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Sample records for air-fuel ratio feedback

  1. Air/fuel ratio controller

    SciTech Connect

    Schechter, M.M.; Simko, A.O.

    1980-12-23

    An internal combustion engine has a fuel injection pump and an air/fuel ratio controller. The controller has a lever that is connected to the pump lever. An aneroid moves the controller lever as a function of changes in intake manifold vacuum to maintain a constant air/fuel ratio to the mixture charge. A fuel enrichment linkage is provided that modifies the movement of the fuel flow control lever by the aneroid in response to changes in manifold gas temperature levels and exhaust gas recirculation to maintain the constant air/fuel ratio. A manual override is provided to obtain a richer air/fuel ratio for maximum acceleration.

  2. Flatness-based embedded control of air-fuel ratio in combustion engines

    NASA Astrophysics Data System (ADS)

    Rigatos, Gerasimos; Siano, Pierluigi; Arsie, Ivan

    2014-10-01

    A nonlinear controller is designed for air-fuel ratio control in combustion engines, making use of differential flatness theory and of the Derivative-free nonlinear Kalman Filter. It is proven that the air-fuel ratio system is a differentially flat one and admits dynamic feedback linearization. Using a change of variables that is based on differential flatness theory it is shown that the air-fuel ratio system can be transformed to the linear canonical form, for which the design of a state feedback controller is easier. Moreover, to compensate for modeling uncertainties and external disturbances the Derivative-free nonlinear Kalman Filter is designed as a disturbance observer. The estimation of the perturbations that effect the air-fuel systems enables their compensation through the inclusion of an additional term in the feedback control law. The efficiency of the proposed nonlinear feedback control scheme is tested through simulation experiments.

  3. Air/fuel ratio visualization in a diesel spray

    NASA Astrophysics Data System (ADS)

    Carabell, Kevin David

    1993-01-01

    To investigate some features of high pressure diesel spray ignition, we have applied a newly developed planar imaging system to a spray in an engine-fed combustion bomb. The bomb is designed to give flow characteristics similar to those in a direct injection diesel engine yet provide nearly unlimited optical access. A high pressure electronic unit injector system with on-line manually adjustable main and pilot injection features was used. The primary scalar of interest was the local air/fuel ratio, particularly near the spray plumes. To make this measurement quantitative, we have developed a calibration LIF technique. The development of this technique is the key contribution of this dissertation. The air/fuel ratio measurement was made using biacetyl as a seed in the air inlet to the engine. When probed by a tripled Nd:YAG laser the biacetyl fluoresces, with a signal proportional to the local biacetyl concentration. This feature of biacetyl enables the fluorescent signal to be used as as indicator of local fuel vapor concentration. The biacetyl partial pressure was carefully controlled, enabling estimates of the local concentration of air and the approximate local stoichiometry in the fuel spray. The results indicate that the image quality generated with this method is sufficient for generating air/fuel ratio contours. The processes during the ignition delay have a marked effect on ignition and the subsequent burn. These processes, vaporization and pre-flame kinetics, very much depend on the mixing of the air and fuel. This study has shown that poor mixing and over-mixing of the air and fuel will directly affect the type of ignition. An optimal mixing arrangement exists and depends on the swirl ratio in the engine, the number of holes in the fuel injector and the distribution of fuel into a pilot and main injection. If a short delay and a diffusion burn is desired, the best mixing parameters among those surveyed would be a high swirl ratio, a 4-hole nozzle and a

  4. Effect of Volatility on Air-Fuel Ratio Distribution and Torque Output of a Carbureted Light Aircraft Piston Engine.

    DTIC Science & Technology

    1982-03-01

    Positive displacement fuel flow sensor Burette type volumetric fuel flowmeter(2) Meriam laminar airflow meter Lamdascan air-fuel ratio meter Lebow inline...therefore the resulting data was not utilized. The volumetric flowrate of engine intake air was calculated from the pressure drop across a Meriam Model 50MC2

  5. Adaptive critic learning techniques for engine torque and air-fuel ratio control.

    PubMed

    Liu, Derong; Javaherian, Hossein; Kovalenko, Olesia; Huang, Ting

    2008-08-01

    A new approach for engine calibration and control is proposed. In this paper, we present our research results on the implementation of adaptive critic designs for self-learning control of automotive engines. A class of adaptive critic designs that can be classified as (model-free) action-dependent heuristic dynamic programming is used in this research project. The goals of the present learning control design for automotive engines include improved performance, reduced emissions, and maintained optimum performance under various operating conditions. Using the data from a test vehicle with a V8 engine, we developed a neural network model of the engine and neural network controllers based on the idea of approximate dynamic programming to achieve optimal control. We have developed and simulated self-learning neural network controllers for both engine torque (TRQ) and exhaust air-fuel ratio (AFR) control. The goal of TRQ control and AFR control is to track the commanded values. For both control problems, excellent neural network controller transient performance has been achieved.

  6. Performance evaluation of an advanced air-fuel ratio controller on a stationary, rich-burn natural gas engine

    NASA Astrophysics Data System (ADS)

    Kochuparampil, Roshan Joseph

    The advent of an era of abundant natural gas is making it an increasingly economical fuel source against incumbents such as crude oil and coal, in end-use sectors such as power generation, transportation and industrial chemical production, while also offering significant environmental benefits over these incumbents. Equipment manufacturers, in turn, are responding to widespread demand for power plants optimized for operation with natural gas. In several applications such as distributed power generation, gas transmission, and water pumping, stationary, spark-ignited, natural gas fueled internal combustion engines (ICEs) are the power plant of choice (over turbines) owing to their lower equipment and operational costs, higher thermal efficiencies across a wide load range, and the flexibility afforded to end-users when building fine-resolution horsepower topologies: modular size increments ranging from 100 kW -- 2 MW per ICE power plant compared to 2 -- 5 MW per turbine power plant. Under the U.S. Environment Protection Agency's (EPA) New Source Performance Standards (NSPS) and Reciprocating Internal Combustion Engine National Emission Standards for Hazardous Air Pollutants (RICE NESHAP) air quality regulations, these natural gas power plants are required to comply with stringent emission limits, with several states mandating even stricter emissions norms. In the case of rich-burn or stoichiometric natural gas ICEs, very high levels of sustained emissions reduction can be achieved through exhaust after-treatment that utilizes Non Selective Catalyst Reduction (NSCR) systems. The primary operational constraint with these systems is the tight air-fuel ratio (AFR) window of operation that needs to be maintained if the NSCR system is to achieve simultaneous reduction of carbon monoxide (CO), nitrogen oxides (NOx), total hydrocarbons (THC), volatile organic compounds (VOCs), and formaldehyde (CH 2O). Most commercially available AFR controllers utilizing lambda (oxygen

  7. Internal combustion engine cylinder-to-cylinder balancing with balanced air-fuel ratios

    DOEpatents

    Harris, Ralph E.; Bourn, Gary D.; Smalley, Anthony J.

    2006-01-03

    A method of balancing combustion among cylinders of an internal combustion engine. For each cylinder, a normalized peak firing pressure is calculated as the ratio of its peak firing pressure to its combustion pressure. Each cylinder's normalized peak firing pressure is compared to a target value for normalized peak firing pressure. The fuel flow is adjusted to any cylinder whose normalized peak firing pressure is not substantially equal to the target value.

  8. High performance zinc air fuel cell stack

    NASA Astrophysics Data System (ADS)

    Pei, Pucheng; Ma, Ze; Wang, Keliang; Wang, Xizhong; Song, Mancun; Xu, Huachi

    2014-03-01

    A zinc air fuel cell (ZAFC) stack with inexpensive manganese dioxide (MnO2) as the catalyst is designed, in which the circulation flowing potassium hydroxide (KOH) electrolyte carries the reaction product away and acts as a coolant. Experiments are carried out to investigate the characteristics of polarization, constant current discharge and dynamic response, as well as the factors affecting the performance and uniformity of individual cells in the stack. The results reveal that the peak power density can be as high as 435 mW cm-2 according to the area of the air cathode sheet, and the influence factors on cell performance and uniformity are cell locations, filled state of zinc pellets, contact resistance, flow rates of electrolyte and air. It is also shown that the time needed for voltages to reach steady state and that for current step-up or current step-down are both in milliseconds, indicating the ZAFC can be excellently applied to vehicles with rapid dynamic response demands.

  9. Fuel Cell Electrodes for Hydrogen-Air Fuel Cell Assemblies.

    DTIC Science & Technology

    The report describes the design and evaluation of a hydrogen-air fuel cell module for use in a portable hydrid fuel cell -battery system. The fuel ... cell module consists of a stack of 20 single assemblies. Each assembly contains 2 electrically independent cells with a common electrolyte compartment

  10. Air/fuel supply system for use in a gas turbine engine

    DOEpatents

    Fox, Timothy A; Schilp, Reinhard; Gambacorta, Domenico

    2014-06-17

    A fuel injector for use in a gas turbine engine combustor assembly. The fuel injector includes a main body and a fuel supply structure. The main body has an inlet end and an outlet end and defines a longitudinal axis extending between the outlet and inlet ends. The main body comprises a plurality of air/fuel passages extending therethrough, each air/fuel passage including an inlet that receives air from a source of air and an outlet. The fuel supply structure communicates with and supplies fuel to the air/fuel passages for providing an air/fuel mixture within each air/fuel passage. The air/fuel mixtures exit the main body through respective air/fuel passage outlets.

  11. The impact of air-fuel mixture composition on SI engine performance during natural gas and producer gas combustion

    NASA Astrophysics Data System (ADS)

    Przybyła, G.; Postrzednik, S.; Żmudka, Z.

    2016-09-01

    The paper summarizers results of experimental tests of SI engine fuelled with gaseous fuels such as, natural gas and three mixtures of producer gas substitute that simulated real producer gas composition. The engine was operated under full open throttle and charged with different air-fuel mixture composition (changed value of air excess ratio). The spark timing was adjusted to obtain maximum brake torque (MBT) for each fuel and air-fuel mixture. This paper reports engine indicated performance based on in-cylinder, cycle resolved pressure measurements. The engine performance utilizing producer gas in terms of indicated efficiency is increased by about 2 percentage points when compared to fuelling with natural gas. The engine power de-rating when producer gas is utilized instead the natural gas, varies from 24% to 28,6% under stoichiometric combustion conditions. For lean burn (λ=1.5) the difference are lower and varies from 22% to 24.5%.

  12. A large population parental care game: polymorphisms and feedback between patterns of care and the operational sex ratio.

    PubMed

    Ramsey, David M

    2010-10-21

    This article presents a game theoretic model of parental care which models the feedback between patterns of care and the operational sex ratio. It is assumed here that males can be in one of two states: searching for a mate or breeding (including caring for their offspring). Females can be in one of three states: receptive (searching), non-receptive or breeding. However, these sets of states can be adapted to the physiology of a particular species. The length of time that an individual remains in the breeding state depends on the level of care an individual gives. When in the searching state, individuals find partners at a rate dependent on the proportion of members of the opposite sex searching. These rates are defined to satisfy the Fisher condition that the total number of offspring of males equals the total number of offspring of females. The operational sex ratio is not defined exogenously, but can be derived from the adult sex ratio and the pattern of parental care. Pure strategy profiles and so-called single sex stable polymorphisms, in which behaviour is varied within one sex, are derived analytically. The difference between mixed evolutionarily stable strategies and stable polymorphisms within this framework is highlighted. The effects of various physiological and demographic parameters on patterns of care are considered.

  13. Fabrication-tolerant 1310 nm laterally-coupled distributed feedback lasers with high side mode suppression ratios

    SciTech Connect

    Millett, R.; Dridi, K.; Benhsaien, A.; Schriemer, H.; Hinzer, K.; Hall, T.

    2010-11-10

    A laterally-coupled distributed feedback (LC-DFB) laser was designed and fabricated using stepper lithography. Such DFB lasers eliminate the need of the commonly required re-growth steps in a conventional DFB laser fabrication process. With LC-DFB lasers, the grating can be lithographically patterned out of the ridge waveguide. High order gratings can enhance the lithographic tolerance for lower resolution patterning, yielding lasers more amenable to mass-manufacturing. 1310 nm InGaAsP/InP LC-DFB laser with third-order gratings was fabricated using i-line 5x stepper lithography. Excellent side mode suppression ratio over 52 dB has been measured with a single mode lasing around 1310 nm.

  14. Zinc/air fuel cell for electric vehicles

    SciTech Connect

    Cherepy, N. J.; Krueger, R.; Cooper, J. F.

    1999-01-01

    We are conducting tests of an advanced zinc/air fuel cell design to determine effectiveness in various commercial applications. Our 322-cm2 cell uses gravity-fed zinc pellets as the anode, 12 M KOH electrolyte, and an air cathode catalyzed by a cobalt-porphyrin complex on carbon black. A single 322 cm2 cell runs at a standard operating power of 38 W (1200 W/m2) at 39 A (1245 A/m2) and 0.96 V with a power density of 2400 W/m2 at 0.67 V. With improved current collection hardware, already demonstrated in the laboratory, power generation increases to -3600 W/m2 at 1V. We conducted a 50-hour test in which a cell generated 587 Ah and 569 Wh. The power that may be generated increases by a factor of 2.5 between T = 28 °C and 52 °C. Electrolyte capacity, without stabilization additives, was measured at 147 Ah/L

  15. The Effects of Varied Ratios of Positive and Negative Nonverbal Audience Feedback on Selected Attitudes and Behaviors of Normal Speaking College Students.

    ERIC Educational Resources Information Center

    Barwind, Jack Alan

    Based on a theoretical rationale derived from dissonance theory, this study investigated the effects of 80%/20% ratios of positive/negative and negative/positive audience feedback on perceptual, attitudinal, and behavioral responses of normal speaking college students. Twenty-six skilled speakers and 30 unskilled speakers were randomly assigned to…

  16. Ratio

    NASA Astrophysics Data System (ADS)

    Webster, Nathan A. S.; Pownceby, Mark I.; Madsen, Ian C.; Studer, Andrew J.; Manuel, James R.; Kimpton, Justin A.

    2014-12-01

    Effects of basicity, B (CaO:SiO2 ratio) on the thermal range, concentration, and formation mechanisms of silico-ferrite of calcium and aluminum (SFCA) and SFCA-I iron ore sinter bonding phases have been investigated using an in situ synchrotron X-ray diffraction-based methodology with subsequent Rietveld refinement-based quantitative phase analysis. SFCA and SFCA-I phases are the key bonding materials in iron ore sinter, and improved understanding of the effects of processing parameters such as basicity on their formation and decomposition may assist in improving efficiency of industrial iron ore sintering operations. Increasing basicity significantly increased the thermal range of SFCA-I, from 1363 K to 1533 K (1090 °C to 1260 °C) for a mixture with B = 2.48, to ~1339 K to 1535 K (1066 °C to 1262 °C) for a mixture with B = 3.96, and to ~1323 K to 1593 K (1050 °C to 1320 °C) at B = 4.94. Increasing basicity also increased the amount of SFCA-I formed, from 18 wt pct for the mixture with B = 2.48 to 25 wt pct for the B = 4.94 mixture. Higher basicity of the starting sinter mixture will, therefore, increase the amount of SFCA-I, considered to be more desirable of the two phases. Basicity did not appear to significantly influence the formation mechanism of SFCA-I. It did, however, affect the formation mechanism of SFCA, with the decomposition of SFCA-I coinciding with the formation of a significant amount of additional SFCA in the B = 2.48 and 3.96 mixtures but only a minor amount in the highest basicity mixture. In situ neutron diffraction enabled characterization of the behavior of magnetite after melting of SFCA produced a magnetite plus melt phase assemblage.

  17. The use of air fuel cell cathodes to remove contaminants from spent chromium plating solutions.

    PubMed

    Huang, K L; Holsen, T M; Chou, T C; Yang, M C

    2004-01-01

    Results from experiments using an impregnation-reduction (I-R) Pt / Nafion membrane electrode assembly (MEA) in an air fuel cell cathode to remove contaminants (Cu(II), Ni(II), and Fe(III)) from spent chromium electroplating baths are presented in this study. A platinum-carbon (Pt-C) / Nafion MEA and a Pb planar cathode were also used for comparison. The average removal rates of Cu(II) and Ni(II) were almost the same (0.39 and 0.40 mM hr(-1) (or 0.117 and 0.12 mmol hr(-1)), respectively) but higher than that of Fe(III) (0.16 mM hr(-1), or 0.048 mmol hr(-1)) in accordance with the Nernst-Planck flux equation. The removal rates for the same cation were independent of the cathode used. The average removal rate of each impurity was approximately proportional to the product of its initial concentration and separator area/anolyte volume ratio using Pb cathodes. Under constant current conditions the system using the Pt-C / Nafion cathode needed the highest cell voltage, about 3 V more than needed for the system with the Pt / Nafion cathode. The cell voltage required using the Pt / Nafion cathode was similar to that using the conventional planar Pb cathode. Analyses of cathode deposits by SEM/EDS and XPS techniques indicated they were minimal on the Pb and Pt / Nafion cathode and more apparent on the Pt-C / Nafion cathode. The primary deposits on the Pb cathode were chromium oxides (e.g., Cr2O3) with minor amount of lead chromate (lead dichromate or lead trichromate) and other chromium solids (Cr black). As expected, the dominant deposit on the lead anode surface was PbO2.

  18. Qualitative tissue differentiation by analysing the intensity ratios of atomic emission lines using laser induced breakdown spectroscopy (LIBS): prospects for a feedback mechanism for surgical laser systems.

    PubMed

    Kanawade, Rajesh; Mahari, Fanuel; Klämpfl, Florian; Rohde, Maximilian; Knipfer, Christian; Tangermann-Gerk, Katja; Adler, Werner; Schmidt, Michael; Stelzle, Florian

    2015-01-01

    The research work presented in this paper focuses on qualitative tissue differentiation by monitoring the intensity ratios of atomic emissions using 'Laser Induced Breakdown Spectroscopy' (LIBS) on the plasma plume created during laser tissue ablation. The background of this study is to establish a real time feedback control mechanism for clinical laser surgery systems during the laser ablation process. Ex-vivo domestic pig tissue samples (muscle, fat, nerve and skin) were used in this experiment. Atomic emission intensity ratios were analyzed to find a characteristic spectral line for each tissue. The results showed characteristic elemental emission intensity ratios for the respective tissues. The spectral lines and intensity ratios of these specific elements varied among the different tissue types. The main goal of this study is to qualitatively and precisely identify different tissue types for tissue specific laser surgery.

  19. Assessment of methanol electro-oxidation for direct methanol-air fuel cells

    SciTech Connect

    Fritts, S.D.; Sen, R.K.

    1988-07-01

    The Office of Energy Storage and Distribution of the US Department of Energy (DOE) supports the development of a methanol-air fuel cell for transportation application. The approach used at Los Alamos National Laboratory converts the methanol fuel to a hydrogen-rich gas in a reformer, then operates the fuel cell on hydrogen and air. The reformer tends to be bulky (raising vehicle packaging problems), has a long startup period, and is not well suited for the transient operation required in a vehicle. Methanol, however, can be oxidized electrochemically in the fuel cell. If this process can be conducted efficiently, a direct methanol-air fuel cell can be used, which does not require a reformer. The objective of this study is to assess the potential of developing a suitable catalyst for the direct electrochemical oxidation of methanol. The primary conclusion of this study is that no acceptable catalysts exist can efficiently oxidize methanol electrochemically and have the desired cost and lifetime for vehicle applications. However, recent progress in understanding the mechanism of methanol oxidation indicates that a predictive base can be developed to search for methanol oxidation catalysts and can be used to methodically develop improved catalysts. Such an approach is strongly recommended. The study also recommends that until further progress in developing high-performance catalysts is achieved, research in cell design and testing is not warranted. 43 refs., 12 figs., 1 tab.

  20. Performance of PEM Liquid-Feed Direct Methanol-Air Fuel Cells

    NASA Technical Reports Server (NTRS)

    Narayanan, S. R.

    1995-01-01

    A direct methanol-air fuel cell operating at near atmospheric pressure, low-flow rate air, and at temperatures close to 60oC would tremendously enlarge the scope of potential applications. While earlier studies have reported performance with oxygen, the present study focuses on characterizing the performance of a PEM liquid feed direct methanol-air cell consisting of components developed in house. These cells employ Pt-Ru catalyst in the anode, Pt at the cathode and Nafion 117 as the PEM. The effect of pressure, flow rate of air and temperature on cell performance has been studied. With air, the performance level is as high as 0.437 V at 300 mA/cm2 (90oC, 20 psig, and excess air flow) has been attained. Even more significant is the performance level at 60oC, 1 atm and low flow rates of air (3-5 times stoichiometric), which is 0.4 V at 150 mA/cm2. Individual electrode potentials for the methanol and air electrode have been separated and analyzed. Fuel crossover rates and the impact of fuel crossover on the performance of the air electrode have also been measured. The study identifies issues specific to the methanol-air fuel cell and provides a basis for improvement strategies.

  1. Morphology control of zinc regeneration for zinc-air fuel cell and battery

    NASA Astrophysics Data System (ADS)

    Wang, Keliang; Pei, Pucheng; Ma, Ze; Xu, Huachi; Li, Pengcheng; Wang, Xizhong

    2014-12-01

    Morphology control is crucial both for zinc-air batteries and for zinc-air fuel cells during zinc regeneration. Zinc dendrite should be avoided in zinc-air batteries and zinc pellets are yearned to be formed for zinc-air fuel cells. This paper is mainly to analyze the mechanism of shape change and to control the zinc morphology during charge. A numerical three-dimensional model for zinc regeneration is established with COMSOL software on the basis of ionic transport theory and electrode reaction electrochemistry, and some experiments of zinc regeneration are carried out. The deposition process is qualitatively analyzed by the kinetics Monte Carlo method to study the morphological change from the electrocrystallization point of view. Morphological evolution of deposited zinc under different conditions of direct currents and pulse currents is also investigated by simulation. The simulation shows that parametric variables of the flowing electrolyte, the surface roughness and the structure of the electrode, the charging current and mode affect morphological evolution. The uniform morphology of deposited zinc is attained at low current, pulsating current or hydrodynamic electrolyte, and granular morphology is obtained by means of an electrode of discrete columnar structure in combination with high current and flowing electrolyte.

  2. Increasing Induction-Level Teachers' Positive-to-Negative Communication Ratio and Use of Behavior-Specific Praise through E-Mailed Performance Feedback and Its Effect on Students' Task Engagement

    ERIC Educational Resources Information Center

    Rathel, Jeanna M.; Drasgow, Erik; Brown, William H.; Marshall, Kathleen J.

    2014-01-01

    The purpose of this study was to examine the effects of e-mailed specific performance feedback that included progress monitoring graphs on induction-level teachers' ratios of positive-to-negative communication behaviors and their use of behavior-specific praise in classrooms for students with emotional and behavioral disorders, mild intellectual…

  3. A review on air cathodes for zinc-air fuel cells

    NASA Astrophysics Data System (ADS)

    Neburchilov, Vladimir; Wang, Haijiang; Martin, Jonathan J.; Qu, Wei

    This paper reviews the compositions, design and methods of fabrication of air cathodes for alkali zinc-air fuel cells (ZAFCs), one of the few successfully commercialized fuel cells. The more promising compositions for air cathodes are based on individual oxides, or mixtures of such, with a spinel, perovskite, or pyrochlore structure: MnO 2, Ag, Co 3O 4, La 2O 3, LaNiO 3, NiCo 2O 4, LaMnO 3, LaNiO 3, etc. These compositions provide the optimal balance of ORR activity and chemical stability in an alkali electrolyte. The sol-gel and reverse micelle methods supply the most uniform distribution of the catalyst on carbon and the highest catalyst BET surface area. It is shown that the design of the air cathode, including types of carbon black, binding agents, current collectors, Teflon membranes, thermal treatment of the GDL, and catalyst layers, has a strong effect on performance.

  4. Audio Feedback -- Better Feedback?

    ERIC Educational Resources Information Center

    Voelkel, Susanne; Mello, Luciane V.

    2014-01-01

    National Student Survey (NSS) results show that many students are dissatisfied with the amount and quality of feedback they get for their work. This study reports on two case studies in which we tried to address these issues by introducing audio feedback to one undergraduate (UG) and one postgraduate (PG) class, respectively. In case study one…

  5. NanoCapillary Network Proton Conducting Membranes for High Temperature Hydrogen/Air Fuel Cells

    SciTech Connect

    Pintauro, Peter

    2012-07-09

    The objective of this proposal is to fabricate and characterize a new class of NanoCapillary Network (NCN) proton conducting membranes for hydrogen/air fuel cells that operate under high temperature, low humidity conditions. The membranes will be intelligently designed, where a high density interconnecting 3-D network of nm-diameter electrospun proton conducting polymer fibers is embedded in an inert (uncharged) water/gas impermeable polymer matrix. The high density of fibers in the resulting mat and the high ion-exchange capacity of the fiber polymer will ensure high proton conductivity. To further enhance water retention, molecular silica will be added to the sulfonated polymer fibers. The uncharged matrix material will control water swelling of the high ion-exchange capacity proton conducting polymer fibers and will impart toughness to the final nanocapillary composite membrane. Thus, unlike other fuel cell membranes, the role of the polymer support matrix will be decoupled from that of the proton-conducting channels. The expected final outcome of this 5-year project is the fabrication of fuel cell membranes with properties that exceed the DOE’s technical targets, in particular a proton conductivity of 0.1 S/cm at a temperature less than or equal to120°C and 25-50% relative humidity.

  6. A Rechargeable Li-Air Fuel Cell Battery Based on Garnet Solid Electrolytes.

    PubMed

    Sun, Jiyang; Zhao, Ning; Li, Yiqiu; Guo, Xiangxin; Feng, Xuefei; Liu, Xiaosong; Liu, Zhi; Cui, Guanglei; Zheng, Hao; Gu, Lin; Li, Hong

    2017-01-24

    Non-aqueous Li-air batteries have been intensively studied in the past few years for their theoretically super-high energy density. However, they cannot operate properly in real air because they contain highly unstable and volatile electrolytes. Here, we report the fabrication of solid-state Li-air batteries using garnet (i.e., Li6.4La3Zr1.4Ta0.6O12, LLZTO) ceramic disks with high density and ionic conductivity as the electrolytes and composite cathodes consisting of garnet powder, Li salts (LiTFSI) and active carbon. These batteries run in real air based on the formation and decomposition at least partially of Li2CO3. Batteries with LiTFSI mixed with polyimide (PI:LiTFSI) as a binder show rechargeability at 200 °C with a specific capacity of 2184 mAh g(-1)carbon at 20 μA cm(-2). Replacement of PI:LiTFSI with LiTFSI dissolved in polypropylene carbonate (PPC:LiTFSI) reduces interfacial resistance, and the resulting batteries show a greatly increased discharge capacity of approximately 20300 mAh g(-1)carbon and cycle 50 times while maintaining a cutoff capacity of 1000 mAh g(-1)carbon at 20 μA cm(-2) and 80 °C. These results demonstrate that the use of LLZTO ceramic electrolytes enables operation of the Li-air battery in real air at medium temperatures, leading to a novel type of Li-air fuel cell battery for energy storage.

  7. A Rechargeable Li-Air Fuel Cell Battery Based on Garnet Solid Electrolytes

    NASA Astrophysics Data System (ADS)

    Sun, Jiyang; Zhao, Ning; Li, Yiqiu; Guo, Xiangxin; Feng, Xuefei; Liu, Xiaosong; Liu, Zhi; Cui, Guanglei; Zheng, Hao; Gu, Lin; Li, Hong

    2017-01-01

    Non-aqueous Li-air batteries have been intensively studied in the past few years for their theoretically super-high energy density. However, they cannot operate properly in real air because they contain highly unstable and volatile electrolytes. Here, we report the fabrication of solid-state Li-air batteries using garnet (i.e., Li6.4La3Zr1.4Ta0.6O12, LLZTO) ceramic disks with high density and ionic conductivity as the electrolytes and composite cathodes consisting of garnet powder, Li salts (LiTFSI) and active carbon. These batteries run in real air based on the formation and decomposition at least partially of Li2CO3. Batteries with LiTFSI mixed with polyimide (PI:LiTFSI) as a binder show rechargeability at 200 °C with a specific capacity of 2184 mAh g‑1carbon at 20 μA cm‑2. Replacement of PI:LiTFSI with LiTFSI dissolved in polypropylene carbonate (PPC:LiTFSI) reduces interfacial resistance, and the resulting batteries show a greatly increased discharge capacity of approximately 20300 mAh g‑1carbon and cycle 50 times while maintaining a cutoff capacity of 1000 mAh g‑1carbon at 20 μA cm‑2 and 80 °C. These results demonstrate that the use of LLZTO ceramic electrolytes enables operation of the Li-air battery in real air at medium temperatures, leading to a novel type of Li-air fuel cell battery for energy storage.

  8. A Rechargeable Li-Air Fuel Cell Battery Based on Garnet Solid Electrolytes

    PubMed Central

    Sun, Jiyang; Zhao, Ning; Li, Yiqiu; Guo, Xiangxin; Feng, Xuefei; Liu, Xiaosong; Liu, Zhi; Cui, Guanglei; Zheng, Hao; Gu, Lin; Li, Hong

    2017-01-01

    Non-aqueous Li-air batteries have been intensively studied in the past few years for their theoretically super-high energy density. However, they cannot operate properly in real air because they contain highly unstable and volatile electrolytes. Here, we report the fabrication of solid-state Li-air batteries using garnet (i.e., Li6.4La3Zr1.4Ta0.6O12, LLZTO) ceramic disks with high density and ionic conductivity as the electrolytes and composite cathodes consisting of garnet powder, Li salts (LiTFSI) and active carbon. These batteries run in real air based on the formation and decomposition at least partially of Li2CO3. Batteries with LiTFSI mixed with polyimide (PI:LiTFSI) as a binder show rechargeability at 200 °C with a specific capacity of 2184 mAh g−1carbon at 20 μA cm−2. Replacement of PI:LiTFSI with LiTFSI dissolved in polypropylene carbonate (PPC:LiTFSI) reduces interfacial resistance, and the resulting batteries show a greatly increased discharge capacity of approximately 20300 mAh g−1carbon and cycle 50 times while maintaining a cutoff capacity of 1000 mAh g−1carbon at 20 μA cm−2 and 80 °C. These results demonstrate that the use of LLZTO ceramic electrolytes enables operation of the Li-air battery in real air at medium temperatures, leading to a novel type of Li-air fuel cell battery for energy storage. PMID:28117359

  9. Feedback & Objectives

    ERIC Educational Resources Information Center

    Butterworth, James R.

    1975-01-01

    Industrial objectives, if they are employee oriented, produce feedback, and the motivation derived from the feedback helps reduce turnover. Feedback is the power to clarify objectives, to stimulate communication, and to motivate people. (Author/MW)

  10. An Iterative Information-Reduced Quadriphase-Shift-Keyed Carrier Synchronization Scheme Using Decision Feedback for Low Signal-to-Noise Ratio Applications

    NASA Technical Reports Server (NTRS)

    Simon, M.; Tkacenko, A.

    2006-01-01

    In a previous publication [1], an iterative closed-loop carrier synchronization scheme for binary phase-shift keyed (BPSK) modulation was proposed that was based on feeding back data decisions to the input of the loop, the purpose being to remove the modulation prior to carrier synchronization as opposed to the more conventional decision-feedback schemes that incorporate such feedback inside the loop. The idea there was that, with sufficient independence between the received data and the decisions on it that are fed back (as would occur in an error-correction coding environment with sufficient decoding delay), a pure tone in the presence of noise would ultimately be produced (after sufficient iteration and low enough error probability) and thus could be tracked without any squaring loss. This article demonstrates that, with some modification, the same idea of iterative information reduction through decision feedback can be applied to quadrature phase-shift keyed (QPSK) modulation, something that was mentioned in the previous publication but never pursued.

  11. A passive microfluidic hydrogen-air fuel cell with exceptional stability and high performance.

    PubMed

    Mitrovski, Svetlana M; Nuzzo, Ralph G

    2006-03-01

    We describe an advanced microfluidic hydrogen-air fuel cell (FC) that exhibits exceptional durability and high performance, most notably yielding stable output power (>100 days) without the use of an anode-cathode separator membrane. This FC embraces an entirely passive device architecture and, unlike conventional microfluidic designs that exploit laminar hydrodynamics, no external pumps are used to sustain or localize the reagent flow fields. The devices incorporate high surface area/porous metal and metal alloy electrodes that are embedded and fully immersed in liquid electrolyte confined in the channels of a poly(dimethylsiloxane) (PDMS)-based microfluidic network. The polymeric network also serves as a self-supporting membrane through which oxygen and hydrogen are supplied to the cathode and alloy anode, respectively, by permeation. The operational stability of the device and its performance is strongly dependent on the nature of the electrolyte used (5 M H2SO4 or 2.5 M NaOH) and composition of the anode material. The latter choice is optimized to decrease the sensitivity of the system to oxygen cross-over while still maintaining high activity towards the hydrogen oxidation reaction (HOR). Three types of high surface area anodes were tested in this work. These include: high-surface area electrodeposited Pt (Pt); high-surface area electrodeposited Pd (Pd); and thin palladium adlayers supported on a "porous" Pt electrode (Pd/Pt). The FCs display their best performance in 5 M H2SO4 using the Pd/Pt anode. This exceptional stability and performance was ascribed to several factors, namely: the high permeabilities of O2, H2, and CO2 in PDMS; the inhibition of the formation of insoluble carbonate species due to the presence of a highly acidic electrolyte; and the selectivity of the Pd/Pt anode toward the HOR. The stability of the device for long-term operation was modeled using a stack of three FCs as a power supply for a portable display that otherwise uses a 3 V

  12. Water isotope ratio (δ2H and δ18O) measurements in atmospheric moisture using an optical feedback cavity enhanced absorption laser spectrometer

    NASA Astrophysics Data System (ADS)

    Iannone, Rosario Q.; Romanini, Daniele; Cattani, Olivier; Meijer, Harro A. J.; Kerstel, Erik R. Th.

    2010-05-01

    Water vapor isotopes represent an innovative and excellent tool for understanding complex mechanisms in the atmospheric water cycle over different time scales, and they can be used for a variety of applications in the fields of paleoclimatology, hydrology, oceanography, and ecology. We use an ultrasensitive near-infrared spectrometer, originally designed for use on airborne platforms in the upper troposphere and lower stratosphere, to measure the water deuterium and oxygen-18 isotope ratios in situ, in ground-level tropospheric moisture, with a high temporal resolution (from 300 s down to less than 1 s). We present some examples of continuous monitoring of near-surface atmospheric moisture, demonstrating that our infrared laser spectrometer could be used successfully to record high-concentration atmospheric water vapor mixing ratios in continuous time series, with a data coverage of ˜90%, interrupted only for daily calibration to two isotope ratio mass spectrometry-calibrated local water standards. The atmospheric data show that the water vapor isotopic composition exhibits a high variability that can be related to weather conditions, especially to changes in relative humidity. Besides, the results suggest that observed spatial and temporal variations of the stable isotope content of atmospheric water vapor are strongly related to water vapor transport in the atmosphere.

  13. PEM fuel cell cathode carbon corrosion due to the formation of air/fuel boundary at the anode

    NASA Astrophysics Data System (ADS)

    Tang, Hao; Qi, Zhigang; Ramani, Manikandan; Elter, John F.

    The impacts of unprotected start up and shut down on fuel cell performance degradation was investigated using both single cell and dual cell configurations. It was found that the air/fuel boundary developed at the anode side after a fuel cell shut down or during its restart caused extremely quick degradation of the cathode. The thickness, the electrochemical active surface area, and the performance of the cathode catalyst layer were significantly reduced. By using a dual cell configuration, cathode potential as high as two times of open circuit voltage was measured, and the corrosion current flowing externally between the two cells was detected and quantified. Carbon catalyst-support corrosion/oxidation at such a high potential was largely responsible for the accelerated fuel cell performance degradation.

  14. Balanced bridge feedback control system

    NASA Technical Reports Server (NTRS)

    Lurie, Boris J. (Inventor)

    1990-01-01

    In a system having a driver, a motor, and a mechanical plant, a multiloop feedback control apparatus for controlling the movement and/or positioning of a mechanical plant, the control apparatus has a first local bridge feedback loop for feeding back a signal representative of a selected ratio of voltage and current at the output driver, and a second bridge feedback loop for feeding back a signal representative of a selected ratio of force and velocity at the output of the motor. The control apparatus may further include an outer loop for feeding back a signal representing the angular velocity and/or position of the mechanical plant.

  15. Effect of the air-fuel mixing on the NOx yield in a low-emission gas-turbine plant combustor

    NASA Astrophysics Data System (ADS)

    Vasil'ev, V. D.; Bulysova, L. A.; Berne, A. L.

    2016-04-01

    The article deals with construction of a simplified model of inhibition of nitric oxides formed in the combustors of the gas-turbine plants (GTPs) operating on natural gas. A combustor in which premixed, lean air-fuel mixtures are burnt is studied theoretically and experimentally. The research was carried out using a full-scale combustor that had parameters characteristic of modern GTPs. The article presents the results computed by the FlowVision software and the results of the experiments carried out on the test bench of the All-Russia Thermal Engineering Institute. The calculations and the tests were conducted under the following conditions: a flow rate of approximately 4.6 kg/s, a pressure to 450 kPa, an air temperature at the combustor inlet of approximately 400°C, the outlet temperature t 3 ≤ 1200°C, and natural gas as the fuel. The comparison of the simulated parameters with the experimental results underlies the constructed correlation dependence of the experimental NO x emission on the calculated parameter of nonuniform fuel concentration at the premixing zone outlet. The postulate about a weak dependence of the emission of NO x formed upon combustion of a perfectly mixed air-fuel mixture—when the methane concentration in air is constant at any point of the air-fuel mixture, i.e., constant in the mixture bulk—on the pressure in the combustor has been experimentally proven. The correctness and the practicability of the stationary mathematical model of the mixing process used to assess the NO x emission by the calculated amount of the air-fuel mixture generated in the premixing zone has been validated. This eliminates some difficulties that arise in the course of calculation of combustion and formation of NO x .

  16. Application of TiC reinforced Fe-based coatings by means of High Velocity Air Fuel Spraying

    NASA Astrophysics Data System (ADS)

    Bobzin, K.; Öte, M.; Knoch, M. A.; Liao, X.; Sommer, J.

    2017-03-01

    In the field of hydraulic applications, different development trends can cause problems for coatings currently used as wear and corrosion protection for piston rods. Aqueous hydraulic fluids and rising raw material prices necessitate the search for alternatives to conventional coatings like galvanic hard chrome or High Velocity Oxygen Fuel (HVOF)-sprayed WC/Co coatings. In a previous study, Fe/TiC coatings sprayed by a HVOF-process, were identified to be promising coating systems for wear and corrosion protection in hydraulic systems. In this feasibility study, the novel High Velocity Air Fuel (HVAF)-process, a modification of the HVOF-process, is investigated using the same feedstock material, which means the powder is not optimized for the HVAF-process. The asserted benefits of the HVAF-process are higher particle velocities and lower process temperatures, which can result in a lower porosity and oxidation of the coating. Further benefits of the HVAF process are claimed to be lower process costs and higher deposition rates. In this study, the focus is set on to the applicability of Fe/TiC coatings by HVAF in general. The Fe/TiC HVAF coating could be produced, successfully. The HVAF- and HVOF-coatings, produced with the same powder, were investigated using micro-hardness, porosity, wear and corrosion tests. A similar wear coefficient and micro-hardness for both processes could be achieved. Furthermore the propane/hydrogen proportion of the HVAF process and its influence on the coating thickness and the porosity was investigated.

  17. ENVIRONMENTAL TECHNOLOGY REPORT, MIRATECH CORPORATION, GECO(TM) 3001 AIR/FUEL RATIO CONTROLLER (MANUFACTURED BY WOODWARD GOVERNOR COMPANY) PHASE II REPORT

    EPA Science Inventory

    In the natural gas industry, transmission pipeline operators use internal combustion (IC) gas-fired engines to provide the mechanical energy needed to drive pipeline gas compressors. As such, owners and operators of compressor stations are interested in the performance of these e...

  18. Feedback: Breakfast of Champions.

    ERIC Educational Resources Information Center

    Justman, Jeffrey J.

    Feedback is an important skill that people need to learn in life. Feedback is crucial in a public speaking class to improve speaking skills. Providing and receiving feedback is what champions feed on to be successful, thus feedback is called the "Breakfast of Champions." Feedback builds speakers' confidence. Providing in-depth feedback…

  19. Variations in the structure and electrochemical characteristics of membrane electrode assemblies during the endurance testing of hydrogen-air fuel cells

    NASA Astrophysics Data System (ADS)

    Avakov, V. B.; Aliev, A. D.; Bogdanovskaya, V. A.; Ivanitskii, B. A.; Kazanskii, L. P.; Kapustin, A. V.; Korchagin, O. V.; Landgraf, I. K.; Tarasevich, M. P.; Chalykh, A. E.

    2015-05-01

    Variations in the characteristics of a membrane-electrode assembly (MEA) are studied during the endurance testing of a hydrogen-air fuel cell (FC) based on a Nafion 212 proton conducting membrane and platinum catalysts. It is shown that the voltage drop observed during MEA testing was mainly due to physicochemical transformations of the cathode catalyst, i.e., the oxidation of platinum and its subsequent recrystallization with nanoparticle coarsening. It is established that the rate of degradation increases along with temperature and loading, and with periodic FC depressurization. It is concluded that the enhancing effects of additional factors of degradation, e.g., platinum ion transport to the proton-conducting membrane and corrosion of the carbon carrier, were responsible for these processes.

  20. Treatment of synthetic arsenate wastewater with iron-air fuel cell electrocoagulation to supply drinking water and electricity in remote areas.

    PubMed

    Kim, Jung Hwan; Maitlo, Hubdar Ali; Park, Joo Yang

    2017-05-15

    Electrocoagulation with an iron-air fuel cell is an innovative arsenate removal system that can operate without an external electricity supply. Thus, this technology is advantageous for treating wastewater in remote regions where it is difficult to supply electricity. In this study, the possibility of real applications of this system for arsenate treatment with electricity production was verified through electrolyte effect investigations using a small-scale fuel cell and performance testing of a liter-scale fuel cell stack. The electrolyte species studied were NaCl, Na2SO4, and NaHCO3. NaCl was overall the most effective electrolyte for arsenate treatment, although Na2SO4 produced the greatest electrical current and power density. In addition, although the current density and power density were proportional to the concentrations of NaCl and Na2SO4, the use of concentrations above 20 mM of NaCl and Na2SO4 inhibited arsenate treatment due to competition effects between anions and arsenate in adsorption onto the iron hydroxide. The dominant iron hydroxide produced at the iron anode was found to be lepidocrocite by means of Raman spectroscopy. A liter-scale four-stack iron-air fuel cell with 10 mM NaCl electrolyte was found to be able to treat about 300 L of 1 ppm arsenate solution to below 10 ppb during 1 day, based on its 60-min treatment capacity, as well as produce the maximum power density of 250 mW/m(2).

  1. Student Engagement with Feedback

    ERIC Educational Resources Information Center

    Scott, Jon; Shields, Cathy; Gardner, James; Hancock, Alysoun; Nutt, Alex

    2011-01-01

    This report considers Biological Sciences students' perceptions of feedback, compared with those of the University as a whole, this includes what forms of feedback were considered most useful and how feedback used. Compared with data from previous studies, Biological Sciences students gave much greater recognition to oral feedback, placing it on a…

  2. RATIO COMPUTER

    DOEpatents

    Post, R.F.

    1958-11-11

    An electronic computer circuit is described for producing an output voltage proportional to the product or quotient of tbe voltages of a pair of input signals. ln essence, the disclosed invention provides a computer having two channels adapted to receive separate input signals and each having amplifiers with like fixed amplification factors and like negatlve feedback amplifiers. One of the channels receives a constant signal for comparison purposes, whereby a difference signal is produced to control the amplification factors of the variable feedback amplifiers. The output of the other channel is thereby proportional to the product or quotient of input signals depending upon the relation of input to fixed signals in the first mentioned channel.

  3. Improved feedback shift register

    NASA Technical Reports Server (NTRS)

    Perlman, M.

    1972-01-01

    Design of feedback shift register with three tap feedback decoding scheme is described. Application for obtaining sequence synchronization patterns is examined. Operation of the circuitry is described and drawings of the systems are included.

  4. Developing Sustainable Feedback Practices

    ERIC Educational Resources Information Center

    Carless, David; Salter, Diane; Yang, Min; Lam, Joy

    2011-01-01

    Feedback is central to the development of student learning, but within the constraints of modularized learning in higher education it is increasingly difficult to handle effectively. This article makes a case for sustainable feedback as a contribution to the reconceptualization of feedback processes. The data derive from the Student Assessment and…

  5. The Mythology of Feedback

    ERIC Educational Resources Information Center

    Adcroft, Andy

    2011-01-01

    Much of the general education and discipline-specific literature on feedback suggests that it is a central and important element of student learning. This paper examines feedback from a social process perspective and suggests that feedback is best understood through an analysis of the interactions between academics and students. The paper argues…

  6. Passage Feedback with IRIS.

    ERIC Educational Resources Information Center

    Yang, Kiduk; Maglaughlin, Kelly L.; Newby, Gregory B.

    2001-01-01

    Compares a user-defined passage feedback system to a document feedback system for information retrieval, based on TREC (Text Retrieval Conference) guidelines. Highlights include a description of IRIS, an interactive retrieval system; text processing; ranking; term weights; feedback models, including the adaptive linear model; and suggestions for…

  7. Preventing Feedback Fizzle

    ERIC Educational Resources Information Center

    Brookhart, Susan M.

    2012-01-01

    Feedback is certainly about saying or writing helpful, learning-focused comments. But that is only part of it. What happens beforehand? What happens afterward? Feedback that is helpful and learning-focused fits into a context. Before a teacher gives feedback, students need to know the learning target so they have a purpose for using the feedback…

  8. Types and Frequencies of Feedback Interventions in Classroom Interaction in Secondary Education

    ERIC Educational Resources Information Center

    Voerman, Lia; Meijer, Paulien C.; Korthagen, Fred A. J.; Simons, Robert Jan

    2012-01-01

    Contributing to the growing amount of literature on learning-enhancing feedback, this article attempts to distinguish between progress feedback and discrepancy feedback. Building on relevant literature drawn from psychology, we propose the use of a ratio of 3:1, positive:negative feedback. We analyzed contiguous 10 min blocks of classroom…

  9. Novel ferrocene-anchored ZnO nanoparticle/carbon nanotube assembly for glucose oxidase wiring: application to a glucose/air fuel cell

    NASA Astrophysics Data System (ADS)

    Haddad, Raoudha; Mattei, Jean-Gabriel; Thery, Jessica; Auger, Aurélien

    2015-06-01

    Glucose oxidase (GOx) is immobilized on ZnO nanoparticle-modified electrodes. The immobilized glucose oxidase shows efficient mediated electron transfer with ZnO nanoparticles to which the ferrocenyl moiety is π-stacked into a supramolecular architecture. The constructed ZnO-Fc/CNT modified electrode exhibits high ferrocene surface coverage, preventing any leakage of the π-stacked ferrocene from the newly described ZnO hybrid nanoparticles. The use of the new architecture of ZnO supported electron mediators to shuttle electrons from the redox centre of the enzyme to the surface of the working electrode can effectively bring about successful glucose oxidation. These modified electrodes evaluated as a highly efficient architecture provide a catalytic current for glucose oxidation and are integrated in a specially designed glucose/air fuel cell prototype using a conventional platinum-carbon (Pt/C) cathode at physiological pH (7.0). The obtained architecture leads to a peak power density of 53 μW cm-2 at 300 mV for the Nafion® based biofuel cell under ``air breathing'' conditions at room temperature.

  10. Novel ferrocene-anchored ZnO nanoparticle/carbon nanotube assembly for glucose oxidase wiring: application to a glucose/air fuel cell.

    PubMed

    Haddad, Raoudha; Mattei, Jean-Gabriel; Thery, Jessica; Auger, Aurélien

    2015-06-28

    Glucose oxidase (GOx) is immobilized on ZnO nanoparticle-modified electrodes. The immobilized glucose oxidase shows efficient mediated electron transfer with ZnO nanoparticles to which the ferrocenyl moiety is π-stacked into a supramolecular architecture. The constructed ZnO-Fc/CNT modified electrode exhibits high ferrocene surface coverage, preventing any leakage of the π-stacked ferrocene from the newly described ZnO hybrid nanoparticles. The use of the new architecture of ZnO supported electron mediators to shuttle electrons from the redox centre of the enzyme to the surface of the working electrode can effectively bring about successful glucose oxidation. These modified electrodes evaluated as a highly efficient architecture provide a catalytic current for glucose oxidation and are integrated in a specially designed glucose/air fuel cell prototype using a conventional platinum-carbon (Pt/C) cathode at physiological pH (7.0). The obtained architecture leads to a peak power density of 53 μW cm(-2) at 300 mV for the Nafion® based biofuel cell under "air breathing" conditions at room temperature.

