Time delays in flight simulator visual displays

NASA Technical Reports Server (NTRS)

Crane, D. F.

1980-01-01

It is pointed out that the effects of delays of less than 100 msec in visual displays on pilot dynamic response and system performance are of particular interest at this time because improvements in the latest computer-generated imagery (CGI) systems are expected to reduce CGI displays delays to this range. Attention is given to data which quantify the effects of display delays in the range of 0-100 msec on system stability and performance, and pilot dynamic response for a particular choice of aircraft dynamics, display, controller, and task. The conventional control system design methods are reviewed, the pilot response data presented, and data for long delays, all suggest lead filter compensation of display delay. Pilot-aircraft system crossover frequency information guides compensation filter specification.

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

NASA Astrophysics Data System (ADS)

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

2018-04-01

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

The effects of time delay in man-machine control systems: Implications for design of flight simulator Visual-Display-Delay compensation

NASA Technical Reports Server (NTRS)

Crane, D. F.

1984-01-01

When human operators are performing precision tracking tasks, their dynamic response can often be modeled by quasilinear describing functions. That fact permits analysis of the effects of delay in certain man machine control systems using linear control system analysis techniques. The analysis indicates that a reduction in system stability is the immediate effect of additional control system delay, and that system characteristics moderate or exaggerate the importance of the delay. A selection of data (simulator and flight test) consistent with the analysis is reviewed. Flight simulator visual-display delay compensation, designed to restore pilot aircraft system stability, was evaluated in several studies which are reviewed here. The studies range from single-axis, tracking-task experiments (with sufficient subjects and trials to establish the statistical significance of the results) to a brief evaluation of compensation of a computer generated imagery (CGI) visual display system in a full six degree of freedom simulation. The compensation was effective, improvements in pilot performance and workload or aircraft handling qualities rating (HQR) were observed. Results from recent aircraft handling qualities research literature, which support the compensation design approach, are also reviewed.

Radar wideband digital beamforming based on time delay and phase compensation

NASA Astrophysics Data System (ADS)

Fu, Wei; Jiang, Defu

2018-07-01

In conventional phased array radars, analogue time delay devices and phase shifters have been used for wideband beamforming. These methods suffer from insertion losses, gain mismatches and delay variations, and they occupy a large chip area. To solve these problems, a compact architecture of digital array antennas based on subarrays was considered. In this study, the receiving beam patterns of wideband linear frequency modulation (LFM) signals were constructed by applying analogue stretch processing via mixing with delayed reference signals at the subarray level. Subsequently, narrowband digital time delaying and phase compensation of the tone signals were implemented with reduced arithmetic complexity. Due to the differences in amplitudes, phases and time delays between channels, severe performance degradation of the beam patterns occurred without corrections. To achieve good beamforming performance, array calibration was performed in each channel to adjust the amplitude, frequency and phase of the tone signal. Using a field-programmable gate array, wideband LFM signals and finite impulse response filters with continuously adjustable time delays were implemented in a polyphase structure. Simulations and experiments verified the feasibility and effectiveness of the proposed digital beamformer.

Fine Output Voltage Control Method considering Time-Delay of Digital Inverter System for X-ray Computed Tomography

NASA Astrophysics Data System (ADS)

Shibata, Junji; Kaneko, Kazuhide; Ohishi, Kiyoshi; Ando, Itaru; Ogawa, Mina; Takano, Hiroshi

This paper proposes a new output voltage control for an inverter system, which has time-delay and nonlinear load. In the next generation X-ray computed tomography of a medical device (X-ray CT) that uses the contactless power transfer method, the feedback signal often contains time-delay due to AD/DA conversion and error detection/correction time. When the PID controller of the inverter system is received the adverse effects of the time-delay, the controller often has an overshoot and a oscillated response. In order to overcome this problem, this paper proposes a compensation method based on the Smith predictor for an inverter system having a time-delay and the nonlinear loads which are the diode bridge rectifier and X-ray tube. The proposed compensation method consists of the hybrid Smith predictor system based on an equivalent analog circuit and DSP. The experimental results confirm the validity of the proposed system.

Advanced Transport Delay Compensation Algorithms: Results of Delay Measurement and Piloted Performance Tests

NASA Technical Reports Server (NTRS)

Guo, Liwen; Cardullo, Frank M.; Kelly, Lon C.

2007-01-01

This report summarizes the results of delay measurement and piloted performance tests that were conducted to assess the effectiveness of the adaptive compensator and the state space compensator for alleviating the phase distortion of transport delay in the visual system in the VMS at the NASA Langley Research Center. Piloted simulation tests were conducted to assess the effectiveness of two novel compensators in comparison to the McFarland predictor and the baseline system with no compensation. Thirteen pilots with heterogeneous flight experience executed straight-in and offset approaches, at various delay configurations, on a flight simulator where different predictors were applied to compensate for transport delay. The glideslope and touchdown errors, power spectral density of the pilot control inputs, NASA Task Load Index, and Cooper-Harper rating of the handling qualities were employed for the analyses. The overall analyses show that the adaptive predictor results in slightly poorer compensation for short added delay (up to 48 ms) and better compensation for long added delay (up to 192 ms) than the McFarland compensator. The analyses also show that the state space predictor is fairly superior for short delay and significantly superior for long delay than the McFarland compensator.

Neutron monitoring systems including gamma thermometers and methods of calibrating nuclear instruments using gamma thermometers

DOEpatents

Moen, Stephan Craig; Meyers, Craig Glenn; Petzen, John Alexander; Foard, Adam Muhling

2012-08-07

A method of calibrating a nuclear instrument using a gamma thermometer may include: measuring, in the instrument, local neutron flux; generating, from the instrument, a first signal proportional to the neutron flux; measuring, in the gamma thermometer, local gamma flux; generating, from the gamma thermometer, a second signal proportional to the gamma flux; compensating the second signal; and calibrating a gain of the instrument based on the compensated second signal. Compensating the second signal may include: calculating selected yield fractions for specific groups of delayed gamma sources; calculating time constants for the specific groups; calculating a third signal that corresponds to delayed local gamma flux based on the selected yield fractions and time constants; and calculating the compensated second signal by subtracting the third signal from the second signal. The specific groups may have decay time constants greater than 5.times.10.sup.-1 seconds and less than 5.times.10.sup.5 seconds.

Contact stiffness and damping identification for hardware-in-the-loop contact simulator with measurement delay compensation

NASA Astrophysics Data System (ADS)

Qi, Chenkun; Zhao, Xianchao; Gao, Feng; Ren, Anye; Sun, Qiao

2016-06-01

The hardware-in-the-loop (HIL) contact simulator is to simulate the contact process of two flying objects in space. The contact stiffness and damping are important parameters used for the process monitoring, compliant contact control and force compensation control. In this study, a contact stiffness and damping identification approach is proposed for the HIL contact simulation with the force measurement delay. The actual relative position of two flying objects can be accurately measured. However, the force measurement delay needs to be compensated because it will lead to incorrect stiffness and damping identification. Here, the phase lead compensation is used to reconstruct the actual contact force from the delayed force measurement. From the force and position data, the contact stiffness and damping are identified in real time using the recursive least squares (RLS) method. The simulations and experiments are used to verify that the proposed stiffness and damping identification approach is effective.

Designing Estimator/Predictor Digital Phase-Locked Loops

NASA Technical Reports Server (NTRS)

Statman, J. I.; Hurd, W. J.

1988-01-01

Signal delays in equipment compensated automatically. New approach to design of digital phase-locked loop (DPLL) incorporates concepts from estimation theory and involves decomposition of closed-loop transfer function into estimator and predictor. Estimator provides recursive estimates of phase, frequency, and higher order derivatives of phase with respect to time, while predictor compensates for delay, called "transport lag," caused by PLL equipment and by DPLL computations.

Compensation for time delay in flight simulator visual-display systems

NASA Technical Reports Server (NTRS)

Crane, D. F.

1983-01-01

A piloted aircraft can be viewed as a closed-loop, man-machine control system. When a simulator pilot is performing a precision maneuver, a delay in the visual display of aircraft response to pilot-control input decreases the stability of the pilot-aircraft system. The less stable system is more difficult to control precisely. Pilot dynamic response and performance change as the pilot attempts to compensate for the decrease in system stability, and these changes bias the simulation results by influencing the pilot's rating of the handling qualities of the simulated aircraft. Delay compensation, designed to restore pilot-aircraft system stability, was evaluated in several studies which are reported here. The studies range from single-axis, tracking-task experiments (with sufficient subjects and trials to establish statistical significance of the results) to a brief evaluation of compensation of a computer-generated-imagery (CGI) visual display system in a full six-degree-of-freedom simulation. The compensation was effective - improvements in pilot performance and workload or aircraft handling-qualities rating (HQR) were observed. Results from recent aircraft handling-qualities research literature which support the compensation design approach are also reviewed.

Transfer Alignment Error Compensator Design Based on Robust State Estimation

NASA Astrophysics Data System (ADS)

Lyou, Joon; Lim, You-Chol

This paper examines the transfer alignment problem of the StrapDown Inertial Navigation System (SDINS), which is subject to the ship’s roll and pitch. Major error sources for velocity and attitude matching are lever arm effect, measurement time delay and ship-body flexure. To reduce these alignment errors, an error compensation method based on state augmentation and robust state estimation is devised. A linearized error model for the velocity and attitude matching transfer alignment system is derived first by linearizing the nonlinear measurement equation with respect to its time delay and dominant Y-axis flexure, and by augmenting the delay state and flexure state into conventional linear state equations. Then an H∞ filter is introduced to account for modeling uncertainties of time delay and the ship-body flexure. The simulation results show that this method considerably decreases azimuth alignment errors considerably.

Mitigating Communication Delays in Remotely Connected Hardware-in-the-loop Experiments

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

Cale, James; Johnson, Brian; Dall'Anese, Emiliano

Here, this paper introduces a potential approach for mitigating the effects of communication delays between multiple, closed-loop hardware-in-the-loop experiments which are virtually connected, yet physically separated. The method consists of an analytical method for the compensation of communication delays, along with the supporting computational and communication infrastructure. The control design leverages tools for the design of observers for the compensation of measurement errors in systems with time-varying delays. The proposed methodology is validated through computer simulation and hardware experimentation connecting hardware-in-the-loop experiments conducted between laboratories separated by a distance of over 100 km.

Mitigating Communication Delays in Remotely Connected Hardware-in-the-loop Experiments

DOE PAGES

Cale, James; Johnson, Brian; Dall'Anese, Emiliano; ...

2018-03-30

Here, this paper introduces a potential approach for mitigating the effects of communication delays between multiple, closed-loop hardware-in-the-loop experiments which are virtually connected, yet physically separated. The method consists of an analytical method for the compensation of communication delays, along with the supporting computational and communication infrastructure. The control design leverages tools for the design of observers for the compensation of measurement errors in systems with time-varying delays. The proposed methodology is validated through computer simulation and hardware experimentation connecting hardware-in-the-loop experiments conducted between laboratories separated by a distance of over 100 km.

Discriminability of Prediction Artifacts in a Time Delayed Virtual Environment

NASA Technical Reports Server (NTRS)

Adelstein, Bernard D.; Jung, Jae Y.; Ellis, Stephen R.

2001-01-01

Overall latency remains an impediment to perceived image stability and consequently to human performance in virtual environment (VE) systems. Predictive compensators have been proposed as a means to mitigate these shortcomings, but they introduce rendering errors because of induced motion overshoot and heightened noise. Discriminability of these compensator artifacts was investigated by a protocol in which head tracked image stability for 35 ms baseline VE system latency was compared against artificially added (16.7 to 100 ms) latency compensated by a previously studied Kalman Filter (K-F) predictor. A control study in which uncompensated 16.7 to 100 ms latencies were compared against the baseline was also performed. Results from 10 subjects in the main study and 8 in the control group indicate that predictive compensation artifacts are less discernible than the disruptions of uncompensated time delay for the shorter but not the longer added latencies. We propose that noise magnification and overshoot are contributory cues to the presence of predictive compensation.

A Control Allocation System for Automatic Detection and Compensation of Phase Shift Due to Actuator Rate Limiting

NASA Technical Reports Server (NTRS)

Yildiz, Yidiray; Kolmanovsky, Ilya V.; Acosta, Diana

2011-01-01

This paper proposes a control allocation system that can detect and compensate the phase shift between the desired and the actual total control effort due to rate limiting of the actuators. Phase shifting is an important problem in control system applications since it effectively introduces a time delay which may destabilize the closed loop dynamics. A relevant example comes from flight control where aggressive pilot commands, high gain of the flight control system or some anomaly in the system may cause actuator rate limiting and effective time delay introduction. This time delay can instigate Pilot Induced Oscillations (PIO), which is an abnormal coupling between the pilot and the aircraft resulting in unintentional and undesired oscillations. The proposed control allocation system reduces the effective time delay by first detecting the phase shift and then minimizing it using constrained optimization techniques. Flight control simulation results for an unstable aircraft with inertial cross coupling are reported, which demonstrate phase shift minimization and recovery from a PIO event.

Compensation of distributed delays in integrated communication and control systems

NASA Technical Reports Server (NTRS)

Ray, Asok; Luck, Rogelio

1991-01-01

The concept, analysis, implementation, and verification of a method for compensating delays that are distributed between the sensors, controller, and actuators within a control loop are discussed. With the objective of mitigating the detrimental effects of these network induced delays, a predictor-controller algorithm was formulated and analyzed. Robustness of the delay compensation algorithm was investigated relative to parametric uncertainties in plant modeling. The delay compensator was experimentally verified on an IEEE 802.4 network testbed for velocity control of a DC servomotor.

Isochronic carrier-envelope phase-shift compensator.

PubMed

Görbe, Mihaly; Osvay, Karoly; Grebing, Christian; Steinmeyer, Günter

2008-11-15

A concept for orthogonal control of phase and group delay inside a laser cavity by a specially designed compensator assembly is discussed. Similar to the construction of variable polarization retarder, this assembly consists of two thin wedge prisms made from appropriately chosen optical materials. Being shifted as a whole, the assembly allows changing the phase delay with no influence on the cavity round-trip time, whereas relative shifting of the prisms enables adjustment of the latter. This scheme is discussed theoretically and verified experimentally, indicating a factor 30 reduction of the influence on the repetition rate compared to the commonly used silica wedge pair. For a 2pi adjustment of the carrier-envelope phase shift, single-pass timing differences are reduced to the single-femtosecond regime. With negligible distortions of timing and dispersion, the described compensator device greatly simplifies carrier-envelope phase control and experiments in extreme nonlinear optics. Copyright (c) 2008 Optical Society of America.

Analysis and experiments for delay compensation in attitude control of flexible spacecraft

NASA Astrophysics Data System (ADS)

Sabatini, Marco; Palmerini, Giovanni B.; Leonangeli, Nazareno; Gasbarri, Paolo

2014-11-01

Space vehicles are often characterized by highly flexible appendages, with low natural frequencies which can generate coupling phenomena during orbital maneuvering. The stability and delay margins of the controlled system are deeply affected by the presence of bodies with different elastic properties, assembled to form a complex multibody system. As a consequence, unstable behavior can arise. In this paper the problem is first faced from a numerical point of view, developing accurate multibody mathematical models, as well as relevant navigation and control algorithms. One of the main causes of instability is identified with the unavoidable presence of time delays in the GNC loop. A strategy to compensate for these delays is elaborated and tested using the simulation tool, and finally validated by means of a free floating platform, replicating the flexible spacecraft attitude dynamics (single axis rotation). The platform is equipped with thrusters commanded according to the on-off modulation of the Linear Quadratic Regulator (LQR) control law. The LQR is based on the estimate of the full state vector, i.e. including both rigid - attitude - and elastic variables, that is possible thanks to the on line measurement of the flexible displacements, realized by processing the images acquired by a dedicated camera. The accurate mathematical model of the system and the rigid and elastic measurements enable a prediction of the state, so that the control is evaluated taking the predicted state relevant to a delayed time into account. Both the simulations and the experimental campaign demonstrate that by compensating in this way the time delay, the instability is eliminated, and the maneuver is performed accurately.

Control optimization, stabilization and computer algorithms for aircraft applications

NASA Technical Reports Server (NTRS)

1975-01-01

Research related to reliable aircraft design is summarized. Topics discussed include systems reliability optimization, failure detection algorithms, analysis of nonlinear filters, design of compensators incorporating time delays, digital compensator design, estimation for systems with echoes, low-order compensator design, descent-phase controller for 4-D navigation, infinite dimensional mathematical programming problems and optimal control problems with constraints, robust compensator design, numerical methods for the Lyapunov equations, and perturbation methods in linear filtering and control.

Effects of the delay and duration of self-generated wind on behavioral compensation in unilaterally cercus-ablated crickets, Gryllus bimaculatus.

PubMed

Takuwa, Hiroyuki; Mori, Daichi; Ozaki, Naoko; Kanou, Masamichi

2013-05-01

The effects of the delay and duration of wind self-generated during walking on the compensational recovery of escape direction were investigated in unilaterally cercus-ablated crickets, Gryllus bimaculatus. Artificial self-generated winds (self-stimulations; hereafter, SSts) from a nozzle set in front of a cricket placed on a styrofoam ball for stationary walking were used for training after unilateral cercus ablation. The delay and duration of artificial SSts were separately controlled. When the stimulus duration was fixed to 100 msec, the crickets trained with artificial SSts of 1000 msec delay showed a compensational recovery of the escape direction. However, no such compensational recovery was observed in crickets trained with artificial SSts of 1200, 1500, and 2000 msec delays. The relationship between the delay and duration of artificial SSts for compensational recovery was investigated. An artificial SSt with a longer delay required a longer-duration air current to cause a recovery of the escape direction. In contrast, an artificial SSt with a shorter delay was effective even when the duration was short. On the basis of the results obtained in the present study, we propose a hypothesis to explain the initial step for the compensation, that is, how the delay and duration of SSts are traded in terms of the compensational recovery of the escape direction.

Prediction and Real-Time Compensation of Qubit Decoherence Via Machine Learning (Open Access, Publisher’s Version)

DTIC Science & Technology

2017-01-16

ARTICLE Received 24 Sep 2016 | Accepted 29 Nov 2016 | Published 16 Jan 2017 Prediction and real- time compensation of qubit decoherence via machine...information to suppress stochastic, semiclassical decoherence, even when access to measurements is limited. First, we implement a time -division...quantum information experiments. Second, we employ predictive feedback during sequential but time delayed measurements to reduce the Dick effect as

Ionospheric Delay Compensation Using a Scale Factor Based on an Altitude of a Receiver

NASA Technical Reports Server (NTRS)

Zhao, Hui (Inventor); Savoy, John (Inventor)

2014-01-01

In one embodiment, a method for ionospheric delay compensation is provided. The method includes determining an ionospheric delay based on a signal having propagated from the navigation satellite to a location below the ionosphere. A scale factor can be applied to the ionospheric delay, wherein the scale factor corresponds to a ratio of an ionospheric delay in the vertical direction based on an altitude of the satellite navigation system receiver. Compensation can be applied based on the ionospheric delay.

Dynamic Chirp Control and Pulse Compression for Attosecond High-Order Harmonic Emission

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

Zheng Yinghui; Zeng Zhinan; Zou Pu

2009-07-24

We propose a scheme to compensate dynamically the intrinsic chirp of the attosecond harmonic pulses. By adding a weak second harmonic laser field to the driving laser field, the chirp compensation can be varied from the negative to the positive continuously by simply adjusting the relative time delay between the two-color pulses. Using this technique, the compensation of the negative chirp in harmonic emission is demonstrated experimentally for the first time and the nearly transform-limited attosecond pulse trains are obtained.

New Predictive Filters for Compensating the Transport Delay on a Flight Simulator

NASA Technical Reports Server (NTRS)

Guo, Liwen; Cardullo, Frank M.; Houck, Jacob A.; Kelly, Lon C.; Wolters, Thomas E.

2004-01-01

The problems of transport delay in a flight simulator, such as its sources and effects, are reviewed. Then their effects on a pilot-in-the-loop control system are investigated with simulations. Three current prominent delay compensators the lead/lag filter, McFarland filter, and the Sobiski/Cardullo filter were analyzed and compared. This paper introduces two novel delay compensation techniques an adaptive predictor using the Kalman estimator and a state space predictive filter using a reference aerodynamic model. Applications of these two new compensators on recorded data from the NASA Langley Research Center Visual Motion Simulator show that they achieve better compensation over the current ones.

Equalizer tap length requirement for mode group delay-compensated fiber link with weakly random mode coupling.

PubMed

Bai, Neng; Li, Guifang

2014-02-24

The equalizer tap length requirement is investigated analytically and numerically for differential modal group delay (DMGD) compensated fiber link with weakly random mode coupling. Each span of the DMGD compensated link comprises multiple pairs of fibers which have opposite signs of DMGD. The result reveals that under weak random mode coupling, the required tap length of the equalizer is proportional to modal group delay of a single DMGD compensated pair, instead of the total modal group delay (MGD) of the entire link. By using small DMGD compensation step sizes, the required tap length (RTL) can be potentially reduced by 2 orders of magnitude.

Advanced techniques for mitigating the effects of temporal distortions in human in the loop control systems

NASA Astrophysics Data System (ADS)

Guo, Liwen

The desire to create more complex visual scenes in modern flight simulators outpaces recent increases in processor speed. As a result, the simulation transport delay remains a problem. Because of the limitations shown in the three prominent existing delay compensators---the lead/lag filter, the McFarland compensator and the Sobiski/Cardullo predictor---new approaches of compensating the transport delay in a flight simulator have been developed. The first novel compensator is the adaptive predictor making use of the Kalman filter algorithm in a unique manner so that the predictor can provide accurately the desired amount of prediction, significantly reducing the large spikes caused by the McFarland predictor. Among several simplified online adaptive predictors it illustrates mathematically why the stochastic approximation algorithm achieves the best compensation results. A second novel approach employed a reference aircraft dynamics model to implement a state space predictor on a flight simulator. The practical implementation formed the filter state vector from the operator's control input and the aircraft states. The relationship between the reference model and the compensator performance was investigated in great detail, and the best performing reference model was selected for implementation in the final tests. Piloted simulation tests were conducted for assessing the effectiveness of the two novel compensators in comparison to the McFarland predictor and no compensation. Thirteen pilots with heterogeneous flight experience executed straight-in and offset approaches, at various delay configurations, on a flight simulator where different predictors were applied to compensate for transport delay. Four metrics---the glide slope and touchdown errors, power spectral density of the pilot control inputs, NASA Task Load Index, and Cooper-Harper rating on the handling qualities---were employed for the analyses. The overall analyses show that while the adaptive predictor results in slightly poorer compensation for short added delay (up to 48 ms) and better compensation for long added delay (up to 192 ms) than the McFarland compensator, the state space predictor is fairly superior for short delay and significantly superior for long delay to the McFarland compensator. The state space predictor also achieves better compensation than the adaptive predictor. The results of the evaluation on the effectiveness of these predictors in the piloted tests agree with those in the theoretical offline tests conducted with the recorded simulation aircraft states.

Broadband true time delay for microwave signal processing, using slow light based on stimulated Brillouin scattering in optical fibers.

PubMed

Chin, Sanghoon; Thévenaz, Luc; Sancho, Juan; Sales, Salvador; Capmany, José; Berger, Perrine; Bourderionnet, Jérôme; Dolfi, Daniel

2010-10-11

We experimentally demonstrate a novel technique to process broadband microwave signals, using all-optically tunable true time delay in optical fibers. The configuration to achieve true time delay basically consists of two main stages: photonic RF phase shifter and slow light, based on stimulated Brillouin scattering in fibers. Dispersion properties of fibers are controlled, separately at optical carrier frequency and in the vicinity of microwave signal bandwidth. This way time delay induced within the signal bandwidth can be manipulated to correctly act as true time delay with a proper phase compensation introduced to the optical carrier. We completely analyzed the generated true time delay as a promising solution to feed phased array antenna for radar systems and to develop dynamically reconfigurable microwave photonic filters.

Amplitude- and rise-time-compensated filters

DOEpatents

Nowlin, Charles H.

1984-01-01

An amplitude-compensated rise-time-compensated filter for a pulse time-of-occurrence (TOOC) measurement system is disclosed. The filter converts an input pulse, having the characteristics of random amplitudes and random, non-zero rise times, to a bipolar output pulse wherein the output pulse has a zero-crossing time that is independent of the rise time and amplitude of the input pulse. The filter differentiates the input pulse, along the linear leading edge of the input pulse, and subtracts therefrom a pulse fractionally proportional to the input pulse. The filter of the present invention can use discrete circuit components and avoids the use of delay lines.

Implementation of High Time Delay Accuracy of Ultrasonic Phased Array Based on Interpolation CIC Filter

PubMed Central

Liu, Peilu; Li, Xinghua; Li, Haopeng; Su, Zhikun; Zhang, Hongxu

2017-01-01

In order to improve the accuracy of ultrasonic phased array focusing time delay, analyzing the original interpolation Cascade-Integrator-Comb (CIC) filter, an 8× interpolation CIC filter parallel algorithm was proposed, so that interpolation and multichannel decomposition can simultaneously process. Moreover, we summarized the general formula of arbitrary multiple interpolation CIC filter parallel algorithm and established an ultrasonic phased array focusing time delay system based on 8× interpolation CIC filter parallel algorithm. Improving the algorithmic structure, 12.5% of addition and 29.2% of multiplication was reduced, meanwhile the speed of computation is still very fast. Considering the existing problems of the CIC filter, we compensated the CIC filter; the compensated CIC filter’s pass band is flatter, the transition band becomes steep, and the stop band attenuation increases. Finally, we verified the feasibility of this algorithm on Field Programming Gate Array (FPGA). In the case of system clock is 125 MHz, after 8× interpolation filtering and decomposition, time delay accuracy of the defect echo becomes 1 ns. Simulation and experimental results both show that the algorithm we proposed has strong feasibility. Because of the fast calculation, small computational amount and high resolution, this algorithm is especially suitable for applications with high time delay accuracy and fast detection. PMID:29023385

Implementation of High Time Delay Accuracy of Ultrasonic Phased Array Based on Interpolation CIC Filter.

PubMed

Liu, Peilu; Li, Xinghua; Li, Haopeng; Su, Zhikun; Zhang, Hongxu

2017-10-12

In order to improve the accuracy of ultrasonic phased array focusing time delay, analyzing the original interpolation Cascade-Integrator-Comb (CIC) filter, an 8× interpolation CIC filter parallel algorithm was proposed, so that interpolation and multichannel decomposition can simultaneously process. Moreover, we summarized the general formula of arbitrary multiple interpolation CIC filter parallel algorithm and established an ultrasonic phased array focusing time delay system based on 8× interpolation CIC filter parallel algorithm. Improving the algorithmic structure, 12.5% of addition and 29.2% of multiplication was reduced, meanwhile the speed of computation is still very fast. Considering the existing problems of the CIC filter, we compensated the CIC filter; the compensated CIC filter's pass band is flatter, the transition band becomes steep, and the stop band attenuation increases. Finally, we verified the feasibility of this algorithm on Field Programming Gate Array (FPGA). In the case of system clock is 125 MHz, after 8× interpolation filtering and decomposition, time delay accuracy of the defect echo becomes 1 ns. Simulation and experimental results both show that the algorithm we proposed has strong feasibility. Because of the fast calculation, small computational amount and high resolution, this algorithm is especially suitable for applications with high time delay accuracy and fast detection.

An observer-based compensator for distributed delays

NASA Technical Reports Server (NTRS)

Luck, Rogelio; Ray, Asok

1990-01-01

This paper presents an algorithm for compensating delays that are distributed between the sensor(s), controller and actuator(s) within a control loop. This observer-based algorithm is specially suited to compensation of network-induced delays in integrated communication and control systems. The robustness of the algorithm relative to plant model uncertainties has been examined.

Influence of group-delay ripple on timing jitter induced by SPM and IXPM in systems with dispersion compensated by CFBG

NASA Astrophysics Data System (ADS)

Qin, Xi; Cao, Jihong; Chen, Yong; Zhang, Feng; Jian, Shuisheng

2007-08-01

An analytical expression was proposed to analyze the influence of group-delay ripple (GDR) on timing jitter induced by self-phase modulation (SPM) and intra-channel cross-phase modulation (IXPM) in pseudo-linear transmission systems when dispersion was compensated by chirped fiber Bragg grating (CFBG). Effects of ripple amplitude, period, and phase on timing jitter were discussed by theoretical and numerical analysis in detail. The results show that the influence of GDR on timing jitter changes linearly with the amplitude of GDR and whether it decreases or increases the timing jitter relies on the ripple period and ripple phase. Timing jitter induced by SPM and IXPM could be suppressed totally by adjusting the relative phase between the center frequency of the pulse and the ripples.

A Comprehensive Study of Three Delay Compensation Algorithms for Flight Simulators

NASA Technical Reports Server (NTRS)

Guo, Liwen; Cardullo, Frank M.; Houck, Jacob A.; Kelly, Lon C.; Wolters, Thomas E.

2005-01-01

This paper summarizes a comprehensive study of three predictors used for compensating the transport delay in a flight simulator; The McFarland, Adaptive and State Space Predictors. The paper presents proof that the stochastic approximation algorithm can achieve the best compensation among all four adaptive predictors, and intensively investigates the relationship between the state space predictor s compensation quality and its reference model. Piloted simulation tests show that the adaptive predictor and state space predictor can achieve better compensation of transport delay than the McFarland predictor.

STUDIES IN WORKMEN'S COMPENSATION AND RADIATION INJURY. VOLUME II, THE INCIDENCE, NATURE AND ADJUDICATION OF WORKMEN'S COMPENSATION CLAIMS INVOLVING RADIATION EXPOSURE AND DELAYED INJURY.

ERIC Educational Resources Information Center

O'TOOLE, THOMAS J.

THE PURPOSE OF THE STUDY WAS TO PROVIDE A FACTUAL BACKGROUND AGAINST WHICH JUDGMENTS CAN BE MADE CONCERNING THE MAGNITUDE OF THE PROBLEM OF INJURY APPEARING SOME TIME AFTER THE EXPOSURE TO IONIZING RADIATION AND DETERMINE WHETHER EXISTING LAWS PERMIT A JUST AND EQUITABLE ADJUDICATION OF RADIATION COMPENSATION CLAIMS. THE STUDY WAS BASED UPON THE…

Sampled-data chain-observer design for a class of delayed nonlinear systems

NASA Astrophysics Data System (ADS)

Kahelras, M.; Ahmed-Ali, T.; Giri, F.; Lamnabhi-Lagarrigue, F.

2018-05-01

The problem of observer design is addressed for a class of triangular nonlinear systems with not-necessarily small delay and sampled output measurements. One more difficulty is that the system state matrix is dependent on the un-delayed output signal which is not accessible to measurement, making existing observers inapplicable. A new chain observer, composed of m elementary observers in series, is designed to compensate for output sampling and arbitrary large delays. The larger the time-delay the larger the number m. Each elementary observer includes an output predictor that is conceived to compensate for the effects of output sampling and a fractional delay. The predictors are defined by first-order ordinary differential equations (ODEs) much simpler than those of existing predictors which involve both output and state predictors. Using a small gain type analysis, sufficient conditions for the observer to be exponentially convergent are established in terms of the minimal number m of elementary observers and the maximum sampling interval.

An observer-based compensator for distributed delays in integrated control systems

NASA Technical Reports Server (NTRS)

Luck, Rogelio; Ray, Asok

1989-01-01

This paper presents an algorithm for compensation of delays that are distributed within a control loop. The observer-based algorithm is especially suitable for compensating network-induced delays that are likely to occur in integrated control systems of the future generation aircraft. The robustness of the algorithm relative to uncertainties in the plant model have been examined.

Flight Simulator Visual-Display Delay Compensation

NASA Technical Reports Server (NTRS)

Crane, D. Francis

1981-01-01

A piloted aircraft can be viewed as a closed-loop man-machine control system. When a simulator pilot is performing a precision maneuver, a delay in the visual display of aircraft response to pilot-control input decreases the stability of the pilot-aircraft system. The less stable system is more difficult to control precisely. Pilot dynamic response and performance change as the pilot attempts to compensate for the decrease in system stability. The changes in pilot dynamic response and performance bias the simulation results by influencing the pilot's rating of the handling qualities of the simulated aircraft. The study reported here evaluated an approach to visual-display delay compensation. The objective of the compensation was to minimize delay-induced change in pilot performance and workload, The compensation was effective. Because the compensation design approach is based on well-established control-system design principles, prospects are favorable for successful application of the approach in other simulations.

Analysis and compensation of synchronous measurement error for multi-channel laser interferometer

NASA Astrophysics Data System (ADS)

Du, Shengwu; Hu, Jinchun; Zhu, Yu; Hu, Chuxiong

2017-05-01

Dual-frequency laser interferometer has been widely used in precision motion system as a displacement sensor, to achieve nanoscale positioning or synchronization accuracy. In a multi-channel laser interferometer synchronous measurement system, signal delays are different in the different channels, which will cause asynchronous measurement, and then lead to measurement error, synchronous measurement error (SME). Based on signal delay analysis of the measurement system, this paper presents a multi-channel SME framework for synchronous measurement, and establishes the model between SME and motion velocity. Further, a real-time compensation method for SME is proposed. This method has been verified in a self-developed laser interferometer signal processing board (SPB). The experiment result showed that, using this compensation method, at a motion velocity 0.89 m s-1, the max SME between two measuring channels in the SPB is 1.1 nm. This method is more easily implemented and applied to engineering than the method of directly testing smaller signal delay.

Dealing with delays does not transfer across sensorimotor tasks.

PubMed

de la Malla, Cristina; López-Moliner, Joan; Brenner, Eli

2014-10-09

It is known that people can learn to deal with delays between their actions and the consequences of such actions. We wondered whether they do so by adjusting their anticipations about the sensory consequences of their actions or whether they simply learn to move in certain ways when performing specific tasks. To find out, we examined details of how people learn to intercept a moving target with a cursor that follows the hand with a delay and examined the transfer of learning between this task and various other tasks that require temporal precision. Subjects readily learned to intercept the moving target with the delayed cursor. The compensation for the delay generalized across modifications of the task, so subjects did not simply learn to move in a certain way in specific circumstances. The compensation did not generalize to completely different timing tasks, so subjects did not generally expect the consequences of their motor commands to be delayed. We conclude that people specifically learn to control the delayed visual consequences of their actions to perform certain tasks. © 2014 ARVO.

Predictive coding of visual object position ahead of moving objects revealed by time-resolved EEG decoding.

PubMed

Hogendoorn, Hinze; Burkitt, Anthony N

2018-05-01

Due to the delays inherent in neuronal transmission, our awareness of sensory events necessarily lags behind the occurrence of those events in the world. If the visual system did not compensate for these delays, we would consistently mislocalize moving objects behind their actual position. Anticipatory mechanisms that might compensate for these delays have been reported in animals, and such mechanisms have also been hypothesized to underlie perceptual effects in humans such as the Flash-Lag Effect. However, to date no direct physiological evidence for anticipatory mechanisms has been found in humans. Here, we apply multivariate pattern classification to time-resolved EEG data to investigate anticipatory coding of object position in humans. By comparing the time-course of neural position representation for objects in both random and predictable apparent motion, we isolated anticipatory mechanisms that could compensate for neural delays when motion trajectories were predictable. As well as revealing an early neural position representation (lag 80-90 ms) that was unaffected by the predictability of the object's trajectory, we demonstrate a second neural position representation at 140-150 ms that was distinct from the first, and that was pre-activated ahead of the moving object when it moved on a predictable trajectory. The latency advantage for predictable motion was approximately 16 ± 2 ms. To our knowledge, this provides the first direct experimental neurophysiological evidence of anticipatory coding in human vision, revealing the time-course of predictive mechanisms without using a spatial proxy for time. The results are numerically consistent with earlier animal work, and suggest that current models of spatial predictive coding in visual cortex can be effectively extended into the temporal domain. Copyright © 2018 Elsevier Inc. All rights reserved.

Adaptive fuzzy predictive sliding control of uncertain nonlinear systems with bound-known input delay.

PubMed

Khazaee, Mostafa; Markazi, Amir H D; Omidi, Ehsan

2015-11-01

In this paper, a new Adaptive Fuzzy Predictive Sliding Mode Control (AFP-SMC) is presented for nonlinear systems with uncertain dynamics and unknown input delay. The control unit consists of a fuzzy inference system to approximate the ideal linearization control, together with a switching strategy to compensate for the estimation errors. Also, an adaptive fuzzy predictor is used to estimate the future values of the system states to compensate for the time delay. The adaptation laws are used to tune the controller and predictor parameters, which guarantee the stability based on a Lyapunov-Krasovskii functional. To evaluate the method effectiveness, the simulation and experiment on an overhead crane system are presented. According to the obtained results, AFP-SMC can effectively control the uncertain nonlinear systems, subject to input delays of known bound. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Compensation Claims for Sub-substandard Care of Patients with Gastroentero-pancreatic Neuroendocrine Tumors: A Nationwide Descriptive Study of Cases Between 2005-2016 in Norway.

PubMed

Desserud, Kari F; Bukholm, Ida; Søreide, Jon Arne

2017-10-01

Management of patients with neuroendocrine tumors of the gastrointestinal tract or pancreas (GEP-NENs) poses diagnostic and therapeutic challenges. This study described the medico-legal claims reported to a national governmental system that oversees compensation to patients with GEP-NENs Materials and Methods: An electronic search of the Norwegian System of Compensation to Patients database was performed to identify claims evaluated between 2005-2016. The clinical information and the medico-legal evaluation were reviewed. We identified seven patients, five women and two men, with a median age of 57 (range=47-73) years. Delayed diagnosis (median diagnostic delay of 18 (range=6-48) months) was the main cause for claims in six out of the seven patients). Four patients received financial compensation based on the claim judgement. This review of claims that were evaluated by the Norwegian System of Compensation to Patients showed that a timely diagnosis of GEP-NENs remains a clinical challenge. Copyright© 2017, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.

A novel control architecture for physiological tremor compensation in teleoperated systems.

PubMed

Ghorbanian, A; Zareinejad, M; Rezaei, S M; Sheikhzadeh, H; Baghestan, K

2013-09-01

Telesurgery delivers surgical care to a 'remote' patient by means of robotic manipulators. When accurate positioning of the surgeon's tool is required, as in microsurgery, physiological tremor causes unwanted imprecision during a surgical operation. Accurate estimation/compensation of physiological tremor in teleoperation systems has been shown to improve performance during telesurgery. A new control architecture is proposed for estimation and compensation of physiological tremor in the presence of communication time delays. This control architecture guarantees stability with satisfactory transparency. In addition, the proposed method can be used for applications that require modifications in transmitted signals through communication channels. Stability of the bilateral tremor-compensated teleoperation is preserved by extending the bilateral teleoperation to the equivalent trilateral Dual-master/Single-slave teleoperation. The bandlimited multiple Fourier linear combiner (BMFLC) algorithm is employed for real-time estimation of the operator's physiological tremor. Two kinds of stability analysis are employed. In the model-base controller, Llewellyn's Criterion is used to analyze the teleoperation absolute stability. In the second method, a nonmodel-based controller is proposed and the stability of the time-delayed teleoperated system is proved by employing a Lyapunov function. Experimental results are presented to validate the effectiveness of the new control architecture. The tremorous motion is measured by accelerometer to be compensated in real time. In addition, a Needle-Insertion setup is proposed as a slave robot for the application of brachytherapy, in which the needle penetrates in the desired position. The slave performs the desired task in two classes of environments (free motion of the slave and in the soft tissue). Experiments show that the proposed control architecture effectively compensates the user's tremorous motion and the slave follows only the master's voluntary motion in a stable manner. Copyright © 2012 John Wiley & Sons, Ltd.

Digital compensation techniques for the effects of time lag in closed-loop simulation using the 6 DOF motion system

NASA Technical Reports Server (NTRS)

Brown, R.

1982-01-01

Efforts are continued to develop digital filter compensation schemes for the correction of momentum gains observed in the closed loop simulation of the docking of two satellites using the 6 DOF motion system. Several filters that work well for small delays ( .100ms) and a non-preloaded probe are discussed.

Experimental test of dense wavelength-division multiplexing using novel, periodic-group-delay-complemented dispersion compensation and dispersion-managed solitons

NASA Astrophysics Data System (ADS)

Mollenauer, Linn F.; Grant, Andrew; Liu, Xiang; Wei, Xing; Xie, Chongjin; Kang, Inuk

2003-11-01

In an all-Raman amplified, recirculating loop containing 100-km spans, we have tested dense wavelength-division multiplexing at 10 Gbits/s per channel, using dispersion-managed solitons and a novel, periodic-group-delay-complemented dispersion-compensation scheme that greatly reduces the timing jitter from interchannel collisions. The achieved working distances are ~9000 and ~20,000 km for uncorrected bit error rates of <10-8 and <10-3, respectively, the latter corresponding to the use of ``enhanced'' forward error correction; significantly, these distances are very close to those achievable in single-channel transmission in the same system.

Vastly accelerated linear least-squares fitting with numerical optimization for dual-input delay-compensated quantitative liver perfusion mapping.

PubMed

Jafari, Ramin; Chhabra, Shalini; Prince, Martin R; Wang, Yi; Spincemaille, Pascal

2018-04-01

To propose an efficient algorithm to perform dual input compartment modeling for generating perfusion maps in the liver. We implemented whole field-of-view linear least squares (LLS) to fit a delay-compensated dual-input single-compartment model to very high temporal resolution (four frames per second) contrast-enhanced 3D liver data, to calculate kinetic parameter maps. Using simulated data and experimental data in healthy subjects and patients, whole-field LLS was compared with the conventional voxel-wise nonlinear least-squares (NLLS) approach in terms of accuracy, performance, and computation time. Simulations showed good agreement between LLS and NLLS for a range of kinetic parameters. The whole-field LLS method allowed generating liver perfusion maps approximately 160-fold faster than voxel-wise NLLS, while obtaining similar perfusion parameters. Delay-compensated dual-input liver perfusion analysis using whole-field LLS allows generating perfusion maps with a considerable speedup compared with conventional voxel-wise NLLS fitting. Magn Reson Med 79:2415-2421, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Latency Determination and Compensation in Real-Time Gnss/ins Integrated Navigation Systems

NASA Astrophysics Data System (ADS)

Solomon, P. D.; Wang, J.; Rizos, C.

2011-09-01

Unmanned Aerial Vehicle (UAV) technology is now commonplace in many defence and civilian environments. However, the high cost of owning and operating a sophisticated UAV has slowed their adoption in many commercial markets. Universities and research groups are actively experimenting with UAVs to further develop the technology, particularly for automated flying operations. The two main UAV platforms used are fixed-wing and helicopter. Helicopter-based UAVs offer many attractive features over fixed-wing UAVs, including vertical take-off, the ability to loiter, and highly dynamic flight. However the control and navigation of helicopters are significantly more demanding than those of fixed-wing UAVs and as such require a high bandwidth real-time Position, Velocity, Attitude (PVA) navigation system. In practical Real-Time Navigation Systems (RTNS) there are delays in the processing of the GNSS data prior to the fusion of the GNSS data with the INS measurements. This latency must be compensated for otherwise it degrades the solution of the navigation filter. This paper investigates the effect of latency in the arrival time of the GNSS data in a RTNS. Several test drives and flights were conducted with a low-cost RTNS, and compared with a high quality GNSS/INS solution. A technique for the real-time, automated and accurate estimation of the GNSS latency in low-cost systems was developed and tested. The latency estimates were then verified through cross-correlation with the time-stamped measurements from the reference system. A delayed measurement Extended Kalman Filter was then used to allow for the real-time fusing of the delayed measurements, and then a final system developed for on-the-fly measurement and compensation of GNSS latency in a RTNS.

Seismic random noise removal by delay-compensation time-frequency peak filtering

NASA Astrophysics Data System (ADS)

Yu, Pengjun; Li, Yue; Lin, Hongbo; Wu, Ning

2017-06-01

Over the past decade, there has been an increasing awareness of time-frequency peak filtering (TFPF) due to its outstanding performance in suppressing non-stationary and strong seismic random noise. The traditional approach based on time-windowing achieves local linearity and meets the unbiased estimation. However, the traditional TFPF (including the improved algorithms with alterable window lengths) could hardly relieve the contradiction between removing noise and recovering the seismic signal, and this situation is more obvious in wave crests and troughs, even for alterable window lengths (WL). To improve the efficiency of the algorithm, the following TFPF in the time-space domain is applied, such as in the Radon domain and radial trace domain. The time-space transforms obtain a reduced-frequency input to reduce the TFPF error and stretch the desired signal along a certain direction, therefore the time-space development brings an improvement by both enhancing reflection events and attenuating noise. It still proves limited in application because the direction should be matched as a straight line or quadratic curve. As a result, waveform distortion and false seismic events may appear when processing the complex stratum record. The main emphasis in this article is placed on the time-space TFPF applicable expansion. The reconstructed signal in delay-compensation TFPF, which is generated according to the similarity among the reflection events, overcomes the limitation of the direction curve fitting. Moreover, the reconstructed signal just meets the TFPF linearity unbiased estimation and integrates signal reservation with noise attenuation. Experiments on both the synthetic model and field data indicate that delay-compensation TFPF has a better performance over the conventional filtering algorithms.

PMD compensation in multilevel coded-modulation schemes with coherent detection using BLAST algorithm and iterative polarization cancellation.

PubMed

Djordjevic, Ivan B; Xu, Lei; Wang, Ting

2008-09-15

We present two PMD compensation schemes suitable for use in multilevel (M>or=2) block-coded modulation schemes with coherent detection. The first scheme is based on a BLAST-type polarization-interference cancellation scheme, and the second scheme is based on iterative polarization cancellation. Both schemes use the LDPC codes as channel codes. The proposed PMD compensations schemes are evaluated by employing coded-OFDM and coherent detection. When used in combination with girth-10 LDPC codes those schemes outperform polarization-time coding based OFDM by 1 dB at BER of 10(-9), and provide two times higher spectral efficiency. The proposed schemes perform comparable and are able to compensate even 1200 ps of differential group delay with negligible penalty.

Time-varying delays compensation algorithm for powertrain active damping of an electrified vehicle equipped with an axle motor during regenerative braking

NASA Astrophysics Data System (ADS)

Zhang, Junzhi; Li, Yutong; Lv, Chen; Gou, Jinfang; Yuan, Ye

2017-03-01

The flexibility of the electrified powertrain system elicits a negative effect upon the cooperative control performance between regenerative and hydraulic braking and the active damping control performance. Meanwhile, the connections among sensors, controllers, and actuators are realized via network communication, i.e., controller area network (CAN), that introduces time-varying delays and deteriorates the control performances of the closed-loop control systems. As such, the goal of this paper is to develop a control algorithm to cope with all these challenges. To this end, the models of the stochastic network induced time-varying delays, based on a real in-vehicle network topology and on a flexible electrified powertrain, were firstly built. In order to further enhance the control performances of active damping and cooperative control of regenerative and hydraulic braking, the time-varying delays compensation algorithm for the electrified powertrain active damping during regenerative braking was developed based on a predictive scheme. The augmented system is constructed and the H∞ performance is analyzed. Based on this analysis, the control gains are derived by solving a nonlinear minimization problem. The simulations and hardware-in-loop (HIL) tests were carried out to validate the effectiveness of the developed algorithm. The test results show that the active damping and cooperative control performances are enhanced significantly.

Accurate time delay technology in simulated test for high precision laser range finder

NASA Astrophysics Data System (ADS)

Chen, Zhibin; Xiao, Wenjian; Wang, Weiming; Xue, Mingxi

2015-10-01

With the continuous development of technology, the ranging accuracy of pulsed laser range finder (LRF) is higher and higher, so the maintenance demand of LRF is also rising. According to the dominant ideology of "time analog spatial distance" in simulated test for pulsed range finder, the key of distance simulation precision lies in the adjustable time delay. By analyzing and comparing the advantages and disadvantages of fiber and circuit delay, a method was proposed to improve the accuracy of the circuit delay without increasing the count frequency of the circuit. A high precision controllable delay circuit was designed by combining the internal delay circuit and external delay circuit which could compensate the delay error in real time. And then the circuit delay accuracy could be increased. The accuracy of the novel circuit delay methods proposed in this paper was actually measured by a high sampling rate oscilloscope actual measurement. The measurement result shows that the accuracy of the distance simulated by the circuit delay is increased from +/- 0.75m up to +/- 0.15m. The accuracy of the simulated distance is greatly improved in simulated test for high precision pulsed range finder.

Effect of time delay on surgical performance during telesurgical manipulation.

PubMed

Fabrizio, M D; Lee, B R; Chan, D Y; Stoianovici, D; Jarrett, T W; Yang, C; Kavoussi, L R

2000-03-01

Telementoring allows a less experienced surgeon to benefit from an expert surgical consultation, reducing cost, travel, and the learning curve associated with new procedures. However, there are several technical limitations that affect practical applications. One potentially serious problem is the time delay that occurs any time data are transferred across long distances. To date, the effect of time delay on surgical performance has not been studied. A two-phase trial was designed to examine the effect of time delay on surgical performance. In the first phase, a series of tasks was performed, and the numbers of robotic movements required for completion was counted. Programmed incremental time delays were made in audiovisual acquisition and robotic controls. The number of errors made while performing each task at various time delay intervals was noted. In the second phase, a remote surgeon in Baltimore performed the tasks 9000 miles away in Singapore. The number of errors made was recorded. As the time delay increased, the number of operator errors increased. The accuracy needed to perform remote robotic procedures was diminished as the time delay increased. A learning curve did exist for each task, but as the time delay interval increased, it took longer to complete the task. Time delay does affect surgical performance. There is an acceptable delay of <700 msec in which surgeons can compensate for this phenomenon. Clinical studies will be needed to evaluate the true impact of time delay.

Research on the critical parameters initialization of optical PMD compensator in high bit-rate systems

NASA Astrophysics Data System (ADS)

Zhao, Wenyu; Zhang, Haiyi; Ji, Yuefeng; Xu, Daxiong

2004-05-01

Based on the proposed polarization mode dispersion (PMD) compensation simulation model and statistical analysis method (Monte-Carlo), the critical parameters initialization of two typical optical domain PMD compensators, which include optical PMD method with fixed compensation differential group delay (DGD) and that with variable compensation DGD, are detailedly investigated by numerical method. In the simulation, the line PMD values are chosen as 3ps, 4ps and 5ps and run samples are set to 1000 in order to achieve statistical evaluation for PMD compensated systems, respectively. The simulation results show that for the PMD value pre-known systems, the value of the fixed DGD compensator should be set to 1.5~1.6 times of line PMD value in order to reach the optimum performance, but for the second kind of PMD compensator, the DGD range of lower limit should be 1.5~1.6 times of line PMD provided that of upper limit is set to 3 times of line PMD, if no effective ways are chosen to resolve the problem of local minimum in optimum process. Another conclusion can be drawn from the simulation is that, although the second PMD compensator holds higher PMD compensation performance, it will spend more feedback loops to look up the optimum DGD value in the real PMD compensation realization, and this will bring more requirements on adjustable DGD device, not only wider adjustable range, but rapid adjusting speed for real time PMD equalization.

Dynamics of the Coupled Human-climate System Resulting from Closed-loop Control of Solar Geoengineering

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

MacMartin, Douglas; Kravitz, Benjamin S.; Keith, David

2014-07-08

If solar radiation management (SRM) were ever implemented, feedback of the observed climate state might be used to adjust the radiative forcing of SRM, in order to compensate for uncertainty in either the forcing or the climate response; this would also compensate for unexpected changes in the system, e.g. a nonlinear change in climate sensitivity. This feedback creates an emergent coupled human-climate system, with entirely new dynamics. In addition to the intended response to greenhouse-gas induced changes, the use of feedback would also result in a geoengineering response to natural climate variability. We use a simple box-diffusion dynamic model tomore » understand how changing feedback-control parameters and time delay affect the behavior of this coupled natural-human system, and verify these predictions using the HadCM3L general circulation model. In particular, some amplification of natural variability is unavoidable; any time delay (e.g., to average out natural variability, or due to decision-making) exacerbates this amplification, with oscillatory behavior possible if there is a desire for rapid correction (high feedback gain), but a delayed response needed for decision making. Conversely, the need for feedback to compensate for uncertainty, combined with a desire to avoid excessive amplification, results in a limit on how rapidly SRM could respond to uncertain changes.« less

Slow-light, band-edge waveguides for tunable time delays.

PubMed

Povinelli, M; Johnson, Steven; Joannopoulos, J

2005-09-05

We propose the use of slow-light, band-edge waveguides for compact, integrated, tunable optical time delays. We show that slow group velocities at the photonic band edge give rise to large changes in time delay for small changes in refractive index, thereby shrinking device size. Figures of merit are introduced to quantify the sensitivity, as well as the accompanying signal degradation due to dispersion. It is shown that exact calculations of the figures of merit for a realistic, three-dimensional grating structure are well predicted by a simple quadratic-band model, simplifying device design. We present adiabatic taper designs that attain <0.1% reflection in short lengths of 10 to 20 times the grating period. We show further that cascading two gratings compensates for signal dispersion and gives rise to a constant tunable time delay across bandwidths greater than 100GHz. Given typical loss values for silicon-on-insulator waveguides, we estimate that gratings can be designed to exhibit tunable delays in the picosecond range using current fabrication technology.

A new kind of relativity: Compensated delays as phenomenal blind spots.

PubMed

Vrobel, Susie

2015-12-01

The French phenomenologist Merleau-Ponty identified the human body as the blind spot of perception and cognition. Being situated in its environment both spatially and temporally, the body forms a primordial field of presence, which is transparent from the obserpant's(1) perspective and therefore creates a sytemic blindness. This paper is primarily concerned with what Merleau-Ponty calls the pulse of the duration of the body, which, in his view, "impregnates" our perception. This notion of duration will be described in terms of the temporal extensions of an embodied obserpant. For biological systems, these extensions may be measured in the obserpant's temporal endo-sphere, a time cone, which extends in two dimensions: succession and simultaneity (Δtlength and Δtdepth, respectively). Obserpants are described not as having, but being a model of the world (including themselves). The perception of Δtlength and Δtdepth results in a fractal temporal structure, which correlates with successive and instantaneous perception. This temporal structure becomes important during temporal recalibration, i.e. delay compensation. During such processes, the distribution of the temporal dimensions succession and simultaneity may vary from one obserpant's Now to another's. Furthermore, recalibration provides a window in which the obserpant's Now may be tipped towards either temporal dimension. We can measure the difference between obserpant A's temporal extension and that of obserpant B in Δtlength and Δtdepth. The complexity of an obserpant's temporal perspective - his temporal interface - can thus be compared and quantified by the size of his time cone. The units of this measurement are the number of compensated and uncompensated delays. During temporal recalibration, an obserpant can turn succession into simultaneity and vice-versa. Moreover, what is successive in obserpant A's Now may be simultaneous for obserpant B and vice-versa. This discrepancy can be modelled as time cones which display a new kind of (Δtlength-Δtdepth-) relativity. This new kind of relativity arises from the oberpants' inability to spot the systemic blindness that manifests itself in anticipated, i.e. compensated, delays. Copyright © 2015. Published by Elsevier Ltd.

Compensating for telecommunication delays during robotic telerehabilitation.

PubMed

Consoni, Leonardo J; Siqueira, Adriano A G; Krebs, Hermano I

2017-07-01

Rehabilitation robotic systems may afford better care and telerehabilitation may extend the use and benefits of robotic therapy to the home. Data transmissions over distance are bound by intrinsic communication delays which can be significant enough to deem the activity unfeasible. Here we describe an approach that combines unilateral robotic telerehabilitation and serious games. This approach has a modular and distributed design that permits different types of robots to interact without substantial code changes. We demonstrate the approach through an online multiplayer game. Two users can remotely interact with each other with no force exchanges, while a smoothing and prediction algorithm compensates motions for the delay in the Internet connection. We demonstrate that this approach can successfully compensate for data transmission delays, even when testing between the United States and Brazil. This paper presents the initial experimental results, which highlight the performance degradation with increasing delays as well as improvements provided by the proposed algorithm, and discusses planned future developments.

Acquisition of control skill with delayed and compensated displays.

PubMed

Ricard, G L

1995-09-01

The difficulty of mastering a two-axis, compensatory, manual control task was manipulated by introducing transport delays into the feedback loop of the controlled element. Realistic aircraft dynamics were used. Subjects' display was a simulation of an "inside-out" artificial horizon instrument perturbed by atmospheric turbulence. The task was to maintain straight and level flight, and delays tested were representative of those found in current training simulators. Delay compensations in the form of first-order lead and first-order lead/lag transfer functions, along with an uncompensated condition, were factorially combined with added delays. Subjects were required to meet a relatively strict criterion for performance. Control activity showed no differences during criterion performance, but the trials needed to achieve the criterion were linearly related to the magnitude of the delay and the compensation condition. These data were collected in the context of aircraft attitude control, but the results can be applied to the simulation of other vehicles, to remote manipulation, and to maneuvering in graphical environments.

Time Delay of CGM Sensors

PubMed Central

Schmelzeisen-Redeker, Günther; Schoemaker, Michael; Kirchsteiger, Harald; Freckmann, Guido; Heinemann, Lutz; del Re, Luigi

2015-01-01

Background: Continuous glucose monitoring (CGM) is a powerful tool to support the optimization of glucose control of patients with diabetes. However, CGM systems measure glucose in interstitial fluid but not in blood. Rapid changes in one compartment are not accompanied by similar changes in the other, but follow with some delay. Such time delays hamper detection of, for example, hypoglycemic events. Our aim is to discuss the causes and extent of time delays and approaches to compensate for these. Methods: CGM data were obtained in a clinical study with 37 patients with a prototype glucose sensor. The study was divided into 5 phases over 2 years. In all, 8 patients participated in 2 phases separated by 8 months. A total number of 108 CGM data sets including raw signals were used for data analysis and were processed by statistical methods to obtain estimates of the time delay. Results: Overall mean (SD) time delay of the raw signals with respect to blood glucose was 9.5 (3.7) min, median was 9 min (interquartile range 4 min). Analysis of time delays observed in the same patients separated by 8 months suggests a patient dependent delay. No significant correlation was observed between delay and anamnestic or anthropometric data. The use of a prediction algorithm reduced the delay by 4 minutes on average. Conclusions: Prediction algorithms should be used to provide real-time CGM readings more consistent with simultaneous measurements by SMBG. Patient specificity may play an important role in improving prediction quality. PMID:26243773

Application of fuzzy adaptive control to a MIMO nonlinear time-delay pump-valve system.

PubMed

Lai, Zhounian; Wu, Peng; Wu, Dazhuan

2015-07-01

In this paper, a control strategy to balance the reliability against efficiency is introduced to overcome the common off-design operation problem in pump-valve systems. The pump-valve system is a nonlinear multi-input-multi-output (MIMO) system with time delays which cannot be accurately measured but can be approximately modeled using Bernoulli Principle. A fuzzy adaptive controller is applied to approximate system parameters and achieve the control of delay-free model since the system model is inaccurate and the direct feedback linearization method cannot be applied. An extended Smith predictor is introduced to compensate time delays of the system using the inaccurate system model. The experiment is carried out to verify the effectiveness of the control strategy whose results show that the control performance is well achieved. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Intraspecific priority effects modify compensatory responses to changes in hatching phenology in an amphibian.

PubMed

Murillo-Rincón, Andrea P; Kolter, Nora A; Laurila, Anssi; Orizaola, Germán

2017-01-01

In seasonal environments, modifications in the phenology of life-history events can alter the strength of time constraints experienced by organisms. Offspring can compensate for a change in timing of hatching by modifying their growth and development trajectories. However, intra- and interspecific interactions may affect these compensatory responses, in particular if differences in phenology between cohorts lead to significant priority effects (i.e. the competitive advantage that early-hatching individuals have over late-hatching ones). Here, we conducted a factorial experiment to determine whether intraspecific priority effects can alter compensatory phenotypic responses to hatching delay in a synchronic breeder by rearing moor frog (Rana arvalis) tadpoles in different combinations of phenological delay and food abundance. Tadpoles compensated for the hatching delay by speeding up their development, but only when reared in groups of individuals with identical hatching phenology. In mixed phenology groups, strong competitive effects by non-delayed tadpoles prevented the compensatory responses and delayed larvae metamorphosed later than in single phenology treatments. Non-delayed individuals gained advantage from developing with delayed larvae by increasing their developmental and growth rates as compared to single phenology groups. Food shortage prolonged larval period and reduced mass at metamorphosis in all treatments, but it did not prevent compensatory developmental responses in larvae reared in single phenology groups. This study demonstrates that strong intraspecific priority effects can constrain the compensatory growth and developmental responses to phenological change, and that priority effects can be an important factor explaining the maintenance of synchronic life histories (i.e. explosive breeding) in seasonal environments. © 2016 The Authors. Journal of Animal Ecology © 2016 British Ecological Society.

Advanced aeroservoelastic stabilization techniques for hypersonic flight vehicles

NASA Technical Reports Server (NTRS)

Chan, Samuel Y.; Cheng, Peter Y.; Myers, Thomas T.; Klyde, David H.; Magdaleno, Raymond E.; Mcruer, Duane T.

1992-01-01

Advanced high performance vehicles, including Single-Stage-To-Orbit (SSTO) hypersonic flight vehicles, that are statically unstable, require higher bandwidth flight control systems to compensate for the instability resulting in interactions between the flight control system, the engine/propulsion dynamics, and the low frequency structural modes. Military specifications, such as MIL-F-9490D and MIL-F-87242, tend to limit treatment of structural modes to conventional gain stabilization techniques. The conventional gain stabilization techniques, however, introduce low frequency effective time delays which can be troublesome from a flying qualities standpoint. These time delays can be alleviated by appropriate blending of gain and phase stabilization techniques (referred to as Hybrid Phase Stabilization or HPS) for the low frequency structural modes. The potential of using HPS for compensating structural mode interaction was previously explored. It was shown that effective time delay was significantly reduced with the use of HPS; however, the HPS design was seen to have greater residual response than a conventional gain stablized design. Additional work performed to advance and refine the HPS design procedure, to further develop residual response metrics as a basis for alternative structural stability specifications, and to develop strategies for validating HPS design and specification concepts in manned simulation is presented. Stabilization design sensitivity to structural uncertainties and aircraft-centered requirements are also assessed.

System design of the annular suspension and pointing system /ASPS/

NASA Technical Reports Server (NTRS)

Cunningham, D. C.; Gismondi, T. P.; Wilson, G. W.

1978-01-01

This paper presents the control system design for the Annular Suspension and Pointing System. Actuator sizing and configuration of the system are explained, and the control laws developed for linearizing and compensating the magnetic bearings, roll induction motor and gimbal torquers are given. Decoupling, feedforward and error compensation for the vernier and gimbal controllers is developed. The algorithm for computing the strapdown attitude reference is derived, and the allowable sampling rates, time delays and quantization of control signals are specified.

Injury Compensation Process Delays Prompt Payment of Benefits to Federal Workers.

DTIC Science & Technology

1981-09-25

Prompt Payment 9f Benefits 0 Federal Workers , "fem of benefits under the Federal Employees ’ Compen- , m Act am not being made on time a measured by the...A worker may also appeal adverse decisions to the Employees ’ Compensation Appeals Board. The Board is a quasi-judicial board of three members...agencies to distribute these pamphlets to workers . Similar instruc- tions are contained on Poster CA-10 "What a Federal Employee Should Do When

Cable delay compensator for microwave signal distribution over optical fibers

NASA Astrophysics Data System (ADS)

Primas, Lori E.

1990-12-01

The basic principles of microwave fiber-optic systems are outlined with emphasis on fiber-optic cable delay compensators (CDC). Degradation of frequency and phase stability is considered, and it is pointed out that the long-term stability of a fiber-optic link is degraded by group delay variations due to temperature fluctuations in the optical fiber and low-frequency noise characteristics of the laser. A CDC employing a voltage-controlled oscillator to correct for phase variations in the optical fiber is presented, and the static as well as dynamic closed-loop analyses of the fiber-optic CDC are discussed. A constructed narrow-band fiber-optic CDC is shown to reduce phase variations caused by temperature fluctuations by a factor of 400. A wide-band CDC utilizing a temperature-controlled coil of fiber to compensate for phase delay is also proposed.

Approximation-based adaptive tracking control of pure-feedback nonlinear systems with multiple unknown time-varying delays.

PubMed

Wang, Min; Ge, Shuzhi Sam; Hong, Keum-Shik

2010-11-01

This paper presents adaptive neural tracking control for a class of non-affine pure-feedback systems with multiple unknown state time-varying delays. To overcome the design difficulty from non-affine structure of pure-feedback system, mean value theorem is exploited to deduce affine appearance of state variables x(i) as virtual controls α(i), and of the actual control u. The separation technique is introduced to decompose unknown functions of all time-varying delayed states into a series of continuous functions of each delayed state. The novel Lyapunov-Krasovskii functionals are employed to compensate for the unknown functions of current delayed state, which is effectively free from any restriction on unknown time-delay functions and overcomes the circular construction of controller caused by the neural approximation of a function of u and [Formula: see text] . Novel continuous functions are introduced to overcome the design difficulty deduced from the use of one adaptive parameter. To achieve uniformly ultimate boundedness of all the signals in the closed-loop system and tracking performance, control gains are effectively modified as a dynamic form with a class of even function, which makes stability analysis be carried out at the present of multiple time-varying delays. Simulation studies are provided to demonstrate the effectiveness of the proposed scheme.

