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Sample records for linear asynchronous motor

  1. Design of an asynchronous electrostatic motor

    NASA Astrophysics Data System (ADS)

    Kobayasi, Syoyu

    1990-02-01

    An asynchronous electrostatic motor that works under a high-voltage pulse controller using LED-phototransistor photosensors is described. The motor produced the torque 1030-dyn-cm at 1500 V and attained the power 0.8 mW at 80 rpm in n-hexane.

  2. Asynchronous parallel generating set search for linearly-constrained optimization.

    SciTech Connect

    Lewis, Robert Michael; Griffin, Joshua D.; Kolda, Tamara Gibson

    2006-08-01

    Generating set search (GSS) is a family of direct search methods that encompasses generalized pattern search and related methods. We describe an algorithm for asynchronous linearly-constrained GSS, which has some complexities that make it different from both the asynchronous bound-constrained case as well as the synchronous linearly-constrained case. The algorithm has been implemented in the APPSPACK software framework and we present results from an extensive numerical study using CUTEr test problems. We discuss the results, both positive and negative, and conclude that GSS is a reliable method for solving small-to-medium sized linearly-constrained optimization problems without derivatives.

  3. Realization of station for testing asynchronous three-phase motors

    NASA Astrophysics Data System (ADS)

    Wróbel, A.; Surma, W.

    2016-08-01

    Nowadays, you cannot imagine the construction and operation of machines without the use of electric motors [13-15]. The proposed position is designed to allow testing of asynchronous three-phase motors. The position consists of a tested engine and the engine running as a load, both engines combined with a mechanical clutch [2]. The value of the load is recorded by measuring shaft created with Strain Gauge Bridge. This concept will allow to study the basic parameters of the engines, visualization motor parameters both vector and scalar controlled, during varying load drive system. In addition, registration during the variable physical parameters of the working electric motor, controlled by a frequency converter or controlled by a contactor will be possible. Position is designed as a teaching and research position to characterize the engines. It will be also possible selection of inverter parameters.

  4. Reciprocating linear motor

    NASA Technical Reports Server (NTRS)

    Goldowsky, Michael P. (Inventor)

    1987-01-01

    A reciprocating linear motor is formed with a pair of ring-shaped permanent magnets having opposite radial polarizations, held axially apart by a nonmagnetic yoke, which serves as an axially displaceable armature assembly. A pair of annularly wound coils having axial lengths which differ from the axial lengths of the permanent magnets are serially coupled together in mutual opposition and positioned with an outer cylindrical core in axial symmetry about the armature assembly. One embodiment includes a second pair of annularly wound coils serially coupled together in mutual opposition and an inner cylindrical core positioned in axial symmetry inside the armature radially opposite to the first pair of coils. Application of a potential difference across a serial connection of the two pairs of coils creates a current flow perpendicular to the magnetic field created by the armature magnets, thereby causing limited linear displacement of the magnets relative to the coils.

  5. Mathematical Description of an Asynchronous Motor with the Indirect Control of the Output Mechanical Variables

    NASA Astrophysics Data System (ADS)

    Glazachev, A. V.; Dementyev, Yu. N.; Negodin, K. N.; Umursakova, A. D.

    2016-02-01

    The article gives the mathematical description of an asynchronous motor with the indirect control of the output mechanical variables of an asynchronous motor in the electric drive. To determine the electromagnetic torque and angular velocity of the asynchronous motor in the electric drive the mathematical description is used in which the values are determined by the readings of the motor and easily measured values by means of known in practice devices. The proposed in the article the mathematical description for the indirect measuring the electromagnetic torque and angular velocity of the asynchronous motor in the electric drive does not contain the integral components that introduce the great error into the value of the controlled electromagnetic torque and angular velocity.

  6. Reciprocating Linear Electric Motor

    NASA Technical Reports Server (NTRS)

    Goldowsky, M. P.

    1984-01-01

    Features include structural simplicity and good force/displacement characteristics. Reciprocating motor has simple, rugged construction, relatively low reciprocating weight, improved power delivery, and improved force control. Wear reduced by use of magnetic bearings. Intended to provide drivers for long-lived Stirling-cycle cryogenic refrigerators, concept has less exotic applications, such as fuel pumps.

  7. Segmented rail linear induction motor

    DOEpatents

    Cowan, Jr., Maynard; Marder, Barry M.

    1996-01-01

    A segmented rail linear induction motor has a segmented rail consisting of a plurality of nonferrous electrically conductive segments aligned along a guideway. The motor further includes a carriage including at least one pair of opposed coils fastened to the carriage for moving the carriage. A power source applies an electric current to the coils to induce currents in the conductive surfaces to repel the coils from adjacent edges of the conductive surfaces.

  8. Segmented rail linear induction motor

    DOEpatents

    Cowan, M. Jr.; Marder, B.M.

    1996-09-03

    A segmented rail linear induction motor has a segmented rail consisting of a plurality of nonferrous electrically conductive segments aligned along a guideway. The motor further includes a carriage including at least one pair of opposed coils fastened to the carriage for moving the carriage. A power source applies an electric current to the coils to induce currents in the conductive surfaces to repel the coils from adjacent edges of the conductive surfaces. 6 figs.

  9. Three-Dimensional Temperature Field Simulation for the Rotor of an Asynchronous Motor

    ERIC Educational Resources Information Center

    Wang, Yanwu; Fan, Chunli; Yang, Li; Sun, Fengrui

    2010-01-01

    A three-dimensional heat transfer model is built according to the rotor structure of an asynchronous motor, and three-dimensional temperature fields of the rotor under different working conditions, such as the unloaded, rated loaded and that with broken rotor bars, are studied based on the finite element numerical method and experiments. The…

  10. Vector control structure of an asynchronous motor at maximum torque

    NASA Astrophysics Data System (ADS)

    Chioncel, C. P.; Tirian, G. O.; Gillich, N.; Raduca, E.

    2016-02-01

    Vector control methods offer the possibility to gain high performance, being widely used. Certain applications require an optimum control in limit operating conditions, as, at maximum torque, that is not always satisfied. The paper presents how the voltage and the frequency for an asynchronous machine (ASM) operating at variable speed are determinate, with an accent on the method that keeps the rotor flux constant. The simulation analyses consider three load types: variable torque and speed, variable torque and constant speed, constant torque and variable speed. The final values of frequency and voltage are obtained through the proposed control schemes with one controller using the simulation language based on the Maple module. The dynamic analysis of the system is done for the case with P and PI controller and allows conclusions on the proposed method, which can have different applications, as the ASM in wind turbines.

  11. Finite-time quantised feedback asynchronously switched control of sampled-data switched linear systems

    NASA Astrophysics Data System (ADS)

    Wang, Ronghao; Xing, Jianchun; Li, Juelong; Xiang, Zhengrong

    2016-10-01

    This paper studies the problem of stabilising a sampled-data switched linear system by quantised feedback asynchronously switched controllers. The idea of a quantised feedback asynchronously switched control strategy originates in earlier work reflecting actual system characteristic of switching and quantising, respectively. A quantised scheme is designed depending on switching time using dynamic quantiser. When sampling time, system switching time and controller switching time are all not uniform, the proposed switching controllers guarantee the system to be finite-time stable by a piecewise Lyapunov function and the average dwell-time method. Simulation examples are provided to show the effectiveness of the developed results.

  12. Torsional stress analysis of the squirrel-cage rotor for three phase asynchronous motors

    NASA Astrophysics Data System (ADS)

    Axinte, T.; Nutu, C.

    2015-11-01

    The paper aims to determine the torsional stress occurring in the rotor's shaft of the three phase asynchronous motors for a given rotational speed of the rotor. The three phase asynchronous motor is started using the main starting variants, each variant having its own torque characteristic which produces a certain maximum shear stress. The model uses several hypotheses regarding the geometry of the domain, the dynamic behavior, the friction phenomenon and the mass of the shaft which is disregarded in a model and it is considered in a more accurate model. The maximum shear stress is produced by the shock which occurs in the starting process of the motors. This maximum stress may lead to the failure of the rotor either because it breaks, or because of the fatigue of the material produced by frequent starting of the motor. Information resulted from this study are useful for the selection of the appropriate material, of the according geometry of the design and elaboration of the specifications for the in-service use of the motor.This theoretical study will be followed by the development of more accurate models which will also include experimental studies employed to calibrate the theoretical models and to verify their accuracy.

  13. Linear Motor Free Piston Compressor

    NASA Astrophysics Data System (ADS)

    Bloomfield, David P.

    1995-02-01

    A Linear Motor Free Piston Compressor (LMFPC), a free piston pressure recovery system for fuel cell powerplants was developed. The LMFPC consists of a reciprocating compressor and a reciprocating expander which are separated by a piston. In the past energy efficient turbochargers have been used for pressure large (over 50 kW) fuel cell powerplants by recovering pressure energy from the powerplant exhaust. A free piston compressor allows pressurizing 3 - 5 kW sized fuel cell powerplants. The motivation for pressurizing PEM fuel cell powerplants is to improve fuel cell performance. Pressurization of direct methanol fuel cells will be required if PEM membranes are to be used Direct methanol oxidation anode catalysts require high temperatures to operate at reasonable power densities. The elevated temperatures above 80 C will cause high water loss from conventional PEM membranes unless pressurization is employed. Because pressurization is an energy intensive process, recovery of the pressure energy is required to permit high efficiency in fuel cell powerplants. A complete LMFPC which can pressurize a 3 kW fuel cell stack was built. This unit is one of several that were constructed during the course of the program.

  14. A new multisplitting asynchronous iterative method for linear system

    SciTech Connect

    Da-Wei Chang

    1995-12-01

    The parallel multisplitting iterative method for solving large nonsingular N x N linear system Ax = b was first presented by O`Leary and White, and it has been further investigated by Neumman and Plemmous, Chang. For improvement and generalization model B by Bru et al, our idea is, if there are more than one processors output y`s concurrently, proc(0) input all these information concurrently and use them to update the old approximation.

  15. An investigation of the dynamic electromechanical coupling effects in machine drive systems driven by asynchronous motors

    NASA Astrophysics Data System (ADS)

    Szolc, Tomasz; Konowrocki, Robert; Michajłow, Maciej; Pręgowska, Agnieszka

    2014-12-01

    In the paper dynamic electromechanical interaction between the rotating machine drive system and the electric driving motor is considered. The investigations are performed by means of the circuit model of the asynchronous motor as well as using an advanced structural hybrid model of the drive system. Using the analytical solutions applied for the electrical and the mechanical systems the electromagnetic stiffness and coefficient of damping, both generated by the electric motor rotationally interacting with the mechanical system of the given dynamic properties, were determined. By means of experimentally validated computational responses obtained for torsional harmonic excitation induced by the driven machine working tool, a modification of dynamic properties of the mechanical system by the electromagnetic flux between the stator and the rotor has been studied.

  16. Asynchronous H∞ filtering for linear switched systems with average dwell time

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Zhang, Hongbin; Wang, Gang; Dang, Chuangyin

    2016-09-01

    This paper is concerned with the H∞ filtering problem for a class of continuous-time linear switched systems with the asynchronous behaviours, where 'asynchronous' means that the switching of the filters to be designed has a lag to the switching of the system modes. By using the Lyapunov-like functions and the average dwell time technique, a sufficient condition is obtained to guarantee the asymptotic stability with a weighted H∞ performance index for the filtering error system. Moreover, the results are formulated in the form of linear matrix inequalities that are numerical feasible. As a result, the filter design problem is solved. Finally, an illustrative numerical example is presented to show the effectiveness of the results.

  17. VA02 series of high voltage explosion-proof asynchronous motors

    NASA Astrophysics Data System (ADS)

    Goryagin, V. F.; Zbarskiy, L. A.; Shirnin, I. G.; Porshnev, Yu. V.; Figotina, M. I.

    1987-04-01

    The VAO2 asynchronous, squirrel cage, explosion-proof electric motors have the same power and r.p.m. range, the same weather, water and dust proofing as the predecessor VAO series and are designed for the same explosion hazards. The nominal r.p.m. ranges from 750 to 3,000, the power ratings from 200 to 1,000 kW, voltage ratings are 6,000 and 10,000 volts with efficiencies running from 93.4 to 95.6% and weights of 1,620 to 5,700 kg. The new VAO2 motors incorporate the following improvements: the use of cold rolled electrical steel with lower specific losses; the use of a bottle configuration for the rotor slot instead of the usual oval; an improved exterior cooling system; and a reduction in the average insulation thickness.

  18. Data-Driven Based Asynchronous Motor Control for Printing Servo Systems

    NASA Astrophysics Data System (ADS)

    Bian, Min; Guo, Qingyun

    Modern digital printing equipment aims to the environmental-friendly industry with high dynamic performances and control precision and low vibration and abrasion. High performance motion control system of printing servo systems was required. Control system of asynchronous motor based on data acquisition was proposed. Iterative learning control (ILC) algorithm was studied. PID control was widely used in the motion control. However, it was sensitive to the disturbances and model parameters variation. The ILC applied the history error data and present control signals to approximate the control signal directly in order to fully track the expect trajectory without the system models and structures. The motor control algorithm based on the ILC and PID was constructed and simulation results were given. The results show that data-driven control method is effective dealing with bounded disturbances for the motion control of printing servo systems.

  19. A linear magnetic motor and generator

    NASA Technical Reports Server (NTRS)

    Studer, P. A.

    1980-01-01

    In linear magnetic motor and generator suitable for remote and hostile environments, magnetic forces drive reciprocating shaft along its axis. Actuator shaft is located in center of cylindrical body and may be supported by either contacting or noncontacting bearings. When device operates as bidirectional motor, drive coil selectively adds and subtracts magnetic flux to and from flux paths, producing forces that drive actuator along axis. When actuator is driven by external reciprocating engine, device becomes ac generator.

  20. Gigahertz resonance characteristics of nanotube linear motor

    NASA Astrophysics Data System (ADS)

    Kang, Jeong-Won; Choi, Young Gyu; Ryu, Gi Han; Won, Chung Sang

    2008-08-01

    We investigated a linear carbon nanotube motor serving as the key building block for nanoscale motion control by using molecular dynamics simulations. This linear nanomotor, is based on the electrostatically telescoping multi-walled carbon-nanotube with ultralow intershell sliding friction, is controlled by the gate potential with the capacitance feedback sensing. The resonant harmonic peaks are induced by the interference between the driving frequencies and its self-frequency. The temperature is very important factor to operate this nanomotor.

  1. Linear summation of cat motor cortex outputs.

    PubMed

    Ethier, Christian; Brizzi, Laurent; Darling, Warren G; Capaday, Charles

    2006-05-17

    Recruitment of movement-related muscle synergies involves the functional linking of motor cortical points. We asked how the outputs of two simultaneously stimulated motor cortical points would interact. To this end, experiments were done in ketamine-anesthetized cats. When prolonged (e.g., 500 ms) trains of intracortical microstimulation were applied in the primary motor cortex, stimulus currents as low as 10-20 microA evoked coordinated movements of the contralateral forelimb. Paw kinematics in three dimensions and the electromyographic (EMG) activity of eight muscles were simultaneously recorded. We show that the EMG outputs of two cortical points simultaneously stimulated are additive. The movements were represented as displacement vectors pointing from initial to final paw position. The displacement vectors resulting from simultaneous stimulation of two cortical points pointed in nearly the same direction as the algebraic resultant vector. Linear summation of outputs was also found when inhibition at one of the cortical points was reduced by GABAA receptor antagonists. A simple principle emerges from these results. Notwithstanding the underlying complex neuronal circuitry, motor cortex outputs combine nearly linearly in terms of movement direction and muscle activation patterns. Importantly, simultaneous activation does not change the nature of the output at each point. An additional implication is that not all possible movements need be explicitly represented in the motor cortex; a large number of different movements may be synthesized from a smaller repertoire.

  2. Hybrid EEG-fNIRS Asynchronous Brain-Computer Interface for Multiple Motor Tasks.

    PubMed

    Buccino, Alessio Paolo; Keles, Hasan Onur; Omurtag, Ahmet

    2016-01-01

    Non-invasive Brain-Computer Interfaces (BCI) have demonstrated great promise for neuroprosthetics and assistive devices. Here we aim to investigate methods to combine Electroencephalography (EEG) and functional Near-Infrared Spectroscopy (fNIRS) in an asynchronous Sensory Motor rhythm (SMR)-based BCI. We attempted to classify 4 different executed movements, namely, Right-Arm-Left-Arm-Right-Hand-Left-Hand tasks. Previous studies demonstrated the benefit of EEG-fNIRS combination. However, since normally fNIRS hemodynamic response shows a long delay, we investigated new features, involving slope indicators, in order to immediately detect changes in the signals. Moreover, Common Spatial Patterns (CSPs) have been applied to both EEG and fNIRS signals. 15 healthy subjects took part in the experiments and since 25 trials per class were available, CSPs have been regularized with information from the entire population of participants and optimized using genetic algorithms. The different features have been compared in terms of performance and the dynamic accuracy over trials shows that the introduced methods diminish the fNIRS delay in the detection of changes. PMID:26730580

  3. Hybrid EEG-fNIRS Asynchronous Brain-Computer Interface for Multiple Motor Tasks

    PubMed Central

    Buccino, Alessio Paolo; Keles, Hasan Onur; Omurtag, Ahmet

    2016-01-01

    Non-invasive Brain-Computer Interfaces (BCI) have demonstrated great promise for neuroprosthetics and assistive devices. Here we aim to investigate methods to combine Electroencephalography (EEG) and functional Near-Infrared Spectroscopy (fNIRS) in an asynchronous Sensory Motor rhythm (SMR)-based BCI. We attempted to classify 4 different executed movements, namely, Right-Arm—Left-Arm—Right-Hand—Left-Hand tasks. Previous studies demonstrated the benefit of EEG-fNIRS combination. However, since normally fNIRS hemodynamic response shows a long delay, we investigated new features, involving slope indicators, in order to immediately detect changes in the signals. Moreover, Common Spatial Patterns (CSPs) have been applied to both EEG and fNIRS signals. 15 healthy subjects took part in the experiments and since 25 trials per class were available, CSPs have been regularized with information from the entire population of participants and optimized using genetic algorithms. The different features have been compared in terms of performance and the dynamic accuracy over trials shows that the introduced methods diminish the fNIRS delay in the detection of changes. PMID:26730580

  4. Linear synchronous motor having enhanced levitational forces

    SciTech Connect

    Tozoni, O.

    1993-07-06

    A linear synchronous motor for a high speed vehicle is described comprising: (a) a linear stator assembly divided into sections and having an air gap, the stator assembly generating a magnetic field traveling wave in the air gap from an alternating current source, the traveling wave having variable speeds and accelerations along different sections of the stator assembly; (b) a rotor assembly having at least one propulsion magnet forming at least one pole-pitch of a selected length that is selectively variable while the vehicle is in motion, the magnet including an upper portion, a lower portion spaced apart from the upper portion, and a nonmagnetic coupler rigidly coupling the upper portion to the lower portion, the rotor assembly coupled to the vehicle and disposed in the air gap of the stator and movable laterally with respect to the stator, the rotor assembly generating a magnetic flux that produces an attractive force between a magnetic field of the rotor assembly and the traveling wave of the stator assembly, the magnetic field of the rotor assembly propelling the vehicle and generating a levitation force levitating the vehicle; and (c) a synchronizing unit operatively associated with the rotor assembly to vary the length of the pole-pitch such that the pole-pitch length is substantially equal to one-half the length of the traveling wave at any given position along the linear stator assembly.

  5. Novel linear piezoelectric motor for precision position stage

    NASA Astrophysics Data System (ADS)

    Chen, Chao; Shi, Yunlai; Zhang, Jun; Wang, Junshan

    2016-03-01

    Conventional servomotor and stepping motor face challenges in nanometer positioning stages due to the complex structure, motion transformation mechanism, and slow dynamic response, especially directly driven by linear motor. A new butterfly-shaped linear piezoelectric motor for linear motion is presented. A two-degree precision position stage driven by the proposed linear ultrasonic motor possesses a simple and compact configuration, which makes the system obtain shorter driving chain. Firstly, the working principle of the linear ultrasonic motor is analyzed. The oscillation orbits of two driving feet on the stator are produced successively by using the anti-symmetric and symmetric vibration modes of the piezoelectric composite structure, and the slider pressed on the driving feet can be propelled twice in only one vibration cycle. Then with the derivation of the dynamic equation of the piezoelectric actuator and transient response model, start-upstart-up and settling state characteristics of the proposed linear actuator is investigated theoretically and experimentally, and is applicable to evaluate step resolution of the precision platform driven by the actuator. Moreover the structure of the two-degree position stage system is described and a special precision displacement measurement system is built. Finally, the characteristics of the two-degree position stage are studied. In the closed-loop condition the positioning accuracy of plus or minus <0.5 μm is experimentally obtained for the stage propelled by the piezoelectric motor. A precision position stage based the proposed butterfly-shaped linear piezoelectric is theoretically and experimentally investigated.

  6. On the asynchronously continuous control of mobile robot movement by motor cortical spiking activity.

    PubMed

    Xu, Zhiming; So, Rosa Q; Toe, Kyaw Kyar; Ang, Kai Keng; Guan, Cuntai

    2014-01-01

    This paper presents an asynchronously intracortical brain-computer interface (BCI) which allows the subject to continuously drive a mobile robot. This system has a great implication for disabled patients to move around. By carefully designing a multiclass support vector machine (SVM), the subject's self-paced instantaneous movement intents are continuously decoded to control the mobile robot. In particular, we studied the stability of the neural representation of the movement directions. Experimental results on the nonhuman primate showed that the overt movement directions were stably represented in ensemble of recorded units, and our SVM classifier could successfully decode such movements continuously along the desired movement path. However, the neural representation of the stop state for the self-paced control was not stably represented and could drift. PMID:25570634

  7. On the asynchronously continuous control of mobile robot movement by motor cortical spiking activity.

    PubMed

    Xu, Zhiming; So, Rosa Q; Toe, Kyaw Kyar; Ang, Kai Keng; Guan, Cuntai

    2014-01-01

    This paper presents an asynchronously intracortical brain-computer interface (BCI) which allows the subject to continuously drive a mobile robot. This system has a great implication for disabled patients to move around. By carefully designing a multiclass support vector machine (SVM), the subject's self-paced instantaneous movement intents are continuously decoded to control the mobile robot. In particular, we studied the stability of the neural representation of the movement directions. Experimental results on the nonhuman primate showed that the overt movement directions were stably represented in ensemble of recorded units, and our SVM classifier could successfully decode such movements continuously along the desired movement path. However, the neural representation of the stop state for the self-paced control was not stably represented and could drift.

  8. Clonal expansion and linear genome evolution through breast cancer progression from pre-invasive stages to asynchronous metastasis

    PubMed Central

    Krøigård, Anne Bruun; Larsen, Martin Jakob; Lænkholm, Anne-Vibeke; Knoop, Ann S.; Jensen, Jeanette D.; Bak, Martin; Mollenhauer, Jan; Kruse, Torben A.; Thomassen, Mads

    2015-01-01

    Evolution of the breast cancer genome from pre-invasive stages to asynchronous metastasis is complex and mostly unexplored, but highly demanded as it may provide novel markers for and mechanistic insights in cancer progression. The increasing use of personalized therapy of breast cancer necessitates knowledge of the degree of genomic concordance between different steps of malignant progression as primary tumors often are used as surrogates of systemic disease. Based on exome sequencing we performed copy number profiling and point mutation detection on successive steps of breast cancer progression from one breast cancer patient, including two different regions of Ductal Carcinoma In Situ (DCIS), primary tumor and an asynchronous metastasis. We identify a remarkable landscape of somatic mutations, retained throughout breast cancer progression and with new mutational events emerging at each step. Our data, contrary to the proposed model of early dissemination of metastatic cells and parallel progression of primary tumors and metastases, provide evidence of linear progression of breast cancer with relatively late dissemination from the primary tumor. The genomic discordance between the different stages of tumor evolution in this patient emphasizes the importance of molecular profiling of metastatic tissue directing molecularly targeted therapy at recurrence. PMID:25730902

  9. Characterization of a small moving-magnet electrodynamic linear motor

    NASA Astrophysics Data System (ADS)

    Liu, Jin; Garrett, Steven

    2005-10-01

    The mechanical and electrodynamic parameters of a small, potentially inexpensive, moving-magnet electrodynamic linear motor are determined experimentally. Employing the formalism introduced by Wakeland, these parameters are used to predict the electromechanical efficiency of the motor. The transduction coefficient, Bl, was observed to be a function of position. But as shown in the paper, the variation in Bl with position has a smaller effect on the driver's output power because Bl is largest around the equilibrium position, where the piston velocity is also largest. By mechanical colinear joining of the armatures of two such motors, an electrodynamic load (dynamometer) is created to measure the efficiency as a function of energy dissipated in the dynamometer. The measured efficiencies are shown to be in good agreement with the predictions if a position-averaged effective transduction coefficient is introduced. Based on these results, this linear motor is judged to be an attractive power source in small electrically driven thermoacoustic refrigerator applications.

  10. Magnetic levitation configuration incorporating levitation, guidance and linear synchronous motor

    DOEpatents

    Coffey, H.T.

    1993-10-19

    A propulsion and suspension system for an inductive repulsion type magnetically levitated vehicle which is propelled and suspended by a system which includes propulsion windings which form a linear synchronous motor and conductive guideways, adjacent to the propulsion windings, where both combine to partially encircling the vehicle-borne superconducting magnets. A three phase power source is used with the linear synchronous motor to produce a traveling magnetic wave which in conjunction with the magnets propel the vehicle. The conductive guideway combines with the superconducting magnets to provide for vehicle levitation. 3 figures.

  11. Magnetic levitation configuration incorporating levitation, guidance and linear synchronous motor

    DOEpatents

    Coffey, Howard T.

    1993-01-01

    A propulsion and suspension system for an inductive repulsion type magnetically levitated vehicle which is propelled and suspended by a system which includes propulsion windings which form a linear synchronous motor and conductive guideways, adjacent to the propulsion windings, where both combine to partially encircling the vehicle-borne superconducting magnets. A three phase power source is used with the linear synchronous motor to produce a traveling magnetic wave which in conjunction with the magnets propel the vehicle. The conductive guideway combines with the superconducting magnets to provide for vehicle leviation.

  12. Resettable binary latch mechanism for use with paraffin linear motors

    NASA Technical Reports Server (NTRS)

    Maus, Daryl; Tibbitts, Scott

    1991-01-01

    A new resettable Binary Latch Mechanism was developed utilizing a paraffin actuator as the motor. This linear actuator alternately latches between extended and retracted positions, maintaining either position with zero power consumption. The design evolution and kinematics of the latch mechanism are presented, as well as the development problems and lessons that were learned.

  13. Position sensor for linear synchronous motors employing halbach arrays

    SciTech Connect

    Post, Richard Freeman

    2014-12-23

    A position sensor suitable for use in linear synchronous motor (LSM) drive systems employing Halbach arrays to create their magnetic fields is described. The system has several advantages over previously employed ones, especially in its simplicity and its freedom from being affected by weather conditions, accumulated dirt, or electrical interference from the LSM system itself.

  14. The Linear Motor in the Human Neutrophil Migration

    NASA Astrophysics Data System (ADS)

    Vereycken, V.; Gruler, H.; Bucherer, C.; Lacombe, C.; Lelièvre, J. C.

    1995-09-01

    The kinematics and dynamics of human neutrophils in a narrow glass tube (4.9 μm to 6.3 μm in diameter) have been investigated both experimentally and theoretically. Cells were activated by the tri-peptide (fMLP) to migrate through a tube with a mean speed of 0.15± 0.03~μm/s (54 activated cells). When a hydrostatic pressure was applied across the cell, the mean speed of the cell leading front linearly decreases when the pressure is increased. At a pressure difference of 1530± 140 Pa (9 activated cells), the cell was forced to stop. The cell migration has been approximated by a tractor-trailer model. The cellular motor (leading front), the tractor, produced a traction force by converting chemical energy into mechanical work. This motor has been characterized as a linear motor with two machine coefficients: (i) the maximum traction T_0~(37.7 nN) at V = 0, where V is the cellular speed (ii) the maximum cellular speed V_max~(0.15~μm/s). A characteristic time of approximately 100 s was measured for the action cycle of the linear motor. A phenomenological description of the chemotactic machine has been presented.

  15. Advanced analysis technique for the evaluation of linear alternators and linear motors

    NASA Technical Reports Server (NTRS)

    Holliday, Jeffrey C.

    1995-01-01

    A method for the mathematical analysis of linear alternator and linear motor devices and designs is described, and an example of its use is included. The technique seeks to surpass other methods of analysis by including more rigorous treatment of phenomena normally omitted or coarsely approximated such as eddy braking, non-linear material properties, and power losses generated within structures surrounding the device. The technique is broadly applicable to linear alternators and linear motors involving iron yoke structures and moving permanent magnets. The technique involves the application of Amperian current equivalents to the modeling of the moving permanent magnet components within a finite element formulation. The resulting steady state and transient mode field solutions can simultaneously account for the moving and static field sources within and around the device.

  16. A standing wave-type noncontact linear ultrasonic motor.

    PubMed

    Hu, J; Li, G; Chan, H L; Choy, C L

    2001-05-01

    In this study, a novel standing wave-type noncontact linear ultrasonic motor is proposed and analyzed. This linear ultrasonic motor uses a properly controlled ultrasonic standing wave to levitate and drive a slider. A prototype of the motor was constructed by using a wedge-shaped aluminum stator, which was placed horizontally and driven by a multilayer PZT vibrator. The levitation and motion of the slider were observed. Assuming that the driving force was generated by the turbulent acoustic streaming in the boundary air layer next to the bottom surface of the slider, a theoretical model was developed. The calculated characteristics of this motor were found to agree quite well with the experimental results. Based on the experimental and theoretical results, guidelines for increasing the displacement and speed of the slider were obtained. It was found that increasing the stator vibration displacement, or decreasing the gradient of the stator vibration velocity and the weight per unit area of the slider, led to an increase of the slider displacement. It was also found that increasing the amplitude and gradient of the stator vibration velocity, or decreasing the weight per unit area of the slider and the driving frequency, gave rise to an increase of the slider speed. There exists an optimum roughness of the bottom surface of the slider at which the slider speed has a maximum. PMID:11381693

  17. Lightweight type linear induction motor and its characteristics

    SciTech Connect

    Osawa, S.; Yoshimuro, M.; Karita, M.; Ebihara, D.; Yokoi, T.

    1994-08-01

    At the Institute for Posts and Telecommunications Policy, a postal transportation system has been studied. This system would make use of linear induction motor (LIM)-driven vehicles for transporting mail between post offices in the Tokyo Metropolitan area. The system would connect the main post offices in the Tokyo area with tunnels circularly constructed underground and would transport mail with linear induction motor-driven vehicles. In this study, it is found that if vehicle weight is reduced, climbing capability could be considerably improved. Accordingly, the potential for reducing the weight of vehicle-mounted LIMs has been explored, and a prototype lightweight LIM has been manufactured. This paper reports on the lightweight LIM and its characteristics. 8 refs.

  18. Development of a linear induction motor based artificial muscle system.

    PubMed

    Gruber, A; Arguello, E; Silva, R

    2013-01-01

    We present the design of a linear induction motor based on electromagnetic interactions. The engine is capable of producing a linear movement from electricity. The design consists of stators arranged in parallel, which produce a magnetic field sufficient to displace a plunger along its axial axis. Furthermore, the winding has a shell and cap of ferromagnetic material that amplifies the magnetic field. This produces a force along the length of the motor that is similar to that of skeletal muscle. In principle, the objective is to use the engine in the development of an artificial muscle system for prosthetic applications, but it could have multiple applications, not only in the medical field, but in other industries.

  19. Development of a linear induction motor based artificial muscle system.

    PubMed

    Gruber, A; Arguello, E; Silva, R

    2013-01-01

    We present the design of a linear induction motor based on electromagnetic interactions. The engine is capable of producing a linear movement from electricity. The design consists of stators arranged in parallel, which produce a magnetic field sufficient to displace a plunger along its axial axis. Furthermore, the winding has a shell and cap of ferromagnetic material that amplifies the magnetic field. This produces a force along the length of the motor that is similar to that of skeletal muscle. In principle, the objective is to use the engine in the development of an artificial muscle system for prosthetic applications, but it could have multiple applications, not only in the medical field, but in other industries. PMID:24111159

  20. A Ca2+-induced Ca2+ Release Mechanism Involved in Asynchronous Exocytosis at Frog Motor Nerve Terminals

    PubMed Central

    Narita, K.; Akita, T.; Osanai, M.; Shirasaki, T.; Kijima, H.; Kuba, K.

    1998-01-01

    The extent to which Ca2+-induced Ca2+ release (CICR) affects transmitter release is unknown. Continuous nerve stimulation (20–50 Hz) caused slow transient increases in miniature end-plate potential (MEPP) frequency (MEPP-hump) and intracellular free Ca2+ ([Ca2+]i) in presynaptic terminals (Ca2+-hump) in frog skeletal muscles over a period of minutes in a low Ca2+, high Mg2+ solution. Mn2+ quenched Indo-1 and Fura-2 fluorescence, thus indicating that stimulation was accompanied by opening of voltage-dependent Ca2+ channels. MEPP-hump depended on extracellular Ca2+ (0.05–0.2 mM) and stimulation frequency. Both the Ca2+- and MEPP-humps were blocked by 8-(N,N-diethylamino)octyl3,4,5-trimethoxybenzoate hydrochloride (TMB-8), ryanodine, and thapsigargin, but enhanced by CN−. Thus, Ca2+-hump is generated by the activation of CICR via ryanodine receptors by Ca2+ entry, producing MEPP-hump. A short interruption of tetanus (<1 min) during MEPP-hump quickly reduced MEPP frequency to a level attained under the effect of TMB-8 or thapsigargin, while resuming tetanus swiftly raised MEPP frequency to the previous or higher level. Thus, the steady/equilibrium condition balancing CICR and Ca2+ clearance occurs in nerve terminals with slow changes toward a greater activation of CICR (priming) during the rising phase of MEPP-hump and toward a smaller activation during the decay phase. A short pause applied after the end of MEPP- or Ca2+-hump affected little MEPP frequency or [Ca2+]i, but caused a quick increase (faster than MEPP- or Ca2+-hump) after the pause, whose magnitude increased with an increase in pause duration (<1 min), suggesting that Ca2+ entry-dependent inactivation, but not depriming process, explains the decay of the humps. The depriming process was seen by giving a much longer pause (>1 min). Thus, ryanodine receptors in frog motor nerve terminals are endowed with Ca2+ entry-dependent slow priming and fast inactivation mechanisms, as well as Ca2+ entry

  1. Design and optimization of a modal- independent linear ultrasonic motor.

    PubMed

    Zhou, Shengli; Yao, Zhiyuan

    2014-03-01

    To simplify the design of the linear ultrasonic motor (LUSM) and improve its output performance, a method of modal decoupling for LUSMs is proposed in this paper. The specific embodiment of this method is decoupling of the traditional LUSM stator's complex vibration into two simple vibrations, with each vibration implemented by one vibrator. Because the two vibrators are designed independently, their frequencies can be tuned independently and frequency consistency is easy to achieve. Thus, the method can simplify the design of the LUSM. Based on this method, a prototype modal- independent LUSM is designed and fabricated. The motor reaches its maximum thrust force of 47 N, maximum unloaded speed of 0.43 m/s, and maximum power of 7.85 W at applied voltage of 200 Vpp. The motor's structure is then optimized by controlling the difference between the two vibrators' resonance frequencies to reach larger output speed, thrust, and power. The optimized results show that when the frequency difference is 73 Hz, the output force, speed, and power reach their maximum values. At the input voltage of 200 Vpp, the motor reaches its maximum thrust force of 64.2 N, maximum unloaded speed of 0.76 m/s, maximum power of 17.4 W, maximum thrust-weight ratio of 23.7, and maximum efficiency of 39.6%.

  2. Propulsion control of superconducting linear synchronous motor vehicle

    SciTech Connect

    Sakamoto, Tetsuzo; Shiromizu, Tsunehiro

    1997-09-01

    The armature current of a superconducting Linear Synchronous Motor (LSM) for a maglev vehicle is controlled to produce a suitable propulsion force so that the vehicle follows the reference speed signal sent from a control station. Besides the power is supplied from some inverters to the LSM armature sections where the vehicle exists. This paper shows an exact mathematical modeling of the propulsion control system to treat the system analytically, which is used for designing controllers and performance computer simulations. The calculated results include the simulations when the vehicle goes through power feeder section borders and tunnels that have a large aerodynamic drag force with taking account of an inverter failure.

  3. Commercializing a U.S. piezoceramic linear motor

    NASA Astrophysics Data System (ADS)

    Diehl, Rick W.

    2000-06-01

    A small low-cost piezoceramic linear motor has been developed in the US and is being commercialized by EDO Corporation, working with a leading motion control OEM and with a prominent US corporate research laboratory. First generation motor design has emphasized high displacement at up to 200mm per second velocity with 3.5 Newtons force with high resolution, short time constant and a 15 volt power supply at a cost of less than 100 dollars. Motor dimensions of 30 by 50 by 4 mm allow broad configuration choices, al hidden within the motion control slide. The EDO approach was to build on its core competence in high reliability electroceramic material engineering and production, and to use a strategy of back-integrating, or outsourcing of recent advances outside Edo in piezoceramics, while forward- integrating into specific emerging applications known intimately by the OEM in the market. The strategy provided design focus that has led to a cost-effective advance in 'solid-state actuation and control'. This is considered a classic case of successful industrial integration of an enabling technology across organizations in order to access the needed mix of technology for development of an innovative and competitive solution.

  4. Linear magnetic spring and spring/motor combination

    NASA Technical Reports Server (NTRS)

    Patt, Paul J. (Inventor); Stolfi, Fred R. (Inventor)

    1991-01-01

    A magnetic spring, or a spring and motor combination, providing a linear spring force characteristic in each direction from a neutral position, in which the spring action may occur for any desired coordinate of a typical orthogonal coordinate system. A set of magnets are disposed, preferably symmetrically about a coordinate axis, poled orthogonally to the desired force direction. A second set of magnets, respectively poled opposite the first set, are arranged on the sprung article. The magnets of one of the sets are spaced a greater distance apart than those of the other, such that an end magnet from each set forms a pair having preferably planar faces parallel to the direction of spring force, the faces being offset so that in a neutral position the outer edge of the closer spaced magnet set is aligned with the inner edge of the greater spaced magnet set. For use as a motor, a coil can be arranged with conductors orthogonal to both the magnet pole directions and the direction of desired spring force, located across from the magnets of one set and fixed with respect to the magnets of the other set. In a cylindrical coordinate system having axial spring force, the magnets are radially poled and motor coils are concentric with the cylinder axis.

  5. The design and analysis of a novel brushless dc linear motor

    NASA Astrophysics Data System (ADS)

    Basak, A.; Filho, A. F. Flores

    1994-05-01

    A novel brushless dc linear motor was designed, with two armature cores and seven high energy product magnets. It was then built and tested. Both the design and the analysis were carried out assuming a linear magnetic circuit. The design procedure and the test results are presented and discussed in this paper. The new motor can also be used as a slotless linear stepping motor.

  6. A square-plate ultrasonic linear motor operating in two orthogonal first bending modes.

    PubMed

    Chen, Zhijiang; Li, Xiaotian; Chen, Jianguo; Dong, Shuxiang

    2013-01-01

    A novel square-plate piezoelectric ultrasonic linear motor operated in two orthogonal first bending vibration modes (B₁) is proposed. The piezoelectric vibrator of the linear motor is simply made of a single PZT ceramic plate (sizes: 15 x 15 x 2 mm) and poled in its thickness direction. The top surface electrode of the square ceramic plate was divided into four active areas along its two diagonal lines for exciting two orthogonal B₁ modes. The achieved driving force and speed from the linear motor are 1.8 N and 230 mm/s, respectively, under one pair orthogonal voltage drive of 150 V(p-p) at the resonance frequency of 92 kHz. The proposed linear motor has advantages over conventional ultrasonic linear motors, such as relatively larger driving force, very simple working mode and structure, and low fabrication cost.

  7. Design and performance testing of an ultrasonic linear motor with dual piezoelectric actuators.

    PubMed

    Smithmaitrie, Pruittikorn; Suybangdum, Panumas; Laoratanakul, Pitak; Muensit, Nantakan

    2012-05-01

    In this work, design and performance testing of an ultrasonic linear motor with dual piezoelectric actuator patches are studied. The motor system consists of a linear stator, a pre-load weight, and two piezoelectric actuator patches. The piezoelectric actuators are bonded with the linear elastic stator at specific locations. The stator generates propagating waves when the piezoelectric actuators are subjected to harmonic excitations. Vibration characteristics of the linear stator are analyzed and compared with finite element and experimental results. The analytical, finite element, and experimental results show agreement. In the experiments, performance of the ultrasonic linear motor is tested. Relationships between velocity and pre-load weight, velocity and applied voltage, driving force and applied voltage, and velocity and driving force are reported. The design of the dual piezoelectric actuators yields a simpler structure with a smaller number of actuators and lower stator stiffness compared with a conventional design of an ultrasonic linear motor with fully laminated piezoelectric actuators.

  8. Minimization of cogging force in a linear permanent magnet motor

    SciTech Connect

    Hor, P.J.; Zhu, Z.Q.; Howe, D.; Rees-Jones, J.

    1998-09-01

    A finite element/analytically based method is used to aid the minimization of cogging force, due to slotting and the finite length of the ferromagnetic core, in a tubular brushless permanent magnet motor. The method is validated against both finite element calculations and measurements on a prototype motor.

  9. Calculation of cogging force in a novel slotted linear tubular brushless permanent magnet motor

    SciTech Connect

    Zhu, Z.Q.; Hor, P.J.; Howe, D.; Rees-Jones, J.

    1997-09-01

    There is an increasing requirement for controlled linear motion over short and long strokes, in the factory automation and packaging industries, for example. Linear brushless PM motors could offer significant advantages over conventional actuation technologies, such as motor driven cams and linkages and pneumatic rams--in terms of efficiency, operating bandwidth, speed and thrust control, stroke and positional accuracy, and indeed over other linear motor technologies, such as induction motors. Here, a finite element/analytical based technique for the prediction of cogging force in a novel topology of slotted linear brushless permanent magnet motor has been developed and validated. The various force components, which influence cogging are pre-calculated by the finite element analysis of some basic magnetic structures, facilitate the analytical synthesis of the resultant cogging force. The technique can be used to aid design for the minimization of cogging.

  10. Design and simulation of a novel impact piezoelectric linear-rotary motor

    NASA Astrophysics Data System (ADS)

    Han, Liling; Zhao, Yahui; Pan, Chengliang; Yu, Liandong

    2016-01-01

    This paper presents a novel impact piezoelectric linear-rotary motor which is driven by a single piezoceramic tube with two parts of electrodes. From the inner and outer electrodes, longitudinal displacement of the tube is generated and used to actuate the shaft with linear motion ability. From the grooved helical interdigitated electrodes, torsional displacement is generated and used to actuate the shaft with rotary motion ability. Working principle and structural design of the motor are introduced and quasi-static longitudinal and torsional displacements of the tube are estimated. With established kinematics model of the motor, the working behaviors of the motor are investigated numerically with MATLAB/Simulink software. The stepping characteristics of the linear and rotary motions are analyzed, compared, and discussed. With optimized material selection, structural design, and driving parameters, the proposed linear-rotary motor will provide remarkable performances as a miniaturized multi-degree driving device for complex positioning and manipulation applications.

  11. Linear summation of outputs in a balanced network model of motor cortex

    PubMed Central

    Capaday, Charles; van Vreeswijk, Carl

    2015-01-01

    Given the non-linearities of the neural circuitry's elements, we would expect cortical circuits to respond non-linearly when activated. Surprisingly, when two points in the motor cortex are activated simultaneously, the EMG responses are the linear sum of the responses evoked by each of the points activated separately. Additionally, the corticospinal transfer function is close to linear, implying that the synaptic interactions in motor cortex must be effectively linear. To account for this, here we develop a model of motor cortex composed of multiple interconnected points, each comprised of reciprocally connected excitatory and inhibitory neurons. We show how non-linearities in neuronal transfer functions are eschewed by strong synaptic interactions within each point. Consequently, the simultaneous activation of multiple points results in a linear summation of their respective outputs. We also consider the effects of reduction of inhibition at a cortical point when one or more surrounding points are active. The network response in this condition is linear over an approximately two- to three-fold decrease of inhibitory feedback strength. This result supports the idea that focal disinhibition allows linear coupling of motor cortical points to generate movement related muscle activation patterns; albeit with a limitation on gain control. The model also explains why neural activity does not spread as far out as the axonal connectivity allows, whilst also explaining why distant cortical points can be, nonetheless, functionally coupled by focal disinhibition. Finally, we discuss the advantages that linear interactions at the cortical level afford to motor command synthesis. PMID:26097452

  12. A standing wave linear ultrasonic motor operating in in-plane expanding and bending modes.

    PubMed

    Chen, Zhijiang; Li, Xiaotian; Ci, Penghong; Liu, Guoxi; Dong, Shuxiang

    2015-03-01

    A novel standing wave linear ultrasonic motor operating in in-plane expanding and bending modes was proposed in this study. The stator (or actuator) of the linear motor was made of a simple single Lead Zirconate Titanate (PZT) ceramic square plate (15 × 15 × 2 mm(3)) with a circular hole (D = 6.7 mm) in the center. The geometric parameters of the stator were computed with the finite element analysis to produce in-plane bi-mode standing wave vibration. The calculated results predicted that a driving tip attached at midpoint of one edge of the stator can produce two orthogonal, approximate straight-line trajectories, which can be used to move a slider in linear motion via frictional forces in forward or reverse direction. The investigations showed that the proposed linear motor can produce a six times higher power density than that of a previously reported square plate motor.

  13. A standing wave linear ultrasonic motor operating in in-plane expanding and bending modes

    NASA Astrophysics Data System (ADS)

    Chen, Zhijiang; Li, Xiaotian; Ci, Penghong; Liu, Guoxi; Dong, Shuxiang

    2015-03-01

    A novel standing wave linear ultrasonic motor operating in in-plane expanding and bending modes was proposed in this study. The stator (or actuator) of the linear motor was made of a simple single Lead Zirconate Titanate (PZT) ceramic square plate (15 × 15 × 2 mm3) with a circular hole (D = 6.7 mm) in the center. The geometric parameters of the stator were computed with the finite element analysis to produce in-plane bi-mode standing wave vibration. The calculated results predicted that a driving tip attached at midpoint of one edge of the stator can produce two orthogonal, approximate straight-line trajectories, which can be used to move a slider in linear motion via frictional forces in forward or reverse direction. The investigations showed that the proposed linear motor can produce a six times higher power density than that of a previously reported square plate motor.

  14. Fluid powered linear piston motor with harmonic coupling

    DOEpatents

    Raymond, David W.

    2016-09-20

    A motor is disclosed that includes a module assembly including a piston that is axially cycled. The piston axial motion is coupled to torque couplers that convert the axial motion into rotary motion. The torque couplers are coupled to a rotor to rotate the rotor.

  15. A T-shape linear piezoelectric motor with single foot.

    PubMed

    Liu, Yingxiang; Chen, Weishan; Yang, Xiaohui; Liu, Junkao

    2015-02-01

    A new T-shape piezoelectric motor using the hybrid of two orthogonal longitudinal vibrations is proposed in this work. Six pieces of PZT ceramic plates are bonded on the upside and downside surfaces of a T-shape duralumin alloy base respectively to form the proposed motor. Elliptical movement can be generated on the driving tip by applying sine and cosine voltages to the PZT elements. The horizontal displacement of the driving tip will push the runner while the vertical displacement can overcome the preload. Finite element method is used to accomplish the design and analysis process. The resonance frequencies of the two vibration modes are tuned to be close by modal analysis, while the motion trajectory of the driving tip is observed by transient analysis. After the fabrication of a prototype, the vibration characteristics and mechanical output ability are measured. The no-load speed and the maximum output thrust force of the proposed motor are tested to be 718 mm/s and 3.5 N under an exciting frequency of 53.1 kHz. The proposed T-shape piezoelectric motor exhibits merits of simple structure, easy to realize miniaturization, easy to be fabricated, and high power-to-weight ratio.

  16. A double B1-mode 4-layer laminated piezoelectric linear motor.

    PubMed

    Li, Xiaotian; Chen, Zhijiang; Dong, Shuxiang

    2012-12-01

    We report a miniature piezoelectric ultrasonic linear motor that is made of four Pb(Zr,Ti)O(3) (PZT) piezoelectric ceramic layers for low-voltage work. The 4-layer piezoelectric laminate works in two orthogonal first-bending modes for producing elliptical oscillations, which are then used to drive a contacting slider into continuous linear motion. Experimental results show that the miniature linear motor (size: 4 × 4 × 12 mm, weight: 1.7 g) can generate a large driving force of 0.48 N and a linear motion speed of up to 160 mm/s, using a 40 V(pp)/mm voltage drive at its resonance frequency of 64.5 kHz. The maximum efficiency of the linear motor is 30%.

  17. Evaluation of synthetic linear motor-molecule actuation energetics

    NASA Astrophysics Data System (ADS)

    Brough, Branden; Northrop, Brian H.; Schmidt, Jacob J.; Tseng, Hsian-Rong; Houk, Kendall N.; Fraser Stoddart, J.; Ho, Chih-Ming

    2006-06-01

    By applying atomic force microscope (AFM)-based force spectroscopy together with computational modeling in the form of molecular force-field simulations, we have determined quantitatively the actuation energetics of a synthetic motor-molecule. This multidisciplinary approach was performed on specifically designed, bistable, redox-controllable [2]rotaxanes to probe the steric and electrostatic interactions that dictate their mechanical switching at the single-molecule level. The fusion of experimental force spectroscopy and theoretical computational modeling has revealed that the repulsive electrostatic interaction, which is responsible for the molecular actuation, is as high as 65 kcal·mol-1, a result that is supported by ab initio calculations. computational modeling | force spectroscopy | molecular motors | switchable rotaxanes

  18. Cogging force rejection method of linear motor based on internal model principle

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Chen, Zhenyu; Yang, Tianbo

    2015-02-01

    The cogging force disturbance of linear motor is one of the main factors affecting the positioning accuracy of ultraprecision moving platform. And this drawback could not be completely overcome by improving the design of motor body, such as location modification of permanent magnet array, or optimization design of the shape of teeth-slot. So the active compensation algorithms become prevalent in cogging force rejection area. This paper proposed a control structure based on internal mode principle to attenuate the cogging force of linear motor which deteriorated the accuracy of position, and this structure could make tracking and anti-disturbing performance of close-loop designed respectively. In the first place, the cogging force was seen as the intrinsic property of linear motor and its model constituting controlled object with motor ontology model was obtained by data driven recursive identification method. Then, a control structure was designed to accommodate tracking and anti-interference ability separately by using internal model principle. Finally, the proposed method was verified in a long stroke moving platform driven by linear motor. The experiment results show that, by employing this control strategy, the positioning error caused by cogging force was decreased by 70%.

  19. Torque linearizing hardware for the electric joint motors of a direct-drive robot

    SciTech Connect

    Muir, P.F.; Bryan, J.R.

    1991-12-31

    Many emerging high-performance robot control algorithms require the command of the joint torques; yet no known commercial robots provide such a capability. In this paper, we describe the design, development, testing and application of a VMEbus-based torque linearizing joint interface board (JIB). One JIB resides between the robot control processor and each joint motor amplifier. The JIB provides the control processor with the capability to read the motor position and apply accurate motor torques. The torque command capability derives from the application of a 128k {times} 8 EPROM lookup table for each motor phase. Because joint motor torque is dependent upon the torque command and the motor position, the hardware is designed to utilize the torque command and the current motor position as the address to retrieve the proper pulse-width for the PWM motor amplifier. The table look-up cycle operates independently of the robot controller at a 40KHz rate to provide constant joint torque as the motor rotates. We identify the proper table entries by an automated in situ data collection procedure. Static torque generation results show that the torque deviations are reduced from as much as 76% to below 5% for each of the three direct-drive motors (two are variable reluctance motors and one is brushless DC) on an AdeptTwo robot. These torque deviations are reduced below 2.5% if only the upper 90% of the torque range is considered. The torque deviations of the non-direct-drive joint are reduced by 50%. Dynamic robot edge following experiments show that the robot speed of operation can be more than doubled for a given applied force accuracy by utilizing the joint torque linearizing boards. 8 refs.

  20. Torque linearizing hardware for the electric joint motors of a direct-drive robot

    SciTech Connect

    Muir, P.F.; Bryan, J.R.

    1991-01-01

    Many emerging high-performance robot control algorithms require the command of the joint torques; yet no known commercial robots provide such a capability. In this paper, we describe the design, development, testing and application of a VMEbus-based torque linearizing joint interface board (JIB). One JIB resides between the robot control processor and each joint motor amplifier. The JIB provides the control processor with the capability to read the motor position and apply accurate motor torques. The torque command capability derives from the application of a 128k {times} 8 EPROM lookup table for each motor phase. Because joint motor torque is dependent upon the torque command and the motor position, the hardware is designed to utilize the torque command and the current motor position as the address to retrieve the proper pulse-width for the PWM motor amplifier. The table look-up cycle operates independently of the robot controller at a 40KHz rate to provide constant joint torque as the motor rotates. We identify the proper table entries by an automated in situ data collection procedure. Static torque generation results show that the torque deviations are reduced from as much as 76% to below 5% for each of the three direct-drive motors (two are variable reluctance motors and one is brushless DC) on an AdeptTwo robot. These torque deviations are reduced below 2.5% if only the upper 90% of the torque range is considered. The torque deviations of the non-direct-drive joint are reduced by 50%. Dynamic robot edge following experiments show that the robot speed of operation can be more than doubled for a given applied force accuracy by utilizing the joint torque linearizing boards. 8 refs.

  1. Torque linearizing hardware for the electric joint motors of a direct-drive robot

    NASA Astrophysics Data System (ADS)

    Muir, P. F.; Bryan, J. R.