  11. In situ STM studies of zinc in aqueous solutions containing PEG DiAcid inhibitor: Correlation with electrochemical performances of zinc-air fuel cells

    NASA Astrophysics Data System (ADS)

    Cohen-Hyams, Tzipi; Ziengerman, Yuli; Ein-Eli, Yair

    Electrochemical performance of prismatic zinc-air fuel cells comprising zinc anode gel containing poly(ethylene glycol) (PEG 600) and poly(ethylene glycol) bis(carboxymethyl) ether (PEG DiAcid 600) as corrosion inhibitor were studied. It was found that in addition to the low zinc corrosion rates obtained from cells utilizing PEG DiAcid 600 as corrosion inhibitor, both analog and global mobile system (GSM) discharge capacities and potential plateaus, in a wide range of temperatures were higher once PEG DiAcid was added to the zinc gel mixtures. The results obtained from in situ scanning tunneling microscopy (STM) studies of zinc substrates immersed in deionized (DI) water containing inhibitors reveal that the film produced on the zinc metal in the presence of PEG DiAcid is by far thinner than the film produced by other inhibitors such as PEG 600 and polyoxyethylene alkyl phosphate ester acid (GAFAC RA 600). These studies also reveal that the addition of PEG DiAcid forms an adherent and a complete protective coverage, while the addition of PEG 600 and GAFAC RA 600 resulted in an incomplete coverage with the appearance of pits and terraces, indicating on a restricted inhibition performance of these two polymers compared with PEG DiAcid. These studies suggest a low interface resistivity of zinc immersed in alkaline solution containing PEG DiAcid, which is expressed in a higher working potential and increased cell capacity in different temperatures at two discharge modes of analog and GSM.

  12. Nitric oxide density measurements in air and air/fuel nanosecond pulse discharges by laser induced fluorescence

    NASA Astrophysics Data System (ADS)

    Uddi, M.; Jiang, N.; Adamovich, I. V.; Lempert, W. R.

    2009-04-01

    Laser induced fluorescence is used to measure absolute nitric oxide concentrations in air, methane-air and ethylene-air non-equilibrium plasmas, as a function of time after initiation of a single pulse, 20 kV peak voltage, 25 ns pulse duration discharge. A mixture of NO and nitrogen with known composition (4.18 ppm NO) is used for calibration. Peak NO density in air at 60 Torr, after a single pulse, is ~8 × 1012 cm-3 (~4.14 ppm) occurring at ~250 µs after the pulse, with decay time of ~16.5 ms. Peak NO atom mole fraction in a methane-air mixture with equivalence ratio of phiv = 0.5 is found to be approximately equal to that in air, with approximately the same rise and decay rate. In an ethylene-air mixture (also with equivalence ratio of phiv = 0.5), the rise and decay times are comparable to air and methane-air, but the peak NO concentration is reduced by a factor of approximately 2.5. Spontaneous emission measurements show that excited electronic states N2(C 3Π) and NO(A 2Σ) in air at P = 60 Torr decay within ~20 ns and ~1 µs, respectively. Kinetic modelling calculations incorporating air plasma kinetics complemented with the GRI Mech 3.0 hydrocarbon oxidation mechanism are compared with the experimental data using three different NO production mechanisms. It is found that NO concentration rise after the discharge pulse is much faster than predicted by Zel'dovich mechanism reactions, by two orders of magnitude, but much slower compared with reactions of electronically excited nitrogen atoms and molecules, also by two orders of magnitude. It is concluded that processes involving long lifetime (~100 µs) metastable states, such as N2(X 1Σ,v) and O2(b 1Σ), formed by quenching of the metastable N2(A 3Σ) state by ground electronic state O2, may play a dominant role in NO formation. NO decay, in all cases, is found to be dominated by the reverse Zel'dovich reaction, NO + O → N + O2, as well as by conversion into NO2 in a reaction of NO with ozone.

  13. High-Compression-Ratio; Atkinson-Cycle Engine Using Low-Pressure Direct Injection and Pneumatic-Electronic Valve Actuation Enabled by Ionization Current and Foward-Backward Mass Air Flow Sensor Feedback

    SciTech Connect

    Harold Schock; Farhad Jaberi; Ahmed Naguib; Guoming Zhu; David Hung

    2007-12-31

    This report describes the work completed over a two and one half year effort sponsored by the US Department of Energy. The goal was to demonstrate the technology needed to produce a highly efficient engine enabled by several technologies which were to be developed in the course of the work. The technologies included: (1) A low-pressure direct injection system; (2) A mass air flow sensor which would measure the net airflow into the engine on a per cycle basis; (3) A feedback control system enabled by measuring ionization current signals from the spark plug gap; and (4) An infinitely variable cam actuation system based on a pneumatic-hydraulic valve actuation These developments were supplemented by the use of advanced large eddy simulations as well as evaluations of fuel air mixing using the KIVA and WAVE models. The simulations were accompanied by experimental verification when possible. In this effort a solid base has been established for continued development of the advanced engine concepts originally proposed. Due to problems with the valve actuation system a complete demonstration of the engine concept originally proposed was not possible. Some of the highlights that were accomplished during this effort are: (1) A forward-backward mass air flow sensor has been developed and a patent application for the device has been submitted. We are optimistic that this technology will have a particular application in variable valve timing direct injection systems for IC engines. (2) The biggest effort on this project has involved the development of the pneumatic-hydraulic valve actuation system. This system was originally purchased from Cargine, a Swedish supplier and is in the development stage. To date we have not been able to use the actuators to control the exhaust valves, although the actuators have been successfully employed to control the intake valves. The reason for this is the additional complication associated with variable back pressure on the exhaust valves when

  14. Feedback stabilization initiative

    SciTech Connect

    1997-06-01

    Much progress has been made in attaining high confinement regimes in magnetic confinement devices. These operating modes tend to be transient, however, due to the onset of MHD instabilities, and their stabilization is critical for improved performance at steady state. This report describes the Feedback Stabilization Initiative (FSI), a broad-based, multi-institutional effort to develop and implement methods for raising the achievable plasma betas through active MHD feedback stabilization. A key element in this proposed effort is the Feedback Stabilization Experiment (FSX), a medium-sized, national facility that would be specifically dedicated to demonstrating beta improvement in reactor relevant plasmas by using a variety of MHD feedback stabilization schemes.

  15. "Feedback" For Instructioal Television.

    ERIC Educational Resources Information Center

    Schramm, Wilbur

    A number of different methods have been used by instructional television (ITV) projects to obtain audience feedback, and some of these are now being used in the ITV system in El Salvador. We know that pretesting programs on a representative sample can bring considerable gains in learning. Another feedback source can be a classroom of pupils in the…

  16. Convolution feedback systems.

    NASA Technical Reports Server (NTRS)

    Desoer, C. A.; Callier, F. M.

    1972-01-01

    Linear time-invariant feedback systems with multiple inputs and multiple outputs are examined. It is demonstrated that no loss of generality takes place considering the feedback to be unity. Necessary and sufficient conditions are derived for the closed-loop impulse response to be stable in a prescribed sense.

  17. Designing Genetic Feedback Controllers.

    PubMed

    Harris, Andreas W K; Dolan, James A; Kelly, Ciarán L; Anderson, James; Papachristodoulou, Antonis

    2015-08-01

    By incorporating feedback around systems we wish to manipulate, it is possible to improve their performance and robustness properties to meet pre-specified design objectives. For decades control engineers have been successfully implementing feedback controllers for complex mechanical and electrical systems such as aircraft and sports cars. Natural biological systems use feedback extensively for regulation and adaptation but apart from the most basic designs, there is no systematic framework for designing feedback controllers in Synthetic Biology. In this paper we describe how classical approaches from linear control theory can be used to close the loop. This includes the design of genetic circuits using feedback control and the presentation of a biological phase lag controller.

  18. Fuel-air ratio controlled carburetion system

    SciTech Connect

    Abbey, H. G.

    1980-02-12

    An automatic control system is disclosed supplying a fuel-air mixture to an internal combustion engine including a variable-venturi carburetor. Air is fed into the input of the venturi, the air passing through the throat thereof whose effective area is adjusted by a mechanism operated by a servo motor. Fuel is fed into the input of the venturi from a fuel reservoir through a main path having a fixed orifice and an auxiliary path formed by a metering valve operated by an auxiliary fuel-control motor. The differential air pressure developed between the inlet of the venturi and the throat thereof is sensed to produce an airvelocity command signal that is applied to a controller adapted to compare the command signal with the servo motor set point to produce an output for governing the servo motor to cause it to seek a null point, thereby defining a closed process control loop. The intake manifold vacuum, which varies in degree as a function of load and speed conditions is sensed to govern the auxiliary fuel-control motor accordingly, is at the same time converted into an auxiliary signal which is applied to the controller in the closed loop to modulate the command signal in a manner establishing an optimum air-fuel ratio under the varying conditions of load and speed.

  19. Radiation feedback in dusty clouds

    NASA Astrophysics Data System (ADS)

    Ishiki, Shohei; Okamoto, Takashi

    2017-03-01

    We have investigated the impact of photoionization and radiation pressure on a dusty star-forming cloud using one-dimensional radiation hydrodynamic simulations, which include absorption and re-emission of photons by dust. We find that, in a cloud of mass 105 M⊙ and radius 17 pc, the effect of radiation pressure is negligible when star formation efficiency is 2 per cent. The importance of radiation pressure increases with increasing star formation efficiency or an increasing dust-to-gas mass ratio. The net effect of radiation feedback, however, becomes smaller with the increasing dust-to-gas mass ratio, since the absorption of ultraviolet photons by dust grains suppresses photoionization and hence photoheating.

  20. FEEDBACK FROM CENTRAL BLACK HOLES IN ELLIPTICAL GALAXIES. II. CAN PURELY MECHANICAL ENERGY FEEDBACK MODELS WORK?

    SciTech Connect

    Shin Minsu; Ostriker, Jeremiah P.; Ciotti, Luca

    2010-03-01

    By using high-resolution one-dimensional hydrodynamical simulations, we investigate the effects of purely mechanical feedback from super massive black holes (SMBHs) in the evolution of elliptical galaxies for a broad range of feedback efficiencies and compare the results to four major observational constraints. In particular, we focus on (1) the central black hole to stellar mass ratio of the host galaxy, (2) the lifetime of the luminous quasar phase, (3) the mass of stars formed in the host galaxy within the last Gyr, and (4) the X-ray luminosity of the hot diffuse gas. As a result, we try to pin down the most successful range of mechanical feedback efficiencies. We find that while low feedback efficiencies result in too much growth of the SMBH, high efficiencies totally blow out the hot interstellar gas, and the models are characterized by very low thermal X-ray luminosity well below the observed range. The net lifetime of the quasar phase is strongly coupled to the mass ratio between SMBH and its host galaxy, while the X-ray luminosity is generally correlated to the recent star formation within the last Gyr. When considering the popularly adopted model of the constant feedback efficiency, the feedback energy deposited into the ambient medium should be more than 0.01% of the SMBH accretion energy to be consistent with the SMBH mass to stellar mass ratio in the local universe. Yet, the X-ray luminosity of the hot gas favors about 0.005% of the accretion energy as the mechanical active galactic nucleus (AGN) feedback energy. We conclude that the purely mechanical feedback mode is unlikely to be simultaneously compatible with all four observable tests, even allowing a broad range of feedback efficiencies, and that including both radiative and mechanical feedback together may be a solution to comply with the observational constraints. In addition to the adopted observational constraints, our simulations also show that the ratio of SMBH growth rate over its current

  1. Strategies for effective feedback.

    PubMed

    Kritek, Patricia A

    2015-04-01

    Provision of regular feedback to trainees on clinical performance by supervising providers is increasingly recognized as an essential component of undergraduate and graduate health sciences education; however, many individuals have not been formally trained in this pedagogical skill. At the bedside or in the clinic, effective performance feedback can be accomplished by following four key steps. Begin by setting expectations that incorporate the trainee's personal goals and external objectives. Delineate how and when you will provide feedback to the learner. Next, directly observe the trainee's performance. This can be challenging while engaged on a busy clinical service, but a focus on discrete activities or interactions (e.g., family meeting, intravascular volume assessment using bedside ultrasound, or obtaining informed consent) is helpful. The third step is to plan and prioritize the feedback session. Feedback is most effective when given in a timely fashion and delivered in a safe environment. Limit the issues addressed because learners often disengage if confronted with too many deficiencies. Finally, when delivering feedback, begin by listening to the trainee's self-evaluation and then take a balanced approach. Describe in detail what the trainee does well and discuss opportunities for improvement with emphasis on specific, modifiable behaviors. The feedback loop is completed with a plan for follow-up reassessment. Through the use of these relatively simple practices, both the trainee and teacher can have a more productive learning experience.

  2. Herbivory and Stoichiometric Feedbacks to Primary Production.

    PubMed

    Krumins, Jennifer Adams; Krumins, Valdis; Forgoston, Eric; Billings, Lora; van der Putten, Wim H

    2015-01-01

    Established theory addresses the idea that herbivory can have positive feedbacks on nutrient flow to plants. Positive feedbacks likely emerge from a greater availability of organic carbon that primes the soil by supporting nutrient turnover through consumer and especially microbially-mediated metabolism in the detrital pool. We developed an entirely novel stoichiometric model that demonstrates the mechanism of a positive feedback. In particular, we show that sloppy or partial feeding by herbivores increases detrital carbon and nitrogen allowing for greater nitrogen mineralization and nutritive feedback to plants. The model consists of differential equations coupling flows among pools of: plants, herbivores, detrital carbon and nitrogen, and inorganic nitrogen. We test the effects of different levels of herbivore grazing completion and of the stoichiometric quality (carbon to nitrogen ratio, C:N) of the host plant. Our model analyses show that partial feeding and plant C:N interact because when herbivores are sloppy and plant biomass is diverted to the detrital pool, more mineral nitrogen is available to plants because of the stoichiometric difference between the organisms in the detrital pool and the herbivore. This model helps to identify how herbivory may feedback positively on primary production, and it mechanistically connects direct and indirect feedbacks from soil to plant production.

  3. Global Feedback Simulator

    SciTech Connect

    Carlos Serrano, Lawrence Doolittle

    2015-10-29

    GFS is a simulation engine that is used for the characterization of Accelerator performance parameters based on the machine layout, configuration and noise sources. It combines extensively tested Feedback models with a longitudinal phase space tracking simulator along with the interaction between the two via beam-based feedback using a computationally efficient simulation engine. The models include beam instrumentation, considerations on loop delays for in both the R and beam-based feedback loops, as well as the ability to inject noise (both correlated and uncorrelated) at different points of the machine including a full characterization of the electron gun performance parameters.

  4. On Gaussian feedback capacity

    NASA Technical Reports Server (NTRS)

    Dembo, Amir

    1989-01-01

    Pinsker and Ebert (1970) proved that in channels with additive Gaussian noise, feedback at most doubles the capacity. Cover and Pombra (1989) proved that feedback at most adds half a bit per transmission. Following their approach, the author proves that in the limit as signal power approaches either zero (very low SNR) or infinity (very high SNR), feedback does not increase the finite block-length capacity (which for nonstationary Gaussian channels replaces the standard notion of capacity that may not exist). Tighter upper bounds on the capacity are obtained in the process. Specializing these results to stationary channels, the author recovers some of the bounds recently obtained by Ozarow.

  5. Stratospheric water vapor feedback.

    PubMed

    Dessler, A E; Schoeberl, M R; Wang, T; Davis, S M; Rosenlof, K H

    2013-11-05

    We show here that stratospheric water vapor variations play an important role in the evolution of our climate. This comes from analysis of observations showing that stratospheric water vapor increases with tropospheric temperature, implying the existence of a stratospheric water vapor feedback. We estimate the strength of this feedback in a chemistry-climate model to be +0.3 W/(m(2)⋅K), which would be a significant contributor to the overall climate sensitivity. One-third of this feedback comes from increases in water vapor entering the stratosphere through the tropical tropopause layer, with the rest coming from increases in water vapor entering through the extratropical tropopause.

  6. Feedback valence affects auditory perceptual learning independently of feedback probability.

    PubMed

    Amitay, Sygal; Moore, David R; Molloy, Katharine; Halliday, Lorna F

    2015-01-01

    Previous studies have suggested that negative feedback is more effective in driving learning than positive feedback. We investigated the effect on learning of providing varying amounts of negative and positive feedback while listeners attempted to discriminate between three identical tones; an impossible task that nevertheless produces robust learning. Four feedback conditions were compared during training: 90% positive feedback or 10% negative feedback informed the participants that they were doing equally well, while 10% positive or 90% negative feedback informed them they were doing equally badly. In all conditions the feedback was random in relation to the listeners' responses (because the task was to discriminate three identical tones), yet both the valence (negative vs. positive) and the probability of feedback (10% vs. 90%) affected learning. Feedback that informed listeners they were doing badly resulted in better post-training performance than feedback that informed them they were doing well, independent of valence. In addition, positive feedback during training resulted in better post-training performance than negative feedback, but only positive feedback indicating listeners were doing badly on the task resulted in learning. As we have previously speculated, feedback that better reflected the difficulty of the task was more effective in driving learning than feedback that suggested performance was better than it should have been given perceived task difficulty. But contrary to expectations, positive feedback was more effective than negative feedback in driving learning. Feedback thus had two separable effects on learning: feedback valence affected motivation on a subjectively difficult task, and learning occurred only when feedback probability reflected the subjective difficulty. To optimize learning, training programs need to take into consideration both feedback valence and probability.

  7. Ambulatory Feedback System

    NASA Technical Reports Server (NTRS)

    Finger, Herbert; Weeks, Bill

    1985-01-01

    This presentation discusses instrumentation that will be used for a specific event, which we hope will carry on to future events within the Space Shuttle program. The experiment is the Autogenic Feedback Training Experiment (AFTE) scheduled for Spacelab 3, currently scheduled to be launched in November, 1984. The objectives of the AFTE are to determine the effectiveness of autogenic feedback in preventing or reducing space adaptation syndrome (SAS), to monitor and record in-flight data from the crew, to determine if prediction criteria for SAS can be established, and, finally, to develop an ambulatory instrument package to mount the crew throughout the mission. The purpose of the Ambulatory Feedback System (AFS) is to record the responses of the subject during a provocative event in space and provide a real-time feedback display to reinforce the training.

  8. Quantifying Contributions of Climate Feedbacks to Global Warming Pattern Formation

    NASA Astrophysics Data System (ADS)

    Song, X.; Zhang, G. J.; Cai, M.

    2013-12-01

    The ';';climate feedback-response analysis method'' (CFRAM) was applied to the NCAR CCSM3.0 simulation to analyze the strength and spatial distribution of climate feedbacks and to quantify their contributions to global and regional surface temperature changes in response to a doubling of CO2. Instead of analyzing the climate sensitivity, the CFRAM directly attributes the temperature change to individual radiative and non-radiative feedbacks. The radiative feedback decomposition is based on hourly model output rather than monthly mean data that are commonly used in climate feedback analysis. This gives a more accurate quantification of the cloud and albedo feedbacks. The process-based decomposition of non-radiative feedback enables us to understand the roles of GCM physical and dynamic processes in climate change. The pattern correlation, the centered root-mean-square (RMS) difference and the ratio of variations (represented by standard deviations) between the partial surface temperature change due to each feedback process and the total surface temperature change in CCSM3.0 simulation are examined to quantify the roles of each feedback process in the global warming pattern formation. The contributions of climate feedbacks to the regional warming are also discussed.

  9. Haptic Feedback in Robot-Assisted Minimally Invasive Surgery

    PubMed Central

    Okamura, Allison M.

    2009-01-01

    Purpose of Review Robot-assisted minimally invasive surgery (RMIS) holds great promise for improving the accuracy and dexterity of a surgeon while minimizing trauma to the patient. However, widespread clinical success with RMIS has been marginal. It is hypothesized that the lack of haptic (force and tactile) feedback presented to the surgeon is a limiting factor. This review explains the technical challenges of creating haptic feedback for robot-assisted surgery and provides recent results that evaluate the effectiveness of haptic feedback in mock surgical tasks. Recent Findings Haptic feedback systems for RMIS are still under development and evaluation. Most provide only force feedback, with limited fidelity. The major challenge at this time is sensing forces applied to the patient. A few tactile feedback systems for RMIS have been created, but their practicality for clinical implementation needs to be shown. It is particularly difficult to sense and display spatially distributed tactile information. The cost-benefit ratio for haptic feedback in RMIS has not been established. Summary The designs of existing commercial RMIS systems are not conducive for force feedback, and creative solutions are needed to create compelling tactile feedback systems. Surgeons, engineers, and neuroscientists should work together to develop effective solutions for haptic feedback in RMIS. PMID:19057225

  10. Feedback: How Does It Function?

    ERIC Educational Resources Information Center

    Bardwell, Rebecca

    1981-01-01

    A study of feedback delay, expectation, and development was conducted in grades four, six, and eight, to assess whether feedback on a school related learning task serves an informational or reinforcing function. Results indicate that feedback serves an informational function and delayed feedback facilitates retention, contrary to reinforcement…

  11. Seven Keys to Effective Feedback

    ERIC Educational Resources Information Center

    Wiggins, Grant

    2012-01-01

    The term "feedback" is often used to describe all kinds of comments made after the fact, including advice, praise, and evaluation. But none of these are feedback, strictly speaking. Basically, feedback is information about how one is doing in his or her efforts to reach a goal. Whether feedback is just there to be grasped or is provided by another…

  12. Feedback: Now with Physics

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.; Quataert, Eliot; Faucher-Giguere, Claude-Andre; Keres, Dusan; Wetzel, Andrew R.; Murray, Norman W.

    2017-01-01

    The most fundamental unsolved problems in galaxy formation revolve around "feedback" from massive stars and black holes. In the last few years, a new generation of theoretical models have emerged which combine new numerical methods and physics in an attempt to realistically model the diverse physics of the interstellar medium, star formation, and feedback from super-massive black holes and massive stars (winds, jets, SNe, and radiation). These mechanisms lead to 'self-regulated' galaxy and star formation, in which global correlations such as the Schmidt-Kennicutt law, the inefficiency of star formation, and the stellar mass function -- emerge naturally. Within galaxies, feedback regulates the structure of the interstellar medium, and many observed properties of the ISM, star formation, and galaxies can be understood as a fundamental consequence of super-sonic turbulence in a rapidly cooling, self-gravitating medium. But feedback also produces galactic super-winds that can dramatically alter the cosmological evolution of galaxies, change the nature of dark matter cores and ‘cusps’, and re-structure the circum-galactic and inter-galactic medium. These winds depend non-linearly on multiple feedback mechanisms in a way that explains why they have been so difficult to model in previous "sub-grid" approaches. This resolves long-standing problems in understanding even apparently "simple" galaxy properties like the mass-metallicity relation. Finally, I'll discuss where feedback fails, and where either additional, exotic physics, or new, previously-dismissed feedback mechanisms, may be needed to explain observations.

  13. Calibrated feedback for laser diodes

    SciTech Connect

    Howard, P.G.

    1986-04-22

    A method is described of calibrating the feedback output from the feedback light detector of the laser diode of an optical disk drive of a laser light pen which consists of mounting a first and a second resistor in a laser light pen; connecting the first resistor between the feedback light detector and ground; connecting the second resistor between the feedback light detector and a feedback output; operating the laser diode to produce a predetermined light power output; adjusting the resistance of the first resistor to produce a predetermined voltage at the feedback output; and adjusting the resistance of the second resistor to produce a predetermined impedance at the feedback output.

  14. Global climate feedbacks

    SciTech Connect

    Manowitz, B.

    1990-10-01

    The important physical, chemical, and biological events that affect global climate change occur on a mesoscale -- requiring high spatial resolution for their analysis. The Department of Energy has formulated two major initiatives under the US Global Change Program: ARM (Atmospheric Radiation Measurements), and CHAMMP (Computer Hardware Advanced Mathematics and Model Physics). ARM is designed to use ground and air-craft based observations to document profiles of atmospheric composition, clouds, and radiative fluxes. With research and models of important physical processes, ARM will delineate the relationships between trace gases, aerosol and cloud structure, and radiative transfer in the atmosphere, and will improve the parameterization of global circulation models. The present GCMs do not model important feedbacks, including those from clouds, oceans, and land processes. The purpose of this workshop is to identify such potential feedbacks, to evaluate the uncertainties in the feedback processes (and, if possible, to parameterize the feedback processes so that they can be treated in a GCM), and to recommend research programs that will reduce the uncertainties in important feedback processes. Individual reports are processed separately for the data bases.

  15. Climate Change and Aerosol Feedbacks

    NASA Astrophysics Data System (ADS)

    Norman, Ann-Lise

    2008-05-01

    Climate instability is expected as mixing ratios of greenhouse gases in the Earth's atmosphere increase. The current trend in rising temperature can be related to anthropogenic greenhouse gas emissions. However, this trend may change as feedback mechanisms amplify; one of the least-understood aspects of climate change. Formation of cloud condensation nuclei from rising sulfate concentrations in the atmosphere may counteract the current warming trend. A key point is where the sulfate, and cloud condensation nuclei are formed. Is cloud formation widespread or localized near sulfate emission sources? A major source of atmospheric sulfate is dimethylsulfide, a compound related to biotic turnover in the surface ocean that constitutes a widespread natural source of aerosols over the remote ocean. A second major source contributing a significant proportion of atmospheric sulfate in the northern hemisphere is produced over continents from industrial activities and fossil fuel combustion. Distinguishing the source of sulfate in well-mixed air is important so that relationships with cloud formation, sea-ice in polar regions, and albedo can be explored. This distinction in sulfate sources can be achieved using isotope apportionment techniques. Recent measurements show an increase in biogenic sulfate coincident with rising temperatures in the Arctic and large amounts sulfur from DMS oxidation over the Atlantic, potentially indicating a widespread biotic feedback to warming over northern oceans.

  16. The lapse-rate feedback leads to polar temperature amplification.

    NASA Astrophysics Data System (ADS)

    Grand Graversen, Rune; Langen, Peter; Mauritsen, Thorsten

    2014-05-01

    The atmospheric temperature will change in response to a radiative forcing of the climate system, but the temperature change may not be constant with height in the atmosphere. The dependence of the temperature change on hight gives rise to the lapse-rate feedback. In a warmer climate, the saturated mixing ratio of water vapour increases more at lower than at upper levels in the troposphere. Therefore due to enhanced latent heat release, the atmosphere tends to warm more in the upper than in the lower troposphere in regions where strong convection is present, such as at tropical latitudes. This results in enhanced radiation back to space, and in a more efficient cooling of the Earth system. This is contributing to a negative lapse-rate feedback. The opposite situation prevails at the high latitudes where stable stratification conditions in the lower troposphere result in a larger warming of the surface-near atmosphere than of the upper troposphere. This is contributing to a positive lapse-rate feedback. Hence the lapse-rate feedback is assumed to be negative at low, and positive at high latitudes. Here we explore the lapse-rate feedback and its effect on the climate system using a slab-ocean climate model, the Community Climate System Model version 4. By locking the temperature change throughout the troposphere to that at the surface in calls to the radiation code, the lapse-rate feedback is suppressed on-line in the model. Doubling-of-CO2 experiments where the lapse-rate feedback is suppressed are compared with experiments where it is retained. In a similar way the surface-albedo feedback is suppressed by keeping the surface albedo fixed in the entire model system. On the basis of model versions where either one or both of the feedbacks are suppressed, we are able to separate the effect of the surface-albedo and lapse-rate feedback. For instance we can estimate the contribution to the polar temperature amplification due to each of the feedbacks. The results show

  17. STABILIZED FEEDBACK AMPLIFIER

    DOEpatents

    Fishbine, H.L.; Sewell, C. Jr.

    1957-08-01

    Negative feedback amplifiers, and particularly a negative feedback circuit which is economical on amode power consumption, are described. Basically, the disclosed circuit comprises two tetrode tubes where the output of the first tube is capacitamce coupled to the grid of the second tube, which in turn has its plate coupled to the cathode of the first tube to form a degenerative feedback circuit. Operating potential for screen of the second tube is supplied by connecting the cathode resistor of the first tube to the screen, while the screen is by-passed to the cathode of its tube for the amplified frequencies. Also, the amplifier incorporates a circuit to stabilize the transconductance of the tubes by making the grid potential of each tube interdependent on anode currents of both lubes by voltage divider circuitry.

  18. Stratospheric water vapor feedback

    PubMed Central

    Dessler, A. E.; Schoeberl, M. R.; Wang, T.; Davis, S. M.; Rosenlof, K. H.

    2013-01-01

    We show here that stratospheric water vapor variations play an important role in the evolution of our climate. This comes from analysis of observations showing that stratospheric water vapor increases with tropospheric temperature, implying the existence of a stratospheric water vapor feedback. We estimate the strength of this feedback in a chemistry–climate model to be +0.3 W/(m2⋅K), which would be a significant contributor to the overall climate sensitivity. One-third of this feedback comes from increases in water vapor entering the stratosphere through the tropical tropopause layer, with the rest coming from increases in water vapor entering through the extratropical tropopause. PMID:24082126

  19. UWB communication receiver feedback loop

    DOEpatents

    Spiridon, Alex; Benzel, Dave; Dowla, Farid U.; Nekoogar, Faranak; Rosenbury, Erwin T.

    2007-12-04

    A novel technique and structure that maximizes the extraction of information from reference pulses for UWB-TR receivers is introduced. The scheme efficiently processes an incoming signal to suppress different types of UWB as well as non-UWB interference prior to signal detection. Such a method and system adds a feedback loop mechanism to enhance the signal-to-noise ratio of reference pulses in a conventional TR receiver. Moreover, sampling the second order statistical function such as, for example, the autocorrelation function (ACF) of the received signal and matching it to the ACF samples of the original pulses for each transmitted bit provides a more robust UWB communications method and system in the presence of channel distortions.

  20. Climate forcings and feedbacks

    NASA Technical Reports Server (NTRS)

    Hansen, James

    1993-01-01

    Global temperature has increased significantly during the past century. Understanding the causes of observed global temperature change is impossible in the absence of adequate monitoring of changes in global climate forcings and radiative feedbacks. Climate forcings are changes imposed on the planet's energy balance, such as change of incoming sunlight or a human-induced change of surface properties due to deforestation. Radiative feedbacks are radiative changes induced by climate change, such as alteration of cloud properties or the extent of sea ice. Monitoring of global climate forcings and feedbacks, if sufficiently precise and long-term, can provide a very strong constraint on interpretation of observed temperature change. Such monitoring is essential to eliminate uncertainties about the relative importance of various climate change mechanisms including tropospheric sulfate aerosols from burning of coal and oil smoke from slash and burn agriculture, changes of solar irradiance changes of several greenhouse gases, and many other mechanisms. The considerable variability of observed temperature, together with evidence that a substantial portion of this variability is unforced indicates that observations of climate forcings and feedbacks must be continued for decades. Since the climate system responds to the time integral of the forcing, a further requirement is that the observations be carried out continuously. However, precise observations of forcings and feedbacks will also be able to provide valuable conclusions on shorter time scales. For example, knowledge of the climate forcing by increasing CFC's relative to the forcing by changing ozone is important to policymakers, as is information on the forcing by CO2 relative to the forcing by sulfate aerosols. It will also be possible to obtain valuable tests of climate models on short time scales, if there is precise monitoring of all forcings and feedbacks during and after events such as a large volcanic eruption

  1. Smart feedback loops

    NASA Astrophysics Data System (ADS)

    Chepurnov, A. S.; Gribov, I. V.; Gudkov, K. A.; Shumakov, A. V.; Shvedunov, V. I.

    1994-12-01

    It is necessary to find the golden mean in allocating the processing resources of a computer control system. Traditionally, feedback loops operate at the lower levels to ensure safe and stable operation of the accelerator. At present we use analogue and digital feedback loops. Some systems, such as the RF, require more complex algorithms. A possible way of providing these, using digital signal processors is described. The results of tests with the Race-Track Microtron Linac are given and the sources of the main internal and external disturbances have been analysed.

  2. School Formative Feedback Systems

    ERIC Educational Resources Information Center

    Halverson, Richard

    2010-01-01

    Data-driven instructional improvement relies on developing coherent systems that allow school staff to generate, interpret, and act upon quality formative information on students and school programs. This article offers a formative feedback system model that captures how school leaders and teachers structure artifacts and practices to create…

  3. Feedback in Information Retrieval.

    ERIC Educational Resources Information Center

    Spink, Amanda; Losee, Robert M.

    1996-01-01

    As Information Retrieval (IR) has evolved, it has become a highly interactive process, rooted in cognitive and situational contexts. Consequently the traditional cybernetic-based IR model does not suffice for interactive IR or the human approach to IR. Reviews different views of feedback in IR and their relationship to cybernetic and social…

  4. Signatures of AGN feedback

    NASA Astrophysics Data System (ADS)

    Wylezalek, Dominika; Zakamska, Nadia L.; MaNGA-GMOS Team

    2017-01-01

    Feedback from actively accreting SMBHs (Active Galactic Nuclei, AGN) is now widely considered to be the main driver in regulating the growth of massive galaxies. Observational proof for this scenario has, however, been hard to come by. Many attempts at finding a conclusive observational proof that AGN may be able to quench star formation and regulate the host galaxies' growth have shown that this problem is highly complex.I will present results from several projects that focus on understanding the power, reach and impact of feedback processes exerted by AGN. I will describe recent efforts in our group of relating feedback signatures to the specific star formation rate in their host galaxies, where our results are consistent with the AGN having a `negative' impact through feedback on the galaxies' star formation history (Wylezalek+2016a,b). Furthermore, I will show that powerful AGN-driven winds can be easily hidden and not be apparent in the integrated spectrum of the galaxy. This implies that large IFU surveys, such as the SDSS-IV MaNGA survey, might uncover many previously unknown AGN and outflows that are potentially very relevant for understanding the role of AGN in galaxy evolution (Wylezalek+2016c)!

  5. Polarization feedback laser stabilization

    DOEpatents

    Esherick, Peter; Owyoung, Adelbert

    1988-01-01

    A system for locking two Nd:YAG laser oscillators includes an optical path for feeding the output of one laser into the other with different polarizations. Elliptical polarization is incorporated into the optical path so that the change in polarization that occurs when the frequencies coincide may be detected to provide a feedback signal to control one laser relative to the other.

  6. Review of Assessment Feedback

    ERIC Educational Resources Information Center

    Li, Jinrui; De Luca, Rosemary

    2014-01-01

    This article reviews 37 empirical studies, selected from 363 articles and 20 journals, on assessment feedback published between 2000 and 2011. The reviewed articles, many of which came out of studies in the UK and Australia, reflect the most current issues and developments in the area of assessing disciplinary writing. The article aims to outline…

  7. Developmental remodeling of corticocortical feedback circuits in ferret visual cortex.

    PubMed

    Khalil, Reem; Levitt, Jonathan B

    2014-10-01

    Visual cortical areas in the mammalian brain are linked through a system of interareal feedforward and feedback connections, which presumably underlie different visual functions. We characterized the refinement of feedback projections to primary visual cortex (V1) from multiple sources in juvenile ferrets ranging in age from 4-10 weeks postnatal. We studied whether the refinement of different aspects of feedback circuitry from multiple visual cortical areas proceeds at a similar rate in all areas. We injected the neuronal tracer cholera toxin B (CTb) into V1 and mapped the areal and laminar distribution of retrogradely labeled cells in extrastriate cortex. Around the time of eye opening at 4 weeks postnatal, the retinotopic arrangement of feedback appears essentially adult-like; however, suprasylvian cortex supplies the greatest proportion of feedback, whereas area 18 supplies the greatest proportion in the adult. The density of feedback cells and the ratio of supragranular/infragranular feedback contribution declined in this period at a similar rate in all cortical areas. We also found significant feedback to V1 from layer IV of all extrastriate areas. The regularity of cell spacing, the proportion of feedback arising from layer IV, and the tangential extent of feedback in each area all remained essentially unchanged during this period, except for the infragranular feedback source in area 18, which expanded. Thus, while much of the basic pattern of cortical feedback to V1 is present before eye opening, there is major synchronous reorganization after eye opening, suggesting a crucial role for visual experience in this remodeling process.

  8. How to Give Professional Feedback

    ERIC Educational Resources Information Center

    Brookhart, Susan M.; Moss, Connie M.

    2015-01-01

    Professional learning "should be a joy," the authors write, "not an affliction." Feedback experts Brookhart and Moss show how professional feedback can best motivate educators to learn. Professional conversations should be dialogs between the teacher and the principal, and feedback should feed teacher professional learning…

  9. Feedback: Part of a System

    ERIC Educational Resources Information Center

    Wiliam, Dylan

    2012-01-01

    Just as a thermostat adjusts room temperature, effective feedback helps maintain a supportive environment for learning. Because of the many factors affecting how recipients respond to feedback, research offers no simple prescription for making feedback work effectively. What works in one classroom for one teacher will not work for another teacher.…

  10. DISTRIBUTED AMPLIFIER INCORPORATING FEEDBACK

    DOEpatents

    Bell, P.R. Jr.

    1958-10-21

    An improved distributed amplifier system employing feedback for stabilization is presented. In accordance with the disclosed invention, a signal to be amplified is applled to one end of a suitable terminated grid transmission line. At intervals along the transmission line, the signal is fed to stable, resistance-capacitance coupled amplifiers incorporating feedback loops therein. The output current from each amplifier is passed through an additional tube to minimize the electrostatic capacitance between the tube elements of the last stage of the amplifier, and fed to appropriate points on an output transmission line, similar to the grid line, but terminated at the opposite (input) end. The output taken from the unterminated end of the plate transmission line is proportional to the input voltage impressed upon the grid line.

  11. Regenerative feedback resonant circuit

    DOEpatents

    Jones, A. Mark; Kelly, James F.; McCloy, John S.; McMakin, Douglas L.

    2014-09-02

    A regenerative feedback resonant circuit for measuring a transient response in a loop is disclosed. The circuit includes an amplifier for generating a signal in the loop. The circuit further includes a resonator having a resonant cavity and a material located within the cavity. The signal sent into the resonator produces a resonant frequency. A variation of the resonant frequency due to perturbations in electromagnetic properties of the material is measured.

  12. Polarization feedback laser stabilization

    DOEpatents

    Esherick, P.; Owyoung, A.

    1987-09-28

    A system for locking two Nd:YAG laser oscillators includes an optical path for feeding the output of one laser into the other with different polarizations. Elliptical polarization is incorporated into the optical path so that the change in polarization that occurs when the frequencies coincide may be detected to provide a feedback signal to control one laser relative to the other. 4 figs.

  13. Feedback on Feedback: Eliciting Learners' Responses to Written Feedback through Student-Generated Screencasts

    ERIC Educational Resources Information Center

    Fernández-Toro, María; Furnborough, Concha

    2014-01-01

    Despite the potential benefits of assignment feedback, learners often fail to use it effectively. This study examines the ways in which adult distance learners engage with written feedback on one of their assignments. Participants were 10 undergraduates studying Spanish at the Open University, UK. Their responses to feedback were elicited by means…

  14. Cosmological galaxy evolution with superbubble feedback - I. Realistic galaxies with moderate feedback

    NASA Astrophysics Data System (ADS)

    Keller, B. W.; Wadsley, J.; Couchman, H. M. P.

    2015-11-01

    We present the first cosmological galaxy evolved using the modern smoothed particle hydrodynamics (SPH) code GASOLINE2 with superbubble feedback. We show that superbubble-driven galactic outflows powered by Type II supernovae alone can produce L* galaxies with flat rotation curves with circular velocities ˜ 200 km s- 1, low bulge-to-disc ratios, and stellar mass fractions that match observed values from high redshift to the present. These features are made possible by the high mass loadings generated by the evaporative growth of superbubbles. Outflows are driven extremely effectively at high redshift, expelling gas at early times and preventing overproduction of stars before z = 2. Centrally concentrated gas in previous simulations has often lead to unrealistically high bulge to total ratios and strongly peaked rotation curves. We show that supernova-powered superbubbles alone can produce galaxies that agree well with observed properties without the need for additional feedback mechanisms or increased feedback energy. We present additional results arising from properly modelled hot feedback.

  15. Analyzing Feedback Control Systems

    NASA Technical Reports Server (NTRS)

    Bauer, Frank H.; Downing, John P.

    1987-01-01

    Interactive controls analysis (INCA) program developed to provide user-friendly environment for design and analysis of linear control systems, primarily feedback control. Designed for use with both small- and large-order systems. Using interactive-graphics capability, INCA user quickly plots root locus, frequency response, or time response of either continuous-time system or sampled-data system. Configuration and parameters easily changed, allowing user to design compensation networks and perform sensitivity analyses in very convenient manner. Written in Pascal and FORTRAN.

  16. Precipitation-Regulated Feedback

    NASA Astrophysics Data System (ADS)

    Voit, Mark

    2016-07-01

    Star formation in the central galaxies of galaxy clusters appears to be fueled by precipitation of cold clouds out of hot circumgalactic gas via thermal instability. I will present both observational and theoretical support for the precipitation mode in large galaxies and discuss how it can be implemented in cosmological simulations of galaxy evolution. Galaxy cluster cores are unique laboratories for studying the astrophysics of thermal instability and may be teaching us valuable lessons about how feedback works in galaxies spanning the entire mass spectrum.

  17. Interresponse Time Structures in Variable-Ratio and Variable-Interval Schedules

    ERIC Educational Resources Information Center

    Bowers, Matthew T.; Hill, Jade; Palya, William L.

    2008-01-01

    The interresponse-time structures of pigeon key pecking were examined under variable-ratio, variable-interval, and variable-interval plus linear feedback schedules. Whereas the variable-ratio and variable-interval plus linear feedback schedules generally resulted in a distinct group of short interresponse times and a broad distribution of longer…

  18. Torque feedback transmission

    SciTech Connect

    Whalen, B.L.

    1987-01-20

    This patent describes an infinitely variable transmission of inline configuration for interconnecting a primer mover with a load for clutch free operation in a range of speed including hydraulic neutral comprising: a. planetary gear train means having a ring gear, planetary gears supported by a planetary gear carrier, and a sun gear, the sun gear being connected mechanically to the load, output shaft means for joining the sun gear to the load; b. variable torque feedback means comprising (i) a variable displacement hydraulic motor whose rotor shaft is in line with the output shaft means and drivingly connected to the prime mover and the planetary gear carrier during the full range of operation of the transmission, and (ii) a fixed displacement hydraulic pump connected hydraulically to the motor, the rotor shaft of the pump being connected mechanically to the ring gear and being axially displaced from the output shaft means; c. means for adjusting the displacement volume within the hydraulic motor for controlling the torque feedback in the transmission to provide infinitely variable coupling between the prime mover and the load over the full range of the transmission including hydraulic neutral; d. a speed reducer between the primer mover and the motor rotor shaft and a speed multiplier between the sun gear and the load; and e. mechanical transmission assembly means between the speed multiplier and the load in line with the motor rotor shaft and the output shaft means for providing selection of drive, reverse, park, and neutral.

  19. Haptic gas pedal feedback.

    PubMed

    Mulder, M; Mulder, M; van Paassen, M M; Abbink, D A

    2008-11-01

    Active driver support systems either automate a control task or present warnings to drivers when their safety is seriously degraded. In a novel approach, utilising neither automation nor discrete warnings, a haptic gas pedal (accelerator) interface was developed that continuously presents car-following support information, keeping the driver in the loop. This interface was tested in a fixed-base driving simulator. Twenty-one drivers between the ages of 24 and 30 years participated in a driving experiment to investigate the effects of haptic gas pedal feedback on car-following behaviour. Results of the experiment indicate that when haptic feedback was presented to the drivers, some improvement in car-following performance was achieved, while control activity decreased. Further research is needed to investigate the effectiveness of the system in more varied driving conditions. Haptics is an under-used modality in the application of human support interfaces, which usually draw on vision or hearing. This study demonstrates how haptics can be used to create an effective driver support interface.

  20. Feedback in clinical medical education.

    PubMed

    Ende, J

    1983-08-12

    In the setting of clinical medical education, feedback refers to information describing students' or house officers' performance in a given activity that is intended to guide their future performance in that same or in a related activity. It is a key step in the acquisition of clinical skills, yet feedback is often omitted or handled improperly in clinical training. This can result in important untoward consequences, some of which may extend beyond the training period. Once the nature of the feedback process is appreciated, however, especially the distinction between feedback and evaluation and the importance of focusing on the trainees' observable behaviors rather than on the trainees themselves, the educational benefit of feedback can be realized. This article presents guidelines for offering feedback that have been set forth in the literature of business administration, psychology, and education, adapted here for use by teachers and students of clinical medicine.

  1. Feedback control of waiting times

    NASA Astrophysics Data System (ADS)

    Brandes, Tobias; Emary, Clive

    2016-04-01

    Feedback loops are known as a versatile tool for controlling transport in small systems, which usually have large intrinsic fluctuations. Here we investigate the control of a temporal correlation function, the waiting-time distribution, under active and passive feedback conditions. We develop a general formalism and then specify to the simple unidirectional transport model, where we compare costs of open-loop and feedback control and use methods from optimal control theory to optimize waiting-time distributions.

  2. Fast feedback for linear colliders

    SciTech Connect

    Hendrickson, L.; Adolphsen, C.; Allison, S.; Gromme, T.; Grossberg, P.; Himel, T.; Krauter, K.; MacKenzie, R.; Minty, M.; Sass, R.

    1995-05-01

    A fast feedback system provides beam stabilization for the SLC. As the SLC is in some sense a prototype for future linear colliders, this system may be a prototype for future feedbacks. The SLC provides a good base of experience for feedback requirements and capabilities as well as a testing ground for performance characteristics. The feedback system controls a wide variety of machine parameters throughout the SLC and associated experiments, including regulation of beam position, angle, energy, intensity and timing parameters. The design and applications of the system are described, in addition to results of recent performance studies.

  3. Modeling climate related feedback processes

    SciTech Connect

    Elzen, M.G.J. den; Rotmans, J. )

    1993-11-01

    In order to assess their impact, the feedbacks which at present can be quantified reasonably are built into the Integrated Model to Assess the Greenhouse Effect (IMAGE). Unlike previous studies, this study describes the scenario- and time-dependent role of biogeochemical feedbacks. A number of simulation experiments are performed with IMAGE to project climate changes. Besides estimates of their absolute importance, the relative importance of individual biogeochemical feedbacks is considered by calculating the gain for each feedback process. This study focuses on feedback processes in the carbon cycle and the methane (semi-) cycle. Modeled feedbacks are then used to balance the past and present carbon budget. This results in substantially lower projections for atmospheric carbon dioxide than the Intergovernmental Panel on Climate Change (IPCC) estimates. The difference is approximately 18% from the 1990 level for the IPCC [open quotes]Business-as-Usual[close quotes] scenario. Furthermore, the IPCC's [open quotes]best guess[close quotes] value of the CO[sub 2] concentration in the year 2100 falls outside the uncertainty range estimated with our balanced modeling approach. For the IPCC [open quotes]Business-as-Usual[close quotes] scenario, the calculated total gain of the feedbacks within the carbon cycle appears to be negative, a result of the dominant role of the fertilization feedback. This study also shows that if temperature feedbacks on methane emissions from wetlands, rice paddies, and hydrates do materialize, methane concentrations might be increased by 30% by 2100. 70 refs., 17 figs., 7 tabs.

  4. A laser feedback interferometer with an oscillating feedback mirror

    NASA Astrophysics Data System (ADS)

    Wang, Zhi-Guo; Wang, Fei; Xiao, Guang-Zong

    2012-11-01

    A method is proposed to solve the problem of direction discrimination for laser feedback interferometers. By vibrating the feedback mirror with a small-amplitude and high-frequency sine wave, laser intensity is modulated accordingly. The modulation amplitude can be extracted using a phase sensitive detector (PSD). When the feedback mirror moves, the PSD output shows a quasi-sine waveform similar to a laser intensity interference fringe but with a phase difference of approximately ±π/2. If the movement direction of the feedback mirror changes, the phase difference sign reverses. Therefore, the laser feedback interferometer offers a potential application in displacement measurement with a resolution of 1/8 wavelength and in-time direction discrimination. Without using optical components such as polarization beam splitters and wave plates, the interferometer is very simple, easy to align, and less costly.

  5. Distributed feedback lasers

    NASA Technical Reports Server (NTRS)

    Ladany, I.; Andrews, J. T.; Evans, G. A.

    1988-01-01

    A ridge waveguide distributed feedback laser was developed in InGaAsP. These devices have demonstrated CW output powers over 7 mW with threshold currents as low as 60 mA at 25 C. Measurements of the frequency response of these devices show a 3 dB bandwidth of about 2 GHz, which may be limited by the mount. The best devices have a single mode spectra over the entire temperature range tested with a side mode suppression of about 20 dB in both CW and pulsed modes. The design of this device, including detailed modeling of the ridge guide structure, effective index calculations, and a discussion of the grating configuration are presented. Also, the fabrication of the devices is presented in some detail, especially the fabrication of and subsequent growth over the grating. In addition, a high frequency fiber pigtailed package was designed and tested, which is a suitable prototype for a commercial package.

  6. Project Echo: FM Demodulators with Negative Feedback

    NASA Technical Reports Server (NTRS)

    Ruthroff, Clyde L.

    1961-01-01

    The primary experimental objective of Project Echo was the transmission of radio communications between points on the earth by reflection from the balloon satellite. Owing to the large path losses from transmitter to receiver via the satellite, a wide-band frequency modulation technique was used in which bandwidth was traded for signal-to-noise ratio. This paper describes the FM receiving demodulators employed. Negative feedback applied to the local oscillator reduces the FM modulation index in the receiver IF amplifiers, resulting in threshold performance superior to that of conventional FM receivers.

  7. Signatures of AGN feedback

    NASA Astrophysics Data System (ADS)

    Wylezalek, D.; Zakamska, N.

    2016-06-01

    Feedback from active galactic nuclei (AGN) is widely considered to be the main driver in regulating the growth of massive galaxies. It operates by either heating or driving the gas that would otherwise be available for star formation out of the galaxy, preventing further increase in stellar mass. Observational proof for this scenario has, however, been hard to come by. We have assembled a large sample of 133 radio-quiet type-2 and red AGN at 0.1100 M_{⊙} yr^{-1} where presumably the coupling of the AGN-driven wind to the gas is strongest. This observation is consistent with the AGN having a net suppression, or `negative' impact, through feedback on the galaxies' star formation history.

