking to increase etiological knowledge. We ran a case-control study. The cases were children aged 0 to 14 diagnosed with leukemia, lymphomas (HL and NHL) or CNS neoplasm in five Spanish regions for the period 1996-2011. As a control group, we used a sample from the Birth Registry matching every case by year of birth, autonomous region of residence and sex with six controls. We geocoded and validated the address of the cases and controls. For our two objectives we used two different methodologies. For the first, for overall spatial clustering detection, we used the differences of K functions from the spatial point patterns perspective proposed by Diggle and Chetwynd and the second, for cluster detection, we used the spatial scan statistic proposed by Kulldorff with a level for statistical significance of 0.05. We had 1062 cases of leukemia, 714 cases of CNS, 92 of HL and 246 of NHL. Accordingly we had 6 times the number of controls, 6372 controls for leukemia, 4284 controls for CNS, 552 controls for HL and 1476 controls for NHL. We found variations in the estimated empirical D(s) for the different regions and cancers, including some overall spatial clustering for specific regions and distances. We did not find statistically significant clusters. The variations in the estimated empirical D(s) for the different regions and cancers could be partially explained by the differences in the spatial distribution of the population; however, according to the literature

  5. On an exciton with a spatially separated electron and hole in quasi-zero-dimensional semiconductor nanosystems

    SciTech Connect

    Pokutnyi, S. I.

    2013-06-15

    The theory of an exciton with a spatially separated electron and hole (the hole is in the quantum dot volume, and the electron is localized at the outer spherical quantum dot-dielectric matrix interface) is developed within the modified effective mass method. The effect of significantly increasing the exciton-binding energy in quantum dots of zinc selenide, synthesized in a borosilicate glass matrix, relative to that in a zinc-selenide single crystal is revealed.

  6. Elimination of the background from polariton CARS spectra by spatial separation of the exciting and probe beams

    SciTech Connect

    Orlov, Sergei N; Polivanov, Yurii N

    1998-02-28

    A method for elimination of the background (resulting from direct four-photon processes) from polariton CARS spectra is proposed and demonstrated experimentally. The method is based on the ability of polaritons to propagate in a medium over macroscopic distances and it requires a geometry of the interacting waves in which the regions of biharmonic excitation of polaritons and probing of the excited polaritons by a probe field are spatially separated in a crystal. (nonlinear optical phenomena and devices)

  7. Amoeba-based computing for traveling salesman problem: long-term correlations between spatially separated individual cells of Physarum polycephalum.

    PubMed

    Zhu, Liping; Aono, Masashi; Kim, Song-Ju; Hara, Masahiko

    2013-04-01

    A single-celled, multi-nucleated amoeboid organism, a plasmodium of the true slime mold Physarum polycephalum, can perform sophisticated computing by exhibiting complex spatiotemporal oscillatory dynamics while deforming its amorphous body. We previously devised an "amoeba-based computer (ABC)" to quantitatively evaluate the optimization capability of the amoeboid organism in searching for a solution to the traveling salesman problem (TSP) under optical feedback control. In ABC, the organism changes its shape to find a high quality solution (a relatively shorter TSP route) by alternately expanding and contracting its pseudopod-like branches that exhibit local photoavoidance behavior. The quality of the solution serves as a measure of the optimality of which the organism maximizes its global body area (nutrient absorption) while minimizing the risk of being illuminated (exposure to aversive stimuli). ABC found a high quality solution for the 8-city TSP with a high probability. However, it remains unclear whether intracellular communication among the branches of the organism is essential for computing. In this study, we conducted a series of control experiments using two individual cells (two single-celled organisms) to perform parallel searches in the absence of intercellular communication. We found that ABC drastically lost its ability to find a solution when it used two independent individuals. However, interestingly, when two individuals were prepared by dividing one individual, they found a solution for a few tens of minutes. That is, the two divided individuals remained correlated even though they were spatially separated. These results suggest the presence of a long-term memory in the intrinsic dynamics of this organism and its significance in performing sophisticated computing. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  8. Spatial Control of Crystal Texture by Laser DMD Process

    DTIC Science & Technology

    2009-02-01

    process for spatial control of crystal texture, and mechanical properties of texture-controlled Ni-based superalloy turbine blade components...times more relative life for corrosion resistance, when compared to equiaxed crystal counter parts [1]. Modern high turbine inlet temperature jet...reported SX airfoils have much longer thermal creep and fatigue life and are corrosion resistant. They can be cast with thinner walls, meaning less

  9. Spatial simulation of instability control by periodic suction blowing

    NASA Technical Reports Server (NTRS)

    Danabasoglu, G.; Biringen, S.; Streett, C. L.

    1991-01-01

    The applicability of active control by periodic suction blowing in spatially evolving plane Poiseuille flow is investigated by the direct simulation of the three-dimensional, incompressible Navier-Stokes equations. The results reveal that significant reductions in perturbation amplitudes can be obtained by a proper choice of the control wave amplitude and phase. The upstream influence of the control wave is shown to be confined to a region in the vicinity of the control slot with no apparent effect on the flow development.

  10. Spatial simulation of instability control by periodic suction blowing

    NASA Technical Reports Server (NTRS)

    Danabasoglu, G.; Biringen, S.; Streett, C. L.

    1991-01-01

    The applicability of active control by periodic suction blowing in spatially evolving plane Poiseuille flow is investigated by the direct simulation of the three-dimensional, incompressible Navier-Stokes equations. The results reveal that significant reductions in perturbation amplitudes can be obtained by a proper choice of the control wave amplitude and phase. The upstream influence of the control wave is shown to be confined to a region in the vicinity of the control slot with no apparent effect on the flow development.

  11. Separating spatial search and efficiency rates as components of predation risk

    PubMed Central

    DeCesare, Nicholas J.

    2012-01-01

    Predation risk is an important driver of ecosystems, and local spatial variation in risk can have population-level consequences by affecting multiple components of the predation process. I use resource selection and proportional hazard time-to-event modelling to assess the spatial drivers of two key components of risk—the search rate (i.e. aggregative response) and predation efficiency rate (i.e. functional response)—imposed by wolves (Canis lupus) in a multi-prey system. In my study area, both components of risk increased according to topographic variation, but anthropogenic features affected only the search rate. Predicted models of the cumulative hazard, or risk of a kill, underlying wolf search paths validated well with broad-scale variation in kill rates, suggesting that spatial hazard models provide a means of scaling up from local heterogeneity in predation risk to population-level dynamics in predator–prey systems. Additionally, I estimated an integrated model of relative spatial predation risk as the product of the search and efficiency rates, combining the distinct contributions of spatial heterogeneity to each component of risk. PMID:22977145

  12. Fundamental study of phosphor separation by controlling magnetic force

    NASA Astrophysics Data System (ADS)

    Wada, Kohei; Mishima, Fumihito; Akiyama, Yoko; Nishijima, Shigehiro

    2013-11-01

    The phosphor wastes consist of phosphors with different emission colors, green (LAP), red (YOX), blue (BAM) and white (HP). It is required to recover and reuse the rare earth phosphors with high market value. In this study, we tried to separate the phosphor using the magnetic separation by HTS bulk magnet utilizing the differences of magnetic susceptibility by the type of phosphors. We succeeded in the successive separation of HP with low market value from YOX and BAM including the rare earth using the magnetic Archimedes method. In this method, vertical and radial components of the magnetic force were used.

  13. Dielectric barrier plasma dynamics for active control of separated flows

    SciTech Connect

    Roy, Subrata; Singh, K.P.; Gaitonde, Datta V.

    2006-03-20

    The dynamics of separation mitigation with asymmetric dielectric barrier discharges is explored by considering the gas flow past a flat plate at an angle of attack. A self-consistent model utilizing motion of electrons, ions, and neutrals is employed to couple the electric force field to the momentum of the fluid. The charge separation and concomitant electric field yield a time-averaged body force which is oriented predominantly downstream, with a smaller transverse component towards the wall. This induces a wall-jet-like feature that effectively eliminates the separation bubble. The impact of several geometric and electrical operating parameters is elucidated.

  14. Separate systems for serotonin and leptin in appetite control.

    PubMed

    Halford, J C; Blundell, J E

    2000-04-01

    Appetite control involves an integration of the drive signals arising form energy stores in the body with the satiety signals generated by periodic episodes of food consumption. Serotonin (5-hydroxytryptamine, 5-HT) has been implicated in the processes of within-meal satiation and postmeal satiety (5-HT1B and 5-HT2C postsynaptic receptors) which are concerned with the signals arising form the pattern of food intake. Central nervous system (CNS) 5-HT is sensitive to circulating levels of the precursor tryptophan, certain macronutrients and peripheral satiety factors such as cholecystokinin (CCK) and enterostatin. Hypothalamic 5-HT receptor systems inhibit neuropeptide Y (NPY), a potent stimulator of hunger and food intake. In contrast to the linking of 5-HT with the consequences of food ingestion, the hormone leptin (OB protein) is regarded as a signal linking adipose tissue status with a number of key CNS circuits. Leptin itself stimulates CNS leptin receptors (OB-r receptor) which link with pro-opiomelanocortin (POMC)/ MC-4 receptors. The effects of leptin may also be modulated by factors such as the corticotrophin-releasing factor (CRF), cocaine and amphetamine-regulated transcript (CART), orexins and galanin. Very little evidence exists to support any direct link between the actions of 5-HT and leptin, suggesting that they are separate systems. 5-HT is a part of an integrated network for short-acting satiety signals (episodic in nature), and leptin is a hormonal indicator of long-term (tonic) energy reserves. At a conceptual level, these may represent the distinction between 'satiety' and 'drive'. Interestingly, both 5-HT and leptin modulate the action of NPY, which may form a part of a common output pathway for the expression of appetite.

  15. Graphene-enabled electrically controlled terahertz spatial light modulators.

    PubMed

    Kakenov, Nurbek; Takan, Taylan; Ozkan, Vedat Ali; Balcı, Osman; Polat, Emre O; Altan, Hakan; Kocabas, Coskun

    2015-05-01

    In this Letter, we demonstrate a broadband terahertz (THz) spatial light modulator using 5×5 arrays of large area graphene supercapacitors. Our approach relies on controlling spatial charge distribution on a passive matrix array of patterned graphene electrodes. By changing the voltage bias applied to the rows and columns, we were able to pattern the THz transmittance through the device with high modulation depth and low operation voltage. We anticipate that the simplicity of the device architecture with high contrast THz modulation over a broad spectral range could provide new tools for THz imaging and communication systems.

  16. Spatial operator approach to flexible multibody system dynamics and control

    NASA Technical Reports Server (NTRS)

    Rodriguez, G.

    1991-01-01

    The inverse and forward dynamics problems for flexible multibody systems were solved using the techniques of spatially recursive Kalman filtering and smoothing. These algorithms are easily developed using a set of identities associated with mass matrix factorization and inversion. These identities are easily derived using the spatial operator algebra developed by the author. Current work is aimed at computational experiments with the described algorithms and at modelling for control design of limber manipulator systems. It is also aimed at handling and manipulation of flexible objects.

  17. Separation Control Using ZNMF Devices: Flow Physics and Scaling Laws

    DTIC Science & Technology

    2007-12-31

    the baseline uncontrolled flow is massively separated and does not reattached before the trailing edge (i.e. post stall). As mentioned earlier, this... massively leading-edge separated flow. In particular, a recursive ARMARKOV system ID algorithm is used to model the flow dynamics and provide the...3, May-June 2001. Soderstrom, T. and Stoica, P., System Identification, Prentice-Hall, New York, 1989. Song, Q., Tian, Y. and Cattafesta, L., " MIMO

  18. A spatial operator algebra for manipulator modeling and control

    NASA Technical Reports Server (NTRS)

    Rodriguez, G.; Kreutz, K.; Milman, M.

    1988-01-01

    A powerful new spatial operator algebra for modeling, control, and trajectory design of manipulators is discussed along with its implementation in the Ada programming language. Applications of this algebra to robotics include an operator representation of the manipulator Jacobian matrix; the robot dynamical equations formulated in terms of the spatial algebra, showing the complete equivalence between the recursive Newton-Euler formulations to robot dynamics; the operator factorization and inversion of the manipulator mass matrix which immediately results in O(N) recursive forward dynamics algorithms; the joint accelerations of a manipulator due to a tip contact force; the recursive computation of the equivalent mass matrix as seen at the tip of a manipulator; and recursive forward dynamics of a closed chain system. Finally, additional applications and current research involving the use of the spatial operator algebra are discussed in general terms.

  19. Evidence for Separate Contributions of High and Low Spatial Frequencies during Visual Word Recognition.

    PubMed

    Winsler, Kurt; Holcomb, Phillip J; Midgley, Katherine J; Grainger, Jonathan

    2017-01-01

    Previous studies have shown that different spatial frequency information processing streams interact during the recognition of visual stimuli. However, it is a matter of debate as to the contributions of high and low spatial frequency (HSF and LSF) information for visual word recognition. This study examined the role of different spatial frequencies in visual word recognition using event-related potential (ERP) masked priming. EEG was recorded from 32 scalp sites in 30 English-speaking adults in a go/no-go semantic categorization task. Stimuli were white characters on a neutral gray background. Targets were uppercase five letter words preceded by a forward-mask (#######) and a 50 ms lowercase prime. Primes were either the same word (repeated) or a different word (un-repeated) than the subsequent target and either contained only high, only low, or full spatial frequency information. Additionally within each condition, half of the prime-target pairs were high lexical frequency, and half were low. In the full spatial frequency condition, typical ERP masked priming effects were found with an attenuated N250 (sub-lexical) and N400 (lexical-semantic) for repeated compared to un-repeated primes. For HSF primes there was a weaker N250 effect which interacted with lexical frequency, a significant reversal of the effect around 300 ms, and an N400-like effect for only high lexical frequency word pairs. LSF primes did not produce any of the classic ERP repetition priming effects, however they did elicit a distinct early effect around 200 ms in the opposite direction of typical repetition effects. HSF information accounted for many of the masked repetition priming ERP effects and therefore suggests that HSFs are more crucial for word recognition. However, LSFs did produce their own pattern of priming effects indicating that larger scale information may still play a role in word recognition.

  20. 33 CFR 239.7 - Separation of flood control works from urban drainage.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Separation of flood control works... COVERED FLOOD CONTROL CHANNELS § 239.7 Separation of flood control works from urban drainage. Covered channels are likely to be considered in boundary areas demarking urban drainage and flood control...

  1. 33 CFR 239.7 - Separation of flood control works from urban drainage.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Separation of flood control works... COVERED FLOOD CONTROL CHANNELS § 239.7 Separation of flood control works from urban drainage. Covered channels are likely to be considered in boundary areas demarking urban drainage and flood control...

  2. 33 CFR 239.7 - Separation of flood control works from urban drainage.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 3 2012-07-01 2012-07-01 false Separation of flood control works... COVERED FLOOD CONTROL CHANNELS § 239.7 Separation of flood control works from urban drainage. Covered channels are likely to be considered in boundary areas demarking urban drainage and flood control...

  3. 33 CFR 239.7 - Separation of flood control works from urban drainage.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 3 2013-07-01 2013-07-01 false Separation of flood control works... COVERED FLOOD CONTROL CHANNELS § 239.7 Separation of flood control works from urban drainage. Covered channels are likely to be considered in boundary areas demarking urban drainage and flood control...

  4. 33 CFR 239.7 - Separation of flood control works from urban drainage.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Separation of flood control works... COVERED FLOOD CONTROL CHANNELS § 239.7 Separation of flood control works from urban drainage. Covered channels are likely to be considered in boundary areas demarking urban drainage and flood control...

  5. Cytoskeletal pinning controls phase separation in multicomponent lipid membranes.

    PubMed

    Arumugam, Senthil; Petrov, Eugene P; Schwille, Petra

    2015-03-10

    We study the effect of a minimal cytoskeletal network formed on the surface of giant unilamellar vesicles by the prokaryotic tubulin homolog, FtsZ, on phase separation in freestanding lipid membranes. FtsZ has been modified to interact with the membrane through a membrane targeting sequence from the prokaryotic protein MinD. FtsZ with the attached membrane targeting sequence efficiently forms a highly interconnected network on membranes with a concentration-dependent mesh size, much similar to the eukaryotic cytoskeletal network underlying the plasma membrane. Using giant unilamellar vesicles formed from a quaternary lipid mixture, we demonstrate that the artificial membrane-associated cytoskeleton, on the one hand, suppresses large-scale phase separation below the phase transition temperature, and, on the other hand, preserves phase separation above the transition temperature. Our experimental observations support the ideas put forward in our previous simulation study: In particular, the picket fence effect on phase separation may explain why micrometer-scale membrane domains are observed in isolated, cytoskeleton-free giant plasma membrane vesicles, but not in intact cell membranes. The experimentally observed suppression of large-scale phase separation much below the transition temperatures also serves as an argument in favor of the cryoprotective role of the cytoskeleton. Copyright © 2015 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  6. Structure having spatially separated photo-excitable electron-hole pairs and method of manufacturing same

    DOEpatents

    Liang, Yong [Richland, WA; Daschbach, John L [Richland, WA; Su, Yali [Richland, WA; Chambers, Scott A [Kennewick, WA

    2003-03-18

    A method for producing quantum dots. The method includes cleaning an oxide substrate and separately cleaning a metal source. The substrate is then heated and exposed to the source in an oxygen environment. This causes metal oxide quantum dots to form on the surface of the substrate.

  7. Structure having spatially separated photo-excitable electron-hole pairs and method of manufacturing same

    DOEpatents

    Liang, Yong; Daschbach, John L.; Su, Yali; Chambers, Scott A.

    2006-08-22

    A method for producing quantum dots. The method includes cleaning an oxide substrate and separately cleaning a metal source. The substrate is then heated and exposed to the source in an oxygen environment. This causes metal oxide quantum dots to form on the surface of the substrate.

  8. First spatial separation of a heavy ion isomeric beam with a multiple-reflection time-of-flight mass spectrometer

    NASA Astrophysics Data System (ADS)

    Dickel, T.; Plaß, W. R.; Ayet San Andres, S.; Ebert, J.; Geissel, H.; Haettner, E.; Hornung, C.; Miskun, I.; Pietri, S.; Purushothaman, S.; Reiter, M. P.; Rink, A.-K.; Scheidenberger, C.; Weick, H.; Dendooven, P.; Diwisch, M.; Greiner, F.; Heiße, F.; Knöbel, R.; Lippert, W.; Moore, I. D.; Pohjalainen, I.; Prochazka, A.; Ranjan, M.; Takechi, M.; Winfield, J. S.; Xu, X.

    2015-05-01

    211Po ions in the ground and isomeric states were produced via 238U projectile fragmentation at 1000 MeV/u. The 211Po ions were spatially separated in flight from the primary beam and other reaction products by the fragment separator FRS. The ions were energy-bunched, slowed-down and thermalized in a gas-filled cryogenic stopping cell (CSC). They were then extracted from the CSC and injected into a high-resolution multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). The excitation energy of the isomer and, for the first time, the isomeric-to-ground state ratio were determined from the measured mass spectrum. In the subsequent experimental step, the isomers were spatially separated from the ions in the ground state by an ion deflector and finally collected with a silicon detector for decay spectroscopy. This pioneering experimental result opens up unique perspectives for isomer-resolved studies. With this versatile experimental method new isomers with half-lives longer than a few milliseconds can be discovered and their decay properties can be measured with highest sensitivity and selectivity. These experiments can be extended to studies with isomeric beams in nuclear reactions.

  9. Separating Spatial and Temporal Variations of the Aurora Using Two Nearly Colocated Satellites

    NASA Technical Reports Server (NTRS)

    Spence, Harlan E.

    2001-01-01

    This final report describes the efforts accomplished during the grant's period of performance, covering the period of 1 May 1997 to 30 April 2001, of a NASA Supporting Research and Technology Program grant under the Ionospheric, Thermospheric, and Mesospheric Physics component of the Sun-Earth Connections program. We have met and exceeded the goals set forth in the proposed research objectives. Referred publications have appeared in the scientific literature and several others are in the review process. In addition, numerous invited and contributed presentations of these studies were presented at national and international meetings during the performance period. One graduate student completed his PhD and won two AGU Best Student Paper awards based on research funded by this grant. These studies are summarized below. The science goal delineated in the initial proposal was "to systematically explore the temporal and spatial characteristics of the aurora in a way heretofore impossible, using data from two coplanar DMSP spacecraft." We accomplished this goal through a series of related studies. One study used these unique data to establish the role of Ps6 waves in coupling between the magnetosphere and the auroral ionosphere (omega bands) during the recovery phase of a magnetic storm; the published paper demonstrated the causal relationships between geospace processes occurring in different regions and established a simple conceptual model based on the fortuitous constellation of observations. In the second string of papers, we used these data to explore velocity-dispersed ions (VDIS) in and near the cusp, to test region identification models, and to look at space/time structure of auroral precipitation. On the first topic, the unique DMSP data revealed a remarkable double VDIS with a latitudinal overlap. This could only be explained in terms of a unified reconnection geometry that builds on several earlier unrelated models. The paper outlining this discovery has drawn

  10. Pre-saccadic perception: Separate time courses for enhancement and spatial pooling at the saccade target.

    PubMed

    Buonocore, Antimo; Fracasso, Alessio; Melcher, David

    2017-01-01

    We interact with complex scenes using eye movements to select targets of interest. Studies have shown that the future target of a saccadic eye movement is processed differently by the visual system. A number of effects have been reported, including a benefit for perceptual performance at the target ("enhancement"), reduced influences of backward masking ("un-masking"), reduced crowding ("un-crowding") and spatial compression towards the saccade target. We investigated the time course of these effects by measuring orientation discrimination for targets that were spatially crowded or temporally masked. In four experiments, we varied the target-flanker distance, the presence of forward/backward masks, the orientation of the flankers and whether participants made a saccade. Masking and randomizing flanker orientation reduced performance in both fixation and saccade trials. We found a small improvement in performance on saccade trials, compared to fixation trials, with a time course that was consistent with a general enhancement at the saccade target. In addition, a decrement in performance (reporting the average flanker orientation, rather than the target) was found in the time bins nearest saccade onset when random oriented flankers were used, consistent with spatial pooling around the saccade target. We did not find strong evidence for un-crowding. Overall, our pattern of results was consistent with both an early, general enhancement at the saccade target and a later, peri-saccadic compression/pooling towards the saccade target.

  11. A spatial operator algebra for manipulator modeling and control

    NASA Technical Reports Server (NTRS)

    Rodriguez, G.; Kreutz, K.; Jain, A.

    1989-01-01

    A spatial operator algebra for modeling the control and trajectory design of manipulation is discussed, with emphasis on its analytical formulation and implementation in the Ada programming language. The elements of this algebra are linear operators whose domain and range spaces consist of forces, moments, velocities, and accelerations. The effect of these operators is equivalent to a spatial recursion along the span of the manipulator. Inversion is obtained using techniques of recursive filtering and smoothing. The operator alegbra provides a high-level framework for describing the dynamic and kinematic behavior of a manipulator and control and trajectory design algorithms. Implementable recursive algorithms can be immediately derived from the abstract operator expressions by inspection, thus greatly simplifying the transition from an abstract problem formulation and solution to the detailed mechanization of a specific algorithm.

  12. Continuous flow system for controlling phases separation near λ transition

    SciTech Connect

    Chorowski, M.; Poliński, J.; Kempiński, W.; Trybuła, Z.; Łoś, Sz.; Chołast, K.; Kociemba, A.

    2014-01-29

    As demands on 3He are increasing and conventional 3He production through tritium decay is decreasing, alternative 3He production methods are becoming economically viable. One such possibility is to use entropy filters for extraction of the 3He isotope from natural gas. According to the phase diagram of the 3He, its solidification is impossible by only lowering of the temperature. Hence during the cooling process at stable pressure we can reach λ-point and pass to the special phase - He II. The total density of HeII is a sum of the two phases: normal the superfluid ones. It is possible to separate these two phases with an entropy filter - the barrier for the classically-behaving normal phase. This barrier can also be used to separate the two main isotopes of He: 4He and 3He, because at temperatures close to the 4He-λ-point the 3He isotope is part of the normal phase. The paper presents continuous flow schemes of different separation methods of 3He from helium commodity coming from natural gas cryogenic processing. An overall thermodynamic efficiency of the 3He/4He separation process is presented. A simplified model of continuous flow HeI -HeII recuperative heat exchanger is given. Ceramic and carbon porous plugs have been tested in entropy filter applications.

  13. Bell's inequality violation for entangled generalized Bernoulli states in two spatially separate cavities

    SciTech Connect

    Lo Franco, R.; Compagno, G.; Messina, A.; Napoli, A.

    2005-11-15

    We consider the entanglement of orthogonal generalized Bernoulli states in two separate single-mode high-Q cavities. The expectation values and the correlations of the electric field in the cavities are obtained. We then define, in each cavity, a dichotomic operator expressible in terms of the field states which can be, in principle, experimentally measured by a probe atom that 'reads' the field. Using the quantum correlations of couples of these operators, we construct a Bell's inequality which is shown to be violated for a wide range of the degree of entanglement and which can be tested in a simple way. Thus the cavity fields directly show quantum nonlocal properties. A scheme is also sketched to generate entangled orthogonal generalized Bernoulli states in the two separate cavities.

  14. Semiconductor diode laser having an intracavity spatial phase controller for beam control and switching

    DOEpatents

    Hohimer, John P.

    1994-01-01

    A high-power broad-area semiconductor laser having a intracavity spatial phase controller is disclosed. The integrated intracavity spatial phase controller is easily formed by patterning an electrical contact metallization layer when fabricating the semiconductor laser. This spatial phase controller changes the normally broad far-field emission beam of such a laser into a single-lobed near-diffraction-limited beam at pulsed output powers of over 400 mW. Two operating modes, a thermal and a gain operating mode, exist for the phase controller, allowing for steering and switching the beam as the modes of operation are switched, and the emission beam may be scanned, for example, over a range of 1.4 degrees or switched by 8 degrees. More than one spatial phase controller may be integrated into the laser structure.

  15. Semiconductor diode laser having an intracavity spatial phase controller for beam control and switching

    DOEpatents

    Hohimer, J.P.

    1994-06-07

    A high-power broad-area semiconductor laser having a intracavity spatial phase controller is disclosed. The integrated intracavity spatial phase controller is easily formed by patterning an electrical contact metallization layer when fabricating the semiconductor laser. This spatial phase controller changes the normally broad far-field emission beam of such a laser into a single-lobed near-diffraction-limited beam at pulsed output powers of over 400 mW. Two operating modes, a thermal and a gain operating mode, exist for the phase controller, allowing for steering and switching the beam as the modes of operation are switched, and the emission beam may be scanned, for example, over a range of 1.4 degrees or switched by 8 degrees. More than one spatial phase controller may be integrated into the laser structure. 6 figs.

  16. Using evolution to generate sustainable malaria control with spatial repellents

    PubMed Central

    Lynch, Penelope Anne; Boots, Mike

    2016-01-01

    Evolution persistently undermines vector control programs through insecticide resistance. Here we propose a novel strategy which instead exploits evolution to generate and sustain new control tools. Effective spatial repellents are needed to keep vectors out of houses. Our approach generates such new repellents by combining a high-toxicity insecticide with a candidate repellent initially effective against only part of the vector population. By killing mosquitoes that enter treated properties the insecticide selects for vector phenotypes deflected by the repellent, increasing efficacy of the repellent against the target vector population and in turn protecting the insecticide against the spread of insecticide resistance. Using such evolved spatial repellents offers an evolutionarily sustainable, ‘double-dip’ system of disease control combining mortality and repellence. We formalize this idea using models which explore vector population genetics and disease transmission probabilities and show that using evolved spatial repellents is theoretically achievable, effective and sustainable. DOI: http://dx.doi.org/10.7554/eLife.15416.001 PMID:27776220

  17. Dynamic control of SRB thrust tailoff for separation

    NASA Technical Reports Server (NTRS)

    Webb, W. W.

    1976-01-01

    The use of the difference in chamber pressure between solid rocket booster engines as a controlling signal to the flight control system during booster thrust tailoff was examined. In addition, the control capability of the Generalized Attitude Control System (GACS) was compared to that of the baseline. Results indicate that the difference in chamber pressure signal provided essentially no improvement. However, the GACS is considerably better than the baseline in controlling during tailoff disturbances.

  18. Control of spatially patterned synchrony with multisite delayed feedback

    NASA Astrophysics Data System (ADS)

    Hauptmann, C.; Omel‘Chenko, O.; Popovych, O. V.; Maistrenko, Y.; Tass, P. A.

    2007-12-01

    We present an analytical study describing a method for the control of spatiotemporal patterns of synchrony in networks of coupled oscillators. Delayed feedback applied through a small number of electrodes effectively induces spatiotemporal dynamics at minimal stimulation intensities. Different arrangements of the delays cause different spatial patterns of synchrony, comparable to central pattern generators (CPGs), i.e., interacting clusters of oscillatory neurons producing patterned output, e.g., for motor control. Multisite delayed feedback stimulation might be used to restore CPG activity in patients with incomplete spinal cord injury or gait ignition disorders.

  19. Controlling Spatial Coupling in Catalytic CO Oxidation on Platinum

    NASA Astrophysics Data System (ADS)

    Lund, C. D.; Yamamoto, S. Y.; Surko, C. M.; Maple, M. B.

    1997-03-01

    Reaction-rate oscillations are known to occur in oxidation reactions on a variety of metal catalysts. The most extensively studied system of this type is the oxidation of carbon monoxide on platinum. Most studies have focused on temporal behavior. Recently, we constructed an experiment in which we can study both the spatial and temporal behavior of CO oxidation on Pt thin-film catalysts, using a continuous-flow reactor and infrared imaging techniques.(S.Y. Yamamoto, C.M. Surko, M.B. Maple, and R.K.Pina, J. Chem. Phys. 102, 8614 (1995).) In most experiments to date, all parts of the catalysts are found to oscillate in phase. By systematically blocking the possible spatial coupling mechanisms, we have shown that the various parts of the catalyst are coupled by diffusion of the reactants in the gas stream.(S.Y. Yamamoto, C.M. Surko, and M.B. Maple, J. Chem. Phys. 103, 8209 (1995).) Using argon instead of helium as the inert buffer gas and increasing the gas flow rate, we find that we are able to control the degree of spatial synchronization. This results in non-trivial spatial patterns which will be discussed.

  20. Dielectric Barrier Plasma Dynamics for Active Control of Separated Flows

    DTIC Science & Technology

    2006-01-01

    flow of neutrals , altering the dynamics of the inertial and adverse pressure gradient terms to eliminate the separation bubble. Since the neutral density...from charged particles to the neutrals results in an ener- gized near-wall flow, facilitating the elimination of a separa- tion bubble. Several...attack. A self-consistent model utilizing motion of electrons, ions, and neutrals is employed to couple the electric force field to the momentum of the

  1. Fixation Strategy Influences the Ability to Focus Attention on Two Spatially Separate Objects

    PubMed Central

    Hüttermann, Stefanie; Memmert, Daniel; Simons, Daniel J.; Bock, Otmar

    2013-01-01

    The ability to devote attention simultaneously to multiple visual objects plays an important role in domains ranging from everyday activities to the workplace. Yet, no studies have systematically explored the fixation strategies that optimize attention to two spatially distinct objects. Assuming the two objects require attention nearly simultaneously, subjects either could fixate one object or they could fixate between the objects. Studies measuring the breadth of attention have focused almost exclusively on the former strategy, by having subjects simultaneously perform one attention-demanding task at fixation and another in the periphery. We compared performance when one object was at fixation and the other was in the periphery to a condition in which both objects were in the periphery and subjects fixated between them. Performance was better with two peripheral stimuli than with one central and one peripheral stimulus, meaning that a strategy of fixating between stimuli permitted greater attention breadth. Consistent with the idea that both measures tap attention breadth, sport experts consistently outperformed novices with both fixation strategies. Our findings suggest a way to improve performance when observers must pay attention to multiple objects across spatial regions. We discuss possible explanations for this performance advantage. PMID:23776524

  2. Daughter cell separation is controlled by cytokinetic ring-activated cell wall hydrolysis

    PubMed Central

    Uehara, Tsuyoshi; Parzych, Katherine R; Dinh, Thuy; Bernhardt, Thomas G

    2010-01-01

    During bacterial cytokinesis, hydrolytic enzymes are used to split wall material shared by adjacent daughter cells to promote their separation. Precise control over these enzymes is critical to prevent breaches in wall integrity that can cause cell lysis. How these potentially lethal hydrolases are regulated has remained unknown. Here, we investigate the regulation of cell wall turnover at the Escherichia coli division site. We show that two components of the division machinery with LytM domains (EnvC and NlpD) are direct regulators of the cell wall hydrolases (amidases) responsible for cell separation (AmiA, AmiB and AmiC). Using in vitro cell wall cleavage assays, we show that EnvC activates AmiA and AmiB, whereas NlpD activates AmiC. Consistent with these findings, we show that an unregulated EnvC mutant requires functional AmiA or AmiB but not AmiC to induce cell lysis, and that the loss of NlpD phenocopies an AmiC− defect. Overall, our results suggest that cellular amidase activity is regulated spatially and temporally by coupling their activation to the assembly of the cytokinetic ring. PMID:20300061

  3. Measurement and control of heat transfer in steady and unsteady turbulent separated flow

    NASA Astrophysics Data System (ADS)

    Lewis, Douglas J.; Simpson, Roger L.

    1995-06-01

    The turbulence structure of convective heat transfer was studied experimentally in complex three- dimensional and separated turbulent boundary layers. Three test cases whose fluid dynamics have been well documented were examined. In case 1, time resolved surface heat transfer was measured in the nose region of a wing-body junction formed by a wing and a flat plate. Mean, statistical and spectral characteristics of the surface heat transfer are reported. The effects of wing shape were investigated by measuring the surface heat transfer in the nose region of a modified NACA 0020, a streamlined cylinder shape and NACA 0015. The effectiveness of a flow control device to reduce surface heat transfer is reported. In case 2, simultaneous surface heat flux and temperature profiles were measured at 11 locations in the spatially-developing pressure-driven three-dimensional turbulent boundary layer upstream of the wing-body junction. In case 3, simultaneous surface heat flux and temperature profiles were measured at 18 stream-wise locations in a mean 2-dimensional adverse-pressure gradient separating turbulent boundary layer. Mean, statistical and spectral heat flux and temperature data are reported. Mean ejection frequencies, turbulence length scales, inclination angles of the turbulence structure. and coherency between the inner and outer regions of the flow were examined from these results. Several useful correlations between surface heat transfer and velocity are reported.

  4. Daughter cell separation is controlled by cytokinetic ring-activated cell wall hydrolysis.

    PubMed

    Uehara, Tsuyoshi; Parzych, Katherine R; Dinh, Thuy; Bernhardt, Thomas G

    2010-04-21

    During bacterial cytokinesis, hydrolytic enzymes are used to split wall material shared by adjacent daughter cells to promote their separation. Precise control over these enzymes is critical to prevent breaches in wall integrity that can cause cell lysis. How these potentially lethal hydrolases are regulated has remained unknown. Here, we investigate the regulation of cell wall turnover at the Escherichia coli division site. We show that two components of the division machinery with LytM domains (EnvC and NlpD) are direct regulators of the cell wall hydrolases (amidases) responsible for cell separation (AmiA, AmiB and AmiC). Using in vitro cell wall cleavage assays, we show that EnvC activates AmiA and AmiB, whereas NlpD activates AmiC. Consistent with these findings, we show that an unregulated EnvC mutant requires functional AmiA or AmiB but not AmiC to induce cell lysis, and that the loss of NlpD phenocopies an AmiC(-) defect. Overall, our results suggest that cellular amidase activity is regulated spatially and temporally by coupling their activation to the assembly of the cytokinetic ring.

  5. Multifunctional and Spatially Controlled Bioconjugation to Melt Coextruded Nanofibers

    PubMed Central

    Kim, Si-Eun; Wallat, Jaqueline D.; Harker, Emily C.; Advincula, Abigail A.

    2015-01-01

    Polymeric fibers have drawn recent interest for uses in biomedical technologies that span drug delivery, regenerative medicine, and wound-healing patches, amongst others. We have recently reported a new class of fibrous biomaterials fabricated using coextrusion and a photochemical modification procedure to introduce functional groups onto the fibers. In this report, we extend our methodology to control surface modification density, describe methods to synthesize multifunctional fibers, and provide methods to spatially control functional group modification. Several different functional fibers are reported for bioconjugation, including propargyl, alkene, alkoxyamine, and ketone modified fibers. The modification scheme allows for control over surface density and provides a handle for downstream functionalization with appropriate bioconjugation chemistries. Through the use of multiple orthogonal chemistries, fiber chemistry could be differentially controlled to append multiple modifications. Spatial control on the fiber surface was also realized, leading to reverse gradients of small molecule dyes. One application is demonstrated for pH-responsive drug delivery of an anti-cancer therapeutics. Finally, the introduction of orthogonal chemical modifications onto these fibers allowed for modification with multiple cell-responsive peptides providing a substrate for osteoblast differentiation. PMID:26604990

  6. Energized outer membrane and spatial separation of metabolic processes in the hyperthermophilic Archaeon Ignicoccus hospitalis.

    PubMed

    Küper, Ulf; Meyer, Carolin; Müller, Volker; Rachel, Reinhard; Huber, Harald

    2010-02-16

    ATP synthase catalyzes ATP synthesis at the expense of an electrochemical ion gradient across a membrane that can be generated by different exergonic reactions. Sulfur reduction is the main energy-yielding reaction in the hyperthermophilic strictly anaerobic Crenarchaeon Ignicoccus hospitalis. This organism is unusual in having an inner and an outer membrane that are separated by a huge intermembrane compartment. Here we show, on the basis of immuno-EM analyses of ultrathin sections and immunofluorescence experiments with whole I. hospitalis cells, that the ATP synthase and H(2):sulfur oxidoreductase complexes of this organism are located in the outer membrane. These two enzyme complexes are mandatory for the generation of an electrochemical gradient and for ATP synthesis. Thus, among all prokaryotes possessing two membranes in their cell envelope (including Planctomycetes, gram-negative bacteria), I. hospitalis is a unique organism, with an energized outer membrane and ATP synthesis within the periplasmic space. In addition, DAPI staining and EM analyses showed that DNA and ribosomes are localized in the cytoplasm, leading to the conclusion that in I. hospitalis energy conservation is separated from information processing and protein biosynthesis. This raises questions regarding the function of the two membranes, the interaction between these compartments, and the general definition of a cytoplasmic membrane.

  7. Spatial and Temporal Control of Fungal Natural Product Synthesis

    PubMed Central

    Lim, Fang Yun; Keller, Nancy P.

    2014-01-01

    Despite their oftentimes-elusive ecological role, fungal natural products have, for better or worse, impacted our daily lives tremendously owing to their diverse and potent bioactive properties. This Janus-faced nature of fungal natural products inevitably ushered in a field of research dedicated towards understanding the ecology, organisms, genes, enzymes, and biosynthetic pathways that give rise to this arsenal of diverse and complex chemistry. Ongoing research in fungal secondary metabolism has not only increased our appreciation for fungal natural products as an asset but also sheds light on the pivotal role that these once-regarded “metabolic wastes” play in fungal biology, defense, and stress response in addition to their potential contributions towards human mycoses. Full orchestration of secondary metabolism requires not only the seamless coordination between temporal and spatial control of SM-associated machineries (e.g. enzymes, cofactors, intermediates, and end-products) but also integration of these machineries into primary metabolic processes and established cellular mechanisms. An intriguing, but little known aspect of microbial natural product synthesis lies in the spatial organization of both pathway intermediates and enzymes responsible for the production of these compounds. In this highlight, we summarize some major breakthroughs in understanding the genes and regulation of fungal natural product synthesis and introduce the current state of knowledge on the spatial and temporal control of fungal natural product synthesis. PMID:25142354

  8. Spatial and temporal control of fungal natural product synthesis.

    PubMed

    Lim, Fang Yun; Keller, Nancy P

    2014-10-01

    Despite their oftentimes-elusive ecological role, fungal natural products have, for better or worse, impacted our daily lives tremendously owing to their diverse and potent bioactive properties. This Janus-faced nature of fungal natural products inevitably ushered in a field of research dedicated towards understanding the ecology, organisms, genes, enzymes, and biosynthetic pathways that give rise to this arsenal of diverse and complex chemistry. Ongoing research in fungal secondary metabolism has not only increased our appreciation for fungal natural products as an asset but also sheds light on the pivotal role that these once-regarded "metabolic wastes" play in fungal biology, defense, and stress response in addition to their potential contributions towards human mycoses. Full orchestration of secondary metabolism requires not only the seamless coordination between temporal and spatial control of SM-associated machineries (e.g. enzymes, cofactors, intermediates, and end-products) but also integration of these machineries into primary metabolic processes and established cellular mechanisms. An intriguing, but little known aspect of microbial natural product synthesis lies in the spatial organization of both pathway intermediates and enzymes responsible for the production of these compounds. In this highlight, we summarize some major breakthroughs in understanding the genes and regulation of fungal natural product synthesis and introduce the current state of knowledge on the spatial and temporal control of fungal natural product synthesis.

