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Sample records for active shape control

  1. Shape control and compartmentalization in active colloidal cells.

    PubMed

    Spellings, Matthew; Engel, Michael; Klotsa, Daphne; Sabrina, Syeda; Drews, Aaron M; Nguyen, Nguyen H P; Bishop, Kyle J M; Glotzer, Sharon C

    2015-08-25

    Small autonomous machines like biological cells or soft robots can convert energy input into control of function and form. It is desired that this behavior emerges spontaneously and can be easily switched over time. For this purpose we introduce an active matter system that is loosely inspired by biology and which we term an active colloidal cell. The active colloidal cell consists of a boundary and a fluid interior, both of which are built from identical rotating spinners whose activity creates convective flows. Similarly to biological cell motility, which is driven by cytoskeletal components spread throughout the entire volume of the cell, active colloidal cells are characterized by highly distributed energy conversion. We demonstrate that we can control the shape of the active colloidal cell and drive compartmentalization by varying the details of the boundary (hard vs. flexible) and the character of the spinners (passive vs. active). We report buckling of the boundary controlled by the pattern of boundary activity, as well as formation of core-shell and inverted Janus phase-separated configurations within the active cell interior. As the cell size is increased, the inverted Janus configuration spontaneously breaks its mirror symmetry. The result is a bubble-crescent configuration, which alternates between two degenerate states over time and exhibits collective migration of the fluid along the boundary. Our results are obtained using microscopic, non-momentum-conserving Langevin dynamics simulations and verified via a phase-field continuum model coupled to a Navier-Stokes equation. PMID:26253763

  2. Shape control and compartmentalization in active colloidal cells

    PubMed Central

    Spellings, Matthew; Engel, Michael; Klotsa, Daphne; Sabrina, Syeda; Drews, Aaron M.; Nguyen, Nguyen H. P.; Bishop, Kyle J. M.; Glotzer, Sharon C.

    2015-01-01

    Small autonomous machines like biological cells or soft robots can convert energy input into control of function and form. It is desired that this behavior emerges spontaneously and can be easily switched over time. For this purpose we introduce an active matter system that is loosely inspired by biology and which we term an active colloidal cell. The active colloidal cell consists of a boundary and a fluid interior, both of which are built from identical rotating spinners whose activity creates convective flows. Similarly to biological cell motility, which is driven by cytoskeletal components spread throughout the entire volume of the cell, active colloidal cells are characterized by highly distributed energy conversion. We demonstrate that we can control the shape of the active colloidal cell and drive compartmentalization by varying the details of the boundary (hard vs. flexible) and the character of the spinners (passive vs. active). We report buckling of the boundary controlled by the pattern of boundary activity, as well as formation of core–shell and inverted Janus phase-separated configurations within the active cell interior. As the cell size is increased, the inverted Janus configuration spontaneously breaks its mirror symmetry. The result is a bubble–crescent configuration, which alternates between two degenerate states over time and exhibits collective migration of the fluid along the boundary. Our results are obtained using microscopic, non–momentum-conserving Langevin dynamics simulations and verified via a phase-field continuum model coupled to a Navier–Stokes equation. PMID:26253763

  3. Active shape control of composite structures under thermal loading

    NASA Astrophysics Data System (ADS)

    Binette, P.; Dano, M.-L.; Gendron, G.

    2009-02-01

    Maintaining the shape of high-precision structures such as space antennas and optical mirrors is still a challenging issue for designers. These structures are subjected to varying temperature conditions which often introduce thermal distortions. The development of smart materials offers great potential to correct the shape and to minimize the surface error. In this study, shape control of a composite structure under thermal loading using piezocomposites is investigated. The composite structure is made of a foam core and two carbon-epoxy face sheets. Macro-fiber composite (MFC™) patches are bonded on one side of the structure. The structure is subjected to a through-the-thickness temperature gradient which induces thermal distortion, essentially in the form of bending. The objective is to apply electric potential to the MFC™ actuators such that the deflection can be minimized. Finite-element analyses are conducted using the commercial software ABAQUS. Experiments are performed to study thermally induced distortion, piezoelectric actuation, and compensation of thermal distortion using MFC™ actuators. Numerical and experimental results are compared. A control loop based on strain measurements is used to actively control the structure. The results show that MFC™ actuators can compensate thermal distortion at all times, and that this is an efficient methodology.

  4. Robust Diffeomorphic Mapping via Geodesically Controlled Active Shapes

    PubMed Central

    Tward, Daniel J.; Ma, Jun; Miller, Michael I.; Younes, Laurent

    2013-01-01

    This paper presents recent advances in the use of diffeomorphic active shapes which incorporate the conservation laws of large deformation diffeomorphic metric mapping. The equations of evolution satisfying the conservation law are geodesics under the diffeomorphism metric and therefore termed geodesically controlled diffeomorphic active shapes (GDAS). Our principal application in this paper is on robust diffeomorphic mapping methods based on parameterized surface representations of subcortical template structures. Our parametrization of the GDAS evolution is via the initial momentum representation in the tangent space of the template surface. The dimension of this representation is constrained using principal component analysis generated from training samples. In this work, we seek to use template surfaces to generate segmentations of the hippocampus with three data attachment terms: surface matching, landmark matching, and inside-outside modeling from grayscale T1 MR imaging data. This is formulated as an energy minimization problem, where energy describes shape variability and data attachment accuracy, and we derive a variational solution. A gradient descent strategy is employed in the numerical optimization. For the landmark matching case, we demonstrate the robustness of this algorithm as applied to the workflow of a large neuroanatomical study by comparing to an existing diffeomorphic landmark matching algorithm. PMID:23690757

  5. Active sway control of a gantry crane using hybrid input shaping and PID control schemes

    NASA Astrophysics Data System (ADS)

    Mohd Tumari, M. Z.; Shabudin, L.; Zawawi, M. A.; Shah, L. H. Ahmad

    2013-12-01

    This project presents investigations into the development of hybrid input-shaping and PID control schemes for active sway control of a gantry crane system. The application of positive input shaping involves a technique that can reduce the sway by creating a common signal that cancels its own vibration and used as a feed-forward control which is for controlling the sway angle of the pendulum, while the proportional integral derivative (PID) controller is used as a feedback control which is for controlling the crane position. The PID controller was tuned using Ziegler-Nichols method to get the best performance of the system. The hybrid input-shaping and PID control schemes guarantee a fast input tracking capability, precise payload positioning and very minimal sway motion. The modeling of gantry crane is used to simulate the system using MATLAB/SIMULINK software. The results of the response with the controllers are presented in time domains and frequency domains. The performances of control schemes are examined in terms of level of input tracking capability, sway angle reduction and time response specification.

  6. Variable Camber Continuous Aerodynamic Control Surfaces and Methods for Active Wing Shaping Control

    NASA Technical Reports Server (NTRS)

    Nguyen, Nhan T. (Inventor)

    2016-01-01

    An aerodynamic control apparatus for an air vehicle improves various aerodynamic performance metrics by employing multiple spanwise flap segments that jointly form a continuous or a piecewise continuous trailing edge to minimize drag induced by lift or vortices. At least one of the multiple spanwise flap segments includes a variable camber flap subsystem having multiple chordwise flap segments that may be independently actuated. Some embodiments also employ a continuous leading edge slat system that includes multiple spanwise slat segments, each of which has one or more chordwise slat segment. A method and an apparatus for implementing active control of a wing shape are also described and include the determination of desired lift distribution to determine the improved aerodynamic deflection of the wings. Flap deflections are determined and control signals are generated to actively control the wing shape to approximate the desired deflection.

  7. Controlling active self-assembly through broken particle-shape symmetry.

    PubMed

    Wensink, H H; Kantsler, V; Goldstein, R E; Dunkel, J

    2014-01-01

    Many structural properties of conventional passive materials are known to arise from the symmetries of their microscopic constituents. By contrast, it is largely unclear how the interplay between particle shape and self-propulsion controls the meso- and macroscale behavior of active matter. Here we use large-scale simulations of homo- and heterogeneous self-propelled particle systems to identify generic effects of broken particle-shape symmetry on collective motion. We find that even small violations of fore-aft symmetry lead to fundamentally different collective behaviors, which may facilitate demixing of differently shaped species as well as the spontaneous formation of stable microrotors. These results suggest that variation of particle shape yields robust physical mechanisms to control self-assembly of active matter, with possibly profound implications for biology and materials design. PMID:24580155

  8. Active vibration control of a flexible cantilever beam using shape memory alloy actuators

    NASA Astrophysics Data System (ADS)

    Suzuki, Y.; Kagawa, Y.

    2010-08-01

    This paper demonstrates the feasibility of using shape memory alloys (SMAs) as actuators to control the vibration of a flexible cantilever beam. In a tendon mechanism, SMAs are controlled in a push-pull fashion based on H-infinity theory and taking into account the uncertainty in the actuator performance. Using this mechanism, the four vibrational modes (three bending and one torsional) of the cantilever beam can be simultaneously damped. To control bending and torsional vibrational modes of a flexible beam, we install SMAs obliquely in a beam-SMA structure, then measure and theoretically model the properties of an actuator consisting of an SMA and a spring. Using the properties of the actuator, we introduce the state equations based on the dynamic model of the proposed beam-SMA structure and design the active control system according to H-infinity theory. Finally, we experimentally verify the functioning of the system.

  9. Progress on Shape Memory Alloy Actuator Development for Active Clearance Control

    NASA Technical Reports Server (NTRS)

    DeCastro, Jonathan; Melcher, Kevin; Noebe, Ronald

    2006-01-01

    Results of a numerical analysis evaluating the feasibility of high-temperature shape memory alloys (HTSMA) for active clearance control actuation in the high-pressure turbine section of a modern turbofan engine has been conducted. The prototype actuator concept considered here consists of parallel HTSMA wires attached to the shroud that is located on the exterior of the turbine case. A transient model of an HTSMA actuator was used to evaluate active clearance control at various operating points in a test bed aircraft engine simulation. For the engine under consideration, each actuator must be designed to counteract loads from 380 to 2000 lbf and displace at least 0.033 in. Design results show that an actuator comprised of 10 wires 2 in. in length is adequate for control at critical engine operating points and still exhibit acceptable failsafe operability and cycle life. A proportional-integral-derivative (PID) controller with integrator windup protection was implemented to control clearance amidst engine transients during a normal mission. Simulation results show that the control system exhibits minimal variability in clearance control performance across the operating envelope. The final actuator design is sufficiently small to fit within the limited space outside the high-pressure turbine case and is shown to consume only small amounts of bleed air to adequately regulate temperature.

  10. Active vibration control of Flexible Joint Manipulator using Input Shaping and Adaptive Parameter Auto Disturbance Rejection Controller

    NASA Astrophysics Data System (ADS)

    Li, W. P.; Luo, B.; Huang, H.

    2016-02-01

    This paper presents a vibration control strategy for a two-link Flexible Joint Manipulator (FJM) with a Hexapod Active Manipulator (HAM). A dynamic model of the multi-body, rigid-flexible system composed of an FJM, a HAM and a spacecraft was built. A hybrid controller was proposed by combining the Input Shaping (IS) technique with an Adaptive-Parameter Auto Disturbance Rejection Controller (APADRC). The controller was used to suppress the vibration caused by external disturbances and input motions. Parameters of the APADRC were adaptively adjusted to ensure the characteristic of the closed loop system to be a given reference system, even if the configuration of the manipulator significantly changes during motion. Because precise parameters of the flexible manipulator are not required in the IS system, the operation of the controller was sufficiently robust to accommodate uncertainties in system parameters. Simulations results verified the effectiveness of the HAM scheme and controller in the vibration suppression of FJM during operation.

  11. Shape-control and electrocatalytic activity-enhancement of Pt-based bimetallic nanocrystals.

    PubMed

    Porter, Nathan S; Wu, Hong; Quan, Zewei; Fang, Jiye

    2013-08-20

    Due to the increasing worldwide energy demand and environ-mental concerns, the need for alternative energy sources is growing stronger, and platinum catalysts in fuel cells may help make the technologies a reality. However, the pursuit of highly active Pt-based electrocatalysts continues to be a challenge. Scientists developing electrocatalysts continue to focus on characterizing and directing the construction of nanocrystals and advancing their electrochemical applications. Although chemists have worked on Pt-based bimetallic (Pt-M) preparations in the past, more recent research shows that both shape-controlled Pt-M nanocrystals and the assembly of these nanocrystals into supercrystals are promising new directions. A solution-based synthesis approach is an effective technique for preparing crystallographic facet-directed nanocatalysts. This is aided by careful selection of the metal precursor, capping ligand, reducing agent, and solvent. Incorporating a secondary metal M into the Pt lattice and manipulating the crystal facets on the surface cooperatively alter the electrocatalytic behavior of these Pt-M bimetallic nanocrystals. Specifically, chemists have extensively studied the {111}- and {100}-terminated crystal facets because they show unique atomic arrangement on surfaces, exhibit different catalytic performance, and possess specific resistance to toxic adsorbed carbon monoxide (COads). For catalysts to have maximum efficiency, they need to have resistance to COads and other poisonous carbon-containing intermediates when the catalysts operate under harsh conditions. A necessary design to any synthesis is to clearly understand and utilize the role of each component in order to successfully induce shape-controlled growth. Since chemists began to understand Pt nanocrystal shape-dependent electrocatalytic activity, the main obstacles blocking proton exchange membrane fuel cells are anode poisoning, sluggish kinetics at the cathode, and low activity. In this

  12. Shape Control of Mesoporous Silica Nanomaterials Templated with Dual Cationic Surfactants and Their Antibacterial Activities

    PubMed Central

    Hao, Nanjing; Chen, Xuan; Jayawardana, Kalana W.; Wu, Bin; Sundhoro, Madanodaya; Yan, Mingdi

    2015-01-01

    Mesoporous silica nanomaterials of different shapes (film, platelet, sphere, rod) were synthesized simply by tuning the mole ratio of dual cationic surfactant templates, cetyltrimethylammonium bromide (CTAB) and tetrabutylammonium iodine (TBAI). The film showed the most potent antibacterial activities against mycobacteria. PMID:26364920

  13. Nanobiomimetic Active Shape Control - Fluidic and Swarm-Intelligence Embodiments for Planetary Exploration

    NASA Astrophysics Data System (ADS)

    Santoli, S.

    The concepts of Active Shape Control ( ASC ) and of Generalized Quantum Holography ( GQH ), respectively embodying a closer approach to biomimicry than the current macrophysics-based attempts at bioinspired robotic systems, and realizing a non-connectionistic, life-like kind of information processing that allows increasingly depths of mimicking of the biological structure-function solidarity, which have been formulated in physical terms in previous papers, are here further investigated for application to bioinspired flying or swimming robots for planetary exploration. It is shown that nano-to-micro integration would give the deepest level of biomimicry, and that both low and very low Reynolds number ( Re ) fluidics would involve GQH and Fiber Bundle Topology ( FBT ) for processing information at the various levels of ASC bioinspired robotics. While very low Re flows lend themselves to geometrization of microrobot dynamics and to FBT design, the general design problem is geometrized through GQH , i.e. made independent of dynamic considerations, thus allowing possible problems of semantic dyscrasias in highly complex hierarchical dynamical chains of sensing information processing actuating to be overcome. A roadmap to near- and medium-term nanostructured and nano-to-micro integration realizations is suggested.

  14. Design of an actively controlled steerable needle with tendon actuation and FBG-based shape sensing.

    PubMed

    van de Berg, Nick J; Dankelman, Jenny; van den Dobbelsteen, John J

    2015-06-01

    This work presents a new steerable needle to facilitate active steering toward predefined target locations. It focuses on mechanical aspects and design choices in relation to the observed response in a tissue phantom. Tip steering with two rotational degrees of freedom was achieved by a tendon actuated ball joint mechanism. During insertion, the flexible cannula bends as a result of asymmetric tip-tissue interaction forces. The stylet was equipped with fiber Bragg gratings to measure the needle shape and tip position during use. A PI-controller was implemented to facilitate steering to predefined targets. During the validation study, nine targets were defined at a depth of 100 mm below the gelatin surface. One was located below the insertion point, the others at a radial offset of 30 mm in each of the eight principle steering directions. Per location, six repetitions were performed. The targeting accuracy was 6.2 ± 1.4 mm (mean ± std). The steering precision was 2.6 ± 1.1 mm. The ability to steer with this new needle steering approach is presented and the mechanical characteristics are discussed for this representative subset of steering directions. PMID:25922213

  15. Epigenetic Control of Macrophage Shape Transition towards an Atypical Elongated Phenotype by Histone Deacetylase Activity.

    PubMed

    Cabanel, Mariana; Brand, Camila; Oliveira-Nunes, Maria Cecilia; Cabral-Piccin, Mariela Pires; Lopes, Marcela Freitas; Brito, Jose Marques; de Oliveira, Felipe Leite; El-Cheikh, Marcia Cury; Carneiro, Katia

    2015-01-01

    Inflammatory chronic pathologies are complex processes characterized by an imbalance between the resolution of the inflammatory phase and the establishment of tissue repair. The main players in these inflammatory pathologies are bone marrow derived monocytes (BMDMs). However, how monocyte differentiation is modulated to give rise to specific macrophage subpopulations (M1 or M2) that may either maintain the chronic inflammatory process or lead to wound healing is still unclear. Considering that inhibitors of Histone Deacetylase (HDAC) have an anti-inflammatory activity, we asked whether this enzyme would play a role on monocyte differentiation into M1 or M2 phenotype and in the cell shape transition that follows. We then induced murine bone marrow progenitors into monocyte/macrophage differentiation pathway using media containing GM-CSF and the HDAC blocker, Trichostatin A (TSA). We found that the pharmacological inhibition of HDAC activity led to a shape transition from the typical macrophage pancake-like shape into an elongated morphology, which was correlated to a mixed M1/M2 profile of cytokine and chemokine secretion. Our results present, for the first time, that HDAC activity acts as a regulator of macrophage differentiation in the absence of lymphocyte stimuli. We propose that HDAC activity down regulates macrophage plasticity favoring the pro-inflammatory phenotype. PMID:26196676

  16. Oriented active shape models.

    PubMed

    Liu, Jiamin; Udupa, Jayaram K

    2009-04-01

    Active shape models (ASM) are widely employed for recognizing anatomic structures and for delineating them in medical images. In this paper, a novel strategy called oriented active shape models (OASM) is presented in an attempt to overcome the following five limitations of ASM: 1) lower delineation accuracy, 2) the requirement of a large number of landmarks, 3) sensitivity to search range, 4) sensitivity to initialization, and 5) inability to fully exploit the specific information present in the given image to be segmented. OASM effectively combines the rich statistical shape information embodied in ASM with the boundary orientedness property and the globally optimal delineation capability of the live wire methodology of boundary segmentation. The latter characteristics allow live wire to effectively separate an object boundary from other nonobject boundaries with similar properties especially when they come very close in the image domain. The approach leads to a two-level dynamic programming method, wherein the first level corresponds to boundary recognition and the second level corresponds to boundary delineation, and to an effective automatic initialization method. The method outputs a globally optimal boundary that agrees with the shape model if the recognition step is successful in bringing the model close to the boundary in the image. Extensive evaluation experiments have been conducted by utilizing 40 image (magnetic resonance and computed tomography) data sets in each of five different application areas for segmenting breast, liver, bones of the foot, and cervical vertebrae of the spine. Comparisons are made between OASM and ASM based on precision, accuracy, and efficiency of segmentation. Accuracy is assessed using both region-based false positive and false negative measures and boundary-based distance measures. The results indicate the following: 1) The accuracy of segmentation via OASM is considerably better than that of ASM; 2) The number of landmarks

  17. Tension in active shapes.

    PubMed

    Papari, Giuseppe

    2014-01-01

    The concept of tension is introduced in the framework of active contours with prior shape information, and it is used to improve image segmentation. In particular, two properties of this new quantity are shown: 1) high values of the tension correspond to undesired equilibrium points of the cost function under minimization and 2) tension decreases if a curve is split into two or more parts. Based on these ideas, a tree is generated whose nodes are different local minima of the cost function. Deeper nodes in the tree are expected to correspond to lower values of the cost function. In this way, the search for the global optimum is reduced to visiting and pruning a binary tree. The proposed method has been applied to the problem of fish segmentation from low quality underwater images. Qualitative and quantitative comparison with existing algorithms based on the Euler–Lagrange diffusion equations shows the superiority of the proposed approach in avoiding undesired local minima. PMID:24235305

  18. PdPt bimetallic nanoparticles enabled by shape control with halide ions and their enhanced catalytic activities

    NASA Astrophysics Data System (ADS)

    Zhang, Jinfeng; Wan, Lei; Liu, Lei; Deng, Yida; Zhong, Cheng; Hu, Wenbin

    2016-02-01

    In this study, a new and convenient one step approach is described for synthesizing shape controlled PdPt bimetallic nanoparticles. It is found that the resultant morphologies of these PdPt nanoparticles can be well controlled by simply altering the participation of different halide ions that serve as shape controlling agents in the reaction solution. The dendritic core-shell PdPt bimetallic nanoparticles generated with Pt atoms adopt usual island growth pattern in the presence of Cl- ions, whereas the introduction of Br- ions with a relatively strong adsorption effect facilitate the formation of a layered core-shell structure due to the layered growth mode of Pt atoms on the exterior surface of the central Pd core. Moreover, the stronger adsorption function of I- ions and the resulting fast atomic diffusion promoted the generation of mesoporous core-shell PdPt bimetallic nanoparticles with many pore channels. In addition, the size of these synthesized PdPt nanoparticles exhibited a significant dependence on the concentration of the halide ions involved. Due to their specific structural features and synergistic effects, these PdPt catalysts exhibited shape-dependent catalytic performance and drastically enhanced electrocatalytic activities relative to that of commercial Pt black and Pt/C toward methanol oxidation.In this study, a new and convenient one step approach is described for synthesizing shape controlled PdPt bimetallic nanoparticles. It is found that the resultant morphologies of these PdPt nanoparticles can be well controlled by simply altering the participation of different halide ions that serve as shape controlling agents in the reaction solution. The dendritic core-shell PdPt bimetallic nanoparticles generated with Pt atoms adopt usual island growth pattern in the presence of Cl- ions, whereas the introduction of Br- ions with a relatively strong adsorption effect facilitate the formation of a layered core-shell structure due to the layered growth

  19. Laser fusion pulse shape controller

    DOEpatents

    Siebert, Larry D.

    1977-01-01

    An apparatus for controlling the pulse shape, i.e., the pulse duration and intensity pattern, of a pulsed laser system, and which is particularly well adapted for controlling the pellet ignition pulse in a laser-driven fusion reaction system. The apparatus comprises a laser generator for providing an optical control pulse of the shape desired, a pulsed laser triggered by the control pulse, and a plurality of optical Kerr-effect gates serially disposed at the output of the pulsed laser and selectively triggered by the control pulse to pass only a portion of the pulsed laser output generally corresponding in shape to the control pulse.

  20. Design and Control of a Proof-of-Concept Active Jet Engine Intake Using Shape Memory Alloy Actuators

    NASA Technical Reports Server (NTRS)

    Song, Gangbing; Ma, Ning; Penney, Nicholas; Barr, Todd; Lee, Ho-Jun; Arnold, Steven M.

    2004-01-01

    The design and control of a novel proof-of-concept active jet engine intake using Nickel-Titanium (Ni-Ti or Nitinol) shape memory alloy (SMA) wire actuators is used to demonstrate the potential of an adaptive intake to improve the fuel efficiency of a jet engine. The Nitinol SMA material is selected for this research due to the material's ability to generate large strains of up to 5 percent for repeated operations, a high power-to-weight ratio, electrical resistive actuation, and easy fabrication into a variety of shapes. The proof-of-concept engine intake employs an overlapping leaf design arranged in a concentric configuration. Each leaf is mounted on a supporting bar that rotates upon actuation by SMA wires electrical resistive heating. Feedback control is enabled through the use of a laser range sensor to detect the movement of a leaf and determine the radius of the intake area. Due to the hysteresis behavior inherent in SMAs, a nonlinear robust controller is used to direct the SMA wire actuation. The controller design utilizes the sliding-mode approach to compensate for the nonlinearities associated with the SMA actuator. Feedback control experiments conducted on a fabricated proof-of-concept model have demonstrated the capability to precisely control the intake area and achieve up to a 25 percent reduction in intake area. The experiments demonstrate the feasibility of engine intake area control using the proposed design.

  1. PdPt bimetallic nanoparticles enabled by shape control with halide ions and their enhanced catalytic activities.

    PubMed

    Zhang, Jinfeng; Wan, Lei; Liu, Lei; Deng, Yida; Zhong, Cheng; Hu, Wenbin

    2016-02-21

    In this study, a new and convenient one step approach is described for synthesizing shape controlled PdPt bimetallic nanoparticles. It is found that the resultant morphologies of these PdPt nanoparticles can be well controlled by simply altering the participation of different halide ions that serve as shape controlling agents in the reaction solution. The dendritic core-shell PdPt bimetallic nanoparticles generated with Pt atoms adopt usual island growth pattern in the presence of Cl(-) ions, whereas the introduction of Br(-) ions with a relatively strong adsorption effect facilitate the formation of a layered core-shell structure due to the layered growth mode of Pt atoms on the exterior surface of the central Pd core. Moreover, the stronger adsorption function of I(-) ions and the resulting fast atomic diffusion promoted the generation of mesoporous core-shell PdPt bimetallic nanoparticles with many pore channels. In addition, the size of these synthesized PdPt nanoparticles exhibited a significant dependence on the concentration of the halide ions involved. Due to their specific structural features and synergistic effects, these PdPt catalysts exhibited shape-dependent catalytic performance and drastically enhanced electrocatalytic activities relative to that of commercial Pt black and Pt/C toward methanol oxidation. PMID:26511671

  2. Input Shaping enhanced Active Disturbance Rejection Control for a twin rotor multi-input multi-output system (TRMS).

    PubMed

    Yang, Xiaoyan; Cui, Jianwei; Lao, Dazhong; Li, Donghai; Chen, Junhui

    2016-05-01

    In this paper, a composite control based on Active Disturbance Rejection Control (ADRC) and Input Shaping is presented for TRMS with two degrees of freedom (DOF). The control tasks consist of accurately tracking desired trajectories and obtaining disturbance rejection in both horizontal and vertical planes. Due to un-measurable states as well as uncertainties stemming from modeling uncertainty and unknown disturbance torques, ADRC is employed, and feed-forward Input Shaping is used to improve the dynamical response. In the proposed approach, because the coupling effects are maintained in controller derivation, there is no requirement to decouple the TRMS into horizontal and vertical subsystems, which is usually performed in the literature. Finally, the proposed method is implemented on the TRMS platform, and the results are compared with those of PID and ADRC in a similar structure. The experimental results demonstrate the effectiveness of the proposed method. The operation of the controller allows for an excellent set-point tracking behavior and disturbance rejection with system nonlinearity and complex coupling conditions. PMID:26922492

  3. System-Level Design of a Shape Memory Alloy Actuator for Active Clearance Control in the High-Pressure Turbine

    NASA Technical Reports Server (NTRS)

    DeCastro, Jonathan A.; Melcher, Kevin J.; Noebe, Ronald D.

    2005-01-01

    This paper describes results of a numerical analysis evaluating the feasibility of high-temperature shape memory alloys (HTSMA) for active clearance control actuation in the high-pressure turbine section of a modern turbofan engine. The prototype actuator concept considered here consists of parallel HTSMA wires attached to the shroud that is located on the exterior of the turbine case. A transient model of an HTSMA actuator was used to evaluate active clearance control at various operating points in a test bed aircraft engine simulation. For the engine under consideration, each actuator must be designed to counteract loads from 380 to 2000 lbf and displace at least 0.033 inches. Design results show that an actuator comprised of 10 wires 2 inches in length is adequate for control at critical engine operating points and still exhibits acceptable failsafe operability and cycle life. A proportional-integral-derivative (PID) controller with integrator windup protection was implemented to control clearance amidst engine transients during a normal mission. Simulation results show that the control system exhibits minimal variability in clearance control performance across the operating envelope. The final actuator design is sufficiently small to fit within the limited space outside the high-pressure turbine case and is shown to consume only small amounts of bleed air to adequately regulate temperature.

  4. Active Control of Interface Shape During the Crystal Growth of Lead Bromide

    NASA Technical Reports Server (NTRS)

    Duval, W. M. B.; Batur, C.; Singh, N. B.

    2003-01-01

    A thermal model for predicting and designing the furnace temperature profile was developed and used for the crystal growth of lead bromide. The model gives the ampoule temperature as a function of the furnace temperature, thermal conductivity, heat transfer coefficients, and ampoule dimensions as variable parameters. Crystal interface curvature was derived from the model and it was compared with the predicted curvature for a particular furnace temperature and growth parameters. Large crystals of lead bromide were grown and it was observed that interface shape was in agreement with the shape predicted by this model.

  5. Weight Control Beliefs, Body Shape Attitudes, and Physical Activity among Adolescents

    ERIC Educational Resources Information Center

    Martin, Scott B.; Rhea, Deborah J.; Greenleaf, Christy A.; Judd, Doryce E.; Chambliss, Heather O.

    2011-01-01

    Background: Relatively little is known about how perceived weight controllability influences important psychological health factors among adolescents. Thus, the purpose of this study is to explore adolescents' weight controllability beliefs and how those beliefs influence weight-related attitudes and behaviors. Methods: Adolescents (N = 369, mean…

  6. Formic acid electrooxidation on thallium-decorated shape-controlled platinum nanoparticles: an improvement in electrocatalytic activity.

    PubMed

    Busó-Rogero, Carlos; Perales-Rondón, Juan V; Farias, Manuel J S; Vidal-Iglesias, Francisco J; Solla-Gullon, Jose; Herrero, Enrique; Feliu, Juan M

    2014-07-21

    Thallium modified shape-controlled Pt nanoparticles were prepared and their electrocatalytic activity towards formic acid electrooxidation was evaluated in 0.5 M sulfuric acid. The electrochemical and in situ FTIR spectroscopic results show a remarkable improvement in the electrocatalytic activity, especially in the low potential region (around 0.1-0.2 V vs. RHE). Cubic Pt nanoparticles modified with Tl were found to be more active than the octahedral Pt ones in the entire range of Tl coverages and potential windows. In situ FTIR spectra indicate that the promotional effect produced by Tl results in the inhibition of the poisoning step leading to COads, thus improving the onset potential for the complete formic acid oxidation to CO2. Chronoamperometric experiments were also performed at 0.2 V to evaluate the stability of the electrocatalysts at constant potential. Finally, experiments with different concentrations of formic acid (0.05-1 M) were also carried out. In all cases, Tl-modified cubic Pt nanoparticles result to be the most active. All these facts reinforce the importance of controlling the surface structure of the electrocatalysts to optimize their electrocatalytic properties. PMID:24638124

  7. Shape control using sidewall imaging

    NASA Astrophysics Data System (ADS)

    Su, Bo; Oshana, Ramiel; Menaker, Mina; Barak, Yogev; Shi, Xuelong

    2000-06-01

    As gate widths shrink below 0.18 micrometer, the SPC (Statistical Process Control) based CD (Critical Dimension) control in lithography process becomes more difficult. Increasing requirements of a shrinking process window have called on the need for advanced CD control using a closed-loop feedback mechanism. This concept has been gaining momentum and shows promising advantages in shortening the time of feedback control. However, the current closed-loop feedback links only the average CD of a lot and the exposure dose (E), leaving out another critical lithography parameter -- stepper, or scanner, defocus (F). Up until now, F has been assumed constant while E has been shown to have one-to-one correlation with CD. Such an assumption is justified for feature sizes larger than 0.25 micrometer with a usable DOF (Depth Of Focus) of more than 1 micrometer. For 0.25 micrometer and below technologies, stepper defocus induces rapid feature profile, as well as CD, changes. Therefore, one parameter (exposure dose versus CD) feedback is not adequate enough to control CD in photolithography and a two-parameter (exposure dose and stepper defocus versus CD) feedback is needed. For stepper defocus variation, resist feature shape needs to be monitored in-line. We will present an innovative way of shape monitoring through sidewall imaging. The scanning beam is bent up to 5 degrees, so that a feature can be viewed from a tilted angle. Such tilted view greatly enhances edge resolution. Shape monitoring applications based on sidewall imaging will be presented. With both CD and shape are monitored in photolithography process, two critical parameters, i.e., exposure dose and defocus, can be easily controlled. Such shape control mechanism provides the base for two-parameter feedback loop.

  8. Controlled synthesis of T-shaped BiVO{sub 4} and enhanced visible light responsive photocatalytic activity

    SciTech Connect

    Dong, Shuying; Yu, Chongfei; Li, Yukun; Li, Yihui; Sun, Jianhui; Geng, Xiaofei

    2014-03-15

    A novel T-shaped BiVO{sub 4} microcrystal photocatalyst was successfully synthesized by the hydrothermal method with the aid of a structure-directing surfactant SDBS in the present study. Having received well characterization with the aid of various techniques and the results showed that the SDBS greatly changed the microstructure of BiVO{sub 4}, which had a unique T shape and belonged to the monoclinic family. The fast exchange dynamics between the surfactants bound to the Bi{sup 3+} seed surface and the free VO{sub 3}{sup −} in the solution significantly increase the rate of heterogeneous nucleation. In addition, the photocatalytic activity of the prepared T-shaped BiVO{sub 4} was evaluated by the degradation of Methylene Blue solution under visible light irradiation, 17% and 47% higher decolorization rates than the commercial P25 and BiVO{sub 4} synthesized without SDBS, respectively. Meanwhile, it has been found that the degradation kinetics of MB fitted the pseudo-first-order kinetics and the T-shaped BiVO{sub 4} also displayed high photocatalytic performance for metronidazole degradation. -- Graphical abstract: H{sub 2}O{sub 2} molecules function as electron trapping reagent to react with e{sup −} to enhance the photocatalytic degradation efficiency of MB in the BiVO{sub 4}/H{sub 2}O{sub 2} system under visible light irradiation. Highlights: • T-shaped BiVO{sub 4} was synthesized using SDBS as a structure-directing surfactant. • SDBS greatly changed the microstructure of BiVO{sub 4}. • The T-shaped BiVO{sub 4} had a better visible-light photocatalytic activity. • Degradation kinetics of MB by BiVO{sub 4} fitted the pseudo-first-order kinetics.

  9. Shaping frequency response of a vibrating plate for passive and active control applications by simultaneous optimization of arrangement of additional masses and ribs. Part I: Modeling

    NASA Astrophysics Data System (ADS)

    Wrona, Stanislaw; Pawelczyk, Marek

    2016-03-01

    An ability to shape frequency response of a vibrating plate according to precisely defined demands has a very high practical potential. It can be applied to improve acoustic radiation of the plate for required frequencies or enhance acoustic isolation of noise barriers and device casings by using both passive and active control. The proposed method is based on mounting severaladditional ribs and masses (passive and/or active) to the plate surface at locations followed from an optimization process. This paper, Part I, concerns derivation of a mathematical model of the plate with attached elements in the function of their shape and placement. The model is validated by means of simulations and laboratory experiments, and compared with models known from the literature. This paper is followed by a companion paper, Part II, where the optimization process is described. It includes arrangement of passive elements as well as actuators and sensors to improve controllability and observability measures, if active control is concerned.

  10. TECHNICAL NOTE: Active control for stress intensity of crack-tips under mixed mode by shape memory TiNi fiber epoxy composites

    NASA Astrophysics Data System (ADS)

    Shimamoto, A.; Zhao, H.; Azakami, T.

    2007-06-01

    The paper presented the effectiveness of a shape memory alloy hybrid composite. It was designed to actively suppress stress intensity in the vicinity of a crack-tip. A shape memory alloy (SMA) TiNi fiber reinforced epoxy composite was fabricated based on the proposed design concept and its material and mechanical properties were investigated by photoelastic examinations. The stress intensity factors, KI and KII, at a crack-tip decreased temperatures greater than Af under mixed mode. The phenomenon was caused by the recovery force of the TiNi fiber. The relationship of the stress intensity factors with the prestrain in the SMA fiber as well as with the ambient temperature in an isothermal furnace was clarified. On this basis, the active control for stress intensity by a shape memory composite was discussed.

  11. An adaptive control system for wing TE shape control

    NASA Astrophysics Data System (ADS)

    Dimino, I.; Concilio, A.; Schueller, M.; Gratias, A.

    2013-03-01

    A key technology to enable morphing aircraft for enhanced aerodynamic performance is the design of an adaptive control system able to emulate target structural shapes. This paper presents an approach to control the shape of a morphing wing by employing internal, integrated actuators acting on the trailing edge. The adaptive-wing concept employs active ribs, driven by servo actuators, controlled in turn by a dedicated algorithm aimed at shaping the wing cross section, according to a pre-defined geometry. The morphing control platform is presented and a suitable control algorithm is implemented in a dedicated routine for real-time simulations. The work is organized as follows. A finite element model of the uncontrolled, non-actuated structure is used to obtain the plant model for actuator torque and displacement control. After having characterized and simulated pure rotary actuator behavior over the structure, selected target wing shapes corresponding to rigid trailing edge rotations are achieved through both open-loop and closed-loop control logics.

  12. Silver ion mediated shape control of platinum nanoparticles: Removal of silver by selective etching leads to increased catalytic activity

    SciTech Connect

    Grass, Michael E.; Yue, Yao; Habas, Susan E.; Rioux, Robert M.; Teall, Chelsea I.; Somorjai, G.A.

    2008-01-09

    A procedure has been developed for the selective etching of Ag from Pt nanoparticles of well-defined shape, resulting in the formation of elementally-pure Pt cubes, cuboctahedra, or octahedra, with a largest vertex-to-vertex distance of {approx}9.5 nm from Ag-modified Pt nanoparticles. A nitric acid etching process was applied Pt nanoparticles supported on mesoporous silica, as well as nanoparticles dispersed in aqueous solution. The characterization of the silica-supported particles by XRD, TEM, and N{sub 2} adsorption measurements demonstrated that the structure of the nanoparticles and the mesoporous support remained conserved during etching in concentrated nitric acid. Both elemental analysis and ethylene hydrogenation indicated etching of Ag is only effective when [HNO{sub 3}] {ge} 7 M; below this concentration, the removal of Ag is only {approx}10%. Ethylene hydrogenation activity increased by four orders of magnitude after the etching of Pt octahedra that contained the highest fraction of silver. High-resolution transmission electron microscopy of the unsupported particles after etching demonstrated that etching does not alter the surface structure of the Pt nanoparticles. High [HNO{sub 3}] led to the decomposition of the capping agent, polyvinylpyrollidone (PVP); infrared spectroscopy confirmed that many decomposition products were present on the surface during etching, including carbon monoxide.

  13. Graphical fiber shaping control interface

    NASA Astrophysics Data System (ADS)

    Basso, Eric T.; Ninomiya, Yasuyuki

    2016-03-01

    In this paper, we present an improved graphical user interface for defining single-pass novel shaping techniques on glass processing machines that allows for streamlined process development. This approach offers unique modularity and debugging capability to researchers during the process development phase not usually afforded with similar scripting languages.

  14. Shape control of inorganic nanoparticles from solution

    NASA Astrophysics Data System (ADS)

    Wu, Zhaohui; Yang, Shuanglei; Wu, Wei

    2016-01-01

    Inorganic materials with controllable shapes have been an intensely studied subject in nanoscience over the past decades. Control over novel and anisotropic shapes of inorganic nanomaterials differing from those of bulk materials leads to unique and tunable properties for widespread applications such as biomedicine, catalysis, fuels or solar cells and magnetic data storage. This review presents a comprehensive overview of shape-controlled inorganic nanomaterials via nucleation and growth theory and the control of experimental conditions (including supersaturation, temperature, surfactants and secondary nucleation), providing a brief account of the shape control of inorganic nanoparticles during wet-chemistry synthetic processes. Subsequently, typical mechanisms for shape-controlled inorganic nanoparticles and the general shape of the nanoparticles formed by each mechanism are also expounded. Furthermore, the differences between similar mechanisms for the shape control of inorganic nanoparticles are also clearly described. The authors envision that this review will provide valuable guidance on experimental conditions and process control for the synthesis of inorganic nanoparticles with tunable shapes in the solution state.

  15. Spatial filters for shape control

    NASA Technical Reports Server (NTRS)

    Lindner, Douglas K.; Reichard, Karl M.

    1992-01-01

    Recently there has emerged a new class of sensors, called spatial filters, for structures which respond over a significant gauge length. Examples include piezoelectric laminate PVDF film, modal domain optical fiber sensors, and holographic sensors. These sensors have a unique capability in that they can be fabricated to locally alter their sensitivity to the measurand. In this paper we discuss how these sensors can be used for the implementation of control algorithms for the suppression of acoustic radiation from flexible structures. Based on this relationship between the total power radiated to the far field to the modal velocities of the structure, we show how the sensor placement to optimize the control algorithm to suppress the radiated power.

  16. Shape-Controlled Deterministic Assembly of Nanowires.

    PubMed

    Zhao, Yunlong; Yao, Jun; Xu, Lin; Mankin, Max N; Zhu, Yinbo; Wu, Hengan; Mai, Liqiang; Zhang, Qingjie; Lieber, Charles M

    2016-04-13

    Large-scale, deterministic assembly of nanowires and nanotubes with rationally controlled geometries could expand the potential applications of one-dimensional nanomaterials in bottom-up integrated nanodevice arrays and circuits. Control of the positions of straight nanowires and nanotubes has been achieved using several assembly methods, although simultaneous control of position and geometry has not been realized. Here, we demonstrate a new concept combining simultaneous assembly and guided shaping to achieve large-scale, high-precision shape controlled deterministic assembly of nanowires. We lithographically pattern U-shaped trenches and then shear transfer nanowires to the patterned substrate wafers, where the trenches serve to define the positions and shapes of transferred nanowires. Studies using semicircular trenches defined by electron-beam lithography yielded U-shaped nanowires with radii of curvature defined by inner surface of the trenches. Wafer-scale deterministic assembly produced U-shaped nanowires for >430,000 sites with a yield of ∼90%. In addition, mechanistic studies and simulations demonstrate that shaping results in primarily elastic deformation of the nanowires and show clearly the diameter-dependent limits achievable for accessible forces. Last, this approach was used to assemble U-shaped three-dimensional nanowire field-effect transistor bioprobe arrays containing 200 individually addressable nanodevices. By combining the strengths of wafer-scale top-down fabrication with diverse and tunable properties of one-dimensional building blocks in novel structural configurations, shape-controlled deterministic nanowire assembly is expected to enable new applications in many areas including nanobioelectronics and nanophotonics. PMID:26999059

  17. Shaping frequency response of a vibrating plate for passive and active control applications by simultaneous optimization of arrangement of additional masses and ribs. Part II: Optimization

    NASA Astrophysics Data System (ADS)

    Wrona, Stanislaw; Pawelczyk, Marek

    2016-03-01

    It was shown in Part I that an ability to shape frequency response of a vibrating plate according to precisely defined demands has a very high practical potential. It can be used to improve acoustic radiation of the plate for required frequencies or enhance acoustic isolation of noise barriers and device casings. It can be used for both passive and active control. The proposed method is based on mounting several additional ribs and masses (passive and/or active) to the plate surface at locations followed from an optimisation process. In Part I a relevant model of such structure, as a function of arrangement of the additional elements was derived and validated. The model allows calculating natural frequencies and mode-shapes of the whole structure. The aim of this companion paper, Part II, is to present the second stage of the method. This is an optimization process that results in arrangement of the elements guaranteeing desired plate frequency response, and enhancement of controllability and observability measures. For that purpose appropriate cost functions, and constraints followed from technological feasibility are defined. Then, a memetic algorithm is employed to obtain a numerical solution with parameters of the arrangement. The optimization results are initially presented for simple cases to validate the method. Then, more complex scenarios are analysed with very special demands concerning the frequency response to present the full potential of the method. Subsequently, a laboratory experiment is presented and discussed. Finally, other areas of applications of the proposed method are shown and conclusions for future research are drawn.

  18. ITER Shape Controller and Transport Simulations

    SciTech Connect

    Casper, T A; Meyer, W H; Pearlstein, L D; Portone, A

    2007-05-31

    We currently use the CORSICA integrated modeling code for scenario studies for both the DIII-D and ITER experiments. In these simulations, free- or fixed-boundary equilibria are simultaneously converged with thermal evolution determined from transport models providing temperature and current density profiles. Using a combination of fixed boundary evolution followed by free-boundary calculation to determine the separatrix and coil currents. In the free-boundary calculation, we use the state-space controller representation with transport simulations to provide feedback modeling of shape, vertical stability and profile control. In addition to a tightly coupled calculation with simulator and controller imbedded inside CORSICA, we also use a remote procedure call interface to couple the CORSICA non-linear plasma simulations to the controller environments developed within the Mathworks Matlab/Simulink environment. We present transport simulations using full shape and vertical stability control with evolution of the temperature profiles to provide simulations of the ITER controller and plasma response.

  19. Shape control of multi-material heterostructures for catalytic applications

    NASA Astrophysics Data System (ADS)

    Habas, Susan Ellen

    Shape control of nanomaterials has become increasingly important, as many of their physical and chemical properties are highly dependent on morphology. A tremendous amount of effort has been spent in attempt to control these properties through manipulation of size, composition, and shape. Nanocrystal shape control for both single- and multiple-material systems, however, remains largely empirical and still presents a major challenge. In this dissertation, new methods are described for the rational synthetic design of heterostructures with controlled morphology which is essential for tailoring the catalytic properties of these multi-material systems. Catalytic activity and selectivity are governed by the nature of the catalyst surface, making shaped nanocrystals ideal substrates for understanding the influence of surface structure on heterogeneous catalysis at the nanoscale. First, synthetic methods were developed to produce catalytically active platinum nanocrystals with control over their shape and surface chemistry. Initially, the focus was on the removal of strongly-bound surface stabilizing molecules by ligand exchange to give catalytically clean surfaces. However, the presence of foreign ions used as a shape control agent to produce cubic, cuboctahedral, and octahedrally shaped nanocrystals was found to inhibit catalytic activity. In response, a method was developed for the shape control of uniform platinum nanoparticles stabilized by weakly interacting alkylammonium ions in the absence of foreign metal ions, which showed improved activity for ethylene hydrogenation. The next section describes the application of these highly-faceted platinum nanocrystals as nucleation centers for overgrowth of a secondary metal to obtain shape-controlled heterostructures. Seeded growth allows for the use of the surface structure and corresponding chemical identity of a well-defined seed to control nucleation and growth of another material. Cubic platinum seeds can direct the

  20. Control of CuO nanocrystal morphology from ultrathin "willow-leaf" to "flower-shaped" for increased hydrazine oxidation activity

    NASA Astrophysics Data System (ADS)

    Ma, Yuanyuan; Wang, Hui; Key, Julian; Ji, Shan; Lv, Weizhong; Wang, Rongfang

    2015-12-01

    Three CuO nanocrystal morphologies (willow-leaf, spiny, and flower-shaped) with different exposed crystal facets are prepared through a two-step liquid-phase procedure. The CuO crystals have high hydrazine oxidation reaction (HOR) activity and good stability. Flower-shaped CuO has the highest HOR activity and stability of the three forms, with a positive onset-potential of -0.14 V and a high oxidation peak current density of 5.23 mA cm-2. HOR activity of the CuO crystals correlates to the type of exposed crystalline facet.

  1. Apodization Control of Line Shape in Spectrometer

    NASA Technical Reports Server (NTRS)

    Pires, Antonio; Niple, Edward; Evans, Nathan L.

    1987-01-01

    Kaiser-Bessel apodization function reduces unwanted sidebands. Report discusses apodization in Fourier-transform spectrometer (FTS) for Advanced Moisture and Temperature Sounder (AMTS). Purpose of apodization in instrument to control shape of spectrum in wavenumber space to keep radiation at other wavelengths in passband of spectrometer out of AMTS wavenumber channel.

  2. Shape-Controlled Metal Nanocrystals for Heterogeneous Catalysis.

    PubMed

    Ruditskiy, Aleksey; Peng, Hsin-Chieh; Xia, Younan

    2016-06-01

    The ability to control the shape of metal nanocrystals allows us to not only maneuver their physicochemical properties but also optimize their activity in a variety of applications. Heterogeneous catalysis, in particular, would benefit tremendously from the availability of metal nanocrystals with controlled shapes and well-defined facets or surface structures. The immediate benefits may include significant enhancements in catalytic activity and/or selectivity along with reductions in the materials cost. We provide a brief account of recent progress in the development of metal nanocrystals with controlled shapes and thereby enhanced catalytic performance for several reactions, including formic acid oxidation, oxygen reduction, and hydrogenation. In addition to monometallic nanocrystals, we also cover a bimetallic system, in which the two metals are formulated as alloyed, core-shell, or core-frame structures. We hope this article will provide further impetus for the development of next-generation heterogeneous catalysts essential to a broad range of applications. PMID:27023659

  3. Static shape control for flexible structures

    NASA Technical Reports Server (NTRS)

    Rodriguez, G.; Scheid, R. E., Jr.

    1986-01-01

    An integrated methodology is described for defining static shape control laws for large flexible structures. The techniques include modeling, identifying and estimating the control laws of distributed systems characterized in terms of infinite dimensional state and parameter spaces. The models are expressed as interconnected elliptic partial differential equations governing a range of static loads, with the capability of analyzing electromagnetic fields around antenna systems. A second-order analysis is carried out for statistical errors, and model parameters are determined by maximizing an appropriate defined likelihood functional which adjusts the model to observational data. The parameter estimates are derived from the conditional mean of the observational data, resulting in a least squares superposition of shape functions obtained from the structural model.

  4. Active Beam Shaping System and Method Using Sequential Deformable Mirrors

    NASA Technical Reports Server (NTRS)

    Norman, Colin A. (Inventor); Pueyo, Laurent A. (Inventor)

    2015-01-01

    An active optical beam shaping system includes a first deformable mirror arranged to at least partially intercept an entrance beam of light and to provide a first reflected beam of light, a second deformable mirror arranged to at least partially intercept the first reflected beam of light from the first deformable mirror and to provide a second reflected beam of light, and a signal processing and control system configured to communicate with the first and second deformable mirrors. The first deformable mirror, the second deformable mirror and the signal processing and control system together provide a large amplitude light modulation range to provide an actively shaped optical beam.

  5. Aerodynamic shape optimization using control theory

    NASA Technical Reports Server (NTRS)

    Reuther, James

    1996-01-01

    Aerodynamic shape design has long persisted as a difficult scientific challenge due its highly nonlinear flow physics and daunting geometric complexity. However, with the emergence of Computational Fluid Dynamics (CFD) it has become possible to make accurate predictions of flows which are not dominated by viscous effects. It is thus worthwhile to explore the extension of CFD methods for flow analysis to the treatment of aerodynamic shape design. Two new aerodynamic shape design methods are developed which combine existing CFD technology, optimal control theory, and numerical optimization techniques. Flow analysis methods for the potential flow equation and the Euler equations form the basis of the two respective design methods. In each case, optimal control theory is used to derive the adjoint differential equations, the solution of which provides the necessary gradient information to a numerical optimization method much more efficiently then by conventional finite differencing. Each technique uses a quasi-Newton numerical optimization algorithm to drive an aerodynamic objective function toward a minimum. An analytic grid perturbation method is developed to modify body fitted meshes to accommodate shape changes during the design process. Both Hicks-Henne perturbation functions and B-spline control points are explored as suitable design variables. The new methods prove to be computationally efficient and robust, and can be used for practical airfoil design including geometric and aerodynamic constraints. Objective functions are chosen to allow both inverse design to a target pressure distribution and wave drag minimization. Several design cases are presented for each method illustrating its practicality and efficiency. These include non-lifting and lifting airfoils operating at both subsonic and transonic conditions.

  6. Cell shape regulation through mechanosensory feedback control

    PubMed Central

    Mohan, Krithika; Luo, Tianzhi; Robinson, Douglas N.; Iglesias, Pablo A.

    2015-01-01

    Cells undergo controlled changes in morphology in response to intracellular and extracellular signals. These changes require a means for sensing and interpreting the signalling cues, for generating the forces that act on the cell's physical material, and a control system to regulate this process. Experiments on Dictyostelium amoebae have shown that force-generating proteins can localize in response to external mechanical perturbations. This mechanosensing, and the ensuing mechanical feedback, plays an important role in minimizing the effect of mechanical disturbances in the course of changes in cell shape, especially during cell division, and likely in other contexts, such as during three-dimensional migration. Owing to the complexity of the feedback system, which couples mechanical and biochemical signals involved in shape regulation, theoretical approaches can guide further investigation by providing insights that are difficult to decipher experimentally. Here, we present a computational model that explains the different mechanosensory and mechanoresponsive behaviours observed in Dictyostelium cells. The model features a multiscale description of myosin II bipolar thick filament assembly that includes cooperative and force-dependent myosin–actin binding, and identifies the feedback mechanisms hidden in the observed mechanoresponsive behaviours of Dictyostelium cells during micropipette aspiration experiments. These feedbacks provide a mechanistic explanation of cellular retraction and hence cell shape regulation. PMID:26224568

  7. Cell shape regulation through mechanosensory feedback control.

    PubMed

    Mohan, Krithika; Luo, Tianzhi; Robinson, Douglas N; Iglesias, Pablo A

    2015-08-01

    Cells undergo controlled changes in morphology in response to intracellular and extracellular signals. These changes require a means for sensing and interpreting the signalling cues, for generating the forces that act on the cell's physical material, and a control system to regulate this process. Experiments on Dictyostelium amoebae have shown that force-generating proteins can localize in response to external mechanical perturbations. This mechanosensing, and the ensuing mechanical feedback, plays an important role in minimizing the effect of mechanical disturbances in the course of changes in cell shape, especially during cell division, and likely in other contexts, such as during three-dimensional migration. Owing to the complexity of the feedback system, which couples mechanical and biochemical signals involved in shape regulation, theoretical approaches can guide further investigation by providing insights that are difficult to decipher experimentally. Here, we present a computational model that explains the different mechanosensory and mechanoresponsive behaviours observed in Dictyostelium cells. The model features a multiscale description of myosin II bipolar thick filament assembly that includes cooperative and force-dependent myosin-actin binding, and identifies the feedback mechanisms hidden in the observed mechanoresponsive behaviours of Dictyostelium cells during micropipette aspiration experiments. These feedbacks provide a mechanistic explanation of cellular retraction and hence cell shape regulation. PMID:26224568

  8. Multi-shape active composites by 3D printing of digital shape memory polymers

    NASA Astrophysics Data System (ADS)

    Wu, Jiangtao; Yuan, Chao; Ding, Zhen; Isakov, Michael; Mao, Yiqi; Wang, Tiejun; Dunn, Martin L.; Qi, H. Jerry

    2016-04-01

    Recent research using 3D printing to create active structures has added an exciting new dimension to 3D printing technology. After being printed, these active, often composite, materials can change their shape over time; this has been termed as 4D printing. In this paper, we demonstrate the design and manufacture of active composites that can take multiple shapes, depending on the environmental temperature. This is achieved by 3D printing layered composite structures with multiple families of shape memory polymer (SMP) fibers – digital SMPs - with different glass transition temperatures (Tg) to control the transformation of the structure. After a simple single-step thermomechanical programming process, the fiber families can be sequentially activated to bend when the temperature is increased. By tuning the volume fraction of the fibers, bending deformation can be controlled. We develop a theoretical model to predict the deformation behavior for better understanding the phenomena and aiding the design. We also design and print several flat 2D structures that can be programmed to fold and open themselves when subjected to heat. With the advantages of an easy fabrication process and the controllable multi-shape memory effect, the printed SMP composites have a great potential in 4D printing applications.

  9. Multi-shape active composites by 3D printing of digital shape memory polymers.

    PubMed

    Wu, Jiangtao; Yuan, Chao; Ding, Zhen; Isakov, Michael; Mao, Yiqi; Wang, Tiejun; Dunn, Martin L; Qi, H Jerry

    2016-01-01

    Recent research using 3D printing to create active structures has added an exciting new dimension to 3D printing technology. After being printed, these active, often composite, materials can change their shape over time; this has been termed as 4D printing. In this paper, we demonstrate the design and manufacture of active composites that can take multiple shapes, depending on the environmental temperature. This is achieved by 3D printing layered composite structures with multiple families of shape memory polymer (SMP) fibers - digital SMPs - with different glass transition temperatures (Tg) to control the transformation of the structure. After a simple single-step thermomechanical programming process, the fiber families can be sequentially activated to bend when the temperature is increased. By tuning the volume fraction of the fibers, bending deformation can be controlled. We develop a theoretical model to predict the deformation behavior for better understanding the phenomena and aiding the design. We also design and print several flat 2D structures that can be programmed to fold and open themselves when subjected to heat. With the advantages of an easy fabrication process and the controllable multi-shape memory effect, the printed SMP composites have a great potential in 4D printing applications. PMID:27071543

  10. Multi-shape active composites by 3D printing of digital shape memory polymers

    PubMed Central

    Wu, Jiangtao; Yuan, Chao; Ding, Zhen; Isakov, Michael; Mao, Yiqi; Wang, Tiejun; Dunn, Martin L.; Qi, H. Jerry

    2016-01-01

    Recent research using 3D printing to create active structures has added an exciting new dimension to 3D printing technology. After being printed, these active, often composite, materials can change their shape over time; this has been termed as 4D printing. In this paper, we demonstrate the design and manufacture of active composites that can take multiple shapes, depending on the environmental temperature. This is achieved by 3D printing layered composite structures with multiple families of shape memory polymer (SMP) fibers – digital SMPs - with different glass transition temperatures (Tg) to control the transformation of the structure. After a simple single-step thermomechanical programming process, the fiber families can be sequentially activated to bend when the temperature is increased. By tuning the volume fraction of the fibers, bending deformation can be controlled. We develop a theoretical model to predict the deformation behavior for better understanding the phenomena and aiding the design. We also design and print several flat 2D structures that can be programmed to fold and open themselves when subjected to heat. With the advantages of an easy fabrication process and the controllable multi-shape memory effect, the printed SMP composites have a great potential in 4D printing applications. PMID:27071543

  11. Shape control of a morphing structure (rotor blade) using a shape memory alloy actuator system

    NASA Astrophysics Data System (ADS)

    Bushnell, Glenn S.; Arbogast, Darin; Ruggeri, Robert

    2008-03-01

    Development and test results of a rotor blade twist control system that utilizes a thermo-mechanical shape memory alloy (SMA) are presented. The actuation system controls the blade shape during flight operations allowing the blade to be configured for greater lift during takeoff and landing. SMA actuators provided an excellent solution because of their very high torque output to weight ratio and suitability to the dynamic environment of a rotor blade. Several challenges related to the behavior of the SMA material are overcome by innovative control system design. Thermoelectric modules (TEM's) are used to actively transfer heat between SMA tubes and other heat conductor and radiator components. Modeling and system identification techniques and a non-trivial solution to nonlinear and coupled thermal response equations are used to insure effective use of the TEM's and to improve control during SMA phase transition.

  12. Experiments on rotamak plasma equilibrium and shape control

    SciTech Connect

    Petrov, Yuri; Yang Xiaokang; Wang Yonghui; Huang, T.-S.

    2010-01-15

    A set of magnetic shaping coils and copper rings is installed in cylindrical chamber rotamak to allow for an active equilibrium control in 40 ms plasma discharges. The coils, which are powered by programmable current source, are used to control both the plasma shape and the boundary poloidal magnetic flux. Without the active equilibrium control, the boundary flux drops from its vacuum value of 0.3 mWb to zero after the plasma current is generated. If the coils are activated, the boundary magnetic flux can be sustained within the 0.2-0.3 mWb range, thus keeping the separatrix away from chamber wall during whole period of the shot. The passive copper rings help in eliminating the fast variations of the boundary magnetic flux. The response of rotamak plasma to the active equilibrium control is drastically different in regimes with or without external toroidal field. A model is presented that describes the change in plasma shape, plasma current, and pressure under the effect of active equilibrium coils.

  13. Mirrors Containing Biomimetic Shape-Control Actuators

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph; Mouroulis, Pantazis; Bao, Xiaoqi; Sherrit, Stewart

    2003-01-01

    Curved mirrors of a proposed type would comprise lightweight sheets or films containing integral, biologically inspired actuators for controlling their surface figures. These mirrors could be useful in such applications as collection of solar energy, focusing of radio beams, and (provided sufficient precision could be achieved) imaging. These mirrors were originally intended for use in outer space, but it should also be possible to develop terrestrial versions. Several prior NASA Tech Briefs articles have described a variety of approaches to the design of curved, lightweight mirrors containing integral shape-control actuators. The primary distinction between the present approach and the prior approaches lies in the actuator design concept, which involves shapes and movements reminiscent of those of a variety of small, multi-armed animals. The shape and movement of an actuator of this type can also be characterized as reminiscent of that of an umbrella. This concept can be further characterized as a derivative of that of multifinger grippers, the fingers of which are bimorph bending actuators (see Figure 1). The fingers of such actuators can be strips containing any of a variety of materials that have been investigated for use as actuators, including such electroactive polymers as ionomeric polymer/metal composites (IPMCs), ferroelectric polymers, and grafted elastomers. A mirror according to this proposal would be made from a sheet of one of the actuator composites mentioned above. The design would involve many variables, including the pre-curvature and stiffness of the mirror sheet, the required precision of figure control, the required range of variation in focal length (see Figure 2), the required precision of figure control for imaging or non-imaging use, the bending and twisting moments needed to effect the required deformations, and voltage-tomoment coefficients of the actuators, and the voltages accordingly required for actuation. A typical design would call

  14. 14 CFR 25.781 - Cockpit control knob shape.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Cockpit control knob shape. 25.781 Section 25.781 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... § 25.781 Cockpit control knob shape. Cockpit control knobs must conform to the general shapes (but...

  15. 14 CFR 25.781 - Cockpit control knob shape.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Cockpit control knob shape. 25.781 Section 25.781 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... § 25.781 Cockpit control knob shape. Cockpit control knobs must conform to the general shapes (but...

  16. 14 CFR 23.781 - Cockpit control knob shape.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Cockpit control knob shape. 23.781 Section... Personnel and Cargo Accommodations § 23.781 Cockpit control knob shape. (a) Flap and landing gear control knobs must conform to the general shapes (but not necessarily the exact sizes or specific...

  17. Shaping Neuronal Network Activity by Presynaptic Mechanisms

    PubMed Central

    Ashery, Uri

    2015-01-01

    Neuronal microcircuits generate oscillatory activity, which has been linked to basic functions such as sleep, learning and sensorimotor gating. Although synaptic release processes are well known for their ability to shape the interaction between neurons in microcircuits, most computational models do not simulate the synaptic transmission process directly and hence cannot explain how changes in synaptic parameters alter neuronal network activity. In this paper, we present a novel neuronal network model that incorporates presynaptic release mechanisms, such as vesicle pool dynamics and calcium-dependent release probability, to model the spontaneous activity of neuronal networks. The model, which is based on modified leaky integrate-and-fire neurons, generates spontaneous network activity patterns, which are similar to experimental data and robust under changes in the model's primary gain parameters such as excitatory postsynaptic potential and connectivity ratio. Furthermore, it reliably recreates experimental findings and provides mechanistic explanations for data obtained from microelectrode array recordings, such as network burst termination and the effects of pharmacological and genetic manipulations. The model demonstrates how elevated asynchronous release, but not spontaneous release, synchronizes neuronal network activity and reveals that asynchronous release enhances utilization of the recycling vesicle pool to induce the network effect. The model further predicts a positive correlation between vesicle priming at the single-neuron level and burst frequency at the network level; this prediction is supported by experimental findings. Thus, the model is utilized to reveal how synaptic release processes at the neuronal level govern activity patterns and synchronization at the network level. PMID:26372048

  18. Shape remodeling and blebbing of active cytoskeletal vesicles

    PubMed Central

    Loiseau, Etienne; Schneider, Jochen A. M.; Keber, Felix C.; Pelzl, Carina; Massiera, Gladys; Salbreux, Guillaume; Bausch, Andreas R.

    2016-01-01

    Morphological transformations of living cells, such as shape adaptation to external stimuli, blebbing, invagination, or tethering, result from an intricate interplay between the plasma membrane and its underlying cytoskeleton, where molecular motors generate forces. Cellular complexity defies a clear identification of the competing processes that lead to such a rich phenomenology. In a synthetic biology approach, designing a cell-like model assembled from a minimal set of purified building blocks would allow the control of all relevant parameters. We reconstruct actomyosin vesicles in which the coupling of the cytoskeleton to the membrane, the topology of the cytoskeletal network, and the contractile activity can all be precisely controlled and tuned. We demonstrate that tension generation of an encapsulated active actomyosin network suffices for global shape transformation of cell-sized lipid vesicles, which are reminiscent of morphological adaptations in living cells. The observed polymorphism of our cell-like model, such as blebbing, tether extrusion, or faceted shapes, can be qualitatively explained by the protein concentration dependencies and a force balance, taking into account the membrane tension, the density of anchoring points between the membrane and the actin network, and the forces exerted by molecular motors in the actin network. The identification of the physical mechanisms for shape transformations of active cytoskeletal vesicles sets a conceptual and quantitative benchmark for the further exploration of the adaptation mechanisms of cells. PMID:27152328

  19. Shape remodeling and blebbing of active cytoskeletal vesicles.

    PubMed

    Loiseau, Etienne; Schneider, Jochen A M; Keber, Felix C; Pelzl, Carina; Massiera, Gladys; Salbreux, Guillaume; Bausch, Andreas R

    2016-04-01

    Morphological transformations of living cells, such as shape adaptation to external stimuli, blebbing, invagination, or tethering, result from an intricate interplay between the plasma membrane and its underlying cytoskeleton, where molecular motors generate forces. Cellular complexity defies a clear identification of the competing processes that lead to such a rich phenomenology. In a synthetic biology approach, designing a cell-like model assembled from a minimal set of purified building blocks would allow the control of all relevant parameters. We reconstruct actomyosin vesicles in which the coupling of the cytoskeleton to the membrane, the topology of the cytoskeletal network, and the contractile activity can all be precisely controlled and tuned. We demonstrate that tension generation of an encapsulated active actomyosin network suffices for global shape transformation of cell-sized lipid vesicles, which are reminiscent of morphological adaptations in living cells. The observed polymorphism of our cell-like model, such as blebbing, tether extrusion, or faceted shapes, can be qualitatively explained by the protein concentration dependencies and a force balance, taking into account the membrane tension, the density of anchoring points between the membrane and the actin network, and the forces exerted by molecular motors in the actin network. The identification of the physical mechanisms for shape transformations of active cytoskeletal vesicles sets a conceptual and quantitative benchmark for the further exploration of the adaptation mechanisms of cells. PMID:27152328

  20. Morphology controlled bulk synthesis of disc-shaped WO3 powder and evaluation of its photocatalytic activity for the degradation of phenols.

    PubMed

    Aslam, M; Ismail, Iqbal M I; Chandrasekaran, S; Hameed, A

    2014-07-15

    The surfactant assisted synthesis of disc-shaped WO3 powder and its photocatalytic performance in sunlight exposure is reported. UV-vis DRS, XRD and FESEM characterized the synthesized WO3. The synthesized powder exhibited a bandgap of ∼2.55eV with cubic lattice and high crystallinity. The photocatalytic activity of the synthesized WO3 was examined for the degradation of phenol, resorcinol, 2-chlorophenol and 2-nitrophenol in complete spectrum and visible segment of sunlight. The highly efficient degradation/mineralization of 2-chloro and 2-nitrophenol compared to that of phenol and resorcinol, under identical experimental conditions, suggested the regulatory role of substituents attached to the aromatic ring in degradation/mineralization process. The time-scale HPLC degradation profiles, identification of intermediates by GC-MS and removal of organic carbon during the course of reaction were utilized to approximate the possible route of degradation/mineralization of phenolic substrates. The measurement of the anions released during the photocatalytic process was used to identify the nature of the major oxidants (O2(•-), OH(•)) and the possible interaction sites. A significant decrease in the photocatalytic activity of synthesized WO3, ∼50%, was observed in visible portion of sunlight however, a sustained activity was observed in the repeated exposures. PMID:24869630

  1. Shape-Controlled Synthesis of Pt Nanopeanuts.

    PubMed

    Zhang, Xuemei; Xia, Zengzilu; Huang, Yingzhou; Jia, Yunpeng; Sun, Xiaonan; Li, Yu; Li, Xueming; Wu, Rui; Liu, Anping; Qi, Xueqiang; Wang, Shuxia; Wen, Weijia

    2016-01-01

    Exploring the novel shape of Pt nanoparticles is one of the most useful ways to improve the electrocatalytic performance of Pt in fuel cells. In this work, the Pt nanopeanuts consisting of two nanospheres grown together have been fabricated through a two-step polyol method. The high resolution scanning electron microscope (SEM) images and energy dispersive x-ray (EDX) spectrum collected at adjacent part point out the Pt nanopeanut is apparently different from the two physical attached nanospheres. To understand the growth mechanism of this nanopeanut, the final products in different synthesis situations are studied. The results indicate the interesting morphology of Pt nanopeanuts mainly benefit from the chemical reagent (FeCl3) while the size and homogeneity are greatly affected by the temperature. Furthermore, the electrocatalytic activity of the Pt nanopeanuts has also been demonstrated here. Our two-step synthesis of Pt nanopeanuts not only enlarges the group of Pt nanoparticles, but also provides a beneficial strategy for the synthesis of novel metal nanoparticles. PMID:27528078

  2. Shape-Controlled Synthesis of Pt Nanopeanuts

    PubMed Central

    Zhang, Xuemei; Xia, Zengzilu; Huang, Yingzhou; Jia, Yunpeng; Sun, Xiaonan; Li, Yu; Li, Xueming; Wu, Rui; Liu, Anping; Qi, Xueqiang; Wang, Shuxia; Wen, Weijia

    2016-01-01

    Exploring the novel shape of Pt nanoparticles is one of the most useful ways to improve the electrocatalytic performance of Pt in fuel cells. In this work, the Pt nanopeanuts consisting of two nanospheres grown together have been fabricated through a two-step polyol method. The high resolution scanning electron microscope (SEM) images and energy dispersive x-ray (EDX) spectrum collected at adjacent part point out the Pt nanopeanut is apparently different from the two physical attached nanospheres. To understand the growth mechanism of this nanopeanut, the final products in different synthesis situations are studied. The results indicate the interesting morphology of Pt nanopeanuts mainly benefit from the chemical reagent (FeCl3) while the size and homogeneity are greatly affected by the temperature. Furthermore, the electrocatalytic activity of the Pt nanopeanuts has also been demonstrated here. Our two-step synthesis of Pt nanopeanuts not only enlarges the group of Pt nanoparticles, but also provides a beneficial strategy for the synthesis of novel metal nanoparticles. PMID:27528078

  3. Waveform command shaping control of multimode systems

    NASA Astrophysics Data System (ADS)

    Alhazza, Khaled A.; Masoud, Ziyad N.