  8. Student Interpretations of Diagnostic Feedback

    ERIC Educational Resources Information Center

    Doe, Christine

    2015-01-01

    Diagnostic assessment is increasingly being recognized as a potentially beneficial tool for teaching and learning (Jang, 2012). There have been calls in the research literature for students to receive diagnostic feedback and for researchers to investigate how such feedback is used by students. Therefore, this study examined how students…

  9. Feedback Seeking in Training Settings.

    ERIC Educational Resources Information Center

    Kuchinke, K. Peter

    The role of feedback in training settings was examined in a survey-based study of feedback in nine 5-day management development training courses in a United Kingdom government agency. The courses followed a highly standardized curriculum and delivery process. Although the courses were primarily instructor-and theory-centered, they also included…

  10. Interpersonal Feedback: Origins and Applications.

    ERIC Educational Resources Information Center

    Barbour, Alton

    This paper identifies the origins of the concept of feedback and its entry into the interpersonal communication literature as a social science variable. It touches on why feedback might be important in interpersonal relations, what it consists of, some of the relevant research, and some possible dangers or misuses. It speaks to how the process of…

  11. Haptic feedback helps bipedal coordination.

    PubMed

    Roelofsen, Eefje G J; Bosga, Jurjen; Rosenbaum, David A; Nijhuis-van der Sanden, Maria W G; Hullegie, Wim; van Cingel, Robert; Meulenbroek, Ruud G J

    2016-10-01

    The present study investigated whether special haptic or visual feedback would facilitate the coordination of in-phase, cyclical feet movements of different amplitudes. Seventeen healthy participants sat with their feet on sliding panels that were moved externally over the same or different amplitudes. The participants were asked to generate simultaneous knee flexion-extension movements, or to let their feet be dragged, resulting in reference foot displacements of 150 mm and experimental foot displacements of 150, 120, or 90 mm. Four types of feedback were given: (1) special haptic feedback, involving actively following the motions of the sliders manipulated by two confederates, (2) haptic feedback resulting from passive motion, (3) veridical visual feedback, and (4) enhanced visual feedback. Both with respect to amplitude assimilation effects, correlations and standard deviation of relative phase, the results showed that enhanced visual feedback did not facilitate bipedal independence, but haptic feedback with active movement did. Implications of the findings for movement rehabilitation contexts are discussed.

  12. Fast Feedback in Classroom Practice

    ERIC Educational Resources Information Center

    Emmett, Katrina; Klaassen, Kees; Eijkelhof, Harrie

    2009-01-01

    In this article we describe one application of the fast feedback method (see Berg 2003 "Aust. Sci. Teach. J." 28-34) in secondary mechanics education. Two teachers tried out a particular sequence twice, in consecutive years, once with and once without the use of fast feedback. We found the method to be successful, and the data that we obtained…

  13. Motivating Students through Formative Feedback

    ERIC Educational Resources Information Center

    Mauch, Lois

    2007-01-01

    Technology tools that are used to help apply standards and benchmarks motivate physical educators to use new methods of teaching, and create new ways to provide students with direct formative feedback, the number one motivator for students. Direct formative feedback refers to verbal communication between the teacher and/or parent and student. The…

  14. Feedback Control for Aerodynamics (Preprint)

    DTIC Science & Technology

    2006-09-01

    AFRL-VA-WP-TP-2006-348 FEEDBACK CONTROL FOR AERODYNAMICS (PREPRINT) R. Chris Camphouse, Seddik M. Djouadi, and James H. Myatt...CONSTRUCTION FOR THE DESIGN OF BOUNDARY FEEDBACK CONTROLS FROM REDUCED ORDER MODELS (PREPRINT) 5c. PROGRAM ELEMENT NUMBER 0601102F 5d. PROJECT NUMBER...

  15. Feedback: Implications for Further Research and Study.

    ERIC Educational Resources Information Center

    Nishikawa, Sue S.

    This report reviews current literature on feedback and suggests practical implications of feedback research for educators. A definition of feedback is offered, and past definitions in prior research are noted. An analysis of the current state of knowledge of feedback discusses the historical development of feedback theory and suggests that…

  16. The Sound of Feedback in Higher Education

    ERIC Educational Resources Information Center

    Savin-Baden, Maggi

    2010-01-01

    Whilst there is considerable literature on feedback for students and on the use of audio feedback, literature in the area of podcasting assignment feedback (PAF) remains sparse. Partly, this may be due to a lack of clarity about what counts as feedback, the way in which feedback is located pedagogically and the relationship between feedback…

  17. Attributes of an Effective Feedback Process

    ERIC Educational Resources Information Center

    Journal of Staff Development, 2015

    2015-01-01

    Not all feedback is created equal. It is actually quite uneven in its design and effectiveness. Feedback forms typically used by educators and the feedback process used to support learning have markedly different attributes. Understanding the key attributes of effective feedback is important for those involved in the feedback process. The tools…

  18. Understanding Feedback: A Learning Theory Perspective

    ERIC Educational Resources Information Center

    Thurlings, Marieke; Vermeulen, Marjan; Bastiaens, Theo; Stijnen, Sjef

    2013-01-01

    This article aims to review literature on feedback to teachers. Because research has hardly focused on feedback among teachers, the review's scope also includes feedback in classrooms. The review proposes that the effectiveness of feedback and feedback processes depend on the learning theory adhered to. Findings show that regardless of the…

  19. Research on output feedback control

    NASA Technical Reports Server (NTRS)

    Calise, Anthony J.

    1988-01-01

    A summary is presented of the main results obtained during the course of research on output feedback control. The term output feedback is used to denote a controller design approach which does not rely on an observer to estimate the states of the system. Thus, the order of the controller is fixed, and can even be zero order, which amounts to constant gain ouput feedback. The emphasis has been on optimal output feedback. That is, a fixed order controller is designed based on minimizing a suitably chosen quadratic performance index. A number of problem areas that arise in this context have been addressed. These include developing suitable methods for selecting an index of performance, both time domain and frequency domain methods for achieving robustness of the closed loop system, developing canonical forms to achieve a minimal parameterization for the controller, two time scale design formulations for ill-conditioned systems, and the development of convergent numerical algorithms for solving the output feedback problem.

  20. Instructor Feedback: How Much Do Students Really Want?

    ERIC Educational Resources Information Center

    Ackerman, David S.; Gross, Barbara L.

    2010-01-01

    Marketing students expect feedback on papers and assignments; and many professors expend much time and effort providing individualized and substantive comments in response to student work. Doing so is challenging and time consuming when faced with large class sizes, high student-faculty ratios, and communications-intensive courses. Furthermore,…

  1. Asymptotically optimal feedback control for a system of linear oscillators

    NASA Astrophysics Data System (ADS)

    Ovseevich, Alexander; Fedorov, Aleksey

    2013-12-01

    We consider problem of damping of an arbitrary number of linear oscillators under common bounded control. We are looking for a feedback control steering the system to the equilibrium. The obtained control is asymptotically optimal: the ratio of motion time to zero with this control to the minimum one is close to 1, if the initial energy of the system is large.

  2. Feedback on the Feedback: Sociocultural Interpretation of Saudi ESL Learners' Opinions about Writing Feedback

    ERIC Educational Resources Information Center

    Mustafa, Rami F.

    2012-01-01

    This qualitative study employed informal conversational interviews and semi-structured individual interviews to capture the Saudi students' opinions about the feedback they receive, and about their perceptions on what constitutes helpful feedback. Sociocultural theory was used as the framework of this study. The findings suggest that the Saudi…

  3. Giving Feedback: Development of Scales for the Mum Effect, Discomfort Giving Feedback, and Feedback Medium Preference

    ERIC Educational Resources Information Center

    Cox, Susie S.; Marler, Laura E.; Simmering, Marcia J.; Totten, Jeff W.

    2011-01-01

    Research in organizational behavior and human resources promotes the view that it is critical for managers to provide accurate feedback to employees, yet little research addresses rater tendencies (i.e., the "mum effect") and attitudes that influence how performance feedback is given. Because technology has changed the nature of…

  4. Epidemiological feedbacks affect evolutionary emergence of pathogens.

    PubMed

    Hartfield, Matthew; Alizon, Samuel

    2014-04-01

    The evolutionary emergence of new pathogens via mutation poses a considerable risk to human and animal populations. Most previous studies have investigated cases where a potentially pandemic strain emerges though mutation from an initial maladapted strain (i.e., its basic reproductive ratio R0 < 1). However, an alternative (and arguably more likely) cause of novel pathogen emergence is where a "weakly adapted" strain (with R0 ≈ 1) mutates into a strongly adapted strain (with R0 ≫ 1). In this case, a proportion of the host susceptible population is removed as the first strain spreads, but the impact this feedback has on emergence of mutated strains has yet to be quantified. We produce a model of pathogen emergence that takes into account changes in the susceptible population over time and find that the ongoing depletion of susceptible individuals by the first strain has a drastic effect on the emergence probability of the mutated strain, above that assumed by just scaling the reproductive ratio. Finally, we apply our model to the documented emergence of Chikungunya virus on La Réunion Island and demonstrate that the emergence probability of the mutated strain was reduced approximately 10-fold, compared to models assuming that susceptible depletion would not affect outbreak probability. These results highlight the importance of taking population feedbacks into account when predicting disease emergence.

  5. Children's reasoning about evaluative feedback.

    PubMed

    Heyman, Gail D; Fu, Genyue; Sweet, Monica A; Lee, Kang

    2009-11-01

    Children's reasoning about the willingness of peers to convey accurate positive and negative performance feedback to others was investigated among a total of 179 6- to 11-year-olds from the USA and China. In Study 1, which was conducted in the USA only, participants responded that peers would be more likely to provide positive feedback than negative feedback, and this tendency was strongest among the younger children. In Study 2, the expectation that peers would preferentially disclose positive feedback was replicated among children from the USA, and was also seen among younger but not older children from China. Participants in all groups took the relationship between communication partners into account when predicting whether peers would express evaluative feedback. Results of open-ended responses suggested cross-cultural differences, including a greater emphasis by Chinese children on the implications of evaluative feedback for future performance, and reference by some older Chinese children to the possibility that positive feedback might make the recipient 'too proud'.

  6. Robust Control Feedback and Learning

    DTIC Science & Technology

    2002-11-30

    98-1-0026 5b. GRANT NUMBER Robust Control, Feedback and Learning F49620-98-1-0026 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER Michael G...Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. Z39.18 Final Report: ROBUST CONTROL FEEDBACK AND LEARNING AFOSR Grant F49620-98-1-0026 October 1...Philadelphia, PA, 2000. [16] M. G. Safonov. Recent advances in robust control, feedback and learning . In S. 0. R. Moheimani, editor, Perspectives in Robust

  7. Global Orbit Feedback in RHIC

    SciTech Connect

    Minty, M.; Hulsart, R.; Marusic, A.; Michnoff, R.; Ptitsyn, V.; Robert-Demolaize, G.; Satogata, T.

    2010-05-23

    For improved reproducibility of good operating conditions and ramp commissioning efficiency, new dual-plane slow orbit feedback during the energy ramp was implemented during run-10 in the Relativistic Heavy Ion Collider (RHIC). The orbit feedback is based on steering the measured orbit, after subtraction of the dispersive component, to either a design orbit or to a previously saved reference orbit. Using multiple correctors and beam position monitors, an SVD-based algorithm is used for determination of the applied corrections. The online model is used as a basis for matrix computations. In this report we describe the feedback design, review the changes made to realize its implementation, and assess system performance.

  8. Ghrelin and feedback systems.

    PubMed

    Nonogaki, Katsunori

    2008-01-01

    Ghrelin is produced primarily in the stomach in response to hunger, and circulates in the blood. Plasma ghrelin levels increase during fasting and decrease after ingesting glucose and lipid, but not protein. The efferent vagus nerve contributes to the fasting-induced increase in ghrelin secretion. Ghrelin secreted by the stomach stimulates the afferent vagus nerve and promotes food intake. Ghrelin also stimulates pituitary gland secretion of growth hormone (GH) via the afferent vagus nerve. GH inhibits stomach ghrelin secretion. These findings indicate that the vagal circuit between the central nervous system and stomach has a crucial role in regulating plasma ghrelin levels. Moreover, body mass index modulates plasma ghrelin levels. In a lean state and anorexia nervosa, plasma ghrelin levels are increased, whereas in obesity, except in Prader-Willi syndrome, plasma ghrelin levels are decreased and the feeding- and sleeping-induced decline in plasma ghrelin levels is disrupted. There are two forms of ghrelin: active n-octanoyl-modified ghrelin and des-acyl ghrelin. Fasting increases both ghrelin types compared with the fed state. Hyperphagia and obesity are likely to decrease plasma des-acyl ghrelin, but not n-octanoyl-modified ghrelin levels. Hypothalamic serum and glucocorticoid-inducible kinase-1 and serotonin 5-HT2C/1B receptor gene expression levels are likely to be proportional to plasma des-acyl ghrelin levels during fasting, whereas they are likely to be inversely proportional to plasma des-acyl ghrelin levels in an increased energy storage state such as obesity. Thus, a dysfunction of the ghrelin feedback systems might contribute to the pathophysiology of obesity and eating disorders.

  9. Feedback Control of Rotor Overspeed

    NASA Technical Reports Server (NTRS)

    Churchill, G. B.

    1984-01-01

    Feedback system for automatically governing helicopter rotor speed promises to lessen pilot's workload, enhance maneuverability, and protect airframe. With suitable modifications, concept applied to control speed of electrical generators, automotive engines and other machinery.

  10. The Golden Ratio

    ERIC Educational Resources Information Center

    Hyde, Hartley

    2004-01-01

    The Golden Ratio is sometimes called the "Golden Section" or the "Divine Proportion", in which three points: A, B, and C, divide a line in this proportion if AC/AB = AB/BC. "Donald in Mathmagicland" includes a section about the Golden Ratio and the ratios within a five-pointed star or pentagram. This article presents two computing exercises that…

  11. Output-feedback control of reactive batch distillation columns

    SciTech Connect

    Monroy-Loperena, R.; Alvarez-Ramirez, J.

    2000-02-01

    In this work, an output-feedback, control for the regulation of distillate purity via manipulations of the reflux ratio in reactive batch distillation is designed. The approach is based on an approximate model of the composition dynamics and makes use of a reduced-order observer to estimate the modeling error. An input/output linearizing feedback is proposed where the estimated modeling error is included to achieve robust tracking of a composition reference. It is shown that the resulting controller has the structure of a proportional-integral derivative (PID) controller with antireset windup. The controller performance is tested using a simulation example including strong uncertainties in the reaction model. An interesting finding is that the required reflux ratio policy to reach asymptotically a constant reference resembles the reflux ratio policy obtained from posing an optimization technique.

  12. Feedback Augmented Sub-Ranging (FASR) Quantizer

    NASA Technical Reports Server (NTRS)

    Guilligan, Gerard

    2012-01-01

    This innovation is intended to reduce the size, power, and complexity of pipeline analog-to-digital converters (ADCs) that require high resolution and speed along with low power. Digitizers are important components in any application where analog signals (such as light, sound, temperature, etc.) need to be digitally processed. The innovation implements amplification of a sampled residual voltage in a switched capacitor amplifier stage that does not depend on charge redistribution. The result is less sensitive to capacitor mismatches that cause gain errors, which are the main limitation of such amplifiers in pipeline ADCs. The residual errors due to mismatch are reduced by at least a factor of 16, which is equivalent to at least 4 bits of improvement. The settling time is also faster because of a higher feedback factor. In traditional switched capacitor residue amplifiers, closed-loop amplification of a sampled and held residue signal is achieved by redistributing sampled charge onto a feedback capacitor around a high-gain transconductance amplifier. The residual charge that was sampled during the acquisition or sampling phase is stored on two or more capacitors, often equal in value or integral multiples of each other. During the hold or amplification phase, all of the charge is redistributed onto one capacitor in the feedback loop of the amplifier to produce an amplified voltage. The key error source is the non-ideal ratios of feedback and input capacitors caused by manufacturing tolerances, called mismatches. The mismatches cause non-ideal closed-loop gain, leading to higher differential non-linearity. Traditional solutions to the mismatch errors are to use larger capacitor values (than dictated by thermal noise requirements) and/or complex calibration schemes, both of which increase the die size and power dissipation. The key features of this innovation are (1) the elimination of the need for charge redistribution to achieve an accurate closed-loop gain of two

  13. Thermodynamics of feedback controlled systems

    NASA Astrophysics Data System (ADS)

    Cao, F. J.; Feito, M.

    2009-04-01

    We compute the entropy reduction in feedback controlled systems due to the repeated operation of the controller. This was the lacking ingredient to establish the thermodynamics of these systems, and in particular of Maxwell’s demons. We illustrate some of the consequences of our general results by deriving the maximum work that can be extracted from isothermal feedback controlled systems. As a case example, we finally study a simple system that performs an isothermal information-fueled particle pumping.

  14. Bisensory force feedback in telerobotics

    NASA Astrophysics Data System (ADS)

    Williams, Lorraine E. P.

    2001-11-01

    Effectively controlling a robot remotely to perform a desired task---teleoperation---offers benefits in improving human safety, reducing workload, providing location accessibility, and in convenience. Because these benefits become more evident under the extreme environmental conditions of space operations, NASA Johnson Space Center has been actively researching the usage of and improvements in teleoperations. Teleoperator task performance has been shown to improve with the addition of sensory feedback. In particular, providing force-feedback to a human operator, has been shown to decrease task completion times and lessen potentially damaging contact forces between the slave robot and its target work environment. We summarize the design, development, and usage of a human interface system built to provide position control as well as both kinesthetic and visual six-axis force-feedback displays to a human teleoperator of a remote manipulator. The system developed is utilized as an experimentation platform evaluating the merit of providing force feedback through both kinesthetic (muscular position and force) and substituted visual displays on a typical space operations task utilizing an anthropomorphic slave robot called "Robonaut". Teleoperator performance of a drill task is measured under four different display scenarios: no force display, visual force display, kinesthetic, and both. Task completion times and contact forces are measured, and subjective questionnaire responses collected. Our results indicate lower maximum force/torque, lower cumulative force/torque, and a greater task consistency with any type of feedback, with no significant differences in task completion time. Cumulative force/torque was reduced between 46--51% with visually substituted force feedback, 69--81% with kinesthetic feedback and 63--92% with both forms of feedback. Maximum force/torque variance between subjects was reduced between 61--90% with any type of force display, indicating improved

  15. Improved dynamics of a tunnelling-injection quantum-dot laser under optical feedback

    NASA Astrophysics Data System (ADS)

    Asadi, Faezeh; Zarifkar, Abbas

    2016-10-01

    We report an investigation of the optical feedback effect on the dynamics of a tunnelling-injection quantum dot (TI QD) semiconductor laser. Assuming the external cavity to be short and using a small signal analysis, the modulation response of a TI QD laser is calculated under optical feedback conditions. The impact of the tunnelling probability, bias-current density, feedback ratio, external cavity length and linewidth enhancement factor on the modulation response of a TI laser is studied. With the optical feedback taken into account, the modulation responses of conventional and TI QD lasers are compared. The obtained results demonstrate that at an appropriate feedback ratio and external cavity length, the laser bandwidth and its relaxation frequency can be improved.

  16. Innovation in healthcare team feedback.

    PubMed

    Plaza, Christine; Beard, Leslie; Fonzo, Anthony Di; Tommaso, Michael Di; Mujawaz, Yaman; Serra-Julia, Marcel; Morra, Dante

    2011-01-01

    Healthcare delivery is evolving from individual, autonomous practice to collaborative team practice. However, barriers such as professional autonomy, time constraints and the perception of error as failure preclude learning behaviours that can facilitate organizational learning and improvement. Although experimentation, engaging in questions and feedback, discussing errors and reflecting on results can facilitate learning and promote effective performance, the cultural barriers within healthcare can prevent or inhibit this type of behaviour among teams. At the University Health Network's Centre for Innovation in Complex Care, we realize the need for a tool that facilitates learning behaviour and is sensitive to the risk-averse nature of the clinical environment. The vehicle for the Team Feedback Tool is a web-based application called Rypple (www.rypple.com), which allows team members to provide anonymous, rapid-fire feedback on team processes and performance. Rypple facilitates communication, elicits feedback and provokes discussion. The process enables follow-up face-to-face team discussions and encourages teams to create actionable solutions for incremental changes to enhance team health and performance. The Team Feedback Tool was implemented and piloted in general internal medicine at the University Health Network's Toronto General Hospital from early May 2009 to July 2009 to address the issues of teamwork and learning behaviour in the clinical environment. This article explores the opportunities and barriers associated with the implementation of the Team Feedback Tool.

  17. Effects of invalid feedback on learning and feedback-related brain activity in decision-making.

    PubMed

    Ernst, Benjamin; Steinhauser, Marco

    2015-10-01

    For adaptive decision-making it is important to utilize only relevant, valid and to ignore irrelevant feedback. The present study investigated how feedback processing in decision-making is impaired when relevant feedback is combined with irrelevant and potentially invalid feedback. We analyzed two electrophysiological markers of feedback processing, the feedback-related negativity (FRN) and the P300, in a simple decision-making task, in which participants processed feedback stimuli consisting of relevant and irrelevant feedback provided by the color and meaning of a Stroop stimulus. We found that invalid, irrelevant feedback not only impaired learning, it also altered the amplitude of the P300 to relevant feedback, suggesting an interfering effect of irrelevant feedback on the processing of relevant feedback. In contrast, no such effect on the FRN was obtained. These results indicate that detrimental effects of invalid, irrelevant feedback result from failures of controlled feedback processing.

  18. Feedback traps for virtual potentials

    NASA Astrophysics Data System (ADS)

    Gavrilov, Momčilo; Bechhoefer, John

    2017-03-01

    Feedback traps are tools for trapping and manipulating single charged objects, such as molecules in solution. An alternative to optical tweezers and other single-molecule techniques, they use feedback to counteract the Brownian motion of a molecule of interest. The trap first acquires information about a molecule's position and then applies an electric feedback force to move the molecule. Since electric forces are stronger than optical forces at small scales, feedback traps are the best way to trap single molecules without `touching' them (e.g. by putting them in a small box or attaching them to a tether). Feedback traps can do more than trap molecules: they can also subject a target object to forces that are calculated to be the gradient of a desired potential function U(x). If the feedback loop is fast enough, it creates a virtual potential whose dynamics will be very close to those of a particle in an actual potential U(x). But because the dynamics are entirely a result of the feedback loop-absent the feedback, there is only an object diffusing in a fluid-we are free to specify and then manipulate in time an arbitrary potential U(x,t). Here, we review recent applications of feedback traps to studies on the fundamental connections between information and thermodynamics, a topic where feedback plays an even more fundamental role. We discuss how recursive maximum-likelihood techniques allow continuous calibration, to compensate for drifts in experiments that last for days. We consider ways to estimate work and heat, using them to measure fluctuating energies to a precision of ±0.03 kT over these long experiments. Finally, we compare work and heat measurements of the costs of information erasure, the Landauer limit of kT ln 2 per bit of information erased. We argue that, when you want to know the average heat transferred to a bath in a long protocol, you should measure instead the average work and then infer the heat using the first law of thermodynamics. This

  19. Multimedia as a Means to Enhance Feedback

    ERIC Educational Resources Information Center

    Tsutsui, Michio

    2004-01-01

    Interactive feedback, the most common feedback method for oral performance, cannot be used in activities that do not allow for instructor-student interaction, such as speeches and presentations, where feedback should occur after the performance. The conventional ways of providing post-performance or delayed feedback, however, are neither efficient…

  20. Dynamics of Team Reflexivity after Feedback

    ERIC Educational Resources Information Center

    Gabelica, Catherine; Van den Bossche, Piet; Segers, Mien; Gijselaers, Wim

    2014-01-01

    A great deal of work has been generated on feedback in teams and has shown that giving performance feedback to teams is not sufficient to improve performance. To achieve the potential of feedback, it is stated that teams need to proactively process this feedback and thus collectively evaluate their performance and strategies, look for…

  1. Electromyograph Feedback as a Relaxation Technique

    ERIC Educational Resources Information Center

    Coursey, Robert D.

    1975-01-01

    An electromyograph (EMG) feedback group of 10 normal undergraduate males received variable-tone feedback from the frontalis muscle. Comparisons showed that the feedback group achieved significantly lower EMG scores than the two control groups, but only one of the six measures of state anxiety favored the feedback group over the controls. (Author)

  2. Feedback Dialogues That Stimulate Students' Reflective Thinking

    ERIC Educational Resources Information Center

    Van der Schaaf, Marieke; Baartman, Liesbeth; Prins, Frans; Oosterbaan, Anne; Schaap, Harmen

    2013-01-01

    How can feedback dialogues stimulate students' reflective thinking? This study aims to investigate: (1) the effects of feedback dialogues between teachers and students on students' perceptions of teacher feedback and (2) the relation between features of feedback dialogues and students' thinking activities as part of reflective thinking. A…

  3. Audiotape Feedback for Essays in Distance Education.

    ERIC Educational Resources Information Center

    Kirschner, Paul A.; And Others

    1991-01-01

    Twelve students writing essays for a photochemistry course at the Open University of the Netherlands received either audiocasette or written feedback. Time spent in recording versus writing feedback differed minimally. Recorded feedback was considerably greater in amount. Students' final grades did not differ, but recorded feedback was more…

  4. Feedback in Videogame-based Adaptive Training

    DTIC Science & Technology

    2011-05-01

    individuals have limited information processing capabilities. Salvati et al. (2003) identified several antecedents and consequences to feedback overload... Antecedents included feedback value and job experience while important consequences were the desire to respond to feedback, stress, and job...Morin, D. (2003). Performance feedback overload: An exploratory field study of its antecedents and consequences . Montreal, Quebec: HEC Montreal

  5. Feedback as Real-Time Constructions

    ERIC Educational Resources Information Center

    Keiding, Tina Bering; Qvortrup, Ane

    2014-01-01

    This article offers a re-description of feedback and the significance of time in feedback constructions based on systems theory. It describes feedback as internal, real-time constructions in a learning system. From this perspective, feedback is neither immediate nor delayed, but occurs in the very moment it takes place. This article argues for a…

  6. Identifying Mentors' Observations for Providing Feedback

    ERIC Educational Resources Information Center

    Hudson, Peter

    2016-01-01

    Mentors' feedback can assist preservice teachers' development; yet feedback tends to be variable from one mentor to the next. What do mentors observe for providing feedback? In this study, 24 mentors observed a final-year preservice teacher through a professionally video-recorded lesson and provided written notes for feedback. They observed the…

  7. A Comparison of Peer and Tutor Feedback

    ERIC Educational Resources Information Center

    Hamer, John; Purchase, Helen; Luxton-Reilly, Andrew; Denny, Paul

    2015-01-01

    We report on a study comparing peer feedback with feedback written by tutors on a large, undergraduate software engineering programming class. Feedback generated by peers is generally held to be of lower quality to feedback from experienced tutors, and this study sought to explore the extent and nature of this difference. We looked at how…

  8. An Improved Force Feedback Control Algorithm for Active Tendons

    PubMed Central

    Guo, Tieneng; Liu, Zhifeng; Cai, Ligang

    2012-01-01

    An active tendon, consisting of a displacement actuator and a co-located force sensor, has been adopted by many studies to suppress the vibration of large space flexible structures. The damping, provided by the force feedback control algorithm in these studies, is small and can increase, especially for tendons with low axial stiffness. This study introduces an improved force feedback algorithm, which is based on the idea of velocity feedback. The algorithm provides a large damping ratio for space flexible structures and does not require a structure model. The effectiveness of the algorithm is demonstrated on a structure similar to JPL-MPI. The results show that large damping can be achieved for the vibration control of large space structures. PMID:23112660

  9. A novel charge sensitive preamplifier without the feedback resistor

    SciTech Connect

    Bertuccio, G. . Dipt. di Elettronica e Informazione); Rehak, P.; Xi, D. )

    1992-01-01

    A novel charge sensitive preamplifier which has no resistor in parallel with the feedback capacitor is presented. No external device or circuit is required to discharge the feedback capacitor. The detector leakage and signal current flows away through the gate of the first JFET which works with its gate to source junction slightly forward biased. The DC stabilization of the preamplifier is accomplished by an additional feedback loop, which permits to equalize the current flowing through the forward baised gate to source junction and the current coming from the detector. An equivalent noise charge of less than 20 electrons r.m.s. has been measured at room temperature by using an input JFET with a transconductance to gate capacitance ratio of 4 mS/5.4 pF.

  10. A novel charge sensitive preamplifier without the feedback resistor

    SciTech Connect

    Bertuccio, G.; Rehak, P.; Xi, D.

    1992-07-01

    A novel charge sensitive preamplifier which has no resistor in parallel with the feedback capacitor is presented. No external device or circuit is required to discharge the feedback capacitor. The detector leakage and signal current flows away through the gate of the first JFET which works with its gate to source junction slightly forward biased. The DC stabilization of the preamplifier is accomplished by an additional feedback loop, which permits to equalize the current flowing through the forward baised gate to source junction and the current coming from the detector. An equivalent noise charge of less than 20 electrons r.m.s. has been measured at room temperature by using an input JFET with a transconductance to gate capacitance ratio of 4 mS/5.4 pF.

  11. Position feedback system for volume holographic storage media

    DOEpatents

    Hays, Nathan J.; Henson, James A.; Carpenter, Christopher M.; Akin, Jr.. William R.; Ehrlich, Richard M.; Beazley, Lance D.

    1998-07-07

    A method of holographic recording in a photorefractive medium wherein stored holograms may be retrieved with maximum signal-to noise ratio (SNR) is disclosed. A plurality of servo blocks containing position feedback information is recorded in the crystal and made non-erasable by heating the crystal. The servo blocks are recorded at specific increments, either angular or frequency, depending whether wavelength or angular multiplexing is applied, and each servo block is defined by one of five patterns. Data pages are then recorded at positions or wavelengths enabling each data page to be subsequently reconstructed with servo patterns which provide position feedback information. The method of recording data pages and servo blocks is consistent with conventional practices. In addition, the recording system also includes components (e.g. voice coil motor) which respond to position feedback information and adjust the angular position of the reference angle of a reference beam to maximize SNR by reducing crosstalk, thereby improving storage capacity.

  12. Auditory feedback modulates development of kitten vocalizations.

    PubMed

    Hubka, Peter; Konerding, Wiebke; Kral, Andrej

    2015-07-01

    Effects of hearing loss on vocal behavior are species-specific. To study the impact of auditory feedback on feline vocal behavior, vocalizations of normal-hearing, hearing-impaired (white) and congenitally deaf (white) cats were analyzed at around weaning age. Eleven animals were placed in a soundproof booth for 30 min at different ages, from the first to the beginning of the fourth postnatal month, every 2 weeks of life. In total, 13,874 vocalizations were analyzed using an automated procedure. Firstly, vocalizations were detected and segmented, with voiced and unvoiced vocalizations being differentiated. The voiced isolation calls ('meow') were further analyzed. These vocalizations showed developmental changes affecting several parameters in hearing controls, whereas the developmental sequence was delayed in congenitally deaf cats. In hearing-impaired and deaf animals, we observed differences both in vocal behavior (loudness and duration) and in the calls' acoustic structure (fundamental frequency and higher harmonics). The fundamental frequency decreased with age in all groups, most likely due to maturation of the vocal apparatus. In deaf cats, however, other aspects of the acoustic structure of the vocalizations did not fully mature. The harmonic ratio (i.e., frequency of first harmonic divided by fundamental frequency) was higher and more variable in deaf cats than in the other study groups. Auditory feedback thus affects the acoustic structure of vocalizations and their ontogenetic development. The study suggests that both the vocal apparatus and its neuronal motor control are subject to maturational processes, whereas the latter is additionally dependent on auditory feedback in cats.

  13. Supernova Feedback in Galaxy Formation

    NASA Astrophysics Data System (ADS)

    Dubois, Y.; Teyssier, R.

    2008-06-01

    The hierarchical model of galaxy formation is known to suffer from the ``over-cooling'' problem: the high efficiency of radiative cooling results in too much baryonic matter in a condensed phase (namely, cold gas or stars) when compared to observations. A solution proposed by many authors (see Springel & Hernquist 2003; Fujita et al. 2004; Rasera & Teyssier 2005) is feedback due to supernova (SN) driven winds or active galactic nuclei. Modeling SN feedback by direct injection of thermal energy usually turns out to be inefficient in galaxy-scale simulations, due to the quasi-instantaneous radiation of the SN energy. To avoid this effect, we have developed a new method to incorporate SN feedback in cosmological simulations: using temporary test particles, we reproduce explicitly a local Sedov blast wave solution in the gas distribution. We have performed several self-consistent runs of isolated Navarro, Frenk, & White (1996, hereafter NFW) halos with radiative cooling, star formation, SN feedback and metal enrichment using the adaptive mesh refinement code RAMSES (Teyssier 2002). We have explored the influence of SN feedback on the formation and the evolution of galaxies with different masses. We have studied the efficiency of the resulting galactic winds, as a function of the mass of the parent halo.

  14. Feedback controlled hybrid fast ferrite tuners

    SciTech Connect

    Remsen, D.B.; Phelps, D.A.; deGrassie, J.S.; Cary, W.P.; Pinsker, R.I.; Moeller, C.P.; Arnold, W.; Martin, S.; Pivit, E.

    1993-09-01

    A low power ANT-Bosch fast ferrite tuner (FFT) was successfully tested into (1) the lumped circuit equivalent of an antenna strap with dynamic plasma loading, and (2) a plasma loaded antenna strap in DIII-D. When the FFT accessible mismatch range was phase-shifted to encompass the plasma-induced variation in reflection coefficient, the 50 {Omega} source was matched (to within the desired 1.4 : 1 voltage standing wave ratio). The time required to achieve this match (i.e., the response time) was typically a few hundred milliseconds, mostly due to a relatively slow network analyzer-computer system. The response time for the active components of the FFT was 10 to 20 msec, or much faster than the present state-of-the-art for dynamic stub tuners. Future FFT tests are planned, that will utilize the DIII-D computer (capable of submillisecond feedback control), as well as several upgrades to the active control circuit, to produce a FFT feedback control system with a response time approaching 1 msec.

  15. DIRECT AMMONIA-AIR FUEL CELL.

    DTIC Science & Technology

    Experimental runs were conducted on direct ammonia fuel cells . Effects of temperature, composition, as well as run effect and block effect were...cells and to electrode flooding are discussed. Data on performance of complete laboratory direct ammonia-oxygen fuel cells are presented and discussed. (Author)

  16. DIRECT AMMONIA-AIR FUEL CELL.

    DTIC Science & Technology

    fuel cell was investigated. This cell is based on the use of a non-aqueous fused hydroxide electrolyte matrix, and operates in the intermediate temperature range of 180-300 C. Studies have been carried out to determine the nature of the ratecontrolling step in the kinetics of the anodic oxidation of ammonia. A new type of Ni/NiOOH reference electrode was developed for the measurement of single electrode potentials in experimental galvanic fuel cells employing this type of matrix electrolyte. In addition to various exploratory studies, two statistical analysis

  17. A methanol/air fuel cell system

    NASA Technical Reports Server (NTRS)

    Asher, W. J.

    1974-01-01

    High power-density, self-regulating fuel cell develops electrical power from catalyzed reaction between methanol and atmospheric oxygen. Cells such as these are of particular interest, because they may one day offer an emission-free, extremely efficient alternative to internal-combustion engines as power source.

  18. Hydrogen/Air Fuel Nozzle Emissions Experiments

    NASA Technical Reports Server (NTRS)

    Smith, Timothy D.

    2001-01-01

    The use of hydrogen combustion for aircraft gas turbine engines provides significant opportunities to reduce harmful exhaust emissions. Hydrogen has many advantages (no CO2 production, high reaction rates, high heating value, and future availability), along with some disadvantages (high current cost of production and storage, high volume per BTU, and an unknown safety profile when in wide use). One of the primary reasons for switching to hydrogen is the elimination of CO2 emissions. Also, with hydrogen, design challenges such as fuel coking in the fuel nozzle and particulate emissions are no longer an issue. However, because it takes place at high temperatures, hydrogen-air combustion can still produce significant levels of NOx emissions. Much of the current research into conventional hydrocarbon-fueled aircraft gas turbine combustors is focused on NOx reduction methods. The Zero CO2 Emission Technology (ZCET) hydrogen combustion project will focus on meeting the Office of Aerospace Technology goal 2 within pillar one for Global Civil Aviation reducing the emissions of future aircraft by a factor of 3 within 10 years and by a factor of 5 within 25 years. Recent advances in hydrocarbon-based gas turbine combustion components have expanded the horizons for fuel nozzle development. Both new fluid designs and manufacturing technologies have led to the development of fuel nozzles that significantly reduce aircraft emissions. The goal of the ZCET program is to mesh the current technology of Lean Direct Injection and rocket injectors to provide quick mixing, low emissions, and high-performance fuel nozzle designs. An experimental program is planned to investigate the fuel nozzle concepts in a flametube test rig. Currently, a hydrogen system is being installed in cell 23 at NASA Glenn Research Center's Research Combustion Laboratory. Testing will be conducted on a variety of fuel nozzle concepts up to combustion pressures of 350 psia and inlet air temperatures of 1200 F. Computational fluid dynamics calculations, with the Glenn developed National Combustor Code, are being performed to optimize the fuel nozzle designs.

  19. A Micro Hydrogen Air Fuel Cell

    DTIC Science & Technology

    2005-10-01

    thin enough that it does not block the channels. This eliminated the step of having to sputter chrome /gold onto the wells and channels. Currently...to make the ink compatible with conventional thick film printing. In addition, the typical process for manufacturing electrode/membrane assemblies...catalytic activity of these inks, polarization curves for hydrogen oxidation were obtained using a pure hydrogen feed at one atmosphere pressure. With

  20. Electrolytes for Hydrocarbon Air Fuel Cells.

    DTIC Science & Technology

    1981-01-01

    performed on four commercially available electrolytes; namely, -methanedisulfonic acid - sulfoacetic acid -10-dl-camphorsulfonic acid -and...hydrocarbon chain can increase the stability of aliphatic sulfonic acids . Sulfoacetic and dl-10-camphorsulfonic acids were tested and found to decompose...thermally. 0 Sulfoacetic acid thermally decomposes at 180 C apparently due to decarboxylation. This is substantially below the 245 C reported by previous

  1. Electrolytes for Hydrocarbon Air Fuel Cells.

    DTIC Science & Technology

    1980-04-01

    available electrolytes; namely, -methanedisulfonic acid - sulfoacetic acid -10-dl-camphorsulfonic acid -and pentadecafluorooctanoic acid . These four...in the hydrocarbon chain can increase the stability of aliphatic sulfonic acids . Sulfoacetic and dl-10-camphorsulfonic acids were tested and found to...decompose thermally. 6 Sulfoacetic acid thermally decomposes at 180 C apparently due to decarboxylation. This is substantially 6 below the 245 C

  2. Regimes of external optical feedback in 5.6 μm distributed feedback mid-infrared quantum cascade lasers

    SciTech Connect

    Jumpertz, L.; Carras, M.; Schires, K.; Grillot, F.

    2014-09-29

    External optical feedback is studied experimentally in mid-infrared quantum cascade lasers. These structures exhibit a dynamical response close to that observed in interband lasers, with threshold reduction and optical power enhancement when increasing the feedback ratio. The study of the optical spectrum proves that the laser undergoes five distinct regimes depending on the phase and amplitude of the reinjected field. These regimes are mapped in the plane of external cavity length and feedback strength, revealing unstable behavior only for a very narrow range of operation, making quantum cascade lasers much more stable than their interband counterparts.

  3. Delayed feedback control of chaos.

    PubMed

    Pyragas, Kestutis

    2006-09-15

    Time-delayed feedback control is well known as a practical method for stabilizing unstable periodic orbits embedded in chaotic attractors. The method is based on applying feedback perturbation proportional to the deviation of the current state of the system from its state one period in the past, so that the control signal vanishes when the stabilization of the target orbit is attained. A brief review on experimental implementations, applications for theoretical models and most important modifications of the method is presented. Recent advancements in the theory, as well as an idea of using an unstable degree of freedom in a feedback loop to avoid a well-known topological limitation of the method, are described in detail.

  4. Klystron equalization for RF feedback

    SciTech Connect

    Corredoura, P.

    1993-01-01

    The next generation of colliding beam storage rings support higher luminosities by significantly increasing the number of bunches and decreasing the spacing between respective bunches. The heavy beam loading requires large RF cavity detuning which drives several lower coupled bunch modes very strongly. One technique which has proven to be very successful in reducing the coupled bunch mode driving impedance is RF feedback around the klystron-cavity combination. The gain and bandwidth of the feedback loop is limited by the group delay around the feedback loop. Existing klystrons on the world market have not been optimized for this application and contribute a large portion of the total loop group delay. This paper describes a technique to reduce klystron group delay by adding an equalizing filter to the klystron RF drive. Such a filter was built and tested on a 500 kill klystron as part of the on going PEP-II R&D effort here at SLAC.

  5. Klystron equalization for RF feedback

    SciTech Connect

    Corredoura, P.

    1993-01-01

    The next generation of colliding beam storage rings support higher luminosities by significantly increasing the number of bunches and decreasing the spacing between respective bunches. The heavy beam loading requires large RF cavity detuning which drives several lower coupled bunch modes very strongly. One technique which has proven to be very successful in reducing the coupled bunch mode driving impedance is RF feedback around the klystron-cavity combination. The gain and bandwidth of the feedback loop is limited by the group delay around the feedback loop. Existing klystrons on the world market have not been optimized for this application and contribute a large portion of the total loop group delay. This paper describes a technique to reduce klystron group delay by adding an equalizing filter to the klystron RF drive. Such a filter was built and tested on a 500 kill klystron as part of the on going PEP-II R D effort here at SLAC.

  6. Optical fiber feedback SQUID magnetometer

    SciTech Connect

    Naito, S.; Sampei, Y.; Takahashi, T. )

    1989-04-01

    This paper describes an optical fiber feedback superconducting quantum interference device (SQUID) magnetometer which was developed to improve electromagnetic interference characteristics. The SQUID consists of an RF SQUID probe, an RF amplifier, two multimode fibers, and a SQUID control unit. Phase-locked pulse width modulation (PWM) was used to construct a flux locked loop (FLL) circuit in the SQUID control unit. The operation of the optical fiber feedback SQUID is stable when a common mode voltage of ac 100 V/50 Hz is applied. It has an energy resolution of 1 x 10/sup -28/ J/Hz. This paper also describes the measurement of an auditory evoked field from the human brain in a magnetically shielded room using the fiber feedback SQUID with a gradiometer type pickup coil.

  7. Parallel multiplex laser feedback interferometry

    SciTech Connect

    Zhang, Song; Tan, Yidong; Zhang, Shulian

    2013-12-15

    We present a parallel multiplex laser feedback interferometer based on spatial multiplexing which avoids the signal crosstalk in the former feedback interferometer. The interferometer outputs two close parallel laser beams, whose frequencies are shifted by two acousto-optic modulators by 2Ω simultaneously. A static reference mirror is inserted into one of the optical paths as the reference optical path. The other beam impinges on the target as the measurement optical path. Phase variations of the two feedback laser beams are simultaneously measured through heterodyne demodulation with two different detectors. Their subtraction accurately reflects the target displacement. Under typical room conditions, experimental results show a resolution of 1.6 nm and accuracy of 7.8 nm within the range of 100 μm.

  8. Cross-Layer Adaptive Feedback Scheduling of Wireless Control Systems

    PubMed Central

    Xia, Feng; Ma, Longhua; Peng, Chen; Sun, Youxian; Dong, Jinxiang

    2008-01-01

    There is a trend towards using wireless technologies in networked control systems. However, the adverse properties of the radio channels make it difficult to design and implement control systems in wireless environments. To attack the uncertainty in available communication resources in wireless control systems closed over WLAN, a cross-layer adaptive feedback scheduling (CLAFS) scheme is developed, which takes advantage of the co-design of control and wireless communications. By exploiting cross-layer design, CLAFS adjusts the sampling periods of control systems at the application layer based on information about deadline miss ratio and transmission rate from the physical layer. Within the framework of feedback scheduling, the control performance is maximized through controlling the deadline miss ratio. Key design parameters of the feedback scheduler are adapted to dynamic changes in the channel condition. An event-driven invocation mechanism for the feedback scheduler is also developed. Simulation results show that the proposed approach is efficient in dealing with channel capacity variations and noise interference, thus providing an enabling technology for control over WLAN. PMID:27879934

  9. Offer/Acceptance Ratio.

    ERIC Educational Resources Information Center

    Collins, Mimi

    1997-01-01

    Explores how human resource professionals, with above average offer/acceptance ratios, streamline their recruitment efforts. Profiles company strategies with internships, internal promotion, cooperative education programs, and how to get candidates to accept offers. Also discusses how to use the offer/acceptance ratio as a measure of program…

  10. Feedback mechanism for smart nozzles and nebulizers

    DOEpatents

    Montaser, Akbar [Potomac, MD; Jorabchi, Kaveh [Arlington, VA; Kahen, Kaveh [Kleinburg, CA

    2009-01-27

    Nozzles and nebulizers able to produce aerosol with optimum and reproducible quality based on feedback information obtained using laser imaging techniques. Two laser-based imaging techniques based on particle image velocimetry (PTV) and optical patternation map and contrast size and velocity distributions for indirect and direct pneumatic nebulizations in plasma spectrometry. Two pulses from thin laser sheet with known time difference illuminate droplets flow field. Charge coupled device (CCL)) captures scattering of laser light from droplets, providing two instantaneous particle images. Pointwise cross-correlation of corresponding images yields two-dimensional velocity map of aerosol velocity field. For droplet size distribution studies, solution is doped with fluorescent dye and both laser induced florescence (LIF) and Mie scattering images are captured simultaneously by two CCDs with the same field of view. Ratio of LIF/Mie images provides relative droplet size information, then scaled by point calibration method via phase Doppler particle analyzer.

  11. Protostellar Outflows and Radiative Feedback from Massive Stars. II. Feedback, Star-formation Efficiency, and Outflow Broadening

    NASA Astrophysics Data System (ADS)

    Kuiper, Rolf; Turner, Neal J.; Yorke, Harold W.

    2016-11-01

    We perform two-dimensional axially symmetric radiation hydrodynamic simulations to assess the impact of outflows and radiative force feedback from massive protostars by varying when the protostellar outflow starts, and to determine the ratio of ejection to accretion rates and the strength of the wide-angle disk wind component. The star-formation efficiency, i.e., the ratio of final stellar mass to initial core mass, is dominated by radiative forces and the ratio of outflow to accretion rates. Increasing this ratio has three effects. First, the protostar grows slower with a lower luminosity at any given time, lowering radiative feedback. Second, bipolar cavities cleared by the outflow become larger, further diminishing radiative feedback on disk and core scales. Third, the higher momentum outflow sweeps up more material from the collapsing envelope, decreasing the protostar's potential mass reservoir via entrainment. The star-formation efficiency varies with the ratio of ejection to accretion rates from 50% in the case of very weak outflows to as low as 20% for very strong outflows. At latitudes between the low-density bipolar cavity and the high-density accretion disk, wide-angle disk winds remove some of the gas, which otherwise would be part of the accretion flow onto the disk; varying the strength of these wide-angle disk winds, however, alters the final star-formation efficiency by only ±6%. For all cases, the opening angle of the bipolar outflow cavity remains below 20° during early protostellar accretion phases, increasing rapidly up to 65° at the onset of radiation pressure feedback.

  12. How Supermassive Black Hole Feedback Might Work

    NASA Astrophysics Data System (ADS)

    Donahue, Megan

    2017-01-01

    How black holes regulate their own growth and the growth of their host galaxy is an unsolved problem in galaxy evolution. The problem is particularly acute in the centers of clusters of galaxies, where the largest and most massive galaxies in the universe are found. That is, coincidentally, also where the interaction between the black hole and the surrounding gas is the easiest to study because the gas is sufficiently hot and dense to emit X-rays. The massive central galaxies of clusters of galaxies (BCGs) exhibit striking patterns in their relationships between star formation, radio AGN activity, and the thermodynamic state of the hot, X-ray emitting intracluster gas (ICM) surrounding the galaxies. The AGN jets excavate giant, kpc-scale cavities in the hot gas, in principle, supplying enough heat to the ICM to replace energy lost to radiative cooling. Simulations suggest (by elimination) that AGN feedback must be required to explain the luminosity and colors of these galaxies, but cosmological simulations still struggle with modeling how AGN feedback works in detail. In clusters of galaxies with active AGN and star-forming BCGs, the AGN somehow regulates the gaseous atmosphere to be marginally critical, with a ratio of the cooling time to the free fall time of ~ 5-20. This behavior is also seen in elliptical galaxies, where the feedback is mostly coming from stars. I will discuss the observations that motivated this model. The precipitation model in BCGs is a class of models known as "preventative" feedback, regulated by jets in BCGs. Further, the complex behaviour seen in recent idealized simulations seem to follow emergent patterns predicted by this model, while reproducing the scatter and the time scales inferred from the observations. The link between the thermal instabilities and the depth of the gravitational potential may explain scaling laws such as the black hole mass-velocity dispersion relation, the galaxy mass-metallicity relation and the baryonic

  13. ASDTIC - A feedback control innovation.

    NASA Technical Reports Server (NTRS)

    Lalli, V. R.; Schoenfeld, A. D.