  9. Cone separation, quadratic control systems and control of spin dynamics in the presence of decoherence.

    PubMed

    Khaneja, Navin

    2017-03-06

    In this paper, we study some control problems related to the control of coupled spin dynamics in the presence of relaxation and decoherence in nuclear magnetic resonance spectroscopy. The decoherence is modelled through a master equation. We study some model problems, whereby, through an appropriate choice of state variables, the system is reduced to a control system, where the state enters linearly and controls quadratically. We study this quadratic control system. Study of this system gives us explicit bounds on how close a coupled spin system can be driven to its target state and how much coherence and polarization can be transferred between coupled spins. Optimal control for the quadratic control system can be understood as the separation of closed cones, and we show how the derived results on optimal efficiency can be interpreted in this formulation. Finally, we study some finite-time optimal control problems for the quadratic control system.This article is part of the themed issue 'Horizons of cybernetical physics'.

  10. Cone separation, quadratic control systems and control of spin dynamics in the presence of decoherence

    NASA Astrophysics Data System (ADS)

    Khaneja, Navin

    2017-03-01

    In this paper, we study some control problems related to the control of coupled spin dynamics in the presence of relaxation and decoherence in nuclear magnetic resonance spectroscopy. The decoherence is modelled through a master equation. We study some model problems, whereby, through an appropriate choice of state variables, the system is reduced to a control system, where the state enters linearly and controls quadratically. We study this quadratic control system. Study of this system gives us explicit bounds on how close a coupled spin system can be driven to its target state and how much coherence and polarization can be transferred between coupled spins. Optimal control for the quadratic control system can be understood as the separation of closed cones, and we show how the derived results on optimal efficiency can be interpreted in this formulation. Finally, we study some finite-time optimal control problems for the quadratic control system. This article is part of the themed issue 'Horizons of cybernetical physics'.

  11. Mechanisms and Functions of Spatial Protein Quality Control.

    PubMed

    Sontag, Emily Mitchell; Samant, Rahul S; Frydman, Judith

    2017-06-20

    A healthy proteome is essential for cell survival. Protein misfolding is linked to a rapidly expanding list of human diseases, ranging from neurodegenerative diseases to aging and cancer. Many of these diseases are characterized by the accumulation of misfolded proteins in intra- and extracellular inclusions, such as amyloid plaques. The clear link between protein misfolding and disease highlights the need to better understand the elaborate machinery that manages proteome homeostasis, or proteostasis, in the cell. Proteostasis depends on a network of molecular chaperones and clearance pathways involved in the recognition, refolding, and/or clearance of aberrant proteins. Recent studies reveal that an integral part of the cellular management of misfolded proteins is their spatial sequestration into several defined compartments. Here, we review the properties, function, and formation of these compartments. Spatial sequestration plays a central role in protein quality control and cellular fitness and represents a critical link to the pathogenesis of protein aggregation-linked diseases.

  12. Bioinspired Composites with Spatial and Orientational Control of Reinforcement

    NASA Astrophysics Data System (ADS)

    Demiroers, Ahmet; Studart, Andre; Complex Materials Team

    Living organisms combine soft and hard components to fabricate composite materials with out-standing mechanical properties. The optimum design and assembly of the anisotropic components reinforce the material in specific directions against multidirectional external loads. Although nature does it quite readily, it is still a challenge for material scientists to control the orientation and position of the colloidal components in a matrix. Here, we use external electric and magnetic fields to achieve positional and orientational control over colloid-polymer composites to fabricate mechanically robust materials to capture some of the essential features of natural systems. We first investigated the assembly of spherical micron-sized colloids using dielectrophoresis, as these particles provided an easily accessible and instructive length scale for performing initial experiments. We used dielectrophoresis for spatial control of reinforcing anisotropic components and magnetic fields to provide control over the orientation of these reinforcing constituents. The obtained composites with different orientational and spatial reinforcement showed enhanced mechanical properties, such as wear resistance, which exhibits similarities to tooth enamel. SNSF Ambizione Grant PZ00P2_148040.

  13. Spatial variability in the isotopic composition of rainfall in a small headwater catchment and its effect on hydrograph separation

    NASA Astrophysics Data System (ADS)

    Fischer, Benjamin M. C.; van Meerveld, H. J. (Ilja); Seibert, Jan

    2017-04-01

    Isotope hydrograph separation (IHS) is a valuable tool to study runoff generation processes. To perform an IHS, samples of baseflow (pre-event water) and streamflow are taken at the catchment outlet. For rainfall (event water) either a bulk sample is collected or it is sampled sequentially during the event. For small headwater catchment studies, event water samples are usually taken at only one sampling location in or near the catchment because the spatial variability in the isotopic composition of rainfall is assumed to be small. However, few studies have tested this assumption. In this study, we investigated the spatiotemporal variability in the isotopic composition of rainfall and its effects on IHS results using detailed measurements from a small pre-alpine headwater catchment in Switzerland. Rainfall was sampled sequentially at eight locations across the 4.3 km2 Zwäckentobel catchment and stream water was collected in three subcatchments (0.15, 0.23, and 0.70 km2) during ten events. The spatial variability in rainfall amount, average and maximum rainfall intensity and the isotopic composition of rainfall was different for each event. There was no significant relation between the isotopic composition of rainfall and total rainfall amount, rainfall intensity or elevation. For eight of the ten studied events the temporal variability in the isotopic composition of rainfall was larger than the spatial variability in the rainfall isotopic composition. The isotope hydrograph separation results, using only one rain sampler, varied considerably depending on which rain sampler was used to represent the isotopic composition of event water. The calculated minimum pre-event water contributions differed up to 60%. The differences were particularly large for events with a large spatial variability in the isotopic composition of rainfall and a small difference between the event and pre-event water isotopic composition. Our results demonstrate that even in small catchments

  14. Process control measurements in the SRP fuel separations plants

    SciTech Connect

    McKibben, J.M.; Pickett, C.E.; Dickert, H.D.

    1982-02-01

    Programs were started to develop new in-line and at-line analytical techniques. Among the more promising techniques being investigated are: (1) an in-line instrument to analyze for percent tributyl phosphate in process solvent, (2) remote laser optrode techniques (using lazer light transmitted to and from the sample cell via light pipes) for a variety of possible analyses, and (3) sonic techniques for concentration analyses in two component systems. A subcommittee was also formed to investigate state-of-the-technology for process control. The final recommendation was to use a distributed control approach to upgrade the process control sytem. The system selected should be modular, easy to expand, and simple to change control strategies. A distributed system using microprocessorbased controllers would allow installation of the control intelligence near the process, thereby simplifying field wiring. Process information collected and stored in the controllers will be transmitted to operating consoles, via a data highway, for process management and display. The overall program has a number of distinct benefits. There are a number of cost savings that will be realized. Excellent annual return on investment - up to 110% - has been predicted for several of the projects in this program that are already funded. In addition, many of the instrument modifications will improve safety performance and production throughput in the specific ways shown.

  15. Spatial patterns and predictors of trophic control in marine ecosystems.

    PubMed

    Boyce, Daniel G; Frank, Kenneth T; Worm, Boris; Leggett, William C

    2015-10-01

    A key question in ecology is under which conditions ecosystem structure tends to be controlled by resource availability vs. consumer pressure. Several hypotheses derived from theory, experiments and observational field studies have been advanced, yet a unified explanation remains elusive. Here, we identify common predictors of trophic control in a synthetic analysis of 52 observational field studies conducted within marine ecosystems across the Northern Hemisphere and published between 1951 and 2014. Spatial regression analysis of 45 candidate variables revealed temperature to be the dominant predictor, with unimodal effects on trophic control operating both directly (r(2) = 0.32; P < 0.0001) and indirectly through influences on turnover rate and quality of primary production, biodiversity and omnivory. These findings indicate that temperature is an overarching determinant of the trophic dynamics of marine ecosystems, and that variation in ocean temperature will affect the trophic structure of marine ecosystems through both direct and indirect mechanisms. © 2015 John Wiley & Sons Ltd/CNRS.

  16. Effects of temporal and spatial separation on velocity and strength of illusory line motion.

    PubMed

    Hubbard, Timothy L; Ruppel, Susan E

    2011-05-01

    The effects of line length and of spatial or temporal distance on illusory line motion (i.e., on the perception that a stationary line unfolds or expands away from a previously presented stationary cue) were examined in five experiments. Ratings of relative velocity decreased with increases in stimulus onset asynchrony between appearance of the cue and appearance of the line (from 50 to 450 ms), whereas the extremity of ratings of direction (i.e., strength of the ratings of illusory line motion) increased with increases in stimulus onset asynchrony (from 50 to either 250 or 450 ms). Ratings of relative velocity increased with increases in line length, whereas ratings of direction were not influenced by increases in line length. Ratings of relative velocity and direction were not influenced by increases in the distance of the near or the far end of the line from the cue. Implications of these data for attentional theories and apparent-motion theories of illusory line motion are discussed.

  17. Separating melanin from hemodynamics in nevi using multimode hyperspectral dermoscopy and spatial frequency domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Vasefi, Fartash; MacKinnon, Nicholas; Saager, Rolf; Kelly, Kristen M.; Maly, Tyler; Booth, Nicholas; Durkin, Anthony J.; Farkas, Daniel L.

    2016-11-01

    Changes in the pattern and distribution of both melanocytes (pigment producing) and vasculature (hemoglobin containing) are important in distinguishing melanocytic proliferations. The ability to accurately measure melanin distribution at different depths and to distinguish it from hemoglobin is clearly important when assessing pigmented lesions (benign versus malignant). We have developed a multimode hyperspectral dermoscope (SkinSpect™) able to more accurately image both melanin and hemoglobin distribution in skin. SkinSpect uses both hyperspectral and polarization-sensitive measurements. SkinSpect's higher accuracy has been obtained by correcting for the effect of melanin absorption on hemoglobin absorption in measurements of melanocytic nevi. In vivo human skin pigmented nevi (N=20) were evaluated with the SkinSpect, and measured melanin and hemoglobin concentrations were compared with spatial frequency domain spectroscopy (SFDS) measurements. We confirm that both systems show low correlation of hemoglobin concentrations with regions containing different melanin concentrations (R=0.13 for SFDS, R=0.07 for SkinSpect).

  18. Low-bias negative differential conductance controlled by electrode separation

    NASA Astrophysics Data System (ADS)

    Yi, Xiao-Hua; Liu, Ran; Bi, Jun-Jie; Jiao, Yang; Wang, Chuan-Kui; Li, Zong-Liang

    2016-12-01

    The electronic transport properties of a single thiolated arylethynylene molecule with 9,10-dihydroanthracene core, denoted as TADHA, is studied by using non-equilibrium Green’s function formalism combined with ab initio calculations. The numerical results show that the TADHA molecule exhibits excellent negative differential conductance (NDC) behavior at lower bias regime as probed experimentally. The NDC behavior of TADHA molecule originates from the Stark effect of the applied bias voltage, by which the highest occupied molecular orbital (HOMO) and the HOMO-1 are pulled apart and become localized. The NDC behavior of TADHA molecular system is tunable by changing the electrode distance. Shortening the electrode separation can enhance the NDC effect which is attributed to the possible increase of coupling between the two branches of TADHA molecule. Project supported by the National Natural Science Foundation of China (Grant Nos. 11374195 and 11405098) and the Natural Science Foundation of Shandong Province, China (Grant No. ZR2013FM006).

  19. Hilar GABAergic Interneuron Activity Controls Spatial Learning and Memory Retrieval

    PubMed Central

    Andrews-Zwilling, Yaisa; Gillespie, Anna K.; Kravitz, Alexxai V.; Nelson, Alexandra B.; Devidze, Nino; Lo, Iris; Yoon, Seo Yeon; Bien-Ly, Nga; Ring, Karen; Zwilling, Daniel; Potter, Gregory B.; Rubenstein, John L. R.; Kreitzer, Anatol C.; Huang, Yadong

    2012-01-01

    Background Although extensive research has demonstrated the importance of excitatory granule neurons in the dentate gyrus of the hippocampus in normal learning and memory and in the pathogenesis of amnesia in Alzheimer's disease (AD), the role of hilar GABAergic inhibitory interneurons, which control the granule neuron activity, remains unclear. Methodology and Principal Findings We explored the function of hilar GABAergic interneurons in spatial learning and memory by inhibiting their activity through Cre-dependent viral expression of enhanced halorhodopsin (eNpHR3.0)—a light-driven chloride pump. Hilar GABAergic interneuron-specific expression of eNpHR3.0 was achieved by bilaterally injecting adeno-associated virus containing a double-floxed inverted open-reading frame encoding eNpHR3.0 into the hilus of the dentate gyrus of mice expressing Cre recombinase under the control of an enhancer specific for GABAergic interneurons. In vitro and in vivo illumination with a yellow laser elicited inhibition of hilar GABAergic interneurons and consequent activation of dentate granule neurons, without affecting pyramidal neurons in the CA3 and CA1 regions of the hippocampus. We found that optogenetic inhibition of hilar GABAergic interneuron activity impaired spatial learning and memory retrieval, without affecting memory retention, as determined in the Morris water maze test. Importantly, optogenetic inhibition of hilar GABAergic interneuron activity did not alter short-term working memory, motor coordination, or exploratory activity. Conclusions and Significance Our findings establish a critical role for hilar GABAergic interneuron activity in controlling spatial learning and memory retrieval and provide evidence for the potential contribution of GABAergic interneuron impairment to the pathogenesis of amnesia in AD. PMID:22792368

  20. Closed-Loop Control of Vortex Formation in Separated Flows

    NASA Technical Reports Server (NTRS)

    Colonius, Tim; Joe, Won Tae; MacMynowski, Doug; Rowley, Clancy; Taira, Sam; Ahuja, Sunil

    2010-01-01

    In order to phase lock the flow at the desired shedding cycle, particularly at Phi,best, We designed a feedback compensator. (Even though the open-loop forcing at Wf below Wn can lead to phase-locked limit cycles with a high average lift,) This feedback controller resulted in the phase-locked limit cycles that the open-loop control could not achieve for alpha=30 and 40 Particularly for alpha=40, the feedback was able to stabilize the limit cycle that was not stable with any of the open-loop periodic forcing. This results in stable phase-locked limit cycles for a larger range of forcing frequencies than the open-loop control. Also, it was shown that the feedback achieved the high-lift unsteady flow states that open-loop control could not sustain even after the states have been achieved for a long period of time.

  1. Impulsive spatial control of invading pests by generalist predators.

    PubMed

    Aniţa, Sebastian; Casas, Jérôme; Suppo, Christelle

    2014-09-01

    We model the conditions for pest eradication in a reaction-diffusion system made of a prey and a generalist predator through spatial impulsive control within a bounded domain. The motivating example is the control of the invasive horse chestnut leafminer moth through the yearly destruction of leaves in autumn, in which both the pest and its parasitoids overwinter. The model is made of two integro-partial differential equations, the integral portion describing the within-year immigration from the whole domain. The problem of pest eradication is strongly related to some appropriate eigenvalue problems. Basic properties of the principal eigenvalues of these problems are derived by using of Krein-Rutman's theorem and of comparison results for parabolic equations with non-local terms. Spatial control of the pest can be achieved, if one of these principal eigenvalues is large enough, at an exponential rate. This is true without and with parasitoids, the latter case being of course more rapid. We discuss the possible implementation of these results to the leafminer invasion problem and discuss complementary methods. © The Authors 2013. Published by Oxford University Press on behalf of the Institute of Mathematics and its Applications. All rights reserved.

  2. A Novel Approach to Adaptive Flow Separation Control

    DTIC Science & Technology

    2016-09-03

    net prediction signal (dotted curve) to adjust to match the measured signal (solid curve) even when the flow conditions change. SBMPC is then...A second series of PIV measurements of the same duration was collected to characterize the controlled flow . Contours of streamwise velocity V_x are...SECURITY CLASSIFICATION OF: Due to their practical import, flow control problems have attracted increasing attention. This research specifically

  3. Custom-tailored spatial mode sorting by controlled random scattering

    NASA Astrophysics Data System (ADS)

    Fickler, Robert; Ginoya, Manit; Boyd, Robert W.

    2017-04-01

    The need to increase data transfer rates constitutes a key challenge in modern information-driven societies. Taking advantage of the transverse spatial modes of light to encode more information is a promising avenue for both classical and quantum photonics. However, to ease access to the encoded information, it is essential to be able to sort spatial modes into different output channels. Here, we introduce a way to customize the sorting of arbitrary spatial light modes. Our method relies on the high degree of control over random scattering processes by preshaping of the phase structure of the incident light. We demonstrate experimentally that various sets of modes, irrespective of their specific modal structure, can be transformed to a broad range of output channel arrangements. Thus, our method enables full access to all of the information encoded in the transverse structure of the field; for example, azimuthal and radial modes. We also demonstrate that coherence is retained in this complex mode transformation, which opens up applications in quantum and classical information science.

  4. Distraction and placebo: two separate routes to pain control.

    PubMed

    Buhle, Jason T; Stevens, Bradford L; Friedman, Jonathan J; Wager, Tor D

    2012-03-01

    An explosion of recent research has studied whether placebo treatments influence health-related outcomes and their biological markers, but almost no research has examined the psychological processes required for placebo effects to occur. This study tested whether placebo treatment and cognitive distraction reduce pain through shared or independent processes. We tested the joint effects of performance of an executive working memory task and placebo treatment on thermal pain perception. An interactive effect of these two manipulations would constitute evidence for shared mechanisms, whereas additive effects would imply separate mechanisms. Participants (N = 33) reported reduced pain both when they performed the working memory task and when they received the placebo treatment, but the reductions were additive, a result indicating that the executive demands of the working memory task did not interfere with placebo analgesia. Furthermore, placebo analgesia did not impair task performance. Together, these data suggest that placebo analgesia does not depend on active redirection of attention and that expectancy and distraction can be combined to maximize pain relief.

  5. Evidence for two spatially separated UV continuum emitting regions in the Cloverleaf broad absorption line quasar

    NASA Astrophysics Data System (ADS)

    Sluse, D.; Hutsemékers, D.; Anguita, T.; Braibant, L.; Riaud, P.

    2015-10-01

    Testing the standard Shakura-Sunyaev model of accretion is a challenging task because the central region of quasars where accretion takes place is unresolved with telescopes. The analysis of microlensing in gravitationally lensed quasars is one of the few techniques that can test this model, yielding to the measurement of the size and of temperature profile of the accretion disc. We present spectroscopic observations of the gravitationally lensed broad absorption line quasar H1413+117, which reveal partial microlensing of the continuum emission that appears to originate from two separated regions: a microlensed region, corresponding the compact accretion disc; and a non-microlensed region, more extended and contributing to at least 30% of the total UV-continuum flux. Because this extended continuum is occulted by the broad absorption line clouds, it is not associated with the host galaxy, but rather with light scattered in the neighbourhood of the central engine. We measure the amplitude of microlensing of the compact continuum over the rest-frame wavelength range 1000-7000 Å. Following a Bayesian scheme, we confront our measurements to microlensing simulations of an accretion disc with a temperature varying as T ∝ R-1/ν. We find a most likely source half-light radius of R1/2 = 0.61 × 1016cm (i.e., 0.002 pc) at 0.18 μm, and a most-likely index of ν = 0.4. The standard disc (ν = 4/3) model is not ruled out by our data, and is found within the 95% confidence interval associated with our measurements. We demonstrate that, for H1413+117, the existence of an extended continuum in addition to the disc emission only has a small impact on the inferred disc parameters, and is unlikely to solve the tension between the microlensing source size and standard disc sizes, as previously reported in the literature. Based on observations made with ESO Telescopes at the Paranal Observatory (Chile). ESO program ID: 386.B-0337.Appendices A and B are available in electronic form

  6. Pilot and Controller Evaluations of Separation Function Allocation in Air Traffic Management

    NASA Technical Reports Server (NTRS)

    Wing, David; Prevot, Thomas; Morey, Susan; Lewis, Timothy; Martin, Lynne; Johnson, Sally; Cabrall, Christopher; Como, Sean; Homola, Jeffrey; Sheth-Chandra, Manasi; hide

    2013-01-01

    Two human-in-the-loop simulation experiments were conducted in coordinated fashion to investigate the allocation of separation assurance functions between ground and air and between humans and automation. The experiments modeled a mixed-operations concept in which aircraft receiving ground-based separation services shared the airspace with aircraft providing their own separation service (i.e., self-separation). Ground-based separation was provided by air traffic controllers without automation tools, with tools, or by ground-based automation with controllers in a managing role. Airborne self-separation was provided by airline pilots using self-separation automation enabled by airborne surveillance technology. The two experiments, one pilot-focused and the other controller-focused, addressed selected key issues of mixed operations, assuming the starting point of current-day operations and modeling an emergence of NextGen technologies and procedures. In the controller-focused experiment, the impact of mixed operations on controller performance was assessed at four stages of NextGen implementation. In the pilot-focused experiment, the limits to which pilots with automation tools could take full responsibility for separation from ground-controlled aircraft were tested. Results indicate that the presence of self-separating aircraft had little impact on the controllers' ability to provide separation services for ground-controlled aircraft. Overall performance was best in the most automated environment in which all aircraft were data communications equipped, ground-based separation was highly automated, and self-separating aircraft had access to trajectory intent information for all aircraft. In this environment, safe, efficient, and highly acceptable operations could be achieved for twice today's peak airspace throughput. In less automated environments, reduced trajectory intent exchange and manual air traffic control limited the safely achievable airspace throughput and

  7. A spatial operator algebra for manipulator modeling and control

    NASA Technical Reports Server (NTRS)

    Rodriguez, G.; Kreutz, Kenneth; Jain, Abhinandan

    1989-01-01

    A recently developed spatial operator algebra, useful for modeling, control, and trajectory design of manipulators is discussed. The elements of this algebra are linear operators whose domain and range spaces consist of forces, moments, velocities, and accelerations. The effect of these operators is equivalent to a spatial recursion along the span of a manipulator. Inversion of operators can be efficiently obtained via techniques of recursive filtering and smoothing. The operator algebra provides a high level framework for describing the dynamic and kinematic behavior of a manipulator and control and trajectory design algorithms. The interpretation of expressions within the algebraic framework leads to enhanced conceptual and physical understanding of manipulator dynamics and kinematics. Furthermore, implementable recursive algorithms can be immediately derived from the abstract operator expressions by inspection. Thus, the transition from an abstract problem formulation and solution to the detailed mechanizaton of specific algorithms is greatly simplified. The analytical formulation of the operator algebra, as well as its implementation in the Ada programming language are discussed.

  8. A Belief-Based Model of Air Traffic Controllers Performing Separation Assurance

    NASA Technical Reports Server (NTRS)

    Landry, S.J.

    2009-01-01

    A model of an air traffic controller performing a separation assurance task was produced. The model was designed to be simple to use and deploy in a simulator, but still provide realistic behavior. The model is based upon an evaluation of the safety function of the controller for separation assurance, and utilizes fast and frugal heuristics and belief networks to establish a knowledge set for the controller model. Based on this knowledge set, the controller acts to keep aircraft separated. Validation results are provided to demonstrate the model s performance.

  9. Control of low-speed turbulent separated flow using jet vortex generators

    NASA Technical Reports Server (NTRS)

    Selby, G. V.; Lin, J. C.; Howard, F. G.

    1992-01-01

    A parametric study has been performed with jet vortex generators to determine their effectiveness in controlling flow separation associated with low-speed turbulent flow over a two-dimensional rearward-facing ramp. Results indicate that flow-separation control can be accomplished, with the level of control achieved being a function of jet speed, jet orientation (with respect to the free-stream direction, and jet location (distance from the separation region in the free-stream direction). Compared to slot blowing, jet vortex generators can provide an equivalent level of flow control over a larger spanwise region (for constant jet flow area and speed).

  10. A Belief-Based Model of Air Traffic Controllers Performing Separation Assurance

    NASA Technical Reports Server (NTRS)

    Landry, S.J.

    2009-01-01

    A model of an air traffic controller performing a separation assurance task was produced. The model was designed to be simple to use and deploy in a simulator, but still provide realistic behavior. The model is based upon an evaluation of the safety function of the controller for separation assurance, and utilizes fast and frugal heuristics and belief networks to establish a knowledge set for the controller model. Based on this knowledge set, the controller acts to keep aircraft separated. Validation results are provided to demonstrate the model s performance.

  11. A fuzzy controlled three-phase centrifuge for waste separation

    SciTech Connect

    Parkinson, W.J.; Smith, R.E.; Miller, N.

    1998-02-01

    The three-phase centrifuge technology discussed in this paper was developed by Neal Miller, president of Centech, Inc. The three-phase centrifuge is an excellent device for cleaning up oil field and refinery wastes which are typically composed of hydrocarbons, water, and solids. The technology is unique. It turns the waste into salable oil, reusable water, and landfill-able solids. No secondary waste is produced. The problem is that only the inventor can set up and run the equipment well enough to provide an optimal cleanup. Demand for this device has far exceeded a one man operation. There is now a need for several centrifuges to be operated at different locations at the same time. This has produced a demand for an intelligent control system, one that could replace a highly skilled operator, or at least supplement the skills of a less experienced operator. The control problem is ideally suited to fuzzy logic, since the centrifuge is a highly complicated machine operated entirely by the skill and experience of the operator. A fuzzy control system was designed for and used with the centrifuge.

  12. Large Spatial and Temporal Separations of Cause and Effect in Policy Making - Dealing with Non-linear Effects

    NASA Astrophysics Data System (ADS)

    McCaskill, John

    There can be large spatial and temporal separation of cause and effect in policy making. Determining the correct linkage between policy inputs and outcomes can be highly impractical in the complex environments faced by policy makers. In attempting to see and plan for the probable outcomes, standard linear models often overlook, ignore, or are unable to predict catastrophic events that only seem improbable due to the issue of multiple feedback loops. There are several issues with the makeup and behaviors of complex systems that explain the difficulty many mathematical models (factor analysis/structural equation modeling) have in dealing with non-linear effects in complex systems. This chapter highlights those problem issues and offers insights to the usefulness of ABM in dealing with non-linear effects in complex policy making environments.

  13. Competition between links in ``producer-consumer'' trophic chains in an aquatic closed system with spatially separated components

    NASA Astrophysics Data System (ADS)

    Pisman, T. I.; Pechurkin, N. S.; Somova, L. A.

    The work analyzes functioning of a "producer-consumer" closed aquatic system with spatially separated links, where each component consisted of two species. Producers in the system were the microalgae of Chlorella vulgaris and Scenedesmus sp., consumers - Paramecium caudatum infusoria and Brachionus sp. rotifers. In the experiment the competing predators were consuming on a mixed culture of algae, and the competition of algae was studied under nitrogen limitation. Under these conditions competitiveness of Scenedesmus was higher than that of Chlorella vulgaris. Metabolism products of Scenedesmus algae have been found to have negative effect on reproduction of Paramecium caudatum protozoa. Predator population dynamics in the "consumer" link demonstrated that the rotifers that consume two algal species are more competitive compared to protozoa feeding on chlorella only.

  14. Competition between links in "producer-consumer" trophic chains in an aquatic closed system with spatially separated components.

    PubMed

    Pisman, T I; Pechurkin, N S; Somova, L A

    2001-01-01

    The work analyzes functioning of a "producer-consumer" closed aquatic system with spatially separated links, where each component consisted of two species. Producers in the system were the microalgae of Chlorella vulgaris and Scenedesmus sp., consumers--Paramecium caudatum infusoria and Brachionus sp. rotifers. In the experiment the competing predators were consuming on a mixed culture of algae, and the competition of algae was studied under nitrogen limitation. Under these conditions competitiveness of Scenedesmus was higher than that of Chlorella vulgaris. Metabolism products of Scenedesmus algae have been found to have negative effect on reproduction of Paramecium caudatum protozoa. Predator population dynamics in the "consumer" link demonstrated that the rotifers that consume two algal species are more competitive compared to protozoa feeding on chlorella only. Grant numbers: N99-04-96017, N25. c 2001. COSPAR. Published by Elsevier Science Ltd. All rights reserved.

  15. Phenylamine-Functionalized rGO/TiO2 Photocatalysts: Spatially Separated Adsorption Sites and Tunable Photocatalytic Selectivity.

    PubMed

    Yu, Huogen; Xiao, Pian; Tian, Jing; Wang, Fazhou; Yu, Jiaguo

    2016-11-02

    The preferential adsorption of targeted contaminants on a photocatalyst surface is highly required to realize its photocatalytic selective decomposition in a complex system. To realize the tunable preferential adsorption, altering the surface charge or polarity property of photocatalysts has widely been reported. However, it is quite difficult for a modified photocatalyst to realize the simultaneously preferential adsorption for both cationic and anionic dyes. In this study, to realize the selective adsorption for both cationic and anionic dyes on a photocatalyst surface, the negative reduced graphene oxide (rGO) nanosheets and positive phenylamine (PhNH2) molecules are successfully loaded on the TiO2 surface (PhNH2/rGO-TiO2) with spatially separated adsorption sites, where the negative rGO and positive PhNH2 molecules work as the preferential adsorption sites for cationic and anionic dyes, respectively. It was interesting to find that although all the TiO2 samples (including the naked TiO2, PhNH2/TiO2, rGO-TiO2, and PhNH2/rGO-TiO2) clearly showed a better adsorption performance for cationic dyes than anionic dyes, only the PhNH2/rGO-TiO2 with spatially separated adsorption-active sites exhibited an opposite photocatalytic selectivity, namely, the naked TiO2, PhNH2/TiO2, and rGO-TiO2 showed a preferential decomposition for cationic dyes, while the resultant PhNH2/rGO-TiO2 exhibited an excellently selective decomposition for anionic dyes. In addition, the resultant PhNH2/rGO-TiO2 photocatalyst not only realizes the tunable photocatalytic selectivity but also can completely and sequentially decompose the opposite cationic and anionic dyes.

  16. Dynamics and Control of Separated Optics Space Telescopes

    NASA Astrophysics Data System (ADS)

    Mettler, E.; Breckenridge, W. G.; Quadrelli, B. M.

    spacecraft composed of 6 bodies: Primary Mirror Membrane, Free Flying Mirror, Focal Plane Assembly, with secondary &tertiary stages, Primary Figure Sensor, Scanning Electron Beam for shape adjustment of PMM, and Orbiting Sunshade. The refractive telescope under consideration represents an advanced concept currently being studied at JPL. Applications of such concept are envisioned in the areas of astrophysical imaging in optical wavelengths, as well as precision Earth observing imaging. The paper describes the dynamics model in the GEO environment, the formation flying estimator model, the control design, the sensor and actuator models, and the performance analysis of the system during a retargeting maneuver under proportional thruster control at the micro-Newton level. We define an orbiting gossamer telescope formation as an ensemble of orbiting optical modules acting as one virtual structure telescope system. After the formation is in place, one may identify what is known as the virtual truss, i.e. the connection between the elements of the formation which provides structural rigidity on account of the information flow between them. The dynamics model takes into account the orbital and spacecraft dynamics of each vehicle. The formation estimator provides estimates of the inter-spacecraft relative position and velocity vectors, given the measurements of a radio-frequency metrology system known as Autonomous Formation Flying sensor. The spacecraft state measurements are provided by models of star trackers, gyros, and accelerometers, together with their bias and noise models. The spacecraft actuation system consists of proportional micro-Newton level field-emission thrusters for precision station-keeping, as well as Newton level thrusters used for retargeting the entire formation. The control system design consists of a proportional-derivative feedback plus acceleration feedforward. This ensures that modeling errors are compensated appropriately, and that the

  17. Quantification of Holocene Asian monsoon rainfall from spatially separated cave records

    NASA Astrophysics Data System (ADS)

    Hu, Chaoyong; Henderson, Gideon M.; Huang, Junhua; Xie, Shucheng; Sun, Ying; Johnson, Kathleen R.

    2008-02-01

    A reconstruction of Holocene rainfall is presented for southwest China — an area prone to drought and flooding due to variability in the East Asian monsoon. The reconstruction is derived by comparing a new high-resolution stalagmite δ18O record with an existing record from the same moisture transport pathway. The new record is from Heshang Cave (30°27'N, 110°25'E; 294 m) and shows no sign of kinetic or evaporative effects so can be reliably interpreted as a record of local rainfall composition and temperature. Heshang lies 600 km downwind from Dongge Cave which has a published high-resolution δ18O record (Wang, Y.J., Cheng, H., Edwards, R.L., He, Y.Q., Kong, X.G., An, Z.S., Wu, J.Y., Kelly, M.J., Dykoski, C.A., Li, X.D., 2005. The Holocene Asian monsoon: links to solar changes and North Atlantic climate. Science 308, 854-857). By differencing co-eval δ18O values for the two caves, secondary controls on δ18O (e.g. moisture source, moisture transport, non-local rainfall, temperature) are circumvented and the resulting Δ δ18O signal is controlled directly by the amount of rain falling between the two sites. This is confirmed by comparison with rainfall data from the instrumental record, which also allows a calibration of the Δ δ18O proxy. The calibrated Δ δ18O record provides a quantitative history of rainfall in southwest China which demonstrates that rainfall was 8% higher than today during the Holocene climatic optimum (≈ 6 ka), but only 3% higher during the early Holocene. Significant multi-centennial variability also occurred, with notable dry periods at 8.2 ka, 4.8-4.1 ka, 3.7-3.1 ka, 1.4-1.0 ka and during the Little Ice Age. This Holocene rainfall record provides a good target with which to test climate models. The approach used here, of combining stalagmite records from more than one location, will also allow quantification of rainfall patterns for past times in other regions.

  18. Unexpected observation of spatially separated Kondo scattering and ferromagnetism in Ta alloyed anatase TiO2 thin films

    NASA Astrophysics Data System (ADS)

    Sarkar, T. P.; Gopinadhan, K.; Motapothula, M.; Saha, S.; Huang, Z.; Dhar, S.; Patra, A.; Lu, W. M.; Telesio, F.; Pallecchi, I.; Ariando; Marré, D.; Venkatesan, T.

    2015-08-01

    We report the observation of spatially separated Kondo scattering and ferromagnetism in anatase Ta0.06Ti0.94O2 thin films as a function of thickness (10-200 nm). The Kondo behavior observed in thicker films is suppressed on decreasing thickness and vanishes below ~25 nm. In 200 nm film, transport data could be fitted to a renormalization group theory for Kondo scattering though the carrier density in this system is lower by two orders of magnitude, the magnetic entity concentration is larger by a similar magnitude and there is strong electronic correlation compared to a conventional system such as Cu with magnetic impurities. However, ferromagnetism is observed at all thicknesses with magnetic moment per unit thickness decreasing beyond 10 nm film thickness. The simultaneous presence of Kondo and ferromagnetism is explained by the spatial variation of defects from the interface to surface which results in a dominantly ferromagnetic region closer to substrate-film interface while the Kondo scattering is dominant near the surface and decreasing towards the interface. This material system enables us to study the effect of neighboring presence of two competing magnetic phenomena and the possibility for tuning them.

  19. Prokaryotes in Subsoil—Evidence for a Strong Spatial Separation of Different Phyla by Analysing Co-occurrence Networks

    PubMed Central

    Uksa, Marie; Schloter, Michael; Endesfelder, David; Kublik, Susanne; Engel, Marion; Kautz, Timo; Köpke, Ulrich; Fischer, Doreen

    2015-01-01

    Microbial communities in soil provide a wide range of ecosystem services. On the small scale, nutrient rich hotspots in soil developed from the activities of animals or plants are important drivers for the composition of microbial communities and their functional patterns. However, in subsoil, the spatial heterogeneity of microbes with differing lifestyles has been rarely considered so far. In this study, the phylogenetic composition of the bacterial and archaeal microbiome based on 16S rRNA gene pyrosequencing was investigated in the soil compartments bulk soil, drilosphere, and rhizosphere in top- and in the subsoil of an agricultural field. With co-occurrence network analysis, the spatial separation of typically oligotrophic and copiotrophic microbes was assessed. Four bacterial clusters were identified and attributed to bulk topsoil, bulk subsoil, drilosphere, and rhizosphere. The bacterial phyla Proteobacteria and Bacteroidetes, representing mostly copiotrophic bacteria, were affiliated mainly to the rhizosphere and drilosphere—both in topsoil and subsoil. Acidobacteria, Actinobacteria, Gemmatimonadetes, Planctomycetes, and Verrucomicrobia, bacterial phyla which harbor many oligotrophic bacteria, were the most abundant groups in bulk subsoil. The bacterial core microbiome in this soil was estimated to cover 7.6% of the bacterial sequencing reads including both oligotrophic and copiotrophic bacteria. In contrast the archaeal core microbiome includes 56% of the overall archaeal diversity. Thus, the spatial variability of nutrient quality and quantity strongly shapes the bacterial community composition and their interaction in subsoil, whereas archaea build a stable backbone of the soil prokaryotes due to their low variability in the different soil compartments. PMID:26635741

  20. Low-coherence terahertz tomography based on spatially separated counterpropagating beams with allowance for probe radiation absorption in the medium

    SciTech Connect

    Mandrosov, V I

    2015-10-31

    This paper analyses low-coherence tomography of absorbing media with the use of spatially separated counterpropagating object and reference beams. A probe radiation source based on a broadband terahertz (THz) generator that emits sufficiently intense THz waves in the spectral range 90 – 350 μm and a prism spectroscope that separates out eight narrow intervals from this range are proposed for implementing this method. This allows media of interest to be examined by low-coherence tomography with counterpropagating beams in each interval. It is shown that, according to the Rayleigh criterion, the method is capable of resolving inhomogeneities with a size near one quarter of the coherence length of the probe radiation. In addition, the proposed tomograph configuration allows one to determine the average surface asperity slope and the refractive index and absorption coefficient of inhomogeneities 180 to 700 mm in size, and obtain spectra of such inhomogeneities in order to determine their chemical composition. (laser applications and other topics in quantum electronics)

  1. Dendrites of dentate gyrus granule cells contribute to pattern separation by controlling sparsity

    PubMed Central

    Chavlis, Spyridon; Petrantonakis, Panagiotis C.

    2016-01-01

    ABSTRACT The hippocampus plays a key role in pattern separation, the process of transforming similar incoming information to highly dissimilar, nonverlapping representations. Sparse firing granule cells (GCs) in the dentate gyrus (DG) have been proposed to undertake this computation, but little is known about which of their properties influence pattern separation. Dendritic atrophy has been reported in diseases associated with pattern separation deficits, suggesting a possible role for dendrites in this phenomenon. To investigate whether and how the dendrites of GCs contribute to pattern separation, we build a simplified, biologically relevant, computational model of the DG. Our model suggests that the presence of GC dendrites is associated with high pattern separation efficiency while their atrophy leads to increased excitability and performance impairments. These impairments can be rescued by restoring GC sparsity to control levels through various manipulations. We predict that dendrites contribute to pattern separation as a mechanism for controlling sparsity. © 2016 The Authors Hippocampus Published by Wiley Periodicals, Inc. PMID:27784124

  2. Excimer laser ablation for spatially controlled protein patterns

    NASA Astrophysics Data System (ADS)

    Thissen, Helmut; Hayes, Jason P.; Kingshott, Peter; Johnson, Graham; Harvey, Erol C.; Griesser, Hans J.

    2001-11-01

    Two-dimensional control over the location of proteins on surfaces is desired for a number of applications including diagnostic tests and tissue engineered medical devices. Many of these applications require patterns of specific proteins that allow subsequent two-dimensionally controlled cell attachment. The ideal technique would allow the deposition of specific protein patterns in areas where cell attachment is required, with complete prevention of unspecific protein adsorption in areas where cells are not supposed to attach. In our study, collagen I was used as an example for an extracellular matrix protein known to support the attachment of bovine corneal epithelial cells. An allylamine plasma polymer was deposited on a silicon wafer substrate, followed by grafting of poly(ethylene oxide). Two-dimensional control over the surface chemistry was achieved using a 248 nm excimer laser. Results obtained by XPS and AFM show that the combination of extremely low-fouling surfaces with excimer laser ablation can be used effectively for the production of spatially controlled protein patterns with a resolution of less than 1 micrometers . Furthermore, it was shown that bovine corneal epithelial cell attachment followed exactly the created protein patterns. The presented method is an effective tool for a number of in vitro and in vivo applications.

  3. An approach to the synthesis of separate surface automatic flight control systems.

    NASA Technical Reports Server (NTRS)

    Roskam, J.; Henry, S.

    1973-01-01

    A method is presented for the analysis of separate surface automatic flight control systems. The feasibility of such systems is demonstrated by the analysis of an example system, a separate surface wing-leveler for a Cessna 172. This example system employs a separate surface aileron with 15% of the basic airplane roll control power. A 90% reduction in bank-angle gust response can be obtained when compared with the basic airplane. The system does not feed back to the pilot's wheel. When failed (even hardover) the pilot retains more than adequate control of the airplane.

  4. Tsetse Fly Control in Kenya's Spatially and Temporally Dynamic Control Reservoirs: A Cost Analysis

    PubMed Central

    McCord, Paul F.; Messina, Joseph P.; Campbell, David J.; Grady, Sue C.