Predictive Compensator Optimization for Head Tracking Lag in Virtual Environments

NASA Technical Reports Server (NTRS)

Adelstein, Barnard D.; Jung, Jae Y.; Ellis, Stephen R.

2001-01-01

We examined the perceptual impact of plant noise parameterization for Kalman Filter predictive compensation of time delays intrinsic to head tracked virtual environments (VEs). Subjects were tested in their ability to discriminate between the VE system's minimum latency and conditions in which artificially added latency was then predictively compensated back to the system minimum. Two head tracking predictors were parameterized off-line according to cost functions that minimized prediction errors in (1) rotation, and (2) rotation projected into translational displacement with emphasis on higher frequency human operator noise. These predictors were compared with a parameterization obtained from the VE literature for cost function (1). Results from 12 subjects showed that both parameterization type and amount of compensated latency affected discrimination. Analysis of the head motion used in the parameterizations and the subsequent discriminability results suggest that higher frequency predictor artifacts are contributory cues for discriminating the presence of predictive compensation.

Which Characteristics are Associated with the Timing of the First Healthcare Consultation, and Does the Time to Care Influence the Duration of Compensation for Occupational Back Pain?

PubMed

Blanchette, Marc-André; Rivard, Michèle; Dionne, Clermont E; Steenstra, Ivan; Hogg-Johnson, Sheilah

2017-09-01

Purpose To identify the characteristics associated with the timing of the first healthcare consultation and to measure the impact of that timing on the duration of the first episode of compensation for occupational back pain following the injury. Methods We analyzed data from a cohort of workers with compensated back pain in 2005 in Ontario obtained from the Workplace Safety and Insurance Board. Cox multivariable survival models were performed to identify factors associated with the time to care and to measure its association with the length of the first episode of 100 % compensation. Results Among the 5520 claims analyzed, 93.7 % of workers accessed care within the first week (average = 2.1 days; median = 1 day). Time to care was shorter for males, for workers who had received previous compensation and for those with access to an early return to work program. Age, number of employees in the company and personal earnings were positively associated with the time to care. More severe nature of injury, employers doubt about the work-relatedness of the injury and consulting a physiotherapist as the first healthcare provider were also associated with longer time to care. Considering potential confounders, longer time to care was significantly associated with a delay in the end of the first episode of compensation (hazard ratio = 0.98; P < 0.001). Conclusion Temporal access to a source of care is not problematic for the vast majority of Ontarian workers who receive compensation for occupational back pain; however, for the minority of workers who do not rapidly access care, the timing of the first healthcare consultation is a significant predictor of the duration of the first episode of compensation.

Cognitive Compensation of Speech Perception With Hearing Impairment, Cochlear Implants, and Aging

PubMed Central

Clarke, Jeanne; Pals, Carina; Benard, Michel R.; Bhargava, Pranesh; Saija, Jefta; Sarampalis, Anastasios; Wagner, Anita; Gaudrain, Etienne

2016-01-01

External degradations in incoming speech reduce understanding, and hearing impairment further compounds the problem. While cognitive mechanisms alleviate some of the difficulties, their effectiveness may change with age. In our research, reviewed here, we investigated cognitive compensation with hearing impairment, cochlear implants, and aging, via (a) phonemic restoration as a measure of top-down filling of missing speech, (b) listening effort and response times as a measure of increased cognitive processing, and (c) visual world paradigm and eye gazing as a measure of the use of context and its time course. Our results indicate that between speech degradations and their cognitive compensation, there is a fine balance that seems to vary greatly across individuals. Hearing impairment or inadequate hearing device settings may limit compensation benefits. Cochlear implants seem to allow the effective use of sentential context, but likely at the cost of delayed processing. Linguistic and lexical knowledge, which play an important role in compensation, may be successfully employed in advanced age, as some compensatory mechanisms seem to be preserved. These findings indicate that cognitive compensation in hearing impairment can be highly complicated—not always absent, but also not easily predicted by speech intelligibility tests only.

Compensation for Transport Delays Produced by Computer Image Generation Systems. Cooperative Training Series.

ERIC Educational Resources Information Center

Ricard, G. L.; And Others

The cooperative Navy/Air Force project described is aimed at the problem of image-flutter encountered when visual displays that present computer generated images are used for the simulation of certain flying situations. Two experiments are described which extend laboratory work on delay compensation schemes to the simulation of formation flight in…

Centering a DDR Strobe in the Middle of a Data Packet

NASA Technical Reports Server (NTRS)

Johnson, Michael; Nelson, Dave; Seefeldt, James; Roper, Weston; Passow, Craig

2014-01-01

The Orion CEV Northstar ASIC (application- specific integrated circuit) project required a DDR (double data rate) memory bus driver/receiver (DDR PHY block) to interface with external DDR memory. The DDR interface (JESD79C) is based on a source synchronous strobe (DQS\\) that is sent along with each packet of data (DQ). New data is provided concurrently with each edge of strobe and is sent irregularly. In order to capture this data, the strobe needs to be delayed and used to latch the data into a register. A circuit solves the need for training a DDR PRY block by incorporating a PVT-compensated delay element in the strobe path. This circuit takes an external reference clock signal and uses the regular clock to calibrate a known delay through a data path. The compensated delay DQS signal is then used to capture the DQ data in a normal register. This register structure can be configured as a FIFO (first in first out), in order to transfer data from the DDR domain to the system clock domain. This design is different in that it does not rely upon the need for training the system response, nor does it use a PLL (phase locked loop) or a DLL (delay locked loop) to provide an offset of the strobe signal. The circuit is created using standard ASIC building blocks, plus the PVT (process, voltage, and temperature) compensated delay line. The design uses a globally available system clock as a reference, alleviating the need to operate synchronously with the remote memory. The reference clock conditions the PVT compensated delay line to provide a pre-determined amount of delay to any data signal that passes through this delay line. The delay line is programmed in degrees of offset, so that one could think of the clock period representing 360deg of delay. In an ideal environment, delaying the strobe 1/4 of a clock cycle (90deg) would place the strobe in the middle of the data packet. This delayed strobe can then be used to clock the data into a register, satisfying setup and hold requirements of the system.

Summary of the effects of engine throttle response on airplane formation-flying qualities

NASA Technical Reports Server (NTRS)

Walsh, Kevin R.

1992-01-01

A flight evaluation as conducted to determine the effect of engine throttle response characteristics on precision formation-flying qualities. A variable electronic throttle control system was developed and flight-tested on a TF-104G airplane with a J79-11B engine at the NASA Dryden Flight Research Facility. Ten research flights were flown to evaluate the effects of throttle gain, time delay, and fuel control rate limiting on engine handling qualities during a demanding precision wing formation task. Handling quality effects of lag filters and lead compensation time delays were also evaluated. Data from pilot ratings and comments indicate that throttle control system time delays and rate limits cause significant degradations in handling qualities. Threshold values for satisfactory (level 1) and adequate (level 2) handling qualities of these key variables are presented.

Development of a decentralized multi-axis synchronous control approach for real-time networks.

PubMed

Xu, Xiong; Gu, Guo-Ying; Xiong, Zhenhua; Sheng, Xinjun; Zhu, Xiangyang

2017-05-01

The message scheduling and the network-induced delays of real-time networks, together with the different inertias and disturbances in different axes, make the synchronous control of the real-time network-based systems quite challenging. To address this challenge, a decentralized multi-axis synchronous control approach is developed in this paper. Due to the limitations of message scheduling and network bandwidth, error of the position synchronization is firstly defined in the proposed control approach as a subset of preceding-axis pairs. Then, a motion message estimator is designed to reduce the effect of network delays. It is proven that position and synchronization errors asymptotically converge to zero in the proposed controller with the delay compensation. Finally, simulation and experimental results show that the developed control approach can achieve the good position synchronization performance for the multi-axis motion over the real-time network. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

The Results of a Simulator Study to Determine the Effects on Pilot Performance of Two Different Motion Cueing Algorithms and Various Delays, Compensated and Uncompensated

NASA Technical Reports Server (NTRS)

Guo, Li-Wen; Cardullo, Frank M.; Telban, Robert J.; Houck, Jacob A.; Kelly, Lon C.

2003-01-01

A study was conducted employing the Visual Motion Simulator (VMS) at the NASA Langley Research Center, Hampton, Virginia. This study compared two motion cueing algorithms, the NASA adaptive algorithm and a new optimal control based algorithm. Also, the study included the effects of transport delays and the compensation thereof. The delay compensation algorithm employed is one developed by Richard McFarland at NASA Ames Research Center. This paper reports on the analyses of the results of analyzing the experimental data collected from preliminary simulation tests. This series of tests was conducted to evaluate the protocols and the methodology of data analysis in preparation for more comprehensive tests which will be conducted during the spring of 2003. Therefore only three pilots were used. Nevertheless some useful results were obtained. The experimental conditions involved three maneuvers; a straight-in approach with a rotating wind vector, an offset approach with turbulence and gust, and a takeoff with and without an engine failure shortly after liftoff. For each of the maneuvers the two motion conditions were combined with four delay conditions (0, 50, 100 & 200ms), with and without compensation.

Further development of the attitude difference method for estimating deflections of the vertical in real time

NASA Astrophysics Data System (ADS)

Zhu, Jing; Zhou, Zebo; Li, Yong; Rizos, Chris; Wang, Xingshu

2016-07-01

An improvement of the attitude difference method (ADM) to estimate deflections of the vertical (DOV) in real time is described in this paper. The ADM without offline processing estimates the DOV with a limited accuracy due to the response delay. The proposed model selection-based self-adaptive delay feedback (SDF) method takes the results of the ADM as the a priori information, then uses fitting and extrapolation to estimate the DOV at the current epoch. The active region selection factor F th is used to take full advantage of the Earth model EGM2008 and the SDF with different DOV exhibitions. The factors which affect the DOV estimation accuracy are analyzed and modeled. An external observation which is specified by the velocity difference between the global navigation satellite system (GNSS) and the inertial navigation system (INS) with DOV compensated is used to select the optimal model. The response delay induced by the weak observability of an integrated INS/GNSS to the violent DOV disturbances in the ADM is compensated. The DOV estimation accuracy of the SDF method is improved by approximately 40% and 50% respectively compared to that of the EGM2008 and the ADM. With an increase in GNSS accuracy, the DOV estimation accuracy could improve further.

Effects of sport expertise on representational momentum during timing control.

PubMed

Nakamoto, Hiroki; Mori, Shiro; Ikudome, Sachi; Unenaka, Satoshi; Imanaka, Kuniyasu

2015-04-01

Sports involving fast visual perception require players to compensate for delays in neural processing of visual information. Memory for the final position of a moving object is distorted forward along its path of motion (i.e., "representational momentum," RM). This cognitive extrapolation of visual perception might compensate for the neural delay in interacting appropriately with a moving object. The present study examined whether experienced batters cognitively extrapolate the location of a fast-moving object and whether this extrapolation is associated with coincident timing control. Nine expert and nine novice baseball players performed a prediction motion task in which a target moved from one end of a straight 400-cm track at a constant velocity. In half of the trials, vision was suddenly occluded when the target reached the 200-cm point (occlusion condition). Participants had to press a button concurrently with the target arrival at the end of the track and verbally report their subjective assessment of the first target-occluded position. Experts showed larger RM magnitude (cognitive extrapolation) than did novices in the occlusion condition. RM magnitude and timing errors were strongly correlated in the fast velocity condition in both experts and novices, whereas in the slow velocity condition, a significant correlation appeared only in experts. This suggests that experts can cognitively extrapolate the location of a moving object according to their anticipation and, as a result, potentially circumvent neural processing delays. This process might be used to control response timing when interacting with moving objects.

Predictive and postdictive mechanisms jointly contribute to visual awareness.

PubMed

Soga, Ryosuke; Akaishi, Rei; Sakai, Katsuyuki

2009-09-01

One of the fundamental issues in visual awareness is how we are able to perceive the scene in front of our eyes on time despite the delay in processing visual information. The prediction theory postulates that our visual system predicts the future to compensate for such delays. On the other hand, the postdiction theory postulates that our visual awareness is inevitably a delayed product. In the present study we used flash-lag paradigms in motion and color domains and examined how the perception of visual information at the time of flash is influenced by prior and subsequent visual events. We found that both types of event additively influence the perception of the present visual image, suggesting that our visual awareness results from joint contribution of predictive and postdictive mechanisms.

Distributed optimisation problem with communication delay and external disturbance

NASA Astrophysics Data System (ADS)

Tran, Ngoc-Tu; Xiao, Jiang-Wen; Wang, Yan-Wu; Yang, Wu

2017-12-01

This paper investigates the distributed optimisation problem for the multi-agent systems (MASs) with the simultaneous presence of external disturbance and the communication delay. To solve this problem, a two-step design scheme is introduced. In the first step, based on the internal model principle, the internal model term is constructed to compensate the disturbance asymptotically. In the second step, a distributed optimisation algorithm is designed to solve the distributed optimisation problem based on the MASs with the simultaneous presence of disturbance and communication delay. Moreover, in the proposed algorithm, each agent interacts with its neighbours through the connected topology and the delay occurs during the information exchange. By utilising Lyapunov-Krasovskii functional, the delay-dependent conditions are derived for both slowly and fast time-varying delay, respectively, to ensure the convergence of the algorithm to the optimal solution of the optimisation problem. Several numerical simulation examples are provided to illustrate the effectiveness of the theoretical results.

Compensating measured intra-wafer ring oscillator stage delay with intra-wafer exposure dose corrections

NASA Astrophysics Data System (ADS)

Verhaegen, Staf; Nackaerts, Axel; Dusa, Mircea; Carpaij, Rene; Vandenberghe, Geert; Finders, Jo

2006-03-01

The purpose of this paper is to use measurements on real working devices to derive more information than typically measured by the classic line-width measurement techniques. The first part of the paper will discuss the principle of the measurements with a ring oscillator, a circuit used to measure the speed of elementary logic gates. These measurements contribute to the understanding of the exact timing dependencies in circuits, which is of utmost importance for the design and simulation of these circuits. When connecting an odd number of digital inverting stages in a ring, the circuit has no stable digital state but acts as an analog oscillator with the oscillation frequency dependent on the analog propagation delay of the signals through the stages. By varying some conditions during a litho step, the delay change caused by the process condition change can be measured very accurately. The response of the ring oscillator delay to exposure dose is measured and presented in this paper together with a comparison of measured line-width values of the poly gate lines. The second part of the paper will focus on improving the intra-wafer variation of the stage delay. A number of ring oscillators are put in a design at different slit and scan locations. 200mm wafers are processed with 48 full dies present. From the intra-wafer delay fingerprint and the dose sensitivity of the delay an intra-wafer dose correction, also called a dose recipe, is calculated. This dose recipe is used on the scanner to compensate for effects that are the root cause for the delay profile; including reticle and processing such as track, etch and annealing.

Multirate parallel distributed compensation of a cluster in wireless sensor and actor networks

NASA Astrophysics Data System (ADS)

Yang, Chun-xi; Huang, Ling-yun; Zhang, Hao; Hua, Wang

2016-01-01

The stabilisation problem for one of the clusters with bounded multiple random time delays and packet dropouts in wireless sensor and actor networks is investigated in this paper. A new multirate switching model is constructed to describe the feature of this single input multiple output linear system. According to the difficulty of controller design under multi-constraints in multirate switching model, this model can be converted to a Takagi-Sugeno fuzzy model. By designing a multirate parallel distributed compensation, a sufficient condition is established to ensure this closed-loop fuzzy control system to be globally exponentially stable. The solution of the multirate parallel distributed compensation gains can be obtained by solving an auxiliary convex optimisation problem. Finally, two numerical examples are given to show, compared with solving switching controller, multirate parallel distributed compensation can be obtained easily. Furthermore, it has stronger robust stability than arbitrary switching controller and single-rate parallel distributed compensation under the same conditions.

Error compensation for hybrid-computer solution of linear differential equations

NASA Technical Reports Server (NTRS)

Kemp, N. H.

1970-01-01

Z-transform technique compensates for digital transport delay and digital-to-analog hold. Method determines best values for compensation constants in multi-step and Taylor series projections. Technique also provides hybrid-calculation error compared to continuous exact solution, plus system stability properties.

Generation of the Human Biped Stance by a Neural Controller Able to Compensate Neurological Time Delay

PubMed Central

Jiang, Ping; Chiba, Ryosuke; Takakusaki, Kaoru; Ota, Jun

2016-01-01

The development of a physiologically plausible computational model of a neural controller that can realize a human-like biped stance is important for a large number of potential applications, such as assisting device development and designing robotic control systems. In this paper, we develop a computational model of a neural controller that can maintain a musculoskeletal model in a standing position, while incorporating a 120-ms neurological time delay. Unlike previous studies that have used an inverted pendulum model, a musculoskeletal model with seven joints and 70 muscular-tendon actuators is adopted to represent the human anatomy. Our proposed neural controller is composed of both feed-forward and feedback controls. The feed-forward control corresponds to the constant activation input necessary for the musculoskeletal model to maintain a standing posture. This compensates for gravity and regulates stiffness. The developed neural controller model can replicate two salient features of the human biped stance: (1) physiologically plausible muscle activations for quiet standing; and (2) selection of a low active stiffness for low energy consumption. PMID:27655271

A Multi-Center Space Data System Prototype Based on CCSDS Standards

NASA Technical Reports Server (NTRS)

Rich, Thomas M.

2016-01-01

Deep space missions beyond earth orbit will require new methods of data communications in order to compensate for increasing RF propagation delay. The Consultative Committee for Space Data Systems (CCSDS) standard protocols Spacecraft Monitor & Control (SM&C), Asynchronous Message Service (AMS), and Delay/Disruption Tolerant Networking (DTN) provide such a method. The maturity level of this protocol set is, however, insufficient for mission inclusion at this time. This prototype is intended to provide experience which will raise the Technical Readiness Level (TRL) of these protocols..

Efficiency analysis of numerical integrations for finite element substructure in real-time hybrid simulation

NASA Astrophysics Data System (ADS)

Wang, Jinting; Lu, Liqiao; Zhu, Fei

2018-01-01

Finite element (FE) is a powerful tool and has been applied by investigators to real-time hybrid simulations (RTHSs). This study focuses on the computational efficiency, including the computational time and accuracy, of numerical integrations in solving FE numerical substructure in RTHSs. First, sparse matrix storage schemes are adopted to decrease the computational time of FE numerical substructure. In this way, the task execution time (TET) decreases such that the scale of the numerical substructure model increases. Subsequently, several commonly used explicit numerical integration algorithms, including the central difference method (CDM), the Newmark explicit method, the Chang method and the Gui-λ method, are comprehensively compared to evaluate their computational time in solving FE numerical substructure. CDM is better than the other explicit integration algorithms when the damping matrix is diagonal, while the Gui-λ (λ = 4) method is advantageous when the damping matrix is non-diagonal. Finally, the effect of time delay on the computational accuracy of RTHSs is investigated by simulating structure-foundation systems. Simulation results show that the influences of time delay on the displacement response become obvious with the mass ratio increasing, and delay compensation methods may reduce the relative error of the displacement peak value to less than 5% even under the large time-step and large time delay.

A programmable time alignment scheme for detector signals from the upgraded muon spectrometer at the ATLAS experiment

NASA Astrophysics Data System (ADS)

Wang, Jinhong; Guan, Liang; Chapman, J.; Zhou, Bing; Zhu, Junjie

2017-11-01

We present a programmable time alignment scheme used in an ASIC for the ATLAS forward muon trigger development. The scheme utilizes regenerated clocks with programmable phases to compensate for the timing offsets introduced by different detector trace lengths. Each ASIC used in the design has 104 input channels with delay compensation circuitry providing steps of ∼3 ns and a full range of 25 ns for each channel. Detailed implementation of the scheme including majority logic to suppress single-event effects is presented. The scheme is flexible and fully synthesizable. The approach is adaptable to other applications with similar phase shifting requirements. In addition, the design is resource efficient and is suitable for cost-effective digital implementation with a large number of channels.

Commissioning of an integrated platform for time-resolved treatment delivery in scanned ion beam therapy by means of optical motion monitoring.

PubMed

Fattori, G; Saito, N; Seregni, M; Kaderka, R; Pella, A; Constantinescu, A; Riboldi, M; Steidl, P; Cerveri, P; Bert, C; Durante, M; Baroni, G

2014-12-01

The integrated use of optical technologies for patient monitoring is addressed in the framework of time-resolved treatment delivery for scanned ion beam therapy. A software application has been designed to provide the therapy control system (TCS) with a continuous geometrical feedback by processing the external surrogates tridimensional data, detected in real-time via optical tracking. Conventional procedures for phase-based respiratory phase detection were implemented, as well as the interface to patient specific correlation models, in order to estimate internal tumor motion from surface markers. In this paper, particular attention is dedicated to the quantification of time delays resulting from system integration and its compensation by means of polynomial interpolation in the time domain. Dedicated tests to assess the separate delay contributions due to optical signal processing, digital data transfer to the TCS and passive beam energy modulation actuation have been performed. We report the system technological commissioning activities reporting dose distribution errors in a phantom study, where the treatment of a lung lesion was simulated, with both lateral and range beam position compensation. The zero-delay systems integration with a specific active scanning delivery machine was achieved by tuning the amount of time prediction applied to lateral (14.61 ± 0.98 ms) and depth (34.1 ± 6.29 ms) beam position correction signals, featuring sub-millimeter accuracy in forward estimation. Direct optical target observation and motion phase (MPh) based tumor motion discretization strategies were tested, resulting in 20.3(2.3)% and 21.2(9.3)% median (IQR) percentual relative dose difference with respect to static irradiation, respectively. Results confirm the technical feasibility of the implemented strategy towards 4D treatment delivery, with negligible percentual dose deviations with respect to static irradiation.

Transport delay compensation for computer-generated imagery systems

NASA Technical Reports Server (NTRS)

Mcfarland, Richard E.

1988-01-01

In the problem of pure transport delay in a low-pass system, a trade-off exists with respect to performance within and beyond a frequency bandwidth. When activity beyond the band is attenuated because of other considerations, this trade-off may be used to improve the performance within the band. Specifically, transport delay in computer-generated imagery systems is reduced to a manageable problem by recognizing frequency limits in vehicle activity and manual-control capacity. Based on these limits, a compensation algorithm has been developed for use in aircraft simulation at NASA Ames Research Center. For direct measurement of transport delays, a beam-splitter experiment is presented that accounts for the complete flight simulation environment. Values determined by this experiment are appropriate for use in the compensation algorithm. The algorithm extends the bandwidth of high-frequency flight simulation to well beyond that of normal pilot inputs. Within this bandwidth, the visual scene presentation manifests negligible gain distortion and phase lag. After a year of utilization, two minor exceptions to universal simulation applicability have been identified and subsequently resolved.

A linearization time-domain CMOS smart temperature sensor using a curvature compensation oscillator.

PubMed

Chen, Chun-Chi; Chen, Hao-Wen

2013-08-28

This paper presents an area-efficient time-domain CMOS smart temperature sensor using a curvature compensation oscillator for linearity enhancement with a -40 to 120 °C temperature range operability. The inverter-based smart temperature sensors can substantially reduce the cost and circuit complexity of integrated temperature sensors. However, a large curvature exists on the temperature-to-time transfer curve of the inverter-based delay line and results in poor linearity of the sensor output. For cost reduction and error improvement, a temperature-to-pulse generator composed of a ring oscillator and a time amplifier was used to generate a thermal sensing pulse with a sufficient width proportional to the absolute temperature (PTAT). Then, a simple but effective on-chip curvature compensation oscillator is proposed to simultaneously count and compensate the PTAT pulse with curvature for linearization. With such a simple structure, the proposed sensor possesses an extremely small area of 0.07 mm2 in a TSMC 0.35-mm CMOS 2P4M digital process. By using an oscillator-based scheme design, the proposed sensor achieves a fine resolution of 0.045 °C without significantly increasing the circuit area. With the curvature compensation, the inaccuracy of -1.2 to 0.2 °C is achieved in an operation range of -40 to 120 °C after two-point calibration for 14 packaged chips. The power consumption is measured as 23 mW at a sample rate of 10 samples/s.

A method for calculating minimum biodiversity offset multipliers accounting for time discounting, additionality and permanence

PubMed Central

Laitila, Jussi; Moilanen, Atte; Pouzols, Federico M

2014-01-01

Biodiversity offsetting, which means compensation for ecological and environmental damage caused by development activity, has recently been gaining strong political support around the world. One common criticism levelled at offsets is that they exchange certain and almost immediate losses for uncertain future gains. In the case of restoration offsets, gains may be realized after a time delay of decades, and with considerable uncertainty. Here we focus on offset multipliers, which are ratios between damaged and compensated amounts (areas) of biodiversity. Multipliers have the attraction of being an easily understandable way of deciding the amount of offsetting needed. On the other hand, exact values of multipliers are very difficult to compute in practice if at all possible. We introduce a mathematical method for deriving minimum levels for offset multipliers under the assumption that offsetting gains must compensate for the losses (no net loss offsetting). We calculate absolute minimum multipliers that arise from time discounting and delayed emergence of offsetting gains for a one-dimensional measure of biodiversity. Despite the highly simplified model, we show that even the absolute minimum multipliers may easily be quite large, in the order of dozens, and theoretically arbitrarily large, contradicting the relatively low multipliers found in literature and in practice. While our results inform policy makers about realistic minimal offsetting requirements, they also challenge many current policies and show the importance of rigorous models for computing (minimum) offset multipliers. The strength of the presented method is that it requires minimal underlying information. We include a supplementary spreadsheet tool for calculating multipliers to facilitate application. PMID:25821578

Design of an optimal preview controller for linear discrete-time descriptor systems with state delay

NASA Astrophysics Data System (ADS)

Cao, Mengjuan; Liao, Fucheng

2015-04-01

In this paper, the linear discrete-time descriptor system with state delay is studied, and a design method for an optimal preview controller is proposed. First, by using the discrete lifting technique, the original system is transformed into a general descriptor system without state delay in form. Then, taking advantage of the first-order forward difference operator, we construct a descriptor augmented error system, including the state vectors of the lifted system, error vectors, and desired target signals. Rigorous mathematical proofs are given for the regularity, stabilisability, causal controllability, and causal observability of the descriptor augmented error system. Based on these, the optimal preview controller with preview feedforward compensation for the original system is obtained by using the standard optimal regulator theory of the descriptor system. The effectiveness of the proposed method is shown by numerical simulation.

Predictor-based control for an inverted pendulum subject to networked time delay.

PubMed

Ghommam, J; Mnif, F

2017-03-01

The inverted pendulum is considered as a special class of underactuated mechanical systems with two degrees of freedom and a single control input. This mechanical configuration allows to transform the underactuated system into a nonlinear system that is referred to as the normal form, whose control design techniques for stabilization are well known. In the presence of time delays, these control techniques may result in inadequate behavior and may even cause finite escape time in the controlled system. In this paper, a constructive method is presented to design a controller for an inverted pendulum characterized by a time-delayed balance control. First, the partial feedback linearization control for the inverted pendulum is modified and coupled with a state predictor to compensate for the delay. Several coordinate transformations are processed to transform the estimated partial linearized system into an upper-triangular form. Second, nested saturation and backstepping techniques are combined to derive the control law of the transformed system that would complete the design of the whole control input. The effectiveness of the proposed technique is illustrated by numerical simulations. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Laminar burning velocity and ignition delay time for premixed isooctane-air flames with syngas addition

NASA Astrophysics Data System (ADS)

Bhattacharya, Atmadeep; Datta, Amitava; Wensing, Michael

2017-03-01

The effects of blending syngas in different proportions to isooctane on the laminar burning velocity and ignition delay time of the fuel-air mixture have been studied in SI engine relevant conditions. The syngas is assumed to be composed of 50% H2 and 50% CO. Simulations have been carried out using a skeletal mechanism containing 143 species and 643 reaction steps. It has been found that the blending of syngas augments the laminar burning velocity of isooctane due to increase of the thermal diffusivity of the reactant mixture and alteration in the chemistry of the flame reactions. For the mixture of 30% isooctane/70% syngas, the laminar burning velocity and the ignition delay time values are very close to those corresponding to pure isooctane. Additionally, the effects of exhaust gas recirculation have been explored for the 30% isooctane/70% syngas-air flame. It is seen that the reduction in laminar burning velocity due to the dilution by the recirculated exhaust gas can be compensated by an increase in the unburnt gas temperature. The effect of the exhaust gas dilution on the ignition delay time of 30% isooctane/70% syngas-air mixture has been found to be negligible.

Internal models and prediction of visual gravitational motion.

PubMed

Zago, Myrka; McIntyre, Joseph; Senot, Patrice; Lacquaniti, Francesco

2008-06-01

Baurès et al. [Baurès, R., Benguigui, N., Amorim, M.-A., & Siegler, I. A. (2007). Intercepting free falling objects: Better use Occam's razor than internalize Newton's law. Vision Research, 47, 2982-2991] rejected the hypothesis that free-falling objects are intercepted using a predictive model of gravity. They argued instead for "a continuous guide for action timing" based on visual information updated till target capture. Here we show that their arguments are flawed, because they fail to consider the impact of sensori-motor delays on interception behaviour and the need for neural compensation of such delays. When intercepting a free-falling object, the delays can be overcome by a predictive model of the effects of gravity on target motion.

Carrier-phase two-way satellite frequency transfer over a very long baseline

NASA Astrophysics Data System (ADS)

Fujieda, M.; Piester, D.; Gotoh, T.; Becker, J.; Aida, M.; Bauch, A.

2014-06-01

In this paper we report that carrier-phase two-way satellite time and frequency transfer (TWSTFT) was successfully demonstrated over a very long baseline of 9000 km, established between the National Institute of Information and Communications Technology (NICT) and the Physikalisch-Technische Bundesanstalt (PTB). We verified that the carrier-phase TWSTFT (TWCP) result agreed with those obtained by conventional TWSTFT and GPS carrier-phase (GPSCP) techniques. Moreover, a much improved short-term instability for frequency transfer of 2 × 10-13 at 1 s was achieved, which is at the same level as previously confirmed over a shorter baseline within Japan. The precision achieved was so high that the effects of ionospheric delay became significant; they are ignored in conventional TWSTFT even over a long link. We compensated for these effects using ionospheric delays computed from regional vertical total electron content maps. The agreement between the TWCP and GPSCP results was improved because of this compensation.

Robust control for a biaxial servo with time delay system based on adaptive tuning technique.

PubMed

Chen, Tien-Chi; Yu, Chih-Hsien

2009-07-01

A robust control method for synchronizing a biaxial servo system motion is proposed in this paper. A new network based cross-coupled control and adaptive tuning techniques are used together to cancel out the skew error. The conventional fixed gain PID cross-coupled controller (CCC) is replaced with the adaptive cross-coupled controller (ACCC) in the proposed control scheme to maintain biaxial servo system synchronization motion. Adaptive-tuning PID (APID) position and velocity controllers provide the necessary control actions to maintain synchronization while following a variable command trajectory. A delay-time compensator (DTC) with an adaptive controller was augmented to set the time delay element, effectively moving it outside the closed loop, enhancing the stability of the robust controlled system. This scheme provides strong robustness with respect to uncertain dynamics and disturbances. The simulation and experimental results reveal that the proposed control structure adapts to a wide range of operating conditions and provides promising results under parameter variations and load changes.

Vehicle Position Estimation Based on Magnetic Markers: Enhanced Accuracy by Compensation of Time Delays.

PubMed

Byun, Yeun-Sub; Jeong, Rag-Gyo; Kang, Seok-Won

2015-11-13

The real-time recognition of absolute (or relative) position and orientation on a network of roads is a core technology for fully automated or driving-assisted vehicles. This paper presents an empirical investigation of the design, implementation, and evaluation of a self-positioning system based on a magnetic marker reference sensing method for an autonomous vehicle. Specifically, the estimation accuracy of the magnetic sensing ruler (MSR) in the up-to-date estimation of the actual position was successfully enhanced by compensating for time delays in signal processing when detecting the vertical magnetic field (VMF) in an array of signals. In this study, the signal processing scheme was developed to minimize the effects of the distortion of measured signals when estimating the relative positional information based on magnetic signals obtained using the MSR. In other words, the center point in a 2D magnetic field contour plot corresponding to the actual position of magnetic markers was estimated by tracking the errors between pre-defined reference models and measured magnetic signals. The algorithm proposed in this study was validated by experimental measurements using a test vehicle on a pilot network of roads. From the results, the positioning error was found to be less than 0.04 m on average in an operational test.

Vehicle Position Estimation Based on Magnetic Markers: Enhanced Accuracy by Compensation of Time Delays

PubMed Central

Byun, Yeun-Sub; Jeong, Rag-Gyo; Kang, Seok-Won

2015-01-01

The real-time recognition of absolute (or relative) position and orientation on a network of roads is a core technology for fully automated or driving-assisted vehicles. This paper presents an empirical investigation of the design, implementation, and evaluation of a self-positioning system based on a magnetic marker reference sensing method for an autonomous vehicle. Specifically, the estimation accuracy of the magnetic sensing ruler (MSR) in the up-to-date estimation of the actual position was successfully enhanced by compensating for time delays in signal processing when detecting the vertical magnetic field (VMF) in an array of signals. In this study, the signal processing scheme was developed to minimize the effects of the distortion of measured signals when estimating the relative positional information based on magnetic signals obtained using the MSR. In other words, the center point in a 2D magnetic field contour plot corresponding to the actual position of magnetic markers was estimated by tracking the errors between pre-defined reference models and measured magnetic signals. The algorithm proposed in this study was validated by experimental measurements using a test vehicle on a pilot network of roads. From the results, the positioning error was found to be less than 0.04 m on average in an operational test. PMID:26580622

Systems for controlling the intensity variations in a laser beam and for frequency conversion thereof

DOEpatents

Skupsky, S.; Craxton, R.S.; Soures, J.

1990-10-02

In order to control the intensity of a laser beam so that its intensity varies uniformly and provides uniform illumination of a target, such as a laser fusion target, a broad bandwidth laser pulse is spectrally dispersed spatially so that the frequency components thereof are spread apart. A disperser (grating) provides an output beam which varies spatially in wavelength in at least one direction transverse to the direction of propagation of the beam. Temporal spread (time delay) across the beam is corrected by using a phase delay device (a time delay compensation echelon). The dispersed beam may be amplified with laser amplifiers and frequency converted (doubled, tripled or quadrupled in frequency) with nonlinear optical elements (birefringent crystals). The spectral variation across the beam is compensated by varying the angle of incidence on one of the crystals with respect to the crystal optical axis utilizing a lens which diverges the beam. Another lens after the frequency converter may be used to recollimate the beam. The frequency converted beam is recombined so that portions of different frequency interfere and, unlike interference between waves of the same wavelength, there results an intensity pattern with rapid temporal oscillations which average out rapidly in time thereby producing uniform illumination on target. A distributed phase plate (also known as a random phase mask), through which the spectrally dispersed beam is passed and then focused on a target, is used to provide the interference pattern which becomes nearly modulation free and uniform in intensity in the direction of the spectral variation. 16 figs.

Systems for controlling the intensity variations in a laser beam and for frequency conversion thereof

DOEpatents

Skupsky, Stanley; Craxton, R. Stephen; Soures, John

1990-01-01

In order to control the intensity of a laser beam so that its intensity varies uniformly and provides uniform illumination of a target, such as a laser fusion target, a broad bandwidth laser pulse is spectrally dispersed spatially so that the frequency components thereof are spread apart. A disperser (grating) provides an output beam which varies spatially in wavelength in at least one direction transverse to the direction of propagation of the beam. Temporal spread (time delay) across the beam is corrected by using a phase delay device (a time delay compensation echelon). The dispersed beam may be amplified with laser amplifiers and frequency converted (doubled, tripled or quadrupled in frequency) with nonlinear optical elements (birefringent crystals). The spectral variation across the beam is compensated by varying the angle of incidence on one of the crystals with respect to the crystal optical axis utilizing a lens which diverges the beam. Another lens after the frequency converter may be used to recollimate the beam. The frequency converted beam is recombined so that portions of different frequency interfere and, unlike interference between waves of the same wavelength, there results an intensity pattern with rapid temoral oscillations which average out rapidly in time thereby producing uniform illumination on target. A distributed phase plate (also known as a random phase mask), through which the spectrally dispersed beam is passed and then focused on a target, is used to provide the interference pattern which becomes nearly modulation free and uniform in intensity in the direction of the spectral variation.

Three-Dimensional ISAR Imaging Method for High-Speed Targets in Short-Range Using Impulse Radar Based on SIMO Array.

PubMed

Zhou, Xinpeng; Wei, Guohua; Wu, Siliang; Wang, Dawei

2016-03-11

This paper proposes a three-dimensional inverse synthetic aperture radar (ISAR) imaging method for high-speed targets in short-range using an impulse radar. According to the requirements for high-speed target measurement in short-range, this paper establishes the single-input multiple-output (SIMO) antenna array, and further proposes a missile motion parameter estimation method based on impulse radar. By analyzing the motion geometry relationship of the warhead scattering center after translational compensation, this paper derives the receiving antenna position and the time delay after translational compensation, and thus overcomes the shortcomings of conventional translational compensation methods. By analyzing the motion characteristics of the missile, this paper estimates the missile's rotation angle and the rotation matrix by establishing a new coordinate system. Simulation results validate the performance of the proposed algorithm.

A dual-loop adaptive control for minimizing time response delay in real-time structural vibration control with magnetorheological (MR) devices

NASA Astrophysics Data System (ADS)

Chen, Xi; Li, Yancheng; Li, Jianchun; Gu, Xiaoyu

2018-01-01

Time delay is a challenge issue faced by the real-time control application of the magnetorheological (MR) devices. Not to deal with it properly may jeopardize the effectiveness of the control, even lead to instability of the control system or catastrophic failure. This paper proposes a dual-loop adaptive control to address the response time delay associated with MR devices. In the proposed dual-loop control, the inner loop is designed to compensate the time delay of MR device induced by the PWM current driver. While the outer loop control can be any structural control algorithm with aims to reducing structural responses of a building during extreme loadings. Here an adaptive control strategy is adopted. To verify the proposed dual-loop control, a smart base isolation system employing magnetorheological elastomer base isolators is used as an example to illustrate the control effect. Numerical study is then conducted using a 5 -storey shear building model equipped with smart base isolation system. The result shows that with the implementation of the inner loop, the control current can instantly follow the control command which reduce the possibility of instability caused by the time delay. Comparative studies are conducted between three control strategies, i.e. dual-loop control, Lyapunov’s direct method based control and optimal passive base isolation control. The results of the study have demonstrated that the proposed dual-loop control strategy can achieve much better performance than the other two control strategies.

Improving brain-machine interface performance by decoding intended future movements

NASA Astrophysics Data System (ADS)

Willett, Francis R.; Suminski, Aaron J.; Fagg, Andrew H.; Hatsopoulos, Nicholas G.

2013-04-01

Objective. A brain-machine interface (BMI) records neural signals in real time from a subject's brain, interprets them as motor commands, and reroutes them to a device such as a robotic arm, so as to restore lost motor function. Our objective here is to improve BMI performance by minimizing the deleterious effects of delay in the BMI control loop. We mitigate the effects of delay by decoding the subject's intended movements a short time lead in the future. Approach. We use the decoded, intended future movements of the subject as the control signal that drives the movement of our BMI. This should allow the user's intended trajectory to be implemented more quickly by the BMI, reducing the amount of delay in the system. In our experiment, a monkey (Macaca mulatta) uses a future prediction BMI to control a simulated arm to hit targets on a screen. Main Results. Results from experiments with BMIs possessing different system delays (100, 200 and 300 ms) show that the monkey can make significantly straighter, faster and smoother movements when the decoder predicts the user's future intent. We also characterize how BMI performance changes as a function of delay, and explore offline how the accuracy of future prediction decoders varies at different time leads. Significance. This study is the first to characterize the effects of control delays in a BMI and to show that decoding the user's future intent can compensate for the negative effect of control delay on BMI performance.

Development of ball surface acoustic wave trace moisture analyzer using burst waveform undersampling circuit

NASA Astrophysics Data System (ADS)

Tsuji, Toshihiro; Oizumi, Toru; Fukushi, Hideyuki; Takeda, Nobuo; Akao, Shingo; Tsukahara, Yusuke; Yamanaka, Kazushi

2018-05-01

The measurement and control of trace moisture, where the water concentration is lower than 1 ppmv [-76.2 °C for the frost point (°CFP)], are essential for improving the yield rate of semiconductor devices and for ensuring their reliability. A ball surface acoustic wave (SAW) sensor with a sol-gel silica coating exhibited useful characteristics for a trace moisture analyzer (TMA) when the temperature drift of the delay time output was precisely compensated using two-frequency measurement (TFM), where the temperature-compensated relative delay time change (RDTC) was obtained by subtracting the RDTC at the fundamental frequency from that at the third harmonic frequency on an identical propagation path. However, the cost of the measurement circuit was a problem. In this study, a burst waveform undersampling (BUS) circuit based on the theory of undersampling measurement was developed as a practical means. The BUS circuit was useful for precise temperature compensation of the RDTC, and the ball SAW TMA was prototyped by calibrating the RDTC using a TMA based on cavity ring-down spectroscopy (CRDS), which is the most reliable method for trace moisture measurement. The ball SAW TMA outputted a similar concentration to that obtained by the CRDS TMA, and its response time at a set concentration in N2 with a flow rate of 1 l/min was about half that of the CRDS TMA, suggesting that moisture of -80 °CFP was measured within only 1 min. The detection limit at a signal-to-noise ratio of 3 was estimated to be 0.05 ppbv, comparable with that of the CRDS TMA. From these results, it was demonstrated that a practical ball SAW TMA can be realized using the developed BUS circuit.

Joint Maximum Likelihood Time Delay Estimation of Unknown Event-Related Potential Signals for EEG Sensor Signal Quality Enhancement

PubMed Central

Kim, Kyungsoo; Lim, Sung-Ho; Lee, Jaeseok; Kang, Won-Seok; Moon, Cheil; Choi, Ji-Woong

2016-01-01

Electroencephalograms (EEGs) measure a brain signal that contains abundant information about the human brain function and health. For this reason, recent clinical brain research and brain computer interface (BCI) studies use EEG signals in many applications. Due to the significant noise in EEG traces, signal processing to enhance the signal to noise power ratio (SNR) is necessary for EEG analysis, especially for non-invasive EEG. A typical method to improve the SNR is averaging many trials of event related potential (ERP) signal that represents a brain’s response to a particular stimulus or a task. The averaging, however, is very sensitive to variable delays. In this study, we propose two time delay estimation (TDE) schemes based on a joint maximum likelihood (ML) criterion to compensate the uncertain delays which may be different in each trial. We evaluate the performance for different types of signals such as random, deterministic, and real EEG signals. The results show that the proposed schemes provide better performance than other conventional schemes employing averaged signal as a reference, e.g., up to 4 dB gain at the expected delay error of 10°. PMID:27322267

Is Early Prescribing of Opioid and Psychotropic Medications Associated With Delayed Return to Work and Increased Final Workers' Compensation Cost?

PubMed

Tao, Xuguang Grant; Lavin, Robert A; Yuspeh, Larry; Weaver, Virginia M; Bernacki, Edward J

2015-12-01

To explore the association between the initial 60 days of prescriptions for psychotropic medications and final workers' compensation claim outcomes. A cohort of 11,394 claimants involved in lost time injuries between 1999 and 2002 were followed through December 31, 2009. Logistic regressions and Cox Proportional Hazard Models were used in the analysis. The initial 60 days of prescriptions for psychotropic medications were significantly associated with a final claim cost at least $100,000. Odds ratios were 1.88 for short-acting opioids, 2.14 for hypnotics, antianxiety agents, or antidepressants, and 3.91 for long-acting opioids, respectively. Significant associations were also found between decreased time lost from work and decreased claim closures during the study period. Early prescription of opioids and other psychotropic drugs may be useful predictors of high claim costs and time lost from work.

Reachable set estimation for Takagi-Sugeno fuzzy systems against unknown output delays with application to tracking control of AUVs.

PubMed

Zhong, Zhixiong; Zhu, Yanzheng; Ahn, Choon Ki

2018-07-01

In this paper, we address the problem of reachable set estimation for continuous-time Takagi-Sugeno (T-S) fuzzy systems subject to unknown output delays. Based on the reachable set concept, a new controller design method is also discussed for such systems. An effective method is developed to attenuate the negative impact from the unknown output delays, which likely degrade the performance/stability of systems. First, an augmented fuzzy observer is proposed to capacitate a synchronous estimation for the system state and the disturbance term owing to the unknown output delays, which ensures that the reachable set of the estimation error is limited via the intersection operation of ellipsoids. Then, a compensation technique is employed to eliminate the influence on the system performance stemmed from the unknown output delays. Finally, the effectiveness and correctness of the obtained theories are verified by the tracking control of autonomous underwater vehicles. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

The Effect of Delayed Auditory Feedback on Activity in the Temporal Lobe while Speaking: A Positron Emission Tomography Study

ERIC Educational Resources Information Center

Takaso, Hideki; Eisner, Frank; Wise, Richard J. S.; Scott, Sophie K.

2010-01-01

Purpose: Delayed auditory feedback is a technique that can improve fluency in stutterers, while disrupting fluency in many nonstuttering individuals. The aim of this study was to determine the neural basis for the detection of and compensation for such a delay, and the effects of increases in the delay duration. Method: Positron emission…

Terrestrial Planet Finder cryogenic delay line development

NASA Technical Reports Server (NTRS)

Smythe, Robert F.; Swain, Mark R.; Alvarez-Salazar, Oscar; Moore, James D.

2004-01-01

Delay lines provide the path-length compensation that makes the measurement of interference fringes possible. When used for nulling interferometry, the delay line must control path-lengths so that the null is stable and controlled throughout the measurement. We report on a low noise, low disturbance, and high bandwidth optical delay line capable of meeting the TPF interferometer optical path length control requirements at cryogenic temperatures.

Load compensation as a function of state during sleep onset.

PubMed

Gora, J; Kay, A; Colrain, I M; Kleiman, J; Trinder, J

1998-06-01

Ventilation decreases and airway resistance increases with the loss of electroencephalogram alpha activity at sleep onset. The aim of this study was to determine whether reflexive load compensation is lost immediately on the loss of alpha activity. Six healthy male subjects were studied under two conditions (load and control-no load), in three states (continuous alpha, continuous theta, and immediately after a transition from alpha to theta), and in two phases (early and late sleep onset). Ventilation and respiratory timing were measured. A comparison of loaded with control conditions indicated that loading had no effect on inspiratory minute ventilation during continuous alpha (differential effect of 0.00 l/min) and only a small, nonsignificant effect in theta immediately after phase 2 transitions (0.31 l/min), indicating a preservation of load compensation at these times. However, there were significant decreases in inspiratory minute ventilation on loaded trials during continuous theta in phase 2 (0.77 l/min) and phase 3 (1.15 l/min) and during theta immediately after a transition in phase 3 (0.87 l/min), indicating a lack of reflexive load compensation. The results indicate that, because reflex load compensation is state dependent, state-related changes in airway resistance contribute to state-related changes in ventilation during sleep onset. However, this effect was slightly delayed with transitions into theta early in sleep.

Active flutter suppression using optical output feedback digital controllers

NASA Technical Reports Server (NTRS)

1982-01-01

A method for synthesizing digital active flutter suppression controllers using the concept of optimal output feedback is presented. A convergent algorithm is employed to determine constrained control law parameters that minimize an infinite time discrete quadratic performance index. Low order compensator dynamics are included in the control law and the compensator parameters are computed along with the output feedback gain as part of the optimization process. An input noise adjustment procedure is used to improve the stability margins of the digital active flutter controller. Sample rate variation, prefilter pole variation, control structure variation and gain scheduling are discussed. A digital control law which accommodates computation delay can stabilize the wing with reasonable rms performance and adequate stability margins.

A Group Neighborhood Average Clock Synchronization Protocol for Wireless Sensor Networks

PubMed Central

Lin, Lin; Ma, Shiwei; Ma, Maode

2014-01-01

Clock synchronization is a very important issue for the applications of wireless sensor networks. The sensors need to keep a strict clock so that users can know exactly what happens in the monitoring area at the same time. This paper proposes a novel internal distributed clock synchronization solution using group neighborhood average. Each sensor node collects the offset and skew rate of the neighbors. Group averaging of offset and skew rate value are calculated instead of conventional point-to-point averaging method. The sensor node then returns compensated value back to the neighbors. The propagation delay is considered and compensated. The analytical analysis of offset and skew compensation is presented. Simulation results validate the effectiveness of the protocol and reveal that the protocol allows sensor networks to quickly establish a consensus clock and maintain a small deviation from the consensus clock. PMID:25120163

Ranging Consistency Based on Ranging-Compensated Temperature-Sensing Sensor for Inter-Satellite Link of Navigation Constellation

PubMed Central

Meng, Zhijun; Yang, Jun; Guo, Xiye; Zhou, Yongbin

2017-01-01

Global Navigation Satellite System performance can be significantly enhanced by introducing inter-satellite links (ISLs) in navigation constellation. The improvement in position, velocity, and time accuracy as well as the realization of autonomous functions requires ISL distance measurement data as the original input. To build a high-performance ISL, the ranging consistency among navigation satellites is an urgent problem to be solved. In this study, we focus on the variation in the ranging delay caused by the sensitivity of the ISL payload equipment to the ambient temperature in space and propose a simple and low-power temperature-sensing ranging compensation sensor suitable for onboard equipment. The experimental results show that, after the temperature-sensing ranging compensation of the ISL payload equipment, the ranging consistency becomes less than 0.2 ns when the temperature change is 90 °C. PMID:28608809

Three-Dimensional ISAR Imaging Method for High-Speed Targets in Short-Range Using Impulse Radar Based on SIMO Array

PubMed Central

Zhou, Xinpeng; Wei, Guohua; Wu, Siliang; Wang, Dawei

2016-01-01

This paper proposes a three-dimensional inverse synthetic aperture radar (ISAR) imaging method for high-speed targets in short-range using an impulse radar. According to the requirements for high-speed target measurement in short-range, this paper establishes the single-input multiple-output (SIMO) antenna array, and further proposes a missile motion parameter estimation method based on impulse radar. By analyzing the motion geometry relationship of the warhead scattering center after translational compensation, this paper derives the receiving antenna position and the time delay after translational compensation, and thus overcomes the shortcomings of conventional translational compensation methods. By analyzing the motion characteristics of the missile, this paper estimates the missile’s rotation angle and the rotation matrix by establishing a new coordinate system. Simulation results validate the performance of the proposed algorithm. PMID:26978372

Dual-user nonlinear teleoperation subjected to varying time delay and bounded inputs.

PubMed

Zakerimanesh, Amir; Hashemzadeh, Farzad; Ghiasi, Amir Rikhtehgar

2017-05-01

A novel trilateral control architecture for Dual-master/Single-slave teleoperation system with taking account of saturation in actuators, nonlinear dynamics for telemanipulators and bounded varying time delay which affects the transmitted signals in the communication channels, is proposed in this paper. In this research, we will address the stability and desired position coordination problem of trilateral teleoperation system by extension of (nP+D) controller that is used for Single-master/Single-slave teleoperation system. Our proposed controller is weighted summation of nonlinear Proportional plus Damping (nP+D) controller that incorporate gravity compensation and the weights are specified by the dominance factor, which determines the supremacy of each user over the slave robot and over the other user. The asymptotic stability of closed loop dynamics is studied using Lyapunov-Krasovskii functional under conditions on the controller parameters, the actuator saturation characteristics and the maximum values of varying time delays. It is shown that these controllers satisfy the desired position coordination problem in free motion condition. To show the effectiveness of the proposed method, a number of simulations have been conducted on a varying time delay Dual-master/Single-slave teleoperation system using 3-DOF planar robots for each telemanipulator subjected to actuator saturation. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Instrumentation for one-way satellite PTTI applications. [calibration and synchronization of clocks from navigation satellite

NASA Technical Reports Server (NTRS)

Osborne, A. E.

1973-01-01

A review of general principles and operational procedures illustrates how the typical passive user and omni receiving antenna can recover Precise Time and Time Interval (PTTI) information from a low altitude navigation satellite system for clock calibration and synchronization. Detailed discussions of concepts and theory of the receiver design are presented. The importance of RF correlation of the received and local PN encoded sequences is emphasized as a means of reducing delay uncertainties of the instrumentation to values compatible with nanosecond to submicrosecond PTTI objectives. Two receiver configurations were fabricated for use in satellite-to-laboratory experiments. In one receiver the delay-locked loop for PN signals synchronization used a dithered amplitude detection process while the second receiver used a complex sums phase detection method for measurement of delay error. The necessity for compensation of Doppler shift is discussed. Differences in theoretical signal acquisition and tracking performance of the design concepts are noted.

Motion-compensated detection of heart rate based on the time registration adaptive filter

NASA Astrophysics Data System (ADS)

Yang, Lei; Zhou, Jinsong; Jing, Juanjuan; Li, Yacan; Wei, Lidong; Feng, Lei; He, Xiaoying; Bu, Meixia; Fu, Xilu

2018-01-01

A non-contact heart rate detection method based on the dual-wavelength technique is proposed and demonstrated experimentally. The heart rate is obtained based on the PhotoPlethysmoGraphy (PPG). Each detection module uses the reflection detection probe which is composed of the LED and the photodiode. It is a well-known fact that the differences in the circuits of two detection modules result in different responses of two modules for motion artifacts. It will cause a time delay between the two signals. This poses a great challenge to compensate the motion artifacts during measurements. In order to solve this problem, we have firstly used the time registration and translated the signals to ensure that the two signals are consistent in time domain. Then the adaptive filter is used to compensate the motion artifacts. Moreover, the data obtained by using this non-contact detection system is compared with those of the conventional finger blood volume pulse (BVP) sensor by simultaneously measuring the heart rate of the subject. During the experiment, the left hand remains stationary and is detected by a conventional finger BVP sensor. Meanwhile, the moving palm of right hand is detected by the proposed system. The data obtained from the proposed non-contact system are consistent and comparable with that of the BVP sensor. This method can effectively suppress the interference caused by the two circuit differences and successfully compensate the motion artifacts. This technology can be used in medical and daily heart rate measurement.

Summary of the effects of engine throttle response on airplane formation-flying qualities

NASA Technical Reports Server (NTRS)

Walsh, Kevin R.

1993-01-01

A flight evaluation was conducted to determine the effect of engine throttle response characteristics on precision formation-flying qualities. A variable electronic throttle control system was developed and flight-tested on a TF-104G airplane with a J79-11B engine at the NASA Dryden Flight Research Facility. This airplane was chosen because of its known, very favorable thrust response characteristics. Ten research flights were flown to evaluate the effects of throttle gain, time delay, and fuel control rate limiting on engine handling qualities during a demanding precision wing formation task. Handling quality effects of lag filters and lead compensation time delays were also evaluated. The Cooper and Harper Pilot Rating Scale was used to assign levels of handling quality. Data from pilot ratings and comments indicate that throttle control system time delays and rate limits cause significant degradations in handling qualities. Threshold values for satisfactory (level 1) and adequate (level 2) handling qualities of these key variables are presented. These results may provide engine manufacturers with guidelines to assure satisfactory handling qualities in future engine designs.

Adaptive iterative learning control of a class of nonlinear time-delay systems with unknown backlash-like hysteresis input and control direction.

PubMed

Wei, Jianming; Zhang, Youan; Sun, Meimei; Geng, Baoliang

2017-09-01

This paper presents an adaptive iterative learning control scheme for a class of nonlinear systems with unknown time-varying delays and control direction preceded by unknown nonlinear backlash-like hysteresis. Boundary layer function is introduced to construct an auxiliary error variable, which relaxes the identical initial condition assumption of iterative learning control. For the controller design, integral Lyapunov function candidate is used, which avoids the possible singularity problem by introducing hyperbolic tangent funciton. After compensating for uncertainties with time-varying delays by combining appropriate Lyapunov-Krasovskii function with Young's inequality, an adaptive iterative learning control scheme is designed through neural approximation technique and Nussbaum function method. On the basis of the hyperbolic tangent function's characteristics, the system output is proved to converge to a small neighborhood of the desired trajectory by constructing Lyapunov-like composite energy function (CEF) in two cases, while keeping all the closed-loop signals bounded. Finally, a simulation example is presented to verify the effectiveness of the proposed approach. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

The analysis and compensation of errors of precise simple harmonic motion control under high speed and large load conditions based on servo electric cylinder

NASA Astrophysics Data System (ADS)

Ma, Chen-xi; Ding, Guo-qing

2017-10-01

Simple harmonic waves and synthesized simple harmonic waves are widely used in the test of instruments. However, because of the errors caused by clearance of gear and time-delay error of FPGA, it is difficult to control servo electric cylinder in precise simple harmonic motion under high speed, high frequency and large load conditions. To solve the problem, a method of error compensation is proposed in this paper. In the method, a displacement sensor is fitted on the piston rod of the electric cylinder. By using the displacement sensor, the real-time displacement of the piston rod is obtained and fed back to the input of servo motor, then a closed loop control is realized. There is compensation of pulses in the next period of the synthetic waves. This paper uses FPGA as the processing core. The software mainly comprises a waveform generator, an Ethernet module, a memory module, a pulse generator, a pulse selector, a protection module, an error compensation module. A durability of shock absorbers is used as the testing platform. The durability mainly comprises a single electric cylinder, a servo motor for driving the electric cylinder, and the servo motor driver.

A pulse-front-tilt–compensated streaked optical spectrometer with high throughput and picosecond time resolution

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

Katz, J., E-mail: jkat@lle.rochester.edu; Boni, R.; Rivlis, R.

A high-throughput, broadband optical spectrometer coupled to the Rochester optical streak system equipped with a Photonis P820 streak tube was designed to record time-resolved spectra with 1-ps time resolution. Spectral resolution of 0.8 nm is achieved over a wavelength coverage range of 480 to 580 nm, using a 300-groove/mm diffraction grating in conjunction with a pair of 225-mm-focal-length doublets operating at an f/2.9 aperture. Overall pulse-front tilt across the beam diameter generated by the diffraction grating is reduced by preferentially delaying discrete segments of the collimated input beam using a 34-element reflective echelon optic. The introduced delay temporally aligns themore » beam segments and the net pulse-front tilt is limited to the accumulation across an individual sub-element. The resulting spectrometer design balances resolving power and pulse-front tilt while maintaining high throughput.« less

Composite pulsed field gradients with refocused chemical shifts and short recovery time.

PubMed

Hu, H; Shaka, A J

1999-01-01

An improved self-compensating pulsed field gradient (PFG) technique that combines antiphase gradient pairs with broadband frequency-modulated 180 degrees pulses is proposed. The antiphase gradient pairs lead to superb system recovery. In addition, evolution under chemical shift and heteronuclear J coupling are refocused during the PFG, making it appear effectively instantaneous. This new approach makes it possible to obtain high-resolution phase-sensitive 2D spectra for the PFG version of many experiments such as COSY, DQF-COSY, and HSQC without adding extra compensating delays or pulses. While reasonable suppression of unwanted magnetization is achieved, this method also gives satisfactory retention of desired signals. As a bonus, the field-frequency lock is not perturbed during the experiments. Copyright 1999 Academic Press.

Spotlight-Mode Synthetic Aperture Radar Processing for High-Resolution Lunar Mapping

NASA Technical Reports Server (NTRS)

Harcke, Leif; Weintraub, Lawrence; Yun, Sang-Ho; Dickinson, Richard; Gurrola, Eric; Hensley, Scott; Marechal, Nicholas

2010-01-01

During the 2008-2009 year, the Goldstone Solar System Radar was upgraded to support radar mapping of the lunar poles at 4 m resolution. The finer resolution of the new system and the accompanying migration through resolution cells called for spotlight, rather than delay-Doppler, imaging techniques. A new pre-processing system supports fast-time Doppler removal and motion compensation to a point. Two spotlight imaging techniques which compensate for phase errors due to i) out of focus-plane motion of the radar and ii) local topography, have been implemented and tested. One is based on the polar format algorithm followed by a unique autofocus technique, the other is a full bistatic time-domain backprojection technique. The processing system yields imagery of the specified resolution. Products enabled by this new system include topographic mapping through radar interferometry, and change detection techniques (amplitude and coherent change) for geolocation of the NASA LCROSS mission impact site.

Human factors optimization of virtual environment attributes for a space telerobotic control station

NASA Astrophysics Data System (ADS)

Lane, Jason Corde

2000-10-01

Remote control of underwater vehicles and other robotic systems has, up until now, proved to be a challenging task for the human operator. With technology advancements in computers and displays, computer interfaces can be used to alleviate the workload on the operator. This research introduces the concept of a commanded display, which is a graphical simulation that shows the commands sent to the actual system in real-time. The primary goal of this research was to show a commanded display as an alternative to the traditional predictive display for reducing the effects of time delay. Several experiments were used to investigate how subjects compensated for time delay under a variety of conditions while controlling a 7-degree of freedom robotic manipulator. Results indicate that time delay increased completion time linearly; this linear relationship occurred even at different manipulator speeds, varying levels of error, and when using a commanded display. The commanded display alleviated the majority of time delay effects, up to 91% reduction. The commanded display also facilitated more accurate control, reducing the number of inadvertent impacts to the task worksite, even when compared to no time delay. Even with a moderate error between the commanded and actual displays, the commanded display was still a useful tool for mitigating time delay. The way subjects controlled the manipulator with the input device was tracked and their control strategies were extracted. A correlation between the subjects' use of the input device and their task completion time was determined. The importance of stereo vision and head tracking was examined and shown to improve a subject's depth perception within a virtual environment. Reports of simulator sickness induced by display equipment, including a head mounted display and LCD shutter glasses, were compared. The results of the above testing were used to develop an effective virtual environment control station to control a multi-arm robot.

Effects of simulator motion and visual characteristics on rotorcraft handling qualities evaluations

NASA Technical Reports Server (NTRS)

Mitchell, David G.; Hart, Daniel C.

1993-01-01

The pilot's perceptions of aircraft handling qualities are influenced by a combination of the aircraft dynamics, the task, and the environment under which the evaluation is performed. When the evaluation is performed in a groundbased simulator, the characteristics of the simulation facility also come into play. Two studies were conducted on NASA Ames Research Center's Vertical Motion Simulator to determine the effects of simulator characteristics on perceived handling qualities. Most evaluations were conducted with a baseline set of rotorcraft dynamics, using a simple transfer-function model of an uncoupled helicopter, under different conditions of visual time delays and motion command washout filters. Differences in pilot opinion were found as the visual and motion parameters were changed, reflecting a change in the pilots' perceptions of handling qualities, rather than changes in the aircraft model itself. The results indicate a need for tailoring the motion washout dynamics to suit the task. Visual-delay data are inconclusive but suggest that it may be better to allow some time delay in the visual path to minimize the mismatch between visual and motion, rather than eliminate the visual delay entirely through lead compensation.

Frequency response control of semiconductor laser by using hybrid modulation scheme.

PubMed

Mieda, Shigeru; Yokota, Nobuhide; Isshiki, Ryuto; Kobayashi, Wataru; Yasaka, Hiroshi

2016-10-31

A hybrid modulation scheme that simultaneously applies the direct current modulation and intra-cavity loss modulation to a semiconductor laser is proposed. Both numerical calculations using rate equations and experiments using a fabricated laser show that the hybrid modulation scheme can control the frequency response of the laser by changing a modulation ratio and time delay between the two modulations. The modulation ratio and time delay provide the degree of signal mixing of the two modulations and an optimum condition is found when a non-flat frequency response for the intra-cavity loss modulation is compensated by that for the direct current modulation. We experimentally confirm a 8.64-dB improvement of the modulation sensitivity at 20 GHz compared with the pure direct current modulation with a 0.7-dB relaxation oscillation peak.

Pipelined digital SAR azimuth correlator using hybrid FFT-transversal filter

NASA Technical Reports Server (NTRS)

Wu, C.; Liu, K. Y. (Inventor)

1984-01-01

A synthetic aperture radar system (SAR) having a range correlator is provided with a hybrid azimuth correlator which utilizes a block-pipe-lined fast Fourier transform (FFT). The correlator has a predetermined FFT transform size with delay elements for delaying SAR range correlated data so as to embed in the Fourier transform operation a corner-turning function as the range correlated SAR data is converted from the time domain to a frequency domain. The azimuth correlator is comprised of a transversal filter to receive the SAR data in the frequency domain, a generator for range migration compensation and azimuth reference functions, and an azimuth reference multiplier for correlation of the SAR data. Following the transversal filter is a block-pipelined inverse FFT used to restore azimuth correlated data in the frequency domain to the time domain for imaging.

Joint transfer of time and frequency signals and multi-point synchronization via fiber network

NASA Astrophysics Data System (ADS)

Nan, Cheng; Wei, Chen; Qin, Liu; Dan, Xu; Fei, Yang; You-Zhen, Gui; Hai-Wen, Cai

2016-01-01

A system of jointly transferring time signals with a rate of 1 pulse per second (PPS) and frequency signals of 10 MHz via a dense wavelength division multiplex-based (DWDM) fiber is demonstrated in this paper. The noises of the fiber links are suppressed and compensated for by a controlled fiber delay line. A method of calibrating and characterizing time is described. The 1PPS is synchronized by feed-forward calibrating the fiber delays precisely. The system is experimentally examined via a 110 km spooled fiber in laboratory. The frequency stabilities of the user end with compensation are 1.8×10-14 at 1 s and 2.0×10-17 at 104 s average time. The calculated uncertainty of time synchronization is 13.1 ps, whereas the direct measurement of the uncertainty is 12 ps. Next, the frequency and 1PPS are transferred via a metropolitan area optical fiber network from one central site to two remote sites with distances of 14 km and 110 km. The frequency stabilities of 14 km link reach 3.0×10-14 averaged in 1 s and 1.4×10-17 in 104 s respectively; and the stabilities of 110 km link are 8.3×10-14 and 1.7×10-17, respectively. The accuracies of synchronization are estimated to be 12.3 ps for the 14 km link and 13.1 ps for the 110 km link, respectively. Project supported by the National Natural Science Foundation of China (Grant No. 61405227).