    1972-01-01

    The ASDTIC (analog signal to discrete time interval converter) control subsystem provides precise output control of high performance aerospace power supplies. The key to ASDTIC operation is that it stably controls output by sensing output energy change as well as output magnitude. The ASDTIC control subsystem and control module were developed to improve power supply performance during static and dynamic input voltage and output load variations, to reduce output voltage or current regulation due to component variations or aging, to maintain a stable feedback control with variations in the loop gain or loop time constants, and to standardize the feedback control subsystem for power conditioning equipment.

  14. EFFECTS OF DUST FEEDBACK ON VORTICES IN PROTOPLANETARY DISKS

    SciTech Connect

    Fu, Wen; Liang, Edison; Li, Hui; Li, Shengtai; Lubow, Stephen

    2014-11-10

    We carried out two-dimensional, high-resolution simulations to study the effect of dust feedback on the evolution of vortices induced by massive planets in protoplanetary disks. Various initial dust to gas disk surface density ratios (0.001-0.01) and dust particle sizes (Stokes number 4 × 10{sup –4}-0.16) are considered. We found that while dust particles migrate inward, vortices are very effective at collecting them. When dust density becomes comparable to gas density within the vortex, a dynamical instability is excited and it alters the coherent vorticity pattern and destroys the vortex. This dust feedback effect is stronger with a higher initial dust/gas density ratio and larger dust grain. Consequently, we found that the disk vortex lifetime can be reduced up to a factor of 10. We discuss the implications of our findings on the survivability of vortices in protoplanetary disks and planet formation.

  15. Feedback: How to Teach How.

    ERIC Educational Resources Information Center

    Krovar, Susan K.; And Others

    1992-01-01

    To give definitive feedback, physical education teachers must be able to teach basic kinesiological and mechanical principles of movement and how they apply to specific sports skills. The article includes a chart with common kinesiological and mechanical principles applied to particular movements. Appropriate teaching cues are noted. (SM)

  16. The Secret of Effective Feedback

    ERIC Educational Resources Information Center

    Wiliam, Dylan

    2016-01-01

    "The only important thing about feedback is what students do with it," declares Dylan Wiliam in this article. The standard school procedure (in which a teacher looks at a piece of student work and writes something on it, and the student later looks at what the teacher has written) does not necessarily increase student learning. Teachers…

  17. LFSC - Linac Feedback Simulation Code

    SciTech Connect

    Ivanov, Valentin; /Fermilab

    2008-05-01

    The computer program LFSC (Feedback Simulation Code>) is a numerical tool for simulation beam based feedback in high performance linacs. The code LFSC is based on the earlier version developed by a collective of authors at SLAC (L.Hendrickson, R. McEwen, T. Himel, H. Shoaee, S. Shah, P. Emma, P. Schultz) during 1990-2005. That code was successively used in simulation of SLC, TESLA, CLIC and NLC projects. It can simulate as pulse-to-pulse feedback on timescale corresponding to 5-100 Hz, as slower feedbacks, operating in the 0.1-1 Hz range in the Main Linac and Beam Delivery System. The code LFSC is running under Matlab for MS Windows operating system. It contains about 30,000 lines of source code in more than 260 subroutines. The code uses the LIAR ('Linear Accelerator Research code') for particle tracking under ground motion and technical noise perturbations. It uses the Guinea Pig code to simulate the luminosity performance. A set of input files includes the lattice description (XSIF format), and plane text files with numerical parameters, wake fields, ground motion data etc. The Matlab environment provides a flexible system for graphical output.

  18. Delayed Auditory Feedback and Movement

    ERIC Educational Resources Information Center

    Pfordresher, Peter Q.; Dalla Bella, Simone

    2011-01-01

    It is well known that timing of rhythm production is disrupted by delayed auditory feedback (DAF), and that disruption varies with delay length. We tested the hypothesis that disruption depends on the state of the movement trajectory at the onset of DAF. Participants tapped isochronous rhythms at a rate specified by a metronome while hearing DAF…

  19. Educational Accountability and Policy Feedback

    ERIC Educational Resources Information Center

    McDonnell, Lorraine M.

    2013-01-01

    Over the past 30 years, accountability policies have become more prominent in public K-12 education and have changed how teaching and learning are organized. It is less clear the extent to which these policies have altered the politics of education. This article begins to address that question through the lens of policy feedback. It identifies…

  20. Global desertification: Drivers and feedbacks

    NASA Astrophysics Data System (ADS)

    D'Odorico, Paolo; Bhattachan, Abinash; Davis, Kyle F.; Ravi, Sujith; Runyan, Christiane W.

    2013-01-01

    Desertification is a change in soil properties, vegetation or climate, which results in a persistent loss of ecosystem services that are fundamental to sustaining life. Desertification affects large dryland areas around the world and is a major cause of stress in human societies. Here we review recent research on the drivers, feedbacks, and impacts of desertification. A multidisciplinary approach to understanding the drivers and feedbacks of global desertification is motivated by our increasing need to improve global food production and to sustainably manage ecosystems in the context of climate change. Classic desertification theories look at this process as a transition between stable states in bistable ecosystem dynamics. Climate change (i.e., aridification) and land use dynamics are the major drivers of an ecosystem shift to a “desertified” (or “degraded”) state. This shift is typically sustained by positive feedbacks, which stabilize the system in the new state. Desertification feedbacks may involve land degradation processes (e.g., nutrient loss or salinization), changes in rainfall regime resulting from land-atmosphere interactions (e.g., precipitation recycling, dust emissions), or changes in plant community composition (e.g., shrub encroachment, decrease in vegetation cover). We analyze each of these feedback mechanisms and discuss their possible enhancement by interactions with socio-economic drivers. Large scale effects of desertification include the emigration of “environmental refugees” displaced from degraded areas, climatic changes, and the alteration of global biogeochemical cycles resulting from the emission and long-range transport of fine mineral dust. Recent research has identified some possible early warning signs of desertification, which can be used as indicators of resilience loss and imminent shift to desert-like conditions. We conclude with a brief discussion on some desertification control strategies implemented in different

  1. Preface: Multiscale feedbacks in ecogeomorphology

    USGS Publications Warehouse

    Wheaton, Joseph M.; Gibbins, Chris; Wainwright, John; Larsen, Laurel G.; McElroy, Brandon

    2011-01-01

    Geomorphic systems are known to exhibit nonlinear responses to physical–biological feedbacks (Thornes, 1985; Baas, 2002; Reinhardt et al., 2010). These responses make understanding and/or predicting system response to change highly challenging. With growing concerns over ecosystem health, a pressing need exists for research that tries to elucidate these feedbacks (Jerolmack, 2008; Darby, 2010; National Research Council, 2010). A session was convened at the Fall 2008 meeting of the American Geophysical Union (AGU) to provide an outlet for some of this truly interdisciplinary and original research, which is central to understanding geomorphic and ecological dynamics. The session attracted over 39 contributions, which were divided into two well-attended oral sessions and a very busy poster session. This special issue presents new research from the AGU session, which highlights clear physical–biological feedbacks. The aim is to bring together contrasting perspectives on biological and geomorphic feedbacks in a diversity of physiographic settings, ranging from wetlands and estuaries, through rivers, to uplands. These papers highlight biological and physical feedbacks which involve the modulation or amplification of geomorphic processes. These papers will be of interest to a core geomorphology audience, and should also draw attention from the fields of ecohydraulics, hydroecology, ecohydrology, ecomorphology, biogeochemistry and biogeography, and biogeomorphology as well as the more traditional fields of hydrology, ecology and biology. In this preface to the special issue, we a) review past contributions to the emerging field of ecogeomorphology and related disciplines, b) provide some context for how this topical special issue came to fruition, and c) summarize the contributions to this special issue.

  2. High Aspect Ratio Wrinkles

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Cheng; Crosby, Alfred

    2015-03-01

    Buckling-induced surface undulations are widely found in living creatures, for instance, gut villi and the surface of flower petal cells. These undulations provide unique functionalities with their extremely high aspect ratios. For the synthetic systems, sinusoidal wrinkles that are induced by buckling a thin film attached on a soft substrate have been proposed to many applications. However, the impact of the synthetic wrinkles have been restricted by limited aspect ratios, ranging from 0 to 0.35. Within this range, wrinkle aspect ratio is known to increase with increasing compressive strain until a critical strain is reached, at which point wrinkles transition to localizations, such as folds or period doublings. Inspired by the living creatures, we propose that wrinkles can be stabilized in high aspect ratio by manipulating the strain energy in the substrate. We experimentally demonstrate this idea by forming a secondary crosslinking network in the wrinkled surface and successfully achieve aspect ratio as large as 0.8. This work not only provides insights for the mechanism of high aspect ratio structures seen in living creatures, but also demonstrates significant promise for future wrinkle-based applications.

  3. Terrestrial ecosystem feedbacks to global climate change

    SciTech Connect

    Lashof, D.A.; DeAngelo, B.J.; Saleska, S.R.; Harte, J.

    1997-12-31

    Anthropogenic greenhouse gases are expected to induce changes in global climate that can alter ecosystems in ways that, in turn, may further affect climate. Such climate-ecosystem interactions can generate either positive or negative feedbacks to the climate system, thereby either enhancing or diminishing the magnitude of global climate change. Important terrestrial feedback mechanisms include CO{sub 2} fertilization (negative feedbacks), carbon storage in vegetation and soils (positive and negative feedbacks), vegetation albedo (positive feedbacks), and peatland methane emissions (positive and negative feedbacks). While the processes involved are complex, not readily quantifiable, and demonstrate both positive and negative feedback potential, the authors conclude that the combined effect of the feedback mechanisms reviewed here will likely amplify climate change relative to current projections that have not yet adequately incorporated these mechanisms. 162 refs., 7 figs., 3 tabs.

  4. Investigating shareable feedback tags for programming assignments

    NASA Astrophysics Data System (ADS)

    Cummins, Stephen; Burd, Liz; Hatch, Andrew

    2011-03-01

    This article presents an investigation into the usage of shareable feedback tags as a way of delivering feedback to three different cohorts of programming students. A series of research questions are examined; these include investigating any perceived benefit from students using feedback tags and exploring how students interact with their feedback. Results indicate that students with both the lower and higher marks in a cohort are more likely to opt to share their feedback and programming work than students with mid-ranged marks. A variety of reasons, both for and against sharing, given by students are discussed. Six categories of student behaviour exhibited during interaction with their feedback have been identified in this article. This article has shown that feedback tags can be used successfully as a form of shareable feedback and that a number of future research possibilities exist that can extend this topic.

  5. Toward Harnessing User Feedback For Machine Learning

    DTIC Science & Technology

    2006-10-02

    feedback and to understand what kinds of feedback users could give . Users were shown explanations of machine learning predictions and asked to provide... learning algorithm. The results show that user feedback has the potential to significantly improve machine learning systems, but that learning ...machine learning predictions and asked to provide feedback to improve the predictions. We found that users had no difficulty providing generous amounts

  6. The Courage to Seek Authentic Feedback

    ERIC Educational Resources Information Center

    Wiggins, Alexis

    2011-01-01

    Educators assess students' work and behavior every day. They are professional feedback-givers, dispensing grades, advice, support, and red ink. They believe in the power of feedback to communicate what students are doing well and how they can do better. However, some teachers shy away from opportunities for feedback on their own work. Some don't…

  7. Feedback and the Reconstruction of Meaning.

    ERIC Educational Resources Information Center

    Langer, Philip; And Others

    This investigation of the impact of feedback upon scrambled discourse was intended to show the effects of idiosyncratic processing and to provide a more sensitive indicator of feedback usefulness. Learner schemata, text organization, and feedback strategies interact in processing discourse, although past research has favored limited models…

  8. A Survey of Psychological Assessment Feedback Practices

    ERIC Educational Resources Information Center

    Smith, Steven R.; Wiggins, Chauntel M.; Gorske, Tad T.

    2007-01-01

    There have been no previous studies on how often psychologists conduct feedback and whether they view this practice as a useful component of assessment. To explore psychologists' feedback practices and their perception of the effects of feedback on their clients, the authors examined survey data from 719 psychologist members of the International…

  9. Effective Feedback Design Using Free Technologies

    ERIC Educational Resources Information Center

    Yuan, Jiangmei; Kim, ChanMin

    2015-01-01

    Feedback plays a critical role in student learning and performance. However, providing students with effective feedback is challenging in online environments because of physical separation between students and instructors. Technologies can be used to enhance the effectiveness of feedback in online courses. In this article, we propose effective…

  10. Why Receiving Feedback Collides with Self Determination

    ERIC Educational Resources Information Center

    ten Cate, Olle Th. J.

    2013-01-01

    Providing feedback to trainees in clinical settings is considered important for development and acquisition of skill. Despite recommendations how to provide feedback that have appeared in the literature, research shows that its effectiveness is often disappointing. To understand why receiving feedback is more difficult than it appears, this paper…

  11. The Impact of Feedback Training for Inspectors

    ERIC Educational Resources Information Center

    Dobbelaer, Marjoleine J.; Prins, Frans J.; van Dongen, Dre

    2013-01-01

    Purpose: The purpose of this paper is to explore whether oral feedback by inspectors of the Dutch Inspectorate of Education is an adequate method to support the professional development of teachers in primary education. This study aims to examine the impact of short feedback training for inspectors (focused on effective feedback conversations) on…

  12. Simple Optoelectronic Feedback in Microwave Oscillators

    NASA Technical Reports Server (NTRS)

    Maleki, Lute; Iltchenko, Vladimir

    2009-01-01

    A proposed method of stabilizing microwave and millimeter-wave oscillators calls for the use of feedback in optoelectronic delay lines characterized by high values of the resonance quality factor (Q). The method would extend the applicability of optoelectronic feedback beyond the previously reported class of optoelectronic oscillators that comprise two-port electronic amplifiers in closed loops with high-Q feedback circuits.

  13. The Art of Giving Online Feedback

    ERIC Educational Resources Information Center

    Leibold, Nancyruth; Schwarz, Laura Marie

    2015-01-01

    The cultivation of providing online feedback that is positive, effective, and enhances the learning experience is a valuable educator skill. Acquisition of the art of providing feedback is through education, practice, and faculty development. This article provides information about the best practices for delivering online feedback to learners. An…

  14. Changing Teachers' Feedback Practices: A Workshop Challenge

    ERIC Educational Resources Information Center

    Fonseca, Jesuína; Carvalho, Carolina; Conboy, Joseph; Valente, Maria Odete; Gama, Ana Paula; Salema, Maria Helena; Fiúza, Edite

    2015-01-01

    Feedback can promote teacher-student relations and student academic involvement, performance and self-regulation. However, some research indicates that teachers do not always employ feedback effectively. There is a need to promote teachers' appropriate use of feedback in the classroom. We describe a long-term workshop designed to enhance teachers'…

  15. Feedback Sandwiches Affect Perceptions but Not Performance

    ERIC Educational Resources Information Center

    Parkes, Jay; Abercrombie, Sara; McCarty, Teresita

    2013-01-01

    The feedback sandwich technique-make positive comments; provide critique; end with positive comments-is commonly recommended to feedback givers despite scant evidence of its efficacy. These two studies (N = 20; N = 350) of written peer feedback with third-year medical students on clinical patient note-writing assignments indicate that students…

  16. The Positive Impact of Negative Feedback

    DTIC Science & Technology

    2011-03-01

    supervisors, subordinates, and peers prior to course start. Following the FRLM lesson on day five, students received individual feedback reports based...Additionally, Nowack (2009) identified where managers who received a small amount of unfavorable feedback actually improved their performance...their arrival at Squadron Officer School, students received a web-based 360-degree feedback survey. Once students completed the surveys, identical

  17. Third-Harmonic Envelope Feedback Method for High-Efficiency Linear Power Amplifiers

    NASA Astrophysics Data System (ADS)

    Oshima, Shoichi; Ugajin, Mamoru; Harada, Mitsuru

    A new low-power feedback structure for a power amplifier (PA) reduces signal distortion while keeping the power efficiency of the PA high. The feedback structure injects the envelope of the third-order harmonics into the input signal. In adopting this method for a class-A amplifier, we obtain over 10% higher efficiency while maintaining the same adjacent channel power ratio (ACPR). The power consumption of additional circuit is 200µW.

  18. Ratio imaging instrumentation.

    PubMed

    Dunn, Kenneth; Maxfield, Frederick R

    2003-01-01

    Using ratio imaging to obtain quantitative information from microscope images is a powerful tool that has been used successfully in numerous studies. Although ratio imaging reduces the effects of many parameters that can interfere with accurate measurements, it is not a panacea. In designing a ratio imaging experiment, all of the potential problems discussed in this chapter must be considered. Undoubtedly, other problems that were not discussed can also interfere with accurate and meaningful measurements. Many of the problems discussed here were observed in the authors' laboratories. In our experience there are no standard routines or methods that can foresee every problem before it has been encountered. Good experimental design can minimize problems, but the investigator must continue to be alert. Progress in instrumentation continues to overcome some of the difficulties encountered in ratio imaging. CCD cameras with 12- to 14-bit pixel depth are being used more frequently, and several confocal microscope manufacturers are now also using 12-bit digitization. The dramatic increase in the use of confocal microscopes over the past decade is now causing microscope manufacturers to more critically evaluate the effect of axial chromatic aberration in objectives, and recent designs to minimize this problem are being implemented. Other developments such as the use of AOTFs to attenuate laser lines extend the applicability of ratio imaging. Ratio imaging is clearly applicable to a wide range of cell biological problems beyond its widespread use for measuring ion concentrations. Imaginative but careful use of this technique should continue to provide novel insights into the properties of cells.

  19. Student Feedback Sensitivity and the Efficacy of Feedback Interventions in Public Speaking Performance Improvement

    ERIC Educational Resources Information Center

    Smith, Camille; King, Paul

    2004-01-01

    Although feedback from teachers to students occupies a central role in learning and instruction, the manner in which feedback functions in performance improvement remains unclear. The current study examined how students' sensitivity to feedback and variations in the wording of feedback messages impacted public speaking performance. Results…

  20. The Nature of Feedback: How Different Types of Peer Feedback Affect Writing Performance

    ERIC Educational Resources Information Center

    Nelson, Melissa M.; Schunn, Christian D.

    2009-01-01

    Although providing feedback is commonly practiced in education, there is no general agreement regarding what type of feedback is most helpful and why it is helpful. This study examined the relationship between various types of feedback, potential internal mediators, and the likelihood of implementing feedback. Five main predictions were developed…

  1. Interpreting Feedback: A Discourse Analysis of Teacher Feedback and Student Identity

    ERIC Educational Resources Information Center

    Torres, J. T.; Anguiano, Carlos J.

    2016-01-01

    Feedback has typically been studied as a means of improving academic performance. Few studies inquire into the processes by which feedback shapes student identity. The authors carry out a discourse analysis of written comments to explore how feedback is discursively constructed by both teachers and students. Analysis of written feedback,…

  2. Students' Feedback Preferences: How Do Students React to Timely and Automatically Generated Assessment Feedback?

    ERIC Educational Resources Information Center

    Bayerlein, Leopold

    2014-01-01

    This study assesses whether or not undergraduate and postgraduate accounting students at an Australian university differentiate between timely feedback and extremely timely feedback, and whether or not the replacement of manually written formal assessment feedback with automatically generated feedback influences students' perception of feedback…

  3. Random distributed feedback fibre lasers

    NASA Astrophysics Data System (ADS)

    Turitsyn, Sergei K.; Babin, Sergey A.; Churkin, Dmitry V.; Vatnik, Ilya D.; Nikulin, Maxim; Podivilov, Evgenii V.

    2014-09-01

    The concept of random lasers exploiting multiple scattering of photons in an amplifying disordered medium in order to generate coherent light without a traditional laser resonator has attracted a great deal of attention in recent years. This research area lies at the interface of the fundamental theory of disordered systems and laser science. The idea was originally proposed in the context of astrophysics in the 1960s by V.S. Letokhov, who studied scattering with “negative absorption” of the interstellar molecular clouds. Research on random lasers has since developed into a mature experimental and theoretical field. A simple design of such lasers would be promising for potential applications. However, in traditional random lasers the properties of the output radiation are typically characterized by complex features in the spatial, spectral and time domains, making them less attractive than standard laser systems in terms of practical applications. Recently, an interesting and novel type of one-dimensional random laser that operates in a conventional telecommunication fibre without any pre-designed resonator mirrors-random distributed feedback fibre laser-was demonstrated. The positive feedback required for laser generation in random fibre lasers is provided by the Rayleigh scattering from the inhomogeneities of the refractive index that are naturally present in silica glass. In the proposed laser concept, the randomly backscattered light is amplified through the Raman effect, providing distributed gain over distances up to 100 km. Although an effective reflection due to the Rayleigh scattering is extremely small (˜0.1%), the lasing threshold may be exceeded when a sufficiently large distributed Raman gain is provided. Such a random distributed feedback fibre laser has a number of interesting and attractive features. The fibre waveguide geometry provides transverse confinement, and effectively one-dimensional random distributed feedback leads to the generation

  4. Research on output feedback control

    NASA Technical Reports Server (NTRS)

    Calise, A. J.; Kramer, F. S.

    1985-01-01

    In designing fixed order compensators, an output feedback formulation has been adopted by suitably augmenting the system description to include the compensator states. However, the minimization of the performance index over the range of possible compensator descriptions was impeded due to the nonuniqueness of the compensator transfer function. A controller canonical form of the compensator was chosen to reduce the number of free parameters to its minimal number in the optimization. In the MIMO case, the controller form requires a prespecified set of ascending controllability indices. This constraint on the compensator structure is rather innocuous in relation to the increase in convergence rate of the optimization. Moreover, the controller form is easily relatable to a unique controller transfer function description. This structure of the compensator does not require penalizing the compensator states for a nonzero or coupled solution, a problem that occurs when following a standard output feedback synthesis formulation.

  5. Vehicular Slip Ratio Control Using Nonlinear Control Theory

    NASA Astrophysics Data System (ADS)

    Ikeda, Yuichi; Nakajima, Takashi; Chida, Yuichi

    In this paper, we discuss integrated vehicle slip ratio control under both deceleration and acceleration without the need for controller switching, and also propose a design method for such an integrated slip ratio controller based on the slip ratio dynamics. When a vehicle switches from acceleration to deceleration and vice versa, the slip ratio varies discontinuously. Here, the slip ratio is approximated to a continuous function by using a sigmoid function. And a controller is then designed by using feedback linearization based on the approximated slip ratio. The stability of the designed control system is proven by Lyapunov stability theorem. Furthermore, we propose a robust control method based on a disturbance observer and sliding mode control theory. Finally, the effectiveness of the proposed control method is verified through numerical simulation.

  6. Comparing Simulations of AGN Feedback

    NASA Astrophysics Data System (ADS)

    Richardson, Mark L. A.; Scannapieco, Evan; Devriendt, Julien; Slyz, Adrianne; Thacker, Robert J.; Dubois, Yohan; Wurster, James; Silk, Joseph

    2016-07-01

    We perform adaptive mesh refinement (AMR) and smoothed particle hydrodynamics (SPH) cosmological zoom simulations of a region around a forming galaxy cluster, comparing the ability of the methods to handle successively more complex baryonic physics. In the simplest, non-radiative case, the two methods are in good agreement with each other, but the SPH simulations generate central cores with slightly lower entropies and virial shocks at slightly larger radii, consistent with what has been seen in previous studies. The inclusion of radiative cooling, star formation, and stellar feedback leads to much larger differences between the two methods. Most dramatically, at z=5, rapid cooling in the AMR case moves the accretion shock to well within the virial radius, while this shock remains near the virial radius in the SPH case, due to excess heating, coupled with poorer capturing of the shock width. On the other hand, the addition of feedback from active galactic nuclei (AGNs) to the simulations results in much better agreement between the methods. For our AGN model, both simulations display halo gas entropies of 100 keV cm2, similar decrements in the star formation rate, and a drop in the halo baryon content of roughly 30%. This is consistent with the AGN growth being self-regulated, regardless of the numerical method. However, the simulations with AGN feedback continue to differ in aspects that are not self-regulated, such that in SPH a larger volume of gas is impacted by feedback, and the cluster still has a lower entropy central core.

  7. Physiological Feedback Method and System

    NASA Technical Reports Server (NTRS)

    Pope, Alan T. (Inventor); Severance, Kurt E. (Inventor)

    2002-01-01

    A method and system provide physiological feedback for a patient and/or physician. At least one physiological effect experienced by a body part of a patient is measured noninvasively. A three-dimensional graphics model serving as an analogous representation of the body part is altered in accordance with the measurements. A binocular image signal representative of the three-dimensional graphics model so-altered is displayed for the patient and/or physician in a virtual reality environment.

  8. Rf feedback free electron laser

    DOEpatents

    Brau, C.A.; Swenson, D.A.; Boyd, T.J. Jr.

    1979-11-02

    A free electron laser system and electron beam system for a free electron laser are provided which use rf feedback to enhance efficiency. Rf energy is extracted from an electron beam by decelerating cavities and returned to accelerating cavities using rf returns such as rf waveguides, rf feedthroughs, etc. This rf energy is added to rf klystron energy to lower the required input energy and thereby enhance energy efficiency of the system.

  9. Rf Feedback free electron laser

    DOEpatents

    Brau, Charles A.; Swenson, Donald A.; Boyd, Jr., Thomas J.

    1981-01-01

    A free electron laser system and electron beam system for a free electron laser which use rf feedback to enhance efficiency. Rf energy is extracted from an electron beam by decelerating cavities and returned to accelerating cavities using rf returns such as rf waveguides, rf feedthroughs, etc. This rf energy is added to rf klystron energy to lower the required input energy and thereby enhance energy efficiency of the system.

  10. Probabilistic models for feedback systems.

    SciTech Connect

    Grace, Matthew D.; Boggs, Paul T.

    2011-02-01

    In previous work, we developed a Bayesian-based methodology to analyze the reliability of hierarchical systems. The output of the procedure is a statistical distribution of the reliability, thus allowing many questions to be answered. The principal advantage of the approach is that along with an estimate of the reliability, we also can provide statements of confidence in the results. The model is quite general in that it allows general representations of all of the distributions involved, it incorporates prior knowledge into the models, it allows errors in the 'engineered' nodes of a system to be determined by the data, and leads to the ability to determine optimal testing strategies. In this report, we provide the preliminary steps necessary to extend this approach to systems with feedback. Feedback is an essential component of 'complexity' and provides interesting challenges in modeling the time-dependent action of a feedback loop. We provide a mechanism for doing this and analyze a simple case. We then consider some extensions to more interesting examples with local control affecting the entire system. Finally, a discussion of the status of the research is also included.

  11. Evapotranspiration—Flooding Feedback in Forested Wetlands

    NASA Astrophysics Data System (ADS)

    Allen, S. T.; Keim, R.

    2015-12-01

    Evapotranspiration (ET) is a principle efflux from flooded swamps. However, for many reasons (e.g., difficulties in measuring across small gradients), controls over ET in wetlands, and swamps particularly, remain unclear. We investigate how the interaction of vegetation and hydrology controls ET and energy partitioning in flooded forests in three different hydrologic landscapes of the southeastern USA: mesohaline coastal shrub forest, floodplain hardwood forest, and backswamp baldcypress-tupelo forest. Energy components were measured by eddy covariance, sapflow, Bowen ratio energy balance, and evaporation pan to partition canopy transpiration, understory transpiration, and evaporation from floodwaters. Together, we found the energy balances of forested wetlands often differed from that of terrestrial systems, because of the potentially substantial role of evaporation from the free water surface, and flood / salinity stress inhibiting transpiration. Highest ET rates were observed in the coastal shrub forest in flooded conditions, when saline water levels dropped below the root zone (on hummocks) with concurrent lateral advection of dry air. The other two sites behaved similar to terrestrial systems, with increasing transpiration during periosd of greater water availability, although with radiation transmitted to the understory mostly partitioned to latent heat which partially compensated for the variability in canopy transpiration. Identifying these differential controls over ET is critical to understanding long-term trajectory of these systems. Many wetlands of the southeastern US have been impounded and disconnected, necessitating some degree of balance between ET and precipitation for sustainability. The positive feedbacks between ET and water levels in the coastal system suggest lower ecosystem resilience than the other two systems that showed negative feedbacks between ET and water levels.

  12. Climate Change and the Permafrost Carbon Feedback

    NASA Astrophysics Data System (ADS)

    Schuur, E. A. G.; McGuire, A. D.; Grosse, G.; Harden, J. W.; Hayes, D. J.; Hugelius, G.; Koven, C. D.; Kuhry, P.; Lawrence, D. M.; Natali, S.; Olefeldt, D.; Romanovsky, V. E.; Schaedel, C.; Schaefer, K. M.; Turetsky, M. R.; Treat, C. C.; Vonk, J.

    2014-12-01

    Approximately twice as much soil carbon is stored in the northern circumpolar permafrost zone than is currently contained in the atmosphere. Permafrost thaw, and the microbial decomposition of previously frozen organic carbon, is considered one of the most likely positive feedbacks from terrestrial ecosystems to the atmosphere in a warmer world. Yet, the rate and form of release is highly uncertain but crucial for predicting the strength and timing of this carbon cycle feedback this century and beyond. New insight brought together under a multi-year synthesis effort by the Permafrost Carbon Network helps constrain current understanding of the permafrost carbon feedback to climate, and provides a framework for newly developing research initiatives in this region. A newly enlarged soil carbon database continues to verify the widespread pattern of large quantities of carbon accumulated deep in permafrost soils. The known pool of permafrost carbon is now estimated to be 1330-1580 Pg C, with the potential for ~400 Pg C in deep permafrost sediments that remain largely unquantified. Laboratory incubations of these permafrost soils reveal that a significant fraction of this material can be mineralized by microbes and converted to CO2 and CH4 on time scales of years to decades, with decade-long average losses from aerobic incubations ranging from 6-34% of initial carbon. Variation in loss rates is depended on the carbon to nitrogen ratio, with higher values leading to more proportional loss. Model scenarios show potential C release from the permafrost zone ranging from 37-174 Pg C by 2100 under the current climate warming trajectory (RCP 8.5), with an average across models of 92±17 Pg C. Furthermore, thawing permafrost C is forecasted to impact global climate for centuries, with models, on average, estimating 59% of total C emissions after 2100. Taken together, greenhouse gas emissions from warming permafrost appear likely to occur at a magnitude similar to other

  13. Realizing actual feedback control of complex network

    NASA Astrophysics Data System (ADS)

    Tu, Chengyi; Cheng, Yuhua

    2014-06-01

    In this paper, we present the concept of feedbackability and how to identify the Minimum Feedbackability Set of an arbitrary complex directed network. Furthermore, we design an estimator and a feedback controller accessing one MFS to realize actual feedback control, i.e. control the system to our desired state according to the estimated system internal state from the output of estimator. Last but not least, we perform numerical simulations of a small linear time-invariant dynamics network and a real simple food network to verify the theoretical results. The framework presented here could make an arbitrary complex directed network realize actual feedback control and deepen our understanding of complex systems.

  14. Digit ratio in birds.

    PubMed

    Lombardo, Michael P; Thorpe, Patrick A; Brown, Barbara M; Sian, Katie

    2008-12-01

    The Homeobox (Hox) genes direct the development of tetrapod digits. The expression of Hox genes may be influenced by endogenous sex steroids during development. Manning (Digit ratio. New Brunswick, NJ: Rutgers University Press, 2002) predicted that the ratio between the lengths of digits 2 (2D) and 4 (4D) should be sexually dimorphic because prenatal exposure to estrogens and androgens positively influence the lengths of 2D and 4D, respectively. We measured digits and other morphological traits of birds from three orders (Passeriformes, house sparrow, Passer domesticus; tree swallow, Tachycineta bicolor; Pscittaciformes, budgerigar, Melopsittacus undulates; Galliformes, chicken, Gallus domesticus) to test this prediction. None were sexually dimorphic for 2D:4D and there were no associations between 2D:4D and other sexually dimorphic traits. When we pooled data from all four species after we averaged right and left side digits from each individual and z-transformed the resulting digit ratios, we found that males had significantly larger 2D:4D than did females. Tetrapods appear to be sexually dimorphic for 2D:4D with 2D:4D larger in males as in some birds and reptiles and 2D:4D smaller in males as in some mammals. The differences between the reptile and mammal lineages in the directionality of 2D:4D may be related to the differences between them in chromosomal sex determination. We suggest that (a) natural selection for a perching foot in the first birds may have overridden the effects of hormones on the development of digit ratio in this group of vertebrates and (b) caution be used in making inferences about prenatal exposure to hormones and digit ratio in birds.

  15. Feedback control and output feedback control for the stabilisation of switched Boolean networks

    NASA Astrophysics Data System (ADS)

    Li, Fangfei; Yu, Zhaoxu

    2016-02-01

    This paper presents the feedback control and output feedback control for the stabilisation of switched Boolean network. A necessary condition for the existence of a state feedback controller for the stabilisation of switched Boolean networks under arbitrary switching signal is derived first, and constructive procedures for feedback control and output feedback control design are provided. An example is introduced to show the effectiveness of this paper.

  16. The feedback-related negativity is modulated by feedback probability in observational learning.

    PubMed

    Kobza, Stefan; Thoma, Patrizia; Daum, Irene; Bellebaum, Christian

    2011-12-01

    The feedback-related negativity (FRN), an event-related potentials (ERPs) component reflecting activity of the anterior cingulate cortex (ACC), has been shown to be modulated by feedback expectancy following active choices in feedback-based learning tasks. A general reduction of FRN amplitude has been described in observational feedback learning, raising the question whether FRN amplitude is modulated in a similar way in this type of learning. The present study investigated whether the FRN and the P300 - a second ERP component related to feedback processing - are modulated by feedback probability in observational learning. Thirty-two subjects participated in the experiment. They observed a virtual person choosing between two symbols and receiving positive or negative feedback. Learning about stimulus-specific feedback probabilities was assessed in active test trials without feedback. In addition, the bias to learn from positive or negative feedback and - in a subsample of 17 subjects - empathy scores were obtained. General FRN and P300 modulations by feedback probability were found across all subjects. Only for the FRN in learners, an interaction between probability and valence was observed. Larger FRN amplitudes for negative relative to positive feedback only emerged for the lowest outcome probability. The results show that feedback expectancy modulates FRN amplitude also in observational learning, suggesting a similar ACC function as in active learning. On the other hand, the modulation is only seen for very low feedback expectancy, which suggests that brain regions other than those of the reward system contribute to feedback processing in an observation setting.

  17. Multi-ratio transmission

    SciTech Connect

    Polak, J.C.

    1987-07-14

    A preselected multi-ratio power transmission is described comprising: input means for transmitting drive forces; output means; first, second and third friction clutch means each selectively engageable with the input means for accepting drive forces. First input gear means drivingly connects with the first friction clutch means; second input gear means drivingly connects with the second friction clutch means; third input gear means drivingly connects with the third clutch means; first output gear means drivingly connects with the first input gear means; second output gear means drivingly connects with the first and second input gear means; third output means drivingly connects between the third input gear means and the output means; and one double-acting synchronizer clutch for selectively engaging the first output gear means with the output means and alternately the second output gear means with the output means. The first friction clutch means and the one double-acting synchronizer clutch cooperates during engagement to establish two forward drive ratios between the input and output means. The second friction clutch means and the one double-acting synchronizer clutch cooperates during engagement to establish two other forward drive ratios between the input and output means. The third friction clutch means is engageable to provide another forward drive ratio between the input means and the output means; and the one double-acting synchronizer clutch is relieved of transmitting drive forces during the engagement of the third friction clutch means and being manipulable for alternate connection with either the first output gear or the second output gear while the third friction clutch means is engaged.

  18. Membrane tension feedback on shape and motility of eukaryotic cells

    NASA Astrophysics Data System (ADS)

    Winkler, Benjamin; Aranson, Igor S.; Ziebert, Falko

    2016-04-01

    In the framework of a phase field model of a single cell crawling on a substrate, we investigate how the properties of the cell membrane affect the shape and motility of the cell. Since the membrane influences the cell dynamics on multiple levels and provides a nontrivial feedback, we consider the following fundamental interactions: (i) the reduction of the actin polymerization rate by membrane tension; (ii) area conservation of the cell's two-dimensional cross-section vs. conservation of the circumference (i.e. membrane inextensibility); and (iii) the contribution from the membrane's bending energy to the shape and integrity of the cell. As in experiments, we investigate two pertinent observables - the cell's velocity and its aspect ratio. We find that the most important effect is the feedback of membrane tension on the actin polymerization. Bending rigidity has only minor effects, visible mostly in dynamic reshaping events, as exemplified by collisions of the cell with an obstacle.

  19. Self-controlled feedback: does it enhance learning because performers get feedback when they need it?

    PubMed

    Chiviacowsky, Suzete; Wulf, Gabriele

    2002-12-01

    This paper examines whether self-controlled feedback schedules enhance learning, because they are more tailored to the performers' needs than externally controlled feedback schedules. Participants practiced a sequential timing task. One group of learners (self-control) was provided with feedback whenever they requested it, whereas another group (yoked) had no influence on the feedback schedule. The self-control group showed learning benefits on a delayed transfer test. Questionnaire results revealed that self-control learners asked for feedback primarily after good trials and yoked learners preferred to receive feedback after good trials. Analyses demonstrated that errors were lower on feedback than no-feedback trials for the self-control group but not for the yoked group. Thus, self-control participants appeared to use a strategy for requesting feedback. This might explain learning advantages of self-controlled practice.

  20. Measuring Feedback in Nearby AGN

    NASA Astrophysics Data System (ADS)

    Crenshaw, D. M.; Fischer, T. C.; Kraemer, S. B.; Schmitt, H. R.; Turner, T. J.

    2012-08-01

    We investigate the impact of feedback from outflowing UV and X-ray absorbers in nearby (z < 0.04) AGN. From studies of the kinematics, physical conditions, and variability of the absorbers in the literature, we calculate the possible ranges in total mass outflow rate (Ṁout) and kinetic luminosity (LK) for each AGN, summed over all of the absorbers. These calculations make use of values (or limits) for the radial locations of the absorbers determined from variability, excited-state absorption, or other considerations. From a sample of 10 Seyfert 1 galaxies with detailed photoionization models for their absorbers, we find that 7 have sufficient constraints on the absorber locations to determine Ṁout and LK. The 6 Seyfert 1s with moderate bolometric luminosities (Lbol = 1043 - 1045 ergs s-1) all have mass outflow rates that are 10 - 1000 times the mass accretion rates needed to generate their observed luminosities, indicating that most of the mass outflow originates from outside the inner accretion disk. Three of these (NGC 4051, NGC 3516, and NGC 3783) have LK in the range 0.5 - 5% Lbol, which is the range typically required by feedback models for efficient self-regulation of black-hole and galactic bulge growth. The other three (NGC 5548, NGC 4151, and NGC 7469) have LK > 0.1%Lbol, although these values may increase if radial locations can be determined for more of the absorbers. We conclude that the outflowing UV and X-ray absorbers in moderate-luminosity AGN have the potential to deliver significant feedback to their environments.

  1. Perceptual Learning Solely Induced by Feedback

    PubMed Central

    Choi, Hoon; Watanabe, Takeo

    2012-01-01

    Although feedback is considered to be an important factor in perceptual learning (PL), its role is normally considered limited to facilitation, rather than direct inducement, of PL. Recent studies, however, have suggested feedback to be more actively involved in the inducement of PL. The current study demonstrates an even more significant role for feedback in PL: feedback can evoke PL of a feature without any bottom-up processing of that feature. We use a “fake feedback” method, in which the feedback is related to an arbitrarily chosen feature, rather than actual performance. We find evidence of PL with this fake feedback method both when the learned feature is absent from the visual stimulus (Experiment 1) and when it conflicts with the visual stimulus (Experiment 2). We call this “feedback-based PL,” in contrast with the classical “exposure-based PL.” We find that feedback-based PL and exposure-based PL can occur independently of each other even while occurring in the same paradigm. These results suggest that feedback not only facilitates PL that is evoked by bottom-up information, but that it can directly induce PL, where such feedback-based PL occurs independently of exposure-based PL. PMID:22269189

  2. Improving Feedback with Modern Technology

    NASA Astrophysics Data System (ADS)

    Lee, K. M.; Siedell, C. M.

    2004-12-01

    The teaching of introductory astronomy has undergone a transformation over the last few years due to advancements in technology. The developments make large amounts of feedback available to both student and instructor regarding student understanding of the material. This presentation will look at two components of that evolution -- peer instruction and web-based assessment -- and show how technology is continuing to make ever greater strides by increasing the sophistication of the prompts to which students react. Demonstration of FLASH animations from the ClassAction Project and the Nebraska Astronomy Applet Project will be used to illustrate these ideas. This work is funded by National Science Foundation grants #0231270 and #0404988.

  3. Adaptive-feedback control algorithm.

    PubMed

    Huang, Debin

    2006-06-01

    This paper is motivated by giving the detailed proofs and some interesting remarks on the results the author obtained in a series of papers [Phys. Rev. Lett. 93, 214101 (2004); Phys. Rev. E 71, 037203 (2005); 69, 067201 (2004)], where an adaptive-feedback algorithm was proposed to effectively stabilize and synchronize chaotic systems. This note proves in detail the strictness of this algorithm from the viewpoint of mathematics, and gives some interesting remarks for its potential applications to chaos control & synchronization. In addition, a significant comment on synchronization-based parameter estimation is given, which shows some techniques proposed in literature less strict and ineffective in some cases.

  4. Visual feedback in stuttering therapy

    NASA Astrophysics Data System (ADS)

    Smolka, Elzbieta

    1997-02-01

    The aim of this paper is to present the results concerning the influence of visual echo and reverberation on the speech process of stutterers. Visual stimuli along with the influence of acoustic and visual-acoustic stimuli have been compared. Following this the methods of implementing visual feedback with the aid of electroluminescent diodes directed by speech signals have been presented. The concept of a computerized visual echo based on the acoustic recognition of Polish syllabic vowels has been also presented. All the research nd trials carried out at our center, aside from cognitive aims, generally aim at the development of new speech correctors to be utilized in stuttering therapy.

  5. Feedback enhanced plasma spray tool

    DOEpatents

    Gevelber, Michael Alan; Wroblewski, Donald Edward; Fincke, James Russell; Swank, William David; Haggard, Delon C.; Bewley, Randy Lee

    2005-11-22

    An improved automatic feedback control scheme enhances plasma spraying of powdered material through reduction of process variability and providing better ability to engineer coating structure. The present inventors discovered that controlling centroid position of the spatial distribution along with other output parameters, such as particle temperature, particle velocity, and molten mass flux rate, vastly increases control over the sprayed coating structure, including vertical and horizontal cracks, voids, and porosity. It also allows improved control over graded layers or compositionally varying layers of material, reduces variations, including variation in coating thickness, and allows increasing deposition rate. Various measurement and system control schemes are provided.

  6. The impact of mechanical AGN feedback on the formation of massive early-type galaxies

    NASA Astrophysics Data System (ADS)

    Choi, Ena; Ostriker, Jeremiah P.; Naab, Thorsten; Oser, Ludwig; Moster, Benjamin P.

    2015-06-01

    We employ cosmological hydrodynamical simulations to investigate the effects of AGN feedback on the formation of massive galaxies with present-day stellar masses of M_stel= 8.8 × 10^{10}-6.0 × 10^{11} M_{⊙}. Using smoothed particle hydrodynamics simulations with a pressure-entropy formulation that allows an improved treatment of contact discontinuities and fluid mixing, we run three sets of simulations of 20 haloes with different AGN feedback models: (1) no feedback, (2) thermal feedback, and (3) mechanical and radiation feedback. We assume that seed black holes are present at early cosmic epochs at the centre of emerging dark matter haloes and trace their mass growth via gas accretion and mergers with other black holes. Both feedback models successfully recover the observed MBH-σ relation and black hole-to-stellar mass ratio for simulated central early-type galaxies. The baryonic conversion efficiencies are reduced by a factor of 2 compared to models without any AGN feedback at all halo masses. However, massive galaxies simulated with thermal AGN feedback show a factor of ˜10-100 higher X-ray luminosities than observed. The mechanical/radiation feedback model reproduces the observed correlation between X-ray luminosities and velocity dispersion, e.g. for galaxies with σ = 200 km s- 1, the X-ray luminosity is reduced from 1042 erg s- 1 to 1040 erg s- 1. It also efficiently suppresses late-time star formation, reducing the specific star formation rate from 10-10.5 yr- 1 to 10-14 yr- 1 on average and resulting in quiescent galaxies since z = 2, whereas the thermal feedback model shows higher late-time in situ star formation rates than observed.

  7. Generative model for feedback networks

    NASA Astrophysics Data System (ADS)

    White, Douglas R.; Kejžar, Nataša; Tsallis, Constantino; Farmer, Doyne; White, Scott

    2006-01-01

    We propose a model for network formation and study some of its statistical properties. The motivation for the model comes from the growth of several kinds of real networks (i.e., kinship and trading networks, networks of corporate alliances, networks of autocatalytic chemical reactions). These networks grow either by establishing closer connections by adding links in the existing network or by adding new nodes. A node in these networks lacks the information of the entire network. In order to establish a closer connection to other nodes it starts a search in the neighboring part of the network and waits for a possible feedback from a distant node that received the “searching signal.” Our model imitates this behavior by growing the network via the addition of a link that creates a cycle in the network or via the addition of a new node with a link to the network. The forming of a cycle creates feedback between the two ending nodes. After choosing a starting node, a search is made for another node at a suitable distance; if such a node is found, a link is established between this and the starting node, otherwise (such a node cannot be found) a new node is added and is linked to the starting node. We simulate this algorithm and find that we cannot reject the hypothesis that the empirical degree distribution is a q -exponential function, which has been used to model long-range processes in nonequilibrium statistical mechanics.

  8. RF power recovery feedback circulator

    DOEpatents

    Sharamentov, Sergey I [Bolingbrook, IL

    2011-03-29

    A device and method for improving the efficiency of RF systems having a Reflective Load. In the preferred embodiment, Reflected Energy from a superconducting resonator of a particle accelerator is reintroduced to the resonator after the phase of the Reflected Energy is aligned with the phase of the Supply Energy from a RF Energy Source. In one embodiment, a Circulator is used to transfer Reflected Energy from the Reflective Load into a Phase Adjuster which aligns the phase of the Reflected Energy with that of the Supply Energy. The phase-aligned energy is then combined with the Supply Energy, and reintroduced into the Reflective Load. In systems having a constant phase shift, the Phase Adjuster may be designed to shift the phase of the Reflected Energy by a constant amount using a Phase Shifter. In systems having a variety (variable) phase shifts, a Phase Shifter controlled by a phase feedback loop comprising a Phase Detector and a Feedback Controller to account for the various phase shifts is preferable.

  9. Reducing the uncertainty in subtropical cloud feedback

    NASA Astrophysics Data System (ADS)

    Myers, Timothy A.; Norris, Joel R.

    2016-03-01

    Large uncertainty remains on how subtropical clouds will respond to anthropogenic climate change and therefore whether they will act as a positive feedback that amplifies global warming or negative feedback that dampens global warming by altering Earth's energy budget. Here we reduce this uncertainty using an observationally constrained formulation of the response of subtropical clouds to greenhouse forcing. The observed interannual sensitivity of cloud solar reflection to varying meteorological conditions suggests that increasing sea surface temperature and atmospheric stability in the future climate will have largely canceling effects on subtropical cloudiness, overall leading to a weak positive shortwave cloud feedback (0.4 ± 0.9 W m-2 K-1). The uncertainty of this observationally based approximation of the cloud feedback is narrower than the intermodel spread of the feedback produced by climate models. Subtropical cloud changes will therefore complement positive cloud feedbacks identified by previous work, suggesting that future global cloud changes will amplify global warming.

  10. Fuzzy cloud concepts for assessing radiation feedbacks

    SciTech Connect

    Hanson, H.

    1995-09-01

    The importance of clouds in the climate system is well-known but poorly understood. Modeling and observational studies have suggested that there may be positive feedbacks associated with certain cloud processes, but it is not known how strong these feedbacks are in the context of the overall system. Examples include ice microphysics feedback, as shown by Liou`s model, and the relationship between SST and cloud cover in the tropics, which is the focus of this research. 2 refs., 3 figs.

  11. Tactile feedback improves auditory spatial localization.

    PubMed

    Gori, Monica; Vercillo, Tiziana; Sandini, Giulio; Burr, David

    2014-01-01

    Our recent studies suggest that congenitally blind adults have severely impaired thresholds in an auditory spatial bisection task, pointing to the importance of vision in constructing complex auditory spatial maps (Gori et al., 2014). To explore strategies that may improve the auditory spatial sense in visually impaired people, we investigated the impact of tactile feedback on spatial auditory localization in 48 blindfolded sighted subjects. We measured auditory spatial bisection thresholds before and after training, either with tactile feedback, verbal feedback, or no feedback. Audio thresholds were first measured with a spatial bisection task: subjects judged whether the second sound of a three sound sequence was spatially closer to the first or the third sound. The tactile feedback group underwent two audio-tactile feedback sessions of 100 trials, where each auditory trial was followed by the same spatial sequence played on the subject's forearm; auditory spatial bisection thresholds were evaluated after each session. In the verbal feedback condition, the positions of the sounds were verbally reported to the subject after each feedback trial. The no feedback group did the same sequence of trials, with no feedback. Performance improved significantly only after audio-tactile feedback. The results suggest that direct tactile feedback interacts with the auditory spatial localization system, possibly by a process of cross-sensory recalibration. Control tests with the subject rotated suggested that this effect occurs only when the tactile and acoustic sequences are spatially congruent. Our results suggest that the tactile system can be used to recalibrate the auditory sense of space. These results encourage the possibility of designing rehabilitation programs to help blind persons establish a robust auditory sense of space, through training with the tactile modality.

  12. Representation of feedback operators for hyperbolic systems

    NASA Technical Reports Server (NTRS)

    Burns, John A.; King, Belinda B.