    2011-01-01

    Human African trypanosomiasis (HAT) and animal African trypanosomiasis (AAT) are significant health concerns throughout much of sub-Saharan Africa. Funding for tsetse fly control operations has decreased since the 1970s, which has in turn limited the success of campaigns to control the disease vector. To maximize the effectiveness of the limited financial resources available for tsetse control, this study develops and analyzes spatially and temporally dynamic tsetse distribution maps of Glossina subgenus Morsitans populations in Kenya from January 2002 to December 2010, produced using the Tsetse Ecological Distribution Model. These species distribution maps reveal seasonal variations in fly distributions. Such variations allow for the identification of “control reservoirs” where fly distributions are spatially constrained by fluctuations in suitable habitat and tsetse population characteristics. Following identification of the control reservoirs, a tsetse management operation is simulated in the control reservoirs using capital and labor control inputs from previous studies. Finally, a cost analysis, following specific economic guidelines from existing tsetse control analyses, is conducted to calculate the total cost of a nationwide control campaign of the reservoirs compared to the cost of a nationwide campaign conducted at the maximum spatial extent of the fly distributions from January 2002 to December 2010. The total cost of tsetse management within the reservoirs sums to $14,212,647, while the nationwide campaign at the maximum spatial extent amounts to $33,721,516. This savings of $19,508,869 represents the importance of identifying seasonally dynamic control reservoirs when conducting a tsetse management campaign, and, in the process, offers an economical means of fly control and disease management for future program planning. PMID:22581989

  5. Spatial Reorientation of Sensorimotor Balance Control in Altered Gravity

    NASA Technical Reports Server (NTRS)

    Paloski, W. H.; Black, F. L.; Kaufman, G. D.; Reschke, M. F.; Wood, S. J.

    2007-01-01

    Sensorimotor coordination of body segments following space flight are more pronounced after landing when the head is actively tilted with respect to the trunk. This suggests that central vestibular processing shifts from a gravitational frame of reference to a head frame of reference in microgravity. A major effect of such changes is a significant postural instability documented by standard head-erect Sensory Organization Tests. Decrements in functional performance may still be underestimated when head and gravity reference frames remained aligned. The purpose of this study was to examine adaptive changes in spatial processing for balance control following space flight by incorporating static and dynamic tilts that dissociate head and gravity reference frames. A second aim of this study was to examine the feasibility of altering the re-adaptation process following space flight by providing discordant visual-vestibular-somatosensory stimuli using short-radius pitch centrifugation.

  6. Control and reduction of unsteady pressure loads in separated shock wave turbulent boundary layer interaction

    NASA Technical Reports Server (NTRS)

    Dolling, David S.; Barter, John W.

    1995-01-01

    The focus was on developing means of controlling and reducing unsteady pressure loads in separated shock wave turbulent boundary layer interactions. Section 1 describes how vortex generators can be used to effectively reduce loads in compression ramp interaction, while Section 2 focuses on the effects of 'boundary-layer separators' on the same interaction.

  7. Controls of Soil Spatial Variability in a Dry Tropical Forest

    PubMed Central

    Pulla, Sandeep; Riotte, Jean; Suresh, H. S.; Dattaraja, H. S.; Sukumar, Raman

    2016-01-01

    We examined the roles of lithology, topography, vegetation and fire in generating local-scale (<1 km2) soil spatial variability in a seasonally dry tropical forest (SDTF) in southern India. For this, we mapped soil (available nutrients, Al, total C, pH, moisture and texture in the top 10cm), rock outcrops, topography, all native woody plants ≥1 cm diameter at breast height (DBH), and spatial variation in fire frequency (times burnt during the 17 years preceding soil sampling) in a permanent 50-ha plot. Unlike classic catenas, lower elevation soils had lesser moisture, plant-available Ca, Cu, Mn, Mg, Zn, B, clay and total C. The distribution of plant-available Ca, Cu, Mn and Mg appeared to largely be determined by the whole-rock chemical composition differences between amphibolites and hornblende-biotite gneisses. Amphibolites were associated with summit positions, while gneisses dominated lower elevations, an observation that concurs with other studies in the region which suggest that hillslope-scale topography has been shaped by differential weathering of lithologies. Neither NO3−-N nor NH4+-N was explained by the basal area of trees belonging to Fabaceae, a family associated with N-fixing species, and no long-term effects of fire on soil parameters were detected. Local-scale lithological variation is an important first-order control over soil variability at the hillslope scale in this SDTF, by both direct influence on nutrient stocks and indirect influence via control of local relief. PMID:27100088

  8. Controlled release of dry reagents in porous media for tunable temporal and spatial distribution upon rehydration

    PubMed Central

    Le, Huy Q.; Fu, Elain; Yager, Paul

    2012-01-01

    Novel methods are demonstrated that enable controlled spatial and temporal rehydration of dried reagents in a porous matrix. These methods can be used in paper-based microfluidic assays to define reagent concentrations over time at zones downstream for improved performance, and can reduce costs by simplifying the manufacturing process with the use of a single porous substrate. First, the creation of uniform reagent pulses from patterned arrays of dried reagent is demonstrated. Second, reagents are stored dry in separate regions of the porous matrix so that they can be combined upon rehydration for immediate use in the device. Third, reagents are reconstituted sequentially from dry storage depots with tunable delivery times. Fourth, the total time for dissolution is varied to achieve a range of reagent delivery times to a downstream region. Finally, the utility of these control methods is demonstrated in the context of real-time reagent rehydration and mixing on a porous device. PMID:22960691

  9. Multiloop control of a pilot-scale membrane system for gas separations

    SciTech Connect

    Henson, M.A.; Koros, W.J. . Dept. of Chemical Engineering)

    1994-08-01

    Membrane systems are preferred for many separations due to their low energy consumption, reduced environmental impact, cost effectiveness at low gas volumes, low maintenance costs, space and weight efficiency, and ease of operation. A multiloop control system for a pilot-scale membrane separation process is designed and evaluated. The process employs hollow fiber membrane modules and is representative of air separation systems in industry. The decentralized control system originally consists of five PID controllers which regulate feed flow rate and pressure, permeate pressure, suction pressure, and module temperature. This configuration yields poor performance as a result of interactions between the feed flow rate and feed pressure controllers. By disabling the flow rate controller and proper tuning of the remaining control loops, satisfactory control is achieved during 4 days of continuous operation.

  10. Spatial Integration under Contextual Control in a Virtual Environment

    ERIC Educational Resources Information Center

    Molet, Mikael; Gambet, Boris; Bugallo, Mehdi; Miller, Ralph R.

    2012-01-01

    The role of context was examined in the selection and integration of independently learned spatial relationships. Using a dynamic 3D virtual environment, participants learned one spatial relationship between landmarks A and B which was established in one virtual context (e.g., A is left of B) and a different spatial relationship which was…

  11. Spatial Integration under Contextual Control in a Virtual Environment

    ERIC Educational Resources Information Center

    Molet, Mikael; Gambet, Boris; Bugallo, Mehdi; Miller, Ralph R.

    2012-01-01

    The role of context was examined in the selection and integration of independently learned spatial relationships. Using a dynamic 3D virtual environment, participants learned one spatial relationship between landmarks A and B which was established in one virtual context (e.g., A is left of B) and a different spatial relationship which was…

  12. A Regenerable VOC Control System (RVCS) for Characterizing Properties of Sorbents Used in Separation Technologies

    NASA Technical Reports Server (NTRS)

    Nolek, Sara D.; Monje, Oscar A.

    2010-01-01

    This slide presentation reviews the design, method of operation, and testing of a regenerable Volatile Organic Compound (VOC) control system that characterizes properties of sorbents used in separation technologies.

  13. Mineral separation and recycle in a Controlled Ecological Life Support System (CELSS)

    NASA Technical Reports Server (NTRS)

    Ballou, E. V.

    1982-01-01

    The background of the mineral nutrition needs of plants are examined along with the applicability of mineral control and separation to a controlled ecological life support system (CELSS). Steps that may be taken in a program to analytically define and experimentally test key mineral control concepts in the nutritional and waste processing loops of a CELSS are delineated.

  14. Investigation of several passive and active methods for turbulent flow separation control

    NASA Technical Reports Server (NTRS)

    Lin, J. C.; Howard, F. G.; Bushnell, D. M.; Selby, G. V.

    1990-01-01

    Relative performance of several passive and active methods for controlling two-dimensional turbulent separated flow associated with a curved backward-facing ramp were investigated at low speeds. Surface static pressure measurement and oil flow visualization results indicate that submerged vortex generators, vortex generator jets, elongated arches at +-alpha, and large-eddy breakup devices at +-alpha placed near the baseline separation location reduce flow separation and increase pressure recovery. Spanwise cylinders reduce flow separation but decrease pressure recovery downstream. Arches with alpha = 0 deg, Helmholtz resonators, and Viets' fluidic flappers examined so far have no significant effect in reducing separation. Wall cooling computation indicates that separation delay on a partially cooled ramp is nearly the same as on a fully-cooled ramp while minimizing the frictional drag increase associated with the wall cooling process.

  15. Controlling the Spatial Organization of Liquid Crystalline Nanoparticles by Composition of the Organic Grafting Layer.

    PubMed

    Wójcik, Michał M; Olesińska, Magdalena; Sawczyk, Michał; Mieczkowski, Józef; Górecka, Ewa

    2015-07-06

    Understanding how the spatial ordering of liquid crystalline nanoparticles can be controlled by different factors is of great importance in the further development of their photonic applications. In this paper, we report a new key parameter to control the mesogenic behavior of gold nanoparticles modified by rodlike thiols. An efficient method to control the spatial arrangement of hybrid nanoparticles in a condensed state is developed by changing the composition of the mesogenic grafting layer on the surface of the nanoparticles. The composition can be tuned by different conditions of the ligand exchange reaction. The thermal and optical behavior of the mesogenic and promesogenic ligands were investigated by using differential scanning calorimetry (DSC) and hot-stage polarized optical microscopy. The chemical structure of the synthesized hybrid nanoparticles was characterized by (1) H NMR spectroscopy, thermogravimetric analysis (TGA), XPS, and elemental analysis, whereas the superstructures were examined by small-angle X-ray diffraction (SAXSRD) analysis. Structural studies showed that the organic sublayer made of mesogenic ligands is denser with an increasing the average ligand number, thereby separating the nanoparticles in the liquid crystalline phases, which changes the parameters of these phases. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Predicting performance in manually controlled rendezvous and docking through spatial abilities

    NASA Astrophysics Data System (ADS)

    Wang, Chunhui; Tian, Yu; Chen, Shanguang; Tian, Zhiqiang; Jiang, Ting; Du, Feng

    2014-01-01

    Manually controlled rendezvous and docking (manual RVD) is a challenging space task for astronauts. This study aims to identify spatial abilities that are critical for accomplishing manual RVD. Based on task analysis, spatial abilities were deduced to be critical for accomplishing manual RVD. 15 Male participants performed manual RVD task simulations and spatial ability tests (the object-manipulation spatial ability and spatial orientation ability). Participants' performance in the test of visualization of viewpoints (which measures the spatial orientation ability) was found to be significantly correlated with their manual RVD performance, indicating that the spatial orientation ability in the sense of perspective taking is particularly important for accomplishing manual RVD.

  17. Closed Loop Active Flow Separation Detection and Control in a Multistage Compressor

    NASA Technical Reports Server (NTRS)

    Bright, Michelle M.; Culley, Dennis E.; Braunscheidel, Edward P.; Welch, Gerard E.

    2005-01-01

    Active closed loop flow control was successfully demonstrated on a full annulus of stator vanes in a low speed axial compressor. Two independent methods of detecting separated flow conditions on the vane suction surface were developed. The first technique detects changes in static pressure along the vane suction surface, while the second method monitors variation in the potential field of the downstream rotor. Both methods may feasibly be used in future engines employing embedded flow control technology. In response to the detection of separated conditions, injection along the suction surface of each vane was used. Injected mass flow on the suction surface of stator vanes is known to reduce separation and the resulting limitation on static pressure rise due to lowered diffusion in the vane passage. A control algorithm was developed which provided a proportional response of the injected mass flow to the degree of separation, thereby minimizing the performance penalty on the compressor system.

  18. Spatially controlled cell adhesion on three-dimensional substrates.

    PubMed

    Richter, Christine; Reinhardt, Martina; Giselbrecht, Stefan; Leisen, Daniel; Trouillet, Vanessa; Truckenmüller, Roman; Blau, Axel; Ziegler, Christiane; Welle, Alexander

    2010-10-01

    The microenvironment of cells in vivo is defined by spatiotemporal patterns of chemical and biophysical cues. Therefore, one important goal of tissue engineering is the generation of scaffolds with defined biofunctionalization in order to control processes like cell adhesion and differentiation. Mimicking extrinsic factors like integrin ligands presented by the extracellular matrix is one of the key elements to study cellular adhesion on biocompatible scaffolds. By using special thermoformable polymer films with anchored biomolecules micro structured scaffolds, e.g. curved and micro-patterned substrates, can be fabricated. Here, we present a novel strategy for the fabrication of micro-patterned scaffolds based on the "Substrate Modification and Replication by Thermoforming" (SMART) technology: The surface of a poly lactic acid membrane, having a low forming temperature of 60 degrees C and being initially very cell attractive, was coated with a photopatterned layer of poly(L-lysine) (PLL) and hyaluronic acid (VAHyal) to gain spatial control over cell adhesion. Subsequently, this modified polymer membrane was thermoformed to create an array of spherical microcavities with diameters of 300 microm for 3D cell culture. Human hepatoma cells (HepG2) and mouse fibroblasts (L929) were used to demonstrate guided cell adhesion. HepG2 cells adhered and aggregated exclusively within these cavities without attaching to the passivated surfaces between the cavities. Also L929 cells adhering very strongly on the pristine substrate polymer were effectively patterned by the cell repellent properties of the hyaluronic acid based hydrogel. This is the first time cell adhesion was controlled by patterned functionalization of a polymeric substrate with UV curable PLL-VAHyal in thermoformed 3D microstructures.

  19. Spatially controlled cell adhesion on three-dimensional substrates

    PubMed Central

    Richter, Christine; Reinhardt, Martina; Giselbrecht, Stefan; Leisen, Daniel; Trouillet, Vanessa; Truckenmüller, Roman; Blau, Axel; Ziegler, Christiane

    2010-01-01

    The microenvironment of cells in vivo is defined by spatiotemporal patterns of chemical and biophysical cues. Therefore, one important goal of tissue engineering is the generation of scaffolds with defined biofunctionalization in order to control processes like cell adhesion and differentiation. Mimicking extrinsic factors like integrin ligands presented by the extracellular matrix is one of the key elements to study cellular adhesion on biocompatible scaffolds. By using special thermoformable polymer films with anchored biomolecules micro structured scaffolds, e.g. curved and µ-patterned substrates, can be fabricated. Here, we present a novel strategy for the fabrication of µ-patterned scaffolds based on the “Substrate Modification and Replication by Thermoforming” (SMART) technology: The surface of a poly lactic acid membrane, having a low forming temperature of 60°C and being initially very cell attractive, was coated with a photopatterned layer of poly(L-lysine) (PLL) and hyaluronic acid (VAHyal) to gain spatial control over cell adhesion. Subsequently, this modified polymer membrane was thermoformed to create an array of spherical microcavities with diameters of 300 µm for 3D cell culture. Human hepatoma cells (HepG2) and mouse fibroblasts (L929) were used to demonstrate guided cell adhesion. HepG2 cells adhered and aggregated exclusively within these cavities without attaching to the passivated surfaces between the cavities. Also L929 cells adhering very strongly on the pristine substrate polymer were effectively patterned by the cell repellent properties of the hyaluronic acid based hydrogel. This is the first time cell adhesion was controlled by patterned functionalization of a polymeric substrate with UV curable PLL-VAHyal in thermoformed 3D microstructures. PMID:20480241

  20. Long-range coupling of electron-hole pairs in spatially separated organic donor-acceptor layers

    PubMed Central

    Nakanotani, Hajime; Furukawa, Taro; Morimoto, Kei; Adachi, Chihaya

    2016-01-01

    Understanding exciton behavior in organic semiconductor molecules is crucial for the development of organic semiconductor-based excitonic devices such as organic light-emitting diodes and organic solar cells, and the tightly bound electron-hole pair forming an exciton is normally assumed to be localized on an organic semiconducting molecule. We report the observation of long-range coupling of electron-hole pairs in spatially separated electron-donating and electron-accepting molecules across a 10-nanometers-thick spacer layer. We found that the exciton energy can be tuned over 100 megaelectron volts and the fraction of delayed fluorescence can be increased by adjusting the spacer-layer thickness. Furthermore, increasing the spacer-layer thickness produced an organic light-emitting diode with an electroluminescence efficiency nearly eight times higher than that of a device without a spacer layer. Our results demonstrate the first example of a long-range coupled charge-transfer state between electron-donating and electron-accepting molecules in a working device. PMID:26933691

  1. Spatial curvilinear path following control of underactuated AUV with multiple uncertainties.

    PubMed

    Miao, Jianming; Wang, Shaoping; Zhao, Zhiping; Li, Yuan; Tomovic, Mileta M

    2017-03-01

    This paper investigates the problem of spatial curvilinear path following control of underactuated autonomous underwater vehicles (AUVs) with multiple uncertainties. Firstly, in order to design the appropriate controller, path following error dynamics model is constructed in a moving Serret-Frenet frame, and the five degrees of freedom (DOFs) dynamic model with multiple uncertainties is established. Secondly, the proposed control law is separated into kinematic controller and dynamic controller via back-stepping technique. In the case of kinematic controller, to overcome the drawback of dependence on the accurate vehicle model that are present in a number of path following control strategies described in the literature, the unknown side-slip angular velocity and attack angular velocity are treated as uncertainties. Whereas in the case of dynamic controller, the model parameters perturbations, unknown external environmental disturbances and the nonlinear hydrodynamic damping terms are treated as lumped uncertainties. Both kinematic and dynamic uncertainties are estimated and compensated by designed reduced-order linear extended state observes (LESOs). Thirdly, feedback linearization (FL) based control law is implemented for the control model using the estimates generated by reduced-order LESOs. For handling the problem of computational complexity inherent in the conventional back-stepping method, nonlinear tracking differentiators (NTDs) are applied to construct derivatives of the virtual control commands. Finally, the closed loop stability for the overall system is established. Simulation and comparative analysis demonstrate that the proposed controller exhibits enhanced performance in the presence of internal parameter variations, external unknown disturbances, unmodeled nonlinear damping terms, and measurement noises.

  2. The Dynamics of Controlled Flow Separation within a Diverter Duct Diffuser

    NASA Astrophysics Data System (ADS)

    Peterson, C. J.; Vukasinovic, B.; Glezer, A.

    2016-11-01

    The evolution and receptivity to fluidic actuation of the flow separation within a rectangular, constant-width, diffuser that is branched off of a primary channel is investigated experimentally at speeds up to M = 0.4. The coupling between the diffuser's adverse pressure gradient and the internal separation that constricts nearly half of the flow passage through the duct is controlled using a spanwise array of fluidic actuators on the surface upstream of the diffuser's inlet plane. The dynamics of the separating surface vorticity layer in the absence and presence of actuation are investigated using high-speed particle image velocimetry combined with surface pressure measurements and total pressure distributions at the primary channel's exit plane. It is shown that the actuation significantly alters the incipient dynamics of the separating vorticity layer as the characteristic cross stream scales of the boundary layer upstream of separation and of the ensuing vorticity concentrations within the separated flow increase progressively with actuation level. It is argued that the dissipative (high frequency) actuation alters the balance between large- and small-scale motions near separation by intensifying the large-scale motions and limiting the small-scale dynamics. Controlling separation within the diffuser duct also has a profound effect on the global flow. In the presence of actuation, the mass flow rate in the primary duct increases 10% while the fraction of the diverted mass flow rate in the diffuser increases by more than 45% at 0.7% actuation mass fraction. Supported by the Boeing Company.

  3. Using spatial context to support prospective memory in simulated air traffic control.

    PubMed

    Loft, Shayne; Finnerty, Dannielle; Remington, Roger W

    2011-12-01

    The aim was to examine whether prospective memory error and response costs to ongoing tasks in an air traffic control simulation could be reduced by providing spatial context. Prospective memory refers to remembering to perform an intended action at an appropriate point in the future. Failures of prospective memory can occur in air traffic control. For this study, three conditions of participants performed an air traffic control task that required them to accept and hand off aircraft and to prevent conflicts. The prospective memory task required participants to remember to press an alternative key rather than the routine key when accepting target aircraft. A red line separated the display into upper and lower regions. Participants in the context condition were told that the prospective memory instruction would apply only to aircraft approaching from one region (upper or lower). Those in the standard condition were not provided this information. In the control condition, participants did not have to perform the prospective memory task. In the context condition, participants made fewer prospective memory errors than did those in the standard condition and made faster acceptance decisions for aircraft approaching from irrelevant compared with relevant regions. Costs to hand-off decision time were also reduced in the context condition. Spatial context provided no benefit to conflict detection. Participants could partially localize their allocation of attentional resources to the prospective memory task to relevant display regions. The findings are potentially applicable to air traffic control, whereby regularities in airspace structure and standard traffic flows allow controllers to anticipate the location of specific air traffic events.

  4. Temporal and spatial control of gene expression in horticultural crops

    PubMed Central

    Dutt, Manjul; Dhekney, Sadanand A; Soriano, Leonardo; Kandel, Raju; Grosser, Jude W

    2014-01-01

    Biotechnology provides plant breeders an additional tool to improve various traits desired by growers and consumers of horticultural crops. It also provides genetic solutions to major problems affecting horticultural crops and can be a means for rapid improvement of a cultivar. With the availability of a number of horticultural genome sequences, it has become relatively easier to utilize these resources to identify DNA sequences for both basic and applied research. Promoters play a key role in plant gene expression and the regulation of gene expression. In recent years, rapid progress has been made on the isolation and evaluation of plant-derived promoters and their use in horticultural crops, as more and more species become amenable to genetic transformation. Our understanding of the tools and techniques of horticultural plant biotechnology has now evolved from a discovery phase to an implementation phase. The availability of a large number of promoters derived from horticultural plants opens up the field for utilization of native sequences and improving crops using precision breeding. In this review, we look at the temporal and spatial control of gene expression in horticultural crops and the usage of a variety of promoters either isolated from horticultural crops or used in horticultural crop improvement. PMID:26504550

  5. Targeted Intracellular Delivery of Proteins with Spatial and Temporal Control

    PubMed Central

    2015-01-01

    While a host of methods exist to deliver genetic materials or small molecules to cells, very few are available for protein delivery to the cytosol. We describe a modular, light-activated nanocarrier that transports proteins into cells by receptor-mediated endocytosis and delivers the cargo to the cytosol by light triggered endosomal escape. The platform is based on hollow gold nanoshells (HGN) with polyhistidine tagged proteins attached through an avidity-enhanced, nickel chelation linking layer; here, we used green fluorescent protein (GFP) as a model deliverable cargo. Endosomal uptake of the GFP loaded nanocarrier was mediated by a C-end Rule (CendR) internalizing peptide fused to the GFP. Focused femtosecond pulsed-laser excitation triggered protein release from the nanocarrier and endosome disruption, and the released protein was capable of targeting the nucleoli, a model intracellular organelle. We further demonstrate the generality of the approach by loading and releasing Sox2 and p53. This method for targeting of individual cells, with resolution similar to microinjection, provides spatial and temporal control over protein delivery. PMID:25490248

  6. Spatial control of mitotic commitment in fission yeast.

    PubMed

    Hagan, Iain M; Grallert, Agnes

    2013-12-01

    The activation of the Cdk1 (cyclin-dependent kinase 1)-cyclin B complex to promote commitment to mitosis is controlled by the phosphorylation status of the Cdk1 catalytic subunit. Cdk1 phosphorylation by Wee1 kinases blocks activation until Cdc25 (cell division cycle 25) phosphatases remove this phosphate to drive division. Feedback inhibition of Wee1 and promotion of Cdc25 activities by the newly activated Cdk1-cyclin B complexes ensure that the transition from interphase to mitosis is a rapid and complete bi-stable switch. Although this level of molecular understanding of the mitotic commitment switch has been clear for over two decades, it is still unclear how the switch is engaged to promote division at the right time for a particular context. We discuss recent work in fission yeast that shows how the spatial organization of signalling networks, in particular events on the centrosome equivalent, the spindle pole body, plays a key role in ensuring that the timing of cell division is coupled to environmental cues.

  7. Spatial and temporal lingual coarticulation and motor control in preadolescents.

    PubMed

    Zharkova, Natalia; Hewlett, Nigel; Hardcastle, William J; Lickley, Robin J

    2014-04-01

    PURPOSE In this study, the authors compared coarticulation and lingual kinematics in preadolescents and adults in order to establish whether preadolescents had a greater degree of random variability in tongue posture and whether their patterns of lingual coarticulation differed from those of adults. METHOD High-speed ultrasound tongue contour data synchronized with the acoustic signal were recorded from 15 children (ages 10-12 years) and 15 adults. Tongue shape contours were analyzed at 9 normalized time points during the fricative phase of schwa-fricative-/a/ and schwa-fricative-/i/ sequences with the consonants /s/ and /ʃ/. RESULTS There was no significant age-related difference in random variability. Where a significant vowel effect occurred, the amount of coarticulation was similar in the 2 groups. However, the onset of the coarticulatory effect on preadolescent /ʃ/ was significantly later than on preadolescent /s/, and also later than on adult /s/ and /ʃ/. CONCLUSIONS Preadolescents have adult-like precision of tongue control and adult-like anticipatory lingual coarticulation with respect to spatial characteristics of tongue posture. However, there remains some immaturity in the motor programming of certain complex tongue movements.

  8. Numerical modeling of separated flows in three-dimensional diffusers and application of synthetic jets for separation control

    NASA Astrophysics Data System (ADS)

    Krasheninnikov, S. Yu.; Pudovikov, D. E.; Torohov, S. A.

    2012-01-01

    Solving the problem of creating an environmentally friendly "green plane" implies development and implementation of several actions aimed at increasing airplane performance and reducing environmental contamination. One possible way to solve this problem is to reduce the powerplant weight, in particular, by decreasing its length. The airplane engine flowpath comprises transition ducts: those between the low- and high-pressure compressors, between the compressor and combustor, and between the high- and low-pressure turbines. In a modern high-bypass turbofan, the flowpath varies in the streamwise direction. Shorter transition ducts have greater curvature. Because of this, intensive separation may occur, which leads to increased losses in the flowpath and to significant growth of nonuniformity of flow parameters. Vast experience of numerical and experimental studies of unsteady separated flows has been accumulated by now. In many cases, however, these investigations are performed in a two-dimensional (2D) formulation, which is primarily caused by the high cost of three-dimensional (3D) unsteady calculations. The numerical and experimental work [1] shows that flows in diffuser ducts can have an essentially unsteady 3D structure. This is valid even for ducts modeling 2D configurations. This paper describes the results of a numerical study of the flow structure and its features in model S-shaped transition ducts, as well as the results of using a synthetic jet generator for flow control and for reduction of total pressure losses. Three-dimensional flows are numerically modeled by the unsteady Reynolds-averaged Navier-Stokes (URANS) / RANS methods. The calculations show that the use of the synthetic jet generator can lead to duct loss reduction by 45%.

  9. Spatial Regulation of Membrane Fusion Controlled by Modification of Phosphoinositides

    PubMed Central

    Dumas, Fabrice; Byrne, Richard D.; Vincent, Ben; Hobday, Tina M. C.; Poccia, Dominic L.; Larijani, Banafshé

    2010-01-01

    Membrane fusion plays a central role in many cell processes from vesicular transport to nuclear envelope reconstitution at mitosis but the mechanisms that underlie fusion of natural membranes are not well understood. Studies with synthetic membranes and theoretical considerations indicate that accumulation of lipids characterised by negative curvature such as diacylglycerol (DAG) facilitate fusion. However, the specific role of lipids in membrane fusion of natural membranes is not well established. Nuclear envelope (NE) assembly was used as a model for membrane fusion. A natural membrane population highly enriched in the enzyme and substrate needed to produce DAG has been isolated and is required for fusions leading to nuclear envelope formation, although it contributes only a small amount of the membrane eventually incorporated into the NE. It was postulated to initiate and regulate membrane fusion. Here we use a multidisciplinary approach including subcellular membrane purification, fluorescence spectroscopy and Förster resonance energy transfer (FRET)/two-photon fluorescence lifetime imaging microscopy (FLIM) to demonstrate that initiation of vesicle fusion arises from two unique sites where these vesicles bind to chromatin. Fusion is subsequently propagated to the endoplasmic reticulum-derived membranes that make up the bulk of the NE to ultimately enclose the chromatin. We show how initiation of multiple vesicle fusions can be controlled by localised production of DAG and propagated bidirectionally. Phospholipase C (PLCγ), GTP hydrolysis and (phosphatidylinsositol-(4,5)-bisphosphate (PtdIns(4,5)P2) are required for the latter process. We discuss the general implications of membrane fusion regulation and spatial control utilising such a mechanism. PMID:20808914

  10. Injection slot location for boundary-layer control in shock-induced separation

    NASA Technical Reports Server (NTRS)

    Viswanath, P. R.; Sankaran, L.; Sagdeo, P. M.; Narasimha, R.; Prabhu, A.

    1978-01-01

    An experimental investigation of the effect of tangential air injection, when the injection slot is located inside of what would otherwise have been the dead air zone in a separated flow, in controlling shock-induced turbulent boundary layer separation is presented. The experiments were carried out at a free-stream Mach number of 2.5 in the separated flow induced by a compression corner with a 20 deg angle. The observations made were wall static pressures, pitot profiles, and schlieren visualizations of the flow. The results show that the present location for injection is more effective in suppressing boundary-layer separation than the more conventional one, where the slot is located upstream of where separation would occur in the absence of injection.

  11. A Separation Control CFD Validation Test Case. Part 1; Baseline and Steady Suction

    NASA Technical Reports Server (NTRS)

    Greenblatt, David; Paschal, Keith B.; Yao, Chung-Sheng; Harris, jerome; Schaeffler, Norman W.; Washburn, Anthony E.

    2004-01-01

    Low speed flow separation over a wall-mounted hump, and its control using steady suction, were studied experimentally in order to generate a data set for a workshop aimed at validating CFD turbulence models. The baseline and controlled data sets comprised static and dynamic surface pressure measurements, flow field measurements using Particle Image Velocimetry (PIV) and wall shear stress obtained via oil-film interferometry. In addition to the specific test cases studied, surface pressures for a wide variety of conditions were reported for different Reynolds numbers and suction rates. Stereoscopic PIV and oil-film flow visualization indicated that the baseline separated flow field was mainly two-dimensional. With the application of control, some three-dimensionality was evident in the spanwise variation of pressure recovery, reattachment location and spanwise pressure fluctuations. Part 2 of this paper, under preparation for the AIAA Meeting in Reno 2005, considers separation control by means of zero-efflux oscillatory blowing.

  12. A Separation Control CFD Validation Test Case. Part 1; Baseline and Steady Suction

    NASA Technical Reports Server (NTRS)

    Greenblatt, David; Paschal, Keith B.; Yao, Chung-Sheng; Harris, Jerome; Schaeffler, Norman W.; Washburn, Anthony E.

    2004-01-01

    Low speed flow separation over a wall-mounted hump, and its control using steady suction, were studied experimentally in order to generate a data set for a workshop aimed at validating CFD turbulence models. The baseline and controlled data sets comprised static and dynamic surface pressure measurements, flow field measurements using Particle Image Velocimetry (PIV) and wall shear stress obtained via oil-film interferometry. In addition to the specific test cases studied, surface pressures for a wide variety of conditions were reported for different Reynolds numbers and suction rates. Stereoscopic PIV and oil-film flow visualization indicated that the baseline separated flow field was mainly two- dimensional. With the application of control, some three-dimensionality was evident in the spanwise variation of pressure recovery, reattachment location and spanwise pressure fluctuations. Part 2 of this paper, under preparation for the AIAA Meeting in Reno 2005, considers separation control by means of zero-efflux oscillatory blowing.

  13. Optimizing and controlling earthmoving operations using spatial technologies

    NASA Astrophysics Data System (ADS)

    Alshibani, Adel

    This thesis presents a model designed for optimizing, tracking, and controlling earthmoving operations. The proposed model utilizes, Genetic Algorithm (GA), Linear Programming (LP), and spatial technologies including Global Positioning Systems (GPS) and Geographic Information Systems (GIS) to support the management functions of the developed model. The model assists engineers and contractors in selecting near optimum crew formations in planning phase and during construction, using GA and LP supported by the Pathfinder Algorithm developed in a GIS environment. GA is used in conjunction with a set of rules developed to accelerate the optimization process and to avoid generating and evaluating hypothetical and unrealistic crew formations. LP is used to determine quantities of earth to be moved from different borrow pits and to be placed at different landfill sites to meet project constraints and to minimize the cost of these earthmoving operations. On the one hand, GPS is used for onsite data collection and for tracking construction equipment in near real-time. On the other hand, GIS is employed to automate data acquisition and to analyze the collected spatial data. The model is also capable of reconfiguring crew formations dynamically during the construction phase while site operations are in progress. The optimization of the crew formation considers: (1) construction time, (2) construction direct cost, or (3) construction total cost. The model is also capable of generating crew formations to meet, as close as possible, specified time and/or cost constraints. In addition, the model supports tracking and reporting of project progress utilizing the earned-value concept and the project ratio method with modifications that allow for more accurate forecasting of project time and cost at set future dates and at completion. The model is capable of generating graphical and tabular reports. The developed model has been implemented in prototype software, using Object

  14. Parental Psychological Control and Dysfunctional Separation--Individuation: A Tale of Two Different Dynamics

    ERIC Educational Resources Information Center

    Kins, Evie; Soenens, Bart; Beyers, Wim

    2012-01-01

    This study examined associations between psychologically controlling parenting and two possible manifestations of problematic separation--individuation (i.e., dysfunctional dependence and dysfunctional independence). To explain these associations, it has been argued that psychological control is an inherently independence-stifling parenting…

  15. Parental Psychological Control and Dysfunctional Separation--Individuation: A Tale of Two Different Dynamics

    ERIC Educational Resources Information Center

    Kins, Evie; Soenens, Bart; Beyers, Wim

    2012-01-01

    This study examined associations between psychologically controlling parenting and two possible manifestations of problematic separation--individuation (i.e., dysfunctional dependence and dysfunctional independence). To explain these associations, it has been argued that psychological control is an inherently independence-stifling parenting…

  16. Glow Discharge Plasma Demonstrated for Separation Control in the Low-Pressure Turbine

    NASA Technical Reports Server (NTRS)

    Ashpis, David e.; Hultgren, Lennart S.

    2004-01-01

    Flow separation in the low-pressure turbine (LPT) is a major barrier that limits further improvements of aerodynamic designs of turbine airfoils. The separation is responsible for performance degradation, and it prevents the design of highly loaded airfoils. The separation can be delayed, reduced, or eliminated completely if flow control techniques are used. Successful flow control technology will enable breakthrough improvements in gas turbine performance and design. The focus of this research project was the development and experimental demonstration of active separation control using glow discharge plasma (GDP) actuators in flow conditions simulating the LPT. The separation delay was shown to be successful, laying the foundation for further development of the technologies to practical application in the LPT. In a fluid mechanics context, the term "flow control" means a technology by which a very small input results in a very large effect on the flow. In this project, the interest is to eliminate or delay flow separation on LPT airfoils by using an active flow control approach, in which disturbances are dynamically inserted into the flow, they interact with the flow, and they delay separation. The disturbances can be inserted using a localized, externally powered, actuating device, examples are acoustic, pneumatic, or mechanical devices that generate vibrations, flow oscillations, or pulses. A variety of flow control devices have been demonstrated in recent years in the context of the external aerodynamics of aircraft wings and airframes, where the incoming flow is quiescent or of a very low turbulence level. However, the flow conditions in the LPT are significantly different because there are high levels of disturbances in the incoming flow that are characterized by high free-stream turbulence intensity. In addition, the Reynolds number, which characterizes the viscous forces in the flow and is related to the flow speed, is very low in the LPT passages.

  17. Controllable Phase Separation by Boc-Modified Lipophilic Acid as a Multifunctional Extractant

    NASA Astrophysics Data System (ADS)

    Tao, Kai; Adler-Abramovich, Lihi; Gazit, Ehud

    2015-12-01

    While phase separation of immiscible liquid-liquid systems has become increasingly significant in diverse areas, the irreversible nature limits their further application in controllable extraction-concentration or capture-release fields. There is a need for the development of simple, efficient and reversible methods for numerous research and industrial extraction and separation applications. We envisioned Boc-modified lipophilic acids as a simple model for such use based on the studies of the multi-phase transitions of Boc-modified supramolecular polymeric systems. Here, we demonstrate that in the presence of Boc-7-aminoheptanoic acid (Boc-7), phase separation occurs in mixtures of miscible organic solvent and water. The separation behavior was confirmed by differential colorimetric development in aqueous and organic phases using methyl orange staining assays. Component substitution experiments verified that the phase separation results from the subtle balance between the aggregation and the solvation forces of Boc-7, and is reversible by adjusting the solution pH. Owing to the intrinsic hydrophobic properties of the organic phase and the hydrogen bonding-forming ability of the carboxyl group of Boc-7, the phase separation system captures and releases Sudan Red, fluorescein, and streptavidin in a controllable manner. Consequently, a reversible and simple phase separation system can be designed as a multifunctional extractant.

  18. Controllable Phase Separation by Boc-Modified Lipophilic Acid as a Multifunctional Extractant

    PubMed Central

    Tao, Kai; Adler-Abramovich, Lihi; Gazit, Ehud

    2015-01-01

    While phase separation of immiscible liquid-liquid systems has become increasingly significant in diverse areas, the irreversible nature limits their further application in controllable extraction-concentration or capture-release fields. There is a need for the development of simple, efficient and reversible methods for numerous research and industrial extraction and separation applications. We envisioned Boc-modified lipophilic acids as a simple model for such use based on the studies of the multi-phase transitions of Boc-modified supramolecular polymeric systems. Here, we demonstrate that in the presence of Boc-7-aminoheptanoic acid (Boc-7), phase separation occurs in mixtures of miscible organic solvent and water. The separation behavior was confirmed by differential colorimetric development in aqueous and organic phases using methyl orange staining assays. Component substitution experiments verified that the phase separation results from the subtle balance between the aggregation and the solvation forces of Boc-7, and is reversible by adjusting the solution pH. Owing to the intrinsic hydrophobic properties of the organic phase and the hydrogen bonding-forming ability of the carboxyl group of Boc-7, the phase separation system captures and releases Sudan Red, fluorescein, and streptavidin in a controllable manner. Consequently, a reversible and simple phase separation system can be designed as a multifunctional extractant. PMID:26627307

  19. [Spatial heterogeneity and classified control of agricultural non-point source pollution in Huaihe River Basin].

    PubMed

    Zhou, Liang; Xu, Jian-Gang; Sun, Dong-Qi; Ni, Tian-Hua

    2013-02-01

    Agricultural non-point source pollution is of importance in river deterioration. Thus identifying and concentrated controlling the key source-areas are the most effective approaches for non-point source pollution control. This study adopts inventory method to analysis four kinds of pollution sources and their emissions intensity of the chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) in 173 counties (cities, districts) in Huaihe River Basin. The four pollution sources include livestock breeding, rural life, farmland cultivation, aquacultures. The paper mainly addresses identification of non-point polluted sensitivity areas, key pollution sources and its spatial distribution characteristics through cluster, sensitivity evaluation and spatial analysis. A geographic information system (GIS) and SPSS were used to carry out this study. The results show that: the COD, TN and TP emissions of agricultural non-point sources were 206.74 x 10(4) t, 66.49 x 10(4) t, 8.74 x 10(4) t separately in Huaihe River Basin in 2009; the emission intensity were 7.69, 2.47, 0.32 t.hm-2; the proportions of COD, TN, TP emissions were 73%, 24%, 3%. The paper achieves that: the major pollution source of COD, TN and TP was livestock breeding and rural life; the sensitivity areas and priority pollution control areas among the river basin of non-point source pollution are some sub-basins of the upper branches in Huaihe River, such as Shahe River, Yinghe River, Beiru River, Jialu River and Qingyi River; livestock breeding is the key pollution source in the priority pollution control areas. Finally, the paper concludes that pollution type of rural life has the highest pollution contribution rate, while comprehensive pollution is one type which is hard to control.

  20. Multi-interface Level Sensors and New Development in Monitoring and Control of Oil Separators

    PubMed Central

    Bukhari, Syed Faisal Ahmed; Yang, Wuqiang

    2006-01-01

    In the oil industry, huge saving may be made if suitable multi-interface level measurement systems are employed for effectively monitoring crude oil separators and efficient control of their operation. A number of techniques, e.g. externally mounted displacers, differential pressure transmitters and capacitance rod devices, have been developed to measure the separation process with gas, oil, water and other components. Because of the unavailability of suitable multi-interface level measurement systems, oil separators are currently operated by the trial-and-error approach. In this paper some conventional techniques, which have been used for level measurement in industry, and new development are discussed.

  1. Generation of a multi-qubit W entangled state through spatially separated semiconductor quantum-dot-molecules in cavity-quantum electrodynamics arrays

    SciTech Connect

    Liu, Siping; Yu, Rong; Li, Jiahua; Wu, Ying

    2014-04-07

    Generating entangled states attract tremendous interest as the most vivid manifestation of nonlocality of quantum mechanics and also for emerging applications in quantum information processing (QIP). Here, we propose theoretically a scheme for the deterministic generation of a three-qubit W sate with three semiconductor quantum-dot-molecules (QDMs) trapped in spatially separated cavities connected by optical fibers. The proposed scheme takes full advantage of the voltage-controlled tunnelling effects in QDMs, which induces the quantum coherence and further controls the generation of the W entangled state. The influences of the system parameters and various decoherence processes including spontaneous decay and photon leakage on the fidelity of the W state are discussed in details. Numerical results indicate that our scheme is not only robust against these decoherence factors but also insensitive to the deviation of the system parameters from the ideal conditions. Furthermore, the present scheme can be directly extended to realize an N-qubit W state. Also, this scheme can be generically transferred to other physical systems, including circuit quantum electrodynamics and photonic crystal cavities. The results obtained here may be useful in real experiments for realizing QIP in a solid-state platform.