    2016-02-01

    A method for eliminating residual vibrations in multimode systems is presented using a command shaping technique. The proposed command shaping technique captures two main advantages. Namely, the independence of the time length of the shaped command from the resonant frequencies of the system, and the ability to generate the command profile without a full system model. Experiments on systems with partial models represented by their resonant frequencies show that shaped command profiles generated using actual measured resonant frequencies of a system outperform those based on mathematical models. This feature of the proposed command shaping technique makes it very attractive for complicated multimode systems where mathematical models are difficult to build. Profiles of the proposed shaped command are simple and do not require intensive calculations. Performance of the proposed shaped command is validated using numerical simulations and experiments. Numerical simulations prove that the shaped commands are capable of completely eliminating residual vibrations of multimode systems. Experiments show that residual vibration elimination depends on the level of accuracy of the measured resonant frequencies of the system.

  4. Study on actuating mode shapes of electro-active paper

    NASA Astrophysics Data System (ADS)

    Sundaresan, Mannur; Park, Yongkun; Craft, William J.; Sankar, Jag; Kim, Jaehwan

    2006-03-01

    This paper focuses on actuating mode shapes of cellulose-based electro-active paper (EAPap) in order to investigate its suitability as actuators. Firstly, actuating mechanism of EAPap is addressed based on intrinsic characteristics of cellulose structures under electric fields. EAPap actuator is then fabricated by embedding gold as electrodes into both sides of cellophane sheets. Actuating mode shapes under electric fields are phenomenological measured via laser scanning vibrometer at different exciting frequencies as well as relative humidity. Various actuating performances with large deformations are obtained by applying low electric fields, which can produce a suitable deformation capability with light weight, low power consumption and simple fabrication. Experimental results provide that EAPap can be used as a potential actuating candidate for shape control of smart structures, along with bio-inspired actuator materials.

  5. Shape control of manipulators with hyper degrees of freedom

    SciTech Connect

    Mochiyama, Hiromi; Shimemura, Etsujiro; Kobayashi, Hisato

    1999-06-01

    This paper provides a theoretical framework for controlling a manipulator with hyper degrees of freedom (HDOF) . An HDOF manipulator has the capability to achieve various kinds of tasks. To make full use of its capability, shape control is proposed here; that is, not only the tip of a manipulator, but also its whole body is controlled. To formulate control objectives for shape control, the authors define a shape correspondence between an HDOF manipulator and a spatial curve that prescribes a desired shape. The shape correspondence is defined by using solutions of a nonlinear optimization problem termed the shape-inverse problem. They give theorems on the existence of the solutions, and on an existence region that allows them to convert shape-control problems into more tractable ones. A shape-regulation control problem is considered first to bring an HDOF manipulator onto a given time-invariant curve. The idea of estimating the desired curve parameters is the crucial key to solving the problem by Lyapunov design. The derived shape-regulation law includes the estimator, which infers the desired curve parameters corresponding to the desired joint positions on the curve. The idea of the desired curve-parameter estimation is also effective for shape tracking where a time-varying curve is used for prescribing a moving desired shape. Considering an estimator with second-order dynamics enables the authors to find two shape-tracking control laws by utilizing conventional tracking methods in manipulator control. They show the simulation results of applying the derived shape-tracking control laws to a 20-DOF manipulator.

  6. Shape-Memory-Alloy Actuator For Flight Controls

    NASA Technical Reports Server (NTRS)

    Barret, Chris

    1995-01-01

    Report proposes use of shape-memory-alloy actuators, instead of hydraulic actuators, for aerodynamic flight-control surfaces. Actuator made of shape-memory alloy converts thermal energy into mechanical work by changing shape as it makes transitions between martensitic and austenitic crystalline phase states of alloy. Because both hot exhaust gases and cryogenic propellant liquids available aboard launch rockets, shape-memory-alloy actuators exceptionally suited for use aboard such rockets.

  7. Shape Optimization for Trailing Edge Noise Control

    NASA Astrophysics Data System (ADS)

    Marsden, Alison; Wang, Meng; Mohammadi, Bijan; Moin, Parviz

    2001-11-01

    Noise generated by turbulent boundary layers near the trailing edge of lifting surfaces continues to pose a challenge for many applications. In this study, we explore noise reduction strategies through shape optimization. A gradient based shape design method is formulated and implemented for use with large eddy simulation of the flow over an airfoil. The cost function gradient is calculated using the method of incomplete sensitivities (Mohammadi and Pironneau 2001 ph Applied shape Optimization for Fluids, Oxford Univ. Press). This method has the advantage that effects of geometry changes on the flow field can be neglected when computing the gradient of the cost function, making it far more cost effective than solving the full adjoint problem. Validation studies are presented for a model problem of the unsteady laminar flow over an acoustically compact airfoil. A section of the surface is allowed to deform and the cost function is derived based on aeroacoustic theroy. Rapid convergence of the trailing-edge shape and significant reduction of the noise due to vortex shedding and wake instability have been achieved. The addition of constraints and issues of extension to fully turbulent flows past an acoustically noncompact airfoil are also discussed.

  8. Shape control of large space structures

    NASA Technical Reports Server (NTRS)

    Hagan, M. T.

    1982-01-01

    A survey has been conducted to determine the types of control strategies which have been proposed for controlling the vibrations in large space structures. From this survey several representative control strategies were singled out for detailed analyses. The application of these strategies to a simplified model of a large space structure has been simulated. These simulations demonstrate the implementation of the control algorithms and provide a basis for a preliminary comparison of their suitability for large space structure control.

  9. Colloid Science of Metal Nanoparticle Catalysts in 2D and 3D Structures. Challenges of Nucleation, Growth, Composition, Particle Shape, Size Control and their Influence on Activity and Selectivity

    SciTech Connect

    Somorjai, Gabor A.; Park, Jeong Y.

    2008-02-13

    Recent breakthroughs in synthesis in nanosciences have achieved control of size and shapes of nanoparticles that are relevant for catalyst design. In this article, we review the advance of synthesis of nanoparticles, fabrication of two and three dimensional model catalyst system, characterization, and studies of activity and selectivity. The ability to synthesize monodispersed platinum and rhodium nanoparticles in the 1-10 nm range permitted us to study the influence of composition, structure, and dynamic properties of monodispersed metal nanoparticle on chemical reactivity and selectivity. We review the importance of size and shape of nanoparticles to determine the reaction selectivity in multi-path reactions. The influence of metal-support interaction has been studied by probing the hot electron flows through the metal-oxide interface in catalytic nanodiodes. Novel designs of nanoparticle catalytic systems are discussed.

  10. Development progress of plasma shaping controls in KSTAR

    NASA Astrophysics Data System (ADS)

    Hahn, Sang-Hee; Eidietis, N. W.; Mueller, D.; Jeon, Y. M.; Yoon, S. W.; Kim, J. H.; Park, S. Y.; Walker, M. L.; Kstar Team

    2011-10-01

    An axisymmetric magnetic shape control system has been developed for creations and sustainment of double-null diverted shape of KSTAR, based on the real-time EFIT/isoflux algorithm. The real-time EFIT scheme is modified to deal with the influences of magnetic materials inside the magnet system. On the design of the isoflux algorithm, various techniques were used in order to decouple the coil responses by the shape changes from the plasma current feedback responses. In this work, we show experimental application results of the developed controls on the KSTAR at the 2011 plasma campaign, and analyze the effects of shaping on the plasma performances.

  11. Magnetically Controlled Shape Memory Behaviour—Materials and Applications

    NASA Astrophysics Data System (ADS)

    Gandy, A. P.; Sheikh, A.; Neumann, K.; Neumann, K.-U.; Pooley, D.; Ziebeck, K. R. A.

    2008-06-01

    For most metals a microscopic change in shape occurs above the elastic limit by the irreversible creation and movement of dislocations. However a large number of metallic systems undergo structural, martensitic, phase transformations which are diffusionless, displacive first order transitions from a high-temperature phase to one of lower symmetry below a certain temperature TM. These transitions which have been studied for more than a century are of vital importance because of their key role in producing shape memory phenomena enabling the system to reverse large deformations in the martensitic phase by heating into the austenite phase. In addition to a change in shape (displacement) the effect can also produce a force or a combination of both. Materials having this unique property are increasing being used in medical applications—scoliosis correction, arterial clips, stents, orthodontic wire, orthopaedic implants etc. The structural phase transition essential for shape memory behaviour is usually activated by a change in temperature or applied stress. However for many applications such as for actuators the transformation is not sufficiently rapid. Poor energy conversion also limits the applicability of many shape memory alloys. In medicine a change of temperature or pressure is often inappropriate and new ferromagnetic materials are being considered in which the phenomena can be controlled by an applied magnetic field at constant temperature. In order to achieve this, it is important to optimise three fundamental parameters. These are the saturation magnetisation σs, the Curie temperature Tc and the martensitic temperature TM. Here, σs is important because the magnetic pressure driving the twin boundary motion is 2σsH. Furthermore the material must be in the martensitic state at the operating temperature which should be at or above room temperature. This may be achieved by alloying or controlling the stoichiometry. Recently new intermetallic compounds based

  12. Reconstructing liver shape and position from MR image slices using an active shape model

    NASA Astrophysics Data System (ADS)

    Fenchel, Matthias; Thesen, Stefan; Schilling, Andreas

    2008-03-01

    We present an algorithm for fully automatic reconstruction of 3D position, orientation and shape of the human liver from a sparsely covering set of n 2D MR slice images. Reconstructing the shape of an organ from slice images can be used for scan planning, for surgical planning or other purposes where 3D anatomical knowledge has to be inferred from sparse slices. The algorithm is based on adapting an active shape model of the liver surface to a given set of slice images. The active shape model is created from a training set of liver segmentations from a group of volunteers. The training set is set up with semi-manual segmentations of T1-weighted volumetric MR images. Searching for the optimal shape model that best fits to the image data is done by maximizing a similarity measure based on local appearance at the surface. Two different algorithms for the active shape model search are proposed and compared: both algorithms seek to maximize the a-posteriori probability of the grey level appearance around the surface while constraining the surface to the space of valid shapes. The first algorithm works by using grey value profile statistics in normal direction. The second algorithm uses average and variance images to calculate the local surface appearance on the fly. Both algorithms are validated by fitting the active shape model to abdominal 2D slice images and comparing the shapes, which have been reconstructed, to the manual segmentations and to the results of active shape model searches from 3D image data. The results turn out to be promising and competitive to active shape model segmentations from 3D data.

  13. Shape Optimization for Aerodynamic Noise Control

    NASA Astrophysics Data System (ADS)

    Marsden, Alison; Wang, Meng; Mohammadi, Bijan; Moin, Parviz

    2002-11-01

    The objective of this work is to develop optimal shape design methods for reducing airfoil trailing-edge noise. Accurate evaluation of the cost function gradient via classical methods is expensive in unsteady turbulent flow simulations. We have evaluated the method of incomplete sensitivities (Mohammadi and Pironneau), which is inexpensive, and has been successful in previous applications. Gradients are approximated by neglecting changes in the flow field relative to geometrical contributions at each time step. Initial tests applied to a model problem seemed promising, however, in some cases the method was found to break down. A systematic evaluation of the incomplete sensitivities method as applied to the present problem has been carried out by comparison with the full gradient. The contribution to the gradient from changes in the flow field were found to be important. The underlying physical reasoning will be discussed and alternative methods including adjoint approaches and evolutionary algorithms will be explored.

  14. Input shaped control of 3-dimensional maneuvers of flexible spacecraft

    NASA Technical Reports Server (NTRS)

    Singh, T.; Vadali, S. R.

    1992-01-01

    This paper deals with the control of three dimensional rotational maneuvers of flexible spacecraft. A spacecraft with a spherical hub and six symmetric appendages is considered here as a model. The appendages are long and flexible leading to low frequency vibration under any control action. To provide a comprehensive treatment of input shaped controllers, both open loop and closed loop controllers are considered. The minimum-time bang-bang and the near-minimum-time controller, used in conjunction with the shaped input technique are studied. In addition, a combination of a Liapunov controller with the shaped input control technique is proposed to take advantage of the simple feedback control strategy and augment it with a technique that can eliminate the vibratory motion of the flexible appendages more efficiently.

  15. Development of Control Models and a Robust Multivariable Controller for Surface Shape Control

    SciTech Connect

    Winters, S

    2003-06-18

    Surface shape control techniques are applied to many diverse disciplines, such as adaptive optics, noise control, aircraft flutter control and satellites, with an objective to achieve a desirable shape for an elastic body by the application of distributed control forces. Achieving the desirable shape is influenced by many factors, such as, actuator locations, sensor locations, surface precision and controller performance. Building prototypes to complete design optimizations or controller development can be costly or impractical. This shortfall, puts significant value in developing accurate modeling and control simulation approaches. This thesis focuses on the field of adaptive optics, although these developments have the potential for application in many other fields. A static finite element model is developed and validated using a large aperture interferometer system. This model is then integrated into a control model using a linear least squares algorithm and Shack-Hartmann sensor. The model is successfully exercised showing functionality for various wavefront aberrations. Utilizing a verified model shows significant value in simulating static surface shape control problems with quantifiable uncertainties. A new dynamic model for a seven actuator deformable mirror is presented and its accuracy is proven through experiment. Bond graph techniques are used to generate the state space model of the multi-actuator deformable mirror including piezo-electric actuator dynamics. Using this verified model, a robust multi-input multi-output (MIMO) H{sub {infinity}} controller is designed and implemented. This controller proved superior performance as compared to a standard proportional-integral controller (PI) design.

  16. Chloride (Cl-) ion-mediated shape control of palladium nanoparticles

    NASA Astrophysics Data System (ADS)

    Nalajala, Naresh; Chakraborty, Arup; Bera, Bapi; Neergat, Manoj

    2016-02-01

    The shape control of Pd nanoparticles is investigated using chloride (Cl-) ions as capping agents in an aqueous medium in the temperature range of 60-100 °C. With weakly adsorbing and strongly etching Cl- ions, oxygen plays a crucial role in shape control. The experimental factors considered are the concentration of the capping agents, reaction time and reaction atmosphere. Thus, Pd nanoparticles of various shapes with high selectivity can be synthesized. Moreover, the removal of Cl- ions from the nanoparticle surface is easier than that of Br- ions (moderately adsorbing and etching) and I- ions (strongly adsorbing and weakly etching). The cleaned Cl- ion-mediated shape-controlled Pd nanoparticles are electrochemically characterized and the order of the half-wave potential of the oxygen reduction reaction in oxygen-saturated 0.1 M HClO4 solution is of the same order as that observed with single-crystal Pd surfaces.

  17. Monodisperse Block Copolymer Particles with Controllable Size, Shape, and Nanostructure

    NASA Astrophysics Data System (ADS)

    Shin, Jae Man; Kim, Yongjoo; Kim, Bumjoon; PNEL Team

    Shape-anisotropic particles are important class of novel colloidal building block for their functionality is more strongly governed by their shape, size and nanostructure compared to conventional spherical particles. Recently, facile strategy for producing non-spherical polymeric particles by interfacial engineering received significant attention. However, achieving uniform size distribution of particles together with controlled shape and nanostructure has not been achieved. Here, we introduce versatile system for producing monodisperse BCP particles with controlled size, shape and morphology. Polystyrene-b-polybutadiene (PS-b-PB) self-assembled to either onion-like or striped ellipsoid particle, where final structure is governed by amount of adsorbed sodium dodecyl sulfate (SDS) surfactant at the particle/surrounding interface. Further control of molecular weight and particle size enabled fine-tuning of aspect ratio of ellipsoid particle. Underlying physics of free energy for morphology formation and entropic penalty associated with bending BCP chains strongly affects particle structure and specification.

  18. G2 cubic transition between two circles with shape control

    NASA Astrophysics Data System (ADS)

    Habib, Zulfiqar; Sakai, Manabu

    2009-01-01

    This paper describes a method for joining two circles with an S-shaped or with a broken back C-shaped transition curve, composed of at most two spiral segments. In highway and railway route design or car-like robot path planning, it is often desirable to have such a transition. It is shown that a single cubic curve can be used for blending or for a transition curve preserving G2 continuity with local shape control parameter and more flexible constraints. Provision of the shape parameter and flexibility provide freedom to modify the shape in a stable manner which is an advantage over previous work by Meek, Walton, Sakai and Habib.

  19. Shape Control in Engineering of Polymeric Nanoparticles for Therapeutic Delivery

    PubMed Central

    Williford, John-Michael; Santos, Jose Luis; Shyam, Rishab; Mao, Hai-Quan

    2015-01-01

    Nanoparticle-mediated delivery of therapeutics holds great potential for the diagnosis and treatment of a wide range of diseases. Significant advances have been made in the design of new polymeric nanoparticle carriers through modulation of their physical and chemical structures and biophysical properties. Nanoparticle shape has been increasingly proposed as an important attribute dictating their transport properties in biological milieu. In this review, we highlight three major methods for preparing polymeric nanoparticles that allow for exquisite control of particle shape. Special attention is given to various approaches to controlling nanoparticle shape by tuning copolymer structural parameters and assembly conditions. This review also provides comparisons of these methods in terms of their unique capabilities, materials choices, and specific delivery cargos, and summarizes the biological effects of nanoparticle shape on transport properties at the tissue and cellular levels. PMID:26146550

  20. Electrochemically shape-controlled synthesis in deep eutectic solvents: triambic icosahedral platinum nanocrystals with high-index facets and their enhanced catalytic activity.

    PubMed

    Wei, Lu; Zhou, Zhi-You; Chen, Sheng-Pei; Xu, Chang-Deng; Su, Dangsheng; Schuster, Manfred Erwin; Sun, Shi-Gang

    2013-12-11

    Pt triambic icosahedral nanocrystals (TIH NCs) enclosed by {771} high-index facets were successfully synthesized electrochemically, for the first time, in ChCl-urea based deep eutectic solvents, and exhibited higher electrocatalytic activity and stability towards ethanol electrooxidation than a commercial Pt black catalyst. PMID:24084858

  1. Shaping Social Activity by Incentivizing Users

    PubMed Central

    Farajtabar, Mehrdad; Du, Nan; Rodriguez, Manuel Gomez; Valera, Isabel; Zha, Hongyuan; Song, Le

    2015-01-01

    Events in an online social network can be categorized roughly into endogenous events, where users just respond to the actions of their neighbors within the network, or exogenous events, where users take actions due to drives external to the network. How much external drive should be provided to each user, such that the network activity can be steered towards a target state? In this paper, we model social events using multivariate Hawkes processes, which can capture both endogenous and exogenous event intensities, and derive a time dependent linear relation between the intensity of exogenous events and the overall network activity. Exploiting this connection, we develop a convex optimization framework for determining the required level of external drive in order for the network to reach a desired activity level. We experimented with event data gathered from Twitter, and show that our method can steer the activity of the network more accurately than alternatives. PMID:26005312

  2. Feedback Control Systems Loop Shaping Design with Practical Considerations

    NASA Technical Reports Server (NTRS)

    Kopsakis, George

    2007-01-01

    This paper describes loop shaping control design in feedback control systems, primarily from a practical stand point that considers design specifications. Classical feedback control design theory, for linear systems where the plant transfer function is known, has been around for a long time. But it s still a challenge of how to translate the theory into practical and methodical design techniques that simultaneously satisfy a variety of performance requirements such as transient response, stability, and disturbance attenuation while taking into account the capabilities of the plant and its actuation system. This paper briefly addresses some relevant theory, first in layman s terms, so that it becomes easily understood and then it embarks into a practical and systematic design approach incorporating loop shaping design coupled with lead-lag control compensation design. The emphasis is in generating simple but rather powerful design techniques that will allow even designers with a layman s knowledge in controls to develop effective feedback control designs.

  3. Dynamically controlled toroidal and ring-shaped magnetic traps

    SciTech Connect

    Fernholz, T.; Gerritsma, R.; Spreeuw, R. J. C.; Krueger, P.

    2007-06-15

    We present traps with toroidal (T{sup 2}) and ring-shaped topologies based on adiabatic potentials for radio-frequency-dressed Zeeman states in a ring-shaped magnetic quadrupole field. Simple adjustment of the radio-frequency fields provides versatile possibilities for dynamical parameter tuning, topology change, and controlled potential perturbation. We show how to induce toroidal and poloidal rotations, and demonstrate the feasibility of preparing degenerate quantum gases with reduced dimensionality and periodic boundary conditions. The great level of dynamical and even state-dependent control is useful for atom interferometry.

  4. Online processing of shape information for control of grasping.

    PubMed

    Chen, Zhongting; Saunders, Jeffrey A

    2015-11-01

    When picking up objects, we tend to grasp at contact points that minimize slippage and torsion, which depend on the particular shape. Normally, grasp points could be planned before initiating movement. We tested whether grasp points can be determined during online control. Subjects reached to grasp virtual planar objects with varied shapes. On some trials, the object was changed during movement, either rotated by 45° or replaced with a different object. In all conditions, grasp axes were well adapted to the target shape, passing near the center of mass with low force closure angles. On perturbed trials, corrective adjustments were detectable within 320 ms and were toward the same grasp axes observed on unperturbed trials. Perturbations had little effect on either kinematics or the optimality of final grasp points. Our results demonstrate that the visuomotor system is capable of online processing of shape information to determine appropriate contact points for grasping. PMID:26195167

  5. Control of drop shape transformations in cooled emulsions.

    PubMed

    Cholakova, Diana; Denkov, Nikolai; Tcholakova, Slavka; Lesov, Ivan; Smoukov, Stoyan K

    2016-09-01

    The general mechanisms of structure and form generation are the keys to understanding the fundamental processes of morphogenesis in living and non-living systems. In our recent study (Denkov et al., Nature 528 (2015) 392) we showed that micrometer sized n-alkane drops, dispersed in aqueous surfactant solutions, can break symmetry upon cooling and "self-shape" into a series of geometric shapes with complex internal structure. This phenomenon is important in two contexts, as it provides: (a) new, highly efficient bottom-up approach for producing particles with complex shapes, and (b) remarkably simple system, from the viewpoint of its chemical composition, which exhibits the basic processes of structure and shape transformations, reminiscent of morphogenesis events in living organisms. In the current study, we show for the first time that drops of other chemical substances, such as long-chain alcohols, triglycerides, alkyl cyclohexanes, and linear alkenes, can also evolve spontaneously into similar non-spherical shapes. We demonstrate that the main factors which control the drop "self-shaping", are the surfactant type and chain length, cooling rate, and initial drop size. The studied surfactants are classified into four distinct groups, with respect to their effect on the "self-shaping" phenomenon. Coherent explanations of the main experimental trends are proposed. The obtained results open new prospects for fundamental and applied research in several fields, as they demonstrate that: (1) very simple chemical systems may show complex structure and shape shifts, similar to those observed in living organisms; (2) the molecular self-assembly in frustrated confinement may result in complex events, governed by the laws of elasto-capillarity and tensegrity; (3) the surfactant type and cooling rate could be used to obtain micro-particles with desired shapes and aspect ratios; and (4) the systems studied serve as a powerful toolbox to investigate systematically these

  6. Controlling the Shapes of Silver Nanocrystals with Different Capping Agents

    SciTech Connect

    Zeng, J.; Tao, J.; Zheng, Y.; Rycenga, M.; Li, Z.-Y.; Zhang, Q.A.; Zhu, Y.; Xia, Y.

    2010-06-30

    This paper provides direct evidence to support the role of a capping agent in controlling the evolution of Ag seeds into nanocrystals with different shapes. Starting with single-crystal seeds (spherical or cubic in shape), we could selectively obtain Ag octahedrons enclosed by {l_brace}111{r_brace} facets and nanocubes/nanobars enclosed by {l_brace}100{r_brace} facets by adding sodium citrate (Na{sub 3}CA) and poly(vinyl pyrrolidone) (PVP), respectively, as a capping agent while all other parameters were kept the same. This research not only offers new insights into the role played by a capping agent in shape-controlled synthesis but also provides, for the first time, Ag octahedrons as small as 40 nm in edge length for optical and spectroscopic studies.

  7. AC Electric Field Activated Shape Memory Polymer Composite

    NASA Technical Reports Server (NTRS)

    Kang, Jin Ho; Siochi, Emilie J.; Penner, Ronald K.; Turner, Travis L.

    2011-01-01

    Shape memory materials have drawn interest for applications like intelligent medical devices, deployable space structures and morphing structures. Compared to other shape memory materials like shape memory alloys (SMAs) or shape memory ceramics (SMCs), shape memory polymers (SMPs) have high elastic deformation that is amenable to tailored of mechanical properties, have lower density, and are easily processed. However, SMPs have low recovery stress and long response times. A new shape memory thermosetting polymer nanocomposite (LaRC-SMPC) was synthesized with conductive fillers to enhance its thermo-mechanical characteristics. A new composition of shape memory thermosetting polymer nanocomposite (LaRC-SMPC) was synthesized with conductive functionalized graphene sheets (FGS) to enhance its thermo-mechanical characteristics. The elastic modulus of LaRC-SMPC is approximately 2.7 GPa at room temperature and 4.3 MPa above its glass transition temperature. Conductive FGSs-doped LaRC-SMPC exhibited higher conductivity compared to pristine LaRC SMP. Applying an electric field at between 0.1 Hz and 1 kHz induced faster heating to activate the LaRC-SMPC s shape memory effect relative to applying DC electric field or AC electric field at frequencies exceeding1 kHz.

  8. Flight Control Using Distributed Shape-Change Effector Arrays

    NASA Technical Reports Server (NTRS)

    Raney, David L.; Montgomery, Raymond C.; Green, Lawrence I.; Park, Michael A.

    2000-01-01

    Recent discoveries in material science and fluidics have been used to create a variety of novel effector devices that offer great potential to enable new approaches to aerospace vehicle flight control. Examples include small inflatable blisters, shape-memory alloy diaphragms, and piezoelectric patches that may be used to produce distortions or bumps on the surface of an airfoil to generate control moments. Small jets have also been used to produce a virtual shape-change through fluidic means by creating a recirculation bubble on the surface of an airfoil. An advanced aerospace vehicle might use distributed arrays of hundreds of such devices to generate moments for stabilization and maneuver control, either augmenting or replacing conventional ailerons, flaps or rudders. This research demonstrates the design and use of shape-change device arrays for a tailless aircraft in a low-rate maneuvering application. A methodology for assessing the control authority of the device arrays is described, and a suite of arrays is used in a dynamic simulation to illustrate allocation and deployment methodologies. Although the authority of the preliminary shape-change array designs studied in this paper appeared quite low, the simulation results indicate that the effector suite possessed sufficient authority to stabilize and maneuver the vehicle in mild turbulence.

  9. Controls-structures integrated design optimization with shape variations

    NASA Technical Reports Server (NTRS)

    Koganti, Gopichand; Hou, Gene

    1993-01-01

    The shape design variables have been introduced into the set of design variables of the Controls-Structure Integrated (CSI) Design of space-structures. The importance of the shape variations in improving the design (obtained with only control and sizing variables) has been aptly illustrated. Two different types of design variables that describe the shape variations of the structure have been introduced. In the first case, the nodal coordinates have been considered as design variables. This has the inherent difficulty of having too many design variables. This not only is time consuming but also memory intensive and may not yield a manufacturable shape to the structure. The second approach has been introduced to overcome this difficulty. The structure is allowed to vary in a particular pre defined pattern. The coefficients of these patterns are considered as the shape design variables. The eigenvalue and eigenvector sensitivity equations with respect to these coefficient design variables have been developed and are used to approximate the eigenvalues and eigenvectors in a perturbed design.

  10. Multivariable shape control development on the DIII-D tokamak

    SciTech Connect

    Walker, M.L.; Humphreys, D.A.; Ferron, J.R.

    1997-11-01

    In this paper, the authors describe recent work on plasma shape and position control at DIII-D. This control consists of two equally challenging problems--the problem of identifying what the plasma actually looks like in real time, i.e. measuring the parameters to be controlled, and the task of determining the feedback algorithm which best controls these plasma parameters in a multiple input-output system. Recent implementation of the EFIT plasma equilibrium reconstruction algorithm in real time code which produces a new equilibrium estimate every 1.5 ms seems to solve the longstanding problem of obtaining sufficiently accurate plasma shape and position estimation. Stabilization of the open-loop unstable vertical motion is also viewed as a solved problem. The primary remaining problem appears to be how best to command the power supplies to achieve a desired shaping control response. They will describe the effort to understand and apply linearized models of plasma evolution to development and implementation of multivariable plasma controllers.

  11. Factors Shaping Students' Opportunities to Engage in Argumentative Activity

    ERIC Educational Resources Information Center

    Ayalon, Michal; Even, Ruhama

    2016-01-01

    This study examines how students' opportunities to engage in argumentative activity are shaped by the teacher, the class, and the mathematical topic. It compares the argumentative activity between two classes taught by the same teacher using the same textbook and across two beginning algebra topics--investigating algebraic expressions and…

  12. Studying Doctoral Education: Using Activity Theory to Shape Methodological Tools

    ERIC Educational Resources Information Center

    Beauchamp, Catherine; Jazvac-Martek, Marian; McAlpine, Lynn

    2009-01-01

    The study reported here, one part of a larger study on doctoral education, describes a pilot study that used Activity Theory to shape a methodological tool for better understanding the tensions inherent in the doctoral experience. As doctoral students may function within a range of activity systems, we designed data collection protocols based on…

  13. Development of electric environment to control mollusk-shaped gel robots made of electroactive polymer PAMPS gel

    NASA Astrophysics Data System (ADS)

    Otake, Mihoko; Inaba, Masayuki; Inoue, Hirochika

    2000-06-01

    This paper describes the design and implementation of electric fields to actuate mollusk-shaped robots made entirely of PAMPS gel, which is a kind of electro-active polymer (EAP). The purpose of this study is to develop a system to control the shape of both simulated and real gel robots using electric fields. We present a modeling framework and experimental results using a prototype mollusk-shaped EAP robot that locomotes by changing the shape of its whole body.

  14. Charting early trajectories of executive control with the shape school.

    PubMed

    Clark, Caron A C; Sheffield, Tiffany D; Chevalier, Nicolas; Nelson, Jennifer Mize; Wiebe, Sandra A; Espy, Kimberly Andrews

    2013-08-01

    Despite acknowledgement of the importance of executive control for learning and behavior, there is a dearth of research charting its developmental trajectory as it unfolds against the background of children's sociofamilial milieus. Using a prospective, cohort-sequential design, this study describes growth trajectories for inhibitory control and cognitive flexibility across the preschool period in relation to child sex and sociofamilial resources. At ages 3, 3.75, 4.5, and 5.25 years, children (N = 388) from a broad range of social backgrounds were assessed using the Shape School, a graduated measure of executive control incorporating baseline, inhibitory control, and cognitive flexibility conditions. Measures of children's proximal access to learning resources and social network supports were collected at study entry. Findings revealed substantial gains in accuracy and speed for all Shape School conditions, these gains being particularly accelerated between ages 3 and 3.75 years. Improvements in inhibitory control were more rapid than those in flexible switching. Age-related differences in error and self-correction patterns on the Shape School also suggest qualitative changes in the underlying processes supporting executive performance across early childhood. Children from homes with fewer learning resources showed a subtle lag in inhibition and cognitive flexibility performance that persisted at kindergarten entry age, despite exhibiting gradual catch up to their more advantaged peers for the nonexecutive, baseline task condition. The study provides a unique characterization of the early developmental pathways for inhibitory control and cognitive flexibility and highlights the critical role of stimulating early educational resources for shaping the dynamic ontogeny of executive control. PMID:23106846

  15. Contact shape controls adhesion of bioinspired fibrillar surfaces.

    PubMed

    del Campo, Aránzazu; Greiner, Christian; Arzt, Eduard

    2007-09-25

    Following a recent bioinspired paradigm, patterned surfaces can exhibit better adhesion than flat contacts. Previous studies have verified that finer contact structures give rise to higher adhesion forces. In this study, we report on the effect of the tip shape, which was varied systematically in fibrillar PDMS surfaces, produced by lithographic and soft-molding methods. For fiber radii between 2.5 and 25 microm, it is found that shape exerts a stronger effect on adhesion than size. The highest adhesion is measured for mushroom-like and spatular terminals, which attain adhesion values 30 times in excess of the flat controls and similar to a gecko toe. These results explain the shapes commonly found in biological systems, and help in the exploration of the parameter space for artificial attachment systems. PMID:17722937

  16. Investigation of thermal distortion and control of spacecraft based on shape memory materials

    NASA Astrophysics Data System (ADS)

    Sun, Hongwei; Du, Xingwen; Tan, Huifeng

    2009-07-01

    Gossamer space structures are relatively large, flimsy, and lightweight. As a result, they are more easily affected or distortion by space thermal environments compared to other space structures. This study examines the structural integrity of a Five-Meter Ka-Band Inflatable/Self-Rigidizable Reflect Antenna under space thermal environments. To maintain the required accuracy of the reflector under orbital temperature changes, the Gossamer space structures will utilize an active control system, consisting of boundary control actuators and an electrostatic figure control system with a real time closed loop feedback. An experimental system is established to verify the control mechanism with photogrammetric measurement technique and Bragg fiber grating (FBG) sensor technique. The shape control experiments are finished by measuring and analyzing small amplitude distortion of Five-Meter Ka-Band Inflatable/Self-Rigidizable Reflect Antenna based on the active components made of shape memory alloy (SMA) and shape memory polymer composite (SMPC) material. Then, simulations are finished by NASTRAN finite element software with active effect which is considered to be deformation applied on the analytical model. The amplitude of distortion is obtained by the simulations. Both the experimental and numerical solution show that the amplitude of accuracy are developed which proves the feasibility of shape control using shape memory materials and this investigation explores the feasibility of utilizing an active cable based control system of shape memory materials to reduce global distortion due to thermal loading. It is found that through proper assemble of cable lengths and attachment points, significant thermal distortion reduction is achieved. Specifically, radial distortion due to on-orbit thermal loading .

  17. Trichomes control flower bud shape by linking together young petals.

    PubMed

    Tan, Jiafu; Walford, Sally-Anne; Dennis, Elizabeth S; Llewellyn, Danny

    2016-01-01

    Trichomes are widespread in plants and develop from surface cells on different tissues(1). They have many forms and functions, from defensive spines to physical barriers that trap layers of air to insulate against desiccation, but there is growing evidence that trichomes can also have developmental roles in regulating flower structure(2,3). We report here that the trichomes on petals of cotton, Gossypium hirsutum L., are essential for correct flower bud shape through a mechanical entanglement of the trichomes on adjacent petals that anchor the edges to counter the opposing force generated by asymmetric expansion of overlapping petals. Silencing a master regulator of petal trichomes, GhMYB-MIXTA-Like10 (GhMYBML10), by RNA interference (RNAi) suppressed petal trichome growth and resulted in flower buds forming into abnormal corkscrew shapes that exposed developing anthers and stigmas to desiccation damage. Artificially gluing petal edges together could partially restore correct bud shape and fertility. Such petal 'Velcro' is present in other Malvaceae and perhaps more broadly in other plant families, although it is not ubiquitous. This mechanism for physical association between separate organs to regulate flower shape and function is different from the usual organ shape control(4) exerted through cell-to-cell communication and differential cell expansion within floral tissues(5,6). PMID:27322517

  18. Thermoelectric control of shape memory alloy microactuators: a thermal model

    NASA Astrophysics Data System (ADS)

    Abadie, J.; Chaillet, Nicolas; Lexcellent, Christian; Bourjault, Alain

    1999-06-01

    Microtechnologies and microsystems engineering use new active materials. These materials are interesting to realize microactuators and microsensors. In this category of materials, Shape Memory Alloys (SMA) are good candidates for microactuation. SMA wires, or thin plates, can be used as active material in microfingers. These microstructures are able to provide very important forces, but have low dynamic response, especially for cooling, in confined environment. The control of the SMA phase transformations, and then the mechanical power generation, is made by the temperature. The Joule effect is an easy and efficiency way to heat the SMA wires, but cooling is not so easy. The dynamic response of the actuator depends on cooling capabilities. The thermal convection and conduction are the traditional ways to cool the SMA, but have limitations for microsystems. We are looking for a reversible way of heating and cooling SMA microactuators, based on the thermoelectric effects. Using Peltier effect, a positive or a negative electrical courant is able to pump or produce heat, in the SMA actuator. A physical model based on thermal exchanges between a Nickel/Titanium (NiTi) SMA, and Bismuth/Telluride (Te3Bi2) thermoelectric material has been developed. For simulation, we use a numerical resolution of our model, with finite elements, which takes into account the Peltier effect, the Joule effect, the convection, the conduction and the phase transformation of the SMA. We have also developed the corresponding experimental system, with two thermoelectric junctions, where the SMA actuator is one of the element of each junction. In this paper, the physical model and its numerical resolution are given, the experimental system used to validate the model is described, and experimental results are shown.

  19. Shape-Controlled Synthesis of Metal Nanocrystals: Simple Chemistry Meets Complex Physics?

    PubMed Central

    Xia, Younan; Xiong, Yujie; Lim, Byungkwon; Skrabalak, Sara E.

    2009-01-01

    Nanocrystals are fundamental to modern science and technology. Mastery over the shape of a nanocrystal enables control of its properties and enhancement of its usefulness for a given application. The aim of this article is to present a comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals. We begin with a brief introduction to nucleation and growth within the context of metal nanocrystal synthesis, followed by a discussion of the possible shapes that a metal nanocrystal might take under different conditions. We then focus on a variety of experimental parameters that have been explored to manipulate the nucleation and growth of metal nanocrystals in solution-phase syntheses in an effort to generate specific shapes. We then elaborate on these approaches by selecting examples in which there is already reasonable understanding for the observed shape control or at least the protocols have proven to be reproducible and controllable. Toward the end of this article, we highlight a number of applications that have been enabled and/or enhanced by the shape-controlled synthesis of metal nanocrystals. We conclude this article with personal perspectives on the directions toward which future research in this field might take. PMID:19053095

  20. Active shape models with optimised texture features for radiotherapy

    NASA Astrophysics Data System (ADS)

    Cheng, K.; Montgomery, D.; Yang, F.; McLaren, D. B.; McLaughlin, S.; Nailon, W. H.

    2014-03-01

    There is now considerable interest in radiation oncology on the use of shape models of anatomy to improve target delineation and assess anatomical disparity at time of radiotherapy. In this paper a texture based active shape model (ASM) is presented for automatic delineation of the gross tumor volume (GTV), containing the prostate, on computed tomography (CT) images of prostate cancer patients. The model was trained on two-dimensional (2D) contours identified by a radiation oncologist on sequential CT image slices. A three-dimensional (3D) GTV shape was constructed from these and iteratively aligned using Procrustes analysis. To train the model the shape deformation variance was learnt using the Active Shape Model (ASM) approach. In a novel development to this approach a profile feature was selected from pre-computed texture features by minimizing the Mahalanobis distance to obtain the most distinct feature for each landmark. The interior of the GTV was modelled using quantile histograms to initialize the shape model on new cases. From the archive of 42 cases of contoured CT scans, 32 cases were randomly selected for training the model and 10 cases for evaluating performance. The gold standard was defined by the radiation oncologist. The shape model achieved an overall Dice coefficient of 0.81 for all test cases. Performance was found to increase, mean Dice coefficient of 0.87, when the volume size of the new case was similar to the mean shape of the model. With further work the approach has the potential to be used in real-time delineation of target volumes and improve segmentation accuracy.

  1. Programmable light-controlled shape changes in layered polymer nanocomposites.

    PubMed

    Zhu, Zhichen; Senses, Erkan; Akcora, Pinar; Sukhishvili, Svetlana A

    2012-04-24

    We present soft, layered nanocomposites that exhibit controlled swelling anisotropy and spatially specific shape reconfigurations in response to light irradiation. The use of gold nanoparticles grafted with a temperature-responsive polymer (poly(N-isopropylacrylamide), PNIPAM) with layer-by-layer (LbL) assembly allowed placement of plasmonic structures within specific regions in the film, while exposure to light caused localized material deswelling by a photothermal mechanism. By layering PNIPAM-grafted gold nanoparticles in between nonresponsive polymer stacks, we have achieved zero Poisson's ratio materials that exhibit reversible, light-induced unidirectional shape changes. In addition, we report rheological properties of these LbL assemblies in their equilibrium swollen states. Moreover, incorporation of dissimilar plasmonic nanostructures (solid gold nanoparticles and nanoshells) within different material strata enabled controlled shrinkage of specific regions of hydrogels at specific excitation wavelengths. The approach is applicable to a wide range of metal nanoparticles and temperature-responsive polymers and affords many advanced build-in options useful in optically manipulated functional devices, including precise control of plasmonic layer thickness, tunability of shape variations to the excitation wavelength, and programmable spatial control of optical response. PMID:22452351

  2. Active shape models incorporating isolated landmarks for medical image annotation

    NASA Astrophysics Data System (ADS)

    Norajitra, Tobias; Meinzer, Hans-Peter; Stieltjes, Bram; Maier-Hein, Klaus H.

    2014-03-01

    Apart from their robustness in anatomic surface segmentation, purely surface based 3D Active Shape Models lack the ability to automatically detect and annotate non-surface key points of interest. However, annotation of anatomic landmarks is desirable, as it yields additional anatomic and functional information. Moreover, landmark detection might help to further improve accuracy during ASM segmentation. We present an extension of surface-based 3D Active Shape Models incorporating isolated non-surface landmarks. Positions of isolated and surface landmarks are modeled conjoint within a point distribution model (PDM). Isolated landmark appearance is described by a set of haar-like features, supporting local landmark detection on the PDM estimates using a kNN-Classi er. Landmark detection was evaluated in a leave-one-out cross validation on a reference dataset comprising 45 CT volumes of the human liver after shape space projection. Depending on the anatomical landmark to be detected, our experiments have shown in about 1/4 up to more than 1/2 of all test cases a signi cant improvement in detection accuracy compared to the position estimates delivered by the PDM. Our results encourage further research with regard to the combination of shape priors and machine learning for landmark detection within the Active Shape Model Framework.

  3. Wingless signaling and the control of cell shape in Drosophila wing imaginal discs.

    PubMed

    Widmann, Thomas J; Dahmann, Christian

    2009-10-01

    The control of cell morphology is important for shaping animals during development. Here we address the role of the Wnt/Wingless signal transduction pathway and two of its target genes, vestigial and shotgun (encoding E-cadherin), in controlling the columnar shape of Drosophila wing disc cells. We show that clones of cells mutant for arrow (encoding an essential component of the Wingless signal transduction pathway), vestigial or shotgun undergo profound cell shape changes and are extruded towards the basal side of the epithelium. Compartment-wide expression of a dominant-negative form of the Wingless transducer T-cell factor (TCF/Pangolin), or double-stranded RNA targeting vestigial or shotgun, leads to abnormally short cells throughout this region, indicating that these genes act cell autonomously to maintain normal columnar cell shape. Conversely, overexpression of Wingless, a constitutively-active form of the Wingless transducer beta-catenin/Armadillo, or Vestigial, results in precocious cell elongation. Co-expression of Vestigial partially suppresses the abnormal cell shape induced by dominant-negative TCF. We conclude that Wingless signal transduction plays a cell-autonomous role in promoting and maintaining the columnar shape of wing disc cells. Furthermore, our data suggest that Wingless controls cell shape, in part, through maintaining vestigial expression. PMID:19627985

  4. Directional decoupling of piezoelectric sheet actuators for shape and vibration control of plate structures

    NASA Astrophysics Data System (ADS)

    Philen, Michael K.; Wang, Kon W.

    2003-08-01

    With the advancement of actuator engineering, adaptive optic technology has grown considerably over the past couple of decades. Recently, there has been attention in lightweight adaptive optics where piezoelectric sheet actuators are directly attached on the back of optical mirrors to achieve a high precision surface shape with minimum addition weight[C. Kuo, R. Bruno, '90, '92; C. Liu and N. Hagood, '93; R. Kapania, P. Mohan, et al, 1998]. Philen and Wang [2001] investigated the shape control performance of a large flexible circular plate structure having directly attached thin strip piezoelectric sheet actuators placed in the plate's radial and circumferential directions. It was discovered that the performance of the system could be further improved if the piezoelectric actuator was decoupled in direction, meaning that the circumferential (radial) action of the radial (circumferential) actuators is eliminated while the radial (circumferential) action is maintained. To realize the decoupling effect, the performance of an active stiffener concept for high-precision shape and vibration control has been studied [Philen and Wang, 2002]. The active stiffener configuration consists of an insert (stiffener) placed between the host structure and the piezoelectric sheet actuator, which could produce the required decoupling effect. Similar to the active stiffener, the Active Fiber Composite (AFC) possesses a unique orthotropic actuation and has many advantages over the commonly used piezoceramic sheet actuator, thus providing a potential actuation scheme for the control of optical surfaces. In this paper, analytical investigations into several piezoelectric-type actuation methods for shape and vibration control of plate structures are presented. For the study, a performance comparison of the Active Fiber Composite (AFC), the Active Stiffener (AS), and the Direct Attached (DA) actuators for shape and vibration control of a circular plate structure is carried out. The shape

  5. Ultra-precise holographic beam shaping for microscopic quantum control.

    PubMed

    Zupancic, Philip; Preiss, Philipp M; Ma, Ruichao; Lukin, Alexander; Eric Tai, M; Rispoli, Matthew; Islam, Rajibul; Greiner, Markus

    2016-06-27

    High-resolution addressing of individual ultracold atoms, trapped ions or solid state emitters allows for exquisite control in quantum optics experiments. This becomes possible through large aperture magnifying optics that project microscopic light patterns with diffraction limited performance. We use programmable amplitude holograms generated on a digital micromirror device to create arbitrary microscopic beam shapes with full phase and amplitude control. The system self-corrects for aberrations of up to several λ and reduces them to λ/50, leading to light patterns with a precision on the 10-4 level. We demonstrate aberration-compensated beam shaping in an optical lattice experiment and perform single-site addressing in a quantum gas microscope for 87Rb. PMID:27410551

  6. Ultra-precise holographic beam shaping for microscopic quantum control

    NASA Astrophysics Data System (ADS)

    Zupancic, Philip; Preiss, Philipp M.; Ma, Ruichao; Lukin, Alexander; Eric Tai, M.; Rispoli, Matthew; Islam, Rajibul; Greiner, Markus

    2016-06-01

    High-resolution addressing of individual ultracold atoms, trapped ions or solid state emitters allows for exquisite control in quantum optics experiments. This becomes possible through large aperture magnifying optics that project microscopic light patterns with diffraction limited performance. We use programmable amplitude holograms generated on a digital micromirror device to create arbitrary microscopic beam shapes with full phase and amplitude control. The system self-corrects for aberrations of up to several $\\lambda$ and reduces them to $\\lambda/50$, leading to light patterns with a precision on the $10^{-4}$ level. We demonstrate aberration-compensated beam shaping in an optical lattice experiment and perform single-site addressing in a quantum gas microscope for $^{87}$Rb.

  7. An input shaping controller enabling cranes to move without sway

    SciTech Connect

    Singer, N.; Singhose, W.; Kriikku, E.

    1997-06-01

    A gantry crane at the Savannah River Technology Center was retrofitted with an Input Shaping controller. The controller intercepts the operator`s pendant commands and modifies them in real time so that the crane is moved without residual sway in the suspended load. Mechanical components on the crane were modified to make the crane suitable for the anti-sway algorithm. This paper will describe the required mechanical modifications to the crane, as well as, a new form of Input Shaping that was developed for use on the crane. Experimental results are presented which demonstrate the effectiveness of the new process. Several practical considerations will be discussed including a novel (patent pending) approach for making small, accurate moves without residual oscillations.

  8. Shape control technology during electrochemical synthesis of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Xiu-yu; Cui, Cong-ying; Cheng, Ying-wen; Ma, Hou-yi; Liu, Duo

    2013-05-01

    Gold nanoparticles with different shapes and sizes were prepared by adding gold precursor (HAuCl4) to an electrolyzed aqueous solution of poly( N-vinylpyrrolidone) (PVP) and KNO3, which indicates the good reducing capacity of the PVP-containing solution after being treated by electrolysis. Using a catholyte and an anolyte as the reducing agents for HAuCl4, respectively, most gold nanoparticles were spherical particles in the former case but plate-like particles in the latter case. The change in the pH value of electrolytes caused by the electrolysis of water would be the origin of the differences in shape and morphology of gold nanoparticles. A hypothesis of the H+ or OH- catalyzed PVP degradation mechanism was proposed to interpret why the pH value played a key role in determining the shape or morphology of gold nanoparticles. These experiments open up a new method for effectively controlling the shape and morphology of metal nanoparticles by using electrochemical methods.

  9. Shape-controlled synthesis of Au-Pd bimetallic nanocrystals for catalytic applications.

    PubMed

    Zhang, Lei; Xie, Zhaoxiong; Gong, Jinlong

    2016-07-21

    Au-Pd nanostructured materials have been recognized as important heterogeneous catalysts in various reactions, due to their superior activities caused by the ensemble and ligand effects. In recent years, shape-controlled synthesis of noble metal nanocrystals (NCs) provided a brand-new insight for improving the performance of catalysts. The electronic properties and catalytic activities of Au-Pd NCs could be optimized by tuning their shape and composition engineering. This review describes recent progress in the design and synthesis of shape-controlled Au-Pd bimetallic NCs and their emerging catalytic applications. The review starts with a general discussion of various applications of Au-Pd catalysts and the significance of preparing shape-controlled Au-Pd NCs, followed by an overview of synthetic strategies for two different structures of Au-Pd bimetallic catalysts: a core-shell structure and an alloy structure. We also put forward the key factors for the preparation of Au-Pd core-shell and alloy structures. Additionally, we discussed the unique optical properties and structural effects of shape-controlled Au-Pd NCs. These recent advancements in the methodology development of Au-Pd bimetallic NCs offer numerous insights for generating Au-Pd NCs with a number of unique geometries in the future. Furthermore, the systematic synthesis of core-shell or alloy structures would provide insights for the preparation of other bimetallic NCs. PMID:27095006

  10. Biomimetic control over size, shape and aggregation in magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Sommerdijk, Nico

    2013-03-01

    Magnetite (Fe3O4) is a widespread magnetic iron oxide encountered in both geological and biomineralizing systems, which also has many technological applications, e.g. in ferrofluids, inks, magnetic data storage materials and as contrast agents in magnetic resonance imaging. As its magnetic properties depend largely on the size and shape of the crystals, control over crystal morphology is an important aspect in the application of magnetite nanoparticles, both in biology and synthetic systems. Indeed, in nature organisms such as magnetotactic bacteria demonstrate a precise control over the magnetite crystal morphology, resulting in uniform and monodisperse nanoparticles. The magnetite formation in these bacteria is believed to occur through the co-precipitation of Fe(II) and Fe(III) ions, which is also the most widely applied synthetic route in industry. Synthetic strategies to magnetite with controlled size and shape exist, but involve high temperatures and rather harsh chemical conditions. However, synthesis via co-precipitation generally yields poor control over the morphology and therefore over the magnetic properties of the obtained crystals. Here we demonstrate that by tuning the reaction kinetics we can achieve biomimetic control over the size and shape of magnetite crystals but also over their organization in solution as well as their magnetic properties. We employ amino acids-based polymers to direct the formation of magnetite in aqueous media at room temperature via both the co-precipitation and the partial oxidation method. By using 2D and 3D (cryo)TEM it is shown that acidic amino acid monomers are most effective in affecting the magnetite particle morphology. By changing the composition of the polymers we can tune the morphology, the dispersibility as well as the magnetic properties of these nanoparticles.

  11. New Ganymede control point network and global shape model

    NASA Astrophysics Data System (ADS)

    Zubarev, A.; Nadezhdina, I.; Oberst, J.; Hussmann, H.; Stark, A.

    2015-11-01

    We computed a 3D control point network for Ganymede using combinations of 126 Voyager-1 and -2 and 87 Galileo images, benefiting from reconstructed trajectory data for the three spacecraft and a more complete Galileo image data base than was available for earlier studies. Using more than 3000 control point coordinates, we determine global shape parameters, including mean radius, spheroid- and ellipsoidal axes, and make tests for various equilibrium shape models, constrained by the most recent estimates for gravity field parameters. We confirm that Ganymede has a pronounced ellipsoidal shape, approximately aligned with the Jupiter-direction, in agreement with Ganymede being in tidal equilibrium. The point heights, suffering from large individual errors, do not reveal any large-scale topography below our typical error levels (97% <5 km). By analysis of data residuals we search for, but cannot detect Ganymede longitudinal forced librations. We conclude that libration amplitudes cannot be larger than 0.1° (corresponding to a lateral displacement of 4.6 km at the equator).

  12. Shape control of magnesium oxysulfate granules using an ethanolamine chelate.

    PubMed

    Kang, Kuk-Hyoun; Lee, Dong-Kyu; Ruh, Hyun; Ahn, Seonghee; Yu, Hyunung

    2014-11-01

    Shape control of inorganic nanomaterials during hydrothermal syntheses is crucial for fine-tuning the function of these materials, which are widely utilized in semiconductors, ceramics, and optical devices. In particular, magnesium compounds possess many desirable physical properties such as high thermal stability, wide band gap and high secondary electron emission yield, which allow their application as polymeric resins, cements, reinforcements, and fillers. However, conventional synthetic methods often require extreme reaction conditions such as high temperatures, high pressures, or prolonged reaction times. Additionally, various shape control methods are typically quite complicated and time consuming under conventional parameters. In this work, magnesium oxysulfate (5Mg(OH)2 x MgSO4 x 3H2O) granules of various shapes were fabricated by introducing ethanolamine chelate during hydrothermal reaction at a relatively low temperature and pressure. The strong interaction between ethanolamine and Mg2+ produced 5Mg(OH)2 x MgSO4 x 3H2O granules in the form of flakes, flowers, or whiskers through self-assembly this formation is dependent on concentration, reaction time, and temperature. The physicochemical properties of the samples were investigated using X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. PMID:25958602

  13. Virtual fuzzy in-process control of Y-shape tube hydroforming with different branch top shapes

    NASA Astrophysics Data System (ADS)

    Manabe, Ken-ichi; Chen, Xu; Kobayashi, Dai

    2014-10-01

    In this study, a new counter punch shape was designed and applied to Y-shape hydroforming to obtain a Y-shape tube with uniform wall thickness. The new counter punch shape effect in Y-shape hydroforming using fuzzy control was investigated in finite element simulation. As a result, the wall thickness thinning in the branch top was restrained and the wall thickness thickening in the die shoulder of obtuse angle side was restrained. The results suggested that the wall thickness could be more uniform by using the new counter punch.

  14. Finite Element Analysis of Adaptive-Stiffening and Shape-Control SMA Hybrid Composites

    NASA Technical Reports Server (NTRS)

    Gao, Xiujie; Burton, Deborah; Turner, Travis L.; Brinson, Catherine

    2005-01-01

    Shape memory alloy hybrid composites with adaptive-stiffening or morphing functions are simulated using finite element analysis. The composite structure is a laminated fiber-polymer composite beam with embedded SMA ribbons at various positions with respect to the neutral axis of the beam. Adaptive stiffening or morphing is activated via selective resistance heating of the SMA ribbons or uniform thermal loads on the beam. The thermomechanical behavior of these composites was simulated in ABAQUS using user-defined SMA elements. The examples demonstrate the usefulness of the methods for the design and simulation of SMA hybrid composites. Keywords: shape memory alloys, Nitinol, ABAQUS, finite element analysis, post-buckling control, shape control, deflection control, adaptive stiffening, morphing, constitutive modeling, user element

  15. DNA directed self-assembly of shape-controlled hydrogels

    PubMed Central

    Qi, Hao; Ghodousi, Majid; Du, Yanan; Grun, Casey; Bae, Hojae; Yin, Peng; Khademhosseini, Ali

    2013-01-01

    Using DNA as programmable, sequence specific ‘glues’, shape-controlled hydrogel units are self-assembled into prescribed structures. Here we report that aggregates are produced using hydrogel cubes with edge length ranging from 30 micrometers to 1 millimeter, demonstrating assembly across scales. In a simple one-pot agitation reaction, 25 dimers are constructed in parallel from 50 distinct hydrogel cube species, demonstrating highly multiplexed assembly. Using hydrogel cuboids displaying face-specific DNA glues, diverse structures are achieved in aqueous and in interfacial agitation systems. These include dimers, extended chains, and open network structures in an aqueous system; and dimers, chains of fixed length, T-junctions, and square shapes in the interfacial system, demonstrating the versatility of the assembly system. PMID:24013352

  16. Agricultural activity shapes the communication and migration patterns in Senegal.

    PubMed

    Martin-Gutierrez, S; Borondo, J; Morales, A J; Losada, J C; Tarquis, A M; Benito, R M

    2016-06-01

    The communication and migration patterns of a country are shaped by its socioeconomic processes. The economy of Senegal is predominantly rural, as agriculture employs over 70% of the labor force. In this paper, we use mobile phone records to explore the impact of agricultural activity on the communication and mobility patterns of the inhabitants of Senegal. We find two peaks of phone calls activity emerging during the growing season. Moreover, during the harvest period, we detect an increase in the migration flows throughout the country. However, religious holidays also shape the mobility patterns of the Senegalese people. Hence, in the light of our results, agricultural activity and religious holidays are the primary drivers of mobility inside the country. PMID:27368795

  17. Agricultural activity shapes the communication and migration patterns in Senegal

    NASA Astrophysics Data System (ADS)

    Martin-Gutierrez, S.; Borondo, J.; Morales, A. J.; Losada, J. C.; Tarquis, A. M.; Benito, R. M.

    2016-06-01

    The communication and migration patterns of a country are shaped by its socioeconomic processes. The economy of Senegal is predominantly rural, as agriculture employs over 70% of the labor force. In this paper, we use mobile phone records to explore the impact of agricultural activity on the communication and mobility patterns of the inhabitants of Senegal. We find two peaks of phone calls activity emerging during the growing season. Moreover, during the harvest period, we detect an increase in the migration flows throughout the country. However, religious holidays also shape the mobility patterns of the Senegalese people. Hence, in the light of our results, agricultural activity and religious holidays are the primary drivers of mobility inside the country.

  18. Sample Stimulus Control Shaping and Restricted Stimulus Control in Capuchin Monkeys: A Methodological Note

    ERIC Educational Resources Information Center

    Brino, Ana Leda F., Barros, Romariz S., Galvao, Ol; Garotti, M.; Da Cruz, Ilara R. N.; Santos, Jose R.; Dube, William V.; McIlvane, William J.

    2011-01-01

    This paper reports use of sample stimulus control shaping procedures to teach arbitrary matching-to-sample to 2 capuchin monkeys ("Cebus apella"). The procedures started with identity matching-to-sample. During shaping, stimulus features of the sample were altered gradually, rendering samples and comparisons increasingly physically dissimilar. The…

  19. Boost of plasma current with active magnetic field shaping coils in rotamak discharges

    SciTech Connect

    Yang Xiaokang; Goss, Jermain; Kalaria, Dhara; Huang, Tian Sen

    2011-08-15

    A set of magnetic shaping coils is installed on the Prairie View (PV) rotamak for the study of active plasma shape control in the regimes with and without toroidal field (TF). In the spherical tokamak regime (with TF), plasma current I{sub p} can be boosted by 200% when all five shaping coils (connected in series) are energized. The enhancement of current drive efficiency is mainly attributed to the radial compression and the substantially axial extension of the plasma column; this in turn improves the impedance matching and thus increases antenna input power. In the field-reversed configuration (without TF), plasma current can be boosted by 100% when one middle coil is used; the appearance of radial shift mode limits the achievable value of I{sub p}. The experiments clearly demonstrate that the plasma shape control plays a role in effectively driving plasma current in rotamaks.

  20. Imaging structure sensitive catalysis on different shape-controlled platinum nanoparticles.

    PubMed

    Sánchez-Sánchez, Carlos M; Solla-Gullón, José; Vidal-Iglesias, Francisco J; Aldaz, Antonio; Montiel, Vicente; Herrero, Enrique

    2010-04-28

    The structure sensitive catalytic activity for oxygen reduction reaction (ORR) on shape-controlled Pt nanoparticles (NPs) is directly imaged using scanning electrochemical microscopy (SECM). We synthesize and compare four types of Pt NPs: spherical, cubic, hexagonal, and tetrahedral-octahedral. Our SECM images show the hexagonal Pt NPs displaying the highest activity for ORR in two acid electrolytes. Meanwhile, cubic and tetrahedral-octahedral NPs drastically change their activity depending on specific adsorption of the different anions in solution. The NPs morphology produces predominant crystallographic planes at the surface of these shape-controlled Pt NPs, which are responsible for their different catalytic activity. Our results translate the studies on Pt single crystal electrodes present in the literature into Pt NPs that are useful as a catalyst in real fuel cells. PMID:20359217

  1. Coupled parametric design of flow control and duct shape

    NASA Technical Reports Server (NTRS)

    Florea, Razvan (Inventor); Bertuccioli, Luca (Inventor)

    2009-01-01

    A method for designing gas turbine engine components using a coupled parametric analysis of part geometry and flow control is disclosed. Included are the steps of parametrically defining the geometry of the duct wall shape, parametrically defining one or more flow control actuators in the duct wall, measuring a plurality of performance parameters or metrics (e.g., flow characteristics) of the duct and comparing the results of the measurement with desired or target parameters, and selecting the optimal duct geometry and flow control for at least a portion of the duct, the selection process including evaluating the plurality of performance metrics in a pareto analysis. The use of this method in the design of inter-turbine transition ducts, serpentine ducts, inlets, diffusers, and similar components provides a design which reduces pressure losses and flow profile distortions.

  2. Shape determination and control for large space structures

    NASA Technical Reports Server (NTRS)

    Weeks, C. J.

    1981-01-01

    An integral operator approach is used to derive solutions to static shape determination and control problems associated with large space structures. Problem assumptions include a linear self-adjoint system model, observations and control forces at discrete points, and performance criteria for the comparison of estimates or control forms. Results are illustrated by simulations in the one dimensional case with a flexible beam model, and in the multidimensional case with a finite model of a large space antenna. Modal expansions for terms in the solution algorithms are presented, using modes from the static or associated dynamic mode. These expansions provide approximated solutions in the event that a used form analytical solution to the system boundary value problem is not available.

  3. Practical Loop-Shaping Design of Feedback Control Systems

    NASA Technical Reports Server (NTRS)

    Kopasakis, George

    2010-01-01

    An improved methodology for designing feedback control systems has been developed based on systematically shaping the loop gain of the system to meet performance requirements such as stability margins, disturbance attenuation, and transient response, while taking into account the actuation system limitations such as actuation rates and range. Loop-shaping for controls design is not new, but past techniques do not directly address how to systematically design the controller to maximize its performance. As a result, classical feedback control systems are designed predominantly using ad hoc control design approaches such as proportional integral derivative (PID), normally satisfied when a workable solution is achieved, without a good understanding of how to maximize the effectiveness of the control design in terms of competing performance requirements, in relation to the limitations of the plant design. The conception of this improved methodology was motivated by challenges in designing control systems of the types needed for supersonic propulsion. But the methodology is generally applicable to any classical control-system design where the transfer function of the plant is known or can be evaluated. In the case of a supersonic aerospace vehicle, a major challenge is to design the system to attenuate anticipated external and internal disturbances, using such actuators as fuel injectors and valves, bypass doors, and ramps, all of which are subject to limitations in actuator response, rates, and ranges. Also, for supersonic vehicles, with long slim type of structures, coupling between the engine and the structural dynamics can produce undesirable effects that could adversely affect vehicle stability and ride quality. In order to design distributed controls that can suppress these potential adverse effects, within the full capabilities of the actuation system, it is important to employ a systematic control design methodology such as this that can maximize the

  4. Vibration and shape control of inflatable deployment structures

    NASA Astrophysics Data System (ADS)

    Lu, Mingyu; Tian, Zhenhui; Tan, Huifeng

    2007-07-01

    This paper describes the status of on-going work at the vibration and shape control of large inflatable deployment structures. It presents a brief summary of the related concepts in inflatable deployment structures, smart structures and the applications between them. Inflatable deployment structures which made of thin membrane can hardly achieve high surface precision and good dynamic properties. Smart materials and structures can be used to adjust boundary and membrane surface, which give the ability of vibration and shape control. Results indicated that the use of smart materials and structures might easily help inflatable deployment structures reduce vibration and achieve higher surface precision. A large-scale and light weight reflector model mixed with inflatable deployment and rib-support structure was developed. It is constructed by five parts: central connection tank, radial supporting ribs, inflation bags, meshed reflective surface and supporting booms. To improve surface precision, some sensors and actuators made of smart materials could be designed to guarantee the reflector model has more control authority over the whole structure.

  5. Shape control in wafer-based aperiodic 3D nanostructures

    NASA Astrophysics Data System (ADS)

    Jeong, Hyeon-Ho; Mark, Andrew G.; Gibbs, John G.; Reindl, Thomas; Waizmann, Ulrike; Weis, Jürgen; Fischer, Peer

    2014-06-01

    Controlled local fabrication of three-dimensional (3D) nanostructures is important to explore and enhance the function of single nanodevices, but is experimentally challenging. We present a scheme based on e-beam lithography (EBL) written seeds, and glancing angle deposition (GLAD) grown structures to create nanoscale objects with defined shapes but in aperiodic arrangements. By using a continuous sacrificial corral surrounding the features of interest we grow isolated 3D nanostructures that have complex cross-sections and sidewall morphology that are surrounded by zones of clean substrate.

  6. Cell shape, cytoskeletal mechanics, and cell cycle control in angiogenesis

    NASA Technical Reports Server (NTRS)

    Ingber, D. E.; Prusty, D.; Sun, Z.; Betensky, H.; Wang, N.