PULSE SYNTHESIZING GENERATOR

DOEpatents

Kerns, Q.A.

1963-08-01

>An electronlc circuit for synthesizing electrical current pulses having very fast rise times includes several sinewave generators tuned to progressively higher harmonic frequencies with signal amplitudes and phases selectable according to the Fourier series of the waveform that is to be synthesized. Phase control is provided by periodically triggering the generators at precisely controlled times. The outputs of the generators are combined in a coaxial transmission line. Any frequency-dependent delays that occur in the transmission line can be readily compensated for so that the desired signal wave shape is obtained at the output of the line. (AEC)

Radar transponder operation with compensation for distortion due to amplitude modulation

DOEpatents

Ormesher, Richard C [Albuquerque, NM; Tise, Bertice L [Albuquerque, NM; Axline, Jr., Robert M.

2011-01-04

In radar transponder operation, a variably delayed gating signal is used to gate a received radar pulse and thereby produce a corresponding gated radar pulse for transmission back to the source of the received radar pulse. This compensates for signal distortion due to amplitude modulation on the retransmitted pulse.

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

PubMed Central

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

2014-01-01

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

PMD compensation in fiber-optic communication systems with direct detection using LDPC-coded OFDM.

PubMed

Djordjevic, Ivan B

2007-04-02

The possibility of polarization-mode dispersion (PMD) compensation in fiber-optic communication systems with direct detection using a simple channel estimation technique and low-density parity-check (LDPC)-coded orthogonal frequency division multiplexing (OFDM) is demonstrated. It is shown that even for differential group delay (DGD) of 4/BW (BW is the OFDM signal bandwidth), the degradation due to the first-order PMD can be completely compensated for. Two classes of LDPC codes designed based on two different combinatorial objects (difference systems and product of combinatorial designs) suitable for use in PMD compensation are introduced.

Robust Real-Time Wide-Area Differential GPS Navigation

NASA Technical Reports Server (NTRS)

Yunck, Thomas P. (Inventor); Bertiger, William I. (Inventor); Lichten, Stephen M. (Inventor); Mannucci, Anthony J. (Inventor); Muellerschoen, Ronald J. (Inventor); Wu, Sien-Chong (Inventor)

1998-01-01

The present invention provides a method and a device for providing superior differential GPS positioning data. The system includes a group of GPS receiving ground stations covering a wide area of the Earth's surface. Unlike other differential GPS systems wherein the known position of each ground station is used to geometrically compute an ephemeris for each GPS satellite. the present system utilizes real-time computation of satellite orbits based on GPS data received from fixed ground stations through a Kalman-type filter/smoother whose output adjusts a real-time orbital model. ne orbital model produces and outputs orbital corrections allowing satellite ephemerides to be known with considerable greater accuracy than from die GPS system broadcasts. The modeled orbits are propagated ahead in time and differenced with actual pseudorange data to compute clock offsets at rapid intervals to compensate for SA clock dither. The orbital and dock calculations are based on dual frequency GPS data which allow computation of estimated signal delay at each ionospheric point. These delay data are used in real-time to construct and update an ionospheric shell map of total electron content which is output as part of the orbital correction data. thereby allowing single frequency users to estimate ionospheric delay with an accuracy approaching that of dual frequency users.

Real-time circumferential mapping catheter tracking for motion compensation in atrial fibrillation ablation procedures

NASA Astrophysics Data System (ADS)

Brost, Alexander; Bourier, Felix; Wimmer, Andreas; Koch, Martin; Kiraly, Atilla; Liao, Rui; Kurzidim, Klaus; Hornegger, Joachim; Strobel, Norbert

2012-02-01

Atrial fibrillation (AFib) has been identified as a major cause of stroke. Radiofrequency catheter ablation has become an increasingly important treatment option, especially when drug therapy fails. Navigation under X-ray can be enhanced by using augmented fluoroscopy. It renders overlay images from pre-operative 3-D data sets which are then fused with X-ray images to provide more details about the underlying soft-tissue anatomy. Unfortunately, these fluoroscopic overlay images are compromised by respiratory and cardiac motion. Various methods to deal with motion have been proposed. To meet clinical demands, they have to be fast. Methods providing a processing frame rate of 3 frames-per-second (fps) are considered suitable for interventional electrophysiology catheter procedures if an acquisition frame rate of 2 fps is used. Unfortunately, when working at a processing rate of 3 fps, the delay until the actual motion compensated image can be displayed is about 300 ms. More recent algorithms can achieve frame rates of up to 20 fps, which reduces the lag to 50 ms. By using a novel approach involving a 3-D catheter model, catheter segmentation and a distance transform, we can speed up motion compensation to 25 fps which results in a display delay of only 40 ms on a standard workstation for medical applications. Our method uses a constrained 2-D/3-D registration to perform catheter tracking, and it obtained a 2-D tracking error of 0.61 mm.

A Low Power Linear Phase Programmable Long Delay Circuit.

PubMed

Rodriguez-Villegas, Esther; Logesparan, Lojini; Casson, Alexander J

2014-06-01

A novel linear phase programmable delay is being proposed and implemented in a 0.35 μm CMOS process. The delay line consists of N cascaded cells, each of which delays the input signal by Td/N, where Td is the total line delay. The delay generated by each cell is programmable by changing a clock frequency and is also fully independent of the frequency of the input signal. The total delay hence depends only on the chosen clock frequency and the total number of cascaded cells. The minimum clock frequency is limited by the maximum time a voltage signal can effectively be held by an individual cell. The maximum number of cascaded cells will be limited by the effects of accumulated offset due to transistor mismatch, which eventually will affect the operating mode of the individual transistors in a cell. This latter limitation has however been dealt with in the topology by having an offset compensation mechanism that makes possible having a large number of cascaded cells and hence a long resulting delay. The delay line has been designed for scalp-based neural activity analysis that is predominantly in the sub-100 Hz frequency range. For these signals, the delay generated by a 31-cell cascade has been demonstrated to be programmable from 30 ms to 3 s. Measurement results demonstrate a 31 stage, 50 Hz bandwidth, 0.3 s delay that operates from a 1.1 V supply with power consumption of 270 nW.

Smith predictor-based robot control for ultrasound-guided teleoperated beating-heart surgery.

PubMed

Bowthorpe, Meaghan; Tavakoli, Mahdi; Becher, Harald; Howe, Robert

2014-01-01

Performing surgery on fast-moving heart structures while the heart is freely beating is next to impossible. Nevertheless, the ability to do this would greatly benefit patients. By controlling a teleoperated robot to continuously follow the heart's motion, the heart can be made to appear stationary. The surgeon will then be able to operate on a seemingly stationary heart when in reality it is freely beating. The heart's motion is measured from ultrasound images and thus involves a non-negligible delay due to image acquisition and processing, estimated to be 150 ms that, if not compensated for, can cause the teleoperated robot's end-effector (i.e., the surgical tool) to collide with and puncture the heart. This research proposes the use of a Smith predictor to compensate for this time delay in calculating the reference position for the teleoperated robot. The results suggest that heart motion tracking is improved as the introduction of the Smith predictor significantly decreases the mean absolute error, which is the error in making the distance between the robot's end-effector and the heart follow the surgeon's motion, and the mean integrated square error.

Functional compensation in the ventromedial prefrontal cortex improves memory-dependent decisions in older adults.

PubMed

Lighthall, Nichole R; Huettel, Scott A; Cabeza, Roberto

2014-11-19

Everyday consumer choices frequently involve memory, as when we retrieve information about consumer products when making purchasing decisions. In this context, poor memory may affect decision quality, particularly in individuals with memory decline, such as older adults. However, age differences in choice behavior may be reduced if older adults can recruit additional neural resources that support task performance. Although such functional compensation is well documented in other cognitive domains, it is presently unclear whether it can support memory-guided decision making and, if so, which brain regions play a role in compensation. The current study engaged younger and older humans in a memory-dependent choice task in which pairs of consumer products from a popular online-shopping site were evaluated with different delays between the first and second product. Using functional imaging (fMRI), we found that the ventromedial prefrontal cortex (vmPFC) supports compensation as defined by three a priori criteria: (1) increased vmPFC activation was observed in older versus younger adults; (2) age-related increases in vmPFC activity were associated with increased retrieval demands; and (3) increased vmPFC activity was positively associated with performance in older adults-evidence of successful compensation. Extending these results, we observed evidence for compensation in connectivity between vmPFC and the dorsolateral PFC during memory-dependent choice. In contrast, we found no evidence for age differences in value-related processing or age-related compensation for choices without delayed retrieval. Together, these results converge on the conclusion that age-related decline in memory-dependent choice performance can be minimized via functional compensation in vmPFC. Copyright © 2014 the authors 0270-6474/14/3415648-10$15.00/0.

Functional Compensation in the Ventromedial Prefrontal Cortex Improves Memory-Dependent Decisions in Older Adults

PubMed Central

Huettel, Scott A.; Cabeza, Roberto

2014-01-01

Everyday consumer choices frequently involve memory, as when we retrieve information about consumer products when making purchasing decisions. In this context, poor memory may affect decision quality, particularly in individuals with memory decline, such as older adults. However, age differences in choice behavior may be reduced if older adults can recruit additional neural resources that support task performance. Although such functional compensation is well documented in other cognitive domains, it is presently unclear whether it can support memory-guided decision making and, if so, which brain regions play a role in compensation. The current study engaged younger and older humans in a memory-dependent choice task in which pairs of consumer products from a popular online-shopping site were evaluated with different delays between the first and second product. Using functional imaging (fMRI), we found that the ventromedial prefrontal cortex (vmPFC) supports compensation as defined by three a priori criteria: (1) increased vmPFC activation was observed in older versus younger adults; (2) age-related increases in vmPFC activity were associated with increased retrieval demands; and (3) increased vmPFC activity was positively associated with performance in older adults—evidence of successful compensation. Extending these results, we observed evidence for compensation in connectivity between vmPFC and the dorsolateral PFC during memory-dependent choice. In contrast, we found no evidence for age differences in value-related processing or age-related compensation for choices without delayed retrieval. Together, these results converge on the conclusion that age-related decline in memory-dependent choice performance can be minimized via functional compensation in vmPFC. PMID:25411493

Representing delayed force feedback as a combination of current and delayed states.

PubMed

Avraham, Guy; Mawase, Firas; Karniel, Amir; Shmuelof, Lior; Donchin, Opher; Mussa-Ivaldi, Ferdinando A; Nisky, Ilana

2017-10-01

To adapt to deterministic force perturbations that depend on the current state of the hand, internal representations are formed to capture the relationships between forces experienced and motion. However, information from multiple modalities travels at different rates, resulting in intermodal delays that require compensation for these internal representations to develop. To understand how these delays are represented by the brain, we presented participants with delayed velocity-dependent force fields, i.e., forces that depend on hand velocity either 70 or 100 ms beforehand. We probed the internal representation of these delayed forces by examining the forces the participants applied to cope with the perturbations. The findings showed that for both delayed forces, the best model of internal representation consisted of a delayed velocity and current position and velocity. We show that participants relied initially on the current state, but with adaptation, the contribution of the delayed representation to adaptation increased. After adaptation, when the participants were asked to make movements with a higher velocity for which they had not previously experienced with the delayed force field, they applied forces that were consistent with current position and velocity as well as delayed velocity representations. This suggests that the sensorimotor system represents delayed force feedback using current and delayed state information and that it uses this representation when generalizing to faster movements. NEW & NOTEWORTHY The brain compensates for forces in the body and the environment to control movements, but it is unclear how it does so given the inherent delays in information transmission and processing. We examined how participants cope with delayed forces that depend on their arm velocity 70 or 100 ms beforehand. After adaptation, participants applied opposing forces that revealed a partially correct representation of the perturbation using the current and the delayed information. Copyright © 2017 the American Physiological Society.

The Abcd Formula of Phase Definition in Optical Interferometry: Combined Effect of Air Dispersion and Broad Passband

NASA Astrophysics Data System (ADS)

Mathar, Richard J.

Long-baseline interferometry detects fringes created by superposition of two beams of light collected by two telescopes pointing into a common direction. The external path difference is commonly compensated by adding a variable optical path length (delay) through air for one beam such that the optical path difference between the beams remains close to zero near the detector. The ABCD formula assigns a (wrapped) phase to the signals A to D of an interference pattern shifted by multiples of 90 degrees in phase. We study the interplay between a broad spectral passband of the optics and the dispersion of the air in the compensating delay, which leads to small deviations between the ABCD phase and the reduced, monochromatic group-delay representation of the wave packets. This adds dispersion to the effects that have been discussed for evacuated interferometers before (Milman 2005).

Evoked-potential recovery during double click stimulation in a beluga whale: implications for biosonar gain control.

PubMed

Supin, Alexander Ya; Popov, Vladimir V

2015-05-01

Auditory evoked potentials (AEPs) were recorded in a beluga whale Delphinapterus leucas using a double-pulse stimulation paradigm, specifically measuring the recovery (release from masking) of the second (test) response as a function of delay after the first (conditioning) pulse at various levels of the conditioning and test stimuli. The conditioning/test stimulus level ratio influenced the recovery time (the higher the ratio, the longer the recovery). This interrelation was used to evaluate the intensity/time trade in release from forward masking. Trade was evaluated as 32.2 dB per time decade. Data were considered as simulating interactions between the transmitted pulse and echo during echolocation, assuming that a transmitted sonar pulse produces forward masking of the echo response. With increased target distance, the attenuation of the echo may be compensated by the release from masking. According to the model, the compensation results in substantial stabilization of the echo response even if the intensity/time trade of release from masking is not precisely equal to the rate of echo attenuation with distance.

Distributed Synchronization Technique for OFDMA-Based Wireless Mesh Networks Using a Bio-Inspired Algorithm

PubMed Central

Kim, Mi Jeong; Maeng, Sung Joon; Cho, Yong Soo

2015-01-01

In this paper, a distributed synchronization technique based on a bio-inspired algorithm is proposed for an orthogonal frequency division multiple access (OFDMA)-based wireless mesh network (WMN) with a time difference of arrival. The proposed time- and frequency-synchronization technique uses only the signals received from the neighbor nodes, by considering the effect of the propagation delay between the nodes. It achieves a fast synchronization with a relatively low computational complexity because it is operated in a distributed manner, not requiring any feedback channel for the compensation of the propagation delays. In addition, a self-organization scheme that can be effectively used to construct 1-hop neighbor nodes is proposed for an OFDMA-based WMN with a large number of nodes. The performance of the proposed technique is evaluated with regard to the convergence property and synchronization success probability using a computer simulation. PMID:26225974

Distributed Synchronization Technique for OFDMA-Based Wireless Mesh Networks Using a Bio-Inspired Algorithm.

PubMed

Kim, Mi Jeong; Maeng, Sung Joon; Cho, Yong Soo

2015-07-28

In this paper, a distributed synchronization technique based on a bio-inspired algorithm is proposed for an orthogonal frequency division multiple access (OFDMA)-based wireless mesh network (WMN) with a time difference of arrival. The proposed time- and frequency-synchronization technique uses only the signals received from the neighbor nodes, by considering the effect of the propagation delay between the nodes. It achieves a fast synchronization with a relatively low computational complexity because it is operated in a distributed manner, not requiring any feedback channel for the compensation of the propagation delays. In addition, a self-organization scheme that can be effectively used to construct 1-hop neighbor nodes is proposed for an OFDMA-based WMN with a large number of nodes. The performance of the proposed technique is evaluated with regard to the convergence property and synchronization success probability using a computer simulation.

Noise interference with echo delay discrimination in bat biosonar.

PubMed

Simmons, J A

2017-11-01

Echolocating big brown bats (Eptesicus fuscus) were trained in a two-choice task to discriminate differences in the delay of electronic echoes at 1.7 ms delay (30 cm simulated range). Difference thresholds (∼45 μs) were comparable to previously published results. At selected above-threshold differences (116 and 232 μs delay), performance was measured in the presence of wideband random noise at increasing amplitudes in 10-dB steps to determine the noise level that prevented discrimination. Performance eventually failed, but the bats increased the amplitude and duration of their broadcasts to compensate for increasing noise, which allowed performance to persist at noise levels about 25 dB higher than without compensation. In the 232-μs delay discrimination condition, echo signal-to-noise ratio (2E/N 0 ) was 8-10 dB at the noise level that depressed performance to chance. Predicted echo-delay accuracy using big brown bat signals follows the Cramér-Rao bound for signal-to-noise ratios above 15 dB, but worsens below 15 dB due to side-peak ambiguity. At 2E/N 0  = 7-10 dB, predicted Cramér-Rao delay accuracy would be about 1 μs; considering side-peak ambiguity it would be about 200-300 μs. The bats' 232 μs performance reflects the intrusion of side-peak ambiguity into delay accuracy at low signal-to-noise ratios.

FBG wavelength demodulation based on a radio frequency optical true time delay method.

PubMed

Wang, Jin; Zhu, Wanshan; Ma, Chenyuan; Xu, Tong

2018-06-01

A new fiber Bragg grating (FBG) wavelength shift demodulation method based on optical true time delay microwave phase detection is proposed. We used a microwave photonic link (MPL) to transport a radio frequency (RF) signal over a dispersion compensation fiber (DCF). The wavelength shift of the FBG will cause the time delay change of the optical carrier that propagates in an optical fiber with chromatic dispersion, which will result in the variation of the RF signal phase. A long DCF was adopted to enlarge the RF signal phase variation. An IQ mixer was used to measure the RF phase variation of the RF signal propagating in the MPL, and the wavelength shift of the FBG can be obtained by the measured RF signal phase variation. The experimental results showed that the wavelength shift measurement resolution is 2 pm when the group velocity dispersion of the DCF is 79.5 ps/nm and the frequency of the RF signal is 18 GHz. The demodulation time is as short as 0.1 ms. The measurement resolution can be improved simply by using a higher frequency of the RF signal and a longer DCF or larger chromatic dispersion value of the DCF.

Method to control artifacts of microstructural fabrication

DOEpatents

Shul, Randy J.; Willison, Christi G.; Schubert, W. Kent; Manginell, Ronald P.; Mitchell, Mary-Anne; Galambos, Paul C.

2006-09-12

New methods for fabrication of silicon microstructures have been developed. In these methods, an etching delay layer is deposited and patterned so as to provide differential control on the depth of features being etched into a substrate material. Compensation for etching-related structural artifacts can be accomplished by proper use of such an etching delay layer.

Radiation Hardened Structured ASIC Platform with Compensation of Delay for Temperature and Voltage Variations for Multiple Redundant Temporal Voting Latch Technology

NASA Technical Reports Server (NTRS)

Ardalan, Sasan (Inventor)

2018-01-01

The invention relates to devices and methods of maintaining the current starved delay at a constant value across variations in voltage and temperature to increase the speed of operation of the sequential logic in the radiation hardened ASIC design.

Language Acquisition Patterns in Normal and Handicapped Children.

ERIC Educational Resources Information Center

Warren, Steven F.; Rogers-Warren, Ann

Delayed language development is compared to normal development along six basic parameters, and the problem of language delay among handicapped children is addressed. Interaction characteristics that occur at an early stage between the mother and handicapped child are also reviewed, along with the way parents tend to compensate for their child's…

Ground controlled robotic assembly operations for Space Station Freedom

NASA Technical Reports Server (NTRS)

Parrish, Joseph C.

1991-01-01

A number of dextrous robotic systems and associated positioning and transportation devices are available on Space Station Freedom (SSF) to perform assembly tasks that would otherwise need to be performed by extravehicular activity (EVA) crewmembers. The currently planned operating mode for these robotic systems during the assembly phase is teleoperation by intravehicular activity (IVA) crewmembers. While this operating mode is less hazardous and expensive than manned EVA operations, and has insignificant control loop time delays, the amount of IVA time available to support telerobotic operations is much less than the anticipated requirements. Some alternative is needed to allow the robotic systems to perform useful tasks without exhausting the available IVA resources; ground control is one such alternative. The issues associated with ground control of SSF robotic systems to alleviate onboard crew time availability constraints are investigated. Key technical issues include the effect of communication time delays, the need for safe, reliable execution of remote operations, and required modifications to the SSF ground and flight system architecture. Time delay compensation techniques such as predictive displays and world model-based force reflection are addressed and collision detection and avoidance strategies to ensure the safety of the on-orbit crew, Orbiter, and SSF are described. Although more time consuming and difficult than IVA controlled teleoperations or manned EVA, ground controlled telerobotic operations offer significant benefits during the SSF assembly phase, and should be considered in assembly planning activities.

Group consensus control for networked multi-agent systems with communication delays.

PubMed

An, Bao-Ran; Liu, Guo-Ping; Tan, Chong

2018-05-01

This paper investigates group consensus problems in networked multi-agent systems (NMAS) with communication delays. Based on the sed state prediction scheme, the group consensus control protocol is designed to compensate the communication delay actively. In light of algebraic graph theories and matrix theories, necessary and(or) sufficient conditions of group consensus with respect to a given admissible control set are obtained for the NMAS with communication delays under mild assumptions. Finally, simulations are performed to demonstrate the effectiveness of the theoretical results. Copyright © 2018 ISA. All rights reserved.

Echo-level compensation and delay tuning in the auditory cortex of the mustached bat.

PubMed

Macías, Silvio; Mora, Emanuel C; Hechavarría, Julio C; Kössl, Manfred

2016-06-01

During echolocation, bats continuously perform audio-motor adjustments to optimize detection efficiency. It has been demonstrated that bats adjust the amplitude of their biosonar vocalizations (known as 'pulses') to stabilize the amplitude of the returning echo. Here, we investigated this echo-level compensation behaviour by swinging mustached bats on a pendulum towards a reflective surface. In such a situation, the bats lower the amplitude of their emitted pulses to maintain the amplitude of incoming echoes at a constant level as they approach a target. We report that cortical auditory neurons that encode target distance have receptive fields that are optimized for dealing with echo-level compensation. In most cortical delay-tuned neurons, the echo amplitude eliciting the maximum response matches the echo amplitudes measured from the bats' biosonar vocalizations while they are swung in a pendulum. In addition, neurons tuned to short target distances are maximally responsive to low pulse amplitudes while neurons tuned to long target distances respond maximally to high pulse amplitudes. Our results suggest that bats dynamically adjust biosonar pulse amplitude to match the encoding of target range and to keep the amplitude of the returning echo within the bounds of the cortical map of echo delays. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

A Hyper-Dense GNSS Receiver Network for Monitoring Time and Spatial Variations of Precipitable Water Vapor (PWV)

NASA Astrophysics Data System (ADS)

Tsuda, T.; Ito, N.; Takeda, Y.; Realini, E.; Shinbori, A.

2016-12-01

We employ the GNSS meteorology technique to measure precipitable water vapor (PWV) from the propagation delay of GNSS signal in the atmosphere. We installed a hyper-dense GNSS network using 15 receivers with a horizontal spacing of 1-2 km in Uji, Japan (Uji network). We also obtained precipitation with a rain gauge at a nearby operational weather station and rain cloud distribution by an X-band radar. We selected 40 days from April 2011 to March 2013, when considerable precipitation was detected. Difference in PWV within 10 km was 3-10 mm during a heavy rain. We found PWV increased 10-20 minutes before a passage of a rain cloud. The maximum value of PWV correlated well with the amount of precipitation on the ground. The variance of PWV between the GNSS sites was enhanced during a heavy rain. For a future practical hyper-dense GNSS network system with many receivers, we consider to use inexpensive single frequency (SF) receivers. Because SF receiver cannot eliminate the ionospheric delay by itself, we interpolate the delay referring the delay measured by the nearby dual frequency (DF) receivers. We investigated ionospheric delay by the Uji network, taking advantages of Quasi-Zenith Satellite System (QZSS) that gives signals at high elevation angles. During a travelling ionospheric disturbance (TID), a wavy structure with a horizontal scale of several tens km was recognized. The ionospheric delay was compensated by a linear and quadratic interpolation, then the resulting error of PWV compared with DF solution was about 1.50 mm in RMS. For a real-time estimation of PWV, we used real-time satellite clock information corrected by GEONET. Difference of PWV between the real-time analysis and the post processing with the final orbit was 0.7 mm in RMS. We estimated an overall error of PWV with a dense SF-receiver network on a real-time basis was 1.7 mm in RMS.

High-precision coseismic displacement estimation with a single-frequency GPS receiver

NASA Astrophysics Data System (ADS)

Guo, Bofeng; Zhang, Xiaohong; Ren, Xiaodong; Li, Xingxing

2015-07-01

To improve the performance of Global Positioning System (GPS) in the earthquake/tsunami early warning and rapid response applications, minimizing the blind zone and increasing the stability and accuracy of both the rapid source and rupture inversion, the density of existing GPS networks must be increased in the areas at risk. For economic reasons, low-cost single-frequency receivers would be preferable to make the sparse dual-frequency GPS networks denser. When using single-frequency GPS receivers, the main problem that must be solved is the ionospheric delay, which is a critical factor when determining accurate coseismic displacements. In this study, we introduce a modified Satellite-specific Epoch-differenced Ionospheric Delay (MSEID) model to compensate for the effect of ionospheric error on single-frequency GPS receivers. In the MSEID model, the time-differenced ionospheric delays observed from a regional dual-frequency GPS network to a common satellite are fitted to a plane rather than part of a sphere, and the parameters of this plane are determined by using the coordinates of the stations. When the parameters are known, time-differenced ionospheric delays for a single-frequency GPS receiver could be derived from the observations of those dual-frequency receivers. Using these ionospheric delay corrections, coseismic displacements of a single-frequency GPS receiver can be accurately calculated based on time-differenced carrier-phase measurements in real time. The performance of the proposed approach is validated using 5 Hz GPS data collected during the 2012 Nicoya Peninsula Earthquake (Mw 7.6, 2012 September 5) in Costa Rica. This shows that the proposed approach improves the accuracy of the displacement of a single-frequency GPS station, and coseismic displacements with an accuracy of a few centimetres are achieved over a 10-min interval.

The corpus callosum in primates: processing speed of axons and the evolution of hemispheric asymmetry

PubMed Central

Phillips, Kimberley A.; Stimpson, Cheryl D.; Smaers, Jeroen B.; Raghanti, Mary Ann; Jacobs, Bob; Popratiloff, Anastas; Hof, Patrick R.; Sherwood, Chet C.

2015-01-01

Interhemispheric communication may be constrained as brain size increases because of transmission delays in action potentials over the length of axons. Although one might expect larger brains to have progressively thicker axons to compensate, spatial packing is a limiting factor. Axon size distributions within the primate corpus callosum (CC) may provide insights into how these demands affect conduction velocity. We used electron microscopy to explore phylogenetic variation in myelinated axon density and diameter of the CC from 14 different anthropoid primate species, including humans. The majority of axons were less than 1 µm in diameter across all species, indicating that conduction velocity for most interhemispheric communication is relatively constant regardless of brain size. The largest axons within the upper 95th percentile scaled with a progressively higher exponent than the median axons towards the posterior region of the CC. While brain mass among the primates in our analysis varied by 97-fold, estimates of the fastest cross-brain conduction times, as conveyed by axons at the 95th percentile, varied within a relatively narrow range between 3 and 9 ms across species, whereas cross-brain conduction times for the median axon diameters differed more substantially between 11 and 38 ms. Nonetheless, for both size classes of axons, an increase in diameter does not entirely compensate for the delay in interhemispheric transmission time that accompanies larger brain size. Such biophysical constraints on the processing speed of axons conveyed by the CC may play an important role in the evolution of hemispheric asymmetry. PMID:26511047

General anesthesia alters time perception by phase shifting the circadian clock.

PubMed

Cheeseman, James F; Winnebeck, Eva C; Millar, Craig D; Kirkland, Lisa S; Sleigh, James; Goodwin, Mark; Pawley, Matt D M; Bloch, Guy; Lehmann, Konstantin; Menzel, Randolf; Warman, Guy R

2012-05-01

Following general anesthesia, people are often confused about the time of day and experience sleep disruption and fatigue. It has been hypothesized that these symptoms may be caused by general anesthesia affecting the circadian clock. The circadian clock is fundamental to our well-being because it regulates almost all aspects of our daily biochemistry, physiology, and behavior. Here, we investigated the effects of the most common general anesthetic, isoflurane, on time perception and the circadian clock using the honeybee (Apis mellifera) as a model. A 6-h daytime anesthetic systematically altered the time-compensated sun compass orientation of the bees, with a mean anticlockwise shift in vanishing bearing of 87° in the Southern Hemisphere and a clockwise shift in flight direction of 58° in the Northern Hemisphere. Using the same 6-h anesthetic treatment, time-trained bees showed a delay in the start of foraging of 3.3 h, and whole-hive locomotor-activity rhythms were delayed by an average of 4.3 h. We show that these effects are all attributable to a phase delay in the core molecular clockwork. mRNA oscillations of the central clock genes cryptochrome-m and period were delayed by 4.9 and 4.3 h, respectively. However, this effect is dependent on the time of day of administration, as is common for clock effects, and nighttime anesthesia did not shift the clock. Taken together, our results suggest that general anesthesia during the day causes a persistent and marked shift of the clock effectively inducing "jet lag" and causing impaired time perception. Managing this effect in humans is likely to help expedite postoperative recovery.

Building Information Modelling (BIM) and Unmanned Aerial Vehicle (UAV) technologies in infrastructure construction project management and delay and disruption analysis

NASA Astrophysics Data System (ADS)

Vacanas, Yiannis; Themistocleous, Kyriacos; Agapiou, Athos; Hadjimitsis, Diofantos

2015-06-01

Time in infrastructure construction projects has always been a fundamental issue as early as from the inception of a project, during the construction process and often after the completion and delivery. In a typical construction contract time related matters such as the completion date and possible delays are among the most important issues that are dealt with by the contract provisions. In the event of delay there are usually provisions for extension of time award to the contractor with possible reimbursement for the extra cost and expenses caused by this extension of time to the contract duration. In the case the contractor is not entitled to extension of time, the owner will be possibly entitled to amounts as compensation for the time prohibited from using his development. Even in the event of completion within the time agreed, under certain circumstances a contractor may have claims for reimbursement for extra costs incurred due to induced acceleration measures he had to take in order to mitigate disruption effects caused to the progress of the works by the owner or his representatives. Depending on the size of the project and the agreement amount, these reimbursement sums may be extremely high. Therefore innovative methods with the exploitation of new technologies for effective project management for the avoidance of delays, delay analysis and mitigation measures are essential; moreover, methods for collecting efficiently information during the construction process so that disputes regarding time are avoided or resolved in a quick and fair manner are required. This paper explores the state of art for existing use of Building Information Modelling (BIM) and Unmanned Aerial Vehicles (UAV) technologies in the construction industry in general. Moreover the paper considers the prospect of using BIM technology in conjunction with the use of UAV technology for efficient and accurate as-built data collection and illustration of the works progress during an infrastructure construction project in order to achieve more effective project management, record keeping and delay analysis.

Source motion detection, estimation, and compensation for underwater acoustics inversion by wideband ambiguity lag-Doppler filtering.

PubMed

Josso, Nicolas F; Ioana, Cornel; Mars, Jérôme I; Gervaise, Cédric

2010-12-01

Acoustic channel properties in a shallow water environment with moving source and receiver are difficult to investigate. In fact, when the source-receiver relative position changes, the underwater environment causes multipath and Doppler scale changes on the transmitted signal over low-to-medium frequencies (300 Hz-20 kHz). This is the result of a combination of multiple paths propagation, source and receiver motions, as well as sea surface motion or water column fast changes. This paper investigates underwater acoustic channel properties in a shallow water (up to 150 m depth) and moving source-receiver conditions using extracted time-scale features of the propagation channel model for low-to-medium frequencies. An average impulse response of one transmission is estimated using the physical characteristics of propagation and the wideband ambiguity plane. Since a different Doppler scale should be considered for each propagating signal, a time-warping filtering method is proposed to estimate the channel time delay and Doppler scale attributes for each propagating path. The proposed method enables the estimation of motion-compensated impulse responses, where different Doppler scaling factors are considered for the different time delays. It was validated for channel profiles using real data from the BASE'07 experiment conducted by the North Atlantic Treaty Organization Undersea Research Center in the shallow water environment of the Malta Plateau, South Sicily. This paper provides a contribution to many field applications including passive ocean tomography with unknown natural sources position and movement. Another example is active ocean tomography where sources motion enables to rapidly cover one operational area for rapid environmental assessment and hydrophones may be drifting in order to avoid additional flow noise.

Chirped-cavity dispersion-compensation filter design.

PubMed

Li, Ya-Ping; Chen, Sheng-Hui; Lee, Cheng-Chung

2006-03-01

A new basic structure of a dispersive-compensation filter, called a chirped-cavity dispersion-compensator (CCDC) filter, was designed to offer the advantages of small ripples in both reflectance and group-delay dispersion (GDD). This filter provides a high dispersion compensation, like the Gires-Tournois interferometer (GTI) filter, and a wide working bandwidth, like the chirped mirror (CM). The structure of the CCDC is a cavity-type Fabry-Perot filter with a spacer layer (2 mH or 2 mL) and a chirped high reflector. The CCDC filter can provide a negative GDD of -50 fs2 over a bandwidth of 56 THz with half the optical thickness of the CM or the GTI.

Chirped-cavity dispersion-compensation filter design

NASA Astrophysics Data System (ADS)

Li, Ya-Ping; Chen, Sheng-Hui; Lee, Cheng-Chung

2006-03-01

A new basic structure of a dispersive-compensation filter, called a chirped-cavity dispersion-compensator (CCDC) filter, was designed to offer the advantages of small ripples in both reflectance and group-delay dispersion (GDD). This filter provides a high dispersion compensation, like the Gires-Tournois interferometer (GTI) filter, and a wide working bandwidth, like the chirped mirror (CM). The structure of the CCDC is a cavity-type Fabry-Perot filter with a spacer layer (2 mH or 2 mL) and a chirped high reflector. The CCDC filter can provide a negative GDD of -50 fs2 over a bandwidth of 56 THz with half the optical thickness of the CM or the GTI.

Intermittent Feedback-Control Strategy for Stabilizing Inverted Pendulum on Manually Controlled Cart as Analogy to Human Stick Balancing

PubMed Central

Yoshikawa, Naoya; Suzuki, Yasuyuki; Kiyono, Ken; Nomura, Taishin

2016-01-01

The stabilization of an inverted pendulum on a manually controlled cart (cart-inverted-pendulum; CIP) in an upright position, which is analogous to balancing a stick on a fingertip, is considered in order to investigate how the human central nervous system (CNS) stabilizes unstable dynamics due to mechanical instability and time delays in neural feedback control. We explore the possibility that a type of intermittent time-delayed feedback control, which has been proposed for human postural control during quiet standing, is also a promising strategy for the CIP task and stick balancing on a fingertip. Such a strategy hypothesizes that the CNS exploits transient contracting dynamics along a stable manifold of a saddle-type unstable upright equilibrium of the inverted pendulum in the absence of control by inactivating neural feedback control intermittently for compensating delay-induced instability. To this end, the motions of a CIP stabilized by human subjects were experimentally acquired, and computational models of the system were employed to characterize the experimental behaviors. We first confirmed fat-tailed non-Gaussian temporal fluctuation in the acceleration distribution of the pendulum, as well as the power-law distributions of corrective cart movements for skilled subjects, which was previously reported for stick balancing. We then showed that the experimental behaviors could be better described by the models with an intermittent delayed feedback controller than by those with the conventional continuous delayed feedback controller, suggesting that the human CNS stabilizes the upright posture of the pendulum by utilizing the intermittent delayed feedback-control strategy. PMID:27148031

Intermittent Feedback-Control Strategy for Stabilizing Inverted Pendulum on Manually Controlled Cart as Analogy to Human Stick Balancing.

PubMed

Yoshikawa, Naoya; Suzuki, Yasuyuki; Kiyono, Ken; Nomura, Taishin

2016-01-01

The stabilization of an inverted pendulum on a manually controlled cart (cart-inverted-pendulum; CIP) in an upright position, which is analogous to balancing a stick on a fingertip, is considered in order to investigate how the human central nervous system (CNS) stabilizes unstable dynamics due to mechanical instability and time delays in neural feedback control. We explore the possibility that a type of intermittent time-delayed feedback control, which has been proposed for human postural control during quiet standing, is also a promising strategy for the CIP task and stick balancing on a fingertip. Such a strategy hypothesizes that the CNS exploits transient contracting dynamics along a stable manifold of a saddle-type unstable upright equilibrium of the inverted pendulum in the absence of control by inactivating neural feedback control intermittently for compensating delay-induced instability. To this end, the motions of a CIP stabilized by human subjects were experimentally acquired, and computational models of the system were employed to characterize the experimental behaviors. We first confirmed fat-tailed non-Gaussian temporal fluctuation in the acceleration distribution of the pendulum, as well as the power-law distributions of corrective cart movements for skilled subjects, which was previously reported for stick balancing. We then showed that the experimental behaviors could be better described by the models with an intermittent delayed feedback controller than by those with the conventional continuous delayed feedback controller, suggesting that the human CNS stabilizes the upright posture of the pendulum by utilizing the intermittent delayed feedback-control strategy.

Delayed repair of distal biceps tendon ruptures is successful: a case-control study.

PubMed

Haverstock, John; Grewal, Ruby; King, Graham J W; Athwal, George S

2017-06-01

The literature has shown an increased complication rate with a delay to surgical repair of acute distal biceps tendon ruptures; however, little has been documented regarding the outcome of delayed repairs. This case-control study compared a study cohort of delayed (>21 days) distal biceps tendon repairs with a control cohort repaired acutely (<21 days). Sixteen delayed repair cases were reviewed and matched with acute controls (1:3) based on repair technique, age, and workers' compensation status. The delayed cohort was reviewed and completed isometric strength testing and the Disabilities of the Arm, Shoulder and Hand questionnaire; Patient-Rated Elbow Evaluation; and American Shoulder and Elbow Surgeons elbow questionnaire. The time to surgery averaged 37 ± 12 days in the delayed cohort versus 10 ± 6 days in the acute cohort. Complications occurred in 63% of patients in the delayed cohort versus 29% in the acute cohort (P = .04); however, 90% of the delayed cohort's complications consisted of transient paresthesias. Follow-up scores on the Patient-Rated Elbow Evaluation, Disabilities of the Arm, Shoulder and Hand questionnaire, and American Shoulder and Elbow Surgeons elbow questionnaire were not statistically different between cohorts (P > .37, P > .22, and P > .46, respectively). Despite a high rate of initial complications, patients treated with distal biceps tendon repair after a delay (>21 days) can expect similar functional outcomes to those treated acutely. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

Robust PI and PID design for first- and second-order processes with zeros, time-delay and structured uncertainties

NASA Astrophysics Data System (ADS)

Parada, M.; Sbarbaro, D.; Borges, R. A.; Peres, P. L. D.

2017-01-01

The use of robust design techniques such as the one based on ? and ? for tuning proportional integral (PI) and proportional integral derivative (PID) controllers have been limited to address a small set of processes. This work addresses the problem by considering a wide set of possible plants, both first- and second-order continuous-time systems with time delays and zeros, leading to PI and PID controllers. The use of structured uncertainties to handle neglected dynamics allows to expand the range of processes to be considered. The proposed approach takes into account the robustness of the controller with respect to these structured uncertainties by using the small-gain theorem. In addition, improved performance is sought through the minimisation of an upper bound to the closed-loop system ? norm. A Lyapunov-Krasovskii-type functional is used to obtain delay-dependent design conditions. The controller design is accomplished by means of a convex optimisation procedure formulated using linear matrix inequalities. In order to illustrate the flexibility of the approach, several examples considering recycle compensation, reduced-order controller design and a practical implementation are addressed. Numerical experiments are provided in each case to highlight the main characteristics of the proposed design method.

System and method for adaptively deskewing parallel data signals relative to a clock

DOEpatents

Jenkins, Philip Nord [Eau Claire, WI; Cornett, Frank N [Chippewa Falls, WI

2008-10-07

A system and method of reducing skew between a plurality of signals transmitted with a transmit clock is described. Skew is detected between the received transmit clock and each of received data signals. Delay is added to the clock or to one or more of the plurality of data signals to compensate for the detected skew. The delay added to each of the plurality of delayed signals is updated to adapt to changes in detected skew.

System and method for adaptively deskewing parallel data signals relative to a clock

DOEpatents

Jenkins, Philip Nord [Redwood Shores, CA; Cornett, Frank N [Chippewa Falls, WI

2011-10-04

A system and method of reducing skew between a plurality of signals transmitted with a transmit clock is described. Skew is detected between the received transmit clock and each of received data signals. Delay is added to the clock or to one or more of the plurality of data signals to compensate for the detected skew. The delay added to each of the plurality of delayed signals is updated to adapt to changes in detected skew.

System and method for adaptively deskewing parallel data signals relative to a clock

DOEpatents

Jenkins, Philip Nord; Cornett, Frank N.

2006-04-18

A system and method of reducing skew between a plurality of signals transmitted with a transmit clock is described. Skew is detected between the received transmit clock and each of received data signals. Delay is added to the clock or to one or more of the plurality of data signals to compensate for the detected skew. Each of the plurality of delayed signals is compared to a reference signal to detect changes in the skew. The delay added to each of the plurality of delayed signals is updated to adapt to changes in the detected skew.

A wide-band fiber optic frequency distribution system employing thermally controlled phase compensation

NASA Technical Reports Server (NTRS)

Johnson, Dean; Calhoun, Malcolm; Sydnor, Richard; Lutes, George

1993-01-01

An active wide-band fiber optic frequency distribution system employing a thermally controlled phase compensator to stabilize phase variations induced by environmental temperature changes is described. The distribution system utilizes bidirectional dual wavelength transmission to provide optical feedback of induced phase variations of 100 MHz signals propagating along the distribution cable. The phase compensation considered differs from earlier narrow-band phase compensation designs in that it uses a thermally controlled fiber delay coil rather than a VCO or phase modulation to compensate for induced phase variations. Two advantages of the wide-band system over earlier designs are (1) that it provides phase compensation for all transmitted frequencies, and (2) the compensation is applied after the optical interface rather than electronically ahead of it as in earlier schemes. Experimental results on the first prototype shows that the thermal stabilizer reduces phase variations and Allan deviation by a factor of forty over an equivalent uncompensated fiber optic distribution system.

A Time-Domain CMOS Oscillator-Based Thermostat with Digital Set-Point Programming

PubMed Central

Chen, Chun-Chi; Lin, Shih-Hao

2013-01-01

This paper presents a time-domain CMOS oscillator-based thermostat with digital set-point programming [without a digital-to-analog converter (DAC) or external resistor] to achieve on-chip thermal management of modern VLSI systems. A time-domain delay-line-based thermostat with multiplexers (MUXs) was used to substantially reduce the power consumption and chip size, and can benefit from the performance enhancement due to the scaling down of fabrication processes. For further cost reduction and accuracy enhancement, this paper proposes a thermostat using two oscillators that are suitable for time-domain curvature compensation instead of longer linear delay lines. The final time comparison was achieved using a time comparator with a built-in custom hysteresis to generate the corresponding temperature alarm and control. The chip size of the circuit was reduced to 0.12 mm2 in a 0.35-μm TSMC CMOS process. The thermostat operates from 0 to 90 °C, and achieved a fine resolution better than 0.05 °C and an improved inaccuracy of ± 0.6 °C after two-point calibration for eight packaged chips. The power consumption was 30 μW at a sample rate of 10 samples/s. PMID:23385403

Real-time ultrawide-band group delay profile monitoring through low-noise incoherent temporal interferometry.

PubMed

Park, Yongwoo; Malacarne, Antonio; Azaña, José

2011-02-28

A simple, highly accurate measurement technique for real-time monitoring of the group delay (GD) profiles of photonic dispersive devices over ultra-broad spectral bandwidths (e.g. an entire communication wavelength band) is demonstrated. The technique is based on time-domain self-interference of an incoherent light pulse after linear propagation through the device under test, providing a measurement wavelength range as wide as the source spectral bandwidth. Significant enhancement in the signal-to-noise ratio of the self-interference signal has been observed by use of a relatively low-noise incoherent light source as compared with the theoretical estimate for a white-noise light source. This fact combined with the use of balanced photo-detection has allowed us to significantly reduce the number of profiles that need to be averaged to reach a targeted GD measurement accuracy, thus achieving reconstruction of the device GD profile in real time. We report highly-accurate monitoring of (i) the group-delay ripple (GDR) profile of a 10-m long chirped fiber Bragg grating over the full C band (~42 nm), and (ii) the group velocity dispersion (GVD) and dispersion slope (DS) profiles of a ~2-km long dispersion compensating fiber module over an ~72-nm wavelength range, both captured at a 15 frames/s video rate update, with demonstrated standard deviations in the captured GD profiles as low as ~1.6 ps.

Predicting time on prolonged benefits for injured workers with acute back pain.

PubMed

Steenstra, Ivan A; Busse, Jason W; Tolusso, David; Davilmar, Arold; Lee, Hyunmi; Furlan, Andrea D; Amick, Ben; Hogg-Johnson, Sheilah

2015-06-01

Some workers with work-related compensated back pain (BP) experience a troubling course of disability. Factors associated with delayed recovery among workers with work-related compensated BP were explored. This is a cohort study of workers with compensated BP in 2005 in Ontario, Canada. Follow up was 2 years. Data was collected from employers, employees and health-care providers by the Workplace Safety and Insurance Board (WSIB). Exclusion criteria were: (1) no-lost-time claims, (2) >30 days between injury and claim filing, (3) <4 weeks benefits duration, and (4) age >65 years. Using proportional hazard models, we examined the prognostic value of information collected in the first 4 weeks after injury. Outcome measures were time on benefits during the first episode and time until recurrence after the first episode. Of 6,657 workers, 1,442 were still on full benefits after 4 weeks. Our final model containing age, physical demands, opioid prescription, union membership, availability of a return-to-work program, employer doubt about work-relatedness of injury, worker's recovery expectations, participation in a rehabilitation program and communication of functional ability was able to identify prolonged claims to a fair degree [area under the curve (AUC) = .79, 95% confidence interval (CI) .74-.84]. A model containing age, sex, physical demands, opioid prescription and communication of functional ability was less successful at predicting time until recurrence (AUC = .61, 95% CI .57, .65). Factors contained in information currently collected by the WSIB during the first 4 weeks on benefits can predict prolonged claims, but not recurrent claims.

Simultaneous chromatic dispersion and PMD compensation by using coded-OFDM and girth-10 LDPC codes.

PubMed

Djordjevic, Ivan B; Xu, Lei; Wang, Ting

2008-07-07

Low-density parity-check (LDPC)-coded orthogonal frequency division multiplexing (OFDM) is studied as an efficient coded modulation scheme suitable for simultaneous chromatic dispersion and polarization mode dispersion (PMD) compensation. We show that, for aggregate rate of 10 Gb/s, accumulated dispersion over 6500 km of SMF and differential group delay of 100 ps can be simultaneously compensated with penalty within 1.5 dB (with respect to the back-to-back configuration) when training sequence based channel estimation and girth-10 LDPC codes of rate 0.8 are employed.

An Acoustic OFDM System with Symbol-by-Symbol Doppler Compensation for Underwater Communication

PubMed Central

MinhHai, Tran; Rie, Saotome; Suzuki, Taisaku; Wada, Tomohisa

2016-01-01

We propose an acoustic OFDM system for underwater communication, specifically for vertical link communications such as between a robot in the sea bottom and a mother ship in the surface. The main contributions are (1) estimation of time varying Doppler shift using continual pilots in conjunction with monitoring the drift of Power Delay Profile and (2) symbol-by-symbol Doppler compensation in frequency domain by an ICI matrix representing nonuniform Doppler. In addition, we compare our proposal against a resampling method. Simulation and experimental results confirm that our system outperforms the resampling method when the velocity changes roughly over OFDM symbols. Overall, experimental results taken in Shizuoka, Japan, show our system using 16QAM, and 64QAM achieved a data throughput of 7.5 Kbit/sec with a transmitter moving at maximum 2 m/s, in a complicated trajectory, over 30 m vertically. PMID:27057558

A model that integrates eye velocity commands to keep track of smooth eye displacements.

PubMed

Blohm, Gunnar; Optican, Lance M; Lefèvre, Philippe

2006-08-01

Past results have reported conflicting findings on the oculomotor system's ability to keep track of smooth eye movements in darkness. Whereas some results indicate that saccades cannot compensate for smooth eye displacements, others report that memory-guided saccades during smooth pursuit are spatially correct. Recently, it was shown that the amount of time before the saccade made a difference: short-latency saccades were retinotopically coded, whereas long-latency saccades were spatially coded. Here, we propose a model of the saccadic system that can explain the available experimental data. The novel part of this model consists of a delayed integration of efferent smooth eye velocity commands. Two alternative physiologically realistic neural mechanisms for this integration stage are proposed. Model simulations accurately reproduced prior findings. Thus, this model reconciles the earlier contradictory reports from the literature about compensation for smooth eye movements before saccades because it involves a slow integration process.

A zero phase adaptive fuzzy Kalman filter for physiological tremor suppression in robotically assisted minimally invasive surgery.

PubMed

Sang, Hongqiang; Yang, Chenghao; Liu, Fen; Yun, Jintian; Jin, Guoguang; Chen, Fa

2016-12-01

Hand physiological tremor of surgeons can cause vibration at the surgical instrument tip, which may make it difficult for the surgeon to perform fine manipulations of tissue, needles, and sutures. A zero phase adaptive fuzzy Kalman filter (ZPAFKF) is proposed to suppress hand tremor and vibration of a robotic surgical system. The involuntary motion can be reduced by adding a compensating signal that has the same magnitude and frequency but opposite phase with the tremor signal. Simulations and experiments using different filters were performed. Results show that the proposed filter can avoid the loss of useful motion information and time delay, and better suppress minor and varying tremor. The ZPAFKF can provide less error, preferred accuracy, better tremor estimation, and more desirable compensation performance, to suppress hand tremor and decrease vibration at the surgical instrument tip. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Control at stability's edge minimizes energetic costs: expert stick balancing

PubMed Central

Meyer, Ryan; Zhvanetsky, Max; Ridge, Sarah; Insperger, Tamás

2016-01-01

Stick balancing on the fingertip is a complex voluntary motor task that requires the stabilization of an unstable system. For seated expert stick balancers, the time delay is 0.23 s, the shortest stick that can be balanced for 240 s is 0.32 m and there is a ° dead zone for the estimation of the vertical displacement angle in the saggital plane. These observations motivate a switching-type, pendulum–cart model for balance control which uses an internal model to compensate for the time delay by predicting the sensory consequences of the stick's movements. Numerical simulations using the semi-discretization method suggest that the feedback gains are tuned near the edge of stability. For these choices of the feedback gains, the cost function which takes into account the position of the fingertip and the corrective forces is minimized. Thus, expert stick balancers optimize control with a combination of quick manoeuvrability and minimum energy expenditures. PMID:27278361

Bilateral control of master-slave manipulators with constant time delay.

PubMed

Forouzantabar, A; Talebi, H A; Sedigh, A K

2012-01-01

This paper presents a novel teleoperation controller for a nonlinear master-slave robotic system with constant time delay in communication channel. The proposed controller enables the teleoperation system to compensate human and environmental disturbances, while achieving master and slave position coordination in both free motion and contact situation. The current work basically extends the passivity based architecture upon the earlier work of Lee and Spong (2006) [14] to improve position tracking and consequently transparency in the face of disturbances and environmental contacts. The proposed controller employs a PID controller in each side to overcome some limitations of a PD controller and guarantee an improved performance. Moreover, by using Fourier transform and Parseval's identity in the frequency domain, we demonstrate that this new PID controller preserves the passivity of the system. Simulation and semi-experimental results show that the PID controller tracking performance is superior to that of the PD controller tracking performance in slave/environmental contacts. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.

Adaptive low-power listening MAC protocol based on transmission rates.

PubMed

Hwang, Kwang-il; Yi, Gangman

2014-01-01

Even though existing low-power listening (LPL) protocols have enabled ultra-low-power operation in wireless sensor networks (WSN), they do not address trade-off between energy and delay, since they focused only on energy aspect. However, in recent years, a growing interest in various WSN applications is requiring new design factors, such as minimum delay and higher reliability, as well as energy efficiency. Therefore, in this paper we propose a novel sensor multiple access control (MAC) protocol, transmission rate based adaptive low-power listening MAC protocol (TRA-MAC), which is a kind of preamble-based LPL but is capable of controlling preamble sensing cycle adaptively to transmission rates. Through experiments, it is demonstrated that TRA-MAC enables LPL cycle (LC) and preamble transmission length to adapt dynamically to varying transmission rates, compensating trade-off between energy and response time.

Distant Speech Recognition Using a Microphone Array Network

NASA Astrophysics Data System (ADS)

Nakano, Alberto Yoshihiro; Nakagawa, Seiichi; Yamamoto, Kazumasa

In this work, spatial information consisting of the position and orientation angle of an acoustic source is estimated by an artificial neural network (ANN). The estimated position of a speaker in an enclosed space is used to refine the estimated time delays for a delay-and-sum beamformer, thus enhancing the output signal. On the other hand, the orientation angle is used to restrict the lexicon used in the recognition phase, assuming that the speaker faces a particular direction while speaking. To compensate the effect of the transmission channel inside a short frame analysis window, a new cepstral mean normalization (CMN) method based on a Gaussian mixture model (GMM) is investigated and shows better performance than the conventional CMN for short utterances. The performance of the proposed method is evaluated through Japanese digit/command recognition experiments.

Using EMG to anticipate head motion for virtual-environment applications

NASA Technical Reports Server (NTRS)

Barniv, Yair; Aguilar, Mario; Hasanbelliu, Erion

2005-01-01

In virtual environment (VE) applications, where virtual objects are presented in a see-through head-mounted display, virtual images must be continuously stabilized in space in response to user's head motion. Time delays in head-motion compensation cause virtual objects to "swim" around instead of being stable in space which results in misalignment errors when overlaying virtual and real objects. Visual update delays are a critical technical obstacle for implementing head-mounted displays in applications such as battlefield simulation/training, telerobotics, and telemedicine. Head motion is currently measurable by a head-mounted 6-degrees-of-freedom inertial measurement unit. However, even given this information, overall VE-system latencies cannot be reduced under about 25 ms. We present a novel approach to eliminating latencies, which is premised on the fact that myoelectric signals from a muscle precede its exertion of force, thereby limb or head acceleration. We thus suggest utilizing neck-muscles' myoelectric signals to anticipate head motion. We trained a neural network to map such signals onto equivalent time-advanced inertial outputs. The resulting network can achieve time advances of up to 70 ms.

Using EMG to anticipate head motion for virtual-environment applications.

PubMed

Barniv, Yair; Aguilar, Mario; Hasanbelliu, Erion

2005-06-01

In virtual environment (VE) applications, where virtual objects are presented in a see-through head-mounted display, virtual images must be continuously stabilized in space in response to user's head motion. Time delays in head-motion compensation cause virtual objects to "swim" around instead of being stable in space which results in misalignment errors when overlaying virtual and real objects. Visual update delays are a critical technical obstacle for implementing head-mounted displays in applications such as battlefield simulation/training, telerobotics, and telemedicine. Head motion is currently measurable by a head-mounted 6-degrees-of-freedom inertial measurement unit. However, even given this information, overall VE-system latencies cannot be reduced under about 25 ms. We present a novel approach to eliminating latencies, which is premised on the fact that myoelectric signals from a muscle precede its exertion of force, thereby limb or head acceleration. We thus suggest utilizing neck-muscles' myoelectric signals to anticipate head motion. We trained a neural network to map such signals onto equivalent time-advanced inertial outputs. The resulting network can achieve time advances of up to 70 ms.

First-Order-hold interpolation digital-to-analog converter with application to aircraft simulation

NASA Technical Reports Server (NTRS)

Cleveland, W. B.

1976-01-01

Those who design piloted aircraft simulations must contend with the finite size and speed of the available digital computer and the requirement for simulation reality. With a fixed computational plant, the more complex the model, the more computing cycle time is required. While increasing the cycle time may not degrade the fidelity of the simulated aircraft dynamics, the larger steps in the pilot cue feedback variables (such as the visual scene cues), may be disconcerting to the pilot. The first-order-hold interpolation (FOHI) digital-to-analog converter (DAC) is presented as a device which offers smooth output, regardless of cycle time. The Laplace transforms of these three conversion types are developed and their frequency response characteristics and output smoothness are compared. The FOHI DAC exhibits a pure one-cycle delay. Whenever the FOHI DAC input comes from a second-order (or higher) system, a simple computer software technique can be used to compensate for the DAC phase lag. When so compensated, the FOHI DAC has (1) an output signal that is very smooth, (2) a flat frequency response in frequency ranges of interest, and (3) no phase error. When the input comes from a first-order system, software compensation may cause the FOHI DAC to perform as an FOHE DAC, which, although its output is not as smooth as that of the FOHI DAC, has a smoother output than that of the ZOH DAC.

Collinear interferometer with variable delay for carrier-envelope offset frequency measurement

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

Pawlowska, Monika; Ozimek, Filip; Fita, Piotr

2009-08-15

We demonstrate a novel scheme for measuring the carrier-envelope offset frequency in a femtosecond optical frequency comb. Our method is based on a common-path interferometer with a calcite Babinet-Soleil compensator employed to control the delay between the two interfering beams of pulses. The large delay range (up to 8 ps) of our device is sufficient for systems that rely on spectral broadening in microstructured fibers. We show an experimental proof that the stability of a common-path arrangement is superior to that of the standard interferometers.

Collinear interferometer with variable delay for carrier-envelope offset frequency measurement

NASA Astrophysics Data System (ADS)

Pawłowska, Monika; Ozimek, Filip; Fita, Piotr; Radzewicz, Czesław

2009-08-01

We demonstrate a novel scheme for measuring the carrier-envelope offset frequency in a femtosecond optical frequency comb. Our method is based on a common-path interferometer with a calcite Babinet-Soleil compensator employed to control the delay between the two interfering beams of pulses. The large delay range (up to 8 ps) of our device is sufficient for systems that rely on spectral broadening in microstructured fibers. We show an experimental proof that the stability of a common-path arrangement is superior to that of the standard interferometers.

Half radiofrequency pulse excitation with a dedicated prescan to correct eddy current effect and gradient delay.

PubMed

Abe, Takayuki

2013-03-01

To improve the slice profile of the half radiofrequency (RF) pulse excitation and image quality of ultrashort echo time (UTE) imaging by compensating for an eddy current effect. The dedicated prescan has been developed to measure the phase accumulation due to eddy currents induced by the slice-selective gradient. The prescan measures two one-dimensional excitation k-space profiles, which can be acquired with a readout gradient in the slice-selection direction by changing the polarity of the slice-selective gradient. The time shifts due to the phase accumulation in the excitation k-space were calculated. The time shift compensated for the start time of the slice-selective gradient. The total prescan time was 6-15 s. The slice profile and the UTE image with the half RF pulse excitation were acquired to evaluate the slice selectivity and the image quality. Improved slice selectivity was obtained. The simple method proposed in this paper can eliminate eddy current effect. Good UTE images were obtained. The slice profile of the half RF pulse excitation and the image quality of UTE images have been improved by using a dedicated prescan. This method has a possibility that can improve the image quality of a clinical UTE imaging.

Real-time auto-adaptive margin generation for MLC-tracked radiotherapy

NASA Astrophysics Data System (ADS)

Glitzner, M.; Fast, M. F.; de Senneville, B. Denis; Nill, S.; Oelfke, U.; Lagendijk, J. J. W.; Raaymakers, B. W.; Crijns, S. P. M.

2017-01-01

In radiotherapy, abdominal and thoracic sites are candidates for performing motion tracking. With real-time control it is possible to adjust the multileaf collimator (MLC) position to the target position. However, positions are not perfectly matched and position errors arise from system delays and complicated response of the electromechanic MLC system. Although, it is possible to compensate parts of these errors by using predictors, residual errors remain and need to be compensated to retain target coverage. This work presents a method to statistically describe tracking errors and to automatically derive a patient-specific, per-segment margin to compensate the arising underdosage on-line, i.e. during plan delivery. The statistics of the geometric error between intended and actual machine position are derived using kernel density estimators. Subsequently a margin is calculated on-line according to a selected coverage parameter, which determines the amount of accepted underdosage. The margin is then applied onto the actual segment to accommodate the positioning errors in the enlarged segment. The proof-of-concept was tested in an on-line tracking experiment and showed the ability to recover underdosages for two test cases, increasing {{V}90 %} in the underdosed area about 47 % and 41 % , respectively. The used dose model was able to predict the loss of dose due to tracking errors and could be used to infer the necessary margins. The implementation had a running time of 23 ms which is compatible with real-time requirements of MLC tracking systems. The auto-adaptivity to machine and patient characteristics makes the technique a generic yet intuitive candidate to avoid underdosages due to MLC tracking errors.

Characterization and quenching of friction-induced limit cycles of electro-hydraulic servovalve control systems with transport delay.

PubMed

Wang, Yuan-Jay

2010-10-01

This paper develops a systematic and straightforward methodology to characterize and quench the friction-induced limit cycle conditions in electro-hydraulic servovalve control systems with transport delay in the transmission line. The nonlinear friction characteristic is linearized by using its corresponding describing function. The delay time in the transmission line, which could accelerate the generation of limit cycles is particularly considered. The stability equation method together with parameter plane method provides a useful tool for the establishment of necessary conditions to sustain a limit cycle directly in the constructed controller coefficient plane. Also, the stable region, the unstable region, and the limit cycle region are identified in the parameter plane. The parameter plane characterizes a clear relationship between limit cycle amplitude, frequency, transport delay, and the controller coefficients to be designed. The stability of the predicted limit cycle is checked by plotting stability curves. The stability of the system is examined when the viscous gain changes with respect to the temperature of the working fluid. A feasible stable region is characterized in the parameter plane to allow a flexible choice of controller gains. The robust prevention of limit cycle is achieved by selecting controller gains from the asymptotic stability region. The predicted results are verified by simulations. It is seen that the friction-induced limit cycles can be effectively predicted, removed, and quenched via the design of the compensator even in the case of viscous gain and delay time variations unconditionally. Copyright © 2010 ISA. Published by Elsevier Ltd. All rights reserved.

One-dimensional photonic crystals for code-division multiple access

NASA Astrophysics Data System (ADS)

Wang, Shamino Yuanliang

One-dimensional photonic crystals exhibit reduced group velocity and huge dispersion at their rejection band edge frequencies. Therefore they are natural candidates as optical delay lines, dispersion compensators, and pulse reshapers. Using wavelength tunable pulses spectrally sliced from a mode-locked fiber laser, the transmission mode measurement was performed in the time domain with single picosecond resolution. Group delays and dispersion were measured with an autocorrelator as an ultrafast optical detector and cross-correlator. Our experimental results agree qualitatively with the theoretical and simulation predictions. A maximum group delay of 10 ps for a commercial 3 mm long uniform fiber Bragg grating and that of 22.6 ps for a research laboratory fabricated 1 cm grating were measured, corresponding to a group velocity 66% of the speed of light in bare fiber. We have also demonstrated in the overlap transmission region of a grating pair both gratings contribute to the group delay while the group velocity dispersion was canceled, resulting in additive delay in transmission with minimal pulse reshaping. This compound grating configuration was further expanded as specially designed grating sequence encoders and decoders in matched filter CDMA. The transmitter grating sequence temporally stretched the input pulse into a long time scale low peak intensity pseudorandom noise, while the conjugate grating sequence in the receiver performed pulse reconstruction and data recovery. A temporal FWHM contrast ratio of 2.5 and a peak intensity contrast ratio of 10 between the correctly and incorrectly decoded signals were achieved. Armed with more sophisticated grating designs we believe this would be a powerful solution to CDMA orthogonal code requirements.

Intelligent measurement and compensation of linear motor force ripple: a projection-based learning approach in the presence of noise

NASA Astrophysics Data System (ADS)

Liu, Yang; Song, Fazhi; Yang, Xiaofeng; Dong, Yue; Tan, Jiubin

2018-06-01

Due to their structural simplicity, linear motors are increasingly receiving attention for use in high velocity and high precision applications. The force ripple, as a space-periodic disturbance, however, would deteriorate the achievable dynamic performance. Conventional force ripple measurement approaches are time-consuming and have high requirements on the experimental conditions. In this paper, a novel learning identification algorithm is proposed for force ripple intelligent measurement and compensation. Existing identification schemes always use all the error signals to update the parameters in the force ripple. However, the error induced by noise is non-effective for force ripple identification, and even deteriorates the identification process. In this paper only the most pertinent information in the error signal is utilized for force ripple identification. Firstly, the effective error signals caused by the reference trajectory and the force ripple are extracted by projecting the overall error signals onto a subspace spanned by the physical model of the linear motor as well as the sinusoidal model of the force ripple. The time delay in the linear motor is compensated in the basis functions. Then, a data-driven approach is proposed to design the learning gain. It balances the trade-off between convergence speed and robustness against noise. Simulation and experimental results validate the proposed method and confirm its effectiveness and superiority.

