Science.gov

Sample records for linear asynchronous motor

  1. Nonlinear H-infinity feedback control for asynchronous motors of electric trains

    NASA Astrophysics Data System (ADS)

    Rigatos, Gerasimos; Siano, Pierluigi; Wira, Patrice

    2015-12-01

    A new method for feedback control of asynchronous electrical machines is introduced, with application example the problem of the traction system of electric trains. The control method consists of a repetitive solution of an H-infinity control problem for the asynchronous motor, that makes use of a locally linearized model of the motor and takes place at each iteration of the control algorithm. The asynchronous motor's model is locally linearized round its current operating point through the computation of the associated Jacobian matrices. Using the linearized model of the electrical machine an H-infinity feedback control law is computed. The known robustness features of H-infinity control enable to compensate for the errors of the approximative linearization, as well as to eliminate the effects of external perturbations. The efficiency of the proposed control scheme is shown analytically and is confirmed through simulation experiments.

  2. Asynchronous Torque Characteristics of VR Type Vernier Motor

    NASA Astrophysics Data System (ADS)

    Suda, Hiroshi; Matsushima, Yoshitaro; Xu, Li; Anazawa, Yoshihisa

    Recently, various types of vernier motor are developed. The VR type vernier motor is a kind of three-phase reluctance motor, and its stator has slots and distributed three-phase windings. The rotor is slotted iron core without windings. Relationship between S, R and P is S = R±2, where S and R are the numbers of stator and rotor slots per pair of poles, and the number of poles P is two. The rotor of the vernier motor moves at a sub-multiple of the angular velocity of the stator mmf. The multiplying factor is P/R. Authors had reported that the VR type vernier motors are analyzed as a three-phase reluctance motor, and have obtained the voltage equations on the γ-δ axis and expression of the torque.However, the asynchronous characteristics of the vernier motor are not clear yet. In this paper, the asynchronous characteristics of the vernier motors are analyzed with the symmetric components transformation and the commutator transformation. The voltage equations on the symmetrical co-ordinates and asynchronous and synchronous torque expression at steady state condition are obtained. The tests were performed on the trial motor. The calculated asynchronous torque has agreed well with the measured values.

  3. 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.

  4. Asynchronous Motor Nonlinear Control with Inverter Output LC Filter

    NASA Astrophysics Data System (ADS)

    Guzinski, J.; Abu-Rub, H.

    2009-03-01

    In many adjustable electric drives the LC filter is used to smooth the voltages and currents supplying AC motors. The LC filter makes it difficult to implement precise control of these motors especially in the case of speed sensorless solution. Because measuring motor currents and capacitor voltages is not practical, a preferable solution is to measure only filter input current. A good approach is to use observers to restore unmeasured state variables. Additionally, it is necessary to modify the used control in case of the drive with LC filter. In this paper the proposed system with nonlinear control method of the asynchronous motor, and the speed and flux observer structure were been adapted regarding the LC filter. In the presented drive only sensors previously used in the system without LC filter were used. 1.5 kW drive was verified in by simulation and experiments.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Linear Synchronous Motor Repeatability Tests

    SciTech Connect

    Ward, C.R.

    2002-10-18

    A cart system using linear synchronous motors was being considered for the Plutonium Immobilization Plant (PIP). One of the applications in the PIP was the movement of a stack of furnace trays, filled with the waste form (pucks) from a stacking/unstacking station to several bottom loaded furnaces. A system was ordered to perform this function in the PIP Ceramic Prototype Test Facility (CPTF). This system was installed and started up in SRTC prior to being installed in the CPTF. The PIP was suspended and then canceled after the linear synchronous motor system was started up. This system was used to determine repeatability of a linear synchronous motor cart system for the Modern Pit Facility.

  11. 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…

  12. 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.

  13. Torque calculation of the asynchronous motor in short-circuit test

    SciTech Connect

    Demski, W.; Szymanski, G.

    1998-09-01

    The paper presents the application of the calculation method of electromagnetic torque for asynchronous motor in short-circuit test. The {rvec A}, {rvec A}-V formulation with a complex notation for time harmonic systems in the finite difference method is used to solve the nonlinear three dimensional problem. The volume Maxwell stress tensor is used for force and torque calculation. The numerical results are compared with measurement.

  14. 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.

  15. Adaptive Feedback Linearization Control for Asynchronous Machine with Nonlinear for Natural Dynamic Complete Observer

    NASA Astrophysics Data System (ADS)

    Bentaallah, Abderrahim; Massoum, Ahmed; Benhamida, Farid; Meroufel, Abdelkader

    2012-03-01

    This paper studies the nonlinear adaptive control of an induction motor with natural dynamic complete nonlinear observer. The aim of this work is to develop a nonlinear control law and adaptive performance for an asynchronous motor with two main objectives: to improve the continuation of trajectories and the stability, robustness to parametric variations and disturbances rejection. This control law will independently control the speed and flux into the machine by restricting supply. A complete nonlinear observer for dynamic nature ensuring closed loop stability of the entire control and observer has been developed. Several simulations have also been carried out to demonstrate system performance.

  16. 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.

  17. 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.

  18. 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.

  19. A model of asynchronous iterative algorithms for solving large, sparse, linear systems

    NASA Technical Reports Server (NTRS)

    Reed, D. A.; Patrick, M. L.

    1984-01-01

    Solving large, sparse, linear systems of equations is one of the fundamental problems in large scale scientific and engineering computation. A model of a general class of asynchronous, iterative solution methods for linear systems is developed. In the model, the system is solved by creating several cooperating tasks that each compute a portion of the solution vector. This model is then analyzed to determine the expected intertask data transfer and task computational complexity as functions of the number of tasks. Based on the analysis, recommendations for task partitioning are made. These recommendations are a function of the sparseness of the linear system, its structure (i.e., randomly sparse or banded), and dimension.

  20. 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.

  1. 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.

  2. 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.

  3. Asynchronous BCI based on motor imagery with automated calibration and neurofeedback training.

    PubMed

    Kus, Rafal; Valbuena, Diana; Zygierewicz, Jaroslaw; Malechka, Tatsiana; Graeser, Axel; Durka, Piotr

    2012-11-01

    A new multiclass brain-computer interface (BCI) based on the modulation of sensorimotor oscillations by imagining movements is described. By the application of advanced signal processing tools, statistics and machine learning, this BCI system offers: 1) asynchronous mode of operation, 2) automatic selection of user-dependent parameters based on an initial calibration, 3) incremental update of the classifier parameters from feedback data. The signal classification uses spatially filtered signals and is based on spectral power estimation computed in individualized frequency bands, which are automatically identified by a specially tailored AR-based model. Relevant features are chosen by a criterion based on Mutual Information. Final recognition of motor imagery is effectuated by a multinomial logistic regression classifier. This BCI system was evaluated in two studies. In the first study, five participants trained the ability to imagine movements of the right hand, left hand and feet in response to visual cues. The accuracy of the classifier was evaluated across four training sessions with feedback. The second study assessed the information transfer rate (ITR) of the BCI in an asynchronous application. The subjects' task was to navigate a cursor along a computer rendered 2-D maze. A peak information transfer rate of 8.0 bit/min was achieved. Five subjects performed with a mean ITR of 4.5 bit/min and an accuracy of 74.84%. These results demonstrate that the use of automated interfaces to reduce complexity for the intended operator (outside the laboratory) is indeed possible. The signal processing and classifier source code embedded in BCI2000 is available from https://www.brain-project.org/downloads.html. PMID:23033330

  4. 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

  5. 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

  6. 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.

  7. Analysis of Current Harmonics in 3kV DC Catenary Caused by Specific Current Harmonics of an Asynchronous Motor

    NASA Astrophysics Data System (ADS)

    Lewandowski, Mirosław

    2010-01-01

    The mathematical model of vehicle supply system as well as the mathematical model of main circuit of locomotive with asynchronous motors have been described in this article. The necessity of analysis of disturbances caused by distorted current run of drive motors emerged together with the introduction of high power vehicles with power electronic converters. Analysis of the compatibility of traction high current circuits with circuits of the signal and traffic control systems requires the knowledge of current spectrum in a catenary, which has been taken by a vehicle. The author has described the algebraic method of calculating of the spectrum amplitudes in a catenary. It does not require laborious and time-consuming simulations of a system, which considerably decreases preliminary costs of designation and dimensioning of a vehicle drive system.

  8. Asynchronous recruitment of low-threshold motor units during repetitive, low-current stimulation of the human tibial nerve.

    PubMed

    Dean, Jesse C; Clair-Auger, Joanna M; Lagerquist, Olle; Collins, David F

    2014-01-01

    Motoneurons receive a barrage of inputs from descending and reflex pathways. Much of our understanding about how these inputs are transformed into motor output in humans has come from recordings of single motor units during voluntary contractions. This approach, however, is limited because the input is ill-defined. Herein, we quantify the discharge of soleus motor units in response to well-defined trains of afferent input delivered at physiologically-relevant frequencies. Constant frequency stimulation of the tibial nerve (10-100 Hz for 30 s), below threshold for eliciting M-waves or H-reflexes with a single pulse, recruited motor units in 7/9 subjects. All 25 motor units recruited during stimulation were also recruited during weak (<10% MVC) voluntary contractions. Higher frequencies recruited more units (n = 3/25 at 10 Hz; n = 25/25 at 100 Hz) at shorter latencies (19.4 ± 9.4 s at 10 Hz; 4.1 ± 4.0 s at 100 Hz) than lower frequencies. When a second unit was recruited, the discharge of the already active unit did not change, suggesting that recruitment was not due to increased synaptic drive. After recruitment, mean discharge rate during stimulation at 20 Hz (7.8 Hz) was lower than during 30 Hz (8.6 Hz) and 40 Hz (8.4 Hz) stimulation. Discharge was largely asynchronous from the stimulus pulses with "time-locked" discharge occurring at an H-reflex latency with only a 24% probability. Motor units continued to discharge after cessation of the stimulation in 89% of trials, although at a lower rate (5.8 Hz) than during the stimulation (7.9 Hz). This work supports the idea that the afferent volley evoked by repetitive stimulation recruits motor units through the integration of synaptic drive and intrinsic properties of motoneurons, resulting in "physiological" recruitment which adheres to Henneman's size principle and results in relatively low discharge rates and asynchronous firing. PMID:25566025

  9. Linear motor free piston compressor. Final report

    SciTech Connect

    Bloomfield, D.P.

    1995-02-17

    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 IC 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 deg 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.

  10. 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.

  11. 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

  12. 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

  13. Neuronal repair. Asynchronous therapy restores motor control by rewiring of the rat corticospinal tract after stroke.

    PubMed

    Wahl, A S; Omlor, W; Rubio, J C; Chen, J L; Zheng, H; Schröter, A; Gullo, M; Weinmann, O; Kobayashi, K; Helmchen, F; Ommer, B; Schwab, M E

    2014-06-13

    The brain exhibits limited capacity for spontaneous restoration of lost motor functions after stroke. Rehabilitation is the prevailing clinical approach to augment functional recovery, but the scientific basis is poorly understood. Here, we show nearly full recovery of skilled forelimb functions in rats with large strokes when a growth-promoting immunotherapy against a neurite growth-inhibitory protein was applied to boost the sprouting of new fibers, before stabilizing the newly formed circuits by intensive training. In contrast, early high-intensity training during the growth phase destroyed the effect and led to aberrant fiber patterns. Pharmacogenetic experiments identified a subset of corticospinal fibers originating in the intact half of the forebrain, side-switching in the spinal cord to newly innervate the impaired limb and restore skilled motor function. PMID:24926013

  14. 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.

  15. Piezoelectric linear motor concepts based on coupling of longitudinal vibrations.

    PubMed

    Hemsel, T; Mracek, M; Twiefel, J; Vasiljev, P

    2006-12-22

    Classically, rotary motors with gears and spindle mechanisms are used to achieve translatory motion. In means of miniaturization and weight reduction piezoelectric linear motors are of interest. Several ultrasonic linear motors found in literature base on the use of two different vibration modes. Most often flexural and longitudinal modes are combined to achieve an elliptic micro-motion of surface points. This micro-motion is converted to direct linear (or translatory) motion of a driven slider. To gain high amplitudes of the micro-motion and thus having a powerful motor, the ultrasonic vibrator should be driven near the eigenfrequency of its modes. Additionally, low mechanical and electrical losses lead to increased efficiency and large amplitude magnification in resonance. This demands a geometrical design that fits the eigenfrequencies of the two different modes. A frequency-deviation of only a few percent leads to non-acceptable disturbance of the elliptical motion. Thus, the mechanical design of the vibrators has to be done very carefully. Within this contribution we discuss different motor designs based on the coupling of two the same longitudinal vibrations within one structure to generate an elliptic motion of surface points. Different concepts based on piezoelectric plates and Langevin transducers are compared. Benefits and drawbacks against the combination of longitudinal and bending modes will be discussed. Numerical results of the stator vibration as well as motor characteristics are validated by measurements on different prototypes. PMID:16782160

  16. 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.

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

    SciTech Connect

    Coffey, H.T.

    1992-12-31

    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.

  18. 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.

  19. Position sensor for linear synchronous motors employing halbach arrays

    DOEpatents

    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.

  20. Precision Motion Control of Linear DC Solenoid Motor

    NASA Astrophysics Data System (ADS)

    Kato, Atsushi; Kubo, Takeharu; Ohnishi, Kouhei

    High speed and high precision control has been required in various cases. Hence, a new linear actuator based on Linear DC Solenoid Motor (LDSM), is developed for that purpose. In addition, we propose a precision motion control for LDSM. LDSM is composed of solenoid stator and moving permanent magnet. It has simple and light structure. Moreover, the solenoid form provides small leakage and generates more power than non-linear motor. Nevertheless, the nonlinear disturbance force such as friction force prevents LDSM from controlling precisely. In this paper, the high gain disturbance observer is applied to LDSM to suppress the force. The observer is able to estimate and compensate the nonlinear disturbance force. It is confirmed that the proposed precision motion control provides LDSM with precise observer control position and force through the experiments.

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

    NASA Astrophysics Data System (ADS)

    Holliday, Jeffrey C.

    1995-12-01

    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.

  2. 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.

  3. 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

  4. Linear moving magnet motor/generator for Stirling engines

    NASA Astrophysics Data System (ADS)

    Shtrikman, S.; Urieli, I.

    Free piston Stirling cycle machines have many inherent advantages, however suffer from the difficulties of extracting power output and controllability of the free displacer, which is usually driven by gas pressure forces. Modern rare earth samarium cobalt magnets allow the use of moving magnet linear electrical devices. This paper discusses the development and testing of moving magnet devices designed specifically for use with Stirling engines, both for generating electricity and for driving the displacer piston. The generator was used as an output stage of a free piston Stirling engine, and is capable of delivering a power of 500 watts at an estimated efficiency of about 90%. The motor was used to drive the displacer of the same Stirling engine. It was found to be completely controllable in amplitude, phase, and mean position. The relative merits of moving magnet linear motor/generators are discussed.

  5. 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.

  6. 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.

  7. Traveling wave type ultrasonic linear motor using twin bending bars

    NASA Astrophysics Data System (ADS)

    Kondo, Shuichi; Yamaura, Hiroshi; Koyama, Daisuke; Nakamura, Kentaro

    2010-01-01

    Ultrasonic linear motors with a small body are highly demanded since efficiency does not decrease very much with downsizing. In this study, we aim at realizing ultrasonic linear motor with the diameter less than 10 mm as an alternative to small air cylinder actuators. We propose a new stator structure using two PZT elements between two parallel bending bars. The PZT elements are bonded at the position of several mm from the bar end. In this structure, both bar ends vibrate resonantly in a bending mode, and high vibration displacement amplitude can be obtained along the bars. The length between the PZT element and the bar end determines the optimum driving frequency. The slider simply consists of three metal plates, which sandwich the bending bars, and the preload can be controlled by springs. The conditions in which the traveling wave can be generated along the bars were investigated. When the bars vibrate in a symmetric mode and traveling waves are generated, the slider moves in the direction to the opposite of traveling wave. Traveling wave could be generated by controlling the driving phase difference between the two PZT elements. It was found that the phase differences depend on the distance between the two PZT elements. We experimentally achieved the stroke of 10 mm and the thrust of 78 mN at 23 kHz.

  8. An ultrasonic linear motor using ridge-mode traveling waves.

    PubMed

    Tominaga, Masahiko; Kaminaga, Ryuta; Friend, James R; Nakamura, Kentaro; Ueha, Sadayuki

    2005-10-01

    A new type of ultrasonic linear motor is presented using traveling waves excited along a ridge atop a substrate. The ridge cross section was designed to permit only the fundamental mode to be excited during operation of the motor, with a Langevin transducer used as the source of vibration in this study. The ridge waveguide was first made of lossy media to avoid reflecting vibration energy back toward the vibration source, forming a traveling wave. A 5-mm-wide, 15-mm-tall rectangular acrylic ridge was used to move a slider placed upon it toward the vibration source, in opposition to the direction of the traveling wave transmitted along the waveguide ridge. Using a low-loss 3 x 6-mm aluminum rectangular ridge combined with a damper clamped onto the far end of the waveguide, similar results were obtained. To obtain bidirectional operation, the damper was replaced with a second Langevin transducer, giving a pair of transducers located perpendicularly to the ends of the ridge and driven with an appropriate phase difference. The moving direction of the slider was reversed by shifting this phase difference by about 180 degrees. With this simple configuration, it may soon be possible to fabricate a linear micromotor system on a silicon substrate or other semiconductor wafer adjacent to other electronic and optoelectronic devices. PMID:16382624

  9. Dynamic Performance of Subway Vehicle with Linear Induction Motor System

    NASA Astrophysics Data System (ADS)

    Wu, Pingbo; Luo, Ren; Hu, Yan; Zeng, Jing

    The light rail vehicle with Linear Induction Motor (LIM) bogie, which is a new type of urban rail traffic tool, has the advantages of low costs, wide applicability, low noise, simple maintenance and better dynamic behavior. This kind of vehicle, supported and guided by the wheel and rail, is not driven by the wheel/rail adhesion force, but driven by the electromagnetic force between LIM and reaction plate. In this paper, three different types of suspensions and their characteristic are discussed with considering the interactions both between wheel and rail and between LIM and reaction plate. A nonlinear mathematical model of the vehicle with LIM bogie is set up by using the software SIMPACK, and the electromechanical model is also set up on Simulink roof. Then the running behavior of the LIM vehicle is simulated, and the influence of suspension on the vehicle dynamic performance is investigated.

  10. Development of High-Force-Density Iron-Core Linear Synchronous Motor

    NASA Astrophysics Data System (ADS)

    Kakihara, Masanobu; Hoshi, Toshiyuki; Shikayama, Toru; Ohto, Motomichi

    The demand for small-sized and high-acceleration linear motors for industrial machines such as semiconductor production equipment and LCD equipment is rapidly increasing in order to maintain the small size of these equipment and to increase productivity. To satisfy the demand, high-force-density (i.e., force per volume) linear motors are required. This paper discusses the development of a high-force-density iron-core linear synchronous motor that consists of a Halbach magnet array with soft magnetic material and a grain-oriented silicon steel sheet core; the motor has a shape-optimized design. The motor constant square density of the new linear motor reaches 10N2/W/cm3, while that of the highest force linear motor available at present is 5N2/W/cm3. In other words, the new motor can deliver a force of 900N per 1000cm3. In this paper, details of the design, especially the structure and performance of the new motor are presented, and the design is validated on the basis of measurements of a prototype motor.

  11. Influence analysis of structural parameters on electromagnetic properties of HTS linear induction motor

    NASA Astrophysics Data System (ADS)

    Zhao, J.; Zheng, T. Q.; Zhang, W.; Fang, J.; Liu, Y. M.