  2. Cobalt Ferrite Bearing Nitrogen-Doped Reduced Graphene Oxide Layers Spatially Separated with Microporous Carbon as Efficient Oxygen Reduction Electrocatalyst.

    PubMed

    Kashyap, Varchaswal; Singh, Santosh K; Kurungot, Sreekumar

    2016-08-17

    The present work discloses how high-quality dispersion of fine particles of cobalt ferrite (CF) could be attained on nitrogen-doped reduced graphene oxide (CF/N-rGO) and how this material in association with a microporous carbon phase could deliver significantly enhanced activity toward electrochemical oxygen reduction reaction (ORR). Our study indicates that the microporous carbon phase plays a critical role in spatially separating the layers of CF/N-rGO and in creating a favorable atmosphere to ensure the seamless distribution of the reactants to the active sites located on CF/N-rGO. In terms of the ORR current density, the heat-treated hybrid catalyst at 150 °C (CF/N-rGO-150) is found to be clearly outperforming (7.4 ± 0.5 mA/cm(2)) the state-of-the-art 20 wt % Pt-supported carbon catalyst (PtC) (5.4 ± 0.5 mA/cm(2)). The mass activity and stability of CF-N-rGO-150 are distinctly superior to PtC even after 5000 electrochemical cycles. As a realistic system level exploration of the catalyst, testing of a primary zinc-air battery could be demonstrated using CF/N-rGO-150 as the cathode catalyst. The battery is giving a galvanostatic discharge time of 15 h at a discharge current density of 20 mA/cm(2) and a specific capacity of ∼630 mAh g(-1) in 6 M KOH by using a Zn foil as the anode. Distinctly, the battery performance of this system is found to be superior to that of PtC in less concentrated KOH solution as the electrolyte.

  3. Entangled microwaves as a resource for entangling spatially separate solid-state qubits: Superconducting qubits, nitrogen-vacancy centers, and magnetic molecules

    NASA Astrophysics Data System (ADS)

    Gómez, Angela Viviana; Rodríguez, Ferney Javier; Quiroga, Luis; García-Ripoll, Juan José

    2016-06-01

    Quantum correlations present in a broadband two-line squeezed microwave state can induce entanglement in a spatially separated bipartite system consisting of either two single qubits or two-qubit ensembles. By using an appropriate master equation for a bipartite quantum system in contact with two separate but entangled baths, the generating entanglement process in spatially separated quantum systems is thoroughly characterized. Decoherence thermal effects on the entanglement transfer are also discussed. Our results provide evidence that this entanglement transfer by dissipation is feasible, yielding to a steady-state amount of entanglement in the bipartite quantum system which can be optimized for a wide range of realistic physical systems that include state-of-the-art experiments with nitrogen-vacancy centers in diamond, superconducting qubits, or even magnetic molecules embedded in a crystalline matrix.

  4. Fine particulate matter measurements in Swiss restaurants, cafés and bars: what is the effect of spatial separation between smoking and non-smoking areas?

    PubMed

    Huss, A; Kooijman, C; Breuer, M; Böhler, P; Zünd, T; Wenk, S; Röösli, M

    2010-02-01

    We performed 124 measurements of particulate matter (PM(2.5)) in 95 hospitality venues such as restaurants, bars, cafés, and a disco, which had differing smoking regulations. We evaluated the impact of spatial separation between smoking and non-smoking areas on mean PM(2.5) concentration, taking relevant characteristics of the venue, such as the type of ventilation or the presence of additional PM(2.5) sources, into account. We differentiated five smoking environments: (i) completely smoke-free location, (ii) non-smoking room spatially separated from a smoking room, (iii) non-smoking area with a smoking area located in the same room, (iv) smoking area with a non-smoking area located in the same room, and (v) smoking location which could be either a room where smoking was allowed that was spatially separated from non-smoking room or a hospitality venue without smoking restriction. In these five groups, the geometric mean PM(2.5) levels were (i) 20.4, (ii) 43.9, (iii) 71.9, (iv) 110.4, and (v) 110.3 microg/m(3), respectively. This study showed that even if non-smoking and smoking areas were spatially separated into two rooms, geometric mean PM(2.5) levels in non-smoking rooms were considerably higher than in completely smoke-free hospitality venues. PM(2.5) levels are considerably increased in the non-smoking area if smoking is allowed anywhere in the same location. Even locating the smoking area in another room resulted in a more than doubling of the PM(2.5) levels in the non-smoking room compared with venues where smoking was not allowed at all. In practice, spatial separation of rooms where smoking is allowed does not prevent exposure to environmental tobacco smoke in nearby non-smoking areas.

  5. Active control of Boundary Layer Separation & Flow Distortion in Adverse Pressure Gradient Flows via Supersonic Microjets

    NASA Technical Reports Server (NTRS)

    Alvi, Farrukh S.; Gorton, Susan (Technical Monitor)

    2005-01-01

    Inlets to aircraft propulsion systems must supply flow to the compressor with minimal pressure loss, flow distortion or unsteadiness. Flow separation in internal flows such as inlets and ducts in aircraft propulsion systems and external flows such as over aircraft wings, is undesirable as it reduces the overall system performance. The aim of this research has been to understand the nature of separation and more importantly, to explore techniques to actively control this flow separation. In particular, the use of supersonic microjets as a means of controlling boundary layer separation was explored. The geometry used for the early part of this study was a simple diverging Stratford ramp, equipped with arrays of supersonic microjets. Initial results, based on the mean surface pressure distribution, surface flow visualization and Planar Laser Scattering (PLS) indicated a reverse flow region. We implemented supersonic microjets to control this separation and flow visualization results appeared to suggest that microjets have a favorable effect, at least to a certain extent. However, the details of the separated flow field were difficult to determine based on surface pressure distribution, surface flow patterns and PLS alone. It was also difficult to clearly determine the exact influence of the supersonic microjets on this flow. In the latter part of this study, the properties of this flow-field and the effect of supersonic microjets on its behavior were investigated in further detail using 2-component (planar) Particle Image Velocimetry (PIV). The results clearly show that the activation of microjets eliminated flow separation and resulted in a significant increase in the momentum of the fluid near the ramp surface. Also notable is the fact that the gain in momentum due to the elimination of flow separation is at least an order of magnitude larger (two orders of magnitude larger in most cases) than the momentum injected by the microjets and is accomplished with very

  6. Spatial separation of semiochemical Lurem-TR and entomopathogenic fungi to enhance their compatibility and infectivity in an autoinoculation system for thrips management.

    PubMed

    Mfuti, David K; Subramanian, Sevgan; van Tol, Rob W H M; Wiegers, Gerrie L; de Kogel, Willem J; Niassy, Saliou; du Plessis, Hannalene; Ekesi, Sunday; Maniania, Nguya K

    2016-01-01

    The effect of spatial separation of the semiochemical Lurem-TR, which has been found to inhibit conidia of entomopathogenic fungi when put together, on the persistence of conidia of Metarhizium brunneum and M. anisopliae was evaluated in the greenhouse and field in order to develop an autodissemination strategy for the management of Megalurothrips sjostedti on cowpea crop. Influence of spatial separation of the semiochemical on thrips attraction and conidial acquisition by thrips from the autoinoculation device was also investigated in the field. Persistence of conidia of M. brunneum and M. anisopliae increased with distance of separation of Lurem-TR. Direct exposure of fungus without separation from Lurem-TR recorded the lowest conidial germination as compared with the other treatments. Attraction of thrips to the device also varied significantly according to distance between device and semiochemical, with a higher number of thrips attracted when Lurem-TR was placed in a container below the device and at 10 cm distance. There was no significant difference in conidial acquisition between spatial separation treatments of conidia and Lurem-TR. Attraction of other insect pests to the device did not significantly vary between treatments. Positive correlations were found between conidial acquisition and thrips attraction. This study suggests that spatial separation of fungal conidia from Lurem-TR in an autoinoculation device could provide a low-cost strategy for effective management of thrips in grain legume cropping systems. © 2015 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

  7. Experimental implementation of automatic 'cycle to cycle' control of a chiral simulated moving bed separation.

    PubMed

    Amanullah, Mohammad; Grossmann, Cristian; Mazzotti, Marco; Morari, Manfred; Morbidelli, Massimo

    2007-09-21

    In the absence of a suitable controller, currently simulated moving beds (SMBs) are operated suboptimally to cope with system uncertainties and to guarantee robustness of operation. Recently, we have developed a 'cycle to cycle' optimizing controller that not only makes use of minimal system information, i.e. only the Henry constants and average bed voidage, but also optimizes the process performance and taps the full economic potential of the SMB technology. The experimental implementation of the 'cycle to cycle' optimizing controller had been carried out for achiral separation. For chiral separation however, application of any online controller has not been possible because an appropriate online monitoring system has not been available. This work reports and discusses the first experimental implementation of the 'cycle to cycle' optimizing control for chiral separations. A mixture of guaifenesin enantiomers is separated on Chiralcel OD columns with ethanol as mobile phase in a eight-column four sections laboratory SMB unit. The results show that the controller, although using minimal information about the retention of the two enantiomers, is able to meet product and process specifications, can optimize the process performance, and is capable of rejecting disturbances that may occur during the operation of the SMB plant.

  8. Review of research on low-profile vortex generators to control boundary-layer separation

    NASA Astrophysics Data System (ADS)

    Lin, John C.

    2002-05-01

    An in-depth review of boundary-layer flow-separation control by a passive method using low-profile vortex generators is presented. The generators are defined as those with a device height between 10% and 50% of the boundary-layer thickness. Key results are presented for several research efforts, all of which were performed within the past decade and a half where the majority of these works emphasize experimentation with some recent efforts on numerical simulations. Topics of discussion consist of both basic fluid dynamics and applied aerodynamics research. The fluid dynamics research includes comparative studies on separation control effectiveness as well as device-induced vortex characterization and correlation. The comparative studies cover the controlling of low-speed separated flows in adverse pressure gradient and supersonic shock-induced separation. The aerodynamics research includes several applications for aircraft performance enhancement and covers a wide range of speeds. Significant performance improvements are achieved through increased lift and/or reduced drag for various airfoils-low-Reynolds number, high-lift, and transonic-as well as highly swept wings. Performance enhancements for non-airfoil applications include aircraft interior noise reduction, inlet flow distortion alleviation inside compact ducts, and a more efficient overwing fairing. The low-profile vortex generators are best for being applied to applications where flow-separation locations are relatively fixed and the generators can be placed reasonably close upstream of the separation. Using the approach of minimal near-wall protuberances through substantially reduced device height, these devices can produce streamwise vortices just strong enough to overcome the separation without unnecessarily persisting within the boundary layer once the flow-control objective is achieved. Practical advantages of low-profile vortex generators, such as their inherent simplicity and low device drag, are

  9. Review of Research on Low-Profile Vortex Generators to Control Boundary-Layer Separation

    NASA Technical Reports Server (NTRS)

    Lin, John C.

    2002-01-01

    An in-depth review of boundary-layer flow-separation control by a passive method using low-profile vortex generators is presented. The generators are defined as those with a device height between 10% and 50% of the boundary layer thickness. Key results are presented for several research efforts, all of which were performed within the past decade and a half where the majority of these works emphasize experimentation with some recent efforts on numerical simulations. Topics of discussion consist of both basic fluid dynamics and applied aerodynamics research. The fluid dynamics research includes comparative studies on separation control effectiveness as well as device-induced vortex characterization and correlation. The comparative studies cover the controlling of low-speed separated flows in adverse pressure gradient and supersonic shock-induced separation. The aerodynamics research includes several applications for aircraft performance enhancement and covers a wide range of speeds. Significant performance improvements are achieved through increased lift and/or reduced drag for various airfoils-low-Reynolds number, high-lift, and transonic-as well as highly swept wings. Performance enhancements for non-airfoil applications include aircraft interior noise reduction, inlet flow distortion alleviation inside compact ducts, and a more efficient overwing fairing. The low-profile vortex generators are best for being applied to applications where flow-separation locations are relatively fixed and the generators can be placed reasonably close upstream of the separation. Using the approach of minimal near-wall proturbances through substantially reduced device height, these devices can produce streamwise vortices just strong enough to overcome the separation without unnecessarily persisting within the boundary layer once the flow-control objective is achieved. Practical advantages of low-profile vortex generators, such as their inherent simplicity and low device drag, are

  10. Sweep and Compressibility Effects on Active Separation Control at High Reynolds Numbers

    NASA Technical Reports Server (NTRS)

    Seifert, Avi; Pack, LaTunia G.

    2000-01-01

    This paper explores the effects of compressibility, sweep and excitation location on active separation control at high Reynolds numbers. The model, which was tested in a cryogenic pressurized wind tunnel, simulates the upper surface of a 20% thick GlauertGoldschmied type airfoil at zero angle of attack. The flow is fully turbulent since the tunnel sidewall boundary layer flows over the model. Without control, the flow separates at the highly convex area and a large turbulent separation bubble is formed. Periodic excitation is applied to gradually eliminate the separation bubble. Two alternative blowing slot locations as well as the effect of compressibility, sweep and steady suction or blowing were studied. During the test the Reynolds numbers ranged from 2 to 40 million and Mach numbers ranged from 0.2 to 0.7. Sweep angles were 0 and 30 deg. It was found that excitation must be introduced slightly upstream of the separation region regardless of the sweep angle at low Mach number. Introduction of excitation upstream of the shock wave is more effective than at its foot. Compressibility reduces the ability of steady mass transfer and periodic excitation to control the separation bubble but excitation has an effect on the integral parameters, which is similar to that observed in low Mach numbers. The conventional swept flow scaling is valid for fully and even partially attached flow, but different scaling is required for the separated 3D flow. The effectiveness of the active control is not reduced by sweep. Detailed flow field dynamics are described in the accompanying paper.

  11. Sweep and Compressibility Effects on Active Separation Control at High Reynolds Numbers

    NASA Technical Reports Server (NTRS)

    Seifert, Avi; Pack, LaTunia G.

    2000-01-01

    This paper explores the effects of compressibility, sweep and excitation location on active separation control at high Reynolds numbers. The model, which was tested in a cryogenic pressurized wind tunnel, 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. Without control, the flow separates at the highly convex area and a large turbulent separation bubble is formed. Periodic excitation is applied to gradually eliminate the separation bubble. Two alternative blowing slot locations as well as the effect of compressibility, sweep and steady suction or blowing were studied. During the test the Reynolds numbers ranged from 2 to 40 million and Mach numbers ranged from 0.2 to 0.7. Sweep angles were 0 and 30 deg. It was found that excitation must be introduced slightly upstream of the separation region regardless of the sweep angle at low Mach number. Introduction of excitation upstream of the shock wave is more effective than at its foot. Compressibility reduces the ability of steady mass transfer and periodic excitation to control the separation bubble but excitation has an effect on the integral parameters, which is similar to that observed in low Mach numbers. The conventional swept flow scaling is valid for fully and even partially attached flow, but different scaling is required for the separated 3D flow. The effectiveness of the active control is not reduced by sweep. Detailed flow field dynamics are described in the accompanying paper.

  12. Experimental study and numerical simulation of flow separation control with pulsed nanosecond discharge actuator

    NASA Astrophysics Data System (ADS)

    Correale, Guiseppe; Popov, Ilya; Nikipelov, Andrey; Pancheshnyi, Sergey; Hulshoff, Seo; Veldhuis, Leo; Starikovskiy, Andrey; neqlab Team; TUDelft Team

    2011-10-01

    Active flow separation control with a nanosecond pulse plasma actuator, which is essentially a simple electrode system on the surface of an airfoil, introducing low-energy gas discharge into the boundary layer, with little extra weight and no mechanical parts, was performed in wind-tunnel experiments on various airfoil models. In stall conditions the significant lift increase up to 30% accompanied by drag reduction (up to 3 times) was observed. The critical angle of attack shifted up to 5{7 degrees. Schlieren imaging shown the shock wave propagation and formation of large-scale vortex structure in the separation zone, which led to separation elimination. The experimental work is supported by numerical simulations of the phenomena. The formation of vortex similar to that observed in experiments was simulated in the case of laminar leading edge separation. Model simulations of free shear layer shown intensification of shear layer instabilities due to shock wave to shear layer interaction.

  13. Control of volume resistivity in inorganic-organic separators. [for alkaline batteries

    NASA Technical Reports Server (NTRS)

    Sheibley, D. W.; Manzo, M. A.

    1980-01-01

    Control of resistivity in NASA inorganic-organic separators is achieved by incorporating small percentages of high surface area, fine-particle silica with other ingredients in the separator coating. The volume resistivity appears to be predictable from coating composition, that is, from the surface area of filler particles in the coating. The approach has been applied to two polymer-'plasticizer'-filler coating systems, where the filler content of each is below the generally acknowledged critical pigment volume concentration of the coating. Application of these coating systems to 0.0254 cm thick (10 mil) fuel-cell grade asbestos sheet produces inexpensive, flexible, microporous separators that perform at least as well as the original inorganic-organic concept, the Astropower separator.

  14. Control of volume resistivity in inorganic-organic separators. [for alkaline batteries

    NASA Technical Reports Server (NTRS)

    Sheibley, D. W.; Manzo, M. A.

    1980-01-01

    Control of resistivity in NASA inorganic-organic separators is achieved by incorporating small percentages of high surface area, fine-particle silica with other ingredients in the separator coating. The volume resistivity appears to be predictable from coating composition, that is, from the surface area of filler particles in the coating. The approach has been applied to two polymer-'plasticizer'-filler coating systems, where the filler content of each is below the generally acknowledged critical pigment volume concentration of the coating. Application of these coating systems to 0.0254 cm thick (10 mil) fuel-cell grade asbestos sheet produces inexpensive, flexible, microporous separators that perform at least as well as the original inorganic-organic concept, the Astropower separator.

  15. Closed-loop separation control over a sharp edge ramp using genetic programming

    NASA Astrophysics Data System (ADS)

    Debien, Antoine; von Krbek, Kai A. F. F.; Mazellier, Nicolas; Duriez, Thomas; Cordier, Laurent; Noack, Bernd R.; Abel, Markus W.; Kourta, Azeddine

    2016-03-01

    We experimentally perform open and closed-loop control of a separating turbulent boundary layer downstream from a sharp edge ramp. The turbulent boundary layer just above the separation point has a Reynolds number Re_{θ }≈ 3500 based on momentum thickness. The goal of the control is to mitigate separation and early re-attachment. The forcing employs a spanwise array of active vortex generators. The flow state is monitored with skin-friction sensors downstream of the actuators. The feedback control law is obtained using model-free genetic programming control (GPC) (Gautier et al. in J Fluid Mech 770:442-457, 2015). The resulting flow is assessed using the momentum coefficient, pressure distribution and skin friction over the ramp and stereo PIV. The PIV yields vector field statistics, e.g. shear layer growth, the back-flow area and vortex region. GPC is benchmarked against the best periodic forcing. While open-loop control achieves separation reduction by locking-on the shedding mode, GPC gives rise to similar benefits by accelerating the shear layer growth. Moreover, GPC uses less actuation energy.

  16. Movable shark scales act as a passive dynamic micro-roughness to control flow separation.

    PubMed

    Lang, Amy W; Bradshaw, Michael T; Smith, Jonathon A; Wheelus, Jennifer N; Motta, Philip J; Habegger, Maria L; Hueter, Robert E

    2014-09-01

    Shark scales on fast-swimming sharks have been shown to be movable to angles in excess of 50°, and we hypothesize that this characteristic gives this shark skin a preferred flow direction. During the onset of separation, flow reversal is initiated close to the surface. However, the movable scales would be actuated by the reversed flow thereby causing a greater resistance to any further flow reversal and this mechanism would disrupt the process leading to eventual flow separation. Here we report for the first time experimental evidence of the separation control capability of real shark skin through water tunnel testing. Using skin samples from a shortfin mako Isurus oxyrinchus, we tested a pectoral fin and flank skin attached to a NACA 4412 hydrofoil and separation control was observed in the presence of movable shark scales under certain conditions in both cases. We hypothesize that the scales provide a passive, flow-actuated mechanism acting as a dynamic micro-roughness to control flow separation.

  17. Toward spatial control of gold nanorod surface functionalization

    NASA Astrophysics Data System (ADS)

    Eller, Jonathan R.

    Gold nanorods (GNRs) show much promise for applications in biological, optoelectronic and energy applications. The resonant generation of a localized surface plasmon resonance (LSPR) at the GNR surface results in interesting optical properties and unique interactions with molecules. Combined with their biocompatibility, ease of synthesis and facile surface functionalization, these anisotropic metal particles are excellent scaffolds for the study of the interactions between nanoscale surfaces and their chemical/biological environments. Regardless of the application, however, GNR utility will not be fully realized until the chemical nature of the surface is understood and controlled. GNRs can enhance various photophysical properties of molecules. In the case of two-photon absorption (TPA), cross-section enhancements have been shown to increase with strong distance-dependence. Here, a dual approach for the conjugation of a TPA chromophore to GNRs is presented, relying on layer-by- layer (LbL) polymer wrapping and direct thiol coating of the same parent chromophore structure. Together, these approaches allow for estimated chromophore-particle distances from <1nm to more than 15 nm. Composites were confirmed using conventional nanoparticle characterization methods. Imaging of GNR polymer shells indicated anisotropic composite structures, as confirmed by both conventional and cryo-TEM. Optical characterizations were performed using two-photon excited fluorescence and Z-scan techniques, to probe the TPA enhancement. The intrinsic nonlinear optical properties of GNRs is shown to contribute strongly to these measurements, suggesting the utility of these materials for bi-modal imaging platforms. GNR properties, like their shape, are anisotropic. The LSPR-induced near- fields are heterogeneously distributed on the nanorod surface, with the tips being much "hotter" than the sides. To understand and utilize fully the spatially- dependent interactions of GNRs with their

  18. Synaptic rectification controls nonlinear spatial integration of natural visual inputs

    PubMed Central

    Turner, Maxwell H; Rieke, Fred

    2016-01-01

    Summary A central goal in the study of any sensory system is to predict neural responses to complex inputs, especially those encountered during natural stimulation. Nowhere is the transformation from stimulus to response better understood than the vertebrate retina. Nevertheless, descriptions of retinal computation are largely based on stimulation using artificial visual stimuli, and it is unclear how these descriptions map onto the encoding of natural stimuli. We demonstrate that nonlinear spatial integration, a common feature of retinal ganglion cell (RGC) processing, shapes neural responses to natural visual stimuli in primate Off parasol RGCs, whereas On parasol RGCs exhibit surprisingly linear spatial integration. Despite this asymmetry, both cell types show strong nonlinear integration when presented with artificial stimuli. We show that nonlinear integration of natural stimuli is a consequence of rectified excitatory synaptic input, and that accounting for nonlinear spatial integration substantially improves models that predict RGC responses to natural images. PMID:27263968

  19. Transition and separation control on a low-Reynolds number airfoil

    NASA Technical Reports Server (NTRS)

    Mangalam, S. M.; Bar-Sever, A.; Zaman, K. B. M. Q.; Harvey, W. D.

    1986-01-01

    The major problem associated with the aerodynamic performance of airfoils at low Reynolds numbers is the presence of extensive laminar boundary-layer separation resulting in a large increase in presssure drag and a decrease in lift. The rapid deterioration in airfoil characteristics can be largely eliminated by artificially controlling the flow through the introduction of suitable disturbances in the boundary layer such that transition occurs ahead of the anticipated laminar separation. This paper presents the results of wind-tunnel tests conducted on a 10-cm model of LRN (1)-1007 airfoil with passive (roughness trips) and active (acoustic excitation) controls to trigger transition and suppress separation. Significant improvements in the aerodynamic characteristics of the airfoil were observed. Results of this study for a chord Reynolds number range of 40,000 to 250,000 are presented in this paper.

  20. Control of the boundary layer separation about an airfoil by active surface heating

    NASA Technical Reports Server (NTRS)

    Maestrello, Lucio; Badavi, Forooz F.; Noonan, Kevin W.

    1988-01-01

    Application of active control to separated flow on the RC(6)-08 airfoil at high angle of attack by localized surface heating is numerically simulated by integrating the compressible two-dimensional nonlinear Navier-Stokes equations solver. Active control is simulated by local modification of the temperature boundary condition over a narrow strip on the upper surface of the airfoil. Both mean and perturbed profiles are favorably altered when excited with the same natural frequency of the shear layer by moderate surface heating for both laminar and turbulent separation. The shear layer is found to be very sensitive to localized surface heating in the vicinity of the separation point. The excitation field at the surface sufficiently altered both the local as well as the global circulation to cause a significant increase in lift and reduction in drag.

  1. Spatial controls of occurrence and spread of wildfires in the Missouri Ozark Highlands

    Treesearch

    Jian Yang; Hong S. He; Stephen R. Shifley

    2008-01-01

    Understanding spatial controls on wildfires is important when designing adaptive fire management plans and optimizing fuel treatment locations on a forest landscape. Previous research about this topic focused primarily on spatial controls for fire origin locations alone. Fire spread and behavior were largely overlooked. This paper contrasts the relative importance of...

  2. Cognitive processing load during listening is reduced more by decreasing voice similarity than by increasing spatial separation between target and masker speech

    PubMed Central

    Zekveld, Adriana A.; Rudner, Mary; Kramer, Sophia E.; Lyzenga, Johannes; Rönnberg, Jerker

    2014-01-01

    We investigated changes in speech recognition and cognitive processing load due to the masking release attributable to decreasing similarity between target and masker speech. This was achieved by using masker voices with either the same (female) gender as the target speech or different gender (male) and/or by spatially separating the target and masker speech using HRTFs. We assessed the relation between the signal-to-noise ratio required for 50% sentence intelligibility, the pupil response and cognitive abilities. We hypothesized that the pupil response, a measure of cognitive processing load, would be larger for co-located maskers and for same-gender compared to different-gender maskers. We further expected that better cognitive abilities would be associated with better speech perception and larger pupil responses as the allocation of larger capacity may result in more intense mental processing. In line with previous studies, the performance benefit from different-gender compared to same-gender maskers was larger for co-located masker signals. The performance benefit of spatially-separated maskers was larger for same-gender maskers. The pupil response was larger for same-gender than for different-gender maskers, but was not reduced by spatial separation. We observed associations between better perception performance and better working memory, better information updating, and better executive abilities when applying no corrections for multiple comparisons. The pupil response was not associated with cognitive abilities. Thus, although both gender and location differences between target and masker facilitate speech perception, only gender differences lower cognitive processing load. Presenting a more dissimilar masker may facilitate target-masker separation at a later (cognitive) processing stage than increasing the spatial separation between the target and masker. The pupil response provides information about speech perception that complements intelligibility data

  3. Experimental parametric study of jet vortex generators for flow separation control

    NASA Technical Reports Server (NTRS)

    Selby, Gregory

    1991-01-01

    A parametric wind-tunnel study was performed with jet vortex generators to determine their effectiveness in controlling flow separation associated with low-speed turbulence flow over a two-dimensional rearward-facing ramp. Results indicate that flow-separation control can be accomplished, with the level of control achieved being a function of jet speed, jet orientation (with respect to the free-stream direction), and orifice pattern (double row of jets vs. single row). Compared to slot blowing, jet vortex generators can provide an equivalent level of flow control over a larger spanwise region (for constant jet flow area and speed). Dye flow visualization tests in a water tunnel indicated that the most effective jet vortex generator configurations produced streamwise co-rotating vortices.

  4. Laminar and turbulent boundary layer separation control of Mako shark skin

    NASA Astrophysics Data System (ADS)

    Afroz, Farhana

    The Shortfin Mako shark (Isurus oxyrinchus) is one of the fastest swimmers in nature. They have an incredible turning agility and are estimated to achieve speeds as high as ten body lengths per second. Shark skin is known to contain flexible denticles or scales, capable of being actuated by the flow whereby a unique boundary layer control (BLC) method could reduce drag. It is hypothesized that shark scales bristle when the flow is reversed, and this bristling may serve to control flow separation by (1) inhibiting the localized flow reversal near the wall and (2) inducing mixing within the boundary layer by cavities formed between the scales that increases the momentum of the flow near the wall. To test this hypothesis, samples of Mako shark skin have been studied under various amounts of adverse pressure gradient (APG). These samples were collected from the flank region of a Shortfin Mako shark where the scales have the greatest potential for separation control due to the highest bristling angles. An easy technique for inducing boundary layer separation has been developed where an APG can be generated and varied using a rotating cylinder. Both the experimental and numerical studies showed that the amount of APG can be varied as a function of cylinder rotation speed or cylinder gap height for a wide range of Reynolds numbers. This method of generating an APG is used effectively for inducing both laminar and turbulent boundary layer separation over a flat plate. Laminar and turbulent boundary layer separation studies conducted over a smooth plate have been compared with the same setup repeated over shark skin. The time-averaged DPIV results showed that shark scale bristling controlled both laminar and turbulent boundary layer separation to a measurable extent. It shows that the shark scales cause an early transition to turbulence and reduce the degree of laminar separation. For turbulent separation, reverse flow near the wall and inside the boundary layer is

  5. Closed-loop control of flow separation using instantaneous trajectory patterns

    NASA Astrophysics Data System (ADS)

    Spohn, Andreas; Parezanović, Vladimir; Kaiser, Eurika; Cordier, Laurent; Noack, Bernd

    2014-11-01

    A new sensor technique based on visualized instantaneous trajectory patterns is tested to control flow separation. A smooth ramp mounted inside the test section of a water tunnel produces canonical separation conditions. Pulsed hydrogen bubbles furnish instantaneous trajectory patterns of the underlying dynamical system. The evolution of these patterns feeds machine learning algorithms to determine actions that reduce the separated flow region. Compared to periodic forcing the results show even with less actuator action, a major impact on the separated flow. The controlled flow states contain strongly reduced recirculation zones which remain robust even under adverse conditions. Additionally, the visualization of instantaneous trajectory patterns is shown to have some promising options: The Lagrangian coherent structures (LCS) of the controlled dynamical system can be deduced in-time without determination and integration of the instantaneous velocity fields. Additionally, classical procedures to reduce the data dimensionality, as for example the principal component analysis (PCA) and its variants, can be applied directly to the visualizations in order to feed the controller. Funding of the ANR program SepaCoDe and the ANR Chair of Excellence TUCOROM is gratefully acknowledged.

  6. Movement Precision and Amplitude as Separate Factors in the Control of Movement.

    ERIC Educational Resources Information Center

    Kerr, Robert

    The purpose of this study was to assess Welford's dual controlling factor interpretation of Fitts' Law--describing movement time as being a linear function of movement distance (or amplitude) and the required precision of the movement (or target width). Welford's amplification of the theory postulates that two separate processes ought to be…

  7. Movement Precision and Amplitude as Separate Factors in the Control of Movement.

    ERIC Educational Resources Information Center

    Kerr, Robert

    The purpose of this study was to assess Welford's dual controlling factor interpretation of Fitts' Law--describing movement time as being a linear function of movement distance (or amplitude) and the required precision of the movement (or target width). Welford's amplification of the theory postulates that two separate processes ought to be…

  8. Theoretical analysis of control mechanisms for boundary layer separation on rotocraft blades

    NASA Astrophysics Data System (ADS)

    Zou, Xiaofeng

    High maneuverability is one of the major goals in rotorcraft design. In practice, this goal is limited by unsteady (dynamic) stall near blade leading edges. Here studies of three-dimensional boundary layer separation on a rotating blade are made. For hovering flight, the blade twist and downwash are included in the effective angle of attack. For forward flight, high angles of attack are used to simulate the most severe situation at the retreating blade. Because of the disparate scales of the leading edge radius and the blade radius, separation is found to be quasi two-dimensional, and local singular behaviors at separation are very similar to the two-dimensional case. Most of the results are obtained using an Eulerian approach, but a Lagrangian formulation is used to study the behavior near the separation singularity. Control mechanisms based on suction and blade oscillations are examined. It is found that oscillations, with a tuned frequency and amplitude, can delay separation. Leading edge suction/injection is also effective in delaying separation for particular (optimized) slot locations.

  9. Kinetic crystallization separation process of the inositol isomers by controlling metastable zones

    NASA Astrophysics Data System (ADS)

    Konuki, Kaname; Hirasawa, Izumi

    2013-06-01

    D-chiro-inositol (DCI) is prepared by the immobilized enzyme reaction which uses myo-inositol (MI) as the substrate and the conversion rate is about 13%. The aim of this study was to develop a separation method for high purity DCI crystals from a reaction solution including low purity DCI only by the crystallization process. We succeeded in separating DCI crystals of 96% purity by water cooling crystallization, but it was presumed that scale-up was difficult. Although we tried anti-solvent crystallization similar to water cooling crystallization, high purity DCI crystals were not obtained. Therefore, we proposed the crystallization separation process by controlling metastable zones. The purity of a desired compound is controlled by this process, because solid-liquid separation is achieved before crystallization of compound in metastable zone. By the crystallization using this method, the DCI crystals of 97% purity were obtained. Although the yield per batch is about 50%, the actual yield is improved as the last mother liquor returns into the process of the following batch. When this process was repeated, the purity and the yield of DCI were reproduced and the robustness of this process was proved. It is expected that scale-up of this process will be successful, and this purification method could be applicable to similar systems such as separation of isomers and analogs.

  10. Vane Separation Control in a Linear Cascade with Area Expansion using AC DBD Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Kleven, Christopher; Corke, Thomas

    2013-11-01

    Experiments are presented on the use of AC dielectric barrier discharge (DBD) plasma actuators to prevent flow separation on vanes in a linear cascade with area expansion. The inlet Mach number to the cascade ranged from 0.3 to 0.5, and the vane chord Reynolds numbers ranged from 0 . 9 ×106 to 1 . 5 ×106 . Three cascade designs with different amounts of area expansion, providing different degrees of adverse pressure gradients, were examined. Surface flow visualization revealed a 3-D separation bubble with strong recirculation that formed on the suction side of the vanes. The pattern agreed well with CFD simulations. Plasma actuators were placed on the suction sides of the vanes, just upstream of the flow separation location. Quantitative measurements were performed in the wakes of the vanes using a 5-hole Pitot probe. The measurements were used to determine the effect of the plasma actuator separation control on the pressure loss coefficient, and flow turning angle through the cascades. Overall, the plasma actuators separation control increased the velocity magnitude and dynamic pressure in the passage between the vanes, resulted in a more spanwise-uniform flow turning angle in the vane passage, and significantly lowered the loss coefficient compared to the baseline.

  11. 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.

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

    PubMed

    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 4.7T 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. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Separation Control at Flight Reynolds Numbers: Lessons Learned and Future Directions

    NASA Technical Reports Server (NTRS)

    Seifert, Avi; Pack, LaTunia G.

    2000-01-01

    Active separation control, using periodic excitation, was studied experimentally at high Reynolds numbers. The effects of compressibility, mild sweep, location o excitation slot and steady momentum transfer on the efficacy of the method were identified. Tests conducted at chord Reynolds numbers as high as 40 x 10(exp 6) demonstrated that active control using oscillatory flow excitation can effectively delay flow separation from and reattach separated flow to aerodynamic surfaces at flight conditions. The effective frequencies generate one to four vortices over the controlled region at all times, regardless of the Reynolds number. The vortices are initially amplified by the separated shear-layer, and after initiating reattachment, the strength of the vortices decay as they are convected downstream. Large amplitude, low frequency vortices break down to smaller ones upon introduction at the excitation slot. The effects of steady mass transfer were compared to those of periodic excitation. It was found that steady blowing is significantly inferior to periodic excitation in terms o performance benefits and that the response to steady blowing is abrupt, and therefore undesirable from a control point of view. Steady suction and periodic excitation are comparable in effectiveness and both exhibit a gradual response to changes in the magnitude of the control input. The combination of weak steady suction and periodic excitation is extremely effective while the addition of steady blowing could be detrimental. Compressibility effects are weak as long as separation is not caused by a shock-wave/boundary-layer interaction The undesirable effects of the shock-induced separation could be alleviated by the introduction of periodic excitation upstream of the shock wave, inside the region of supersonic flow. The effects of mild sweep were also studied and periodic excitation was found to be very effective in reattaching three-dimensional separated flow. Scaling laws that correlate 2D

  14. Active Flow Separation Control of a Stator Vane Using Surface Injection in a Multistage Compressor Experiment

    NASA Technical Reports Server (NTRS)

    Culley, Dennis E.; Bright, Michelle M.; Prahst, Patricia S.; Strazisar, Anthony J.

    2003-01-01

    Micro-flow control actuation embedded in a stator vane was used to successfully control separation and improve near stall performance in a multistage compressor rig at NASA Glenn. Using specially designed stator vanes configured with internal actuation to deliver pulsating air through slots along the suction surface, a research study was performed to identify performance benefits using this microflow control approach. Pressure profiles and unsteady pressure measurements along the blade surface and at the shroud provided a dynamic look at the compressor during microflow air injection. These pressure measurements lead to a tracking algorithm to identify the onset of separation. The testing included steady air injection at various slot locations along the vane. The research also examined the benefit of pulsed injection and actively controlled air injection along the stator vane. Two types of actuation schemes were studied, including an embedded actuator for on-blade control. Successful application of an online detection and flow control scheme will be discussed. Testing showed dramatic performance benefit for flow reattachment and subsequent improvement in diffusion through the use of pulsed controlled injection. The paper will discuss the experimental setup, the blade configurations, and preliminary CFD results which guided the slot location along the blade. The paper will also show the pressure profiles and unsteady pressure measurements used to track flow control enhancement, and will conclude with the tracking algorithm for adjusting the control.

  15. Flight test evaluation of a separate surface attitude command control system on a Beech 99 airplane

    NASA Technical Reports Server (NTRS)

    Gee, S. W.; Jenks, G. E.; Roskam, J.; Stone, R. L.

    1976-01-01

    A joint NASA/university/industry program was conducted to flight evaluate a potentially low cost separate surface implementation of attitude command in a Beech 99 airplane. Saturation of the separate surfaces was the primary cause of many problems during development. Six experienced professional pilots who made simulated instrument flight evaluations experienced improvements in airplane handling qualities in the presence of turbulence and a reduction in pilot workload. For ride quality, quantitative data show that the attitude command control system results in all cases of airplane motion being removed from the uncomfortable ride region.

  16. Floating-point scaling technique for sources separation automatic gain control

    NASA Astrophysics Data System (ADS)

    Fermas, A.; Belouchrani, A.; Ait-Mohamed, O.

    2012-07-01

    Based on the floating-point representation and taking advantage of scaling factor indetermination in blind source separation (BSS) processing, we propose a scaling technique applied to the separation matrix, to avoid the saturation or the weakness in the recovered source signals. This technique performs an automatic gain control in an on-line BSS environment. We demonstrate the effectiveness of this technique by using the implementation of a division-free BSS algorithm with two inputs, two outputs. The proposed technique is computationally cheaper and efficient for a hardware implementation compared to the Euclidean normalisation.

  17. Controlling phase separation of binary Bose-Einstein condensates via mixed-spin-channel Feshbach resonance

    SciTech Connect

    Tojo, Satoshi; Taguchi, Yoshihisa; Masuyama, Yuta; Hayashi, Taro; Hirano, Takuya; Saito, Hiroki

    2010-09-15

    We investigate controlled phase separation of a binary Bose-Einstein condensate in the proximity of a mixed-spin-channel Feshbach resonance in the |F=1,m{sub F}=+1> and |F=2,m{sub F}=-1> states of {sup 87}Rb at a magnetic field of 9.10 G. Phase separation occurs on the lower-magnetic-field side of the Feshbach resonance while the two components overlap on the higher-magnetic-field side. The Feshbach resonance curve of the scattering length is obtained from the shape of the atomic cloud by comparison with the numerical analysis of coupled Gross-Pitaevskii equations.

  18. Control of Separation and Diameter of Ag Nanorods through Self-organized Seeds

    NASA Astrophysics Data System (ADS)

    Elliott, Paul R.; Stagon, Stephen P.; Huang, Hanchen

    2015-11-01

    This paper proposes a mechanism of controlling the diameter and separation of metallic nanorods from physical vapor deposition through self-organized seeds and experimentally demonstrates the feasibility using Ag as the prototype metal, In as the seed, and Si the substrate. Being non-wetting on Si substrates, deposited In atoms self-organize into islands. Subsequently deposited Ag atoms attach to In islands, rather than to Si substrates, due to preferential bonding and geometrical shadowing. The experimental results show that self-organized In seeds of 5 nm nominal thickness give rise to the best separation and the smallest diameter of Ag nanorods.

  19. Depressive-Like Behavior in Adolescents after Maternal Separation: Sex Differences, Controllability, and GABA

    PubMed Central

    Leussis, Melanie P.; Freund, Nadja; Brenhouse, Heather C.; Thompson, Britta S.; Andersen, Susan L.

