Dynamical compensation and structural identifiability of biological models: Analysis, implications, and reconciliation

PubMed Central

2017-01-01

The concept of dynamical compensation has been recently introduced to describe the ability of a biological system to keep its output dynamics unchanged in the face of varying parameters. However, the original definition of dynamical compensation amounts to lack of structural identifiability. This is relevant if model parameters need to be estimated, as is often the case in biological modelling. Care should we taken when using an unidentifiable model to extract biological insight: the estimated values of structurally unidentifiable parameters are meaningless, and model predictions about unmeasured state variables can be wrong. Taking this into account, we explore alternative definitions of dynamical compensation that do not necessarily imply structural unidentifiability. Accordingly, we show different ways in which a model can be made identifiable while exhibiting dynamical compensation. Our analyses enable the use of the new concept of dynamical compensation in the context of parameter identification, and reconcile it with the desirable property of structural identifiability. PMID:29186132

An adaptive actuator failure compensation scheme for two linked 2WD mobile robots

NASA Astrophysics Data System (ADS)

Ma, Yajie; Al-Dujaili, Ayad; Cocquempot, Vincent; El Badaoui El Najjar, Maan

2017-01-01

This paper develops a new adaptive compensation control scheme for two linked mobile robots with actuator failurs. A configuration with two linked two-wheel drive (2WD) mobile robots is proposed, and the modelling of its kinematics and dynamics are given. An adaptive failure compensation scheme is developed to compensate actuator failures, consisting of a kinematic controller and a multi-design integration based dynamic controller. The kinematic controller is a virtual one, and based on which, multiple adaptive dynamic control signals are designed which covers all possible failure cases. By combing these dynamic control signals, the dynamic controller is designed, which ensures system stability and asymptotic tracking properties. Simulation results verify the effectiveness of the proposed adaptive failure compensation scheme.

ODECS -- A computer code for the optimal design of S.I. engine control strategies

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

Arsie, I.; Pianese, C.; Rizzo, G.

1996-09-01

The computer code ODECS (Optimal Design of Engine Control Strategies) for the design of Spark Ignition engine control strategies is presented. This code has been developed starting from the author`s activity in this field, availing of some original contributions about engine stochastic optimization and dynamical models. This code has a modular structure and is composed of a user interface for the definition, the execution and the analysis of different computations performed with 4 independent modules. These modules allow the following calculations: (1) definition of the engine mathematical model from steady-state experimental data; (2) engine cycle test trajectory corresponding to amore » vehicle transient simulation test such as ECE15 or FTP drive test schedule; (3) evaluation of the optimal engine control maps with a steady-state approach; (4) engine dynamic cycle simulation and optimization of static control maps and/or dynamic compensation strategies, taking into account dynamical effects due to the unsteady fluxes of air and fuel and the influences of combustion chamber wall thermal inertia on fuel consumption and emissions. Moreover, in the last two modules it is possible to account for errors generated by a non-deterministic behavior of sensors and actuators and the related influences on global engine performances, and compute robust strategies, less sensitive to stochastic effects. In the paper the four models are described together with significant results corresponding to the simulation and the calculation of optimal control strategies for dynamic transient tests.« less

A dimension reduction method for flood compensation operation of multi-reservoir system

NASA Astrophysics Data System (ADS)

Jia, B.; Wu, S.; Fan, Z.

2017-12-01

Multiple reservoirs cooperation compensation operations coping with uncontrolled flood play vital role in real-time flood mitigation. This paper come up with a reservoir flood compensation operation index (ResFCOI), which formed by elements of flood control storage, flood inflow volume, flood transmission time and cooperation operations period, then establish a flood cooperation compensation operations model of multi-reservoir system, according to the ResFCOI to determine a computational order of each reservoir, and lastly the differential evolution algorithm is implemented for computing single reservoir flood compensation optimization in turn, so that a dimension reduction method is formed to reduce computational complexity. Shiguan River Basin with two large reservoirs and an extensive uncontrolled flood area, is used as a case study, results show that (a) reservoirs' flood discharges and the uncontrolled flood are superimposed at Jiangjiaji Station, while the formed flood peak flow is as small as possible; (b) cooperation compensation operations slightly increase in usage of flood storage capacity in reservoirs, when comparing to rule-based operations; (c) it takes 50 seconds in average when computing a cooperation compensation operations scheme. The dimension reduction method to guide flood compensation operations of multi-reservoir system, can make each reservoir adjust its flood discharge strategy dynamically according to the uncontrolled flood magnitude and pattern, so as to mitigate the downstream flood disaster.

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.

Further development of the dynamic gas temperature measurement system. Volume 1: Technical efforts

NASA Technical Reports Server (NTRS)

Elmore, D. L.; Robinson, W. W.; Watkins, W. B.

1986-01-01

A compensated dynamic gas temperature thermocouple measurement method was experimentally verified. Dynamic gas temperature signals from a flow passing through a chopped-wheel signal generator and an atmospheric pressure laboratory burner were measured by the dynamic temperature sensor and other fast-response sensors. Compensated data from dynamic temperature sensor thermoelements were compared with fast-response sensors. Results from the two experiments are presented as time-dependent waveforms and spectral plots. Comparisons between compensated dynamic temperature sensor spectra and a commercially available optical fiber thermometer compensated spectra were made for the atmospheric burner experiment. Increases in precision of the measurement method require optimization of several factors, and directions for further work are identified.

On the rejection of internal and external disturbances in a wind energy conversion system with direct-driven PMSG.

PubMed

Li, Shengquan; Zhang, Kezhao; Li, Juan; Liu, Chao

2016-03-01

This paper deals with the critical issue in a wind energy conversion system (WECS) based on a direct-driven permanent magnet synchronous generator (PMSG): the rejection of lumped disturbance, including the system uncertainties in the internal dynamics and unknown external forces. To simultaneously track the motor speed in real time and capture the maximum power, a maximum power point tracking strategy is proposed based on active disturbance rejection control (ADRC) theory. In real application, system inertia, drive torque and some other parameters change in a wide range with the variations of disturbances and wind speeds, which substantially degrade the performance of WECS. The ADRC design must incorporate the available model information into an extended state observer (ESO) to compensate the lumped disturbance efficiently. Based on this principle, a model-compensation ADRC is proposed in this paper. Simulation study is conducted to evaluate the performance of the proposed control strategy. It is shown that the effect of lumped disturbance is compensated in a more effective way compared with the traditional ADRC approach. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Transient switching control strategy from regenerative braking to anti-lock braking with a semi-brake-by-wire system

NASA Astrophysics Data System (ADS)

Li, Liang; Li, Xujian; Wang, Xiangyu; Liu, Yahui; Song, Jian; Ran, Xu

2016-02-01

Regenerative braking is an important technology in improving fuel economy of an electric vehicle (EV). However, additional motor braking will change the dynamic characteristics of the vehicle, leading to braking instability, especially when the anti-lock braking system (ABS) is triggered. In this paper, a novel semi-brake-by-wire system, without the use of a pedal simulator and fail-safe device, is proposed. In order to compensate for the hysteretic characteristics of the designed brake system while ensure braking reliability and fuel economy when the ABS is triggered, a novel switching compensation control strategy using sliding mode control is brought forward. The proposed strategy converts the complex coupling braking process into independent control of hydraulic braking and regenerative braking, through which a balance between braking performance, braking reliability, braking safety and fuel economy is achieved. Simulation results show that the proposed strategy is effective and adaptable in different road conditions while the large wheel slip rate is triggered during a regenerative braking course. The research provides a new possibility of low-cost equipment and better control performance for the regenerative braking in the EV and the hybrid EV.

Online compensation for target motion with scanned particle beams: simulation environment.

PubMed

Li, Qiang; Groezinger, Sven Oliver; Haberer, Thomas; Rietzel, Eike; Kraft, Gerhard

2004-07-21

Target motion is one of the major limitations of each high precision radiation therapy. Using advanced active beam delivery techniques, such as the magnetic raster scanning system for particle irradiation, the interplay between time-dependent beam and target position heavily distorts the applied dose distribution. This paper presents a simulation environment in which the time-dependent effect of target motion on heavy-ion irradiation can be calculated with dynamically scanned ion beams. In an extension of the existing treatment planning software for ion irradiation of static targets (TRiP) at GSI, the expected dose distribution is calculated as the sum of several sub-distributions for single target motion states. To investigate active compensation for target motion by adapting the position of the therapeutic beam during irradiation, the planned beam positions can be altered during the calculation. Applying realistic parameters to the planned motion-compensation methods at GSI, the effect of target motion on the expected dose uniformity can be simulated for different target configurations and motion conditions. For the dynamic dose calculation, experimentally measured profiles of the beam extraction in time were used. Initial simulations show the feasibility and consistency of an active motion compensation with the magnetic scanning system and reveal some strategies to improve the dose homogeneity inside the moving target. The simulation environment presented here provides an effective means for evaluating the dose distribution for a moving target volume with and without motion compensation. It contributes a substantial basis for the experimental research on the irradiation of moving target volumes with scanned ion beams at GSI which will be presented in upcoming papers.

More than just the mean: moving to a dynamic view of performance-based compensation.

PubMed

Barnes, Christopher M; Reb, Jochen; Ang, Dionysius

2012-05-01

Compensation decisions have important consequences for employees and organizations and affect factors such as retention, motivation, and recruitment. Past research has primarily focused on mean performance as a predictor of compensation, promoting the implicit assumption that alternative aspects of dynamic performance are not relevant. To address this gap in the literature, we examined the influence of dynamic performance characteristics on compensation decisions in the National Basketball Association (NBA). We predicted that, in addition to performance mean, performance trend and variability would also affect compensation decisions. Results revealed that performance mean and trend, but not variability, were significantly and positively related to changes in compensation levels of NBA players. Moreover, trend (but not mean or variability) predicted compensation when controlling for future performance, suggesting that organizations overweighted trend in their compensation decisions. Theoretical and practical implications are discussed. (PsycINFO Database Record (c) 2012 APA, all rights reserved).

Considering low-rank, sparse and gas-inflow effects constraints for accelerated pulmonary dynamic hyperpolarized 129Xe MRI

NASA Astrophysics Data System (ADS)

Xiao, Sa; Deng, He; Duan, Caohui; Xie, Junshuai; Zhang, Huiting; Sun, Xianping; Ye, Chaohui; Zhou, Xin

2018-05-01

Dynamic hyperpolarized (HP) 129Xe MRI is able to visualize the process of lung ventilation, which potentially provides unique information about lung physiology and pathophysiology. However, the longitudinal magnetization of HP 129Xe is nonrenewable, making it difficult to achieve high image quality while maintaining high temporal-spatial resolution in the pulmonary dynamic MRI. In this paper, we propose a new accelerated dynamic HP 129Xe MRI scheme incorporating the low-rank, sparse and gas-inflow effects (L + S + G) constraints. According to the gas-inflow effects of HP gas during the lung inspiratory process, a variable-flip-angle (VFA) strategy is designed to compensate for the rapid attenuation of the magnetization. After undersampling k-space data, an effective reconstruction algorithm considering the low-rank, sparse and gas-inflow effects constraints is developed to reconstruct dynamic MR images. In this way, the temporal and spatial resolution of dynamic MR images is improved and the artifacts are lessened. Simulation and in vivo experiments implemented on the phantom and healthy volunteers demonstrate that the proposed method is not only feasible and effective to compensate for the decay of the magnetization, but also has a significant improvement compared with the conventional reconstruction algorithms (P-values are less than 0.05). This confirms the superior performance of the proposed designs and their ability to maintain high quality and temporal-spatial resolution.

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.

Improved control strategy for PI-R current of DFIG considering voltage and current harmonics compensation

NASA Astrophysics Data System (ADS)

Song, S. Y.; Liu, Q. H.; Zhao, Y. N.; Liu, S. Y.

2016-08-01

With the rapid development of wind power generation, the related research of wind power control and integration issues has attracted much attention, and the focus of the research are shifting away from the ideal power grid environment to the actual power grid environment. As the main stream wind turbine generator, a doubly-fed induction generator (DFIG) is connected to the power grid directly by its stator, so it is particularly sensitive to the power grid. This paper studies the improvement of DFIG control technology in the power grid harmonic environment. Based on the DFIG dynamic model considering the power grid harmonic environment, this paper introduces the shortcomings of the common control strategy of DFIG, and puts forward the enhanced method. The decoupling control of the system is realized by compensating the coupling between the rotor harmonic voltage and harmonic current, improving the control performance. In addition, the simulation experiments on PSCAD/EMTDC are carried out to verify the correctness and effectiveness of the improved scheme.

A compound control strategy combining velocity compensation with ADRC of electro-hydraulic position servo control system.

PubMed

Gao, Bingwei; Shao, Junpeng; Yang, Xiaodong

2014-11-01

In order to enhance the anti-jamming ability of electro-hydraulic position servo control system at the same time improve the control precision of the system, a compound control strategy that combines velocity compensation with Active Disturbance Rejection Controller (ADRC) is proposed, and the working principle of the compound control strategy is given. ADRC controller is designed, and the extended state observer is used for observing internal parameters uncertainties and external disturbances, so that the disturbances of the system are suppressed effectively. Velocity compensation controller is designed and the compensation model is derived to further improve the positioning accuracy of the system and to achieve the velocity compensation without disturbance. The compound control strategy is verified by the simulation and experiment respectively, and the simulation and experimental results show that the electro-hydraulic position servo control system with ADRC controller can effectively inhibit the external disturbances, the precise positioning control is realized after introducing the velocity compensation controller, and verify that the compound control strategy is effective. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Power Quality Improvement Using an Enhanced Network-Side-Shunt-Connected Dynamic Voltage Restorer

NASA Astrophysics Data System (ADS)

Fereidouni, Alireza; Masoum, Mohammad A. S.; Moghbel, Moayed

2015-10-01

Among the four basic dynamic voltage restorer (DVR) topologies, the network-side shunt-connected DVR (NSSC-DVR) has a relatively poor performance and is investigated in this paper. A new configuration is proposed and implemented for NSSC-DVR to enhance its performance in compensating (un)symmetrical deep and long voltage sags and mitigate voltage harmonics. The enhanced NSSC-DVR model includes a three-phase half-bridge semi-controlled network-side-shunt-connected rectifier and a three-phase full-bridge series-connected inverter implemented with a back-to-back configuration through a bidirectional buck-boost converter. The network-side-shunt-connected rectifier is employed to inject/draw the required energy by NSSC-DVR to restore the load voltage to its pre-fault value under sag/swell conditions. The buck-boost converter is responsible for maintaining the DC-link voltage of the series-connected inverter at its designated value in order to improve the NSSC-DVR capability in compensating deep and long voltage sags/swells. The full-bridge series-connected inverter permits to compensate unbalance voltage sags containing zero-sequence component. The harmonic compensation of the load voltage is achieved by extracting harmonics from the distorted network voltage using an artificial neural network (ANN) method called adaptive linear neuron (Adaline) strategy. Detailed simulations are performed by SIMULINK/MATLAB software for six case studies to verify the highly robustness of the proposed NSSC-DVR model under various conditions.

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.

Consequences of biodiversity loss diverge from expectation due to post-extinction compensatory responses

NASA Astrophysics Data System (ADS)

Thomsen, Matthias S.; Garcia, Clement; Bolam, Stefan G.; Parker, Ruth; Godbold, Jasmin A.; Solan, Martin

2017-03-01

Consensus has been reached that global biodiversity loss impairs ecosystem functioning and the sustainability of services beneficial to humanity. However, the ecosystem consequences of extinction in natural communities are moderated by compensatory species dynamics, yet these processes are rarely accounted for in impact assessments and seldom considered in conservation programmes. Here, we use marine invertebrate communities to parameterise numerical models of sediment bioturbation - a key mediator of biogeochemical cycling - to determine whether post-extinction compensatory mechanisms alter biodiversity-ecosystem function relations following non-random extinctions. We find that compensatory dynamics lead to trajectories of sediment mixing that diverge from those without compensation, and that the form, magnitude and variance of each probabilistic distribution is highly influenced by the type of compensation and the functional composition of surviving species. Our findings indicate that the generalized biodiversity-function relation curve, as derived from multiple empirical investigations of random species loss, is unlikely to yield representative predictions for ecosystem properties in natural systems because the influence of post-extinction community dynamics are under-represented. Recognition of this problem is fundamental to management and conservation efforts, and will be necessary to ensure future plans and adaptation strategies minimize the adverse impacts of the biodiversity crisis.

Robust fixed order dynamic compensation for large space structure control

NASA Technical Reports Server (NTRS)

Calise, Anthony J.; Byrns, Edward V., Jr.

1989-01-01

A simple formulation for designing fixed order dynamic compensators which are robust to both uncertainty at the plant input and structured uncertainty in the plant dynamics is presented. The emphasis is on designing low order compensators for systems of high order. The formulation is done in an output feedback setting which exploits an observer canonical form to represent the compensator dynamics. The formulation also precludes the use of direct feedback of the plant output. The main contribution lies in defining a method for penalizing the states of the plant and of the compensator, and for choosing the distribution on initial conditions so that the loop transfer matrix approximates that of a full state design. To improve robustness to parameter uncertainty, the formulation avoids the introduction of sensitivity states, which has led to complex formulations in earlier studies where only structured uncertainty has been considered.

How Fire History, Fire Suppression Practices and Climate Change Affect Wildfire Regimes in Mediterranean Landscapes

PubMed Central

Brotons, Lluís; Aquilué, Núria; de Cáceres, Miquel; Fortin, Marie-Josée; Fall, Andrew

2013-01-01

Available data show that future changes in global change drivers may lead to an increasing impact of fires on terrestrial ecosystems worldwide. Yet, fire regime changes in highly humanised fire-prone regions are difficult to predict because fire effects may be heavily mediated by human activities We investigated the role of fire suppression strategies in synergy with climate change on the resulting fire regimes in Catalonia (north-eastern Spain). We used a spatially-explicit fire-succession model at the landscape level to test whether the use of different firefighting opportunities related to observed reductions in fire spread rates and effective fire sizes, and hence changes in the fire regime. We calibrated this model with data from a period with weak firefighting and later assess the potential for suppression strategies to modify fire regimes expected under different levels of climate change. When comparing simulations with observed fire statistics from an eleven-year period with firefighting strategies in place, our results showed that, at least in two of the three sub-regions analysed, the observed fire regime could not be reproduced unless taking into account the effects of fire suppression. Fire regime descriptors were highly dependent on climate change scenarios, with a general trend, under baseline scenarios without fire suppression, to large-scale increases in area burnt. Fire suppression strategies had a strong capacity to compensate for climate change effects. However, strong active fire suppression was necessary to accomplish such compensation, while more opportunistic fire suppression strategies derived from recent fire history only had a variable, but generally weak, potential for compensation of enhanced fire impacts under climate change. The concept of fire regime in the Mediterranean is probably better interpreted as a highly dynamic process in which the main determinants of fire are rapidly modified by changes in landscape, climate and socioeconomic factors such as fire suppression strategies. PMID:23658726

How fire history, fire suppression practices and climate change affect wildfire regimes in Mediterranean landscapes.

PubMed

Brotons, Lluís; Aquilué, Núria; de Cáceres, Miquel; Fortin, Marie-Josée; Fall, Andrew

2013-01-01

Available data show that future changes in global change drivers may lead to an increasing impact of fires on terrestrial ecosystems worldwide. Yet, fire regime changes in highly humanised fire-prone regions are difficult to predict because fire effects may be heavily mediated by human activities We investigated the role of fire suppression strategies in synergy with climate change on the resulting fire regimes in Catalonia (north-eastern Spain). We used a spatially-explicit fire-succession model at the landscape level to test whether the use of different firefighting opportunities related to observed reductions in fire spread rates and effective fire sizes, and hence changes in the fire regime. We calibrated this model with data from a period with weak firefighting and later assess the potential for suppression strategies to modify fire regimes expected under different levels of climate change. When comparing simulations with observed fire statistics from an eleven-year period with firefighting strategies in place, our results showed that, at least in two of the three sub-regions analysed, the observed fire regime could not be reproduced unless taking into account the effects of fire suppression. Fire regime descriptors were highly dependent on climate change scenarios, with a general trend, under baseline scenarios without fire suppression, to large-scale increases in area burnt. Fire suppression strategies had a strong capacity to compensate for climate change effects. However, strong active fire suppression was necessary to accomplish such compensation, while more opportunistic fire suppression strategies derived from recent fire history only had a variable, but generally weak, potential for compensation of enhanced fire impacts under climate change. The concept of fire regime in the Mediterranean is probably better interpreted as a highly dynamic process in which the main determinants of fire are rapidly modified by changes in landscape, climate and socioeconomic factors such as fire suppression strategies.

Divergence compensation for hardware-in-the-loop simulation of stiffness-varying discrete contact in space

NASA Astrophysics Data System (ADS)

Qi, Chenkun; Zhao, Xianchao; Gao, Feng; Ren, Anye; Hu, Yan

2016-11-01

The hardware-in-the-loop (HIL) contact simulation for flying objects in space is challenging due to the divergence caused by the time delay. In this study, a divergence compensation approach is proposed for the stiffness-varying discrete contact. The dynamic response delay of the motion simulator and the force measurement delay are considered. For the force measurement delay, a phase lead based force compensation approach is used. For the dynamic response delay of the motion simulator, a response error based force compensation approach is used, where the compensation force is obtained from the real-time identified contact stiffness and real-time measured position response error. The dynamic response model of the motion simulator is not required. The simulations and experiments show that the simulation divergence can be compensated effectively and satisfactorily by using the proposed approach.

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.

Local dynamic range compensation for scanning electron microscope imaging system.

PubMed

Sim, K S; Huang, Y H

2015-01-01

This is the extended project by introducing the modified dynamic range histogram modification (MDRHM) and is presented in this paper. This technique is used to enhance the scanning electron microscope (SEM) imaging system. By comparing with the conventional histogram modification compensators, this technique utilizes histogram profiling by extending the dynamic range of each tile of an image to the limit of 0-255 range while retains its histogram shape. The proposed technique yields better image compensation compared to conventional methods. © Wiley Periodicals, Inc.

Control of a haptic gear shifting assistance device utilizing a magnetorheological clutch

NASA Astrophysics Data System (ADS)

Han, Young-Min; Choi, Seung-Bok

2014-10-01

This paper proposes a haptic clutch driven gear shifting assistance device that can help when the driver shifts the gear of a transmission system. In order to achieve this goal, a magnetorheological (MR) fluid-based clutch is devised to be capable of the rotary motion of an accelerator pedal to which the MR clutch is integrated. The proposed MR clutch is then manufactured, and its transmission torque is experimentally evaluated according to the magnetic field intensity. The manufactured MR clutch is integrated with the accelerator pedal to transmit a haptic cue signal to the driver. The impending control issue is to cue the driver to shift the gear via the haptic force. Therefore, a gear-shifting decision algorithm is constructed by considering the vehicle engine speed concerned with engine combustion dynamics, vehicle dynamics and driving resistance. Then, the algorithm is integrated with a compensation strategy for attaining the desired haptic force. In this work, the compensator is also developed and implemented through the discrete version of the inverse hysteretic model. The control performances, such as the haptic force tracking responses and fuel consumption, are experimentally evaluated.

A new model predictive control algorithm by reducing the computing time of cost function minimization for NPC inverter in three-phase power grids.

PubMed

Taheri, Asghar; Zhalebaghi, Mohammad Hadi

2017-11-01

This paper presents a new control strategy based on finite-control-set model-predictive control (FCS-MPC) for Neutral-point-clamped (NPC) three-level converters. Containing some advantages like fast dynamic response, easy inclusion of constraints and simple control loop, makes the FCS-MPC method attractive to use as a switching strategy for converters. However, the large amount of required calculations is a problem in the widespread of this method. In this way, to resolve this problem this paper presents a modified method that effectively reduces the computation load compare with conventional FCS-MPC method and at the same time does not affect on control performance. The proposed method can be used for exchanging power between electrical grid and DC resources by providing active and reactive power compensations. Experiments on three-level converter for three Power Factor Correction (PFC), inductive and capacitive compensation modes verify the good and comparable performance. The results have been simulated using MATLAB/SIMULINK software. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Adaptive relative pose control for autonomous spacecraft rendezvous and proximity operations with thrust misalignment and model uncertainties

NASA Astrophysics Data System (ADS)

Sun, Liang; Zheng, Zewei

2017-04-01

An adaptive relative pose control strategy is proposed for a pursue spacecraft in proximity operations on a tumbling target. Relative position vector between two spacecraft is required to direct towards the docking port of the target while the attitude of them must be synchronized. With considering the thrust misalignment of pursuer, an integrated controller for relative translational and relative rotational dynamics is developed by using norm-wise adaptive estimations. Parametric uncertainties, unknown coupled dynamics, and bounded external disturbances are compensated online by adaptive update laws. It is proved via Lyapunov stability theory that the tracking errors of relative pose converge to zero asymptotically. Numerical simulations including six degrees-of-freedom rigid body dynamics are performed to demonstrate the effectiveness of the proposed controller.

Effects of assessing the productivity of faculty in academic medical centres: a systematic review.

PubMed

Akl, Elie A; Meerpohl, Joerg J; Raad, Dany; Piaggio, Giulia; Mattioni, Manlio; Paggi, Marco G; Gurtner, Aymone; Mattarocci, Stefano; Tahir, Rizwan; Muti, Paola; Schünemann, Holger J

2012-08-07

Many academic medical centres have introduced strategies to assess the productivity of faculty as part of compensation schemes. We conducted a systematic review of the effects of such strategies on faculty productivity. We searched the MEDLINE, Healthstar, Embase and PsycInfo databases from their date of inception up to October 2011. We included studies that assessed academic productivity in clinical, research, teaching and administrative activities, as well as compensation, promotion processes and satisfaction. Of 531 full-text articles assessed for eligibility, we included 9 articles reporting on eight studies. The introduction of strategies for assessing academic productivity as part of compensation schemes resulted in increases in clinical productivity (in six of six studies) in terms of clinical revenue, the work component of relative-value units (these units are nonmonetary standard units of measure used to indicate the value of services provided), patient satisfaction and other departmentally used standards. Increases in research productivity were noted (in five of six studies) in terms of funding and publications. There was no change in teaching productivity (in two of five studies) in terms of educational output. Such strategies also resulted in increases in compensation at both individual and group levels (in three studies), with two studies reporting a change in distribution of compensation in favour of junior faculty. None of the studies assessed effects on administrative productivity or promotion processes. The overall quality of evidence was low. Strategies introduced to assess productivity as part of a compensation scheme appeared to improve productivity in research activities and possibly improved clinical productivity, but they had no effect in the area of teaching. Compensation increased at both group and individual levels, particularly among junior faculty. Higher quality evidence about the benefits and harms of such assessment strategies is needed.

Dynamic gas temperature measurement system. Volume 2: Operation and program manual

NASA Technical Reports Server (NTRS)

Purpura, P. T.

1983-01-01

The hot section technology (HOST) dynamic gas temperature measurement system computer program acquires data from two type B thermocouples of different diameters. The analysis method determines the in situ value of an aerodynamic parameter T, containing the heat transfer coefficient from the transfer function of the two thermocouples. This aerodynamic parameter is used to compute a fequency response spectrum and compensate the dynamic portion of the signal of the smaller thermocouple. The calculations for the aerodynamic parameter and the data compensation technique are discussed. Compensated data are presented in either the time or frequency domain, time domain data as dynamic temperature vs time, or frequency domain data.

CSI, optimal control, and accelerometers: Trials and tribulations

NASA Technical Reports Server (NTRS)

Benjamin, Brian J.; Sesak, John R.

1994-01-01

New results concerning optimal design with accelerometers are presented. These results show that the designer must be concerned with the stability properties of two Linear Quadratic Gaussian (LQG) compensators, one of which does not explicitly appear in the closed-loop system dynamics. The new concepts of virtual and implemented compensators are introduced to cope with these subtleties. The virtual compensator appears in the closed-loop system dynamics and the implemented compensator appears in control electronics. The stability of one compensator does not guarantee the stability of the other. For strongly stable (robust) systems, both compensators should be stable. The presence of controlled and uncontrolled modes in the system results in two additional forms of the compensator with corresponding terms that are of like form, but opposite sign, making simultaneous stabilization of both the virtual and implemented compensator difficult. A new design algorithm termed sensor augmentation is developed that aids stabilization of these compensator forms by incorporating a static augmentation term associated with the uncontrolled modes in the design process.

Compensating Losses in Bridge Employment? Examining Relations between Compensation Strategies, Health Problems, and Intention to Remain at Work

ERIC Educational Resources Information Center

Muller, Andreas; De Lange, Annet; Weigl, Matthias; Oxfart, Caroline; Van der Heijden, Beatrice

2013-01-01

In order to better understand the precursors of bridge employment, this study aimed to investigate whether individual action strategies in terms of selection, optimization, and compensation (SOC; Baltes & Baltes, 1990) are able to buffer the well-known negative impact of poor health on the intention to remain in the workforce. 784 employees (60-85…

Compensating temperature-induced ultrasonic phase and amplitude changes

NASA Astrophysics Data System (ADS)

Gong, Peng; Hay, Thomas R.; Greve, David W.; Junker, Warren R.; Oppenheim, Irving J.

2016-04-01

In ultrasonic structural health monitoring (SHM), environmental and operational conditions, especially temperature, can significantly affect the propagation of ultrasonic waves and thus degrade damage detection. Typically, temperature effects are compensated using optimal baseline selection (OBS) or optimal signal stretch (OSS). The OSS method achieves compensation by adjusting phase shifts caused by temperature, but it does not fully compensate phase shifts and it does not compensate for accompanying signal amplitude changes. In this paper, we develop a new temperature compensation strategy to address both phase shifts and amplitude changes. In this strategy, OSS is first used to compensate some of the phase shifts and to quantify the temperature effects by stretching factors. Based on stretching factors, empirical adjusting factors for a damage indicator are then applied to compensate for the temperature induced remaining phase shifts and amplitude changes. The empirical adjusting factors can be trained from baseline data with temperature variations in the absence of incremental damage. We applied this temperature compensation approach to detect volume loss in a thick wall aluminum tube with multiple damage levels and temperature variations. Our specimen is a thick-walled short tube, with dimensions closely comparable to the outlet region of a frac iron elbow where flow-induced erosion produces the volume loss that governs the service life of that component, and our experimental sequence simulates the erosion process by removing material in small damage steps. Our results show that damage detection is greatly improved when this new temperature compensation strategy, termed modified-OSS, is implemented.

Dual-arm manipulators with adaptive control

NASA Technical Reports Server (NTRS)

Seraji, Homayoun (Inventor)

1991-01-01

The described and improved multi-arm invention of this application presents three strategies for adaptive control of cooperative multi-arm robots which coordinate control over a common load. In the position-position control strategy, the adaptive controllers ensure that the end-effector positions of both arms track desired trajectories in Cartesian space despite unknown time-varying interaction forces exerted through a load. In the position-hybrid control strategy, the adaptive controller of one arm controls end-effector motions in the free directions and applied forces in the constraint directions; while the adaptive controller of the other arm ensures that the end-effector tracks desired position trajectories. In the hybrid-hybrid control strategy, the adaptive controllers ensure that both end-effectors track reference position trajectories while simultaneously applying desired forces on the load. In all three control strategies, the cross-coupling effects between the arms are treated as disturbances which are compensated for by the adaptive controllers while following desired commands in a common frame of reference. The adaptive controllers do not require the complex mathematical model of the arm dynamics or any knowledge of the arm dynamic parameters or the load parameters such as mass and stiffness. Circuits in the adaptive feedback and feedforward controllers are varied by novel adaptation laws.

Method and apparatus for adaptive force and position control of manipulators

NASA Technical Reports Server (NTRS)

Seraji, Homayoun (Inventor)

1995-01-01

The described and improved multi-arm invention of this application presents three strategies for adaptive control of cooperative multi-arm robots which coordinate control over a common load. In the position-position control strategy, the adaptive controllers ensure that the end-effector positions of both arms track desired trajectories in Cartesian space despite unknown time-varying interaction forces exerted through a load. In the position-hybrid control strategy, the adaptive controller of one arm controls end-effector motions in the free directions and applied forces in the constraint directions; while the adaptive controller of the other arm ensures that the end-effector tracks desired position trajectories. In the hybrid-hybrid control strategy, the adaptive controllers ensure that both end-effectors track reference position trajectories while simultaneously applying desired forces on the load. In all three control strategies, the cross-coupling effects between the arms are treated as disturbances which are compensated for by the adaptive controllers while following desired commands in a common frame of reference. The adaptive controllers do not require the complex mathematical model of the arm dynamics or any knowledge of the arm dynamic parameters or the load parameters such as mass and stiffness. Circuits in the adaptive feedback and feedforward controllers are varied by novel adaptation laws.

Evidence for differential control of tibial position in perturbed unilateral stance after acute ACL rupture.

PubMed

Chmielewski, T L; Ramsey, D K; Snyder-Mackler, L

2005-01-01

Functional outcomes in anterior cruciate ligament-deficient "potential copers" and "non-copers" may be related to their knee stabilization strategies. Therefore, the purpose of this study was to differentiate dynamic knee stabilization strategies of potential copers and non-copers through analysis of sagittal plane knee angle and tibia position during disturbed and undisturbed unilateral standing. Ten uninjured potential coper and non-coper subjects stood in unilateral stance on a platform that translated anteriorly, posteriorly and laterally. Knee angle and tibia position with reference to the femur were calculated before and after platform movement. During perturbation trials, potential copers maintained kinematics that were similar to uninjured subjects across conditions. Conversely, non-copers stood with greater knee flexion than uninjured subjects and a tibia position that was more posterior than the other groups. Both non-copers and potential copers demonstrated small changes in tibia position following platform movement, but direction of movement was not similar. The similarities between the knee kinematics of potential copers and uninjured subjects suggest that potential copers compensated well from their injury by utilizing analogous dynamic knee stabilization strategies. In comparison to the other groups, by keeping the knee in greater flexion and the tibia in a more posterior position, non-copers appear to constrain the tibia in response to a challenging task, which is consistent with a "stiffening strategy". Based on the poor functional outcomes of non-copers, a stiffening strategy does not lead to dynamic knee stability, and the strategy may increase compressive forces which could contribute to or exacerbate articular cartilage degeneration.

Object impedance control for cooperative manipulation - Theory and experimental results

NASA Technical Reports Server (NTRS)

Schneider, Stanley A.; Cannon, Robert H., Jr.

1992-01-01

This paper presents the dynamic control module of the Dynamic and Strategic Control of Cooperating Manipulators (DASCCOM) project at Stanford University's Aerospace Robotics Laboratory. First, the cooperative manipulation problem is analyzed from a systems perspective, and the desirable features of a control system for cooperative manipulation are discussed. Next, a control policy is developed that enforces a controlled impedance not of the individual arm endpoints, but of the manipulated object itself. A parallel implementation for a multiprocessor system is presented. The controller fully compensates for the system dynamics and directly controls the object internal forces. Most importantly, it presents a simple, powerful, intuitive interface to higher level strategic control modules. Experimental results from a dual two-link-arm robotic system are used to compare the object impedance controller with other strategies, both for free-motion slews and environmental contact.

Dynamic impedance compensation for wireless power transfer using conjugate power

NASA Astrophysics Data System (ADS)

Liu, Suqi; Tan, Jianping; Wen, Xue

2018-02-01

Wireless power transfer (WPT) via coupled magnetic resonances has been in development for over a decade. However, the frequency splitting phenomenon occurs in the over-coupled region. Thus, the output power of the two-coil system achieves the maximum output power at the two splitting angular frequencies, and not at the natural resonant angular frequency. According to the maximum power transfer theorem, the impedance compensation method was adopted in many WPT projects. However, it remains a challenge to achieve the maximum output power and transmission efficiency in a fixed-frequency mode. In this study, dynamic impedance compensation for WPT was presented by utilizing the compensator within a virtual three-coil WPT system. First, the circuit model was established and transfer characteristics of a system were studied by utilizing circuit theories. Second, the power superposition of the WPT system was carefully researched. When a pair of compensating coils was inserted into the transmitter loop, the conjugate power of the compensator loop was created via magnetic coupling of the two compensating coils that insert into the transmitter loop. The mechanism for dynamic impedance compensation for wireless power transfer was then provided by investigating a virtual three-coil WPT system. Finally, the experimental circuit of a virtual three-coil WPT system was designed, and experimental results are consistent with the theoretical analysis, which achieves the maximum output power and transmission efficiency.

A comprehensive inversion approach for feedforward compensation of piezoactuator system at high frequency

NASA Astrophysics Data System (ADS)

Tian, Lizhi; Xiong, Zhenhua; Wu, Jianhua; Ding, Han

2016-09-01

Motion control of the piezoactuator system over broadband frequencies is limited due to its inherent hysteresis and system dynamics. One of the suggested ways is to use feedforward controller to linearize the input-output relationship of the piezoactuator system. Although there have been many feedforward approaches, it is still a challenge to develop feedforward controller for the piezoactuator system at high frequency. Hence, this paper presents a comprehensive inversion approach in consideration of the coupling of hysteresis and dynamics. In this work, the influence of dynamics compensation on the input-output relationship of the piezoactuator system is investigated first. With system dynamics compensation, the input-output relationship of the piezoactuator system will be further represented as rate-dependent nonlinearity due to the inevitable dynamics compensation error, especially at high frequency. Base on this result, the feedforward controller composed by a cascade of linear dynamics inversion and rate-dependent nonlinearity inversion is developed. Then, the system identification of the comprehensive inversion approach is proposed. Finally, experimental results show that the proposed approach can improve the performance on tracking of both periodic and non-periodic trajectories at medium and high frequency compared with the conventional feedforward approaches.

Dynamic gas temperature measurement system

NASA Technical Reports Server (NTRS)

Elmore, D. L.; Robinson, W. W.; Watkins, W. B.

1983-01-01

A gas temperature measurement system with compensated frequency response of 1 KHz and capability to operate in the exhaust of a gas turbine combustor was developed. Environmental guidelines for this measurement are presented, followed by a preliminary design of the selected measurement method. Transient thermal conduction effects were identified as important; a preliminary finite-element conduction model quantified the errors expected by neglecting conduction. A compensation method was developed to account for effects of conduction and convection. This method was verified in analog electrical simulations, and used to compensate dynamic temperature data from a laboratory combustor and a gas turbine engine. Detailed data compensations are presented. Analysis of error sources in the method were done to derive confidence levels for the compensated data.

Effects of assessing the productivity of faculty in academic medical centres: a systematic review

PubMed Central

Akl, Elie A.; Meerpohl, Joerg J.; Raad, Dany; Piaggio, Giulia; Mattioni, Manlio; Paggi, Marco G.; Gurtner, Aymone; Mattarocci, Stefano; Tahir, Rizwan; Muti, Paola; Schünemann, Holger J.

2012-01-01

Background: Many academic medical centres have introduced strategies to assess the productivity of faculty as part of compensation schemes. We conducted a systematic review of the effects of such strategies on faculty productivity. Methods: We searched the MEDLINE, Healthstar, Embase and PsycInfo databases from their date of inception up to October 2011. We included studies that assessed academic productivity in clinical, research, teaching and administrative activities, as well as compensation, promotion processes and satisfaction. Results: Of 531 full-text articles assessed for eligibility, we included 9 articles reporting on eight studies. The introduction of strategies for assessing academic productivity as part of compensation schemes resulted in increases in clinical productivity (in six of six studies) in terms of clinical revenue, the work component of relative-value units (these units are nonmonetary standard units of measure used to indicate the value of services provided), patient satisfaction and other departmentally used standards. Increases in research productivity were noted (in five of six studies) in terms of funding and publications. There was no change in teaching productivity (in two of five studies) in terms of educational output. Such strategies also resulted in increases in compensation at both individual and group levels (in three studies), with two studies reporting a change in distribution of compensation in favour of junior faculty. None of the studies assessed effects on administrative productivity or promotion processes. The overall quality of evidence was low. Interpretation: Strategies introduced to assess productivity as part of a compensation scheme appeared to improve productivity in research activities and possibly improved clinical productivity, but they had no effect in the area of teaching. Compensation increased at both group and individual levels, particularly among junior faculty. Higher quality evidence about the benefits and harms of such assessment strategies is needed. PMID:22641686

Effects of Instantaneous Multiband Dynamic Compression on Speech Intelligibility

NASA Astrophysics Data System (ADS)

Herzke, Tobias; Hohmann, Volker

2005-12-01

The recruitment phenomenon, that is, the reduced dynamic range between threshold and uncomfortable level, is attributed to the loss of instantaneous dynamic compression on the basilar membrane. Despite this, hearing aids commonly use slow-acting dynamic compression for its compensation, because this was found to be the most successful strategy in terms of speech quality and intelligibility rehabilitation. Former attempts to use fast-acting compression gave ambiguous results, raising the question as to whether auditory-based recruitment compensation by instantaneous compression is in principle applicable in hearing aids. This study thus investigates instantaneous multiband dynamic compression based on an auditory filterbank. Instantaneous envelope compression is performed in each frequency band of a gammatone filterbank, which provides a combination of time and frequency resolution comparable to the normal healthy cochlea. The gain characteristics used for dynamic compression are deduced from categorical loudness scaling. In speech intelligibility tests, the instantaneous dynamic compression scheme was compared against a linear amplification scheme, which used the same filterbank for frequency analysis, but employed constant gain factors that restored the sound level for medium perceived loudness in each frequency band. In subjective comparisons, five of nine subjects preferred the linear amplification scheme and would not accept the instantaneous dynamic compression in hearing aids. Four of nine subjects did not perceive any quality differences. A sentence intelligibility test in noise (Oldenburg sentence test) showed little to no negative effects of the instantaneous dynamic compression, compared to linear amplification. A word intelligibility test in quiet (one-syllable rhyme test) showed that the subjects benefit from the larger amplification at low levels provided by instantaneous dynamic compression. Further analysis showed that the increase in intelligibility resulting from a gain provided by instantaneous compression is as high as from a gain provided by linear amplification. No negative effects of the distortions introduced by the instantaneous compression scheme in terms of speech recognition are observed.

A model predictive current control of flux-switching permanent magnet machines for torque ripple minimization

NASA Astrophysics Data System (ADS)

Huang, Wentao; Hua, Wei; Yu, Feng

2017-05-01

Due to high airgap flux density generated by magnets and the special double salient structure, the cogging torque of the flux-switching permanent magnet (FSPM) machine is considerable, which limits the further applications. Based on the model predictive current control (MPCC) and the compensation control theory, a compensating-current MPCC (CC-MPCC) scheme is proposed and implemented to counteract the dominated components in cogging torque of an existing three-phase 12/10 FSPM prototyped machine, and thus to alleviate the influence of the cogging torque and improve the smoothness of electromagnetic torque as well as speed, where a comprehensive cost function is designed to evaluate the switching states. The simulated results indicate that the proposed CC-MPCC scheme can suppress the torque ripple significantly and offer satisfactory dynamic performances by comparisons with the conventional MPCC strategy. Finally, experimental results validate both the theoretical and simulated predictions.

Direct observation of coherent energy transfer in nonlinear micromechanical oscillators.

PubMed

Chen, Changyao; Zanette, Damián H; Czaplewski, David A; Shaw, Steven; López, Daniel

2017-05-26

Energy dissipation is an unavoidable phenomenon of physical systems that are directly coupled to an external environmental bath. In an oscillatory system, it leads to the decay of the oscillation amplitude. In situations where stable oscillations are required, the energy dissipated by the vibrations is usually compensated by replenishment from external energy sources. Consequently, if the external energy supply is removed, the amplitude of oscillations start to decay immediately, since there is no means to restitute the energy dissipated. Here, we demonstrate a novel dissipation engineering strategy that can support stable oscillations without supplying external energy to compensate losses. The fundamental intrinsic mechanism of resonant mode coupling is used to redistribute and store mechanical energy among vibrational modes and coherently transfer it back to the principal mode when the external excitation is off. To experimentally demonstrate this phenomenon, we exploit the nonlinear dynamic response of microelectromechanical oscillators to couple two different vibrational modes through an internal resonance.

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.

L2 Skills and the Use of Compensation Strategies: The Case of Adult Learners

ERIC Educational Resources Information Center

Lopez Medina, Beatriz

2010-01-01

The following article is based on the analysis of the compensation strategies used by two groups of intermediate students of English language at the Official School of Languages of Moratalaz (Madrid) in the academic year 2009/2010. Our analysis tries to describe to what extent adult learners make use of suitable learning strategies in the four…

A Report on Administrative Compensation Planning for St. Paul Public School Personnel.

ERIC Educational Resources Information Center

Hooker, Clifford P.; Mueller, Van D.

This report describes and analyzes various devices and techniques that may be utilized in planning local school administrative compensation. The document outlines broad overall goals for compensation planning, describes and evaluates the application of a compensation plan in the St. Paul schools, and proposes alternative strategies for…

Motion-Compensated Compression of Dynamic Voxelized Point Clouds.

PubMed

De Queiroz, Ricardo L; Chou, Philip A

2017-05-24

Dynamic point clouds are a potential new frontier in visual communication systems. A few articles have addressed the compression of point clouds, but very few references exist on exploring temporal redundancies. This paper presents a novel motion-compensated approach to encoding dynamic voxelized point clouds at low bit rates. A simple coder breaks the voxelized point cloud at each frame into blocks of voxels. Each block is either encoded in intra-frame mode or is replaced by a motion-compensated version of a block in the previous frame. The decision is optimized in a rate-distortion sense. In this way, both the geometry and the color are encoded with distortion, allowing for reduced bit-rates. In-loop filtering is employed to minimize compression artifacts caused by distortion in the geometry information. Simulations reveal that this simple motion compensated coder can efficiently extend the compression range of dynamic voxelized point clouds to rates below what intra-frame coding alone can accommodate, trading rate for geometry accuracy.

Compensation Techniques in Accelerator Physics

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

Sayed, Hisham Kamal

2011-05-01

Accelerator physics is one of the most diverse multidisciplinary fields of physics, wherein the dynamics of particle beams is studied. It takes more than the understanding of basic electromagnetic interactions to be able to predict the beam dynamics, and to be able to develop new techniques to produce, maintain, and deliver high quality beams for different applications. In this work, some basic theory regarding particle beam dynamics in accelerators will be presented. This basic theory, along with applying state of the art techniques in beam dynamics will be used in this dissertation to study and solve accelerator physics problems. Twomore » problems involving compensation are studied in the context of the MEIC (Medium Energy Electron Ion Collider) project at Jefferson Laboratory. Several chromaticity (the energy dependence of the particle tune) compensation methods are evaluated numerically and deployed in a figure eight ring designed for the electrons in the collider. Furthermore, transverse coupling optics have been developed to compensate the coupling introduced by the spin rotators in the MEIC electron ring design.« less

Synthesis of nonlinear control strategies from fuzzy logic control algorithms

NASA Technical Reports Server (NTRS)

Langari, Reza

1993-01-01

Fuzzy control has been recognized as an alternative to conventional control techniques in situations where the plant model is not sufficiently well known to warrant the application of conventional control techniques. Precisely what fuzzy control does and how it does what it does is not quite clear, however. This important issue is discussed and in particular it is shown how a given fuzzy control scheme can resolve into a nonlinear control law and that in those situations the success of fuzzy control hinges on its ability to compensate for nonlinearities in plant dynamics.

Nonlinear fractional order proportion-integral-derivative active disturbance rejection control method design for hypersonic vehicle attitude control

NASA Astrophysics Data System (ADS)

Song, Jia; Wang, Lun; Cai, Guobiao; Qi, Xiaoqiang

2015-06-01

Near space hypersonic vehicle model is nonlinear, multivariable and couples in the reentry process, which are challenging for the controller design. In this paper, a nonlinear fractional order proportion integral derivative (NFOPIλDμ) active disturbance rejection control (ADRC) strategy based on a natural selection particle swarm (NSPSO) algorithm is proposed for the hypersonic vehicle flight control. The NFOPIλDμ ADRC method consists of a tracking-differentiator (TD), an NFOPIλDμ controller and an extended state observer (ESO). The NFOPIλDμ controller designed by combining an FOPIλDμ method and a nonlinear states error feedback control law (NLSEF) is to overcome concussion caused by the NLSEF and conversely compensate the insufficiency for relatively simple and rough signal processing caused by the FOPIλDμ method. The TD is applied to coordinate the contradiction between rapidity and overshoot. By attributing all uncertain factors to unknown disturbances, the ESO can achieve dynamic feedback compensation for these disturbances and thus reduce their effects. Simulation results show that the NFOPIλDμ ADRC method can make the hypersonic vehicle six-degree-of-freedom nonlinear model track desired nominal signals accurately and fast, has good stability, dynamic properties and strong robustness against external environmental disturbances.

[Functional and dysfunctional emotion regulation strategies for depressive symptoms in adolescents].

PubMed

Fern, Julia; Nitkowski, Dennis; Petermann, Ulrike; Petermann, Franz

2018-01-01

Dysfunctional and functional emotion regulation strategies in adolescence have so far been examined separately, but not in interaction. Our aim is to analyze a possible compensation of dysfunctional regulation strategies through functional strategies in depressive symptoms. Method: The Regulation of Emotions Questionnaire (REQ) was used to examine the ability of emotion regulation in 247 adolescents between 12 to 17 years (M = 14.41, SD = 1.39). To measure depressive symptoms, Allgemeine Depressionsskala (ADS) was established. Results speak for a compensation of internal-dysfunctional emotion regulation strategies with internal-functional emotion regulation strategies in girls. In boys, functional emotion regulation strategies strengthen the relationship between internal-dysfunctional emotion regulation strategies and depressive symptoms. Other strategies do not interact with each another. Results indicate a compensative effect in girls, while in boys functional emotion regulation seems to have an amplifying effect on depressive symptoms. Results suggest that boys use functional strategies in a dysfunctional way, while girls are able to use them appropriately. An exploration of the understanding of functional emotion regulation may enable approaches to treatment.

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.

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.

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.

Compensatory strategies during manual wheelchair propulsion in response to weakness in individual muscle groups: A simulation study.

PubMed

Slowik, Jonathan S; McNitt-Gray, Jill L; Requejo, Philip S; Mulroy, Sara J; Neptune, Richard R

2016-03-01

The considerable physical demand placed on the upper extremity during manual wheelchair propulsion is distributed among individual muscles. The strategy used to distribute the workload is likely influenced by the relative force-generating capacities of individual muscles, and some strategies may be associated with a higher injury risk than others. The objective of this study was to use forward dynamics simulations of manual wheelchair propulsion to identify compensatory strategies that can be used to overcome weakness in individual muscle groups and identify specific strategies that may increase injury risk. Identifying these strategies can provide rationale for the design of targeted rehabilitation programs aimed at preventing the development of pain and injury in manual wheelchair users. Muscle-actuated forward dynamics simulations of manual wheelchair propulsion were analyzed to identify compensatory strategies in response to individual muscle group weakness using individual muscle mechanical power and stress as measures of upper extremity demand. The simulation analyses found the upper extremity to be robust to weakness in any single muscle group as the remaining groups were able to compensate and restore normal propulsion mechanics. The rotator cuff muscles experienced relatively high muscle stress levels and exhibited compensatory relationships with the deltoid muscles. These results underline the importance of strengthening the rotator cuff muscles and supporting muscles whose contributions do not increase the potential for impingement (i.e., the thoracohumeral depressors) and minimize the risk of upper extremity injury in manual wheelchair users. Copyright © 2016 Elsevier Ltd. All rights reserved.

Compensatory Strategies during Manual Wheelchair Propulsion in Response to Weakness in Individual Muscle Groups: A Simulation Study

PubMed Central

Slowik, Jonathan S.; McNitt-Gray, Jill L.; Requejo, Philip S.; Mulroy, Sara J.; Neptune, Richard R.

2016-01-01

Background The considerable physical demand placed on the upper extremity during manual wheelchair propulsion is distributed among the individual muscles. The strategy used to distribute the workload is likely influenced by the relative force-generating capacities of individual muscles, and some strategies may be associated with a higher injury risk than others. The objective of this study was to use forward dynamics simulations of manual wheelchair propulsion to identify compensatory strategies that can be used to overcome weakness in individual muscle groups and identify specific strategies that may increase injury risk. Identifying these strategies can provide rationale for the design of targeted rehabilitation programs aimed at preventing the development of pain and injury in manual wheelchair users. Methods Muscle-actuated forward dynamics simulations of manual wheelchair propulsion were analyzed to identify compensatory strategies in response to individual muscle group weakness, using individual muscle mechanical power and stress as measures of upper extremity demand. Findings The simulation analyses found the upper extremity to be robust to weakness in any single muscle group as the remaining groups were able to compensate and restore normal propulsion mechanics. The rotator cuff muscles experienced relatively high muscle stress levels and exhibited compensatory relationships with the deltoid muscles. Interpretation These results underline the importance of strengthening the rotator cuff muscles and supporting muscles whose contributions do not increase the potential for impingement (i.e., the thoracohumeral depressors) and minimize the risk of upper extremity injury in manual wheelchair users. PMID:26945719

Tackling Energy Loss for High-Efficiency Organic Solar Cells with Integrated Multiple Strategies.

PubMed

Zuo, Lijian; Shi, Xueliang; Jo, Sae Byeok; Liu, Yun; Lin, Fracis; Jen, Alex K-Y

2018-04-01

Limited by the various inherent energy losses from multiple channels, organic solar cells show inferior device performance compared to traditional inorganic photovoltaic techniques, such as silicon and CuInGaSe. To alleviate these fundamental limitations, an integrated multiple strategy is implemented including molecular design, interfacial engineering, optical manipulation, and tandem device construction into one cell. Considering the close correlation among these loss channels, a sophisticated quantification of energy-loss reduction is tracked along with each strategy in a perspective to reach rational overall optimum. A novel nonfullerene acceptor, 6TBA, is synthesized to resolve the thermalization and V OC loss, and another small bandgap nonfullerene acceptor, 4TIC, is used in the back sub-cell to alleviate transmission loss. Tandem architecture design significantly reduces the light absorption loss, and compensates carrier dynamics and thermalization loss. Interfacial engineering further reduces energy loss from carrier dynamics in the tandem architecture. As a result of this concerted effort, a very high power conversion efficiency (13.20%) is obtained. A detailed quantitative analysis on the energy losses confirms that the improved device performance stems from these multiple strategies. The results provide a rational way to explore the ultimate device performance through molecular design and device engineering. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The "perfect storm" in compensation: convergence of events leads to a greater need to review compensation strategies.

PubMed

Jones, Robert B

2004-01-01

The recent unprecedented convergence of significant strategic events in the compensation arena has created the need for ongoing and extensive compensation planning. This article reviews the events leading to this point, describes the implications of the results from a recent Aon study with WorldatWork, and suggests what employers can do to successfully navigate the "perfect storm" in compensation.

Field Balancing and Harmonic Vibration Suppression in Rigid AMB-Rotor Systems with Rotor Imbalances and Sensor Runout.

PubMed

Xu, Xiangbo; Chen, Shao

2015-08-31

Harmonic vibrations of high-speed rotors in momentum exchange devices are primary disturbances for attitude control of spacecraft. Active magnetic bearings (AMBs), offering the ability to control the AMB-rotor dynamic behaviors, are preferred in high-precision and micro-vibration applications, such as high-solution Earth observation satellites. However, undesirable harmonic displacements, currents, and vibrations also occur in the AMB-rotor system owing to the mixed rotor imbalances and sensor runout. To compensate the rotor imbalances and to suppress the harmonic vibrations, two control methods are presented. Firstly, a four degrees-of-freedom AMB-rotor model with the static imbalance, dynamic imbalance, and the sensor runout are described. Next, a synchronous current reduction approach with a variable-phase notch feedback is proposed, so that the rotor imbalances can be identified on-line through the analysis of the synchronous displacement relationships of the geometric, inertial, and rotational axes of the rotor. Then, the identified rotor imbalances, which can be represented at two prescribed balancing planes of the rotor, are compensated by discrete add-on weights whose masses are calculated in the vector form. Finally, a repetitive control algorithm is utilized to suppress the residual harmonic vibrations. The proposed field balancing and harmonic vibration suppression strategies are verified by simulations and experiments performed on a control moment gyro test rig with a rigid AMB-rotor system. Compared with existing methods, the proposed strategies do not require trial weights or an accurate model of the AMB-rotor system. Moreover, the harmonic displacements, currents, and vibrations can be well-attenuated simultaneously.

Field Balancing and Harmonic Vibration Suppression in Rigid AMB-Rotor Systems with Rotor Imbalances and Sensor Runout

PubMed Central

Xu, Xiangbo; Chen, Shao

2015-01-01

Harmonic vibrations of high-speed rotors in momentum exchange devices are primary disturbances for attitude control of spacecraft. Active magnetic bearings (AMBs), offering the ability to control the AMB-rotor dynamic behaviors, are preferred in high-precision and micro-vibration applications, such as high-solution Earth observation satellites. However, undesirable harmonic displacements, currents, and vibrations also occur in the AMB-rotor system owing to the mixed rotor imbalances and sensor runout. To compensate the rotor imbalances and to suppress the harmonic vibrations, two control methods are presented. Firstly, a four degrees-of-freedom AMB-rotor model with the static imbalance, dynamic imbalance, and the sensor runout are described. Next, a synchronous current reduction approach with a variable-phase notch feedback is proposed, so that the rotor imbalances can be identified on-line through the analysis of the synchronous displacement relationships of the geometric, inertial, and rotational axes of the rotor. Then, the identified rotor imbalances, which can be represented at two prescribed balancing planes of the rotor, are compensated by discrete add-on weights whose masses are calculated in the vector form. Finally, a repetitive control algorithm is utilized to suppress the residual harmonic vibrations. The proposed field balancing and harmonic vibration suppression strategies are verified by simulations and experiments performed on a control moment gyro test rig with a rigid AMB-rotor system. Compared with existing methods, the proposed strategies do not require trial weights or an accurate model of the AMB-rotor system. Moreover, the harmonic displacements, currents, and vibrations can be well-attenuated simultaneously. PMID:26334281

The Use of Compensation Strategies in the Iranian EFL Learners' Speaking and Its Relationship with Their Foreign Language Proficiency

ERIC Educational Resources Information Center

Taheri, Ali Akbar; Davoudi, Mohammad

2016-01-01

Compensation Strategies (CpSs) are strategies which a language user employs in order to achieve his intended meaning when precise linguistic forms are for some reasons not available at that point of communication. Different factors may influence the use of CpSs, among which the level of language proficiency is one of the most important ones. The…

Memory compensation in older adults: the role of health, emotion regulation, and trait mindfulness.

PubMed

de Frias, Cindy M

2014-09-01

The current study examined associations between everyday memory compensation and 3 person-level resource domains (i.e., health, emotion regulation, and trait mindfulness) in older adults. In this cross-sectional study, 89 healthy, community-dwelling older adults (ages 51-85 years) completed the multidimensional Memory Compensation Questionnaire, along with measures of self-reported health status, emotion regulation strategies, and trait mindfulness. Hierarchical regressions (covarying for age, gender, and education) showed that poorer mental health (especially for older adults) and physical health functioning were related to using compensatory strategies (e.g., reliance on others and investment of time and effort) more frequently. Cognitive reappraisers reported using more internal mnemonic strategies. Conversely, having a more mindful predisposition was associated with less frequent use of compensatory strategies, especially for middle-aged adults. The results suggest that health-related quality of life, adaptive strategies to regulate emotions, and trait mindfulness are additional contexts that determine the degree of engagement in everyday memory compensation and ultimately to successful aging. © The Author 2013. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Compound Velocity Synchronizing Control Strategy for Electro-Hydraulic Load Simulator and Its Engineering Application.

PubMed

Han, Songshan; Jiao, Zongxia; Yao, Jianyong; Shang, Yaoxing

2014-09-01

An electro-hydraulic load simulator (EHLS) is a typical case of torque systems with strong external disturbances from hydraulic motion systems. A new velocity synchronizing compensation strategy is proposed in this paper to eliminate motion disturbances, based on theoretical and experimental analysis of a structure invariance method and traditional velocity synchronizing compensation controller (TVSM). This strategy only uses the servo-valve's control signal of motion system and torque feedback of torque system, which could avoid the requirement on the velocity and acceleration signal in the structure invariance method, and effectively achieve a more accurate velocity synchronizing compensation in large loading conditions than a TVSM. In order to facilitate the implementation of this strategy in engineering cases, the selection rules for compensation parameters are proposed. It does not rely on any accurate information of structure parameters. This paper presents the comparison data of an EHLS with various typical operating conditions using three controllers, i.e., closed loop proportional integral derivative (PID) controller, TVSM, and the proposed improved velocity synchronizing controller. Experiments are conducted to confirm that the new strategy performs well against motion disturbances. It is more effective to improve the tracking accuracy and is a more appropriate choice for engineering applications.

Inertial measurement unit using rotatable MEMS sensors

DOEpatents

Kohler, Stewart M [Albuquerque, NM; Allen, James J [Albuquerque, NM

2007-05-01

A MEM inertial sensor (e.g. accelerometer, gyroscope) having integral rotational means for providing static and dynamic bias compensation is disclosed. A bias compensated MEM inertial sensor is described comprising a MEM inertial sense element disposed on a rotatable MEM stage. A MEM actuator drives the rotation of the stage between at least two predetermined rotational positions. Measuring and comparing the output of the MEM inertial sensor in the at least two rotational positions allows for both static and dynamic bias compensation in inertial calculations based on the sensor's output. An inertial measurement unit (IMU) comprising a plurality of independently rotatable MEM inertial sensors and methods for making bias compensated inertial measurements are disclosed.

Inertial measurement unit using rotatable MEMS sensors

DOEpatents

Kohler, Stewart M.; Allen, James J.

2006-06-27

A MEM inertial sensor (e.g. accelerometer, gyroscope) having integral rotational means for providing static and dynamic bias compensation is disclosed. A bias compensated MEM inertial sensor is described comprising a MEM inertial sense element disposed on a rotatable MEM stage. A MEM actuator for drives the rotation of the stage between at least two predetermined rotational positions. Measuring and comparing the output of the MEM inertial sensor in the at least two rotational positions allows, for both static and dynamic bias compensation in inertial calculations based on the sensor's output. An inertial measurement unit (IMU) comprising a plurality of independently rotatable MEM inertial sensors and methods for making bias compensated inertial measurements are disclosed.

Satellite Dynamic Damping via Active Force Control Augmentation

NASA Astrophysics Data System (ADS)

Varatharajoo, Renuganth

2012-07-01

An approach that incorporates the Active Force Control (AFC) technique into a conventional Proportional-Derivative (PD) controller is proposed for a satellite active dynamic damping towards a full attitude control. The AFC method has been established to facilitate a robust motion control of dynamical systems in the presence of disturbances, parametric uncertainties and changes that are commonly prevalent in the real-world environment. The usefulness of the method can be extended by introducing intelligent mechanisms to approximate the mass or inertia matrix of the dynamic system to trigger the compensation effect of the controller. AFC is a technique that relies on the appropriate estimation of the inertial or mass parameters of the dynamic system and the measurements of the acceleration and force signals induced by the system if practical implementation is ever considered. In AFC, it is shown that the system subjected to a number of disturbances remains stable and robust via the compensating action of the control strategy. We demonstrate that it is possible to design a spacecraft attitude feedback controller that will ensure the system dynamics set point remains unchanged even in the presence of the disturbances provided that the actual disturbances can be modeled effectively. In order to further facilitate this analysis, a combined energy and attitude control system (CEACS) is proposed as a model satellite attitude control actuator. All the governing equations are established and the proposed satellite attitude control architecture is made amenable to numerical treatments. The results show that the PD-AFC attitude damping performances are superiorly better than that of the solely PD type. It is also shown that the tunings of the AFC system gains are crucial to ensure a better attitude damping performance and this process is mandatory for AFC systems. Finally, the results demonstrate an important satellite dynamic damping enhancement capability using the AFC technique. Keywords: Satellite, Dynamic Damping, Attitude Control, AFC Technique,

Dynamic neural network-based methods for compensation of nonlinear effects in multimode communication lines

NASA Astrophysics Data System (ADS)

Sidelnikov, O. S.; Redyuk, A. A.; Sygletos, S.

2017-12-01

We consider neural network-based schemes of digital signal processing. It is shown that the use of a dynamic neural network-based scheme of signal processing ensures an increase in the optical signal transmission quality in comparison with that provided by other methods for nonlinear distortion compensation.