    Many emerging high-performance robot control algorithms require the command of the joint torques, yet no known commercial robots provide such a capability. We describe the design, development, testing, and application of a VMEbus-based torque linearizing joint interface board (JIB). One JIB resides between the robot control processor and each joint motor amplifier. The JIB provides the control processor with the capability to read the motor position and apply accurate motor torques. The torque command capability derives from the application of a 128k x 8 EPROM lookup table for each motor phase. Because joint motor torque is dependent upon the torque command and the motor position, the hardware is designed to utilize the torque command and the current motor position as the address to retrieve the proper pulse-width for the PWM motor amplifier. The table look-up cycle operates independently of the robot controller at a 40KHz rate to provide constant joint torque as the motor rotates. We identify the proper table entries by an automated in situ data collection procedure. Static torque generation results show that the torque deviations are reduced from as much as 76 percent to below 5 percent for each of the three direct-drive motors (two are variable reluctance motors and one is brushless DC) on an AdeptTwo robot. These torque deviations are reduced below 2.5 percent if only the upper 90 percent of the torque range is considered. The torque deviations of the non-direct-drive joint are reduced by 50 percent. Dynamic robot edge following experiments show that the robot speed of operation can be more than doubled for a given applied force accuracy by utilizing the joint torque linearizing boards.

  2. A standing wave linear ultrasonic motor operating in face-diagonal-bending mode

    NASA Astrophysics Data System (ADS)

    Ci, Penghong; Liu, Guoxi; Chen, Zhijiang; Dong, Shuxiang

    2013-09-01

    We report a piezoelectric standing wave linear ultrasonic motor with double driving tips for generating precision motion. The motor's piezoelectric actuator was made of a simple Pb(Zr,Ti)O3 square-plate (15 × 15 × 2 mm3) operating in a single face-diagonal-bending standing wave mode to produce symmetric, bi-directional linear motion. The motor generated a driving force of 3.0 N and a moving speed of up to 165 mm/s under a relatively low applied electric field of 75 Vpp/mm at a resonance frequency of 141.5 kHz. This motor is superior to those previously reported because of the double friction-tip standing wave driving mechanism and the operating mode.

  3. A U-shaped linear ultrasonic motor using longitudinal vibration transducers with double feet.

    PubMed

    Liu, Yingxiang; Liu, Junkao; Chen, Weishan; Shi, Shengjun

    2012-05-01

    A U-shaped linear ultrasonic motor using longitudinal vibration transducers with double feet was proposed in this paper. The proposed motor contains a horizontal transducer and two vertical transducers. The horizontal transducer includes two exponential shape horns located at the leading ends, and each vertical transducer contains one exponential shape horn. The horns of the horizontal transducer and the vertical transducer intersect at the tip ends where the driving feet are located. Longitudinal vibrations are superimposed in the motor and generate elliptical motions at the driving feet. The two vibration modes of the motor are discussed, and the motion trajectories of driving feet are deduced. By adjusting the structural parameters, the resonance frequencies of two vibration modes were degenerated. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 854 mm/s and maximum thrust force of 40 N at a voltage of 200 V(rms).

  4. A high-temperature double-mode piezoelectric ultrasonic linear motor

    NASA Astrophysics Data System (ADS)

    Li, Xiaotian; Chen, Jianguo; Chen, Zhijiang; Dong, Shuxiang

    2012-08-01

    A miniature piezoelectric ultrasonic linear motor (piezoelectric vibrator sizes: 4.7 × 13.5 × 2 mm3) has been studied for precise actuation at 200 °C high-temperature. This piezoelectric linear motor was made of (1-x)BiScO3-xPbTiO3 piezoelectric ceramic with a high curie temperature (428 °C) and it was operated in first longitudinal and the second bending double-mode. Our experimental results showed that the linear motor moves smoothly at the temperature as high as 200 °C with a driving force of 0.35 N and a speed up to 42 mm/s.

  5. 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.

  6. Apparatus and method to pulverize rock using a superconducting electromagnetic linear motor

    NASA Technical Reports Server (NTRS)

    Ignatiev, Alex (Inventor)

    2009-01-01

    A rock pulverizer device based on a superconducting linear motor. The superconducting electromagnetic rock pulverizer accelerates a projectile via a superconducting linear motor and directs the projectile at high speed toward a rock structure that is to be pulverized by collision of the speeding projectile with the rock structure. The rock pulverizer is comprised of a trapped field superconducting secondary magnet mounted on a movable car following a track, a wire wound series of primary magnets mounted on the track, and the complete magnet/track system mounted on a vehicle used for movement of the pulverizer through a mine as well as for momentum transfer during launch of the rock breaking projectile.

  7. Design of an integral computer-based wheelchair controller/linear synchronous motor system.

    PubMed

    Kelly, G W; Ross, D A; Bass, R M; Davey, K R

    1986-06-01

    The purpose of this paper is to illustrate the advantages of designing computer-based motor controllers together with innovative motors, such that maximum controller/motor system benefits are obtained. Specifically, this paper describes how a computer-based controller/drive system for powered wheelchairs has been designed and is being built and tested. This type of integral controller/drive system has been possible to build into a wheelchair only with the advent of the microprocessor-based feedback motor controller. The type of motor chosen for this project was a linear synchronous motor (LSM), which is highly efficient (90%+) and could easily be made an integral part of a wheelchair wheel, providing a "no-moving-parts" drive system. However, an LSM cannot be variable-speed-controlled without knowledge of, and controlled adjustment to, the absolute rotor versus stator position at each point in time. Microprocessor-based feedback motor controllers make precise, efficient control of LSMs possible at a reasonable cost. In addition, this combination of controller and motor provides a very flexible wheelchair control/drive system that may be easily programmed to suit the needs and necessities of the wide variety of over 200,000 persons now using powered wheelchairs. PMID:3537184

  8. Influence analysis of structural parameters and operating parameters on electromagnetic properties of HTS linear induction motor

    NASA Astrophysics Data System (ADS)

    Fang, J.; Sheng, L.; Li, D.; Zhao, J.; Li, Sh.; Qin, W.; Fan, Y.; Zheng, Q. L.; Zhang, W.

    A novel High Temperature Superconductor Linear Induction Motor (HTS LIM) is researched in this paper. Since the critical current and the electromagnetic force of the motor are determined mainly by the primary slot leakage flux, the main magnetic flux and eddy current respectively, in order to research the influence of structural parameters and operating parameters on electromagnetic properties of HTS LIM, the motor was analyzed by 2D transient Finite Element Method (FEM). The properties of the motor, such as the maximum slot leakage flux density, motor thrust, motor vertical force and critical current are analyzed with different structural parameters and operating parameters. In addition, an experimental investigation was carried out on prototype HTS motor. Electrical parameters were deduced from these tests and also compared with the analysis results from FEM. AC losses of one HTS coil in the motor were measured and AC losses of all HTS coils in HTS LIM were estimated. The results in this paper could provide reference for the design and research on the HTS LIM.

  9. The non-linear elasticity of the muscle sarcomere and the compliance of myosin motors

    PubMed Central

    Fusi, Luca; Brunello, Elisabetta; Reconditi, Massimo; Piazzesi, Gabriella; Lombardi, Vincenzo

    2014-01-01

    Force in striated muscle is due to attachment of the heads of the myosin, the molecular motors extending from the myosin filament, to the actin filament in each half-sarcomere, the functional unit where myosin motors act in parallel. Mechanical and X-ray structural evidence indicates that at the plateau of isometric contraction (force T0), less than half of the elastic strain of the half-sarcomere is due to the strain in the array of myosin motors (s), with the remainder being accounted for by the compliance of filaments acting as linear elastic elements in series with the motor array. Early during the development of isometric force, however, the half-sarcomere compliance has been found to be less than that expected from the linear elastic model assumed above, and this non-linearity may affect the estimate of s. This question is investigated here by applying nanometre–microsecond-resolution mechanics to single intact fibres from frog skeletal muscle at 4°C, to record the mechanical properties of the half-sarcomere throughout the development of force in isometric contraction. The results are interpreted with mechanical models to estimate the compliance of the myosin motors. Our conclusions are as follows: (i) early during the development of an isometric tetanus, an elastic element is present in parallel with the myosin motors, with a compliance of ∼200 nm MPa−1 (∼20 times larger than the compliance of the motor array at T0); and (ii) during isometric contraction, s is 1.66 ± 0.05 nm, which is not significantly different from the value estimated with the linear elastic model. PMID:24344166

  10. A Novel MagPipe Pipeline transportation system using linear motor drives

    SciTech Connect

    Fang, J.R.; Montgomery, D.B.; Roderick, L.

    2009-11-15

    A novel capsule pipeline transportation system using linear motor drives, called Magplane MagPipe, is under development with the intention to replace trucks and railways for hauling materials from the mine to the rail head, power plant, or processing plant with reduced operating cost and energy consumption. The initial demonstration of a MagPipe line in Inner Mongolia will be a 500-m-long double-pipe coal transport system with the design transportation capacity of 3 Mega-Mg per year. The pipeline consists of 6-m-long plastic pipe modules with an I-beam suspension system inside the pipe to carry sets of five coupled capsules. The pipe will also contain noncontinuous motor winding modules spaced at 50-m intervals. A set of Halbach-arrayed permanent magnets on the bottom of the capsules interact with the linear motor windings to provide propulsion. The motor is driven by variable frequency drives outside the pipe to control the speed. This paper briefly describes the overall MagPipe pipeline transportation system, including the preliminary conclusions of the linear synchronous motor analysis.

  11. Force prediction in permanent magnet flat linear motors (abstract)

    NASA Astrophysics Data System (ADS)

    Eastham, J. F.; Akmese, R.

    1991-11-01

    The advent of neodymium iron boron rare-earth permanent magnet material has afforded the opportunity to construct linear machines of high force to weight ratio. The paper describes the design and construction of an axial flux machine and rotating drum test rig. The machine occupies an arc of 45° on a drum 1.22 m in diameter. The excitation is provided by blocks of NdFeB material which are skewed in order to minimize the force variations due to slotting. The stator carries a three-phase short-chorded double-layer winding of four poles. The machine is supplied by a PWM inverter the fundamental component of which is phase locked to the rotor position so that a ``dc brushless'' drive system is produced. Electromagnetic forces including ripple forces are measured at supply frequencies up to 100 Hz. They are compared with finite-element analysis which calculates the force variation over the time period. The paper then considers some of the causes of ripple torque. In particular, the force production due solely to the permanent magnet excitation is considered. This has two important components each acting along the line of motion of the machine, one is due to slotting and the other is due to the finite length of the primary. In the practical machine the excitation poles are skewed to minimize the slotting force and the effectiveness of this is confirmed by both results from the experiments and the finite-element analysis. The end effect force is shown to have a space period of twice that of the excitation. The amplitude of this force and its period are again confirmed by practical results.

  12. Rotor position sensing in brushless ac motors with self-shielding magnets using linear Hall sensors

    NASA Astrophysics Data System (ADS)

    Zhu, Z. Q.; Shi, Y. F.; Howe, D.

    2006-04-01

    This paper investigates the use of low cost linear Hall sensors for rotor position sensing in brushless ac motors equipped with self-shielding magnets, addresses practical issues, such as the influence of magnetic and mechanical tolerances, temperature variations, and the armature reaction field, and describes the performance which is achieved.

  13. Dynamic modeling and characteristics analysis of a modal-independent linear ultrasonic motor.

    PubMed

    Li, Xiang; Yao, Zhiyuan; Zhou, Shengli; Lv, Qibao; Liu, Zhen

    2016-12-01

    In this paper, an integrated model is developed to analyze the fundamental characteristics of a modal-independent linear ultrasonic motor with double piezoelectric vibrators. The energy method is used to model the dynamics of the two piezoelectric vibrators. The interface forces are coupled into the dynamic equations of the two vibrators and the moving platform, forming a whole machine model of the motor. The behavior of the force transmission of the motor is analyzed via the resulting model to understand the drive mechanism. In particular, the relative contact length is proposed to describe the intermittent contact characteristic between the stator and the mover, and its role in evaluating motor performance is discussed. The relations between the output speed and various inputs to the motor and the start-stop transients of the motor are analyzed by numerical simulations, which are validated by experiments. Furthermore, the dead-zone behavior is predicted and clarified analytically using the proposed model, which is also observed in experiments. These results are useful for designing servo control scheme for the motor.

  14. Dynamic modeling and characteristics analysis of a modal-independent linear ultrasonic motor.

    PubMed

    Li, Xiang; Yao, Zhiyuan; Zhou, Shengli; Lv, Qibao; Liu, Zhen

    2016-12-01

    In this paper, an integrated model is developed to analyze the fundamental characteristics of a modal-independent linear ultrasonic motor with double piezoelectric vibrators. The energy method is used to model the dynamics of the two piezoelectric vibrators. The interface forces are coupled into the dynamic equations of the two vibrators and the moving platform, forming a whole machine model of the motor. The behavior of the force transmission of the motor is analyzed via the resulting model to understand the drive mechanism. In particular, the relative contact length is proposed to describe the intermittent contact characteristic between the stator and the mover, and its role in evaluating motor performance is discussed. The relations between the output speed and various inputs to the motor and the start-stop transients of the motor are analyzed by numerical simulations, which are validated by experiments. Furthermore, the dead-zone behavior is predicted and clarified analytically using the proposed model, which is also observed in experiments. These results are useful for designing servo control scheme for the motor. PMID:27518427

  15. Universal Linear Motor Driven Leg Press Dynamometer and Concept of Serial Stretch Loading

    PubMed Central

    2015-01-01

    Paper deals with backgrounds and principles of universal linear motor driven leg press dynamometer and concept of serial stretch loading. The device is based on two computer controlled linear motors mounted to the horizontal rails. As the motors can keep either constant resistance force in selected position or velocity in both directions, the system allows simulation of any mode of muscle contraction. In addition, it also can generate defined serial stretch stimuli in a form of repeated force peaks. This is achieved by short segments of reversed velocity (in concentric phase) or acceleration (in eccentric phase). Such stimuli, generated at the rate of 10 Hz, have proven to be a more efficient means for the improvement of rate of the force development. This capability not only affects performance in many sports, but also plays a substantial role in prevention of falls and their consequences. Universal linear motor driven and computer controlled dynamometer with its unique feature to generate serial stretch stimuli seems to be an efficient and useful tool for enhancing strength training effects on neuromuscular function not only in athletes, but as well as in senior population and rehabilitation patients. PMID:26913159

  16. A rectangle-type linear ultrasonic motor using longitudinal vibration transducers with four driving feet.

    PubMed

    Liu, Yingxiang; Chen, Weishan; Liu, Junkao; Shi, Shengjun

    2013-04-01

    To make full use of the vibrational energy of a longitudinal transducer, a rectangle-type linear ultrasonic motor with four driving feet is proposed in this paper. This new motor consists of four longitudinal vibration transducers which are arranged in a rectangle and form an enclosed construction. Lead zirconate titanate ceramics are embedded into the middle of the transducer and fastened by a wedge-caulking mechanism. Each transducer includes an exponentially shaped horn located on each end. The horns of the vertical transducers intersect at the base of the horizontal transducers' horns; the tip ends of the horizontal transducers' horns are used as the driving feet. Longitudinal vibrations are superimposed in the motor and generate elliptical movements at the tip ends of the horns. The working principle of the proposed motor is analyzed. The resonance frequencies of two working modes are tuned to be close to each other by adjusting the structural parameters. Transient analysis is developed to gain the vibration characteristics of the motor. A prototype motor is fabricated and measured. The vibration test results verify the feasibility of the proposed design. Typical output of the prototype is a no-load speed of 928 mm/s and maximum thrust force of 60 N at a voltage of 200 Vrms.

  17. Development of an ultrasonic linear motor with ultra-positioning capability and four driving feet.

    PubMed

    Zhu, Cong; Chu, Xiangcheng; Yuan, Songmei; Zhong, Zuojin; Zhao, Yanqiang; Gao, Shuning

    2016-12-01

    This paper presents a novel linear piezoelectric motor which is suitable for rapid ultra-precision positioning. The finite element analysis (FEA) was applied for optimal design and further analysis, then experiments were conducted to investigate its performance. By changing the input signal, the proposed motor was found capable of working in the fast driving mode as well as in the precision positioning mode. When working in the fast driving mode, the motor acts as an ultrasonic motor with maximum no-load speed up to 181.2mm/s and maximum thrust of 1.7N at 200Vp-p. Also, when working in precision positioning mode, the motor can be regarded as a flexible hinge piezoelectric actuator with arbitrary motion in the range of 8μm. The measurable minimum output displacement was found to be 0.08μm, but theoretically, can be even smaller. More importantly, the motor can be quickly and accurately positioned in a large stroke.

  18. Development of an ultrasonic linear motor with ultra-positioning capability and four driving feet.

    PubMed

    Zhu, Cong; Chu, Xiangcheng; Yuan, Songmei; Zhong, Zuojin; Zhao, Yanqiang; Gao, Shuning

    2016-12-01

    This paper presents a novel linear piezoelectric motor which is suitable for rapid ultra-precision positioning. The finite element analysis (FEA) was applied for optimal design and further analysis, then experiments were conducted to investigate its performance. By changing the input signal, the proposed motor was found capable of working in the fast driving mode as well as in the precision positioning mode. When working in the fast driving mode, the motor acts as an ultrasonic motor with maximum no-load speed up to 181.2mm/s and maximum thrust of 1.7N at 200Vp-p. Also, when working in precision positioning mode, the motor can be regarded as a flexible hinge piezoelectric actuator with arbitrary motion in the range of 8μm. The measurable minimum output displacement was found to be 0.08μm, but theoretically, can be even smaller. More importantly, the motor can be quickly and accurately positioned in a large stroke. PMID:27479230

  19. Design and testing of a coaxial linear magnetic spring with integral linear motor. [for spacecraft energy storage

    NASA Technical Reports Server (NTRS)

    Patt, P. J.

    1985-01-01

    The design of a coaxial linear magnetic spring which incorporates a linear motor to control axial motion and overcome system damping is presented, and the results of static and dynamic tests are reported. The system has nominal stiffness 25,000 N/m and is designed to oscillate a 900-g component over a 4.6-mm stroke in a Stirling-cycle cryogenic refrigerator being developed for long-service (5-10-yr) space applications (Stolfi et al., 1983). Mosaics of 10 radially magnetized high-coercivity SmCO5 segments enclosed in Ti cans are employed, and the device is found to have quality factor 70-100, corresponding to energy-storage efficiency 91-94 percent. Drawings, diagrams, and graphs are provided.

  20. A high-power linear ultrasonic motor using longitudinal vibration transducers with single foot.

    PubMed

    Liu, Yingxiang; Chen, Weishan; Liu, Junkao; Shi, Shengjun

    2010-08-01

    A high-power linear ultrasonic motor using longitudinal vibration transducers with single foot was proposed in this paper. The stator of proposed motor contains a horizontal transducer and a vertical transducer. Longitudinal vibrations are superimposed in the stator and generate an elliptical trajectory at the driving foot. The sensitivity analysis of structural parameters to the resonance frequencies of two working modes of the stator was performed using the finite element method. The resonance frequencies of two working modes were degenerated by adjusting the structural parameters. The vibration characteristics of stator were studied and discussed. A prototype motor was fabricated and measured. Typical output of the prototype is a no-load speed of 1160 mm/s and maximum thrust force of 20 N at a voltage of 200 V(rms).

  1. Characteristics of Ultrasonic Linear Motor that Incorporates Two Transducers at an Acute Angle

    NASA Astrophysics Data System (ADS)

    Suzuki, Atsuyuki; Tsunoji, Masaki; Tsujino, Jiromaru

    2013-07-01

    In this study, we have developed an ultrasonic linear motor that incorporates two transducers at an acute angle. The two transducers are used to generate the vertical and horizontal vibration components. The complex vibration is excited using two electrical sources with a phase shift. Ultrasonic motors have unique characteristics such as silent motion and absence of magnetic noise. These characteristics are suitable for use in hospitals and so on. Therefore, we focus on developing actuators for use in a medical bed, specifically a bedsore prevention bed. A study of the vibration characteristics of the motor showed that the resonant frequencies of the transducers were appropriate, although the vibration amplitude of one transducer was less than that of the other. A study of the load characteristics showed that a no-load speed of 267 mm/s and a maximum thrust of 40 N were obtained.

  2. Linear magnetic motor/generator. [to generate electric energy using magnetic flux for spacecraft power supply

    NASA Technical Reports Server (NTRS)

    Studer, P. A. (Inventor)

    1982-01-01

    A linear magnetic motor/generator is disclosed which uses magnetic flux to provide mechanical motion or electrical energy. The linear magnetic motor/generator includes an axially movable actuator mechanism. A permament magnet mechanism defines a first magnetic flux path which passes through a first end portion of the actuator mechanism. Another permament magnet mechanism defines a second magnetic flux path which passes through a second end portion of the actuator mechanism. A drive coil defines a third magnetic flux path passing through a third central portion of the actuator mechanism. A drive coil selectively adds magnetic flux to and subtracts magnetic flux from magnetic flux flowing in the first and second magnetic flux path.

  3. Design of a superconducting linear synchronous motor with YBCO coil magnet

    NASA Astrophysics Data System (ADS)

    Li, Jing; Tang, Junjie; Zhang, Ya

    2015-09-01

    The forces of the flat single-sided linear motor with four superconducting coils on the excitation system were presented by experimental method. The influences of the coil height and number of turns on the forces were investigated by the simulation method. Although the maximum thrust increased monotonically with the value of turns, the corresponding increment of the thrust decreased with the value of turns. The thrust reaches a certain saturation value with increasing the height of the superconducting coil. Continuing to increase the height of the coil could lead to an increase of the normal force. The superconducting linear motor is finally designed with the capability to generate thrust of 1 kN/m.

  4. Study of Thrust Ripple Suppression Using Interpoles of Intermittent Stator Permanent Magnet Linear Synchronous Motor

    NASA Astrophysics Data System (ADS)

    Suzuki, Kenji; Ishikawa, Atsushi; Dohmeki, Hideo

    For short and intermediate distance conveyance using intermittent stator permanent magnet linear synchronous motor (ISPM-LSM), a linear synchronous motor with a short stator (armature) is desirable for increasing the stroke length. A PM-LSM with four poles and three teeth has previously been proposed. However, in the case of few teeth, the generated thrust at the outlet edge decreases and a ripple is produced for the generated thrust. In addition, the generated thrust is affected by the cogging force. This paper discusses the use of an interpole at the stator outlet edge and a method to decrease the thrust ripple. Moreover, a method to decrease the cogging force is also presented.

  5. Experimental Manufacture and Performance Evaluation of Linear Switched Reluctance Motor with HTS Excitation Windings

    NASA Astrophysics Data System (ADS)

    Hirayama, Tadashi; Oto, Satoshi; Higashijima, Atsushi; Kawabata, Shuma

    This paper presents an experimental manufacture and performance evaluation of prototype linear switched reluctance motor with HTS excitation windings (HTS-LSRM). The Ag-alloy sheathed Bi-2223 tapes are used for HTS coils. We first present a structure of the prototype HTS-LSRM. Next, current-carrying properties of the HTS coils are measured. Furthermore, current and voltage waveforms are measured and we evaluation a control performance of the current and voltage.

  6. A new approach to detect mover position in linear motors using magnetic sensors.

    PubMed

    Paul, Sarbajit; Chang, Junghwan

    2015-10-21

    A new method to detect the mover position of a linear motor is proposed in this paper. This method employs a simple cheap Hall Effect sensor-based magnetic sensor unit to detect the mover position of the linear motor. With the movement of the linear motor, Hall Effect sensor modules electrically separated 120° along with the idea of three phase balanced condition ( va + vb + vc = 0 ) are used to produce three phase signals. The amplitude of the sensor output voltage signals are adjusted to unit amplitude to minimize the amplitude errors. With the unit amplitude signals three to two phase transformation is done to reduce the three multiples of harmonic components. The final output thus obtained is converted to position data by the use of arctangent function. The measurement accuracy of the new method is analyzed by experiments and compared with the conventional two phase method. Using the same number of sensor modules as the conventional two phase method, the proposed method gives more accurate position information compared to the conventional system where sensors are separated by 90° electrical angles.

  7. Influence of a high vacuum on the precise positioning using an ultrasonic linear motor.

    PubMed

    Kim, Wan-Soo; Lee, Dong-Jin; Lee, Sun-Kyu

    2011-01-01

    This paper presents an investigation of the ultrasonic linear motor stage for use in a high vacuum environment. The slider table is driven by the hybrid bolt-clamped Langevin-type ultrasonic linear motor, which is excited with its different modes of natural frequencies in both lateral and longitudinal directions. In general, the friction behavior in a vacuum environment becomes different from that in an environment of atmospheric pressure and this difference significantly affects the performance of the ultrasonic linear motor. In this paper, to consistently provide stable and high power of output in a high vacuum, frequency matching was conducted. Moreover, to achieve the fine control performance in the vacuum environment, a modified nominal characteristic trajectory following control method was adopted. Finally, the stage was operated under high vacuum condition, and the operating performances were investigated compared with that of a conventional PI compensator. As a result, robustness of positioning was accomplished in a high vacuum condition with nanometer-level accuracy.

  8. Influence of a high vacuum on the precise positioning using an ultrasonic linear motor

    SciTech Connect

    Kim, Wan-Soo; Lee, Dong-Jin; Lee, Sun-Kyu

    2011-01-15

    This paper presents an investigation of the ultrasonic linear motor stage for use in a high vacuum environment. The slider table is driven by the hybrid bolt-clamped Langevin-type ultrasonic linear motor, which is excited with its different modes of natural frequencies in both lateral and longitudinal directions. In general, the friction behavior in a vacuum environment becomes different from that in an environment of atmospheric pressure and this difference significantly affects the performance of the ultrasonic linear motor. In this paper, to consistently provide stable and high power of output in a high vacuum, frequency matching was conducted. Moreover, to achieve the fine control performance in the vacuum environment, a modified nominal characteristic trajectory following control method was adopted. Finally, the stage was operated under high vacuum condition, and the operating performances were investigated compared with that of a conventional PI compensator. As a result, robustness of positioning was accomplished in a high vacuum condition with nanometer-level accuracy.

  9. A New Approach to Detect Mover Position in Linear Motors Using Magnetic Sensors

    PubMed Central

    Paul, Sarbajit; Chang, Junghwan

    2015-01-01

    A new method to detect the mover position of a linear motor is proposed in this paper. This method employs a simple cheap Hall Effect sensor-based magnetic sensor unit to detect the mover position of the linear motor. With the movement of the linear motor, Hall Effect sensor modules electrically separated 120° along with the idea of three phase balanced condition (va + vb + vc = 0) are used to produce three phase signals. The amplitude of the sensor output voltage signals are adjusted to unit amplitude to minimize the amplitude errors. With the unit amplitude signals three to two phase transformation is done to reduce the three multiples of harmonic components. The final output thus obtained is converted to position data by the use of arctangent function. The measurement accuracy of the new method is analyzed by experiments and compared with the conventional two phase method. Using the same number of sensor modules as the conventional two phase method, the proposed method gives more accurate position information compared to the conventional system where sensors are separated by 90° electrical angles. PMID:26506348

  10. Magnetically Suspended Linear Pulse Motor for Semiconductor Wafer Transfer in Vacuum Chamber

    NASA Technical Reports Server (NTRS)

    Moriyama, Shin-Ichi; Hiraki, Naoji; Watanabe, Katsuhide; Kanemitsu, Yoichi

    1996-01-01

    This paper describes a magnetically suspended linear pulse motor for a semiconductor wafer transfer robot in a vacuum chamber. The motor can drive a wafer transfer arm horizontally without mechanical contact. In the construction of the magnetic suspension system, four pairs of linear magnetic bearings for the lift control are used for the guidance control as well. This approach allows us to make the whole motor compact in size and light in weight. The tested motor consists of a double-sided stator and a transfer arm with a width of 50 mm and a total length of 700 mm. The arm, like a ladder in shape, is designed as the floating element with a tooth width of 4 mm (a tooth pitch of 8 mm). The mover mass is limited to about 1.6 kg by adopting such an arm structure, and the ratio of thrust to mover mass reaches to 3.2 N/kg under a broad air gap (1 mm) between the stator teeth and the mover teeth. The performance testing was carried out with a transfer distance less than 450 mm and a transfer speed less than 560 mm/s. The attitude of the arm was well controlled by the linear magnetic bearings with a combined use, and consequently the repeatability on the positioning of the arm reached to about 2 micron. In addition, the positioning accuracy was improved up to about 30 micron through a compensation of the 128-step wave current which was used for the micro-step drive with a step increment of 62.5 micron.

  11. Novel permanent magnet linear motor with isolated movers: Analytical, numerical and experimental study

    NASA Astrophysics Data System (ADS)

    Yan, Liang; Peng, Juanjuan; Jiao, Zongxia; Chen, Chin-Yin; Chen, I.-Ming

    2014-10-01

    This paper proposes a novel permanent magnet linear motor possessing two movers and one stator. The two movers are isolated and can interact with the stator poles to generate independent forces and motions. Compared with conventional multiple motor driving system, it helps to increase the system compactness, and thus improve the power density and working efficiency. The magnetic field distribution is obtained by using equivalent magnetic circuit method. Following that, the formulation of force output considering armature reaction is carried out. Then inductances are analyzed with finite element method to investigate the relationships of the two movers. It is found that the mutual-inductances are nearly equal to zero, and thus the interaction between the two movers is negligible. A research prototype of the linear motor and a measurement apparatus on thrust force have been developed. Both numerical computation and experiment measurement are conducted to validate the analytical model of thrust force. Comparison shows that the analytical model matches the numerical and experimental results well.

  12. Novel permanent magnet linear motor with isolated movers: analytical, numerical and experimental study.

    PubMed

    Yan, Liang; Peng, Juanjuan; Jiao, Zongxia; Chen, Chin-Yin; Chen, I-Ming

    2014-10-01

    This paper proposes a novel permanent magnet linear motor possessing two movers and one stator. The two movers are isolated and can interact with the stator poles to generate independent forces and motions. Compared with conventional multiple motor driving system, it helps to increase the system compactness, and thus improve the power density and working efficiency. The magnetic field distribution is obtained by using equivalent magnetic circuit method. Following that, the formulation of force output considering armature reaction is carried out. Then inductances are analyzed with finite element method to investigate the relationships of the two movers. It is found that the mutual-inductances are nearly equal to zero, and thus the interaction between the two movers is negligible. A research prototype of the linear motor and a measurement apparatus on thrust force have been developed. Both numerical computation and experiment measurement are conducted to validate the analytical model of thrust force. Comparison shows that the analytical model matches the numerical and experimental results well.

  13. A Low Mass Translation Mechanism for Planetary FTIR Spectrometry using an Ultrasonic Piezo Linear Motor

    NASA Technical Reports Server (NTRS)

    Heverly, Matthew; Dougherty, Sean; Toon, Geoffrey; Soto, Alejandro; Blavier, Jean-Francois

    2004-01-01

    One of the key components of a Fourier Transform Infrared Spectrometer (FTIR) is the linear translation stage used to vary the optical path length between the two arms of the interferometer. This translation mechanism must produce extremely constant velocity motion across its entire range of travel to allow the instrument to attain high signal-to-noise ratio and spectral resolving power. A new spectrometer is being developed at the Jet Propulsion Laboratory under NASA s Planetary Instrument Definition and Development Program (PIDDP). The goal of this project is to build upon existing spaceborne FTIR spectrometer technology to produce a new instrument prototype that has drastically superior spectral resolution and substantially lower mass, making it feasible for planetary exploration. In order to achieve these goals, Alliance Spacesystems, Inc. (ASI) has developed a linear translation mechanism using a novel ultrasonic piezo linear motor in conjunction with a fully kinematic, fault tolerant linear rail system. The piezo motor provides extremely smooth motion, is inherently redundant, and is capable of producing unlimited travel. The kinematic rail uses spherical Vespel(R). rollers and bushings, which eliminates the need for wet lubrication, while providing a fault tolerant platform for smooth linear motion that will not bind under misalignment or structural deformation. This system can produce velocities from 10 - 100 mm/s with less than 1% velocity error over the entire 100-mm length of travel for a total mechanism mass of less than 850 grams. This system has performed over half a million strokes under vacuum without excessive wear or degradation in performance. This paper covers the design, development, and testing of this linear translation mechanism as part of the Planetary Atmosphere Occultation Spectrometer (PAOS) instrument prototype development program.

  14. An electrostatic 3-phase linear stepper motor fabricated by vertical trench isolation technology

    NASA Astrophysics Data System (ADS)

    Sarajlic, Edin; Yamahata, Christophe; Cordero, Mauricio; Fujita, Hiroyuki

    2009-07-01

    We present the design, microfabrication and characterization of an electrostatic 3-phase linear stepper micromotor constructed with vertical trench isolation technology. This suitable technology was used to create a monolithic stepper motor with high-aspect-ratio poles and an integrated 3-phase electrical network in the bulk of a standard single-crystal silicon wafer. The shuttle of the stepper motor is suspended by a flexure to avoid any mechanical contact during operation, enhancing the precision, repeatability and reliability of the stepping motion. The prototype is capable of a maximum travel of +/-26 µm (52 µm) at an actuation voltage of 30 V and a step size of 1.4 µm during a half-stepping sequence. This work was presented in part at the 19th MicroMechanics Europe Workshop (MME), 28-30 September 2008, Aachen, Germany.

  15. FPGA-based Elman neural network control system for linear ultrasonic motor.

    PubMed

    Lin, Faa-Jeng; Hung, Ying-Chih

    2009-01-01

    A field-programmable gate array (FPGA)-based Elman neural network (ENN) control system is proposed to control the mover position of a linear ultrasonic motor (LUSM) in this study. First, the structure and operating principle of the LUSM are introduced. Because the dynamic characteristics and motor parameters of the LUSM are nonlinear and time-varying, an ENN control system is designed to achieve precision position control. The network structure and online learning algorithm using delta adaptation law of the ENN are described in detail. Then, a piecewise continuous function is adopted to replace the sigmoid function in the hidden layer of the ENN to facilitate hardware implementation. In addition, an FPGA chip is adopted to implement the developed control algorithm for possible low-cost and high-performance industrial applications. The effectiveness of the proposed control scheme is verified by some experimental results.

  16. The pulsed linear induction motor concept for high-speed trains

    SciTech Connect

    Turman, B.N.; Marder, B.M.; Rohwein, G.J.; Aeschliman, D.P.; Kelley, J.B.; Cowan, M.; Zimmerman, R.M.

    1995-06-01

    The SERAPBIM (SEgmented RAil PHased Induction Motor) concept is a linear induction motor concept which uses rapidly-pulsed magnetic fields and a segmented reaction rail, as opposed to low-frequency fields and continuous reaction rails found in conventional linear induction motors. These improvements give a high-traction, compact, and efficient linear motor that has potential for advanced high speed rail propulsion. In the SERAPBIM concept, coils on the vehicle push against a segmented aluminum rail, which is mounted on the road bed. Current is pulsed as the coils cross an edge of the segmented rail, inducing surface currents which repel the coil. The coils must be pulsed in synchronization with the movement by reaction rail segments. This is provided by a sense-and-fire circuit that controls the pulsing of the power modulators. Experiments were conducted to demonstrate the feasibility of the pulsed induction motor and to collect data that could be used for scaling calculations. A 14.4 kg aluminum plate was accelerated down a 4 m track to speeds of over 15 m/sec with peak thrust up to 18 kN per coilset. For a trainset capable of 200 mph speed, the SERAPHIM concept design is based on coils which are each capable of producing up to 3.5 kN thrust, and 30 coil pairs are mounted on each power car. Two power cars, one at each end of the train, provide 6 MW from two gas turbine prime power units. The thrust is about 210.000 N and is essentially constant up to 200 km/hr since wheel slippage does not limit thrust as with conventional wheeled propulsion. A key component of the SERAPHIM concept is the use of passive wheel-on-rah support for the high speed vehicle. Standard steel wheels are capable of handling over 200 mph. The SERAPHIM cost is comparable to that for steel-wheel high-speed rail, and about 10% to 25% of the projected costs for a comparable Maglev system.

  17. Evaluation of mechanical losses in a linear motor pressure wave generator

    NASA Astrophysics Data System (ADS)

    Jacob, Subhash; Rangasamy, Karunanithi; Jonnalagadda, Kranthi Kumar; Chakkala, Damu; Achanur, Mallappa; Govindswamy, Jagadish; Gour, Abhay Singh

    2012-06-01

    A moving magnet linear motor compressor or pressure wave generator (PWG) of 2 cc swept volume with dual opposed piston configuration has been developed to operate miniature pulse tube coolers. Prelimnary experiments yielded only a no-load cold end temperature of 180 K. Auxiliary tests and the interpretation of detailed modeling of a PWG suggest that much of the PV power has been lost in the form of blow-by at piston seals due to large and non-optimum clearance seal gap between piston and cylinder. The results of experimental parameters simulated using Sage provide the optimum seal gap value for maximizing the delivered PV power.

  18. Improved linear ultrasonic motor performance with square-wave based driving-tip trajectory

    NASA Astrophysics Data System (ADS)

    Le, Adam Y.; Mills, James K.; Benhabib, Beno

    2015-03-01

    This paper proposes the application of a non-sinusoidal periodic excitation voltage to induce a near-square-wave driving tip trajectory in linear ultrasonic motors (LUSMs). A square-wave-based trajectory can deliver superior frictional force to the moving stage in the forward stroke of the driving tip motion and reduced frictional force during the return stroke. This would reduce lost power in the periodic driving tip motion, thereby, increasing the output force and power of the LUSM. An implementation procedure is suggested to achieve the near-square-wave driving tip trajectory. The proposed approach is illustrated through realistic finite-element-based simulations using a bimodal LUSM configuration.

  19. Decentralized control of the COFS-I Mast using linear dc motors

    NASA Technical Reports Server (NTRS)

    Lindner, Douglas K.; Celano, Tom; Ide, Eric

    1989-01-01

    Consideration is given to a decentralized control design for vibration suppression in the COFS-I Mast using linear dc motors for actuators. The decentralized control design is based results from power systems using root locus techniques that are not well known. The approach is effective because the loop gain is low due to low actuator authority. The frequency-dependent nonlinearities of the actuator are taken into account. Because of the tendency of the transients to saturate the the stroke length of the actuator, its effectiveness is limited.

  20. A method of optimal design of single-sided linear induction motor for transit

    SciTech Connect

    Yoon, S.B.; Hur, J.; Hyun, D.S.

    1997-09-01

    An optimal design method for a single-sided linear induction motor (SLIM) for transit is described. The authors propose the method which determines the overall parameters of SLIM for transit using only the rated mechanical output. When the optimization is carried out, the slot depth is used as the initial value so that the exact slot depth is calculated iteratively from the circuit equation. The optimization problem of a SLIM design is approached by use of the sequential quadratic programming (SQP). The influence of design variables is analyzed by the rated thrust and the rated velocity respectively.

  1. A new standing-wave-type linear ultrasonic motor based on in-plane modes.

    PubMed

    Shi, Yunlai; Zhao, Chunsheng

    2011-05-01

    This paper presents a new standing-wave-type linear ultrasonic motor using combination of the first longitudinal and the second bending modes. Two piezoelectric plates in combination with a metal thin plate are used to construct the stator. The superior point of the stator is its isosceles triangular structure part of the stator, which can amplify the displacement in horizontal direction of the stator in perpendicular direction when the stator is operated in the first longitudinal mode. The influence of the base angle θ of the triangular structure part on the amplitude of the driving foot has been analyzed by numerical analysis. Four prototype stators with different angles θ have been fabricated and the experimental investigation of these stators has validated the numerical simulation. The overall dimensions of the prototype stators are no more than 40 mm (length) × 20 mm (width) × 5 mm (thickness). Driven by an AC signal with the driving frequency of 53.3 kHz, the no-load speed and the maximal thrust of the prototype motor using the stator with base angle 20° were 98 mm/s and 3.2N, respectively. The effective elliptical motion trajectory of the contact point of the stator can be achieved by the isosceles triangular structure part using only two PZTs, and thus it makes the motor low cost in fabrication, simple in structure and easy to realize miniaturization.

  2. Single-Phase Drive Ultrasonic Linear Motor Using a Linked Twin Square Plate Vibrator

    NASA Astrophysics Data System (ADS)

    Yokoyama, Keiji; Tamura, Hideki; Masuda, Kentaro; Takano, Takehiro

    2013-07-01

    A novel linear motion ultrasonic motor, which uses a single resonance mode driven by a single phase and has the same motor characteristics for operation in reverse directions, is developed. An in-plane breathing mode in the square plate is strongly driven by the transverse effect of a piezoelectric ceramic. A stator resonator consists of twin square plates linked by V-shaped beams. Only one side of the square plate can be excited by the resonance of the breathing mode, when the other passive side plate is electrically opened so that the effective elasticities and the resonant frequencies between both plates are different; as a result, the friction edge of the resonator vibrates in a slant locus to move a load slider. The reverse operation is easily obtained by switching the driving side of the square plates. We designed the stator resonator by FEM analysis and fabricated a prototype for our experiment. The prototype motor showed good characteristics, for example, a moving slider velocity of 100 mm/s, a thrust force of 3.5 N, and an efficiency of 30% when the preload was 10 N, the input effective voltage was 5 V, and the input power was 1.2 W.

  3. Development of moving magnet type linear motor for dual piston compressor for pulse tube cryocooler

    NASA Astrophysics Data System (ADS)

    Karunanithi, R.; Jacob, Subhash; Singh Gour, Abhay Singh; Damu, C.; Das, M.

    2012-06-01

    This paper describes the design, fabrication and testing of a moving magnet type linear motor of dual piston configuration for a pulse tube cryocooler for ground applications. Eight radially magnetized segmented magnets were used to form one set of a magnet ring. Four magnet rings of such type were constructed, in which one pair of rings has north-pole on its outer diameter and south-pole on inner diameter, while the other pair is it's complementary. The magnets were mounted with opposite poles together on the magnet holder with an axial moving shaft having a piston mounted on both ends of the shaft. The shaft movement was restricted to the axial direction by using C-clamp type flexures, mounted on both sides of the shaft. The force requirement for driving the compressor was calculated based on which the electrical circuit of motor is designed by proper selection of wire gauge and Ampere-turns. The flexure spring force estimation was done through simulation using ANSYS 11.0 and was verified experimentally; while the magnet spring force was determined experimentally. The motor with mounted piston was tested using a variable voltage and variable frequency power supply capable of driving 140 watts of load.

  4. Linear motor drive system for continuous-path closed-loop position control of an object

    DOEpatents

    Barkman, William E.

    1980-01-01

    A precision numerical controlled servo-positioning system is provided for continuous closed-loop position control of a machine slide or platform driven by a linear-induction motor. The system utilizes filtered velocity feedback to provide system stability required to operate with a system gain of 100 inches/minute/0.001 inch of following error. The filtered velocity feedback signal is derived from the position output signals of a laser interferometer utilized to monitor the movement of the slide. Air-bearing slides mounted to a stable support are utilized to minimize friction and small irregularities in the slideway which would tend to introduce positioning errors. A microprocessor is programmed to read command and feedback information and converts this information into the system following error signal. This error signal is summed with the negative filtered velocity feedback signal at the input of a servo amplifier whose output serves as the drive power signal to the linear motor position control coil.

  5. Feasibility study on linear-motor-assisted take-off (LMATO) of winged launch vehicle

    NASA Astrophysics Data System (ADS)

    Nagatomo, Makoto; Kyotani, Yoshihiro

    1987-11-01

    Application of technology of magnetically levitated transportation to horizontal take-off of an experimental space vehicle has been studied. An experimental system of linear-motor-assisted take-off (LMATO) consists of the HIMES space vehicle and a magnetically levitated and propelled sled which is a modified MLU model developed by the JNR. The original MLU model is a train of three cars which weighs 30 tons and is driven by a thrust of 15 tons. The maximum speed is 400 km/h. The highest speed of 517 km/h has been obtained by the first JNR linear motor car. Since the take-off speed of the HIMES vehicle with the initial mass of 14 tons is 470 km/h, the existing technology can be used for the LMATO of the vehicle. The concept of the HIMES/LMATO is to use the MLU vehicles to accelerate the HIMES vehicle at 0.33 g on a 5 km guide track until the speed reaches 300 km/h, when the rocket engines of the space vehicle are started to increase the acceleration up to 1 g. The total system will take the final checkout for take-off during the acceleration phase and the speed exceeds 470 km/h which is large enough to aerodynamically lift the space vehicle, then the fastening mechanism is unlocked to separate the vehicles. The experimental system can be applied for initial acceleration of a vehicle with air-breathing propulsion.

  6. Synchronization of Asynchronous Switched Boolean Network.

    PubMed

    Zhang, Hao; Wang, Xingyuan; Lin, Xiaohui

    2015-01-01

    In this paper, the complete synchronizations for asynchronous switched Boolean network with free Boolean sequence controllers and close-loop controllers are studied. First, the basic asynchronous switched Boolean network model is provided. With the method of semi-tensor product, the Boolean dynamics is translated into linear representation. Second, necessary and sufficient conditions for ASBN synchronization with free Boolean sequence control and close-loop control are derived, respectively. Third, some illustrative examples are provided to show the efficiency of the proposed methods.

  7. Design of decoupled dual servo stage with voice coil motor and linear motor for XY long stroke ultra-precision scanning system

    NASA Astrophysics Data System (ADS)

    Kim, Ki-Hyun; Choi, Young-Man; Gweon, Dae-Gab; Hong, Dong-Pyo; Kim, Koung-Suk; Lee, Suk-Won; Lee, Moon-Gu

    2005-12-01

    A decoupled dual servo (DDS) stage for ultra-precision scanning system is introduced in this paper. The proposed DDS consists of a 3 axis fine stage for handling and carrying workpieces and a XY coarse stage. Especially, the DDS uses three voice coil motors (VCM) as a planar actuation system of the fine stage to reduce the disturbances due to any mechanical connections with its coarse stage. VCMs are governed by Lorentz law. According to the law and its structure, there are no mechanical connections between coils and magnetic circuits. Moreover, the VCM doesn't have force ripples due to imperfections of commutation components of linear motor systems - currents and flux densities. However, due to the VCM's mechanical constraints the working range of the fine is about 5mm2. To break that hurdle, the coarse stage with linear motors is used for the fine stage to move about 200mm2. Because of the above reasons, the proposed DDS can achieve higher precision scanning than other stages with only one servo. Using MATLAB's Sequential Quadratic Programming (SQP), the VCMs are optimally designed for the highest force under conditions and constraints such as thermal dissipations due to its coil, its size, and so on. For linear motors, Halbach magnet linear motor is proposed and optimally designed in this paper. In addition, for their smooth movements without any frictions, guide systems of the DDS are composed of air bearings. And then, precisely to get their positions, linear scales with 0.1um resolution are used for the coarse's XY motions and plane mirror laser interferometers with 20nm for the fine's XYθz. On scanning, the two stages have same trajectories and are controlled. The control algorithm is Parallel method. The embodied ultra-precision scanning system has about 100nm tracking error and in-positioning stability.

  8. Recession in a linear stepper motor based on piezoelectric actuator and electrorheological clampers

    NASA Astrophysics Data System (ADS)

    Li, Cuihong; Meng, Yonggang; Tian, Yu

    2012-12-01

    A linear inchworm-type stepper motor based on piezoelectric actuator and comb shape electrorheological (ER) clampers was developed and tested. A recession phenomenon in the movement of the motor was found and was significantly affected by the driving voltage of the piezoelectric actuator and ER fluids. A dynamic model to analyze the mechanism of the recession was established. The force ratio of the viscoelastic clamping force (applied high electric field) to the viscous damping force (zero field) of ER fluids is the critical factor which determines the recession. The ratio is also affected by the extension or contraction rate of the actuator during movement, which is affected by the charging and discharging processes. With a relatively large distance between the clamper electrodes and a small displacement activated by the extension of the piezoelectric actuator, the instantaneous shear rate might not be sufficiently high, preventing ER fluids from attaining a shear-thickened and high-strength state. The ratio of yield strength to the viscous strength of ER fluids during movement should be as large as possible to reduce the recession displacement.

  9. Adaptive hybrid control for linear piezoelectric ceramic motor drive using diagonal recurrent CMAC network.

    PubMed

    Wai, Rong-Jong; Lin, Chih-Min; Peng, Ya-Fu

    2004-11-01

    This paper presents an adaptive hybrid control system using a diagonal recurrent cerebellar-model-articulation-computer (DRCMAC) network to control a linear piezoelectric ceramic motor (LPCM) driven by a two-inductance two-capacitance (LLCC) resonant inverter. Since the dynamic characteristics and motor parameters of the LPCM are highly nonlinear and time varying, an adaptive hybrid control system is therefore designed based on a hypothetical dynamic model to achieve high-precision position control. The architecture of DRCMAC network is a modified model of a cerebellar-model-articulation-computer (CMAC) network to attain a small number of receptive-fields. The novel idea of this study is that it employs the concept of diagonal recurrent neural network (DRNN) in order to capture the system dynamics and convert the static CMAC into a dynamic one. This adaptive hybrid control system is composed of two parts. One is a DRCMAC network controller that is used to mimic a conventional computed torque control law due to unknown system dynamics, and the other is a compensated controller with bound estimation algorithm that is utilized to recover the residual approximation error for guaranteeing the stable characteristic. The effectiveness of the proposed driving circuit and control system is verified with hardware experiments under the occurrence of uncertainties. In addition, the advantages of the proposed control scheme are indicated in comparison with a traditional integral-proportional (IP) position control system.

  10. Studying the force characteristics of a high temperature superconducting linear synchronous motor

    NASA Astrophysics Data System (ADS)

    Zheng, Luhai; Jin, Jianxun

    2011-08-01

    A single-sided high temperature superconducting (HTS) linear synchronous motor (HTSLSM) with an HTS bulk magnet array as its secondary has been developed. A field-cooled magnetization system has also been developed to obtain the magnet array with alternate magnetic poles. In order to identify the performance and force characteristics of the HTSLSM, an equivalent 3D finite element analysis (FEA) model has been built up to analyze its field distributions and cogging force characteristics, and an experimental system has been constructed to measure its thrust and normal force characteristics. The traits of the thrust and the normal force have been extracted by comprehensive experiments, including the trends versus different exciting currents, different air gap lengths and variable magnetic poles. The analysis and experimental results are fundamental to the electromagnetic optimum design and control scheme evaluation for the HTSLSM.

  11. Rail Brake System Using a Linear Induction Motor for Dynamic Braking

    NASA Astrophysics Data System (ADS)

    Sakamoto, Yasuaki; Kashiwagi, Takayuki; Tanaka, Minoru; Hasegawa, Hitoshi; Sasakawa, Takashi; Fujii, Nobuo

    One type of braking system for railway vehicles is the eddy current brake. Because this type of brake has the problem of rail heating, it has not been used for practical applications in Japan. Therefore, we proposed the use of a linear induction motor (LIM) for dynamic braking in eddy current brake systems. The LIM reduces rail heating and uses an inverter for self excitation. In this paper, we estimated the performance of an LIM from experimental results of a fundamental test machine and confirmed that the LIM generates an approximately constant braking force under constant current excitation. At relatively low frequencies, this braking force remains unaffected by frequency changes. The reduction ratio of rail heating is also approximately proportional to the frequency. We also confirmed that dynamic braking resulting in no electrical output can be used for drive control of the LIM. These characteristics are convenient for the realization of the LIM rail brake system.

  12. Study on Thrust Improvement and Ripple Suppression of HTS Linear Switched Reluctance Motor with Coreless HTS Excitation Windings

    NASA Astrophysics Data System (ADS)

    Oto, Satoshi; Hirayama, Tadashi; Kawabata, Shuma

    This paper describes a linear switched reluctance motor (LSRM) in which HTS tapes are used for coreless excitation windings in order to reduce the thrust ripple and normal force. This LSRM consists of a mover with saliency structure, coreless HTS coils and a stator back yoke. In this paper, we first describe the operating principle of the HTS-LSRM. Next, we calculate performances of the HTS-LSRM using 3-D FEM analysis. The effects of the motor structure on the thrust characteristic and normal force characteristics are clarified from the numerical results. Furthermore, we investigate the motor structure for thrust improvement, thrust ripple and normal force reduction.

  13. The linear electric motor: Instability at 1,000 g`s

    SciTech Connect

    Hunter, S.

    1997-03-01

    When fluid of high density is supported against gravity by a less dense liquid, the system is unstable, and microscopic perturbations grow at the interface between the fluids. This phenomenon, called the Rayleigh-Taylor instability, also occurs when a bottle of oil-and-vinegar salad dressing is turned upside down. The instability causes spikes of the dense fluid to penetrate the light fluid, while bubbles of the lighter fluid rise into the dense fluid. The same phenomenon occurs when a light fluid is used to accelerate a dense fluid, causing the two fluids to mix at a very high rate. For example, during the implosion of an ICF capsule, this instability can cause enough mixing to contaminate, cool, and degrade the yield of the thermonuclear fuel. The LEM is an excellent tool for studying this instability, but what is it? Think of a miniature high-speed electric train (the container) hurtling down a track (the electrodes) while diagnostic equipment (optical and laser) photographs it. The LEM, consists of four linear electrodes, or rails, that carry an electrical current to a pair of sliding armatures on the container. A magnetic field is produced that works in concert with the rail-armature current to accelerate the container--just as in an electric motor, but in a linear fashion rather than in rotation. The magnetic field is augmented with elongated coils just as in a conventional electric motor. This configuration also helps hold the armatures against the electrodes to prevent arcing. The electrical energy (0.6 megajoules) is provided by 16 capacitor banks that can be triggered independently to produce different acceleration profiles (i.e., how the acceleration varies with time).

  14. Evidence from retractor bulbi EMG for linearized motor control of conditioned nictitating membrane responses.

    PubMed

    Lepora, N F; Mavritsaki, E; Porrill, J; Yeo, C H; Evinger, C; Dean, P

    2007-10-01

    Classical conditioning of nictitating membrane (NM) responses in rabbits is a robust model learning system, and experimental evidence indicates that conditioned responses (CRs) are controlled by the cerebellum. It is unknown whether cerebellar control signals deal directly with the complex nonlinearities of the plant (blink-related muscles and peripheral tissues) or whether the plant is linearized to ensure a simple relation between cerebellar neuronal firing and CR profile. To study this question, the retractor bulbi muscle EMG was recorded with implanted electrodes during NM conditioning. Pooled activity in accessory abducens motoneurons was estimated from spike trains extracted from the EMG traces, and its temporal profile was found to have an approximately Gaussian shape with peak amplitude linearly related to CR amplitude. The relation between motoneuron activity and CR profiles was accurately fitted by a first-order linear filter, with each spike input producing an exponentially decaying impulse response with time constant of order 0.1 s. Application of this first-order plant model to CR data from other laboratories suggested that, in these cases also, motoneuron activity had a Gaussian profile, with time-of-peak close to unconditioned stimulus (US) onset and SD proportional to the interval between conditioned stimulus and US onsets. These results suggest that for conditioned NM responses the cerebellum is presented with a simplified "virtual" plant that is a linearized version of the underlying nonlinear biological system. Analysis of a detailed plant model suggests that one method for linearising the plant would be appropriate recruitment of motor units.