    2017-01-01

    Exposure to adversity during development is an identified risk factor for depression later in life. In humans, early adversity accelerates the onset of depressive symptoms, which manifest during adolescence. Animal studies have used maternal separation as a model of early adversity to produce adult depressive-like behaviors, but have yet to examine these behaviors during adolescence. Moreover, the nature of depressive-like behaviors has not been well characterized in this model. Here, we used the triadic model of learned helplessness to understand controllability, helplessness, and motivational factors following maternal separation in male and female adolescent rats. We found sex-dependent changes in the effects of separation, with males demonstrating loss of controllability in an escapable shock condition, whereas females demonstrated motivational impairment in a no-shock condition. The effect, however, did not endure as adult females were no longer helpless. Reductions in parvalbumin, a GABAergic marker, in the prefrontal cortex of separated subjects relative to age-matched controls were evident and paralleled depressive-like behavior. Understanding the risk factors for depression, the nature of depressive-like behaviors, and their unique sex dependency may ultimately provide insight into improved treatments. PMID:22776911

  20. Effects of boundary-layer separation controllers on a desktop fume hood.

    PubMed

    Huang, Rong Fung; Chen, Jia-Kun; Hsu, Ching Min; Hung, Shuo-Fu

    2016-10-02

    A desktop fume hood installed with an innovative design of flow boundary-layer separation controllers on the leading edges of the side plates, work surface, and corners was developed and characterized for its flow and containment leakage characteristics. The geometric features of the developed desktop fume hood included a rearward offset suction slot, two side plates, two side-plate boundary-layer separation controllers on the leading edges of the side plates, a slanted surface on the leading edge of the work surface, and two small triangular plates on the upper left and right corners of the hood face. The flow characteristics were examined using the laser-assisted smoke flow visualization technique. The containment leakages were measured by the tracer gas (sulphur hexafluoride) detection method on the hood face plane with a mannequin installed in front of the hood. The results of flow visualization showed that the smoke dispersions induced by the boundary-layer separations on the leading edges of the side plates and work surface, as well as the three-dimensional complex flows on the upper-left and -right corners of the hood face, were effectively alleviated by the boundary-layer separation controllers. The results of the tracer gas detection method with a mannequin standing in front of the hood showed that the leakage levels were negligibly small (≤0.003 ppm) at low face velocities (≥0.19 m/s).

  1. Shark Skin Bristling: A Passive Flow-Actuated Separation Control Mechanism

    NASA Astrophysics Data System (ADS)

    Lang, Amy; Smith, Jonathon; Bradshaw, Michael; Wheelus, Jennifer; Motta, Philip; Habegger, Maria; Davis, Jessica; Hueter, Robert

    2012-11-01

    A collaborative experimental effort between biologists and engineers has proven the separation control capability of shark skin, with a specific focus on the shortfin mako (Isurus oxyrinchus) known for its high speed and agility. Biological measurements of the denticles, or scales, as a function of body location (DOI:10.1002/jmor.20047) will be presented together with data on bristling angle of scales and the morphological implications. Results show key regions of high bristling capability to correspond with those most prone to flow separation; these include the tail, flank regions aft of the gills, and on pectoral fins with scale flexibility increasing towards the trailing edge. Fresh shark skin samples were also tested in a water tunnel facility using DPIV and evidence of flow separation control was observed under laminar and tripped boundary layer conditions. It was concluded that the experiments conducted in the Re ~ 105 range resulted in sufficiently strong backflow induced close to the surface such that the shear threshold to induce bristling on the real skin sample was achieved since flow control at lower Re was not as evident. It is hypothesized that backflow initiated close to the wall in a region of adverse pressure gradient induces localized scale bristling thereby interrupting the subsequent flow development that leads to global flow separation from the surface and increased drag. Funding from NSF CBET grant 0932352 and US DOD AMRDEC.

  2. Proceedings of the 2004 Workshop on CFD Validation of Synthetic Jets and Turbulent Separation Control

    NASA Technical Reports Server (NTRS)

    Rumsey, Christopher L. (Compiler)

    2007-01-01

    The papers presented here are from the Langley Research Center Workshop on Computational Fluid Dynamics (CFD) Validation of Synthetic Jets and Turbulent Separation Control (nicknamed "CFDVAL2004"), held March 2004 in Williamsburg, Virginia. The goal of the workshop was to bring together an international group of CFD practitioners to assess the current capabilities of different classes of turbulent flow solution methodologies to predict flow fields induced by synthetic jets and separation control geometries. The workshop consisted of three flow-control test cases of varying complexity, and participants could contribute to any number of the cases. Along with their workshop submissions, each participant included a short write-up describing their method for computing the particular case(s). These write-ups are presented as received from the authors with no editing. Descriptions of each of the test cases and experiments are also included.

  3. Active Control of Separation From the Flap of a Supercritical Airfoil

    NASA Technical Reports Server (NTRS)

    Melton, La Tunia Pack; Yao, Chung-Sheng; Seifert, Avi

    2003-01-01

    Active flow control in the form of periodic zero-mass-flux excitation was applied at several regions on the leading edge and trailing edge flaps of a simplified high-lift system t o delay flow separation. The NASA Energy Efficient Transport (EET) supercritical airfoil was equipped with a 15% chord simply hinged leading edge flap and a 25% chord simply hinged trailing edge flap. Detailed flow features were measured in an attempt to identify optimal actuator placement. The measurements included steady and unsteady model and tunnel wall pressures, wake surveys, arrays of surface hot-films, flow visualization, and particle image velocimetry (PIV). The current paper describes the application of active separation control at several locations on the deflected trailing edge flap. High frequency (F(+) approx.= 10) and low frequency amplitude modulation (F(+)AM approx.= 1) of the high frequency excitation were used for control. Preliminary efforts to combine leading and trailing edge flap excitations are also reported.

  4. Active Flow Control and Global Stability Analysis of Separated Flow Over a NACA 0012 Airfoil

    NASA Astrophysics Data System (ADS)

    Munday, Phillip M.

    The objective of this computational study is to examine and quantify the influence of fundamental flow control inputs in suppressing flow separation over a canonical airfoil. Most flow control studies to this date have relied on the development of actuator technology, and described the control input based on specific actuators. Taking advantage of a computational framework, we generalize the inputs to fundamental perturbations without restricting inputs to a particular actuator. Utilizing this viewpoint, generalized control inputs aim to aid in the quantification and support the design of separation control techniques. This study in particular independently introduces wall-normal momentum and angular momentum to the separated flow using swirling jets through model boundary conditions. The response of the flow field and the surface vorticity fluxes to various combinations of actuation inputs are examined in detail. By closely studying different variables, the influence of the wall-normal and angular momentum injections on separated flow is identified. As an example, open-loop control of fully separated, incompressible flow over a NACA 0012 airfoil at alpha = 6° and 9° with Re = 23,000 is examined with large-eddy simulations. For the shallow angle of attack alpha = 6°, the small recirculation region is primarily affected by wall-normal momentum injection. For a larger separation region at alpha = 9°, it is observed that the addition of angular momentum input to wall-normal momentum injection enhances the suppression of flow separation. Reducing the size of the separated flow region significantly impacts the forces, and in particular reduces drag and increases lift on the airfoil. It was found that the influence of flow control on the small recirculation region (alpha = 6°) can be sufficiently quantified with the traditional coefficient of momentum. At alpha = 9°, the effects of wall-normal and angular momentum inputs are captured by modifying the standard

  5. ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS: Entanglement Properties Between Two Spatially Separated Atoms with Cascade Configuration in Free Space

    NASA Astrophysics Data System (ADS)

    Yang, Guo-Hui; Zhang, Jun-Feng; Miao, Xiang-Yang; Zhou, Ling

    2010-03-01

    We investigate the entanglement properties between two identical atoms with cascade configuration through the retarded dipole-dipole interaction in free space when their spatial separation is on the order of radiation wavelength or less. We analyze the function of Hamiltonian induced by dipole-dipole interaction. By solving master equation, we show that the spontaneous emission induce entanglement and destroy entanglement too. We also show the long life time of entanglement within cascade configuration.

  6. Abiotic and biotic controls of spatial pattern at alpine treeline

    USGS Publications Warehouse

    Malanson, George P.; Xiao, Ningchuan; Alftine, K.J.; Bekker, Mathew; Butler, David R.; Brown, Daniel G.; Cairns, David M.; Fagre, Daniel; Walsh, Stephen J.

    2000-01-01

    At alpine treeline, trees and krummholz forms affect the environment in ways that increase their growth and reproduction. We assess the way in which these positive feedbacks combine in spatial patterns to alter the environment in the neighborhood of existing plants. The research is significant because areas of alpine tundra are susceptible to encroachment by woody species as climate changes. Moreover, understanding the general processes of plant invasion is important. The importance of spatial pattern has been recognized, but the spatial pattern of positive feedbacks per se has not been explored in depth. We present a linked set of models of vegetation change at an alpine forest-tundra ecotone. Our aim is to create models that are as simple as possible in order to test specific hypotheses. We present results from a model of the resource averaging hypothesis and the positive feedback switch hypothesis of treelines. We compare the patterns generated by the models to patterns observed in fine scale remotely sensed data.

  7. Feedback control of chromosome separation by a midzone Aurora B gradient.

    PubMed

    Afonso, Olga; Matos, Irina; Pereira, António J; Aguiar, Paulo; Lampson, Michael A; Maiato, Helder

    2014-07-18

    Accurate chromosome segregation during mitosis requires the physical separation of sister chromatids before nuclear envelope reassembly (NER). However, how these two processes are coordinated remains unknown. Here, we identified a conserved feedback control mechanism that delays chromosome decondensation and NER in response to incomplete chromosome separation during anaphase. A midzone-associated Aurora B gradient was found to monitor chromosome position along the division axis and to prevent premature chromosome decondensation by retaining Condensin I. PP1/PP2A phosphatases counteracted this gradient and promoted chromosome decondensation and NER. Thus, an Aurora B gradient appears to mediate a surveillance mechanism that prevents chromosome decondensation and NER until effective separation of sister chromatids is achieved. This allows the correction and reintegration of lagging chromosomes in the main nuclei before completion of NER.

  8. Separation control over an airfoil at high angles of attack by sound emanating from the surface

    NASA Technical Reports Server (NTRS)

    Huang, L. S.; Maestrello, L.; Bryant, T. D.

    1987-01-01

    Active control by sound emanating from a narrow gap in the vicinity of the leading edge of a symmetrical airfoil is used to study the influence of sound on the pressure distribution and the wake at high angles of attack. The results from experiments conducted at a Reynolds number based on the chord of 35,000 show that, with injection of sound at twice the shedding frequency of the shear layer, the region of separation becomes drastically reduced. The shear layer is found to be very sensitive to sound excitation in the vicinity of the separation point. The excitation sufficiently alters the global circulation to cause an increase in lift and reduction in drag. Furthermore, experimental results describing stall and post-stall conditions compare well with the limited data available and indicate that stall is delayed by sound injection into the separated region.

  9. The control system of the CERN-ISOLDE on-line mass-separator facility

    NASA Astrophysics Data System (ADS)

    Jonsson, O. C.; Borch, O.; Bret, A.; Catherall, R.; Deloose, I.; Focker, G. J.; Forkel, D.; Kugler, E.; Olesen, G.; Pace, A.; Ravn, H. L.; Richard-Serre, C.; Shering, G.; Tengblad, O.; Torgersen, H. J.; Isolde Collaboration

    1992-08-01

    With the move of the ISOLDE facility to the PS-Booster from the now closed Synchro-Cyclotron at CERN, a new control system will be implemented for the two separators. Personal computers, based on the Intel 80386 microprocessor running under MS-DOS and Microsoft Windows, are used. Network-wide distributed front end computers, which access the hardware for controls and measurements, are controlled by PC-consoles via a local area network with a PC file server used as a database.

  10. Controlling the spatial arrangement of organic magnetic anions adsorbed on epitaxial graphene on Ru(0001).

    PubMed

    Stradi, Daniele; Garnica, Manuela; Díaz, Cristina; Calleja, Fabián; Barja, Sara; Martín, Nazario; Alcamí, Manuel; Vazquez de Parga, Amadeo L; Miranda, Rodolfo; Martín, Fernando

    2014-12-21

    Achieving control over the self-organization of functional molecules on graphene is critical for the development of graphene technology in organic electronic and spintronic. Here, by using a scanning tunneling microscope (STM), we show that the electron acceptor molecule 7,7',8,8'-tetracyano-p-quinodimethane (TCNQ) and its fluorinated derivative 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyano-p-quinodimethane (F4-TCNQ), co-deposited on the surface of epitaxial graphene on Ru(0001), transform spontaneously into their corresponding magnetic anions and self-organize in two remarkably different structures. TCNQ forms densely packed linear magnetic arrays, while F4-TCNQ molecules remain as isolated non interacting magnets. With the help of density functional theory (DFT) calculations, we trace back the origin of this behavior in the competition between the intermolecular repulsion experienced by the individual charged anions, which tends to separate the molecules, and the delocalization of the electrons transferred from the surface to the molecules, which promotes the formation of molecular oligomers. Our results demonstrate that it is possible to control the spatial arrangement of organic magnetic anions co-adsorbed on a surface by means of chemical substitution, paving the way for the design of two-dimensional fully organic magnetic structures on graphene and on other surfaces.

  11. The Automatic and Controlled Processing of Temporal and Spatial Patterns.

    DTIC Science & Technology

    1980-02-01

    Schneider, 1977; Laberge , 1973, 1975). There is a need to expand automatic processing to inputs where an event is defined by a sequence of stimuli. In this...that found by LaBerge (1973). In the LaBerge experiment, subjects were tested on both familiar and unfamiliar characters. For the familiar characters... LaBerge argued that the separate features were unitized into letters automatically. For unfamiliar characters, subjects could not initially

  12. A Matter of Balance: Motor Control is Related to Children's Spatial and Proportional Reasoning Skills.

    PubMed

    Frick, Andrea; Möhring, Wenke

    2015-01-01

    Recent research has shown close links between spatial and mathematical thinking and between spatial abilities and motor skills. However, longitudinal research examining the relations between motor, spatial, and mathematical skills is rare, and the nature of these relations remains unclear. The present study thus investigated the relation between children's motor control and their spatial and proportional reasoning. We measured 6-year-olds' spatial scaling (i.e., the ability to reason about different-sized spaces), their mental transformation skills, and their ability to balance on one leg as an index for motor control. One year later (N = 126), we tested the same children's understanding of proportions. We also assessed several control variables (verbal IQ and socio-economic status) as well as inhibitory control, visuo-spatial and verbal working memory. Stepwise hierarchical regressions showed that, after accounting for effects of control variables, children's balance skills significantly increased the explained variance in their spatial performance and proportional reasoning. Our results suggest specific relations between balance skills and spatial as well as proportional reasoning skills that cannot be explained by general differences in executive functioning or intelligence.

  13. Thinking in spatial terms: decoupling spatial representation from sensorimotor control in monkey posterior parietal areas 7a and LIP.

    PubMed

    Chafee, Matthew V; Crowe, David A

    2012-01-01

    Perhaps the simplest and most complete description of the cerebral cortex is that it is a sensorimotor controller whose primary purpose is to represent stimuli and movements, and adaptively control the mapping between them. However, in order to think, the cerebral cortex has to generate patterns of neuronal activity that encode abstract, generalized information independently of ongoing sensorimotor events. A critical question confronting cognitive systems neuroscience at present therefore is how neural signals encoding abstract information emerge within the sensorimotor control networks of the brain. In this review, we approach that question in the context of the neural representation of space in posterior parietal cortex of non-human primates. We describe evidence indicating that parietal cortex generates a hierarchy of spatial representations with three basic levels: including (1) sensorimotor signals that are tightly coupled to stimuli or movements, (2) sensorimotor signals modified in strength or timing to mediate cognition (examples include attention, working memory, and decision-processing), as well as (3) signals that encode frankly abstract spatial information (such as spatial relationships or categories) generalizing across a wide diversity of specific stimulus conditions. Here we summarize the evidence for this hierarchy, and consider data showing that signals at higher levels derive from signals at lower levels. That in turn could help characterize neural mechanisms that derive a capacity for abstraction from sensorimotor experience.

  14. Thinking in spatial terms: decoupling spatial representation from sensorimotor control in monkey posterior parietal areas 7a and LIP

    PubMed Central

    Chafee, Matthew V.; Crowe, David A.

    2013-01-01

    Perhaps the simplest and most complete description of the cerebral cortex is that it is a sensorimotor controller whose primary purpose is to represent stimuli and movements, and adaptively control the mapping between them. However, in order to think, the cerebral cortex has to generate patterns of neuronal activity that encode abstract, generalized information independently of ongoing sensorimotor events. A critical question confronting cognitive systems neuroscience at present therefore is how neural signals encoding abstract information emerge within the sensorimotor control networks of the brain. In this review, we approach that question in the context of the neural representation of space in posterior parietal cortex of non-human primates. We describe evidence indicating that parietal cortex generates a hierarchy of spatial representations with three basic levels: including (1) sensorimotor signals that are tightly coupled to stimuli or movements, (2) sensorimotor signals modified in strength or timing to mediate cognition (examples include attention, working memory, and decision-processing), as well as (3) signals that encode frankly abstract spatial information (such as spatial relationships or categories) generalizing across a wide diversity of specific stimulus conditions. Here we summarize the evidence for this hierarchy, and consider data showing that signals at higher levels derive from signals at lower levels. That in turn could help characterize neural mechanisms that derive a capacity for abstraction from sensorimotor experience. PMID:23355813

  15. Active Flow Separation Control on a NACA 0015 Wing Using Fluidic Actuators

    NASA Technical Reports Server (NTRS)

    Melton, Latunia P.

    2014-01-01

    Results are presented from a recent set of wind tunnel experiments using sweeping jet actuators to control ow separation on the 30% chord trailing edge ap of a 30 deg. swept wing model with an aspect ratio (AR) of 4.35. Two sweeping jet actuator locations were examined, one on the flap shoulder and one on the trailing edge flap. The parameters that were varied included actuator momentum, freestream velocity, and trailing edge flap deflection (Delta f ) angle. The primary focus of this set of experiments was to determine the mass flow and momentum requirements for controlling separation on the flap, especially at large flap deflection angles which would be characteristic of a high lift system. Surface pressure data, force and moment data, and stereoscopic particle image velocimetry (PIV) data were acquired to evaluate the performance benefits due to applying active flow control. Improvements in lift over the majority of the wing span were obtained using sweeping jet actuator control. High momentum coefficient, Cu, levels were needed when using the actuators on the ap because they were located downstream of separation. Actuators on the flap shoulder performed slightly better but actuator size, orientation, and spacing still need to be optimized.

  16. Flow Separation Control on A Full-Scale Vertical Tail Model Using Sweeping Jet Actuators

    NASA Technical Reports Server (NTRS)

    Andino, Marlyn Y.; Lin, John C.; Washburn, Anthony E.; Whalen, Edward A.; Graff, Emilio C.; Wygnanski, Israel J.

    2015-01-01

    This paper describes test results of a joint NASA/Boeing research effort to advance Active Flow Control (AFC) technology to enhance aerodynamic efficiency. A full-scale Boeing 757 vertical tail model equipped with sweeping jets AFC was tested at the National Full-Scale Aerodynamics Complex 40- by 80-Foot Wind Tunnel at NASA Ames Research Center. The flow separation control optimization was performed at 100 knots, a maximum rudder deflection of 30deg, and sideslip angles of 0deg and -7.5deg. Greater than 20% increments in side force were achieved at the two sideslip angles with a 31-actuator AFC configuration. Flow physics and flow separation control associated with the AFC are presented in detail. AFC caused significant increases in suction pressure on the actuator side and associated side force enhancement. The momentum coefficient (C sub mu) is shown to be a useful parameter to use for scaling-up sweeping jet AFC from sub-scale tests to full-scale applications. Reducing the number of actuators at a constant total C(sub mu) of approximately 0.5% and tripling the actuator spacing did not significantly affect the flow separation control effectiveness.

  17. Parental psychological control and dysfunctional separation-individuation: a tale of two different dynamics.

    PubMed

    Kins, Evie; Soenens, Bart; Beyers, Wim

    2012-10-01

    This study examined associations between psychologically controlling parenting and two possible manifestations of problematic separation-individuation (i.e., dysfunctional dependence and dysfunctional independence). To explain these associations, it has been argued that psychological control is an inherently independence-stifling parenting dimension that gives rise to a dysfunctional dependent orientation. In this study, it was argued that psychological control may relate to dysfunctional dependence and dysfunctional independence, depending on whether parents' use of psychological control is driven by issues of interpersonal closeness (i.e., dependency-oriented psychological control) or by issues of achievement (i.e., achievement-oriented psychological control). A Belgian sample of 232 emerging adults, involved in the process of home leaving, and their parents completed self-report questionnaires. Regression analyses indicated that domain-specific expressions of psychological control were related differentially to dysfunctional dependent and dysfunctional independent manifestations of problematic separation-individuation. Emerging adults' residential status did not moderate these associations. Implications and directions for future research are discussed. Copyright © 2012 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.

  18. On the properties and mechanisms of microjet arrays in crossflow for the control of flow separation

    NASA Astrophysics Data System (ADS)

    Fernandez, Erik J.

    By utilizing passive and active methods of flow control, the aerodynamic performance of external and internal components can be greatly improved. Recently however, the benefits of applying active flow control methods to turbomachinery components for improved fuel efficiency, reduced engine size, and greater operational envelope has sparked a renewed interest in some of these flow control techniques. The more attractive of these, is active control in the form of jets in cross flow. With their ability to be turned on and off, as well as their negligible effect on drag when not being actuated, they are well suited for applications such as compressor and turbine blades, engine inlet diffusers, internal engine passages, and general external aerodynamics. This study consists of two parts. The first is the application of active control on a low-pressure turbine (LPT) cascade to determine the effectiveness of microjet actuators on flow separation at relatively low speeds. The second study, motivated by the first, involves a parametric study on a more canonical model to examine the effects of various microjet parameters on the efficacy of separation control and to provide a better understanding of the relevant flow physics governing this control approach. With data obtained from velocity measurements across the wide parametric range, correlations for the growth of the counter-rotating vortex pairs generated by these actuators are deduced. From the information and models obtained throughout the study, basic suggestions for microjet actuator design are presented.

  19. Modelling aspects regarding the control in 13C isotope separation column

    NASA Astrophysics Data System (ADS)

    Boca, M. L.

    2016-08-01

    Carbon represents the fourth most abundant chemical element in the world, having two stable and one radioactive isotope. The 13Carbon isotopes, with a natural abundance of 1.1%, plays an important role in numerous applications, such as the study of human metabolism changes, molecular structure studies, non-invasive respiratory tests, Alzheimer tests, air pollution and global warming effects on plants [9] A manufacturing control system manages the internal logistics in a production system and determines the routings of product instances, the assignment of workers and components, the starting of the processes on not-yet-finished product instances. Manufacturing control does not control the manufacturing processes themselves, but has to cope with the consequences of the processing results (e.g. the routing of products to a repair station). In this research it was fulfilled some UML (Unified Modelling Language) diagrams for modelling the C13 Isotope Separation column, implement in STARUML program. Being a critical process and needing a good control and supervising, the critical parameters in the column, temperature and pressure was control using some PLC (Programmable logic controller) and it was made some graphic analyze for this to observe some critical situation than can affect the separation process. The main parameters that need to be control are: -The liquid nitrogen (N2) level in the condenser. -The electrical power supplied to the boiler. -The vacuum pressure.

  20. Spatial separation of photogenerated electrons and holes among {010} and {110} crystal facets of BiVO4

    NASA Astrophysics Data System (ADS)

    Li, Rengui; Zhang, Fuxiang; Wang, Donge; Yang, Jingxiu; Li, Mingrun; Zhu, Jian; Zhou, Xin; Han, Hongxian; Li, Can

    2013-02-01

    Charge separation is crucial for increasing the activity of semiconductor-based photocatalysts, especially in water splitting reactions. Here we show, using monoclinic bismuth vanadate crystal as a model photocatalyst, that efficient charge separation can be achieved on different crystal facets, as evidenced by the reduction reaction with photogenerated electrons and oxidation reaction with photogenerated holes, which take place separately on the {010} and {110} facets under photo-irradiation. Based on this finding, the reduction and oxidation cocatalysts are selectively deposited on the {010} and {110} facets respectively, resulting in much higher activity in both photocatalytic and photoelectrocatalytic water oxidation reactions, compared with the photocatalyst with randomly distributed cocatalysts. These results show that the photogenrated electrons and holes can be separated between the different facets of semiconductor crystals. This finding may be useful in semiconductor physics and chemistry to construct highly efficient solar energy conversion systems.

  1. Spatial separation of photogenerated electrons and holes among {010} and {110} crystal facets of BiVO4.

    PubMed

    Li, Rengui; Zhang, Fuxiang; Wang, Donge; Yang, Jingxiu; Li, Mingrun; Zhu, Jian; Zhou, Xin; Han, Hongxian; Li, Can

    2013-01-01

    Charge separation is crucial for increasing the activity of semiconductor-based photocatalysts, especially in water splitting reactions. Here we show, using monoclinic bismuth vanadate crystal as a model photocatalyst, that efficient charge separation can be achieved on different crystal facets, as evidenced by the reduction reaction with photogenerated electrons and oxidation reaction with photogenerated holes, which take place separately on the {010} and {110} facets under photo-irradiation. Based on this finding, the reduction and oxidation cocatalysts are selectively deposited on the {010} and {110} facets respectively, resulting in much higher activity in both photocatalytic and photoelectrocatalytic water oxidation reactions, compared with the photocatalyst with randomly distributed cocatalysts. These results show that the photogenrated electrons and holes can be separated between the different facets of semiconductor crystals. This finding may be useful in semiconductor physics and chemistry to construct highly efficient solar energy conversion systems.

  2. Gravity packaging final waste recovery based on gravity separation and chemical imaging control.

    PubMed

    Bonifazi, Giuseppe; Serranti, Silvia; Potenza, Fabio; Luciani, Valentina; Di Maio, Francesco

    2017-02-01

    Plastic polymers are characterized by a high calorific value. Post-consumer plastic waste can be thus considered, in many cases, as a typical secondary solid fuels according to the European Commission directive on End of Waste (EoW). In Europe the practice of incineration is considered one of the solutions for waste disposal waste, for energy recovery and, as a consequence, for the reduction of waste sent to landfill. A full characterization of these products represents the first step to profitably and correctly utilize them. Several techniques have been investigated in this paper in order to separate and characterize post-consumer plastic packaging waste fulfilling the previous goals, that is: gravity separation (i.e. Reflux Classifier), FT-IR spectroscopy, NIR HyperSpectralImaging (HSI) based techniques and calorimetric test. The study demonstrated as the proposed separation technique and the HyperSpectral NIR Imaging approach allow to separate and recognize the different polymers (i.e. PolyVinyl Chloride (PVC), PolyStyrene (PS), PolyEthylene (PE), PoliEtilene Tereftalato (PET), PolyPropylene (PP)) in order to maximize the removal of the PVC fraction from plastic waste and to perform the full quality control of the resulting products, can be profitably utilized to set up analytical/control strategies finalized to obtain a low content of PVC in the final Solid Recovered Fuel (SRF), thus enhancing SRF quality, increasing its value and reducing the "final waste". Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Separation control in a hypersonic shock wave / turbulent boundary-layer interaction

    NASA Astrophysics Data System (ADS)

    Schreyer, Anne-Marie; Bermejo-Moreno, Ivan; Kim, Jeonglae; Urzay, Javier

    2016-11-01

    Hypersonic vehicles play a key role for affordable access to space. The associated flow fields are strongly affected by shock wave/turbulent boundary-layer interactions, and the inherent separation causes flow distortion and low-frequency unsteadiness. Microramp sub-boundary layer vortex generators are a promising means to control separation and diminish associated detrimental effects. We investigate the effect of a microramp on the low-frequency unsteadiness in a fully separated interaction. A large eddy simulation of a 33 ∘ -compression-ramp interaction was performed for an inflow Mach number of 7.2 and a Reynolds number based on momentum thickness of Reθ = 3500 , matching the experiment of Schreyer et al. (2011). For the control case, we introduced a counter-rotating vortex pair, as induced by a single microramp, into the boundary layer through the inflow conditions. We applied a dynamic mode decomposition (DMD) on both cases to identify coherent structures that are responsible for the dynamic behavior. Based on the DMD, we discuss the reduction of the separation zone and the stabilization of the shock motion achieved by the microramp, and contribute to the description of the governing mechanisms. Pursued during the 2016 CTR Summer Program at Stanford University.

  4. Characterization and Control of Separated Entrance Flow in a Branched Channel

    NASA Astrophysics Data System (ADS)

    Peterson, C. J.; Vukasinovic, B.; Glezer, A.

    2015-11-01

    The evolution of the flow downstream of the inlet of a rectangular channel that is branched along the entire span of the side wall of a primary channel of the same height is investigated experimentally in an air facility. Of particular interest is the formation and scaling of a separated flow domain downstream of the entrance plane into the secondary channel and its interaction with the flow surfaces at speeds up to M = 0 . 4 . The separation is actively controlled using a spanwise array of fluidic actuators on the primary channel's surface upstream of the inlet plane of the secondary duct. The effects of the actuation on the evolution of the separation and attachment of the vorticity layer between upstream surface of the primary duct and the surface of the secondary duct downstream of the branched inlet in the presence of a strong confined adverse pressure gradient are investigated using particle image velocimetry coupled with detailed static surface pressure distributions. The effects of the controlled separation within the secondary channel on the global flow within the primary duct and on flow split between primary and secondary channels are assessed, and it is demonstrated that actuation can effect significant changes in the flow fractions between the channels. Copyright 2015 Boeing. All rights reserved.

  5. Enhanced reliable transmission control protocol for spatial information networks

    NASA Astrophysics Data System (ADS)

    Qin, Zhihong; Zhang, Juan; Wang, Junfeng

    2009-12-01

    Satellites channels are generally featured by high bit error rate (BER), long propagation delay, large bandwidth-delay product (BDP) and so on. This tends to make the traditional TCP suffer from serious performance degradation in satellite networks. Therefore, a TCP-compatible reliable transmission protocol (i.e., TCP-AX) for spatial information networks is proposed in this paper. And a bandwidth probing mechanism is designed to distinguish network congestion and link error. Simulation results show that TCP-AX has better performance than some popular enhanced TCP protocols.

  6. Compressive Feedback Control Design for Spatially Distributed Systems

    DTIC Science & Technology

    2017-01-03

    i.e., ρ ( N (LG) ) = ρ ( N (ULGUT ) ) , for all orthogonal matrices UUT = UTU = In. Hp–based Schur–convex systemic measures: For a given linear...G = Z and the state-space operators of system ψ̇(t) = Aψ(t) + Bu(t), (11) y(t) = Cψ(t) + Du(t) (12) are infinite-dimensional matrices . In order to...admissible coupling weight function w, the class of matrices Sq,w(Z) consists of all spatially decaying matrices A = ( aij ) i,j∈Z such that A is

  7. A and D genomes spatial separation at somatic metaphase in tetraploid cotton: evidence for genomic disposition in a polyploid plant.

    PubMed

    Han, Jinlei; Zhou, Baoliang; Shan, Wenbo; Yu, Liying; Wu, Weiren; Wang, Kai

    2015-12-01

    Chromosomal dispositions were analyzed on the metaphase plate of tetraploid cotton (AADD). At metaphase, the two subgenomes, A and D, were separated in a radial pattern in which the small D subgenome chromosomes tended to concentrate at the center and the large A subgenome chromosomes were scattered about the periphery on the metaphase plate. Although the ordered chromosome arrangement was disturbed in an artificial hexaploid (AADDGG), the separation pattern could be recovered after the majority of the additional genome (GG) chromosomes were removed by backcrossing the artificial hexaploid with the tetraploid cotton (AADD). A similar genome separation phenomenon was also found in synthesized tetraploid cotton (AAGG). These results indicate that the genome separation pattern could be established immediately after tetraploid cotton formation and could be stably inherited in tetraploid cotton. Given the evidence of parental genome separation in other plants and animals, we speculated that genome separation might be a normal phenomenon in diploid and polyploid species. These finding will shed light on the chromosome conformation in plant cells.

  8. Separation-Compliant, Optimal Routing and Control of Scheduled Arrivals in a Terminal Airspace

    NASA Technical Reports Server (NTRS)

    Sadovsky, Alexander V.; Davis, Damek; Isaacson, Douglas R.

    2013-01-01

    We address the problem of navigating a set (fleet) of aircraft in an aerial route network so as to bring each aircraft to its destination at a specified time and with minimal distance separation assured between all aircraft at all times. The speed range, initial position, required destination, and required time of arrival at destination for each aircraft are assumed provided. Each aircraft's movement is governed by a controlled differential equation (state equation). The problem consists in choosing for each aircraft a path in the route network and a control strategy so as to meet the constraints and reach the destination at the required time. The main contribution of the paper is a model that allows to recast this problem as a decoupled collection of problems in classical optimal control and is easily generalized to the case when inertia cannot be neglected. Some qualitative insight into solution behavior is obtained using the Pontryagin Maximum Principle. Sample numerical solutions are computed using a numerical optimal control solver. The proposed model is first step toward increasing the fidelity of continuous time control models of air traffic in a terminal airspace. The Pontryagin Maximum Principle implies the polygonal shape of those portions of the state trajectories away from those states in which one or more aircraft pair are at minimal separation. The model also confirms the intuition that, the narrower the allowed speed ranges of the aircraft, the smaller the space of optimal solutions, and that an instance of the optimal control problem may not have a solution at all (i.e., no control strategy that meets the separation requirement and other constraints).

  9. Contact guidance requires spatial control of leading-edge protrusion

    PubMed Central

    Ramirez-San Juan, G. R.; Oakes, P. W.; Gardel, M. L.

    2017-01-01

    In vivo, geometric cues from the extracellular matrix (ECM) are critical for the regulation of cell shape, adhesion, and migration. During contact guidance, the fibrillar architecture of the ECM promotes an elongated cell shape and migration along the fibrils. The subcellular mechanisms by which cells sense ECM geometry and translate it into changes in shape and migration direction are not understood. Here we pattern linear fibronectin features to mimic fibrillar ECM and elucidate the mechanisms of contact guidance. By systematically varying patterned line spacing, we show that a 2-μm spacing is sufficient to promote cell shape elongation and migration parallel to the ECM, or contact guidance. As line spacing is increased, contact guidance increases without affecting migration speed. To elucidate the subcellular mechanisms of contact guidance, we analyze quantitatively protrusion dynamics and find that the structured ECM orients cellular protrusions parallel to the ECM. This spatial organization of protrusion relies on myosin II contractility, and feedback between adhesion and Rac-mediated protrusive activity, such that we find Arp2/3 inhibition can promote contact guidance. Together our data support a model for contact guidance in which the ECM enforces spatial constraints on the lamellipodia that result in cell shape elongation and enforce migration direction. PMID:28228548

  10. Contact guidance requires spatial control of leading-edge protrusion.

    PubMed

    Ramirez-San Juan, G R; Oakes, P W; Gardel, M L

    2017-04-15

    In vivo, geometric cues from the extracellular matrix (ECM) are critical for the regulation of cell shape, adhesion, and migration. During contact guidance, the fibrillar architecture of the ECM promotes an elongated cell shape and migration along the fibrils. The subcellular mechanisms by which cells sense ECM geometry and translate it into changes in shape and migration direction are not understood. Here we pattern linear fibronectin features to mimic fibrillar ECM and elucidate the mechanisms of contact guidance. By systematically varying patterned line spacing, we show that a 2-μm spacing is sufficient to promote cell shape elongation and migration parallel to the ECM, or contact guidance. As line spacing is increased, contact guidance increases without affecting migration speed. To elucidate the subcellular mechanisms of contact guidance, we analyze quantitatively protrusion dynamics and find that the structured ECM orients cellular protrusions parallel to the ECM. This spatial organization of protrusion relies on myosin II contractility, and feedback between adhesion and Rac-mediated protrusive activity, such that we find Arp2/3 inhibition can promote contact guidance. Together our data support a model for contact guidance in which the ECM enforces spatial constraints on the lamellipodia that result in cell shape elongation and enforce migration direction.

  11. Numerical Study of Control of Flow Separation Over a Ramp with Nanosecond Plasma Actuator

    NASA Astrophysics Data System (ADS)

    Zheng, J. G.; Khoo, B. C.; Cui, Y. D.; Zhao, Z. J.; Li, J.

    2016-06-01

    The nanosecond plasma discharge actuator driven by high voltage pulse with typical rise and decay time of several to tens of nanoseconds is emerging as a promising active flow control means in recent years and is being studied intensively. The characterization study reveals that the discharge induced shock wave propagates through ambient air and introduces highly transient perturbation to the flow. On the other hand, the residual heat remaining in the discharge volume may trigger the instability of external flow. In this study, this type of actuator is used to suppress flow separation over a ramp model. Numerical simulation is carried out to investigate the interaction of the discharge induced disturbance with the external flow. It is found that the flow separation region over the ramp can be reduced significantly. Our work may provide some insights into the understanding of the control mechanism of nanosecond pulse actuator.

  12. Controlling the intermediate structure of an ionic liquid for f-block element separations

    DOE PAGES

    Abney, Carter W.; Do, Changwoo; Luo, Huimin; ...

    2017-04-19

    Recent research has revealed molecular structure beyond the inner coordination sphere is essential in defining the performance of separations processes, but nevertheless remains largely unexplored. Here we apply small angle neutron scattering (SANS) and x-ray absorption fine structure (XAFS) spectroscopy to investigate the structure of an ionic liquid system studied for f-block element separations. SANS data reveal dramatic changes in the ionic liquid microstructure (~150 Å) which we demonstrate can be controlled by judicious selection of counter ion. Mesoscale structural features (> 500 Å) are also observed as a function of metal concentration. XAFS analysis supports formation of extended aggregatemore » structures, similar to those observed in traditional solvent extraction processes, and suggest additional parallels may be drawn from further study. As a result, achieving precise tunability over the intermediate features is an important development in controlling mesoscale structure and realizing advanced new forms of soft matter.« less

  13. An investigation of passive control methods for shock-induced separation at hypersonic speeds

    NASA Technical Reports Server (NTRS)

    Rallo, R.; Walsh, M.; Van Leer, Bram

    1992-01-01

    The effectiveness of several passive control techniques on shock-induced boundary-layer separation at hypersonic speed was investigated. Two approaches for alleviating the turbulent separation losses were examined: porous surface mass transfer and surface grooving. A total of four perforated surfaces with varying porosities were evaluated, and three groove orientations with respect to the freestream direction were studied. A comparison of the results from passive control techniques with those from an 'uncontrolled' shock impingement showed that the porous surface with the greatest porosity provided the greatest reduction in the pressure rise across the oblique shock wave. The grooved surface tested were found to be not effective; each of the grooved configurations examined increased the peak pressure value.

  14. Spatiotemporal control of apical and basal living subcellular chemical environments through vertical phase separation.

    PubMed

    Yang, Jui-Ming; Didier, Jonathan E; Cassino, Theresa R; LeDuc, Philip R

    2009-09-01

    Molecular distribution within living cells is organized through multiscaled compartmentalization that enables specialized processes to occur with high efficiency. The ability to control the chemical environment at a subcellular level is limited due to deficient positional control over the aqueous stimulant. Here, a multilayered microfluidic system built from polydimethylsiloxane to separate chemical stimulants over single living cells vertically through aqueous-phase separation under laminar flow is demonstrated. Cells are cultured on top of single micrometer-scale channels inside a larger channel, allowing labeling of the apical domain of single cells through the main channel with simultaneous and distinct labeling of the basal domain via the lower microchannels. The system is transparent, which allows the use of optical microscopy to investigate the spatiotemporal response of labeled components. By employing this technique, the examination of localized subcellular domain responses in polarization, lipid bilayer mobility, and apical-to-basal signal transduction can be explored.

  15. ABOVE- AND BELOWGROUND CONTROLS ON FOREST TREE GROWTH, MORTALITY AND SPATIAL PATTERN

    EPA Science Inventory

    We investigated the relative importance of above- and belowground competition in controlling growth, mortality and spatial patterns of trees in a nitrogen-limited, old-growth forest in western Oregon. To assess the effects of competition for light, we applied a spatially-explici...

  16. ABOVE- AND BELOWGROUND CONTROLS ON FOREST TREE GROWTH, MORTALITY AND SPATIAL PATTERN

    EPA Science Inventory

    We investigated the relative importance of above- and belowground competition in controlling growth, mortality and spatial patterns of trees in a nitrogen-limited, old-growth forest in western Oregon. To assess the effects of competition for light, we applied a spatially-explici...

  17. Optimal Control Modification Adaptive Law for Time-Scale Separated Systems

    NASA Technical Reports Server (NTRS)

    Nguyen, Nhan T.

    2010-01-01

    Recently a new optimal control modification has been introduced that can achieve robust adaptation with a large adaptive gain without incurring high-frequency oscillations as with the standard model-reference adaptive control. This modification is based on an optimal control formulation to minimize the L2 norm of the tracking error. The optimal control modification adaptive law results in a stable adaptation in the presence of a large adaptive gain. This study examines the optimal control modification adaptive law in the context of a system with a time scale separation resulting from a fast plant with a slow actuator. A singular perturbation analysis is performed to derive a modification to the adaptive law by transforming the original system into a reduced-order system in slow time. A model matching conditions in the transformed time coordinate results in an increase in the actuator command that effectively compensate for the slow actuator dynamics. Simulations demonstrate effectiveness of the method.

  18. Actuator fault tolerant multi-controller scheme using set separation based diagnosis

    NASA Astrophysics Data System (ADS)

    Seron, María M.; De Doná, José A.