Clinical evaluation of 4D PET motion compensation strategies for treatment verification in ion beam therapy

NASA Astrophysics Data System (ADS)

Gianoli, Chiara; Kurz, Christopher; Riboldi, Marco; Bauer, Julia; Fontana, Giulia; Baroni, Guido; Debus, Jürgen; Parodi, Katia

2016-06-01

A clinical trial named PROMETHEUS is currently ongoing for inoperable hepatocellular carcinoma (HCC) at the Heidelberg Ion Beam Therapy Center (HIT, Germany). In this framework, 4D PET-CT datasets are acquired shortly after the therapeutic treatment to compare the irradiation induced PET image with a Monte Carlo PET prediction resulting from the simulation of treatment delivery. The extremely low count statistics of this measured PET image represents a major limitation of this technique, especially in presence of target motion. The purpose of the study is to investigate two different 4D PET motion compensation strategies towards the recovery of the whole count statistics for improved image quality of the 4D PET-CT datasets for PET-based treatment verification. The well-known 4D-MLEM reconstruction algorithm, embedding the motion compensation in the reconstruction process of 4D PET sinograms, was compared to a recently proposed pre-reconstruction motion compensation strategy, which operates in sinogram domain by applying the motion compensation to the 4D PET sinograms. With reference to phantom and patient datasets, advantages and drawbacks of the two 4D PET motion compensation strategies were identified. The 4D-MLEM algorithm was strongly affected by inverse inconsistency of the motion model but demonstrated the capability to mitigate the noise-break-up effects. Conversely, the pre-reconstruction warping showed less sensitivity to inverse inconsistency but also more noise in the reconstructed images. The comparison was performed by relying on quantification of PET activity and ion range difference, typically yielding similar results. The study demonstrated that treatment verification of moving targets could be accomplished by relying on the whole count statistics image quality, as obtained from the application of 4D PET motion compensation strategies. In particular, the pre-reconstruction warping was shown to represent a promising choice when combined with intra-reconstruction smoothing.

Adaptive Optics Analysis of Visual Benefit with Higher-order Aberrations Correction of Human Eye - Poster Paper

NASA Astrophysics Data System (ADS)

Xue, Lixia; Dai, Yun; Rao, Xuejun; Wang, Cheng; Hu, Yiyun; Liu, Qian; Jiang, Wenhan

2008-01-01

Higher-order aberrations correction can improve visual performance of human eye to some extent. To evaluate how much visual benefit can be obtained with higher-order aberrations correction we developed an adaptive optics vision simulator (AOVS). Dynamic real time optimized modal compensation was used to implement various customized higher-order ocular aberrations correction strategies. The experimental results indicate that higher-order aberrations correction can improve visual performance of human eye comparing with only lower-order aberration correction but the improvement degree and higher-order aberration correction strategy are different from each individual. Some subjects can acquire great visual benefit when higher-order aberrations were corrected but some subjects acquire little visual benefit even though all higher-order aberrations were corrected. Therefore, relative to general lower-order aberrations correction strategy, customized higher-order aberrations correction strategy is needed to obtain optimal visual improvement for each individual. AOVS provides an effective tool for higher-order ocular aberrations optometry for customized ocular aberrations correction.

Resitting or Compensating a Failed Examination: Does It Affect Subsequent Results?

ERIC Educational Resources Information Center

Arnold, Ivo

2017-01-01

Institutions of higher education commonly employ a conjunctive standard setting strategy, which requires students to resit failed examinations until they pass all tests. An alternative strategy allows students to compensate a failing grade with other test results. This paper uses regression discontinuity design to compare the effect of first-year…

Self-Regulatory Strategies in Daily Life: Selection, Optimization, and Compensation and Everyday Memory Problems

ERIC Educational Resources Information Center

Robinson, Stephanie A.; Rickenbach, Elizabeth H.; Lachman, Margie E.

2016-01-01

The effective use of self-regulatory strategies, such as selection, optimization, and compensation (SOC) requires resources. However, it is theorized that SOC use is most advantageous for those experiencing losses and diminishing resources. The present study explored this seeming paradox within the context of limitations or constraints due to…

3D dosimetric validation of motion compensation concepts in radiotherapy using an anthropomorphic dynamic lung phantom

NASA Astrophysics Data System (ADS)

Mann, P.; Witte, M.; Moser, T.; Lang, C.; Runz, A.; Johnen, W.; Berger, M.; Biederer, J.; Karger, C. P.

2017-01-01

In this study, we developed a new setup for the validation of clinical workflows in adaptive radiation therapy, which combines a dynamic ex vivo porcine lung phantom and three-dimensional (3D) polymer gel dosimetry. The phantom consists of an artificial PMMA-thorax and contains a post mortem explanted porcine lung to which arbitrary breathing patterns can be applied. A lung tumor was simulated using the PAGAT (polyacrylamide gelatin gel fabricated at atmospheric conditions) dosimetry gel, which was evaluated in three dimensions by magnetic resonance imaging (MRI). To avoid bias by reaction with oxygen and other materials, the gel was collocated inside a BAREX™ container. For calibration purposes, the same containers with eight gel samples were irradiated with doses from 0 to 7 Gy. To test the technical feasibility of the system, a small spherical dose distribution located completely within the gel volume was planned. Dose delivery was performed under static and dynamic conditions of the phantom with and without motion compensation by beam gating. To verify clinical target definition and motion compensation concepts, the entire gel volume was homogeneously irradiated applying adequate margins in case of the static phantom and an additional internal target volume in case of dynamically operated phantom without and with gated beam delivery. MR-evaluation of the gel samples and comparison of the resulting 3D dose distribution with the planned dose distribution revealed a good agreement for the static phantom. In case of the dynamically operated phantom without motion compensation, agreement was very poor while additional application of motion compensation techniques restored the good agreement between measured and planned dose. From these experiments it was concluded that the set up with the dynamic and anthropomorphic lung phantom together with 3D-gel dosimetry provides a valuable and versatile tool for geometrical and dosimetrical validation of motion compensated treatment concepts in adaptive radiotherapy.

Working on reform. How workers' compensation medical care is affected by health care reform.

PubMed

Himmelstein, J; Rest, K

1996-01-01

The medical component of workers' compensation programs-now costing over $24 billion annually-and the rest of the nation's medical care system are linked. They share the same patients and providers. They provide similar benefits and services. And they struggle over who should pay for what. Clearly, health care reform and restructuring will have a major impact on the operation and expenditures of the workers' compensation system. For a brief period, during the 1994 national health care reform debate, these two systems were part of the same federal policy development and legislative process. With comprehensive health care reform no longer on the horizon, states now are tackling both workers' compensation and medical system reforms on their own. This paper reviews the major issues federal and state policy makers face as they consider reforms affecting the relationship between workers' compensation and traditional health insurance. What is the relationship of the workers' compensation cost crisis to that in general health care? What strategies are being considered by states involved in reforming the medical component of workers compensation? What are the major policy implications of these strategies?

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…

Nursing performance under high workload: a diary study on the moderating role of selection, optimization and compensation strategies.

PubMed

Baethge, Anja; Müller, Andreas; Rigotti, Thomas

2016-03-01

The aim of this study was to investigate whether selective optimization with compensation constitutes an individualized action strategy for nurses wanting to maintain job performance under high workload. High workload is a major threat to healthcare quality and performance. Selective optimization with compensation is considered to enhance the efficient use of intra-individual resources and, therefore, is expected to act as a buffer against the negative effects of high workload. The study applied a diary design. Over five consecutive workday shifts, self-report data on workload was collected at three randomized occasions during each shift. Self-reported job performance was assessed in the evening. Self-reported selective optimization with compensation was assessed prior to the diary reporting. Data were collected in 2010. Overall, 136 nurses from 10 German hospitals participated. Selective optimization with compensation was assessed with a nine-item scale that was specifically developed for nursing. The NASA-TLX scale indicating the pace of task accomplishment was used to measure workload. Job performance was assessed with one item each concerning performance quality and forgetting of intentions. There was a weaker negative association between workload and both indicators of job performance in nurses with a high level of selective optimization with compensation, compared with nurses with a low level. Considering the separate strategies, selection and compensation turned out to be effective. The use of selective optimization with compensation is conducive to nurses' job performance under high workload levels. This finding is in line with calls to empower nurses' individual decision-making. © 2015 John Wiley & Sons Ltd.

Compensation Strategies: Tracking Movement in EFL Learners' Speaking Skills

ERIC Educational Resources Information Center

Karbalaei, Alireza; Negin Taji, Tania

2014-01-01

The present study aimed to determine the compensation strategies used by Iranian elementary EFL learners across the speaking skill. The participants of this study were a sample of 120 EFL elementary male and female learners whose ages ranged between 11 and 25 at a language institute in Rostam, Iran. The main participants were homogenized through…

Dynamic CT perfusion imaging of the myocardium: a technical note on improvement of image quality.

PubMed

Muenzel, Daniela; Kabus, Sven; Gramer, Bettina; Leber, Vivian; Vembar, Mani; Schmitt, Holger; Wildgruber, Moritz; Fingerle, Alexander A; Rummeny, Ernst J; Huber, Armin; Noël, Peter B

2013-01-01

To improve image and diagnostic quality in dynamic CT myocardial perfusion imaging (MPI) by using motion compensation and a spatio-temporal filter. Dynamic CT MPI was performed using a 256-slice multidetector computed tomography scanner (MDCT). Data from two different patients-with and without myocardial perfusion defects-were evaluated to illustrate potential improvements for MPI (institutional review board approved). Three datasets for each patient were generated: (i) original data (ii) motion compensated data and (iii) motion compensated data with spatio-temporal filtering performed. In addition to the visual assessment of the tomographic slices, noise and contrast-to-noise-ratio (CNR) were measured for all data. Perfusion analysis was performed using time-density curves with regions-of-interest (ROI) placed in normal and hypoperfused myocardium. Precision in definition of normal and hypoperfused areas was determined in corresponding coloured perfusion maps. The use of motion compensation followed by spatio-temporal filtering resulted in better alignment of the cardiac volumes over time leading to a more consistent perfusion quantification and improved detection of the extend of perfusion defects. Additionally image noise was reduced by 78.5%, with CNR improvements by a factor of 4.7. The average effective radiation dose estimate was 7.1±1.1 mSv. The use of motion compensation and spatio-temporal smoothing will result in improved quantification of dynamic CT MPI using a latest generation CT scanner.

Non-linear dynamic compensation system

NASA Technical Reports Server (NTRS)

Lin, Yu-Hwan (Inventor); Lurie, Boris J. (Inventor)

1992-01-01

A non-linear dynamic compensation subsystem is added in the feedback loop of a high precision optical mirror positioning control system to smoothly alter the control system response bandwidth from a relatively wide response bandwidth optimized for speed of control system response to a bandwidth sufficiently narrow to reduce position errors resulting from the quantization noise inherent in the inductosyn used to measure mirror position. The non-linear dynamic compensation system includes a limiter for limiting the error signal within preselected limits, a compensator for modifying the limiter output to achieve the reduced bandwidth response, and an adder for combining the modified error signal with the difference between the limited and unlimited error signals. The adder output is applied to control system motor so that the system response is optimized for accuracy when the error signal is within the preselected limits, optimized for speed of response when the error signal is substantially beyond the preselected limits and smoothly varied therebetween as the error signal approaches the preselected limits.

Can money heal all wounds? Social exchange norm modulates the preference for monetary versus social compensation.

PubMed

Cao, Yulong; Yu, Hongbo; Wu, Yanhong; Zhou, Xiaolin

2015-01-01

Compensation is a kind of pro-social behavior that can restore a social relationship jeopardized by interpersonal transgression. The effectiveness of a certain compensation strategy (e.g., repaying money, sharing loss, etc.) may vary as a function of the social norm/relationship. Previous studies have shown that two types of norms (or relationships), monetary/exchange and social/communal, differentially characterize people's appraisal of and response to social exchanges. In this study, we investigated how individual differences in preference for these norms affect individuals' perception of others' as well as the selection of their own reciprocal behaviors. In a two-phase experiment with interpersonal transgression, we asked the participant to perform a dot-estimation task with two partners who occasionally and unintentionally inflicted noise stimulation upon the participant (first phase). As compensation one partner gave money to the participant 80% of the time (the monetary partner) and the other bore the noise for the participant 80% of the time (the social partner). Results showed that the individuals' preference for compensation (repaying money versus bearing noise) affected their relationship (exchange versus communal) with the partners adopting different compensation strategies: participants tended to form communal relationships and felt closer to the partner whose compensation strategy matched their own preference. The participants could be differentiated into a social group, who tended to form communal relationship with the social partner, and a monetary group, who tended to form communal relationship with the monetary partner. In the second phase of the experiment, when the participants became transgressors and were asked to compensate for their transgression with money, the social group offered more compensation to the social partners than to the monetary partners, while the monetary group compensated less than the social group in general and showed no difference in their offers to the monetary and social partners. These findings demonstrate that the effectiveness of compensation varies as a function of individuals' preference for communal versus monetary norm and that monetary compensation alone does not heal all wounds.

Can money heal all wounds? Social exchange norm modulates the preference for monetary versus social compensation

PubMed Central

Cao, Yulong; Yu, Hongbo; Wu, Yanhong; Zhou, Xiaolin

2015-01-01

Compensation is a kind of pro-social behavior that can restore a social relationship jeopardized by interpersonal transgression. The effectiveness of a certain compensation strategy (e.g., repaying money, sharing loss, etc.) may vary as a function of the social norm/relationship. Previous studies have shown that two types of norms (or relationships), monetary/exchange and social/communal, differentially characterize people’s appraisal of and response to social exchanges. In this study, we investigated how individual differences in preference for these norms affect individuals’ perception of others’ as well as the selection of their own reciprocal behaviors. In a two-phase experiment with interpersonal transgression, we asked the participant to perform a dot-estimation task with two partners who occasionally and unintentionally inflicted noise stimulation upon the participant (first phase). As compensation one partner gave money to the participant 80% of the time (the monetary partner) and the other bore the noise for the participant 80% of the time (the social partner). Results showed that the individuals’ preference for compensation (repaying money versus bearing noise) affected their relationship (exchange versus communal) with the partners adopting different compensation strategies: participants tended to form communal relationships and felt closer to the partner whose compensation strategy matched their own preference. The participants could be differentiated into a social group, who tended to form communal relationship with the social partner, and a monetary group, who tended to form communal relationship with the monetary partner. In the second phase of the experiment, when the participants became transgressors and were asked to compensate for their transgression with money, the social group offered more compensation to the social partners than to the monetary partners, while the monetary group compensated less than the social group in general and showed no difference in their offers to the monetary and social partners. These findings demonstrate that the effectiveness of compensation varies as a function of individuals’ preference for communal versus monetary norm and that monetary compensation alone does not heal all wounds. PMID:26441783

Predictability and Robustness in the Manipulation of Dynamically Complex Objects

PubMed Central

Hasson, Christopher J.

2017-01-01

Manipulation of complex objects and tools is a hallmark of many activities of daily living, but how the human neuromotor control system interacts with such objects is not well understood. Even the seemingly simple task of transporting a cup of coffee without spilling creates complex interaction forces that humans need to compensate for. Predicting the behavior of an underactuated object with nonlinear fluid dynamics based on an internal model appears daunting. Hence, this research tests the hypothesis that humans learn strategies that make interactions predictable and robust to inaccuracies in neural representations of object dynamics. The task of moving a cup of coffee is modeled with a cart-and-pendulum system that is rendered in a virtual environment, where subjects interact with a virtual cup with a rolling ball inside using a robotic manipulandum. To gain insight into human control strategies, we operationalize predictability and robustness to permit quantitative theory-based assessment. Predictability is quantified by the mutual information between the applied force and the object dynamics; robustness is quantified by the energy margin away from failure. Three studies are reviewed that show how with practice subjects develop movement strategies that are predictable and robust. Alternative criteria, common for free movement, such as maximization of smoothness and minimization of force, do not account for the observed data. As manual dexterity is compromised in many individuals with neurological disorders, the experimental paradigm and its analyses are a promising platform to gain insights into neurological diseases, such as dystonia and multiple sclerosis, as well as healthy aging. PMID:28035560

Intelligent on-line fault tolerant control for unanticipated catastrophic failures.

PubMed

Yen, Gary G; Ho, Liang-Wei

2004-10-01

As dynamic systems become increasingly complex, experience rapidly changing environments, and encounter a greater variety of unexpected component failures, solving the control problems of such systems is a grand challenge for control engineers. Traditional control design techniques are not adequate to cope with these systems, which may suffer from unanticipated dynamic failures. In this research work, we investigate the on-line fault tolerant control problem and propose an intelligent on-line control strategy to handle the desired trajectories tracking problem for systems suffering from various unanticipated catastrophic faults. Through theoretical analysis, the sufficient condition of system stability has been derived and two different on-line control laws have been developed. The approach of the proposed intelligent control strategy is to continuously monitor the system performance and identify what the system's current state is by using a fault detection method based upon our best knowledge of the nominal system and nominal controller. Once a fault is detected, the proposed intelligent controller will adjust its control signal to compensate for the unknown system failure dynamics by using an artificial neural network as an on-line estimator to approximate the unexpected and unknown failure dynamics. The first control law is derived directly from the Lyapunov stability theory, while the second control law is derived based upon the discrete-time sliding mode control technique. Both control laws have been implemented in a variety of failure scenarios to validate the proposed intelligent control scheme. The simulation results, including a three-tank benchmark problem, comply with theoretical analysis and demonstrate a significant improvement in trajectory following performance based upon the proposed intelligent control strategy.

Burnout and job performance: the moderating role of selection, optimization, and compensation strategies.

PubMed

Demerouti, Evangelia; Bakker, Arnold B; Leiter, Michael

2014-01-01

The present study aims to explain why research thus far has found only low to moderate associations between burnout and performance. We argue that employees use adaptive strategies that help them to maintain their performance (i.e., task performance, adaptivity to change) at acceptable levels despite experiencing burnout (i.e., exhaustion, disengagement). We focus on the strategies included in the selective optimization with compensation model. Using a sample of 294 employees and their supervisors, we found that compensation is the most successful strategy in buffering the negative associations of disengagement with supervisor-rated task performance and both disengagement and exhaustion with supervisor-rated adaptivity to change. In contrast, selection exacerbates the negative relationship of exhaustion with supervisor-rated adaptivity to change. In total, 42% of the hypothesized interactions proved to be significant. Our study uncovers successful and unsuccessful strategies that people use to deal with their burnout symptoms in order to achieve satisfactory job performance. PsycINFO Database Record (c) 2014 APA, all rights reserved.

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.

An Integrated Processing Strategy for Mountain Glacier Motion Monitoring Based on SAR Images

NASA Astrophysics Data System (ADS)

Ruan, Z.; Yan, S.; Liu, G.; LV, M.

2017-12-01

Mountain glacier dynamic variables are important parameters in studies of environment and climate change in High Mountain Asia. Due to the increasing events of abnormal glacier-related hazards, research of monitoring glacier movements has attracted more interest during these years. Glacier velocities are sensitive and changing fast under complex conditions of high mountain regions, which implies that analysis of glacier dynamic changes requires comprehensive and frequent observations with relatively high accuracy. Synthetic aperture radar (SAR) has been successfully exploited to detect glacier motion in a number of previous studies, usually with pixel-tracking and interferometry methods. However, the traditional algorithms applied to mountain glacier regions are constrained by the complex terrain and diverse glacial motion types. Interferometry techniques are prone to fail in mountain glaciers because of their narrow size and the steep terrain, while pixel-tracking algorithm, which is more robust in high mountain areas, is subject to accuracy loss. In order to derive glacier velocities continually and efficiently, we propose a modified strategy to exploit SAR data information for mountain glaciers. In our approach, we integrate a set of algorithms for compensating non-glacial-motion-related signals which exist in the offset values retrieved by sub-pixel cross-correlation of SAR image pairs. We exploit modified elastic deformation model to remove the offsets associated with orbit and sensor attitude, and for the topographic residual offset we utilize a set of operations including DEM-assisted compensation algorithm and wavelet-based algorithm. At the last step of the flow, an integrated algorithm combining phase and intensity information of SAR images will be used to improve regional motion results failed in cross-correlation related processing. The proposed strategy is applied to the West Kunlun Mountain and Muztagh Ata region in western China using ALOS/PALSAR data. The results show that the strategy can effectively improve the accuracy of velocity estimation by reducing the mean and standard deviation values from 0.32 m and 0.4 m to 0.16 m. It is proved to be highly appropriate for monitoring glacier motion over a widely varying range of ice velocities with a relatively high accuracy.

Evaluating sustainable adaptation strategies for vulnerable mega-deltas using system dynamics modelling: Rice agriculture in the Mekong Delta's An Giang Province, Vietnam.

PubMed

Chapman, Alexander; Darby, Stephen

2016-07-15

Challenging dynamics are unfolding in social-ecological systems around the globe as society attempts to mitigate and adapt to climate change while sustaining rapid local development. The IPCC's 5th assessment suggests these changing systems are susceptible to unforeseen and dangerous 'emergent risks'. An archetypal example is the Vietnamese Mekong Delta (VMD) where the river dyke network has been heightened and extended over the last decade with the dual objectives of (1) adapting the delta's 18 million inhabitants and their livelihoods to increasingly intense river-flooding, and (2) developing rice production through a shift from double to triple-cropping. Negative impacts have been associated with this shift, particularly in relation to its exclusion of fluvial sediment deposition from the floodplain. A deficit in our understanding of the dynamics of the rice-sediment system, which involve unintuitive delays, feedbacks, and tipping points, is addressed here, using a system dynamics (SD) approach to inform sustainable adaptation strategies. Specifically, we develop and test a new SD model which simulates the dynamics between the farmers' economic system and their rice agriculture operations, and uniquely, integrates the role of fluvial sediment deposition within their dyke compartment. We use the model to explore a range of alternative rice cultivation strategies. Our results suggest that the current dominant strategy (triple-cropping) is only optimal for wealthier groups within society and over the short-term (ca. 10years post-implementation). The model suggests that the policy of opening sluice gates and leaving paddies fallow during high-flood years, in order to encourage natural sediment deposition and the nutrient replenishment it supplies, is both a more equitable and a more sustainable policy. But, even with this approach, diminished supplies of sediment-bound nutrients and the consequent need to compensate with artificial fertilisers will mean that smaller-scale farmers in the VMD are more vulnerable to accruing debt. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Next Generation Robots for STEM Education andResearch at Huston Tillotson University

DTIC Science & Technology

2017-11-10

dynamics through the following command: roslaunch mtb_lab6_feedback_linearization gravity_compensation.launch Part B: Gravity Inversion : After...understood the system’s natural dynamics. roslaunch mtb_lab6_feedback_linearization gravity_compensation.launch Part B: Gravity Inversion ...is created using the following command: roslaunch mtb_lab6_feedback_linearization gravity_inversion.launch Gravity inversion is just one

Direct observation of coherent energy transfer in nonlinear micromechanical oscillators

DOE PAGES

Chen, Changyao; Zanette, Damian H.; Czaplewski, David A.; ...

2017-05-26

Energy dissipation is an unavoidable phenomenon of physical systems that are directly coupled to an external environmental bath. In an oscillatory system, it leads to the decay of the oscillation amplitude. In situations where stable oscillations are required, the energy dissipated by the vibrations is usually compensated by replenishment from external energy sources. Consequently, if the external energy supply is removed, the amplitude of oscillations start to decay immediately, since there is no means to restitute the energy dissipated. Here, we demonstrate a novel dissipation engineering strategy that can support stable oscillations without supplying external energy to compensate losses. Themore » fundamental intrinsic mechanism of resonant mode coupling is used to redistribute and store mechanical energy among vibrational modes and coherently transfer it back to the principal mode when the external excitation is off. To experimentally demonstrate this phenomenon, we exploit the nonlinear dynamic response of microelectromechanical oscillators to couple two different vibrational modes through an internal resonance.« less

Direct observation of coherent energy transfer in nonlinear micromechanical oscillators

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

Chen, Changyao; Zanette, Damian H.; Czaplewski, David A.

Energy dissipation is an unavoidable phenomenon of physical systems that are directly coupled to an external environmental bath. In an oscillatory system, it leads to the decay of the oscillation amplitude. In situations where stable oscillations are required, the energy dissipated by the vibrations is usually compensated by replenishment from external energy sources. Consequently, if the external energy supply is removed, the amplitude of oscillations start to decay immediately, since there is no means to restitute the energy dissipated. Here, we demonstrate a novel dissipation engineering strategy that can support stable oscillations without supplying external energy to compensate losses. Themore » fundamental intrinsic mechanism of resonant mode coupling is used to redistribute and store mechanical energy among vibrational modes and coherently transfer it back to the principal mode when the external excitation is off. To experimentally demonstrate this phenomenon, we exploit the nonlinear dynamic response of microelectromechanical oscillators to couple two different vibrational modes through an internal resonance.« less

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 nonlinear control method based on ANFIS and multiple models for a class of SISO nonlinear systems and its application.

PubMed

Zhang, Yajun; Chai, Tianyou; Wang, Hong

2011-11-01

This paper presents a novel nonlinear control strategy for a class of uncertain single-input and single-output discrete-time nonlinear systems with unstable zero-dynamics. The proposed method combines adaptive-network-based fuzzy inference system (ANFIS) with multiple models, where a linear robust controller, an ANFIS-based nonlinear controller and a switching mechanism are integrated using multiple models technique. It has been shown that the linear controller can ensure the boundedness of the input and output signals and the nonlinear controller can improve the dynamic performance of the closed loop system. Moreover, it has also been shown that the use of the switching mechanism can simultaneously guarantee the closed loop stability and improve its performance. As a result, the controller has the following three outstanding features compared with existing control strategies. First, this method relaxes the assumption of commonly-used uniform boundedness on the unmodeled dynamics and thus enhances its applicability. Second, since ANFIS is used to estimate and compensate the effect caused by the unmodeled dynamics, the convergence rate of neural network learning has been increased. Third, a "one-to-one mapping" technique is adapted to guarantee the universal approximation property of ANFIS. The proposed controller is applied to a numerical example and a pulverizing process of an alumina sintering system, respectively, where its effectiveness has been justified.

Ten objectives for sustainable development.

PubMed

Hu, A

2000-02-01

Sustainable development is one of the fundamental strategies for China's socioeconomic development in its 10th 5-Year Plan (2001-2005) period and beyond. It is a human-centered strategy focusing on improved quality of life in which environmental quality is an important part. This article presents 10 objectives that must be achieved for the sustainable development strategy to succeed. These objectives are: 1) continue to implement the family planning program; 2) maintain a dynamic balance of arable land (not less than 123 million hectares) and implement an agricultural development strategy; 3) maintain a dynamic balance of water resources by reducing water consumption for every unit of gross development product growth and agricultural value added; 4) import large quantities of oil and natural gas; 5) control emissions of carbon dioxide and sulfur dioxide by large cities and industries and close high-pollution thermal power plants; 6) compensate for ¿forest deficit¿ with ¿trade surplus¿ by reducing timber production and increase timber import; 7) import large quantities of iron ore, copper, zinc, aluminum, and other minerals and encourage foreign participation in resource exploration and development; 8) make time-bound commitments to clean up large cities, rivers, and lakes and forcefully close down seriously polluting enterprises; 9) implement a massive ecological construction project to slow down ecological degradation; and 10) develop the environmental industry and eco-buildup to expand domestic demand, increase employment, and alleviate poverty.

Robust independent modal space control of a coupled nano-positioning piezo-stage

NASA Astrophysics Data System (ADS)

Zhu, Wei; Yang, Fufeng; Rui, Xiaoting

2018-06-01

In order to accurately control a coupled 3-DOF nano-positioning piezo-stage, this paper designs a hybrid controller. In this controller, a hysteresis observer based on a Bouc-Wen model is established to compensate the hysteresis nonlinearity of the piezoelectric actuator first. Compared to hysteresis compensations using Preisach model and Prandt-Ishlinskii model, the compensation method using the hysteresis observer is computationally lighter. Then, based on the proposed dynamics model, by constructing the modal filter, a robust H∞ independent modal space controller is designed and utilized to decouple the piezo-stage and deal with the unmodeled dynamics, disturbance, and hysteresis compensation error. The effectiveness of the proposed controller is demonstrated experimentally. The experimental results show that the proposed controller can significantly achieve the high-precision positioning.

Quadrupedal rodent gait compensations in a low dose monoiodoacetate model of osteoarthritis.

PubMed

Lakes, Emily H; Allen, Kyle D

2018-06-01

Rodent gait analysis provides robust, quantitative results for preclinical musculoskeletal and neurological models. In prior work, surgical models of osteoarthritis have been found to result in a hind limb shuffle-stepping gait compensation, while a high dose monoiodoacetate (MIA, 3 mg) model resulted in a hind limb antalgic gait. However, it is unknown whether the antalgic gait caused by MIA is associated with severity of degeneration from the high dosage or the whole-joint degeneration associated with glycolysis inhibition. This study evaluates rodent gait changes resulting from a low dose, 1 mg unilateral intra-articular injection of MIA compared to saline injected and naïve rats. Spatiotemporal and dynamic gait parameters were collected from a total of 42 male Lewis rats spread across 3 time points: 1, 2, and 4 weeks post-injection. To provide a detailed analysis of this low dose MIA model, gait analysis was used to uniquely quantify both fore and hind limb gait parameters. Our data indicate that 1 mg of MIA caused relatively minor degeneration and a shuffle-step gait compensation, similar to the compensation observed in prior surgical models. These data from a 1 mg MIA model show a different gait compensation compared to a previously studied 3 mg model. This 1 mg MIA model resulted in gait compensations more similar to a previously studied surgical model of osteoarthritis. Additionally, this study provides detailed 4 limb analysis of rodent gait that includes spatiotemporal and dynamic data from the same gait trial. These data highlight the importance of measuring dynamic data in combination with spatiotemporal data, since compensatory gait patterns may not be captured by spatial, temporal, or dynamic characterizations alone. Copyright © 2018 Elsevier B.V. All rights reserved.

Motion compensation for fully 4D PET reconstruction using PET superset data

NASA Astrophysics Data System (ADS)

Verhaeghe, J.; Gravel, P.; Mio, R.; Fukasawa, R.; Rosa-Neto, P.; Soucy, J.-P.; Thompson, C. J.; Reader, A. J.

2010-07-01

Fully 4D PET image reconstruction is receiving increasing research interest due to its ability to significantly reduce spatiotemporal noise in dynamic PET imaging. However, thus far in the literature, the important issue of correcting for subject head motion has not been considered. Specifically, as a direct consequence of using temporally extensive basis functions, a single instance of movement propagates to impair the reconstruction of multiple time frames, even if no further movement occurs in those frames. Existing 3D motion compensation strategies have not yet been adapted to 4D reconstruction, and as such the benefits of 4D algorithms have not yet been reaped in a clinical setting where head movement undoubtedly occurs. This work addresses this need, developing a motion compensation method suitable for fully 4D reconstruction methods which exploits an optical tracking system to measure the head motion along with PET superset data to store the motion compensated data. List-mode events are histogrammed as PET superset data according to the measured motion, and a specially devised normalization scheme for motion compensated reconstruction from the superset data is required. This work proceeds to propose the corresponding time-dependent normalization modifications which are required for a major class of fully 4D image reconstruction algorithms (those which use linear combinations of temporal basis functions). Using realistically simulated as well as real high-resolution PET data from the HRRT, we demonstrate both the detrimental impact of subject head motion in fully 4D PET reconstruction and the efficacy of our proposed modifications to 4D algorithms. Benefits are shown both for the individual PET image frames as well as for parametric images of tracer uptake and volume of distribution for 18F-FDG obtained from Patlak analysis.

Motion compensation for fully 4D PET reconstruction using PET superset data.

PubMed

Verhaeghe, J; Gravel, P; Mio, R; Fukasawa, R; Rosa-Neto, P; Soucy, J-P; Thompson, C J; Reader, A J

2010-07-21

Fully 4D PET image reconstruction is receiving increasing research interest due to its ability to significantly reduce spatiotemporal noise in dynamic PET imaging. However, thus far in the literature, the important issue of correcting for subject head motion has not been considered. Specifically, as a direct consequence of using temporally extensive basis functions, a single instance of movement propagates to impair the reconstruction of multiple time frames, even if no further movement occurs in those frames. Existing 3D motion compensation strategies have not yet been adapted to 4D reconstruction, and as such the benefits of 4D algorithms have not yet been reaped in a clinical setting where head movement undoubtedly occurs. This work addresses this need, developing a motion compensation method suitable for fully 4D reconstruction methods which exploits an optical tracking system to measure the head motion along with PET superset data to store the motion compensated data. List-mode events are histogrammed as PET superset data according to the measured motion, and a specially devised normalization scheme for motion compensated reconstruction from the superset data is required. This work proceeds to propose the corresponding time-dependent normalization modifications which are required for a major class of fully 4D image reconstruction algorithms (those which use linear combinations of temporal basis functions). Using realistically simulated as well as real high-resolution PET data from the HRRT, we demonstrate both the detrimental impact of subject head motion in fully 4D PET reconstruction and the efficacy of our proposed modifications to 4D algorithms. Benefits are shown both for the individual PET image frames as well as for parametric images of tracer uptake and volume of distribution for (18)F-FDG obtained from Patlak analysis.

New method to improve dynamic stiffness of electro-hydraulic servo systems

NASA Astrophysics Data System (ADS)

Bai, Yanhong; Quan, Long

2013-09-01

Most current researches working on improving stiffness focus on the application of control theories. But controller in closed-loop hydraulic control system takes effect only after the controlled position is deviated, so the control action is lagged. Thus dynamic performance against force disturbance and dynamic load stiffness can’t be improved evidently by advanced control algorithms. In this paper, the elementary principle of maintaining piston position unchanged under sudden external force load change by charging additional oil is analyzed. On this basis, the conception of raising dynamic stiffness of electro hydraulic position servo system by flow feedforward compensation is put forward. And a scheme using double servo valves to realize flow feedforward compensation is presented, in which another fast response servo valve is added to the regular electro hydraulic servo system and specially utilized to compensate the compressed oil volume caused by load impact in time. The two valves are arranged in parallel to control the cylinder jointly. Furthermore, the model of flow compensation is derived, by which the product of the amplitude and width of the valve’s pulse command signal can be calculated. And determination rules of the amplitude and width of pulse signal are concluded by analysis and simulations. Using the proposed scheme, simulations and experiments at different positions with different force changes are conducted. The simulation and experimental results show that the system dynamic performance against load force impact is largely improved with decreased maximal dynamic position deviation and shortened settling time. That is, system dynamic load stiffness is evidently raised. This paper proposes a new method which can effectively improve the dynamic stiffness of electro-hydraulic servo systems.

Field Crickets Compensate for Unattractive Static Long-Distance Call Components by Increasing Dynamic Signalling Effort.

PubMed

McAuley, Emily M; Bertram, Susan M

2016-01-01

The evolution of multiple sexual signals presents a dilemma since individuals selecting a mate should pay attention to the most honest signal and ignore the rest; however, multiple signals may evolve if, together, they provide more information to the receiver than either one would alone. Static and dynamic signals, for instance, can act as multiple messages, providing information on different aspects of signaller quality that reflect condition at different time scales. While the nature of static signals makes them difficult or impossible for individuals to augment, dynamic signals are much more susceptible to temporary fluctuations in effort. We investigated whether male Texas field crickets, Gryllus texensis, that produce unattractive static signals compensate by dynamically increasing their calling effort. Our findings lend partial support to the compensation hypothesis, as males that called at unattractive carrier frequencies (a static trait) spent more time calling each night (a dynamic trait). Interestingly, this finding was most pronounced in males that called with attractive pulse characteristics (static traits) but did not occur in males that called with unattractive pulse characteristics. Males that signalled with unattractive pulse characteristics (duration and pause) spent less time calling through the night. Our correlative findings on wild caught males suggest that only males that signal with attractive pulse characteristics may be able to afford to pay the costs of both trait exaggeration and increased calling effort to compensate for poor carrier frequencies.

Targeting pre-exposure prophylaxis among men who have sex with men in the United States and Peru: partnership types, contact rates, and sexual role

PubMed Central

Carnegie, Nicole Bohme; Goodreau, Steven M.; Liu, Albert; Vittinghoff, Eric; Sanchez, Jorge; Lama, Javier R.; Buchbinder, Susan

2015-01-01

Background We aim to identify optimal strategies for deploying pre-exposure prophylaxis among men who have sex with men in the US and Peru to maximize population-level effectiveness in an efficient manner. We use epidemic models to simulate the impact of targeting strategies. Most studies have focused on targeting either the general population or high-risk MSM. Alternative strategies, including serodiscordant couples, may better balance effectiveness and efficiency. Methods We use dynamic, stochastic sexual network models based in exponential-family random graph modeling, parameterized from behavioral surveys of MSM in the US and Peru. These models represent main partnerships and casual contacts separately, permitting modeling of interventions targeting men whose risk derives from combinations of relational types. We also model varying rates of uptake and adherence to PrEP. We assess sensitivity of results to risk compensation via increases in condomless casual contacts and condomless sex in main partnerships. Results Targeting all men who are not exclusively insertive has the largest impact on HIV incidence, but targeting only those with high levels of casual activity yields comparable results using fewer person-years on PrEP. The effect is robust to risk compensation in the US, but less so in Peru. Targeting serodiscordant main partnerships does not significantly impact incidence, but requires fewer person-years on PrEP per infection averted than other strategies. Conclusions PrEP could be effective in reducing new infections at the population level in both settings. Serodiscordant partnerships are an attractive component of a targeting program, but targeting should include other high-risk men. PMID:25942463

Targeting pre-exposure prophylaxis among men who have sex with men in the United States and Peru: partnership types, contact rates, and sexual role.

PubMed

Carnegie, Nicole B; Goodreau, Steven M; Liu, Albert; Vittinghoff, Eric; Sanchez, Jorge; Lama, Javier R; Buchbinder, Susan

2015-05-01

We aim to identify optimal strategies for deploying pre-exposure prophylaxis among men who have sex with men (MSM) in the United States and Peru to maximize population-level effectiveness in an efficient manner. We use epidemic models to simulate the impact of targeting strategies. Most studies have focused on targeting either the general population or high-risk MSM. Alternative strategies, including serodiscordant couples, may better balance effectiveness and efficiency. We use dynamic stochastic sexual network models based on exponential-family random graph modeling, parameterized from behavioral surveys of MSM in the United States and Peru. These models represent main partnerships and casual contacts separately, permitting modeling of interventions targeting men whose risk derives from combinations of relational types. We also model varying rates of uptake and adherence to pre-exposure prophylaxis (PrEP). We assess sensitivity of results to risk compensation through increases in condomless casual contacts and condomless sex in main partnerships. Targeting all men who are not exclusively insertive has the largest impact on HIV incidence, but targeting only those with high levels of casual activity yields comparable results using fewer person-years on PrEP. The effect is robust to risk compensation in the United States, but less so in Peru. Targeting serodiscordant main partnerships does not significantly impact incidence, but requires fewer person-years on PrEP per infection averted than other strategies. PrEP could be effective in reducing new infections at the population level in both settings. Serodiscordant partnerships are an attractive component of a targeting program, but targeting should include other high-risk men.

Compensator design for improved counterbalancing in high speed atomic force microscopy.

PubMed

Bozchalooi, I S; Youcef-Toumi, K; Burns, D J; Fantner, G E

2011-11-01

High speed atomic force microscopy can provide the possibility of many new scientific observations and applications ranging from nano-manufacturing to the study of biological processes. However, the limited imaging speed has been an imperative drawback of the atomic force microscopes. One of the main reasons behind this limitation is the excitation of the AFM dynamics at high scan speeds, severely undermining the reliability of the acquired images. In this research, we propose a piezo based, feedforward controlled, counter actuation mechanism to compensate for the excited out-of-plane scanner dynamics. For this purpose, the AFM controller output is properly filtered via a linear compensator and then applied to a counter actuating piezo. An effective algorithm for estimating the compensator parameters is developed. The information required for compensator design is extracted from the cantilever deflection signal, hence eliminating the need for any additional sensors. The proposed approach is implemented and experimentally evaluated on the dynamic response of a custom made AFM. It is further assessed by comparing the imaging performance of the AFM with and without the application of the proposed technique and in comparison with the conventional counterbalancing methodology. The experimental results substantiate the effectiveness of the method in significantly improving the imaging performance of AFM at high scan speeds. © 2011 American Institute of Physics

Compensator design for improved counterbalancing in high speed atomic force microscopy

PubMed Central

Bozchalooi, I. S.; Youcef-Toumi, K.; Burns, D. J.; Fantner, G. E.

2011-01-01

High speed atomic force microscopy can provide the possibility of many new scientific observations and applications ranging from nano-manufacturing to the study of biological processes. However, the limited imaging speed has been an imperative drawback of the atomic force microscopes. One of the main reasons behind this limitation is the excitation of the AFM dynamics at high scan speeds, severely undermining the reliability of the acquired images. In this research, we propose a piezo based, feedforward controlled, counter actuation mechanism to compensate for the excited out-of-plane scanner dynamics. For this purpose, the AFM controller output is properly filtered via a linear compensator and then applied to a counter actuating piezo. An effective algorithm for estimating the compensator parameters is developed. The information required for compensator design is extracted from the cantilever deflection signal, hence eliminating the need for any additional sensors. The proposed approach is implemented and experimentally evaluated on the dynamic response of a custom made AFM. It is further assessed by comparing the imaging performance of the AFM with and without the application of the proposed technique and in comparison with the conventional counterbalancing methodology. The experimental results substantiate the effectiveness of the method in significantly improving the imaging performance of AFM at high scan speeds. PMID:22128989

Compensator design for improved counterbalancing in high speed atomic force microscopy

NASA Astrophysics Data System (ADS)

Bozchalooi, I. S.; Youcef-Toumi, K.; Burns, D. J.; Fantner, G. E.

2011-11-01

High speed atomic force microscopy can provide the possibility of many new scientific observations and applications ranging from nano-manufacturing to the study of biological processes. However, the limited imaging speed has been an imperative drawback of the atomic force microscopes. One of the main reasons behind this limitation is the excitation of the AFM dynamics at high scan speeds, severely undermining the reliability of the acquired images. In this research, we propose a piezo based, feedforward controlled, counter actuation mechanism to compensate for the excited out-of-plane scanner dynamics. For this purpose, the AFM controller output is properly filtered via a linear compensator and then applied to a counter actuating piezo. An effective algorithm for estimating the compensator parameters is developed. The information required for compensator design is extracted from the cantilever deflection signal, hence eliminating the need for any additional sensors. The proposed approach is implemented and experimentally evaluated on the dynamic response of a custom made AFM. It is further assessed by comparing the imaging performance of the AFM with and without the application of the proposed technique and in comparison with the conventional counterbalancing methodology. The experimental results substantiate the effectiveness of the method in significantly improving the imaging performance of AFM at high scan speeds.

Eddy current compensation for delta relaxation enhanced MR by dynamic reference phase modulation.

PubMed

Hoelscher, Uvo Christoph; Jakob, Peter M

2013-04-01

Eddy current compensation by dynamic reference phase modulation (eDREAM) is a compensation method for eddy current fields induced by B 0 field-cycling which occur in delta relaxation enhanced MR (dreMR) imaging. The presented method is based on a dynamic frequency adjustment and prevents eddy current related artifacts. It is easy to implement and can be completely realized in software for any imaging sequence. In this paper, the theory of eDREAM is derived and two applications are demonstrated. The theory describes how to model the behavior of the eddy currents and how to implement the compensation. Phantom and in vivo measurements are carried out and demonstrate the benefits of eDREAM. A comparison of images acquired with and without eDREAM shows a significant improvement in dreMR image quality. Images without eDREAM suffer from severe artifacts and do not allow proper interpretation while images with eDREAM are artifact free. In vivo experiments demonstrate that dreMR imaging without eDREAM is not feasible as artifacts completely change the image contrast. eDREAM is a flexible eddy current compensation for dreMR. It is capable of completely removing the influence of eddy currents such that the dreMR images do not suffer from artifacts.

Further development of the dynamic gas temperature measurement system. Volume 2: Computer program user's manual

NASA Technical Reports Server (NTRS)

Stocks, Dana R.

1986-01-01

The Dynamic Gas Temperature Measurement System compensation software accepts digitized data from two different diameter thermocouples and computes a compensated frequency response spectrum for one of the thermocouples. Detailed discussions of the physical system, analytical model, and computer software are presented in this volume and in Volume 1 of this report under Task 3. Computer program software restrictions and test cases are also presented. Compensated and uncompensated data may be presented in either the time or frequency domain. Time domain data are presented as instantaneous temperature vs time. Frequency domain data may be presented in several forms such as power spectral density vs frequency.

An Experiment of GMPLS-Based Dispersion Compensation Control over In-Field Fibers

NASA Astrophysics Data System (ADS)

Seno, Shoichiro; Horiuchi, Eiichi; Yoshida, Sota; Sugihara, Takashi; Onohara, Kiyoshi; Kamei, Misato; Baba, Yoshimasa; Kubo, Kazuo; Mizuochi, Takashi

As ROADMs (Reconfigurable Optical Add/Drop Multiplexers) are becoming widely used in metro/core networks, distributed control of wavelength paths by extended GMPLS (Generalized MultiProtocol Label Switching) protocols has attracted much attention. For the automatic establishment of an arbitrary wavelength path satisfying dynamic traffic demands over a ROADM or WXC (Wavelength Cross Connect)-based network, precise determination of chromatic dispersion over the path and optimized assignment of dispersion compensation capabilities at related nodes are essential. This paper reports an experiment over in-field fibers where GMPLS-based control was applied for the automatic discovery of chromatic dispersion, path computation, and wavelength path establishment with dynamic adjustment of variable dispersion compensation. The GMPLS-based control scheme, which the authors called GMPLS-Plus, extended GMPLS's distributed control architecture with attributes for automatic discovery, advertisement, and signaling of chromatic dispersion. In this experiment, wavelength paths with distances of 24km and 360km were successfully established and error-free data transmission was verified. The experiment also confirmed path restoration with dynamic compensation adjustment upon fiber failure.

Aberration compensation in a Skew parametric-resonance ionization cooling channel

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

Sy, Amy V.; Derbenev, Yaroslav S.; Morozov, Vasiliy

Skew Parametric-resonance Ionization Cooling (Skew PIC) represents a novel method for focusing of highly divergent particle beams, as in the final 6D cooling stage of a high-luminosity muon collider. In the muon collider concept, the resultant equilibrium transverse emittances from cooling with Skew PIC are an order of magnitude smaller than in conventional ionization cooling. The concept makes use of coupling of the transverse dynamic behavior, and the linear dynamics are well-behaved with good agreement between analytic solutions and simulation results. Compared to the uncoupled system, coupling of the transverse dynamic behavior purports to reduce the number of multipoles requiredmore » for aberration compensation while also avoiding unwanted resonances. Aberration compensation is more complicated in the coupled case, especially in the high-luminosity muon collider application where equilibrium angular spreads in the cooling channel are on the order of 200 mrad. We present recent progress on aberration compensation for control of highly divergent muon beams in the coupled correlated optics channel, and a simple cooling model to test the transverse acceptance of the channel.« less

Dynamics and flight control of a flapping-wing robotic insect in the presence of wind gusts.

PubMed

Chirarattananon, Pakpong; Chen, Yufeng; Helbling, E Farrell; Ma, Kevin Y; Cheng, Richard; Wood, Robert J

2017-02-06

With the goal of operating a biologically inspired robot autonomously outside of laboratory conditions, in this paper, we simulated wind disturbances in a laboratory setting and investigated the effects of gusts on the flight dynamics of a millimetre-scale flapping-wing robot. Simplified models describing the disturbance effects on the robot's dynamics are proposed, together with two disturbance rejection schemes capable of estimating and compensating for the disturbances. The proposed methods are experimentally verified. The results show that these strategies reduced the root-mean-square position errors by more than 50% when the robot was subject to 80 cm s -1 horizontal wind. The analysis of flight data suggests that modulation of wing kinematics to stabilize the flight in the presence of wind gusts may indirectly contribute an additional stabilizing effect, reducing the time-averaged aerodynamic drag experienced by the robot. A benchtop experiment was performed to provide further support for this observed phenomenon.

Dynamics and flight control of a flapping-wing robotic insect in the presence of wind gusts

PubMed Central

Chen, Yufeng; Helbling, E. Farrell; Ma, Kevin Y.; Cheng, Richard; Wood, Robert J.

2017-01-01

With the goal of operating a biologically inspired robot autonomously outside of laboratory conditions, in this paper, we simulated wind disturbances in a laboratory setting and investigated the effects of gusts on the flight dynamics of a millimetre-scale flapping-wing robot. Simplified models describing the disturbance effects on the robot's dynamics are proposed, together with two disturbance rejection schemes capable of estimating and compensating for the disturbances. The proposed methods are experimentally verified. The results show that these strategies reduced the root-mean-square position errors by more than 50% when the robot was subject to 80 cm s−1 horizontal wind. The analysis of flight data suggests that modulation of wing kinematics to stabilize the flight in the presence of wind gusts may indirectly contribute an additional stabilizing effect, reducing the time-averaged aerodynamic drag experienced by the robot. A benchtop experiment was performed to provide further support for this observed phenomenon. PMID:28163872

Reaction wheel low-speed compensation using a dither signal

NASA Astrophysics Data System (ADS)

Stetson, John B., Jr.

1993-08-01

A method for improving low-speed reaction wheel performance on a three-axis controlled spacecraft is presented. The method combines a constant amplitude offset with an unbiased, oscillating dither to harmonically linearize rolling solid friction dynamics. The complete, nonlinear rolling solid friction dynamics using an analytic modification to the experimentally verified Dahl solid friction model were analyzed using the dual-input describing function method to assess the benefits of dither compensation. The modified analytic solid friction model was experimentally verified with a small dc servomotor actuated reaction wheel assembly. Using dither compensation abrupt static friction disturbances are eliminated and near linear behavior through zero rate can be achieved. Simulated vehicle response to a wheel rate reversal shows that when the dither and offset compensation is used, elastic modes are not significantly excited, and the uncompensated attitude error reduces by 34:1.

Making Work Pay in the Child Care Industry: Promising Practices for Improving Compensation.

ERIC Educational Resources Information Center

Bellm, Dan; And Others

Based on the finding that the most important determinant of child care quality is the presence of consistent, well-trained, and well-compensated caregivers, this report discusses strategies to improve compensation in child care. It analyzes structural and social barriers to investing in decent-paying child care jobs; profiles a wide range of…

Fast domain wall motion in the vicinity of the angular momentum compensation temperature of ferrimagnets

NASA Astrophysics Data System (ADS)

Kim, Kab-Jin; Kim, Se Kwon; Hirata, Yuushou; Oh, Se-Hyeok; Tono, Takayuki; Kim, Duck-Ho; Okuno, Takaya; Ham, Woo Seung; Kim, Sanghoon; Go, Gyoungchoon; Tserkovnyak, Yaroslav; Tsukamoto, Arata; Moriyama, Takahiro; Lee, Kyung-Jin; Ono, Teruo

2017-12-01

Antiferromagnetic spintronics is an emerging research field which aims to utilize antiferromagnets as core elements in spintronic devices. A central motivation towards this direction is that antiferromagnetic spin dynamics is expected to be much faster than its ferromagnetic counterpart. Recent theories indeed predicted faster dynamics of antiferromagnetic domain walls (DWs) than ferromagnetic DWs. However, experimental investigations of antiferromagnetic spin dynamics have remained unexplored, mainly because of the magnetic field immunity of antiferromagnets. Here we show that fast field-driven antiferromagnetic spin dynamics is realized in ferrimagnets at the angular momentum compensation point TA. Using rare earth-3d-transition metal ferrimagnetic compounds where net magnetic moment is nonzero at TA, the field-driven DW mobility is remarkably enhanced up to 20 km s-1 T-1. The collective coordinate approach generalized for ferrimagnets and atomistic spin model simulations show that this remarkable enhancement is a consequence of antiferromagnetic spin dynamics at TA. Our finding allows us to investigate the physics of antiferromagnetic spin dynamics and highlights the importance of tuning of the angular momentum compensation point of ferrimagnets, which could be a key towards ferrimagnetic spintronics.

Modelling a Compensation Standard for a Regional Forest Ecosystem: A Case Study in Yanqing District, Beijing, China

PubMed Central

Li, Tan; Zhang, Qingguo; Zhang, Ying

2018-01-01

The assessment of forest ecosystem services can quantify the impact of these services on human life and is the main basis for formulating a standard of compensation for these services. Moreover, the calculation of the indirect value of forest ecosystem services should not be ignored, as has been the case in some previous publications. A low compensation standard and the lack of a dynamic coordination mechanism are the main problems existing in compensation implementation. Using comparison and analysis, this paper employed accounting for both the costs and benefits of various alternatives. The analytic hierarchy process (AHP) method and the Pearl growth-curve method were used to adjust the results. This research analyzed the contribution of each service value from the aspects of forest produce services, ecology services, and society services. We also conducted separate accounting for cost and benefit, made a comparison of accounting and evaluation methods, and estimated the implementation period of the compensation standard. The main conclusions of this research include the fact that any compensation standard should be determined from the points of view of both benefit and cost in a region. The results presented here allow the range between the benefit and cost compensation to be laid out more reasonably. The practical implications of this research include the proposal that regional decision-makers should consider a dynamic compensation method to meet with the local economic level by using diversified ways to raise the compensation standard, and that compensation channels should offer a mixed mode involving both the market and government. PMID:29561789

Modelling a Compensation Standard for a Regional Forest Ecosystem: A Case Study in Yanqing District, Beijing, China.

PubMed

Li, Tan; Zhang, Qingguo; Zhang, Ying

2018-03-21

The assessment of forest ecosystem services can quantify the impact of these services on human life and is the main basis for formulating a standard of compensation for these services. Moreover, the calculation of the indirect value of forest ecosystem services should not be ignored, as has been the case in some previous publications. A low compensation standard and the lack of a dynamic coordination mechanism are the main problems existing in compensation implementation. Using comparison and analysis, this paper employed accounting for both the costs and benefits of various alternatives. The analytic hierarchy process (AHP) method and the Pearl growth-curve method were used to adjust the results. This research analyzed the contribution of each service value from the aspects of forest produce services, ecology services, and society services. We also conducted separate accounting for cost and benefit, made a comparison of accounting and evaluation methods, and estimated the implementation period of the compensation standard. The main conclusions of this research include the fact that any compensation standard should be determined from the points of view of both benefit and cost in a region. The results presented here allow the range between the benefit and cost compensation to be laid out more reasonably. The practical implications of this research include the proposal that regional decision-makers should consider a dynamic compensation method to meet with the local economic level by using diversified ways to raise the compensation standard, and that compensation channels should offer a mixed mode involving both the market and government.

Algorithms to automate gap-dependent integral tuning for the 2.8-meter long horizontal field undulator with a dynamic force compensation mechanism

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

Xu, Joseph Z., E-mail: x@anl.gov; Vasserman, Isaac; Strelnikov, Nikita

2016-07-27

A 2.8-meter long horizontal field prototype undulator with a dynamic force compensation mechanism has been developed and tested at the Advanced Photon Source (APS) at Argonne National Laboratory (Argonne). The magnetic tuning of the undulator integrals has been automated and accomplished by applying magnetic shims. A detailed description of the algorithms and performance is reported.

Modified compensation algorithm of lever-arm effect and flexural deformation for polar shipborne transfer alignment based on improved adaptive Kalman filter

NASA Astrophysics Data System (ADS)

Wang, Tongda; Cheng, Jianhua; Guan, Dongxue; Kang, Yingyao; Zhang, Wei

2017-09-01

Due to the lever-arm effect and flexural deformation in the practical application of transfer alignment (TA), the TA performance is decreased. The existing polar TA algorithm only compensates a fixed lever-arm without considering the dynamic lever-arm caused by flexural deformation; traditional non-polar TA algorithms also have some limitations. Thus, the performance of existing compensation algorithms is unsatisfactory. In this paper, a modified compensation algorithm of the lever-arm effect and flexural deformation is proposed to promote the accuracy and speed of the polar TA. On the basis of a dynamic lever-arm model and a noise compensation method for flexural deformation, polar TA equations are derived in grid frames. Based on the velocity-plus-attitude matching method, the filter models of polar TA are designed. An adaptive Kalman filter (AKF) is improved to promote the robustness and accuracy of the system, and then applied to the estimation of the misalignment angles. Simulation and experiment results have demonstrated that the modified compensation algorithm based on the improved AKF for polar TA can effectively compensate the lever-arm effect and flexural deformation, and then improve the accuracy and speed of TA in the polar region.

Passive and semi-active heave compensator: Project design methodology and control strategies.

PubMed

Cuellar Sanchez, William Humberto; Linhares, Tássio Melo; Neto, André Benine; Fortaleza, Eugênio Libório Feitosa

2017-01-01

Heave compensator is a system that mitigates transmission of heave movement from vessels to the equipment in the vessel. In drilling industry, a heave compensator enables drilling in offshore environments. Heave compensator attenuates movement transmitted from the vessel to the drill string and drill bit ensuring security and efficiency of the offshore drilling process. Common types of heave compensators are passive, active and semi-active compensators. This article presents 4 main points. First, a bulk modulus analysis obtains a simple condition to determine if the bulk modulus can be neglected in the design of hydropneumatic passive heave compensator. Second, the methodology to design passive heave compensators with the desired frequency response. Third, four control methodologies for semi-active heave compensator are tested and compared numerically. Lastly, we show experimental results obtained from a prototype with the methodology developed to design passive heave compensator.

Passive and semi-active heave compensator: Project design methodology and control strategies

PubMed Central

Cuellar Sanchez, William Humberto; Neto, André Benine; Fortaleza, Eugênio Libório Feitosa

2017-01-01

Heave compensator is a system that mitigates transmission of heave movement from vessels to the equipment in the vessel. In drilling industry, a heave compensator enables drilling in offshore environments. Heave compensator attenuates movement transmitted from the vessel to the drill string and drill bit ensuring security and efficiency of the offshore drilling process. Common types of heave compensators are passive, active and semi-active compensators. This article presents 4 main points. First, a bulk modulus analysis obtains a simple condition to determine if the bulk modulus can be neglected in the design of hydropneumatic passive heave compensator. Second, the methodology to design passive heave compensators with the desired frequency response. Third, four control methodologies for semi-active heave compensator are tested and compared numerically. Lastly, we show experimental results obtained from a prototype with the methodology developed to design passive heave compensator. PMID:28813494

Working on reform. How workers' compensation medical care is affected by health care reform.

PubMed Central

Himmelstein, J; Rest, K

1996-01-01

The medical component of workers' compensation programs-now costing over $24 billion annually-and the rest of the nation's medical care system are linked. They share the same patients and providers. They provide similar benefits and services. And they struggle over who should pay for what. Clearly, health care reform and restructuring will have a major impact on the operation and expenditures of the workers' compensation system. For a brief period, during the 1994 national health care reform debate, these two systems were part of the same federal policy development and legislative process. With comprehensive health care reform no longer on the horizon, states now are tackling both workers' compensation and medical system reforms on their own. This paper reviews the major issues federal and state policy makers face as they consider reforms affecting the relationship between workers' compensation and traditional health insurance. What is the relationship of the workers' compensation cost crisis to that in general health care? What strategies are being considered by states involved in reforming the medical component of workers compensation? What are the major policy implications of these strategies? Images p13-a p14-a p15-a p16-a p18-a p19-a p20-a p22-a p24-a PMID:8610187

Vertical vibration analysis for elevator compensating sheave

NASA Astrophysics Data System (ADS)

Watanabe, Seiji; Okawa, Takeya; Nakazawa, Daisuke; Fukui, Daiki

2013-07-01

Most elevators applied to tall buildings include compensating ropes to satisfy the balanced rope tension between the car and the counter weight. The compensating ropes receive tension by the compensating sheave, which is installed at the bottom space of the elevator shaft. The compensating sheave is only suspended by the compensating ropes, therefore, the sheave can move vertically while the car is traveling. This paper shows the elevator dynamic model to evaluate the vertical motion of the compensating sheave. Especially, behavior in emergency cases, such as brake activation and buffer strike, was investigated to evaluate the maximum upward motion of the sheave. The simulation results were validated by experiments and the most influenced factor for the sheave vertical motion was clarified.

Inverse dynamic investigation of voluntary leg lateral movements in weightlessness: a new microgravity-specific strategy.

PubMed

Pedrocchi, Alessandra; Baroni, Guido; Pedotti, Antonio; Massion, Jean; Ferrigno, Giancarlo

2005-04-01

This study deals with the quantitative assessment of exchanged forces and torques at the restraint point during whole body posture perturbation movements in long-term microgravity. The work was based on the results of a previous study focused on trunk bending protocol, which suggested that the minimization of the torques exchanged at the restraint point could be a strategy for movement planning in microgravity (J. Biomech. 36(11) (2003) 1691). Torques minimization would lead to the optimization of muscles activity, to the minimization of energy expenditure and, ultimately, to higher movement control capabilities. Here, we focus on leg lateral abduction from anchored stance. The analysis was based on inverse dynamic modelling, leading to the estimation of the total angular momentum at the supporting ankle joint. Results agree with those obtained for trunk bending movements and point out a consistent minimization of the torques exchanged at the restraint point in weightlessness. Given the kinematic features of the examined motor task, this strategy was interpreted as a way to master the rotational dynamic effects on the frontal plane produced by leg lateral abduction. This postural stabilizing effects was the result of a multi-segmental compensation strategy, consisting of the counter rotation of the supporting limb and trunk accompanying the leg raising. The observed consistency of movement-posture co-ordination patterns among lateral leg raising and trunk bending is put forward as a novel interpretative issue of the adaptation mechanisms of the motor system to sustained microgravity, especially if one considers the completely different kinematics of the centre of mass, which was observed in weightlessness for these two motor tasks.

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

Gluskin, Efim; Trakhtenberg, Emil; Xu, Joseph Z.

A method and apparatus for implementing dynamic compensation of magnetic forces for undulators are provided. An undulator includes a respective set of magnet arrays, each attached to a strongback, and placed on horizontal slides and positioned parallel relative to each other with a predetermined gap. Magnetic forces are compensated by a set of compensation springs placed along the strongback. The compensation springs are conical springs having exponential-force characteristics that substantially match undulator magnetic forces independently of the predetermined gap. The conical springs are positioned along the length of the magnets.

Role of self-efficacy and anxiety among pre-clinically disabled older adults when using compensatory strategies to complete daily tasks

PubMed Central

Higgins, Torrance J.; Janelle, Christopher M.; Naugle, Kelly M.; Knaggs, Jeffrey; Hoover, Brian M.; Marsiske, Michael; Manini, Todd M.

2012-01-01

Classic developmental theory suggests that aging is associated with using compensatory strategies to prolong independence. While compensatory strategies are typically considered positive adaptations, they also signify an early phase in the disablement process — commonly known as pre-clinical disability. To build a better understanding of psychological constructs related to these early signs of disability, we examined the contribution of self-efficacy and state anxiety on using compensatory strategies among pre-clinically disabled older adults. Compensatory strategies were observed during performance of daily activities in 257 pre-clinically disabled older adults (67.6 ± 7.04), and self-efficacy and state anxiety were evaluated prior to performing each task. In univariate models, lower self-efficacy and higher anxiety were associated with more compensation (Spearman correlations: 0.15-0.48, p < 0.05). Multivariate logistic regression indicated that low self-efficacy [Odds Ratio (OR): 1.70; 95% Confidence Interval (CI): 1.40-2.08) and high anxiety (OR: 1.34; 95% CI: 1.10-1.63) were positively associated with using ≥ 6 compensatory strategies – a level signifying substantial compensation. When considered jointly with self-efficacy, the association with anxiety was reversed— higher anxiety demonstrated a lower likelihood of using compensation (OR: 0.70-0.73; 95% CI: 0.50-0.99). The addition of self-efficacy might remove the self-defeating cognitions characterizing anxiety allowing the remaining arousal component to appear beneficial. In conclusion, lower self-efficacy and higher anxiety are associated with using compensation to complete daily tasks among pre-clinically disabled older adults. Such psychological constructs may contribute to the use of compensatory strategies and represent future intervention targets to help reduce early signs of disability. PMID:22770713

Field Crickets Compensate for Unattractive Static Long-Distance Call Components by Increasing Dynamic Signalling Effort

PubMed Central

McAuley, Emily M.

2016-01-01

The evolution of multiple sexual signals presents a dilemma since individuals selecting a mate should pay attention to the most honest signal and ignore the rest; however, multiple signals may evolve if, together, they provide more information to the receiver than either one would alone. Static and dynamic signals, for instance, can act as multiple messages, providing information on different aspects of signaller quality that reflect condition at different time scales. While the nature of static signals makes them difficult or impossible for individuals to augment, dynamic signals are much more susceptible to temporary fluctuations in effort. We investigated whether male Texas field crickets, Gryllus texensis, that produce unattractive static signals compensate by dynamically increasing their calling effort. Our findings lend partial support to the compensation hypothesis, as males that called at unattractive carrier frequencies (a static trait) spent more time calling each night (a dynamic trait). Interestingly, this finding was most pronounced in males that called with attractive pulse characteristics (static traits) but did not occur in males that called with unattractive pulse characteristics. Males that signalled with unattractive pulse characteristics (duration and pause) spent less time calling through the night. Our correlative findings on wild caught males suggest that only males that signal with attractive pulse characteristics may be able to afford to pay the costs of both trait exaggeration and increased calling effort to compensate for poor carrier frequencies. PMID:27936045

Volumetric imaging of fast biological dynamics in deep tissue via wavefront engineering

NASA Astrophysics Data System (ADS)

Kong, Lingjie; Tang, Jianyong; Cui, Meng

2016-03-01

To reveal fast biological dynamics in deep tissue, we combine two wavefront engineering methods that were developed in our laboratory, namely optical phase-locked ultrasound lens (OPLUL) based volumetric imaging and iterative multiphoton adaptive compensation technique (IMPACT). OPLUL is used to generate oscillating defocusing wavefront for fast axial scanning, and IMPACT is used to compensate the wavefront distortions for deep tissue imaging. We show its promising applications in neuroscience and immunology.