  15. 3-D analysis of permanent magnet linear synchronous motor with magnet arrangement using equivalent magnetic circuit network method

    SciTech Connect

    Jung, I.S.; Hur, J.; Hyun, D.S.

    1999-09-01

    Permanent magnet linear synchronous motors (PMLSM's) are proposed for many applications ranging from ground transportation to servo system and conveyance system. In this paper, the fields and forces of permanent magnet linear synchronous motor (PMLSM) with segmented or skewed magnet arrangement are analyzed according to length of segment or skew. And, the effects according to the lateral overhang of magnet are investigated. For the analysis, 3-dimensional equivalent magnetic circuit network (3-D EMCN) method is used. The analysis results are compared with the experimental ones and shown a reasonable agreement.

  16. Signal transmission from motor axons to group Ia muscle spindle afferents: frequency responses and second-order non-linearities.

    PubMed

    Windhorst, U; Kokkoroyiannis, T; Laouris, Y; Meyer-Lohmann, J

    1994-03-01

    Spinal recurrent inhibition via Renshaw cells and proprioceptive feedback via skeletal muscle and muscle spindle afferents have been hypothesized to constitute a compound feedback system [Windhorst (1989) Afferent Control of Posture and Locomotion; Windhorst (1993) Robots and Biological Systems--Towards a New Bionics]. To assess their detailed functions, it is necessary to know their dynamic characteristics. Previously we have extensively described the properties of signal transmission from motor axons to Renshaw cells using random motor axon stimulation and data analysis methods based thereupon. Using the same methods, we here compare these properties, in the cat, with those between motor axons and group Ia muscle spindle afferents in terms of frequency responses and nonlinear features. The frequency responses depend on the mean rate (carrier rate) of activation of motor axons and on the strength of coupling between motor units and spindles. In general, they are those of a second-order low-pass system with a cut-off at fairly low frequencies. This contrasts with the dynamics of motor axon-Renshaw cell couplings which are those of a much broader band-pass with its peak in the range of c. 2-15 Hz [Christakos (1987) Neuroscience 23, 613-623]. The second-order non-linearities in motor unit-muscle spindle signal lines are much more diverse than those in motor axon-Renshaw cell couplings. Although the average strength of response declines with mean stimulus rate in both subsystems, there is no systematic relationship between the amount of non-linearity and the average response in the former, whilst there is in the latter. The qualitative appearance of motor unit-muscle spindle non-linearities was complicated as was the average response to motor unit twitches. Thus, whilst Renshaw cells appear to dynamically reflect motor output rather faithfully, muscle spindles seem to signal local muscle fibre length changes and their dynamics. This would be consistent with the

  17. Modeling and experimental analysis of the linear ultrasonic motor with in-plane bending and longitudinal mode.

    PubMed

    Wan, Zhijian; Hu, Hong

    2014-03-01

    A novel linear ultrasonic motor based on in-plane longitudinal and bending mode vibration is presented in this paper. The stator of the motor is composed of a metal plate and eight piezoelectric ceramic patches. There are four long holes in the plate, designed for consideration of the longitudinal and bending mode coupling. The corresponding model is developed to optimize the mechanical and electrical coupling of the stator, which causes an ellipse motion at the contact tip of the stator when the composite vibrations with longitudinal and bending are excited. Its harmonic and transient responses are simulated and inspected. A prototype based on the model is fabricated and used to conduct experiments. Results show that the amplitude of the stator's contact tips is significantly increased, which helps to amplify the driving force and speed of the motor. It is therefore feasible to implement effective linear movement using the developed prototype.

  18. Design and characterization of a microelectromechanical system electro-thermal linear motor with interlock mechanism for micro manipulators.

    PubMed

    Hu, Tengjiang; Zhao, Yulong; Li, Xiuyuan; Zhao, You; Bai, Yingwei

    2016-03-01

    The design, fabrication, and testing of a novel electro-thermal linear motor for micro manipulators is presented in this paper. The V-shape electro-thermal actuator arrays, micro lever, micro spring, and slider are introduced. In moving operation, the linear motor can move nearly 1 mm displacement with 100 μm each step while keeping the applied voltage as low as 17 V. In holding operation, the motor can stay in one particular position without consuming energy and no creep deformation is found. Actuation force of 12.7 mN indicates the high force generation capability of the device. Experiments of lifetime show that the device can wear over two million cycles of operation. A silicon-on-insulator wafer is introduced to fabricate a high aspect ratio structure and the chip size is 8.5 mm × 8.5 mm × 0.5 mm.

  19. Modeling and experimental analysis of the linear ultrasonic motor with in-plane bending and longitudinal mode.

    PubMed

    Wan, Zhijian; Hu, Hong

    2014-03-01

    A novel linear ultrasonic motor based on in-plane longitudinal and bending mode vibration is presented in this paper. The stator of the motor is composed of a metal plate and eight piezoelectric ceramic patches. There are four long holes in the plate, designed for consideration of the longitudinal and bending mode coupling. The corresponding model is developed to optimize the mechanical and electrical coupling of the stator, which causes an ellipse motion at the contact tip of the stator when the composite vibrations with longitudinal and bending are excited. Its harmonic and transient responses are simulated and inspected. A prototype based on the model is fabricated and used to conduct experiments. Results show that the amplitude of the stator's contact tips is significantly increased, which helps to amplify the driving force and speed of the motor. It is therefore feasible to implement effective linear movement using the developed prototype. PMID:24360816

  20. Design and characterization of a microelectromechanical system electro-thermal linear motor with interlock mechanism for micro manipulators

    NASA Astrophysics Data System (ADS)

    Hu, Tengjiang; Zhao, Yulong; Li, Xiuyuan; Zhao, You; Bai, Yingwei

    2016-03-01

    The design, fabrication, and testing of a novel electro-thermal linear motor for micro manipulators is presented in this paper. The V-shape electro-thermal actuator arrays, micro lever, micro spring, and slider are introduced. In moving operation, the linear motor can move nearly 1 mm displacement with 100 μm each step while keeping the applied voltage as low as 17 V. In holding operation, the motor can stay in one particular position without consuming energy and no creep deformation is found. Actuation force of 12.7 mN indicates the high force generation capability of the device. Experiments of lifetime show that the device can wear over two million cycles of operation. A silicon-on-insulator wafer is introduced to fabricate a high aspect ratio structure and the chip size is 8.5 mm × 8.5 mm × 0.5 mm.

  1. Design and characterization of a microelectromechanical system electro-thermal linear motor with interlock mechanism for micro manipulators.

    PubMed

    Hu, Tengjiang; Zhao, Yulong; Li, Xiuyuan; Zhao, You; Bai, Yingwei

    2016-03-01

    The design, fabrication, and testing of a novel electro-thermal linear motor for micro manipulators is presented in this paper. The V-shape electro-thermal actuator arrays, micro lever, micro spring, and slider are introduced. In moving operation, the linear motor can move nearly 1 mm displacement with 100 μm each step while keeping the applied voltage as low as 17 V. In holding operation, the motor can stay in one particular position without consuming energy and no creep deformation is found. Actuation force of 12.7 mN indicates the high force generation capability of the device. Experiments of lifetime show that the device can wear over two million cycles of operation. A silicon-on-insulator wafer is introduced to fabricate a high aspect ratio structure and the chip size is 8.5 mm × 8.5 mm × 0.5 mm. PMID:27036807

  2. Redundant Asynchronous Microprocessor System

    NASA Technical Reports Server (NTRS)

    Meyer, G.; Johnston, J. O.; Dunn, W. R.

    1985-01-01

    Fault-tolerant computer structure called RAMPS (for redundant asynchronous microprocessor system) has simplicity of static redundancy but offers intermittent-fault handling ability of complex, dynamically redundant systems. New structure useful wherever several microprocessors are employed for control - in aircraft, industrial processes, robotics, and automatic machining, for example.

  3. Optimized linear motor and digital PID controller setup used in Mössbauer spectrometer

    NASA Astrophysics Data System (ADS)

    Kohout, Pavel; Kouřil, Lukáš; Navařík, Jakub; Novák, Petr; Pechoušek, Jiří

    2014-10-01

    Optimization of a linear motor and digital PID controller setup used in a Mössbauer spectrometer is presented. Velocity driving system with a digital PID feedback subsystem was developed in the LabVIEW graphical environment and deployed on the sbRIO real-time hardware device (National Instruments). The most important data acquisition processes are performed as real-time deterministic tasks on an FPGA chip. Velocity transducer of a double loudspeaker type with a power amplifier circuit is driven by the system. Series of calibration measurements were proceeded to find the optimal setup of the P, I, D parameters together with velocity error signal analysis. The shape and given signal characteristics of the velocity error signal are analyzed in details. Remote applications for controlling and monitoring the PID system from computer or smart phone, respectively, were also developed. The best setup and P, I, D parameters were set and calibration spectrum of α-Fe sample with an average nonlinearity of the velocity scale below 0.08% was collected. Furthermore, the width of the spectral line below 0.30 mm/s was observed. Powerful and complex velocity driving system was designed.

  4. Integrating optopiezoelectric actuators and a two-mode excited linear ultrasonic motor for microfluidics

    NASA Astrophysics Data System (ADS)

    Chen, Tsun-Hsu; Wang, Hsin-Hu; Hsu, Yu-Hsiang; Lee, Chih-Kung

    2016-03-01

    In comparison to more developed optical method for microparticle manipulation like optical tweezers, an optopiezoelectric actuating system could provide force output that is several orders higher. Taking advantages of photoconductive materials, the concept of integrating a virtual electrode in a distributed opto-piezoelectric actuators was developed for real-time in-situ spatial tailoring for vast varieties of applications in biochips, smart structures, etc. In this study, photoconductive material titanium oxide phthalocyanine (TiOPc) was used as the active ingredient to enable the virtual electrode in an opto-piezoelectric material based distributed actuator. By illuminating light of proper wavelength and enough intensity onto TiOPc photoconductive material, the effective impedance of the illuminated portion of TiOPc could drop significantly. The contributions of using additives in the TiOPc photoconductive electrode to adjust the electrical properties was investigated for optimization. Further, the two-mode excited linear ultrasonic motor was also studied and the feasibility to integrate the TiOPc photoconductive electrode was discussed. The flexibility provided by this newly developed system could potential deliver versatile performance in biochip applications.

  5. Design of an advanced non linear controller for induction motors and experimental validation on an industrial benchmark

    NASA Astrophysics Data System (ADS)

    Lubineau, D.; Dion, J. M.; Dugard, L.; Roye, D.

    2000-02-01

    This paper mainly deals with the design of an advanced control law for induction motors and its real-time implementation on an experimental test benchmark. First, relationship between the classical field oriented control (FOC) and non linear linearizing control laws is studied. It is shown that both control laws are similar. Classical non linear linearizing control improves the performances but not in a spectacular way when the observer and the controller are designed independently. A new non linear observer based control law is designed, which is shown to be globally stable and is implemented on an experimental test-bench. The control algorithm is studied and applied in many configurations (various set-points, flux and speed profiles and torque disturbances) and is shown to be very efficient.

  6. Comparison of experimental and theoretical reaction rail currents, rail voltages, and airgap fields for the linear induction motor research vehicle

    NASA Technical Reports Server (NTRS)

    Elliott, D. G.

    1977-01-01

    Measurements of reaction rail currents, reaction rail voltages, and airgap magnetic fields in tests of the Linear Induction Motor Research Vehicle (LIMRV) were compared with theoretical calculations from the mesh/matrix theory. It was found that the rail currents and magnetic fields predicted by the theory are within 20 percent of the measured currents and fields at most motor locations in most of the runs, but differ by as much as a factor of two in some cases. The most consistent difference is a higher experimental than theoretical magnetic field near the entrance of the motor and a lower experimental than theoretical magnetic field near the exit. The observed differences between the theoretical and experimental magnetic fields and currents do not account for the differences of as much as 26 percent between the theoretical and experimental thrusts.

  7. Ultraprecision XY stage using a hybrid bolt-clamped Langevin-type ultrasonic linear motor for continuous motion

    NASA Astrophysics Data System (ADS)

    Lee, Dong-Jin; Lee, Sun-Kyu

    2015-01-01

    This paper presents a design and control system for an XY stage driven by an ultrasonic linear motor. In this study, a hybrid bolt-clamped Langevin-type ultrasonic linear motor was manufactured and then operated at the resonance frequency of the third longitudinal and the sixth lateral modes. These two modes were matched through the preload adjustment and precisely tuned by the frequency matching method based on the impedance matching method with consideration of the different moving weights. The XY stage was evaluated in terms of position and circular motion. To achieve both fine and stable motion, the controller consisted of a nominal characteristics trajectory following (NCTF) control for continuous motion, dead zone compensation, and a switching controller based on the different NCTFs for the macro- and micro-dynamics regimes. The experimental results showed that the developed stage enables positioning and continuous motion with nanometer-level accuracy.

  8. Ultraprecision XY stage using a hybrid bolt-clamped Langevin-type ultrasonic linear motor for continuous motion.

    PubMed

    Lee, Dong-Jin; Lee, Sun-Kyu

    2015-01-01

    This paper presents a design and control system for an XY stage driven by an ultrasonic linear motor. In this study, a hybrid bolt-clamped Langevin-type ultrasonic linear motor was manufactured and then operated at the resonance frequency of the third longitudinal and the sixth lateral modes. These two modes were matched through the preload adjustment and precisely tuned by the frequency matching method based on the impedance matching method with consideration of the different moving weights. The XY stage was evaluated in terms of position and circular motion. To achieve both fine and stable motion, the controller consisted of a nominal characteristics trajectory following (NCTF) control for continuous motion, dead zone compensation, and a switching controller based on the different NCTFs for the macro- and micro-dynamics regimes. The experimental results showed that the developed stage enables positioning and continuous motion with nanometer-level accuracy.

  9. Ultraprecision XY stage using a hybrid bolt-clamped Langevin-type ultrasonic linear motor for continuous motion

    SciTech Connect

    Lee, Dong-Jin; Lee, Sun-Kyu

    2015-01-15

    This paper presents a design and control system for an XY stage driven by an ultrasonic linear motor. In this study, a hybrid bolt-clamped Langevin-type ultrasonic linear motor was manufactured and then operated at the resonance frequency of the third longitudinal and the sixth lateral modes. These two modes were matched through the preload adjustment and precisely tuned by the frequency matching method based on the impedance matching method with consideration of the different moving weights. The XY stage was evaluated in terms of position and circular motion. To achieve both fine and stable motion, the controller consisted of a nominal characteristics trajectory following (NCTF) control for continuous motion, dead zone compensation, and a switching controller based on the different NCTFs for the macro- and micro-dynamics regimes. The experimental results showed that the developed stage enables positioning and continuous motion with nanometer-level accuracy.

  10. Influence of electromagnetic interference on implanted cardiac arrhythmia devices in and around a magnetically levitated linear motor car.

    PubMed

    Fukuta, Motoyuki; Mizutani, Noboru; Waseda, Katsuhisa

    2005-01-01

    This study was designed to determine the susceptibility of implanted cardiac arrhythmia devices to electromagnetic interference in and around a magnetically levitated linear motor car [High-Speed Surface Transport (HSST)]. During the study, cardiac devices were connected to a phantom model that had similar characteristics to the human body. Three pacemakers from three manufacturers and one implantable cardioverter-defibrillator (ICD) were evaluated in and around the magnetically levitated vehicle. The system is based on a normal conductive system levitated by the attractive force of magnets and propelled by a linear induction motor without wheels. The magnetic field strength at 40 cm from the vehicle in the nonlevitating state was 0.12 mT and that during levitation was 0.20 mT. The magnetic and electric field strengths on a seat close to the variable voltage/variable frequency inverter while the vehicle was moving and at rest were 0.13 mT, 2.95 V/m and 0.04 mT, 0.36 V/m, respectively. Data recorded on a seat close to the reactor while the vehicle was moving and at rest were 0.09 mT, 2.45 V/m and 0.05 mT, 1.46 V/m, respectively. Measured magnetic and electric field strengths both inside and outside the linear motor car were too low to result in device inactivation. No sensing, pacing, or arrhythmic interactions were noted with any pacemaker or ICD programmed in either bipolar and unipolar configurations. In conclusion, our data suggest that a permanent programming change or a device failure is unlikely to occur and that the linear motor car system is probably safe for patients with one of the four implanted cardiac arrhythmia devices used in this study under the conditions tested.

  11. Asynchronous OGC web services mechanisms

    NASA Astrophysics Data System (ADS)

    Min, Min; Di, Liping; Yu, Genong; Chen, Nengcheng; Gong, Jianya

    2008-12-01

    The Open Geospatial Consortium, Inc (OGC) Web Services (OWS) were initially primarily simple synchronous Web services based on the HTTP transport protocol, which is perfectly valid in the case of simple geoprocessing of simple data available from local sources. However, with the development of Web-based geospatial technologies, especially the development of the Sensor Web, a number of limitations have been identified with using HTTP-GET/POST binding in OGC OWS, which cannot meet the needs of asynchronous communication and operations between clients and services or in OGC services chain. Asynchronicity in Web services could be achieved in different ways. Callback pattern is widely supported in client asynchronous invocation. Message-based middleware often can be used together with the asynchronous invocation alternatives. Web Notification Service (WNS) is designed to provide asynchronous messagebased communication in OGC. This paper describes a mechanism for an asynchronous, message-based, event-driven, dynamic geospatial Web system based on OGC Web services. The addition of asynchronicity in OGC Web services has two components. One is the augmentation of OGC Web services with asynchronous message-based notification. The other is asynchronous OGC Web service orchestration based on BPEL.

  12. Design of Linear DC Motor Two-degree-of-freedom Positioning System using Model Reference type Sliding Mode Controller

    NASA Astrophysics Data System (ADS)

    Urushihara, Shiro; Kamano, Takuya; Yura, Satoshi; Yasuno, Takashi; Suzuki, Takayuki

    One of fundamental problems in the factory automation is how to obtain linear motion. Linear motors produce directly the linear motion force without a motion-transform mechanism. Linear d.c. motors (LDMs) have excellent performance and controllability. However, the dynamics of small-sized LDMs is adversely affected by the dead-band due to the friction between brushes and commutators. In this paper, it is described that the design of the two-degree-of-freedom positioning system with a LDM using model reference type sliding mode controller (SMC). The proposed positioning system consists of a fixed gain feedforward controller and a SMC used as a feedback controller. The objective of the SMC is to repress the influence of nonlinear characteristics (the dead-band and parameter variations etc.). The tracking performance can be improved as the fixed gain feedforward controller makes a dynamic inverse system in the feedforward path. The effectiveness of the proposed system for improvement of the tracking performance is demonstrated by experimental results.

  13. Labeled Postings for Asynchronous Interaction

    ERIC Educational Resources Information Center

    ChanLin, Lih-Juan; Chen, Yong-Ting; Chan, Kung-Chi

    2009-01-01

    The Internet promotes computer-mediated communications, and so asynchronous learning network systems permit more flexibility in time, space, and interaction than synchronous mode of learning. The key point of asynchronous learning is the materials for web-aided teaching and the flow of knowledge. This research focuses on improving online…

  14. An investigation on the characteristics of a single-sided linear induction motor at standstill for maglev vehicles

    SciTech Connect

    Cho, Y.; Lee, J.

    1997-03-01

    This paper presents the single-sided linear induction motor (SLIM) developed as electrical drives for magnetic levitation vehicle with a cruising speed 40--100Km/h for EXPO`93 in Taejon, Korea. The SLIM is designed to produce a 2,440 Newtons thrust from an active area of 2,836mm long by 235 mm wide at the airgap of 14 mm. In order to investigate its performance characteristics both experimentally and theoretically, the static test facilities was designed and equipped. At standstill, the experimental results are compared with the analytical ones.

  15. The Asynchronous Bounded-Cycle model☆

    PubMed Central

    Robinson, Peter; Schmid, Ulrich

    2011-01-01

    This paper shows how synchrony conditions can be added to the purely asynchronous model in a way that avoids any reference to message delays and computing step times, as well as system-wide constraints on execution patterns and network topology. Our Asynchronous Bounded-Cycle (ABC) model just bounds the ratio of the number of forward- and backward-oriented messages in certain (“relevant”) cycles in the space–time diagram of an asynchronous execution. We show that clock synchronization and lock-step rounds can be implemented and proved correct in the ABC model, even in the presence of Byzantine failures. Furthermore, we prove that any algorithm working correctly in the partially synchronous Θ-Model also works correctly in the ABC model. In our proof, we first apply a novel method for assigning certain message delays to asynchronous executions, which is based on a variant of Farkas’ theorem of linear inequalities and a non-standard cycle space of graphs. Using methods from point-set topology, we then prove that the existence of this delay assignment implies model indistinguishability for time-free safety and liveness properties. We also introduce several weaker variants of the ABC model, and relate our model to the existing partially synchronous system models, in particular, the classic models of Dwork, Lynch and Stockmayer and the query–response model by Mostefaoui, Mourgaya, and Raynal. Finally, we discuss some aspects of the ABC model’s applicability in real systems, in particular, in the context of VLSI Systems-on-Chip. PMID:22031790

  16. Polarized Linear Motor Combined With Levitation Actuators Working in a Partial Vacuum Environment—Application to Swissmetro

    NASA Astrophysics Data System (ADS)

    Cassat, Alain; Espanet, Christophe; Bourquin, Vincent; Hagmann, Pascal; Jufer, Marcel

    Worldwide high speed Maglev (> 400km/h) developments refer to Maglev such as the Japanese JR-Maglev MLX, the German Transrapid and the USA Inductrack Maglev. Other world projects exist such as the Japan HSST (< 300km/h) and the China HTC. The JR-Maglev, the Transrapid and the HSST have reached industrial levels. The Swissmetro Project presents a unique aspect of Maglev: it is designed to work under partial vacuum (< 10kPa) in two tunnels and for high speeds (>400km/h). The authors investigate new possibilities to combine both the propulsion and the levitation. In order to minimize the heat due to the motor levitation and guidance losses, a polarized excitation is proposed. The use of permanent magnet NdFeB for the excitation is still not applied for high speed Maglev, requiring mechanical power greater than 6MW. Such a solution only appears in Urban Rapid Transit Maglev (<160km/h), such as the USA MagneMotion M3 and the General Atomic Urban Maglev. For Swissmetro, the authors study the polarized inductors for the levitation, implying a polarized synchronous linear motor. The polarization is obtained with permanent magnets NdFeB. This paper presents some key issues related to such technical choices. The motor design is described and the power balance is presented. The thermal behavior is analyzed using a numerical platform of the complete vehicle-tunnel system, based on computation of the air flow dynamic.

  17. Asynchronous interpretation of parallel microprograms

    SciTech Connect

    Bandman, O.L.

    1984-03-01

    In this article, the authors demonstrate how to pass from a given synchronous interpretation of a parallel microprogram to an equivalent asynchronous interpretation, and investigate the cost associated with the rejection of external synchronization in parallel microprogram structures.

  18. Amplitude modulation drive to rectangular-plate linear ultrasonic motors with vibrators dimensions 8 mm x 2.16 mm X 1 mm.

    PubMed

    Ming, Yang; Hanson, Ben; Levesley, Martin C; Walker, Peter G; Watterson, Kevin G

    2006-12-01

    In this paper, to exploit the contribution from not only the stators but also from other parts of miniature ultrasonic motors, an amplitude modulation drive is proposed to drive a miniature linear ultrasonic motor consisting of two rectangular piezoelectric ceramic plates. Using finite-element software, the first longitudinal and second lateral-bending frequencies of the vibrator are shown to be very close when its dimensions are 8 mm x 2.16 mm x 1 mm. So one single frequency power should be able to drive the motor. However, in practice the motor is found to be hard to move with a single frequency power because of its small vibration amplitudes and big frequency difference between its longitudinal and bending resonance, which is induced by the boundary condition variation. To drive the motor effectively, an amplitude modulation drive is used by superimposing two signals with nearly the same frequencies, around the resonant frequency of the vibrators of the linear motor. When the amplitude modulation frequency is close to the resonant frequency of the vibrator's surroundings, experimental results show that the linear motor can move back and forward with a maximum thrust force (over 0.016 N) and a maximum velocity (over 50 mm/s).

  19. Steering by hearing: a bat's acoustic gaze is linked to its flight motor output by a delayed, adaptive linear law.

    PubMed

    Ghose, Kaushik; Moss, Cynthia F

    2006-02-01

    Adaptive behaviors require sensorimotor computations that convert information represented initially in sensory coordinates to commands for action in motor coordinates. Fundamental to these computations is the relationship between the region of the environment sensed by the animal (gaze) and the animal's locomotor plan. Studies of visually guided animals have revealed an anticipatory relationship between gaze direction and the locomotor plan during target-directed locomotion. Here, we study an acoustically guided animal, an echolocating bat, and relate acoustic gaze (direction of the sonar beam) to flight planning as the bat searches for and intercepts insect prey. We show differences in the relationship between gaze and locomotion as the bat progresses through different phases of insect pursuit. We define acoustic gaze angle, theta(gaze), to be the angle between the sonar beam axis and the bat's flight path. We show that there is a strong linear linkage between acoustic gaze angle at time t [theta(gaze)(t)] and flight turn rate at time t + tau into the future [theta(flight) (t + tau)], which can be expressed by the formula theta(flight) (t + tau) = ktheta(gaze)(t). The gain, k, of this linkage depends on the bat's behavioral state, which is indexed by its sonar pulse rate. For high pulse rates, associated with insect attacking behavior, k is twice as high compared with low pulse rates, associated with searching behavior. We suggest that this adjustable linkage between acoustic gaze and motor output in a flying echolocating bat simplifies the transformation of auditory information to flight motor commands.

  20. Experimental study of thrusts of a cylindrical linear synchronous motor with an HTS coil magnet as the excitation system

    NASA Astrophysics Data System (ADS)

    Duan, Wanqing; Yan, Zhongming; Luo, Wenbo; Zhang, Peixing; Gui, Zhixing; Wang, Zhiquan; Wang, Yu

    2015-01-01

    The thrusts of a cylindrical linear synchronous motor with an HTS coil magnet as the excitation system were measured the first time and will be presented in this paper. The HTS coil magnet is made of second generation YBCO wire. The coil is a double pancake coil consisting of 34 turns wire. The inner diameter, outer diameter and height of the coil are 20, 30 and 13 mm, respectively. The armature of the motor is three phases, and the inner diameter is 40 mm. It is made of copper windings. With a direct current of 40 A for the HTS coil magnet and a RMS current of 10 A for the armature, a peak thrust of 3.8 N was measured at the temperature of 77 K and a radial gap of 5 mm between the armature and the excitation system. Effects of armature current, coil current, running time, magnetizers and seams between magnetizers were also studied. In the experiments, the peak thrusts of different types of HTS coil magnets were about from 1.3 times to 8 times as strong as the peak thrust of the coreless coil magnet under the same conditions.

  1. Investigation on Prototype Superconducting Linear Synchronous Motor (LSM) for 600-km/h Wheel-Type Railway

    NASA Astrophysics Data System (ADS)

    Eom, Beomyong; Lee, Changhyeong; Kim, Seokho; Lee, Changyoung; Yun, Sangwon

    The existing wheel-type high-speed railway with a rotatable motor has a limit of 600 km/h speed. The normal conducting electromagnet has several disadvantages to realize 600 km/h speed. Several disadvantages are the increased space and weight, and the decreased electric efficiency to generate the required high magnetic field. In order to reduce the volume and weight, superconducting electromagnets can be considered for LSM (Linear Synchronous Motor). Prior to the fabrication of the real system, a prototype demo-coil is designed and fabricated using 2G high temperature superconducting wire. The prototype HTS coil is cooled by the conduction using a GM cryocooler. To reduce the heat penetration, thermal design was performed for the current leads, supporting structure and radiation shield considering the thermal stress. The operating temperature and current are 30∼40 K and 100 A. The coil consists of two double pancake coils (N, S pole, respectively) and it is driven on a test rail, which is installed for the test car. This paper describes the design and test results of the prototype HTS LSM system. Thermal characteristics are investigated with additional dummy thermal mass on the coil after turning off the cryocooler.

  2. High-resolution inchworm linear motor based on electrostatic twisting microactuators

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Ho; Hwang, Il-Han; Jo, Kyoung-Woo; Yoon, Eui-Sung; Lee, Jong-Hyun

    2005-09-01

    A new inchworm micromotor using new electrostatic in-plane twisting microactuators has been designed, fabricated and characterized for nano-resolution manipulators. The proposed twisting mechanism was implemented employing a pair of differential electrostatic actuators with a high stiffness in the driving direction for stable positioning. The electromechanically coupled motion of the voltage-displacement relation was analyzed using a finite element method (FEM), confirming that the twisting actuator makes a tiny step movement efficiently. The proposed actuator was fabricated on a silicon-on-insulator (SOI) wafer with the device footprint of 2.2 × 2.8 mm2, and its nano-stepping characteristics were measured by an optical interferometer consisting of an integrated micromirror and optical fiber. The fabricated inchworm motor showed a minimum step displacement of 5.2 ± 3.8 nm (2σ) and 4.1 ± 2.9 nm (2σ) for cyclic motion in the +y- and the -y-directions, respectively, with the gripping voltage of 15 V and differential voltage of 1 V. As a result, the proposed inchworm micromotor could operate with a stroke of 3 µm and a bi-directional step displacement of less than 10 nm. The step displacement is the smallest value of in-plane-type micromotors so far, and its magnitude was controllable up to 120 nm/cycle by changing the differential voltage.

  3. Linear motor compressor with pressure stabilization ports for use in refrigeration systems

    SciTech Connect

    Young, N. O.

    1985-11-19

    A pressure stabilization system for a linear compressor piston in which a check valve and passages within the piston permit communication between a compressor work space and a non-working volume of gas through an orifice in the piston cylinder. The check valve and ports allow momentary fluid communication between the dead space volume and the working volume. The fluid communication serves to stabilize working volume pressure and counteract the effects of gas leakage about the piston and into the dead volume. This fluid communication only occurs when dead volume pressure is greater than working volume pressure and port and are axially aligned.

  4. The performance of asynchronous algorithms on hypercubes

    SciTech Connect

    Womble, D.E.

    1988-12-01

    Many asynchronous algorithms have been developed for parallel computers. Most implementations of asynchronous algorithms, however, have been for shared memory machines. In this paper, we study the implementation and performance of some common asynchronous algorithms on the NCUBE/ten, a 1024 node hypercube. In addition, we summarize existing theoretical work and discuss some classes of algorithms that can be made asynchronous and some that cannot. 16 refs., 3 figs.

  5. Controllability of asynchronous Boolean multiplex control networks

    NASA Astrophysics Data System (ADS)

    Luo, Chao; Wang, Xingyuan; Liu, Hong

    2014-09-01

    In this article, the controllability of asynchronous Boolean multiplex control networks (ABMCNs) is studied. First, the model of Boolean multiplex control networks under Harvey' asynchronous update is presented. By means of semi-tensor product approach, the logical dynamics is converted into linear representation, and a generalized formula of control-depending network transition matrices is achieved. Second, a necessary and sufficient condition is proposed to verify that only control-depending fixed points of ABMCNs can be controlled with probability one. Third, using two types of controls, the controllability of system is studied and formulae are given to show: (a) when an initial state is given, the reachable set at time s under a group of specified controls; (b) the reachable set at time s under arbitrary controls; (c) the specific probability values from a given initial state to destination states. Based on the above formulae, an algorithm to calculate overall reachable states from a specified initial state is presented. Moreover, we also discuss an approach to find the particular control sequence which steers the system between two states with maximum probability. Examples are shown to illustrate the feasibility of the proposed scheme.

  6. A massively asynchronous, parallel brain.

    PubMed

    Zeki, Semir

    2015-05-19

    Whether the visual brain uses a parallel or a serial, hierarchical, strategy to process visual signals, the end result appears to be that different attributes of the visual scene are perceived asynchronously--with colour leading form (orientation) by 40 ms and direction of motion by about 80 ms. Whatever the neural root of this asynchrony, it creates a problem that has not been properly addressed, namely how visual attributes that are perceived asynchronously over brief time windows after stimulus onset are bound together in the longer term to give us a unified experience of the visual world, in which all attributes are apparently seen in perfect registration. In this review, I suggest that there is no central neural clock in the (visual) brain that synchronizes the activity of different processing systems. More likely, activity in each of the parallel processing-perceptual systems of the visual brain is reset independently, making of the brain a massively asynchronous organ, just like the new generation of more efficient computers promise to be. Given the asynchronous operations of the brain, it is likely that the results of activities in the different processing-perceptual systems are not bound by physiological interactions between cells in the specialized visual areas, but post-perceptually, outside the visual brain. PMID:25823871

  7. Acquiring Knowledge from Asynchronous Discussion

    ERIC Educational Resources Information Center

    Teo, Yiong Hwee; Webster, Len

    2008-01-01

    This article discusses a study which was designed to explore how online scaffolding can be incorporated to support knowledge acquisition in asynchronous discussion. A group of Singapore preservice teachers engaged in collaborative critiquing of videos before they embarked on their video projects to illustrate what constitutes good and bad video…

  8. Effect of the size of GdBCO-Ag secondary magnet on the static forces performance of linear synchronous motors

    NASA Astrophysics Data System (ADS)

    Zheng, Jun; Shi, Yunhua; He, Dabo; Jing, Hailian; Li, Jing; Deng, Zigang; Wang, Suyu; Wang, Jiasu; Cardwell, David A.

    2014-11-01

    Bulk high temperature superconductor magnets (HTSMs) have a higher flux-generating capability compared to conventional permanent magnets (PMs). These materials potentially can be used in high temperature superconducting (HTS) linear synchronous motors (LSMs) as superconducting secondary magnets, what will result in a reduced volume and weight as well as in higher force density and efficiency of these devices when compared to conventional PMs. The focus of this paper is on the effect of size of the secondary HTSM on the static performance (thrust force and normal force) of a LSM. In order to obtain high-field HTSM as the secondary, single grain bulk GdBCO-Ag superconductors of diameter 20 mm, 30 mm and 40 mm, which have higher Jc and trapped fields than YBCO superconductors, were used in this device for the first time following application by the same optimized magnetization condition. It was found that both thrust and normal forces increase and saturate with the increasing size of the HTSM secondary at the small size range, and then potentially distort when the physical size of the HTSM secondary approaches the pole pitch of the linear three-phase primary windings of the LSM. Furthermore, more experiments of a larger-sized multi-seeded HTSM secondary, confirmed that the relationship between the HTSM secondary size and the pole pitch of the primary is an important factor for achieving higher thrust and normal forces. It is suggested that the multi-pole HTSM secondary will be more beneficial to future HTS LSM designs since the single-pole HTSM secondary size should be equal to or smaller than the stator pole pitch in the paper.

  9. Process membership in asynchronous environments

    NASA Technical Reports Server (NTRS)

    Ricciardi, Aleta M.; Birman, Kenneth P.

    1993-01-01

    The development of reliable distributed software is simplified by the ability to assume a fail-stop failure model. The emulation of such a model in an asynchronous distributed environment is discussed. The solution proposed, called Strong-GMP, can be supported through a highly efficient protocol, and was implemented as part of a distributed systems software project at Cornell University. The precise definition of the problem, the protocol, correctness proofs, and an analysis of costs are addressed.

  10. An Asynchronous Augmentation to Traditional Course Delivery.

    ERIC Educational Resources Information Center

    Wolverton, Marvin L.; Wolverton, Mimi

    Asynchronous augmentation facilitates distributed learning, which relies heavily on technology and self-learning. This paper reports the results of delivering a real estate principles course using an asynchronous course delivery format. It highlights one of many ways to enhance learning using technology, and it provides information concerning how…

  11. Asynchronous Learning Forums for Business Acculturation

    ERIC Educational Resources Information Center

    Pence, Christine Cope; Wulf, Catharina

    2009-01-01

    The use of IT as a facilitator for student collaboration in higher business education has grown rapidly since 2000. Asynchronous discussion forums are used abundantly for collaborative training purposes and for teaching students business-relevant tools for their future careers. This article presents an analysis of the asynchronous discussion forum…

  12. The Use of Efficient Broadcast Protocols in Asynchronous Distributed Systems. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Schmuck, Frank Bernhard

    1988-01-01

    Reliable broadcast protocols are important tools in distributed and fault-tolerant programming. They are useful for sharing information and for maintaining replicated data in a distributed system. However, a wide range of such protocols has been proposed. These protocols differ in their fault tolerance and delivery ordering characteristics. There is a tradeoff between the cost of a broadcast protocol and how much ordering it provides. It is, therefore, desirable to employ protocols that support only a low degree of ordering whenever possible. This dissertation presents techniques for deciding how strongly ordered a protocol is necessary to solve a given application problem. It is shown that there are two distinct classes of application problems: problems that can be solved with efficient, asynchronous protocols, and problems that require global ordering. The concept of a linearization function that maps partially ordered sets of events to totally ordered histories is introduced. How to construct an asynchronous implementation that solves a given problem if a linearization function for it can be found is shown. It is proved that in general the question of whether a problem has an asynchronous solution is undecidable. Hence there exists no general algorithm that would automatically construct a suitable linearization function for a given problem. Therefore, an important subclass of problems that have certain commutativity properties are considered. Techniques for constructing asynchronous implementations for this class are presented. These techniques are useful for constructing efficient asynchronous implementations for a broad range of practical problems.

  13. Balancing Vibrations at Harmonic Frequencies by Injecting Harmonic Balancing Signals into the Armature of a Linear Motor/Alternator Coupled to a Stirling Machine

    NASA Technical Reports Server (NTRS)

    Holliday, Ezekiel S. (Inventor)

    2014-01-01

    Vibrations at harmonic frequencies are reduced by injecting harmonic balancing signals into the armature of a linear motor/alternator coupled to a Stirling machine. The vibrations are sensed to provide a signal representing the mechanical vibrations. A harmonic balancing signal is generated for selected harmonics of the operating frequency by processing the sensed vibration signal with adaptive filter algorithms of adaptive filters for each harmonic. Reference inputs for each harmonic are applied to the adaptive filter algorithms at the frequency of the selected harmonic. The harmonic balancing signals for all of the harmonics are summed with a principal control signal. The harmonic balancing signals modify the principal electrical drive voltage and drive the motor/alternator with a drive voltage component in opposition to the vibration at each harmonic.

  14. Carrying Synchronous Voice Data On Asynchronous Networks

    NASA Technical Reports Server (NTRS)

    Bergman, Larry A.

    1990-01-01

    Buffers restore synchronism for internal use and permit asynchronism in external transmission. Proposed asynchronous local-area digital communication network (LAN) carries synchronous voice, data, or video signals, or non-real-time asynchronous data signals. Network uses double buffering scheme that reestablishes phase and frequency references at each node in network. Concept demonstrated in token-ring network operating at 80 Mb/s, pending development of equipment operating at planned data rate of 200 Mb/s. Technique generic and used with any LAN as long as protocol offers deterministic (or bonded) access delays and sufficient capacity.

  15. Automatic defensive control of asynchronous sequential machines

    NASA Astrophysics Data System (ADS)

    Hammer, Jacob

    2016-01-01

    Control theoretic techniques are utilised to develop automatic controllers that counteract robotic adversarial interventions in the operation of asynchronous sequential machines. The scenario centres on automatic protection against pre-programmed adversarial agents that attempt to subvert the operation of an asynchronous computing system. Necessary and sufficient conditions for the existence of defensive controllers that automatically defeat such adversarial agents are derived. These conditions are stated in terms of skeleton matrices - matrices of zeros and ones obtained directly from the given description of the asynchronous sequential machine being protected. When defensive controllers exist, a procedure for their design is outlined.

  16. Asynchronous collision integrators: Explicit treatment of unilateral contact with friction and nodal restraints

    PubMed Central

    Wolff, Sebastian; Bucher, Christian

    2013-01-01

    This article presents asynchronous collision integrators and a simple asynchronous method treating nodal restraints. Asynchronous discretizations allow individual time step sizes for each spatial region, improving the efficiency of explicit time stepping for finite element meshes with heterogeneous element sizes. The article first introduces asynchronous variational integration being expressed by drift and kick operators. Linear nodal restraint conditions are solved by a simple projection of the forces that is shown to be equivalent to RATTLE. Unilateral contact is solved by an asynchronous variant of decomposition contact response. Therein, velocities are modified avoiding penetrations. Although decomposition contact response is solving a large system of linear equations (being critical for the numerical efficiency of explicit time stepping schemes) and is needing special treatment regarding overconstraint and linear dependency of the contact constraints (for example from double-sided node-to-surface contact or self-contact), the asynchronous strategy handles these situations efficiently and robust. Only a single constraint involving a very small number of degrees of freedom is considered at once leading to a very efficient solution. The treatment of friction is exemplified for the Coulomb model. Special care needs the contact of nodes that are subject to restraints. Together with the aforementioned projection for restraints, a novel efficient solution scheme can be presented. The collision integrator does not influence the critical time step. Hence, the time step can be chosen independently from the underlying time-stepping scheme. The time step may be fixed or time-adaptive. New demands on global collision detection are discussed exemplified by position codes and node-to-segment integration. Numerical examples illustrate convergence and efficiency of the new contact algorithm. Copyright © 2013 The Authors. International Journal for Numerical Methods in

  17. Asynchronous P300-based brain-computer interface to control a virtual environment: initial tests on end users.

    PubMed

    Aloise, Fabio; Schettini, Francesca; Aricò, Pietro; Salinari, Serenella; Guger, Christoph; Rinsma, Johanna; Aiello, Marco; Mattia, Donatella; Cincotti, Febo

    2011-10-01

    Motor disability and/or ageing can prevent individuals from fully enjoying home facilities, thus worsening their quality of life. Advances in the field of accessible user interfaces for domotic appliances can represent a valuable way to improve the independence of these persons. An asynchronous P300-based Brain-Computer Interface (BCI) system was recently validated with the participation of healthy young volunteers for environmental control. In this study, the asynchronous P300-based BCI for the interaction with a virtual home environment was tested with the participation of potential end-users (clients of a Frisian home care organization) with limited autonomy due to ageing and/or motor disabilities. System testing revealed that the minimum number of stimulation sequences needed to achieve correct classification had a higher intra-subject variability in potential end-users with respect to what was previously observed in young controls. Here we show that the asynchronous modality performed significantly better as compared to the synchronous mode in continuously adapting its speed to the users' state. Furthermore, the asynchronous system modality confirmed its reliability in avoiding misclassifications and false positives, as previously shown in young healthy subjects. The asynchronous modality may contribute to filling the usability gap between BCI systems and traditional input devices, representing an important step towards their use in the activities of daily living.

  18. Steering by Hearing: A Bat’s Acoustic Gaze Is Linked to Its Flight Motor Output by a Delayed, Adaptive Linear Law

    PubMed Central

    Ghose, Kaushik; Moss, Cynthia F.

    2012-01-01

    Adaptive behaviors require sensorimotor computations that convert information represented initially in sensory coordinates to commands for action in motor coordinates. Fundamental to these computations is the relationship between the region of the environment sensed by the animal (gaze) and the animal’s locomotor plan. Studies of visually guided animals have revealed an anticipatory relationship between gaze direction and the locomotor plan during target-directed locomotion. Here, we study an acoustically guided animal, an echolocating bat, and relate acoustic gaze (direction of the sonar beam) to flight planning as the bat searches for and intercepts insect prey. We show differences in the relationship between gaze and locomotion as the bat progresses through different phases of insect pursuit. We define acoustic gaze angle, θgaze, to be the angle between the sonar beam axis and the bat’s flight path. We show that there is a strong linear linkage between acoustic gaze angle at time t [θgaze(t)] and flight turn rate at time t + τ into the future [θ̇flight (t + τ)], which can be expressed by the formula θ̇flight (t + τ) = kθgaze(t). The gain, k, of this linkage depends on the bat’s behavioral state, which is indexed by its sonar pulse rate. For high pulse rates, associated with insect attacking behavior, k is twice as high compared with low pulse rates, associated with searching behavior. We suggest that this adjustable linkage between acoustic gaze and motor output in a flying echolocating bat simplifies the transformation of auditory information to flight motor commands. PMID:16467518

  19. Asynchronous Message Service Reference Implementation

    NASA Technical Reports Server (NTRS)

    Burleigh, Scott C.

    2011-01-01

    This software provides a library of middleware functions with a simple application programming interface, enabling implementation of distributed applications in conformance with the CCSDS AMS (Consultative Committee for Space Data Systems Asynchronous Message Service) specification. The AMS service, and its protocols, implement an architectural concept under which the modules of mission systems may be designed as if they were to operate in isolation, each one producing and consuming mission information without explicit awareness of which other modules are currently operating. Communication relationships among such modules are self-configuring; this tends to minimize complexity in the development and operations of modular data systems. A system built on this model is a society of generally autonomous, inter-operating modules that may fluctuate freely over time in response to changing mission objectives, modules functional upgrades, and recovery from individual module failure. The purpose of AMS, then, is to reduce mission cost and risk by providing standard, reusable infrastructure for the exchange of information among data system modules in a manner that is simple to use, highly automated, flexible, robust, scalable, and efficient. The implementation is designed to spawn multiple threads of AMS functionality under the control of an AMS application program. These threads enable all members of an AMS-based, distributed application to discover one another in real time, subscribe to messages on specific topics, and to publish messages on specific topics. The query/reply (client/server) communication model is also supported. Message exchange is optionally subject to encryption (to support confidentiality) and authorization. Fault tolerance measures in the discovery protocol minimize the likelihood of overall application failure due to any single operational error anywhere in the system. The multi-threaded design simplifies processing while enabling application nodes to

  20. Acceptability of an Asynchronous Learning Forum on Mobile Devices

    ERIC Educational Resources Information Center

    Chang, Chih-Kai

    2010-01-01

    Mobile learning has recently become noteworthy because mobile devices have become popular. To construct an asynchronous learning forum on mobile devices is important because an asynchronous learning forum is always an essential part of networked asynchronous distance learning. However, the input interface in handheld learning devices, which is…

  1. Parallel asynchronous hardware implementation of image processing algorithms

    NASA Technical Reports Server (NTRS)

    Coon, Darryl D.; Perera, A. G. U.

    1990-01-01

    Research is being carried out on hardware for a new approach to focal plane processing. The hardware involves silicon injection mode devices. These devices provide a natural basis for parallel asynchronous focal plane image preprocessing. The simplicity and novel properties of the devices would permit an independent analog processing channel to be dedicated to every pixel. A laminar architecture built from arrays of the devices would form a two-dimensional (2-D) array processor with a 2-D array of inputs located directly behind a focal plane detector array. A 2-D image data stream would propagate in neuron-like asynchronous pulse-coded form through the laminar processor. No multiplexing, digitization, or serial processing would occur in the preprocessing state. High performance is expected, based on pulse coding of input currents down to one picoampere with noise referred to input of about 10 femtoamperes. Linear pulse coding has been observed for input currents ranging up to seven orders of magnitude. Low power requirements suggest utility in space and in conjunction with very large arrays. Very low dark current and multispectral capability are possible because of hardware compatibility with the cryogenic environment of high performance detector arrays. The aforementioned hardware development effort is aimed at systems which would integrate image acquisition and image processing.

  2. Interaction and Cognition in Asynchronous Computer Conferencing

    ERIC Educational Resources Information Center

    Schrire, Sarah

    2004-01-01

    This paper is based on a multiple-case study of the learning process in three asynchronous computer conferences. The conferences were part of the distance learning component in doctoral degree courses in computing technology in education offered at an American university. The conferences were analyzed from a number of perspectives, the emphasis in…

  3. FIFO Buffer for Asynchronous Data Streams

    NASA Technical Reports Server (NTRS)

    Bascle, K. P.

    1985-01-01

    Variable-rate, asynchronous data signals from up to four measuring instruments or other sources combined in first-in/first-out (FIFO) buffer for transmission on single channel. Constructed in complementary metal-oxide-semiconductor (CMOS) logic, buffer consumes low power (only 125 mW at 5V) and conforms to aerospace standards of reliability and maintainability.

  4. Blending Online Asynchronous and Synchronous Learning

    ERIC Educational Resources Information Center

    Yamagata-Lynch, Lisa C.

    2014-01-01

    In this article I will share a qualitative self-study about a 15-week blended 100% online graduate level course facilitated through synchronous meetings on Blackboard Collaborate and asynchronous discussions on Blackboard. I taught the course at the University of Tennessee (UT) during the spring 2012 semester and the course topic was online…

  5. Increasing Student Engagement Using Asynchronous Learning

    ERIC Educational Resources Information Center

    Northey, Gavin; Bucic, Tania; Chylinski, Mathew; Govind, Rahul

    2015-01-01

    Student engagement is an ongoing concern for educators because of its positive association with deep learning and educational outcomes. This article tests the use of a social networking site (Facebook) as a tool to facilitate asynchronous learning opportunities that complement face-to-face interactions and thereby enable a stronger learning…

  6. Photometric Survey for Asynchronous Binary Asteroids

    NASA Astrophysics Data System (ADS)

    Pravec, P.

    2005-05-01

    Asynchronous binary asteroids have been found to be abundant among fast- spinning near-Earth asteroids (NEAs) smaller than 2 km in diameter; Pravec et al. (2005, Icarus, submitted) derived that 15 +/- 4 % of NEAs in the size range 0.3 to 2 km are binary with the secondary-to-primary mean diameter ratio >=0.18. The early re-sults from the surveys of the Vesta family and the Hungaria group (Ryan et al., 2004, Planet. Space Sci. 42, 1093; 2004, Bull. Amer. Astron. Society 36, 1181; Warner et al., 2005, IAU Circ. 8511) suggest that the popula-tion extends beyond the region of terrestrial planets, but with characteristics shifted to larger sizes and longer periods; the four known binaries in the Vesta family/Hungaria group are 3 to 6 km large and they have primary rotation periods in a range of 3 to ~4 h, i.e., on the tail of the distribution of primary rotation periods of NEAs. The comparison suggests that formation and evolution mechanisms of asynchronous NEA and main-belt binaries may be similar and are related to their fast spins and rubble-pile structure. None of the current theories of their formation of evolution, however, explains the observed properties of both NEA and main- belt asynchronous bina-ries in full. We have established a collaborative observational program, called "Photometric Survey for Asynchro-nous Binary Asteroids" to discover and describe asynchronous binaries over a range of heliocentric distances from NEAs through Mars-crossers to inner main-belt asteroids. One new binary Amor asteroid, 2005 AB has been found during the first few months of the survey operation (Reddy et al., 2005, IAU Circ. 8483), and we have obtained follow-up data for two other binary systems. I outline the motivations, the technique, and the strategy of the Survey.

  7. Motor task event detection using Subthalamic Nucleus Local Field Potentials.

    PubMed

    Niketeghad, Soroush; Hebb, Adam O; Nedrud, Joshua; Hanrahan, Sara J; Mahoor, Mohammad H

    2015-08-01

    Deep Brain Stimulation (DBS) provides significant therapeutic benefit for movement disorders such as Parkinson's disease. Current DBS devices lack real-time feedback (thus are open loop) and stimulation parameters are adjusted during scheduled visits with a clinician. A closed-loop DBS system may reduce power consumption and DBS side effects. In such systems, DBS parameters are adjusted based on patient's behavior, which means that behavior detection is a major step in designing such systems. Various physiological signals can be used to recognize the behaviors. Subthalamic Nucleus (STN) Local Field Potential (LFP) is a great candidate signal for the neural feedback, because it can be recorded from the stimulation lead and does not require additional sensors. A practical behavior detection method should be able to detect behaviors asynchronously meaning that it should not use any prior knowledge of behavior onsets. In this paper, we introduce a behavior detection method that is able to asynchronously detect the finger movements of Parkinson patients. As a result of this study, we learned that there is a motor-modulated inter-hemispheric connectivity between LFP signals recorded bilaterally from STN. We used non-linear regression method to measure this connectivity and use it to detect the finger movements. Performance of this method is evaluated using Receiver Operating Characteristic (ROC). PMID:26737550

  8. Inhibition Controls Asynchronous States of Neuronal Networks

    PubMed Central

    Treviño, Mario

    2016-01-01

    Computations in cortical circuits require action potentials from excitatory and inhibitory neurons. In this mini-review, I first provide a quick overview of findings that indicate that GABAergic neurons play a fundamental role in coordinating spikes and generating synchronized network activity. Next, I argue that these observations helped popularize the notion that network oscillations require a high degree of spike correlations among interneurons which, in turn, produce synchronous inhibition of the local microcircuit. The aim of this text is to discuss some recent experimental and computational findings that support a complementary view: one in which interneurons participate actively in producing asynchronous states in cortical networks. This requires a proper mixture of shared excitation and inhibition leading to asynchronous activity between neighboring cells. Such contribution from interneurons would be extremely important because it would tend to reduce the spike correlation between neighboring pyramidal cells, a drop in redundancy that could enhance the information-processing capacity of neural networks. PMID:27274721

  9. Inhibition Controls Asynchronous States of Neuronal Networks.

    PubMed

    Treviño, Mario

    2016-01-01

    Computations in cortical circuits require action potentials from excitatory and inhibitory neurons. In this mini-review, I first provide a quick overview of findings that indicate that GABAergic neurons play a fundamental role in coordinating spikes and generating synchronized network activity. Next, I argue that these observations helped popularize the notion that network oscillations require a high degree of spike correlations among interneurons which, in turn, produce synchronous inhibition of the local microcircuit. The aim of this text is to discuss some recent experimental and computational findings that support a complementary view: one in which interneurons participate actively in producing asynchronous states in cortical networks. This requires a proper mixture of shared excitation and inhibition leading to asynchronous activity between neighboring cells. Such contribution from interneurons would be extremely important because it would tend to reduce the spike correlation between neighboring pyramidal cells, a drop in redundancy that could enhance the information-processing capacity of neural networks.

  10. Synchronous motor with hybrid permanent magnets on the rotor.

    PubMed

    Slusarek, Barbara; Kapelski, Dariusz; Antal, Ludwik; Zalas, Pawel; Gwoździewicz, Maciej

    2014-07-10

    Powder metallurgy allows designers of electric motors to implement new magnetic circuit structures. A relatively new concept is the use of a magnet system consisting of various types of magnets on one rotor, for example sintered and bonded magnets. This concept has been applied to the design and manufacture of the four-pole rotor of a synchronous motor with 400 W power and a rotational speed of 1500 rpm. In this motor, the stator of an asynchronous motor type Sh 71-4B is applied. The application of the new construction of the rotor resulted in an increase in motor efficiency and power factor compared to an asynchronous motor with the same volume.