    1995-01-01

    Capillary endothelial cells can be switched between growth and differentiation by altering cell-extracellular matrix interactions and thereby, modulating cell shape. Studies were carried out to determine when cell shape exerts its growth-regulatory influence during cell cycle progression and to explore the role of cytoskeletal structure and mechanics in this control mechanism. When G0-synchronized cells were cultured in basic fibroblast growth factor (FGF)-containing defined medium on dishes coated with increasing densities of fibronectin or a synthetic integrin ligand (RGD-containing peptide), cell spreading, nuclear extension, and DNA synthesis all increased in parallel. To determine the minimum time cells must be adherent and spread on extracellular matrix (ECM) to gain entry into S phase, cells were removed with trypsin or induced to retract using cytochalasin D at different times after plating. Both approaches revealed that cells must remain extended for approximately 12-15 h and hence, most of G1, in order to enter S phase. After this restriction point was passed, normally 'anchorage-dependent' endothelial cells turned on DNA synthesis even when round and in suspension. The importance of actin-containing microfilaments in shape-dependent growth control was confirmed by culturing cells in the presence of cytochalasin D (25-1000 ng ml-1): dose-dependent inhibition of cell spreading, nuclear extension, and DNA synthesis resulted. In contrast, induction of microtubule disassembly using nocodazole had little effect on cell or nuclear spreading and only partially inhibited DNA synthesis. Interestingly, combination of nocodazole with a suboptimal dose of cytochalasin D (100 ng ml-1) resulted in potent inhibition of both spreading and growth, suggesting that microtubules are redundant structural elements which can provide critical load-bearing functions when microfilaments are partially compromised. Similar synergism between nocodazole and cytochalasin D was observed

  7. Graphene blisters with switchable shapes controlled by pressure and adhesion.

    PubMed

    Boddeti, Narasimha G; Liu, Xinghui; Long, Rong; Xiao, Jianliang; Bunch, J Scott; Dunn, Martin L

    2013-01-01

    We created graphene blisters that cover and seal an annular cylinder-shaped microcavity in a SiO2 substrate filled with a gas. By controlling the pressure difference between the gas inside and outside of the microcavity, we switch the graphene membrane between multiple stable equilibrium configurations. We carried out experiments starting from the situation where the pressure of the gas inside and outside of the microcavity is set equal to a prescribed charging pressure, p0 and the graphene membrane covers the cavity like an annular drum, adhered to the central post and the surrounding substrate due to van der Waals forces. We decrease the outside pressure to a value, pe which causes it to bulge into an annular blister. We systematically increase the charging pressure by repeating this procedure causing the annular blister to continue to bulge until a critical charging pressure pc(i) is reached. At this point the graphene membrane delaminates from the post in an unstable manner, resulting in a switch of graphene membrane shape from an annular to a spherical blister. Continued increase of the charging pressure results in the spherical blister growing with its height increasing, but maintaining a constant radius until a second critical charging pressure pc(o) is reached at which point the blister begins to delaminate from the periphery of the cavity in a stable manner. Here, we report a series of experiments as well as a mechanics and thermodynamic model that demonstrate how the interplay among system parameters (geometry, graphene stiffness (number of layers), pressure, and adhesion energy) results in the ability to controllably switch graphene blisters among different shapes. Arrays of these blisters can be envisioned to create pressure-switchable surface properties where the difference between patterns of annular versus spherical blisters will impact functionalities such as wettability, friction, adhesion, and surface wave characteristics. PMID:24224793

  8. Midbrain volume segmentation using active shape models and LBPs

    NASA Astrophysics Data System (ADS)

    Olveres, Jimena; Nava, Rodrigo; Escalante-Ramírez, Boris; Cristóbal, Gabriel; García-Moreno, Carla María.

    2013-09-01

    In recent years, the use of Magnetic Resonance Imaging (MRI) to detect different brain structures such as midbrain, white matter, gray matter, corpus callosum, and cerebellum has increased. This fact together with the evidence that midbrain is associated with Parkinson's disease has led researchers to consider midbrain segmentation as an important issue. Nowadays, Active Shape Models (ASM) are widely used in literature for organ segmentation where the shape is an important discriminant feature. Nevertheless, this approach is based on the assumption that objects of interest are usually located on strong edges. Such a limitation may lead to a final shape far from the actual shape model. This paper proposes a novel method based on the combined use of ASM and Local Binary Patterns for segmenting midbrain. Furthermore, we analyzed several LBP methods and evaluated their performance. The joint-model considers both global and local statistics to improve final adjustments. The results showed that our proposal performs substantially better than the ASM algorithm and provides better segmentation measurements.

  9. Shape control of slack space reflectors using modulated solar pressure

    PubMed Central

    Borggräfe, Andreas; Heiligers, Jeannette; Ceriotti, Matteo; McInnes, Colin R.

    2015-01-01

    The static deflection profile of a large spin-stabilized space reflector because of solar radiation pressure acting on its surface is investigated. Such a spacecraft consists of a thin reflective circular film, which is deployed from a supporting hoop structure in an untensioned, slack manner. This paper investigates the use of a variable reflectivity distribution across the surface to control the solar pressure force and hence the deflected shape. In this first analysis, the film material is modelled as one-dimensional slack radial strings with no resistance to bending or transverse shear, which enables a semi-analytic derivation of the nominal deflection profile. An inverse method is then used to find the reflectivity distribution that generates a specific, for example, parabolic deflection shape of the strings. Applying these results to a parabolic reflector, short focal distances can be obtained when large slack lengths of the film are employed. The development of such optically controlled reflector films enables future key mission applications such as solar power collection, radio-frequency antennae and optical telescopes. PMID:26345083

  10. Volume Changes During Active Shape Fluctuations in Cells

    NASA Astrophysics Data System (ADS)

    La Porta, Caterina A. M.; Taloni, Alessandro; Kardash, Elena; Salman, Oguz Umut; Truskinovsky, Lev; Zapperi, Stefano

    Cells modify their volume in response to changes in osmotic pressure but it is usually assumed that other active shape variations do not involve significant volume fluctuations. Here we report experiments demonstrating that water transport in and out of the cell is needed for the formation of blebs, commonly observed protrusions in the plasma membrane driven by cortex contraction. We develop and simulate a model of fluid-mediated membrane-cortex deformations and show that a permeable membrane is necessary for bleb formation which is otherwise impaired. Taken together, our experimental and theoretical results emphasize the subtle balance between hydrodynamics and elasticity in actively driven cell morphological changes.

  11. Volume Changes During Active Shape Fluctuations in Cells

    NASA Astrophysics Data System (ADS)

    Taloni, Alessandro; Kardash, Elena; Salman, Oguz Umut; Truskinovsky, Lev; Zapperi, Stefano; La Porta, Caterina A. M.

    2015-05-01

    Cells modify their volume in response to changes in osmotic pressure but it is usually assumed that other active shape variations do not involve significant volume fluctuations. Here we report experiments demonstrating that water transport in and out of the cell is needed for the formation of blebs, commonly observed protrusions in the plasma membrane driven by cortex contraction. We develop and simulate a model of fluid-mediated membrane-cortex deformations and show that a permeable membrane is necessary for bleb formation which is otherwise impaired. Taken together, our experimental and theoretical results emphasize the subtle balance between hydrodynamics and elasticity in actively driven cell morphological changes.

  12. Shape-retainment control using an antagonistic shape memory alloy system

    NASA Astrophysics Data System (ADS)

    Ikeda, T.; Sawamura, K.; Senba, A.; Tamayama, M.

    2015-04-01

    Since shape memory alloy (SMA) actuators can generate large force per unit weight, they are expected as one of the next generation actuators for aircraft. To keep a position of conventional control surfaces or morphing wings with SMA actuators, the SMA actuators must keep being heated, and the heating energy is not small. To save the energy, a new control method proposed for piezoelectric actuators utilizing hysteresis in deformation [Ikeda and Takahashi, Proc. SPIE 8689 (2013), 86890C] is applied to an antagonistic SMA system. By using the control method any position can be an equilibrium point within hysteresis of stress-strain diagrams. To confirm a feasibility of the control method, a fundamental experiment is performed. The SMA wires are heated by applying electric current to the wires. When a pulsed current is applied to the two SMA wires alternately, the equilibrium position changes between two positions alternately, and when a series of pulse whose amplitude increases gradually is applied to one SMA wire, the equilibrium position changes like a staircase. However, just after the pulse the position returns slightly, that is, overshoot takes place. To investigate such a behavior of the system, numerical simulation is also performed. The one-dimensional phase transformation model [Ikeda, Proc. SPIE 5757 (2005), 344-352] is used for a constitutive model of the SMA wires. The simulated result agrees with the experiment qualitatively, including the overshoot. By examining volume fraction of each phase, it is found that the overshoot is caused by that austenite phase transforms into stress-induced martensite phase during the cooling process after the pulse.

  13. Selection of actuator locations for static shape control of large space structures by heuristic integer programing

    NASA Technical Reports Server (NTRS)

    Haftka, R. T.; Adelman, H. M.

    1985-01-01

    Orbiting spacecraft such as large space antennas have to maintain a highly accurate shape to operate satisfactorily. Such structures require active and passive controls to maintain an accurate shape under a variety of disturbances. Methods for the optimum placement of control actuators for correcting static deformations are described. In particular, attention is focused on the case were control locations have to be selected from a large set of available sites, so that integer programing methods are called for. The effectiveness of three heuristic techniques for obtaining a near-optimal site selection is compared. In addition, efficient reanalysis techniques for the rapid assessment of control effectiveness are presented. Two examples are used to demonstrate the methods: a simple beam structure and a 55m space-truss-parabolic antenna.

  14. Active control of buckling of flexible beams

    NASA Technical Reports Server (NTRS)

    Baz, A.; Tampe, L.

    1989-01-01

    The feasibility of using the rapidly growing technology of the shape memory alloys actuators in actively controlling the buckling of large flexible structures is investigated. The need for such buckling control systems is becoming inevitable as the design trends of large space structures have resulted in the use of structural members that are long, slender, and very flexible. In addition, as these truss members are subjected mainly to longitudinal loading they become susceptible to structural instabilities due to buckling. Proper control of such instabilities is essential to the effective performance of the structures as stable platforms for communication and observation. Mathematical models are presented that simulate the dynamic characteristics of the shape memory actuator, the compressive structural members, and the associated active control system. A closed-loop computer-controlled system is designed, based on the developed mathematical models, and implemented to control the buckling of simple beams. The performance of the computer-controlled system is evaluated experimentally and compared with the theoretical predictions to validate the developed models. The obtained results emphasize the importance of buckling control and suggest the potential of the shape memory actuators as attractive means for controlling structural deformation in a simple and reliable way.

  15. Shape-Dependent Surface Reactivity and Antimicrobial Activity of Nano-Cupric Oxide.

    PubMed

    Gilbertson, Leanne M; Albalghiti, Eva M; Fishman, Zachary S; Perreault, François; Corredor, Charlie; Posner, Jonathan D; Elimelech, Menachem; Pfefferle, Lisa D; Zimmerman, Julie B

    2016-04-01

    Shape of engineered nanomaterials (ENMs) can be used as a design handle to achieve controlled manipulation of physicochemical properties. This tailored material property approach necessitates the establishment of relationships between specific ENM properties that result from such manipulations (e.g., surface area, reactivity, or charge) and the observed trend in behavior, from both a functional performance and hazard perspective. In this study, these structure-property-function (SPF) and structure-property-hazard (SPH) relationships are established for nano-cupric oxide (n-CuO) as a function of shape, including nanospheres and nanosheets. In addition to comparing these shapes at the nanoscale, bulk CuO is studied to compare across length scales. The results from comprehensive material characterization revealed correlations between CuO surface reactivity and bacterial toxicity with CuO nanosheets having the highest surface reactivity, electrochemical activity, and antimicrobial activity. While less active than the nanosheets, CuO nanoparticles (sphere-like shape) demonstrated enhanced reactivity compared to the bulk CuO. This is in agreement with previous studies investigating differences across length-scales. To elucidate the underlying mechanisms of action to further explain the shape-dependent behavior, kinetic models applied to the toxicity data. In addition to revealing different CuO material kinetics, trends in observed response cannot be explained by surface area alone. The compiled results contribute to further elucidate pathways toward controlled design of ENMs. PMID:26943499

  16. Passive and active pulse stacking scheme for pulse shaping

    DOEpatents

    Harney, Robert C.; Schipper, John F.

    1977-01-01

    Apparatus and method for producing a sequence of radiation pulses with a pulse envelope of time variation which is controllable by an external electromagnetic signal applied to an active medium or by a sectored reflector, through which the radiation passes.

  17. Water levels shape fishing participation in flood-control reservoirs

    USGS Publications Warehouse

    Miranda, Leandro E.; Meals, K. O.

    2013-01-01

    We examined the relationship between fishing effort (hours fished) and average March–May water level in 3 flood control reservoirs in Mississippi. Fishing effort increased as water level rose, peaked at intermediate water levels, and decreased at high water levels. We suggest that the observed arched-shaped relationship is driven by the shifting influence of fishability (adequacy of the fishing circumstances from an angler's perspective) and catch rate along a water level continuum. Fishability reduces fishing effort during low water, despite the potential for higher catch rates. Conversely, reduced catch rates and fishability at high water also curtail effort. Thus, both high and low water levels seem to discourage fishing effort, whereas anglers seem to favor intermediate water levels. Our results have implications for water level management in reservoirs with large water level fluctuations.

  18. 14 CFR 23.781 - Cockpit control knob shape.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... knobs must conform to the general shapes (but not necessarily the exact sizes or specific proportions... general shapes (but not necessarily the exact sizes or specific proportions) in the following figure:...

  19. 14 CFR 23.781 - Cockpit control knob shape.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... knobs must conform to the general shapes (but not necessarily the exact sizes or specific proportions... general shapes (but not necessarily the exact sizes or specific proportions) in the following figure:...

  20. 14 CFR 23.781 - Cockpit control knob shape.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... knobs must conform to the general shapes (but not necessarily the exact sizes or specific proportions... general shapes (but not necessarily the exact sizes or specific proportions) in the following figure:...

  1. 14 CFR 23.781 - Cockpit control knob shape.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... knobs must conform to the general shapes (but not necessarily the exact sizes or specific proportions... general shapes (but not necessarily the exact sizes or specific proportions) in the following figure:...

  2. Optimal quantum control via numerical pulse shape optimization for two exciton qubits confined to semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Mathew, Reuble; Shi Yang, Hong Yi; Hall, Kimberley

    2015-03-01

    Optimal quantum control (OQC), which iteratively optimizes the control Hamiltonian to achieve a target quantum state, is a versatile approach for manipulating quantum systems. For optically-active transitions, OQC can be implemented using femtosecond pulse shaping which provides control over the amplitude and/or phase of the electric field. Optical pulse shaping has been employed to optimize physical processes such as nonlinear optical signals, photosynthesis, and has recently been applied to optimizing single-qubit gates in multiple semiconductor quantum dots. In this work, we examine the use of numerical pulse shape optimization for optimal quantum control of multiple qubits confined to quantum dots as a function of their electronic structure parameters. The numerically optimized pulse shapes were found to produce high fidelity quantum gates for a range of transition frequencies, dipole moments, and arbitrary initial and final states. This work enhances the potential for scalability by reducing the laser resources required to control multiple qubits.

  3. Pupil segmentation using active contour with shape prior

    NASA Astrophysics Data System (ADS)

    Ukpai, Charles O.; Dlay, Satnam S.; Woo, Wai L.

    2015-03-01

    Iris segmentation is the process of defining the valid part of the eye image used for further processing (feature extraction, matching and decision making). Segmentation of the iris mostly starts with pupil boundary segmentation. Most pupil segmentation techniques are based on the assumption that the pupil is circular shape. In this paper, we propose a new pupil segmentation technique which combines shape, location and spatial information for accurate and efficient segmentation of the pupil. Initially, the pupil's position and radius is estimated using a statistical approach and circular Hough transform. In order to segment the irregular boundary of the pupil, an active contour model is initialized close to the estimated boundary using information from the first step and segmentation is achieved using energy minimization based active contour. Pre-processing and post-processing were carried out to remove noise and occlusions respectively. Experimental results on CASIA V1.0 and 4.0 shows that the proposed method is highly effective at segmenting irregular boundaries of the pupil.

  4. Shape control of composite plates and shells with embedded actuators. 2: Desired shape specified

    NASA Astrophysics Data System (ADS)

    Koconis, David B.; Kollar, Laszlo P.; Springer, George S.

    The changes in shapes of fiber-reinforced composite beams, plates and shells affected by embedded piezoelectric actuators were investigated. An analytical method was developed to determine the voltages needed to achieve a specified desired shape. The method is formulated on the basis of mathematical models using two-dimensional, linear, shallow shell theory including transverse shear effects which are important in the case of sandwich construction. The solution technique is a minimization of an error function which is a measure of the difference between the deformed shape caused by the application of voltages and the desired shape. A computationally efficient, user-friendly computer code was written which is suitable for performing the numerical calculations. The code, designated as SHAPE2, gives the voltages needed to achieve specified changes in shape. To validate the method and the computer code, results generated by the code were compared to existing analytical and experimental results. The predictions provided by the SHAPE2 code were in excellent agreement with the results of the other analyses and data.

  5. Social Support Can Buffer against Stress and Shape Brain Activity

    PubMed Central

    Hostinar, Camelia E.; Gunnar, Megan R.

    2015-01-01

    Social support from close relationship partners is an important resource for coping with stress, particularly during childhood. We discuss ethical challenges associated with studying stress and its social buffering in the laboratory, as well as emerging evidence regarding two potential neural substrates for the social buffering of stress: hypothalamic oxytocin activity and activation of areas in the prefrontal cortex associated with effective self-regulation. We also address the role of early-life social experiences in shaping brain development, as well as recommendations for practice and policy that would advance the ethical treatment of children and reduce social inequalities in early-life experiences and opportunities–e.g., investing in programs that prevent child maltreatment and facilitating access to high-quality child care for economically disadvantaged families. We also debate the ethical implications of using oxytocin nasal sprays to simulate the stress-reducing properties of social support and advise waiting for more evidence before recommending their use. PMID:26478822

  6. Tuning selectivity in catalysis by controlling particle shape

    NASA Astrophysics Data System (ADS)

    Lee, Ilkeun; Delbecq, Françoise; Morales, Ricardo; Albiter, Manuel A.; Zaera, Francisco

    2009-02-01

    A catalytic process for the selective formation of cis olefins would help minimize the production of unhealthy trans fats during the partial hydrogenation of edible oils. Here we report on the design of such a process on the basis of studies with model systems. Temperature programmed desorption data on single crystals showed that the isomerization of trans olefins to their cis counterparts is promoted by (111) facets of platinum, and that such selectivity is reversed on more open surfaces. Quantum mechanics calculations suggested that the extra stability of cis olefins seen on hydrogen-saturated Pt(111) surfaces may be due to a lesser degree of surface reconstruction, a factor found to be significant in the adsorption on close-packed platinum surfaces. Kinetic data using catalysts made out of dispersed tetrahedral Pt nanoparticles corroborated the selective promotion of the trans-to-cis isomerization on the (111) facets of the metal. Our work provides an example for how catalytic selectivity may be controlled by controlling the shape of the catalytic particles.

  7. Shape-controlled bridged silsesquioxanes: hollow tubes and spheres.

    PubMed

    Moreau, Joël J E; Vellutini, Luc; Wong Chi Man, Michel; Bied, Catherine

    2003-04-01

    A new approach for the morphological control of bridged silsesquioxanes has been achieved by the hydrolysis of silylated organic molecules bearing urea groups. The urea groups are responsible for the auto-association of the molecules through intermolecular hydrogen-bonding interactions. The self-assembly leads to supramolecular architectures that have the ability to direct the organization of hybrid silicas under controlled hydrolysis. The hydrolysis of the chiral diureido derivatives of trans-(1,2)-diaminocyclohexane 1 under basic conditions has been examined. The solid-state NMR spectra ((29)Si and (13)C) showed the hybrid nature of these materials with wholly preserved S-C bond covalent bonds throughout the silicate network. Hybrid silicas with hollow tubular morphologies were obtained by the hydrolysis of the enantiomerically pure compounds, (R,R)-1 or (S,S)-1, whereas the corresponding racemic mixture, rac-1, led to a hybrid with ball-like structures. The tubular shape is likely to result from a combination of two phenomena: the auto-association abilities and a self-templating structuration of the hybrid materials by the organic crystalline precursor. Electronic microscopy techniques (SEM and TEM) gave evidence for the self-templating pathway. The formation of the ball-like structures occurs through a usual nucleation growth phenomenon owing to a higher solubility of the corresponding crystals in the same medium. PMID:12658658

  8. Preliminary Assessment of Optimal Longitudinal-Mode Control for Drag Reduction through Distributed Aeroelastic Shaping

    NASA Technical Reports Server (NTRS)

    Ippolito, Corey; Nguyen, Nhan; Lohn, Jason; Dolan, John

    2014-01-01

    The emergence of advanced lightweight materials is resulting in a new generation of lighter, flexible, more-efficient airframes that are enabling concepts for active aeroelastic wing-shape control to achieve greater flight efficiency and increased safety margins. These elastically shaped aircraft concepts require non-traditional methods for large-scale multi-objective flight control that simultaneously seek to gain aerodynamic efficiency in terms of drag reduction while performing traditional command-tracking tasks as part of a complete guidance and navigation solution. This paper presents results from a preliminary study of a notional multi-objective control law for an aeroelastic flexible-wing aircraft controlled through distributed continuous leading and trailing edge control surface actuators. This preliminary study develops and analyzes a multi-objective control law derived from optimal linear quadratic methods on a longitudinal vehicle dynamics model with coupled aeroelastic dynamics. The controller tracks commanded attack-angle while minimizing drag and controlling wing twist and bend. This paper presents an overview of the elastic aircraft concept, outlines the coupled vehicle model, presents the preliminary control law formulation and implementation, presents results from simulation, provides analysis, and concludes by identifying possible future areas for research

  9. Optimal shape control of a beam using piezoelectric actuators with low control voltage

    NASA Astrophysics Data System (ADS)

    Yu, Y.; Zhang, X. N.; Xie, S. L.

    2009-09-01

    This paper deals with the shape control of a cantilever beam structure by using laminated piezoelectric actuators (LPAs) with a low control voltage. The shape control equation of the cantilever beam partially covered with LPAs is derived based on the constitutive relations of the elastic material and piezoelectric material and shear deformation beam theory (Timoshenko theory). The actuating forces produced by the LPAs are formulated as well. It reveals how the actuating forces depend on the number of piezoelectric layers, the thickness of piezoelectric layers and the position of the actuators. The driving voltages of the LPAs are then determined by a genetic optimization algorithm. The shape control of the cantilever beam from applying the optimal voltage to the LPAs is simulated. The simulation results show that an LPA of large layer number is able to diminish effectively the pre-deflection of the beam under a low control voltage. The voltage applied to the LPA of five layers was almost five times smaller than that of one layer. In addition, increasing the number of LPA layers can significantly improve the control performance as the acting forces of the LPA are a quadratic function of the LPA layer number. The L2 norm of the displacement array of all nodes is diminished about 30% after optimization. Also with the same low control voltage, the LPA can obtain a better control performance than the conventional single layer piezoelectric actuator.

  10. Shaping inhibition: activity dependent structural plasticity of GABAergic synapses

    PubMed Central

    Flores, Carmen E.; Méndez, Pablo

    2014-01-01

    Inhibitory transmission through the neurotransmitter γ-aminobutyric acid (GABA) shapes network activity in the mammalian cerebral cortex by filtering synaptic incoming information and dictating the activity of principal cells. The incredibly diverse population of cortical neurons that use GABA as neurotransmitter shows an equally diverse range of mechanisms that regulate changes in the strength of GABAergic synaptic transmission and allow them to dynamically follow and command the activity of neuronal ensembles. Similarly to glutamatergic synaptic transmission, activity-dependent functional changes in inhibitory neurotransmission are accompanied by alterations in GABAergic synapse structure that range from morphological reorganization of postsynaptic density to de novo formation and elimination of inhibitory contacts. Here we review several aspects of structural plasticity of inhibitory synapses, including its induction by different forms of neuronal activity, behavioral and sensory experience and the molecular mechanisms and signaling pathways involved. We discuss the functional consequences of GABAergic synapse structural plasticity for information processing and memory formation in view of the heterogenous nature of the structural plasticity phenomena affecting inhibitory synapses impinging on somatic and dendritic compartments of cortical and hippocampal neurons. PMID:25386117

  11. Shaping inhibition: activity dependent structural plasticity of GABAergic synapses.

    PubMed

    Flores, Carmen E; Méndez, Pablo

    2014-01-01

    Inhibitory transmission through the neurotransmitter γ-aminobutyric acid (GABA) shapes network activity in the mammalian cerebral cortex by filtering synaptic incoming information and dictating the activity of principal cells. The incredibly diverse population of cortical neurons that use GABA as neurotransmitter shows an equally diverse range of mechanisms that regulate changes in the strength of GABAergic synaptic transmission and allow them to dynamically follow and command the activity of neuronal ensembles. Similarly to glutamatergic synaptic transmission, activity-dependent functional changes in inhibitory neurotransmission are accompanied by alterations in GABAergic synapse structure that range from morphological reorganization of postsynaptic density to de novo formation and elimination of inhibitory contacts. Here we review several aspects of structural plasticity of inhibitory synapses, including its induction by different forms of neuronal activity, behavioral and sensory experience and the molecular mechanisms and signaling pathways involved. We discuss the functional consequences of GABAergic synapse structural plasticity for information processing and memory formation in view of the heterogenous nature of the structural plasticity phenomena affecting inhibitory synapses impinging on somatic and dendritic compartments of cortical and hippocampal neurons. PMID:25386117

  12. Shape-controlled continuous synthesis of metal nanostructures

    NASA Astrophysics Data System (ADS)

    Sebastian, Victor; Smith, Christopher D.; Jensen, Klavs F.

    2016-03-01

    A segmented flow-based microreactor is used for the continuous production of faceted nanocrystals. Flow segmentation is proposed as a versatile tool to manipulate the reduction kinetics and control the growth of faceted nanostructures; tuning the size and shape. Switching the gas from oxygen to carbon monoxide permits the adjustment in nanostructure growth from 1D (nanorods) to 2D (nanosheets). CO is a key factor in the formation of Pd nanosheets and Pt nanocubes; operating as a second phase, a reductant, and a capping agent. This combination confines the growth to specific structures. In addition, the segmented flow microfluidic reactor inherently has the ability to operate in a reproducible manner at elevated temperatures and pressures whilst confining potentially toxic reactants, such as CO, in nanoliter slugs. This continuous system successfully synthesised Pd nanorods with an aspect ratio of 6; thin palladium nanosheets with a thickness of 1.5 nm; and Pt nanocubes with a 5.6 nm edge length, all in a synthesis time as low as 150 s.A segmented flow-based microreactor is used for the continuous production of faceted nanocrystals. Flow segmentation is proposed as a versatile tool to manipulate the reduction kinetics and control the growth of faceted nanostructures; tuning the size and shape. Switching the gas from oxygen to carbon monoxide permits the adjustment in nanostructure growth from 1D (nanorods) to 2D (nanosheets). CO is a key factor in the formation of Pd nanosheets and Pt nanocubes; operating as a second phase, a reductant, and a capping agent. This combination confines the growth to specific structures. In addition, the segmented flow microfluidic reactor inherently has the ability to operate in a reproducible manner at elevated temperatures and pressures whilst confining potentially toxic reactants, such as CO, in nanoliter slugs. This continuous system successfully synthesised Pd nanorods with an aspect ratio of 6; thin palladium nanosheets with a

  13. Biomedical Applications of Thermally Activated Shape Memory Polymers

    SciTech Connect

    Small IV, W; Singhal, P; Wilson, T S; Maitland, D J

    2009-04-10

    Shape memory polymers (SMPs) are smart materials that can remember a primary shape and can return to this primary shape from a deformed secondary shape when given an appropriate stimulus. This property allows them to be delivered in a compact form via minimally invasive surgeries in humans, and deployed to achieve complex final shapes. Here we review the various biomedical applications of SMPs and the challenges they face with respect to actuation and biocompatibility. While shape memory behavior has been demonstrated with heat, light and chemical environment, here we focus our discussion on thermally stimulated SMPs.

  14. Biomedical applications of thermally activated shape memory polymers†

    PubMed Central

    Small, Ward; Singhal, Pooja; Wilson, Thomas S.

    2011-01-01

    Shape memory polymers (SMPs) are smart materials that can remember a primary shape and can return to this primary shape from a deformed secondary shape when given an appropriate stimulus. This property allows them to be delivered in a compact form via minimally invasive surgeries in humans, and deployed to achieve complex final shapes. Here we review the various biomedical applications of SMPs and the challenges they face with respect to actuation and biocompatibility. While shape memory behavior has been demonstrated with heat, light and chemical environment, here we focus our discussion on thermally stimulated SMPs. PMID:21258605

  15. Minimal-effort planning of active alignment processes for beam-shaping optics

    NASA Astrophysics Data System (ADS)

    Haag, Sebastian; Schranner, Matthias; Müller, Tobias; Zontar, Daniel; Schlette, Christian; Losch, Daniel; Brecher, Christian; Roßmann, Jürgen

    2015-03-01

    In science and industry, the alignment of beam-shaping optics is usually a manual procedure. Many industrial applications utilizing beam-shaping optical systems require more scalable production solutions and therefore effort has been invested in research regarding the automation of optics assembly. In previous works, the authors and other researchers have proven the feasibility of automated alignment of beam-shaping optics such as collimation lenses or homogenization optics. Nevertheless, the planning efforts as well as additional knowledge from the fields of automation and control required for such alignment processes are immense. This paper presents a novel approach of planning active alignment processes of beam-shaping optics with the focus of minimizing the planning efforts for active alignment. The approach utilizes optical simulation and the genetic programming paradigm from computer science for automatically extracting features from a simulated data basis with a high correlation coefficient regarding the individual degrees of freedom of alignment. The strategy is capable of finding active alignment strategies that can be executed by an automated assembly system. The paper presents a tool making the algorithm available to end-users and it discusses the results of planning the active alignment of the well-known assembly of a fast-axis collimator. The paper concludes with an outlook on the transferability to other use cases such as application specific intensity distributions which will benefit from reduced planning efforts.

  16. Abdomen and spinal cord segmentation with augmented active shape models.

    PubMed

    Xu, Zhoubing; Conrad, Benjamin N; Baucom, Rebeccah B; Smith, Seth A; Poulose, Benjamin K; Landman, Bennett A

    2016-07-01

    Active shape models (ASMs) have been widely used for extracting human anatomies in medical images given their capability for shape regularization of topology preservation. However, sensitivity to model initialization and local correspondence search often undermines their performances, especially around highly variable contexts in computed-tomography (CT) and magnetic resonance (MR) images. In this study, we propose an augmented ASM (AASM) by integrating the multiatlas label fusion (MALF) and level set (LS) techniques into the traditional ASM framework. Using AASM, landmark updates are optimized globally via a region-based LS evolution applied on the probability map generated from MALF. This augmentation effectively extends the searching range of correspondent landmarks while reducing sensitivity to the image contexts and improves the segmentation robustness. We propose the AASM framework as a two-dimensional segmentation technique targeting structures with one axis of regularity. We apply AASM approach to abdomen CT and spinal cord (SC) MR segmentation challenges. On 20 CT scans, the AASM segmentation of the whole abdominal wall enables the subcutaneous/visceral fat measurement, with high correlation to the measurement derived from manual segmentation. On 28 3T MR scans, AASM yields better performances than other state-of-the-art approaches in segmenting white/gray matter in SC. PMID:27610400

  17. Shape-controlled synthesis of Pd nanocrystals and their catalytic applications.

    PubMed

    Zhang, Hui; Jin, Mingshang; Xiong, Yujie; Lim, Byungkwon; Xia, Younan

    2013-08-20

    Palladium is a marvelous catalyst for a rich variety of reactions in industrial processes and commercial devices. Most Pd-catalyzed reactions exhibit structure sensitivity, meaning that the activity or selectivity depends on the arrangement of atoms on the surface. Previously, such reactions could only be studied in ultrahigh vacuum using Pd single crystals cut with a specific crystallographic plane. However, these model catalysts are far different from real catalytic systems owing to the absence of atoms at corners and edges and the extremely small specific surface areas for the model systems. Indeed, enhancing the performance of a Pd-based catalyst, in part to reduce the amount needed of this precious and rare metal for a given reaction, requires the use of Pd with the highest possible specific surface area. Recent advances in nanocrystal synthesis are offering a great opportunity to investigate and quantify the structural sensitivity of catalysts based on Pd and other metals. For a structure-sensitive reaction, the catalytic properties of Pd nanocrystals are strongly dependent on both the size and shape. The shape plays a more significant role in controlling activity and selectivity, because the shape controls not only the facets but also the proportions of surface atoms at corners, edges, and planes, which affect the outcomes of possible reactions. We expect catalysts based on Pd nanocrystals with optimized shapes to meet the increasing demands of industrial applications at reduced loadings and costs. In this Account, we discuss recent advances in the synthesis of Pd nanocrystals with controlled shapes and their resulting performance as catalysts for a large number of reactions. First, we review various synthetic strategies based on oxidative etching, surface capping, and kinetic control that have been used to direct the shapes of nanocrystals. When crystal growth is under thermodynamic control, the capping agent plays a pivotal role in determining the shape of

  18. On the shape and orientation control of an orbiting shallow spherical shell structure. [shape and orientation control of large dish type receivers/reflectors

    NASA Technical Reports Server (NTRS)

    Bainum, P. M.; Reddy, A. S. S. R.

    1981-01-01

    A proposed method for controlling the shape and orientation of very large shallow dish type receiver/reflectors to be used in communication, radiometry and in electronic orbital based mail systems involves connecting a rigid light weight dumbell with heavy tip masses to the shell at its apex by a spring loaded double gimballed joint with dampling. To completely damp the system transient motion in all of the important lower frequency modes, an active control system is required. A mathematical model is extended to include the effects of point actuators located at preselected positions on the shell surface. The formulation of the uncontrolled dynamics assumes an a priori knowledge of the frequencies of all the elastic modes to be incorporated within the system model. As an example, three rigid body modes and six elastic modes are included in the model and six actuators are assumed, none of which lies on a nodal line or circle.

  19. Template-based syntheses for shape controlled nanostructures.

    PubMed

    Pérez-Page, María; Yu, Erick; Li, Jun; Rahman, Masoud; Dryden, Daniel M; Vidu, Ruxandra; Stroeve, Pieter

    2016-08-01

    A variety of nanostructured materials are produced through template-based synthesis methods, including zero-dimensional, one-dimensional, and two-dimensional structures. These span different forms such as nanoparticles, nanowires, nanotubes, nanoflakes, and nanosheets. Many physical characteristics of these materials such as the shape and size can be finely controlled through template selection and as a result, their properties as well. Reviewed here are several examples of these nanomaterials, with emphasis specifically on the templates and synthesis routes used to produce the final nanostructures. In the first section, the templates have been discussed while in the second section, their corresponding synthesis methods have been briefly reviewed, and lastly in the third section, applications of the materials themselves are highlighted. Some examples of the templates frequently encountered are organic structure directing agents, surfactants, polymers, carbon frameworks, colloidal sol-gels, inorganic frameworks, and nanoporous membranes. Synthesis methods that adopt these templates include emulsion-based routes and template-filling approaches, such as self-assembly, electrodeposition, electroless deposition, vapor deposition, and other methods including layer-by-layer and lithography. Template-based synthesized nanomaterials are frequently encountered in select fields such as solar energy, thermoelectric materials, catalysis, biomedical applications, and magnetowetting of surfaces. PMID:27154387

  20. Geometric shape control of thin film ferroelectrics and resulting structures

    DOEpatents

    McKee, Rodney A.; Walker, Frederick J.

    2000-01-01

    A monolithic crystalline structure and a method of making involves a semiconductor substrate, such as silicon, and a ferroelectric film, such as BaTiO.sub.3, overlying the surface of the substrate wherein the atomic layers of the ferroelectric film directly overlie the surface of the substrate. By controlling the geometry of the ferroelectric thin film, either during build-up of the thin film or through appropriate treatment of the thin film adjacent the boundary thereof, the in-plane tensile strain within the ferroelectric film is relieved to the extent necessary to permit the ferroelectric film to be poled out-of-plane, thereby effecting in-plane switching of the polarization of the underlying substrate material. The method of the invention includes the steps involved in effecting a discontinuity of the mechanical restraint at the boundary of the ferroelectric film atop the semiconductor substrate by, for example, either removing material from a ferroelectric film which has already been built upon the substrate, building up a ferroelectric film upon the substrate in a mesa-shaped geometry or inducing the discontinuity at the boundary by ion beam deposition techniques.

  1. Shape-controlled continuous synthesis of metal nanostructures.

    PubMed

    Sebastian, Victor; Smith, Christopher D; Jensen, Klavs F

    2016-04-14

    A segmented flow-based microreactor is used for the continuous production of faceted nanocrystals. Flow segmentation is proposed as a versatile tool to manipulate the reduction kinetics and control the growth of faceted nanostructures; tuning the size and shape. Switching the gas from oxygen to carbon monoxide permits the adjustment in nanostructure growth from 1D (nanorods) to 2D (nanosheets). CO is a key factor in the formation of Pd nanosheets and Pt nanocubes; operating as a second phase, a reductant, and a capping agent. This combination confines the growth to specific structures. In addition, the segmented flow microfluidic reactor inherently has the ability to operate in a reproducible manner at elevated temperatures and pressures whilst confining potentially toxic reactants, such as CO, in nanoliter slugs. This continuous system successfully synthesised Pd nanorods with an aspect ratio of 6; thin palladium nanosheets with a thickness of 1.5 nm; and Pt nanocubes with a 5.6 nm edge length, all in a synthesis time as low as 150 s. PMID:26927867

  2. Sand availability control on dune shape and orientation

    NASA Astrophysics Data System (ADS)

    Gao, Xin; Narteau, Clement; Rozier, Olivier; Courrech Du Pont, Sylvain

    2015-04-01

    An increasing body of evidence indicates that sand availability does not only control dune type but also the underlying dune growth mechanism. Consequently, the same wind regime can produce different bedform orientations. Here, we use numerical simulations with different conditions of sand availability to predict dune shape and alignment in asymmetric bimodal wind regimes. In zones of abundant sand supply, linear dunes grow in height and propagate selecting the orientation for which the normal to crest components of transport reaches a maximum. In zones of limited sand supply, linear dunes grow by extension in the direction of the resultant sand flux. Considering these two independent dune growth mechanisms, we find good agreement between numerical and analytical models, and estimate the magnitude of wind velocity acceleration up the dune stoss slopes. In the extensional mode of linear dune formation, there is no abrupt change in dune trend when the divergence angle between the two winds crosses 90°. Instead, there are systematic transitions in dune type from linear to barchan for critical values of the divergence angle that depend on the transport ratio. We show how the growth rates of the two dune growth mechanisms may be used to infer the dune field morphology in zones of low sediment availability.

  3. Control of atomic transition rates via laser-light shaping

    NASA Astrophysics Data System (ADS)

    Jáuregui, R.

    2015-04-01

    A modular systematic analysis of the feasibility of modifying atomic transition rates by tailoring the electromagnetic field of an external coherent light source is presented. The formalism considers both the center of mass and internal degrees of freedom of the atom, and all properties of the field: frequency, angular spectrum, and polarization. General features of recoil effects for internal forbidden transitions are discussed. A comparative analysis of different structured light sources is explicitly worked out. It includes spherical waves, Gaussian beams, Laguerre-Gaussian beams, and propagation invariant beams with closed analytical expressions. It is shown that increments in the order of magnitude of the transition rates for Gaussian and Laguerre-Gaussian beams, with respect to those obtained in the paraxial limit, require waists of the order of the wavelength, while propagation invariant modes may considerably enhance transition rates under more favorable conditions. For transitions that can be naturally described as modifications of the atomic angular momentum, this enhancement is maximal (within propagation invariant beams) for Bessel modes, Mathieu modes can be used to entangle the internal and center-of-mass involved states, and Weber beams suppress this kind of transition unless they have a significant component of odd modes. However, if a recoil effect of the transition with an adequate symmetry is allowed, the global transition rate (center of mass and internal motion) can also be enhanced using Weber modes. The global analysis presented reinforces the idea that a better control of the transitions between internal atomic states requires both a proper control of the available states of the atomic center of mass, and shaping of the background electromagnetic field.

  4. Thermally activated retainer means utilizing shape memory alloy

    NASA Technical Reports Server (NTRS)

    Grimaldi, Margaret E. (Inventor); Hartz, Leslie S. (Inventor)

    1993-01-01

    A retainer member suitable for retaining a gap filler placed in gaps between adjacent tile members is presented. One edge of the retainer member may be attached to the gap filler and another edge may be provided with a plurality of tab members which in an intermediate position do not interfere with placement or removal of the gap filler between tile members. The retainer member may be fabricated from a shape memory alloy which when heated to a specified memory temperature will thermally activate the tab members to predetermined memory positions engaging the tile members to retain the gap filler in the gap. This invention has particular application to the thermal tiles on space vehicles such as the Space Shuttle Orbiter.

  5. Wind Tunnel Test of an RPV with Shape-Change Control Effector and Sensor Arrays

    NASA Technical Reports Server (NTRS)

    Raney, David L.; Cabell, Randolph H.; Sloan, Adam R.; Barnwell, William G.; Lion, S. Todd; Hautamaki, Bret A.

    2004-01-01

    A variety of novel control effector concepts have recently emerged that may enable new approaches to flight control. In particular, the potential exists to shift the composition of the typical aircraft control effector suite from a small number of high authority, specialized devices (rudder, aileron, elevator, flaps), toward larger numbers of smaller, less specialized, distributed device arrays. The concept envisions effector and sensor networks composed of relatively small high-bandwidth devices able to simultaneously perform a variety of control functions using feedback from disparate data sources. To investigate this concept, a remotely piloted flight vehicle has been equipped with an array of 24 trailing edge shape-change effectors and associated pressure measurements. The vehicle, called the Multifunctional Effector and Sensor Array (MESA) testbed, was recently tested in NASA Langley's 12-ft Low Speed wind tunnel to characterize its stability properties, control authorities, and distributed pressure sensitivities for use in a dynamic simulation prior to flight testing. Another objective was to implement and evaluate a scheme for actively controlling the spanwise pressure distribution using the shape-change array. This report describes the MESA testbed, design of the pressure distribution controller, and results of the wind tunnel test.

  6. Prefrontal parvalbumin interneurons shape neuronal activity to drive fear expression.

    PubMed

    Courtin, Julien; Chaudun, Fabrice; Rozeske, Robert R; Karalis, Nikolaos; Gonzalez-Campo, Cecilia; Wurtz, Hélène; Abdi, Azzedine; Baufreton, Jerome; Bienvenu, Thomas C M; Herry, Cyril

    2014-01-01

    Synchronization of spiking activity in neuronal networks is a fundamental process that enables the precise transmission of information to drive behavioural responses. In cortical areas, synchronization of principal-neuron spiking activity is an effective mechanism for information coding that is regulated by GABA (γ-aminobutyric acid)-ergic interneurons through the generation of neuronal oscillations. Although neuronal synchrony has been demonstrated to be crucial for sensory, motor and cognitive processing, it has not been investigated at the level of defined circuits involved in the control of emotional behaviour. Converging evidence indicates that fear behaviour is regulated by the dorsomedial prefrontal cortex (dmPFC). This control over fear behaviour relies on the activation of specific prefrontal projections to the basolateral complex of the amygdala (BLA), a structure that encodes associative fear memories. However, it remains to be established how the precise temporal control of fear behaviour is achieved at the level of prefrontal circuits. Here we use single-unit recordings and optogenetic manipulations in behaving mice to show that fear expression is causally related to the phasic inhibition of prefrontal parvalbumin interneurons (PVINs). Inhibition of PVIN activity disinhibits prefrontal projection neurons and synchronizes their firing by resetting local theta oscillations, leading to fear expression. Our results identify two complementary neuronal mechanisms mediated by PVINs that precisely coordinate and enhance the neuronal activity of prefrontal projection neurons to drive fear expression. PMID:24256726

  7. Plasmonic and Catalytic Properties of Shape-Controlled Metal Nanoparticles and their Assemblies

    NASA Astrophysics Data System (ADS)

    Klinkova, Anna

    This work explores the effect of the shape of metal nanoscale building blocks on the structural, optical, and plasmonic properties of their assemblies, as well as on the catalytic performance and hydrogen interactions of individual nanoparticles with specific shapes. In Chapter 3, I describe the linear self-assembly of bifunctional metal nanoparticles in the presence of monofunctional nanoscale chain stoppers. Chain stoppers with controlled reactivity were synthesized allowing control over the morphology of the self-assembled structures. Analysis of the degree of polymerization of linear nanostructures provided information about self-assembly kinetics, side reactions, and the distribution of species in the reaction. This work facilitated testing of theoretical models developed for molecular polymerization and fabrication of linear nanoparticle assemblies with controllable properties. In Chapter 4, I developed linear solution-based self-assembly of cubic metal nanoparticles, examined the morphology of the nanocube chains and their optical characteristics. In comparison with chains of nanospheres with similar dimensions, compositions, and surface chemistry, predominant face-to-face assembly of nanocubes leads to a larger volume of plasmonic hot spots, uniform electromagnetic field enhancement in the gaps between nanocubes, and a new coupling mode for nanocube chains, associated with Fabry-Perot structure. In Chapter 5, I investigated plasmon-mediated enhancement of the catalysis by palladium-based nanoparticles with different shapes and composition, bearing surface plasmon resonance in visible range. The photocatalytic activity of palladium-based nanoparticles depended more on their shape than internal structure. These findings pave the way for the design of palladium nanocatalysts with enhanced performance acting under visible light illumination. In Chapter 6, I developed a facile scaled-up synthesis of monodisperse palladium nanoparticles with various shapes

  8. Shape control of solar collectors using torsional shape memory alloy actuators

    SciTech Connect

    Lobitz, D.W.; Rice, T.M.; Grossman, J.W.

    1996-03-01

    Solar collectors that are focused on a central receiver are designed with a mechanism for defocusing the collector or disabling it by turning it out of the path of the sun`s rays. This is required to avoid damaging the receiver during periods of inoperability. In either of these two cases a fail-safe operation is very desirable where during power outages the collector passively goes to its defocused or deactivated state. This paper will be principally concerned with focusing and defocusing the collector in a fail-safe manner using shape memory alloy actuators. Shape memory alloys are well suited to this application in that once calibrated the actuators can be operated in an on/off mode using a small amount of electric power. Also, in contrast to other smart materials that were investigated for this application, shape memory alloys are capable of providing enough stroke at the appropriate force levels to focus the collector. In order to accommodate the large, nonlinear deformations required in the solar collector plate to obtain desired focal lengths, a torsional shape memory alloy actuator was developed that produces a stroke of 0.5 inches. Design and analysis details presented, along with comparisons to test data taken from an actual prototype, demonstrate that the collector can be repeatedly focused and defocused within accuracies required by typical solar energy systems.

  9. Shape direction and size control of novel nanostructures: Towards a fundamental understanding of growth

    NASA Astrophysics Data System (ADS)

    Leong, G. Jeremy

    Shape control of metal nanoparticles has had a great deal of attention in the past decade due to the enhanced catalytic properties based on structure and surface faceting. Numerous methods have been developed to synthesize various nanostructures that make more efficient use of the active surfaces by tuning porosity, shapes, sizes, and facets by adding foreign ions which promote or restrict growth on specific sites; however, a fundamental mechanistic understanding of how and why ions and other synthetic parameters direct growth resulting in specific shapes and porosity have only been hypothesized. Herein, we first demonstrate the importance of shaped metal nanoparticles in terms of active sites in Au icosahedra, which motivates a full literature review of shaped Pt nanostructures. The conclusions regarding need for understanding towards growth systems motivates the study of both direct (wet chemical reduction) and indirect (galvanic displacement) synthesis techniques, which is then followed by the probing of nanoparticle growth kinetics as well as mesopore expansion in silica. Synergistic capabilities of computationally-guided synthetic routes as proposed by the Materials Genome Initiative (MGI) are demonstrated by testing hypotheses, then utilizing experimental insight from platinum systems to predict the growth of faceted palladium nanocrystals. Mechanistic insight on growth kinetics can be elucidated by studying the role of directing ions during the growth process, thereby obtaining a general fundamental understanding of directed nanoparticle formation. The pore expansion mechanisms in mesoporous materials via hydrothermal treatments allows us to understand pore sizes as a function of solution etching, thus giving rise to size-dependent separation and sequestration applications. Understanding structure and activity relationships of our resulting products will assist in the synthesis of next generation materials with enhanced properties, thereby advancing the

  10. Shaping tissues by balancing active forces and geometric constraints

    NASA Astrophysics Data System (ADS)

    Foolen, Jasper; Yamashita, Tadahiro; Kollmannsberger, Philip

    2016-02-01

    The self-organization of cells into complex tissues during growth and regeneration is a combination of physical-mechanical events and biochemical signal processing. Cells actively generate forces at all stages in this process, and according to the laws of mechanics, these forces result in stress fields defined by the geometric boundary conditions of the cell and tissue. The unique ability of cells to translate such force patterns into biochemical information and vice versa sets biological tissues apart from any other material. In this topical review, we summarize the current knowledge and open questions of how forces and geometry act together on scales from the single cell to tissues and organisms, and how their interaction determines biological shape and structure. Starting with a planar surface as the simplest type of geometric constraint, we review literature on how forces during cell spreading and adhesion together with geometric constraints impact cell shape, stress patterns, and the resulting biological response. We then move on to include cell-cell interactions and the role of forces in monolayers and in collective cell migration, and introduce curvature at the transition from flat cell sheets to three-dimensional (3D) tissues. Fibrous 3D environments, as cells experience them in the body, introduce new mechanical boundary conditions and change cell behaviour compared to flat surfaces. Starting from early work on force transmission and collagen remodelling, we discuss recent discoveries on the interaction with geometric constraints and the resulting structure formation and network organization in 3D. Recent literature on two physiological scenarios—embryonic development and bone—is reviewed to demonstrate the role of the force-geometry balance in living organisms. Furthermore, the role of mechanics in pathological scenarios such as cancer is discussed. We conclude by highlighting common physical principles guiding cell mechanics, tissue patterning and

  11. Self-activated mesh device using shape memory alloy for periosteal expansion osteogenesis.

    PubMed

    Yamauchi, Kensuke; Takahashi, Tetsu; Tanaka, Kenko; Nogami, Shinnosuke; Kaneuji, Takeshi; Kanetaka, Hiroyasu; Miyazaki, Toshiki; Lethaus, Bernd; Kessler, Peter

    2013-07-01

    The present study evaluated the use of this self-activated shape memory alloy (SMA) device, with a focus on its effects in the region under the periosteum. Twelve Japanese white rabbits were used in this study. The device was inserted under the periosteum at the forehead. In the experimental group, the device was pushed, bent, and attached to the bone surface and fixed with a titanium screw. In control group, the device was only inserted under the periosteum. After 14 days, the screw was removed and the mesh was activated in the experimental group. Rabbits were sacrificed 5 and 8 weeks after the operation and newly formed bone was histologically and radiographically evaluated. The quantitative data by the area and the occupation of newly formed bone indicated that the experimental group had a higher volume of new bone than the control group at each consolidation period. Histologically, some newly formed bone was observed and most of the subperiosteal space underneath the device was filled with fibrous tissue, and a thin layer of immature bone was observed in the control group. In the experimental group, multiple dome-shaped bones, outlined by thin and scattered trabeculae, were clearly observed under the SMA mesh device. The use of self-activated devices for the periosteal expansion technique may make it possible to avoid donor site morbidity, trans-skin activation rods, any bone-cutting procedure, and the following intermittent activation procedure. PMID:23359561

  12. Coherent Control of Multiphoton Transitions in the Gas and Condensed Phases with Shaped Ultrashort Pulses

    SciTech Connect

    Marcos Dantus

    2008-09-23

    Controlling laser-molecule interactions has become an integral part of developing devices and applications in spectroscopy, microscopy, optical switching, micromachining and photochemistry. Coherent control of multiphoton transitions could bring a significant improvement of these methods. In microscopy, multi-photon transitions are used to activate different contrast agents and suppress background fluorescence; coherent control could generate selective probe excitation. In photochemistry, different dissociative states are accessed through two, three, or more photon transitions; coherent control could be used to select the reaction pathway and therefore the yield-specific products. For micromachining and processing a wide variety of materials, femtosecond lasers are now used routinely. Understanding the interactions between the intense femtosecond pulse and the material could lead to technologically important advances. Pulse shaping could then be used to optimize the desired outcome. The scope of our research program is to develop robust and efficient strategies to control nonlinear laser-matter interactions using ultrashort shaped pulses in gas and condensed phases. Our systematic research has led to significant developments in a number of areas relevant to the AMO Physics group at DOE, among them: generation of ultrashort phase shaped pulses, coherent control and manipulation of quantum mechanical states in gas and condensed phases, behavior of isolated molecules under intense laser fields, behavior of condensed phase matter under intense laser field and implications on micromachining with ultrashort pulses, coherent control of nanoparticles their surface plasmon waves and their nonlinear optical behavior, and observation of coherent Coulomb explosion processes at 10^16 W/cm^2. In all, the research has resulted in 36 publications (five journal covers) and nine invention disclosures, five of which have continued on to patenting

  13. Selection of actuator locations for static shape control of large space structures by heuristic integer programing

    NASA Technical Reports Server (NTRS)

    Haftka, R. T.; Adelman, H. M.

    1984-01-01

    Orbiting spacecraft such as large space antennas have to maintain a highly accurate space to operate satisfactorily. Such structures require active and passive controls to mantain an accurate shape under a variety of disturbances. Methods for the optimum placement of control actuators for correcting static deformations are described. In particular, attention is focused on the case were control locations have to be selected from a large set of available sites, so that integer programing methods are called for. The effectiveness of three heuristic techniques for obtaining a near-optimal site selection is compared. In addition, efficient reanalysis techniques for the rapid assessment of control effectiveness are presented. Two examples are used to demonstrate the methods: a simple beam structure and a 55m space-truss-parabolic antenna.

  14. Bacterial lifestyle shapes the regulation of stringent response activation

    PubMed Central

    Boutte, Cara C.; Crosson, Sean

    2014-01-01

    Bacteria inhabit enormously diverse niches and have a correspondingly large array of regulatory mechanisms to adapt to often inhospitable and variable environments. The stringent response allows bacteria to quickly reprogram transcription in response to changes in nutrient availability. Although the proteins controlling this response are conserved in almost all bacterial species, recent work has illuminated considerable diversity in the starvation cues and regulatory mechanisms that activate stringent signaling proteins in bacteria from different environments. In this review we describe the signals and genetic circuitries that control the stringent signaling systems of a copiotroph, a bacteriovore, an oligotroph and a mammalian pathogen – Escherichia coli, Myxococcus xanthus, Caulobacter crescentus and Mycobacterium tuberculosis, respectively – and discuss how control of the stringent response in these species is adapted to their particular lifestyles. PMID:23419217

  15. folded gastrulation, cell shape change and the control of myosin localization.

    PubMed

    Dawes-Hoang, Rachel E; Parmar, Kush M; Christiansen, Audrey E; Phelps, Chris B; Brand, Andrea H; Wieschaus, Eric F

    2005-09-01

    The global cell movements that shape an embryo are driven by intricate changes to the cytoarchitecture of individual cells. In a developing embryo, these changes are controlled by patterning genes that confer cell identity. However, little is known about how patterning genes influence cytoarchitecture to drive changes in cell shape. In this paper, we analyze the function of the folded gastrulation gene (fog), a known target of the patterning gene twist. Our analysis of fog function therefore illuminates a molecular pathway spanning all the way from patterning gene to physical change in cell shape. We show that secretion of Fog protein is apically polarized, making this the earliest polarized component of a pathway that ultimately drives myosin to the apical side of the cell. We demonstrate that fog is both necessary and sufficient to drive apical myosin localization through a mechanism involving activation of myosin contractility with actin. We determine that this contractility driven form of localization involves RhoGEF2 and the downstream effector Rho kinase. This distinguishes apical myosin localization from basal myosin localization, which we find not to require actinomyosin contractility or FOG/RhoGEF2/Rho-kinase signaling. Furthermore, we demonstrate that once localized apically, myosin continues to contract. The force generated by continued myosin contraction is translated into a flattening and constriction of the cell surface through a tethering of the actinomyosin cytoskeleton to the apical adherens junctions. Our analysis of fog function therefore provides a direct link from patterning to cell shape change. PMID:16123312

  16. New developments in actuator materials as reflected in magnetically controlled shape memory alloys and high-strength shape memory steels

    NASA Astrophysics Data System (ADS)

    Ullakko, Kari; Yakovenko, Peter G.; Gavriljuk, Valentin G.

    1996-05-01

    Shape memory alloys (SMA) are applied as actuator materials in smart structures and in fastening and pre-stressing devices. Shape memory alloys can be divided into three groups: one-way alloys, two-way alloys and magnetically controlled SMAs. The magnetically controlled SMAs recently suggested by one of the present authors are potential actuator materials for smart structures because they may provide rapid strokes with large amplitudes under precise control. The most extensively applied conventional SMAs are Ni-Ti and Cu- based alloys. Iron-based shape memory alloys, especially Fe-Mn-Si steels, are becoming more and more important in engineering applications due to their low price. The properties of Fe- Mn-Si steels have been improved by alloying, for example, with Cr, Ni and Co. Nitrogen alloying was shown to significantly improve shape memory, mechanical and corrosion properties of Fe-Mn-Si-based steels. Tensile strengths over 1500 MPa, recovery stresses of 300 MPa and recoverable strains of 4% have been attained. In fasteners made from these steels, stresses of 700 MPa were reached. The beneficial effect of nitrogen alloying on shape memory and mechanical properties is based on the decrease of stacking fault energy and increase of the strength of austenite caused by nitrogen atoms. Nitrogen alloyed Fe-Mn-Si- based steels are expected to be employed as actuator materials in pre-stressing and fastening applications in many fields of engineering. Nitrogen alloyed shape memory steels possess good manufacturing properties and weldability, and they are economical to process using conventional industrial methods.

  17. Passive control of a sphere by complex-shaped appendages

    NASA Astrophysics Data System (ADS)

    Bagheri, Shervin; Lacis, Ugis; Olivieri, Stefano; Mazzino, Andrea

    2015-11-01

    Appendages of various shapes and sizes (e.g. plumes, barbs, tails, feathers, hairs, fins) play an important role in dispersion and locomotion. In our previous work (Lacis, U. et al. Passive appendages generate drift through symmetry breaking. Nat. Commun. 5:5310, doi: 10.1038/ncomms6310, 2014), we showed that a free-falling cylinder with a splitter plate turns and drifts due to a symmetry-breaking instability (called inverted-pendulum instability or IPL). In other words, in a separated flow, the straight position of a short splitter plate is unstable and as a consequence a side force and a torque are induced on the cylinder. In this work, we seek the three-dimensional (3D) appendage shape (on a sphere at Re =200) that induces the largest drift of the sphere. We find that highly non-trivial shapes of appendages on a sphere increase the side force significantly compared to trivial shapes (such as an elliptic sheet). We also find that appendages may be designed to generate drift in either direction, that is, a free-falling sphere can drift either in the direction in which appendage is tilted or in the opposite direction depending on the particular geometry of the appendage. We discuss the physical mechanisms behind these optimal appendage shapes in the context of the IPL instability.

  18. Active control of convection

    SciTech Connect

    Bau, H.H.

    1995-12-31

    Using stability theory, numerical simulations, and in some instances experiments, it is demonstrated that the critical Rayleigh number for the bifurcation (1) from the no-motion (conduction) state to the motion state and (2) from time-independent convection to time-dependent, oscillatory convection in the thermal convection loop and Rayleigh-Benard problems can be significantly increased or decreased. This is accomplished through the use of a feedback controller effectuating small perturbations in the boundary data. The controller consists of sensors which detect deviations in the fluid`s temperature from the motionless, conductive values and then direct actuators to respond to these deviations in such a way as to suppress the naturally occurring flow instabilities. Actuators which modify the boundary`s temperature/heat flux are considered. The feedback controller can also be used to control flow patterns and generate complex dynamic behavior at relatively low Rayleigh numbers.

  19. Statistical analysis of static shape control in space structures

    NASA Technical Reports Server (NTRS)

    Burdisso, Ricardo A.; Haftka, Raphael T.

    1990-01-01

    The article addresses the problem of efficient analysis of the statistics of initial and corrected shape distortions in space structures. Two approaches for improving efficiency are considered. One is an adjoint technique for calculating distortion shapes: the second is a modal expansion of distortion shapes in terms of pseudo-vibration modes. The two techniques are applied to the problem of optimizing actuator locations on a 55 m radiometer antenna. The adjoint analysis technique is used with a discrete-variable optimization method. The modal approximation technique is coupled with a standard conjugate-gradient continuous optimization method. The agreement between the two sets of results is good, validating both the approximate analysis and optimality of the results.

  20. Interface Shape Control Using Localized Heating during Bridgman Growth

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Mazuruk, K.; Aggarwal, M. D.; Croll, A.

    2008-01-01

    Numerical calculations were performed to assess the effect of localized radial heating on the melt-crystal interface shape during vertical Bridgman growth. System parameters examined include the ampoule, melt and crystal thermal conductivities, the magnitude and width of localized heating, and the latent heat of crystallization. Concave interface shapes, typical of semiconductor systems, could be flattened or made convex with localized heating. Although localized heating caused shallower thermal gradients ahead of the interface, the magnitude of the localized heating required for convexity was less than that which resulted in a thermal inversion ahead of the interface. A convex interface shape was most readily achieved with ampoules of lower thermal conductivity. Increasing melt convection tended to flatten the interface, but the amount of radial heating required to achieve a convex interface was essentially independent of the convection intensity.

  1. Controlled Aeroelastic Response and Airfoil Shaping Using Adaptive Materials and Integrated Systems

    NASA Technical Reports Server (NTRS)

    Pinkerton, Jennifer L.; McGowan, Anna-Maria R.; Moses, Robert W.; Scott, Robert C.; Heeg, Jennifer

    1996-01-01

    This paper presents an overview of several activities of the Aeroelasticity Branch at the NASA Langley Research Center in the area of applying adaptive materials and integrated systems for controlling both aircraft aeroelastic response and airfoil shape. The experimental results of four programs are discussed: the Piezoelectric Aeroelastic Response Tailoring Investigation (PARTI); the Adaptive Neural Control of Aeroelastic Response (ANCAR) program; the Actively Controlled Response of Buffet Affected Tails (ACROBAT) program; and the Airfoil THUNDER Testing to Ascertain Characteristics (ATTACH) project. The PARTI program demonstrated active flutter control and significant rcductions in aeroelastic response at dynamic pressures below flutter using piezoelectric actuators. The ANCAR program seeks to demonstrate the effectiveness of using neural networks to schedule flutter suppression control laws. Th,e ACROBAT program studied the effectiveness of a number of candidate actuators, including a rudder and piezoelectric actuators, to alleviate vertical tail buffeting. In the ATTACH project, the feasibility of using Thin-Layer Composite-Uimorph Piezoelectric Driver and Sensor (THUNDER) wafers to control airfoil aerodynamic characteristics was investigated. Plans for future applications are also discussed.

  2. Controlled aeroelastic response and airfoil shaping using adaptive materials and integrated systems

    NASA Astrophysics Data System (ADS)

    Pinkerton, Jennifer L.; McGowan, Anna-Maria R.; Moses, Robert W.; Scott, Robert C.; Heeg, Jennifer

    1996-05-01

    This paper presents an overview of several activities of the Aeroelasticity Branch at the NASA Langley Research Center in the area of applying adaptive materials and integrated systems for controlling both aircraft aeroelastic response and airfoil shape. The experimental results of four programs are discussed: the Piezoelectric Aeroelastic Response Tailoring Investigation (PARTI); the adaptive neural control of aeroelastic response (ANCAR) program; the actively controlled response of buffet affected tails (ACROBAT) program; and the Airfoil THUNDER Testing to ascertain charcteristics (ATTACH) project. The PARTI program demonstrated active flutter control and significant reductions in aeroelastic response at dynamic pressures below flutter using piezoelectric actuators. The ANCAR program seeks to demonstrate the effectiveness of using neural networks to schedule flutter suppression control laws. The ACROBAT program studied the effectiveness of a number of candidate actuators, including a rudder and piezoelectric actuators, to alleviate vertical tail buffeting. In the ATTACH project, the feasibility of using thin-layer composite-unimorph piezoelectric driver and sensor (THUNDER) wafers to control airfoil aerodynamic characteristics was investigated. Plans for future applications are also discussed.

  3. SHADE: A Shape-Memory-Activated Device Promoting Ankle Dorsiflexion

    NASA Astrophysics Data System (ADS)

    Pittaccio, S.; Viscuso, S.; Rossini, M.; Magoni, L.; Pirovano, S.; Villa, E.; Besseghini, S.; Molteni, F.

    2009-08-01

    Acute post-stroke rehabilitation protocols include passive mobilization as a means to prevent contractures. A device (SHADE) that provides repetitive passive motion to a flaccid ankle by using shape memory alloy actuators could be of great help in providing this treatment. A suitable actuator was designed as a cartridge of approximately 150 × 20 × 15 mm, containing 2.5 m of 0.25 mm diameter NiTi wire. This actuator was activated by Joule’s effect employing a 7 s current input at 0.7 A, which provided 10 N through 76 mm displacement. Cooling and reset by natural convection took 30 s. A prototype of SHADE was assembled with two thermoplastic shells hinged together at the ankle and strapped on the shin and foot. Two actuators were fixed on the upper shell while an inextensible thread connected each NiTi wire to the foot shell. The passive ankle motion (passive range of motion, PROM) generated by SHADE was evaluated optoelectronically on three flaccid patients (58 ± 5 years old); acceptability was assessed by a questionnaire presented to further three flaccid patients (44 ± 11.5 years old) who used SHADE for 5 days, 30 min a day. SHADE was well accepted by all patients, produced good PROM, and caused no pain. The results prove that suitable limb mobilization can be produced by SMA actuators.

  4. Active sensing via movement shapes spatiotemporal patterns of sensory feedback.

    PubMed

    Stamper, Sarah A; Roth, Eatai; Cowan, Noah J; Fortune, Eric S

    2012-05-01

    Previous work has shown that animals alter their locomotor behavior to increase sensing volumes. However, an animal's own movement also determines the spatial and temporal dynamics of sensory feedback. Because each sensory modality has unique spatiotemporal properties, movement has differential and potentially independent effects on each sensory system. Here we show that weakly electric fish dramatically adjust their locomotor behavior in relation to changes of modality-specific information in a task in which increasing sensory volume is irrelevant. We varied sensory information during a refuge-tracking task by changing illumination (vision) and conductivity (electroreception). The gain between refuge movement stimuli and fish tracking responses was functionally identical across all sensory conditions. However, there was a significant increase in the tracking error in the dark (no visual cues). This was a result of spontaneous whole-body oscillations (0.1 to 1 Hz) produced by the fish. These movements were costly: in the dark, fish swam over three times further when tracking and produced more net positive mechanical work. The magnitudes of these oscillations increased as electrosensory salience was degraded via increases in conductivity. In addition, tail bending (1.5 to 2.35 Hz), which has been reported to enhance electrosensory perception, occurred only during trials in the dark. These data show that both categories of movements - whole-body oscillations and tail bends - actively shape the spatiotemporal dynamics of electrosensory feedback. PMID:22496294

  5. Roots shaping their microbiome: global hotspots for microbial activity.

    PubMed

    Reinhold-Hurek, Barbara; Bünger, Wiebke; Burbano, Claudia Sofía; Sabale, Mugdha; Hurek, Thomas

    2015-01-01

    Land plants interact with microbes primarily at roots. Despite the importance of root microbial communities for health and nutrient uptake, the current understanding of the complex plant-microbe interactions in the rhizosphere is still in its infancy. Roots provide different microhabitats at the soil-root interface: rhizosphere soil, rhizoplane, and endorhizosphere. We discuss technical aspects of their differentiation that are relevant for the functional analysis of their different microbiomes, and we assess PCR (polymerase chain reaction)-based methods to analyze plant-associated bacterial communities. Development of novel primers will allow a less biased and more quantitative view of these global hotspots of microbial activity. Based on comparison of microbiome data for the different root-soil compartments and on knowledge of bacterial functions, a three-step enrichment model for shifts in community structure from bulk soil toward roots is presented. To unravel how plants shape their microbiome, a major research field is likely to be the coupling of reductionist and molecular ecological approaches, particularly for specific plant genotypes and mutants, to clarify causal relationships in complex root communities. PMID:26243728

  6. Stathmin Activity Influences Sarcoma Cell Shape, Motility, and Metastatic Potential

    PubMed Central

    Belletti, Barbara; Nicoloso, Milena S.; Schiappacassi, Monica; Berton, Stefania; Lovat, Francesca; Wolf, Katarina; Canzonieri, Vincenzo; D'Andrea, Sara; Zucchetto, Antonella; Friedl, Peter; Colombatti, Alfonso

    2008-01-01

    The balanced activity of microtubule-stabilizing and -destabilizing proteins determines the extent of microtubule dynamics, which is implicated in many cellular processes, including adhesion, migration, and morphology. Among the destabilizing proteins, stathmin is overexpressed in different human malignancies and has been recently linked to the regulation of cell motility. The observation that stathmin was overexpressed in human recurrent and metastatic sarcomas prompted us to investigate stathmin contribution to tumor local invasiveness and distant dissemination. We found that stathmin stimulated cell motility in and through the extracellular matrix (ECM) in vitro and increased the metastatic potential of sarcoma cells in vivo. On contact with the ECM, stathmin was negatively regulated by phosphorylation. Accordingly, a less phosphorylable stathmin point mutant impaired ECM-induced microtubule stabilization and conferred a higher invasive potential, inducing a rounded cell shape coupled with amoeboid-like motility in three-dimensional matrices. Our results indicate that stathmin plays a significant role in tumor metastasis formation, a finding that could lead to exploitation of stathmin as a target of new antimetastatic drugs. PMID:18305103

  7. Design and simulation of the surface shape control system for membrane mirror

    NASA Astrophysics Data System (ADS)

    Zhang, Gengsheng; Tang, Minxue

    2009-11-01

    The surface shape control is one of the key technologies for the manufacture of membrane mirror. This paper presents a design of membrane mirror's surface shape control system on the basis of fuzzy logic control. The system contains such function modules as surface shape design, surface shape control, surface shape analysis, and etc. The system functions are realized by using hybrid programming technology of Visual C# and MATLAB. The finite element method is adopted to simulate the surface shape control of membrane mirror. The finite element analysis model is established through ANSYS Parametric Design Language (APDL). ANSYS software kernel is called by the system in background running mode when doing the simulation. The controller is designed by means of controlling the sag of the mirror's central crosssection. The surface shape of the membrane mirror and its optical aberration are obtained by applying Zernike polynomial fitting. The analysis of surface shape control and the simulation of disturbance response are performed for a membrane mirror with 300mm aperture and F/2.7. The result of the simulation shows that by using the designed control system, the RMS wavefront error of the mirror can reach to 142λ (λ=632.8nm), which is consistent to the surface accuracy of the membrane mirror obtained by the large deformation theory of membrane under the same condition.