InGaAs/InP SPAD photon-counting module with auto-calibrated gate-width generation and remote control

NASA Astrophysics Data System (ADS)

Tosi, Alberto; Ruggeri, Alessandro; Bahgat Shehata, Andrea; Della Frera, Adriano; Scarcella, Carmelo; Tisa, Simone; Giudice, Andrea

2013-01-01

We present a photon-counting module based on InGaAs/InP SPAD (Single-Photon Avalanche Diode) for detecting single photons up to 1.7 μm. The module exploits a novel architecture for generating and calibrating the gate width, along with other functions (such as module supervision, counting and processing of detected photons, etc.). The gate width, i.e. the time interval when the SPAD is ON, is user-programmable in the range from 500 ps to 1.5 μs, by means of two different delay generation methods implemented with an FPGA (Field-Programmable Gate Array). In order to compensate chip-to-chip delay variation, an auto-calibration circuit picks out a combination of delays in order to match at best the selected gate width. The InGaAs/InP module accepts asynchronous and aperiodic signals and introduces very low timing jitter. Moreover the photon counting module provides other new features like a microprocessor for system supervision, a touch-screen for local user interface, and an Ethernet link for smart remote control. Thanks to the fullyprogrammable and configurable architecture, the overall instrument provides high system flexibility and can easily match all requirements set by many different applications requiring single photon-level sensitivity in the near infrared with very low photon timing jitter.

Input and output compensation for the cochlear traveling wave delay in wide-band ABR recordings: implications for small acoustic tumor detection.

PubMed

Don, Manuel; Elberling, Claus; Maloff, Erin

2009-02-01

The Stacked ABR (auditory brainstem response) attempts at the output of the auditory periphery to compensate for the temporal dispersion of neural activation caused by the cochlear traveling wave in response to click stimulation. Compensation can also be made at the input by using a chirp stimulus. It has been demonstrated that the Stacked ABR is sensitive to small tumors that are often missed by standard ABR latency measures. Because a chirp stimulus requires only a single data acquisition run whereas the Stacked ABR requires six, we try to evaluate some indirect evidence justifying the use of a chirp for small tumor detection. We compared the sensitivity and specificity of different Stacked ABRs formed by aligning the derived-band ABRs according to (1) the individual's peak latencies, (2) the group mean latencies, and (3) the modeled latencies used to develop a chirp. For tumor detection with a chosen sensitivity of 95%, a relatively high specificity of 85% may be achieved with a chirp. It appears worthwhile to explore the actual use of a chirp because significantly shorter test and analysis times might be possible.

Medical care surrounding work-related back injury claims among Washington State Union Carpenters, 1989-2003.

PubMed

Kucera, Kristen L; Lipscomb, Hester J; Silverstein, Barbara

2011-01-01

We describe medical care received through workers' compensation (WC) and union-provided insurance surrounding work-related back injuries and examine relationships between care provided and time off work among a large cohort of carpenters. Union records identified a cohort of 20,642 carpenters working in Washington State from 1989-2003 and their private health insurance claims. These data were linked to workers' compensation files from this state-run program including records of medical care. Over 74,000 WC medical encounters resulted from 2959 work-related back injuries. Eleven percent received private care for musculoskeletal back pain within 90 days of work-related injury; this proportion increased with increasing lost days. Delay to physical therapy was more prevalent among those out of work longest. The proportion of claimants with care from both systems and from private utilization only increased after the first 90 days and, for the subset with at least one paid lost work day, after return to work. Examination of medical care through both systems versus solely in workers' compensation provides a more complete understanding of back injury care while also demonstrating complexity. Differences in outcomes based upon treatment shortly after injury are worthy of further exploration.

The Effect of Age in the Alteration in Fluid Balance of Rats in Response to Centrifugation

NASA Technical Reports Server (NTRS)

Fuller, Charles A.

2000-01-01

With an increase in gravity load induced by centrifugation or upon return to Earth following spaceflight, there is a period of adjustment in fluid balance in rats. With centrifugation there is a reduced fluid intake with maintenance of the rate of urine excretion. Following spaceflight there is an increase in urine output and maintenance of fluid intake. The initial period of acclimation to hypergravity is associated with a net loss of fluids. In the present study in response to centrifugation at 2.0 G this period of acclimation is present in mature rats for a longer period of time, about 24 hours. Following this initial response a period of over compensation has previously been reported. In the present study this was not observed. The net effect of these alterations in water intake and output in response to centrifugation for 14 days was slight increase in the percent total body water, with effective compensation seen in both young and mature rats. Older rats have been shown to have a reduced relative thirst and compensatory renal function in response to hypohydration, hyperosmolality and pharmacological stimuli. Responsiveness to these stimuli are delayed and/or attenuated in older animals. Similar findings were noted in the present study in the initial response to centrifugation. The older animal had a delayed return of fluid intake to control levels. The delay of one day did not appear to effect long-term fluid homeostasis, as there was difference in the response of percent total body water at the end of 14 days of centrifugation with both age groups having a slight but significant increase. This increase has been attributed to the increase in lean body mass induced by centrifugation.

Practice effects on intra-team synergies in football teams.

PubMed

Silva, Pedro; Chung, Dante; Carvalho, Thiago; Cardoso, Tiago; Davids, Keith; Araújo, Duarte; Garganta, Júlio

2016-04-01

Developing synchronised player movements for fluent competitive match play is a common goal for coaches of team games. An ecological dynamics approach advocates that intra-team synchronization is governed by locally created information, which specifies shared affordances responsible for synergy formation. To verify this claim we evaluated coordination tendencies in two newly-formed teams of recreational players during association football practice games, weekly, for fifteen weeks (thirteen matches). We investigated practice effects on two central features of synergies in sports teams - dimensional compression and reciprocal compensation here captured through near in-phase modes of coordination and time delays between coupled players during forward and backwards movements on field while attacking and defending. Results verified that synergies were formed and dissolved rapidly as a result of the dynamic creation of informational properties, perceived as shared affordances among performers. Practising once a week led to small improvements in the readjustment delays between co-positioning team members, enabling faster regulation of coordinated team actions. Mean values of the number of player and team synergies displayed only limited improvements, possibly due to the timescales of practice. No relationship between improvements in dimensional compression and reciprocal compensation were found for number of shots, amount of ball possession and number of ball recoveries made. Findings open up new perspectives for monitoring team coordination processes in sport. Copyright © 2015 Elsevier B.V. All rights reserved.

Short-term visual memory for location in depth: A U-shaped function of time.

PubMed

Reeves, Adam; Lei, Quan

2017-10-01

Short-term visual memory was studied by displaying arrays of four or five numerals, each numeral in its own depth plane, followed after various delays by an arrow cue shown in one of the depth planes. Subjects reported the numeral at the depth cued by the arrow. Accuracy fell with increasing cue delay for the first 500 ms or so, and then recovered almost fully. This dipping pattern contrasts with the usual iconic decay observed for memory traces. The dip occurred with or without a verbal or color-shape retention load on working memory. In contrast, accuracy did not change with delay when a tonal cue replaced the arrow cue. We hypothesized that information concerning the depths of the numerals decays over time in sensory memory, but that cued recall is aided later on by transfer to a visual memory specialized for depth. This transfer is sufficiently rapid with a tonal cue to compensate for the sensory decay, but it is slowed by the need to tag the arrow cue's depth relative to the depths of the numerals, exposing a dip when sensation has decayed and transfer is not yet complete. A model with a fixed rate of sensory decay and varied transfer rates across individuals captures the dip as well as the cue modality effect.

Sensorimotor responsiveness and resolution in the giraffe.

PubMed

More, Heather L; O'Connor, Shawn M; Brøndum, Emil; Wang, Tobias; Bertelsen, Mads F; Grøndahl, Carsten; Kastberg, Karin; Hørlyck, Arne; Funder, Jonas; Donelan, J Maxwell

2013-03-15

The ability of an animal to detect and respond to changes in the environment is crucial to its survival. However, two elements of sensorimotor control - the time required to respond to a stimulus (responsiveness) and the precision of stimulus detection and response production (resolution) - are inherently limited by a competition for space in peripheral nerves and muscles. These limitations only become more acute as animal size increases. In this paper, we investigated whether the physiology of giraffes has found unique solutions for maintaining sensorimotor performance in order to compensate for their extreme size. To examine responsiveness, we quantified three major sources of delay: nerve conduction delay, muscle electromechanical delay and force generation delay. To examine resolution, we quantified the number and size distribution of nerve fibers in the sciatic nerve. Rather than possessing a particularly unique sensorimotor system, we found that our measurements in giraffes were broadly comparable to size-dependent trends seen across other terrestrial mammals. Consequently, both giraffes and other large animals must contend with greater sensorimotor delays and lower innervation density in comparison to smaller animals. Because of their unconventional leg length, giraffes may experience even longer delays compared with other animals of the same mass when sensing distal stimuli. While there are certainly advantages to being tall, there appear to be challenges as well - our results suggest that giraffes are less able to precisely and accurately sense and respond to stimuli using feedback alone, particularly when moving quickly.

Inferential modeling and predictive feedback control in real-time motion compensation using the treatment couch during radiotherapy

NASA Astrophysics Data System (ADS)

Qiu, Peng; D'Souza, Warren D.; McAvoy, Thomas J.; Liu, K. J. Ray

2007-09-01

Tumor motion induced by respiration presents a challenge to the reliable delivery of conformal radiation treatments. Real-time motion compensation represents the technologically most challenging clinical solution but has the potential to overcome the limitations of existing methods. The performance of a real-time couch-based motion compensation system is mainly dependent on two aspects: the ability to infer the internal anatomical position and the performance of the feedback control system. In this paper, we propose two novel methods for the two aspects respectively, and then combine the proposed methods into one system. To accurately estimate the internal tumor position, we present partial-least squares (PLS) regression to predict the position of the diaphragm using skin-based motion surrogates. Four radio-opaque markers were placed on the abdomen of patients who underwent fluoroscopic imaging of the diaphragm. The coordinates of the markers served as input variables and the position of the diaphragm served as the output variable. PLS resulted in lower prediction errors compared with standard multiple linear regression (MLR). The performance of the feedback control system depends on the system dynamics and dead time (delay between the initiation and execution of the control action). While the dynamics of the system can be inverted in a feedback control system, the dead time cannot be inverted. To overcome the dead time of the system, we propose a predictive feedback control system by incorporating forward prediction using least-mean-square (LMS) and recursive least square (RLS) filtering into the couch-based control system. Motion data were obtained using a skin-based marker. The proposed predictive feedback control system was benchmarked against pure feedback control (no forward prediction) and resulted in a significant performance gain. Finally, we combined the PLS inference model and the predictive feedback control to evaluate the overall performance of the feedback control system. Our results show that, with the tumor motion unknown but inferred by skin-based markers through the PLS model, the predictive feedback control system was able to effectively compensate intra-fraction motion.

Stable fiber-optic time transfer by active radio frequency phase locking.

PubMed

Yin, Feifei; Wu, Zhongle; Dai, Yitang; Ren, Tianpeng; Xu, Kun; Lin, Jintong; Tang, Geshi

2014-05-15

In this Letter we demonstrate a fiber link capable of stable time signal transfer utilizing our active long-distance radio frequency (RF) stabilization technology. Taking advantage of the chromatic dispersion in optical fiber, our scheme compensates dynamically the link delay variation by tuning the optical carrier wavelength to phase lock a round-trip RF reference. Since the time signal and the RF reference are carried by the same optical carrier, a highly stable time transfer is achieved at the same time. Experimentally, we demonstrate a stability of the time signal transfer over 50-km fiber with a time deviation of 40 ps at 1-s average and 2.3 ps at 1000-s average. The performance of the RF reference delivery is also tested, with an Allan deviation of 2×10(-15) at 1000-s average. According to our proposal, a simultaneous stable time and frequency transfer is expected.

Socket preservation.

PubMed

Fee, L

2017-04-21

Socket preservation maintains bone volume post-extraction in anticipation of an implant placement or fixed partial denture pontic site. This procedure helps compensate for the resorption of the facial bone wall. Socket preservation should be considered when implant placement needs to be delayed for patient or site-related reasons. The ideal healing time before implant placement is six months. Socket preservation can reduce the need for later bone augmentation. By reducing bone resorption and accelerating bone formation it increases implant success and survival. Biomaterials for socket grafting including autograft, allograft, xenograft and alloplast. A bone substitute with a low substitution rate is recommended.

The Technology of Suppressing Harmonics with Complex Neural Network is Applied to Microgrid

NASA Astrophysics Data System (ADS)

Zhang, Jing; Li, Zhan-Ying; Wang, Yan-ping; Li, Yang; Zong, Ke-yong

2018-03-01

According to the traits of harmonics in microgrid, a new CANN controller which combines BP and RBF neural network is proposed to control APF to detect and suppress harmonics. This controller has the function of current prediction. By simulation in Matlab / Simulink, this design can shorten the delay time nearly 0.02s (a power supply current cycle) in comparison with the traditional controller based on ip-iq method. The new controller also has higher compensation accuracy and better dynamic tracking traits, it can greatly suppress the harmonics and improve the power quality.

A new antenna concept for satellite communications

NASA Technical Reports Server (NTRS)

Skahill, G.; Ciccolella, D.

1982-01-01

A novel antenna configuration of two reflecting surfaces and a phased array is examined for application to satellite communications and shown to be superior in every respect to earlier designs for service to the continental United States from synchronous orbit. The vignetting that afflicts other two reflector optical systems is eliminated by use of a reflecting field element. The remaining aberrations, predominantly coma, are isolated in the time delay distribution at the surface of the array and can be compensated by ordinary array techniques. The optics exhibits infinite bandwidth and the frequency range is limited only by the design of the array.

Design of Low Power CMOS Read-Out with TDI Function for Infrared Linear Photodiode Array Detectors

NASA Technical Reports Server (NTRS)

Vizcaino, Paul; Ramirez-Angulo, Jaime; Patel, Umesh D.

2007-01-01

A new low voltage CMOS infrared readout circuit using the buffer-direct injection method is presented. It uses a single supply voltage of 1.8 volts and a bias current of 1uA. The time-delay integration technique is used to increase the signal to noise ratio. A current memory circuit with faulty diode detection is used to remove dark current for background compensation and to disable a photodiode in a cell if detected as faulty. Simulations are shown that verify the circuit that is currently in fabrication in 0.5ym CMOS technology.

Delay Within the 3-Hour Surviving Sepsis Campaign Guideline on Mortality for Patients With Severe Sepsis and Septic Shock.

PubMed

Pruinelli, Lisiane; Westra, Bonnie L; Yadav, Pranjul; Hoff, Alexander; Steinbach, Michael; Kumar, Vipin; Delaney, Connie W; Simon, Gyorgy

2018-04-01

To specify when delays of specific 3-hour bundle Surviving Sepsis Campaign guideline recommendations applied to severe sepsis or septic shock become harmful and impact mortality. Retrospective cohort study. One health system composed of six hospitals and 45 clinics in a Midwest state from January 01, 2011, to July 31, 2015. All adult patients hospitalized with billing diagnosis of severe sepsis or septic shock. Four 3-hour Surviving Sepsis Campaign guideline recommendations: 1) obtain blood culture before antibiotics, 2) obtain lactate level, 3) administer broad-spectrum antibiotics, and 4) administer 30 mL/kg of crystalloid fluid for hypotension (defined as "mean arterial pressure" < 65) or lactate (> 4). To determine the effect of t minutes of delay in carrying out each intervention, propensity score matching of "baseline" characteristics compensated for differences in health status. The average treatment effect in the treated computed as the average difference in outcomes between those treated after shorter versus longer delay. To estimate the uncertainty associated with the average treatment effect in the treated metric and to construct 95% CIs, bootstrap estimation with 1,000 replications was performed. From 5,072 patients with severe sepsis or septic shock, 1,412 (27.8%) had in-hospital mortality. The majority of patients had the four 3-hour bundle recommendations initiated within 3 hours. The statistically significant time in minutes after which a delay increased the risk of death for each recommendation was as follows: lactate, 20.0 minutes; blood culture, 50.0 minutes; crystalloids, 100.0 minutes; and antibiotic therapy, 125.0 minutes. The guideline recommendations showed that shorter delays indicates better outcomes. There was no evidence that 3 hours is safe; even very short delays adversely impact outcomes. Findings demonstrated a new approach to incorporate time t when analyzing the impact on outcomes and provide new evidence for clinical practice and research.

Advantages and disadvantages of the Belgian not-only-fault system for medical incidents.

PubMed

Vandersteegen, Tom; Marneffe, Wim; Vandijck, Dominique

2017-02-01

In 2010, the Belgian compensation system for medical incidents was reformed, in order to overcome some important deficiencies of court procedures. This resulted in a not-only-fault compensation system, following the establishment of the Fund for Medical Accidents (FMA). This paper seeks to clarify the main advantages and disadvantages of this reform. After all, the legislator paid little attention to the impact on physicians, who also seem to be insufficiently informed. However, currently the FMA experiences a significant delay in processing compensation requests. The true effects of the not-only-fault system for patients and physicians as well as for health care quality therefore still remain unclear today.

Line length dependencies in interconnect optimization

NASA Astrophysics Data System (ADS)

Kadoch, Daniel; Duane, Michael; Lee, Yohan

1997-09-01

Metal line delay has become increasingly important for ULSI devices. Numerous expressions and software tools have been developed to describe interconnect delay as a function of the geometry and layout. Although many of these formulas have line length effects, this has not been explored in depth. Most software tools are either geared towards circuit designers, or involve more complex and CPU-intensive 3D modeling. In this work, PISCES (a 2D device simulator) was used to extract metal capacitance per unit length. We extend this approach for various lengths by creating a ladder network of the RC components and simulating in SPICE, or using simple closed-form Elmore delay equations. A new key result is that there are optimum metal line width/space for a fixed pitch and height/space ratios that are metal length dependent. For metal lines shorter than about 1500 micrometers , it is better to have narrower metal lines, and for lengths less than 500 micrometers , shrinking metal height is desirable because the penalty in resistance is more than compensated by the decrease in capacitance. For longer lines, the time delay is dominated by resistance, and wider, taller lines are better. Increasing metal spacing or reducing dielectric constant were beneficial for both long and short metal lines.

In need of remedy: US policy for compensating injured research participants.

PubMed

Pike, Elizabeth R

2014-03-01

There is an emerging ethical consensus that injured research participants should receive medical care and compensation for their research-related injuries. This consensus is premised on notions of beneficence, distributive justice, compensatory justice and reciprocity. In response, countries around the world have implemented no-fault compensation systems to ensure that research participants are adequately protected in the event of injury. The United States, the world's leading sponsor of research, has chosen instead to rely on its legal system to provide injured research participants with medical care and compensation. This article argues that US reliance on its legal system leaves injured research participants unprotected in the event of injury. Nearly every injured research participant will have difficulty receiving compensation in court, and certain classes of research participants will be barred from receiving compensation altogether. The United States' outlier status also threatens to impede US-sponsored multinational research, potentially delaying important biomedical advances. To rectify this injustice, researchers, Institutional Review Boards, sponsors and research institutions should advocate systematic no-fault compensation in the United States to bring US law into accord with global ethical norms and ensure that injured research participants are adequately protected.

Accounting for exhaust gas transport dynamics in instantaneous emission models via smooth transition regression.

PubMed

Kamarianakis, Yiannis; Gao, H Oliver

2010-02-15

Collecting and analyzing high frequency emission measurements has become very usual during the past decade as significantly more information with respect to formation conditions can be collected than from regulated bag measurements. A challenging issue for researchers is the accurate time-alignment between tailpipe measurements and engine operating variables. An alignment procedure should take into account both the reaction time of the analyzers and the dynamics of gas transport in the exhaust and measurement systems. This paper discusses a statistical modeling framework that compensates for variable exhaust transport delay while relating tailpipe measurements with engine operating covariates. Specifically it is shown that some variants of the smooth transition regression model allow for transport delays that vary smoothly as functions of the exhaust flow rate. These functions are characterized by a pair of coefficients that can be estimated via a least-squares procedure. The proposed models can be adapted to encompass inherent nonlinearities that were implicit in previous instantaneous emissions modeling efforts. This article describes the methodology and presents an illustrative application which uses data collected from a diesel bus under real-world driving conditions.

The across frequency independence of equalization of interaural time delay in the equalization-cancellation model of binaural unmasking.

PubMed

Akeroyd, Michael A

2004-08-01

The equalization stage in the equalization-cancellation model of binaural unmasking compensates for the interaural time delay (ITD) of a masking noise by introducing an opposite, internal delay [N. I. Durlach, in Foundations of Modern Auditory Theory, Vol. II., edited by J. V. Tobias (Academic, New York, 1972)]. Culling and Summerfield [J. Acoust. Soc. Am. 98, 785-797 (1995)] developed a multi-channel version of this model in which equalization was "free" to use the optimal delay in each channel. Two experiments were conducted to test if equalization was indeed free or if it was "restricted" to the same delay in all channels. One experiment measured binaural detection thresholds, using an adaptive procedure, for 1-, 5-, or 17-component tones against a broadband masking noise, in three binaural configurations (N0S180, N180S0, and N90S270). The thresholds for the 1-component stimuli were used to normalize the levels of each of the 5- and 17-component stimuli so that they were equally detectable. If equalization was restricted, then, for the 5- and 17-component stimuli, the N90S270 and N180S0 configurations would yield a greater threshold than the N0S180 configurations. No such difference was found. A subsequent experiment measured binaural detection thresholds, via psychometric functions, for a 2-component complex tone in the same three binaural configurations. Again, no differential effect of configuration was observed. An analytic model of the detection of a complex tone showed that the results were more consistent with free equalization than restricted equalization, although the size of the differences was found to depend on the shape of the psychometric function for detection.

LQG control of a deformable mirror adaptive optics system with time-delayed measurements

NASA Astrophysics Data System (ADS)

Anderson, David J.

1991-12-01

This thesis proposes a linear quadratic Gaussian (LQG) control law for a ground-based deformable mirror adaptive optics system. The incoming image wavefront is distorted, primarily in phase, due to the turbulent effects of the earth's atmosphere. The adaptive optics system attempts to compensate for the distortion with a deformable mirror. A Hartman wavefront sensor measures the degree of distortion in the image wavefront. The measurements are input to a Kalman filter which estimates the system states. The state estimates are processed by a linear quadratic regulator which generates the appropriate control voltages to apply to the deformable mirror actuators. The dynamics model for the atmospheric phase distortion consists of 14 Zernike coefficient states; each modeled as a first-order linear time-invariant shaping filter driven by zero-mean white Gaussian noise. The dynamics of the deformable mirror are also model as 14 Zernike coefficients with first-order deterministic dynamics. A significant reduction in total wavefront phase distortion is achieved in the presence of time-delayed measurements. Wavefront sensor sampling rate is the major factor limiting system performance. The Multimode Simulation for Optimal Filter Evaluation (MSOFE) software is the performance evaluation tool of choice for this research.

Improving the performance of interferometric imaging through the use of disturbance feedforward.

PubMed

Böhm, Michael; Glück, Martin; Keck, Alexander; Pott, Jörg-Uwe; Sawodny, Oliver

2017-05-01

In this paper, we present a disturbance compensation technique to improve the performance of interferometric imaging for extremely large ground-based telescopes, e.g., the Large Binocular Telescope (LBT), which serves as the application example in this contribution. The most significant disturbance sources at ground-based telescopes are wind-induced mechanical vibrations in the range of 8-60 Hz. Traditionally, their optical effect is eliminated by feedback systems, such as the adaptive optics control loop combined with a fringe tracking system within the interferometric instrument. In this paper, accelerometers are used to measure the vibrations. These measurements are used to estimate the motion of the mirrors, i.e., tip, tilt and piston, with a dynamic estimator. Additional delay compensation methods are presented to cancel sensor network delays and actuator input delays, improving the estimation result even more, particularly at higher frequencies. Because various instruments benefit from the implementation of telescope vibration mitigation, the estimator is implemented as a separate, independent software on the telescope, publishing the estimated values via multicast on the telescope's ethernet. Every client capable of using and correcting the estimated disturbances can subscribe and use these values in a feedforward for its compensation device, e.g., the deformable mirror, the piston mirror of LINC-NIRVANA, or the fast path length corrector of the Large Binocular Telescope Interferometer. This easy-to-use approach eventually leveraged the presented technology for interferometric use at the LBT and now significantly improves the sky coverage, performance, and operational robustness of interferometric imaging on a regular basis.

Numerical modelling of multimode fibre-optic communication lines

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

Sidelnikov, O S; Fedoruk, M P; Sygletos, S

The results of numerical modelling of nonlinear propagation of an optical signal in multimode fibres with a small differential group delay are presented. It is found that the dependence of the error vector magnitude (EVM) on the differential group delay can be reduced by increasing the number of ADC samples per symbol in the numerical implementation of the differential group delay compensation algorithm in the receiver. The possibility of using multimode fibres with a small differential group delay for data transmission in modern digital communication systems is demonstrated. It is shown that with increasing number of modes the strong couplingmore » regime provides a lower EVM level than the weak coupling one. (fibre-optic communication lines)« less

High spatial resolution imaging for structural health monitoring based on virtual time reversal

NASA Astrophysics Data System (ADS)

Cai, Jian; Shi, Lihua; Yuan, Shenfang; Shao, Zhixue

2011-05-01

Lamb waves are widely used in structural health monitoring (SHM) of plate-like structures. Due to the dispersion effect, Lamb wavepackets will be elongated and the resolution for damage identification will be strongly affected. This effect can be automatically compensated by the time reversal process (TRP). However, the time information of the compensated waves is also removed at the same time. To improve the spatial resolution of Lamb wave detection, virtual time reversal (VTR) is presented in this paper. In VTR, a changing-element excitation and reception mechanism (CERM) rather than the traditional fixed excitation and reception mechanism (FERM) is adopted for time information conservation. Furthermore, the complicated TRP procedure is replaced by simple signal operations which can make savings in the hardware cost for recording and generating the time-reversed Lamb waves. After the effects of VTR for dispersive damage scattered signals are theoretically analyzed, the realization of VTR involving the acquisition of the transfer functions of damage detecting paths under step pulse excitation is discussed. Then, a VTR-based imaging method is developed to improve the spatial resolution of the delay-and-sum imaging with a sparse piezoelectric (PZT) wafer array. Experimental validation indicates that the damage scattered wavepackets of A0 mode in an aluminum plate are partly recompressed and focalized with their time information preserved by VTR. Both the single damage and the dual adjacent damages in the plate can be clearly displayed with high spatial resolution by the proposed VTR-based imaging method.

High spatial resolution shortwave infrared imaging technology based on time delay and digital accumulation method

NASA Astrophysics Data System (ADS)

Jia, Jianxin; Wang, Yueming; Zhuang, Xiaoqiong; Yao, Yi; Wang, Shengwei; Zhao, Ding; Shu, Rong; Wang, Jianyu

2017-03-01

Shortwave infrared (SWIR) imaging technology attracts more and more attention by its fascinating ability of penetrating haze and smoke. For application of spaceborne remote sensing, spatial resolution of SWIR is lower compared with that of visible light (VIS) wavelength. It is difficult to balance between the spatial resolution and signal to noise ratio (SNR). Some conventional methods, such as enlarging aperture of telescope, image motion compensation, and analog time delay and integration (TDI) technology are used to gain SNR. These techniques bring in higher cost of satellite, complexity of system or other negative factors. In this paper, time delay and digital accumulation (TDDA) method is proposed to achieve higher spatial resolution. The method can enhance the SNR and non-uniformity of system theoretically. A prototype of SWIR imager consists of opto-mechanical, 1024 × 128 InGaAs detector, and electronics is designed and integrated to prove TDDA method. Both of measurements and experimental results indicate TDDA method can promote SNR of system approximated of the square root of accumulative stage. The results exhibit that non-uniformity of system is also improved by this approach to some extent. The experiment results are corresponded with the theoretical analysis. Based on the experiments results, it is proved firstly that the goal of 1 m ground sample distance (GSD) in orbit of 500 km is feasible with the TDDA stage of 30 for SWIR waveband (0.9-1.7 μm).

Time-delay control of a magnetic levitated linear positioning system

NASA Technical Reports Server (NTRS)

Tarn, J. H.; Juang, K. Y.; Lin, C. E.

1994-01-01

In this paper, a high accuracy linear positioning system with a linear force actuator and magnetic levitation is proposed. By locating a permanently magnetized rod inside a current-carrying solenoid, the axial force is achieved by the boundary effect of magnet poles and utilized to power the linear motion, while the force for levitation is governed by Ampere's Law supplied with the same solenoid. With the levitation in a radial direction, there is hardly any friction between the rod and the solenoid. The high speed motion can hence be achieved. Besides, the axial force acting on the rod is a smooth function of rod position, so the system can provide nanometer resolution linear positioning to the molecule size. Since the force-position relation is highly nonlinear, and the mathematical model is derived according to some assumptions, such as the equivalent solenoid of the permanently magnetized rod, so there exists unknown dynamics in practical application. Thus 'robustness' is an important issue in controller design. Meanwhile the load effect reacts directly on the servo system without transmission elements, so the capability of 'disturbance rejection; is also required. With the above consideration, a time-delay control scheme is chosen and applied. By comparing the input-output relation and the mathematical model, the time-delay controller calculates an estimation of unmodeled dynamics and disturbances and then composes the desired compensation into the system. Effectiveness of the linear positioning system and control scheme are illustrated with simulation results.

Residual translation compensations in radar target narrowband imaging based on trajectory information

NASA Astrophysics Data System (ADS)

Yue, Wenjue; Peng, Bo; Wei, Xizhang; Li, Xiang; Liao, Dongping

2018-05-01

High velocity translation will result in defocusing scattering centers in radar imaging. In this paper, we propose a Residual Translation Compensations (RTC) method based on target trajectory information to eliminate the translation effects in radar imaging. Translation could not be simply regarded as a uniformly accelerated motion in reality. So the prior knowledge of the target trajectory is introduced to enhance compensation precision. First we use the two-body orbit model to figure out the radial distance. Then, stepwise compensations are applied to eliminate residual propagation delay based on conjugate multiplication method. Finally, tomography is used to confirm the validity of the method. Compare with translation parameters estimation method based on the spectral peak of the conjugate multiplied signal, RTC method in this paper enjoys a better tomography result. When the Signal Noise Ratio (SNR) of the radar echo signal is 4dB, the scattering centers can also be extracted clearly.

Acoustic Calibration of the Exterior Effects Room at the NASA Langley Research Center

NASA Technical Reports Server (NTRS)

Faller, Kenneth J., II; Rizzi, Stephen A.; Klos, Jacob; Chapin, William L.; Surucu, Fahri; Aumann, Aric R.

2010-01-01

The Exterior Effects Room (EER) at the NASA Langley Research Center is a 39-seat auditorium built for psychoacoustic studies of aircraft community noise. The original reproduction system employed monaural playback and hence lacked sound localization capability. In an effort to more closely recreate field test conditions, a significant upgrade was undertaken to allow simulation of a three-dimensional audio and visual environment. The 3D audio system consists of 27 mid and high frequency satellite speakers and 4 subwoofers, driven by a real-time audio server running an implementation of Vector Base Amplitude Panning. The audio server is part of a larger simulation system, which controls the audio and visual presentation of recorded and synthesized aircraft flyovers. The focus of this work is on the calibration of the 3D audio system, including gains used in the amplitude panning algorithm, speaker equalization, and absolute gain control. Because the speakers are installed in an irregularly shaped room, the speaker equalization includes time delay and gain compensation due to different mounting distances from the focal point, filtering for color compensation due to different installations (half space, corner, baffled/unbaffled), and cross-over filtering.

Modulation and synchronization technique for MF-TDMA system

NASA Technical Reports Server (NTRS)

Faris, Faris; Inukai, Thomas; Sayegh, Soheil

1994-01-01

This report addresses modulation and synchronization techniques for a multi-frequency time division multiple access (MF-TDMA) system with onboard baseband processing. The types of synchronization techniques analyzed are asynchronous (conventional) TDMA, preambleless asynchronous TDMA, bit synchronous timing with a preamble, and preambleless bit synchronous timing. Among these alternatives, preambleless bit synchronous timing simplifies onboard multicarrier demultiplexer/demodulator designs (about 2:1 reduction in mass and power), requires smaller onboard buffers (10:1 to approximately 3:1 reduction in size), and provides better frame efficiency as well as lower onboard processing delay. Analysis and computer simulation illustrate that this technique can support a bit rate of up to 10 Mbit/s (or higher) with proper selection of design parameters. High bit rate transmission may require Doppler compensation and multiple phase error measurements. The recommended modulation technique for bit synchronous timing is coherent QPSK with differential encoding for the uplink and coherent QPSK for the downlink.

Day-to-day variations in the amplitude of the soil temperature cycle and impact on adult eclosion timing of the onion fly.

PubMed

Tanaka, Kazuhiro; Watari, Yasuhiko

2017-06-01

The onion fly Delia antiqua advances its eclosion timing with decreasing temperature amplitude to compensate for a depth-dependent phase delay of the zeitgeber. To elucidate whether or not naturally occurring day-to-day variations in the amplitude of soil temperature cycle disturb this compensatory response, we monitored daily variations in the temperature amplitude in natural soils and evaluated the impact on adult eclosion timing. Our results indicated that both median and variance of the soil temperature amplitude become smaller as depth increases. Insertion of a larger temperature fluctuation into the thermoperiod with smaller temperature amplitude induced a stronger phase delay, while insertion of a smaller temperature fluctuation into the thermoperiod with larger temperature amplitude had a weaker phase-advancing effect. It is therefore expected that larger diurnal temperature fluctuations disturb the compensatory response, particularly if they occur at deeper locations, while smaller temperature fluctuations do so only at shallower locations. Under natural conditions, however, the probability of occurrence of smaller or larger temperature fluctuations in shallower or deeper soils, respectively, is relatively small. Thus, naturally occurring day-to-day variations in the temperature amplitude rarely disturb the compensatory response, thereby having a subtle or negligible impact on adult eclosion timing.

Comparison of approaches for mobile document image analysis using server supported smartphones

NASA Astrophysics Data System (ADS)

Ozarslan, Suleyman; Eren, P. Erhan

2014-03-01

With the recent advances in mobile technologies, new capabilities are emerging, such as mobile document image analysis. However, mobile phones are still less powerful than servers, and they have some resource limitations. One approach to overcome these limitations is performing resource-intensive processes of the application on remote servers. In mobile document image analysis, the most resource consuming process is the Optical Character Recognition (OCR) process, which is used to extract text in mobile phone captured images. In this study, our goal is to compare the in-phone and the remote server processing approaches for mobile document image analysis in order to explore their trade-offs. For the inphone approach, all processes required for mobile document image analysis run on the mobile phone. On the other hand, in the remote-server approach, core OCR process runs on the remote server and other processes run on the mobile phone. Results of the experiments show that the remote server approach is considerably faster than the in-phone approach in terms of OCR time, but adds extra delays such as network delay. Since compression and downscaling of images significantly reduce file sizes and extra delays, the remote server approach overall outperforms the in-phone approach in terms of selected speed and correct recognition metrics, if the gain in OCR time compensates for the extra delays. According to the results of the experiments, using the most preferable settings, the remote server approach performs better than the in-phone approach in terms of speed and acceptable correct recognition metrics.

Method for enhancing signals transmitted over optical fibers

DOEpatents

Ogle, James W.; Lyons, Peter B.

1983-01-01

A method for spectral equalization of high frequency spectrally broadband signals transmitted through an optical fiber. The broadband signal input is first dispersed by a grating. Narrow spectral components are collected into an array of equalizing fibers. The fibers serve as optical delay lines compensating for material dispersion of each spectral component during transmission. The relative lengths of the individual equalizing fibers are selected to compensate for such prior dispersion. The output of the equalizing fibers couple the spectrally equalized light onto a suitable detector for subsequent electronic processing of the enhanced broadband signal.

Multi-objective optimization of discrete time-cost tradeoff problem in project networks using non-dominated sorting genetic algorithm

NASA Astrophysics Data System (ADS)

Shahriari, Mohammadreza

2016-06-01

The time-cost tradeoff problem is one of the most important and applicable problems in project scheduling area. There are many factors that force the mangers to crash the time. This factor could be early utilization, early commissioning and operation, improving the project cash flow, avoiding unfavorable weather conditions, compensating the delays, and so on. Since there is a need to allocate extra resources to short the finishing time of project and the project managers are intended to spend the lowest possible amount of money and achieve the maximum crashing time, as a result, both direct and indirect costs will be influenced in the project, and here, we are facing into the time value of money. It means that when we crash the starting activities in a project, the extra investment will be tied in until the end date of the project; however, when we crash the final activities, the extra investment will be tied in for a much shorter period. This study is presenting a two-objective mathematical model for balancing compressing the project time with activities delay to prepare a suitable tool for decision makers caught in available facilities and due to the time of projects. Also drawing the scheduling problem to real world conditions by considering nonlinear objective function and the time value of money are considered. The presented problem was solved using NSGA-II, and the effect of time compressing reports on the non-dominant set.

ROTEX-TRIIFEX: Proposal for a joint FRG-USA telerobotic flight experiment

NASA Technical Reports Server (NTRS)

Hirzinger, G.; Bejczy, A. K.

1989-01-01

The concepts and main elements of a RObot Technology EXperiment (ROTEX) proposed to fly with the next German spacelab mission, D2, are presented. It provides a 1 meter size, six axis robot inside a spacelab rack, equipped with a multisensory gripper (force-torque sensors, an array of range finders, and mini stereo cameras). The robot will perform assembly and servicing tasks in a generic way, and will grasp a floating object. The man machine and supervisory control concepts for teleoperation from the spacelab and from ground are discussed. The predictive estimation schemes for an extensive use of time-delay compensating 3D computer graphics are explained.

Recovering from research: a no-fault proposal to compensate injured research participants.

PubMed

Pike, Elizabeth R

2012-01-01

National advisory committees have considered the obligations owed to research participants in the event of research-related injuries. These committees have repeatedly concluded that injured research participants are entitled to compensation for their injuries, that the tort system provides inadequate remedies, and that the United States should adopt no-fault compensation. But because the advisory committees have made no concrete proposals and have taken no steps toward implementing no-fault compensation, the United States continues to rely on the tort system to compensate injured research participants. This Article argues that recent legal developments and a transformation in the global research landscape make maintaining the status quo morally indefensible and practically unsustainable. Recent legal developments exacerbate the longstanding difficulties associated with the tort system as a method of compensation; nearly every injured research participant will have difficulty recovering damages, and certain classes of injured research participants--those in federal research and those abroad--are prevented from recovering altogether, resulting in substantial unfairness. In the past ten years, many of the countries substantially involved in research have mandated systematic compensation. By not mandating compensation, the United States has become a moral outlier and risks having its noncompliant research embargoed by foreign ethics committees, thereby delaying important biomedical advances. This Article examines alternative compensation mechanisms and offers a concrete no-fault compensation proposal built on systems already in place. The proposed system can be implemented in the United States and countries around the world to help harmonize various national compensation systems and to more equitably and effectively make those injured by research whole.

29 CFR 525.6 - Compensable time.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 29 Labor 3 2010-07-01 2010-07-01 false Compensable time. 525.6 Section 525.6 Labor Regulations... WITH DISABILITIES UNDER SPECIAL CERTIFICATES § 525.6 Compensable time. Individuals employed subject to this part must be compensated for all hours worked. Compensable time includes not only those hours...

29 CFR 525.6 - Compensable time.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 29 Labor 3 2014-07-01 2014-07-01 false Compensable time. 525.6 Section 525.6 Labor Regulations... WITH DISABILITIES UNDER SPECIAL CERTIFICATES § 525.6 Compensable time. Individuals employed subject to this part must be compensated for all hours worked. Compensable time includes not only those hours...

29 CFR 525.6 - Compensable time.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 29 Labor 3 2012-07-01 2012-07-01 false Compensable time. 525.6 Section 525.6 Labor Regulations... WITH DISABILITIES UNDER SPECIAL CERTIFICATES § 525.6 Compensable time. Individuals employed subject to this part must be compensated for all hours worked. Compensable time includes not only those hours...

Gravity Compensation Using EGM2008 for High-Precision Long-Term Inertial Navigation Systems

PubMed Central

Wu, Ruonan; Wu, Qiuping; Han, Fengtian; Liu, Tianyi; Hu, Peida; Li, Haixia

2016-01-01

The gravity disturbance vector is one of the major error sources in high-precision and long-term inertial navigation applications. Specific to the inertial navigation systems (INSs) with high-order horizontal damping networks, analyses of the error propagation show that the gravity-induced errors exist almost exclusively in the horizontal channels and are mostly caused by deflections of the vertical (DOV). Low-frequency components of the DOV propagate into the latitude and longitude errors at a ratio of 1:1 and time-varying fluctuations in the DOV excite Schuler oscillation. This paper presents two gravity compensation methods using the Earth Gravitational Model 2008 (EGM2008), namely, interpolation from the off-line database and computing gravity vectors directly using the spherical harmonic model. Particular attention is given to the error contribution of the gravity update interval and computing time delay. It is recommended for the marine navigation that a gravity vector should be calculated within 1 s and updated every 100 s at most. To meet this demand, the time duration of calculating the current gravity vector using EGM2008 has been reduced to less than 1 s by optimizing the calculation procedure. A few off-line experiments were conducted using the data of a shipborne INS collected during an actual sea test. With the aid of EGM2008, most of the low-frequency components of the position errors caused by the gravity disturbance vector have been removed and the Schuler oscillation has been attenuated effectively. In the rugged terrain, the horizontal position error could be reduced at best 48.85% of its regional maximum. The experimental results match with the theoretical analysis and indicate that EGM2008 is suitable for gravity compensation of the high-precision and long-term INSs. PMID:27999351

Gravity Compensation Using EGM2008 for High-Precision Long-Term Inertial Navigation Systems.

PubMed

Wu, Ruonan; Wu, Qiuping; Han, Fengtian; Liu, Tianyi; Hu, Peida; Li, Haixia

2016-12-18

The gravity disturbance vector is one of the major error sources in high-precision and long-term inertial navigation applications. Specific to the inertial navigation systems (INSs) with high-order horizontal damping networks, analyses of the error propagation show that the gravity-induced errors exist almost exclusively in the horizontal channels and are mostly caused by deflections of the vertical (DOV). Low-frequency components of the DOV propagate into the latitude and longitude errors at a ratio of 1:1 and time-varying fluctuations in the DOV excite Schuler oscillation. This paper presents two gravity compensation methods using the Earth Gravitational Model 2008 (EGM2008), namely, interpolation from the off-line database and computing gravity vectors directly using the spherical harmonic model. Particular attention is given to the error contribution of the gravity update interval and computing time delay. It is recommended for the marine navigation that a gravity vector should be calculated within 1 s and updated every 100 s at most. To meet this demand, the time duration of calculating the current gravity vector using EGM2008 has been reduced to less than 1 s by optimizing the calculation procedure. A few off-line experiments were conducted using the data of a shipborne INS collected during an actual sea test. With the aid of EGM2008, most of the low-frequency components of the position errors caused by the gravity disturbance vector have been removed and the Schuler oscillation has been attenuated effectively. In the rugged terrain, the horizontal position error could be reduced at best 48.85% of its regional maximum. The experimental results match with the theoretical analysis and indicate that EGM2008 is suitable for gravity compensation of the high-precision and long-term INSs.

An Inequality Constrained Least-Squares Approach as an Alternative Estimation Procedure for Atmospheric Parameters from VLBI Observations

NASA Astrophysics Data System (ADS)

Halsig, Sebastian; Artz, Thomas; Iddink, Andreas; Nothnagel, Axel

2016-12-01

On its way through the atmosphere, radio signals are delayed and affected by bending and attenuation effects relative to a theoretical path in vacuum. In particular, the neutral part of the atmosphere contributes considerably to the error budget of space-geodetic observations. At the same time, space-geodetic techniques become more and more important in the understanding of the Earth's atmosphere, because atmospheric parameters can be linked to the water vapor content in the atmosphere. The tropospheric delay is usually taken into account by applying an adequate model for the hydrostatic component and by additionally estimating zenith wet delays for the highly variable wet component. Sometimes, the Ordinary Least Squares (OLS) approach leads to negative estimates, which would be equivalent to negative water vapor in the atmosphere and does, of course, not reflect meteorological and physical conditions in a plausible way. To cope with this phenomenon, we introduce an Inequality Constrained Least Squares (ICLS) method from the field of convex optimization and use inequality constraints to force the tropospheric parameters to be non-negative allowing for a more realistic tropospheric parameter estimation in a meteorological sense. Because deficiencies in the a priori hydrostatic modeling are almost fully compensated by the tropospheric estimates, the ICLS approach urgently requires suitable a priori hydrostatic delays. In this paper, we briefly describe the ICLS method and validate its impact with regard to station positions.

Robust terahertz self-heterodyne system using a phase noise compensation technique.

PubMed

Song, Hajun; Song, Jong-In

2015-08-10

We propose and demonstrate a robust terahertz self-heterodyne system using a phase noise compensation technique. Conventional terahertz self-heterodyne systems suffer from degraded phase noise performance due to phase noise of the laser sources. The proposed phase noise compensation technique uses an additional photodiode and a simple electric circuit to produce phase noise identical to that observed in the terahertz signal produced by the self-heterodyne system. The phase noise is subsequently subtracted from the terahertz signal produced by the self-heterodyne system using a lock-in amplifier. While the terahertz self-heterodyne system using a phase noise compensation technique offers improved phase noise performance, it also provides a reduced phase drift against ambient temperature variations. The terahertz self-heterodyne system using a phase noise compensation technique shows a phase noise of 0.67 degree in terms of a standard deviation value even without using overall delay balance control. It also shows a phase drift of as small as approximately 10 degrees in an open-to-air measurement condition without any strict temperature control.

Generating synchrony from the asynchronous: compensation for cochlear traveling wave delays by the dendrites of individual brainstem neurons

PubMed Central

McGinley, Matthew J.; Liberman, M. Charles; Bal, Ramazan; Oertel, Donata

2012-01-01

Broadband transient sounds, such as clicks and consonants, activate a traveling wave in the cochlea. This wave evokes firing in auditory nerve fibers that are tuned to high frequencies several milliseconds earlier than in fibers tuned to low frequencies. Despite this substantial traveling wave delay, octopus cells in the brainstem receive broadband input and respond to clicks with submillisecond temporal precision. The dendrites of octopus cells lie perpendicular to the tonotopically organized array of auditory nerve fibers, placing the earliest arriving inputs most distally and the latest arriving closest to the soma. Here, we test the hypothesis that the topographic arrangement of synaptic inputs on dendrites of octopus cells allows octopus cells to compensate the traveling wave delay. We show that in mice the full cochlear traveling wave delay is 1.6 ms. Because the dendrites of each octopus cell spread across about one third of the tonotopic axis, a click evokes a soma directed sweep of synaptic input lasting 0.5 ms in individual octopus cells. Morphologically and biophysically realistic, computational models of octopus cells show that soma-directed sweeps with durations matching in vivo measurements result in the largest and sharpest somatic excitatory postsynaptic potentials (EPSPs). A low input resistance and activation of a low-voltage-activated potassium conductance that are characteristic of octopus cells are important determinants of sweep sensitivity. We conclude that octopus cells have dendritic morphologies and biophysics tailored to accomplish the precise encoding of broadband transient sounds. PMID:22764237

[A comparison of leak compensation in six acute care ventilators during non-invasive ventilation].

PubMed

Hu, X S; Wang, Y; Wang, Z T; Yan, P; Zhang, X G; Zhao, S F; Xie, F; Gu, H J; Xie, L X

2017-02-12

Objective: To compare the ability of leak compensation in 6 medical ventilators during non-invasive ventilation. Methods: Six medical ventilators were selected, including 3 non-invasive ventilators (V60, Flexo and Stellar150), and 3 invasive ventilators(Avea, Servo I and BellaVist). Using a lung simulator, the ability of leak compensation was evaluated during triggering and cycling in 2 respiratory mechanics conditions (high airway resistance condition and high elastance resistance condition), and each condition was performed under 2 PEEP levels (4, and 8 cmH(2)O, 1 mmHg=0.098 kPa) at 4 air leak level conditions (L0: 2-3 L/min, L1: 8-10 L/min, L2: 22-27 L/min, L3: 35-40 L/min). Results: In the high elastance resistance condition (L2, L3)with different leak levels, the number of auto-triggering and miss-triggering of the non-invasive ventilator Flexo was significantly less than those of the others (L2: 1, 1; L3: 1.67, 1.33, P <0.01), and had better synchronization (L2: 2.33, 2.33; L3: 3.33, 3.33, P <0.01). In the high airway resistance condition with PEEP 4 cmH(2)O, V60 had less number of auto-triggering than other ventilators ( P <0.01), while in the high airway resistance condition with PEEP 8 cmH(2)O, Stellar150 had less number of miss-triggering than other ventilators (1, 0.67, 0, P <0.01). Flexo had a shorter trigger delay time than other ventilators in both high airway resistance and high elastance resistance conditions with L0 and L1 leak levels and PEEP levels [ARDS, PEEP=4: (109.8±1.8) ms, (112.0±0.6) ms; ARDS, PEEP=8: (103.1±0.7) ms, (109.7±0.7) ms; COPD, PEEP=4: (207.3±1.1) ms, (220.8±1.1) ms; COPD, PEEP=8: (195.6±6.7) ms, (200.0±1.2) ms , P <0.01]. Stellar150 had the shortest trigger delay time in high airway resistance condition with PEEP 4 cmH(2)O and high leak level L3[(262.8±0.8) ms , P <0.01]. V60 had a good performance on trigger delay time in high elastance resistance condition with PEEP 4 and 8 cmH(2)O, and also was most stable in increasing leak levels. Conclusion: In high airway resistance and high elastance resistance conditions with different PEEP levels and leak levels, V60, Stellar150, Flexo and BellaVista ventilators could be synchronized, among which V60, Stellar150 and Flexo presented a good performance features in specific conditions.

Research on the adaptive optical control technology based on DSP

NASA Astrophysics Data System (ADS)

Zhang, Xiaolu; Xue, Qiao; Zeng, Fa; Zhao, Junpu; Zheng, Kuixing; Su, Jingqin; Dai, Wanjun

2018-02-01

Adaptive optics is a real-time compensation technique using high speed support system for wavefront errors caused by atmospheric turbulence. However, the randomness and instantaneity of atmospheric changing introduce great difficulties to the design of adaptive optical systems. A large number of complex real-time operations lead to large delay, which is an insurmountable problem. To solve this problem, hardware operation and parallel processing strategy are proposed, and a high-speed adaptive optical control system based on DSP is developed. The hardware counter is used to check the system. The results show that the system can complete a closed loop control in 7.1ms, and improve the controlling bandwidth of the adaptive optical system. Using this system, the wavefront measurement and closed loop experiment are carried out, and obtain the good results.

20 CFR 209.15 - Compensation reportable when paid.

Code of Federal Regulations, 2011 CFR

2011-04-01

... time lost. Compensation which is pay for time lost, as provided in § 211.3 of this chapter, shall be reported with respect to the period in which the time and compensation were lost. For example, if an... compensation with respect to the year in which the time and compensation were lost. (c) Separation allowance or...

20 CFR 209.15 - Compensation reportable when paid.

Code of Federal Regulations, 2010 CFR

2010-04-01

... time lost. Compensation which is pay for time lost, as provided in § 211.3 of this chapter, shall be reported with respect to the period in which the time and compensation were lost. For example, if an... compensation with respect to the year in which the time and compensation were lost. (c) Separation allowance or...

TH-AB-202-04: Auto-Adaptive Margin Generation for MLC-Tracked Radiotherapy

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

Glitzner, M; Lagendijk, J; Raaymakers, B

Purpose: To develop an auto-adaptive margin generator for MLC tracking. The generator is able to estimate errors arising in image guided radiotherapy, particularly on an MR-Linac, which depend on the latencies of machine and image processing, as well as on patient motion characteristics. From the estimated error distribution, a segment margin is generated, able to compensate errors up to a user-defined confidence. Method: In every tracking control cycle (TCC, 40ms), the desired aperture D(t) is compared to the actual aperture A(t), a delayed and imperfect representation of D(t). Thus an error e(t)=A(T)-D(T) is measured every TCC. Applying kernel-density-estimation (KDE), themore » cumulative distribution (CDF) of e(t) is estimated. With CDF-confidence limits, upper and lower error limits are extracted for motion axes along and perpendicular leaf-travel direction and applied as margins. To test the dosimetric impact, two representative motion traces were extracted from fast liver-MRI (10Hz). The traces were applied onto a 4D-motion platform and continuously tracked by an Elekta Agility 160 MLC using an artificially imposed tracking delay. Gafchromic film was used to detect dose exposition for static, tracked, and error-compensated tracking cases. The margin generator was parameterized to cover 90% of all tracking errors. Dosimetric impact was rated by calculating the ratio between underexposed points (>5% underdosage) to the total number of points inside FWHM of static exposure. Results: Without imposing adaptive margins, tracking experiments showed a ratio of underexposed points of 17.5% and 14.3% for two motion cases with imaging delays of 200ms and 300ms, respectively. Activating the margin generated yielded total suppression (<1%) of underdosed points. Conclusion: We showed that auto-adaptive error compensation using machine error statistics is possible for MLC tracking. The error compensation margins are calculated on-line, without the need of assuming motion or machine models. Further strategies to reduce consequential overdosages are currently under investigation. This work was funded by the SoRTS consortium, which includes the industry partners Elekta, Philips and Technolution.« less

Coherent detection in optical fiber systems.

PubMed

Ip, Ezra; Lau, Alan Pak Tao; Barros, Daniel J F; Kahn, Joseph M

2008-01-21

The drive for higher performance in optical fiber systems has renewed interest in coherent detection. We review detection methods, including noncoherent, differentially coherent, and coherent detection, as well as a hybrid method. We compare modulation methods encoding information in various degrees of freedom (DOF). Polarization-multiplexed quadrature-amplitude modulation maximizes spectral efficiency and power efficiency, by utilizing all four available DOF, the two field quadratures in the two polarizations. Dual-polarization homodyne or heterodyne downconversion are linear processes that can fully recover the received signal field in these four DOF. When downconverted signals are sampled at the Nyquist rate, compensation of transmission impairments can be performed using digital signal processing (DSP). Linear impairments, including chromatic dispersion and polarization-mode dispersion, can be compensated quasi-exactly using finite impulse response filters. Some nonlinear impairments, such as intra-channel four-wave mixing and nonlinear phase noise, can be compensated partially. Carrier phase recovery can be performed using feedforward methods, even when phase-locked loops may fail due to delay constraints. DSP-based compensation enables a receiver to adapt to time-varying impairments, and facilitates use of advanced forward-error-correction codes. We discuss both single- and multi-carrier system implementations. For a given modulation format, using coherent detection, they offer fundamentally the same spectral efficiency and power efficiency, but may differ in practice, because of different impairments and implementation details. With anticipated advances in analog-to-digital converters and integrated circuit technology, DSP-based coherent receivers at bit rates up to 100 Gbit/s should become practical within the next few years.

A high precision position sensor design and its signal processing algorithm for a maglev train.

PubMed

Xue, Song; Long, Zhiqiang; He, Ning; Chang, Wensen

2012-01-01

High precision positioning technology for a kind of high speed maglev train with an electromagnetic suspension (EMS) system is studied. At first, the basic structure and functions of the position sensor are introduced and some key techniques to enhance the positioning precision are designed. Then, in order to further improve the positioning signal quality and the fault-tolerant ability of the sensor, a new kind of discrete-time tracking differentiator (TD) is proposed based on nonlinear optimal control theory. This new TD has good filtering and differentiating performances and a small calculation load. It is suitable for real-time signal processing. The stability, convergence property and frequency characteristics of the TD are studied and analyzed thoroughly. The delay constant of the TD is figured out and an effective time delay compensation algorithm is proposed. Based on the TD technology, a filtering process is introduced in to improve the positioning signal waveform when the sensor is under bad working conditions, and a two-sensor switching algorithm is designed to eliminate the positioning errors caused by the joint gaps of the long stator. The effectiveness and stability of the sensor and its signal processing algorithms are proved by the experiments on a test train during a long-term test run.

A High Precision Position Sensor Design and Its Signal Processing Algorithm for a Maglev Train

PubMed Central

Xue, Song; Long, Zhiqiang; He, Ning; Chang, Wensen

2012-01-01

High precision positioning technology for a kind of high speed maglev train with an electromagnetic suspension (EMS) system is studied. At first, the basic structure and functions of the position sensor are introduced and some key techniques to enhance the positioning precision are designed. Then, in order to further improve the positioning signal quality and the fault-tolerant ability of the sensor, a new kind of discrete-time tracking differentiator (TD) is proposed based on nonlinear optimal control theory. This new TD has good filtering and differentiating performances and a small calculation load. It is suitable for real-time signal processing. The stability, convergence property and frequency characteristics of the TD are studied and analyzed thoroughly. The delay constant of the TD is figured out and an effective time delay compensation algorithm is proposed. Based on the TD technology, a filtering process is introduced in to improve the positioning signal waveform when the sensor is under bad working conditions, and a two-sensor switching algorithm is designed to eliminate the positioning errors caused by the joint gaps of the long stator. The effectiveness and stability of the sensor and its signal processing algorithms are proved by the experiments on a test train during a long-term test run. PMID:22778582

Comparison between an African town and a neighbouring village shows delayed, but not decreased, sleep during the early stages of urbanisation.

PubMed

Beale, Andrew D; Pedrazzoli, Mario; Gonçalves, Bruno da Silva B; Beijamini, Felipe; Duarte, Núbia E; Egan, Kieren J; Knutson, Kristen L; Schantz, Malcolm von; Roden, Laura C

2017-07-18

The well-established negative health outcomes of sleep deprivation, and the suggestion that availability of electricity may enable later bed times without compensating sleep extension in the morning, have stimulated interest in studying communities whose sleep pattern may resemble a pre-industrial state. Here, we describe sleep and activity in two neighbouring communities, one urban (Milange) and one rural (Tengua), in a region of Mozambique where urbanisation is an ongoing process. The two communities differ in the amount and timing of daily activity and of light exposure, with later bedtimes (≈1 h) associated with more evening and less daytime light exposure seen in the town of Milange. In contrast to previous reports comparing communities with and without electricity, sleep duration did not differ between Milange (7.28 h) and Tengua (7.23 h). Notably, calculated sleep quality was significantly poorer in rural Tengua than in Milange, and poor sleep quality was associated with a number of attributes more characteristic of rural areas, including more intense physical labour and less comfortable sleeping arrangements. Thus, whilst our data support the hypothesis that access to electricity delays sleep timing, the higher sleep quality in the urban population also suggests that some aspects of industrialisation are beneficial to sleep.

Differential sensory cortical involvement in auditory and visual sensorimotor temporal recalibration: Evidence from transcranial direct current stimulation (tDCS).

PubMed

Aytemür, Ali; Almeida, Nathalia; Lee, Kwang-Hyuk

2017-02-01

Adaptation to delayed sensory feedback following an action produces a subjective time compression between the action and the feedback (temporal recalibration effect, TRE). TRE is important for sensory delay compensation to maintain a relationship between causally related events. It is unclear whether TRE is a sensory modality-specific phenomenon. In 3 experiments employing a sensorimotor synchronization task, we investigated this question using cathodal transcranial direct-current stimulation (tDCS). We found that cathodal tDCS over the visual cortex, and to a lesser extent over the auditory cortex, produced decreased visual TRE. However, both auditory and visual cortex tDCS did not produce any measurable effects on auditory TRE. Our study revealed different nature of TRE in auditory and visual domains. Visual-motor TRE, which is more variable than auditory TRE, is a sensory modality-specific phenomenon, modulated by the auditory cortex. The robustness of auditory-motor TRE, unaffected by tDCS, suggests the dominance of the auditory system in temporal processing, by providing a frame of reference in the realignment of sensorimotor timing signals. Copyright © 2017 Elsevier Ltd. All rights reserved.

Modeling and Measurement of Correlation between Blood and Interstitial Glucose Changes

PubMed Central

Shi, Ting; Li, Dachao; Li, Guoqing; Zhang, Yiming; Xu, Kexin; Lu, Luo

2016-01-01

One of the most effective methods for continuous blood glucose monitoring is to continuously measure glucose in the interstitial fluid (ISF). However, multiple physiological factors can modulate glucose concentrations and affect the lag phase between blood and ISF glucose changes. This study aims to develop a compensatory tool for measuring the delay in ISF glucose variations in reference to blood glucose changes. A theoretical model was developed based on biophysics and physiology of glucose transport in the microcirculation system. Blood and interstitial fluid glucose changes were measured in mice and rats by fluorescent and isotope methods, respectively. Computer simulation mimicked curves were fitted with data resulting from fluorescent measurements of mice and isotope measurements of rats, indicating that there were lag times for ISF glucose changes. It also showed that there was a required diffusion distance for glucose to travel from center of capillaries to interstitial space in both mouse and rat models. We conclude that it is feasible with the developed model to continuously monitor dynamic changes of blood glucose concentration through measuring glucose changes in ISF with high accuracy, which requires correct parameters for determining and compensating for the delay time of glucose changes in ISF. PMID:27239479

Method for enhancing signals transmitted over optical fibers

DOEpatents

Ogle, J.W.; Lyons, P.B.

1981-02-11

A method for spectral equalization of high frequency spectrally broadband signals transmitted through an optical fiber is disclosed. The broadband signal input is first dispersed by a grating. Narrow spectral components are collected into an array of equalizing fibers. The fibers serve as optical delay lines compensating for material dispersion of each spectral component during transmission. The relative lengths of the individual equalizing fibers are selected to compensate for such prior dispersion. The output of the equalizing fibers couple the spectrally equalized light onto a suitable detector for subsequent electronic processing of the enhanced broadband signal.

Satellite diversity and its implications on the RAKE receiver architecture for CDMA-based S-PCN's

NASA Technical Reports Server (NTRS)

Taaghol, P.; Sammut, A.; Tafazolli, R.; Evans, B. G.

1995-01-01

In this paper we examine the applicability of RAKE receivers in a mobile LEO satellite channel and identify the potential problem areas. We then proceed to investigate the possibility of a coherent combining architecture (downlink) in the presence of satellite diversity. We closely examine the path delay difference statistics of a diversity channel and propose a delay compensation scheme for the downlink in order to reduce the complexity of the user terminal. Finally, the required modifications to the conventional RAKE receiver are proposed and discussed.

Compensation for Lithography Induced Process Variations during Physical Design

NASA Astrophysics Data System (ADS)

Chin, Eric Yiow-Bing

This dissertation addresses the challenge of designing robust integrated circuits in the deep sub micron regime in the presence of lithography process variability. By extending and combining existing process and circuit analysis techniques, flexible software frameworks are developed to provide detailed studies of circuit performance in the presence of lithography variations such as focus and exposure. Applications of these software frameworks to select circuits demonstrate the electrical impact of these variations and provide insight into variability aware compact models that capture the process dependent circuit behavior. These variability aware timing models abstract lithography variability from the process level to the circuit level and are used to estimate path level circuit performance with high accuracy with very little overhead in runtime. The Interconnect Variability Characterization (IVC) framework maps lithography induced geometrical variations at the interconnect level to electrical delay variations. This framework is applied to one dimensional repeater circuits patterned with both 90nm single patterning and 32nm double patterning technologies, under the presence of focus, exposure, and overlay variability. Studies indicate that single and double patterning layouts generally exhibit small variations in delay (between 1--3%) due to self compensating RC effects associated with dense layouts and overlay errors for layouts without self-compensating RC effects. The delay response of each double patterned interconnect structure is fit with a second order polynomial model with focus, exposure, and misalignment parameters with 12 coefficients and residuals of less than 0.1ps. The IVC framework is also applied to a repeater circuit with cascaded interconnect structures to emulate more complex layout scenarios, and it is observed that the variations on each segment average out to reduce the overall delay variation. The Standard Cell Variability Characterization (SCVC) framework advances existing layout-level lithography aware circuit analysis by extending it to cell-level applications utilizing a physically accurate approach that integrates process simulation, compact transistor models, and circuit simulation to characterize electrical cell behavior. This framework is applied to combinational and sequential cells in the Nangate 45nm Open Cell Library, and the timing response of these cells to lithography focus and exposure variations demonstrate Bossung like behavior. This behavior permits the process parameter dependent response to be captured in a nine term variability aware compact model based on Bossung fitting equations. For a two input NAND gate, the variability aware compact model captures the simulated response to an accuracy of 0.3%. The SCVC framework is also applied to investigate advanced process effects including misalignment and layout proximity. The abstraction of process variability from the layout level to the cell level opens up an entire new realm of circuit analysis and optimization and provides a foundation for path level variability analysis without the computationally expensive costs associated with joint process and circuit simulation. The SCVC framework is used with slight modification to illustrate the speedup and accuracy tradeoffs of using compact models. With variability aware compact models, the process dependent performance of a three stage logic circuit can be estimated to an accuracy of 0.7% with a speedup of over 50,000. Path level variability analysis also provides an accurate estimate (within 1%) of ring oscillator period in well under a second. Another significant advantage of variability aware compact models is that they can be easily incorporated into existing design methodologies for design optimization. This is demonstrated by applying cell swapping on a logic circuit to reduce the overall delay variability along a circuit path. By including these variability aware compact models in cell characterization libraries, design metrics such as circuit timing, power, area, and delay variability can be quickly assessed to optimize for the correct balance of all design metrics, including delay variability. Deterministic lithography variations can be easily captured using the variability aware compact models described in this dissertation. However, another prominent source of variability is random dopant fluctuations, which affect transistor threshold voltage and in turn circuit performance. The SCVC framework is utilized to investigate the interactions between deterministic lithography variations and random dopant fluctuations. Monte Carlo studies show that the output delay distribution in the presence of random dopant fluctuations is dependent on lithography focus and exposure conditions, with a 3.6 ps change in standard deviation across the focus exposure process window. This indicates that the electrical impact of random variations is dependent on systematic lithography variations, and this dependency should be included for precise analysis.