  11. Asynchronous Communication Scheme For Hypercube Computer

    NASA Technical Reports Server (NTRS)

    Madan, Herb S.

    1988-01-01

    Scheme devised for asynchronous-message communication system for Mark III hypercube concurrent-processor network. Network consists of up to 1,024 processing elements connected electrically as though were at corners of 10-dimensional cube. Each node contains two Motorola 68020 processors along with Motorola 68881 floating-point processor utilizing up to 4 megabytes of shared dynamic random-access memory. Scheme intended to support applications requiring passage of both polled or solicited and unsolicited messages.

  12. How Linear Motor Proteins Work

    NASA Astrophysics Data System (ADS)

    Oiwa, K.; Manstein, D. J.

    Most animals perform sophisticated forms of movement such as walking, running, flying and swimming using their skeletal muscles. Although directed movement is not generally associated with plants, cytoplasmic streaming in plant cells can reach velocities greater than 50 μm/s and thus constitutes one of the fastest forms of directed movement. Unicellular eukaryotic organisms and prokaryotes display diverse mechanisms by which they are able to actively move towards a food source, light or other sensory stimuli. On the cellular level active transport of vesicles and organelles is required, since the cytoplasm resembles a gel with a mesh size of approximately 50 nm, which makes the passive transport of organelle-sized particles impossible. For elongated cells such as neurons, even proteins and small metabolites have to be actively transported.

  13. Asynchronous event-based binocular stereo matching.

    PubMed

    Rogister, Paul; Benosman, Ryad; Ieng, Sio-Hoi; Lichtsteiner, Patrick; Delbruck, Tobi

    2012-02-01

    We present a novel event-based stereo matching algorithm that exploits the asynchronous visual events from a pair of silicon retinas. Unlike conventional frame-based cameras, recent artificial retinas transmit their outputs as a continuous stream of asynchronous temporal events, in a manner similar to the output cells of the biological retina. Our algorithm uses the timing information carried by this representation in addressing the stereo-matching problem on moving objects. Using the high temporal resolution of the acquired data stream for the dynamic vision sensor, we show that matching on the timing of the visual events provides a new solution to the real-time computation of 3-D objects when combined with geometric constraints using the distance to the epipolar lines. The proposed algorithm is able to filter out incorrect matches and to accurately reconstruct the depth of moving objects despite the low spatial resolution of the sensor. This brief sets up the principles for further event-based vision processing and demonstrates the importance of dynamic information and spike timing in processing asynchronous streams of visual events. PMID:24808513

  14. Asynchronous detection of kinesthetic attention during mobilization of lower limbs using EEG measurements

    NASA Astrophysics Data System (ADS)

    Melinscak, Filip; Montesano, Luis; Minguez, Javier

    2016-02-01

    Objective. Attention is known to modulate the plasticity of the motor cortex, and plasticity is crucial for recovery in motor rehabilitation. This study addresses the possibility of using an EEG-based brain-computer interface (BCI) to detect kinesthetic attention to movement. Approach. A novel experiment emulating physical rehabilitation was designed to study kinesthetic attention. The protocol involved continuous mobilization of lower limbs during which participants reported levels of attention to movement—from focused kinesthetic attention to mind wandering. For this protocol an asynchronous BCI detector of kinesthetic attention and deliberate mind wandering was designed. Main results. EEG analysis showed significant differences in theta, alpha, and beta bands, related to the attentional state. These changes were further pinpointed to bands relative to the frequency of the individual alpha peak. The accuracy of the designed BCI ranged between 60.8% and 68.4% (significantly above chance level), depending on the used analysis window length, i.e. acceptable detection delay. Significance. This study shows it is possible to use self-reporting to study attention-related changes in EEG during continuous mobilization. Such a protocol is used to develop an asynchronous BCI detector of kinesthetic attention, with potential applications to motor rehabilitation.

  15. Facilitating Asynchronous Distance Learning: Exploiting Opportunities for Knowledge Building in Asynchronous Distance Learning Environments.

    ERIC Educational Resources Information Center

    Prestera, Gustavo E.; Moller, Leslie A.

    Computer mediated communication tools enable today's distance learners to engage in collaborative problem solving, threaded discussions, and peer tutoring through asynchronous distance learning environments. This paper suggests that these are best accomplished by establishing virtual learning communities, which break down traditional…

  16. A Novel Approach to Asynchronous MVP Data Interpretation Based on Elliptical-Vectors

    NASA Astrophysics Data System (ADS)

    Kruglyakov, M.; Trofimov, I.; Korotaev, S.; Shneyer, V.; Popova, I.; Orekhova, D.; Scshors, Y.; Zhdanov, M. S.

    2014-12-01

    We suggest a novel approach to asynchronous magnetic-variation profiling (MVP) data interpretation. Standard method in MVP is based on the interpretation of the coefficients of linear relation between vertical and horizontal components of the measured magnetic field.From mathematical point of view this pair of linear coefficients is not a vector which leads to significant difficulties in asynchronous data interpretation. Our approach allows us to actually treat such a pair of complex numbers as a special vector called an ellipse-vector (EV). By choosing the particular definitions of complex length and direction, the basic relation of MVP can be considered as the dot product. This considerably simplifies the interpretation of asynchronous data. The EV is described by four real numbers: the values of major and minor semiaxes, the angular direction of the major semiaxis and the phase. The notation choice is motivated by historical reasons. It is important that different EV's components have different sensitivity with respect to the field sources and the local heterogeneities. Namely, the value of major semiaxis and the angular direction are mostly determined by the field source and the normal cross-section. On the other hand, the value of minor semiaxis and the phase are responsive to local heterogeneities. Since the EV is the general form of complex vector, the traditional Schmucker vectors can be explicitly expressed through its components.The proposed approach was successfully applied to interpretation the results of asynchronous measurements that had been obtained in the Arctic Ocean at the drift stations "North Pole" in 1962-1976.

  17. Asynchronous multiuser underwater acoustic communications (L).

    PubMed

    Cho, S E; Song, H C; Hodgkiss, W S

    2012-07-01

    An asynchronous multiuser system is proposed to support multiple-access underwater communications without the use of code-division multiple-access or a feedback channel. The rich multipath channels experienced by spatially separated users will be sufficient to ensure separation of collided packets at the base station. The iterative receiver will employ a combination of adaptive time-reversal processing, matching pursuit, and successive interference cancellation in a block-wise fashion to achieve multiuser separability. Data collected during the KAM11 experiment are used to illustrate the system's capability in a dynamic, time-varying environment.

  18. DAI-CLIPS: Distributed, Asynchronous, Interacting CLIPS

    NASA Technical Reports Server (NTRS)

    Gagne, Denis; Garant, Alain

    1994-01-01

    DAI-CLIPS is a distributed computational environment within which each CLIPS is an active independent computational entity with the ability to communicate freely with other CLIPS. Furthermore, new CLIPS can be created, others can be deleted or modify their expertise, all dynamically in an asynchronous and independent fashion during execution. The participating CLIPS are distributed over a network of heterogeneous processors taking full advantage of the available processing power. We present the general framework encompassing DAI-CLIPS and discuss some of its advantages and potential applications.

  19. Asynchronous Event-Driven Particle Algorithms

    SciTech Connect

    Donev, A

    2007-02-28

    We present in a unifying way the main components of three examples of asynchronous event-driven algorithms for simulating physical systems of interacting particles. The first example, hard-particle molecular dynamics (MD), is well-known. We also present a recently-developed diffusion kinetic Monte Carlo (DKMC) algorithm, as well as a novel event-driven algorithm for Direct Simulation Monte Carlo (DSMC). Finally, we describe how to combine MD with DSMC in an event-driven framework, and discuss some promises and challenges for event-driven simulation of realistic physical systems.

  20. Asynchronous Event-Driven Particle Algorithms

    SciTech Connect

    Donev, A

    2007-08-30

    We present, in a unifying way, the main components of three asynchronous event-driven algorithms for simulating physical systems of interacting particles. The first example, hard-particle molecular dynamics (MD), is well-known. We also present a recently-developed diffusion kinetic Monte Carlo (DKMC) algorithm, as well as a novel stochastic molecular-dynamics algorithm that builds on the Direct Simulation Monte Carlo (DSMC). We explain how to effectively combine event-driven and classical time-driven handling, and discuss some promises and challenges for event-driven simulation of realistic physical systems.

  1. Integrating Asynchronous Digital Design Into the Computer Engineering Curriculum

    ERIC Educational Resources Information Center

    Smith, S. C.; Al-Assadi, W. K.; Di, J.

    2010-01-01

    As demand increases for circuits with higher performance, higher complexity, and decreased feature size, asynchronous (clockless) paradigms will become more widely used in the semiconductor industry, as evidenced by the International Technology Roadmap for Semiconductors' (ITRS) prediction of a likely shift from synchronous to asynchronous design…

  2. Assessment of Alternate Delivery Mechanisms for Asynchronous Adult Distance Learners.

    ERIC Educational Resources Information Center

    Usrey, Michael W.

    Within a course at the University of Colorado addressing the management of research and development, a comparison of alternate asynchronous delivery media was conducted. For the course session on the management of intellectual property, asynchronous students were given access to the VHS tapes traditionally utilized, plus World Wide Web-based and…

  3. Using Asynchronous Online Discussions in Primary School Project Work

    ERIC Educational Resources Information Center

    Jamaludin, Azilawati; Lang, Quek Choon

    2006-01-01

    Using asynchronous online discussions for interschool collaborative project work represents one of the innovative practices in the Singapore classroom. With anytime, anywhere access to interactions among the students and teachers, the asynchronous nature of these interactions leads to new paradigms for teaching and learning, with both unique…

  4. Localized radio frequency communication using asynchronous transfer mode protocol

    DOEpatents

    Witzke, Edward L.; Robertson, Perry J.; Pierson, Lyndon G.

    2007-08-14

    A localized wireless communication system for communication between a plurality of circuit boards, and between electronic components on the circuit boards. Transceivers are located on each circuit board and electronic component. The transceivers communicate with one another over spread spectrum radio frequencies. An asynchronous transfer mode protocol controls communication flow with asynchronous transfer mode switches located on the circuit boards.

  5. Asynchronous Learning Sources in a High-Tech Organization

    ERIC Educational Resources Information Center

    Bouhnik, Dan; Giat, Yahel; Sanderovitch, Yafit

    2009-01-01

    Purpose: The purpose of this study is to characterize learning from asynchronous sources among research and development (R&D) personnel. It aims to examine four aspects of asynchronous source learning: employee preferences regarding self-learning; extent of source usage; employee satisfaction with these sources and the effect of the sources on the…

  6. Exploring Asynchronous and Synchronous Tool Use in Online Courses

    ERIC Educational Resources Information Center

    Oztok, Murat; Zingaro, Daniel; Brett, Clare; Hewitt, Jim

    2013-01-01

    While the independent contributions of synchronous and asynchronous interaction in online learning are clear, comparatively less is known about the pedagogical consequences of using both modes in the same environment. In this study, we examine relationships between students' use of asynchronous discussion forums and synchronous private messages…

  7. Asynchronous Access to Conventional Course Delivery: A Pilot Project

    ERIC Educational Resources Information Center

    Simpson, Natalie

    2006-01-01

    This study describes a technological pilot project providing 160 graduate students with asynchronous access to the ongoing proceedings of a lecture-based course. Exactly half of the students spoke the language of instruction, English, as a second language (ESL). While the asynchronous video-on-demand service proved popular overall, ESL students…

  8. Asynchronicity of facial blood perfusion in migraine.

    PubMed

    Zaproudina, Nina; Teplov, Victor; Nippolainen, Ervin; Lipponen, Jukka A; Kamshilin, Alexei A; Närhi, Matti; Karjalainen, Pasi A; Giniatullin, Rashid

    2013-01-01

    Asymmetrical changes in blood perfusion and asynchronous blood supply to head tissues likely contribute to migraine pathophysiology. Imaging was widely used in order to understand hemodynamic variations in migraine. However, mapping of blood pulsations in the face of migraineurs has not been performed so far. We used the Blood Pulsation Imaging (BPI) technique, which was recently developed in our group, to establish whether 2D-imaging of blood pulsations parameters can reveal new biomarkers of migraine. BPI characteristics were measured in migraineurs during the attack-free interval and compared to healthy subjects with and without a family history of migraine. We found a novel phenomenon of transverse waves of facial blood perfusion in migraineurs in contrast to healthy subjects who showed synchronous blood delivery to both sides of the face. Moreover, the amplitude of blood pulsations was symmetrically distributed over the face of healthy subjects, but asymmetrically in migraineurs and subjects with a family history of migraine. In the migraine patients we found a remarkable correlation between the side of unilateral headache and the direction of the blood perfusion wave. Our data suggest that migraine is associated with lateralization of blood perfusion and asynchronous blood pulsations in the facial area, which could be due to essential dysfunction of the autonomic vascular control in the face. These findings may further enhance our understanding of migraine pathophysiology and suggest new easily available biomarkers of this pathology. PMID:24324592

  9. Forming the wide asynchronous binary asteroid population

    NASA Astrophysics Data System (ADS)

    Jacobson, S.; Scheeres, D.; McMahon, J.

    2014-07-01

    We propose and analyze a new mechanism for the formation of the wide asynchronous binary population. These binary asteroids have wide semi-major axes relative to most near-Earth-asteroid and main-belt-asteroid systems as shown in the attached table. Confirmed members have rapidly rotating primaries and satellites that are not tidally locked. Previously suggested formation mechanisms from impact ejecta, from planetary flybys, and directly from rotational-fission events cannot satisfy all of the observations. The newly hypothesized mechanism works as follows: (1) these systems are formed from rotational fission, (2) their satellites are tidally locked, (3) their orbits are expanded by the binary Yarkovsky-O'Keefe-Radzievskii-Paddack (BYORP) effect, (4) their satellites desynchronize as a result of the adiabatic invariance between the libration of the secondary and the mutual orbit, and (5) the secondary avoids resynchronization because of the YORP effect. This seemingly complex chain of events is a natural pathway for binaries with satellites that have particular shapes, which define the BYORP effect torque that acts on the system. After detailing the theory, we analyze each of the wide-asynchronous-binary members and candidates to assess their most likely formation mechanism. Finally, we suggest possible future observations to check and constrain our hypothesis.

  10. Selective particle capture by asynchronously beating cilia

    NASA Astrophysics Data System (ADS)

    Ding, Yang; Kanso, Eva

    2015-12-01

    Selective particle filtration is fundamental in many engineering and biological systems. For example, many aquatic microorganisms use filter feeding to capture food particles from the surrounding fluid, using motile cilia. One of the capture strategies is to use the same cilia to generate feeding currents and to intercept particles when the particles are on the downstream side of the cilia. Here, we develop a 3D computational model of ciliary bands interacting with flow suspended particles and calculate particle trajectories for a range of particle sizes. Consistent with experimental observations, we find optimal particle sizes that maximize capture rate. The optimal size depends nonlinearly on cilia spacing and cilia coordination, synchronous vs. asynchronous. These parameters affect the cilia-generated flow field, which in turn affects particle trajectories. The low capture rate of smaller particles is due to the particles' inability to cross the flow streamlines of neighboring cilia. Meanwhile, large particles have difficulty entering the sub-ciliary region once advected downstream, also resulting in low capture rates. The optimal range of particle sizes is enhanced when cilia beat asynchronously. These findings have potentially important implications on the design and use of biomimetic cilia in processes such as particle sorting in microfluidic devices.

  11. Phase and speed synchronization control of four eccentric rotors driven by induction motors in a linear vibratory feeder with unknown time-varying load torques using adaptive sliding mode control algorithm

    NASA Astrophysics Data System (ADS)

    Kong, Xiangxi; Zhang, Xueliang; Chen, Xiaozhe; Wen, Bangchun; Wang, Bo

    2016-05-01

    In this paper, phase and speed synchronization control of four eccentric rotors (ERs) driven by induction motors in a linear vibratory feeder with unknown time-varying load torques is studied. Firstly, the electromechanical coupling model of the linear vibratory feeder is established by associating induction motor's model with the dynamic model of the system, which is a typical under actuated model. According to the characteristics of the linear vibratory feeder, the complex control problem of the under actuated electromechanical coupling model converts to phase and speed synchronization control of four ERs. In order to keep the four ERs operating synchronously with zero phase differences, phase and speed synchronization controllers are designed by employing adaptive sliding mode control (ASMC) algorithm via a modified master-slave structure. The stability of the controllers is proved by Lyapunov stability theorem. The proposed controllers are verified by simulation via Matlab/Simulink program and compared with the conventional sliding mode control (SMC) algorithm. The results show the proposed controllers can reject the time-varying load torques effectively and four ERs can operate synchronously with zero phase differences. Moreover, the control performance is better than the conventional SMC algorithm and the chattering phenomenon is attenuated. Furthermore, the effects of reference speed and parametric perturbations are discussed to show the strong robustness of the proposed controllers. Finally, experiments on a simple vibratory test bench are operated by using the proposed controllers and without control, respectively, to validate the effectiveness of the proposed controllers further.

  12. Asynchronous and corrected-asynchronous numerical solutions of parabolic PDES on MIMD multiprocessors

    NASA Technical Reports Server (NTRS)

    Amitai, Dganit; Averbuch, Amir; Itzikowitz, Samuel; Turkel, Eli

    1991-01-01

    A major problem in achieving significant speed-up on parallel machines is the overhead involved with synchronizing the concurrent process. Removing the synchronization constraint has the potential of speeding up the computation. The authors present asynchronous (AS) and corrected-asynchronous (CA) finite difference schemes for the multi-dimensional heat equation. Although the discussion concentrates on the Euler scheme for the solution of the heat equation, it has the potential for being extended to other schemes and other parabolic partial differential equations (PDEs). These schemes are analyzed and implemented on the shared memory multi-user Sequent Balance machine. Numerical results for one and two dimensional problems are presented. It is shown experimentally that the synchronization penalty can be about 50 percent of run time: in most cases, the asynchronous scheme runs twice as fast as the parallel synchronous scheme. In general, the efficiency of the parallel schemes increases with processor load, with the time level, and with the problem dimension. The efficiency of the AS may reach 90 percent and over, but it provides accurate results only for steady-state values. The CA, on the other hand, is less efficient, but provides more accurate results for intermediate (non steady-state) values.

  13. Asynchronous parallel pattern search for nonlinear optimization

    SciTech Connect

    P. D. Hough; T. G. Kolda; V. J. Torczon

    2000-01-01

    Parallel pattern search (PPS) can be quite useful for engineering optimization problems characterized by a small number of variables (say 10--50) and by expensive objective function evaluations such as complex simulations that take from minutes to hours to run. However, PPS, which was originally designed for execution on homogeneous and tightly-coupled parallel machine, is not well suited to the more heterogeneous, loosely-coupled, and even fault-prone parallel systems available today. Specifically, PPS is hindered by synchronization penalties and cannot recover in the event of a failure. The authors introduce a new asynchronous and fault tolerant parallel pattern search (AAPS) method and demonstrate its effectiveness on both simple test problems as well as some engineering optimization problems

  14. Ultrawideband asynchronous tracking system and method

    NASA Technical Reports Server (NTRS)

    Arndt, G. Dickey (Inventor); Ngo, Phong H. (Inventor); Phan, Chau T. (Inventor); Gross, Julia A. (Inventor); Ni, Jianjun (Inventor); Dusl, John (Inventor)

    2012-01-01

    A passive tracking system is provided with a plurality of ultrawideband (UWB) receivers that is asynchronous with respect to a UWB transmitter. A geometry of the tracking system may utilize a plurality of clusters with each cluster comprising a plurality of antennas. Time Difference of Arrival (TDOA) may be determined for the antennas in each cluster and utilized to determine Angle of Arrival (AOA) based on a far field assumption regarding the geometry. Parallel software communication sockets may be established with each of the plurality of UWB receivers. Transfer of waveform data may be processed by alternately receiving packets of waveform data from each UWB receiver. Cross Correlation Peak Detection (CCPD) is utilized to estimate TDOA information to reduce errors in a noisy, multipath environment.

  15. Fluorescence lifetime imaging by asynchronous pump-probe microscopy.

    PubMed Central

    Dong, C Y; So, P T; French, T; Gratton, E

    1995-01-01

    We report the development of a scanning lifetime fluorescence microscope using the asynchronous, pump-probe (stimulated emission) approach. There are two significant advantages of this technique. First, the cross-correlation signal produced by overlapping the pump and probe lasers results in i) an axial sectioning effect similar to that in confocal and two-photon excitation microscopy, and ii) improved spatial resolution compared to conventional one-photon fluorescence microscopy. Second, the low-frequency, cross-correlation signal generated allows lifetime-resolved imaging without using fast photodetectors. The data presented here include 1) determination of laser sources' threshold powers for linearity in the pump-probe signal; 2) characterization of the pump-probe intensity profile using 0.28 microns fluorescent latex spheres; 3) high frequency (up to 6.7 GHz) lifetime measurement of rhodamine B in water; and 4) lifetime-resolved images of fluorescent latex spheres, human erythrocytes and a mouse fibroblast cell stained by rhodamine DHPE, and a mouse fibroblast labeled with ethidium bromide and rhodamine DHPE. Images FIGURE 2 FIGURE 6 FIGURE 7 FIGURE 8 PMID:8599631

  16. Fault tolerant vector control of induction motor drive

    NASA Astrophysics Data System (ADS)

    Odnokopylov, G.; Bragin, A.

    2014-10-01

    For electric composed of technical objects hazardous industries, such as nuclear, military, chemical, etc. an urgent task is to increase their resiliency and survivability. The construction principle of vector control system fault-tolerant asynchronous electric. Displaying recovery efficiency three-phase induction motor drive in emergency mode using two-phase vector control system. The process of formation of a simulation model of the asynchronous electric unbalance in emergency mode. When modeling used coordinate transformation, providing emergency operation electric unbalance work. The results of modeling transient phase loss motor stator. During a power failure phase induction motor cannot save circular rotating field in the air gap of the motor and ensure the restoration of its efficiency at rated torque and speed.

  17. Asynchronous spiking photonic neuron for lightwave neuromorphic signal processing.

    PubMed

    Fok, Mable P; Tian, Yue; Rosenbluth, David; Prucnal, Paul R

    2012-08-15

    We developed an asynchronous spiking photonic neuron that forms the basic building block for hybrid analog/digital lightwave neuromorphic processing. Our approach enables completely asynchronous spiking in response to input signals while maximizing the throughput relative to synchronous approaches. Asynchronous operation is achieved by generating the spike source for the photonic neuron through four-wave mixing. This hybrid analog/digital photonic neuron has an electro-absorption modulator as the temporal integration unit for analog processing, while the digital processing portion employs optical thresholding in a highly Ge-doped nonlinear loop mirror.

  18. Operational aspects of asynchronous filtering for improved flood forecasting

    NASA Astrophysics Data System (ADS)

    Rakovec, Oldrich; Weerts, Albrecht; Sumihar, Julius; Uijlenhoet, Remko

    2014-05-01

    Hydrological forecasts can be made more reliable and less uncertain by recursively improving initial conditions. A common way of improving the initial conditions is to make use of data assimilation (DA), a feedback mechanism or update methodology which merges model estimates with available real world observations. The traditional implementation of the Ensemble Kalman Filter (EnKF; e.g. Evensen, 2009) is synchronous, commonly named a three dimensional (3-D) assimilation, which means that all assimilated observations correspond to the time of update. Asynchronous DA, also called four dimensional (4-D) assimilation, refers to an updating methodology, in which observations being assimilated into the model originate from times different to the time of update (Evensen, 2009; Sakov 2010). This study investigates how the capabilities of the DA procedure can be improved by applying alternative Kalman-type methods, e.g., the Asynchronous Ensemble Kalman Filter (AEnKF). The AEnKF assimilates observations with smaller computational costs than the original EnKF, which is beneficial for operational purposes. The results of discharge assimilation into a grid-based hydrological model for the Upper Ourthe catchment in Belgian Ardennes show that including past predictions and observations in the AEnKF improves the model forecasts as compared to the traditional EnKF. Additionally we show that elimination of the strongly non-linear relation between the soil moisture storage and assimilated discharge observations from the model update becomes beneficial for an improved operational forecasting, which is evaluated using several validation measures. In the current study we employed the HBV-96 model built within a recently developed open source modelling environment OpenStreams (2013). The advantage of using OpenStreams (2013) is that it enables direct communication with OpenDA (2013), an open source data assimilation toolbox. OpenDA provides a number of algorithms for model calibration

  19. Modeling and Analysis of Mixed Synchronous/Asynchronous Systems

    NASA Technical Reports Server (NTRS)

    Driscoll, Kevin R.; Madl. Gabor; Hall, Brendan

    2012-01-01

    Practical safety-critical distributed systems must integrate safety critical and non-critical data in a common platform. Safety critical systems almost always consist of isochronous components that have synchronous or asynchronous interface with other components. Many of these systems also support a mix of synchronous and asynchronous interfaces. This report presents a study on the modeling and analysis of asynchronous, synchronous, and mixed synchronous/asynchronous systems. We build on the SAE Architecture Analysis and Design Language (AADL) to capture architectures for analysis. We present preliminary work targeted to capture mixed low- and high-criticality data, as well as real-time properties in a common Model of Computation (MoC). An abstract, but representative, test specimen system was created as the system to be modeled.

  20. Stand-alone and hybrid positioning using asynchronous pseudolites.

    PubMed

    Gioia, Ciro; Borio, Daniele

    2014-12-24

    global navigation satellite system (GNSS) receivers are usually unable to achieve satisfactory performance in difficult environments, such as open-pit mines, urban canyons and indoors. Pseudolites have the potential to extend GNSS usage and significantly improve receiver performance in such environments by providing additional navigation signals. This also applies to asynchronous pseudolite systems, where different pseudolites operate in an independent way. Asynchronous pseudolite systems require, however, dedicated strategies in order to properly integrate GNSS and pseudolite measurements. In this paper, several asynchronous pseudolite/GNSS integration strategies are considered: loosely- and tightly-coupled approaches are developed and combined with pseudolite proximity and receiver signal strength (RSS)-based positioning. The performance of the approaches proposed has been tested in different scenarios, including static and kinematic conditions. The tests performed demonstrate that the methods developed are effective techniques for integrating heterogeneous measurements from different sources, such as asynchronous pseudolites and GNSS.

  1. Solving SAT and Hamiltonian Cycle Problem Using Asynchronous P Systems

    NASA Astrophysics Data System (ADS)

    Tagawa, Hirofumi; Fujiwara, Akihiro

    In the present paper, we consider fully asynchronous parallelism in membrane computing, and propose two asynchronous P systems for the satisfiability (SAT) and Hamiltonian cycle problem. We first propose an asynchronous P system that solves SAT with n variables and m clauses, and show that the proposed P system computes SAT in O(mn2n) sequential steps or O(mn) parallel steps using O(mn) kinds of objects. We next propose an asynchronous P system that solves the Hamiltonian cycle problem with n nodes, and show that the proposed P system computes the problem in O(n!) sequential steps or O(n2) parallel steps using O(n2) kinds of objects.

  2. Building asynchronous geospatial processing workflows with web services

    NASA Astrophysics Data System (ADS)

    Zhao, Peisheng; Di, Liping; Yu, Genong

    2012-02-01

    Geoscience research and applications often involve a geospatial processing workflow. This workflow includes a sequence of operations that use a variety of tools to collect, translate, and analyze distributed heterogeneous geospatial data. Asynchronous mechanisms, by which clients initiate a request and then resume their processing without waiting for a response, are very useful for complicated workflows that take a long time to run. Geospatial contents and capabilities are increasingly becoming available online as interoperable Web services. This online availability significantly enhances the ability to use Web service chains to build distributed geospatial processing workflows. This paper focuses on how to orchestrate Web services for implementing asynchronous geospatial processing workflows. The theoretical bases for asynchronous Web services and workflows, including asynchrony patterns and message transmission, are examined to explore different asynchronous approaches to and architecture of workflow code for the support of asynchronous behavior. A sample geospatial processing workflow, issued by the Open Geospatial Consortium (OGC) Web Service, Phase 6 (OWS-6), is provided to illustrate the implementation of asynchronous geospatial processing workflows and the challenges in using Web Services Business Process Execution Language (WS-BPEL) to develop them.

  3. Asynchronous Rate Chaos in Spiking Neuronal Circuits.

    PubMed

    Harish, Omri; Hansel, David

    2015-07-01

    The brain exhibits temporally complex patterns of activity with features similar to those of chaotic systems. Theoretical studies over the last twenty years have described various computational advantages for such regimes in neuronal systems. Nevertheless, it still remains unclear whether chaos requires specific cellular properties or network architectures, or whether it is a generic property of neuronal circuits. We investigate the dynamics of networks of excitatory-inhibitory (EI) spiking neurons with random sparse connectivity operating in the regime of balance of excitation and inhibition. Combining Dynamical Mean-Field Theory with numerical simulations, we show that chaotic, asynchronous firing rate fluctuations emerge generically for sufficiently strong synapses. Two different mechanisms can lead to these chaotic fluctuations. One mechanism relies on slow I-I inhibition which gives rise to slow subthreshold voltage and rate fluctuations. The decorrelation time of these fluctuations is proportional to the time constant of the inhibition. The second mechanism relies on the recurrent E-I-E feedback loop. It requires slow excitation but the inhibition can be fast. In the corresponding dynamical regime all neurons exhibit rate fluctuations on the time scale of the excitation. Another feature of this regime is that the population-averaged firing rate is substantially smaller in the excitatory population than in the inhibitory population. This is not necessarily the case in the I-I mechanism. Finally, we discuss the neurophysiological and computational significance of our results. PMID:26230679

  4. Asynchronous event-based hebbian epipolar geometry.

    PubMed

    Benosman, Ryad; Ieng, Sio-Hoï; Rogister, Paul; Posch, Christoph

    2011-11-01

    Epipolar geometry, the cornerstone of perspective stereo vision, has been studied extensively since the advent of computer vision. Establishing such a geometric constraint is of primary importance, as it allows the recovery of the 3-D structure of scenes. Estimating the epipolar constraints of nonperspective stereo is difficult, they can no longer be defined because of the complexity of the sensor geometry. This paper will show that these limitations are, to some extent, a consequence of the static image frames commonly used in vision. The conventional frame-based approach suffers from a lack of the dynamics present in natural scenes. We introduce the use of neuromorphic event-based--rather than frame-based--vision sensors for perspective stereo vision. This type of sensor uses the dimension of time as the main conveyor of information. In this paper, we present a model for asynchronous event-based vision, which is then used to derive a general new concept of epipolar geometry linked to the temporal activation of pixels. Practical experiments demonstrate the validity of the approach, solving the problem of estimating the fundamental matrix applied, in a first stage, to classic perspective vision and then to more general cameras. Furthermore, this paper shows that the properties of event-based vision sensors allow the exploration of not-yet-defined geometric relationships, finally, we provide a definition of general epipolar geometry deployable to almost any visual sensor. PMID:21954205

  5. Rapid, generalized adaptation to asynchronous audiovisual speech.

    PubMed

    Van der Burg, Erik; Goodbourn, Patrick T

    2015-04-01

    The brain is adaptive. The speed of propagation through air, and of low-level sensory processing, differs markedly between auditory and visual stimuli; yet the brain can adapt to compensate for the resulting cross-modal delays. Studies investigating temporal recalibration to audiovisual speech have used prolonged adaptation procedures, suggesting that adaptation is sluggish. Here, we show that adaptation to asynchronous audiovisual speech occurs rapidly. Participants viewed a brief clip of an actor pronouncing a single syllable. The voice was either advanced or delayed relative to the corresponding lip movements, and participants were asked to make a synchrony judgement. Although we did not use an explicit adaptation procedure, we demonstrate rapid recalibration based on a single audiovisual event. We find that the point of subjective simultaneity on each trial is highly contingent upon the modality order of the preceding trial. We find compelling evidence that rapid recalibration generalizes across different stimuli, and different actors. Finally, we demonstrate that rapid recalibration occurs even when auditory and visual events clearly belong to different actors. These results suggest that rapid temporal recalibration to audiovisual speech is primarily mediated by basic temporal factors, rather than higher-order factors such as perceived simultaneity and source identity.

  6. Asynchronous origins of ectomycorrhizal clades of Agaricales.

    PubMed

    Ryberg, Martin; Matheny, P Brandon

    2012-05-22

    The ectomycorrhizal (ECM) symbiosis is the most widespread biotrophic nutritional mode in mushroom-forming fungi. ECM fungi include, though are not limited to, about 5000 described species of Agaricales from numerous, independently evolved lineages. Two central hypotheses suggest different explanations for the origin of ECM fungal diversity: (i) dual origins, initially with the Pinaceae in the Jurassic and later with angiosperms during the Late Cretaceous, and (ii) a simultaneous and convergent radiation of ECM lineages in response to cooling climate during the Palaeogene and advancing temperate ECM plant communities. Neither of these hypotheses is supported here. While we demonstrate support for asynchronous origins of ECM Agaricales, the timing of such events appears to have occurred more recently than suggested by the first hypothesis, first during the Cretaceous and later during the Palaeogene. We are also unable to reject models of rate constancy, which suggests that the diversity of ECM Agaricales is not a consequence of convergent rapid radiations following evolutionary transitions from saprotrophic to ECM habits. ECM lineages of Agaricales differ not only in age, but also in rates of diversification and rate of substitution at nuclear ribosomal RNA loci. These results question the biological uniformity of the ECM guild.

  7. Rapid, generalized adaptation to asynchronous audiovisual speech

    PubMed Central

    Van der Burg, Erik; Goodbourn, Patrick T.

    2015-01-01

    The brain is adaptive. The speed of propagation through air, and of low-level sensory processing, differs markedly between auditory and visual stimuli; yet the brain can adapt to compensate for the resulting cross-modal delays. Studies investigating temporal recalibration to audiovisual speech have used prolonged adaptation procedures, suggesting that adaptation is sluggish. Here, we show that adaptation to asynchronous audiovisual speech occurs rapidly. Participants viewed a brief clip of an actor pronouncing a single syllable. The voice was either advanced or delayed relative to the corresponding lip movements, and participants were asked to make a synchrony judgement. Although we did not use an explicit adaptation procedure, we demonstrate rapid recalibration based on a single audiovisual event. We find that the point of subjective simultaneity on each trial is highly contingent upon the modality order of the preceding trial. We find compelling evidence that rapid recalibration generalizes across different stimuli, and different actors. Finally, we demonstrate that rapid recalibration occurs even when auditory and visual events clearly belong to different actors. These results suggest that rapid temporal recalibration to audiovisual speech is primarily mediated by basic temporal factors, rather than higher-order factors such as perceived simultaneity and source identity. PMID:25716790

  8. Asynchronous Rate Chaos in Spiking Neuronal Circuits

    PubMed Central

    Harish, Omri; Hansel, David

    2015-01-01

    The brain exhibits temporally complex patterns of activity with features similar to those of chaotic systems. Theoretical studies over the last twenty years have described various computational advantages for such regimes in neuronal systems. Nevertheless, it still remains unclear whether chaos requires specific cellular properties or network architectures, or whether it is a generic property of neuronal circuits. We investigate the dynamics of networks of excitatory-inhibitory (EI) spiking neurons with random sparse connectivity operating in the regime of balance of excitation and inhibition. Combining Dynamical Mean-Field Theory with numerical simulations, we show that chaotic, asynchronous firing rate fluctuations emerge generically for sufficiently strong synapses. Two different mechanisms can lead to these chaotic fluctuations. One mechanism relies on slow I-I inhibition which gives rise to slow subthreshold voltage and rate fluctuations. The decorrelation time of these fluctuations is proportional to the time constant of the inhibition. The second mechanism relies on the recurrent E-I-E feedback loop. It requires slow excitation but the inhibition can be fast. In the corresponding dynamical regime all neurons exhibit rate fluctuations on the time scale of the excitation. Another feature of this regime is that the population-averaged firing rate is substantially smaller in the excitatory population than in the inhibitory population. This is not necessarily the case in the I-I mechanism. Finally, we discuss the neurophysiological and computational significance of our results. PMID:26230679

  9. Parallel asynchronous systems and image processing algorithms

    NASA Technical Reports Server (NTRS)

    Coon, D. D.; Perera, A. G. U.

    1989-01-01

    A new hardware approach to implementation of image processing algorithms is described. The approach is based on silicon devices which would permit an independent analog processing channel to be dedicated to evey pixel. A laminar architecture consisting of a stack of planar arrays of the device would form a two-dimensional array processor with a 2-D array of inputs located directly behind a focal plane detector array. A 2-D image data stream would propagate in neuronlike asynchronous pulse coded form through the laminar processor. Such systems would integrate image acquisition and image processing. Acquisition and processing would be performed concurrently as in natural vision systems. The research is aimed at implementation of algorithms, such as the intensity dependent summation algorithm and pyramid processing structures, which are motivated by the operation of natural vision systems. Implementation of natural vision algorithms would benefit from the use of neuronlike information coding and the laminar, 2-D parallel, vision system type architecture. Besides providing a neural network framework for implementation of natural vision algorithms, a 2-D parallel approach could eliminate the serial bottleneck of conventional processing systems. Conversion to serial format would occur only after raw intensity data has been substantially processed. An interesting challenge arises from the fact that the mathematical formulation of natural vision algorithms does not specify the means of implementation, so that hardware implementation poses intriguing questions involving vision science.

  10. Asynchronous event-based hebbian epipolar geometry.

    PubMed

    Benosman, Ryad; Ieng, Sio-Hoï; Rogister, Paul; Posch, Christoph

    2011-11-01

    Epipolar geometry, the cornerstone of perspective stereo vision, has been studied extensively since the advent of computer vision. Establishing such a geometric constraint is of primary importance, as it allows the recovery of the 3-D structure of scenes. Estimating the epipolar constraints of nonperspective stereo is difficult, they can no longer be defined because of the complexity of the sensor geometry. This paper will show that these limitations are, to some extent, a consequence of the static image frames commonly used in vision. The conventional frame-based approach suffers from a lack of the dynamics present in natural scenes. We introduce the use of neuromorphic event-based--rather than frame-based--vision sensors for perspective stereo vision. This type of sensor uses the dimension of time as the main conveyor of information. In this paper, we present a model for asynchronous event-based vision, which is then used to derive a general new concept of epipolar geometry linked to the temporal activation of pixels. Practical experiments demonstrate the validity of the approach, solving the problem of estimating the fundamental matrix applied, in a first stage, to classic perspective vision and then to more general cameras. Furthermore, this paper shows that the properties of event-based vision sensors allow the exploration of not-yet-defined geometric relationships, finally, we provide a definition of general epipolar geometry deployable to almost any visual sensor.

  11. Multiple-input single-output closed-loop isometric force control using asynchronous intrafascicular multi-electrode stimulation.

    PubMed

    Frankel, Mitchell A; Dowden, Brett R; Mathews, V John; Normann, Richard A; Clark, Gregory A; Meek, Sanford G

    2011-06-01

    Although asynchronous intrafascicular multi-electrode stimulation (IFMS) can evoke fatigue-resistant muscle force, a priori determination of the necessary stimulation parameters for precise force production is not possible. This paper presents a proportionally-modulated, multiple-input single-output (MISO) controller that was designed and experimentally validated for real-time, closed-loop force-feedback control of asynchronous IFMS. Experiments were conducted on anesthetized felines with a Utah Slanted Electrode Array implanted in the sciatic nerve, either acutely or chronically ( n = 1 for each). Isometric forces were evoked in plantar-flexor muscles, and target forces consisted of up to 7 min of step, sinusoidal, and more complex time-varying trajectories. The controller was successful in evoking steps in force with time-to-peak of less than 0.45 s, steady-state ripple of less than 7% of the mean steady-state force, and near-zero steady-state error even in the presence of muscle fatigue, but with transient overshoot of near 20%. The controller was also successful in evoking target sinusoidal and complex time-varying force trajectories with amplitude error of less than 0.5 N and time delay of approximately 300 ms. This MISO control strategy can potentially be used to develop closed-loop asynchronous IFMS controllers for a wide variety of multi-electrode stimulation applications to restore lost motor function.

  12. Non-linear stimulus-response behavior of the human stance control system is predicted by optimization of a system with sensory and motor noise.

    PubMed

    van der Kooij, Herman; Peterka, Robert J

    2011-06-01

    We developed a theory of human stance control that predicted (1) how subjects re-weight their utilization of proprioceptive and graviceptive orientation information in experiments where eyes closed stance was perturbed by surface-tilt stimuli with different amplitudes, (2) the experimentally observed increase in body sway variability (i.e. the "remnant" body sway that could not be attributed to the stimulus) with increasing surface-tilt amplitude, (3) neural controller feedback gains that determine the amount of corrective torque generated in relation to sensory cues signaling body orientation, and (4) the magnitude and structure of spontaneous body sway. Responses to surface-tilt perturbations with different amplitudes were interpreted using a feedback control model to determine control parameters and changes in these parameters with stimulus amplitude. Different combinations of internal sensory and/or motor noise sources were added to the model to identify the properties of noise sources that were able to account for the experimental remnant sway characteristics. Various behavioral criteria were investigated to determine if optimization of these criteria could predict the identified model parameters and amplitude-dependent parameter changes. Robust findings were that remnant sway characteristics were best predicted by models that included both sensory and motor noise, the graviceptive noise magnitude was about ten times larger than the proprioceptive noise, and noise sources with signal-dependent properties provided better explanations of remnant sway. Overall results indicate that humans dynamically weight sensory system contributions to stance control and tune their corrective responses to minimize the energetic effects of sensory noise and external stimuli.

  13. Linear mass actuator

    NASA Technical Reports Server (NTRS)

    Holloway, Sidney E., III (Inventor); Crossley, Edward A., Jr. (Inventor); Jones, Irby W. (Inventor); Miller, James B. (Inventor); Davis, C. Calvin (Inventor); Behun, Vaughn D. (Inventor); Goodrich, Lewis R., Sr. (Inventor)

    1992-01-01

    A linear mass actuator includes an upper housing and a lower housing connectable to each other and having a central passageway passing axially through a mass that is linearly movable in the central passageway. Rollers mounted in the upper and lower housings in frictional engagement with the mass translate the mass linearly in the central passageway and drive motors operatively coupled to the roller means, for rotating the rollers and driving the mass axially in the central passageway.

  14. Gigabit Ethernet Asynchronous Clock Compensation FIFO

    NASA Technical Reports Server (NTRS)

    Duhachek, Jeff

    2012-01-01

    Clock compensation for Gigabit Ethernet is necessary because the clock recovered from the 1.25 Gb/s serial data stream has the potential to be 200 ppm slower or faster than the system clock. The serial data is converted to 10-bit parallel data at a 125 MHz rate on a clock recovered from the serial data stream. This recovered data needs to be processed by a system clock that is also running at a nominal rate of 125 MHz, but not synchronous to the recovered clock. To cross clock domains, an asynchronous FIFO (first-in-first-out) is used, with the write pointer (wprt) in the recovered clock domain and the read pointer (rptr) in the system clock domain. Because the clocks are generated from separate sources, there is potential for FIFO overflow or underflow. Clock compensation in Gigabit Ethernet is possible by taking advantage of the protocol data stream features. There are two distinct data streams that occur in Gigabit Ethernet where identical data is transmitted for a period of time. The first is configuration, which happens during auto-negotiation. The second is idle, which occurs at the end of auto-negotiation and between every packet. The identical data in the FIFO can be repeated by decrementing the read pointer, thus compensating for a FIFO that is draining too fast. The identical data in the FIFO can also be skipped by incrementing the read pointer, which compensates for a FIFO draining too slowly. The unique and novel features of this FIFO are that it works in both the idle stream and the configuration streams. The increment or decrement of the read pointer is different in the idle and compensation streams to preserve disparity. Another unique feature is that the read pointer to write pointer difference range changes between compensation and idle to minimize FIFO latency during packet transmission.

  15. Asynchronous reference frame agreement in a quantum network

    NASA Astrophysics Data System (ADS)

    Islam, Tanvirul; Wehner, Stephanie

    2016-03-01

    An efficient implementation of many multiparty protocols for quantum networks requires that all the nodes in the network share a common reference frame. Establishing such a reference frame from scratch is especially challenging in an asynchronous network where network links might have arbitrary delays and the nodes do not share synchronised clocks. In this work, we study the problem of establishing a common reference frame in an asynchronous network of n nodes of which at most t are affected by arbitrary unknown error, and the identities of the faulty nodes are not known. We present a protocol that allows all the correctly functioning nodes to agree on a common reference frame as long as the network graph is complete and not more than t\\lt n/4 nodes are faulty. As the protocol is asynchronous, it can be used with some assumptions to synchronise clocks over a network. Also, the protocol has the appealing property that it allows any existing two-node asynchronous protocol for reference frame agreement to be lifted to a robust protocol for an asynchronous quantum network.

  16. Full-order Luenberger observer based on fuzzy-logic control for sensorless field-oriented control of a single-sided linear induction motor.

    PubMed

    Holakooie, Mohammad Hosein; Ojaghi, Mansour; Taheri, Asghar

    2016-01-01

    This paper investigates sensorless indirect field oriented control (IFOC) of SLIM with full-order Luenberger observer. The dynamic equations of SLIM are first elaborated to draw full-order Luenberger observer with some simplifying assumption. The observer gain matrix is derived from conventional procedure so that observer poles are proportional to SLIM poles to ensure the stability of system for wide range of linear speed. The operation of observer is significantly impressed by adaptive scheme. A fuzzy logic control (FLC) is proposed as adaptive scheme to estimate linear speed using speed tuning signal. The parameters of FLC are tuned using an off-line method through chaotic optimization algorithm (COA). The performance of the proposed observer is verified by both numerical simulation and real-time hardware-in-the-loop (HIL) implementation. Moreover, a detailed comparative study among proposed and other speed observers is obtained under different operation conditions.

  17. Full-order Luenberger observer based on fuzzy-logic control for sensorless field-oriented control of a single-sided linear induction motor.

    PubMed

    Holakooie, Mohammad Hosein; Ojaghi, Mansour; Taheri, Asghar

    2016-01-01

    This paper investigates sensorless indirect field oriented control (IFOC) of SLIM with full-order Luenberger observer. The dynamic equations of SLIM are first elaborated to draw full-order Luenberger observer with some simplifying assumption. The observer gain matrix is derived from conventional procedure so that observer poles are proportional to SLIM poles to ensure the stability of system for wide range of linear speed. The operation of observer is significantly impressed by adaptive scheme. A fuzzy logic control (FLC) is proposed as adaptive scheme to estimate linear speed using speed tuning signal. The parameters of FLC are tuned using an off-line method through chaotic optimization algorithm (COA). The performance of the proposed observer is verified by both numerical simulation and real-time hardware-in-the-loop (HIL) implementation. Moreover, a detailed comparative study among proposed and other speed observers is obtained under different operation conditions. PMID:26653579

  18. Pulvinar thalamic nucleus allows for asynchronous spike propagation through the cortex

    PubMed Central

    Cortes, Nelson; van Vreeswijk, Carl

    2015-01-01

    We create two multilayered feedforward networks composed of excitatory and inhibitory integrate-and-fire neurons in the balanced state to investigate the role of cortico-pulvino-cortical connections. The first network consists of ten feedforward levels where a Poisson spike train with varying firing rate is applied as an input in layer one. Although the balanced state partially avoids spike synchronization during the transmission, the average firing-rate in the last layer either decays or saturates depending on the feedforward pathway gain. The last layer activity is almost independent of the input even for a carefully chosen intermediate gain. Adding connections to the feedforward pathway by a nine areas Pulvinar structure improves the firing-rate propagation to become almost linear among layers. Incoming strong pulvinar spikes balance the low feedforward gain to have a unit input-output relation in the last layer. Pulvinar neurons evoke a bimodal activity depending on the magnitude input: synchronized spike bursts between 20 and 80 Hz and an asynchronous activity for very both low and high frequency inputs. In the first regime, spikes of last feedforward layer neurons are asynchronous with weak, low frequency, oscillations in the rate. Here, the uncorrelated incoming feedforward pathway washes out the synchronized thalamic bursts. In the second regime, spikes in the whole network are asynchronous. As the number of cortical layers increases, long-range pulvinar connections can link directly two or more cortical stages avoiding their either saturation or gradual activity falling. The Pulvinar acts as a shortcut that supplies the input-output firing-rate relationship of two separated cortical areas without changing the strength of connections in the feedforward pathway. PMID:26042026

  19. Distributed asynchronous microprocessor architectures in fault tolerant integrated flight systems

    NASA Technical Reports Server (NTRS)

    Dunn, W. R.

    1983-01-01

    The paper discusses the implementation of fault tolerant digital flight control and navigation systems for rotorcraft application. It is shown that in implementing fault tolerance at the systems level using advanced LSI/VLSI technology, aircraft physical layout and flight systems requirements tend to define a system architecture of distributed, asynchronous microprocessors in which fault tolerance can be achieved locally through hardware redundancy and/or globally through application of analytical redundancy. The effects of asynchronism on the execution of dynamic flight software is discussed. It is shown that if the asynchronous microprocessors have knowledge of time, these errors can be significantly reduced through appropiate modifications of the flight software. Finally, the papear extends previous work to show that through the combined use of time referencing and stable flight algorithms, individual microprocessors can be configured to autonomously tolerate intermittent faults.

  20. Simulating fail-stop in asynchronous distributed systems

    NASA Technical Reports Server (NTRS)

    Sabel, Laura; Marzullo, Keith

    1994-01-01

    The fail-stop failure model appears frequently in the distributed systems literature. However, in an asynchronous distributed system, the fail-stop model cannot be implemented. In particular, it is impossible to reliably detect crash failures in an asynchronous system. In this paper, we show that it is possible to specify and implement a failure model that is indistinguishable from the fail-stop model from the point of view of any process within an asynchronous system. We give necessary conditions for a failure model to be indistinguishable from the fail-stop model, and derive lower bounds on the amount of process replication needed to implement such a failure model. We present a simple one-round protocol for implementing one such failure model, which we call simulated fail-stop.

  1. Dynamic modelling and estimation of the error due to asynchronism in a redundant asynchronous multiprocessor system

    NASA Technical Reports Server (NTRS)

    Huynh, Loc C.; Duval, R. W.

    1986-01-01

    The use of Redundant Asynchronous Multiprocessor System to achieve ultrareliable Fault Tolerant Control Systems shows great promise. The development has been hampered by the inability to determine whether differences in the outputs of redundant CPU's are due to failures or to accrued error built up by slight differences in CPU clock intervals. This study derives an analytical dynamic model of the difference between redundant CPU's due to differences in their clock intervals and uses this model with on-line parameter identification to idenitify the differences in the clock intervals. The ability of this methodology to accurately track errors due to asynchronisity generate an error signal with the effect of asynchronisity removed and this signal may be used to detect and isolate actual system failures.

  2. Design issues in the semantics and scheduling of asynchronous tasks.

    SciTech Connect

    Olivier, Stephen L.

    2013-07-01

    The asynchronous task model serves as a useful vehicle for shared memory parallel programming, particularly on multicore and manycore processors. As adoption of model among programmers has increased, support has emerged for the integration of task parallel language constructs into mainstream programming languages, e.g., C and C++. This paper examines some of the design decisions in Cilk and OpenMP concerning semantics and scheduling of asynchronous tasks with the aim of informing the efforts of committees considering language integration, as well as developers of new task parallel languages and libraries.

  3. Emergence of Motor Circuit Activity

    PubMed Central

    Law, Chris; Paquet, Michel; Kania, Artur

    2014-01-01

    In the developing nervous system, ordered neuronal activity patterns can occur even in the absence of sensory input and to investigate how these arise, we have used the model system of the embryonic chicken spinal motor circuit, focusing on motor neurons of the lateral motor column (LMC). At the earliest stages of their molecular differentiation, we can detect differences between medial and lateral LMC neurons in terms of expression of neurotransmitter receptor subunits, including CHRNA5, CHRNA7, GRIN2A, GRIK1, HTR1A and HTR1B, as well as the KCC2 transporter. Using patch-clamp recordings we also demonstrate that medial and lateral LMC motor neurons have subtly different activity patterns that reflect the differential expression of neurotransmitter receptor subunits. Using a combination of patch-clamp recordings in single neurons and calcium-imaging of motor neuron populations, we demonstrate that inhibition of nicotinic, muscarinic or GABA-ergic activity, has profound effects of motor circuit activity during the initial stages of neuromuscular junction formation. Finally, by analysing the activity of large populations of motor neurons at different developmental stages, we show that the asynchronous, disordered neuronal activity that occurs at early stages of circuit formation develops into organised, synchronous activity evident at the stage of LMC neuron muscle innervation. In light of the considerable diversity of neurotransmitter receptor expression, activity patterns in the LMC are surprisingly similar between neuronal types, however the emergence of patterned activity, in conjunction with the differential expression of transmitter systems likely leads to the development of near-mature patterns of locomotor activity by perinatal ages. PMID:24722186

  4. The Influence of Asynchronous Video Communication on Learner Social Presence: A Narrative Analysis of Four Cases

    ERIC Educational Resources Information Center

    Borup, Jered; West, Richard E.; Graham, Charles R.

    2013-01-01

    Online courses are increasingly using asynchronous video communication. However, little is known about how asynchronous video communication influences students' communication patterns. This study presents four narratives of students with varying characteristics who engaged in asynchronous video communication. The extrovert valued the efficiency of…

  5. Asynchronous RTK precise DGNSS positioning method for deriving a low-latency high-rate output

    NASA Astrophysics Data System (ADS)

    Liang, Zhang; Hanfeng, Lv; Dingjie, Wang; Yanqing, Hou; Jie, Wu

    2015-07-01

    Low-latency high-rate (1 Hz) precise real-time kinematic (RTK) can be applied in high-speed scenarios such as aircraft automatic landing, precise agriculture and intelligent vehicle. The classic synchronous RTK (SRTK) precise differential GNSS (DGNSS) positioning technology, however, is not able to obtain a low-latency high-rate output for the rover receiver because of long data link transmission time delays (DLTTD) from the reference receiver. To overcome the long DLTTD, this paper proposes an asynchronous real-time kinematic (ARTK) method using asynchronous observations from two receivers. The asynchronous observation model (AOM) is developed based on undifferenced carrier phase observation equations of the two receivers at different epochs with short baseline. The ephemeris error and atmosphere delay are the possible main error sources on positioning accuracy in this model, and they are analyzed theoretically. In a short DLTTD and during a period of quiet ionosphere activity, the main error sources decreasing positioning accuracy are satellite orbital errors: the "inverted ephemeris error" and the integration of satellite velocity error which increase linearly along with DLTTD. The cycle slip of asynchronous double-differencing carrier phase is detected by TurboEdit method and repaired by the additional ambiguity parameter method. The AOM can deal with synchronous observation model (SOM) and achieve precise positioning solution with synchronous observations as well, since the SOM is only a specific case of AOM. The proposed method not only can reduce the cost of data collection and transmission, but can also support the mobile phone network data link transfer mode for the data of the reference receiver. This method can avoid data synchronizing process besides ambiguity initialization step, which is very convenient for real-time navigation of vehicles. The static and kinematic experiment results show that this method achieves 20 Hz or even higher rate output in

  6. Precision magnetic suspension linear bearing

    NASA Technical Reports Server (NTRS)

    Trumper, David L.; Queen, Michael A.