    2010-11-01

    We present a fault tolerant control strategy based on a new principle for actuator fault diagnosis. The scheme employs a standard bank of observers which match the different fault situations that can occur in the plant. Each of these observers has an associated estimation error with distinctive dynamics when an estimator matches the current fault situation of the plant. Based on the information from each observer, a fault detection and isolation (FDI) module is able to reconfigure the control loop by selecting the appropriate control law from a bank of controllers, each of them designed to stabilise and achieve reference tracking for one of the given fault models. The main contribution of this article is to propose a new FDI principle which exploits the separation of sets that characterise healthy system operation from sets that characterise transitions from healthy to faulty behaviour. The new principle allows to provide pre-checkable conditions for guaranteed fault tolerance of the overall multi-controller scheme.

  19. Propulsion-free separation and rendezvous of small shuttle free-flyers using controlled differential drag

    NASA Technical Reports Server (NTRS)

    King, J. C.

    1979-01-01

    A natural successor in the Shuttle era to many sounding rocket flights is the free-flyer mode of operation, in which the Shuttle Orbiter releases a subsatellite (with payloads), effects a desired separation, and approaches and retrieves the free-layer. The propulsive maneuvers required of the Orbiter by equivalent relative motions obtained through controlled differential drag (via changes in free-layer effective area and/or Orbiter attitude changes) are replaced. Simplified analytical techniques are developed and feasibility is verified.

  20. Simulation and simulator development of a separate surface attitude command control system for light aircraft

    NASA Technical Reports Server (NTRS)

    Roskam, J.

    1976-01-01

    A detailed description is presented of the simulation philosophy and process used in the development of a Separate Surface Attitude Command control system (SSAC) for a Beech Model 99 Airliner. The intent of this system is to provide complete three axes stability augmentation at low cost and without the need for system redundancy. The system, although aimed at the general aviation market, also has applications to certain military airplanes as well as to miniature submarines.

  1. Aspects regarding at 13C isotope separation column control using Petri nets system

    NASA Astrophysics Data System (ADS)

    Boca, M. L.; Ciortea, M. E.

    2015-11-01

    This paper is intended to show that Petri nets can be also applicable in the chemical industry. It used linear programming, modeling underlying Petri nets, especially discrete event systems for isotopic separation, the purpose of considering and control events in real-time through graphical representations. In this paper it is simulate the control of 13C Isotope Separation column using Petri nets. The major problem with 13C comes from the difficulty of obtaining it and raising its natural fraction. Carbon isotopes can be obtained using many methods, one of them being the cryogenic distillation of carbon monoxide. Some few aspects regarding operating conditions and the construction of such cryogenic plants are known today, and even less information are available as far as the separation process modeling and control are concerned. In fact, the efficient control of the carbon monoxide distillation process represents a necessity for large-scale 13C production. Referring to a classic distillation process, some models for carbon isotope separation have been proposed, some based on mass, component and energy balance equations, some on the nonlinear wave theory or the Cohen equations. For modeling the system it was used Petri nets because in this case it is deal with discrete event systems. In use of the non-timed and with auxiliary times Petri model, the transport stream was divided into sections and these sections will be analyzed successively. Because of the complexity of the system and the large amount of calculations required it was not possible to analyze the system as a unitary whole. A first attempt to model the system as a unitary whole led to the blocking of the model during simulation, because of the large processing times.

  2. Active Control of Airfoil Boundary Layer Separation and Wake using Ns-DBD Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Durasiewicz, Claudia; Castro Maldonado, Jorge; Little, Jesse

    2016-11-01

    Nanosecond pulse driven dielectric barrier discharge (ns-DBD) plasma actuators are employed to control boundary layer separation and the wake of a NACA 0012 airfoil having aspect ratio of three. Ns-DBD plasma actuators are known to operate via a thermal mechanism in contrast to ac-DBDs which are momentum-based devices. Nominally 2D forcing is applied to the airfoil leading edge with pulse energy of 0.35 mJ/cm. Experiments are conducted at a Reynolds number of 0 . 74 ×106 primarily at 18° incidence which is well within the stalled regime. Baseline and controlled flow fields are studied using surface pressure measurements, constant temperature anemometry (CTA) and PIV. Forcing at a dimensionless frequency of F+ = fc /U∞ = 1 . 14 results in reattachment of nominally separated flow to the airfoil surface. Lower frequency forcing is less optimal for separation control, but produces strong fluctuations in the wake which are intended for use in the study of vortex body interaction in the future. Actuation below F+ = 0 . 23 shows behavior consistent with an impulse-like response while forcing in the range 0 . 23

  3. Development of flow separation control system to reduce the vibration of wind turbine blades

    NASA Astrophysics Data System (ADS)

    Kim, Ho-Young; Kim, Ho-Hyun; Han, Jong-Seob; Han, Jae-Hung

    2017-04-01

    The size of wind turbine blade has been continuously increased. Large-scale wind turbine blades induce loud noise, vibration; and maintenance difficulty is also increased. It causes the eventual increases of the cost of energy. The vibration of wind turbine blade is caused by several reasons such as a blade rotation, tower shadow, wind shear, and flow separation of a wind turbine blade. This wind speed variation changes in local angle of attack of the blades and create the vibration. The variation of local angle of attack influences the lift coefficient and causes the large change of the lift. In this study, we focus on the lift coefficient control using a flow control device to reduce the vibration. DU35-A15 airfoil was employed as baseline model. A plasma actuator was installed to generate the upwind jet in order to control the lift coefficient. Wind tunnel experiment was performed to demonstrate of the performance of the plasma actuator. The results show the plasma actuator can induce the flow separation compared with the baseline model. In addition, the actuator can delay the flow separation depending on the input AC frequency with the same actuator configuration.

  4. Recent Observations on Shortfin Mako Scale Flexibility as a Mechanism for Separation Control

    NASA Astrophysics Data System (ADS)

    Lang, Amy; Motta, Philip; Habegger, Maria; Jones, Emily; Hueter, Robert

    2010-11-01

    Recent results obtained from examining the skin of the shortfin mako (Isurus oxyrinchus) suggest that scale flexibility may provide a passive, flow actuated mechanism for controlling flow separation. The shortfin mako is considered to be one of the fastest and most agile marine predators. High contragility, or the ability to change direction while already in a turn, requires minimal form drag and thus control of flow separation on body regions aft of the point of maximum girth. Recent biological observations have found that the shortfin mako has highly flexible scales, or denticles, particularly on the sides of the body downstream of the gills; in these regions scale crowns can be easily manipulated to angles in excess of 60 degrees. Histological data of the skin provides preliminary evidence that this flexibility is achieved due, in part, to a reduction in the size of the base of the scale where it is anchored into the skin. Experimental measurements of maximum angle of denticle bristling observed as a function of body location will be presented and a probable mechanism leading to separation control will be discussed.

  5. Spatial separation from family in the mobile young of a biparental fish: risks and dynamics of returning home

    NASA Astrophysics Data System (ADS)

    Lee-Jenkins, Stacey S. Y.; Jeswiet, Sarah B.; Godin, Jean-Guy J.

    2014-01-01

    In species with extended parental care, mobile dependent young are potentially more vulnerable to predators when they stray and become separated from their parents. We would expect that the likelihood of, and latency time for, a separated young to safely return to its `family unit' (i.e. parents and brood mates) to be, respectively, inversely and positively related to the initial distance of separation and potentially mediated by its age or body size. Using the biparental convict cichlid fish ( Amatitlania siquia), we tested these predictions by capturing individual young and displacing them at varying distances from their family unit in both the field and laboratory. As expected, displaced fish were less likely, and took longer, to return to their family with increasing separation distance from the family unit. The body length of displaced young mediated these relationships and their antipredator behaviour; larger young refuged more than smaller ones and were also less likely to be eaten by predators. These results suggest that selection should favour strong affiliative behaviour in mobile young animals towards their brood mates and protective parents because straying from the family unit leads to increased exposure to predation and a reduced likelihood of returning home with increasing separation distance.

  6. Hydrogels with Spatially and Temporally Controlled Properties to Control Cellular Interactions

    NASA Astrophysics Data System (ADS)

    Burdick, Jason

    2011-03-01

    Stem cells (e.g., mesenchymal stem cells, MSCs) respond to many cues from their microenvironment, which may include chemical signals, mechanics, and topography. Importantly, these cues may be incorporated into scaffolding to control stem cell differentiation and optimize their ability to produce tissues in regenerative medicine. Despite the significant amount of work in this area, the materials have been primarily static and uniform. To this end, we have developed a sequential crosslinking process that relies on our ability to crosslinked functional biopolymers (e.g., methacrylated hyaluronic acid, HA) in two steps, namely a Michael-type addition reaction to partially consume reactive groups and then a light-initiated free-radical polymerization to further crosslink the material. With light exposure during the second step comes control over the material in space (via masks and lasers) and time (via intermittent light exposure). We are applying this technique for numerous applications. For example, when the HA hydrogels are crosslinked with MMP degradable peptides with thiol termini during the first step, a material that can be degraded by cells is obtained. However, cell-mediated degradation is obstructed with the introduction of kinetic chains during the second step, leading to spatially controlled cell degradability. Due to the influence of cellular spreading on MSC differentiation, we have controlled cell fates by controlling their spread ability, for instance towards osteoblasts in spread areas and adipocytes when cell remained rounded. We are also using the process of stiffening with time to investigate mechanically induced differentiation, particularly in materials with evolving mechanics. Overall, these advanced HA hydrogels provide us the opportunity to investigate diverse and controlled material properties on MSC interactions.

  7. Defect pair separation as the controlling step in homogeneous ice melting.

    PubMed

    Mochizuki, Kenji; Matsumoto, Masakazu; Ohmine, Iwao

    2013-06-20

    On being heated, ice melts into liquid water. Although in practice this process tends to be heterogeneous, it can occur homogeneously inside bulk ice. The thermally induced homogeneous melting of solids is fairly well understood, and involves the formation and growth of melting nuclei. But in the case of water, resilient hydrogen bonds render ice melting more complex. We know that the first defects appearing during homogeneous ice melting are pairs of five- and seven-membered rings, which appear and disappear repeatedly and randomly in space and time in the crystalline ice structure. However, the accumulation of these defects to form an aggregate is nearly additive in energy, and results in a steep free energy increase that suppresses further growth. Here we report molecular dynamics simulations of homogeneous ice melting that identify as a crucial first step not the formation but rather the spatial separation of a defect pair. We find that once it is separated, the defect pair--either an interstitial (I) and a vacancy (V) defect pair (a Frenkel pair), or an L and a D defect pair (a Bjerrum pair)--is entropically stabilized, or 'entangled'. In this state, defects with threefold hydrogen-bond coordination persist and grow, and thereby prepare the system for subsequent rapid melting.

  8. Separate adaptive mechanisms for controlling trajectory and final position in reaching.

    PubMed

    Scheidt, Robert A; Ghez, Claude

    2007-12-01

    We examined control of the hand's trajectory (direction and shape) and final equilibrium position in horizontal planar arm movements by quantifying transfer of learned visuomotor rotations between two tasks that required aiming the hand to the same spatial targets. In a trajectory-reversal task ("slicing"), the hand reversed direction within the target and returned to the origin. In a positioning task ("reaching"), subjects moved the hand to the target and held it there; cursor feedback was provided only after movement ended to isolate learning of final position from trajectory direction. We asked whether learning acquired in one task would transfer to the other. Transfer would suggest that the hand's entire trajectory, including its endpoint, was controlled using a common spatial plan. Instead we found minimal transfer, suggesting that the brain used different representations of target position to specify the hand's initial trajectory and its final stabilized position. We also observed asymmetrical practice effects on hand trajectory, including systematic curvature of reaches made after rotation training and hypermetria of untrained slice reversals after reach training. These are difficult to explain with a unified control model, but were replicated in computer simulations that specified the hand's initial trajectory and its final equilibrium position. Our results suggest that the brain uses different mechanisms to plan the hand's initial trajectory and final position in point-to-point movements, that it implements these control actions sequentially, and that trajectory planning does not account for specific impedance values to be implemented about the final stabilized posture.

  9. Transitioning Resolution Responsibility between the Controller and Automation Team in Simulated NextGen Separation Assurance

    NASA Technical Reports Server (NTRS)

    Cabrall, C.; Gomez, A.; Homola, J.; Hunt, S..; Martin, L.; Merccer, J.; Prevott, T.

    2013-01-01

    As part of an ongoing research effort on separation assurance and functional allocation in NextGen, a controller- in-the-loop study with ground-based automation was conducted at NASA Ames' Airspace Operations Laboratory in August 2012 to investigate the potential impact of introducing self-separating aircraft in progressively advanced NextGen timeframes. From this larger study, the current exploratory analysis of controller-automation interaction styles focuses on the last and most far-term time frame. Measurements were recorded that firstly verified the continued operational validity of this iteration of the ground-based functional allocation automation concept in forecast traffic densities up to 2x that of current day high altitude en-route sectors. Additionally, with greater levels of fully automated conflict detection and resolution as well as the introduction of intervention functionality, objective and subjective analyses showed a range of passive to active controller- automation interaction styles between the participants. Not only did the controllers work with the automation to meet their safety and capacity goals in the simulated future NextGen timeframe, they did so in different ways and with different attitudes of trust/use of the automation. Taken as a whole, the results showed that the prototyped controller-automation functional allocation framework was very flexible and successful overall.

  10. Active Flow Separation Control of a Laminar Airfoil at Low Reynolds Number

    NASA Astrophysics Data System (ADS)

    Packard, Nathan Owen

    Detailed investigation of the NACA 643-618 is obtained at a Reynolds number of 6.4x104 and angle of attack sweep of -5° < alpha < 25°. The baseline flow is characterized by four distinct regimes depending on angle of attack, each exhibiting unique flow behavior. Active flow control is exploited from a row of discrete holes located at five percent chord on the upper surface of the airfoil. Steady normal blowing is employed at four representative angles; blowing ratio is optimized by maximizing the lift coefficient with minimal power requirement. The range of effectiveness of pulsed actuation with varying frequency, duty cycle and blowing ratio is explored. Pulsed blowing successfully reduces separation over a wide range of reduced frequency (0.1-1), blowing ratio (0.5--2), and duty cycle (0.6--50%). A phase-locked investigation, by way of particle image velocimetry, at ten degrees angle of attack illuminates physical mechanisms responsible for separation control of pulsed actuation at a low frequency and duty cycle. Temporal resolution of large structure formation and wake shedding is obtained, revealing a key mechanism for separation control. The Kelvin-Helmholtz instability is identified as responsible for the formation of smaller structures in the separation region which produce favorable momentum transfer, assisting in further thinning the separation region and then fully attaching the boundary layer. Closed-loop separation control of an oscillating NACA 643-618 airfoil at Re = 6.4x104 is investigated in an effort to autonomously minimize control effort while maximizing aerodynamic performance. High response sensing of unsteady flow with on-surface hot-film sensors placed at zero, twenty, and forty percent chord monitors the airfoil performance and determines the necessity of active flow control. Open-loop characterization identified the use of the forty percent sensor as the actuation trigger. Further, the sensor at twenty percent chord is used to distinguish

  11. Thermo and pH dual-responsive materials for controllable oil/water separation.

    PubMed

    Cao, Yingze; Liu, Na; Fu, Changkui; Li, Kan; Tao, Lei; Feng, Lin; Wei, Yen

    2014-02-12

    Thermo and pH dual-controllable oil/water separation materials are successfully fabricated by photo initiated free radical polymerization of dimethylamino ethyl methacrylate (DMAEMA). The PDMAEMA hydrogel coated mesh shows superhydrophilicity and underwater superoleophobicity at certain temperature and pH. Due to the double responsiveness of PDMAEMA hydrogel, the as-prepared mesh can selectively separate water from oil/water mixtures and make water and oil permeate through the mesh orderly and be collected separately by adjusting the temperature or pH. Water can pass through the as-prepared mesh under 55 °C (pH 7) and pH less than 13 (T = 25 °C) while oil is kept on the mesh. When the temperature is above 55 °C or pH is larger than 13, the water retention capacity of PDMAEMA hydrogel is significantly reduced and the swelling volume is decreased. Therefore, oil can permeate through the mesh and be collected in situ. Additionally, this material has excellent potential to be used in practical applications and has created a new field for water/oil separation in which the process can be diversified and more intelligent.

  12. Boundary layer and separation control on wings at low Reynolds numbers

    NASA Astrophysics Data System (ADS)

    Yang, Shanling

    Results on boundary layer and separation control through acoustic excitation at low Re numbers are reported. The Eppler 387 profile is specifically chosen because of its pre-stall hysteresis and bi-stable state behavior in the transitional Re regime, which is a result of flow separation and reattachment. External acoustic forcing on the wing yields large improvements (more than 70%) in lift-to-drag ratio and flow reattachment at forcing frequencies that correlate with the measured anti-resonances in the wind tunnel. The optimum St/Re1/2 range for Re = 60,000 matches the proposed optimum range in the literature, but there is less agreement for Re = 40,000, which suggests that correct St scaling has not been determined. The correlation of aerodynamic improvements to wind tunnel resonances implies that external acoustic forcing is facility-dependent, which inhibits practical application. Therefore, internal acoustic excitation for the same wing profile is also pursued. Internal acoustic forcing is designed to be accomplished by embedding small speakers inside a custom-designed wing that contains many internal cavities and small holes in the suction surface. However, initial testing of this semi-porous wing model shows that the presence of the small holes in the suction surface completely transforms the aerodynamic performance by changing the mean chordwise separation location and causing an originally separated, low-lift state flow to reattach into a high-lift state. The aerodynamic improvements are not caused by the geometry of the small holes themselves, but rather by Helmholtz resonance that occurs in the cavities, which generate tones that closely match the intrinsic flow instabilities. Essentially, opening and closing holes in the suction surface of a wing, perhaps by digital control, can be used as a means of passive separation control. Given the similarity of wing-embedded pressure tap systems to Helmholtz resonators, particular attention must be given to the

  13. A Time Scale Separation Method for the Coordination of Voltage Controls for SVC and SVR

    NASA Astrophysics Data System (ADS)

    Yorino, Naoto; Miki, Takahiro; Yamato, Yuuki; Zoka, Yoshifumi; Sasaki, Hiroshi

    A time scale separation (TSS) method is proposed for the coordination of voltage controls of different time scales. The method is applied to a design of voltage regulator for static var compensator (SVC) which will be used with a step voltage regulator (SVR) in a distribution system. A simple filter, an input filter to the conventional SVC, is developed for the coordination with SVR controllers. The proposed filter can also be used as an input filter to AVR of the dispersed generators for the coordination controls with the conventional tap control devices. Effectiveness of the proposed method is demonstrated through numerical simulations in a distribution system having a large disturbance source of a wind power generator.

  14. Spatial organisation of vegetation in water controlled landscapes: the role of vegetation dispersion strategies.

    NASA Astrophysics Data System (ADS)

    Thompson, S. E.; Katul, G.

    2007-12-01

    When investigating the spatial organization of biomass resulting from plant-water feedbacks in arid ecosystems, spatial movement of plants is generally represented as a diffusive processes. Diffusive representations of plant movement have two consequences: they fix the length scale of dispersion to the immediate vicinity of the parent plant, and thus cannot explicitly represent long distance dispersal; and they treat the local gradient of biomass as the determinant of the rate and direction of dispersal. An adaptation of an existing model (Rietkerk et al. 2002) is used to investigate the significance of these assumptions on predicted spatial distributions of vegetation. Model runs were conducted separately with a diffusive and a long-distance dispersive kernel for spatial movement and the resulting spatial organization of vegetation was contrasted. The results indicate that dispersion behavior strongly influences the spatial organization of vegetation in arid landscapes, destabilizing the regular spatial patterns often predicted by models utilizing diffusive representations of biomass movement. The model results provide insight into ecological hypotheses regarding the preponderance of short-range dispersion behavior observed in arid ecosystems, and suggest that this is a consequence of the highly organized nature of the soil water resource. Rietkerk, M., M. C. Boerlijst, F. van Langevelde, R. HilleRisLambers, J. van de Koppel, L. Kumar, H. H. T. Prins, and A. M. de Roos. 2002. Self-organization of vegetation in arid ecosystems. American Naturalist 160:524-530.

  15. Spatially Controlled Fe Isotope Variations at Torres del Paine

    NASA Astrophysics Data System (ADS)

    Gajos, N.; Lundstrom, C.

    2013-12-01

    Recent advances in mass-spectrometry have identified systematic trends of non-traditional stable isotope variation in igneous rocks with differentiation index. We present new Fe isotope data for the Torres del Paine igneous complex in southern Chile. The multi-composition pluton consists of a 1 km vertical exposure of homogenous granite overlying a contemporaneous and possibly cogenetic 0.5 km mafic gabbro suite. Whereas previous isotopic investigations do little to address variations across important magmatic contacts, this study focuses on a first-of-its-kind spatially dependent non-traditional stable isotope investigation of an igneous pluton. Samples were collected at Torres del Paine in spatially significant transects, focusing on major contacts between country rock, granite and mafic units. Results collected by bracketed double spike MC-ICP-MS (2s precision of ×0.03) show an increase in δ56Fe towards the high silica margins of the pluton with values as high as δ56Fe 0.36. Additionally, the data show a decrease in δ56Fe toward the mafic center of the pluton with δ56Fe values ranging from δ56Fe -0.05 to 0.18. Samples collected on the contact between the granite and mafic complex show intermediate values of δ56Fe= 0.18(×) 0.03. Country rock samples in contact with granite show an isotopically light signature of δ56Fe=0.04 (×) 0.03. Analysis of 50 samples in total show a trend of increasing δ56Fe with SiO2 content. The process responsible for Fe isotope variations remains debated but is suggested to reflect four mechanisms: (1) crustal assimilation, (2) fractional crystallization, (3) late stage fluid exsolution [1] and (4) thermal migration [3]. Preliminary results show that mechanisms #1 and #2 would produce isotopic signatures opposite of those seen at Torres del Paine and other plutonic rocks. Isotopically light Torres country rock samples reveal that assimilation of rocks would not produce the isotopically heavy granites seen at Torres. Based on

  16. Spatially controlled carbon sponge for targeting internalized radioactive materials in human body.

    PubMed

    Hong, Jin-Yong; Oh, Wan-Kyu; Shin, Keun-Young; Kwon, Oh Seok; Son, Suim; Jang, Jyongsik

    2012-07-01

    Carbon sponge, an adsorbent with spatially controlled structure is demonstrated for targeting internalized radiocesium and other radionuclides in human body. Three dimensionally ordered macroporous (3DOM) carbons derived from inverse opal replicas of colloidal-crystal template exhibit large surface area and high porosity, resulting in highly efficient adsorbents for radionuclides. It is also possible to enhance binding affinity and selectivity to radionuclide targets by decoration of 3DOM carbon surfaces with Prussian blue (PB) nanoparticles, and synthesized PB nanoparticles reveal low toxicity toward macrophage cells with potential advantages over oral administration. It is noteworthy that the maximum (133)Cs adsorption capacity of PB-decorated 3DOM carbons is 40.07 mmol g(-1) which is ca. 30 and 200 times higher than that of commercialized medicine Radiogardase(®) and bulk PB, respectively. Further, adsorption kinetics study indicates that the PB-decorated 3DOM carbons have the homogenous surface for (133)Cs ion adsorption and all sites have equal adsorption energies in terms of ion exchange between the cyano groups of the PB-decorated 3DOM carbons and radionuclides. As a concept of the oral-administrable "carbon sponge", the PB-decorated 3DOM carbons offer useful implications in the separation science of radioactive materials and important insight for designing novel materials for treatment of patients or suspected internal contamination with radioactive materials. Copyright © 2012 Elsevier Ltd. All rights reserved.

  17. Controlling effective interactions and spatial dispersion of nanoparticles in multiblock copolymer melts

    SciTech Connect

    Banerjee, Debapriya; Schweizer, Kenneth S.

    2015-06-04

    The microscopic Polymer Reference Interaction Site Model theory is employed to study, for the first time, the effective interactions, spatial organization, and miscibility of dilute spherical nanoparticles in non-microphase separating, chemically heterogeneous, compositionally symmetric AB multiblock copolymer melts of varying monomer sequence or architecture. The dependence of nanoparticle wettability on copolymer sequence and chemistry results in interparticle potentials-of-mean force that are qualitatively different from homopolymers. An important prediction is the ability to improve nanoparticle dispersion via judicious choice of block length and monomer adsorption-strengths which control both local surface segregation and chain connectivity induced packing constraints and frustration. The degree of dispersion also depends strongly on nanoparticle diameter relative to the block contour length. Small particles in copolymers with longer block lengths experience a more homopolymer-like environment which renders them relatively insensitive to copolymer chemical heterogeneity and hinders dispersion. Larger particles (sufficiently larger than the monomer diameter) in copolymers of relatively short block lengths provide better dispersion than either a homopolymer or random copolymer. The theory also predicts a novel widening of the miscibility window for large particles upon increasing the overall molecular weight of copolymers composed of relatively long blocks. The influence of a positive chi-parameter in the pure copolymer melt is briefly studied. Quantitative application to fullerenes in specific copolymers of experimental interest is performed, and miscibility predictions are made.

  18. Spatial protein quality control and the evolution of lineage-specific ageing

    PubMed Central

    Nyström, Thomas

    2011-01-01

    Propagation of a species requires periodic cell renewal to avoid clonal extinction. Sexual reproduction and the separation of germ cells from the soma provide a mechanism for such renewal, but are accompanied by an apparently mandatory ageing of the soma. Data obtained during the last decade suggest that a division of labour exists also between cells of vegetatively reproducing unicellular organisms, leading to the establishment of a soma-like and germ-like lineage with distinct fitness and longevity characteristics. This division of labour in both bacteria and yeast entails segregation of damaged and aggregated proteins such that the germ-like lineage is kept free of damage to the detriment of the soma-like lineage. In yeast, this spatial protein quality control (SQC) encompasses a CCT-chaperonin-dependent translocation and merging of cytotoxic protein aggregates. This process is regulated by Sir2, a protein deacetylase that modulates the rate of ageing in organisms ranging from yeast to worms and flies. Recent data also demonstrate that SQC is intimately integrated with the machinery establishing proper cell polarity and that this machinery is required for generating a soma-like and germ-like lineage in yeast. Deciphering the details of the SQC network may increase our understanding of the development of age-related protein folding disorders and shed light on the selective forces that paved the way for polarity and lineage-specific ageing to evolve. PMID:21115532

  19. Scaling impacts on environmental controls and spatial heterogeneity of soil organic carbon stocks

    DOE PAGES

    Mishra, U.; Riley, W. J.

    2015-07-02

    The spatial heterogeneity of land surfaces affects energy, moisture, and greenhouse gas exchanges with the atmosphere. However, representing the heterogeneity of terrestrial hydrological and biogeochemical processes in Earth system models (ESMs) remains a critical scientific challenge. We report the impact of spatial scaling on environmental controls, spatial structure, and statistical properties of soil organic carbon (SOC) stocks across the US state of Alaska. We used soil profile observations and environmental factors such as topography, climate, land cover types, and surficial geology to predict the SOC stocks at a 50 m spatial scale. These spatially heterogeneous estimates provide a data setmore » with reasonable fidelity to the observations at a sufficiently high resolution to examine the environmental controls on the spatial structure of SOC stocks. We upscaled both the predicted SOC stocks and environmental variables from finer to coarser spatial scales (s = 100, 200, and 500 m and 1, 2, 5, and 10 km) and generated various statistical properties of SOC stock estimates. We found different environmental factors to be statistically significant predictors at different spatial scales. Only elevation, temperature, potential evapotranspiration, and scrub land cover types were significant predictors at all scales. The strengths of control (the median value of geographically weighted regression coefficients) of these four environmental variables on SOC stocks decreased with increasing scale and were accurately represented using mathematical functions (R2 = 0.83–0.97). The spatial structure of SOC stocks across Alaska changed with spatial scale. Although the variance (sill) and unstructured variability (nugget) of the calculated variograms of SOC stocks decreased exponentially with scale, the correlation length (range) remained relatively constant across scale. The variance of predicted SOC stocks decreased with spatial scale over the range of 50 m to ~ 500 m

  20. Scaling impacts on environmental controls and spatial heterogeneity of soil organic carbon stocks

    DOE PAGES

    Mishra, U.; Riley, W. J.

    2015-01-01

    The spatial heterogeneity of land surfaces affects energy, moisture, and greenhouse gas exchanges with the atmosphere. However, representing heterogeneity of terrestrial hydrological and biogeochemical processes in earth system models (ESMs) remains a critical scientific challenge. We report the impact of spatial scaling on environmental controls, spatial structure, and statistical properties of soil organic carbon (SOC) stocks across the US state of Alaska. We used soil profile observations and environmental factors such as topography, climate, land cover types, and surficial geology to predict the SOC stocks at a 50 m spatial scale. These spatially heterogeneous estimates provide a dataset with reasonablemore » fidelity to the observations at a sufficiently high resolution to examine the environmental controls on the spatial structure of SOC stocks. We upscaled both the predicted SOC stocks and environmental variables from finer to coarser spatial scales (s = 100, 200, 500 m, 1, 2, 5, 10 km) and generated various statistical properties of SOC stock estimates. We found different environmental factors to be statistically significant predictors at different spatial scales. Only elevation, temperature, potential evapotranspiration, and scrub land cover types were significant predictors at all scales. The strengths of control (the median value of geographically weighted regression coefficients) of these four environmental variables on SOC stocks decreased with increasing scale and were accurately represented using mathematical functions (R2 = 0.83–0.97). The spatial structure of SOC stocks across Alaska changed with spatial scale. Although the variance (sill) and unstructured variability (nugget) of the calculated variograms of SOC stocks decreased exponentially with scale, the correlation length (range) remained relatively constant across scale. The variance of predicted SOC stocks decreased with spatial scale over the range of 50 to ~ 500 m, and remained

  1. Scaling impacts on environmental controls and spatial heterogeneity of soil organic carbon stocks

    SciTech Connect

    Mishra, U.; Riley, W. J.

    2015-01-01

    The spatial heterogeneity of land surfaces affects energy, moisture, and greenhouse gas exchanges with the atmosphere. However, representing heterogeneity of terrestrial hydrological and biogeochemical processes in earth system models (ESMs) remains a critical scientific challenge. We report the impact of spatial scaling on environmental controls, spatial structure, and statistical properties of soil organic carbon (SOC) stocks across the US state of Alaska. We used soil profile observations and environmental factors such as topography, climate, land cover types, and surficial geology to predict the SOC stocks at a 50 m spatial scale. These spatially heterogeneous estimates provide a dataset with reasonable fidelity to the observations at a sufficiently high resolution to examine the environmental controls on the spatial structure of SOC stocks. We upscaled both the predicted SOC stocks and environmental variables from finer to coarser spatial scales (s = 100, 200, 500 m, 1, 2, 5, 10 km) and generated various statistical properties of SOC stock estimates. We found different environmental factors to be statistically significant predictors at different spatial scales. Only elevation, temperature, potential evapotranspiration, and scrub land cover types were significant predictors at all scales. The strengths of control (the median value of geographically weighted regression coefficients) of these four environmental variables on SOC stocks decreased with increasing scale and were accurately represented using mathematical functions (R2 = 0.83–0.97). The spatial structure of SOC stocks across Alaska changed with spatial scale. Although the variance (sill) and unstructured variability (nugget) of the calculated variograms of SOC stocks decreased exponentially with scale, the correlation length (range) remained relatively constant across scale. The variance of predicted SOC stocks decreased with spatial scale over the range of 50 to ~ 500 m, and

  2. Scaling impacts on environmental controls and spatial heterogeneity of soil organic carbon stocks

    NASA Astrophysics Data System (ADS)

    Mishra, U.; Riley, W. J.

    2015-01-01

    The spatial heterogeneity of land surfaces affects energy, moisture, and greenhouse gas exchanges with the atmosphere. However, representing heterogeneity of terrestrial hydrological and biogeochemical processes in earth system models (ESMs) remains a critical scientific challenge. We report the impact of spatial scaling on environmental controls, spatial structure, and statistical properties of soil organic carbon (SOC) stocks across the US state of Alaska. We used soil profile observations and environmental factors such as topography, climate, land cover types, and surficial geology to predict the SOC stocks at a 50 m spatial scale. These spatially heterogeneous estimates provide a dataset with reasonable fidelity to the observations at a sufficiently high resolution to examine the environmental controls on the spatial structure of SOC stocks. We upscaled both the predicted SOC stocks and environmental variables from finer to coarser spatial scales (s = 100, 200, 500 m, 1, 2, 5, 10 km) and generated various statistical properties of SOC stock estimates. We found different environmental factors to be statistically significant predictors at different spatial scales. Only elevation, temperature, potential evapotranspiration, and scrub land cover types were significant predictors at all scales. The strengths of control (the median value of geographically weighted regression coefficients) of these four environmental variables on SOC stocks decreased with increasing scale and were accurately represented using mathematical functions (R2 = 0.83-0.97). The spatial structure of SOC stocks across Alaska changed with spatial scale. Although the variance (sill) and unstructured variability (nugget) of the calculated variograms of SOC stocks decreased exponentially with scale, the correlation length (range) remained relatively constant across scale. The variance of predicted SOC stocks decreased with spatial scale over the range of 50 to ~ 500 m, and remained constant beyond

  3. Scaling impacts on environmental controls and spatial heterogeneity of soil organic carbon stocks

    NASA Astrophysics Data System (ADS)

    Mishra, U.; Riley, W. J.

    2015-07-01

    The spatial heterogeneity of land surfaces affects energy, moisture, and greenhouse gas exchanges with the atmosphere. However, representing the heterogeneity of terrestrial hydrological and biogeochemical processes in Earth system models (ESMs) remains a critical scientific challenge. We report the impact of spatial scaling on environmental controls, spatial structure, and statistical properties of soil organic carbon (SOC) stocks across the US state of Alaska. We used soil profile observations and environmental factors such as topography, climate, land cover types, and surficial geology to predict the SOC stocks at a 50 m spatial scale. These spatially heterogeneous estimates provide a data set with reasonable fidelity to the observations at a sufficiently high resolution to examine the environmental controls on the spatial structure of SOC stocks. We upscaled both the predicted SOC stocks and environmental variables from finer to coarser spatial scales (s = 100, 200, and 500 m and 1, 2, 5, and 10 km) and generated various statistical properties of SOC stock estimates. We found different environmental factors to be statistically significant predictors at different spatial scales. Only elevation, temperature, potential evapotranspiration, and scrub land cover types were significant predictors at all scales. The strengths of control (the median value of geographically weighted regression coefficients) of these four environmental variables on SOC stocks decreased with increasing scale and were accurately represented using mathematical functions (R2 = 0.83-0.97). The spatial structure of SOC stocks across Alaska changed with spatial scale. Although the variance (sill) and unstructured variability (nugget) of the calculated variograms of SOC stocks decreased exponentially with scale, the correlation length (range) remained relatively constant across scale. The variance of predicted SOC stocks decreased with spatial scale over the range of 50 m to ~ 500 m, and remained

  4. An instrument to control parallel plate separation for nanoscale flow control

    NASA Astrophysics Data System (ADS)

    White, J.; Ma, H.; Lang, J.; Slocum, A.

    2003-11-01

    The handling of extremely small samples of gases and liquids has long been a subject of research among biologists, chemists, and engineers. A few scientific instruments, notably the surface force apparatus, have been used extensively to investigate very short-range molecular phenomena. This article describes the design, fabrication, and characterization of an easily manufactured, gas and liquid flow control device called the Nanogate. The Nanogate controls liquid flows under very high planar confinement, wherein the liquid film is, in one dimension, on the scale of nanometers, but is on the scale of hundreds of microns in its other dimensions. The liquid film is confined between a silica (Pyrex) surface with a typical roughness of Ra≈6 nm and a gold-covered silicon surface with a typical roughness of Ra≈2 nm. During the manufacturing process, the Pyrex flows and conforms to the gold-covered silicon surface, improving the mating properties of the two surfaces. The fluid film thickness can be controlled within 2 Å, from sub-10 nm up to 1 μm. Control of helium gas flow rates in the 10-9 atm cm3/s range, and sub-nl/s flow rates of water and methanol have been predicted and experimentally verified.

  5. Separation control effects of mako shark skin applied to a cylinder

    NASA Astrophysics Data System (ADS)

    Bradshaw, Michael; Lang, Amy; Motta, Philip; Habegger, Maria; Hueter, Robert

    2012-11-01

    Shark skin is investigated as a means of passive flow separation control due to its preferential flow direction and the potential for its scales to obstruct low-momentum backflow induced by an adverse pressure gradient. In this study, the effect of the scales on unsteady flow reversal is observed in laminar flow conditions for flow over a cylinder covered with real mako shark skin. These samples were taken from the shark's flank region because the scales at this location have been shown to have the greatest angle of bristling, and thus the best potential for separation control. All sets of flow data in this study were obtained using Time-Resolved Digital Particle Image Velocimetry and recorded at various Reynolds numbers. The flow was primarily analyzed by means of the backflow coefficient (a value based on the percentage of time that flow in a region over the hydrofoil is reversed), average backflow magnitude, and the time history of instantaneous flow velocity values at specific points in the boundary layer over the cylinder models. The point of separation from the cylinder surface was also of interest. Research funded by NSF REU Grant # 1062611.

  6. An Experimental Study of Flow Separation Control by Shortfin Mako Shark Skin

    NASA Astrophysics Data System (ADS)

    Afroz, Farhana; Lang, Amy; Motta, Philip; Habegger, Maria

    2013-11-01

    The shortfin mako shark (Isurus oxyrinchus) is a fast swimmer and has incredible turning agility. Shark skin is covered with flexible scales and this bristling capability may result in a unique Boundary Layer Control (BLC) method to reduce drag. It is hypothesized that scales bristle when the flow above it is reversed, and between the bristled scales embedded micro-vortices form in the cavities which induce boundary layer mixing and aid in delaying flow separation. To testify this hypothesis, samples of mako shark skin have been tested in a water tunnel under various strengths of adverse pressure gradient (APG). Laminar and turbulent separation over shark skin was studied experimentally using Time-Resolved Digital Particle Image Velocimetry (TR-DPIV) system, where the APG was generated and varied using a rotating cylinder. Then shark skin results were compared with that of a flat plate data for a given amount of APG. The study reveals that shark skin is capable of controlling both laminar and turbulent flow separation. Support under NSF grant 0932352 is gratefully acknowledged. First author Farhana Afroz was also supported by a scholarship through the Alabama EPSCoR Graduate Research Scholars Program.

  7. A frequency-control particle separation device based on resultant effects of electroosmosis and dielectrophoresis

    NASA Astrophysics Data System (ADS)

    Lin, Shiang-Chi; Tung, Yi-Chung; Lin, Chih-Ting

    2016-08-01

    Particle separation plays an important role in microfluidic sample preparation for various biomedical applications. In this paper, we report a particle manipulation and separation scheme using a microfluidic device based on low-volume/low-voltage electrokinetic frequency modulation. Utilizing a circular micro-electrode array, both electroosmosis and dielectrophoresis can be contributed to manipulate particles in the device by controlling the frequency of applied sinusoidal travelling wave signals. Theoretical simulations based on finite-element methods are employed to establish fundamental understanding of the developed scheme. For experimental demonstration, polystyrene beads (6 μm in diameter) and human promyelocytic leukaemia cells (HL-60) are used to validate the frequency-modulation effect. Furthermore, different diameter polystyrene beads (6 μm and 10 μm in diameter) are mixed to show potentials of precise particle separations (˜90% efficiency) by the reported frequency-controlled electrokinetic device. The developed technique can be exploited as an actuation scheme and particle manipulation method for microfluidic sample preparations of low ionic concentration samples.

  8. Control of Germination in Striga asiatica: Chemistry of Spatial Definition.

    PubMed

    Fate, G; Chang, M; Lynn, D G

    1990-05-01

    Striga asiatica (Scrophulariaceae), a member of a heterogeneous group known as the parasitic plants, is totally dependent on host root attachment for survival. In agar, Striga seeds germinated in high percentages within 5 millimeters of a sorghum (Sorghum bicolor (L.) Moench) host root surface, and no germination was observed at distances greater than 1 centimeter. This spatially restricted germination may be explained by the chemistry of a single compound, 2-hydroxy-5-methoxy-3-[8'Z, 11'Z)-8', 11', 14' -pentadecatriene]-p-hydroquinone, structure 1, which is exuded by sorghum roots. The presence of the compound was chemically imaged with pigments such as methylene blue. The use of methylene blue suggested that structure 1 was exuded along the entire surface of the root for long periods. This exudation and the inherent instability of structure 1 together establish an apparent steady state concentration gradient of the germination stimulant around the sorghum root. The Striga seed must be exposed to micromolar concentrations of 1 for >/=5 hours before high germination percentages were observed. Such a requirement for a long term exposure to a steady state concentration of an inherently labile, exuded compound would provide an extra degree of resolution to signal detection and host commitment in Striga parasitism.

  9. Chromatic aberration control with liquid crystal spatial phase modulators.

    PubMed

    Martinez, Jose L; Fernandez, Enrique J; Prieto, Pedro M; Artal, Pablo

    2017-05-01

    The chromatic behavior of diffractive optical elements, exhibiting 2π-wrapped phase profiles, implemented into liquid crystal spatial light modulators (LC-SLM) is described. A wrapped phase map is only equivalent to the original continuous profile for the design wavelength while at other wavelengths there are unwanted phase jumps and the profile does not correspond to a pure defocus. For those conditions the wrapped profile behaves as a multiple order lens (multi-focal lens). The optical power dispersion for each order is linearly proportional to the wavelength, while the energy of each order depends on the design wavelength and the material dispersion. For practical purposes, for most of the visible range only first order (main defocus) is relevant but two other orders may also be considered depending on the actual PSF of the system. As an application, we demonstrate that the longitudinal chromatic aberration of the eye can be compensated by the diffractive lens dispersion when the appropriate defocus is programmed into the SLM.