Annular suspension and pointing system with controlled DC electromagnets

NASA Technical Reports Server (NTRS)

Vu, Josephine Lynn; Tam, Kwok Hung

1993-01-01

The Annular Suspension and Pointing System (ASPS) developed by the Flight System division of Sperry Corporation is a six-degree of freedom payload pointing system designed for use with the space shuttle. This magnetic suspension and pointing system provides precise controlled pointing in six-degrees of freedom, isolation of payload-carrier disturbances, and end mount controlled pointing. Those are great advantages over the traditional mechanical joints for space applications. In this design, we first analyzed the assumed model of the single degree ASPS bearing actuator and obtained the plant dynamics equations. By linearizing the plant dynamics equations, we designed the cascade and feedback compensators such that a stable and satisfied result was obtained. The specified feedback compensator was computer simulated with the nonlinearized plant dynamics equations. The results indicated that an unstable output occurred. In other words, the designed feedback compensator failed. The failure of the design is due to the Taylor's series expansion not converging.

Intelligence moderates the benefits of strategy instructions on memory performance: an adult-lifespan examination.

PubMed

Frankenmolen, Nikita L; Altgassen, Mareike; Kessels, Renée; de Waal, Marleen M; Hindriksen, Julie-Anne; Verhoeven, Barbara; Fasotti, Luciano; Scheres, Anouk; Kessels, Roy P C; Oosterman, Joukje M

2017-01-01

Whether older adults can compensate for their associative memory deficit by using memory strategies efficiently might depend on their general cognitive abilities. This study examined the moderating role of an IQ estimate on the beneficial effects of strategy instructions. A total of 142 participants (aged 18-85 years) received either intentional learning or strategy ("sentence generation") instructions during encoding of word pairs. Whereas young adults with a lower IQ benefited from strategy instructions, those with a higher IQ did not, presumably because they already use strategies spontaneously. Older adults showed the opposite effect: following strategy instructions, older adults with a higher IQ showed a strong increase in memory performance (approximately achieving the level of younger adults), whereas older adults with a lower IQ did not, suggesting that they have difficulties implementing the provided strategies. These results highlight the importance of the role of IQ in compensating for the aging-related memory decline.

Applying Strategies of Selection, Optimization, and Compensation to Maintain Work Ability-A Psychosocial Resource Complementing the Job Demand-Control Model? Results From the Representative lidA Cohort Study on Work, Age, and Health in Germany.

PubMed

Riedel, Natalie; Müller, Andreas; Ebener, Melanie

2015-05-01

To investigate whether aging employees' selection, optimization, and compensation (SOC) strategies were associated with work ability over and above job demand and control variables, as well as across professions. Multivariable linear regressions were conducted using a representative sample of German employees born in 1959 and 1965 (N = 6057). SOC was assessed to have an independent effect on work ability. Associations of job demands and control variables with work ability were more prominent. The SOC tended to enhance the positive association between decision authority and work ability. Individual strategies of selection, optimization, and compensation could be considered as psychosocial resources adding up to a better work ability and complement prevention programs. Workplace interventions should deal with job demands and control to maintain older employees' work ability in times of working population shrinkage.

High-speed adaptive optics for imaging of the living human eye

PubMed Central

Yu, Yongxin; Zhang, Tianjiao; Meadway, Alexander; Wang, Xiaolin; Zhang, Yuhua

2015-01-01

The discovery of high frequency temporal fluctuation of human ocular wave aberration dictates the necessity of high speed adaptive optics (AO) correction for high resolution retinal imaging. We present a high speed AO system for an experimental adaptive optics scanning laser ophthalmoscope (AOSLO). We developed a custom high speed Shack-Hartmann wavefront sensor and maximized the wavefront detection speed based upon a trade-off among the wavefront spatial sampling density, the dynamic range, and the measurement sensitivity. We examined the temporal dynamic property of the ocular wavefront under the AOSLO imaging condition and improved the dual-thread AO control strategy. The high speed AO can be operated with a closed-loop frequency up to 110 Hz. Experiment results demonstrated that the high speed AO system can provide improved compensation for the wave aberration up to 30 Hz in the living human eye. PMID:26368408

Sliding mode controller with modified sliding function for DC-DC Buck Converter.

PubMed

Naik, B B; Mehta, A J

2017-09-01

This article presents design of Sliding Mode Controller with proportional integral type sliding function for DC-DC Buck Converter for the controlled power supply. The converter with conventional sliding mode controller results in a steady state error in load voltage. The proposed modified sliding function improves the steady state and dynamic performance of the Convertor and facilitates better choices of controller tuning parameters. The conditions for existence of sliding modes for proposed control scheme are derived. The stability of the closed loop system with proposed sliding mode control is proved and improvement in steady state performance is exemplified. The idea of adaptive tuning for the proposed controller to compensate load variations is outlined. The comparative study of conventional and proposed control strategy is presented. The efficacy of the proposed strategy is endowed by the simulation and experimental results. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Laser Beam Oscillation Strategies for Fillet Welds in Lap Joints

NASA Astrophysics Data System (ADS)

Müller, Alexander; Goecke, Sven-F.; Sievi, Pravin; Albert, Florian; Rethmeier, Michael

Laser beam oscillation opens up new possibilities of influencing the welding process in terms of compensation of tolerances and reduction of process emissions that occur in industrial applications, such as in body-in-white manufacturing. The approaches are to adapt the melt pool width in order to generate sufficient melt volume or to influence melt pool dynamics, e.g. for a better degassing. Welding results are highly dependent on the natural frequency of the melt pool, the used spot diameter and the oscillation speed of the laser beam. The conducted investigations with an oscillated 300 μm laser spot show that oscillation strategies, which are adjusted to the joining situation improve welding result for zero-gap welding as well as for bridging gaps to approximately 0.8 mm. However, a complex set of parameters has to be considered in order to generate proper welding results. This work puts emphasize on introducing them.

Software compensation of eddy current fields in multislice high order dynamic shimming.

PubMed

Sengupta, Saikat; Avison, Malcolm J; Gore, John C; Brian Welch, E

2011-06-01

Dynamic B(0) shimming (DS) can produce better field homogeneity than static global shimming by dynamically updating slicewise shim values in a multislice acquisition. The performance of DS however is limited by eddy current fields produced by the switching of 2nd and 3rd order unshielded shims. In this work, we present a novel method of eddy field compensation (EFC) applied to higher order shim induced eddy current fields in multislice DS. This method does not require shim shielding, extra hardware for eddy current compensation or subject specific prescanning. The interactions between shim harmonics are modeled assuming steady state of the medium and long time constant, cross and self term eddy fields in a DS experiment and 'correction factors' characterizing the entire set of shim interactions are derived. The correction factors for a given time between shim switches are shown to be invariable with object scanned, shim switching pattern and actual shim values, allowing for their generalized prospective use. Phantom and human head, 2nd and 3rd order DS experiments performed without any hardware eddy current compensation using the technique show large reductions in field gradients and offsets leading to significant improvements in image quality. This method holds promise as an alternative to expensive hardware based eddy current compensation required in 2nd and 3rd order DS. Copyright © 2011 Elsevier Inc. All rights reserved.

Study designs for identifying risk compensation behavior among users of biomedical HIV prevention technologies: balancing methodological rigor and research ethics.

PubMed

Underhill, Kristen

2013-10-01

The growing evidence base for biomedical HIV prevention interventions - such as oral pre-exposure prophylaxis, microbicides, male circumcision, treatment as prevention, and eventually prevention vaccines - has given rise to concerns about the ways in which users of these biomedical products may adjust their HIV risk behaviors based on the perception that they are prevented from infection. Known as risk compensation, this behavioral adjustment draws on the theory of "risk homeostasis," which has previously been applied to phenomena as diverse as Lyme disease vaccination, insurance mandates, and automobile safety. Little rigorous evidence exists to answer risk compensation concerns in the biomedical HIV prevention literature, in part because the field has not systematically evaluated the study designs available for testing these behaviors. The goals of this Commentary are to explain the origins of risk compensation behavior in risk homeostasis theory, to reframe risk compensation as a testable response to the perception of reduced risk, and to assess the methodological rigor and ethical justification of study designs aiming to isolate risk compensation responses. Although the most rigorous methodological designs for assessing risk compensation behavior may be unavailable due to ethical flaws, several strategies can help investigators identify potential risk compensation behavior during Phase II, Phase III, and Phase IV testing of new technologies. Where concerns arise regarding risk compensation behavior, empirical evidence about the incidence, types, and extent of these behavioral changes can illuminate opportunities to better support the users of new HIV prevention strategies. This Commentary concludes by suggesting a new way to conceptualize risk compensation behavior in the HIV prevention context. Copyright © 2013 Elsevier Ltd. All rights reserved.

Study designs for identifying risk compensation behavior among users of biomedical HIV prevention technologies: Balancing methodological rigor and research ethics

PubMed Central

Underhill, Kristen

2014-01-01

The growing evidence base for biomedical HIV prevention interventions – such as oral pre-exposure prophylaxis, microbicides, male circumcision, treatment as prevention, and eventually prevention vaccines – has given rise to concerns about the ways in which users of these biomedical products may adjust their HIV risk behaviors based on the perception that they are prevented from infection. Known as risk compensation, this behavioral adjustment draws on the theory of “risk homeostasis,” which has previously been applied to phenomena as diverse as Lyme disease vaccination, insurance mandates, and automobile safety. Little rigorous evidence exists to answer risk compensation concerns in the biomedical HIV prevention literature, in part because the field has not systematically evaluated the study designs available for testing these behaviors. The goals of this Commentary are to explain the origins of risk compensation behavior in risk homeostasis theory, to reframe risk compensation as a testable response to the perception of reduced risk, and to assess the methodological rigor and ethical justification of study designs aiming to isolate risk compensation responses. Although the most rigorous methodological designs for assessing risk compensation behavior may be unavailable due to ethical flaws, several strategies can help investigators identify potential risk compensation behavior during Phase II, Phase III, and Phase IV testing of new technologies. Where concerns arise regarding risk compensation behavior, empirical evidence about the incidence, types, and extent of these behavioral changes can illuminate opportunities to better support the users of new HIV prevention strategies. This Commentary concludes by suggesting a new way to conceptualize risk compensation behavior in the HIV prevention context. PMID:23597916

An Energy Saving Green Plug Device for Nonlinear Loads

NASA Astrophysics Data System (ADS)

Bloul, Albe; Sharaf, Adel; El-Hawary, Mohamed

2018-03-01

The paper presents a low cost a FACTS Based flexible fuzzy logic based modulated/switched tuned arm filter and Green Plug compensation (SFC-GP) scheme for single-phase nonlinear loads ensuring both voltage stabilization and efficient energy utilization. The new Green Plug-Switched filter compensator SFC modulated LC-Filter PWM Switched Capacitive Compensation Devices is controlled using a fuzzy logic regulator to enhance power quality, improve power factor at the source and reduce switching transients and inrush current conditions as well harmonic contents in source current. The FACTS based SFC-GP Device is a member of family of Green Plug/Filters/Compensation Schemes used for efficient energy utilization, power quality enhancement and voltage/inrush current/soft starting control using a dynamic error driven fuzzy logic controller (FLC). The device with fuzzy logic controller is validated using the Matlab / Simulink Software Environment for enhanced power quality (PQ), improved power factor and reduced inrush currents. This is achieved using modulated PWM Switching of the Filter-Capacitive compensation scheme to cope with dynamic type nonlinear and inrush cyclical loads..

Research on the control strategy of distributed energy resources inverter based on improved virtual synchronous generator.

PubMed

Gao, Changwei; Liu, Xiaoming; Chen, Hai

2017-08-22

This paper focus on the power fluctuations of the virtual synchronous generator(VSG) during the transition process. An improved virtual synchronous generator(IVSG) control strategy based on feed-forward compensation is proposed. Adjustable parameter of the compensation section can be modified to achieve the goal of reducing the order of the system. It can effectively suppress the power fluctuations of the VSG in transient process. To verify the effectiveness of the proposed control strategy for distributed energy resources inverter, the simulation model is set up in MATLAB/SIMULINK platform and physical experiment platform is established. Simulation and experiment results demonstrate the effectiveness of the proposed IVSG control strategy.

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

Hurricane Katrina: Utilization of Private, Non-Governmental Health Professionals Time for New Strategies

DTIC Science & Technology

2006-09-01

governmental employees specific to workers compensation and death compensation. Potential long-term financial drain on federal budgets. 48 • Health ...coverage for identified/verified and pre-credentialed health professionals to be made “emergency state employees ” to provide liability and workers ...governmental health professionals for workers compensation and death benefits. A review of the potential deployment mechanisms provides insight to the

The coupled nonlinear dynamics of a lift system

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

Crespo, Rafael Sánchez, E-mail: rafael.sanchezcrespo@northampton.ac.uk, E-mail: stefan.kaczmarczyk@northampton.ac.uk, E-mail: phil.picton@northampton.ac.uk, E-mail: huijuan.su@northampton.ac.uk; Kaczmarczyk, Stefan, E-mail: rafael.sanchezcrespo@northampton.ac.uk, E-mail: stefan.kaczmarczyk@northampton.ac.uk, E-mail: phil.picton@northampton.ac.uk, E-mail: huijuan.su@northampton.ac.uk; Picton, Phil, E-mail: rafael.sanchezcrespo@northampton.ac.uk, E-mail: stefan.kaczmarczyk@northampton.ac.uk, E-mail: phil.picton@northampton.ac.uk, E-mail: huijuan.su@northampton.ac.uk

2014-12-10

Coupled lateral and longitudinal vibrations of suspension and compensating ropes in a high-rise lift system are often induced by the building motions due to wind or seismic excitations. When the frequencies of the building become near the natural frequencies of the ropes, large resonance motions of the system may result. This leads to adverse coupled dynamic phenomena involving nonplanar motions of the ropes, impact loads between the ropes and the shaft walls, as well as vertical vibrations of the car, counterweight and compensating sheave. Such an adverse dynamic behaviour of the system endangers the safety of the installation. This papermore » presents two mathematical models describing the nonlinear responses of a suspension/ compensating rope system coupled with the elevator car / compensating sheave motions. The models accommodate the nonlinear couplings between the lateral and longitudinal modes, with and without longitudinal inertia of the ropes. The partial differential nonlinear equations of motion are derived using Hamilton Principle. Then, the Galerkin method is used to discretise the equations of motion and to develop a nonlinear ordinary differential equation model. Approximate numerical solutions are determined and the behaviour of the system is analysed.« less

Computerized method to compensate for breathing body motion in dynamic chest radiographs

NASA Astrophysics Data System (ADS)

Matsuda, H.; Tanaka, R.; Sanada, S.

2017-03-01

Dynamic chest radiography combined with computer analysis allows quantitative analyses on pulmonary function and rib motion. The accuracy of kinematic analysis is directly linked to diagnostic accuracy, and thus body motion compensation is a major concern. Our purpose in this study was to develop a computerized method to reduce a breathing body motion in dynamic chest radiographs. Dynamic chest radiographs of 56 patients were obtained using a dynamic flat-panel detector. The images were divided into a 1 cm-square and the squares on body counter were used to detect the body motion. Velocity vector was measured using cross-correlation method on the body counter and the body motion was then determined on the basis of the summation of motion vector. The body motion was then compensated by shifting the images based on the measured vector. By using our method, the body motion was accurately detected by the order of a few pixels in clinical cases, mean 82.5% in right and left directions. In addition, our method detected slight body motion which was not able to be identified by human observations. We confirmed our method effectively worked in kinetic analysis of rib motion. The present method would be useful for the reduction of a breathing body motion in dynamic chest radiography.

Neuromodulation to the Rescue: Compensation of Temperature-Induced Breakdown of Rhythmic Motor Patterns via Extrinsic Neuromodulatory Input

PubMed Central

Städele, Carola; Heigele, Stefanie; Stein, Wolfgang

2015-01-01

Stable rhythmic neural activity depends on the well-coordinated interplay of synaptic and cell-intrinsic conductances. Since all biophysical processes are temperature dependent, this interplay is challenged during temperature fluctuations. How the nervous system remains functional during temperature perturbations remains mostly unknown. We present a hitherto unknown mechanism of how temperature-induced changes in neural networks are compensated by changing their neuromodulatory state: activation of neuromodulatory pathways establishes a dynamic coregulation of synaptic and intrinsic conductances with opposing effects on neuronal activity when temperature changes, hence rescuing neuronal activity. Using the well-studied gastric mill pattern generator of the crab, we show that modest temperature increase can abolish rhythmic activity in isolated neural circuits due to increased leak currents in rhythm-generating neurons. Dynamic clamp-mediated addition of leak currents was sufficient to stop neuronal oscillations at low temperatures, and subtraction of additional leak currents at elevated temperatures was sufficient to rescue the rhythm. Despite the apparent sensitivity of the isolated nervous system to temperature fluctuations, the rhythm could be stabilized by activating extrinsic neuromodulatory inputs from descending projection neurons, a strategy that we indeed found to be implemented in intact animals. In the isolated nervous system, temperature compensation was achieved by stronger extrinsic neuromodulatory input from projection neurons or by augmenting projection neuron influence via bath application of the peptide cotransmitter Cancer borealis tachykinin-related peptide Ia (CabTRP Ia). CabTRP Ia activates the modulator-induced current IMI (a nonlinear voltage-gated inward current) that effectively acted as a negative leak current and counterbalanced the temperature-induced leak to rescue neuronal oscillations. Computational modelling revealed the ability of IMI to reduce detrimental leak-current influences on neuronal networks over a broad conductance range and indicated that leak and IMI are closely coregulated in the biological system to enable stable motor patterns. In conclusion, these results show that temperature compensation does not need to be implemented within the network itself but can be conditionally provided by extrinsic neuromodulatory input that counterbalances temperature-induced modifications of circuit-intrinsic properties. PMID:26417944

Modeling and distributed gain scheduling strategy for load frequency control in smart grids with communication topology changes.

PubMed

Liu, Shichao; Liu, Xiaoping P; El Saddik, Abdulmotaleb

2014-03-01

In this paper, we investigate the modeling and distributed control problems for the load frequency control (LFC) in a smart grid. In contrast with existing works, we consider more practical and real scenarios, where the communication topology of the smart grid changes because of either link failures or packet losses. These topology changes are modeled as a time-varying communication topology matrix. By using this matrix, a new closed-loop power system model is proposed to integrate the communication topology changes into the dynamics of a physical power system. The globally asymptotical stability of this closed-loop power system is analyzed. A distributed gain scheduling LFC strategy is proposed to compensate for the potential degradation of dynamic performance (mean square errors of state vectors) of the power system under communication topology changes. In comparison to conventional centralized control approaches, the proposed method can improve the robustness of the smart grid to the variation of the communication network as well as to reduce computation load. Simulation results show that the proposed distributed gain scheduling approach is capable to improve the robustness of the smart grid to communication topology changes. © 2013 ISA. Published by ISA. All rights reserved.

Verlet scheme non-conservativeness for simulation of spherical particles collisional dynamics and method of its compensation

NASA Astrophysics Data System (ADS)

Savin, Andrei V.; Smirnov, Petr G.

2018-05-01

Simulation of collisional dynamics of a large ensemble of monodisperse particles by the method of discrete elements is considered. Verle scheme is used for integration of the equations of motion. Non-conservativeness of the finite-difference scheme is discovered depending on the time step, which is equivalent to a pure-numerical energy source appearance in the process of collision. Compensation method for the source is proposed and tested.

Behavioral compensation before and after eating at the Minnesota State Fair.

PubMed

Lenne, Richie L; Panos, Mary E; Auster-Gussman, Lisa; Scherschel, Heather; Zhou, Lucy; Mann, Traci

2017-11-01

People regulate their eating behavior in many ways. They may respond to overeating by compensating with healthy eating behavior or increased exercise (i.e., a sensible tradeoff), or by continuing to eat poorly (i.e., disinhibition). Conversely, people may respond to a healthy eating event by subsequently eating poorly (i.e., self-licensing) or by continuing to eat healthily (i.e., promotion spillover). We propose that people may also change their behaviors in anticipation of an unhealthy eating event, a phenomenon that we will refer to as pre-compensation. Using a survey of 430 attendees of the Minnesota State Fair over two years, we explored whether, when, and how people compensated before and after this tempting eating event. We found evidence that people use both pre-compensatory and post-compensatory strategies, with a preference for changing their eating (rather than exercise) behavior. There was no evidence that people who pre-compensated were more likely to self-license by indulging in a greater number of foods or calories at the fair than those who did not. Finally, people who pre-compensated were more likely to also post-compensate. These results suggest that changing eating or exercise behavior before exposure to a situation with many tempting foods may be a successful strategy for enjoying oneself without excessively overeating. Copyright © 2017 Elsevier Ltd. All rights reserved.

[Academic burnout and selection-optimization-compensation strategy in medical students].

PubMed

Chun, Kyung Hee; Park, Young Soon; Lee, Young Hwan; Kim, Seong Yong

2014-12-01

This study was conducted to examine the relationship between academic demand, academic burnout, and the selection-optimization-compensation (SOC) strategy in medical students. A total of 317 students at Yeungnam University, comprising 90 premedical course students, 114 medical course students, and 113 graduate course students, completed a survey that addressed the factors of academic burnout and the selection-optimization-compensation strategy. We analyzed variances of burnout and SOC strategy use by group, and stepwise multiple regression analysis was conducted. There were significant differences in emotional exhaustion and cynicism between groups and year in school. In the SOC strategy, there were no significant differences between groups except for elective selection. The second-year medical and graduate students experienced significantly greater exhaustion (p<0.001), and first-year premedical students experienced significantly higher cynicism (p<0.001). By multiple regression analysis, subfactors of academic burnout and emotional exhaustion were significantly affected by academic demand (p<0.001), and 46% of the variance was explained. Cynicism was significantly affected by elective selection (p<0.05), and inefficacy was significantly influenced by optimization (p<0.001). To improve adaptation, prescriptive strategies and preventive support should be implemented with regard to academic burnout in medical school. Longitudinal and qualitative studies on burnout must be conducted.

SOC Strategies and Organizational Citizenship Behaviors toward the Benefits of Co-workers: A Multi-Source Study.

PubMed

Müller, Andreas; Weigl, Matthias

2017-01-01

Background: Individuals' behavioral strategies like selection, optimization, and compensation (SOC) contribute to efficient use of available resources. In the work context, previous studies revealed positive associations between employees' SOC use and favorable individual outcomes, like engagement and job performance. However, the social implications of self-directed behaviors like SOC that are favorable for the employee but may imply consequences for coworkers have not been investigated yet in an interpersonal work context. Objective: This study aimed to assess associations between employees' use of SOC behaviors at work and their organizational citizenship behaviors (OCB) toward the benefits of co-workers rated by their peers at work. We further sought to identify age-specific associations between SOC use and OCB. Design and Method: A cross-sectional design combining multi-source data was applied in primary school teachers (age range: 23-58 years) who frequently teach in dyads. N = 114 dyads were finally included. Teachers reported on their SOC strategies at work. Their peer colleagues evaluated teachers' OCB. Control variables were gender, workload, working hours, and perceived proximity of relationship between the dyads. Results: We observed a positive effect of loss-based selection behaviors on peer-rated OCB. Moreover, there was a significant two-way interaction effect between the use of compensation strategies and age on OCB, such that there was a positive association for older employees and a negative association for younger employees. There were no significant main and age-related interaction effects of elective selection, optimization, and of overall SOC strategies on OCB. Conclusion: Our study suggests that high use of loss-based selection and high use of compensation strategies in older employees is positively related with OCB as perceived by their colleagues. However, high use of compensation strategies in younger employees is perceived negatively related with OCB. Our findings contribute to a better understanding of the age-differentiated interpersonal effects of successful aging strategies in terms of SOC in organizations.

SOC Strategies and Organizational Citizenship Behaviors toward the Benefits of Co-workers: A Multi-Source Study

PubMed Central

Müller, Andreas; Weigl, Matthias

2017-01-01

Background: Individuals’ behavioral strategies like selection, optimization, and compensation (SOC) contribute to efficient use of available resources. In the work context, previous studies revealed positive associations between employees’ SOC use and favorable individual outcomes, like engagement and job performance. However, the social implications of self-directed behaviors like SOC that are favorable for the employee but may imply consequences for coworkers have not been investigated yet in an interpersonal work context. Objective: This study aimed to assess associations between employees’ use of SOC behaviors at work and their organizational citizenship behaviors (OCB) toward the benefits of co-workers rated by their peers at work. We further sought to identify age-specific associations between SOC use and OCB. Design and Method: A cross-sectional design combining multi-source data was applied in primary school teachers (age range: 23–58 years) who frequently teach in dyads. N = 114 dyads were finally included. Teachers reported on their SOC strategies at work. Their peer colleagues evaluated teachers’ OCB. Control variables were gender, workload, working hours, and perceived proximity of relationship between the dyads. Results: We observed a positive effect of loss-based selection behaviors on peer-rated OCB. Moreover, there was a significant two-way interaction effect between the use of compensation strategies and age on OCB, such that there was a positive association for older employees and a negative association for younger employees. There were no significant main and age-related interaction effects of elective selection, optimization, and of overall SOC strategies on OCB. Conclusion: Our study suggests that high use of loss-based selection and high use of compensation strategies in older employees is positively related with OCB as perceived by their colleagues. However, high use of compensation strategies in younger employees is perceived negatively related with OCB. Our findings contribute to a better understanding of the age-differentiated interpersonal effects of successful aging strategies in terms of SOC in organizations. PMID:29085315

Backstepping fuzzy-neural-network control design for hybrid maglev transportation system.

PubMed

Wai, Rong-Jong; Yao, Jing-Xiang; Lee, Jeng-Dao

2015-02-01

This paper focuses on the design of a backstepping fuzzy-neural-network control (BFNNC) for the online levitated balancing and propulsive positioning of a hybrid magnetic levitation (maglev) transportation system. The dynamic model of the hybrid maglev transportation system including levitated hybrid electromagnets to reduce the suspension power loss and the friction force during linear movement and a propulsive linear induction motor based on the concepts of mechanical geometry and motion dynamics is first constructed. The ultimate goal is to design an online fuzzy neural network (FNN) control methodology to cope with the problem of the complicated control transformation and the chattering control effort in backstepping control (BSC) design, and to directly ensure the stability of the controlled system without the requirement of strict constraints, detailed system information, and auxiliary compensated controllers despite the existence of uncertainties. In the proposed BFNNC scheme, an FNN control is utilized to be the major control role by imitating the BSC strategy, and adaptation laws for network parameters are derived in the sense of projection algorithm and Lyapunov stability theorem to ensure the network convergence as well as stable control performance. The effectiveness of the proposed control strategy for the hybrid maglev transportation system is verified by experimental results, and the superiority of the BFNNC scheme is indicated in comparison with the BSC strategy and the backstepping particle-swarm-optimization control system in previous research.

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

Load Balancing Unstructured Adaptive Grids for CFD Problems

NASA Technical Reports Server (NTRS)

Biswas, Rupak; Oliker, Leonid

1996-01-01

Mesh adaption is a powerful tool for efficient unstructured-grid computations but causes load imbalance among processors on a parallel machine. A dynamic load balancing method is presented that balances the workload across all processors with a global view. After each parallel tetrahedral mesh adaption, the method first determines if the new mesh is sufficiently unbalanced to warrant a repartitioning. If so, the adapted mesh is repartitioned, with new partitions assigned to processors so that the redistribution cost is minimized. The new partitions are accepted only if the remapping cost is compensated by the improved load balance. Results indicate that this strategy is effective for large-scale scientific computations on distributed-memory multiprocessors.

Robust leader-follower formation tracking control of multiple underactuated surface vessels

NASA Astrophysics Data System (ADS)

Peng, Zhou-hua; Wang, Dan; Lan, Wei-yao; Sun, Gang

2012-09-01

This paper is concerned with the formation control problem of multiple underactuated surface vessels moving in a leader-follower formation. The formation is achieved by the follower to track a virtual target defined relative to the leader. A robust adaptive target tracking law is proposed by using neural network and backstepping techniques. The advantage of the proposed control scheme is that the uncertain nonlinear dynamics caused by Coriolis/centripetal forces, nonlinear damping, unmodeled hydrodynamics and disturbances from the environment can be compensated by on line learning. Based on Lyapunov analysis, the proposed controller guarantees the tracking errors converge to a small neighborhood of the origin. Simulation results demonstrate the effectiveness of the control strategy.

Minimal complexity control law synthesis

NASA Technical Reports Server (NTRS)

Bernstein, Dennis S.; Haddad, Wassim M.; Nett, Carl N.

1989-01-01

A paradigm for control law design for modern engineering systems is proposed: Minimize control law complexity subject to the achievement of a specified accuracy in the face of a specified level of uncertainty. Correspondingly, the overall goal is to make progress towards the development of a control law design methodology which supports this paradigm. Researchers achieve this goal by developing a general theory of optimal constrained-structure dynamic output feedback compensation, where here constrained-structure means that the dynamic-structure (e.g., dynamic order, pole locations, zero locations, etc.) of the output feedback compensation is constrained in some way. By applying this theory in an innovative fashion, where here the indicated iteration occurs over the choice of the compensator dynamic-structure, the paradigm stated above can, in principle, be realized. The optimal constrained-structure dynamic output feedback problem is formulated in general terms. An elegant method for reducing optimal constrained-structure dynamic output feedback problems to optimal static output feedback problems is then developed. This reduction procedure makes use of star products, linear fractional transformations, and linear fractional decompositions, and yields as a byproduct a complete characterization of the class of optimal constrained-structure dynamic output feedback problems which can be reduced to optimal static output feedback problems. Issues such as operational/physical constraints, operating-point variations, and processor throughput/memory limitations are considered, and it is shown how anti-windup/bumpless transfer, gain-scheduling, and digital processor implementation can be facilitated by constraining the controller dynamic-structure in an appropriate fashion.

Dynamic compensation in the central Pacific Ocean

NASA Technical Reports Server (NTRS)

Hinojosa, Juan Homero; Marsh, Bruce D.

1988-01-01

The intermediate-wavelength geoid (lambda similar to 2000 km) and sea-floor topography fields in the central Pacific Ocean were studied in terms of static and dynamic compensation models. Topographic features on the sea-floor with lambda less than 1000 km were found to be compensated both regionally, by the elastic strength of the lithosphere, and locally, by displacing mantle material to reach isostatic adjustment. The larger-scale sea-floor topography and the corresponding geoid anomalies with lambda similar to 2000 km cannot be explained by either local or regional compensation. The topography and the resulting geoid anomaly at this wavelength were modeled by considering the dynamic effects arising from viscous stresses in a layer of fluid with a highly temperature-dependent viscosity for the cases of: (1) surface cooling, and (2) basal heating. In this model, the mechanical properties of the elastic part of the lithosphere were taken into account by considering an activation energy of about 520 kJ/mol in the Arrhenius law for the viscosity. Numerical predictions of the topography, total geoid anomaly, and admittance were obtained, and the results show that the thermal perturbation in the layer, which accounts for the mass deficit, must be located close to the surface to compensate the gravitational effect of the surface deformation. For the case of basal heating, the temperature dependence of viscosity results in a separation of the upper, quasi-rigid lid from the lower mobile fluid, hence inhibiting the development of a compensating thermal perturbation at shallow depths. The results clearly rule out small-scale, upper-mantle convection as the source of these anomalies. Instead, the geophysical observables can be well explained by a shallow, transient thermal perturbation.

Compensator improvement for multivariable control systems

NASA Technical Reports Server (NTRS)

Mitchell, J. R.; Mcdaniel, W. L., Jr.; Gresham, L. L.

1977-01-01

A theory and the associated numerical technique are developed for an iterative design improvement of the compensation for linear, time-invariant control systems with multiple inputs and multiple outputs. A strict constraint algorithm is used in obtaining a solution of the specified constraints of the control design. The result of the research effort is the multiple input, multiple output Compensator Improvement Program (CIP). The objective of the Compensator Improvement Program is to modify in an iterative manner the free parameters of the dynamic compensation matrix so that the system satisfies frequency domain specifications. In this exposition, the underlying principles of the multivariable CIP algorithm are presented and the practical utility of the program is illustrated with space vehicle related examples.

Fault-tolerant nonlinear adaptive flight control using sliding mode online learning.

PubMed

Krüger, Thomas; Schnetter, Philipp; Placzek, Robin; Vörsmann, Peter

2012-08-01

An expanded nonlinear model inversion flight control strategy using sliding mode online learning for neural networks is presented. The proposed control strategy is implemented for a small unmanned aircraft system (UAS). This class of aircraft is very susceptible towards nonlinearities like atmospheric turbulence, model uncertainties and of course system failures. Therefore, these systems mark a sensible testbed to evaluate fault-tolerant, adaptive flight control strategies. Within this work the concept of feedback linearization is combined with feed forward neural networks to compensate for inversion errors and other nonlinear effects. Backpropagation-based adaption laws of the network weights are used for online training. Within these adaption laws the standard gradient descent backpropagation algorithm is augmented with the concept of sliding mode control (SMC). Implemented as a learning algorithm, this nonlinear control strategy treats the neural network as a controlled system and allows a stable, dynamic calculation of the learning rates. While considering the system's stability, this robust online learning method therefore offers a higher speed of convergence, especially in the presence of external disturbances. The SMC-based flight controller is tested and compared with the standard gradient descent backpropagation algorithm in the presence of system failures. Copyright © 2012 Elsevier Ltd. All rights reserved.

Learning to interpret one's own outcome as unjustified amplifies altruistic compensation: a training study

PubMed Central

Maltese, Simona; Baumert, Anna; Knab, Nadine; Schmitt, Manfred

2013-01-01

Interpretational tendencies in ambiguous situations were investigated as causal mechanisms of altruistic compensation. We used a training procedure to induce a tendency to interpret one's own advantages as unjustified. In a subsequent mixed-game, participants had to decide whether to invest their own money to compensate a victim of a norm violation. The amount of one's own resources invested as an altruistic compensation was enhanced after the training procedure compared to controls. These findings suggest that interpretational patterns with regard to injustice determine prosocial behavior. The training procedure offers a potential intervention strategy for enhancing altruistic compensation in bystander situations in which people must invest their own resources to restore justice. PMID:24391614

Responding to home maintenance challenge scenarios: the role of selection, optimization, and compensation in aging-in-place.

PubMed

Kelly, Andrew John; Fausset, Cara Bailey; Rogers, Wendy; Fisk, Arthur D

2014-12-01

This study examined potential issues faced by older adults in managing their homes and their proposed solutions for overcoming hypothetical difficulties. Forty-four diverse, independently living older adults (66-85) participated in structured group interviews in which they discussed potential solutions to manage difficulties presented in four scenarios: perceptual, mobility, physical, and cognitive difficulties. The proposed solutions were classified using the Selection, Optimization, and Compensation (SOC) model. Participants indicated they would continue performing most tasks and reported a range of strategies to manage home maintenance challenges. Most participants reported that they would manage home maintenance challenges using compensation; the most frequently mentioned compensation strategy was using tools and technologies. There were also differences across the scenarios: Optimization was discussed most frequently with perceptual and cognitive difficulty scenarios. These results provide insights into supporting older adults' potential needs for aging-in-place and provide evidence of the value of the SOC model in applied research. © The Author(s) 2012.

Compensation strategy for machining optical freeform surfaces by the combined on- and off-machine measurement.

PubMed

Zhang, Xiaodong; Zeng, Zhen; Liu, Xianlei; Fang, Fengzhou

2015-09-21

Freeform surface is promising to be the next generation optics, however it needs high form accuracy for excellent performance. The closed-loop of fabrication-measurement-compensation is necessary for the improvement of the form accuracy. It is difficult to do an off-machine measurement during the freeform machining because the remounting inaccuracy can result in significant form deviations. On the other side, on-machine measurement may hides the systematic errors of the machine because the measuring device is placed in situ on the machine. This study proposes a new compensation strategy based on the combination of on-machine and off-machine measurement. The freeform surface is measured in off-machine mode with nanometric accuracy, and the on-machine probe achieves accurate relative position between the workpiece and machine after remounting. The compensation cutting path is generated according to the calculated relative position and shape errors to avoid employing extra manual adjustment or highly accurate reference-feature fixture. Experimental results verified the effectiveness of the proposed method.

The role of predation and food limitation on claims for compensation, reindeer demography and population dynamics

PubMed Central

Tveraa, Torkild; Stien, Audun; Brøseth, Henrik; Yoccoz, Nigel G

2014-01-01

A major challenge in biodiversity conservation is to facilitate viable populations of large apex predators in ecosystems where they were recently driven to ecological extinction due to resource conflict with humans. Monetary compensation for losses of livestock due to predation is currently a key instrument to encourage human–carnivore coexistence. However, a lack of quantitative estimates of livestock losses due to predation leads to disagreement over the practice of compensation payments. This disagreement sustains the human–carnivore conflict. The level of depredation on year-round, free-ranging, semi-domestic reindeer by large carnivores in Fennoscandia has been widely debated over several decades. In Norway, the reindeer herders claim that lynx and wolverine cause losses of tens of thousands of animals annually and cause negative population growth in herds. Conversely, previous research has suggested that monetary predator compensation can result in positive population growth in the husbandry, with cascading negative effects of high grazer densities on the biodiversity in tundra ecosystems. We utilized a long-term, large-scale data set to estimate the relative importance of lynx and wolverine predation and density-dependent and climatic food limitation on claims for losses, recruitment and population growth rates in Norwegian reindeer husbandry. Claims of losses increased with increasing predator densities, but with no detectable effect on population growth rates. Density-dependent and climatic effects on claims of losses, recruitment and population growth rates were much stronger than the effects of variation in lynx and wolverine densities. Synthesis and applications. Our analysis provides a quantitative basis for predator compensation and estimation of the costs of reintroducing lynx and wolverine in areas with free-ranging semi-domestic reindeer. We outline a potential path for conflict management which involves adaptive monitoring programmes, open access to data, herder involvement and development of management strategy evaluation (MSE) models to disentangle complex responses including multiple stakeholders and individual harvester decisions. PMID:25558085

Effects of blindness on production-perception relationships: Compensation strategies for a lip-tube perturbation of the French [u].

PubMed

Ménard, Lucie; Turgeon, Christine; Trudeau-Fisette, Paméla; Bellavance-Courtemanche, Marie

2016-01-01

The impact of congenital visual deprivation on speech production in adults was examined in an ultrasound study of compensation strategies for lip-tube perturbation. Acoustic and articulatory analyses of the rounded vowel /u/ produced by 12 congenitally blind adult French speakers and 11 sighted adult French speakers were conducted under two conditions: normal and perturbed (with a 25-mm diameter tube inserted between the lips). Vowels were produced with auditory feedback and without auditory feedback (masked noise) to evaluate the extent to which both groups relied on this type of feedback to control speech movements. The acoustic analyses revealed that all participants mainly altered F2 and F0 and, to a lesser extent, F1 in the perturbed condition - only when auditory feedback was available. There were group differences in the articulatory strategies recruited to compensate; while all speakers moved their tongues more backward in the perturbed condition, blind speakers modified tongue-shape parameters to a greater extent than sighted speakers.

A compensation method of lever arm effect for tri-axis hybrid inertial navigation system based on fiber optic gyro

NASA Astrophysics Data System (ADS)

Liu, Zengjun; Wang, Lei; Li, Kui; Gao, Jiaxin

2017-05-01

Hybrid inertial navigation system (HINS) is a new kind of inertial navigation system (INS), which combines advantages of platform INS, strap-down INS and rotational INS. HINS has a physical platform to isolate the angular motion as platform INS does, HINS also uses strap-down attitude algorithms and applies rotation modulation technique. Tri-axis HINS has three gimbals to isolate the angular motion in the dynamic base, in which way the system can reduce the effects of angular motion and improve the positioning precision. However, the angular motion will affect the compensation of some error parameters, especially for the lever arm effect. The lever arm effect caused by position errors between the accelerometers and rotation center cannot be ignored due to the rapid rotation of inertial measurement unit (IMU) and it will cause fluctuation and stage in velocity in HINS. The influences of angular motion on the lever arm effect compensation are analyzed firstly in this paper, and then the compensation method of lever arm effect based on the photoelectric encoders in dynamic base is proposed. Results of experiments on turntable show that after compensation, the fluctuations and stages in velocity curve disappear.

Temperature-compensated distributed hydrostatic pressure sensor with a thin-diameter polarization-maintaining photonic crystal fiber based on Brillouin dynamic gratings.

PubMed

Teng, Lei; Zhang, Hongying; Dong, Yongkang; Zhou, Dengwang; Jiang, Taofei; Gao, Wei; Lu, Zhiwei; Chen, Liang; Bao, Xiaoyi

2016-09-15

A temperature-compensated distributed hydrostatic pressure sensor based on Brillouin dynamic gratings (BDGs) is proposed and demonstrated experimentally for the first time, to the best of our knowledge. The principle is to measure the hydrostatic pressure induced birefringence changes through exciting and probing the BDGs in a thin-diameter pure silica polarization-maintaining photonic crystal fiber. The temperature cross-talk to the hydrostatic pressure sensing can be compensated through measuring the temperature-induced Brillouin frequency shift (BFS) changes using Brillouin optical time-domain analysis. A distributed measurement of hydrostatic pressure is demonstrated experimentally using a 4-m sensing fiber, which has a high sensitivity, with a maximum measurement error less than 0.03 MPa at a 20-cm spatial resolution.

Fast vortex oscillations in a ferrimagnetic disk near the angular momentum compensation point

NASA Astrophysics Data System (ADS)

Kim, Se Kwon; Tserkovnyak, Yaroslav

2017-07-01

We theoretically study the oscillatory dynamics of a vortex core in a ferrimagnetic disk near its angular momentum compensation point, where the spin density vanishes but the magnetization is finite. Due to the finite magnetostatic energy, a ferrimagnetic disk of suitable geometry can support a vortex as a ground state similar to a ferromagnetic disk. In the vicinity of the angular momentum compensation point, the dynamics of the vortex resemble those of an antiferromagnetic vortex, which is described by equations of motion analogous to Newton's second law for the motion of particles. Owing to the antiferromagnetic nature of the dynamics, the vortex oscillation frequency can be an order of magnitude larger than the frequency of a ferromagnetic vortex, amounting to tens of GHz in common transition-metal based alloys. We show that the frequency can be controlled either by applying an external field or by changing the temperature. In particular, the latter property allows us to detect the angular momentum compensation temperature, at which the lowest eigenfrequency attains its maximum, by performing ferromagnetic resonance measurements on the vortex disk. Our work proposes a ferrimagnetic vortex disk as a tunable source of fast magnetic oscillations and a useful platform to study the properties of ferrimagnets.

A Task-Based Language Teaching Approach to Developing Metacognitive Strategies for Listening Comprehension

ERIC Educational Resources Information Center

Chou, Mu-Hsuan

2017-01-01

In second (L2) or foreign language (FL) learning, learning strategies help learners perform tasks, solve specific problems, and compensate for learning deficits. Of the strategy types, metacognitive strategies manage and regulate the construction of L2 or FL knowledge. Although learning strategies are frequently taught via teacher demonstration,…

Cross-entropy optimization for neuromodulation.

PubMed

Brar, Harleen K; Yunpeng Pan; Mahmoudi, Babak; Theodorou, Evangelos A

2016-08-01

This study presents a reinforcement learning approach for the optimization of the proportional-integral gains of the feedback controller represented in a computational model of epilepsy. The chaotic oscillator model provides a feedback control systems view of the dynamics of an epileptic brain with an internal feedback controller representative of the natural seizure suppression mechanism within the brain circuitry. Normal and pathological brain activity is simulated in this model by adjusting the feedback gain values of the internal controller. With insufficient gains, the internal controller cannot provide enough feedback to the brain dynamics causing an increase in correlation between different brain sites. This increase in synchronization results in the destabilization of the brain dynamics, which is representative of an epileptic seizure. To provide compensation for an insufficient internal controller an external controller is designed using proportional-integral feedback control strategy. A cross-entropy optimization algorithm is applied to the chaotic oscillator network model to learn the optimal feedback gains for the external controller instead of hand-tuning the gains to provide sufficient control to the pathological brain and prevent seizure generation. The correlation between the dynamics of neural activity within different brain sites is calculated for experimental data to show similar dynamics of epileptic neural activity as simulated by the network of chaotic oscillators.

Relationship between the Macroscopic and Quantum Characteristics of Dynamic Viscosity for Hydrocarbons upon the Compensation Effect

NASA Astrophysics Data System (ADS)

Dolomatov, M. Yu.; Kovaleva, E. A.; Khamidullina, D. A.

2018-05-01

An approach that allows the calculation of dynamic viscosity for liquid hydrocarbons from quantum (ionization energies) and molecular (Wiener topological indices) parameters is proposed. A physical relationship is revealed between ionization and the energies of viscous flow activation. This relationship is due to the contribution from the dispersion component of Van der Waals forces to intermolecular interaction. A two-parameter dependence of the energy of viscous flow activation, energy of ionization, and Wiener topological indices is obtained. The dynamic viscosities of liquid hydrocarbons can be calculated from the kinetic compensation effect of dynamic viscosity, which indicates a relationship between the energy of activation and the Arrhenius pre-exponental factor of the Frenkel-Eyring hole model. Calculation results are confirmed through statistical processing of the experimental data.

Communicating with Investigators about Financial Compensation for Statistical Collaboration

ERIC Educational Resources Information Center

Ittenbach, Richard F.; DeAngelis, Francis W.; Altaye, Mekibib

2013-01-01

Communicating with investigators about financial compensation in the area of statistical collaboration represents an important but often underemphasized component of biomedical research. The more complex the area, the greater the need for sound and effective communication strategies. Ittenbach and DeAngelis (2012) recently compared two…

Hybrid Smith predictor and phase lead based divergence compensation for hardware-in-the-loop contact simulation with measurement delay

NASA Astrophysics Data System (ADS)

Qi, Chenkun; Gao, Feng; Zhao, Xianchao; Wang, Qian; Ren, Anye

2018-06-01

On the ground the hardware-in-the-loop (HIL) simulation is a good approach to test the contact dynamics of spacecraft docking process in space. Unfortunately, due to the time delay in the system the HIL contact simulation becomes divergent. However, the traditional first-order phase lead compensation approach still result in a small divergence for the pure time delay. The serial Smith predictor and phase lead compensation approach proposed by the authors recently will lead to an over-compensation and an obvious convergence. In this study, a hybrid Smith predictor and phase lead compensation approach is proposed. The hybrid Smith predictor and phase lead compensation can achieve a higher simulation fidelity with a little convergence. The phase angle of the compensator is analyzed and the stability condition of the HIL simulation system is given. The effectiveness of the proposed compensation approach is tested by simulations on an undamped elastic contact process.

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.

Adaptive fuzzy-neural-network control for maglev transportation system.

PubMed

Wai, Rong-Jong; Lee, Jeng-Dao

2008-01-01

A magnetic-levitation (maglev) transportation system including levitation and propulsion control is a subject of considerable scientific interest because of highly nonlinear and unstable behaviors. In this paper, the dynamic model of a maglev transportation system including levitated electromagnets and a propulsive linear induction motor (LIM) based on the concepts of mechanical geometry and motion dynamics is developed first. Then, a model-based sliding-mode control (SMC) strategy is introduced. In order to alleviate chattering phenomena caused by the inappropriate selection of uncertainty bound, a simple bound estimation algorithm is embedded in the SMC strategy to form an adaptive sliding-mode control (ASMC) scheme. However, this estimation algorithm is always a positive value so that tracking errors introduced by any uncertainty will cause the estimated bound increase even to infinity with time. Therefore, it further designs an adaptive fuzzy-neural-network control (AFNNC) scheme by imitating the SMC strategy for the maglev transportation system. In the model-free AFNNC, online learning algorithms are designed to cope with the problem of chattering phenomena caused by the sign action in SMC design, and to ensure the stability of the controlled system without the requirement of auxiliary compensated controllers despite the existence of uncertainties. The outputs of the AFNNC scheme can be directly supplied to the electromagnets and LIM without complicated control transformations for relaxing strict constrains in conventional model-based control methodologies. The effectiveness of the proposed control schemes for the maglev transportation system is verified by numerical simulations, and the superiority of the AFNNC scheme is indicated in comparison with the SMC and ASMC strategies.

A new rate-dependent model for high-frequency tracking performance enhancement of piezoactuator system

NASA Astrophysics Data System (ADS)

Tian, Lizhi; Xiong, Zhenhua; Wu, Jianhua; Ding, Han

2017-05-01

Feedforward-feedback control is widely used in motion control of piezoactuator systems. Due to the phase lag caused by incomplete dynamics compensation, the performance of the composite controller is greatly limited at high frequency. This paper proposes a new rate-dependent model to improve the high-frequency tracking performance by reducing dynamics compensation error. The rate-dependent model is designed as a function of the input and input variation rate to describe the input-output relationship of the residual system dynamics which mainly performs as phase lag in a wide frequency band. Then the direct inversion of the proposed rate-dependent model is used to compensate the residual system dynamics. Using the proposed rate-dependent model as feedforward term, the open loop performance can be improved significantly at medium-high frequency. Then, combining the with feedback controller, the composite controller can provide enhanced close loop performance from low frequency to high frequency. At the frequency of 1 Hz, the proposed controller presents the same performance as previous methods. However, at the frequency of 900 Hz, the tracking error is reduced to be 30.7% of the decoupled approach.

Cigarette price minimization strategies in the United States: price reductions and responsiveness to excise taxes.

PubMed

Pesko, Michael F; Licht, Andrea S; Kruger, Judy M

2013-11-01

Because cigarette price minimization strategies can provide substantial price reductions for individuals continuing their usual smoking behaviors following federal and state cigarette excise tax increases, we examined independent price reductions compensating for overlapping strategies. The possible availability of larger independent price reduction opportunities in states with higher cigarette excise taxes is explored. Regression analysis used the 2006-2007 Tobacco Use Supplement of the Current Population Survey (N = 26,826) to explore national and state-level independent price reductions that smokers obtained from purchasing cigarettes (a) by the carton, (b) in a state with a lower average after-tax cigarette price than in the state of residence, and (c) in "some other way," including online or in another country. Price reductions from these strategies are estimated jointly to compensate for known overlapping strategies. Each strategy reduced the price of cigarettes by 64-94 cents per pack. These price reductions are 9%-22% lower than conventionally estimated results not compensating for overlapping strategies. Price reductions vary substantially by state. Following cigarette excise tax increases, the price reduction available from purchasing cigarettes by cartons increased. Additionally, the price reduction from purchasing cigarettes in a state with a lower average after-tax cigarette price is positively associated with state cigarette excise tax rates and border state cigarette excise tax rate differentials. Findings from this large, nationally representative study of cigarette smokers suggest that price reductions are larger in states with higher cigarette excise taxes, and increase as cigarette excise taxes rise.

Mechanical design of deformation compensated flexural pivots structured for linear nanopositioning stages

DOEpatents

Shu, Deming; Kearney, Steven P.; Preissner, Curt A.

2015-02-17

A method and deformation compensated flexural pivots structured for precision linear nanopositioning stages are provided. A deformation-compensated flexural linear guiding mechanism includes a basic parallel mechanism including a U-shaped member and a pair of parallel bars linked to respective pairs of I-link bars and each of the I-bars coupled by a respective pair of flexural pivots. The basic parallel mechanism includes substantially evenly distributed flexural pivots minimizing center shift dynamic errors.

Dynamic Neuroplasticity after Human Prefrontal Cortex Damage

PubMed Central

Voytek, Bradley; Davis, Matar; Yago, Elena; Barceló, Francisco; Vogel, Edward K.; Knight, Robert T.

2010-01-01

Summary Memory and attention deficits are common after prefrontal cortex (PFC) damage, yet people generally recover some function over time. Recovery is thought to be dependent upon undamaged brain regions but the temporal dynamics underlying cognitive recovery are poorly understood. Here we provide evidence that the intact PFC compensates for damage in the lesioned PFC on a trial-by-trial basis dependent on cognitive load. The extent of this rapid functional compensation is indexed by transient increases in electrophysiological measures of attention and memory in the intact PFC, detectable within a second after stimulus presentation and only when the lesioned hemisphere is challenged. These observations provide evidence supporting a dynamic and flexible model of compensatory neural plasticity. PMID:21040843

Language Learning Strategy Use In Palestine.

ERIC Educational Resources Information Center

Shmais, Wafa Abu

2003-01-01

Reports on current English language learning strategies used by Arabic-speaking English-majors enrolled at a University in Palestine. Results showed that gender and proficiency had no significant differences on the use of strategies. Recommends that more training should be given in using cognitive, memory and compensation strategies by embedding…

Engineering model of the electric drives of separation device for simulation of automatic control systems of reactive power compensation by means of serially connected capacitors

NASA Astrophysics Data System (ADS)

Juromskiy, V. M.

2016-09-01

It is developed a mathematical model for an electric drive of high-speed separation device in terms of the modeling dynamic systems Simulink, MATLAB. The model is focused on the study of the automatic control systems of the power factor (Cosφ) of an actuator by compensating the reactive component of the total power by switching a capacitor bank in series with the actuator. The model is based on the methodology of the structural modeling of dynamic processes.

The Molecular Origin of Enthalpy/Entropy Compensation in Biomolecular Recognition.

PubMed

Fox, Jerome M; Zhao, Mengxia; Fink, Michael J; Kang, Kyungtae; Whitesides, George M

2018-05-20

Biomolecular recognition can be stubborn; changes in the structures of associating molecules, or the environments in which they associate, often yield compensating changes in enthalpies and entropies of binding and no net change in affinities. This phenomenon-termed enthalpy/entropy (H/S) compensation-hinders efforts in biomolecular design, and its incidence-often a surprise to experimentalists-makes interactions between biomolecules difficult to predict. Although characterizing H/S compensation requires experimental care, it is unquestionably a real phenomenon that has, from an engineering perspective, useful physical origins. Studying H/S compensation can help illuminate the still-murky roles of water and dynamics in biomolecular recognition and self-assembly. This review summarizes known sources of H/ S compensation (real and perceived) and lays out a conceptual framework for understanding and dissecting-and, perhaps, avoiding or exploiting-this phenomenon in biophysical systems.

Safety Is 99 Percent Attitude: Strategies to Contain Workers' Compensation Costs.

ERIC Educational Resources Information Center

Parnell, Janet

1993-01-01

The University of Denver (Colorado) reduced workers' compensation losses 97 percent in 1990-91 by developing a master safety plan, sponsoring safety training, managing medical costs, providing modified duty for injured employees, screening applicants, orienting new employees, investigating claims thoroughly, performing life-safety audits, and…

Feedforward compensation for novel dynamics depends on force field orientation but is similar for the left and right arms.

PubMed

Reuter, Eva-Maria; Cunnington, Ross; Mattingley, Jason B; Riek, Stephan; Carroll, Timothy J

2016-11-01

There are well-documented differences in the way that people typically perform identical motor tasks with their dominant and the nondominant arms. According to Yadav and Sainburg's (Neuroscience 196: 153-167, 2011) hybrid-control model, this is because the two arms rely to different degrees on impedance control versus predictive control processes. Here, we assessed whether differences in limb control mechanisms influence the rate of feedforward compensation to a novel dynamic environment. Seventy-five healthy, right-handed participants, divided into four subsamples depending on the arm (left, right) and direction of the force field (ipsilateral, contralateral), reached to central targets in velocity-dependent curl force fields. We assessed the rate at which participants developed predictive compensation for the force field using intermittent error-clamp trials and assessed both kinematic errors and initial aiming angles in the field trials. Participants who were exposed to fields that pushed the limb toward ipsilateral space reduced kinematic errors more slowly, built up less predictive field compensation, and relied more on strategic reaiming than those exposed to contralateral fields. However, there were no significant differences in predictive field compensation or kinematic errors between limbs, suggesting that participants using either the left or the right arm could adapt equally well to novel dynamics. It therefore appears that the distinct preferences in control mechanisms typically observed for the dominant and nondominant arms reflect a default mode that is based on habitual functional requirements rather than an absolute limit in capacity to access the controller specialized for the opposite limb. Copyright © 2016 the American Physiological Society.

Feedforward compensation for novel dynamics depends on force field orientation but is similar for the left and right arms

PubMed Central

Cunnington, Ross; Mattingley, Jason B.; Riek, Stephan; Carroll, Timothy J.

2016-01-01

There are well-documented differences in the way that people typically perform identical motor tasks with their dominant and the nondominant arms. According to Yadav and Sainburg's (Neuroscience 196: 153–167, 2011) hybrid-control model, this is because the two arms rely to different degrees on impedance control versus predictive control processes. Here, we assessed whether differences in limb control mechanisms influence the rate of feedforward compensation to a novel dynamic environment. Seventy-five healthy, right-handed participants, divided into four subsamples depending on the arm (left, right) and direction of the force field (ipsilateral, contralateral), reached to central targets in velocity-dependent curl force fields. We assessed the rate at which participants developed predictive compensation for the force field using intermittent error-clamp trials and assessed both kinematic errors and initial aiming angles in the field trials. Participants who were exposed to fields that pushed the limb toward ipsilateral space reduced kinematic errors more slowly, built up less predictive field compensation, and relied more on strategic reaiming than those exposed to contralateral fields. However, there were no significant differences in predictive field compensation or kinematic errors between limbs, suggesting that participants using either the left or the right arm could adapt equally well to novel dynamics. It therefore appears that the distinct preferences in control mechanisms typically observed for the dominant and nondominant arms reflect a default mode that is based on habitual functional requirements rather than an absolute limit in capacity to access the controller specialized for the opposite limb. PMID:27582293

Dual Rate Adaptive Control for an Industrial Heat Supply Process Using Signal Compensation Approach

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

Chai, Tianyou; Jia, Yao; Wang, Hong

The industrial heat supply process (HSP) is a highly nonlinear cascaded process which uses a steam valve opening as its control input, the steam flow-rate as its inner loop output and the supply water temperature as its outer loop output. The relationship between the heat exchange rate and the model parameters, such as steam density, entropy, and fouling correction factor and heat exchange efficiency are unknown and nonlinear. Moreover, these model parameters vary in line with steam pressure, ambient temperature and the residuals caused by the quality variations of the circulation water. When the steam pressure and the ambient temperaturemore » are of high values and are subjected to frequent external random disturbances, the supply water temperature and the steam flow-rate would interact with each other and fluctuate a lot. This is also true when the process exhibits unknown characteristic variations of the process dynamics caused by the unexpected changes of the heat exchange residuals. As a result, it is difficult to control the supply water temperature and the rates of changes of steam flow-rate well inside their targeted ranges. In this paper, a novel compensation signal based dual rate adaptive controller is developed by representing the unknown variations of dynamics as unmodeled dynamics. In the proposed controller design, such a compensation signal is constructed and added onto the control signal obtained from the linear deterministic model based feedback control design. Such a compensation signal aims at eliminating the unmodeled dynamics and the rate of changes of the currently sample unmodeled dynamics. A successful industrial application is carried out, where it has been shown that both the supply water temperature and the rate of the changes of the steam flow-rate can be controlled well inside their targeted ranges when the process is subjected to unknown variations of its dynamics.« less

An accurate reactive power control study in virtual flux droop control

NASA Astrophysics Data System (ADS)

Wang, Aimeng; Zhang, Jia

2017-12-01

This paper investigates the problem of reactive power sharing based on virtual flux droop method. Firstly, flux droop control method is derived, where complicated multiple feedback loops and parameter regulation are avoided. Then, the reasons for inaccurate reactive power sharing are theoretically analyzed. Further, a novel reactive power control scheme is proposed which consists of three parts: compensation control, voltage recovery control and flux droop control. Finally, the proposed reactive power control strategy is verified in a simplified microgrid model with two parallel DGs. The simulation results show that the proposed control scheme can achieve accurate reactive power sharing and zero deviation of voltage. Meanwhile, it has some advantages of simple control and excellent dynamic and static performance.

Three-Level 48-Pulse STATCOM with Pulse Width Modulation

NASA Astrophysics Data System (ADS)

Singh, Bhim; Srinivas, Kadagala Venkata

2016-03-01

In this paper, a new control strategy of a three-level 48-pulse static synchronous compensator (STATCOM) is proposed with a constant dc link voltage and pulse width modulation at fundamental frequency switching. The proposed STATCOM is realized using eight units of three-level voltage source converters (VSCs) to form a three-level 48-pulse STATCOM. The conduction angle of each three-level VSC is modulated to control the ac converter output voltage, which controls the reactive power of the STATCOM. A fuzzy logic controller is used to control the STATCOM. The dynamic performance of the STATCOM is studied for the control of the reference reactive power, the reference terminal voltage and under the switching of inductive and capacitive loads.

Environmental stress speeds up DNA replication in Pseudomonas putida in chemostat cultivations.

PubMed

Lieder, Sarah; Jahn, Michael; Koepff, Joachim; Müller, Susann; Takors, Ralf

2016-01-01

Cellular response to different types of stress is the hallmark of the cell's strategy for survival. How organisms adjust their cell cycle dynamics to compensate for changes in environmental conditions is an important unanswered question in bacterial physiology. A cell using binary fission for reproduction passes through three stages during its cell cycle: a stage from cell birth to initiation of replication, a DNA replication phase and a period of cell division. We present a detailed analysis of durations of cell cycle phases, investigating their dynamics under environmental stress conditions. Applying continuous steady state cultivations (chemostats), the DNA content of a Pseudomonas putida KT2440 population was quantified with flow cytometry at distinct growth rates. Data-driven modeling revealed that under stress conditions, such as oxygen deprivation, solvent exposure and decreased iron availability, DNA replication was accelerated correlated to the severity of the imposed stress (up to 1.9-fold). Cells maintained constant growth rates by balancing the shortened replication phase with extended cell cycle phases before and after replication. Transcriptome data underpin the transcriptional upregulation of crucial genes of the replication machinery. Hence adaption of DNA replication speed appears to be an important strategy to withstand environmental stress. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Robust adaptive backstepping neural networks control for spacecraft rendezvous and docking with input saturation.

PubMed

Xia, Kewei; Huo, Wei

2016-05-01

This paper presents a robust adaptive neural networks control strategy for spacecraft rendezvous and docking with the coupled position and attitude dynamics under input saturation. Backstepping technique is applied to design a relative attitude controller and a relative position controller, respectively. The dynamics uncertainties are approximated by radial basis function neural networks (RBFNNs). A novel switching controller consists of an adaptive neural networks controller dominating in its active region combined with an extra robust controller to avoid invalidation of the RBFNNs destroying stability of the system outside the neural active region. An auxiliary signal is introduced to compensate the input saturation with anti-windup technique, and a command filter is employed to approximate derivative of the virtual control in the backstepping procedure. Globally uniformly ultimately bounded of the relative states is proved via Lyapunov theory. Simulation example demonstrates effectiveness of the proposed control scheme. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Exploiting temporal collateral sensitivity in tumor clonal evolution

PubMed Central

Zhao, Boyang; Sedlak, Joseph C.; Srinivas, Raja; Creixell, Pau; Pritchard, Justin R.; Tidor, Bruce; Lauffenburger, Douglas A.; Hemann, Michael T.

2016-01-01

SUMMARY The prevailing approach to addressing secondary drug resistance in cancer focuses on treating the resistance mechanisms at relapse. However, the dynamic nature of clonal evolution, along with potential fitness costs and cost compensations, may present exploitable vulnerabilities; a notion that we term ‘temporal collateral sensitivity’. Using a combined pharmacological screen and drug resistance selection approach in a murine model of Ph+ acute lymphoblastic leukemia, we indeed find that temporal and/or persistent collateral sensitivity to non-classical BCR-ABL1 drugs arises in emergent tumor subpopulations during the evolution of resistance toward initial treatment with BCR-ABL1 targeted inhibitors. We determined the sensitization mechanism via genotypic, phenotypic, signaling, and binding measurements in combination with computational models, and demonstrated significant overall survival extension in mice. Additional stochastic mathematical models and small molecule screens extended our insights, indicating the value of focusing on evolutionary trajectories and pharmacological profiles to identify new strategies to treat dynamic tumor vulnerabilities. PMID:26924578

Decentralized Fuzzy MPC on Spatial Power Control of a Large PHWR

NASA Astrophysics Data System (ADS)

Liu, Xiangjie; Jiang, Di; Lee, Kwang Y.