    1992-01-01

    We have shown the design and analyzed the electromechanics of a linear motor suitable for independently controlling two suspension degrees of freedom. This motor, at least on paper, meets the requirements for driving an X-Y stage of 10 Kg mass with about 4 m/sq sec acceleration, with travel of several hundred millimeters in X and Y, and with reasonable power dissipation. A conceptual design for such a stage is presented. The theoretical feasibility of linear and planar bearings using single or multiple magnetic suspension linear motors is demonstrated.

  7. The theory of asynchronous relative motion II: universal and regular solutions

    NASA Astrophysics Data System (ADS)

    Roa, Javier; Peláez, Jesús

    2016-09-01

    Two fully regular and universal solutions to the problem of spacecraft relative motion are derived from the Sperling-Burdet (SB) and the Kustaanheimo-Stiefel (KS) regularizations. There are no singularities in the resulting solutions, and their form is not affected by the type of reference orbit (circular, elliptic, parabolic, or hyperbolic). In addition, the solutions to the problem are given in compact tensorial expressions and directly referred to the initial state vector of the leader spacecraft. The SB and KS formulations introduce a fictitious time by means of the Sundman transformation. Because of using an alternative independent variable, the solutions are built based on the theory of asynchronous relative motion. This technique simplifies the required derivations. Closed-form expressions of the partial derivatives of orbital motion with respect to the initial state are provided explicitly. Numerical experiments show that the performance of a given representation of the dynamics depends strongly on the time transformation, whereas it is virtually independent from the choice of variables to parameterize orbital motion. In the circular and elliptic cases, the linear solutions coincide exactly with the results obtained with the Clohessy-Wiltshire and Yamanaka-Ankersen state-transition matrices. Examples of relative orbits about parabolic and hyperbolic reference orbits are also presented. Finally, the theory of asynchronous relative motion provides a simple mechanism to introduce nonlinearities in the solution, improving its accuracy.

  8. The Socratic Dialogue in Asynchronous Online Discussions: Is Constructivism Redundant?

    ERIC Educational Resources Information Center

    Kingsley, Paul

    2011-01-01

    Purpose: This paper aims to examine Socratic dialogue in asynchronous online discussions in relation to constructivism. The links between theory and practice in teaching are to be discussed whilst tracing the origins of Socratic dialogue and recent trends and use of seminar in research based institutions. Design/methodology/approach: Many online…

  9. Improving the Asynchronous Online Learning Environment Using Discussion Boards

    ERIC Educational Resources Information Center

    Ringler, Ilene; Schubert, Carol; Deem, Jack; Flores, Jimmie; Friestad-Tate, Jill; Lockwood, Robert

    2015-01-01

    Discussion Boards are at the heart of an Asynchronous Online Learning or Distance Education Environment and can have a great impact on the learning experience. Understanding the individual factors that create a high quality discussion board experience for students and their interrelationships is critical to continuous improvement in distance…

  10. Reliable interface design for combining asynchronous and synchronous circuits

    NASA Technical Reports Server (NTRS)

    Josephson, Lueli; Brunvand, Erik L.; Gopalakrishan, Ganesh; Hurdle, John F.

    1993-01-01

    In order to successfully integrate asynchronous and synchronous designs, great care must be taken at the interface between the two types of systems. Synchronizing asynchronous inputs with a free running clock can cause well-known problems with metastability in the synchronization circuits. Stretchable clocks allow a clock cycle to expand dynamically in response to the metastability effects of sampling asynchronous inputs. We use an interface organization where the special circuitry for detecting metastability and for stretching the clock that is delivered to the synchronous part of the system is encapsulated in a Q-flop-based interface. This provides a very convenient method for interfacing mixed systems, as the interface and clock generation circuitry are isolated into one special module, and neither the asynchronous nor the synchronous system need be modified internally to accommodate the interface. This is especially important when standard synchronous components are used as there is no opportunity to modify these parts. We show that this interface module is suitable for most mixed design needs and conclude with an example.

  11. Reflections of Students in Their Use of Asynchronous Online Seminars

    ERIC Educational Resources Information Center

    Groves, Mark; O'Donoghue, John

    2009-01-01

    This paper reports on research that has been carried out into the use, process, and effectiveness of an asynchronous online seminar within an undergraduate sports studies degree programme. Contemporary sources are used to justify the use of technology supported learning (TSL) in higher education and to inform a reflective and critical account of…

  12. Comparison of the Asynchronous Differential Evolution and JADE Minimization Algorithms

    NASA Astrophysics Data System (ADS)

    Zhabitsky, Mikhail

    2016-02-01

    Differential Evolution (DE) is an efficient evolutionary algorithm to solve global optimization problems. In this work we compare performance of the recently proposed Asynchronous Differential Evolution with Adaptive Correlation Matrix (ADEACM) to the widely used JADE algorithm, a DE variant with adaptive control parameters.

  13. Students' Use of Asynchronous Discussions for Academic Discourse Socialization

    ERIC Educational Resources Information Center

    Beckett, Gulbahar H.; Amaro-Jimenez, Carla; Beckett, Kelvin S.

    2010-01-01

    Our universities are becoming increasingly diverse at the same time as online asynchronous discussions (OADs) are emerging as the most important forum for computer mediated communication (CMC) in distance education. But there is shortage of studies that explore how graduate students from different ethnic, linguistic and cultural backgrounds use…

  14. Asynchronous Assessment in a Large Lecture Marketing Course

    ERIC Educational Resources Information Center

    Downey, W. Scott; Schetzsle, Stacey

    2012-01-01

    Asynchronous assessment, which includes quizzes or exams online or outside class, offers marketing educators an opportunity to make more efficient use of class time and to enhance students' learning experiences by giving them more flexibility and choice in their assessment environment. In this paper, we examine the performance difference between…

  15. Synchronous versus Asynchronous CMC and Transfer to Japanese Oral Performance

    ERIC Educational Resources Information Center

    Hirotani, Maki

    2009-01-01

    This study investigated the effects of synchronous and asynchronous CMC (computer-mediated communication)on the development of linguistic features of learners' speech in Japanese. Using learners from fourth-semester Japanese classes, the following research questions were examined: (a) Does CMC have positive effects on the development of oral…

  16. Student Moderators in Asynchronous Online Discussion: A Question of Questions

    ERIC Educational Resources Information Center

    Zingaro, Daniel

    2012-01-01

    Much current research exalts the benefits of having students facilitate weekly discussions in asynchronous online courses. This study seeks to add to what is known about student moderation through an analysis of the types of questions students use to spur each discussion. Prior experimental work has demonstrated that the types of questions posed…

  17. An Investigation of Student Practices in Asynchronous Computer Conferencing Courses

    ERIC Educational Resources Information Center

    Peters, Vanessa L.; Hewitt, Jim

    2010-01-01

    This study investigated the online practices of students enrolled in graduate-level distance education courses. Using interviews and a questionnaire as data sources, the study sought to: (a) identify common practices that students adopt in asynchronous discussions, and (b) gain an understanding of why students adopt them. An analysis of the data…

  18. Reconceptualising Moderation in Asynchronous Online Discussions Using Grounded Theory

    ERIC Educational Resources Information Center

    Vlachopoulos, Panos; Cowan, John

    2010-01-01

    This article reports a grounded theory study of the moderation of asynchronous online discussions, to explore the processes by which tutors in higher education decide when and how to moderate. It aims to construct a theory of e-moderation based on some key factors which appear to influence e-moderation. It discusses previous research on the…

  19. Rubrics for Designing and Evaluating Online Asynchronous Discussions

    ERIC Educational Resources Information Center

    Penny, Lana; Murphy, Elizabeth

    2009-01-01

    The purpose of the study reported on in this paper was to identify performance criteria and ratings in rubrics designed for the evaluation of learning in online asynchronous discussions (OADs) in post-secondary contexts. We analysed rubrics collected from Internet sources. Using purposive sampling, we reached saturation with the selection of 50…

  20. Superconducting magnetic energy storage for asynchronous electrical systems

    DOEpatents

    Boenig, H.J.

    1984-05-16

    It is an object of the present invention to provide superconducting magnetic energy storage for a plurality of asynchronous electrical systems. It is a further object of the present invention to provide load leveling and stability improvement in a plurality of independent ac systems using a single superconducting magnetic energy storage coil.

  1. Group Learning Environment Linking Synchronous and Asynchronous Learning.

    ERIC Educational Resources Information Center

    Hayashi, Toshihiro; Nakanishi, Yoshinari; Hayashida, Yukuo

    This paper describes the design and features of LEA (Learning Environment with Agent), an educational system which has the features of both synchronous and asynchronous group learning environments. The first section discusses group learning environments, including differences between individual learning and group learning, and the classification…

  2. Developing a Successful Asynchronous Online Extension Program for Forest Landowners

    ERIC Educational Resources Information Center

    Zobrist, Kevin W.

    2014-01-01

    Asynchronous online Extension classes can reach a wide audience, is convenient for the learner, and minimizes ongoing demands on instructor time. However, producing such classes takes significant effort up front. Advance planning and good communication with contributors are essential to success. Considerations include delivery platforms, content…

  3. Engaging Graduate Students in Rich Asynchronous Online Discussions

    ERIC Educational Resources Information Center

    Wuttikietpaiboon, Kanya

    2012-01-01

    Given the importance of online instructional procedures that engage students in rich online discussions and enhance the quantity and the quality of the discussions, the purpose of this study was to investigate how a particular online instructor engaged graduate students in rich asynchronous online discussions, what roles the instructor played to…

  4. Cyber Asynchronous versus Blended Cyber Approach in Distance English Learning

    ERIC Educational Resources Information Center

    Ge, Zi-Gang

    2012-01-01

    This study aims to compare the single cyber asynchronous learning approach with the blended cyber learning approach in distance English education. Two classes of 70 students participated in this study, which lasted one semester of about four months, with one class using the blended approach for their English study and the other only using the…

  5. Designs, Management Tactics, and Strategies in Asynchronous Learning Discussions.

    ERIC Educational Resources Information Center

    Tu, Chih-Hsiung; Corry, Michael

    2003-01-01

    Discusses effective designs, management tactics, and strategies to produce ideal asynchronous network discussions that allow contemplation and encourage the development of critical thinking. A model of an online collaborative learning community is applied to implement the designs. A sample of online collaborative moderation guidelines is…

  6. Students' Activity Focus in Online Asynchronous Peer Learning Forums

    ERIC Educational Resources Information Center

    Gaspar, Alessio; Langevin, Sarah; Boyer, Naomi; Armitage, William

    2010-01-01

    This qualitative study explores how using Peer Learning Forums (PLF) in an online asynchronous computer programming course can be analyzed to derive information about Student Activity Focus (SAF) for adult Information Technology students. Three instruments are proposed to assist instructors classify questions posted by students on these forums,…

  7. Analysis of the Relevance of Posts in Asynchronous Discussions

    ERIC Educational Resources Information Center

    Azevedo, Breno T.; Reategui, Eliseo; Behar, Patrícia A.

    2014-01-01

    This paper presents ForumMiner, a tool for the automatic analysis of students' posts in asynchronous discussions. ForumMiner uses a text mining system to extract graphs from texts that are given to students as a basis for their discussion. These graphs contain the most relevant terms found in the texts, as well as the relationships between them.…

  8. Language Use in Asynchronous Computer-Mediated Communication in Taiwan

    ERIC Educational Resources Information Center

    Huang, Daphne Li-jung

    2009-01-01

    This paper describes how Chinese-English bilinguals in Taiwan use their languages in asynchronous computer-mediated communication, specifically, via Bulletin Board System (BBS) and email. The main data includes two types: emails collected from a social network and postings collected from two BBS websites. By examining patterns of language choice…

  9. Online Graduate Education: Developing Scholars through Asynchronous Discussion

    ERIC Educational Resources Information Center

    Bowden, Randall

    2012-01-01

    Considerable effort has been placed on understanding and enhancing online interaction to increase student learning, examine teaching strategies, and build learning communities. This research explored another aspect of interaction: the emergence of scholarship by graduate students through asynchronous discussion. Qualitative analysis of archived…

  10. [A delayed motor production of open chains of linear strokes presented visually in static and dynamic modes: a comparison between 9 to 11 years old children and adults].

    PubMed

    Antonova, A A; Absatova, K A; Korneev, A A; Kurgansky, A V

    2015-01-01

    The production of drawing movements was studied in 29 right-handed children of 9-to-11 years old. The movements were the sequences of horizontal and vertical linear stokes conjoined at right angle (open polygonal chains) referred to throughout the paper as trajectories. The length of a trajectory varied from 4 to 6. The trajectories were presented visually to a subject in static (linedrawing) and dynamic (moving cursor that leaves no trace) modes. The subjects were asked to draw (copy) a trajectory in response to delayed go-signal (short click) as fast as possible without lifting the pen. The production latency time, the average movement duration along a trajectory segment, and overall number of errors committed by a subject during trajectory production were analyzed. A comparison of children's data with similar data in adults (16 subjects) shows the following. First, a substantial reduction in error rate is observed in the age range between 9 and 11 years old for both static and dynamic modes of trajectory presentation, with children of 11 still committing more error than adults. Second, the averaged movement duration shortens with age while the latency time tends to increase. Third, unlike the adults, the children of 9-11 do not show any difference in latency time between static and dynamic modes of visual presentation of trajectories. The difference in trajectory production between adult and children is attributed to the predominant involvement of on-line programming in children and pre-programming in adults.

  11. Magnetostrictive direct drive motor

    NASA Technical Reports Server (NTRS)

    Naik, Dipak; Dehoff, P. H.

    1991-01-01

    Highly magnetostrictive materials such as Tb.3Dy.7Fe2, commercially known as TERFENOL-D, have been used to date in a variety of devices such as high power actuators and linear motors. The larger magnetostriction available in twinned single crystal TERFENOL-D, approx. 2000 ppm at moderate magnetic field strengths, makes possible a new generation of magnetomechanical devices. NASA researchers are studying the potential of this material as the basis for a direct microstepping rotary motor with torque densities on the order of industrial hydraulics and five times greater than that of the most efficient, high power electric motors. Such a motor would be a micro-radian stepper, capable of precision movements and self-braking in the power-off state. Innovative mechanical engineering techniques are juxtaposed on proper magnetic circuit design to reduce losses in structural flexures, inertias, thermal expansions, eddy currents, and magneto-mechanical coupling, thus optimizing motor performance and efficiency. Mathematical models are presented, including magnetic, structural, and both linear and nonlinear dynamic calculations and simulations. In addition, test results on prototypes are presented.

  12. Asynchronous telehealth: a scoping review of analytic studies

    PubMed Central

    Deshpande, Amol; Khoja, Shariq; Lorca, Julio; McKibbon, Ann; Rizo, Carlos; Husereau, Donald; Jadad, Alejandro R

    2009-01-01

    Background Asynchronous telehealth captures clinically important digital samples (e.g., still images, video, audio, text files) and relevant data in one location and subsequently transmits these files for interpretation at a remote site by health professionals without requiring the simultaneous presence of the patient involved and his or her health care provider. Its utility in the health care system, however, still remains poorly defined. We conducted this scoping review to determine the impact of asynchronous telehealth on health outcomes, process of care, access to health services, and health resources. Methods A search was performed up to December 2006 of MEDLINE, CINAHL, HealthSTAR, the Database of Abstracts of Reviews of Effectiveness, and The Cochrane Library. Studies were included if they contained original data on the use of asynchronous telehealth and were published in English in a peer-reviewed journal. Two independent reviewers screened all articles and extracted data, reaching consensus on the articles and data identified. Data were extracted on general study characteristics, clinical domain, technology, setting, category of outcome, and results. Study quality (internal validity) was assessed using the Jadad scale for randomized controlled trials and the Downs and Black index for non-randomized studies. Summary data were categorized by medical specialty and presented qualitatively. Results The scoping review included 52 original studies from 238 citations identified; of these 52, almost half focused on the use of telehealth in dermatology. Included studies were characterized by diverse designs, interventions, and outcomes. Only 16 studies were judged to be of high quality. Most studies showed beneficial effects in terms of diagnostic accuracy, wait times, referral management, and satisfaction with services. Evidence on the impact of asynchronous telehealth on resource use in dermatology suggests a reduction in the number of, or avoidance of, in

  13. Asynchronous Message Service for Deep Space Mission Operations

    NASA Technical Reports Server (NTRS)

    Burleigh, Scott C.

    2006-01-01

    While the CCSDS (Consultative Committee for Space Data Systems) File Delivery Protocol (CFDP) provides internationally standardized file transfer functionality that can offer significant benefits for deep space mission operations, not all spacecraft communication requirements are necessarily best met by file transfer. In particular, continuous event-driven asynchronous message exchange may also be useful for communications with, among, and aboard spacecraft. CCSDS has therefore undertaken the development of a new Asynchronous Message Service (AMS) standard, designed to provide common functionality over a wide variety of underlying transport services, ranging from shared memory message queues to CCSDS telemetry systems. The present paper discusses the design concepts of AMS, their applicability to deep space mission operations problems, and the results of preliminary performance testing obtained from exercise of a prototype implementation.

  14. State assignment approach to asynchronous CMOS circuit design

    NASA Astrophysics Data System (ADS)

    Kantabutra, Vitit; Andreou, Andreas G.

    1994-04-01

    We present a new algorithm for state assignment in asynchronous circuits so that for each circuit state transition, only one (secondary) state variable switches. No intermediate unstable states are used. The resultant circuits operate at optimum speed in terms of the number of transitions made and use only static CMOS gates. By reducing the number of switching events per state transition, noise due to the switching events is reduced and dynamic power dissipation may also be reduced. Our approach is suitable for asynchronous sequential circuits that are designed from flow tables or state transition diagrams. The proposed approach may also be useful for designing synchronous circuits, but explorations into the subject of clock power would be necessary to determine its usefulness.

  15. Asynchronous and timing jitter insensitive data echo cancellation

    NASA Astrophysics Data System (ADS)

    Messerschmitt, David G.

    1986-12-01

    An approach to the implementation of asynchronous and timing jitter insensitive data echo cancellation is described. This approach introduces a small amount of jitter in the transmitted data signal, or alternatively in the received signal sampling, and uses a simple digital phase-locked loop together with the storage of two sets of echo canceller coefficients. The effect of derived timing jitter on the echo cancellation accuracy is completely eliminated for a loop timed transceiver (as in a digital subscriber loop network termination transceiver), and is easily reduced to negligible levels for a nonloop timed transceiver (as in a digital subscriber loop line card transceiver or a voiceband data modem). In the case of a voiceband data modem, this approach is one method to achieve asynchronous echo cancellation without the need to recover and resample a continuous-time far-end data signal.

  16. Parallel, Asynchronous Executive (PAX): System concepts, facilities, and architecture

    NASA Technical Reports Server (NTRS)

    Jones, W. H.

    1983-01-01

    The Parallel, Asynchronous Executive (PAX) is a software operating system simulation that allows many computers to work on a single problem at the same time. PAX is currently implemented on a UNIVAC 1100/42 computer system. Independent UNIVAC runstreams are used to simulate independent computers. Data are shared among independent UNIVAC runstreams through shared mass-storage files. PAX has achieved the following: (1) applied several computing processes simultaneously to a single, logically unified problem; (2) resolved most parallel processor conflicts by careful work assignment; (3) resolved by means of worker requests to PAX all conflicts not resolved by work assignment; (4) provided fault isolation and recovery mechanisms to meet the problems of an actual parallel, asynchronous processing machine. Additionally, one real-life problem has been constructed for the PAX environment. This is CASPER, a collection of aerodynamic and structural dynamic problem simulation routines. CASPER is not discussed in this report except to provide examples of parallel-processing techniques.

  17. Inference of asynchronous Boolean network from biological pathways.

    PubMed

    Das, Haimabati; Layek, Ritwik Kumar

    2015-01-01

    Gene regulation is a complex process with multiple levels of interactions. In order to describe this complex dynamical system with tractable parameterization, the choice of the dynamical system model is of paramount importance. The right abstraction of the modeling scheme can reduce the complexity in the inference and intervention design, both computationally and experimentally. This article proposes an asynchronous Boolean network framework to capture the transcriptional regulation as well as the protein-protein interactions in a genetic regulatory system. The inference of asynchronous Boolean network from biological pathways information and experimental evidence are explained using an algorithm. The suitability of this paradigm for the variability of several reaction rates is also discussed. This methodology and model selection open up new research challenges in understanding gene-protein interactive system in a coherent way and can be beneficial for designing effective therapeutic intervention strategy.

  18. Motor Starters

    NASA Astrophysics Data System (ADS)

    1986-01-01

    The power factor controller (PFC) was invented by a NASA engineer. It matches voltage with a motor's actual need by sensing shifts in the relationship between voltage and current flow. With the device, power can be trimmed as much as 65%. Intellinet adopted this technology and designed "soft start" and "load-responsive" control modes to start engines gradually and recycle voltage without reducing motor speed. Other features are lower motor heat and faster fault identification.

  19. Asynchronous Transfer Mode (ATM) Switch Technology and Vendor Survey

    NASA Technical Reports Server (NTRS)

    Berry, Noemi

    1995-01-01

    Asynchronous Transfer Mode (ATM) switch and software features are described and compared in order to make switch comparisons meaningful. An ATM switch's performance cannot be measured solely based on its claimed switching capacity; traffic management and congestion control are emerging as the determining factors in an ATM network's ultimate throughput. Non-switch ATM products and experiences with actual installations of ATM networks are described. A compilation of select vendor offerings as of October 1994 is provided in chart form.

  20. Divorce and asynchronous arrival in common terns, Sterna hirundo.

    PubMed

    GonzáLez-SolíS; Becker; Wendeln

    1999-11-01

    We investigated which of three hypotheses (better option, incompatibility or asynchronous arrival) best explains divorce in the common tern. One partner did not return the next year in 18.5% of 150 pairs. Among the 106 pairs in which both mates returned, the divorce rate was 18.9%. We found no significant differences in: breeding performance or condition in relation to the probability of divorce; quality of previous mates and new mates, mean age in relation to pair bond status; breeding success before and after divorce nor did this differ from breeding success of reunited pairs. Hence the better option and incompatibility hypotheses were not supported. However, divorce was more likely in pairs in which mates arrived asynchronously on the breeding grounds, supporting the asynchronous arrival hypothesis. Median arrival asynchrony for divorced pairs was 7.5 days and for reunited pairs 2 days; mates arriving more than 16 days apart always split up. About 20% of divorced birds lost breeding status in the year of divorce, probably as a consequence of their late arrival. Our results suggest that terns search for a new mate as soon as they arrive on the breeding grounds and that mates remain faithful to each other to avoid the costs of searching for a new partner. Thus, synchrony in arrival facilitates pair bond maintenance rather than asynchrony promoting divorce, since divorce appears to be a side-effect of asynchrony and not an active decision. Copyright 1999 The Association for the Study of Animal Behaviour. PMID:10564616

  1. Non-detection of nova shells around asynchronous polars

    NASA Astrophysics Data System (ADS)

    Pagnotta, Ashley; Zurek, David

    2016-05-01

    Asynchronous polars (APs) are accreting white dwarfs (WDs) that have different WD and orbital angular velocities, unlike the rest of the known polars, which rotate synchronously (i.e. their WD and orbital angular velocities are the same). Past nova eruptions are the predicted cause of the asynchronicity, in part due to the fact that one of the APs, V1500 Cyg, was observed to undergo a nova eruption in 1975. We used the Southern African Large Telescope 10 m class telescope and the MDM 2.4 m Hiltner telescope to search for nova shells around three of the remaining four APs (V1432 Aql, BY Cam, and CD Ind) as well as one Intermediate Polar with a high asynchronicity (EX Hya). We found no evidence of nova shells in any of our images. We therefore cannot say that any of the systems besides V1500 Cyg had nova eruptions, but because not all post-nova systems have detectable shells, we also cannot exclude the possibility of a nova eruption occurring in any of these systems and knocking the rotation out of sync.

  2. Non-Detection of Nova Shells Around Asynchronous Polars

    NASA Astrophysics Data System (ADS)

    Pagnotta, Ashley; Zurek, David

    2016-01-01

    Asynchronous polars (APs) are accreting white dwarfs (WDs) that have different WD and orbital angular velocities, unlike the rest of the known polars, which rotate synchronously (i.e., their WD and orbital angular velocities are the same). Past nova eruptions are the predicted cause of the asynchronicity, in part due to the fact that one of the APs, V1500 Cyg, was observed to undergo a nova eruption in 1975. We used the SALT 10m-class telescope and the MDM 2.4m Hiltner telescope to search for nova shells around three of the remaining four APs (V1432 Aql, BY Cam, and CD Ind) as well as one Intermediate Polar with a high asynchronicity (EX Hya). We found no evidence of nova shells in any of our images. We therefore cannot say that any of the systems besides V1500 Cyg had nova eruptions, but because not all post-nova systems have detectable shells, we also cannot exclude the possibility of a nova eruption occurring in any of these systems and knocking the rotation out of sync.

  3. Asynchronous hatching and food limitation: a test of Lack's hypothesis

    USGS Publications Warehouse

    Skagen, Susan Knight

    1988-01-01

    Lack’s (1954, 1968) hypothesis that asynchronous hatching of altricial birds is an adaptive response to unpredictable food shortages during the breeding season was examined in the highly granivorous Zebra Finch (Poephila guttata). I compared growth and survival of nestlings in asynchronous and artificially created synchronous brood reared under food-limited and food-abundant conditions in an aviary. I also examined the role of parental experience on survival and growth of nestlings. There was no differential mortality of Zebra Finch nestlings due to either asynchrony or food abundance. Young in abundant food treatments grew more rapidly, however, than those in food restricted treatments. Heaviest Zebra Finch nestlings in a brood grew more quickly than their lightest siblings when food was limited, supporting Lack’s hypothesis. Further, differential survival of light and heavy siblings occurred when food was abundant, suggesting that asynchronous hatching can be maladaptive under some ecological conditions. Nestlings reared by inexperienced parents suffered greater mortality and slower growth when food was abundant than nestlings raised by experienced parents. Prefledging mass was correlated with size at adulthood.

  4. Rapid marine deglaciation: asynchronous retreat dynamics between the Irish Sea Ice Stream and terrestrial outlet glaciers

    NASA Astrophysics Data System (ADS)

    Patton, H.; Hubbard, A.; Bradwell, T.; Glasser, N. F.; Hambrey, M. J.; Clark, C. D.

    2013-08-01

    Understanding the retreat behaviour of past marine-ice sheets provides vital context to accurate assessment of the present stability and long-term response of contemporary polar-ice sheets to climate and oceanic warming. Here new multibeam swath-bathymetry data and sedimentological analysis are combined with high resolution ice-sheet modelling to reveal complex landform assemblages and process-dynamics associated with deglaciation of the British-Celtic Ice Sheet (BCIS) within the Irish Sea Basin. Our reconstruction indicates a non-linear relationship between the rapidly receding Irish Sea Ice Stream, the largest draining the BCIS, and the retreat of outlet glaciers draining the adjacent, terrestrially based ice sheet centred over Wales. Retreat of Welsh ice was episodic; superimposed over low-order oscillations of its margin are asynchronous outlet re-advances driven by catchment-wide mass balance variations that are amplified through migration of the ice cap's main ice-divide. Formation of large, linear ridges which extend at least 12.5 km offshore (locally known as sarns) and dominate the regional bathymetry are attributed to repeated frontal and medial morainic deposition associated with the re-advancing phases of these outlet glaciers. Our study provides new insight into ice-sheet extent, dynamics and non-linear retreat across a major palaeo-ice stream confluence zone, and has ramifications for the interpretation of recent fluctuations observed by satellites over short-time scales across marine-sectors of the Greenland and Antarctic ice sheets.

  5. Rapid marine deglaciation: asynchronous retreat dynamics between the Irish Sea Ice Stream and terrestrial outlet glaciers

    NASA Astrophysics Data System (ADS)

    Patton, H.; Hubbard, A.; Bradwell, T.; Glasser, N. F.; Hambrey, M. J.; Clark, C. D.

    2013-12-01

    Understanding the retreat behaviour of past marine-based ice sheets provides vital context for accurate assessments of the present stability and long-term response of contemporary polar ice sheets to climate and oceanic warming. Here new multibeam swath bathymetry data and sedimentological analysis are combined with high resolution ice-sheet modelling to reveal complex landform assemblages and process dynamics associated with deglaciation of the Celtic ice sheet within the Irish Sea Basin. Our reconstruction indicates a non-linear relationship between the rapidly receding Irish Sea Ice Stream and the retreat of outlet glaciers draining the adjacent, terrestrially based ice cap centred over Wales. Retreat of Welsh ice was episodic; superimposed over low-order oscillations of its margin are asynchronous outlet readvances driven by catchment-wide mass balance variations that are amplified through migration of the ice cap's main ice divide. Formation of large, linear ridges which extend at least 12.5 km offshore (locally known as sarns) and which dominate the regional bathymetry are attributed to repeated frontal and medial morainic deposition associated with the readvancing phases of these outlet glaciers. Our study provides new insight into ice-sheet extent, dynamics and non-linear retreat across a major palaeo-ice stream confluence zone, and has ramifications for the interpretation of recent fluctuations observed by satellites over short timescales across marine sectors of the Greenland and Antarctic ice sheets.

  6. Molecular motors

    NASA Astrophysics Data System (ADS)

    Allemand, Jean François Desbiolles, Pierre

    2015-10-01

    How do we move? More precisely, what are the molecular mechanisms that can explain that our muscles, made of very small components can move at a osopic scale? To answer these questions we must introduce molecular motors. Those motors are proteins, or small protein assemblies that, in our cells, transform chemical energy into mechanical work. Then, like we could do for a oscopic motor, used in a car or in a fan, we are going to study the basic behavior of these molecular machines, present what are their energy sources, calculate their power, their yield. If molecular motors are crucial for our oscopic movements, we are going to see that they are also essential to cellular transport and that considering the activity of some enzymes as molecular motors bring some interesting new insights on their activity.

  7. Linear force device

    NASA Technical Reports Server (NTRS)

    Clancy, John P.

    1988-01-01

    The object of the invention is to provide a mechanical force actuator which is lightweight and manipulatable and utilizes linear motion for push or pull forces while maintaining a constant overall length. The mechanical force producing mechanism comprises a linear actuator mechanism and a linear motion shaft mounted parallel to one another. The linear motion shaft is connected to a stationary or fixed housing and to a movable housing where the movable housing is mechanically actuated through actuator mechanism by either manual means or motor means. The housings are adapted to releasably receive a variety of jaw or pulling elements adapted for clamping or prying action. The stationary housing is adapted to be pivotally mounted to permit an angular position of the housing to allow the tool to adapt to skewed interfaces. The actuator mechanisms is operated by a gear train to obtain linear motion of the actuator mechanism.

  8. Venom regeneration in the centipede Scolopendra polymorpha: evidence for asynchronous venom component synthesis.

    PubMed

    Cooper, Allen M; Kelln, Wayne J; Hayes, William K

    2014-12-01

    Venom regeneration comprises a vital process in animals that rely on venom for prey capture and defense. Venom regeneration in scolopendromorph centipedes likely influences their ability to subdue prey and defend themselves, and may influence the quantity and quality of venom extracted by researchers investigating the venom's biochemistry. We investigated venom volume and total protein regeneration during the 14-day period subsequent to venom extraction in the North American centipede Scolopendra polymorpha. We further tested the hypothesis that venom protein components, separated by reversed-phase fast protein liquid chromatography (RP-FPLC), undergo asynchronous (non-parallel) synthesis. During the first 48 h, volume and protein mass increased linearly. Protein regeneration lagged behind volume regeneration, with 65–86% of venom volume and 29–47% of protein mass regenerated during the first 2 days. No additional regeneration occurred over the subsequent 12 days, and neither volume nor protein mass reached initial levels 7 months later (93% and 76%, respectively). Centipede body length was negatively associated with rate of venom regeneration. Analysis of chromatograms of individual venom samples revealed that 5 of 10 chromatographic regions and 12 of 28 peaks demonstrated changes in percent of total peak area (i.e., percent of total protein) among milking intervals, indicating that venom proteins are regenerated asynchronously. Moreover, specimens from Arizona and California differed in relative amounts of some venom components. The considerable regeneration of venom occurring within the first 48 h, despite the reduced protein content, suggests that predatory and defensive capacities are minimally constrained by the timing of venom replacement.

  9. Venom regeneration in the centipede Scolopendra polymorpha: evidence for asynchronous venom component synthesis.

    PubMed

    Cooper, Allen M; Kelln, Wayne J; Hayes, William K

    2014-12-01

    Venom regeneration comprises a vital process in animals that rely on venom for prey capture and defense. Venom regeneration in scolopendromorph centipedes likely influences their ability to subdue prey and defend themselves, and may influence the quantity and quality of venom extracted by researchers investigating the venom's biochemistry. We investigated venom volume and total protein regeneration during the 14-day period subsequent to venom extraction in the North American centipede Scolopendra polymorpha. We further tested the hypothesis that venom protein components, separated by reversed-phase fast protein liquid chromatography (RP-FPLC), undergo asynchronous (non-parallel) synthesis. During the first 48 h, volume and protein mass increased linearly. Protein regeneration lagged behind volume regeneration, with 65–86% of venom volume and 29–47% of protein mass regenerated during the first 2 days. No additional regeneration occurred over the subsequent 12 days, and neither volume nor protein mass reached initial levels 7 months later (93% and 76%, respectively). Centipede body length was negatively associated with rate of venom regeneration. Analysis of chromatograms of individual venom samples revealed that 5 of 10 chromatographic regions and 12 of 28 peaks demonstrated changes in percent of total peak area (i.e., percent of total protein) among milking intervals, indicating that venom proteins are regenerated asynchronously. Moreover, specimens from Arizona and California differed in relative amounts of some venom components. The considerable regeneration of venom occurring within the first 48 h, despite the reduced protein content, suggests that predatory and defensive capacities are minimally constrained by the timing of venom replacement. PMID:25456977

  10. Analysis and asynchronous detection of gradually unfolding errors during monitoring tasks.

    PubMed

    Omedes, Jason; Iturrate, Iñaki; Minguez, Javier; Montesano, Luis

    2015-10-01

    Human studies on cognitive control processes rely on tasks involving sudden-onset stimuli, which allow the analysis of these neural imprints to be time-locked and relative to the stimuli onset. Human perceptual decisions, however, comprise continuous processes where evidence accumulates until reaching a boundary. Surpassing the boundary leads to a decision where measured brain responses are associated to an internal, unknown onset. The lack of this onset for gradual stimuli hinders both the analyses of brain activity and the training of detectors. This paper studies electroencephalographic (EEG)-measurable signatures of human processing for sudden and gradual cognitive processes represented as a trajectory mismatch under a monitoring task. Time-locked potentials and brain-source analysis of the EEG of sudden mismatches revealed the typical components of event-related potentials and the involvement of brain structures related to cognitive control processing. For gradual mismatch events, time-locked analyses did not show any discernible EEG scalp pattern, despite related brain areas being, to a lesser extent, activated. However, and thanks to the use of non-linear pattern recognition algorithms, it is possible to train an asynchronous detector on sudden events and use it to detect gradual mismatches, as well as obtaining an estimate of their unknown onset. Post-hoc time-locked scalp and brain-source analyses revealed that the EEG patterns of detected gradual mismatches originated in brain areas related to cognitive control processing. This indicates that gradual events induce latency in the evaluation process but that similar brain mechanisms are present in sudden and gradual mismatch events. Furthermore, the proposed asynchronous detection model widens the scope of applications of brain-machine interfaces to other gradual processes. PMID:26193332

  11. An Electrostatic Stepper Motor

    NASA Astrophysics Data System (ADS)

    Partington, E. C.; Wong, Edward Chun Kay; Bullough, W. A.

    This paper describes a new concept in pulse controlled motor and precision linear actuator techniques. Piezo translators [PZT] employed to provide reciprocating primary motion are connected to a load via a controllable electrorheological fluid [ERF] clutch to form a programmable speed and step-width drive. Ideal considerations are used to quantify the limiting potential of the drive and details are given of its development and progress.

  12. Control of Dynamic Limb Motion Using Fatigue-Resistant Asynchronous Intrafascicular Multi-Electrode Stimulation

    PubMed Central

    Frankel, Mitchell A.; Mathews, V John; Clark, Gregory A.; Normann, Richard A.; Meek, Sanford G.

    2016-01-01

    Asynchronous intrafascicular multi-electrode stimulation (aIFMS) of small independent populations of peripheral nerve motor axons can evoke selective, fatigue-resistant muscle forces. We previously developed a real-time proportional closed-loop control method for aIFMS generation of isometric muscle force and the present work extends and adapts this closed-loop controller to the more demanding task of dynamically controlling joint position in the presence of opposing joint torque. A proportional-integral-velocity controller, with integrator anti-windup strategies, was experimentally validated as a means to evoke motion about the hind-limb ankle joint of an anesthetized feline via aIFMS stimulation of fast-twitch plantar-flexor muscles. The controller was successful in evoking steps in joint position with 2.4% overshoot, 2.3-s rise time, 4.5-s settling time, and near-zero steady-state error. Controlled step responses were consistent across changes in step size, stable against external disturbances, and reliable over time. The controller was able to evoke smooth eccentric motion at joint velocities up to 8 deg./s, as well as sinusoidal trajectories with frequencies up to 0.1 Hz, with time delays less than 1.5 s. These experiments provide important insights toward creating a robust closed-loop aIFMS controller that can evoke precise fatigue-resistant motion in paralyzed individuals, despite the complexities introduced by aIFMS. PMID:27679557

  13. Control of Dynamic Limb Motion Using Fatigue-Resistant Asynchronous Intrafascicular Multi-Electrode Stimulation

    PubMed Central

    Frankel, Mitchell A.; Mathews, V John; Clark, Gregory A.; Normann, Richard A.; Meek, Sanford G.

    2016-01-01

    Asynchronous intrafascicular multi-electrode stimulation (aIFMS) of small independent populations of peripheral nerve motor axons can evoke selective, fatigue-resistant muscle forces. We previously developed a real-time proportional closed-loop control method for aIFMS generation of isometric muscle force and the present work extends and adapts this closed-loop controller to the more demanding task of dynamically controlling joint position in the presence of opposing joint torque. A proportional-integral-velocity controller, with integrator anti-windup strategies, was experimentally validated as a means to evoke motion about the hind-limb ankle joint of an anesthetized feline via aIFMS stimulation of fast-twitch plantar-flexor muscles. The controller was successful in evoking steps in joint position with 2.4% overshoot, 2.3-s rise time, 4.5-s settling time, and near-zero steady-state error. Controlled step responses were consistent across changes in step size, stable against external disturbances, and reliable over time. The controller was able to evoke smooth eccentric motion at joint velocities up to 8 deg./s, as well as sinusoidal trajectories with frequencies up to 0.1 Hz, with time delays less than 1.5 s. These experiments provide important insights toward creating a robust closed-loop aIFMS controller that can evoke precise fatigue-resistant motion in paralyzed individuals, despite the complexities introduced by aIFMS.

  14. Control of Dynamic Limb Motion Using Fatigue-Resistant Asynchronous Intrafascicular Multi-Electrode Stimulation.

    PubMed

    Frankel, Mitchell A; Mathews, V John; Clark, Gregory A; Normann, Richard A; Meek, Sanford G

    2016-01-01

    Asynchronous intrafascicular multi-electrode stimulation (aIFMS) of small independent populations of peripheral nerve motor axons can evoke selective, fatigue-resistant muscle forces. We previously developed a real-time proportional closed-loop control method for aIFMS generation of isometric muscle force and the present work extends and adapts this closed-loop controller to the more demanding task of dynamically controlling joint position in the presence of opposing joint torque. A proportional-integral-velocity controller, with integrator anti-windup strategies, was experimentally validated as a means to evoke motion about the hind-limb ankle joint of an anesthetized feline via aIFMS stimulation of fast-twitch plantar-flexor muscles. The controller was successful in evoking steps in joint position with 2.4% overshoot, 2.3-s rise time, 4.5-s settling time, and near-zero steady-state error. Controlled step responses were consistent across changes in step size, stable against external disturbances, and reliable over time. The controller was able to evoke smooth eccentric motion at joint velocities up to 8 deg./s, as well as sinusoidal trajectories with frequencies up to 0.1 Hz, with time delays less than 1.5 s. These experiments provide important insights toward creating a robust closed-loop aIFMS controller that can evoke precise fatigue-resistant motion in paralyzed individuals, despite the complexities introduced by aIFMS.

  15. Contrôle d'une machine asynchrone par estimation robuste de la vitesse

    NASA Astrophysics Data System (ADS)

    Roboam, X.; Hapiot, J. C.; de Fornel, B.; Andrieux, C.

    1992-03-01

    This paper describes the study and the implementation of a variable speed drive for induction motor with no mechanical sensor. Power is supplied by a current-controlled voltage-source inverter. The lack of information (only two line-current sensors) requires an accurate and reliable reconstitution of the main quantities not sensed (flux, speed, torque). The results obtained show the excellent quality of the estimated speed, whatever the operating condition and despite the perturbations applied to the system. This study finally leads to the construction of a prototype. Cet article décrit l'étude et la mise en oeuvre d'un variateur de vitesse pour machine asynchrone sans capteur mécanique et alimentée par un onduleur de tension cotrôlé en courant. Le manque d'information (2 capteurs de courants de ligne uniquement) nécessite la reconstitution fiable et précise des grandeurs fondamentales non mesurées (flux, vitesse, couple). Les résultats obtenus montrent notamment l'excellente qualité de l'estimation de vitesse, quel que soit le point de fonctionnement et en dépit des perturbations auxquelles le système est soumis. Cette étude donne lieu à la réalisation d'un variateur prototype.

  16. Control of Dynamic Limb Motion Using Fatigue-Resistant Asynchronous Intrafascicular Multi-Electrode Stimulation.

    PubMed

    Frankel, Mitchell A; Mathews, V John; Clark, Gregory A; Normann, Richard A; Meek, Sanford G

    2016-01-01

    Asynchronous intrafascicular multi-electrode stimulation (aIFMS) of small independent populations of peripheral nerve motor axons can evoke selective, fatigue-resistant muscle forces. We previously developed a real-time proportional closed-loop control method for aIFMS generation of isometric muscle force and the present work extends and adapts this closed-loop controller to the more demanding task of dynamically controlling joint position in the presence of opposing joint torque. A proportional-integral-velocity controller, with integrator anti-windup strategies, was experimentally validated as a means to evoke motion about the hind-limb ankle joint of an anesthetized feline via aIFMS stimulation of fast-twitch plantar-flexor muscles. The controller was successful in evoking steps in joint position with 2.4% overshoot, 2.3-s rise time, 4.5-s settling time, and near-zero steady-state error. Controlled step responses were consistent across changes in step size, stable against external disturbances, and reliable over time. The controller was able to evoke smooth eccentric motion at joint velocities up to 8 deg./s, as well as sinusoidal trajectories with frequencies up to 0.1 Hz, with time delays less than 1.5 s. These experiments provide important insights toward creating a robust closed-loop aIFMS controller that can evoke precise fatigue-resistant motion in paralyzed individuals, despite the complexities introduced by aIFMS. PMID:27679557

  17. P300-based brain-computer interface for environmental control: an asynchronous approach

    NASA Astrophysics Data System (ADS)

    Aloise, F.; Schettini, F.; Aricò, P.; Leotta, F.; Salinari, S.; Mattia, D.; Babiloni, F.; Cincotti, F.

    2011-04-01

    Brain-computer interface (BCI) systems allow people with severe motor disabilities to communicate and interact with the external world. The P300 potential is one of the most used control signals for EEG-based BCIs. Classic P300-based BCIs work in a synchronous mode; the synchronous control assumes that the user is constantly attending to the stimulation, and the number of stimulation sequences is fixed a priori. This issue is an obstacle for the use of these systems in everyday life; users will be engaged in a continuous control state, their distractions will cause misclassification and the speed of selection will not take into account users' current psychophysical condition. An efficient BCI system should be able to understand the user's intentions from the ongoing EEG instead. Also, it has to refrain from making a selection when the user is engaged in a different activity and it should increase or decrease its speed of selection depending on the current user's state. We addressed these issues by introducing an asynchronous BCI and tested its capabilities for effective environmental monitoring, involving 11 volunteers in three recording sessions. Results show that this BCI system can increase the bit rate during control periods while the system is proved to be very efficient in avoiding false negatives when the users are engaged in other tasks.

  18. Stepper motor

    NASA Technical Reports Server (NTRS)

    Dekramer, Cornelis

    1994-01-01

    The purpose of this document is to describe the more commonly used permanent magnet stepper motors for spaceflight. It will discuss the mechanical and electrical aspects of the devices, their torque behavior, those parameters which need to be controlled and measured, and test methods to be employed. It will also discuss torque margins, compare these to the existing margin requirements, and determine the applicability of these requirements. Finally it will attempt to generate a set of requirements which will be used in any stepper motor procurement and will fully characterize the stepper motor behavior in a consistent and repeatable fashion.

  19. Direct drive field actuator motors

    DOEpatents

    Grahn, A.R.

    1998-03-10

    A positive-drive field actuator motor is described which includes a stator carrying at least one field actuator which changes in dimension responsive to application of an energy field, and at least one drive shoe movable by the dimensional changes of the field actuator to contact and move a rotor element with respect to the stator. Various embodiments of the motor are disclosed, and the rotor element may be moved linearly or arcuately. 62 figs.

  20. Direct drive field actuator motors

    DOEpatents

    Grahn, Allen R.

    1998-01-01

    A positive-drive field actuator motor including a stator carrying at least one field actuator which changes in dimension responsive to application of an energy field, and at least one drive shoe movable by the dimensional changes of the field actuator to contact and move a rotor element with respect to the stator. Various embodiments of the motor are disclosed, and the rotor element may be moved linearly or arcuately.

  1. Molecular Motors: A Theorist's Perspective

    NASA Astrophysics Data System (ADS)

    Kolomeisky, Anatoly B.; Fisher, Michael E.

    2007-05-01

    Individual molecular motors, or motor proteins, are enzymatic molecules that convert chemical energy, typically obtained from the hydrolysis of ATP (adenosine triphosphate), into mechanical work and motion. Processive motor proteins, such as kinesin, dynein, and certain myosins, step unidirectionally along linear tracks, specifically microtubules and actin filaments, and play a crucial role in cellular transport processes, organization, and function. In this review some theoretical aspects of motor-protein dynamics are presented in the light of current experimental methods that enable the measurement of the biochemical and biomechanical properties on a single-molecule basis. After a brief discussion of continuum ratchet concepts, we focus on discrete kinetic and stochastic models that yield predictions for the mean velocity, V(F, [ATP], …), and other observables as a function of an imposed load force F, the ATP concentration, and other variables. The combination of appropriate theory with single-molecule observations should help uncover the mechanisms underlying motor-protein function.

  2. Linear Proof-Mass Actuator

    NASA Technical Reports Server (NTRS)

    Holloway, Sidney E., III; Crossley, Edward A.; Miller, James B.; Jones, Irby W.; Davis, C. Calvin; Behun, Vaughn D.; Goodrich, Lewis R., Sr.

    1995-01-01

    Linear proof-mass actuator (LPMA) is friction-driven linear mass actuator capable of applying controlled force to structure in outer space to damp out oscillations. Capable of high accelerations and provides smooth, bidirectional travel of mass. Design eliminates gears and belts. LPMA strong enough to be used terrestrially where linear actuators needed to excite or damp out oscillations. High flexibility designed into LPMA by varying size of motors, mass, and length of stroke, and by modifying control software.

  3. Asynchronous Laser Transponders for Precise Interplanetary Ranging and Time Transfer

    NASA Technical Reports Server (NTRS)

    Degnan, John J.; Smith, David E. (Technical Monitor)

    2001-01-01

    The feasibility of a two-way asynchronous (i.e. independently firing) interplanetary laser transponder pair, capable of decimeter ranging and subnanosecond time transfer from Earth to a spacecraft anywhere within the inner Solar System, is discussed. In the Introduction, we briefly discuss the current state-of-the-art in Satellite Laser Ranging (SLR) and Lunar Laser Ranging (LLR) which use single-ended range measurements to a passive optical reflector, and the limitations of this approach in ranging beyond the Moon to the planets. In Section 2 of this paper, we describe two types of transponders (echo and asynchronous), introduce the transponder link equation and the concept of "balanced" transponders, describe how range and time can be transferred between terminals, and preview the potential advantages of photon counting asynchronous transponders for interplanetary applications. In Section 3, we discuss and provide mathematical models for the various sources of noise in an interplanetary transponder link including planetary albedo, solar or lunar illumination of the local atmosphere, and laser backscatter off the local atmosphere. In Section 4, we introduce the key engineering elements of an interplanetary laser transponder and develop an operational scenario for the acquisition and tracking of the opposite terminal. In Section 5, we use the theoretical models of th previous sections to perform an Earth-Mars link analysis over a full synodic period of 780 days under the simplifying assumption of coaxial, coplanar, circular orbits. We demonstrate that, using slightly modified versions of existing space and ground based laser systems, an Earth-Mars transponder link is not only feasible but quite robust. We also demonstrate through analysis the advantages and feasibility of compact, low output power (<300 mW photon-counting transponders using NASA's developmental SLR2000 satellite laser ranging system as the Earth terminal. Section 6 provides a summary of the results

  4. Using process groups to implement failure detection in asynchronous environments

    NASA Technical Reports Server (NTRS)

    Ricciardi, Aleta M.; Birman, Kenneth P.

    1991-01-01

    Agreement on the membership of a group of processes in a distributed system is a basic problem that arises in a wide range of applications. Such groups occur when a set of processes cooperate to perform some task, share memory, monitor one another, subdivide a computation, and so forth. The group membership problems is discussed as it relates to failure detection in asynchronous, distributed systems. A rigorous, formal specification for group membership is presented under this interpretation. A solution is then presented for this problem.

  5. A wavelet approach to binary blackholes with asynchronous multitasking

    NASA Astrophysics Data System (ADS)

    Lim, Hyun; Hirschmann, Eric; Neilsen, David; Anderson, Matthew; Debuhr, Jackson; Zhang, Bo

    2016-03-01

    Highly accurate simulations of binary black holes and neutron stars are needed to address a variety of interesting problems in relativistic astrophysics. We present a new method for the solving the Einstein equations (BSSN formulation) using iterated interpolating wavelets. Wavelet coefficients provide a direct measure of the local approximation error for the solution and place collocation points that naturally adapt to features of the solution. Further, they exhibit exponential convergence on unevenly spaced collection points. The parallel implementation of the wavelet simulation framework presented here deviates from conventional practice in combining multi-threading with a form of message-driven computation sometimes referred to as asynchronous multitasking.

  6. Using Television Sitcoms to Facilitate Asynchronous Discussions in the Online Communication Course

    ERIC Educational Resources Information Center

    Tolman, Elizabeth; Asbury, Bryan

    2012-01-01

    Asynchronous discussions are a useful instructional resource in the online communication course. In discussion groups students have the opportunity to actively participate and interact with students and the instructor. Asynchronous communication allows for flexibility because "participants can interact with significant amounts of time between…

  7. Designing Asynchronous, Text-Based Computer Conferences: Ten Research-Based Suggestions

    ERIC Educational Resources Information Center

    Choitz, Paul; Lee, Doris

    2006-01-01

    Asynchronous computer conferencing refers to the use of computer software and a network enabling participants to post messages that allow discourse to continue even though interactions may be extended over days and weeks. Asynchronous conferences are time-independent, adapting to multiple time zones and learner schedules. Such activities as…

  8. Fostering Critical Reflection in a Computer-Based, Asynchronously Delivered Diversity Training Course

    ERIC Educational Resources Information Center

    Givhan, Shawn T.