    2011-11-01

    A new type high temperature superconductor linear induction motor is designed and analyzed as a prototype to ensure applicability aimed at industrial motors. Made of Bi-2223/Ag, primary windings are distributed with the double-layer concentrated structure. The motor is analyzed by 2D electromagnetic Finite Element Method to get magnetic field distribution, thrust force, vertical force and so on. The critical current of motor and the electromagnetic force are mostly decided by the leakage flux density of primary slot and by the main magnetic flux and eddy current respectively. The structural parameters of motor have a great influence on the distribution of magnetic field. Under constant currents, the properties of motor are analyzed with different slot widths, slot heights and winding turns. The properties of motor, such as the maximum slot leakage flux density, motor thrust and motor vertical force, are analyzed with different structural parameters.

  12. 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

  13. Propulsive characteristics of a novel linear hybrid motor with both induction and synchronous operations

    SciTech Connect

    Jeon, W.J.; Katoh, S.; Iwamoto, T.; Kamiya, Y.; Onuki, T.

    1999-09-01

    This paper treats a novel linear hybrid motor (LHM) by both induction and synchronous operations. The proposed motor consists of one pair of linear synchronous motors (LSMs) and a linear induction motor (LIM). The primary-cores of both LSM and LIM have a common ring winding, and the secondary solid-conductor is arranged in both LIM and the interpole space of LSM. The feature of the motor is that the undesirable vertical force in LSM is offset by the symmetrical double-sided construction and the secondary is capable of self-starting by induction operation. From the investigation by the three-dimensional finite element analysis and experiment, the authors derive an optimal exciting condition for starting, and then verify that the proposed LHM is effective for practical use.

  14. 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. PMID:25832267

  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. PMID:25454095

  16. 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.

  17. 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.

  18. 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.

  19. Drive control and position measurement of RailCab vehicles driven by linear motors

    NASA Astrophysics Data System (ADS)

    Pottharst, Andreas; Henke, Christian; Schneider, Tobias; Böcker, Joachim; Grotstollen, Horst

    2006-11-01

    The novel railway system RailCab makes use of autonomous vehicles which are driven by an AC linear motor. Depending on the track-side motor part, long-stator or short-stator operations are possible. The paper deals with the operation of the doubly-fed induction motor which is used for motion control and for transferring the energy required onboard the vehicle. This type of linear motor synchronization of the traveling fields generated by the stationary primary and moving secondary windings is an important and demanding task because the instantaneous positions of the vehicle or the primary traveling wave must be determined with high accuracy. The paper shows how this task is solved at the moment and what improvements are under development.

  20. Induction Motor Drive System Based on Linear Active Disturbance Rejection Controller

    NASA Astrophysics Data System (ADS)

    Liu, Liying; Zhang, Yongli; Yao, Qingmei

    It is difficult to establish an exact mathematical model for the induction motor and the robustness is poor of the vector control system using PI regulator. This paper adopts the linear active disturbance rejection controller (LADRC) to control inductor motor. LADRC doesn't need the exact mathematical model of motor and it can not only estimate but also compensate the general disturbance that includes the coupling items in model of motor and parameters perturbations by linear extended state observer (LESO), so the rotor flux and torque fully decouple. As a result, the performance is improved. To prove the above control scheme, the proposed control system has been simulated in MATLAB/SIMULINK, and the comparison was made with PID. Simulation results show that LADRC' has better performance and robustness than PID.

  1. 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.

  2. Analysis of a tubular linear motor with soft magnetic composites for reciprocating compressors

    NASA Astrophysics Data System (ADS)

    Hsieh, Min-Fu; Hu, Kai-Hsiang

    2008-04-01

    This paper presents the analysis of a single-phase tubular linear motor formed with soft magnetic composites for direct driving reciprocating compressors. This direct-drive design can solve the potential cylinder wearing problem caused by the crank side force in conventional reciprocating compressors. The overall size may also be reduced without transmission mechanism. To produce sufficient thrust for the cooling cycles, the designed motor features a structure of three-dimensional flux distributions that allows an increase of slot-fill factor to enhance the thrust density. Moreover, the motor makes use of the inherent cogging force which contributes to the overall thrust. Finite element analysis is employed to verify the performance. The results show that the motor is capable of producing high thrust with a compact size compared to other types of motors.

  3. Disc Motor: Conventional and Superconductor Simulated Results Analysis

    NASA Astrophysics Data System (ADS)

    Inácio, David; Martins, João; Neves, Mário Ventim; Álvarez, Alfredo; Rodrigues, Amadeu Leão

    Taking into consideration the development and integration of electrical machines with lower dimensions and higher performance, this paper presents the design and development of a three-phase axial flux disc motor, with 50 Hz frequency supply. It is made with two conventional semi-stators and a rotor, which can be implemented with a conventional aluminum disc or a high temperature-superconducting disc. The analysis of the motor characteristics is done with a 2D commercial finite elements package, being the modeling performed as a linear motor. The obtained results allow concluding that the superconductor motor provides a higher force than the conventional one. The conventional disc motor presents an asynchronous behavior, like a conventional induction motor, while the superconductor motor presents both synchronous and asynchronous behaviors.

  4. Modeling and Simulating of Single Side Short Stator Linear Induction Motor with the End Effect

    NASA Astrophysics Data System (ADS)

    Hamzehbahmani, Hamed

    2011-09-01

    Linear induction motors are under development for a variety of demanding applications including high speed ground transportation and specific industrial applications. These applications require machines that can produce large forces, operate at high speeds, and can be controlled precisely to meet performance requirements. The design and implementation of these systems require fast and accurate techniques for performing system simulation and control system design. In this paper, a mathematical model for a single side short stator linear induction motor with a consideration of the end effects is presented; and to study the dynamic performance of this linear motor, MATLAB/SIMULINK based simulations are carried out, and finally, the experimental results are compared to simulation results.

  5. A 400-watt, tri-state switching controller for reciprocating linear motors

    NASA Astrophysics Data System (ADS)

    Maresca, R. L.

    Improved efficiency, better steady-state performance, and reduced complexity were the objectives set for a new control system for reciprocating linear motors. The control system conprises a low-frequency tristate switching circuit, a linear motor, and an axial position sensor along with three distinct feedbak loops (peak-amplitude, average-position, and phase feedback). The system was tested on a 400-watt reciprocating compressor and achieved efficiencies of greater than 90 percent with excellent control of the critical operating parameters: speed, stroke, phase, and center position of the linear motor. The system replaces a 70 percent-efficient high-frequency switching amplifier and classical servocontrol system previously used in long-life Stirling-cycle refrigerators for space applications.

  6. Simple and Robust Indirect Thrust Control for Positioning of Linear Induction Motors

    NASA Astrophysics Data System (ADS)

    Martínez-Iturralde, Miguel; Martínez, Gonzalo; Castelli, Marcelo; Rico, Andrés García; Flórez, Julián

    Dealing with position control of Linear Induction Motors (LIM), most strategies in bibliography are based on Secondary Flux Oriented Control (SFOC) and Direct Thrust Control (DTC). However, SFOC of linear induction motors needs complex identification methods to compensate parameter variation during operation, mainly due to local heating and end-effects. On the other hand, DTC based methods for LIMs present thrust ripple and have problems at low and zero speeds. In this paper, a new Indirect Thrust Control (ITC) based strategy for position control of linear induction motors that makes up for these drawbacks is presented. The position control loop design methodology and the method for automatic adjustment of compensators are described. Experimental results are presented to evaluate the performance and sensitivity of the control strategy. Finally, some conclusions are drawn about the applicability of the new algorithm that demonstrate the main advantages versus SFOC and DTC.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Motor properties from persistence: a linear molecular walker lacking spatial and temporal asymmetry

    NASA Astrophysics Data System (ADS)

    Zuckermann, Martin J.; Angstmann, Christopher N.; Schmitt, Regina; Blab, Gerhard A.; Bromley, Elizabeth HC; Forde, Nancy R.; Linke, Heiner; Curmi, Paul MG

    2015-05-01

    The stepping direction of linear molecular motors is usually defined by a spatial asymmetry of the motor, its track, or both. Here we present a model for a molecular walker that undergoes biased directional motion along a symmetric track in the presence of a temporally symmetric chemical cycle. Instead of using asymmetry, directionality is achieved by persistence. At small load force the walker can take on average thousands of steps in a given direction until it stochastically reverses direction. We discuss a specific experimental implementation of a synthetic motor based on this design and find, using Langevin and Monte Carlo simulations, that a realistic walker can work against load forces on the order of picoNewtons with an efficiency of ∼18%, comparable to that of kinesin. In principle, the walker can be turned into a permanent motor by externally monitoring the walker’s momentary direction of motion, and using feedback to adjust the direction of a load force. We calculate the thermodynamic cost of using feedback to enhance motor performance in terms of the Shannon entropy, and find that it reduces the efficiency of a realistic motor only marginally. We discuss the implications for natural protein motor performance in the context of the strong performance of this design based only on a thermal ratchet.

  12. 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

  13. High Precision Piezoelectric Linear Motors for Operations at Cryogenic Temperatures and Vacuum

    NASA Technical Reports Server (NTRS)

    Wong, D.; Carman, G.; Stam, M.; Bar-Cohen, Y.; Sen, A.; Henry, P.; Bearman, G.; Moacanin, J.

    1995-01-01

    The use of an electromechanical device for optically positioning a mirror system during the pre-project phase of the Pluto Fast Flyby mission was evaluated at JPL. The device under consideration was a piezoelectric driven linear motor functionally dependent upon a time varying electric field which induces displacements ranging from submicrons to millimeters with positioning accuracy within nanometers.

  14. A superconducting linear motor drive for a positive displacement bellows pump for use in the g-2 cryogenics system

    SciTech Connect

    Green, M.A.

    1994-10-01

    Forced two-phase cooling of indirectly cooled magnets requires circulation of liquid helium through the magnet cooling channel. A bellows helium pump is one possible way of providing helium flow to a magnet cooling system. Since the bellows type of helium pump is immersed in liquid helium, a superconducting linear motor drive appears to be an attractive option. This report describes a linear motor drive that employs oriented permanent magnet materials such as samarium-cobalt as the stator magnet system and a superconducting loud speaker voice coil type of drive as the armature of the linear motor. This report examines drive motor requirements for a helium pump.

  15. Unmasking the linear behaviour of slow motor adaptation to prolonged convergence.

    PubMed

    Erkelens, Ian M; Thompson, Benjamin; Bobier, William R

    2016-06-01

    Adaptation to changing environmental demands is central to maintaining optimal motor system function. Current theories suggest that adaptation in both the skeletal-motor and oculomotor systems involves a combination of fast (reflexive) and slow (recalibration) mechanisms. Here we used the oculomotor vergence system as a model to investigate the mechanisms underlying slow motor adaptation. Unlike reaching with the upper limbs, vergence is less susceptible to changes in cognitive strategy that can affect the behaviour of motor adaptation. We tested the hypothesis that mechanisms of slow motor adaptation reflect early neural processing by assessing the linearity of adaptive responses over a large range of stimuli. Using varied disparity stimuli in conflict with accommodation, the slow adaptation of tonic vergence was found to exhibit a linear response whereby the rate (R(2)  = 0.85, P < 0.0001) and amplitude (R(2)  = 0.65, P < 0.0001) of the adaptive effects increased proportionally with stimulus amplitude. These results suggest that this slow adaptive mechanism is an early neural process, implying a fundamental physiological nature that is potentially dominated by subcortical and cerebellar substrates. PMID:26991129

  16. 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

  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. PMID:27479230

  18. Linearization Method for Starting Control of Speed-Sensorless Vector-Controlled Induction Motors

    NASA Astrophysics Data System (ADS)

    Fujinami, Kazuki; Kondo, Keiichiro

    A linearization method is proposed for controlling the start-up operation of a rotating induction motor. The dynamics of this motor are deteriorated when the starting operation is carried out at high frequencies. In this method, the characteristics of the method are analyzed to reveal that the aforementioned problem is caused by the low equivalent gain of the induced voltage during the rotor flux establishment. A method to compensate for the angle of the rotor-flux-induced voltage vector is proposed to overcome this problem. The proposed method is experimentally verified by a test set, and the influence of changes in the rotor resistance is analyzed.

  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. Device with Functions of Linear Motor and Non-contact Power Collector for Wireless Drive

    NASA Astrophysics Data System (ADS)

    Fujii, Nobuo; Mizuma, Tsuyoshi

    The authors propose a new apparatus with functions of propulsion and non-contact power collection for a future vehicle which can run like an electric vehicle supplied from the onboard battery source in most of the root except near stations. The batteries or power-capacitors are non-contact charged from the winding connected with commercial power on ground in the stations etc. The apparatus has both functions of linear motor and transformer, and the basic configuration is a wound-secondary type linear induction motor (LIM). In the paper, the wound type LIM with the concentrated single-phase winding for the primary member on the ground is dealt from the viewpoint of low cost arrangement. The secondary winding is changed to the single-phase connection for zero thrust in the transformer operation, and the two-phase connection for the linear motor respectively. The change of connection is done by the special converter for charge and linear drive on board. The characteristics are studied analytically.

  1. Innervation zones of fasciculating motor units: observations by a linear electrode array

    PubMed Central

    Jahanmiri-Nezhad, Faezeh; Barkhaus, Paul E.; Rymer, William Z.; Zhou, Ping

    2015-01-01

    This study examines the innervation zone (IZ) in the biceps brachii muscle in healthy subjects and those with amyotrophic lateral sclerosis (ALS) using a 20-channel linear electromyogram (EMG) electrode array. Raster plots of individual waveform potentials were studied to estimate the motor unit IZ. While this work mainly focused on fasciculation potentials (FPs), a limited number of motor unit potentials (MUPs) from voluntary activity of 12 healthy and seven ALS subjects were also examined. Abnormal propagation of MUPs and scattered IZs were observed in fasciculating units, compared with voluntarily activated MUPs in healthy and ALS subjects. These findings can be related to muscle fiber reinnervation following motor neuron degeneration in ALS and the different origin sites of FPs compared with voluntary MUPs. PMID:26029076

  2. Speed and efficiency control of an induction motor with input-output linearization

    SciTech Connect

    Wang, W.J.; Wang, C.C.

    1999-09-01

    A combination of a composite adaptive speed controller and an explicit efficiency control algorithm is proposed to control the speed and power efficiency of the induction motor in this paper. First, the input-output linearization method is used to dynamically decouple the motor speed and rotor flux. Then, a composite adaptive control algorithm is designed to control the speed of the induction motor. At steady-state light-load conditions, the magnetizing current command is adjusted on the basis of the product of magnetizing current command and torque current command such that the steady-state power loss is minimum. A PC-based experimental drive system has been implemented, and some experimental results are provided to demonstrate the effectiveness of the presented approach.

  3. High Precision Piezoelectric Linear Motors for Operations at Cryogenic Temperatures and Vacuum

    NASA Technical Reports Server (NTRS)

    Wong, D.; Carman, G.; Stam, M.; Bar-Cohen, Y.; Sen, A.; Henry, P.; Bearman, G.; Moacanin, J.

    1995-01-01

    The Jet Propulsion Laboratory evaluated the use of an electromechanical device for optically positioning a mirror system during the pre-project phase of the Pluto-Fast-Flyby (PFF) mission. The device under consideration was a piezoelectric driven linear motor functionally dependent upon a time varying electric field which induces displacements ranging from submicrons to millimeters with positioning accuracy within nanometers. Using a control package, the mirror system provides image motion compensation and mosaicking capabilities. While this device offers unique advantages, there were concerns pertaining to its operational capabilities for the PFF mission. The issues include irradiation effects and thermal concerns. A literature study indicated that irradiation effects will not significantly impact the linear motor's operational characteristics. On the other hand, thermal concerns necessitated an in depth study.

  4. 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.

  5. 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.

  6. 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.

  7. A new direct torque control scheme for induction motors using linear state feedback

    SciTech Connect

    Kandianis, A.; Manias, S.N.; Griva, G.; Profumo, F.

    1995-12-31

    In this paper a new Direct Torque Control (DTC) scheme for induction motor drives is described, based on the linear state feedback method with dynamic output feedback. The DTC has been shown to be a good solution in torque controlled drives applications when the speed control is not required (e.g. traction drives for electric vehicles). In such cases, the torque command comes directly from the user input. By considering the torque and flux as the outputs of the linearized motor model, it is possible to design an optimum controller with constant gain state feedback and dynamic output feedback through an integral term. The design procedure of the proposed control scheme is described and the simulation results are presented to show the overall performance of the system.

  8. A combined lift and propulsion system of a steel plate by transverse flux linear induction motors

    SciTech Connect

    Hayashiya, H.; Ohsaki, H.; Masada, E.

    1999-09-01

    To realize a non-contacting conveyance of a steel plate, a combined lift and propulsion system of a steel plate by transverse flux linear induction motors (LIMs) is proposed. By introducing the DC biased AC feeding to the LIM< a steel plate is supported stably and efficiently. In this paper, after showing the advantages of the system, the magnetic levitation experiments are carried out to investigate the feasibility of the system.

  9. 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.

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

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

    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.

  12. 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

  13. 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.

  14. Adaptive PI control strategy for flat permanent magnet linear synchronous motor vibration suppression

    NASA Astrophysics Data System (ADS)

    Meng, Fanwei; Liu, Chengying; Li, Zhijun; Wang, Liping

    2013-01-01

    Due to low damping ratio, flat permanent magnet linear synchronous motor's vibration is difficult to be damped and the accuracy is limited. The vibration suppressing results are not good enough in the existing research because only the longitudinal direction vibration is considered while the normal direction vibration is neglected. The parameters of the direct-axis current controller are set to be the same as those of the quadrature-axis current controller commonly. This causes contradiction between signal noise and response. To suppress the vibration, the electromagnetic force model of the flat permanent magnet synchronous linear motor is formulated first. Through the analysis of the effect that direct-axis current noise and quadrature-axis current noise have on both direction vibration, it can be declared that the conclusion that longitudinal direction vibration is only related to the quadrature-axis current noise while the normal direction vibration is related to both the quadrature-axis current noise and direct-axis current noise. Then, the simulation test on current loop with a low-pass filter is conducted and the results show that the low-pass filter can not suppress the vibration but makes the vibration more severe. So a vibration suppressing strategy that the proportional gain of direct-axis current controller adapted according to quadrature-axis reference current is proposed. This control strategy can suppress motor vibration by suppressing direct-axis current noise. The experiments results about the effect of K p and T i on normal direction vibration, longitudinal vibration and the position step response show that this strategy suppresses vibration effectively while the motor's motion performance is not affected. The maximum reduction of vibration can be up to 40%. In addition, current test under rated load condition is also conducted and the results show that the control strategy can avoid the conflict between the direct-axis current and the quadrature

  15. 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. PMID:25362449

  16. 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.

  17. 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.

  18. Adaptive H∞ nonlinear velocity tracking using RBFNN for linear DC brushless motor

    NASA Astrophysics Data System (ADS)

    Tsai, Ching-Chih; Chan, Cheng-Kain; Li, Yi Yu

    2012-01-01

    This article presents an adaptive H ∞ nonlinear velocity control for a linear DC brushless motor. A simplified model of this motor with friction is briefly recalled. The friction dynamics is described by the Lu Gre model and the online tuning radial basis function neural network (RBFNN) is used to parameterise the nonlinear friction function and un-modelled errors. An adaptive nonlinear H ∞ control method is then proposed to achieve velocity tracking, by assuming that the upper bounds of the ripple force, the changeable load and the nonlinear friction can be learned by the RBFNN. The closed-loop system is proven to be uniformly bounded using the Lyapunov stability theory. The feasibility and the efficacy of the proposed control are exemplified by conducting two velocity tracking experiments.

  19. 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.

  20. Finite Element Analysis and Optimization of Flexure Bearing for Linear Motor Compressor

    NASA Astrophysics Data System (ADS)

    Khot, Maruti; Gawali, Bajirao

    Nowadays linear motor compressors are commonly used in miniature cryocoolers instead of rotary compressors because rotary compressors apply large radial forces to the piston, which provide no useful work, cause large amount of wear and usually require lubrication. Recent trends favour flexure supported configurations for long life. The present work aims at designing and geometrical optimization of flexure bearings using finite element analysis and the development of design charts for selection purposes. The work also covers the manufacturing of flexures using different materials and the validation of the experimental finite element analysis results.