2016-08-01

Reliable power control for stabilizing the spatial oscillations is quite important for ensuring the safe operation of a modern pressurized heavy water reactor (PHWR), since these spatial oscillations can cause “flux tilting” in the reactor core. In this paper, a decentralized fuzzy model predictive control (DFMPC) is proposed for spatial control of PHWR. Due to the load dependent dynamics of the nuclear power plant, fuzzy modeling is used to approximate the nonlinear process. A fuzzy Lyapunov function and “quasi-min-max” strategy is utilized in designing the DFMPC, to reduce the conservatism. The plant-wide stability is achieved by the asymptotically positive realness constraint (APRC) for this decentralized MPC. The solving optimization problem is based on a receding horizon scheme involving the linear matrix inequalities (LMIs) technique. Through dynamic simulations, it is demonstrated that the designed DFMPC can effectively suppress spatial oscillations developed in PHWR, and further, shows the advantages over the typical parallel distributed compensation (PDC) control scheme.

Exploiting Temporal Collateral Sensitivity in Tumor Clonal Evolution.

PubMed

Zhao, Boyang; Sedlak, Joseph C; Srinivas, Raja; Creixell, Pau; Pritchard, Justin R; Tidor, Bruce; Lauffenburger, Douglas A; Hemann, Michael T

2016-03-24

The prevailing approach to addressing secondary drug resistance in cancer focuses on treating the resistance mechanisms at relapse. However, the dynamic nature of clonal evolution, along with potential fitness costs and cost compensations, may present exploitable vulnerabilities-a notion that we term "temporal collateral sensitivity." Using a combined pharmacological screen and drug resistance selection approach in a murine model of Ph(+) acute lymphoblastic leukemia, we indeed find that temporal and/or persistent collateral sensitivity to non-classical BCR-ABL1 drugs arises in emergent tumor subpopulations during the evolution of resistance toward initial treatment with BCR-ABL1-targeted inhibitors. We determined the sensitization mechanism via genotypic, phenotypic, signaling, and binding measurements in combination with computational models and demonstrated significant overall survival extension in mice. Additional stochastic mathematical models and small-molecule screens extended our insights, indicating the value of focusing on evolutionary trajectories and pharmacological profiles to identify new strategies to treat dynamic tumor vulnerabilities. Copyright © 2016 Elsevier Inc. All rights reserved.

Experimental Rectification of Entropy Production by Maxwell's Demon in a Quantum System

NASA Astrophysics Data System (ADS)

Camati, Patrice A.; Peterson, John P. S.; Batalhão, Tiago B.; Micadei, Kaonan; Souza, Alexandre M.; Sarthour, Roberto S.; Oliveira, Ivan S.; Serra, Roberto M.

2016-12-01

Maxwell's demon explores the role of information in physical processes. Employing information about microscopic degrees of freedom, this "intelligent observer" is capable of compensating entropy production (or extracting work), apparently challenging the second law of thermodynamics. In a modern standpoint, it is regarded as a feedback control mechanism and the limits of thermodynamics are recast incorporating information-to-energy conversion. We derive a trade-off relation between information-theoretic quantities empowering the design of an efficient Maxwell's demon in a quantum system. The demon is experimentally implemented as a spin-1 /2 quantum memory that acquires information, and employs it to control the dynamics of another spin-1 /2 system, through a natural interaction. Noise and imperfections in this protocol are investigated by the assessment of its effectiveness. This realization provides experimental evidence that the irreversibility in a nonequilibrium dynamics can be mitigated by assessing microscopic information and applying a feed-forward strategy at the quantum scale.

Experimental Rectification of Entropy Production by Maxwell's Demon in a Quantum System.

PubMed

Camati, Patrice A; Peterson, John P S; Batalhão, Tiago B; Micadei, Kaonan; Souza, Alexandre M; Sarthour, Roberto S; Oliveira, Ivan S; Serra, Roberto M

2016-12-09

Maxwell's demon explores the role of information in physical processes. Employing information about microscopic degrees of freedom, this "intelligent observer" is capable of compensating entropy production (or extracting work), apparently challenging the second law of thermodynamics. In a modern standpoint, it is regarded as a feedback control mechanism and the limits of thermodynamics are recast incorporating information-to-energy conversion. We derive a trade-off relation between information-theoretic quantities empowering the design of an efficient Maxwell's demon in a quantum system. The demon is experimentally implemented as a spin-1/2 quantum memory that acquires information, and employs it to control the dynamics of another spin-1/2 system, through a natural interaction. Noise and imperfections in this protocol are investigated by the assessment of its effectiveness. This realization provides experimental evidence that the irreversibility in a nonequilibrium dynamics can be mitigated by assessing microscopic information and applying a feed-forward strategy at the quantum scale.

Otolith and Vertical Canal Contributions to Dynamic Postural Control

NASA Technical Reports Server (NTRS)

Black, F. Owen

1999-01-01

The objective of this project is to determine: 1) how do normal subjects adjust postural movements in response to changing or altered otolith input, for example, due to aging? and 2) how do patients adapt postural control after altered unilateral or bilateral vestibular sensory inputs such as ablative inner ear surgery or ototoxicity, respectively? The following hypotheses are under investigation: 1) selective alteration of otolith input or abnormalities of otolith receptor function will result in distinctive spatial, frequency, and temporal patterns of head movements and body postural sway dynamics. 2) subjects with reduced, altered, or absent vertical semicircular canal receptor sensitivity but normal otolith receptor function or vice versa, should show predictable alterations of body and head movement strategies essential for the control of postural sway and movement. The effect of altered postural movement control upon compensation and/or adaptation will be determined. These experiments provide data for the development of computational models of postural control in normals, vestibular deficient subjects and normal humans exposed to unusual force environments, including orbital space flight.

Per-pack price reductions available from different cigarette purchasing strategies: United States, 2009-2010.

PubMed

Pesko, Michael F; Xu, Xin; Tynan, Michael A; Gerzoff, Robert B; Malarcher, Ann M; Pechacek, Terry F

2014-06-01

Following cigarette excise tax increases, smokers may use cigarette price minimization strategies to continue their usual cigarette consumption rather than reducing consumption or quitting. This reduces the public health benefits of the tax increase. This paper estimates the price reductions for a wide-range of strategies, compensating for overlapping strategies. We performed regression analysis on the 2009-2010 National Adult Tobacco Survey (N=13,394) to explore price reductions that smokers in the United States obtained from purchasing cigarettes. We examined five cigarette price minimization strategies: 1) purchasing discount brand cigarettes, 2) using price promotions, 3) purchasing cartons, 4) purchasing on Indian reservations, and 5) purchasing online. Price reductions from these strategies were estimated jointly to compensate for overlapping strategies. Each strategy provided price reductions between 26 and 99cents per pack. Combined price reductions were possible. Additionally, price promotions were used with regular brands to obtain larger price reductions than when price promotions were used with generic brands. Smokers can realize large price reductions from price minimization strategies, and there are many strategies available. Policymakers and public health officials should be aware of the extent that these strategies can reduce cigarette prices. Published by Elsevier Inc.

System level modeling and component level control of fuel cells

NASA Astrophysics Data System (ADS)

Xue, Xingjian

This dissertation investigates the fuel cell systems and the related technologies in three aspects: (1) system-level dynamic modeling of both PEM fuel cell (PEMFC) and solid oxide fuel cell (SOFC); (2) condition monitoring scheme development of PEM fuel cell system using model-based statistical method; and (3) strategy and algorithm development of precision control with potential application in energy systems. The dissertation first presents a system level dynamic modeling strategy for PEM fuel cells. It is well known that water plays a critical role in PEM fuel cell operations. It makes the membrane function appropriately and improves the durability. The low temperature operating conditions, however, impose modeling difficulties in characterizing the liquid-vapor two phase change phenomenon, which becomes even more complex under dynamic operating conditions. This dissertation proposes an innovative method to characterize this phenomenon, and builds a comprehensive model for PEM fuel cell at the system level. The model features the complete characterization of multi-physics dynamic coupling effects with the inclusion of dynamic phase change. The model is validated using Ballard stack experimental result from open literature. The system behavior and the internal coupling effects are also investigated using this model under various operating conditions. Anode-supported tubular SOFC is also investigated in the dissertation. While the Nernst potential plays a central role in characterizing the electrochemical performance, the traditional Nernst equation may lead to incorrect analysis results under dynamic operating conditions due to the current reverse flow phenomenon. This dissertation presents a systematic study in this regard to incorporate a modified Nernst potential expression and the heat/mass transfer into the analysis. The model is used to investigate the limitations and optimal results of various operating conditions; it can also be utilized to perform the optimal design of tubular SOFC. With the system-level dynamic model as a basis, a framework for the robust, online monitoring of PEM fuel cell is developed in the dissertation. The monitoring scheme employs the Hotelling T2 based statistical scheme to handle the measurement noise and system uncertainties and identifies the fault conditions through a series of self-checking and conformal testing. A statistical sampling strategy is also utilized to improve the computation efficiency. Fuel/gas flow control is the fundamental operation for fuel cell energy systems. In the final part of the dissertation, a high-precision and robust tracking control scheme using piezoelectric actuator circuit with direct hysteresis compensation is developed. The key characteristic of the developed control algorithm includes the nonlinear continuous control action with the adaptive boundary layer strategy.

The plasticity of extracellular fluid homeostasis in insects.

PubMed

Beyenbach, Klaus W

2016-09-01

In chemistry, the ratio of all dissolved solutes to the solution's volume yields the osmotic concentration. The present Review uses this chemical perspective to examine how insects deal with challenges to extracellular fluid (ECF) volume, solute content and osmotic concentration (pressure). Solute/volume plots of the ECF (hemolymph) reveal that insects tolerate large changes in all three of these ECF variables. Challenges beyond those tolerances may be 'corrected' or 'compensated'. While a correction simply reverses the challenge, compensation accommodates the challenge with changes in the other two variables. Most insects osmoregulate by keeping ECF volume and osmotic concentration within a wide range of tolerance. Other insects osmoconform, allowing the ECF osmotic concentration to match the ambient osmotic concentration. Aphids are unique in handling solute and volume loads largely outside the ECF, in the lumen of the gut. This strategy may be related to the apparent absence of Malpighian tubules in aphids. Other insects can suspend ECF homeostasis altogether in order to survive extreme temperatures. Thus, ECF homeostasis in insects is highly dynamic and plastic, which may partly explain why insects remain the most successful class of animals in terms of both species number and biomass. © 2016. Published by The Company of Biologists Ltd.

The Geoid: Effect of compensated topography and uncompensated oceanic trenches

USGS Publications Warehouse

Chase, C.G.; McNutt, Marcia K.

1982-01-01

The geoid is becoming increasingly important in interpretation of global tectonics. Most of the topography of the earth is isostatically compensated, so removal of its effect from the geoid is appropriate before tectonic modeling. The oceanic trenches, however, are dynamically depressed features and cannot be isostatically compensated in the classical way. Continental topography compensated at 35 km gives intracontinental geoidal undulations of up to 15 m over mountain ranges in a spherical harmonic expansion to order and degree 22. Oceanic topography compensated at 40 km, reasonable for the thermally supported long wavelengths, matches the +10 m difference between old continents and old oceans in a detailed NASA/GSFC geoid. Removing the assumed compensation for the oceanic trenches leaves negative anomalies of up to 9 m amplitude caused by their uncompensated mass deficit. This mass deficit acts as a partial "regional compensation" for the excess mass of the subducting slabs, and partly explains why geoidal (and gravity) anomalies over the cold slabs are less than thermal models predict.

Determinants of R and D Compensation Strategies in the High Tech Industry.

ERIC Educational Resources Information Center

Balkin, David B.; Gomez-Mejia, Luis R.

1984-01-01

Interviewed managers in high technology and traditional firms (N=105) to explore the determinants of research and development compensation practices and policies in high technology firms. Results indicated that sales volume, stage in the product life cycle, profitabilty, and turnover are predictors of the method and magnitude of financial rewards.…

A Failed Marriage between Standardization and Incentivism: Divergent Perspectives on Performance-Based Compensation in Shanghai

ERIC Educational Resources Information Center

La Londe, Priya G.

2017-01-01

The Chinese province of Shanghai has gained international recognition as a high performing education system with strong teaching and learning outcomes. One accountability mechanism in Shanghai's education reform strategy is statewide performance-based compensation (PBC), also known as performance- or merit pay. Providing a first time account of…

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.

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.

Dosage Compensation of the Sex Chromosomes

PubMed Central

Disteche, Christine M.

2013-01-01

Differentiated sex chromosomes evolved because of suppressed recombination once sex became genetically controlled. In XX/XY and ZZ/ZW systems, the heterogametic sex became partially aneuploid after degeneration of the Y or W. Often, aneuploidy causes abnormal levels of gene expression throughout the entire genome. Dosage compensation mechanisms evolved to restore balanced expression of the genome. These mechanisms include upregulation of the heterogametic chromosome as well as repression in the homogametic sex. Remarkably, strategies for dosage compensation differ between species. In organisms where more is known about molecular mechanisms of dosage compensation, specific protein complexes containing noncoding RNAs are targeted to the X chromosome. In addition, the dosage-regulated chromosome often occupies a specific nuclear compartment. Some genes escape dosage compensation, potentially resulting in sex-specific differences in gene expression. This review focuses on dosage compensation in mammals, with comparisons to fruit flies, nematodes, and birds. PMID:22974302

Cigarette Price Minimization Strategies in the United States: Price Reductions and Responsiveness to Excise Taxes

PubMed Central

2013-01-01

Introduction: Because cigarette price minimization strategies can provide substantial price reductions for individuals continuing their usual smoking behaviors following federal and state cigarette excise tax increases, we examined independent price reductions compensating for overlapping strategies. The possible availability of larger independent price reduction opportunities in states with higher cigarette excise taxes is explored. Methods: Regression analysis used the 2006–2007 Tobacco Use Supplement of the Current Population Survey (N = 26,826) to explore national and state-level independent price reductions that smokers obtained from purchasing cigarettes (a) by the carton, (b) in a state with a lower average after-tax cigarette price than in the state of residence, and (c) in “some other way,” including online or in another country. Price reductions from these strategies are estimated jointly to compensate for known overlapping strategies. Results: Each strategy reduced the price of cigarettes by 64–94 cents per pack. These price reductions are 9%–22% lower than conventionally estimated results not compensating for overlapping strategies. Price reductions vary substantially by state. Following cigarette excise tax increases, the price reduction available from purchasing cigarettes by cartons increased. Additionally, the price reduction from purchasing cigarettes in a state with a lower average after-tax cigarette price is positively associated with state cigarette excise tax rates and border state cigarette excise tax rate differentials. Conclusions: Findings from this large, nationally representative study of cigarette smokers suggest that price reductions are larger in states with higher cigarette excise taxes, and increase as cigarette excise taxes rise. PMID:23729501

LaAlO3:Mn4+ as Near-Infrared Emitting Persistent Luminescence Phosphor for Medical Imaging: A Charge Compensation Study

PubMed Central

De Clercq, Olivier Q.; Korthout, Katleen

2017-01-01

Mn4+-activated phosphors are emerging as a novel class of deep red/near-infrared emitting persistent luminescence materials for medical imaging as a promising alternative to Cr3+-doped nanomaterials. Currently, it remains a challenge to improve the afterglow and photoluminescence properties of these phosphors through a traditional high-temperature solid-state reaction method in air. Herein we propose a charge compensation strategy for enhancing the photoluminescence and afterglow performance of Mn4+-activated LaAlO3 phosphors. LaAlO3:Mn4+ (LAO:Mn4+) was synthesized by high-temperature solid-state reaction in air. The charge compensation strategies for LaAlO3:Mn4+ phosphors were systematically discussed. Interestingly, Cl−/Na+/Ca2+/Sr2+/Ba2+/Ge4+ co-dopants were all found to be beneficial for enhancing LaAlO3:Mn4+ luminescence and afterglow intensity. This strategy shows great promise and opens up new avenues for the exploration of more promising near-infrared emitting long persistent phosphors for medical imaging. PMID:29231901

Adaptive robust motion trajectory tracking control of pneumatic cylinders with LuGre model-based friction compensation

NASA Astrophysics Data System (ADS)

Meng, Deyuan; Tao, Guoliang; Liu, Hao; Zhu, Xiaocong

2014-07-01

Friction compensation is particularly important for motion trajectory tracking control of pneumatic cylinders at low speed movement. However, most of the existing model-based friction compensation schemes use simple classical models, which are not enough to address applications with high-accuracy position requirements. Furthermore, the friction force in the cylinder is time-varying, and there exist rather severe unmodelled dynamics and unknown disturbances in the pneumatic system. To deal with these problems effectively, an adaptive robust controller with LuGre model-based dynamic friction compensation is constructed. The proposed controller employs on-line recursive least squares estimation (RLSE) to reduce the extent of parametric uncertainties, and utilizes the sliding mode control method to attenuate the effects of parameter estimation errors, unmodelled dynamics and disturbances. In addition, in order to realize LuGre model-based friction compensation, the modified dual-observer structure for estimating immeasurable friction internal state is developed. Therefore, a prescribed motion tracking transient performance and final tracking accuracy can be guaranteed. Since the system model uncertainties are unmatched, the recursive backstepping design technology is applied. In order to solve the conflicts between the sliding mode control design and the adaptive control design, the projection mapping is used to condition the RLSE algorithm so that the parameter estimates are kept within a known bounded convex set. Finally, the proposed controller is tested for tracking sinusoidal trajectories and smooth square trajectory under different loads and sudden disturbance. The testing results demonstrate that the achievable performance of the proposed controller is excellent and is much better than most other studies in literature. Especially when a 0.5 Hz sinusoidal trajectory is tracked, the maximum tracking error is 0.96 mm and the average tracking error is 0.45 mm. This paper constructs an adaptive robust controller which can compensate the friction force in the cylinder.

Society of Pediatric Psychology Workforce Survey: Factors Related to Compensation of Pediatric Psychologists.

PubMed

Brosig, Cheryl L; Hilliard, Marisa E; Williams, Andre; Armstrong, F Daniel; Christidis, Peggy; Kichler, Jessica; Pendley, Jennifer Shroff; Stamm, Karen E; Wysocki, Tim

2017-05-01

To summarize compensation results from the 2015 Society of Pediatric Psychology (SPP) Workforce Survey and identify factors related to compensation of pediatric psychologists. 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.   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. 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. © The Author 2017. Published by Oxford University Press on behalf of the Society of Pediatric Psychology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com

The force synergy of human digits in static and dynamic cylindrical grasps.

PubMed

Kuo, Li-Chieh; Chen, Shih-Wei; Lin, Chien-Ju; Lin, Wei-Jr; Lin, Sheng-Che; Su, Fong-Chin

2013-01-01

This study explores the force synergy of human digits in both static and dynamic cylindrical grasping conditions. The patterns of digit force distribution, error compensation, and the relationships among digit forces are examined to quantify the synergetic patterns and coordination of multi-finger movements. This study recruited 24 healthy participants to perform cylindrical grasps using a glass simulator under normal grasping and one-finger restricted conditions. Parameters such as the grasping force, patterns of digit force distribution, and the force coefficient of variation are determined. Correlation coefficients and principal component analysis (PCA) are used to estimate the synergy strength under the dynamic grasping condition. Specific distribution patterns of digit forces are identified for various conditions. The compensation of adjacent fingers for the force in the normal direction of an absent finger agrees with the principle of error compensation. For digit forces in anti-gravity directions, the distribution patterns vary significantly by participant. The forces exerted by the thumb are closely related to those exerted by other fingers under all conditions. The index-middle and middle-ring finger pairs demonstrate a significant relationship. The PCA results show that the normal forces of digits are highly coordinated. This study reveals that normal force synergy exists under both static and dynamic cylindrical grasping conditions.

The Force Synergy of Human Digits in Static and Dynamic Cylindrical Grasps

PubMed Central

Kuo, Li-Chieh; Chen, Shih-Wei; Lin, Chien-Ju; Lin, Wei-Jr; Lin, Sheng-Che; Su, Fong-Chin

2013-01-01

This study explores the force synergy of human digits in both static and dynamic cylindrical grasping conditions. The patterns of digit force distribution, error compensation, and the relationships among digit forces are examined to quantify the synergetic patterns and coordination of multi-finger movements. This study recruited 24 healthy participants to perform cylindrical grasps using a glass simulator under normal grasping and one-finger restricted conditions. Parameters such as the grasping force, patterns of digit force distribution, and the force coefficient of variation are determined. Correlation coefficients and principal component analysis (PCA) are used to estimate the synergy strength under the dynamic grasping condition. Specific distribution patterns of digit forces are identified for various conditions. The compensation of adjacent fingers for the force in the normal direction of an absent finger agrees with the principle of error compensation. For digit forces in anti-gravity directions, the distribution patterns vary significantly by participant. The forces exerted by the thumb are closely related to those exerted by other fingers under all conditions. The index-middle and middle-ring finger pairs demonstrate a significant relationship. The PCA results show that the normal forces of digits are highly coordinated. This study reveals that normal force synergy exists under both static and dynamic cylindrical grasping conditions. PMID:23544151

Robust dynamic 3-D measurements with motion-compensated phase-shifting profilometry

NASA Astrophysics Data System (ADS)

Feng, Shijie; Zuo, Chao; Tao, Tianyang; Hu, Yan; Zhang, Minliang; Chen, Qian; Gu, Guohua

2018-04-01

Phase-shifting profilometry (PSP) is a widely used approach to high-accuracy three-dimensional shape measurements. However, when it comes to moving objects, phase errors induced by the movement often result in severe artifacts even though a high-speed camera is in use. From our observations, there are three kinds of motion artifacts: motion ripples, motion-induced phase unwrapping errors, and motion outliers. We present a novel motion-compensated PSP to remove the artifacts for dynamic measurements of rigid objects. The phase error of motion ripples is analyzed for the N-step phase-shifting algorithm and is compensated using the statistical nature of the fringes. The phase unwrapping errors are corrected exploiting adjacent reliable pixels, and the outliers are removed by comparing the original phase map with a smoothed phase map. Compared with the three-step PSP, our method can improve the accuracy by more than 95% for objects in motion.

[NEUROSEMANTIC AND PSYCHOPHYSIOLOGICAL CORRELATES OF RHYTHM-SUGGESTIVE CORRECTION OF STRESS CONDITIONS].

PubMed

Ushakov, I B; Ivanov, A V; Kvasovets, S V; Bubeev, Yu A

2015-01-01

Correlates of successful rhythm-suggestive compensation of stress in sportsmen with neurotic symptoms developed in consequence of painful experience of failure were studied. Effectiveness of the rhythm-suggestive and rational psychological methods was compared by measuring the evoked potentials response to emotionally significant extramental verbal stimuli and images, and using psychophysiological test MASTER to track dynamics of a number of body functional parameters. The rational compensation has been shown to reduce the psychic tension and to set right the voluntary control process. Rhythm-suggestive programs are good for compensation of post-stress emotions and affectations, and the involuntary control process. It was found that correction potentialities of the rhythm-suggestive programs together with the psychodiagnostic advantages of test MASTER are promising instruments for dynamic monitoring of the mental state with the aim to prevent workplace stresses and to provide rehabilitation treatment of aftermaths.

Effects of stinger axial dynamics and mass compensation methods on experimental modal analysis

NASA Astrophysics Data System (ADS)

Hu, Ximing

1992-06-01

A longitudinal bar model that includes both stinger elastic and inertia properties is used to analyze the stinger's axial dynamics as well as the mass compensation that is required to obtain accurate input forces when a stinger is installed between the excitation source, force transducer, and the structure under test. Stinger motion transmissibility and force transmissibility, axial resonance and excitation energy transfer problems are discussed in detail. Stinger mass compensation problems occur when the force transducer is mounted on the exciter end of the stinger. These problems are studied theoretically, numerically, and experimentally. It is found that the measured Frequency Response Function (FRF) can be underestimated if mass compensation is based on the stinger exciter-end acceleration and can be overestimated if the mass compensation is based on the structure-end acceleration due to the stinger's compliance. A new mass compensation method that is based on two accelerations is introduced and is seen to improve the accuracy considerably. The effects of the force transducer's compliance on the mass compensation are also discussed. A theoretical model is developed that describes the measurement system's FRD around a test structure's resonance. The model shows that very large measurement errors occur when there is a small relative phase shift between the force and acceleration measurements. These errors can be in hundreds of percent corresponding to a phase error on the order of one or two degrees. The physical reasons for this unexpected error pattern are explained. This error is currently unknown to the experimental modal analysis community. Two sample structures consisting of a rigid mass and a double cantilever beam are used in the numerical calculations and experiments.

Aeromagnetic Compensation for UAVs

NASA Astrophysics Data System (ADS)

Naprstek, T.; Lee, M. D.

2017-12-01

Aeromagnetic data is one of the most widely collected types of data in exploration geophysics. With the continuing prevalence of unmanned air vehicles (UAVs) in everyday life there is a strong push for aeromagnetic data collection using UAVs. However, apart from the many political and legal barriers to overcome in the development of UAVs as aeromagnetic data collection platforms, there are also significant scientific hurdles, primary of which is magnetic compensation. This is a well-established process in manned aircraft achieved through a combination of platform magnetic de-noising and compensation routines. However, not all of this protocol can be directly applied to UAVs due to fundamental differences in the platforms, most notably the decrease in scale causing magnetometers to be significantly closer to the avionics. As such, the methodology must be suitably adjusted. The National Research Council of Canada has collaborated with Aeromagnetic Solutions Incorporated to develop a standardized approach to de-noising and compensating UAVs, which is accomplished through a series of static and dynamic experiments. On the ground, small static tests are conducted on individual components to determine their magnetization. If they are highly magnetic, they are removed, demagnetized, or characterized such that they can be accounted for in the compensation. Dynamic tests can include measuring specific components as they are powered on and off to assess their potential effect on airborne data. The UAV is then flown, and a modified compensation routine is applied. These modifications include utilizing onboard autopilot current sensors as additional terms in the compensation algorithm. This process has been applied with success to fixed-wing and rotary-wing platforms, with both a standard manned-aircraft magnetometer, as well as a new atomic magnetometer, much smaller in scale.

6 DOF articulated-arm robot and mobile platform: Dynamic modelling as Multibody System and its validation via Experimental Modal Analysis.

NASA Astrophysics Data System (ADS)

Toledo Fuentes, A.; Kipfmueller, M.; José Prieto, M. A.

2017-10-01

Mobile manipulators are becoming a key instrument to increase the flexibility in industrial processes. Some of their requirements include handling of objects with different weights and sizes and their “fast” transportation, without jeopardizing production workers and machines. The compensation of forces affecting the system dynamic is therefore needed to avoid unwanted oscillations and tilting by sudden accelerations and decelerations. One general solution may be the implementation of external positioning elements to active stabilize the system. To accomplish the approach, the dynamic behavior of a robotic arm and a mobile platform was investigated to develop the stabilization mechanism using multibody simulations. The methodology used was divided into two phases for each subsystem: their natural frequencies and modal shapes were obtained using experimental modal analyses. Then, based on these experimental results, multibody simulation models (MBS) were set up and its dynamical parameters adjusted. Their modal shapes together with their obtained natural frequencies allowed a quantitative and qualitative analysis. In summary, the MBS models were successfully validated with the real subsystems, with a maximal percentage error of 15%. These models will serve as the basis for future steps in the design of the external actuators and its control strategy using a co-simulation tool.

The fabrication of flip-covered plasmonic nanostructure surfaces with enhanced wear resistance

NASA Astrophysics Data System (ADS)

Jung, Joo-Yun; Sung, Sang-Keun; Kim, Kwang-Seop; Cheon, So-Hui; Lee, Jihye; Choi, Jun-Hyuk; Lee, Eungsug

2017-01-01

Exposed nanostructure surfaces often suffer from external dynamic wear, particularly when used in human interaction, resulting in surface defects and the degradation of plasmonic resonance properties particularly in terms of transmittance extinction rate and peak-to-valley slope. In this work, a method for the fabrication of flip-covered silver nanostructure-arrayed surfaces is shown to enhance wear resistance. Selectively transferred silver dot and silver webbed-trench exposed reference samples were fabricated by metal nanoimprint, and flip-covered samples were created by flipping and bonding reference samples onto a PET film coated with an adhesive layer. The samples' spectral transmittance was measured before and after a dynamic wear test. Some spectral shift was observed due to the change in refractive index of the surrounding media, but this was not as significant as the effects of the other chosen geometry factors. It was found that dynamic wear had a greater effect on the plasmonic resonance behavior of the exposed samples than in those that had been flip-covered. This suggests that flip-covering may be an effective strategy for the protection of plasmonic resonators against dynamic wear. It is expected that the slight variations in spectral transmittance could be compensated through proper tuning of the sample geometry.

Tunable dispersion compensation of quantum cascade laser frequency combs.

PubMed

Hillbrand, Johannes; Jouy, Pierre; Beck, Mattias; Faist, Jérôme

2018-04-15

Compensating for group velocity dispersion is an important challenge to achieve stable midinfrared quantum cascade laser (QCL) frequency combs with large spectral coverage. We present a tunable dispersion compensation scheme consisting of a planar mirror placed behind the back facet of the QCL. Dispersion can be either enhanced or decreased depending on the position of the mirror. We demonstrate that the fraction of the comb regime in the dynamic range of the laser increases considerably when the dispersion induced by the Gires-Tournois interferometer compensates the intrinsic dispersion of the laser. Furthermore, it is possible to tune to the offset frequency of the comb with the Gires-Tournois interferometer while the repetition frequency is almost unaffected.

Extremum Seeking Control of Smart Inverters for VAR Compensation

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

Arnold, Daniel; Negrete-Pincetic, Matias; Stewart, Emma

2015-09-04

Reactive power compensation is used by utilities to ensure customer voltages are within pre-defined tolerances and reduce system resistive losses. While much attention has been paid to model-based control algorithms for reactive power support and Volt Var Optimization (VVO), these strategies typically require relatively large communications capabilities and accurate models. In this work, a non-model-based control strategy for smart inverters is considered for VAR compensation. An Extremum Seeking control algorithm is applied to modulate the reactive power output of inverters based on real power information from the feeder substation, without an explicit feeder model. Simulation results using utility demand informationmore » confirm the ability of the control algorithm to inject VARs to minimize feeder head real power consumption. In addition, we show that the algorithm is capable of improving feeder voltage profiles and reducing reactive power supplied by the distribution substation.« less

Compensation for oil pollution damage

NASA Astrophysics Data System (ADS)

Matugina, E. G.; Glyzina, T. S.; Kolbysheva, Yu V.; Klyuchnikov, A. S.; Vusovich, O. V.

2015-11-01

The commitment of national industries to traditional energy sources, as well as constantly growing energy demand combined with adverse environmental impact of petroleum production and transportation urge to establish and maintain an appropriate legal and administrative framework for oil pollution damage compensation. The article considers management strategies for petroleum companies that embrace not only production benefits but also environmental issues.

Flexible Modes Control Using Sliding Mode Observers: Application to Ares I

NASA Technical Reports Server (NTRS)

Shtessel, Yuri B.; Hall, Charles E.; Baev, Simon; Orr, Jeb S.

2010-01-01

The launch vehicle dynamics affected by bending and sloshing modes are considered. Attitude measurement data that are corrupted by flexible modes could yield instability of the vehicle dynamics. Flexible body and sloshing modes are reconstructed by sliding mode observers. The resultant estimates are used to remove the undesirable dynamics from the measurements, and the direct effects of sloshing and bending modes on the launch vehicle are compensated by means of a controller that is designed without taking the bending and sloshing modes into account. A linearized mathematical model of Ares I launch vehicle was derived based on FRACTAL, a linear model developed by NASA/MSFC. The compensated vehicle dynamics with a simple PID controller were studied for the launch vehicle model that included two bending modes, two slosh modes and actuator dynamics. A simulation study demonstrated stable and accurate performance of the flight control system with the augmented simple PID controller without the use of traditional linear bending filters.

District nurses' experiences of caring for leg ulcers in accordance with clinical guidelines: a grounded theory study.

PubMed

Lagerin, Annica; Hylander, Ingrid; Törnkvist, Lena

2017-12-01

This qualitative study used the grounded theory method to investigate district nurses' experiences of caring for leg ulcers in accordance with clinical guidelines at seven primary health care centres in Stockholm, Sweden. Group interviews were conducted with 30 nurses. The results describe how district nurses strive to stay on track in order to follow clinical guidelines and remain motivated despite prolonged wound treatment and feelings of hopelessness. Three main obstacles to following the guidelines were found. District nurses used compensating strategies so the obstacles would not lead to negative consequences. If the compensating strategies were insufficient, perceived prolonged wound treatment and feelings of hopelessness could result. District nurses then used motivating strategies to overcome these feelings of hopelessness. Sometimes, despite the motivating strategies, treatment in accordance with guidelines could not be achieved. With some patients, district nurses had to compromise and follow the guidelines as far as possible.

Knowledge-based load leveling and task allocation in human-machine systems

NASA Technical Reports Server (NTRS)

Chignell, M. H.; Hancock, P. A.

1986-01-01

Conventional human-machine systems use task allocation policies which are based on the premise of a flexible human operator. This individual is most often required to compensate for and augment the capabilities of the machine. The development of artificial intelligence and improved technologies have allowed for a wider range of task allocation strategies. In response to these issues a Knowledge Based Adaptive Mechanism (KBAM) is proposed for assigning tasks to human and machine in real time, using a load leveling policy. This mechanism employs an online workload assessment and compensation system which is responsive to variations in load through an intelligent interface. This interface consists of a loading strategy reasoner which has access to information about the current status of the human-machine system as well as a database of admissible human/machine loading strategies. Difficulties standing in the way of successful implementation of the load leveling strategy are examined.

Bend compensated large-mode-area fibers: achieving robust single-modedness with transformation optics.

PubMed

Fini, John M; Nicholson, Jeffrey W

2013-08-12

Fibers with symmetric bend compensated claddings are proposed, and demonstrate performance much better than conventional designs. These fibers can simultaneously achieve complete HOM suppression, negligible bend loss, and mode area >1000 square microns. The robust single-modedness of these fibers offers a path to overcoming mode instability limits on high-power amplifiers and lasers. The proposed designs achieve many of the advantages of our previous (asymmetric) bend compensation strategy in the regime of moderately large area, and are much easier to fabricate and utilize.

Local dynamic stability of lower extremity joints in lower limb amputees during slope walking.

PubMed

Chen, Jin-Ling; Gu, Dong-Yun

2013-01-01

Lower limb amputees have a higher fall risk during slope walking compared with non-amputees. However, studies on amputees' slope walking were not well addressed. The aim of this study was to identify the difference of slope walking between amputees and non-amputees. Lyapunov exponents λS was used to estimate the local dynamic stability of 7 transtibial amputees' and 7 controls' lower extremity joint kinematics during uphill and downhill walking. Compared with the controls, amputees exhibited significantly lower λS in hip (P=0.04) and ankle (P=0.01) joints of the sound limb, and hip joints (P=0.01) of the prosthetic limb during uphill walking, while they exhibited significantly lower λS in knee (P=0.02) and ankle (P=0.03) joints of the sound limb, and hip joints (P=0.03) of the prosthetic limb during downhill walking. Compared with amputees level walking, they exhibited significantly lower λS in ankle joints of the sound limb during both uphill (P=0.01) and downhill walking (P=0.01). We hypothesized that the better local dynamic stability of amputees was caused by compensation strategy during slope walking.

Dynamic gas temperature measurement system, volume 1

NASA Technical Reports Server (NTRS)

Elmore, D. L.; Robinson, W. W.; Watkins, W. B.

1983-01-01

A gas temperature measurement system with compensated frequency response of 1 kHz and capability to operate in the exhaust of a gas turbine engine combustor was developed. A review of available technologies which could attain this objective was done. The most promising method was identified as a two wire thermocouple, with a compensation method based on the responses of the two different diameter thermocouples to the fluctuating gas temperature field. In a detailed design of the probe, transient conduction effects were identified as significant. A compensation scheme was derived to include the effects of gas convection and wire conduction. The two wire thermocouple concept was tested in a laboratory burner exhaust to temperatures of about 3000 F and in a gas turbine engine to combustor exhaust temperatures of about 2400 F. Uncompensated and compensated waveforms and compensation spectra are presented.

Self-enforcing strategies to deter free-riding in the climate change mitigation game and other repeated public good games

PubMed Central

Heitzig, Jobst; Lessmann, Kai; Zou, Yong

2011-01-01

As the Copenhagen Accord indicates, most of the international community agrees that global mean temperature should not be allowed to rise more than two degrees Celsius above preindustrial levels to avoid unacceptable damages from climate change. The scientific evidence distilled in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change and recent reports by the US National Academies shows that this can only be achieved by vast reductions of greenhouse gas emissions. Still, international cooperation on greenhouse gas emissions reductions suffers from incentives to free-ride and to renegotiate agreements in case of noncompliance, and the same is true for other so-called “public good games.” Using game theory, we show how one might overcome these problems with a simple dynamic strategy of linear compensation when the parameters of the problem fulfill some general conditions and players can be considered to be sufficiently rational. The proposed strategy redistributes liabilities according to past compliance levels in a proportionate and timely way. It can be used to implement any given allocation of target contributions, and we prove that it has several strong stability properties. PMID:21903930

Skills and compensation strategies in adult ADHD – A qualitative study

PubMed Central

Buadze, Anna; Dube, Anish; Eich, Dominique; Liebrenz, Michael

2017-01-01

Objective The primary objectives of this study were to investigate how adult patients with ADHD coped with their symptoms prior to diagnosis and treatment, what skills and compensation strategies they had developed and what their self-perceptions of these strategies were. Methods We used a qualitative approach to analyze interviews with 32 outpatients of a specialty care unit at a university hospital. Results Patients reported frequent use of diverse compensatory strategies with varying degrees of effectiveness. These were classified into five categories (organizational, motoric, attentional, social, psychopharmacological). In certain circumstances, ADHD symptoms were even perceived as useful. Conclusion Before diagnosis and treatment, patients with ADHD may develop a variety of skills to cope with their symptoms. Several of these skills are perceived as helpful. Knowledge of self-generated coping strategies may help better understand patients and their histories and thus facilitate patient cooperation. Moreover, knowing ways in which such patients cope with their symptoms may help elucidate reasons for late or under-diagnosing of the disorder. PMID:28953946

Skills and compensation strategies in adult ADHD - A qualitative study.

PubMed

Canela, Carlos; Buadze, Anna; Dube, Anish; Eich, Dominique; Liebrenz, Michael

2017-01-01

The primary objectives of this study were to investigate how adult patients with ADHD coped with their symptoms prior to diagnosis and treatment, what skills and compensation strategies they had developed and what their self-perceptions of these strategies were. We used a qualitative approach to analyze interviews with 32 outpatients of a specialty care unit at a university hospital. Patients reported frequent use of diverse compensatory strategies with varying degrees of effectiveness. These were classified into five categories (organizational, motoric, attentional, social, psychopharmacological). In certain circumstances, ADHD symptoms were even perceived as useful. Before diagnosis and treatment, patients with ADHD may develop a variety of skills to cope with their symptoms. Several of these skills are perceived as helpful. Knowledge of self-generated coping strategies may help better understand patients and their histories and thus facilitate patient cooperation. Moreover, knowing ways in which such patients cope with their symptoms may help elucidate reasons for late or under-diagnosing of the disorder.

Per-pack price reductions available from different cigarette purchasing strategies: United States, 2009–2010☆

PubMed Central

Pesko, Michael F.; Xu, Xin; Tynan, Michael A.; Gerzoff, Robert B.; Malarcher, Ann M.; Pechacek, Terry F.

2015-01-01

Objective Following cigarette excise tax increases, smokers may use cigarette price minimization strategies to continue their usual cigarette consumption rather than reducing consumption or quitting. This reduces the public health benefits of the tax increase. This paper estimates the price reductions for a wide-range of strategies, compensating for overlapping strategies. Method We performed regression analysis on the 2009–2010 National Adult Tobacco Survey (N = 13,394) to explore price reductions that smokers in the United States obtained from purchasing cigarettes. We examined five cigarette price minimization strategies: 1) purchasing discount brand cigarettes, 2) using price promotions, 3) purchasing cartons, 4) purchasing on Indian reservations, and 5) purchasing online. Price reductions from these strategies were estimated jointly to compensate for overlapping strategies. Results Each strategy provided price reductions between 26 and 99 cents per pack. Combined price reductions were possible. Additionally, price promotions were used with regular brands to obtain larger price reductions than when price promotions were used with generic brands. Conclusion Smokers can realize large price reductions from price minimization strategies, and there are many strategies available. Policymakers and public health officials should be aware of the extent that these strategies can reduce cigarette prices. PMID:24594102

X-Chromosome dosage compensation.

PubMed

Meyer, Barbara J

2005-06-25

In mammals, flies, and worms, sex is determined by distinctive regulatory mechanisms that cause males (XO or XY) and females (XX) to differ in their dose of X chromosomes. In each species, an essential X chromosome-wide process called dosage compensation ensures that somatic cells of either sex express equal levels of X-linked gene products. The strategies used to achieve dosage compensation are diverse, but in all cases, specialized complexes are targeted specifically to the X chromosome(s) of only one sex to regulate transcript levels. In C. elegans, this sex-specific targeting of the dosage compensation complex (DCC) is controlled by the same developmental signal that establishes sex, the ratio of X chromosomes to sets of autosomes (X:A signal). Molecular components of this chromosome counting process have been defined. Following a common step of regulation, sex determination and dosage compensation are controlled by distinct genetic pathways. C. elegans dosage compensation is implemented by a protein complex that binds both X chromosomes of hermaphrodites to reduce transcript levels by one-half. The dosage compensation complex resembles the conserved 13S condensin complex required for both mitotic and meiotic chromosome resolution and condensation, implying the recruitment of ancient proteins to the new task of regulating gene expression. Within each C. elegans somatic cell, one of the DCC components also participates in the separate mitotic/meiotic condensin complex. Other DCC components play pivotal roles in regulating the number and distribution of crossovers during meiosis. The strategy by which C. elegans X chromosomes attract the condensin-like DCC is known. Small, well-dispersed X-recognition elements act as entry sites to recruit the dosage compensation complex and to nucleate spreading of the complex to X regions that lack recruitment sites. In this manner, a repressed chromatin state is spread in cis over short or long distances, thus establishing the global, epigenetic regulation of X chromosomes that is maintained throughout the lifetime of hermaphrodites.

Does Cognitive Strategy Training on Word Problems Compensate for Working Memory Capacity in Children with Math Difficulties?

ERIC Educational Resources Information Center

Swanson, H. Lee

2014-01-01

Cognitive strategies are important tools for children with math difficulties (MD) in learning to solve word problems. The effectiveness of strategy training, however, depends on working memory capacity (WMC). Thus, children with MD but with relatively higher WMC are more likely to benefit from strategy training, whereas children with lower WMC may…

Overload Control for Signaling Congestion of Machine Type Communications in 3GPP Networks

PubMed Central

Lu, Zhaoming; Pan, Qi; Wang, Luhan; Wen, Xiangming

2016-01-01

Because of the limited resources on radio access channels of third generation partnership projection (3GPP) network, one of the most challenging tasks posted by 3GPP cellular-based machine type communications (MTC) is congestion due to massive requests for connection to radio access network (RAN). In this paper, an overload control algorithm in 3GPP RAN is proposed, which proactively disperses the simultaneous access attempts in evenly distributed time window. Through periodic reservation strategy, massive access requests of MTC devices are dispersed in time, which reduces the probability of confliction of signaling. By the compensation and prediction mechanism, each device can communicate with MTC server with dynamic load of air interface. Numerical results prove that proposed method makes MTC applications friendly to 3GPP cellular network. PMID:27936011

Overload Control for Signaling Congestion of Machine Type Communications in 3GPP Networks.

PubMed

Lu, Zhaoming; Pan, Qi; Wang, Luhan; Wen, Xiangming

2016-01-01

Because of the limited resources on radio access channels of third generation partnership projection (3GPP) network, one of the most challenging tasks posted by 3GPP cellular-based machine type communications (MTC) is congestion due to massive requests for connection to radio access network (RAN). In this paper, an overload control algorithm in 3GPP RAN is proposed, which proactively disperses the simultaneous access attempts in evenly distributed time window. Through periodic reservation strategy, massive access requests of MTC devices are dispersed in time, which reduces the probability of confliction of signaling. By the compensation and prediction mechanism, each device can communicate with MTC server with dynamic load of air interface. Numerical results prove that proposed method makes MTC applications friendly to 3GPP cellular network.

Anonymous, Yet Trustworthy Auctions

NASA Astrophysics Data System (ADS)

Chanda, Prasit Bikash; Naessens, Vincent; de Decker, Bart

An auction is an inevitable market mechanism to setup prices of goods or services in a competitive and dynamic environment. Anonymity of bidders is required to conceal their business strategies from competitors. However, it is also essential to provide the seller guarantees that a bidder is trustworthy and competent enough to perform certain tasks (e.g transports). This paper proposes an auction protocol where bidders will participate anonymously, yet prove to be trustworthy and competent and can be held accountable towards auctioneers and sellers. Moreover, the protocol introduces promises, bonuses and compensations to ensure the best price for the sellers, extra profit for bidders and opportunities for newcomers in the business. It also handles ties, and copes with last minute bidding. Finally, the auction’s fair proceedings and outcome can be verified by everyone.

Photoelectric panel with equatorial mounting of drive

NASA Astrophysics Data System (ADS)

Kukhta, M. S.; Krauinsh, P. Y.; Krauinsh, D. P.; Sokolov, A. P.; Mainy, S. B.

2018-03-01

The relevance of the work is determined by the need to create effective models for sunny energy. The article considers a photoelectric panel equipped with a system for tracking the sun. Efficiency of the system is provided by equatorial mounting, which compensates for the rotation of the Earth by rotating the sunny panel in the plane of the celestial equator. The specificity of climatic and geographical conditions of Tomsk is estimated. The dynamics of power variations of photoelectric panels with equatorial mounting during seasonal fluctuations in Tomsk is calculated. A mobile photovoltaic panel with equatorial mounting of the drive has been developed. The methods of design strategy for placing photovoltaic panels in the architectural environment of the city are presented. Key words: sunny energy, photovoltaics, equatorial mounting, mechatronic model, wave reducer, electric drive.

Complexities in understanding the role of compensation-related factors on recovery from whiplash-associated disorders: discussion paper 2.

PubMed

Carroll, Linda J; Connelly, Luke B; Spearing, Natalie M; Côté, Pierre; Buitenhuis, Jan; Kenardy, Justin

2011-12-01

Focused discussion. To present some of the complexities in conducting research on the role of compensation and compensation-related factors in recovery from whiplash-associated disorders (WAD) and to suggest directions for future research. There is divergence of opinion, primary research findings, and systematic reviews on the role of compensation and/or compensation-related factors in WAD recovery. The topic of research of compensation/compensation-related factors was discussed at an international summit meeting of 21 researchers from diverse fields of scientific enquiry. This article summarizes the main points raised in that discussion. Traffic injury compensation is a complex sociopolitical construct, which varies widely across jurisdictions. This leads to conceptual and methodological challenges in conducting and interpreting research in this area. It is important that researchers and their audiences be clear about what aspect of the compensation system is being addressed, what compensation-related variables are being studied, and what social/economic environment the compensation system exists in. In addition, summit participants also recommended that nontraditional, sophisticated study designs and analysis strategies be employed to clarify the complex causal pathways and mechanisms of effects. Care must be taken by both researchers and their audiences not to overgeneralize or confuse different aspects of WAD compensation. In considering the role of compensation/compensation-related factors on WAD and WAD recovery, it is important to retain a broad-based conceptualization of the range of biological, psychological, social, and economic factors that combine and interact to define and determine how people recover from WAD.

In situ triaxial magnetic field compensation for the spin-exchange-relaxation-free atomic magnetometer.

PubMed

Fang, Jiancheng; Qin, Jie

2012-10-01

The spin-exchange-relaxation-free (SERF) atomic magnetometer is an ultra-high sensitivity magnetometer, but it must be operated in a magnetic field with strength less than about 10 nT. Magnetic field compensation is an effective way to shield the magnetic field, and this paper demonstrates an in situ triaxial magnetic field compensation system for operating the SERF atomic magnetometer. The proposed hardware is based on optical pumping, which uses some part of the SERF atomic magnetometer itself, and the compensation method is implemented by analyzing the dynamics of the atomic spin. The experimental setup for this compensation system is described, and with this configuration, a residual magnetic field of strength less than 2 nT (±0.38 nT in the x axis, ±0.43 nT in the y axis, and ±1.62 nT in the z axis) has been achieved after compensation. The SERF atomic magnetometer was then used to verify that the residual triaxial magnetic fields were coincident with what were achieved by the compensation system.

Star centroiding error compensation for intensified star sensors.

PubMed

Jiang, Jie; Xiong, Kun; Yu, Wenbo; Yan, Jinyun; Zhang, Guangjun

2016-12-26

A star sensor provides high-precision attitude information by capturing a stellar image; however, the traditional star sensor has poor dynamic performance, which is attributed to its low sensitivity. Regarding the intensified star sensor, the image intensifier is utilized to improve the sensitivity, thereby further improving the dynamic performance of the star sensor. However, the introduction of image intensifier results in star centroiding accuracy decrease, further influencing the attitude measurement precision of the star sensor. A star centroiding error compensation method for intensified star sensors is proposed in this paper to reduce the influences. First, the imaging model of the intensified detector, which includes the deformation parameter of the optical fiber panel, is established based on the orthographic projection through the analysis of errors introduced by the image intensifier. Thereafter, the position errors at the target points based on the model are obtained by using the Levenberg-Marquardt (LM) optimization method. Last, the nearest trigonometric interpolation method is presented to compensate for the arbitrary centroiding error of the image plane. Laboratory calibration result and night sky experiment result show that the compensation method effectively eliminates the error introduced by the image intensifier, thus remarkably improving the precision of the intensified star sensors.

Acceleration and torque feedback for robotic control - Experimental results

NASA Technical Reports Server (NTRS)

Mclnroy, John E.; Saridis, George N.

1990-01-01

Gross motion control of robotic manipulators typically requires significant on-line computations to compensate for nonlinear dynamics due to gravity, Coriolis, centripetal, and friction nonlinearities. One controller proposed by Luo and Saridis avoids these computations by feeding back joint acceleration and torque. This study implements the controller on a Puma 600 robotic manipulator. Joint acceleration measurement is obtained by measuring linear accelerations of each joint, and deriving a computationally efficient transformation from the linear measurements to the angular accelerations. Torque feedback is obtained by using the previous torque sent to the joints. The implementation has stability problems on the Puma 600 due to the extremely high gains inherent in the feedback structure. Since these high gains excite frequency modes in the Puma 600, the algorithm is modified to decrease the gain inherent in the feedback structure. The resulting compensator is stable and insensitive to high frequency unmodeled dynamics. Moreover, a second compensator is proposed which uses acceleration and torque feedback, but still allows nonlinear terms to be fed forward. Thus, by feeding the increment in the easily calculated gravity terms forward, improved responses are obtained. Both proposed compensators are implemented, and the real time results are compared to those obtained with the computed torque algorithm.

Great Apes and Biodiversity Offset Projects in Africa: The Case for National Offset Strategies

PubMed Central

Kormos, Rebecca; Kormos, Cyril F.; Humle, Tatyana; Lanjouw, Annette; Rainer, Helga; Victurine, Ray; Mittermeier, Russell A.; Diallo, Mamadou S.; Rylands, Anthony B.; Williamson, Elizabeth A.

2014-01-01

The development and private sectors are increasingly considering “biodiversity offsets” as a strategy to compensate for their negative impacts on biodiversity, including impacts on great apes and their habitats in Africa. In the absence of national offset policies in sub-Saharan Africa, offset design and implementation are guided by company internal standards, lending bank standards or international best practice principles. We examine four projects in Africa that are seeking to compensate for their negative impacts on great ape populations. Our assessment of these projects reveals that not all apply or implement best practices, and that there is little standardization in the methods used to measure losses and gains in species numbers. Even if they were to follow currently accepted best-practice principles, we find that these actions may still fail to contribute to conservation objectives over the long term. We advocate for an alternative approach in which biodiversity offset and compensation projects are designed and implemented as part of a National Offset Strategy that (1) takes into account the cumulative impacts of development in individual countries, (2) identifies priority offset sites, (3) promotes aggregated offsets, and (4) integrates biodiversity offset and compensation projects with national biodiversity conservation objectives. We also propose supplementary principles necessary for biodiversity offsets to contribute to great ape conservation in Africa. Caution should still be exercised, however, with regard to offsets until further field-based evidence of their effectiveness is available. PMID:25372894

Great apes and biodiversity offset projects in Africa: the case for national offset strategies.

PubMed

Kormos, Rebecca; Kormos, Cyril F; Humle, Tatyana; Lanjouw, Annette; Rainer, Helga; Victurine, Ray; Mittermeier, Russell A; Diallo, Mamadou S; Rylands, Anthony B; Williamson, Elizabeth A

2014-01-01

The development and private sectors are increasingly considering "biodiversity offsets" as a strategy to compensate for their negative impacts on biodiversity, including impacts on great apes and their habitats in Africa. In the absence of national offset policies in sub-Saharan Africa, offset design and implementation are guided by company internal standards, lending bank standards or international best practice principles. We examine four projects in Africa that are seeking to compensate for their negative impacts on great ape populations. Our assessment of these projects reveals that not all apply or implement best practices, and that there is little standardization in the methods used to measure losses and gains in species numbers. Even if they were to follow currently accepted best-practice principles, we find that these actions may still fail to contribute to conservation objectives over the long term. We advocate for an alternative approach in which biodiversity offset and compensation projects are designed and implemented as part of a National Offset Strategy that (1) takes into account the cumulative impacts of development in individual countries, (2) identifies priority offset sites, (3) promotes aggregated offsets, and (4) integrates biodiversity offset and compensation projects with national biodiversity conservation objectives. We also propose supplementary principles necessary for biodiversity offsets to contribute to great ape conservation in Africa. Caution should still be exercised, however, with regard to offsets until further field-based evidence of their effectiveness is available.

Adaptive Failure Compensation for Aircraft Flight Control Using Engine Differentials: Regulation

NASA Technical Reports Server (NTRS)

Yu, Liu; Xidong, Tang; Gang, Tao; Joshi, Suresh M.

2005-01-01

The problem of using engine thrust differentials to compensate for rudder and aileron failures in aircraft flight control is addressed in this paper in a new framework. A nonlinear aircraft model that incorporates engine di erentials in the dynamic equations is employed and linearized to describe the aircraft s longitudinal and lateral motion. In this model two engine thrusts of an aircraft can be adjusted independently so as to provide the control flexibility for rudder or aileron failure compensation. A direct adaptive compensation scheme for asymptotic regulation is developed to handle uncertain actuator failures in the linearized system. A design condition is specified to characterize the system redundancy needed for failure compensation. The adaptive regulation control scheme is applied to the linearized model of a large transport aircraft in which the longitudinal and lateral motions are coupled as the result of using engine thrust differentials. Simulation results are presented to demonstrate the effectiveness of the adaptive compensation scheme.

Narratives of Compensated Dating of Girls in Hong Kong Using Routine Activity Theory: Results of a Focus Group Study of Guardians.

PubMed

Li, Jessica C M; Cheung, Chau-Kiu; Jia, Cindy X S; Yu, Yolanda M Y; Nguyen, Ping

2018-02-01

This article presents public discourses on compensated dating of adolescent girls in Chinese society. Data are obtained from eight focus groups comprising 50 guardians at private, parochial, and public levels (i.e., social workers, police officers, parents of students, and community representatives). Qualitative data are used to demonstrate how the guardians conceptualize and contextualize compensated dating as an outcome of the dynamics of societal features. Social features such as contemporary ideologies, Internet technology advancement, commercialization of human relationships, and ambiguity between "right" and "wrong" motivate the service providers and customers of compensated dating, and accelerate their convergence and weakened levels of guardianship in society. This study is the first to connect the features of compensated dating of adolescent girls with recent societal changes using the routine activity approach. The findings confirm the application of the routine activity approach in the phenomenon of girls' compensated dating, and also offer theoretical and practical implications.

Pursuing Information: A Conversation Analytic Perspective on Communication Strategies

ERIC Educational Resources Information Center

Burch, Alfred R.

2014-01-01

Research on second language (L2) communication strategies over the past three decades has concerned itself broadly with defining their usage in terms of planning and compensation, as well as with the use of taxonomies for coding different types of strategies. Taking a Conversation Analytic (CA) perspective, this article examines the fine-grained…

Implementation Planning and Progress on Physical Activity Goals: The Mediating Role of Life-Management Strategies

ERIC Educational Resources Information Center

Dugas, Michelle; Gaudreau, Patrick; Carraro, Natasha

2012-01-01

This 4-week prospective study examined whether the use of life-management strategies mediates the relationship between implementation planning and short-term progress on physical activity goals. In particular, the strategies of elective selection, compensation, and loss-based selection were disentangled to assess their specific mediating effects.…

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.

New workers' compensation legislation: expected pharmaceutical cost savings.

PubMed

Wilson, Leslie; Gitlin, Matthew

2005-10-01

California Workers' Compensation (WC) system costs are under review. With recently approved California State Assembly Bill (AB) 749 and Senate Bill (SB) 228, an assessment of proposed pharmaceutical cost savings is needed. A large workers' compensation database provided by the California Workers' Compensation Institute (CWCI) and Medi-Cal pharmacy costs obtained from the State Drug Utilization Project are utilized to compare frequency, costs and savings to Workers' Compensation in 2002 with the new pharmacy legislation. Compared to the former California Workers' Compensation fee schedule, the newly implemented 100% Medi-Cal fee schedule will result in savings of 29.5% with a potential total pharmacy cost savings of $125 million. Further statistical analysis demonstrated that a large variability in savings across drugs could not be controlled with this drug pricing system. Despite the large savings in pharmaceuticals, inconsistencies between the two pharmaceutical payment systems could lead to negative incentives and uncertainty for long-term savings. Proposed alternative pricing systems could be considered. However, pain management implemented along with other cost containment strategies could more effectively reduce overall drug spending in the workers' compensation system.

Impact of wind generator infed on dynamic performance of a power system

NASA Astrophysics Data System (ADS)

Alam, Md. Ahsanul

Wind energy is one of the most prominent sources of electrical energy in the years to come. A tendency to increase the amount of electricity generation from wind turbine can be observed in many countries. One of the major concerns related to the high penetration level of the wind energy into the existing power grid is its influence on power system dynamic performance. In this thesis, the impact of wind generation system on power system dynamic performance is investigated through detailed dynamic modeling of the entire wind generator system considering all the relevant components. Nonlinear and linear models of a single machine as well as multimachine wind-AC system have been derived. For the dynamic model of integrated wind-AC system, a general transformation matrix is determined for the transformation of machine and network quantities to a common reference frame. Both time-domain and frequency domain analyses on single machine and multimachine systems have been carried out. The considered multimachine systems are---A 4 machine 12 bus system, and 10 machine 39 bus New England system. Through eigenvalue analysis, impact of asynchronous wind system on overall network damping has been quantified and modes responsible for the instability have been identified. Over with a number of simulation studies it is observed that for a induction generator based wind generation system, the fixed capacitor located at the generator terminal cannot normally cater for the reactive power demand during the transient disturbances like wind gust and fault on the system. For weak network connection, system instability may be initiated because of induction generator terminal voltage collapse under certain disturbance conditions. Incorporation of dynamic reactive power compensation scheme through either variable susceptance control or static compensator (STATCOM) is found to improve the dynamic performance significantly. Further improvement in transient profile has been brought in by supporting STATCOM with bulk energy storage devices. Two types of energy storage system (ESS) have been considered---battery energy storage system, and supercapacitor based energy storage system. A decoupled P -- Q control strategy has been implemented on STATCOM/ESS. It is observed that wind generators when supported by STATCOM/ESS can achieve significant withstand capability in the presence of grid fault of reasonable duration. It experiences almost negligible rotor speed variation, maintains constant terminal voltage, and resumes delivery of smoothed (almost transient free) power to the grid immediately after the fault is cleared. Keywords: Wind energy, induction generator, dynamic performance of wind generators, energy storage system, decoupled P -- Q control, multimachine system.

Optimal design strategy of switching converters employing current injected control

NASA Astrophysics Data System (ADS)

Lee, F. C.; Fang, Z. D.; Lee, T. H.

1985-01-01

This paper analyzes a buck/boost regulator employing current-injected control (CIC). It reveals the complex interactions between the dc loop and the current-injected loop and underlines the fundamental principle that governs the loop gain determination. Three commonly used compensation techniques are compared. The integral and lead/lag compensation are shown to be most desirable for performance optimization and stability.

Insights into the Experiences of Older Workers and Change: Through the Lens of Selection, Optimization, and Compensation

ERIC Educational Resources Information Center

Unson, Christine; Richardson, Margaret

2013-01-01

Purpose: The study examined the barriers faced, the goals selected, and the optimization and compensation strategies of older workers in relation to career change. Method: Thirty open-ended interviews, 12 in the United States and 18 in New Zealand, were conducted, recorded, transcribed verbatim, and analyzed for themes. Results: Barriers to…

Forced Migration and Changing Livelihoods in the Brazilian Amazon.

PubMed

Randell, Heather

2017-09-01

Forced migration due to development projects or environmental change impacts livelihoods, as affected households are faced with new-and often less favorable-environmental, social, and economic conditions. This article examines changing livelihood strategies among a population of rural agricultural households displaced by the Belo Monte Dam in the Brazilian Amazon. Using longitudinal data, I find that many households used compensation payments to concentrate income generation efforts on the most lucrative strategies-cacao and cattle production and business or rental income. Poorer households and those that received the least compensation were more likely to continue relying on agricultural wage labor-a less desirable income source associated with not owning land or with persons needing to supplement income with additional work as a day laborer. Results also indicate that the amount of compensation received by most households was sufficient to enable them to make productive investments beyond attaining replacement land and housing. Many households invested in assets such as agricultural infrastructure, cattle, rental houses, or tractors-all of which directly contribute to future income. Displacement compensation, similar to remittances or conditional cash transfers, can therefore act as an important infusion of capital to promote socioeconomic development and poverty reduction.

An improved synchronous reference frame current control strategy for a photovoltaic grid-connected inverter under unbalanced and nonlinear load conditions.

PubMed

Naderipour, Amirreza; Asuhaimi Mohd Zin, Abdullah; Bin Habibuddin, Mohd Hafiz; Miveh, Mohammad Reza; Guerrero, Josep M

2017-01-01

In recent years, renewable energy sources have been considered the most encouraging resources for grid and off-grid power generation. This paper presents an improved current control strategy for a three-phase photovoltaic grid-connected inverter (GCI) under unbalanced and nonlinear load conditions. It is challenging to suppress the harmonic content in the output current below a pre-set value in the GCI. It is also difficult to compensate for unbalanced loads even when the grid is under disruption due to total harmonic distortion (THD) and unbalanced loads. The primary advantage and objective of this method is to effectively compensate for the harmonic current content of the grid current and microgrid without the use of any compensation devices, such as active and passive filters. This method leads to a very low THD in both the GCI currents and the current exchanged with the grid. The control approach is designed to control the active and reactive power and harmonic current compensation, and it also corrects the system unbalance. The proposed control method features the synchronous reference frame (SRF) method. Simulation results are presented to demonstrate the effective performance of the proposed method.

An improved synchronous reference frame current control strategy for a photovoltaic grid-connected inverter under unbalanced and nonlinear load conditions

PubMed Central

Naderipour, Amirreza; Asuhaimi Mohd Zin, Abdullah; Bin Habibuddin, Mohd Hafiz; Miveh, Mohammad Reza; Guerrero, Josep M.

2017-01-01

In recent years, renewable energy sources have been considered the most encouraging resources for grid and off-grid power generation. This paper presents an improved current control strategy for a three-phase photovoltaic grid-connected inverter (GCI) under unbalanced and nonlinear load conditions. It is challenging to suppress the harmonic content in the output current below a pre-set value in the GCI. It is also difficult to compensate for unbalanced loads even when the grid is under disruption due to total harmonic distortion (THD) and unbalanced loads. The primary advantage and objective of this method is to effectively compensate for the harmonic current content of the grid current and microgrid without the use of any compensation devices, such as active and passive filters. This method leads to a very low THD in both the GCI currents and the current exchanged with the grid. The control approach is designed to control the active and reactive power and harmonic current compensation, and it also corrects the system unbalance. The proposed control method features the synchronous reference frame (SRF) method. Simulation results are presented to demonstrate the effective performance of the proposed method. PMID:28192436

Compensating for intersegmental dynamics across the shoulder, elbow, and wrist joints during feedforward and feedback control.