  8. Synthesis of heterogeneous catalysts with well shaped platinum particles to control reaction selectivity

    PubMed Central

    Lee, Ilkeun; Morales, Ricardo; Albiter, Manuel A.; Zaera, Francisco

    2008-01-01

    Colloidal and sol-gel procedures have been used to prepare heterogeneous catalysts consisting of platinum metal particles with narrow size distributions and well defined shapes dispersed on high-surface-area silica supports. The overall procedure was developed in three stages. First, tetrahedral and cubic colloidal metal particles were prepared in solution by using a procedure derived from that reported by El-Sayed and coworkers [Ahmadi TS, Wang ZL, Green TC, Henglein A, El-Sayed MA (1996) Science 272:1924–1926]. This method allowed size and shape to be controlled independently. Next, the colloidal particles were dispersed onto high-surface-area solids. Three approaches were attempted: (i) in situ reduction of the colloidal mixture in the presence of the support, (ii) in situ sol-gel synthesis of the support in the presence of the colloidal particles, and (iii) direct impregnation of the particles onto the support. Finally, the resulting catalysts were activated and tested for the promotion of carbon–carbon double-bond cis-trans isomerization reactions in olefins. Our results indicate that the selectivity of the reaction may be controlled by using supported catalysts with appropriate metal particle shapes. PMID:18832170

  9. Limits on static shape control for space structures

    NASA Technical Reports Server (NTRS)

    Haftka, Raphael T.

    1991-01-01

    This paper deals with correction of shape distortion due to zero-mean normally distributed errors in structural sizes. The concept of ideal actuators - actuators that can produce any desired displacement field - is introduced. Using this concept, a bound on the possible improvement in the expected value of the root-mean-square shape error is obtained. The shape correction associated with the ideal actuators is also characterized. An actuator effectiveness index is developed by comparing the displacement field generated by the actuator to the ideal. The results are specialized to a simple form for truss structures composed of nominally identical members. The bound and effectiveness index are tested on a 55-m radiometer antenna truss structure. It is found that previously obtained results for optimum actuators had a performance close to the bound obtained here. Also, it is found that large numbers of actuators are needed for large reductions in shape errors. Furthermore, the actuators associated with the optimum design are shown to have high effectiveness indices. Since only a small fraction of truss elements tend to have high effectiveness indices, the use of the effectiveness index can greatly reduce the number of truss members that need to be considered actuator sites.

  10. Active weld control

    NASA Technical Reports Server (NTRS)

    Powell, Bradley W.; Burroughs, Ivan A.

    1994-01-01

    Through the two phases of this contract, sensors for welding applications and parameter extraction algorithms have been developed. These sensors form the foundation of a weld control system which can provide action weld control through the monitoring of the weld pool and keyhole in a VPPA welding process. Systems of this type offer the potential of quality enhancement and cost reduction (minimization of rework on faulty welds) for high-integrity welding applications. Sensors for preweld and postweld inspection, weld pool monitoring, keyhole/weld wire entry monitoring, and seam tracking were developed. Algorithms for signal extraction were also developed and analyzed to determine their application to an adaptive weld control system. The following sections discuss findings for each of the three sensors developed under this contract: (1) weld profiling sensor; (2) weld pool sensor; and (3) stereo seam tracker/keyhole imaging sensor. Hardened versions of these sensors were designed and built under this contract. A control system, described later, was developed on a multiprocessing/multitasking operating system for maximum power and flexibility. Documentation for sensor mechanical and electrical design is also included as appendices in this report.

  11. Pulse-Shape Control in an All Fiber Multi-Wavelength Doppler Lidar

    NASA Astrophysics Data System (ADS)

    Töws, Albert; Lehmann, Jan; Kurtz, Alfred

    2016-06-01

    Pulse distortion during amplification in fiber amplifiers due to gain saturation and cross talk in a multi-wavelength Doppler lidar are discussed. We present a feedback control technique which is capable of adjusting any predefined pulse shape and show some examples of feedback controlled pulse shapes.

  12. Sensorless control for a sophisticated artificial myocardial contraction by using shape memory alloy fibre.

    PubMed

    Shiraishi, Y; Yambe, T; Saijo, Y; Sato, F; Tanaka, A; Yoshizawa, M; Sugai, T K; Sakata, R; Luo, Y; Park, Y; Uematsu, M; Umezu, M; Fujimoto, T; Masumoto, N; Liu, H; Baba, A; Konno, S; Nitta, S; Imachi, K; Tabayashi, K; Sasada, H; Homma, D

    2008-01-01

    The authors have been developing an artificial myocardium, which is capable of supporting natural contractile function from the outside of the ventricle. The system was originally designed by using sophisticated covalent shape memory alloy fibres, and the surface did not implicate blood compatibility. The purpose of our study on the development of artificial myocardium was to achieve the assistance of myocardial functional reproduction by the integrative small mechanical elements without sensors, so that the effective circulatory support could be accomplished. In this study, the authors fabricated the prototype artificial myocardial assist unit composed of the sophisticated shape memory alloy fibre (Biometal), the diameter of which was 100 microns, and examined the mechanical response by using pulse width modulation (PWM) control method in each unit. Prior to the evaluation of dynamic characteristics, the relationship between strain and electric resistance and also the initial response of each unit were obtained. The component for the PWM control was designed in order to regulate the myocardial contractile function, which consisted of an originally-designed RISC microcomputer with the input of displacement, and its output signal was controlled by pulse wave modulation method. As a result, the optimal PWM parameters were confirmed and the fibrous displacement was successfully regulated under the different heat transfer conditions simulating internal body temperature as well as bias tensile loading. Then it was indicated that this control theory might be applied for more sophisticated ventricular passive or active restraint by the artificial myocardium on physiological demand. PMID:19162754

  13. Active Control of Engine Dynamics

    NASA Astrophysics Data System (ADS)

    2002-11-01

    Active control can alleviate design constraints and improve the response to operational requirements in gas turbines. The Course presented the state-of-the-art including experimental, theoretical knowledge and practical information. Topics treated: stability characteristics; active control approaches; robustness and fundamental limits; combustion systems processes; combustor dynamics; compression system dynamics models; diagnostics and control of compression instabilities; sensor and actuator architectures; R&D needs of future prospects. The course has shown that for combustion systems, as well as in actuator and sensor technologies the active control approach is a viable option even at full scale with potential for aero engines and air breathing missiles.

  14. Closed-loop control of a shape memory alloy actuation system for variable area fan nozzle

    NASA Astrophysics Data System (ADS)

    Barooah, Prabir; Rey, Nancy

    2002-07-01

    Shape Memory Alloys have been used in a wide variety of actuation applications. A bundled shape memory alloy cable actuator, capable of providing large force and displacement has been developed by United Technologies Corporation (patents pending) for actuating a Variable Area fan Nozzle (VAN). The ability to control fan nozzle exit area is an enabling technology for the next generation turbofan engines. Performance benefits for VAN engines are estimated to be up to 9% in Thrust Specific Fuel Consumption (TSFC) compared to traditional fixed geometry designs. The advantage of SMA actuated VAN design is light weight and low complexity compared to conventionally actuated designs. To achieve the maximum efficiency from a VAN engine, the nozzle exit area has to be continuously varied for a certain period of time during climb, since the optimum nozzle exit area is a function of several flight variables (flight Mach number, altitude etc). Hence, the actuator had to be controlled to provide the time varying desired nozzle area. A new control algorithm was developed for this purpose, which produced the desired flap area by metering the resistive heating of the SMA actuator. Since no active cooling was used, reducing overshoot was a significant challenge of the controller. A full scale, 2 flap model of the VAN system was built, which was capable of simulating a 20% nozzle area variation, and tested under full scale aerodynamic load in NASA Langley Jet Exit Test facility. The controller met all the requirements of the actuation system and was able to drive the flap position to the desired position with less than 2% overshoot in step input tests. The controller is based on a adaptive algorithm formulation with logical switches that reduces its overshoot error. Although the effectiveness of the controller was demonstrated in full scale model tests, no theoretical results as to its stability and robustness has been derived. Stability of the controller will have to be investigated

  15. Ultrasound common carotid artery segmentation based on active shape model.

    PubMed

    Yang, Xin; Jin, Jiaoying; Xu, Mengling; Wu, Huihui; He, Wanji; Yuchi, Ming; Ding, Mingyue

    2013-01-01

    Carotid atherosclerosis is a major reason of stroke, a leading cause of death and disability. In this paper, a segmentation method based on Active Shape Model (ASM) is developed and evaluated to outline common carotid artery (CCA) for carotid atherosclerosis computer-aided evaluation and diagnosis. The proposed method is used to segment both media-adventitia-boundary (MAB) and lumen-intima-boundary (LIB) on transverse views slices from three-dimensional ultrasound (3D US) images. The data set consists of sixty-eight, 17 × 2 × 2, 3D US volume data acquired from the left and right carotid arteries of seventeen patients (eight treated with 80 mg atorvastatin and nine with placebo), who had carotid stenosis of 60% or more, at baseline and after three months of treatment. Manually outlined boundaries by expert are adopted as the ground truth for evaluation. For the MAB and LIB segmentations, respectively, the algorithm yielded Dice Similarity Coefficient (DSC) of 94.4% ± 3.2% and 92.8% ± 3.3%, mean absolute distances (MAD) of 0.26 ± 0.18 mm and 0.33 ± 0.21 mm, and maximum absolute distances (MAXD) of 0.75 ± 0.46 mm and 0.84 ± 0.39 mm. It took 4.3 ± 0.5 mins to segment single 3D US images, while it took 11.7 ± 1.2 mins for manual segmentation. The method would promote the translation of carotid 3D US to clinical care for the monitoring of the atherosclerotic disease progression and regression. PMID:23533535

  16. Ultrasound Common Carotid Artery Segmentation Based on Active Shape Model

    PubMed Central

    Yang, Xin; Jin, Jiaoying; Xu, Mengling; Wu, Huihui; He, Wanji; Yuchi, Ming; Ding, Mingyue

    2013-01-01

    Carotid atherosclerosis is a major reason of stroke, a leading cause of death and disability. In this paper, a segmentation method based on Active Shape Model (ASM) is developed and evaluated to outline common carotid artery (CCA) for carotid atherosclerosis computer-aided evaluation and diagnosis. The proposed method is used to segment both media-adventitia-boundary (MAB) and lumen-intima-boundary (LIB) on transverse views slices from three-dimensional ultrasound (3D US) images. The data set consists of sixty-eight, 17 × 2 × 2, 3D US volume data acquired from the left and right carotid arteries of seventeen patients (eight treated with 80 mg atorvastatin and nine with placebo), who had carotid stenosis of 60% or more, at baseline and after three months of treatment. Manually outlined boundaries by expert are adopted as the ground truth for evaluation. For the MAB and LIB segmentations, respectively, the algorithm yielded Dice Similarity Coefficient (DSC) of 94.4% ± 3.2% and 92.8% ± 3.3%, mean absolute distances (MAD) of 0.26 ± 0.18 mm and 0.33 ± 0.21 mm, and maximum absolute distances (MAXD) of 0.75 ± 0.46 mm and 0.84 ± 0.39 mm. It took 4.3 ± 0.5 mins to segment single 3D US images, while it took 11.7 ± 1.2 mins for manual segmentation. The method would promote the translation of carotid 3D US to clinical care for the monitoring of the atherosclerotic disease progression and regression. PMID:23533535

  17. Controlled-Shape, Ultrasonic-Angle-Beam Standard Reflector

    NASA Technical Reports Server (NTRS)

    Berry, J., Robertf.

    1986-01-01

    New ultrasonic angle-beam standard reflector uses impression of letter "l" steel-die stamp. NDE techniques and standard reflector apply to use of pulse-echo-type ultrasonic equipment for inspection of wrought metals including forgings and forging stock; rolled billet, bar or plate; and extruded bar, tube, and shapes. "l" reference standard reflector affords advantages of easy insertion in inspected item using common hand-tools and greatly reduced implementation time through elimination of machining operations.

  18. A simple route to shape controlled CdS nanoparticles

    NASA Astrophysics Data System (ADS)

    Nejo, Ayorinde O.; Nejo, Adeola A.; Pullabhotla, Rajasekhar V. S. R.; Revaprasadu, Neerish

    2013-02-01

    We report the synthesis of CdS nanoparticles in the form of spheres, triangles and wire-like structures. The method involves the reaction of reduced sulfur with a cadmium salt followed by thermolysis in hexadecylamine (HDA). The different shapes were obtained by variation of reaction conditions such as reaction time, temperature and cadmium source. The optical studies show the particles to be quantum confined and luminescent at room temperature.

  19. Actively controlled vibration welding system and method

    SciTech Connect

    Cai, Wayne W.; Kang, Bongsu; Tan, Chin-An

    2013-04-02

    A vibration welding system includes a controller, welding horn, an active material element, and anvil assembly. The assembly may include an anvil body connected to a back plate and support member. The element, e.g., a piezoelectric stack or shape memory alloy, is positioned with respect to the assembly. The horn vibrates in a desirable first direction to form a weld on a work piece. The element controls any vibrations in a second direction by applying calibrated response to the anvil body in the second direction. A method for controlling undesirable vibrations in the system includes positioning the element with respect to the anvil assembly, connecting the anvil body to the support member through the back plate, vibrating the horn in a desirable first direction, and transmitting an input signal to the element to control vibration in an undesirable second direction.

  20. How Life Experience Shapes Cognitive Control Strategies: The Case of Air Traffic Control Training.

    PubMed

    Arbula, Sandra; Capizzi, Mariagrazia; Lombardo, Nicoletta; Vallesi, Antonino

    2016-01-01

    Although human flexible behavior relies on cognitive control, it would be implausible to assume that there is only one, general mode of cognitive control strategy adopted by all individuals. For instance, different reliance on proactive versus reactive control strategies could explain inter-individual variability. In particular, specific life experiences, like a highly demanding training for future Air Traffic Controllers (ATCs), could modulate cognitive control functions. A group of ATC trainees and a matched group of university students were tested longitudinally on task-switching and Stroop paradigms that allowed us to measure indices of cognitive control. The results showed that the ATCs, with respect to the control group, had substantially smaller mixing costs during long cue-target intervals (CTI) and a reduced Stroop interference effect. However, this advantage was present also prior to the training phase. Being more capable in managing multiple task sets and less distracted by interfering events suggests a more efficient selection and maintenance of task relevant information as an inherent characteristic of the ATC group, associated with proactive control. Critically, the training that the ATCs underwent improved their accuracy in general and reduced response time switching costs during short CTIs only. These results indicate a training-induced change in reactive control, which is described as a transient process in charge of stimulus-driven task detection and resolution. This experience-based enhancement of reactive control strategy denotes how cognitive control and executive functions in general can be shaped by real-life training and underlines the importance of experience in explaining inter-individual variability in cognitive functioning. PMID:27311017

  1. How Life Experience Shapes Cognitive Control Strategies: The Case of Air Traffic Control Training

    PubMed Central

    Arbula, Sandra; Capizzi, Mariagrazia; Lombardo, Nicoletta; Vallesi, Antonino

    2016-01-01

    Although human flexible behavior relies on cognitive control, it would be implausible to assume that there is only one, general mode of cognitive control strategy adopted by all individuals. For instance, different reliance on proactive versus reactive control strategies could explain inter-individual variability. In particular, specific life experiences, like a highly demanding training for future Air Traffic Controllers (ATCs), could modulate cognitive control functions. A group of ATC trainees and a matched group of university students were tested longitudinally on task-switching and Stroop paradigms that allowed us to measure indices of cognitive control. The results showed that the ATCs, with respect to the control group, had substantially smaller mixing costs during long cue-target intervals (CTI) and a reduced Stroop interference effect. However, this advantage was present also prior to the training phase. Being more capable in managing multiple task sets and less distracted by interfering events suggests a more efficient selection and maintenance of task relevant information as an inherent characteristic of the ATC group, associated with proactive control. Critically, the training that the ATCs underwent improved their accuracy in general and reduced response time switching costs during short CTIs only. These results indicate a training-induced change in reactive control, which is described as a transient process in charge of stimulus-driven task detection and resolution. This experience-based enhancement of reactive control strategy denotes how cognitive control and executive functions in general can be shaped by real-life training and underlines the importance of experience in explaining inter-individual variability in cognitive functioning. PMID:27311017

  2. Stepwise assembly of a cross-linked free-standing nanoparticle sheet with controllable shape

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Liu, Mei; Zhou, Tian; Dong, Bin; Li, Christopher Y.

    2015-06-01

    In this paper, we report a free-standing thin lamella consisting of nanoparticles with controllable shape. A self-assembly technique is utilized to obtain this sheet in a step by step fashion with nanoparticles and polymer single crystals as the basic building blocks. Inside the thin lamella, nanoparticles are not only immobilized on the surface of a polymer single crystal, which functions as a template, but also interconnected by a bifunctional crosslinker, i.e. 1,6-hexane dithiol. As a consequence, the nanoparticle lamella is crosslinked and cannot be destructed by solvent and heat treatment. This fabrication strategy is generally applicable and can be applied to a variety of different nanoparticles with various properties, including catalytically active platinum nanoparticles, superparamagnetic iron oxide nanoparticles or luminescent quantum dots, and different types of polymer single crystals, such as hexagonal polycaprolactone and square-shaped polyethylene glycol ones. Based on the abundant properties originating from both nanoparticles and polymer single crystals, we have demonstrated that the resulting ensemble can function as recyclable catalytically active materials or magnetically responsive luminescent materials.In this paper, we report a free-standing thin lamella consisting of nanoparticles with controllable shape. A self-assembly technique is utilized to obtain this sheet in a step by step fashion with nanoparticles and polymer single crystals as the basic building blocks. Inside the thin lamella, nanoparticles are not only immobilized on the surface of a polymer single crystal, which functions as a template, but also interconnected by a bifunctional crosslinker, i.e. 1,6-hexane dithiol. As a consequence, the nanoparticle lamella is crosslinked and cannot be destructed by solvent and heat treatment. This fabrication strategy is generally applicable and can be applied to a variety of different nanoparticles with various properties, including

  3. Nonimaging active system determination of target shape through turbulent medium

    NASA Astrophysics Data System (ADS)

    Chandler, Susan M.; Lukesh, Gordon W.

    2001-01-01

    Image reconstruction techniques for atmospheric applications often work best with an initial estimate of the object support. This paper examines the ability of a non-imaging laser pointing system to obtain an estimate of target size and shape based on the statistics of the return signal. Fundamental limits on system pointing, such as the tracking errors, corrupt a simple raster scan that would provide gross object shape form the convolution of the far-field pattern with the target. Using techniques developed previously for the estimation of pointing performance, it is possible to distinguish between simple shapes such as bars, circles and T's based on the statistics of the received time signal. Simulated space objects, such as those illuminated during field experiments, may also be distinguished.

  4. Piezoelectric Polymers Actuators for Precise Shape Control of Large Scale Space Antennas

    NASA Technical Reports Server (NTRS)

    Chen, Qin; Natale, Don; Neese, Bret; Ren, Kailiang; Lin, Minren; Zhang, Q. M.; Pattom, Matthew; Wang, K. W.; Fang, Houfei; Im, Eastwood

    2007-01-01

    Extremely large, lightweight, in-space deployable active and passive microwave antennas are demanded by future space missions. This paper investigates the development of PVDF based piezopolymer actuators for controlling the surface accuracy of a membrane reflector. Uniaxially stretched PVDF films were poled using an electrodeless method which yielded high quality poled piezofilms required for this application. To further improve the piezoperformance of piezopolymers, several PVDF based copolymers were examined. It was found that one of them exhibits nearly three times improvement in the in-plane piezoresponse compared with PVDF and P(VDF-TrFE) piezopolymers. Preliminary experimental results indicate that these flexible actuators are very promising in controlling precisely the shape of the space reflectors.

  5. Thermal control of shape memory alloy artificial anal sphincters for complete implantation

    NASA Astrophysics Data System (ADS)

    Luo, Yun; Okuyama, Takeshi; Takagi, Toshiyuki; Kamiyama, Takamichi; Nishi, Kotaro; Yambe, Tomoyuki

    2005-02-01

    This paper presents an approach for the thermal control of an artificial anal sphincter using shape memory alloys. An artificial anal sphincter has been proposed by the authors to resolve problems of severe fecal incontinence in patients. The basic design of the artificial sphincter consists of two all-round shape memory alloy plates as the main functional parts, and heaters that are attached to the SMA plates for generating the thermal cycles required for the phase transformation accompanied shape changes of the plates. The SMA artificial sphincter could be fitted around intestines, performing an occlusion function at body temperature and a release function upon heating. Thermal compatibility of such prostheses is most important and is critical for practical use. Since a temperature rise of approximately 20 °C from body temperature is needed to activate a complete transformation of SMA plates, an earlier model of ours allowed only a short period of heating, resulting in incomplete evacuation. In this work, a thermal control approach using a temperature-responsive reed switch has been incorporated into the device to prevent the SMA plates from overheating. Then, with thermal insulation the artificial anal sphincter is expected to allow a long enough opening period for fecal continence; without any thermal impact to the surrounding tissues that would be in contact with the artificial sphincter. Thermal control was confirmed in both in vitro and in vivo experiments, suggesting the effectiveness of the present approach. The modified SMA artificial anal sphincter has been implanted into animal models for chronic experiments of up to 4 weeks, and has exhibited good performance by maintaining occlusion and release functions. At autopsy, no anomaly due to thermal impact was found on the surfaces of intestines that had been in contact with the artificial anal sphincter.

  6. Global cortical activity predicts shape of hand during grasping.

    PubMed

    Agashe, Harshavardhan A; Paek, Andrew Y; Zhang, Yuhang; Contreras-Vidal, José L

    2015-01-01

    Recent studies show that the amplitude of cortical field potentials is modulated in the time domain by grasping kinematics. However, it is unknown if these low frequency modulations persist and contain enough information to decode grasp kinematics in macro-scale activity measured at the scalp via electroencephalography (EEG). Further, it is unclear as to whether joint angle velocities or movement synergies are the optimal kinematics spaces to decode. In this offline decoding study, we infer from human EEG, hand joint angular velocities as well as synergistic trajectories as subjects perform natural reach-to-grasp movements. Decoding accuracy, measured as the correlation coefficient (r) between the predicted and actual movement kinematics, was r = 0.49 ± 0.02 across 15 hand joints. Across the first three kinematic synergies, decoding accuracies were r = 0.59 ± 0.04, 0.47 ± 0.06, and 0.32 ± 0.05. The spatial-temporal pattern of EEG channel recruitment showed early involvement of contralateral frontal-central scalp areas followed by later activation of central electrodes over primary sensorimotor cortical areas. Information content in EEG about the grasp type peaked at 250 ms after movement onset. The high decoding accuracies in this study are significant not only as evidence for time-domain modulation in macro-scale brain activity, but for the field of brain-machine interfaces as well. Our decoding strategy, which harnesses the neural "symphony" as opposed to local members of the neural ensemble (as in intracranial approaches), may provide a means of extracting information about motor intent for grasping without the need for penetrating electrodes and suggests that it may be soon possible to develop non-invasive neural interfaces for the control of prosthetic limbs. PMID:25914616

  7. Global cortical activity predicts shape of hand during grasping

    PubMed Central

    Agashe, Harshavardhan A.; Paek, Andrew Y.; Zhang, Yuhang; Contreras-Vidal, José L.

    2015-01-01

    Recent studies show that the amplitude of cortical field potentials is modulated in the time domain by grasping kinematics. However, it is unknown if these low frequency modulations persist and contain enough information to decode grasp kinematics in macro-scale activity measured at the scalp via electroencephalography (EEG). Further, it is unclear as to whether joint angle velocities or movement synergies are the optimal kinematics spaces to decode. In this offline decoding study, we infer from human EEG, hand joint angular velocities as well as synergistic trajectories as subjects perform natural reach-to-grasp movements. Decoding accuracy, measured as the correlation coefficient (r) between the predicted and actual movement kinematics, was r = 0.49 ± 0.02 across 15 hand joints. Across the first three kinematic synergies, decoding accuracies were r = 0.59 ± 0.04, 0.47 ± 0.06, and 0.32 ± 0.05. The spatial-temporal pattern of EEG channel recruitment showed early involvement of contralateral frontal-central scalp areas followed by later activation of central electrodes over primary sensorimotor cortical areas. Information content in EEG about the grasp type peaked at 250 ms after movement onset. The high decoding accuracies in this study are significant not only as evidence for time-domain modulation in macro-scale brain activity, but for the field of brain-machine interfaces as well. Our decoding strategy, which harnesses the neural “symphony” as opposed to local members of the neural ensemble (as in intracranial approaches), may provide a means of extracting information about motor intent for grasping without the need for penetrating electrodes and suggests that it may be soon possible to develop non-invasive neural interfaces for the control of prosthetic limbs. PMID:25914616

  8. Fuel-efficient feedback control of orbital motion around irregular-shaped asteroids

    NASA Astrophysics Data System (ADS)

    Winkler, Timothy Michael

    Unmanned probes are the primary technologies used when exploring celestial bodies in our solar system. As these deep space exploration missions are becoming more and more complex, there is a need for advanced autonomous operation capabilities in order to meet mission objectives. These autonomous capabilities are required as ground-based guidance and navigation commands will not be able to be issued in real time due to the large distance from the Earth. For long-duration asteroid exploration missions, this also entails how to keep the spacecraft around or on the body in order for the mission to be successfully completed. Unlike with larger bodies such as planets, though, the dynamical environment around these smaller bodies can be difficult to characterize. The weak gravitational fields are not uniform due to irregular shapes and non-homogeneous mass distribution, especially when orbiting in close-proximity to the body. On top of that, small perturbation forces such as solar radiation pressure can be strong enough to destabilize an orbit around an asteroid. The best solution for keeping a spacecraft in orbit about a small body is to implement some form of control technique. With conventional propulsion thrusters, active control algorithms tend to have a higher than acceptable propellant requirements for long-duration asteroid exploration missions, which has led to much research being devoted to finding open-loop solutions to long-term stable orbits about small bodies. These solutions can prove to be highly sensitive to the orbit's initial conditions, making them potentially unreliable in the presence of orbit injection errors. This research investigates a fuel-efficient, active control scheme to safely control a spacecraft's orbit in close-proximity to an asteroid. First, three different gravitational models capable of simulating the non-homogeneous gravity fields of asteroids are presented: the polyhedron gravity shape model, a spherical harmonics expansion, and an

  9. Aeroelastic Wing Shaping Control Subject to Actuation Constraints.

    NASA Technical Reports Server (NTRS)

    Swei, Sean Shan-Min; Nguyen, Nhan

    2014-01-01

    This paper considers the control of coupled aeroelastic aircraft model which is configured with Variable Camber Continuous Trailing Edge Flap (VCCTEF) system. The relative deflection between two adjacent flaps is constrained and this actuation constraint is accounted for when designing an effective control law for suppressing the wing vibration. A simple tuned-mass damper mechanism with two attached masses is used as an example to demonstrate the effectiveness of vibration suppression with confined motion of tuned masses. In this paper, a dynamic inversion based pseudo-control hedging (PCH) and bounded control approach is investigated, and for illustration, it is applied to the NASA Generic Transport Model (GTM) configured with VCCTEF system.

  10. Controls Considerations for Turbine Active Clearance Control

    NASA Technical Reports Server (NTRS)

    Melcher, Kevin J.

    2004-01-01

    This presentation discusses active control of turbine tip clearance from a control systems perspective. It is a subset of charts that were presented at the 2003 meeting of the International Society of Air Breathing Engines which was held August 31 through September 5 in Cleveland, Ohio. The associated reference paper is cited at the end of the presentation. The presentation describes active tip clearance control research being conducted by NASA to improve turbine engine systems. The target application for this effort is commercial aircraft engines. However, it is believed that the technologies developed as part of this research will benefit a broad spectrum of current and future turbomachinery. The first part of the presentation discusses the concept of tip clearance, problems associated with it, and the benefits of controlling it. It lays out a framework for implementing tip clearance controls that enables the implementation to progress from purely analytical to hardware-in-the-loop to fully experimental. And it briefly discusses how the technologies developed will be married to the previously described ACC Test Rig for hardware-in-the-loop demonstrations. The final portion of the presentation, describes one of the key technologies in some detail by presenting equations and results for a functional dynamic model of the tip clearance phenomena. As shown, the model exhibits many of the clearance dynamics found in commercial gas turbine engines. However, initial attempts to validate the model identified limitations that are being addressed to make the model more realistic.

  11. Root Cohesion Controls on Shallow Landslide Size, Shape and Location

    NASA Astrophysics Data System (ADS)

    Douglas, M.; Bellugi, D. G.; Perron, J.; Coe, J. A.; Schmidt, K. M.

    2013-12-01

    Many environmental factors, including ground cover, local hydrology, and recent weather events interact to cause shallow landslides and determine landslide characteristics. Vegetation is of particular interest, because changes in vegetation density, age, and composition are expected consequences of human land use and climate change. These changes alter effective cohesion due to root reinforcement, which is known to impact landslide abundance, but the effects of root cohesion on landslide size, shape and location have not been quantified. The Elliott State Forest, a 376 km2 managed forest in Douglas County, Oregon, provides an ideal venue to study these effects. There, a single storm in November 1996 triggered 154 shallow landslides, which were subsequently mapped using aerial images onto laser altimetry data, in an area with a range of vegetation ages but relatively uniform soil properties, topography, and lithology. We used aerial imagery to categorize areas with different land use histories into 3 vegetation classes, ranging from clear-cuts to forest with mature trees over 100 years old. Each mapped landslide was then assigned to a class, and its size, shape and location was recorded. Our results show that, in addition to the expected decrease in landslide abundance in more-vegetated areas (which could be influenced by a bias against detecting landslides under trees), landslides in those areas were also larger and more elongated in the down-slope direction. Although landslides in all three classes generally occurred at locations with similar drainage area and slope, we observed that slides with a larger ratio of drainage area to slope were slightly more abundant in areas with lower vegetation cover. To investigate the causes of these variations, we used a new shallow landslide model calibrated for the Oregon Coast Range to predict the size, shape and location of landslides triggered by the 1996 storm under a range of root cohesion values in a subset of the study

  12. Experimental demonstration of static shape control. [using flexible beam facility for large space structure development

    NASA Technical Reports Server (NTRS)

    Eldred, D.; Schaechter, D.

    1981-01-01

    Results of a microprocessor-controlled implementation of static shape control using a specially constructed flexible beam facility are presented. The discussion covers the development of shape control algorithms, adaptation of the algorithms for use with finite element models, construction of a flexible beam, characterization and calibration of the facility, development of a finite element model for the beam, and the development of computer hardware and software. It is shown that feedback control yields better results than open-loop control, and that the use of more than two sensors in the control loop has little effect on the system performance.

  13. The contents of predictions in sentence comprehension: activation of the shape of objects before they are referred to.

    PubMed

    Rommers, Joost; Meyer, Antje S; Praamstra, Peter; Huettig, Falk

    2013-02-01

    When comprehending concrete words, listeners and readers can activate specific visual information such as the shape of the words' referents. In two experiments we examined whether such information can be activated in an anticipatory fashion. In Experiment 1, listeners' eye movements were tracked while they were listening to sentences that were predictive of a specific critical word (e.g., "moon" in "In 1969 Neil Armstrong was the first man to set foot on the moon"). 500 ms before the acoustic onset of the critical word, participants were shown four-object displays featuring three unrelated distractor objects and a critical object, which was either the target object (e.g., moon), an object with a similar shape (e.g., tomato), or an unrelated control object (e.g., rice). In a time window before shape information from the spoken target word could be retrieved, participants already tended to fixate both the target and the shape competitors more often than they fixated the control objects, indicating that they had anticipatorily activated the shape of the upcoming word's referent. This was confirmed in Experiment 2, which was an ERP experiment without picture displays. Participants listened to the same lead-in sentences as in Experiment 1. The sentence-final words corresponded to the predictable target, the shape competitor, or the unrelated control object (yielding, for instance, "In 1969 Neil Armstrong was the first man to set foot on the moon/tomato/rice"). N400 amplitude in response to the final words was significantly attenuated in the shape-related compared to the unrelated condition. Taken together, these results suggest that listeners can activate perceptual attributes of objects before they are referred to in an utterance. PMID:23238371

  14. Line-by-line pulse shaping control for optical arbitrary waveform generation.

    PubMed

    Jiang, Z; Leaird, D E; Weiner, A M

    2005-12-12

    We demonstrate a fundamental operation for generating complex waveforms in the optical domain - line-by-line pulse shaping control for optical arbitrary waveform generation (O-AWG). Independent manipulation of the spectral amplitude and phase of individual lines from a mode-locked frequency comb, or spectral line-by-line pulse shaping, leads to synthesis of user-specified ultrafast optical waveforms with unprecedented control. Coupled with recent advances in frequency stabilized mode-locked lasers, line-by-line pulse shaping control should have significant impact to fields drawing upon developments in the field of ultrafast science. PMID:19503258

  15. MICROWAVE-ASSISTED SHAPE-CONTROLLED BULK SYNTHESIS OF NOBLE NANOCRYSTALS AND THEIR CATALYTIC PROPERTIES

    EPA Science Inventory

    Bulk and shape-controlled synthesis of gold (Au) nanostructures with various shapes such as prisms, cubes and hexagons is described that occurs via microwave-assisted spontaneous reduction of noble metal salts using an aqueous solution of α-D-glucose, sucrose and maltose. The exp...

  16. Modeling injection molding of net-shape active ceramic components.

    SciTech Connect

    Baer, Tomas; Cote, Raymond O.; Grillet, Anne Mary; Yang, Pin; Hopkins, Matthew Morgan; Noble, David R.; Notz, Patrick K.; Rao, Rekha Ranjana; Halbleib, Laura L.; Castaneda, Jaime N.; Burns, George Robert; Mondy, Lisa Ann; Brooks, Carlton, F.

    2006-11-01

    To reduce costs and hazardous wastes associated with the production of lead-based active ceramic components, an injection molding process is being investigated to replace the current machining process. Here, lead zirconate titanate (PZT) ceramic particles are suspended in a thermoplastic resin and are injected into a mold and allowed to cool. The part is then bisque fired and sintered to complete the densification process. To help design this new process we use a finite element model to describe the injection molding of the ceramic paste. Flow solutions are obtained using a coupled, finite-element based, Newton-Raphson numerical method based on the GOMA/ARIA suite of Sandia flow solvers. The evolution of the free surface is solved with an advanced level set algorithm. This approach incorporates novel methods for representing surface tension and wetting forces that affect the evolution of the free surface. Thermal, rheological, and wetting properties of the PZT paste are measured for use as input to the model. The viscosity of the PZT is highly dependent both on temperature and shear rate. One challenge in modeling the injection process is coming up with appropriate constitutive equations that capture relevant phenomenology without being too computationally complex. For this reason we model the material as a Carreau fluid and a WLF temperature dependence. Two-dimensional (2D) modeling is performed to explore the effects of the shear in isothermal conditions. Results indicate that very low viscosity regions exist near walls and that these results look similar in terms of meniscus shape and fill times to a simple Newtonian constitutive equation at the shear-thinned viscosity for the paste. These results allow us to pick a representative viscosity to use in fully three-dimensional (3D) simulation, which because of numerical complexities are restricted to using a Newtonian constitutive equation. Further 2D modeling at nonisothermal conditions shows that the choice of

  17. Active beam shaping in multiple laser guide stars

    NASA Astrophysics Data System (ADS)

    Jones, Katharine J.

    2012-10-01

    Adaptive beam shaping is a critical part of multiple Laser Guide Stars (LGS) for Multiple Conjugate Adaptive Optics (MCAO) for ground-based astronomical telescopes. There are two kinds of Laser Guide Stars: Na Laser Guide Stars (at 589 nm and 92 km altitude) and Rayleigh Laser Guide Stars (at 532 nm and 20 km altitude). Multiple Conjugate Adaptive Optics (MCAO) corrects for each "layer" of atmosphere independently. Multiple Laser Guide Stars are being developed to achieve a measure of tilt and increase the isoplanatic patch. Multiple Laser Guide Stars are being combined with Multiple Conjugate Optics in the Large Binocular Telescope (LBT): more than one Laser Guide Star (4-5) and two different wavelengths: 589 nm and 532 nm. Other observatories have multiple Laser Guide Stars but only one wavelength: 589 nm or 532 nm. Because Laser Guide Stars are launched into the atmosphere, adaptive beam shaping will be carried out before the laser is launched and will be different depending on which laser is being used, presumably to effect the tightest beam which can be achieved at the power level which is required to provide the requisite return to gound-based wavefront sensors. A complete range of devices are used. Beam attenuation and divergnece will take place. Multiple Laser Guide Stars of major observatories (SOR, LBT, MMT, ESO VLT and Gemini South) will be evaluated for effective adaptive beam shaping and impact on performance

  18. Control of gas phase nanoparticle shape and its effect on MRI relaxivity

    NASA Astrophysics Data System (ADS)

    Aktaş, Sıtkı; Thornton, Stuart C.; Binns, Chris; Lari, Leonardo; Pratt, Andrew; Kröger, Roland; Horsfield, Mark A.

    2015-03-01

    We have used a sputtering gas aggregation source to produce Fe@FeO nanoparticles with different shapes, by annealing them at different temperatures in the gas phase. Without annealing, the most common shape found for the nanoparticles is cubic but annealing the nanoparticles at 1129 °C transforms the cubes into cuboctahedra. Measurements of the MRI relaxivity show that the cubic nanoparticles have a higher performance by a factor of two, which is attributed to a higher saturation magnetization for this shape. This indicates that the shape-control enabled by gas-phase synthesis is important for obtaining optimal performance in applications.

  19. Gain-scheduling Control of Rotary Inverted Pendulum by Weight Optimization and H∞ Loop Shaping Procedure

    NASA Astrophysics Data System (ADS)

    Yubai, Kazuhiro; Okuhara, Kazunori; Hirai, Junji

    Gain-scheduling control is one of effective methods for plants whose dynamics changes significantly according to its operating point. A frozen parameter method is known to be a practical gain-scheduling controller synthesis, which interpolates the controllers designed at the prespecified (frozen) operating points according to the current operation point. Hyde et al. proposed a gain-scheduling control that H∞ loop shaping procedure is adopted as a controller synthesis at each operating point. H∞ loop shaping procedure is based on loop shaping of an open loop characteristic by frequency weights and is known to be effective for plants with bad condition number. However, weight selection satisfying control specifications is hard job for a designer. This paper describes the design of a suboptimal weight and a controller by means of algorithm that maximizes the robust stability margin and shapes the open loop characteristic into the desired shape at each operating point. Moreover, we formulate a weight optimization problem as a generalized eigenvalue minimization problem, which reduces the designer's burden of weight selection. Finally, we realize robust and high performance control system by scheduling both weights and controllers. The effectiveness of the proposed control system is verified in terms of the achieved robust stability margin and experimental time responses of a rotary inverted pendulum which involves strong nonlinear dynamics.

  20. Controllable pulse parameter transcranial magnetic stimulator with enhanced circuit topology and pulse shaping

    PubMed Central

    D’Ostilio, Kevin; Rothwell, John C; Murphy, David L

    2014-01-01

    Objective This work aims at flexible and practical pulse parameter control in transcranial magnetic stimulation (TMS), which is currently very limited in commercial devices. Approach We present a third generation controllable pulse parameter device (cTMS3) that uses a novel circuit topology with two energy-storage capacitors. It incorporates several implementation and functionality advantages over conventional TMS devices and other devices with advanced pulse shape control. cTMS3 generates lower internal voltage differences and is implemented with transistors with lower voltage rating than prior cTMS devices. Main results cTMS3 provides more flexible pulse shaping since the circuit topology allows four coil-voltage levels during a pulse, including approximately zero voltage. The near-zero coil voltage enables snubbing of the ringing at the end of the pulse without the need for a separate active snubber circuit. cTMS3 can generate powerful rapid pulse sequences (<10 ms inter pulse interval) by increasing the width of each subsequent pulse and utilizing the large capacitor energy storage, allowing the implementation of paradigms such as paired-pulse and quadripulse TMS with a single pulse generation circuit. cTMS3 can also generate theta (50 Hz) burst stimulation with predominantly unidirectional electric field pulses. The cTMS3 device functionality and output strength are illustrated with electrical output measurements as well as a study of the effect of pulse width and polarity on the active motor threshold in 10 healthy volunteers. Significance The cTMS3 features could extend the utility of TMS as a research, diagnostic, and therapeutic tool. PMID:25242286

  1. Controllable pulse parameter transcranial magnetic stimulator with enhanced circuit topology and pulse shaping

    NASA Astrophysics Data System (ADS)

    Peterchev, Angel V.; DʼOstilio, Kevin; Rothwell, John C.; Murphy, David L.

    2014-10-01

    Objective. This work aims at flexible and practical pulse parameter control in transcranial magnetic stimulation (TMS), which is currently very limited in commercial devices. Approach. We present a third generation controllable pulse parameter device (cTMS3) that uses a novel circuit topology with two energy-storage capacitors. It incorporates several implementation and functionality advantages over conventional TMS devices and other devices with advanced pulse shape control. cTMS3 generates lower internal voltage differences and is implemented with transistors with a lower voltage rating than prior cTMS devices. Main results. cTMS3 provides more flexible pulse shaping since the circuit topology allows four coil-voltage levels during a pulse, including approximately zero voltage. The near-zero coil voltage enables snubbing of the ringing at the end of the pulse without the need for a separate active snubber circuit. cTMS3 can generate powerful rapid pulse sequences (\\lt 10 ms inter pulse interval) by increasing the width of each subsequent pulse and utilizing the large capacitor energy storage, allowing the implementation of paradigms such as paired-pulse and quadripulse TMS with a single pulse generation circuit. cTMS3 can also generate theta (50 Hz) burst stimulation with predominantly unidirectional electric field pulses. The cTMS3 device functionality and output strength are illustrated with electrical output measurements as well as a study of the effect of pulse width and polarity on the active motor threshold in ten healthy volunteers. Significance. The cTMS3 features could extend the utility of TMS as a research, diagnostic, and therapeutic tool.

  2. Shape-controlled synthesis of nanocarbons through direct conversion of carbon dioxide

    PubMed Central

    Zhang, Haitao; Zhang, Xiong; Sun, Xianzhong; Ma, Yanwei

    2013-01-01

    Morphology control of carbon-based nanomaterials (nanocarbons) is critical to practical applications because their physical and chemical properties are highly shape-dependent. The discovery of novel shaped nanocarbons stimulates new development in carbon science and technology. Based on direct reaction of CO2 with Mg metal, we achieved controlled synthesis of several different types of nanocarbons including mesoporous graphene, carbon nanotubes, and hollow carbon nanoboxes. The last one, to our knowledge, has not been previously reported to this date. The method described here allows effective control of the shape and dimensions of nanocarbons through manipulation of reaction temperature. The formation mechanism of nanocarbons is proposed. As a proof of concept, the synthesized nanocarbons are used for electrodes in symmetrical supercapacitors, which exhibit high capacitance and good cycling stability. The reported protocols are instructive to production of nanocarbons with controlled shape and dimensions which are much desirable for many practical applications. PMID:24346481

  3. Optical control of antibacterial activity

    NASA Astrophysics Data System (ADS)

    Velema, Willem A.; van der Berg, Jan Pieter; Hansen, Mickel J.; Szymanski, Wiktor; Driessen, Arnold J. M.; Feringa, Ben L.

    2013-11-01

    Bacterial resistance is a major problem in the modern world, stemming in part from the build-up of antibiotics in the environment. Novel molecular approaches that enable an externally triggered increase in antibiotic activity with high spatiotemporal resolution and auto-inactivation are highly desirable. Here we report a responsive, broad-spectrum, antibacterial agent that can be temporally activated with light, whereupon it auto-inactivates on the scale of hours. The use of such a ‘smart’ antibiotic might prevent the build-up of active antimicrobial material in the environment. Reversible optical control over active drug concentration enables us to obtain pharmacodynamic information. Precisely localized control of activity is achieved, allowing the growth of bacteria to be confined to defined patterns, which has potential for the development of treatments that avoid interference with the endogenous microbial population in other parts of the organism.

  4. Charting Early Trajectories of Executive Control with the Shape School

    ERIC Educational Resources Information Center

    Clark, Caron A. C.; Sheffield, Tiffany D.; Chevalier, Nicolas; Nelson, Jennifer Mize; Wiebe, Sandra A.; Espy, Kimberly Andrews

    2013-01-01

    Despite acknowledgement of the importance of executive control for learning and behavior, there is a dearth of research charting its developmental trajectory as it unfolds against the background of children's sociofamilial milieus. Using a prospective, cohort-sequential design, this study describes growth trajectories for inhibitory control…

  5. Shape-controlled anisotropy of superparamagnetic micro-/nanohelices

    NASA Astrophysics Data System (ADS)

    Leshansky, Alexander M.; Morozov, Konstantin I.; Rubinstein, Boris Y.

    2016-07-01

    propose a semi-quantitative energy criterion to rank polarizable helices with different geometries of the filament by their propulsive capacity and also estimate their maximal propulsion speed. Electronic supplementary information (ESI) available: Effective concentration of magnetic inclusions, geometry of micro-/nanohelices and shape parametrization, effective magnetization: slender body theory. See DOI: 10.1039/C6NR01803C

  6. Demonstration of Active Combustion Control

    NASA Technical Reports Server (NTRS)

    Lovett, Jeffrey A.; Teerlinck, Karen A.; Cohen, Jeffrey M.

    2008-01-01

    The primary objective of this effort was to demonstrate active control of combustion instabilities in a direct-injection gas turbine combustor that accurately simulates engine operating conditions and reproduces an engine-type instability. This report documents the second phase of a two-phase effort. The first phase involved the analysis of an instability observed in a developmental aeroengine and the design of a single-nozzle test rig to replicate that phenomenon. This was successfully completed in 2001 and is documented in the Phase I report. This second phase was directed toward demonstration of active control strategies to mitigate this instability and thereby demonstrate the viability of active control for aircraft engine combustors. This involved development of high-speed actuator technology, testing and analysis of how the actuation system was integrated with the combustion system, control algorithm development, and demonstration testing in the single-nozzle test rig. A 30 percent reduction in the amplitude of the high-frequency (570 Hz) instability was achieved using actuation systems and control algorithms developed within this effort. Even larger reductions were shown with a low-frequency (270 Hz) instability. This represents a unique achievement in the development and practical demonstration of active combustion control systems for gas turbine applications.

  7. Active Flow Control Activities at NASA Langley

    NASA Technical Reports Server (NTRS)

    Anders, Scott G.; Sellers, William L., III; Washburn, Anthony E.

    2004-01-01

    NASA Langley continues to aggressively investigate the potential advantages of active flow control over more traditional aerodynamic techniques. This paper provides an update to a previous paper and describes both the progress in the various research areas and the significant changes in the NASA research programs. The goals of the topics presented are focused on advancing the state of knowledge and understanding of controllable fundamental mechanisms in fluids as well as to address engineering challenges. An organizational view of current research activities at NASA Langley in active flow control as supported by several projects is presented. On-center research as well as NASA Langley funded contracts and grants are discussed at a relatively high level. The products of this research are to be demonstrated either in bench-top experiments, wind-tunnel investigations, or in flight as part of the fundamental NASA R&D program and then transferred to more applied research programs within NASA, DOD, and U.S. industry.

  8. Acoustic contrast control in an arc-shaped area using a linear loudspeaker array.

    PubMed

    Zhao, Sipei; Qiu, Xiaojun; Burnett, Ian

    2015-02-01

    This paper proposes a method of creating acoustic contrast control in an arc-shaped area using a linear loudspeaker array. The boundary of the arc-shaped area is treated as the envelope of the tangent lines that can be formed by manipulating the phase profile of the loudspeakers in the array. When compared with the existing acoustic contrast control method, the proposed method is able to generate sound field inside an arc-shaped area and achieve a trade-off between acoustic uniformity and acoustic contrast. The acoustic contrast created by the proposed method increases while the acoustic uniformity decreases with frequency. PMID:25698035

  9. Fractional active disturbance rejection control.

    PubMed

    Li, Dazi; Ding, Pan; Gao, Zhiqiang

    2016-05-01

    A fractional active disturbance rejection control (FADRC) scheme is proposed to improve the performance of commensurate linear fractional order systems (FOS) and the robust analysis shows that the controller is also applicable to incommensurate linear FOS control. In FADRC, the traditional extended states observer (ESO) is generalized to a fractional order extended states observer (FESO) by using the fractional calculus, and the tracking differentiator plus nonlinear state error feedback are replaced by a fractional proportional-derivative controller. To simplify controller tuning, the linear bandwidth-parameterization method has been adopted. The impacts of the observer bandwidth ωo and controller bandwidth ωc on system performance are then analyzed. Finally, the FADRC stability and frequency-domain characteristics for linear single-input single-output FOS are analyzed. Simulation results by FADRC and ADRC on typical FOS are compared to demonstrate the superiority and effectiveness of the proposed scheme. PMID:26928516

  10. Energy shaping non-linear acceleration control for a pendulum-type mobility and experimental verification

    NASA Astrophysics Data System (ADS)

    Yokoyama, Kazuto; Takahashi, Masaki

    2015-02-01

    A dynamics-based non-linear controller with energy shaping to accelerate a pendulum-type mobility is proposed. The concept of this study is to control translational acceleration of the vehicle in a dynamically reasonable manner. The body angle is controlled to maintain a reference state where the vehicle is statically unstable but dynamically stable, which leads to a constant translational acceleration due to instability of the system. The accelerating motion is like a sprinter moving from crouch start and it fully exploits dynamics of the vehicle. To achieve it, the total energy of the system is shaped to have the minimum at a given reference state and the system is controlled to converge to it. The controller can achieve various properties through the energy shaping procedure. Especially, an energy function that will lead to safe operation of the vehicle is proposed. The effectiveness of the controller is verified in simulations and experiments.

  11. Pattern curvature to control pore shape and its ordering

    NASA Astrophysics Data System (ADS)

    Yu, Guiduk; Shin, Kyusoon

    2013-03-01

    Triangular pore in inverse-hexagonal packing was fabricated by anodizing Al with convex pattern in hexagonal packing. The convexly patterned Al was prepared via replication of the concave structure formed in self-assembled anodized aluminum oxide (AAO). Self-assembled AAO without pre-patterning produces hexagonal packing circular pores. Exploitation of the inversed structure was found to create well-defined triangular pores in inverse-hexagonal packing. Anisotropic pore feature was discussed to come from the alternating distance between the pits and the curvature of the pattern. Also, by controlling the topography of the convex pattern around pits, we investigated the effect of pattern topography on pore initiation.

  12. Recent Advances in Shape-Controlled Synthesis of Noble Metal Nanoparticles by Radiolysis Route.

    PubMed

    Abedini, Alam; Bakar, Ahmad Ashrif A; Larki, Farhad; Menon, P Susthitha; Islam, Md Shabiul; Shaari, Sahbudin

    2016-12-01

    This paper focuses on the recent advances on radiolysis-assisted shape-controlled synthesis of noble metal nanostructures. The techniques and protocols for producing desirable shapes of noble metal nanoparticles are discussed through introducing the critical parameters which can influence the nucleation and growth mechanisms. Nucleation rate plays a vital role on the crystallinity of seeds while growth rate of different seeds' facets determines the final shape of resultant nanoparticles. Nucleation and growth rate both can be altered with factors such as absorbed dose, capping agents, and experimental environment condition to control the final shape. Remarkable physical and chemical properties of synthesized noble metal nanoparticles by controlled morphology have been systematically evaluated to fully explore their applications. PMID:27283051

  13. Recent Advances in Shape-Controlled Synthesis of Noble Metal Nanoparticles by Radiolysis Route

    NASA Astrophysics Data System (ADS)

    Abedini, Alam; Bakar, Ahmad Ashrif A.; Larki, Farhad; Menon, P. Susthitha; Islam, Md. Shabiul; Shaari, Sahbudin

    2016-06-01

    This paper focuses on the recent advances on radiolysis-assisted shape-controlled synthesis of noble metal nanostructures. The techniques and protocols for producing desirable shapes of noble metal nanoparticles are discussed through introducing the critical parameters which can influence the nucleation and growth mechanisms. Nucleation rate plays a vital role on the crystallinity of seeds while growth rate of different seeds' facets determines the final shape of resultant nanoparticles. Nucleation and growth rate both can be altered with factors such as absorbed dose, capping agents, and experimental environment condition to control the final shape. Remarkable physical and chemical properties of synthesized noble metal nanoparticles by controlled morphology have been systematically evaluated to fully explore their applications.

  14. Symmetry-controlled colloidal nanocrystals: nonhydrolytic chemical synthesis and shape determining parameters.

    PubMed

    Jun, Young-wook; Lee, Jae-Hyun; Choi, Jin-sil; Cheon, Jinwoo

    2005-08-11

    Since inorganic nanocrystals exhibit unique shape-dependent nanoscale properties and can be utilized as basic building blocks for futuristic nanodevices, a systematic study on the shape control of these nanocrystals remains an important subject in materials and physical chemistry. In this feature article, we overview the recent progress on the synthetic development of symmetry-controlled colloidal nanocrystals of semiconductor and metal oxide, which are prepared through nonhydrolytic chemical routes. We describe their shape-guiding processes and illustrate the detailed key factors controlling their growth by examining various case studies of zero-dimensional spheres and cubes, one-dimensional rods, and quasi multidimensional structures such as disks, multipods, and stars. Specifically, the crystalline phase of nucleating seeds, surface energy, kinetic vs thermodynamic growth, and selective adhesion processes of capping ligands are found to be most crucial for the determination of the nanocrystal shape. PMID:16852873

  15. Reducing Environmental Toxicity of Silver Nanoparticles through Shape Control.

    PubMed

    Gorka, Danielle E; Osterberg, Joshua S; Gwin, Carley A; Colman, Benjamin P; Meyer, Joel N; Bernhardt, Emily S; Gunsch, Claudia K; DiGulio, Richard T; Liu, Jie

    2015-08-18

    The use of antibacterial silver nanomaterials in consumer products ranging from textiles to toys has given rise to concerns over their environmental toxicity. These materials, primarily nanoparticles, have been shown to be toxic to a wide range of organisms; thus methods and materials that reduce their environmental toxicity while retaining their useful antibacterial properties can potentially solve this problem. Here we demonstrate that silver nanocubes display a lower toxicity toward the model plant species Lolium multiflorum while showing similar toxicity toward other environmentally relevant and model organisms (Danio rerio and Caenorhabditis elegans) and bacterial species (Esherichia coli, Bacillus cereus, and Pseudomonas aeruginosa) compared to quasi-spherical silver nanoparticles and silver nanowires. More specifically, in the L. multiflorum experiments, the roots of silver nanocube treated plants were 5.3% shorter than the control, while silver nanoparticle treated plant roots were 39.6% shorter than the control. The findings here could assist in the future development of new antibacterial products that cause less environmental toxicity after their intended use. PMID:26146787

  16. High-Precision Shape Control of In-Space Deployable Large Membrane/Thin-Shell Reflectors

    NASA Technical Reports Server (NTRS)

    Watkins, Ronald; Goebel, Dan; Hofer, Richard

    2010-01-01

    This innovation has been developed to improve the resolutions of future spacebased active and passive microwave antennas for earth-science remote sensing missions by maintaining surface figure precisions of large membrane/thin-shell reflectors during orbiting. The intention is for these sensing instruments to be deployable at orbit altitudes one or two orders of magnitude higher than Low Earth Orbit (LEO), but still being able to acquire measurements at spatial resolution and sensitivity similar to those of LEO. Because active and passive microwave remote sensors are able to penetrate through clouds to acquire vertical profile measurements of geophysical parameters, it is desirable to elevate them to the higher orbits to obtain orbital geometries that offer large spatial coverage and more frequent observations. This capability is essential for monitoring and for detailed understanding of the life cycles of natural hazards, such as hurricanes, tropical storms, flash floods, and tsunamis. Major components of this high-precision antenna-surface-control system include a membrane/thin shell reflector, a metrology sensor, a controller, actuators, and corresponding power amplifier and signal conditioning electronics (see figure). Actuators are attached to the back of the reflector to produce contraction/ expansion forces to adjust the shape of the thin-material reflector. The wavefront-sensing metrology system continuously measures the surface figure of the reflector, converts the surface figure to digital data and feeds the data to the controller. The controller determines the control parameters and generates commands to the actuator system. The flexible, piezoelectric polymer actuators are thus activated, providing the control forces needed to correct any distortions that exist in the reflector surface. Piezoelectric polymer actuators are very thin and flexible. They can be implemented on the back of the membrane/thin-shell reflector without introducing significant

  17. Plasma shape control by pulsed solenoid on laser ion source

    NASA Astrophysics Data System (ADS)

    Sekine, M.; Ikeda, S.; Romanelli, M.; Kumaki, M.; Fuwa, Y.; Kanesue, T.; Hayashizaki, N.; Lambiase, R.; Okamura, M.

    2015-09-01

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. However, it was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. This approach may also be useful to reduce beam emittance of a LIS.

  18. Plasma shape control by pulsed solenoid on laser ion source

    DOE PAGESBeta

    Sekine, M.; Ikeda, S.; Romanelli, M.; Kumaki, M.; Fuwa, Y.; Kanesue, T.; Hayashizaki, N.; Lambiase, R.; Okamura, M.

    2015-05-28

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. It was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled bymore » the pulsed magnetic field. Thus, this approach may also be useful to reduce beam emittance of a LIS.« less

  19. Plasma shape control by pulsed solenoid on laser ion source

    SciTech Connect

    Sekine, M.; Ikeda, S.; Romanelli, M.; Kumaki, M.; Fuwa, Y.; Kanesue, T.; Hayashizaki, N.; Lambiase, R.; Okamura, M.

    2015-05-28

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. It was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. Thus, this approach may also be useful to reduce beam emittance of a LIS.

  20. Analog computation system for plasma position and shape control

    SciTech Connect

    Haskovec, J.S.; Kellman, A.G.; Moore, C.D.; Strait, E.J.; Taylor, T.S.

    1987-10-01

    Part of the DIII-D upgrade of the Doublet III. Fusion experiment involves incorporation of more extensive feedback control of various plasma parameters. More than 200 sensors and measuring instruments generate the primary analog signals during the experiment. These signals are conditioned and transformed to standard voltages by amplifiers, integrators, and sometimes more complicated circuits. To obtain suitable feedback control variables, subsets of primary signals are combined in the form of mathematical functions. A five-input summing amplifier, a two-input divider/two-input multiplier, and a three-input summing amplifier with a two-input multiplier are the standard module functions. In order to eliminate stability problems in feedback loops, the transfer function of the computing circuits must introduce minimal time delay in the required frequency band, even if multiple cascading is used. Long term stability and accuracy is also required, along with high reliability, to save limited maintenance resources and minimize shutdown time of the experiment. During the initial stage of implementation, high flexibility in the circuit configuration and programming was required because of the empirical nature of many of the parameters. Digital and analog solutions were considered before a modular analog system was selected. The VME mechanical standard was chosen mainly because of the high density backplane connectors and availability of shielded backplanes and flat cables, which provide easy and inexpensive signal routing to any module in the system. All inputs are single-ended. Low output noise levels permit daisy chaining of modules which allows implementation of complicated functions. All inputs and outputs are also accessible via miniature coaxial connectors on the front panel, together with polarity and range switches and ten turn precision potentiometers for constant factor selection. 3 figs.

  1. Subjective Significance Shapes Arousal Effects on Modified Stroop Task Performance: A Duality of Activation Mechanisms Account.

    PubMed

    Imbir, Kamil K

    2016-01-01

    Activation mechanisms such as arousal are known to be responsible for slowdown observed in the Emotional Stroop and modified Stroop tasks. Using the duality of mind perspective, we may conclude that both ways of processing information (automatic or controlled) should have their own mechanisms of activation, namely, arousal for an experiential mind, and subjective significance for a rational mind. To investigate the consequences of both, factorial manipulation was prepared. Other factors that influence Stroop task processing such as valence, concreteness, frequency, and word length were controlled. Subjective significance was expected to influence arousal effects. In the first study, the task was to name the color of font for activation charged words. In the second study, activation charged words were, at the same time, combined with an incongruent condition of the classical Stroop task around a fixation point. The task was to indicate the font color for color-meaning words. In both studies, subjective significance was found to shape the arousal impact on performance in terms of the slowdown reduction for words charged with subjective significance. PMID:26869974

  2. Subjective Significance Shapes Arousal Effects on Modified Stroop Task Performance: A Duality of Activation Mechanisms Account

    PubMed Central

    Imbir, Kamil K.

    2016-01-01

    Activation mechanisms such as arousal are known to be responsible for slowdown observed in the Emotional Stroop and modified Stroop tasks. Using the duality of mind perspective, we may conclude that both ways of processing information (automatic or controlled) should have their own mechanisms of activation, namely, arousal for an experiential mind, and subjective significance for a rational mind. To investigate the consequences of both, factorial manipulation was prepared. Other factors that influence Stroop task processing such as valence, concreteness, frequency, and word length were controlled. Subjective significance was expected to influence arousal effects. In the first study, the task was to name the color of font for activation charged words. In the second study, activation charged words were, at the same time, combined with an incongruent condition of the classical Stroop task around a fixation point. The task was to indicate the font color for color-meaning words. In both studies, subjective significance was found to shape the arousal impact on performance in terms of the slowdown reduction for words charged with subjective significance. PMID:26869974

  3. Extended Active Disturbance Rejection Controller

    NASA Technical Reports Server (NTRS)

    Gao, Zhiqiang (Inventor); Tian, Gang (Inventor)

    2016-01-01

    Multiple designs, systems, methods and processes for controlling a system or plant using an extended active disturbance rejection control (ADRC) based controller are presented. The extended ADRC controller accepts sensor information from the plant. The sensor information is used in conjunction with an extended state observer in combination with a predictor that estimates and predicts the current state of the plant and a co-joined estimate of the system disturbances and system dynamics. The extended state observer estimates and predictions are used in conjunction with a control law that generates an input to the system based in part on the extended state observer estimates and predictions as well as a desired trajectory for the plant to follow.

  4. Extended Active Disturbance Rejection Controller

    NASA Technical Reports Server (NTRS)

    Gao, Zhiqiang (Inventor); Tian, Gang (Inventor)

    2014-01-01

    Multiple designs, systems, methods and processes for controlling a system or plant using an extended active disturbance rejection control (ADRC) based controller are presented. The extended ADRC controller accepts sensor information from the plant. The sensor information is used in conjunction with an extended state observer in combination with a predictor that estimates and predicts the current state of the plant and a co-joined estimate of the system disturbances and system dynamics. The extended state observer estimates and predictions are used in conjunction with a control law that generates an input to the system based in part on the extended state observer estimates and predictions as well as a desired trajectory for the plant to follow.

  5. Extended active disturbance rejection controller

    NASA Technical Reports Server (NTRS)

    Gao, Zhiqiang (Inventor); Tian, Gang (Inventor)

    2012-01-01

    Multiple designs, systems, methods and processes for controlling a system or plant using an extended active disturbance rejection control (ADRC) based controller are presented. The extended ADRC controller accepts sensor information from the plant. The sensor information is used in conjunction with an extended state observer in combination with a predictor that estimates and predicts the current state of the plant and a co-joined estimate of the system disturbances and system dynamics. The extended state observer estimates and predictions are used in conjunction with a control law that generates an input to the system based in part on the extended state observer estimates and predictions as well as a desired trajectory for the plant to follow.

  6. The sliding mode control for different shapes and dimensions of IPMC on resisting its creep characteristics

    NASA Astrophysics Data System (ADS)

    Hao, Lina; Chen, Yang; Sun, Zhiyong

    2015-04-01

    Ionic polymer metal composite (IPMC) is a novel smart material which has been widely implemented in MEMS, biomimetic mechanical and electrical integrated system and micro operation system. While the IPMC with different shapes and dimensions has been implemented in many different types of biomechanical integrated systems, one of its inherent properties called creep characteristic is difficult to be handled, which limits the further application of different IPMCs in integrated systems. A promising control method called sliding mode control (SMC) is proposed to resist the creep characteristics in this paper. The SMC controller can regulate IPMC actuators with different shapes and dimensions effectively to resist the creep characteristics without changing parameters of the control system. Experiments of four different types of IPMC actuators were conducted on the semi-physical SMC experimental platform. All the experimental results confirm the feasibility of the SMC control approach on regulating the multi-IPMCs with different shapes and dimensions based integrated system.

  7. Surface-Engineered Graphene Quantum Dots for Shape Control of Block Copolymer Particles

    NASA Astrophysics Data System (ADS)

    Yang, Hyunseung; Ku, Kang Hee; Shin, Jae Man; Lee, Junhyuk; Park, Chan Ho; Cho, Han-Hee; Jang, Se Gyu; Kim, Bumjoon; KIST Collaboration

    Surface-engineered, 10 nm-sized graphene quantum dots (GQDs) are shown to be efficient surfactants for producing poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) particles that feature tunable shapes and internal morphologies. The surface properties of GQDs were modified by grafting different alkyl ligands, such as hexylamine and oleylamine, to generate the surfactant behavior of the GQDs. In stark contrast to the behavior of the unmodified GQDs, hexylamine-grafted GQDs and oleylamine-grafted GQD surfactants were selectively positioned on the PS and P4VP domains, respectively, at the surface of the particles. This positioning effectively tuned the interfacial interaction between two different PS/P4VP domains of the particles and the surrounding water during emulsification and induced a dramatic morphological transition to an unconventional convex lens-shaped particles. Precise and systematic control of interfacial activity of GQD surfactants was also demonstrated by varying the density of the alkyl ligands on the GQDs. The excellent surface tunability of 10 nm-sized GQDs combined with their significant optical and electrical properties highlight their importance as surfactants for producing colloidal particles with novel functions.

  8. Active control of buckling of flexible beams

    NASA Technical Reports Server (NTRS)

    Baz, A.; Tampe, L.

    1989-01-01

    Mathematical models are presented that simulate the dynamic characteristics of shape memory alloy actuators made of nickel-titanium alloy (Nitinol) controlling the buckling of compressive structural members. A closed-loop computer-controlled system has been designed, based on the proposed mathematical models, and has been implemented to control the buckling of simple beams. The performance of the computer-controlled system is evaluated experimentally and compared with the theoretical predictions to validate the developed models. The results emphasized the importance of buckling control and suggest the potential of shape memory alloy actuators as attractive means for controlling structural deformation in a simple and reliable way.

  9. Shape Control of Doctor blade coated Polymer Electrodes via Microflow Control in a Drying Droplet

    NASA Astrophysics Data System (ADS)

    Jang, Yunseok; Jo, Jeongdai; Lee, Seung-Hyun; PEMS Team

    2012-11-01

    We demonstrated a simple patterning method for polymer electrodes such as poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) by using the doctor blade coater. We controlled the surface tension for controlling the polymer electrodes shape. We made use of the difference in wettability between hydrophobic surfaces and hydrophilic surfaces to make the polymer electrodes patterns. However, the polymer electrodes patterns made with our patterning method created undesirable ring-like stains, which were caused by the outward flow of the solute within the PEDOT/PSS solution drop. To achieve homogenous device performance, we proposed a simple process for removing this ring-like stain by making the surface tension gradient in the PEDOT/PSS solution drop. Because this surface tension gradient causes the inward flow of the solute within the PEDOT/PSS solution drop, the ring-like stain is removed. Finally, we confirmed the potential of our patterning method for polymer electrodes such as the PEDOT/PSS by fabricating pentacene thin-film transistors (TFTs) and measuring the electrical properties of the pentacene TFTs. This study was supported by a grant (B551179-08-03-00/ B551179-10-01-00/ NK167D/ SC0830) from the cooperative R&D Program funded by the Korea Research Council Industrial Science and Technology, Republic of Korea.