    2013-01-01

    This dissertation study chronicles the creation of a computer-based, asynchronously delivered diversity training course for a state agency. The course format enabled efficient delivery of a mandatory curriculum to the Massachusetts Department of State Police workforce. However, the asynchronous format posed a challenge to achieving the learning…

  9. Anonymity and Motivation in Asynchronous Discussions and L2 Vocabulary Learning

    ERIC Educational Resources Information Center

    Polat, Nihat; Mancilla, Rae; Mahalingappa, Laura

    2013-01-01

    This study investigates L2 attainment in asynchronous online environments, specifically possible relationships among anonymity, L2 motivation, participation in discussions, quality of L2 production, and success in L2 vocabulary learning. It examines, in asynchronous discussions, (a) if participation and (b) motivation contribute to L2 vocabulary…

  10. Elements that Impact Facilitation of an Asynchronous Professional Learning Community: A Participatory Action Research Exploration

    ERIC Educational Resources Information Center

    Hofer, Marilyn

    2009-01-01

    Despite that fact that the demand for asynchronous learning is booming, the literature on distance learning facilitation skills is lacking (Sherry, 1996). This study supports the premise that the use of paraphrasing strategies impacts learners in an asynchronous environment. The research question has been narrowed to inspect the particular…

  11. Designing Asynchronous Online Discussion Environments: Recent Progress and Possible Future Directions

    ERIC Educational Resources Information Center

    Gao, Fei; Zhang, Tianyi; Franklin, Teresa

    2013-01-01

    Asynchronous online discussion environments are important platforms to support learning. Research suggests, however, threaded forums, one of the most popular asynchronous discussion environments, do not often foster productive online discussions naturally. This paper explores how certain properties of threaded forums have affected or constrained…

  12. A Multi-Perspective Investigation into Learners' Interaction in Asynchronous Computer-Mediated Communication (CMC)

    ERIC Educational Resources Information Center

    Çardak, Çigdem Suzan

    2016-01-01

    This article focusses on graduate level students' interactions during asynchronous CMC activities of an online course about the teaching profession in Turkey. The instructor of the course designed and facilitated a semester-long asynchronous CMC on forum discussions, and investigated the interaction of learners in multiple perspectives: learners'…

  13. Postgraduate Students' Knowledge Construction during Asynchronous Computer Conferences in a Blended Learning Environment: A Malaysian Experience

    ERIC Educational Resources Information Center

    Kian-Sam, Hong; Lee, Julia Ai Cheng

    2008-01-01

    Blended learning, using e-learning tools to supplement existing on campus learning, often incorporates asynchronous computer conferencing as a means of augmenting knowledge construction among students. This case study reports findings about levels of knowledge construction amongst adult postgraduate students in six asynchronous computer…

  14. The Role of Offline Metalanguage Talk in Asynchronous Computer-Mediated Communication

    ERIC Educational Resources Information Center

    Kitade, Keiko

    2008-01-01

    In order to demonstrate how learners utilize the text-based asynchronous attributes of the Bulletin Board System, this study explored Japanese-as-a-second-language learners' metalanguage episodes (Swain & Lapkin, 1995, 1998) in offline verbal peer speech and online asynchronous discussions with their Japanese key pals. The findings suggest the…

  15. Designing Asynchronous Communication Tools for Optimization of Patient-Clinician Coordination.

    PubMed

    Eschler, Jordan; Liu, Leslie S; Vizer, Lisa M; McClure, Jennifer B; Lozano, Paula; Pratt, Wanda; Ralston, James D

    2015-01-01

    Asynchronous communication outside the clinical setting has both enriched and complicated patient-clinician interactions. Many patients can now interact with a patient portal 24 hours a day, asking questions of their clinicians via secure message, checking lab results, ordering medication refills, or making appointments. However, the mode of communication (asynchronous) and the nature of the interaction (lacking tone or body language) strip valuable information from each side of patient-clinician asynchronous communication. Using interviews with 34 individuals who actively manage a chronic illness of their own, or for a child or partner, we elicited narratives about patients' experiences and expectations for using asynchronous communication to address medical issues with their clinicians. Based on these perspectives, we present opportunities for designing asynchronous communication tools to better facilitate understanding of and coordination around care activities between patients and clinicians.

  16. Designing Asynchronous Communication Tools for Optimization of Patient-Clinician Coordination

    PubMed Central

    Eschler, Jordan; Liu, Leslie S.; Vizer, Lisa M.; McClure, Jennifer B.; Lozano, Paula; Pratt, Wanda; Ralston, James D.

    2015-01-01

    Asynchronous communication outside the clinical setting has both enriched and complicated patient-clinician interactions. Many patients can now interact with a patient portal 24 hours a day, asking questions of their clinicians via secure message, checking lab results, ordering medication refills, or making appointments. However, the mode of communication (asynchronous) and the nature of the interaction (lacking tone or body language) strip valuable information from each side of patient-clinician asynchronous communication. Using interviews with 34 individuals who actively manage a chronic illness of their own, or for a child or partner, we elicited narratives about patients’ experiences and expectations for using asynchronous communication to address medical issues with their clinicians. Based on these perspectives, we present opportunities for designing asynchronous communication tools to better facilitate understanding of and coordination around care activities between patients and clinicians. PMID:26958188

  17. Cooperative and asynchronous stereo vision for dynamic vision sensors

    NASA Astrophysics Data System (ADS)

    Piatkowska, E.; Belbachir, A. N.; Gelautz, M.

    2014-05-01

    Dynamic vision sensors (DVSs) encode visual input as a stream of events generated upon relative light intensity changes in the scene. These sensors have the advantage of allowing simultaneously high temporal resolution (better than 10 µs) and wide dynamic range (>120 dB) at sparse data representation, which is not possible with clocked vision sensors. In this paper, we focus on the task of stereo reconstruction. The spatiotemporal and asynchronous aspects of data provided by the sensor impose a different stereo reconstruction approach from the one applied for synchronous frame-based cameras. We propose to model the event-driven stereo matching by a cooperative network (Marr and Poggio 1976 Science 194 283-7). The history of the recent activity in the scene is stored in the network, which serves as spatiotemporal context used in disparity calculation for each incoming event. The network constantly evolves in time, as events are generated. In our work, not only the spatiotemporal aspect of the data is preserved but also the matching is performed asynchronously. The results of the experiments prove that the proposed approach is well adapted for DVS data and can be successfully used for disparity calculation.

  18. Asynchronous Detection of Trials Onset from Raw EEG Signals.

    PubMed

    Lopez-Gordo, M A; Grima Murcia, M D; Padilla, Pablo; Pelayo, F; Fernandez, E

    2016-11-01

    Clinical processing of event-related potentials (ERPs) requires a precise synchrony between the stimulation and the acquisition units that are guaranteed by means of a physical link between them. This precise synchrony is needed since temporal misalignments during trial averaging can lead to high deviations of peak times, thus causing error in diagnosis or inefficiency in classification in brain-computer interfaces (BCIs). Out of the laboratory, mobile EEG systems and BCI headsets are not provided with the physical link, thus being inadequate for acquisition of ERPs. In this study, we propose a method for the asynchronous detection of trials onset from raw EEG without physical links. We validate it with a BCI application based on the dichotic listening task. The user goal was to attend the cued auditory message and to report three keywords contained in it while ignoring the other message. The BCI goal was to detect the attended message from the analysis of auditory ERPs. The rate of successful onset detection in both synchronous (using the real onset) and asynchronous (blind detection of trial onset from raw EEG) was 73% with a synchronization error of less than 1[Formula: see text]ms. The level of synchronization provided by this proposal would allow home-based acquisition of ERPs with low cost BCI headsets and any media player unit without physical links between them. PMID:27377663

  19. Experience with synchronous and asynchronous digital control systems

    NASA Technical Reports Server (NTRS)

    Regenie, V. A.; Chacon, C. V.; Lock, W. P.

    1986-01-01

    Flight control systems have undergone a revolution since the days of simple mechanical linkages; presently the most advanced systems are full-authority, full-time digital systems controlling unstable aircraft. With the use of advanced control systems, the aerodynamic design can incorporate features that allow greater performance and fuel savings, as can be seen on the new Airbus design and advanced tactical fighter concepts. These advanced aircraft will be and are relying on the flight control system to provide the stability and handling qualities required for safe flight and to allow the pilot to control the aircraft. Various design philosophies have been proposed and followed to investigate system architectures for these advanced flight control systems. One major area of discussion is whether a multichannel digital control system should be synchronous or asynchronous. This paper addressed the flight experience at the Dryden Flight Research Facility of NASA's Ames Research Center with both synchronous and asynchronous digital flight control systems. Four different flight control systems are evaluated against criteria such as software reliability, cost increases, and schedule delays.

  20. A Parallel Particle Swarm Optimization Algorithm Accelerated by Asynchronous Evaluations

    NASA Technical Reports Server (NTRS)

    Venter, Gerhard; Sobieszczanski-Sobieski, Jaroslaw

    2005-01-01

    A parallel Particle Swarm Optimization (PSO) algorithm is presented. Particle swarm optimization is a fairly recent addition to the family of non-gradient based, probabilistic search algorithms that is based on a simplified social model and is closely tied to swarming theory. Although PSO algorithms present several attractive properties to the designer, they are plagued by high computational cost as measured by elapsed time. One approach to reduce the elapsed time is to make use of coarse-grained parallelization to evaluate the design points. Previous parallel PSO algorithms were mostly implemented in a synchronous manner, where all design points within a design iteration are evaluated before the next iteration is started. This approach leads to poor parallel speedup in cases where a heterogeneous parallel environment is used and/or where the analysis time depends on the design point being analyzed. This paper introduces an asynchronous parallel PSO algorithm that greatly improves the parallel e ciency. The asynchronous algorithm is benchmarked on a cluster assembled of Apple Macintosh G5 desktop computers, using the multi-disciplinary optimization of a typical transport aircraft wing as an example.

  1. Asynchronous glaciation at Nanga Parbat, northwestern Himalaya Mountains, Pakistan

    NASA Astrophysics Data System (ADS)

    Phillips, William M.; Sloan, Valerie F.; Shroder, John F., Jr.; Sharma, Pankaj; Clarke, Michèle L.; Rendell, Helen M.

    2000-05-01

    We present a new glacial chronology demonstrating asynchroneity between advances of Himalayan glaciers and Northern Hemisphere ice-sheet volumes. Glaciers at Nanga Parbat expanded during the early to middle Holocene ca. 9.0 5.5 ka. No major advances at Nanga Parbat during the last global glacial stage of marine oxygen isotope stage 2 (MIS-2) between 24 and 11 ka were identified. Preliminary evidence also indicates advances between ca. 60 and 30 ka. These periods of high ice volume coincide with warm, wet regional climates dominated by a strong southwest Asian summer monsoon. The general lack of deposits dating from MIS-2 suggests that Nanga Parbat was too arid to support expanded ice during this period of low monsoon intensity. Advances during warm, wet periods are possible for the high-altitude summer accumulation glaciers typical of the Himalayas, and explain asynchronous behavior. However, the Holocene advances at Nanga Parbat appear to have been forced by an abrupt drop in temperature ca. 8.4 8.0 ka and an increase in winter precipitation ca. 7 5.5 ka. These results highlight the overall sensitivity of Himalayan glaciation to orbital forcing of monsoon intensity, and on millennial or shorter time scales, to changes in North Atlantic circulation.

  2. Formation of the wide asynchronous binary asteroid population

    SciTech Connect

    Jacobson, Seth A.; Scheeres, Daniel J.; McMahon, Jay

    2014-01-01

    We propose and analyze a new mechanism for the formation of the wide asynchronous binary population. These binary asteroids have wide semimajor axes relative to most near-Earth and main belt asteroid systems. Confirmed members have rapidly rotating primaries and satellites that are not tidally locked. Previously suggested formation mechanisms from impact ejecta, from planetary flybys, and directly from rotational fission events cannot satisfy all of the observations. The newly hypothesized mechanism works as follows: (1) these systems are formed from rotational fission, (2) their satellites are tidally locked, (3) their orbits are expanded by the binary Yarkovsky-O'Keefe-Radzievskii-Paddack (BYORP) effect, (4) their satellites desynchronize as a result of the adiabatic invariance between the libration of the secondary and the mutual orbit, and (5) the secondary avoids resynchronization because of the YORP effect. This seemingly complex chain of events is a natural pathway for binaries with satellites that have particular shapes, which define the BYORP effect torque that acts on the system. After detailing the theory, we analyze each of the wide asynchronous binary members and candidates to assess their most likely formation mechanism. Finally, we suggest possible future observations to check and constrain our hypothesis.

  3. The Role of Online Instructors in Asynchronous Discussion Forums

    NASA Astrophysics Data System (ADS)

    Maddison, Sarah T.; Mazzolini, M. M.; Gay, P. L.

    2007-05-01

    We present qualitative results and advice on the role of online instructors in asynchronous discussion forums and the technologies used to support online interactive learning. Results are based on six years of designing, coordinating, evaluating and teaching into the distance learning program Swinburne Astronomy Online. We discuss why we chose to use asynchronous rather than synchronous discussion forums and how we have implemented them; how we train our online instructors and their role as a 'guide on the side'; techniques for moderating the volume of forum postings while ensuring a constructive learning environment; and methods for dealing with both mixed class preparedness and 'challenging' students within an online environment. Our research into the interaction between students and instructors in online forums provides some interesting (and often counter-intuitive) insights into the relationship between the number and length of student postings and the posting patterns of their instructors. We compare these results with qualitative feedback from both students and instructors on their perception of the online learning and teaching experience.

  4. Asynchronous replica exchange software for grid and heterogeneous computing

    NASA Astrophysics Data System (ADS)

    Gallicchio, Emilio; Xia, Junchao; Flynn, William F.; Zhang, Baofeng; Samlalsingh, Sade; Mentes, Ahmet; Levy, Ronald M.

    2015-11-01

    Parallel replica exchange sampling is an extended ensemble technique often used to accelerate the exploration of the conformational ensemble of atomistic molecular simulations of chemical systems. Inter-process communication and coordination requirements have historically discouraged the deployment of replica exchange on distributed and heterogeneous resources. Here we describe the architecture of a software (named ASyncRE) for performing asynchronous replica exchange molecular simulations on volunteered computing grids and heterogeneous high performance clusters. The asynchronous replica exchange algorithm on which the software is based avoids centralized synchronization steps and the need for direct communication between remote processes. It allows molecular dynamics threads to progress at different rates and enables parameter exchanges among arbitrary sets of replicas independently from other replicas. ASyncRE is written in Python following a modular design conducive to extensions to various replica exchange schemes and molecular dynamics engines. Applications of the software for the modeling of association equilibria of supramolecular and macromolecular complexes on BOINC campus computational grids and on the CPU/MIC heterogeneous hardware of the XSEDE Stampede supercomputer are illustrated. They show the ability of ASyncRE to utilize large grids of desktop computers running the Windows, MacOS, and/or Linux operating systems as well as collections of high performance heterogeneous hardware devices.

  5. Asynchronous Transfer Mode Quality-of-Service Testing

    NASA Technical Reports Server (NTRS)

    Ivancic, William D.

    1998-01-01

    In support of satellite-ATM interoperability, researchers at the NASA Lewis Research Center performed asynchronous transfer mode (ATM) quality-of-service experiments using MPEG-2 (ATM application layer 5, AAL5) over ATM over an emulated satellite link. The purpose of these experiments was to determine the free-space link quality necessary to use the ATM protocol to transmit high-quality multimedia information. The experimental results have been submitted to various International Telecommunications Union (ITU) study groups in order to improve and modify current standards and recommendations for the telecommunications industry. Quality-of-service parameters for Class I, stringent class requirements for ITU-T I.356 are currently being debated. The experimental results presented will help to establish these quality-of-service thresholds. This material will also be useful in the development of the ITU-R WP-4B's Draft Preliminary New Recommendation on the Transmission of Asynchronous Transfer Mode Traffic via Satellite (Rec. S.atm).

  6. Formation of the Wide Asynchronous Binary Asteroid Population

    NASA Astrophysics Data System (ADS)

    Jacobson, Seth A.; Scheeres, Daniel J.; McMahon, Jay

    2014-01-01

    We propose and analyze a new mechanism for the formation of the wide asynchronous binary population. These binary asteroids have wide semimajor axes relative to most near-Earth and main belt asteroid systems. Confirmed members have rapidly rotating primaries and satellites that are not tidally locked. Previously suggested formation mechanisms from impact ejecta, from planetary flybys, and directly from rotational fission events cannot satisfy all of the observations. The newly hypothesized mechanism works as follows: (1) these systems are formed from rotational fission, (2) their satellites are tidally locked, (3) their orbits are expanded by the binary Yarkovsky-O'Keefe-Radzievskii-Paddack (BYORP) effect, (4) their satellites desynchronize as a result of the adiabatic invariance between the libration of the secondary and the mutual orbit, and (5) the secondary avoids resynchronization because of the YORP effect. This seemingly complex chain of events is a natural pathway for binaries with satellites that have particular shapes, which define the BYORP effect torque that acts on the system. After detailing the theory, we analyze each of the wide asynchronous binary members and candidates to assess their most likely formation mechanism. Finally, we suggest possible future observations to check and constrain our hypothesis.

  7. Synaptic scaling stabilizes persistent activity driven by asynchronous neurotransmitter release.

    PubMed

    Volman, Vladislav; Gerkin, Richard C

    2011-04-01

    Small networks of cultured hippocampal neurons respond to transient stimulation with rhythmic network activity (reverberation) that persists for several seconds, constituting an in vitro model of synchrony, working memory, and seizure. This mode of activity has been shown theoretically and experimentally to depend on asynchronous neurotransmitter release (an essential feature of the developing hippocampus) and is supported by a variety of developing neuronal networks despite variability in the size of populations (10-200 neurons) and in patterns of synaptic connectivity. It has previously been reported in computational models that "small-world" connection topology is ideal for the propagation of similar modes of network activity, although this has been shown only for neurons utilizing synchronous (phasic) synaptic transmission. We investigated how topological constraints on synaptic connectivity could shape the stability of reverberations in small networks that also use asynchronous synaptic transmission. We found that reverberation duration in such networks was resistant to changes in topology and scaled poorly with network size. However, normalization of synaptic drive, by reducing the variance of synaptic input across neurons, stabilized reverberation in such networks. Our results thus suggest that the stability of both normal and pathological states in developing networks might be shaped by variance-normalizing constraints on synaptic drive. We offer an experimental prediction for the consequences of such regulation on the behavior of small networks.

  8. Advanced Motors

    SciTech Connect

    Knoth, Edward A; Chelluri, Bhanumathi; Schumaker, Edward J

    2012-12-14

    vProject Summary Transportation energy usage is predicted to increase substantially by 2020. Hybrid vehicles and fuel cell powered vehicles are destined to become more prominent as fuel prices rise with the demand. Hybrid and fuel cell vehicle platforms are both dependent on high performance electric motors. Electric motors for transportation duty will require sizeable low-speed torque to accelerate the vehicle. As motor speed increases, the torque requirement decreases which results in a nearly constant power motor output. Interior permanent magnet synchronous motors (IPMSM) are well suited for this duty. , , These rotor geometries are configured in straight lines and semi circular arc shapes. These designs are of limited configurations because of the lack of availability of permanent magnets of any other shapes at present. We propose to fabricate rotors via a novel processing approach where we start with magnet powders and compact them into a net shape rotor in a single step. Using this approach, widely different rotor designs can be implemented for efficiency. The current limitation on magnet shape and thickness will be eliminated. This is accomplished by co-filling magnet and soft iron powders at specified locations in intricate shapes using specially designed dies and automatic powder filling station. The process fundamentals for accomplishing occurred under a previous Applied Technology Program titled, Motors and Generators for the 21st Century. New efficient motor designs that are not currently possible (or cost prohibitive) can be accomplished by this approach. Such an approach to motor fabrication opens up a new dimension in motor design. Feasibility Results We were able to optimize a IPMSM rotor to take advantage of the powder co-filling and DMC compaction processing methods. The minimum low speed torque requirement of 5 N-m can be met through an optimized design with magnet material having a Br capability of 0.2 T. This level of magnetic performance can

  9. Motor neglect.

    PubMed Central

    Laplane, D; Degos, J D

    1983-01-01

    Motor neglect is characterised by an underutilisation of one side, without defects of strength, reflexes or sensibility. Twenty cases of frontal, parietal and thalamic lesions causing motor neglect, but all without sensory neglect, are reported. It is proposed that the cerebral structures involved in motor neglect are the same as those for sensory neglect and for the preparation of movement. As in sensory neglect, the multiplicity of the structures concerned suggests that this interconnection is necessary to maintain a sufficient level of activity. Predominance of left sided neglect by right sided lesions suggests that the left hemisphere is dominant for deliberate activity; hemispheric dominance could be applied to sensory neglect where conscious awareness would play the role of deliberate activity. PMID:6842219

  10. Additional Drive Circuitry for Piezoelectric Screw Motors

    NASA Technical Reports Server (NTRS)

    Smythe, Robert; Palmer, Dean; Gursel, Yekta; Reder, Leonard; Savedra, Raymond

    2004-01-01

    Modules of additional drive circuitry have been developed to enhance the functionality of a family of commercially available positioning motors (Picomotor . or equivalent) that provide linear motion controllable, in principle, to within increments .30 nm. A motor of this type includes a piezoelectric actuator that turns a screw. Unlike traditional piezoelectrically actuated mechanisms, a motor of this type does not rely on the piezoelectric transducer to hold position: the screw does not turn except when the drive signal is applied to the actuator.

  11. Magnetostrictive direct drive motors

    NASA Technical Reports Server (NTRS)

    Naik, Dipak; Dehoff, P. H.

    1992-01-01

    A new rare earth alloy, Terfenol-D, combines low frequency operation and extremely high energy density with high magnetostriction. Its material properties make it suitable as a drive element for actuators requiring high output torque. The high strains, the high forces and the high controllability of Terfenol alloys provide a powerful and challenging basis for new ways to generate motion in actuators. Two prototypes of motors using Terfenol-D rods were developed at NASA Goddard. The basic principles of operation are provided of the motor along with other relevant details. A conceptual design of a torque limiting safety clutch/brake under development is illustrated. Also, preliminary design drawings of a linear actuator using Terfenol-D is shown.

  12. Motor learning.

    PubMed

    Wolpert, Daniel M; Flanagan, J Randall

    2010-06-01

    Although learning a motor skill, such as a tennis stroke, feels like a unitary experience, researchers who study motor control and learning break the processes involved into a number of interacting components. These components can be organized into four main groups. First, skilled performance requires the effective and efficient gathering of sensory information, such as deciding where and when to direct one's gaze around the court, and thus an important component of skill acquisition involves learning how best to extract task-relevant information. Second, the performer must learn key features of the task such as the geometry and mechanics of the tennis racket and ball, the properties of the court surface, and how the wind affects the ball's flight. Third, the player needs to set up different classes of control that include predictive and reactive control mechanisms that generate appropriate motor commands to achieve the task goals, as well as compliance control that specifies, for example, the stiffness with which the arm holds the racket. Finally, the successful performer can learn higher-level skills such as anticipating and countering the opponent's strategy and making effective decisions about shot selection. In this Primer we shall consider these components of motor learning using as an example how we learn to play tennis. PMID:20541489

  13. Motor Controllers

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Kollmorgen Corporation's Mermaid II two person submersible is propeller-driven by a system of five DC brushless motors with new electronic controllers that originated in work performed in a NASA/DOE project managed by Lewis Research Center. A key feature of the system is electric commutation rather than mechanical commutation for converting AC current to DC.

  14. Motor learning.

    PubMed

    Wolpert, Daniel M; Flanagan, J Randall

    2010-06-01

    Although learning a motor skill, such as a tennis stroke, feels like a unitary experience, researchers who study motor control and learning break the processes involved into a number of interacting components. These components can be organized into four main groups. First, skilled performance requires the effective and efficient gathering of sensory information, such as deciding where and when to direct one's gaze around the court, and thus an important component of skill acquisition involves learning how best to extract task-relevant information. Second, the performer must learn key features of the task such as the geometry and mechanics of the tennis racket and ball, the properties of the court surface, and how the wind affects the ball's flight. Third, the player needs to set up different classes of control that include predictive and reactive control mechanisms that generate appropriate motor commands to achieve the task goals, as well as compliance control that specifies, for example, the stiffness with which the arm holds the racket. Finally, the successful performer can learn higher-level skills such as anticipating and countering the opponent's strategy and making effective decisions about shot selection. In this Primer we shall consider these components of motor learning using as an example how we learn to play tennis.

  15. Therma motor

    DOEpatents

    Kandarian, R.

    The disclosure is directed to a thermal motor utilizing two tapered prestressed parallel adjacent cylinders lengthwise disposed about one third in a coolant. Heat is applied to contacting portions of the cylinders outside the coolant to cause them to deform and turn. Heat sources such as industrial waste heat, geothermal hot water, solar radiation, etc. can be used.

  16. Comparaison de méthodes d'identification des paramètres d'une machine asynchrone

    NASA Astrophysics Data System (ADS)

    Bellaaj-Mrabet, N.; Jelassi, K.

    1998-07-01

    Interests, in Genetic Algorithms (G.A.) expands rapidly. This paper consists initially to apply G.A. for identifying induction motor parameters. Next, we compare the performances with classical methods like Maximum Likelihood and classical electrotechnical methods. These methods are applied on three induction motors of different powers to compare results following a set of criteria. Les algorithmes génétiques sont des méthodes adaptatives de plus en plus utilisée pour la résolution de certains problèmes d'optimisation. Le présent travail consiste d'une part, à mettre en œuvre un A.G sur des problèmes d'identification des machines électriques, et d'autre part à comparer ses performances avec les méthodes classiques tels que la méthode du maximum de vraisemblance et la méthode électrotechnique basée sur des essais à vides et en court-circuit. Ces méthodes sont appliquées sur des machines asynchrones de différentes puissances. Les résultats obtenus sont comparés selon certains critères, permettant de conclure sur la validité et la performance de chaque méthode.

  17. Security technologies and protocols for Asynchronous Transfer Mode networks

    SciTech Connect

    Tarman, T.D.

    1996-06-01

    Asynchronous Transfer Mode (ATM) is a new data communications technology that promises to integrate voice, video, and data traffic into a common network infrastructure. In order to fully utilize ATM`s ability to transfer real-time data at high rates, applications will start to access the ATM layer directly. As a result of this trend, security mechanisms at the ATM layer will be required. A number of research programs are currently in progress which seek to better understand the unique issues associated with ATM security. This paper describes some of these issues, and the approaches taken by various organizations in the design of ATM layer security mechanisms. Efforts within the ATM Forum to address the user communities need for ATM security are also described.

  18. Estimation of delays in generalized asynchronous Boolean networks.

    PubMed

    Das, Haimabati; Layek, Ritwik Kumar

    2016-10-20

    A new generalized asynchronous Boolean network (GABN) model has been proposed in this paper. This continuous-time discrete-state model captures the biological reality of cellular dynamics without compromising the computational efficiency of the Boolean framework. The GABN synthesis procedure is based on the prior knowledge of the logical structure of the regulatory network, and the experimental transcriptional parameters. The novelty of the proposed methodology lies in considering different delays associated with the activation and deactivation of a particular protein (especially the transcription factors). A few illustrative examples of some well-studied network motifs have been provided to explore the scope of using the GABN model for larger networks. The GABN model of the p53-signaling pathway in response to γ-irradiation has also been simulated in the current paper to provide an indirect validation of the proposed schema. PMID:27464825

  19. Asynchronous extinction of late Quaternary sloths on continents and islands

    PubMed Central

    Steadman, David W.; Martin, Paul S.; MacPhee, Ross D. E.; Jull, A. J. T.; McDonald, H. Gregory; Woods, Charles A.; Iturralde-Vinent, Manuel; Hodgins, Gregory W. L.

    2005-01-01

    Whatever the cause, it is extraordinary that dozens of genera of large mammals became extinct during the late Quaternary throughout the Western Hemisphere, including 90% of the genera of the xenarthran suborder Phyllophaga (sloths). Radiocarbon dates directly on dung, bones, or other tissue of extinct sloths place their “last appearance” datum at ≈11,000 radiocarbon years before present (yr BP) or slightly less in North America, ≈10,500 yr BP in South America, and ≈4,400 yr BP on West Indian islands. This asynchronous situation is not compatible with glacial–interglacial climate change forcing these extinctions, especially given the great elevational, latitudinal, and longitudinal variation of the sloth-bearing continental sites. Instead, the chronology of last appearance of extinct sloths, whether on continents or islands, more closely tracks the first arrival of people. PMID:16085711

  20. Asynchronous extinction of late Quaternary sloths on continents and islands.

    PubMed

    Steadman, David W; Martin, Paul S; MacPhee, Ross D E; Jull, A J T; McDonald, H Gregory; Woods, Charles A; Iturralde-Vinent, Manuel; Hodgins, Gregory W L

    2005-08-16

    Whatever the cause, it is extraordinary that dozens of genera of large mammals became extinct during the late Quaternary throughout the Western Hemisphere, including 90% of the genera of the xenarthran suborder Phyllophaga (sloths). Radiocarbon dates directly on dung, bones, or other tissue of extinct sloths place their "last appearance" datum at approximately 11,000 radiocarbon years before present (yr BP) or slightly less in North America, approximately 10,500 yr BP in South America, and approximately 4,400 yr BP on West Indian islands. This asynchronous situation is not compatible with glacial-interglacial climate change forcing these extinctions, especially given the great elevational, latitudinal, and longitudinal variation of the sloth-bearing continental sites. Instead, the chronology of last appearance of extinct sloths, whether on continents or islands, more closely tracks the first arrival of people.

  1. Asynchronous Messaging and Data Transfer in a Spacecraft: An Implementation

    NASA Technical Reports Server (NTRS)

    Moholt, Joseph M.

    2005-01-01

    Data transfer and messaging is an important part of a spacecraft. Creating a standard protocol for messaging that can be used for a variety of applications is an extremely beneficial project at the Jet Propulsion Laboratory (JPL). The Asynchronous Messaging Service (AMS) is a protocol outlining how subsystems initialize and conduct communication between each other. There are currently two implementations of AMS in the works. At JPL, my task is to get a working implementation of AMS onto vxWorks as a proof of concept. An Autocoder, a program used to convert visually created state chart diagrams to C++, has also been created to accomplish a part of the implementation. I was assigned to make the program portable on any Unix type environment. Lastly, I was to develop a program to demonstrate messaging between two FireWire cards running vxworks.

  2. An Asynchronous Cellular Automata-Based Adaptive Illumination Facility

    NASA Astrophysics Data System (ADS)

    Bandini, Stefania; Bonomi, Andrea; Vizzari, Giuseppe; Acconci, Vito

    The term Ambient Intelligence refers to electronic environments that are sensitive and responsive to the presence of people; in the described scenario the environment itself is endowed with a set of sensors (to perceive humans or other physical entities such as dogs, bicycles, etc.), interacting with a set of actuators (lights) that choose their actions (i.e. state of illumination) in an attempt improve the overall experience of these users. The model for the interaction and action of sensors and actuators is an asynchronous Cellular Automata (CA) with memory, supporting a self-organization of the system as a response to the presence and movements of people inside it. The paper will introduce the model, as well as an ad hoc user interface for the specification of the relevant parameters of the CA transition rule that determines the overall system behaviour.

  3. Asynchronous transfer mode link performance over ground networks

    NASA Technical Reports Server (NTRS)

    Chow, E. T.; Markley, R. W.

    1993-01-01

    The results of an experiment to determine the feasibility of using asynchronous transfer mode (ATM) technology to support advanced spacecraft missions that require high-rate ground communications and, in particular, full-motion video are reported. Potential nodes in such a ground network include Deep Space Network (DSN) antenna stations, the Jet Propulsion Laboratory, and a set of national and international end users. The experiment simulated a lunar microrover, lunar lander, the DSN ground communications system, and distributed science users. The users were equipped with video-capable workstations. A key feature was an optical fiber link between two high-performance workstations equipped with ATM interfaces. Video was also transmitted through JPL's institutional network to a user 8 km from the experiment. Variations in video depending on the networks and computers were observed, the results are reported.

  4. Asynchronous Multilateral Control for Simplified Walking Haptic System

    NASA Astrophysics Data System (ADS)

    Okura, Takeshi; Katsura, Seiichiro

    Recently, there has been extensive development in remote communication technologies such as telephone, radio, and television. Haptic information is studied as the third type of multimedia information. Real-world haptics is getting attention not only for the feedback of real-world haptic information in teleoperation but also as the key technology for future human support. Most of the objects of study in haptics are stationary. Therefore, the moving range of such haptic systems is limited. This paper proposes a novel haptic device that receives force feedback of walking motion from a remote environment and manipulates remote system. Thus, its moving range is unrestricted. To drive this haptic system, the paper also proposes asynchronous multilateral control. By using this control, an operator can operate the remote system without changing his/her position. The proposed haptic system is expected to act as an effective interface for virtual reality applications and teleoperation.

  5. Estimation of delays in generalized asynchronous Boolean networks.

    PubMed

    Das, Haimabati; Layek, Ritwik Kumar

    2016-10-20

    A new generalized asynchronous Boolean network (GABN) model has been proposed in this paper. This continuous-time discrete-state model captures the biological reality of cellular dynamics without compromising the computational efficiency of the Boolean framework. The GABN synthesis procedure is based on the prior knowledge of the logical structure of the regulatory network, and the experimental transcriptional parameters. The novelty of the proposed methodology lies in considering different delays associated with the activation and deactivation of a particular protein (especially the transcription factors). A few illustrative examples of some well-studied network motifs have been provided to explore the scope of using the GABN model for larger networks. The GABN model of the p53-signaling pathway in response to γ-irradiation has also been simulated in the current paper to provide an indirect validation of the proposed schema.

  6. Minor Planet 1016 Anitra: A Likely Asynchronous Binary

    NASA Astrophysics Data System (ADS)

    Pilcher, Frederick; Benishek, Vladimir; Jacobsen, Jens; Kristensen, Leif Hugo; Lang, Kim; Larsen, Frank R.; Odden, Caroline; Pravec, Petr

    2016-07-01

    Analysis of photometry data for 1016 Anitra using a single period analysis shows a lightcurve with a period of 5.9296 hours and amplitude of 0.30 mag, with short period fluctuations. A simultaneous two-period analysis of the data found two smooth bimodal lightcurves with periods and amplitudes of P1 = 5.92951 h, A1 = 0.30 mag and P2 = 2.609143 h, A2 = 0.10 mag. These results are interpreted as the rotation of the two components of an asynchronous binary system. Four additional attenuations were observed that may have been caused by satellite mutual events, but those data were insufficient to yield an orbital period.

  7. Linear Accelerators

    SciTech Connect

    Sidorin, Anatoly

    2010-01-05

    In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

  8. How to build fast muscles: synchronous and asynchronous designs.

    PubMed

    Syme, Douglas A; Josephson, Robert K

    2002-08-01

    In animals, muscles are the most common effectors that translate neuronal activity into behavior. Nowhere is behavior more restricted by the limits of muscle performance than at the upper range of high-frequency movements. Here, we see new and multiple designs to cope with the demands for speed. Extremely rapid oscillations in force are required to power cyclic activities such as flight in insects or to produce vibrations for sound. Such behaviors are seen in a variety of invertebrates and vertebrates, and are powered by both synchronous and asynchronous muscles. In synchronous muscles, each contraction/relaxation cycle is accompanied by membrane depolarization and subsequent repolarization, release of activator calcium, attachment of cross-bridges and muscle shortening, then removal of activator calcium and cross-bridge detachment. To enable all of these to occur at extremely high frequencies a suite of modifications are required, including precise neural control, hypertrophy of the calcium handling machinery, innovative mechanisms to bind calcium, and molecular modification of the cross-bridges and regulatory proteins. Side effects are low force and power output and low efficiency, but the benefit of direct, neural control is maintained. Asynchronous muscles, in which there is not a 1:1 correspondence between neural activation and contraction, are a radically different design. Rather than rapid calcium cycling, they rely on delayed activation and deactivation, and the resonant characteristics of the wings and exoskeleton to guide their extremely high-frequency contractions. They thus avoid many of the modifications and attendant trade-offs mentioned above, are more powerful and more efficient than high-frequency synchronous muscles, but are considerably more restricted in their application. PMID:21708773

  9. Asynchronous learning: student utilization out of sync with their preference

    PubMed Central

    Lew, Edward K.; Nordquist, Erik K.

    2016-01-01

    Background Asynchronous learning is gaining popularity. Data are limited regarding this learning method in medical students rotating in emergency medicine (EM). In EM, faculty time is limited to give in-person lectures. The authors sought to create an online curriculum that students could utilize as an additional learning modality. Objective The goal was to evaluate effectiveness, participation, and preference for this mode of learning. Methods We developed five online, narrated PowerPoint presentations. After orientation, access to the online curriculum was provided to the students, which they could review at their leisure. Results One hundred and seven fourth-year medical students participated. They reported the curriculum to be of high quality. Pretest scores were similar for those that viewed all lectures – compliant group (CG) (9.5 [CI 4.8–14.1]) and those that did not view any – non-compliant group (NCG) (9.6 [CI 5.9–13.4]). There was no statistical significant difference in posttest scores between the groups although there was improvement overall: CG 14.6 (CI 6.9–22.1); NCG 11.4 (CI 5.7–17.1). A majority (69.2%) favored inclusion of asynchronous learning, but less than a quarter (22.4%) reported viewing all five modules and more than a third (36.4%) viewed none. Conclusion Despite student-expressed preference for an online curriculum, they used the online resource less than expected. This should give pause to educators looking to convert core EM topics to an online format. However, when high-quality online lectures are utilized as a learning tool, this study demonstrates that they had neither a positive nor a negative impact on test scores. PMID:27280385

  10. Motor Neuron Diseases

    MedlinePlus

    ... called upper motor neurons ) are transmitted to nerve cells in the brain stem and spinal cord (called lower motor neurons ) and from them to particular muscles. Upper motor neurons direct the lower motor neurons ...

  11. Motor Neuron Diseases

    MedlinePlus

    ... Enhancing Diversity Find People About NINDS NINDS Motor Neuron Diseases Information Page Condensed from Motor Neuron Diseases ... and Information Publicaciones en Español What are Motor Neuron Diseases? The motor neuron diseases (MNDs) are a ...

  12. PULSAR TIMING ERRORS FROM ASYNCHRONOUS MULTI-FREQUENCY SAMPLING OF DISPERSION MEASURE VARIATIONS

    SciTech Connect

    Lam, M. T.; Cordes, J. M.; Chatterjee, S.; Dolch, T.

    2015-03-10

    Free electrons in the interstellar medium cause frequency-dependent delays in pulse arrival times due to both scattering and dispersion. Multi-frequency measurements are used to estimate and remove dispersion delays. In this paper, we focus on the effect of any non-simultaneity of multi-frequency observations on dispersive delay estimation and removal. Interstellar density variations combined with changes in the line of sight from pulsar and observer motions cause dispersion measure (DM) variations with an approximately power-law power spectrum, augmented in some cases by linear trends. We simulate time series, estimate the magnitude and statistical properties of timing errors that result from non-simultaneous observations, and derive prescriptions for data acquisition that are needed in order to achieve a specified timing precision. For nearby, highly stable pulsars, measurements need to be simultaneous to within about one day in order for the timing error from asynchronous DM correction to be less than about 10 ns. We discuss how timing precision improves when increasing the number of dual-frequency observations used in DM estimation for a given epoch. For a Kolmogorov wavenumber spectrum, we find about a factor of two improvement in precision timing when increasing from two to three observations but diminishing returns thereafter.

  13. Asynchronous Video Interviewing as a New Technology in Personnel Selection: The Applicant's Point of View.

    PubMed

    Brenner, Falko S; Ortner, Tuulia M; Fay, Doris

    2016-01-01

    The present study aimed to integrate findings from technology acceptance research with research on applicant reactions to new technology for the emerging selection procedure of asynchronous video interviewing. One hundred six volunteers experienced asynchronous video interviewing and filled out several questionnaires including one on the applicants' personalities. In line with previous technology acceptance research, the data revealed that perceived usefulness and perceived ease of use predicted attitudes toward asynchronous video interviewing. Furthermore, openness revealed to moderate the relation between perceived usefulness and attitudes toward this particular selection technology. No significant effects emerged for computer self-efficacy, job interview self-efficacy, extraversion, neuroticism, and conscientiousness. Theoretical and practical implications are discussed.

  14. Redundant asynchronous microprocessor system for fault tolerant flight control and navigation

    NASA Technical Reports Server (NTRS)

    Dunn, W. R.

    1983-01-01

    Unlike their synchronized counterparts, redundant channels in an asynchronous flight system can, under no-fault conditions, exhibit cross-channel data disparities. Sources of these errors are examined in terms of the general, individual functions of the flight control and navigation application in the asynchronous digital environment. The effects of asynchronism on trajectory programmers, dynamic control algorithms and data reconstruction processes are examined in terms of data skews, data latencies, and clock rate uncertainties. An example is presented in which time corrections are applied to reduce the data disparities. Practical limitations of the approach of the example are discussed.

  15. Modeling and Analysis of Asynchronous Systems Using SAL and Hybrid SAL

    NASA Technical Reports Server (NTRS)

    Tiwari, Ashish; Dutertre, Bruno

    2013-01-01

    We present formal models and results of formal analysis of two different asynchronous systems. We first examine a mid-value select module that merges the signals coming from three different sensors that are each asynchronously sampling the same input signal. We then consider the phase locking protocol proposed by Daly, Hopkins, and McKenna. This protocol is designed to keep a set of non-faulty (asynchronous) clocks phase locked even in the presence of Byzantine-faulty clocks on the network. All models and verifications have been developed using the SAL model checking tools and the Hybrid SAL abstractor.

  16. A low-power asynchronous ECG acquisition system in CMOS technology.

    PubMed

    Hwang, Sungkil; Trakimas, Michael; Sonkusale, Sameer

    2010-01-01

    An asynchronous electrocardiogram (ECG) acquisition system is presented for wearable ambulatory monitoring. The proposed system consists of a low noise front-end amplifier (AFE) with tunable bandwidth, an asynchronous analog-to-digital converter (ADC), and digital signal processing (DSP). Data compression is achieved by the inherent signal dependent sampling rate of the asynchronous architecture. This makes the system attractive for compact wearable ECG monitoring applications. The AFE and ADC were fabricated in a 0.18 microm CMOS technology and consume a total of 79 microW. Measured results demonstrating ECG monitoring are presented. PMID:21096052

  17. The theory of asynchronous relative motion I: time transformations and nonlinear corrections

    NASA Astrophysics Data System (ADS)

    Roa, Javier; Peláez, Jesús

    2016-09-01

    Using alternative independent variables in lieu of time has important advantages when propagating the partial derivatives of the trajectory. This paper focuses on spacecraft relative motion, but the concepts presented here can be extended to any problem involving the variational equations of orbital motion. A usual approach for modeling the relative dynamics is to evaluate how the reference orbit changes when modifying the initial conditions slightly. But when the time is a mere dependent variable, changes in the initial conditions will result in changes in time as well: a time delay between the reference and the neighbor solution will appear. The theory of asynchronous relative motion shows how the time delay can be corrected to recover the physical sense of the solution and, more importantly, how this correction can be used to improve significantly the accuracy of the linear solutions to relative motion found in the literature. As an example, an improved version of the Clohessy-Wiltshire (CW) solution is presented explicitly. The correcting terms are extremely compact, and the solution proves more accurate than the second and even third order CW equations for long propagations. The application to the elliptic case is also discussed. The theory is not restricted to Keplerian orbits, as it holds under any perturbation. To prove this statement, two examples of realistic trajectories are presented: a pair of spacecraft orbiting the Earth and perturbed by a realistic force model; and two probes describing a quasi-periodic orbit in the Jupiter-Europa system subject to third-body perturbations. The numerical examples show that the new theory yields reductions in the propagation error of several orders of magnitude, both in position and velocity, when compared to the linear approach.

  18. Linear Colliders

    NASA Astrophysics Data System (ADS)

    Yamamoto, Akira; Yokoya, Kaoru

    2015-02-01

    An overview of linear collider programs is given. The history and technical challenges are described and the pioneering electron-positron linear collider, the SLC, is first introduced. For future energy frontier linear collider projects, the International Linear Collider (ILC) and the Compact Linear Collider (CLIC) are introduced and their technical features are discussed. The ILC is based on superconducting RF technology and the CLIC is based on two-beam acceleration technology. The ILC collaboration completed the Technical Design Report in 2013, and has come to the stage of "Design to Reality." The CLIC collaboration published the Conceptual Design Report in 2012, and the key technology demonstration is in progress. The prospects for further advanced acceleration technology are briefly discussed for possible long-term future linear colliders.

  19. Linear Colliders

    NASA Astrophysics Data System (ADS)

    Yamamoto, Akira; Yokoya, Kaoru

    An overview of linear collider programs is given. The history and technical challenges are described and the pioneering electron-positron linear collider, the SLC, is first introduced. For future energy frontier linear collider projects, the International Linear Collider (ILC) and the Compact Linear Collider (CLIC) are introduced and their technical features are discussed. The ILC is based on superconducting RF technology and the CLIC is based on two-beam acceleration technology. The ILC collaboration completed the Technical Design Report in 2013, and has come to the stage of "Design to Reality." The CLIC collaboration published the Conceptual Design Report in 2012, and the key technology demonstration is in progress. The prospects for further advanced acceleration technology are briefly discussed for possible long-term future linear colliders.

  20. Strict optical orthogonal codes for purely asynchronous code-division multiple-access applications.

    PubMed

    Zhang, J G

    1996-12-10

    Strict optical orthogonal codes are presented for purely asynchronous optical code-division multiple-access (CDMA) applications. The proposed code can strictly guarantee the peaks of its cross-correlation functions and the sidelobes of any of its autocorrelation functions to have a value of 1 in purely asynchronous data communications. The basic theory of the proposed codes is given. An experiment on optical CDMA systems is also demonstrated to verify the characteristics of the proposed code.

  1. Lead screw linear actuator

    NASA Technical Reports Server (NTRS)

    Perkins, Gerald S. (Inventor)

    1980-01-01

    A linear actuator which can apply high forces is described, which includes a reciprocating rod having a threaded portion engaged by a nut that is directly coupled to the rotor of an electric motor. The nut is connected to the rotor in a manner that minimizes loading on the rotor, by the use of a coupling that transmits torque to the nut but permits it to shift axially and radially with respect to the rotor. The nut has a threaded hydrostatic bearing for engaging the threaded rod portion, with an oilcarrying groove in the nut being interrupted.

  2. Linear Collisions

    ERIC Educational Resources Information Center

    Walkiewicz, T. A.; Newby, N. D., Jr.

    1972-01-01

    A discussion of linear collisions between two or three objects is related to a junior-level course in analytical mechanics. The theoretical discussion uses a geometrical approach that treats elastic and inelastic collisions from a unified point of view. Experiments with a linear air track are described. (Author/TS)

  3. Siphon motor

    SciTech Connect

    Bunn, C.H.

    1980-01-01

    A siphon motor comprises the combination of siphon means and generating means for generating electrical energy from a water source located below the generating means and a water discharge at a lower level than the water source. Water rises by siphonic action upward from the water source to a sealed working region maintained under partial vacuum, and descends to the water discharge. The working region contains the generating means. The system has particular utility as a source of power generation in remote locations having a water table within about 30 feet of the ground.

  4. Active training paradigm for motor imagery BCI.

    PubMed

    Li, Junhua; Zhang, Liqing

    2012-06-01

    Brain-computer interface (BCI) allows the use of brain activities for people to directly communicate with the external world or to control external devices without participation of any peripheral nerves and muscles. Motor imagery is one of the most popular modes in the research field of brain-computer interface. Although motor imagery BCI has some advantages compared with other modes of BCI, such as asynchronization, it is necessary to require training sessions before using it. The performance of trained BCI system depends on the quality of training samples or the subject engagement. In order to improve training effect and decrease training time, we proposed a new paradigm where subjects participated in training more actively than in the traditional paradigm. In the traditional paradigm, a cue (to indicate what kind of motor imagery should be imagined during the current trial) is given to the subject at the beginning of a trial or during a trial, and this cue is also used as a label for this trial. It is usually assumed that labels for trials are accurate in the traditional paradigm, although subjects may not have performed the required or correct kind of motor imagery, and trials may thus be mislabeled. And then those mislabeled trials give rise to interference during model training. In our proposed paradigm, the subject is required to reconfirm the label and can correct the label when necessary. This active training paradigm may generate better training samples with fewer inconsistent labels because it overcomes mistakes when subject's motor imagination does not match the given cues. The experiments confirm that our proposed paradigm achieves better performance; the improvement is significant according to statistical analysis. PMID:22476215

  5. Asynchronous parallel hybrid optimization combining DIRECT and GSS.

    SciTech Connect

    Griffin, Joshua D.; Kolda, Tamara Gibson

    2008-10-01

    In this talk, we explore the benefits of hybrid optimization using parallel versions of DIRECT and asynchronous generating set search (GSS) for optimization. Both of these methods are derivative-free, making them useful for a variety of science and engineering problems. Our goal is to ideally find a global minimum, but practically to find a good local minimum in a small amount of time. DIRECT is a global search method that systematically divides the search space into ever-smaller rectangles, and GSS is a local search method. The combination of these method guarantees a good local minimum but is better than a purely local approach because it finds more global solutions. We compare the performance of hybrid and non-hybrid methods on a suite of standard global optimization test problems. Overall, the hybrid methods are more robust than the non-hybrid methods at the cost of more function evaluations. In terms of wall-clock time on a parallel system, the hybrid methods are actually less expensive due to nearly perfect parallel load balance and scaling.

  6. Asynchronous visual event-based time-to-contact.

    PubMed

    Clady, Xavier; Clercq, Charles; Ieng, Sio-Hoi; Houseini, Fouzhan; Randazzo, Marco; Natale, Lorenzo; Bartolozzi, Chiara; Benosman, Ryad

    2014-01-01

    Reliable and fast sensing of the environment is a fundamental requirement for autonomous mobile robotic platforms. Unfortunately, the frame-based acquisition paradigm at the basis of main stream artificial perceptive systems is limited by low temporal dynamics and redundant data flow, leading to high computational costs. Hence, conventional sensing and relative computation are obviously incompatible with the design of high speed sensor-based reactive control for mobile applications, that pose strict limits on energy consumption and computational load. This paper introduces a fast obstacle avoidance method based on the output of an asynchronous event-based time encoded imaging sensor. The proposed method relies on an event-based Time To Contact (TTC) computation based on visual event-based motion flows. The approach is event-based in the sense that every incoming event adds to the computation process thus allowing fast avoidance responses. The method is validated indoor on a mobile robot, comparing the event-based TTC with a laser range finder TTC, showing that event-based sensing offers new perspectives for mobile robotics sensing. PMID:24570652

  7. Asynchronous visual event-based time-to-contact.

    PubMed

    Clady, Xavier; Clercq, Charles; Ieng, Sio-Hoi; Houseini, Fouzhan; Randazzo, Marco; Natale, Lorenzo; Bartolozzi, Chiara; Benosman, Ryad

    2014-01-01

    Reliable and fast sensing of the environment is a fundamental requirement for autonomous mobile robotic platforms. Unfortunately, the frame-based acquisition paradigm at the basis of main stream artificial perceptive systems is limited by low temporal dynamics and redundant data flow, leading to high computational costs. Hence, conventional sensing and relative computation are obviously incompatible with the design of high speed sensor-based reactive control for mobile applications, that pose strict limits on energy consumption and computational load. This paper introduces a fast obstacle avoidance method based on the output of an asynchronous event-based time encoded imaging sensor. The proposed method relies on an event-based Time To Contact (TTC) computation based on visual event-based motion flows. The approach is event-based in the sense that every incoming event adds to the computation process thus allowing fast avoidance responses. The method is validated indoor on a mobile robot, comparing the event-based TTC with a laser range finder TTC, showing that event-based sensing offers new perspectives for mobile robotics sensing.

  8. Obstacle avoidance in social groups: new insights from asynchronous models.

    PubMed

    Croft, Simon; Budgey, Richard; Pitchford, Jonathan W; Wood, A Jamie

    2015-05-01

    For moving animals, the successful avoidance of hazardous obstacles is an important capability. Despite this, few models of collective motion have addressed the relationship between behavioural and social features and obstacle avoidance. We develop an asynchronous individual-based model for social movement which allows social structure within groups to be included. We assess the dynamics of group navigation and resulting collision risk in the context of information transfer through the system. In agreement with previous work, we find that group size has a nonlinear effect on collision risk. We implement examples of possible network structures to explore the impact social preferences have on collision risk. We show that any social heterogeneity induces greater obstacle avoidance with further improvements corresponding to groups containing fewer influential individuals. The model provides a platform for both further theoretical investigation and practical application. In particular, we argue that the role of social structures within bird flocks may have an important role to play in assessing the risk of collisions with wind turbines, but that new methods of data analysis are needed to identify these social structures.

  9. Obstacle avoidance in social groups: new insights from asynchronous models

    PubMed Central

    Croft, Simon; Budgey, Richard; Pitchford, Jonathan W.; Wood, A. Jamie

    2015-01-01

    For moving animals, the successful avoidance of hazardous obstacles is an important capability. Despite this, few models of collective motion have addressed the relationship between behavioural and social features and obstacle avoidance. We develop an asynchronous individual-based model for social movement which allows social structure within groups to be included. We assess the dynamics of group navigation and resulting collision risk in the context of information transfer through the system. In agreement with previous work, we find that group size has a nonlinear effect on collision risk. We implement examples of possible network structures to explore the impact social preferences have on collision risk. We show that any social heterogeneity induces greater obstacle avoidance with further improvements corresponding to groups containing fewer influential individuals. The model provides a platform for both further theoretical investigation and practical application. In particular, we argue that the role of social structures within bird flocks may have an important role to play in assessing the risk of collisions with wind turbines, but that new methods of data analysis are needed to identify these social structures. PMID:25833245

  10. Asynchronous vehicle pose correction using visual detection of ground features

    NASA Astrophysics Data System (ADS)

    Harnarinesingh, Randy E. S.; Syan, Chanan S.

    2014-07-01

    The inherent noise associated with odometry manifests itself as errors in localization for autonomous vehicles. Visual odometry has been previously used in order to supplement classical vehicle odometry. However, visual odometry is limited in its ability to reduce errors in localization for large travel distances that entail the cumulative summing of individual frame-to-frame image errors. In this paper, a novel machine vision approach for tiled surfaces is proposed to address this problem. Tile edges in a laboratory environment are used to define a travel trajectory for the Quansar Qbot (autonomous vehicle) built on the iRobot iRoomba platform with a forward facing camera. Tile intersections are used to enable asynchronous error recovery for vehicle position and orientation. The proposed approach employs real-time image classification and is feasible for error mitigation for large travel distances. The average position error for an 8m travel distance using classical odometry was measured to be 0.28m. However, implementation of the proposed approach resulted in an error of 0.028m. The proposed approach therefore significantly reduces pose estimation error and could be used to supplement existing modalities such as GPS and Laser-based range sensors.

  11. Normalized and asynchronous mirror alignment for Cherenkov telescopes

    NASA Astrophysics Data System (ADS)

    Ahnen, M. L.; Baack, D.; Balbo, M.; Bergmann, M.; Biland, A.; Blank, M.; Bretz, T.; Bruegge, K. A.; Buss, J.; Domke, M.; Dorner, D.; Einecke, S.; Hempfling, C.; Hildebrand, D.; Hughes, G.; Lustermann, W.; Mannheim, K.; Mueller, S. A.; Neise, D.; Neronov, A.; Noethe, M.; Overkemping, A.-K.; Paravac, A.; Pauss, F.; Rhode, W.; Shukla, A.; Temme, F.; Thaele, J.; Toscano, S.; Vogler, P.; Walter, R.; Wilbert, A.

    2016-09-01

    Imaging Atmospheric Cherenkov Telescopes (IACTs) need imaging optics with large apertures and high image intensities to map the faint Cherenkov light emitted from cosmic ray air showers onto their image sensors. Segmented reflectors fulfill these needs, and as they are composed from mass production mirror facets they are inexpensive and lightweight. However, as the overall image is a superposition of the individual facet images, alignment is a challenge. Here we present a computer vision based star tracking alignment method, which also works for limited or changing star light visibility. Our method normalizes the mirror facet reflection intensities to become independent of the reference star's intensity or the cloud coverage. Using two CCD cameras, our method records the mirror facet orientations asynchronously of the telescope drive system, and thus makes the method easy to integrate into existing telescopes. It can be combined with remote facet actuation, but does not require one to work. Furthermore, it can reconstruct all individual mirror facet point spread functions without moving any mirror. We present alignment results on the 4 m First Geiger-mode Avalanche Cherenkov Telescope (FACT).