Pathology-related cases in the Norwegian System of Patient Injury Compensation in the period 2010-2015.

PubMed

Alfsen, G Cecilie; Chen, Ying; Kähler, Hanne; Bukholm, Ida Rashida Khan

2016-12-01

The Norwegian System of Patient Injury Compensation (NPE) processes compensation claims from patients who complain about malpractice in the health services. A wrong diagnosis in pathology may cause serious injury to the patient, but the incidence of compensation claims is unknown, because pathology is not specified as a separate category in NPE’s statistics. Knowledge about errors is required to assess quality-enhancing measures. We have therefore searched through the NPE records to identify cases whose background stems from errors committed in pathology departments and laboratories. We have searched through the NPE records for cases related to pathology for the years 2010 – 2015. During this period the NPE processed a total of 26 600 cases, of which 93 were related to pathology. The compensation claim was upheld in 66 cases, resulting in total compensation payments amounting to NOK 63 million. False-negative results in the form of undetected diagnoses were the most frequent grounds for compensation claims (63 cases), with an undetected malignant melanoma (n = 23) or atypia in cell samples from the cervix uteri (n = 16) as the major groups. Sixteen cases involved non-diagnostic issues such as mix-up of samples (n = 8), contamination of samples (n = 4) or delayed responses (n = 4). The number of compensation claims caused by errors in pathology diagnostics is low in relative terms. The errors may, however, be of a serious nature, especially if malignant conditions are overlooked or samples mixed up.

Blind Compensation of I/Q Impairments in Wireless Transceivers

PubMed Central

Aziz, Mohsin; Ghannouchi, Fadhel M.; Helaoui, Mohamed

2017-01-01

The majority of techniques that deal with the mitigation of in-phase and quadrature-phase (I/Q) imbalance at the transmitter (pre-compensation) require long training sequences, reducing the throughput of the system. These techniques also require a feedback path, which adds more complexity and cost to the transmitter architecture. Blind estimation techniques are attractive for avoiding the use of long training sequences. In this paper, we propose a blind frequency-independent I/Q imbalance compensation method based on the maximum likelihood (ML) estimation of the imbalance parameters of a transceiver. A closed-form joint probability density function (PDF) for the imbalanced I and Q signals is derived and validated. ML estimation is then used to estimate the imbalance parameters using the derived joint PDF of the output I and Q signals. Various figures of merit have been used to evaluate the efficacy of the proposed approach using extensive computer simulations and measurements. Additionally, the bit error rate curves show the effectiveness of the proposed method in the presence of the wireless channel and Additive White Gaussian Noise. Real-world experimental results show an image rejection of greater than 30 dB as compared to the uncompensated system. This method has also been found to be robust in the presence of practical system impairments, such as time and phase delay mismatches. PMID:29257081

Laser-Ranging Transponders for Science Investigations of the Moon and Mars

NASA Technical Reports Server (NTRS)

Hemmati, Hamid; Chen, Yijiang; Bimbaum, Kevin

2012-01-01

An active laser was developed ranging in real-time with two terminals, emulating interplanetary distances, and with submillimeter accuracy. In order to overcome the limitations to ranging accuracy from jitters and delay drifts within the transponders, architecture was proposed based on asynchronous paired one-way ranging with local references. A portion of the transmitted light is directed, via a reference path, to the local detector. This allows for compensation of any jitter in the timing of the emitted laser pulse. The same detector is used to measure the time of the received pulses emitted from the remote terminal. This approach removes any change in the delay caused by the detector or its electronics. Two separate terminals using commercial off-the-shelf hardware were built to emulate active laser ranging over interplanetary distances. The communication link for the command to start recording pulse arrival times and data transfer from one terminal to the other was achieved using a standard wireless link, emulating free space laser communication. The deviation is well below the goal of 1-mm precision. This leaves enough margin to achieve 1-mm precision when including the fluctuations due to atmospheric turbulence while ranging to Mars through the Earth s atmosphere. The two terminals are mounted on translation stages, which can be moved freely on rails to yield a wide range of distances with fine adjustment. The two terminals were separated by approximately 16 meters.

Performance of Digital Communications over Selective Fading Channels.

DTIC Science & Technology

1983-09-01

and we assume that the "" receiver has compensated for the mean path delay td . Equivalently, we let d - : - 0 in order to establish a time reference...Pv dl g(V v( 4bd 2G2 E 211v/T2 (3.37) N0 4’. .4 which implies that iv is the key parameter in determining the signal-to-noise ratio for single-pulse...in (4.8) are defined by R-77 7777 7777,077 7-7.7 70 jnht(-b )/ Td Kv(h,bi,:) = , v(t) v(t-4) e h i dt (4.10a) and R=hbit v(t) v(t+T-4) e•j uh t (1- b

Altimeter waveform software design

NASA Technical Reports Server (NTRS)

Hayne, G. S.; Miller, L. S.; Brown, G. S.

1977-01-01

Techniques are described for preprocessing raw return waveform data from the GEOS-3 radar altimeter. Topics discussed include: (1) general altimeter data preprocessing to be done at the GEOS-3 Data Processing Center to correct altimeter waveform data for temperature calibrations, to convert between engineering and final data units and to convert telemetered parameter quantities to more appropriate final data distribution values: (2) time "tagging" of altimeter return waveform data quantities to compensate for various delays, misalignments and calculational intervals; (3) data processing procedures for use in estimating spacecraft attitude from altimeter waveform sampling gates; and (4) feasibility of use of a ground-based reflector or transponder to obtain in-flight calibration information on GEOS-3 altimeter performance.

The absence or temporal offset of visual feedback does not influence adaptation to novel movement dynamics.

PubMed

McKenna, Erin; Bray, Laurence C Jayet; Zhou, Weiwei; Joiner, Wilsaan M

2017-10-01

Delays in transmitting and processing sensory information require correctly associating delayed feedback to issued motor commands for accurate error compensation. The flexibility of this alignment between motor signals and feedback has been demonstrated for movement recalibration to visual manipulations, but the alignment dependence for adapting movement dynamics is largely unknown. Here we examined the effect of visual feedback manipulations on force-field adaptation. Three subject groups used a manipulandum while experiencing a lag in the corresponding cursor motion (0, 75, or 150 ms). When the offset was applied at the start of the session (continuous condition), adaptation was not significantly different between groups. However, these similarities may be due to acclimation to the offset before motor adaptation. We tested additional subjects who experienced the same delays concurrent with the introduction of the perturbation (abrupt condition). In this case adaptation was statistically indistinguishable from the continuous condition, indicating that acclimation to feedback delay was not a factor. In addition, end-point errors were not significantly different across the delay or onset conditions, but end-point correction (e.g., deceleration duration) was influenced by the temporal offset. As an additional control, we tested a group of subjects who performed without visual feedback and found comparable movement adaptation results. These results suggest that visual feedback manipulation (absence or temporal misalignment) does not affect adaptation to novel dynamics, independent of both acclimation and perceptual awareness. These findings could have implications for modeling how the motor system adjusts to errors despite concurrent delays in sensory feedback information. NEW & NOTEWORTHY A temporal offset between movement and distorted visual feedback (e.g., visuomotor rotation) influences the subsequent motor recalibration, but the effects of this offset for altered movement dynamics are largely unknown. Here we examined the influence of 1 ) delayed and 2 ) removed visual feedback on the adaptation to novel movement dynamics. These results contribute to understanding of the control strategies that compensate for movement errors when there is a temporal separation between motion state and sensory information. Copyright © 2017 the American Physiological Society.

Improving Accuracy in Arrhenius Models of Cell Death: Adding a Temperature-Dependent Time Delay.

PubMed

Pearce, John A

2015-12-01

The Arrhenius formulation for single-step irreversible unimolecular reactions has been used for many decades to describe the thermal damage and cell death processes. Arrhenius predictions are acceptably accurate for structural proteins, for some cell death assays, and for cell death at higher temperatures in most cell lines, above about 55 °C. However, in many cases--and particularly at hyperthermic temperatures, between about 43 and 55 °C--the particular intrinsic cell death or damage process under study exhibits a significant "shoulder" region that constant-rate Arrhenius models are unable to represent with acceptable accuracy. The primary limitation is that Arrhenius calculations always overestimate the cell death fraction, which leads to severely overoptimistic predictions of heating effectiveness in tumor treatment. Several more sophisticated mathematical model approaches have been suggested and show much-improved performance. But simpler models that have adequate accuracy would provide useful and practical alternatives to intricate biochemical analyses. Typical transient intrinsic cell death processes at hyperthermic temperatures consist of a slowly developing shoulder region followed by an essentially constant-rate region. The shoulder regions have been demonstrated to arise chiefly from complex functional protein signaling cascades that generate delays in the onset of the constant-rate region, but may involve heat shock protein activity as well. This paper shows that acceptably accurate and much-improved predictions in the simpler Arrhenius models can be obtained by adding a temperature-dependent time delay. Kinetic coefficients and the appropriate time delay are obtained from the constant-rate regions of the measured survival curves. The resulting predictions are seen to provide acceptably accurate results while not overestimating cell death. The method can be relatively easily incorporated into numerical models. Additionally, evidence is presented to support the application of compensation law behavior to the cell death processes--that is, the strong correlation between the kinetic coefficients, ln{A} and E(a), is confirmed.

Effect of perioperative inefficiency on neurosurgical theatre efficacy: A 15-year analysis.

PubMed

Kamat, Ameya S; Parker, Andrew

2015-01-01

Effective utilisation of operating theatre time is an important issue in neurosurgery. There is a commonly held belief amongst surgeons that throughput of theatre is decreasing secondary to worsening perioperative delays. The aim of this paper is to explore some of the factors that lead to delays in the perioperative period by determining whether there has been a trend in the increasing length of case time over a fifteen-year period. Case notes of all elective patients who consented for surgery between January 1998 and the end of 2012 were reviewed. Only patients who underwent elective surgery were included. Variables recorded included transit time from the ward to theatre, anaesthetic time, surgical time and time spent in recovery. These were compared over the 15-year period to look for apparent trends. The total number of patients who consented for elective surgery at our institution between January 1998 and December 2012 was 6760. The mean anaesthetic time considering all operations performed was 43 mins each over the 15-year period. Anaesthetic time was deemed to be trending upwards from 1998 where the mean time was 27 -60 mins in December 2012, thus reflecting an increase of 33 mins. The mean surgical times over the 15-year period were 131 mins. However in 1998, mean surgical time was 127 mins compared with 133 mins in 2012. For the operations analysed, anaesthetic time seems to be increasing and has effectively doubled over a 15-year period. Surgical time and non-clinical time are shown to be virtually constant. This delays the overall theatre list and increases the cancellation rate. For compensating this, changes need to be made when allocating resources to both elective and emergency theatres. Staff recruitment needs to be assessed and internal audits need to be conducted within institutions to analyse ways to optimise the throughput of an operation theatre. If these principles are not adhered to, it will have a negative impact as our populations, and hence our case loads increase to instrumental levels. This will in turn have a negative impact on health workers and patients alike.

A direct approach for the design of chirp stimuli used for the recording of auditory brainstem responses

PubMed Central

Elberling, Claus; Don, Manuel

2010-01-01

A recent study evaluates auditory brainstem responses (ABRs) evoked by chirps of different durations (sweeping rates) [Elberling et al. (2010). J. Acoust. Soc. Am. 128, 215–223]. The study demonstrates that shorter chirps are most efficient at higher levels of stimulation whereas longer chirps are most efficient at lower levels. Mechanisms other than the traveling wave delay, in particular, upward spread of excitation and changes in cochlear-neural delay with level, are suggested to be responsible for these findings. As a consequence, delay models based on estimates of the traveling wave delay are insufficient for the design of chirp stimuli, and another delay model based on a direct approach is therefore proposed. The direct approach uses ABR-latencies from normal-hearing subjects in response to octave-band chirps over a wide range of levels. The octave-band chirps are constructed by decomposing a broad-band chirp, and constitute a subset of the chirp. The delay compensations of the proposed model are similar to those found in the previous experimental study, which thus verifies the results of the proposed model. PMID:21110591

Repeated Summer Drought and Re-watering during the First Growing Year of Oak (Quercus petraea) Delay Autumn Senescence and Bud Burst in the Following Spring

PubMed Central

Vander Mijnsbrugge, Kristine; Turcsán, Arion; Maes, Jorne; Duchêne, Nils; Meeus, Steven; Steppe, Kathy; Steenackers, Marijke

2016-01-01

Climate change predicts harsher summer droughts for mid-latitudes in Europe. To enhance our understanding of the putative impacts on forest regeneration, we studied the response of oak seedlings (Quercus petraea) to water deficit. Potted seedlings originating from three locally sourced provenances were subjected to two successive drought periods during the first growing season each followed by a plentiful re-watering. Here, we describe survival and phenological responses after the second drought treatment, applying general linear mixed modeling. From the 441 drought treated seedlings 189 subsisted with higher chances of survival among smaller plants and among single plants per pot compared to doubles. Remarkably, survival was independent of the provenance, although relatively more plants had died off in two provenances compared to the third one with mean plant height being higher in one provenance and standard deviation of plant height being higher in the other. Timing of leaf senescence was clearly delayed after the severe drought treatment followed by re-watering, with two seedlings per pot showing a lesser retardation compared to single plants. This delay can be interpreted as a compensation time in which plants recover before entering the subsequent developmental process of leaf senescence, although it renders seedlings more vulnerable to early autumn frosts because of the delayed hardening of the shoots. Onset of bud flush in the subsequent spring still showed a significant but small delay in the drought treated group, independent of the number of seedlings per pot, and can be considered as an after effect of the delayed senescence. In both phenological models significant differences among the three provenances were detected independent from the treatment. The only provenance that is believed to be local of origin, displayed the earliest leaf senescence and the latest flushing, suggesting an adaptation to the local maritime climate. This provenance also displayed the highest standard deviation of plant height, which can be interpreted as an adaptation to variable and unpredictable weather conditions, favoring smaller plants in drought-prone summers and higher plants in more normal growing seasons. PMID:27064667

78 FR 27308 - Loan Originator Compensation Requirements Under the Truth In Lending Act (Regulation Z...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-10

... implementation of its new mortgage rules (Implementation Plan),\\3\\ under which the Bureau would work with the... dwelling.\\4\\ The prohibition applies to credit life, credit disability, credit unemployment, credit... proposal. The Bureau believes that the temporary delay would balance the need for consumers to receive the...

Dispersion control with a Fourier-domain optical delay line in a fiber-optic imaging interferometer.

PubMed

Lee, Kye-Sung; Akcay, A Ceyhun; Delemos, Tony; Clarkson, Eric; Rolland, Jannick P

2005-07-01

Recently, Fourier-domain (FD) optical delay lines (ODLs) were introduced for high-speed scanning and dispersion compensation in imaging interferometry. We investigate the effect of first- and second-order dispersion on the photocurrent signal associated with an optical coherence imaging system implemented with a single-mode fiber, a superluminescent diode centered at 950 nm +/- 35 nm, a FD ODL, a mirror, and a layered LiTAO3 that has suitable dispersion characteristics to model a skin specimen. We present a practical and useful method to minimize the effect of dispersion through the interferometer and the specimen combined, as well as to quantify the results using two general metrics for resolution. Theoretical and associated experimental results show that, under the optimum solution, the maximum broadening of the point-spread function through a 1-mm-deep specimen is limited to 57% of its original rms width value (i.e., 8.1 microm optimal, 12.7 microm at maximum broadening) compared with approximately 110% when compensation is performed without the specimen taken into account.

Tracking control of WMRs on loose soil based on mixed H2/H∞ control with longitudinal slip ratio estimation

NASA Astrophysics Data System (ADS)

Gao, Haibo; Chen, Chao; Ding, Liang; Li, Weihua; Yu, Haitao; Xia, Kerui; Liu, Zhen

2017-11-01

Wheeled mobile robots (WMRs) often suffer from the longitudinal slipping when moving on the loose soil of the surface of the moon during exploration. Longitudinal slip is the main cause of WMRs' delay in trajectory tracking. In this paper, a nonlinear extended state observer (NESO) is introduced to estimate the longitudinal velocity in order to estimate the slip ratio and the derivative of the loss of velocity which are used in modelled disturbance compensation. Owing to the uncertainty and disturbance caused by estimation errors, a multi-objective controller using the mixed H2/H∞ method is employed to ensure the robust stability and performance of the WMR system. The final inputs of the trajectory tracking consist of the feedforward compensation, compensation for the modelled disturbances and designed multi-objective control inputs. Finally, the simulation results demonstrate the effectiveness of the controller, which exhibits a satisfactory tracking performance.

Air Temperature Distribution Measurement Using Asynchronous-Type Sound Probe

NASA Astrophysics Data System (ADS)

Katano, Yosuke; Wakatsuki, Naoto; Mizutani, Koichi

2009-07-01

In conventional temperature measurement using a sound probe, the operation beginnings of two acoustic sensors must be completely synchronized to measure time of flight (TOF), tf, because the precision of synchronization determines TOF measurement accuracy. A wireless local area network (LAN) is convenient for constructing a sensing grid; however, it causes a fluctuation in the delay of millisecond order. Therefore, it cannot provide sufficient precision for synchronizing acoustic sensors. In previous studies, synchronization was achieved by a trigger line using a coaxial cable; however, the cable reduces the flexibility of a wireless sensing grid especially in larger-scale measurement. In this study, an asynchronous-type sound probe is devised to compensate for the effect of the delay of millisecond order caused by the network. The validity of the probe was examined, and the air temperature distribution was measured using this means. A matrix method is employed to obtain the distribution. Similar results were observed using both asynchronous-type sound probes and thermocouples. This shows the validity of the use of a sensing grid with an asynchronous-type sound probe for temperature distribution measurement even if the trigger line is omitted.

Comparison of in-situ delay monitors for use in Adaptive Voltage Scaling

NASA Astrophysics Data System (ADS)

Pour Aryan, N.; Heiß, L.; Schmitt-Landsiedel, D.; Georgakos, G.; Wirnshofer, M.

2012-09-01

In Adaptive Voltage Scaling (AVS) the supply voltage of digital circuits is tuned according to the circuit's actual operating condition, which enables dynamic compensation to PVTA variations. By exploiting the excessive safety margins added in state-of-the-art worst-case designs considerable power saving is achieved. In our approach, the operating condition of the circuit is monitored by in-situ delay monitors. This paper presents different designs to implement the in-situ delay monitors capable of detecting late but still non-erroneous transitions, called Pre-Errors. The developed Pre-Error monitors are integrated in a 16 bit multiplier test circuit and the resulting Pre-Error AVS system is modeled by a Markov chain in order to determine the power saving potential of each Pre-Error detection approach.

Mechanisms for Adjusting Interaural Time Differences to Achieve Binaural Coincidence Detection

PubMed Central

Seidl, Armin H.; Rubel, Edwin W; Harris, David M.

2010-01-01

Understanding binaural perception requires detailed analyses of the neural circuitry responsible for the computation of interaural time differences (ITDs). In the avian brainstem, this circuit consists of internal axonal delay lines innervating an array of coincidence detector neurons that encode external ITDs. Nucleus magnocellularis (NM) neurons project to the dorsal dendritic field of the ipsilateral nucleus laminaris (NL) and to the ventral field of the contralateral NL. Contralateral-projecting axons form a delay line system along a band of NL neurons. Binaural acoustic signals in the form of phase-locked action potentials from NM cells arrive at NL and establish a topographic map of sound source location along the azimuth. These pathways are assumed to represent a circuit similar to the Jeffress model of sound localization, establishing a place code along an isofrequency contour of NL. Three-dimensional measurements of axon lengths reveal major discrepancies with the current model; the temporal offset based on conduction length alone makes encoding of physiological ITDs impossible. However, axon diameter and distances between Nodes of Ranvier also influence signal propagation times along an axon. Our measurements of these parameters reveal that diameter and internode distance can compensate for the temporal offset inferred from axon lengths alone. Together with other recent studies these unexpected results should inspire new thinking on the cellular biology, evolution and plasticity of the circuitry underlying low frequency sound localization in both birds and mammals. PMID:20053889

Adaptive fuzzy wavelet network control of second order multi-agent systems with unknown nonlinear dynamics.

PubMed

Taheri, Mehdi; Sheikholeslam, Farid; Najafi, Majddedin; Zekri, Maryam

2017-07-01

In this paper, consensus problem is considered for second order multi-agent systems with unknown nonlinear dynamics under undirected graphs. A novel distributed control strategy is suggested for leaderless systems based on adaptive fuzzy wavelet networks. Adaptive fuzzy wavelet networks are employed to compensate for the effect of unknown nonlinear dynamics. Moreover, the proposed method is developed for leader following systems and leader following systems with state time delays. Lyapunov functions are applied to prove uniformly ultimately bounded stability of closed loop systems and to obtain adaptive laws. Three simulation examples are presented to illustrate the effectiveness of the proposed control algorithms. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Method and system for selecting data sampling phase for self timed interface logic

DOEpatents

Hoke, Joseph Michael; Ferraiolo, Frank D.; Lo, Tin-Chee; Yarolin, John Michael

2005-01-04

An exemplary embodiment of the present invention is a method for transmitting data among processors over a plurality of parallel data lines and a clock signal line. A receiver processor receives both data and a clock signal from a sender processor. At the receiver processor a bit of the data is phased aligned with the transmitted clock signal. The phase aligning includes selecting a data phase from a plurality of data phases in a delay chain and then adjusting the selected data phase to compensate for a round-off error. Additional embodiments include a system and storage medium for transmitting data among processors over a plurality of parallel data lines and a clock signal line.

High-temperature langatate elastic constants and experimental validation up to 900 degrees C.

PubMed

Davulis, Peter M; da Cunha, Mauricio Pereira

2010-01-01

This paper reports on a set of langatate (LGT) elastic constants extracted from room temperature to 1100 degrees C using resonant ultrasound spectroscopy techniques and an accompanying assessment of these constants at high temperature. The evaluation of the constants employed SAW device measurements from room temperature to 900 degrees C along 6 different LGT wafer orientations. Langatate parallelepipeds and wafers were aligned, cut, ground, and polished, and acoustic wave devices were fabricated at the University of Maine facilities along specific orientations for elastic constant extraction and validation. SAW delay lines were fabricated on LGT wafers prepared at the University of Maine using 100-nm platinumrhodium- zirconia electrodes capable of withstanding temperatures up to 1000 degrees C. The numerical predictions based on the resonant ultrasound spectroscopy high-temperature constants were compared with SAW phase velocity, fractional frequency variation, and temperature coefficients of delay extracted from SAW delay line frequency response measurements. In particular, the difference between measured and predicted fractional frequency variation is less than 2% over the 25 degrees C to 900 degrees C temperature range and within the calculated and measured discrepancies. Multiple temperature-compensated orientations at high temperature were predicted and verified in this paper: 4 of the measured orientations had turnover temperatures (temperature coefficient of delay = 0) between 200 and 420 degrees C, and 2 had turnover temperatures below 100 degrees C. In summary, this work reports on extracted high-temperature elastic constants for LGT up to 1100 degrees C, confirmed the validity of those constants by high-temperature SAW device measurements up to 900 degrees C, and predicted and identified temperature-compensated LGT orientations at high temperature.

Coherent detection and digital signal processing for fiber optic communications

NASA Astrophysics Data System (ADS)

Ip, Ezra

The drive towards higher spectral efficiency in optical fiber systems has generated renewed interest in coherent detection. We review different detection methods, including noncoherent, differentially coherent, and coherent detection, as well as hybrid detection methods. We compare the modulation methods that are enabled and their respective performances in a linear regime. An important system parameter is the number of degrees of freedom (DOF) utilized in transmission. Polarization-multiplexed quadrature-amplitude modulation maximizes spectral efficiency and power efficiency as it uses all four available DOF contained in the two field quadratures in the two polarizations. Dual-polarization homodyne or heterodyne downconversion are linear processes that can fully recover the received signal field in these four DOF. When downconverted signals are sampled at the Nyquist rate, compensation of transmission impairments can be performed using digital signal processing (DSP). Software based receivers benefit from the robustness of DSP, flexibility in design, and ease of adaptation to time-varying channels. Linear impairments, including chromatic dispersion (CD) and polarization-mode dispersion (PMD), can be compensated quasi-exactly using finite impulse response filters. In practical systems, sampling the received signal at 3/2 times the symbol rate is sufficient to enable an arbitrary amount of CD and PMD to be compensated for a sufficiently long equalizer whose tap length scales linearly with transmission distance. Depending on the transmitted constellation and the target bit error rate, the analog-to-digital converter (ADC) should have around 5 to 6 bits of resolution. Digital coherent receivers are naturally suited for the implementation of feedforward carrier recovery, which has superior linewidth tolerance than phase-locked loops, and does not suffer from feedback delay constraints. Differential bit encoding can be used to prevent catastrophic receiver failure due to cycle slips. In systems where nonlinear effects are concentrated mostly at fiber locations with small accumulated dispersion, nonlinear phase de-rotation is a low-complexity algorithm that can partially mitigate nonlinear effects. For systems with arbitrary dispersion maps, however, backpropagation is the only universal technique that can jointly compensate dispersion and fiber nonlinearity. Backpropagation requires solving the nonlinear Schrodinger equation at the receiver, and has high computational cost. Backpropagation is most effective when dispersion compensation fibers are removed, and when signal processing is performed at three times oversampling. Backpropagation can improve system performance and increase transmission distance. With anticipated advances in analog-to-digital converters and integrated circuit technology, DSP-based coherent receivers at bit rates up to 100 Gb/s should become practical in the near future.

A Fixed-Pattern Noise Correction Method Based on Gray Value Compensation for TDI CMOS Image Sensor.

PubMed

Liu, Zhenwang; Xu, Jiangtao; Wang, Xinlei; Nie, Kaiming; Jin, Weimin

2015-09-16

In order to eliminate the fixed-pattern noise (FPN) in the output image of time-delay-integration CMOS image sensor (TDI-CIS), a FPN correction method based on gray value compensation is proposed. One hundred images are first captured under uniform illumination. Then, row FPN (RFPN) and column FPN (CFPN) are estimated based on the row-mean vector and column-mean vector of all collected images, respectively. Finally, RFPN are corrected by adding the estimated RFPN gray value to the original gray values of pixels in the corresponding row, and CFPN are corrected by subtracting the estimated CFPN gray value from the original gray values of pixels in the corresponding column. Experimental results based on a 128-stage TDI-CIS show that, after correcting the FPN in the image captured under uniform illumination with the proposed method, the standard-deviation of row-mean vector decreases from 5.6798 to 0.4214 LSB, and the standard-deviation of column-mean vector decreases from 15.2080 to 13.4623 LSB. Both kinds of FPN in the real images captured by TDI-CIS are eliminated effectively with the proposed method.

Single-shot EPI with Nyquist ghost compensation: Interleaved Dual-Echo with Acceleration (IDEA) EPI

PubMed Central

Poser, Benedikt A; Barth, Markus; Goa, Pål-Erik; Deng, Weiran; Stenger, V Andrew

2012-01-01

Echo planar imaging is most commonly used for BOLD fMRI, owing to its sensitivity and acquisition speed. A major problem with EPI is Nyquist (N/2) ghosting, most notably at high field. EPI data are acquired under an oscillating readout gradient and hence vulnerable to gradient imperfections such as eddy current delays and off-resonance effects, as these cause inconsistencies between odd and even k-space lines after time reversal. We propose a straightforward and pragmatic method herein termed Interleaved Dual Echo with Acceleration (IDEA) EPI: Two k-spaces (echoes) are acquired under the positive and negative readout lobes, respectively, by performing phase blips only before alternate readout gradients. From these two k-spaces, two almost entirely ghost free images per shot can be constructed, without need for phase correction. The doubled echo train length can be compensated by parallel imaging and/or partial Fourier acquisition. The two k-spaces can either be complex-averaged during reconstruction, which results in near-perfect cancellation of residual phase errors, or reconstructed into separate images. We demonstrate the efficacy of IDEA EPI and show phantom and in vivo images at both 3 and 7 Tesla. PMID:22411762

New Perspectives on Compensation Strategies for the Out-of-School Time Workforce. Working Paper Series. Report.

ERIC Educational Resources Information Center

Morgan, Gwen; Harvey, Brooke

Noting that the quality, continuity, and stability of out-of-school time programs depend, in part, on the presence of a well-trained and fairly compensated staff, this paper examines the unique characteristics of the out-of-school time workforce that contribute to inadequate compensation and explores workforce compensation from an economic…

Surface Acoustic Wave Monitor for Deposition and Analysis of Ultra-Thin Films

NASA Technical Reports Server (NTRS)

Hines, Jacqueline H. (Inventor)

2015-01-01

A surface acoustic wave (SAW) based thin film deposition monitor device and system for monitoring the deposition of ultra-thin films and nanomaterials and the analysis thereof is characterized by acoustic wave device embodiments that include differential delay line device designs, and which can optionally have integral reference devices fabricated on the same substrate as the sensing device, or on a separate device in thermal contact with the film monitoring/analysis device, in order to provide inherently temperature compensated measurements. These deposition monitor and analysis devices can include inherent temperature compensation, higher sensitivity to surface interactions than quartz crystal microbalance (QCM) devices, and the ability to operate at extreme temperatures.

Method for measuring retardation of infrared wave-plate by modulated-polarized visible light

NASA Astrophysics Data System (ADS)

Zhang, Ying; Song, Feijun

2012-11-01

A new method for precisely measuring the optical phase retardation of wave-plates in the infrared spectral region is presented by using modulated-polarized visible light. An electro-optic modulator is used to accurately determine the zero point by the frequency-doubled signal of the Modulated-polarized light. A Babinet-Soleil compensator is employed to make the phase delay compensation. Based on this method, an instrument is set up to measure the retardations of the infrared wave-plates with visible region laser. Measurement results with high accuracy and sound repetition are obtained by simple calculation. Its measurement precision is less than and repetitive precision is within 0.3%.

Lossless microwave photonic delay line using a ring resonator with an integrated semiconductor optical amplifier

NASA Astrophysics Data System (ADS)

Xie, Yiwei; Zhuang, Leimeng; Boller, Klaus-Jochen; Lowery, Arthur James

2017-06-01

Optical delay lines implemented in photonic integrated circuits (PICs) are essential for creating robust and low-cost optical signal processors on miniaturized chips. In particular, tunable delay lines enable a key feature of programmability for the on-chip processing functions. However, the previously investigated tunable delay lines are plagued by a severe drawback of delay-dependent loss due to the propagation loss in the constituent waveguides. In principle, a serial-connected amplifier can be used to compensate such losses or perform additional amplitude manipulation. However, this solution is generally unpractical as it introduces additional burden on chip area and power consumption, particularly for large-scale integrated PICs. Here, we report an integrated tunable delay line that overcomes the delay-dependent loss, and simultaneously allows for independent manipulation of group delay and amplitude responses. It uses a ring resonator with a tunable coupler and a semiconductor optical amplifier in the feedback path. A proof-of-concept device with a free spectral range of 11.5 GHz and a delay bandwidth in the order of 200 MHz is discussed in the context of microwave photonics and is experimentally demonstrated to be able to provide a lossless delay up to 1.1 to a 5 ns Gaussian pulse. The proposed device can be designed for different frequency scales with potential for applications across many other areas such as telecommunications, LIDAR, and spectroscopy, serving as a novel building block for creating chip-scale programmable optical signal processors.

Using random forests to diagnose aviation turbulence.

PubMed

Williams, John K

Atmospheric turbulence poses a significant hazard to aviation, with severe encounters costing airlines millions of dollars per year in compensation, aircraft damage, and delays due to required post-event inspections and repairs. Moreover, attempts to avoid turbulent airspace cause flight delays and en route deviations that increase air traffic controller workload, disrupt schedules of air crews and passengers and use extra fuel. For these reasons, the Federal Aviation Administration and the National Aeronautics and Space Administration have funded the development of automated turbulence detection, diagnosis and forecasting products. This paper describes a methodology for fusing data from diverse sources and producing a real-time diagnosis of turbulence associated with thunderstorms, a significant cause of weather delays and turbulence encounters that is not well-addressed by current turbulence forecasts. The data fusion algorithm is trained using a retrospective dataset that includes objective turbulence reports from commercial aircraft and collocated predictor data. It is evaluated on an independent test set using several performance metrics including receiver operating characteristic curves, which are used for FAA turbulence product evaluations prior to their deployment. A prototype implementation fuses data from Doppler radar, geostationary satellites, a lightning detection network and a numerical weather prediction model to produce deterministic and probabilistic turbulence assessments suitable for use by air traffic managers, dispatchers and pilots. The algorithm is scheduled to be operationally implemented at the National Weather Service's Aviation Weather Center in 2014.

75 FR 18835 - Submission for OMB Review; American Recovery and Reinvestment Act-One-Time Reporting...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-13

... Recovery and Reinvestment Act--One-Time Reporting, Compensation Requirements AGENCY: Department of Defense... requirement concerning the one-time reporting, compensation requirements. A request for public comments was.... 9000-0168, American Recovery and Reinvestment Act--One-time Reporting, Compensation Requirements, in...

Variable Delay Element For Jitter Control In High Speed Data Links

DOEpatents

Livolsi, Robert R.

2002-06-11

A circuit and method for decreasing the amount of jitter present at the receiver input of high speed data links which uses a driver circuit for input from a high speed data link which comprises a logic circuit having a first section (1) which provides data latches, a second section (2) which provides a circuit generates a pre-destorted output and for compensating for level dependent jitter having an OR function element and a NOR function element each of which is coupled to two inputs and to a variable delay element as an input which provides a bi-modal delay for pulse width pre-distortion, a third section (3) which provides a muxing circuit, and a forth section (4) for clock distribution in the driver circuit. A fifth section is used for logic testing the driver circuit.

76 FR 45181 - Enhancing Airline Passenger Protections: Limited Delay of Effective Date for Certain Provisions

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-28

...The Department of Transportation is delaying the effective date for certain requirements adopted in an April 25, 2011 final rule on enhancing airline passenger protections. Specifically, the Department is delaying the effective date from August 23, 2011 to January 24, 2012, for requirements pertaining to baggage fees, post purchase price increases, flight status changes and holding a reservation without payment for twenty-four hours. The Department is also delaying the effective date from October 24, 2011 to January 24, 2012 for requirements pertaining to full fare advertising. The effective date remains August 23, 2011 for all the other requirements in the April 25, 2011 final rule, including the requirement not to permit an international flight to remain on the tarmac at a U.S. airport for more than four hours without allowing passengers to deplane, the requirement increasing the denied boarding compensation airlines must pay to passengers bumped from flights, and the requirement to disclose prominently all fees for optional aviation services on carriers' Web sites.

A comparison of atmospheric effects on differential phase for a two-element antenna array and nearby site test interferometer

NASA Astrophysics Data System (ADS)

Morabito, David D.; D'Addario, Larry; Finley, Susan

2016-02-01

Phased arrays of reflector antennas can be used to obtain effective area and gain that are much larger than is practical with a single antenna. This technique is routinely used by NASA for receiving weak signals from deep space. Phase alignment of the signals can be disrupted by turbulence in the troposphere, which causes fluctuations in the differences of signal delays among the antennas. At the Deep Space Network stations, site test interferometers (STIs) are being used for long-term monitoring of these delay fluctuations using signals from geostationary satellites. In this paper, we compare the STI measurements with the phase variations seen by a nearby two-element array of 34 m diameter antennas tracking 8.4 GHz and 32 GHz signals from the Cassini spacecraft in orbit around Saturn. It is shown that the statistics of the STI delay fluctuations, after appropriate scaling for differences in antenna separation and elevation angle and conversion to phase at the spacecraft frequencies, provide reliable estimates of the phase fluctuations seen by the large antennas on the deep space signal. Techniques for adaptive compensation of the phase fluctuations are available when receiving a sufficiently strong signal, but compensation is often impractical or impossible when using the array for transmitting. These results help to validate the use of long-term STI data for assessing the feasibility of large transmitting arrays at various sites.

38 CFR 3.6 - Duty periods.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., Compensation, and Dependency and Indemnity Compensation General § 3.6 Duty periods. (a) Active military, naval... dependency and indemnity compensation. (3) Full-time duty as a commissioned officer of the Coast and Geodetic... dependency and indemnity compensation. (4) Service at any time as a cadet at the United States Military, Air...

38 CFR 3.6 - Duty periods.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., Compensation, and Dependency and Indemnity Compensation General § 3.6 Duty periods. (a) Active military, naval... dependency and indemnity compensation. (3) Full-time duty as a commissioned officer of the Coast and Geodetic... dependency and indemnity compensation. (4) Service at any time as a cadet at the United States Military, Air...

38 CFR 3.6 - Duty periods.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., Compensation, and Dependency and Indemnity Compensation General § 3.6 Duty periods. (a) Active military, naval... dependency and indemnity compensation. (3) Full-time duty as a commissioned officer of the Coast and Geodetic... dependency and indemnity compensation. (4) Service at any time as a cadet at the United States Military, Air...

38 CFR 3.6 - Duty periods.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., Compensation, and Dependency and Indemnity Compensation General § 3.6 Duty periods. (a) Active military, naval... dependency and indemnity compensation. (3) Full-time duty as a commissioned officer of the Coast and Geodetic... dependency and indemnity compensation. (4) Service at any time as a cadet at the United States Military, Air...

38 CFR 3.6 - Duty periods.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., Compensation, and Dependency and Indemnity Compensation General § 3.6 Duty periods. (a) Active military, naval... dependency and indemnity compensation. (3) Full-time duty as a commissioned officer of the Coast and Geodetic... dependency and indemnity compensation. (4) Service at any time as a cadet at the United States Military, Air...

Forward masking as a mechanism of automatic gain control in odontocete biosonar: a psychophysical study.

PubMed

Supin, Alexander Ya; Nachtigall, Paul E; Breese, Marlee

2008-07-01

In a false killer whale Pseudorca crassidens, echo perception thresholds were measured using a go/no-go psychophysical paradigm and one-up-one-down staircase procedure. Computer controlled echoes were electronically synthesized pulses that were played back through a transducer and triggered by whale emitted biosonar pulses. The echo amplitudes were proportional to biosonar pulse amplitudes; echo levels were specified in terms of the attenuation of the echo sound pressure level near the animal's head relative to the source level of the biosonar pulses. With increasing echo delay, the thresholds (echo attenuation factor) decreased from -49.3 dB at 2 ms to -79.5 dB at 16 ms, with a regression slope of -9.5 dB per delay doubling (-31.5 dB per delay decade). At the longer delays, the threshold remained nearly constant around -80.4 dB. Levels of emitted pulses slightly increased with delay prolongation (threshold decrease), with a regression slope of 3.2 dB per delay doubling (10.7 dB per delay decade). The echo threshold dependence on delay is interpreted as a release from forward masking by the preceding emitted pulse. This release may compensate for the echo level decrease with distance, thus keeping the echo sensation level for the animal near constant within a certain distance range.

Anchorage Arrival Scheduling Under Off-Nominal Weather Conditions

NASA Technical Reports Server (NTRS)

Grabbe, Shon; Chan, William N.; Mukherjee, Avijit

2012-01-01

Weather can cause flight diversions, passenger delays, additional fuel consumption and schedule disruptions at any high volume airport. The impacts are particularly acute at the Ted Stevens Anchorage International Airport in Anchorage, Alaska due to its importance as a major international portal. To minimize the impacts due to weather, a multi-stage scheduling process is employed that is iteratively executed, as updated aircraft demand and/or airport capacity data become available. The strategic scheduling algorithm assigns speed adjustments for flights that originate outside of Anchorage Center to achieve the proper demand and capacity balance. Similarly, an internal departure-scheduling algorithm assigns ground holds for pre-departure flights that originate from within Anchorage Center. Tactical flight controls in the form of airborne holding are employed to reactively account for system uncertainties. Real-world scenarios that were derived from the January 16, 2012 Anchorage visibility observations and the January 12, 2012 Anchorage arrival schedule were used to test the initial implementation of the scheduling algorithm in fast-time simulation experiments. Although over 90% of the flights in the scenarios arrived at Anchorage without requiring any delay, pre-departure scheduling was the dominant form of control for Anchorage arrivals. Additionally, tactical scheduling was used extensively in conjunction with the pre-departure scheduling to reactively compensate for uncertainties in the arrival demand. For long-haul flights, the strategic scheduling algorithm performed best when the scheduling horizon was greater than 1,000 nmi. With these long scheduling horizons, it was possible to absorb between ten and 12 minutes of delay through speed control alone. Unfortunately, the use of tactical scheduling, which resulted in airborne holding, was found to increase as the strategic scheduling horizon increased because of the additional uncertainty in the arrival times of the aircraft. Findings from these initial experiments indicate that it is possible to schedule arrivals into Anchorage with minimal delays under low-visibility conditions with less disruption to high-cost, international flights.

Acoustic Database for Turbofan Engine Core-Noise Sources. I; Volume

NASA Technical Reports Server (NTRS)

Gordon, Grant

2015-01-01

In this program, a database of dynamic temperature and dynamic pressure measurements were acquired inside the core of a TECH977 turbofan engine to support investigations of indirect combustion noise. Dynamic temperature and pressure measurements were recorded for engine gas dynamics up to temperatures of 3100 degrees Fahrenheit and transient responses as high as 1000 hertz. These measurements were made at the entrance of the high pressure turbine (HPT) and at the entrance and exit of the low pressure turbine (LPT). Measurements were made at two circumferential clocking positions. In the combustor and inter-turbine duct (ITD), measurements were made at two axial locations to enable the exploration of time delays. The dynamic temperature measurements were made using dual thin-wire thermocouple probes. The dynamic pressure measurements were made using semi-infinite probes. Prior to the engine test, a series of bench, oven, and combustor rig tests were conducted to characterize the performance of the dual wire temperature probes and to define and characterize the data acquisition systems. A measurement solution for acquiring dynamic temperature and pressure data on the engine was defined. A suite of hardware modifications were designed to incorporate the dynamic temperature and pressure instrumentation into the TECH977 engine. In particular, a probe actuation system was developed to protect the delicate temperature probes during engine startup and transients in order to maximize sensor life. A set of temperature probes was procured and the TECH977 engine was assembled with the suite of new and modified hardware. The engine was tested at four steady state operating speeds, with repeats. Dynamic pressure and temperature data were acquired at each condition for at least one minute. At the two highest power settings, temperature data could not be obtained at the forward probe locations since the mean temperatures exceeded the capability of the probes. The temperature data were processed using software that accounts for the effects of convective and conductive heat transfer. The software was developed under previous NASA sponsored programs. Compensated temperature spectra and compensated time histories corresponding to the dynamic temperature of the gas stream were generated. Auto-spectral and cross-spectral analyses of the data were performed to investigate spectral features, acoustic circumferential mode content, signal coherence, and time delays. The dynamic temperature data exhibit a wideband and fairly flat spectral content. The temperature spectra do not change substantially with operating speed. The pressure spectra in the combustor and ITD exhibit generally similar shapes and amplitudes, making it difficult to identify any features that suggest the presence of indirect combustion noise. Cross-spectral analysis reveal a strong correlation between pressure and temperature fluctuations in the ITD, but little correlation between temperature fluctuations at the entrance of the HPT and pressure fluctuations downstream of it. Temperature fluctuations at the entrance of the low pressure turbine were an order of magnitude smaller than those at the entrance to the high pressure turbine. Time delay analysis of the temperature fluctuations in the combustor was inconclusive, perhaps due to the substantial mixing that occurs between the upstream and downstream locations. Time delay analysis of the temperature fluctuations in the ITD indicate that they convect at the mean flow speed. Analysis of the data did not reveal any convincing indications of the presence of indirect combustion noise. However, this analysis has been preliminary and additional exploration of the data is recommended including the use of more sophisticated signal processing to explore subtle issues that have been revealed but which are not yet fully understood or explained.

Teaching Reading to Children with Down Syndrome: A Guide for Parents and Teachers. Topics in Down Syndrome.

ERIC Educational Resources Information Center

Oelwein, Patricia Logan

This book is designed to give parents and teachers of children with Down syndrome and other developmental delays an alternative reading program. The program is based on a functional, language-experience approach which attempts to compensate for common deficits in auditory memory and verbal skills. The seven chapters of Part 1 describe how children…

Imaginal discs secrete insulin-like peptide 8 to mediate plasticity of growth and maturation.

PubMed

Garelli, Andres; Gontijo, Alisson M; Miguela, Veronica; Caparros, Esther; Dominguez, Maria

2012-05-04

Developing animals frequently adjust their growth programs and/or their maturation or metamorphosis to compensate for growth disturbances (such as injury or tumor) and ensure normal adult size. Such plasticity entails tissue and organ communication to preserve their proportions and symmetry. Here, we show that imaginal discs autonomously activate DILP8, a Drosophila insulin-like peptide, to communicate abnormal growth and postpone maturation. DILP8 delays metamorphosis by inhibiting ecdysone biosynthesis, slowing growth in the imaginal discs, and generating normal-sized animals. Loss of dilp8 yields asymmetric individuals with an unusually large variation in size and a more varied time of maturation. Thus, DILP8 is a fundamental element of the hitherto ill-defined machinery governing the plasticity that ensures developmental stability and robustness.

Two-stage optical parametric chirped-pulse amplifier using sub-nanosecond pump pulse generated by stimulated Brillouin scattering compression

NASA Astrophysics Data System (ADS)

Ogino, Jumpei; Miyamoto, Sho; Matsuyama, Takahiro; Sueda, Keiichi; Yoshida, Hidetsugu; Tsubakimoto, Koji; Miyanaga, Noriaki

2014-12-01

We demonstrate optical parametric chirped-pulse amplification (OPCPA) based on two-beam pumping, using sub-nanosecond pulses generated by stimulated Brillouin scattering compression. Seed pulse energy, duration, and center wavelength were 5 nJ, 220 ps, and ˜1065 nm, respectively. The 532 nm pulse from a Q-switched Nd:YAG laser was compressed to ˜400 ps in heavy fluorocarbon FC-40 liquid. Stacking of two time-delayed pump pulses reduced the amplifier gain fluctuation. Using a walk-off-compensated two-stage OPCPA at a pump energy of 34 mJ, a total gain of 1.6 × 105 was obtained, yielding an output energy of 0.8 mJ. The amplified chirped pulse was compressed to 97 fs.

Telerobotic Surgery: An Intelligent Systems Approach to Mitigate the Adverse Effects of Communication Delay. Chapter 4

NASA Technical Reports Server (NTRS)

Cardullo, Frank M.; Lewis, Harold W., III; Panfilov, Peter B.

2007-01-01

An extremely innovative approach has been presented, which is to have the surgeon operate through a simulator running in real-time enhanced with an intelligent controller component to enhance the safety and efficiency of a remotely conducted operation. The use of a simulator enables the surgeon to operate in a virtual environment free from the impediments of telecommunication delay. The simulator functions as a predictor and periodically the simulator state is corrected with truth data. Three major research areas must be explored in order to ensure achieving the objectives. They are: simulator as predictor, image processing, and intelligent control. Each is equally necessary for success of the project and each of these involves a significant intelligent component in it. These are diverse, interdisciplinary areas of investigation, thereby requiring a highly coordinated effort by all the members of our team, to ensure an integrated system. The following is a brief discussion of those areas. Simulator as a predictor: The delays encountered in remote robotic surgery will be greater than any encountered in human-machine systems analysis, with the possible exception of remote operations in space. Therefore, novel compensation techniques will be developed. Included will be the development of the real-time simulator, which is at the heart of our approach. The simulator will present real-time, stereoscopic images and artificial haptic stimuli to the surgeon. Image processing: Because of the delay and the possibility of insufficient bandwidth a high level of novel image processing is necessary. This image processing will include several innovative aspects, including image interpretation, video to graphical conversion, texture extraction, geometric processing, image compression and image generation at the surgeon station. Intelligent control: Since the approach we propose is in a sense predictor based, albeit a very sophisticated predictor, a controller, which not only optimizes end effector trajectory but also avoids error, is essential. We propose to investigate two different approaches to the controller design. One approach employs an optimal controller based on modern control theory; the other one involves soft computing techniques, i.e. fuzzy logic, neural networks, genetic algorithms and hybrids of these.

Work status and disability trajectories over 12 months after injury among workers in New Zealand.

PubMed

Langley, John; Lilley, Rebbecca; Samaranayaka, Ari; Derrett, Sarah

2014-03-07

To describe work and disability trajectories over 12 months following injury among workers. Workers injured at work or elsewhere (n=2626) were sourced from the Prospective Outcomes of Injury Study, a longitudinal cohort study in New Zealand, with the primary objective of identifying factors associated with disability following injury. Work and disability status was assessed at 3- and 12-months post injury. The measure of disability was the brief WHODAS II 12-item instrument. Participants were dichotomised into 'disability' or 'no disability' groups based on whether their WHODAS score was greater than, or equal to, 10. In terms of 12-month work status, there are 16 different scenarios. These were grouped into 4 categories: sustained work (SW), delayed return to work (RTW), non-sustained RTW, and sustained off-work. We had complete information for 1975 workers. The largest group (68%) was SW, 32% of which had disability at either time point. The second largest group consisted of 17% of workers who were classified as delayed RTW, 76% of whom were disabled at either time point. Among the non-sustained RTW group (7%), 52% had disability at either time point. Of the sustained off-work group (8%), 80% were disabled at either 3- or 12-months. Although return to work is a useful provider performance indicator of injury compensation and rehabilitation it is inadequate from a wider societal perspective and needs to be complemented by other important outcome measures such as disability status.

Group Delay Tracking with the Sydney University Stellar Interferometer

NASA Astrophysics Data System (ADS)

Lawson, Peter R.

1994-08-01

The Sydney University Stellar Interferometer (SUSI) is a long baseline optical interferometer, located at the Paul Wild Observatory near Narrabri, in northern New South Wales, Australia. It is designed to measure stellar angular diameters using light collected from a pair of siderostats, with 11 fixed siderostats giving separations between 5 and 640 m. Apertures smaller than Fried's coherence length, r_0, are used and active tilt-compensation is employed. This ensures that when the beams are combined in the pupil plane the wavefronts are parallel. Fringes are detected when the optical path-difference between the arriving wavefronts is less than tne coherence length of light used for the observation. While observing a star it is necessary to compensate for the changes in pathlength due to the earth's rotation. It is also highly desirable to compensate for path changes due to the effects of atmospheric turbulence. Tracking the path-difference permits an accurate calibration of the fringe visibility, allows larger bandwidths to be used, and therefore improves the sensitivity of the instrument. I describe a fringe tracking system which I developed for SUSI, based on group delay tracking with a PAPA (Precision Analog Photon Address) detector. The method uses short exposure images of fringes, 1-10 ms, detected in the dispersed spectra of the combined starlight. The number of fringes across a fixed bandwidth of channeled spectrum is directly proportional to the path-difference between the arriving wavefronts. A Fast Fourier Transform, implemented in hardware, is used to calculate the spatial power spectrum of the fringes, thereby locating the delay. The visibility loss due to a non-constant fringe spacing on the detector is investigated, and the improvements obtained from rebinning the photon data are shown. The low light level limitations of group delay tracking are determined theoretically with emphasis on the probability of tracking error, rather than the signal-to-noise ratio. Experimental results from both laboratory studies and stellar observations are presented. These show the first closed-loop operation of a fringe tracking system based on observations of group delay with a stellar interferometer. The Sydney University PAPA camera, a photon counting array detector developed for use in this work, is also described. The design principles of the PAPA camera are outlined and the potential sources of image artifacts are identified. The artifacts arise from the use of optical encoding with Gray coded masks, and teh new camera is distinguished by its mask-plate, which was designed to overcome artifacts due to vignetting. Nw lens mounts are also presented which permit a simplified optical alignment without the need for tilt-plates. The performance of the camera is described. (SECTION: Dissertation Summaries)

Part-time physician faculty in a pediatrics department: a study of equity in compensation and academic advancement.

PubMed

Darbar, Mumtaz; Emans, S Jean; Harris, Z Leah; Brown, Nancy J; Scott, Theresa A; Cooper, William O

2011-08-01

To assess equity in compensation and academic advancement in an academic pediatrics department in which a large proportion of the physician faculty hold part-time appointments. The authors analyzed anonymized data from Vanderbilt University School of Medicine Department of Pediatrics databases for physician faculty (faculty with MD or MD/PhD degrees) employed during July 1, 2007 to June 30, 2008. The primary outcomes were total compensation and years at assistant professor rank. They compared compensation and years at junior rank by part-time versus full-time status, controlling for gender, rank, track, years since first appointment as an assistant professor, and clinical productivity. Of the 119 physician faculty in the department, 112 met inclusion criteria. Among those 112 faculty, 23 (21%) were part-time and 89 (79%) were full-time faculty. Part-time faculty were more likely than full-time faculty to be women (74% versus 28%, P < .001) and married (100% versus 84%, P = .042). Analyses accounting for gender, years since first appointment, rank, clinical productivity, and track did not demonstrate significant differences in compensation by part-time versus full-time status. In other adjusted analyses, faculty with part-time appointments spent an average of 2.48 more years as an assistant professor than did faculty with full-time appointments. Overall group differences in total compensation were not apparent in this department, but physician faculty with part-time appointments spent more time at the rank of assistant professor. This study provides a model for determining and analyzing compensation and effort to ensure equity and transparency across faculty.

Mitigation of nonlinear fiber distortion using optical phase conjugation for mode-division multiplexed transmission

NASA Astrophysics Data System (ADS)

Zhang, Kai; Gao, Guanjun; Zhang, Jie; Fei, Aimei; Cvijetic, Milorad

2018-07-01

We have investigated and proposed the use of optical phase conjugation (OPC) technique to mitigate the impact of fiber nonlinearities in mode-division multiplexed transmission systems. Numerical simulations are performed for three wavelengths, each loaded with 200 Gb/s dual-polarization 16-level quadrature amplitude modulation (DP-16QAM) format, in weakly guided two-mode fiber. It is known that differential mode group delay (DMGD) in mode-division multiplexed (MDM) transmission systems could be beneficial for system performance of MDM system with MIMO compensation in place. On the other side, for MDM system with OPC in place, the presence of DMGD may limit the overall benefits since signal power evolution per spatial modes should be symmetrical at the system midpoint in order to realize an effective compensation of the nonlinear effects. Our simulation results show that in the reference case (in the absence of DMGD), the employment of OPC module would lead to an average Q-factor improvement of approximately 10 dB. At the same time, in the presence of DMGD, an average Q-factor improvement would be ∼2.8 dB for WDM case. In addition, due to asymmetrical signal power map, the penalties induced by a periodic amplification process cannot be ideally compensated by the midpoint insertion of OPC. However, by accounting the impacts of both DMGD and asymmetrical signal power map, the insertion of the OPC system will still lead to an average Q-factor improvement of ∼1 dB for WDM channel arrangement.

The discrete-time compensated Kalman filter

NASA Technical Reports Server (NTRS)

Lee, W. H.; Athans, M.

1978-01-01

A suboptimal dynamic compensator to be used in conjunction with the ordinary discrete time Kalman filter was derived. The resultant compensated Kalman Filter has the property that steady state bias estimation errors, resulting from modelling errors, were eliminated.

20 CFR 10.736 - What are the time limits for filing a LEO claim?

Code of Federal Regulations, 2011 CFR

2011-04-01

... LABOR FEDERAL EMPLOYEES' COMPENSATION ACT CLAIMS FOR COMPENSATION UNDER THE FEDERAL EMPLOYEES' COMPENSATION ACT, AS AMENDED Special Provisions Non-Federal Law Enforcement Officers § 10.736 What are the time...

20 CFR 10.736 - What are the time limits for filing a LEO claim?

Code of Federal Regulations, 2013 CFR

2013-04-01

... LABOR FEDERAL EMPLOYEES' COMPENSATION ACT CLAIMS FOR COMPENSATION UNDER THE FEDERAL EMPLOYEES' COMPENSATION ACT, AS AMENDED Special Provisions Non-Federal Law Enforcement Officers § 10.736 What are the time...

Usefulness of Guided Breathing for Dose Rate-Regulated Tracking

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

Han-Oh, Sarah; Department of Radiation Oncology, University of Maryland Medical System, Baltimore, MD; Yi, Byong Yong

2009-02-01

Purpose: To evaluate the usefulness of guided breathing for dose rate-regulated tracking (DRRT), a new technique to compensate for intrafraction tumor motion. Methods and Materials: DRRT uses a preprogrammed multileaf collimator sequence that tracks the tumor motion derived from four-dimensional computed tomography and the corresponding breathing signals measured before treatment. Because the multileaf collimator speed can be controlled by adjusting the dose rate, the multileaf collimator positions are adjusted in real time during treatment by dose rate regulation, thereby maintaining synchrony with the tumor motion. DRRT treatment was simulated with free, audio-guided, and audiovisual-guided breathing signals acquired from 23 lungmore » cancer patients. The tracking error and duty cycle for each patient were determined as a function of the system time delay (range, 0-1.0 s). Results: The tracking error and duty cycle averaged for all 23 patients was 1.9 {+-} 0.8 mm and 92% {+-} 5%, 1.9 {+-} 1.0 mm and 93% {+-} 6%, and 1.8 {+-} 0.7 mm and 92% {+-} 6% for the free, audio-guided, and audiovisual-guided breathing, respectively, for a time delay of 0.35 s. The small differences in both the tracking error and the duty cycle with guided breathing were not statistically significant. Conclusion: DRRT by its nature adapts well to variations in breathing frequency, which is also the motivation for guided-breathing techniques. Because of this redundancy, guided breathing does not result in significant improvements for either the tracking error or the duty cycle when DRRT is used for real-time tumor tracking.« less

Development of an in vitro diaphragm motion reproduction system.

PubMed

Liao, Ai-Ho; Chuang, Ho-Chiao; Shih, Ming-Chih; Hsu, Hsiao-Yu; Tien, Der-Chi; Kuo, Chia-Chun; Jeng, Shiu-Chen; Chiou, Jeng-Fong

2017-07-01

This study developed an in vitro diaphragm motion reproduction system (IVDMRS) based on noninvasive and real-time ultrasound imaging to track the internal displacement of the human diaphragm and diaphragm phantoms with a respiration simulation system (RSS). An ultrasound image tracking algorithm (UITA) was used to retrieve the displacement data of the tracking target and reproduce the diaphragm motion in real time using a red laser to irradiate the diaphragm phantom in vitro. This study also recorded the respiration patterns in 10 volunteers. Both simulated and the respiration patterns in 10 human volunteers signals were input to the RSS for conducting experiments involving the reproduction of diaphragm motion in vitro using the IVDMRS. The reproduction accuracy of the IVDMRS was calculated and analyzed. The results indicate that the respiration frequency substantially affects the correlation between ultrasound and kV images, as well as the reproduction accuracy of the IVDMRS due to the system delay time (0.35s) of ultrasound imaging and signal transmission. The utilization of a phase lead compensator (PLC) reduced the error caused by this delay, thereby improving the reproduction accuracy of the IVDMRS by 14.09-46.98%. Applying the IVDMRS in clinical treatments will allow medical staff to monitor the target displacements in real time by observing the movement of the laser beam. If the target displacement moves outside the planning target volume (PTV), the treatment can be immediately stopped to ensure that healthy tissues do not receive high doses of radiation. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Neuromuscular mechanisms and neural strategies in the control of time-varying muscle contractions.

PubMed

Erimaki, Sophia; Agapaki, Orsalia M; Christakos, Constantinos N

2013-09-01

The organization of the neural input to motoneurons that underlies time-varying muscle force is assumed to depend on muscle transfer characteristics and neural strategies or control modes utilizing sensory signals. We jointly addressed these interlinked, but previously studied individually and partially, issues for sinusoidal (range 0.5-5.0 Hz) force-tracking contractions of a human finger muscle. Using spectral and correlation analyses of target signal, force signal, and motor unit (MU) discharges, we studied 1) patterns of such discharges, allowing inferences on the motoneuronal input; 2) transformation of MU population activity (EMG) into quasi-sinusoidal force; and 3) relation of force oscillation to target, carrying information on the input's organization. A broad view of force control mechanisms and strategies emerged. Specifically, synchronized MU and EMG modulations, reflecting a frequency-modulated motoneuronal input, accompanied the force variations. Gain and delay drops between EMG modulation and force oscillation, critical for the appropriate organization of this input, occurred with increasing target frequency. According to our analyses, gain compensation was achieved primarily through rhythmical activation/deactivation of higher-threshold MUs and secondarily through the adaptation of the input's strength expected during tracking tasks. However, the input's timing was not adapted to delay behaviors and seemed to depend on the control modes employed. Thus, for low-frequency targets, the force oscillation was highly coherent with, but led, a target, this timing error being compatible with predictive feedforward control partly based on the target's derivatives. In contrast, the force oscillation was weakly coherent, but in phase, with high-frequency targets, suggesting control mainly based on a target's rhythm.

Internal model control for industrial wireless plant using WirelessHART hardware-in-the-loop simulator.

PubMed

Tran, Chung Duc; Ibrahim, Rosdiazli; Asirvadam, Vijanth Sagayan; Saad, Nordin; Sabo Miya, Hassan

2018-04-01

The emergence of wireless technologies such as WirelessHART and ISA100 Wireless for deployment at industrial process plants has urged the need for research and development in wireless control. This is in view of the fact that the recent application is mainly in monitoring domain due to lack of confidence in control aspect. WirelessHART has an edge over its counterpart as it is based on the successful Wired HART protocol with over 30 million devices as of 2009. Recent works on control have primarily focused on maintaining the traditional PID control structure which is proven not adequate for the wireless environment. In contrast, Internal Model Control (IMC), a promising technique for delay compensation, disturbance rejection and setpoint tracking has not been investigated in the context of WirelessHART. Therefore, this paper discusses the control design using IMC approach with a focus on wireless processes. The simulation and experimental results using real-time WirelessHART hardware-in-the-loop simulator (WH-HILS) indicate that the proposed approach is more robust to delay variation of the network than the PID. Copyright © 2017. Published by Elsevier Ltd.

Application of encapsulated superabsorbent polymers in cementitious materials for stimulated autogenous healing

NASA Astrophysics Data System (ADS)

Pelto, Jani; Leivo, Markku; Gruyaert, Elke; Debbaut, Brenda; Snoeck, Didier; De Belie, Nele

2017-10-01

Superabsorbent polymers have shown potential for use in mortar and concrete as self-healing agents. The main drawback is, however, that these superabsorbent polymers also absorb mixing water during the preparation and casting of mortar or concrete, leading to a loss in workability. To avoid the absorption of mixing water, superabsorbent polymers were coated using a fluid bed spraying process. The barrier coating consisted of three successive coating layers: polyvinylbutyral as primer/wetting layer, cyclo-olefin copolymer as a barrier layer and a sol-gel derived zirconium-silicon oxide as an adhesion-promoting topcoat layer. The coated SAPs were characterized, and their swelling determined to quantify the delay in uptake of water and Ca(OH)2 solution. The last was considered as the most important, as the SAPs will finally be applied in mortar or concrete having a pore solution with high pH. The results showed that swelling could be delayed to a large extent, but for a short time. Results showed that the self-sealing efficiency of mortars was not affected by coating the SAPs. Moreover, due to the reduced uptake of mixing water, the strength reduction, noticed when uncoated SAPs were added to the mortar, could partly be compensated.

Robust master-slave synchronization for general uncertain delayed dynamical model based on adaptive control scheme.

PubMed

Wang, Tianbo; Zhou, Wuneng; Zhao, Shouwei; Yu, Weiqin

2014-03-01

In this paper, the robust exponential synchronization problem for a class of uncertain delayed master-slave dynamical system is investigated by using the adaptive control method. Different from some existing master-slave models, the considered master-slave system includes bounded unmodeled dynamics. In order to compensate the effect of unmodeled dynamics and effectively achieve synchronization, a novel adaptive controller with simple updated laws is proposed. Moreover, the results are given in terms of LMIs, which can be easily solved by LMI Toolbox in Matlab. A numerical example is given to illustrate the effectiveness of the method. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

Control of complex components with Smart Flexible Phased Arrays.

PubMed

Casula, O; Poidevin, C; Cattiaux, G; Dumas, Ph

2006-12-22

The inspection is mainly performed in contact with ultrasonic wedge transducers; However, the shape cannot fit the changing geometries of components (butt weld, nozzle, elbow). The variable thickness of the coupling layer, between the wedge and the local surface, leads to beam distortions and losses of sensitivity. Previous studies have shown that these two phenomena contribute to reduce the inspection performances leading to shadow area, split beam.... Flexible phased arrays have been developed to fit the complex profile and improve such controls. The radiating surface is composed with independent piezoelectric elements mechanically assembled and a profilometer, embedded in the transducer, measures the local distortion. The computed shape is used by an algorithm to compute in real-time the adapted delay laws compensating the distortions of 2D or 3D profiles. Those delay laws are transferred to the real-time UT acquisition system, which applies them to the piezoelectric elements. This self-adaptive process preserves, during the scanning, the features of the focused beam (orientation and focal depth) in the specimen. To validate the concept of the Smart Flexible Phased Array Transducer, prototypes have been integrated to detect flaws machined in mock-ups with realistic irregular 2D and 3D shapes. Inspections have been carried out on samples showing the enhancement performances of the "Smart Flexible Phased Array" and validating the mechanical and acoustical behaviors of these probes.