  10. Controllable shrinking and shaping of glass nanocapillaries under electron irradiation.

    PubMed

    Steinbock, L J; Steinbock, J F; Radenovic, A

    2013-04-10

    The ability to reshape nanopores and observe their shrinkage under an electron microscope is a powerful and novel technique. It increases the sensitivity of the resistive pulse sensing and enables to detect very short and small molecules. However, this has not yet been shown for glass nanocapillaries. In contrast to their solid-state nanopore counterparts, nanocapillaries are cheap, easily fabricated and in the production do not necessitate clean room facilities. We show for the first time that quartz nanocapillaries can be shrunken under a scanning electron microscope beam. Since the shrinking is caused by the thermal heating of the electrons, increasing the beam current increases the shrink rate. Higher acceleration voltage on the contrary increases the electron penetration depth and reduces the electron density causing slower shrinkage. This allows us to fine control the shrink rate and to stop the shrinking process at any desired diameter. We show that a shrunken nanocapillary detects DNA translocation with six times higher signal amplitudes than an unmodified nanocapillary. This will open a new path to detect small and short molecules such as proteins or RNA with nanocapillaries. PMID:23506620

  11. Experimental evaluation of a shape memory alloy wire actuator with a modulated adaptive controller for position control

    NASA Astrophysics Data System (ADS)

    Senthilkumar, P.; Dayananda, G. N.; Umapathy, M.; Shankar, V.

    2012-01-01

    This paper presents an experimental investigation of position control of a shape memory alloy (SMA) wire actuator with adaptive and modulated adaptive controllers. The transfer function model of the SMA wire actuator is determined from the experimental open loop response. Adaptive controllers, namely LMS-GSPI, RLS-GSPI and Kalman-GSPI, and modulated adaptive controllers using pulse width modulation (PWM) are designed. The performances of these controllers are experimentally investigated for the position control of an SMA wire actuator with and without thermal disturbance. Experimental results demonstrate that the modulated adaptive controllers outperform adaptive controllers.

  12. Shape bistability of a membrane neck: A toggle switch to control vesicle content release

    PubMed Central

    Frolov, Vadim A.; Lizunov, Vladimir A.; Dunina-Barkovskaya, Antonina Ya.; Samsonov, Andrey V.; Zimmerberg, Joshua

    2003-01-01

    Shape dynamics and permeability of a membrane neck connecting a vesicle and plasma membrane are considered. The neck is modeled by a lipid membrane tubule extended between two parallel axisymmetric rings. Within a range of lengths, defined by system geometry and mechanical properties of the membrane, the tubule has two stable shapes: catenoidal microtubule and cylindrical nanotubule. The permeabilities of these two shapes, measured as ionic conductivity of the tubule interior, differ by up to four orders of magnitude. Near the critical length the transitions between the shapes occur within less than a millisecond. Theoretical estimates show that the shape switching is controlled by a single parameter, the tubule length. Thus the tubule connection can operate as a conductivity microswitch, toggling the release of vesicle content in such cellular processes as “kiss-and-run” exocytosis. In support of this notion, bistable behavior of membrane connections between vesicles and the cell plasma membrane in macrophages is demonstrated. PMID:12857952

  13. Dual control active superconductive devices

    DOEpatents

    Martens, Jon S.; Beyer, James B.; Nordman, James E.; Hohenwarter, Gert K. G.

    1993-07-20

    A superconducting active device has dual control inputs and is constructed such that the output of the device is effectively a linear mix of the two input signals. The device is formed of a film of superconducting material on a substrate and has two main conduction channels, each of which includes a weak link region. A first control line extends adjacent to the weak link region in the first channel and a second control line extends adjacent to the weak link region in the second channel. The current flowing from the first channel flows through an internal control line which is also adjacent to the weak link region of the second channel. The weak link regions comprise small links of superconductor, separated by voids, through which the current flows in each channel. Current passed through the control lines causes magnetic flux vortices which propagate across the weak link regions and control the resistance of these regions. The output of the device taken across the input to the main channels and the output of the second main channel and the internal control line will constitute essentially a linear mix of the two input signals imposed on the two control lines. The device is especially suited to microwave applications since it has very low input capacitance, and is well suited to being formed of high temperature superconducting materials since all of the structures may be formed coplanar with one another on a substrate.

  14. Shape-Controlled Paclitaxel Nanoparticles with Multiple Morphologies: Rod-Shaped, Worm-Like, Spherical, and Fingerprint-Like

    PubMed Central

    2015-01-01

    Although many nanocarriers have been developed to encapsulate paclitaxel (PTX), the drug loading and circulation time in vivo always are not ideal because of its rigid “brickdust” molecular structure. People usually concentrate their attention on the spherical nanocarriers, here paclitaxel nanoparticles with different geometries were established through the chemical modification of PTX, nanoprecipitation, and core-matched cargos. Previously we have developed rod-shape paclitaxel nanocrystals using block copolymer, pluronic F127. Unfortunately, the pharmacokinetic (PK) profile of PTX nanocrystals is very poor. However, when PTX was replaced by its prodrug, the geometry of the nanoparticles changed from rod-shaped to worm-like. The worm-like nanoparticles can be further changed to spherical nanoparticles using the nanoprecipitation method, and changed to fingerprint-like nanoparticles upon the addition of the core-matched PTX. The nanoparticles with nonspherical morphologies, including worm-like nanoparticles and fingerprint-like nanoparticles, offer significant advantages in regards to key PK parameters in vivo. More important, in this report the application of the core-matching technology in creating a core-matched environment capable of controlling the in vivo PK of paclitaxel was demonstrated, and it revealed a novel technique platform to construct nanoparticles and improve the poor PK profiles of the drugs. PMID:25188586

  15. Anion-Mediated End-Shape Control in Seed-Mediated Growth of Gold Nanorods.

    PubMed

    Kim, Tae Youl; Kim, Joo-Hyung; Kim, Minsoo P; Yi, Gi-Ra

    2016-06-01

    End-shape-controlled gold nanorods (GNRs) were synthesized at room-temperature by a seeded-growth method, in which hexadecyltrimethylammonium bromide (CTAB) was used as a stabilizer and capping agent. The average dimension of the GNRs was 46 nm in length and 15 nm in diameter, which corresponds to aspect ratio of c.a. 3.0. Then, their both ends were further grown at the presence of silver precursor (AgNO3), resulting in formation of arrow-head GNRs. By tuning the amount of the silver precursor, the end-shape of the GNRs was changed to dumbbell like shape. Moreover, the growth rate of gold could be controlled by tuning the amount of hydrochloric acid (HCl). While arrow-headed GNRs having sharp edges were produced without HCl, the GNRs having dog-bone like or round-head shape at both ends were obtained with HCl. PMID:27427712

  16. Active Interior Noise Control Studies

    NASA Technical Reports Server (NTRS)

    Park, J.; Veeramani, S.; Sampath, A.; Balachandran, B.; Wereley, N.

    1996-01-01

    Analytical and experimental investigations into the control of noise in the interior of a three-dimensional enclosure with a flexible boundary are presented. The rigid boundaries are constructed from acrylic material, and in the different cases considered the flexible boundary is constructed from either aluminum or composite material. Noise generated by an external speaker is transmitted into the enclosure through the flexible boundary and active control is realized by using Lead Zirconate Titanate (PZT) piezoelectric actuators bonded to the flexible boundary. Condenser microphones are used for noise measurements inside and outside the enclosure. Minimization schemes for global and local noise control in the presence of a harmonic disturbance are developed and discussed. In the experiments, analog feedforward control is implemented by using the harmonic disturbance as a reference signal.

  17. Locomotion and Control of a Self-Propelled Shape-Changing Body in a Fluid

    NASA Astrophysics Data System (ADS)

    Chambrion, Thomas; Munnier, Alexandre

    2011-06-01

    In this paper we study the locomotion of a shape-changing body swimming in a two-dimensional perfect fluid of infinite extent. The shape changes are prescribed as functions of time satisfying constraints ensuring that they result from the work of internal forces only: conditions necessary for the locomotion to be termed self-propelled. The net rigid motion of the body results from the exchange of momentum between these shape changes and the surrounding fluid. The aim of this paper is three-fold. First, it describes a rigorous framework for the study of animal locomotion in fluid. Our model differs from previous ones mostly in that the number of degrees of freedom related to the shape changes is infinite. The Euler-Lagrange equation is obtained by applying the least action principle to the system body fluid. The formalism of Analytic Mechanics provides a simple way to handle the strong coupling between the internal dynamics of the body causing the shape changes and the dynamics of the fluid. The Euler-Lagrange equation takes the form of a coupled system of ordinary differential equations (ODEs) and partial differential equations (PDEs). The existence and uniqueness of solutions for this system are rigorously proved. Second, we are interested in making clear the connection between shape changes and internal forces. Although classical, it can be quite surprising to select the shape changes to play the role of control because the internal forces they are due to seem to be a more natural and realistic choice. We prove that, when the number of degrees of freedom relating to the shape changes is finite, both choices are actually equivalent in the sense that there is a one-to-one relation between shape changes and internal forces. Third, we show how the control problem, consisting in associating with each shape change the resulting trajectory of the swimming body, can be analysed within the framework of geometric control theory. This allows us to take advantage of the

  18. Adaptive feedback active noise control

    NASA Astrophysics Data System (ADS)

    Kuo, Sen M.; Vijayan, Dipa

    Feedforward active noise control (ANC) systems use a reference sensor that senses a reference input to the controller. This signal is assumed to be unaffected by the secondary source and is a good measure of the undesired noise to be cancelled by the system. The reference sensor may be acoustic (e.g., microphone) or non-acoustic (e.g., tachometer, optical transducer). An obvious problem when using acoustic sensors is that the reference signal may be corrupted by the canceling signal generated by the secondary source. This problem is known as acoustic feedback. One way of avoiding this is by using a feedback active noise control (FANC) system which dispenses with the reference sensor. The FANC technique originally proposed by Olson and May employs a high gain negative feedback amplifier. This system suffered from the drawback that the error microphone had to be placed very close to the loudspeaker. The operation of the system was restricted to low frequency range and suffered from instability due to the possibility of positive feedback. Feedback systems employing adaptive filtering techniques for active noise control were developed. This paper presents the FANC system modeled as an adaptive prediction scheme.

  19. Motor-driven marginal band coiling promotes cell shape change during platelet activation

    PubMed Central

    Diagouraga, Boubou; Grichine, Alexei; Fertin, Arnold; Wang, Jin; Khochbin, Saadi

    2014-01-01

    Platelets float in the blood as discoid particles. Their shape is maintained by microtubules organized in a ring structure, the so-called marginal band (MB), in the periphery of resting platelets. Platelets are activated after vessel injury and undergo a major shape change known as disc to sphere transition. It has been suggested that actomyosin tension induces the contraction of the MB to a smaller ring. In this paper, we show that antagonistic microtubule motors keep the MB in its resting state. During platelet activation, dynein slides microtubules apart, leading to MB extension rather than contraction. The MB then starts to coil, thereby inducing the spherical shape of activating platelets. Newly polymerizing microtubules within the coiled MB will then take a new path to form the smaller microtubule ring, in concerted action with actomyosin tension. These results present a new view of the platelet activation mechanism and reveal principal mechanistic features underlying cellular shape changes. PMID:24421335

  20. Hippocampal sub-regional shape and physical activity in older adults.

    PubMed

    Varma, Vijay R; Tang, Xiaoying; Carlson, Michelle C

    2016-08-01

    Hippocampal atrophy is a hallmark of Alzheimer's disease pathology, and a target biomarker region for testing intervention efficacy. Over the last few decades, a growing body of evidence from animal and human models suggests that physical activity (PA) is associated with structural benefits to the hippocampus in older adults. Very few human studies, however have explored hippocampal sub-regional specificity of PA; this is significant considering that sub-regions of the hippocampus are associated with distinct cognitive tasks and are differentially affected by disease pathology. This study used objective and self-reported measures of daily walking activity and exercise, and surface-based regional shape analysis using high-field hippocampal sub-regional partitions to explore sub-region specific hippocampal associations in a sample of nondemented, community-dwelling older adults at elevated sociodemographic risk for cognitive decline. Vertex-wise surface areas, which may be more sensitive than global volume measures, were calculated using shape diffeomorphometry, and PA was assessed using step activity monitors and PA questionnaires. We found that daily walking activity in a participant's environment was associated in cross-section mainly with larger surface areas of the subiculum in women. Associations remained significant when controlling for self-reported exercise. Prior studies have found that PA related to exercise and aerobic fitness may be most closely associated with the anterior hippocampus, particularly the dentate gyrus of the hippocampus. These novel findings are the first, to our knowledge, in human models to suggest that PA related to navigation that may not reach the level of moderate-intensity exercise may be associated with specific sub-regions of the hippocampus. These findings underscore the importance of better understanding the independent and related biological mechanisms and pathways by which increasing exercise as well as non

  1. Green synthesis of anatase TiO(2) nanocrystals with diverse shapes and their exposed facets-dependent photoredox activity.

    PubMed

    Roy, Nitish; Park, Yohan; Sohn, Youngku; Leung, Kam Tong; Pradhan, Debabrata

    2014-10-01

    The exposed facets of a crystal are known to be one of the key factors to its physical, chemical and electronic properties. Herein, we demonstrate the role of amines on the controlled synthesis of TiO2 nanocrystals (NCs) with diverse shapes and different exposed facets. The chemical, physical and electronic properties of the as-synthesized TiO2 NCs were evaluated and their photoredox activity was tested. It was found that the intrinsic photoredox activity of TiO2 NCs can be enhanced by controlling the chemical environment of the surface, i.e.; through morphology evolution. In particular, the rod shape TiO2 NCs with ∼25% of {101} and ∼75% of {100}/{010} exposed facets show 3.7 and 3.1 times higher photocatalytic activity than that of commercial Degussa P25 TiO2 toward the degradation of methyl orange and methylene blue, respectively. The higher activity of the rod shape TiO2 NCs is ascribed to the facetsphilic nature of the photogenerated carriers within the NCs. The photocatalytic activity of TiO2 NCs are found to be in the order of {101}+{100}/{010} (nanorods) > {101}+{001}+{100}/{010} (nanocuboids and nanocapsules) > {101} (nanoellipsoids) > {001} (nanosheets) providing the direct evidence of exposed facets-depended photocatalytic activity. PMID:25188808

  2. From formation mechanisms to synthetic methods toward shape-controlled oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Nguyen, Thanh-Dinh

    2013-09-01

    Metal oxide nanomaterials have been intensively pursued for modern science and nanotechnology. Control over the size and shape of the oxide nanoparticles enables tunability of their unique properties sought for many useful applications. This review presents a comprehensive overview of the recent advances in the shape-controlled synthesis of colloidal oxide nanoparticles. We introduce the size- and shape-dependent properties of the oxide nanoparticles along with their potential applications and subsequent descriptions of the kinetic regime concepts of the formation of the monodisperse nanocolloids. Variations of the experimental conditions including capping molecules, precursor monomer concentration, and reaction temperature/aging have been explored to control the shape of the oxide nanoparticles in wet-chemistry syntheses. The different capping molecule-assisted synthetic methods of the hydro-solvothermal route, the two-phase route, heating-up thermolysis, and reverse micelle are presented as a collection of clear examples of the regular oxide nanoparticles. We also discuss the advantages and obstacles of the synthetic methods that have proven to be controllable and reproducible. The author concludes this review with valuable portraits on working hypotheses for the shape-controlled oxide nanoparticle synthesis.

  3. Shaping Student Activists: Discursive Sensemaking of Activism and Participation Research

    ERIC Educational Resources Information Center

    Taha, Diane E.; Hastings, Sally O.; Minei, Elizabeth M.

    2015-01-01

    As social media becomes a more potent force in society, particularly for younger generations, the role in activism has been contested. This qualitative study examines 35 interviews with students regarding their perceptions of the use of social media in social change, their perceptions of activists, and their level of self-identification as an…

  4. Plasma shape and position controller design for advance plasma configurations in TCV

    NASA Astrophysics Data System (ADS)

    Anand, Himank; Coda, Stefano; Felici, Federico; Moret, Jean Marc; Le, Hoang Bao

    2015-11-01

    The performance and stability of tokamak plasma configurations depend strongly on its shape and position. They play a particularly important role in the stability of global magneto-hydrodynamics (MHD) modes and in heat and particle transport. We report on the controller design of a new generalised plasma shape and position controller for advance plasma configurations, using the linearised plasma model RZIP. The controller design is based on an isoflux control scheme and utilises singular value decomposition (SVD), which provides a natural framework for limiting the controlled parameters to the set with the largest singular values, while respecting the combined poloidal field coil current (PF) limits. It also includes the option of weighting the various observers based on the level of importance for a given plasma configuration. The generalised plasma shape and position control algorithm has been successfully tested off-line for limiter and diverted plasma (single null and snowflake configuration) shapes. The testing and commissioning of the controller will commence in the next TCV experimental campaign.

  5. Novel Active Combustion Control Valve

    NASA Technical Reports Server (NTRS)

    Caspermeyer, Matt

    2014-01-01

    This project presents an innovative solution for active combustion control. Relative to the state of the art, this concept provides frequency modulation (greater than 1,000 Hz) in combination with high-amplitude modulation (in excess of 30 percent flow) and can be adapted to a large range of fuel injector sizes. Existing valves often have low flow modulation strength. To achieve higher flow modulation requires excessively large valves or too much electrical power to be practical. This active combustion control valve (ACCV) has high-frequency and -amplitude modulation, consumes low electrical power, is closely coupled with the fuel injector for modulation strength, and is practical in size and weight. By mitigating combustion instabilities at higher frequencies than have been previously achieved (approximately 1,000 Hz), this new technology enables gas turbines to run at operating points that produce lower emissions and higher performance.

  6. Control over overall shape and size in de novo designed proteins.

    PubMed

    Lin, Yu-Ru; Koga, Nobuyasu; Tatsumi-Koga, Rie; Liu, Gaohua; Clouser, Amanda F; Montelione, Gaetano T; Baker, David

    2015-10-01

    We recently described general principles for designing ideal protein structures stabilized by completely consistent local and nonlocal interactions. The principles relate secondary structure patterns to tertiary packing motifs and enable design of different protein topologies. To achieve fine control over protein shape and size within a particular topology, we have extended the design rules by systematically analyzing the codependencies between the lengths and packing geometry of successive secondary structure elements and the backbone torsion angles of the loop linking them. We demonstrate the control afforded by the resulting extended rule set by designing a series of proteins with the same fold but considerable variation in secondary structure length, loop geometry, β-strand registry, and overall shape. Solution NMR structures of four designed proteins for two different folds show that protein shape and size can be precisely controlled within a given protein fold. These extended design principles provide the foundation for custom design of protein structures performing desired functions. PMID:26396255

  7. Control over overall shape and size in de novo designed proteins

    PubMed Central

    Lin, Yu-Ru; Koga, Nobuyasu; Tatsumi-Koga, Rie; Liu, Gaohua; Clouser, Amanda F.; Montelione, Gaetano T.; Baker, David

    2015-01-01

    We recently described general principles for designing ideal protein structures stabilized by completely consistent local and nonlocal interactions. The principles relate secondary structure patterns to tertiary packing motifs and enable design of different protein topologies. To achieve fine control over protein shape and size within a particular topology, we have extended the design rules by systematically analyzing the codependencies between the lengths and packing geometry of successive secondary structure elements and the backbone torsion angles of the loop linking them. We demonstrate the control afforded by the resulting extended rule set by designing a series of proteins with the same fold but considerable variation in secondary structure length, loop geometry, β-strand registry, and overall shape. Solution NMR structures of four designed proteins for two different folds show that protein shape and size can be precisely controlled within a given protein fold. These extended design principles provide the foundation for custom design of protein structures performing desired functions. PMID:26396255

  8. Shape-controllable, bottom-up fabrication of microlens using oblique angle deposition.

    PubMed

    Choi, Hee Ju; Kang, Eun Kyu; Ju, Gun Wu; Song, Young Min; Lee, Yong Tak

    2016-07-15

    This Letter reports a novel method for the simple fabrication of microlens arrays with a controlled shape and diameter on glass substrates. Multilayer stacks of silicon dioxide deposited by oblique angle deposition with hole mask patterns enable microlens formation. Precise control of mask height and distance, as well as oblique angle steps between deposited layers, supports the controllability of microlens geometry. The fabricated microlens arrays with designed geometry exhibit uniform optical properties. PMID:27420527

  9. Theory of simple biochemical ``shape recognition'' via diffusion from activator coated nanoshapes

    NASA Astrophysics Data System (ADS)

    Daniels, D. R.

    2008-09-01

    Inspired by recent experiments, we model the shape sensitivity, via a typical threshold initiation response, of an underlying complex biochemical reaction network to activator coated nanoshapes. Our theory re-emphasizes that shape effects can be vitally important for the onset of functional behavior in nanopatches and nanoparticles. For certain critical or particular shapes, activator coated nanoshapes do not evoke a threshold response in a complex biochemical network setting, while for different critical or specific shapes, the threshold response is rapidly achieved. The model thus provides a general theoretical understanding for how activator coated nanoshapes can enable a chemical system to perform simple "shape recognition," with an associated "all or nothing" response. The novel and interesting cases of the chemical response due to a nanoshape that shrinks with time is additionally considered, as well as activator coated nanospheres. Possible important applications of this work include the initiation of blood clotting by nanoshapes, nanoshape effects in nanocatalysis, physiological toxicity to nanoparticles, as well as nanoshapes in nanomedicine, drug delivery, and T cell immunological response. The aim of the theory presented here is that it inspires further experimentation on simple biochemical shape recognition via diffusion from activator coated nanoshapes.

  10. Active Shape Discrimination with Compliant Bodies as Reservoir Computers.

    PubMed

    Johnson, Chris; Philippides, Andrew; Husbands, Philip

    2016-01-01

    Compliant bodies with complex dynamics can be used both to simplify control problems and to lead to adaptive reflexive behavior when engaged with the environment in the sensorimotor loop. By revisiting an experiment introduced by Beer and replacing the continuous-time recurrent neural network therein with reservoir computing networks abstracted from compliant bodies, we demonstrate that adaptive behavior can be produced by an agent in which the body is the main computational locus. We show that bodies with complex dynamics are capable of integrating, storing, and processing information in meaningful and useful ways, and furthermore that with the addition of the simplest of nervous systems such bodies can generate behavior that could equally be described as reflexive or minimally cognitive. PMID:26934092

  11. CetZ tubulin-like proteins control archaeal cell shape

    PubMed Central

    Duggin, Iain G.; Aylett, Christopher H. S.; Walsh, James C.; Michie, Katharine A.; Wang, Qing; Turnbull, Lynne; Dawson, Emma M.; Harry, Elizabeth J.; Whitchurch, Cynthia B.; Amos, Linda A.; Löwe, Jan

    2014-01-01

    Tubulin is a major component of the eukaryotic cytoskeleton, controlling cell shape, structure and dynamics, whereas its bacterial homolog FtsZ establishes the cytokinetic ring that constricts during cell division1,2. How such different roles of tubulin and FtsZ evolved is unknown. Archaea may hold clues as these organisms share characteristics with Eukarya and Bacteria3. Here we report the structure and function of proteins from a distinct family related to tubulin and FtsZ, named CetZ, which co-exists with FtsZ in many archaea. CetZ crystal structures showed the FtsZ/tubulin superfamily fold, and one crystal form contained sheets of protofilaments, suggesting a structural role. However, inactivation of the CetZs in Haloferax volcanii did not affect cell division. Instead, CetZ1 was required for differentiation of the irregular plate-shaped cells into a rod-shaped cell type that was essential for normal swimming motility. CetZ1 formed dynamic cytoskeletal structures in vivo, relating to its capacity to remodel the cell envelope and direct rod formation. CetZ2 was also implicated in H. volcanii cell shape control. Our findings expand the known roles of the FtsZ/tubulin superfamily to include archaeal cell shape dynamics, suggesting that a cytoskeletal role might predate eukaryotic cell evolution, and they support the premise that a major function of microbial rod-shape is to facilitate swimming. PMID:25533961

  12. Dynamics and Control of a Quadrotor with Active Geometric Morphing

    NASA Astrophysics Data System (ADS)

    Wallace, Dustin A.

    Quadrotors are manufactured in a wide variety of shapes, sizes, and performance levels to fulfill a multitude of roles. Robodub Inc. has patented a morphing quadrotor which will allow active reconfiguration between various shapes for performance optimization across a wider spectrum of roles. The dynamics of the system are studied and modeled using Newtonian Mechanics. Controls are developed and simulated using both Linear Quadratic and Numerical Nonlinear Optimal control for a symmetric simplificiation of the system dynamics. Various unique vehicle capabilities are investigated, including novel single-throttle flight control using symmetric geometric morphing, as well as recovery from motor loss by reconfiguring into a trirotor configuration. The system dynamics were found to be complex and highly nonlinear. All attempted control strategies resulted in controllability, suggesting further research into each may lead to multiple viable control strategies for a physical prototype.

  13. Efficient thermolysis route to monodisperse Cu₂ZnSnS₄ nanocrystals with controlled shape and structure.

    PubMed

    Zhang, Xiaoyan; Guo, Guobiao; Ji, Cheng; Huang, Kai; Zha, Chenyang; Wang, Yifeng; Shen, Liming; Gupta, Arunava; Bao, Ningzhong

    2014-01-01

    Monodisperse Cu2ZnSnS4 (CZTS) nanocrystals with tunable shape, crystalline phase, and composition are synthesized by efficient thermolysis of a single source precursor of mixed metal-oleate complexes in hot organic solvents with dissolved sulfur sources. Suitable tuning of the synthetic conditions and the Cu/(Zn + Sn) ratio of the precursor has enabled precise control of the crystalline phase in the form of kesterite, or a newly observed wurtzite structure. Nanocrystals with morphology in the form of spherical, rice-like, or rod-like shapes are obtained over a wide range of compositions (0.5 ≤ Cu/(Zn + Sn) ≤ 1.2). Both the final products and intermediates for each shape exhibit consistent composition and structure, indicating homogenous nucleation and growth of single-phase nanocrystals. Thin films prepared from colloidal nanocrystal suspensions display interesting shape-dependent photoresponse behavior under white light illumination from a solar simulator. PMID:24866987

  14. Controllable fabrication of PS/Ag core-shell-shaped nanostructures

    PubMed Central

    2012-01-01

    In this paper, based on the previous steps, a facile in situ reduction method was developed to controllably prepare polystyrene/Ag (PS/Ag) core-shell-shaped nanostructures. The crucial procedure includes surface treatment of polystyrene core particles by cationic polyelectrolyte polyethyleneimine, in situ formation of Ag nanoparticles, and immobilization of the Ag nanoparticles onto the surface of the polystyrene colloids via functional group NH from the polyethyleneimine. The experimental parameters, such as the reaction temperature, the reaction time, and the silver precursors were optimized for improvement of dispersion and Ag coat coverage of the core-shell-shaped nanostructures. Ultimately, the optimum parameters were obtained through a series of experiments, and well-dispersed, uniformly coated PS/Ag core-shell-shaped nanostructures were successfully fabricated. The formation mechanism of the PS/Ag core-shell-shaped nanostructures was also explained. PMID:23092195

  15. Effortful Control and Context Interact in Shaping Neuroendocrine Stress Responses during Childhood

    PubMed Central

    Mayer, Stefanie E.; Abelson, James L.; Lopez-Duran, Nestor L.

    2014-01-01

    Trait and contextual factors can shape individual and group differences in hypothalamic-pituitary-adrenal (HPA) response to stress; but the ways in which these factors may interact with each other to modulate stress activity has rarely been examined. Here, we investigated whether the association between a temperamental self-regulatory trait – Effortful Control (EC) – and HPA axis stress response is moderated by type of laboratory stress in sixty-five children (35 boys). EC was measured at age 3 and 6 using age-appropriate laboratory batteries as well as mother reports. HPA axis responses were measured at age 7 by randomly assigning children to one of two laboratory stress tasks (frustration vs. fear). Results indicated that EC interacted with stress context in predicting cortisol response. Specifically, lower EC was associated with greater cortisol response (steeper reactivity slopes) in the context of a frustration stressor but this was reversed in a fear context where lower EC was associated with flatter, more gradual activation. It is likely that different components of EC, such as emotion regulation and attention, differentially interact with the stress context. These types of effects and interactions need to be more thoroughly understood in order to meaningfully interpret cortisol reactivity data and better characterize the role of the HPA axis in human psychopathology. PMID:25019964

  16. [INVITED] Control of femtosecond pulsed laser ablation and deposition by temporal pulse shaping

    NASA Astrophysics Data System (ADS)

    Garrelie, Florence; Bourquard, Florent; Loir, Anne--Sophie; Donnet, Christophe; Colombier, Jean-Philippe

    2016-04-01

    This study explores the effects of temporal laser pulse shaping on femtosecond pulsed laser deposition (PLD). The potential of laser pulses temporally tailored on ultrafast time scales is used to control the expansion and the excitation degree of ablation products including atomic species and nanoparticles. The ablation plume generated by temporally shaped femtosecond pulsed laser ablation of aluminum and graphite targets is studied by in situ optical diagnostic methods. Taking advantage of automated pulse shaping techniques, an adaptive procedure based on spectroscopic feedback regulates the irradiance for the enhancement of typical plasma features. Thin films elaborated by unshaped femtosecond laser pulses and by optimized sequence indicate that the nanoparticles generation efficiency is strongly influenced by the temporal shaping of the laser irradiation. The ablation processes leading either to the generation of the nanoparticles either to the formation of plasma can be favored by using a temporal shaping of the laser pulse. Insights are given on the possibility to control the quantity of the nanoparticles. The temporal laser pulse shaping is shown also to strongly modify the laser-induced plasma contents and kinetics for graphite ablation. Temporal pulse shaping proves its capability to reduce the number of slow radicals while increasing the proportion of monomers, with the addition of ionized species in front of the plume. This modification of the composition and kinetics of plumes in graphite ablation using temporal laser pulse shaping is discussed in terms of modification of the structural properties of deposited Diamond-Like Carbon films (DLC). This gives rise to a better understanding of the growth processes involved in femtosecond-PLD and picosecond-PLD of DLC suggesting the importance of neutral C atoms, which are responsible for the subplantation process.

  17. Plasma shape control on the National Spherical Torus Experiment (NSTX) using real-time equilibrium reconstruction

    NASA Astrophysics Data System (ADS)

    Gates, D. A.; Ferron, J. R.; Bell, M.; Gibney, T.; Johnson, R.; Marsala, R. J.; Mastrovito, D.; Menard, J. E.; Mueller, D.; Penaflor, B.; Sabbagh, S. A.; Stevenson, T.

    2006-01-01

    Plasma shape control using real-time equilibrium reconstruction has been implemented on the National Spherical Torus Experiment (NSTX). The rtEFIT code originally developed for use on DIII-D was adapted for use on NSTX. The real-time equilibria provide calculations of the flux at points on the plasma boundary, which are used as input to a shape control algorithm known as isoflux control. The flux at the desired boundary location is compared with a reference flux value, and this flux error is used as the basic feedback quantity for the poloidal field coils on NSTX. The hardware that comprises the control system is described, as well as the software infrastructure. Examples of precise boundary control are also presented.

  18. Plasma Shape Control on the National Spherical Torus Experiment (NSTX) using Real-time Equilibrium Reconstruction

    SciTech Connect

    D.A. Gates; J.R. Ferron; M. Bell; T. Gibney; R. Johnson; R.J. Marsala; D. Mastrovito; J.E. Menard; D. Mueller; B. Penaflor; S.A. Sabbagh; T. Stevenson

    2005-04-15

    Plasma shape control using real-time equilibrium reconstruction has been implemented on the National Spherical Torus Experiment (NSTX). The rtEFIT code originally developed for use on DIII-D was adapted for use on NSTX. The real-time equilibria provide calculations of the flux at points on the plasma boundary, which is used as input to a shape control algorithm known as isoflux control. The flux at the desired boundary location is compared to a reference flux value, and this flux error is used as the basic feedback quantity for the poloidal-field coils on NSTX. The hardware that comprises the control system is described, as well as the software infrastructure. Examples of precise boundary control are also presented.

  19. Shape-Controlled Synthesis of Pd Nanocrystals inAqueous Solutions

    SciTech Connect

    Lim,B.; Tao,J.

    2009-01-23

    This article provides an overview of recent developments regarding synthesis of Pd nanocrystals with well-controlled shapes in aqueous solutions. In a solution-phase synthesis, the final shape taken by a nanocrystal is determined by the twin structures of seeds and the growth rates of different crystallographic facets. Here, the maneuvering of these factors in an aqueous system to achieve shape control for Pd nanocrystals is discussed. L-ascorbic acid, citric acid, and poly(vinyl pyrrolidone) are tested for manipulating the reduction kinetics, with citric acid and B-ions used as capping agents to selectively promote the formation of {111} and {100} facets, respectively. The distribution of single-crystal versus multiple-twinned seeds can be further manipulated by employing or blocking oxidative etching. The shapes obtained for the Pd nanocrystals include truncated octahedron, icosahedron,octahedron, decahedron, hexagonal and triangular plates, rectangular bar, and cube. The ability to control the shape of Pd nanocrystals provides a great opportunity to systematically investigate their catalytic, electrical, and plasmonic properties.

  20. Shape-Controlled Synthesis of Isotopic Yttrium-90-Labeled Rare Earth Fluoride Nanocrystals for Multimodal Imaging.

    PubMed

    Paik, Taejong; Chacko, Ann-Marie; Mikitsh, John L; Friedberg, Joseph S; Pryma, Daniel A; Murray, Christopher B

    2015-09-22

    Isotopically labeled nanomaterials have recently attracted much attention in biomedical research, environmental health studies, and clinical medicine because radioactive probes allow the elucidation of in vitro and in vivo cellular transport mechanisms, as well as the unambiguous distribution and localization of nanomaterials in vivo. In addition, nanocrystal-based inorganic materials have a unique capability of customizing size, shape, and composition; with the potential to be designed as multimodal imaging probes. Size and shape of nanocrystals can directly influence interactions with biological systems, hence it is important to develop synthetic methods to design radiolabeled nanocrystals with precise control of size and shape. Here, we report size- and shape-controlled synthesis of rare earth fluoride nanocrystals doped with the β-emitting radioisotope yttrium-90 ((90)Y). Size and shape of nanocrystals are tailored via tight control of reaction parameters and the type of rare earth hosts (e.g., Gd or Y) employed. Radiolabeled nanocrystals are synthesized in high radiochemical yield and purity as well as excellent radiolabel stability in the face of surface modification with different polymeric ligands. We demonstrate the Cerenkov radioluminescence imaging and magnetic resonance imaging capabilities of (90)Y-doped GdF3 nanoplates, which offer unique opportunities as a promising platform for multimodal imaging and targeted therapy. PMID:26257288

  1. Passive resting state and history of antagonist muscle activity shape active extensions in an insect limb.

    PubMed

    Ache, Jan M; Matheson, Thomas

    2012-05-01

    Limb movements can be driven by muscle contractions, external forces, or intrinsic passive forces. For lightweight limbs like those of insects or small vertebrates, passive forces can be large enough to overcome the effects of gravity and may even generate limb movements in the absence of active muscle contractions. Understanding the sources and actions of such forces is therefore important in understanding motor control. We describe passive properties of the femur-tibia joint of the locust hind leg. The resting angle is determined primarily by passive properties of the relatively large extensor tibiae muscle and is influenced by the history of activation of the fast extensor tibiae motor neuron. The resting angle is therefore better described as a history-dependent resting state. We selectively stimulated different flexor tibiae motor neurons to generate a range of isometric contractions of the flexor tibiae muscle and then stimulated the fast extensor tibiae motor neuron to elicit active tibial extensions. Residual forces in the flexor muscle have only a small effect on subsequent active extensions, but the effect is larger for distal than for proximal flexor motor neurons and varies with the strength of flexor activation. We conclude that passive properties of a lightweight limb make substantial and complex contributions to the resting state of the limb that must be taken into account in the patterning of neuronal control signals driving its active movements. Low variability in the effects of the passive forces may permit the nervous system to accurately predict their contributions to behavior. PMID:22357791

  2. Neuronal activity controls transsynaptic geometry.

    PubMed

    Glebov, Oleg O; Cox, Susan; Humphreys, Lawrence; Burrone, Juan

    2016-01-01

    The neuronal synapse is comprised of several distinct zones, including presynaptic vesicle zone (SVZ), active zone (AZ) and postsynaptic density (PSD). While correct relative positioning of these zones is believed to be essential for synaptic function, the mechanisms controlling their mutual localization remain unexplored. Here, we employ high-throughput quantitative confocal imaging, super-resolution and electron microscopy to visualize organization of synaptic subdomains in hippocampal neurons. Silencing of neuronal activity leads to reversible reorganization of the synaptic geometry, resulting in a increased overlap between immunostained AZ and PSD markers; in contrast, the SVZ-AZ spatial coupling is decreased. Bayesian blinking and bleaching (3B) reconstruction reveals that the distance between the AZ-PSD distance is decreased by 30 nm, while electron microscopy shows that the width of the synaptic cleft is decreased by 1.1 nm. Our findings show that multiple aspects of synaptic geometry are dynamically controlled by neuronal activity and suggest mutual repositioning of synaptic components as a potential novel mechanism contributing to the homeostatic forms of synaptic plasticity. PMID:26951792

  3. Neuronal activity controls transsynaptic geometry

    PubMed Central

    Glebov, Oleg O.; Cox, Susan; Humphreys, Lawrence; Burrone, Juan

    2016-01-01

    The neuronal synapse is comprised of several distinct zones, including presynaptic vesicle zone (SVZ), active zone (AZ) and postsynaptic density (PSD). While correct relative positioning of these zones is believed to be essential for synaptic function, the mechanisms controlling their mutual localization remain unexplored. Here, we employ high-throughput quantitative confocal imaging, super-resolution and electron microscopy to visualize organization of synaptic subdomains in hippocampal neurons. Silencing of neuronal activity leads to reversible reorganization of the synaptic geometry, resulting in a increased overlap between immunostained AZ and PSD markers; in contrast, the SVZ-AZ spatial coupling is decreased. Bayesian blinking and bleaching (3B) reconstruction reveals that the distance between the AZ-PSD distance is decreased by 30 nm, while electron microscopy shows that the width of the synaptic cleft is decreased by 1.1 nm. Our findings show that multiple aspects of synaptic geometry are dynamically controlled by neuronal activity and suggest mutual repositioning of synaptic components as a potential novel mechanism contributing to the homeostatic forms of synaptic plasticity. PMID:26951792

  4. Reversible ubiquitination shapes NLRC5 function and modulates NF-κB activation switch.

    PubMed

    Meng, Qingcai; Cai, Chunmei; Sun, Tingzhe; Wang, Qianliang; Xie, Weihong; Wang, Rongfu; Cui, Jun

    2015-12-01

    NLRC5 is an important regulator in innate immune responses. However, the ability of NLRC5 to inhibit NF-κB activation is controversial in different cell types. How dynamic modification of NLRC5 shapes NF-κB signaling remains unknown. We demonstrated that NLRC5 undergoes robust ubiquitination by TRAF2/6 after lipopolysaccharide treatment, which leads to dissociation of the NLRC5-IκB kinase complex. Experimental and mathematical analyses revealed that the K63-linked ubiquitination of NLRC5 at lysine 1,178 generates a coherent feedforward loop to further sensitize NF-κB activation. Meanwhile, we found USP14 specifically removes the polyubiquitin chains from NLRC5 to enhance NLRC5-mediated inhibition of NF-κB signaling. Furthermore, we found that different cell types may exhibit different sensitivities to NF-κB activation in response to NLRC5 ablation, possibly as a result of the various intrinsic levels of deubiquitinases and NLRC5. This might partially reconcile controversial studies and explain why NLRC5 exhibits diverse inhibitory efficiencies. Collectively, our results provide the regulatory mechanisms of reversible NLRC5 ubiquitination and its role in the dynamic control of innate immunity. PMID:26620909

  5. Reversible ubiquitination shapes NLRC5 function and modulates NF-κB activation switch

    PubMed Central

    Meng, Qingcai; Cai, Chunmei; Wang, Qianliang; Xie, Weihong

    2015-01-01

    NLRC5 is an important regulator in innate immune responses. However, the ability of NLRC5 to inhibit NF-κB activation is controversial in different cell types. How dynamic modification of NLRC5 shapes NF-κB signaling remains unknown. We demonstrated that NLRC5 undergoes robust ubiquitination by TRAF2/6 after lipopolysaccharide treatment, which leads to dissociation of the NLRC5–IκB kinase complex. Experimental and mathematical analyses revealed that the K63-linked ubiquitination of NLRC5 at lysine 1,178 generates a coherent feedforward loop to further sensitize NF-κB activation. Meanwhile, we found USP14 specifically removes the polyubiquitin chains from NLRC5 to enhance NLRC5-mediated inhibition of NF-κB signaling. Furthermore, we found that different cell types may exhibit different sensitivities to NF-κB activation in response to NLRC5 ablation, possibly as a result of the various intrinsic levels of deubiquitinases and NLRC5. This might partially reconcile controversial studies and explain why NLRC5 exhibits diverse inhibitory efficiencies. Collectively, our results provide the regulatory mechanisms of reversible NLRC5 ubiquitination and its role in the dynamic control of innate immunity. PMID:26620909

  6. Controlling the velocity of jumping nanodroplets via their initial shape and temperature

    SciTech Connect

    Fuentes-Cabrera, Miguel A; Rhodes, Bradley H; Baskes, Mike I.; Terrones Maldonado, Humberto; Fowlkes, Jason Davidson; Simpson, Michael L; Rack, Philip D

    2011-01-01

    Controlling the movement of nanoscale objects is a significant goal of nanotechnology. Dewetting-induced ejection of nanodroplets could provide another means of achieving that goal. Molecular dynamics simulations were used to investigate the dewetting-induced ejection of nanoscale liquid copper nanostructures that were deposited on a graphitic substrate. Nanostructures in the shape of a circle, square, equilateral, and isosceles triangle dewet and form nanodroplets that are ejected from the substrate with a velocity that depends on the initial shape and temperature. The dependence of the ejected velocity on shape is ascribed to the temporal asymmetry of the mass coalescence during the droplet formation; the dependence on temperature is ascribed to changes in the density and viscosity. The results suggest that dewetting induced by nanosecond laser pulses could be used to control the velocity of ejected nanodroplets.

  7. Controlling the Velocity of Jumping Nanodroplets Via Their Initial Shape and Temperature

    SciTech Connect

    Kent, Paul R

    2011-01-01

    Controlling the movement of nanoscale objects is a significant goal of nanotechnology. Dewetting-induced ejection of nanodroplets could provide another means of achieving that goal. Molecular dynamics simulations were used to investigate the dewetting-induced ejection of nanoscale liquid copper nanostructures that were deposited on a graphitic substrate. Nanostructures in the shape of a circle, square, equilateral, and isosceles triangle dewet and form nanodroplets that are ejected from the substrate with a velocity that depends on the initial shape and temperature. The dependence of the ejected velocity on shape is ascribed to the temporal asymmetry of the mass coalescence during the droplet formation; the dependence on temperature is ascribed to changes in the density and viscosity. The results suggest that dewetting induced by nanosecond laser pulses could be used to control the velocity of ejected nanodroplets.

  8. Shape and feature size control of colloidal crystal-based patterns using stretched polydimethylsiloxane replica molds.

    PubMed

    Choi, Hong Kyoon; Im, Sang Hyuk; Park, O Ok

    2009-10-20

    In this work, we fabricated various patterns using colloidal crystals as master molds via the soft lithography method. Even though colloidal crystals consist of spherical colloidal particles, nonspherical shaped patterns such as rectangular or elongated hexagonal shaped patterns can be fabricated using a stretched polydimethylsiloxane (PDMS) replica mold. The pattern shape and feature size can be easily controlled by changing the stretching axis and ratio of the PDMS replica mold. The deformations of the PDMS mold were simulated using the finite element method, and they are consistent with experimental results. The elongated patterns were used as templates to offer new types of colloidal crystal superlattice structures. A proposed pattern-control method will significantly expand the usefulness and diversity of micro/nanopatterning technology. PMID:19821618

  9. Self-folding origami: shape memory composites activated by uniform heating

    NASA Astrophysics Data System (ADS)

    Tolley, Michael T.; Felton, Samuel M.; Miyashita, Shuhei; Aukes, Daniel; Rus, Daniela; Wood, Robert J.

    2014-09-01

    Self-folding is an approach used frequently in nature for the efficient fabrication of structures, but is seldom used in engineered systems. Here, self-folding origami are presented, which consist of shape memory composites that are activated with uniform heating in an oven. These composites are rapidly fabricated using inexpensive materials and tools. The folding mechanism based on the in-plane contraction of a sheet of shape memory polymer is modeled, and parameters for the design of composites that self-fold into target shapes are characterized. Four self-folding shapes are demonstrated: a cube, an icosahedron, a flower, and a Miura pattern; each of which is activated in an oven in less than 4 min. Self-sealing is also investigated using hot melt adhesive, and the resulting structures are found to bear up to twice the load of unsealed structures.

  10. Trans-Membrane Area Asymmetry Controls the Shape of Cellular Organelles

    PubMed Central

    Beznoussenko, Galina V.; Pilyugin, Sergei S.; Geerts, Willie J. C.; Kozlov, Michael M.; Burger, Koert N. J.; Luini, Alberto; Derganc, Jure; Mironov, Alexander A.

    2015-01-01

    Membrane organelles often have complicated shapes and differ in their volume, surface area and membrane curvature. The ratio between the surface area of the cytosolic and luminal leaflets (trans-membrane area asymmetry (TAA)) determines the membrane curvature within different sites of the organelle. Thus, the shape of the organelle could be critically dependent on TAA. Here, using mathematical modeling and stereological measurements of TAA during fast transformation of organelle shapes, we present evidence that suggests that when organelle volume and surface area are constant, TAA can regulate transformation of the shape of the Golgi apparatus, endosomal multivesicular bodies, and microvilli of brush borders of kidney epithelial cells. Extraction of membrane curvature by small spheres, such as COPI-dependent vesicles within the Golgi (extraction of positive curvature), or by intraluminal vesicles within endosomes (extraction of negative curvature) controls the shape of these organelles. For instance, Golgi tubulation is critically dependent on the fusion of COPI vesicles with Golgi cisternae, and vice versa, for the extraction of membrane curvature into 50–60 nm vesicles, to induce transformation of Golgi tubules into cisternae. Also, formation of intraluminal ultra-small vesicles after fusion of endosomes allows equilibration of their TAA, volume and surface area. Finally, when microvilli of the brush border are broken into vesicles and microvilli fragments, TAA of these membranes remains the same as TAA of the microvilli. Thus, TAA has a significant role in transformation of organelle shape when other factors remain constant. PMID:25761238

  11. FUNCTION FOLLOWS FORM: ACTIVATION OF SHAPE & FUNCTION FEATURES DURING OBJECT IDENTIFICATION

    PubMed Central

    Yee, Eiling; Huffstetler, Stacy; Thompson-Schill, Sharon L.

    2011-01-01

    Most theories of semantic memory characterize knowledge of a given object as comprising a set of semantic features. But how does conceptual activation of these features proceed during object identification? We present the results of a pair of experiments that demonstrate that object recognition is a dynamically unfolding process in which function follows form. We used eye movements to explore whether activating one object’s concept leads to the activation of others that share perceptual (shape) or abstract (function) features. Participants viewed four-picture displays and clicked on the picture corresponding to a heard word. In critical trials, the conceptual representation of one of the objects in the display was similar in shape or function (i.e., its purpose) to the heard word. Importantly, this similarity was not apparent in the visual depictions (e.g., for the target “frisbee,” the shape-related object was a triangular slice of pizza – a shape that a frisbee cannot take); preferential fixations on the related object were therefore attributable to overlap of the conceptual representations on the relevant features. We observed relatedness effects for both shape and function, but shape effects occurred earlier than function effects. We discuss the implications of these findings for current accounts of the representation of semantic memory. PMID:21417543

  12. Control of sound radiation with active/adaptive structures

    NASA Technical Reports Server (NTRS)

    Fuller, C. R.; Rogers, C. A.; Robertshaw, H. H.

    1992-01-01

    Recent research is discussed in the area of active structural acoustic control with active/adaptive structures. Progress in the areas of structural acoustics, actuators, sensors, and control approaches is presented. Considerable effort has been given to the interaction of these areas with each other due to the coupled nature of the problem. A discussion is presented on actuators bonded to or embedded in the structure itself. The actuators discussed are piezoceramic actuators and shape memory alloy actuators. The sensors discussed are optical fiber sensors, Nitinol fiber sensors, piezoceramics, and polyvinylidene fluoride sensors. The active control techniques considered are state feedback control techniques and least mean square adaptive algorithms. Results presented show that significant progress has been made towards controlling structurally radiated noise by active/adaptive means applied directly to the structure.

  13. Shape-dependent bactericidal activity of copper oxide nanoparticle mediated by DNA and membrane damage

    SciTech Connect

    Laha, Dipranjan; Pramanik, Arindam; Laskar, Aparna; Jana, Madhurya; Pramanik, Panchanan; Karmakar, Parimal

    2014-11-15

    Highlights: • Spherical and sheet shaped copper oxide nanoparticles were synthesized. • Physical characterizations of these nanoparticles were done by TEM, DLS, XRD, FTIR. • They showed shape dependent antibacterial activity on different bacterial strain. • They induced both membrane damage and ROS mediated DNA damage in bacteria. - Abstract: In this work, we synthesized spherical and sheet shaped copper oxide nanoparticles and their physical characterizations were done by the X-ray diffraction, fourier transform infrared spectroscopy, transmission electron microscopy and dynamic light scattering. The antibacterial activity of these nanoparticles was determined on both gram positive and gram negative bacterial. Spherical shaped copper oxide nanoparticles showed more antibacterial property on gram positive bacteria where as sheet shaped copper oxide nanoparticles are more active on gram negative bacteria. We also demonstrated that copper oxide nanoparticles produced reactive oxygen species in both gram negative and gram positive bacteria. Furthermore, they induced membrane damage as determined by atomic force microscopy and scanning electron microscopy. Thus production of and membrane damage are major mechanisms of the bactericidal activity of these copper oxide nanoparticles. Finally it was concluded that antibacterial activity of nanoparticles depend on physicochemical properties of copper oxide nanoparticles and bacterial strain.

  14. Adaptive control of lasers and their interactions with matter using femtosecond pulse shaping

    NASA Astrophysics Data System (ADS)

    Efimov, Anatoly

    Coherent control of chemical reactions, atomic and molecular systems, lattice dynamics, and electronic motion rely on femtosecond laser sources capable of producing programmable arbitrarily shaped waveforms. To enter the time scale of natural dynamic processes in many systems, femtosecond pulse shaping techniques must be extended to the ultrashort pulse domain (<50 fs). Concurrently, reliable high-fidelity amplification of shaped waveforms is required in many applications. We demonstrate ultrabroad bandwidth pulse shaping of 13 fs pulses with Fourier-domain phase-only filtering using a liquid crystal array. We further demonstrate the amplification of shaped pulses in a multipass chirped pulse amplifier (CPA) system to produce millijoule-level optical waveforms with 30 fs resolution. Recently, a new approach to coherent control of physical systems was introduced, which, instead of relying on formidable theoretical calculations of complex system dynamics, makes use of an appropriate experimental feedback from the system itself to control its evolution. We apply this adaptive feedback approach for enhancement of ionization rates in a femtosecond plasma with the goal of minimization of phase distortions in the amplifier system. With the help of a learning algorithm and survival principles of nature, we teach our laser to control its own phase by using spectral blueshifting in a rapidly created plasma as a feedback to the algorithm. Control of lattice vibrations has long been sought as a means of studying phonon-related processes in solids. In addition, generation and control of large-amplitude optical phonon modes may open a path to femtosecond time- resolved studies of structural phase transitions and production of ultrashort shaped X-ray pulses. We perform pump-probe phase-resolved measurements and control of optical A1g mode in sapphire through shaped-pulse impulsive stimulated Raman scattering (ISRS). We chose this material as a candidate for possible nonlinear

  15. Natural Variation Identifies Multiple Loci Controlling Petal Shape and Size in Arabidopsis thaliana

    PubMed Central

    Abraham, Mary C.; Metheetrairut, Chanatip; Irish, Vivian F.

    2013-01-01

    Natural variation in organ morphologies can have adaptive significance and contribute to speciation. However, the underlying allelic differences responsible for variation in organ size and shape remain poorly understood. We have utilized natural phenotypic variation in three Arabidopsis thaliana ecotypes to examine the genetic basis for quantitative variation in petal length, width, area, and shape. We identified 23 loci responsible for such variation, many of which appear to correspond to genes not previously implicated in controlling organ morphology. These analyses also demonstrated that allelic differences at distinct loci can independently affect petal length, width, area or shape, suggesting that these traits behave as independent modules. We also showed that ERECTA (ER), encoding a leucine-rich repeat (LRR) receptor-like serine-threonine kinase, is a major effect locus determining petal shape. Allelic variation at the ER locus was associated with differences in petal cell proliferation and concomitant effects on petal shape. ER has been previously shown to be required for regulating cell division and expansion in other contexts; the ER receptor-like kinase functioning to also control organ-specific proliferation patterns suggests that allelic variation in common signaling components may nonetheless have been a key factor in morphological diversification. PMID:23418598

  16. Free convection in parallelogram-shaped enclosures with isothermal active walls: viscous shear stress in active systems

    NASA Astrophysics Data System (ADS)

    Baïri, A.; Zarco-Pernia, E.; García de María, J.-M.; Laraqi, N.

    2012-10-01

    Thermocouples are often used for thermoregulation of active thermal systems. When the junctions of these sensors are under a natural convection flow, it is necessary to take into account the viscous stress that can affect the measurement of temperature and therefore the regulation set points. The main objective of this work is to study the viscous shear stress taking place close to the active hot wall in closed air-filled cavities of parallelogrammic shape. The influence of shear stress is examined for different inclination angles of the cavity and large Rayleigh numbers which are usual in thermal applications. The local stress distributions are presented for the steady state for all the geometric configurations considered. The Nusselt number at the hot wall as well as the temperature and stream function distributions in the cavities are also included. The findings obtained from the numerical simulation using the finite volume method are validated by thermal measurements on an experimental cavity. This study confirms the need to properly choose the location of thermocouples in the reference cell used for controlling the active system.

  17. Vibration and shape control of hinged light structures using electromagnetic forces

    NASA Astrophysics Data System (ADS)

    Matsuzaki, Yuji; Miyachi, Shigenobu; Sasaki, Toshiyuki

    2003-08-01

    This paper describes a new electromagnetic device for vibration control of a light-weighted deployable/retractable structure which consists of many small units connected with mechanical hinges. A typical example of such a structure is a solar cell paddle of an artificial satellite which is composed of many thin flexible blankets connected in series. Vibration and shape control of the paddle is not easy, because control force and energy do not transmit well between the blankets which are discretely connected by hinges with each other. The new device consists of a permanent magnet glued along an edge of a blanket and an electric current-conducting coil glued along an adjoining edge of another adjacent blanket. Conduction of the electric current in a magnetic field from the magnet generates an electromagnetic force on the coil. By changing the current in the coil, therefore, we may control the vibration and shape of the blankets. To confirm the effectiveness of the new device, constructing a simple paddle model consisting eight hinge- panels, we have carried out a model experiment of vibration and shape control of the paddle. In addition, a numerical simulation of vibration control of the hinge structure is performed to compare with measured data.

  18. Numerical simulation of the activation behavior of thermal shape memory alloys

    NASA Astrophysics Data System (ADS)

    Neugebauer, Reimund; Bucht, André; Pagel, Kenny; Jung, Jakob

    2010-04-01

    Problems in using shape memory alloys (SMA) in industrial applications are often caused by the fragmentary knowledge of the complex activation behavior. To solve this problem, Fraunhofer IWU developed a Matlab®-based simulation tool to emulate the properties of a SMA wire based on the energy balance. The contained terms result of the characteristic material behavior combined with thermal, electrical, and mechanical conditions. Model validation is performed by laboratory tests. It is shown that there is almost no difference between the measured and the simulated actuator movement. Due to the good quality of the model it is possible to use it in a control loop. Knowing current and voltage enables the computation of the electrical resistance of the actuator and can therefore be used for feedback control. Implementation of the results into industrial applications is exemplified by integration of an actuator in a flap as used in air condition systems of cars. Furthermore, the SMA-based drive will be compared to an electromechanical drive.

  19. On-Demand Removal of Bacterial Biofilms via Shape Memory Activation.

    PubMed

    Gu, Huan; Lee, Sang Won; Buffington, Shelby Lois; Henderson, James H; Ren, Dacheng

    2016-08-24

    Bacterial biofilms are a major cause of chronic infections and biofouling; however, effective removal of established biofilms remains challenging. Here we report a new strategy for biofilm control using biocompatible shape memory polymers with defined surface topography. These surfaces can both prevent bacterial adhesion and remove established biofilms upon rapid shape change with moderate increase of temperature, thereby offering more prolonged antifouling properties. We demonstrate that this strategy can achieve a total reduction of Pseudomonas aeruginosa biofilms by 99.9% compared to the static flat control. It was also found effective against biofilms of Staphylococcus aureus and an uropathogenic strain of Escherichia coli. PMID:27517738

  20. Somatostatin and Somatostatin-Containing Neurons in Shaping Neuronal Activity and Plasticity

    PubMed Central

    Liguz-Lecznar, Monika; Urban-Ciecko, Joanna; Kossut, Malgorzata

    2016-01-01

    Since its discovery over four decades ago, somatostatin (SOM) receives growing scientific and clinical interest. Being localized in the nervous system in a subset of interneurons somatostatin acts as a neurotransmitter or neuromodulator and its role in the fine-tuning of neuronal activity and involvement in synaptic plasticity and memory formation are widely recognized in the recent literature. Combining transgenic animals with electrophysiological, anatomical and molecular methods allowed to characterize several subpopulations of somatostatin-containing interneurons possessing specific anatomical and physiological features engaged in controlling the output of cortical excitatory neurons. Special characteristic and connectivity of somatostatin-containing neurons set them up as significant players in shaping activity and plasticity of the nervous system. However, somatostatin is not just a marker of particular interneuronal subpopulation. Somatostatin itself acts pre- and postsynaptically, modulating excitability and neuronal responses. In the present review, we combine the knowledge regarding somatostatin and somatostatin-containing interneurons, trying to incorporate it into the current view concerning the role of the somatostatinergic system in cortical plasticity. PMID:27445703

  1. Multistep-shaping control based on the static and dynamic behavior of nonlinear optical torsional micromirror

    NASA Astrophysics Data System (ADS)

    Bai, Cheng; Huang, Jin

    2014-05-01

    Electrostatically driven torsional micromirrors are suitable for optical microelectromechanical systems due to their good dynamic response, low adhesion, and simple structure for large-scale-integrated applications. For these devices, how to eliminate the excessive residual vibration in order to achieve more accurate positioning and faster switching is an important research topic. Because of the known nonlinearity issues, traditional shaping techniques based on linear theories are not suitable for nonlinear torsional micromirrors. In addition, due to the difficulties in calculating energy dissipation, the existing nonlinear command shaping techniques using energy method have neglected the effect of damping. We analyze the static and dynamic behavior of the electrostatically actuated torsional micromirrors. Based on the response of these devices, a multistep-shaping control considering the damping effects and the nonlinearity is proposed. Compared to the conventional closed-loop control, the proposed multistep-shaping control is a feedforward approach which can yield a good enough performance without extra sensors and actuators. Simulation results show that, without changing the system structure, the preshaping input reduces the settling time from 4.3 to 0.97 ms, and the overshoot percentage of the mirror response is decreased from 33.2% to 0.2%.

  2. From active shape model to active optical flow model: a shape-based approach to predicting voxel-level dose distributions in spine SBRT

    NASA Astrophysics Data System (ADS)

    Liu, Jianfei; Wu, Q. Jackie; Kirkpatrick, John P.; Yin, Fang-Fang; Yuan, Lulin; Ge, Yaorong

    2015-03-01

    Prediction of achievable dose distribution in spine stereotactic body radiation therapy (SBRT) can help in designing high-quality treatment plans to maximally protect spinal cords and to effectively control tumours. Dose distributions at spinal cords are primarily affected by the shapes of adjacent planning target volume (PTV) contours. In this work, we estimate such contour effects and predict dose distributions by exploring active optical flow model (AOFM) and active shape model (ASM). We first collect a sequence of dose sub-images and PTV contours near spinal cords from fifteen SBRT plans in the training dataset. The data collection is then classified into five groups according to the PTV locations in relation to spinal cords. In each group, we randomly choose a dose sub-image as the reference and register all other sub-images to the reference using an optical flow method. AOFM is then constructed by importing optical flow vectors and dose values into the principal component analysis (PCA). Similarly, we build ASM by using PCA on PTV contour points. The correlation between ASM and AOFM is estimated via a stepwise multiple regression model. When predicting dose distribution of a new case, the group is first determined based on the PTV contour. The prediction model of the selected group is used to estimate dose distributions by mapping the PTV contours from the ASM space to the AOFM space. This method was validated on fifteen SBRT plans in the testing dataset. Analysis of dose-volume histograms revealed that the important D2%, D5%, D10% and D0.1cc dosimetric parameters of spinal cords between the prediction and the clinical plans were 11.7  ±  1.7 Gy versus 11.8  ±  1.7 Gy (p = 0.95), 10.9  ±  1.7 Gy versus 11.1  ±  1.9 Gy (p = 0.8295), 10.2  ±  1.6 Gy versus 10.1  ±  1.7 (p = 0.9036) and 11.2  ±  2.0 Gy versus 11.1  ±  2.2 Gy (p = 0.5208), respectively. Here, the ‘cord’ is the spinal cord proper (not the

  3. Differential hippocampal shapes in posterior cortical atrophy patients: A comparison with control and typical AD subjects

    PubMed Central

    Macdonald, Kate E.; Leung, Kelvin K.; Young, Jonathan; Pepple, Tracey; Lehmann, Manja; Zuluaga, Maria A.; Cardoso, M. Jorge; Schott, Jonathan M.; Ourselin, Sebastien; Crutch, Sebastian; Fox, Nick C.; Barnes, Josephine

    2015-01-01

    Abstract Posterior cortical atrophy (PCA) is a neurodegenerative syndrome characterized by predominant visual deficits and parieto‐occipital atrophy, and is typically associated with Alzheimer's disease (AD) pathology. In AD, assessment of hippocampal atrophy is widely used in diagnosis, research, and clinical trials; its utility in PCA remains unclear. Given the posterior emphasis of PCA, we hypothesized that hippocampal shape measures may give additional group differentiation information compared with whole‐hippocampal volume assessments. We investigated hippocampal volume and shape in subjects with PCA (n = 47), typical AD (n = 29), and controls (n = 48). Hippocampi were outlined on MRI scans and their 3D meshes were generated. We compared hippocampal volume and shape between disease groups. Mean adjusted hippocampal volumes were ∼8% smaller in PCA subjects (P < 0.001) and ∼22% smaller in tAD subject (P < 0.001) compared with controls. Significant inward deformations in the superior hippocampal tail were observed in PCA compared with controls even after adjustment for hippocampal volume. Inward deformations in large areas of the hippocampus were seen in tAD subjects compared with controls and PCA subjects, but only localized shape differences remained after adjusting for hippocampal volume. The shape differences observed, even allowing for volume differences, suggest that PCA and tAD are each associated with different patterns of hippocampal tissue loss that may contribute to the differential range and extent of episodic memory dysfunction in the two groups. Hum Brain Mapp 36:5123–5136, 2015. © 2015 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc. PMID:26461053

  4. Femtosecond laser microchannels fabrication based on electrons dynamics control using temporally or spatially shaped pulses

    NASA Astrophysics Data System (ADS)

    Yan, Xueliang; Hu, Jie; Li, Xiaowei; Xia, Bo; Liu, Pengjun; Lu, Yongfeng; Jiang, Lan

    2014-11-01

    With ultrashort pulse durations and ultrahigh power densities, femtosecond laser presents unique advantages of high precision and high quality fabrication of microchannels in transparent materials. In our study, by shaping femtosecond laser pulse energy distribution in temporal or spatial domains, localized transient electrons dynamics and the subsequent processes, such as phase changes, can be controlled, leading to the dramatic increases in the capability of femtosecond laser microchannels fabrication. The temporally shaped femtosecond laser pulse trains can significantly enhance the material removal rate in both water-assisted femtosecond laser drilling and femtosecond laser irradiation followed by chemical etching. Besides, high-aspect-ratio and small-diameter microchannels are drilled by spatially shaped femtosecond laser pulses.

  5. Controlling high harmonics generation by spatial shaping of high-energy femtosecond beam.

    PubMed

    Dubrouil, A; Mairesse, Y; Fabre, B; Descamps, D; Petit, S; Mével, E; Constant, E

    2011-07-01

    We demonstrate controlled high-order harmonic generation in gas using high-energy femtosecond pulses (50 fs-50 mJ on target) by performing spatial shaping of the terrawatt fundamental laser beam. We have developed a two optical paths mirror that can withstand high power and shape the pump beam into a quasi-flat-top profile (super Gaussian) near focus. We observe clear signatures of the spatial shaping on the harmonic beam in terms of profile, divergence, level of signal, and spectrum. The harmonic generation in neon with a quasi-flat-top beam results in a broadband extreme UV beam with extremely low divergence (~340 μrad). PMID:21725453

  6. Active control technology and the use of multiple control surfaces

    NASA Technical Reports Server (NTRS)

    Hart, J. E.

    1976-01-01

    Needed criteria for active control technology applications in commercial transports are lacking. Criteria for redundancy requirements, believed to be consistent with certification philosophy, are postulated to afford a discussion of the relative value of multiple control surfaces. The control power and frequency bandpass requirements of various active control technology applications are shown to be such that multiple control surfaces offer advantages in minimizing the hydraulic or auxiliary power for the control surface actuators.

  7. Active Spacecraft Potential Control Investigation

    NASA Astrophysics Data System (ADS)

    Torkar, K.; Nakamura, R.; Tajmar, M.; Scharlemann, C.; Jeszenszky, H.; Laky, G.; Fremuth, G.; Escoubet, C. P.; Svenes, K.

    2016-03-01

    In tenuous plasma the floating potential of sunlit spacecraft reaches tens of volts, positive. The corresponding field disturbs measurements of the ambient plasma by electron and ion sensors and can reduce micro-channel plate lifetime in electron detectors owing to large fluxes of attracted photoelectrons. Also the accuracy of electric field measurements may suffer from a high spacecraft potential. The Active Spacecraft Potential Control (ASPOC) neutralizes the spacecraft potential by releasing positive charge produced by indium ion emitters. The method has been successfully applied on other spacecraft such as Cluster and Double Star. Two ASPOC units are present on each spacecraft. Each unit contains four ion emitters, whereby one emitter per instrument is operated at a time. ASPOC for the Magnetospheric Multiscale (MMS) mission includes new developments in the design of the emitters and the electronics. New features include the use of capillaries instead of needles, new materials for the emitters and their internal thermal insulators, an extended voltage and current range of the electronics, both for ion emission and heating purposes, and a more capable control software. This enables lower spacecraft potentials, higher reliability, and a more uniform potential structure in the spacecraft's sheath compared to previous missions. Results from on-ground testing demonstrate compliance with requirements. Model calculations confirm the findings from previous applications that the plasma measurements will not be affected by the beam's space charge. Finally, the various operating modes to adapt to changing boundary conditions are described along with the main data products.

  8. Intact vinculin protein is required for control of cell shape, cell mechanics, and rac-dependent lamellipodia formation

    NASA Technical Reports Server (NTRS)

    Goldmann, Wolfgang H.; Ingber, Donald E.

    2002-01-01

    Studies were carried out using vinculin-deficient F9 embryonic carcinoma (gamma229) cells to analyze the relationship between structure and function within the focal adhesion protein vinculin, in the context of control of cell shape, cell mechanics, and movement. Atomic force microscopy studies revealed that transfection of the head (aa 1-821) or tail (aa 811-1066) domain of vinculin, alone or together, was unable to fully reverse the decrease in cell stiffness, spreading, and lamellipodia formation caused by vinculin deficiency. In contrast, replacement with intact vinculin completely restored normal cell mechanics and spreading regardless of whether its tyrosine phosphorylation site was deleted. Constitutively active rac also only induced extension of lamellipodia when microinjected into cells that expressed intact vinculin protein. These data indicate that vinculin's ability to physically couple integrins to the cytoskeleton, to mechanically stabilize cell shape, and to support rac-dependent lamellipodia formation all appear to depend on its intact three-dimensional structure.