  1. 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.

  2. 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.

  3. 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.

  4. Finite element analysis of direct thrust-controlled linear induction motor

    SciTech Connect

    Kwon, B.I.; Woo, K.I.; Kim, S. . Dept. of Electrical Engineering)

    1999-05-01

    This paper describes the finite element analysis of a direct thrust-controlled linear induction motor (LIM). The time-stepping finite element method and the moving mesh technique are used to calculate the dynamic characteristics of LIM during the direct thrust control. Because LIM has the end effect, thrust correction coefficient is introduced to predict an actual thrust in control. The simulation results, the thrust and the stator flux linkage are shown below and the stator current is compared with an experimental one.

  5. Theoretical principles for designing long stator/linear motors with iron

    NASA Astrophysics Data System (ADS)

    Hellinger, Rolf

    Elements for dimensioning synchronous linear motors for rail transportation are presented. A calculation analytic method was developed, which is based on the introduction of the specific magnetic conductance function, which takes into account the influence of stator and excitation windings. Electromotive and inertia forces were estimated with the stator current function and the magnetic air gap flux density and the results were verified using the finite element method for solving Maxwell equations. The short circuit currents in the stator winding were evaluated by means of calculated inductivities. Some perturbations, such as sliding and oscillation forces were calculated. Some results were validated on the TRANSRAPID test vehicle.

  6. Calculation and Measurement of Coil Inductance Profile in Tubular Linear Reluctance Motor and its Validation by Three Dimensional FEM

    NASA Astrophysics Data System (ADS)

    Mosallanejad, Ali; Shoulaie, Abbas

    2011-07-01

    This paper reports a study of coil inductance profile in all positions of plunger in tubular linear reluctance motors (TLRMs) with open type magnetic circuits. In this paper, maximum inductance calculation methods in winding of tubular linear reluctance motors are described based on energy method. Furthermore, in order to calculate the maximum inductance, equivalent permeability is measured. Electromagnetic finite-element analysis for simulation and calculation of coil inductance in this motor is used. Simulation results of coil inductance calculation using 3-D FEM with coil current excitation is compared to theoretical and experimental results. The comparison yields a good agreement.

  7. The Experimental Study of Rayleigh-Taylor Instability using a Linear Induction Motor Accelerator

    NASA Astrophysics Data System (ADS)

    Yamashita, Nicholas; Jacobs, Jeffrey

    2009-11-01

    The experiments to be presented utilize an incompressible system of two stratified miscible liquids of different densities that are accelerated in order to produce the Rayleigh-Taylor instability. Three liquid combinations are used: isopropyl alcohol with water, a calcium nitrate solution or a lithium polytungstate solution, giving Atwood numbers of 0.11, 0.22 and 0.57, respectively. The acceleration required to drive the instability is produced by two high-speed linear induction motors mounted to an 8 m tall drop tower. The motors are mounted in parallel and have an effective acceleration length of 1.7 m and are each capable of producing 15 kN of thrust. The liquid system is contained within a square acrylic tank with inside dimensions 76 x76x184 mm. The tank is mounted to an aluminum plate, which is driven by the motors to create constant accelerations in the range of 1-20 g's, though the potential exists for higher accelerations. Also attached to the plate are a high-speed camera and an LED backlight to provide continuous video of the instability. In addition, an accelerometer is used to provide acceleration measurements during each experiment. Experimental image sequences will be presented which show the development of a random three-dimensional instability from an unforced initial perturbation. Measurements of the mixing zone width will be compared with traditional growth models.

  8. 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.

  9. 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.

  10. 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.

  11. Application of the Hyper-Poisson Generalized Linear Model for Analyzing Motor Vehicle Crashes.

    PubMed

    Khazraee, S Hadi; Sáez-Castillo, Antonio Jose; Geedipally, Srinivas Reddy; Lord, Dominique

    2015-05-01

    The hyper-Poisson distribution can handle both over- and underdispersion, and its generalized linear model formulation allows the dispersion of the distribution to be observation-specific and dependent on model covariates. This study's objective is to examine the potential applicability of a newly proposed generalized linear model framework for the hyper-Poisson distribution in analyzing motor vehicle crash count data. The hyper-Poisson generalized linear model was first fitted to intersection crash data from Toronto, characterized by overdispersion, and then to crash data from railway-highway crossings in Korea, characterized by underdispersion. The results of this study are promising. When fitted to the Toronto data set, the goodness-of-fit measures indicated that the hyper-Poisson model with a variable dispersion parameter provided a statistical fit as good as the traditional negative binomial model. The hyper-Poisson model was also successful in handling the underdispersed data from Korea; the model performed as well as the gamma probability model and the Conway-Maxwell-Poisson model previously developed for the same data set. The advantages of the hyper-Poisson model studied in this article are noteworthy. Unlike the negative binomial model, which has difficulties in handling underdispersed data, the hyper-Poisson model can handle both over- and underdispersed crash data. Although not a major issue for the Conway-Maxwell-Poisson model, the effect of each variable on the expected mean of crashes is easily interpretable in the case of this new model. PMID:25385093

  12. A piezoelectric linear ultrasonic motor with the structure of a circular cylindrical stator and slider

    NASA Astrophysics Data System (ADS)

    Sun, Dongming; Wang, Sheng; Sakurai, Junpei; Choi, Kee-Bong; Shimokohbe, Akira; Hata, Seiichi

    2010-04-01

    A piezoelectric linear ultrasonic motor is proposed, with a cylindrical stator and slider structure. The length and diameter of the motor are about 10 and 1.5 mm, respectively. The stator consists of two piezoelectric ceramic (PZT) tubes connected by a thin film metallic glass (TFMG) pipe. The stator is designed based on theoretical analyses and finite element method (FEM) simulation. The traveling wave propagation is obtained in the FEM simulation under the proper geometrical sizes, suitable boundary conditions and driving voltage signals. The trajectories of particles on the TFMG pipe are elliptical motion. In the experiment, a 25 µm thick TFMG pipe is fabricated using the rotating magnetron sputtering technique and the vibration characteristics of the stator are measured by a laser Doppler vibrometer (LDV) system. Bidirectional motion of the slider is observed around 600 kHz, the maximum velocity is near to 40 mm s - 1 at 50 Vp-p for the loose slider and the maximum output force is 6 mN at 70 Vp-p for the tight slider.

  13. 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.

  14. 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.

  15. 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).

  16. Fuzzy virtual reference model sensorless tracking control for linear induction motors.

    PubMed

    Hung, Cheng-Yao; Liu, Peter; Lian, Kuang-Yow

    2013-06-01

    This paper introduces a fuzzy virtual reference model (FVRM) synthesis method for linear induction motor (LIM) speed sensorless tracking control. First, we represent the LIM as a Takagi-Sugeno fuzzy model. Second, we estimate the immeasurable mover speed and secondary flux by a fuzzy observer. Third, to convert the speed tracking control into a stabilization problem, we define the internal desired states for state tracking via an FVRM. Finally, by solving a set of linear matrix inequalities (LMIs), we obtain the observer gains and the control gains where exponential convergence is guaranteed. The contributions of the approach in this paper are threefold: 1) simplified approach--speed tracking problem converted into stabilization problem; 2) omit need of actual reference model--FVRM generates internal desired states; and 3) unification of controller and observer design--control objectives are formulated into an LMI problem where powerful numerical toolboxes solve controller and observer gains. Finally, experiments are carried out to verify the theoretical results and show satisfactory performance both in transient response and robustness. PMID:23076069

  17. 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

  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. PMID:27036807

  19. 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.

  20. 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

  1. Asynchronous FPGA risks

    NASA Technical Reports Server (NTRS)

    Erickson, K.

    2000-01-01

    The worst case timing margin of a synchronous design implemented with a field-programmable gate array (FPGA) is easy to perform using available FPGA design tools. However, it may be difficult to impossible to verify that worst case timing requirements are met for complex asynchronous logic design.

  2. Motor Behavior: From Telegraph Keys and Twins to Linear Slides and Stepping

    ERIC Educational Resources Information Center

    Thomas, Jerry R.

    2006-01-01

    Motor behavior is a significant area of scholarship with 64 Fellows from the American Academy of Kinesiology and Physical Education engaged in that work since 1930. This paper provides a brief overview of the history of research in motor development and motor control/learning, particularly noting the contributions to scholarship of Academy…

  3. A study on the integration of contactless energy transfer in the end teeth of a PM synchronous linear motor

    NASA Astrophysics Data System (ADS)

    Krop, D. C. J.; Lomonova, E. A.; Jansen, J. W.; Paulides, J. J. H.

    2009-04-01

    Linear motors find their utilization in an increasing number of industrial applications. Permanent magnet linear synchronous motors (PMLSMs) are favorable in many applications due to their servo characteristics, robustness, and high force density. The major disadvantage of moving coil type PMLSMs is the cable slab that energizes the coils from the fixed world to the moving parts of the machine. These cable slabs introduce extra wear and dynamical distortions. Moreover, in precision application the cable slab is supported by additional linear drives. These disadvantages can be eliminated if the coils could be powered wirelessly. In this paper two topologies are proposed that are capable of transferring 1 kW of power at most. The transformer part of the CET is characterized by means of two dimensional finite element analysis, and the influence of using additional capacitors to boost the output power is examined. Furthermore, an analysis of the core losses is conducted. Conclusions are drawn from the results.

  4. Thrust and normal force characteristics analysis of linear synchronous motor for direct drive conveyer

    NASA Astrophysics Data System (ADS)

    Zhu, Yu-wu; Kim, Do-sun; Cho, Yun-hyun

    2007-12-01

    The problem in improving the high positioning precision of permanent magnet linear synchronous motor (PMLSM) for direct drive conveyer is the large detent force, which contains two components: one is the cogging force caused by the interaction between the permanent magnet (PM) and the iron core, the other is the end effect caused by the finite mover length. In this paper a force compensator in the field oriented control (FOC) algorithm is employed to reduce this detent force, so the thrust and the normal force characteristics analysis of PMLSM are of the most importance. First the characteristics of the thrust and the normal force are simulated by finite element method (FEM), and the relation of the thrust and the normal force to the q-axis current is analyzed. Then the components of detent force are defined by Fourier series using the curve fitting method, and compensated by injecting the instantaneous currents using the FOC method. Finally the dynamic characteristics of this PMLSM for direct drive conveyer are investigated, and the numerical results are reported to validate the effectiveness of this proposed method.

  5. Dual-Position-Controller Design for the Linear-Motor-Driven Motion System

    NASA Astrophysics Data System (ADS)

    Huang, Yuan-Yong; Horng, Rong-Hwang; Shih, Yi-Ti; Lee, An-Chen

    This work develops a dual-controller composed of a macroscopic controller (MAC) and a microscopic controller (MIC) for improving motion precision of a linear-motor-driven motion system. Based on the macroscopic model in which Coulomb friction model is considered, the MAC is designed. In the presliding region however, the MIC design is based on the lineralized microscopic model. Furthermore, a switching algorithm is developed for bumpless transfer in shifting control action between two controllers. Thus, when the table of motion stage moves to the desired position, the control action can be smoothly switched from the MAC to the MIC. The whole system with the proposed dual-controller has the advantage that it serves as a long stroke (coarse stage) and a short stroke (fine stage) to achieve high precision motion control. The experimental results reveal that it totally takes 2.59 seconds to reach the 1000μm target position with the accuracy of one BLU (basic length unit; sensor resolution), 20nm the result has over 29% improvement when compared with the result using single MAC. In addition, good nanometer-scale tracking performance with the accuracy of one BLU, 20nm, can be obtained by using the MIC.

  6. 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.

  7. 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.

  8. Design of Feedforward Controller to Reduce Force Ripple for Linear Motor using Halbach Magnet Array with T Shape Magnet

    NASA Astrophysics Data System (ADS)

    Kim, Moojong; Kim, Jinyoung; Lee, Moon G.

    Recently, in micro/nano fabrication equipments, linear motors are widely used as an actuator to position workpiece, machining tool and measurement head. To control them faster and more precise, the motor should have high actuating force and small force ripple. High actuating force enable us to more workpiece with high acceleration. Eventually, it may provide higher throughput. Force ripple gives detrimental effect on the precision and tracking performance of the equipments. In order to accomplish more precise motion, it is important to make lower the force ripple. Force ripple is categorized into cogging and mutual ripple. First is dependent on the shape of magnets and/or core. The second is not dependent on them but dependent on current commutation. In this work, coreless mover i.e. coil winding is applied to the linear motor to avoid the cogging ripple. Therefore, the mutual ripple is only considered to be minimized. Ideal Halbach magnet array has continuously varying magnetization. The THMA (Halbach magnet array with T shape magnets) is proposed to approximate the ideal one. The THMA can not produce ideal sinusoidal flux, therefore, the linear motor with THMA and sinusoidal commutation of current generates the mutual force ripple. In this paper, in order to compensate mutual force ripple by feedforward(FF) controller, we calculate the optimized commutation of input current. The ripple is lower than 1.17% of actuating force if the commutation current agree with the magnetic flux from THMA. The performance of feedforward(FF) controller is verified by experiment.

  9. 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.

  10. Design of a linear synchronous motor with high temperature superconductor materials in the armature and in the field excitation system

    NASA Astrophysics Data System (ADS)

    Pina, J. M.; Neves, M. V.; McCulloch, M. D.; Rodrigues, A. L.

    2006-06-01

    The high diamagnetism observed in high temperature superconducting (HTS) materials lead to applications involving levitation such as the linear synchronous motor (LSM). Certain features taken into account in conventional LSM design cannot be applied in the HTS case, due to these materials characteristics, such as BSCCO stiffness, when used as armature windings. Also other design features, e.g. slot skewing, which reduces the space harmonics of the air gap magnetic flux density, thus influencing motor performance, plays an important role in final cost. These and other aspects such as the thrust force or the effect of motor control through an inverter are examined in this paper, where the analytical and numerical methodologies involved in the design optimisation of a LSM demonstrator with premagnetised YBCO pellets in the field excitation system and BSCCO armature windings are described. Simulation results are also included.

  11. 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.

  12. 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.

  13. A new viewpoint of end effect of linear induction motor from secondary side in ladder type model

    SciTech Connect

    Fujii, N.; Harada, T.

    1999-09-01

    In Japan, the subway trains driven by linear induction motors (LIMs) have been used in metropolitans of Tokyo and Osaka. As a new viewpoint, the physical phenomenon of end effect in ladder type linear induction motor (LIM) is observed from secondary side by making use of the structural feature. The phenomena in the ladder type and the sheet type LIM are the same fundamentally. The analytical method for the study is the special two-dimensional electromagnetic analysis, in which the current in each conducting bar is determined considering with time harmonics of secondary current. A new factor t{sub p}/t{sub s} is proposed to present the degree of end effect, in where t{sub p} is the passing duration of primary core at a secondary point and t{sub s} the half-period of slip frequency. The factor will be useful for the design grasping the essential of end effect of LIM.

  14. 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. PMID:16235032

  15. 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…

  16. Asynchronous & Synchronous E-Learning

    ERIC Educational Resources Information Center

    Hrastinski, Stefan

    2008-01-01

    An ongoing debate addresses the usefulness of asynchronous versus synchronous e-learning. "Asynchronous e-learning," commonly facilitated by media such as e-mail and discussion boards, supports work relations among learners and with teachers, even when participants cannot be online at the same time. "Synchronous e-learning," commonly supported by…

  17. 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.

  18. A High Power Ultrasonic Linear Motor Using a Longitudinal and Bending Hybrid Bolt-Clamped Langevin Type Transducer

    NASA Astrophysics Data System (ADS)

    Yun, Cheol-Ho; Ishii, Takaaki; Nakamura, Kentaro; Ueha, Sadayuki; Akashi, Koji

    2001-05-01

    A hybrid transducer type ultrasonic linear motor using the 1st longitudinal and the 2nd bending vibration modes of a bolt-clamped Langevin type transducer has been proposed and studied for accomplishing high mechanical output. The longitudinal vibration generates the mechanical driving force and the bending vibration controls the frictional force. To obtain large vibration amplitude and large mechanical output, a method of tuning the longitudinal resonance frequency to the bending one was investigated using finite element simulations, and demonstrated experimentally. To avoid magnetic interaction, we employed phosphor bronze for the bolt of the transducer. The prototype motor achieved the no-load velocity of 0.47 m/s and the maximum output mechanical force of 92 N.

  19. 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.

  20. 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). PMID:17186925

  1. Asynchronous interactive control systems

    NASA Technical Reports Server (NTRS)

    Vuskovic, M. I.; Heer, E.

    1980-01-01

    A class of interactive control systems is derived by generalizing interactive manipulator control systems. The general structural properties of such systems are discussed and an appropriate general software implementation is proposed. This is based on the fact that tasks of interactive control systems can be represented as a network of a finite set of actions which have specific operational characteristics and specific resource requirements, and which are of limited duration. This has enabled the decomposition of the overall control algorithm into a set of subalgorithms, called subcontrollers, which can operate simultaneously and asynchronously. Coordinate transformations of sensor feedback data and actuator set-points have enabled the further simplification of the subcontrollers and have reduced their conflicting resource requirements. The modules of the decomposed control system are implemented as parallel processes with disjoint memory space communicating only by I/O. The synchronization mechanisms for dynamic resource allocation among subcontrollers and other synchronization mechanisms are also discussed in this paper. Such a software organization is suitable for the general form of multiprocessing using computer networks with distributed storage.

  2. Asynchronous parallel status comparator

    DOEpatents

    Arnold, Jeffrey W.; Hart, Mark M.

    1992-01-01

    Apparatus for matching asynchronously received signals and determining whether two or more out of a total number of possible signals match. The apparatus comprises, in one embodiment, an array of sensors positioned in discrete locations and in communication with one or more processors. The processors will receive signals if the sensors detect a change in the variable sensed from a nominal to a special condition and will transmit location information in the form of a digital data set to two or more receivers. The receivers collect, read, latch and acknowledge the data sets and forward them to decoders that produce an output signal for each data set received. The receivers also periodically reset the system following each scan of the sensor array. A comparator then determines if any two or more, as specified by the user, of the output signals corresponds to the same location. A sufficient number of matches produces a system output signal that activates a system to restore the array to its nominal condition.

  3. Comparisons between designs for single-sided linear electric motors: Homopolar synchronous and induction

    NASA Astrophysics Data System (ADS)

    Nondahl, T. A.; Richter, E.

    1980-09-01

    A design study of two types of single sided (with a passive rail) linear electric machine designs, namely homopolar linear synchronous machines (LSM's) and linear induction machines (LIM's), is described. It is assumed the machines provide tractive effort for several types of light rail vehicles and locomotives. These vehicles are wheel supported and require tractive powers ranging from 200 kW to 3735 kW and top speeds ranging from 112 km/hr to 400 km/hr. All designs are made according to specified magnetic and thermal criteria. The LSM advantages are a higher power factor, much greater restoring forces for track misalignments, and less track heating. The LIM advantages are no need to synchronize the excitation frequency precisely to vehicle speed, simpler machine construction, and a more easily anchored track structure. The relative weights of the two machine types vary with excitation frequency and speed; low frequencies and low speeds favor the LSM.

  4. 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.

  5. Propulsion and guidance simulation of HTS bulk linear synchronous motor taking into account /E-J characteristic

    NASA Astrophysics Data System (ADS)

    Yoshida, K.; Matsumoto, H.

    2003-10-01

    We have proposed a new linear synchronous motor (LSM) theory which is based on an idea of considering the pinning force as synchronizing one in using current-carrying-armature-winding instead of permanent magnets. We have carried out basic experiments on two-dimensional electromagnetic forces produced in HTS bulk within DC-magnetic-field. As a result, we found that HTS bulk magnet in a cooling case can be levitated and guided stably according to the flux conditions between bulk and DC magnet. HTS bulk LSM can produce propulsion, levitation and guidance forces from zero speed, and be used in many applications. This paper proposes HTS bulk LSM analyzed and designed taking into account E- J characteristic. The LSM can produce stable guidance force without control. The LSM propulsion and guidance motion can be simulated numerically only by a simple propulsion control, which is not only closed-loop control but also open-loop control.