PubMed

Maeda, Rodrigo S; Cluff, Tyler; Gribble, Paul L; Pruszynski, J Andrew

2017-10-01

Moving the arm is complicated by mechanical interactions that arise between limb segments. Such intersegmental dynamics cause torques applied at one joint to produce movement at multiple joints, and in turn, the only way to create single joint movement is by applying torques at multiple joints. We investigated whether the nervous system accounts for intersegmental limb dynamics across the shoulder, elbow, and wrist joints during self-initiated planar reaching and when countering external mechanical perturbations. Our first experiment tested whether the timing and amplitude of shoulder muscle activity account for interaction torques produced during single-joint elbow movements from different elbow initial orientations and over a range of movement speeds. We found that shoulder muscle activity reliably preceded movement onset and elbow agonist activity, and was scaled to compensate for the magnitude of interaction torques arising because of forearm rotation. Our second experiment tested whether elbow muscles compensate for interaction torques introduced by single-joint wrist movements. We found that elbow muscle activity preceded movement onset and wrist agonist muscle activity, and thus the nervous system predicted interaction torques arising because of hand rotation. Our third and fourth experiments tested whether shoulder muscles compensate for interaction torques introduced by different hand orientations during self-initiated elbow movements and to counter mechanical perturbations that caused pure elbow motion. We found that the nervous system predicted the amplitude and direction of interaction torques, appropriately scaling the amplitude of shoulder muscle activity during self-initiated elbow movements and rapid feedback control. Taken together, our results demonstrate that the nervous system robustly accounts for intersegmental dynamics and that the process is similar across the proximal to distal musculature of the arm as well as between feedforward (i.e., self-initiated) and feedback (i.e., reflexive) control. NEW & NOTEWORTHY Intersegmental dynamics complicate the mapping between applied joint torques and the resulting joint motions. We provide evidence that the nervous system robustly predicts these intersegmental limb dynamics across the shoulder, elbow, and wrist joints during reaching and when countering external perturbations. Copyright © 2017 the American Physiological Society.

Parameterized LMI Based Diagonal Dominance Compensator Study for Polynomial Linear Parameter Varying System

NASA Astrophysics Data System (ADS)

Han, Xiaobao; Li, Huacong; Jia, Qiusheng

2017-12-01

For dynamic decoupling of polynomial linear parameter varying(PLPV) system, a robust dominance pre-compensator design method is given. The parameterized precompensator design problem is converted into an optimal problem constrained with parameterized linear matrix inequalities(PLMI) by using the conception of parameterized Lyapunov function(PLF). To solve the PLMI constrained optimal problem, the precompensator design problem is reduced into a normal convex optimization problem with normal linear matrix inequalities (LMI) constraints on a new constructed convex polyhedron. Moreover, a parameter scheduling pre-compensator is achieved, which satisfies robust performance and decoupling performances. Finally, the feasibility and validity of the robust diagonal dominance pre-compensator design method are verified by the numerical simulation on a turbofan engine PLPV model.

Hysteresis Compensation of Piezoresistive Carbon Nanotube/Polydimethylsiloxane Composite-Based Force Sensors

PubMed Central

Kim, Ji-Sik; Kim, Gi-Woo

2017-01-01

This paper provides a preliminary study on the hysteresis compensation of a piezoresistive silicon-based polymer composite, poly(dimethylsiloxane) dispersed with carbon nanotubes (CNTs), to demonstrate its feasibility as a conductive composite (i.e., a force-sensitive resistor) for force sensors. In this study, the potential use of the nanotube/polydimethylsiloxane (CNT/PDMS) as a force sensor is evaluated for the first time. The experimental results show that the electrical resistance of the CNT/PDMS composite changes in response to sinusoidal loading and static compressive load. The compensated output based on the Duhem hysteresis model shows a linear relationship. This simple hysteresis model can compensate for the nonlinear frequency-dependent hysteresis phenomenon when a dynamic sinusoidal force input is applied. PMID:28125046

Design and application of quadrature compensation patterns in bulk silicon micro-gyroscopes.

PubMed

Ni, Yunfang; Li, Hongsheng; Huang, Libin

2014-10-29

This paper focuses on the detailed design issues of a peculiar quadrature reduction method named system stiffness matrix diagonalization, whose key technology is the design and application of quadrature compensation patterns. For bulk silicon micro-gyroscopes, a complete design and application case was presented. The compensation principle was described first. In the mechanical design, four types of basic structure units were presented to obtain the basic compensation function. A novel layout design was proposed to eliminate the additional disturbing static forces and torques. Parameter optimization was carried out to maximize the available compensation capability in a limited layout area. Two types of voltage loading methods were presented. Their influences on the sense mode dynamics were analyzed. The proposed design was applied on a dual-mass silicon micro-gyroscope developed in our laboratory. The theoretical compensation capability of a quadrature equivalent angular rate no more than 412 °/s was designed. In experiments, an actual quadrature equivalent angular rate of 357 °/s was compensated successfully. The actual compensation voltages were a little larger than the theoretical ones. The correctness of the design and the theoretical analyses was verified. They can be commonly used in planar linear vibratory silicon micro-gyroscopes for quadrature compensation purpose.

System for computer controlled shifting of an automatic transmission

DOEpatents

Patil, Prabhakar B.

1989-01-01

In an automotive vehicle having an automatic transmission that driveably connects a power source to the driving wheels, a method to control the application of hydraulic pressure to a clutch, whose engagement produces an upshift and whose disengagement produces a downshift, the speed of the power source, and the output torque of the transmission. The transmission output shaft torque and the power source speed are the controlled variables. The commanded power source torque and commanded hydraulic pressure supplied to the clutch are the control variables. A mathematical model is formulated that describes the kinematics and dynamics of the powertrain before, during and after a gear shift. The model represents the operating characteristics of each component and the structural arrangement of the components within the transmission being controlled. Next, a close loop feedback control is developed to determine the proper control law or compensation strategy to achieve an acceptably smooth gear ratio change, one in which the output torque disturbance is kept to a minimum and the duration of the shift is minimized. Then a computer algorithm simulating the shift dynamics employing the mathematical model is used to study the effects of changes in the values of the parameters established from a closed loop control of the clutch hydraulic and the power source torque on the shift quality. This computer simulation is used also to establish possible shift control strategies. The shift strategies determine from the prior step are reduced to an algorithm executed by a computer to control the operation of the power source and the transmission.

Closed loop computer control for an automatic transmission

DOEpatents

Patil, Prabhakar B.

1989-01-01

In an automotive vehicle having an automatic transmission that driveably connects a power source to the driving wheels, a method to control the application of hydraulic pressure to a clutch, whose engagement produces an upshift and whose disengagement produces a downshift, the speed of the power source, and the output torque of the transmission. The transmission output shaft torque and the power source speed are the controlled variables. The commanded power source torque and commanded hydraulic pressure supplied to the clutch are the control variables. A mathematical model is formulated that describes the kinematics and dynamics of the powertrain before, during and after a gear shift. The model represents the operating characteristics of each component and the structural arrangement of the components within the transmission being controlled. Next, a close loop feedback control is developed to determine the proper control law or compensation strategy to achieve an acceptably smooth gear ratio change, one in which the output torque disturbance is kept to a minimum and the duration of the shift is minimized. Then a computer algorithm simulating the shift dynamics employing the mathematical model is used to study the effects of changes in the values of the parameters established from a closed loop control of the clutch hydraulic and the power source torque on the shift quality. This computer simulation is used also to establish possible shift control strategies. The shift strategies determined from the prior step are reduced to an algorithm executed by a computer to control the operation of the power source and the transmission.

Fixman compensating potential for general branched molecules

NASA Astrophysics Data System (ADS)

Jain, Abhinandan; Kandel, Saugat; Wagner, Jeffrey; Larsen, Adrien; Vaidehi, Nagarajan

2013-12-01

The technique of constraining high frequency modes of molecular motion is an effective way to increase simulation time scale and improve conformational sampling in molecular dynamics simulations. However, it has been shown that constraints on higher frequency modes such as bond lengths and bond angles stiffen the molecular model, thereby introducing systematic biases in the statistical behavior of the simulations. Fixman proposed a compensating potential to remove such biases in the thermodynamic and kinetic properties calculated from dynamics simulations. Previous implementations of the Fixman potential have been limited to only short serial chain systems. In this paper, we present a spatial operator algebra based algorithm to calculate the Fixman potential and its gradient within constrained dynamics simulations for branched topology molecules of any size. Our numerical studies on molecules of increasing complexity validate our algorithm by demonstrating recovery of the dihedral angle probability distribution function for systems that range in complexity from serial chains to protein molecules. We observe that the Fixman compensating potential recovers the free energy surface of a serial chain polymer, thus annulling the biases caused by constraining the bond lengths and bond angles. The inclusion of Fixman potential entails only a modest increase in the computational cost in these simulations. We believe that this work represents the first instance where the Fixman potential has been used for general branched systems, and establishes the viability for its use in constrained dynamics simulations of proteins and other macromolecules.

Optimal compensation for neuron loss

PubMed Central

Barrett, David GT; Denève, Sophie; Machens, Christian K

2016-01-01

The brain has an impressive ability to withstand neural damage. Diseases that kill neurons can go unnoticed for years, and incomplete brain lesions or silencing of neurons often fail to produce any behavioral effect. How does the brain compensate for such damage, and what are the limits of this compensation? We propose that neural circuits instantly compensate for neuron loss, thereby preserving their function as much as possible. We show that this compensation can explain changes in tuning curves induced by neuron silencing across a variety of systems, including the primary visual cortex. We find that compensatory mechanisms can be implemented through the dynamics of networks with a tight balance of excitation and inhibition, without requiring synaptic plasticity. The limits of this compensatory mechanism are reached when excitation and inhibition become unbalanced, thereby demarcating a recovery boundary, where signal representation fails and where diseases may become symptomatic. DOI: http://dx.doi.org/10.7554/eLife.12454.001 PMID:27935480

Tracking control of time-varying knee exoskeleton disturbed by interaction torque.

PubMed

Li, Zhan; Ma, Wenhao; Yin, Ziguang; Guo, Hongliang

2017-11-01

Knee exoskeletons have been increasingly applied as assistive devices to help lower-extremity impaired people to make their knee joints move through providing external movement compensation. Tracking control of knee exoskeletons guided by human intentions often encounters time-varying (time-dependent) issues and the disturbance interaction torque, which may dramatically put an influence up on their dynamic behaviors. Inertial and viscous parameters of knee exoskeletons can be estimated to be time-varying due to unexpected mechanical vibrations and contact interactions. Moreover, the interaction torque produced from knee joint of wearers has an evident disturbance effect on regular motions of knee exoskeleton. All of these points can increase difficultly of accurate control of knee exoskeletons to follow desired joint angle trajectories. This paper proposes a novel control strategy for controlling knee exoskeleton with time-varying inertial and viscous coefficients disturbed by interaction torque. Such designed controller is able to make the tracking error of joint angle of knee exoskeletons exponentially converge to zero. Meanwhile, the proposed approach is robust to guarantee the tracking error bounded when the interaction torque exists. Illustrative simulation and experiment results are presented to show efficiency of the proposed controller. Additionally, comparisons with gradient dynamic (GD) approach and other methods are also presented to demonstrate efficiency and superiority of the proposed control strategy for tracking joint angle of knee exoskeleton. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Extraneous torque and compensation control on the electric load simulator

NASA Astrophysics Data System (ADS)

Jiao, Zongxia; Li, Chenggong; Ren, Zhiting

2003-09-01

In this paper a novel motor-drive load simulator based on compensation control strategy is proposed and designed. Through analyzing the torque control system consisting of DC torque motor, PWM module and torque sensor, it is shown that performance of the motor-drive load simulator is possible to be as good as that of the electro-hydraulic load simulator in the range of small torque. In the course of loading, the rotation of the actuator would cause a strong disturbance torque through the motor back-EMF, which produces extraneous torque similar as in electro-hydraulic load simulator. This paper analyzes the cause of extraneous torque inside the torque motor in detail and presents an appropriate compensation control with which the extraneous torque can be compensated and the good performance of the torque control system can be obtained. The results of simulation indicate that the compensation is very effective and the track performance is according with the request.

Advanced Respiratory Motion Compensation for Coronary MR Angiography

PubMed Central

Henningsson, Markus; Botnar, Rene M.

2013-01-01

Despite technical advances, respiratory motion remains a major impediment in a substantial amount of patients undergoing coronary magnetic resonance angiography (CMRA). Traditionally, respiratory motion compensation has been performed with a one-dimensional respiratory navigator positioned on the right hemi-diaphragm, using a motion model to estimate and correct for the bulk respiratory motion of the heart. Recent technical advancements has allowed for direct respiratory motion estimation of the heart, with improved motion compensation performance. Some of these new methods, particularly using image-based navigators or respiratory binning, allow for more advanced motion correction which enables CMRA data acquisition throughout most or all of the respiratory cycle, thereby significantly reducing scan time. This review describes the three components typically involved in most motion compensation strategies for CMRA, including respiratory motion estimation, gating and correction, and how these processes can be utilized to perform advanced respiratory motion compensation. PMID:23708271

A Novel Speed Compensation Method for ISAR Imaging with Low SNR

PubMed Central

Liu, Yongxiang; Zhang, Shuanghui; Zhu, Dekang; Li, Xiang

2015-01-01

In this paper, two novel speed compensation algorithms for ISAR imaging under a low signal-to-noise ratio (SNR) condition have been proposed, which are based on the cubic phase function (CPF) and the integrated cubic phase function (ICPF), respectively. These two algorithms can estimate the speed of the target from the wideband radar echo directly, which breaks the limitation of speed measuring in a radar system. With the utilization of non-coherent accumulation, the ICPF-based speed compensation algorithm is robust to noise and can meet the requirement of speed compensation for ISAR imaging under a low SNR condition. Moreover, a fast searching implementation strategy, which consists of coarse search and precise search, has been introduced to decrease the computational burden of speed compensation based on CPF and ICPF. Experimental results based on radar data validate the effectiveness of the proposed algorithms. PMID:26225980

Automatic Road Gap Detection Using Fuzzy Inference System

NASA Astrophysics Data System (ADS)

Hashemi, S.; Valadan Zoej, M. J.; Mokhtarzadeh, M.

2011-09-01

Automatic feature extraction from aerial and satellite images is a high-level data processing which is still one of the most important research topics of the field. In this area, most of the researches are focused on the early step of road detection, where road tracking methods, morphological analysis, dynamic programming and snakes, multi-scale and multi-resolution methods, stereoscopic and multi-temporal analysis, hyper spectral experiments, are some of the mature methods in this field. Although most researches are focused on detection algorithms, none of them can extract road network perfectly. On the other hand, post processing algorithms accentuated on the refining of road detection results, are not developed as well. In this article, the main is to design an intelligent method to detect and compensate road gaps remained on the early result of road detection algorithms. The proposed algorithm consists of five main steps as follow: 1) Short gap coverage: In this step, a multi-scale morphological is designed that covers short gaps in a hierarchical scheme. 2) Long gap detection: In this step, the long gaps, could not be covered in the previous stage, are detected using a fuzzy inference system. for this reason, a knowledge base consisting of some expert rules are designed which are fired on some gap candidates of the road detection results. 3) Long gap coverage: In this stage, detected long gaps are compensated by two strategies of linear and polynomials for this reason, shorter gaps are filled by line fitting while longer ones are compensated by polynomials.4) Accuracy assessment: In order to evaluate the obtained results, some accuracy assessment criteria are proposed. These criteria are obtained by comparing the obtained results with truly compensated ones produced by a human expert. The complete evaluation of the obtained results whit their technical discussions are the materials of the full paper.

Dual-thread parallel control strategy for ophthalmic adaptive optics.

PubMed

Yu, Yongxin; Zhang, Yuhua

To improve ophthalmic adaptive optics speed and compensate for ocular wavefront aberration of high temporal frequency, the adaptive optics wavefront correction has been implemented with a control scheme including 2 parallel threads; one is dedicated to wavefront detection and the other conducts wavefront reconstruction and compensation. With a custom Shack-Hartmann wavefront sensor that measures the ocular wave aberration with 193 subapertures across the pupil, adaptive optics has achieved a closed loop updating frequency up to 110 Hz, and demonstrated robust compensation for ocular wave aberration up to 50 Hz in an adaptive optics scanning laser ophthalmoscope.

Dual-thread parallel control strategy for ophthalmic adaptive optics

PubMed Central

Yu, Yongxin; Zhang, Yuhua

2015-01-01

To improve ophthalmic adaptive optics speed and compensate for ocular wavefront aberration of high temporal frequency, the adaptive optics wavefront correction has been implemented with a control scheme including 2 parallel threads; one is dedicated to wavefront detection and the other conducts wavefront reconstruction and compensation. With a custom Shack-Hartmann wavefront sensor that measures the ocular wave aberration with 193 subapertures across the pupil, adaptive optics has achieved a closed loop updating frequency up to 110 Hz, and demonstrated robust compensation for ocular wave aberration up to 50 Hz in an adaptive optics scanning laser ophthalmoscope. PMID:25866498

Serially-Connected Compensator for Eliminating the Unbalanced Three-Phase Voltage Impact on Wind Turbine Generators: Preprint

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

Wu, Z.; Hsu, P.; Muljadi, E.

2015-04-06

Untransposed transmission lines, unbalanced tap changer operations, and unbalanced loading in weak distribution lines can cause unbalanced-voltage conditions. The resulting unbalanced voltage at the point of interconnection affects proper gird integration and reduces the lifetime of wind turbines due to power oscillations, torque pulsations, mechanical stresses, energy losses, and uneven and overheating of the generator stator winding. This work investigates the dynamic impact of unbalanced voltage on the mechanical and electrical components of integrated Fatigue, Aerodynamics, Structures, and Turbulence (FAST) wind turbine generation systems (WTGs) of Type 1 (squirrel-cage induction generator) and Type 3 (doubly-fed induction generator). To alleviate thismore » impact, a serially-connected compensator for a three-phase power line is proposed to balance the wind turbine-side voltage. Dynamic simulation studies are conducted in MATLAB/Simulink to compare the responses of these two types of wind turbine models under normal and unbalanced-voltage operation conditions and demonstrate the effectiveness of the proposed compensator.« less

A Serially-Connected Compensator for Eliminating the Unbalanced Three-Phase Voltage Impact on Wind Turbine Generators

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

Wu, Ziping; Hsu, Ping; Muljadi, Eduard

2015-10-05

Untransposed transmission lines, unbalanced tap changer operations, and unbalanced loading in weak distribution lines can cause unbalanced-voltage conditions. The resulting unbalanced voltage at the point of interconnection affects proper gird integration and reduces the lifetime of wind turbines due to power oscillations, torque pulsations, mechanical stresses, energy losses, and uneven and overheating of the generator stator winding. This work investigates the dynamic impact of unbalanced voltage on the mechanical and electrical components of integrated Fatigue, Aerodynamics, Structures, and Turbulence (FAST) wind turbine generation systems (WTGs) of Type 1 (squirrel-cage induction generator) and Type 3 (doubly-fed induction generator). To alleviate thismore » impact, a serially-connected compensator for a three-phase power line is proposed to balance the wind turbine-side voltage. Dynamic simulation studies are conducted in MATLAB/Simulink to compare the responses of these two types of wind turbine models under normal and unbalanced-voltage operation conditions and demonstrate the effectiveness of the proposed compensator.« less

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

Park, Chong Shik; Shiltsev, Vladimir; Stancari, Giulio

The ability to transport a high current proton beam in a ring is ultimately limited by space charge effects. Two novel ways to overcome this limit in a proton ring are by adding low energy, externally matched electron beams (electron lens, e-lens), and by taking advantage of residual gas ionization induced neutralization to create an electron column (e-column). Theory predicts that an appropriately confined electrons can completely compensate the space charge through neutralization, both transversely and longitudinally. In this report, we will discuss the current status of the Fermilab’s e-lens experiment for the space charge compensation. In addition, we willmore » show how the IOTA e-column compensates space charge with theWARP simulations. The dynamics of proton beams inside of the e-column is understood by changing the magnetic field of a solenoid, the voltage on the electrodes, and the vacuum pressure, and by looking for electron accumulation, as well as by considering various beam dynamics in the IOTA ring.« less

Modeling, analysis, control and design application guidelines of Doubly Fed Induction Generator (DFIG) for wind power applications

NASA Astrophysics Data System (ADS)

Masaud, Tarek

Double Fed Induction Generators (DFIG) has been widely used for the past two decades in large wind farms. However, there are many open-ended problems yet to be solved before they can be implemented in some specific applications. This dissertation deals with the general analysis, modeling, control and applications of the DFIG for large wind farm applications. A detailed "d-q" model of DFIG along with other applications is simulated using the MATLAB/Simulink platform. The simulation results have been discussed in detail in both sub-synchronous and super-synchronous mode of operation. An improved vector control strategy based on the rotor flux oriented vector control has been proposed to control the active power output of the DFIG. The new vector control strategy is compared with the stator flux oriented vector control which is commonly used. It is observed that the new improved vector control method provides a better active power tracking accuracy compare with the stator flux oriented vector control. The behavior of the DFIG -based wind farm under the various grid disturbances is also studied in this dissertation. The implementation of the Flexible AC Transmission System devices (FACTS) to overcome the voltage stability issue for such applications is investigated. The study includes the implementation of both a static synchronous compensator (STATCOM), and the static VAR compensator (SVC) as dynamic reactive power compensators at the point of common coupling to support DFIG-based wind farm during disturbances. Integrating FACTS protect the grid connected DFIG-based wind farm from going offline during and after the disturbances. It is found that the both devices improve the transient performance and therefore helps the wind turbine generator system to remain in service during grid faults. A comparison between the performance of the two devices in terms of the amount of reactive power injected, time response and the application cost has been discussed in this dissertation. Finally, the integration of the battery energy storage system (BESS) into a grid connected DFIG- based wind turbine as a proposed solution to smooth out the output power during wind speed variations is also addressed.

Theoretical and experimental research on machine tool servo system for ultra-precision position compensation on CNC lathe

NASA Astrophysics Data System (ADS)

Ma, Zhichao; Hu, Leilei; Zhao, Hongwei; Wu, Boda; Peng, Zhenxing; Zhou, Xiaoqin; Zhang, Hongguo; Zhu, Shuai; Xing, Lifeng; Hu, Huang

2010-08-01

The theories and techniques for improving machining accuracy via position control of diamond tool's tip and raising resolution of cutting depth on precise CNC lathes have been extremely focused on. A new piezo-driven ultra-precision machine tool servo system is designed and tested to improve manufacturing accuracy of workpiece. The mathematical model of machine tool servo system is established and the finite element analysis is carried out on parallel plate flexure hinges. The output position of diamond tool's tip driven by the machine tool servo system is tested via a contact capacitive displacement sensor. Proportional, integral, derivative (PID) feedback is also implemented to accommodate and compensate dynamical change owing cutting forces as well as the inherent non-linearity factors of the piezoelectric stack during cutting process. By closed loop feedback controlling strategy, the tracking error is limited to 0.8 μm. Experimental results have shown the proposed machine tool servo system could provide a tool positioning resolution of 12 nm, which is much accurate than the inherent CNC resolution magnitude. The stepped shaft of aluminum specimen with a step increment of cutting depth of 1 μm is tested, and the obtained contour illustrates the displacement command output from controller is accurately and real-time reflected on the machined part.

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.

Nonlinear dynamic range transformation in visual communication channels.

PubMed

Alter-Gartenberg, R

1996-01-01

The article evaluates nonlinear dynamic range transformation in the context of the end-to-end continuous-input/discrete processing/continuous-display imaging process. Dynamic range transformation is required when we have the following: (i) the wide dynamic range encountered in nature is compressed into the relatively narrow dynamic range of the display, particularly for spatially varying irradiance (e.g., shadow); (ii) coarse quantization is expanded to the wider dynamic range of the display; and (iii) nonlinear tone scale transformation compensates for the correction in the camera amplifier.

Cost-Effectiveness of Direct-Acting Anti-viral Treatment in Hepatitis C-infected Liver Transplant Candidates with Compensated Cirrhosis and Hepatocellular Carcinoma

PubMed Central

Salazar, James; Saxena, Varun; Kahn, James G.; Roberts, John P.; Mehta, Neil; Volk, Michael; Lai, Jennifer C.

2016-01-01

Background HCV(+) donors represent an effective strategy to increase liver donor availability to HCV-infected recipients. However, many HCV(+) transplant candidates are now receiving treatment with direct acting anti-virals (DAA) that lower the risk of posttransplant HCV recurrence but could make the patient ineligible for HCV(+) livers. Methods We compared pretransplant DAA treatment versus deferred DAA treatment using a cost-effectiveness decision analysis model to estimate incremental cost-effectiveness ratios (ICERs; cost per quality-adjusted life year [QALY] gained) from the societal perspective across a range of HCV(+) liver availability rates. For practical considerations, the population modelled was restricted to well-compensated HCV(+) cirrhotics listed for liver transplantation with HCC MELD exception points. Results Under base case conditions, the deferred DAA treatment strategy was found to be the “dominant” strategy. That is, it provided superior health outcomes at cost savings compared to the pretransplant DAA treatment strategy. The pretransplant DAA treatment strategy trended towards cost-effectiveness as HCV(+) donor liver availability declined. However, only in 1 scenario that was highly optimized for favorable outcomes in the pretransplant DAA treatment arm (low availability of HCV(+) organs, low cost of DAA treatment, high cost of HCV recurrence) was the ICER associated with HCV DAA treatment before transplant <$150,000/QALY gained. Conclusions Deferring HCV treatment until after liver transplant and maintaining access to the expanded pool of HCV(+) donors appears to be the most cost-effective strategy for well-compensated HCV-infected cirrhotics listed for liver transplantation with HCC, even in geographic areas of relatively low HCV(+) donor availability. PMID:27926593

Cost-Effectiveness of Direct-Acting Antiviral Treatment in Hepatitis C-Infected Liver Transplant Candidates With Compensated Cirrhosis and Hepatocellular Carcinoma.

PubMed

Salazar, James; Saxena, Varun; Kahn, James G; Roberts, John P; Mehta, Neil; Volk, Michael; Lai, Jennifer C

2017-05-01

Hepatitis C virus (HCV)(+) donors represent an effective strategy to increase liver donor availability to HCV-infected recipients. However, many HCV(+) transplant candidates are now receiving treatment with direct-acting anti-viral (DAA) agents that lower the risk of posttransplant HCV recurrence but could make the patient ineligible for HCV(+) livers. We compared pretransplant DAA treatment versus deferred DAA treatment using a cost-effectiveness decision analysis model to estimate incremental cost-effectiveness ratios (cost per quality-adjusted life year gained) from the societal perspective across a range of HCV(+) liver availability rates. For practical considerations, the population modeled was restricted to well-compensated HCV(+) cirrhotics listed for liver transplantation with hepatocellular carcinoma MELD exception points. Under base case conditions, the deferred DAA treatment strategy was found to be the "dominant" strategy. That is, it provided superior health outcomes at cost savings compared to the pretransplant DAA treatment strategy. The pretransplant DAA treatment strategy trended towards cost-effectiveness as HCV(+) donor liver availability declined. However, only in 1 scenario that was highly optimized for favorable outcomes in the pretransplant DAA treatment arm (low availability of HCV(+) organs, low cost of DAA treatment, high cost of HCV recurrence) was the incremental cost-effectiveness ratio associated with HCV DAA treatment before transplant less than US $150 000/quality-adjusted life-year gained. Deferring HCV treatment until after liver transplant and maintaining access to the expanded pool of HCV(+) donors appears to be the most cost-effective strategy for well-compensated HCV-infected cirrhotics listed for liver transplantation with hepatocellular carcinoma, even in geographic areas of relatively low HCV(+) donor availability.

Memory control beliefs and everyday forgetfulness in adulthood: the effects of selection, optimization, and compensation strategies.

PubMed

Scheibner, Gunnar Benjamin; Leathem, Janet

2012-01-01

Controlling for age, gender, education, and self-rated health, the present study used regression analyses to examine the relationships between memory control beliefs and self-reported forgetfulness in the context of the meta-theory of Selective Optimization with Compensation (SOC). Findings from this online survey (N = 409) indicate that, among adult New Zealanders, a higher sense of memory control accounts for a 22.7% reduction in self-reported forgetfulness. Similarly, optimization was found to account for a 5% reduction in forgetfulness while the strategies of selection and compensation were not related to self-reports of forgetfulness. Optimization partially mediated the beneficial effects that some memory beliefs (e.g., believing that memory decline is inevitable and believing in the potential for memory improvement) have on forgetfulness. It was concluded that memory control beliefs are important predictors of self-reported forgetfulness while the support for the SOC model in the context of memory controllability and everyday forgetfulness is limited.

Anticipatory Neurofuzzy Control

NASA Technical Reports Server (NTRS)

Mccullough, Claire L.

1994-01-01

Technique of feedback control, called "anticipatory neurofuzzy control," developed for use in controlling flexible structures and other dynamic systems for which mathematical models of dynamics poorly known or unknown. Superior ability to act during operation to compensate for, and adapt to, errors in mathematical model of dynamics, changes in dynamics, and noise. Also offers advantage of reduced computing time. Hybrid of two older fuzzy-logic control techniques: standard fuzzy control and predictive fuzzy control.

Quantum Yang-Mills Dark Energy

NASA Astrophysics Data System (ADS)

Pasechnik, Roman

2016-02-01

In this short review, I discuss basic qualitative characteristics of quantum non-Abelian gauge dynamics in the non-stationary background of the expanding Universe in the framework of the standard Einstein--Yang--Mills formulation. A brief outlook of existing studies of cosmological Yang--Mills fields and their properties will be given. Quantum effects have a profound impact on the gauge field-driven cosmological evolution. In particular, a dynamical formation of the spatially-homogeneous and isotropic gauge field condensate may be responsible for both early and late-time acceleration, as well as for dynamical compensation of non-perturbative quantum vacua contributions to the ground state of the Universe. The main properties of such a condensate in the effective QCD theory at the flat Friedmann--Lema\\'itre--Robertson--Walker (FLRW) background will be discussed within and beyond perturbation theory. Finally, a phenomenologically consistent dark energy can be induced dynamically as a remnant of the QCD vacua compensation arising from leading-order graviton-mediated corrections to the QCD ground state.

Controlling laser-induced magnetization reversal dynamics in a rare-earth iron garnet across the magnetization compensation point

NASA Astrophysics Data System (ADS)

Deb, Marwan; Molho, Pierre; Barbara, Bernard; Bigot, Jean-Yves

2018-04-01

In this work we explore the ultrafast magnetization dynamics induced by femtosecond laser pulses in a doped film of gadolinium iron garnet over a broad temperature range including the magnetization compensation point TM. By exciting the phonon-assisted 6S→4G and 6S→4P electronic d -d transitions simultaneously by one- and two-photon absorption processes, we find out that the transfer of heat energy from the lattice to the spin has, at a temperature slightly below TM, a large influence on the magnetization dynamics. In particular, we show that the speed and the amplitude of the magnetization dynamics can be strongly increased when increasing either the external magnetic field or the laser energy density. The obtained results are explained by a magnetization reversal process across TM. Furthermore, we find that the dynamics has unusual characteristics which can be understood by considering the weak spin-phonon coupling in magnetic garnets. These results open new perspectives for controlling the magnetic state of magnetic dielectrics using an ultrashort optically induced heat pulse.

A hybrid Bayesian network approach for trade-offs between environmental flows and agricultural water using dynamic discretization

NASA Astrophysics Data System (ADS)

Xue, Jie; Gui, Dongwei; Lei, Jiaqiang; Sun, Huaiwei; Zeng, Fanjiang; Feng, Xinlong

2017-12-01

Agriculture and the eco-environment are increasingly competing for water. The extension of intensive farmland for ensuring food security has resulted in excessive water exploitation by agriculture. Consequently, this has led to a lack of water supply in natural ecosystems. This paper proposes a trade-off framework to coordinate the water-use conflict between agriculture and the eco-environment, based on economic compensation for irrigation stakeholders. A hybrid Bayesian network (HBN) is developed to implement the framework, including: (a) agricultural water shortage assessments after meeting environmental flows; (b) water-use tradeoff analysis between agricultural irrigation and environmental flows using the HBN; and (c) quantification of the agricultural economic compensation for different irrigation stakeholders. The constructed HBN is computed by dynamic discretization, which is a more robust and accurate propagation algorithm than general static discretization. A case study of the Qira oasis area in Northwest China demonstrates that the water trade-off based on economic compensation depends on the available water supply and environmental flows at different levels. Agricultural irrigation water extracted for grain crops should be preferentially guaranteed to ensure food security, in spite of higher economic compensation in other cash crops' irrigation for water coordination. Updating water-saving engineering and adopting drip irrigation technology in agricultural facilities after satisfying environmental flows would greatly relieve agricultural water shortage and save the economic compensation for different irrigation stakeholders. The approach in this study can be easily applied in water-stressed areas worldwide for dealing with water competition.

Compensated control loops for a 30-cm ion thruster

NASA Technical Reports Server (NTRS)

Robson, R. R.

1976-01-01

The vaporizer dynamic control characteristics of a 30-cm diameter mercury ion thruster were determined by operating the thruster in an open loop steady state mode and then introducing a small sinusoidal signal on the main, cathode, or neutralizer vaporizer current and observing the response of the beam current, discharge voltage, and neutralizer keeper voltage, respectively. This was done over a range of frequencies and operating conditions. From these data, Bode plots for gain and phase were made and mathematical models were obtained. The Bode plots and mathematical models were analyzed for stability and appropriate compensation networks determined. The compensated control loops were incorporated into a power processor and operated with a thruster. The time responses of the compensated loops to changes in set points and recovery from arc conditions are presented.

Fast time-of-flight camera based surface registration for radiotherapy patient positioning.

PubMed

Placht, Simon; Stancanello, Joseph; Schaller, Christian; Balda, Michael; Angelopoulou, Elli

2012-01-01

This work introduces a rigid registration framework for patient positioning in radiotherapy, based on real-time surface acquisition by a time-of-flight (ToF) camera. Dynamic properties of the system are also investigated for future gating/tracking strategies. A novel preregistration algorithm, based on translation and rotation-invariant features representing surface structures, was developed. Using these features, corresponding three-dimensional points were computed in order to determine initial registration parameters. These parameters became a robust input to an accelerated version of the iterative closest point (ICP) algorithm for the fine-tuning of the registration result. Distance calibration and Kalman filtering were used to compensate for ToF-camera dependent noise. Additionally, the advantage of using the feature based preregistration over an "ICP only" strategy was evaluated, as well as the robustness of the rigid-transformation-based method to deformation. The proposed surface registration method was validated using phantom data. A mean target registration error (TRE) for translations and rotations of 1.62 ± 1.08 mm and 0.07° ± 0.05°, respectively, was achieved. There was a temporal delay of about 65 ms in the registration output, which can be seen as negligible considering the dynamics of biological systems. Feature based preregistration allowed for accurate and robust registrations even at very large initial displacements. Deformations affected the accuracy of the results, necessitating particular care in cases of deformed surfaces. The proposed solution is able to solve surface registration problems with an accuracy suitable for radiotherapy cases where external surfaces offer primary or complementary information to patient positioning. The system shows promising dynamic properties for its use in gating/tracking applications. The overall system is competitive with commonly-used surface registration technologies. Its main benefit is the usage of a cost-effective off-the-shelf technology for surface acquisition. Further strategies to improve the registration accuracy are under development.

Forest Ecosystem Services and Eco-Compensation Mechanisms in China

NASA Astrophysics Data System (ADS)

Deng, Hongbing; Zheng, Peng; Liu, Tianxing; Liu, Xin

2011-12-01

Forests are a major terrestrial ecosystem providing multiple ecosystem services. However, the importance of forests is frequently underestimated from an economic perspective because of the externalities and public good properties of these services. Forest eco-compensation is a transfer mechanism that serves to internalize the externalities of forest ecosystem services by compensating individuals or companies for the losses or costs resulting from the provision of these services. China's current forest eco-compensation system is centered mainly on noncommercial forest. The primary measures associated with ecosystem services are (1) a charge on destructive activities, such as indiscriminate logging, and (2) compensation for individual or local activities and investments in forest conservation. The Compensation Fund System for Forest Ecological Benefits was first listed in the Forest Law of the People's Republic of China in 1998. In 2004, the Central Government Financial Compensation Fund, an important source for the Compensation Fund for Forest Ecological Benefits, was formally established. To improve the forest eco-compensation system, it is crucial to design and establish compensation criteria for noncommercial forests. These criteria should take both theoretical and practical concerns into account, and they should be based on the quantitative valuation of ecosystem services. Although some initial headway has been made on this task, the implementation of an effective forest eco-compensation system in China still has deficiencies and still faces problems. Implementing classification-based and dynamic management for key noncommercial forests and establishing an eco-compensation mechanism with multiple funding sources in the market economy are the key measures needed to conquer these problems and improve the forest eco-compensation system and China's forestry development in sequence.

Compensatory strategies during walking in response to excessive muscle co-contraction at the ankle joint.

PubMed

Wang, Ruoli; Gutierrez-Farewik, Elena M

2014-03-01

Excessive co-contraction causes inefficient or abnormal movement in several neuromuscular pathologies. How synergistic muscles spanning the ankle, knee and hip adapt to co-contraction of ankle muscles is not well understood. This study aimed to identify the compensation strategies required to retain normal walking with excessive antagonistic ankle muscle co-contraction. Muscle-actuated simulations of normal walking were performed to quantify compensatory mechanisms of ankle and knee muscles during stance in the presence of normal, medium and high levels of co-contraction of antagonistic pairs gastrocnemius+tibialis anterior and soleus+tibialis anterior. The study showed that if co-contraction increases, the synergistic ankle muscles can compensate; with gastrocmemius+tibialis anterior co-contraction, the soleus will increase its contribution to ankle plantarflexion acceleration. At the knee, however, almost all muscles spanning the knee and hip are involved in compensation. We also found that ankle and knee muscles alone can provide sufficient compensation at the ankle joint, but hip muscles must be involved to generate sufficient knee moment. Our findings imply that subjects with a rather high level of dorsiflexor+plantarflexor co-contraction can still perform normal walking. This also suggests that capacity of other lower limb muscles to compensate is important to retain normal walking in co-contracted persons. The compensatory mechanisms can be useful in clinical interpretation of motion analyses, when secondary muscle co-contraction or other deficits may present simultaneously in subjects with motion disorders. Copyright © 2014 Elsevier B.V. All rights reserved.

Reducing interaction in simultaneous paired stimulation with CI.

PubMed

Vellinga, Dirk; Bruijn, Saskia; Briaire, Jeroen J; Kalkman, Randy K; Frijns, Johan H M

2017-01-01

In this study simultaneous paired stimulation of electrodes in cochlear implants is investigated by psychophysical experiments in 8 post-lingually deaf subjects (and one extra subject who only participated in part of the experiments). Simultaneous and sequential monopolar stimulation modes are used as references and are compared to channel interaction compensation, partial tripolar stimulation and a novel sequential stimulation strategy named phased array compensation. Psychophysical experiments are performed to investigate both the loudness integration during paired stimulation at the main electrodes as well as the interaction with the electrode contact located halfway between the stimulating pair. The study shows that simultaneous monopolar stimulation has more loudness integration on the main electrodes and more interaction in between the electrodes than sequential stimulation. Channel interaction compensation works to reduce the loudness integration at the main electrodes, but does not reduce the interaction in between the electrodes caused by paired stimulation. Partial tripolar stimulation uses much more current to reach the needed loudness, but shows the same interaction in between the electrodes as sequential monopolar stimulation. In phased array compensation we have used the individual impedance matrix of each subject to calculate the current needed on each electrode to exactly match the stimulation voltage along the array to that of sequential stimulation. The results show that the interaction in between the electrodes is the same as monopolar stimulation. The strategy uses less current than partial tripolar stimulation, but more than monopolar stimulation. In conclusion, the paper shows that paired stimulation is possible if the interaction is compensated.

Error Model and Compensation of Bell-Shaped Vibratory Gyro

PubMed Central

Su, Zhong; Liu, Ning; Li, Qing

2015-01-01

A bell-shaped vibratory angular velocity gyro (BVG), inspired by the Chinese traditional bell, is a type of axisymmetric shell resonator gyroscope. This paper focuses on development of an error model and compensation of the BVG. A dynamic equation is firstly established, based on a study of the BVG working mechanism. This equation is then used to evaluate the relationship between the angular rate output signal and bell-shaped resonator character, analyze the influence of the main error sources and set up an error model for the BVG. The error sources are classified from the error propagation characteristics, and the compensation method is presented based on the error model. Finally, using the error model and compensation method, the BVG is calibrated experimentally including rough compensation, temperature and bias compensation, scale factor compensation and noise filter. The experimentally obtained bias instability is from 20.5°/h to 4.7°/h, the random walk is from 2.8°/h1/2 to 0.7°/h1/2 and the nonlinearity is from 0.2% to 0.03%. Based on the error compensation, it is shown that there is a good linear relationship between the sensing signal and the angular velocity, suggesting that the BVG is a good candidate for the field of low and medium rotational speed measurement. PMID:26393593

Reconstructing matter profiles of spherically compensated cosmic regions in ΛCDM cosmology

NASA Astrophysics Data System (ADS)

de Fromont, Paul; Alimi, Jean-Michel

2018-02-01

The absence of a physically motivated model for large-scale profiles of cosmic voids limits our ability to extract valuable cosmological information from their study. In this paper, we address this problem by introducing the spherically compensated cosmic regions, named CoSpheres. Such cosmic regions are identified around local extrema in the density field and admit a unique compensation radius R1 where the internal spherical mass is exactly compensated. Their origin is studied by extending the standard peak model and implementing the compensation condition. Since the compensation radius evolves as the Universe itself, R1(t) ∝ a(t), CoSpheres behave as bubble Universes with fixed comoving volume. Using the spherical collapse model, we reconstruct their profiles with a very high accuracy until z = 0 in N-body simulations. CoSpheres are symmetrically defined and reconstructed for both central maximum (seeding haloes and galaxies) and minimum (identified with cosmic voids). We show that the full non-linear dynamics can be solved analytically around this particular compensation radius, providing useful predictions for cosmology. This formalism highlights original correlations between local extremum and their large-scale cosmic environment. The statistical properties of these spherically compensated cosmic regions and the possibilities to constrain efficiently both cosmology and gravity will be investigated in companion papers.

District nurses’ experiences of caring for leg ulcers in accordance with clinical guidelines: a grounded theory study

PubMed Central

Lagerin, Annica; Hylander, Ingrid; Törnkvist, Lena

2017-01-01

ABSTRACT This qualitative study used the grounded theory method to investigate district nurses’ experiences of caring for leg ulcers in accordance with clinical guidelines at seven primary health care centres in Stockholm, Sweden. Group interviews were conducted with 30 nurses. The results describe how district nurses strive to stay on track in order to follow clinical guidelines and remain motivated despite prolonged wound treatment and feelings of hopelessness. Three main obstacles to following the guidelines were found. District nurses used compensating strategies so the obstacles would not lead to negative consequences. If the compensating strategies were insufficient, perceived prolonged wound treatment and feelings of hopelessness could result. District nurses then used motivating strategies to overcome these feelings of hopelessness. Sometimes, despite the motivating strategies, treatment in accordance with guidelines could not be achieved. With some patients, district nurses had to compromise and follow the guidelines as far as possible. PMID:28747091

Statistics of Stacked Strata on Experimental Shelf Margins

NASA Astrophysics Data System (ADS)

Fernandes, A. M.; Straub, K. M.

2015-12-01

Continental margin deposits provide the most complete record on Earth of paleo-landscapes, but these records are complex and difficult to interpret. To a seismic geomorphologist or stratigrapher, mapped surfaces often present a static diachronous record of these landscapes through time. We present data that capture the dynamics of experimental shelf-margin landscapes at high-temporal resolution and define internal hierarchies within stacked channelized and weakly channelized deposits from the shelf to the slope. Motivated by observations from acoustically-imaged continental margins offshore Brunei and in the Gulf of Mexico, we use physical experiments to quantify stratal patterns of sub-aqueous slope channels and lobes that are linked to delta-top channels. The data presented here are from an experiment that was run for 26 hours of experimental run time. Overhead photographs and topographic scans captured flow dynamics and surface aggradation/degradation every ten minutes. Currents rich in sediment built a delta that prograded to the shelf-edge. These currents were designed to plunge at the shoreline and travel as turbidity currents beyond the delta and onto the continental slope. Pseudo-subsidence was imposed by a slight base-level rise that generated accommodation space and promoted the construction of stratigraphy on the delta-top. Compensational stacking is a term that is frequently applied to deposits that tend to fill in topographic lows in channelized and weakly channelized systems. The compensation index, a metric used to quantify the strength of compensation, is used here to characterize deposits at different temporal scales on the experimental landscape. The compensation timescale is the characteristic time at which the accumulated deposits begins to match the shape of basin-wide subsidence rates (uniform for these experiments). We will use the compensation indices along strike transects across the delta, proximal slope and distal slope to evaluate the degree of compensation and the trends in the compensation time-scale, tied to a reduced degree of channelization in the down-slope direction.

Enhanced damping for bridge cables using a self-sensing MR damper

NASA Astrophysics Data System (ADS)

Chen, Z. H.; Lam, K. H.; Ni, Y. Q.

2016-08-01

This paper investigates enhanced damping for protecting bridge stay cables from excessive vibration using a newly developed self-sensing magnetorheological (MR) damper. The semi-active control strategy for effectively operating the self-sensing MR damper is formulated based on the linear-quadratic-Gaussian (LQG) control by further considering a collocated control configuration, limited measurements and nonlinear damper dynamics. Due to its attractive feature of sensing-while-damping, the self-sensing MR damper facilitates the collocated control. On the other hand, only the sensor measurements from the self-sensing device are employed in the feedback control. The nonlinear dynamics of the self-sensing MR damper, represented by a validated Bayesian NARX network technique, are further accommodated in the control formulation to compensate for its nonlinearities. Numerical and experimental investigations are conducted on stay cables equipped with the self-sensing MR damper operated in passive and semi-active control modes. The results verify that the collocated self-sensing MR damper facilitates smart damping for inclined cables employing energy-dissipative LQG control with only force and displacement measurements at the damper. It is also demonstrated that the synthesis of nonlinear damper dynamics in the LQG control enhances damping force tracking efficiently, explores the features of the self-sensing MR damper, and achieves better control performance over the passive MR damping control and the Heaviside step function-based LQG control that ignores the damper dynamics.

Compensation and additivity of anthropogenic mortality: life-history effects and review of methods.

PubMed

Péron, Guillaume

2013-03-01

Demographic compensation, the increase in average individual performance following a perturbation that reduces population size, and, its opposite, demographic overadditivity (or superadditivity) are central processes in both population ecology and wildlife management. A continuum of population responses to changes in cause-specific mortality exists, of which additivity and complete compensation constitute particular points. The position of a population on that continuum influences its ability to sustain exploitation and predation. Here I describe a method for quantifying where a population is on the continuum. Based on variance-covariance formulae, I describe a simple metric for the rate of compensation-additivity. I synthesize the results from 10 wildlife capture-recapture monitoring programmes from the literature and online databases, reviewing current statistical methods and the treatment of common sources of bias. These results are used to test hypotheses regarding the effects of life-history strategy, population density, average cause-specific mortality and age class on the rate of compensation-additivity. This comparative analysis highlights that long-lived species compensate less than short-lived species and that populations below their carrying capacity compensate less than those above. © 2012 The Authors. Journal of Animal Ecology © 2012 British Ecological Society.

Energy compensation following consumption of sugar-reduced products: a randomized controlled trial.

PubMed

Markey, Oonagh; Le Jeune, Julia; Lovegrove, Julie A

2016-09-01

Consumption of sugar-reformulated products (commercially available foods and beverages that have been reduced in sugar content through reformulation) is a potential strategy for lowering sugar intake at a population level. The impact of sugar-reformulated products on body weight, energy balance (EB) dynamics and cardiovascular disease risk indicators has yet to be established. The REFORMulated foods (REFORM) study examined the impact of an 8-week sugar-reformulated product exchange on body weight, EB dynamics, blood pressure, arterial stiffness, glycemia and lipemia. A randomized, controlled, double-blind, crossover dietary intervention study was performed with fifty healthy normal to overweight men and women (age 32.0 ± 9.8 year, BMI 23.5 ± 3.0 kg/m(2)) who were randomly assigned to consume either regular sugar or sugar-reduced foods and beverages for 8 weeks, separated by 4-week washout period. Body weight, energy intake (EI), energy expenditure and vascular markers were assessed at baseline and after both interventions. We found that carbohydrate (P < 0.001), total sugars (P < 0.001) and non-milk extrinsic sugars (P < 0.001) (% EI) were lower, whereas fat (P = 0.001) and protein (P = 0.038) intakes (% EI) were higher on the sugar-reduced than the regular diet. No effects on body weight, blood pressure, arterial stiffness, fasting glycemia or lipemia were observed. Consumption of sugar-reduced products, as part of a blinded dietary exchange for an 8-week period, resulted in a significant reduction in sugar intake. Body weight did not change significantly, which we propose was due to energy compensation.

Cold adaptation mechanisms in the ghost moth Hepialus xiaojinensis: Metabolic regulation and thermal compensation.

PubMed

Zhu, Wei; Zhang, Huan; Li, Xuan; Meng, Qian; Shu, Ruihao; Wang, Menglong; Zhou, Guiling; Wang, Hongtuo; Miao, Lin; Zhang, Jihong; Qin, Qilian

2016-02-01

Ghost moths (Lepidoptera: Hepialidae) are cold-adapted stenothermal species inhabiting alpine meadows on the Tibetan Plateau. They have an optimal developmental temperature of 12-16 °C but can maintain feeding and growth at 0 °C. Their survival strategies have received little attention, but these insects are a promising model for environmental adaptation. Here, biochemical adaptations and energy metabolism in response to cold were investigated in larvae of the ghost moth Hepialus xiaojinensis. Metabolic rate and respiratory quotient decreased dramatically with decreasing temperature (15-4 °C), suggesting that the energy metabolism of ghost moths, especially glycometabolism, was sensitive to cold. However, the metabolic rate at 4 °C increased with the duration of cold exposure, indicating thermal compensation to sustain energy budgets under cold conditions. Underlying regulation strategies were studied by analyzing metabolic differences between cold-acclimated (4 °C for 48 h) and control larvae (15 °C). In cold-acclimated larvae, the energy generating pathways of carbohydrates, instead of the overall consumption of carbohydrates, was compensated in the fat body by improving the transcription of related enzymes. The mobilization of lipids was also promoted, with higher diacylglycerol, monoacylglycerol and free fatty acid content in hemolymph. These results indicated that cold acclimation induced a reorganization on metabolic structure to prioritise energy metabolism. Within the aerobic process, flux throughout the tricarboxylic acid (TCA) cycle was encouraged in the fat body, and the activity of α-ketoglutarate dehydrogenase was the likely compensation target. Increased mitochondrial cristae density was observed in the midgut of cold-acclimated larvae. The thermal compensation strategies in this ghost moth span the entire process of energy metabolism, including degration of metabolic substrate, TCA cycle and oxidative phosphorylation, and from an energy budget perspective explains how ghost moths sustain physiological activity in cold environments. Copyright © 2015 Elsevier Ltd. All rights reserved.

[Ecological compensation standard in Dongting Lake region of returning cropland to lake based on emergy analysis].

PubMed

Mao, De-Hua; Hu, Guang-Wei; Liu, Hui-Jie; Li, Zheng-Zui; Li, Zhi-Long; Tan, Zi-Fang

2014-02-01

The annual emergy and currency value of the main ecological service value of returning cropland to lake in Dongting Lake region from 1999 to 2010 was calculated based on emergy analysis. The calculation method of ecological compensation standard was established by calculating annual total emergy of ecological service function increment since the starting year of returning cropland to lake, and the annual ecological compensation standard and compensation area were analyzed from 1999 to 2010. The results indicated that ecological compensation standard from 1999 to 2010 was 40.31-86.48 yuan x m(-2) with the mean of 57.33 yuan x m(-2). The ecological compensation standard presented an increase trend year by year due to the effect of eco-recovery of returning cropland to lake. The ecological compensation standard in the research area presented a swift and steady growth trend after 2005 mainly due to the intensive economy development of Hunan Province, suggesting the value of natural ecological resources would increase along with the development of society and economy. Appling the emergy analysis to research the ecological compensation standard could reveal the dynamics of annual ecological compensation standard, solve the abutment problem of matter flow, energy flow and economic flow, and overcome the subjective and arbitrary of environment economic methods. The empirical research of ecological compensation standard in Dongting Lake region showed that the emergy analysis was feasible and advanced.

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.

Using particle swarm optimization to enhance PI controller performances for active and reactive power control in wind energy conversion systems

NASA Astrophysics Data System (ADS)

Taleb, M.; Cherkaoui, M.; Hbib, M.

2018-05-01

Recently, renewable energy sources are impacting seriously power quality of the grids in term of frequency and voltage stability, due to their intermittence and less forecasting accuracy. Among these sources, wind energy conversion systems (WECS) received a great interest and especially the configuration with Doubly Fed Induction Generator. However, WECS strongly nonlinear, are making their control not easy by classical approaches such as a PI. In this paper, we continue deepen study of PI controller used in active and reactive power control of this kind of WECS. Particle Swarm Optimization (PSO) is suggested to improve its dynamic performances and its robustness against parameters variations. This work highlights the performances of PSO optimized PI control against classical PI tuned with poles compensation strategy. Simulations are carried out on MATLAB-SIMULINK software.

Global finite-time attitude stabilization for rigid spacecraft in the exponential coordinates

NASA Astrophysics Data System (ADS)

Shi, Xiao-Ning; Zhou, Zhi-Gang; Zhou, Di

2018-06-01

This paper addresses the global finite-time attitude stabilisation problem on the special orthogonal group (SO(3)) for a rigid spacecraft via homogeneous feedback approach. Considering the topological and geometric properties of SO(3), the logarithm map is utilised to transform the stabilisation problem on SO(3) into the one on its associated Lie algebra (?). A model-independent discontinuous state feedback plus dynamics compensation scheme is constructed to achieve the global finite-time attitude stabilisation in a coordinate-invariant way. In addition, to address the absence of angular velocity measurements, a sliding mode observer is proposed to reconstruct the unknown angular velocity information within finite time. Then, an observer-based finite-time output feedback control strategy is obtained. Numerical simulations are finally performed to demonstrate the effectiveness of the proposed finite-time controllers.

Communicative Strategies Used by Spouses of Individuals with Communication Disorders Related to Stroke-Induced Aphasia and Parkinson's Disease

ERIC Educational Resources Information Center

Carlsson, Emilia; Hartelius, Lena; Saldert, Charlotta

2014-01-01

Background: A communicative disability interferes with the affected person's ability to take active part in social interaction, but non-disabled communication partners may use different strategies to support communication. However, it is not known whether similar strategies can be used to compensate for different types of communicative…

Active Wireline Heave Compensation for Ocean Drilling

NASA Astrophysics Data System (ADS)

Goldberg, D.; Liu, T.; Swain, K.; Furman, C.; Iturrino, G. J.

2014-12-01

The up-and-down heave motion of a ship causes a similar motion on any instruments tethered on wireline cable below it. If the amplitude of this motion is greater than a few tens of cm, significant discrepancy in the depth below the ship is introduced, causing uncertainty in the acquired data. Large and irregular cabled motions also increase the risk of damaging tethered instruments, particularly those with relatively delicate sensors. In 2005, Schlumberger and Deep Down, Inc built an active wireline heave compensator (AHC) system for use onboard the JOIDES Resolution to compensate for heave motion on wireline logging tools deployed in scientific drill holes. The goals for the new AHC system were to (1) design a reliable heave compensation system; and (2) devise a robust and quantitative methodology for routine assessment of compensation efficiency (CE) during wireline operations. Software programs were developed to monitor CE and the dynamics of logging tools in real-time, including system performance under variable parameters such as water depth, sea state, cable length, logging speed and direction. We present the CE results from the AHC system on the JOIDES Resolution during a 5-year period of recent IODP operations and compare the results to those from previous compensation systems deployed during ODP and IODP. Based on new data under heave conditions of ±0.2-2.0 m and water depths of 300-4,800 m in open holes, the system reduces 65-80% of downhole tool displacement under stationary conditions and 50-60% during normal logging operations. Moreover, down/up tool motion at low speeds (300-600 m/h) reduces the system's CE values by 15-20%, and logging down at higher speeds (1,000-1,200 m/h) reduces CE values by 55-65%. Furthermore, the system yields slightly lower CE values of 40-50% without tension feedback of the downhole cable while logging. These results indicate that the new system's compensation efficiency is comparable to or better than previous systems, with additional advantages that include upgradable compensation control software and the capability for continued assessment under varying environmental conditions. Future integration of downhole cable dynamics as an input feedback could further improve CE during logging operations.­

Effects of Dynamic Topography on the Cenozoic Carbonate Compensation Depth

NASA Astrophysics Data System (ADS)

Campbell, Siobhan M.; Moucha, Robert; Derry, Louis A.; Raymo, Maureen E.

2018-04-01

Reconstructions of the carbonate compensation depth (CCD) in the past have been used to inform hypotheses about the nature of weathering, tectonics, climate change, and the major ion content of the world's oceans over the Cenozoic. These reconstructions are sensitive to uncertainties in the input data, in particular, the paleodepth estimates of sediment cores. Here we propose that a significant, previously unconsidered contributor to uncertainties in paleodepth estimates is from dynamic topography produced by radial stresses exerted on the Earth's surface by the convecting mantle; these stresses can warp the ocean floor by hundreds of meters over broad regions and also vary significantly over millions of years. We present new reconstructions of the equatorial Pacific and Indian Ocean CCDs over the last 30 and 23 Myr, respectively, which demonstrate an overall deepening trend since the Miocene, and illustrate the possible effect of long-term changes in dynamic topography on these reconstructions.

Role of Dynamics in the Autoinhibition and Activation of the Exchange Protein Directly Activated by Cyclic AMP (EPAC)*

PubMed Central

VanSchouwen, Bryan; Selvaratnam, Rajeevan; Fogolari, Federico; Melacini, Giuseppe

2011-01-01

The exchange protein directly activated by cAMP (EPAC) is a key receptor of cAMP in eukaryotes and controls critical signaling pathways. Currently, no residue resolution information is available on the full-length EPAC dynamics, which are known to be pivotal determinants of allostery. In addition, no information is presently available on the intermediates for the classical induced fit and conformational selection activation pathways. Here these questions are addressed through molecular dynamics simulations on five key states along the thermodynamic cycle for the cAMP-dependent activation of a fully functional construct of EPAC2, which includes the cAMP-binding domain and the integral catalytic region. The simulations are not only validated by the agreement with the experimental trends in cAMP-binding domain dynamics determined by NMR, but they also reveal unanticipated dynamic attributes, rationalizing previously unexplained aspects of EPAC activation and autoinhibition. Specifically, the simulations show that cAMP binding causes an extensive perturbation of dynamics in the distal catalytic region, assisting the recognition of the Rap1b substrate. In addition, analysis of the activation intermediates points to a possible hybrid mechanism of EPAC allostery incorporating elements of both the induced fit and conformational selection models. In this mechanism an entropy compensation strategy results in a low free-energy pathway of activation. Furthermore, the simulations indicate that the autoinhibitory interactions of EPAC are more dynamic than previously anticipated, leading to a revised model of autoinhibition in which dynamics fine tune the stability of the autoinhibited state, optimally sensitizing it to cAMP while avoiding constitutive activation. PMID:21873431

Using higher doses to compensate for tubing residuals in extended-infusion piperacillin-tazobactam.

PubMed

Lam, Wendy J; Bhowmick, Tanaya; Gross, Alan; Vanschooneveld, Trevor C; Weinstein, Melvin P

2013-06-01

To mathematically assess drug losses due to infusion line residuals and evaluate methods to compensate for drug loss due to residual volumes in intravenous pump tubing. Literature was accessed through Ovid MEDLINE (1996-February 2013), using combinations of the search terms tubing residuals, residual volume, residual medication, intravenous infusions, intravenous injections, piperacillin, piperacillin-tazobactam, β-lactams, equipment design, infusion pumps, extended infusion, extended administration, and prolonged infusion. In addition, select reference citations from publications identified were reviewed. All articles that involved extended-infusion piperacillin-tazobactam implementation strategies were included in the review. Infusion pump characteristics and tubing residuals can affect extended-infusion piperacillin-tazobactam dosing strategies. Two studies addressing tubing residuals were identified. Both studies recommended increasing infusion volumes to compensate for tubing residuals. One study also recommended decreasing infusion-line dead space by using alternative infusion pump systems. Study calculations suggest that higher doses of piperacillin-tazobactam may be used to account for medication left in tubing residuals if alternative infusion pump systems cannot be obtained, and increased infusion volumes are not an option. Extended-infusion piperacillin-tazobactam has been used as a method of maximizing pharmacodynamic target attainment. Use of higher doses of piperacillin-tazobactam may be a reasonable method to compensate for drug loss due to residual volumes in large-bore intravenous pump tubing.

Volumetric error modeling, identification and compensation based on screw theory for a large multi-axis propeller-measuring machine

NASA Astrophysics Data System (ADS)

Zhong, Xuemin; Liu, Hongqi; Mao, Xinyong; Li, Bin; He, Songping; Peng, Fangyu

2018-05-01

Large multi-axis propeller-measuring machines have two types of geometric error, position-independent geometric errors (PIGEs) and position-dependent geometric errors (PDGEs), which both have significant effects on the volumetric error of the measuring tool relative to the worktable. This paper focuses on modeling, identifying and compensating for the volumetric error of the measuring machine. A volumetric error model in the base coordinate system is established based on screw theory considering all the geometric errors. In order to fully identify all the geometric error parameters, a new method for systematic measurement and identification is proposed. All the PIGEs of adjacent axes and the six PDGEs of the linear axes are identified with a laser tracker using the proposed model. Finally, a volumetric error compensation strategy is presented and an inverse kinematic solution for compensation is proposed. The final measuring and compensation experiments have further verified the efficiency and effectiveness of the measuring and identification method, indicating that the method can be used in volumetric error compensation for large machine tools.

MO-FG-BRA-07: Intrafractional Motion Effect Can Be Minimized in Tomotherapy Stereotactic Body Radiotherapy (SBRT)

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

Price, A; Chang, S; Matney, J

2016-06-15

Purpose: Tomotherapy has unique challenges in handling intrafractional motion compared to conventional LINAC. In this study, we analyzed the impact of intrafractional motion on cumulative dosimetry using actual patient motion data and investigated real time jaw/MLC compensation approaches to minimize the motion-induced dose discrepancy in Tomotherapy SBRT treatment. Methods: Intrafractional motion data recorded in two CyberKnife lung treatment cases through fiducial tracking and two LINAC prostate cases through Calypso tracking were used in this study. For each treatment site, one representative case has an average motion (6mm) and one has a large motion (10mm for lung and 15mm for prostate).more » The cases were re-planned on Tomotherapy for SBRT. Each case was planned with 3 different jaw settings: 1cm static, 2.5cm dynamic, and 5cm dynamic. 4D dose accumulation software was developed to compute dose with the recorded motions and theoretically compensate motions by modifying original jaw and MLC to track the trajectory of the tumor. Results: PTV coverage in Tomotherapy SBRT for patients with intrafractional motion depends on motion type, amplitude and plan settings. For the prostate patient with large motion, PTV coverage changed from 97.2% (motion-free) to 47.1% (target motion-included), 96.6% to 58.5% and 96.3% to 97.8% for the 1cm static jaw, 2.5cm dynamic jaw and 5cm dynamic jaw setting, respectively. For the lung patient with large motion, PTV coverage discrepancies showed a similar trend of change. When the jaw and MLC compensation program was engaged, the motion compromised PTV coverage was recovered back to >95% for all cases and plans. All organs at risk (OAR) were spared with < 5% increase from original motion-free plans. Conclusion: Tomotherapy SBRT is less motion-impacted when 5cm dynamic jaw is used. Once the motion pattern is known, the jaw and MLC compensation program can largely minimize the compromised target coverage and OAR sparing.« less

Maintenance of Mitochondrial Oxygen Homeostasis by Cosubstrate Compensation

PubMed Central

Kueh, Hao Yuan; Niethammer, Philipp; Mitchison, Timothy J.