    1995-01-01

    We consider the problem of obtaining integral representation of feedback operators for damped hyperbolic control systems. We show that for the wave equation with Kelvin-Voigt damping and non-compact input operator, the feedback gain operator is Hilbert-Schmidt. This result is then used to provide an explicit integral representation for the feedback operator in terms of functional gains. Numerical results are given to illustrate the role that damping plays in the smoothness of these gains.

  13. [Complex biotechnical feedback in electrostimulation systems].

    PubMed

    Osipov, A N; Dik, S K; Senkovskiĭ, K G

    2002-01-01

    Basic principles in design of electrostimulating equipment with complex biotechnical coupling combining biotechnical feedback and biological feedback are formulated. Realization of these principles in one system leads to qualitatively new capacities of enhancing the efficiency of implemented rehabilitative measures, which is the basis of the designed multichannel electromyostimulation device MYOS having a complex biotechnical feedback, which is used to treat a number of central and peripheral motor disorders (paralyses, pareses), to correct movements, to learn motor skills during training, etc.

  14. Studies Of Positive-Position-Feedback Control

    NASA Technical Reports Server (NTRS)

    Fanson, James L.; Caughey, Thomas K.

    1992-01-01

    Report discusses theoretical and experimental studies of positive-position-feedback control for suppressing vibrations in large flexible structures. Positive-position-feedback control involves placement of actuators and sensors on structure; control voltages applied to actuators in response to outputs of sensors processed via compensator algorithm. Experiments demonstrate feasibility of suppressing vibrations by positive position feedback, and spillover of vibrational energy into uncontrolled modes has stabilizing effect if control gain sufficiently small.

  15. Feedback power control strategies in wireless sensor networks with joint channel decoding.

    PubMed

    Abrardo, Andrea; Ferrari, Gianluigi; Martalò, Marco; Perna, Fabio

    2009-01-01

    In this paper, we derive feedback power control strategies for block-faded multiple access schemes with correlated sources and joint channel decoding (JCD). In particular, upon the derivation of the feasible signal-to-noise ratio (SNR) region for the considered multiple access schemes, i.e., the multidimensional SNR region where error-free communications are, in principle, possible, two feedback power control strategies are proposed: (i) a classical feedback power control strategy, which aims at equalizing all link SNRs at the access point (AP), and (ii) an innovative optimized feedback power control strategy, which tries to make the network operational point fall in the feasible SNR region at the lowest overall transmit energy consumption. These strategies will be referred to as "balanced SNR" and "unbalanced SNR," respectively. While they require, in principle, an unlimited power control range at the sources, we also propose practical versions with a limited power control range. We preliminary consider a scenario with orthogonal links and ideal feedback. Then, we analyze the robustness of the proposed power control strategies to possible non-idealities, in terms of residual multiple access interference and noisy feedback channels. Finally, we successfully apply the proposed feedback power control strategies to a limiting case of the class of considered multiple access schemes, namely a central estimating officer (CEO) scenario, where the sensors observe noisy versions of a common binary information sequence and the AP's goal is to estimate this sequence by properly fusing the soft-output information output by the JCD algorithm.

  16. Constraints on the Longwave Cloud Altitude Feedback

    NASA Astrophysics Data System (ADS)

    Zelinka, M. D.; Klein, S. A.

    2011-12-01

    Cloud feedback represents the source of largest spread among global climate model projections of future climate change. Though most studies to date have focused on the large spread in cloud feedback that arises from disparate responses of subtropical low clouds, we show using a new technique for quantifying the contribution to cloud feedback from individual cloud types that a significant spread exists in the response of high clouds, with implications for both longwave and shortwave feedbacks. In this talk, we focus on the inter-model spread in longwave altitude feedback, defined as the impact on top of atmosphere longwave fluxes due solely to changes in the vertical distribution of clouds, holding both the total amount and the optical depth distribution fixed. Among the ten models analyzed, this feedback varies from 0.06 to 0.80 W m-2 K-1. We show that the magnitude of this feedback is dependent on two key variables: the effective high cloud amount in the control climate and the change in mean cloud top pressure under doubling of CO2. The latter component is governed by the degree to which the troposphere deepens under doubling of CO2, suggesting an inverse relationship with the lapse rate feedback. To the extent that realistic bounds can be placed on effective high cloud amount using observations, the range of plausible longwave cloud altitude feedback magnitudes can be further reduced.

  17. Wingful, an extracellular feedback inhibitor of Wingless

    PubMed Central

    Gerlitz, Offer; Basler, Konrad

    2002-01-01

    Secreted peptide signals control many fundamental processes during animal development. Proper responses to these signals require cognate inducible feedback antagonists. Here we report the identification of a novel Drosophila Wingless (Wg) target gene, wingful (wf), and show that it encodes a potent extracellular feedback inhibitor of Wg. In contrast to the cytoplasmic protein Naked cuticle (Nkd), the only known Wg feedback antagonist, Wf functions during larval stages, when Nkd function is dispensable. We propose that Wf may provide feedback control for the long-range morphogen activities of Wg. PMID:12000788

  18. Peak power ratio generator

    DOEpatents

    Moyer, R.D.

    A peak power ratio generator is described for measuring, in combination with a conventional power meter, the peak power level of extremely narrow pulses in the gigahertz radio frequency bands. The present invention in a preferred embodiment utilizes a tunnel diode and a back diode combination in a detector circuit as the only high speed elements. The high speed tunnel diode provides a bistable signal and serves as a memory device of the input pulses for the remaining, slower components. A hybrid digital and analog loop maintains the peak power level of a reference channel at a known amount. Thus, by measuring the average power levels of the reference signal and the source signal, the peak power level of the source signal can be determined.

  19. Peak power ratio generator

    DOEpatents

    Moyer, Robert D.

    1985-01-01

    A peak power ratio generator is described for measuring, in combination with a conventional power meter, the peak power level of extremely narrow pulses in the gigahertz radio frequency bands. The present invention in a preferred embodiment utilizes a tunnel diode and a back diode combination in a detector circuit as the only high speed elements. The high speed tunnel diode provides a bistable signal and serves as a memory device of the input pulses for the remaining, slower components. A hybrid digital and analog loop maintains the peak power level of a reference channel at a known amount. Thus, by measuring the average power levels of the reference signal and the source signal, the peak power level of the source signal can be determined.

  20. Biological Feedbacks in Global Desertification

    NASA Astrophysics Data System (ADS)

    Schlesinger, William H.; Reynolds, James F.; Cunningham, Gary L.; Huenneke, Laura F.; Jarrell, Wesley M.; Virginia, Ross A.; Whitford, Walter G.

    1990-03-01

    Studies of ecosystem processes on the Jornada Experimental Range in southern New Mexico suggest that long-term grazing of semiarid grasslands leads to an increase in the spatial and temporal heterogeneity of water, nitrogen, and other soil resources. Heterogeneity of soil resources promotes invasion by desert shrubs, which leads to a further localization of soil resources under shrub canopies. In the barren area between shrubs, soil fertility is lost by erosion and gaseous emissions. This positive feedback leads to the desertification of formerly productive land in southern New Mexico and in other regions, such as the Sahel. Future desertification is likely to be exacerbated by global climate warming and to cause significant changes in global biogeochemical cycles.

  1. Biological feedbacks in global desertification.

    PubMed

    Schlesinger, W H; Reynolds, J F; Cunningham, G L; Huenneke, L F; Jarrell, W M; Virginia, R A; Whitford, W G

    1990-03-02

    Studies of ecosystem processes on the Jornada Experimental Range in southern New Mexico suggest that longterm grazing of semiarid grasslands leads to an increase in the spatial and temporal heterogeneity of water, nitrogen, and other soil resources. Heterogeneity of soil resources promotes invasion by desert shrubs, which leads to a further localization of soil resources under shrub canopies. In the barren area between shrubs, soil fertility is lost by erosion and gaseous emissions. This positive feedback leads to the desertification of formerly productive land in southern New Mexico and in other regions, such as the Sahel. Future desertification is likely to be exacerbated by global climate warming and to cause significant changes in global biogeochemical cycles.

  2. Control and diagnostic uses of feedback

    SciTech Connect

    Sen, A. K.

    2000-05-01

    Recent results on multimode feedback control of magnetohydrodynamic (MHD) modes and a variety of diagnostic uses of feedback are summarized. First, is the report on reduction and scaling of transport under feedback. By controlling the fluctuation amplitudes and consequently the transport via feedback, it is found that the scaling of the diffusion coefficient is linear with root-mean-square rms fluctuation level. The scaling appears not to agree with any generic theory. A variety of other diagnostic uses of feedback have been developed. The primary goal is an experimental methodology for the determination of dynamic models of plasma turbulence, both for better transport understanding and more credible feedback controller designs. A specific motivation is to search for a low-order dynamic model, suitable for the convenient study of both transport and feedback. First, the time series analysis method is used for the determination of chaotic attractor dimension of plasma fluctuations. For ExB rotational flute modes it is found to be close to three, indicating that a low-order dynamic model may be adequate for transport prediction and feedback controller design. Second, a new method for direct experimental determination of nonlinear dynamical models of plasma turbulence using feedback has been developed. Specifically, the process begins with a standard three-wave coupling model and introduces a variable feedback gain. The power spectrum, delayed power spectrum, and bispectrum of fluctuations are then experimentally obtained. By varying the feedback gain continuously, an arbitrary number of numerical equations for a fixed number of unknowns can be generated. Their numerical solution yields the linear dispersion, as well as nonlinear coupling coefficients. This method has been successfully applied for ExB rotationally driven flute modes. (c) 2000 American Institute of Physics.

  3. Multimedia Feedback Systems for Engineering

    SciTech Connect

    Gladwell, S.; Gottlieb, E.J.; McDonald, M.J.; Slutter, C.L.

    1998-12-15

    The World Wide Web has become a key tool for information sharing. Engineers and scientists are finding that the web is especially suited to publishing the graphical, multi-layered information that is typical of their work. Web pages are easier to distribute than hardcopy. Web movies have become more accessible, in many offices, than videos. Good VRML viewing software, bundled with most new PCs, has sufficient power to support many engineering needs. In addition to publishing information science and engineering has an important tradition of peer and customer review. Reports, drawings and graphs are typically printed, distributed, reviewed, marked up, and returned to the author. Adding review comments to paper is easy. When, however, the information is in electronic form, this ease of review goes away. It's hard to write on videos. It's even harder to write comments on animated 3D models. These feedback limitations reduce the value of the information overall. Fortunately, the web can also be a useful tool for collecting peer and customer review information. When properly formed, web reports, movies, and 3D animations can be readily linked to review notes. This paper describes three multimedia feed-back systems that Sandia National Laboratories has developed to tap that potential. Each system allows people to make context-sensitive comments about specific web content and electronically ties the comments back to the web content being referenced. The fuel system ties comments to specific web pages, the second system ties the comments to specific frames of digital movies, and the third ties the comments to specific times and viewpoints within 3D animations. In addition to the technologies, this paper describes how they are being used to support intelligent machine systems design at Sandia.

  4. Relative Effects of Daily Feedback and Weekly Feedback on Customer Service Behavior at a Gas Station

    ERIC Educational Resources Information Center

    So, Yongjoon; Lee, Kyehoon; Oah, Shezeen

    2013-01-01

    The relative effects of daily and weekly feedback on customer service behavior at a gas station were assessed using an ABC within-subjects design. Four critical service behaviors were identified and measured daily. After baseline (A), weekly feedback (B) was introduced, and daily feedback (C) was introduced in the next phase. The results indicated…

  5. Effects of Feedback Timing on Second Language Vocabulary Learning: Does Delaying Feedback Increase Learning?

    ERIC Educational Resources Information Center

    Nakata, Tatsuya

    2015-01-01

    Feedback, or information given to learners regarding their performance, is found to facilitate second language (L2) learning. Research also suggests that the timing of feedback (whether it is provided immediately or after a delay) may affect learning. The purpose of the present study was to identify the optimal feedback timing for L2 vocabulary…

  6. Explanation Feedback Is Better than Correct Answer Feedback for Promoting Transfer of Learning

    ERIC Educational Resources Information Center

    Butler, Andrew C.; Godbole, Namrata; Marsh, Elizabeth J.

    2013-01-01

    Among the many factors that influence the efficacy of feedback on learning, the information contained in the feedback message is arguably the most important. One common assumption is that there is a benefit to increasing the complexity of the feedback message beyond providing the correct answer. Surprisingly, studies that have manipulated the…

  7. Feedback Perceptions and Attribution by Secretarial Employees: Effects of Feedback-Content and Sender Characteristics

    ERIC Educational Resources Information Center

    Raemdonck, Isabel; Strijbos, Jan-Willem

    2013-01-01

    Purpose: Theoretical explanations for the diverse reactive feedback from secretarial employees in different career phases are relatively unexplored. However, research examining age differences in the impact of feedback suggests that the effects of performance feedback may differ for employees in the early career phase and employees in the late…

  8. Can Performance Feedback during Instruction Boost Knowledge Acquisition? Contrasting Criterion-Based and Social Comparison Feedback

    ERIC Educational Resources Information Center

    Kollöffel, Bas; de Jong, Ton

    2016-01-01

    Feedback indicating how well students are performing during a learning task can be very stimulating. In this study with a pre- and post-test design, the effects of two types of performance feedback on learning results were compared: feedback during a learning task was either stated in terms of how well the students were performing relative to…

  9. The Impact of Middle-School Students' Feedback Choices and Performance on Their Feedback Memory

    ERIC Educational Resources Information Center

    Cutumisu, Maria; Schwartz, Daniel L.

    2016-01-01

    This paper presents a novel examination of the impact of students' feedback choices and performance on their feedback memory. An empirical study was designed to collect the choices to seek critical feedback from a hundred and six Grade 8 middle-school students via Posterlet, a digital assessment game in which students design posters. Upon…

  10. High-Ratio Gear Train

    NASA Technical Reports Server (NTRS)

    Lefever, A. E.

    1982-01-01

    Proposed arrangement of two connected planetary differentials results in gear ratio many times that obtainable in conventional series gear assembly of comparable size. Ratios of several thousand would present no special problems. Selection of many different ratios is available with substantially similar gear diameters. Very high gear ratios would be obtained from small mechanism.

  11. Steep switching characteristics of single-gated feedback field-effect transistors

    NASA Astrophysics Data System (ADS)

    Kim, Minsuk; Kim, Yoonjoong; Lim, Doohyeok; Woo, Sola; Cho, Kyoungah; Kim, Sangsig

    2017-02-01

    In this study, we propose newly designed feedback field-effect transistors that utilize the positive feedback of charge carriers in single-gated silicon channels to achieve steep switching behaviors. The band diagram, I-V characteristics, subthreshold swing, and on/off current ratio are analyzed using a commercial device simulator. Our proposed feedback field-effect transistors exhibit subthreshold swings of less than 0.1 mV dec-1, an on/off current ratio of approximately 1011, and an on-current of approximately 10-4 A at room temperature, demonstrating that the switching characteristics are superior to those of other silicon-based devices. In addition, the device parameters that affect the device performance, hysteresis characteristics, and temperature-dependent device characteristics are discussed in detail.

  12. Stock price dynamics and option valuations under volatility feedback effect

    NASA Astrophysics Data System (ADS)

    Kanniainen, Juho; Piché, Robert

    2013-02-01

    According to the volatility feedback effect, an unexpected increase in squared volatility leads to an immediate decline in the price-dividend ratio. In this paper, we consider the properties of stock price dynamics and option valuations under the volatility feedback effect by modeling the joint dynamics of stock price, dividends, and volatility in continuous time. Most importantly, our model predicts the negative effect of an increase in squared return volatility on the value of deep-in-the-money call options and, furthermore, attempts to explain the volatility puzzle. We theoretically demonstrate a mechanism by which the market price of diffusion return risk, or an equity risk-premium, affects option prices and empirically illustrate how to identify that mechanism using forward-looking information on option contracts. Our theoretical and empirical results support the relevance of the volatility feedback effect. Overall, the results indicate that the prevailing practice of ignoring the time-varying dividend yield in option pricing can lead to oversimplification of the stock market dynamics.

  13. Providing Effective Feedback to EFL Student Teachers

    ERIC Educational Resources Information Center

    Ali, Holi Ibrahim Holi; Al-Adawi, Hamed Ahmed

    2013-01-01

    Feedback on school practicum is of utmost importance for student teachers to help them to develop their pedagogical and teaching skills. This paper attempts to collect data from both student teachers and their mentors in an ELT teacher training programme in Oman to answer the questions which are raised by this study: 1) What kind of feedback do…

  14. Feedback for Teachers: Focused, Specific, and Constructive

    ERIC Educational Resources Information Center

    Westerberg, Tim R.

    2013-01-01

    Across the country, there is a renewed emphasis on using teacher evaluation not only to rate teachers but also to give them formative feedback that will help them improve classroom instruction. Recent research shows that applying the strategies that teachers use to give students effective feedback to the teacher evaluation process produces…

  15. Computer-Generated Feedback on Student Writing

    ERIC Educational Resources Information Center

    Ware, Paige

    2011-01-01

    A distinction must be made between "computer-generated scoring" and "computer-generated feedback". Computer-generated scoring refers to the provision of automated scores derived from mathematical models built on organizational, syntactic, and mechanical aspects of writing. In contrast, computer-generated feedback, the focus of this article, refers…

  16. The Tuckman Teacher Feedback Form (TTFF).

    ERIC Educational Resources Information Center

    Tuckman, Bruce Wayne

    Originally designed to provide teachers with feedback and also used as a quantitative tool for specifying teacher behavior consistent with a psychological model of teaching described by Tuckman (1974), the Tuckman Teacher Feedback Form (TTFF) is a 28-item semantic differential which generates four scores in the areas of creativity, dynamism…

  17. Enhancing Students' Learning: Instant Feedback Cards

    ERIC Educational Resources Information Center

    Mohrweis, Lawrence C.; Shinham, Kathe M.

    2015-01-01

    This study illustrates an active learning approach using instant feedback cards in the first course in accounting. The objectives of this study are to (1) describe instant feedback cards and (2) show how this tool, when used in an active learning environment, can enhance learning. We examined whether students exposed to immediate feedback…

  18. Preregulator feedback circuit utilizes Light Actuated Switch

    NASA Technical Reports Server (NTRS)

    Hayser, T. P.

    1966-01-01

    Preregulator feedback circuit employing a Light Actuated Switch /LAS/ provides a simple and efficient feedback device in a power supply preregulator which maintains dc isolation between input and output grounds. The LAS consists of a diode PN junction infrared source close to, but electrically isolated from, a photodetector.

  19. Feedback for Web-based Assignments.

    ERIC Educational Resources Information Center

    Collis, Betty; De Boer, W.; Slotman, K.

    2001-01-01

    Discusses a concept used at the University of Twente based on increased flexibility in learning options and the active student in which there are assignments submitted and monitored via a Web-based course management system. Outlines conceptual aspects of feedback as part of the assessment process, particularly feedback supported by a Web-based…

  20. Feedbacks in human-landscape systems.

    PubMed

    Chin, Anne; Florsheim, Joan L; Wohl, Ellen; Collins, Brian D

    2014-01-01

    This article identifies key questions and challenges for geomorphologists in investigating coupled feedbacks in human-landscape systems. While feedbacks occur in the absence of human influences, they are also altered by human activity. Feedbacks are a key element to understanding human-influenced geomorphic systems in ways that extend our traditional approach of considering humans as unidirectional drivers of change. Feedbacks have been increasingly identified in Earth-environmental systems, with studies of coupled human-natural systems emphasizing ecological phenomena in producing emerging concepts for social-ecological systems. Enormous gaps or uncertainties in knowledge remain with respect to understanding impact-feedback loops within geomorphic systems with significant human alterations, where the impacted geomorphic systems in turn affect humans. Geomorphology should play an important role in public policy by identifying the many diffuse and subtle feedbacks of both local- and global-scale processes. This role is urgent, while time may still be available to mitigate the impacts that limit the sustainability of human societies. Challenges for geomorphology include identification of the often weak feedbacks that occur over varied time and space scales ranging from geologic time to single isolated events and very short time periods, the lack of available data linking impact with response, the identification of multiple thresholds that trigger feedback mechanisms, the varied tools and metrics needed to represent both physical and human processes, and the need to collaborate with social scientists with expertise in the human causes of geomorphic change, as well as the human responses to such change.

  1. Optical feedback structures and methods of making

    DOEpatents

    Snee, Preston T; Chan, Yin Thai; Nocera, Daniel G; Bawendi, Moungi G

    2014-11-18

    An optical resonator can include an optical feedback structure disposed on a substrate, and a composite including a matrix including a chromophore. The composite disposed on the substrate and in optical communication with the optical feedback structure. The chromophore can be a semiconductor nanocrystal. The resonator can provide laser emission when excited.

  2. Engaging Feedback: Meaning, Identity and Power

    ERIC Educational Resources Information Center

    Sutton, Paul; Gill, Wendy

    2010-01-01

    This paper uses a methodology that synthesises an Academic Literacies approach and Critical Discourse Analysis to explore student experiences of feedback on written assessments in two higher education institutions. The qualitative analysis of student interviews is oriented around three topics: (1) the socially situated meaning of feedback; (2)…

  3. Students' Reflections on Mathematics Homework Feedback

    ERIC Educational Resources Information Center

    Landers, Mara; Reinholz, Daniel

    2015-01-01

    Homework is considered an important aspect of learning mathematics, but little research has considered how students utilize feedback as part of the homework process. This mixed methods, quasi-experimental study examines how community college students in a developmental intermediate algebra course participated in a feedback reflection activity…

  4. Feedback Control Analysis Using Parameter Plane Techniques.

    DTIC Science & Technology

    1986-06-01

    compensation of linear control systems. General equations have been derived for the cases of feedback, cascade, and combination feedback-cascade...Bode and root-locus analyses, the program provides the capability to investigate ř% the entire gamut of linear control system architecture. A basis

  5. Peer Feedback on Language Form in Telecollaboration

    ERIC Educational Resources Information Center

    Ware, Paige D.; O'Dowd, Robert

    2008-01-01

    We performed a two-phase, year-long research project that explored the impact of peer feedback on language development. We investigated specifically how and when post-secondary learners of English and Spanish provide corrective feedback on their partners' use of the target language in weekly asynchronous discussions by assigning them to one of two…

  6. Does Automated Feedback Improve Writing Quality?

    ERIC Educational Resources Information Center

    Wilson, Joshua; Olinghouse, Natalie G.; Andrada, Gilbert N.

    2014-01-01

    The current study examines data from students in grades 4-8 who participated in a statewide computer-based benchmark writing assessment that featured automated essay scoring and automated feedback. We examined whether the use of automated feedback was associated with gains in writing quality across revisions to an essay, and with transfer effects…

  7. Student Views on the Value of Feedback

    ERIC Educational Resources Information Center

    Marie, Jenny A.

    2016-01-01

    This paper investigates the value that a sample of students placed on feedback, what they valued it for and the conditions that affected this value judgement. I show that not all students value feedback particularly highly, especially when considered in relation to other factors in their education and when considered for its intrinsic value as…

  8. Advanced Feedback Methods in Information Retrieval.

    ERIC Educational Resources Information Center

    Salton, G.; And Others

    1985-01-01

    In this study, automatic feedback techniques are applied to Boolean query statements in online information retrieval to generate improved query statements based on information contained in previously retrieved documents. Feedback operations are carried out using conventional Boolean logic and extended logic. Experimental output is included to…

  9. Feedback Processes in Multimedia Language Learning Software

    ERIC Educational Resources Information Center

    Kartal, Erdogan

    2010-01-01

    Feedback has been one of the important elements of learning and teaching theories and still pervades the literature and instructional models, especially computer and web-based ones. However, the mechanisms about feedback dominating the fundamentals of all the instructional models designed for self-learning have changed considerably with the…

  10. Feedback after Good Trials Enhances Learning

    ERIC Educational Resources Information Center

    Chiviacowsky, Suzete; Wulf, Gabriele

    2007-01-01

    Recent studies (Chiviacowsky & Wulf, 2002, 2005) have shown that learners prefer to receive feedback after they believe they had a "good" rather than "poor" trial. The present study followed up on this finding and examined whether learning would benefit if individuals received feedback after good relative to poor trials. Participants practiced a…

  11. Technologies for Learner-Centered Feedback

    ERIC Educational Resources Information Center

    Costello, Jane; Crane, Daph

    2013-01-01

    As the number, type, and use of technologies to support learning increases, so do the opportunities for using these technologies for feedback. Learner-centered feedback is a core to the teaching-learning process. It is related to assessment in describing how learners perform in their learning, their gain in knowledge, skills, and attitudes.…

  12. Supporting Second Language Writing Using Multimodal Feedback

    ERIC Educational Resources Information Center

    Elola, Idoia; Oskoz, Ana

    2016-01-01

    The educational use of computer-based feedback in the classroom is becoming widespread. However, less is known about (1) the extent to which tools influence how instructors provide written and oral comments, and (2) whether receiving oral or written feedback influences the nature of learners' revisions. This case study, which expands existing…

  13. Feedback Effectiveness in Professional Learning Contexts

    ERIC Educational Resources Information Center

    Johnson, Martin

    2016-01-01

    Assessment organisations that operate at a national level in the UK employ hierarchic assessor monitoring arrangements, where the most senior assessors (known as team leaders) feedback to assessors in their teams on their marking performance. According to a sociocultural viewpoint, this feedback possesses learning potential as it allows assessors…

  14. Teaching Writing Using Peer Feedback Checklists.

    ERIC Educational Resources Information Center

    Furneaux, Clare

    2002-01-01

    Discusses incorporation of peer feedback check lists in the English-as-a-Second-Language writing classroom. Highlights different types of check lists, including generic and text-specific, and how to use check lists for peer feedback. (Author/VWL)

  15. SOIL N:P RATIO INFLUENCES MYCORRHIZAL FUNCTION AND SOIL ORGANISM FEEDBACKS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The degree to which plants benefit from mycorrhizal symbioses is influenced by soil fertility. Plants generally benefit the most from arbuscular mycorrhizal (AM) associations when they are growing in phosphorus (P) deficient soil; however soil nitrogen (N) availability can also influence mycorrhizal...

  16. Visual Feedback of Intonation I: Effectiveness and Induced Practice Behavior.

    ERIC Educational Resources Information Center

    de Bot, K.

    1983-01-01

    Attempts to show that audio-visual feedback is more effective in intonation learning than auditory feedback. While practice time did not seem to be a major factor, results showed audio-visual feedback to be more effective than auditory feedback. In addition, feedback modality was shown to influence learning behavior. (SL)

  17. Feedbacks and landscape-level vegetation dynamics.

    PubMed

    Bowman, David M J S; Perry, George L W; Marston, J B

    2015-05-01

    Alternative stable-state theory (ASS) is widely accepted as explaining landscape-level vegetation dynamics, such as switches between forest and grassland. This theory argues that webs of feedbacks stabilise vegetation composition and structure, and that abrupt state shifts can occur if stabilising feedbacks are weakened. However, it is difficult to identify stabilising feedback loops and the disturbance thresholds beyond which state changes occur. Here, we argue that doing this requires a synthetic approach blending observation, experimentation, simulation, conceptual models, and narratives. Using forest boundaries and large mammal extinctions, we illustrate how a multifaceted research program can advance understanding of feedback-driven ecosystem change. Our integrative approach has applicability to other complex macroecological systems controlled by numerous feedbacks where controlled experimentation is impossible.

  18. Feedback in Clinical Education, Part I: Characteristics of Feedback Provided by Approved Clinical Instructors

    PubMed Central

    Nottingham, Sara; Henning, Jolene

    2014-01-01

    Context Providing students with feedback is an important component of athletic training clinical education; however, little information is known about the feedback that Approved Clinical Instructors (ACIs; now known as preceptors) currently provide to athletic training students (ATSs). Objective To characterize the feedback provided by ACIs to ATSs during clinical education experiences. Design Qualitative study. Setting One National Collegiate Athletic Association Division I athletic training facility and 1 outpatient rehabilitation clinic that were clinical sites for 1 entry-level master's degree program accredited by the Commission on Accreditation of Athletic Training Education. Patients or Other Participants A total of 4 ACIs with various experience levels and 4 second-year ATSs. Data Collection and Analysis Extensive field observations were audio recorded, transcribed, and integrated with field notes for analysis. The constant comparative approach of open, axial, and selective coding was used to inductively analyze data and develop codes and categories. Member checking, triangulation, and peer debriefing were used to promote trustworthiness of the study. Results The ACIs gave 88 feedback statements in 45 hours and 10 minutes of observation. Characteristics of feedback categories included purpose, timing, specificity, content, form, and privacy. Conclusions Feedback that ACIs provided included several components that made each feedback exchange unique. The ACIs in our study provided feedback that is supported by the literature, suggesting that ACIs are using current recommendations for providing feedback. Feedback needs to be investigated across multiple athletic training education programs to gain more understanding of certain areas of feedback, including frequency, privacy, and form. PMID:24143902

  19. The password is praise: content of feedback affects categorization of feedback sources.

    PubMed

    Rabinovich, Anna; Morton, Thomas A; Landon, Emily; Neill, Caitlin; Mason-Brown, Sapphire; Burdett, Lucie

    2014-09-01

    In three experimental studies, we investigated the effect of the content of group-directed feedback on categorization of the feedback source as an ingroup or an outgroup member. In all studies, feedback valence (criticism vs. praise) and the attributional content of feedback (attributing outcomes to internal properties of the group vs. external circumstances) were experimentally manipulated. The results demonstrated that anonymous (Study 1) and ambiguous (Studies 2 and 3) sources of feedback are more likely to be seen as (typical) ingroup members when they provide praise rather than criticism. In addition, in all studies there was a significant interaction between valence and the attributional content of feedback, such that sources of praise were more likely to be seen as ingroup members when they attributed the group's success to internal (rather than external) causes, while the opposite was observed for critics. These effects were mediated by perceived group image threat. Implications for research on group-based feedback and social categorization are discussed.

  20. Feedback and assessment for clinical placements: achieving the right balance

    PubMed Central

    Burgess, Annette; Mellis, Craig

    2015-01-01

    During clinical placements, the provision of feedback forms an integral part of the learning process and enriches students’ learning experiences. The purpose of feedback is to improve the learner’s knowledge, skills, or behavior. Receipt of accurate feedback can help to narrow the gap between actual and desired performance. Effective and regular feedback has the potential to reinforce good practice and motivate the learner toward the desired outcome. Despite the obvious role of feedback in effective teaching and learning, a common complaint from students is that they do not receive adequate feedback. Unfortunately, skills in giving and receiving feedback are rarely taught to students or clinicians. This study aims to provide an understanding of the role of feedback within the learning process, consider consequences of inadequate or poorly given feedback, consider the barriers to the feedback process, provide practical guidelines for providing feedback, and consider the need for student and faculty development in feedback skills. PMID:26056511

  1. Wide-Angle Quasar Feedback

    NASA Astrophysics Data System (ADS)

    Chartas, George; Strickland, Sarah

    We present results from the detection of relativistic winds launched near the innermost stable circular orbits of supermassive black holes. A recent detection of a powerful wind in the X-ray-bright narrow absorption line (NAL) z=1.51 quasar HS 0810+2554 strengthens the case that quasars play a significant role in feedback. In both deep Chandra and XMM-Newton observations of HS 0810 we detected blueshifted absorption lines implying outflowing velocities ranging from 0.1c and 0.4c. The presence of both an emission line at 6.8 keV and an absorption line at 7.8 keV in the spectral line profile of HS 0810 is a characteristic feature of a P-Cygni profile supporting the presence of an expanding outflowing highly ionized Fe absorber. A hard excess component is detected in the XMM-Newton observation of HS 0810 possibly originating from reflection off the disk. Modelling of the XMM-Newton spectrum constrains the inclination angle to be < 35° (68% confidence). The presence of relativistic winds in both low inclination angle NAL quasars as well as in high inclination angle BAL quasars implies that the solid angle of quasar winds may be quite large. The larger solid angle of quasar winds would also indicate that their contribution to the regulation of the host galaxy may be more important than previously thought.

  2. Visual feedback for retuning to just intonation intervals

    NASA Astrophysics Data System (ADS)

    Ayers, R. Dean; Nordquist, Peter R.; Corn, Justin S.

    2005-04-01

    Musicians become used to equal temperament pitch intervals due to their widespread use in tuning pianos and other fixed-pitch instruments. For unaccompanied singing and some other performance situations, a more harmonious blending of sounds can be achieved by shifting to just intonation intervals. Lissajous figures provide immediate and striking visual feedback that emphasizes the frequency ratios and pitch intervals found among the first few members of a single harmonic series. Spirograph patterns (hypotrochoids) are also especially simple for ratios of small whole numbers, and their use for providing feedback to singers has been suggested previously [G. W. Barton, Jr., Am. J. Phys. 44(6), 593-594 (1976)]. A hybrid mixture of these methods for comparing two frequencies generates what appears to be a three dimensional Lissajous figure-a cylindrical wire mesh that rotates about its tilted vertical axis, with zero tilt yielding the familiar Lissajous figure. Sine wave inputs work best, but the sounds of flute, recorder, whistling, and a sung ``oo'' are good enough approximations to work well. This initial study compares the three modes of presentation in terms of the ease with which a singer can obtain a desired pattern and recognize its shape.

  3. Pseudo-Haptic Feedback in Teleoperation.

    PubMed

    Neupert, Carsten; Matich, Sebastian; Scherping, Nick; Kupnik, Mario; Werthschutzky, Roland; Hatzfeld, Christian

    2016-01-01

    In this paper, we develop possible realizations of pseudo-haptic feedback in teleoperation systems based on existing works for pseudo-haptic feedback in virtual reality and the intended applications. We derive four potential factors affecting the performance of haptic feedback (calculation operator, maximum displacement, offset force, and scaling factor), which are analyzed in three compliance identification experiments. First, we analyze the principle usability of pseudo-haptic feedback by comparing information transfer measures for teleoperation and direct interaction. Pseudo-haptic interaction yields well above-chance performance, while direct interaction performs almost perfectly. In order to optimize pseudo-haptic feedback, in the second study we perform a full-factorial experimental design with 36 subjects performing 6,480 trials with 36 different treatments. Information transfer ranges from 0.68 bit to 1.72 bit in a task with a theoretical maximum of 2.6 bit, with a predominant effect of the calculation operator and a minor effect of the maximum displacement. In a third study, short- and long-term learning effects are analyzed. Learning effects regarding the performance of pseudo-haptic feedback cannot be observed for single-day experiments. Tests over 10 days show a maximum increase in information transfer of 0.8 bit. The results show the feasibility of pseudo-haptic feedback for teleoperation and can be used as design basis for task-specific systems.

  4. Nonlinear and Nonlocal Feedbacks in an Aquaplanet

    NASA Astrophysics Data System (ADS)

    Feldl, N.; Roe, G.

    2012-12-01

    The power of the feedback framework lies in its ability to reveal the energy pathways by which the climate system adjusts to an imposed forcing. By understanding the closure of the energy budget in as much detail and precision as possible, and within as clean an experimental set-up as possible, we are also able to isolate nonlinear interactions between feedbacks. For an aquaplanet simulation under perpetual equinox conditions, we account for rapid tropospheric adjustments to CO2 and diagnose radiative kernels for this precise model set-up. We characterize the contributions of feedbacks, heat transport, and nonlinearities in controlling the meridional structure of the climate response. The presence of strongly positive subtropical feedbacks, combined with polar amplification, implies a critical role for transport and nonlinear effects, with the latter acting to substantially reduce global climate sensitivity. At the hemispheric scale, a rich picture emerges: net heat divergence away from strong positive feedbacks in the tropics; nonlinearities induced by circulation changes that cool the tropics and warm the high-latitudes; and strong ice-line feedbacks that drive further amplification of polar warming. Overall, these results highlight how spatial patterns in feedbacks affect both the local and nonlocal climate response, with implications for regional predictability.

  5. Novel tactile feedback to reduce overt stuttering.

    PubMed

    Waddell, Dwight E; Goggans, Paul M; Snyder, Gregory J

    2012-08-22

    Stuttering is generally considered to be a speech disorder that affects ∼1% of the global population. Various forms of speech feedback have been shown to reduce overt stuttered speaking, and in particular, second speech signal through speech feedback has drastically reduced utterances of stuttered speech in adults with persistent stuttering. This study reports data for increased overt fluency of speech in an adult stuttering population, whereby the vocalization of the speaker is captured by a microphone or an accelerometer, signal processed, and returned as mechanical tactile speech feedback to the speaker's skin. A repeated measures analysis of variance was used to show that both the microphone and the accelerometer speaking conditions were significantly more fluent than a control (no feedback) condition, with the microphone-driven tactile feedback reducing instances of stuttering by 71% and the accelerometer-driven tactile feedback reducing instances of stuttering by 80%. It is apparent that self-generated tactile feedback can be used to enhance fluency significantly in those who stutter.

  6. Feedbacks in human-landscape systems

    NASA Astrophysics Data System (ADS)

    Chin, Anne

    2015-04-01

    As human interactions with Earth systems intensify in the "Anthropocene", understanding the complex relationships among human activity, landscape change, and societal responses to those changes is increasingly important. Interdisciplinary research centered on the theme of "feedbacks" in human-landscape systems serves as a promising focus for unraveling these interactions. Deciphering interacting human-landscape feedbacks extends our traditional approach of considering humans as unidirectional drivers of change. Enormous challenges exist, however, in quantifying impact-feedback loops in landscapes with significant human alterations. This paper illustrates an example of human-landscape interactions following a wildfire in Colorado (USA) that elicited feedback responses. After the 2012 Waldo Canyon Fire, concerns for heightened flood potential and debris flows associated with post-fire hydrologic changes prompted local landowners to construct tall fences at the base of a burned watershed. These actions changed the sediment transport regime and promoted further landscape change and human responses in a positive feedback cycle. The interactions ultimately increase flood and sediment hazards, rather than dampening the effects of fire. A simple agent-based model, capable of integrating social and hydro-geomorphological data, demonstrates how such interacting impacts and feedbacks could be simulated. Challenges for fully capturing human-landscape feedback interactions include the identification of diffuse and subtle feedbacks at a range of scales, the availability of data linking impact with response, the identification of multiple thresholds that trigger feedback mechanisms, and the varied metrics and data needed to represent both the physical and human systems. By collaborating with social scientists with expertise in the human causes of landscape change, as well as the human responses to those changes, geoscientists could more fully recognize and anticipate the coupled

  7. AGN-starburst evolutionary connection: a physical interpretation based on radiative feedback

    NASA Astrophysics Data System (ADS)

    Ishibashi, W.; Fabian, A. C.

    2016-12-01

    Observations point towards a close connection between nuclear starbursts, active galactic nuclei (AGN), and outflow phenomena. An evolutionary sequence, starting from a dust-obscured ultra-luminous infrared galaxy and eventually leading to an unobscured optical quasar, has been proposed and discussed in the literature. AGN feedback is usually invoked to expel the obscuring gas and dust in a blow-out event, but the underlying physical mechanism remains unclear. We consider AGN feedback driven by radiation pressure on dust, which directly acts on the obscuring dusty gas. We obtain that radiative feedback can potentially disrupt dense gas in the infrared-optically thick regime, and that an increase in the dust-to-gas fraction leads to an increase in the effective Eddington ratio. Thus, the more dusty gas is preferentially expelled by radiative feedback, and the central AGN is prone to efficiently remove its own obscuring dust cocoon. Large amounts of dust imply heavy obscuration but also powerful feedback, suggesting a causal link between dust obscuration and blow-out. In this picture, AGN feedback and starburst phenomena are intrinsically coupled through the production of dust in supernova explosions, leading to a natural interpretation of the observed evolutionary path.

  8. Ratio estimation in SIMS analysis

    NASA Astrophysics Data System (ADS)

    Ogliore, R. C.; Huss, G. R.; Nagashima, K.

    2011-09-01

    The determination of an isotope ratio by secondary ion mass spectrometry (SIMS) traditionally involves averaging a number of ratios collected over the course of a measurement. We show that this method leads to an additive positive bias in the expectation value of the estimated ratio that is approximately equal to the true ratio divided by the counts of the denominator isotope of an individual ratio. This bias does not decrease as the number of ratios used in the average increases. By summing all counts in the numerator isotope, then dividing by the sum of counts in the denominator isotope, the estimated ratio is less biased: the bias is approximately equal to the ratio divided by the summed counts of the denominator isotope over the entire measurement. We propose a third ratio estimator (Beale's estimator) that can be used when the bias from the summed counts is unacceptably large for the hypothesis being tested. We derive expressions for the variance of these ratio estimators as well as the conditions under which they are normally distributed. Finally, we investigate a SIMS dataset showing the effects of ratio bias, and discuss proper ratio estimation for SIMS analysis.

  9. Facial Feedback Mechanisms in Autistic Spectrum Disorders

    PubMed Central

    van den Heuvel, Claudia; Smeets, Raymond C.

    2008-01-01

    Facial feedback mechanisms of adolescents with Autistic Spectrum Disorders (ASD) were investigated utilizing three studies. Facial expressions, which became activated via automatic (Studies 1 and 2) or intentional (Study 2) mimicry, or via holding a pen between the teeth (Study 3), influenced corresponding emotions for controls, while individuals with ASD remained emotionally unaffected. Thus, individuals with ASD do not experience feedback from activated facial expressions as controls do. This facial feedback-impairment enhances our understanding of the social and emotional lives of individuals with ASD. PMID:18293075

  10. The effects of outcome and process feedback

    NASA Technical Reports Server (NTRS)

    Johnson, Debra Steele

    1990-01-01

    A study was conducted to examine the effects of process and outcome feedback on performance during a skill acquisition phase and a transfer test phase. The research also examined the role of two moderators: self-efficacy and intrinsic motivation. Subjects were college students participating for course credit. The task involved using a computerized simulation of the Space Shuttle's Remote Manipulation System (RMS). Results provided evidence of the beneficial effects of process feedback during skill acquisition. Results also provided evidence that self-efficacy and intrinsic motivation moderate the effects of feedback type on performance.

  11. Feedback Requirements for SASE-FELs

    SciTech Connect

    Loos, Henrik; /SLAC

    2012-07-06

    The operation of a Self Amplified Spontaneous Emission (SASE) Free Electron Lasers (FEL) at soft and hard X-ray wavelengths driven by a high brightness electron beam imposes strong requirements on the stability of the accelerator and feedback systems are necessary to both guarantee saturation of the SASE process as well as a stable photon beam for user experiments. Diagnostics for the relevant transverse and longitudinal beam parameters are presented and various examples of feedback systems for bunches with low repetition rate as well as systems for intra bunch train feedbacks are discussed.

  12. Haptic seat for fuel economy feedback

    DOEpatents

    Bobbitt, III, John Thomas

    2016-08-30

    A process of providing driver fuel economy feedback is disclosed in which vehicle sensors provide for haptic feedback on fuel usage. Such sensors may include one or more of a speed sensors, global position satellite units, vehicle pitch/roll angle sensors, suspension displacement sensors, longitudinal accelerometer sensors, throttle position in sensors, steering angle sensors, break pressure sensors, and lateral accelerometer sensors. Sensors used singlely or collectively can provide enhanced feedback as to various environmental conditions and operating conditions such that a more accurate assessment of fuel economy information can be provided to the driver.

  13. Multibunch feedback: Strategy, technology and implementation options

    SciTech Connect

    Fox, J.D.; Eisen, N.; Hindi, H.; Oxoby, G.; Sapozhnikov, L.; Linscott, I.; Serio, M.

    1992-10-01

    The proposed next generation accelerator and synchrotron light facilities will require active feedback systems to control multi-bunch instabilities. These feedback systems must operate in machines with thousands of circulating bunches and with short (2--4 ns) interbunch intervals. The functional requirements for transverse (betatron) and longitudinal (synchrotron) feedback systems are presented. Several possible implementation options are discussed and system requirements developed. Results are presented from a digital signal processing based synchrotron oscillation damper operating at the SSRL/SLAC SPEAR storage ring.

  14. Feedback on flood risk management

    NASA Astrophysics Data System (ADS)

    Moreau, K.; Roumagnac, A.

    2009-09-01

    For several years, as floods were increasing in South of France, local communities felt deprive to assume their mission of protection and information of citizens, and were looking for assistance in flood management. In term of flood disaster, the fact is that physical protection is necessary but inevitably limited. Tools and structures of assistance to anticipation remain slightly developed. To manage repeated crisis, local authorities need to be able to base their policy against flood on prevention, warnings, post-crisis analysis and feedback from former experience. In this objective, after 3 years of test and improvement since 2003, the initiative Predict-Services was developed in South of France: it aims at helping communities and companies to face repeated flood crisis. The principle is to prepare emergency plans, to organize crisis management and reduce risks; to help and assist communities and companies during crisis to activate and adapt their emergency plans with enough of anticipation; and to analyse floods effects and improve emergency plans afterwards. With the help of Meteo France datas and experts, Predict services helps local communities and companies in decision making for flood management. In order to reduce risks, and to keep the benefits of such an initiative, local communities and companies have to maintain the awareness of risk of the citizens and employees. They also have to maintain their safety plans to keep them constantly operational. This is a part of the message relayed. Companies, Local communities, local government authorities and basin stakeholders are the decision makers. Companies and local communities have to involve themselves in the elaboration of safety plans. They are also completely involved in their activation that is their own responsability. This applies to other local government authorities, like districts one's and basin stakeholders, which participle in the financing community safety plans and adminitrative district which

  15. Feedback on flood risk management

    NASA Astrophysics Data System (ADS)

    Moreau, K.; Roumagnac, A.

    2009-09-01

    For several years, as floods were increasing in South of France, local communities felt deprive to assume their mission of protection and information of citizens, and were looking for assistance in flood management. In term of flood disaster, the fact is that physical protection is necessary but inevitably limited. Tools and structures of assistance to anticipation remain slightly developed. To manage repeated crisis, local authorities need to be able to base their policy against flood on prevention, warnings, post-crisis analysis and feedback from former experience. In this objective, after 3 years of test and improvement since 2003, the initiative Predict-Services was developped in South of France: it aims at helping communities and companies to face repeated flood crisis. The principle is to prepare emergency plans, to organize crisis management and reduce risks; to help and assist communities and companies during crisis to activate and adapt their emergency plans with enough of anticipation; and to analyse floods effects and improve emergency plans afterwards. In order to reduce risks, and to keep the benefits of such an initiative, local communities and companies have to maintain the awareness of risk of the citizens and employees. They also have to maintain their safety plans to keep them constantly operational. This is a part of the message relayed. Companies, Local communities, local government authorities and basin stakeholders are the decision makers. Companies and local communities have to involve themselves in the elaboration of safety plans. They are also completely involved in their activation that is their own responsability. This applies to other local government authorities, like districts one's and basin stakeholders, which participle in the financing community safety plans and adminitrative district which are responsible of the transmission of meteorological alert and of rescue actions. In the crossing of the géo-information stemming from the

  16. Pinhole Luminosity Monitor with Feedback

    SciTech Connect

    Spencer, J

    2004-05-17

    Previously, the generalized luminosity L was defined and calculated for all incident channels based on an NLC e{sup +}e{sup -} design. Alternatives were then considered to improve the differing beam-beam e{sup -}e{sup -} e{gamma} and {gamma}{gamma} channels. Regardless of the channel, there was a large flux of outgoing, high energy photons that were produced from the beam-beam interaction e.g. beamsstrahlung that needs to be disposed of and whose flux depended on L. One approach to this problem is to consider it a resource and attempt to take advantage of it by disposing of these straight-ahead photons in more useful ways than simply dumping them. While there are many options for monitoring the luminosity, any method that allows feedback and optimization in real time and in a non-intercepting and non-interfering way during normal data taking is extremely important--especially if it provides other capabilities such as high resolution tuning of spot sizes and can be used for all incident channels without essential modifications to their setup. Our ''pin-hole'' camera appears to be such a device if it can be made to work with high energy photons in ways that are compatible with the many other constraints and demands on space around the interaction region. The basis for using this method is that it has, in principle, the inherent resolution and bandwidth to monitor the very small spot sizes and their stabilities that are required for very high, integrated luminosity. While there are many possible, simultaneous uses of these outgoing photon beams, we limit our discussion to a single, blind, proof-of-principle experiment that was done on the FFTB line at SLAC to certify the concept of a camera obscura for high energy photons.

  17. Calcium wave of tubuloglomerular feedback.

    PubMed

    Peti-Peterdi, János

    2006-08-01

    ATP release from macula densa (MD) cells into the interstitium of the juxtaglomerular (JG) apparatus (JGA) is an integral component of the tubuloglomerular feedback (TGF) mechanism that controls the glomerular filtration rate. Because the cells of the JGA express a number of calcium-coupled purinergic receptors, these studies tested the hypothesis that TGF activation triggers a calcium wave that spreads from the MD toward distant cells of the JGA and glomerulus. Ratiometric calcium imaging of in vitro microperfused isolated JGA-glomerulus complex dissected from rabbits was performed with fluo-4/fura red and confocal fluorescence microscopy. Activation of TGF by increasing tubular flow rate at the MD rapidly produced a significant elevation in intracellular Ca(2+) concentration ([Ca(2+)](i)) in extraglomerular mesangial cells (by 187.6 +/- 45.1 nM) and JG renin granular cells (by 281.4 +/- 66.6 nM). Subsequently, cell-to-cell propagation of the calcium signal at a rate of 12.6 +/- 1.1 microm/s was observed upstream toward proximal segments of the afferent arteriole and adjacent glomeruli, as well as toward intraglomerular elements including the most distant podocytes (5.9 +/- 0.4 microm/s). The same calcium wave was observed in nonperfusing glomeruli, causing vasoconstriction and contractions of the glomerular tuft. Gap junction uncoupling, an ATP scavenger enzyme cocktail, and pharmacological inhibition of P(2) purinergic receptors, but not adenosine A(1) receptor blockade, abolished the changes in [Ca(2+)](i) and propagation of the calcium wave. These studies provided evidence that both gap junctional communication and extracellular ATP are integral components of the TGF calcium wave.