  9. Use of reduction rate as a quantitative knob for controlling the twin structure and shape of palladium nanocrystals.

    PubMed

    Wang, Yi; Peng, Hsin-Chieh; Liu, Jingyue; Huang, Cheng Zhi; Xia, Younan

    2015-02-11

    Kinetic control is a powerful means for maneuvering the twin structure and shape of metal nanocrystals and thus optimizing their performance in a variety of applications. However, there is only a vague understanding of the explicit roles played by reaction kinetics due to the lack of quantitative information about the kinetic parameters. With Pd as an example, here we demonstrate that kinetic parameters, including rate constant and activation energy, can be derived from spectroscopic measurements and then used to calculate the initial reduction rate and further have this parameter quantitatively correlated with the twin structure of a seed and nanocrystal. On a quantitative basis, we were able to determine the ranges of initial reduction rates required for the formation of nanocrystals with a specific twin structure, including single-crystal, multiply twinned, and stacking fault-lined. This work represents a major step forward toward the deterministic syntheses of colloidal noble-metal nanocrystals with specific twin structures and shapes. PMID:25629786

  10. Application of smart materials to helicopter rotor active control

    NASA Astrophysics Data System (ADS)

    Straub, Friedrich K.; Ealey, Mark A.; Schetky, Lawrence M.

    1997-05-01

    Helicopter design is limited by the compromise inherent in meeting hover and forward flight requirements, and the unsteady environment encountered in forward flight. Active control of helicopter rotors using smart material, in-blade actuation can overcome these barriers and provide substantial reductions in noise and vibrations and improved performance. The present study covers the blade/actuator integration and actuator development for a full scale system to demonstrate active control of noise and vibrations as well as inflight blade tracking on the MD Explorer helicopter. A piezoelectric multilayer stack actuator, driving a trailing edge flap, is used for active control. A shape memory alloy torsion actuator, driving a trailing edge trim tab, is used for inflight tracking. Overall, this DARPA sponsored program entails the design, development, and fabrication of the full scale active control rotor system. If successful, an entry in the NASA Ames 40 X 80 foot wind tunnel and flight tests are planned for a follow on program.

  11. Actively controlled thin-shell space optics

    NASA Astrophysics Data System (ADS)

    Denoyer, Keith K.; Flint, Eric M.; Main, John A.; Lindler, Jason E.

    2003-08-01

    Increasingly, scientific and military missions require the use of space-based optical systems. For example, new capabilities are required for imaging terrestrial like planets, for surveillance, and for directed energy applications. Given the difficulties in producing and launching large optics, it is doubtful that refinements of conventional technology will meet future needs, particularly in a cost-effective manner. To meet this need, recent research has been investigating the feasibility of a new class of ultra-lightweight think-skin optical elements that combine recent advances in lightweight thermally formed materials, active materials, and novel sensing and control architectures. If successful, the approach may lead to an order of magnitude reduction in space optics areal density, improved large scale manufacturing capability, and dramatic reductions in manufacturing and launch costs. In a recent effort, a one meter thin-film mirror like structure was fabricated. This paper provides an overview of tools used to model and simulate this structure as well as results from structural dynamic testing. In addition, progress in the area of non-contact global shape control using smart materials is presented.

  12. Activity and effective connectivity of parietal and occipital cortical regions during haptic shape perception.

    PubMed

    Peltier, Scott; Stilla, Randall; Mariola, Erica; LaConte, Stephen; Hu, Xiaoping; Sathian, K

    2007-02-01

    It is now widely accepted that visual cortical areas are active during normal tactile perception, but the underlying mechanisms are still not clear. The goal of the present study was to use functional magnetic resonance imaging (fMRI) to investigate the activity and effective connectivity of parietal and occipital cortical areas during haptic shape perception, with a view to potentially clarifying the role of top-down and bottom-up inputs into visual areas. Subjects underwent fMRI scanning while engaging in discrimination of haptic shape or texture, and in separate runs, visual shape or texture. Accuracy did not differ significantly between tasks. Haptic shape-selective regions, identified on a contrast between the haptic shape and texture conditions in individual subjects, were found bilaterally in the postcentral sulcus (PCS), multiple parts of the intraparietal sulcus (IPS) and the lateral occipital complex (LOC). The IPS and LOC foci tended to be shape-selective in the visual modality as well. Structural equation modelling was used to study the effective connectivity among the haptic shape-selective regions in the left hemisphere, contralateral to the stimulated hand. All possible models were tested for their fit to the correlations among the observed time-courses of activity. Two equivalent models emerged as the winners. These models, which were quite similar, were characterized by both bottom-up paths from the PCS to parts of the IPS, and top-down paths from the LOC and parts of the IPS to the PCS. We conclude that interactions between unisensory and multisensory cortical areas involve bidirectional information flow. PMID:16616940

  13. Phase control of a two-photon transition with shaped femtosecond laser-pulse sequences

    SciTech Connect

    Praekelt, A.; Wollenhaupt, M.; Sarpe-Tudoran, C.; Baumert, T.

    2004-12-01

    Phase effects in a quantum control experiment on the two-photon transition 4s <-<- 3s of atomic sodium are studied. In our experiment, we combine the generation of phase-locked interferometrically generated pulses with pulse-shaping techniques to study in detail the interplay of optical and quantum-mechanical phases. Subtle differences in the physical realization of the pulse sequences produce large difference in the control objective--the 4s population. The control mechanisms of more complex pulse sequences generated by periodic and discontinuous phase-modulation functions are investigated systematically and analyzed on the basis of quantum-mechanical interference.

  14. Complex shape product tolerance and accuracy control method for virtual assembly

    NASA Astrophysics Data System (ADS)

    Ma, Huiping; Jin, Yuanqiang; Zhang, Xiaoguang; Zhou, Hai

    2015-02-01

    The simulation of virtual assembly process for engineering design lacks of accuracy in the software of three-dimension CAD at present. Product modeling technology with tolerance, assembly precision preanalysis technique and precision control method are developed. To solve the problem of lack of precision information transmission in CAD, tolerance mathematical model of Small Displacement Torsor (SDT) is presented, which can bring about technology transfer and establishment of digital control function for geometric elements from the definition, description, specification to the actual inspection and evaluation process. Current tolerance optimization design methods for complex shape product are proposed for optimization of machining technology, effective cost control and assembly quality of the products.

  15. Formation Mechanism and Shape Control of Monodisperse Magnetic CoFe2O4 Nanocrystals

    SciTech Connect

    Bao, Ningzhong; Shen, Liming; An, Wei; Padhan, Prahallad; Turner, C. H.; Gupta, Arunuba

    2009-07-28

    The formation mechanism and shape control of monodisperse magnetic cobalt ferrite (CoFe2O4) nanocrystals produced by thermolysis of a stoichiometric Co2+Fe2 3+-oleate complex in organic solution has been investigated. Synthesis of the pure ternary CoFe2O4 inverse spinel phase, without formation of any intermediate binary cobalt and iron oxides, is favored by the close thermal decomposition temperature of the Co2+-oleate and Fe3+-oleate precursors. For reaction temperatures between 250 and 320 ˚C, the nucleation and growth dynamics dictate the size and shape evolution of the nanocrystals. Prenucleation of CoFe2O4 occurs at 250-300 ˚C but without any growth of nanocrystals, because the monomer concentration is lower than the critical nucleation concentration. For temperatures in the range of 300-320 ˚C,which is above the thermolysis temperature of the mixed Co2+Fe2 3+-oleate complex, the monomer concentration increases rapidly resulting in homogeneous nucleation. Atomic clusters of CoFe2O4 with size<2 nm are initially formed at 314 ˚C that then grow rapidly when the temperature is raised to 320 ˚C in less than a minute. The shape of the CoFe2O4 nanocrystals can be reproducibly controlled by prolonging the aging time at 320 ˚C, evolving from initial spherical, to spherical-to-cubic, cubic, corner-grown cubic, or starlike shapes. Thus, with careful choice of reaction parameters, such as the precursor concentration and the heating rate, it is possible to achieve large-scale synthesis of shape-controlled monodisperse CoFe2O4 nanocrystals with high yield.

  16. Shape-controlled synthesis of cubic-like selenium nanoparticles via the self-assembly method.

    PubMed

    Luesakul, Urarika; Komenek, Seamkwan; Puthong, Songchan; Muangsin, Nongnuj

    2016-11-20

    The ability to control the morphology of nanoparticles by molecular design and synthesis is gaining increasing attention for achieving improved unique properties. In this work, we designed the chemical structure of a stabilizer for controlling the shape of selenium nanoparticles (SeNPs) via a self-assembly process. When folic acid-gallic acid-N,N,N-trimethyl chitosan (FA-GA-TMC) was used as a stabilizer, SeNPs were observed to self-organize into cubic-like structures with an average size of approximately 300nm. In contrast to the product obtained when unmodified chitosan was used as a stabilizer, this method resulted in spherical shape with an average size of approximately 200nm. The data suggested that the cubic-like SeNPs were controlled by a combination of electrostatic interaction, π-π stacking and hydrogen bonding between neighboring particles. Furthermore, the cubic-like SeNPs exhibited good anticancer efficacy and cellular uptake against breast cancer cells while exhibiting low toxicity against normal cells. These data demonstrates a simple approach for the shape-controlled synthesis of cubic-like SeNPs for biological applications via the self-assembly method. PMID:27561515

  17. Actively compensation of low order aberrations by refractive shaping system for high power slab lasers

    NASA Astrophysics Data System (ADS)

    Xue, Zheng-wei; Guo, Ya-ding; Chen, Zhong-zheng; Li, Shuai; Xu, Yi-ting; Xu, Jian; Wang, Bao-shan; Gong, Ke-ling; Gao, Hong-wei; Bo, Yong; Peng, Qin-jun; Cui, Da-fu; Xu, Zu-yan

    2015-12-01

    We present a compact refractive shaping system for actively compensating low order aberrations of high power slab lasers. The shaping system includes three spherical lenses and two cylindrical lenses. Both theoretical and experimental investigations were performed to evaluate the compensation capability of the refractive shaping system. For a typical input beam with large low order aberrations of peak-to-valley (PV)=66.10λ and root-mean-square (RMS)=16.05λ, adjusting the distance between lenses, the wavefront aberrations are reduced to PV=0.48λ, RMS=0.10λ for the theoretical simulation and PV=0.50λ, RMS=0.11λ for the experimental result, respectively. It indicates that the main low order aberrations of defocus and 0° astigmatism can be significantly compensated by actively adjusting the distance between lenses and the experimental result agree well with the theoretical simulation.

  18. Feedback shape control for deployable mesh reflectors using gain scheduling method

    NASA Astrophysics Data System (ADS)

    Xie, Yangmin; Shi, Hang; Alleyne, Andrew; Yang, Bingen

    2016-04-01

    This paper presents a theoretical study on the dynamic shape control problem of deployable mesh reflectors (DMRs) via feedback approaches. The reflector structure is simplified from a nonlinear model to be quasi-static with respect to temperature variations but dynamic with respect to mechanical vibrations. The orbital cycle is segmented into multiple temperature zones, and an H∞ robust state feedback controller is designed for each zone to guarantee the local stability of the system under the model uncertainty caused by thermal effects and to reject external force disturbances. At the same time, gain scheduling control method is adopted to compensate thermal distortions and to ensure smooth transition response when switching among the local robust controllers. A DMR model is considered in the case study to show the effectiveness of the control approach. The structural vibrations caused by external force disturbances can be sufficiently suppressed in a much shorter time. The closed loop response of the DMR structure shows that much higher surface accuracy is obtained during the orbiting mission compared to the open-loop configuration, and transient focal length and transient de-focus of the reflector are well controlled within the satisfactory bounds, demonstrating the numerical feasibility of the proposed method to solve the dynamic shape control problem of DMRs.

  19. Pulse width modulation-based temperature tracking for feedback control of a shape memory alloy actuator.

    PubMed

    Ayvali, Elif; Desai, Jaydev P

    2014-04-01

    This work presents a temperature-feedback approach to control the radius of curvature of an arc-shaped shape memory alloy (SMA) wire. The nonlinear properties of the SMA such as phase transformation and its dependence on temperature and stress make SMA actuators difficult to control. Tracking a desired trajectory is more challenging than controlling just the position of the SMA actuator since the desired path is continuously changing. Consequently, tracking the desired strain directly or tracking the parameters such as temperature and electrical resistance that are related to strain with a model is a challenging task. Temperature-feedback is an attractive approach when direct measurement of strain is not practical. Pulse width modulation (PWM) is an effective method for SMA actuation and it can be used along with a compensator to control the temperature of the SMA. Using the constitutive model of the SMA, the desired temperature profile can be obtained for a given strain trajectory. A PWM-based nonlinear PID controller with a feed-forward heat transfer model is proposed to use temperature-feedback for tracking a desired temperature trajectory. The proposed controller is used during the heating phase of the SMA actuator. The controller proves to be effective in tracking step-wise and continuous trajectories. PMID:24791130

  20. Pulse width modulation-based temperature tracking for feedback control of a shape memory alloy actuator

    PubMed Central

    Ayvali, Elif; Desai, Jaydev P.

    2013-01-01

    This work presents a temperature-feedback approach to control the radius of curvature of an arc-shaped shape memory alloy (SMA) wire. The nonlinear properties of the SMA such as phase transformation and its dependence on temperature and stress make SMA actuators difficult to control. Tracking a desired trajectory is more challenging than controlling just the position of the SMA actuator since the desired path is continuously changing. Consequently, tracking the desired strain directly or tracking the parameters such as temperature and electrical resistance that are related to strain with a model is a challenging task. Temperature-feedback is an attractive approach when direct measurement of strain is not practical. Pulse width modulation (PWM) is an effective method for SMA actuation and it can be used along with a compensator to control the temperature of the SMA. Using the constitutive model of the SMA, the desired temperature profile can be obtained for a given strain trajectory. A PWM-based nonlinear PID controller with a feed-forward heat transfer model is proposed to use temperature-feedback for tracking a desired temperature trajectory. The proposed controller is used during the heating phase of the SMA actuator. The controller proves to be effective in tracking step-wise and continuous trajectories. PMID:24791130

  1. Shape-controlled ceria-reduced graphene oxide nanocomposites toward high-sensitive in situ detection of nitric oxide.

    PubMed

    Hu, Fang Xin; Xie, Jia Le; Bao, Shu Juan; Yu, Ling; Li, Chang Ming

    2015-08-15

    Nitric oxide (NO) is an important signal molecule released by most cancer cells under drug stimulation or/and disease development but it is extremely challenging to in situ while real-time sensitively detect NO due to its large diffusivity, low concentration and fast decay. Herein, shape-controlled reduced graphene oxide nanocomposing with ceria (rGO-CeO2) was synthesized via hydrothermal reaction to construct a highly sensitive real-time sensing platform for NO detection. The crystal shape of CeO2 nanoparticles in rGO-CeO2 composites significantly affects the sensing performance of rGO-CeO2, of which the regular hexagonal nanocrystal CeO2 achieves the highest sensitivity (1676.06 mA cm(-2) M(-1)), a wide dynamic range (18.0 nM to 5.6 µM) and a low detection limit (9.6 nM). This attributes to a synergical effect from high catalytic activity of the specifically shaped CeO2 nanocrystal and good conductivity/high surface area of rGO. This work demonstrates a way by rationally compose individual merit components while well control the nanostructure for a superior synergistic effect to build a smart sensing platform, while offering a great application potential to sensitively real-time detect NO released from living cells for diagnosis or/and studies of complicated biological processes. PMID:25840016

  2. Elemental Anisotropic Growth and Atomic-Scale Structure of Shape-Controlled Octahedral Pt-Ni-Co Alloy Nanocatalysts.

    PubMed

    Arán-Ais, Rosa M; Dionigi, Fabio; Merzdorf, Thomas; Gocyla, Martin; Heggen, Marc; Dunin-Borkowski, Rafal E; Gliech, Manuel; Solla-Gullón, José; Herrero, Enrique; Feliu, Juan M; Strasser, Peter

    2015-11-11

    Multimetallic shape-controlled nanoparticles offer great opportunities to tune the activity, selectivity, and stability of electrocatalytic surface reactions. However, in many cases, our synthetic control over particle size, composition, and shape is limited requiring trial and error. Deeper atomic-scale insight in the particle formation process would enable more rational syntheses. Here we exemplify this using a family of trimetallic PtNiCo nanooctahedra obtained via a low-temperature, surfactant-free solvothermal synthesis. We analyze the competition between Ni and Co precursors under coreduction "one-step" conditions when the Ni reduction rates prevailed. To tune the Co reduction rate and final content, we develop a "two-step" route and track the evolution of the composition and morphology of the particles at the atomic scale. To achieve this, scanning transmission electron microscopy and energy dispersive X-ray elemental mapping techniques are used. We provide evidence of a heterogeneous element distribution caused by element-specific anisotropic growth and create octahedral nanoparticles with tailored atomic composition like Pt1.5M, PtM, and PtM1.5 (M = Ni + Co). These trimetallic electrocatalysts have been tested toward the oxygen reduction reaction (ORR), showing a greatly enhanced mass activity related to commercial Pt/C and less activity loss than binary PtNi and PtCo after 4000 potential cycles. PMID:26441293

  3. Scalable shape-controlled fabrication of curved microstructures using a femtosecond laser wet-etching process.

    PubMed

    Bian, Hao; Yang, Qing; Chen, Feng; Liu, Hewei; Du, Guangqing; Deng, Zefang; Si, Jinhai; Yun, Feng; Hou, Xun

    2013-07-01

    Materials with curvilinear surface microstructures are highly desirable for micro-optical and biomedical devices. However, realization of such devices efficiently remains technically challenging. This paper demonstrates a facile and flexible method to fabricate curvilinear microstructures with controllable shapes and dimensions. The method composes of femtosecond laser exposures and chemical etching process with the hydrofluoric acid solutions. By fixed-point and step-in laser irradiations followed by the chemical treatments, concave microstructures with different profiles such as spherical, conical, bell-like and parabola were fabricated on silica glasses. The convex structures were replicated on polymers by the casting replication process. In this work, we used this technique to fabricate high-quality microlens arrays and high-aspect-ratio microwells which can be used in 3D cell culture. This approach offers several advantages such as high-efficient, scalable shape-controllable and easy manipulations. PMID:23623098

  4. Atypical Balance between Occipital and Fronto-Parietal Activation for Visual Shape Extraction in Dyslexia

    PubMed Central

    Zhang, Ying; Whitfield-Gabrieli, Susan; Christodoulou, Joanna A.; Gabrieli, John D. E.

    2013-01-01

    Reading requires the extraction of letter shapes from a complex background of text, and an impairment in visual shape extraction would cause difficulty in reading. To investigate the neural mechanisms of visual shape extraction in dyslexia, we used functional magnetic resonance imaging (fMRI) to examine brain activation while adults with or without dyslexia responded to the change of an arrow’s direction in a complex, relative to a simple, visual background. In comparison to adults with typical reading ability, adults with dyslexia exhibited opposite patterns of atypical activation: decreased activation in occipital visual areas associated with visual perception, and increased activation in frontal and parietal regions associated with visual attention. These findings indicate that dyslexia involves atypical brain organization for fundamental processes of visual shape extraction even when reading is not involved. Overengagement in higher-order association cortices, required to compensate for underengagment in lower-order visual cortices, may result in competition for top-down attentional resources helpful for fluent reading. PMID:23825653

  5. IgE epitope proximity determines immune complex shape and effector cell activation capacity

    PubMed Central

    Gieras, Anna; Linhart, Birgit; Roux, Kenneth H.; Dutta, Moumita; Khodoun, Marat; Zafred, Domen; Cabauatan, Clarissa R.; Lupinek, Christian; Weber, Milena; Focke-Tejkl, Margarete; Keller, Walter; Finkelman, Fred D.; Valenta, Rudolf

    2016-01-01

    Background IgE-allergen complexes induce mast cell and basophil activation and thus immediate allergic inflammation. They are also important for IgE-facilitated allergen presentation to T cells by antigen-presenting cells. Objective To investigate whether the proximity of IgE binding sites on an allergen affects immune complex shape and subsequent effector cell activation in vitro and in vivo. Methods We constructed artificial allergens by grafting IgE epitopes in different numbers and proximity onto a scaffold protein. The shape of immune complexes formed between artificial allergens and the corresponding IgE was studied by negative-stain electron microscopy. Allergenic activity was determined using basophil activation assays. Mice were primed with IgE, followed by injection of artificial allergens to evaluate their in vivo allergenic activity. Severity of systemic anaphylaxis was measured by changes in body temperature. Results We could demonstrate simultaneous binding of 4 IgE antibodies in close vicinity to each other. The proximity of IgE binding sites on allergens influenced the shape of the resulting immune complexes and the magnitude of effector cell activation and in vivo inflammation. Conclusions Our results demonstrate that the proximity of IgE epitopes on an allergen affects its allergenic activity. We thus identified a novel mechanism by which IgE-allergen complexes regulate allergic inflammation. This mechanism should be important for allergy and other immune complex–mediated diseases. PMID:26684291

  6. Perceiving Object Shape from Specular Highlight Deformation, Boundary Contour Deformation, and Active Haptic Manipulation.

    PubMed

    Norman, J Farley; Phillips, Flip; Cheeseman, Jacob R; Thomason, Kelsey E; Ronning, Cecilia; Behari, Kriti; Kleinman, Kayla; Calloway, Autum B; Lamirande, Davora

    2016-01-01

    It is well known that motion facilitates the visual perception of solid object shape, particularly when surface texture or other identifiable features (e.g., corners) are present. Conventional models of structure-from-motion require the presence of texture or identifiable object features in order to recover 3-D structure. Is the facilitation in 3-D shape perception similar in magnitude when surface texture is absent? On any given trial in the current experiments, participants were presented with a single randomly-selected solid object (bell pepper or randomly-shaped "glaven") for 12 seconds and were required to indicate which of 12 (for bell peppers) or 8 (for glavens) simultaneously visible objects possessed the same shape. The initial single object's shape was defined either by boundary contours alone (i.e., presented as a silhouette), specular highlights alone, specular highlights combined with boundary contours, or texture. In addition, there was a haptic condition: in this condition, the participants haptically explored with both hands (but could not see) the initial single object for 12 seconds; they then performed the same shape-matching task used in the visual conditions. For both the visual and haptic conditions, motion (rotation in depth or active object manipulation) was present in half of the trials and was not present for the remaining trials. The effect of motion was quantitatively similar for all of the visual and haptic conditions-e.g., the participants' performance in Experiment 1 was 93.5 percent higher in the motion or active haptic manipulation conditions (when compared to the static conditions). The current results demonstrate that deforming specular highlights or boundary contours facilitate 3-D shape perception as much as the motion of objects that possess texture. The current results also indicate that the improvement with motion that occurs for haptics is similar in magnitude to that which occurs for vision. PMID:26863531

  7. Perceiving Object Shape from Specular Highlight Deformation, Boundary Contour Deformation, and Active Haptic Manipulation

    PubMed Central

    Cheeseman, Jacob R.; Thomason, Kelsey E.; Ronning, Cecilia; Behari, Kriti; Kleinman, Kayla; Calloway, Autum B.; Lamirande, Davora

    2016-01-01

    It is well known that motion facilitates the visual perception of solid object shape, particularly when surface texture or other identifiable features (e.g., corners) are present. Conventional models of structure-from-motion require the presence of texture or identifiable object features in order to recover 3-D structure. Is the facilitation in 3-D shape perception similar in magnitude when surface texture is absent? On any given trial in the current experiments, participants were presented with a single randomly-selected solid object (bell pepper or randomly-shaped “glaven”) for 12 seconds and were required to indicate which of 12 (for bell peppers) or 8 (for glavens) simultaneously visible objects possessed the same shape. The initial single object’s shape was defined either by boundary contours alone (i.e., presented as a silhouette), specular highlights alone, specular highlights combined with boundary contours, or texture. In addition, there was a haptic condition: in this condition, the participants haptically explored with both hands (but could not see) the initial single object for 12 seconds; they then performed the same shape-matching task used in the visual conditions. For both the visual and haptic conditions, motion (rotation in depth or active object manipulation) was present in half of the trials and was not present for the remaining trials. The effect of motion was quantitatively similar for all of the visual and haptic conditions–e.g., the participants’ performance in Experiment 1 was 93.5 percent higher in the motion or active haptic manipulation conditions (when compared to the static conditions). The current results demonstrate that deforming specular highlights or boundary contours facilitate 3-D shape perception as much as the motion of objects that possess texture. The current results also indicate that the improvement with motion that occurs for haptics is similar in magnitude to that which occurs for vision. PMID:26863531

  8. Wnt ligand/Frizzled 2 receptor signaling regulates tube shape and branch-point formation in the lung through control of epithelial cell shape

    PubMed Central

    Kadzik, Rachel S.; Cohen, Ethan David; Morley, Michael P.; Stewart, Kathleen M.; Lu, Min Min; Morrisey, Edward E.

    2014-01-01

    Changing the morphology of a simple epithelial tube to form a highly ramified branching network requires changes in cell behavior that lead to tissue-wide changes in organ shape. How epithelial cells in branched organs modulate their shape and behavior to promote bending and sculpting of the epithelial sheet is not well understood, and the mechanisms underlying this process remain obscure. We show that the Wnt receptor Frizzled 2 (Fzd2) is required for domain branch formation during the initial establishment of the respiratory tree. Live imaging and transcriptome analysis of lung-branching morphogenesis demonstrate that Fzd2 promotes changes in epithelial cell length and shape. These changes in cell morphology deform the developing epithelial tube to generate and maintain new domain branches. Fzd2 controls branch formation and the shape of the epithelial tube by regulating Rho signaling and by the localization of phospho-myosin light chain 2, in turn controlling the changes in the shape of epithelial cells during morphogenesis. This study demonstrates the importance of Wnt/Fzd2 signaling in promoting and maintaining changes in epithelial cell shape that affect development of a branching network. PMID:25114215

  9. High Performance Piezoelectric Thin Films for Shape Control in Large Inflatable Structures

    NASA Technical Reports Server (NTRS)

    Neurgaonkar, R. R.; Nelson, J. G.

    1999-01-01

    The objective of this research and development program was to develop PbZr(1-x)Ti(x)O3 (PZT) and Pb(1-x)Ba(x)Nb2O6 (PBN) materials with large piezoelectric response which are suitable for shape control in large inflatable structures. Two approaches were to be considered: (1) direct deposition of PZT and PBN films on flexible plastic or thin metal foil substrates, and (2) deposition on Si followed by fabrication of hybrid structures on mylar or kapton. Testing in shape control concepts was carried out at JPL and based on their results, the required modifications were made in the final film compositions and deposition techniques. The program objective was to identify and then optimize piezoelectric materials for NASA shape control applications. This involved the bulk piezoelectric and photovoltaic responses and the compatibility of the thin films with appropriate substrate structures. Within the PZT system, Rockwell has achieved the highest reported piezoelectric coefficient (d(sub 33) greater than 100 pC/N) of any ceramic composition. We used this experience in piezoelectric technology to establish compositions that can effectively address the issues of this program. The performance of piezoelectric thin films depends directly on d(sub ij) and Epsilon. The challenge was to find PZT compositions that maintained high d(sub ij) and Epsilon, while also exhibiting a large photovoltaic effect and integrate thin films of this composition into the system structure necessary to meet shape control applications. During the course of this program, several PZT and PLZT compositions were identified that meet these requirements. Two such compositions were successfully used in electrical and optical actuation studies of thin film structures.

  10. High Performance Piezoelectric Thin Films for Shape Control in Large Inflatable Structures

    NASA Technical Reports Server (NTRS)

    Neurgaonkar, R. R.; Nelson, J. G.

    1999-01-01

    The objective of this research and development program was to develop PbZr(1-x)Ti(x)O3 (PZT) and Pb(1-x)Ba(x)Nb2O6 (PBN) materials with large piezoelectric response which are suitable for shape control in large inflatable structures. Two approaches were to be considered: (1) direct deposition of PZT and PBN films on flexible plastic or thin metal foil substrates, and (2) deposition on Si followed by fabrication of hybrid structures on mylar or kapton. Testing in shape control concepts was carried out at JPL and based on their results, the required modifications were made in the final film compositions and deposition techniques. The program objective was to identify and then optimize piezoelectric materials for NASA shape control applications. This involved the bulk piezoelectric and photovoltaic responses and the compatibility of the thin films with appropriate substrate structures. Within the PZT system, Rockwell has achieved the highest reported piezoelectric coefficient (d(sub 33) greater than 100 pC/N) of any ceramic composition. We used this experience in piezoelectric technology to establish compositions that can effectively address the issues of this program. The performance of piezoelectric thin films depends directly on d(sub ij) and epsilin. The challenge was to find PZT compositions that maintained high d(sub ij) and epsilon, while also exhibiting a large photovoltaic effect and integrate thin films of this composition into the system structure necessary to meet shape control applications. During the course of this program, several PZT and PLZT compositions were identified that meet these requirements. Two such compositions were successfully used in electrical and optical actuation studies of thin film structures.

  11. Changes in diet and physical activity resulting from the Shape Up Somerville community intervention

    PubMed Central

    2013-01-01

    Background The purpose of this study is to describe the behavioral changes in children resulting from Shape Up Somerville (SUS), a community-based, participatory obesity prevention intervention that used a multi-level, systems-based approach. It was set in Somerville, an urban, culturally diverse community in Massachusetts, USA. Methods This was a non-randomized, controlled 2-year community-based intervention trial with children enrolled in grades 1 to 3 (ages 6-8 years). Overall, the SUS intervention was designed to create environmental and policy change to impact all aspects of a child’s day. Pre-post outcomes were compared between Somerville and two control communities that were chosen based on socio-demographic similarities. Behavioral outcomes were fruit and vegetable and sugar-sweetened beverage consumption; number of organized sports and physical activities per year; walking to and from school; screen and television time; television in bedroom; and dinner in room with television on. These measures were assessed by parent/caregiver report using a 68-item Family Survey Form. Data were analyzed using multiple linear regression, accounting for covariates and clustering by community. Results Intervention group children, compared to the control group, significantly reduced sugar-sweetened beverage consumption (-2.0 ounces per day; 95% CI -3.8 to -0.2), increased participation in organized sports and physical activities (0.20 sports or activities per year; 95% CI 0.06 to 0.33), and reduced their screen time (-0.24 hours per day; 95% CI -0.42 to -0.06). Conclusions Results of this study, particularly intake of sugar-sweetened beverages and screen time, are similar to others that used a multi-level approach to realize change in behavior. These results support the efficacy of a multi-level and systems-based approach for promoting the behavioral changes necessary for childhood obesity prevention. This study is registered at ClinicalTrials.gov as NCT00153322. PMID

  12. Active thermal control system evolution

    NASA Technical Reports Server (NTRS)

    Petete, Patricia A.; Ames, Brian E.

    1991-01-01

    The 'restructured' baseline of the Space Station Freedom (SSF) has eliminated many of the growth options for the Active Thermal Control System (ATCS). Modular addition of baseline technology to increase heat rejection will be extremely difficult. The system design and the available real estate no longer accommodate this type of growth. As the station matures during its thirty years of operation, a demand of up to 165 kW of heat rejection can be expected. The baseline configuration will be able to provide 82.5 kW at Eight Manned Crew Capability (EMCC). The growth paths necessary to reach 165 kW have been identified. Doubling the heat rejection capability of SSF will require either the modification of existing radiator wings or the attachment of growth structure to the baseline truss for growth radiator wing placement. Radiator performance can be improved by enlarging the surface area or by boosting the operating temperature with a heat pump. The optimal solution will require both modifications. The addition of growth structure would permit the addition of a parallel ATCS using baseline technology. This growth system would simplify integration. The feasibility of incorporating these growth options to improve the heat rejection capacity of SSF is under evaluation.

  13. Active control of combustion instability

    SciTech Connect

    Lang, W.; Poinsot, T.; Candel, S.

    1987-12-01

    The principle of 'antisound' is used to construct a method for the suppression of combustion instabilities. This active instability control (AIC) method uses external acoustic excitation by a loudspeaker to suppress the oscillations of a flame. The excitation signal is provided by a microphone located upstream of the flame. This signal is filtered, processed, amplified, and sent to the loudspeaker. The AIC method is validated on a laboratory combustor. It allows the suppression of all unstable modes of the burner for any operating ratio. The influence of the microphone and loudspeaker locations on the performance of the AIC system is described. For a given configuration, domains of stability, i.e., domains where the AIC system parameters provide suppression of the oscillation, are investigated. Measurements of the electric input of the loudspeaker show that the energy consumption of the AIC system is almost negligible and suggest that this method could be used for industrial combustor stabilization. Finally, a simple model describing the effects of the AIC system is developed and its results compared to the experiment.

  14. Method for generating fractal mountains with controllable macroscopic shapes by spectral synthesis

    NASA Astrophysics Data System (ADS)

    Wang, Humin

    1996-03-01

    Let a 2D random function X(x,y) to denote fBm with exponent 0 < H < 1, then its spectral density Sx(u,v) has relation: Sx(u,v) 1/(u2 + v2)H+1. Such algorithm based on fBm has shown us beautiful pictures of fractal mountains. But the mountains (fractal surfaces) were produced naturally by random process. As a result, the macroscopic shapes and global positions of fractal mounts are not controllable. This paper presents a method that generates fractal mountains with controllable macroscopic shapes and positions using spectral synthesis. First, the discrete data of Y(x,y) on finite grids are inputted, and FFT is employed to produce discrete spectral F(u,v). Second, by InvFFT, low frequency components of F(u,v) together with high frequency components of F(u,v) are transformed to produce Z(x,y)--fractal surface. The macroscopic shapes are controlled by low frequency; meanwhile, the high frequency describes texture of fractal mountains.

  15. Shape-Controlled Synthesis of Hybrid Nanomaterials via Three-Dimensional Hydrodynamic Focusing

    PubMed Central

    2015-01-01

    Shape-controlled synthesis of nanomaterials through a simple, continuous, and low-cost method is essential to nanomaterials research toward practical applications. Hydrodynamic focusing, with its advantages of simplicity, low-cost, and precise control over reaction conditions, has been used for nanomaterial synthesis. While most studies have focused on improving the uniformity and size control, few have addressed the potential of tuning the shape of the synthesized nanomaterials. Here we demonstrate a facile method to synthesize hybrid materials by three-dimensional hydrodynamic focusing (3D-HF). While keeping the flow rates of the reagents constant and changing only the flow rate of the buffer solution, the molar ratio of two reactants (i.e., tetrathiafulvalene (TTF) and HAuCl4) within the reaction zone varies. The synthesized TTF–Au hybrid materials possess very different and predictable morphologies. The reaction conditions at different buffer flow rates are studied through computational simulation, and the formation mechanisms of different structures are discussed. This simple one-step method to achieve continuous shape-tunable synthesis highlights the potential of 3D-HF in nanomaterials research. PMID:25268035

  16. 3D nanopore shape control by current-stimulus dielectric breakdown

    NASA Astrophysics Data System (ADS)

    Ying, Cuifeng; Zhang, Yuechuan; Feng, Yanxiao; Zhou, Daming; Wang, Deqiang; Xiang, Yinxiao; Zhou, Wenyuan; Chen, Yongsheng; Du, Chunlei; Tian, Jianguo

    2016-08-01

    We propose a simple and cost-effect method, current-stimulus dielectric breakdown, to manipulate the 3D shapes of the nanochannels in 20-nm-thick SiNx membranes. Besides the precise control of nanopore size, the cone orientation can be determined by the pulse polarity. The cone angle of nanopores can be systematically tuned by simply changing the stimulus pulse waveform, allowing the gradual shape control from conical to obconical. After they are formed, the cone angle of these nanopores can be further tuned in a certain range by adjusting the widening pulse. Such size and 3D shape controllable abiotic nanopores can construct a constriction in the nanochannel and hence produce a sub-nm "sensing zone" to suit any desired bio-sensing or precise DNA sequencing. Using these conical nanopores, 20-nt ssDNA composed of homopolymers (poly(dA)20, poly(dC)20, and poly(dT)20) can be clearly differentiated by their ionic current signals.

  17. On the shape and orientation control of an orbiting shallow spherical shell structure

    NASA Technical Reports Server (NTRS)

    Bainum, P. M.; Reddy, A. S. S. R.

    1982-01-01

    The dynamics of orbiting shallow flexible spherical shell structures under the influence of control actuators was studied. Control laws are developed to provide both attitude and shape control of the structure. The elastic modal frequencies for the fundamental and lower modes are closely grouped due to the effect of the shell curvature. The shell is gravity stabilized by a spring loaded dumbbell type damper attached at its apex. Control laws are developed based on the pole clustering techniques. Savings in fuel consumption can be realized by using the hybrid shell dumbbell system together with point actuators. It is indicated that instability may result by not including the orbital and first order gravity gradient effects in the plant prior to control law design.

  18. On the shape and orientation control of orbiting shallow spherical shell structure

    NASA Technical Reports Server (NTRS)

    Bainum, P. M.; Reddy, A. S. S. R.

    1983-01-01

    The dynamics of orbiting shallow flexible spherical shell structures under the influence of control actuators was studied. Control laws are developed to provide both attitude and shape control of the structure. The elastic modal frequencies for the fundamental and lower modes are closely grouped due to the effect of the shell curvature. The shell is gravity stabilized by a spring loaded dumbell type damper attached at its apex. Control laws are developed based on the pole clustering techniques. Savings in fuel consumption can be realized by using the hybrid shell dumbbell system together with point actuators. It is indicated that instability may result by not including the orbital and first order gravity gradient effects in the plant prior to control law design. Previously announced in STAR as N82-17243

  19. Chemical Control of Lead Sulfide Quantum Dot Shape, Self-Assembly, and Charge Transport

    NASA Astrophysics Data System (ADS)

    McPhail, Martin R.

    Lead(II) sulfide quantum dots (PbS QDs) are a promising excitonic material for numerous application that require that control of fluxes of charge and energy at nanoscale interfaces, such as solar energy conversion, photo- and electrocatalysis, light emitting diodes, chemical sensing, single-electron logic elements, field effect transistors, and photovoltaics. PbS QDs are particularly suitable for photonics applications because they exhibit size-tunable band-edge absorption and fluorescence across the entire near-infrared spectrum, undergo efficient multi-exciton generation, exhibit a long radiative lifetime, and possess an eight-fold degenerate ground-state. The effective integration of PbS QDs into these applications requires a thorough understanding of how to control their synthesis, self-assembly, and charge transport phenomena. In this document, I describe a series of experiments to elucidate three levels of chemical control on the emergent properties of PbS QDs: (1) the role of surface chemistry in controlling PbS QD shape during solvothermal synthesis, (2) the role of QD shape and ligand functionalization in self-assembly at a liquid-air interface, and (3) the role of QD packing structure on steady-state conductivity and transient current dynamics. At the synthetic level (1), I show that the final shape and surface chemistry of PbS QDs is highly sensitive to the formation of organosulfur byproducts by commonly used sulfur reagents. The insight into PbS QD growth gained from this work is then developed to controllably tune PbS QD shape from cubic to octahedral to hexapodal while maintaining QD size. At the following level of QD self-assembly (2), I show how QD size and shape dictate packing geometry in extended 2D arrays and how this packing can be controllably interrupted in mixed monolayers. I also study the role of ligand structure on the reorganization of QD arrays at a liquid-air interface and find that the specific packing defects in QD arrays vary

  20. Feedforward-Feedback Hybrid Control for Magnetic Shape Memory Alloy Actuators Based on the Krasnosel'skii-Pokrovskii Model

    PubMed Central

    Zhou, Miaolei; Zhang, Qi; Wang, Jingyuan

    2014-01-01

    As a new type of smart material, magnetic shape memory alloy has the advantages of a fast response frequency and outstanding strain capability in the field of microdrive and microposition actuators. The hysteresis nonlinearity in magnetic shape memory alloy actuators, however, limits system performance and further application. Here we propose a feedforward-feedback hybrid control method to improve control precision and mitigate the effects of the hysteresis nonlinearity of magnetic shape memory alloy actuators. First, hysteresis nonlinearity compensation for the magnetic shape memory alloy actuator is implemented by establishing a feedforward controller which is an inverse hysteresis model based on Krasnosel'skii-Pokrovskii operator. Secondly, the paper employs the classical Proportion Integration Differentiation feedback control with feedforward control to comprise the hybrid control system, and for further enhancing the adaptive performance of the system and improving the control accuracy, the Radial Basis Function neural network self-tuning Proportion Integration Differentiation feedback control replaces the classical Proportion Integration Differentiation feedback control. Utilizing self-learning ability of the Radial Basis Function neural network obtains Jacobian information of magnetic shape memory alloy actuator for the on-line adjustment of parameters in Proportion Integration Differentiation controller. Finally, simulation results show that the hybrid control method proposed in this paper can greatly improve the control precision of magnetic shape memory alloy actuator and the maximum tracking error is reduced from 1.1% in the open-loop system to 0.43% in the hybrid control system. PMID:24828010

  1. Active Control of Noise Using Actuator/Sensor Arrays

    NASA Technical Reports Server (NTRS)

    Lindner, Douglas K.; Winder, Patrice; Kirby, George

    1996-01-01

    Current research in smart structures is directed toward the integration of many actuators and sensors into a material. In this paper we investigate the possibility of using this instrumentation for active noise control from a vibrating structures. Current technology for reducing radiated sound is limited by the instrumentation for the control system. These control systems employ relatively small numbers of sensors and actuators. Hence, these control systems must rely on a model of the structure to estimate and control the global vibrations that contribute to the far field pressure. For complex, realistic structures the development of such a model is a formidable task. The model is a limiting factor in the continuing development of structural acoustics. In this paper we propose to increase the number of actuators and sensors of a smart material to offset the complexity of the model used for control design. The sensor arrays will be used to directly sense the shape of the structure rather than using a model of the structures to indirectly sense the shape of the structure. The actuator array is used to apply distributed forces to the structure, rather than using the structure itself as a load path. A control system for the active cancellation of sound is derived from standard control system methodologies.

  2. Experimental evaluation of active-member control of precision structures

    NASA Technical Reports Server (NTRS)

    Fanson, James; Blackwood, Gary; Chu, Cheng-Chih

    1989-01-01

    The results of closed loop experiments that use piezoelectric active-members to control the flexible motion of a precision truss structure are described. These experiments are directed toward the development of high-performance structural systems as part of the Control/Structure Interaction (CSI) program at JPL. The focus of CSI activity at JPL is to develop the technology necessary to accurately control both the shape and vibration levels in the precision structures from which proposed large space-based observatories will be built. Structural error budgets for these types of structures will likely be in the sub-micron regime; optical tolerances will be even tighter. In order to achieve system level stability and local positioning at this level, it is generally expected that some form of active control will be required.

  3. Control of Gas Tungsten Arc welding pool shape by trace element addition to the weld pool

    DOEpatents

    Heiple, C.R.; Burgardt, P.

    1984-03-13

    An improved process for Gas Tungsten Arc welding maximizes the depth/width ratio of the weld pool by adding a sufficient amount of a surface active element to insure inward fluid flow, resulting in deep, narrow welds. The process is especially useful to eliminate variable weld penetration and shape in GTA welding of steels and stainless steels, particularly by using a sulfur-doped weld wire in a cold wire feed technique.

  4. Status and trends in active control technology

    NASA Technical Reports Server (NTRS)

    Rediess, H. A.; Szalai, K. J.

    1975-01-01

    The emergence of highly reliable fly-by-wire flight control systems makes it possible to consider a strong reliance on automatic control systems in the design optimization of future aircraft. This design philosophy has been referred to as the control configured vehicle approach or the application of active control technology. Several studies and flight tests sponsored by the Air Force and NASA have demonstrated the potential benefits of control configured vehicles and active control technology. The present status and trends of active control technology are reviewed and the impact it will have on aircraft designs, design techniques, and the designer is predicted.

  5. Shape controllers enhance the efficiency of graphene-TiO2 hybrids in pollutant abatement

    NASA Astrophysics Data System (ADS)

    Sordello, F.; Odorici, E.; Hu, K.; Minero, C.; Cerruti, M.; Calza, P.

    2016-02-01

    The addition of graphene nanoplatelets (GNP) to TiO2 nanoparticles (NPs) has been recently considered as a method to improve the photocatalytic efficiency of TiO2 by favoring charge carrier separation. Here, we show that it is possible to improve the efficiency of GNP-TiO2 composites by controlling the shape, stability, and facets of TiO2 NPs grown on GNP functionalized with either COOH or NH2 groups, while adding ethylendiamine (EDA) and oleic acid (OA) during a hydrothermal synthesis. We studied the photocatalytic activity of all synthesized materials under UV-A light using phenol as a target molecule. GNP-TiO2 composites synthesized on COOH-functionalized GNP, exposing {101} facets, were more efficient at abating phenol than those synthesized on NH2-functionalized GNP, exposing {101} and {100} facets. However, neither of these composites was stable under irradiation. The addition of both OA and EDA stabilized the materials under irradiation; however, only the composite prepared on COOH-functionalized GNP in the presence of EDA showed a significant increase in phenol degradation rate, leading to results that were better than those obtained with TiO2 alone. This result can be attributed to Ti-OH complexation by EDA, which protects GNP from oxidation. The orientation of the most reducing {101} facets toward GNP and the most oxidizing {100} facets toward the solution induces faster phenol degradation owing to a better separation of the charge carriers.The addition of graphene nanoplatelets (GNP) to TiO2 nanoparticles (NPs) has been recently considered as a method to improve the photocatalytic efficiency of TiO2 by favoring charge carrier separation. Here, we show that it is possible to improve the efficiency of GNP-TiO2 composites by controlling the shape, stability, and facets of TiO2 NPs grown on GNP functionalized with either COOH or NH2 groups, while adding ethylendiamine (EDA) and oleic acid (OA) during a hydrothermal synthesis. We studied the photocatalytic

  6. Midpoint Shapes.

    ERIC Educational Resources Information Center

    Welchman, Rosamond; Urso, Josephine

    2000-01-01

    Emphasizes the importance of children exploring hands-on and minds-on mathematics. Presents a midpoint shape activity for students to explore the midpoint shape of familiar quadrilaterals, such as squares and rectangles. (KHR)

  7. Tracking Control of a Magnetic Shape Memory Actuator Using an Inverse Preisach Model with Modified Fuzzy Sliding Mode Control.

    PubMed

    Lin, Jhih-Hong; Chiang, Mao-Hsiung

    2016-01-01

    Magnetic shape memory (MSM) alloys are a new class of smart materials with extraordinary strains up to 12% and frequencies in the range of 1 to 2 kHz. The MSM actuator is a potential device which can achieve high performance electromagnetic actuation by using the properties of MSM alloys. However, significant non-linear hysteresis behavior is a significant barrier to control the MSM actuator. In this paper, the Preisach model was used, by capturing experiments from different input signals and output responses, to model the hysteresis of MSM actuator, and the inverse Preisach model, as a feedforward control, provided compensational signals to the MSM actuator to linearize the hysteresis non-linearity. The control strategy for path tracking combined the hysteresis compensator and the modified fuzzy sliding mode control (MFSMC) which served as a path controller. Based on the experimental results, it was verified that a tracking error in the order of micrometers was achieved. PMID:27571081

  8. Controlling the spectral shape of nonlinear Thomson scattering with proper laser chirping

    NASA Astrophysics Data System (ADS)

    Rykovanov, S. G.; Geddes, C. G. R.; Schroeder, C. B.; Esarey, E.; Leemans, W. P.

    2016-03-01

    Effects of nonlinearity in Thomson scattering of a high intensity laser pulse from electrons are analyzed. Analytic expressions for laser pulse shaping in frequency (chirping) are obtained which control spectrum broadening for high laser pulse intensities. These analytic solutions allow prediction of the spectral form and required laser parameters to avoid broadening. Results of analytical and numerical calculations agree well. The control over the scattered radiation bandwidth allows narrow bandwidth sources to be produced using high scattering intensities, which in turn greatly improves scattering yield for future x- and gamma-ray sources.

  9. Invisible cloak design with controlled constitutive parameters and arbitrary shaped boundaries through Helmholtz's equation.

    PubMed

    Chen, Xi; Fu, Yunqi; Yuan, Naichang

    2009-03-01

    An approach to design an invisible cloak with controlled constitutive parameters and arbitrary shaped boundaries is presented. Helmholtz's equation is adopted to establish a mapping between original and transformed coordinates inside the cloak. Then the constitutive parameters are obtained by the established mapping. The analytical solution of a regular cloak and the numerical solution of an irregular cloak both verify that that our method will guide electromagnetic wave efficiently and control the constitutive parameters of the cloak conveniently. It has great significance in realizing a cloak practically. PMID:19259197

  10. Experimental study of absorption band controllable planar metamaterial absorber using asymmetrical snowflake-shaped configuration

    NASA Astrophysics Data System (ADS)

    Huang, Yongjun; Tian, Yiran; Wen, Guangjun; Zhu, Weiren

    2013-05-01

    In this paper, we systematically discuss a novel planar metamaterial absorber (PMA) based on asymmetrical snowflake-shaped resonators, which can exhibit two distinctly different absorption states, single- and dual-band absorptions, by controlling the branch lengths of the proposed resonators. Numerical simulations and experimental measurements are employed to investigate these two kinds of absorption characteristic in an X-band rectangular waveguide. Both results indicate that such a PMA exhibits a wide range of controllable operating frequencies for the single- and dual-band conditions. The proposed PMA is simple and easy to make, and it has wide applications in the fields of stealth technologies, thermal detectors, and imaging.

  11. Dynamical Control of the Shape and Size of Stereocilia and Microvilli

    PubMed Central

    Prost, Jacques; Barbetta, Camilla; Joanny, Jean-François

    2007-01-01

    We discuss theoretically the shape of actin-based protrusions such as stereocilia or microvilli that have important functions in many biological systems. These linear protrusions are dynamical structures continuously renewed by treadmilling: actin polymerizes at the tip of the cilium and depolymerizes in its bulk. They also often have a well-controlled length such as in the hair bundles of the inner ear cells where they appear in a graded staircase structure. Recent experimental results by another group of researchers show that the treadmilling velocity of the hair cell stereocilia is proportional to their length. We use generic arguments to describe the physics of stereocilia taking into account the effect of many individual proteins at a coarse-grained level by a few phenomenological parameters. At the tip of the cilium, we find that actin polymerization induces an effective pressure. Below the tip, the shape of the cilium is determined by depolymerization: Agreement with the observed shape requires that depolymerization occurs at least in two steps. Under these conditions, we calculate the cilium shape and provide physical grounds for the proportionality between treadmilling velocity and cilium length. We also calculate the penetration of the stereocilium in the actin cortical layer. PMID:17526588

  12. The shapes of bird beaks are highly controlled by nondietary factors.

    PubMed

    Bright, Jen A; Marugán-Lobón, Jesús; Cobb, Samuel N; Rayfield, Emily J

    2016-05-10

    Bird beaks are textbook examples of ecological adaptation to diet, but their shapes are also controlled by genetic and developmental histories. To test the effects of these factors on the avian craniofacial skeleton, we conducted morphometric analyses on raptors, a polyphyletic group at the base of the landbird radiation. Despite common perception, we find that the beak is not an independently targeted module for selection. Instead, the beak and skull are highly integrated structures strongly regulated by size, with axes of shape change linked to the actions of recently identified regulatory genes. Together, size and integration account for almost 80% of the shape variation seen between different species to the exclusion of morphological dietary adaptation. Instead, birds of prey use size as a mechanism to modify their feeding ecology. The extent to which shape variation is confined to a few major axes may provide an advantage in that it facilitates rapid morphological evolution via changes in body size, but may also make raptors especially vulnerable when selection pressures act against these axes. The phylogenetic position of raptors suggests that this constraint is prevalent in all landbirds and that breaking the developmental correspondence between beak and braincase may be the key novelty in classic passerine adaptive radiations. PMID:27125856

  13. Overview of Langley activities in active controls research

    NASA Technical Reports Server (NTRS)

    Abel, I.; Newsom, J. R.

    1981-01-01

    The application of active controls technology to reduce aeroelastic response of aircraft structures offers a potential for significant payoffs in terms of aerodynamic efficiency and weight savings. The activities of the Langley Research Center (laRC) in advancing active controls technology. Activities are categorized into the development of appropriate analysis tools, control law synthesis methodology, and experimental investigations aimed at verifying both analysis and synthesis methodology.

  14. Single Input Fuzzy Controller with Command Shaping Schemes for Double-Pendulum Overhead Crane

    NASA Astrophysics Data System (ADS)

    Ahmad, M. A.; Saealal, M. S.; Ismail, R. M. T. Raja; Zawawi, M. A.; Nasir, A. N. K.; Ramli, M. S.

    2011-06-01

    This paper presents investigations into the development of composite control schemes for trajectory tracking and anti-sway control of a double-pendulum-type overhead crane (DPTOC) system. A nonlinear DPTOC system is considered and the dynamic model of the system is derived using the Euler-Lagrange formulation. The proposed method, known as the Single Input Fuzzy Logic Controller (SIFLC), reduces the conventional two-input FLC (CFLC) to a single input single output (SISO) controller. The SIFLC is developed for position control of cart movement. This is then extended to incorporate input shaping schemes for anti-swaying control of the system. The input shapers with different mode selection are designed based on the properties of the system. The results of the response with the controllers are presented in time and frequency domains. The performances of control schemes are examined in terms of level of input tracking capability, sway angle reduction and time response specifications in comparison to SIFLC controller. Finally, a comparative assessment of the control techniques is discussed and presented.

  15. Research on PID controller with input shaping algorithm for linear motor

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Dong, Yue; Fan, Wenchao; Fu, Zhenxian

    2015-02-01

    The reticle stage of lithography is a high precision servo motion platform, which requires using macro movement of linear motor and micro movement of voice coil motor to realize an nm-level positioning precision and tracking. In order to increase the control effect and response speed of macro movement linear motor of reticle stage of lithography, the paper presents an efficient control for linear motor. The method use input shaping technique with Proportional Integral Derivative (PID) controller to realize the high position precision in small stetting time. In the paper we firstly build the linear motor mathematical modeling which is end to velocity loop or position loop. so that we mainly focus on the tracking of speed signal. Then a PID controller is introduced in the system, which is high frequency used in industrial control. Finally, as the need of high positioning precision and small stetting time, we apply input shaping algorithm to solve the problem. The simulation of the system is performed by using MATLAB/Simulation. The evaluation of the method is the performance of input tracking capability.

  16. Shape memory alloy film for deployment and control of membrane apertures

    NASA Astrophysics Data System (ADS)

    Hill, Lisa R.; Carman, Greg; Lee, Dong-Gun; Patrick, Brian

    2004-02-01

    Nickel Titanium (NiTi) film shape memory alloy (SMA) is integrated with space-qualified polymer and mesh materials for potential use as deployment mechanisms and actuation of flexible space apertures. SMA thin film is successfully applied to Astromesh metal mesh, Kapton, Upilex, and CP-1 polymer films. Sputter deposition of NiTi onto the substrate is used to validate the material system process and demonstrate the NiTi deployment capability. Although successful, the relatively high processing temperatures required to crystallize NiTi onto the substrates requires care. A second approach is demonstrated that deposits NiTi onto a silicon substrate, followed by coating the NiTi with the desired polymer, e.g. CP-1. Micro-electro-mechanical (MEMS) processing steps are then used to remove the silicon substrate beneath the NiTi, thus freeing up the composite membrane (i.e. NiTi + CP-1). Using MEMS fabrication techniques, a hot-shaped small dome shape structure is shaped into the NiTi before deposition of the CP-1 polymer. Activation of the integrated SMA/CP-1 produces deformation of this composite structure without damage. The test articles demonstrate the feasibility to both grossly deploy and locally actuate space-qualified polymer materials.

  17. Novel active comb-shaped dry electrode for EEG measurement in hairy site.

    PubMed

    Huang, Yan-Jun; Wu, Chung-Yu; Wong, Alice May-Kuen; Lin, Bor-Shyh

    2015-01-01

    Electroencephalography (EEG) is an important biopotential, and has been widely applied in clinical applications. The conventional EEG electrode with conductive gels is usually used for measuring EEG. However, the use of conductive gel also encounters with the issue of drying and hardening. Recently, many dry EEG electrodes based on different conductive materials and techniques were proposed to solve the previous issue. However, measuring EEG in the hairy site is still a difficult challenge. In this study, a novel active comb-shaped dry electrode was proposed to measure EEG in hairy site. Different form other comb-shaped or spike-shaped dry electrodes, it can provide more excellent performance of avoiding the signal attenuation, phase distortion, and the reduction of common mode rejection ratio. Even under walking motion, it can effectively acquire EEG in hairy site. Finally, the experiments for alpha rhythm and steady-state visually evoked potential were also tested to validate the proposed electrode. PMID:25137719

  18. A Minimal Path Searching Approach for Active Shape Model (ASM)-based Segmentation of the Lung.

    PubMed

    Guo, Shengwen; Fei, Baowei

    2009-03-27

    We are developing a minimal path searching method for active shape model (ASM)-based segmentation for detection of lung boundaries on digital radiographs. With the conventional ASM method, the position and shape parameters of the model points are iteratively refined and the target points are updated by the least Mahalanobis distance criterion. We propose an improved searching strategy that extends the searching points in a fan-shape region instead of along the normal direction. A minimal path (MP) deformable model is applied to drive the searching procedure. A statistical shape prior model is incorporated into the segmentation. In order to keep the smoothness of the shape, a smooth constraint is employed to the deformable model. To quantitatively assess the ASM-MP segmentation, we compare the automatic segmentation with manual segmentation for 72 lung digitized radiographs. The distance error between the ASM-MP and manual segmentation is 1.75 ± 0.33 pixels, while the error is 1.99 ± 0.45 pixels for the ASM. Our results demonstrate that our ASM-MP method can accurately segment the lung on digital radiographs. PMID:24386531

  19. A minimal path searching approach for active shape model (ASM)-based segmentation of the lung

    NASA Astrophysics Data System (ADS)

    Guo, Shengwen; Fei, Baowei

    2009-02-01

    We are developing a minimal path searching method for active shape model (ASM)-based segmentation for detection of lung boundaries on digital radiographs. With the conventional ASM method, the position and shape parameters of the model points are iteratively refined and the target points are updated by the least Mahalanobis distance criterion. We propose an improved searching strategy that extends the searching points in a fan-shape region instead of along the normal direction. A minimal path (MP) deformable model is applied to drive the searching procedure. A statistical shape prior model is incorporated into the segmentation. In order to keep the smoothness of the shape, a smooth constraint is employed to the deformable model. To quantitatively assess the ASM-MP segmentation, we compare the automatic segmentation with manual segmentation for 72 lung digitized radiographs. The distance error between the ASM-MP and manual segmentation is 1.75 +/- 0.33 pixels, while the error is 1.99 +/- 0.45 pixels for the ASM. Our results demonstrate that our ASM-MP method can accurately segment the lung on digital radiographs.

  20. Simple and Reliable Fabrication of Bioinspired Mushroom-Shaped Micropillars with Precisely Controlled Tip Geometries.

    PubMed

    Yi, Hoon; Kang, Minsu; Kwak, Moon Kyu; Jeong, Hoon Eui

    2016-08-31

    We present a simple yet scalable method with detailed process protocols for fabricating dry adhesives with mushroom-shaped micropillars of controlled tip geometries. The method involves using photo-lithography with a bilayer stack combining SU-8 and lift-off resist, and subsequent replica molding process. This approach utilizes widely used and commercially available materials and can thus be used to generate mushroom-shaped micropillars with precisely controlled tip diameters and thicknesses in a simple, reproducible, and cost-effective manner. The fabricated mushroom-shaped micropillar arrays exhibited highly different tendencies in adhesion strength and repeatability depending on tip geometries, such as tip diameter and thickness, thereby demonstrating the importance of precise tunability of tip geometry of micropillars. The fabricated dry adhesives with optimized tip geometries not only exhibited strong pull-off strength of up to ∼34.8 N cm(-2) on the Si surface but also showed high durability. By contrast, dry adhesives with nonoptimized tips displayed low pull-off strength of ∼3.6 N cm(-2) and poor durability. PMID:27548917

  1. Light storage in a doped solid enhanced by feedback-controlled pulse shaping

    SciTech Connect

    Beil, F.; Buschbeck, M.; Heinze, G.; Halfmann, T.

    2010-05-15

    We report on experiments dealing with feedback-controlled pulse shaping to optimize the efficiency of light storage by electromagnetically induced transparency (EIT) in a Pr{sup 3+}:Y{sub 2}SiO{sub 5} crystal. A learning loop in combination with an evolutionary algorithm permits the automatic determination of optimal temporal profiles of intensities and frequencies in the driving laser pulses (i.e., the probe and coupling pulses). As a main advantage, the technique finds optimal solutions even in the complicated multilevel excitation scheme of a doped solid, involving large inhomogeneous broadening. The learning loop experimentally determines optimal temporal intensity profiles of the coupling pulses for a given probe pulse. The optimized intensity pulse shapes enhance the light-storage efficiency in the doped solid by a factor of 2. The learning loop also determines a fast and efficient preparation pulse sequence, which serves to optically prepare the crystal prior to light-storage experiments. The optimized preparation sequence is 5 times faster than standard preparation sequences. Moreover, the optimized preparation sequence enhances the optical depth in the medium by a factor of 5. As a consequence, the efficiency of light storage also increases by another factor of 3. Our experimental data clearly demonstrate the considerable potential of feedback-controlled pulse shaping, applied to EIT-driven light storage in solid media.

  2. Controlling the light distribution through turbid media with wavefront shaping based on volumetric optoacoustic feedback

    NASA Astrophysics Data System (ADS)

    Deán-Ben, X. Luís.; Estrada, Héctor; Özbek, Ali; Razansky, Daniel

    2016-03-01

    Wavefront shaping based on optoacoustic (photoacoustic) feedback has recently emerged as a promising tool to control the light distribution in optically-scattering media. In this approach, the phase of a short-pulsed light beam is spatially-modulated to create constructive light interference (focusing) at specific locations in the speckle pattern of the scattered wavefield. The optoacoustic signals generated by light absorption provide a convenient feedback mechanism to optimize the phase mask of the spatial light modulator in order to achieve the desired light intensity distribution. The optimization procedure can be done by directly considering the acquired signals or the reconstructed images of the light absorption distribution. Recently, our group has introduced a volumetric (three-dimensional) optoacoustic wavefront shaping platform that enables monitoring the distribution of light absorption in an entire volume with frame rates of tens of Hz. With this approach, it is possible to simultaneously control the volumetric light distribution through turbid media. Experiments performed with absorbing microparticles distributed in a three-dimensional region showcase the feasibility of enhancing the light intensity at specific points, where the size of particles is also essential to maximize the signal enhancement. The advantages provided by optoacoustic imaging in terms of spatial and temporal resolution anticipate new capabilities of wavefront shaping techniques in biomedical optics.

  3. Overvaluation of shape and weight among overweight children and adolescents with loss of control eating.

    PubMed

    Goldschmidt, Andrea; Wilfley, Denise E; Eddy, Kamryn T; Boutelle, Kerri; Zucker, Nancy; Peterson, Carol B; Celio-Doyle, Angela; Le Grange, Daniel

    2011-10-01

    Little is known about the phenomenology of pediatric loss of control (LOC) eating. Overvaluation of shape and weight, however, appears to be diagnostically meaningful among binge eating adults. We explored the significance of shape and weight overvaluation among children and adolescents with LOC eating. Participants (n = 526) included 149 overweight youth with LOC eating and 377 overweight controls (CON). Participants were categorized as those reporting at least moderate overvaluation (LOC-Mod, n = 74; CON-Mod, n = 106) or less than moderate overvaluation (LOC-Low, n = 75; CON-Low, n = 271), and compared on measures of eating-related and general psychopathology. LOC-Mod evidenced lower self-esteem than CON-Low, and greater behavioral problems than CON-Mod and CON-Low, but did not differ from LOC-Low in these domains. With the exception of LOC-Low and CON-Mod, all groups differed on global eating-disorder severity, with LOC-Mod scoring the highest. Overvaluation of shape and weight appears to be of questionable importance in defining subtypes of youth with LOC eating. However, as overvaluation and LOC eating each independently predicts eating-disorder onset, their confluence may confer even further risk for eating-disorder development. Longitudinal studies should address this possibility. Developmentally appropriate discussion about body image disturbance may be indicated in interventions targeting pediatric LOC eating and/or obesity. PMID:21835393

  4. Microwave-Controlled Generation of Shaped Single Photons in Circuit Quantum Electrodynamics

    NASA Astrophysics Data System (ADS)

    Pechal, M.; Huthmacher, L.; Eichler, C.; Zeytinoǧlu, S.; Abdumalikov, A. A.; Berger, S.; Wallraff, A.; Filipp, S.

    2014-10-01

    Large-scale quantum information processors or quantum communication networks will require reliable exchange of information between spatially separated nodes. The links connecting these nodes can be established using traveling photons that need to be absorbed at the receiving node with high efficiency. This is achievable by shaping the temporal profile of the photons and absorbing them at the receiver by time reversing the emission process. Here, we demonstrate a scheme for creating shaped microwave photons using a superconducting transmon-type three-level system coupled to a transmission line resonator. In a second-order process induced by a modulated microwave drive, we controllably transfer a single excitation from the third level of the transmon to the resonator and shape the emitted photon. We reconstruct the density matrices of the created single-photon states and show that the photons are antibunched. We also create multipeaked photons with a controlled amplitude and phase. In contrast to similar existing schemes, the one we present here is based solely on microwave drives, enabling operation with fixed frequency transmons.

  5. Study on global control network precision positioning method in visual shape measurement

    NASA Astrophysics Data System (ADS)

    Long, Chang-yu; Zhu, Ji-gui

    2013-08-01

    Large-size visual shape measurement based on ICP (iterative closest point) mosaicing algorithm generally has a larger cumulative error; however, this problem can be well solved by precision positioning global control network. Therefore, this method is widely used in large-size visual shape measurement. Since the positioning accuracy of the global control network is the key influencing factor of the final measurement accuracy, the method of precision positioning global control network is researched, which is dependent on the principle of portable close-range photogrammetry. The precision positioning theory and mathematical model of global control network are investigated in this paper. Bundle adjustment optimization algorithm is the core of this measurement system, the solution method of this algorithm is introduced in detail, which can improve the model solution accuracy. As is known, the initial value of the algorithm has a direct influence on the convergence of the result, so obtaining the initial value is a key part of the measurement system, including control points matching technology, stations orientation technology and the technology of obtaining the initial value of the three-dimensional coordinates of global control points. New technological breakthroughs were made based on the existing researches to get a more precious and stable initial value. Firstly, a nonlinear adjustment model based control points matching method is proposed, which significantly improves the correct matching rate when the control points distribute intensively. Secondly, a new station orientation method without using an external orientation device is studied, which greatly improves the shooting freedom and expands the range of the spatial distribution of the measurement stations. Finally, a camera calibration method independent with the imaging model is explored, which converts image coordinate information into image angle information. Thus, the initial value calculation accuracy of

  6. Shape effect on the antibacterial activity of silver nanoparticles synthesized via a microwave-assisted method.

    PubMed

    Hong, Xuesen; Wen, Junjie; Xiong, Xuhua; Hu, Yongyou

    2016-03-01

    Silver nanoparticles (AgNPs) are used as sustained-release bactericidal agents for water treatment. Among the physicochemical characteristics of AgNPs, shape is an important parameter relevant to the antibacterial activity. Three typically shaped AgNPs, nanocubes, nanospheres, and nanowires, were prepared via a microwave-assisted method and characterized by TEM, UV-vis, and XRD. The antibacterial activity of AgNPs was determined by OD growth curves tests, MIC tests, and cell viability assay against Escherichia coli. The interaction between AgNPs and bacterial cells was observed by TEM. The results showed that the three differently shaped AgNPs were nanoscale, 55 ± 10 nm in edge length for nanocubes, 60 ± 15 nm in diameter for nanospheres, 60 ± 10 nm in diameter and 2-4 μm in length for nanowires. At the bacterial concentration of 10(4) CFU/mL, the MIC of nanocubes, nanospheres, and nanowires were 37.5, 75, and 100 μg/mL, respectively. Due to the worst contact with bacteria, silver nanowires exhibited the weakest antibacterial activity compared with silver nanocubes and silver nanospheres. Besides, silver nanocubes mainly covered by {100} facets showed stronger antibacterial activity than silver nanospheres covered by {111} facets. It suggests that the shape effect on the antibacterial activity of AgNPs is attributed to the specific surface areas and facets reactivity; AgNPs with larger effective contact areas and higher reactive facets exhibit stronger antibacterial activity. PMID:26511259

  7. 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.

  8. Shape-Controlled Synthesis of Colloidal Metal Nanocrystals: Thermodynamic versus Kinetic Products.

    PubMed

    Xia, Younan; Xia, Xiaohu; Peng, Hsin-Chieh

    2015-07-01

    This Perspective provides a contemporary understanding of the shape evolution of colloidal metal nanocrystals under thermodynamically and kinetically controlled conditions. It has been extremely challenging to investigate this subject in the setting of one-pot synthesis because both the type and number of seeds involved would be changed whenever the experimental conditions are altered, making it essentially impossible to draw conclusions when comparing the outcomes of two syntheses conducted under different conditions. Because of the uncertainty about seeds, most of the mechanistic insights reported in literature for one-pot syntheses of metal nanocrystals with different shapes are either incomplete or ambiguous, and some of them might be misleading or even wrong. Recently, with the use of well-defined seeds for such syntheses, it became possible to separate growth from nucleation and therefore investigate the explicit role(s) played by a specific thermodynamic or kinetic parameter in directing the evolution of colloidal metal nanocrystals into a specific shape. Starting from single-crystal seeds enclosed by a mix of {100}, {111}, and {110} facets, for example, one can obtain colloidal nanocrystals with diversified shapes by adjusting various thermodynamic or kinetic parameters. The mechanistic insights learnt from these studies can also be extended to account for the products of conventional one-pot syntheses that involve self-nucleation only. The knowledge can be further applied to many other types of seeds with twin defects or stacking faults, making it an exciting time to design and synthesize colloidal metal nanocrystals with the shapes sought for a variety of fundamental studies and technologically important applications. PMID:26020837

  9. Static shape determination and control for large space structures. I - The flexible beam. II - A large space antenna

    NASA Technical Reports Server (NTRS)

    Weeks, C. J.