2013-01-01

Mitochondria maintain a constant rate of aerobic respiration over a wide range of oxygen levels. However, the control strategies underlying oxygen homeostasis are still unclear. Using mathematical modeling, we found that the mitochondrial electron transport chain (ETC) responds to oxygen level changes by undergoing compensatory changes in reduced electron carrier levels. This emergent behavior, which we named cosubstrate compensation (CSC), enables the ETC to maintain homeostasis over a wide of oxygen levels. When performing CSC, our ETC models recapitulated a classic scaling relationship discovered by Chance [Chance B (1965) J. Gen. Physiol. 49:163-165] relating the extent of oxygen homeostasis to the kinetics of mitochondrial electron transport. Analysis of an in silico mitochondrial respiratory system further showed evidence that CSC constitutes the dominant control strategy for mitochondrial oxygen homeostasis during active respiration. Our findings indicate that CSC constitutes a robust control strategy for homeostasis and adaptation in cellular biochemical networks. PMID:23528093

Pathogen dynamics during invasion and establishment of white-nose syndrome explain mechanisms of host persistence.

PubMed

Frick, Winifred F; Cheng, Tina L; Langwig, Kate E; Hoyt, Joseph R; Janicki, Amanda F; Parise, Katy L; Foster, Jeffrey T; Kilpatrick, A Marm

2017-03-01

Disease dynamics during pathogen invasion and establishment determine the impacts of disease on host populations and determine the mechanisms of host persistence. Temporal progression of prevalence and infection intensity illustrate whether tolerance, resistance, reduced transmission, or demographic compensation allow initially declining populations to persist. We measured infection dynamics of the fungal pathogen Pseudogymnoascus destructans that causes white-nose syndrome in bats by estimating pathogen prevalence and load in seven bat species at 167 hibernacula over a decade as the pathogen invaded, became established, and some host populations stabilized. Fungal loads increased rapidly and prevalence rose to nearly 100% at most sites within 2 yr of invasion in six of seven species. Prevalence and loads did not decline over time despite huge reductions in colony sizes, likely due to an extensive environmental reservoir. However, there was substantial variation in fungal load among sites with persisting colonies, suggesting that both tolerance and resistance developed at different sites in the same species. In contrast, one species disappeared from hibernacula within 3 yr of pathogen invasion. Variable host responses to pathogen invasion require different management strategies to prevent disease-induced extinction and to facilitate evolution of tolerance or resistance in persisting populations. © 2016 by the Ecological Society of America.

Protecting the next generation: what is the role of the duration of human papillomavirus vaccine-related immunity?

PubMed

Günther, Oliver P; Ogilvie, Gina; Naus, Monika; Young, Eric; Patrick, David M; Dobson, Simon; Duval, Bernard; Noël, Pierre-André; Marra, Fawziah; Miller, Dianne; Brunham, Robert C; Pourbohloul, Babak

2008-06-15

There is strong evidence that human papillomavirus (HPV) is necessary for the development of cervical cancer. A prophylactic HPV vaccine with high reported efficacy was approved in North America in 2006. A mathematical model of HPV transmission dynamics was used to simulate different scenarios of natural disease outcomes and intervention strategies. A sensitivity analysis was performed to compensate for uncertainties surrounding key epidemiological parameters. The expected impact that HPV vaccines have on cervical cancer incidence and HPV prevalence in the province of British Columbia in Canada revealed that, for lifelong vaccine-related protection, an immunization routine targeting younger females (grade 6), combined with a 3-year program for adolescent females (grade 9), is the most effective strategy. If vaccine-related protection continues for <10 years, then the targeting of adolescent females would be more beneficial than the targeting of younger females. The incremental benefit if boys, as well as girls, are vaccinated is small. Optimization of the design of immunization strategies for treatment of HPV depends substantially on the duration of vaccine-induced immunity. Given the uncertainty in estimating this duration, it may be prudent to assume a value close to the lower limit reported and adjust the program when more-accurate information for the length of vaccine-induced immunity becomes available.

Optimal orientation in flows: providing a benchmark for animal movement strategies.

PubMed

McLaren, James D; Shamoun-Baranes, Judy; Dokter, Adriaan M; Klaassen, Raymond H G; Bouten, Willem

2014-10-06

Animal movements in air and water can be strongly affected by experienced flow. While various flow-orientation strategies have been proposed and observed, their performance in variable flow conditions remains unclear. We apply control theory to establish a benchmark for time-minimizing (optimal) orientation. We then define optimal orientation for movement in steady flow patterns and, using dynamic wind data, for short-distance mass movements of thrushes (Turdus sp.) and 6000 km non-stop migratory flights by great snipes, Gallinago media. Relative to the optimal benchmark, we assess the efficiency (travel speed) and reliability (success rate) of three generic orientation strategies: full compensation for lateral drift, vector orientation (single-heading movement) and goal orientation (continually heading towards the goal). Optimal orientation is characterized by detours to regions of high flow support, especially when flow speeds approach and exceed the animal's self-propelled speed. In strong predictable flow (short distance thrush flights), vector orientation adjusted to flow on departure is nearly optimal, whereas for unpredictable flow (inter-continental snipe flights), only goal orientation was near-optimally reliable and efficient. Optimal orientation provides a benchmark for assessing efficiency of responses to complex flow conditions, thereby offering insight into adaptive flow-orientation across taxa in the light of flow strength, predictability and navigation capacity.

Optimal orientation in flows: providing a benchmark for animal movement strategies

PubMed Central

McLaren, James D.; Shamoun-Baranes, Judy; Dokter, Adriaan M.; Klaassen, Raymond H. G.; Bouten, Willem

2014-01-01

Animal movements in air and water can be strongly affected by experienced flow. While various flow-orientation strategies have been proposed and observed, their performance in variable flow conditions remains unclear. We apply control theory to establish a benchmark for time-minimizing (optimal) orientation. We then define optimal orientation for movement in steady flow patterns and, using dynamic wind data, for short-distance mass movements of thrushes (Turdus sp.) and 6000 km non-stop migratory flights by great snipes, Gallinago media. Relative to the optimal benchmark, we assess the efficiency (travel speed) and reliability (success rate) of three generic orientation strategies: full compensation for lateral drift, vector orientation (single-heading movement) and goal orientation (continually heading towards the goal). Optimal orientation is characterized by detours to regions of high flow support, especially when flow speeds approach and exceed the animal's self-propelled speed. In strong predictable flow (short distance thrush flights), vector orientation adjusted to flow on departure is nearly optimal, whereas for unpredictable flow (inter-continental snipe flights), only goal orientation was near-optimally reliable and efficient. Optimal orientation provides a benchmark for assessing efficiency of responses to complex flow conditions, thereby offering insight into adaptive flow-orientation across taxa in the light of flow strength, predictability and navigation capacity. PMID:25056213

Characterization and Compensation of Network-Level Anomalies in Mixed-Signal Neuromorphic Modeling Platforms

PubMed Central

Petrovici, Mihai A.; Vogginger, Bernhard; Müller, Paul; Breitwieser, Oliver; Lundqvist, Mikael; Muller, Lyle; Ehrlich, Matthias; Destexhe, Alain; Lansner, Anders; Schüffny, René; Schemmel, Johannes; Meier, Karlheinz

2014-01-01

Advancing the size and complexity of neural network models leads to an ever increasing demand for computational resources for their simulation. Neuromorphic devices offer a number of advantages over conventional computing architectures, such as high emulation speed or low power consumption, but this usually comes at the price of reduced configurability and precision. In this article, we investigate the consequences of several such factors that are common to neuromorphic devices, more specifically limited hardware resources, limited parameter configurability and parameter variations due to fixed-pattern noise and trial-to-trial variability. Our final aim is to provide an array of methods for coping with such inevitable distortion mechanisms. As a platform for testing our proposed strategies, we use an executable system specification (ESS) of the BrainScaleS neuromorphic system, which has been designed as a universal emulation back-end for neuroscientific modeling. We address the most essential limitations of this device in detail and study their effects on three prototypical benchmark network models within a well-defined, systematic workflow. For each network model, we start by defining quantifiable functionality measures by which we then assess the effects of typical hardware-specific distortion mechanisms, both in idealized software simulations and on the ESS. For those effects that cause unacceptable deviations from the original network dynamics, we suggest generic compensation mechanisms and demonstrate their effectiveness. Both the suggested workflow and the investigated compensation mechanisms are largely back-end independent and do not require additional hardware configurability beyond the one required to emulate the benchmark networks in the first place. We hereby provide a generic methodological environment for configurable neuromorphic devices that are targeted at emulating large-scale, functional neural networks. PMID:25303102

Characterization and compensation of network-level anomalies in mixed-signal neuromorphic modeling platforms.

PubMed

Petrovici, Mihai A; Vogginger, Bernhard; Müller, Paul; Breitwieser, Oliver; Lundqvist, Mikael; Muller, Lyle; Ehrlich, Matthias; Destexhe, Alain; Lansner, Anders; Schüffny, René; Schemmel, Johannes; Meier, Karlheinz

2014-01-01

Advancing the size and complexity of neural network models leads to an ever increasing demand for computational resources for their simulation. Neuromorphic devices offer a number of advantages over conventional computing architectures, such as high emulation speed or low power consumption, but this usually comes at the price of reduced configurability and precision. In this article, we investigate the consequences of several such factors that are common to neuromorphic devices, more specifically limited hardware resources, limited parameter configurability and parameter variations due to fixed-pattern noise and trial-to-trial variability. Our final aim is to provide an array of methods for coping with such inevitable distortion mechanisms. As a platform for testing our proposed strategies, we use an executable system specification (ESS) of the BrainScaleS neuromorphic system, which has been designed as a universal emulation back-end for neuroscientific modeling. We address the most essential limitations of this device in detail and study their effects on three prototypical benchmark network models within a well-defined, systematic workflow. For each network model, we start by defining quantifiable functionality measures by which we then assess the effects of typical hardware-specific distortion mechanisms, both in idealized software simulations and on the ESS. For those effects that cause unacceptable deviations from the original network dynamics, we suggest generic compensation mechanisms and demonstrate their effectiveness. Both the suggested workflow and the investigated compensation mechanisms are largely back-end independent and do not require additional hardware configurability beyond the one required to emulate the benchmark networks in the first place. We hereby provide a generic methodological environment for configurable neuromorphic devices that are targeted at emulating large-scale, functional neural networks.

Physiological impacts of elevated carbon dioxide and ocean acidification on fish.

PubMed

Heuer, Rachael M; Grosell, Martin

2014-11-01

Most fish studied to date efficiently compensate for a hypercapnic acid-base disturbance; however, many recent studies examining the effects of ocean acidification on fish have documented impacts at CO2 levels predicted to occur before the end of this century. Notable impacts on neurosensory and behavioral endpoints, otolith growth, mitochondrial function, and metabolic rate demonstrate an unexpected sensitivity to current-day and near-future CO2 levels. Most explanations for these effects seem to center on increases in Pco2 and HCO3- that occur in the body during pH compensation for acid-base balance; however, few studies have measured these parameters at environmentally relevant CO2 levels or directly related them to reported negative endpoints. This compensatory response is well documented, but noted variation in dynamic regulation of acid-base transport pathways across species, exposure levels, and exposure duration suggests that multiple strategies may be utilized to cope with hypercapnia. Understanding this regulation and changes in ion gradients in extracellular and intracellular compartments during CO2 exposure could provide a basis for predicting sensitivity and explaining interspecies variation. Based on analysis of the existing literature, the present review presents a clear message that ocean acidification may cause significant effects on fish across multiple physiological systems, suggesting that pH compensation does not necessarily confer tolerance as downstream consequences and tradeoffs occur. It remains difficult to assess if acclimation responses during abrupt CO2 exposures will translate to fitness impacts over longer timescales. Nonetheless, identifying mechanisms and processes that may be subject to selective pressure could be one of many important components of assessing adaptive capacity. Copyright © 2014 the American Physiological Society.

Adaptive Fading Memory H∞ Filter Design for Compensation of Delayed Components in Self Powered Flux Detectors

NASA Astrophysics Data System (ADS)

Tamboli, Prakash Kumar; Duttagupta, Siddhartha P.; Roy, Kallol

2015-08-01

The paper deals with dynamic compensation of delayed Self Powered Flux Detectors (SPFDs) using discrete time H∞ filtering method for improving the response of SPFDs with significant delayed components such as Platinum and Vanadium SPFD. We also present a comparative study between the Linear Matrix Inequality (LMI) based H∞ filtering and Algebraic Riccati Equation (ARE) based Kalman filtering methods with respect to their delay compensation capabilities. Finally an improved recursive H∞ filter based on the adaptive fading memory technique is proposed which provides an improved performance over existing methods. The existing delay compensation algorithms do not account for the rate of change in the signal for determining the filter gain and therefore add significant noise during the delay compensation process. The proposed adaptive fading memory H∞ filter minimizes the overall noise very effectively at the same time keeps the response time at minimum values. The recursive algorithm is easy to implement in real time as compared to the LMI (or ARE) based solutions.

Compensation Still Matters: Language Learning Strategies in Third Millennium ESL Learners

ERIC Educational Resources Information Center

Shakarami, Alireza; Hajhashemi, Karim; Caltabiano, Nerina J.

2017-01-01

Digital media play enormous roles in much of the learning, communication, socializing, and ways of working for "Net-Generation" learners who are growing up in a wired world. Living in this digital era may require different ways of communicating, thinking, approaching learning, prioritizing strategies, interpersonally communicating, and…

Dynamic simulation of Static Var Compensators in distribution systems

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

Koessler, R.J.

1992-08-01

This paper is a system study guide for the correction of voltage dips due to large motor startups with Static Var Compensators (SVCs). The method utilizes time simulations, which are an important aid in the equipment design and specification. The paper illustrates the process of setting-up a computer model and performing time simulations. The study process is demonstrated through an example, the Shawnee feeder in the Niagara Mohawk Power Corporation service area.

Investigation of influence of errors of cutting machines with CNC on displacement trajectory accuracy of their actuating devices

NASA Astrophysics Data System (ADS)

Fedonin, O. N.; Petreshin, D. I.; Ageenko, A. V.

2018-03-01

In the article, the issue of increasing a CNC lathe accuracy by compensating for the static and dynamic errors of the machine is investigated. An algorithm and a diagnostic system for a CNC machine tool are considered, which allows determining the errors of the machine for their compensation. The results of experimental studies on diagnosing and improving the accuracy of a CNC lathe are presented.

Influence of vision on head stabilization strategies in older adults during walking.

PubMed

Cromwell, Ronita L; Newton, Roberta A; Forrest, Gail

2002-07-01

Maintaining balance during dynamic activities is essential for preventing falls in older adults. Head stabilization contributes to dynamic balance, especially during the functional task of walking. Head stability and the role of vision in this process have not been studied during walking in older adults. Seventeen older adults (76.2 +/- 6.9 years) and 20 young adults (26.0 +/- 3.4 years) walked with their eyes open (EO), with their eyes closed (EC), and with fixed gaze (FG). Participants performed three trials of each condition. Sagittal plane head and trunk angular velocities in space were obtained using an infrared camera system with passive reflective markers. Frequency analyses of head-on-trunk with respect to trunk gains and phases were examined for head-trunk movement strategies used for head stability. Average walking velocity, cadence, and peak head velocity were calculated for each condition. Differences between age groups demonstrated that older adults decreased walking velocity in EO (p =.022). FG (p = .021), and EC (p = .022). and decreased cadence during EC (p = .007). Peak head velocity also decreased across conditions (p < .0001) for older adults. Movement patterns demonstrated increased head stability during EO. diminished head stability with EC, and improved head stability with FG as older adult patterns resembled those of young adults. Increased stability of the lower extremity outcome measures for older adults was indicated by reductions in walking velocity and cadence. Concomitant increases in head stability were related to visual tasks. Increased stability may serve as a protective mechanism to prevent falls. Further, vision facilitates the head stabilization process for older adults to compensate for age-related decrements in other sensory systems subserving dynamic balance.

A Hybrid Memetic Framework for Coverage Optimization in Wireless Sensor Networks.

PubMed

Chen, Chia-Pang; Mukhopadhyay, Subhas Chandra; Chuang, Cheng-Long; Lin, Tzu-Shiang; Liao, Min-Sheng; Wang, Yung-Chung; Jiang, Joe-Air

2015-10-01

One of the critical concerns in wireless sensor networks (WSNs) is the continuous maintenance of sensing coverage. Many particular applications, such as battlefield intrusion detection and object tracking, require a full-coverage at any time, which is typically resolved by adding redundant sensor nodes. With abundant energy, previous studies suggested that the network lifetime can be maximized while maintaining full coverage through organizing sensor nodes into a maximum number of disjoint sets and alternately turning them on. Since the power of sensor nodes is unevenly consumed over time, and early failure of sensor nodes leads to coverage loss, WSNs require dynamic coverage maintenance. Thus, the task of permanently sustaining full coverage is particularly formulated as a hybrid of disjoint set covers and dynamic-coverage-maintenance problems, and both have been proven to be nondeterministic polynomial-complete. In this paper, a hybrid memetic framework for coverage optimization (Hy-MFCO) is presented to cope with the hybrid problem using two major components: 1) a memetic algorithm (MA)-based scheduling strategy and 2) a heuristic recursive algorithm (HRA). First, the MA-based scheduling strategy adopts a dynamic chromosome structure to create disjoint sets, and then the HRA is utilized to compensate the loss of coverage by awaking some of the hibernated nodes in local regions when a disjoint set fails to maintain full coverage. The results obtained from real-world experiments using a WSN test-bed and computer simulations indicate that the proposed Hy-MFCO is able to maximize sensing coverage while achieving energy efficiency at the same time. Moreover, the results also show that the Hy-MFCO significantly outperforms the existing methods with respect to coverage preservation and energy efficiency.

Applying dynamic data collection to improve dry electrode system performance for a P300-based brain-computer interface

NASA Astrophysics Data System (ADS)

Clements, J. M.; Sellers, E. W.; Ryan, D. B.; Caves, K.; Collins, L. M.; Throckmorton, C. S.

2016-12-01

Objective. Dry electrodes have an advantage over gel-based ‘wet’ electrodes by providing quicker set-up time for electroencephalography recording; however, the potentially poorer contact can result in noisier recordings. We examine the impact that this may have on brain-computer interface communication and potential approaches for mitigation. Approach. We present a performance comparison of wet and dry electrodes for use with the P300 speller system in both healthy participants and participants with communication disabilities (ALS and PLS), and investigate the potential for a data-driven dynamic data collection algorithm to compensate for the lower signal-to-noise ratio (SNR) in dry systems. Main results. Performance results from sixteen healthy participants obtained in the standard static data collection environment demonstrate a substantial loss in accuracy with the dry system. Using a dynamic stopping algorithm, performance may have been improved by collecting more data in the dry system for ten healthy participants and eight participants with communication disabilities; however, the algorithm did not fully compensate for the lower SNR of the dry system. An analysis of the wet and dry system recordings revealed that delta and theta frequency band power (0.1-4 Hz and 4-8 Hz, respectively) are consistently higher in dry system recordings across participants, indicating that transient and drift artifacts may be an issue for dry systems. Significance. Using dry electrodes is desirable for reduced set-up time; however, this study demonstrates that online performance is significantly poorer than for wet electrodes for users with and without disabilities. We test a new application of dynamic stopping algorithms to compensate for poorer SNR. Dynamic stopping improved dry system performance; however, further signal processing efforts are likely necessary for full mitigation.

Chromatic aberration compensation in numerical reconstruction of digital holograms by Fresnel-Bluestein propagation.

PubMed

Hincapie, Diego; Velasquez, Daniel; Garcia-Sucerquia, Jorge

2017-12-15

In this Letter, we present a method for chromatic compensation in numerical reconstruction of digitally recorded holograms based on Fresnel-Bluestein propagation. The proposed technique is applied to correct the chromatic aberration that arises in the reconstruction of RGB holograms of both millimeter- and micrometer-sized objects. The results show the feasibility of this strategy to remove the wavelength dependence of the size of the numerically propagated wavefields.

Planar-focusing cathodes.

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

Lewellen, J. W.; Noonan, J.; Accelerator Systems Division

2005-01-01

Conventional {pi}-mode rf photoinjectors typically use magnetic solenoids for emittance compensation. This provides independent focusing strength but can complicate rf power feed placement, introduce asymmetries (due to coil crossovers), and greatly increase the cost of the photoinjector. Cathode-region focusing can also provide for a form of emittance compensation. Typically this method strongly couples focusing strength to the field gradient on the cathode, however, and usually requires altering the longitudinal position of the cathode to change the focusing. We propose a new method for achieving cathode-region variable-strength focusing for emittance compensation. The new method reduces the coupling to the gradient onmore » the cathode and does not require a change in the longitudinal position of the cathode. Expected performance for an S-band system is similar to conventional solenoid-based designs. This paper presents the results of rf cavity and beam dynamics simulations of the new design. We have proposed a method for performing emittance compensation using a cathode-region focusing scheme. This technique allows the focusing strength to be adjusted somewhat independently of the on-axis field strength. Beam dynamics calculations indicate performance should be comparable to presently in-use emittance compensation schemes, with a simpler configuration and fewer possibilities for emittance degradation due to the focusing optics. There are several potential difficulties with this approach, including cathode material selection, cathode heating, and peak fields in the gun. We hope to begin experimenting with a cathode of this type in the near future, and several possibilities exist for reducing the peak gradients to more acceptable levels.« less

Effect of water chemistry upsets on the dynamics of corrective reagent dosing systems at thermal power stations

NASA Astrophysics Data System (ADS)

Voronov, V. N.; Yegoshina, O. V.; Bolshakova, N. A.; Yarovoi, V. O.; Latt, Aie Min

2016-12-01

Typical disturbances in the dynamics of a corrective reagent dosing system under unsteady-state conditions during the unsatisfactory operation of a chemical control system with some water chemistry upsets at thermal and nuclear power stations are considered. An experimental setup representing a physical model for the water chemistry control system is described. The two disturbances, which are most frequently encountered in water chemistry control practice, such as a breakdown or shutdown of temperature compensation during pH measurement and an increase in the heat-transfer fluid flow rate, have been modeled in the process of study. The study of the effect produced by the response characteristics of chemical control analyzers on the operation of a reagent dosing system under unsteady-state conditions is important for the operative control of a water chemistry regime state. The effect of temperature compensation during pH measurement on the dynamics of an ammonia-dosing system in the manual and automatic cycle chemistry control modes has been studied. It has been demonstrated that the reading settling time of a pH meter in the manual ammonia- dosing mode grows with a breakdown in temperature compensation and a simultaneous increase in the temperature of a heat-transfer fluid sample. To improve the efficiency of water chemistry control, some systems for the quality control of a heat-transfer fluid by a chemical parameter with the obligatory compensation of a disturbance in its flow rate have been proposed for use. Experimental results will possibly differ from industrial data due to a great length of sampling lines. For this reason, corrective reagent dosing systems must be adapted to the conditions of a certain power-generating unit in the process of their implementation.

In situ magnetic compensation for potassium spin-exchange relaxation-free magnetometer considering probe beam pumping effect.

PubMed

Fang, Jiancheng; Wang, Tao; Quan, Wei; Yuan, Heng; Zhang, Hong; Li, Yang; Zou, Sheng

2014-06-01

A novel method to compensate the residual magnetic field for an atomic magnetometer consisting of two perpendicular beams of polarizations was demonstrated in this paper. The method can realize magnetic compensation in the case where the pumping rate of the probe beam cannot be ignored. In the experiment, the probe beam is always linearly polarized, whereas, the probe beam contains a residual circular component due to the imperfection of the polarizer, which leads to the pumping effect of the probe beam. A simulation of the probe beam's optical rotation and pumping rate was demonstrated. At the optimized points, the wavelength of the probe beam was optimized to achieve the largest optical rotation. Although, there is a small circular component in the linearly polarized probe beam, the pumping rate of the probe beam was non-negligible at the optimized wavelength which if ignored would lead to inaccuracies in the magnetic field compensation. Therefore, the dynamic equation of spin evolution was solved by considering the pumping effect of the probe beam. Based on the quasi-static solution, a novel magnetic compensation method was proposed, which contains two main steps: (1) the non-pumping compensation and (2) the sequence compensation with a very specific sequence. After these two main steps, a three-axis in situ magnetic compensation was achieved. The compensation method was suitable to design closed-loop spin-exchange relaxation-free magnetometer. By a combination of the magnetic compensation and the optimization, the magnetic field sensitivity was approximately 4 fT/Hz(1/2), which was mainly dominated by the noise of the magnetic shield.

Comparing the Nutritional Impact of Dietary Strategies to Reduce Discretionary Choice Intake in the Australian Adult Population: A Simulation Modelling Study.

PubMed

Grieger, Jessica A; Johnson, Brittany J; Wycherley, Thomas P; Golley, Rebecca K

2017-05-03

Dietary strategies to reduce discretionary choice intake are commonly utilized in practice, but evidence on their relative efficacy is lacking. The aim was to compare the potential impact on nutritional intake of three strategies to reducing discretionary choices intake in the Australian adult (19-90 years) population. Dietary simulation modelling using data from the National Nutrition and Physical Activity Survey 2011-2012 was conducted ( n = 9341; one 24 h dietary recall). Strategies modelled were: moderation (reduce discretionary choices by 50%, with 0%, 25% or 75% energy compensation); substitution (replace 50% of discretionary choices with core choices); reformulation (replace 50% SFA with unsaturated fats, reduce added sugars by 25%, and reduce sodium by 20%). Compared to the base case (observed) intake, modelled intakes in the moderation scenario showed: -17.3% lower energy (sensitivity analyses, 25% energy compensation -14.2%; 75% energy compensation -8.0%), -20.9% lower SFA (-17.4%; -10.5%), -43.3% lower added sugars (-41.1%; -36.7%) and 17.7% lower sodium (-14.3%; -7.5%). Substitution with a range of core items, or with fruits, vegetables and core beverages only, resulted in similar changes in energy intake (-13.5% and -15.4%), SFA (-17.7% and -20.1%), added sugars (-42.6% and -43%) and sodium (-13.7% and -16.5%), respectively. Reformulating discretionary choices had minimal impact on reducing energy intake but reduced SFA (-10.3% to -30.9%), added sugars (-9.3% to -52.9%), and alcohol (-25.0% to -49.9%) and sodium (-3.3% to -13.2%). The substitution and reformulation scenarios minimized negative changes in fiber, protein and micronutrient intakes. While each strategy has strengths and limitations, substitution of discretionary choices with core foods and beverages may optimize the nutritional impact.

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

Characterizing the relationship between in-hospital measures and workers' compensation outcomes among severely injured construction workers using a data linkage strategy.

PubMed

Ruestow, Peter S; Friedman, Lee S

2013-10-01

To characterize the relationship between acute measures of severity and three important workers' compensation outcomes associated with a worker's ability to return to work and the cost of a work-related injury. Probabilistic data linkage of workers' compensation claims made by injured construction workers from 2000 to 2005 with two Illinois medical record registries. Multivariable robust regression models were built to assess the relationship between three in-hospital measures and three outcomes captured in the Workers' Compensation data. In the final multivariable models, a categorical increase in injury severity was associated with an extra $7,830 (95% CI: $4,729-$10,930) of monetary compensation awarded, though not with temporary total disability (TTD) or permanent partial disability (PPD). Our models also predicted that every extra day spent in the hospital results in an increase of 0.51 (95% CI: 0.23-0.80) weeks of TTD and an extra $1,248 (95% CI: $810-$1,686) in monetary compensation. Discharge to an intermediate care facility following the initial hospitalization was associated with an increase of 8.15 (95% CI: 4.03-12.28) weeks of TTD and an increase of $23,440 (95% CI: $17,033-$29,847) in monetary compensation. We were able to link data from the initial hospitalization for an injured worker with the final workers' compensation claims decision or settlement. The in-hospital measures of injury severity were associated with total monetary compensation as captured in the workers' compensation process. Copyright © 2013 Wiley Periodicals, Inc.

Novel adaptive neural control design for a constrained flexible air-breathing hypersonic vehicle based on actuator compensation

NASA Astrophysics Data System (ADS)

Bu, Xiangwei; Wu, Xiaoyan; He, Guangjun; Huang, Jiaqi

2016-03-01

This paper investigates the design of a novel adaptive neural controller for the longitudinal dynamics of a flexible air-breathing hypersonic vehicle with control input constraints. To reduce the complexity of controller design, the vehicle dynamics is decomposed into the velocity subsystem and the altitude subsystem, respectively. For each subsystem, only one neural network is utilized to approach the lumped unknown function. By employing a minimal-learning parameter method to estimate the norm of ideal weight vectors rather than their elements, there are only two adaptive parameters required for neural approximation. Thus, the computational burden is lower than the ones derived from neural back-stepping schemes. Specially, to deal with the control input constraints, additional systems are exploited to compensate the actuators. Lyapunov synthesis proves that all the closed-loop signals involved are uniformly ultimately bounded. Finally, simulation results show that the adopted compensation scheme can tackle actuator constraint effectively and moreover velocity and altitude can stably track their reference trajectories even when the physical limitations on control inputs are in effect.

Fixed-Order Mixed Norm Designs for Building Vibration Control

NASA Technical Reports Server (NTRS)

Whorton, Mark S.; Calise, Anthony J.

2000-01-01

This study investigates the use of H2, mu-synthesis, and mixed H2/mu methods to construct full order controllers and optimized controllers of fixed dimensions. The benchmark problem definition is first extended to include uncertainty within the controller bandwidth in the form of parametric uncertainty representative of uncertainty in the natural frequencies of the design model. The sensitivity of H2 design to unmodeled dynamics and parametric uncertainty is evaluated for a range of controller levels of authority. Next, mu-synthesis methods are applied to design full order compensators that are robust to both unmodeled dynamics and to parametric uncertainty. Finally, a set of mixed H2/mu compensators are designed which are optimized for a fixed compensator dimension. These mixed norm designs recover the H2 design performance levels while providing the same levels of robust stability as the mu designs. It is shown that designing with the mixed norm approach permits higher levels of controller authority for which the H2 designs are destabilizing. The benchmark problem is that of an active tendon system. The controller designs are all based on the use of acceleration feedback.

Passive stiffness of coupled wrist and forearm rotations.

PubMed

Drake, Will B; Charles, Steven K

2014-09-01

Coordinated movement requires that the neuromuscular system account and compensate for movement dynamics. One particularly complex aspect of movement dynamics is the interaction that occurs between degrees of freedom (DOF), which may be caused by inertia, damping, and/or stiffness. During wrist rotations, the two DOF of the wrist (flexion-extension and radial-ulnar deviation, FE and RUD) are coupled through interaction torques arising from passive joint stiffness. One important unanswered question is whether the DOF of the forearm (pronation-supination, PS) is coupled to the two DOF of the wrist. Answering this question, and understanding the dynamics of wrist and forearm rotations in general, requires knowledge of the stiffness encountered during rotations involving all three DOF (PS, FE, and RUD). Here we present the first-ever measurement of the passive stiffness encountered during simultaneous wrist and forearm rotations. Using a wrist and forearm robot, we measured coupled wrist and forearm stiffness in 10 subjects and present it as a 3-by-3 stiffness matrix. This measurement of passive wrist and forearm stiffness will enable future studies investigating the dynamics of wrist and forearm rotations, exposing the dynamics for which the neuromuscular system must plan and compensate during movements involving the wrist and forearm.

Patching. Restitching business portfolios in dynamic markets.

PubMed

Eisenhardt, K M; Brown, S L

1999-01-01

In turbulent markets, businesses and opportunities are constantly falling out of alignment. New technologies and emerging markets create fresh opportunities. Converging markets produce more. And of course, some markets fade. In this landscape of continuous flux, it's more important to build corporate-level strategic processes that enable dynamic repositioning than it is to build any particular defensible position. That's why smart corporate strategists use patching, a process of mapping and remapping business units to create a shifting mix of highly focused, tightly aligned businesses that can respond to changing market opportunities. Patching is not just another name for reorganizing; patchers have a distinctive mindset. Traditional managers see structure as stable; patching managers believe structure is inherently temporary. Traditional managers set corporate strategy first, but patching managers keep the organization focused on the right set of business opportunities and let strategy emerge from individual businesses. Although the focus of patching is flexibility, the process itself follows a pattern. Patching changes are usually small in scale and made frequently. Patching should be done quickly; the emphasis is on getting the patch about right and fixing problems later. Patches should have a test drive before they're formalized but then be tightly scripted after they've been announced. And patching won't work without the right infrastructure: modular business units, fine-grained and complete unit-level metrics, and companywide compensation parity. The authors illustrate how patching works and point out some common stumbling blocks.

Analysis and compensation of an aircraft simulator control loading system with compliant linkage. [using hydraulic equipment

NASA Technical Reports Server (NTRS)

Johnson, P. R.; Bardusch, R. E.

1974-01-01

A hydraulic control loading system for aircraft simulation was analyzed to find the causes of undesirable low frequency oscillations and loading effects in the output. The hypothesis of mechanical compliance in the control linkage was substantiated by comparing the behavior of a mathematical model of the system with previously obtained experimental data. A compensation scheme based on the minimum integral of the squared difference between desired and actual output was shown to be effective in reducing the undesirable output effects. The structure of the proposed compensation was computed by use of a dynamic programing algorithm and a linear state space model of the fixed elements in the system.

Coupling Dynamics Interlip Coordination in Lower Lip Load Compensation

ERIC Educational Resources Information Center

van Lieshout, Pascal; Neufeld, Chris

2014-01-01

Purpose: To study the effects of lower lip loading on lower and upper lip movements and their coordination to test predictions on coupling dynamics derived from studies in limb control. Method: Movement data were acquired using electromagnetic midsagittal articulography under 4 conditions: (a) without restrictions, serving as a baseline; (b) with…

Finite BRST-BFV transformations for dynamical systems with second-class constraints

NASA Astrophysics Data System (ADS)

Batalin, Igor A.; Lavrov, Peter M.; Tyutin, Igor V.

2015-06-01

We study finite field-dependent BRST-BFV transformations for dynamical systems with first- and second-class constraints within the generalized Hamiltonian formalism. We find explicitly their Jacobians and the form of a solution to the compensation equation necessary for generating an arbitrary finite change of gauge-fixing functionals in the path integral.

Enhanced power quality based single phase photovoltaic distributed generation system

NASA Astrophysics Data System (ADS)

Panda, Aurobinda; Pathak, M. K.; Srivastava, S. P.

2016-08-01

This article presents a novel control strategy for a 1-ϕ 2-level grid-tie photovoltaic (PV) inverter to enhance the power quality (PQ) of a PV distributed generation (PVDG) system. The objective is to obtain the maximum benefits from the grid-tie PV inverter by introducing current harmonics as well as reactive power compensation schemes in its control strategy, thereby controlling the PV inverter to achieve multiple functions in the PVDG system such as: (1) active power flow control between the PV inverter and the grid, (2) reactive power compensation, and (3) grid current harmonics compensation. A PQ enhancement controller (PQEC) has been designed to achieve the aforementioned objectives. The issue of underutilisation of the PV inverter in nighttime has also been addressed in this article and for the optimal use of the system; the PV inverter is used as a shunt active power filter in nighttime. A prototype model of the proposed system is developed in the laboratory, to validate the effectiveness of the control scheme, and is tested with the help of the dSPACE DS1104 platform.

Feedforward hysteresis compensation in trajectory control of piezoelectrically-driven nanostagers

NASA Astrophysics Data System (ADS)

Bashash, Saeid; Jalili, Nader

2006-03-01

Complex structural nonlinearities of piezoelectric materials drastically degrade their performance in variety of micro- and nano-positioning applications. From the precision positioning and control perspective, the multi-path time-history dependent hysteresis phenomenon is the most concerned nonlinearity in piezoelectric actuators to be analyzed. To realize the underlying physics of this phenomenon and to develop an efficient compensation strategy, the intelligent properties of hysteresis with the effects of non-local memories are discussed. Through performing a set of experiments on a piezoelectrically-driven nanostager with high resolution capacitive position sensor, it is shown that for the precise prediction of hysteresis path, certain memory units are required to store the previous hysteresis trajectory data. Based on the experimental observations, a constitutive memory-based mathematical modeling framework is developed and trained for the precise prediction of hysteresis path for arbitrarily assigned input profiles. Using the inverse hysteresis model, a feedforward control strategy is then developed and implemented on the nanostager to compensate for the system everpresent nonlinearity. Experimental results demonstrate that the controller remarkably eliminates the nonlinear effect if memory units are sufficiently chosen for the inverse model.

Insurability and mitigation of flood losses in private households in Germany.

PubMed

Thieken, Annegret H; Petrow, Theresia; Kreibich, Heidi; Merz, Bruno

2006-04-01

In Germany, flood insurance is provided by private insurers as a supplement to building or contents insurance. This article presents the results of a survey of insurance companies with regard to eligibility conditions for flood insurance changes after August 2002, when a severe flood caused 1.8 billion euro of insured losses in the Elbe and the Danube catchment areas, and the general role of insurance in flood risk management in Germany. Besides insurance coverage, governmental funding and public donations played an important role in loss compensation after the August 2002 flood. Therefore, this article also analyzes flood loss compensation, risk awareness, and mitigation in insured and uninsured private households. Insured households received loss compensation earlier. They also showed slightly better risk awareness and mitigation strategies. Appropriate incentives should be combined with flood insurance in order to strengthen future private flood loss mitigation. However, there is some evidence that the surveyed insurance companies do little to encourage precautionary measures. To overcome this problem, flood hazards and mitigation strategies should be better communicated to both insurance companies and property owners.

Dynamic modeling and experiments on the coupled vibrations of building and elevator ropes

NASA Astrophysics Data System (ADS)

Yang, Dong-Ho; Kim, Ki-Young; Kwak, Moon K.; Lee, Seungjun

2017-03-01

This study is concerned with the theoretical modelling and experimental verification of the coupled vibrations of building and elevator ropes. The elevator ropes consist of a main rope which supports the cage and the compensation rope which is connected to the compensation sheave. The elevator rope is a flexible wire with a low damping, so it is prone to vibrations. In the case of a high-rise building, the rope length also increases significantly, so that the fundamental frequency of the elevator rope approaches the fundamental frequency of the building thus increasing the possibility of resonance. In this study, the dynamic model for the analysis of coupled vibrations of building and elevator ropes was derived by using Hamilton's principle, where the cage motion was also considered. An experimental testbed was built to validate the proposed dynamic model. It was found that the experimental results are in good agreement with the theoretical predictions thus validating the proposed dynamic model. The proposed model was then used to predict the vibrations of real building and elevator ropes.

The contact condition influence on stability and energy efficiency of quadruped robot

NASA Astrophysics Data System (ADS)

Lei, Jingtao; Wang, Tianmiao; Gao, Feng

2008-10-01

Quadruped robot has attribute of serial and parallel manipulator with multi-loop mechanism, with more DOF of each leg and intermittent contact with ground during walking, the trot gait of quadruped robot belongs to dynamic waking, compared to the crawl gait, the walking speed is higher, but the robot becomes unstable, it is difficult to keep dynamically stable walking. In this paper, we mainly analyze the condition for the quadruped robot to realize dynamically stable walking, establish centroid orbit equation based on ZMP (Zero Moment Point) stability theory, on the other hand , we study contact impact and friction influence on stability and energy efficiency. Because of the periodic contact between foots and ground, the contact impact and friction are considered to establish spring-damp nonlinear dynamics model. Robot need to be controlled to meet ZMP stability condition and contact constraint condition. Based on the virtual prototyping model, we study control algorithm considering contact condition, the contact compensator and friction compensator are adopted. The contact force and the influence of different contact conditions on the energy efficiency during whole gait cycle are obtained.

Geostationary Operational Environmental Satellite (GOES-N report). Volume 2: Technical appendix

NASA Technical Reports Server (NTRS)

1992-01-01

The contents include: operation with inclinations up to 3.5 deg to extend life; earth sensor improvements to reduce noise; sensor configurations studied; momentum management system design; reaction wheel induced dynamic interaction; controller design; spacecraft motion compensation; analog filtering; GFRP servo design - modern control approach; feedforward compensation as applied to GOES-1 sounder; discussion of allocation of navigation, inframe registration and image-to-image error budget overview; and spatial response and cloud smearing study.

Direct Adaptive Control of Systems with Actuator Failures: State of the Art and Continuing Challenges

NASA Technical Reports Server (NTRS)

Tao, Gang; Joshi, Suresh M.

2008-01-01

In this paper, the problem of controlling systems with failures and faults is introduced, and an overview of recent work on direct adaptive control for compensation of uncertain actuator failures is presented. Actuator failures may be characterized by some unknown system inputs being stuck at some unknown (fixed or varying) values at unknown time instants, that cannot be influenced by the control signals. The key task of adaptive compensation is to design the control signals in such a manner that the remaining actuators can automatically and seamlessly take over for the failed ones, and achieve desired stability and asymptotic tracking. A certain degree of redundancy is necessary to accomplish failure compensation. The objective of adaptive control design is to effectively use the available actuation redundancy to handle failures without the knowledge of the failure patterns, parameters, and time of occurrence. This is a challenging problem because failures introduce large uncertainties in the dynamic structure of the system, in addition to parametric uncertainties and unknown disturbances. The paper addresses some theoretical issues in adaptive actuator failure compensation: actuator failure modeling, redundant actuation requirements, plant-model matching, error system dynamics, adaptation laws, and stability, tracking, and performance analysis. Adaptive control designs can be shown to effectively handle uncertain actuator failures without explicit failure detection. Some open technical challenges and research problems in this important research area are discussed.

Robust Crossfeed Design for Hovering Rotorcraft

NASA Technical Reports Server (NTRS)

Catapang, David R.

1993-01-01

Control law design for rotorcraft fly-by-wire systems normally attempts to decouple angular responses using fixed-gain crossfeeds. This approach can lead to poor decoupling over the frequency range of pilot inputs and increase the load on the feedback loops. In order to improve the decoupling performance, dynamic crossfeeds may be adopted. Moreover, because of the large changes that occur in rotorcraft dynamics due to small changes about the nominal design condition, especially for near-hovering flight, the crossfeed design must be 'robust'. A new low-order matching method is presented here to design robust crossfeed compensators for multi-input, multi-output (MIMO) systems. The technique identifies degrees-of-freedom that can be decoupled using crossfeeds, given an anticipated set of parameter variations for the range of flight conditions of concern. Cross-coupling is then reduced for degrees-of-freedom that can use crossfeed compensation by minimizing off-axis response magnitude average and variance. Results are presented for the analysis of pitch, roll, yaw and heave coupling of the UH-60 Black Hawk helicopter in near-hovering flight. Robust crossfeeds are designed that show significant improvement in decoupling performance and robustness over nominal, single design point, compensators. The design method and results are presented in an easily used graphical format that lends significant physical insight to the design procedure. This plant pre-compensation technique is an appropriate preliminary step to the design of robust feedback control laws for rotorcraft.

Motion-compensated compressed sensing for dynamic contrast-enhanced MRI using regional spatiotemporal sparsity and region tracking: Block LOw-rank Sparsity with Motion-guidance (BLOSM)

PubMed Central

Chen, Xiao; Salerno, Michael; Yang, Yang; Epstein, Frederick H.

2014-01-01

Purpose Dynamic contrast-enhanced MRI of the heart is well-suited for acceleration with compressed sensing (CS) due to its spatiotemporal sparsity; however, respiratory motion can degrade sparsity and lead to image artifacts. We sought to develop a motion-compensated CS method for this application. Methods A new method, Block LOw-rank Sparsity with Motion-guidance (BLOSM), was developed to accelerate first-pass cardiac MRI, even in the presence of respiratory motion. This method divides the images into regions, tracks the regions through time, and applies matrix low-rank sparsity to the tracked regions. BLOSM was evaluated using computer simulations and first-pass cardiac datasets from human subjects. Using rate-4 acceleration, BLOSM was compared to other CS methods such as k-t SLR that employs matrix low-rank sparsity applied to the whole image dataset, with and without motion tracking, and to k-t FOCUSS with motion estimation and compensation that employs spatial and temporal-frequency sparsity. Results BLOSM was qualitatively shown to reduce respiratory artifact compared to other methods. Quantitatively, using root mean squared error and the structural similarity index, BLOSM was superior to other methods. Conclusion BLOSM, which exploits regional low rank structure and uses region tracking for motion compensation, provides improved image quality for CS-accelerated first-pass cardiac MRI. PMID:24243528

Exploring the Interplay of Adaptive and Maladaptive Strategies: Prevalence and Functionality of Anger Regulation Profiles in Early Adolescence

ERIC Educational Resources Information Center

Otterpohl, Nantje; Schwinger, Malte; Wild, Elke

2016-01-01

In emotion regulation research, it is common to distinguish adaptive from maladaptive emotion regulation strategies. However, little is known about their interactional impact (compensational or interfering effects) on adolescents' adjustment. We collected longitudinal, multiple informant questionnaire data from N = 608 adolescents and their…

Highly Dynamic Anion-Quadrupole Networks in Proteins.

PubMed

Kapoor, Karan; Duff, Michael R; Upadhyay, Amit; Bucci, Joel C; Saxton, Arnold M; Hinde, Robert J; Howell, Elizabeth E; Baudry, Jerome

2016-11-01

The dynamics of anion-quadrupole (or anion-π) interactions formed between negatively charged (Asp/Glu) and aromatic (Phe) side chains are for the first time computationally characterized in RmlC (Protein Data Bank entry 1EP0 ), a homodimeric epimerase. Empirical force field-based molecular dynamics simulations predict anion-quadrupole pairs and triplets (anion-anion-π and anion-π-π) are formed by the protein during the simulated trajectory, which suggests that the anion-quadrupole interactions may provide a significant contribution to the overall stability of the protein, with an average of -1.6 kcal/mol per pair. Some anion-π interactions are predicted to form during the trajectory, extending the number of anion-quadrupole interactions beyond those predicted from crystal structure analysis. At the same time, some anion-π pairs observed in the crystal structure exhibit marginal stability. Overall, most anion-π interactions alternate between an "on" state, with significantly stabilizing energies, and an "off" state, with marginal or null stabilizing energies. The way proteins possibly compensate for transient loss of anion-quadrupole interactions is characterized in the RmlC aspartate 84-phenylalanine 112 anion-quadrupole pair observed in the crystal structure. A double-mutant cycle analysis of the thermal stability suggests a possible loss of anion-π interactions compensated by variations of hydration of the residues and formation of compensating electrostatic interactions. These results suggest that near-planar anion-quadrupole pairs can exist, sometimes transiently, which may play a role in maintaining the structural stability and function of the protein, in an otherwise very dynamic interplay of a nonbonded interaction network as well as solvent effects.

Morphological Awareness and Its Role in Compensation in Adults with Dyslexia.

PubMed

Law, Jeremy M; Wouters, Jan; Ghesquière, Pol

2015-08-01

This study examines the role of morphological awareness (MA) in literacy achievement and compensation in word reading of adults with dyslexia through an exploration of three questions: (1) Do adult dyslexics demonstrate a deficit in MA, and how is this potential deficit related to phonological awareness (PA)? (2) Does MA contribute independently to literacy skills equally in dyslexics and control readers? and (3) Do MA and PA skills differ in compensated and noncompensated dyslexics? A group of dyslexic and normal reading university students matched for age, education and IQ participated in this study. Group analysis demonstrated an MA deficit in dyslexics; as well, MA was found to significantly predict a greater proportion of word reading and spelling within the dyslexic group compared with the controls. Compensated dyslexics were also found to perform significantly better on the morphological task than noncompensated dyslexics. Additionally, no statistical difference was observed in MA between the normal reading controls and the compensated group (independent of PA and vocabulary). Results suggest that intact and strong MA skills contribute to the achieved compensation of this group of adults with dyslexia. Implications for MA based intervention strategies for people with dyslexia are discussed. Copyright © 2015 John Wiley & Sons, Ltd.

In Flight Evaluation of Active Inceptor Force-Feel Characteristics and Handling Qualities

DTIC Science & Technology

2012-05-01

DEGRADED ACCEPTABLE Mitchell Aponso (1995) Watson Schroeder (1990) 0.75 lb/in 2.3 lb/in2.9 lb/in5.9 lb/in Side Stk - lon Side Stk - lat Center Stk Figure...vestibular feedback ( and respectively), and the visual error compensation ( ). A key feature of this approach is the modeling of proprioceptive...and vestibular feedback, and is the proportional component of the visual compensation strategy. At its core the fundamental concept of the HQSF

Reforming Military Retirement: Analysis in Support of the Military Compensation and Retirement Modernization Commission

DTIC Science & Technology

2015-01-01

of the Actuary cheerfully provided key input for our analysis, no matter the time pressure. We also thank our RAND colleagues David Knapp and... Science Board Task Force on Human Resources Strategy (Defense Science Board, 2000), the Defense Advisory Committee on Mili- tary Compensation (2006...DoD Actuary . The final task was to analyze the cost savings and change in government outlays during the transition to the steady state, including

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

Study of a Car Body Tilting System Using a Variable Link Mechanism: Fundamental Characteristics of Pendulum Motion and Strategy for Perfect Tilting

NASA Astrophysics Data System (ADS)

Yoshida, Hidehisa; Nagai, Masao

This paper analyzes the fundamental dynamic characteristics of a tilting railway vehicle using a variable link mechanism for compensating both the lateral acceleration experienced by passengers and the wheel load imbalance between the inner and outer rails. The geometric relations between the center of rotation, the center of gravity, and the positions of all four links of the tilting system are analyzed. Then, equations of the pendulum motions of the railway vehicle body with a four-link mechanism are derived. A theoretically discussion is given on the geometrical shapes employed in the link mechanism that can simultaneously provide zero lateral acceleration and zero wheel load fluctuation. Then, the perfect tilting condition, which is the control target of the feedforward tilting control, is derived from the linear equation of tilting motion.

Fuzzy control of a fluidized bed dryer

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

Taprantzis, A.V.; Siettos, C.I.; Bafas, G.V.

1997-05-01

Fluidized bed dryers are utilized in almost every area of drying applications and therefore improved control strategies are always of great interest. The nonlinear character of the process, exhibited in the mathematical model and the open loop analysis, implies that a fuzzy logic controller is appropriate because, in contrast with conventional control schemes, fuzzy control inherently compensates for process nonlinearities and exhibits more robust behavior. In this study, a fuzzy logic controller is proposed; its design is based on a heuristic approach and its performance is compared against a conventional PI controller for a variety of responses. It is shownmore » that the fuzzy controller exhibits a remarkable dynamic behavior, equivalent if not better than the PI controller, for a wide range of disturbances. In addition, the proposed fuzzy controller seems to be less sensitive to the nonlinearities of the process, achieves energy savings and enables MIMO control.« less

Planar maneuvering control of underwater snake robots using virtual holonomic constraints.

PubMed

Kohl, Anna M; Kelasidi, Eleni; Mohammadi, Alireza; Maggiore, Manfredi; Pettersen, Kristin Y

2016-11-24

This paper investigates the problem of planar maneuvering control for bio-inspired underwater snake robots that are exposed to unknown ocean currents. The control objective is to make a neutrally buoyant snake robot which is subject to hydrodynamic forces and ocean currents converge to a desired planar path and traverse the path with a desired velocity. The proposed feedback control strategy enforces virtual constraints which encode biologically inspired gaits on the snake robot configuration. The virtual constraints, parametrized by states of dynamic compensators, are used to regulate the orientation and forward speed of the snake robot. A two-state ocean current observer based on relative velocity sensors is proposed. It enables the robot to follow the path in the presence of unknown constant ocean currents. The efficacy of the proposed control algorithm for several biologically inspired gaits is verified both in simulations for different path geometries and in experiments.

Applying High-Speed Vision Sensing to an Industrial Robot for High-Performance Position Regulation under Uncertainties

PubMed Central

Huang, Shouren; Bergström, Niklas; Yamakawa, Yuji; Senoo, Taku; Ishikawa, Masatoshi

2016-01-01

It is traditionally difficult to implement fast and accurate position regulation on an industrial robot in the presence of uncertainties. The uncertain factors can be attributed either to the industrial robot itself (e.g., a mismatch of dynamics, mechanical defects such as backlash, etc.) or to the external environment (e.g., calibration errors, misalignment or perturbations of a workpiece, etc.). This paper proposes a systematic approach to implement high-performance position regulation under uncertainties on a general industrial robot (referred to as the main robot) with minimal or no manual teaching. The method is based on a coarse-to-fine strategy that involves configuring an add-on module for the main robot’s end effector. The add-on module consists of a 1000 Hz vision sensor and a high-speed actuator to compensate for accumulated uncertainties. The main robot only focuses on fast and coarse motion, with its trajectories automatically planned by image information from a static low-cost camera. Fast and accurate peg-and-hole alignment in one dimension was implemented as an application scenario by using a commercial parallel-link robot and an add-on compensation module with one degree of freedom (DoF). Experimental results yielded an almost 100% success rate for fast peg-in-hole manipulation (with regulation accuracy at about 0.1 mm) when the workpiece was randomly placed. PMID:27483274

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

PubMed

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

2017-03-01

This paper investigates the problem of spatial curvilinear path following control of underactuated autonomous underwater vehicles (AUVs) with multiple uncertainties. Firstly, in order to design the appropriate controller, path following error dynamics model is constructed in a moving Serret-Frenet frame, and the five degrees of freedom (DOFs) dynamic model with multiple uncertainties is established. Secondly, the proposed control law is separated into kinematic controller and dynamic controller via back-stepping technique. In the case of kinematic controller, to overcome the drawback of dependence on the accurate vehicle model that are present in a number of path following control strategies described in the literature, the unknown side-slip angular velocity and attack angular velocity are treated as uncertainties. Whereas in the case of dynamic controller, the model parameters perturbations, unknown external environmental disturbances and the nonlinear hydrodynamic damping terms are treated as lumped uncertainties. Both kinematic and dynamic uncertainties are estimated and compensated by designed reduced-order linear extended state observes (LESOs). Thirdly, feedback linearization (FL) based control law is implemented for the control model using the estimates generated by reduced-order LESOs. For handling the problem of computational complexity inherent in the conventional back-stepping method, nonlinear tracking differentiators (NTDs) are applied to construct derivatives of the virtual control commands. Finally, the closed loop stability for the overall system is established. Simulation and comparative analysis demonstrate that the proposed controller exhibits enhanced performance in the presence of internal parameter variations, external unknown disturbances, unmodeled nonlinear damping terms, and measurement noises. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Dynamics of Preferential Substrate Recognition in HIV-1 Protease: Redefining the Substrate Envelope

PubMed Central

Özen, Ayşegül; Haliloğlu, Türkan; Schiffer, Celia A.

2011-01-01

HIV-1 protease (PR) permits viral maturation by processing the Gag and Gag-Pro-Pol polyproteins. Though HIV-1 PR inhibitors (PIs) are used in combination antiviral therapy, the emergence of drug resistance has limited their efficacy. The rapid evolution of HIV-1 necessitates the consideration of drug resistance in novel drug-design strategies. Drug-resistant HIV-1 PR variants, while no longer efficiently inhibited, continue to efficiently hydrolyze the natural viral substrates. Though highly diverse in sequence, the HIV-1 PR substrates bind in a conserved three-dimensional shape we defined as the “substrate envelope”. We previously showed that resistance mutations arise where PIs protrude beyond the substrate envelope, as these regions are crucial for drug binding but not for substrate recognition. Here, we extend this model by considering the role of protein dynamics in the interaction of HIV-1 PR with its substrates. Seven molecular dynamics simulations of PR-substrate complexes were performed to estimate the conformational flexibility of substrates in their complexes. Interdependency of the substrate-protease interactions may compensate for the variations in cleavage-site sequences, and explain how a diverse set of sequences can be recognized as substrates by the same enzyme. This diversity may be essential for regulating sequential processing of substrates. We also define a dynamic substrate envelope as a more accurate representation of PR-substrate interactions. This dynamic substrate envelope, described by a probability distribution function, is a powerful tool for drug design efforts targeting ensembles of resistant HIV-1 PR variants with the aim of developing drugs that are less susceptible to resistance. PMID:21762811

Dynamic boundary layer based neural network quasi-sliding mode control for soft touching down on asteroid

NASA Astrophysics Data System (ADS)

Liu, Xiaosong; Shan, Zebiao; Li, Yuanchun

2017-04-01

Pinpoint landing is a critical step in some asteroid exploring missions. This paper is concerned with the descent trajectory control for soft touching down on a small irregularly-shaped asteroid. A dynamic boundary layer based neural network quasi-sliding mode control law is proposed to track a desired descending path. The asteroid's gravitational acceleration acting on the spacecraft is described by the polyhedron method. Considering the presence of input constraint and unmodeled acceleration, the dynamic equation of relative motion is presented first. The desired descending path is planned using cubic polynomial method, and a collision detection algorithm is designed. To perform trajectory tracking, a neural network sliding mode control law is given first, where the sliding mode control is used to ensure the convergence of system states. Two radial basis function neural networks (RBFNNs) are respectively used as an approximator for the unmodeled term and a compensator for the difference between the actual control input with magnitude constraint and nominal control. To improve the chattering induced by the traditional sliding mode control and guarantee the reachability of the system, a specific saturation function with dynamic boundary layer is proposed to replace the sign function in the preceding control law. Through the Lyapunov approach, the reachability condition of the control system is given. The improved control law can guarantee the system state move within a gradually shrinking quasi-sliding mode band. Numerical simulation results demonstrate the effectiveness of the proposed control strategy.

Design and Modeling of a Test Bench for Dual-Motor Electric Drive Tracked Vehicles Based on a Dynamic Load Emulation Method.

PubMed

Wang, Zhe; Lv, Haoliang; Zhou, Xiaojun; Chen, Zhaomeng; Yang, Yong

2018-06-21

Dual-motor Electric Drive Tracked Vehicles (DDTVs) have attracted increasing attention due to their high transmission efficiency and economical fuel consumption. A test bench for the development and validation of new DDTV technologies is necessary and urgent. How to load the vehicle on a DDTV test bench exactly the same as on a real road is a crucial issue when designing the bench. This paper proposes a novel dynamic load emulation method to address this problem. The method adopts dual dynamometers to simulate both the road load and the inertia load that are imposed on the dual independent drive systems. The vehicle’s total inertia equivalent to the drive wheels is calculated with separate consideration of vehicle body, tracks and road wheels to obtain a more accurate inertia load. A speed tracking control strategy with feedforward compensation is implemented to control the dual dynamometers, so as to make the real-time dynamic load emulation possible. Additionally, a MATLAB/Simulink model of the test bench is built based on a dynamics analysis of the platform. Experiments are finally carried out on this test bench under different test conditions. The outcomes show that the proposed load emulation method is effective, and has good robustness and adaptability to complex driving conditions. Besides, the accuracy of the established test bench model is also demonstrated by comparing the results obtained from the simulation model and experiments.

In situ magnetic compensation for potassium spin-exchange relaxation-free magnetometer considering probe beam pumping effect

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

Fang, Jiancheng; Wang, Tao, E-mail: wangtaowt@aspe.buaa.edu.cn; Quan, Wei

2014-06-15

A novel method to compensate the residual magnetic field for an atomic magnetometer consisting of two perpendicular beams of polarizations was demonstrated in this paper. The method can realize magnetic compensation in the case where the pumping rate of the probe beam cannot be ignored. In the experiment, the probe beam is always linearly polarized, whereas, the probe beam contains a residual circular component due to the imperfection of the polarizer, which leads to the pumping effect of the probe beam. A simulation of the probe beam's optical rotation and pumping rate was demonstrated. At the optimized points, the wavelengthmore » of the probe beam was optimized to achieve the largest optical rotation. Although, there is a small circular component in the linearly polarized probe beam, the pumping rate of the probe beam was non-negligible at the optimized wavelength which if ignored would lead to inaccuracies in the magnetic field compensation. Therefore, the dynamic equation of spin evolution was solved by considering the pumping effect of the probe beam. Based on the quasi-static solution, a novel magnetic compensation method was proposed, which contains two main steps: (1) the non-pumping compensation and (2) the sequence compensation with a very specific sequence. After these two main steps, a three-axis in situ magnetic compensation was achieved. The compensation method was suitable to design closed-loop spin-exchange relaxation-free magnetometer. By a combination of the magnetic compensation and the optimization, the magnetic field sensitivity was approximately 4 fT/Hz{sup 1/2}, which was mainly dominated by the noise of the magnetic shield.« less

Development of a Design Methodology for Reconfigurable Flight Control Systems

NASA Technical Reports Server (NTRS)

Hess, Ronald A.; McLean, C.

2000-01-01

A methodology is presented for the design of flight control systems that exhibit stability and performance-robustness in the presence of actuator failures. The design is based upon two elements. The first element consists of a control law that will ensure at least stability in the presence of a class of actuator failures. This law is created by inner-loop, reduced-order, linear dynamic inversion, and outer-loop compensation based upon Quantitative Feedback Theory. The second element consists of adaptive compensators obtained from simple and approximate time-domain identification of the dynamics of the 'effective vehicle' with failed actuator(s). An example involving the lateral-directional control of a fighter aircraft is employed both to introduce the proposed methodology and to demonstrate its effectiveness and limitations.

Vertically polarizing undulator with dynamic compensation of magnetic forces

DOE PAGES

Strelnikov, N.; Vasserman, I.; Xu, J.; ...

2017-01-20

As part of the R&D program of the LCLS-II project, a novel 3.4-meter-long undulator prototype with horizontal magnetic field and dynamic force compensation has recently been developed at the Advanced Photon Source (APS). Some previous steps in this development were the shorter 0.8-meter-long and 2.8-meter-long prototypes. Extensive mechanical and magnetic testing was carried out for each prototype, and each prototype was magnetically tuned using magnetic shims. Furthermore, the resulting performance of the 3.4-meter-long undulator prototype meets all requirements for the LCLS-II insertion device, including limits on the field integrals, phase errors, higher-order magnetic moments, and electron-beam trajectory for all operationalmore » gaps, as well as the reproducibility and accuracy of the gap settings.« less

Optimal Control Method of Robot End Position and Orientation Based on Dynamic Tracking Measurement

NASA Astrophysics Data System (ADS)

Liu, Dalong; Xu, Lijuan

2018-01-01

In order to improve the accuracy of robot pose positioning and control, this paper proposed a dynamic tracking measurement robot pose optimization control method based on the actual measurement of D-H parameters of the robot, the parameters is taken with feedback compensation of the robot, according to the geometrical parameters obtained by robot pose tracking measurement, improved multi sensor information fusion the extended Kalan filter method, with continuous self-optimal regression, using the geometric relationship between joint axes for kinematic parameters in the model, link model parameters obtained can timely feedback to the robot, the implementation of parameter correction and compensation, finally we can get the optimal attitude angle, realize the robot pose optimization control experiments were performed. 6R dynamic tracking control of robot joint robot with independent research and development is taken as experimental subject, the simulation results show that the control method improves robot positioning accuracy, and it has the advantages of versatility, simplicity, ease of operation and so on.

Enhanced High Performance Power Compensation Methodology by IPFC Using PIGBT-IDVR

PubMed Central

Arumugom, Subramanian; Rajaram, Marimuthu

2015-01-01

Currently, power systems are involuntarily controlled without high speed control and are frequently initiated, therefore resulting in a slow process when compared with static electronic devices. Among various power interruptions in power supply systems, voltage dips play a central role in causing disruption. The dynamic voltage restorer (DVR) is a process based on voltage control that compensates for line transients in the distributed system. To overcome these issues and to achieve a higher speed, a new methodology called the Parallel IGBT-Based Interline Dynamic Voltage Restorer (PIGBT-IDVR) method has been proposed, which mainly spotlights the dynamic processing of energy reloads in common dc-linked energy storage with less adaptive transition. The interline power flow controller (IPFC) scheme has been employed to manage the power transmission between the lines and the restorer method for controlling the reactive power in the individual lines. By employing the proposed methodology, the failure of a distributed system has been avoided and provides better performance than the existing methodologies. PMID:26613101

Hysteresis compensation for piezoelectric actuators in single-point diamond turning

NASA Astrophysics Data System (ADS)

Wang, Haifeng; Hu, Dejin; Wan, Daping; Liu, Hongbin

2006-02-01

In recent years, interests have been growing for fast tool servo (FTS) systems to increase the capability of existing single-point diamond turning machines. Although piezoelectric actuator is the most universal base of FTS system due to its high stiffness, accuracy and bandwidth, nonlinearity in piezoceramics limits both the static and dynamic performance of piezoelectric-actuated control systems evidently. To compensate the nonlinear hysteresis behavior of piezoelectric actuators, a hybrid model coupled with Preisach model and feedforward neural network (FNN) has been described. Since the training of FNN does not require a special calibration sequence, it is possible for on-line identification and real-time implementation with general operating data of a specific piezoelectric actuator. To describe the rate dependent behavior of piezoelectric actuators, a hybrid dynamic model was developed to predict the response of piezoelectric actuators in a wider range of input frequency. Experimental results show that a maximal error of less than 3% was accomplished by this dynamic model.

Is clinician refusal to treat an emerging problem in injury compensation systems?

PubMed

Brijnath, Bianca; Mazza, Danielle; Kosny, Agnieszka; Bunzli, Samantha; Singh, Nabita; Ruseckaite, Rasa; Collie, Alex

2016-01-20

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. 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. Compensable injury management in general practice in Melbourne, Australia. 25 GPs who were treating, or had treated a patient with compensable injury. 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. 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. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

A Novel Adaptive H∞ Filtering Method with Delay Compensation for the Transfer Alignment of Strapdown Inertial Navigation Systems.