  18. Black-Hole Feedback in Quasars

    NASA Video Gallery

    This animation illustrates how black-hole feedback works in quasars. Dense gas and dust in the center simultaneously fuels the black hole and shrouds it from view. The black-hole wind propels large...

  19. RHIC 10 Hz global orbit feedback system

    SciTech Connect

    Michnoff, R.; Arnold, L.; Carboni, L.; Cerniglia, P; Curcio, A.; DeSanto, L.; Folz, C.; Ho, C.; Hoff, L.; Hulsart, R.; Karl, R.; Luo, Y.; Liu, C.; MacKay, W.; Mahler, G.; Meng, W.; Mernick, K.; Minty, M.; Montag, C.; Olsen, R.; Piacentino, J.; Popken, P.; Przybylinski, R.; Ptitsyn, V.; Ritter, J.; Schoenfeld, R.; Thieberger, P.; Tuozzolo, J.; Weston, A.; White, J.; Ziminski, P.; Zimmerman, P.

    2011-03-28

    Vibrations of the cryogenic triplet magnets at the Relativistic Heavy Ion Collider (RHIC) are suspected to be causing the horizontal beam perturbations observed at frequencies around 10 Hz. Several solutions to counteract the effect have been considered in the past, including a local beam feedback system at each of the two experimental areas, reinforcing the magnet base support assembly, and a mechanical servo feedback system. However, the local feedback system was insufficient because perturbation amplitudes outside the experimental areas were still problematic, and the mechanical solutions are very expensive. A global 10 Hz orbit feedback system consisting of 36 beam position monitors (BPMs) and 12 small dedicated dipole corrector magnets in each of the two 3.8 km circumference counter-rotating rings has been developed and commissioned in February 2011. A description of the system architecture and results with beam will be discussed.

  20. Final report, Feedback limitations of photosynthesis

    SciTech Connect

    Sharkey, Thomas D.

    1999-07-22

    Final report of research on carbon metabolism of photosynthesis. The feedback from carbon metabolism to primary photosynthetic processes is summarized, and a comprehensive list of published scientific papers is provided.

  1. Nonlinear feedback control of multiple robot arms

    NASA Technical Reports Server (NTRS)

    Tarn, T. J.; Yun, X.; Bejczy, A. K.

    1987-01-01

    Multiple coordinated robot arms are modeled by considering the arms: (1) as closed kinematic chains, and (2) as a force constrained mechanical system working on the same object simultaneously. In both formulations a new dynamic control method is discussed. It is based on a feedback linearization and simultaneous output decoupling technique. Applying a nonlinear feedback and a nonlinear coordinate transformation, the complicated model of the multiple robot arms in either formulation is converted into a linear and output decoupled system. The linear system control theory and optimal control theory are used to design robust controllers in the task space. The first formulation has the advantage of automatically handling the coordination and load distribution among the robot arms. In the second formulation, by choosing a general output equation, researchers can superimpose the position and velocity error feedback with the force-torque error feedback in the task space simultaneously.

  2. Reactivity feedback mechanisms in aqueous fissile solutions

    SciTech Connect

    Kornreich, D.E. . Dept. of Nuclear and Energy Engineering)

    1993-09-01

    Solutions of fissile materials are often encountered during spent-fuel reprocessing. To estimate the hazards from accidental criticalities in these solutions, models have been developed to understand better the dynamics involved. Accurate representation of reactivity feedback mechanisms is a crucial part of such models. Reactivity feedback from uniform volumetric solution expansion is studied. For faster transients, density redistribution may also occur because of a variation of nuclear energy as a function of position in the assembly. Neutronic spectral temperature reactivity effects are studied by creating temperature-dependent cross sections from ENDF/B-VI data. The volumetric and temperature reactivity feedback coefficients are determined for the CRAC, KEWB-5, SILENE, and SHEBA solution assemblies. Spectral temperature coefficients are also calculated for poisoned, unpoisoned, and reflected plutonium solutions. Feedback coefficients are seen to be functions of geometry and isotopic contents of the assemblies. Results for plutonium solutions agree with other calculations, which confirms the possibility of autocatalytic excursions in large, dilute solutions.

  3. Self-Directed Learning with Feedback

    ERIC Educational Resources Information Center

    Choi, Youngeun; Anderson, William

    2016-01-01

    This article describes a weekly writing assignment named SelFeed (Self-Directed Learning with Feedback), in which students are asked to identify their own questions relevant to the lecture content and provide logical answers.

  4. Distinguishing Feedback Mechanisms in Clock Models

    NASA Astrophysics Data System (ADS)

    Golden, Alexander; Lubensky, David

    Biological oscillators are very diverse but can be classified based on dynamical motifs such as type of feedback. The S. Elongatus circadian oscillator is a novel circadian oscillator that can operate at constant protein number by modifying covalent states. It can be reproduced in vitro with only 3 different purified proteins: KaiA, KaiB, and KaiC. We use computational and analytic techniques to compare models of the S. Elongatus post-translational oscillator that rely on positive feedback with models that rely on negative feedback. We show that introducing a protein that binds competitively with KaiA to the KaiB-KaiC complex can distinguish between positive and negative feedback as the primary driver of the rhythm, which has so far been difficult to address experimentally. NSF Grant DMR-1056456.

  5. Negative feedback system reduces pump oscillations

    NASA Technical Reports Server (NTRS)

    Rosenmann, W.

    1967-01-01

    External negative feedback system counteracts low frequency oscillations in rocket engine propellant pumps. The system uses a control piston to sense pump discharge fluid on one side and a gas pocket on the other.

  6. Cirrus feedback on interannual climate fluctuations

    SciTech Connect

    Zhou, C.; Dessler, A. E.; Zelinka, M. D.; Yang, P.; Wang, T.

    2014-12-28

    Cirrus clouds are not only important in determining the current climate, but also play an important role in climate change and variability. Analysis of satellite observations shows that the amount and altitude of cirrus clouds (optical depth <3.6, cloud top pressure <440 hPa) increase in response to inter-annual surface warming. Thus, cirrus clouds are likely to act as a positive feedback on short-term climate fluctuations, by reducing the planet’s ability to radiate longwave radiation to space in response to planetary surface warming. Using cirrus cloud radiative kernels, the magnitude of cirrus feedback is estimated to be 0.20±0.21W/m2/°C, which is comparable to the surface albedo feedback. Most of the cirrus feedback comes from increasing cloud amount in the tropical tropopause layer (TTL) and subtropical upper troposphere.

  7. The Greenhouse Effect and Climate Feedbacks

    NASA Astrophysics Data System (ADS)

    Covey, C.; Haberle, R. M.; McKay, C. P.; Titov, D. V.

    This chapter reviews the theory of the greenhouse effect and climate feedback. It also compares the theory with observations, using examples taken from all four known terrestrial worlds with substantial atmospheres: Venus, Earth, Mars, and Titan. The greenhouse effect traps infrared radiation in the atmosphere, thereby increasing surface temperature. It is one of many factors that affect a world's climate. (Others include solar luminosity and the atmospheric scattering and absorption of solar radiation.) A change in these factors — defined as climate forcing — may change the climate in a way that brings other processes — defined as feedbacks — into play. For example, when Earth's atmospheric carbon dioxide increases, warming the surface, the water vapor content of the atmosphere increases. This is a positive feedback on global warming because water vapor is itself a potent greenhouse gas. Many positive and negative feedback processes are significant in determining Earth's climate, and probably the climates of our terrestrial neighbors.

  8. Observers and output feedback stabilising controllers for nonlinear strict-feedback systems with sampled observation

    NASA Astrophysics Data System (ADS)

    Katayama, Hitoshi

    2016-02-01

    The design of observers and output feedback stabilising controllers for continuous-time strict-feedback systems with sampled observation is considered. First two types of observers are designed. One is a discrete-time semiglobal and practical reduced-order observer for the exact model and the other is a continuous-time semiglobal and practical full-order observer for continuous-time strict feedback systems with sampled observation. Then by combining the designed continuous-time observers and continuous-time state feedback laws that are continuous, zero at the origin, and uniformly globally asymptotically stabilise continuous-time systems, output feedback semiglobally practically uniformly asymptotically stabilising controllers are constructed. Numerical examples are given to illustrate the proposed design of observers and output feedback controllers.

  9. Different aspects of performance feedback engage different brain areas: Disentangling valence and expectancy in feedback processing

    PubMed Central

    Ferdinand, Nicola K.; Opitz, Bertram

    2014-01-01

    Evaluating the positive and negative outcomes of our behaviour is important for action selection and learning. Such reinforcement learning has been shown to engage a specific neural circuitry including the mesencephalic dopamine system and its target areas, the striatum and medial frontal cortex, especially the anterior cingulate cortex (ACC). An intensively pursued debate regards the prevailing influence of feedback expectancy and feedback valence on the engagement of these two brain regions in reinforcement learning and their respective roles are far from being understood. To this end, we used a time estimation task with three different types of feedback that allows disentangling the effect of feedback valence and expectancy using functional magnetic resonance imaging (fMRI). Our results show greater ACC activation after unexpected positive and unexpected negative feedback than after expected feedback and by this sensitivity to unexpected events in general irrespective of their valence. PMID:25100234

  10. Software feedback for monochromator tuning at UNICAT (abstract)

    NASA Astrophysics Data System (ADS)

    Jemian, Pete R.

    2002-03-01

    Automatic tuning of double-crystal monochromators presents an interesting challenge in software. The goal is to either maximize, or hold constant, the throughput of the monochromator. An additional goal of the software feedback is to disable itself when there is no beam and then, at the user's discretion, re-enable itself when the beam returns. These and other routine goals, such as adherence to limits of travel for positioners, are maintained by software controls. Many solutions exist to lock in and maintain a fixed throughput. Among these include a hardware solution involving a wave form generator, and a lock-in amplifier to autocorrelate the movement of a piezoelectric transducer (PZT) providing fine adjustment of the second crystal Bragg angle. This solution does not work when the positioner is a slow acting device such as a stepping motor. Proportional integral differential (PID) loops have been used to provide feedback through software but additional controls must be provided to maximize the monochromator throughput. Presented here is a software variation of the PID loop which meets the above goals. By using two floating point variables as inputs, representing the intensity of x rays measured before and after the monochromator, it attempts to maximize (or hold constant) the ratio of these two inputs by adjusting an output floating point variable. These floating point variables are connected to hardware channels corresponding to detectors and positioners. When the inputs go out of range, the software will stop making adjustments to the control output. Not limited to monochromator feedback, the software could be used, with beam steering positioners, to maintain a measure of beam position. Advantages of this software feedback are the flexibility of its various components. It has been used with stepping motors and PZTs as positioners. Various devices such as ion chambers, scintillation counters, photodiodes, and photoelectron collectors have been used as

  11. Remote feedback stabilization of tokamak instabilities

    SciTech Connect

    Sen, A.K. )

    1994-05-01

    A novel remote suppressor consisting of an injected ion beam has been used for the stabilization of plasma instabilities. A collisionless curvature-driven trapped-particle instability, an [bold E][times][bold B] flute mode and an ion temperature gradient (ITG) instability have been successfully suppressed down to noise levels using this scheme. Furthermore, the first experimental demonstration of a multimode feedback stabilization with a single sensor--suppressor pair has been achieved. Two modes (an [bold E][times][bold B] flute and an ITG mode) were simultaneously stabilized with a simple state-feedback-type method where more state'' information was generated from a single-sensor Langmuir probe by appropriate signal processing. The above experiments may be considered as paradigms for controlling several important tokamak instabilities. First, feedback suppression of edge fluctuations in a tokamak with a suitable form of insulated segmented poloidal limiter sections used as Langmuir-probe-like suppressors is proposed. Other feedback control schemes are proposed for the suppression of electrostatic core fluctuations via appropriately phased ion density input from a modulated neutral beam. Most importantly, a scheme to control major disruptions in tokamaks via feedback suppression of kink (and possibly) tearing modes is discussed. This may be accomplished by using a modulated neutral beam suppressor in a feedback loop, which will supply a momentum input of appropriate phase and amplitude. Simple theoretical models predict modest levels of beam energy, current, and power.

  12. Feedback-charging a metallic island

    NASA Astrophysics Data System (ADS)

    Schaller, Gernot

    2017-03-01

    We consider electronic transport through a single-electron quantum dot that is tunnel-coupled to an electronic lead and a metallic island. A background reservoir keeps the metallic island at a thermal state with the ambient temperature, while the charge accumulated on the island is reflected in a time-dependent chemical potential. Without feedback, a current would flow through the system until the chemical potentials of island and lead are equilibrated. A feedback loop can be implemented by a quantum point contact detecting the dot state, classical processing of the result and appropriate feedback actions on the electronic tunneling rates taken, with the objective to direct the current in a preferred direction. Since we directly take the detector counting statistics into account, this automatically includes measurement errors in the description. When mainly the rates are modified but hardly any energy is exchanged with the system, this feedback loop effectively implements a Maxwell demon, capable of transporting electrons against an electric bias and thereby charging the metallic island. Once the feedback protocol is stopped, the metallic island simply discharges. We find that a quantitative detector model may be useful for a realistic statistical description of feedback loops.

  13. Lidar ratio and depolarization ratio for cirrus clouds.

    PubMed

    Chen, Wei-Nai; Chiang, Chih-Wei; Nee, Jan-Bai

    2002-10-20

    We report on studies of the lidar and the depolarization ratios for cirrus clouds. The optical depth and effective lidar ratio are derived from the transmission of clouds, which is determined by comparing the backscattering signals at the cloud base and cloud top. The lidar signals were fitted to a background atmospheric density profile outside the cloud region to warrant the linear response of the return signals with the scattering media. An average lidar ratio, 29 +/- 12 sr, has been found for all clouds measured in 1999 and 2000. The height and temperature dependences ofthe lidar ratio, the optical depth, and the depolarization ratio were investigated and compared with results of LITE and PROBE. Cirrus clouds detected near the tropopause are usually optically thin and mostly subvisual. Clouds with the largest optical depths were found near 12 km with a temperature of approximately -55 degrees C. The multiple-scattering effect is considered for clouds with high optical depths, and this effect lowers the lidar ratios compared with a single-scattering condition. Lidar ratios are in the 20-40 range for clouds at heights of 12.5-15 km and are smaller than approximately 30 in height above 15 km. Clouds are usually optically thin for temperatures below approximately -65 degrees C, and in this region the optical depth tends to decrease with height. The depolarization ratio is found to increase with a height at 11-15 km and smaller than 0.3 above 16 km. The variation in the depolarization ratio with the lidar ratio was also reported. The lidar and depolarization ratios were discussed in terms of the types of hexagonal ice crystals.

  14. Sex Ratio Elasticity Influences the Selection of Sex Ratio Strategy.

    PubMed

    Wang, Yaqiang; Wang, Ruiwu; Li, Yaotang; Sam Ma, Zhanshan

    2016-12-23

    There are three sex ratio strategies (SRS) in nature-male-biased sex ratio, female-biased sex ratio and, equal sex ratio. It was R. A. Fisher who first explained why most species in nature display a sex ratio of ½. Consequent SRS theories such as Hamilton's local mate competition (LMC) and Clark's local resource competition (LRC) separately explained the observed deviations from the seemingly universal 1:1 ratio. However, to the best of our knowledge, there is not yet a unified theory that accounts for the mechanisms of the three SRS. Here, we introduce the price elasticity theory in economics to define sex ratio elasticity (SRE), and present an analytical model that derives three SRSs based on the following assumption: simultaneously existing competitions for both resources A and resources B influence the level of SRE in both sexes differently. Consequently, it is the difference (between two sexes) in the level of their sex ratio elasticity that leads to three different SRS. Our analytical results demonstrate that the elasticity-based model not only reveals a highly plausible mechanism that explains the evolution of SRS in nature, but also offers a novel framework for unifying two major classical theories (i.e., LMC &LRC) in the field of SRS research.

  15. Sex Ratio Elasticity Influences the Selection of Sex Ratio Strategy

    PubMed Central

    Wang, Yaqiang; Wang, Ruiwu; Li, Yaotang; (Sam) Ma, Zhanshan

    2016-01-01

    There are three sex ratio strategies (SRS) in nature—male-biased sex ratio, female-biased sex ratio and, equal sex ratio. It was R. A. Fisher who first explained why most species in nature display a sex ratio of ½. Consequent SRS theories such as Hamilton’s local mate competition (LMC) and Clark’s local resource competition (LRC) separately explained the observed deviations from the seemingly universal 1:1 ratio. However, to the best of our knowledge, there is not yet a unified theory that accounts for the mechanisms of the three SRS. Here, we introduce the price elasticity theory in economics to define sex ratio elasticity (SRE), and present an analytical model that derives three SRSs based on the following assumption: simultaneously existing competitions for both resources A and resources B influence the level of SRE in both sexes differently. Consequently, it is the difference (between two sexes) in the level of their sex ratio elasticity that leads to three different SRS. Our analytical results demonstrate that the elasticity-based model not only reveals a highly plausible mechanism that explains the evolution of SRS in nature, but also offers a novel framework for unifying two major classical theories (i.e., LMC & LRC) in the field of SRS research. PMID:28009000

  16. Sex Ratio Elasticity Influences the Selection of Sex Ratio Strategy

    NASA Astrophysics Data System (ADS)

    Wang, Yaqiang; Wang, Ruiwu; Li, Yaotang; (Sam) Ma, Zhanshan

    2016-12-01

    There are three sex ratio strategies (SRS) in nature—male-biased sex ratio, female-biased sex ratio and, equal sex ratio. It was R. A. Fisher who first explained why most species in nature display a sex ratio of ½. Consequent SRS theories such as Hamilton’s local mate competition (LMC) and Clark’s local resource competition (LRC) separately explained the observed deviations from the seemingly universal 1:1 ratio. However, to the best of our knowledge, there is not yet a unified theory that accounts for the mechanisms of the three SRS. Here, we introduce the price elasticity theory in economics to define sex ratio elasticity (SRE), and present an analytical model that derives three SRSs based on the following assumption: simultaneously existing competitions for both resources A and resources B influence the level of SRE in both sexes differently. Consequently, it is the difference (between two sexes) in the level of their sex ratio elasticity that leads to three different SRS. Our analytical results demonstrate that the elasticity-based model not only reveals a highly plausible mechanism that explains the evolution of SRS in nature, but also offers a novel framework for unifying two major classical theories (i.e., LMC & LRC) in the field of SRS research.

  17. Software For Computing Image Ratios

    NASA Technical Reports Server (NTRS)

    Yates, Gigi L.

    1993-01-01

    RATIO_TOOL is interactive computer program for viewing and analyzing large sets of multispectral image data created by imaging spectrometer. Uses ratios between intensities in different spectral bands in order to spot significant areas of interest within multispectral image. Each image band viewed iteratively, or selected image band of set of data requested and displayed. When image ratios computed, result displayed as grayscale image. Written in C Language.

  18. Feedback versus no feedback in improving patient outcome in group psychotherapy for eating disorders (F-EAT): protocol for a randomized clinical trial

    PubMed Central

    2014-01-01

    Background Continuous feedback on patient improvement and the therapeutic alliance may reduce the number of dropouts and increase patient outcome. There are, however, only three published randomized trials on the effect of feedback on the treatment of eating disorders, showing inconclusive results, and there are no randomized trials on the effect of feedback in group therapy. Accordingly the current randomized clinical trial, initiated in September 2012 at the outpatient clinic for eating disorders at Stolpegaard Psychotherapy Centre, aims to investigate the impact of continuous feedback on attendance and outcome in group psychotherapy. Methods/design The hypothesis is that continuous feedback to both patient and therapist on treatment progress and alliance will increase attendance and treatment outcome. The trial is set up using a randomized design with a minimum of 128 patients allocated to either an experimental or control group at a ratio of 1:1. The experimental group will receive standard treatment (systemic and narrative group psychotherapy) with feedback intervention, whereas the control group will receive standard treatment only. The participants are diagnosed with bulimia nervosa, binge eating disorder, or an eating disorder not otherwise specified, according to the DSM-IV. In the experimental group feedback to the participants, based on the Outcome Rating Scale (ORS) and the Group Session Rating Scale (GSRS), is actively added to standard treatment. The ORS assesses areas of life functioning known to change as a result of therapeutic intervention. The GSRS assesses key dimensions of effective therapeutic relationships. In the control group, the patients fill out the Outcome Rating Scale only, and feedback is not provided. The primary outcome is the rate of attendance to treatment sessions. The secondary outcome is the severity of eating disorder symptoms. Exploratory outcomes are the level of psychological and social functioning, and suicide or self

  19. Prevalence odds ratio versus prevalence ratio: choice comes with consequences.

    PubMed

    Tamhane, Ashutosh R; Westfall, Andrew O; Burkholder, Greer A; Cutter, Gary R

    2016-12-30

    Odds ratio, risk ratio, and prevalence ratio are some of the measures of association which are often reported in research studies quantifying the relationship between an independent variable and the outcome of interest. There has been much debate on the issue of which measure is appropriate to report depending on the study design. However, the literature on selecting a particular category of the outcome to be modeled and/or change in reference group for categorical independent variables and the effect on statistical significance, although known, is scantly discussed nor published with examples. In this article, we provide an example of a cross-sectional study wherein prevalence ratio was chosen over (Prevalence) odds ratio and demonstrate the analytic implications of the choice of category to be modeled and choice of reference level for independent variables. Copyright © 2016 John Wiley & Sons, Ltd.

  20. Exploring Occupational Therapy Students' Meaning of Feedback during Fieldwork Experiences

    ERIC Educational Resources Information Center

    Rathgeber, Karen Lynne

    2014-01-01

    Researchers have revealed that students' confidence and performance improve after they receive feedback from clinical supervisors regarding the delivery of quality patient care. Multiple studies of feedback have focused on the provision and acceptance of feedback; however, it was not known if or how students internalized feedback to promote…

  1. Feedback Expectancy and EFL Learners' Achievement in English

    ERIC Educational Resources Information Center

    Alavi, Seyyed Mohammad; Kaivanpanah, Shiva

    2007-01-01

    This study aims to explore the relationship between feedback expectancy of Iranian learners of English and their level of education, achievement in English, and attitude toward peer and teacher feedback. To fulfill the purpose of this study, a sixty-item questionnaire focusing on issues related to feedback expectancy, peer feedback, teacher…

  2. Rethinking Feedback Practices in Higher Education: A Peer Review Perspective

    ERIC Educational Resources Information Center

    Nicol, David; Thomson, Avril; Breslin, Caroline

    2014-01-01

    Peer review is a reciprocal process whereby students produce feedback reviews on the work of peers and receive feedback reviews from peers on their own work. Prior research has primarily examined the learning benefits that result from the receipt of feedback reviews, with few studies specifically exploring the merits of producing feedback reviews…

  3. Immediate Feedback and Learning in Athletic Training Education

    ERIC Educational Resources Information Center

    Bowman, Thomas G.; Laurent, Tim

    2011-01-01

    Context: Immediate feedback has been shown to improve student learning more efficiently than delayed feedback in lower-level general education courses. No research exists examining the effects of immediate feedback on learning in higher-level athletic training coursework. Objective: To determine if using the Immediate Feedback Assessment Technique…

  4. Using Screencasts to Enhance Assessment Feedback: Students' Perceptions and Preferences

    ERIC Educational Resources Information Center

    Marriott, Pru; Teoh, Lim Keong

    2012-01-01

    In the UK, assessment and feedback have been regularly highlighted by the National Student Survey as critical aspects that require improvement. An innovative approach to delivering feedback that has proved successful in non-business-related disciplines is the delivery of audio and visual feedback using screencast technology. The feedback on…

  5. Adapting Progress Feedback and Emotional Support to Learner Personality

    ERIC Educational Resources Information Center

    Dennis, Matt; Masthoff, Judith; Mellish, Chris

    2016-01-01

    As feedback is an important part of learning and motivation, we investigate how to adapt the feedback of a conversational agent to learner personality (as well as to learner performance, as we expect an interaction effect between personality and performance on feedback). We investigate two aspects of feedback. Firstly, we investigate whether the…

  6. A Role for Technology in Enhancing Students' Engagement with Feedback

    ERIC Educational Resources Information Center

    Parkin, Helen J.; Hepplestone, Stuart; Holden, Graham; Irwin, Brian; Thorpe, Louise

    2012-01-01

    This paper explores the potential of technology-enabled feedback to improve student learning. "Technology, Feedback, Action!: The impact of learning technology upon students' engagement with their feedback" aimed to evaluate how a range of technical interventions might encourage students to engage with feedback and formulate actions to…

  7. Feedback Frequency in Treatment for Childhood Apraxia of Speech

    ERIC Educational Resources Information Center

    Maas, Edwin; Butalla, Christine E.; Farinella, Kimberly A.

    2012-01-01

    Purpose: To examine the role of feedback frequency in treatment for childhood apraxia of speech (CAS). Reducing the frequency of feedback enhances motor learning, and recently, such feedback frequency reductions have been recommended for the treatment of CAS. However, no published studies have explicitly compared different feedback frequencies in…

  8. EFL Teachers' Attempts at Feedback Innovation in the Writing Classroom

    ERIC Educational Resources Information Center

    Lee, Icy; Mak, Pauline; Burns, Anne

    2016-01-01

    To date, research on feedback in second language (L2) writing has primarily focused on feedback per se, with little attention paid to the teachers' professional development with regard to feedback in writing. This study aims to explore the ways in which two secondary teachers in Hong Kong attempted to implement feedback innovation in their writing…

  9. Factors Influencing Spanish Instructors' In-Class Feedback Decisions

    ERIC Educational Resources Information Center

    Gurzynski-Weiss, Laura

    2016-01-01

    While oral corrective feedback is a principal focus in second language acquisition research, most studies examine feedback once it has been provided. Investigating how instructors make in-class feedback decisions has not been thoroughly explored, despite the fact that classroom feedback occurs at the discretion of the individual language…

  10. Effects of Web-Based Feedback on Students' Learning

    ERIC Educational Resources Information Center

    van Kol, Simone; Rietz, Christian

    2016-01-01

    Feedback plays an important role in supporting students' learning process. Nonetheless, providing feedback is still rather unusual in higher education. Moreover, research on the design of ideal feedback as well as its effects is rare. In order to contribute to the development of this field, a web-based feedback system was implemented in a lecture…

  11. Uncovering Embedded Face Threat Mitigation in Landscape Architecture Critique Feedback

    ERIC Educational Resources Information Center

    Housley Gaffney, Amy L.

    2015-01-01

    Receiving public feedback on academic work may threaten students' face, particularly when such feedback is critical. One way that feedback may be cushioned is through face-threat mitigation techniques. I analyzed the use of such techniques in the feedback given by faculty and professionals to landscape architecture students as preparation for…

  12. Design and application of feedback-sustained target waves in excitable medium

    NASA Astrophysics Data System (ADS)

    Wu, Ningjie; Chen, Jiangxing; Gao, Hongjun; Ying, Heping

    2013-01-01

    In this paper, we present a formulas of rational ratios between the frequency of external stimulus and its paced target waves, considering the existence of the absolute refractory period and the relative refractory period. Based on this, we design a self-sustained high-frequency target waves by feeding back few periphery field points to the center to responsibly play the role of source for pacemaker. Such constructed target waves, to all appearances, are shown as a repetition of their initial condition. We explore further in application that those feedback-sustained targets can eliminate both a freely rotating spiral waves and a pinned ones only if frequencies, feedback lengths and radius of obstacles are appropriately chosen. After feedback stimuli are removed, the system eventually returns to the rest state.

  13. Magnetospheric Feedback Effects on Mercury's Dynamo

    NASA Astrophysics Data System (ADS)

    Gomez Perez, N.; Heyner, D.; Wicht, J.; Solomon, S. C.; Glassmeier, K.

    2010-12-01

    The internal magnetic field of Mercury has been sampled by the Mariner 10 and MESSENGER spacecraft during a combined total of five flybys to date. The measurements are consistent with a magnetic dipole moment of ~ 250 nT RM3, where RM is the radius of Mercury. The action of high solar wind pressure at Mercury’s solar distance on such a weak internal field produces a small magnetosphere for which the dayside magnetopause is unusually close to the surface of the planet (at a planetocentric distance of about 1.5 RM). Because of this small magnetosphere and Mercury’s relatively thin silicate mantle, it has been proposed that magnetospheric currents may influence the internal dynamo process. From numerical simulations, we have previously demonstrated that magnetic field sources external to the dynamo-generating region may modify core dynamics and that this magnetospheric feedback may have influenced the history of Mercury’s dipole field. Here we combine new results from two types of numerical simulations. First, we estimate the magnitude of magnetospheric surface currents with a semi-empirical Earth model adapted to Mercury’s conditions. These currents are calculated for a range of internal dipole moments to establish the functional dependence of the feedback magnitude on internal field amplitude. Second, we implement this feedback function in the internal dynamo model. Earlier magnetospheric feedback models, such as those by Glassmeier and others and Heyner and others, demonstrated that this process is able to sustain an extremely weak magnetic field. Our new, more realistic feedback function leads to slower secular variation than in previous dynamic feedback models, but the secular variation is still typically faster than for isolated dynamos that neglect the external field altogether. Most generally, magnetospheric feedback is able to stabilize a weak dipole field with characteristics that are consistent in magnitude and form with measurements at Mercury.

  14. How stellar feedback simultaneously regulates star formation and drives outflows

    NASA Astrophysics Data System (ADS)

    Hayward, Christopher C.; Hopkins, Philip F.

    2017-02-01

    We present an analytic model for how momentum deposition from stellar feedback simultaneously regulates star formation and drives outflows in a turbulent interstellar medium (ISM). Because the ISM is turbulent, a given patch of ISM exhibits sub-patches with a range of surface densities. The high-density patches are 'pushed' by feedback, thereby driving turbulence and self-regulating local star formation. Sufficiently low-density patches, however, are accelerated to above the escape velocity before the region can self-adjust and are thus vented as outflows. When the gas fraction is ≳ 0.3, the ratio of the turbulent velocity dispersion to the circular velocity is sufficiently high that at any given time, of the order of half of the ISM has surface density less than the critical value and thus can be blown out on a dynamical time. The resulting outflows have a mass-loading factor (η ≡ dot{M}_{out}/M_{star }) that is inversely proportional to the gas fraction times the circular velocity. At low gas fractions, the star formation rate needed for local self-regulation, and corresponding turbulent Mach number, declines rapidly; the ISM is 'smoother', and it is actually more difficult to drive winds with large mass-loading factors. Crucially, our model predicts that stellar-feedback-driven outflows should be suppressed at z ≲ 1 in M⋆ ≳ 1010 M⊙ galaxies. This mechanism allows massive galaxies to exhibit violent outflows at high redshifts and then 'shut down' those outflows at late times, thereby enabling the formation of a smooth, extended thin stellar disc. We provide simple fitting functions for η that should be useful for sub-resolution and semi-analytic models.

  15. Self-Controlled Feedback in 10-Year-Old Children: Higher Feedback Frequencies Enhance Learning

    ERIC Educational Resources Information Center

    Chiviacowsky, Suzete; Wulf, Gabriele; de Medeiros, Franklin Laroque; Kaefer, Angelica; Wally, Raquel

    2008-01-01

    The purpose of the present study was to examine whether learning in 10-year-old children--that is, the age group for which the Chiviacowsky et al. (2006) study found benefits of self-controlled knowledge of results (KR)--would differ depending on the frequency of feedback they chose. The authors surmised that a relatively high feedback frequency…

  16. Partial Compensation for Altered Auditory Feedback: A Tradeoff with Somatosensory Feedback?

    ERIC Educational Resources Information Center

    Katseff, Shira; Houde, John; Johnson, Keith

    2012-01-01

    Talkers are known to compensate only partially for experimentally-induced changes to their auditory feedback. In a typical experiment, talkers might hear their F1 feedback shifted higher (so that /[epsilon]/ sounds like /[ash]/, for example), and compensate by lowering F1 in their subsequent speech by about a quarter of that distance. Here, we…

  17. Enhancing the Impact of Formative Feedback on Student Learning through an Online Feedback System

    ERIC Educational Resources Information Center

    Hatziapostolou, Thanos; Paraskakis, Iraklis

    2010-01-01

    Formative feedback is instrumental in the learning experience of a student. It can be effective in promoting learning if it is timely, personal, manageable, motivational, and in direct relation with assessment criteria. Despite its importance, however, research suggests that students are discouraged from engaging in the feedback process primarily…

  18. Accounting Students' Feedback on Feedback in Australian Universities: They're Less than Impressed

    ERIC Educational Resources Information Center

    Watty, Kim; de Lange, Paul; Carr, Rodney; O'Connell, Brendan; Howieson, Bryan; Jacobsen, Ben

    2013-01-01

    Undergraduate accounting students in Australian universities are dissatisfied with the feedback that they currently receive. Recent evidence from the Course Experience Questionnaire (CEQ, a national survey of Australian university graduates) suggests that the accounting discipline ranks poorly on assessment feedback when compared to other…

  19. Self-reinnervated muscles lose autogenic length feedback, but intermuscular feedback can recover functional connectivity.

    PubMed

    Lyle, Mark A; Prilutsky, Boris I; Gregor, Robert J; Abelew, Thomas A; Nichols, T Richard

    2016-09-01

    In this study, we sought to identify sensory circuitry responsible for motor deficits or compensatory adaptations after peripheral nerve cut and repair. Self-reinnervation of the ankle extensor muscles abolishes the stretch reflex and increases ankle yielding during downslope walking, but it remains unknown whether this finding generalizes to other muscle groups and whether muscles become completely deafferented. In decerebrate cats at least 19 wk after nerve cut and repair, we examined the influence of quadriceps (Q) muscles' self-reinnervation on autogenic length feedback, as well as intermuscular length and force feedback, among the primary extensor muscles in the cat hindlimb. Effects of gastrocnemius and soleus self-reinnervation on intermuscular circuitry were also evaluated. We found that autogenic length feedback was lost after Q self-reinnervation, indicating that loss of the stretch reflex appears to be a generalizable consequence of muscle self-reinnervation. However, intermuscular force and length feedback, evoked from self-reinnervated muscles, was preserved in most of the interactions evaluated with similar relative inhibitory or excitatory magnitudes. These data indicate that intermuscular spinal reflex circuitry has the ability to regain functional connectivity, but the restoration is not absolute. Explanations for the recovery of intermuscular feedback are discussed, based on identified mechanisms responsible for lost autogenic length feedback. Functional implications, due to permanent loss of autogenic length feedback and potential for compensatory adaptations from preserved intermuscular feedback, are discussed.

  20. The Effect of Combination of Video Feedback and Audience Feedback on Social Anxiety: Preliminary Findings.

    PubMed

    Chen, Junwen; Mak, Rebecca; Fujita, Satoko

    2015-09-01

    Although video feedback (VF) is shown to improve appraisals of social performance in socially anxious individuals, its impact on state anxiety during a social situation is mixed. The current study investigated the effect of combined video feedback and audience feedback (AF) on self-perceptions of performance and bodily sensations as well as state anxiety pertaining to a speech task. Forty-one socially anxious students were randomly allocated to combined video feedback with audience feedback (VF + AF), video feedback only (VF), audience feedback only (AF), or a control condition. Following a 3-min speech, participants in the VF + AF, VF, and AF conditions watched the videotape of their speech with cognitive preparation in the presence of three confederates who served as audience, and/or received feedback from the confederates, while the control group watched their videotaped speech without cognitive preparation. Both VF + AF and AF conditions improved distorted appraisal of performance and bodily sensations as well as state anxiety. The clinical implications of these findings are discussed.

  1. Is transverse feedback necessary for the SSC emittance preservation? (Vibration noise analysis and feedback parameters optimization)

    SciTech Connect

    Parkhomchuk, V.V.; Shiltsev, V.D.

    1993-06-01

    The paper considers the Superconducting Super Collider (SSC) site ground motion measurements as well as data from accelerators worldwide about noises that worsen beam performance. Unacceptably fast emittance growth due to these noises is predicted for the SSC. A transverse feedback system was found to be the only satisfactory alternative to prevent emittance decay. Optimization of the primary feedback parameters was done.

  2. Investigating Feedback on Practice among Teachers: Coherence of Observed and Perceived Feedback

    ERIC Educational Resources Information Center

    Thurlings, Marieke; Vermeulen, Marjan; Bastiaens, Theo; Stijnen, Sjef

    2012-01-01

    Despite that benefits of feedback in student learning are reported in much research, little has been reported regarding the use of feedback from teachers to other teachers--a key tool in professional development. In this study, we triangulated data from videotaped peer coaching sessions, questionnaires, and interviews regarding 12 primary school…

  3. Feedback Providing Improvement Strategies and Reflection on Feedback Use: Effects on Students' Writing Motivation, Process, and Performance

    ERIC Educational Resources Information Center

    Duijnhouwer, Hendrien; Prins, Frans J.; Stokking, Karel M.

    2012-01-01

    This study investigated the effects of feedback providing improvement strategies and a reflection assignment on students' writing motivation, process, and performance. Students in the experimental feedback condition (n = 41) received feedback including improvement strategies, whereas students in the control feedback condition (n = 41) received…

  4. Prompting Secondary Students' Use of Criteria, Feedback Specificity and Feedback Levels during an Investigative Task

    ERIC Educational Resources Information Center

    Gan, Mark J. S.; Hattie, John

    2014-01-01

    This study investigates the effects of prompting on secondary students' written peer feedback in chemistry investigation reports. In particular, we examined students' feedback features in relation to the use of criteria, feedback specificity, and feedback levels. A quasi-experimental pre-test post-test design was adopted. Reviewers in…

  5. Proprioceptive feedback determines visuomotor gain in Drosophila

    PubMed Central

    Bartussek, Jan; Lehmann, Fritz-Olaf

    2016-01-01

    Multisensory integration is a prerequisite for effective locomotor control in most animals. Especially, the impressive aerial performance of insects relies on rapid and precise integration of multiple sensory modalities that provide feedback on different time scales. In flies, continuous visual signalling from the compound eyes is fused with phasic proprioceptive feedback to ensure precise neural activation of wing steering muscles (WSM) within narrow temporal phase bands of the stroke cycle. This phase-locked activation relies on mechanoreceptors distributed over wings and gyroscopic halteres. Here we investigate visual steering performance of tethered flying fruit flies with reduced haltere and wing feedback signalling. Using a flight simulator, we evaluated visual object fixation behaviour, optomotor altitude control and saccadic escape reflexes. The behavioural assays show an antagonistic effect of wing and haltere signalling on visuomotor gain during flight. Compared with controls, suppression of haltere feedback attenuates while suppression of wing feedback enhances the animal’s wing steering range. Our results suggest that the generation of motor commands owing to visual perception is dynamically controlled by proprioception. We outline a potential physiological mechanism based on the biomechanical properties of WSM and sensory integration processes at the level of motoneurons. Collectively, the findings contribute to our general understanding how moving animals integrate sensory information with dynamically changing temporal structure. PMID:26909184

  6. Determinants of feedback retention in soccer players

    PubMed Central

    Januário, Nuno; Rosado, António; Mesquita, Isabel; Aguilar-Parra, José M.

    2016-01-01

    Abstract This study analyzed soccer players’ retention of coaches’ feedback during training sessions. We intended to determine if the retention of information was influenced by the athletes’ personal characteristic (age, gender and the sports level), the quantity of information included in coach’s feedback (the number of ideas and redundancy), athletes’ perception of the relevance of the feedback information and athletes’ motivation as well as the attention level. The study that was conducted over the course of 18 sessions of soccer practice, involved 12 coaches (8 males, 4 females) and 342 athletes (246 males, 96 females), aged between 10 and 18 years old. All coach and athlete interventions were transposed to a written protocol and submitted to content analysis. Descriptive statistics and multiple linear regression were calculated. The results showed that a substantial part of the information was not retained by the athletes; in 65.5% of cases, athletes experienced difficulty in completely reproducing the ideas of the coaches and, on average, the value of feedback retention was 57.0%. Six variables with a statistically significant value were found: gender, the athletes’ sports level, redundancy, the number of transmitted ideas, athletes’ perception of the relevance of the feedback information and the athletes’ motivation level. PMID:28149387

  7. Mesoscale modeling of smoke radiative feedback over the Sahel region

    NASA Astrophysics Data System (ADS)

    Yang, Z.; Wang, J.; Ichoku, C. M.; Ellison, L.; Zhang, F.; Yue, Y.

    2013-12-01

    This study employs satellite observations and a fully-coupled meteorology-chemistry-aerosol model, Weather Research and Forecasting model with Chemistry (WRF-Chem) to study the smoke radative feedback on surface energy budget, boundary layer processes, and atmospheric lapse rate in February 2008 over the Sahel region. The smoke emission inventories we use come from various sources, including but not limited to the Fire Locating and Modeling of Burning Emissions (FLAMBE) developed by NRL and the Fire Energetic and Emissions Research (FEER) developed by NASA GSFC. Model performance is evaluated using numerous satellite and ground-based datasets: MODIS true color images, ground-based Aerosol Optical Depth (AOD) measurements from AERONET, MODIS AOD retrievals, and Cloud-Aerosol Lidar data with Orthogonal Polarization (CALIOP) atmospheric backscattering and extinction products. Specification of smoke injection height of 650 m in WRF-Chem yields aerosol vertical profiles that are most consistent with CALIOP observations of aerosol layer height. Statistically, 5% of the CALIPSO valid measurements of aerosols in February 2008 show aerosol layers either above the clouds or between the clouds, reinforcing the importance of the aerosol vertical distribution for quantifying aerosol impact on climate in the Sahel region. The results further show that the smoke radiative feedbacks are sensitive to assumptions of black carbon and organic carbon ratio in the particle emission inventory. Also investigated is the smoke semi-direct effect as a function of cloud fraction.

  8. Coaxial needle insertion assistant with enhanced force feedback.

    PubMed

    De Lorenzo, Danilo; Koseki, Yoshihiko; De Momi, Elena; Chinzei, Kiyoyuki; Okamura, Allison M

    2013-02-01

    Many medical procedures involving needle insertion into soft tissues, such as anesthesia, biopsy, brachytherapy, and placement of electrodes, are performed without image guidance. In such procedures, haptic detection of changing tissue properties at different depths during needle insertion is important for needle localization and detection of subsurface structures. However, changes in tissue mechanical properties deep inside the tissue are difficult for human operators to sense, because the relatively large friction force between the needle shaft and the surrounding tissue masks the smaller tip forces. A novel robotic coaxial needle insertion assistant, which enhances operator force perception, is presented. This one-degree-of-freedom cable-driven robot provides to the operator a scaled version of the force applied by the needle tip to the tissue, using a novel design and sensors that separate the needle tip force from the shaft friction force. The ability of human operators to use the robot to detect membranes embedded in artificial soft tissue was tested under the conditions of 1) tip force and shaft force feedback, and 2) tip force only feedback. The ratio of successful to unsuccessful membrane detections was significantly higher (up to 50%) when only the needle tip force was provided to the user.

  9. Effects of Partial Absence of Visual Feedback Information on Gait Symmetry.

    PubMed

    Kim, Seung-Jae; Kayitesi, Marie Aimee; Chan, Amy; Graham, Kimberli

    2017-03-14

    The incorporation of real-time visual feedback during gait rehabilitation can improve the efficacy of training. Our prior work demonstrated that the imposed distortion of simple visual feedback information of step lengths entails an unintentional adaptive process in the subjects' spatial gait pattern, thereby suggesting the important role of implicit learning in the context of gait rehabilitation that employs visual feedback. The purpose of this study was to investigate whether the removal of a portion of visual feedback information-after it had initially been provided-had any impact on gait symmetry. Eighteen healthy subjects walked on a treadmill for 10-min periods at their preferred walking speed and at a slower walking speed (1.3 mph) during the experimental trials, in which two simple vertical bars corresponding to subject's right and left step length were displayed on a computer screen. Halfway through the trial, one of the bars was removed from the visual feedback via random selection. Subjects were instructed to continually walk normally and also look at the visual feedback until the trials were completed. The changes in step length symmetry ratio were computed and analyzed. We found that displaying only one side of visual feedback influenced subjects to spontaneously modulate gait symmetry away from the baseline, and also that the amount of modulated gait symmetry slightly increased when their walking speed decreased. The changes in gait symmetry occurred by producing either longer right steps produced than left steps or vice versa, but we were unable to find any correlation between side of removal (right or left side) and the different types of trend in response. This warrants further investigation in a study with a larger population. Nonetheless, the results of this study demonstrated the effect of partial absence of visual feedback on changes in step symmetry, and that the perturbation of visual information caused implicit (unintentional) motor

  10. Appearance and Disappearance of Quantum Correlations in Measurement-Based Feedback Control of a Mechanical Oscillator

    NASA Astrophysics Data System (ADS)

    Sudhir, V.; Wilson, D. J.; Schilling, R.; Schütz, H.; Fedorov, S. A.; Ghadimi, A. H.; Nunnenkamp, A.; Kippenberg, T. J.

    2017-01-01

    Quantum correlations between imprecision and backaction are a hallmark of continuous linear measurements. Here, we study how measurement-based feedback can be used to improve the visibility of quantum correlations due to the interaction of a laser field with a nanomechanical oscillator. Backaction imparted by the meter laser, due to radiation-pressure quantum fluctuations, gives rise to correlations between its phase and amplitude quadratures. These quantum correlations are observed in the experiment both as squeezing of the meter field fluctuations below the vacuum level in a homodyne measurement and as sideband asymmetry in a heterodyne measurement, demonstrating the common origin of both phenomena. We show that quantum feedback, i.e., feedback that suppresses measurement backaction, can be used to increase the visibility of the sideband asymmetry ratio. In contrast, by operating the feedback loop in the regime of noise squashing, where the in-loop photocurrent variance is reduced below the vacuum level, the visibility of the sideband asymmetry is reduced. This is due to backaction arising from vacuum noise in the homodyne detector. These experiments demonstrate the possibility, as well as the fundamental limits, of measurement-based feedback as a tool to manipulate quantum correlations.

  11. Anomalous feedback and negative domain wall resistance

    NASA Astrophysics Data System (ADS)

    Cheng, Ran; Zhu, Jian-Gang; Xiao, Di

    2016-11-01

    Magnetic induction can be regarded as a negative feedback effect, where the motive-force opposes the change of magnetic flux that generates the motive-force. In artificial electromagnetics emerging from spintronics, however, this is not necessarily the case. By studying the current-induced domain wall dynamics in a cylindrical nanowire, we show that the spin motive-force exerting on electrons can either oppose or support the applied current that drives the domain wall. The switching into the anomalous feedback regime occurs when the strength of the dissipative torque β is about twice the value of the Gilbert damping constant α. The anomalous feedback manifests as a negative domain wall resistance, which has an analogy with the water turbine.

  12. Nonlinear plants, factorizations and stable feedback systems

    NASA Technical Reports Server (NTRS)

    Desoer, Charles A.; Kabuli, M. Guntekin

    1987-01-01

    For nonlinear plants represented by causal maps defined over extended spaces, right factorization and normalized right-coprime factorization concepts are discussed in terms of well-posed stable feedback systems. This setup covers continuous-time, discrete-time, time-invariant or time-varying input-output maps. The nonlinear maps are factored in terms of causal bounded-input bounded-output stable maps. In factored form, all instabilities of the original map are represented by the inverse of a causal stable `denominator' map. The existence of maps with right factorizations and normalized right-coprime factorizations is shown using a well-posed stable unity-feedback system. In the case where one of the subsystems has a normalized right-coprime factorization, the stability of the feedback system is equivalent to the stability of the pseudostate map.

  13. Preceptor Development: Providing Effective Feedback, Part 2

    PubMed Central

    Wilkinson, Samaneh T.; Phillips, Holly

    2014-01-01

    Abstract An integral part of providing effective feedback to pharmacy residents occurs during the evaluation process. Residency evaluation involves measuring and documenting performance as it relates to standardized residency outcomes, goals, and learning objectives. Evaluations may be formative or summative and include the preceptor’s evaluation of the resident’s performance, the resident’s self-assessments, and the resident’s evaluation of the preceptor and learning experience. Evaluations are more structured than feedback, and they involve documentation of the verbal feedback that was provided throughout the learning experience. This article will focus on the preceptor’s role in providing effective resident evaluations based on specific learning activities. PMID:24958969

  14. Stellar feedback in dwarf galaxy formation.

    PubMed

    Mashchenko, Sergey; Wadsley, James; Couchman, H M P

    2008-01-11

    Dwarf galaxies pose substantial challenges for cosmological models. In particular, current models predict a dark-matter density that is divergent at the center, which is in sharp contrast with observations that indicate a core of roughly constant density. Energy feedback, from supernova explosions and stellar winds, has been proposed as a major factor shaping the evolution of dwarf galaxies. We present detailed cosmological simulations with sufficient resolution both to model the relevant physical processes and to directly assess the impact of stellar feedback on observable properties of dwarf galaxies. We show that feedback drives large-scale, bulk motions of the interstellar gas, resulting in substantial gravitational potential fluctuations and a consequent reduction in the central matter density, bringing the theoretical predictions in agreement with observations.