Does time off work after injury vary by jurisdiction? A comparative study of eight Australian workers' compensation systems

PubMed Central

Collie, Alex; Lane, Tyler J; Hassani-Mahmooei, Behrooz; Thompson, Jason; McLeod, Chris

2016-01-01

Objectives To determine whether the jurisdiction in which a work-related injury compensation claim is made is an independent predictor of duration of time off work following work injury, and if so, the magnitude of the effect. Setting Eight Australian state and territory workers' compensation systems, providing coverage for more than 90% of the Australian labour force. Administrative claims data from these systems were provided by government regulatory authorities for the study. Participants 95 976 Australian workers with workers' compensation claims accepted in 2010 and with at least 2 weeks of compensated time off work. Primary outcome measure Duration of time lost from work in weeks, censored at 104 weeks. Results After controlling for demographic, worker, injury and employer factors in a Cox regression model, significant differences in duration of time loss between state and territory of claim were observed. Compared with New South Wales, workers in Victoria, South Australia and Comcare had significantly longer durations of time off work and were more likely to be receiving income benefits at 104 weeks postinjury, while workers in Tasmania and Queensland had significantly shorter durations of time off work. Conclusions The jurisdiction in which an injured worker makes a compensation claim has a significant and independent impact on duration of time loss. Further research is necessary to identify specific compensation system policies and practices that promote timely and appropriate return to work and reduce duration of time off work. PMID:27150186

Information-Driven Blind Doppler Shift Estimation and Compensation Methods for Underwater Wireless Sensor Networks

DTIC Science & Technology

2015-08-24

SUPPLEMENTARY NOTES 12. DISTRIBUTION AVAILIBILITY STATEMENT 6. AUTHORS 7. PERFORMING ORGANIZATION NAMES AND ADDRESSES 15. SUBJECT TERMS b. ABSTRACT 2...network keeping constraints such as transmission rate, transmission delay, Signal-to-Interference and Noise Ratio (SINR) under consideration. Table...distances. It is advantageous to accomplish such transmission using sensors in a multi-hop relay form keeping constraints such as transmission rate

Feedback and feedforward adaptation to visuomotor delay during reaching and slicing movements.

PubMed

Botzer, Lior; Karniel, Amir

2013-07-01

It has been suggested that the brain and in particular the cerebellum and motor cortex adapt to represent the environment during reaching movements under various visuomotor perturbations. It is well known that significant delay is present in neural conductance and processing; however, the possible representation of delay and adaptation to delayed visual feedback has been largely overlooked. Here we investigated the control of reaching movements in human subjects during an imposed visuomotor delay in a virtual reality environment. In the first experiment, when visual feedback was unexpectedly delayed, the hand movement overshot the end-point target, indicating a vision-based feedback control. Over the ensuing trials, movements gradually adapted and became accurate. When the delay was removed unexpectedly, movements systematically undershot the target, demonstrating that adaptation occurred within the vision-based feedback control mechanism. In a second experiment designed to broaden our understanding of the underlying mechanisms, we revealed similar after-effects for rhythmic reversal (out-and-back) movements. We present a computational model accounting for these results based on two adapted forward models, each tuned for a specific modality delay (proprioception or vision), and a third feedforward controller. The computational model, along with the experimental results, refutes delay representation in a pure forward vision-based predictor and suggests that adaptation occurred in the forward vision-based predictor, and concurrently in the state-based feedforward controller. Understanding how the brain compensates for conductance and processing delays is essential for understanding certain impairments concerning these neural delays as well as for the development of brain-machine interfaces. © 2013 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Protecting Patients from an Unsafe System: The Etiology & Recovery of Intra-Operative Deviations in Care

PubMed Central

Hu, Yue-Yung; Arriaga, Alexander F.; Roth, Emilie M.; Peyre, Sarah E.; Corso, Katherine A.; Swanson, Richard S.; Osteen, Robert T.; Schmitt, Pamela; Bader, Angela M.; Zinner, Michael J.; Greenberg, Caprice C.

2012-01-01

Objective To understand the etiology and resolution of unanticipated events in the operating room (OR). Background The majority of surgical adverse events occur intra-operatively. The OR represents a complex, high-risk system. The influence of different human, team, and organizational/environmental factors on safety and performance is unknown. Methods We video-recorded and transcribed 10 high-acuity operations, representing 43.7 hours of patient care. Deviations, defined as delays and/or episodes of decreased patient safety, were identified by majority consensus of a multidisciplinary team. Factors that contributed to each event and/or mitigated its impact were determined and attributed to the patient, providers, or environment/organization. Results Thirty-three deviations (10 delays, 17 safety compromises, 6 both) occurred – with a mean of one every 79.4 minutes. These deviations were multifactorial (mean 3.1 factors). Problems with communication and organizational structure appeared repeatedly at the root of both types of deviations. Delays tended to be resolved with vigilance, communication, coordination, and cooperation, while mediation of safety compromises was most frequently accomplished with vigilance, leadership, communication, and/or coordination. The organization/environment was not found to play a direct role in compensation. Conclusions Unanticipated events are common in the OR. Deviations result from poor organizational/environmental design and suboptimal team dynamics, with caregivers compensating to avoid patient harm. While recognized in other high risk domains, such human resilience has not yet been described in surgery and has major implications for the design of safety interventions. PMID:22750753

Impact on access to medicines from TRIPS-Plus: a case study of Thai-US FTA.

PubMed

Kessomboon, Nusaraporn; Limpananont, Jiraporn; Kulsomboon, Vidhaya; Maleewong, Usawadee; Eksaengsri, Achara; Paothong, Prinya

2010-05-01

This study assessed the impact of the Thai-US Free Trade Agreement (FTA) on access to medicines in Thailand. We first interpreted the text of the sixth round of Thai-US negotiations in 2006 on intellectual property rights (IPR). The impact was estimated using a macroeconomic model of the impact of changes in IPR. The estimated impact is based on a comparison between the current IPR situation and the proposed changes to IPR. The FTA text involves the period of patent extension from the Trade-Related Aspects of Intellectual Property Rights Agreement (TRIPS Agreement). The provisions involve the period of patent extension, which have to do with compensation for delays in patent registration and/or drug registration, data exclusivity that would result in a delay in generic drug entry, and the enforcing role of the Thai Food and Drug Administration of patent linkages. As a worst case scenario for this single provision, a 10 year patent extension would be given to compensate for delays in patent registration and/or drug registration. The impact on access to medicine, in the year 2027, would be: 1) A 32% increase in the medicine price index, 2) spending on medicines would increase to approximately USD 11,191 million, (USD1 = THB 33.9 on September 2, 2009), and 3) the domestic industry could loss USD 3.3 million. These results suggest there would be a severe restriction on the access to medicines under the TRIPS-Plus proposal. IPR protection of pharmaceuticals per the TRIPS-Plus proposal should be excluded from FTA negotiations.

Study on Misalignment Angle Compensation during Scale Factor Matching for Two Pairs of Accelerometers in a Gravity Gradient Instrument.

PubMed

Huang, Xiangqing; Deng, Zhongguang; Xie, Yafei; Fan, Ji; Hu, Chenyuan; Tu, Liangcheng

2018-04-18

A method for automatic compensation of misalignment angles during matching the scale factors of two pairs of the accelerometers in developing the rotating accelerometer gravity gradient instrument (GGI) is proposed and demonstrated in this paper. The purpose of automatic scale factor matching of the four accelerometers in GGI is to suppress the common mode acceleration of the moving-based platforms. However, taking the full model equation of the accelerometer into consideration, the other two orthogonal axes which is the pendulous axis and the output axis, will also sense the common mode acceleration and reduce the suppression performance. The coefficients from the two axes to the output are δ O and δ P respectively, called the misalignment angles. The angle δ O , coupling with the acceleration along the pendulous axis perpendicular to the rotational plane, will not be modulated by the rotation and gives little contribution to the scale factors matching. On the other hand, because of coupling with the acceleration along the centripetal direction in the rotating plane, the angle δ P would produce a component with 90 degrees phase delay relative to the scale factor component. Hence, the δ P component coincides exactly with the sensitive direction of the orthogonal accelerometers. To improve the common mode acceleration rejection, the misalignment angle δ P is compensated by injecting a trimming current, which is proportional to the output of an orthogonal accelerometer, into the torque coil of the accelerometer during the scale factor matching. The experimental results show that the common linear acceleration suppression achieved three orders after the scale factors balance and five orders after the misalignment angles compensation, which is almost down to the noise level of the used accelerometers of 1~2 × 10 −7 g/√Hz (1 g ≈ 9.8 m/s²).

Impact of alignment to gravito-inertial force on motion sickness and cardiopulmonary variables.

PubMed

Mert, Agali; Bles, Willem

2011-07-01

In tilting trains partial alignment to the gravito-inertial force (GIF) in the curves seems to be the best tilt compensation to reduce the incidence of motion sickness. We investigated the effect of alignment to the GIF on the development of motion sickness during low-frequency horizontal motion. There were 12 healthy subjects who participated. The design was a three-period, single-blind, crossover trial, counterbalanced for order. Cardiopulmonary measurements, Misery SCores (MISC), and questionnaire data (Motion Sickness Susceptibility Questionnaire, Nijmegen Questionnaire for Hyperventilation) were obtained. The stimulus was a sinusoidal movement (0.176 Hz, 0.2 g peak acceleration) on the ESA-sled. The cabin was compensated for 0% (A-0), 50% (A-50), and 100% (A-100) to the GIF. Runs were 1 wk apart. The A-50 condition may delay the development of motion sickness. Based on the survival curves the possible effect seems temporary. However, MISC 2 early in the runs resulted in high positive and negative predictive values for dropout and survival during the runs. No synchronization of the respiratory frequency with the sled motion was observed. There was a significant (P = 0.002) drop in relative end-tidal CO2 levels. There seems to be a rationale for partially compensating to the GIF while trying to prevent motion sickness in tilting trains. Sitting comfort is just better than without compensation at all and Coriolis effects are not as nauseating as with complete tilt compensation. Also, a drop in end-tidal CO2 levels might be a sign of pulmonary compensation for the nauseating stimulus.

A study of the additional costs of dispensing workers' compensation prescriptions.

PubMed

Schafermeyer, Kenneth W

2007-03-01

Although there is a significant amount of additional work involved in dispensing workers' compensation prescriptions, these costs have not been quantified. A study of the additional costs to dispense a workers' compensation prescription is needed to measure actual costs and to help determine the reasonableness of reimbursement for prescriptions dispensed under workers' compensation programs. The purpose of this study was to determine the minimum additional time and costs required to dispense workers' compensation prescriptions in Texas. A convenience sample of 30 store-level pharmacy staff members involved in submitting and processing prescription claims for the Texas Mutual workers' compensation program were interviewed by telephone. Data collected to determine the additional costs of dispensing a workers' compensation prescription included (1) the amount of additional time and personnel costs required to dispense and process an average workers' compensation prescription claim, (2) the difference in time required for a new versus a refilled prescription, (3) overhead costs for processing workers' compensation prescription claims by experienced experts at a central processing facility, (4) carrying costs for workers' compensation accounts receivable, and (5) bad debts due to uncollectible workers' compensation claims. The median of the sample pharmacies' additional costs for dispensing a workers' compensation prescription was estimated to be at least $9.86 greater than for a cash prescription. This study shows that the estimated costs for workers' compensation prescriptions were significantly higher than for cash prescriptions. These costs are probably much more than most employers, workers' compensation payers, and pharmacy managers would expect. It is recommended that pharmacy managers should estimate their own costs and compare these costs to actual reimbursement when considering the reasonableness of workers' compensation prescriptions and whether to accept these prescriptions.

Health care professionals' attitudes towards evidence-based medicine in the workers' compensation setting: a cohort study.

PubMed

Elbers, Nieke A; Chase, Robin; Craig, Ashley; Guy, Lyn; Harris, Ian A; Middleton, James W; Nicholas, Michael K; Rebbeck, Trudy; Walsh, John; Willcock, Simon; Lockwood, Keri; Cameron, Ian D

2017-05-22

Problems may arise during the approval process of treatment after a compensable work injury, which include excess paperwork, delays in approving services, disputes, and allegations of over-servicing. This is perceived as undesirable for injured people, health care professionals and claims managers, and costly to the health care system, compensation system, workplaces and society. Introducing an Evidence Based Medicine (EBM) decision tool in the workers' compensation system could provide a partial solution, by reducing uncertainty about effective treatment. The aim of this study was to investigate attitudes of health care professionals (HCP) to the potential implementation of an EBM tool in the workers' compensation setting. The study has a mixed methods design. The quantitative study consisted of an online questionnaire asking about self-reported knowledge, attitudes and behaviour to EBM in general. The qualitative study consisted of interviews about an EBM tool being applied in the workers' compensation process. Participants were health care practitioners from different clinical specialties. They were recruited through the investigators' clinical networks and the workers' compensation government regulator's website. Participants completing the questionnaire (n = 231) indicated they were knowledgeable about the evidence-base in their field, but perceived some difficulties when applying EBM. General practitioners reported having the greatest obstacles to applying EBM. Participants who were interviewed (n = 15) perceived that an EBM tool in the workers' compensation setting could potentially have some advantages, such as reducing inappropriate treatment, or over-servicing, and providing guidance for clinicians. However, participants expressed substantial concerns that the EBM tool would not adequately reflect the impact of psychosocial factors on recovery. They also highlighted a lack of timeliness in decision making and proper assessment, particularly in pain management. Overall, HCP are supportive of EBM, but have strong concerns about implementation of EBM based decision making in the workers' compensation setting. The participants felt that an EBM tool should not be applied rigidly and should take into account clinical judgement and patient variability and preferences. In general, the treatment approval process in the workers' compensation insurance system is a sensitive area, in which the interaction between HCP and claims managers can be improved.

Relationship between stressfulness of claiming for injury compensation and long-term recovery: a prospective cohort study.

PubMed

Grant, Genevieve M; O'Donnell, Meaghan L; Spittal, Matthew J; Creamer, Mark; Studdert, David M

2014-04-01

Each year, millions of persons worldwide seek compensation for transport accident and workplace injuries. Previous research suggests that these claimants have worse long-term health outcomes than persons whose injuries fall outside compensation schemes. However, existing studies have substantial methodological weaknesses and have not identified which aspects of the claiming experience may drive these effects. To determine aspects of claims processes that claimants to transport accident and workers' compensation schemes find stressful and whether such stressful experiences are associated with poorer long-term recovery. Prospective cohort study of a random sample of 1010 patients hospitalized in 3 Australian states for injuries from 2004 through 2006. At 6-year follow-up, we interviewed 332 participants who had claimed compensation from transport accident and workers' compensation schemes ("claimants") to determine which aspects of the claiming experience they found stressful. We used multivariable regression analysis to test for associations between compensation-related stress and health status at 6 years, adjusting for baseline determinants of long-term health status and predisposition to stressful experiences (via propensity scores). Disability, quality of life, anxiety, and depression. Among claimants, 33.9% reported high levels of stress associated with understanding what they needed to do for their claim; 30.4%, with claim delays; 26.9%, with the number of medical assessments; and 26.1%, with the amount of compensation they received. Six years after their injury, claimants who reported high levels of stress had significantly higher levels of disability (+6.94 points, World Health Organization Disability Assessment Schedule sum score), anxiety and depression (+1.89 points and +2.61 points, respectively, Hospital Anxiety and Depression Scale), and lower quality of life (-0.73 points, World Health Organization Quality of Life instrument, overall item), compared with other claimants. Adjusting for claimants' vulnerability to stress attenuated the strength of these associations, but most remained strong and statistically significant. Many claimants experience high levels of stress from engaging with injury compensation schemes, and this experience is positively correlated with poor long-term recovery. Intervening early to boost resilience among those at risk of stressful claims experiences and redesigning compensation processes to reduce their stressfulness may improve recovery and save money.

Evolution of the heteroharmonic strategy for target-range computation in the echolocation of Mormoopidae

PubMed Central

Mora, Emanuel C.; Macías, Silvio; Hechavarría, Julio; Vater, Marianne; Kössl, Manfred

2013-01-01

Echolocating bats use the time elapsed from biosonar pulse emission to the arrival of echo (defined as echo-delay) to assess target-distance. Target-distance is represented in the brain by delay-tuned neurons that are classified as either “heteroharmonic” or “homoharmormic.” Heteroharmonic neurons respond more strongly to pulse-echo pairs in which the timing of the pulse is given by the fundamental biosonar harmonic while the timing of echoes is provided by one (or several) of the higher order harmonics. On the other hand, homoharmonic neurons are tuned to the echo delay between similar harmonics in the emitted pulse and echo. It is generally accepted that heteroharmonic computations are advantageous over homoharmonic computations; i.e., heteroharmonic neurons receive information from call and echo in different frequency-bands which helps to avoid jamming between pulse and echo signals. Heteroharmonic neurons have been found in two species of the family Mormoopidae (Pteronotus parnellii and Pteronotus quadridens) and in Rhinolophus rouxi. Recently, it was proposed that heteroharmonic target-range computations are a primitive feature of the genus Pteronotus that was preserved in the evolution of the genus. Here, we review recent findings on the evolution of echolocation in Mormoopidae, and try to link those findings to the evolution of the heteroharmonic computation strategy (HtHCS). We stress the hypothesis that the ability to perform heteroharmonic computations evolved separately from the ability of using long constant-frequency echolocation calls, high duty cycle echolocation, and Doppler Shift Compensation. Also, we present the idea that heteroharmonic computations might have been of advantage for categorizing prey size, hunting eared insects, and living in large conspecific colonies. We make five testable predictions that might help future investigations to clarify the evolution of the heteroharmonic echolocation in Mormoopidae and other families. PMID:23781209

Plug-in module acceleration feedback control for fast steering mirror-based beam stabilization systems

NASA Astrophysics Data System (ADS)

Deng, Chao; Ren, Wei; Mao, Yao; Ren, Ge

2017-08-01

A plug-in module acceleration feedback control (Plug-In AFC) strategy based on the disturbance observer (DOB) principle is proposed for charge-coupled device (CCD)-based fast steering mirror (FSM) stabilization systems. In classical FSM tracking systems, dual-loop control (DLC), including velocity feedback and position feedback, is usually utilized to enhance the closed-loop performance. Due to the mechanical resonance of the system and CCD time delay, the closed-loop bandwidth is severely restricted. To solve this problem, cascade acceleration feedback control (AFC), which is a kind of high-precision robust control method, is introduced to strengthen the disturbance rejection property. However, in practical applications, it is difficult to realize an integral algorithm in an acceleration controller to compensate for the quadratic differential contained in the FSM acceleration model, resulting in a challenging controller design and a limited improvement. To optimize the acceleration feedback framework in the FSM system, different from the cascade AFC, the accelerometers are used to construct DOB to compensate for the platform vibrations directly. The acceleration nested loop can be plugged into the velocity loop without changing the system stability, and the controller design is quite simple. A series of comparative experimental results demonstrate that the disturbance rejection property of the CCD-based FSM can be effectively improved by the proposed approach.

Control of a HexaPOD treatment couch for robot-assisted radiotherapy.

PubMed

Hermann, Christian; Ma, Lei; Wilbert, Jürgen; Baier, Kurt; Schilling, Klaus

2012-10-01

Moving tumors, for example in the vicinity of the lungs, pose a challenging problem in radiotherapy, as healthy tissue should not be irradiated. Apart from gating approaches, one standard method is to irradiate the complete volume within which a tumor moves plus a safety margin containing a considerable volume of healthy tissue. This work deals with a system for tumor motion compensation using the HexaPOD® robotic treatment couch (Medical Intelligence GmbH, Schwabmünchen, Germany). The HexaPOD, carrying the patient during treatment, is instructed to perform translational movements such that the tumor motion, from the beams-eye view of the linear accelerator, is eliminated. The dynamics of the HexaPOD are characterized by time delays, saturations, and other non-linearities that make the design of control a challenging task. The focus of this work lies on two control methods for the HexaPOD that can be used for reference tracking. The first method uses a model predictive controller based on a model gained through system identification methods, and the second method uses a position control scheme useful for reference tracking. We compared the tracking performance of both methods in various experiments with real hardware using ideal reference trajectories, prerecorded patient trajectories, and human volunteers whose breathing motion was compensated by the system.

Satellite teleradiology test bed for digital mammography

NASA Astrophysics Data System (ADS)

Barnett, Bruce G.; Dudding, Kathryn E.; Abdel-Malek, Aiman A.; Mitchell, Robert J.

1996-05-01

Teleradiology offers significant improvement in efficiency and patient compliance over current practices in traditional film/screen-based diagnosis. The increasing number of women who need to be screened for breast cancer, including those in remote rural regions, make the advantages of teleradiology especially attractive for digital mammography. At the same time, the size and resolution of digital mammograms are among the most challenging to support in a cost effective teleradiology system. This paper will describe a teleradiology architecture developed for use with digital mammography by GE Corporate Research and Development in collaboration with Massachusetts General Hospital under National Cancer Institute (NCI/NIH) grant number R01 CA60246-01. The testbed architecture is based on the Digital Imaging and Communications in Medicine (DICOM) standard, created by the American College of Radiology and National Electrical Manufacturers Association. The testbed uses several Sun workstations running SunOS, which emulate a rural examination facility connected to a central diagnostic facility, and uses a TCP-based DICOM application to transfer images over a satellite link. Network performance depends on the product of the bandwidth times the round- trip time. A satellite link has a round trip of 513 milliseconds, making the bandwidth-delay a significant problem. This type of high bandwidth, high delay network is called a Long Fat Network, or LFN. The goal of this project was to quantify the performance of the satellite link, and evaluate the effectiveness of TCP over an LFN. Four workstations have Sun's HSI/S (High Speed Interface) option. Two are connected by a cable, and two are connected through a satellite link. Both interfaces have the same T1 bandwidth (1.544 Megabits per second). The only difference was the round trip time. Even with large window buffers, the time to transfer a file over the satellite link was significantly longer, due to the bandwidth-delay. To compensate for this, TCP extensions for LFNs such as the Window Scaling Option (described in RFC1323) were necessary to optimize the use of the link. A high level analysis of throughput, with and without these TCP extensions, will be discussed. Recommendations will be made as to the critical areas for future work.

Apparatus and method for compensating for clock drift in downhole drilling components

DOEpatents

Hall, David R [Provo, UT; Pixton, David S [Lehi, UT; Johnson, Monte L [Orem, UT; Bartholomew, David B [Springville, UT; Hall, Jr., H. Tracy

2007-08-07

A precise downhole clock that compensates for drift includes a prescaler configured to receive electrical pulses from an oscillator. The prescaler is configured to output a series of clock pulses. The prescaler outputs each clock pulse after counting a preloaded number of electrical pulses from the oscillator. The prescaler is operably connected to a compensator module for adjusting the number loaded into the prescaler. By adjusting the number that is loaded into the prescaler, the timing may be advanced or retarded to more accurately synchronize the clock pulses with a reference time source. The compensator module is controlled by a counter-based trigger module configured to trigger the compensator module to load a value into the prescaler. Finally, a time-base logic module is configured to calculate the drift of the downhole clock by comparing the time of the downhole clock with a reference time source.

Complete PMD compensation in 40-Gbit/s optical transmission system

NASA Astrophysics Data System (ADS)

Luo, Rui; Li, Tangjun; Wang, Muguang; Cui, Jie; Jian, Shuisheng

2004-04-01

In this paper, we successfully demonstrated automatic PMD compensation in 40Gbit/s NRZ transmission for the first time. Using a PMD monitor of 20GHz intensity extracted from the receive 40Gbit/s NRZ base band signal, we accomplished the feedback control of an optical PMD compensator consisting of a polarization controller and a polarization-maintaining fiber. And we report the statistical assessment of an adaptive optical PMD compensator at 40Gbit/s. The mitigator, described in, is experimentally tested in many PMD conditions (not limited to first order) covering Maxwellian-like PMD statistics. Experimental results, including bit error rate measurements, are successfully compared with theory, hereby demonstrating the compensator efficiency at 40Gbit/s. Furthermore, this letter introduces a two-stage PMD compensator. Our experimental results shows that, the compensators based on the two-stages of compensator can be used to PMD compensation in a 40Gbit/s OTDM system with 60 km high PMD fiber. The first-order PMD was max.274ps before PMD compensation. It was smaller than 7ps after PMD compensation. At the same time, the tunable FBG have a function of dispersion compensation.

Signal Construction-Based Dispersion Compensation of Lamb Waves Considering Signal Waveform and Amplitude Spectrum Preservation

PubMed Central

Cai, Jian; Yuan, Shenfang; Wang, Tongguang

2016-01-01

The results of Lamb wave identification for the aerospace structures could be easily affected by the nonlinear-dispersion characteristics. In this paper, dispersion compensation of Lamb waves is of particular concern. Compared with the similar research works on the traditional signal domain transform methods, this study is based on signal construction from the viewpoint of nonlinear wavenumber linearization. Two compensation methods of linearly-dispersive signal construction (LDSC) and non-dispersive signal construction (NDSC) are proposed. Furthermore, to improve the compensation effect, the influence of the signal construction process on the other crucial signal properties, including the signal waveform and amplitude spectrum, is considered during the investigation. The linear-dispersion and non-dispersion effects are firstly analyzed. Then, after the basic signal construction principle is explored, the numerical realization of LDSC and NDSC is discussed, in which the signal waveform and amplitude spectrum preservation is especially regarded. Subsequently, associated with the delay-and-sum algorithm, LDSC or NDSC is employed for high spatial resolution damage imaging, so that the adjacent multi-damage or quantitative imaging capacity of Lamb waves can be strengthened. To verify the proposed signal construction and damage imaging methods, the experimental and numerical validation is finally arranged on the aluminum plates. PMID:28772366

Signal Construction-Based Dispersion Compensation of Lamb Waves Considering Signal Waveform and Amplitude Spectrum Preservation.

PubMed

Cai, Jian; Yuan, Shenfang; Wang, Tongguang

2016-12-23

The results of Lamb wave identification for the aerospace structures could be easily affected by the nonlinear-dispersion characteristics. In this paper, dispersion compensation of Lamb waves is of particular concern. Compared with the similar research works on the traditional signal domain transform methods, this study is based on signal construction from the viewpoint of nonlinear wavenumber linearization. Two compensation methods of linearly-dispersive signal construction (LDSC) and non-dispersive signal construction (NDSC) are proposed. Furthermore, to improve the compensation effect, the influence of the signal construction process on the other crucial signal properties, including the signal waveform and amplitude spectrum, is considered during the investigation. The linear-dispersion and non-dispersion effects are firstly analyzed. Then, after the basic signal construction principle is explored, the numerical realization of LDSC and NDSC is discussed, in which the signal waveform and amplitude spectrum preservation is especially regarded. Subsequently, associated with the delay-and-sum algorithm, LDSC or NDSC is employed for high spatial resolution damage imaging, so that the adjacent multi-damage or quantitative imaging capacity of Lamb waves can be strengthened. To verify the proposed signal construction and damage imaging methods, the experimental and numerical validation is finally arranged on the aluminum plates.

Tulip-form variable-curvature mirrors: interferometry and field compensation

NASA Astrophysics Data System (ADS)

Lemaitre, Gerard R.; Mazzanti, Silvio; Ferrari, Marc

1998-07-01

Active Optics methods are now capable to provide variable curvature mirrors (VCMs) having controlled sags in the focal range from f/(infinity) to f/2.5. Those development have been carried out by the authors for the optical path equalizer dedicated to each Mersenne focus of the VLTI. The basic principle is to use VCMs as cat's eye mirrors in each delay line in order to achieve field compensations at the recombined Mersenne focii. During the VLTI development phase, cycloid form VCMs controlled by air pressure have been performed with a 10(superscript -4) mirror sag resolution. The cycloid form has been selected for the VLTi delay lines. However, other analytical solutions from circular plates elasticity theory have been found. Two thickness distributions lead to tulip form VCMs controlled by a central force. One of them, using a lineic reaction at the edge is the object of this paper. Active optics design, construction features, test and experimental He-Ne interferograms obtained with 16mm boundary aperture and 10mm clear aperture are presented. The mean aspect-ratio of the tulip from VCM is d/t(subscript 0.5) approximately equals 60, providing a focal zoom range from f/(infinity) to f/2.5. The experiment is carried out form f/(infinity) to f/5.

Comparing plant and fungal gravitropism using imitational models based on reiterative computation

NASA Astrophysics Data System (ADS)

Moore, David; Stočkus, Alvidas

Mathematical models which imitate plant gravitropic responses were used to compare plant and fungal gravitropism with kinetic data from the agarics Coprinus cinereus and Flammulina velutipes. Similarities were: bending depends on differential growth; growth of the organ is most intensive just behind the apex; gravitropisms exhibit a substantial time delay. Differences were: the agaric stem apex always returns to the vertical (some plant organs show stable plagiogravitropic growth); curvature compensation occurred in C. cinereus; C. cinereus stems rarely overshot or oscillated around the vertical although data for F. velutipes showed a single overshoot and oscillation. The work focused attention on the need for data on detection-level thresholds, angle-response and acceleration-response relationships in fungi, and the need for detailed observations of gravitropism kinetics in a larger number and wider range of fungi.

MIT research in telerobotics

NASA Technical Reports Server (NTRS)

Sheridan, T. B.

1987-01-01

Ongoing MIT research in telerobotics (vehicles capable of some autonomous sensing and manipulating, having some remote supervisory control by people) and teleoperation (vehicles for sensing and manipulating which are fully controlled remotely by people) is discussed. The current efforts mix human and artificial intelligence/control. The idea of adjustable impedance at either end of pure master-slave teleoperation, and simultaneous coordinated control of teleoperator/telerobotic systems which have more than six degrees of freedom (e.g., a combined vehicle and arm, each with five or six DOF) are discussed. A new cable-controlled parallel link arm which offers many advantages over conventional arms for space is briefly described. Predictor displays to compensate for time delay in teleoperator loops, the use of state estimation to help human control decisions in space, and ongoing research in supervisory command language are covered. Finally, efforts to build a human flyable real-time dynamic computer-graphic telerobot simulator are described. These projects represent most, but not all, of the telerobotics research in our laboratory, supported by JPL, NASA Ames and NOAA.

Reactive power compensating system

DOEpatents

Williams, Timothy J.; El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.

1987-01-01

The reactive power of an induction machine is compensated by providing fixed capacitors on each phase line for the minimum compensation required, sensing the current on one line at the time its voltage crosses zero to determine the actual compensation required for each phase, and selecting switched capacitors on each line to provide the balance of the compensation required.

Early return to work in workers' compensation patients after arthroscopic full-thickness rotator cuff repair.

PubMed

Bhatia, Sanjeev; Piasecki, Dana P; Nho, Shane Jay; Romeo, Anthony A; Cole, Brian J; Nicholson, Gregory P; Boniquit, Nicole; Verma, Nikhil N

2010-08-01

The purpose of this study was to investigate the ability of patients to return to their preoperative work level and to identify functional prognostic factors in a group of Workers' Compensation (WC) patients after arthroscopic repair of full-thickness rotator cuff tears at a minimum follow-up of 1 year. Seventy-eight consecutive WC patients underwent arthroscopic rotator cuff repair (ARCR) and were retrospectively reviewed. Potential predictors of occupational outcomes were recorded. The primary outcomes included work level at the time of discharge, time to maximum medical improvement (MMI), and failures requiring revision rotator cuff repair. Secondary outcomes including physical examination and subjective scoring scales were also recorded. Overall, 88.5% of patients (n = 69) returned to their preoperative level of work at a mean time to MMI of 7.6 +/- 2.6 months. Of the WC patients, 55 (70.5%) were followed up for purposes of assessing shoulder function, with a mean follow-up of 33.6 +/- 13.9 months. The mean American Shoulder and Elbow Surgeons score at this time was 82.3 +/- 20.9, and the mean score on a visual analog scale was 1.7 +/- 2.3. An association was found between patients who underwent ARCR with open biceps tenodesis and delay in MMI (P = .01). WC patients undergoing ARCR may expect a high likelihood of return to full duty at a mean time to MMI of 7.6 months. At the time of follow-up, patients reported good outcomes using validated scoring scales, but subjective outcomes remained inferior to non-WC patients based on historical controls. Alcohol use was the only prognostic factor to show a significant association with return to restricted-duty employment and repair failure. Level IV, therapeutic case series. 2010 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Real-time implementing wavefront reconstruction for adaptive optics

NASA Astrophysics Data System (ADS)

Wang, Caixia; Li, Mei; Wang, Chunhong; Zhou, Luchun; Jiang, Wenhan

2004-12-01

The capability of real time wave-front reconstruction is important for an adaptive optics (AO) system. The bandwidth of system and the real-time processing ability of the wave-front processor is mainly affected by the speed of calculation. The system requires enough number of subapertures and high sampling frequency to compensate atmospheric turbulence. The number of reconstruction operation is increased accordingly. Since the performance of AO system improves with the decrease of calculation latency, it is necessary to study how to increase the speed of wavefront reconstruction. There are two methods to improve the real time of the reconstruction. One is to convert the wavefront reconstruction matrix, such as by wavelet or FFT. The other is enhancing the performance of the processing element. Analysis shows that the latency cutting is performed with the cost of reconstruction precision by the former method. In this article, the latter method is adopted. From the characteristic of the wavefront reconstruction algorithm, a systolic array by FPGA is properly designed to implement real-time wavefront reconstruction. The system delay is reduced greatly by the utilization of pipeline and parallel processing. The minimum latency of reconstruction is the reconstruction calculation of one subaperture.

A Real-Time Greedy-Index Dispatching Policy for using PEVs to Provide Frequency Regulation Service

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

Ke, Xinda; Wu, Di; Lu, Ning

This article presents a real-time greedy-index dispatching policy (GIDP) for using plug-in electric vehicles (PEVs) to provide frequency regulation services. A new service cost allocation mechanism is proposed to award PEVs based on the amount of service they provided, while considering compensations for delayed-charging and reduction of battery lifetime due to participation of the service. The GIDP transforms the optimal dispatch problem from a high-dimensional space into a one-dimensional space while preserving the solution optimality. When solving the transformed problem in real-time, the global optimality of the GIDP solution can be guaranteed by mathematically proved “indexability”. Because the GIDP indexmore » can be calculated upon the PEV’s arrival and used for the entire decision making process till its departure, the computational burden is minimized and the complexity of the aggregator dispatch process is significantly reduced. Finally, simulation results are used to evaluate the proposed GIDP, and to demonstrate the potential profitability from providing frequency regulation service by using PEVs.« less

Minimization of betatron oscillations of electron beam injected into a time-varying lattice via extremum seeking

DOE PAGES

Scheinker, Alexander; Huang, Xiaobiao; Wu, Juhao

2017-02-20

Here, we report on a beam-based experiment performed at the SPEAR3 storage ring of the Stanford Synchrotron Radiation Lightsource at the SLAC National Accelerator Laboratory, in which a model-independent extremum-seeking optimization algorithm was utilized to minimize betatron oscillations in the presence of a time-varying kicker magnetic field, by automatically tuning the pulsewidth, voltage, and delay of two other kicker magnets, and the current of two skew quadrupole magnets, simultaneously, in order to optimize injection kick matching. Adaptive tuning was performed on eight parameters simultaneously. The scheme was able to continuously maintain the match of a five-magnet lattice while the fieldmore » strength of a kicker magnet was continuously varied at a rate much higher (±6% sinusoidal voltage change over 1.5 h) than typically experienced in operation. Lastly, the ability to quickly tune or compensate for time variation of coupled components, as demonstrated here, is very important for the more general, more difficult problem of global accelerator tuning to quickly switch between various experimental setups.« less

A Real-Time Greedy-Index Dispatching Policy for using PEVs to Provide Frequency Regulation Service

DOE PAGES

Ke, Xinda; Wu, Di; Lu, Ning

2017-09-18

This article presents a real-time greedy-index dispatching policy (GIDP) for using plug-in electric vehicles (PEVs) to provide frequency regulation services. A new service cost allocation mechanism is proposed to award PEVs based on the amount of service they provided, while considering compensations for delayed-charging and reduction of battery lifetime due to participation of the service. The GIDP transforms the optimal dispatch problem from a high-dimensional space into a one-dimensional space while preserving the solution optimality. When solving the transformed problem in real-time, the global optimality of the GIDP solution can be guaranteed by mathematically proved “indexability”. Because the GIDP indexmore » can be calculated upon the PEV’s arrival and used for the entire decision making process till its departure, the computational burden is minimized and the complexity of the aggregator dispatch process is significantly reduced. Finally, simulation results are used to evaluate the proposed GIDP, and to demonstrate the potential profitability from providing frequency regulation service by using PEVs.« less

A Systematic Review for Functional Neuroimaging Studies of Cognitive Reserve Across the Cognitive Aging Spectrum.

PubMed

Anthony, Mia; Lin, Feng

2017-12-13

Cognitive reserve has been proposed to explain the discrepancy between clinical symptoms and the effects of aging or Alzheimer's pathology. Functional magnetic resonance imaging (fMRI) may help elucidate how neural reserve and compensation delay cognitive decline and identify brain regions associated with cognitive reserve. This systematic review evaluated neural correlates of cognitive reserve via fMRI (resting-state and task-related) studies across the cognitive aging spectrum (i.e., normal cognition, mild cognitive impairment, and Alzheimer's disease). This review examined published articles up to March 2017. There were 13 cross-sectional observational studies that met the inclusion criteria, including relevance to cognitive reserve, subjects 60 years or older with normal cognition, mild cognitive impairment, and/or Alzheimer's disease, at least one quantitative measure of cognitive reserve, and fMRI as the imaging modality. Quality assessment of included studies was conducted using the Newcastle-Ottawa Scale adapted for cross-sectional studies. Across the cognitive aging spectrum, medial temporal regions and an anterior or posterior cingulate cortex-seeded default mode network were associated with neural reserve. Frontal regions and the dorsal attentional network were related to neural compensation. Compared to neural reserve, neural compensation was more common in mild cognitive impairment and Alzheimer's disease. Neural reserve and compensation both support cognitive reserve, with compensation more common in later stages of the cognitive aging spectrum. Longitudinal and intervention studies are needed to investigate changes between neural reserve and compensation during the transition between clinical stages, and to explore the causal relationship between cognitive reserve and potential neural substrates. © The Author(s) 2017. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Novel Estimation of Pilot Performance Characteristics

NASA Technical Reports Server (NTRS)

Bachelder, Edward N.; Aponso, Bimal

2017-01-01

Two mechanisms internal to the pilot that affect performance during a tracking task are: 1) Pilot equalization (i.e. lead/lag); and 2) Pilot gain (i.e. sensitivity to the error signal). For some applications McRuer's Crossover Model can be used to anticipate what equalization will be employed to control a vehicle's dynamics. McRuer also established approximate time delays associated with different types of equalization - the more cognitive processing that is required due to equalization difficulty, the larger the time delay. However, the Crossover Model does not predict what the pilot gain will be. A nonlinear pilot control technique, observed and coined by the authors as 'amplitude clipping', is shown to improve stability, performance, and reduce workload when employed with vehicle dynamics that require high lead compensation by the pilot. Combining linear and nonlinear methods a novel approach is used to measure the pilot control parameters when amplitude clipping is present, allowing precise measurement in real time of key pilot control parameters. Based on the results of an experiment which was designed to probe workload primary drivers, a method is developed that estimates pilot spare capacity from readily observable measures and is tested for generality using multi-axis flight data. This paper documents the initial steps to developing a novel, simple objective metric for assessing pilot workload and its variation over time across a wide variety of tasks. Additionally, it offers a tangible, easily implementable methodology for anticipating a pilot's operating parameters and workload, and an effective design tool. The model shows promise in being able to precisely predict the actual pilot settings and workload, and observed tolerance of pilot parameter variation over the course of operation. Finally, an approach is proposed for generating Cooper-Harper ratings based on the workload and parameter estimation methodology.

Improving the Accuracy of a Heliocentric Potential (HCP) Prediction Model for the Aviation Radiation Dose

NASA Astrophysics Data System (ADS)

Hwang, Junga; Yoon, Kyoung-Won; Jo, Gyeongbok; Noh, Sung-Jun

2016-12-01

The space radiation dose over air routes including polar routes should be carefully considered, especially when space weather shows sudden disturbances such as coronal mass ejections (CMEs), flares, and accompanying solar energetic particle events. We recently established a heliocentric potential (HCP) prediction model for real-time operation of the CARI-6 and CARI-6M programs. Specifically, the HCP value is used as a critical input value in the CARI-6/6M programs, which estimate the aviation route dose based on the effective dose rate. The CARI-6/6M approach is the most widely used technique, and the programs can be obtained from the U.S. Federal Aviation Administration (FAA). However, HCP values are given at a one month delay on the FAA official webpage, which makes it difficult to obtain real-time information on the aviation route dose. In order to overcome this critical limitation regarding the time delay for space weather customers, we developed a HCP prediction model based on sunspot number variations (Hwang et al. 2015). In this paper, we focus on improvements to our HCP prediction model and update it with neutron monitoring data. We found that the most accurate method to derive the HCP value involves (1) real-time daily sunspot assessments, (2) predictions of the daily HCP by our prediction algorithm, and (3) calculations of the resultant daily effective dose rate. Additionally, we also derived the HCP prediction algorithm in this paper by using ground neutron counts. With the compensation stemming from the use of ground neutron count data, the newly developed HCP prediction model was improved.

Understanding changes over time in workers' compensation claim rates using time series analytical techniques.

PubMed

Moore, Ian C; Tompa, Emile

2011-11-01

The objective of this study is to better understand the inter-temporal variation in workers' compensation claim rates using time series analytical techniques not commonly used in the occupational health and safety literature. We focus specifically on the role of unemployment rates in explaining claim rate variations. The major components of workers' compensation claim rates are decomposed using data from a Canadian workers' compensation authority for the period 1991-2007. Several techniques are used to undertake the decomposition and assess key factors driving rates: (i) the multitaper spectral estimator, (ii) the harmonic F test, (iii) the Kalman smoother and (iv) ordinary least squares. The largest component of the periodic behaviour in workers' compensation claim rates is seasonal variation. Business cycle fluctuations in workers' compensation claim rates move inversely to unemployment rates. The analysis suggests that workers' compensation claim rates between 1991 and 2008 were driven by (in order of magnitude) a strong negative long term growth trend, periodic seasonal trends and business cycle fluctuations proxied by the Ontario unemployment rate.

Simulation of ultrasonic focus aberration and correction through human tissue.

PubMed

Tabei, Makoto; Mast, T Douglas; Waag, Robert C

2003-02-01

Ultrasonic focusing in two dimensions has been investigated by calculating the propagation of ultrasonic pulses through cross-sectional models of human abdominal wall and breast. Propagation calculations used a full-wave k-space method that accounts for spatial variations in density, sound speed, and frequency-dependent absorption and includes perfectly matched layer absorbing boundary conditions. To obtain a distorted receive wavefront, propagation from a point source through the tissue path was computed. Receive focusing used an angular spectrum method. Transmit focusing was accomplished by propagating a pressure wavefront from a virtual array through the tissue path. As well as uncompensated focusing, focusing that employed time-shift compensation and time-shift compensation after backpropagation was investigated in both transmit and receive and time reversal was investigated for transmit focusing in addition. The results indicate, consistent with measurements, that breast causes greater focus degradation than abdominal wall. The investigated compensation methods corrected the receive focus better than the transmit focus. Time-shift compensation after backpropagation improved the focus from that obtained using time-shift compensation alone but the improvement was less in transmit focusing than in receive focusing. Transmit focusing by time reversal resulted in lower sidelobes but larger mainlobes than the other investigated transmit focus compensation methods.

Comparisons of lesion detectability in ultrasound images acquired using time-shift compensation and spatial compounding.

PubMed

Lacefield, James C; Pilkington, Wayne C; Waag, Robert C

2004-12-01

The effects of aberration, time-shift compensation, and spatial compounding on the discrimination of positive-contrast lesions in ultrasound b-scan images are investigated using a two-dimensional (2-D) array system and tissue-mimicking phantoms. Images were acquired within an 8.8 x 12-mm2 field of view centered on one of four statistically similar 4-mm diameter spherical lesions. Each lesion was imaged in four planes offset by successive 45 degree rotations about the central scan line. Images of the lesions were acquired using conventional geometric focusing through a water path, geometric focusing through a 35-mm thick distributed aberration phantom, and time-shift compensated transmit and receive focusing through the aberration phantom. The views of each lesion were averaged to form sets of water path, aberrated, and time-shift compensated 4:1 compound images and 16:1 compound images. The contrast ratio and detectability index of each image were computed to assess lesion differentiation. In the presence of aberration representative of breast or abdominal wall tissue, time-shift compensation provided statistically significant improvements of contrast ratio but did not consistently affect the detectability index, and spatial compounding significantly increased the detectability index but did not alter the contrast ratio. Time-shift compensation and spatial compounding thus provide complementary benefits to lesion detection.

Imaging of the Galapagos Plume Using a Network of Mermaids

NASA Astrophysics Data System (ADS)

Nolet, G.; Hello, Y.; Chen, J.; Pazmino, A.; Van der Lee, S.; Bonnieux, S.; Deschamps, A.; Regnier, M. M.; Font, Y.; Simons, F.

2017-12-01

A network of nine submarine seismographs (Mermaids) has been floating freely from 2014 to 2016 around the Galapagos islands, with the aim to enhance the resolving power of deep tomographic images of the mantle plume in this region (see poster by Hello et al. in session S002 for technical details).Analysing a total of 1329 triggered signals transmitted by satellite, we were able to pick the onset times of 434 P waves, 95 PKP and 26 pP arrivals. For the events recorded by at least one Mermaid, these data were complemented with hand-picked onsets from stations on the islands, or on the continent nearby, for a total of 3892 onset times of rays crossing the mantle beneath the Galapagos, many of them with a small standard error estimated at 0.3s. These data are used in a local inversion using ray theory, as is appropriate for onset times. To compensate for delays acquired in the rest of the Earth, the local model is embedded in a global inversion of P delays from the EHB data set most recently published by the ISC for 2000-2003. By selecting a strongly redundant subset of more than one million EHB P wave arrivals, we determined an objective standard error for these delays of 0.51s using the method of Voronin et al. (GJI, 2014). Using a combination of (strong) smoothing and (weak) damping, we force the tomographic model to fit the data close to the level of the estimated standard errors.Preliminary images obtained at the time of writing of this abstract indicate a deep reaching plume that is stronger in the lower mantle than near the surface.Most importantly, the experiment shows how even a limited number of Mermaids can contribute a significant gain in resolution. This is a direct consequence of the fact that they float with abyssal currents, thus avoiding redundancy in raypaths even for aftershocks.The final tomographic images and an analysis of their significance will be subject of the presentation.

Age, sex, and the changing disability burden of compensated work-related musculoskeletal disorders in Canada and Australia.

PubMed

Macpherson, Robert A; Lane, Tyler J; Collie, Alex; McLeod, Christopher B

2018-06-19

The objectives of this study were (1) to identify age and sex trends in the disability burden of compensated work-related musculoskeletal disorders (MSDs) in Canada and Australia; and (2) to demonstrate a means of comparing workers' compensation data internationally. All non-fatal, work-related MSD claims with at least one day of compensated time-loss were extracted for workers aged 15-80 during a 10-year period (2004-2013) using workers' compensation data from five Canadian and eight Australian jurisdictions. Disability burden was calculated for both countries by sex, age group, and injury classification, using cumulative compensated time-loss payments of up to two years post-injury. A total of 1.2 million MSD claims were compensated for time-loss in the Canadian and Australian jurisdictions during 2004-2013. This resulted in time-loss equivalent to 239,345 years in the Canadian jurisdictions and 321,488 years in the Australian jurisdictions. The number of time-loss years declined overall among male and female workers, but greater declines were observed for males and younger workers. The proportion of the disability burden grew among older workers (aged 55+), particularly males in the Canadian jurisdictions (Annual Percent Change [APC]: 7.2, 95% CI 6.7 to 7.7%) and females in the Australian jurisdictions (APC: 7.5, 95% CI 6.2 to 8.9%). The compensated disability burden of work-related MSDs is shifting towards older workers and particularly older females in Australia and older males in Canada. Employers and workers' compensation boards should consider the specific needs of older workers to reduce injuries and time off work. Comparative research made possible through research-stakeholder partnerships offers a unique opportunity to use existing administrative data to identify long-term trends in disability burden. Future research can apply similar approaches for estimating long-term trends in occupational health.

75 FR 22804 - Submission for OMB Review; American Recovery and Reinvestment Act-One-Time Reporting...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-30

... Recovery and Reinvestment Act--One-Time Reporting, Compensation Requirements AGENCIES: Department of... and Reinvestment Act--One-time Reporting, Compensation Requirements published in the Federal Register...

Species loss, delayed numerical responses, and functional compensation in an antbird guild.

PubMed

Touchton, Janeene M; Smith, James N M

2011-05-01

When a community loses species through fragmentation, its total food consumption may drop. Compensatory responses of remaining species, whereby survivors assume roles of extinct competitors, may reduce the impact of species loss through numerical or functional responses. We measured compensatory responses in two remaining antbird species on Barro Colorado Island, Panama, four decades after the loss of their dominant competitor, the Ocellated Antbird, Phaenostictus mcleannani. We compared current abundances and behavior of these two species on Barro Colorado to those reported before the island lost Ocellated Antbirds, and to those in a nearby mainland population where all three species still exist as a space-for-time substitution. The smaller, more subordinate Spotted Antbird, Hylophylax naevioides, responded far more strongly than the larger Bicolored Antbird, Gymnopithys leucaspis, which is functionally more like the Ocellated Antbird. Islandwide density of Spotted Antbirds has more than doubled since the loss of Ocellated Antbirds. Moreover, Spotted Antbirds now spend so much more of their time following ant swarms that their metabolic biomass at these swarms has more than tripled since Ocellated Antbirds disappeared. These responses in Spotted Antbirds were apparently delayed by >20 years. Bicolored Antbirds have not increased substantially in islandwide density or metabolic biomass at ant swarms. We hypothesize that behavioral flexibility, as shown by Spotted Antbirds on Barro Colorado Island, is a major factor governing the extent to which fragmented ecosystems can buffer the impacts of species loss.

Local Stability of AIDS Epidemic Model Through Treatment and Vertical Transmission with Time Delay

NASA Astrophysics Data System (ADS)

Novi W, Cascarilla; Lestari, Dwi

2016-02-01

This study aims to explain stability of the spread of AIDS through treatment and vertical transmission model. Human with HIV need a time to positively suffer AIDS. The existence of a time, human with HIV until positively suffer AIDS can be delayed for a time so that the model acquired is the model with time delay. The model form is a nonlinear differential equation with time delay, SIPTA (susceptible-infected-pre AIDS-treatment-AIDS). Based on SIPTA model analysis results the disease free equilibrium point and the endemic equilibrium point. The disease free equilibrium point with and without time delay are local asymptotically stable if the basic reproduction number is less than one. The endemic equilibrium point will be local asymptotically stable if the time delay is less than the critical value of delay, unstable if the time delay is more than the critical value of delay, and bifurcation occurs if the time delay is equal to the critical value of delay.

Associations with duration of compensation following whiplash sustained in a motor vehicle crash.

PubMed

Casey, Petrina P; Feyer, Anne Marie; Cameron, Ian D

2015-09-01

Continued exposure to compensation systems has been reported as deleterious to the health of participants. Understanding the associations with time to claim closure could allow for targeted interventions aimed at minimising the time participants are exposed to the compensation system. To identify the associations of extended time receiving compensation benefits with the aim of developing a prognostic model that predicts time to claim closure. Prospective cohort study in people with whiplash associated disorder. Time to claim closure, in a privately underwritten fault based third party traffic crash insurance scheme in New South Wales, Australia. Cox proportional hazard regression modelling. Of the 246 participants, 25% remained in the compensation system longer than 24 months with 15% remaining longer than three years. Higher initial disability (Functional Rating Index≥25 at baseline) (HRR: 95% CI, 1.916: 1.324-2.774, p<0.001); and lower initial mental health as measured by SF-36 Mental Component Score (HRR: 95% CI, 0.973: 0.960-0.987, p<0.001) were significantly and independently associated with an increased time-to-claim closure. Shorter time to claim closure was associated with having no legal involvement (HRR: 95% CI, 1.911: 1.169-3.123, p=0.009); and, not having a prior claim for compensation (HRR: 95% CI, 1.523: 1.062-2.198, p=0.022). Health and insurance related factors are independently associated with time to claim closure. Both factors need to be considered by insurers in their assessment of complexity of claims. Interventions aimed at minimising the impact of these factors could reduce claimants' exposure to the compensation system. In turn insurers can potentially reduce claims duration and cost, while improving the health outcomes of claimants. Copyright © 2015 Elsevier Ltd. All rights reserved.

Evaluation of large girth LDPC codes for PMD compensation by turbo equalization.

PubMed

Minkov, Lyubomir L; Djordjevic, Ivan B; Xu, Lei; Wang, Ting; Kueppers, Franko

2008-08-18

Large-girth quasi-cyclic LDPC codes have been experimentally evaluated for use in PMD compensation by turbo equalization for a 10 Gb/s NRZ optical transmission system, and observing one sample per bit. Net effective coding gain improvement for girth-10, rate 0.906 code of length 11936 over maximum a posteriori probability (MAP) detector for differential group delay of 125 ps is 6.25 dB at BER of 10(-6). Girth-10 LDPC code of rate 0.8 outperforms the girth-10 code of rate 0.906 by 2.75 dB, and provides the net effective coding gain improvement of 9 dB at the same BER. It is experimentally determined that girth-10 LDPC codes of length around 15000 approach channel capacity limit within 1.25 dB.

Design of a compensation for an ARMA model of a discrete time system. M.S. Thesis

NASA Technical Reports Server (NTRS)

Mainemer, C. I.

1978-01-01

The design of an optimal dynamic compensator for a multivariable discrete time system is studied. Also the design of compensators to achieve minimum variance control strategies for single input single output systems is analyzed. In the first problem the initial conditions of the plant are random variables with known first and second order moments, and the cost is the expected value of the standard cost, quadratic in the states and controls. The compensator is based on the minimum order Luenberger observer and it is found optimally by minimizing a performance index. Necessary and sufficient conditions for optimality of the compensator are derived. The second problem is solved in three different ways; two of them working directly in the frequency domain and one working in the time domain. The first and second order moments of the initial conditions are irrelevant to the solution. Necessary and sufficient conditions are derived for the compensator to minimize the variance of the output.

The effects of the framing of time on delay discounting.

PubMed

DeHart, William Brady; Odum, Amy L

2015-01-01

We examined the effects of the framing of time on delay discounting. Delay discounting is the process by which delayed outcomes are devalued as a function of time. Time in a titrating delay discounting task is often framed in calendar units (e.g., as 1 week, 1 month, etc.). When time is framed as a specific date, delayed outcomes are discounted less compared to the calendar format. Other forms of framing time; however, have not been explored. All participants completed a titrating calendar unit delay-discounting task for money. Participants were also assigned to one of two delay discounting tasks: time as dates (e.g., June 1st, 2015) or time in units of days (e.g., 5000 days), using the same delay distribution as the calendar delay-discounting task. Time framed as dates resulted in less discounting compared to the calendar method, whereas time framed as days resulted in greater discounting compared to the calendar method. The hyperboloid model fit best compared to the hyperbola and exponential models. How time is framed may alter how participants attend to the delays as well as how the delayed outcome is valued. Altering how time is framed may serve to improve adherence to goals with delayed outcomes. © Society for the Experimental Analysis of Behavior.

Adaptive pseudolinear compensators of dynamic characteristics of automatic control systems

NASA Astrophysics Data System (ADS)

Skorospeshkin, M. V.; Sukhodoev, M. S.; Timoshenko, E. A.; Lenskiy, F. V.

2016-04-01

Adaptive pseudolinear gain and phase compensators of dynamic characteristics of automatic control systems are suggested. The automatic control system performance with adaptive compensators has been explored. The efficiency of pseudolinear adaptive compensators in the automatic control systems with time-varying parameters has been demonstrated.

Approximation of discrete-time LQG compensators for distributed systems with boundary input and unbounded measurement

NASA Technical Reports Server (NTRS)

Gibson, J. S.; Rosen, I. G.

1987-01-01

The approximation of optimal discrete-time linear quadratic Gaussian (LQG) compensators for distributed parameter control systems with boundary input and unbounded measurement is considered. The approach applies to a wide range of problems that can be formulated in a state space on which both the discrete-time input and output operators are continuous. Approximating compensators are obtained via application of the LQG theory and associated approximation results for infinite dimensional discrete-time control systems with bounded input and output. Numerical results for spline and modal based approximation schemes used to compute optimal compensators for a one dimensional heat equation with either Neumann or Dirichlet boundary control and pointwise measurement of temperature are presented and discussed.

38 CFR 3.109 - Time limit.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Time limit. 3.109 Section..., Compensation, and Dependency and Indemnity Compensation Administrative § 3.109 Time limit. (a) Notice of time... and evidence originally submitted is not so included. (b) Extension of time limit. Time limits within...

38 CFR 3.109 - Time limit.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 38 Pensions, Bonuses, and Veterans' Relief 1 2012-07-01 2012-07-01 false Time limit. 3.109 Section..., Compensation, and Dependency and Indemnity Compensation Administrative § 3.109 Time limit. (a) Notice of time... and evidence originally submitted is not so included. (b) Extension of time limit. Time limits within...

38 CFR 3.109 - Time limit.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 38 Pensions, Bonuses, and Veterans' Relief 1 2011-07-01 2011-07-01 false Time limit. 3.109 Section..., Compensation, and Dependency and Indemnity Compensation Administrative § 3.109 Time limit. (a) Notice of time... and evidence originally submitted is not so included. (b) Extension of time limit. Time limits within...

38 CFR 3.109 - Time limit.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 38 Pensions, Bonuses, and Veterans' Relief 1 2014-07-01 2014-07-01 false Time limit. 3.109 Section..., Compensation, and Dependency and Indemnity Compensation Administrative § 3.109 Time limit. (a) Notice of time... and evidence originally submitted is not so included. (b) Extension of time limit. Time limits within...

38 CFR 3.109 - Time limit.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 38 Pensions, Bonuses, and Veterans' Relief 1 2013-07-01 2013-07-01 false Time limit. 3.109 Section..., Compensation, and Dependency and Indemnity Compensation Administrative § 3.109 Time limit. (a) Notice of time... and evidence originally submitted is not so included. (b) Extension of time limit. Time limits within...

Improved symbol rate identification method for on-off keying and advanced modulation format signals based on asynchronous delayed sampling

NASA Astrophysics Data System (ADS)

Cui, Sheng; Jin, Shang; Xia, Wenjuan; Ke, Changjian; Liu, Deming

2015-11-01

Symbol rate identification (SRI) based on asynchronous delayed sampling is accurate, cost-effective and robust to impairments. For on-off keying (OOK) signals the symbol rate can be derived from the periodicity of the second-order autocorrelation function (ACF2) of the delay tap samples. But it is found that when applied this method to advanced modulation format signals with auxiliary amplitude modulation (AAM), incorrect results may be produced because AAM has significant impact on ACF2 periodicity, which makes the symbol period harder or even unable to be correctly identified. In this paper it is demonstrated that for these signals the first order autocorrelation function (ACF1) has stronger periodicity and can be used to replace ACF2 to produce more accurate and robust results. Utilizing the characteristics of the ACFs, an improved SRI method is proposed to accommodate both OOK and advanced modulation formant signals in a transparent manner. Furthermore it is proposed that by minimizing the peak to average ratio (PAPR) of the delay tap samples with an additional tunable dispersion compensator (TDC) the limited dispersion tolerance can be expanded to desired values.

Dynamics of scroll waves with time-delay propagation in excitable media

NASA Astrophysics Data System (ADS)

Chen, Jiang-Xing; Xiao, Jie; Qiao, Li-Yan; Xu, Jiang-Rong

2018-06-01

Information transmission delay can be widely observed in various systems. Here, we study the dynamics of scroll waves with time-delay propagation among slices in excitable media. Weak time delay induces scroll waves to meander. Through increasing the time delay, we find a series of dynamical transitions. Firstly, the straight filament of a scroll wave becomes twisted. Then, the scroll wave breaks and forms interesting patterns. With long time delay, loosed scroll waves are maintained while their period are greatly decreased. Also, cylinder waves appears. The influences of diffusively coupling strength on the time-delay-induced scroll waves are studied. It is found that the critical time delay characterizing those transitions decreases as the coupling strength is increased. A phase diagram in the diffusive coupling-time delay plane is presented.

Deletion of MAOA and MAOB in a male patient causes severe developmental delay, intermittent hypotonia and stereotypical hand movements

PubMed Central

Whibley, Annabel; Urquhart, Jill; Dore, Jonathan; Willatt, Lionel; Parkin, Georgina; Gaunt, Lorraine; Black, Graeme; Donnai, Dian; Raymond, F Lucy

2010-01-01

Monoamine oxidases (MAO-A and MAO-B) have a key role in the degradation of amine neurotransmitters, such as dopamine, norepinephrine and serotonin. We identified an inherited 240 kb deletion on Xp11.3–p11.4, which encompasses both monoamine oxidase genes but, unlike other published reports, does not affect the adjacent Norrie disease gene (NDP). The brothers who inherited the deletion, and thus have no monoamine oxidase function, presented with severe developmental delay, intermittent hypotonia and stereotypical hand movements. The clinical features accord with published reports of larger microdeletions and selective MAO-A and MAO-B deficiencies in humans and mouse models and suggest considerable functional compensation between MAO-A and MAO-B under normal conditions. PMID:20485326

Investigation on dispersion in the active optical waveguide resonator

NASA Astrophysics Data System (ADS)

Qiu, Zihan; Gao, Yining; Xie, Wei

2018-03-01

Introducing active gain in the optical waveguide resonator not only compensates the loss, but also can change the dispersion relationship in the ring resonator. It is demonstrated that the group delay time is negative when the resonator is in the undercoupled condition, which also means the resonator exhibits the fast light effect. Theoretical analysis indicates that fast light effect due to anomalous dispersion, would be manipulated by the gain coefficient controlled by the input pump light power and that fast light would enhance scale factor of the optical resonant gyroscope. Resonance optical gyroscope (ROG)'s scale factor for measuring rotation rate is enhanced by anomalous dispersion with superluminal light propagation. The sensitivity of ROG could be enhanced by anomalous dispersion by coupled resonators even considering the effect of anomalous dispersion and propagation gain on broadened linewidth, and this could result in at least two orders of magnitude enhancement in sensitivity.

Compact first and second order polarization mode dispersion emulator

NASA Astrophysics Data System (ADS)

Zhang, Yang; Li, Shiguang; Yang, Changxi

2005-08-01

We propose a 1st and 2nd order polarization mode dispersion emulator (PMDE) with one variable differential group delay (DGD) element using birefringence crystals and four polarization controllers (PCs). Monte Carlo simulations demonstrate that the output 1st and 2nd order polarization mode dispersion (PMD) generated by the PMDE consists with statistic theory. Compared with former PMDEs, this design is tunable, lower-cost, and more integrated for fabrication, which shows response time of 150 ?s, response frequency of 3.8 kHz, working wavelength of 1550 nm, total power consumption of less than 3 W, working range of 0---84 ps and 0---3600 ps2 for 1st and 2nd order PMD emulation, respectively. Also, it is programmable and can be controlled by either singlechip or computer. It can be applied to study the outage probability of optical communication systems due to PMD effect and the effectiveness of PMD compensation.

Wheel slide protection control using a command map and Smith predictor for the pneumatic brake system of a railway vehicle

NASA Astrophysics Data System (ADS)

Lee, Nam-Jin; Kang, Chul-Goo

2016-10-01

In railway vehicles, excessive sliding or wheel locking can occur while braking because of a temporarily degraded adhesion between the wheel and the rail caused by the contaminated or wet surface of the rail. It can damage the wheel tread and affect the performance of the brake system and the safety of the railway vehicle. To safeguard the wheelset from these phenomena, almost all railway vehicles are equipped with wheel slide protection (WSP) systems. In this study, a new WSP algorithm is proposed. The features of the proposed algorithm are the use of the target sliding speed, the determination of a command for WSP valves using command maps, and compensation for the time delay in pneumatic brake systems using the Smith predictor. The proposed WSP algorithm was verified using experiments with a hardware-in-the-loop simulation system including the hardware of the pneumatic brake system.

Towards the Development of a Smart Flying Sensor: Illustration in the Field of Precision Agriculture.

PubMed

Hernandez, Andres; Murcia, Harold; Copot, Cosmin; De Keyser, Robin

2015-07-10

Sensing is an important element to quantify productivity, product quality and to make decisions. Applications, such as mapping, surveillance, exploration and precision agriculture, require a reliable platform for remote sensing. This paper presents the first steps towards the development of a smart flying sensor based on an unmanned aerial vehicle (UAV). The concept of smart remote sensing is illustrated and its performance tested for the task of mapping the volume of grain inside a trailer during forage harvesting. Novelty lies in: (1) the development of a position-estimation method with time delay compensation based on inertial measurement unit (IMU) sensors and image processing; (2) a method to build a 3D map using information obtained from a regular camera; and (3) the design and implementation of a path-following control algorithm using model predictive control (MPC). Experimental results on a lab-scale system validate the effectiveness of the proposed methodology.