  6. A single-sided linear synchronous motor with a high temperature superconducting coil as the excitation system

    NASA Astrophysics Data System (ADS)

    Yen, F.; Li, J.; Zheng, S. J.; Liu, L.; Ma, G. T.; Wang, J. S.; Wang, S. Y.; Liu, Wei

    2010-10-01

    Thrust measurements were performed on a coil made of a YBa2Cu3O7 - δ coated conductor acting as the excitation system of a single-sided linear synchronous motor. The superconducting coil was a single pancake in the shape of a racetrack with 100 turns, the width and effective lengths were 42 mm and 84 mm, respectively. The stator was made of conventional copper wire. At 77 K and a gap of 10 mm, with an operating direct current of IDC = 30 A for the superconducting coil and alternating current of IAC = 9 A for the stator coils, a thrust of 24 N was achieved. With addition of an iron core, thrust was increased by 49%. With addition of an iron back-plate, thrust was increased by 70%.

  7. Linear and nonlinear auditory response properties of interneurons in a high-order avian vocal motor nucleus during wakefulness

    PubMed Central

    Raksin, Jonathan N.; Glaze, Christopher M.; Smith, Sarah

    2012-01-01

    Motor-related forebrain areas in higher vertebrates also show responses to passively presented sensory stimuli. However, sensory tuning properties in these areas, especially during wakefulness, and their relation to perception, are poorly understood. In the avian song system, HVC (proper name) is a vocal-motor structure with auditory responses well defined under anesthesia but poorly characterized during wakefulness. We used a large set of stimuli including the bird's own song (BOS) and many conspecific songs (CON) to characterize auditory tuning properties in putative interneurons (HVCIN) during wakefulness. Our findings suggest that HVC contains a diversity of responses that vary in overall excitability to auditory stimuli, as well as bias in spike rate increases to BOS over CON. We used statistical tests to classify cells in order to further probe auditory responses, yielding one-third of neurons that were either unresponsive or suppressed and two-thirds with excitatory responses to one or more stimuli. A subset of excitatory neurons were tuned exclusively to BOS and showed very low linearity as measured by spectrotemporal receptive field analysis (STRF). The remaining excitatory neurons responded well to CON stimuli, although many cells still expressed a bias toward BOS. These findings suggest the concurrent presence of a nonlinear and a linear component to responses in HVC, even within the same neuron. These characteristics are consistent with perceptual deficits in distinguishing BOS from CON stimuli following lesions of HVC and other song nuclei and suggest mirror neuronlike qualities in which “self” (here BOS) is used as a referent to judge “other” (here CON). PMID:22205651

  8. 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.

  9. Motor variability in sports: a non-linear analysis of race walking.

    PubMed

    Preatoni, Ezio; Ferrario, Manuela; Donà, Giulia; Hamill, Joseph; Rodano, Renato

    2010-10-01

    This aim of this study was to analyse the nature of movement variability and to assess whether entropy measures may represent a valuable synthetic index of neuromuscular organization. The regularity of kinematic/kinetic time series during race walking, the changes in the structure of intra-individual variability over the test session, and the influence of athletic skill in (inter)national rank athletes were investigated. Motion analysis techniques were used. Sample entropy (SampEn) was adopted to examine fluctuations in lower limb angles and ground reaction forces. The regularity of both original and surrogate time series was assessed and compared, by estimating SampEn, to verify the presence of non-linear features in movement variability. SampEn was statistically lower in the original data than in surrogates. In contrast, the regularity of time series did not change significantly throughout the subsequent intra-individual repetitions. Hip and ankle joint angles and vertical ground reaction force manifested increased entropy for skilled athletes. Results suggest that race walking variability was not only the product of random noise but also contained information about the inherent propriety of the neuro-musculo-skeletal system. Furthermore, they provide some indications about neuromuscular control of the lower limb joints during race walking gait, and about the differences between more and less skilled individuals. PMID:20853204

  10. Student Satisfaction with Asynchronous Learning

    ERIC Educational Resources Information Center

    Dziuban, Charles; Moskal, Patsy; Brophy, Jay; Shea, Peter

    2007-01-01

    The authors discuss elements that potentially impact student satisfaction with asynchronous learning: the media culture, digital, personal and mobile technologies, student learning preferences, pedagogy, complexities of measurement, and the digital generation. They describe a pilot study to identify the underlying dimensions of student…

  11. Creating Asynchronous Online Learning Communities

    ERIC Educational Resources Information Center

    Kerr, Crystal

    2009-01-01

    This research project examined how to develop and sustain online, asynchronous learning communities in continuous intake, distance education environments for learners in grades 7 through 10. The study is an action research project that is based upon in-depth, qualitative data. Interviews were conducted with distance education teachers,…

  12. 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…

  13. Current Control Method to Achieve Wide-Range Power Driving for Linear Synchronous Motor with Half-Wave-Rectified Self-Excitation

    NASA Astrophysics Data System (ADS)

    Hirayama, Tadashi; Higuchi, Tsuyoshi

    In a previous paper, we proposed a novel linear synchronous motor with half-wave-rectified self-excitation. The long-stator-type linear synchronous motor was built, and its performance was verified by performing experiments. This paper presents a new current control method for the linear synchronous motor for achieving a wide range of speeds and high-power operations. First, we propose the current control method for high-thrust operation in the constant-thrust region. This operation is realized by using a reluctance thrust resulting from the saliency of the linear synchronous motor. Furthermore, we propose a control method that maximizes the ratio of the thrust to the voltage; this method can be used to expand the operating range. Wide-range-speed operation can be achieved by applying this new control method along with field-weakening control. The thrust and operation characteristics of the proposed control methods are estimated by performing experiments and an electric and magnetic coupled analysis.

  14. Estimation of Locomotion States of a Rat by Neural Signals from the Motor Cortices Based on a Linear Correlation Model

    NASA Astrophysics Data System (ADS)

    Fukayama, Osamu; Taniguchi, Noriyuki; Suzuki, Takafumi; Mabuchi, Kunihiko

    We are developing a brain-machine interface (BMI) called “RatCar," a small vehicle controlled by the neural signals of a rat's brain. An unconfined adult rat with a set of bundled neural electrodes in the brain rides on the vehicle. Each bundle consists of four tungsten wires isolated with parylene polymer. These bundles were implanted in the primary motor and premotor cortices in both hemispheres of the brain. In this paper, methods and results for estimating locomotion speed and directional changes are described. Neural signals were recorded as the rat moved in a straight line and as it changed direction in a curve. Spike-like waveforms were then detected and classified into several clusters to calculate a firing rate for each neuron. The actual locomotion velocity and directional changes of the rat were recorded concurrently. Finally, the locomotion states were correlated with the neural firing rates using a simple linear model. As a result, the abstract estimation of the locomotion velocity and directional changes were achieved.

  15. 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.

  16. Developing asynchronous online interprofessional education.

    PubMed

    Sanborn, Heidi

    2016-09-01

    For many health programmes, developing interprofessional education (IPE) has been a challenge. Evidence on the best method for design and implementation of IPE has been slow to emerge, with little research on how to best incorporate IPE in the asynchronous online learning environment. This leaves online programmes with no clear guidance when embarking upon an initiative to integrate IPE into the curriculum. One tool that can be effective at guiding the incorporation of IPE across all learning platforms is the Interprofessional Education Collaborative (IPEC) competencies. A project was designed to integrate the nationally defined IPEC competencies throughout an asynchronous, online baccalaureate nursing completion programme. A programme-wide review led to targeted revision of course and unit-level objectives, learning experiences, and assessments based on the IPEC framework. As a result of this effort, the programme curriculum now provides interprofessional learning activities across all courses. This report provides a method for using the IPEC competencies to incorporate IPE within various asynchronous learning assessments, assuring students learn about, with, and from other professions. PMID:27310063

  17. Partition algebraic design of asynchronous sequential circuits

    NASA Technical Reports Server (NTRS)

    Maki, Gary K.; Chen, Kristen Q.; Gopalakrishnan, Suresh K.

    1993-01-01

    Tracey's Theorem has long been recognized as essential in generating state assignments for asynchronous sequential circuits. This paper shows that partitioning variables derived from Tracey's Theorem also has a significant impact in generating the design equations. Moreover, this theorem is important to the fundamental understanding of asynchronous sequential operation. The results of this work simplify asynchronous logic design. Moreover, detection of safe circuits is made easier.

  18. Practical parameter estimation through space harmonic method and experiment of permanent magnet linear synchronous motor for high accuracy field orient control

    NASA Astrophysics Data System (ADS)

    Jang, Seok-Myeong; You, Dae-Joon; Jang, Won-Bum; Park, Ji-Hoon

    2005-05-01

    This paper presents the practical parameter estimation for a slotless air-cored permanent magnet linear synchronous motor (PMLSM) using an analytical method and experiment. In the analytical method, the linkage flux is calculated through the generalized magnetic vector potential obtained by the space harmonics and transfer relation with each region of permanent magnet (PM) mover, air gap, and winding stator. This linkage flux is used to estimate the dynamic parameters such as magnetization inductance, backemf, and thrust constant. Also, the resistance and self-inductance with one phase are obtained by the experiment. Therefore, dynamic simulation of a linear synchronous motor composed of dynamic parameters is performed by the nonrotating (d-q) voltage equation. In good agreement with the estimated parameter values, the experimental results confirm the validity of the analysis method and simulation.

  19. Dynamic two-axis model of a linear synchronous reluctance motor based on current and position-dependent characteristics of flux linkages

    NASA Astrophysics Data System (ADS)

    Štumberger, Gorazd; Štumberger, Bojan; Dolinar, Drago

    2006-09-01

    This paper analyses the impact of armature slotting and magnetically nonlinear and anisotropic iron core on the trajectories of a kinematically controlled linear synchronous reluctance motor (LSRM). A new magnetically nonlinear dynamic two-axis LSRM model is introduced in order to perform the analysis. The magnetic nonlinearities and slotting effects are accounted for by the current and position-dependent characteristics of flux linkages.

  20. Asynchronous Discussions and Assessment in Online Learning

    ERIC Educational Resources Information Center

    Vonderwell, Selma; Liang, Xin; Alderman, Kay

    2007-01-01

    This case study explored asynchronous online discussions, assessment processes, and the meaning students derived from their experiences in five online graduate courses at the Colleges of Education of two Midwestern higher education institutions. The findings suggest that asynchronous online discussions facilitate a multidimensional process of…

  1. Improved self arbitrated VLSI asynchronous circuits

    NASA Technical Reports Server (NTRS)

    Winterrowd, P.

    1991-01-01

    This paper introduces an improved method for designing the class of CMOS VLSI asynchronous sequential circuits introduced in the paper by Sterling R. Whitaker and Gary K. Maki, 'Self Arbitrated VLSI Asynchronous Circuits.' Of main interest here is the simple design by inspection rules that arise from these circuits. This paper presents a variation on these circuits which reduces the number of transistors required.

  2. 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…

  3. 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…

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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. PMID:22208118

  9. Remote Asynchronous Message Service Gateway

    NASA Technical Reports Server (NTRS)

    Wang, Shin-Ywan; Burleigh, Scott C.

    2011-01-01

    The Remote Asynchronous Message Service (RAMS) gateway is a special-purpose AMS application node that enables exchange of AMS messages between nodes residing in different AMS "continua," notionally in different geographical locations. JPL s implementation of RAMS gateway functionality is integrated with the ION (Interplanetary Overlay Network) implementation of the DTN (Delay-Tolerant Networking) bundle protocol, and with JPL s implementation of AMS itself. RAMS protocol data units are encapsulated in ION bundles and are forwarded to the neighboring RAMS gateways identified in the source gateway s AMS management information base. Each RAMS gateway has interfaces in two communication environments: the AMS message space it serves, and the RAMS network - the grid or tree of mutually aware RAMS gateways - that enables AMS messages produced in one message space to be forwarded to other message spaces of the same venture. Each gateway opens persistent, private RAMS network communication channels to the RAMS gateways of other message spaces for the same venture, in other continua. The interconnected RAMS gateways use these communication channels to forward message petition assertions and cancellations among themselves. Each RAMS gateway subscribes locally to all subjects that are of interest in any of the linked message spaces. On receiving its copy of a message on any of these subjects, the RAMS gateway node uses the RAMS network to forward the message to every other RAMS gateway whose message space contains at least one node that has subscribed to messages on that subject. On receiving a message via the RAMS network from some other RAMS gateway, the RAMS gateway node forwards the message to all subscribers in its own message space.

  10. 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

  11. Asynchronous vibration problem of centrifugal compressor

    NASA Technical Reports Server (NTRS)

    Fujikawa, T.; Ishiguro, N.; Ito, M.

    1980-01-01

    An unstable asynchronous vibration problem in a high pressure centrifugal compressor and the remedial actions against it are described. Asynchronous vibration of the compressor took place when the discharge pressure (Pd) was increased, after the rotor was already at full speed. The typical spectral data of the shaft vibration indicate that as the pressure Pd increases, pre-unstable vibration appears and becomes larger, and large unstable asynchronous vibration occurs suddenly (Pd = 5.49MPa). A computer program was used which calculated the logarithmic decrement and the damped natural frequency of the rotor bearing systems. The analysis of the log-decrement is concluded to be effective in preventing unstable vibration in both the design stage and remedial actions.

  12. Photon detection with parallel asynchronous processing

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    An approach to photon detection with a parallel asynchronous signal processor is described. The visible or IR photon-detection capability of the silicon p(+)-n-n(+) detectors and the parallel asynchronous processing are addressed separately. This approach would permit an independent analog processing channel to be dedicated to every pixel. A laminar architecture consisting of a stack of planar arrays of the devices would form a 2D array processor with a 2D array of inputs located directly behind a focal-plane detector array. A 2D image data stream would propagate in neuronlike asynchronous pulse-coded form through the laminar processor. Such systems can integrate image acquisition and image processing. Acquisition and processing would be performed concurrently as in natural vision systems. The possibility of multispectral image processing is addressed.

  13. 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

  14. Implications of Tracey's theorem to asynchronous sequential circuit design

    NASA Technical Reports Server (NTRS)

    Gopalakrishnan, S.; Kim, G.; Maki, G.

    1990-01-01

    Tracey's Theorem has long been recognized as essential in generating state assignments for asynchronous sequential circuits. This paper shows that Tracey's Theorem also has a significant impact in generating the design equations. Moreover, this theorem is important to the fundamental understanding of asynchronous sequential operation. The results of this work simplify asynchronous logic design. Moreover, detection of safe circuits is made easier.

  15. 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…

  16. Emergence of Asynchronous Local Clocks in Excitable Media

    PubMed Central

    Gerum, Richard Carl; Fabry, Ben; Metzner, Claus

    2015-01-01

    Excitable media such as the myocardium or the brain consist of arrays of coupled excitable elements, in which the local excitation of a single element can propagate to its neighbors in the form of a non-linear autowave. Since each element has to pass through a refractory period immediately after excitation, the frequency of autowaves is self-limiting. In this work, we consider the case where each element is spontaneously excited at a fixed average rate and thereby initiates a new autowave. Although these spontaneous self-excitation events are modelled as independent Poisson point processes with exponentially distributed waiting times, the travelling autowaves lead collectively to a non-exponential, unimodal waiting time distribution for the individual elements. With increasing system size, a global ‘clock’ period T emerges as the most probable waiting time for each element, which fluctuates around T with an increasingly small but non-zero variance. This apparent synchronization between asynchronous, temporally uncorrelated point processes differs from synchronization effects between perfect oscillators interacting in a phase-aligning manner. Finally, we demonstrate that asynchronous local clocks also emerge in non-homogeneous systems in which the rates of self-excitation are different for all individuals, suggesting that this novel mechanism can occur in a wide range of excitable media. PMID:26559528

  17. 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.

  18. Bowhead whale localization using asynchronous hydrophones in the Chukchi Sea.

    PubMed

    Warner, Graham A; Dosso, Stan E; Hannay, David E; Dettmer, Jan

    2016-07-01

    This paper estimates bowhead whale locations and uncertainties using non-linear Bayesian inversion of their modally-dispersed calls recorded on asynchronous recorders in the Chukchi Sea, Alaska. Bowhead calls were recorded on a cluster of 7 asynchronous ocean-bottom hydrophones that were separated by 0.5-9.2 km. A warping time-frequency analysis is used to extract relative mode arrival times as a function of frequency for nine frequency-modulated whale calls that dispersed in the shallow water environment. Each call was recorded on multiple hydrophones and the mode arrival times are inverted for: the whale location in the horizontal plane, source instantaneous frequency (IF), water sound-speed profile, seabed geoacoustic parameters, relative recorder clock drifts, and residual error standard deviations, all with estimated uncertainties. A simulation study shows that accurate prior environmental knowledge is not required for accurate localization as long as the inversion treats the environment as unknown. Joint inversion of multiple recorded calls is shown to substantially reduce uncertainties in location, source IF, and relative clock drift. Whale location uncertainties are estimated to be 30-160 m and relative clock drift uncertainties are 3-26 ms. PMID:27475129

  19. Asynchronous compressed beamformer for portable diagnostic ultrasound systems.

    PubMed

    Zhou, Jun; Hoyos, Sebastian; Sadler, Brian

    2014-11-01

    State-of-the-art portable ultrasound imaging systems employ a small transducer array and a low carrier frequency to fit stringent constraints on power and form factor, and this tends to compromise the ultrasound imaging quality. In this paper, we present a low-complexity low-power asynchronous compressed beamformer (ACB) for portable diagnostic ultrasound. The proposed ACB integrates asynchronous sampling and compressive sensing (CS), and is capable of reducing data conversion power and handling a large data volume at the mixed-signal interface. A high-rate continuoustime ternary encoding (CT-TE) scheme eliminates the need for interpolation filters and coordinate rotation digital computer (CORDIC) units typically used in a conventional architecture. A split-projection least squares (SPLS) signal reconstruction algorithm is applied that replaces high-cost nonlinear signal recovery with a series of low-complexity and independent linear problems. Experiments with measured ultrasound data demonstrate the proposed ACB architecture, and the SPLS reconstruction algorithm achieves 9-fold data compression compared with Nyquist sampling. PMID:25389158

  20. 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.

  1. 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…

  2. 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…

  3. 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…

  4. An Agent Architecture for Asynchronous Learning.

    ERIC Educational Resources Information Center

    Rochefort, Stephen

    Education delivery systems have evolved from content delivery mechanisms to collaborative environments. The next step in this evolution is to provide greater support for asynchronous learners, those that progress through course material with little or no support from the instructional team. The integration of Web technologies with artificial…

  5. Asynchronous Learning in Manufacturing: Review of Research.

    ERIC Educational Resources Information Center

    Bundy, Gail E.

    This research paper examines the potential for asynchronous learning networks as a viable training alternative for small and medium manufacturing businesses. This first phase of the project, conducted by the Colorado Community College and Occupational System and the National Association of Manufacturers reviews existing research with a specific…

  6. 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

  7. Blind CMA-Based Asynchronous Multiuser Detection Using Generalized Sidelobe Canceller with Decision Feedback

    NASA Astrophysics Data System (ADS)

    Chang, Ann-Chen; Jen, Chih-Wei

    This letter deals with blind multiuser detection based on the multi-channel linearly constrained constant modulus algorithm (MLCCMA) for asynchronous code division multiple access (CDMA) systems over frequency-selective Rayleigh fading channels. In conjunction with the decision-feedback generalized sidelobe canceller (DFGSC), we present an efficient approach to combat multiple access interference and intersymbol interference. Computer simulations confirm that the proposed MLCCMA-based DFGSC can significantly speed up convergence and improve the output performance.

  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. Asynchronous file transfer to IBM PC's

    NASA Technical Reports Server (NTRS)

    Hoerger, J.