  12. Commande vectorielle d'un moteur asynchrone sans capteur

    NASA Astrophysics Data System (ADS)

    Ourth, T.

    1993-06-01

    A field-oriented control strategy for induction machines which does not use mechanical sensors is presented. The rotor flux is observed by a reduced-order Luenberger-type observer based on a model using a stator-fixed reference frame. An estimate of the rotation speed is derived from the flux vector, the measured stator currents and the field orientation angle. Simulations demonstrate that this control strategy performs well even in the presence of parameter variations up to ± 50% (resistances). Ce papier présente la commande par flux orienté d'une machine asynchrone sans capteur de vitesse ou de position. Le flux rotorique est évalué grâce à un observateur d'ordre réduit d'un type voisin de Luenberger travaillant dans un repère fixe statorique. L'estimation de la vitesse est obtenue à partir du module du flux rotorique, des courants statoriques mesurés et de l'angle d'orientation du flux rotorique. Cette étude basée sur des simulations démontre un comportement acceptable de la commande malgré la variation des paramètres comme les résistances de la machine.

  13. Obstacle avoidance in social groups: new insights from asynchronous models.

    PubMed

    Croft, Simon; Budgey, Richard; Pitchford, Jonathan W; Wood, A Jamie

    2015-05-01

    For moving animals, the successful avoidance of hazardous obstacles is an important capability. Despite this, few models of collective motion have addressed the relationship between behavioural and social features and obstacle avoidance. We develop an asynchronous individual-based model for social movement which allows social structure within groups to be included. We assess the dynamics of group navigation and resulting collision risk in the context of information transfer through the system. In agreement with previous work, we find that group size has a nonlinear effect on collision risk. We implement examples of possible network structures to explore the impact social preferences have on collision risk. We show that any social heterogeneity induces greater obstacle avoidance with further improvements corresponding to groups containing fewer influential individuals. The model provides a platform for both further theoretical investigation and practical application. In particular, we argue that the role of social structures within bird flocks may have an important role to play in assessing the risk of collisions with wind turbines, but that new methods of data analysis are needed to identify these social structures. PMID:25833245

  14. Sparse asynchronous cortical generators can produce measurable scalp EEG signals.

    PubMed

    von Ellenrieder, Nicolás; Dan, Jonathan; Frauscher, Birgit; Gotman, Jean

    2016-09-01

    We investigate to what degree the synchronous activation of a smooth patch of cortex is necessary for observing EEG scalp activity. We perform extensive simulations to compare the activity generated on the scalp by different models of cortical activation, based on intracranial EEG findings reported in the literature. The spatial activation is modeled as a cortical patch of constant activation or as random sets of small generators (0.1 to 3cm(2) each) concentrated in a cortical region. Temporal activation models for the generation of oscillatory activity are either equal phase or random phase across the cortical patches. The results show that smooth or random spatial activation profiles produce scalp electric potential distributions with the same shape. Also, in the generation of oscillatory activity, multiple cortical generators with random phase produce scalp activity attenuated on average only 2 to 4 times compared to generators with equal phase. Sparse asynchronous cortical generators can produce measurable scalp EEG. This is a possible explanation for seemingly paradoxical observations of simultaneous disorganized intracranial activity and scalp EEG signals. Thus, the standard interpretation of scalp EEG might constitute an oversimplification of the underlying brain activity. PMID:27262240

  15. Remote control for motor vehicle

    NASA Technical Reports Server (NTRS)

    Johnson, Dale R. (Inventor); Ciciora, John A. (Inventor)

    1984-01-01

    A remote controller is disclosed for controlling the throttle, brake and steering mechanism of a conventional motor vehicle, with the remote controller being particularly advantageous for use by severely handicapped individuals. The controller includes a remote manipulator which controls a plurality of actuators through interfacing electronics. The remote manipulator is a two-axis joystick which controls a pair of linear actuators and a rotary actuator, with the actuators being powered by electric motors to effect throttle, brake and steering control of a motor vehicle adapted to include the controller. The controller enables the driver to control the adapted vehicle from anywhere in the vehicle with one hand with minimal control force and range of motion. In addition, even though a conventional vehicle is adapted for use with the remote controller, the vehicle may still be operated in the normal manner.

  16. Portable Linear Sled (PLS) for biomedical research

    NASA Technical Reports Server (NTRS)

    Vallotton, Will; Matsuhiro, Dennis; Wynn, Tom; Temple, John

    1993-01-01

    The PLS is a portable linear motion generating device conceived by researchers at Ames Research Center's Vestibular Research Facility and designed by engineers at Ames for the study of motion sickness in space. It is an extremely smooth apparatus, powered by linear motors and suspended on air bearings which ride on precision ground ceramic ways.

  17. Scalability of Asynchronous Networks Is Limited by One-to-One Mapping between Effective Connectivity and Correlations

    PubMed Central

    van Albada, Sacha Jennifer; Helias, Moritz; Diesmann, Markus

    2015-01-01

    Network models are routinely downscaled compared to nature in terms of numbers of nodes or edges because of a lack of computational resources, often without explicit mention of the limitations this entails. While reliable methods have long existed to adjust parameters such that the first-order statistics of network dynamics are conserved, here we show that limitations already arise if also second-order statistics are to be maintained. The temporal structure of pairwise averaged correlations in the activity of recurrent networks is determined by the effective population-level connectivity. We first show that in general the converse is also true and explicitly mention degenerate cases when this one-to-one relationship does not hold. The one-to-one correspondence between effective connectivity and the temporal structure of pairwise averaged correlations implies that network scalings should preserve the effective connectivity if pairwise averaged correlations are to be held constant. Changes in effective connectivity can even push a network from a linearly stable to an unstable, oscillatory regime and vice versa. On this basis, we derive conditions for the preservation of both mean population-averaged activities and pairwise averaged correlations under a change in numbers of neurons or synapses in the asynchronous regime typical of cortical networks. We find that mean activities and correlation structure can be maintained by an appropriate scaling of the synaptic weights, but only over a range of numbers of synapses that is limited by the variance of external inputs to the network. Our results therefore show that the reducibility of asynchronous networks is fundamentally limited. PMID:26325661

  18. LINEAR ACCELERATOR

    DOEpatents

    Christofilos, N.C.; Polk, I.J.

    1959-02-17

    Improvements in linear particle accelerators are described. A drift tube system for a linear ion accelerator reduces gap capacity between adjacent drift tube ends. This is accomplished by reducing the ratio of the diameter of the drift tube to the diameter of the resonant cavity. Concentration of magnetic field intensity at the longitudinal midpoint of the external sunface of each drift tube is reduced by increasing the external drift tube diameter at the longitudinal center region.

  19. Effects of synchronous and asynchronous embryo transfer on postnatal development, adult health, and behavior in mice.

    PubMed

    López-Cardona, Angela P; Fernández-González, Raúl; Pérez-Crespo, Miriam; Alén, Francisco; de Fonseca, Fernando Rodriguez; Orio, Laura; Gutierrez-Adan, Alfonso

    2015-10-01

    Asynchronous embryo transfer (ET) is a common assisted reproduction technique used in several species, but its biological effects on postnatal and early development remain unknown. The aim of this study was to determine whether asynchronous ET produces long-term effects in mice. Postnatal development, animal weight, systolic blood pressure (SBP), relative organ weight (liver, spleen, kidneys, heart, lungs, brain, and testicles), and behavior (assessed in open-field and elevated plus maze tests) were assessed in CD1 mice produced by different ET procedures: 1) the transfer of Day 3.5 (D3.5) blastocysts to the uterus (BL-UT); 2) the transfer of D3.5 blastocysts to the oviduct (BL-OV); or 3) the transfer of D0.5 zygotes to the oviduct (Z-OV). In vivo conceived animals served as controls (CT). The transfer of blastocysts to the uterus or zygotes to the oviduct was defined as synchronous, and transfer of blastocysts to the oviduct was defined as asynchronous. Both synchronous and asynchronous ET resulted in increased weight at birth that normalized thereafter with the exception of asynchronous ET females. In this group, female BL-OV, a clear lower body weight was recorded along postnatal life when compared with controls (P < 0.05). No effects on animal weight were produced during postnatal development in the synchronous ET groups (BL-UT, Z-OV, and CT). Both synchronous and asynchronous ET had impacts on adult (Wk 30) organ weight. SBP was modified in animals derived from blastocyst but not zygote ET. Effects on behavior (anxiety in the plus maze) were only detected in the BL-UT group (P < 0.05). Our findings indicate that zygotes are less sensitive than blastocysts to ET and that both synchronous and asynchronous blastocyst ET may have long-term consequences on health, with possible impacts on weight, arterial pressure, relative organ weight, and behavior.

  20. [A novel proposal explaining sleep disturbance of children in Japan--asynchronization].

    PubMed

    Kohyama, Jun

    2008-07-01

    It has been reported that more than half of the children in Japan suffer from daytime sleepiness. In contrast, about one quarter of junior high-school students in Japan complain of insomnia. According to the International Classification of Sleep Disorders (Second edition), these children could be diagnosed as having behaviorally-induced insufficient sleep syndrome due to inadequate sleeping habits. Getting on adequate amount of sleep should solve such problems;however, such a therapeutic approach often fails. Although social factors are involved in these sleep disturbances, I feel that a novel notion - asynchronization - leads to an understanding of the pathophysiology of disturbances in these children. Further, it could contribute to resolve their problems. The essence of asynchronization is a disturbance of various aspects (e.g., cycle, amplitude, phase, and interrelationship) of the biological rhythms that normally exhibits circadian oscillation. The main cause of asynchronization is hypothesized to be the combination of light exposure during night and the lack of light exposure in the morning. Asynchronization results in the disturbance of variable systems. Thus, symptoms of asynchronization include disturbances of the autonomic nervous system (sleepiness, insomnia, disturbance of hormonal excretion, gastrointestinal problems, etc.) and higher brain function (disorientation, loss of sociality, loss of will or motivation, impaired alertness and performance, etc.). Neurological (attention deficit, aggression, impulsiveness, hyperactivity, etc.), psychiatric (depressive disorders, personality disorders, anxiety disorders, etc.) and somatic (tiredness, fatigue, etc.) disturbances could also be symptoms of asynchronization. At the initial phase of asynchronization, disturbances are functional and can be resolved relatively easily, such as by the establishment of a regular sleep-wakefulness cycle;however, without adequate intervention the disturbances could gradually

  1. Multifocal Motor Neuropathy

    MedlinePlus

    ... Diversity Find People About NINDS NINDS Multifocal Motor Neuropathy Information Page Table of Contents (click to jump ... done? Clinical Trials Organizations What is Multifocal Motor Neuropathy? Multifocal motor neuropathy is a progressive muscle disorder ...

  2. Towards Cloud-based Asynchronous Elasticity for Iterative HPC Applications

    NASA Astrophysics Data System (ADS)

    da Rosa Righi, Rodrigo; Facco Rodrigues, Vinicius; André da Costa, Cristiano; Kreutz, Diego; Heiss, Hans-Ulrich

    2015-10-01

    Elasticity is one of the key features of cloud computing. It allows applications to dynamically scale computing and storage resources, avoiding over- and under-provisioning. In high performance computing (HPC), initiatives are normally modeled to handle bag-of-tasks or key-value applications through a load balancer and a loosely-coupled set of virtual machine (VM) instances. In the joint-field of Message Passing Interface (MPI) and tightly-coupled HPC applications, we observe the need of rewriting source codes, previous knowledge of the application and/or stop-reconfigure-and-go approaches to address cloud elasticity. Besides, there are problems related to how profit this new feature in the HPC scope, since in MPI 2.0 applications the programmers need to handle communicators by themselves, and a sudden consolidation of a VM, together with a process, can compromise the entire execution. To address these issues, we propose a PaaS-based elasticity model, named AutoElastic. It acts as a middleware that allows iterative HPC applications to take advantage of dynamic resource provisioning of cloud infrastructures without any major modification. AutoElastic provides a new concept denoted here as asynchronous elasticity, i.e., it provides a framework to allow applications to either increase or decrease their computing resources without blocking the current execution. The feasibility of AutoElastic is demonstrated through a prototype that runs a CPU-bound numerical integration application on top of the OpenNebula middleware. The results showed the saving of about 3 min at each scaling out operations, emphasizing the contribution of the new concept on contexts where seconds are precious.

  3. Motor control for a brushless DC motor

    NASA Technical Reports Server (NTRS)

    Peterson, William J. (Inventor); Faulkner, Dennis T. (Inventor)

    1985-01-01

    This invention relates to a motor control system for a brushless DC motor having an inverter responsively coupled to the motor control system and in power transmitting relationship to the motor. The motor control system includes a motor rotor speed detecting unit that provides a pulsed waveform signal proportional to rotor speed. This pulsed waveform signal is delivered to the inverter to thereby cause an inverter fundamental current waveform output to the motor to be switched at a rate proportional to said rotor speed. In addition, the fundamental current waveform is also pulse width modulated at a rate proportional to the rotor speed. A fundamental current waveform phase advance circuit is controllingly coupled to the inverter. The phase advance circuit is coupled to receive the pulsed waveform signal from the motor rotor speed detecting unit and phase advance the pulsed waveform signal as a predetermined function of motor speed to thereby cause the fundamental current waveform to be advanced and thereby compensate for fundamental current waveform lag due to motor winding reactance which allows the motor to operate at higher speeds than the motor is rated while providing optimal torque and therefore increased efficiency.

  4. Vesicles derived via AP-3 dependent recycling contribute to asynchronous release and influence information transfer

    PubMed Central

    Evstratova, Alesya; Chamberland, Simon; Faundez, Victor; Tóth, Katalin

    2014-01-01

    Summary Action potentials trigger synchronous and asynchronous neurotransmitter release. Temporal properties of both types of release could be altered in an activity-dependent manner. While the effects of activity-dependent changes in synchronous release on postsynaptic signal integration have been studied, the contribution of asynchronous release to information transfer during natural stimulus patterns is unknown. Here we find that during trains of stimulations, asynchronous release contributes to the precision of action potential firing. Our data show that this form of release is selectively diminished in AP-3b2 KO animals, which lack functional neuronal AP-3, an adaptor protein regulating vesicle formation from endosomes generated during bulk endocytosis. We find that in the absence of neuronal AP-3, asynchronous release is attenuated and the activity-dependent increase in the precision of action potential timing is compromised. Lack of asynchronous release decreases the capacity of synaptic information transfer and renders synaptic communication less reliable in response to natural stimulus patterns. PMID:25410111

  5. Bufferless Compression of Asynchronously Sampled ECG Signals in Cubic Hermitian Vector Space.

    PubMed

    Marisa, T; Niederhauser, T; Haeberlin, A; Wildhaber, R A; Vogel, R; Jacomet, M; Goette, J

    2015-12-01

    Asynchronous level crossing sampling analog-to-digital converters (ADCs) are known to be more energy efficient and produce fewer samples than their equidistantly sampling counterparts. However, as the required threshold voltage is lowered, the number of samples and, in turn, the data rate and the energy consumed by the overall system increases. In this paper, we present a cubic Hermitian vector-based technique for online compression of asynchronously sampled electrocardiogram signals. The proposed method is computationally efficient data compression. The algorithm has complexity O(n), thus well suited for asynchronous ADCs. Our algorithm requires no data buffering, maintaining the energy advantage of asynchronous ADCs. The proposed method of compression has a compression ratio of up to 90% with achievable percentage root-mean-square difference ratios as a low as 0.97. The algorithm preserves the superior feature-to-feature timing accuracy of asynchronously sampled signals. These advantages are achieved in a computationally efficient manner since algorithm boundary parameters for the signals are extracted a priori.

  6. Neurochemical and Neuropharmacological Aspects of Circadian Disruptions: An Introduction to Asynchronization

    PubMed Central

    Kohyama, Jun

    2011-01-01

    Circadian disruptions are common in modern society, and there is an urgent need for effective treatment strategies. According to standard diagnostic criteria, most adolescents showing both insomnia and daytime sleepiness are diagnosed as having behavioral-induced sleep efficiency syndrome resulting from insomnia due to inadequate sleep hygiene. However, a simple intervention of adequate sleep hygiene often fails to treat them. As a solution to this clinical problem, the present review first overviews the basic neurochemical and neuropharmachological aspects of sleep and circadian rhythm regulation, then explains several circadian disruptions from similar viewpoints, and finally introduces the clinical notion of asynchronization. Asynchronization is designated to explain the pathophysiology/pathogenesis of exhibition of both insomnia and hypersomnia in adolescents, which comprises disturbances in various aspects of biological rhythms. The major triggers for asynchronization are considered to be a combination of light exposure during the night, which disturbs the biological clock and decreases melatonin secretion, as well as a lack of light exposure in the morning, which prohibits normal synchronization of the biological clock to the 24-hour cycle of the earth and decreases the activity of serotonin. In the chronic phase of asynchronization, involvement of both wake- and sleep-promoting systems is suggested. Both conventional and alternative therapeutic approaches for potential treatment of asynchronization are suggested. PMID:22131941

  7. Research on inverter test system of synchronous motor using modbus communication

    NASA Astrophysics Data System (ADS)

    Cao, Wenlun; Chen, Bei; He, Yuyao

    2013-03-01

    In this paper, the hardware architecture of the servo system composed by self-made inverter and permanent magnet synchronous motor is introduced as well as its measurement and control system software features. Basing on the Modbus-RTU protocols which contain the CRC data verification between IPC and the inverter, we have built a communication system. The measurement and control software of servo system are realized, which consists of self-made inverter and PMSM. Compared with the servo system which consists of Schindler's ATV31 inverter and SIMO's asynchronous motor, the results are given. The experiment parameters include harmonic content which is contained by phase current and voltage, and also the motor speed. The results show that the measurement and control system are stable and reliable. Both the harmonic content of the Inverter output and the motor speed meet the requirements.

  8. Direct-drive field actuator motors

    DOEpatents

    Grahn, A.R.

    1995-07-11

    A high-torque, low speed, positive-drive field actuator motor is disclosed including a stator carrying at least one field actuator which changes in dimension responsive to application of an energy field, and at least one drive shoe movable by the dimensional changes of the field actuator to contact and move a rotor element with respect to the stator. Various embodiments of the motor are disclosed, and the rotor element may be moved linearly or arcuately. 37 figs.

  9. Direct-drive field actuator motors

    DOEpatents

    Grahn, Allen R.

    1995-01-01

    A high-torque, low speed, positive-drive field actuator motor including a stator carrying at least one field actuator which changes in dimension responsive to application of an energy field, and at least one drive shoe movable by the dimensional changes of the field actuator to contact and move a rotor element with respect to the stator. Various embodiments of the motor are disclosed, and the rotor element may be moved linearly or arcuately.

  10. Split-Stirling-cycle displacer linear-electric drive

    NASA Technical Reports Server (NTRS)

    Ackermann, R. A.; Bhate, S. K.; Byrne, D. V.

    1983-01-01

    The retrofit of a 1/4-W split-Stirling cooler with a linear driven on the displacer was achieved and its performance characterized. The objective of this work was to demonstrate that a small linear motor could be designed to meet the existing envelope specifications of the cooler and that an electric linear drive on the displacer could improve the cooler's reliability and performance. The paper describes the characteristics of this motor and presents cooler test results.

  11. Dual stator winding variable speed asynchronous generator: magnetic equivalent circuit with saturation, FEM analysis and experiments

    NASA Astrophysics Data System (ADS)

    Tutelea, L. N.; Muntean, N.; Deaconu, S. I.; Cunţan, C. D.

    2016-02-01

    The authors carried out a theoretical and experimental study of dual stator winding squirrel cage asynchronous generator (DSWA) behaviour in the presence of saturation regime (non-sinusoidal) due to the variable speed operation. The main aims are the determination of the relations of calculating the equivalent parameters of the machine windings, FEM validation of parameters and characteristics with free FEMM 4.2 computing software and the practice experimental tests for verifying them. Issue is limited to three phase range of double stator winding cage-asynchronous generator of small sized powers, the most currently used in the small adjustable speed wind or hydro power plants. The tests were carried out using three-phase asynchronous generator having rated power of 6 [kVA].

  12. Gigabit Ethernet signal transmission using asynchronous optical code division multiple access.

    PubMed

    Ma, Philip Y; Fok, Mable P; Shastri, Bhavin J; Wu, Ben; Prucnal, Paul R

    2015-12-15

    We propose and experimentally demonstrate a novel architecture for interfacing and transmitting a Gigabit Ethernet (GbE) signal using asynchronous incoherent optical code division multiple access (OCDMA). This is the first such asynchronous incoherent OCDMA system carrying GbE data being demonstrated to be working among multi-users where each user is operating with an independent clock/data rate and is granted random access to the network. Three major components, the GbE interface, the OCDMA transmitter, and the OCDMA receiver are discussed in detail. The performance of the system is studied and characterized through measuring eye diagrams, bit-error rate and packet loss rate in real-time file transfer. Our Letter also addresses the near-far problem and realizes asynchronous transmission and detection of signal.

  13. Towards asynchronous brain-computer interfaces: a P300-based approach with statistical models.

    PubMed

    Zhang, Haihong; Wang, Chuanchu; Guan, Cuntai

    2007-01-01

    Asynchronous control is a critical issue in developing brain-computer interfaces for real-life applications, where the machine should be able to detect the occurrence of a mental command. In this paper we propose a computational approach for robust asynchronous control using the P300 signal, in a variant of oddball paradigm. First, we use Gaussian models in the support vector margin space to describe various types of EEG signals that are present in an asynchronous P300-based BCI. This allows us to derive a probability measure of control state given EEG observations. Second, we devise a recursive algorithm to detect and locate control states in ongoing EEG. Experimental results indicate that our system allows information transfer at approx. 20bit/min at low false alarm rate (1/min). PMID:18003145

  14. Cell cycle timing regulation during asynchronous divisions of the early C. elegans embryo.

    PubMed

    Tavernier, N; Labbé, J C; Pintard, L

    2015-10-01

    A fundamental question in developmental biology is how different cell lineages acquire different cell cycle durations. With its highly stereotypical asymmetric and asynchronous cell divisions, the early Caenorhabditis elegans embryo provides an ideal system to study lineage-specific cell cycle timing regulation during development, with high spatio-temporal resolution. The first embryonic division is asymmetric and generates two blastomeres of different sizes (AB>P1) and developmental potentials that divide asynchronously, with the anterior somatic blastomere AB dividing reproducibly two minutes before the posterior germline blastomere P1. The evolutionarily conserved PAR proteins (abnormal embryonic PARtitioning of cytoplasm) regulate all of the asymmetries in the early embryo including cell cycle asynchrony between AB and P1 blastomeres. Here we discuss our current understanding and open questions on the mechanism by which the PAR proteins regulate asynchronous cell divisions in the early C. elegans embryo.

  15. Asynchronous Video Interviewing as a New Technology in Personnel Selection: The Applicant's Point of View.

    PubMed

    Brenner, Falko S; Ortner, Tuulia M; Fay, Doris

    2016-01-01

    The present study aimed to integrate findings from technology acceptance research with research on applicant reactions to new technology for the emerging selection procedure of asynchronous video interviewing. One hundred six volunteers experienced asynchronous video interviewing and filled out several questionnaires including one on the applicants' personalities. In line with previous technology acceptance research, the data revealed that perceived usefulness and perceived ease of use predicted attitudes toward asynchronous video interviewing. Furthermore, openness revealed to moderate the relation between perceived usefulness and attitudes toward this particular selection technology. No significant effects emerged for computer self-efficacy, job interview self-efficacy, extraversion, neuroticism, and conscientiousness. Theoretical and practical implications are discussed. PMID:27378969

  16. FAST: A fully asynchronous and status-tracking pattern for geoprocessing services orchestration

    NASA Astrophysics Data System (ADS)

    Wu, Huayi; You, Lan; Gui, Zhipeng; Gao, Shuang; Li, Zhenqiang; Yu, Jingmin

    2014-09-01

    Geoprocessing service orchestration (GSO) provides a unified and flexible way to implement cross-application, long-lived, and multi-step geoprocessing service workflows by coordinating geoprocessing services collaboratively. Usually, geoprocessing services and geoprocessing service workflows are data and/or computing intensive. The intensity feature may make the execution process of a workflow time-consuming. Since it initials an execution request without blocking other interactions on the client side, an asynchronous mechanism is especially appropriate for GSO workflows. Many critical problems remain to be solved in existing asynchronous patterns for GSO including difficulties in improving performance, status tracking, and clarifying the workflow structure. These problems are a challenge when orchestrating performance efficiency, making statuses instantly available, and constructing clearly structured GSO workflows. A Fully Asynchronous and Status-Tracking (FAST) pattern that adopts asynchronous interactions throughout the whole communication tier of a workflow is proposed for GSO. The proposed FAST pattern includes a mechanism that actively pushes the latest status to clients instantly and economically. An independent proxy was designed to isolate the status tracking logic from the geoprocessing business logic, which assists the formation of a clear GSO workflow structure. A workflow was implemented in the FAST pattern to simulate the flooding process in the Poyang Lake region. Experimental results show that the proposed FAST pattern can efficiently tackle data/computing intensive geoprocessing tasks. The performance of all collaborative partners was improved due to the asynchronous mechanism throughout communication tier. A status-tracking mechanism helps users retrieve the latest running status of a GSO workflow in an efficient and instant way. The clear structure of the GSO workflow lowers the barriers for geospatial domain experts and model designers to

  17. Differences in Electronic Exchanges in Synchronous and Asynchronous Computer-Mediated Communication: The Effect of Culture as a Mediating Variable

    ERIC Educational Resources Information Center

    Angeli, Charoula; Schwartz, Neil H.

    2016-01-01

    Two hundred and eighty undergraduates from universities in two countries were asked to read didactic material, and then think and write about potential solutions to an ill-defined problem. The writing was conducted within a synchronous or asynchronous computer-mediated communication (CMC) environment. Asynchronous CMC took the form of email…

  18. The Effects of Metacognitive Instruction Embedded within an Asynchronous Learning Network on Scientific Inquiry Skills. Research Report

    ERIC Educational Resources Information Center

    Zion, Michal; Michalsky, Tova; Mevarech, Zemira R.

    2005-01-01

    The study is aimed at investigating the effects of four learning methods on students' scientific inquiry skills. The four learning methods are: (a) metacognitive-guided inquiry within asynchronous learning networked technology (MINT); (b) an asynchronous learning network (ALN) with no metacognitive guidance; (c) metacognitive-guided inquiry…

  19. Good Quality Discussion Is Necessary but Not Sufficient in Asynchronous Tuition: A Brief Narrative Review of the Literature

    ERIC Educational Resources Information Center

    Fear, William James; Erikson-Brown, Andrew

    2014-01-01

    Online learning is a growing field of education with a corresponding increase in the use of asynchronous discussion. Asynchronous discussion is a form of interaction that is mediated rather than direct and where there is a time lag in the interactions between discussants. In this paper we conducted a brief narrative review of the literature on…

  20. Distributed Teaching Presence and Participants' Activity Profiles: A Theoretical Approach to the Structural Analysis of Asynchronous Learning Networks

    ERIC Educational Resources Information Center

    Coll, Cesar; Engel, Anna; Bustos, Alfonso

    2009-01-01

    The rapid spread of learning networks based on asynchronous written communication--Asynchronous Learning Networks (ALNs)--makes it crucial to assess the possibilities offered by these new environments to facilitate and promote learning processes and learning outcomes. Our interest in this area is specifically directed towards the study of…

  1. Enhancing Discussions in the Asynchronous Online Classroom: The Lack of Face-to-Face Interaction Does Not Lessen the Lesson

    ERIC Educational Resources Information Center

    Comer, Debra R.; Lenaghan, Janet A.

    2013-01-01

    This article addresses educators' concerns about using asynchronous online discussions in lieu of face-to-face discussions. Drawing from research on asynchronous online education and Bloom's taxonomy, the authors introduce the system of "original examples" and "value-added comments" that they have developed to promote engaging and meaningful…

  2. The Negotiation Model in Asynchronous Computer-Mediated Communication (CMC): Negotiation in Task-Based Email Exchanges

    ERIC Educational Resources Information Center

    Kitade, Keiko

    2006-01-01

    Based on recent studies, computer-mediated communication (CMC) has been considered a tool to aid in language learning on account of its distinctive interactional features. However, most studies have referred to "synchronous" CMC and neglected to investigate how "asynchronous" CMC contributes to language learning. Asynchronous CMC possesses…

  3. An Examination of the Effectiveness of Embedded Audio Feedback for English as a Foreign Language Students in Asynchronous Online Discussions

    ERIC Educational Resources Information Center

    Olesova, Larisa A.

    2011-01-01

    This study examined the effect of asynchronous embedded audio feedback on English as a Foreign Language (EFL) students' higher-order learning and perception of the audio feedback versus text-based feedback when the students participated in asynchronous online discussions. In addition, this study examined how the impact and perceptions…

  4. Scenario Decomposition for 0-1 Stochastic Programs: Improvements and Asynchronous Implementation

    DOE PAGES

    Ryan, Kevin; Rajan, Deepak; Ahmed, Shabbir

    2016-05-01

    We recently proposed scenario decomposition algorithm for stochastic 0-1 programs finds an optimal solution by evaluating and removing individual solutions that are discovered by solving scenario subproblems. In our work, we develop an asynchronous, distributed implementation of the algorithm which has computational advantages over existing synchronous implementations of the algorithm. Improvements to both the synchronous and asynchronous algorithm are proposed. We also test the results on well known stochastic 0-1 programs from the SIPLIB test library and is able to solve one previously unsolved instance from the test set.

  5. Asynchronous teaching of psychomotor skills through VR annotations: evaluation in digital rectal examination.

    PubMed

    Rissanen, Mikko J; Kume, Naoto; Kuroda, Yoshihiro; Kuroda, Tomohiro; Yoshimura, Koji; Yoshihara, Hiroyuki

    2008-01-01

    Many VR technology based training systems use expert's motion data as the training aid, but would not provide any short-cut to teaching medical skills that do not depend on exact motions. Earlier we presented Annotated Simulation Records (ASRs), which can be used to encapsulate experts' insight on psychomotor skills. Annotations made to behavioural parameters in training simulators enable asynchronous teaching instead of just motion training in a proactive way to the learner. We evaluated ASRs for asynchronous teaching of Digital Rectal Examination (DRE) with 3 urologists and 8 medical students. The ASRs were found more effective than motion-based training with verbal feedback.

  6. Miniaturization of Planar Horn Motors

    NASA Technical Reports Server (NTRS)

    Sherrit, Stewart; Ostlund, Patrick N.; Chang, Zensheu; Bao, Xiaoqi; Bar-Cohen, Yoseph; Widholm, Scott E.; Badescu, Mircea

    2012-01-01

    There is a great need for compact, efficient motors for driving various mechanisms including robots or mobility platforms. A study is currently underway to develop a new type of piezoelectric actuators with significantly more strength, low mass, small footprint, and efficiency. The actuators/motors utilize piezoelectric actuated horns which have a very high power density and high electromechanical conversion efficiency. The horns are fabricated using our recently developed novel pre-stress flexures that make them thermally stable and increases their coupling efficiency. The monolithic design and integrated flexures that pre-stresses the piezoelectric stack eliminates the use of stress bolt. This design allows embedding solid-state motors and actuators in any structure so that the only macroscopically moving parts are the rotor or the linear translator. The developed actuator uses a stack/horn actuation and has a Barth motor configuration, which potentially generates very large torque and speeds that do not require gearing. Finite element modeling and design tools were investigated to determine the requirements and operation parameters and the results were used to design and fabricate a motor. This new design offers a highly promising actuation mechanism that can potentially be miniaturized and integrated into systems and structures. It can be configured in many shapes to operate as multi-degrees of freedom and multi-dimensional motors/actuators including unidirectional, bidirectional, 2D and 3D. In this manuscript, we are reporting the experimental measurements from a bench top design and the results from the efforts to miniaturize the design using 2x2x2 mm piezoelectric stacks integrated into thin plates that are of the order of3 x 3x 0.2 cm.

  7. Miniaturization of planar horn motors

    NASA Astrophysics Data System (ADS)

    Sherrit, Stewart; Ostlund, Patrick N.; Chang, Zensheu; Bao, Xiaoqi; Bar-Cohen, Yoseph; Widholm, Scott E.; Badescu, Mircea

    2012-04-01

    There is a great need for compact, efficient motors for driving various mechanisms including robots or mobility platforms. A study is currently underway to develop a new type of piezoelectric actuators with significantly more strength, low mass, small footprint, and efficiency. The actuators/motors utilize piezoelectric actuated horns which have a very high power density and high electromechanical conversion efficiency. The horns are fabricated using our recently developed novel pre-stress flexures that make them thermally stable and increases their coupling efficiency. The monolithic design and integrated flexures that pre-stresses the piezoelectric stack eliminates the use of a stress bolt. This design allows embedding solid-state motors and actuators in any structure so that the only macroscopically moving parts are the rotor or the linear translator. The developed actuator uses a stack/horn actuation and has a Barth motor configuration, which potentially generates very large torque and speeds that do not require gearing. Finite element modeling and design tools were investigated to determine the requirements and operation parameters and the results were used to design and fabricate a motor. This new design offers a highly promising actuation mechanism that can potentially be miniaturized and integrated into systems and structures. It can be configured in many shapes to operate as multi-degrees of freedom and multi-dimensional motors/actuators including unidirectional, bidirectional, 2D and 3D. In this manuscript, we are reporting the experimental measurements from a bench top design and the results from the efforts to miniaturize the design using 2×2×2 mm piezoelectric stacks integrated into thin plates that are of the order of 3 × 3 × 0.2 cm.

  8. Linear Proof Mass Actuator

    NASA Technical Reports Server (NTRS)

    Holloway, Sidney E., III

    1994-01-01

    This paper describes the mechanical design, analysis, fabrication, testing, and lessons learned by developing a uniquely designed spaceflight-like actuator. The linear proof mass actuator (LPMA) was designed to attach to both a large space structure and a ground test model without modification. Previous designs lacked the power to perform in a terrestrial environment while other designs failed to produce the desired accelerations or frequency range for spaceflight applications. Thus, the design for a unique actuator was conceived and developed at NASA Langley Research Center. The basic design consists of four large mechanical parts (mass, upper housing, lower housing, and center support) and numerous smaller supporting components including an accelerometer, encoder, and four drive motors. Fabrication personnel were included early in the design phase of the LPMA as part of an integrated manufacturing process to alleviate potential difficulties in machining an already challenging design. Operating testing of the LPMA demonstrated that the actuator is capable of various types of load functions.

  9. Linear Proof Mass Actuator

    NASA Technical Reports Server (NTRS)

    Holloway, S. E., III

    1995-01-01

    This paper describes the mechanical design, analysis, fabrication, testing, and lessons learned by developing a uniquely designed spaceflight-like actuator. The Linear Proof Mass Actuator (LPMA) was designed to attach to both a large space structure and a ground test model without modification. Previous designs lacked the power to perform in a terrestrial environment while other designs failed to produce the desired accelerations or frequency range for spaceflight applications. Thus, the design for a unique actuator was conceived and developed at NASA Langley Research Center. The basic design consists of four large mechanical parts (Mass, Upper Housing, Lower Housing, and Center Support) and numerous smaller supporting components including an accelerometer, encoder, and four drive motors. Fabrication personnel were included early in the design phase of the LPMA as part of an integrated manufacturing process to alleviate potential difficulties in machining an already challenging design. Operational testing of the LPMA demonstrated that the actuator is capable of various types of load functions.

  10. Sparse optimal motor estimation (SOME) for extracting commands for prosthetic limbs.

    PubMed

    Li, Yao; Smith, Lauren H; Hargrove, Levi J; Weber, Douglas J; Loeb, Gerald E

    2013-01-01

    It is possible to replace amputated limbs with mechatronic prostheses, but their operation requires the user's intentions to be detected and converted into control signals to the actuators. Fortunately, the motoneurons (MNs) that controlled the amputated muscles remain intact and capable of generating electrical signals, but these signals are difficult to record. Even the latest microelectrode array technologies and targeted motor reinnervation can provide only sparse sampling of the hundreds of motor units that comprise the motor pool for each muscle. Simple rectification and integration of such records is likely to produce noisy and delayed estimates of the actual intentions of the user. We have developed a novel algorithm for optimal estimation of motor pool excitation based on the recruitment and firing rates of a small number (2-10) of discriminated motor units. We first derived the motor estimation algorithm from normal patterns of modulated MN activity based on a previously published model of individual MN recruitment and asynchronous frequency modulation. The algorithm was then validated on a target motor reinnervation subject using intramuscular fine-wire recordings to obtain single motor units.

  11. LINEAR ACCELERATOR

    DOEpatents

    Colgate, S.A.

    1958-05-27

    An improvement is presented in linear accelerators for charged particles with respect to the stable focusing of the particle beam. The improvement consists of providing a radial electric field transverse to the accelerating electric fields and angularly introducing the beam of particles in the field. The results of the foregoing is to achieve a beam which spirals about the axis of the acceleration path. The combination of the electric fields and angular motion of the particles cooperate to provide a stable and focused particle beam.

  12. Flipping the Online Classroom with Web 2.0: The Asynchronous Workshop

    ERIC Educational Resources Information Center

    Cummings, Lance

    2016-01-01

    This article examines how Web 2.0 technologies can be used to "flip" the online classroom by creating asynchronous workshops in social environments where immediacy and social presence can be maximized. Using experience teaching several communication and writing classes in Google Apps (Google+, Google Hangouts, Google Drive, etc.), I…

  13. Distributed Teaching Presence and Communicative Patterns in Asynchronous Learning: Name versus Reply Networks

    ERIC Educational Resources Information Center

    Engel, Anna; Coll, Cesar; Bustos, Alfonso

    2013-01-01

    This work explores some methodological challenges in the application of Social Network Analysis (SNA) to the study of "Asynchronous Learning Networks" (ALN). Our interest in the SNA is situated within the framework of the study of Distributed Teaching Presence (DTP), understood as the exercise of educational influence, through a multi-method…

  14. Lessons Learned: Using Asynchronous Computer-Mediated Conferencing To Facilitate Group Discussion.

    ERIC Educational Resources Information Center

    Cartwright, Juliana

    2000-01-01

    A nursing school used asynchronous computer conferencing for student discussion groups and three distance sites and one host site. Course evaluation showed students appreciated the ability to review discussions and reflect before commenting and felt team collegiality. A switch to different software reduced the technology learning curve, but…

  15. Developing Asynchronous Online Courses: Key Instructional Strategies in a Social Metacognitive Constructivist Learning Trajectory

    ERIC Educational Resources Information Center

    Niess, Margaret; Gillow-Wiles, Henry

    2013-01-01

    This qualitative, design-based research study resulted in a proposal for a comprehensive set of best instructional practices immersed in a learning trajectory, outlining the tools, processes and the content development for online asynchronous, text-based learning in graduate level professional development courses. The outcome provides a rich…

  16. Use of Podcasting as an Innovative Asynchronous E-Learning Tool for Students

    ERIC Educational Resources Information Center

    Jalali, Alireza; Leddy, John; Gauthier, Martin; Sun, Rong; Hincke, Maxwell; Carnegie, Jacqueline

    2011-01-01

    Podcasting is an innovative, asynchronous communication tool. A pilot study was conducted to assess the utility of podcasting as an educational tool for undergraduate medical students. A paper-and-pencil questionnaire was developed and distributed to the 40 first-year students enrolled in the francophone stream of the medical curriculum at the…

  17. Relationship of Metacognitive Monitoring with Interaction in an Asynchronous Online Discussion Forum

    ERIC Educational Resources Information Center

    Topcu, Abdullah

    2010-01-01

    Monitoring one's own performance accurately is essential for information-processing and self-regulation, which are indispensable in an online learning environment. In this article, the effect of metacognitive monitoring (MM) on interaction in an asynchronous online discussion forum was investigated. Transcripts of this forum, which was integrated…

  18. Participation in Asynchronous Online Discussion Forums Does Improve Student Learning of Gross Anatomy

    ERIC Educational Resources Information Center

    Green, Rodney A.; Farchione, Davide; Hughes, Diane L.; Chan, Siew-Pang

    2014-01-01

    Asynchronous online discussion forums are common in blended learning models and are popular with students. A previous report has suggested that participation in these forums may assist student learning in a gross anatomy subject but it was unclear as to whether more academically able students post more often or whether participation led to…

  19. Student Outcomes Associated with Use of Asynchronous Online Discussion Forums in Gross Anatomy Teaching

    ERIC Educational Resources Information Center

    Green, Rodney A.; Hughes, Diane L.

    2013-01-01

    Asynchronous online discussion forums are increasingly common in blended learning environments but the relationship to student learning outcomes has not been reported for anatomy teaching. Forums were monitored in two multicampus anatomy courses; an introductory first year course and a second year physiotherapy-specific course. The forums are…

  20. Theoretically Based Pedagogical Strategies Leading to Deep Learning in Asynchronous Online Gerontology Courses

    ERIC Educational Resources Information Center

    Majeski, Robin; Stover, Merrily

    2007-01-01

    Online learning has enjoyed increasing popularity in gerontology. This paper presents instructional strategies grounded in Fink's (2003) theory of significant learning designed for the completely asynchronous online gerontology classroom. It links these components with the development of mastery learning goals and provides specific guidelines for…

  1. Self-Efficacy for Learning Mathematics Asynchronously: Instrument Refinement and the Relationship to Mathematics Achievement

    ERIC Educational Resources Information Center

    Hodges, Charles; Jones, R. Caroline; Prater, Alyssa

    2014-01-01

    The purpose of this paper is to report the results of a two-part study. Study 1 was conducted to refine and validate a survey instrument, SELMA (Hodges, 2008), used to measure learners' self-efficacy toward learning mathematics in online or technology-intensive, asynchronous learning environments. Study 2 was conducted to investigate the…

  2. Asynchronous Discussion and Communication Patterns in Online and Hybrid History Courses. Scholarship of Teaching and Learning

    ERIC Educational Resources Information Center

    Vess, Deborah L.

    2005-01-01

    Asynchronous online discussion has been shown to enhance communication between students and to elicit many cognitive indicators. Nevertheless, historians have often been reluctant to make use of such instructional technology. Students enrolled in a fully online world civilization course corroborated qualitative research findings regarding the…

  3. Learning about the Literacy Development of English Language Learners in Asynchronous Online Discussions

    ERIC Educational Resources Information Center

    De Oliveira, Luciana C.; Olesova, Larisa

    2013-01-01

    This study examined asynchronous online discussions in the online course "English Language Development" to identify themes related to participants' learning about the language and literacy development of English Language Learners when they facilitated online discussions to determine whether the participants developed sufficient…

  4. Pre-Service Teachers' Perceptions of Asynchronous Online Discussion on Blackboard

    ERIC Educational Resources Information Center

    Yeh, Hsin-Te; Lahman, Maria

    2007-01-01

    The purpose of this phenomenological study was to understand students' perceptions of using asynchronous online discussion as a learning tool. Six pre-service teachers who took a course in educational technology applications for secondary grades at a Rocky Mountain region mid-sized university were selected to be interviewed. Phenomenological data…

  5. Effects of Synchronous Lessons on Students in an Asynchronous Online Art Course

    ERIC Educational Resources Information Center

    Werner, Polly D.

    2011-01-01

    The purpose of this study was to determine what effects synchronous instruction has on students in an asynchronous online art course. Action research was selected as the research method as it allows the researcher to study his or her own classroom in order to improve their own instruction. Data was collected for a period of one month from five…

  6. The Influence of Group Size on Nonmandatory Asynchronous Instructional Discussion Groups.

    ERIC Educational Resources Information Center

    Caspi, Avner; Gorsky, Paul; Chajut, Eran

    2003-01-01

    Examines the effect of group size on students' behavior in asynchronous, nonmandatory instructional discussion groups. Focuses on four main questions on whether group size: affects the proportion of learner-learner and instructor-learner interactions; influences number of messages instructors post; have an effect on number of contributions that…

  7. Factor Validity of the Motivated Strategies for Learning Questionnaire (MSLQ) in Asynchronous Online Learning Environments (AOLE)

    ERIC Educational Resources Information Center

    Cho, Moon-Heum; Summers, Jessica

    2012-01-01

    The purpose of this study was to investigate the factor validity of the Motivated Strategies for Learning Questionnaire (MSLQ) in asynchronous online learning environments. In order to check the factor validity, confirmatory factor analysis (CFA) was conducted with 193 cases. Using CFA, it was found that the original measurement model fit for…

  8. Asynchronous remodeling is a driver of failed regeneration in Duchenne muscular dystrophy

    PubMed Central

    Dadgar, Sherry; Wang, Zuyi; Johnston, Helen; Kesari, Akanchha; Nagaraju, Kanneboyina; Chen, Yi-Wen; Hill, D. Ashley; Partridge, Terence A.; Giri, Mamta; Freishtat, Robert J.; Nazarian, Javad; Xuan, Jianhua; Wang, Yue

    2014-01-01

    We sought to determine the mechanisms underlying failure of muscle regeneration that is observed in dystrophic muscle through hypothesis generation using muscle profiling data (human dystrophy and murine regeneration). We found that transforming growth factor β–centered networks strongly associated with pathological fibrosis and failed regeneration were also induced during normal regeneration but at distinct time points. We hypothesized that asynchronously regenerating microenvironments are an underlying driver of fibrosis and failed regeneration. We validated this hypothesis using an experimental model of focal asynchronous bouts of muscle regeneration in wild-type (WT) mice. A chronic inflammatory state and reduced mitochondrial oxidative capacity are observed in bouts separated by 4 d, whereas a chronic profibrotic state was seen in bouts separated by 10 d. Treatment of asynchronously remodeling WT muscle with either prednisone or VBP15 mitigated the molecular phenotype. Our asynchronous regeneration model for pathological fibrosis and muscle wasting in the muscular dystrophies is likely generalizable to tissue failure in chronic inflammatory states in other regenerative tissues. PMID:25313409

  9. Socially Shared Metacognitive Regulation in Asynchronous CSCL in Science: Functions, Evolution and Participation

    ERIC Educational Resources Information Center

    Iiskala, Tuike; Volet, Simone; Lehtinen, Erno; Vauras, Marja

    2015-01-01

    The significance of socially shared metacognitive regulation (SSMR) in collaborative learning is gaining momentum. To date, however, there is still a paucity of research of how SSMR is manifested in asynchronous computer-supported collaborative learning (CSCL), and hardly any systematic investigation of SSMR's functions and evolution across…

  10. Collaborative Learning Processes in an Asynchronous Environment: An Analysis through Discourse and Social Networks

    ERIC Educational Resources Information Center

    Tirado, Ramon; Aguaded, Ignacio; Hernando, Angel

    2011-01-01

    This article analyses an experience in collaborative learning in an asynchronous writing environment through discussion forums on a WebCt platform of the University of Huelva's virtual campus, and was part of an innovative teaching project in 2007-08. The main objectives are to describe the processes of collaborative knowledge construction and the…

  11. A Study of Synchronous versus Asynchronous Collaboration in an Online Business Writing Class

    ERIC Educational Resources Information Center

    Mabrito, Mark

    2006-01-01

    A case study examined the collaborative experiences of students in an online business writing classroom. The purpose was to examine the same groups of students working on collaborative writing assignments in both a synchronous (real-time) and an asynchronous (non-real-time) discussion forum. This study focused on examining the amount, pattern, and…

  12. Solving Ill-Structured Problems in Asynchronous Online Discussions: Built-in Scaffolds vs. No Scaffolds

    ERIC Educational Resources Information Center

    Ng, Connie Siew Ling; Cheung, Wing Sum; Hew, Khe Foon

    2010-01-01

    Solving ill-structured problems is regarded as an important learning outcome in education as it allows learners to apply theories learnt into real practice. An asynchronous online discussion, with extended time for reflection, is an appropriate learning environment to engage learners in solving ill-structured problems. However, scaffolds may be…

  13. Using Asynchronous Learning Technology To Make the Connections among Faculty, Students, and Teachers.

    ERIC Educational Resources Information Center

    McMullen, David W.; Goldbaum, Howard; Wolffe, Robert J.; Sattler, Joan L.

    This paper traces the evolution and application of asynchronous teaching and learning tools at Bradley University (Illinois), emphasizing their use in teacher education. The paper details the utilization of e-mail, the World Wide Web, and CyberProf, highlighting collaborative projects that emphasize mentoring and professional development. In the…

  14. Using the Community of Inquiry Model to Investigate Students' Knowledge Construction in Asynchronous Online Discussions

    ERIC Educational Resources Information Center

    Liu, Chien-Jen; Yang, Shu Ching

    2014-01-01

    This study used the Community of Inquiry (CoI) model proposed by Garrison to investigate students' level of knowledge construction in asynchronous discussions. The participants included 36 senior students (27 males) majoring in information management. The students attended 18 weeks of an online information ethics course. In this study, four types…

  15. The Role of Beliefs and Motivation in Asynchronous Online Learning in College-Level Classes

    ERIC Educational Resources Information Center

    Xie, Kui; Huang, Kun

    2014-01-01

    Epistemic and learning beliefs were found to affect college students' cognitive engagement and study strategies, as well as motivation in classroom settings. However, the relationships between epistemic and learning beliefs, motivation, learning perception, and students' actual learning participation in asynchronous online settings have been…

  16. Facilitating Asynchronous Discussions in Learning Communities: The Impact of Moderation Strategies

    ERIC Educational Resources Information Center

    Kienle, Andrea; Ritterskamp, Carsten

    2007-01-01

    A facilitator or moderator is often responsible for supporting processes and their progress in learning communities. In this article we present an approach for supporting moderators of asynchronous processes in learning communities. This approach follows the socio-technical perspective: it includes a theory-based development of moderator tasks and…

  17. The Effects of Self-Generated Synchronous and Asynchronous Visual Speech Feedback on Overt Stuttering Frequency

    ERIC Educational Resources Information Center

    Snyder, Gregory J.; Hough, Monica Strauss; Blanchet, Paul; Ivy, Lennette J.; Waddell, Dwight

    2009-01-01

    Purpose: Relatively recent research documents that visual choral speech, which represents an externally generated form of synchronous visual speech feedback, significantly enhanced fluency in those who stutter. As a consequence, it was hypothesized that self-generated synchronous and asynchronous visual speech feedback would likewise enhance…

  18. Visual Search in a Multi-Element Asynchronous Dynamic (MAD) World

    ERIC Educational Resources Information Center

    Kunar, Melina A.; Watson, Derrick G.

    2011-01-01

    In visual search tasks participants search for a target among distractors in strictly controlled displays. We show that visual search principles observed in these tasks do not necessarily apply in more ecologically valid search conditions, using dynamic and complex displays. A multi-element asynchronous dynamic (MAD) visual search was developed in…

  19. Asynchronous and Synchronous Online Teaching: Perspectives of Canadian High School Distance Education Teachers

    ERIC Educational Resources Information Center

    Murphy, Elizabeth; Rodriguez-Manzanares, Maria A.; Barbour, Michael

    2011-01-01

    This paper presents the results of an inductive, interpretive analysis of the perspectives of 42 Canadian high school distance education (DE) teachers on asynchronous and synchronous online teaching. The paper includes a conceptual overview of the affordances and constraints of each form of teaching. Findings provided insight into the following…

  20. Relationships between Self-Regulation and Social Experiences in Asynchronous Online Learning Environments

    ERIC Educational Resources Information Center

    Cho, Moon-Heum; Demei, Shen; Laffey, James

    2010-01-01

    The purpose of this study was to determine the extent to which students' self-regulated learning predicts peer social presence, instructor social presence, sense of connectedness, and sense of learning in asynchronous online learning environments. Self-regulated learning has been measured with self-regulation for learning tasks (SRLT) and…

  1. Cooperative Learning in Graduate Student Projects: Comparing Synchronous versus Asynchronous Collaboration

    ERIC Educational Resources Information Center

    Strang, Kenneth

    2013-01-01

    Cooperative learning was applied in a graduate project management course to compare the effectiveness of asynchronous versus synchronous online team meetings. An experiment was constructed to allocate students to project teams while ensuring there was a balance of requisite skills, namely systems analysis and design along with HTML/Javascript…

  2. Using Asynchronous Video to Achieve Instructor Immediacy and Closeness in Online Classes: Experiences from Three Cases

    ERIC Educational Resources Information Center

    Griffiths, Michael; Graham, Charles

    2010-01-01

    This research sought to understand the experiences of students and instructors with asynchronous video (video-mail) using webcams in three online sections of teacher education classes at Brigham Young University. We examined the experiences of students through scores and comments posted in student ratings surveys, and the experiences of…

  3. Effects of asynchronous snowmelt on flushing of dissolved organic carbon: A mixing model approach

    USGS Publications Warehouse

    Boyer, E.W.; Hornberger, G.M.; Bencala, K.E.; McKnight, Diane M.

    2000-01-01

    In many snowmelt-dominated catchments, stream dissolved organic carbon (DOC) levels typically increase rapidly as spring melt commences, peak before maximum discharge, and decrease quickly as melting continues. We present data from Deer Creek (Summit County, CO) that shows this distinctive flushing response of DOC during snowmelt runoff, with DOC stored in landscape soils flushed to the stream in response to infiltrating melt waters. Our prior studies show that asynchronous melting of the snowpack across the landscape causes the spring DOC flush to be initiated at different times throughout the catchment. In this study we quantify characteristics of the asynchronous melt and its effect on DOC flushing. We investigated whether a simple mixing model can be used to capture the essentials of the asynchronous melting of a seasonal snowpack and its controls on DOC transport. We divided the catchment into zones of aspect and elevation, which largely determine spatial and temporal variations in the distribution of snow. TOPMODEL was used to simulate the hydrology in each zone, and the simulated flow paths were routed through a simple DOC mixing model to predict contributions of DOC to the stream. The zonal responses were aggregated to give a predicted response of hydrology and DOC fluxes for the entire catchment. Our results indicate that asynchronous melting-which determines the timing of contributions of discharge and DOC to streamflow from different areas of the landscape-can be quantified using a simple modeling approach. Copyright ?? 2000 John Wiley & Sons, Ltd.