Towards the Development of a Smart Flying Sensor: Illustration in the Field of Precision Agriculture

PubMed Central

Hernandez, Andres; Murcia, Harold; Copot, Cosmin; De Keyser, Robin

2015-01-01

Sensing is an important element to quantify productivity, product quality and to make decisions. Applications, such as mapping, surveillance, exploration and precision agriculture, require a reliable platform for remote sensing. This paper presents the first steps towards the development of a smart flying sensor based on an unmanned aerial vehicle (UAV). The concept of smart remote sensing is illustrated and its performance tested for the task of mapping the volume of grain inside a trailer during forage harvesting. Novelty lies in: (1) the development of a position-estimation method with time delay compensation based on inertial measurement unit (IMU) sensors and image processing; (2) a method to build a 3D map using information obtained from a regular camera; and (3) the design and implementation of a path-following control algorithm using model predictive control (MPC). Experimental results on a lab-scale system validate the effectiveness of the proposed methodology. PMID:26184205

In situ industrial applications of optics; Proceedings of the Meeting, Brussels, Belgium, June 25-27, 1986

NASA Astrophysics Data System (ADS)

Ebbeni, Jean

Included in this volume are papers on real-time image enhancement by simple video systems, automatic identification and data collection via barcode laser scanning, the optimization of the cutting up of a strip of float glass, optical sensors for factory automation, and the use of a digital theodolite with infrared radiation. Attention is also given to ISIS (integrated shape imaging system), a new system for follow-up of scoliosis; optical diffraction extensometers; a cross-spectrum technique for high-sensitivity remote vibration analysis by optical interferometry; the compensation and measurement of any motion of three-dimensional objects in holographic interferometry; and stereoscreen. Additional papers are on holographic double pulse YAG lasers, miniature optic connectors, stress-field analysis in an adhesively bonded joint with laser photoelasticimetry, and the locking of the light pulse delay in externally triggered gas lasers.

49 CFR 236.563 - Delay time.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 4 2010-10-01 2010-10-01 false Delay time. 236.563 Section 236.563 Transportation... Cab Signal Systems Rules and Instructions; Locomotives § 236.563 Delay time. Delay time of automatic... requirements of § 236.24 shall take into consideration the delay time. ...

49 CFR 236.563 - Delay time.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 4 2014-10-01 2014-10-01 false Delay time. 236.563 Section 236.563 Transportation... Cab Signal Systems Rules and Instructions; Locomotives § 236.563 Delay time. Delay time of automatic... requirements of § 236.24 shall take into consideration the delay time. ...

11 CFR 100.54 - Compensation for personal services.

Code of Federal Regulations, 2010 CFR

2010-01-01

... considered his or her own to use as he or she sees fit. (c) Vacation or earned leave time. No contribution... compensable, vacation time or other earned leave time. ..., provided that the taken or released time is made up or completed by the employee within a reasonable time...

11 CFR 100.54 - Compensation for personal services.

Code of Federal Regulations, 2011 CFR

2011-01-01

... considered his or her own to use as he or she sees fit. (c) Vacation or earned leave time. No contribution... compensable, vacation time or other earned leave time. ..., provided that the taken or released time is made up or completed by the employee within a reasonable time...

Employment Status and Posttraumatic Stress Disorder following Compensation Seeking in Victims of Violence

ERIC Educational Resources Information Center

Kunst, Maarten J. J.

2011-01-01

The current study was developed to explore the associations between posttraumatic stress disorder (PTSD), level of compensation for pain and suffering, and employment status in a sample of victims of violence (n = 226) who had held a full-time job at time of victimization and had filed a claim with the Dutch Victim Compensation Fund (DVCF)…

Increased photosynthesis compensates for shorter growing season in subarctic tundra - seven years of snow accumulation manipulations

NASA Astrophysics Data System (ADS)

Bosiö, Julia; Johansson, Margareta; Njuabe, Herbert; Christensen, Torben R.

2013-04-01

This study was initiated to analyze the effect of snow cover on photosynthesis and plant growth in subarctic mires underlain by permafrost. Due to their narrow environmental window these raised bogs, often referred to as palsa mires, are highly sensitive to climatic changes. In Fennoscandia palsa mires are currently subjected to climate related thawing and shift in vegetational and hydrological patterns. Yet, we know little of how these subarctic permafrost mires react and feed back to such changes. By using snow fences to hinder snow drift the accumulation of snow was increased in six plots (10x20 m) in a snow manipulation experiment on a subarctic permafrost mire in northern Sweden. The thicker snow pack prolongs the duration of the snow cover in spring, causing a delay in the onset, as well as an overall shortening of the growing season. By measuring incoming and reflected photosynthetic active radiation (PAR) we wanted to address the question whether the increased snow thickness and associated delay of the growing season start affected the absorbed PAR and the accumulated gross primary production (GPP) over the season. The reflected PAR was measured at twelve plots where six of the plots experienced increased snow accumulation (treatment), and remaining six plots were untreated (control). Minikin QT sensors with integrated data loggers logged incoming and reflected PAR hourly throughout the growing seasons of 2011 and 2012. In July - September 2010 PAR measurements were coupled with flux chamber measurements to assess GPP and light use efficiency of the plots. The increased accumulation of snow prolonged the duration of the snow cover in spring, causing a delay in the onset, as well as an overall shortening of the growing season in the treated plots. The end of the growing season was not affected by the snow manipulation. The delay of the growing season start and hence overall shortening of the growing season in the treatment plots was 18 days in 2011 and 3 days in 2012 in relation to control plots. Results show higher PAR absorption together with almost 50% higher light use efficiency in treatment plots compared with control plots. Estimations of GPP suggest that the loss in early season photosynthesis due to the shortening of the growing season in the treatment plots is well compensated for by the increased absorption of PAR and higher light use efficiency throughout the whole growing seasons. This compensation is likely to be explained by increased soil moisture and nutrient availability together with a shift in vegetation composition associated with the accelerated permafrost thaw in the treatment plots. In our presentation implications and possible feedbacks of the increased absorbed PAR and estimated change in GPP will be discussed.

Time-lapse processing of 2D seismic profiles with testing of static correction methods at the CO2 injection site Ketzin (Germany)

NASA Astrophysics Data System (ADS)

Bergmann, Peter; Yang, Can; Lüth, Stefan; Juhlin, Christopher; Cosma, Calin

2011-09-01

The Ketzin project provides an experimental pilot test site for the geological storage of CO2. Seismic monitoring of the Ketzin site comprises 2D and 3D time-lapse experiments with baseline experiments in 2005. The first repeat 2D survey was acquired in 2009 after 22 kt of CO2 had been injected into the Stuttgart Formation at approximately 630 m depth. Main objectives of the 2D seismic surveys were the imaging of geological structures, detection of injected CO2, and comparison with the 3D surveys. Time-lapse processing highlighted the importance of detailed static corrections to account for travel time delays, which are attributed to different near-surface velocities during the survey periods. Compensation for these delays has been performed using both pre-stack static corrections and post-stack static corrections. The pre-stack method decomposes the travel time delays of baseline and repeat datasets in a surface consistent manner, while the latter cross-aligns baseline and repeat stacked sections along a reference horizon. Application of the static corrections improves the S/N ratio of the time-lapse sections significantly. Based on our results, it is recommended to apply a combination of both corrections when time-lapse processing faces considerable near-surface velocity changes. Processing of the datasets demonstrates that the decomposed solution of the pre-stack static corrections can be used for interpretation of changes in near-surface velocities. In particular, the long-wavelength part of the solution indicates an increase in soil moisture or a shallower groundwater table in the repeat survey. Comparison with the processing results of 2D and 3D surveys shows that both image the subsurface, but with local variations which are mainly associated to differences in the acquisition geometry and source types used. Interpretation of baseline and repeat stacks shows that no CO2 related time-lapse signature is observable where the 2D lines allow monitoring of the reservoir. This finding is consistent with the time-lapse results of the 3D surveys, which show an increase in reflection amplitude centered around the injection well. To further investigate any potential CO2 signature, an amplitude versus offset (AVO) analysis was performed. The time-lapse analysis of the AVO does not indicate the presence of CO2, as expected, but shows signs of a pressure response in the repeat data.

Peer Outreach Work as Economic Activity: Implications for HIV Prevention Interventions among Female Sex Workers

PubMed Central

George, Annie; Blankenship, Kim M.

2015-01-01

Female sex workers (FSWs) who work as peer outreach workers in HIV prevention programs are drawn from poor socio-economic groups and consider outreach work, among other things, as an economic activity. Yet, while successful HIV prevention outcomes by such programs are attributed in part to the work of peers who have dense relations with FSW communities, there is scant discussion of the economic implications for FSWs of their work as peers. Using observational data obtained from an HIV prevention intervention for FSWs in south India, we examined the economic benefits and costs to peers of doing outreach work and their implications for sex workers’ economic security. We found that peers considered their payment incommensurate with their workload, experienced long delays receiving compensation, and at times had to advance money from their pockets to do their assigned peer outreach work. For the intervention these conditions resulted in peer attrition and difficulties in recruitment of new peer workers. We discuss the implications of these findings for uptake of services, and the possibility of reaching desired HIV outcomes. Inadequate and irregular compensation to peers and inadequate budgetary outlays to perform their community-based outreach work could weaken peers’ relationships with FSW community members, undermine the effectiveness of peer-mediated HIV prevention programs and invalidate arguments for the use of peers. PMID:25775122

Peer outreach work as economic activity: implications for HIV prevention interventions among female sex workers.

PubMed

George, Annie; Blankenship, Kim M

2015-01-01

Female sex workers (FSWs) who work as peer outreach workers in HIV prevention programs are drawn from poor socio-economic groups and consider outreach work, among other things, as an economic activity. Yet, while successful HIV prevention outcomes by such programs are attributed in part to the work of peers who have dense relations with FSW communities, there is scant discussion of the economic implications for FSWs of their work as peers. Using observational data obtained from an HIV prevention intervention for FSWs in south India, we examined the economic benefits and costs to peers of doing outreach work and their implications for sex workers' economic security. We found that peers considered their payment incommensurate with their workload, experienced long delays receiving compensation, and at times had to advance money from their pockets to do their assigned peer outreach work. For the intervention these conditions resulted in peer attrition and difficulties in recruitment of new peer workers. We discuss the implications of these findings for uptake of services, and the possibility of reaching desired HIV outcomes. Inadequate and irregular compensation to peers and inadequate budgetary outlays to perform their community-based outreach work could weaken peers' relationships with FSW community members, undermine the effectiveness of peer-mediated HIV prevention programs and invalidate arguments for the use of peers.

Nonlinear adaptive control based on fuzzy sliding mode technique and fuzzy-based compensator.

PubMed

Nguyen, Sy Dzung; Vo, Hoang Duy; Seo, Tae-Il

2017-09-01

It is difficult to efficiently control nonlinear systems in the presence of uncertainty and disturbance (UAD). One of the main reasons derives from the negative impact of the unknown features of UAD as well as the response delay of the control system on the accuracy rate in the real time of the control signal. In order to deal with this, we propose a new controller named CO-FSMC for a class of nonlinear control systems subjected to UAD, which is constituted of a fuzzy sliding mode controller (FSMC) and a fuzzy-based compensator (CO). Firstly, the FSMC and CO are designed independently, and then an adaptive fuzzy structure is discovered to combine them. Solutions for avoiding the singular cases of the fuzzy-based function approximation and reducing the calculating cost are proposed. Based on the solutions, fuzzy sliding mode technique, lumped disturbance observer and Lyapunov stability analysis, a closed-loop adaptive control law is formulated. Simulations along with a real application based on a semi-active train-car suspension are performed to fully evaluate the method. The obtained results reflected that vibration of the chassis mass is insensitive to UAD. Compared with the other fuzzy sliding mode control strategies, the CO-FSMC can provide the best control ability to reduce unwanted vibrations. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

MULTIMERMAID: A dedicated multichannel seismic/weather/zoological float for monitoring of the oceans

NASA Astrophysics Data System (ADS)

Hello, Y. M.; Bonnieux, S.; Joubert, C.; Sukhovich, A.; Argentino, J.; Yegikyan, M.; Nolet, G.

2013-12-01

Delays of seismic P waves are used to make scans or 3D images of the variations in seismic wave speed in the Earth's interior using the techniques of seismic tomography. Observations of such delays are ubiquitous on the continents but rare in oceanic regions, mostly because of the large cost associated with deploying ocean-bottom seismometers. At the same time, several thousand free-drifting profiling floats measure the temperature, salinity and current of the upper 2000 m of the ocean in the Argo program, but are incapable to record and transmit seismic signals. Simons et al. (JGR, 2009) developed the idea to use such floats in order to compensate for the lack of seismic delay observations, especially in the southern hemisphere. We built and tested a prototype of such a seismological sensor using an Apex float from Teledyne Webb Research, a Rafos hydrophone, and electronics developed in collaboration with Osean, a small engineering firm in France. This `MERMAID', for `Mobile Earthquake Recorder in Marine Areas by Independent Divers', has concluded its final design stage and a fleet of 20 units is available for experiments. Since 2012, half of these floats have been deployed in the Mediterranean and in the South Indian Ocean. 10 more will be deployed early in 2014 near the Galapagos islands in the Pacific. Analysis of the first data is allowing us to sharpen the wavelet-based algorithm parameters used to discriminate P-waves from the continuous input signal and adapt it to specific noise conditions. A new multidisciplinary version of Mermaid using a dedicated hydrophone is designed to enlarge the band pass for acoustic signals with much higher frequency than seismic. By combining the same algorithm using wavelet transforms, and by adopting a different monitoring strategy with a dedicated processing, Mermaid is able to continuously analyzes acoustic signals to detect major seismic events, while at the same time regularly checking for weather phenomena such rain, drizzle, open sea and ice, or whale migration. This extension to multi-purpose applications makes the Mermaid very attractive for the Argo program. In fact, Mermaids using passive low cost sensors form a very light and complementary solution that can easily be integrated with an Argo float since CTD data are taken during ascent. Such multidisciplinary approach should allow seismologists to participate in international programs such as Argo and obtain the dense ocean coverage needed to image the deep structure of the Earth. We estimate that about 300 Mermaids, operated over a time span of five years, can provide a ray coverage beneath the oceans comparable to that now available beneath the continents with the Global Seismic Network (GSN). To compensate for the extra energy needed for multidisciplinary applications, Geoazur and Osean are developing a new float, called Multimermaid, that uses the same 17' glass sphere as the Ocean Bottom Seismometers constructed by Geoazur. The Multimermaid can navigate up to a depth of 3000 m and hold 2.5 times more battery power than a conventional float.

Compensation of strong thermal lensing in high-optical-power cavities.

PubMed

Zhao, C; Degallaix, J; Ju, L; Fan, Y; Blair, D G; Slagmolen, B J J; Gray, M B; Lowry, C M Mow; McClelland, D E; Hosken, D J; Mudge, D; Brooks, A; Munch, J; Veitch, P J; Barton, M A; Billingsley, G

2006-06-16

In an experiment to simulate the conditions in high optical power advanced gravitational wave detectors, we show for the first time that the time evolution of strong thermal lenses follows the predicted infinite sum of exponentials (approximated by a double exponential), and that such lenses can be compensated using an intracavity compensation plate heated on its cylindrical surface. We show that high finesse approximately 1400 can be achieved in cavities with internal compensation plates, and that mode matching can be maintained. The experiment achieves a wave front distortion similar to that expected for the input test mass substrate in the Advanced Laser Interferometer Gravitational Wave Observatory, and shows that thermal compensation schemes are viable. It is also shown that the measurements allow a direct measurement of substrate optical absorption in the test mass and the compensation plate.

Joint compensation scheme of polarization crosstalk, intersymbol interference, frequency offset, and phase noise based on cascaded Kalman filter

NASA Astrophysics Data System (ADS)

Zhang, Qun; Yang, Yanfu; Xiang, Qian; Zhou, Zhongqing; Yao, Yong

2018-02-01

A joint compensation scheme based on cascaded Kalman filter is proposed, which can implement polarization tracking, channel equalization, frequency offset, and phase noise compensation simultaneously. The experimental results show that the proposed algorithm can not only compensate multiple channel impairments simultaneously but also improve the polarization tracking capacity and accelerate the convergence speed. The scheme has up to eight times faster convergence speed compared with radius-directed equalizer (RDE) + Max-FFT (maximum fast Fourier transform) + BPS (blind phase search) and can track up polarization rotation 60 times and 15 times faster than that of RDE + Max-FFT + BPS and CMMA (cascaded multimodulus algorithm) + Max-FFT + BPS, respectively.

Polygyny and its fitness consequences for primary and secondary female pied flycatchers

PubMed Central

Huk, Thomas; Winkel, Wolfgang

2006-01-01

In polygynous species with biparental care, the amount of paternal support often varies considerably. In the pied flycatcher (Ficedula hypoleuca), females mated with monogamous males receive more male assistance during the nestling phase than females mated with bigynous males, as the latter have to share their mates with another female. Bigynous males, however, give more support to their primary broods than to their secondary broods. Using a long-term dataset (31 years), the present study revealed that direct reproductive success, i.e. number of fledglings, was lower in females that mated with bigynous males, especially in secondary broods without male assistance, than in females that mated with monogamous males. Secondary broods with male assistance were more affected than primary broods. Female survival was independent of mating status. In primary broods, a delayed compensation for inferior direct reproductive success was found in terms of the number of grandoffspring, a phenomenon that did not occur in secondary broods. Delayed compensation in primary broods refers to indirect effects, i.e. good genes. According to the sexy son hypothesis, genetically superior (i.e. sexy) males may have sons with a higher number of broods belonging to a polygynous breeding status than do sons from broods with a monogamous father. This was indeed the case for sons descending from primary broods, but not for sons descending from secondary broods. PMID:16769641

Return to work outcomes for workers with mental health conditions: A retrospective cohort study.

PubMed

Prang, Khic-Houy; Bohensky, Megan; Smith, Peter; Collie, Alex

2016-01-01

The aims of this study were to describe predictors of sustained return to work (RTW) among a cohort of workers with compensated work-related mental health conditions (MHCs); and to examine predictors of subsequent absences due to the same condition. This study was a retrospective analysis of compensation claims data in Victoria, Australia. We selected workers with an accepted wage replacement claim due to a work-related MHC from 1 January 2002 to 31 December 2009, with two years of follow-up data. We identified 8358 workers meeting our inclusion criteria. The median age of workers was 44 years (Interquartile range (IQR): 36-51) and 56% were female. In a multivariable Cox regression analysis, older age, being from a small organisation, working in some specific industry segments, consulting a psychiatrist or psychologist, using medications, and having a previous claim were all associated with a delayed RTW. Workers experiencing work pressure, assault/workplace violence or other mental stress factors, working in the public administration and safety industry and having a medical incapacity certification between 3-4 days and 5-7 days had a higher rate of multiple RTW attempts. This study identified a number of risk factors associated with a delayed RTW and multiple attempts at RTW. Predictors may help identify high-risk groups and facilitate the RTW process of workers with MHCs. Copyright © 2015 Elsevier Ltd. All rights reserved.

Wigner time delay in photodetachment of Tm-and in photoionization of Yb: A comparative study

NASA Astrophysics Data System (ADS)

Saha, Soumyajit; Jose, Jobin; Deshmukh, Pranawa; Dolmatov, Valeriy; Kheifets, Anatoli; Manson, Steven

2017-04-01

Preliminary studies of Wigner time delay in photodetachment spectra of negative ions have been reported. Photodetachment time delay for some dipole channels of Tm- and of Cl- were calculated using relativistic random phase approximation (RRPA). Comparisons between photodetachment time delay of Cl- and photoionization time delay of Ar were made. We investigate the photodetachment time delay for all three relativistically split nd -> ɛ f channels of Tm- and for nd -> ɛ f channels of Yb (isoelectronic to Tm-) using RRPA. We study the effect of the shape resonance, brought about by the centrifugal barrier potential, on photodetachment time delay. A negative ion is a good laboratory for studying the effects of shape resonances on time delay since the phase is unaffected by the Coulomb component. Wigner time delay in photodetachment of Tm- and in photoionization of Yb: A comparative study.

38 CFR 3.750 - Entitlement to concurrent receipt of military retired pay and disability compensation.

Code of Federal Regulations, 2010 CFR

2010-07-01

... disability compensation. (a) Definition of military retired pay. For the purposes of this part, military... compensation. A veteran may reelect between benefits covered by this section at any time by submitting a... receipt of military retired pay and disability compensation. 3.750 Section 3.750 Pensions, Bonuses, and...

23 CFR 751.15 - Just compensation.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 23 Highways 1 2010-04-01 2010-04-01 false Just compensation. 751.15 Section 751.15 Highways... AND ACQUISITION § 751.15 Just compensation. (a) Just compensation shall be paid the owner for the... nonconforming junkyard as provided in § 751.11 must pertain at the time of the taking or removal in order to...

23 CFR 751.15 - Just compensation.

Code of Federal Regulations, 2011 CFR

2011-04-01

... nonconforming junkyard as provided in § 751.11 must pertain at the time of the taking or removal in order to... 23 Highways 1 2011-04-01 2011-04-01 false Just compensation. 751.15 Section 751.15 Highways... AND ACQUISITION § 751.15 Just compensation. (a) Just compensation shall be paid the owner for the...

22 CFR 221.21 - Event of Default; Application for Compensation; payment.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 22 Foreign Relations 1 2013-04-01 2013-04-01 false Event of Default; Application for Compensation... GUARANTEE STANDARD TERMS AND CONDITIONS Procedure for Obtaining Compensation § 221.21 Event of Default; Application for Compensation; payment. At any time after an Event of Default, as this term is defined in an...

22 CFR 221.21 - Event of Default; Application for Compensation; payment.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 22 Foreign Relations 1 2012-04-01 2012-04-01 false Event of Default; Application for Compensation... GUARANTEE STANDARD TERMS AND CONDITIONS Procedure for Obtaining Compensation § 221.21 Event of Default; Application for Compensation; payment. At any time after an Event of Default, as this term is defined in an...

22 CFR 221.21 - Event of Default; Application for Compensation; payment.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 22 Foreign Relations 1 2011-04-01 2011-04-01 false Event of Default; Application for Compensation... GUARANTEE STANDARD TERMS AND CONDITIONS Procedure for Obtaining Compensation § 221.21 Event of Default; Application for Compensation; payment. At any time after an Event of Default, as this term is defined in an...

22 CFR 221.21 - Event of Default; Application for Compensation; payment.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 22 Foreign Relations 1 2014-04-01 2014-04-01 false Event of Default; Application for Compensation... GUARANTEE STANDARD TERMS AND CONDITIONS Procedure for Obtaining Compensation § 221.21 Event of Default; Application for Compensation; payment. At any time after an Event of Default, as this term is defined in an...

No-fault compensation in New Zealand: harmonizing injury compensation, provider accountability, and patient safety.

PubMed

Bismark, Marie; Paterson, Ron

2006-01-01

In 1974 New Zealand jettisoned a tort-based system for compensating medical injuries in favor of a government-funded compensation system. Although the system retained some residual fault elements, it essentially barred medical malpractice litigation. Reforms in 2005 expanded eligibility for compensation to all "treatment injuries," creating a true no-fault compensation system. Compared with a medical malpractice system, the New Zealand system offers more-timely compensation to a greater number of injured patients and more-effective processes for complaint resolution and provider accountability. The unfinished business lies in realizing its full potential for improving patient safety.

Effects of partial time delays on phase synchronization in Watts-Strogatz small-world neuronal networks.

PubMed

Sun, Xiaojuan; Perc, Matjaž; Kurths, Jürgen

2017-05-01

In this paper, we study effects of partial time delays on phase synchronization in Watts-Strogatz small-world neuronal networks. Our focus is on the impact of two parameters, namely the time delay τ and the probability of partial time delay p delay , whereby the latter determines the probability with which a connection between two neurons is delayed. Our research reveals that partial time delays significantly affect phase synchronization in this system. In particular, partial time delays can either enhance or decrease phase synchronization and induce synchronization transitions with changes in the mean firing rate of neurons, as well as induce switching between synchronized neurons with period-1 firing to synchronized neurons with period-2 firing. Moreover, in comparison to a neuronal network where all connections are delayed, we show that small partial time delay probabilities have especially different influences on phase synchronization of neuronal networks.

Delay-range-dependent chaos synchronization approach under varying time-lags and delayed nonlinear coupling.

PubMed

Zaheer, Muhammad Hamad; Rehan, Muhammad; Mustafa, Ghulam; Ashraf, Muhammad

2014-11-01

This paper proposes a novel state feedback delay-range-dependent control approach for chaos synchronization in coupled nonlinear time-delay systems. The coupling between two systems is esteemed to be nonlinear subject to time-lags. Time-varying nature of both the intrinsic and the coupling delays is incorporated to broad scope of the present study for a better-quality synchronization controller synthesis. Lyapunov-Krasovskii (LK) functional is employed to derive delay-range-dependent conditions that can be solved by means of the conventional linear matrix inequality (LMI)-tools. The resultant control approach for chaos synchronization of the master-slave time-delay systems considers non-zero lower bound of the intrinsic as well as the coupling time-delays. Further, the delay-dependent synchronization condition has been established as a special case of the proposed LK functional treatment. Furthermore, a delay-range-dependent condition, independent of the delay-rate, has been provided to address the situation when upper bound of the delay-derivative is unknown. A robust state feedback control methodology is formulated for synchronization of the time-delay chaotic networks against the L2 norm bounded perturbations by minimizing the L2 gain from the disturbance to the synchronization error. Numerical simulation results are provided for the time-delay chaotic networks to show effectiveness of the proposed delay-range-dependent chaos synchronization methodologies. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Improved Short-Term Clock Prediction Method for Real-Time Positioning.

PubMed

Lv, Yifei; Dai, Zhiqiang; Zhao, Qile; Yang, Sheng; Zhou, Jinning; Liu, Jingnan

2017-06-06

The application of real-time precise point positioning (PPP) requires real-time precise orbit and clock products that should be predicted within a short time to compensate for the communication delay or data gap. Unlike orbit correction, clock correction is difficult to model and predict. The widely used linear model hardly fits long periodic trends with a small data set and exhibits significant accuracy degradation in real-time prediction when a large data set is used. This study proposes a new prediction model for maintaining short-term satellite clocks to meet the high-precision requirements of real-time clocks and provide clock extrapolation without interrupting the real-time data stream. Fast Fourier transform (FFT) is used to analyze the linear prediction residuals of real-time clocks. The periodic terms obtained through FFT are adopted in the sliding window prediction to achieve a significant improvement in short-term prediction accuracy. This study also analyzes and compares the accuracy of short-term forecasts (less than 3 h) by using different length observations. Experimental results obtained from International GNSS Service (IGS) final products and our own real-time clocks show that the 3-h prediction accuracy is better than 0.85 ns. The new model can replace IGS ultra-rapid products in the application of real-time PPP. It is also found that there is a positive correlation between the prediction accuracy and the short-term stability of on-board clocks. Compared with the accuracy of the traditional linear model, the accuracy of the static PPP using the new model of the 2-h prediction clock in N, E, and U directions is improved by about 50%. Furthermore, the static PPP accuracy of 2-h clock products is better than 0.1 m. When an interruption occurs in the real-time model, the accuracy of the kinematic PPP solution using 1-h clock prediction product is better than 0.2 m, without significant accuracy degradation. This model is of practical significance because it solves the problems of interruption and delay in data broadcast in real-time clock estimation and can meet the requirements of real-time PPP.

Downhole delay assembly for blasting with series delay

DOEpatents

Ricketts, Thomas E.

1982-01-01

A downhole delay assembly is provided which can be placed into a blasthole for initiation of explosive in the blasthole. The downhole delay assembly includes at least two detonating time delay devices in series in order to effect a time delay of longer than about 200 milliseconds in a round of explosions. The downhole delay assembly provides a protective housing to prevent detonation of explosive in the blasthole in response to the detonation of the first detonating time delay device. There is further provided a connection between the first and second time delay devices. The connection is responsive to the detonation of the first detonating time delay device and initiates the second detonating time delay device. A plurality of such downhole delay assemblies are placed downhole in unfragmented formation and are initiated simultaneously for providing a round of explosive expansions. The explosive expansions can be used to form an in situ oil shale retort containing a fragmented permeable mass of formation particles.

Parenting Predictors of Delay Inhibition in Socioeconomically Disadvantaged Preschoolers

PubMed Central

Merz, Emily C.; Landry, Susan H.; Zucker, Tricia A.; Barnes, Marcia A.; Assel, Michael; Taylor, Heather B.; Lonigan, Christopher J.; Phillips, Beth M.; Clancy-Menchetti, Jeanine; Eisenberg, Nancy; Spinrad, Tracy L.; Valiente, Carlos; de Villiers, Jill; Consortium, the School Readiness Research

2016-01-01

This study examined longitudinal associations between specific parenting factors and delay inhibition in socioeconomically disadvantaged preschoolers. At Time 1, parents and 2- to 4-year-old children (mean age = 3.21 years; N = 247) participated in a videotaped parent-child free play session, and children completed delay inhibition tasks (gift delay-wrap, gift delay-bow, and snack delay tasks). Three months later, at Time 2, children completed the same set of tasks. Parental responsiveness was coded from the parent-child free play sessions, and parental directive language was coded from transcripts of a subset of 127 of these sessions. Structural equation modeling was used, and covariates included age, gender, language skills, parental education, and Time 1 delay inhibition. Results indicated that in separate models, Time 1 parental directive language was significantly negatively associated with Time 2 delay inhibition, and Time 1 parental responsiveness was significantly positively associated with Time 2 delay inhibition. When these parenting factors were entered simultaneously, Time 1 parental directive language significantly predicted Time 2 delay inhibition whereas Time 1 parental responsiveness was no longer significant. Findings suggest that parental language that modulates the amount of autonomy allotted the child may be an important predictor of early delay inhibition skills. PMID:27833461

Compensated transnational surrogacy in Australia: time for a comprehensive review.

PubMed

Newson, Ainsley J

2016-01-18

Commercial or compensated surrogacy involves providing payment for a woman to gestate a fetus to term and then hand over the child to commissioning parent(s). Compensated surrogacy is currently restricted by law or regulation in all Australian states and territories. New South Wales, Queensland and the Australian Capital Territory also restrict commissioning transnational compensated surrogacy, although there is evidence that this is not acting as a deterrent. Ethical issues arising in transnational compensated surrogacy include concerns relating to exploitation, commodification and welfare. The current status quo is unsatisfactory on legal, ethical and practical grounds. It is time to openly debate how Australia should balance the desire for childbearing through surrogacy with the limited domestic availability of women willing to act as surrogates.

Structure and agency in development-induced forced migration: the case of Brazil’s Belo Monte Dam

PubMed Central

2017-01-01

This paper examines how structure and agency interact to shape forced migration outcomes. Specifically, I ask how structural factors such as compensation policies as well as social, financial, and human capital may either foster or constrain migration aspirations and capabilities. I use longitudinal, semi-structured interview data to study forced migration among farmers displaced by the Belo Monte Dam in the Brazilian Amazon. Results from baseline interviews indicate that nearly all community members aspired to purchase rural land in the region and maintain livelihoods as cacao farmers or cattle ranchers. Constraints limiting the ability to attain aspirations included strict requirements on land titles for properties, delays in receiving compensation, rising land prices, and the lack of power to negotiate for better compensation. Despite these constraints, most migrants succeeded in attaining aspirations, as they were able to mobilize resources such as social networks, financial capital, skills, and knowledge. These findings highlight the importance of considering the relationship between structure and agency within forced migration research. I conclude by discussing how the findings may inform resettlement policies for future cases of development- or environment-induced forced migration. PMID:28298745

Determinants of escalating costs in low risk workers' compensation claims.

PubMed

Bernacki, Edward J; Yuspeh, Larry; Tao, Xuguang

2007-07-01

To identify and quantify attributes that lead to unanticipated cost escalation in workers' compensation claims. We constructed four claim categories: low initial reserve/low cost, migrated catastrophic (low initial reserve/high cost), high initial reserve/low cost, and catastrophic (high initial reserve/high cost). To assess the attributes associated with the increased cost of migrated catastrophic claims, we analyzed 36,329 Louisiana workers' compensation claims in the four categories over a 5-year period. In the 729 claims initially thought to be low-cost claims (migrated catastrophic), the most significant predictors for cost escalation were attorney involvement and claim duration, followed by low back disorder, married/single/divorced status, male gender, small company size, high premium, reporting delays, and older age. These injuries accounted for 2% of all claims but 32.3% of the costs. Accelerated escalation of costs occurred late in the claim cycle (2 years). Certain attributes, particularly attorney involvement and claim duration, are associated with unanticipated cost escalation in a small number of claims that drastically affect overall losses. The results of this study suggest that these cases may be identified and addressed before rapid escalation occurs.

The Property Value Protection Program - How the Compensation Plan is Working and Evolving to Meet Changing Needs - 13149

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

Faught, Jeff; Herod, Judy; Mahabir, Alexandra

2013-07-01

The Property Value Protection (PVP) Program offers an innovative approach to address the risk of individual property value loss resulting from the cleanup and long-term management of historic low level radioactive waste in the Port Hope area in Southern Ontario, Canada. This cleanup is taking place through the Port Hope Area Initiative (PHAI), a federally sponsored waste remediation project. The PVP Program came into effect on October 1, 2000, having been established as a key element of the PHAI Legal Agreement between the Government of Canada and the municipalities of Port Hope and Clarington. The PVP Program was designed inmore » direct response to the concern expressed by the agreement's two municipal signatories that protection of local property owners from the risk of property value loss was critical to their acceptance of the Port Hope and Port Granby projects. The PVP Program compensates owners of residential, commercial or industrial properties for a loss in fair market value on the sale or rental of their properties. Increased mortgage refinancing costs and expenses incurred as a result of delayed sales that can be attributed to the Port Hope Area Initiative are also compensated. (authors)« less

Time-delayed feedback control of diffusion in random walkers.

PubMed

Ando, Hiroyasu; Takehara, Kohta; Kobayashi, Miki U

2017-07-01

Time delay in general leads to instability in some systems, while specific feedback with delay can control fluctuated motion in nonlinear deterministic systems to a stable state. In this paper, we consider a stochastic process, i.e., a random walk, and observe its diffusion phenomenon with time-delayed feedback. As a result, the diffusion coefficient decreases with increasing delay time. We analytically illustrate this suppression of diffusion by using stochastic delay differential equations and justify the feasibility of this suppression by applying time-delayed feedback to a molecular dynamics model.

34 CFR 75.519 - Dual compensation of staff.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 34 Education 1 2011-07-01 2011-07-01 false Dual compensation of staff. 75.519 Section 75.519... by a Grantee? Project Staff § 75.519 Dual compensation of staff. A grantee may not use its grantee to pay a project staff member for time or work for which that staff member is compensated from some other...

34 CFR 75.519 - Dual compensation of staff.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 34 Education 1 2014-07-01 2014-07-01 false Dual compensation of staff. 75.519 Section 75.519... by a Grantee? Project Staff § 75.519 Dual compensation of staff. A grantee may not use its grantee to pay a project staff member for time or work for which that staff member is compensated from some other...

34 CFR 75.519 - Dual compensation of staff.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 34 Education 1 2012-07-01 2012-07-01 false Dual compensation of staff. 75.519 Section 75.519... by a Grantee? Project Staff § 75.519 Dual compensation of staff. A grantee may not use its grantee to pay a project staff member for time or work for which that staff member is compensated from some other...

34 CFR 75.519 - Dual compensation of staff.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 34 Education 1 2013-07-01 2013-07-01 false Dual compensation of staff. 75.519 Section 75.519... by a Grantee? Project Staff § 75.519 Dual compensation of staff. A grantee may not use its grantee to pay a project staff member for time or work for which that staff member is compensated from some other...

34 CFR 75.519 - Dual compensation of staff.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 34 Education 1 2010-07-01 2010-07-01 false Dual compensation of staff. 75.519 Section 75.519... by a Grantee? Project Staff § 75.519 Dual compensation of staff. A grantee may not use its grantee to pay a project staff member for time or work for which that staff member is compensated from some other...

Effects of partial time delays on phase synchronization in Watts-Strogatz small-world neuronal networks

NASA Astrophysics Data System (ADS)

Sun, Xiaojuan; Perc, Matjaž; Kurths, Jürgen

2017-05-01

In this paper, we study effects of partial time delays on phase synchronization in Watts-Strogatz small-world neuronal networks. Our focus is on the impact of two parameters, namely the time delay τ and the probability of partial time delay pdelay, whereby the latter determines the probability with which a connection between two neurons is delayed. Our research reveals that partial time delays significantly affect phase synchronization in this system. In particular, partial time delays can either enhance or decrease phase synchronization and induce synchronization transitions with changes in the mean firing rate of neurons, as well as induce switching between synchronized neurons with period-1 firing to synchronized neurons with period-2 firing. Moreover, in comparison to a neuronal network where all connections are delayed, we show that small partial time delay probabilities have especially different influences on phase synchronization of neuronal networks.

Finite time synchronization of memristor-based Cohen-Grossberg neural networks with mixed delays.

PubMed

Chen, Chuan; Li, Lixiang; Peng, Haipeng; Yang, Yixian

2017-01-01

Finite time synchronization, which means synchronization can be achieved in a settling time, is desirable in some practical applications. However, most of the published results on finite time synchronization don't include delays or only include discrete delays. In view of the fact that distributed delays inevitably exist in neural networks, this paper aims to investigate the finite time synchronization of memristor-based Cohen-Grossberg neural networks (MCGNNs) with both discrete delay and distributed delay (mixed delays). By means of a simple feedback controller and novel finite time synchronization analysis methods, several new criteria are derived to ensure the finite time synchronization of MCGNNs with mixed delays. The obtained criteria are very concise and easy to verify. Numerical simulations are presented to demonstrate the effectiveness of our theoretical results.

Predictive Interfaces for Long-Distance Tele-Operations

NASA Technical Reports Server (NTRS)

Wheeler, Kevin R.; Martin, Rodney; Allan, Mark B.; Sunspiral, Vytas

2005-01-01

We address the development of predictive tele-operator interfaces for humanoid robots with respect to two basic challenges. Firstly, we address automating the transition from fully tele-operated systems towards degrees of autonomy. Secondly, we develop compensation for the time-delay that exists when sending telemetry data from a remote operation point to robots located at low earth orbit and beyond. Humanoid robots have a great advantage over other robotic platforms for use in space-based construction and maintenance because they can use the same tools as astronauts do. The major disadvantage is that they are difficult to control due to the large number of degrees of freedom, which makes it difficult to synthesize autonomous behaviors using conventional means. We are working with the NASA Johnson Space Center's Robonaut which is an anthropomorphic robot with fully articulated hands, arms, and neck. We have trained hidden Markov models that make use of the command data, sensory streams, and other relevant data sources to predict a tele-operator's intent. This allows us to achieve subgoal level commanding without the use of predefined command dictionaries, and to create sub-goal autonomy via sequence generation from generative models. Our method works as a means to incrementally transition from manual tele-operation to semi-autonomous, supervised operation. The multi-agent laboratory experiments conducted by Ambrose et. al. have shown that it is feasible to directly tele-operate multiple Robonauts with humans to perform complex tasks such as truss assembly. However, once a time-delay is introduced into the system, the rate of tele\\ioperation slows down to mimic a bump and wait type of activity. We would like to maintain the same interface to the operator despite time-delays. To this end, we are developing an interface which will allow for us to predict the intentions of the operator while interacting with a 3D virtual representation of the expected state of the robot. The predictive interface anticipates the intention of the operator, and then uses this prediction to initiate appropriate sub-goal autonomy tasks.

The Role of Compensation Criteria to Minimize Face-Time Bias and Support Faculty Career Flexibility

PubMed Central

Elsbach, Kimberly D.; Villablanca, Amparo C.

2016-01-01

Work-life balance is important to recruitment and retention of the younger generation of medical faculty, but medical school flexibility policies have not been fully effective. We have reported that our school’s policies are underutilized due to faculty concerns about looking uncommitted to career or team. Since policies include leaves and accommodations that reduce physical presence, faculty may fear “face-time bias,” which negatively affects evaluation of those not “seen” at work. Face-time bias is reported to negatively affect salary and career progress. We explored face-time bias on a leadership level and described development of compensation criteria intended to mitigate face-time bias, raise visibility, and reward commitment and contribution to team/group goals. Leaders from 6 partner departments participated in standardized interviews and group meetings. Ten compensation plans were analyzed, and published literature was reviewed. Leaders did not perceive face-time issues but saw team pressure and perception of availability as performance motivators. Compensation plans were multifactor productivity based with many quantifiable criteria; few addressed team contributions. Using these findings, novel compensation criteria were developed based on a published model to mitigate face-time bias associated with team perceptions. Criteria for organizational citizenship to raise visibility and reward group outcomes were included. We conclude that team pressure and perception of availability have the potential to lead to bias and may contribute to underuse of flexibility policies. Recognizing organizational citizenship and cooperative effort via specific criteria in a compensation plan may enhance a culture of flexibility. These novel criteria have been effective in one pilot department. PMID:28725757

Time-delayed chameleon: Analysis, synchronization and FPGA implementation

NASA Astrophysics Data System (ADS)

Rajagopal, Karthikeyan; Jafari, Sajad; Laarem, Guessas

2017-12-01

In this paper we report a time-delayed chameleon-like chaotic system which can belong to different families of chaotic attractors depending on the choices of parameters. Such a characteristic of self-excited and hidden chaotic flows in a simple 3D system with time delay has not been reported earlier. Dynamic analysis of the proposed time-delayed systems are analysed in time-delay space and parameter space. A novel adaptive modified functional projective lag synchronization algorithm is derived for synchronizing identical time-delayed chameleon systems with uncertain parameters. The proposed time-delayed systems and the synchronization algorithm with controllers and parameter estimates are then implemented in FPGA using hardware-software co-simulation and the results are presented.

Aircraft Pitch Control With Fixed Order LQ Compensators

NASA Technical Reports Server (NTRS)

Green, James; Ashokkumar, C. R.; Homaifar, Abdollah

1997-01-01

This paper considers a given set of fixed order compensators for aircraft pitch control problem. By augmenting compensator variables to the original state equations of the aircraft, a new dynamic model is considered to seek a LQ controller. While the fixed order compensators can achieve a set of desired poles in a specified region, LQ formulation provides the inherent robustness properties. The time response for ride quality is significantly improved with a set of dynamic compensators.

Aircraft Pitch Control with Fixed Order LQ Compensators

NASA Technical Reports Server (NTRS)

Green, James; Ashokkumar, Cr.; Homaifar, A.

1997-01-01

This paper considers a given set of fixed order compensators for aircraft pitch control problem. By augmenting compensator variables to the original state equations of the aircraft, a new dynamic model is considered to seek a LQ controller. While the fixed order compensators can achieve a set of desired poles in a specified region, LQ formulation provides the inherent robustness properties. The time response for ride quality is significantly improved with a set of dynamic compensators.

Pre-surgery Disability Compensation Predicts Long-Term Disability among Workers with Carpal Tunnel Syndrome

PubMed Central

Spector, June T.; Turner, Judith A.; Fulton-Kehoe, Deborah; Franklin, Gary

2012-01-01

Background We sought to identify early risk factors for work disability compensation prior to and after carpal tunnel syndrome (CTS) surgery, and to determine whether pre-surgery disability compensation is associated with long-term disability. Methods Washington State workers’ compensation administrative data and data from interviews with workers 18 days (median) after submitting new workers’ compensation claims for CTS were examined. Baseline risk factors for pre-surgery disability compensation and for long-term disability (≥365 days of work disability compensation prior to two years after claim filing) were evaluated for workers who underwent CTS surgery and had at least one day of disability compensation (N=670). Results After adjustment for baseline long-term disability risk factors, workers with pre-surgery disability compensation had over five times the odds of long-term disability. Baseline factors in multiple domains, including job, psychosocial, clinical, and worker pain and function, were associated with both pre-surgery disability compensation and long-term disability. Conclusions Risk factors for work disability prior to and after CTS surgery are similar, and early work disability is a risk factor for long-term CTS-related disability. An integrated approach to CTS-related disability prevention could include identifying and addressing combined risk factors soon after claim filing, more efficient use of conservative treatments and appropriate work modifications to minimize early work loss, and, when indicated, timely surgical intervention. PMID:22392804

Tests of the standard (30 hz) NCER FM multiplex telemetry system, augmented by two timing channels and a compensation reference signal, used to record multiplexed seismic network data on magnetic tape

USGS Publications Warehouse

Eaton, Jerry P.

1976-01-01

The application of subtractive compensation to USGS seismic magnetic tape recording and playback systems was examined in a recent USGS Open-file report (1). It was found, for the standard (30 Hz) NCER multiplex system, that subtractive compensation utilizing a 4688 Hz reference signal multiplexed onto each data track was more effective than that utilizing a 3125 Hz reference signal recorded separately on a different track. Moreover, it was found that the portion of the spectrum between the uppermost data channel (3060 Hz + or - 125 Hz) and the compensation reference signal (4688 Hz) could be used to record an additional timing signal, with a center frequency of 3700 Hz and a broader playback bandwidth (ca 0 to 100 Hz) than that of the standard data channels. Accordingly, for the tests described in that report, the standard 8-datachannel multiplex system was augmented by one additional timing channel with a center frequency of 3700 Hz. The 3700 Hz discriminator used in those tests was not successfully set up to utilize subtractive compensation; so its output from a tape playback was quite noisy. Subsequently, further tests have been carried out on the application of subtractive compensation to a 4-channel broad-band multiplex system and to the standard multiplex system, both recorded on field tape recorders with relatively poor tape speed control (2), (3). In the course of these experiments, it was discovered that two separate timing channe1s, not just one, can be inserted between the uppermost data channel and the compensation reference signal, Furthermore, it was possible to adjust the discriminators used to playback these timing channels so that they profited significantly from subtractive compensation even though the playback bandwidth was 0 to 100 Hz (for short rise times of square wave timing signals). The advantages of recording two timing signals on each data track include: 1) one standard time signal to be used for critical timing, e.g. IRIG E, can be recorded with the data on each track, eliminating any problem that might arise from tape head misalignment if the timing base were recorded on a separate track from the data signals being timed, 2) other essential timing signals e.g. WWVB and IRIG C, can each be recorded on several tracks, to insure more reliable recording through redundancy, without displacing data from standard data channels, 3) the broader playback bandwidth of the special timing channels reproduces the sharp-edged timing codes with much less distortion than is obtained from the standard data channels. In order to implement subtractive compensation with the 4688 Hz multiplexed signal and to record timing signals on the proposed special timing channels, it was necessary to design and build a signal generator/multiplexer unit. The functions of this unit are: 1) generate a stable (x-tal controlled) compensation reference frequency (4688 Hz), 2) generate two timing channel subcarriers (3500 Hz and 3950 Hz) and provide for their modulation by appropriate timing signals, 3) separately, for each of th~14 tape tracks, adjust the relative levels of the timing and compensation subcarriers and multiplex them, at the appropriate level, with the incoming multiplexed data signals for introduction to the tape system direct record amplifiers. These units will be described in detail by Gray Jensen, who designed and built them, as well as being shown diagrammatically in this report. This report continues the work described in reference (1), and it should be read as a supplement to that report rather than as an independent effort. It introduces changes in the multiplex system and test circuits employed in the tests and then repeats the tests from the earlier report that are required to illustrate the characteristics of the modified system.

Reversal of age-related neural timing delays with training

PubMed Central

Anderson, Samira; White-Schwoch, Travis; Parbery-Clark, Alexandra; Kraus, Nina

2013-01-01

Neural slowing is commonly noted in older adults, with consequences for sensory, motor, and cognitive domains. One of the deleterious effects of neural slowing is impairment of temporal resolution; older adults, therefore, have reduced ability to process the rapid events that characterize speech, especially in noisy environments. Although hearing aids provide increased audibility, they cannot compensate for deficits in auditory temporal processing. Auditory training may provide a strategy to address these deficits. To that end, we evaluated the effects of auditory-based cognitive training on the temporal precision of subcortical processing of speech in noise. After training, older adults exhibited faster neural timing and experienced gains in memory, speed of processing, and speech-in-noise perception, whereas a matched control group showed no changes. Training was also associated with decreased variability of brainstem response peaks, suggesting a decrease in temporal jitter in response to a speech signal. These results demonstrate that auditory-based cognitive training can partially restore age-related deficits in temporal processing in the brain; this plasticity in turn promotes better cognitive and perceptual skills. PMID:23401541

Femtosecond Lasers with Diode Pumping for Using in Precision Metrology and Optical Fiber Communication

DTIC Science & Technology

2008-11-24

folding angle of 32° to compensate astigmatism of the Brewster -cut Cr:F crystal. The gain crystal was 17 mm long and introduced positive group-delay...accomplished. For complete stabilization of the femtosecond comb one needs to control its absolute frequency. To realize this we use either angle - tilted...Kerr- lens mode-locking. To the best of our knowledge there is no published works on KLM ytterbium femtosecond lasers with multimode pumping. Stable

Water Vapor Measurement and Compensation in the Near and Mid-infrared with the Keck Interferometer Nuller

NASA Technical Reports Server (NTRS)

Koresko, Chris D.; Colavita, Mark M.; Serabyn, Eugene; Booth, Andrew; Garcia, Jean I.

2006-01-01

A viewgraph presentation describing the methods, motivation and methods for water vapor measurement with the Keck interferometer near and mid infrared radiation band is shown. The topics include: 1) Motivation: Why measure H2O?; 2) Method: How do we measure H2O?; 3) Data: Phase and Group Delays for the K and N Bands; 4) Predicted and Actual Nband Phase and Dispersion; and 5) Validation of Atmospheric Turbulence Models with KI Data.

Photonic sensing based on variation of propagation properties of photonic crystal fibres

NASA Astrophysics Data System (ADS)

Rothwell, John H.; Flavin, Dónal A.; MacPherson, William N.; Jones, Julian D.; Knight, Jonathan C.; Russell, Philip St. J.

2006-12-01

We report on a low-coherence interferometric scheme for the measurement of the strain and temperature dependences of group delay and dispersion in short, index-guiding, 'endlessly-single-mode' photonic crystal fibre elements in the 840 nm and 1550 nm regions. Based on the measurements, we propose two schemes for simultaneous strain and temperature measurement using a single unmodified PCF element, without a requirement for any compensating components, and we project the measurement accuracies of these schemes.

The time delay in strong gravitational lensing with Gauss-Bonnet correction

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

Man, Jingyun; Cheng, Hongbo, E-mail: jingyunman@mail.ecust.edu.cn, E-mail: hbcheng@ecust.edu.cn

2014-11-01

The time delay between two relativistic images in the strong gravitational lensing governed by Gauss-Bonnet gravity is studied. We make a complete analytical derivation of the expression of time delay in presence of Gauss-Bonnet coupling. With respect to Schwarzschild, the time delay decreases as a consequence of the shrinking of the photon sphere. As the coupling increases, the second term in the time delay expansion becomes more relevant. Thus time delay in strong limit encodes some new information about geometry in five-dimensional spacetime with Gauss-Bonnet correction.

29 CFR 553.226 - Training time.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 29 Labor 3 2011-07-01 2011-07-01 false Training time. 553.226 Section 553.226 Labor Regulations... Enforcement Employees of Public Agencies Tour of Duty and Compensable Hours of Work Rules § 553.226 Training time. (a) The general rules for determining the compensability of training time under the FLSA are set...

A primer for workers' compensation.

PubMed

Bible, Jesse E; Spengler, Dan M; Mir, Hassan R

2014-07-01

A physician's role within a workers' compensation injury extends far beyond just evaluation and treatment with several socioeconomic and psychological factors at play compared with similar injuries occurring outside of the workplace. Although workers' compensation statutes vary among states, all have several basic features with the overall goal of returning the injured worker to maximal function in the shortest time period, with the least residual disability and shortest time away from work. To help physicians unfamiliar with the workers' compensation process accomplish these goals. Review. Educational review. The streamlined review addresses the topics of why is workers' compensation necessary; what does workers' compensation cover; progression after work injury; impairment and maximum medical improvement, including how to use the sixth edition of American Medical Association's (AMA) Guides to the evaluation of permanent impairment (Guides); completion of work injury claim after impairment rating; independent medical evaluation; and causation. In the "no-fault" workers' compensation system, physicians play a key role in progressing the claim along and, more importantly, getting the injured worker back to work as soon as safely possible. Physicians should remain familiar with the workers' compensation process, along with how to properly use the AMA Guides. Copyright © 2014 Elsevier Inc. All rights reserved.

A flatness-based control approach to drug infusion for cardiac function regulation

NASA Astrophysics Data System (ADS)

Rigatos, Gerasimos; Zervos, Nikolaos; Melkikh, Alexey

2016-12-01

A new control method based on differential flatness theory is developed in this article, aiming at solving the problem of regulation of haemodynamic parameters, Actually control of the cardiac output (volume of blood pumped out by heart per unit of time) and of the arterial blood pressure is achieved through the administered infusion of cardiovascular drugs, such as dopamine and sodium nitroprusside. Time delays between the control inputs and the system's outputs are taken into account. Using the principle of dynamic extension, which means that by considering certain control inputs and their derivatives as additional state variables, a state-space description for the heart's function is obtained. It is proven that the dynamic model of the heart is a differentially flat one. This enables its transformation into a linear canonical and decoupled form, for which the design of a stabilizing feedback controller becomes possible. The proposed feedback controller is of proven stability and assures fast and accurate tracking of the reference setpoints by the outputs of the heart's dynamic model. Moreover, by using a Kalman Filter-based disturbances' estimator, it becomes possible to estimate in real-time and compensate for the model uncertainty and external perturbation inputs that affect the heart's model.

Application of discrete choice experiment to assess farmers' willingness to report swine diseases in the Red River Delta region, Vietnam.

PubMed

Pham, Hoa T T; Peyre, Marisa; Trinh, Tuyen Quang; Nguyen, Oanh Cong; Vu, Ton Dinh; Rukkwamsuk, Theera; Antoine-Moussiaux, Nicolas

2017-03-01

A discrete choice experiment (DCE) is carried out to value socio-economic factors influencing the farmer's decision to report swine diseases and to assess the willingness of farmers to report swine diseases. Data were collected between March and July 2015 in two provinces in the Red River Delta, Northern Vietnam, from 196 pig producers by face-to face interview. A conditional logit model is used to measure the relative importance of the socio-economic factors and calculate the expected probability of disease reporting under changes of levels of these factors. Results of the study indicated that the likelihood of compensation and the type of culling implemented (all or only unrecovered pigs) are the two most important factors influencing farmer reporting. Compensation level, movement restriction and delay in compensation payment also have significant impacts on farmer's decision to report animal disease but they are not as important as the above factors. Three different scenarios including changes in six different factors (attributes) are tested to predict probability of animal disease reporting. Under the current situation (uncertainty of being compensated), only 4% of the farmers would report swine disease outbreak to the official surveillance system if the culling policy involves all pigs in affected farms. This number is increased to 26% if culling in affected farms is restricted to unrecovered pigs only. Ensuring certainty of compensation increases reporting probability by up to 50% and 90% if all or only unrecovered pigs are destroyed, respectively. The results of this study are important for improving the performance and sustainability of swine disease surveillance system in Vietnam. Copyright © 2017 Elsevier B.V. All rights reserved.

Experimental investigation of a moving averaging algorithm for motion perpendicular to the leaf travel direction in dynamic MLC target tracking.

PubMed

Yoon, Jai-Woong; Sawant, Amit; Suh, Yelin; Cho, Byung-Chul; Suh, Tae-Suk; Keall, Paul

2011-07-01

In dynamic multileaf collimator (MLC) motion tracking with complex intensity-modulated radiation therapy (IMRT) fields, target motion perpendicular to the MLC leaf travel direction can cause beam holds, which increase beam delivery time by up to a factor of 4. As a means to balance delivery efficiency and accuracy, a moving average algorithm was incorporated into a dynamic MLC motion tracking system (i.e., moving average tracking) to account for target motion perpendicular to the MLC leaf travel direction. The experimental investigation of the moving average algorithm compared with real-time tracking and no compensation beam delivery is described. The properties of the moving average algorithm were measured and compared with those of real-time tracking (dynamic MLC motion tracking accounting for both target motion parallel and perpendicular to the leaf travel direction) and no compensation beam delivery. The algorithm was investigated using a synthetic motion trace with a baseline drift and four patient-measured 3D tumor motion traces representing regular and irregular motions with varying baseline drifts. Each motion trace was reproduced by a moving platform. The delivery efficiency, geometric accuracy, and dosimetric accuracy were evaluated for conformal, step-and-shoot IMRT, and dynamic sliding window IMRT treatment plans using the synthetic and patient motion traces. The dosimetric accuracy was quantified via a tgamma-test with a 3%/3 mm criterion. The delivery efficiency ranged from 89 to 100% for moving average tracking, 26%-100% for real-time tracking, and 100% (by definition) for no compensation. The root-mean-square geometric error ranged from 3.2 to 4.0 mm for moving average tracking, 0.7-1.1 mm for real-time tracking, and 3.7-7.2 mm for no compensation. The percentage of dosimetric points failing the gamma-test ranged from 4 to 30% for moving average tracking, 0%-23% for real-time tracking, and 10%-47% for no compensation. The delivery efficiency of moving average tracking was up to four times higher than that of real-time tracking and approached the efficiency of no compensation for all cases. The geometric accuracy and dosimetric accuracy of the moving average algorithm was between real-time tracking and no compensation, approximately half the percentage of dosimetric points failing the gamma-test compared with no compensation.

A Real-Time Brain-Machine Interface Combining Motor Target and Trajectory Intent Using an Optimal Feedback Control Design

PubMed Central

Shanechi, Maryam M.; Williams, Ziv M.; Wornell, Gregory W.; Hu, Rollin C.; Powers, Marissa; Brown, Emery N.

2013-01-01

Real-time brain-machine interfaces (BMI) have focused on either estimating the continuous movement trajectory or target intent. However, natural movement often incorporates both. Additionally, BMIs can be modeled as a feedback control system in which the subject modulates the neural activity to move the prosthetic device towards a desired target while receiving real-time sensory feedback of the state of the movement. We develop a novel real-time BMI using an optimal feedback control design that jointly estimates the movement target and trajectory of monkeys in two stages. First, the target is decoded from neural spiking activity before movement initiation. Second, the trajectory is decoded by combining the decoded target with the peri-movement spiking activity using an optimal feedback control design. This design exploits a recursive Bayesian decoder that uses an optimal feedback control model of the sensorimotor system to take into account the intended target location and the sensory feedback in its trajectory estimation from spiking activity. The real-time BMI processes the spiking activity directly using point process modeling. We implement the BMI in experiments consisting of an instructed-delay center-out task in which monkeys are presented with a target location on the screen during a delay period and then have to move a cursor to it without touching the incorrect targets. We show that the two-stage BMI performs more accurately than either stage alone. Correct target prediction can compensate for inaccurate trajectory estimation and vice versa. The optimal feedback control design also results in trajectories that are smoother and have lower estimation error. The two-stage decoder also performs better than linear regression approaches in offline cross-validation analyses. Our results demonstrate the advantage of a BMI design that jointly estimates the target and trajectory of movement and more closely mimics the sensorimotor control system. PMID:23593130

Transmission mode adaptive beamforming for planar phased arrays and its application to 3D ultrasonic transcranial imaging

NASA Astrophysics Data System (ADS)

Shapoori, Kiyanoosh; Sadler, Jeffrey; Wydra, Adrian; Malyarenko, Eugene; Sinclair, Anthony; Maev, Roman G.

2013-03-01

A new adaptive beamforming method for accurately focusing ultrasound behind highly scattering layers of human skull and its application to 3D transcranial imaging via small-aperture planar phased arrays are reported. Due to its undulating, inhomogeneous, porous, and highly attenuative structure, human skull bone severely distorts ultrasonic beams produced by conventional focusing methods in both imaging and therapeutic applications. Strong acoustical mismatch between the skull and brain tissues, in addition to the skull's undulating topology across the active area of a planar ultrasonic probe, could cause multiple reflections and unpredictable refraction during beamforming and imaging processes. Such effects could significantly deflect the probe's beam from the intended focal point. Presented here is a theoretical basis and simulation results of an adaptive beamforming method that compensates for the latter effects in transmission mode, accompanied by experimental verification. The probe is a custom-designed 2 MHz, 256-element matrix array with 0.45 mm element size and 0.1mm kerf. Through its small footprint, it is possible to accurately measure the profile of the skull segment in contact with the probe and feed the results into our ray tracing program. The latter calculates the new time delay patterns adapted to the geometrical and acoustical properties of the skull phantom segment in contact with the probe. The time delay patterns correct for the refraction at the skull-brain boundary and bring the distorted beam back to its intended focus. The algorithms were implemented on the ultrasound open-platform ULA-OP (developed at the University of Florence).

SU-E-T-357: Electronic Compensation Technique to Deliver Total Body Dose

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

Lakeman, T; Wang, I; Podgorsak, M

Purpose: Total body irradiation (TBI) uses large parallel-opposed radiation fields to suppress the patient’s immune system and eradicate the residual cancer cells in preparation of recipient for bone marrow transplant. The manual placement of lead compensators has conventionally been used to compensate for the varying thickness through the entire body in large-field TBI. The goal of this study is to pursue utilizing the modern electronic compensation technique to more accurately and efficiently deliver dose to patients in need of TBI. Methods: Treatment plans utilizing electronic compensation to deliver a total body dose were created retrospectively for patients for whom CTmore » data had been previously acquired. Each treatment plan includes two, specifically weighted, pair of opposed fields. One pair of open, large fields (collimator=45°), to encompass the patient’s entire anatomy, and one pair of smaller fields (collimator=0°) focused only on the thicker midsection of the patient. The optimal fluence for each one of the smaller fields was calculated at a patient specific penetration depth. Irregular surface compensators provide a more uniform dose distribution within the smaller opposed fields. Results: Dose-volume histograms (DVH) were calculated for the evaluating the electronic compensation technique. In one case, the maximum body doses calculated from the DVH were reduced from the non-compensated 195.8% to 165.3% in the electronically compensated plans, indicating a more uniform dose with the region of electronic compensation. The mean body doses calculated from the DVH were also reduced from the non-compensated 120.6% to 112.7% in the electronically compensated plans, indicating a more accurate delivery of the prescription dose. All calculated monitor units were well within clinically acceptable limits. Conclusion: Electronic compensation technique for TBI will not substantially increase the beam on time while it can significantly reduce the compensator setup time and the potential risk of errors in manually placing lead compensators.« less

Self-compensating design for reduction of timing and leakage sensitivity to systematic pattern dependent variation

NASA Astrophysics Data System (ADS)

Gupta, Puneet; Kahng, Andrew B.; Kim, Youngmin; Sylvester, Dennis

2006-03-01

Focus is one of the major sources of linewidth variation. CD variation caused by defocus is largely systematic after the layout is finished. In particular, dense lines "smile" through focus while isolated lines "frown" in typical Bossung plots. This well-defined systematic behavior of focus-dependent CD variation allows us to develop a self-compensating design methodology. In this work, we propose a novel design methodology that allows explicit compensation of focus-dependent CD variation, either within a cell (self-compensated cells) or across cells in a critical path (self-compensated design). By creating iso and dense variants for each library cell, we can achieve designs that are more robust to focus variation. Optimization with a mixture of iso and dense cell variants is possible both for area and leakage power, with the latter providing an interesting complement to existing leakage reduction techniques such as dual-Vth. We implement both heuristic and Mixed-Integer Linear Programming (MILP) solution methods to address this optimization, and experimentally compare their results. Our results indicate that designing with a self-compensated cell library incurs ~12% area penalty and ~6% leakage increase over original layouts while compensating for focus-dependent CD variation (i.e., the design meets timing constraints across a large range of focus variation). We observe ~27% area penalty and ~7% leakage increase at the worst-case defocus condition using only single-pitch cells. The area penalty of circuits after using either the heuristic or MILP optimization approach is reduced to ~3% while maintaining timing. We also apply our optimizations to leakage, which traditionally shows very large variability due to its exponential relationship with gate CD. We conclude that a mixed iso/dense library combined with a sensitivity-based optimization approach yields much better area/timing/leakage tradeoffs than using a self-compensated cell library alone. Self-compensated design shows an average of 25% leakage reduction at the worst defocus condition for the benchmark designs that we have studied.

Study on the balance mechanism of interests in marine ecological compensation

NASA Astrophysics Data System (ADS)

Qian, Cao; Hongjun, Cao; Hongcai, Yan

2017-11-01

From the point of view of game theory and through establishing the game model of the subject and object of marine ecological compensation, this paper makes a research on the balance mechanism the interests of marine ecological compensation. The results show that the optimal amount of capital investment of environmental protection enterprises for ecological compensation depends not only on energy conservation and emission reduction of itself as well as competition enterprises, but also on the policy support for ecological compensation. At the same time, it is limited by the public’s understanding and acceptance for ecological compensation.

Fixed order dynamic compensation for multivariable linear systems

NASA Technical Reports Server (NTRS)

Kramer, F. S.; Calise, A. J.