    1984-01-01

    The Asynchronous File Transfer System is used for interactively selecting and tramsmitting text files from the Langley Research Center's Business Data Systems Division (BDSD) host processor to an IBM Personal Computer. The IBM asynchronous communications support package is used for handling the communications on the personal computer. An application program (NATURAL, COBOL, etc.) is used for selecting and formatting the records to be transmitted, and three subroutine modules residing on the BDSD host processor are used for interfacing the application program and the communications software. Each record transmitted to the Personal Computer must be in the standard ASCII format. This record format is directly accessible by BASIC and many of the personal computer software packages provide utility programs for converting them to the format required for the particular package in question.

  10. 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.

  11. 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

  12. Enabling techniques for asynchronous coherent OCDMA

    NASA Astrophysics Data System (ADS)

    Wang, Xu; Wada, Naoya; Kitayama, Ken-ichi

    2005-11-01

    The coherent OCDMA system could suffer from severe multiple access interference (MAI) and beat noise, which limit the maximum number of active users that can be supported in a network. One effective method to reduce the beat noise as well as the MAI noise is to lower the interference level by adopting ultra-long optical code. Applying optical thresholding technique is also crucial to enable data-rate detection for achieving a practical OCDMA system. In this paper, we review the recent progress in the key enabling techniques for asynchronous coherent OCDMA: the novel encoder/decoders including spatial lightwave phase modulator, micro-ring resonator for spectral phase coding and superstructured FBG (SSFBG) and AWG type encode/decoder for time-spreading coding; optical thresholding techniques with PPLN and nonlinearity in fiber. The FEC has also been applied in OCDMA system recently. With 511-chip SSFBG and SC-based optical thresholder, 10-user, truly-asynchronous gigabit OCDMA transmission has been successfully achieved. Most recently, a record throughput 12×10.71 Gbps truly-asynchronous OCDMA has been demonstrated by using the 16×16 ports AWG-type encoder/decoder and FEC transmit ITU-T G.709 OTN frames.

  13. 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.

  14. 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.

  15. Identifying scale-emergent, nonlinear, asynchronous processes of wetland methane exchange

    NASA Astrophysics Data System (ADS)

    Sturtevant, Cove; Ruddell, Benjamin L.; Knox, Sara Helen; Verfaillie, Joseph; Matthes, Jaclyn Hatala; Oikawa, Patricia Y.; Baldocchi, Dennis

    2016-01-01

    Methane (CH4) exchange in wetlands is complex, involving nonlinear asynchronous processes across diverse time scales. These processes and time scales are poorly characterized at the whole-ecosystem level, yet are crucial for accurate representation of CH4 exchange in process models. We used a combination of wavelet analysis and information theory to analyze interactions between whole-ecosystem CH4 flux and biophysical drivers in two restored wetlands of Northern California from hourly to seasonal time scales, explicitly questioning assumptions of linear, synchronous, single-scale analysis. Although seasonal variability in CH4 exchange was dominantly and synchronously controlled by soil temperature, water table fluctuations, and plant activity were important synchronous and asynchronous controls at shorter time scales that propagated to the seasonal scale. Intermittent, subsurface water table decline promoted short-term pulses of methane emission but ultimately decreased seasonal CH4 emission through subsequent inhibition after rewetting. Methane efflux also shared information with evapotranspiration from hourly to multiday scales and the strength and timing of hourly and diel interactions suggested the strong importance of internal gas transport in regulating short-term emission. Traditional linear correlation analysis was generally capable of capturing the major diel and seasonal relationships, but mesoscale, asynchronous interactions and nonlinear, cross-scale effects were unresolved yet important for a deeper understanding of methane flux dynamics. We encourage wider use of these methods to aid interpretation and modeling of long-term continuous measurements of trace gas and energy exchange.

  16. 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…

  17. Pass-transistor asynchronous sequential circuits

    NASA Astrophysics Data System (ADS)

    Whitaker, Sterling R.; Maki, Gary K.

    1989-02-01

    Design methods for asynchronous sequential pass-transistor circuits, which result in circuits that are hazard- and critical-race-free and which have added degrees of freedom for the input signals, are discussed. The design procedures are straightforward and easy to implement. Two single-transition-time state assignment methods are presented, and hardware bounds for each are established. A surprising result is that the hardware realizations for each next state variable and output variable is identical for a given flow table. Thus, a state machine with N states and M outputs can be constructed using a single layout replicated N + M times.

  18. 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.

  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. 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.

  1. 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.

  2. 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.

  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. 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…

  5. 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…

  6. Interactional Coherence in Asynchronous Learning Networks: A Rhetorical Approach

    ERIC Educational Resources Information Center

    Potter, Andrew

    2008-01-01

    Numerous studies have affirmed the value of asynchronous online communication as a learning resource. Several investigations, however, have indicated that discussions in asynchronous environments are often neither interactive nor coherent. The research reported sought to develop an enhanced understanding of interactional coherence, argumentation,…

  7. Teaching Presence and Communication Timeliness in Asynchronous Online Courses

    ERIC Educational Resources Information Center

    Skramstad, Erik; Schlosser, Charles; Orellana, Anymir

    2012-01-01

    This study examined student perceptions of teaching presence and communication timeliness in asynchronous online courses. Garrison, Anderson, and Archer's (2000) community of inquiry model provided the framework for the survey research methodology used. Participants were 59 student volunteers taking 1 or more asynchronous online graduate courses.…

  8. 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…

  9. A Phenomenological Synapse Model for Asynchronous Neurotransmitter Release

    PubMed Central

    Wang, Tao; Yin, Luping; Zou, Xiaolong; Shu, Yousheng; Rasch, Malte J.; Wu, Si

    2016-01-01

    Neurons communicate with each other via synapses. Action potentials cause release of neurotransmitters at the axon terminal. Typically, this neurotransmitter release is tightly time-locked to the arrival of an action potential and is thus called synchronous release. However, neurotransmitter release is stochastic and the rate of release of small quanta of neurotransmitters can be considerably elevated even long after the ceasing of spiking activity, leading to asynchronous release of neurotransmitters. Such asynchronous release varies for tissue and neuron types and has been shown recently to be pronounced in fast-spiking neurons. Notably, it was found that asynchronous release is enhanced in human epileptic tissue implicating a possibly important role in generating abnormal neural activity. Current neural network models for simulating and studying neural activity virtually only consider synchronous release and ignore asynchronous transmitter release. Here, we develop a phenomenological model for asynchronous neurotransmitter release, which, on one hand, captures the fundamental features of the asynchronous release process, and, on the other hand, is simple enough to be incorporated in large-size network simulations. Our proposed model is based on the well-known equations for short-term dynamical synaptic interactions and includes an additional stochastic term for modeling asynchronous release. We use experimental data obtained from inhibitory fast-spiking synapses of human epileptic tissue to fit the model parameters, and demonstrate that our model reproduces the characteristics of realistic asynchronous transmitter release. PMID:26834617

  10. 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…

  11. 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…

  12. Purifying Cytokinetic Cells from an Asynchronous Population

    PubMed Central

    Panet, Einat; Ozer, Efrat; Mashriki, Tal; Lazar, Itay; Itzkovich, Devora; Tzur, Amit

    2015-01-01

    Cytokinesis is an intensively studied process by which the cell cytoplasm divides to produce two daughter cells. Like any other aspect of cell cycle research, the study of cytokinesis relies heavily on cell synchronization. However, the synchronization of cells during cytokinesis is challenging due to the rapid nature of this process and the shortage of cell cycle blocking agents specifically targeting this phase. Here, we demonstrate the use of standard flow cytometry for directly isolating cytokinetic cells from an asynchronous population of normally proliferating cells. This approach is based on a cell cycle marker whose temporal proteolysis, in combination with DNA quantification or cell size approximation, distinguishes cells undergoing cytokinesis. Furthermore, by avoiding doublet discrimination, typically used in flow cytometry analyses, we were able to further increase selectivity, specifically purifying cells at late cytokinesis. Our method circumvents checkpoint activation, cell cycle arrest, and any other means of pre-synchronization. These qualities, as demonstrated for both unattached and adherent cells, enable high selectivity for cytokinetic cells despite their overall low abundance in an asynchronous population. The sorted cells can then be readily used for cell biological, biochemical, and genomic applications to facilitate cytokinesis and cell cycle research. PMID:26260981

  13. Asynchronicity of Facial Blood Perfusion in Migraine

    PubMed Central

    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

  14. Commande optimale à flux libre des machines asynchrones

    NASA Astrophysics Data System (ADS)

    Biedinger, J. M.; Poullain, S.; Yvon, J. P.

    1992-01-01

    The subject of this paper is the optimal control with unconstrained flux of an induction motor being considered as a distributed parameter system described by a nonlinear diffusion equation. This approach allows to describe the electrodynamic state of the motor by taking into account, in a natural way, the influence of saturation and eddy-currents, as well as the nonlinearities due to the variable flux operation. Equations are approximated via a finite element formulation which leads to a finite dimensional dynamical system to which the techniques of optimal control may be applied. The generality of the methodology allows to treat various criteria. The objective aimed in this paper is to force the motor torque to follow a given input, especially under initially demagnetized conditions and with, naturally, constraints on the currents. For this purpose the criterion will be chosen as a norm of the difference between the electromagnetic torque and a given reference torque. Numerical simulations are presented for the case of a squirrel-cage rotor and for a solid iron rotor. Results are compared with those deduced from strategies based on lumped-parameter models. Torque responses obtained with field-oriented control method adapted to the case of flux-variable operation are also presented. Finally a modification of the criterion is proposed for identifying the command which allows to obtain the larger torque during transient states. Dans cet article on traite le problème du contrôle optimal à flux libre d'un moteur asynchrone considéré comme un système à paramètres répartis gouverné par une équation de diffusion non linéaire. Cette approche permet de décrire l'état électrodynamique de la machine en prenant naturellement en compte les effets de la saturation et des courants induits, ainsi que les non-linéarités liées au fonctionnement à flux variable. La formulation éléments finis est utilisée pour traduire le problème continu sous la forme d

  15. Control discrete-time switched singular systems with state delays under asynchronous switching

    NASA Astrophysics Data System (ADS)

    Lin, Jinxing; Fei, Shumin; Gao, Zhifeng

    2013-06-01

    This article is concerned with the problem of state feedback control for a class of discrete-time switched singular systems with time-varying state delays under asynchronous switching. The asynchronous switching considered here means that the switching instants of the candidate controllers lag behind those of the system modes. The concept of mismatched control rate is introduced. By using the multiple Lyapunov function approach and the average dwell time technique, a sufficient condition for the existence a stabilising switching law is first derived to guarantee the regularity, causality and exponential stability of the closed-loop system in the presence of asynchronous switching. The stabilising switching law is characterised by a upper bound on the mismatched control rate and a lower bound on the average dwell time. Then, the corresponding solvability condition for a set of mode-dependent state feedback controllers is established by using the linear matrix inequality (LMI) technique. Finally, a numerical example is provided to illustrate the effectiveness of the proposed method.

  16. Design of a reluctance motor with increased efficiency and power factor for widespread industrial application

    NASA Astrophysics Data System (ADS)

    Hansen-Goos, P.; Pieper, W.

    1981-09-01

    The motors were designed in the range of 0.6-4 kW with 4-pole windings. An increase of nominal power by approximately 100%, and an increase of quality factor by approximately 50% are reported. The efficiency is equal to asynchronous motors of the same IEC size.

  17. Faulty behavior of asynchronous storage elements

    NASA Technical Reports Server (NTRS)

    Al-Assadi, Waleed K.; Lu, Ding; Jayasumana, Anura P.; Malaiya, Yashwant K.; Tong, Carol Q.

    1993-01-01

    It is often assumed that the faults in storage elements (SE's) can be modeled as output/input stuck-at-faults of the element. They are implicitly considered equivalent to the stuck-at faults in the combinational logic surrounding the SE cells. A more accurate higher level fault model for elementary SE's used in asynchronous circuits is presented. This model offers better representation of the physical failures. It is shown that the stuck-at model may be adequate if only modest fault coverage is desired. The enhanced model includes some common fault behaviors of SE's that are not covered by the stuck-at model. These include data-feed-through behaviors that cause the SE to be combinational. Fault models for complex SE cells can be obtained without a significant loss of information about the structure of the circuit.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. Stand-Alone and Hybrid Positioning Using Asynchronous Pseudolites

    PubMed Central

    Gioia, Ciro; Borio, Daniele

    2015-01-01

    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. PMID:25609041

  3. 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.

  4. A Comparison of Distance Education Competencies Delivered Synchronously and Asynchronously.

    ERIC Educational Resources Information Center

    Dooley, Kim E.; Lindner, James R.; Richards, Lance J.

    2003-01-01

    Comparison of agriculture courses delivered synchronously via interactive television (20 students) and asynchronously via the Web (22 students) showed similar achievement of core distance education competencies: adult learning, technology knowledge, instructional design, communication skills, graphic design, administration) regardless of delivery…

  5. 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.

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

    PubMed

    Gioia, Ciro; Borio, Daniele

    2015-01-01

    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. PMID:25609041

  7. Asynchronous Communication of TLNS3DMB Boundary Exchange

    NASA Technical Reports Server (NTRS)

    Hammond, Dana P.

    1997-01-01

    This paper describes the recognition of implicit serialization due to coarse-grain, synchronous communication and demonstrates the conversion to asynchronous communication for the exchange of boundary condition information in the Thin-Layer Navier Stokes 3-Dimensional Multi Block (TLNS3DMB) code. The implementation details of using asynchronous communication is provided including buffer allocation, message identification, and barrier control. The IBM SP2 was used for the tests presented.

  8. 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.

  9. Asynchronous blepharospasm, facial and cervical dystonia, and bilateral asynchronous hemifacial spasm.

    PubMed

    Katz, Bradley J; Burroughs, John R; Anderson, Richard L; Bownds, Shannon; McCann, John D

    2007-01-15

    We present a patient with a facial movement disorder that has characteristics of both blepharospasm and bilateral asynchronous hemifacial spasm. Because of the increased incidence of blepharospasm in patients with hemifacial spasm, our patient's clinical presentation is probably not a chance occurrence, but rather a manifestation of some predisposition for these two movement disorders. This unusual constellation of signs and symptoms challenges the current diagnostic criteria and suggests that some of these facial movement disorders may lie on a spectrum, rather than represent distinct entities. PMID:17133455

  10. Asynchronous electrical activity in epileptic seizures

    NASA Astrophysics Data System (ADS)

    Holman, Katherine; Lim, Eugene; Gliske, Stephen; Stacey, William; Fink, Christian

    High-frequency oscillations (HFOs) have been postulated to be potential biomarkers for focal epileptic seizures, with fast ripples (>250 Hz) as the most interesting candidate. The mechanisms underlying the generation of fast ripples, however, are not well understood. In this study, we draw upon results from previous computational studies on HFOs to develop a new mathematical model from first principles describing the generation of HFOs through asynchronous neuronal firing. Asynchrony in the model is obtained with the introduction of two parameters of heterogeneity: variability in the inter-spike interval (ISI) and jitter. The model predicts the generation of harmonic narrow-band oscillations if the heterogeneity-governing parameters do not differ from the predefined ISI by more than 20%. Comparisons against results from a separately constructed computational model verify the accuracy of the model in study. These results provide us with a rigorous framework in which we may investigate the mechanisms driving the generation of abnormal HFOs, and may serve as groundwork for future research in epileptogenesis. Nsf Grant 1003992, Ohio Wesleyan University SSRP.

  11. Asynchronous origins of ectomycorrhizal clades of Agaricales

    PubMed Central

    Ryberg, Martin; Matheny, P. Brandon

    2012-01-01

    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. PMID:22171078

  12. 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

  13. 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. PMID:25716790

  14. 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

  15. 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

  16. 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. PMID:21385670

  17. Robot drive mechanism uses conventional electric motors

    NASA Astrophysics Data System (ADS)

    Demchenko, I.

    1986-02-01

    The development and use of three phase asynchronous electric motors in robot technology are presented. The mechanical arm of a robot has as many drives as it has joints. Manipulators in use in modern industry must have six to nine degrees of mobility, and experimental prototypes with 18 coordinates of movement are already developed. A simple, common, and inexpensive industrial electric motor is proposed for use in the robots. This motor was previously considered unsuitable for delicate work because of its low precision in executing commands and the difficulty in controlling it. Control methods were developed to overcome this difficulty. Integrated microcircuits and a power converter control the operation of the single motor. A cassette made up of six units controls the operation of the whole mechanical arm. This cassette is linked with the brain of the robot (a microprocessor system or microcomputer).

  18. 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.

  19. 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.

  20. 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

  1. Molecular mechanisms for synchronous, asynchronous, and spontaneous neurotransmitter release.

    PubMed

    Kaeser, Pascal S; Regehr, Wade G

    2014-01-01

    Most neuronal communication relies upon the synchronous release of neurotransmitters, which occurs through synaptic vesicle exocytosis triggered by action potential invasion of a presynaptic bouton. However, neurotransmitters are also released asynchronously with a longer, variable delay following an action potential or spontaneously in the absence of action potentials. A compelling body of research has identified roles and mechanisms for synchronous release, but asynchronous release and spontaneous release are less well understood. In this review, we analyze how the mechanisms of the three release modes overlap and what molecular pathways underlie asynchronous and spontaneous release. We conclude that the modes of release have key fusion processes in common but may differ in the source of and necessity for Ca(2+) to trigger release and in the identity of the Ca(2+) sensor for release. PMID:24274737

  2. Molecular Mechanisms for Synchronous, Asynchronous, and Spontaneous Neurotransmitter Release

    PubMed Central

    Kaeser, Pascal S.; Regehr, Wade G.

    2015-01-01

    Most neuronal communication relies upon the synchronous release of neurotransmitters, which occurs through synaptic vesicle exocytosis triggered by action potential invasion of a presynaptic bouton. However, neurotransmitters are also released asynchronously with a longer, variable delay following an action potential or spontaneously in the absence of action potentials. A compelling body of research has identified roles and mechanisms for synchronous release, but asynchronous release and spontaneous release are less well understood. In this review, we analyze how the mechanisms of the three release modes overlap and what molecular pathways underlie asynchronous and spontaneous release. We conclude that the modes of release have key fusion processes in common but may differ in the source of and necessity for Ca2+ to trigger release and in the identity of the Ca2+ sensor for release. PMID:24274737

  3. Extended Self Organised Criticality in Asynchronously Tuned Cellular Automata

    NASA Astrophysics Data System (ADS)

    Gunji, Yukio-Pegio

    2014-12-01

    Systems at a critical point in phase transitions can be regarded as being relevant to biological complex behaviour. Such a perspective can only result, in a mathematical consistent manner, from a recursive structure. We implement a recursive structure based on updating by asynchronously tuned elementary cellular automata (AT ECA), and show that a large class of elementary cellular automata (ECA) can reveal critical behavior due to the asynchronous updating and tuning.We show that the obtained criticality coincides with the criticality in phase transitions of asynchronous ECA with respect to density decay, and that multiple distributed ECAs, synchronously updated, can emulate critical behavior in AT ECA. Our approach draws on concepts and tools from category and set theory, in particular on "adjunction dualities" of pairs of adjoint functors.

  4. 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.

  5. Asynchronous event-based corner detection and matching.

    PubMed

    Clady, Xavier; Ieng, Sio-Hoi; Benosman, Ryad

    2015-06-01

    This paper introduces an event-based luminance-free method to detect and match corner events from the output of asynchronous event-based neuromorphic retinas. The method relies on the use of space-time properties of moving edges. Asynchronous event-based neuromorphic retinas are composed of autonomous pixels, each of them asynchronously generating "spiking" events that encode relative changes in pixels' illumination at high temporal resolutions. Corner events are defined as the spatiotemporal locations where the aperture problem can be solved using the intersection of several geometric constraints in events' spatiotemporal spaces. A regularization process provides the required constraints, i.e. the motion attributes of the edges with respect to their spatiotemporal locations using local geometric properties of visual events. Experimental results are presented on several real scenes showing the stability and robustness of the detection and matching. PMID:25828960

  6. 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

  7. Real-time two-dimensional asynchronous control of a computer cursor with a single subdural electrode

    PubMed Central

    Márquez-Chin, César; Popovic, Milos R.; Sanin, Egor; Chen, Robert; Lozano, Andres M.