    1984-01-01

    A method for determining and controlling the shape of large, continuous space structures by means of discrete or pointwise observations and control devices is presented. The general linear boundary value problem satisfied by a one-dimensional shape function is defined, and the existence of solutions is studied. The static shape control problems for one-dimensional systems with and without rigid body modes and the static shape estimation problem are presented and solved. Eigenfunction expansions are presented which provide approximations to the algorithm terms when the associated Green's function is not known. An integral operator approach is applied to the multidimensional static problem, and the results are illustrated with a finite element model of the disk of a large space antenna which assumes no rigid body modes. It is shown that the shape control algorithm must be modified for systems with rigid body modes.

  10. MIT Middeck Active Control Experiment (MACE): noncollocated payload pointing control

    NASA Astrophysics Data System (ADS)

    MacMartin, Douglas G.; Miller, David W.

    1993-09-01

    The Middeck Active Control Experiment is a space shuttle flight experiment intended to demonstrate high authority active structural control in zero gravity conditions. The prediction of on-orbit closed-loop dynamics is based on analysis and ground testing. The MACE test article is representative of multiple payload platforms, and includes two 2-axis gimballing payloads connected by a flexible bus. The goal of active control is to maintain pointing accuracy of one payload, while the remaining payload is moving independently. Current control results on the ground test article are presented. Multiple input, multiple output controllers are designed based on high order measurement based models. Linear Quadratic Gaussian controllers yield reasonable performance. At high authority, however, these controllers destabilize the actual structure, due to parametric errors in the control design model. A robust control design procedure is required to yield high performance in the presence of these errors.

  11. Active Shielding and Control of Environmental Noise

    NASA Technical Reports Server (NTRS)

    Tsynkov, S. V.

    2001-01-01

    In the framework of the research project supported by NASA under grant # NAG-1-01064, we have studied the mathematical aspects of the problem of active control of sound, i.e., time-harmonic acoustic disturbances. The foundations of the methodology are described in our paper [1]. Unlike. many other existing techniques, the approach of [1] provides for the exact volumetric cancellation of the unwanted noise on a given predetermined region airspace, while leaving unaltered those components of the total acoustic field that are deemed as friendly. The key finding of the work is that for eliminating the unwanted component of the acoustic field in a given area, one needs to know relatively little; in particular, neither the locations nor structure nor strength of the exterior noise sources need to be known. Likewise, there is no need to know the volumetric properties of the supporting medium across which the acoustic signals propagate, except, maybe, in a narrow area of space near the perimeter of the protected region. The controls are built based solely on the measurements performed on the perimeter of the domain to be shielded; moreover, the controls themselves (i.e., additional sources) are concentrated also only on or near this perimeter. Perhaps as important, the measured quantities can refer to the total acoustic field rather than to its unwanted component only, and the methodology can automatically distinguish between the two. In [1], we have constructed the general solution for controls. The apparatus used for deriving this general solution is closely connected to the concepts of generalized potentials and boundary projections of Calderon's type. For a given total wave field, the application of a Calderon's projection allows one to definitively tell between its incoming and outgoing components with respect to a particular domain of interest, which may have arbitrary shape. Then, the controls are designed so that they suppress the incoming component for the domain

  12. The effect of sensor and actuator errors on static shape control for large space structures

    NASA Technical Reports Server (NTRS)

    Haftka, R. T.; Adelman, H. M.

    1985-01-01

    An analytical study was performed to predict and assess the effect of actuator and sensor errors on the performance of a shape control procedure for flexible space structures using applied temperatures. Approximate formulas were derived for the expected value and variance of the rms distortion ratio (ratio of rms distortions with and without corrections) based on the assumption of zero-mean normally distributed random errors in measured distortions and actuator output temperatures. Studies were carried out for a 55-meter radiometer antenna reflector distorted from its ideal parabolic shape by nonuniform orbital heating. The first study consisted of varying the sensor and actuator errors for the case of 12 actuators and computing the distortion ratio. In the second study, sensor and actuator errors were prescribed and the effect of increasing the number of actuators was evaluated.

  13. Effect of sensor and actuator errors on static shape control for large space structures

    NASA Technical Reports Server (NTRS)

    Haftka, Raphael T.; Adelman, Howard M.

    1987-01-01

    An analytical study was performed to predict and assess the effect of actuator and sensor errors on the performance of a shape control procedure for flexible space structures using applied temperatures. Approximate formulas were derived for the expected value and variance of the rms distortion ratio (ratio of rms distortions with and without corrections) based on the assumption of zero-mean normally distributed random errors in measured distortions and actuator output temperatures. Studies were carried out for a 55-meter radiometer antenna reflector distorted from its ideal parabolic shape by nonuniform orbital heating. The first study consisted of varying the sensor and actuator errors for the case of 12 actuators and computing the distortion ratio. In the second study, sensor and actuator errors were prescribed and the effect of increasing the number of actuators was evaluated.

  14. Band-selective shaped pulse for high fidelity quantum control in diamond

    SciTech Connect

    Chang, Yan-Chun; Xing, Jian; Liu, Gang-Qin; Jiang, Qian-Qing; Li, Wu-Xia; Zhang, Fei-Hao; Gu, Chang-Zhi; Pan, Xin-Yu; Long, Gui-Lu

    2014-06-30

    High fidelity quantum control of qubits is crucially important for realistic quantum computing, and it becomes more challenging when there are inevitable interactions between qubits. We introduce a band-selective shaped pulse, refocusing BURP (REBURP) pulse, to cope with the problems. The electron spin of nitrogen-vacancy centers in diamond is flipped with high fidelity by the REBURP pulse. In contrast with traditional rectangular pulses, the shaped pulse has almost equal excitation effect in a sharply edged region (in frequency domain). So the three sublevels of host {sup 14}N nuclear spin can be flipped accurately simultaneously, while unwanted excitations of other sublevels (e.g., of a nearby {sup 13}C nuclear spin) is well suppressed. Our scheme can be used for various applications such as quantum metrology, quantum sensing, and quantum information process.

  15. Control Theory based Shape Design for the Incompressible Navier-Stokes Equations

    NASA Astrophysics Data System (ADS)

    Cowles, G.; Martinelli, L.

    2003-12-01

    A design method for shape optimization in incompressible turbulent viscous flow has been developed and validated for inverse design. The gradient information is determined using a control theory based algorithm. With such an approach, the cost of computing the gradient is negligible. An additional adjoint system must be solved which requires the cost of a single steady state flow solution. Thus, this method has an enormous advantage over traditional finite-difference based algorithms. The method of artificial compressibility is utilized to solve both the flow and adjoint systems. An algebraic turbulence model is used to compute the eddy viscosity. The method is validated using several inverse wing design test cases. In each case, the program must modify the shape of the initial wing such that its pressure distribution matches that of the target wing. Results are shown for the inversion of both finite thickness wings as well as zero thickness wings which can be considered a model of yacht sails.

  16. Band-selective shaped pulse for high fidelity quantum control in diamond

    NASA Astrophysics Data System (ADS)

    Chang, Yan-Chun; Xing, Jian; Zhang, Fei-Hao; Liu, Gang-Qin; Jiang, Qian-Qing; Li, Wu-Xia; Gu, Chang-Zhi; Long, Gui-Lu; Pan, Xin-Yu

    2014-06-01

    High fidelity quantum control of qubits is crucially important for realistic quantum computing, and it becomes more challenging when there are inevitable interactions between qubits. We introduce a band-selective shaped pulse, refocusing BURP (REBURP) pulse, to cope with the problems. The electron spin of nitrogen-vacancy centers in diamond is flipped with high fidelity by the REBURP pulse. In contrast with traditional rectangular pulses, the shaped pulse has almost equal excitation effect in a sharply edged region (in frequency domain). So the three sublevels of host 14N nuclear spin can be flipped accurately simultaneously, while unwanted excitations of other sublevels (e.g., of a nearby 13C nuclear spin) is well suppressed. Our scheme can be used for various applications such as quantum metrology, quantum sensing, and quantum information process.

  17. Shape control of the magnetic iron oxide nanoparticles under different chain length of reducing agents

    SciTech Connect

    Ngoi, Kuan Hoon; Chia, Chin-Hua Zakaria, Sarani; Chiu, Wee Siong

    2015-09-25

    We report on the effect of using reducing agents with different chain-length on the synthesis of iron oxide nanoparticles by thermal decomposition of iron (III) acetylacetonate in 1-octadecene. This modification allows us to control the shape of nanoparticles into spherical and cubic iron oxide nanoparticles. The highly monodisperse 14 nm spherical nanoparticles are obtained under 1,2-dodecanediol and average 14 nm edge-length cubic iron oxide nanoparticles are obtained under 1,2-tetradecanediol. The structural characterization such as transmission electron microscope (TEM) and X-ray diffraction (XRD) shows similar properties between two particles with different shapes. The vibrating sample magnetometer (VSM) shows no significant difference between spherical and cubic nanoparticles, which are 36 emu/g and 37 emu/g respectively and superparamagnetic in nature.

  18. Controlling the rates of biochemical reactions and signaling networks by shape and volume changes.

    PubMed

    Lizana, L; Bauer, B; Orwar, O

    2008-03-18

    In biological systems, chemical activity takes place in micrometer- and nanometer-sized compartments that constantly change in shape and volume. These ever-changing cellular compartments embed chemical reactions, and we demonstrate that the rates of such incorporated reactions are directly affected by the ongoing shape reconfigurations. First, we show that the rate of product formation in an enzymatic reaction can be regulated by simple volume contraction-dilation transitions. The results suggest that mitochondria may regulate the dynamics of interior reaction pathways (e.g., the Krebs cycle) by volume changes. We then show the effect of shape changes on reactions occurring in more complex and structured systems by using biomimetic networks composed of micrometer-sized compartments joined together by nanotubes. Chemical activity was measured by implementing an enzymatic reaction-diffusion system. During ongoing reactions, the network connectivity is changed suddenly (similar to the dynamic tube formations found inside Golgi stacks, for example), and the effect on the reaction is registered. We show that spatiotemporal properties of the reaction-diffusion system are extremely sensitive to sudden changes in network topology and that chemical reactions can be initiated, or boosted, in certain nodes as a function of connectivity. PMID:18337513

  19. Passive control of vortex induced vibration in internal flow using body shape

    NASA Astrophysics Data System (ADS)

    Sánchez–Sanz, M.; Velazquez, A.

    2011-10-01

    We present a concept for passive control of vortex induced vibration (VIV) that uses the body shape of a prismatic body as the control parameter in 2D internal flow. We consider that the Reynolds number based on the prism cross section height is 200 and that the blockage ratio of the channel is 2.5. The working fluid is water and the solid-to-fluid density ratio is 1, so that the prism presents neutral buoyancy and the body shape parameter γ acts as the only control parameter. Two very different fluid dynamics regimes are observed depending on γ with an abrupt transition between them for γ = γ c , where γ c represents a critical value obtained numerically. For γ < γ c the cylinder oscillation is controlled by vortex shedding and represents a typical case of vortex induced vibration. For γ > γ c the oscillation is a mixture of galloping and vortex induced vibration that causes the prism motion to shift from a stable periodic motion to a highly irregular pattern. The physical explanation for the change of regime is given based on the cylinder equation of motion.

  20. Independent control of the shape and composition of ionic nanocrystals through sequential cation exchange reactions

    SciTech Connect

    Luther, Joseph Matthew; Zheng, Haimei; Sadtler, Bryce; Alivisatos, A. Paul

    2009-07-06

    Size- and shape-controlled nanocrystal growth is intensely researched for applications including electro-optic, catalytic, and medical devices. Chemical transformations such as cation exchange overcome the limitation of traditional colloidal synthesis, where the nanocrystal shape often reflects the inherent symmetry of the underlying lattice. Here we show that nanocrystals, with established synthetic protocols for high monodispersity, can be templates for independent composition control. Specifically, controlled interconversion between wurtzite CdS, chalcocite Cu2S, and rock salt PbS occurs while preserving the anisotropic dimensions unique to the as-synthesized materials. Sequential exchange reactions between the three sulfide compositions are driven by the disparate solubilites of the metal ion exchange pair in specific coordinating molecules. Starting with CdS, highly anisotropic PbS nanorods are created, which serve as an important material for studying strong 2-dimensional quantum confinement, as well as for optoelectronic applications. Furthermore, interesting nanoheterostructures of CdS|PbS are obtained by precise control over ion insertion and removal.

  1. Biosynthesis and recovery of rod-shaped tellurium nanoparticles and their bactericidal activities

    SciTech Connect

    Zare, Bijan; Faramarzi, Mohammad Ali; Sepehrizadeh, Zargham; Shakibaie, Mojtaba; Rezaie, Sassan; Shahverdi, Ahmad Reza

    2012-11-15

    Highlights: ► Biosynthesis of rod shape tellurium nanoparticles with a hexagonal crystal structure. ► Extraction procedure for isolation of tellurium nanoparticles from Bacillus sp. BZ. ► Extracted tellurium nanoparticles have good bactericidal activity against some bacteria. -- Abstract: In this study, a tellurium-transforming Bacillus sp. BZ was isolated from the Caspian Sea in northern Iran. The isolate was identified by various tests and 16S rDNA analysis, and then used to prepare elemental tellurium nanoparticles. The isolate was subsequently used for the intracellular biosynthesis of elemental tellurium nanoparticles. The biogenic nanoparticles were released by liquid nitrogen and purified by an n-octyl alcohol water extraction system. The shape, size, and composition of the extracted nanoparticles were characterized. The transmission electron micrograph showed rod-shaped nanoparticles with dimensions of about 20 nm × 180 nm. The energy dispersive X-ray and X-ray diffraction spectra respectively demonstrated that the extracted nanoparticles consisted of only tellurium and have a hexagonal crystal structure. This is the first study to demonstrate a biological method for synthesizing rod-shaped elemental tellurium by a Bacillus sp., its extraction and its antibacterial activity against different clinical isolates.

  2. Segmentation of 4D cardiac computer tomography images using active shape models

    NASA Astrophysics Data System (ADS)

    Leiner, Barba-J.; Olveres, Jimena; Escalante-Ramírez, Boris; Arámbula, Fernando; Vallejo, Enrique

    2012-06-01

    This paper describes a segmentation method for time series of 3D cardiac images based on deformable models. The goal of this work is to extend active shape models (ASM) of tree-dimensional objects to the problem of 4D (3D + time) cardiac CT image modeling. The segmentation is achieved by constructing a point distribution model (PDM) that encodes the spatio-temporal variability of a training set, i.e., the principal modes of variation of the temporal shapes are computed using some statistical parameters. An active search is used in the segmentation process where an initial approximation of the spatio-temporal shape is given and the gray level information in the neighborhood of the landmarks is analyzed. The starting shape is able to deform so as to better fit the data, but in the range allowed by the point distribution model. Several time series consisting of eleven 3D images of cardiac CT are employed for the method validation. Results are compared with manual segmentation made by an expert. The proposed application can be used for clinical evaluation of the left ventricle mechanical function. Likewise, the results can be taken as the first step of processing for optic flow estimation algorithms.

  3. Segmentation of risk structures for otologic surgery using the Probabilistic Active Shape Model (PASM)

    NASA Astrophysics Data System (ADS)

    Becker, Meike; Kirschner, Matthias; Sakas, Georgios

    2014-03-01

    Our research project investigates a multi-port approach for minimally-invasive otologic surgery. For planning such a surgery, an accurate segmentation of the risk structures is crucial. However, the segmentation of these risk structures is a challenging task: The anatomical structures are very small and some have a complex shape, low contrast and vary both in shape and appearance. Therefore, prior knowledge is needed which is why we apply model-based approaches. In the present work, we use the Probabilistic Active Shape Model (PASM), which is a more flexible and specific variant of the Active Shape Model (ASM), to segment the following risk structures: cochlea, semicircular canals, facial nerve, chorda tympani, ossicles, internal auditory canal, external auditory canal and internal carotid artery. For the evaluation we trained and tested the algorithm on 42 computed tomography data sets using leave-one-out tests. Visual assessment of the results shows in general a good agreement of manual and algorithmic segmentations. Further, we achieve a good Average Symmetric Surface Distance while the maximum error is comparatively large due to low contrast at start and end points. Last, we compare the PASM to the standard ASM and show that the PASM leads to a higher accuracy.

  4. Finite Element Analysis of Adaptive-Stiffening and Shape-Control SMA Hybrid Composites

    NASA Technical Reports Server (NTRS)

    Gao, Xiu-Jie; Turner, Travis L.; Burton, Deborah; Brinson, L. Catherine

    2005-01-01

    The usage of shape memory materials has extended rapidly to many fields, including medical devices, actuators, composites, structures and MEMS devices. For these various applications, shape memory alloys (SMAs) are available in various forms: bulk, wire, ribbon, thin film, and porous. In this work, the focus is on SMA hybrid composites with adaptive-stiffening or morphing functions. These composites are created by using SMA ribbons or wires embedded in a polymeric based composite panel/beam. Adaptive stiffening or morphing is activated via selective resistance heating or uniform thermal loads. To simulate the thermomechanical behavior of these composites, a SMA model was implemented using ABAQUS user element interface and finite element simulations of the systems were studied. Several examples are presented which show that the implemented model can be a very useful design and simulation tool for SMA hybrid composites.

  5. Extracellular matrix and cell shape: potential control points for inhibition of angiogenesis

    NASA Technical Reports Server (NTRS)

    Ingber, D.

    1991-01-01

    Capillary endothelial (CE) cells require two extracellular signals in order to switch from quiescence to growth and back to differentiation during angiogenesis: soluble angiogenic factors and insoluble extracellular matrix (ECM) molecules. Soluble endothelial mitogens, such as basic fibroblast growth factor (FGF), act over large distances to trigger capillary growth, whereas ECM molecules act locally to modulate cell responsiveness to these soluble cues. Recent studies reveal that ECM molecules regulate CE cell growth and differentiation by modulating cell shape and by activating intracellular chemical signaling pathways inside the cell. Recognition of the importance of ECM and cell shape during capillary morphogenesis has led to the identification of a series of new angiogenesis inhibitors. Elucidation of the molecular mechanism of capillary regulation may result in development of even more potent angiogenesis modulators in the future.

  6. Input-Shaped Link Motion Control of Planar Space Robot Equipped with Flexible Appendage

    NASA Astrophysics Data System (ADS)

    Kasai, Shinya; Kojima, Hirohisa

    Control of a space robot without actuators on the main body is an underactuated control problem. Various stabilization methods, such as the time-varying feedback control method, discontinuous feedback control method, center manifold-based method, zero-dynamics method and sliding-mode control method have been proposed. However, past studies have not considered underactuated space robots equipped with a flexible appendage, such as solar panels. If the manipulators are simply controlled to achieve the target state for the robot using the past controllers without taking a flexible appendage into consideration, residual vibration remains even after the link motion has finished. In order to suppress the residual vibration on the flexible appendage, we apply the input-shaping technique to the link motion of an underactuated planar space robot. Numerical and experimental studies are carried out to validate the proposed method for a planar dual-link space robot with a flexible appendage. The results show that the proposed method is capable of not only controlling the link angles and the main body attitude to the goal angles, but also suppressing the residual vibration on the flexible appendage.

  7. An innovative ultra-capacitor driven shape memory alloy actuator with an embedded control system

    NASA Astrophysics Data System (ADS)

    Li, Peng; Song, Gangbing

    2014-08-01

    In this paper, an innovative ultra-capacitor driven shape memory alloy (SMA) actuator with an embedded control system is proposed targeting high power high-duty cycle SMA applications. The ultra-capacitor, which is capable of delivering massive amounts of instantaneous current in a compact dimension for high power applications, is chosen as the main component of the power supply. A specialized embedded system is designed from the ground up to control the ultra-capacitor driven SMA system. The control of the ultra-capacitor driven SMA is different from that of a regular constant voltage powered SMA system in that the energy and the voltage of the ultra-capacitor decrease as the system load increases. The embedded control system is also different from a computer-based control system in that it has limited computational power, and the control algorithm has to be designed to be simple while effective so that it can fit into the embedded system environment. The problem of a variable voltage power source induced by the use of the ultra-capacitor is solved by using a fuzzy PID (proportional integral and derivative) control. The method of using an ultra-capacitor to drive SMA actuators enabled SMA as a good candidate for high power high-duty cycle applications. The proposed embedded control system provides a good and ready-to-use solution for SMA high power applications.

  8. Orbiter active thermal control system description

    NASA Technical Reports Server (NTRS)

    Laubach, G. E.

    1975-01-01

    A brief description of the Orbiter Active Thermal Control System (ATCS) including (1) major functional requirements of heat load, temperature control and heat sink utilization, (2) the overall system arrangement, and (3) detailed description of the elements of the ATCS.

  9. Developing Internal Controls through Activities

    ERIC Educational Resources Information Center

    Barnes, F. Herbert

    2009-01-01

    Life events can include the Tuesday afternoon cooking class with the group worker or the Saturday afternoon football game, but in the sense that Fritz Redl thought of them, these activities are only threads in a fabric of living that includes all the elements of daily life: playing, working, school-based learning, learning through activities,…

  10. Active and passive control of zinc phthalocyanine photodynamics.

    PubMed

    Sharma, Divya; Huijser, Annemarie; Savolainen, Janne; Steen, Gerwin; Herek, Jennifer L

    2013-01-01

    In this work we report on the ultrafast photodynamics of the photosensitizer zinc phthalocyanine (ZnPc) and manipulation thereof. Two approaches are followed: active control via pulse shaping and passive control via strategic manipulation in the periphery of the molecular structure. The objective of both of these control experiments is the same: to enhance the yield of the functional pathway and to minimize loss channels. The aim of the active control experiments is to increase the intersystem crossing yield in ZnPc, which is important for application in photodynamic therapy (PDT). Pulse shaping allowed an improvement in triplet to singlet ratio of 15% as compared to a transform-limited pulse. This effect is ascribed to a control mechanism that utilizes multiphoton pathways to higher-lying states from where intersystem crossing is more likely to occur. The passive control experiments are performed on ZnPc derivatives deposited onto TiO2, serving as a model system of a dye-sensitized solar cell (DSSC). Modification of the anchoring ligand of the molecular structure resulted in an increased rate for electron injection into TiO2 and slower back electron transfer, improving the DSSC efficiency. PMID:24020214

  11. Drivers shaping the diversity and biogeography of total and active bacterial communities in the South China Sea

    PubMed Central

    Zhang, Yao; Zhao, Zihao; Dai, Minhan; Jiao, Nianzhi; Herndl, Gerhard J

    2014-01-01

    To test the hypothesis that different drivers shape the diversity and biogeography of the total and active bacterial community, we examined the bacterial community composition along two transects, one from the inner Pearl River estuary to the open waters of the South China Sea (SCS) and the other from the Luzon Strait to the SCS basin, using 454 pyrosequencing of the 16S rRNA and 16S rRNA gene (V1-3 regions) and thereby characterizing the active and total bacterial community, respectively. The diversity and biogeographic patterns differed substantially between the active and total bacterial communities. Although the composition of both the total and active bacterial community was strongly correlated with environmental factors and weakly correlated with geographic distance, the active bacterial community displayed higher environmental sensitivity than the total community and particularly a greater distance effect largely caused by the active assemblage from deep waters. The 16S rRNA vs. rDNA relationships indicated that the active bacteria were low in relative abundance in the SCS. This might be due to a high competition between active bacterial taxa as indicated by our community network models. Based on these analyses, we speculate that high competition could cause some dispersal limitation of the active bacterial community resulting in a distinct distance-decay relationship. Altogether, our results indicated that the biogeographic distribution of bacteria in the SCS is the result of both environmental control and distance decay. PMID:24684298

  12. Directional control of lamellipodia extension by constraining cell shape and orienting cell tractional forces

    NASA Technical Reports Server (NTRS)

    Parker, Kevin Kit; Brock, Amy Lepre; Brangwynne, Cliff; Mannix, Robert J.; Wang, Ning; Ostuni, Emanuele; Geisse, Nicholas A.; Adams, Josephine C.; Whitesides, George M.; Ingber, Donald E.

    2002-01-01

    Directed cell migration is critical for tissue morphogenesis and wound healing, but the mechanism of directional control is poorly understood. Here we show that the direction in which cells extend their leading edge can be controlled by constraining cell shape using micrometer-sized extracellular matrix (ECM) islands. When cultured on square ECM islands in the presence of motility factors, cells preferentially extended lamellipodia, filopodia, and microspikes from their corners. Square cells reoriented their stress fibers and focal adhesions so that tractional forces were concentrated in these corner regions. When cell tension was dissipated, lamellipodia extension ceased. Mechanical interactions between cells and ECM that modulate cytoskeletal tension may therefore play a key role in the control of directional cell motility.

  13. PATH OPTIMIZATION AND CONTROL OF A SHAPE MEMORY ALLOY ACTUATED CATHETER FOR ENDOCARDIAL RADIOFREQUENCY ABLATION

    PubMed Central

    Wiest, Jennifer H.; Buckner, Gregory D.

    2014-01-01

    This paper introduces a real-time path optimization and control strategy for shape memory alloy (SMA) actuated cardiac ablation catheters, potentially enabling the creation of more precise lesions with reduced procedure times and improved patient outcomes. Catheter tip locations and orientations are optimized using parallel genetic algorithms to produce continuous ablation paths with near normal tissue contact through physician-specified points. A nonlinear multivariable control strategy is presented to compensate for SMA hysteresis, bandwidth limitations, and coupling between system inputs. Simulated and experimental results demonstrate efficient generation of ablation paths and optimal reference trajectories. Closed-loop control of the SMA-actuated catheter along optimized ablation paths is validated experimentally. PMID:25684857

  14. Aerodynamic shape optimization of wing and wing-body configurations using control theory

    NASA Technical Reports Server (NTRS)

    Reuther, James; Jameson, Antony

    1995-01-01

    This paper describes the implementation of optimization techniques based on control theory for wing and wing-body design. In previous studies it was shown that control theory could be used to devise an effective optimization procedure for airfoils and wings in which the shape and the surrounding body-fitted mesh are both generated analytically, and the control is the mapping function. Recently, the method has been implemented for both potential flows and flows governed by the Euler equations using an alternative formulation which employs numerically generated grids, so that it can more easily be extended to treat general configurations. Here results are presented both for the optimization of a swept wing using an analytic mapping, and for the optimization of wing and wing-body configurations using a general mesh.

  15. Use of Soybean Lecithin in Shape Controlled Synthesis of Gold Nanoparticles

    NASA Astrophysics Data System (ADS)

    Ayres, Benjamin Robert

    The work presented in this dissertation is a composite of experiments in the growth of gold nanoparticles with specific optical properties of interest. The goal is to synthesize these gold nanoparticles using soybean extract for not only shape control, but for propensity as a biocompatible delivery system. The optical properties of these nanoparticles has found great application in coloring glass during the Roman empire and, over the centuries, has grown into its own research field in applications of nanoparticulate materials. Many of the current functions include use in biological systems as biosensors and therapeutic applications, thus making biocompatibility a necessity. Current use of cetyltrimethylammonium bromide leads to rod-shaped gold nanoparticles, however, the stability of these gold nanoparticles does not endure for extended periods of time in aqueous media. In my research, two important components were found to be necessary for stable, anisotropic growth of gold nanoparticles. In the first experiments, it was found that bromide played a key role in shape control. Bromide exchange on the gold atoms led to specific packing of the growing crystals, allowing for two-dimensional growth of gold nanoparticles. It was also discerned that soybean lecithin contained ligands that blocked specific gold facets leading to prismatic gold nanoparticle growth. These gold nanoprisms give a near infrared plasmon absorption similar to that of rod-shaped gold nanoparticles. These gold nanoprisms are discovered to be extremely stable in aqueous media and remain soluble for extended periods of time, far longer than that of gold nanoparticles grown using cetyltrimethylammonium bromide. Since soy lecithin has a plethora of compounds present, it became necessary to discover which compound was responsible for the shape control of the gold nanoprisms in order to optimize the synthesis and allow for a maximum yield of the gold nanoprisms. Many of these components were identified

  16. Active Compliance And Damping In Telemanipulator Control

    NASA Technical Reports Server (NTRS)

    Kim, Won S.; Bejczy, Antal K.; Hannaford, Blake

    1991-01-01

    Experimental telemanipulator system of force-reflecting-hand-controller type provides for active compliance and damping in remote, robotic manipulator hand. Distributed-computing and -control system for research in various combinations of force-reflecting and active-compliance control regimes. Shared compliance control implemented by low-pass-filtered force/torque feedback. Variable simulated springs and shock absorbers soften collisions and increase dexterity.

  17. The Middeck Active Control Experiment (MACE)

    NASA Technical Reports Server (NTRS)

    Miller, David W.

    1992-01-01

    Viewgraphs on the Middeck Active Control Experiment (MACE) are presented. Topics covered include: program objectives; program features; flight experiment features; current activities; MACE development model lab testing; MACE test article deployed on STS middeck; and development model testing.

  18. The Middeck Active Control Experiment (MACE)

    NASA Astrophysics Data System (ADS)

    Miller, David W.

    Viewgraphs on the Middeck Active Control Experiment (MACE) are presented. Topics covered include: program objectives; program features; flight experiment features; current activities; MACE development model lab testing; MACE test article deployed on STS middeck; and development model testing.

  19. Modeling and Control of 2-D Grasping of an Object with Arbitrary Shape under Rolling Contact

    NASA Astrophysics Data System (ADS)

    Arimoto, Suguru; Yoshida, Morio; Sekimoto, Masahiro; Tahara, Kenji

    Modeling, control, and stabilization of dynamics of two-dimensional object grasping by using a pair of multi-joint robot fingers are investigated under rolling contact constraints and an arbitrary geometry of the object and fingertips. First, a fundamental testbed problem of modeling and control of rolling motion between 2-D rigid bodies with an arbitrary shape is treated under the assumption that the two contour curves coincide at the contact point and share the same tangent. The rolling constraint induces the Euler equation of motion that is parameterized by a common arclength parameter and constrained onto the kernel space orthogonally complemented to the image space spanned from the constraint gradient. By extending the analysis to the problem of stable grasp of a 2-D object with an arbitrary shape by a pair of robot fingers, the Euler-Lagrange equation of motion of the overall fingers/object system parametrized by arclength parameters is derived, together with a couple of first-order differential equations that express evolutions of contact points in terms of the second fundamental form. It is shown that 2-D rolling constraints are integrable in the sense of Frobonius even if their Pfaffian forms are characterized by arclength parameters. A control signal called “blind grasping” is introduced and shown to be effective in stabilization of grasping without using the details of the object shape and parameters or external sensing. An extension of the Dirichlet-Lagrange stability theorem to a class of systems with DOF-redundancy under constraints is suggested by using a Morse-Bott-Lyapunov function.

  20. Controlled wettability based on reversible micro-cracking on a shape memory polymer surface.

    PubMed

    Han, Yu; Liu, Yuxuan; Wang, Wenxin; Leng, Jinsong; Jin, Peng

    2016-03-14

    Wettability modification on a polymer surface is of immense importance for flexible electronics and biomedical applications. Herein, controlled wettability of a styrene-based shape memory polymer has been realized by introducing micro-cracks on the polymer surface for the first time. The cracks were purposely prepared by thin metal film constrained deformation on the polymer. After the removal of the metallic film, wettability was dramatically enhanced by showing a remarkable reduction in the contact angle with water droplets from 85° to 25°. Subsequent systematic characterization techniques like XPS and SEM revealed that such observation could be attributed to the increased density of hydrophilic groups and the roughened surface. In addition, by controlling the temperature for annealing the treated polymer, the surface could be switched reversely to water-repellent. Therefore, this paper offers a smart tactic to manipulate the surface wettability of a shape memory polymer freely. The features of the controlled wettability surface such as high tenability, high stability and easy fabrication are promising for microfluidic switching and molecule/cell capture-release. PMID:26865175

  1. Controlling shape and position of vascular formation in engineered tissues by arbitrary assembly of endothelial cells.

    PubMed

    Takehara, Hiroaki; Sakaguchi, Katsuhisa; Kuroda, Masatoshi; Muraoka, Megumi; Itoga, Kazuyoshi; Okano, Teruo; Shimizu, Tatsuya

    2015-12-01

    Cellular self-assembly based on cell-to-cell communication is a well-known tissue organizing process in living bodies. Hence, integrating cellular self-assembly processes into tissue engineering is a promising approach to fabricate well-organized functional tissues. In this research, we investigated the capability of endothelial cells (ECs) to control shape and position of vascular formation using arbitral-assembling techniques in three-dimensional engineered tissues. To quantify the degree of migration of ECs in endothelial network formation, image correlation analysis was conducted. Positive correlation between the original positions of arbitrarily assembled ECs and the positions of formed endothelial networks indicated the potential for controlling shape and position of vascular formations in engineered tissues. To demonstrate the feasibility of controlling vascular formations, engineered tissues with vascular networks in triangle and circle patterns were made. The technique reported here employs cellular self-assembly for tissue engineering and is expected to provide fundamental beneficial methods to supply various functional tissues for drug screening and regenerative medicine. PMID:26545138

  2. Design of an antagonistic shape memory alloy actuator for flap type control surfaces

    NASA Astrophysics Data System (ADS)

    Dönmez, Burcu; Özkan, Bülent

    2011-03-01

    This paper deals with the flap control of unmanned aerial vehicles (UAVs) using shape memory alloy (SMA) actuators in an antagonistic configuration. The use of SMA actuators has the advantage of significant weight and cost reduction over the conventional actuation of the UAV flaps by electric motors or hydraulic actuators. In antagonistic configuration, two SMA actuators are used: one to rotate the flap clockwise and the other to rotate the flap counterclockwise. In this content, mathematical modeling of strain and power dissipation of SMA wire is obtained through characterization tests. Afterwards, the model of the antagonistic flap mechanism is derived. Later, based on these models both flap angle and power dissipation of the SMA wire are controlled in two different loops employing proportional-integral type and neural network based control schemes. The angle commands are converted to power commands through the outer loop controller later, which are updated using the error in the flap angle induced because of the indirect control and external effects. In this study, power consumption of the wire is introduced as a new internal feedback variable. Constructed simulation models are run and performance specifications of the proposed control systems are investigated. Consequently, it is shown that proposed controllers perform well in terms of achieving small tracking errors.

  3. A parabolic model to control quantum interference in T-shaped molecular junctions.

    PubMed

    Nozaki, Daijiro; Sevinçli, Hâldun; Avdoshenko, Stanislav M; Gutierrez, Rafael; Cuniberti, Gianaurelio

    2013-09-01

    Quantum interference (QI) effects in molecular devices have drawn increasing attention over the past years due to their unique features observed in the conductance spectrum. For the further development of single molecular devices exploiting QI effects, it is of great theoretical and practical interest to develop simple methods controlling the emergence and the positions of QI effects like anti-resonances or Fano line shapes in conductance spectra. In this work, starting from a well-known generic molecular junction with a side group (T-shaped molecule), we propose a simple graphical method to visualize the conditions for the appearance of quantum interference, Fano resonances or anti-resonances, in the conductance spectrum. By introducing a simple graphical representation (parabolic diagram), we can easily visualize the relation between the electronic parameters and the positions of normal resonant peaks and anti-resonant peaks induced by quantum interference in the conductance spectrum. This parabolic model not only can predict the emergence and energetic position of quantum interference from a few electronic parameters but also can enable one to know the coupling between the side group and the main conduction channel from measurements in the case of orthogonal basis. The results obtained within the parabolic model are validated using density-functional based quantum transport calculations in realistic T-shaped molecular junctions. PMID:23558406

  4. A Finger-Shaped Tactile Sensor for Fabric Surfaces Evaluation by 2-Dimensional Active Sliding Touch

    PubMed Central

    Hu, Haihua; Han, Yezhen; Song, Aiguo; Chen, Shanguang; Wang, Chunhui; Wang, Zheng

    2014-01-01

    Sliding tactile perception is a basic function for human beings to determine the mechanical properties of object surfaces and recognize materials. Imitating this process, this paper proposes a novel finger-shaped tactile sensor based on a thin piezoelectric polyvinylidene fluoride (PVDF) film for surface texture measurement. A parallelogram mechanism is designed to ensure that the sensor applies a constant contact force perpendicular to the object surface, and a 2-dimensional movable mechanical structure is utilized to generate the relative motion at a certain speed between the sensor and the object surface. By controlling the 2-dimensional motion of the finger-shaped sensor along the object surface, small height/depth variation of surface texture changes the output charge of PVDF film then surface texture can be measured. In this paper, the finger-shaped tactile sensor is used to evaluate and classify five different kinds of linen. Fast Fourier Transformation (FFT) is utilized to get original attribute data of surface in the frequency domain, and principal component analysis (PCA) is used to compress the attribute data and extract feature information. Finally, low dimensional features are classified by Support Vector Machine (SVM). The experimental results show that this finger-shaped tactile sensor is effective and high accurate for discriminating the five textures. PMID:24618775

  5. A finger-shaped tactile sensor for fabric surfaces evaluation by 2-dimensional active sliding touch.

    PubMed

    Hu, Haihua; Han, Yezhen; Song, Aiguo; Chen, Shanguang; Wang, Chunhui; Wang, Zheng

    2014-01-01

    Sliding tactile perception is a basic function for human beings to determine the mechanical properties of object surfaces and recognize materials. Imitating this process, this paper proposes a novel finger-shaped tactile sensor based on a thin piezoelectric polyvinylidene fluoride (PVDF) film for surface texture measurement. A parallelogram mechanism is designed to ensure that the sensor applies a constant contact force perpendicular to the object surface, and a 2-dimensional movable mechanical structure is utilized to generate the relative motion at a certain speed between the sensor and the object surface. By controlling the 2-dimensional motion of the finger-shaped sensor along the object surface, small height/depth variation of surface texture changes the output charge of PVDF film then surface texture can be measured. In this paper, the finger-shaped tactile sensor is used to evaluate and classify five different kinds of linen. Fast Fourier Transformation (FFT) is utilized to get original attribute data of surface in the frequency domain, and principal component analysis (PCA) is used to compress the attribute data and extract feature information. Finally, low dimensional features are classified by Support Vector Machine (SVM). The experimental results show that this finger-shaped tactile sensor is effective and high accurate for discriminating the five textures. PMID:24618775

  6. Parallelogram plate shaped foldecture from the controlled self-assembly of α/β-peptide foldamer

    NASA Astrophysics Data System (ADS)

    Eom, Jae-Hoon; Gong, Jintaek; Jeong, Rokam; Driver, Russell W.; Lee, Hee-Seung

    2015-10-01

    Foldecture is a versatile material for the design of functional and well-defined 3D peptide architectures. In order to develop design principles for this emerging class of material, a systematic study of the relationship between foldecture morphology and molecular-level structure is necessary. Herein we report the formation of parallelogram plate shaped foldecture by the controlled self-assembly of heterogeneous α/β-peptide foldamer. Physical properties of foldecture were examined by IR, TGA, DSC, PXRD analysis. The foldecture packing motif was determined by high-resolution powder X-ray diffraction techniques and provides a link between the molecular-level structure and microscale morphologies.

  7. Optimum shape control of flexible beams by piezo-electric actuators

    NASA Technical Reports Server (NTRS)

    Baz, A.; Poh, S.

    1987-01-01

    The utilization of piezoelectric actuators in controlling the static deformation and shape of flexible beams is examined. An optimum design procedure is presented to enable the selection of the optimal location, thickness and excitation voltage of the piezoelectric actuators in a way that would minimize the deflection of the beam to which these actuators are bonded. Numerical examples are presented to illustrate the application of the developed optimization procedure in minimizing structural deformation of beams using ceramic and polymeric piezoelectric actuators bonded to the beams with a typical bonding agent. The obtained results emphasize the importance of the devised rational produce in designing beam-actuator systems with minimal elastic distortions.

  8. Shape-Controlled Metal-Metal and Metal-Polymer Janus Structures by Thermoplastic Embossing.

    PubMed

    Hasan, Molla; Kahler, Niloofar; Kumar, Golden

    2016-05-01

    We report the fabrication of metal-metal and metal-polymer Janus structures by embossing of thermoplastic metallic glasses and polymers. Hybrid structures with controllable shapes and interfaces are synthesized by template-assisted embossing. Different manufacturing strategies such as co-embossing and additive embossing are demonstrated for joining the materials with diverse compositions and functionalities. Structures with distinct combinations of properties such as hydrophobic-hydrophilic, opaque-transparent, insulator-conductor, and nonmagnetic-ferromagnetic are produced using this approach. These anisotropic properties are further utilized for selective functionalization of Janus structures. PMID:27064306

  9. Parameter for the vertical-position control of dee-shaped plasmas in Doublet III

    SciTech Connect

    Yokomizo, H.; Seki, S.; Shimada, M.; Nagami, M.; Konoshima, S.; Fujisawa, N.; Ohara, Y.; Ioki, K.; Kitsunezaki, A.

    1981-06-01

    A simple method has been developed using three magnetic probes to detect the vertical position of the center of dee-shaped plasmas located in the upper lobe of Doublet III. This parameter has no dependence on the plasma current and only a small dependence on the horizontal (radial) position of the plasma column. The comparison between the new parameter and the result of MHD calculation shows good correlation with the vertical position of the plasma center. This provides an effective means for improving control of the plasma position and maintaining stable dee plasmas.

  10. Final Technical Report: Numerical and Experimental Investigation of Turbulent Transport Control via Shaping of Radial Plasma Flow Profiles

    SciTech Connect

    Schuster, Eugenio

    2014-05-02

    The strong coupling between the different physical variables involved in the plasma transport phenomenon and the high complexity of its dynamics call for a model-based, multivariable approach to profile control where those predictive models could be exploited. The overall objective of this project has been to extend the existing body of work by investigating numerically and experimentally active control of unstable fluctuations, including fully developed turbulence and the associated cross-field particle transport, via manipulation of flow profiles in a magnetized laboratory plasma device. Fluctuations and particle transport can be monitored by an array of electrostatic probes, and Ex B flow profiles can be controlled via a set of biased concentric ring electrodes that terminate the plasma column. The goals of the proposed research have been threefold: i- to develop a predictive code to simulate plasma transport in the linear HELCAT (HELicon-CAThode) plasma device at the University of New Mexico (UNM), where the experimental component of the proposed research has been carried out; ii- to establish the feasibility of using advanced model-based control algorithms to control cross-field turbulence-driven particle transport through appropriate manipulation of radial plasma flow profiles, iii- to investigate the fundamental nonlinear dynamics of turbulence and transport physics. Lehigh University (LU), including Prof. Eugenio Schuster and one full-time graduate student, has been primarily responsible for control-oriented modeling and model-based control design. Undergraduate students have also participated in this project through the National Science Foundation Research Experience for Undergraduate (REU) program. The main goal of the LU Plasma Control Group has been to study the feasibility of controlling turbulence-driven transport by shaping the radial poloidal flow profile (i.e., by controlling flow shear) via biased concentric ring electrodes.

  11. The Middeck Active Control Experiment (MACE): Identification for robust control

    NASA Astrophysics Data System (ADS)

    Karlov, Valery I.

    Viewgraphs on identification for robust control for the Middeck Active Control Experiment (MACE) are presented. Topics covered include: identification for robust control; three levels of identification; basic elements of the approach; advantages of 'post-ID' model of uncertainty; advantages of optimization; and practical realization.

  12. The Middeck Active Control Experiment (MACE): Identification for robust control

    NASA Technical Reports Server (NTRS)

    Karlov, Valery I.

    1992-01-01

    Viewgraphs on identification for robust control for the Middeck Active Control Experiment (MACE) are presented. Topics covered include: identification for robust control; three levels of identification; basic elements of the approach; advantages of 'post-ID' model of uncertainty; advantages of optimization; and practical realization.

  13. The relationship between three-dimensional knee MRI bone shape and total knee replacement—a case control study: data from the Osteoarthritis Initiative

    PubMed Central

    Barr, Andrew J.; Dube, Bright; Hensor, Elizabeth M. A.; Kingsbury, Sarah R.; Peat, George; Bowes, Mike A.; Sharples, Linda D.

    2016-01-01

    Objective. There is growing understanding of the importance of bone in OA. Our aim was to determine the relationship between 3D MRI bone shape and total knee replacement (TKR). Methods. A nested case-control study within the Osteoarthritis Initiative cohort identified case knees with confirmed TKR for OA and controls that were matched using propensity scores. Active appearance modelling quantification of the bone shape of all knee bones identified vectors between knees having or not having OA. Vectors were scaled such that −1 and +1 represented the mean non-OA and mean OA shapes. Results. Compared to controls (n = 310), TKR cases (n = 310) had a more positive mean baseline 3D bone shape vector, indicating more advanced structural OA, for the femur [mean 0.98 vs −0.11; difference (95% CI) 1.10 (0.88, 1.31)], tibia [mean 0.86 vs −0.07; difference (95% CI) 0.94 (0.72, 1.16)] and patella [mean 0.95 vs 0.03; difference (95% CI) 0.92 (0.65, 1.20)]. Odds ratios (95% CI) for TKR per normalized unit of 3D bone shape vector for the femur, tibia and patella were: 1.85 (1.59, 2.16), 1.64 (1.42, 1.89) and 1.36 (1.22, 1.50), respectively, all P < 0.001. After including Kellgren–Lawrence grade in a multivariable analysis, only the femur 3D shape vector remained significantly associated with TKR [odds ratio 1.24 (1.02, 1.51)]. Conclusion. 3D bone shape was associated with the endpoint of this study, TKR, with femoral shape being most associated. This study contributes to the validation of quantitative MRI bone biomarkers for OA structure-modification trials. PMID:27185958

  14. Segmentation of the Left Ventricle in Myocardial Perfusion SPECT Using Active Shape Model

    NASA Astrophysics Data System (ADS)

    Tan, Wooi-Haw; Besar, Rosli

    In the quantification of myocardial perfusion SPECT (MPS), numerous processes are involved. Automation is desired as it will considerably reduce the laboriousness of the underlying tasks. In this paper, we propose a segmentation scheme for the delineation of left ventricle (LV) using the Active Shape Models. Our scheme will reduce the labour-intensiveness in MPS quantification, while still allowing interactive guidance from the medical experts. The proposed scheme has been applied on clinical MPS tomograms in which it has successfully delineated the LV in 94% of the test data. In addition, it has also shown to be more suitable for LV segmentation than the rivaling Active Contour Model.

  15. Hysteresis Analysis and Positioning Control for a Magnetic Shape Memory Actuator

    PubMed Central

    Lin, Jhih-Hong; Chiang, Mao-Hsiung

    2015-01-01

    Magnetic shape memory alloys (MSM alloys), a new kind of smart materials, have become a potential candidate in many engineering fields. MSMs have the advantage of bearing a huge strain, much larger than other materials. In addition, they also have fast response. These characteristics make MSM a good choice in micro engineering. However, MSMs display the obvious hysteresis phenomenon of nonlinear behavior. Thus the difficulty in using the MSM element as a positioning actuator is increased due to the hysteresis. In this paper, the hysteresis phenomenon of the MSM actuator is analyzed, and the closed-loop positioning control is also implemented experimentally. For that, a modified fuzzy sliding mode control (MFSMC) is proposed. The MFSMC and the PID control are used to design the controllers for realizing the positioning control. The experimental results are compared under different experimental conditions, such as different frequency, amplitude, and loading. The experimental results show that the precise positioning control of MFSMC can be achieved satisfactorily. PMID:25853405

  16. Control of Metal Arrays Based on Heterometallics Masquerading in Heterochiral Aggregations of Chiral Clothespin-Shaped Complexes.

    PubMed

    Naito, Masaya; Inoue, Ryo; Iida, Masayuki; Kuwajima, Yuuki; Kawamorita, Soichiro; Komiya, Naruyoshi; Naota, Takeshi

    2015-09-01

    Heterometal arrays in molecular aggregations were obtained by the spontaneous and ultrasound-induced gelation of organic liquids containing the chiral, clothespin-shaped trans-bis(salicylaldiminato) d8 transition-metal complexes 1. Heterometallic mixtures of complexes 1 a (Pd) and 1 b (Pt) underwent strict heterochiral aggregation entirely due to the organic shell structure of the clothespin shape, with no effect of the metal cores. This phenomenon provides an unprecedented means of generating highly controlled heterometallic arrangements such as alternating sequences [(+)-Pd(-)-Pt(+)-Pd(-)-Pt⋅⋅⋅] as well as a variety of single metal-enriched arrays (e.g., [(+)-Pt(-)-Pd(+)-Pd(-)-Pd(+)-Pd(-)-Pd⋅⋅⋅] and [(+)-Pd(-)-Pt(+)-Pt(-)-Pt(+)-Pt(-)-Pt⋅⋅⋅]) upon the introduction of an optically active masquerading unit with a different metal core in the heterochiral single-metal sequence. The present method can be applied to form various new aggregates with optically active Pd and Pt units, to allow 1) tuning of the gelation ultrasound sensitivity based on the different hearing abilities of the metal units; 2) aggregation-induced chirality transfer between heterometallic species; and 3) aggregation-induced chirality enhancement. A mechanistic rationale is proposed for these molecular aggregations based on the molecular structures of the units and the morphologies of the aggregates. PMID:26212577

  17. Shape-dependent control of cell growth, differentiation, and apoptosis: switching between attractors in cell regulatory networks

    NASA Technical Reports Server (NTRS)

    Huang, S.; Ingber, D. E.

    2000-01-01

    Development of characteristic tissue patterns requires that individual cells be switched locally between different phenotypes or "fates;" while one cell may proliferate, its neighbors may differentiate or die. Recent studies have revealed that local switching between these different gene programs is controlled through interplay between soluble growth factors, insoluble extracellular matrix molecules, and mechanical forces which produce cell shape distortion. Although the precise molecular basis remains unknown, shape-dependent control of cell growth and function appears to be mediated by tension-dependent changes in the actin cytoskeleton. However, the question remains: how can a generalized physical stimulus, such as cell distortion, activate the same set of genes and signaling proteins that are triggered by molecules which bind to specific cell surface receptors. In this article, we use computer simulations based on dynamic Boolean networks to show that the different cell fates that a particular cell can exhibit may represent a preprogrammed set of common end programs or "attractors" which self-organize within the cell's regulatory networks. In this type of dynamic network model of information processing, generalized stimuli (e.g., mechanical forces) and specific molecular cues elicit signals which follow different trajectories, but eventually converge onto one of a small set of common end programs (growth, quiescence, differentiation, apoptosis, etc.). In other words, if cells use this type of information processing system, then control of cell function would involve selection of preexisting (latent) behavioral modes of the cell, rather than instruction by specific binding molecules. Importantly, the results of the computer simulation closely mimic experimental data obtained with living endothelial cells. The major implication of this finding is that current methods used for analysis of cell function that rely on characterization of linear signaling pathways or

  18. Controlling the Size and Shape of the Elastin-Like Polypeptide based Micelles

    NASA Astrophysics Data System (ADS)

    Streletzky, Kiril; Shuman, Hannah; Maraschky, Adam; Holland, Nolan

    Elastin-like polypeptide (ELP) trimer constructs make reliable environmentally responsive micellar systems because they exhibit a controllable transition from being water-soluble at low temperatures to aggregating at high temperatures. It has been shown that depending on the specific details of the ELP design (length of the ELP chain, pH and salt concentration) micelles can vary in size and shape between spherical micelles with diameter 30-100 nm to elongated particles with an aspect ratio of about 10. This makes ELP trimers a convenient platform for developing potential drug delivery and bio-sensing applications as well as for understanding micelle formation in ELP systems. Since at a given salt concentration, the headgroup area for each foldon should be constant, the size of the micelles is expected to be proportional to the volume of the linear ELP available per foldon headgroup. Therefore, adding linear ELPs to a system of ELP-foldon should result in changes of the micelle volume allowing to control micelle size and possibly shape. The effects of addition of linear ELPs on size, shape, and molecular weight of micelles at different salt concentrations were studied by a combination of Dynamic Light Scattering and Static Light Scattering. The initial results on 50 µM ELP-foldon samples (at low salt) show that Rh of mixed micelles increases more than 5-fold as the amount of linear ELP raised from 0 to 50 µM. It was also found that a given mixture of linear and trimer constructs has two temperature-based transitions and therefore displays three predominant size regimes.

  19. Student Activity Funds: Procedures & Controls.

    ERIC Educational Resources Information Center

    Cuzzetto, Charles E.

    Student activity funds may create educational opportunities for students, but they frequently create problems for business administrators. The first part of this work reviews the types of organizational issues and transactions an organized student group is likely to encounter, including establishing a constitution, participant roles,…

  20. Optimization of ultra-fast interactions using laser pulse temporal shaping controlled by a deterministic algorithm

    NASA Astrophysics Data System (ADS)

    Galvan-Sosa, M.; Portilla, J.; Hernandez-Rueda, J.; Siegel, J.; Moreno, L.; Ruiz de la Cruz, A.; Solis, J.

    2014-02-01

    Femtosecond laser pulse temporal shaping techniques have led to important advances in different research fields like photochemistry, laser physics, non-linear optics, biology, or materials processing. This success is partly related to the use of optimal control algorithms. Due to the high dimensionality of the solution and control spaces, evolutionary algorithms are extensively applied and, among them, genetic ones have reached the status of a standard adaptive strategy. Still, their use is normally accompanied by a reduction of the problem complexity by different modalities of parameterization of the spectral phase. Exploiting Rabitz and co-authors' ideas about the topology of quantum landscapes, in this work we analyze the optimization of two different problems under a deterministic approach, using a multiple one-dimensional search (MODS) algorithm. In the first case we explore the determination of the optimal phase mask required for generating arbitrary temporal pulse shapes and compare the performance of the MODS algorithm to the standard iterative Gerchberg-Saxton algorithm. Based on the good performance achieved, the same method has been applied for optimizing two-photon absorption starting from temporally broadened laser pulses, or from laser pulses temporally and spectrally distorted by non-linear absorption in air, obtaining similarly good results which confirm the validity of the deterministic search approach.

  1. Optimization of ultra-fast interactions using laser pulse temporal shaping controlled by a deterministic algorithm

    NASA Astrophysics Data System (ADS)

    Galvan-Sosa, M.; Portilla, J.; Hernandez-Rueda, J.; Siegel, J.; Moreno, L.; Ruiz de la Cruz, A.; Solis, J.

    2013-04-01

    Femtosecond laser pulse temporal shaping techniques have led to important advances in different research fields like photochemistry, laser physics, non-linear optics, biology, or materials processing. This success is partly related to the use of optimal control algorithms. Due to the high dimensionality of the solution and control spaces, evolutionary algorithms are extensively applied and, among them, genetic ones have reached the status of a standard adaptive strategy. Still, their use is normally accompanied by a reduction of the problem complexity by different modalities of parameterization of the spectral phase. Exploiting Rabitz and co-authors' ideas about the topology of quantum landscapes, in this work we analyze the optimization of two different problems under a deterministic approach, using a multiple one-dimensional search (MODS) algorithm. In the first case we explore the determination of the optimal phase mask required for generating arbitrary temporal pulse shapes and compare the performance of the MODS algorithm to the standard iterative Gerchberg-Saxton algorithm. Based on the good performance achieved, the same method has been applied for optimizing two-photon absorption starting from temporally broadened laser pulses, or from laser pulses temporally and spectrally distorted by non-linear absorption in air, obtaining similarly good results which confirm the validity of the deterministic search approach.

  2. Shape-controllable and versatile synthesis of copper nanocrystals with amino acids as capping agents.

    PubMed

    Yu, Jin-Cheng; Zhao, Fu-Gang; Shao, Wei; Ge, Cong-Wu; Li, Wei-Shi

    2015-05-21

    Thanks to their outstanding properties and a wide range of promising applications, the development of a versatile and convenient preparation method for metallic copper nanocrystals with controllable shape is of primary significance. Different from the literature that utilized a capping agent bearing only one kind of Cu binding functionality, either an amino or a carboxylic unit, for their preparation and shape control, this contribution reports a convenient method to engage both amino and carboxylic binding units at the same time. In this method, natural amino acids have been chosen as capping agents and demonstrated their versatile capabilities for the preparation of both Cu nanoparticles and nanowires. Detailed X-ray photoelectron spectroscopy revealed that the binding mode between amino acids and the Cu surface is highly dependent on their chemical structures. Interestingly, the produced Cu nanocrystals, exhibited an extraordinarily excellent anti-oxidation power. Furthermore, it was found that the multiple functionalities of amino acids not only have a great impact on the properties of their capped nanocrystals, such as solvent dispersibility, but also provide a convenient route for their further modification and functionalization. PMID:25908551

  3. Shape- and Interface-Induced Control of Spin Dynamics of Two-Dimensional Bicomponent Magnonic Crystals.

    PubMed

    Choudhury, Samiran; Saha, Susmita; Mandal, Ruma; Barman, Saswati; Otani, YoshiChika; Barman, Anjan

    2016-07-20

    Controlled fabrication of periodically arranged embedded nanostructures with strong interelement interaction through the interface between the two different materials has great potential applications in spintronics, spin logic, and other spin-based communication devices. Here, we report the fabrication of two-dimensional bicomponent magnonic crystals in form of embedded Ni80Fe20 nanostructures in Co50Fe50 thin films by nanolithography. The spin wave (SW) spectra studied by a broadband ferromagnetic resonance spectroscopy showed a significant variation as the shape of the embedded nanostructure changes from circular to square. Significantly, in both shapes, a minimum in frequency is obtained at a negative value of bias field during the field hysteresis confirming the presence of a strong exchange coupling at the interface between the two materials, which can potentially increase the spin wave propagation velocity in such structures leading to faster gigahertz frequency magnetic communication and logic devices. The spin wave frequencies and bandgaps show bias field tunability, which is important for above device applications. Numerical simulations qualitatively reproduced the experimental results, and simulated mode profiles revealed the spatial distribution of the SW modes and internal magnetic fields responsible for this observation. Development of such controlled arrays of embedded nanostructures with improved interface can be easily applied to other forms of artificial crystals. PMID:27345034

  4. Shape-controlled synthesis of Cu2O nanocrystals assisted by Triton X-100

    NASA Astrophysics Data System (ADS)

    Luo, Fang; Wu, Di; Gao, Lei; Lian, Suoyuan; Wang, Enbo; Kang, Zhenhui; Lan, Yang; Xu, Lin

    2005-12-01

    Cuprous oxide (Cu2O) nanocrystals with tubular, cubic and hollow cubic morphologies were obtained in simple solution-phase reduction systems using nonionic surfactant octylphenyl ether (Triton X-100) as solvent. Uniform single crystal nanotubes with outer diameters of ˜20 nm, inner diameters of ˜10 nm and lengths of ˜120 nm were prepared through reduction of CuCl2 by glucose. When a little amount of water was dispersed into Triton X-100, uniform cube-shaped polycrystals with edge lengths of ˜180 nm were synthesized, with ascorbic acid as the reducing agent. The water cores formed by surrounded Triton X-100 molecules with hydrophilic heads immersed provided the reaction rooms. With the help of ethanol introduced into water cores by Triton X-100 molecules, Cu2O nanocubes turned to hollow cubes with edge lengths of ˜200 nm during the ripening process. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) were used to investigate the different morphologies of the as-synthesized products. X-ray powder diffraction (XRD) and selected area electron diffraction (SAED) were applied to characterize the composition and crystal phases of the products. It was proposed that molecules and molecule assemblies of Triton X-100 played different roles in the shape-controlled synthesis process, which were realized by carefully controlling the experiment conditions.

  5. Controlling the growth and shape of chiral supramolecular polymers in water

    PubMed Central

    Besenius, Pol; Portale, Giuseppe; Bomans, Paul H. H.; Janssen, Henk M.; Palmans, Anja R. A.; Meijer, E. W.

    2010-01-01

    A challenging target in the noncovalent synthesis of nanostructured functional materials is the formation of uniform features that exhibit well-defined properties, e.g., precise control over the aggregate shape, size, and stability. In particular, for aqueous-based one-dimensional supramolecular polymers, this is a daunting task. Here we disclose a strategy based on self-assembling discotic amphiphiles that leads to the control over stack length and shape of ordered, chiral columnar aggregates. By balancing out attractive noncovalent forces within the hydrophobic core of the polymerizing building blocks with electrostatic repulsive interactions on the hydrophilic rim we managed to switch from elongated, rod-like assemblies to small and discrete objects. Intriguingly this rod-to-sphere transition is expressed in a loss of cooperativity in the temperature-dependent self-assembly mechanism. The aggregates were characterized using circular dichroism, UV and 1H-NMR spectroscopy, small angle X-ray scattering, and cryotransmission electron microscopy. In analogy to many systems found in biology, mechanistic details of the self-assembly pathways emphasize the importance of cooperativity as a key feature that dictates the physical properties of the produced supramolecular polymers. PMID:20921365

  6. Shape-specific activation of occipital cortex in an early blind echolocation expert.

    PubMed

    Arnott, Stephen R; Thaler, Lore; Milne, Jennifer L; Kish, Daniel; Goodale, Melvyn A

    2013-04-01

    We have previously reported that an early-blind echolocating individual (EB) showed robust occipital activation when he identified distant, silent objects based on echoes from his tongue clicks (Thaler, Arnott, & Goodale, 2011). In the present study we investigated the extent to which echolocation activation in EB's occipital cortex reflected general echolocation processing per se versus feature-specific processing. In the first experiment, echolocation audio sessions were captured with in-ear microphones in an anechoic chamber or hallway alcove as EB produced tongue clicks in front of a concave or flat object covered in aluminum foil or a cotton towel. All eight echolocation sessions (2 shapes×2 surface materials×2 environments) were then randomly presented to him during a sparse-temporal scanning fMRI session. While fMRI contrasts of chamber versus alcove-recorded echolocation stimuli underscored the importance of auditory cortex for extracting echo information, main task comparisons demonstrated a prominent role of occipital cortex in shape-specific echo processing in a manner consistent with latent, multisensory cortical specialization. Specifically, relative to surface composition judgments, shape judgments elicited greater BOLD activity in ventrolateral occipital areas and bilateral occipital pole. A second echolocation experiment involving shape judgments of objects located 20° to the left or right of straight ahead activated more rostral areas of EB's calcarine cortex relative to location judgments of those same objects and, as we previously reported, such calcarine activity was largest when the object was located in contralateral hemispace. Interestingly, other echolocating experts (i.e., a congenitally blind individual in Experiment 1, and a late blind individual in Experiment 2) did not show the same pattern of feature-specific echo-processing calcarine activity as EB, suggesting the possible significance of early visual experience and early

  7. Three-dimensional active shape model matching for left ventricle segmentation in cardiac CT

    NASA Astrophysics Data System (ADS)

    van Assen, Hans C.; van der Geest, Rob J.; Danilouchkine, Mikhail G.; Lamb, Hildo J.; Reiber, Johan H. C.; Lelieveldt, Boudewijn P. F.

    2003-05-01

    Manual quantitative analysis of cardiac left ventricular function using multi-slice CT is labor intensive because of the large datasets. We present an automatic, robust and intrinsically three-dimensional segmentation method for cardiac CT images, based on 3D Active Shape Models (ASMs). ASMs describe shape and shape variations over a population as a mean shape and a number of eigenvariations, which can be extracted by e.g. Principal Component Analysis (PCA). During the iterative ASM matching process, the shape deformation is restricted within statistically plausible constraints (+/-3σ). Our approach has two novel aspects: the 3D-ASM application to volume data of arbitrary planar orientation, and the application to image data from another modality than which was used to train the model, without the necessity of retraining it. The 3D-ASM was trained on MR data and quantitatively evaluated on 17 multi-slice cardiac CT data sets, with respect to calculated LV volume (blood pool plus myocardium) and endocardial volume. In all cases, model matching was convergent and final results showed a good model performance. Bland-Altman analysis however, showed that bloodpool volume was slightly underestimated and LV volume was slightly overestimated by the model. Nevertheless, these errors remain within clinically acceptable margins. Based on this evaluation, we conclude that our 3D-ASM combines robustness with clinically acceptable accuracy. Without retraining for cardiac CT, we could adapt a model trained on cardiac MR data sets for application in cardiac CT volumes, demonstrating the flexibility and feasibility of our matching approach. Causes for the systematic errors are edge detection, model constraints, or image data reconstruction. For all these categories, solutions are discussed.

  8. Inverse problem for shape control of flexible space reflectors using distributed solar pressure

    NASA Astrophysics Data System (ADS)

    Borggräfe, A.; Heiligers, J.; Ceriotti, M.; McInnes, C. R.

    2014-07-01

    This paper investigates controlled elastic deflection of thin circular space reflectors using an inverse problem approach to non-linear thin membrane theory. When changing the surface reflectivity across the membrane, the distributed loads due to ambient solar radiation pressure can be manipulated optically, thus controlling the surface shape without using mechanical or piezo-electric systems. The surface reflectivity can in principle be modulated using uniformly distributed thin-film electro-chromic coatings. We present an analytic solution to the inverse problem of finding the necessary reflectivity distribution that creates a specific membrane deflection, for example that of a parabolic reflector. Importantly, the reflectivity distribution across the surface is found to be independent of membrane size, thickness and solar distance, enabling engineering of the reflectivity distribution directly during the manufacture of the membrane.

  9. Coherent control in quantum dot gain media using shaped pulses: a numerical study.

    PubMed

    Mishra, Akhilesh Kumar; Karni, Ouri; Eisenstein, Gadi

    2015-11-16

    We present a numerical study of coherent control in a room temperature InAs/InP quantum dot (QD) semiconductor optical amplifier (SOA) using shaped ultra-short pulses. Both the gain and absorption regimes were analyzed for pulses with central wavelengths lying on either side of the inhomogeneously broadened gain spectrum. The numerical experiments predict that in the gain regime the coherent interactions between a QD SOA and a pulse can be controlled by incorporating a quadratic spectral phase (QSP) in the pulse profile. The sequential interaction with the gain medium of different spectral components of the pulse results in either suppression or enhancement of the coherent signatures on the pulse profile depending upon their proximity to the gain spectrum peak. In the absorption regime, positive QSP induces a negative chirp that adds up to that of a two photon absorption induced Kerr-like effect resulting in pulse compression while negative QSP enhances dispersive broadening of the pulse. PMID:26698476

  10. Fabrication of shape controlled Fe{sub 3}O{sub 4} nanostructure

    SciTech Connect

    Zheng, Y.Y.; Wang, X.B.; Shang, L.; Li, C.R.; Cui, C.; Dong, W.J.; Tang, W.H.; Chen, B.Y.

    2010-04-15

    Shape-controlled Fe{sub 3}O{sub 4} nanostructure has been successfully prepared using polyethylene glycol as template in a water system at room temperature. Different morphologies of Fe{sub 3}O{sub 4} nanostructures, including spherical, cubic, rod-like, and dendritic nanostructure, were obtained by carefully controlling the concentration of the Fe{sup 3+}, Fe{sup 2+}, and the molecular weight of the polyethylene glycol. Transmission Electron Microscope images, X-ray powder diffraction patterns and magnetic properties were used to characterize the final product. This easy procedure for Fe{sub 3}O{sub 4} nanostructure fabrication offers the possibility of a generalized approach to the production of single and complex nanocrystalline oxide with tunable morphology.

  11. Shape regulated anticancer activities and systematic toxicities of drug nanocrystals in vivo.

    PubMed

    Zhou, Mengjiao; Zhang, Xiujuan; Yu, Caitong; Nan, Xueyan; Chen, Xianfeng; Zhang, Xiaohong

    2016-01-01

    In this paper, shape regulated anticancer activities as well as systematic toxicities of hydroxycamptothecin nanorods and nanoparticles (HCPT NRs and NPs) were systematically studied. In vitro and in vivo therapeutic efficacies were evaluated in cancer cells and tumor-bearing mice, indicating that NRs possessed superior antitumor efficacy over NPs at the equivalent dose, while systematic toxicity of the differently shaped nanodrugs assessed in healthy mice, including the maximum tolerated dose, blood analysis and histology examinations and so on, suggested that the NRs also caused higher toxicities than NPs, and also had a long-term toxicity. These results imply that the balance between anticancer efficiency and systematic toxicity of drug nanocrystals should be fully considered in practice, which will provide new concept in the future design of drug nanocrystals for cancer therapy. From the Clinical Editor: Advances in nanotechnology have enabled the design of novel nanosized drugs for the treatment of cancer. One of the interesting findings thus far is the different biological effects seen with different shaped nanoparticles. In this article, the authors investigated and compared the anticancer activities of hydroxycamptothecin nanorods and nanoparticles. The experimental data would provide a better understanding for future drug design. PMID:26427356

  12. Active-member control of precision structures

    NASA Technical Reports Server (NTRS)

    Fanson, J. L.; Blackwood, G. H.; Chu, C. C.