  15. Visual Feedback Leader-following Attitude Synchronization

    NASA Astrophysics Data System (ADS)

    Ibuki, Tatsuya; Hatanaka, Takeshi; Fujita, Masayuki

    In this paper we investigate visual feedback attitude synchronization in leader-follower type visibility structures on the Special Euclidean group SE(3). We first define visual robotic networks consisting of the dynamics describing rigid body motion, visibility structures among bodies and visual measurements. We then propose a visual feedback attitude synchronization law combining a vision-based observer with the attitude synchronization law presented in our previous works. We then prove that when the leader does not rotate, the visual robotic network with the control law achieves visual feedback attitude synchronization. Moreover, for a rotating leader, we evaluate the tracking performance of the other bodies. In analysis, we employ the notion of input-to-state stability and L2-gain performance regarding the leader’s angular velocity as an external disturbance. Finally, the validity of the proposed control law and the analysis is demonstrated through simulations.

  16. Feedback, Lineages and Self-Organizing Morphogenesis

    PubMed Central

    Calof, Anne L.; Lowengrub, John S.; Lander, Arthur D.

    2016-01-01

    Feedback regulation of cell lineage progression plays an important role in tissue size homeostasis, but whether such feedback also plays an important role in tissue morphogenesis has yet to be explored. Here we use mathematical modeling to show that a particular feedback architecture in which both positive and negative diffusible signals act on stem and/or progenitor cells leads to the appearance of bistable or bi-modal growth behaviors, ultrasensitivity to external growth cues, local growth-driven budding, self-sustaining elongation, and the triggering of self-organization in the form of lamellar fingers. Such behaviors arise not through regulation of cell cycle speeds, but through the control of stem or progenitor self-renewal. Even though the spatial patterns that arise in this setting are the result of interactions between diffusible factors with antagonistic effects, morphogenesis is not the consequence of Turing-type instabilities. PMID:26989903

  17. Time-Delayed Quantum Feedback Control.

    PubMed

    Grimsmo, Arne L

    2015-08-07

    A theory of time-delayed coherent quantum feedback is developed. More specifically, we consider a quantum system coupled to a bosonic reservoir creating a unidirectional feedback loop. It is shown that the dynamics can be mapped onto a fictitious series of cascaded quantum systems, where the system is driven by past versions of itself. The derivation of this model relies on a tensor network representation of the system-reservoir time propagator. For concreteness, this general theory is applied to a driven two-level atom scattering into a coherent feedback loop. We demonstrate how delay effects can qualitatively change the dynamics of the atom and how quantum control can be implemented in the presence of time delays.

  18. High ratio recirculating gas compressor

    DOEpatents

    Weinbrecht, John F.

    1989-01-01

    A high ratio positive displacement recirculating rotary compressor is disclosed. The compressor includes an integral heat exchanger and recirculation conduits for returning cooled, high pressure discharge gas to the compressor housing to reducing heating of the compressor and enable higher pressure ratios to be sustained. The compressor features a recirculation system which results in continuous and uninterrupted flow of recirculation gas to the compressor with no direct leakage to either the discharge port or the intake port of the compressor, resulting in a capability of higher sustained pressure ratios without overheating of the compressor.

  19. High ratio recirculating gas compressor

    DOEpatents

    Weinbrecht, J.F.

    1989-08-22

    A high ratio positive displacement recirculating rotary compressor is disclosed. The compressor includes an integral heat exchanger and recirculation conduits for returning cooled, high pressure discharge gas to the compressor housing to reducing heating of the compressor and enable higher pressure ratios to be sustained. The compressor features a recirculation system which results in continuous and uninterrupted flow of recirculation gas to the compressor with no direct leakage to either the discharge port or the intake port of the compressor, resulting in a capability of higher sustained pressure ratios without overheating of the compressor. 10 figs.

  20. 40 CFR 1051.115 - What other requirements apply?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... range (specified in paragraph (d)(1) of this section) must include all air-fuel ratios between the lean... lean limit is the air-fuel ratio that produces the highest engine power output (averaged over the...

  1. 40 CFR 1051.115 - What other requirements apply?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... range (specified in paragraph (d)(1) of this section) must include all air-fuel ratios between the lean... lean limit is the air-fuel ratio that produces the highest engine power output (averaged over the...

  2. Metrology with AN Optical Feedback Frequency Stabilized Crds

    NASA Astrophysics Data System (ADS)

    Kassi, Samir; Burkart, Johannes

    2015-06-01

    We will present a metrological application of our recently developed Optical Feedback Frequency Stabilized - Cavity Ring Down Spectrometer (OFFS-CRDS). This instrument, which ideally fits with an optical frequency comb for absolute frequency calibration, relies on the robust lock of a steady cavity ring down resonator against a highly stable, radiofrequency tuned optical source. At 1.6 μm, over 7 nm, we demonstrate Lamb dip spectroscopy of CO_2 with line frequency retrieval at the kHz level, a dynamic in excess of 700,000 on the absorption scale and a detectivity of 4x10-13cm-1Hz-1/2. Such an instrument nicely meets the requirements for the most demanding spectroscopy spanning from accurate isotopic ratio determination and very precise lineshape recordings to Boltzmann constant redefinition.

  3. Thermally widely tunable laser diodes with distributed feedback

    SciTech Connect

    Todt, R.; Jacke, T.; Meyer, R.; Amann, M.-C.

    2005-07-11

    A thermally widely tunable buried heterostructure laser diode with distributed feedback (DFB) is demonstrated. This device requires only two tuning currents for wide quasicontinuous wavelength tuning, thereby facilitating easy and fast device calibration and control. Furthermore, being based on regular DFB laser fabrication technology, it is readily manufacturable. By using window structures instead of cleaved facets plus antireflection coatings, a regular tuning behavior has been achieved for a DFB-like widely tunable laser diode with only two tuning currents. The laser diode covers the wavelength range between 1552 and 1602 nm. Requiring side-mode suppression ratio and output power above 30 dB and 10 mW, respectively, a wavelength range of 43 nm is accessible.

  4. Thermally widely tunable laser diodes with distributed feedback

    NASA Astrophysics Data System (ADS)

    Todt, R.; Jacke, T.; Meyer, R.; Amann, M.-C.

    2005-07-01

    A thermally widely tunable buried heterostructure laser diode with distributed feedback (DFB) is demonstrated. This device requires only two tuning currents for wide quasicontinuous wavelength tuning, thereby facilitating easy and fast device calibration and control. Furthermore, being based on regular DFB laser fabrication technology, it is readily manufacturable. By using window structures instead of cleaved facets plus antireflection coatings, a regular tuning behavior has been achieved for a DFB-like widely tunable laser diode with only two tuning currents. The laser diode covers the wavelength range between 1552 and 1602 nm. Requiring side-mode suppression ratio and output power above 30 dB and 10 mW, respectively, a wavelength range of 43 nm is accessible.

  5. Feedback linearization application for LLRF control system

    SciTech Connect

    Kwon, S.; Regan, A.; Wang, Y.M.; Rohlev, T.

    1998-12-31

    The Low Energy Demonstration Accelerator (LEDA) being constructed at Los Alamos National Laboratory will serve as the prototype for the low energy section of Acceleration Production of Tritium (APT) accelerator. This paper addresses the problem of the LLRF control system for LEDA. The authors propose a control law which is based on exact feedback linearization coupled with gain scheduling which reduces the effect of the deterministic klystron cathode voltage ripple that is due to harmonics of the high voltage power supply and achieves tracking of desired set points. Also, they propose an estimator of the ripple and its time derivative and the estimates based feedback linearization controller.

  6. Fiber ring laser with a feedback mirror.

    PubMed

    Abitan, H; Bohr, H; Pedersen, C F

    2005-12-20

    We describe the spectral and power features of a ytterbium-doped double-clad photonic crystal fiber laser that is operated in a ring configuration with an external mirror that feeds back only one of its two output beams. We compare the operation of the laser with and without an external feedback mirror. We find that the feedback mirror reduces significantly the spectral and power fluctuations. It is also responsible for an interesting spectral phenomenon: The laser frequency is drifting periodically over 9 nm at a rate of 2 nm/s from a short wavelength to a longer wavelength and vice versa.

  7. Balanced-Bridge Feedback Control Of Motor

    NASA Technical Reports Server (NTRS)

    Lurie, Boris J.

    1990-01-01

    Sensitivity to variations in electrical and mechanical characteristics reduced. Proposed control system for motor-driven rotary actuator includes three nested feedback loops which, when properly designed, decoupled from each other. Intended to increase accuracy of control by mitigating such degrading effects as vibrations and variations in electrical and mechanical characteristics of structure rotated. Lends itself to optimization of performance via independent optimization of each of three loops. Includes outer, actuator, and driver feedback loops, configured so that actuator is subsystem, and driver is subsystem of actuator.

  8. The fast correction coil feedback control system

    SciTech Connect

    Coffield, F.; Caporaso, G.; Zentler, J.M.

    1989-01-01

    A model-based feedback control system has been developed to correct beam displacement errors in the Advanced Test Accelerator (ATA) electron beam accelerator. The feedback control system drives an X/Y dipole steering system that has a 40-MHz bandwidth and can produce {+-}300-Gauss-cm dipole fields. A simulator was used to develop the control algorithm and to quantify the expected performance in the presence of beam position measurement noise and accelerator timing jitter. The major problem to date has been protecting the amplifiers from the voltage that is inductively coupled to the steering bars by the beam. 3 refs., 8 figs.

  9. Feedback strategies for visual search in airframe structural inspection.

    PubMed

    Gramopadhye, A K; Drury, C G; Sharit, J

    1997-05-01

    Feedback of information has consistently shown positive results in human inspection, provided it is given in a timely and appropriate manner. Feedback serves as the basis of most training schemes; traditionally this has been performance feedback. Other forms of feedback which provide strategy information rather than performance information may have a role in improving inspection. This study compared performance feedback and cognitive feedback in a realistic simulation of an aircraft structural inspection task. Performance (time, errors) feedback showed the greatest improvements in performance measures. Cognitive feedback enhanced efficiency measures of search strategy. When cognitive feedback consisted of visual representations of the path and the coverage of the search sequence, subjects also were able to use this task information to improve their search performance.

  10. The influence of feedback valence in associative learning.

    PubMed

    Bischoff-Grethe, Amanda; Hazeltine, Eliot; Bergren, Lindsey; Ivry, Richard B; Grafton, Scott T

    2009-01-01

    The neural systems engaged by intrinsic positive or negative feedback were defined in an associative learning task. Through trial and error, participants learned the arbitrary assignments of a set of stimuli to one of two response categories. Informative feedback was provided on less than 25% of the trials. During positive feedback blocks, half of the trials were eligible for informative feedback; of these, informative feedback was only provided when the response was correct. A similar procedure was used on negative feedback blocks, but here informative feedback was only provided when the response was incorrect. In this manner, we sought to identify regions that were differentially responsive to positive and negative feedback as well as areas that were responsive to both types of informative feedback. Several regions of interest, including the bilateral nucleus accumbens, caudate nucleus, anterior insula, right cerebellar lobule VI, and left putamen, were sensitive to informative feedback regardless of valence. In contrast, several regions were more selective to positive feedback compared to negative feedback. These included the insula, amygdala, putamen, and supplementary motor area. No regions were more strongly activated by negative feedback compared to positive feedback. These results indicate that the neural areas supporting associative learning vary as a function of how that information is learned. In addition, areas linked to intrinsic reinforcement showed considerable overlap with those identified in studies using extrinsic reinforcers.

  11. Feedback-related brain activity predicts learning from feedback in multiple-choice testing.

    PubMed

    Ernst, Benjamin; Steinhauser, Marco

    2012-06-01

    Different event-related potentials (ERPs) have been shown to correlate with learning from feedback in decision-making tasks and with learning in explicit memory tasks. In the present study, we investigated which ERPs predict learning from corrective feedback in a multiple-choice test, which combines elements from both paradigms. Participants worked through sets of multiple-choice items of a Swahili-German vocabulary task. Whereas the initial presentation of an item required the participants to guess the answer, corrective feedback could be used to learn the correct response. Initial analyses revealed that corrective feedback elicited components related to reinforcement learning (FRN), as well as to explicit memory processing (P300) and attention (early frontal positivity). However, only the P300 and early frontal positivity were positively correlated with successful learning from corrective feedback, whereas the FRN was even larger when learning failed. These results suggest that learning from corrective feedback crucially relies on explicit memory processing and attentional orienting to corrective feedback, rather than on reinforcement learning.

  12. Pressure Ratio to Thermal Environments

    NASA Technical Reports Server (NTRS)

    Lopez, Pedro; Wang, Winston

    2012-01-01

    A pressure ratio to thermal environments (PRatTlE.pl) program is a Perl language code that estimates heating at requested body point locations by scaling the heating at a reference location times a pressure ratio factor. The pressure ratio factor is the ratio of the local pressure at the reference point and the requested point from CFD (computational fluid dynamics) solutions. This innovation provides pressure ratio-based thermal environments in an automated and traceable method. Previously, the pressure ratio methodology was implemented via a Microsoft Excel spreadsheet and macro scripts. PRatTlE is able to calculate heating environments for 150 body points in less than two minutes. PRatTlE is coded in Perl programming language, is command-line-driven, and has been successfully executed on both the HP and Linux platforms. It supports multiple concurrent runs. PRatTlE contains error trapping and input file format verification, which allows clear visibility into the input data structure and intermediate calculations.

  13. Continually variable transmission having fixed ratio and variable ratio mechanisms

    SciTech Connect

    Moan, R.D

    1989-06-06

    This patent describes a transmission for producing a stepless, continually variable range of ratios of the speed of its output to its input comprising: a fluid coupling having an impeller adapted for connection to a power source and a turbine hydrodynamically connected to the impeller; as planetary gearset having a ring gear, a sun gear, a first set of planet pinions meshing with the sun gear, a second set of planet pinions meshing with the first set of pinions and with the ring gear, and a pinion carrier on which the first and second sets of pinions are rotatably supported; first drive means drivable connecting the turbine and the sun gear for producing a variable speed ratio therebetween having a range between an underdrive ratio and an overdrive ratio; second drive means drivably connecting the impeller and the ring gear for producing a fixed speed ratio therebetween; a first clutch means for drivably connecting and disconnecting the ring gear and the second drive means; and a second clutch means for drivably connecting and disconnecting the first drive means and the pinion carrier.

  14. Combined input shaping and feedback control for double-pendulum systems

    NASA Astrophysics Data System (ADS)

    Mar, Robert; Goyal, Anurag; Nguyen, Vinh; Yang, Tianle; Singhose, William

    2017-02-01

    A control system combining input shaping and feedback is developed for double-pendulum systems subjected to external disturbances. The proposed control method achieves fast point-to-point response similar to open-loop input-shaping control. It also minimizes transient deflections during the motion of the system, and disturbance-induced residual swing using the feedback control. Effects of parameter variations such as the mass ratio of the double pendulum, the suspension length ratio, and the move distance were studied via numerical simulation. The most important results were also verified with experiments on a small-scale crane. The controller effectively suppresses the disturbances and is robust to modelling uncertainties and task variations.

  15. Galaxies on FIRE (Feedback In Realistic Environments): stellar feedback explains cosmologically inefficient star formation

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.; Kereš, Dušan; Oñorbe, José; Faucher-Giguère, Claude-André; Quataert, Eliot; Murray, Norman; Bullock, James S.

    2014-11-01

    We present a series of high-resolution cosmological simulations1 of galaxy formation to z = 0, spanning halo masses ˜108-1013 M⊙, and stellar masses ˜104-1011 M⊙. Our simulations include fully explicit treatment of the multiphase interstellar medium and stellar feedback. The stellar feedback inputs (energy, momentum, mass, and metal fluxes) are taken directly from stellar population models. These sources of feedback, with zero adjusted parameters, reproduce the observed relation between stellar and halo mass up to Mhalo ˜ 1012 M⊙. We predict weak redshift evolution in the M*-Mhalo relation, consistent with current constraints to z > 6. We find that the M*-Mhalo relation is insensitive to numerical details, but is sensitive to feedback physics. Simulations with only supernova feedback fail to reproduce observed stellar masses, particularly in dwarf and high-redshift galaxies: radiative feedback (photoheating and radiation pressure) is necessary to destroy giant molecular clouds and enable efficient coupling of later supernovae to the gas. Star formation rates (SFRs) agree well with the observed Kennicutt relation at all redshifts. The galaxy-averaged Kennicutt relation is very different from the numerically imposed law for converting gas into stars, and is determined by self-regulation via stellar feedback. Feedback reduces SFRs and produces reservoirs of gas that lead to rising late-time star formation histories, significantly different from halo accretion histories. Feedback also produces large short-time-scale variability in galactic SFRs, especially in dwarfs. These properties are not captured by common `sub-grid' wind models.

  16. The effect of AGN feedback on the X-ray morphologies of clusters: Simulations vs. observations

    NASA Astrophysics Data System (ADS)

    Chon, Gayoung; Puchwein, Ewald; Böhringer, Hans

    2016-07-01

    Clusters of galaxies probe the large-scale distribution of matter and are a useful tool to test the cosmological models by constraining cosmic structure growth and the expansion of the Universe. It is the scaling relations between mass observables and the true mass of a cluster through which we obtain the cosmological constraints by comparing to theoretical cluster mass functions. These scaling relations are, however, heavily influenced by cluster morphology. The presence of the slight tension in recent cosmological constraints on Ωm and σ8 based on the CMB and clusters has boosted the interests in looking for possible sources for the discrepancy. Therefore we study here the effect of active galactic nucleus (AGN) feedback as one of the major mechanisms modifying the cluster morphology influencing scaling relations. It is known that AGN feedback injects energies up to 1062 erg into the intracluster medium, controls the heating and cooling of a cluster, and re-distributes cold gas from the centre to outer radii. We have also learned that cluster simulations with AGN feedback can reproduce observed cluster properties, for example, the X-ray luminosity, temperature, and cooling rate at the centre better than without the AGN feedback. In this paper using cosmological hydrodynamical simulations we investigate how the AGN feedback changes the X-ray morphology of the simulated systems, and compare this to the observed Representative XMM-Newton Cluster Structure Survey (REXCESS) clusters. We apply two substructure measures, centre shifts (w) and power ratios (e.g. P3/P0), to characterise the cluster morphology, and find that our simulated clusters are more substructured than the observed clusters based on the values of w and P3/P0. We also show that the degree of this discrepancy is affected by the inclusion of AGN feedback. While the clusters simulated with the AGN feedback are in much better agreement with the REXCESS LX-T relation, they are also more substructured

  17. Adaptive tuning of feedback gain in time-delayed feedback control.

    PubMed

    Lehnert, J; Hövel, P; Flunkert, V; Guzenko, P Yu; Fradkov, A L; Schöll, E

    2011-12-01

    We demonstrate that time-delayed feedback control can be improved by adaptively tuning the feedback gain. This adaptive controller is applied to the stabilization of an unstable fixed point and an unstable periodic orbit embedded in a chaotic attractor. The adaptation algorithm is constructed using the speed-gradient method of control theory. Our computer simulations show that the adaptation algorithm can find an appropriate value of the feedback gain for single and multiple delays. Furthermore, we show that our method is robust to noise and different initial conditions.

  18. Noise-Induced Phase Locking and Frequency Mixing in an Optical Bistable System with Delayed Feedback

    NASA Astrophysics Data System (ADS)

    Misono, Masatoshi; Miyakawa, Kenji

    2011-11-01

    The interplay between stochastic resonance (SR) and coherence resonance (CR) is experimentally studied in an optical bistable system with a time-delayed feedback loop. We demonstrate that the phase of the noise-induced motion is locked to that of the periodic input when the ratio of their frequencies is a simple rational number. We also demonstrate that the interplay between SR and CR generates frequency-mixed modes, and that the efficiency of frequency mixing is enhanced by the optimum noise.

  19. Carbon cycle feedbacks and future climate change.

    PubMed

    Friedlingstein, Pierre

    2015-11-13

    Climate and carbon cycle are tightly coupled on many timescales, from interannual to multi-millennial timescales. Observations always evidence a positive feedback, warming leading to release of carbon to the atmosphere; however, the processes at play differ depending on the timescales. State-of-the-art Earth System Models now represent these climate-carbon cycle feedbacks, always simulating a positive feedback over the twentieth and twenty-first centuries, although with substantial uncertainty. Recent studies now help to reduce this uncertainty. First, on short timescales, El Niño years record larger than average atmospheric CO2 growth rate, with tropical land ecosystems being the main drivers. These climate-carbon cycle anomalies can be used as emerging constraint on the tropical land carbon response to future climate change. Second, centennial variability found in last millennium records can be used to constrain the overall global carbon cycle response to climatic excursions. These independent methods point to climate-carbon cycle feedback at the low-end of the Earth System Models range, indicating that these models overestimate the carbon cycle sensitivity to climate change. These new findings also help to attribute the historical land and ocean carbon sinks to increase in atmospheric CO2 and climate change.

  20. Postidentification Feedback Affects Subsequent Eyewitness Identification Performance

    ERIC Educational Resources Information Center

    Palmer, Matthew A.; Brewer, Neil; Weber, Nathan

    2010-01-01

    Eyewitnesses sometimes view more than one lineup during an investigation. We investigated the effects of postidentification feedback following one lineup on responses to a second lineup. Witnesses (N = 621) viewed a mock crime and, later, attempted to identify the culprit from an initial (target-absent) lineup and a second (target-present or…

  1. TRANSIENT FEEDBACK AND ROBUST SIGNALING GRADIENTS

    PubMed Central

    Simonyan, Aghavni; Wan, Frederic Y. M.

    2016-01-01

    Robust development of biological organisms in the presence of genetic and epi-genetic perturbations is important for time spans short relative to evolutionary time. Gradients of receptor bound signaling morphogens are responsible for patterning formation and development. A variety of inhibitors for reducing ectopic signaling activities are known to exist and their specific role in down-regulating the undesirable ectopic activities reasonably well understood. However, how a developing organism manages to adjust inhibition/stimulation in response to genetic and/or environmental changes remains to be uncovered. The need to adjust for ectopic signaling activities requires the presence of one or more feedback mechanisms to stimulate the needed adjustment. As the ultimate effect of many inhibitors (including those of the nonreceptor type) is to reduce the availability of signaling morphogens for binding with signaling receptors, a negative feedback on signaling morphogen synthesis rate based on a root-mean-square measure of the spatial distribution of signaling concentration offers a simple approach to robusness and has been demonstrated to be effective in a proof-of-concept implementation. In this paper, we complement the previous investigation of feedback in steady state by examining the effect of one or more feedback adjustments during the transient phase of the biological development. PMID:27840649

  2. The Tuckman Teacher Feedback Form (TTFF)

    ERIC Educational Resources Information Center

    Tuckman, Bruce W.

    1976-01-01

    The Tuckman Teacher Feedback Form is a short, 28-item semantic differential which generates four scores, based on a factor structure described by Tuckman (1974), in the areas of creativity, dynamism (energy plus dominance), organized demeaner (organization plus control), and warmth and acceptance. (Author/MV)

  3. Group-Level Formative Feedback and Metadiscourse

    ERIC Educational Resources Information Center

    Resendes, Monica; Scardamalia, Marlene; Bereiter, Carl; Chen, Bodong; Halewood, Cindy

    2015-01-01

    This research explores the ability of grade 2 students to engage in productive discussion about the state of their knowledge building using group-level feedback tools to support their metadiscourse. Two aspects of knowledge work were common to the comparison and experimental classes: "Knowledge Building talk" (KB talk) involving…

  4. Gathering Teacher's Perceptions of Evaluator Feedback

    ERIC Educational Resources Information Center

    Cherasaro, Trudy L.; Brodersen, Marc

    2016-01-01

    In response to initiatives to increase educator effectiveness states throughout the nation are placing greater emphasis on teacher evaluation tools that differentiate teacher effectiveness and include timely and constructive feedback. One of the three principles of the Elementary and Secondary Education Act (ESEA) flexibility waivers requires that…

  5. Timely Diagnostic Feedback for Database Concept Learning

    ERIC Educational Resources Information Center

    Lin, Jian-Wei; Lai, Yuan-Cheng; Chuang, Yuh-Shy

    2013-01-01

    To efficiently learn database concepts, this work adopts association rules to provide diagnostic feedback for drawing an Entity-Relationship Diagram (ERD). Using association rules and Asynchronous JavaScript and XML (AJAX) techniques, this work implements a novel Web-based Timely Diagnosis System (WTDS), which provides timely diagnostic feedback…

  6. From Nonlinear to Hamiltonian via Feedback1

    DTIC Science & Technology

    2002-01-01

    distribution unlimited. 13. Abstract Mechanical control systems are a very important class of nonlinear control systems . They posses a rich mathematical...methodologies developed for mechanical control systel logically rendering nonlinear control systems , mechanical by a proper choice of feedback. In particular, w...OF PA Nonlinear mechanical control systems , Hamiltonian Control Systems x 16. PRICE CODE 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19

  7. Chaos control using notch filter feedback.

    PubMed

    Ahlborn, Alexander; Parlitz, Ulrich

    2006-01-27

    A method for stabilizing periodic orbits and steady states of chaotic systems is presented using specifically filtered feedback signals. The efficiency of this control technique is illustrated with simulations (Rössler system, laser model) and a successful experimental application for stabilizing intensity fluctuations of an intracavity frequency-doubled Nd:YAG laser.

  8. Pairwise Document Classification for Relevance Feedback

    DTIC Science & Technology

    2009-11-01

    Pairwise Document Classification for Relevance Feedback Jonathan L. Elsas, Pinar Donmez, Jamie Callan, Jaime G. Carbonell Language Technologies...Collins-Thompson and J. Callan. Query expansion using random walk models. In CIKM ’05, page 711. ACM, 2005. [5] P. Donmez and J. Carbonell . Paired

  9. A Surprising Effect of Feedback on Learning

    ERIC Educational Resources Information Center

    Vollmeyer, Regina; Rheinberg, Falko

    2005-01-01

    As meta-analyses demonstrate feedback effects on performance, our study examined possible mediators. Based on our cognitive-motivational model [Vollmeyer, R., & Rheinberg, F. (1998). Motivationale Einflusse auf Erwerb und Anwendung von Wissen in einem computersimulierten System [Motivational influences on the acquisition and application of…

  10. The Effect of Feedback on Group Cohesiveness.

    ERIC Educational Resources Information Center

    Mears, Peter M.

    The effect of feedback on group cohesiveness (measured in terms of group and task attractiveness) for a person who is performing a simple, highly repetitive task was studied. One hundred business administration students, randomly assigned to five member groups, completed a series of trials having the goal of determining the number commonly held by…

  11. Mechanical feedback stabilizes budding yeast morphogenesis

    NASA Astrophysics Data System (ADS)

    Banavar, Samhita; Trogdon, Michael; Petzold, Linda; Campas, Otger

    Walled cells have the ability to remodel their shape while sustaining an internal turgor pressure that can reach values up to 10 atmospheres. This requires a tight and simultaneous regulation of cell wall assembly and mechanochemistry, but the underlying mechanisms by which this is achieved remain unclear. Using the growth of mating projections in budding yeast (S. cerevisiae) as a motivating example, we have developed a theoretical description that couples the mechanics of cell wall expansion and assembly via a mechanical feedback. In the absence of a mechanical feedback, cell morphogenesis is inherently unstable. The presence of a mechanical feedback stabilizes changes in cell shape and growth, and provides a mechanism to prevent cell lysis in a wide range of conditions. We solve for the dynamics of the system and obtain the different dynamical regimes. In particular, we show that several parameters affect the stability of growth, including the strength of mechanical feedback in the system. Finally, we compare our results to existing experimental data.

  12. An Investigation into Effectiveness of Peer Feedback

    ERIC Educational Resources Information Center

    Lin, Grace Hui Chin; Chien, Paul Shih Chieh

    2009-01-01

    Copious researches argue the effectiveness of peer-correction in writing courses (e.g., Connor & Asenavage, 1994). Also, Coit (2004) mentions using peer feedback for correcting articles through a student-centered environment is a beneficial pedagogy to extend learners' academic-style writing practice. Therefore, this study focused on…

  13. Oral Corrective Feedback in Second Language Classrooms

    ERIC Educational Resources Information Center

    Lyster, Roy; Saito, Kazuya; Sato, Masatoshi

    2013-01-01

    This article reviews research on oral corrective feedback (CF) in second language (L2) classrooms. Various types of oral CF are first identified, and the results of research revealing CF frequency across instructional contexts are presented. Research on CF preferences is then reviewed, revealing a tendency for learners to prefer receiving CF more…

  14. FEEDBACK SCORING SYSTEMS FOR REUSABLE KINDERGARTEN WORKBOOKS.

    ERIC Educational Resources Information Center

    GACH, PENELOPE J.; AND OTHERS

    THE DEVELOPMENT OF ECONOMICAL FEEDBACK SCORING SYSTEMS FOR REUSABLE KINDERGARTEN WORKBOOKS IS DESCRIBED. THREE PROTOTYPE SYSTEMS WERE DEVELOPED--(1) A METAL FOIL ACTIVATING AN ELECTRICAL PROBE, (2) A METAL FOIL REACTING WITH A MAGNETIC PROBE, AND (3) INVISIBLE FLUORESCENT INK REVEALED BY THE APPLICATION OF LONGWAVE ULTRAVIOLET LIGHT. (MS)

  15. Feed up, Feedback, and Feed Forward

    ERIC Educational Resources Information Center

    Fisher, Douglas; Frey, Nancy

    2011-01-01

    "Feeding up" establishes a substantive line of inquiry that compels learners to engage in investigation and inquire. It also forms the basis for the assessments that follow. Once students understand the purpose and begin to work, they receive "feedback" that is timely and scaffolds their understanding. Based on their responses, the teacher gains a…

  16. Positive force feedback in bouncing gaits?

    PubMed Central

    Geyer, Hartmut; Seyfarth, Andre; Blickhan, Reinhard

    2003-01-01

    During bouncing gaits (running, hopping, trotting), passive compliant structures (e.g. tendons, ligaments) store and release part of the stride energy. Here, active muscles must provide the required force to withstand the developing tendon strain and to compensate for the inevitable energy losses. This requires an appropriate control of muscle activation. In this study, for hopping, the potential involvement of afferent information from muscle receptors (muscle spindles, Golgi tendon organs) is investigated using a two-segment leg model with one extensor muscle. It is found that: (i) positive feedbacks of muscle-fibre length and muscle force can result in periodic bouncing; (ii) positive force feedback (F+) stabilizes bouncing patterns within a large range of stride energies (maximum hopping height of 16.3 cm, almost twofold higher than the length feedback); and (iii) when employing this reflex scheme, for moderate hopping heights (up to 8.8 cm), an overall elastic leg behaviour is predicted (hopping frequency of 1.4-3 Hz, leg stiffness of 9-27 kN m(-1)). Furthermore, F+ could stabilize running. It is suggested that, during the stance phase of bouncing tasks, the reflex-generated motor control based on feedbacks might be an efficient and reliable alternative to central motor commands. PMID:14561282

  17. Learning to learn about uncertain feedback.

    PubMed

    Faraut, Maïlys C M; Procyk, Emmanuel; Wilson, Charles R E

    2016-02-01

    Unexpected outcomes can reflect noise in the environment or a change in the current rules. We should ignore noise but shift strategy after rule changes. How we learn to do this is unclear, but one possibility is that it relies on learning to learn in uncertain environments. We propose that acquisition of latent task structure during learning to learn, even when not necessary, is crucial. We report results consistent with this hypothesis. Macaque monkeys acquired adaptive responses to feedback while learning to learn serial stimulus-response associations with probabilistic feedback. Monkeys learned well, decreasing their errors to criterion, but they also developed an apparently nonadaptive reactivity to unexpected stochastic feedback, even though that unexpected feedback never predicted problem switch. This surprising learning trajectory permitted the same monkeys, naïve to relearning about previously learned stimuli, to transfer to a task of stimulus-response remapping at immediately asymptotic levels. Our results suggest that learning new problems in a stochastic environment promotes the acquisition of performance rules from latent task structure, providing behavioral flexibility. Learning to learn in a probabilistic and volatile environment thus appears to induce latent learning that may be beneficial to flexible cognition.

  18. Sex Differences, Positive Feedback and Intrinsic Motivation.

    ERIC Educational Resources Information Center

    Deci, Edward L.; And Others

    The paper presents two experiments which test the "change in feelings of competence and self-determination" proposition of cognitive evaluation theory. This proposition states that when a person receives feedback about his performance on an intrinsically motivated activity this information will affect his sense of competence and…

  19. 10 CFR 850.40 - Performance feedback.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 4 2010-01-01 2010-01-01 false Performance feedback. 850.40 Section 850.40 Energy DEPARTMENT OF ENERGY CHRONIC BERYLLIUM DISEASE PREVENTION PROGRAM Specific Program Requirements § 850.40... representing beryllium-associated workers who request such information....

  20. 10 CFR 850.40 - Performance feedback.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 4 2012-01-01 2012-01-01 false Performance feedback. 850.40 Section 850.40 Energy DEPARTMENT OF ENERGY CHRONIC BERYLLIUM DISEASE PREVENTION PROGRAM Specific Program Requirements § 850.40... representing beryllium-associated workers who request such information....

  1. 10 CFR 850.40 - Performance feedback.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 4 2013-01-01 2013-01-01 false Performance feedback. 850.40 Section 850.40 Energy DEPARTMENT OF ENERGY CHRONIC BERYLLIUM DISEASE PREVENTION PROGRAM Specific Program Requirements § 850.40... representing beryllium-associated workers who request such information....

  2. 10 CFR 850.40 - Performance feedback.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 4 2011-01-01 2011-01-01 false Performance feedback. 850.40 Section 850.40 Energy DEPARTMENT OF ENERGY CHRONIC BERYLLIUM DISEASE PREVENTION PROGRAM Specific Program Requirements § 850.40... representing beryllium-associated workers who request such information....

  3. 10 CFR 850.40 - Performance feedback.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 4 2014-01-01 2014-01-01 false Performance feedback. 850.40 Section 850.40 Energy DEPARTMENT OF ENERGY CHRONIC BERYLLIUM DISEASE PREVENTION PROGRAM Specific Program Requirements § 850.40... representing beryllium-associated workers who request such information....

  4. Mining Feedback in Ranking and Recommendation Systems

    ERIC Educational Resources Information Center

    Zhuang, Ziming

    2009-01-01

    The amount of online information has grown exponentially over the past few decades, and users become more and more dependent on ranking and recommendation systems to address their information seeking needs. The advance in information technologies has enabled users to provide feedback on the utilities of the underlying ranking and recommendation…

  5. The Problems of Multiple Feedback Estimation.

    ERIC Educational Resources Information Center

    Bulcock, Jeffrey W.

    The use of two-stage least squares (2SLS) for the estimation of feedback linkages is inappropriate for nonorthogonal data sets because 2SLS is extremely sensitive to multicollinearity. It is argued that what is needed is use of a different estimating criterion than the least squares criterion. Theoretically the variance normalization criterion has…

  6. Information Feedback Systems (IFS) and Educational Goals.

    ERIC Educational Resources Information Center

    White, William F.

    An information feedback system for use in evaluating an educational program is described, and its effectiveness in evaluating the Follow Through program and its use in relation to the Iowa Tests of Basic Skills are discussed. The systems approach to program evaluation consists of objectives clarification, decision making, and program planning. In…

  7. Give Better Feedback on Engineering Drawings

    ERIC Educational Resources Information Center

    Cobb, Robert, Jr.; Graham, Tony; Kapur, Arjun; Rhodes, Craig; Blackwell, Ellinor

    2005-01-01

    Most, if not all, systems have a mechanism that collects information to facilitate monitoring performance. This information is primarily used to modify the system to make it more efficient in performing desired tasks and, thus, attaining desired results. Similar to electrical, mechanical, or hydraulic systems, the feedback mechanism in an…

  8. Designing Educational Social Machines for Effective Feedback

    ERIC Educational Resources Information Center

    Yee-King, Matthew; Krivenski, Maria; Brenton, Harry; Grimalt-Reynes, Andreu; d'Inverno, Mark

    2014-01-01

    We report on our development of an educational social machine based on the concept that feedback in communities is an effective means to support the development of communities of learning and practice. Key challenges faced by this work are how best to support educational and social interactions, how to deliver personalised tuition, and how to…

  9. Diversity in School Performance Feedback Systems

    ERIC Educational Resources Information Center

    Verhaeghe, Goedele; Schildkamp, Kim; Luyten, Hans; Valcke, Martin

    2015-01-01

    As data-based decision making is receiving increased attention in education, more and more school performance feedback systems (SPFSs) are being developed and used worldwide. These systems provide schools with data on their functioning. However, little research is available on the characteristics of the different SPFSs. Therefore, this study…

  10. Hysteresis and feedback of ice sheet response

    NASA Astrophysics Data System (ADS)

    Abe-Ouchi, A.; Saito, F.; Takahashi, K.

    2014-12-01

    Investigating the response of ice sheets to climatic forcings in the past by climate-ice sheet modelling is important for understanding the ice sheets' change. The 100-kyr cycle of the large Northern Hemisphere ice sheets and fast termination of the glacial cycle are the prominent pattern known from paleoclimate records. We simulate the past glacial cycles with an ice sheet model, IcIES in combination with a general circulation model, MIROC, using the time series of insolation and atmospheric CO2. Feedback processes between ice sheet and atmosphere such as the ice albedo feedback, the elevation-mass balance feedback, desertification effect and stationary wave feedback are analyzed. We show that the threshold of termination of the glacial cycles can be explained by the pattern of the hysteresis of ice sheet change, i.e. multiple steady states of the ice sheets under climatic forcings. We find that slope of the upper branch of the multiple equilibria curve for Laurentide ice volumes is fundamental for the observed glacial patterns. Finally, we discuss the similarity and difference between the hysteresis structure of ice sheets variation for Northern Hemisphere ice sheets, Antarctica and Greenland.

  11. Assessing feedback in a mobile videogame

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Player feedback is an important part of serious games, although there is no consensus regarding its delivery or optimal content. "Mommio" is a serious game designed to help mothers motivate their preschoolers to eat vegetables. The purpose of this study was to assess optimal format and content of pl...

  12. Facial Feedback Mechanisms in Autistic Spectrum Disorders

    ERIC Educational Resources Information Center

    Stel, Marielle; van den Heuvel, Claudia; Smeets, Raymond C.

    2008-01-01

    Facial feedback mechanisms of adolescents with Autistic Spectrum Disorders (ASD) were investigated utilizing three studies. Facial expressions, which became activated via automatic (Studies 1 and 2) or intentional (Study 2) mimicry, or via holding a pen between the teeth (Study 3), influenced corresponding emotions for controls, while individuals…

  13. Distributed feedback imprinted electrospun fiber lasers.

    PubMed

    Persano, Luana; Camposeo, Andrea; Del Carro, Pompilio; Fasano, Vito; Moffa, Maria; Manco, Rita; D'Agostino, Stefania; Pisignano, Dario

    2014-10-01

    Imprinted, distributed feedback lasers are demonstrated on individual, active electrospun polymer nanofibers. In addition to advantages related to miniaturization, optical confinement and grating nanopatterning lead to a significant threshold reduction compared to conventional thin-film lasers. The possibility of imprinting arbitrary photonic crystal geometries on electrospun lasing nanofibers opens new opportunities for realizing optical circuits and chips.

  14. Learning to learn about uncertain feedback

    PubMed Central

    Procyk, Emmanuel

    2016-01-01

    Unexpected outcomes can reflect noise in the environment or a change in the current rules. We should ignore noise but shift strategy after rule changes. How we learn to do this is unclear, but one possibility is that it relies on learning to learn in uncertain environments. We propose that acquisition of latent task structure during learning to learn, even when not necessary, is crucial. We report results consistent with this hypothesis. Macaque monkeys acquired adaptive responses to feedback while learning to learn serial stimulus-response associations with probabilistic feedback. Monkeys learned well, decreasing their errors to criterion, but they also developed an apparently nonadaptive reactivity to unexpected stochastic feedback, even though that unexpected feedback never predicted problem switch. This surprising learning trajectory permitted the same monkeys, naïve to relearning about previously learned stimuli, to transfer to a task of stimulus-response remapping at immediately asymptotic levels. Our results suggest that learning new problems in a stochastic environment promotes the acquisition of performance rules from latent task structure, providing behavioral flexibility. Learning to learn in a probabilistic and volatile environment thus appears to induce latent learning that may be beneficial to flexible cognition. PMID:26787780

  15. Feedback on Developmental Writing Students' First Drafts

    ERIC Educational Resources Information Center

    Gulley, Beth

    2012-01-01

    Many writing teachers provide feedback to their students through writing conferences; however, the existing literature indicates teachers may unintentionally harm their weaker students by using this strategy. To better understand the effect of the writing conference on developmental writing students, the researcher created a mixed design ANCOVA to…

  16. Potential of Automated Writing Evaluation Feedback

    ERIC Educational Resources Information Center

    Cotos, Elena

    2011-01-01

    This paper presents an empirical evaluation of automated writing evaluation (AWE) feedback used for L2 academic writing teaching and learning. It introduces the Intelligent Academic Discourse Evaluator (IADE), a new web-based AWE program that analyzes the introduction section to research articles and generates immediate, individualized, and…

  17. Rehabilitation and motor learning through vibrotactile feedback

    NASA Astrophysics Data System (ADS)

    Panchanathan, Roshan; Rosenthal, Jacob; McDaniel, Troy

    2014-05-01

    Group instruction is the most common delivery method of motor skill training given its cost and time effectiveness. This is also the case during rehabilitation where therapists divide their attention among several patients. Compared to dedicated one-on-one instruction, group instruction often suffers from reduced quality and quantity of instruction and feedback. Further, during rehabilitation programs, patients struggle outside of therapy sessions given the lack of instruction and feedback found only during clinic visits. We propose a wearable, low-cost motion sensing and actuation system capable of providing real-time vibrotactile feedback for trainer-defined goal movements and repetitions. The trainer inputs movement goals for the user, and adapts these values (joint angles, movement speeds) over time for continued progress. In this paper, we present a novel second generation design, and introduce a flexible vibrotactile strip to overcome construction challenges of these types of systems. The flexible display is constructed using commercial LED strips that have been modified by attaching pancake style vibration motors. The flexible display does not require external microcontrollers to enable or disable motors, and may allow these systems to be expanded to the whole body. We also summarize two previous studies that have assessed appropriate body sites and pattern designs for vibrotactile motor instructions and feedback signals.

  18. Improving Feedback through Online Professional Development

    ERIC Educational Resources Information Center

    Klein, Valerie; Fukawa-Connelly, Timothy; Silverman, Jason

    2016-01-01

    Teachers' focus on student thinking--and moving beyond superficial "right or wrong" analysis--is essential to effective teaching (Grossman and McDonald 2008; NCTM 2000; Son and Sinclair 2010). Interpreting and evaluating student thinking and providing high-quality feedback are seen as high-leverage practices and are "likely to lead…

  19. Teacher Language Awareness in Supervisory Feedback Cycles

    ERIC Educational Resources Information Center

    Lindahl, Kristen; Baecher, Laura

    2016-01-01

    This study investigates pre- and post-observation feedback provided to TESOL teacher candidates who are preparing to work in content-based instruction/content and language integrated learning contexts, extending the conceptualization of teacher language awareness (TLA) to candidate supervision. It examines the extent to which TLA is manifested by…

  20. Spelling: Computerised Feedback for Self-Correction

    ERIC Educational Resources Information Center

    Lawley, Jim

    2016-01-01

    Research has shown that any assumption that L2 learners of English do well to rely on the feedback provided by generic spell checkers (for example, the MS Word spell checker) is misplaced. Efforts to develop spell checkers specifically for L2 learners have focused on training software to offer more appropriate suggestion lists for replacing…

  1. Optimal uniform-damping ratio controller for sequential design of multivariable systems

    NASA Technical Reports Server (NTRS)

    Shieh, Leang G.; Liu, Zhen; Sunkel, John W.

    1991-01-01

    An optimal uniform-damping ratio controller is developed for the sequential design of a multivariable control system so that the designed closed-loop poles of the respective multivariable system and reduced-order observer are exactly placed on the negative real axis and/or the boundaries of desired sectors with constant-damping ratios. The functions in the quadratic performance index to be minimized are chosen as a combination of the weighted outputs, reduced states and inputs. Also, the optimal uniform-damping ratio controller is a combination of optimal output-feedback and optimal reduced-order state-feedback controllers. A numerical example is given to demonstrate the design procedure.

  2. 40 CFR 1051.115 - What other requirements apply?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... control the air-fuel ratio may be treated separately under paragraph (d) of this section. An operating... air-fuel ratio in less than one hour with a few parts whose total cost is under $50 (in 2001 dollars... meet all the requirements of this part for any air-fuel ratio within the adjustable range described...

  3. Alterations in Neural Control of Constant Isometric Contraction with the Size of Error Feedback

    PubMed Central

    Hwang, Ing-Shiou; Lin, Yen-Ting; Huang, Wei-Min; Yang, Zong-Ru; Hu, Chia-Ling; Chen, Yi-Ching

    2017-01-01

    Discharge patterns from a population of motor units (MUs) were estimated with multi-channel surface electromyogram and signal processing techniques to investigate parametric differences in low-frequency force fluctuations, MU discharges, and force-discharge relation during static force-tracking with varying sizes of execution error presented via visual feedback. Fourteen healthy adults produced isometric force at 10% of maximal voluntary contraction through index abduction under three visual conditions that scaled execution errors with different amplification factors. Error-augmentation feedback that used a high amplification factor (HAF) to potentiate visualized error size resulted in higher sample entropy, mean frequency, ratio of high-frequency components, and spectral dispersion of force fluctuations than those of error-reducing feedback using a low amplification factor (LAF). In the HAF condition, MUs with relatively high recruitment thresholds in the dorsal interosseous muscle exhibited a larger coefficient of variation for inter-spike intervals and a greater spectral peak of the pooled MU coherence at 13–35 Hz than did those in the LAF condition. Manipulation of the size of error feedback altered the force-discharge relation, which was characterized with non-linear approaches such as mutual information and cross sample entropy. The association of force fluctuations and global discharge trace decreased with increasing error amplification factor. Our findings provide direct neurophysiological evidence that favors motor training using error-augmentation feedback. Amplification of the visualized error size of visual feedback could enrich force gradation strategies during static force-tracking, pertaining to selective increases in the discharge variability of higher-threshold MUs that receive greater common oscillatory inputs in the β-band. PMID:28125658

  4. The influence of visual feedback and prior knowledge about feedback on vertical aiming strategies.

    PubMed

    Elliott, Digby; Dutoy, Chris; Andrew, Matthew; Burkitt, James J; Grierson, Lawrence E M; Lyons, James L; Hayes, Spencer J; Bennett, Simon J

    2014-01-01

    Two experiments were conducted to examine time and energy optimization strategies for movements made with and against gravity. In Experiment 1, the authors manipulated concurrent visual feedback, and knowledge about feedback. When vision was eliminated upon movement initiation, participants exhibited greater undershooting, both with their primary submovement and their final endpoint, than when vision was available. When aiming downward, participants were more likely to terminate their aiming following the primary submovement or complete a lower amplitude corrective submovement. This strategy reduced the frequency of energy-consuming corrections against gravity. In Experiment 2, the authors eliminated vision of the hand and the target at the end of the movement. This procedure was expected to have its greatest impact under no-vision conditions where no visual feedback was available for subsequent planning. As anticipated, direction and concurrent visual feedback had a profound impact on endpoint bias. Participants exhibited pronounced undershooting when aiming downward and without vision. Differences in undershooting between vision and no vision were greater under blocked feedback conditions. When performers were uncertain about the impending feedback, they planned their movements for the worst-case scenario. Thus movement planning considers the variability in execution, and avoids outcomes that require time and energy to correct.

  5. A technology using feedback to manage experience based learning.

    PubMed

    Dornan, Tim; Brown, Martin; Powley, Dan; Hopkins, Mike

    2004-12-01

    The aim was to establish how ICT could apply feedback principles to experience based learning. Based on a survey of student and staff requirements, we developed a personalized educational technology ('iSUS') that: (1) Made students clear what they should learn; (2) Helped them meet appropriate real patients; (3) Encouraged reflective feedback; (4) Calculated benchmarks from accumulated feedback; (5) Compared individual students' feedback against those benchmarks; (6) Matched clinical activities to curriculum objectives; (7) Gave feedback to teachers and course leads. Bench testing proved the system usable. During seven weeks of real time use, a whole year group of 111 students feedback on 1183 learning episodes. Five hundred and forty-one (46%) of feedback episodes were self initiated. We have successfully prototyped an application of feedback principles to experience based learning that students seem to find useful.

  6. Effects of Mechanical and Radiative Supernova Feedback on Subhalo Evolution

    NASA Astrophysics Data System (ADS)

    Quirk, Amanda; Choi, Ena; Ostriker, Jeremiah P.

    2017-01-01

    Using cosmological hydrodynamical simulations, we investigate the effects supernova feedback has on populations of subhalos at current redshift. A group of halos was run through two simulations, each with different feedback models. One had thermal feedback, and the other had mechanical and radiative feedback. We used a friend-of-friend halo finder on the output of these simulations to explore the stellar and dark matter subhalos created. The number of stellar subhalos created by the mechanical feedback simulation was significantly less than the number created by the thermal feedback model, especially at low mass. Thus, the mechanical feedback model created a number of stellar subhalos more consistent with observations. The mechanical feedback model also showed a presence of dark matter subhalos that lacked stellar particles, or dark subhalos. The results of this analysis can give insight to the Missing Satellite Problem.