    2012-01-01

    Objective To test the feasibility of controlling a computer cursor asynchronously in two dimensions using one subdural electrode. Design Proof of concept study. Setting Acute care hospital in Toronto, Canada. Participant A 68-year-old woman with a subdural electrode implanted for the treatment of essential tremor (ET) using direct brain stimulation of the primary motor cortex (MI). Interventions Power changes in the electrocorticography signals were used to implement a “brain switch”. To activate the switch the subject had to decrease the power in the 7–13 Hz frequency range using motor imagery of the left hand. The brain switch was connected to a system for asynchronous control of movement in two dimensions. Each time the user reduced the amplitude in the 7–13 Hz frequency band below an experimentally defined threshold the direction of cursor changed randomly. The new direction was always different from those previously rejected ensuring the convergence of the system on the desired direction. Outcome measures Training time, time and number of switch activations required to reach specific targets, information transfer rate. Results The user was able to control the cursor to specific targets on the screen after only 15 minutes of training. Each target was reached in 51.7 ± 40.2 seconds (mean ± SD) and after 9.4 ± 6.8 switch activations. Information transfer rate of the system was estimated to be 0.11 bit/second. Conclusion A novel brain–machine interface for asynchronous two-dimensional control using one subdural electrode was developed. PMID:23031175

  8. 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.

  9. Evaluation of attractors and basins of asynchronous random Boolean networks

    NASA Astrophysics Data System (ADS)

    Yang, Meng; Chu, Tianguang

    2012-05-01

    We present an algebraic approach for determining the attractors and their basins of random Boolean networks under an asynchronous stochastic update based on the recently developed matrix semitensor product theory, which allows for converting the logical dynamics of a Boolean network into a standard iterative dynamics. In this setting, all attractors and basins are specified by the network transition matrices. We then devise procedures that can find all attractors and their basins exactly. We also discuss the issue of overlapping basins in asynchronous random Boolean networks, and we propose methods to compute the weight of each attractor and the basin entropy of the systems.

  10. 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…

  11. 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

  12. Online image acquisition system for wheel set measurement based on asynchronous reset mode

    NASA Astrophysics Data System (ADS)

    Wu, Kaihua; Guo, Yu; Chen, Yixin

    2011-11-01

    The wearing degree of the wheel set is one of the main factors that influence the safety and stability of running train. Measurement of wheel set wear has significant importance to railway safety. An automatic measurement method for geometrical parameters of wheel set based on optoelectronic technique was proposed. In the method, linear structured laser light was projected on the wheel tread surface. The geometrical parameters can be deduced from the profile image. An online image acquisition system was designed based on asynchronous reset of CCD. The entire time sequence of asynchronous reset was designed. The image was acquired only when wheel moved into the designed position. Image acquisition was fulfilled by hardware interrupt mode. Quantitative relation between position accuracy and speed, timedelay error, CCD resolution and imaging region was deuced. Relation between moving blur and speed, exposure time was also decided. The measuring system was installed along the straight railway section. When the wheel set was running in a limited speed, the devices placed alone railway line can measure the geometrical parameters automatically. Position accuracy achieved 1.1mm when moving speed reached 2km/h and moving blur was limited in less than one pixel size while exposure time set to be 1/5550s. The image definition can meet the demand of real and online measurement.

  13. 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.

  14. 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…

  15. Fostering Knowledge Construction in University Students through Asynchronous Discussion Groups

    ERIC Educational Resources Information Center

    Schellens, Tammy; Valcke, Martin

    2006-01-01

    Does collaborative learning in asynchronous discussion groups result in enhancing academic discourse and knowledge construction? This general research question has been researched in a study involving 300 students, working during six months in 38 electronic discussion groups. The transcripts of the discussions were coded and analysed to test…

  16. Asynchronous Education: A Blueprint for the Future of Adult Learning.

    ERIC Educational Resources Information Center

    Krueger, Lyle L.; Porter, Cyndi Wilson; Burke, Daniel

    While the distance learning curriculum at Lakeland College (Wisconsin) began 20 years ago, the idea for Lakeland Online was conceived about two and one-half years ago. A variety of delivery modes were considered before discovering Convene software. Since the communication process enabled by the Convene software is asynchronous and requires only a…

  17. Content Analysis Coding Schemes for Online Asynchronous Discussion

    ERIC Educational Resources Information Center

    Weltzer-Ward, Lisa

    2011-01-01

    Purpose: Researchers commonly utilize coding-based analysis of classroom asynchronous discussion contributions as part of studies of online learning and instruction. However, this analysis is inconsistent from study to study with over 50 coding schemes and procedures applied in the last eight years. The aim of this article is to provide a basis…

  18. 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…

  19. 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…

  20. 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,…

  1. 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…

  2. 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…

  3. Psychological Type and Asynchronous Written Dialogue in Adult Learning

    ERIC Educational Resources Information Center

    Lin, Lin; Cranton, Patricia; Bridglall, Beatrice

    2005-01-01

    This study explores how adults learn from asynchronous written dialogue through the lens of psychological type preferences. We asked participants to discover their dominant and auxiliary psychological preferences using the Personal Empowerment through Type inventory. Participants then completed an open-ended survey in which they described their…

  4. Interaction in Asynchronous Discussion Forums: Peer Facilitation Techniques

    ERIC Educational Resources Information Center

    Ng, C. S. L.; Cheung, W. S.; Hew, K. F.

    2012-01-01

    Peer facilitation is proposed as a solution to counter limited interaction in asynchronous online discussions. However, there is a lack of empirical research on online peer facilitation. This study identifies, through cross-case comparison of two graduate-level blended courses attended by Asian Pacific students, the actual peer facilitation…

  5. 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…

  6. 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.

  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. 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…

  10. 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…

  11. 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…

  12. 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.

  13. 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…

  14. 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…

  15. 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…

  16. Promoting and Scaffolding Argumentation through Reflective Asynchronous Discussions

    ERIC Educational Resources Information Center

    Lin, Huann-shyang; Hong, Zuway-R.; Lawrenz, Frances

    2012-01-01

    The purpose of this quasi-experimental study was to explore the impact of asynchronous discussion on the quality and complexity of college students' arguments. Three different cohorts of students registered in a physical science course in 2009 Fall, 2010 Spring, and 2010 Fall semesters were briefly supported with scaffolding in class and then…

  17. 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

  18. 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.

  19. Asynchronous emergence by loggerhead turtle (Caretta caretta) hatchlings

    NASA Astrophysics Data System (ADS)

    Houghton, J. D. R.; Hays, G. C.

    2001-03-01

    For many decades it has been accepted that marine turtle hatchlings from the same nest generally emerge from the sand together. However, for loggerhead turtles (Caretta caretta) nesting on the Greek Island of Kefalonia, a more asynchronous pattern of emergence has been documented. By placing temperature loggers at the top and bottom of nests laid on Kefalonia during 1998, we examined whether this asynchronous emergence was related to the thermal conditions within nests. Pronounced thermal variation existed not only between, but also within, individual nests. These within-nest temperature differences were related to the patterns of hatchling emergence, with hatchlings from nests displaying large thermal ranges emerging over a longer time-scale than those characterised by more uniform temperatures.

  20. Asynchronous Cooperative e-Learning System and Its Evaluation

    NASA Astrophysics Data System (ADS)

    Eto, Kazuhiro; Miyoshi, Takumi

    Much attention has been attracted to collaborative learning on an e-learning system. However, it is difficult to implement the collaborative environment to an asynchronous e-learning system since collaboration would be realized only when learners join the system at the same time. On the other hand, cooperative learning has been proposed. In this method, learners can study on their own pace without making mutual agreement but with receiving cognitive information from others. In this paper, the authors have developed the asynchronous cooperative e-learning system that provides learners' attendance and studying progress as the cognitive information. The subjective evaluation experiments show that our system is slightly inferior to the synchronous collaborative e-learning system, but it can motivate the learners more than the conventional system.

  1. 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.

  2. 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.

  3. Asynchronous sequential circuit design using pass transistor iterative logic arrays

    NASA Technical Reports Server (NTRS)

    Liu, M. N.; Maki, G. K.; Whitaker, S. R.

    1991-01-01

    The iterative logic array (ILA) is introduced as a new architecture for asynchronous sequential circuits. This is the first ILA architecture for sequential circuits reported in the literature. The ILA architecture produces a very regular circuit structure. Moreover, it is immune to both 1-1 and 0-0 crossovers and is free of hazards. This paper also presents a new critical race free STT state assignment which produces a simple form of design equations that greatly simplifies the ILA realizations.

  4. 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.

  5. Motor Starters

    NASA Technical Reports Server (NTRS)

    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.

  6. Motor syndromes.

    PubMed

    Corea, Francesco; Micheli, Sara

    2012-01-01

    Motor disturbances alone or associated with other focal deficits are the most common symptoms suggesting a neurovascular event. An appropriate clinical assessment of these signs and symptoms may help physicians to better diagnose and to both better treat and predict outcome. In this paper the main clinical features of motor deficit are described together with other motor-related events such as ataxia and movement disturbances. PMID:22377850

  7. 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.

  8. Robust Read Channel System Directly Processing Asynchronous Sampling Data

    NASA Astrophysics Data System (ADS)

    Yamamoto, Akira; Mouri, Hiroki; Yamamoto, Takashi

    2006-02-01

    In this study, we describe a robust read channel employing a novel timing recovery system and a unique Viterbi detector which extracts channel timing and channel data directly from asynchronous sampling data. The timing recovery system in the proposed read channel has feed-forward architecture and consists entirely of digital circuits. Thus, it enables robust timing recovery at high-speed and has no performance deterioration caused by variations in analog circuits. The Viterbi detector not only detects maximum-likelihood data using a reference level generator, but also transforms asynchronous data into pseudosynchronous data using two clocks, such as an asynchronous clock generated by a frequency synthesizer and a pseudosynchronous clock generated by a timing detector. The proposed read channel has achieved a constant and fast frequency acquisition time against initial frequency error and has improved its bit error rate performance. This robust read channel system can be used for high-speed signal processing and LSIs using nanometer-scale semiconductor processes.

  9. Asynchronous Stoichiometric Response in Lithium Iron Phosphate Batteries

    SciTech Connect

    Paxton, William A.; Akdogan, E. Koray; Savkliyidiz, Ilyas; Choksi, Ankur U.; Silver, Scott X.; Tsakalokos, Thomas; Zhong, Zhong

    2014-11-11

    The operando energy-dispersive x-ray diffraction (EDXRD) was carried out on a newly formed 8 Ah lithium iron phosphate (LiFePO4) battery with the goal of elucidating the origin of asynchronous phase transformation commonly seen with in situ x-ray diffraction studies. The high-energy photons at the NSLS X17B1 beamline allow for penetration into a fully assembled battery and therefore negate any need for a specially designed in situ cell which often uses modified current collectors to minimize x-ray attenuation. Spatially-and-temporally resolved phase-mapping was conducted with a semiquantitative reference intensity ratio (RIR) analysis to estimate the relative abundance of the delithiated phase. The data show an asynchronous response in the stoichiometry versus the electrochemical profile and suggest limited diffusion in the electrode toward the end of discharge. These results confirm that the asynchronous electrode response is not just limited to specially designed cells but occurs in fully assembled cells alike. We attribute this behavior to be a consequence of performing a local measurement over a wide-area heterogeneous reaction.

  10. Data Collection for Mobile Group Consumption: An Asynchronous Distributed Approach.

    PubMed

    Zhu, Weiping; Chen, Weiran; Hu, Zhejie; Li, Zuoyou; Liang, Yue; Chen, Jiaojiao

    2016-01-01

    Mobile group consumption refers to consumption by a group of people, such as a couple, a family, colleagues and friends, based on mobile communications. It differs from consumption only involving individuals, because of the complex relations among group members. Existing data collection systems for mobile group consumption are centralized, which has the disadvantages of being a performance bottleneck, having single-point failure and increasing business and security risks. Moreover, these data collection systems are based on a synchronized clock, which is often unrealistic because of hardware constraints, privacy concerns or synchronization cost. In this paper, we propose the first asynchronous distributed approach to collecting data generated by mobile group consumption. We formally built a system model thereof based on asynchronous distributed communication. We then designed a simulation system for the model for which we propose a three-layer solution framework. After that, we describe how to detect the causality relation of two/three gathering events that happened in the system based on the collected data. Various definitions of causality relations based on asynchronous distributed communication are supported. Extensive simulation results show that the proposed approach is effective for data collection relating to mobile group consumption. PMID:27058544

  11. A Synchronous-Asynchronous Particle Swarm Optimisation Algorithm

    PubMed Central

    Ab Aziz, Nor Azlina; Mubin, Marizan; Mohamad, Mohd Saberi; Ab Aziz, Kamarulzaman

    2014-01-01

    In the original particle swarm optimisation (PSO) algorithm, the particles' velocities and positions are updated after the whole swarm performance is evaluated. This algorithm is also known as synchronous PSO (S-PSO). The strength of this update method is in the exploitation of the information. Asynchronous update PSO (A-PSO) has been proposed as an alternative to S-PSO. A particle in A-PSO updates its velocity and position as soon as its own performance has been evaluated. Hence, particles are updated using partial information, leading to stronger exploration. In this paper, we attempt to improve PSO by merging both update methods to utilise the strengths of both methods. The proposed synchronous-asynchronous PSO (SA-PSO) algorithm divides the particles into smaller groups. The best member of a group and the swarm's best are chosen to lead the search. Members within a group are updated synchronously, while the groups themselves are asynchronously updated. Five well-known unimodal functions, four multimodal functions, and a real world optimisation problem are used to study the performance of SA-PSO, which is compared with the performances of S-PSO and A-PSO. The results are statistically analysed and show that the proposed SA-PSO has performed consistently well. PMID:25121109

  12. 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

  13. 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.

  14. 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.

  15. Collective Dynamics of Elastically Coupled Myosin V Motors*

    PubMed Central

    Lu, Hailong; Efremov, Artem K.; Bookwalter, Carol S.; Krementsova, Elena B.; Driver, Jonathan W.; Trybus, Kathleen M.; Diehl, Michael R.

    2012-01-01

    Characterization of the collective behaviors of different classes of processive motor proteins has become increasingly important to understand various intracellular trafficking and transport processes. This work examines the dynamics of structurally-defined motor complexes containing two myosin Va (myoVa) motors that are linked together via a molecular scaffold formed from a single duplex of DNA. Dynamic changes in the filament-bound configuration of these complexes due to motor binding, stepping, and detachment were monitored by tracking the positions of different color quantum dots that report the position of one head of each myoVa motor on actin. As in studies of multiple kinesins, the run lengths produced by two myosins are only slightly larger than those of single motor molecules. This suggests that internal strain within the complexes, due to asynchronous motor stepping and the resultant stretching of motor linkages, yields net negative cooperative behaviors. In contrast to multiple kinesins, multiple myosin complexes move with appreciably lower velocities than a single-myosin molecule. Although similar trends are predicted by a discrete state stochastic model of collective motor dynamics, these analyses also suggest that multiple myosin velocities and run lengths depend on both the compliance and the effective size of their cargo. Moreover, it is proposed that this unique collective behavior occurs because the large step size and relatively small stalling force of myoVa leads to a high sensitivity of motor stepping rates to strain. PMID:22718762

  16. Pharmacists’ Perception of Synchronous Versus Asynchronous Distance Learning for Continuing Education Programs

    PubMed Central

    2014-01-01

    Objective. To evaluate and compare pharmacists’ satisfaction with the content and learning environment of a continuing education program series offered as either synchronous or asynchronous webinars. Methods. An 8-lecture series of online presentations on the topic of new drug therapies was offered to pharmacists in synchronous and asynchronous webinar formats. Participants completed a 50-question online survey at the end of the program series to evaluate their perceptions of the distance learning experience. Results. Eighty-two participants completed the survey instrument (41 participants from the live webinar series and 41 participants from the asynchronous webinar series.) Responses indicated that while both groups were satisfied with the program content, the asynchronous group showed greater satisfaction with many aspects of the learning environment. Conclusion. The synchronous and asynchronous webinar participants responded positively regarding the quality of the programming and the method of delivery, but asynchronous participants rated their experience more positively overall. PMID:24558276

  17. 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.

  18. 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.

  19. Peripheral electrical stimulation triggered by self-paced detection of motor intention enhances motor evoked potentials.

    PubMed

    Niazi, Imran Khan; Mrachacz-Kersting, Natalie; Jiang, Ning; Dremstrup, Kim; Farina, Dario

    2012-07-01

    This paper proposes the development and experimental tests of a self-paced asynchronous brain-computer interfacing (BCI) system that detects movement related cortical potentials (MRCPs) produced during motor imagination of ankle dorsiflexion and triggers peripheral electrical stimulations timed with the occurrence of MRCPs to induce corticospinal plasticity. MRCPs were detected online from EEG signals in eight healthy subjects with a true positive rate (TPR) of 67.15 ± 7.87% and false positive rate (FPR) of 22.05 ±9.07%. The excitability of the cortical projection to the target muscle (tibialis anterior) was assessed before and after the intervention through motor evoked potentials (MEP) using transcranial magnetic stimulation (TMS). The peak of the evoked potential significantly (P=0.02) increased after the BCI intervention by 53 ± 43% (relative to preintervention measure), although the spinal excitability (tested by stretch reflexes) did not change. These results demonstrate for the first time that it is possible to alter the corticospinal projections to the tibialis anterior muscle by using an asynchronous BCI system based on online motor imagination that triggered peripheral stimulation. This type of repetitive proprioceptive feedback training based on self-generated brain signal decoding may be a requirement for purposeful skill acquisition in intact humans and in the rehabilitation of persons with brain damage. PMID:22547461

  20. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  2. 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

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Motor Controller

    NASA Technical Reports Server (NTRS)

    1988-01-01

    M.H. Marks Enterprises' Power Factor Controller (PFC) matches voltage with motor's actual need. Plugged into a motor, PFC continuously determines motor load by sensing shifts between voltage and current flow. When it senses a light load, it cuts voltage to the minimum needed. It offers potential energy savings ranging from eight percent up to 65 percent depending on the application. Myles Marks started out with the notion of writing an article for Popular Electronics magazine at the same time offering to furnish kits to readers interested in assembling PFC's. Within two weeks from publication he had orders for 500 kits and orders are still coming three years later.

  9. 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.

  10. 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

  11. 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.

  12. RAPID COMMUNICATION: Asynchronous data-driven classification of weapon systems

    NASA Astrophysics Data System (ADS)

    Jin, Xin; Mukherjee, Kushal; Gupta, Shalabh; Ray, Asok; Phoha, Shashi; Damarla, Thyagaraju

    2009-12-01

    This communication addresses real-time weapon classification by analysis of asynchronous acoustic data, collected from microphones on a sensor network. The weapon classification algorithm consists of two parts: (i) feature extraction from time-series data using symbolic dynamic filtering (SDF), and (ii) pattern classification based on the extracted features using the language measure (LM) and support vector machine (SVM). The proposed algorithm has been tested on field data, generated by firing of two types of rifles. The results of analysis demonstrate high accuracy and fast execution of the pattern classification algorithm with low memory requirements. Potential applications include simultaneous shooter localization and weapon classification with soldier-wearable networked sensors.

  13. Entry of Ebola Virus is an Asynchronous Process.

    PubMed

    Reynard, Olivier; Volchkov, Viktor E

    2015-10-01

    Ebola virus (EBOV) is responsible for a severe fever with a high mortality rate. The diverse nature of the attachment of the virus to the cell surface, the initial step of virus entry, raises questions concerning the kinetics of the virus internalization process. We investigated EBOV entry kinetics using the activity of a particular monoclonal antibody that neutralizes virus infectivity. We demonstrate that inoculation of cells with EBOV results in an asynchronous entry process, as revealed by the ability of the virus to remain in a cell-bound state for an extended period of time before it is internalized. PMID:25941332

  14. Chaotic motors

    NASA Astrophysics Data System (ADS)

    Laroche, C.; Labbé, R.; Pétrélis, F.; Fauve, S.