  10. Controls on spatial and temporal distribution of Precambrian eolianites

    NASA Astrophysics Data System (ADS)

    Eriksson, Kenneth A.; Simpson, Edward L.

    1998-09-01

    Inversely graded stratification, generated by the migration of wind ripples, and adhesion structures permit unequivocal identification of Precambrian eolianites. These criteria, in combination with scale of cross-beds, angle of inclination of foresets, geometry of depositional units, and associated non-eolian facies, are used to discriminate between Precambrian dune/draa, dune-plinth, sand-sheet, and interdune deposits that formed in inland and coastal settings. Based on an analysis of published literature, fundamental conclusions can be drawn on the spatial and temporal distribution of Precambrian eolianites. The oldest reported eolianites are from the ca. 2.1 Ga Deweras Group in Zimbabwe and Hurwitz Group in Canada and numerous examples of eolianites are reported from the 1.8 Ga and younger rock record. Lack of Archean and early Paleoproterozoic eolianites and their widespread development after 1.8 Ga are examined with respect to: absence of vegetation, crustal growth and tectonic setting, relative sea-level fluctuations, unfavorable atmospheric and/or climatic change, and non-recognition. The lack of pre-2.2 Ga eolianites may be related to reworking by braided rivers combing across non-vegetated floodplains, reworking of coastal eolianites during transgression or their non-recognition in the Early Precambrian record. The temporal concentration of eolianites at 1.8 Ga may best be related to the early stages of breakup and the assembly phases of supercontinents.

  11. Spatial and Temporal Control of Transgene Expression in Zebrafish

    PubMed Central

    Stankunas, Kryn

    2014-01-01

    Transgenic zebrafish research has provided valuable insights into gene functions and cell behaviors directing vertebrate development, physiology, and disease models. Most approaches use constitutive transgene expression and therefore do not provide control over the timing or levels of transgene induction. We describe an inducible gene expression system that uses new tissue-specific zebrafish transgenic lines that express the Gal4 transcription factor fused to the estrogen-binding domain of the human estrogen receptor. We show these Gal4-ERT driver lines confer rapid, tissue-specific induction of UAS-controlled transgenes following tamoxifen exposure in both embryos and adult fish. We demonstrate how this technology can be used to define developmental windows of gene function by spatiotemporal-controlled expression of constitutively active Notch1 in embryos. Given the array of existing UAS lines, the modular nature of this system will enable many previously intractable zebrafish experiments. PMID:24643048

  12. Formation of asymmetrical structured silica controlled by a phase separation process and implication for biosilicification.

    PubMed

    Shi, Jia-Yuan; Yao, Qi-Zhi; Li, Xi-Ming; Zhou, Gen-Tao; Fu, Sheng-Quan

    2013-01-01

    Biogenetic silica displays intricate patterns assembling from nano- to microsize level and interesting non-spherical structures differentiating in specific directions. Several model systems have been proposed to explain the formation of biosilica nanostructures. Of them, phase separation based on the physicochemical properties of organic amines was considered to be responsible for the pattern formation of biosilica. In this paper, using tetraethyl orthosilicate (TEOS, Si(OCH2CH3)4) as silica precursor, phospholipid (PL) and dodecylamine (DA) were introduced to initiate phase separation of organic components and influence silica precipitation. Morphology, structure and composition of the mineralized products were characterized using a range of techniques including field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), infrared spectra (IR), and nitrogen physisorption. The results demonstrate that the phase separation process of the organic components leads to the formation of asymmetrically non-spherical silica structures, and the aspect ratios of the asymmetrical structures can be well controlled by varying the concentration of PL and DA. On the basis of the time-dependent experiments, a tentative mechanism is also proposed to illustrate the asymmetrical morphogenesis. Therefore, our results imply that in addition to explaining the hierarchical porous nanopatterning of biosilica, the phase separation process may also be responsible for the growth differentiation of siliceous structures in specific directions. Because organic amine (e.g., long-chair polyamines), phospholipids (e.g., silicalemma) and the phase separation process are associated with the biosilicification of diatoms, our results may provide a new insight into the mechanism of biosilicification.

  13. Formation of Asymmetrical Structured Silica Controlled by a Phase Separation Process and Implication for Biosilicification

    PubMed Central

    Shi, Jia-Yuan; Yao, Qi-Zhi; Li, Xi-Ming; Zhou, Gen-Tao; Fu, Sheng-Quan

    2013-01-01

    Biogenetic silica displays intricate patterns assembling from nano- to microsize level and interesting non-spherical structures differentiating in specific directions. Several model systems have been proposed to explain the formation of biosilica nanostructures. Of them, phase separation based on the physicochemical properties of organic amines was considered to be responsible for the pattern formation of biosilica. In this paper, using tetraethyl orthosilicate (TEOS, Si(OCH2CH3)4) as silica precursor, phospholipid (PL) and dodecylamine (DA) were introduced to initiate phase separation of organic components and influence silica precipitation. Morphology, structure and composition of the mineralized products were characterized using a range of techniques including field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), infrared spectra (IR), and nitrogen physisorption. The results demonstrate that the phase separation process of the organic components leads to the formation of asymmetrically non-spherical silica structures, and the aspect ratios of the asymmetrical structures can be well controlled by varying the concentration of PL and DA. On the basis of the time-dependent experiments, a tentative mechanism is also proposed to illustrate the asymmetrical morphogenesis. Therefore, our results imply that in addition to explaining the hierarchical porous nanopatterning of biosilica, the phase separation process may also be responsible for the growth differentiation of siliceous structures in specific directions. Because organic amine (e.g., long-chair polyamines), phospholipids (e.g., silicalemma) and the phase separation process are associated with the biosilicification of diatoms, our results may provide a new insight into the mechanism of biosilicification. PMID:23585878

  14. Separating Thermal and Nonthermal X-Rays in Supernova Remnants. II. Spatially Resolved Fits to SN 1006 AD

    NASA Astrophysics Data System (ADS)

    Dyer, K. K.; Reynolds, S. P.; Borkowski, K. J.

    2004-01-01

    We present a spatially resolved spectral analysis of full ASCA observations of the remnant of the supernova of A.D. 1006. This remnant shows both nonthermal X-ray emission from bright limbs, generally interpreted as synchrotron emission from the loss-steepened tail of the nonthermal electron population also responsible for radio emission, and thermal emission from elsewhere in the remnant. In earlier work, we showed that the spatially integrated spectrum was well described by a theoretical synchrotron model in which shock acceleration of electrons was limited by escape, in combination with thermal models indicating high levels of iron from ejecta. Here we use new spatially resolved subsets of the earlier theoretical nonthermal models for the analysis. We find that emission from the bright limbs remains well described by those models and refine the values for the characteristic break frequency. We show that differences between the northeast and southwest nonthermal limbs are small, too small to account easily for the presence of the northeast limb, but not the southwest, in TeV γ-rays. Comparison of spectra of the nonthermal limbs and other regions confirms that simple cylindrically symmetric nonthermal models cannot describe the emission, and we put limits on nonthermal contributions to emission from the center and the northwest and southeast limbs. We can rule out solar-abundance models in all regions, finding evidence for elevated abundances. However, more sophisticated models will be required to accurately characterize these abundances.

  15. Controlling Directionality and Dimensionality of Radiation by Perturbing Separable Bound States in the Continuum

    PubMed Central

    Rivera, Nicholas; Hsu, Chia Wei; Zhen, Bo; Buljan, Hrvoje; Joannopoulos, John D.; Soljačić, Marin

    2016-01-01

    A bound state in the continuum (BIC) is an unusual localized state that is embedded in a continuum of extended states. Here, we present the general condition for BICs to arise from wave equation separability. Then we show that by exploiting perturbations of certain symmetry such BICs can be turned into resonances that radiate with a tailorable directionality and dimensionality. Using this general framework, we construct new examples of separable BICs and resonances that can exist in optical potentials for ultracold atoms, photonic systems, and systems described by tight binding. Such resonances with easily reconfigurable radiation allow for applications such as the storage and release of waves at a controllable rate and direction, as well systems that switch between different dimensions of confinement. PMID:27641540

  16. Generation of optical vortices with the same topological charges and controllable separation distances using diffraction gratings

    NASA Astrophysics Data System (ADS)

    Ghasempour Ardakani, Abbas; Safarzadeh, Fatemeh

    2016-08-01

    In this paper, we first generate optical vortices with different topological charges, using the method of computer-generated holograms. Then, we separate one of the optical vortices from others with a special topological charge and pass it through a diffraction grating with a specified line spacing. It is observed that the vortex beam, after passing through the grating, converts to several separated vortices with the same topological charge whose value is similar to the topological charge of the input vortex. Finally, we show that the distance between generated vortices can be controlled with the variation of spacing between grating lines. So, the proposed setup in this paper can be exploited as an optical vortex divider which is useful in communication and trapping systems.

  17. Cluster-based control of a separating flow over a smoothly contoured ramp

    NASA Astrophysics Data System (ADS)

    Kaiser, Eurika; Noack, Bernd R.; Spohn, Andreas; Cattafesta, Louis N.; Morzyński, Marek

    2017-01-01

    The ability to manipulate and control fluid flows is of great importance in many scientific and engineering applications. The proposed closed-loop control framework addresses a key issue of model-based control: The actuation effect often results from slow dynamics of strongly nonlinear interactions which the flow reveals at timescales much longer than the prediction horizon of any model. Hence, we employ a probabilistic approach based on a cluster-based discretization of the Liouville equation for the evolution of the probability distribution. The proposed methodology frames high-dimensional, nonlinear dynamics into low-dimensional, probabilistic, linear dynamics which considerably simplifies the optimal control problem while preserving nonlinear actuation mechanisms. The data-driven approach builds upon a state space discretization using a clustering algorithm which groups kinematically similar flow states into a low number of clusters. The temporal evolution of the probability distribution on this set of clusters is then described by a control-dependent Markov model. This Markov model can be used as predictor for the ergodic probability distribution for a particular control law. This probability distribution approximates the long-term behavior of the original system on which basis the optimal control law is determined. We examine how the approach can be used to improve the open-loop actuation in a separating flow dominated by Kelvin-Helmholtz shedding. For this purpose, the feature space, in which the model is learned, and the admissible control inputs are tailored to strongly oscillatory flows.

  18. Control and optimization of apheresis procedures in a COBE 2997 cell separator.

    PubMed

    Wooten, S L; Petersen, J N; Van Wie, B J

    1991-02-01

    To obtain more efficient operation of a COBE Model 2997 clinical cell separator using either a Single Stage II (SS II) or a Dual Stage separation chamber, modifications were made to allow complete computer control. Product cell density was detected using an optical sensor and controlled by automatic feedback through a microcomputer interface. Control was accomplished by automatically adjusting the red blood cell (RBC) and plasma product flow rates using a proportional-integral (PI) algorithm. Results show that, using either chamber, the product cell density can be maintained at a preselected value for extended periods of time without operator intervention. This system allowed investigation of optimal operating regions for plateletpheresis and leukapheresis procedures. The effects of centrifuge rpm and controller set point on centrifuge operation were investigated using a second order factorial experimental design. Theoretical significance of model parameters was assessed with the aid of a hindered settling model and simple reasoning about the interface position relative to the collection port. The results suggest that, in either chamber, the optimum operating region for plateletpheresis procedures occurs at moderate controller set points and high centrifuge rpm. The resultant operating efficiency and product purity values are approximately 63 percent and 0.65 respectively in the SS II chamber and approximately 70 percent and 0.70 respectively in the Dual Chamber. In the SS II, the optimum operating region for leukapheresis procedures occurred at high controller set point values for any centrifuge rpm above 1200 with an operating efficiency near 100 percent. However, in the Dual Chamber, the optimum operating region for leukapheresis procedures occurred at high controller set points and high centrifuge rpm's, again providing an operating efficiency near 100 percent.

  19. Nanoscale tissue engineering: spatial control over cell-materials interactions.

    PubMed

    Wheeldon, Ian; Farhadi, Arash; Bick, Alexander G; Jabbari, Esmaiel; Khademhosseini, Ali

    2011-05-27

    Cells interact with the surrounding environment by making tens to hundreds of thousands of nanoscale interactions with extracellular signals and features. The goal of nanoscale tissue engineering is to harness these interactions through nanoscale biomaterials engineering in order to study and direct cellular behavior. Here, we review two- and three-dimensional (2- and 3D) nanoscale tissue engineering technologies, and provide a holistic overview of the field. Techniques that can control the average spacing and clustering of cell adhesion ligands are well established and have been highly successful in describing cell adhesion and migration in 2D. Extension of these engineering tools to 3D biomaterials has created many new hydrogel and nanofiber scaffold technologies that are being used to design in vitro experiments with more physiologically relevant conditions. Researchers are beginning to study complex cell functions in 3D. However, there is a need for biomaterials systems that provide fine control over the nanoscale presentation of bioactive ligands in 3D. Additionally, there is a need for 2- and 3D techniques that can control the nanoscale presentation of multiple bioactive ligands and that can control the temporal changes in the cellular microenvironment.

  20. Sub-optimal control of unsteady boundary layer separation and optimal control of Saltzman-Lorenz model

    NASA Astrophysics Data System (ADS)

    Sardesai, Chetan R.

    The primary objective of this research is to explore the application of optimal control theory in nonlinear, unsteady, fluid dynamical settings. Two problems are considered: (1) control of unsteady boundary-layer separation, and (2) control of the Saltzman-Lorenz model. The unsteady boundary-layer equations are nonlinear partial differential equations that govern the eruptive events that arise when an adverse pressure gradient acts on a boundary layer at high Reynolds numbers. The Saltzman-Lorenz model consists of a coupled set of three nonlinear ordinary differential equations that govern the time-dependent coefficients in truncated Fourier expansions of Rayleigh-Renard convection and exhibit deterministic chaos. Variational methods are used to derive the nonlinear optimal control formulations based on cost functionals that define the control objective through a performance measure and a penalty function that penalizes the cost of control. The resulting formulation consists of the nonlinear state equations, which must be integrated forward in time, and the nonlinear control (adjoint) equations, which are integrated backward in time. Such coupled forward-backward time integrations are computationally demanding; therefore, the full optimal control problem for the Saltzman-Lorenz model is carried out, while the more complex unsteady boundary-layer case is solved using a sub-optimal approach. The latter is a quasi-steady technique in which the unsteady boundary-layer equations are integrated forward in time, and the steady control equation is solved at each time step. Both sub-optimal control of the unsteady boundary-layer equations and optimal control of the Saltzman-Lorenz model are found to be successful in meeting the control objectives for each problem. In the case of boundary-layer separation, the control results indicate that it is necessary to eliminate the recirculation region that is a precursor to the unsteady boundary-layer eruptions. In the case of the

  1. Control of unsteady separated flow associated with the dynamic stall of airfoils

    NASA Technical Reports Server (NTRS)

    Wilder, M. C.

    1994-01-01

    A unique active flow-control device is proposed for the control of unsteady separated flow associated with the dynamic stall of airfoils. The device is an adaptive-geometry leading-edge which will allow controlled, dynamic modification of the leading-edge profile of an airfoil while the airfoil is executing an angle-of-attack pitch-up maneuver. A carbon-fiber composite skin has been bench tested, and a wind tunnel model is under construction. A baseline parameter study of compressible dynamic stall was performed for flow over an NACA 0012 airfoil. Parameters included Mach number, pitch rate, pitch history, and boundary layer tripping. Dynamic stall data were recorded via point-diffraction interferometry and the interferograms were analyzed with in-house developed image processing software. A new high-speed phase-locked photographic image recording system was developed for real-time documentation of dynamic stall.

  2. Thermodynamic stability of driven open systems and control of phase separation by electro-autocatalysis.

    PubMed

    Bazant, Martin Z

    2017-07-01

    Motivated by the possibility of electrochemical control of phase separation, a variational theory of thermodynamic stability is developed for driven reactive mixtures, based on a nonlinear generalization of the Cahn-Hilliard and Allen-Cahn equations. The Glansdorff-Prigogine stability criterion is extended for driving chemical work, based on variations of nonequilibrium Gibbs free energy. Linear stability is generally determined by the competition of chemical diffusion and driven autocatalysis. Novel features arise for electrochemical systems, related to controlled total current (galvanostatic operation), concentration-dependent exchange current (Butler-Volmer kinetics), and negative differential reaction resistance (Marcus kinetics). The theory shows how spinodal decomposition can be controlled by solo-autocatalytic charge transfer, with only a single faradaic reaction. Experimental evidence is presented for intercalation and electrodeposition in rechargeable batteries, and further applications are discussed in solid state ionics, electrovariable optics, electrochemical precipitation, and biological pattern formation.

  3. Spatial control of recollision wave packets with attosecond precision.

    PubMed

    Kitzler, Markus; Lezius, Matthias

    2005-12-16

    We propose orthogonally polarized two-color laser pulses to steer tunneling electrons with attosecond precision around the ion core. We numerically demonstrate that the angles of birth and recollision, the recollision energy, and the temporal structure of the recolliding wave packet can be controlled without stabilization of the carrier-envelope phase of the laser, and that the wave packet's properties can be described by classical relations for a point charge. This establishes unique mapping between parameters of the laser field and attributes of the recolliding wave packet. The method is capable of probing ionic wave packet dynamics with attosecond resolution from an adjustable direction and might be used as an alternative to aligning molecules. Shaping the properties of the recollision wave packet by controlling the laser field may also provide new routes for improvement of attosecond pulse generation via high harmonic radiation.

  4. Spatial design and control of graphene flake motion

    NASA Astrophysics Data System (ADS)

    Ghorbanfekr-Kalashami, H.; Peeters, F. M.; Novoselov, K. S.; Neek-Amal, M.

    2017-08-01

    The force between a sharp scanning probe tip and a surface can drive a graphene flake over crystalline substrates. The recent design of particular patterns of structural defects on a graphene surface allows us to propose an alternative approach for controlling the motion of a graphene flake over a graphene substrate. The thermally induced motion of a graphene flake is controlled by engineering topological defects in the substrate. Such defect regions lead to an inhomogeneous energy landscape and are energetically unfavorable for the motion of the flake, and will invert and scatter graphene flakes when they are moving toward the defect line. Engineering the distribution of these energy barriers results in a controllable trajectory for the thermal motion of the flake without using any external force. We predict superlubricity of the graphene flake for motion along and between particular defect lines. This Rapid Communication provides insights into the frictional forces of interfaces and opens a route to the engineering of the stochastic motion of a graphene flake over any crystalline substrate.

  5. Temporal and spatial control of germ plasm RNAs

    PubMed Central

    Rangan, Prashanth; DeGennaro, Matthew; Jaime-Bustamante, Kean; Coux, Rémi- Xavier; Martinho, Rui; Lehmann, Ruth

    2009-01-01

    In many species germ cells form in a specialized germ plasm, which contains localized maternal RNAs [1–5]. In the absence of active transcription in early germ cells, these maternal RNAs encode germ cell components with critical functions in germ cell specification, migration and development [6, 7]. For several RNAs, localization has been correlated with release from translational repression, suggesting an important regulatory function linked to localization [3, 4, 8, 9]. To address the role of RNA localization and translational control more systematically, we assembled a comprehensive set of RNAs that are localized to polar granules, the characteristic germ plasm organelles. We find that the 3′-untranslated regions (UTRs) of all RNAs tested control RNA localization and instruct distinct temporal patterns of translation of the localized RNAs. We demonstrate necessity for translational timing by swapping the 3′UTR of polar granular component (pgc), which controls translation in germ cells, with that of nanos, which is translated earlier. Translational activation of pgc is concurrent with extension of its poly(A) tail length, but appears largely independent of the Drosophila CPEB homolog ORB. Our results demonstrate a role for 3′UTR mediated translational regulation in fine-tuning the temporal expression of localized RNA and may provide a paradigm for other RNAs that are found enriched at common cellular locations such as the leading edge of fibroblasts or the neuronal synapse. PMID:19110432

  6. Summary of the 2004 CFD Validation Workshop on Synthetic Jets and Turbulent Separation Control

    NASA Technical Reports Server (NTRS)

    Rumsey, C. L.; Gatski, T. B.; Sellers, W. L., III; Vatsa, V. N.; Viken, S. A.

    2006-01-01

    A computational fluid dynamics (CFD) validation workshop for synthetic jets and turbulent separation control (CFDVAL2004) was held in Williamsburg, Virginia in March 2004. Three cases were investigated: synthetic jet into quiescent air, synthetic jet into a turbulent boundary layer crossflow, and flow over a hump model with no-flow-control, steady suction, and oscillatory control. This paper is a summary of the CFD results from the workshop. Although some detailed results are shown, mostly a broad viewpoint is taken, and the CFD state-of-the-art for predicting these types of flows is evaluated from a general point of view. Overall, for synthetic jets, CFD can only qualitatively predict the flow physics, but there is some uncertainty regarding how to best model the unsteady boundary conditions from the experiment consistently. As a result, there is wide variation among CFD results. For the hump flow, CFD as a whole is capable of predicting many of the particulars of this flow provided that tunnel blockage is accounted for, but the length of the separated region compared to experimental results is consistently overpredicted.

  7. Investigating the Complexity of Transitioning Separation Assurance Tools into NextGen Air Traffic Control

    NASA Technical Reports Server (NTRS)

    Gomez, Ashley Nicole; Martin, Lynne Hazel; Homola, Jeffrey; Morey, Susan; Cabrall, Christopher; Mercer, Joey; Prevot, Thomas

    2013-01-01

    In a study, that introduced ground-based separation assurance automation through a series of envisioned transitional phases of concept maturity, it was found that subjective responses to scales of workload, situation awareness, and acceptability in a post run questionnaire revealed as-predicted results for three of the four study conditions but not for the third, Moderate condition. The trend continued for losses of separation (LOS) where the number of LOS events were far greater than expected in the Moderate condition. To offer an account of why the Moderate condition was perceived to be more difficult to manage than predicted, researchers examined the increase in amount and complexity of traffic, increase in communication load, and increased complexities as a result of the simulation's mix of aircraft equipage. Further analysis compared the tools presented through the phases, finding that controllers took advantage of the informational properties of the tools presented but shied away from using their decision support capabilities. Taking into account similar findings from other studies, it is suggested that the Moderate condition represented the first step into a "shared control" environment, which requires the controller to use the automation as a decision making partner rather than just a provider of information. Viewed in this light, the combination of tools offered in the Moderate condition was reviewed and some tradeoffs that may offset the identified complexities were suggested.

  8. Control of Chemical Effects in the Separation Process of a Differential Mobility / Mass Spectrometer System

    PubMed Central

    Schneider, Bradley B.; Coy, Stephen L.; Krylov, Evgeny V.; Nazarov, Erkinjon G.

    2013-01-01

    Differential mobility spectrometry (DMS) separates ions on the basis of the difference in their migration rates under high versus low electric fields. Several models describing the physical nature of this field mobility dependence have been proposed but emerging as a dominant effect is the clusterization model sometimes referred to as the dynamic cluster-decluster model. DMS resolution and peak capacity is strongly influenced by the addition of modifiers which results in the formation and dissociation of clusters. This process increases selectivity due to the unique chemical interactions that occur between an ion and neutral gas phase molecules. It is thus imperative to bring the parameters influencing the chemical interactions under control and find ways to exploit them in order to improve the analytical utility of the device. In this paper we describe three important areas that need consideration in order to stabilize and capitalize on the chemical processes that dominate a DMS separation. The first involves means of controlling the dynamic equilibrium of the clustering reactions with high concentrations of specific reagents. The second area involves a means to deal with the unwanted heterogeneous cluster ion populations emitted from the electrospray ionization process that degrade resolution and sensitivity. The third involves fine control of parameters that affect the fundamental collision processes, temperature and pressure. PMID:20065515

  9. Summary of the 2004 CFD Validation Workshop on Synthetic Jets and Turbulent Separation Control

    NASA Technical Reports Server (NTRS)

    Rumsey, C. L.; Gatski, T. B.; Sellers, W. L., III; Vatsa, V. N.; Viken, S. A.

    2004-01-01

    A CFD validation workshop for synthetic jets and turbulent separation control (CFDVAL2004) was held in Williamsburg, Virginia in March 2004. Three cases were investigated: synthetic jet into quiescent air, synthetic jet into a turbulent boundary layer crossflow, and flow over a hump model with no-flow-control, steady suction, and oscillatory control. This paper is a summary of the CFD results from the workshop. Although some detailed results are shown, mostly a broad viewpoint is taken, and the CFD state-of-the-art for predicting these types of flows is evaluated from a general point of view. Overall, for synthetic jets, CFD can only qualitatively predict the flow physics, but there is some uncertainty regarding how to best model the unsteady boundary conditions from the experiment consistently. As a result. there is wide variation among CFD results. For the hump flow, CFD as a whole is capable of predicting many of the particulars of this flow provided that tunnel blockage is accounted for, but the length of the separated region compared to experimental results is consistently overpredicted.

  10. Separable systems for recovery of finger strength and control after stroke.

    PubMed

    Xu, Jing; Ejaz, Naveed; Hertler, Benjamin; Branscheidt, Meret; Widmer, Mario; Faria, Andreia V; Harran, Michelle D; Cortes, Juan C; Kim, Nathan; Celnik, Pablo A; Kitago, Tomoko; Luft, Andreas R; Krakauer, John W; Diedrichsen, Jörn

    2017-08-01

    Impaired hand function after stroke is a major cause of long-term disability. We developed a novel paradigm that quantifies two critical aspects of hand function, strength, and independent control of fingers (individuation), and also removes any obligatory dependence between them. Hand recovery was tracked in 54 patients with hemiparesis over the first year after stroke. Most recovery of strength and individuation occurred within the first 3 mo. A novel time-invariant recovery function was identified: recovery of strength and individuation were tightly correlated up to a strength level of ~60% of estimated premorbid strength; beyond this threshold, strength improvement was not accompanied by further improvement in individuation. Any additional improvement in individuation was attributable instead to a second process that superimposed on the recovery function. We conclude that two separate systems are responsible for poststroke hand recovery: one contributes almost all of strength and some individuation; the other contributes additional individuation.NEW & NOTEWORTHY We tracked recovery of the hand over a 1-yr period after stroke in a large cohort of patients, using a novel paradigm that enabled independent measurement of finger strength and control. Most recovery of strength and control occurs in the first 3 mo after stroke. We found that two separable systems are responsible for motor recovery of hand: one contributes strength and some dexterity, whereas a second contributes additional dexterity. Copyright © 2017 the American Physiological Society.

  11. Factors Controlling Redox Speciation of Plutonium and Neptunium in Extraction Separation Processes

    SciTech Connect

    Paulenova, Alena; Vandegrift, III, George F.

    2013-09-24

    The objective of the project was to examine the factors controlling redox speciation of plutonium and neptunium in UREX+ extraction in terms of redox potentials, redox mechanism, kinetics and thermodynamics. Researchers employed redox-speciation extractions schemes in parallel to the spectroscopic experiments. The resulting distribution of redox species w studied uring spectroscopic, electrochemical, and spectro-electrochemical methods. This work reulted in collection of data on redox stability and distribution of redox couples in the nitric acid/nitrate electrolyte and the development of redox buffers to stabilize the desired oxidation state of separated radionuclides. The effects of temperature and concentrations on the redox behavior of neptunium were evaluated.

  12. Stabilizing Spatially-Structured Populations through Adaptive Limiter Control

    PubMed Central

    Sah, Pratha; Dey, Sutirth

    2014-01-01

    Stabilizing the dynamics of complex, non-linear systems is a major concern across several scientific disciplines including ecology and conservation biology. Unfortunately, most methods proposed to reduce the fluctuations in chaotic systems are not applicable to real, biological populations. This is because such methods typically require detailed knowledge of system specific parameters and the ability to manipulate them in real time; conditions often not met by most real populations. Moreover, real populations are often noisy and extinction-prone, which can sometimes render such methods ineffective. Here, we investigate a control strategy, which works by perturbing the population size, and is robust to reasonable amounts of noise and extinction probability. This strategy, called the Adaptive Limiter Control (ALC), has been previously shown to increase constancy and persistence of laboratory populations and metapopulations of Drosophila melanogaster. Here, we present a detailed numerical investigation of the effects of ALC on the fluctuations and persistence of metapopulations. We show that at high migration rates, application of ALC does not require a priori information about the population growth rates. We also show that ALC can stabilize metapopulations even when applied to as low as one-tenth of the total number of subpopulations. Moreover, ALC is effective even when the subpopulations have high extinction rates: conditions under which another control algorithm had previously failed to attain stability. Importantly, ALC not only reduces the fluctuation in metapopulation sizes, but also the global extinction probability. Finally, the method is robust to moderate levels of noise in the dynamics and the carrying capacity of the environment. These results, coupled with our earlier empirical findings, establish ALC to be a strong candidate for stabilizing real biological metapopulations. PMID:25153073

  13. Spatial control of the actin cytoskeleton in Drosophila epithelial cells.

    PubMed

    Baum, B; Perrimon, N

    2001-10-01

    The actin cytoskeleton orders cellular space and transduces many of the forces required for morphogenesis. Here we combine genetics and cell biology to identify genes that control the polarized distribution of actin filaments within the Drosophila follicular epithelium. We find that profilin and cofilin regulate actin-filament formation throughout the cell cortex. In contrast, CAP-a Drosophila homologue of Adenylyl Cyclase Associated Proteins-functions specifically to limit actin-filament formation catalysed by Ena at apical cell junctions. The Abl tyrosine kinase also collaborates in this process. We therefore propose that CAP, Ena and Abl act in concert to modulate the subcellular distribution of actin filaments in Drosophila.

  14. Controlling Phase Separation of Tough Interpenetrating Polymer Networks via Addition of Amphiphilic Block Copolymers

    NASA Astrophysics Data System (ADS)

    Rohde, Brian; Krishnamoorti, Ramanan; Robertson, Megan

    Interpenetrating polymer networks (IPNs) offer a unique way to combine the mechanical properties of two thermoset systems. Often used to create a material that possesses both high toughness and tensile properties, here we use polydicyclopentadiene, cured via ring opening metathesis polymerization, to contribute high toughness and diglycidyl ether of bisphenol A cured via anhydride chemistry to contribute high tensile strength and modulus. As the uncompatibilized system reacts in the presence of one another, mesoscopic phase separation occurs and dictates the overall efficacy of combining mechanical properties. To control phase separation and drive the system towards more mechanically robust nanostructed IPNs, amphiphilic block copolymers of polybutadiene- b-polyethylene oxide, where one block possesses strong affinity to polyDCPD and the other the DGEBA, were added to the system. Here we present a systematic study of the influence of block copolymer composition in the overall blend on degree of phase separation and morphology using a combination of small-angle x-ray scattering (SAXS) and scanning electron microscopy (SEM) techniques. The resultant mechanical properties are then explored in an effort to link mechanical properties to blend morphology.

  15. Controlling Phase Separation of Interpenetrating Polymer Networks by Addition of Block Copolymers

    NASA Astrophysics Data System (ADS)

    Rohde, Brian; Krishnamoorti, Ramanan; Robertson, Megan

    2015-03-01

    Interpenetrating polymer networks (IPNs) offer a unique way to produce mechanically superior thermoset blends relative to the neat components. In this study, IPNs were prepared consisting of polydicyclopentadiene (polyDCPD), contributing high fracture toughness, and an epoxy resin (the diglycidyl ether of bisphenol A cured with nadic methyl anhydride), contributing high tensile strength and modulus. In the absence of compatibilization, the simultaneous curing of the networks leads to a macroscopically phase separated blend that exhibits poor mechanical behavior. To control phase separation and drive the system towards more mechanically robust nanostructured IPNs, block copolymers were designed to compatibilize this system, where one block possesses affinity to polyDCPD (polynorbornene in this study) and the other block possesses affinity to DGEBA (poly(ɛ-caprolactone) in this study). The influence of the block copolymer composition on the degree of phase separation and interfacial adhesion in the IPN was studied using a combination of small-angle scattering and imaging techniques. The resultant mechanical properties were explored and structure-property relationships were developed in this blend system.

  16. Control of Crystallization to Promote Microphase Separation in Fully Conjugated Block Copolymers

    NASA Astrophysics Data System (ADS)

    Lee, Youngmin; Le, Thinh P.; Seibers, Zach; Kilbey, S. Michael, II; Wang, Qing; Gomez, Enrique D.

    Donor -acceptor fully conjugated block copolymers, where donor and acceptor conjugated polymers are covalently bonded together, are interesting as single-component active-layer materials for photovoltaics because it can adopt mesoscale microphase separated structures with length scales comparable to the exciton diffusion length. Nevertheless, due to the strong crystallization of poly(3-hexylthiophene-2,5-diyl) (P3HT), morphologies of fully conjugated block copolymers containing P3HT are predominantly driven by crystallization as opposed to microphase separation. We control the crystallization in block copolymers to promote microphase separation in fully conjugated block copolymers through the addition of small amounts of 3-octylthiophene to the polymerization of P3HT. Poly(3-hexylthiophene-2,5-diyl- r-3-octylthiophene-2,5-diyl)-block-poly((9,9-dioctylfluorene-2,7-diyl)-alt-(4,7-di(thiophene-2-yl)-2,1,3-benzothiadiazole)-5',5''-diyl) (P3HT- b-PFTBT) copolymers were prepared by Grignard metathesis for the alkylthiophene block followed by chain extension through a Suzuki-Miyaura polycondensation. We compare the crystallization, self-assembly and performance in devices of P3HT-b-PFTBT with a few mole percent of 3-octylthiophene in the P3HT block. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831.

  17. Controlling turbulent boundary layer separation using biologically inspired 2D transverse grooves

    NASA Astrophysics Data System (ADS)

    Lang, Amy; Jones, Emily; Afroz, Farhana

    2013-11-01

    It is theorized that the presence of grooves, such as the sinusoidal ones found on dolphin skin or the cavities that form between bristled shark skin scales, can lead to induced boundary layer mixing and result in the control of turbulent boundary layer separation. To test this hypothesis, a series of water tunnel experiments using DPIV studied the characteristics of a flat plate turbulent boundary layer whereby a rotating cylinder was used to induce an adverse pressure gradient and resulting flow separation. The experiments were repeated with the use of a plate covered with two types of grooves, rectangular and sinusoidal, with a spacing of 2 mm in size. Flow similarity of the cavity flow was preserved between the experiments and flow over bristled shark skin scales. Both geometries resulted in a reduction of flow separation as measured by backflow coefficient. In addition, Reynolds stress profiles showed that as the pressure gradient was increased, the sinusoidal geometry outperformed the rectangular grooves in terms of increased mixing close to the wall. The sinusoidal plate also generated a lower momentum deficit within the boundary layer which would indicate a smaller drag penalty. Support from NSF grant CBET 0932352 and a UA Graduate Council Fellowship is gratefully acknowledged.

  18. Lower critical solution temperature (LCST) phase separation of glycol ethers for forward osmotic control.

    PubMed

    Nakayama, Daichi; Mok, Yeongbong; Noh, Minwoo; Park, Jeongseon; Kang, Sunyoung; Lee, Yan

    2014-03-21

    Lower critical solution temperature (LCST) phase transition of glycol ether (GE)-water mixtures induces an abrupt change in osmotic pressure driven by a mild temperature change. The temperature-controlled osmotic change was applied for the forward osmosis (FO) desalination. Among three GEs evaluated, di(ethylene glycol) n-hexyl ether (DEH) was selected as a potential FO draw solute. A DEH-water mixture with a high osmotic pressure could draw fresh water from a high-salt feed solution such as seawater through a semipermeable membrane at around 10 °C. The water-drawn DEH-water mixture was phase-separated into a water-rich phase and a DEH-rich phase at around 30 °C. The water-rich phase with a much reduced osmotic pressure released water into a low-salt solution, and the DEH-rich phase was recovered into the initial DEH-water mixture. The phase separation behaviour, the residual GE concentration in the water-rich phase, the osmotic pressure of the DEH-water mixture, and the osmotic flux between the DEH-water mixture and salt solutions were carefully analysed for FO desalination. The liquid-liquid phase separation of the GE-water mixture driven by the mild temperature change between 10 °C and 30 °C is very attractive for the development of an ideal draw solute for future practical FO desalination.

  19. Upgrading of PVC rich wastes by magnetic density separation and hyperspectral imaging quality control.

    PubMed

    Luciani, Valentina; Bonifazi, Giuseppe; Rem, Peter; Serranti, Silvia

    2015-11-01

    Polyvinylchloride (PVC) is one of the most produced polymers in Europe, with a share of 11% in terms of mass (8 milliontons) of total polymer consumption, but in 2010 only 5% of the total PVC production came from recycled materials, where other polymer recycling achieves a level of 15% on average. In order to find an innovative process to extract PVC from window frames waste, a combination of two innovative technologies was tested: magnetic density separation (MDS) and hyperspectral imaging (HSI). By its nature, MDS is a flexible high precision density separation technology that is applicable to any mixture of polymers and contaminants with non-overlapping densities. As PVC has a very distinctive high density, this technology was tested to obtain high-grade PVC pre-concentrates from window frame waste. HSI was used to perform a quality control of the products obtained by MDS showing that PVC was clearly discriminated from unwanted rubber particles of different colors. The results showed that the combined application of MDS and HSI techniques allowed to separate and to check the purity of PVC from window frame waste.

  20. Separate and unequal: the influence of neighborhood and school characteristics on spatial proximity between fast food and schools.

    PubMed

    Kwate, Naa Oyo A; Loh, Ji Meng

    2010-08-01

    Social science and health literature have identified residential segregation as a critical factor in exposure to health-related resources, including food environments. Differential spatial patterning of food environments surrounding schools has significant import for youth. We examined whether fast food restaurants clustered around schools in New York City, and whether any observed clustering varied as a function of school type, school racial demographics, and area racial and socioeconomic demographics. We geocoded fast food locations from 2006 (n=817) and schools from 2004-2005 (n=2096; public and private, elementary and secondary) in the five boroughs of New York City. A point process model (inhomogeneous cross-K function) examined spatial clustering. A minimum of 25% of schools had a fast food restaurant within 400 m. High schools had higher fast food clustering than elementary schools. Public elementary and high schools with large proportions of Black students or in block groups with large proportions of Black residents had higher clustering than White counterparts. Finally, public high schools had higher clustering than private counterparts, with 1.25 to 2 times as many restaurants than expected by chance. The results suggest that the geography of opportunity as it relates to school food environments is unequal in New York City. Copyright 2010 Elsevier Inc. All rights reserved.

  1. Spatially controlled surface energy traps on superhydrophobic surfaces.

    PubMed

    Milionis, Athanasios; Fragouli, Despina; Martiradonna, Luigi; Anyfantis, George C; Cozzoli, P Davide; Bayer, Ilker S; Athanassiou, Athanassia

    2014-01-22

    Water wetting and adhesion control on polymeric patterns are achieved by tuning the configuration of their surface's structural characteristics from single to dual and triple length-scale. In particular, surfaces with combined micro-, submicrometer-,and nanoroughness are developed, using photolithographically structured SU-8 micro-pillars as substrates for the consecutive spray deposition of polytetrafluoroethylene (PTFE) submicrometer particles and hydrophobically capped iron oxide colloidal nanoparticles. The PTFE particles alone or in combination with the nanoparticles render the SU-8 micropillars superhydrophobic. The water adhesion behaviour of the sprayed pillars is more complex since they can be tuned gradually from totally adhesive to completely non adhesive. The influence of the hierarchical geometrical features of the functionalized surfaces on this behaviour is discussed within the frame of the theory. Specially designed surfaces using the described technique are presented for selective drop deposition and evaporation. This simple method for liquid adhesion control on superhydrophobic surfaces can find various applications in the field of microfluidics, sensors, biotechnology, antifouling materials, etc.

  2. Morphology control through hierarchical phase separation in Langmuir monolayers of poly(methyl methacrylate)-b-poly(n-butyl acrylate).

    PubMed

    Watanabe, Atsushi; Kumaki, Jiro

    2017-01-15

    Precise morphology control of ultrathin films is one of the important issues in nanotechnology. To this end, we describe that various controlled morphologies of hierarchical phase separation can be attained using poly(methyl methacrylate)-b-poly(n-butyl acrylate) (PMMA-b-PBA) monolayers spread on a water surface. At a low surface pressure, they were miscible, but upon compression, phase separated with a monolayer of the major component block spreading on the water surface, on top of which the minor component block separated out (hierarchical phase separation). The morphology of the minor component block separated out on top of the monolayer varied from a sphere/short string mixture, to long strings, and a mesh-like structure having a regular domain-domain spacing with the increasing content of the minor block, and the hierarchical phase separation was reversible depending on the surface pressure. However, these well-ordered hierarchical phase separations were observed only in the PBA-rich polymers, and a clear morphology was not observed in the PMMA-rich polymers, because of insufficient domain growth after the hierarchical phase separation for the PMMA-rich block copolymers which are more rigid than the PBA-rich polymers. Although the clear hierarchical phase separation was limited in flexible composition, we noted that the hierarchical phase separation provided a unique well-controlled morphology in the Langmuir monolayers. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. Effects of Elevated Free-Stream Turbulence on Active Control of a Separation Bubble

    NASA Technical Reports Server (NTRS)

    Ashpis, D. (Technical Monitor); Halfon, E.; Nishri, B.; Seifert, A.; Wygnanski, I.