  4. University Instructor Perceptions of the Use of Asynchronous Text-Based Discussion in Distance Courses.

    ERIC Educational Resources Information Center

    Kanuka, Heather; Collett, Dave; Caswell, Cynthia

    2002-01-01

    Describes a study that was conducted to investigate instructor perceptions of the impact on instruction when asynchronous text-based Internet communication technology was integrated into distance courses at the University of Alberta. Highlights include the theory of transactional distance; and results of interviews with instructors regarding…

  5. Toward an Understanding of Why Students Contribute in Asynchronous Online Discussions

    ERIC Educational Resources Information Center

    Cheung, Wing Sum; Hew, Khe Foon; Ling Ng, Connie Siew

    2008-01-01

    The use of online learning is growing very fast in universities. Consequently, understanding how to promote student contribution in asynchronous online discussions, which is considered an integral part of online learning, has become increasingly crucial. Previous research has examined how factors, such as instructor facilitation techniques may…

  6. Cultural Influences on Chinese Students' Asynchronous Online Learning in a Canadian University

    ERIC Educational Resources Information Center

    Zhao, Naxin; McDougall, Douglas

    2008-01-01

    This study explored six Chinese graduate students' asynchronous online learning in a large urban Canadian university. Individual interviews in Mandarin elicited their perceptions of online learning, their participation in it, and the cultural factors that influenced their experiences. In general, the participants had a positive attitude towards…

  7. Tagging Thinking Types in Asynchronous Discussion Groups: Effects on Critical Thinking

    ERIC Educational Resources Information Center

    Schellens, T.; Van Keer, H.; De Wever, B.; Valcke, M.

    2009-01-01

    The present study focuses on the use of thinking types as a possible way to structure university students' discourse in asynchronous discussion groups and consequently promote their learning. More specifically, the aim of the study is to determine how requiring students to label their contributions by means of De Bono's (1991) thinking hats…

  8. Universal filtered multi-carrier system for asynchronous uplink transmission in optical access network

    NASA Astrophysics Data System (ADS)

    Kang, Soo-Min; Kim, Chang-Hun; Han, Sang-Kook

    2016-02-01

    In passive optical network (PON), orthogonal frequency division multiplexing (OFDM) has been studied actively due to its advantages such as high spectra efficiency (SE), dynamic resource allocation in time or frequency domain, and dispersion robustness. However, orthogonal frequency division multiple access (OFDMA)-PON requires tight synchronization among multiple access signals. If not, frequency orthogonality could not be maintained. Also its sidelobe causes inter-channel interference (ICI) to adjacent channel. To prevent ICI caused by high sidelobes, guard band (GB) is usually used which degrades SE. Thus, OFDMA-PON is not suitable for asynchronous uplink transmission in optical access network. In this paper, we propose intensity modulation/direct detection (IM/DD) based universal filtered multi-carrier (UFMC) PON for asynchronous multiple access. The UFMC uses subband filtering to subsets of subcarriers. Since it reduces sidelobe of each subband by applying subband filtering, it could achieve better performance compared to OFDM. For the experimental demonstration, different sample delay was applied to subbands to implement asynchronous transmission condition. As a result, time synchronization robustness of UFMC was verified in asynchronous multiple access system.

  9. Evaluation of a Computer-Based, Asynchronous Activity on Student Learning of Leadership Concepts.

    ERIC Educational Resources Information Center

    Boyd, Barry L.; Murphrey, Theresa Pesl

    2002-01-01

    Students taught leadership and ethics using asynchronous computer simulation (n=83) were compared with 113 taught conventionally. The treatment group performed better on questions written at the knowledge, comprehension, and analysis levels of Bloom's Taxonomy, regardless of learning mode preferences. (Contains 26 references.) (SK)

  10. Effects of Asynchronous Music on Students' Lesson Satisfaction and Motivation at the Situational Level

    ERIC Educational Resources Information Center

    Digelidis, Nikolaos; Karageorghis, Costas I.; Papapavlou, Anastasia; Papaioannou, Athanasios G.

    2014-01-01

    The aim of this study was to examine the effects of asynchronous (background) music on senior students' motivation and lesson satisfaction at the situational level. A counterbalanced mixed-model design was employed with two factors comprising condition (three levels) and gender (two levels). Two hundred students (82 boys, 118 girls; M…

  11. Exploring Singapore Primary School Students' Perceptions of Chinese Asynchronous Online Discussions

    ERIC Educational Resources Information Center

    Chin, Wong Wan; Sum, Cheung Wing; Foon, Hew Khe

    2008-01-01

    Background: Asynchronous online discussion (AOD) has found widespread use in tertiary education and adult learning environment; however, there has been little research on its use in elementary school, especially in the context of the teaching of the Chinese Language. This study explores the use of AOD in a Chinese Language class in a primary…

  12. An Investigation of Assessment and Feedback Practices in Fully Asynchronous Online Undergraduate Mathematics Courses

    ERIC Educational Resources Information Center

    Trenholm, Sven; Alcock, Lara; Robinson, Carol

    2015-01-01

    Research suggests it is difficult to learn mathematics in the fully asynchronous online (FAO) instructional modality, yet little is known about associated teaching and assessment practices. In this study, we investigate FAO mathematics assessment and feedback practices in particular consideration of both claims and findings that these practices…

  13. Asynchronous Vowel-Pair Identification across the Adult Life Span for Monaural and Dichotic Presentations

    ERIC Educational Resources Information Center

    Fogerty, Daniel; Kewley-Port, Diane; Humes, Larry E.

    2012-01-01

    Purpose: Temporal order abilities decrease with age. Declining temporal processing abilities may influence the identification of rapid vowel sequences. Identification patterns for asynchronous vowel pairs were explored across the life span. Method: Young, middle-aged, and older listeners completed temporal order tasks for pairs of 70-ms and 40-ms…

  14. Support Services and Learning Styles Influencing Interaction in Asynchronous Online Discussions

    ERIC Educational Resources Information Center

    Kucuk, M.; Genc-Kumtepe, E.; Tasci, D.

    2010-01-01

    This paper reports a case of online classes from the English Language Teaching Programme at Anadolu University, Turkey. The study used an explanatory case oriented research design that assisted to examine relations between students' learning styles and factors influencing students' participation in asynchronous interactions in online courses. The…

  15. Pattern of Accesses over Time in an Online Asynchronous Forum and Academic Achievements

    ERIC Educational Resources Information Center

    Canal, Luisa; Ghislandi, Patrizia; Micciolo, Rocco

    2015-01-01

    In this study, the participation of 119 students in an online asynchronous forum as part of an academic course on statistical methods was evaluated. The pattern of accesses during the course was analyzed by means of the cumulative mean function. Taking into account the times (hours) at which accesses occurred, it is possible to achieve more…

  16. Anonymity to Promote Peer Feedback: Pre-Service Teachers' Comments in Asynchronous Computer-Mediated Communication

    ERIC Educational Resources Information Center

    Howard, Craig D.; Barrett, Andrew F.; Frick, Theodore W.

    2010-01-01

    In this quasi-experimental case study, we compared five sections of a basic undergraduate technology course. Within an asynchronous web forum, pre-service teachers wrote short critiques of websites designed by their classmates. This peer feedback was provided anonymously by students in two classes (n = 35) whereas providers and recipients of peer…

  17. Does the Medium Dictate the Message? Cultivating E-Communication in an Asynchronous Environment.

    ERIC Educational Resources Information Center

    Kiernan, Mary; Thomas, Pete; Woodroffe, Mark

    Virtual learning environments (VLEs) are often perceived by education establishments as an opportunity to widen access without traditional overheads. An integral part of most VLEs is asynchronous computer conferencing and on-line moderators must help students migrate quickly to the new virtual environment to minimize learning disruption. This…

  18. Corrective Feedback in Asynchronous Online Interaction: Developing Novice Online Language Instructors

    ERIC Educational Resources Information Center

    Samburskiy, Denis; Quah, Joy

    2014-01-01

    This design-based research study investigates the instructional moves employed by novice online tutors to provide form-focused feedback to Belorussian college-level English language learners during written interactions in an online asynchronous language course. The investigation focused on the amount and effectiveness of implicit and explicit…

  19. Trajectory exploration within asynchronous binary asteroid systems using refined Lagrangian coherent structures

    NASA Astrophysics Data System (ADS)

    Shang, Haibin; Wu, Xiaoyu; Cui, Pingyuan

    2016-09-01

    Ground observations have found that asynchronous systems constitute most of the population of the near-Earth binary asteroids. This paper concerns the trajectory of a particle in the asynchronous system which is systematically described using periodic ellipsoidal and spherical body models. Due to the non-autonomous characteristics of the asynchronous system, Lagrangian coherent structures (LCS) are employed to identify the various dynamical behaviors. To enhance the accuracy of LCS, a robust LCS finding algorithm is developed incorporating hierarchical grid refinement, one-dimensional search and variational theory verification. In this way, the intricate dynamical transport boundaries are detected efficiently. These boundaries indicate that a total of 15 types of trajectories exist near asynchronous binary asteroids. According to their Kepler energy variations, these trajectories can be grouped into four basic categories, i.e., transitory, escape, impact and flyby trajectories. Furthermore, the influence of the ellipsoid's spin period on the dynamical behavior is discussed in the context of the change of dynamical regions. We found that the transitory and impact motions occur easily in the synchronous-like binary systems, in which the rotation period of the ellipsoid is nearly equal to that of the mutual orbit. Meanwhile, the results confirm a positive correlation between the spinning rate of the ellipsoid and the probability of the escape and flyby trajectories. The LCS also reveal a marked increase in trajectory diversity after a larger initial energy is selected.

  20. Asynchronous Knowledge Sharing and Conversation Interaction Impact on Grade in an Online Business Course

    ERIC Educational Resources Information Center

    Strang, Kenneth David

    2011-01-01

    Student knowledge sharing and conversation theory interactions were coded from asynchronous discussion forums to measure the effect of learning-oriented utterances on academic performance. The sample was 3 terms of an online business course (in an accredited MBA program) at a U.S.-based university. Correlation, stepwise regression, and multiple…

  1. A Survey of Factors Contributing to Learners' "Listening" Behaviors in Asynchronous Online Discussions

    ERIC Educational Resources Information Center

    Wise, Alyssa Friend; Marbouti, Farshid; Hsiao, Ying-Ting; Hausknecht, Simone

    2012-01-01

    Sixty-seven undergraduates taking either a Blended Business Course (BBC) or an Online Education Course (OEC) were surveyed about factors influencing their "listening" behaviors in asynchronous online course discussions. These are the ways they attend to the posts made by others: which posts they open, how they engage with open posts, and which…

  2. Student Perceptions of Peer versus Instructor Facilitation of Asynchronous Online Discussions: Further Findings from Three Cases

    ERIC Educational Resources Information Center

    Hew, Khe Foon

    2015-01-01

    This study aims to extend a previous work on the role of peer facilitation of asynchronous online discussions. Specifically, in this paper I report three cases that examine students' preference for peer or instructor facilitation of online discussion forums, as well as their respective reasons for it. These three cases involved the following…

  3. Computer Learner Corpora: Analysing Interlanguage Errors in Synchronous and Asynchronous Communication

    ERIC Educational Resources Information Center

    MacDonald, Penny; Garcia-Carbonell, Amparo; Carot, Sierra, Jose Miguel

    2013-01-01

    This study focuses on the computer-aided analysis of interlanguage errors made by the participants in the telematic simulation IDEELS (Intercultural Dynamics in European Education through on-Line Simulation). The synchronous and asynchronous communication analysed was part of the MiLC Corpus, a multilingual learner corpus of texts written by…

  4. An Examination of Computer Engineering Students' Perceptions about Asynchronous Discussion Forums

    ERIC Educational Resources Information Center

    Ozyurt, Ozcan; Ozyurt, Hacer

    2013-01-01

    This study was conducted in order to reveal the usage profiles and perceptions of Asynchronous Discussion Forums (ADFs) of 126 computer engineering students from the Computer Engineering Department in a university in Turkey. By using a mixed methods research design both quantitative and qualitative data were collected and analyzed. Research…

  5. Is It Live or Is It Memorex? Students' Synchronous and Asynchronous Communication with Scientists

    ERIC Educational Resources Information Center

    Kubasko, Dennis; Jones, M. Gail; Tretter, Thomas; Andre, Thomas

    2008-01-01

    This study compared students' investigations with an atomic force microscope and viruses in real-time synchronous and asynchronous learning environments. Student interactions with scientists (live videoconference versus email) were examined to see whether communication patterns were different for the different modes of instruction. Students'…

  6. Identifying and Measuring Ill-Structured Problem Formulation and Resolution in Online Asynchronous Discussions

    ERIC Educational Resources Information Center

    Murphy, Elizabeth

    2004-01-01

    This paper reports on a study involving the development and application of an instrument to identify and measure ill-structured problem formulation and resolution (PFR) in online asynchronous discussions (OADs). The instrument was developed by first determining PFR processes relevant to ill-structured problems in professional practice. The…

  7. Facing Off: Comparing an In-Person Library Orientation Lecture with an Asynchronous Online Library Orientation

    ERIC Educational Resources Information Center

    Gall, Dan

    2014-01-01

    A study to compare the effectiveness of an in-person library orientation with an online asynchronous orientation was conducted with three sections of Social Work Research Methods, a required course in the University of Iowa's Master of Social Work program. Two sections of the course received an online orientation involving short videos, text…

  8. The Effect of Instructor Information Provision on Critical Thinking in Students Using Asynchronous Online Discussion

    ERIC Educational Resources Information Center

    Klisc, Chris; McGill, Tanya; Hobbs, Valerie

    2012-01-01

    The facilitation of critical thinking is one of the most frequently discussed potential benefits of the asynchronous online discussion environment, but many studies have reported that it does not occur to any great extent. This study investigated the effect of information provided to students on the facilitation of their critical thinking outcomes…

  9. The Development of a Content Analysis Model for Assessing Students' Cognitive Learning in Asynchronous Online Discussions

    ERIC Educational Resources Information Center

    Yang, Dazhi; Richardson, Jennifer C.; French, Brian F.; Lehman, James D.

    2011-01-01

    The purpose of this study was to develop and validate a content analysis model for assessing students' cognitive learning in asynchronous online discussions. It adopted a fully mixed methods design, in which qualitative and quantitative methods were employed sequentially for data analysis and interpretation. Specifically, the design was a…

  10. Asynchronous P300 classification in a reactive brain-computer interface during an outlier detection task

    NASA Astrophysics Data System (ADS)

    Krumpe, Tanja; Walter, Carina; Rosenstiel, Wolfgang; Spüler, Martin

    2016-08-01

    Objective. In this study, the feasibility of detecting a P300 via an asynchronous classification mode in a reactive EEG-based brain-computer interface (BCI) was evaluated. The P300 is one of the most popular BCI control signals and therefore used in many applications, mostly for active communication purposes (e.g. P300 speller). As the majority of all systems work with a stimulus-locked mode of classification (synchronous), the field of applications is limited. A new approach needs to be applied in a setting in which a stimulus-locked classification cannot be used due to the fact that the presented stimuli cannot be controlled or predicted by the system. Approach. A continuous observation task requiring the detection of outliers was implemented to test such an approach. The study was divided into an offline and an online part. Main results. Both parts of the study revealed that an asynchronous detection of the P300 can successfully be used to detect single events with high specificity. It also revealed that no significant difference in performance was found between the synchronous and the asynchronous approach. Significance. The results encourage the use of an asynchronous classification approach in suitable applications without a potential loss in performance.

  11. Factors Affecting Pre-Service Teachers' Participation in Asynchronous Discussion: The Case of Iran

    ERIC Educational Resources Information Center

    Ebrahimi, Alice; Faghih, Esmail; Marandi, Seyyedeh Susan

    2016-01-01

    This study reports on a qualitative small-scale exploratory study which examined the factors influencing 32 Iranian pre-service language teachers' participation in online asynchronous text-based discussion forums. By adopting a multiple case study design and analysing data gathered through semi-structured interviews and participants' online…

  12. Ecological Affordance and Anxiety in an Oral Asynchronous Computer-Mediated Environment

    ERIC Educational Resources Information Center

    McNeil, Levi

    2014-01-01

    Previous research suggests that the affordances (van Lier, 2000) of asynchronous computer-mediated communication (ACMC) environments help reduce foreign language anxiety (FLA). However, FLA is rarely the focus of these studies and research has not adequately addressed the relationship between FLA and the affordances that students use. This study…

  13. An Integrated Approach to Preempt Cheating on Asynchronous, Objective, Online Assessments in Graduate Business Classes

    ERIC Educational Resources Information Center

    Sullivan, Daniel P.

    2016-01-01

    Cheating, left untended, erodes the validity of evaluation and, ultimately, corrupts the legitimacy of a course. We profile an approach to manage, with an eye toward preempting, cheating on asynchronous, objective, online quizzes. This approach taps various technological and social solutions to academic dishonesty, integrating them into a…

  14. Using Data Mining as a Strategy for Assessing Asynchronous Discussion Forums

    ERIC Educational Resources Information Center

    Dringus, Laurie P.; Ellis, Timothy

    2005-01-01

    The purpose of this paper is to show how data mining may offer promise as a strategy for discovering and building alternative representations for the data underlying asynchronous discussion forums. Presently, the instructor's view of the output of a threaded forum is limited to reviewing a transcript or print version of the written dialogue…

  15. Asynchronous Electronic Discussion Group: Analysis of Postings and Perception of In-Service Teachers

    ERIC Educational Resources Information Center

    Kim, Tina Lim Swee; Wah, Wong Kiet; Lee, Tan Ai

    2007-01-01

    This paper examines the practice of online discussion in a course specially tailored for in-service teachers who are pursuing their basic degree qualification at a teacher training institute. Analyses of postings to the asynchronous electronic discussion group were made according to the type of postings as proposed by Poole (2000). Four focus…

  16. The Role of Technology-Based Scaffolding in Problem-Based Online Asynchronous Discussion

    ERIC Educational Resources Information Center

    Ak, Serife

    2016-01-01

    This study examined the effects of technology-based scaffolds that were composed through the use of the seven-stage, problem-based learning strategy on knowledge construction in a problem-based online asynchronous discussion. In a quasi-experimental setting, 60 students in an undergraduate Instructional Technology and Material Design course were…

  17. Thematic Analysis of the "Games" Students Play in Asynchronous Learning Environments

    ERIC Educational Resources Information Center

    MacMillan, Thalia; Forte, Michele; Grant, Cynthia

    2014-01-01

    The dynamics of the student-student relationship within the asynchronous online classroom, as evidenced by conversations in an online discussion board, is a balancing act potentially more complex than those occurring in real-time. In order for learning to truly be considered effective, a collaborative, safe environment needs to exist among…

  18. Asynchronous mid-infrared broadband optical parametric oscillator for dual-comb spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Zhaowei; Gu, Chenglin; Sun, Jinghua; Wang, Chingyue; Gardiner, Tom; Reid, Derryck T.

    2013-03-01

    Two asynchronous, broadband 3.3-μm pulse trains with a stabilized repetition-rate difference of up to 5-kHz were generated from a single optical parametric oscillator. With additional carrier-envelope-offset stabilization, it could be applied to coherent dual-frequency-comb spectroscopy.

  19. Synchronous and Asynchronous E-Language Learning: A Case Study of Virtual University of Pakistan

    ERIC Educational Resources Information Center

    Perveen, Ayesha

    2016-01-01

    This case study evaluated the impact of synchronous and asynchronous E-Language Learning activities (ELL-ivities) in an E-Language Learning Environment (ELLE) at Virtual University of Pakistan. The purpose of the study was to assess e-language learning analytics based on the constructivist approach of collaborative construction of knowledge. The…

  20. Using Asynchronous Electronic Surveys to Help In-Class Revision: A Case Study

    ERIC Educational Resources Information Center

    Tong, Vincent C. H.

    2012-01-01

    Synchronous e-voting systems (commonly known as "clickers") have become increasingly popular as they can be used to enhance interactivity in lectures. Asynchronous electronic surveys (AESs), unlike these voting system, usually serve as a method of gathering feedback before or after teaching sessions. This paper describes and evaluates a project…

  1. Interaction in an Asynchronous Online Course: A Synthesis of Quantitative Predictors

    ERIC Educational Resources Information Center

    Zingaro, Daniel; Oztok, Murat

    2012-01-01

    The effectiveness and potential of asynchronous online courses hinge on sustained, purposeful interaction. And while many factors affecting interaction have been uncovered by prior literature, there are few accounts of the relative importance of these factors when studied in the same online course. In this paper, we develop a literature-informed…

  2. Credit Hours with No Set Time: A Study of Credit Policies in Asynchronous Online Education

    ERIC Educational Resources Information Center

    Prasuhn, Frederick Carl

    2014-01-01

    U.S. public university system policies were examined to learn how credit hours were determined for asynchronous online education. Findings indicated that (a) credit hour meaning and use are not consistent, (b) primary responsibility for credit hour decisions was at the local level, and (c) no policies exist to guide credit hour application for…

  3. Growth Patterns and E-Moderating Supports in Asynchronous Online Discussions in an Undergraduate Blended Course

    ERIC Educational Resources Information Center

    Ghadirian, Hajar; Ayub, Ahmad Fauzi Mohd; Bakar, Kamariah Binti Abu; Hassanzadeh, Maryam

    2016-01-01

    This study presents a case study of asynchronous online discussions' (AOD) growth patterns in an undergraduate blended course to address the gap in our current understanding of how threads are developed in peer-moderated AODs. Building on a taxonomy of thread pattern proposed by Chan, Hew and Cheung (2009), growth patterns of thirty-six forums…

  4. Linear Clouds

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA03667 Linear Clouds

    These clouds are located near the edge of the south polar region. The cloud tops are the puffy white features in the bottom half of the image.

    Image information: VIS instrument. Latitude -80.1N, Longitude 52.1E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  5. Directed flux motor

    NASA Technical Reports Server (NTRS)

    Wilson, Andrew (Inventor); Punnoose, Andrew (Inventor); Strausser, Katherine (Inventor); Parikh, Neil (Inventor)

    2011-01-01

    A directed flux motor described utilizes the directed magnetic flux of at least one magnet through ferrous material to drive different planetary gear sets to achieve capabilities in six actuated shafts that are grouped three to a side of the motor. The flux motor also utilizes an interwoven magnet configuration which reduces the overall size of the motor. The motor allows for simple changes to modify the torque to speed ratio of the gearing contained within the motor as well as simple configurations for any number of output shafts up to six. The changes allow for improved manufacturability and reliability within the design.

  6. T-Slide Linear Actuators

    NASA Technical Reports Server (NTRS)

    Vranish, John

    2009-01-01

    T-slide linear actuators use gear bearing differential epicyclical transmissions (GBDETs) to directly drive a linear rack, which, in turn, performs the actuation. Conventional systems use a rotary power source in conjunction with a nut and screw to provide linear motion. Non-back-drive properties of GBDETs make the new actuator more direct and simpler. Versions of this approach will serve as a long-stroke, ultra-precision, position actuator for NASA science instruments, and as a rugged, linear actuator for NASA deployment duties. The T slide can operate effectively in the presence of side forces and torques. Versions of the actuator can perform ultra-precision positioning. A basic T-slide actuator is a long-stroke, rack-and-pinion linear actuator that, typically, consists of a T-slide, several idlers, a transmission to drive the slide (powered by an electric motor) and a housing that holds the entire assembly. The actuator is driven by gear action on its top surface, and is guided and constrained by gear-bearing idlers on its other two parallel surfaces. The geometry, implemented with gear-bearing technology, is particularly effective. An electronic motor operating through a GBDET can directly drive the T slide against large loads, as a rack and pinion linear actuator, with no break and no danger of back driving. The actuator drives the slide into position and stops. The slide holes position with power off and no brake, regardless of load. With the T slide configuration, this GBDET has an entire T-gear surface on which to operate. The GB idlers coupling the other two T slide parallel surfaces to their housing counterpart surfaces provide constraints in five degrees-of-freedom and rolling friction in the direction of actuation. Multiple GB idlers provide roller bearing strength sufficient to support efficient, rolling friction movement, even in the presence of large, resisting forces. T-slide actuators can be controlled using the combination of an off

  7. Imparting Motion to a Test Object Such as a Motor Vehicle in a Controlled Fashion

    NASA Technical Reports Server (NTRS)

    Southward, Stephen C. (Inventor); Reubush, Chandler (Inventor); Pittman, Bryan (Inventor); Roehrig, Kurt (Inventor); Gerard, Doug (Inventor)

    2014-01-01

    An apparatus imparts motion to a test object such as a motor vehicle in a controlled fashion. A base has mounted on it a linear electromagnetic motor having a first end and a second end, the first end being connected to the base. A pneumatic cylinder and piston combination have a first end and a second end, the first end connected to the base so that the pneumatic cylinder and piston combination is generally parallel with the linear electromagnetic motor. The second ends of the linear electromagnetic motor and pneumatic cylinder and piston combination being commonly linked to a mount for the test object. A control system for the linear electromagnetic motor and pneumatic cylinder and piston combination drives the pneumatic cylinder and piston combination to support a substantial static load of the test object and the linear electromagnetic motor to impart controlled motion to the test object.

  8. Chronic motor tic disorder

    MedlinePlus

    Chronic vocal tic disorder; Tic - chronic motor tic disorder ... Chronic motor tic disorder is more common than Tourette syndrome . Chronic tics may be forms of Tourette syndrome. Tics usually start ...

  9. Introduction to ultrasonic motors

    SciTech Connect

    Sashida, Toshiiku; Kenjo, Takashi.

    1993-01-01

    The ultrasonic motor, invented in 1980, utilizes the piezoelectric effect in the ultrasonic frequency range to provide the motive force. (In conventional electric motors the motive force is electromagnetic.) The result is a motor with unusually good low-speed high-torque and power-to-weight characteristics. It has already found applications in camera autofocus mechanisms, medical equipment subject to high magnetic fields, and motorized car accessories. Its applications will increase as designers become more familiar with its unique characteristics. This book is the result of a collaboration between the inventor and an expert in conventional electric motors: the result is an introduction to the general theory presented in a way that links it to conventional motor theory. It will be invaluable both to motor designers and to those who design with and use electric motors as an introduction to this important new invention.

  10. Fine motor control

    MedlinePlus

    ... out the child's developmental age. Children develop fine motor skills over time, by practicing and being taught. To have fine motor control, children need: Awareness and planning Coordination Muscle ...

  11. Fuzzy control of small servo motors

    NASA Technical Reports Server (NTRS)

    Maor, Ron; Jani, Yashvant

    1993-01-01

    To explore the benefits of fuzzy logic and understand the differences between the classical control methods and fuzzy control methods, the Togai InfraLogic applications engineering staff developed and implemented a motor control system for small servo motors. The motor assembly for testing the fuzzy and conventional controllers consist of servo motor RA13M and an encoder with a range of 4096 counts. An interface card was designed and fabricated to interface the motor assembly and encoder to an IBM PC. The fuzzy logic based motor controller was developed using the TILShell and Fuzzy C Development System on an IBM PC. A Proportional-Derivative (PD) type conventional controller was also developed and implemented in the IBM PC to compare the performance with the fuzzy controller. Test cases were defined to include step inputs of 90 and 180 degrees rotation, sine and square wave profiles in 5 to 20 hertz frequency range, as well as ramp inputs. In this paper we describe our approach to develop a fuzzy as well as PH controller, provide details of hardware set-up and test cases, and discuss the performance results. In comparison, the fuzzy logic based controller handles the non-linearities of the motor assembly very well and provides excellent control over a broad range of parameters. Fuzzy technology, as indicated by our results, possesses inherent adaptive features.

  12. Molecular motors: nature's nanomachines.

    PubMed

    Tyreman, M J A; Molloy, J E

    2003-12-01

    Molecular motors are protein-based machines that convert chemical potential energy into mechanical work. This paper aims to introduce the non-specialist reader to molecular motors, in particular, acto-myosin, the prototype system for motor protein studies. These motors produce their driving force from changes in chemical potential arising directly from chemical reactions and are responsible for muscle contraction and a variety of other cell motilities.

  13. Smart motor technology

    NASA Technical Reports Server (NTRS)

    Packard, D.; Schmitt, D.

    1984-01-01

    Current spacecraft design relies upon microprocessor control; however, motors usually require extensive additional electronic circuitry to interface with these microprocessor controls. An improved control technique that allows a smart brushless motor to connect directly to a microprocessor control system is described. An actuator with smart motors receives a spacecraft command directly and responds in a closed loop control mode. In fact, two or more smart motors can be controlled for synchronous operation.

  14. Asynchronous global optimization techniques for medium and large inversion problems

    SciTech Connect

    Pereyra, V.; Koshy, M.; Meza, J.C.

    1995-04-01

    We discuss global optimization procedures adequate for seismic inversion problems. We explain how to save function evaluations (which may involve large scale ray tracing or other expensive operations) by creating a data base of information on what parts of parameter space have already been inspected. It is also shown how a correct parallel implementation using PVM speeds up the process almost linearly with respect to the number of processors, provided that the function evaluations are expensive enough to offset the communication overhead.

  15. Solid propellant motor

    NASA Technical Reports Server (NTRS)

    Shafer, J. I.; Marsh, H. E., Jr. (Inventor)

    1978-01-01

    A case bonded end burning solid propellant rocket motor is described. A propellant with sufficiently low modulus to avoid chamber buckling on cooling from cure and sufficiently high elongation to sustain the stresses induced without cracking is used. The propellant is zone cured within the motor case at high pressures equal to or approaching the pressure at which the motor will operate during combustion. A solid propellant motor with a burning time long enough that its spacecraft would be limited to a maximum acceleration of less than 1 g is provided by one version of the case bonded end burning solid propellant motor of the invention.

  16. Motor/generator

    DOEpatents

    Hickam, Christopher Dale

    2008-05-13

    A motor/generator is provided for connecting between a transmission input shaft and an output shaft of a prime mover. The motor/generator may include a motor/generator housing, a stator mounted to the motor/generator housing, a rotor mounted at least partially within the motor/generator housing and rotatable about a rotor rotation axis, and a transmission-shaft coupler drivingly coupled to the rotor. The transmission-shaft coupler may include a clamp, which may include a base attached to the rotor and a plurality of adjustable jaws.

  17. Rapid Feedforward Inhibition and Asynchronous Excitation Regulate Granule Cell Activity in the Mammalian Main Olfactory Bulb

    PubMed Central

    Burton, Shawn D.

    2015-01-01

    Granule cell-mediated inhibition is critical to patterning principal neuron activity in the olfactory bulb, and perturbation of synaptic input to granule cells significantly alters olfactory-guided behavior. Despite the critical role of granule cells in olfaction, little is known about how sensory input recruits granule cells. Here, we combined whole-cell patch-clamp electrophysiology in acute mouse olfactory bulb slices with biophysical multicompartmental modeling to investigate the synaptic basis of granule cell recruitment. Physiological activation of sensory afferents within single glomeruli evoked diverse modes of granule cell activity, including subthreshold depolarization, spikelets, and suprathreshold responses with widely distributed spike latencies. The generation of these diverse activity modes depended, in part, on the asynchronous time course of synaptic excitation onto granule cells, which lasted several hundred milliseconds. In addition to asynchronous excitation, each granule cell also received synchronous feedforward inhibition. This inhibition targeted both proximal somatodendritic and distal apical dendritic domains of granule cells, was reliably recruited across sniff rhythms, and scaled in strength with excitation as more glomeruli were activated. Feedforward inhibition onto granule cells originated from deep short-axon cells, which responded to glomerular activation with highly reliable, short-latency firing consistent with tufted cell-mediated excitation. Simulations showed that feedforward inhibition interacts with asynchronous excitation to broaden granule cell spike latency distributions and significantly attenuates granule cell depolarization within local subcellular compartments. Collectively, our results thus identify feedforward inhibition onto granule cells as a core feature of olfactory bulb circuitry and establish asynchronous excitation and feedforward inhibition as critical regulators of granule cell activity. SIGNIFICANCE

  18. Synchronous and asynchronous multiplexer circuits for medical imaging realized in CMOS 0.18um technology

    NASA Astrophysics Data System (ADS)

    Długosz, R.; Iniewski, K.

    2007-05-01

    Multiplexers are one of the most important elements in readout front-end ASICs for multi-element detectors in medical imaging. The purpose of these ASICs is to detect signals appearing randomly in many channels and to collect the detected data in an ordered fashion (de-randomization) in order to send it to an external ADC. ASIC output stage functionality can be divided into two: pulse detection and multiplexing. The pulse detection block is responsible for detecting maximum values of signals arriving from the shaper, sending a flag signal indicating that the peak signal has been detected and storing the pulse in an analog memory until read by ADC. The multiplexer in turn is responsible for searching for active flags, controlling the channel that has detected the peak signal and performing reset functions after readout. There are several types of multiplexers proposed in this paper, which can be divided into several classes: synchronous, synchronized and asynchronous. Synchronous circuits require availability of the multiphase clock generator, which increases the power dissipation, but simultaneously provide very convenient mechanism that enables unambiguous choice of the active channel. This characteristics leads to 100% effectiveness in data processing and no data loss. Asynchronous multiplexers do not require clock generators and because of that have simpler structure, are faster and more power efficient, especially when data samples occur seldom at the ASIC's inputs. The main problem of the asynchronous solution is when data on two or more inputs occur almost at the same time, shorter than the multiplexer's reaction time. In this situation some data can be lost. In many applications loss of the order of 1% of the data is acceptable, which makes use of asynchronous multiplexers possible. For applications when the lower loss is desirable a new hierarchy mechanism has been introduced. One of proposed solutions is a synchronized binary tree structure, that uses many

  19. LETTER: On the exactness of the cavity method for weighted b-matchings on arbitrary graphs and its relation to linear programs

    NASA Astrophysics Data System (ADS)

    Bayati, Mohsen; Borgs, Christian; Chayes, Jennifer; Zecchina, Riccardo

    2008-06-01

    We consider the general problem of finding the minimum weight b-matching on arbitrary graphs. We prove that, whenever the linear programing relaxation of the problem has no fractional solutions, then the cavity or belief propagation equations converge to the correct solution both for synchronous and asynchronous updating.

  20. Piezoceramic Ultrasonic Motor Technology

    SciTech Connect

    Burden, J.S.

    1999-02-24

    The objective of this project was to team Aerotech and AlliedSignal FM and T (AS) to develop a cost-efficient process for small-batch, high performance PZT motor production. Aerotech would acquire the basic process expertise in motor fabrication, assembly, and testing from AS. Together, Aerotech and AS were to identify appropriate process improvements, focusing on raw material quality, manufacturing processes, and durability assessment. Aerotech would then design and build a motor in consultation with AS. Aerotech engineering observed motor manufacturing in the AS piezo lab and worked side by side with AS personnel to build and test a prototype motor to facilitate learning the technology. Using information from AS and hands-on experience with the AS motor drive system enabled Aerotech to design and build its own laboratory drive system to operate motors. The team compiled information to establish a potential piezo motor users' list, and an intellectual property search was conducted to understand current patent and IP (intellectual property) status of motor design. Work was initiated to identify and develop an American source for piezo motor elements; however, due to manpower restraints created by the resignation of the AS Ph.D. ceramist responsible for these tasks, the project schedule slipped. The project was subsequently terminated before significant activities were accomplished. AS did, however, provide Aerotech with contacts in Japanese industry that are willing and capable of supplying them with special design motor elements.

  1. Motorized support jack

    DOEpatents

    Haney, Steven J.; Herron, Donald Joe

    2001-01-01

    A compact, vacuum compatible motorized jack for supporting heavy loads and adjusting their positions is provided. The motorized jack includes: (a) a housing having a base; (b) a first roller device that provides a first slidable surface and that is secured to the base; (c) a second roller device that provides a second slidable surface and that has an upper surface; (d) a wedge that is slidably positioned between the first roller device and the second roller device so that the wedge is in contact with the first slidable surface and the second slidable surface; (e) a motor; and (d) a drive mechanism that connects the motor and the wedge to cause the motor to controllably move the wedge forwards or backwards. Individual motorized jacks can support and lift of an object at an angle. Two or more motorized jacks can provide tip, tilt and vertical position adjustment capabilities.

  2. Motor degradation prediction methods

    SciTech Connect

    Arnold, J.R.; Kelly, J.F.; Delzingaro, M.J.

    1996-12-01

    Motor Operated Valve (MOV) squirrel cage AC motor rotors are susceptible to degradation under certain conditions. Premature failure can result due to high humidity/temperature environments, high running load conditions, extended periods at locked rotor conditions (i.e. > 15 seconds) or exceeding the motor`s duty cycle by frequent starts or multiple valve stroking. Exposure to high heat and moisture due to packing leaks, pressure seal ring leakage or other causes can significantly accelerate the degradation. ComEd and Liberty Technologies have worked together to provide and validate a non-intrusive method using motor power diagnostics to evaluate MOV rotor condition and predict failure. These techniques have provided a quick, low radiation dose method to evaluate inaccessible motors, identify degradation and allow scheduled replacement of motors prior to catastrophic failures.

  3. Motorized support jack

    DOEpatents

    Haney, Steven J.; Herron, Donald Joe

    2003-05-13

    A compact, vacuum compatible motorized jack for supporting heavy loads and adjusting their positions is provided. The motorized jack includes: (a) a housing having a base; (b) a first roller device that provides a first slidable surface and that is secured to the base; (c) a second roller device that provides a second slidable surface and that has an upper surface; (d) a wedge that is slidably positioned between the first roller device and the second roller device so that the wedge is in contact with the first slidable surface and the second slidable surface; (e) a motor; and (d) a drive mechanism that connects the motor and the wedge to cause the motor to controllably move the wedge forwards or backwards. Individual motorized jacks can support and lift of an object at an angle. Two or more motorized jacks can provide tip, tilt and vertical position adjustment capabilities.

  4. Improved Multiple-DOF SAW Piezoelectric Motors

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph; Bao, Xiaoqi; Hull, Anthony; Wright, John

    2003-01-01

    Surface-acoustic-wave (SAW) piezoelectric motors of a proposed type would be capable of operating in multiple degrees of freedom (DOFs) simultaneously and would be amenable to integration into diverse structures and mechanisms. These motors would be compact and structurally simple and would not contain bearings or lead screws. One example of a particularly useful motor of this type would be a two-dimensional- translation stage. Another such example would be a self-actuated spherical joint that could be made to undergo controlled, simultaneous rotations about two orthogonal axes: Such a motor could serve as a mechanism for aiming an "eyeball" camera or as a compact transducer in, and an integral part of, a joint in a robot arm. The multiple-DOF SAW piezoelectric motors as now proposed would be successors to the ones reported in "Multiple-DOF Surface-Acoustic-Wave Piezoelectric Motors" (NPO-20735), NASA Tech Briefs, Vol. 24, No. 12 (December 2000), page 5b. The basic principle of operation of a multiple-DOF SAW piezoelectric motor is a straightforward extension of that of single-DOF SAW piezoelectric motors, which have been reported in several previous NASA Tech Briefs articles: For example, in the case of a linear SAW piezoelectric motor, piezoelectric transducers at opposite ends of a stator excite surface acoustic waves that travel along the surface of the stator. An object (denoted the slider) is pressed against the stator with sufficient pressure (in practice .300 MPa) that it remains in frictional contact with the stator at all times. The slider rides the crests of the waves and is thereby made to move along the surface of the stator. The direction of motion (forward or backward) is controlled by selecting the relative phase of waves generated by the two piezoelectric transducers. The speed increases with the amplitude of the waves and thus with the magnitude of the voltage applied to the transducers.

  5. Synthetic Motors and Nanomachines.

    NASA Astrophysics Data System (ADS)

    Flood, Amar

    2006-03-01

    A bistable and palindromically-constituted [3]rotaxane incorporating two mechanically-mobile rings interlocked around a linear dumbbell component, has been designed to operate like the sarcomeres of skeletal muscle. Contraction and extension occurs when the inter-ring distance of the two rings switch, ideally, between 4.2 and 1.4 nm upon redox stimulation either chemically or electrochemically in the solution phase. When the mobile rings of these artificial molecular muscles are bound onto the tops of gold-coated, micron-scale cantilever beams, their controllable nanometer motions have a chance to be amplified along the long axis of each cantilever. It turns out that ˜6 billion of the self-assembled [3]rotaxanes can bend the cantilevers in a bistable manner concomitant with the cycled addition of redox agents. The extent of bending is commensurate with 10's of pN of force per [3]rotaxane. Recent studies on a set of ``single-shot'' control [2]rotaxanes have provided additional evidence for the origins of the force generation as it arises from a molecule-based electrostatic repulsion energy of about 10 kcal/mol at 300 K. These findings will be presented in terms of the underlying thermodynamics and kinetics that have been utilized extensively to direct the design and synthesis of artificial molecular machines and which may also serve as a guide for the rational design of unidirectional molecular motors.

  6. Proceedings of the IEEE international conference on Maglev and linear drives

    SciTech Connect

    Not Available

    1987-01-01

    These proceedings collect papers on linear induction motors and magnetic levitation. Topics include: linear induction propulsion, eddy current analysis of cryostat outer vessel in superconductive magnetically levitated vehicles, dynamics of maglev vehicles, and high-speed maglev trains.

  7. Cyclic motor activity; migrating motor complex: 1985.

    PubMed

    Sarna, S K

    1985-10-01

    Most of the gastrointestinal tract and the biliary tract have a cyclic motor activity. The electric counterpart of this motor activity is called cyclic myoelectric activity. A typical motor cycle in the LES, stomach, and small intestine is composed of a quiescent state, followed by progressively increasing amplitude and frequency of contractions culminating in a state of maximal contractile activity. The colonic motor cycle has only the quiescent and the contractile states. In the small intestine, these motor complexes migrate in an aborad direction, and in the colon in both orad and aborad directions. The mechanisms of initiation and migration of these complexes are best understood in the small intestine. Both the initiation and migration of these complexes seem to be controlled by enteric neural mechanisms. The functions of the enteric mechanisms may be modulated by the central nervous system and by circulating endogenous substances. The mechanisms of initiation of these complexes are not completely understood in the rest of the gastrointestinal tract and in the biliary tract. The physiologic function of these motor complexes that occur only after several hours of fast in the upper gastrointestinal tract of nonruminants may be to clean the digestive tract of residual food, secretions, and cellular debris. This function is aided by a coordinated secretion of enzymes, acid, and bicarbonate. In ruminants, phase III activity is associated with the distal propulsion of ingested food. The function of colonic motor complexes that are not coordinated with the cyclic motor activities of the rest of the gastrointestinal tract may be only to move contents back and forth for optimal absorption. PMID:3896912

  8. Dissociating motor cortex from the motor

    PubMed Central

    Schieber, Marc H

    2011-01-01

    Abstract During closed-loop control of a brain–computer interface, neurons in the primary motor cortex can be intensely active even though the subject may be making no detectable movement or muscle contraction. How can neural activity in the primary motor cortex become dissociated from the movements and muscles of the native limb that it normally controls? Here we examine circumstances in which motor cortex activity is known to dissociate from movement – including mental imagery, visuo-motor dissociation and instructed delay. Many such motor cortex neurons may be related to muscle activity only indirectly. Furthermore, the integration of thousands of synaptic inputs by individual α-motoneurons means that under certain circumstances even cortico-motoneuronal cells, which make monosynaptic connections to α-motoneurons, can become dissociated from muscle activity. The natural ability of motor cortex neurons under voluntarily control to become dissociated from bodily movement may underlie the utility of this cortical area for controlling brain–computer interfaces. PMID:22005673

  9. Asynchronous rotation of Earth-mass planets in the habitable zone of lower-mass stars

    NASA Astrophysics Data System (ADS)

    Leconte, Jérémy; Wu, Hanbo; Menou, Kristen; Murray, Norman

    2015-02-01

    Planets in the habitable zone of lower-mass stars are often assumed to be in a state of tidally synchronized rotation, which would considerably affect their putative habitability. Although thermal tides cause Venus to rotate retrogradely, simple scaling arguments tend to attribute this peculiarity to the massive Venusian atmosphere. Using a global climate model, we show that even a relatively thin atmosphere can drive terrestrial planets’ rotation away from synchronicity. We derive a more realistic atmospheric tide model that predicts four asynchronous equilibrium spin states, two being stable, when the amplitude of the thermal tide exceeds a threshold that is met for habitable Earth-like planets with a 1-bar atmosphere around stars more massive than ~0.5 to 0.7 solar mass. Thus, many recently discovered terrestrial planets could exhibit asynchronous spin-orbit rotation, even with a thin atmosphere.

  10. Asynchronous, macrotasked relaxation strategies for the solution of viscous, hypersonic flows

    NASA Technical Reports Server (NTRS)

    Gnoffo, Peter A.

    1991-01-01

    A point-implicit, asynchronous macrotasked relaxation of the steady, thin-layer, Navier-Stokes equations is presented. The method employs multidirectional, single-level storage Gauss-Seidel relaxation sweeps, which effectively communicate perturbations across the entire domain in 2n sweeps, where n is the dimension of the domain. In order to enhance convergence the application of relaxation factors to specific components of the Jacobian is examined using a stability analysis of the advection and diffusion equations. Attention is also given to the complications associated with asynchronous multitasking. Solutions are generated for hypersonic flows over blunt bodies in two and three dimensions with chemical reactions, utilizing single-tasked and multitasked relaxation strategies.

  11. Booming during a bust: Asynchronous population responses of arid zone lizards to climatic variables

    NASA Astrophysics Data System (ADS)

    Read, John L.; Kovac, Kelli-Jo; Brook, Barry W.; Fordham, Damien A.

    2012-04-01

    The productivity of arid environments and the reproductive success of vertebrates in these systems, are typically thought to be primarily influenced by rainfall patterns. Data from our 15 year study at an Australian arid zone site reveals asynchronous demographic responses to rainfall and other climatic variables among different lizard species. We show that, in addition to precipitation, key demographic rates (fecundity, recruitment and survival) are correlated strongly with temporal variability in temperature, during and prior to the breeding season, and also to the density of sympatric lizard species. There were nine-fold fluctuations through time in the relative abundance of two similar-sized Ctenotus species, and asynchronous recruitment success and survival among other species, despite the absence of direct anthropogenic affects Understanding the drivers and magnitude of the substantial natural variability in arid-zone lizard assemblages is integral to predicting and interpreting their responses to future land use or climate-change scenarios.

  12. Performance of asynchronous tandem standard 32 Kb/s ADPCM systems using QAM signal

    NASA Astrophysics Data System (ADS)

    AL-Rawi, Muhanned Farhan Abdul-Hameed; AL-Rawi, Muaayed Farhan Abdul-Hameed

    2011-12-01

    This paper deals with the performance of standard 32 kb/s ADPCM. This performance is measured using signal-tonoise ratio (SNR). Here, the new contribution is related with mathematical derivation of SNR for asynchronous tandem ADPCM systems as given in section 5. Another contribution is study this performance using QAM modem signal with different constellations. A computer simulation program has been developed and a number of simulation tests have been carried out using QAM modem signal at 9.6 Kb/s with four types of constellations, rectangular, and (5,11), (4,12), (8,8) circular. The results of testing asynchronous tandem ADPCM systems show that the performance degrades with increasing the stages of ADPCM. Also, the results show that the performance with circular constellation is better than rectangular constellation.

  13. A 0.6-V 8.3-ENOB asynchronous SAR ADC for biomedical applications

    NASA Astrophysics Data System (ADS)

    Yan, Song; Zhongming, Xue; Pengcheng, Yan; Jueying, Zhang; Li, Geng

    2014-08-01

    A microwatt asynchronous successive approximation register (SAR) analog-to-digital converter (ADC) is presented. The supply voltage of the SAR ADC is decreased to 0.6 V to fit the low voltage and low power requirements of biomedical systems. The tail capacitor of the DAC array is reused for least significant bit conversion to decrease the total DAC capacitance thus reducing the power. Asynchronous control logic avoids the high frequency clock generator and further reduces the power consumption. The prototype ADC is fabricated with a standard 0.18 μm CMOS technology. Experimental results show that it achieves an ENOB of 8.3 bit at a 300-kS/s sampling rate. Very low power consumption of 3.04 μW is achieved, resulting in a figure of merit of 32 fJ/conv.-step.

  14. Asynchronous cellular automaton-based neuron: theoretical analysis and on-FPGA learning.

    PubMed

    Matsubara, Takashi; Torikai, Hiroyuki

    2013-05-01

    A generalized asynchronous cellular automaton-based neuron model is a special kind of cellular automaton that is designed to mimic the nonlinear dynamics of neurons. The model can be implemented as an asynchronous sequential logic circuit and its control parameter is the pattern of wires among the circuit elements that is adjustable after implementation in a field-programmable gate array (FPGA) device. In this paper, a novel theoretical analysis method for the model is presented. Using this method, stabilities of neuron-like orbits and occurrence mechanisms of neuron-like bifurcations of the model are clarified theoretically. Also, a novel learning algorithm for the model is presented. An equivalent experiment shows that an FPGA-implemented learning algorithm enables an FPGA-implemented model to automatically reproduce typical nonlinear responses and occurrence mechanisms observed in biological and model neurons.

  15. The effects of metacognitive instruction embedded within an asynchronous learning network on scientific inquiry skills

    NASA Astrophysics Data System (ADS)

    Zion, Michal; Michalsky, Tova; Mevarech, Zemira R.

    2005-08-01

    The study is aimed at investigating the effects of four learning methods on students’ scientific inquiry skills. The four learning methods are: (a) metacognitive-guided inquiry within asynchronous learning networked technology (MINT); (b) an asynchronous learning network (ALN) with no metacognitive guidance; (c) metacognitive-guided inquiry embedded within face-to-face (F2F) interaction; and (d) F2F interaction with no metacognitive guidance. The study examined general scientific ability and domain-specific inquiry skills in microbiology. Participants were 407 10th-grade students (15 years old). The MINT research group significantly outperformed all other research groups, and F2F (group d) acquired the lowest mean scores. No significant differences were found between research groups (b) and (c). MINT makes significant contributions to students’ achievements in designing experiments and drawing conclusions. The novel use of metacognitive training within an ALN environment demonstrates the advantage of enhancing the effects of ALN on students’ achievements in science.

  16. Event-Based Tone Mapping for Asynchronous Time-Based Image Sensor.

    PubMed

    Simon Chane, Camille; Ieng, Sio-Hoi; Posch, Christoph; Benosman, Ryad B

    2016-01-01

    The asynchronous time-based neuromorphic image sensor ATIS is an array of autonomously operating pixels able to encode luminance information with an exceptionally high dynamic range (>143 dB). This paper introduces an event-based methodology to display data from this type of event-based imagers, taking into account the large dynamic range and high temporal accuracy that go beyond available mainstream display technologies. We introduce an event-based tone mapping methodology for asynchronously acquired time encoded gray-level data. A global and a local tone mapping operator are proposed. Both are designed to operate on a stream of incoming events rather than on time frame windows. Experimental results on real outdoor scenes are presented to evaluate the performance of the tone mapping operators in terms of quality, temporal stability, adaptation capability, and computational time. PMID:27642275

  17. Event-Based Tone Mapping for Asynchronous Time-Based Image Sensor

    PubMed Central

    Simon Chane, Camille; Ieng, Sio-Hoi; Posch, Christoph; Benosman, Ryad B.

    2016-01-01

    The asynchronous time-based neuromorphic image sensor ATIS is an array of autonomously operating pixels able to encode luminance information with an exceptionally high dynamic range (>143 dB). This paper introduces an event-based methodology to display data from this type of event-based imagers, taking into account the large dynamic range and high temporal accuracy that go beyond available mainstream display technologies. We introduce an event-based tone mapping methodology for asynchronously acquired time encoded gray-level data. A global and a local tone mapping operator are proposed. Both are designed to operate on a stream of incoming events rather than on time frame windows. Experimental results on real outdoor scenes are presented to evaluate the performance of the tone mapping operators in terms of quality, temporal stability, adaptation capability, and computational time.

  18. An asynchronous metamodel-assisted memetic algorithm for CFD-based shape optimization

    NASA Astrophysics Data System (ADS)

    Kontoleontos, Evgenia A.; Asouti, Varvara G.; Giannakoglou, Kyriakos C.

    2012-02-01

    This article presents an asynchronous metamodel-assisted memetic algorithm for the solution of CFD-based optimization problems. This algorithm is appropriate for use on multiprocessor platforms and may solve computationally expensive optimization problems in reduced wall-clock time, compared to conventional evolutionary or memetic algorithms. It is, in fact, a hybridization of non-generation-based (asynchronous) evolutionary algorithms, assisted by surrogate evaluation models, a local search method and the Lamarckian learning process. For the objective function gradient computation, in CFD applications, the adjoint method is used. Issues concerning the 'smart' implementation of local search in multi-objective problems are discussed. In this respect, an algorithmic scheme for reducing the number of calls to the adjoint equations to just one, irrespective of the number of objectives, is proposed. The algorithm is applied to the CFD-based shape optimization of the tubes of a heat exchanger and of a turbomachinery cascade.

  19. Event-Based Tone Mapping for Asynchronous Time-Based Image Sensor

    PubMed Central

    Simon Chane, Camille; Ieng, Sio-Hoi; Posch, Christoph; Benosman, Ryad B.

    2016-01-01

    The asynchronous time-based neuromorphic image sensor ATIS is an array of autonomously operating pixels able to encode luminance information with an exceptionally high dynamic range (>143 dB). This paper introduces an event-based methodology to display data from this type of event-based imagers, taking into account the large dynamic range and high temporal accuracy that go beyond available mainstream display technologies. We introduce an event-based tone mapping methodology for asynchronously acquired time encoded gray-level data. A global and a local tone mapping operator are proposed. Both are designed to operate on a stream of incoming events rather than on time frame windows. Experimental results on real outdoor scenes are presented to evaluate the performance of the tone mapping operators in terms of quality, temporal stability, adaptation capability, and computational time. PMID:27642275

  20. Analysis of an FBMC/OQAM scheme for asynchronous access in wireless communications

    NASA Astrophysics Data System (ADS)

    Mattera, Davide; Tanda, Mario; Bellanger, Maurice

    2015-12-01

    The OFDM/OQAM transceiver belongs to the filter-bank-based multicarrier (FBMC) family and, unlike OFDM schemes, it is particularly able to meet the requirements of the physical layer of cognitive radio networks such as high level of adjacent channel leakage ratio and asynchronous communications. The paper proposes and analyzes a new implementation structure, named frequency spreading, for the OFDM/OQAM transceiver. On flat channels, it is equivalent to the standard one in terms of input-output relations, though more complex. On multipath channels, it offers a crucial advantage in terms of equalization, which is performed in the frequency domain, leading to high performance and no additional delay. With its flexibility and level of performance, the analyzed scheme has the potential to outperform OFDM in the asynchronous access context and in cognitive radio networks.