PubMed

Lyu, Weiwei; Cheng, Xianghong

2017-11-28

Transfer alignment is always a key technology in a strapdown inertial navigation system (SINS) because of its rapidity and accuracy. In this paper a transfer alignment model is established, which contains the SINS error model and the measurement model. The time delay in the process of transfer alignment is analyzed, and an H∞ filtering method with delay compensation is presented. Then the H∞ filtering theory and the robust mechanism of H∞ filter are deduced and analyzed in detail. In order to improve the transfer alignment accuracy in SINS with time delay, an adaptive H∞ filtering method with delay compensation is proposed. Since the robustness factor plays an important role in the filtering process and has effect on the filtering accuracy, the adaptive H∞ filter with delay compensation can adjust the value of robustness factor adaptively according to the dynamic external environment. The vehicle transfer alignment experiment indicates that by using the adaptive H∞ filtering method with delay compensation, the transfer alignment accuracy and the pure inertial navigation accuracy can be dramatically improved, which demonstrates the superiority of the proposed filtering method.

Recognition and modification of seX chromosomes.

PubMed

Nusinow, Dmitri A; Panning, Barbara

2005-04-01

Flies, worms and mammals employ dosage compensation complexes that alter chromatin or chromosome structure to equalize X-linked gene expression between the sexes. Recent work has improved our understanding of how dosage compensation complexes achieve X chromosome-wide association and has provided significant insight into the epigenetic modifications directed by these complexes to modulate gene expression. In flies, the prevailing view that dosage compensation complexes assemble on the X chromosome at approximately 35 chromatin-entry sites and then spread in cis to cover the chromosome has been re-evaluated in light of the evidence that these chromatin-entry sites are not required for localization of the complex. By contrast, identification of discrete recruitment elements indicates that nucleation at and spread from a limited number of sites directs dosage compensation complex localization on the worm X-chromosome. Studies in flies and mammals have extended our understanding of how ribonucleoprotein complexes are used to modify X chromatin, for either activation or repression of transcription. Finally, evidence from mammals suggests that the chromatin modifications that mediate dosage compensation are very dynamic, because they are established, reversed and re-established early in development.

Adaptive Control of Four-Leg VSC Based DSTATCOM in Distribution System

NASA Astrophysics Data System (ADS)

Singh, Bhim; Arya, Sabha Raj

2014-01-01

This work discusses an experimental performance of a four-leg Distribution Static Compensator (DSTATCOM) using an adaptive filter based approach. It is used for estimation of reference supply currents through extracting the fundamental active power components of three-phase distorted load currents. This control algorithm is implemented on an assembled DSTATCOM for harmonics elimination, neutral current compensation and load balancing, under nonlinear loads. Experimental results are discussed, and it is noticed that DSTATCOM is effective solution to perform satisfactory performance under load dynamics.

Monolithic amplifier with stable, high resistance feedback element and method for fabricating the same

DOEpatents

O'Connor, Paul

1998-08-11

A monolithic amplifier includes a stable, high resistance feedback circuit and a dynamic bias circuit. The dynamic bias circuit is formed with active elements matched to those in the amplifier and feedback circuit to compensate for variations in the operating and threshold voltages thereby maintaining a stable resistance in the feedback circuit.

The relationship between motivation, monetary compensation, and data quality among US- and India-based workers on Mechanical Turk.

PubMed

Litman, Leib; Robinson, Jonathan; Rosenzweig, Cheskie

2015-06-01

In this study, we examined data quality among Amazon Mechanical Turk (MTurk) workers based in India, and the effect of monetary compensation on their data quality. Recent studies have shown that work quality is independent of compensation rates, and that compensation primarily affects the quantity but not the quality of work. However, the results of these studies were generally based on compensation rates below the minimum wage, and far below a level that was likely to play a practical role in the lives of workers. In this study, compensation rates were set around the minimum wage in India. To examine data quality, we developed the squared discrepancy procedure, which is a task-based quality assurance approach for survey tasks whose goal is to identify inattentive participants. We showed that data quality is directly affected by compensation rates for India-based participants. We also found that data were of a lesser quality among India-based than among US participants, even when optimal payment strategies were utilized. We additionally showed that the motivation of MTurk users has shifted, and that monetary compensation is now reported to be the primary reason for working on MTurk, among both US- and India-based workers. Overall, MTurk is a constantly evolving marketplace where multiple factors can contribute to data quality. High-quality survey data can be acquired on MTurk among India-based participants when an appropriate pay rate is provided and task-specific quality assurance procedures are utilized.

Compensation for occupational injuries and diseases in special populations: farmers and soldiers.

PubMed

Kwon, Young-Jun; Lee, Soo-Jin

2014-06-01

Some types of workers such as farmers and soldiers are at a higher risk of work-related injury and illness than workers from other occupations. Despite this fact, they are not covered under the Industrial Safety Health (ISH) Act or the Industrial Accident Compensation Insurance (IACI) Act. The Safety Aid System for Farmers (SASF) is a voluntary insurance scheme, and it is the only public compensation plan for self-employed farmers. Fifty percent of SASF premiums are subsidized by the Korean government. Soldiers are compensated by the Veterans' Pension (VP) Act. The approval standard of and procedure for the VP Act are provided in the Decree of VP Act, and the Council for VP Benefits determines work-relatedness in the claimed cases. Meanwhile, SASF applies the insurance clause automatically without any expert advice or additional procedures. Furthermore, compared with IACI, these programs pay fewer benefits to workers. Thus, a stronger institutional strategy is needed to maintain a safe work environment, to protect workers' health in unavoidably hazardous environments, and to compensate for work-related injuries and diseases.

Everyday Experiences of Memory Problems and Control: The Adaptive Role of Selective Optimization with Compensation in the Context of Memory Decline

PubMed Central

Hahn, Elizabeth A.; Lachman, Margie E.

2014-01-01

The present study examined the role of long-term working memory decline in the relationship between everyday experiences of memory problems and perceived control, and we also considered whether the use of accommodative strategies [selective optimization with compensation (SOC)] would be adaptive. The study included Boston-area participants (n=103) from the Midlife in the United States study (MIDUS) who completed two working memory assessments over ten years and weekly diaries following Time 2. In adjusted multi-level analyses, greater memory decline and lower general perceived control were associated with more everyday memory problems. Low perceived control reported in a weekly diary was associated with more everyday memory problems among those with greater memory decline and low SOC strategy use (Est.=−0.28, SE=0.13, p=.036). These results suggest that the use of SOC strategies in the context of declining memory may help to buffer the negative effects of low perceived control on everyday memory. PMID:24597768

[Effects of planning and executive functions on young children's script change strategy: A developmental perspective].

PubMed

Yanaoka, Kaichi

2016-02-01

This research examined the effects of planning and executive functions on young children's (ages 3-to 5-years) strategies in changing scripts. Young children (N = 77) performed a script task (doll task), three executive function tasks (DCCS, red/blue task, and nine box task), a planning task, and a receptive vocabulary task. In the doll task, young children first enacted a "changing clothes" script, and then faced a situation in which some elements of the script were inappropriate. They needed to enact a script by compensating inappropriate items for the other-script items or by changing to the other script in advance. The results showed that shifting, a factor of executive function, had a positive influence on whether young children could compensate inappropriate items. In addition, planning was also an important factor that helped children to change to the other script in advance. These findings suggest that shifting and planning play different roles in using the two strategies appropriately when young children enact scripts in unexpected situations.

Navigating north: how body mass and winds shape avian flight behaviours across a North American migratory flyway.

PubMed

Horton, Kyle G; Van Doren, Benjamin M; La Sorte, Frank A; Fink, Daniel; Sheldon, Daniel; Farnsworth, Andrew; Kelly, Jeffrey F

2018-05-07

The migratory patterns of birds have been the focus of ecologists for millennia. What behavioural traits underlie these remarkably consistent movements? Addressing this question is central to advancing our understanding of migratory flight strategies and requires the integration of information across levels of biological organisation, e.g. species to communities. Here, we combine species-specific observations from the eBird citizen-science database with observations aggregated from weather surveillance radars during spring migration in central North America. Our results confirm a core prediction of migration theory at an unprecedented national scale: body mass predicts variation in flight strategies across latitudes, with larger-bodied species flying faster and compensating more for wind drift. We also find evidence that migrants travelling northward earlier in the spring increasingly compensate for wind drift at higher latitudes. This integration of information across biological scales provides new insight into patterns and determinants of broad-scale flight strategies of migratory birds. © 2018 John Wiley & Sons Ltd/CNRS.

A pulse coding and decoding strategy to perform Lamb wave inspections using simultaneously multiple actuators

NASA Astrophysics Data System (ADS)

De Marchi, Luca; Marzani, Alessandro; Moll, Jochen; Kudela, Paweł; Radzieński, Maciej; Ostachowicz, Wiesław

2017-07-01

The performance of Lamb wave based monitoring systems, both in terms of diagnosis time and data complexity, can be enhanced by increasing the number of transducers used to actuate simultaneously the guided waves in the inspected medium. However, in case of multiple simultaneously-operated actuators the interference among the excited wave modes within the acquired signals has to be considered for the further processing. To this aim, in this work a code division strategy based on the Warped Frequency Transform is presented. At first, the proposed procedure encodes actuation pulses using Gold sequences. Next, for each considered actuator the acquired signals are compensated from dispersion by cross correlating the warped version of the actuated and received signals. Compensated signals form the base for a final wavenumber imaging meant at emphasizing defects and or anomalies by removing incident wavefield and edge reflections. The proposed strategy is tested numerically, and validated through an experiment in which guided waves are actuated in a plate by four piezoelectric transducers operating simultaneously.

Everyday experiences of memory problems and control: the adaptive role of selective optimization with compensation in the context of memory decline.

PubMed

Hahn, Elizabeth A; Lachman, Margie E

2015-01-01

The present study examined the role of long-term working memory decline in the relationship between everyday experiences of memory problems and perceived control, and we also considered whether the use of accommodative strategies [selective optimization with compensation (SOC)] would be adaptive. The study included Boston-area participants (n = 103) from the Midlife in the United States study (MIDUS) who completed two working memory assessments over 10 years and weekly diaries following Time 2. In adjusted multi-level analyses, greater memory decline and lower general perceived control were associated with more everyday memory problems. Low perceived control reported in a weekly diary was associated with more everyday memory problems among those with greater memory decline and low SOC strategy use (Est. = -0.28, SE= 0.13, p = .036). These results suggest that the use of SOC strategies in the context of declining memory may help to buffer the negative effects of low perceived control on everyday memory.

Aligning incentives in health care: physician practice and health system partnership.

PubMed

Levin, L Scott; Gustave, Lori

2013-06-01

The key to successfully aligning hospitals and physicians is financial integration and joint incentives for academic, quality, and clinical productivity. Many physician practices and health systems are moving toward closer integration, but mainly through consolidation and employment strategies. We describe a fully integrated physician and hospital relationship including an overview of an aligned funds flow process that affords the department support for clinical services and teaching, research, and administrative activity. We also describe a physician compensation model that provides incentive not only for increased clinical performance, but also quality and academic objectives. The content of this article was acquired through our own experience in managing the Department of Orthopaedic Surgery at the University of Pennsylvania Health System including the health system's funds flow process. Based on input from both health system leaders and the faculty, the department's compensation plan was totally redesigned to create a line-of-sight plan that credits clinical performance and academic productivity. Our model is multifactorial and provides sustainable support for the department and a compensation plan that is competitive within the local market and nationally. The health system's funds flow process has enhanced alignment of the faculty and hospitals by providing compensation for nonclinical time and assists the department's growth strategies by providing funding for new faculty and gain-sharing of improved hospital margin. The implementation of the compensation plan increased productivity by 8% in its first year with no additional resources. Academic productivity in that same year was arguably at or above any other year in the department's history in terms of accepted publications, national presentations, and research grants awarded. A model of complete integration between an academic department and a health system is achievable through a systematic process of mission-based support.

Decoupled macro/micro-manipulator for fast and precise assembly operations: design and experiments

NASA Astrophysics Data System (ADS)

Hodac, Agathe; Siegwart, Roland Y.

1999-08-01

This paper presents a high performance single arm robot configuration, based on a macro-manipulator coupled with a micro-manipulator. The system is well suited to fast and precise positioning tasks for repetitive pick and place applications in the manufacturing industry. Firstly, the paper focuses on the design of the micro-manipulator, particularly on the selection of the proper micro-actuator type and location. We show that the micro-manipulator's design with an actuator placed between endpoint and ground and with a flexible suspension system can reduce the dynamic coupling between the macro-manipulator and the micro- manipulator. The overall system performance can then be improved. We describe two different designs of compact and fast micro-manipulators composed of voice coil actuators and a monolithic flexure suspension with notch hinges. Secondly, the paper presents a control strategy that allows both correction of possible misalignments of the end-effector relative to the target and compensation of tip oscillations. The dynamic interaction is analyzed and stability is verified. Finally, experimental results demonstrate significant improvements in acceleration, endpoint accuracy and settling time achieved by the novel configuration of the macro/micro-manipulator.

Low speed hybrid generalized predictive control of a gasoline-propelled car.

PubMed

Romero, M; de Madrid, A P; Mañoso, C; Milanés, V

2015-07-01

Low-speed driving in traffic jams causes significant pollution and wasted time for commuters. Additionally, from the passengers׳ standpoint, this is an uncomfortable, stressful and tedious scene that is suitable to be automated. The highly nonlinear dynamics of car engines at low-speed turn its automation in a complex problem that still remains as unsolved. Considering the hybrid nature of the vehicle longitudinal control at low-speed, constantly switching between throttle and brake pedal actions, hybrid control is a good candidate to solve this problem. This work presents the analytical formulation of a hybrid predictive controller for automated low-speed driving. It takes advantage of valuable characteristics supplied by predictive control strategies both for compensating un-modeled dynamics and for keeping passengers security and comfort analytically by means of the treatment of constraints. The proposed controller was implemented in a gas-propelled vehicle to experimentally validate the adopted solution. To this end, different scenarios were analyzed varying road layouts and vehicle speeds within a private test track. The production vehicle is a commercial Citroën C3 Pluriel which has been modified to automatically act over its throttle and brake pedals. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Combined feedforward and model-assisted active disturbance rejection control for non-minimum phase system.

PubMed

Sun, Li; Li, Donghai; Gao, Zhiqiang; Yang, Zhao; Zhao, Shen

2016-09-01

Control of the non-minimum phase (NMP) system is challenging, especially in the presence of modelling uncertainties and external disturbances. To this end, this paper presents a combined feedforward and model-assisted Active Disturbance Rejection Control (MADRC) strategy. Based on the nominal model, the feedforward controller is used to produce a tracking performance that has minimum settling time subject to a prescribed undershoot constraint. On the other hand, the unknown disturbances and uncertain dynamics beyond the nominal model are compensated by MADRC. Since the conventional Extended State Observer (ESO) is not suitable for the NMP system, a model-assisted ESO (MESO) is proposed based on the nominal observable canonical form. The convergence of MESO is proved in time domain. The stability, steady-state characteristics and robustness of the closed-loop system are analyzed in frequency domain. The proposed strategy has only one tuning parameter, i.e., the bandwidth of MESO, which can be readily determined with a prescribed robustness level. Some comparative examples are given to show the efficacy of the proposed method. This paper depicts a promising prospect of the model-assisted ADRC in dealing with complex systems. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

An in vitro model of a system of electrical potential compensation in extracorporeal circulation.

PubMed

Carletti, Umberto; Cattini, Stefano; Lodi, Renzo; Petralia, Antonio; Rovati, Luigi; Zaffe, Davide

2014-02-01

Extracorporeal circulation (ECC) in patients undergoing cardiac surgery induces systemic immune-inflammatory reaction that results in increased postoperative morbidity. Many factors are responsible for the adverse response after ECC. The present in vitro study aimed to investigate electric charges (ECs) generated during ECC, to set a device compensating the ECs, and checking its effect on red blood cells (RBC). The electrical signals of blood in ECC were collected by a custom developed low-noise electronic circuit, processed by a digital oscilloscope (DSO) and a dynamic signal analyzer (DSA). The compensation of ECs was performed using a compensation device, injecting a nulling charge into the blood circuit. The compensation effect of the ECs on RBCs was evaluated by scanning electron microscope (SEM). The electrical analysis performed using both the DSO and the DSA confirmed the EC formation during ECC. The notable electric signals recorded in standard ECC circuits substantially nulled once the compensation device was used, thus confirming efficient EC compensation. After two hours of ECC, the SEM non-blended test on human RBC samples highlighted morphological changes in acanthocytes of the normal biconcave-shaped RBC. The outcomes confirm the development of parasitic ECs during ECC and that a suppressor system may decrease the potential damage of ECs. Nevertheless, further studies are ongoing in order to investigate the complex mechanisms related to lymphocytes and platelet morphological and physiological chances during triboelectric charges in ECC.

Combining correlative and mechanistic habitat suitability models to improve ecological compensation.

PubMed

Meineri, Eric; Deville, Anne-Sophie; Grémillet, David; Gauthier-Clerc, Michel; Béchet, Arnaud

2015-02-01

Only a few studies have shown positive impacts of ecological compensation on species dynamics affected by human activities. We argue that this is due to inappropriate methods used to forecast required compensation in environmental impact assessments. These assessments are mostly descriptive and only valid at limited spatial and temporal scales. However, habitat suitability models developed to predict the impacts of environmental changes on potential species' distributions should provide rigorous science-based tools for compensation planning. Here we describe the two main classes of predictive models: correlative models and individual-based mechanistic models. We show how these models can be used alone or synoptically to improve compensation planning. While correlative models are easier to implement, they tend to ignore underlying ecological processes and lack accuracy. On the contrary, individual-based mechanistic models can integrate biological interactions, dispersal ability and adaptation. Moreover, among mechanistic models, those considering animal energy balance are particularly efficient at predicting the impact of foraging habitat loss. However, mechanistic models require more field data compared to correlative models. Hence we present two approaches which combine both methods for compensation planning, especially in relation to the spatial scale considered. We show how the availability of biological databases and software enabling fast and accurate population projections could be advantageously used to assess ecological compensation requirement efficiently in environmental impact assessments. © 2014 The Authors. Biological Reviews © 2014 Cambridge Philosophical Society.

Going Beyond Standard English: An Instructional Module for Improving International Business Communication.

ERIC Educational Resources Information Center

Jarvis, Scott; Stephens, Robert

It is proposed that because (1) adult learners of English as a Second Language face great challenges in communicating with native English speakers; and (2) native English-speakers can learn strategies to compensate for some of these difficulties, there is a need for instruction in these strategies and skills for Americans in international…

Compensation and exotic livestock disease management: the views of animal keepers and veterinarians in England.

PubMed

Hamilton-Webb, A; Naylor, R; Little, R; Maye, D

2016-11-19

Relatively little is known about the perceived influence of different compensation systems on animal keepers' management of exotic livestock disease. This paper aims to address this research gap by drawing on interviews with 61 animal keepers and 21 veterinarians, as well as a series of nine animal keeper focus groups across five different livestock sectors in England. The perceived influence of current compensation systems on disease control behaviour was explored and alternative compensation systems that respectively reward positive practices and penalise poor practices were presented in the form of scenarios, alongside a third system that considered the option of a cost-sharing levy system between industry and government. The results indicate that animal keepers consider themselves to be influenced by a range of non-financial factors, for example, feelings of responsibility, reputation and animal welfare concerns, in the context of their exotic disease management practices. The majority of animal keepers were unaware of the current compensation systems in place for exotic diseases, and were therefore not consciously influenced by financial recompense. Concerns were raised about linking compensation to disease management behaviour due to auditing difficulties. A cost-sharing levy system would likely raise awareness of exotic disease and compensation among animal keepers, but differentiation of payments based upon individual farm-level risk assessments was called for by participants as a strategy to promote positive disease management practices. British Veterinary Association.

Measurement and Compensation of BPM Chamber Motion in HLS

NASA Astrophysics Data System (ADS)

Li, J. W.; Sun, B. G.; Cao, Y.; Xu, H. L.; Lu, P.; Li, C.; Xuan, K.; Wang, J. G.

2010-06-01

Significant horizontal drifts in the beam orbit in the storage ring of HLS (Hefei Light Source) have been seen for many years. What leads to the motion of Beam Position Monitor (BPM) chamber is thermal expansion mainly caused by the synchrotron light. To monitor the BPM chamber motions for all BPMs, a BPM chamber motion measurement system is built in real-time. The raster gauges are used to measure the displacements. The results distinctly show the relation between the BPM chamber motion and the beam current. To suppress the effect of BPM chamber motion, a compensation strategy is implemented at HLS. The horizontal drifts of beam orbit have been really suppressed within 20μm without the compensation of BPM chamber motion in the runtime.

Dynamic Modeling and Interactive Performance of PARM: A Parallel Upper-Limb Rehabilitation Robot Using Impedance Control for Patients after Stroke.

PubMed

Guang, Hui; Ji, Linhong; Shi, Yingying; Misgeld, Berno J E

2018-01-01

The robot-assisted therapy has been demonstrated to be effective in the improvements of limb function and even activities of daily living for patients after stroke. This paper presents an interactive upper-limb rehabilitation robot with a parallel mechanism and an isometric screen embedded in the platform to display trajectories. In the dynamic modeling for impedance control, the effects of friction and inertia are reduced by introducing the principle of virtual work and derivative of Jacobian matrix. To achieve the assist-as-needed impedance control for arbitrary trajectories, the strategy based on orthogonal deviations is proposed. Simulations and experiments were performed to validate the dynamic modeling and impedance control. Besides, to investigate the influence of the impedance in practice, a subject participated in experiments and performed two types of movements with the robot, that is, rectilinear and circular movements, under four conditions, that is, with/without resistance or impedance, respectively. The results showed that the impedance and resistance affected both mean absolute error and standard deviation of movements and also demonstrated the significant differences between movements with/without impedance and resistance ( p < 0.001). Furthermore, the error patterns were discussed, which suggested that the impedance environment was capable of alleviating movement deviations by compensating the synergetic inadequacy between the shoulder and elbow joints.

Dynamic Modeling and Interactive Performance of PARM: A Parallel Upper-Limb Rehabilitation Robot Using Impedance Control for Patients after Stroke

PubMed Central

Shi, Yingying; Misgeld, Berno J. E.

2018-01-01

The robot-assisted therapy has been demonstrated to be effective in the improvements of limb function and even activities of daily living for patients after stroke. This paper presents an interactive upper-limb rehabilitation robot with a parallel mechanism and an isometric screen embedded in the platform to display trajectories. In the dynamic modeling for impedance control, the effects of friction and inertia are reduced by introducing the principle of virtual work and derivative of Jacobian matrix. To achieve the assist-as-needed impedance control for arbitrary trajectories, the strategy based on orthogonal deviations is proposed. Simulations and experiments were performed to validate the dynamic modeling and impedance control. Besides, to investigate the influence of the impedance in practice, a subject participated in experiments and performed two types of movements with the robot, that is, rectilinear and circular movements, under four conditions, that is, with/without resistance or impedance, respectively. The results showed that the impedance and resistance affected both mean absolute error and standard deviation of movements and also demonstrated the significant differences between movements with/without impedance and resistance (p < 0.001). Furthermore, the error patterns were discussed, which suggested that the impedance environment was capable of alleviating movement deviations by compensating the synergetic inadequacy between the shoulder and elbow joints. PMID:29850004

Laser-Based Slam with Efficient Occupancy Likelihood Map Learning for Dynamic Indoor Scenes

NASA Astrophysics Data System (ADS)

Li, Li; Yao, Jian; Xie, Renping; Tu, Jinge; Feng, Chen

2016-06-01

Location-Based Services (LBS) have attracted growing attention in recent years, especially in indoor environments. The fundamental technique of LBS is the map building for unknown environments, this technique also named as simultaneous localization and mapping (SLAM) in robotic society. In this paper, we propose a novel approach for SLAMin dynamic indoor scenes based on a 2D laser scanner mounted on a mobile Unmanned Ground Vehicle (UGV) with the help of the grid-based occupancy likelihood map. Instead of applying scan matching in two adjacent scans, we propose to match current scan with the occupancy likelihood map learned from all previous scans in multiple scales to avoid the accumulation of matching errors. Due to that the acquisition of the points in a scan is sequential but not simultaneous, there unavoidably exists the scan distortion at different extents. To compensate the scan distortion caused by the motion of the UGV, we propose to integrate a velocity of a laser range finder (LRF) into the scan matching optimization framework. Besides, to reduce the effect of dynamic objects such as walking pedestrians often existed in indoor scenes as much as possible, we propose a new occupancy likelihood map learning strategy by increasing or decreasing the probability of each occupancy grid after each scan matching. Experimental results in several challenged indoor scenes demonstrate that our proposed approach is capable of providing high-precision SLAM results.

Effect of loss control service on reported injury incidence.

PubMed

Nave, Michael E; Veltri, Anthony

2004-01-01

A retrospective analysis evaluated the effectiveness of an insurance carrier's flexible loss control service strategy in reducing workers' compensation policyholders' reported injury and illness claims. To assess the effects of a loss control service strategy on workers' compensation claim frequency rates, on medical-only claim rates, on severity-claim rates, and on claim cost among a group of California employers. Eighty-two small- and medium-sized companies with workers' compensation policies expiring in 1999 were randomly selected from a population of policyholders assigned to loss control consultants for two or more years. Claim performance data were obtained for each company's first expired in-force policy year and its 1999 expired policy year. The retrospective design was combined with a control component based on a randomly selected comparison group of 45 companies whose first policy year with the insurer expired in 1999 and who received safety services from the loss control staff. The flexible loss control consultation service strategy was associated with lower average claim rates and costs. Companies assigned to a loss control consultant for two or more years (the "outcome group") had an average claim rate of 1.24 per $10,000 premium, compared with a rate of 1.62 in the "initial group" and a rate of 1.60 in the "comparison group." The average severity-claim rate of the outcome group was 0.32, compared with the initial-year and comparison-group means of 0.48 and 0.46, respectively. The average medical-only claim rate was 0.92, compared with the initial- and comparison-group means of 1.14 and 1.14. The outcome group's average loss ratio was over 10% lower than that of the initial and comparison groups. Statistical analysis indicated that differences among the groups' claim rates and severity-claim rates were [F=(2,206) 4.938, P=0.008] and [F=(2,206) 8.208, P<0.001], respectively. A loss control service strategy that provides service flexibility and develops partnership between employer and consultant can help reduce the frequency and severity of workers' compensation claims. Barriers to consultation service flexibility, both internal and external, should be identified and removed to enhance service efficacy.

Temperature compensation via cooperative stability in protein degradation

NASA Astrophysics Data System (ADS)

Peng, Yuanyuan; Hasegawa, Yoshihiko; Noman, Nasimul; Iba, Hitoshi

2015-08-01

Temperature compensation is a notable property of circadian oscillators that indicates the insensitivity of the oscillator system's period to temperature changes; the underlying mechanism, however, is still unclear. We investigated the influence of protein dimerization and cooperative stability in protein degradation on the temperature compensation ability of two oscillators. Here, cooperative stability means that high-order oligomers are more stable than their monomeric counterparts. The period of an oscillator is affected by the parameters of the dynamic system, which in turn are influenced by temperature. We adopted the Repressilator and the Atkinson oscillator to analyze the temperature sensitivity of their periods. Phase sensitivity analysis was employed to evaluate the period variations of different models induced by perturbations to the parameters. Furthermore, we used experimental data provided by other studies to determine the reasonable range of parameter temperature sensitivity. We then applied the linear programming method to the oscillatory systems to analyze the effects of protein dimerization and cooperative stability on the temperature sensitivity of their periods, which reflects the ability of temperature compensation in circadian rhythms. Our study explains the temperature compensation mechanism for circadian clocks. Compared with the no-dimer mathematical model and linear model for protein degradation, our theoretical results show that the nonlinear protein degradation caused by cooperative stability is more beneficial for realizing temperature compensation of the circadian clock.

Robust crossfeed design for hovering rotorcraft. M.S. Thesis

NASA Technical Reports Server (NTRS)

Catapang, David R.

1993-01-01

Control law design for rotorcraft fly-by-wire systems normally attempts to decouple angular responses using fixed-gain crossfeeds. This approach can lead to poor decoupling over the frequency range of pilot inputs and increase the load on the feedback loops. In order to improve the decoupling performance, dynamic crossfeeds may be adopted. Moreover, because of the large changes that occur in rotorcraft dynamics due to small changes about the nominal design condition, especially for near-hovering flight, the crossfeed design must be 'robust.' A new low-order matching method is presented here to design robost crossfeed compensators for multi-input, multi-output (MIMO) systems. The technique identifies degrees-of-freedom that can be decoupled using crossfeeds, given an anticipated set of parameter variations for the range of flight conditions of concern. Cross-coupling is then reduced for degrees-of-freedom that can use crossfeed compensation by minimizing off-axis response magnitude average and variance. Results are presented for the analysis of pitch, roll, yaw, and heave coupling of the UH-60 Black Hawk helicopter in near-hovering flight. Robust crossfeeds are designed that show significant improvement in decoupling performance and robustness over nominal, single design point, compensators. The design method and results are presented in an easily-used graphical format that lends significant physical insight to the design procedure. This plant pre-compensation technique is an appropriate preliminary step to the design of robust feedback control laws for rotorcraft.

A Study of Fixed-Order Mixed Norm Designs for a Benchmark Problem in Structural Control

NASA Technical Reports Server (NTRS)

Whorton, Mark S.; Calise, Anthony J.; Hsu, C. C.

1998-01-01

This study investigates the use of H2, p-synthesis, and mixed H2/mu methods to construct full-order controllers and optimized controllers of fixed dimensions. The benchmark problem definition is first extended to include uncertainty within the controller bandwidth in the form of parametric uncertainty representative of uncertainty in the natural frequencies of the design model. The sensitivity of H2 design to unmodelled dynamics and parametric uncertainty is evaluated for a range of controller levels of authority. Next, mu-synthesis methods are applied to design full-order compensators that are robust to both unmodelled dynamics and to parametric uncertainty. Finally, a set of mixed H2/mu compensators are designed which are optimized for a fixed compensator dimension. These mixed norm designs recover the H, design performance levels while providing the same levels of robust stability as the u designs. It is shown that designing with the mixed norm approach permits higher levels of controller authority for which the H, designs are destabilizing. The benchmark problem is that of an active tendon system. The controller designs are all based on the use of acceleration feedback.

Evaluation and Compensation of Detector Solenoid Effects in the JLEIC

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

Wei, Guohui; Morozov, Vasiliy; Zhang, Yuhong

2016-05-01

The JLEIC detector solenoid has a strong 3 T field in the IR area, and its tails extend over a range of several meters. One of the main effects of the solenoid field is coupling of the horizontal and vertical betatron motions which must be corrected in order to preserve the dynamical stability and beam spot size match at the IP. Additional effects include influence on the orbit and dispersion caused by the angle between the solenoid axis and the beam orbit. Meanwhile it affects ion polarization breaking the figure-8 spin symmetry. Crab dynamics further complicates the picture. All ofmore » these effects have to be compensated or accounted for. The proposed correction system is equivalent to the Rotating Frame Method. However, it does not involve physical rotation of elements. It provides local compensation of the solenoid effects independently for each side of the IR. It includes skew quadrupoles, dipole correctors and anti-solenoids to cancel perturbations to the orbit and linear optics. The skew quadrupoles and FFQ together generate an effect equivalent to adjustable rotation angle to do the decoupling task. Details of all of the correction systems are presented.« less

Leveraging Disturbance Observer Based Torque Control for Improved Impedance Rendering with Series Elastic Actuators

NASA Technical Reports Server (NTRS)

Mehling, Joshua S.; Holley, James; O'Malley, Marcia K.

2015-01-01

The fidelity with which series elastic actuators (SEAs) render desired impedances is important. Numerous approaches to SEA impedance control have been developed under the premise that high-precision actuator torque control is a prerequisite. Indeed, the design of an inner torque compensator has a significant impact on actuator impedance rendering. The disturbance observer (DOB) based torque control implemented in NASA's Valkyrie robot is considered here and a mathematical model of this torque control, cascaded with an outer impedance compensator, is constructed. While previous work has examined the impact a disturbance observer has on torque control performance, little has been done regarding DOBs and impedance rendering accuracy. Both simulation and a series of experiments are used to demonstrate the significant improvements possible in an SEA's ability to render desired dynamic behaviors when utilizing a DOB. Actuator transparency at low impedances is improved, closed loop hysteresis is reduced, and the actuator's dynamic response to both commands and interaction torques more faithfully matches that of the desired model. All of this is achieved by leveraging DOB based control rather than increasing compensator gains, thus making improved SEA impedance control easier to achieve in practice.

[Dynamics of soil water reservoir of wheat field in rain-fed area of the Loess Tableland, China].

PubMed

Li, Peng Zhan; Wang, Li; Wang, Di

2017-11-01

Soil reservoir is the basis of stable grain production and sustainable development in dry farming area. Based on the long-term field experiment, this paper investigated the changes of soil moisture in wheat field located in the rain-fed Changwu Tableland, and analyzed the interannual and annual variation characteristics and dynamics trends of soil reservoir from 2012 to 2015. The results showed that the vertical distribution curves of average soil water content were double peaks and double valleys: first peak and valley occurred in the 10-20 and 50 cm soil layer, respectively, while for the second peak and valley, the corresponding soil layer was the 100 and 280 cm soil layer. Soil reservoir did not coincide with precipitation for all yearly precipitation patterns but lagged behind. Yearly precipitation patterns had a great influence on the interannual and annual dynamic changes of soil reservoir. Compared with rainy year, the depth of soil moisture consumption decreased and supplementary effect of precipitation on soil moisture became obvious under effects of drought year and normal year. In rainy year, soil reservoir had a large surplus (84.2 mm), water balance was compensated; in normal year, it had a slight surplus (9.5 mm), water balance was compensated; while in drought year, it was slightly deficient (1.5 mm), water balance was negatively compensated. The dynamics of soil water in winter wheat field in the rain-fed Changwu Tableland could be divided into four periods: seedling period, slow consumption period, large consumption period, and harvest period, the order of evapotranspiration was large consumption period> seedling period> harvest period> slow consumption period.

Simulations of Operation Dynamics of Different Type GaN Particle Sensors

PubMed Central

Gaubas, Eugenijus; Ceponis, Tomas; Kalesinskas, Vidas; Pavlov, Jevgenij; Vysniauskas, Juozas

2015-01-01

The operation dynamics of the capacitor-type and PIN diode type detectors based on GaN have been simulated using the dynamic and drift-diffusion models. The drift-diffusion current simulations have been implemented by employing the software package Synopsys TCAD Sentaurus. The monopolar and bipolar drift regimes have been analyzed by using dynamic models based on the Shockley-Ramo theorem. The carrier multiplication processes determined by impact ionization have been considered in order to compensate carrier lifetime reduction due to introduction of radiation defects into GaN detector material. PMID:25751080

Binocular video ophthalmoscope for simultaneous recording of sequences of the human retina to compare dynamic parameters

NASA Astrophysics Data System (ADS)

Tornow, Ralf P.; Milczarek, Aleksandra; Odstrcilik, Jan; Kolar, Radim

2017-07-01

A parallel video ophthalmoscope was developed to acquire short video sequences (25 fps, 250 frames) of both eyes simultaneously with exact synchronization. Video sequences were registered off-line to compensate for eye movements. From registered video sequences dynamic parameters like cardiac cycle induced reflection changes and eye movements can be calculated and compared between eyes.

Monolithic amplifier with stable, high resistance feedback element and method for fabricating the same

DOEpatents

O`Connor, P.

1998-08-11

A monolithic amplifier includes a stable, high resistance feedback circuit and a dynamic bias circuit. The dynamic bias circuit is formed with active elements matched to those in the amplifier and feedback circuit to compensate for variations in the operating and threshold voltages thereby maintaining a stable resistance in the feedback circuit. 11 figs.

Dynamic properties of hot-wire anemometric measurement circuits in the aspect of measurements in mine conditions / Właściwości dynamiczne termoanemometrycznych układów pomiarowych w aspekcie pomiarów w warunkach kopalnianych

NASA Astrophysics Data System (ADS)

Jamróz, Paweł; Ligęza, Paweł; Socha, Katarzyna

2012-12-01

The use of measurement apparatus under conditions which differ significantly from those under which the apparatus was adjusted carries the risk of altering the previously determined measurement characteristics. This is of special concern in the case of apparatus which is sensitive to external measurement conditions. Advanced measurement systems are equipped with algorithms which allow the negative effect of unstable environmental conditions on their static characteristics to be compensated for. Meanwhile, the problem of altered dynamic properties of such systems is often neglected. This paper presents a model study in which the effect of variable operational conditions on dynamic response of hot-wire anemometric measurement system in the case of simulated mine flows was investigated. A mathematical model of measurement system able to compensate the negative effect of changes in flow velocity and configuration of measurement apparatus itself on its dynamic properties was developed and investigated. Based on conducted experiments, we have developed an automatic regulation algorithm enabling the transmission band of measurement apparatus to be optimized for measurement conditions prevailing in mine environment.

Experimental Verification of a Dynamic Voltage Restorer Capable of Significantly Reducing an Energy-Storage Element

NASA Astrophysics Data System (ADS)

Jimichi, Takushi; Fujita, Hideaki; Akagi, Hirofumi

This paper deals with a dynamic voltage restorer (DVR) characterized by installing the shunt converter at the load side. The DVR can compensate for the load voltage when a voltage sag appears in the supply voltage. An existing DVR requires a large capacitor bank or other energy-storage elements such as double-layer capacitors or batteries. The DVR presented in this paper requires only a small dc capacitor intended for smoothing the dc-link voltage. Moreover, three control methods for the series converter are compared and discussed to reduce the series-converter rating, paying attention to the zero-sequence voltages included in the supply voltage and the compensating voltage. Experimental results obtained from a 200-V, 5-kW laboratory system are shown to verify the viability of the system configuration and the control methods.

High precision tracking control of a servo gantry with dynamic friction compensation.

PubMed

Zhang, Yangming; Yan, Peng; Zhang, Zhen

2016-05-01

This paper is concerned with the tracking control problem of a voice coil motor (VCM) actuated servo gantry system. By utilizing an adaptive control technique combined with a sliding mode approach, an adaptive sliding mode control (ASMC) law with friction compensation scheme is proposed in presence of both frictions and external disturbances. Based on the LuGre dynamic friction model, a dual-observer structure is used to estimate the unmeasurable friction state, and an adaptive control law is synthesized to effectively handle the unknown friction model parameters as well as the bound of the disturbances. Moreover, the proposed control law is also implemented on a VCM servo gantry system for motion tracking. Simulations and experimental results demonstrate good tracking performance, which outperform traditional control approaches. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Origin of the spin Seebeck effect in compensated ferrimagnets

PubMed Central

Geprägs, Stephan; Kehlberger, Andreas; Coletta, Francesco Della; Qiu, Zhiyong; Guo, Er-Jia; Schulz, Tomek; Mix, Christian; Meyer, Sibylle; Kamra, Akashdeep; Althammer, Matthias; Huebl, Hans; Jakob, Gerhard; Ohnuma, Yuichi; Adachi, Hiroto; Barker, Joseph; Maekawa, Sadamichi; Bauer, Gerrit E. W.; Saitoh, Eiji; Gross, Rudolf; Goennenwein, Sebastian T. B.; Kläui, Mathias

2016-01-01

Magnons are the elementary excitations of a magnetically ordered system. In ferromagnets, only a single band of low-energy magnons needs to be considered, but in ferrimagnets the situation is more complex owing to different magnetic sublattices involved. In this case, low lying optical modes exist that can affect the dynamical response. Here we show that the spin Seebeck effect (SSE) is sensitive to the complexities of the magnon spectrum. The SSE is caused by thermally excited spin dynamics that are converted to a voltage by the inverse spin Hall effect at the interface to a heavy metal contact. By investigating the temperature dependence of the SSE in the ferrimagnet gadolinium iron garnet, with a magnetic compensation point near room temperature, we demonstrate that higher-energy exchange magnons play a key role in the SSE. PMID:26842873

Notes on a broad-band variant of the NCER seismic data multiplex system for use with field tape recorders

USGS Publications Warehouse

Eaton, Jerry P.

1976-01-01

Tests of the standard NCER multiplex system recorded and played back on both the Bell and Howell 3700B (about 0.1% tape speed variation) and on the Sony TC-126 cassette recorder (about 1% tape speed variation) showed that subtractive compensation employing a reference frequency multiplexed on the data track was remarkably effective in reducing tape-speed-variation-induced noise 1 and, hence, in increasing the dynamic range of the record/playback system. Further tests suggested that the 0 to 30 Hz bandwidth of the standard system (8 data channels) might be increased substantially, at the 'price' of reducing the number of data channels to 3 or 4, without serious loss of dynamic range if subtractive compensation could be implemented effectively with the broader-band system.

Decentralized adaptive robust control based on sliding mode and nonlinear compensator for the control of ankle movement using functional electrical stimulation of agonist-antagonist muscles

NASA Astrophysics Data System (ADS)

Kobravi, Hamid-Reza; Erfanian, Abbas

2009-08-01

A decentralized control methodology is designed for the control of ankle dorsiflexion and plantarflexion in paraplegic subjects with electrical stimulation of tibialis anterior and calf muscles. Each muscle joint is considered as a subsystem and individual controllers are designed for each subsystem. Each controller operates solely on its associated subsystem, with no exchange of information between the subsystems. The interactions between the subsystems are taken as external disturbances for each isolated subsystem. In order to achieve robustness with respect to external disturbances, unmodeled dynamics, model uncertainty and time-varying properties of muscle-joint dynamics, a robust control framework is proposed which is based on the synergistic combination of an adaptive nonlinear compensator with a sliding mode control and is referred to as an adaptive robust control. Extensive simulations and experiments on healthy and paraplegic subjects were performed to demonstrate the robustness against the time-varying properties of muscle-joint dynamics, day-to-day variations, subject-to-subject variations, fast convergence, stability and tracking accuracy of the proposed method. The results indicate that the decentralized robust control provides excellent tracking control for different reference trajectories and can generate control signals to compensate the muscle fatigue and reject the external disturbance. Moreover, the controller is able to automatically regulate the interaction between agonist and antagonist muscles under different conditions of operating without any preprogrammed antagonist activities.

Decentralized adaptive robust control based on sliding mode and nonlinear compensator for the control of ankle movement using functional electrical stimulation of agonist-antagonist muscles.

PubMed

Kobravi, Hamid-Reza; Erfanian, Abbas

2009-08-01

A decentralized control methodology is designed for the control of ankle dorsiflexion and plantarflexion in paraplegic subjects with electrical stimulation of tibialis anterior and calf muscles. Each muscle joint is considered as a subsystem and individual controllers are designed for each subsystem. Each controller operates solely on its associated subsystem, with no exchange of information between the subsystems. The interactions between the subsystems are taken as external disturbances for each isolated subsystem. In order to achieve robustness with respect to external disturbances, unmodeled dynamics, model uncertainty and time-varying properties of muscle-joint dynamics, a robust control framework is proposed which is based on the synergistic combination of an adaptive nonlinear compensator with a sliding mode control and is referred to as an adaptive robust control. Extensive simulations and experiments on healthy and paraplegic subjects were performed to demonstrate the robustness against the time-varying properties of muscle-joint dynamics, day-to-day variations, subject-to-subject variations, fast convergence, stability and tracking accuracy of the proposed method. The results indicate that the decentralized robust control provides excellent tracking control for different reference trajectories and can generate control signals to compensate the muscle fatigue and reject the external disturbance. Moreover, the controller is able to automatically regulate the interaction between agonist and antagonist muscles under different conditions of operating without any preprogrammed antagonist activities.

Transfer of Dynamic Learning Across Postures

PubMed Central

Wolpert, Daniel M.

2009-01-01

When learning a difficult motor task, we often decompose the task so that the control of individual body segments is practiced in isolation. But on re-composition, the combined movements can result in novel and possibly complex internal forces between the body segments that were not experienced (or did not need to be compensated for) during isolated practice. Here we investigate whether dynamics learned in isolation by one part of the body can be used by other parts of the body to immediately predict and compensate for novel forces between body segments. Subjects reached to targets while holding the handle of a robotic, force-generating manipulandum. One group of subjects was initially exposed to the novel robot dynamics while seated and was then tested in a standing position. A second group was tested in the reverse order: standing then sitting. Both groups adapted their arm dynamics to the novel environment, and this movement learning transferred between seated and standing postures and vice versa. Both groups also generated anticipatory postural adjustments when standing and exposed to the force field for several trials. In the group that had learned the dynamics while seated, the appropriate postural adjustments were observed on the very first reach on standing. These results suggest that the CNS can immediately anticipate the effect of learned movement dynamics on a novel whole-body posture. The results support the existence of separate mappings for posture and movement, which encode similar dynamics but can be adapted independently. PMID:19710374

Postural stability in a population of dancers, healthy non-dancers, and vestibular neuritis patients.

PubMed

Martin-Sanz, Eduardo; Ortega Crespo, Isabel; Esteban-Sanchez, Jonathan; Sanz, Ricardo

2017-09-01

Several studies have indicated better balance control in dancers than in control participants, but some controversy remains. The aim of our study is to evaluate the postural stability in a cohort of dancers, non-dancers, compensated, and non-compensated unilateral vestibular neuritis (VN). This is a prospective study of control subjects, dancers, and VN patients between June 2009 and December 2015. Dancers from the Dance Conservatory of Madrid and VN patients were referred to our department for analysis. After the clinical history, neuro-otological examination, audiogram, and caloric tests, the diagnosis was done. Results from clinical examination were used for the categorization of compensation situation. A computerized dynamic posturography was performed to every subject. Forty dancers and 38 women formed both 'dancer' and 'normal' cohorts. Forty-two compensated and 39 uncompensated patients formed both 'compensated' and 'uncompensated' cohorts. Dancers had significantly greater antero-posterior (AP) body sway than controls during condition 5 and 6 in the Sensory Organization Test (SOT) (p < .05). When we compared the uncompensated cohort with both control and dancers groups, we found significant greater body sway in every SOT studied condition (p < .05). While mean AP body say in SOT 5 and 6, showed greater values in compensated patients than the control group, the mean analysis did not show any statistical difference between the compensated and dancer groups, in such SOT conditions. Dancers demonstrated greater sways than non-dancers when they relied their postural control on vestibular input alone. Compensated patients had a similar posturographic pattern that the dancers cohort, suggesting a similar shift from visual to somatosensory information.

The Differential Impact of Pre-College and Self-Regulatory Factors on Academic Achievement of University Students with and without Learning Disabilities.

ERIC Educational Resources Information Center

Ruban, Lilia; McCoach, D. Betsy; Nora, Amaury

Even though research on academic self-regulation has proliferated in recent years, no studies have investigated the question of whether the perceived usefulness and the use of standard self-regulated learning strategies and compensation strategies provide a differential prediction of academic achievement for college students with and without…

Measurement Structure of the Coping Strategies Questionnaire-24 in a Sample of Individuals with Musculoskeletal Pain: A Confirmatory Factor Analysis

ERIC Educational Resources Information Center

Chiu, Chung-Yi; Jochman, Joseph; Fujikawa, Mayu; Strand, David; Cheing, Gladys; Lee, Gloria; Chan, Fong

2014-01-01

Purpose: To examine the factorial structure of the "Coping Strategy Questionnaire"-24 (CSQ-24) in a sample of Canadians with chronic musculoskeletal pain. Method: The sample included 171 workers' compensation clients (50.9% men) recruited from outpatient rehabilitation facilities in Canada. Mean age of participants was 42.45 years (SD =…

What Is Compensatory Pedagogy Trying to Compensate for? Compensatory Strategies and the Ethnic "Other"

ERIC Educational Resources Information Center

Moller, Asa

2012-01-01

Compensatory pedagogy is in theory a strategy used to manage social and cultural diversity (Sleeter, 2007) by providing extra resources or special treatment for so-called deprived groups. A problem with this particular kind of approach to social and cultural diversity is that it lacks critical awareness of the way social differences (i.e. race,…

29 CFR 2510.3-21 - Definition of “Fiduciary.”

Code of Federal Regulations, 2010 CFR

2010-07-01

... regarding such matters as, among other things, investment policies or strategy, overall portfolio... compensation, direct or indirect, with respect to any moneys or other property of such plan, or having any...

New tax laws require slight shifts in hospitals' funding strategies.

PubMed

Bromberg, R S

1979-07-16

Recent tax laws that affect hospitals' deferred compensation plans, employment taxes, annuities, foundation grants, unrelated business income, and gifts of appreciated property will not seriously affect charitable giving to hospitals.

A novel disturbance-observer based friction compensation scheme for ball and plate system.

PubMed

Wang, Yongkun; Sun, Mingwei; Wang, Zenghui; Liu, Zhongxin; Chen, Zengqiang

2014-03-01

Friction is often ignored when designing a controller for the ball and plate system, which can lead to steady-error and stick-slip phenomena, especially for the small amplitude command. It is difficult to achieve high-precision control performance for the ball and plate system because of its friction. A novel reference compensation strategy is presented to attenuate the aftereffects caused by the friction. To realize this strategy, a linear control law is proposed based on a reduced-order observer. Neither the accurate friction model nor the estimation of specific characteristic parameters is needed in this design. Moreover, the describing function method illustrates that the limit cycle can be avoided. Finally, the comparative mathematical simulations and the practical experiments are used to validate the effectiveness of the proposed method. © 2013 ISA Published by ISA All rights reserved.

Apparatus and Method for Compensating for Process, Voltage, and Temperature Variation of the Time Delay of a Digital Delay Line

NASA Technical Reports Server (NTRS)

Seefeldt, James (Inventor); Feng, Xiaoxin (Inventor); Roper, Weston (Inventor)

2013-01-01

A process, voltage, and temperature (PVT) compensation circuit and a method of continuously generating a delay measure are provided. The compensation circuit includes two delay lines, each delay line providing a delay output. The two delay lines may each include a number of delay elements, which in turn may include one or more current-starved inverters. The number of delay lines may differ between the two delay lines. The delay outputs are provided to a combining circuit that determines an offset pulse based on the two delay outputs and then averages the voltage of the offset pulse to determine a delay measure. The delay measure may be one or more currents or voltages indicating an amount of PVT compensation to apply to input or output signals of an application circuit, such as a memory-bus driver, dynamic random access memory (DRAM), a synchronous DRAM, a processor or other clocked circuit.

An 1.4 ppm/°C bandgap voltage reference with automatic curvature-compensation technique

NASA Astrophysics Data System (ADS)

Zhou, Zekun; Yu, Hongming; Shi, Yue; Zhang, Bo

2017-12-01

A high-precision Bandgap voltage reference (BGR) with a novel curvature-compensation scheme is proposed in this paper. The temperature coefficient (TC) can be automatically optimized with a built-in adaptive curvature-compensation technique, which is realized in a digitization control way. Firstly, an exponential curvature compensation method is adopted to reduce the TC in a certain degree, especially in low temperature range. Then, the temperature drift of BGR in higher temperature range can be further minimized by dynamic zero-temperature-coefficient point tracking with temperature changes. With the help of proposed adaptive signal processing, the output voltage of BGR can approximately maintain zero TC in a wider temperature range. Experiment results of the BGR proposed in this paper, which is implemented in 0.35-μm BCD process, illustrate that the TC of 1.4ppm/°C is realized under the power supply voltage of 3.6V and the power supply rejection of the proposed circuit is -67dB.

Kinematic differences exist between transtibial amputee fallers and non-fallers during downwards step transitioning.

PubMed

Vanicek, Natalie; Strike, Siobhán C; Polman, Remco

2015-08-01

Stair negotiation is biomechanically more challenging than level gait. There are few biomechanical assessments of transtibial amputees descending stairs and none specifically related to falls. Stair descent may elicit more differences than level gait in amputees with and without a previous falls history. The aim of this study was to compare the gait kinematics of fallers and non-fallers during downwards step transitioning in transtibial amputees. Cross-sectional study. Six fallers and five non-fallers completed step transition trials on a three-step staircase at their self-selected pace. Nine participants exhibited a clear preference to lead with the affected limb, while two had no preference. Four participants self-selected a step-to rather than a reciprocal stair descent strategy. The fallers who used a reciprocal strategy walked 44% more quickly than the non-fallers. To compensate for the lack of active plantar flexion of the prosthetic foot, exaggerated range of motion occurred proximally at the pelvis during swing. The step-to group was more reliant on the handrails than the reciprocal group and walked more slowly. As anticipated, the fallers walked faster than the non-fallers despite employing the more difficult 'roll-over' technique. Handrail use could help to improve dynamic control during downwards step transitions. Transtibial amputees are advised to descend steps using external support, such as handrails, for enhanced dynamic control. Hip abductor and knee extensor eccentric strength should be improved through targeted exercise. Prosthetic socket fit should be checked to allow adequate knee range of motion on the affected side. © The International Society for Prosthetics and Orthotics 2014.

Access to Health Care Services for the Disabled Elderly

PubMed Central

Taylor, Donald H; Hoenig, Helen

2006-01-01

Objective To determine whether difficulty walking and the strategies persons use to compensate for this deficit influenced downstream Medicare expenditures. Data Source Secondary data analysis of Medicare claims data (1999–2000) for age-eligible Medicare beneficiaries (N = 4,997) responding to the community portion of the 1999 National Long Term Care Survey (NLTCS). Study Design Longitudinal cohort study. Walking difficulty and compensatory strategy were measured at the 1999 NLTCS, and used to predict health care use as measured in Medicare claims data from the survey date through year-end 2000. Data Extraction Respondents to the 1999 community NLTCS with complete information on key explanatory variables (walking difficulty and compensatory strategy) were linked with Medicare claims to define outcome variables (health care use and cost). Principal Findings Persons who reported it was very difficult to walk had more downstream home health visits (1.1/month, p<.001), but fewer outpatient physician visits (−0.16/month, p<.001) after controlling for overall disease burden. Those using a compensatory strategy for walking also had increased home health visits/month (0.55 for equipment, 1.0 for personal assistance, p<.001 for both) but did not have significantly reduced outpatient visits. Persons reporting difficulty walking had increased downstream Medicare costs ranging from $163 to $222/month (p<.001) depending upon how difficult walking was. Less than half of the persons who used equipment to adapt to walking difficulty had their difficulty fully compensated by the use of equipment. Persons using equipment that fully compensated their difficulty used around $300/month less in Medicare-financed costs compared with those with residual difficulty. Conclusions Difficulty walking and use of compensatory strategies are correlated with the use of Medicare-financed services. The potential impact on the Medicare program is large, given how common such limitations are among the elderly. PMID:16704510

Comparing the Nutritional Impact of Dietary Strategies to Reduce Discretionary Choice Intake in the Australian Adult Population: A Simulation Modelling Study

PubMed Central

Grieger, Jessica A.; Johnson, Brittany J.; Wycherley, Thomas P.; Golley, Rebecca K.

2017-01-01

Dietary strategies to reduce discretionary choice intake are commonly utilized in practice, but evidence on their relative efficacy is lacking. The aim was to compare the potential impact on nutritional intake of three strategies to reducing discretionary choices intake in the Australian adult (19–90 years) population. Dietary simulation modelling using data from the National Nutrition and Physical Activity Survey 2011–2012 was conducted (n = 9341; one 24 h dietary recall). Strategies modelled were: moderation (reduce discretionary choices by 50%, with 0%, 25% or 75% energy compensation); substitution (replace 50% of discretionary choices with core choices); reformulation (replace 50% SFA with unsaturated fats, reduce added sugars by 25%, and reduce sodium by 20%). Compared to the base case (observed) intake, modelled intakes in the moderation scenario showed: −17.3% lower energy (sensitivity analyses, 25% energy compensation −14.2%; 75% energy compensation −8.0%), −20.9% lower SFA (−17.4%; −10.5%), −43.3% lower added sugars (−41.1%; −36.7%) and 17.7% lower sodium (−14.3%; −7.5%). Substitution with a range of core items, or with fruits, vegetables and core beverages only, resulted in similar changes in energy intake (−13.5% and −15.4%), SFA (−17.7% and −20.1%), added sugars (−42.6% and −43%) and sodium (−13.7% and −16.5%), respectively. Reformulating discretionary choices had minimal impact on reducing energy intake but reduced SFA (−10.3% to −30.9%), added sugars (−9.3% to −52.9%), and alcohol (−25.0% to −49.9%) and sodium (−3.3% to −13.2%). The substitution and reformulation scenarios minimized negative changes in fiber, protein and micronutrient intakes. While each strategy has strengths and limitations, substitution of discretionary choices with core foods and beverages may optimize the nutritional impact. PMID:28467387

Environmental flows for rivers and economic compensation for irrigators.

PubMed

Sisto, Nicholas P

2009-02-01

Securing flows for environmental purposes from an already fully utilized river is an impossible task--unless users are either coerced into freeing up water, or offered incentives to do so. One sensible strategy for motivating users to liberate volumes is to offer them economic compensation. The right amount for that compensation then becomes a key environmental management issue. This paper analyses a proposal to restore and maintain ecosystems on a stretch of the Río Conchos in northern Mexico, downstream from a large irrigation district that consumes nearly all local flows. We present here estimates of environmental flow requirements for these ecosystems and compute compensation figures for irrigators. These figures are derived from crop-specific irrigation water productivities we statistically estimate from a large set of historical production and irrigation data obtained from the district. This work has general implications for river ecosystem management in water-stressed basins, particularly in terms of the design of fair and effective water sharing mechanisms.

Dosage compensation, the origin and the afterlife of sex chromosomes.

PubMed

Larsson, Jan; Meller, Victoria H

2006-01-01

Over the past 100 years Drosophila has been developed into an outstanding model system for the study of evolutionary processes. A fascinating aspect of evolution is the differentiation of sex chromosomes. Organisms with highly differentiated sex chromosomes, such as the mammalian X and Y, must compensate for the imbalance in gene dosage that this creates. The need to adjust the expression of sex-linked genes is a potent force driving the rise of regulatory mechanisms that act on an entire chromosome. This review will contrast the process of dosage compensation in Drosophila with the divergent strategies adopted by other model organisms. While the machinery of sex chromosome compensation is different in each instance, all share the ability to direct chromatin modifications to an entire chromosome. This review will also explore the idea that chromosome-targeting systems are sometimes adapted for other purposes. This appears the likely source of a chromosome-wide targeting system displayed by the Drosophila fourth chromosome.

Design of digital load torque observer in hybrid electric vehicle

NASA Astrophysics Data System (ADS)

Sun, Yukun; Zhang, Haoming; Wang, Yinghai

2008-12-01

In hybrid electric vehicle, engine begain to work only when motor was in high speed in order to decrease tail gas emission. However, permanent magnet motor was sensitive to its load, adding engine to the system always made its speed drop sharply, which caused engine to work in low efficiency again and produced much more environment pollution. Dynamic load torque model of permanent magnet synchronous motor is established on the basic of motor mechanical equation and permanent magnet synchronous motor vector control theory, Full- digital load torque observer and compensation control system is made based on TMS320F2407A. Experiment results prove load torque observer and compensation control system can detect and compensate torque disturbing effectively, which can solve load torque disturbing and decrease gas pollution of hybrid electric vehicle.

A study of digital gyro compensation loops. [data conversion routines and breadboard models

NASA Technical Reports Server (NTRS)

1975-01-01

The feasibility is discussed of replacing existing state-of-the-art analog gyro compensation loops with digital computations. This was accomplished by designing appropriate compensation loops for the dry turned TDF gyro, selecting appropriate data conversion and processing techniques and algorithms, and breadboarding the design for laboratory evaluation. A breadboard design was established in which one axis of a Teledyne turned-gimbal TDF gyro was caged digitally while the other was caged using conventional analog electronics. The digital loop was designed analytically to closely resemble the analog loop in performance. The breadboard was subjected to various static and dynamic tests in order to establish the relative stability characteristics and frequency responses of the digital and analog loops. Several variations of the digital loop configuration were evaluated. The results were favorable.

Advanced Motion Compensation Methods for Intravital Optical Microscopy

PubMed Central

Vinegoni, Claudio; Lee, Sungon; Feruglio, Paolo Fumene; Weissleder, Ralph

2013-01-01

Intravital microscopy has emerged in the recent decade as an indispensible imaging modality for the study of the micro-dynamics of biological processes in live animals. Technical advancements in imaging techniques and hardware components, combined with the development of novel targeted probes and new mice models, have enabled us to address long-standing questions in several biology areas such as oncology, cell biology, immunology and neuroscience. As the instrument resolution has increased, physiological motion activities have become a major obstacle that prevents imaging live animals at resolutions analogue to the ones obtained in vitro. Motion compensation techniques aim at reducing this gap and can effectively increase the in vivo resolution. This paper provides a technical review of some of the latest developments in motion compensation methods, providing organ specific solutions. PMID:24273405

Adaptive Failure Compensation for Aircraft Tracking Control Using Engine Differential Based Model

NASA Technical Reports Server (NTRS)

Liu, Yu; Tang, Xidong; Tao, Gang; Joshi, Suresh M.

2006-01-01

An aircraft model that incorporates independently adjustable engine throttles and ailerons is employed to develop an adaptive control scheme in the presence of actuator failures. This model captures the key features of aircraft flight dynamics when in the engine differential mode. Based on this model an adaptive feedback control scheme for asymptotic state tracking is developed and applied to a transport aircraft model in the presence of two types of failures during operation, rudder failure and aileron failure. Simulation results are presented to demonstrate the adaptive failure compensation scheme.

Vibration suppression with approximate finite dimensional compensators for distributed systems: Computational methods and experimental results

NASA Technical Reports Server (NTRS)

Banks, H. T.; Smith, Ralph C.; Wang, Yun

1994-01-01

Based on a distributed parameter model for vibrations, an approximate finite dimensional dynamic compensator is designed to suppress vibrations (multiple modes with a broad band of frequencies) of a circular plate with Kelvin-Voigt damping and clamped boundary conditions. The control is realized via piezoceramic patches bonded to the plate and is calculated from information available from several pointwise observed state variables. Examples from computational studies as well as use in laboratory experiments are presented to demonstrate the effectiveness of this design.

Gain-Compensating Circuit For NDE and Ultrasonics

NASA Technical Reports Server (NTRS)

Kushnick, Peter W.

1987-01-01

High-frequency gain-compensating circuit designed for general use in nondestructive evaluation and ultrasonic measurements. Controls gain of ultrasonic receiver as function of time to aid in measuring attenuation of samples with high losses; for example, human skin and graphite/epoxy composites. Features high signal-to-noise ratio, large signal bandwidth and large dynamic range. Control bandwidth of 5 MHz ensures accuracy of control signal. Currently being used for retrieval of more information from ultrasonic signals sent through composite materials that have high losses, and to measure skin-burn depth in humans.

When will a stuttering moment occur? The determining role of speech motor preparation.

PubMed

Vanhoutte, Sarah; Cosyns, Marjan; van Mierlo, Pieter; Batens, Katja; Corthals, Paul; De Letter, Miet; Van Borsel, John; Santens, Patrick

2016-06-01

The present study aimed to evaluate whether increased activity related to speech motor preparation preceding fluently produced words reflects a successful compensation strategy in stuttering. For this purpose, a contingent negative variation (CNV) was evoked during a picture naming task and measured by use of electro-encephalography. A CNV is a slow, negative event-related potential known to reflect motor preparation generated by the basal ganglia-thalamo-cortical (BGTC) - loop. In a previous analysis, the CNV of 25 adults with developmental stuttering (AWS) was significantly increased, especially over the right hemisphere, compared to the CNV of 35 fluent speakers (FS) when both groups were speaking fluently (Vanhoutte et al., (2015) doi: 10.1016/j.neuropsychologia.2015.05.013). To elucidate whether this increase is a compensation strategy enabling fluent speech in AWS, the present analysis evaluated the CNV of 7 AWS who stuttered during this picture naming task. The CNV preceding AWS stuttered words was statistically compared to the CNV preceding AWS fluent words and FS fluent words. Though no difference emerged between the CNV of the AWS stuttered words and the FS fluent words, a significant reduction was observed when comparing the CNV preceding AWS stuttered words to the CNV preceding AWS fluent words. The latter seems to confirm the compensation hypothesis: the increased CNV prior to AWS fluent words is a successful compensation strategy, especially when it occurs over the right hemisphere. The words are produced fluently because of an enlarged activity during speech motor preparation. The left CNV preceding AWS stuttered words correlated negatively with stuttering frequency and severity suggestive for a link between the left BGTC - network and the stuttering pathology. Overall, speech motor preparatory activity generated by the BGTC - loop seems to have a determining role in stuttering. An important divergence between left and right hemisphere is hypothesized. Copyright © 2016 Elsevier Ltd. All rights reserved.