    2012-02-01

    We show that electric motors and dynamos can be used to illustrate most elementary instabilities or bifurcations discussed in courses on nonlinear oscillators and dynamical systems. These examples are easier to understand and display a richer behavior than the ones commonly used from mechanics, electronics, hydrodynamics, lasers, chemical reactions, and population dynamics. In particular, an electric motor driven by a dynamo can display stationary, Hopf, and codimension-two bifurcations by tuning the driving speed of the dynamo and the electric current in the stator of the electric motor. When the dynamo is driven at constant torque instead of constant rotation rate, chaotic reversals of the generated current and of the angular rotation of the motor are observed. Simple deterministic models are presented which capture the observed dynamical regimes.

  15. 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…

  16. 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…

  17. Asynchronous Discussion Board Facilitation and Rubric Use in a Blended Learning Environment

    ERIC Educational Resources Information Center

    Giacumo, Lisa

    2012-01-01

    The purpose of this study was to investigate the effects of instructor response prompts and rubrics on students' performance in an asynchronous discussion-board assignment, their learning achievement on an objective-type posttest, and their reported satisfaction levels. Researchers who have studied asynchronous computer-mediated student…

  18. 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…

  19. 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…

  20. 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…

  1. An Investigation of the Impact of Asynchronous Online Learning on Student Achievement

    ERIC Educational Resources Information Center

    Hill, Sylvia

    2009-01-01

    Asynchronous online learning is well documented with adults, but fewer studies of effectiveness have emphasized elementary education learning environments. This study investigated student achievement on the Texas Assessment of Knowledge and Skills (TAKS) test for fifth grade students who had participated in synchronous and asynchronous courses…

  2. 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…

  3. Combining Live Video and Audio Broadcasting, Synchronous Chat, and Asynchronous Open Forum Discussions in Distance Education

    ERIC Educational Resources Information Center

    Teng, Tian-Lih; Taveras, Marypat

    2004-01-01

    This article outlines the evolution of a unique distance education program that began as a hybrid--combining face-to-face instruction with asynchronous online teaching--and evolved to become an innovative combination of synchronous education using live streaming video, audio, and chat over the Internet, blended with asynchronous online discussions…

  4. 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…

  5. 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

  6. Asynchronously sampled blind source separation for coherent optical links

    NASA Astrophysics Data System (ADS)

    Detwiler, Thomas F.; Searcy, Steven M.; Stark, Andrew J.; Ralph, Stephen E.; Basch, Bert E.

    2011-01-01

    Polarization multiplexing is an integral technique for generating spectrally efficient 100 Gb/s and higher optical links. Post coherent detection DSP-based polarization demultiplexing of QPSK links is commonly performed after timing recovery. We propose and demonstrate a method of asynchronous blind source separation using the constant modulus algorithm (CMA) on the asynchronously sampled signal to initially separate energy from arbitrarily aligned polarization states. This method lends well to implementation as it allows for an open-loop sampling frequency for analog-to-digital conversion at less than twice the symbol rate. We show that the performance of subsequent receiver functions is enhanced by the initial pol demux operation. CMA singularity behavior is avoided through tap settling constraints. The method is applicable to QPSK transmissions and many other modulation formats as well, including general QAM signals, offset-QPSK, and CPM, or a combination thereof. We present the architecture and its performance under several different formats and link conditions. Comparisons of complexity and performance are drawn between the proposed architecture and conventional receivers.

  7. Experience with synchronous and asynchronous digital control systems. [for flight

    NASA Technical Reports Server (NTRS)

    Regenie, Victoria A.; Chacon, Claude V.; Lock, Wilton 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.

  8. 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).

  9. Asynchronous algorithms for heat conductors in composite media

    SciTech Connect

    El-Tarazi, M.N.; Anwar, M.N. )

    1989-01-01

    In this paper the authors treat the problem of two dimensional steady-state heat conduction in a medium composed of two homogeneous and isotropic, but physically dissimilar materials. In situations where the boundary conditions are not simple elementary functions that exact analytical solution of such problems is impossible even for regions having a simple geometry. Thus a numerical technique is needed and the authors propose in this paper to discretize the considered heat conduction problem by the method of lines to obtain a system of second order differential equations with multipoint boundary conditions. This differential system is converted, using invariant imbedding for each one dimensional problem, into a fixed point problem for which several iterative algorithms can be used. If the asynchronous parallel algorithms are used, we obtain an approach which combines both simplicity (referring to the classical invariant imbedding associated with the by lines approximation) and efficiency (referring to the asynchronous parallel algorithms). In Section 2, The authors give the mathematical formulation of the problem considered in this paper together with the appropriate boundary and auxiliary conditions.

  10. 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.

  11. Spatiotemporal features for asynchronous event-based data

    PubMed Central

    Lagorce, Xavier; Ieng, Sio-Hoi; Clady, Xavier; Pfeiffer, Michael; Benosman, Ryad B.

    2015-01-01

    Bio-inspired asynchronous event-based vision sensors are currently introducing a paradigm shift in visual information processing. These new sensors rely on a stimulus-driven principle of light acquisition similar to biological retinas. They are event-driven and fully asynchronous, thereby reducing redundancy and encoding exact times of input signal changes, leading to a very precise temporal resolution. Approaches for higher-level computer vision often rely on the reliable detection of features in visual frames, but similar definitions of features for the novel dynamic and event-based visual input representation of silicon retinas have so far been lacking. This article addresses the problem of learning and recognizing features for event-based vision sensors, which capture properties of truly spatiotemporal volumes of sparse visual event information. A novel computational architecture for learning and encoding spatiotemporal features is introduced based on a set of predictive recurrent reservoir networks, competing via winner-take-all selection. Features are learned in an unsupervised manner from real-world input recorded with event-based vision sensors. It is shown that the networks in the architecture learn distinct and task-specific dynamic visual features, and can predict their trajectories over time. PMID:25759637

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. An Examination of Asynchronous Communication Experiences and Perspectives of Students in an Online Course: A Case Study.

    ERIC Educational Resources Information Center

    Vonderwell, Selma

    2003-01-01

    Explores asynchronous communication perspectives and experiences of undergraduate students in an online course. Interviews with 22 preservice teachers, student-to-instructor email transcripts, asynchronous discussion transcripts, and two independent reviewers' reviews of the asynchronous discussions were used to collect and analyze the data.…

  17. 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

  18. Motor Planning.

    PubMed

    Wong, Aaron L; Haith, Adrian M; Krakauer, John W

    2015-08-01

    Motor planning colloquially refers to any process related to the preparation of a movement that occurs during the reaction time prior to movement onset. However, this broad definition encompasses processes that are not strictly motor-related, such as decision-making about the identity of task-relevant stimuli in the environment. Furthermore, the assumption that all motor-planning processes require processing time, and can therefore be studied behaviorally by measuring changes in the reaction time, needs to be reexamined. In this review, we take a critical look at the processes leading from perception to action and suggest a definition of motor planning that encompasses only those processes necessary for a movement to be executed-that is, processes that are strictly movement related. These processes resolve the ambiguity inherent in an abstract goal by defining a specific movement to achieve it. We propose that the majority of processes that meet this definition can be completed nearly instantaneously, which means that motor planning itself in fact consumes only a small fraction of the reaction time. PMID:24981338

  19. 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.

  20. 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.

  1. Improvements In Ball-Screw Linear Actuators

    NASA Technical Reports Server (NTRS)

    Iskenderian, Theodore; Joffe, Benjamin; Summers, Robert

    1996-01-01

    Report describes modifications of design of type of ball-screw linear actuator driven by dc motor, with linear-displacement feedback via linear variable-differential transformer (LVDT). Actuators used to position spacecraft engines to direct thrust. Modifications directed toward ensuring reliable and predictable operation during planned 12-year cruise and interval of hard use at end of cruise.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  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. 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.

  8. 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

  9. 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.

  10. 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.

  11. Reliable asynchronous image transfer protocol in wireless multimedia sensor networks.

    PubMed

    Lee, Joa-Hyoung; Jung, In-Bum

    2010-01-01

    In the paper, we propose a reliable asynchronous image transfer protocol, RAIT. RAIT applies a double sliding window method to node-to-node transfer, with one sliding window for the receiving queue, which is used to prevent packet loss caused by communication failure between nodes, and another sliding window for the sending queue, which prevents packet loss caused by network congestion. The routing node prevents packet loss between nodes by preemptive scheduling of multiple packets for a given image. RAIT implements a double sliding window method by means of a cross-layer design between the RAIT layer, routing layer, and queue layer. We demonstrate that RAIT guarantees a higher reliability of image transmission compared to the existing protocols. PMID:22294883

  12. 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

  13. 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

  14. 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 ...

  15. 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 ...

  16. 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.

  17. Linear Accelerators

    NASA Astrophysics Data System (ADS)

    Sidorin, Anatoly

    2010-01-01

    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.

  18. 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.

  19. Distributed Consensus of Stochastic Delayed Multi-agent Systems Under Asynchronous Switching.

    PubMed

    Wu, Xiaotai; Tang, Yang; Cao, Jinde; Zhang, Wenbing

    2016-08-01

    In this paper, the distributed exponential consensus of stochastic delayed multi-agent systems with nonlinear dynamics is investigated under asynchronous switching. The asynchronous switching considered here is to account for the time of identifying the active modes of multi-agent systems. After receipt of confirmation of mode's switching, the matched controller can be applied, which means that the switching time of the matched controller in each node usually lags behind that of system switching. In order to handle the coexistence of switched signals and stochastic disturbances, a comparison principle of stochastic switched delayed systems is first proved. By means of this extended comparison principle, several easy to verified conditions for the existence of an asynchronously switched distributed controller are derived such that stochastic delayed multi-agent systems with asynchronous switching and nonlinear dynamics can achieve global exponential consensus. Two examples are given to illustrate the effectiveness of the proposed method. PMID:26292354

  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. PMID:21151299

  1. Comparing face-to-face, synchronous, and asynchronous learning: postgraduate dental resident preferences.

    PubMed

    Kunin, Marc; Julliard, Kell N; Rodriguez, Tobias E

    2014-06-01

    The Department of Dental Medicine of Lutheran Medical Center has developed an asynchronous online curriculum consisting of prerecorded PowerPoint presentations with audio explanations. The focus of this study was to evaluate if the new asynchronous format satisfied the educational needs of the residents compared to traditional lecture (face-to-face) and synchronous (distance learning) formats. Lectures were delivered to 219 dental residents employing face-to-face and synchronous formats, as well as the new asynchronous format; 169 (77 percent) participated in the study. Outcomes were assessed with pretests, posttests, and individual lecture surveys. Results found the residents preferred face-to-face and asynchronous formats to the synchronous format in terms of effectiveness and clarity of presentations. This preference was directly related to the residents' perception of how well the technology worked in each format. The residents also rated the quality of student-instructor and student-student interactions in the synchronous and asynchronous formats significantly higher after taking the lecture series than they did before taking it. However, they rated the face-to-face format as significantly more conducive to student-instructor and student-student interaction. While the study found technology had a major impact on the efficacy of this curricular model, the results suggest that the asynchronous format can be an effective way to teach a postgraduate course. PMID:24882771

  2. Simulating Quantitative Cellular Responses Using Asynchronous Threshold Boolean Network Ensembles

    PubMed Central

    2011-01-01

    Background With increasing knowledge about the potential mechanisms underlying cellular functions, it is becoming feasible to predict the response of biological systems to genetic and environmental perturbations. Due to the lack of homogeneity in living tissues it is difficult to estimate the physiological effect of chemicals, including potential toxicity. Here we investigate a biologically motivated model for estimating tissue level responses by aggregating the behavior of a cell population. We assume that the molecular state of individual cells is independently governed by discrete non-deterministic signaling mechanisms. This results in noisy but highly reproducible aggregate level responses that are consistent with experimental data. Results We developed an asynchronous threshold Boolean network simulation algorithm to model signal transduction in a single cell, and then used an ensemble of these models to estimate the aggregate response across a cell population. Using published data, we derived a putative crosstalk network involving growth factors and cytokines - i.e., Epidermal Growth Factor, Insulin, Insulin like Growth Factor Type 1, and Tumor Necrosis Factor α - to describe early signaling events in cell proliferation signal transduction. Reproducibility of the modeling technique across ensembles of Boolean networks representing cell populations is investigated. Furthermore, we compare our simulation results to experimental observations of hepatocytes reported in the literature. Conclusion A systematic analysis of the results following differential stimulation of this model by growth factors and cytokines suggests that: (a) using Boolean network ensembles with asynchronous updating provides biologically plausible noisy individual cellular responses with reproducible mean behavior for large cell populations, and (b) with sufficient data our model can estimate the response to different concentrations of extracellular ligands. Our results suggest that this

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. HYPERS: A Unidimensional Asynchronous Framework for Multiscale Hybrid Simulations

    NASA Astrophysics Data System (ADS)

    Omelchenko, Y. A.; Karimabadi, H.; Vu, H. X.

    2011-12-01

    Kinetic ion-driven processes are crucial for understanding the complex dynamics of the closely coupled Earth magnetosphere-ionosphere system. Largely varying time and length scales impose severe numerical constraints on global simulations with hybrid (particle ions + fluid electrons) codes. To enable larger simulations we developed a unique, uni-dimensional multiscale hybrid code, HYPERS. Instead of stepping all simulation variables uniformly in time, HYPERS tracks physically meaningful changes to individual particles and cell-based electromagnetic fields via asynchronous discrete events. HYPERS has been parallelized with the Preemptive Event Processing (PEP) technique. The parallel algorithm enables arbitrary domain decompositions and processor configurations on restarts. This is a critical prerequisite for implementing a full load balancing functionality in the future. We validate HYPERS by simulating the interaction of streaming plasmas with dipole magnetospheres and show that our approach results in superior numerical metrics (stability, accuracy and speed) compared to conventional techniques. We also discuss further extensions to the HYPERS framework that would enable seemless integration of ion fluid and kinetic schemes.

  8. 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.

  9. Visual tracking using neuromorphic asynchronous event-based cameras.

    PubMed

    Ni, Zhenjiang; Ieng, Sio-Hoi; Posch, Christoph; Régnier, Stéphane; Benosman, Ryad

    2015-04-01

    This letter presents a novel computationally efficient and robust pattern tracking method based on a time-encoded, frame-free visual data. Recent interdisciplinary developments, combining inputs from engineering and biology, have yielded a novel type of camera that encodes visual information into a continuous stream of asynchronous, temporal events. These events encode temporal contrast and intensity locally in space and time. We show that the sparse yet accurately timed information is well suited as a computational input for object tracking. In this letter, visual data processing is performed for each incoming event at the time it arrives. The method provides a continuous and iterative estimation of the geometric transformation between the model and the events representing the tracked object. It can handle isometry, similarities, and affine distortions and allows for unprecedented real-time performance at equivalent frame rates in the kilohertz range on a standard PC. Furthermore, by using the dimension of time that is currently underexploited by most artificial vision systems, the method we present is able to solve ambiguous cases of object occlusions that classical frame-based techniques handle poorly. PMID:25710087

  10. 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

  11. 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

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

    PubMed Central

    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

  13. 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).

  14. Asynchronous vs didactic education: it’s too early to throw in the towel on tradition

    PubMed Central

    2013-01-01

    Background Asynchronous, computer based instruction is cost effective, allows self-directed pacing and review, and addresses preferences of millennial learners. Current research suggests there is no significant difference in learning compared to traditional classroom instruction. Data are limited for novice learners in emergency medicine. The objective of this study was to compare asynchronous, computer-based instruction with traditional didactics for senior medical students during a week-long intensive course in acute care. We hypothesized both modalities would be equivalent. Methods This was a prospective observational quasi-experimental study of 4th year medical students who were novice learners with minimal prior exposure to curricular elements. We assessed baseline knowledge with an objective pre-test. The curriculum was delivered in either traditional lecture format (shock, acute abdomen, dyspnea, field trauma) or via asynchronous, computer-based modules (chest pain, EKG interpretation, pain management, trauma). An interactive review covering all topics was followed by a post-test. Knowledge retention was measured after 10 weeks. Pre and post-test items were written by a panel of medical educators and validated with a reference group of learners. Mean scores were analyzed using dependent t-test and attitudes were assessed by a 5-point Likert scale. Results 44 of 48 students completed the protocol. Students initially acquired more knowledge from didactic education as demonstrated by mean gain scores (didactic: 28.39% ± 18.06; asynchronous 9.93% ± 23.22). Mean difference between didactic and asynchronous = 18.45% with 95% CI [10.40 to 26.50]; p = 0.0001. Retention testing demonstrated similar knowledge attrition: mean gain scores −14.94% (didactic); -17.61% (asynchronous), which was not significantly different: 2.68% ± 20.85, 95% CI [−3.66 to 9.02], p = 0.399. The attitudinal survey revealed that 60.4% of students believed the asynchronous

  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. 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)

  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. Gross motor control

    MedlinePlus

    Gross motor control is the ability to make large, general movements (such as waving an arm or lifting a ... Gross motor control is a milestone in the development of an infant. Infants develop gross motor control before they ...

  19. 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 ...

  20. 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.

  1. 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.

  2. Transposed firing activation of motor units

    PubMed Central

    Kline, Joshua C.; Contessa, Paola

    2014-01-01

    Muscles are composed of groups of muscle fibers, called motor units, each innervated by a single motoneuron originating in the spinal cord. During constant or linearly varying voluntary force contractions, motor units are activated in a hierarchical order, with the earlier-recruited motor units having greater firing rates than the later-recruited ones. We found that this normal pattern of firing activation can be altered during oscillatory contractions where the force oscillates at frequencies ≥2 Hz. During these high-frequency oscillations, the activation of the lower-threshold motor units effectively decreases and that of the higher-threshold motor units effectively increases. This transposition of firing activation provides means to activate higher-threshold motor units preferentially. Our results demonstrate that the hierarchical regulation of motor unit activation can be manipulated to activate specific motoneuron populations preferentially. This finding can be exploited to develop new forms of physical therapies and exercise programs that enhance muscle performance or that target the preferential atrophy of high-threshold motor units as a result of aging or motor disorders such as stroke and amyotrophic lateral sclerosis. PMID:24899671

  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. Synchronous and asynchronous modes of synaptic transmission utilize different calcium sources.

    PubMed

    Wen, Hua; Hubbard, Jeffrey M; Rakela, Benjamin; Linhoff, Michael W; Mandel, Gail; Brehm, Paul

    2013-01-01

    Asynchronous transmission plays a prominent role at certain synapses but lacks the mechanistic insights of its synchronous counterpart. The current view posits that triggering of asynchronous release during repetitive stimulation involves expansion of the same calcium domains underlying synchronous transmission. In this study, live imaging and paired patch clamp recording at the zebrafish neuromuscular synapse reveal contributions by spatially distinct calcium sources. Synchronous release is tied to calcium entry into synaptic boutons via P/Q type calcium channels, whereas asynchronous release is boosted by a propagating intracellular calcium source initiated at off-synaptic locations in the axon and axonal branch points. This secondary calcium source fully accounts for the persistence following termination of the stimulus and sensitivity to slow calcium buffers reported for asynchronous release. The neuromuscular junction and CNS neurons share these features, raising the possibility that secondary calcium sources are common among synapses with prominent asynchronous release. DOI: http://dx.doi.org/10.7554/eLife.01206.001. PMID:24368731

  5. 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

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

    PubMed

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

    2014-01-01

    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

  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. 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.

  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. 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.