    1989-01-01

    This paper presents the results of closed loop experiments that use piezoelectric active-members to control the flexible motion of a precision truss structure. These experiments are directed toward the development of high performance structural systems as part of the Control/Structure Interaction program at JPL. Order of magnitude reductions in dynamic response are achieved with relatively simple control techniques. The practical implementation of high stiffness, high bandwidth active-members in a precision structure highlights specific issues of importance relating to the modelling and implementation of active-member control.

  13. Actively controlled shaft seals for aerospace applications

    NASA Technical Reports Server (NTRS)

    Salant, Richard F.

    1991-01-01

    Actively controlled mechanical seals have recently been developed for industrial use. This study investigates the feasibility of using such seals for aerospace applications. In a noncontacting mechanical seal, the film thickness depends on the geometry of the seal interface. The amount of coning, which is a measure of the radial convergence or divergence of the seal interface, has a primary effect on the film thickness. Active control of the film thickness is established by controlling the coning with a piezoelectric material. A mathematical model has been formulated to predict the performance of an actively controlled mechanical seal.

  14. A deformable lung tumor tracking method in fluoroscopic video using active shape models: a feasibility study

    NASA Astrophysics Data System (ADS)

    Xu, Qianyi; Hamilton, Russell J.; Schowengerdt, Robert A.; Jiang, Steve B.

    2007-09-01

    A dynamic multi-leaf collimator (DMLC) can be used to track a moving target during radiotherapy. One of the major benefits for DMLC tumor tracking is that, in addition to the compensation for tumor translational motion, DMLC can also change the aperture shape to conform to a deforming tumor projection in the beam's eye view. This paper presents a method that can track a deforming lung tumor in fluoroscopic video using active shape models (ASM) (Cootes et al 1995 Comput. Vis. Image Underst. 61 38-59). The method was evaluated by comparing tracking results against tumor projection contours manually edited by an expert observer. The evaluation shows the feasibility of using this method for precise tracking of lung tumors with deformation, which is important for DMLC-based real-time tumor tracking.

  15. Controller Parameter Tuning for Systems with Hysteresis and Its Application to Shape Memory Alloy Actuators

    NASA Astrophysics Data System (ADS)

    Wakasa, Yuji; Kanagawa, Shinji; Tanaka, Kanya; Nishimura, Yuki

    This paper proposes a simple controller parameter tuning method that can compensate for hysteresis. The proposed method is based on the so-called fictitious reference iterative tuning (FRIT) technique which can easily tune controller parameters such as proportional-integral-derivative gains using a one-shot closed-loop experimental data. In the proposed framework, a simple hysteresis model is introduced to a control system, and its inverse is used as a hysteresis compensator. Since the hysteresis model is characterized with only three parameters, the related computational burden is moderate in the parameter tuning process. Also, the proposed FRIT method needs an only one-shot experiment as in the standard FRIT one, which implies that the feature of FRIT is well-maintained. In the optimization process, the so-called covariance matrix adaptation evolution strategy is used for simultaneously searching hysteresis parameters as well as controller parameters. The proposed FRIT method is applied to an experimental control system that comprises a shape memory alloy actuator, and its effectiveness is verified.

  16. Real-time equilibrium reconstruction and isoflux control of plasma shape and position in NSTX

    NASA Astrophysics Data System (ADS)

    Stevenson, Tim; Gates, Dave A.; Mueller, Dennis; Ferron, John R.

    2004-11-01

    The rtEFIT - isoflux algorithm for real-time plasma control, developed at General Atomics, has been modified for control of the plasma equilibrium in NSTX. Real-time equilibrium reconstruction using the rtEFIT code provides the shape of the plasma boundary based on 62 magnetic field and flux measurements, 11 poloidal field coil current measurements as well as 9 loop voltage measurements to estimate the axi-symmetric components of the eddy currents induced in the vacuum vessel. The calculated plasma boundary is used in isoflux control algorithms that generate voltage requests to the coil power supplies based on the difference from the requested boundary flux and positions of the X-points. These plasma boundaries compare well to those reconstructed using the off-line equilibrium reconstruction code EFIT. Recent efforts reduced the latency in the real-time data flow from the sensors to the power supplies from 4 ms to less than 1ms and improved vertical position control which allows control of plasmas nearer stability boundaries.

  17. Active self-polarization of contractile cells in asymmetrically shaped domains.

    PubMed

    Zemel, A; Safran, S A

    2007-08-01

    Mechanical forces generated by contractile cells allow the cells to sense their environment and to interact with other cells. By locally pulling on their environment, cells can sense and respond to mechanical features such as the local stress (or strain), the shape of a cellular domain, and the surrounding rigidity; at the same time, they also modify the mechanical state of the system. This creates a mechanical feedback loop that can result in self-polarization of cells. In this paper, we present a quantitative mechanical model that predicts the self-polarization of cells in spheroidally shaped domains, comprising contractile cells and an elastic matrix, that are embedded in a three-dimensional, cell-free gel. The theory is based on a generalization of the known results for passive inclusions in solids to include the effects of cell activity. We use the active cellular susceptibility tensor presented by Zemel [Phys. Rev. Lett. 97, 128103 (2006)] to calculate the polarization response and hence the elastic stress field developed by the cells in the cellular domain. The cell polarization is analyzed as a function of the shape and the elastic moduli of the cellular domain compared with the cell-free surrounding material. Consistent with experiment, our theory predicts the development of a stronger contractile force for cells in a gel that is surrounded by a large, cell-free material whose elastic modulus is stiffer than that of the gel that contains the cells. This provides a quantitative explanation of the differences in the development of cellular forces as observed in free and fixed gels. In the case of an asymmetrically shaped (spheroidal) domain of cells, we show that the anisotropic elastic field within the domain leads to a spontaneous self-polarization of the cells along the long axis of the domain. PMID:17930063

  18. Shape-Dependent Biomimetic Inhibition of Enzyme by Nanoparticles and Their Antibacterial Activity.

    PubMed

    Cha, Sang-Ho; Hong, Jin; McGuffie, Matt; Yeom, Bongjun; VanEpps, J Scott; Kotov, Nicholas A

    2015-09-22

    Enzyme inhibitors are ubiquitous in all living systems, and their biological inhibitory activity is strongly dependent on their molecular shape. Here, we show that small zinc oxide nanoparticles (ZnO NPs)-pyramids, plates, and spheres-possess the ability to inhibit activity of a typical enzyme β-galactosidase (GAL) in a biomimetic fashion. Enzyme inhibition by ZnO NPs is reversible and follows classical Michaelis-Menten kinetics with parameters strongly dependent on their geometry. Diverse spectroscopic, biochemical, and computational experimental data indicate that association of GAL with specific ZnO NP geometries interferes with conformational reorganization of the enzyme necessary for its catalytic activity. The strongest inhibition was observed for ZnO nanopyramids and compares favorably to that of the best natural GAL inhibitors while being resistant to proteases. Besides the fundamental significance of this biomimetic function of anisotropic NPs, their capacity to serve as degradation-resistant enzyme inhibitors is technologically attractive and is substantiated by strong shape-specific antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), endemic for most hospitals in the world. PMID:26325486

  19. Active Control Of Structure-Borne Noise

    NASA Astrophysics Data System (ADS)

    Elliott, S. J.

    1994-11-01

    The successful practical application of active noise control requires an understanding of both its acoustic limitations and the limitations of the electrical control strategy used. This paper is concerned with the active control of sound in enclosures. First, a review is presented of the fundamental physical limitations of using loudspeakers to achieve either global or local control. Both approaches are seen to have a high frequency limit, due to either the acoustic modal overlap, or the spatial correlation function of the pressure field. These physical performance limits could, in principle, be achieved with either a feedback or a feedforward control strategy. These strategies are reviewed and the use of adaptive digital filters is discussed for both approaches. The application of adaptive feedforward control in the control of engine and road noise in cars is described. Finally, an indirect approach to the active control of sound is discussed, in which the vibration is suppressed in the structural paths connecting the source of vibration to the enclosure. Two specific examples of this strategy are described, using an active automotive engine mount and the incorporation of actuators into helicopter struts to control gear-meshing tones. In both cases good passive design can minimize the complexity of the active controller.

  20. Active vibration control of lightweight floor systems

    NASA Astrophysics Data System (ADS)

    Baader, J.; Fontana, M.

    2016-04-01

    Wide-span and lightweight floors are often prone to structural vibrations due to their low resonance frequency and poor material damping. Their dynamic behaviour can be improved using passive, semi-active or active vibration control devices. The following article proposes a novel method for the controller synthesis for active vibration control. An existing passive TMD (tuned mass damper) is modelled and equipped with an actuator in order to provide more efficient damping. Using an iterative optimization approach under constraints, an optimal controller is found which minimizes a quadratic cost function in frequency domain. A simulation of an existing test bench shows that the active vibration control device is able to provide increased damping compared to the passive TMD.

  1. Design, modelling and control of a micro-positioning actuator based on magnetic shape memory alloys

    NASA Astrophysics Data System (ADS)

    Minorowicz, Bartosz; Leonetti, Giuseppe; Stefanski, Frederik; Binetti, Giulio; Naso, David

    2016-07-01

    This paper presents an actuator based on magnetic shape memory alloys (MSMAs) suitable for precise positioning in a wide range (up to 1 mm). The actuator is based on the spring returned operating mode and uses a Smalley wave spring to maintain the same operating parameters of a classical coil spring, while being characterized by a smaller dimension. The MSMA element inside the actuator provides a deformation when excited by an external magnetic field, but its behavior is characterized by an asymmetric and saturated hysteresis. Thus, two models are exploited in this work to represent such a non-linear behavior, i.e., the modified and generalized Prandtl–Ishlinskii models. These models are particularly suitable for control purposes due to the existence of their analytical inversion that can be easily exploited in real time control systems. To this aim, this paper investigates three closed-loop control strategies, namely a classical PID regulator, a PID regulator with direct hysteresis compensation, and a combined PID and feedforward compensation strategy. The effectiveness of both modelling and control strategies applied to the designed MSMA-based actuator is illustrated by means of experimental results.

  2. Shape-controlled synthesis of Pd polyhedron supported on polyethyleneimine-reduced graphene oxide for enhancing the efficiency of hydrogen evolution reaction

    NASA Astrophysics Data System (ADS)

    Li, Jing; Zhou, Panpan; Li, Feng; Ma, Jianxin; Liu, Yang; Zhang, Xueyao; Huo, Hongfei; Jin, Jun; Ma, Jiantai

    2016-01-01

    The catalytic activity of noble-metal nanoparticles (NPs) often has closely connection with their sizes and geometric shape. In the work, polyhedral NPs of palladium (Pd) with controlled sizes, shapes, and different proportions of {100} to {111} facets on the surface were prepared by a seed-mediated approach. Electrochemical experiment demonstrates that the catalytic performance of the Pd nanocubes (NCs) enclosed by {100} facets is more active than Pd octahedrons enclosed by {111} facets for the hydrogen evolution reaction (HER), which is consistent with density functional theory (DFT) calculation results. Meanwhile, with the assistance of a polyethyleneimine-reduced graphene oxide (PEI-rGO) support, the examined Pd cube/PEI-rGO50:1 (10 wt. %) electrocatalyst presents outstanding HER activity comparable with that of commercial Pt/C catalyst. This correlation between the HER catalytic activity and surface structure will contribute to the reasonable design of Pd catalysts for HER with high efficiency and low metal loading.

  3. Shape- and dimension-controlled single-crystalline silicon and SiGe nanotubes: toward nanofluidic FET devices.

    PubMed

    Ben Ishai, Moshit; Patolsky, Fernando

    2009-03-18

    We report here on the formation of robust and entirely hollow single-crystalline silicon nanotubes, from various tubular to conical structures, with uniform and well-controlled inner diameter, ranging from as small as 1.5 up to 500 nm, and controllable wall thickness. Second, and most important, these nanotubes can be doped in situ with different concentrations of boron and phosphine to give p/n-type semiconductor nanotubes. Si(x)Ge(1-x)-alloy nanotubes can also be prepared. This synthetic approach enables independent and precise control of diameter, wall thickness, shape, taper angle, crystallinity, and chemical/electrical characteristics of the nanotubular structures obtained. Notably, diameter and wall thickness of nearly any size can be obtained. This unique advantage allows the achievement of novel and perfectly controlled high-quality electronic materials and the tailoring of the tube properties to better fit many biological, chemical, and electrical applications. Electrical devices based on this new family of electrically active nanotubular building-block structures are also described with a view toward the future realization of nanofluidic FET devices. PMID:19226180

  4. Do informal musical activities shape auditory skill development in preschool-age children?

    PubMed Central

    Putkinen, Vesa; Saarikivi, Katri; Tervaniemi, Mari

    2013-01-01

    The influence of formal musical training on auditory cognition has been well established. For the majority of children, however, musical experience does not primarily consist of adult-guided training on a musical instrument. Instead, young children mostly engage in everyday musical activities such as singing and musical play. Here, we review recent electrophysiological and behavioral studies carried out in our laboratory and elsewhere which have begun to map how developing auditory skills are shaped by such informal musical activities both at home and in playschool-type settings. Although more research is still needed, the evidence emerging from these studies suggests that, in addition to formal musical training, informal musical activities can also influence the maturation of auditory discrimination and attention in preschool-aged children. PMID:24009597

  5. Active-shape-model-based segmentation of abdominal aortic aneurysms in CTA images

    NASA Astrophysics Data System (ADS)

    de Bruijne, Marleen; van Ginneken, Bram; Niessen, Wiro J.; Maintz, J. B. Antoine; Viergever, Max A.

    2002-05-01

    An automated method for the segmentation of thrombus in abdominal aortic aneurysms from CTA data is presented. The method is based on Active Shape Model (ASM) fitting in sequential slices, using the contour obtained in one slice as the initialisation in the adjacent slice. The optimal fit is defined by maximum correlation of grey value profiles around the contour in successive slices, in contrast to the original ASM scheme as proposed by Cootes and Taylor, where the correlation with profiles from training data is maximised. An extension to the proposed approach prevents the inclusion of low-intensity tissue and allows the model to refine to nearby edges. The applied shape models contain either one or two image slices, the latter explicitly restricting the shape change from slice to slice. To evaluate the proposed methods a leave-one-out experiment was performed, using six datasets containing 274 slices to segment. Both adapted ASM schemes yield significantly better results than the original scheme (p<0.0001). The extended slice correlation fit of a one-slice model showed best overall performance. Using one manually delineated image slice as a reference, on average a number of 29 slices could be automatically segmented with an accuracy within the bounds of manual inter-observer variability.

  6. A 3-D active shape model driven by fuzzy inference: application to cardiac CT and MR.

    PubMed

    van Assen, Hans C; Danilouchkine, Mikhail G; Dirksen, Martijn S; Reiber, Johan H C; Lelieveldt, Boudewijn P F

    2008-09-01

    Manual quantitative analysis of cardiac left ventricular function using Multislice CT and MR is arduous because of the large data volume. In this paper, we present a 3-D active shape model (ASM) for semiautomatic segmentation of cardiac CT and MR volumes, without the requirement of retraining the underlying statistical shape model. A fuzzy c-means based fuzzy inference system was incorporated into the model. Thus, relative gray-level differences instead of absolute gray values were used for classification of 3-D regions of interest (ROIs), removing the necessity of training different models for different modalities/acquisition protocols. The 3-D ASM was evaluated using 25 CT and 15 MR datasets. Automatically generated contours were compared to expert contours in 100 locations. For CT, 82.4% of epicardial contours and 74.1% of endocardial contours had a maximum error of 5 mm along 95% of the contour arc length. For MR, those numbers were 93.2% (epicardium) and 91.4% (endocardium). Volume regression analysis revealed good linear correlations between manual and semiautomatic volumes, r(2) >/= 0.98. This study shows that the fuzzy inference 3-D ASM is a robust promising instrument for semiautomatic cardiac left ventricle segmentation. Without retraining its statistical shape component, it is applicable to routinely acquired CT and MR studies. PMID:18779074

  7. Seamless tube shape is constrained by endocytosis-dependent regulation of active Moesin.

    PubMed

    Schottenfeld-Roames, Jodi; Rosa, Jeffrey B; Ghabrial, Amin S

    2014-08-01

    Most tubes have seams (intercellular or autocellular junctions that seal membranes together into a tube), but "seamless" tubes also exist. In Drosophila, stellate-shaped tracheal terminal cells make seamless tubes, with single branches running through each of dozens of cellular extensions. We find that mutations in braided impair terminal cell branching and cause formation of seamless tube cysts. We show that braided encodes Syntaxin7 and that cysts also form in cells deficient for other genes required either for membrane scission (shibire) or for early endosome formation (Rab5, Vps45, and Rabenosyn-5). These data define a requirement for early endocytosis in shaping seamless tube lumens. Importantly, apical proteins Crumbs and phospho-Moesin accumulate to aberrantly high levels in braided terminal cells. Overexpression of either Crumbs or phosphomimetic Moesin induced lumenal cysts and decreased terminal branching. Conversely, the braided seamless tube cyst phenotype was suppressed by mutations in crumbs or Moesin. Indeed, mutations in Moesin dominantly suppressed seamless tube cyst formation and restored terminal branching. We propose that early endocytosis maintains normal steady-state levels of Crumbs, which recruits apical phosphorylated (active) Moe, which in turn regulates seamless tube shape through modulation of cortical actin filaments. PMID:25065756

  8. Reliable and Affordable Control Systems Active Combustor Pattern Factor Control

    NASA Technical Reports Server (NTRS)

    McCarty, Bob; Tomondi, Chris; McGinley, Ray

    2004-01-01

    Active, closed-loop control of combustor pattern factor is a cooperative effort between Honeywell (formerly AlliedSignal) Engines and Systems and the NASA Glenn Research Center to reduce emissions and turbine-stator vane temperature variations, thereby enhancing engine performance and life, and reducing direct operating costs. Total fuel flow supplied to the engine is established by the speed/power control, but the distribution to individual atomizers will be controlled by the Active Combustor Pattern Factor Control (ACPFC). This system consist of three major components: multiple, thin-film sensors located on the turbine-stator vanes; fuel-flow modulators for individual atomizers; and control logic and algorithms within the electronic control.

  9. Shape and size controlled lead sulfide quantum dots for optical refrigeration applications

    NASA Astrophysics Data System (ADS)

    Kaur, Gurinder; Bakshi, M. S.; Kashyap, Raman

    2015-02-01

    Lead sulfide (PbS) quantum dots are attractive candidates for optical refrigeration due to the tuneability of their band gap as a function of size and the resulting quantum confinement. We focus on the simple and straightforward method of synthesis of PbS NPs coated with zein protein with well-defined morphologies which show remarkable pH responsive behavior and excellent photo physical properties. The synthesis of PbS NPs in the presence of zein depicts a fine shape control effect as indicated in TEM images. At 0.4 %, zein produces nanocubes of ~ 42 nm which convert into spheres of almost equal dimensions with 0.2 % and 0.1 % zein. Since all reactions contain equal amount of precursor with identical conditions except the amount of zein, the shape transformation from nanocubes to spheres is mainly due to the decrease in the amount of zein from 0.4 to 0.2 %. The presence of protein coating makes the NPs bioactive and pH responsive. An increase in the pH systematically increases the absorbance of PbS NPs with a significant red shift which is simultaneously shown by remarkable color change in the solution from light grey with orange tinge to dark brown. These photo physical properties may have implications on laser cooling and it will be discussed.

  10. A contractile and counterbalancing adhesion system controls the 3D shape of crawling cells

    PubMed Central

    Burnette, Dylan T.; Shao, Lin; Ott, Carolyn; Pasapera, Ana M.; Fischer, Robert S.; Baird, Michelle A.; Der Loughian, Christelle; Delanoe-Ayari, Helene; Paszek, Matthew J.; Davidson, Michael W.; Betzig, Eric

    2014-01-01

    How adherent and contractile systems coordinate to promote cell shape changes is unclear. Here, we define a counterbalanced adhesion/contraction model for cell shape control. Live-cell microscopy data showed a crucial role for a contractile meshwork at the top of the cell, which is composed of actin arcs and myosin IIA filaments. The contractile actin meshwork is organized like muscle sarcomeres, with repeating myosin II filaments separated by the actin bundling protein α-actinin, and is mechanically coupled to noncontractile dorsal actin fibers that run from top to bottom in the cell. When the meshwork contracts, it pulls the dorsal fibers away from the substrate. This pulling force is counterbalanced by the dorsal fibers’ attachment to focal adhesions, causing the fibers to bend downward and flattening the cell. This model is likely to be relevant for understanding how cells configure themselves to complex surfaces, protrude into tight spaces, and generate three-dimensional forces on the growth substrate under both healthy and diseased conditions. PMID:24711500

  11. Focal adhesions control cleavage furrow shape and spindle tilt during mitosis

    PubMed Central

    Taneja, Nilay; Fenix, Aidan M.; Rathbun, Lindsay; Millis, Bryan A.; Tyska, Matthew J.; Hehnly, Heidi; Burnette, Dylan T.

    2016-01-01

    The geometry of the cleavage furrow during mitosis is often asymmetric in vivo and plays a critical role in stem cell differentiation and the relative positioning of daughter cells during development. Early observations of adhesive cell lines revealed asymmetry in the shape of the cleavage furrow, where the bottom (i.e., substrate attached side) of the cleavage furrow ingressed less than the top (i.e., unattached side). This data suggested substrate attachment could be regulating furrow ingression. Here we report a population of mitotic focal adhesions (FAs) controls the symmetry of the cleavage furrow. In single HeLa cells, stronger adhesion to the substrate directed less ingression from the bottom of the cell through a pathway including paxillin, focal adhesion kinase (FAK) and vinculin. Cell-cell contacts also direct ingression of the cleavage furrow in coordination with FAs in epithelial cells—MDCK—within monolayers and polarized cysts. In addition, mitotic FAs established 3D orientation of the mitotic spindle and the relative positioning of mother and daughter centrosomes. Therefore, our data reveals mitotic FAs as a key link between mitotic cell shape and spindle orientation, and may have important implications in our understanding stem cell homeostasis and tumorigenesis. PMID:27432211

  12. Bio-inspired bending actuator for controlling conical nose shape using piezoelectric patches.

    PubMed

    Na, Tae-Won; Jung, Jin-Young; Oh, Ii-Kwon

    2014-10-01

    In this paper, a bio-inspired bending actuator was designed and fabricated using piezoelectric patches and cantilever-shaped beam for controlling nose shape. The aim of this study is to investigate the use of the bending actuator. PZT and single crystal PMN-PT actuators were used to generate translational strain and shear stress. The piezoelectric patches were attached on the clamped cantilever beam to convert their translational strains to bending motion of the beam. First, finite element analysis was performed to identify and to make an accurate estimate of the feasibility on the bending actuation by applying various voltages and frequencies. Based on the results of the FEM analysis, the experiments were also performed. Static voltages and dynamic voltages with various frequencies were applied to the bending actuators with PZTs and PMN-PTs, and the rotation angles of the nose connected to the top of bending actuators were measured, respectively. As the results, the bending actuator using PMN-PT patches showed better performances in all cases. With the increases of signal frequency and input voltage, the rotation angle also found to be increased. Especially at the frequency of 5 Hz and input voltage of 600 V, the nose generated the maximum rotation angle of 3.15 degree. PMID:25942810

  13. Activation of shape and semantic information during ambiguous homophone processing: eye tracking evidence from Hindi.

    PubMed

    Mishra, Ramesh Kumar; Singh, Siddharth

    2014-11-01

    In two visual world eye tracking studies, we examined the activation of subordinate meanings of ambiguous homophones in Hindi and particularly when the sentence context is biased towards the dominant meaning. Participants listened to sentences that were either neutral or biased towards the dominant meaning of the homophone and saw a display containing four pictures. In experiment 1, the display had a shape competitor of the subordinate meaning of the homophone in both neutral and biased conditions along with three unrelated distractors. Experiment 2 had semantic competitors of the subordinate meaning of the homophones along with three distractors. Proportion of fixations to different objects overtime suggested that participants activated the subordinate meanings and oriented their attention to the shape and semantic competitors even when the prior context was biased towards the dominant meaning. Overall, these data from Hindi provide further support to those models of lexical access that assume exhaustive access of both the meanings of an ambiguous homophone. These data suggest even a dominant bias does not eliminate the activation of perceptual and conceptual features of the subordinate meaning. PMID:25015722

  14. Chimeric Protein Template-Induced Shape Control of Bone Mineral Nanoparticles and Its Impact on Mesenchymal Stem Cell Fate

    PubMed Central

    Wang, Yifan; Du, Yinying; Liu, Haoming; Zhu, Ye; Mao, Chuanbin; Zhang, Shengmin

    2016-01-01

    Protein-mediated molecular self-assembly has become a powerful strategy to fabricate biomimetic biomaterials with controlled shapes. Here we designed a novel chimeric molecular template made of two proteins, silk fibroin (SF) and albumin (ALB), which serve as a promoter and an inhibitor for hydroxyapatite (HA) formation, respectively, to synthesize HA nanoparticles with controlled shapes. HA nanospheres were produced by the chimeric ALB-SF template, whereas HA nanorods were generated by the SF template alone. The success in controlling the shape of HA nanoparticles allowed us to further study the effect of the shape of HA nanoparticles on the fate of rat mesenchymal stem cells (MSCs). We found that the nanoparticle shape had a crucial impact on the cellular uptake and HA nanospheres were internalized in MSCs at a faster rate. Both HA nanospheres and nanorods showed no significant influence on cell proliferation and migration. However, HA nanospheres significantly promoted the osteoblastic differentiation of MSCs in comparison to HA nanorods. Our work suggests that a chimeric combination of promoter and inhibitor proteins is a promising approach to tuning the shape of nanoparticles. It also sheds new light into the role of the shape of the HA nanoparticles in directing stem cell fate. PMID:26079683

  15. Optimal feature point selection and automatic initialization in active shape model search.

    PubMed

    Lekadir, Karim; Yang, Guang-Zhong

    2008-01-01

    This paper presents a novel approach for robust and fully automatic segmentation with active shape model search. The proposed method incorporates global geometric constraints during feature point search by using interlandmark conditional probabilities. The A* graph search algorithm is adapted to identify in the image the optimal set of valid feature points. The technique is extended to enable reliable and fast automatic initialization of the ASM search. Validation with 2-D and 3-D MR segmentation of the left ventricular epicardial border demonstrates significant improvement in robustness and overall accuracy, while eliminating the need for manual initialization. PMID:18979776

  16. Modeling and vibration control of an active membrane mirror

    NASA Astrophysics Data System (ADS)

    Ruggiero, Eric J.; Inman, Daniel J.

    2009-09-01

    The future of space satellite technology lies in ultra-large mirrors and radar apertures for significant improvements in imaging and communication bandwidths. The availability of optical-quality membranes drives a parallel effort for structural models that can capture the dominant dynamics of large, ultra-flexible satellite payloads. Unfortunately, the inherent flexibility of membrane mirrors wreaks havoc with the payload's on-orbit stability and maneuverability. One possible means of controlling these undesirable dynamics is by embedding active piezoelectric ceramics near the boundary of the membrane mirror. In doing so, active feedback control can be used to eliminate detrimental vibration, perform static shape control, and evaluate the health of the structure. The overall motivation of the present work is to design a control system using distributed bimorph actuators to eliminate any detrimental vibration of the membrane mirror. As a basis for this study, a piezoceramic wafer was attached in a bimorph configuration near the boundary of a tensioned rectangular membrane sample. A finite element model of the system was developed to capture the relevant system dynamics from 0 to 300 Hz. The finite element model was compared against experimental results, and fair agreement found. Using the validated finite element models, structural control using linear quadratic regulator control techniques was then used to numerically demonstrate effective vibration control. Typical results show that less than 12 V of actuation voltage is required to eliminate detrimental vibration of the membrane samples in less than 15 ms. The functional gains of the active system are also derived and presented. These spatially descriptive control terms dictate favorable regions within the membrane domain for placing sensors and can be used as a design guideline for structural control applications. The results of the present work demonstrate that thin plate theory is an appropriate modeling

  17. Study on the activation of styrene-based shape memory polymer by medium-infrared laser light

    SciTech Connect

    Leng Jinsong; Yu Kai; Lan Xin; Zhang Dawei; Liu Yanju

    2010-03-15

    This paper demonstrates the feasibility of shape memory polymer (SMP) activation by medium-infrared laser light. Medium-infrared light is transmitted by an optical fiber embedded in the SMP matrix, and the shape recovery process and temperature distribution are recorded by an infrared camera. Light-induced SMP exhibits potential applications in biomedicines and flexible displays.

  18. Active Control by Conservation of Energy Concept

    NASA Technical Reports Server (NTRS)

    Maestrello, Lucio

    2000-01-01

    Three unrelated experiments are discussed; each was extremely sensitive to initial conditions. The initial conditions are the beginnings of the origins of the information that nonlinearity displays. Initial conditions make the phenomenon unstable and unpredictable. With the knowledge of the initial conditions, active control requires far less power than that present in the system response. The first experiment is on the control of shocks from an axisymmetric supersonic jet; the second, control of a nonlinear panel response forced by turbulent boundary layer and sound; the third, control of subharmonic and harmonics of a panel forced by sound. In all three experiments, control is achieved by redistribution of periodic energy response such that the energy is nearly preserved from a previous uncontrolled state. This type of active control improves the performance of the system being controlled.

  19. Neonatal rearing conditions distinctly shape locus coeruleus neuronal activity, dendritic arborization, and sensitivity to corticotrophin-releasing factor

    PubMed Central

    Swinny, Jerome D.; O'Farrell, Eimear; Bingham, Brian C.; Piel, David A.; Valentino, Rita J.; Beck, Sheryl G.

    2010-01-01

    Early life events influence vulnerability to psychiatric illness. This has been modelled in rats and it has been demonstrated that different durations of maternal separation shape adult endocrine and behavioural stress reactivity. One system through which maternal separation may act is the locus coeruleus (LC)–norepinephrine system that regulates emotional arousal. Here we demonstrate that different durations of maternal separation have distinct effects on LC physiology and dendritic morphology. Rat pups were separated from the dam for 15 min/d (HMS-15) or 180 min/d (HMS-180) from post-natal days 2–14. Others were either undisturbed (HMS-0) or were vendor-purchased controls. LC characteristics were compared at age 22–35 d using whole-cell recordings in vitro. Cells were filled with biocytin for morphological analysis. LC neurons of HMS-180 rats were tonically activated compared to HMS-15 and control rats, with firing rates that were 2-fold higher than these groups. Corticotrophin-releasing factor (CRF) application did not further activate LC neurons of HMS-180 rats but increased LC firing rate in HMS-0 and control rats. LC neurons of HMS-15 rats were resistant to excitation by CRF. Maternal separation also affected LC dendritic morphology. LC dendrites of HMS-15 rats exhibited less branching and decreased total dendritic length, an effect that could decrease the probability of contacting limbic afferents that terminate in the pericoerulear region. This effect may provide a structural basis for an attenuated magnitude of emotional arousal. Together, these results demonstrate long-term consequences of early life events on the LC–norepinephrine system that may shape adult behaviour. PMID:19653930

  20. In situ surface characterization and oxygen reduction reaction on shape-controlled gold nanoparticles.

    PubMed

    Hernández, J; Solla-Gullón, J; Herrero, E; Feliu, J M; Aldaz, A

    2009-04-01

    Gold nanoparticles of different shapes/surface structures were synthesized and electrochemically characterized. An in-situ surface characterization of the Au nanoparticles, which was able to obtain qualitative information about the type and relative sizes of the different facets present in the surface of the Au nanoparticles, was carried out by using Pb Under Potential Deposition (UPD) in alkaline solutions as a surface sensitive tool. The results obtained show that the final atomic arrangement on the surface can be different from that expected from the bulk structure of the well-defined shape Au nanoparticles. In this way, the development of precise in-situ methods to measure the distribution of the different sites on the nanoparticle surface, as lead UPD on gold surfaces, is highlighted. Oxygen Reduction Reaction (ORR) was performed on the different Au nanoparticles. In agreement with the particular sensitivity of the oxygen reduction to the presence of Au(100) surface domains, cubic Au nanoparticles show much better electrocatalytic activity for ORR than small spherical particles and long nanorods, in agreement with the presence of a great fraction of (100) terrace sites on the surface of cubic gold nanoparticles. PMID:19437963

  1. Active control of buildings during earthquakes

    NASA Technical Reports Server (NTRS)

    Vance, Vicki L.

    1993-01-01

    The objective of this report is to provide an overview of the different types of control systems used in buildings, to discuss the problems associated with current active control mechanisms, and to show the cost-effectiveness of applying active control to buildings. In addition, a small case study investigates the feasibility and benefits of using embedded actuators in buildings. Use of embedded actuators could solve many of the current problems associated with active control by providing a wider bandwidth of control, quicker speed of response, increased reliability and reduced power requirement. Though embedded actuators have not been developed for buildings, they have previously been used in space structures. Many similarities exist between large civil and aerospace structures indicating that direct transfer of concepts between the two disciplines may be possible. In particular, much of the Controls-Structures Interaction (CSI) technology currently being developed could be beneficially applied to civil structures. While several buildings with active control systems have been constructed in Japan, additional research and experimental verification are necessary before active control systems become widely accepted and implemented.

  2. Controlling pathway dynamics of a four-level quantum system with pulse shaping

    NASA Astrophysics Data System (ADS)

    Cao, Dewen; Yang, Ling; Wang, Yaoxiong; Shuang, Feng; Gao, Fang

    2016-07-01

    The dynamics of two two-photon absorption (TPA) pathways in a four-level quantum system driven by a laser pulse is investigated in this work. An analytical solution for pulse shaping is proposed to be globally optimal for constructive interference between the two pathways, and accurate spectral boundaries for phase modulation are obtained. The TPA rate can be enhanced by a factor of 8.33 with the optimal pulse instead of the transform limited pulse (TL pulse). Simple control strategies modulating both amplitudes and phases are also designed to increase the TPA amplitude along one pathway while decreasing that along the other simultaneously. The strategies are intuitive and the two pathway amplitudes can differ by two orders of magnitude.

  3. Optical boundary reconstruction of tokamak plasmas for feedback control of plasma position and shape

    SciTech Connect

    Hommen, G.; Baar, M. de; Nuij, P.; Steinbuch, M.; McArdle, G.; Akers, R.

    2010-11-15

    A new diagnostic is developed to reconstruct the plasma boundary using visible wavelength images. Exploiting the plasma's edge localized and toroidally symmetric emission profile, a new coordinate transform is presented to reconstruct the plasma boundary from a poloidal view image. The plasma boundary reconstruction is implemented in MATLAB and applied to camera images of Mega-Ampere Spherical Tokamak discharges. The optically reconstructed plasma boundaries are compared to magnetic reconstructions from the offline reconstruction code EFIT, showing very good qualitative and quantitative agreement. Average errors are within 2 cm and correlation is high. In the current software implementation, plasma boundary reconstruction from a single image takes 3 ms. The applicability and system requirements of the new optical boundary reconstruction, called OFIT, for use in both feedback control of plasma position and shape and in offline reconstruction tools are discussed.

  4. Spatial, High-Accuracy, Positioning-Encoding Sensor (SHAPES) for large space system control applications

    NASA Technical Reports Server (NTRS)

    Mclauchlan, J. M.

    1982-01-01

    The Spatial, High-Accuracy, Position-Encoding Sensor is a controls sensor suitable for the determination of the static shape and vibrational motion of large space structures and similar systems and for the determination of position and velocity in rendezvous and docking. It uses a combination of electro-optical techniques to measure the three-dimensional coordinates distributed over the structure at reading rates high compared to the rates at which the coordinates are changing. The technical approach is that of measuring the distance to and the direction of points on the structure from a single sensor head. Many points can be measured simultaneously from a single head without significantly increasing the complexity of the system.

  5. Nanofibrous Microposts and Microwells of Controlled Shapes and Their Hybridization with Hydrogels for Cell Encapsulation

    PubMed Central

    2015-01-01

    A simple, robust, and cost-effective method is developed to fabricate nanofibrous micropatterns particularly microposts and microwells of controlled shapes. The key to this method is the use of an easily micropatternable and intrinsically conductive metal alloy as a template to collect electrospun fibers. The micropatterned alloy allows conformal fiber deposition with high fidelity on its topographical features and in situ formation of diverse, free-standing micropatterned nanofibrous membranes. Interestingly, these membranes can serve as structural frames to form robust hydrogel micropatterns that may otherwise be fragile on their own. These hybrid micropatterns represent a new platform for cell encapsulation where the nanofiber frames enhance the mechanical integrity of hydrogel and the micropatterns provide additional surface area for mass transfer and cell loading. PMID:24806031

  6. Manually controlled neutron-activation system

    NASA Astrophysics Data System (ADS)

    Johns, R. A.; Carothers, G. A.

    1982-01-01

    A manually controlled neutron activation system, the Manual Reactor Activation System, was designed and built and has been operating at one of the Savannah River Plant's production reactors. With this system, samples can be irradiated for up to 24 hours and pneumatically transferred to a shielded repository for decay until their activity is low enough for them to be handled at a radiobench. The Manual Reactor Activation System was built to provide neutron activation of solid waste forms for the Alternative Waste Forms Leach Testing Program. Neutron activation of the bulk sample prior to leaching permits sensitive multielement radiometric analyses of the leachates.

  7. Controls on fire activity over the Holocene

    NASA Astrophysics Data System (ADS)

    Kloster, S.; Brucher, T.; Brovkin, V.; Wilkenskjeld, S.

    2015-05-01

    Changes in fire activity over the last 8000 years are simulated with a global fire model driven by changes in climate and vegetation cover. The changes were separated into those caused through variations in fuel availability, fuel moisture or wind speed, which react differently to changes in climate. Disentangling these controlling factors helps in understanding the overall climate control on fire activity over the Holocene. Globally the burned area is simulated to increase by 2.5% between 8000 and 200 cal yr BP, with larger regional changes compensating nearly evening out on a global scale. Despite the absence of anthropogenic fire ignitions, the simulated trends in fire activity agree reasonably well with continental-scale reconstructions from charcoal records, with the exception of Europe. For some regions the change in fire activity is predominantly controlled through changes in fuel availability (Australia monsoon, Central America tropics/subtropics). For other regions changes in fuel moisture are more important for the overall trend in fire activity (North America, Sub-Saharan Africa, Europe, Asia monsoon). In Sub-Saharan Africa, for example, changes in fuel moisture alone lead to an increase in fire activity between 8000 and 200 cal yr BP, while changes in fuel availability lead to a decrease. Overall, the fuel moisture control is dominating the simulated fire activity for Sub-Saharan Africa. The simulations clearly demonstrate that both changes in fuel availability and changes in fuel moisture are important drivers for the fire activity over the Holocene. Fuel availability and fuel moisture do, however, have different climate controls. As such, observed changes in fire activity cannot be related to single climate parameters such as precipitation or temperature alone. Fire models, as applied in this study, in combination with observational records can help in understanding the climate control on fire activity, which is essential to project future fire

  8. Effect of shape on wing kinematics control in dragonfly maneuvering flight

    NASA Astrophysics Data System (ADS)

    Bode-Oke, Ayodeji; Zeyghami, Samane; Dong, Haibo; FSRG Team

    2014-11-01

    Flying insects execute aerial maneuvers through fine modulations in their wing kinematics. It's yet not known that to what extend the wing kinematics can be controlled and altered by the insect. To investigate the question, we recorded a yaw turn maneuver of a dragonfly in free flight. Our measurements show that this flight consists of two kinematically and dynamically distinct phases; acceleration and deceleration. In a systematic study, we first clipped the left forewing and then the right forewing of the same dragonfly and recorded its yaw turn maneuver. The signatures (in kinematics and dynamics) of the two identified phases stay unchanged by wing damage but the duration of both phases extends. The rotational velocity of the body drops dramatically by wing damage which implies the dragonfly is incapable of controlling the wing kinematics to achieve similar performance as in the intact wing. Our results suggest that the wing kinematics control is tightly influenced by the wing shapes and the aerodynamics of flapping flight. This work was supported by NSF Grant Number CEBT-1313217 and REU program.

  9. An accurately controlled antagonistic shape memory alloy actuator with self-sensing.

    PubMed

    Wang, Tian-Miao; Shi, Zhen-Yun; Liu, Da; Ma, Chen; Zhang, Zhen-Hua

    2012-01-01

    With the progress of miniaturization, shape memory alloy (SMA) actuators exhibit high energy density, self-sensing ability and ease of fabrication, which make them well suited for practical applications. This paper presents a self-sensing controlled actuator drive that was designed using antagonistic pairs of SMA wires. Under a certain pre-strain and duty cycle, the stress between two wires becomes constant. Meanwhile, the strain to resistance curve can minimize the hysteresis gap between the heating and the cooling paths. The curves of both wires are then modeled by fitting polynomials such that the measured resistance can be used directly to determine the difference between the testing values and the target strain. The hysteresis model of strains to duty cycle difference has been used as compensation. Accurate control is demonstrated through step response and sinusoidal tracking. The experimental results show that, under a combination control program, the root-mean-square error can be reduced to 1.093%. The limited bandwidth of the frequency is estimated to be 0.15 Hz. Two sets of instruments with three degrees of freedom are illustrated to show how this type actuator could be potentially implemented. PMID:22969368

  10. ACTIVELY CONTROLLED AFTERBURNER FOR COMPACT WASTE INCINERATION

    EPA Science Inventory

    In a continuing research program directed at developing technology for compact shipboard incinerators, active control of fluid dynamics has been used to enhance mixing in incinerator afterburner (AB) experiments and increase the DRE for a waste surrogate. Experiments were conduc...

  11. The Middeck Active Control Experiment (MACE)

    NASA Astrophysics Data System (ADS)

    Miller, David W.

    1991-07-01

    Viewgraphs on the Middeck Active Control Experiment (MACE) are presented. Topics covered include: science program objectives and rationale; science requirements; capturing the essential physics; science development approach; development model hardware; development model test plan; and flight hardware and operations.

  12. The Middeck Active Control Experiment (MACE)

    NASA Technical Reports Server (NTRS)

    Miller, David W.

    1991-01-01

    Viewgraphs on the Middeck Active Control Experiment (MACE) are presented. Topics covered include: science program objectives and rationale; science requirements; capturing the essential physics; science development approach; development model hardware; development model test plan; and flight hardware and operations.

  13. Far-Red and Near-IR AIE-Active Fluorescent Organic Nanoprobes with Enhanced Tumor-Targeting Efficacy: Shape-Specific Effects.

    PubMed

    Shao, Andong; Xie, Yongshu; Zhu, Shaojia; Guo, Zhiqian; Zhu, Shiqin; Guo, Jin; Shi, Ping; James, Tony D; Tian, He; Zhu, Wei-Hong

    2015-06-15

    The rational design of high-performance fluorescent materials for cancer targeting in vivo is still challenging. A unique molecular design strategy is presented that involves tailoring aggregation-induced emission (AIE)-active organic molecules to realize preferable far-red and NIR fluorescence, well-controlled morphology (from rod-like to spherical), and also tumor-targeted bioimaging. The shape-tailored organic quinoline-malononitrile (QM) nanoprobes are biocompatible and highly desirable for cell-tracking applications. Impressively, the spherical shape of QM-5 nanoaggregates exhibits excellent tumor-targeted bioimaging performance after intravenously injection into mice, but not the rod-like aggregates of QM-2. PMID:25950152

  14. Active control of turbomachine discrete tones

    NASA Astrophysics Data System (ADS)

    Fleeter, Sanford

    This paper was directed at active control of discrete frequency noise generated by subsonic blade rows through cancellation of the blade row interaction generated propagating acoustic waves. First discrete frequency noise generated by a rotor and stator in a duct was analyzed to determine the propagating acoustic pressure waves. Then a mathematical model was developed to analyze and predict the active control of discrete frequency noise generated by subsonic blade rows through cancellation of the propagating acoustic waves, accomplished by utilizing oscillating airfoil surfaces to generate additional control propagating pressure waves. These control waves interact with the propagating acoustic waves, thereby, in principle, canceling the acoustic waves and thus, the far field discrete frequency tones. This model was then applied to a fan exit guide vane to investigate active airfoil surface techniques for control of the propagating acoustic waves, and thus the far field discrete frequency tones, generated by blade row interactions.

  15. Global shape estimates and GIS cartography of Io and Enceladus using new control point network

    NASA Astrophysics Data System (ADS)

    Nadezhdina, I.; Patraty, V.; Shishkina, L.; Zhukov, D.; Zubarev, A.; Karachevtseva, I.; Oberst, J.

    2012-04-01

    analysis for small planetary bodies by means of the software «PHOTOMOD» is fast and efficient. Using the new control points and shape models of the satellites we are currently preparing new maps of Io and Enceladus using GIS tools. For parts of the surface for which we have quality stereo-images we will produce DEMs and orthoimages, which will be shown at the conference. Acknowledgments: This research was funded by the Ministry of Education and Science of the Russian Federation (MEGA-GRANT, Project name: "Geodesy, cartography and the study of planets and satellites", contract No. 11.G34.31.0021).

  16. Prostate contours delineation using interactive directional active contours model and parametric shape prior model.

    PubMed

    Derraz, Foued; Forzy, Gérard; Delebarre, Arnaud; Taleb-Ahmed, Abdelmalik; Oussalah, Mourad; Peyrodie, Laurent; Verclytte, Sebastien

    2015-11-01

    Prostate contours delineation on Magnetic Resonance (MR) images is a challenging and important task in medical imaging with applications of guiding biopsy, surgery and therapy. While a fully automated method is highly desired for this application, it can be a very difficult task due to the structure and surrounding tissues of the prostate gland. Traditional active contours-based delineation algorithms are typically quite successful for piecewise constant images. Nevertheless, when MR images have diffuse edges or multiple similar objects (e.g. bladder close to prostate) within close proximity, such approaches have proven to be unsuccessful. In order to mitigate these problems, we proposed a new framework for bi-stage contours delineation algorithm based on directional active contours (DAC) incorporating prior knowledge of the prostate shape. We first explicitly addressed the prostate contour delineation problem based on fast globally DAC that incorporates both statistical and parametric shape prior model. In doing so, we were able to exploit the global aspects of contour delineation problem by incorporating a user feedback in contours delineation process where it is shown that only a small amount of user input can sometimes resolve ambiguous scenarios raised by DAC. In addition, once the prostate contours have been delineated, a cost functional is designed to incorporate both user feedback interaction and the parametric shape prior model. Using data from publicly available prostate MR datasets, which includes several challenging clinical datasets, we highlighted the effectiveness and the capability of the proposed algorithm. Besides, the algorithm has been compared with several state-of-the-art methods. PMID:26009857

  17. Active Polymer Microfiber with Controlled Polarization Sensitivity

    PubMed Central

    Xia, Hongyan; Wang, Ruxue; Liu, Yingying; Cheng, Junjie; Zou, Gang; Zhang, Qijin; Zhang, Douguo; Wang, Pei; Ming, Hai; Badugu, Ramachandram; Lakowicz, Joseph R.

    2016-01-01

    Controlled Polarization Sensitivity of an active polymer microfiber has been proposed and realized with the electrospun method. The fluorescence intensity guiding through this active polymer microfiber shows high sensitivity to the polarization state of the excitation light. What is more, the fluorescence out-coupled from tip of the microfiber can be of designed polarization state. Principle of these phenomena lies on the ordered and controlled orientation of the polydiacetylene (PDA) main chains inside polymer microfiber. PMID:27099828

  18. Active control of helicopter transmission noise

    NASA Astrophysics Data System (ADS)

    Spencer, R. H.; Burke, M. J.; Tye, G. W.

    An account is given of an effort to reduce helicopter transmission noise by 10 dB, using active methods, as part of the NASA-Lewis/U.S. Army Propulsion Directorate Advanced Rotorcraft Transmission technology integration and demonstration program. The transmission used as a test stand is that of the CH-47C forward rotor. Attention is presently given to the active control system's actuators, sensors, and control algorithms.

  19. Active control of helicopter transmission noise

    NASA Technical Reports Server (NTRS)

    Spencer, R. H.; Burke, M. J.; Tye, G. W.

    1991-01-01

    An account is given of an effort to reduce helicopter transmission noise by 10 dB, using active methods, as part of the NASA-Lewis/U.S. Army Propulsion Directorate Advanced Rotorcraft Transmission technology integration and demonstration program. The transmission used as a test stand is that of the CH-47C forward rotor. Attention is presently given to the active control system's actuators, sensors, and control algorithms.

  20. Vector control activities, fiscal year 1983

    SciTech Connect

    Pickard, E.; Cooney, J.C.; McDuff, B.R.

    1984-07-01

    The goal of the Vector Control Program is to safeguard public health and well-being in the Tennessee Valley region by controlling arthropod pests of medical importance that are propagated on TVA lands or waters or that are produced as a result of TVA activities. To achieve this goal the program is divided into two major categories consisting of operations and support studies. The latter is geared to improving the operational effectiveness and efficiency of the control program and to identify additional vector control problems requiring TVA attention and study. Nonchemical methods of control are emphasized and are supplemented with chemical measures as needed.

  1. Cortical activation to object shape and speed of motion during the first year

    PubMed Central

    Wilcox, Teresa; Hawkins, Laura B.; Hirskkowitz, Amy; Boas, David A.

    2014-01-01

    A great deal is known about the functional organization of cortical networks that mediate visual object processing in the adult. The current research is part of a growing effort to identify the functional maturation of these pathways in the developing brain. The current research used near-infrared spectroscopy to investigate functional activation of the infant cortex during the processing of featural information (shape) and spatiotemporal information (speed of motion) during the first year of life. Our investigation focused on two areas that were implicated in previous studies: anterior temporal cortex and posterior parietal cortex. Neuroimaging data were collected with 207 infants across three age groups: 3 to 6 months (Experiment 1), 7 to 8 months (Experiment 2), and 10 to 12 months (Experiments 3 and 4). The neuroimaging data revealed age-related changes in patterns of activation to shape and speed information, mostly involving posterior parietal areas, some of which were predicted and others that were not. We suggest that these changes reflect age-related differences in the perceptual and/or cognitive processes engaged during the task. PMID:24821531

  2. Effects of shape and size of cobalt ferrite nanostructures on their MRI contrast and thermal activation

    PubMed Central

    Joshi, Hrushikesh M.; Lin, Yen Po; Aslam, Mohammed; Prasad, P. V.; Schultz-Sikma, Elise A.; Edelman, Robert; Meade, Thomas; Dravid, Vinayak P.

    2010-01-01

    Cobalt ferrite magnetic nanostructures were synthesized via a high temperature solution phase method. Spherical nanostructures of various sizes were synthesized with the help of seed mediated growth of the nanostructures in organic phase, while faceted irregular (FI) cobalt ferrite nanostructures were synthesized via the same method but in the presence of a magnetic field. Magnetic properties were characterized by SQUID magnetometry, relaxivity measurements and thermal activation under RF field, as a function of size and shape. The results show that the saturation magnetization of the nanostructures increases with an increase in size, and the FI nanostructures exhibit lower saturation magnetization than their spherical counterparts. The relaxivity coefficient of cobalt ferrite nanostructures increases with increase in size; while FI nanostructures show a higher relaxivity coefficient than spherical nanostructures with respect to their saturation magnetization. In the case of RF thermal activation, the specific absorption rate (SAR) of nanostructures increases with increase in the size. The contribution sheds light on the role of size and shape on important magnetic properties of the nanostructures in relation to their biomedical applications. PMID:21850276

  3. Transitioning Active Flow Control to Applications

    NASA Technical Reports Server (NTRS)

    Joslin, Ronald D.; Horta, Lucas G.; Chen, Fang-Jenq

    1999-01-01

    Active Flow Control Programs at NASA, the U.S. Air Force, and DARPA have been initiated with the goals of obtaining revolutionary advances in aerodynamic performance and maneuvering compared to conventional approaches. These programs envision the use of actuators, sensors, and controllers on applications such as aircraft wings/tails, engine nacelles, internal ducts, nozzles, projectiles, weapons bays, and hydrodynamic vehicles. Anticipated benefits of flow control include reduced weight, part count, and operating cost and reduced fuel burn (and emissions), noise and enhanced safety if the sensors serve a dual role of flow control and health monitoring. To get from the bench-top or laboratory test to adaptive distributed control systems on realistic applications, reliable validated design tools are needed in addition to sub- and large-scale wind-tunnel and flight experiments. This paper will focus on the development of tools for active flow control applications.

  4. Active load control techniques for wind turbines.

    SciTech Connect

    van Dam, C.P.; Berg, Dale E.; Johnson, Scott J.

    2008-07-01

    This report provides an overview on the current state of wind turbine control and introduces a number of active techniques that could be potentially used for control of wind turbine blades. The focus is on research regarding active flow control (AFC) as it applies to wind turbine performance and loads. The techniques and concepts described here are often described as 'smart structures' or 'smart rotor control'. This field is rapidly growing and there are numerous concepts currently being investigated around the world; some concepts already are focused on the wind energy industry and others are intended for use in other fields, but have the potential for wind turbine control. An AFC system can be broken into three categories: controls and sensors, actuators and devices, and the flow phenomena. This report focuses on the research involved with the actuators and devices and the generated flow phenomena caused by each device.

  5. Cost-efficient and flexible fabrication of rectangular-shaped microlens arrays with controllable aspect ratio and spherical morphology

    NASA Astrophysics Data System (ADS)

    Hu, Yang; Yang, Qing; Chen, Feng; Bian, Hao; Deng, Zefang; Du, Guangqing; Si, Jinhai; Yun, Feng; Hou, Xun

    2014-02-01

    This paper presents a cost-efficient and flexible approach to the development of controllable-shape concave and convex microlens arrays by using femtosecond laser wet etch and replication techniques. Periodic concave rectangular-shaped microlens arrays with different length-width ratios were achieved by firstly introducing periodic microcraters on silica glass using an 800 nm femtosecond laser, and subsequently enlarging the craters into microlens with smooth curved surfaces in hydrofluoric (HF) acid solution. The concave microlens can serve as molds of replication to obtain convex microlenses on polymers. Over 10,000 rectangular-shaped concave and convex microlens with controllable aspect ratio, high fill factor and spherical morphology can be fabricated in 5 h. A simulation result and a projection experiment result verify the optical performance of these rectangular-shaped spherical microlens arrays (MLAs).

  6. Student Activity Funds: Procedures and Controls.

    ERIC Educational Resources Information Center

    Cuzzetto, Charles E.

    2000-01-01

    An effective internal-control system can help school business administrators meet the challenges of accounting for student activity funds. Such a system should include appropriate policies and procedures, identification of key control points, self-assessments, audit trails, and internal and external audits. (MLH)

  7. Control of grating-coupled ultrafast surface plasmon pulse and its nonlinear emission by shaping femtosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Toma, Kazunori; Masaki, Yuta; Kusaba, Miyuki; Hirosawa, Kenichi; Kannari, Fumihiko

    2015-09-01

    Spatiotemporal nanofocusing of ultrafast surface plasmon polaritons (SPPs) coupled on a metal Au tapered tip with a curvature radius of a few tens of nanometers is deterministically controlled based on the measured plasmon response function. We control the SPP pulse shape and the second harmonic generation at the apex of the Au tapered tip by shaping the excitation femtosecond laser pulses based on the response function. We also adapted a similar control scheme for coherent anti-Stokes Raman scattering (CARS) and achieved selective CARS excitation of a single Raman mode of carbon nanotubes with only a single excitation laser pulse at the apex of the tip.

  8. Optimal active control for Burgers equations

    NASA Technical Reports Server (NTRS)

    Ikeda, Yutaka

    1994-01-01

    A method for active fluid flow control based on control theory is discussed. Dynamic programming and fixed point successive approximations are used to accommodate the nonlinear control problem. The long-term goal of this project is to establish an effective method applicable to complex flows such as turbulence and jets. However, in this report, the method is applied to stochastic Burgers equation as an intermediate step towards this goal. Numerical results are compared with those obtained by gradient search methods.

  9. Shape memory system with integrated actuation using embedded particles

    DOEpatents

    Buckley, Patrick R.; Maitland, Duncan J.

    2009-09-22

    A shape memory material with integrated actuation using embedded particles. One embodiment provides a shape memory material apparatus comprising a shape memory material body and magnetic pieces in the shape memory material body. Another embodiment provides a method of actuating a device to perform an activity on a subject comprising the steps of positioning a shape memory material body in a desired position with regard to the subject, the shape memory material body capable of being formed in a specific primary shape, reformed into a secondary stable shape, and controllably actuated to recover the specific primary shape; including pieces in the shape memory material body; and actuating the shape memory material body using the pieces causing the shape memory material body to be controllably actuated to recover the specific primary shape and perform the activity on the subject.

  10. Shape memory system with integrated actuation using embedded particles

    DOEpatents

    Buckley, Patrick R; Maitland, Duncan J

    2014-04-01

    A shape memory material with integrated actuation using embedded particles. One embodiment provides a shape memory material apparatus comprising a shape memory material body and magnetic pieces in the shape memory material body. Another embodiment provides a method of actuating a device to perform an activity on a subject comprising the steps of positioning a shape memory material body in a desired position with regard to the subject, the shape memory material body capable of being formed in a specific primary shape, reformed into a secondary stable shape, and controllably actuated to recover the specific primary shape; including pieces in the shape memory material body; and actuating the shape memory material body using the pieces causing the shape memory material body to be controllably actuated to recover the specific primary shape and perform the activity on the subject.

  11. Shape memory system with integrated actuation using embedded particles

    DOEpatents

    Buckley, Patrick R.; Maitland, Duncan J.

    2012-05-29

    A shape memory material with integrated actuation using embedded particles. One embodiment provides a shape memory material apparatus comprising a shape memory material body and magnetic pieces in the shape memory material body. Another embodiment provides a method of actuating a device to perform an activity on a subject comprising the steps of positioning a shape memory material body in a desired position with regard to the subject, the shape memory material body capable of being formed in a specific primary shape, reformed into a secondary stable shape, and controllably actuated to recover the specific primary shape; including pieces in the shape memory material body; and actuating the shape memory material body using the pieces causing the shape memory material body to be controllably actuated to recover the specific primary shape and perform the activity on the subject.

  12. System ID modern control algorithms for active aerodynamic load control and impact on gearbox loading.

    SciTech Connect

    Berg, Jonathan Charles; Halse, Chris; Crowther, Ashley; Barlas, Thanasis; Wilson, David Gerald; Berg, Dale E.; Resor, Brian Ray

    2010-06-01

    Prior work on active aerodynamic load control (AALC) of wind turbine blades has demonstrated that appropriate use of this technology has the potential to yield significant reductions in blade loads, leading to a decrease in wind cost of energy. While the general concept of AALC is usually discussed in the context of multiple sensors and active control devices (such as flaps) distributed over the length of the blade, most work to date has been limited to consideration of a single control device per blade with very basic Proportional Derivative controllers, due to limitations in the aeroservoelastic codes used to perform turbine simulations. This work utilizes a new aeroservoelastic code developed at Delft University of Technology to model the NREL/Upwind 5 MW wind turbine to investigate the relative advantage of utilizing multiple-device AALC. System identification techniques are used to identify the frequencies and shapes of turbine vibration modes, and these are used with modern control techniques to develop both Single-Input Single-Output (SISO) and Multiple-Input Multiple-Output (MIMO) LQR flap controllers. Comparison of simulation results with these controllers shows that the MIMO controller does yield some improvement over the SISO controller in fatigue load reduction, but additional improvement is possible with further refinement. In addition, a preliminary investigation shows that AALC has the potential to reduce off-axis gearbox loads, leading to reduced gearbox bearing fatigue damage and improved lifetimes.

  13. Optimizing coherent anti-Stokes Raman scattering by genetic algorithm controlled pulse shaping

    NASA Astrophysics Data System (ADS)

    Yang, Wenlong; Sokolov, Alexei

    2010-10-01

    The hybrid coherent anti-Stokes Raman scattering (CARS) has been successful applied to fast chemical sensitive detections. As the development of femto-second pulse shaping techniques, it is of great interest to find the optimum pulse shapes for CARS. The optimum pulse shapes should minimize the non-resonant four wave mixing (NRFWM) background and maximize the CARS signal. A genetic algorithm (GA) is developed to make a heuristic searching for optimized pulse shapes, which give the best signal the background ratio. The GA is shown to be able to rediscover the hybrid CARS scheme and find optimized pulse shapes for customized applications by itself.

  14. Shape-Controllable Synthesis of Peroxidase-Like Fe3O4 Nanoparticles for Catalytic Removal of Organic Pollutants

    NASA Astrophysics Data System (ADS)

    Wan, Dong; Li, Wenbing; Wang, Guanghua; Wei, Xiaobi

    2016-08-01

    The shape of Fe3O4 nanoparticles is controlled using a simple oxidation-precipitation method without any surfactant. The morphology and structure of the obtained Fe3O4 nanoparticles were characterized by using x-ray diffraction, scanning electron microscopy, x-ray photoelectron spectroscopy, N2 physisorption and vibrating sample magnetometer. As-prepared Fe3O4 samples showed octahedron, cube, hexagonal plate and sphere morphologies. Peroxidase-like activity of the four nanostructures was evaluated for catalytic removal of organic pollutants in the presence of H2O2, using rhodamine B as a model compound. The results showed that the H2O2-activating ability of the Fe3O4 nanocrystals was structure dependent and followed the order sphere > cube > octahedron > hexagonal plate, which was closely related to their surface FeII/FeIII ratios or crystal planes. The reusability of Fe3O4 spheres was also investigated after five successive runs, which demonstrated the promising application of the catalyst in the degradation of organic pollutants. This investigation is of great significance for the heterogeneous catalysts with enhanced activity and practical application.

  15. Controllable shape-matched propagation of two signal beams in a double-Λ atomic ensemble

    NASA Astrophysics Data System (ADS)

    Li, Zhuan; Deng, Li-Ping; Xu, Li-Sen; Wang, Kaige

    2006-10-01

    We study a four-level double-Λ atomic ensemble interacting with two time-dependent signal fields and two stationary control fields. Though, in each Λ channel, a pair of signal and control fields couple resonantly with the two lower levels of atoms, the occurrences of electromagnetically induced transparency (EIT) is affected by the coherence of the four fields. In the discussion of atomic susceptibilities, we show that the quantum coherence between the two lower levels can be either formed or released according to the phase matching of the four fields. We analyze the propagation equation of the two signal fields, and find two characteristic solutions: the stationary transmission wave and the transient decay wave. The former corresponds to a correlated EIT effect in which two signal pulses are shape-matched. The latter is an opposite effect to the correlated EIT in which two pulses quench simultaneously, thus named as the correlated two-signal absorption (CTSA). We propose the CTSA condition in correspondence with the EIT condition. The numerical simulation shows that the double-Λ configuration is capable of manipulating synchronous optical signals and thus provides multiplicity and versatility in quantum information process.

  16. Shape and size control of nano dispersed Mg/Al layered double hydroxide.

    PubMed

    Panda, H S; Srivastava, R; Bahadur, D

    2008-08-01

    Controlling the shape and size of the layered inorganic-organic hybrid particles is a challenge with conventional methods of synthesis. The co-precipitation method has been modified to synthesize Mg/Al Layered double hydroxide by controlling the particle growth using ultrasonic wave at the time of nucleation. In this project, magnesium and aluminum ions were considered as model systems with carbonate anion as intercalating agent. The resulting particles are compared with those of LDHs produced by conventional co-precipitation method at constant pH. Powder X-ray diffraction confirmed formation of the layered double hydroxide phases having crystallite size 19-20 nm in both 'a' and 'c' crystallographic directions. Transmission electron microscope and dynamic light scattering revealed nano disperse hexagonal platelets with narrow size distribution and average size was around 48 nm. The modified method reduces the particle size, increases the surface charge, narrows down the size distribution and also reduces the aspect ratio of the particles. Therefore, it is suggested that low amplitude ultrasonic wave prevents the aggregation of the nuclei, thus restricting the particle growth and results in uniform size particles. PMID:19049206

  17. The shape of Mars before global surveyor: Results from reanalysis of the Viking control point network

    NASA Astrophysics Data System (ADS)

    Zeitler, Wolfgang; Oberst, Jürgen

    1999-06-01

    Three-dimensional coordinates of 3739 globally distributed control points derived from photogrammetric analysis of Viking Orbiter image data are studied with respect to the shape and large-scale morphology of Mars. Spheres, spheroids, spherical functions, and a Digital Terrain Model (DTM) of 50 km grid spacing are fitted to the data. Prominent topographic features in the terrain model include the Tharsis volcanoes, Olympus Mons, Alba Patera and prominent mare and highland regions as well as the major impact basins. While the global dichotomy is clearly visible in our data, our model does not reveal any distinct signature associated with the presumed dichotomy boundary at this global scale. Rather, it suggests a smooth topographic transition from southern to northern hemisphere. This model is unique among existing topographic data sets for Mars, as it combines global coverage, a spatial resolution sufficient to resolve regional topography, and absolute elevation data more accurate than in previous control point network analyses. Formal errors and a comparison with the first released topographic profiles obtained by Mars Global Surveyor's Laser Altimeter (MOLA) suggest that 70% and 90% of the DTM grid elements represent the topography of the planet to better than 1000 m and 2000 m, respectively.

  18. Distinct protease pathways control cell shape and apoptosis in v-src-transformed quail neuroretina cells

    SciTech Connect

    Neel, Benjamin D.; Gillet, Germain . E-mail: g.gillet@ibcp.fr

    2005-11-15

    Intracellular proteases play key roles in cell differentiation, proliferation and apoptosis. In nerve cells, little is known about their relative contribution to the pathways which control cell physiology, including cell death. Neoplastic transformation of avian neuroretina cells by p60 {sup v-src} tyrosine kinase results in dramatic morphological changes and deregulation of apoptosis. To identify the proteases involved in the cellular response to p60 {sup v-src}, we evaluated the effect of specific inhibitors of caspases, calpains and the proteasome on cell shape changes and apoptosis induced by p60 {sup v-src} inactivation in quail neuroretina cells transformed by tsNY68, a thermosensitive strain of Rous sarcoma virus. We found that the ubiquitin-proteasome pathway is recruited early after p60 {sup v-src} inactivation and is critical for morphological changes, whereas caspases are essential for cell death. This study provides evidence that distinct intracellular proteases are involved in the control of the morphology and fate of v-src-transformed cells.

  19. Active vibration control of civil structures

    SciTech Connect

    Farrar, C.; Baker, W.; Fales, J.; Shevitz, D.

    1996-11-01

    This is a final report of a one year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Active vibration control (AVC) of structural and mechanical systems is one of the rapidly advancing areas of engineering research. The multifaceted nature of AVC covers many disciplines, such as sensors and instrumentation, numerical modeling, experimental mechanics, and advanced power systems. This work encompassed a review of the literature on active control of structures focusing both on active control hardware and on control algorithms, a design of an isolation systems using magneto-rheological fluid-filled (MRF) dampers and numerical simulations to study the enhanced vibration mitigation effects of this technology.

  20. Shape memory alloy adaptive control of gas turbine engine compressor blade tip clearance

    NASA Astrophysics Data System (ADS)

    Schetky, Lawrence M.; Steinetz, Bruce M.

    1998-06-01

    The ambient air ingested through the inlet of a gas turbine is first compressed by an axial compressor followed by further compression in a centrifugal compressor and then fed into the combustion chamber where ignition and expansion take place to produce the engine thrust. The axial compressor typically has five or more stages which consist of revolving blades and stators and the overall performance of the turbine is strongly affected by the compressor efficiency. When the turbine is turned on, to accommodate the rapid initial increase in the compressor blade length due to centrifugal force, the cold turbine has a built in clearance between the turbine blade tip and the casing. As the turbine reached its operating temperature there is a further increase in the blade length due to thermal expansion and, at the same time, the diameter of the casing increases. The net result is that when these various components have reached their equilibrium temperatures, the initial cold build clearance is reduced, but there remains a residual clearance. The magnitude of this clearance has a direct effect on the compressor efficiency and can be stated as: Δη/Δ CLR equals 0.5 where η is efficiency and CLR is the tip clearance. The concept of adaptive tip clearance control is based on the ability of a shape memory alloy ring to shrink to a predetermined diameter when heated to the temperature of a particular stage, and thus reducing the tip clearance. The ring is fabricated from a CuAlNi shape memory alloy and is mounted in the casing so as to be coaxial with the rotating blades of the particular stage. When cold, the ring dimensions are such as to provide the required cold build clearance, but when at operating temperature the reduced diameter creates a very small tip clearance. The clearance provided by this concept is much smaller than the clearance normally obtained for a turbine of the size being studied.