    2004-01-01

    The Effects of elevated free-stream turbulence (FST) on the natural and periodically excited separation bubbles were studied experimentally, due to the relevance of this flow to low-pressure turbine blades at low Reynolds numbers. A bubble was formed at the leading edge of a flat plate and the FST level was altered by placing a grid across the flow at different locations upstream of the plate. The mixing across the separated shear-layer, forming the free boundary of the bubble, increased due to the elevated FST and due to nominally two-dimensional periodic excitation, both flattening and shortening the bubble. Periodic excitation at frequencies that were at least an order of magnitude lower than those associated with the initial shear-layer instability, were very effective at low FST, because the amplitudes of the excitation frequency and its harmonic were amplified over the bubble. High frequency excitation (F+ 3, based on the length of the baseline low FST bubble) had a major effect close to the separation location, while farther downstream the excited fluctuations rapidly decayed in the reattachment region. Low frequency excitation, that generated waves comparable to the length of the unperturbed bubble (F+ 1) were less effective and their magnitude decayed at a slower rate downstream of reattachment. An increase in the level of the FST reduced the net effect of the periodic excitation on the mixing enhancement and subsequent reattachment process, probably due to a destructive interference between the nominally 2D excitation and the random (in space and time) FST, reducing the spanwise coherence and therefore the effectiveness of the current control strategy. However, even at the reduced effectiveness of 2D periodic excitation at elevated FST, it accelerated the reattachment process and the recovery rate of the reattached boundary layer, enhancing the boundary layer resistance to repeat separation and reducing its momentum loss further downstream.

  4. Active separation control of high-Re turbulent separated flow over a wall-mounted hump using RANS, DES, and LES turbulence modeling approaches

    NASA Astrophysics Data System (ADS)

    Gan, Subhadeep

    Most practical flows in engineering applications are turbulent, and exhibit separation which is generally undesirable because of its adverse effects on performance and efficiency. Therefore, control of turbulent separated flows has been a topic of significant interest as it can reduce separation losses. Often, flow control work employs passive techniques to manipulate the flow. Passive-flow control does not require any additional energy source to achieve the control, but is accompanied by additional viscous losses. It is more desirable to employ active techniques as these can be turned on and off, depending on the flow control requirement. The primary goal of the present work is to numerically investigate a high Reynolds number turbulent separated flow. It is Case 3 of the 2004 CFD Validation on Synthetic Jets and Turbulent Separation Control Workshop, http://cfdval2004.larc.nasa.gov/case3.html, conducted by NASA for the flow over a wall-mounted hump. Followed by the baseline flow simulation, i.e., without flow control, active flow control will be investigated using both steady suction jet as well as a "synthetic" jet. Use of synthetic jets has gained popularity in recent times for active flow control because of their ability to transfer linear momentum to the flow system without net-mass injection across the boundary in the vicinity of separation. The present work also implements the use of two jets (steady suction and synthetic jets) as have not been previously implemented for this flow model. For the synthetic-jets case, the work also studies the effect of two jets in opposite phase. The secondary goal of this work is to bring together a variety of turbulence models and simulation approaches for one flow problem. Turbulent Couette flow was used as a model flow problem to validate the flow solver and investigate the performance of different turbulence models and approaches. The flow is simulated using steady and unsteady-state three-dimensional Reynolds

  5. Spatial control of reflexes, posture and movement in normal conditions and after neurological lesions

    PubMed Central

    Feldman, Anatol G.; Levin, Mindy F.

    2016-01-01

    Abstract Control of reflexes is usually associated with central modulation of their sensitivity (gain) or phase-dependent inhibition and facilitation of their influences on motoneurons (reflex gating). Accumulated empirical findings show that the gain modulation and reflex gating are secondary, emergent properties of central control of spatial thresholds at which reflexes become functional. In this way, the system pre-determines, in a feedforward and task-specific way, where, in a spatial domain or a frame of reference, muscles are allowed to work without directly prescribing EMG activity and forces. This control strategy is illustrated by considering reflex adaptation to repeated muscle stretches in healthy subjects, a process associated with implicit learning and generalization. It has also been shown that spasticity, rigidity, weakness and other neurological motor deficits may have a common source – limitations in the range of spatial threshold control elicited by neural lesions. PMID:28149391

  6. Analysis of an atom laser based on the spatial control of the scattering length

    SciTech Connect

    Carpentier, Alicia V.; Michinel, Humberto; Rodas-Verde, Maria I.; Perez-Garcia, Victor M.

    2006-07-15

    In this paper we analyze atom lasers based on the spatial modulation of the scattering length of a Bose-Einstein condensate. We demonstrate, through numerical simulations and approximate analytical methods, the controllable emission of matter-wave bursts and study the dependence of the process on the spatial shape of the scattering length along the axis of emission. We also study the role of an additional modulation of the scattering length in time.

  7. Unmanned air vehicle flow separation control using dielectric barrier discharge plasma at high wind speed

    NASA Astrophysics Data System (ADS)

    Zhang, Xin; Huang, Yong; Wang, WanBo; Wang, XunNian; Li, HuaXing

    2014-06-01

    The present paper described an experimental investigation of separation control of an Unmanned Aerial Vehicle (UAV) at high wind speeds. The plasma actuator was based on Dielectric Barrier Discharge (DBD) and operated in a steady manner. The flow over a wing of UAV was performed with smoke flow visualization in the ϕ0.75 m low speed wind tunnel to reveal the flow structure over the wing so that the locations of plasma actuators could be optimized. A full model of the UAV was experimentally investigated in the ϕ3.2 m low speed wind tunnel using a six-component internal strain gauge balance. The effects of the key parameters, including the locations of the plasma actuators, the applied voltage amplitude and the operating frequency, were obtained. The whole test model was made of aluminium and acted as a cathode of the actuator. The results showed that the plasma acting on the surface of UAV could obviously suppress the boundary layer separation and reduce the model vibration at the high wind speeds. It was found that the maximum lift coefficient of the UAV was increased by 2.5% and the lift/drag ratio was increased by about 80% at the wind speed of 100 m/s. The control mechanism of the plasma actuator at the test configuration was also analyzed.

  8. Selective Separation of Similar Metals in Chloride Solution by Sulfide Precipitation Under Controlled Potential

    NASA Astrophysics Data System (ADS)

    Liu, Weifeng; Sun, Baiqi; Zhang, Duchao; Chen, Lin; Yang, Tianzu

    2017-08-01

    A new process of sulfide precipitation under controlled potential was proposed to separate selectively similar metals in a Bis(2-ethylhexyl) phosphoric acid (P204) stripping solution of the Co extraction system. Theoretical calculations revealed that Cu2+, Co2+, Zn2+, and Mn2+ could be separated by fractional precipitation with sulfide by controlling the solution potential and pH value simultaneously. The results demonstrated a Cu precipitation ratio reaching 99.9% during sulfide precipitation of Cu at the potential of 330 mV; the Cu/Co mass ratio in the Cu precipitate was 224. The Co precipitation ratio in the xanthate precipitation of Co, at a potential of 170 mV, was 99.9%, and the Co/Zn mass ratio in the Co precipitate was 28.0. The Zn precipitation ratio reached 99.9% for sulfide precipitation of Zn at the potential of 30 mV, and the Zn/Mn mass ratio in the Zn precipitate was 1.41. The Mn precipitation ratio reached 99.9% after neutralization.

  9. Control of unsteady separated flow associated with the dynamic pitching of airfoils

    NASA Technical Reports Server (NTRS)

    Ahmed, Sajeer

    1991-01-01

    Although studies have been done to understand the dependence of parameters for the occurrence of deep stall, studies to control the flow for sustaining lift for a longer time has been little. To sustain the lift for a longer time, an understanding of the development of the flow over the airfoil is essential. Studies at high speed are required to study how the flow behavior is dictated by the effects of compressibility. When the airfoil is pitched up in ramp motion or during the upstroke of an oscillatory cycle, the flow development on the upper surface of the airfoil and the formation of the vortex dictates the increase in lift behavior. Vortex shedding past the training edge decreases the lift. It is not clear what is the mechanism associated with the unsteady separation and vortex formation in present unsteady environment. To develop any flow control device, to suppress the vortex formation or delay separation, it is important that this mechanism be properly understood. The research activities directed toward understanding these questions are presented and the results are summarized.

  10. Construction of macroscopic cytomimetic vesicle aggregates based on click chemistry: controllable vesicle fusion and phase separation.

    PubMed

    Jin, Haibao; Huang, Wei; Zheng, Yongli; Zhou, Yongfeng; Yan, Deyue

    2012-07-09

    Vesicle-vesicle aggregation to mimic cell-cell aggregation has attracted much attention. Here, hyperbranched polymer vesicles (branched-polymersomes, BPs) with a cell-like size were selected as model membranes, and the vesicle aggregation process, triggered by click chemistry of the copper-catalysed azide-alkyne cycloaddition reaction, was systematically studied. For this purpose, azide and alkynyl groups were loaded on the membranes of BPs through the co-assembly method to obtain N(3)-BPs and Alk-BPs, respectively. Subsequently, macroscopic vesicle aggregates were obtained when these two kinds of functional BPs were mixed together with the ratio of azide to alkynyl groups of about 1:1. Both the vesicle fusion events and lateral phase separation on the vesicle membrane occurred during such a vesicle aggregation process, and the fusion rate and phase-separation degree could be controlled by adjusting the clickable group content. The vesicle aggregation process with N(3) -micelles as desmosome mimics to connect with Alk-BPs through click-chemistry reaction was also studied, and large-scale vesicle aggregates without vesicle fusion were obtained in this process. The present work has extended the controllable cytomimetic vesicle aggregation process with the use of covalent bonds, instead of noncovalent bonds, as the driving force.

  11. Active Control of Separation From the Flap of a Supercritical Airfoil

    NASA Technical Reports Server (NTRS)

    Melton, LaTunia Pack; Yao, Chung-Sheng; Seifert, Avi

    2006-01-01

    Zero-mass-flux periodic excitation was applied at several regions on a simplified high-lift system to delay the occurrence of flow separation. The NASA Energy Efficient Transport (EET) supercritical airfoil was equipped with a 15% chord simply hinged leading edge flap and a 25% chord simply hinged trailing edge flap. Detailed flow features were measured in an attempt to identify optimal actuator placement. The measurements included steady and unsteady model and tunnel wall pressures, wake surveys, arrays of surface hot-films, flow visualization, and particle image velocimetry (PIV). The current paper describes the application of active separation control at several locations on the deflected trailing edge flap. High frequency (F(+) approximately equal to 10) and low frequency amplitude modulation (F(+) sub AM approximately equal to 1) of the high frequency excitation were used for control. It was noted that the same performance gains were obtained with amplitude modulation and required only 30% of the momentum input required by pure sine excitation.

  12. Shape and spatial correlation control of InAs-InAlAs-InP (001) nanostructure superlattices

    SciTech Connect

    Lei, W.; Chen, Y.H.; Jin, P.; Ye, X.L.; Wang, Y.L.; Xu, B.; Wang, Z.G.

    2006-02-06

    The control of shape and spatial correlation of InAs-InAlAs-InP(001) nanostructure superlattices has been realized by changing the As overpressure during the molecular-beam epitaxy (MBE) growth of InAs layers. InAs quantum wires (QWRs) are obtained under higher As overpressure (1x10{sup -5} Torr), while elongated InAs quantum dots (QDs) are formed under lower As overpressure (5x10{sup -6} or 2.5x10{sup -6} Torr). Correspondingly, spatial correlation changes from vertical anti-correlation in QWR superlattices to vertical correlation in QD superlattices, which is well explained by the different alloy phase separation in InAlAs spacer layers triggered by the InAs nanostrcutures. It was observed that the alloy phase separation in QD superlattices could extend a long distance along the growth direction, indicating the vertical correlation of QD superlattices can be kept in a wide range of spacer layer thickness.

  13. Investigation of airfoil leading edge separation control with nanosecond plasma actuator

    NASA Astrophysics Data System (ADS)

    Zheng, J. G.; Cui, Y. D.; Zhao, Z. J.; Li, J.; Khoo, B. C.

    2016-11-01

    A combined numerical and experimental investigation of airfoil leading edge flow separation control with a nanosecond dielectric barrier discharge (DBD) plasma actuator is presented. Our study concentrates on describing dynamics of detailed flow actuation process and elucidating the nanosecond DBD actuation mechanism. A loose coupling methodology is employed to perform simulation, which consists of a self-similar plasma model for the description of pulsed discharge and two-dimensional Reynolds averaged Navier-Stokes (RANS) equations for the calculation of external airflow. A series of simulations of poststall flows around a NACA0015 airfoil is conducted with a Reynolds number range covering both low and high Re at Re=(0.05 ,0.15 ,1.2 ) ×106 . Meanwhile, wind-tunnel experiment is performed for two low Re flows to measure aerodynamic force on airfoil model and transient flow field with time-resolved particle image velocimetry (PIV). The PIV measurement provides possibly the clearest view of flow reattachment process under the actuation of a nanosecond plasma actuator ever observed in experiments, which is highly comparable to that predicted by simulation. It is found from the detailed simulation that the discharge-induced residual heat rather than shock wave plays a dominant role in flow control. For any leading edge separations, the preliminary flow reattachment is realized by residual heat-induced spanwise vortices. After that, the nanosecond actuator functions by continuing exciting flow instability at poststall attack angles or acting as an active trip near stall angle. As a result, the controlled flow is characterized by a train of repetitive, downstream moving vortices over suction surface or an attached turbulent boundary layer, which depends on both angle of attack and Reynolds number. The advection of residual temperature with external flow offers a nanosecond plasma actuator a lot of flexibility to extend its influence region. Animations are provided for

  14. Separating physical and biological controls on evapotranspiration fluctuations in a teak plantation subjected to monsoonal rainfall

    NASA Astrophysics Data System (ADS)

    Igarashi, Y.; Katul, G. G.; Kumagai, T.; Yoshifuji, N.; Sato, T.; Tanaka, N.; Tanaka, K.; Fujinami, H.; Chatchai, T.; Suzuki, M.

    2014-12-01

    Evapotranspiration (ET), especially in the mainland of the Indochina peninsula, can impact and is impacted by the Asian monsoonal (AM) system, thereby prompting interest in its long-term variability. To separate physical and biological factors controlling ET variability in a tropical deciduous forest under the AM influence, 7-year eddy-covariance and ancillary measurements were collected and analyzed. The 7-year mean rainfall (Pr) and ET along with their standard deviations were 1335 ± 256 and 1027 ± 77.9 mm (about 77% of Pr), respectively, suggesting close coupling between these two hydrologic fluxes. However, other physical and biological drivers de-couple seasonal and annual variations of ET from Pr. To explore them, a big-leaf model complemented by perturbation analysis was employed. The big-leaf model agreed well with measured ET at daily to multi-year time scales, lending confidence in its skill to separate biological from physical controls on ET. Using this formulation, both first-order and second-order Taylor series expansion of total ET derivatives were applied to the big-leaf model and compare with measured changes in ET (dET). Higher-order and joint-terms in the second-order expansion were necessary for matching measured and analyzed dET. Vapor pressure deficit (D) was the primary external physical controlling driver on ET. The leaf area index (LAI) and bulk stomatal conductance (gs) were shown to be the main significant biological drivers on the transpiration component of ET. It can be surmised that rainfall variability controls long-term ET through physical (mainly D) and biological (mainly LAI and gs) in this ecosystem.

  15. The Effects of Sweeping Jet Actuator Parameters on Flow Separation Control

    NASA Technical Reports Server (NTRS)

    Koklu, Mehti

    2015-01-01

    A parametric experimental study was performed with sweeping jet actuators (fluidic oscillators) to determine their effectiveness in controlling flow separation on an adverse pressure gradient ramp. Actuator parameters that were investigated include blowing coefficients, operation mode, pitch and spreading angles, streamwise location, aspect ratio, and scale. Surface pressure measurements and surface oil flow visualization were used to characterize the effects of these parameters on the actuator performance. 2D Particle Image Velocimetry measurements of the flow field over the ramp and hot-wire measurements of the actuator's jet flow were also obtained for selective cases. In addition, the sweeping jet actuators were compared to other well-known flow control techniques such as micro-vortex generators, steady blowing, and steady vortex-generating jets. The results confirm that the sweeping jet actuators are more effective than steady blowing and steady vortex-generating jets. The results also suggest that an actuator with a larger spreading angle placed closer to the location where the flow separates provides better performance. For the cases tested, an actuator with an aspect ratio, which is the width/depth of the actuator throat, of 2 was found to be optimal. For a fixed momentum coefficient, decreasing the aspect ratio to 1 produced weaker vortices while increasing the aspect ratio to 4 reduced coverage area. Although scaling down the actuator (based on the throat dimensions) from 0.25 inch x 0.125 inch to 0.15 inch x 0.075 inch resulted in similar flow control performance, scaling down the actuator further to 0.075 inch x 0.0375 inch reduced the actuator efficiency by reducing the coverage area and the amount of mixing in the near-wall region. The results of this study provide insight that can be used to design and select the optimal sweeping jet actuator configuration for flow control applications.

  16. Experimental implementation of automatic 'cycle to cycle' control to a nonlinear chiral simulated moving bed separation.

    PubMed

    Grossmann, Cristian; Langel, Christian; Mazzotti, Marco; Morari, Manfred; Morbidelli, Massimo

    2010-03-26

    In order to better exploit the economic potential of the simulated moving bed chromatography a 'cycle to cycle' controller which only requires the information about the linear adsorption behavior and the overall average porosity of the columns has been proposed. Recently, an automated on-line HPLC monitoring system which determines the concentrations in the two product streams averaged over one cycle, and returns them as feedback information to the controller was implemented. The new system allows for an accurate determination of the average concentration of the product streams even if the plant is operated at high concentrations. This paper presents the experimental implementation of the 'cycle to cycle' control concept to the separation of guaifenesin enantiomers under nonlinear chromatographic conditions, i.e. at high feed concentrations. Different case studies have been carried out to challenge the controller under realistic operation conditions, e.g. introducing pump disturbances and changing the feed concentration during the operation. The experimental results clearly demonstrate that the controller can indeed deliver the specified purities and improve the process performance.

  17. Spatially-based quality control for daily precipitation datasets

    NASA Astrophysics Data System (ADS)

    Serrano-Notivoli, Roberto; de Luis, Martín; Beguería, Santiago; Ángel Saz, Miguel

    2016-04-01

    There are many reasons why wrong data can appear in original precipitation datasets but their common characteristic is that all of them do not correspond to the natural variability of the climate variable. For this reason, is necessary a comprehensive analysis of the data of each station in each day, to be certain that the final dataset will be consistent and reliable. Most of quality control techniques applied over daily precipitation are based on the comparison of each observed value with the rest of values in same series or in reference series built from its nearest stations. These methods are inherited from monthly precipitation studies, but in daily scale the variability is bigger and the methods have to be different. A common character shared by all of these approaches is that they made reconstructions based on the best-correlated reference series, which could be a biased decision because, for example, a extreme precipitation occurred in one day in more than one station could be flagged as erroneous. We propose a method based on the specific conditions of the day and location to determine the reliability of each observation. This method keeps the local variance of the variable and the time-structure independence. To do that, individually for each daily value, we first compute the probability of precipitation occurrence through a multivariate logistic regression using the 10 nearest observations in a binomial mode (0=dry; 1=wet), this produces a binomial prediction (PB) between 0 and 1. Then, we compute a prediction of precipitation magnitude (PM) with the raw data of the same 10 nearest observations. Through these predictions we explore the original data in each day and location by five criteria: 1) Suspect data; 2) Suspect zero; 3) Suspect outlier; 4) Suspect wet and 5) Suspect dry. Tests over different datasets addressed that flagged data depend mainly on the number of available data and the homogeneous distribution of them.

  18. Reversal of prenatal diazepam-induced deficit in a spatial-object learning task by brief, periodic maternal separation in adult rats.

    PubMed

    Cannizzaro, E; Martire, M; Gagliano, M; Plescia, F; La Barbera, M; Mantia, G; Mineo, A; Cannizzaro, G; Cannizzaro, C

    2005-06-20

    In the rat, prenatal exposure to diazepam (DZ) induces a permanent reduction in GABA/BZ receptor (R) function and behavioural abnormalities. Environmental modifications during early stages of life can influence brain development and induce neurobiological and behavioural changes throughout adulthood. Indeed, a subtle, periodic, postnatal manipulation increases GABA/BZ R activity and produces facilitatory effects on neuroendocrine and behavioural responses. We here investigated the impact of prenatal treatment with DZ on learning performance in adult 3- and 8-month-old male rats and the influence of a brief, periodic maternal separation on the effects exerted by prenatal DZ exposure. Learning performance was examined employing a non-aversive spatial, visual and/or tactile task, the "Can test". Behavioural reactivity, emotional state and fear/anxiety-driven behaviour were also examined using open field (OF), acoustic startle reflex (ASR) and elevated plus-maze (EPM) tests. A single daily injection of DZ (1.5mg/kg, s.c.), over gestational days (GD) 14-20, induced, in an age-independent manner, a severe deficit in learning performance, a decrease in locomotor and explorative activity and an increase in peak amplitude in the ASR. Furthermore, anxiety-driven behaviour in EPM was disrupted. Daily maternal separation for 15 min over postnatal days 2-21 exerted opposite effects in all the paradigms examined. Prenatally DZ-exposed maternal separated rats, in contrast to respective non-separated rats, showed an improvement in learning performance, a decrease in emotionality and a normalization of the exploratory behaviour in EPM. These results suggest that a greater maternal care, induced by separation, can serve as a source for the developing brain to enhance neuronal plasticity and to prevent the behavioural abnormalities induced by prenatal DZ exposure.

  19. A Solvothermal Route Decorated on Different Substrates: Controllable Separation of an Oil/Water Mixture to a Stabilized Nanoscale Emulsion.

    PubMed

    Zhang, Weifeng; Liu, Na; Cao, Yingze; Chen, Yuning; Xu, Liangxin; Lin, Xin; Feng, Lin

    2015-12-02

    A facile solvothermal route is developed to fabricate polydivinylbenzene (PDVB) and decorate the polymer onto porous substrates. "Controllable" separation can be realized by selecting substrates with different pore sizes. The PDVB-modified mesh shows superhydrophobicity/superoleophilicity, and can be used for oil/seawater mixture separation, while the PDVB-modified membrane exhibits high hydrophobicity/superoleophilicity, and is able to separate surfactant stabilized nanoscale water-in-oil emulsions.

  20. Bound state in the continuum by spatially separated ensembles of atoms in a coupled-cavity array

    NASA Astrophysics Data System (ADS)

    Fong, P. T.; Law, C. K.

    2017-08-01

    We present an analytic solution of bound states in the continuum (BICs) for photons and atoms in a one-dimensional coupled-cavity array. These bound states are formed by two ensembles of two-level atoms confined in separated cavities of the array. We show that in the regime where the photon hopping rate between neighboring cavities is high compared with the collective Rabi frequency the BIC corresponds to a nonradiating collective atomic state in which the two ensembles of atoms are strongly entangled. On the other hand, in the low photon hopping rate regime, the BIC behaves as a quantum cavity in which photons can be trapped between the two ensembles of atoms.

  1. Morphological control of multihollow polymer latex particles through a controlled phase separation in the seeded emulsion polymerization.

    PubMed

    Li, Bingxin; Xu, Yongfei; Wang, Mozhen; Ge, Xuewu

    2013-12-03

    In this work, we first reported that the phase separation can take place both inside and outside of a multihollow-structured cross-linked seed microspheres swollen by styrene monomers in water during the radiation-induced seeded emulsion polymerization. The phase separation process in these two opposite directions will determine the morphology of final latex particles. First, sulfonated cross-linked polystyrene (SCPS) seed microspheres were swollen by styrene in water. Water will permeate into the SCPS seed microspheres during the swelling process, forced by the osmotic pressure produced by the strong hydrophilicity of the sulfonic acid groups. New aqueous phases are created and stabilized by the hydrophilic -SO3H groups, resulting in a multihollow structure of swollen SCPS seed microspheres. When the polymerization of styrene is induced by (60)Co γ-ray radiation, the phase separation of newly formed polystyrene phase will occur at the seed microsphere-water interface inside and/or outside of the SCPS seed microspheres through adjusting the diameter of seed microsphere, the content of cross-link agent, and the sulfonation degree of SCPS seed microspheres. As a result, SCPS latex particles with a variety of special morphologies, such as spherical multihollow, plum-like, and walnut-like latex particles were obtained. The results of this study provide not only a simple and interesting way to design and synthesize multihollow polymer latex particles with controllable surface morphologies but also a better understanding on phase separation mechanism during the swelling and polymerization of monomers in cross-linked amphiphilic polymer networks.

  2. Rats (Rattus norvegicus) flexibly retrieve objects' non-spatial and spatial information from their visuospatial working memory: effects of integrated and separate processing of these features in a missing-object recognition task.

    PubMed

    Keshen, Corrine; Cohen, Jerome

    2016-01-01

    After being trained to find a previous missing object within an array of four different objects, rats received occasional probe trials with such test arrays rotated from that of their respective three-object study arrays. Only animals exposed to each object's non-spatial features consistently paired with both its spatial features (feeder's relative orientation and direction) in the first experiment or with only feeder's relative orientation in the second experiment (Fixed Configuration groups) were adversely affected by probe trial test array rotations. This effect, however, was less persistent for this group in the second experiment but re-emerged when objects' non-spatial features were later rendered uninformative. Animals that had both types of each object's features randomly paired over trials but not between a trial's study and test array (Varied Configuration groups) were not adversely affected on probe trials but improved their missing-object recognition in the first experiment. These findings suggest that the Fixed Configuration groups had integrated each object's non-spatial with both (in Experiment 1) or one (in Experiment 2) of its spatial features to construct a single representation that they could not easily compare to any object in a rotated probe test array. The Varied Configuration groups must maintain separate representations of each object's features to solve this task. This prevented them from exhibiting such adverse effects on rotated probe trial test arrays but enhanced the rats' missing-object recognition in the first experiment. We discussed how rats' flexible use (retrieval) of encoded information from their visuospatial working memory corresponds to that of humans' visuospatial memory in object change detection and complex object recognition tasks. We also discussed how foraging-specific factors may have influenced each group's performance in this task.

  3. High-fidelity spatial and polarization addressing of +43Ca qubits using near-field microwave control

    NASA Astrophysics Data System (ADS)

    Aude Craik, D. P. L.; Linke, N. M.; Sepiol, M. A.; Harty, T. P.; Goodwin, J. F.; Ballance, C. J.; Stacey, D. N.; Steane, A. M.; Lucas, D. M.; Allcock, D. T. C.

    2017-02-01

    Individual addressing of qubits is essential for scalable quantum computation. Spatial addressing allows unlimited numbers of qubits to share the same frequency, while enabling arbitrary parallel operations. We demonstrate addressing of long-lived +43Ca "atomic clock" qubits held in separate zones (960 μ m apart) of a microfabricated surface trap with integrated microwave electrodes. Such zones could form part of a "quantum charge-coupled device" architecture for a large-scale quantum information processor. By coherently canceling the microwave field in one zone we measure a ratio of Rabi frequencies between addressed and nonaddressed qubits of up to 1400, from which we calculate a spin-flip probability on the qubit transition of the nonaddressed ion of 1.3 ×10-6 . Off-resonant excitation then becomes the dominant error process, at around 5 ×10-3 . It can be prevented either by working at higher magnetic field, or by polarization control of the microwave field. We implement polarization control with error 2 ×10-5 , which would suffice to suppress off-resonant excitation to the ˜10-9 level if combined with spatial addressing. Such polarization control could also enable fast microwave operations.

  4. Control from below: the role of a midbrain network in spatial attention

    PubMed Central

    Knudsen, Eric I.

    2011-01-01

    Spatial attention enables the brain to analyze and evaluate information selectively from a specific location in space, a capacity essential for any animal to behave adaptively in a complex world. We usually think of spatial attention as being controlled by a fronto-parietal network in the forebrain. However, emerging evidence shows that a midbrain network also plays a critical role in controlling spatial attention. Moreover, the highly differentiated, retinotopic organization of the midbrain network, especially in birds, makes it amenable to detailed analysis with modern techniques that can elucidate circuit, cellular and synaptic mechanisms of attention. The following review discusses the role of the midbrain network in controlling attention, the neural circuits that support this role, and current knowledge about the computations performed by these circuits. PMID:21645092

  5. Spatial variation of the colonic microbiota in patients with ulcerative colitis and control volunteers

    PubMed Central

    Lavelle, A; Lennon, G; O'Sullivan, O; Docherty, N; Balfe, A; Maguire, A; Mulcahy, H E; Doherty, G; O'Donoghue, D; Hyland, J; Ross, R P; Coffey, J C; Sheahan, K; Cotter, P D; Shanahan, F; Winter, D C; O'Connell, P R

    2015-01-01

    Objectives The relevance of spatial composition in the microbial changes associated with UC is unclear. We coupled luminal brush samples, mucosal biopsies and laser capture microdissection with deep sequencing of the gut microbiota to develop an integrated spatial assessment of the microbial community in controls and UC. Design A total of 98 samples were sequenced to a mean depth of 31 642 reads from nine individuals, four control volunteers undergoing routine colonoscopy and five patients undergoing surgical colectomy for medically-refractory UC. Samples were retrieved at four colorectal locations, incorporating the luminal microbiota, mucus gel layer and whole mucosal biopsies. Results Interpersonal variability accounted for approximately half of the total variance. Surprisingly, within individuals, asymmetric Eigenvector map analysis demonstrated differentiation between the luminal and mucus gel microbiota, in both controls and UC, with no differentiation between colorectal regions. At a taxonomic level, differentiation was evident between both cohorts, as well as between the luminal and mucosal compartments, with a small group of taxa uniquely discriminating the luminal and mucosal microbiota in colitis. There was no correlation between regional inflammation and a breakdown in this spatial differentiation or bacterial diversity. Conclusions Our study demonstrates a conserved spatial structure to the colonic microbiota, differentiating the luminal and mucosal communities, within the context of marked interpersonal variability. While elements of this structure overlap between UC and control volunteers, there are differences between the two groups, both in terms of the overall taxonomic composition and how spatial structure is ascribable to distinct taxa. PMID:25596182

  6. Control of unsteady separated flow associated with the dynamic stall of airfoils

    NASA Technical Reports Server (NTRS)

    Wilder, M. C.

    1995-01-01

    An effort to understand and control the unsteady separated flow associated with the dynamic stall of airfoils was funded for three years through the NASA cooperative agreement program. As part of this effort a substantial data base was compiled detailing the effects various parameters have on the development of the dynamic stall flow field. Parameters studied include Mach number, pitch rate, and pitch history, as well as Reynolds number (through two different model chord lengths) and the condition of the boundary layer at the leading edge of the airfoil (through application of surface roughness). It was found for free stream Mach numbers as low as 0.4 that a region of supersonic flow forms on the leading edge of the suction surface of the airfoil at moderate angles of attack. The shocks which form in this supersonic region induce boundary-layer separation and advance the dynamic stall process. Under such conditions a supercritical airfoil profile is called for to produce a flow field having a weaker leading-edge pressure gradient and no leading-edge shocks. An airfoil having an adaptive-geometry, or dynamically deformable leading edge (DDLE), is under development as a unique active flow-control device. The DDLE, formed of carbon-fiber composite and fiberglass, can be flexed between a NACA 0012 profile and a supercritical profile in a controllable fashion while the airfoil is executing an angle-of-attack pitch-up maneuver. The dynamic stall data were recorded using point diffraction interferometry (PDI), a noninvasive measurement technique. A new high-speed cinematography system was developed for recording interferometric images. The system is capable of phase-locking with the pitching airfoil motion for real-time documentation of the development of the dynamic stall flow field. Computer-aided image analysis algorithms were developed for fast and accurate reduction of the images, improving interpretation of the results.

  7. A Resonant Pulse Detonation Actuator for High-Speed Boundary Layer Separation Control

    NASA Technical Reports Server (NTRS)

    Beck, B. T.; Cutler, A. D.; Drummond, J. P.; Jones, S. B.

    2004-01-01

    A variety of different types of actuators have been previously investigated as flow control devices. Potential applications include the control of boundary layer separation in external flows, as well as jet engine inlet and diffuser flow control. The operating principles for such devices are typically based on either mechanical deflection of control surfaces (which include MEMS flap devices), mass injection (which includes combustion driven jet actuators), or through the use of synthetic jets (diaphragm devices which produce a pulsating jet with no net mass flow). This paper introduces some of the initial flow visualization work related to the development of a relatively new type of combustion-driven jet actuator that has been proposed based on a pulse detonation principle. The device is designed to utilize localized detonation of a premixed fuel (Hydrogen)-air mixture to periodically inject a jet of gas transversely into the primary flow. Initial testing with airflow successfully demonstrated resonant conditions within the range of acoustic frequencies expected for the design. Schlieren visualization of the pulsating air jet structure revealed axially symmetric vortex flow, along with the formation of shocks. Flow visualization of the first successful sustained oscillation condition is also demonstrated for one configuration of the current test section. Future testing will explore in more detail the onset of resonant combustion and the approach to conditions of sustained resonant detonation.

  8. Genetically variable nucleopolyhedroviruses isolated from spatially separate populations of the winter moth Operophtera brumata (Lepidoptera: Geometridae) in Orkney.

    PubMed

    Graham, Robert I; Tyne, William I; Possee, Robert D; Sait, Steven M; Hails, Rosemary S

    2004-09-01

    Here we report a lepidopteran system in which a pathogen is both abundant and genotypically variable. Geographically separate populations of winter moth (Operophtera brumata L.) were sampled in heather habitats on the Orkney Isles to investigate the prevalence of a pathogen, O. brumata Nucleopolyhedrovirus (OpbuNPV), within the natural system. Virus was recorded in 11 of the 13 winter moth populations sampled, with two populations suffering mortality due to virus at levels of 50%. The virus genome from 200 single insect isolations was investigated for variation using restriction endonuclease digests. Twenty-six variants of OpbuNPV were detected using SalI. The polyhedrin gene of the virus was partially sequenced, allowing the relationship between the 26 variants to be portrayed as a cladogram. The phylogenetic relationship between OpbuNPV and other known baculovirus polyhedrin gene sequences was also established. The discovery of virus at such high prevalence is discussed with reference to occurrence and genetic variation of pathogens in other lepidopteran host populations. This study shows encouraging results for further studies into the role of pathogens in the regulation of host insect populations.

  9. Development of high-power, compact synthetic jet actuators for flow separation control

    NASA Astrophysics Data System (ADS)

    Gilarranz Runge, Jose Luis

    This work presents the development of high-power, compact synthetic jet actuators (SJA) for flow separation control. The developed actuator is compact enough to fit in the interior of a NACA0015 profiled wing with a chord of 0.375 in. Test bench experiments showed that the multi-piston actuator array was capable of producing exit velocities of up to 90 m/s for an actuator frequency of 130 Hz. The actuator was placed in a NACA 0015 wing and tested in a wind tunnel. An experimental investigation into the effects of a synthetic jet actuator on the performance of the wing is described. Emphasis is placed on the capabilities of the actuator to control the separation of the flow over the wing at high angles of attack. The investigation included the use of force balance measurements, on-surface flow visualization with oil and tufts, off-surface flow visualizations with smoke, surface pressure distribution measurements and wake surveys. In addition to flow separation control data, results corresponding to hot wire measurements at the exit of the slot, are also presented and are used for the characterization of the flowfield generated by the synthetic jet actuators. Most of the tests were performed at a freestream velocity of 35 m/s, corresponding to a Reynolds number of 8.96 x 105. The angle of attack was varied from -2.0 to 29 degrees. For the tests presented here, at angles of attack lower than 10 degrees the actuator tends to increase the lift curve slope as the actuation frequency is increased. At higher angles of attack, the SJA extends the range of angle of attack for which the wing may be operated without stalling. The use of the actuator causes an 80% increase in the value of maximum lift coefficient, and the angle at which stall occurs is increased from 12 to 18 degrees (for the Reynolds number range of the test). The drag on the wing is decreased as a consequence of SJA actuation. This was verified with the force balance measurements and by analysis of the wake

  10. Zoom lens design for a novel imaging spectrometer that controls spatial and spectral resolution individually.

    PubMed

    Choi, Jin; Kim, T H; Kong, H J; Lee, Jong Ung

    2006-05-20

    A novel imaging spectrometer can individually control spatial and spectral resolution by using zoom lenses as the foreoptics of the system and a focusing lens. By varying the focal length we can use the focusing lens to change the spatial and spectral dimensions; with the foreoptics, however, we can change only the spatial dimension. Therefore the spectral resolution and the spectral range are affected by the zoom ratio of the focusing lens, whereas the spatial resolution and the field of view are affected by the multiplication of the zoom ratios of the foreoptics and the focusing lens. By properly combining two zoom ratios, we can control the spectral resolution with a fixed spatial resolution or the spatial resolution with a fixed spectral resolution. For an imaging spectrometer with this novel zooming function, we used the lens module method and third-order aberration theory to design an initial four-group zoom system with an external entrance pupil for the focusing lens. Furthermore, using the optical design software CODE V, we obtained an optimized zoom lens with a focal-length range of 50 to 150 mm. Finally, the zoom system with its transmission grating in the Littrow configuration performs satisfactorily as the focusing lens of an imaging spectrometer in the wavelength range 450-900 nm.

  11. Open-loop control of noise amplification in a separated boundary layer flow

    SciTech Connect

    Boujo, E. Gallaire, F.; Ehrenstein, U.

    2013-12-15

    Linear optimal gains are computed for the subcritical two-dimensional separated boundary-layer flow past a bump. Very large optimal gain values are found, making it possible for small-amplitude noise to be strongly amplified and to destabilize the flow. The optimal forcing is located close to the summit of the bump, while the optimal response is the largest in the shear layer. The largest amplification occurs at frequencies corresponding to eigenvalues which first become unstable at higher Reynolds number. Nonlinear direct numerical simulations show that a low level of noise is indeed sufficient to trigger random flow unsteadiness, characterized here by large-scale vortex shedding. Next, a variational technique is used to compute efficiently the sensitivity of optimal gains to steady control (through source of momentum in the flow, or blowing/suction at the wall). A systematic analysis at several frequencies identifies the bump summit as the most sensitive region for control with wall actuation. Based on these results, a simple open-loop control strategy is designed, with steady wall suction at the bump summit. Linear calculations on controlled base flows confirm that optimal gains can be drastically reduced at all frequencies. Nonlinear direct numerical simulations also show that this control allows the flow to withstand a higher level of stochastic noise without becoming nonlinearly unstable, thereby postponing bypass transition. In the supercritical regime, sensitivity analysis of eigenvalues supports the choice of this control design. Full restabilization of the flow is obtained, as evidenced by direct numerical simulations and linear stability analysis.

  12. Open-loop control of noise amplification in a separated boundary layer flow

    NASA Astrophysics Data System (ADS)

    Boujo, E.; Ehrenstein, U.; Gallaire, F.

    2013-12-01

    Linear optimal gains are computed for the subcritical two-dimensional separated boundary-layer flow past a bump. Very large optimal gain values are found, making it possible for small-amplitude noise to be strongly amplified and to destabilize the flow. The optimal forcing is located close to the summit of the bump, while the optimal response is the largest in the shear layer. The largest amplification occurs at frequencies corresponding to eigenvalues which first become unstable at higher Reynolds number. Nonlinear direct numerical simulations show that a low level of noise is indeed sufficient to trigger random flow unsteadiness, characterized here by large-scale vortex shedding. Next, a variational technique is used to compute efficiently the sensitivity of optimal gains to steady control (through source of momentum in the flow, or blowing/suction at the wall). A systematic analysis at several frequencies identifies the bump summit as the most sensitive region for control with wall actuation. Based on these results, a simple open-loop control strategy is designed, with steady wall suction at the bump summit. Linear calculations on controlled base flows confirm that optimal gains can be drastically reduced at all frequencies. Nonlinear direct numerical simulations also show that this control allows the flow to withstand a higher level of stochastic noise without becoming nonlinearly unstable, thereby postponing bypass transition. In the supercritical regime, sensitivity analysis of eigenvalues supports the choice of this control design. Full restabilization of the flow is obtained, as evidenced by direct numerical simulations and linear stability analysis.

  13. Beam control and diagnostic functions in the NIF transport spatial filter

    SciTech Connect

    Holdener, F.R.; Ables, E.; Bliss, E.S.

    1996-10-01

    Beam control and diagnostic systems are required to align the National Ignition Facility (NIF) laser prior to a shot as well as to provide diagnostics on 192 beam lines at shot time. A design that allows each beam`s large spatial filter lenses to also serve as objective lenses for beam control and diagnostic sensor packages helps to accomplish the task at a reasonable cost. However, this approach also causes a high concentration of small optics near the pinhole plane of the transport spatial filter (TSF) at the output of each beam. This paper describes the optomechanical design in and near the central vacuum vessel of the TSF.

  14. Stabilization and control of distributed systems with time-dependent spatial domains

    NASA Technical Reports Server (NTRS)

    Wang, P. K. C.

    1990-01-01

    This paper considers the problem of the stabilization and control of distributed sys