Measurement and Compensation of BPM Chamber Motion in HLS

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

Li, J. W.; Sun, B. G.; Cao, Y.

2010-06-23

Significant horizontal drifts in the beam orbit in the storage ring of HLS (Hefei Light Source) have been seen for many years. What leads to the motion of Beam Position Monitor (BPM) chamber is thermal expansion mainly caused by the synchrotron light. To monitor the BPM chamber motions for all BPMs, a BPM chamber motion measurement system is built in real-time. The raster gauges are used to measure the displacements. The results distinctly show the relation between the BPM chamber motion and the beam current. To suppress the effect of BPM chamber motion, a compensation strategy is implemented at HLS.more » The horizontal drifts of beam orbit have been really suppressed within 20{mu}m without the compensation of BPM chamber motion in the runtime.« less

A Readout Integrated Circuit (ROIC) employing self-adaptive background current compensation technique for Infrared Focal Plane Array (IRFPA)

NASA Astrophysics Data System (ADS)

Zhou, Tong; Zhao, Jian; He, Yong; Jiang, Bo; Su, Yan

2018-05-01

A novel self-adaptive background current compensation circuit applied to infrared focal plane array is proposed in this paper, which can compensate the background current generated in different conditions. Designed double-threshold detection strategy is to estimate and eliminate the background currents, which could significantly reduce the hardware overhead and improve the uniformity among different pixels. In addition, the circuit is well compatible to various categories of infrared thermo-sensitive materials. The testing results of a 4 × 4 experimental chip showed that the proposed circuit achieves high precision, wide application and high intelligence. Tape-out of the 320 × 240 readout circuit, as well as the bonding, encapsulation and imaging verification of uncooled infrared focal plane array, have also been completed.

A Novel Adaptive H∞ Filtering Method with Delay Compensation for the Transfer Alignment of Strapdown Inertial Navigation Systems

PubMed Central

Lyu, Weiwei

2017-01-01

Transfer alignment is always a key technology in a strapdown inertial navigation system (SINS) because of its rapidity and accuracy. In this paper a transfer alignment model is established, which contains the SINS error model and the measurement model. The time delay in the process of transfer alignment is analyzed, and an H∞ filtering method with delay compensation is presented. Then the H∞ filtering theory and the robust mechanism of H∞ filter are deduced and analyzed in detail. In order to improve the transfer alignment accuracy in SINS with time delay, an adaptive H∞ filtering method with delay compensation is proposed. Since the robustness factor plays an important role in the filtering process and has effect on the filtering accuracy, the adaptive H∞ filter with delay compensation can adjust the value of robustness factor adaptively according to the dynamic external environment. The vehicle transfer alignment experiment indicates that by using the adaptive H∞ filtering method with delay compensation, the transfer alignment accuracy and the pure inertial navigation accuracy can be dramatically improved, which demonstrates the superiority of the proposed filtering method. PMID:29182592

Dynamic stress compensation by smart actuation

NASA Astrophysics Data System (ADS)

Irschik, Hans; Gusenbauer, Markus; Pichler, Uwe

2004-07-01

The actuating physical mechanisms utilized in smart materials can be described by eigenstrains. E.g., the converse piezoelectric effect in a piezoelastic body may be understood as an actuating eigenstrain. In the last decades, piezoelectricity has been extensively applied for the sake of actuation and sensing of structural vibrations. An important field of research in this respect has been devoted to the goal of compensating force-induced vibrations by means of eigenstrains. Considering the state-of-the-art in structural control and smart materials, almost no research has been performed on the problem of compensating stresses in force-loaded engineering structures by eigenstrains. It is well-known that stresses can influence the characteristics and the age of structures in various unpleasant ways. The present contribution is concerned with corresponding concepts for stress compensation which may have a highly beneficial influence upon the lifetime and structural integrity of the structure under consideration. We discuss the possibilities offered by displacement compensation to reduce the stresses to their quasi-static parts. As a numerical example, we consider the step response of an irregularly shaped cantilevered elastic plate under the action of an assigned traction at its boundary.

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.

Modified artificial fish school algorithm for free space optical communication with sensor-less adaptive optics system

NASA Astrophysics Data System (ADS)

Cao, Jingtai; Zhao, Xiaohui; Li, Zhaokun; Liu, Wei; Gu, Haijun

2017-11-01

The performance of free space optical (FSO) communication system is limited by atmospheric turbulent extremely. Adaptive optics (AO) is the significant method to overcome the atmosphere disturbance. Especially, for the strong scintillation effect, the sensor-less AO system plays a major role for compensation. In this paper, a modified artificial fish school (MAFS) algorithm is proposed to compensate the aberrations in the sensor-less AO system. Both the static and dynamic aberrations compensations are analyzed and the performance of FSO communication before and after aberrations compensations is compared. In addition, MAFS algorithm is compared with artificial fish school (AFS) algorithm, stochastic parallel gradient descent (SPGD) algorithm and simulated annealing (SA) algorithm. It is shown that the MAFS algorithm has a higher convergence speed than SPGD algorithm and SA algorithm, and reaches the better convergence value than AFS algorithm, SPGD algorithm and SA algorithm. The sensor-less AO system with MAFS algorithm effectively increases the coupling efficiency at the receiving terminal with fewer numbers of iterations. In conclusion, the MAFS algorithm has great significance for sensor-less AO system to compensate atmospheric turbulence in FSO communication system.

Nonlinear Blind Compensation for Array Signal Processing Application

PubMed Central

Ma, Hong; Jin, Jiang; Zhang, Hua

2018-01-01

Recently, nonlinear blind compensation technique has attracted growing attention in array signal processing application. However, due to the nonlinear distortion stemming from array receiver which consists of multi-channel radio frequency (RF) front-ends, it is too difficult to estimate the parameters of array signal accurately. A novel nonlinear blind compensation algorithm aims at the nonlinearity mitigation of array receiver and its spurious-free dynamic range (SFDR) improvement, which will be more precise to estimate the parameters of target signals such as their two-dimensional directions of arrival (2-D DOAs). Herein, the suggested method is designed as follows: the nonlinear model parameters of any channel of RF front-end are extracted to synchronously compensate the nonlinear distortion of the entire receiver. Furthermore, a verification experiment on the array signal from a uniform circular array (UCA) is adopted to testify the validity of our approach. The real-world experimental results show that the SFDR of the receiver is enhanced, leading to a significant improvement of the 2-D DOAs estimation performance for weak target signals. And these results demonstrate that our nonlinear blind compensation algorithm is effective to estimate the parameters of weak array signal in concomitance with strong jammers. PMID:29690571

Rain Fade Compensation for Ka-Band Communications Satellites

NASA Technical Reports Server (NTRS)

Mitchell, W. Carl; Nguyen, Lan; Dissanayake, Asoka; Markey, Brian; Le, Anh

1997-01-01

This report provides a review and evaluation of rain fade measurement and compensation techniques for Ka-band satellite systems. This report includes a description of and cost estimates for performing three rain fade measurement and compensation experiments. The first experiment deals with rain fade measurement techniques while the second one covers the rain fade compensation techniques. The third experiment addresses a feedback flow control technique for the ABR service (for ATM-based traffic). The following conclusions were observed in this report; a sufficient system signal margin should be allocated for all carriers in a network, that is a fixed clear-sky margin should be typically in the range of 4-5 dB and should be more like 15 dB in the up link for moderate and heavy rain zones; to obtain a higher system margin it is desirable to combine the uplink power control technique with the technique that implements the source information rate and FEC code rate changes resulting in a 4-5 dB increase in the dynamic part of the system margin. The experiments would assess the feasibility of the fade measurements and compensation techniques, and ABR feedback control technique.

Chinese farmers' willingness to accept compensation to practice safe disposal of HPAI infected chicken.

PubMed

Huang, Zeying; Wang, Jimin; Zuo, Alec

2017-04-01

Highly Pathogenic Avian Influenza (HPAI) is a high morbidity and mortality zoonotic disease, which threatens poultry and human health. An outbreak of disease in China requires strict slaughter and disposal of all chickens within a three-kilometer radius, incurring large private costs for farmers and encouraging black market transactions. A stated preference survey of 331 farmers across six provinces in China was conducted in 2015, in order to measure the responsiveness of farmers to accept various compensation prices for safely disposing of HPAI infected chicken. Findings suggest that about 25% and 40% of farmers in South and North China respectively would not adopt safe disposal at the current compensation price (10 yuan/bird) offered by the government. However, 80% of farmers would adopt safe disposal if the compensation price increased to 14.1 yuan in South China and 18.9 yuan in North China. The adoption of safe disposal by farmers was positively and significantly influenced by compensation price (p=0.000) and regular contact with epidemic prevention staff (p=0.094). However, adoption was negatively and significantly influenced by net farm income (p=0.100) and chicken production income percentage (p=0.014). Although half of (51%) of farmers were willing to receive zero compensation, a reasonable compensation scheme along with strengthened supervision, may be considered the most effective strategy to encourage safe disposal of HPAI infected chicken and reduce the risks associated with black market transactions. Copyright © 2017 Elsevier B.V. All rights reserved.

Applying PWM to control overcurrents at unbalanced faults of force-commutated VSCs used as static var compensators

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

Jiang, Y.; Ekstroem, A.

1997-01-01

This study is devoted to investigating the possibility of controlling the overcurrent of a forced-commutated voltage source converter (VSC) by PWM when the ac system is undergoing large unbalanced disturbance. The converter is supposed to be used as a static var compensator at a high power level. A novel control strategy is proposed for controlling the reactive current and the dc side voltage independently. Digital simulation results are presented and compared with the results by using just the reactive current control with fundamental switching frequency.

A hybrid strategy of offline adaptive planning and online image guidance for prostate cancer radiotherapy.

PubMed

Lei, Yu; Wu, Qiuwen

2010-04-21

Offline adaptive radiotherapy (ART) has been used to effectively correct and compensate for prostate motion and reduce the required margin. The efficacy depends on the characteristics of the patient setup error and interfraction motion through the whole treatment; specifically, systematic errors are corrected and random errors are compensated for through the margins. In online image-guided radiation therapy (IGRT) of prostate cancer, the translational setup error and inter-fractional prostate motion are corrected through pre-treatment imaging and couch correction at each fraction. However, the rotation and deformation of the target are not corrected and only accounted for with margins in treatment planning. The purpose of this study was to investigate whether the offline ART strategy is necessary for an online IGRT protocol and to evaluate the benefit of the hybrid strategy. First, to investigate the rationale of the hybrid strategy, 592 cone-beam-computed tomography (CBCT) images taken before and after each fraction for an online IGRT protocol from 16 patients were analyzed. Specifically, the characteristics of prostate rotation were analyzed. It was found that there exist systematic inter-fractional prostate rotations, and they are patient specific. These rotations, if not corrected, are persistent through the treatment fraction, and rotations detected in early fractions are representative of those in later fractions. These findings suggest that the offline adaptive replanning strategy is beneficial to the online IGRT protocol with further margin reductions. Second, to quantitatively evaluate the benefit of the hybrid strategy, 412 repeated helical CT scans from 25 patients during the course of treatment were included in the replanning study. Both low-risk patients (LRP, clinical target volume, CTV = prostate) and intermediate-risk patients (IRP, CTV = prostate + seminal vesicles) were included in the simulation. The contours of prostate and seminal vesicles were delineated on each CT. The benefit of margin reduction to compensate for both rotation and deformation in the hybrid strategy was evaluated geometrically. With the hybrid strategy, the planning margins can be reduced by 1.4 mm for LRP, and 2.0 mm for IRP, compared with the standard online IGRT only, to maintain the same 99% target volume coverage. The average relative reduction in planning target volume (PTV) based on the internal target volume (ITV) from PTV based on CTV is 19% for LRP, and 27% for IRP.

Optimizing symmetry-based recoupling sequences in solid-state NMR by pulse-transient compensation and asynchronous implementation

NASA Astrophysics Data System (ADS)

Hellwagner, Johannes; Sharma, Kshama; Tan, Kong Ooi; Wittmann, Johannes J.; Meier, Beat H.; Madhu, P. K.; Ernst, Matthias

2017-06-01

Pulse imperfections like pulse transients and radio-frequency field maladjustment or inhomogeneity are the main sources of performance degradation and limited reproducibility in solid-state nuclear magnetic resonance experiments. We quantitatively analyze the influence of such imperfections on the performance of symmetry-based pulse sequences and describe how they can be compensated. Based on a triple-mode Floquet analysis, we develop a theoretical description of symmetry-based dipolar recoupling sequences, in particular, R2 6411, calculating first- and second-order effective Hamiltonians using real pulse shapes. We discuss the various origins of effective fields, namely, pulse transients, deviation from the ideal flip angle, and fictitious fields, and develop strategies to counteract them for the restoration of full transfer efficiency. We compare experimental applications of transient-compensated pulses and an asynchronous implementation of the sequence to a supercycle, SR26, which is known to be efficient in compensating higher-order error terms. We are able to show the superiority of R26 compared to the supercycle, SR26, given the ability to reduce experimental error on the pulse sequence by pulse-transient compensation and a complete theoretical understanding of the sequence.

Mesothelioma incidence surveillance systems and claims for workers' compensation. Epidemiological evidence and prospects for an integrated framework.

PubMed

Marinaccio, Alessandro; Scarselli, Alberto; Merler, Enzo; Iavicoli, Sergio

2012-07-05

Malignant mesothelioma is an aggressive and lethal tumour strongly associated with exposure to asbestos (mainly occupational). In Italy a large proportion of workers are protected from occupational diseases by public insurance and an epidemiological surveillance system for incident mesothelioma cases. We set up an individual linkage between the Italian national mesothelioma register (ReNaM) and the Italian workers' compensation authority (INAIL) archives. Logistic regression models were used to identify and test explanatory variables. We extracted 3270 mesothelioma cases with occupational origins from the ReNaM, matching them with 1625 subjects in INAIL (49.7%); 91.2% (1,482) of the claims received compensation. The risk of not seeking compensation is significantly higher for women and the elderly. Claims have increased significantly in recent years and there is a clear geographical gradient (northern and more developed regions having higher claims rates). The highest rates of compensation claims were after work known to involve asbestos. Our data illustrate the importance of documentation and dissemination of all asbestos exposure modalities. Strategies focused on structural and systematic interaction between epidemiological surveillance and insurance systems are needed.

Mesothelioma incidence surveillance systems and claims for workers’ compensation. Epidemiological evidence and prospects for an integrated framework

PubMed Central

2012-01-01

Background Malignant mesothelioma is an aggressive and lethal tumour strongly associated with exposure to asbestos (mainly occupational). In Italy a large proportion of workers are protected from occupational diseases by public insurance and an epidemiological surveillance system for incident mesothelioma cases. Methods We set up an individual linkage between the Italian national mesothelioma register (ReNaM) and the Italian workers’ compensation authority (INAIL) archives. Logistic regression models were used to identify and test explanatory variables. Results We extracted 3270 mesothelioma cases with occupational origins from the ReNaM, matching them with 1625 subjects in INAIL (49.7%); 91.2% (1,482) of the claims received compensation. The risk of not seeking compensation is significantly higher for women and the elderly. Claims have increased significantly in recent years and there is a clear geographical gradient (northern and more developed regions having higher claims rates). The highest rates of compensation claims were after work known to involve asbestos. Conclusions Our data illustrate the importance of documentation and dissemination of all asbestos exposure modalities. Strategies focused on structural and systematic interaction between epidemiological surveillance and insurance systems are needed. PMID:22545679

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.

BLGAN: Bayesian learning and genetic algorithm for supporting negotiation with incomplete information.

PubMed

Sim, Kwang Mong; Guo, Yuanyuan; Shi, Benyun

2009-02-01

Automated negotiation provides a means for resolving differences among interacting agents. For negotiation with complete information, this paper provides mathematical proofs to show that an agent's optimal strategy can be computed using its opponent's reserve price (RP) and deadline. The impetus of this work is using the synergy of Bayesian learning (BL) and genetic algorithm (GA) to determine an agent's optimal strategy in negotiation (N) with incomplete information. BLGAN adopts: 1) BL and a deadline-estimation process for estimating an opponent's RP and deadline and 2) GA for generating a proposal at each negotiation round. Learning the RP and deadline of an opponent enables the GA in BLGAN to reduce the size of its search space (SP) by adaptively focusing its search on a specific region in the space of all possible proposals. SP is dynamically defined as a region around an agent's proposal P at each negotiation round. P is generated using the agent's optimal strategy determined using its estimations of its opponent's RP and deadline. Hence, the GA in BLGAN is more likely to generate proposals that are closer to the proposal generated by the optimal strategy. Using GA to search around a proposal generated by its current strategy, an agent in BLGAN compensates for possible errors in estimating its opponent's RP and deadline. Empirical results show that agents adopting BLGAN reached agreements successfully, and achieved: 1) higher utilities and better combined negotiation outcomes (CNOs) than agents that only adopt GA to generate their proposals, 2) higher utilities than agents that adopt BL to learn only RP, and 3) higher utilities and better CNOs than agents that do not learn their opponents' RPs and deadlines.

Controls design with crossfeeds for hovering rotorcraft using quantitative feedback theory

NASA Technical Reports Server (NTRS)

Tischler, Mark B.; Biezad, Daniel J.; Cheng, Rendy

1996-01-01

A multi-input, multi-output controls design with dynamic crossfeed pre-compensation is presented for rotorcraft in near-hovering flight using Quantitative Feedback Theory (QFT). The resulting closed-loop control system bandwidth allows the rotorcraft to be considered for use as an inflight simulator. The use of dynamic, robust crossfeeds prior to the QFT design reduces the magnitude of required feedback gain and results in performance that meets most handling qualities specifications relative to the decoupling of off-axis responses. Handling qualities are Level 1 for both low-gain tasks and high-gain tasks in the roll, pitch, and yaw axes except for the 10 deg/sec moderate-amplitude yaw command where the rotorcraft exhibits Level 2 handling qualities in the yaw axis caused by phase lag. The combined effect of the QFT feedback design following the implementation of low-order, dynamic crossfeed compensators successfully decouples ten of twelve off-axis channels. For the other two channels it was not possible to find a single, low-order crossfeed that was effective. This is an area to be investigated in future research.

A compensation method for the full phase retardance nonuniformity in phase-only liquid crystal on silicon spatial light modulators.

PubMed

Teng, Long; Pivnenko, Mike; Robertson, Brian; Zhang, Rong; Chu, Daping

2014-10-20

A simple and efficient compensation method for the full correction of both the anisotropic and isotropic nonuniformity of the light phase retardance in a liquid crystal (LC) layer is presented. This is achieved by accurate measurement of the spatial variation of the LC layer's thickness with the help of a calibrated liquid crystal wedge, rather than solely relying on the light intensity profile recorded using two crossed polarizers. Local phase retardance as a function of the applied voltage is calculated with its LC thickness and a set of reference data measured from the intensity of the reflected light using two crossed polarizers. Compensation of the corresponding phase nonuniformity is realized by applying adjusted local voltage signals for different grey levels. To demonstrate its effectiveness, the proposed method is applied to improve the performance of a phase-only liquid crystal on silicon (LCOS) spatial light modulator (SLM). The power of the first diffraction order measured with the binary phase gratings compensated by this method is compared with that compensated by the conventional crossed-polarizer method. The results show that the phase compensation method proposed here can increase the dynamic range of the first order diffraction power significantly from 15~21 dB to over 38 dB, while the crossed-polarizer method can only increase it to 23 dB.

Compressing the fluctuation of the magnetic field by dynamic compensation

NASA Astrophysics Data System (ADS)

Wang, Wenli; Dong, Richang; Wei, Rong; Chen, Tingting; Wang, Qian; Wang, Yuzhu

2018-03-01

We present a dynamic compensation method to compress the spatial fluctuation of the static magnetic field (C-field) that provides a quantization axis in the atomic fountain clock. The coil current of the C-field is point-by-point modulated in accordance with the atoms probing the magnetic field along the flight trajectory. A homogeneous field with a 0.2 nT inhomogeneity is produced compared to a 5 nT under the static magnetic field with a constant current during the Ramsey interrogation. The corresponding uncertainty associated with the second-order Zeeman shift that we calculate is improved by one order of magnitude. The technique provides an alternative method to improve the uniformity of the magnetic field, particularly for large-scale equipment that is difficult to construct with an effective magnetic shielding. Our method is simple, robust, and essentially important in frequency evaluations concerning the dominant uncertainty contribution due to the quadratic Zeeman shift.

Active vibration control using a modal-domain fiber optic sensor

NASA Technical Reports Server (NTRS)

Cox, David E.

1992-01-01

A closed-loop control experiment is described in which vibrations of a cantilevered beam are suppressed using measurements from a modal-domain fiber optic sensor. Modal-domain sensors are interference between the modes of a few-mode optical waveguide to detect strain. The fiber is bonded along the length of the beam and provides a measurement related to the strain distribution on the surface of the beam. A model for the fiber optic sensor is derived, and this model is integrated with the dynamic model of the beam. A piezoelectric actuator is also bonded to the beam and used to provide control forces. Control forces are obtained through dynamic compensation of the signal from the fiber optic sensor. The compensator is implemented with a real-time digital controller. Analytical models are verified by comparing simulations to experimental results for both open-loop and closed-loop configurations.

Thermally controlled femtosecond pulse shaping using metasurface based optical filters

NASA Astrophysics Data System (ADS)

Rahimi, Eesa; Şendur, Kürşat

2018-02-01

Shaping of the temporal distribution of the ultrashort pulses, compensation of pulse deformations due to phase shift in transmission and amplification are of interest in various optical applications. To address these problems, in this study, we have demonstrated an ultra-thin reconfigurable localized surface plasmon (LSP) band-stop optical filter driven by insulator-metal phase transition of vanadium dioxide. A Joule heating mechanism is proposed to control the thermal phase transition of the material. The resulting permittivity variation of vanadium dioxide tailors spectral response of the transmitted pulse from the stack. Depending on how the pulse's spectrum is located with respect to the resonance of the band-stop filter, the thin film stack can dynamically compress/expand the output pulse span up to 20% or shift its phase up to 360°. Multi-stacked filters have shown the ability to dynamically compensate input carrier frequency shifts and pulse span variations besides their higher span expansion rates.

A Reconfiguration Scheme for Accommodating Actuator Failures in Multi-Input, Multi-Output Flight Control Systems

NASA Technical Reports Server (NTRS)

Siwakosit, W.; Hess, R. A.; Bacon, Bart (Technical Monitor); Burken, John (Technical Monitor)

2000-01-01

A multi-input, multi-output reconfigurable flight control system design utilizing a robust controller and an adaptive filter is presented. The robust control design consists of a reduced-order, linear dynamic inversion controller with an outer-loop compensation matrix derived from Quantitative Feedback Theory (QFT). A principle feature of the scheme is placement of the adaptive filter in series with the QFT compensator thus exploiting the inherent robustness of the nominal flight control system in the presence of plant uncertainties. An example of the scheme is presented in a pilot-in-the-loop computer simulation using a simplified model of the lateral-directional dynamics of the NASA F18 High Angle of Attack Research Vehicle (HARV) that included nonlinear anti-wind up logic and actuator limitations. Prediction of handling qualities and pilot-induced oscillation tendencies in the presence of these nonlinearities is included in the example.

Catheter tracking via online learning for dynamic motion compensation in transcatheter aortic valve implantation.

PubMed

Wang, Peng; Zheng, Yefeng; John, Matthias; Comaniciu, Dorin

2012-01-01

Dynamic overlay of 3D models onto 2D X-ray images has important applications in image guided interventions. In this paper, we present a novel catheter tracking for motion compensation in the Transcatheter Aortic Valve Implantation (TAVI). To address such challenges as catheter shape and appearance changes, occlusions, and distractions from cluttered backgrounds, we present an adaptive linear discriminant learning method to build a measurement model online to distinguish catheters from background. An analytic solution is developed to effectively and efficiently update the discriminant model and to minimize the classification errors between the tracking object and backgrounds. The online learned discriminant model is further combined with an offline learned detector and robust template matching in a Bayesian tracking framework. Quantitative evaluations demonstrate the advantages of this method over current state-of-the-art tracking methods in tracking catheters for clinical applications.

Modelling voltage sag mitigation using dynamic voltage restorer and analyzing power quality issue

NASA Astrophysics Data System (ADS)

Ismail, Nor Laili; Hidzir, Hizrin Dayana Mohd; Thanakodi, Suresh; Nazar, Nazatul Shiema Moh; Ibrahim, Pungut; Ali, Che Ku Muhammad Sabri Che Ku

2018-02-01

Power quality problem which are arise due to a fault or a pulsed load can have caused an interruption of critical load. The modern power systems are becoming more sensitive to the quality of the power supplied by the utility company. Voltage sags and swells, flicker, interruptions, harmonic distortion and other distortion to the sinusoidal waveform are the examples of the power quality problems. The most affected due to these problems is industrial customers who use a lot of sensitive equipment. There has suffered a huge loss to these problems. Resulting of broken or damage equipment if voltage sag exceeds the sensitive threshold of the equipment. Thus, device such as Static Synchronous Compensator (STATCOM) and Dynamic Voltage Restorer (DVR) has been created to solve this problem among users. DVR is a custom power device that most effective and efficient. This paper intended to report the DVR operations during voltage sag compensation.

Dynamic integral imaging technology for 3D applications (Conference Presentation)

NASA Astrophysics Data System (ADS)

Huang, Yi-Pai; Javidi, Bahram; Martínez-Corral, Manuel; Shieh, Han-Ping D.; Jen, Tai-Hsiang; Hsieh, Po-Yuan; Hassanfiroozi, Amir

2017-05-01

Depth and resolution are always the trade-off in integral imaging technology. With the dynamic adjustable devices, the two factors of integral imaging can be fully compensated with time-multiplexed addressing. Those dynamic devices can be mechanical or electrical driven. In this presentation, we will mainly focused on discussing various Liquid Crystal devices which can change the focal length, scan and shift the image position, or switched in between 2D/3D mode. By using the Liquid Crystal devices, dynamic integral imaging have been successfully applied on 3D Display, capturing, and bio-imaging applications.

Single neural adaptive controller and neural network identifier based on PSO algorithm for spherical actuators with 3D magnet array

NASA Astrophysics Data System (ADS)

Yan, Liang; Zhang, Lu; Zhu, Bo; Zhang, Jingying; Jiao, Zongxia

2017-10-01

Permanent magnet spherical actuator (PMSA) is a multi-variable featured and inter-axis coupled nonlinear system, which unavoidably compromises its motion control implementation. Uncertainties such as external load and friction torque of ball bearing and manufacturing errors also influence motion performance significantly. Therefore, the objective of this paper is to propose a controller based on a single neural adaptive (SNA) algorithm and a neural network (NN) identifier optimized with a particle swarm optimization (PSO) algorithm to improve the motion stability of PMSA with three-dimensional magnet arrays. The dynamic model and computed torque model are formulated for the spherical actuator, and a dynamic decoupling control algorithm is developed. By utilizing the global-optimization property of the PSO algorithm, the NN identifier is trained to avoid locally optimal solution and achieve high-precision compensations to uncertainties. The employment of the SNA controller helps to reduce the effect of compensation errors and convert the system to a stable one, even if there is difference between the compensations and uncertainties due to external disturbances. A simulation model is established, and experiments are conducted on the research prototype to validate the proposed control algorithm. The amplitude of the parameter perturbation is set to 5%, 10%, and 15%, respectively. The strong robustness of the proposed hybrid algorithm is validated by the abundant simulation data. It shows that the proposed algorithm can effectively compensate the influence of uncertainties and eliminate the effect of inter-axis couplings of the spherical actuator.

Where Have All the Custodians Gone?

ERIC Educational Resources Information Center

Fickes, Michael

2001-01-01

Examines how to reduce college and university custodial turnover rates by forging connections between the job and the campus community. Key points to building these connections are outlined, including training requirements, benefit compensation package design, and cleaning strategies. (GR)

Good Agreements Make Good Friends

PubMed Central

Han, The Anh; Pereira, Luís Moniz; Santos, Francisco C.; Lenaerts, Tom

2013-01-01

When starting a new collaborative endeavor, it pays to establish upfront how strongly your partner commits to the common goal and what compensation can be expected in case the collaboration is violated. Diverse examples in biological and social contexts have demonstrated the pervasiveness of making prior agreements on posterior compensations, suggesting that this behavior could have been shaped by natural selection. Here, we analyze the evolutionary relevance of such a commitment strategy and relate it to the costly punishment strategy, where no prior agreements are made. We show that when the cost of arranging a commitment deal lies within certain limits, substantial levels of cooperation can be achieved. Moreover, these levels are higher than that achieved by simple costly punishment, especially when one insists on sharing the arrangement cost. Not only do we show that good agreements make good friends, agreements based on shared costs result in even better outcomes. PMID:24045873

Railway crossing risk area detection using linear regression and terrain drop compensation techniques.

PubMed

Chen, Wen-Yuan; Wang, Mei; Fu, Zhou-Xing

2014-06-16

Most railway accidents happen at railway crossings. Therefore, how to detect humans or objects present in the risk area of a railway crossing and thus prevent accidents are important tasks. In this paper, three strategies are used to detect the risk area of a railway crossing: (1) we use a terrain drop compensation (TDC) technique to solve the problem of the concavity of railway crossings; (2) we use a linear regression technique to predict the position and length of an object from image processing; (3) we have developed a novel strategy called calculating local maximum Y-coordinate object points (CLMYOP) to obtain the ground points of the object. In addition, image preprocessing is also applied to filter out the noise and successfully improve the object detection. From the experimental results, it is demonstrated that our scheme is an effective and corrective method for the detection of railway crossing risk areas.

Railway Crossing Risk Area Detection Using Linear Regression and Terrain Drop Compensation Techniques

PubMed Central

Chen, Wen-Yuan; Wang, Mei; Fu, Zhou-Xing

2014-01-01

Most railway accidents happen at railway crossings. Therefore, how to detect humans or objects present in the risk area of a railway crossing and thus prevent accidents are important tasks. In this paper, three strategies are used to detect the risk area of a railway crossing: (1) we use a terrain drop compensation (TDC) technique to solve the problem of the concavity of railway crossings; (2) we use a linear regression technique to predict the position and length of an object from image processing; (3) we have developed a novel strategy called calculating local maximum Y-coordinate object points (CLMYOP) to obtain the ground points of the object. In addition, image preprocessing is also applied to filter out the noise and successfully improve the object detection. From the experimental results, it is demonstrated that our scheme is an effective and corrective method for the detection of railway crossing risk areas. PMID:24936948

Design of active temperature compensated composite free-free beam MEMS resonators in a standard process

NASA Astrophysics Data System (ADS)

Xereas, George; Chodavarapu, Vamsy P.

2014-03-01

Frequency references are used in almost every modern electronic device including mobile phones, personal computers, and scientific and medical instrumentation. With modern consumer mobile devices imposing stringent requirements of low cost, low complexity, compact system integration and low power consumption, there has been significant interest to develop batch-manufactured MEMS resonators. An important challenge for MEMS resonators is to match the frequency and temperature stability of quartz resonators. We present 1MHz and 20MHz temperature compensated Free-Free beam MEMS resonators developed using PolyMUMPS, which is a commercial multi-user process available from MEMSCAP. We introduce a novel temperature compensation technique that enables high frequency stability over a wide temperature range. We used three strategies: passive compensation by using a structural gold (Au) layer on the resonator, active compensation through using a heater element, and a Free-Free beam design that minimizes the effects of thermal mismatch between the vibrating structure and the substrate. Detailed electro-mechanical simulations were performed to evaluate the frequency response and Quality Factor (Q). Specifically, for the 20MHz device, a Q of 10,000 was obtained for the passive compensated design. Finite Element Modeling (FEM) simulations were used to evaluate the Temperature Coefficient of frequency (TCf) of the resonators between -50°C and 125°C which yielded +0.638 ppm/°C for the active compensated, compared to -1.66 ppm/°C for the passively compensated design and -8.48 ppm/°C for uncompensated design for the 20MHz device. Electro-thermo-mechanical simulations showed that the heater element was capable of increasing the temperature of the resonators by approximately 53°C with an applied voltage of 10V and power consumption of 8.42 mW.

Women's reasons for participation in a clinical trial for menstrual pain: a qualitative study

PubMed Central

Blödt, Susanne; Witt, Claudia M; Holmberg, Christine

2016-01-01

Objectives The aim of the study was to explore women's motivations for participating in a clinical trial and to evaluate how financial compensation impacts women's explanations for participation. Design, setting and participants Semistructured interviews were conducted face to face or by telephone with 25 of 220 women who participated in a pragmatic randomised trial for app-administered self-care acupressure for dysmenorrhoea (AKUD). Of these 25 women, 10 had entered AKUD knowing they would receive a financial compensation of €30. A purposive sampling strategy was used. Results Women had a long history of seeking help and were unsatisfied with the options available, namely painkillers and oral contraceptives. While interviewees were open to painkillers, they were uneasy about taking them on a monthly basis. The AKUD trial offered the possibility to find an alternative solution. A second reason for participation was the desire to add a new treatment to routine medical care, for which the interviewees considered randomised trials a prerequisite. The financial incentive was a subsidiary motivation in the interviewees' narratives. Conclusions Our results contribute to the ongoing discussion of the impact of financial compensation on research participants' assessment of risk. The interviewed women considered all research participants able to make their own choices regarding trial participation, even in the face of financial compensation or payment of study participants. Furthermore, the importance of clinical trials providing new treatments that could change medical practice might be an overlooked reason for trial participation and could be used in future recruitment strategies. PMID:27965251

An Integrated Approach to Damage Accommodation in Flight Control

NASA Technical Reports Server (NTRS)

Boskovic, Jovan D.; Knoebel, Nathan; Mehra, Raman K.; Gregory, Irene

2008-01-01

In this paper we present an integrated approach to in-flight damage accommodation in flight control. The approach is based on Multiple Models, Switching and Tuning (MMST), and consists of three steps: In the first step the main objective is to acquire a realistic aircraft damage model. Modeling of in-flight damage is a highly complex problem since there is a large number of issues that need to be addressed. One of the most important one is that there is strong coupling between structural dynamics, aerodynamics, and flight control. These effects cannot be studied separately due to this coupling. Once a realistic damage model is available, in the second step a large number of models corresponding to different damage cases are generated. One possibility is to generate many linear models and interpolate between them to cover a large portion of the flight envelope. Once these models have been generated, we will implement a recently developed-Model Set Reduction (MSR) technique. The technique is based on parameterizing damage in terms of uncertain parameters, and uses concepts from robust control theory to arrive at a small number of "centered" models such that the controllers corresponding to these models assure desired stability and robustness properties over a subset in the parametric space. By devising a suitable model placement strategy, the entire parametric set is covered with a relatively small number of models and controllers. The third step consists of designing a Multiple Models, Switching and Tuning (MMST) strategy for estimating the current operating regime (damage case) of the aircraft, and switching to the corresponding controller to achieve effective damage accommodation and the desired performance. In the paper present a comprehensive approach to damage accommodation using Model Set Design,MMST, and Variable Structure compensation for coupling nonlinearities. The approach was evaluated on a model of F/A-18 aircraft dynamics under control effector damage, augmented by nonlinear cross-coupling terms and a structural dynamics model. The proposed approach achieved excellent performance under severe damage effects.

Modeling the cost-benefit of nerve conduction studies in pre-employment screening for carpal tunnel syndrome.

PubMed

Evanoff, Bradley; Kymes, Steve

2010-06-01

The aim of this study was to evaluate the costs associated with pre-employment nerve conduction testing as a screening tool for carpal tunnel syndrome (CTS) in the workplace. We used a Markov decision analysis model to compare the costs associated with a strategy of screening all prospective employees for CTS and not hiring those with abnormal nerve conduction, versus a strategy of not screening for CTS. The variables included in our model included employee turnover rate, the incidence of CTS, the prevalence of median nerve conduction abnormalities, the relative risk of developing CTS conferred by abnormal nerve conduction screening, the costs of pre-employment screening, and the worker's compensation costs to the employer for each case of CTS. In our base case, total employer costs for CTS from the perspective of the employer (cost of screening plus costs for workers' compensation associated with CTS) were higher when screening was used. Median costs per employee position over five years were US$503 for the screening strategy versus US$200 for a no-screening strategy. A sensitivity analysis showed that a strategy of screening was cost-beneficial from the perspective of the employer only under a few circumstances. Using Monte Carlo simulation varying all parameters, we found a 30% probability that screening would be cost-beneficial. A strategy of pre-employment screening for CTS should be carefully evaluated for yield and social consequences before being implemented. Our model suggests such screening is not appropriate for most employers.

Perceptions of health stakeholders on task shifting and motivation of community health workers in different socio demographic contexts in Kenya (nomadic, peri-urban and rural agrarian).

PubMed

Ochieng, Beverly; Akunja, Edith; Edwards, Nancy; Mombo, Diana; Marende, Leah; Kaseje, Dan C O

2014-01-01

The shortage of health professionals in low income countries is recognized as a crisis. Community health workers are part of a "task-shift" strategy to address this crisis. Task shifting in this paper refers to the delegation of tasks from health professionals to lay, trained volunteers. In Kenya, there is a debate as to whether these volunteers should be compensated, and what motivation strategies would be effective in different socio-demographic contexts, based type of tasks shifted. The purpose of this study was to find out, from stakeholders' perspectives, the type of tasks to be shifted to community health workers and the appropriate strategies to motivate and retain them. This was an analytical comparative study employing qualitative methods: key informant interviews with health policy makers, managers, and service providers, and focus group discussions with community health workers and service consumers, to explore their perspectives on tasks to be shifted and appropriate motivation strategies. The study found that there were tasks to be shifted and motivation strategies that were common to all three contexts. Common tasks were promotive, preventive, and simple curative services. Common motivation strategies were supportive supervision, means of identification, equitable allocation of resources, training, compensation, recognition, and evidence based community dialogue. The study concluded that inclusion of curative tasks for community health workers, particularly in nomadic contexts, is inevitable but raises the need for accreditation of their training and regulation of their tasks.

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.

Strapdown system performance optimization test evaluations (SPOT), volume 1

NASA Technical Reports Server (NTRS)

Blaha, R. J.; Gilmore, J. P.

1973-01-01

A three axis inertial system was packaged in an Apollo gimbal fixture for fine grain evaluation of strapdown system performance in dynamic environments. These evaluations have provided information to assess the effectiveness of real-time compensation techniques and to study system performance tradeoffs to factors such as quantization and iteration rate. The strapdown performance and tradeoff studies conducted include: (1) Compensation models and techniques for the inertial instrument first-order error terms were developed and compensation effectivity was demonstrated in four basic environments; single and multi-axis slew, and single and multi-axis oscillatory. (2) The theoretical coning bandwidth for the first-order quaternion algorithm expansion was verified. (3) Gyro loop quantization was identified to affect proportionally the system attitude uncertainty. (4) Land navigation evaluations identified the requirement for accurate initialization alignment in order to pursue fine grain navigation evaluations.

Parameter tuning method for dither compensation of a pneumatic proportional valve with friction

NASA Astrophysics Data System (ADS)

Wang, Tao; Song, Yang; Huang, Leisheng; Fan, Wei

2016-05-01

In the practical application of pneumatic control devices, the nonlinearity of a pneumatic control valve become the main factor affecting the control effect, which comes mainly from the dynamic friction force. The dynamic friction inside the valve may cause hysteresis and a dead zone. In this paper, a dither compensation mechanism is proposed to reduce negative effects on the basis of analyzing the mechanism of friction force. The specific dither signal (using a sinusoidal signal) was superimposed on the control signal of the valve. Based on the relationship between the parameters of the dither signal and the inherent characteristics of the proportional servo valve, a parameter tuning method was proposed, which uses a displacement sensor to measure the maximum static friction inside the valve. According to the experimental results, the proper amplitude ranges are determined for different pressures. In order to get the optimal parameters of the dither signal, some dither compensation experiments have been carried out on different signal amplitude and gas pressure conditions. Optimal parameters are determined under two kinds of pressure conditions. Using tuning parameters the valve spool displacement experiment has been taken. From the experiment results, hysteresis of the proportional servo valve is significantly reduced. And through simulation and experiments, the cut-off frequency of the proportional valve has also been widened. Therefore after adding the dither signal, the static and dynamic characteristics of the proportional valve are both improved to a certain degree. This research proposes a parameter tuning method of dither signal, and the validity of the method is verified experimentally.

Examination of the relationship between theory-driven policies and allowed lost-time back claims in workers' compensation: a system dynamics model.

PubMed

Wong, Jessica J; McGregor, Marion; Mior, Silvano A; Loisel, Patrick

2014-01-01

The purpose of this study was to develop a model that evaluates the impact of policy changes on the number of workers' compensation lost-time back claims in Ontario, Canada, over a 30-year timeframe. The model was used to test the hypothesis that a theory- and policy-driven model would be sufficient in reproducing historical claims data in a robust manner and that policy changes would have a major impact on modeled data. The model was developed using system dynamics methods in the Vensim simulation program. The theoretical effects of policies for compensation benefit levels and experience rating fees were modeled. The model was built and validated using historical claims data from 1980 to 2009. Sensitivity analysis was used to evaluate the modeled data at extreme end points of variable input and timeframes. The degree of predictive value of the modeled data was measured by the coefficient of determination, root mean square error, and Theil's inequality coefficients. Correlation between modeled data and actual data was found to be meaningful (R(2) = 0.934), and the modeled data were stable at extreme end points. Among the effects explored, policy changes were found to be relatively minor drivers of back claims data, accounting for a 13% improvement in error. Simulation results suggested that unemployment, number of no-lost-time claims, number of injuries per worker, and recovery rate from back injuries outside of claims management to be sensitive drivers of back claims data. A robust systems-based model was developed and tested for use in future policy research in Ontario's workers' compensation. The study findings suggest that certain areas within and outside the workers' compensation system need to be considered when evaluating and changing policies around back claims. © 2014. Published by National University of Health Sciences All rights reserved.

Nonlinear Decoupling Control With ANFIS-Based Unmodeled Dynamics Compensation for a Class of Complex Industrial Processes.

PubMed

Zhang, Yajun; Chai, Tianyou; Wang, Hong; Wang, Dianhui; Chen, Xinkai

2018-06-01

Complex industrial processes are multivariable and generally exhibit strong coupling among their control loops with heavy nonlinear nature. These make it very difficult to obtain an accurate model. As a result, the conventional and data-driven control methods are difficult to apply. Using a twin-tank level control system as an example, a novel multivariable decoupling control algorithm with adaptive neural-fuzzy inference system (ANFIS)-based unmodeled dynamics (UD) compensation is proposed in this paper for a class of complex industrial processes. At first, a nonlinear multivariable decoupling controller with UD compensation is introduced. Different from the existing methods, the decomposition estimation algorithm using ANFIS is employed to estimate the UD, and the desired estimating and decoupling control effects are achieved. Second, the proposed method does not require the complicated switching mechanism which has been commonly used in the literature. This significantly simplifies the obtained decoupling algorithm and its realization. Third, based on some new lemmas and theorems, the conditions on the stability and convergence of the closed-loop system are analyzed to show the uniform boundedness of all the variables. This is then followed by the summary on experimental tests on a heavily coupled nonlinear twin-tank system that demonstrates the effectiveness and the practicability of the proposed method.

Vertically polarizing undulator with the dynamic compensation of magnetic forces for the next generation of light sources

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

Strelnikov, N.; Budker Institute of Nuclear Physics, Novosibirsk 630090; Trakhtenberg, E.

2014-11-15

A short prototype (847-mm-long) of an Insertion Device (ID) with the dynamic compensation of ID magnetic forces has been designed, built, and tested at the Advanced Photon Source (APS) of the Argonne National Laboratory. The ID magnetic forces were compensated by the set of conical springs placed along the ID strongback. Well-controlled exponential characteristics of conical springs permitted a very close fit to the ID magnetic forces. Several effects related to the imperfections of actual springs, their mounting and tuning, and how these factors affect the prototype performance has been studied. Finally, series of tests to determine the accuracy andmore » reproducibility of the ID magnetic gap settings have been carried out. Based on the magnetic measurements of the ID B{sub eff}, it has been demonstrated that the magnetic gaps within an operating range were controlled accurately and reproducibly within ±1 μm. Successful tests of this ID prototype led to the design of a 3-m long device based on the same concept. The 3-m long prototype is currently under construction. It represents R and D efforts by the APS toward APS Upgrade Project goals as well as the future generation of IDs for the Linac Coherent Light Source (LCLS)« less

Positioning pharmacists' roles in primary health care: a discourse analysis of the compensation plan in Alberta, Canada.

PubMed

Hughes, Christine A; Breault, Rene R; Hicks, Deborah; Schindel, Theresa J

2017-11-23

A comprehensive Compensation Plan for pharmacy services delivered by community pharmacists was implemented in Alberta, Canada in July 2012. Services covered by the Compensation Plan include care planning services, prescribing services such as adapting prescriptions, and administering a drug or publicly-funded vaccine by injection. Understanding how the Compensation Plan was framed and communicated provides insight into the roles of pharmacists and the potential influence of language on the implementation of services covered by the Compensation Plan by Albertan pharmacists. The objective of this study is to examine the positioning of pharmacists' roles in documents used to communicate the Compensation Plan to Albertan pharmacists and other audiences. Publicly available documents related to the Compensation Plan, such as news releases or reports, published between January 2012 and December 2015 were obtained from websites such as the Government of Alberta, Alberta Blue Cross, the Alberta College of Pharmacists, the Alberta Pharmacists' Association, and the Blueprint for Pharmacy. Searches of the Canadian Newsstand database and Google identified additional documents. Discourse analysis was performed using social positioning theory to explore how pharmacists' roles were constructed in communications about the Compensation Plan. In total, 65 publicly available documents were included in the analysis. The Compensation Plan was put forward as a framework for payment for professional services and formal legitimization of pharmacists' changing professional roles. The discourse associated with the Compensation Plan positioned pharmacists' roles as: (1) expanding to include services such as medication management for chronic diseases, (2) contributing to primary health care by providing access to services such as prescription renewals and immunizations, and (3) collaborating with other health care team members. Pharmacists' changing roles were positioned in alignment with the aims of primary health care. Social positioning theory provides a useful lens to examine the dynamic and evolving roles of pharmacists. This study provides insight into how communications regarding the Compensation Plan in Alberta, Canada positioned pharmacists' changing roles in the broader context of changes to primary health care delivery. Our findings may be useful for other jurisdictions considering implementation of remunerated clinical services provided by pharmacists.

An Ultrasound Image-Based Dynamic Fusion Modeling Method for Predicting the Quantitative Impact of In Vivo Liver Motion on Intraoperative HIFU Therapies: Investigations in a Porcine Model

PubMed Central

N'Djin, W. Apoutou; Chapelon, Jean-Yves; Melodelima, David

2015-01-01

Organ motion is a key component in the treatment of abdominal tumors by High Intensity Focused Ultrasound (HIFU), since it may influence the safety, efficacy and treatment time. Here we report the development in a porcine model of an Ultrasound (US) image-based dynamic fusion modeling method for predicting the effect of in vivo motion on intraoperative HIFU treatments performed in the liver in conjunction with surgery. A speckle tracking method was used on US images to quantify in vivo liver motions occurring intraoperatively during breathing and apnea. A fusion modeling of HIFU treatments was implemented by merging dynamic in vivo motion data in a numerical modeling of HIFU treatments. Two HIFU strategies were studied: a spherical focusing delivering 49 juxtapositions of 5-second HIFU exposures and a toroidal focusing using 1 single 40-second HIFU exposure. Liver motions during breathing were spatially homogenous and could be approximated to a rigid motion mainly encountered in the cranial-caudal direction (f = 0.20Hz, magnitude >13mm). Elastic liver motions due to cardiovascular activity, although negligible, were detectable near millimeter-wide sus-hepatic veins (f = 0.96Hz, magnitude <1mm). The fusion modeling quantified the deleterious effects of respiratory motions on the size and homogeneity of a standard “cigar-shaped” millimetric lesion usually predicted after a 5-second single spherical HIFU exposure in stationary tissues (Dice Similarity Coefficient: DSC<45%). This method assessed the ability to enlarge HIFU ablations during respiration, either by juxtaposing “cigar-shaped” lesions with spherical HIFU exposures, or by generating one large single lesion with toroidal HIFU exposures (DSC>75%). Fusion modeling predictions were preliminarily validated in vivo and showed the potential of using a long-duration toroidal HIFU exposure to accelerate the ablation process during breathing (from 0.5 to 6 cm3·min-1). To improve HIFU treatment control, dynamic fusion modeling may be interesting for assessing numerically focusing strategies and motion compensation techniques in more realistic conditions. PMID:26398366

Gender Differences in Hospital CEO Compensation: A National Investigation of Not-for-Profit Hospitals.

PubMed

Song, Paula H; Lee, Shoou-Yih Daniel; Toth, Matthew; Singh, Simone R; Young, Gary J

2018-01-01

Gender pay equity is a desirable social value and an important strategy to fill every organizational stratum with gender-diverse talent to fulfill an organization's goals and mission. This study used national, large-sample data to examine gender difference in CEO compensation among not-for-profit hospitals. Results showed the average unadjusted annual compensation for female CEOs in 2009 was $425,085 compared with $581,121 for male CEOs. With few exceptions, the difference existed across all types of not-for-profit hospitals. After controlling for hospital- and area-level characteristics, female CEOs of not-for-profit hospitals earned 22.6% less than male CEOs of not-for-profit hospitals. This translates into an earnings differential of $132,652 associated with gender. Explanations and implications of the results are discussed.

Identification of the feedforward component in manual control with predictable target signals.

PubMed

Drop, Frank M; Pool, Daan M; Damveld, Herman J; van Paassen, Marinus M; Mulder, Max

2013-12-01

In the manual control of a dynamic system, the human controller (HC) often follows a visible and predictable reference path. Compared with a purely feedback control strategy, performance can be improved by making use of this knowledge of the reference. The operator could effectively introduce feedforward control in conjunction with a feedback path to compensate for errors, as hypothesized in literature. However, feedforward behavior has never been identified from experimental data, nor have the hypothesized models been validated. This paper investigates human control behavior in pursuit tracking of a predictable reference signal while being perturbed by a quasi-random multisine disturbance signal. An experiment was done in which the relative strength of the target and disturbance signals were systematically varied. The anticipated changes in control behavior were studied by means of an ARX model analysis and by fitting three parametric HC models: two different feedback models and a combined feedforward and feedback model. The ARX analysis shows that the experiment participants employed control action on both the error and the target signal. The control action on the target was similar to the inverse of the system dynamics. Model fits show that this behavior can be modeled best by the combined feedforward and feedback model.

Identifying highly connected counties compensates for resource limitations when evaluating national spread of an invasive pathogen.

PubMed

Sutrave, Sweta; Scoglio, Caterina; Isard, Scott A; Hutchinson, J M Shawn; Garrett, Karen A

2012-01-01

Surveying invasive species can be highly resource intensive, yet near-real-time evaluations of invasion progress are important resources for management planning. In the case of the soybean rust invasion of the United States, a linked monitoring, prediction, and communication network saved U.S. soybean growers approximately $200 M/yr. Modeling of future movement of the pathogen (Phakopsora pachyrhizi) was based on data about current disease locations from an extensive network of sentinel plots. We developed a dynamic network model for U.S. soybean rust epidemics, with counties as nodes and link weights a function of host hectarage and wind speed and direction. We used the network model to compare four strategies for selecting an optimal subset of sentinel plots, listed here in order of increasing performance: random selection, zonal selection (based on more heavily weighting regions nearer the south, where the pathogen overwinters), frequency-based selection (based on how frequently the county had been infected in the past), and frequency-based selection weighted by the node strength of the sentinel plot in the network model. When dynamic network properties such as node strength are characterized for invasive species, this information can be used to reduce the resources necessary to survey and predict invasion progress.

Perceptions of health stakeholders on task shifting and motivation of community health workers in different socio demographic contexts in Kenya (nomadic, peri-urban and rural agrarian)

PubMed Central

2014-01-01

Background The shortage of health professionals in low income countries is recognized as a crisis. Community health workers are part of a “task-shift” strategy to address this crisis. Task shifting in this paper refers to the delegation of tasks from health professionals to lay, trained volunteers. In Kenya, there is a debate as to whether these volunteers should be compensated, and what motivation strategies would be effective in different socio-demographic contexts, based type of tasks shifted. The purpose of this study was to find out, from stakeholders’ perspectives, the type of tasks to be shifted to community health workers and the appropriate strategies to motivate and retain them. Methods This was an analytical comparative study employing qualitative methods: key informant interviews with health policy makers, managers, and service providers, and focus group discussions with community health workers and service consumers, to explore their perspectives on tasks to be shifted and appropriate motivation strategies. Results The study found that there were tasks to be shifted and motivation strategies that were common to all three contexts. Common tasks were promotive, preventive, and simple curative services. Common motivation strategies were supportive supervision, means of identification, equitable allocation of resources, training, compensation, recognition, and evidence based community dialogue. Further, in the nomadic and peri-urban sites, community health workers had assumed curative services beyond the range provided for in the Kenyan task shifting policy. This was explained to be influenced by lack of access to care due to distance to health facilities, population movement, and scarcity of health providers in the nomadic setting and the harsh economic realities in peri-urban set up. Therefore, their motivation strategies included training on curative skills, technical support, and resources for curative care. Data collection was viewed as an important task in the rural site, but was not recognized as priority in nomadic and peri-urban sites, where they sought monetary compensation for data collection. Conclusions The study concluded that inclusion of curative tasks for community health workers, particularly in nomadic contexts, is inevitable but raises the need for accreditation of their training and regulation of their tasks. PMID:25079588

Correlates of individual differences in compensatory nicotine self-administration in rats following a decrease in nicotine unit dose

PubMed Central

Harris, Andrew C.; Pentel, Paul R.; LeSage, Mark G.

2013-01-01

Rationale The ability of tobacco harm reduction strategies to produce significant reductions in toxin exposure is limited by compensatory increases in smoking behavior. Characterizing factors contributing to the marked individual variability in compensation may be useful for understanding this phenomenon and assessing the feasibility of harm reduction interventions. Objective To use an animal model of human compensatory smoking that involves a decrease in unit dose supporting nicotine self-administration (NSA) to examine potential contributors to individual differences in compensation. Methods Rats were trained for NSA during daily 23 hr sessions at a unit dose of 0.06 mg/kg/inf until responding was stable. The unit dose was then reduced to 0.03 mg/kg/inf for at least 10 sessions. Following reacquisition of NSA at the training dose and extinction, single-dose nicotine pharmacokinetic parameters were determined. Results Decreases in nicotine intake following dose reduction were proportionally less than the decrease in unit dose, indicating partial compensation. Compensatory increases in infusion rates were observed across the course of the 23 hr sessions. The magnitude of compensation differed considerably between rats. Rats exhibiting the highest baseline infusion rates exhibited the lowest levels of compensation. Nicotine pharmacokinetic parameters were not significantly correlated with compensation. Infusion rates immediately returned to pre-reduction levels when baseline conditions were restored. Conclusions These findings provide initial insights into correlates of individual differences in compensation following a reduction in nicotine unit dose. The present assay may be useful for characterizing mechanisms and potential consequences of the marked individual differences in compensatory smoking observed in humans. PMID:19475400

Reliable fusion of control and sensing in intelligent machines. Thesis

NASA Technical Reports Server (NTRS)

Mcinroy, John E.

1991-01-01

Although robotics research has produced a wealth of sophisticated control and sensing algorithms, very little research has been aimed at reliably combining these control and sensing strategies so that a specific task can be executed. To improve the reliability of robotic systems, analytic techniques are developed for calculating the probability that a particular combination of control and sensing algorithms will satisfy the required specifications. The probability can then be used to assess the reliability of the design. An entropy formulation is first used to quickly eliminate designs not capable of meeting the specifications. Next, a framework for analyzing reliability based on the first order second moment methods of structural engineering is proposed. To ensure performance over an interval of time, lower bounds on the reliability of meeting a set of quadratic specifications with a Gaussian discrete time invariant control system are derived. A case study analyzing visual positioning in robotic system is considered. The reliability of meeting timing and positioning specifications in the presence of camera pixel truncation, forward and inverse kinematic errors, and Gaussian joint measurement noise is determined. This information is used to select a visual sensing strategy, a kinematic algorithm, and a discrete compensator capable of accomplishing the desired task. Simulation results using PUMA 560 kinematic and dynamic characteristics are presented.

Irrelevant stimulus processing in ADHD: catecholamine dynamics and attentional networks.

PubMed

Aboitiz, Francisco; Ossandón, Tomás; Zamorano, Francisco; Palma, Bárbara; Carrasco, Ximena

2014-01-01

A cardinal symptom of attention deficit and hyperactivity disorder (ADHD) is a general distractibility where children and adults shift their attentional focus to stimuli that are irrelevant to the ongoing behavior. This has been attributed to a deficit in dopaminergic signaling in cortico-striatal networks that regulate goal-directed behavior. Furthermore, recent imaging evidence points to an impairment of large scale, antagonistic brain networks that normally contribute to attentional engagement and disengagement, such as the task-positive networks and the default mode network (DMN). Related networks are the ventral attentional network (VAN) involved in attentional shifting, and the salience network (SN) related to task expectancy. Here we discuss the tonic-phasic dynamics of catecholaminergic signaling in the brain, and attempt to provide a link between this and the activities of the large-scale cortical networks that regulate behavior. More specifically, we propose that a disbalance of tonic catecholamine levels during task performance produces an emphasis of phasic signaling and increased excitability of the VAN, yielding distractibility symptoms. Likewise, immaturity of the SN may relate to abnormal tonic signaling and an incapacity to build up a proper executive system during task performance. We discuss different lines of evidence including pharmacology, brain imaging and electrophysiology, that are consistent with our proposal. Finally, restoring the pharmacodynamics of catecholaminergic signaling seems crucial to alleviate ADHD symptoms; however, the possibility is open to explore cognitive rehabilitation strategies to top-down modulate network dynamics compensating the pharmacological deficits.

Irrelevant stimulus processing in ADHD: catecholamine dynamics and attentional networks

PubMed Central

Aboitiz, Francisco; Ossandón, Tomás; Zamorano, Francisco; Palma, Bárbara; Carrasco, Ximena

2014-01-01

A cardinal symptom of attention deficit and hyperactivity disorder (ADHD) is a general distractibility where children and adults shift their attentional focus to stimuli that are irrelevant to the ongoing behavior. This has been attributed to a deficit in dopaminergic signaling in cortico-striatal networks that regulate goal-directed behavior. Furthermore, recent imaging evidence points to an impairment of large scale, antagonistic brain networks that normally contribute to attentional engagement and disengagement, such as the task-positive networks and the default mode network (DMN). Related networks are the ventral attentional network (VAN) involved in attentional shifting, and the salience network (SN) related to task expectancy. Here we discuss the tonic–phasic dynamics of catecholaminergic signaling in the brain, and attempt to provide a link between this and the activities of the large-scale cortical networks that regulate behavior. More specifically, we propose that a disbalance of tonic catecholamine levels during task performance produces an emphasis of phasic signaling and increased excitability of the VAN, yielding distractibility symptoms. Likewise, immaturity of the SN may relate to abnormal tonic signaling and an incapacity to build up a proper executive system during task performance. We discuss different lines of evidence including pharmacology, brain imaging and electrophysiology, that are consistent with our proposal. Finally, restoring the pharmacodynamics of catecholaminergic signaling seems crucial to alleviate ADHD symptoms; however, the possibility is open to explore cognitive rehabilitation strategies to top-down modulate network dynamics compensating the pharmacological deficits. PMID:24723897

Finite-time adaptive sliding mode force control for electro-hydraulic load simulator based on improved GMS friction model

NASA Astrophysics Data System (ADS)

Kang, Shuo; Yan, Hao; Dong, Lijing; Li, Changchun

2018-03-01

This paper addresses the force tracking problem of electro-hydraulic load simulator under the influence of nonlinear friction and uncertain disturbance. A nonlinear system model combined with the improved generalized Maxwell-slip (GMS) friction model is firstly derived to describe the characteristics of load simulator system more accurately. Then, by using particle swarm optimization (PSO) algorithm ​combined with the system hysteresis characteristic analysis, the GMS friction parameters are identified. To compensate for nonlinear friction and uncertain disturbance, a finite-time adaptive sliding mode control method is proposed based on the accurate system model. This controller has the ability to ensure that the system state moves along the nonlinear sliding surface to steady state in a short time as well as good dynamic properties under the influence of parametric uncertainties and disturbance, which further improves the force loading accuracy and rapidity. At the end of this work, simulation and experimental results are employed to demonstrate the effectiveness of the proposed sliding mode control strategy.

High precision locating control system based on VCM for Talbot lithography

NASA Astrophysics Data System (ADS)

Yao, Jingwei; Zhao, Lixin; Deng, Qian; Hu, Song

2016-10-01

Aiming at the high precision and efficiency requirements of Z-direction locating in Talbot lithography, a control system based on Voice Coil Motor (VCM) was designed. In this paper, we built a math model of VCM and its moving characteristic was analyzed. A double-closed loop control strategy including position loop and current loop were accomplished. The current loop was implemented by driver, in order to achieve the rapid follow of the system current. The position loop was completed by the digital signal processor (DSP) and the position feedback was achieved by high precision linear scales. Feed forward control and position feedback Proportion Integration Differentiation (PID) control were applied in order to compensate for dynamic lag and improve the response speed of the system. And the high precision and efficiency of the system were verified by simulation and experiments. The results demonstrated that the performance of Z-direction gantry was obviously improved, having high precision, quick responses, strong real-time and easily to expend for higher precision.

Adaptive piezoelectric sensoriactuator

NASA Technical Reports Server (NTRS)

Clark, Jr., Robert L. (Inventor); Vipperman, Jeffrey S. (Inventor); Cole, Daniel G. (Inventor)

1996-01-01

An adaptive algorithm implemented in digital or analog form is used in conjunction with a voltage controlled amplifier to compensate for the feedthrough capacitance of piezoelectric sensoriactuator. The mechanical response of the piezoelectric sensoriactuator is resolved from the electrical response by adaptively altering the gain imposed on the electrical circuit used for compensation. For wideband, stochastic input disturbances, the feedthrough capacitance of the sensoriactuator can be identified on-line, providing a means of implementing direct-rate-feedback control in analog hardware. The device is capable of on-line system health monitoring since a quasi-stable dynamic capacitance is indicative of sustained health of the piezoelectric element.

Generation of constant-amplitude radio-frequency sweeps at a tunnel junction for spin resonance STM

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

Paul, William; Lutz, Christopher P.; Heinrich, Andreas J.

2016-07-15

We describe the measurement and successful compensation of the radio-frequency transfer function of a scanning tunneling microscope over a wide frequency range (15.5–35.5 GHz) and with high dynamic range (>50 dB). The precise compensation of cabling resonances and attenuations is critical for the production of constant-voltage frequency sweeps for electric-field driven electron spin resonance (ESR) experiments. We also demonstrate that a well-calibrated tunnel junction voltage is necessary to avoid spurious ESR peaks that can arise due to a non-flat transfer function.

Effects on the medical revenue of comprehensive pricing reform in Chinese urban public hospitals after removing drug markups: case of Nanjing.

PubMed

Tang, Wenxi; Xie, Jing; Lu, Yijuan; Liu, Qizhi; Malone, Daniel; Ma, Aixia

2018-04-01

The State Council of China requires that all urban public hospitals must eliminate drug markups by September 2017, and that hospital drugs must be sold at the purchase price. Nanjing-one of the first provincial capital cities to implement the reform-is studied to evaluate the effects of the comprehensive reform on drug prices in public hospitals, and to explore differential compensation plans. Sixteen hospitals were selected, and financial data were collected over the 48-month period before the reform and for 12 months after the reform. An analysis was carried out using a simple linear interrupted time series model. The average difference ratio of drug surplus fell 13.39% after the reform, and the drug markups were basically eliminated. Revenue from medical services showed a net growth of 28.25%. The overall compensation received from government financial budget and medical service revenue growth was 103.69% for the loss from policy-permitted 15% markup sales, and 116.48% for the net loss. However, there were large differences in compensation levels at different hospitals, ranging from -21.92% to 413.74% by medical services revenue growth, causing the combined rate of both financial and service compensation to vary from 28.87-413.74%, There was a significant positive correlation between the services compensation rate and the proportion of medical service revenue (p < .001), and the compensation rate increased by 8% for every 1% increase in the proportion of services revenue. Nanjing's pricing and compensation reform has basically achieved the policy targets of eliminating the drug markups, promoting the growth of medical services revenue, and adjusting the structure of medical revenue. However, the growth rate of service revenue of hospitals varied significantly from one another. Nanjing's reform represents successful pricing and compensation reform in Chinese urban public hospitals. It is recommended that a differentiated and dynamic compensation plan should be established in accordance with the revenue structure of different hospitals.