  11. Asynchronous Programming in UPC: A Case Study and Potential for Improvement

    SciTech Connect

    Shet, Aniruddha G; Tipparaju, Vinod; Harrison, Robert J

    2009-01-01

    In a traditional Partitioned Global Address Space language like UPC, an application programmer works with the model of a static set of threads performing locality-aware accesses on a global address space. On the other hand, asynchronous programming provides a simple interface for expressing the concurrency in dynamic, irregular algorithms, with the prospect of efficient portable execution from sophisticated runtime schemes handling the exposed concurrency. In this paper, we adopt the asynchronous style of programming to parallelize a nested, tree-based code in UPC. To maximize performance without losing the ease of application programming, we design Asynchronous Remote Methods as a potential extension to the UPC standard. Our prototype implementation of this construct in Berkeley UPC yields within 7% of ideal performance and 20-fold improvement over the original Standard UPC solution in some cases.

  12. 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

  13. Asynchronous multimedia annotations for web-based collaboration in biology education

    NASA Astrophysics Data System (ADS)

    Petkovic, Dragutin; Lank, E.; Ramirez, F. A.; Raghavendra, S.; Chen, F.; Pekiner, C.; Fregoso, A.; Marquez, A.

    2004-12-01

    The focus of this paper is on the design, implementation, and validation of asynchronous multimedia annotations designed for Web-based collaboration in educational and research settings. The two key questions we explore in this paper are: How useful are such annotations and what purpose do annotations serve? What is the ease of use of our specific implementation of annotations? The context of our project has been in the area of multimedia information usage and collaboration in the biological sciences. We have developed asynchronous annotations for HTML and image data. Our annotations can be executed via any browser and require no downloads. They are stored in a central database allowing search and asynchronous access by all registered users. An easy to use user interface allows users to add, view and search annotations. We also performed a usability study that showed that our implementation of text annotations to validate our implementation.

  14. Asynchronous multimedia annotations for web-based collaboration in biology education

    NASA Astrophysics Data System (ADS)

    Petkovic, Dragutin; Lank, E.; Ramirez, F. A.; Raghavendra, S.; Chen, F.; Pekiner, C.; Fregoso, A.; Marquez, A.

    2005-01-01

    The focus of this paper is on the design, implementation, and validation of asynchronous multimedia annotations designed for Web-based collaboration in educational and research settings. The two key questions we explore in this paper are: How useful are such annotations and what purpose do annotations serve? What is the ease of use of our specific implementation of annotations? The context of our project has been in the area of multimedia information usage and collaboration in the biological sciences. We have developed asynchronous annotations for HTML and image data. Our annotations can be executed via any browser and require no downloads. They are stored in a central database allowing search and asynchronous access by all registered users. An easy to use user interface allows users to add, view and search annotations. We also performed a usability study that showed that our implementation of text annotations to validate our implementation.

  15. 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. PMID:26670529

  16. 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].

  17. 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

  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. 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…

  20. 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…

  1. Sources of Difference in Reliability: Identifying Sources of Difference in Reliability in Content Analysis of Online Asynchronous Discussions

    ERIC Educational Resources Information Center

    Murphy, Elizabeth; Ciszewska-Carr, Justyna

    2005-01-01

    This paper reports on a case study which identifies and illustrates sources of difference in agreement in relation to reliability in a context of quantitative content analysis of a transcript of an online asynchronous discussion (OAD). Transcripts of 10 students in a month-long online asynchronous discussion were coded by two coders using an…

  2. 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…

  3. 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…

  4. Comparison between Synchronous and Asynchronous Instructional Delivery Method of Training Programme on In-Service Physical Educators' Knowledge

    ERIC Educational Resources Information Center

    Emmanouilidou, Kyriaki; Derri, Vassiliki; Antoniou, Panagiotis; Kyrgiridis, Pavlos

    2012-01-01

    The purpose of the study was to compare the influences of a training programme's instructional delivery method (synchronous and asynchronous) on Greek in-service physical educators' cognitive understanding on student assessment. Forty nine participants were randomly divided into synchronous, asynchronous, and control group. The experimental groups…

  5. 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…

  6. 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.

  7. On Input-to-State Stability of Switched Stochastic Nonlinear Systems Under Extended Asynchronous Switching.

    PubMed

    Kang, Yu; Zhai, Di-Hua; Liu, Guo-Ping; Zhao, Yun-Bo

    2016-05-01

    An extended asynchronous switching model is investigated for a class of switched stochastic nonlinear retarded systems in the presence of both detection delay and false alarm, where the extended asynchronous switching is described by two independent and exponentially distributed stochastic processes, and further simplified as Markovian. Based on the Razumikhin-type theorem incorporated with average dwell-time approach, the sufficient criteria for global asymptotic stability in probability and stochastic input-to-state stability are given, whose importance and effectiveness are finally verified by numerical examples. PMID:26068932

  8. Scenario Decomposition for 0-1 Stochastic Programs: Improvements and Asynchronous Implementation

    DOE PAGESBeta

    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.

  9. Thrust Characteristics of High-Thrust Spiral Motor Using FEM Analysis

    NASA Astrophysics Data System (ADS)

    Kwon, Hyuk-Jin; Fujimoto, Yasutaka

    We propose a spiral-type motor that has high thrust characteristics as a linear actuator. This motor generates torque around the axis and thrust in the axial direction only by electromagnetic force. It has little friction because no additional hardware is required for straight-line movement. This paper presents the concept of the spiral motor. The finite-element method (FEM) analysis certifies that this motor has high motor constant as same as High Density Linear Motor (HDL). We also study a method to compensate the thrust fluctuation of 5-pitch-stator 6-pitch-mover model

  10. 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.

  11. 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.

  12. 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.

  13. Deadlock-free asynchronous communication strategies for unstructured computations on iPSC/860

    SciTech Connect

    Venugopal, S.; Naik, V.K.

    1994-12-31

    In this paper, we describe efficient, scalable, and deadlock-free asynchronous communication strategies suitable for unstructured computations on iPSC/860. Using these deadlock-free strategies, which incur small overhead, we have optimized the communication in parallel sparse Cholesky factorization. We present experimental results to show that such optimizations can lead to more than 50% saving in communication costs.

  14. Asynchronous remodeling is a driver of failed regeneration in Duchenne muscular dystrophy.

    PubMed

    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; Hoffman, Eric P

    2014-10-13

    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

  15. 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…

  16. 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…

  17. Comparing Asynchronous and Synchronous Video vs. Text Based Discussions in an Online Teacher Education Course

    ERIC Educational Resources Information Center

    Clark, Cynthia; Strudler, Neal; Grove, Karen

    2015-01-01

    The purpose of this study was to investigate whether asynchronous video posts and synchronous videoconferencing would create higher levels of teaching and social presence within an online course when compared with the university's current text-based discussion platform. Undergraduate students in an online teacher education course were randomly…

  18. 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…

  19. 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…

  20. 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…

  1. Comparative Analysis of Preservice Teachers' Reflective Thinking in Synchronous versus Asynchronous Online Case Discussions

    ERIC Educational Resources Information Center

    Levin, Barbara B.; He, Ye; Robbins, Holly H.

    2006-01-01

    This study was undertaken to better understand the nature of preservice teachers' reflective thinking during case discussions about classroom management in two online formats: synchronous versus asynchronous. Findings indicated that when participants engaged in synchronous online case discussions they had higher levels of critical reflection than…

  2. Student Contribution in Asynchronous Online Discussion: A Review of the Research and Empirical Exploration

    ERIC Educational Resources Information Center

    Hew, Khe Foon; Cheung, Wing Sum; Ng, Connie Siew Ling

    2010-01-01

    The increasingly prevalent use of Internet in schools and homes has resulted in asynchronous online discussion becoming an increasingly common means to facilitate dialogue between instructors and students, as well as students and students beyond the boundaries of their physical classrooms. This article is organized into two main sections. In the…

  3. 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…

  4. A Computational Model for Asynchronous Oocyte Growth Dynamics in Spawning Fish

    EPA Science Inventory

    This manuscript describes the development of a computational model that simulates a time course of oocyte growth and spawning for asynchronous spawning fish, based upon plasma vitellogenin concentrations and a critical oocyte size for spawning. The model provides a framework that...

  5. A Model for Evaluating the Process of Learning in Asynchronous Computer Conferencing.

    ERIC Educational Resources Information Center

    Schrire, Sarah

    2003-01-01

    Presents a qualitative multiple-case study of three online asynchronous computer conferences that were part of a doctoral program at Nova Southeastern University. Examines the learning process from the points of view of interaction, cognition, and discourse analysis and proposes a model for assessing sociocognitive processes in computer…

  6. Examining Facilitators' Habits of Mind in an Asynchronous Online Discussion Environment: A Two Cases Study

    ERIC Educational Resources Information Center

    Cheung, Wing Sum; Hew, Khe Foon

    2010-01-01

    Asynchronous online discussion has been widely used by faculty members and students in schools and universities. Previous research has examined how factors such as the discussion activity, knowledge about the discussion topic, and the behaviour of other participants can affect learner participation. This study explored student facilitators'…

  7. Critical Thinking in Asynchronous Online Discussion: An Investigation of Student Facilitation Techniques

    ERIC Educational Resources Information Center

    Lim, Sze Chung Raymond; Cheung, Wing Sum; Hew, Khe Foon

    2011-01-01

    Background: In the last decade, asynchronous online discussion forums have become a primary focus of many educational researchers. Some advocates believed that the process of typing out messages in itself can promote in-depth critical thinking skills. Nevertheless, empirical research has not provided much support for this claim in natural…

  8. 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…

  9. 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…

  10. 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…

  11. 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…

  12. 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…

  13. 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…

  14. Asynchronous Computer-Mediated Corrective Feedback and the Correct Use of Prepositions: Is It Really Effective?

    ERIC Educational Resources Information Center

    Hosseini, Seyyed Behrooz

    2012-01-01

    An area that has recently attracted increasing attention is providing feedback on learners' writing accuracy through the Internet. However, research in this area has largely focused on synchronous communication, i.e., chatting, with fewer studies assessing asynchronous technologies, i.e., e-mailing. Therefore, this study investigates the…

  15. Designing a Discussion Environment to Enhance Connectivity and Sustainability in Asynchronous Online Discussion

    ERIC Educational Resources Information Center

    Gao, Fei

    2011-01-01

    Lack of connectivity and sustainability are two common problems in asynchronous online discussions. In this paper, the author proposes that the two problems may have to do with the structure of threaded forums, that is, the design of threaded forums may constrain participants from having well-connected and sustained discussions. A new discussion…

  16. Using Reflective Peer Assessment to Promote Students' Conceptual Understanding through Asynchronous Discussions

    ERIC Educational Resources Information Center

    Lin, Huann-shyang; Hong, Zuway-R; Wang, Hsin-Hui; Lee, Sung-Tao

    2011-01-01

    This study explores the impact of using assessment items with competing theories to encourage students to practice evaluative reflection and collaborative argumentation in asynchronous discussions. Thirty undergraduate students from various departments worked in small groups and took turns collaboratively discussing the given item's answer,…

  17. Audio-Based versus Text-Based Asynchronous Online Discussion: Two Case Studies

    ERIC Educational Resources Information Center

    Hew, Khe Foon; Cheung, Wing Sum

    2013-01-01

    The main objective of this paper is to examine the use of audio- versus text-based asynchronous online discussions. We report two case studies conducted within the context of semester-long teacher education courses at an Asian Pacific university. Forty-one graduate students participated in Study I. After the online discussions (both audio-based as…

  18. 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…

  19. 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…

  20. 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…

  1. The excitation control system of the ASK-100-4 asynchronous compensator

    SciTech Connect

    Dovganyuk, I. Ya.; Labunets, I. A.; Plotnikova, T. V.; Sokur, P. V. Shakaryan, Yu. G.

    2010-12-15

    The excitation regulation system of the ASK-100-4 asynchronous compensator is described. The main modes of operation of the compensators in the Beskudnikovo substation of the 'Mosenergo' JSC are considered. The results of an investigation of an actual sample of an AER-ASC automatic excitation regulator on a computer bench, operating in real time, are presented.

  2. 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'…

  3. 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…

  4. 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…

  5. 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…

  6. 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…

  7. 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…

  8. 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…

  9. 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…

  10. 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…

  11. Digging beneath the Surface: Analyzing the Complexity of Instructors' Participation in Asynchronous Discussion

    ERIC Educational Resources Information Center

    Clarke, Lane Whitney; Bartholomew, Audrey

    2014-01-01

    The purpose of this study was to investigate instructor participation in asynchronous discussions through an in-depth content analysis of instructors' postings and comments through the Community of Inquiry (COI) framework (Garrison et. al, 2001). We developed an analytical tool based on this framework in order to better understand what…

  12. 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…

  13. 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…

  14. Time Students Spend Reading Threaded Discussions in Online Graduate Courses Requiring Asynchronous Participation

    ERIC Educational Resources Information Center

    Brown, Abbie H.; Green, Tim

    2009-01-01

    The authors report the results of a study that provides bases for comparison between the time necessary to participate in courses delivered asynchronously online and courses delivered in a traditional classroom setting. Weekly discussion threads from 21 sections of six courses offered as part of online, degree-granting, accredited, graduate…

  15. 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…

  16. 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…

  17. 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…

  18. 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…

  19. 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…

  20. 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…

  1. 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…

  2. 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…

  3. Constructivist Pedagogy in Asynchronous Online Education: Examining Proactive Behavior and the Impact on Student Engagement Levels

    ERIC Educational Resources Information Center

    Peters, Linda; Shmerling, Shirley; Karren, Ronald

    2011-01-01

    Asynchronous learning environments have gained popularity over the past decade and have rapidly gained acceptance in both the academic and business worlds. This study investigates the impact that student characteristics of proactive behavior and learning style preference have on student engagement levels when a collaborative learning process such…

  4. 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.

  5. 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…

  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. 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…

  8. 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…

  9. 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…

  10. A Qualitative Case Study Illustrating the Benefits of Discussion Roles in Online Asynchronous Discussion

    ERIC Educational Resources Information Center

    Hancock, Cheryl J.

    2012-01-01

    This research describes a qualitative, naturalistic case study of a situation-specific, in-depth exploration of the use of ten student discussion roles in and adult education, online asynchronous discussions. Discussion roles were designed in order to enable students to respond better and create deeper and more meaning-filled threaded discussions,…

  11. 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…

  12. 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…

  13. 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…

  14. A Study of Asynchronous and Synchronous Discussion on Cognitive Maps in a Distributed Learning Environment.

    ERIC Educational Resources Information Center

    Bhattacharya, Madhumita

    This paper reports on a comparative study of the use of asynchronous (bulletin board) and synchronous (chat) discussion on three learning units based on the cognitive maps developed by the learners. Cognitive maps have been found to be an effective tool for learners for discussion in a distributed learning environment. Cognitive maps provided…

  15. Comparing Asynchronous Online Discussions and Face-to-Face Discussions in a Classroom Setting

    ERIC Educational Resources Information Center

    Wang, Qiyun; Woo, Huay Lit

    2007-01-01

    The purpose of this study is to investigate the perceived differences between asynchronous online discussions and face-to-face discussions in a classroom setting. The students' reflections were analysed by following a qualitative research approach. The results showed that atmosphere, response, efficiency, interactivity and communication were the…

  16. Static stability of parallel operation of asynchronized generators in an electrical system

    NASA Astrophysics Data System (ADS)

    Plotnikova, T. V.; Sokur, P. V.; Tuzov, P. Yu.; Shakaryan, Yu. G.

    2014-12-01

    The static stability of single and parallel operations of an asynchronized generator (ASG) in a long-distance power transmission line is investigated. The synthesis of the ASG excitation control law at which set of the machine's stable operating conditions G s will comprise sufficiently conservative set of permissible operating conditions G p is considered.

  17. Asynchronous electro-optic sampling of all-electronically generated ultrashort voltage pulses

    NASA Astrophysics Data System (ADS)

    Füser, Heiko; Bieler, Mark; Ahmed, Sajjad; Verbeyst, Frans

    2015-02-01

    We measure the output of an electrical pulse generator with a repetition rate of 76 MHz employing a laser-based asynchronous sampling technique with an effective sampling frequency of 250 GHz. A best estimate of the resulting 13 ns long waveform is obtained from multiple waveform measurements, which are taken without any trigger event and subsequently aligned in time. This asynchronous sampling scheme can even be adopted in situations where small phase drifts between the electrical pulse generator and the laser occur, making synchronized sampling very difficult. In addition to accurate measurements, the proposed asynchronous measurement scheme allows for the construction of covariance matrices with full rank since a large number of time traces is acquired. Such matrices might reveal correlations which do not appear in low-rank matrices. We believe that the asynchronous sampling technique advocated in this paper will prove to be a valuable characterization tool covering an ultra-broadband frequency range from below 100 MHz to above 100 GHz.

  18. 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…

  19. 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…

  20. 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…

  1. 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…

  2. 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…

  3. 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…

  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. Socialization in the "Virtual Hallway": Instant Messaging in the Asynchronous Web-Based Distance Education Classroom.

    ERIC Educational Resources Information Center

    Nicholson, Scott

    2002-01-01

    Examined differences in communication between masters degree students at Syracuse University who used instant messaging (IM) services and those who did not in the same asynchronous distance education Web-based course. Results showed that students who used IM found it easier to communicate and felt a stronger sense of community. (Author/LRW)

  6. 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.

  7. 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…

  8. Author On-Line: Using Asynchronous Computer Conferencing To Support Literacy.

    ERIC Educational Resources Information Center

    Clarke, Linda; Heaney, Peter

    2003-01-01

    Describes the Author-On-Line (AOL) project that used asynchronous computer conferencing to support the teaching and learning of literacy with pupils aged 10-12 years from two schools in Ireland. Presents the AOL-APT model which summarizes the key components: Author, Pedagogy and Technology (APT); and discusses its value for online, social,…

  9. 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

  10. 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…

  11. 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…

  12. 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…

  13. 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.

  14. Linearization problem in pseudolite surveys

    NASA Astrophysics Data System (ADS)

    Cellmer, Slawomir; Rapinski, Jacek

    2010-06-01

    GPS augmented with pseudolites (PL), can be used in various engineering surveys. Also pseudolite—only navigation system can be designed and used in any place, even if GPS signal is not available (Kee et al. Development of indoor navigation system using asynchronous pseudolites, 1038-1045, 2000). Especially in engineering surveys, where harsh survey environment is common, pseudolites have a lot of applications. Pseudolites may be used in construction sites, open pit mines, city canyons, GPS and PL baseline processing is similar, although there are few differences that must be taken into account. One of the major issues is linearization problem. The source of the problem is neglecting second terms of Taylor series expansion in GPS baseline processing software. This problem occurs when the pseudolite is relatively close to the receiver, which is the case in PL surveys. In this paper authors presents the algorithm for GPS + PL data processing including, neglected in classical GPS only approach, second terms of Taylor series expansion. The mathematical model of adjustment problem, detailed proposal of application in baseline processing algorithms, and numerical tests are presented.

  15. 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.

  16. 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.

  17. Fine motor control

    MedlinePlus

    ... figure 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 ...

  18. 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 ...

  19. Asynchronous space-time algorithm based on a domain decomposition method for structural dynamics problems on non-matching meshes

    NASA Astrophysics Data System (ADS)

    Subber, Waad; Matouš, Karel

    2016-02-01

    Large-scale practical engineering problems featuring localized phenomena often benefit from local control of mesh and time resolutions to efficiently capture the spatial and temporal scales of interest. To this end, we propose an asynchronous space-time algorithm based on a domain decomposition method for structural dynamics problems on non-matching meshes. The three-field algorithm is based on the dual-primal like domain decomposition approach utilizing the localized Lagrange multipliers along the space and time common-refinement-based interface. The proposed algorithm is parallel in nature and well suited for a heterogeneous computing environment. Moreover, two-levels of parallelism are embedded in this novel scheme. For linear dynamical problems, the algorithm is unconditionally stable, shows an optimal order of convergence with respect to space and time discretizations as well as ensures conservation of mass, momentum and energy across the non-matching grid interfaces. The method of manufactured solutions is used to verify the implementation, and an engineering application is considered, where a sandwich plate is impacted by a projectile.

  20. 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.