  7. Feedback effect on flute dynamics in a mirror machine

    NASA Astrophysics Data System (ADS)

    Be'Ery, Ilan; Seemann, Omri

    2015-11-01

    Active feedback techniques may stabilize the flute instability in mirror traps and make them viable candidates for fusion machines. A fast feedback with optical sensors and electrical actuators was implemented in a table-top mirror machine and used to study several aspects of feedback stabilization. For a cold, dense plasma the feedback reduces dramatically the flute amplitude of the first two mode. For higher temperature plasma, a significant increase of plasma density due to feedback stabilization is also demonstrated. The effect of changing feedback gain and phase has some interesting feature such as asymmetry with respect to positive and negative phase shifts and non-monotonic dependence of flute amplitude on feedback gain. These effects are explained using simplified analytic model of the flute and feedback.

  8. It's all about timing: An electrophysiological examination of feedback-based learning with immediate and delayed feedback.

    PubMed

    Arbel, Yael; Hong, Lucia; Baker, Travis E; Holroyd, Clay B

    2017-03-09

    Feedback regarding an individual's action can occur immediately or with a temporal delay. Processing of feedback that varies in its delivery time is proposed to engage different brain mechanisms. fMRI data implicate the striatum in the processing of immediate feedback, and the medial temporal lobe (MTL) in the processing of delayed feedback. The present study offers an electrophysiological examination of feedback processing in the context of timing, by studying the effects of feedback timing on the feedback-related negativity (FRN), a product of the midbrain dopamine system, and elucidating whether the N170 ERP component could capture MTL activation associated with the processing of delayed feedback. Participants completed a word-object paired association learning task; they received feedback 500ms (immediate feedback condition) following a button press during the learning of two sets of 14 items, and at a delay of 6500ms (delayed feedback condition) during the learning of the other two sets. The results indicated that while learning outcomes did not differ under the two timing conditions, Event Related Potential (ERPs) pointed to differential activation of the examined ERP components. FRN amplitude was found to be larger following the immediate feedback condition when compared with the delayed feedback condition, and sensitive to valence and learning only under the immediate feedback condition. Additionally, the amplitude of the N170 was found larger following the delayed feedback condition when compared with the immediate feedback condition. Taken together, the findings of the present study support the contention that the processing of delayed feedback involves a shift away from midbrain dopamine activation to the recruitment of the MTL.

  9. Feedback implementation options and issues for B factory accelerators

    SciTech Connect

    Fox, J.D.; Briggs, D.; Eisen, N.; Hindi, H.; Hosseini, W.; Oxoby, G.; Linscott, I.; Coiro, O.; Ghigo, A.; Serio, M.; Lambertson, G.; Voelker, F.

    1992-09-01

    The proposed B factory accelerator facilities will require active feedback systems to control multibunch instabilities. These feedback systems must operate in machines with thousands of circulating bunches and with short (2--4 ns) interbunch intervals. The functional requirements for transverse (betatron) and longitudinal (synchrotron) feedback systems are presented. Several possible implementation options are discussed and system requirements developed. Conceptual designs are presented for the PEP II transverse and longitudinal feedback systems.

  10. A Ratio Explanation for Evolution.

    ERIC Educational Resources Information Center

    Riss, Pam Helfers

    1993-01-01

    Describes hands-on physical anthropology activities for teaching students about evolution. Using evidence found in hominid skulls, students conduct investigations that involve calculating ratios. Eight full-page photographs of skulls from the program Stones and Bones are included. (PR)

  11. Overconfidence, Incentives and Digit Ratio

    PubMed Central

    Neyse, Levent; Bosworth, Steven; Ring, Patrick; Schmidt, Ulrich

    2016-01-01

    This paper contributes to a better understanding of the biological underpinnings of overconfidence by analyzing performance predictions in the Cognitive Reflection Test with and without monetary incentives. In line with the existing literature we find that the participants are too optimistic about their performance on average; incentives lead to higher performance; and males score higher than females on this particular task. The novelty of this paper is an analysis of the relation between participants’ performance prediction accuracy and their second to fourth digit ratio. It has been reported that the digit ratio is a negatively correlated bio-marker of prenatal testosterone exposure. In the un-incentivized treatment, we find that males with low digit ratios, on average, are significantly more overconfident about their performance. In the incentivized treatment, however, we observe that males with low digit ratios, on average, are less overconfident about their performance. These effects are not observed in females. We discuss how these findings fit into the literature on testosterone and decision making and how they might help to explain seemingly opposing evidence. PMID:27039893

  12. Studies on Feedback Control of Cardiac Alternans

    PubMed Central

    Dubljevic, Stevan; Lin, Shien-Fong; Christofides, Panagiotis

    2011-01-01

    A beat-to-beat variation in the electric wave propagation morphology in myocardium is referred to as cardiac alternans and it has been linked to the onset of life threatening arrhythmias and sudden cardiac death. Experimental studies have demonstrated that alternans can be annihilated by the feedback modulation of the basic pacing interval in a small piece of cardiac tissue. In this work, we study the capability of feedback control to suppress alternans both spatially and temporally in an extracted rabbit heart and in a cable of cardiac cells. This work demonstrates real-time control of cardiac alternans in an extracted rabbit heart and provides an analysis of the control methodology applied in the case of a one-dimensional (1D) cable of cardiac cells. The real-time system control is realized through feedback by proportional perturbation of the basic pacing cycle length (PCL). The measurements of the electric wave propagation are obtained by optical mapping of fluorescent dye from the surface of the heart and are fed into a custom-designed software that provides the control action signal that perturbs the basic pacing cycle length. In addition, a novel pacing protocol that avoids conduction block is applied. A numerical analysis, complementary to the experimental study is also carried out, by the ionic model of a 1D cable of cardiac cells under a self-referencing feedback protocol, which is identical to the one applied in the experimental study. Further, the amplitude of alternans linear parabolic PDE that is associated with the 1D ionic cardiac cell cable model under full state feedback control is analyzed. We provide an analysis of the amplitude of alternans parabolic PDE which admits a standard evolutionary form in a well defined functional space. Standard modal decomposition techniques are used in the analysis and the controller synthesis is carried out through pole-placement. State and output feedback controller realizations are developed and the important

  13. Positive feedback in the transition from sexual reproduction to parthenogenesis.

    PubMed

    Schwander, Tanja; Vuilleumier, Séverine; Dubman, Janie; Crespi, Bernard J

    2010-05-07

    Understanding how new phenotypes evolve is challenging because intermediate stages in transitions from ancestral to derived phenotypes often remain elusive. Here we describe and evaluate a new mechanism facilitating the transition from sexual reproduction to parthenogenesis. In many sexually reproducing species, a small proportion of unfertilized eggs can hatch spontaneously ('tychoparthenogenesis') and develop into females. Using an analytical model, we show that if females are mate-limited, tychoparthenogenesis can result in the loss of males through a positive feedback mechanism whereby tychoparthenogenesis generates female-biased sex ratios and increasing mate limitation. As a result, the strength of selection for tychoparthenogenesis increases in concert with the proportion of tychoparthenogenetic offspring in the sexual population. We then tested the hypothesis that mate limitation selects for tychoparthenogenesis and generates female-biased sex ratios, using data from natural populations of sexually reproducing Timema stick insects. Across 41 populations, both the tychoparthenogenesis rates and the proportions of females increased exponentially as the density of individuals decreased, consistent with the idea that low densities of individuals result in mate limitation and selection for reproductive insurance through tychoparthenogenesis. Our model and data from Timema populations provide evidence for a simple mechanism through which parthenogenesis can evolve rapidly in a sexual population.

  14. Academic Writing and Grammatical Accuracy: The Role of Corrective Feedback

    ERIC Educational Resources Information Center

    Baleghizadeh, Sasan; Gordani, Yahya

    2012-01-01

    Investigations into the effect of providing corrective feedback on L2 writing have often produced contradictory results. This study, following a line of research concerned with the role of corrective feedback in writing, contributes to this line of research by analyzing different feedback types in an EFL academic writing context. 45 graduate…

  15. The Effects of Online Feedback Training on Students' Text Revision

    ERIC Educational Resources Information Center

    Yang, Yu-Fen; Meng, Wen-Ting

    2013-01-01

    Oftentimes, college students who learn English as a Foreign Language (EFL) provide their peers with incorrect and misleading feedback during text revision. To improve the effectiveness of peer feedback, this study examined the degree to which online feedback training impacted EFL college students' text revisions. A sample of 50 college students…

  16. Relaxation oscillations and hierarchy of feedbacks in MAPK signaling

    PubMed Central

    Kochańczyk, Marek; Kocieniewski, Paweł; Kozłowska, Emilia; Jaruszewicz-Błońska, Joanna; Sparta, Breanne; Pargett, Michael; Albeck, John G.; Hlavacek, William S.; Lipniacki, Tomasz

    2017-01-01

    We formulated a computational model for a MAPK signaling cascade downstream of the EGF receptor to investigate how interlinked positive and negative feedback loops process EGF signals into ERK pulses of constant amplitude but dose-dependent duration and frequency. A positive feedback loop involving RAS and SOS, which leads to bistability and allows for switch-like responses to inputs, is nested within a negative feedback loop that encompasses RAS and RAF, MEK, and ERK that inhibits SOS via phosphorylation. This negative feedback, operating on a longer time scale, changes switch-like behavior into oscillations having a period of 1 hour or longer. Two auxiliary negative feedback loops, from ERK to MEK and RAF, placed downstream of the positive feedback, shape the temporal ERK activity profile but are dispensable for oscillations. Thus, the positive feedback introduces a hierarchy among negative feedback loops, such that the effect of a negative feedback depends on its position with respect to the positive feedback loop. Furthermore, a combination of the fast positive feedback involving slow-diffusing membrane components with slower negative feedbacks involving faster diffusing cytoplasmic components leads to local excitation/global inhibition dynamics, which allows the MAPK cascade to transmit paracrine EGF signals into spatially non-uniform ERK activity pulses. PMID:28045041

  17. Using Online Annotations to Support Error Correction and Corrective Feedback

    ERIC Educational Resources Information Center

    Yeh, Shiou-Wen; Lo, Jia-Jiunn

    2009-01-01

    Giving feedback on second language (L2) writing is a challenging task. This research proposed an interactive environment for error correction and corrective feedback. First, we developed an online corrective feedback and error analysis system called "Online Annotator for EFL Writing". The system consisted of five facilities: Document Maker,…

  18. Effects of Progress Monitoring Feedback on Early Literacy Student Achievement

    ERIC Educational Resources Information Center

    Lopuch, Jeremy Jon

    2016-01-01

    The purpose of this study was to examine the effects of diagnostic formative assessment feedback on early literacy skills. The participants were 12 first-grade general education teachers and 51 of their students who were assigned to the following treatments, diagnostic feedback and skills feedback (control) which lasted for 10 weeks. During the…

  19. Assessment Certitude as a Feedback Strategy for Learners' Constructed Responses

    ERIC Educational Resources Information Center

    Kealy, W. A.; Ritzhaupt, A. D.

    2010-01-01

    Educational researchers have "rarely" addressed the problem of how to provide feedback on constructed responses. All participants (N = 76) read a story and completed short-answer questions based on the text, with some receiving feedback consisting of the exact material on which the questions were based. During feedback, two groups receiving…

  20. Evaluating Preference for Graphic Feedback on Correct versus Incorrect Performance

    ERIC Educational Resources Information Center

    Sigurdsson, Sigurdur O.; Ring, Brandon M.

    2013-01-01

    The current study evaluated preferences of undergraduate students for graphic feedback on percentage of incorrect performance versus feedback on percentage of correct performance. A total of 108 participants were enrolled in the study and received graphic feedback on performance on 12 online quizzes. One half of participants received graphic…

  1. Students' Perceptions of Interventions for Supporting Their Engagement with Feedback

    ERIC Educational Resources Information Center

    Parker, Michael; Winstone, Naomi E.

    2016-01-01

    Recent approaches to assessment and feedback in higher education stress the importance of students' involvement in these processes, where effective reception of feedback is as important as effective delivery. Many interventions have been developed to support students' active use of feedback; however, students' engagement will be influenced by…

  2. Group Projects in Interior Design Studio Classes: Peer Feedback Benefits

    ERIC Educational Resources Information Center

    Jurado, Juan A.

    2011-01-01

    Group projects have been shown to be effective for providing peer feedback in classrooms. While students in regular enrollment classes benefit from peer feedback, low-enrollment classes face many challenges. This study compares peer feedback effectiveness between two interior design studio classes with different design projects. In one class,…

  3. Making Movies: The Next Big Thing in Feedback?

    ERIC Educational Resources Information Center

    Hope, Sheila A.

    2011-01-01

    Good quality, timely feedback is a key factor to help students achieve their full potential. Increased class sizes have put significant strain on the ability to return work promptly without compromising feedback quality. In the current study, two screencasting technologies were used to produce audiovisual feedback. For essays, Jing was used,…

  4. Feedback to Support Learning: Changes in Teachers' Practice and Beliefs

    ERIC Educational Resources Information Center

    Gamlem, Siv M.

    2015-01-01

    There are indications that teachers' feedback practice is related to beliefs they hold about pupils' learning and the purpose of feedback. This article presents changes in beliefs and practices of three teachers in lower secondary school taking part in an intervention to improve formative classroom feedback. Data includes interviews, observations…

  5. Teachers' Classroom Feedback: Still Trying to Get It Right

    ERIC Educational Resources Information Center

    Hargreaves, Eleanore

    2012-01-01

    This article examines feedback traditionally given by teachers in schools. Such feedback tends to focus on children's acquisition and retrieval of externally prescribed knowledge which is then assessed against mandated tests. It suggests that, from a sociocultural learning perspective, feedback directed towards such objectives may limit children's…

  6. Planning in Feedback: Insights from Concurrent Verbal Protocols

    ERIC Educational Resources Information Center

    Sharmini, Sharon; Kumar, Vijay

    2011-01-01

    Feedback plays an intervention role in the writing process. It is through feedback that writers are guided to achieve negotiated writing goals. Feedback encourages a process of discovery and this plays a developmental role in the writing process. In this paper, we report on three case studies that sought to understand cognitive processes when…

  7. Measuring the Impact of High Quality Instant Feedback on Learning

    ERIC Educational Resources Information Center

    Nutbrown, Stephen; Higgins, Colin; Beesley, Su

    2016-01-01

    This paper examines the impact of a novel assessment technique that has been used to improve the feedback given to second year Computer Science students at the University of Nottingham. Criteria for effective, high quality feedback are discussed. An automated marking system (The Marker's Apprentice--TMA) produces instant feedback in synergy with…

  8. Feedback Systems for Use with Paper-Based Instructional Products.

    ERIC Educational Resources Information Center

    Strandberg, Joel E.

    This survey describes 15 systems that provide feedback to students. Feedback is defined as information transfer from the instructional material to the student after a response is made by the student. The feedback is directed primarily to the student, but when a permanent record of the response occurs this information is also available to the…

  9. The Performance versus Ability Distinction Following Social Comparison Feedback

    ERIC Educational Resources Information Center

    Buckingham, Justin T.; LeBeau, Lavonia Smith; Klein, William M. P.

    2011-01-01

    Previous research suggests that self-evaluations can be influenced by social comparison feedback. The present study tested whether social comparison feedback has stronger effects on self-evaluations of performance than ability. Participants received social comparison feedback indicating that they had performed above or below average. In addition…

  10. Relaxation oscillations and hierarchy of feedbacks in MAPK signaling

    NASA Astrophysics Data System (ADS)

    Kochańczyk, Marek; Kocieniewski, Paweł; Kozłowska, Emilia; Jaruszewicz-Błońska, Joanna; Sparta, Breanne; Pargett, Michael; Albeck, John G.; Hlavacek, William S.; Lipniacki, Tomasz

    2017-01-01

    We formulated a computational model for a MAPK signaling cascade downstream of the EGF receptor to investigate how interlinked positive and negative feedback loops process EGF signals into ERK pulses of constant amplitude but dose-dependent duration and frequency. A positive feedback loop involving RAS and SOS, which leads to bistability and allows for switch-like responses to inputs, is nested within a negative feedback loop that encompasses RAS and RAF, MEK, and ERK that inhibits SOS via phosphorylation. This negative feedback, operating on a longer time scale, changes switch-like behavior into oscillations having a period of 1 hour or longer. Two auxiliary negative feedback loops, from ERK to MEK and RAF, placed downstream of the positive feedback, shape the temporal ERK activity profile but are dispensable for oscillations. Thus, the positive feedback introduces a hierarchy among negative feedback loops, such that the effect of a negative feedback depends on its position with respect to the positive feedback loop. Furthermore, a combination of the fast positive feedback involving slow-diffusing membrane components with slower negative feedbacks involving faster diffusing cytoplasmic components leads to local excitation/global inhibition dynamics, which allows the MAPK cascade to transmit paracrine EGF signals into spatially non-uniform ERK activity pulses.

  11. Feedback on Courses and Programmes of Study: A Handbook.

    ERIC Educational Resources Information Center

    Hounsell, Dai; Tait, Hilary; Day, Kate

    This handbook offers guidance to teachers for obtaining and evaluating feedback on courses and programs of study at institutions of higher education in the United Kingdom and South Africa. Part 1 examines the purposes and functions of feedback, defines key terms, and summarizes key steps in the feedback process. Part 2 discusses the preparation…

  12. Increasing Verbal Empathy as a Function of Feedback and Instructions.

    ERIC Educational Resources Information Center

    Carlson, Keith W.

    Counselor-trainee response uncertainty and delayed supervisor feedback are two apparent difficulties when looking at the normal practicum procedures from a learning theory frame of reference. Twenty-four counselor-trainees were randomly assigned to three experimental groups and one control group, ie., immediate feedback, feedback and instructions,…

  13. Critical Thinking in Gifted Children's Offline and Online Peer Feedback

    ERIC Educational Resources Information Center

    Miller, Myriah T.; Olthouse, Jill

    2013-01-01

    This comparative study identified the differences between gifted children's offline and online peer feedback within a summer talented writer's workshop. Researchers analyzed ten students' writings for degrees of critical thinking evident in their feedback. Online feedback included students' writings in social writing sites Storybird.com and…

  14. Developing First-Year Engagement with Written Feedback

    ERIC Educational Resources Information Center

    Cramp, Andy

    2011-01-01

    Assessment feedback continues to be a relatively under-researched area in higher education despite its fundamental role in learning and teaching. This article positions assessment feedback as a complex meaning-making process requiring dialogue and interpretation.The article outlines an evaluative case study investigating a feedback review meeting…

  15. Student and Peer Evaluation: Feedback for All Learners

    ERIC Educational Resources Information Center

    Carr, Sonya C.

    2008-01-01

    Assessment for learning provides feedback to improve teaching and learning in the classroom. However, many teachers focus on measuring what students have learned at the end of a unit of instruction and fail to allow opportunities for feedback and revision during instruction. As Bransford, Brown, and Cocking (2000) explained, "Feedback is…

  16. Student Perceptions of Quality Feedback in Teacher Education

    ERIC Educational Resources Information Center

    Ferguson, Peter

    2011-01-01

    Many reports have identified a perceived lack of quality in regard to assessment feedback in higher education contexts. One research study in 2007 on undergraduate university students found that less than half of the students (46%) collected their formative feedback, suggesting that from their perspective feedback clearly was not fulfilling the…

  17. Enhancing Feedback via Peer Learning in Large Classrooms

    ERIC Educational Resources Information Center

    Zher, Ng Huey; Hussein, Raja Maznah Raja; Saat, Rohaida Mohd

    2016-01-01

    Feedback has been lauded as a key pedagogical tool in higher education. Unfortunately, the value of feedback falls short when being carried out in large classrooms. In this study, strategies for sustaining feedback in large classroom based on peer learning are explored. All the characteristics identified within the concept of peer learning were…

  18. Teacher Feedback during Active Learning: Current Practices in Primary Schools

    ERIC Educational Resources Information Center

    van den Bergh, Linda; Ros, Anje; Beijaard, Douwe

    2013-01-01

    Background: Feedback is one of the most powerful tools, which teachers can use to enhance student learning. It appears dif?cult for teachers to give qualitatively good feedback, especially during active learning. In this context, teachers should provide facilitative feedback that is focused on the development of meta-cognition and social learning.…

  19. The Personal Dimension in Teaching: Why Students Value Feedback

    ERIC Educational Resources Information Center

    Rowe, Anna

    2011-01-01

    Purpose: Feedback is a central element of the learning experience yet, until recently, few studies have focused directly on what students think about feedback. This paper seeks to address this issue. Design/methodology/approach: Data collected as part of a larger study investigating reasons for consistently low ratings of feedback across the…

  20. Using "Signals" for Appropriate Feedback: Perceptions and Practices

    ERIC Educational Resources Information Center

    Tanes, Zeynep; Arnold, Kimberly E.; King, Abigail Selzer; Remnet, Mary Ann

    2011-01-01

    Feedback is a crucial form of information for learners. With the availability of new educational technologies, the manner in which feedback is delivered has changed tremendously. Existing research on the learning outcomes of the content and nature of computer mediated feedback is limited and contradictory. "Signals" is an educational data-mining…

  1. Differences in the Uptake of Peer and Teacher Feedback

    ERIC Educational Resources Information Center

    Ruegg, Rachael

    2015-01-01

    This study aimed to determine differences in the uptake of peer and teacher feedback after writing students received longitudinal feedback from only one of these sources. It also investigates the types of feedback given by peers and a teacher in order to explain those any differences. Data was collected from 64 Japanese university students in four…

  2. Formative Feedback in a Malaysian Primary School ESL Context

    ERIC Educational Resources Information Center

    Sardareh, Sedigheh Abbasnasab

    2016-01-01

    The idea of providing students with formative feedback is a crucial part of formative assessment. Teachers need to provide students with feedback that improves their learning. In other words, formative feedback should provide learners with information that help them bridge their learning gap. As formative assessment itself is a newly introduced…

  3. A Content Analysis of Peer Feedback in Triadic Supervision

    ERIC Educational Resources Information Center

    Avent, Janeé R.; Wahesh, Edward; Purgason, Lucy L.; Borders, L. DiAnne; Mobley, A. Keith

    2015-01-01

    There is limited research on the types of peer feedback exchanged during triadic supervision. Through a content analysis, the authors found that students provided feedback about counseling performance and cognitive counseling skills most often in supervision sessions. However, there were differences in the types of feedback exchanged across three…

  4. Using Screen Capture Feedback to Improve Academic Performance

    ERIC Educational Resources Information Center

    Denton, David W.

    2014-01-01

    Feedback is an effective instructional practice for improving achievement. The importance of feedback has been understood by teachers for many years, yet recent research has elevated its status. One characteristic of effective feedback is personalized comments, which assist students in understanding their performance. Most research analyzes the…

  5. Master's Thesis Projects: Student Perceptions of Supervisor Feedback

    ERIC Educational Resources Information Center

    de Kleijn, Renske A. M.; Mainhard, M. Tim; Meijer, Paulien C.; Brekelmans, Mieke; Pilot, Albert

    2013-01-01

    A growing body of research has investigated student perceptions of written feedback in higher education coursework, but few studies have considered feedback perceptions in one-on-one and face-to-face contexts such as master's thesis projects. In this article, student perceptions of feedback are explored in the context of the supervision of…

  6. Grade One Peer and Teacher Feedback on Student Writing

    ERIC Educational Resources Information Center

    Peterson, Shelley Stagg; Portier, Christine

    2014-01-01

    This article examines a grade one teacher's support for her students' writing development through formal peer and teacher feedback. The teacher modelled and provided examples of effective feedback and good writing in whole-class and small-group lessons and in her own one-on-one verbal feedback on student writing. She allocated time for the…

  7. Focusing on Form: Student Engagement with Teacher Feedback.

    ERIC Educational Resources Information Center

    Hyland, Fiona

    2003-01-01

    Explores the relationship between teacher feedback and student revision in two academic writing classes. Adopts a case study approach and looks at all the feedback given to six students over a complete course. Examines the extent to which teachers focused on formal language concerns when they gave feedback and the use that students made of this…

  8. Actual and Preferred Teacher Feedback on Student Blog Writing

    ERIC Educational Resources Information Center

    Chen, Wen-Chun

    2014-01-01

    This research illustrates the provisions and receptivity of teacher feedback in a blogmediated writing project between two colleges. The blog serves as a peer collaboration platform, as well as a mediating tool for teachers to offer timely feedback or prompt student idea exchanges. This paper discusses how teacher feedback may alter in response to…

  9. Beam-based Feedback for the NLC Linac

    SciTech Connect

    Hendrickson, L

    2004-07-21

    The NLC linac train-by-train feedback system is designed to stabilize the beam trajectory, but is also a valuable element in the strategy for emittance preservation. New simulations employ improved strategies [1], allowing beam steering to be performed significantly less often than without the feedback system. Additional simulations indicate that the linac feedback can contribute towards successful operation at noisier sites.

  10. Geometric foundations of the theory of feedback equivalence

    NASA Technical Reports Server (NTRS)

    Hermann, R.

    1987-01-01

    A description of feedback control is presented within the context of differential equations, differential geometry, and Lie theory. Work related to the integration of differential geometry with the control techniques of feedback linearization is summarized. Particular attention is given to the application of the theory of vector field systems. Feedback invariants for control systems in state space form are also addressed.

  11. Facilitating Productive Use of Feedback in Higher Education

    ERIC Educational Resources Information Center

    Jonsson, Anders

    2013-01-01

    Although feedback has a great potential for learning, students do not always make use of this potential. This article therefore reviews research literature on students' use of feedback in higher education. This is done in order to find answers as to why some students do not use the feedback they receive and which factors are important in…

  12. Effects of Differential Feedback on Students' Examination Performance

    ERIC Educational Resources Information Center

    Lipnevich, Anastasiya A.; Smith, Jeffrey K.

    2009-01-01

    The effects of feedback on performance and factors associated with it were examined in a large introductory psychology course. The experiment involved college students (N = 464) working on an essay examination under 3 conditions: no feedback, detailed feedback that was perceived by participants to be provided by the course instructor, and detailed…

  13. Smart building temperature control using occupant feedback

    NASA Astrophysics Data System (ADS)

    Gupta, Santosh K.

    This work was motivated by the problem of computing optimal commonly-agreeable thermal settings in spaces with multiple occupants. In this work we propose algorithms that take into account each occupant's preferences along with the thermal correlations between different zones in a building, to arrive at optimal thermal settings for all zones of the building in a coordinated manner. In the first part of this work we incorporate active occupant feedback to minimize aggregate user discomfort and total energy cost. User feedback is used to estimate the users comfort range, taking into account possible inaccuracies in the feedback. The control algorithm takes the energy cost into account, trading it off optimally with the aggregate user discomfort. A lumped heat transfer model based on thermal resistance and capacitance is used to model a multi-zone building. We provide a stability analysis and establish convergence of the proposed solution to a desired temperature that minimizes the sum of energy cost and aggregate user discomfort. However, for convergence to the optimal, sufficient separation between the user feedback frequency and the dynamics of the system is necessary; otherwise, the user feedback provided do not correctly reflect the effect of current control input value on user discomfort. The algorithm is further extended using singular perturbation theory to determine the minimum time between successive user feedback solicitations. Under sufficient time scale separation, we establish convergence of the proposed solution. Simulation study and experimental runs on the Watervliet based test facility demonstrates performance of the algorithm. In the second part we develop a consensus algorithm for attaining a common temperature set-point that is agreeable to all occupants of a zone in a typical multi-occupant space. The information on the comfort range functions is indeed held privately by each occupant. Using occupant differentiated dynamically adjusted prices as

  14. The Effect of Information Feedback Upon Psychophysical Judgments

    NASA Technical Reports Server (NTRS)

    Atkinson, Richard C.; Carterette, Edward C.; Kinchla, Ronald A.

    1964-01-01

    An analysis was made of the role of presentation schedules and information feedback on performance in a forced-choice signal detection task. The experimental results indicate that information feedback facilitates performance, but only for certain presentation schedules. The present study was designed to assess performance in a signal detection task under two conditions of information feedback. In the I-condition, S was told on each trial whether his detection response was correct or incorrect; in the !-condition S was given no feedback regarding the correctness of his response. The task involved a 2-response, forced-choice auditory detection problem. On each trial 2 temporal intervals were defined and S was required to report which interval he believed contained the signal; i. e., in one interval a tone burst in a background of white noise was presented, while the other interval contained only white noise. A trial will be denoted as s1 or s2, depending on whether the signal was embedded in the 1st or 2nd interval; the S's response will be denoted A1 or A2 to indicate which interval he reported contained the signal. The probability of an s1 trial will be denoted as y. In this study two values of y were used (.50 and.75) and, as indicated above, two conditions of information feedback. Thus there were 4 experimental conditions (501, · 50I, 751, 75I); each S was run under all 4 conditions. Method Gaussian noise was presented binaurally in S's headphones throughout a test session and the signal was a 1000-cps sinusoid tone; the tone was presented for 100 msec. including equal fall and rise times of 20 msec. The ratio of signal energy to noise power in a unit bandwidth was 2.9, and was constant throughout the study. The. S was seated before a stimulus display board. On each trial a red warning light was flashed for 100 msec. Two amber lights then came on successively each for 1 sec.; these lights defined the 2 observation intervals. The onset of the signal occurred 500

  15. Nonlinear dynamics of neural delayed feedback

    SciTech Connect

    Longtin, A.

    1990-01-01

    Neural delayed feedback is a property shared by many circuits in the central and peripheral nervous systems. The evolution of the neural activity in these circuits depends on their present state as well as on their past states, due to finite propagation time of neural activity along the feedback loop. These systems are often seen to undergo a change from a quiescent state characterized by low level fluctuations to an oscillatory state. We discuss the problem of analyzing this transition using techniques from nonlinear dynamics and stochastic processes. Our main goal is to characterize the nonlinearities which enable autonomous oscillations to occur and to uncover the properties of the noise sources these circuits interact with. The concepts are illustrated on the human pupil light reflex (PLR) which has been studied both theoretically and experimentally using this approach. 5 refs., 3 figs.

  16. Delayed feedback control in quantum transport.

    PubMed

    Emary, Clive

    2013-09-28

    Feedback control in quantum transport has been predicted to give rise to several interesting effects, among them quantum state stabilization and the realization of a mesoscopic Maxwell's daemon. These results were derived under the assumption that control operations on the system are affected instantaneously after the measurement of electronic jumps through it. In this contribution, I describe how to include a delay between detection and control operation in the master equation theory of feedback-controlled quantum transport. I investigate the consequences of delay for the state stabilization and Maxwell's daemon schemes. Furthermore, I describe how delay can be used as a tool to probe coherent oscillations of electrons within a transport system and how this formalism can be used to model finite detector bandwidth.

  17. Feedback regulation of microscopes by image processing.

    PubMed

    Tsukada, Yuki; Hashimoto, Koichi

    2013-05-01

    Computational microscope systems are becoming a major part of imaging biological phenomena, and the development of such systems requires the design of automated regulation of microscopes. An important aspect of automated regulation is feedback regulation, which is the focus of this review. As modern microscope systems become more complex, often with many independent components that must work together, computer control is inevitable since the exact orchestration of parameters and timings for these multiple components is critical to acquire proper images. A number of techniques have been developed for biological imaging to accomplish this. Here, we summarize the basics of computational microscopy for the purpose of building automatically regulated microscopes focus on feedback regulation by image processing. These techniques allow high throughput data acquisition while monitoring both short- and long-term dynamic phenomena, which cannot be achieved without an automated system.

  18. Assessing biosphere feedbacks on Earth System Processes

    NASA Astrophysics Data System (ADS)

    McElwain, Jennifer

    2016-04-01

    The evolution and ecology of plant life has been shaped by the direct and indirect influence of plate tectonics. Climatic change and environmental upheaval associated with the emplacement of large igneous provinces have triggered biosphere level ecological change, physiological modification and pulses of both extinction and origination. This talk will investigate the influence of large scale changes in atmospheric composition on plant ecophysiology at key intervals of the Phanerozoic. Furthermore, I will assess the extent to which plant ecophysiological response can in turn feedback on earth system processes such as the global hydrological cycle and biogeochemical cycling of nitrogen and carbon. Palaeo-atmosphere simulation experiments, palaeobotanical data and recent historical (last 50 years) data-model comparison will be used to address the extent to which plant physiological responses to atmospheric CO2 can modulate global climate change via biosphere level feedback.

  19. Stabilizing feedbacks in glacier-bed erosion.

    PubMed

    Alley, R B; Lawson, D E; Larson, G J; Evenson, E B; Baker, G S

    2003-08-14

    Glaciers often erode, transport and deposit sediment much more rapidly than nonglacial environments, with implications for the evolution of glaciated mountain belts and their associated sedimentary basins. But modelling such glacial processes is difficult, partly because stabilizing feedbacks similar to those operating in rivers have not been identified for glacial landscapes. Here we combine new and existing data of glacier morphology and the processes governing glacier evolution from diverse settings to reveal such stabilizing feedbacks. We find that the long profiles of beds of highly erosive glaciers tend towards steady-state angles opposed to and slightly more than 50 per cent steeper than the overlying ice-air surface slopes, and that additional subglacial deepening must be enabled by non-glacial processes. Climatic or glaciological perturbations of the ice-air surface slope can have large transient effects on glaciofluvial sediment flux and apparent glacial erosion rate.

  20. Recursion and feedback in image algebra

    NASA Astrophysics Data System (ADS)

    Ritter, Gerhard X.; Davidson, Jennifer L.

    1991-04-01

    Recursion and feedback are two important processes in image processing. Image algebra, a unified algebraic structure developed for use in image processing and image analysis, provides a common mathematical environment for expressing image processing transforms. It is only recently that image algebra has been extended to include recursive operations [1]. Recently image algebra was shown to incorporate neural nets [2], including a new type of neural net, the morphological neural net [3]. This paper presents the relationship of the recursive image algebra to the field of fractions of the ring of matrices, and gives the two dimensional moving average filter as an example. Also, the popular multilayer perceptron with back propagation and a morphology neural network with learning rule are presented in image algebra notation. These examples show that image algebra can express these important feedback concepts in a succinct way.

  1. Tissue modification with feedback: the smart scalpel

    NASA Astrophysics Data System (ADS)

    Sebern, Elizabeth L.; Brenan, Colin J. H.; Anderson, R. Rox; Hunter, Ian W.

    1998-10-01

    While feedback control is widespread throughout many engineering fields, there are almost no examples of surgical instruments that utilize a real-time detection and intervention strategy. This concept of closed loop feedback can be applied to the development of autonomous or semi- autonomous minimally invasive robotic surgical systems for efficient excision or modification of diseased tissue. Spatially localized regions of the tissue are first probed to distinguish pathological from healthy tissue based on differences in histochemical and morphological properties. Energy is directed to only the diseased tissue, minimizing collateral damage by leaving the adjacent healthy tissue intact. Continuous monitoring determines treatment effectiveness and, if needed, enables real-time treatment modifications to produce optimal therapeutic outcomes. The present embodiment of this general concept is a microsurgical instrument we call the Smart Scalpel, designed to treat skin angiodysplasias such as port wine stains. Other potential Smart Scalpel applications include psoriasis treatment and early skin cancer detection and intervention.

  2. FAST DIGITAL ORBIT FEEDBACK SYSTEMS AT NSLS.

    SciTech Connect

    PODOBEDOV,B.; KUSHNER,B.; RAMAMOORTHY,S.; TANG,Y.; ZITVOGEL,E.

    2001-06-18

    We are implementing digital orbit feedback systems to replace the analog ones in both the VUV and the X-ray rings. We developed an original VME-based design which is run by a powerful Motorola 2305 CPU and consists entirely of off-the-shelf VME boards. This makes the system inexpensive and easy to configure, and allows for high digitizing rates. The new 5 kHz digital global feedback system is currently operational in the VUV ring, and the X-ray system is in the commissioning phase. Some of the parameters achieved include vertical correction bandwidth of 200 Hz (at DC gain of 100) and typical orbit drift over a fill of <3% of the rms beam size. In this paper we discuss the system architecture, implementation and performance.

  3. The Importance of Winds for AGN Feedback

    NASA Astrophysics Data System (ADS)

    Crenshaw, D. M.; Kraemer, S. B.; Schmitt, H. R.; Fischer, T. C.; Gagne, J.

    2014-01-01

    Active galactic nuclei (AGN) are fed by accretion of matter onto supermassive black holes (SMBHs), generating huge amounts of radiation from very small volumes. AGN also provide feedback to their environments via mass outflows of ionized gas, which could play a critical role in the formation of large-scale structure in the early Universe, chemical enrichment of the intergalactic medium, and self-regulation of SMBH and galactic bulge growth. We provide an update on our research on the winds in nearby moderate-luminosity AGN, In particular, we concentrate on winds that occur on relatively large scales (hundreds of parsecs) that are revealed through spatially resolved HST spectra of emission-line gas in the narrow line regions (NLRs) of nearby AGN. We discuss the techniques for measuring the mass outflow rates and kinetic luminosities of these AGN winds and gauge their importance for providing significant AGN feedback.

  4. Flux-Feedback Magnetic-Suspension Actuator

    NASA Technical Reports Server (NTRS)

    Groom, Nelson J.

    1990-01-01

    Flux-feedback magnetic-suspension actuator provides magnetic suspension and control forces having linear transfer characteristics between force command and force output over large range of gaps. Hall-effect devices used as sensors for electronic feedback circuit controlling currents flowing in electromagnetic windings to maintain flux linking suspended element at substantially constant value independent of changes in length of gap. Technique provides effective method for maintenance of constant flux density in gap and simpler than previous methods. Applications include magnetic actuators for control of shapes and figures of antennas and of precise segmented reflectors, magnetic suspensions in devices for storage of angular momentum and/or kinetic energy, and systems for control, pointing, and isolation of instruments.

  5. AGN feedback in the Perseus cluster

    NASA Astrophysics Data System (ADS)

    Gendron-Marsolais, Marie-Lou; Hlavacek-Larrondo, Julie; Clarke, Tracy E.; Intema, Huib; Fabian, Andrew C.; Taylor, Gregory B.; Blundell, Katherine

    2016-04-01

    Deep Chandra images of the Perseus cluster of galaxies have revealed a succession of cavities created by the jets of the central supermassive black hole, pushing away the X-ray emitting gas and leaving bubbles filled with radio emission. Perseus is one of the rare examples showing buoyantly rising lobes from past radio outbursts, characterized by a steep spectral index and known as ghost cavities. All of these structures trace the complete history of mechanical AGN feedback over the past 500 Myrs. I will present results on new, ultra deep 230-470 MHz JVLA data. This low-frequency view of the Perseus cluster will probe the old radio-emitting electron population and will allow us to build the most detailed map of AGN feedback in a cluster thus far.

  6. Feedback control laws for highly maneuverable aircraft

    NASA Technical Reports Server (NTRS)

    Garrard, William L.; Balas, Gary J.

    1992-01-01

    The results of a study of the application of H infinity and mu synthesis techniques to the design of feedback control laws for the longitudinal dynamics of the High Angle of Attack Research Vehicle (HARV) are presented. The objective of this study is to develop methods for the design of feedback control laws which cause the closed loop longitudinal dynamics of the HARV to meet handling quality specifications over the entire flight envelope. Control law designs are based on models of the HARV linearized at various flight conditions. The control laws are evaluated by both linear and nonlinear simulations of typical maneuvers. The fixed gain control laws resulting from both the H infinity and mu synthesis techniques result in excellent performance even when the aircraft performs maneuvers in which the system states vary significantly from their equilibrium design values. Both the H infinity and mu synthesis control laws result in performance which compares favorably with an existing baseline longitudinal control law.

  7. Modeling the relativistic runaway electron avalanche and the feedback mechanism with GEANT4

    PubMed Central

    Skeltved, Alexander Broberg; Østgaard, Nikolai; Carlson, Brant; Gjesteland, Thomas; Celestin, Sebastien

    2014-01-01

    This paper presents the first study that uses the GEometry ANd Tracking 4 (GEANT4) toolkit to do quantitative comparisons with other modeling results related to the production of terrestrial gamma ray flashes and high-energy particle emission from thunderstorms. We will study the relativistic runaway electron avalanche (RREA) and the relativistic feedback process, as well as the production of bremsstrahlung photons from runaway electrons. The Monte Carlo simulations take into account the effects of electron ionization, electron by electron (Møller), and electron by positron (Bhabha) scattering as well as the bremsstrahlung process and pair production, in the 250 eV to 100 GeV energy range. Our results indicate that the multiplication of electrons during the development of RREAs and under the influence of feedback are consistent with previous estimates. This is important to validate GEANT4 as a tool to model RREAs and feedback in homogeneous electric fields. We also determine the ratio of bremsstrahlung photons to energetic electrons Nγ/Ne. We then show that the ratio has a dependence on the electric field, which can be expressed by the avalanche time τ(E) and the bremsstrahlung coefficient α(ε). In addition, we present comparisons of GEANT4 simulations performed with a “standard” and a “low-energy” physics list both validated in the 1 keV to 100 GeV energy range. This comparison shows that the choice of physics list used in GEANT4 simulations has a significant effect on the results. Key Points Testing the feedback mechanism with GEANT4 Validating the GEANT4 programming toolkit Study the ratio of bremsstrahlung photons to electrons at TGF source altitude PMID:26167437

  8. Modeling heart rate variability by stochastic feedback

    NASA Technical Reports Server (NTRS)

    Amaral, L. A.; Goldberger, A. L.; Stanley, H. E.

    1999-01-01

    We consider the question of how the cardiac rhythm spontaneously self-regulates and propose a new mechanism as a possible answer. We model the neuroautonomic regulation of the heart rate as a stochastic feedback system and find that the model successfully accounts for key characteristics of cardiac variability, including the 1/f power spectrum, the functional form and scaling of the distribution of variations of the interbeat intervals, and the correlations in the Fourier phases which indicate nonlinear dynamics.

  9. Feedback and efficiency in limit order markets

    NASA Astrophysics Data System (ADS)

    Challet, Damien

    2008-06-01

    A consistency criterion for price impact functions in limit order markets is proposed that prohibits chain arbitrage exploitation. Both the bid-ask spread and the feedback of sequential market orders of the same kind onto both sides of the order book are essential to ensure consistency at the smallest time scale. All the stocks investigated in Paris Stock Exchange have consistent price impact functions.

  10. High gain feedback and telerobotic tracking

    NASA Technical Reports Server (NTRS)

    Koditschek, D. E.

    1987-01-01

    Asymptotically stable linear time invariant systems are capable of tracking arbitrary reference signals with a bounded error proportional to the magnitude of the reference signal (and its derivatives). It is shown that a similar property holds for a general class of nonlinear dynamical systems which includes all robots. As in the linear case, the error bound may be made arbitrarily small by increasing the magnitude of the feedback gains which stabilize the system.

  11. Feedback control of bimodal wake dynamics

    NASA Astrophysics Data System (ADS)

    Li, Ruiying; Barros, Diogo; Borée, Jacques; Cadot, Olivier; Noack, Bernd R.; Cordier, Laurent

    2016-10-01

    Feedback control is applied to symmetrize the bimodal dynamics of a turbulent blunt body wake. The flow is actuated with two lateral slit jets and monitored with pressure sensors at the rear surface. The physics-based controller is inferred from preliminary open-loop tests and is capable of symmetrizing the wake. A slight pressure recovery is achieved due to the net balance between the favourable effect of wake symmetrization and adverse effect of shear-layer mixing and vortex shedding amplification.

  12. PEP-II RF Feedback System Simulation

    SciTech Connect

    Tighe, R.

    2004-03-11

    A model containing the fundamental impedance of the PEP-II cavity along with the longitudinal beam dynamics and feedback system components is in use. It is prepared in a format allowing time-domain as well as frequency-domain analysis and full graphics capability. Matlab and Simulink are control system design and analysis programs (widely available) with many built-in tools. The model allows the use of compiled C-code modules for compute intensive portions.

  13. Phenomenology and participant feedback: convention or contention?

    PubMed

    Bradbury-Jones, Caroline; Irvine, Fiona; Sambrook, Sally

    2010-01-01

    Steps to enhance the rigour of qualitative research are much debated in nursing research. Prolonged engagement in the field, maintaining a journal and member checks (participant feedback) can help with this. This paper examines the latter, principally as we have been intrigued by the opposing viewpoints of nurse scholars regarding this matter. A process of critically analysing our research practice, coupled with an exploration of available literature has led to some clarity on the issue, as shared here.

  14. Force feedback systems in undersea manipulator applications

    NASA Technical Reports Server (NTRS)

    Pesch, A. J.; Bertsche, W. R.; Winget, C. L.

    1975-01-01

    The manual control behavior of the operator with various levels of manipulator system complexity was studied in order to determine the relationships among control system dynamics, certain base engineering variables, controller designs and system performance. Based on the data obtained, a set of general transfer functions were prepared to provide a mathematical model of the various levels of potential force feedback fidelity as a function of force backlash present in alternate engineering designs.

  15. Frequency-feedback cavity enhanced spectrometer

    DOEpatents

    Hovde, David Christian; Gomez, Anthony

    2015-08-18

    A spectrometer comprising an optical cavity, a light source capable of producing light at one or more wavelengths transmitted by the cavity and with the light directed at the cavity, a detector and optics positioned to collect light transmitted by the cavity, feedback electronics causing oscillation of amplitude of the optical signal on the detector at a frequency that depends on cavity losses, and a sensor measuring the oscillation frequency to determine the cavity losses.

  16. The value proposition of patient feedback.

    PubMed

    Gingold, Scott R

    2011-01-01

    Medical practices need to listen to patients and value their opinions in order to provide the best possible service. But too often practitioners don't make the effort to satisfy customers and build loyalty, something of value to every business. The road to failure is littered with companies that did not listen to customers. Research from Powerfeedback shows that soliciting feedback and acting on that information is critical to the success of a medical practice, as it is with any business.

  17. Water Vapor Feedbacks to Climate Change

    NASA Technical Reports Server (NTRS)

    Rind, David

    1999-01-01

    The response of water vapor to climate change is investigated through a series of model studies with varying latitudinal temperature gradients, mean temperatures, and ultimately, actual climate change configurations. Questions to be addressed include: what role does varying convection have in water vapor feedback; do Hadley Circulation differences result in differences in water vapor in the upper troposphere; and, does increased eddy energy result in greater eddy vertical transport of water vapor in varying climate regimes?

  18. The effect of galaxy mass ratio on merger-driven starbursts

    NASA Astrophysics Data System (ADS)

    Cox, T. J.; Jonsson, Patrik; Somerville, Rachel S.; Primack, Joel R.; Dekel, Avishai

    2008-02-01

    We employ numerical simulations of galaxy mergers to explore the effect of galaxy mass ratio on merger-driven starbursts. Our numerical simulations include radiative cooling of gas, star formation, and stellar feedback to follow the interaction and merger of four disc galaxies. The galaxy models span a factor of 23 in total mass and are designed to be representative of typical galaxies in the local universe. We find that the merger-driven star formation is a strong function of merger mass ratio, with very little, if any, induced star formation for large mass ratio mergers. We define a burst efficiency that is useful to characterize the merger-driven star formation and test that it is insensitive to uncertainties in the feedback parametrization. In accord with previous work we find that the burst efficiency depends on the structure of the primary galaxy. In particular, the presence of a massive stellar bulge stabilizes the disc and suppresses merger-driven star formation for large mass ratio mergers. Direct, coplanar merging orbits produce the largest tidal disturbance and yield the most intense burst of star formation. Contrary to naive expectations, a more compact distribution of gas or an increased gas fraction both decrease the burst efficiency. Owing to the efficient feedback model and the newer version of smoothed particle hydrodynamics employed here, the burst efficiencies of the mergers presented here are smaller than in previous studies.

  19. BLACK HOLE FORAGING: FEEDBACK DRIVES FEEDING

    SciTech Connect

    Dehnen, Walter; King, Andrew E-mail: ark@astro.le.ac.uk

    2013-11-10

    We suggest a new picture of supermassive black hole (SMBH) growth in galaxy centers. Momentum-driven feedback from an accreting hole gives significant orbital energy, but little angular momentum to the surrounding gas. Once central accretion drops, the feedback weakens and swept-up gas falls back toward the SMBH on near-parabolic orbits. These intersect near the black hole with partially opposed specific angular momenta, causing further infall and ultimately the formation of a small-scale accretion disk. The feeding rates into the disk typically exceed Eddington by factors of a few, growing the hole on the Salpeter timescale and stimulating further feedback. Natural consequences of this picture include (1) the formation and maintenance of a roughly toroidal distribution of obscuring matter near the hole; (2) random orientations of successive accretion disk episodes; (3) the possibility of rapid SMBH growth; (4) tidal disruption of stars and close binaries formed from infalling gas, resulting in visible flares and ejection of hypervelocity stars; (5) super-solar abundances of the matter accreting on to the SMBH; and (6) a lower central dark-matter density, and hence annihilation signal, than adiabatic SMBH growth implies. We also suggest a simple subgrid recipe for implementing this process in numerical simulations.

  20. Feedback control of subcritical oscillatory instabilities.

    PubMed

    Golovin, A A; Nepomnyashchy, A A

    2006-04-01

    Feedback control of a subcritical oscillatory instability is investigated in the framework of a globally-controlled complex Ginzburg-Landau equation that describes the nonlinear dynamics near the instability threshold. The control is based on a feedback loop between the system linear growth rate and the maximum of the amplitude of the emerging pattern. It is shown that such control can suppress the blow up and result in the formation of spatially localized pulses similar to oscillons. In the one-dimensional case, depending on the values of the linear and nonlinear dispersion coefficients, several types of the pulse dynamics are possible in which the computational domain contains: (i) a single stationary pulse; (ii) several coexisting stationary pulses; (iii) competing pulses that appear one after another at random locations so that at each moment of time there is only one pulse in the domain; (iv) spatiotemporally chaotic system of short pulses; (v) spatially-synchronized pulses. Similar dynamic behavior is found also in the two-dimensional case. The effect of the feedback delay is also studied. It is shown that the increase of the delay leads to an oscillatory instability of the pulses and the formation of pulses with oscillating amplitude.