1986-01-01

This paper considers the design of fixed order dynamic compensators for multivariable time invariant linear systems, minimizing a linear quadratic performance cost functional. Attention is given to robustness issues in terms of multivariable frequency domain specifications. An output feedback formulation is adopted by suitably augmenting the system description to include the compensator states. Either a controller or observer canonical form is imposed on the compensator description to reduce the number of free parameters to its minimal number. The internal structure of the compensator is prespecified by assigning a set of ascending feedback invariant indices, thus forming a Brunovsky structure for the nominal compensator.

Resolution Enhancement In Ultrasonic Imaging By A Time-Varying Filter

NASA Astrophysics Data System (ADS)

Ching, N. H.; Rosenfeld, D.; Braun, M.

1987-09-01

The study reported here investigates the use of a time-varying filter to compensate for the spreading of ultrasonic pulses due to the frequency dependence of attenuation by tissues. The effect of this pulse spreading is to degrade progressively the axial resolution with increasing depth. The form of compensation required to correct for this effect is impossible to realize exactly. A novel time-varying filter utilizing a bank of bandpass filters is proposed as a realizable approximation of the required compensation. The performance of this filter is evaluated by means of a computer simulation. The limits of its application are discussed. Apart from improving the axial resolution, and hence the accuracy of axial measurements, the compensating filter could be used in implementing tissue characterization algorithms based on attenuation data.

Is Biology Destiny? Birth Weight and Differential Parental Treatment

PubMed Central

Hsin, Amy

2016-01-01

Time diaries of sibling pairs from the PSID-CDS are used to determine whether maternal time investments compensate for or reinforce birth-weight differences among children. The findings demonstrate that the direction and degree of differential treatment vary by mother's education. Less-educated mothers devote more total time and more educationally oriented time to heavier-birth-weight children, whereas better-educated mothers devote more total and more educationally oriented time to lower-birth-weight children. The compensating effects observed among highly educated mothers are substantially larger than the reinforcing effects among the least-educated mothers. The findings show that families redistribute resources in ways that both compensate for and exacerbate early-life disadvantages. PMID:22865101

Deferred Compensation as a Method for Payment of Part-Time Dental Faculty Members.

ERIC Educational Resources Information Center

Bentz, George H.; And Others

1980-01-01

By using a deferred compensation plan, dental schools can provide the part-time educator with a greater return at a time when that money will be of more benefit. Through a contractual agreement, a plan can be constructed that can significantly increase the real value of part-time earnings. (Author/MLW)

Real-Time Imaging System for the OpenPET

NASA Astrophysics Data System (ADS)

Tashima, Hideaki; Yoshida, Eiji; Kinouchi, Shoko; Nishikido, Fumihiko; Inadama, Naoko; Murayama, Hideo; Suga, Mikio; Haneishi, Hideaki; Yamaya, Taiga

2012-02-01

The OpenPET and its real-time imaging capability have great potential for real-time tumor tracking in medical procedures such as biopsy and radiation therapy. For the real-time imaging system, we intend to use the one-pass list-mode dynamic row-action maximum likelihood algorithm (DRAMA) and implement it using general-purpose computing on graphics processing units (GPGPU) techniques. However, it is difficult to make consistent reconstructions in real-time because the amount of list-mode data acquired in PET scans may be large depending on the level of radioactivity, and the reconstruction speed depends on the amount of the list-mode data. In this study, we developed a system to control the data used in the reconstruction step while retaining quantitative performance. In the proposed system, the data transfer control system limits the event counts to be used in the reconstruction step according to the reconstruction speed, and the reconstructed images are properly intensified by using the ratio of the used counts to the total counts. We implemented the system on a small OpenPET prototype system and evaluated the performance in terms of the real-time tracking ability by displaying reconstructed images in which the intensity was compensated. The intensity of the displayed images correlated properly with the original count rate and a frame rate of 2 frames per second was achieved with average delay time of 2.1 s.

Effect of Time Delay on Recognition Memory for Pictures: The Modulatory Role of Emotion

PubMed Central

Wang, Bo

2014-01-01

This study investigated the modulatory role of emotion in the effect of time delay on recognition memory for pictures. Participants viewed neutral, positive and negative pictures, and took a recognition memory test 5 minutes, 24 hours, or 1 week after learning. The findings are: 1) For neutral, positive and negative pictures, overall recognition accuracy in the 5-min delay did not significantly differ from that in the 24-h delay. For neutral and positive pictures, overall recognition accuracy in the 1-week delay was lower than in the 24-h delay; for negative pictures, overall recognition in the 24-h and 1-week delay did not significantly differ. Therefore negative emotion modulates the effect of time delay on recognition memory, maintaining retention of overall recognition accuracy only within a certain frame of time. 2) For the three types of pictures, recollection and familiarity in the 5-min delay did not significantly differ from that in the 24-h and the 1-week delay. Thus emotion does not appear to modulate the effect of time delay on recollection and familiarity. However, recollection in the 24-h delay was higher than in the 1-week delay, whereas familiarity in the 24-h delay was lower than in the 1-week delay. PMID:24971457

Compensators: An alternative IMRT delivery technique

PubMed Central

Chang, Sha X.; Cullip, Timothy J.; Deschesne, Katharin M.; Miller, Elizabeth P.; Rosenman, Julian G.

2004-01-01

Seven years of experience in compensator intensity‐modulated radiotherapy (IMRT) clinical implementation are presented. An inverse planning dose optimization algorithm was used to generate intensity modulation maps, which were delivered via either the compensator or segmental multileaf collimator (MLC) IMRT techniques. The in‐house developed compensator‐IMRT technique is presented with the focus on several design issues. The dosimetry of the delivery techniques was analyzed for several clinical cases. The treatment time for both delivery techniques on Siemens accelerators was retrospectively analyzed based on the electronic treatment record in LANTIS for 95 patients. We found that the compensator technique consistently took noticeably less time for treatment of equal numbers of fields compared to the segmental technique. The typical time needed to fabricate a compensator was 13 min, 3 min of which was manual processing. More than 80% of the approximately 700 compensators evaluated had a maximum deviation of less than 5% from the calculation in intensity profile. Seventy‐two percent of the patient treatment dosimetry measurements for 340 patients have an error of no more than 5%. The pros and cons of different IMRT compensator materials are also discussed. Our experience shows that the compensator‐IMRT technique offers robustness, excellent intensity modulation resolution, high treatment delivery efficiency, simple fabrication and quality assurance (QA) procedures, and the flexibility to be used in any teletherapy unit. PACS numbers: 87.53Mr, 87.53Tf PMID:15753937

The Role of Compensation Criteria to Minimize Face-Time Bias and Support Faculty Career Flexibility: An Approach to Enhance Career Satisfaction in Academic Pathology.

PubMed

Howell, Lydia Pleotis; Elsbach, Kimberly D; Villablanca, Amparo C

2016-01-01

Work-life balance is important to recruitment and retention of the younger generation of medical faculty, but medical school flexibility policies have not been fully effective. We have reported that our school's policies are underutilized due to faculty concerns about looking uncommitted to career or team. Since policies include leaves and accommodations that reduce physical presence, faculty may fear "face-time bias," which negatively affects evaluation of those not "seen" at work. Face-time bias is reported to negatively affect salary and career progress. We explored face-time bias on a leadership level and described development of compensation criteria intended to mitigate face-time bias, raise visibility, and reward commitment and contribution to team/group goals. Leaders from 6 partner departments participated in standardized interviews and group meetings. Ten compensation plans were analyzed, and published literature was reviewed. Leaders did not perceive face-time issues but saw team pressure and perception of availability as performance motivators. Compensation plans were multifactor productivity based with many quantifiable criteria; few addressed team contributions. Using these findings, novel compensation criteria were developed based on a published model to mitigate face-time bias associated with team perceptions. Criteria for organizational citizenship to raise visibility and reward group outcomes were included. We conclude that team pressure and perception of availability have the potential to lead to bias and may contribute to underuse of flexibility policies. Recognizing organizational citizenship and cooperative effort via specific criteria in a compensation plan may enhance a culture of flexibility. These novel criteria have been effective in one pilot department.

The Effects of Age and Preoral Sensorimotor Cues on Anticipatory Mouth Movement During Swallowing

PubMed Central

Moon, Jerald B.; Goodman, Shawn S.

2016-01-01

Purpose The aim of this study was to investigate the effects of preoral sensorimotor cues on anticipatory swallowing/eating-related mouth movements in older and younger adults. It was hypothesized that these cues are essential to timing anticipatory oral motor patterns, and these movements are delayed in older as compared with younger adults. Method Using a 2 × 2 repeated-measures design, eating-related lip, jaw, and hand movements were recorded from 24 healthy older (ages 70–85 years) and 24 healthy younger (ages 18–30 years) adults under 4 conditions: typical self-feeding, typical assisted feeding (proprioceptive loss), sensory-loss self-feeding (auditory and visual loss/degradation), and sensory-loss assisted feeding (loss/degradation of all cues). Results All participants demonstrated anticipatory mouth opening. The absence of proprioception delayed lip-lowering onset, and sensory loss more negatively affected offset. Given at least 1 preoral sensorimotor cue, older adults initiated movement earlier than younger adults. Conclusions Preoral sensorimotor information influences anticipatory swallowing/eating-related mouth movements, highlighting the importance of these cues. Earlier movement in older adults may be a compensation, facilitating safe swallowing given other age-related declines. Further research is needed to determine if the negative impact of cue removal may be further exacerbated in a nonhealthy system (e.g., presence of dysphagia or disease), potentially increasing swallowing- and eating-related risks. PMID:26540553

Electronic compensation technique to deliver a total body dose

NASA Astrophysics Data System (ADS)

Lakeman, Tara E.

Purpose: Total body irradiation (TBI) uses large parallel-opposed radiation fields to suppress the patient's immune system and eradicate the residual cancer cells in preparation of recipient for bone marrow transplant. The manual placement of lead compensators has been conventionally used to compensate for the varying thickness throughout the body in large-field TBI. The goal of this study is to pursue utilizing the modern electronic compensation technique to more accurately and efficiently deliver dose to patients in need of TBI. Method: Treatment plans utilizing the electronic compensation to deliver a total body dose were created retrospectively for patients for whom CT data had been previously acquired. Each treatment plan includes two pair of parallel opposed fields. One pair of large fields is used to encompass the majority of the patient's anatomy. The other pair are very small open fields focused only on the thin bottom portion of the patient's anatomy, which requires much less radiation than the rest of the body to reach 100% of the prescribed dose. A desirable fluence pattern was manually painted within each of the larger fields for each patient to provide a more uniform distribution. Results: Dose-volume histograms (DVH) were calculated for evaluating the electronic compensation technique. In the electronically compensated plans, the maximum body doses calculated from the DVH were reduced from the conventionally-compensated plans by an average of 15%, indicating a more uniform dose. The mean body doses calculated from the electronically compensated DVH remained comparable to that of the conventionally-compensated plans, indicating an accurate delivery of the prescription dose using electronic compensation. All calculated monitor units were within clinically acceptable limits. Conclusion: Electronic compensation technique for TBI will not increase the beam on time beyond clinically acceptable limits while it can substantially reduce the compensator setup time and the potential risk of errors in manually placing lead compensators.

Compensation for Work-Related Injury and Illness

DTIC Science & Technology

1992-01-01

Falls Church, Va., 1990. U.S. Chamber of Commerce , 1990 Analysis of Workers’ Compensation Laws, Washington, D.C., 1990. U.S. Department of Defense...both begin the time limits at the date of discovery of the disease. The remaining states have time limits of one year (U.S. Chamber of Commerce , 1990...allowable according to state law (U.S. Chamber of Commerce , 1990). Workers’ compensation benefits are nontaxable income. Total Disability In the case of

Angular dependence of EWS time delay for photoionization of @Xe

NASA Astrophysics Data System (ADS)

Mandal, Ankur; Deshmukh, Pranawa; Kheifets, Anatoli; Dolmatov, Valeriy; Manson, Steven

2017-04-01

Interference between photoionization channels leads to angular dependence in photoionization time delay. Angular dependence is found to be a common effect for two-photon absorption experiments very recently. The effect of confinement on the time delay where each partial wave contributions to the ionization are studied. In this work we report angular dependence and confinement effects on Eisenbud-Wigner-Smith (EWS) time delay in atomic photoionization. Using and we computed the EWS time delay for free and confined Xe atom for photoionization from inner 4d3/2 and 4d5/2 and outer 5p1/2 and 5p3/2 subshells at various angles. The calculated EWS time delay is few tens to few hundreds of attoseconds (10-18 second). The photoionization time delay for @Xe follows that in the free Xe atom on which the confinement oscillations are built. The present work reveals the effect of confinement on the photoionization time delay at different angles between photoelectron ejection and the photon polarization.

Crash testing difference-smoothing algorithm on a large sample of simulated light curves from TDC1

NASA Astrophysics Data System (ADS)

Rathna Kumar, S.

2017-09-01

In this work, we propose refinements to the difference-smoothing algorithm for the measurement of time delay from the light curves of the images of a gravitationally lensed quasar. The refinements mainly consist of a more pragmatic approach to choose the smoothing time-scale free parameter, generation of more realistic synthetic light curves for the estimation of time delay uncertainty and using a plot of normalized χ2 computed over a wide range of trial time delay values to assess the reliability of a measured time delay and also for identifying instances of catastrophic failure. We rigorously tested the difference-smoothing algorithm on a large sample of more than thousand pairs of simulated light curves having known true time delays between them from the two most difficult 'rungs' - rung3 and rung4 - of the first edition of Strong Lens Time Delay Challenge (TDC1) and found an inherent tendency of the algorithm to measure the magnitude of time delay to be higher than the true value of time delay. However, we find that this systematic bias is eliminated by applying a correction to each measured time delay according to the magnitude and sign of the systematic error inferred by applying the time delay estimator on synthetic light curves simulating the measured time delay. Following these refinements, the TDC performance metrics for the difference-smoothing algorithm are found to be competitive with those of the best performing submissions of TDC1 for both the tested 'rungs'. The MATLAB codes used in this work and the detailed results are made publicly available.

Performance Analysis of a De-correlated Modified Code Tracking Loop for Synchronous DS-CDMA System under Multiuser Environment

NASA Astrophysics Data System (ADS)

Wu, Ya-Ting; Wong, Wai-Ki; Leung, Shu-Hung; Zhu, Yue-Sheng

This paper presents the performance analysis of a De-correlated Modified Code Tracking Loop (D-MCTL) for synchronous direct-sequence code-division multiple-access (DS-CDMA) systems under multiuser environment. Previous studies have shown that the imbalance of multiple access interference (MAI) in the time lead and time lag portions of the signal causes tracking bias or instability problem in the traditional correlating tracking loop like delay lock loop (DLL) or modified code tracking loop (MCTL). In this paper, we exploit the de-correlating technique to combat the MAI at the on-time code position of the MCTL. Unlike applying the same technique to DLL which requires an extensive search algorithm to compensate the noise imbalance which may introduce small tracking bias under low signal-to-noise ratio (SNR), the proposed D-MCTL has much lower computational complexity and exhibits zero tracking bias for the whole range of SNR, regardless of the number of interfering users. Furthermore, performance analysis and simulations based on Gold codes show that the proposed scheme has better mean square tracking error, mean-time-to-lose-lock and near-far resistance than the other tracking schemes, including traditional DLL (T-DLL), traditional MCTL (T-MCTL) and modified de-correlated DLL (MD-DLL).

The epidemiology of malpractice claims in primary care: a systematic review

PubMed Central

Wallace, E; Lowry, J; Smith, S M; Fahey, T

2013-01-01

Objectives The aim of this systematic review was to examine the epidemiology of malpractice claims in primary care. Design A computerised systematic literature search was conducted. Studies were included if they reported original data (≥10 cases) pertinent to malpractice claims, were based in primary care and were published in the English language. Data were synthesised using a narrative approach. Setting Primary care. Participants Malpractice claimants. Primary outcome Malpractice claim (defined as a written demand for compensation for medical injury). We recorded: medical misadventure cited in claims, missed/delayed diagnoses cited in claims, outcome of claims, prevalence of claims and compensation awarded to claimants. Results Of the 7152 articles retrieved by electronic search, a total of 34 studies met the inclusion criteria and were included in the narrative analysis. Twenty-eight studies presented data from medical indemnity malpractice claims databases and six studies presented survey data. Fifteen studies were based in the USA, nine in the UK, seven in Australia, one in Canada and two in France. The commonest medical misadventure resulting in claims was failure to or delay in diagnosis, which represented 26–63% of all claims across included studies. Common missed or delayed diagnoses included cancer and myocardial infarction in adults and meningitis in children. Medication error represented the second commonest domain representing 5.6–20% of all claims across included studies. The prevalence of malpractice claims in primary care varied across countries. In the USA and Australia when compared with other clinical disciplines, general practice ranked in the top five specialties accounting for the most claims, representing 7.6–20% of all claims. However, the majority of claims were successfully defended. Conclusions This review of malpractice claims in primary care highlights diagnosis and medication error as areas to be prioritised in developing educational strategies and risk management systems. PMID:23869100

A Multi-Center Space Data System Prototype Based on CCSDS Standards

NASA Technical Reports Server (NTRS)

Rich, Thomas M.

2016-01-01

Deep space missions beyond earth orbit will require new methods of data communications in order to compensate for increasing Radio Frequency (RF) propagation delay. The Consultative Committee for Space Data Systems (CCSDS) standard protocols Spacecraft Monitor & Control (SM&C), Asynchronous Message Service (AMS), and Delay/Disruption Tolerant Networking (DTN) provide such a method. However, the maturity level of this protocol stack is insufficient for mission inclusion at this time. This Space Data System prototype is intended to provide experience which will raise the Technical Readiness Level (TRL) of this protocol set. In order to reduce costs, future missions can take advantage of these standard protocols, which will result in increased interoperability between control centers. This prototype demonstrates these capabilities by implementing a realistic space data system in which telemetry is published to control center applications at the Jet Propulsion Lab (JPL), the Marshall Space Flight Center (MSFC), and the Johnson Space Center (JSC). Reverse publishing paths for commanding from each control center are also implemented. The target vehicle consists of realistic flight computer hardware running Core Flight Software (CFS) in the integrated Power, Avionics, and Power (iPAS) Pathfinder Lab at JSC. This prototype demonstrates a potential upgrade path for future Deep Space Network (DSN) modification, in which the automatic error recovery and communication gap compensation capabilities of DTN would be exploited. In addition, SM&C provides architectural flexibility by allowing new service providers and consumers to be added efficiently anywhere in the network using the common interface provided by SM&C's Message Abstraction Layer (MAL). In FY 2015, this space data system was enhanced by adding telerobotic operations capability provided by the Robot API Delegate (RAPID) family of protocols developed at NASA. RAPID is one of several candidates for consideration and inclusion in a new international standard being developed by the CCSDS Telerobotic Operations Working Group. Software gateways for the purpose of interfacing RAPID messages with the existing SM&C based infrastructure were developed. Telerobotic monitor, control, and bridge applications were written in the RAPID framework, which were then tailored to the NAO telerobotic test article hardware, a product of Aldebaran Robotics.

An idea whose time has come: Compensation for vaccine-related injuries and death in India.

PubMed

Nadimpally, Sarojini; Banerjee, Sneha; Venkatachalam, Deepa; Bhagianadh, Divya

2017-01-01

This paper emphasises the urgent need for a compensation policy for those affected by adverse events following immunisation in India. In the absence of such a mechanism in the country, people claim compensation by taking recourse to tort law and have to face the ensuing uncertainty and challenges with regard to the award of compensation. The paper argues that people should be provided compensation in the event of death and serious adverse events following compulsory immunisation, irrespective of whether there is a causal association between the adverse event and the vaccine, on the basis of no fault compensation.

a Transplantable Compensation Scheme for the Effect of the Radiance from the Interior of a Camera on the Accuracy of Temperature Measurement

NASA Astrophysics Data System (ADS)

Dong, Shidu; Yang, Xiaofan; He, Bo; Liu, Guojin

2006-11-01

Radiance coming from the interior of an uncooled infrared camera has a significant effect on the measured value of the temperature of the object. This paper presents a three-phase compensation scheme for coping with this effect. The first phase acquires the calibration data and forms the calibration function by least square fitting. Likewise, the second phase obtains the compensation data and builds the compensation function by fitting. With the aid of these functions, the third phase determines the temperature of the object in concern from any given ambient temperature. It is known that acquiring the compensation data of a camera is very time-consuming. For the purpose of getting the compensation data at a reasonable time cost, we propose a transplantable scheme. The idea of this scheme is to calculate the ratio between the central pixel’s responsivity of the child camera to the radiance from the interior and that of the mother camera, followed by determining the compensation data of the child camera using this ratio and the compensation data of the mother camera Experimental results show that either of the child camera and the mother camera can measure the temperature of the object with an error of no more than 2°C.

Comparison of delay enhancement mechanisms for SBS-based slow light systems.

PubMed

Schneider, Thomas; Henker, Ronny; Lauterbach, Kai-Uwe; Junker, Markus

2007-07-23

We compare two simple mechanisms for the enhancement of the time delay in slow light systems. Both are based on the superposition of the Brillouin gain with additional loss. As we will show in theory and experiment if two losses are placed at the wings of a SBS gain, contrary to other methods, the loss power increases the time delay. This leads to higher delay times at lower optical powers and to an increase of the zero gain delay of more than 50%. With this method we achieved a time delay of more than 120ns for pulses with a temporal width of 30ns. To the best of our knowledge, this is the highest time delay in just one fiber spool. Beside the enhancement of the time delay the method could have the potential to decrease the pulse distortions for high bit rate signals.

Global model of zenith tropospheric delay proposed based on EOF analysis

NASA Astrophysics Data System (ADS)

Sun, Langlang; Chen, Peng; Wei, Erhu; Li, Qinzheng

2017-07-01

Tropospheric delay is one of the main error budgets in Global Navigation Satellite System (GNSS) measurements. Many empirical correction models have been developed to compensate this delay, and models which do not require meteorological parameters have received the most attention. This study established a global troposphere zenith total delay (ZTD) model, called Global Empirical Orthogonal Function Troposphere (GEOFT), based on the empirical orthogonal function (EOF, also known as geographically weighted PCAs) analysis method and the Global Geodetic Observing System (GGOS) Atmosphere data from 2012 to 2015. The results showed that ZTD variation could be well represented by the characteristics of the EOF base function Ek and associated coefficients Pk. Here, E1 mainly signifies the equatorial anomaly; E2 represents north-south asymmetry, and E3 and E4 reflects regional variation. Moreover, P1 mainly reflects annual and semiannual variation components; P2 and P3 mainly contains annual variation components, and P4 displays semiannual variation components. We validated the proposed GEOFT model using tropospheric delay data of GGOS ZTD grid data and the tropospheric product of the International GNSS Service (IGS) over the year 2016. The results showed that GEOFT model has high accuracy with bias and RMS of -0.3 and 3.9 cm, respectively, with respect to the GGOS ZTD data, and of -0.8 and 4.1 cm, respectively, with respect to the global IGS tropospheric product. The accuracy of GEOFT demonstrating that the use of the EOF analysis method to characterize ZTD variation is reasonable.

Impact of Partial Time Delay on Temporal Dynamics of Watts-Strogatz Small-World Neuronal Networks

NASA Astrophysics Data System (ADS)

Yan, Hao; Sun, Xiaojuan

2017-06-01

In this paper, we mainly discuss effects of partial time delay on temporal dynamics of Watts-Strogatz (WS) small-world neuronal networks by controlling two parameters. One is the time delay τ and the other is the probability of partial time delay pdelay. Temporal dynamics of WS small-world neuronal networks are discussed with the aid of temporal coherence and mean firing rate. With the obtained simulation results, it is revealed that for small time delay τ, the probability pdelay could weaken temporal coherence and increase mean firing rate of neuronal networks, which indicates that it could improve neuronal firings of the neuronal networks while destroying firing regularity. For large time delay τ, temporal coherence and mean firing rate do not have great changes with respect to pdelay. Time delay τ always has great influence on both temporal coherence and mean firing rate no matter what is the value of pdelay. Moreover, with the analysis of spike trains and histograms of interspike intervals of neurons inside neuronal networks, it is found that the effects of partial time delays on temporal coherence and mean firing rate could be the result of locking between the period of neuronal firing activities and the value of time delay τ. In brief, partial time delay could have great influence on temporal dynamics of the neuronal networks.

Piloted simulator study of allowable time delay in pitch flight control system of a transport airplane with negative static stability

NASA Technical Reports Server (NTRS)

Grantham, William D.; Smith, Paul M.; Person, Lee H., Jr.; Meyer, Robert T.; Tingas, Stephen A.

1987-01-01

A piloted simulation study was conducted to determine the permissible time delay in the flight control system of a 10-percent statically unstable transport airplane during cruise flight conditions. The math model used for the simulation was a derivative Lockheed L-1011 wide-body jet transport. Data were collected and analyzed from a total of 137 cruising flights in both calm- and turbulent-air conditions. Results of this piloted simulation study verify previous findings that show present military specifications for allowable control-system time delay may be too stringent when applied to transport-size airplanes. Also, the degree of handling-qualities degradation due to time delay is shown to be strongly dependent on the source of the time delay in an advanced flight control system. Maximum allowable time delay for each source of time delay in the control system, in addition to a less stringent overall maximum level of time delay, should be considered for large aircraft. Preliminary results also suggest that adverse effects of control-system time delay may be at least partially offset by variations in control gearing. It is recommended that the data base include different airplane baselines, control systems, and piloting tasks with many pilots participating, so that a reasonable set of limits for control-system time delay can be established to replace the military specification limits currently being used.

Log amplifier with pole-zero compensation

DOEpatents

Brookshier, W.

1985-02-08

A logarithmic amplifier circuit provides pole-zero compensation for improved stability and response time over 6-8 decades of input signal frequency. The amplifer circuit includes a first operational amplifier with a first feedback loop which includes a second, inverting operational amplifier in a second feedstock loop. The compensated output signal is provided by the second operational amplifier with the log elements, i.e., resistors, and the compensating capacitors in each of the feedback loops having equal values so that each break point is offset by a compensating break point or zero.

Log amplifier with pole-zero compensation

DOEpatents

Brookshier, William

1987-01-01

A logarithmic amplifier circuit provides pole-zero compensation for improved stability and response time over 6-8 decades of input signal frequency. The amplifier circuit includes a first operational amplifier with a first feedback loop which includes a second, inverting operational amplifier in a second feedback loop. The compensated output signal is provided by the second operational amplifier with the log elements, i.e., resistors, and the compensating capacitors in each of the feedback loops having equal values so that each break point or pole is offset by a compensating break point or zero.

29 CFR 785.34 - Effect of section 4 of the Portal-to-Portal Act.

Code of Federal Regulations, 2010 CFR

2010-07-01

... failure to pay the minimum wage or overtime compensation for time spent in “walking, riding, or traveling... employee is employed to perform either prior to the time on any particular workday at which such employee... from time clock to work-bench) need not be counted as working time unless it is compensable by contract...

Four-fold increase in users of time-wavelength division multiplexing (TWDM) passive optical network (PON) by delayed optical amplitude modulation (AM) upstream

NASA Astrophysics Data System (ADS)

Kachhatiya, Vivek; Prince, Shanthi

2016-12-01

In this paper, we have proposed and simulated optical time division multiplexed passive optical network (TDM-PON) using delayed optical amplitude modulation (AM). Eight upstream wavelengths are demonstrated to show optical time wavelength division multiplexed (TWDM) by combining optical network units (ONU) users data at the remote node (RN). Each ONU generates 2.5 Gb/s user data, and it is modulated using novel return to zero (RZ) delayed AM. Optical TDM aggregates 10 Gb/s data per wavelength from four 2.5 Gb/s upstream user data, which facilitates four different ONU data on the same wavelength as 10 Gb/s per upstream wavelength and, simplify the laser requirements (2.5 Gb/s) at each optical network unit (ONU) transmitter. Upstream optical TWDM-PON is investigated for eight wavelengths with wavelength spacing of 100 GHz. Novel optical TDM for upstream increased the number of the simultaneous user to fourfold from conventional TWDM-PON using delayed AM with a high-quality-factor of received signal. Despite performance degradation due to different fiber reach and dispersion compensation technique, Optical TWDM link shows significant improvement regarding receiver sensitivity when compared with common TWDM link. Hence, it offers optimistic thinking to show optical TDM at this phase as one of the future direction, where complex digital signal processing (DSP) and coherent optical communication are frequently demonstrated to serve the access network. Downstream side conventional TWDM eight wavelengths are multiplexed at the OLT and sent downstream to serve distributed tunable ONU receivers through an optical distribution network (ODN). Each downstream wavelengths are modulated at the peak rate of 10 Gb/s using non-return to zero external modulation (NRZ-EM). The proposed architecture is cost efficient and supports high data rates as well as ;pay as you grow; network for both service providers and the users perspectives. Users are classified into two categories viz home-user and business-user, with an option for easy up-gradation. Proposed architecture operates on next generation passive optical network stage 2 (NG-PON2) wavelength plan, with symmetrical data rate. Downstream performance is investigated by comparing, high power laser source with a conventional laser source and the L-band Erbium-doped fiber amplifier (EDFA) of gain 10 dB and 20 dB. Downstream eight wavelengths perform error-free up to 40 Km fiber reach and 1024 splitting points. Power budget of the proposed architecture incorporates the N1, N2, E1 and E2 optical path loss class.

Noncontact on-machine measurement system based on capacitive displacement sensors for single-point diamond turning

NASA Astrophysics Data System (ADS)

Li, Xingchang; Zhang, Zhiyu; Hu, Haifei; Li, Yingjie; Xiong, Ling; Zhang, Xuejun; Yan, Jiwang

2018-04-01

On-machine measurements can improve the form accuracy of optical surfaces in single-point diamond turning applications; however, commercially available linear variable differential transformer sensors are inaccurate and can potentially scratch the surface. We present an on-machine measurement system based on capacitive displacement sensors for high-precision optical surfaces. In the proposed system, a position-trigger method of measurement was developed to ensure strict correspondence between the measurement points and the measurement data with no intervening time-delay. In addition, a double-sensor measurement was proposed to reduce the electric signal noise during spindle rotation. Using the proposed system, the repeatability of 80-nm peak-to-valley (PV) and 8-nm root-mean-square (RMS) was achieved through analyzing four successive measurement results. The accuracy of 109-nm PV and 14-nm RMS was obtained by comparing with the interferometer measurement result. An aluminum spherical mirror with a diameter of 300 mm was fabricated, and the resulting measured form error after one compensation cut was decreased to 254 nm in PV and 52 nm in RMS. These results confirm that the measurements of the surface form errors were successfully used to modify the cutting tool path during the compensation cut, thereby ensuring that the diamond turning process was more deterministic. In addition, the results show that the noise level was significantly reduced with the reference sensor even under a high rotational speed.

Development of a 64 channel ultrasonic high frequency linear array imaging system.

PubMed

Hu, ChangHong; Zhang, Lequan; Cannata, Jonathan M; Yen, Jesse; Shung, K Kirk

2011-12-01

In order to improve the lateral resolution and extend the field of view of a previously reported 48 element 30 MHz ultrasound linear array and 16-channel digital imaging system, the development of a 256 element 30 MHz linear array and an ultrasound imaging system with increased channel count has been undertaken. This paper reports the design and testing of a 64 channel digital imaging system which consists of an analog front-end pulser/receiver, 64 channels of Time-Gain Compensation (TGC), 64 channels of high-speed digitizer as well as a beamformer. A Personal Computer (PC) is used as the user interface to display real-time images. This system is designed as a platform for the purpose of testing the performance of high frequency linear arrays that have been developed in house. Therefore conventional approaches were taken it its implementation. Flexibility and ease of use are of primary concern whereas consideration of cost-effectiveness and novelty in design are only secondary. Even so, there are many issues at higher frequencies but do not exist at lower frequencies need to be solved. The system provides 64 channels of excitation pulsers while receiving simultaneously at a 20-120 MHz sampling rate to 12-bits. The digitized data from all channels are first fed through Field Programmable Gate Arrays (FPGAs), and then stored in memories. These raw data are accessed by the beamforming processor to re-build the image or to be downloaded to the PC for further processing. The beamformer that applies delays to the echoes of each channel is implemented with the strategy that combines coarse (8.3 ns) and fine delays (2 ns). The coarse delays are integer multiples of the sampling clock rate and are achieved by controlling the write enable pin of the First-In-First-Out (FIFO) memory to obtain valid beamforming data. The fine delays are accomplished with interpolation filters. This system is capable of achieving a maximum frame rate of 50 frames per second. Wire phantom images acquired with this system show a spatial resolution of 146 μm (lateral) and 54 μm (axial). Images with excised rabbit and pig eyeball as well as mouse embryo were also acquired to demonstrate its imaging capability. Copyright © 2011 Elsevier B.V. All rights reserved.

Development of a 64 channel ultrasonic high frequency linear array imaging system

PubMed Central

Hu, ChangHong; Zhang, Lequan; Cannata, Jonathan M.; Yen, Jesse; Shung, K. Kirk

2011-01-01

In order to improve the lateral resolution and extend the field of view of a previously reported 48 element 30 MHz ultrasound linear array and 16-channel digital imaging system, the development of a 256 element 30 MHz linear array and an ultrasound imaging system with increased channel count has been undertaken. This paper reports the design and testing of a 64 channel digital imaging system which consists of an analog front-end pulser/receiver, 64 channels of Time-Gain Compensation (TGC), 64 channels of high-speed digitizer as well as a beamformer. A Personal Computer (PC) is used as the user interface to display real-time images. This system is designed as a platform for the purpose of testing the performance of high frequency linear arrays that have been developed in house. Therefore conventional approaches were taken it its implementation. Flexibility and ease of use are of primary concern whereas consideration of cost-effectiveness and novelty in design are only secondary. Even so, there are many issues at higher frequencies but do not exist at lower frequencies need to be solved. The system provides 64 channels of excitation pulsers while receiving simultaneously at a 20 MHz–120 MHz sampling rate to 12-bits. The digitized data from all channels are first fed through Field Programmable Gate Arrays (FPGAs), and then stored in memories. These raw data are accessed by the beamforming processor to re-build the image or to be downloaded to the PC for further processing. The beamformer that applies delays to the echoes of each channel is implemented with the strategy that combines coarse (8.3ns) and fine delays (2 ns). The coarse delays are integer multiples of the sampling clock rate and are achieved by controlling the write enable pin of the First-In-First-Out (FIFO) memory to obtain valid beamforming data. The fine delays are accomplished with interpolation filters. This system is capable of achieving a maximum frame rate of 50 frames per second. Wire phantom images acquired with this system show a spatial resolution of 146 μm (lateral) and 54 μm (axial). Images with excised rabbit and pig eyeball as well as mouse embryo were also acquired to demonstrate its imaging capability. PMID:21684568

76 FR 68734 - Taking and Importing Marine Mammals: Taking Marine Mammals Incidental to Navy Training Exercises...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-07

... marine mammal is likely to travel during the time associated with the TDFD's time delay, and that... Navy provided the approximate distance that an animal would typically travel within a given time-delay... Speed and Length of Time-Delay Potential distance Species group Swim speed Time-delay traveled Delphinid...

Comparison of Human and Humanoid Robot Control of Upright Stance

PubMed Central

Peterka, Robert J.

2009-01-01

There is considerable recent interest in developing humanoid robots. An important substrate for many motor actions in both humans and biped robots is the ability to maintain a statically or dynamically stable posture. Given the success of the human design, one would expect there are lessons to be learned in formulating a postural control mechanism for robots. In this study we limit ourselves to considering the problem of maintaining upright stance. Human stance control is compared to a suggested method for robot stance control called zero moment point (ZMP) compensation. Results from experimental and modeling studies suggest there are two important subsystems that account for the low- and mid-frequency (DC to ~1 Hz) dynamic characteristics of human stance control. These subsystems are 1) a “sensory integration” mechanism whereby orientation information from multiple sensory systems encoding body kinematics (i.e. position, velocity) is flexibly combined to provide an overall estimate of body orientation while allowing adjustments (sensory re-weighting) that compensate for changing environmental conditions, and 2) an “effort control” mechanism that uses kinetic-related (i.e., force-related) sensory information to reduce the mean deviation of body orientation from upright. Functionally, ZMP compensation is directly analogous to how humans appear to use kinetic feedback to modify the main sensory integration feedback loop controlling body orientation. However, a flexible sensory integration mechanism is missing from robot control leaving the robot vulnerable to instability in conditions were humans are able to maintain stance. We suggest the addition of a simple form of sensory integration to improve robot stance control. We also investigate how the biological constraint of feedback time delay influences the human stance control design. The human system may serve as a guide for improved robot control, but should not be directly copied because the constraints on robot and human control are different. PMID:19665564

Comparison of human and humanoid robot control of upright stance.

PubMed

Peterka, Robert J

2009-01-01

There is considerable recent interest in developing humanoid robots. An important substrate for many motor actions in both humans and biped robots is the ability to maintain a statically or dynamically stable posture. Given the success of the human design, one would expect there are lessons to be learned in formulating a postural control mechanism for robots. In this study we limit ourselves to considering the problem of maintaining upright stance. Human stance control is compared to a suggested method for robot stance control called zero moment point (ZMP) compensation. Results from experimental and modeling studies suggest there are two important subsystems that account for the low- and mid-frequency (DC to approximately 1Hz) dynamic characteristics of human stance control. These subsystems are (1) a "sensory integration" mechanism whereby orientation information from multiple sensory systems encoding body kinematics (i.e. position, velocity) is flexibly combined to provide an overall estimate of body orientation while allowing adjustments (sensory re-weighting) that compensate for changing environmental conditions and (2) an "effort control" mechanism that uses kinetic-related (i.e., force-related) sensory information to reduce the mean deviation of body orientation from upright. Functionally, ZMP compensation is directly analogous to how humans appear to use kinetic feedback to modify the main sensory integration feedback loop controlling body orientation. However, a flexible sensory integration mechanism is missing from robot control leaving the robot vulnerable to instability in conditions where humans are able to maintain stance. We suggest the addition of a simple form of sensory integration to improve robot stance control. We also investigate how the biological constraint of feedback time delay influences the human stance control design. The human system may serve as a guide for improved robot control, but should not be directly copied because the constraints on robot and human control are different.

Unified dead-time compensation structure for SISO processes with multiple dead times.

PubMed

Normey-Rico, Julio E; Flesch, Rodolfo C C; Santos, Tito L M

2014-11-01

This paper proposes a dead-time compensation structure for processes with multiple dead times. The controller is based on the filtered Smith predictor (FSP) dead-time compensator structure and it is able to control stable, integrating, and unstable processes with multiple input/output dead times. An equivalent model of the process is first computed in order to define the predictor structure. Using this equivalent model, the primary controller and the predictor filter are tuned to obtain an internally stable closed-loop system which also attempts some closed-loop specifications in terms of set-point tracking, disturbance rejection, and robustness. Some simulation case studies are used to illustrate the good properties of the proposed approach. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Probability of Loss of Assured Safety in Systems with Multiple Time-Dependent Failure Modes: Incorporation of Delayed Link Failure in the Presence of Aleatory Uncertainty.

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

Helton, Jon C.; Brooks, Dusty Marie; Sallaberry, Cedric Jean-Marie.

Probability of loss of assured safety (PLOAS) is modeled for weak link (WL)/strong link (SL) systems in which one or more WLs or SLs could potentially degrade into a precursor condition to link failure that will be followed by an actual failure after some amount of elapsed time. The following topics are considered: (i) Definition of precursor occurrence time cumulative distribution functions (CDFs) for individual WLs and SLs, (ii) Formal representation of PLOAS with constant delay times, (iii) Approximation and illustration of PLOAS with constant delay times, (iv) Formal representation of PLOAS with aleatory uncertainty in delay times, (v) Approximationmore » and illustration of PLOAS with aleatory uncertainty in delay times, (vi) Formal representation of PLOAS with delay times defined by functions of link properties at occurrence times for failure precursors, (vii) Approximation and illustration of PLOAS with delay times defined by functions of link properties at occurrence times for failure precursors, and (viii) Procedures for the verification of PLOAS calculations for the three indicated definitions of delayed link failure.« less

Sun compensation by bees.

PubMed

Gould, J L

1980-02-01

In both their navigation and dance communication, bees are able to compensate for the sun's movement. When foragers are prevented from seeing the sun for 2 hours, they compensate by extrapolation, using the sun's rate of movement when last observed. These and other data suggest a time-averaging processing strategy in honey bee orientation.

76 FR 8965 - National Vaccine Injury Compensation Program: Revisions to the Vaccine Injury Table

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-16

... DEPARTMENT OF HEALTH AND HUMAN SERVICES 42 CFR Part 100 RIN 0907-AA National Vaccine Injury Compensation Program: Revisions to the Vaccine Injury Table AGENCY: Health Resources and Services... ``National Vaccine Injury Compensation Program: Revisions to the Vaccine Injury Table.'' Date and Time: The...

Time delay can facilitate coherence in self-driven interacting-particle systems

NASA Astrophysics Data System (ADS)

Sun, Yongzheng; Lin, Wei; Erban, Radek

2014-12-01

Directional switching in a self-propelled particle model with delayed interactions is investigated. It is shown that the average switching time is an increasing function of time delay. The presented results are applied to studying collective animal behavior. It is argued that self-propelled particle models with time delays can explain the state-dependent diffusion coefficient measured in experiments with locust groups. The theory is further generalized to heterogeneous groups where each individual can respond to its environment with a different time delay.

Delay banking for air traffic management

NASA Technical Reports Server (NTRS)

Green, Steven M. (Inventor)

2007-01-01

A method and associated system for time delay banking for aircraft arrival time, aircraft departure time and/or en route flight position. The delay credit value for a given flight may decrease with passage of time and may be transferred to or traded with other flights having the same or a different user (airline owner or operator). The delay credit value for a given aircraft flight depends upon an initial delay credit value, which is determined by a central system and depends upon one or more other flight characteristics. Optionally, the delay credit value decreases with passage of time. Optionally, a transaction cost is assessed against a delay credit value that is used on behalf of another flight with the same user or is traded with a different user.

General relation between the group delay and dwell time in multicomponent electron systems

NASA Astrophysics Data System (ADS)

Zhai, Feng; Lu, Junqiang

2016-10-01

For multicomponent electron scattering states, we derive a general relation between the Wigner group delay and the Bohmian dwell time. It is found that the definition of group delay should account for the phase of the spinor wave functions of propagating modes. The difference between the group delay and dwell time comes from both the interference delay and the decaying modes. For barrier tunneling of helical electrons on a surface of topological insulators, our calculations including the trigonal-warping term show that the decaying modes can contribute greatly to the group delay. The derived relation between the group delay and the dwell time is helpful to unify the two definitions of tunneling time in a quite general situation.

Efficient laser noise reduction method via actively stabilized optical delay line.

PubMed

Li, Dawei; Qian, Cheng; Li, Ye; Zhao, Jianye

2017-04-17

We report a fiber laser noise reduction method by locking it to an actively stabilized optical delay line, specifically a fiber-based Mach-Zehnder interferometer with a 10 km optical fiber spool. The fiber spool is used to achieve large arm imbalance. The heterodyne signal of the two arms converts the laser noise from the optical domain to several megahertz, and it is used in laser noise reduction by a phase-locked loop. An additional phase-locked loop is induced in the system to compensate the phase noise due to environmentally induced length fluctuations of the optical fiber spool. A major advantage of this structure is the efficient reduction of out-of-loop frequency noise, particularly at low Fourier frequency. The frequency noise reaches -30 dBc/Hz at 1 Hz, which is reduced by more than 90 dB compared with that of the laser in its free-running state.

CAN LARGE TIME DELAYS OBSERVED IN LIGHT CURVES OF CORONAL LOOPS BE EXPLAINED IN IMPULSIVE HEATING?

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

Lionello, Roberto; Linker, Jon A.; Mikić, Zoran

The light curves of solar coronal loops often peak first in channels associated with higher temperatures and then in those associated with lower temperatures. The delay times between the different narrowband EUV channels have been measured for many individual loops and recently for every pixel of an active region observation. The time delays between channels for an active region exhibit a wide range of values. The maximum time delay in each channel pair can be quite large, i.e., >5000 s. These large time delays make-up 3%–26% (depending on the channel pair) of the pixels where a trustworthy, positive time delaymore » is measured. It has been suggested that these time delays can be explained by simple impulsive heating, i.e., a short burst of energy that heats the plasma to a high temperature, after which the plasma is allowed to cool through radiation and conduction back to its original state. In this paper, we investigate whether the largest observed time delays can be explained by this hypothesis by simulating a series of coronal loops with different heating rates, loop lengths, abundances, and geometries to determine the range of expected time delays between a set of four EUV channels. We find that impulsive heating cannot address the largest time delays observed in two of the channel pairs and that the majority of the large time delays can only be explained by long, expanding loops with photospheric abundances. Additional observations may rule out these simulations as an explanation for the long time delays. We suggest that either the time delays found in this manner may not be representative of real loop evolution, or that the impulsive heating and cooling scenario may be too simple to explain the observations, and other potential heating scenarios must be explored.« less

Cognitive person variables in the delay of gratification of older children at risk.

PubMed

Rodriguez, M L; Mischel, W; Shoda, Y

1989-08-01

The components of self-regulation were analyzed, extending the self-imposed delay of gratification paradigm to older children with social adjustment problems. Delay behavior was related to a network of conceptually relevant cognitive person variables, consisting of attention deployment strategies during delay, knowledge of delay rules, and intelligence. A positive relationship was demonstrated between concurrent indexes of intelligence, attention deployment, and actual delay time. Moreover, attention deployment, measured as an individual differences variable during the delay process, had a direct, positive effect on delay behavior. Specifically, as the duration of delay and the frustration of the situation increased, children who spent a higher proportion of the time distracting themselves from the tempting elements of the delay situation were able to delay longer. The effect of attention deployment on delay behavior was significant even when age, intelligence, and delay rule knowledge were controlled. Likewise, delay rule knowledge significantly predicted delay time, even when age, attention deployment, and intelligence were controlled.

Scale dependant compensational stacking of channelized sedimentary deposits

NASA Astrophysics Data System (ADS)

Wang, Y.; Straub, K. M.; Hajek, E. A.

2010-12-01

Compensational stacking, the tendency for sediment transport system to preferentially fill topographic lows, thus smoothing out topographic relief is a concept used in the interpretation of the stratigraphic record. Recently, a metric was developed to quantify the strength of compensation in sedimentary basins by comparing observed stacking patterns to what would be expected from simple, uncorrelated stacking. This method uses the rate of decay of spatial variability in sedimentation between picked depositional horizons with increasing vertical stratigraphic averaging distance. We explore how this metric varies as a function of stratigraphic scale using data from physical experiments, stratigraphy exposed in outcrops and numerical models. In an experiment conducted at Tulane University’s Sediment Dynamics Laboratory, the topography of a channelized delta formed by weakly cohesive sediment was monitored along flow-perpendicular transects at a high temporal resolution relative to channel kinematics. Over the course of this experiment a uniform relative subsidence pattern, designed to isolate autogenic processes, resulted in the construction of a stratigraphic package that is 25 times as thick as the depth of the experimental channels. We observe a scale-dependence on the compensational stacking of deposits set by the system’s avulsion time-scale. Above the avulsion time-scale deposits stack purely compensationally, but below this time-scale deposits stack somewhere between randomly and deterministically. The well-exposed Ferris Formation (Cretaceous/Paleogene, Hanna Basin, Wyoming, USA) also shows scale-dependant stratigraphic organization which appears to be set by an avulsion time-scale. Finally, we utilize simple object-based models to illustrate how channel avulsions influence compensation in alluvial basins.

NOTE: Acceleration of Monte Carlo-based scatter compensation for cardiac SPECT

NASA Astrophysics Data System (ADS)

Sohlberg, A.; Watabe, H.; Iida, H.

2008-07-01

Single proton emission computed tomography (SPECT) images are degraded by photon scatter making scatter compensation essential for accurate reconstruction. Reconstruction-based scatter compensation with Monte Carlo (MC) modelling of scatter shows promise for accurate scatter correction, but it is normally hampered by long computation times. The aim of this work was to accelerate the MC-based scatter compensation using coarse grid and intermittent scatter modelling. The acceleration methods were compared to un-accelerated implementation using MC-simulated projection data of the mathematical cardiac torso (MCAT) phantom modelling 99mTc uptake and clinical myocardial perfusion studies. The results showed that when combined the acceleration methods reduced the reconstruction time for 10 ordered subset expectation maximization (OS-EM) iterations from 56 to 11 min without a significant reduction in image quality indicating that the coarse grid and intermittent scatter modelling are suitable for MC-based scatter compensation in cardiac SPECT.

Are people who claim compensation "cured by a verdict"? A longitudinal study of health outcomes after whiplash.

PubMed

Spearing, Natalie M; Gyrd-Hansen, Dorte; Pobereskin, Louis H; Rowell, David S; Connelly, Luke B

2012-09-01

This study examines whether the lure of injury compensation prompts whiplash claimants to overstate their symptoms. Claim settlement is the intervention of interest, as it represents the point at which there is no further incentive to exaggerate symptoms, and neck pain at 24 months is the outcome of interest. Longitudinal data on neck pain scores and timing of claim settlement were regressed, controlling for the effect of time on recovery, to compare outcomes in claimants who had and had not settled their compensation claims. The results show clearly that removing the financial incentive to over-report symptoms has no effect on self-reported neck pain in a fault-based compensation scheme, and this finding concurs with other studies on this topic. Policy decisions to limit compensation in the belief that claimants systematically misrepresent their health status are not supported empirically Claimants do not appear to be "cured by a verdict".

Firing patterns transition and desynchronization induced by time delay in neural networks

NASA Astrophysics Data System (ADS)

Huang, Shoufang; Zhang, Jiqian; Wang, Maosheng; Hu, Chin-Kun

2018-06-01

We used the Hindmarsh-Rose (HR) model (Hindmarsh and Rose, 1984) to study the effect of time delay on the transition of firing behaviors and desynchronization in neural networks. As time delay is increased, neural networks exhibit diversity of firing behaviors, including regular spiking or bursting and firing patterns transitions (FPTs). Meanwhile, the desynchronization of firing and unstable bursting with decreasing amplitude in neural system, are also increasingly enhanced with the increase of time delay. Furthermore, we also studied the effect of coupling strength and network randomness on these phenomena. Our results imply that time delays can induce transition and desynchronization of firing behaviors in neural networks. These findings provide new insight into the role of time delay in the firing activities of neural networks, and can help to better understand the firing phenomena in complex systems of neural networks. A possible mechanism in brain that can cause the increase of time delay is discussed.

Is clinician refusal to treat an emerging problem in injury compensation systems?

PubMed Central

Brijnath, Bianca; Mazza, Danielle; Kosny, Agnieszka; Bunzli, Samantha; Singh, Nabita; Ruseckaite, Rasa; Collie, Alex

2016-01-01

Objective The reasons that doctors may refuse or be reluctant to treat have not been widely explored in the medical literature. To understand the ethical implications of reluctance to treat there is a need to recognise the constraints of doctors working in complex systems and to consider how these constraints may influence reluctance. The aim of this paper is to illustrate these constraints using the case of compensable injury in the Australian context. Design Between September and December 2012, a qualitative investigation involving face-to-face semistructured interviews examined the knowledge, attitudes and practices of general practitioners (GPs) facilitating return to work in people with compensable injuries. Setting Compensable injury management in general practice in Melbourne, Australia. Participants 25 GPs who were treating, or had treated a patient with compensable injury. Results The practice of clinicians refusing treatment was described by all participants. While most GPs reported refusal to treat among their colleagues in primary and specialist care, many participants also described their own reluctance to treat people with compensable injuries. Reasons offered included time and financial burdens, in addition to the clinical complexities involved in compensable injury management. Conclusions In the case of compensable injury management, reluctance and refusal to treat is likely to have a domino effect by increasing the time and financial burden of clinically complex patients on the remaining clinicians. This may present a significant challenge to an effective, sustainable compensation system. Urgent research is needed to understand the extent and implications of reluctance and refusal to treat and to identify strategies to engage clinicians in treating people with compensable injuries. PMID:26792215

Torpor use during gestation and lactation in a primate

NASA Astrophysics Data System (ADS)

Canale, Cindy I.; Perret, Martine; Henry, Pierre-Yves

2012-02-01

Torpor is an energy-saving mechanism that allows endotherms to overcome energetic challenges. Torpor should be avoided during reproduction because of potential incompatibility with offspring growth. To test if torpor can be used during gestation and lactation to compensate for food shortage, we exposed reproductive female grey mouse lemurs ( Microcebus murinus), a heterothermic primate, to different levels of food availability. Torpor use was characterised by daily skin temperature profiles, and its energetic outcome was assessed from changes in body mass. Food shortage triggered torpor during the end of the gestation period ( n = 1), ranging from shallow in response to 40% food restriction to deep daily torpor in response to 80% restriction. During the early period of lactation, females fed ad libitum ( n = 2) or exposed to a 40% restriction ( n = 4) remained normothermic; but 80% food restricted females ( n = 5) gave priority to energy saving, increasing the frequency and depth of torpor bouts. The use of torpor was insufficient to compensate for 80% energetic shortage during lactation resulting in loss of mass from the mother and delayed growth in the pups. This study provides the first evidence that a heterothermic primate can use torpor to compensate for food shortages even during reproduction. This physiological flexibility likely evolved as a response to climate-driven fluctuations in food availability in Madagascar.

Delay time in a single barrier for a movable quantum shutter

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

Hernandez, Alberto

2010-05-15

The transient solution and delay time for a {delta} potential scatterer with a movable quantum shutter is calculated by solving analytically the time-dependent Schroedinger equation. The delay time is analyzed as a function of the distance between the shutter and the potential barrier and also as a function of the distance between the potential barrier and the detector. In both cases, it is found that the delay time exhibits a dynamical behavior and that it tends to a saturation value {Delta}t{sub sat} in the limit of very short distances, which represents the maximum delay produced by the potential barrier nearmore » the interaction region. The phase time {tau}{sub {theta},} on the other hand, is not an appropriate time scale for measuring the time delay near the interaction region, except if the shutter is moved far away from the potential. The role played by the antibound state of the system on the behavior of the delay time is also discussed.« less

LiDAR-IMU Time Delay Calibration Based on Iterative Closest Point and Iterated Sigma Point Kalman Filter.

PubMed

Liu, Wanli

2017-03-08

The time delay calibration between Light Detection and Ranging (LiDAR) and Inertial Measurement Units (IMUs) is an essential prerequisite for its applications. However, the correspondences between LiDAR and IMU measurements are usually unknown, and thus cannot be computed directly for the time delay calibration. In order to solve the problem of LiDAR-IMU time delay calibration, this paper presents a fusion method based on iterative closest point (ICP) and iterated sigma point Kalman filter (ISPKF), which combines the advantages of ICP and ISPKF. The ICP algorithm can precisely determine the unknown transformation between LiDAR-IMU; and the ISPKF algorithm can optimally estimate the time delay calibration parameters. First of all, the coordinate transformation from the LiDAR frame to the IMU frame is realized. Second, the measurement model and time delay error model of LiDAR and IMU are established. Third, the methodology of the ICP and ISPKF procedure is presented for LiDAR-IMU time delay calibration. Experimental results are presented that validate the proposed method and demonstrate the time delay error can be accurately calibrated.

Design and Testing of a Ground-based System for Phase Stabilized Standard Frequency Transmission

NASA Astrophysics Data System (ADS)

Wang, J. Q.; Jiang, Y. C.; Gou, W.; Yu, L. F.; Liu, Q. H.; Fan, Q. Y.; Lou, F. X.; Lao, B. Q.

2014-09-01

In this paper, a 1.5 GHz phase stabilized frequency transmission system is described. Compatible with the coaxial cable and optical fiber transmission media, the system has both the capabilities of real-time and post phase compensation. The phase stabilizing principle of the equipment is analyzed, and its performance is evaluated. Under the test environment, the results of the prototype system based on a coaxial cable show that the real-time compensation mode can improve the phase stabilities by more than 112 times in comparison with the uncompensated cables. The frequency stabilities are also improved significantly with a 7-second integration time, and one order-of-magnitude improvement is achieved after 60 seconds. The post compensation mode can improve phase fluctuations by 40 times. The frequency stabilities can be improved significantly after 2.5-second integration, while a 10-fold enhancement is achieved after 40 seconds. With longer integration time, both real-time and post compensation modes can improve the frequency stabilities by more than 1.5 orders of magnitude. The proposed equipment can effectively reduce slowly stretching effects due to the factors such as the temperature coefficient variations of the transmission medium and mechanical disturbances.

On Time Delay Margin Estimation for Adaptive Control and Optimal Control Modification

NASA Technical Reports Server (NTRS)

Nguyen, Nhan T.

2011-01-01

This paper presents methods for estimating time delay margin for adaptive control of input delay systems with almost linear structured uncertainty. The bounded linear stability analysis method seeks to represent an adaptive law by a locally bounded linear approximation within a small time window. The time delay margin of this input delay system represents a local stability measure and is computed analytically by three methods: Pade approximation, Lyapunov-Krasovskii method, and the matrix measure method. These methods are applied to the standard model-reference adaptive control, s-modification adaptive law, and optimal control modification adaptive law. The windowing analysis results in non-unique estimates of the time delay margin since it is dependent on the length of a time window and parameters which vary from one time window to the next. The optimal control modification adaptive law overcomes this limitation in that, as the adaptive gain tends to infinity and if the matched uncertainty is linear, then the closed-loop input delay system tends to a LTI system. A lower bound of the time delay margin of this system can then be estimated uniquely without the need for the windowing analysis. Simulation results demonstrates the feasibility of the bounded linear stability method for time delay margin estimation.

20 CFR 10.336 - What are the time frames for submitting bills?

Code of Federal Regulations, 2010 CFR

2010-04-01

... 20 Employees' Benefits 1 2010-04-01 2010-04-01 false What are the time frames for submitting bills? 10.336 Section 10.336 Employees' Benefits OFFICE OF WORKERS' COMPENSATION PROGRAMS, DEPARTMENT OF...' COMPENSATION ACT, AS AMENDED Medical and Related Benefits Medical Bills § 10.336 What are the time frames for...

Leveraging delay discounting for health: Can time delays influence food choice?

PubMed

Appelhans, Bradley M; French, Simone A; Olinger, Tamara; Bogucki, Michael; Janssen, Imke; Avery-Mamer, Elizabeth F; Powell, Lisa M

2018-07-01

Delay discounting, the tendency to choose smaller immediate rewards over larger delayed rewards, is theorized to promote consumption of immediately rewarding but unhealthy foods at the expense of long-term weight maintenance and nutritional health. An untested implication of delay discounting models of decision-making is that selectively delaying access to less healthy foods may promote selection of healthier (immediately available) alternatives, even if they may be less desirable. The current study tested this hypothesis by measuring healthy versus regular vending machine snack purchasing before and during the implementation of a 25-s time delay on the delivery of regular snacks. Purchasing was also examined under a $0.25 discount on healthy snacks, a $0.25 tax on regular snacks, and the combination of both pricing interventions with the 25-s time delay. Across 32,019 vending sales from three separate vending locations, the 25-s time delay increased healthy snack purchasing from 40.1% to 42.5%, which was comparable to the impact of a $0.25 discount (43.0%). Combining the delay and the discount had a roughly additive effect (46.0%). However, the strongest effects were seen under the $0.25 tax on regular snacks (53.7%) and the combination of the delay and the tax (50.2%). Intervention effects varied substantially between vending locations. Importantly, time delays did not harm overall vending sales or revenue, which is relevant to the real-world feasibility of this intervention. More investigation is needed to better understand how the impact of time delays on food choice varies across populations, evaluate the effects of time delays on beverage vending choices, and extend this approach to food choices in contexts other than vending machines. ClinicalTrials.gov, NCT02359916. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effect of time delay on flying qualities: An update

NASA Technical Reports Server (NTRS)

Smith, R. E.; Sarrafian, S. K.

1986-01-01

Flying qualities problems of modern, full-authority electronic flight control systems are most often related to the introduction of additional time delay in aircraft response to a pilot input. These delays can have a significant effect on the flying qualities of the aircraft. Time delay effects are reexamined in light of recent flight test experience with aircraft incorporating new technology. Data from the X-29A forward-swept-wing demonstrator, a related preliminary in-flight experiment, and other flight observations are presented. These data suggest that the present MIL-F-8785C allowable-control system time delay specifications are inadequate or, at least, incomplete. Allowable time delay appears to be a function of the shape of the aircraft response following the initial delay. The cockpit feel system is discussed as a dynamic element in the flight control system. Data presented indicate that the time delay associated with a significant low-frequency feel system does not result in the predicted degradation in aircraft flying qualities. The impact of the feel system is discussed from two viewpoints: as a filter in the control system which can alter the initial response shape and, therefore, the allowable time delay, and as a unique dynamic element whose delay contribution can potentially be discounted by special pilot loop closures.

Describing-function analysis of a ripple regulator with slew-rate limits and time delays

NASA Technical Reports Server (NTRS)

Wester, Gene W.

1990-01-01

The effects of time delays and slew-rate limits on the steady-state operating points and performance of a free-running ripple regulator are evaluated using describing-function analysis. The describing function of an ideal comparator (no time delays or slew rate limits) has no phase shift and is independent of frequency. It is found that turn-on delay and turn-off delay have different effects on gain and phase and cannot be combined. Comparator hysteresis affects both gain and phase; likewise, time delays generally affect both gain and phase. It is found that the effective time delay around the feedback loop is one half the sum of turn-on and turn-off delays, regardless of whether the delays are caused by storage time or slew rate limits. Expressions are formulated for the switching frequency, switch duty ratio, dc output, and output ripple. For the case of no hysteresis, a simple, graphical solution for the switching frequency is possible, and the resulting switching frequency is independent of first-order variations of input or load.

Loss compensation symmetry in dimers made of gain and lossy nanoparticles

NASA Astrophysics Data System (ADS)

Klimov, V. V.; Zabkov, I. V.; Guzatov, D. V.; Vinogradov, A. P.

2018-03-01

The eigenmodes in a two-dimensional dimer made of gain and lossy nanoparticles have been investigated within an exact analytical approach. It has been shown that there are eigenmodes for which all Joule losses are exactly compensated by the gain. Among such solutions there are solutions with a new type of symmetry, which we refer to as loss compensation symmetry, as well as well-known parity-time (PT) symmetric solutions. Unlike PT symmetric ones, the modes with loss compensation symmetry allow one to achieve full loss compensation with significantly less gain that in the case of PT symmetry. This effect paves the way to new loss compensation methods in optics.

The association of social functioning, social relationships and the receipt of compensation with time to return to work following unintentional injuries to Victorian workers.

PubMed

Clay, Fiona J; Fitzharris, Michael; Kerr, Emily; McClure, Roderick J; Watson, Wendy L

2012-09-01

Understanding individual factors associated with return to work (RTW) post-injury is an important goal of compensation systems research. The aim of the present study was to determine factors associated with time to return to work following acute unintentional injuries. A prospective cohort study was conducted in Victoria, Australia. The cohort comprised 133 persons who were employed at the time they were admitted to one of three study hospitals. Baseline health status data was obtained retrospectively at one-week post-injury and participants were further surveyed at 1, 6, 12, 26 and 52 weeks post-injury to measure recovery. Multivariate Cox proportional hazards regression analysis was used to examine the association between potential prognostic factors and time to RTW during the 12 month study. At the end of 12 months follow-up, 81.2% of the study cohort had returned to work. Older age, increased injury severity, self reported symptomatic pain and poor mental health at 1 week post-injury were associated with extended time to RTW. A significant statistical interaction between the receipt of compensation and high social functioning as measured by the SF-36 or strong social relationships as measured by the Assessment of Quality of Life was associated with earlier RTW. Participants reporting strong social relationships and high social functioning at 1 week post-injury and entitled to injury compensation returned to work 2.05 and 3.66 times earlier respectively, than similar participants with no entitlement to compensation. Both injury-related and psychosocial factors were associated with the duration of time to RTW following acute unintentional injuries. This study replicated previously reported findings on social functioning and compensation from an independent acute trauma sample. Programs or policies to improve social functioning early post-injury may provide opportunities to improve the duration of time to RTW following injury.

Society of Pediatric Psychology Workforce Survey: Factors Related to Compensation of Pediatric Psychologists

PubMed Central

Brosig, Cheryl L.; Hilliard, Marisa E.; Williams, Andre; Armstrong, F. Daniel; Christidis, Peggy; Kichler, Jessica; Pendley, Jennifer Shroff; Stamm, Karen E.; Wysocki, Tim

2017-01-01

Abstract Objective To summarize compensation results from the 2015 Society of Pediatric Psychology (SPP) Workforce Survey and identify factors related to compensation of pediatric psychologists. Methods All full members of SPP (n = 1,314) received the online Workforce Survey; 404 (32%) were returned with usable data. The survey assessed salary, benefits, and other income sources. The relationship between demographic and employment-related factors and overall compensation was explored. Results Academic rank, level of administrative responsibility, and cost of living index of employment location were associated with compensation. Compensation did not vary by gender; however, women were disproportionately represented at the assistant and associate professor level. Conclusions Compensation of pediatric psychologists is related to multiple factors. Longitudinal administration of the Workforce Survey is needed to determine changes in compensation and career advancement for this profession over time. Strategies to increase the response rate of future Workforce Surveys are discussed. PMID:28369549